50 results on '"Dixon CL"'
Search Results
2. Sublogics of a branching time logic of robustness
- Author
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McCabe-Dansted, John, Dixon, CL, French, Tim, and Reynolds, Mark
- Subjects
Tableau ,RoCTL ,CTL ,Bundles - Abstract
In this paper we study sublogics of RoCTL*, a recently proposed logic for specifying robustness. RoCTL* allows specifying robustness in terms of properties that are robust to a certain number of failures. RoCTL* is an extension of the branching time logic CTL* which in turn extends CTL by removing the requirement that temporal operators be paired with path quantifiers. In this paper we consider three sublogics of RoCTL*. We present a tableau for RoBCTL*, a bundled variant of RoCTL* that allows fairness constraints to be placed on allowable paths. We then examine two CTL-like restrictions of CTL*. Pair-RoCTL* requires a temporal operator to be paired with a path quantifier; we show that Pair-RoCTL* is as hard to reason about as the full CTL*. State-RoCTL* is restricted to State formulas, and we show that there is a linear truth preserving translation of State-RoCTL into CTL, allowing State-RoCTL to be reasoned about as efficiently as CTL.
- Published
- 2019
3. CRutoN: Automatic Verification of a Robotic Assistant's Behaviours
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Gainer, P, Dixon, CL, Dautenhahn, K, Fisher, M, Hustadt, U, Saunders, J, and Webster, M
- Published
- 2017
4. Use and usability of software verification methods to detect behaviour interference when teaching an assistive home companion robot: A proof-of-concept study
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Koay Kheng Lee, Webster Matt, Dixon Clare, Gainer Paul, Syrdal Dag, Fisher Michael, and Dautenhahn Kerstin
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human–robot interaction ,companion robots ,behaviour interference ,formal verification ,Technology - Abstract
When studying the use of assistive robots in home environments, and especially how such robots can be personalised to meet the needs of the resident, key concerns are issues related to behaviour verification, behaviour interference and safety. Here, personalisation refers to the teaching of new robot behaviours by both technical and non-technical end users. In this article, we consider the issue of behaviour interference caused by situations where newly taught robot behaviours may affect or be affected by existing behaviours and thus, those behaviours will not or might not ever be executed. We focus in particular on how such situations can be detected and presented to the user. We describe the human–robot behaviour teaching system that we developed as well as the formal behaviour checking methods used. The online use of behaviour checking is demonstrated, based on static analysis of behaviours during the operation of the robot, and evaluated in a user study. We conducted a proof-of-concept human–robot interaction study with an autonomous, multi-purpose robot operating within a smart home environment. Twenty participants individually taught the robot behaviours according to instructions they were given, some of which caused interference with other behaviours. A mechanism for detecting behaviour interference provided feedback to participants and suggestions on how to resolve those conflicts. We assessed the participants’ views on detected interference as reported by the behaviour teaching system. Results indicate that interference warnings given to participants during teaching provoked an understanding of the issue. We did not find a significant influence of participants’ technical background. These results highlight a promising path towards verification and validation of assistive home companion robots that allow end-user personalisation.
- Published
- 2021
- Full Text
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5. KSP A Resolution-Based Theorem Prover for Kn: Architecture, Refinements, Strategies and Experiments
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Nalon, Claudia, Hustadt, Ullrich, and Dixon, CL
6. Towards Robots for Social Engagement
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Cucco, E, Fisher, MD, Dennis, LA, Dixon, CL, Webster, M, Broecker, B, Williams, R, Collenette, J, Atkinson, K, and Tuyls, K
7. AMPA receptor GluA2 subunit defects are a cause of neurodevelopmental disorders
- Author
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Vincenzo Salpietro1, 2 3, 140, Christine L. Dixon4, Hui Guo5, 6 140, Oscar D. Bello Stephanie Efthymiou 1, 4, Reza Maroofian1, Gali Heimer7, Lydie Burglen 8, Stephanie Valence 9, Erin Torti 10, Moritz Hacke11, Julia Rankin12, Huma Tariq1, Estelle Colin13, Vincent Procaccio13, Pasquale Striano2, 3, Kshitij Mankad15, Andreas Lieb 4, Sharon Chen16, Laura Pisani16, Conceicao Bettencourt 17, Roope Männikkö 1, Andreea Manole1, Alfredo Brusco 18, Enrico Grosso18, Giovanni Battista Ferrero19, Judith Armstrong-Moron20, Sophie Gueden21, Omer Bar-Yosef7, Michal Tzadok7, Kristin G. Monaghan10, Teresa Santiago-Sim10, Richard E. Person10, Megan T. Cho10, Rebecca Willaert10, Yongjin Yoo22, Jong-Hee Chae23, Yingting Quan6, Huidan Wu6, Tianyun Wang5, 6, Raphael A. Bernier24, Kun Xia6, Alyssa Blesson25, Mahim Jain25, Mohammad M. Motazacker26, Bregje Jaeger27, Amy L. Schneider 28, Katja Boysen28, Alison M. Muir 29, Candace T. Myers30, Ralitza H. Gavrilova31, Lauren Gunderson31, Laura Schultz-Rogers 31, Eric W. Klee31, David Dyment32, Matthew Osmond32, 33 34, Mara Parellada35, Cloe Llorente36, Javier Gonzalez-Peñas37, Angel Carracedo38, Arie Van Haeringen40, Claudia Ruivenkamp40, Caroline Nava41, Delphine Heron41, Rosaria Nardello42, Michele Iacomino43, Carlo Minetti2, Aldo Skabar44, Antonella Fabretto44, SYNAPS Study GroupMiquel Raspall-Chaure45, Michael Chez46, Anne Tsai47, Emily Fassi48, Marwan Shinawi48, John N. Constantino49, Rita De Zorzi50, Sara Fortuna 50, Fernando Kok51, Boris Keren41, Dominique Bonneau13, Murim Choi 22, Bruria Benzeev7, Federico Zara43, Heather C. Mefford29, Ingrid E. Scheffer28, Jill Clayton-Smith53, Alfons Macaya45, James E. Rothman4, Evan E. Eichler 5, Dimitri M. Kullmann 4, Henry Houlden 1, SYNAPS Study Group Michael G. Hanna1, Enrico Bugiardini1, Isabel Hostettler1, Benjamin O’Callaghan1, Alaa Khan1, Andrea Cortese1, Emer O’Connor1, Wai Y. Yau1, Thomas Bourinaris1, Rauan Kaiyrzhanov1, Viorica Chelban1, Monika Madej1, Maria C. Diana2, Maria S. Vari2, Marina Pedemonte2, Claudio Bruno2, Ganna Balagura3, Marcello Scala3, Chiara Fiorillo3, Lino Nobili3, Nancy T. Malintan4, Maria N. Zanetti4, Shyam S. Krishnakumar4, Gabriele Lignani4, James E. C. Jepson4, Paolo Broda43, Simona Baldassari43, Pia Rossi43, Floriana Fruscione43, Francesca Madia43, Monica Traverso43, Patrizia De-Marco43, Belen Pérez-Dueñas45, Francina Munell45, Yamna Kriouile57, Mohamed El-Khorassani57, Blagovesta Karashova58, Daniela Avdjieva58, Hadil Kathom58, Radka Tincheva58, Lionel Van-Maldergem59, Wolfgang Nachbauer60, Sylvia Boesch60, Antonella Gagliano61, Elisabetta Amadori62, Jatinder S. Goraya63, Tipu Sultan64, Salman Kirmani65, Shahnaz Ibrahim66, Farida Jan66, Jun Mine67, Selina Banu68, Pierangelo Veggiotti69, Gian V. Zuccotti69, Michel D. Ferrari70, Arn M. J. Van Den Maagdenberg70, Alberto Verrotti71, Gian L. Marseglia72, Salvatore Savasta72, Miguel A. Soler73, Carmela Scuderi74, Eugenia Borgione74, Roberto Chimenz75, Eloisa Gitto75, Valeria Dipasquale75, Alessia Sallemi75, Monica Fusco75, Caterina Cuppari75, Maria C. Cutrupi75, Martino Ruggieri76, Armando Cama77, Valeria Capra77, Niccolò E. Mencacci78, Richard Boles79, Neerja Gupta80, Madhulika Kabra80, Savvas Papacostas81, Eleni Zamba-Papanicolaou81, Efthymios Dardiotis82, Shazia Maqbool83, Nuzhat Rana84, Osama Atawneh85, Shen Y. Lim86, Farooq Shaikh87, George Koutsis88, Marianthi Breza88, Domenico A. Coviello89, Yves A. Dauvilliers90, Issam AlKhawaja91, Mariam AlKhawaja92, Fuad Al-Mutairi93, Tanya Stojkovic94, Veronica Ferrucci, Massimo Zollo, Fowzan S. Alkuraya96, Maria Kinali97, Hamed Sherifa98, Hanene Benrhouma99, Ilhem B. Y. Turki99, Meriem Tazir100, Makram Obeid101, Sophia Bakhtadze102, Nebal W. Saadi103, Maha S. Zaki104, Chahnez C. Triki105, Fabio Benfenati106, Stefano Gustincich106, Majdi Kara107, Vincenzo Belcastro108, Nicola Specchio109, Giuseppe Capovilla110, Ehsan G. Karimiani111, Ahmed M. Salih112, Njideka U. Okubadejo113, Oluwadamilola O. Ojo113, Olajumoke O. Oshinaike113, Olapeju Oguntunde113, Kolawole Wahab114, Abiodun H. Bello114, Sanni Abubakar115, Yahaya Obiabo116, Ernest Nwazor117, Oluchi Ekenze118, Uduak Williams119, Alagoma Iyagba120, Lolade Taiwo121, Morenikeji Komolafe122, Konstantin Senkevich123, Chingiz Shashkin124, Nazira Zharkynbekova125, Kairgali Koneyev126, Ganieva Manizha127, Maksud Isrofilov127, Ulviyya Guliyeva128, Kamran Salayev129, Samson Khachatryan130, Salvatore Rossi131, Gabriella Silvestri131, Nourelhoda Haridy132, Luca A. Ramenghi133, Georgia Xiromerisiou134, Emanuele David135, Mhammed Aguennouz136, Liana Fidani137, Cleanthe Spanaki138, Arianna Tucci139, University College of London [London] (UCL), Instituto Giannina Gaslini, Genoa, University of Genoa (UNIGE), University of Washington [Seattle], Institute of Neurology, Queen Square, London, King‘s College London, UCL Institute of Neurology, National Hospital for Neurology and Neurosurgery, Queen Square, London, Molecular and Clinical Sciences Institute - St George’s [London, UK] (Genetics Research Centre), University of London [London], Tel Aviv University Sackler School of Medicine [Tel Aviv, Israël], Service de génétique et embryologie médicales [CHU Trousseau], CHU Trousseau [APHP], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU), Service de Neuropédiatrie [CHU Trousseau], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-CHU Trousseau [APHP], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Sorbonne Université (SU), GeneDx [Gaithersburg, MD, USA], Heidelberg University Hospital [Heidelberg], Royal Devon and Exeter NHS Foundation Trust [UK], Biologie Neurovasculaire et Mitochondriale Intégrée (BNMI), Université d'Angers (UA)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Centre Hospitalier Universitaire d'Angers (CHU Angers), PRES Université Nantes Angers Le Mans (UNAM), Universita degli studi di Genova, Great Ormond Street Hospital for Children [London] (GOSH), The University of Sydney, Hofstra University [Hempstead], Università degli studi di Torino (UNITO), Hospital Sant Joan de Déu [Barcelona], Safra Children's Hospital, Seoul National University Hospital, Central South University [Changsha], Kennedy Krieger Institute [Baltimore], University of Amsterdam [Amsterdam] (UvA), University of Melbourne, Mayo Clinic [Rochester], Department of Health Sciences Research [Mayo Clinic] (HSR), Mayo Clinic, University of Ottawa [Ottawa], University of British Columbia (UBC), Universidad Complutense de Madrid = Complutense University of Madrid [Madrid] (UCM), Universidade de Santiago de Compostela [Spain] (USC ), Universiteit Leiden [Leiden], Institut du Cerveau et de la Moëlle Epinière = Brain and Spine Institute (ICM), Institut National de la Santé et de la Recherche Médicale (INSERM)-CHU Pitié-Salpêtrière [AP-HP], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), CHU Pitié-Salpêtrière [AP-HP], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU), Università degli studi di Palermo - University of Palermo, University of Trieste, Universitat Autònoma de Barcelona (UAB), Department of Neurology and Center for Neuroscience, University of California at Davis, Sacramento, University of California [Davis] (UC Davis), University of California-University of California, Children’s Hospital Colorado, University of Colorado Anschutz [Aurora], Washington University in Saint Louis (WUSTL), Department of Molecular and Human Genetics, Baylor College of Medicine (BCM), Baylor University-Baylor University, Department of Psychiatry, Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, University of Oxford [Oxford], University of São Paulo (USP), Service de Génétique Cytogénétique et Embryologie [CHU Pitié-Salpêtrière], Service de Pédiatrie, CHUR Poitiers, Seoul National University [Seoul] (SNU), Pediatric Neurology and Neuromuscular Diseases Unit, University of Manchester [Manchester], Yale University School of Medicine, Centre Hospitalier Régional Universitaire [Montpellier] (CHRU Montpellier), Salvy-Córdoba, Nathalie, Università degli studi di Genova = University of Genoa (UniGe), Tel Aviv University (TAU), Università degli studi di Torino = University of Turin (UNITO), Institut du Cerveau = Paris Brain Institute (ICM), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Institut National de la Santé et de la Recherche Médicale (INSERM)-CHU Pitié-Salpêtrière [AP-HP], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Sorbonne Université (SU)-Sorbonne Université (SU)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Università degli studi di Trieste = University of Trieste, University of California (UC)-University of California (UC), University of Oxford, Universidade de São Paulo = University of São Paulo (USP), Yale School of Medicine [New Haven, Connecticut] (YSM), Salpietro V, Dixon CL, Guo H, Bello OD, Vandrovcova J, Efthymiou S, Maroofian R, Heimer G, Burglen L, Valence S, Torti E, Hacke M, Rankin J, Tariq H, Colin E, Procaccio V, Striano P, Mankad K, Lieb A, Chen S, Pisani L, Bettencourt C, Männikkö R, Manole A, Brusco A, Grosso E, Ferrero GB, Armstrong-Moron J, Gueden S, Bar-Yosef O, Tzadok M, Monaghan KG, Santiago-Sim T, Person RE, Cho MT, Willaert R, Yoo Y, Chae JH, Quan Y, Wu H, Wang T, Bernier RA, Xia K, Blesson A, Jain M, Motazacker MM, Jaeger B, Schneider AL, Boysen K, Muir AM, Myers CT, Gavrilova RH, Gunderson L, Schultz-Rogers L, Klee EW, Dyment D, Osmond M, Parellada M, Llorente C, Gonzalez-Peñas J, Carracedo A, Van Haeringen A, Ruivenkamp C, Nava C, Heron D, Nardello R, Iacomino M, Minetti C, Skabar A, Fabretto A, SYNAPS Study Group, Raspall-Chaure M, Chez M, Tsai A, Fassi E, Shinawi M, Constantino JN, De Zorzi R, Fortuna S, Kok F, Keren B, Bonneau D, Choi M, Benzeev B, Zara F, Mefford HC, Scheffer IE, Clayton-Smith J, Macaya A, Rothman JE, Eichler EE, Kullmann DM, Houlden H, Salpietro, Vincenzo, Dixon, Christine L, Guo, Hui, Bello, Oscar D, Vandrovcova, Jana, Efthymiou, Stephanie, Maroofian, Reza, Heimer, Gali, Burglen, Lydie, Valence, Stephanie, Torti, Erin, Hacke, Moritz, Rankin, Julia, Tariq, Huma, Colin, Estelle, Procaccio, Vincent, Striano, Pasquale, Mankad, Kshitij, Lieb, Andrea, Chen, Sharon, Pisani, Laura, Bettencourt, Conceicao, Männikkö, Roope, Manole, Andreea, Brusco, Alfredo, Grosso, Enrico, Ferrero, Giovanni Battista, Armstrong-Moron, Judith, Gueden, Sophie, Bar-Yosef, Omer, Tzadok, Michal, Monaghan, Kristin G, Santiago-Sim, Teresa, Person, Richard E, Cho, Megan T, Willaert, Rebecca, Yoo, Yongjin, Chae, Jong-Hee, Quan, Yingting, Wu, Huidan, Wang, Tianyun, Bernier, Raphael A, Xia, Kun, Blesson, Alyssa, Jain, Mahim, Motazacker, Mohammad M, Jaeger, Bregje, Schneider, Amy L, Boysen, Katja, Muir, Alison M, Myers, Candace T, Gavrilova, Ralitza H, Gunderson, Lauren, Schultz-Rogers, Laura, Klee, Eric W, Dyment, David, Osmond, Matthew, Parellada, Mara, Llorente, Cloe, Gonzalez-Peñas, Javier, Carracedo, Angel, Van Haeringen, Arie, Ruivenkamp, Claudia, Nava, Caroline, Heron, Delphine, Nardello, Rosaria, Iacomino, Michele, Minetti, Carlo, Skabar, Aldo, Fabretto, Antonella, Raspall-Chaure, Miquel, Chez, Michael, Tsai, Anne, Fassi, Emily, Shinawi, Marwan, Constantino, John N, De Zorzi, Rita, Fortuna, Sara, Kok, Fernando, Keren, Bori, Bonneau, Dominique, Choi, Murim, Benzeev, Bruria, Zara, Federico, Mefford, Heather C, Scheffer, Ingrid E, Clayton-Smith, Jill, Macaya, Alfon, Rothman, James E, Eichler, Evan E, Kullmann, Dimitri M, Houlden, Henry, Salpietro1, Vincenzo, 3, 2, Dixon4, Christine L., Guo5, Hui, 140, 6, Bello Stephanie Efthymiou 1, Oscar D., Maroofian1, Reza, Heimer7, Gali, 8, Lydie Burglen, 9, Stephanie Valence, Torti 10, Erin, Hacke11, Moritz, Rankin12, Julia, Tariq1, Huma, Colin13, Estelle, Procaccio13, Vincent, Striano2, Pasquale, Mankad15, Kshitij, 4, Andreas Lieb, Chen16, Sharon, Pisani16, Laura, Bettencourt 17, Conceicao, 1, Roope Männikkö, Manole1, Andreea, Brusco 18, Alfredo, Grosso18, Enrico, Battista Ferrero19, Giovanni, Armstrong-Moron20, Judith, Gueden21, Sophie, Bar-Yosef7, Omer, Tzadok7, Michal, Monaghan10, Kristin G., Santiago-Sim10, Teresa, Person10, Richard E., Cho10, Megan T., Willaert10, Rebecca, Yoo22, Yongjin, Chae23, Jong-Hee, Quan6, Yingting, Wu6, Huidan, Wang5, Tianyun, Bernier24, Raphael A., Xia6, Kun, Blesson25, Alyssa, Jain25, Mahim, Motazacker26, Mohammad M., Jaeger27, Bregje, Schneider 28, Amy L., Boysen28, Katja, Muir 29, Alison M., Myers30, Candace T., Gavrilova31, Ralitza H., Gunderson31, Lauren, Schultz-Rogers 31, Laura, Klee31, Eric W., Dyment32, David, Osmond32, Matthew, 34, 33, Parellada35, Mara, Llorente36, Cloe, Gonzalez-Peñas37, Javier, Carracedo38, Angel, Van Haeringen40, Arie, Ruivenkamp40, Claudia, Nava41, Caroline, Heron41, Delphine, Nardello42, Rosaria, Iacomino43, Michele, Minetti2, Carlo, Skabar44, Aldo, Fabretto44, Antonella, Study GroupMiquel Raspall-Chaure45, Synap, Chez46, Michael, Tsai47, Anne, Fassi48, Emily, Shinawi48, Marwan, Constantino49, John N., De Zorzi50, Rita, Fortuna 50, Sara, Kok51, Fernando, Keren41, Bori, Bonneau13, Dominique, Choi 22, Murim, Benzeev7, Bruria, Zara43, Federico, Mefford29, Heather C., Scheffer28, Ingrid E., Clayton-Smith53, Jill, Macaya45, Alfon, Rothman4, James E., Eichler 5, Evan E., Kullmann 4 &, Dimitri M., 1, Henry Houlden, Hanna1, SYNAPS Study Group Michael G., Bugiardini1, Enrico, Hostettler1, Isabel, O’Callaghan1, Benjamin, Khan1, Alaa, Cortese1, Andrea, O’Connor1, Emer, Yau1, Wai Y., Bourinaris1, Thoma, Kaiyrzhanov1, Rauan, Chelban1, Viorica, Madej1, Monika, Diana2, Maria C., Vari2, Maria S., Pedemonte2, Marina, Bruno2, Claudio, Balagura3, Ganna, Scala3, Marcello, Fiorillo3, Chiara, Nobili3, Lino, Malintan4, Nancy T., Zanetti4, Maria N., Krishnakumar4, Shyam S., Lignani4, Gabriele, Jepson4, James E. C., Broda43, Paolo, Baldassari43, Simona, Rossi43, Pia, Fruscione43, Floriana, Madia43, Francesca, Traverso43, Monica, De-Marco43, Patrizia, Pérez-Dueñas45, Belen, Munell45, Francina, Kriouile57, Yamna, El-Khorassani57, Mohamed, Karashova58, Blagovesta, Avdjieva58, Daniela, Kathom58, Hadil, Tincheva58, Radka, Van-Maldergem59, Lionel, Nachbauer60, Wolfgang, Boesch60, Sylvia, Gagliano61, Antonella, Amadori62, Elisabetta, Goraya63, Jatinder S., Sultan64, Tipu, Kirmani65, Salman, Ibrahim66, Shahnaz, Jan66, Farida, Mine67, Jun, Banu68, Selina, Veggiotti69, Pierangelo, Zuccotti69, Gian V., Ferrari70, Michel D., Van Den Maagdenberg70, Arn M. J., Verrotti71, Alberto, Marseglia72, Gian L., Savasta72, Salvatore, Soler73, Miguel A., Scuderi74, Carmela, Borgione74, Eugenia, Chimenz75, Roberto, Gitto75, Eloisa, Dipasquale75, Valeria, Sallemi75, Alessia, Fusco75, Monica, Cuppari75, Caterina, Cutrupi75, Maria C., Ruggieri76, Martino, Cama77, Armando, Capra77, Valeria, Mencacci78, Niccolò E., Boles79, Richard, Gupta80, Neerja, Kabra80, Madhulika, Papacostas81, Savva, Zamba-Papanicolaou81, Eleni, Dardiotis82, Efthymio, Maqbool83, Shazia, Rana84, Nuzhat, Atawneh85, Osama, Lim86, Shen Y., Shaikh87, Farooq, Koutsis88, George, Breza88, Marianthi, Coviello89, Domenico A., Dauvilliers90, Yves A., Alkhawaja91, Issam, Alkhawaja92, Mariam, Al-Mutairi93, Fuad, Stojkovic94, Tanya, Ferrucci, Veronica, Zollo, Massimo, Alkuraya96, Fowzan S., Kinali97, Maria, Sherifa98, Hamed, Benrhouma99, Hanene, Turki99, Ilhem B. Y., Tazir100, Meriem, Obeid101, Makram, Bakhtadze102, Sophia, Saadi103, Nebal W., Zaki104, Maha S., Triki105, Chahnez C., Benfenati106, Fabio, Gustincich106, Stefano, Kara107, Majdi, Belcastro108, Vincenzo, Specchio109, Nicola, Capovilla110, Giuseppe, Karimiani111, Ehsan G., Salih112, Ahmed M., Okubadejo113, Njideka U., Ojo113, Oluwadamilola O., Oshinaike113, Olajumoke O., Oguntunde113, Olapeju, Wahab114, Kolawole, Bello114, Abiodun H., Abubakar115, Sanni, Obiabo116, Yahaya, Nwazor117, Ernest, Ekenze118, Oluchi, Williams119, Uduak, Iyagba120, Alagoma, Taiwo121, Lolade, Komolafe122, Morenikeji, Senkevich123, Konstantin, Shashkin124, Chingiz, Zharkynbekova125, Nazira, Koneyev126, Kairgali, Manizha127, Ganieva, Isrofilov127, Maksud, Guliyeva128, Ulviyya, Salayev129, Kamran, Khachatryan130, Samson, Rossi131, Salvatore, Silvestri131, Gabriella, Haridy132, Nourelhoda, Ramenghi133, Luca A., Xiromerisiou134, Georgia, David135, Emanuele, Aguennouz136, Mhammed, Fidani137, Liana, Spanaki138 &, Cleanthe, and Tucci139, Arianna
- Subjects
Male ,[SDV.GEN] Life Sciences [q-bio]/Genetics ,Ion channels in the nervous system ,Cohort Studies ,fluids and secretions ,Loss of Function Mutation ,Receptors ,AMPA ,AMPA receptor ,lcsh:Science ,Child ,reproductive and urinary physiology ,AMPA receptor, GluA2, neurodevelopmental disorders, autism spectrum disorder, glutamatergic synaptic transmission, GRIA2 ,neurodevelopmental disorders ,Developmental disorders ,Neurodevelopmental disorders ,Brain ,Magnetic Resonance Imaging ,Settore MED/26 - NEUROLOGIA ,GluA2 ,Child, Preschool ,Female ,Adult ,Heterozygote ,Adolescent ,Science ,autism spectrum disorder ,Article ,Young Adult ,[SDV.MHEP.PED] Life Sciences [q-bio]/Human health and pathology/Pediatrics ,MESH: Intellectual Disability/genetics ,Neurodevelopmental Disorders/genetics ,Receptors AMPA/genetics ,Intellectual Disability ,mental disorders ,Humans ,Infant ,Neurodevelopmental Disorders ,Receptors, AMPA ,GRIA2 ,Preschool ,Ion channel in the nervous system, Developmental disorders, Synaptic development, NG sequencing ,[SDV.GEN]Life Sciences [q-bio]/Genetics ,[SDV.MHEP.PED]Life Sciences [q-bio]/Human health and pathology/Pediatrics ,glutamatergic synaptic transmission ,[SCCO.NEUR]Cognitive science/Neuroscience ,[SCCO.NEUR] Cognitive science/Neuroscience ,NG sequencing ,Synaptic development ,Ion channel in the nervous system ,Next-generation sequencing ,lcsh:Q - Abstract
AMPA receptors (AMPARs) are tetrameric ligand-gated channels made up of combinations of GluA1-4 subunits encoded by GRIA1-4 genes. GluA2 has an especially important role because, following post-transcriptional editing at the Q607 site, it renders heteromultimeric AMPARs Ca2+-impermeable, with a linear relationship between current and trans-membrane voltage. Here, we report heterozygous de novo GRIA2 mutations in 28 unrelated patients with intellectual disability (ID) and neurodevelopmental abnormalities including autism spectrum disorder (ASD), Rett syndrome-like features, and seizures or developmental epileptic encephalopathy (DEE). In functional expression studies, mutations lead to a decrease in agonist-evoked current mediated by mutant subunits compared to wild-type channels. When GluA2 subunits are co-expressed with GluA1, most GRIA2 mutations cause a decreased current amplitude and some also affect voltage rectification. Our results show that de-novo variants in GRIA2 can cause neurodevelopmental disorders, complementing evidence that other genetic causes of ID, ASD and DEE also disrupt glutamatergic synaptic transmission., Genetic variants in ionotropic glutamate receptors have been implicated in neurodevelopmental disorders. Here, the authors report heterozygous de novo mutations in the GRIA2 gene in 28 individuals with intellectual disability and neurodevelopmental abnormalities associated with reduced Ca2+ transport and AMPAR currents.”
- Published
- 2019
8. AMPA receptor GluA2 subunit defects are a cause of neurodevelopmental disorders
- Author
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Salpietro, Vincenzo, Dixon, Christine L, Guo, Hui, Bello, Oscar D, Vandrovcova, Jana, Efthymiou, Stephanie, Raspall Chaure, Miquel, Macaya Ruíz, Alfons, Institut Català de la Salut, [Salpietro V] Department of Neuromuscular Disorders, UCL Queen Square Institute of Neurology, London, UK. Pediatric Neurology and Muscular Diseases Unit, IRCCS Istituto 'Giannina Gaslini', Genoa, Italy. Department of Neurosciences, Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health, University of Genoa, Genoa, Italy. [Dixon CL, Bello OD] Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, UK. [Guo H] Department of Genome Sciences, University of Washington School of Medicine, Seattle, USA. Center for Medical Genetics & Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, China. [Vandrovcova J] Department of Neuromuscular Disorders, UCL Queen Square Institute of Neurology, London, UK. [Efthymiou S] Department of Neuromuscular Disorders, UCL Queen Square Institute of Neurology, London, UK. Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, UK. [Raspall-Chaure M, Macaya A] Servei de Neurologia Pediatrica, Hospital Universitari Vall d'Hebron, Barcelona, Spain. Universitat Autònoma de Barcelona, Barcelona, Spain., Hospital Universitari Vall d'Hebron, and Vall d'Hebron Barcelona Hospital Campus
- Subjects
Trastornos Mentales::Trastornos del Neurodesarrollo [PSIQUIATRÍA Y PSICOLOGÍA] ,Otros calificadores::Otros calificadores::/genética [Otros calificadores] ,trastornos mentales::trastornos del desarrollo neurológico [PSIQUIATRÍA Y PSICOLOGÍA] ,Mutació (Biologia) ,Proteïnes de membrana ,Other subheadings::Other subheadings::/genetics [Other subheadings] ,Genetic Phenomena::Genetic Variation::Mutation [PHENOMENA AND PROCESSES] ,Amino Acids, Peptides, and Proteins::Proteins::Carrier Proteins::Membrane Transport Proteins::Ion Channels::Ligand-Gated Ion Channels::Receptors, Ionotropic Glutamate::Receptors, AMPA [CHEMICALS AND DRUGS] ,Trastorns del desenvolupament - Aspectes genètics ,Aminoácidos, Péptidos y Proteínas::Proteínas::Proteínas Portadoras::Proteínas de Transporte de Membrana::Canales Iónicos::Canales Iónicos Activados por Ligandos::Receptores Ionotrópicos de Glutamato::Receptores AMPA [COMPUESTOS QUÍMICOS Y DROGAS] ,fenómenos genéticos::variación genética::mutación [FENÓMENOS Y PROCESOS] ,aminoácidos, péptidos y proteínas::proteínas::proteínas transportadoras::proteínas de transporte de membrana::canales iónicos::canales iónicos de apertura por ligandos::receptores ionotrópicos de glutamato::receptores AMPA [COMPUESTOS QUÍMICOS Y DROGAS] ,Mental Disorders::Neurodevelopmental Disorders [PSYCHIATRY AND PSYCHOLOGY] - Abstract
Neurodevelopmental disorders; AMPA; GluA2 Trastorns del neurodesenvolupament; AMPA; GluA2 Trastornos del neurodesarrollo; AMPA; GluA2 AMPA receptors (AMPARs) are tetrameric ligand-gated channels made up of combinations of GluA1-4 subunits encoded by GRIA1-4 genes. GluA2 has an especially important role because, following post-transcriptional editing at the Q607 site, it renders heteromultimeric AMPARs Ca2+-impermeable, with a linear relationship between current and trans-membrane voltage. Here, we report heterozygous de novo GRIA2 mutations in 28 unrelated patients with intellectual disability (ID) and neurodevelopmental abnormalities including autism spectrum disorder (ASD), Rett syndrome-like features, and seizures or developmental epileptic encephalopathy (DEE). In functional expression studies, mutations lead to a decrease in agonist-evoked current mediated by mutant subunits compared to wild-type channels. When GluA2 subunits are co-expressed with GluA1, most GRIA2 mutations cause a decreased current amplitude and some also affect voltage rectification. Our results show that de-novo variants in GRIA2 can cause neurodevelopmental disorders, complementing evidence that other genetic causes of ID, ASD and DEE also disrupt glutamatergic synaptic transmission. Supported by the Wellcome Trust (WT093205MA and WT104033AIA), Medical Research Council (H.H. and D.M.K.), European Community’s Seventh Framework Programme (FP7/2007‐2013, under grant agreement No. 2012‐305121 to H.H.), Muscular Dystrophy Association (MDA), Muscular Dystrophy UK, The MSA Trust, Ataxia UK, The Sparkes Children’s Medical Research Charity, The Great Ormond Street Hospital Charity, Rosetrees Trust, Brain Research UK, The UK HSP Society, The European Union’s Horizon 2020 research and innovation programme Solve-RD project (No 779257), The Pakistan Council (Scholarship to HT), The National Natural Science Foundation of China (31671114, 81871079, 81330027, and 81525007 to H.G. and K.X.), the US National Institutes of Health (NIH grant R01MH101221 to E.E.E), the National Institute for Health Research (NIHR) University College London Hospitals (UCLH) and the Biomedical Research Centre (BRC)
9. S-acylation of ATGL is required for lipid droplet homoeostasis in hepatocytes.
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Zheng Y, Chen J, Macwan V, Dixon CL, Li X, Liu S, Yu Y, Xu P, Sun Q, Hu Q, Liu W, Raught B, Fairn GD, and Neculai D
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- Animals, Mice, Acylation, Humans, Lipid Metabolism, Lipid Droplets metabolism, Hepatocytes metabolism, Acyltransferases metabolism, Acyltransferases genetics, Homeostasis, Lipase metabolism, Lipase genetics, Lipolysis
- Abstract
Lipid droplets (LDs) are organelles specialized in the storage of neutral lipids, cholesterol esters and triglycerides, thereby protecting cells from the toxicity of excess lipids while allowing for the mobilization of lipids in times of nutrient deprivation. Defects in LD function are associated with many diseases. S-acylation mediated by zDHHC acyltransferases modifies thousands of proteins, yet the physiological impact of this post-translational modification on individual proteins is poorly understood. Here, we show that zDHHC11 regulates LD catabolism by modifying adipose triacylglyceride lipase (ATGL), the rate-limiting enzyme of lipolysis, both in hepatocyte cultures and in mice. zDHHC11 S-acylates ATGL at cysteine 15. Preventing the S-acylation of ATGL renders it catalytically inactive despite proper localization. Overexpression of zDHHC11 reduces LD size, whereas its elimination enlarges LDs. Mutating ATGL cysteine 15 phenocopies zDHHC11 loss, causing LD accumulation, defective lipolysis and lipophagy. Our results reveal S-acylation as a mode of regulation of ATGL function and LD homoeostasis. Modulating this pathway may offer therapeutic potential for treating diseases linked to defective lipolysis, such as fatty liver disease., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)
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- 2024
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10. Attenuating ABHD17 enhances S- palmitoylation, membrane localization and signal transduction of NOD2 and Crohn's disease-associated variants.
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Dixon CL, Martin NR, Niphakis MJ, Cravatt BF, and Fairn GD
- Abstract
NOD2 is an intracellular innate immune receptor that senses bacterial peptidoglycans. Although soluble in the cytosol, a portion of the protein is associated with the plasma membrane and endosomal compartments for microbial surveillance. Palmitoylation of NOD2 by zDHHC5 promotes its membrane recruitment to drive proinflammatory and antimicrobial responses to pathogenic invasion. A depalmitoylation step by an unknown protein, thioesterase, releases NOD2 from membranes into the cytosol, where the protein can then enter a new cycle of palmitoylation-depalmitoylation. Here, we identify α/β -hydrolase domain-containing protein 17 isoforms (ABHD17A, 17B, 17C) as the thioesterases responsible for depalmitoylation of NOD2. Inhibiting ABHD17 increased the plasmalemmal localization of both wild-type NOD2 and a subset of hypo-palmitoylated Crohn's disease-associated variants, resulting in increased NF-κB activation and production of pro-inflammatory cytokines in epithelial cells. These results suggest that targeted inhibition of ABHD17 may rescue some Crohn's disease-associated NOD2 variants.
- Published
- 2023
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11. Multifaceted roles and regulation of nucleotide-binding oligomerization domain containing proteins.
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Dixon CL, Wu A, and Fairn GD
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- Humans, Nod2 Signaling Adaptor Protein metabolism, Inflammation, Nucleotides metabolism, Nod Signaling Adaptor Proteins metabolism, Nod1 Signaling Adaptor Protein
- Abstract
Nucleotide-binding oligomerization domain-containing proteins, NOD1 and NOD2, are cytosolic receptors that recognize dipeptides and tripeptides derived from the bacterial cell wall component peptidoglycan (PGN). During the past two decades, studies have revealed several roles for NODs beyond detecting PGN fragments, including activation of an innate immune anti-viral response, NOD-mediated autophagy, and ER stress induced inflammation. Recent studies have also clarified the dynamic regulation of NODs at cellular membranes to generate specific and balanced immune responses. This review will describe how NOD1 and NOD2 detect microbes and cellular stress and detail the molecular mechanisms that regulate activation and signaling while highlighting new evidence and the impact on inflammatory disease pathogenesis., Competing Interests: The authors declare that the manuscript was written in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Dixon, Wu and Fairn.)
- Published
- 2023
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12. Differences in cord blood extracellular vesicle cargo in preterm and term births.
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Menon R, Dixon CL, Cayne S, Radnaa E, Salomon C, and Sheller-Miller S
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- Chromatography, Liquid, Cross-Sectional Studies, Female, Fetal Blood metabolism, Humans, Infant, Newborn, Pregnancy, Proteomics, Retrospective Studies, Tandem Mass Spectrometry, Term Birth, Exosomes metabolism, Extracellular Vesicles metabolism, Premature Birth metabolism
- Abstract
Objective: This study determined the cord plasma-derived extracellular vesicle (exosomes; 30-160 nm particles) proteomic profile in patients who had spontaneous preterm birth (PTB) or preterm premature rupture of membranes (pPROM), compared to those who delivered at term regardless of labor status., Methods: This is a cross-sectional analysis of a retrospective cohort that quantified and determined the proteomic cargo content of exosomes present in cord blood plasma samples in PTB or pPROM, and normal term in labor (TL) or term not in labor (TNIL) pregnancies. Exosomes were isolated by differential centrifugation followed by size exclusion chromatography. Exosomes were characterized by nanoparticle tracking analysis (quantity and size) and markers (dot blots for exosome markers). The exosomal proteomic profile was identified by liquid chromatography-mass spectrometry (LC-MS/MS). Ingenuity pathway analysis determined canonical pathways and biofunctions associated with dysregulated proteins., Results: Cord plasma exosomes have similar quantity and exhibit both tetraspanin and ESCRT protein markers specific of exosomes regardless of the conditions. Proteomics analysis exhibited several similar markers as well as very unique markers in exosomes from each condition; however, bioinformatics analysis revealed a generalized and non-specific inflammatory condition represented in exosomes from different condition that is not indicative of any specific underlying biological functions indicative of an underlying pathology., Conclusions: Compared to maternal plasma and amniotic fluid exosomes, the value of cord plasma derived exosomes is limited. Quantity, character, and proteomic cargo contents in exosomes or the pathways and functions represented by differentially expressed proteins do not distinguish specific conditions regarding normal and abnormal parturition. The value of cord plasma exosome proteomic cargo has limited value as an indicator of an underlying physiology or as a biomarker of fetal well-being., (© 2022 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)
- Published
- 2022
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13. Examining the Underappreciated Role of S -Acylated Proteins as Critical Regulators of Phagocytosis and Phagosome Maturation in Macrophages.
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Dixon CL, Mekhail K, and Fairn GD
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- Acylation, Animals, Humans, Macrophages metabolism, Phagosomes metabolism, Proteome metabolism, Proteomics methods, Signal Transduction immunology, Macrophages immunology, Phagocytosis immunology, Phagosomes immunology, Protein Processing, Post-Translational, Proteome immunology
- Abstract
Phagocytosis is a receptor-mediated process used by cells to engulf a wide variety of particulates, including microorganisms and apoptotic cells. Many of the proteins involved in this highly orchestrated process are post-translationally modified with lipids as a means of regulating signal transduction, membrane remodeling, phagosome maturation and other immunomodulatory functions of phagocytes. S -acylation, generally referred to as S -palmitoylation, is the post-translational attachment of fatty acids to a cysteine residue exposed topologically to the cytosol. This modification is reversible due to the intrinsically labile thioester bond between the lipid and sulfur atom of cysteine, and thus lends itself to a variety of regulatory scenarios. Here we present an overview of a growing number of S -acylated proteins known to regulate phagocytosis and phagosome biology in macrophages., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Dixon, Mekhail and Fairn.)
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- 2021
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14. S-palmitoylation of NOD2 controls its localization to the plasma membrane.
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Dixon CL and Fairn GD
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- Cell Membrane chemistry, HCT116 Cells, Humans, Models, Molecular, Nod2 Signaling Adaptor Protein chemistry, Protein S chemistry, Cell Membrane metabolism, Nod2 Signaling Adaptor Protein metabolism, Protein S metabolism
- Published
- 2021
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15. Fetal membrane extracellular vesicle profiling reveals distinct pathways induced by infection and inflammation in vitro.
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Monsivais LA, Sheller-Miller S, Russell W, Saade GR, Dixon CL, Urrabaz-Garza R, and Menon R
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- Adolescent, Adult, Amnion cytology, Chorion cytology, Epithelial Cells, Female, Humans, Mesoderm cytology, Pregnancy, Young Adult, Exosomes immunology, Extraembryonic Membranes immunology, Inflammation immunology, Pregnancy Complications, Infectious immunology, Proteome immunology
- Abstract
Problem: Fetal inflammatory signals can be propagated to maternal tissues to initiate labor via exosomes (extracellular vesicles; 30-150 nm). We tested the hypothesis that fetal membrane cells exposed to infectious and inflammatory mediators associated with preterm birth (PTB) produce exosomes with distinct protein cargo contents indicative of underlying pathobiology., Methods of Study: Fetal membrane explants (FM) as well as primary amnion epithelial (AEC) and mesenchymal cells (AMC), and chorion cells (CC) from term deliveries were maintained in normal conditions (control) or exposed to LPS 100 ng/mL or TNF-α 50 ng/mL for 48 hours. Exosomes were isolated from media by differential centrifugation and size exclusion chromatography and characterized using cryo-electron microscopy (morphology), nanoparticle tracking analysis (size and quantity), Western blot (markers), and mass spectroscopy (cargo proteins). Ingenuity pathway analysis (IPA) determined pathways indicated by differentially expressed proteins., Results: Irrespective of source or treatment, exosomes were spherical, had similar size, quantities, and markers (ALIX, CD63, and CD81). However, exosome cargo proteins were different between FM and individual fetal membrane cell-derived exosomes in response to treatments. Several common proteins were seen; however, there are several unique proteins expressed by exosomes from different cell types in response to distinct stimuli indicative of unique pathways and physiological functions in cells., Conclusions: We demonstrate collective tissue and independent cell response reflected in exosomes in response to infectious and inflammatory stimuli. These cargoes determined underlying physiology and their potential in enhancing inflammation in a paracrine fashion., (© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)
- Published
- 2020
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16. The Effect of Distraction during Labor Induction on Timing of Analgesia Request: A Randomized Clinical Trial.
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Dixon CL, Monsivais L, Chamseddine P, Olson G, Pacheco LD, Saade GR, and Costantine MM
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- Adult, Analgesia, Epidural, Analgesics, Opioid therapeutic use, Female, Humans, Kaplan-Meier Estimate, Pain drug therapy, Pain etiology, Pain Measurement, Patient Satisfaction, Pregnancy, Statistics, Nonparametric, Time Factors, Young Adult, Analgesia, Obstetrical, Labor, Induced adverse effects, Music, Pain prevention & control, Video Games
- Abstract
Objective: To assess whether distraction using music and/or video games influences timing of analgesia request and improves pain outcomes in women undergoing labor induction., Study Design: A total of 219 pregnant women with singleton gestation undergoing labor induction with a Foley bulb (FB) at term were randomized to distraction with music and video games via iPod ( n = 109) or no iPod ( n = 110). The primary outcome was the time from FB placement to request for pain medication. Secondary outcomes included number of patients requesting pain medication within 6 and 12 hours, type of pain medication received, pain visual analog scale scores, and patient satisfaction. Mann-Whitney's, chi-square, Kaplan-Meier's curves, and Pearson's product moment correlation were used for statistical analysis (significance: p < 0.05)., Results: Baseline characteristics were similar between the two groups. There was no difference in the time from FB placement until pain medication request between the groups. There were no significant differences in secondary outcomes. Increased per cent time of iPod use correlated with a longer time until pain medication request ( R
2 = 0.22, p = 0.03)., Conclusion: We were not able to show that distraction using music and video games delays timing of analgesia request or improve pain outcomes in pregnant women undergoing mechanical labor induction at term., Competing Interests: None declared., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)- Published
- 2019
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17. Glycine receptor autoantibodies disrupt inhibitory neurotransmission.
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Crisp SJ, Dixon CL, Jacobson L, Chabrol E, Irani SR, Leite MI, Leschziner G, Slaght SJ, Vincent A, and Kullmann DM
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- Aged, Animals, Cells, Cultured, Excitatory Postsynaptic Potentials drug effects, Female, Humans, Immunoglobulin Fab Fragments immunology, Immunoglobulin G genetics, Male, Middle Aged, Motor Neurons drug effects, Patch-Clamp Techniques, Pregnancy, Rats, Rats, Sprague-Dawley, Spinal Cord cytology, Stiff-Person Syndrome immunology, Synapses drug effects, Autoantibodies immunology, Autoantibodies pharmacology, Neural Inhibition drug effects, Neural Inhibition immunology, Receptors, Glycine antagonists & inhibitors, Synaptic Transmission immunology
- Abstract
Chloride-permeable glycine receptors have an important role in fast inhibitory neurotransmission in the spinal cord and brainstem. Human immunoglobulin G (IgG) autoantibodies to glycine receptors are found in a substantial proportion of patients with progressive encephalomyelitis with rigidity and myoclonus, and less frequently in other variants of stiff person syndrome. Demonstrating a pathogenic role of glycine receptor autoantibodies would help justify the use of immunomodulatory therapies and provide insight into the mechanisms involved. Here, purified IgGs from four patients with progressive encephalomyelitis with rigidity and myoclonus or stiff person syndrome, and glycine receptor autoantibodies, were observed to disrupt profoundly glycinergic neurotransmission. In whole-cell patch clamp recordings from cultured rat spinal motor neurons, glycinergic synaptic currents were almost completely abolished following incubation in patient IgGs. Most human autoantibodies targeting other CNS neurotransmitter receptors, such as N-methyl-d-aspartate (NMDA) receptors, affect whole cell currents only after several hours incubation and this effect has been shown to be the result of antibody-mediated crosslinking and internalization of receptors. By contrast, we observed substantial reductions in glycinergic currents with all four patient IgG preparations with 15 min of exposure to patient IgGs. Moreover, monovalent Fab fragments generated from the purified IgG of three of four patients also profoundly reduced glycinergic currents compared with control Fab-IgG. We conclude that human glycine receptor autoantibodies disrupt glycinergic neurotransmission, and also suggest that the pathogenic mechanisms include direct antagonistic actions on glycine receptors., (© The Author(s) (2019). Published by Oxford University Press on behalf of the Guarantors of Brain.)
- Published
- 2019
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18. AMPA receptor GluA2 subunit defects are a cause of neurodevelopmental disorders.
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Salpietro V, Dixon CL, Guo H, Bello OD, Vandrovcova J, Efthymiou S, Maroofian R, Heimer G, Burglen L, Valence S, Torti E, Hacke M, Rankin J, Tariq H, Colin E, Procaccio V, Striano P, Mankad K, Lieb A, Chen S, Pisani L, Bettencourt C, Männikkö R, Manole A, Brusco A, Grosso E, Ferrero GB, Armstrong-Moron J, Gueden S, Bar-Yosef O, Tzadok M, Monaghan KG, Santiago-Sim T, Person RE, Cho MT, Willaert R, Yoo Y, Chae JH, Quan Y, Wu H, Wang T, Bernier RA, Xia K, Blesson A, Jain M, Motazacker MM, Jaeger B, Schneider AL, Boysen K, Muir AM, Myers CT, Gavrilova RH, Gunderson L, Schultz-Rogers L, Klee EW, Dyment D, Osmond M, Parellada M, Llorente C, Gonzalez-Peñas J, Carracedo A, Van Haeringen A, Ruivenkamp C, Nava C, Heron D, Nardello R, Iacomino M, Minetti C, Skabar A, Fabretto A, Raspall-Chaure M, Chez M, Tsai A, Fassi E, Shinawi M, Constantino JN, De Zorzi R, Fortuna S, Kok F, Keren B, Bonneau D, Choi M, Benzeev B, Zara F, Mefford HC, Scheffer IE, Clayton-Smith J, Macaya A, Rothman JE, Eichler EE, Kullmann DM, and Houlden H
- Subjects
- Adolescent, Adult, Brain diagnostic imaging, Child, Child, Preschool, Cohort Studies, Female, Heterozygote, Humans, Infant, Loss of Function Mutation, Magnetic Resonance Imaging, Male, Neurodevelopmental Disorders diagnostic imaging, Young Adult, Intellectual Disability genetics, Neurodevelopmental Disorders genetics, Receptors, AMPA genetics
- Abstract
AMPA receptors (AMPARs) are tetrameric ligand-gated channels made up of combinations of GluA1-4 subunits encoded by GRIA1-4 genes. GluA2 has an especially important role because, following post-transcriptional editing at the Q607 site, it renders heteromultimeric AMPARs Ca
2+ -impermeable, with a linear relationship between current and trans-membrane voltage. Here, we report heterozygous de novo GRIA2 mutations in 28 unrelated patients with intellectual disability (ID) and neurodevelopmental abnormalities including autism spectrum disorder (ASD), Rett syndrome-like features, and seizures or developmental epileptic encephalopathy (DEE). In functional expression studies, mutations lead to a decrease in agonist-evoked current mediated by mutant subunits compared to wild-type channels. When GluA2 subunits are co-expressed with GluA1, most GRIA2 mutations cause a decreased current amplitude and some also affect voltage rectification. Our results show that de-novo variants in GRIA2 can cause neurodevelopmental disorders, complementing evidence that other genetic causes of ID, ASD and DEE also disrupt glutamatergic synaptic transmission.- Published
- 2019
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19. Quantitative Proteomics by SWATH-MS of Maternal Plasma Exosomes Determine Pathways Associated With Term and Preterm Birth.
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Menon R, Dixon CL, Sheller-Miller S, Fortunato SJ, Saade GR, Palma C, Lai A, Guanzon D, and Salomon C
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- Adult, Case-Control Studies, Female, Humans, Mass Spectrometry, Pregnancy, Young Adult, Exosomes metabolism, Premature Birth blood, Proteome, Term Birth blood
- Abstract
Exosomes are membrane-bound nanovesicles that transport molecular signals between cells. This study determined changes in maternal plasma exosome proteomics contents in term and preterm births. Maternal plasma (MP) samples were collected from group 1: term not in labor (TNIL, n = 13); group 2: term in labor (TL, n = 11); group 3: preterm premature rupture of membranes (pPROM, n = 8); and group 4: preterm birth (PTB, n = 13). Exosomes isolated from plasma by differential density centrifugation followed by size exclusion chromatography were characterized by morphology (electron microscopy), quantity and size (nanoparticle tracking analysis), and markers (western blot). A quantitative, information-independent acquisition [sequential windowed acquisition of all theoretical mass spectra (SWATH-MS)] approach was used to determine the protein profile in exosomes. Ingenuity Pathway Analysis determined pathways associated with the protein profile identified in exosomes. MP exosomes were spherical, had a mean diameter of 120 nm, and were positive for exosomal proteins CD63 and TSG101 irrespective of pregnancy status. No distinct changes in exosome quantities were seen in maternal circulation across the groups. SWATH-MS identified 72 statistically significant proteins across the groups studied. Bioinformatics analysis showed the proteins within the exosomes in TNIL, TL, pPROM, and PTB target pathways mainly associated with inflammatory and metabolic signals. Exosomal data suggest that homeostatic imbalances, specifically inflammatory and endocrine signaling, might disrupt pregnancy maintenance resulting in labor-related changes both at term and preterm. Reflection of physiologic changes in exosomes is suggestive of its usefulness as biomarkers and cellular function indicators., (Copyright © 2019 Endocrine Society.)
- Published
- 2019
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20. Loss of Frrs1l disrupts synaptic AMPA receptor function, and results in neurodevelopmental, motor, cognitive and electrographical abnormalities.
- Author
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Stewart M, Lau P, Banks G, Bains RS, Castroflorio E, Oliver PL, Dixon CL, Kruer MC, Kullmann DM, Acevedo-Arozena A, Wells SE, Corrochano S, and Nolan PM
- Subjects
- Animals, Animals, Newborn, Body Size, Brain metabolism, Brain pathology, Cognition Disorders pathology, Cytoplasm metabolism, Glycosylation, Membrane Proteins genetics, Mice, Inbred C57BL, Nerve Tissue Proteins genetics, Nervous System physiopathology, Sleep, Survival Analysis, Cognition, Electrophysiological Phenomena, Membrane Proteins metabolism, Motor Activity, Nerve Tissue Proteins metabolism, Nervous System growth & development, Nervous System pathology, Receptors, AMPA metabolism, Synapses metabolism
- Abstract
Loss-of-function mutations in a human AMPA receptor-associated protein, ferric chelate reductase 1-like (FRRS1L), are associated with a devastating neurological condition incorporating choreoathetosis, cognitive deficits and epileptic encephalopathies. Furthermore, evidence from overexpression and ex vivo studies has implicated FRRS1L in AMPA receptor biogenesis, suggesting that changes in glutamatergic signalling might underlie the disorder. Here, we investigated the neurological and neurobehavioural correlates of the disorder using a mouse Frrs1l null mutant. The study revealed several neurological defects that mirrored those seen in human patients. We established that mice lacking Frrs1l suffered from a broad spectrum of early-onset motor deficits with no progressive, age-related deterioration. Moreover, Frrs1l
-/- mice were hyperactive, irrespective of test environment, exhibited working memory deficits and displayed significant sleep fragmentation. Longitudinal electroencephalographic (EEG) recordings also revealed abnormal EEG results in Frrs1l-/- mice. Parallel investigations into disease aetiology identified a specific deficiency in AMPA receptor levels in the brain of Frrs1l-/- mice, while the general levels of several other synaptic components remained unchanged, with no obvious alterations in the number of synapses. Furthermore, we established that Frrsl1 deletion results in an increased proportion of immature AMPA receptors, indicated by incomplete glycosylation of GLUA2 (also known as GRIA2) and GLUA4 (also known as GRIA4) AMPA receptor proteins. This incomplete maturation leads to cytoplasmic retention and a reduction of those specific AMPA receptor levels in the postsynaptic membrane. Overall, this study determines, for the first time in vivo , how loss of FRRS1L function can affect glutamatergic signalling, and provides mechanistic insight into the development and progression of a human hyperkinetic disorder.This article has an associated First Person interview with the first author of the paper., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2019. Published by The Company of Biologists Ltd.)- Published
- 2019
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21. Oxidative stress-induced TGF-beta/TAB1-mediated p38MAPK activation in human amnion epithelial cells.
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Richardson L, Dixon CL, Aguilera-Aguirre L, and Menon R
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- Adult, Enzyme Activation, Epithelial Cells drug effects, Female, Humans, MAP Kinase Kinase Kinase 5 metabolism, MAP Kinase Kinase Kinases metabolism, Phosphorylation, Pregnancy, RNA, Small Interfering pharmacology, Smoke, Nicotiana chemistry, Adaptor Proteins, Signal Transducing metabolism, Amnion cytology, Epithelial Cells metabolism, Oxidative Stress, Transforming Growth Factor beta metabolism, p38 Mitogen-Activated Protein Kinases metabolism
- Abstract
Term and preterm parturition are associated with oxidative stress (OS)-induced p38 mitogen-activated protein kinase (p38MAPK)-mediated fetal tissue (amniochorion) senescence. p38MAPK activation is a complex cell- and stimulant-dependent process. Two independent pathways of OS-induced p38MAPK activation were investigated in amnion epithelial cells (AECs) in response to cigarette smoke extract (CSE: a validated OS inducer in fetal cells): (1) the OS-mediated oxidation of apoptosis signal-regulating kinase (ASK)-1 bound Thioredoxin (Trx[SH]2) dissociates this complex, creating free and activated ASK1-signalosome and (2) transforming growth factor-mediated activation of (TGF)-beta-activated kinase (TAK)1 and TGF-beta-activated kinase 1-binding protein (TAB)1. AECs isolated from normal term, not-in-labor fetal membranes increased p38MAPK in response to CSE and downregulated it in response to antioxidant N-acetylcysteine. In AECs, both Trx and ASK1 were localized; however, they remained dissociated and not complexed, regardless of conditions. Silencing either ASK1 or its downstream effectors (MKK3/6) did not affect OS-induced p38MAPK activation. Conversely, OS increased TGF-beta's release from AECs and increased phosphorylation of both p38MAPK and TAB1. Silencing of TAB1, but not TAK1, prevented p38MAPK activation, which is indicative of TAB1-mediated autophosphorylation of p38MAPK, an activation mechanism seldom seen. OS-induced p38MAPK activation in AECs is ASK1-Trx signalosome-independent and is mediated by the TGF-beta pathway. This knowledge will help to design strategies to reduce p38MAPK activation-associated pregnancy risks.
- Published
- 2018
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22. Past and Present: A Review of Antenatal Corticosteroids and Recommendations for Late Preterm Birth Steroids.
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Dixon CL, Too G, Saade GR, and Gyamfi-Bannerman C
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- Female, Humans, Infant, Newborn, Pregnancy, Premature Birth prevention & control, Risk Assessment, Adrenal Cortex Hormones pharmacology, Prenatal Care methods, Prenatal Care trends, Prenatal Exposure Delayed Effects chemically induced, Prenatal Exposure Delayed Effects diagnosis
- Abstract
Since 1972, the beneficial neonatal effects of antenatal corticosteroids (ACSs) have been repeatedly demonstrated in pregnancies at risk of preterm birth before 34 weeks' gestation. While ACS utilization before 34 weeks has been high since the 1990s, knowledge gaps regarding the risks and benefits of ACS continue to exist. Recent evidence has been published regarding the benefit of ACS in the late preterm period. This review addresses the evidence and knowledge gaps for ACS use before and after 34 weeks' gestation. We also provide recommendations for ACS use in the late preterm period., Competing Interests: None., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)
- Published
- 2018
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23. Biochemical autoregulatory gene therapy for focal epilepsy.
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Lieb A, Qiu Y, Dixon CL, Heller JP, Walker MC, Schorge S, and Kullmann DM
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- Animals, Brain pathology, Brain physiopathology, Cell Line, Tumor, Disease Models, Animal, Glutamic Acid metabolism, Humans, Mice, Rats, Epilepsies, Partial genetics, Epilepsies, Partial therapy, Genetic Therapy, Homeostasis
- Abstract
Despite the introduction of more than one dozen new antiepileptic drugs in the past 20 years, approximately one-third of people who develop epilepsy continue to have seizures on mono- or polytherapy
1 . Viral-vector-mediated gene transfer offers the opportunity to design a rational treatment that builds on mechanistic understanding of seizure generation and that can be targeted to specific neuronal populations in epileptogenic foci2 . Several such strategies have shown encouraging results in different animal models, although clinical translation is limited by possible effects on circuits underlying cognitive, mnemonic, sensory or motor function. Here, we describe an autoregulatory antiepileptic gene therapy, which relies on neuronal inhibition in response to elevations in extracellular glutamate. It is effective in a rodent model of focal epilepsy and is well tolerated, thus lowering the barrier to clinical translation.- Published
- 2018
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24. Amniotic Fluid Exosome Proteomic Profile Exhibits Unique Pathways of Term and Preterm Labor.
- Author
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Dixon CL, Sheller-Miller S, Saade GR, Fortunato SJ, Lai A, Palma C, Guanzon D, Salomon C, and Menon R
- Subjects
- Adult, Case-Control Studies, Chromatography, Liquid, Cohort Studies, Cross-Sectional Studies, Female, Humans, Labor, Obstetric metabolism, Nanoparticles, Pregnancy, Proteomics, Retrospective Studies, Tandem Mass Spectrometry, Young Adult, Amniotic Fluid metabolism, Exosomes metabolism, Fetal Membranes, Premature Rupture metabolism, Obstetric Labor, Premature metabolism, Premature Birth metabolism, Proteome metabolism
- Abstract
Our objective was to determine the amniotic fluid-derived exosomal proteomic profile in patients who had spontaneous preterm birth (PTB) or preterm premature rupture of membranes (pPROM) compared with those who delivered at term. A cross-sectional study of a retrospective cohort was used to quantify and determine the protein content of exosomes present in amniotic fluid, in PTB or pPROM, and normal term labor (TL) or term not in labor (TNIL) pregnancies. Exosomes were isolated by differential centrifugation and quantified using nanocrystals (Qdot) coupled to CD63 and placental alkaline phosphatase (PLAP) by fluorescence nanoparticle tracking analysis. The exosomal proteomic profile was identified by liquid chromatography-tandem mass spectrometry, and a small ion library was constructed to quantify the proteomic data by Sequential Window Acquisition of All Theoretical analysis. Ingenuity Pathway Analysis determined canonical pathways and biofunctions associated with dysregulated proteins. Amniotic fluid exosomes have similar shape and quantity regardless of the conditions; however, the PLAP/CD63 ratios for TL, PTB, and pPROM were significantly higher (∼3.8-, ∼4.4-, and ∼3.5-fold, respectively) compared with TNIL. The PLAP/CD63 ratio was also significantly higher (∼1.3-fold) in PTB compared with pPROM. Biological functions primarily indicated nonspecific inflammatory response regardless of condition, but unique profiles were also identified in cases (PTB and pPROM) compared with term. Amniotic fluid exosomes provide information specific to normal and abnormal parturition. Inflammatory marker enrichment and its uniqueness in term and preterm pregnancies support the value of exosomes in determining underlying physiology associated with term and preterm parturition.
- Published
- 2018
- Full Text
- View/download PDF
25. SAHA (Vorinostat) Corrects Inhibitory Synaptic Deficits Caused by Missense Epilepsy Mutations to the GABA A Receptor γ2 Subunit.
- Author
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Durisic N, Keramidas A, Dixon CL, and Lynch JW
- Abstract
The GABA
A receptor (GABAA R) α1 subunit A295D epilepsy mutation reduces the surface expression of α1A295D β2γ2 GABAA Rs via ER-associated protein degradation. Suberanilohydroxamic acid (SAHA, also known as Vorinostat) was recently shown to correct the misfolding of α1A295D subunits and thereby enhance the functional surface expression of α1A295D β2γ2 GABAA Rs. Here we investigated whether SAHA can also restore the surface expression of γ2 GABAA R subunits that incorporate epilepsy mutations (N40S, R43Q, P44S, R138G) known to reduce surface expression via ER-associated protein degradation. As a control, we also investigated the γ2K289M epilepsy mutation that impairs gating without reducing surface expression. Effects of mutations were evaluated on inhibitory postsynaptic currents (IPSCs) mediated by the major synaptic α1β2γ2 GABAA R isoform. Recordings were performed in neuron-HEK293 cell artificial synapses to minimise contamination by GABAA Rs of undefined subunit composition. Transfection with α1β2γ2N40S , α1β2γ2R43Q , α1β2γ2P44S and α1β2γ2R138G subunits produced IPSCs with decay times slower than those of unmutated α1β2γ2 GABAA Rs due to the low expression of mutant γ2 subunits and the correspondingly high expression of slow-decaying α1β2 GABAA Rs. SAHA pre-treatment significantly accelerated the decay time constants of IPSCs consistent with the upregulation of mutant γ2 subunit expression. This increase in surface expression was confirmed by immunohistochemistry. SAHA had no effect on either the IPSC kinetics or surface expression levels of α1β2γ2K289M GABAA Rs, confirming its specificity for ER-retained mutant γ2 subunits. We also found that α1β2γ2K289M GABAA Rs and SAHA-treated α1β2γ2R43Q , α1β2γ2P44S and α1β2γ2R138G GABAA Rs all mediated IPSCs that decayed at significantly faster rates than wild type receptors as temperature was increased from 22 to 40°C. This may help explain why these mutations cause febrile seizures (FS). Given that SAHA is approved by therapeutic regulatory agencies for human use, we propose that it may be worth investigating as a treatment for epilepsies caused by the N40S, R43Q, P44S and R138G mutations. Although SAHA has already been proposed as a therapeutic for patients harbouring the α1A295D epilepsy mutation, the present study extends its potential utility to a new subunit and four new mutations.- Published
- 2018
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- View/download PDF
26. A distinct mechanism of senescence activation in amnion epithelial cells by infection, inflammation, and oxidative stress.
- Author
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Dixon CL, Richardson L, Sheller-Miller S, Saade G, and Menon R
- Subjects
- Cells, Cultured, Cellular Senescence, Female, Humans, Imidazoles pharmacology, Interleukin-6 metabolism, Lipopolysaccharides immunology, Oxidative Stress, Pregnancy, Primary Cell Culture, Pyridines pharmacology, Tumor Necrosis Factor-alpha immunology, p38 Mitogen-Activated Protein Kinases metabolism, Amnion pathology, Epithelial Cells immunology, Extraembryonic Membranes pathology, Infections immunology, Inflammation immunology, Premature Birth immunology
- Abstract
Problem: We investigated p38MAPK activation-induced fetal membrane cell senescence in response to inflammation (tumour necrosis factor-alpha [TNF-α]) and infection (lipopolysaccharide [LPS]), factors associated with spontaneous preterm birth., Method of Study: Primary amnion epithelial cells (AECs) were exposed to TNF-α, 50 ng/mL and LPS, 100 ng/mL. Cigarette smoke extract (CSE), a known OS inducer, was used as positive control. AECs were cotreated with the antioxidant N-acetyl cysteine (NAC) and p38MAPK inhibitor SB203580 to determine the effect of OS and p38MAPK. Western blot analysis was performed for active (Phospho-p38MAPK) and total p38MAPK. Senescence was determined by flow cytometry, and culture supernatants were tested for IL-6 using ELISA., Results: TNF-α, but not LPS, increased p38MAPK activation compared to untreated cells (P = .01). The number of senescent cells and senescence-associated IL-6 was higher in both TNF-α and LPS-treated cells compared to control (P = .001, P = .01, respectively). Antioxidant NAC inhibited p38MAPK activation by TNF-α. p38MAPK inhibitor SB203580 reduced the development of senescence and IL-6 by TNF-α and LPS. CSE treatment validated our current data., Conclusion: TNF-α caused OS-mediated p38MAPK induction, senescence, and IL-6 increase from AECs. LPS also induced senescence and IL-6 increase. Inflammatory and infectious factors may cause premature fetal cell senescence contributing to preterm birth pathophysiology., (© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)
- Published
- 2018
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- View/download PDF
27. Placental Exosomes During Gestation: Liquid Biopsies Carrying Signals for the Regulation of Human Parturition.
- Author
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Salomon C, Nuzhat Z, Dixon CL, and Menon R
- Subjects
- Female, Gestational Age, Humans, Liquid Biopsy, Pregnancy, Exosomes metabolism, Parturition metabolism, Placenta metabolism
- Abstract
Parturition is defined as the action or process of giving birth to offspring. Normal term human parturition ensues following the maturation of fetal organ systems typically between 37 and 40 weeks of gestation. Our conventional understanding of how parturition initiation is signaled revolves around feto-maternal immune and endocrine changes occurring in the intrauterine cavity. These changes in turn correlate with the sequence of fetal growth and development. These important physiological changes also result in homeostatic imbalances which result in heightened inflammatory signaling. This disrupts the maintenance of pregnancy, thus leading to laborrelated changes. However, the precise mechanisms of the signaling cascades that lead to the initiation of parturition remain unclear, although exosomes may be a mediator of this process. Exosomes are a subtype of extracellular vesicles characterised by their endocytic origin. This involves the trafficking of intraluminal vesicles into multivesicular bodies (MVB) and then exocytosis via the plasmatic membranes. Exosomes are highly stable nanovesicles that are released by a wide range of cells and organs including the human placenta and fetal membranes. Interestingly, exosomes from placental origin have been uncovered in maternal circulation across gestation. In addition, their concentration is higher in pregnancies with complications such as gestational diabetes and preeclampsia. In normal gestation, the concentration of placental exosomes in maternal circulation correlates with placental weight at third trimester. The role of placental exosomes across gestation has not been fully elucidated, although recent studies suggest that placental exosomes are involved in maternal-fetal inmmuno-tolerance, maternal systemic inflammation and nutrient transport. The content of exosomes is of particular importance, encompassing a large range of molecules such as mRNA, miRNAs, DNA, lipids, cell-surface receptors, and protein mediators. These can in turn interact with either adjacent or distal cells to reprogram their phenotype and regulate their function. Many of the pro-parturition proinflammatory mediators reach maternal compartments from the fetal side via circulation, but major impediments remain, such as degradation at various levels and limited halflife in circulation. Recent findings suggest that a more effective mode of communication and signal transport is through exosomes, where signals are protected and will not succumb to degradation. Thus, understanding how exosomes regulate key events throughout pregnancy and parturition will provide an opportunity to understand the mechanisms involved in the maternal and fetal metabolic adaptations during normal and pathological pregnancies. Subsequently, this will assist in identifying those pregnancies at risk of developing complications. This may also allow more appropriate modifications of their clinical management. This review will hence examine the current body of data to summarise our understanding of how signaling pathways lead to the beginning of parturition. In addition, we propose that extracellular vesicles, namely exosomes, may be an integral component of these signaling events by transporting specific signals to prepare the maternal physiology to initiate parturition. Understanding these signals and their mechanisms in normal term pregnancies can provide insight into pathological activation of these signals, which can cause spontaneous preterm parturition. Hence, this review expands on our knowledge of exosomes as professional carriers of fetal signals to instigate human parturition., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.)
- Published
- 2018
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28. Effect of Low-Dose Aspirin on the Time of Onset of Preeclampsia and Time of Delivery.
- Author
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Dixon CL, Marrs C, Costantine MM, Pacheco LD, Saade GR, and Chiossi G
- Subjects
- Adult, Female, Humans, Logistic Models, Multivariate Analysis, Pregnancy, Risk Assessment, Risk Factors, Texas epidemiology, Time Factors, Young Adult, Aspirin administration & dosage, Gestational Age, Pre-Eclampsia epidemiology, Pre-Eclampsia prevention & control
- Abstract
Competing Interests: Conflict of Interest: None.
- Published
- 2017
- Full Text
- View/download PDF
29. γ1-Containing GABA-A Receptors Cluster at Synapses Where they Mediate Slower Synaptic Currents than γ2-Containing GABA-A Receptors.
- Author
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Dixon CL, Sah P, Keramidas A, Lynch JW, and Durisic N
- Abstract
GABA-A receptors (GABA
A Rs) are pentameric ligand-gated ion channels that are assembled mainly from α (α1-6), β (β1-3) and γ (γ1-3) subunits. Although GABAA Rs containing γ2L subunits mediate most of the inhibitory neurotransmission in the brain, significant expression of γ1 subunits is seen in the amygdala, pallidum and substantia nigra. However, the location and function of γ1-containing GABAA Rs in these regions remains unclear. In "artificial" synapses, where the subunit composition of postsynaptic receptors is specifically controlled, γ1 incorporation slows the synaptic current decay rate without affecting channel deactivation, suggesting that γ1-containing receptors are not clustered and therefore activated by diffuse neurotransmitter. However, we show that γ1-containing receptors are localized at neuronal synapses and form clusters in both synaptic and extrasynaptic regions. In addition, they exhibit rapid membrane diffusion and a higher frequency of exchange between synaptic and perisynaptic populations compared to γ2L-containing GABAA Rs. A point mutation in the large intracellular domain and a pharmacological analysis reveal that when a single non-conserved γ2L residue is mutated to its γ1 counterpart (T349L), the synaptic current decay is slowed from γ2L- to γ1-like without changing the clustering or diffusion properties of the receptors. In addition, previous fast perfusion and single channel kinetic experiments revealed no difference in the intrinsic closing rates of γ2L- and γ1-containing receptors when expressed in HEK293 cells. These observations together with Monte Carlo simulations of synaptic function confirm that decreased clustering does not control γ1-containing GABAA R kinetics. Rather, they suggest that γ1- and γ2L-containing receptors exhibit differential synaptic current decay rates due to differential gating dynamics when localized at the synapse.- Published
- 2017
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30. Effect of a "Hard Stop" on Elective Labor Inductions and Cesarean Delivery Rate.
- Author
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Dixon CL, Bhullar A, Romanski P, and Carlan S
- Subjects
- Adult, Female, Gestational Age, Humans, Postpartum Hemorrhage epidemiology, Pregnancy, Retrospective Studies, Cesarean Section statistics & numerical data, Clinical Protocols, Labor, Induced statistics & numerical data
- Abstract
Objective: To evaluate the effect of a "hard stop" on elective induction prior to 39 weeks at a large volume obstetrics hospital., Study Design: From July 1, 2011, to June 30, 2013, there were 27,435 deliveries at our institution. We performed a retrospective chart review of all elective inductions I year before and after the implementation of a 39 week "hard stop" .policy. All women (n=2,574) who underwent elective induction of labor were analyzed., Results: The rate of cesarean delivery was not sta- tistically different between the group evaluated before the "hard stop" and those after (20.6% vs 18%). The rate of postpartum hemorrhage decreased significantly following the policy change (6.2% vs 3.2%, respectively). There were no other clinically important differences in maternal or neonatal outcomes., Conclusion: The implementation of a "hard stop" policy aimed at eliminating elective inductions before 39 weeks did not affect the rate of cesarean birth.
- Published
- 2016
31. Conservative Management and Planned Surgery for Periviable Advanced Extrauterine Abdominal Pregnancy with Favorable Outcome: Report of Two Cases.
- Author
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Harirah HM, Smith JM, Dixon CL, and Hankins GD
- Abstract
Advanced abdominal pregnancy is an extremely rare condition that poses diagnostic and management challenges. A high index of suspicion and careful assessment of the patient's symptoms, supplemented with obstetric ultrasound, and magnetic resonance imaging, are crucial for timely diagnosis and management to prevent life-threatening complications. The presence of periviable fetuses in advanced abdominal pregnancies increases the challenge to achieve a balance between maternal and fetal benefits and risks. Early diagnosis and management decisions via a multidisciplinary approach and planned delivery are of paramount importance to minimize complications and achieve favorable maternal and fetal outcomes. Even in the setting of oligohydramnios and suspected preterm premature rupture of membranes, in-patient conservative management and an individualized planned surgical approach that includes removing or leaving the placenta in place are appropriate for managing the periviable abdominal pregnancy.
- Published
- 2016
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32. Generation of Functional Inhibitory Synapses Incorporating Defined Combinations of GABA(A) or Glycine Receptor Subunits.
- Author
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Dixon CL, Zhang Y, and Lynch JW
- Abstract
Fast inhibitory neurotransmission in the brain is mediated by wide range of GABAA receptor (GABAAR) and glycine receptor (GlyR) isoforms, each with different physiological and pharmacological properties. Because multiple isoforms are expressed simultaneously in most neurons, it is difficult to define the properties of individual isoforms under synaptic stimulation conditions in vivo. Although recombinant expression systems permit the expression of individual isoforms in isolation, they require exogenous agonist application which cannot mimic the dynamic neurotransmitter profile characteristic of native synapses. We describe a neuron-HEK293 cell co-culture technique for generating inhibitory synapses incorporating defined combinations of GABAAR or GlyR subunits. Primary neuronal cultures, prepared from embryonic rat cerebral cortex or spinal cord, are used to provide presynaptic GABAergic and glycinergic terminals, respectively. When the cultures are mature, HEK293 cells expressing the subunits of interest plus neuroligin 2A are plated onto the neurons, which rapidly form synapses onto HEK293 cells. Patch clamp electrophysiology is then used to analyze the physiological and pharmacological properties of the inhibitory postsynaptic currents mediated by the recombinant receptors. The method is suitable for investigating the kinetic properties or the effects of drugs on inhibitory postsynaptic currents mediated by defined GABAAR or GlyR isoforms of interest, the effects of hereditary disease mutations on the formation and function of both types of synapses, and synaptogenesis and synaptic clustering mechanisms. The entire cell preparation procedure takes 2-5 weeks.
- Published
- 2015
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33. Zolpidem and eszopiclone prime α1β2γ2 GABAA receptors for longer duration of activity.
- Author
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Dixon CL, Harrison NL, Lynch JW, and Keramidas A
- Subjects
- Cells, Cultured, Dose-Response Relationship, Drug, HEK293 Cells, Humans, Structure-Activity Relationship, Time Factors, Zolpidem, Eszopiclone pharmacology, Pyridines pharmacology, Receptors, GABA-A metabolism
- Abstract
Background and Purpose: GABAA receptors mediate neuronal inhibition in the brain. They are the primary targets for benzodiazepines, which are widely used to treat neurological disorders including anxiety, epilepsy and insomnia. The mechanism by which benzodiazepines enhance GABAA receptor activity has been extensively studied, but there is little mechanistic information on how non-benzodiazepine drugs that bind to the same site exert their effects. Eszopiclone and zolpidem are two non-benzodiazepine drugs for which no mechanism of action has yet been proposed, despite their clinical importance as sleeping aids. Here we investigate how both drugs enhance the activity of α1β2γ2 GABAA receptors., Experimental Approach: We used rapid ligand application onto macropatches and single-channel kinetic analysis to assess rates of current deactivation. We also studied synaptic currents in primary neuronal cultures and in heterosynapses, whereby native GABAergic nerve terminals form synapses with HEK293 cells expressing α1β2γ2 GABAA receptors. Drug binding and modulation was quantified with the aid of an activation mechanism., Key Results: At the single-channel level, the drugs prolonged the duration of receptor activation, with similar KD values of ∼80 nM. Channel activation was prolonged primarily by increasing the equilibrium constant between two connected shut states that precede channel opening., Conclusions and Implications: As the derived mechanism successfully simulated the effects of eszopiclone and zolpidem on ensemble currents, we propose it as the definitive mechanism accounting for the effects of both drugs. Importantly, eszopiclone and zolpidem enhanced GABAA receptor currents via a mechanism that differs from that proposed for benzodiazepines., (© 2015 The British Pharmacological Society.)
- Published
- 2015
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34. Functional reconstitution of glycinergic synapses incorporating defined glycine receptor subunit combinations.
- Author
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Zhang Y, Dixon CL, Keramidas A, and Lynch JW
- Subjects
- Animals, Cells, Cultured, Embryo, Mammalian, Hexachlorocyclohexane pharmacology, Humans, Inhibitory Postsynaptic Potentials drug effects, Inhibitory Postsynaptic Potentials genetics, Insecticides pharmacology, Mutation genetics, Neurons drug effects, Patch-Clamp Techniques, Protein Subunits genetics, Rats, Receptors, Glycine genetics, Spinal Cord cytology, Synapses drug effects, Transfection, Glycine metabolism, Inhibitory Postsynaptic Potentials physiology, Neurons physiology, Protein Subunits metabolism, Receptors, Glycine metabolism, Synapses physiology
- Abstract
Glycine receptor (GlyR) chloride channels mediate fast inhibitory neurotransmission in the spinal cord and brainstem. Four GlyR subunits (α1-3, β) have been identified in humans, and their differential anatomical distributions underlie a diversity of synaptic isoforms with unique physiological and pharmacological properties. To improve our understanding of these properties, we induced the formation of recombinant synapses between cultured spinal neurons and HEK293 cells expressing GlyR subunits of interest plus the synapse-promoting molecule, neuroligin-2A. In the heterosynapses thus formed, recombinant α1β and α3β GlyRs mediated fast decaying inhibitory postsynaptic currents (IPSCs) whereas α2β GlyRs mediated slow decaying IPSCs. These results are consistent with the fragmentary information available from native synapses and single channel kinetic studies. As β subunit incorporation is considered essential for localizing GlyRs at the synapse, we were surprised that α1-3 homomers supported robust IPSCs with β subunit incorporation accelerating IPSC rise and decay times in α2β and α3β heteromers only. Finally, heterosynapses incorporating α1(D80A)β and α1(A52S)β GlyRs exhibited accelerated IPSC decay rates closely resembling those recorded in native synapses from mutant mice homozygous for these mutations, providing an additional validation of our technique. Glycinergic heterosynapses should prove useful for evaluating the effects of drugs, hereditary disease mutations or other interventions on defined GlyR subunit combinations under realistic synaptic activation conditions.
- Published
- 2015
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- View/download PDF
35. Definition, willingness-to-pay, and ranking of quality attributes of U.S. pork as defined by importers in Asia and Mexico.
- Author
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Murphy RG, Howard ST, Woerner DR, Pendell DL, Dixon CL, Desimone TL, Green MD, Igo JL, Tatum JD, and Belk KE
- Subjects
- Animals, Asia, Mexico, Swine, United States, Commerce, Meat economics, Meat standards
- Abstract
A survey was conducted from November 2009 to April 2010 to determine how importers of pork define 7 predetermined quality categories (food safety, customer service, eating quality, product specification, packaging, visual characteristics, and production history) and to estimate willingness-to-pay (WTP) and establish best-worst (B/W) scaling (rank) for the 7 quality categories. Interviews were conducted in Hong Kong/China (n = 83), Japan (n = 48), Mexico (n = 70) and Russia (n = 54) with importers of U.S. pork or those who had purchased U.S. pork from distributors in the last 3 yr. Interviews used dynamic routing software and were structured such that economic factors for purchase were addressed first, allowing all responses to focus on quality. Questions about WTP and B/W were asked and then each respondent was asked to define what each quality category meant to them. Generalized linear mixed models were used to analyze frequency data. Over 70% of interviewees in Hong Kong/China, Japan, and Mexico responded that purchase price was influential in deciding whether or not to purchase imported pork. This number was lower in Russia, where respondents stated tariff rates were also important, indicating market access was a larger issue in Russia. Food safety was the most important quality category (price was not included as a part of quality) for imported pork followed by specifications. Respondents indicated some form of government inspection was how they defined food safety, whereas product size, weight, and subcutaneous fat were all included in the definition of specifications. Interviewees were more likely to pay premiums for customer service and less likely to pay premiums for packaging (P < 0.05). The premiums that were willing to be paid for guarantees of quality for imported pork variety meats were numerically lower than for whole muscle cuts or processed products. A guarantee associated with food safety of processed pork products was found to be the quality attribute for which importers would be willing to pay the highest premium. Production history was found to be the least important quality attribute for importers of all types of U.S. pork, except those in Japan. Exporters could increase profitability if a guarantee of customer service was made. Price, tariffs, and exchange rates are important to pork importers; these results indicated that if certain quality attributes could be guaranteed, exporters could increase profitability.
- Published
- 2015
- Full Text
- View/download PDF
36. A divergent Pseudomonas aeruginosa palmitoyltransferase essential for cystic fibrosis-specific lipid A.
- Author
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Thaipisuttikul I, Hittle LE, Chandra R, Zangari D, Dixon CL, Garrett TA, Rasko DA, Dasgupta N, Moskowitz SM, Malmström L, Goodlett DR, Miller SI, Bishop RE, and Ernst RK
- Subjects
- Acidic Glycosphingolipids, Acyltransferases chemistry, Amino Acid Motifs, Amino Acid Sequence, Antimicrobial Cationic Peptides immunology, Antimicrobial Cationic Peptides metabolism, Bacterial Proteins chemistry, Catalytic Domain, Cystic Fibrosis metabolism, Cystic Fibrosis microbiology, Cytokines metabolism, Drug Resistance, Bacterial, Escherichia coli Proteins chemistry, Escherichia coli Proteins genetics, Escherichia coli Proteins metabolism, Humans, Immunity, Innate, Lipid A immunology, Lipoylation, Models, Molecular, Molecular Sequence Data, Mutation, Phylogeny, Polymyxin B pharmacology, Protein Conformation, Protein Structure, Tertiary, Pseudomonas aeruginosa chemistry, Pseudomonas aeruginosa drug effects, Pseudomonas aeruginosa immunology, Pseudomonas aeruginosa metabolism, Acyltransferases genetics, Acyltransferases metabolism, Bacterial Proteins genetics, Bacterial Proteins metabolism, Cystic Fibrosis immunology, Lipid A metabolism, Palmitates metabolism
- Abstract
Strains of Pseudomonas aeruginosa (PA) isolated from the airways of cystic fibrosis patients constitutively add palmitate to lipid A, the membrane anchor of lipopolysaccharide. The PhoPQ regulated enzyme PagP is responsible for the transfer of palmitate from outer membrane phospholipids to lipid A. This enzyme had previously been identified in many pathogenic Gram-negative bacteria, but in PA had remained elusive, despite abundant evidence that its lipid A contains palmitate. Using a combined genetic and biochemical approach, we identified PA1343 as the PA gene encoding PagP. Although PA1343 lacks obvious primary structural similarity with known PagP enzymes, the β-barrel tertiary structure with an interior hydrocarbon ruler appears to be conserved. PA PagP transfers palmitate to the 3' position of lipid A, in contrast to the 2 position seen with the enterobacterial PagP. Palmitoylated PA lipid A alters host innate immune responses, including increased resistance to some antimicrobial peptides and an elevated pro-inflammatory response, consistent with the synthesis of a hexa-acylated structure preferentially recognized by the TLR4/MD2 complex. Palmitoylation commonly confers resistance to cationic antimicrobial peptides, however, increased cytokine production resulting in inflammation is not seen with other palmitoylated lipid A, indicating a unique role for this modification in PA pathogenesis., (© 2013 John Wiley & Sons Ltd.)
- Published
- 2014
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37. Quantifying the aging response and nutrient composition for muscles of the beef round.
- Author
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Dixon CL, Woerner DR, Tokach RJ, Chapman PL, Engle TE, Tatum JD, and Belk KE
- Subjects
- Animals, Cattle, Fatty Acids chemistry, Lipids chemistry, Meat standards, Time Factors, Water chemistry, Food Handling methods, Meat analysis, Muscle, Skeletal physiology
- Abstract
The objective of this study was to determine the optimal postmortem aging period and nutrient composition for Beef Value Cuts of the round. Forty USDA Select and 40 Premium USDA Choice beef carcasses were selected from a commercial beef packing plant in Colorado over a 12-wk period. The bottom and inside rounds were collected from both sides of each carcass for further fabrication into the following muscles: adductor, gastrocnemius, gracilis, pectineus, and superficial digital flexor. Each pair of muscles was cut into 7 steaks and randomly assigned to 1 of the following aging periods: 2, 4, 6, 10, 14, 21, and 28 d, and placed in refrigerated storage (2°C, never frozen). Upon completion of the designated aging period, steaks were removed from storage, cooked to a peak internal temperature of 72°C, and evaluated using Warner-Bratzler shear force (WBSF). A 2-way interaction was detected (P < 0.05) between individual muscle and postmortem aging period. The WBSF of all muscles except the superficial digital flexor decreased with increased time of postmortem aging. Quality grade did not affect (P > 0.05) WBSF values for the adductor, gastrocnemius, pectineus, and superficial digital flexor muscles. Exponential decay models were used to predict the change in WBSF from 2 to 28 d postmortem (aging response). The adductor, gastrocnemius, Select gracilis, Premium Choice gracilis, and pectineus required 21, 14, 23, 23, and 25 d, respectively, to complete the majority of the aging response. To determine the nutrient composition of the adductor, gastrocnemius, gracilis, pectineus, semimembranosus, and superficial digital flexor, bottom and inside rounds were collected from 10 USDA Select and 10 Premium USDA Choice carcasses and fabricated into the respective muscles, cut into 2.54-cm cubes, frozen (-20°C), and then homogenized. The adductor, gracilis, pectineus, semimembranosus, and superficial digital flexor were analyzed for DM, moisture, CP, and ash percentages. All muscles were evaluated for total lipid, fatty acid, and cholesterol composition. When quality grades were combined, all muscles fell into the extra lean or lean categories specified by USDA guidelines. Results of this study illustrate the potential for Beef Value Cuts of the round to be sold in food service operations and retail stores with marketing emphasis being placed on the exceptional leanness and acceptable tenderness of these cuts.
- Published
- 2012
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38. Molecular determinants of ivermectin sensitivity at the glycine receptor chloride channel.
- Author
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Lynagh T, Webb TI, Dixon CL, Cromer BA, and Lynch JW
- Subjects
- Animals, Antiparasitic Agents chemistry, Antiparasitic Agents pharmacology, Benzofurans chemistry, Caenorhabditis elegans metabolism, Crystallography, X-Ray methods, Cysteine chemistry, Electrophysiology methods, Glycine chemistry, Hydrogen Bonding, Ivermectin analogs & derivatives, Ivermectin pharmacology, Mutagenesis, Site-Directed, Mutation, Chloride Channels chemistry, Ivermectin chemistry, Receptors, Glycine chemistry
- Abstract
Ivermectin is an anthelmintic drug that works by activating glutamate-gated chloride channel receptors (GluClRs) in nematode parasites. GluClRs belong to the Cys-loop receptor family that also includes glycine receptor (GlyR) chloride channels. GluClRs and A288G mutant GlyRs are both activated by low nanomolar ivermectin concentrations. The crystal structure of the Caenorhabditis elegans α GluClR complexed with ivermectin has recently been published. Here, we probed ivermectin sensitivity determinants on the α1 GlyR using site-directed mutagenesis and electrophysiology. Based on a mutagenesis screen of transmembrane residues, we identified Ala288 and Pro230 as crucial sensitivity determinants. A comparison of the actions of selamectin and ivermectin suggested the benzofuran C05-OH was required for high efficacy. When taken together with docking simulations, these results supported a GlyR ivermectin binding orientation similar to that seen in the GluClR crystal structure. However, whereas the crystal structure shows that ivermectin interacts with the α GluClR via H-bonds with Leu218, Ser260, and Thr285 (α GluClR numbering), our data indicate that H-bonds with residues homologous to Ser260 and Thr285 are not important for high ivermectin sensitivity or direct agonist efficacy in A288G α1 GlyRs or three other GluClRs. Our data also suggest that van der Waals interactions between the ivermectin disaccharide and GlyR M2-M3 loop residues are unimportant for high ivermectin sensitivity. Thus, although our results corroborate the ivermectin binding orientation as revealed by the crystal structure, they demonstrate that some of the binding interactions revealed by this structure do not pertain to other highly ivermectin-sensitive Cys-loop receptors.
- Published
- 2011
- Full Text
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39. Tin protoporphyrin provides protection following cerebral hypoxia-ischemia: involvement of alternative pathways.
- Author
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Sutherland BA, Shaw OM, Clarkson AN, Winburn IC, Errington AC, Dixon CL, Lees G, Sammut IA, and Appleton I
- Subjects
- Animals, Brain metabolism, Electron Transport Complex I metabolism, Electron Transport Complex IV metabolism, Male, Nitric Oxide Synthase metabolism, Prostaglandin-Endoperoxide Synthases metabolism, Rats, Rats, Wistar, Brain drug effects, Enzyme Inhibitors pharmacology, Heme Oxygenase (Decyclizing) antagonists & inhibitors, Hemin pharmacology, Hypoxia-Ischemia, Brain metabolism, Metalloporphyrins pharmacology, Protoporphyrins pharmacology
- Abstract
The contribution of heme oxygenase (HO)-linked pathways to neurodegeneration following cerebral hypoxia-ischemia (HI) remains unclear. We investigated whether HO modulators affected HI-induced brain damage and explored potential mechanisms involved. HI was induced in 26-day-old male Wistar rats by left common carotid artery ligation, followed by exposure to a humidified atmosphere of 8% oxygen for 1 hr. Tin protoporphyrin (SnPP; an HO inhibitor), ferriprotoporphyrin (FePP; an HO inducer), or saline was administered intraperitoneally once daily from 1 day prior to HI until sacrifice at 3 days post-HI. SnPP reduced (P < 0.05) infarct volume compared with saline-treated animals, but FePP had no effect on brain injury. SnPP did not significantly inhibit HO activity at 3 days post-HI, but SnPP increased (P < 0.001) total nitric oxide synthase (NOS) activity compared with HI + saline. Both inducible NOS and cyclooxygenase activities were attenuated (P < 0.05) by SnPP, whereas mitochondrial complex I and V activities were augmented (P < 0.05) by SnPP. SnPP had no effect on NMDA receptor currents. Overall, like other HO inhibitors, SnPP produced many nonselective effects, such as attenuation of inflammatory enzymes and increased mitochondrial respiratory function, which were associated with a protective response 3 days post-HI., (Copyright © 2011 Wiley-Liss, Inc.)
- Published
- 2011
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40. Pharmacological profile of essential oils derived from Lavandula angustifolia and Melissa officinalis with anti-agitation properties: focus on ligand-gated channels.
- Author
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Huang L, Abuhamdah S, Howes MJ, Dixon CL, Elliot MS, Ballard C, Holmes C, Burns A, Perry EK, Francis PT, Lees G, and Chazot PL
- Subjects
- Animals, Binding, Competitive, Dose-Response Relationship, Drug, Electrophysiology, Inhibitory Concentration 50, Ion Channel Gating drug effects, Ligands, Male, Oils, Volatile administration & dosage, Oils, Volatile isolation & purification, Prosencephalon drug effects, Prosencephalon metabolism, Psychomotor Agitation drug therapy, Radioligand Assay, Rats, Rats, Sprague-Dawley, Rats, Wistar, Receptors, GABA-A drug effects, Receptors, GABA-A metabolism, Ion Channels drug effects, Lavandula chemistry, Melissa chemistry, Oils, Volatile pharmacology
- Abstract
Both Melissa officinalis (Mo) and Lavandula angustifolia (La) essential oils have putative anti-agitation properties in humans, indicating common components with a depressant action in the central nervous system. A dual radioligand binding and electrophysiological study, focusing on a range of ligand-gated ion channels, was performed with a chemically validated essential oil derived from La, which has shown clinical benefit in treating agitation. La inhibited [35S] TBPS binding to the rat forebrain gamma aminobutyric acid (GABA)(A) receptor channel (apparent IC50 = 0.040 +/- 0.001 mg mL(-1)), but had no effect on N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) or nicotinic acetylcholine receptors. A 50:50 mixture of Mo and La essential oils inhibited [3H] flunitrazepam binding, whereas the individual oils had no significant effect. Electrophysiological analyses with rat cortical primary cultures demonstrated that La reversibly inhibited GABA-induced currents in a concentration-dependent manner (0.01-1 mg mL(-1)), whereas no inhibition of NMDA- or AMPA-induced currents was noted. La elicited a significant dose-dependent reduction in both inhibitory and excitatory transmission, with a net depressant effect on neurotransmission (in contrast to the classic GABA(A) antagonist picrotoxin which evoked profound epileptiform burst firing in these cells). These properties are similar to those recently reported for Mo. The anti-agitation effects in patients and the depressant effects of La we report in neural membranes in-vitro are unlikely to reflect a sedative interaction with any of the ionotropic receptors examined here. These data suggest that components common to the two oils are worthy of focus to identify the actives underlying the neuronal depressant and anti-agitation activities reported.
- Published
- 2008
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41. PPAR-alpha ligands inhibit H2O2-mediated activation of transforming growth factor-beta1 in human mesangial cells.
- Author
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Wilmer WA, Dixon CL, Hebert C, Lu L, and Rovin BH
- Subjects
- Cells, Cultured, Dose-Response Relationship, Drug, Genetic Vectors, Glomerular Mesangium cytology, Humans, Hydrogen Peroxide pharmacology, Immunohistochemistry, Ligands, Luciferases genetics, Mitogen-Activated Protein Kinases metabolism, Plasmids, Promoter Regions, Genetic physiology, Transcription Factors pharmacology, Transduction, Genetic, Transforming Growth Factor beta genetics, Transforming Growth Factor beta1, Clofibrate pharmacology, Glomerular Mesangium metabolism, Hydrogen Peroxide antagonists & inhibitors, Pyrimidines pharmacology, Receptors, Cytoplasmic and Nuclear metabolism, Transcription Factors metabolism, Transforming Growth Factor beta metabolism
- Abstract
Transforming growth factor-beta1 (TGF-beta1) mediates the development of glomerulosclerosis by stimulating mesangial cell production of extracellular matrix (ECM) proteins. TGF-beta1 and several ECM genes are regulated by promoter O-tetradecanoylphorbol 13-acetate-responsive elements (TREs) that are transactivated by the activator protein-1 (AP-1) transcription factor complex. AP-1-TRE interactions are regulated by redox changes. Recently, peroxisome proliferator-activated receptors (PPARs) were shown to negatively regulate several transcription factor families. In these studies, we postulated that PPAR-alpha could antagonize TGF-beta1 expression by cultured human mesangial cells (HMC). A TGF-beta1 luciferase expression plasmid was transduced into HMC via recombinant deficient adenoviral vectors. The TGF-beta1 promoter activity increased twofold (209%) following 18-h treatments with H(2)O(2) (1,000 micro M). Using RT-PCR, we demonstrated that HMC possess PPAR-alpha RNA, and PPAR-alpha protein was identified by immunohistochemistry. Pretreatment of cells with the PPAR-alpha ligands WY14643 (100-500 micro M) or clofibrate (100-500 micro M) dose-dependently inhibited oxidant-mediated induction of TGF-beta1. This inhibition occurred without affecting the H(2)O(2)-mediated activation of the mitogen-activated protein kinase (MAPK) pathways extracellular regulated kinase, p38 MAPK, or Jun N-terminal kinase, which are responsible for the regulation of AP-1 phosphorylation. These studies are the first to identify PPAR-alpha expression by HMC. The results of these studies suggest that TGF-beta1 expression mediated by oxidant stress may be suppressible by PPAR-alpha activation.
- Published
- 2002
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42. Chronic exposure of human mesangial cells to high glucose environments activates the p38 MAPK pathway.
- Author
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Wilmer WA, Dixon CL, and Hebert C
- Subjects
- Antioxidants pharmacology, Cells, Cultured, Dose-Response Relationship, Drug, Enzyme Activation, Glomerular Mesangium enzymology, Glucose antagonists & inhibitors, Humans, Mannitol pharmacology, Osmotic Pressure, Phorbol Esters pharmacology, Transcription Factor AP-1 metabolism, p38 Mitogen-Activated Protein Kinases, Glomerular Mesangium drug effects, Glucose pharmacology, Mitogen-Activated Protein Kinases metabolism
- Abstract
Background: High glucose (HG) environments activate several protein kinase pathways in mesangial cells, including the mitogen-activated protein kinase (MAPK) pathway, ERK. The p38 MAPK pathway is activated by events that occur in the setting of diabetes, such as protein kinase C (PKC) up-regulation and cellular stresses (osmotic stress and redox changes). Substrates of activated p38 MAPK include transcription factors that are involved in the microvascular complications of diabetes. This current study investigated the mechanisms of HG-mediated activation of p38 MAPK in cultured human mesangial cells (HMCs) and the effects of p38 MAPK activation on the transcription factor activator protein-1 (AP-1)., Methods: HMCs were cultured in 5 mmol/L D-glucose [normal glucose (NG)] or 30 mmol/L D-glucose (HG) for seven days. Cells were also treated with HG for brief periods of time (0.5 to 4 hours) to assess the acute effects of HG on p38 MAPK. Using Western blotting of HMC lysates, changes in the tyrosine and threonine phosphorylation of p38 MAPK were measured. The kinase activity of immunoprecipitated p38 MAPK was determined by an in vitro assay that measured the phosphorylation and activation of MAPKAP kinase-2, an intermediary signaling protein downstream of p38 MAPK. To investigate the role of osmotic stress in HG activation of p38 MAPK, cells were acutely treated with mannitol (25 to 250 mOsm/L x 5 to 60 min) or were grown seven days in media supplemented with mannitol at concentrations iso-osmotic to HG media. To investigate the role of PKC in HG-mediated p38 MAPK activation, HMCs were treated with the PKC inhibitors GF 109203X, Ro 32-0432, or rottlerin during the last several hours of HG treatment. HG conditioned cells were also treated with the antioxidants L-N-acetylcysteine (L-NAC) or diphenyliodonium (DPI) prior to harvest. To determine a functional significance of HG-mediated p38 MAPK activation, the DNA binding of the transcription factor complex AP-1 was measured by electrophoretic mobility shift assay., Results: The p38 MAPK pathway was not activated by the acute addition of HG to the HMCs. However, activation of p38 MAPK in HMCs grown seven days in HG was demonstrated by increased tyrosine and threonine phosphorylation of p38 MAPK proteins and increased kinase activity of immunoprecipitated p38 MAPK. As assessed by a kinase assay, p38 MAPK activity in cells grown in HG for seven days exceeded that of NG cells by more than 250%. This difference was not due to differences in the amount of p38 MAPK protein between the treatment groups. Acute osmotic activation of p38 MAPK occurred at extremely high mannitol concentrations (250 mOsm/L) that exceeded the osmotic stress of acute HG. Furthermore, in cells grown for seven days in mannitol at concentrations similar to HG, p38 MAPK activity was similar to control values. Phorbol ester (PMA) treatment stimulated a twofold increase in p38 MAPK activity. The addition of GFX or Ro 32-0432 to HG cells, at concentrations that inhibited PMA activation of p38 MAPK, did not inhibit the glucose-mediated p38 MAPK activation. Rottlerin, a PKC delta inhibitor, also failed to reverse the HG-mediated p38 MAPK activation. Treatment of HG cells with L-NAC or DPI inhibited the HG-mediated p38 MAPK phosphorylation. As we have previously shown, DNA binding of the transcription factor complex AP-1 was increased in HG cells. This binding was reversed by treatment of the HG cells with the p38 MAPK inhibitor SB 203580., Conclusions: Chronic exposure of HMC to HG concentrations activates the p38 MAPK pathway. This activation appears to be independent of changes in the amount of total p38 MAPK produced by the cells, independent of chronic osmotic stress and independent of PKC activation. The reversal of p38 MAPK by L-NAC and DPI suggests the glucose-mediated p38 MAPK activation may occur via reactive oxygen species. The activity of AP-1, a transcription factor complex that regulates several genes involved in diabetic nephropathy, is reversed when the p38 MAPK pathway is inhibited. These findings suggest the p38 MAPK pathway may be an important pathway involved in diabetic complications.
- Published
- 2001
- Full Text
- View/download PDF
43. The mitogen-activated protein kinase p38 is necesssary for interleukin 1beta-induced monocyte chemoattractant protein 1 expression by human mesangial cells.
- Author
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Rovin BH, Wilmer WA, Danne M, Dickerson JA, Dixon CL, and Lu L
- Subjects
- Calcium-Calmodulin-Dependent Protein Kinases antagonists & inhibitors, Calcium-Calmodulin-Dependent Protein Kinases metabolism, Cells, Cultured, Enzyme Activation drug effects, Enzyme Inhibitors pharmacology, Flavonoids pharmacology, Gene Expression drug effects, Glomerular Mesangium drug effects, Humans, Imidazoles pharmacology, Mitogen-Activated Protein Kinase 1, NF-kappa B metabolism, Pyridines pharmacology, RNA, Messenger metabolism, p38 Mitogen-Activated Protein Kinases, Calcium-Calmodulin-Dependent Protein Kinases physiology, Chemokine CCL2 biosynthesis, Glomerular Mesangium metabolism, Interleukin-1 pharmacology, Mitogen-Activated Protein Kinases
- Abstract
Mitogen-activated protein (MAP) kinases have been suggested as potential mediators for interleukin 1beta (IL-1beta)-induced gene activation. This study investigated the role of the MAP kinases p38 and ERK2 in IL-1beta-mediated expression of the chemokine MCP-1 by human mesangial cells. Phosphorylation of p38 kinase, which is necessary for activation, increased significantly after IL-1beta treatment. p38 kinase immunoprecipitated from IL-1beta-treated cells phosphorylated target substrates to a greater extent than p38 kinase from controls. SB 203580, a selective p38 kinase inhibitor, was used to examine the role of p38 kinase in MCP-1 expression. SB 203580 decreased IL-1beta-induced MCP-1 mRNA and protein levels, but did not affect MCP-1 mRNA stability. Because NF-kappaB is necessary for MCP-1 gene expression, the effect of p38 kinase inhibition on IL-1beta induction of NF-kappaB was measured. SB 203580 (up to 25 microM) had no effect on IL-1beta-induced NF-kappaB nuclear translocation or DNA binding activity. Our previous work showed that IL-1beta also activates the MAP kinase ERK2 in human mesangial cells. PD 098059, a selective inhibitor of the ERK activating kinase MEK1, had no effect on IL-1beta-induced MCP-1 mRNA or protein levels, or on IL-1beta activation of NF-kappaB. These data indicate that p38 kinase is necessary for the induction of MCP-1 expression by IL-1beta, but is not involved at the level of cytoplasmic activation of NF-kappaB. In contrast, ERK2 does not mediate IL-1beta induced MCP-1 gene expression., (Copyright 1999 Academic Press.)
- Published
- 1999
- Full Text
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44. Computer-modulated patient-controlled analgesia. Preliminary evaluation of a prototype.
- Author
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Mies RJ, van der Aa JJ, Dixon CL, Kaltenbach M, Derendorf H, and Gravenstein N
- Subjects
- Algorithms, Animals, Dogs, Female, Infusions, Intravenous, Male, Models, Biological, Morphine administration & dosage, Morphine pharmacokinetics, Morphine pharmacology, Analgesia, Patient-Controlled instrumentation, Microcomputers
- Abstract
Background and Objectives: To provide patients with better postoperative pain relief, the authors developed a prototype computer-controlled infusion pump capable of establishing a steady drug plasma concentration based on patient needs., Methods: A two-compartment pharmacokinetic model was used to compute the required infusion scheme. Using known pharmacokinetic parameters, the model and the pump's accuracy were studied in four dogs. In the first part of the study, the morphine pharmacokinetic profile of each dog was analyzed and used to develop the parameters of a model tailored to that particular dog. In the second part, this tailored model was implemented to test whether the infusion device was able to achieve the desired concentration profile., Results: The computer-controlled infusion device was able to achieve all the desired plasma concentrations., Conclusions: These data suggest that it is possible to refine postoperative pain management with adaptive computer algorithms implemented to establish stable plasma analgesic concentrations and to automatically wean the analgesic over time.
- Published
- 1994
45. The Sprotte, Whitacre, and Quincke spinal needles.
- Author
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Dixon CL
- Subjects
- Anesthesia, Epidural adverse effects, Anesthesia, Obstetrical adverse effects, Anesthesia, Obstetrical instrumentation, Anesthesia, Spinal adverse effects, Equipment Design, Female, Headache etiology, Humans, Anesthesia, Epidural instrumentation, Anesthesia, Spinal instrumentation, Needles
- Published
- 1991
46. Role of elective brain irradiation during combined chemoradiotherapy for limited disease non-small cell lung cancer.
- Author
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Umsawasdi T, Valdivieso M, Chen TT, Barkley HT Jr, Booser DJ, Chiuten DF, Dhingra HM, Murphy WK, Dixon CL, and Farha P
- Subjects
- Antineoplastic Combined Chemotherapy Protocols, Brain Neoplasms radiotherapy, Cisplatin administration & dosage, Clinical Trials as Topic, Combined Modality Therapy, Cyclophosphamide administration & dosage, Doxorubicin administration & dosage, Female, Humans, Male, Middle Aged, Prospective Studies, Random Allocation, Brain Neoplasms secondary, Lung Neoplasms therapy
- Abstract
We have studied the clinical impact of elective brain irradiation (EBI) in patients with locally advanced, non-small cell lung cancer (LA-NSC). All patients received combination chemotherapy (cyclophosphamide + doxorubicin (Adriamycin) + cisplatin = CAP) or CAP plus radiotherapy as the initial treatment for their active tumor or as an adjuvant therapy. Of 97 evaluable patients, 46 were randomized to receive EBI (3 000 rad in 10 fractions given over two weeks). The characteristics of both groups were comparable by sex, age, performance status, pretherapy weight loss, histologic cell type, clinical staging, and type of prior therapy. EBI significantly decreased the incidence of central nervous system (CNS) metastasis in the treated group compared to the control group (4% vs 27%, p = .002). CNS involvement occurred in the treated group after failure at other sites whereas 12 of 14 control patients had CNS metastases as the first site of relapse. EBI decreased the incidence of CNS metastasis in all prognostic categories. Using multivariate analysis, the beneficial effect was shown to be significant in females, patients with good performance status, weight loss less than 6%, squamous cell histology, state III disease or no prior therapy. EBI significantly increased CNS metastasis-free interval with a beneficial effect that was significant in males, patients with weight loss less than 6%, squamous cell histology or responders. Although no survival benefit was observed for the treated group because of the adverse effect from other relapses, EBI will become more important as better treatment programs are developed.(ABSTRACT TRUNCATED AT 250 WORDS)
- Published
- 1984
- Full Text
- View/download PDF
47. Regional and overall pulmonary function changes in lung cancer. Correlations with tumor stage, extent of pulmonary resection, and patient survival.
- Author
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Ali MK, Ewer MS, Atallah MR, Mountain CF, Dixon CL, Johnston DA, and Haynie TP
- Subjects
- Adult, Aged, Female, Humans, Lung Neoplasms diagnostic imaging, Lung Neoplasms surgery, Male, Middle Aged, Neoplasm Staging, Prognosis, Radionuclide Imaging, Respiratory Function Tests, Ventilation-Perfusion Ratio, Lung physiology, Lung Neoplasms physiopathology
- Abstract
Spirometry and regional pulmonary function studies using xenon 133 gas were performed in 251 patients who had primary lung cancer. Surgical resection was undertaken in 150 while the remainder were treated with nonsurgical modalities. Pulmonary function studies were repeated postoperatively in 54 patients. Regional ventilation and perfusion of the tumor-bearing lung were decreased in patients with larger primary tumors and in those with involvement of ipsilateral hilar lymph nodes. Reduced regional function was also directly related to the proximity of the primary tumor to the hilum. Significant hypoperfusion did not contraindicate operation in 14 patients; however, 13 of them required pneumonectomy. Estimated postoperative forced expiratory volume in 1 second (FEV1.0), derived from preoperative spirometry and regional function of the tumor-bearing lung, correlated well with the measured postoperative values. These estimations were valuable in determining the extent of safe resection and correlated well with short-term survival. Long-term survival correlated better with the stage of disease.
- Published
- 1983
48. Small cell bronchogenic carcinoma: factors associated with pneumonia during chemotherapy.
- Author
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Dixon CL, Valdivieso M, Umsawasdi T, Dubois G, Patton D, Chen T, Ali MK, and Bodey GP
- Subjects
- Adult, Age Factors, Aged, Antineoplastic Combined Chemotherapy Protocols therapeutic use, Bone Marrow drug effects, Carcinoma, Bronchogenic complications, Carcinoma, Bronchogenic physiopathology, Carcinoma, Small Cell complications, Carcinoma, Small Cell physiopathology, Female, Forced Expiratory Flow Rates, Humans, Lung Neoplasms complications, Lung Neoplasms physiopathology, Male, Middle Aged, Oxygen blood, Prognosis, Regression Analysis, Risk, Antineoplastic Combined Chemotherapy Protocols adverse effects, Carcinoma, Bronchogenic drug therapy, Carcinoma, Small Cell drug therapy, Lung Neoplasms drug therapy, Pneumonia etiology
- Abstract
Sixty-five patients with small cell bronchogenic carcinoma were treated with intensive induction chemotherapy and supportive treatment. The clinical course of 43 patients who had pretreatment spirometry and arterial blood gases was studied. Thirteen patients developed pneumonia. Moderate hypoxemia, advanced age, and a low forced expiratory flow 25%-75% were associated with the development of pneumonia. Endobronchial obstruction and neutropenia, other factors associated with infection in cancer patients, appeared to be less important in this patient population.
- Published
- 1984
- Full Text
- View/download PDF
49. Coagulase-negative staphylococcal infections.
- Author
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Valadez JA, Boldrick RW, and Dixon CL
- Subjects
- Anti-Bacterial Agents therapeutic use, Cross Infection diagnosis, Cross Infection drug therapy, Cross Infection microbiology, Drug Resistance, Microbial, Humans, Staphylococcal Infections diagnosis, Staphylococcal Infections drug therapy, Staphylococcus epidermidis drug effects, Staphylococcus epidermidis pathogenicity, Coagulase deficiency, Staphylococcal Infections microbiology, Staphylococcus epidermidis enzymology
- Published
- 1988
50. Esophageal complications from combined chemoradiotherapy (cyclophosphamide + Adriamycin + cisplatin + XRT) in the treatment of non-small cell lung cancer.
- Author
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Umsawasdi T, Valdivieso M, Barkley HT Jr, Booser DJ, Chiuten DF, Murphy WK, Dhingra HM, Dixon CL, Farha P, and Spitzer G
- Subjects
- Adenocarcinoma drug therapy, Adenocarcinoma radiotherapy, Adult, Aged, Carcinoma, Squamous Cell drug therapy, Carcinoma, Squamous Cell radiotherapy, Combined Modality Therapy, Cyclophosphamide adverse effects, Doxorubicin adverse effects, Esophageal Fistula etiology, Esophageal Stenosis etiology, Esophagitis etiology, Female, Humans, Lung Neoplasms drug therapy, Lung Neoplasms radiotherapy, Male, Middle Aged, Peptichemio adverse effects, Antineoplastic Combined Chemotherapy Protocols adverse effects, Esophageal Diseases etiology, Lung Neoplasms therapy, Radiotherapy adverse effects
- Abstract
Esophageal complications from combined chemoradiotherapy (CCRT) were analyzed in 55 patients with limited non-small cell lung cancer. CCRT consisted of chemotherapy (cyclophosphamide, doxorubicin (Adriamycin), and cisplatin: CAP) and chest irradiation (5000 rad in 25 fractions/5 weeks). Forty-five patients received two courses of CAP, followed by five weekly courses of low dose CAP and irradiation followed by maintenance courses of CAP (Group 1). Ten patients received concomitant CCRT from the onset of treatment (Group 2). Esophagitis occurred in 80% of all patients. Severe esophagitis occurred in 27% of patients of Group 1 and 40% of patients of Group 2. Esophageal stricture or fistula developed in 1 of 45 (2%) patients in Group 1, and 3 of 10 (30%) patients in Group 2 (p less than 0.025). Weekly low-dose chemotherapy administered concomitantly with chest irradiation (R) at the onset of treatment significantly increases esophageal complications. A review of the literature suggests that CCRT may be used safely with split courses of R. The duration between onset of chemotherapy either before or after R should be greater than one week.
- Published
- 1985
- Full Text
- View/download PDF
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