287 results on '"White SH"'
Search Results
2. Effects of Dietary Selenium and Training on Oxidative Stress in Young Horses
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White, SH, primary and Warren, LK, additional
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- 2014
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3. Arthroscopic removal of large loose body: an improved technique
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Gallacher, PD, primary and White, SH, additional
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- 2011
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4. The Avon patellofemoral joint replacement: independent assessment of early functional outcomes.
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Starks I, Roberts S, and White SH
- Published
- 2009
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5. Anteromedial osteoarthritis of the knee
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White, SH, primary, Ludkowski, PF, additional, and Goodfellow, JW, additional
- Published
- 1991
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6. Axial movement and tibial fractures. A controlled randomised trial of treatment
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Kenwright, J, primary, Richardson, JB, additional, Cunningham, JL, additional, White, SH, additional, Goodship, AE, additional, Adams, MA, additional, Magnussen, PA, additional, and Newman, JH, additional
- Published
- 1991
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7. Sagittal plane laxity following knee arthroplasty
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White, SH, primary, O'Connor, JJ, additional, and Goodfellow, JW, additional
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- 1991
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8. The timing of distraction of an osteotomy
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White, SH, primary and Kenwright, J, additional
- Published
- 1990
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9. Documentation on withdrawal of life support in adult patients in the intensive care unit [corrected] [published erratum appears in AM J CRIT CARE 2004 Sep;13(5):370].
- Author
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Kirchhoff KT, Anumandla PR, Foth KT, Lues SN, and Gilbertson-White SH
- Abstract
BACKGROUND: Patients' charts have been a source of data for retrospective studies of the quality of end-of-life care. In the intensive care unit, most patients die after withdrawal of life support. Chart reviews of this process could be used not only to assess the quality of documentation but also to provide information for quality improvement and research. OBJECTIVE: To assess the documentation of end-of-life care of patients and their families by care providers in the intensive care unit. METHOD: Charts of 50 adult patients who died in the intensive care unit at a large midwestern hospital after initiation of withdrawal of life support (primarily mechanical ventilation) were reviewed. A form developed for the study was used for data collection. RESULTS: The initiation of the decision making for withdrawal was documented in all 50 charts. Sixteen charts (32%) had no information on advance directives. Eight charts (16%) had no documentation on resuscitation status. About two thirds of the charts documented nurses' participation during the withdrawal process; only one tenth documented physicians' participation. A total of 13 charts (26%) had no information on the time of initiation of the withdrawal process, and 11 (22%) had no documentation of medications administered for withdrawal. Thirty-seven charts (74%) had information on whether the patient was or was not extubated during withdrawal. CONCLUSION: Comprehensive documentation of end-of-life care is lacking. [ABSTRACT FROM AUTHOR]
- Published
- 2004
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10. Posterior interosseous nerve palsy in rheumatoid arthritis
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White, SH, Goodfellow, JW, and Mowat, A
- Abstract
Bilateral posterior interosseous nerve palsy in a rheumatoid patient is described. Six previous case reports and our experience indicate that steroid injection into the elbow may not produce lasting recovery and may lead to unacceptable delay before surgical decompression. An anterolateral approach for division of the arcade of Frohse is effective in cases with diffuse synovitis; where there is a local cystic swelling a posterolateral approach provides better access. Good recovery of nerve function can be expected after early operation.
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- 1988
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11. Cell line selection using the Duetz Microflask system
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Warr Steve R C, White Sharon L, Chim Yuen-Ting, Patel Jai, and Bosteels Hella
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Medicine ,Science - Published
- 2011
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12. Paraneoplastic leukocytoclastic vasculitis as an initial presentation of malignant pleural mesothelioma: a case report
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Wong Shu, Newland Lisa, John Thomas, and White Shane C
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Leukocytoclastic vasculitis ,Mesothelioma ,Paraneoplastic ,Medicine - Abstract
Abstract Introduction Vasculitis has been associated with malignancies, more commonly hematological rather than solid malignancies. Due to the rarity of these conditions and the lack of a temporal association, the relationship between vasculitis and malignancy remains unclear. Paraneoplastic vasculitis as a phenomenon of lung cancer has been described in the literature. To the best of our knowledge, this is the first case report of leukocytoclastic vasculitis being an initial presentation of malignant pleural mesothelioma. Case presentation We report the case of an 84-year old Greek man who presented to our facility with an erythematous, pruritic and purpuric rash affecting his limbs. This was biopsy-proven to be leukocytoclastic vasculitis and treated conservatively with topical corticosteroids as well as oral prednisolone, with good results. Six months later, he was diagnosed as having malignant pleural mesothelioma. As he remained asymptomatic from his malignancy, no systemic chemotherapy was instituted. He had a recurrence of biopsy-proven leukocytoclastic vasculitis two months after he was diagnosed as having mesothelioma, which again settled with conservative measures. Conclusions It is important to remain vigilant with regard to the association between leukocytoclastic vasculitis and malignancies. A diagnosis of vasculitis requires a search for malignancies as well as other possible etiologies. This is particularly of relevance when the vasculitis becomes chronic, recurrent or treatment is no longer effective. Should our patient have experienced refractory vasculitis, we would have instituted systemic chemotherapy to treat the underlying malignancy.
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- 2012
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13. Callus distraction in Ollier's disease: a case report.
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Pandy R, White SH, and Kenwright J
- Published
- 1995
14. Psychedelic Experiences Increase Mind Perception but do not Change Atheist-Believer Status: A Prospective Longitudinal Study.
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Nayak SM, White SH, Hilbert SN, Lowe MX, Jackson H, Griffiths RR, Garcia-Romeu A, and Yaden DB
- Abstract
Recent studies suggest psychedelic use may be associated with changes in a variety of beliefs or belief-like states, including increased 1) mind perception, 2) non-naturalistic beliefs, and 3) Atheist-Believer status (e.g. believer, agnostic, or nonbeliever). We conducted a prospective longitudinal study among participants ( N = 657) who planned to have a psilocybin experience outside a laboratory setting. We asked participants about their beliefs concerning mind perception of various entities, specific metaphysical positions, and Atheist-Believer status both before (and after their experience. Replicating previous findings, we observed increases in mind perception across a variety of living and non-living targets (e.g. plants, rocks). However, we found little to no change in metaphysical beliefs (e.g. dualism) or Atheist-Believer status. Taken together, these findings contrast with those from cross-sectional studies that psilocybin experiences result in changes to Atheist-Believer status and non-naturalistic beliefs but support the relevance of mind perception and mentalization.
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- 2024
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15. Disruption of the autism-associated gene SCN2A alters synaptic development and neuronal signaling in patient iPSC-glutamatergic neurons.
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Brown CO, Uy JA, Murtaza N, Rosa E, Alfonso A, Dave BM, Kilpatrick S, Cheng AA, White SH, Scherer SW, and Singh KK
- Abstract
SCN2A is an autism spectrum disorder (ASD) risk gene and encodes a voltage-gated sodium channel. However, the impact of ASD-associated SCN2A de novo variants on human neuron development is unknown. We studied SCN2A using isogenic SCN2A
-/- induced pluripotent stem cells (iPSCs), and patient-derived iPSCs harboring a de novo R607* truncating variant. We used Neurogenin2 to generate excitatory (glutamatergic) neurons and found that SCN2A+/ R 607* and SCN2A-/- neurons displayed a reduction in synapse formation and excitatory synaptic activity. We found differential impact on actional potential dynamics and neuronal excitability that reveals a loss-of-function effect of the R607* variant. Our study reveals that a de novo truncating SCN2A variant impairs the development of human neuronal function., 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 © 2024 Brown, Uy, Murtaza, Rosa, Alfonso, Dave, Kilpatrick, Cheng, White, Scherer and Singh.)- Published
- 2024
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16. Repurposing dimethyl fumarate as an antiepileptogenic and disease-modifying treatment for drug-resistant epilepsy.
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Sandouka S, Singh PK, Saadi A, Taiwo RO, Sheeni Y, Zhang T, Deeb L, Guignet M, White SH, and Shekh-Ahmad T
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- Humans, Rats, Animals, Dimethyl Fumarate pharmacology, Dimethyl Fumarate therapeutic use, NF-E2-Related Factor 2 metabolism, Drug Repositioning, Seizures drug therapy, Disease Models, Animal, Epilepsy drug therapy, Epilepsy prevention & control, Status Epilepticus complications, Status Epilepticus drug therapy
- Abstract
Background: Epilepsy affects over 65 million people worldwide and significantly burdens patients, caregivers, and society. Drug-resistant epilepsy occurs in approximately 30% of patients and growing evidence indicates that oxidative stress contributes to the development of such epilepsies. Activation of the Nrf2 pathway, which is involved in cellular defense, offers a potential strategy for reducing oxidative stress and epilepsy treatment. Dimethyl fumarate (DMF), an Nrf2 activator, exhibits antioxidant and anti-inflammatory effects and is used to treat multiple sclerosis., Methods: The expression of Nrf2 and its related genes in vehicle or DMF treated rats were determined via RT-PCR and Western blot analysis. Neuronal cell death was evaluated by immunohistochemical staining. The effects of DMF in preventing the onset of epilepsy and modifying the disease were investigated in the kainic acid-induced status epilepticus model of temporal lobe epilepsy in rats. The open field, elevated plus maze and T-Maze spontaneous alteration tests were used for behavioral assessments., Results: We demonstrate that administration of DMF following status epilepticus increased Nrf2 activity, attenuated status epilepticus-induced neuronal cell death, and decreased seizure frequency and the total number of seizures compared to vehicle-treated animals. Moreover, DMF treatment reversed epilepsy-induced behavioral deficits in the treated rats. Moreover, DMF treatment even when initiated well after the diagnosis of epilepsy, reduced symptomatic seizures long after the drug was eliminated from the body., Conclusions: Taken together, these findings suggest that DMF, through the activation of Nrf2, has the potential to serve as a therapeutic target for preventing epileptogenesis and modifying epilepsy., (© 2023. The Author(s).)
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- 2023
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17. Fifty Years of Biophysics at the Membrane Frontier.
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White SH
- Abstract
The author first describes his childhood in the South and the ways in which it fostered the values he has espoused throughout his life, his development of a keen fascination with science, and the influences that supported his progress toward higher education. His experiences in ROTC as a student, followed by two years in the US Army during the Vietnam War, honed his leadership skills. The bulk of the autobiography is a chronological journey through his scientific career, beginning with arrival at the University of California, Irvine in 1972, with an emphasis on the postdoctoral students and colleagues who have contributed substantially to each phase of his lab's progress. White's fundamental findings played a key role in the development of membrane biophysics, helping establish it as fertile ground for research. A story gradually unfolds that reveals the deeply collaborative and painstakingly executed work necessary for a successful career in science.
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- 2023
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18. DOTAP: Structure, hydration, and the counterion effect.
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Mihailescu M, Worcester DL, Carroll CL, Chamberlin AR, and White SH
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- Quaternary Ammonium Compounds chemistry, Fatty Acids, Monounsaturated chemistry, Water, Cations chemistry, Propane, Liposomes chemistry
- Abstract
The cationic lipid 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) is one of the original synthetic cationic lipids used for the liposomal transfection of oligonucleotides in gene therapy. The key structural element of DOTAP is its quaternary ammonium headgroup that is responsible for interactions with both nucleic acids and target cell membranes. Because these interactions are fundamental to the design of a major class of transfection lipids, it is important to understand the structure of DOTAP and how it interacts with halide counterions. Here, we use x-ray and neutron diffraction techniques to examine the structure of DOTAP and how chloride (Cl-) and iodide (I-) counterions alter the hydration properties of the DOTAP headgroup. A problem of particular interest is the poor solubility of DOTAP/I- in water solutions. Our results show that the poor solubility results from very tight binding of the I- counterion to the headgroup and the consequent expulsion of water. The structural principles we report here are important for assessing the suitability of DOTAP and its quaternary ammonium derivatives for transfection., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2023 Biophysical Society. All rights reserved.)
- Published
- 2023
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19. Topology of the SecA ATPase Bound to Large Unilamellar Vesicles.
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Roussel G, Lindner E, and White SH
- Subjects
- Cryoelectron Microscopy, Protein Binding, Protein Domains, Protein Multimerization, Protein Transport, SEC Translocation Channels chemistry, Escherichia coli metabolism, Escherichia coli Proteins chemistry, SecA Proteins chemistry, Unilamellar Liposomes chemistry
- Abstract
The soluble cytoplasmic ATPase motor protein SecA powers protein transport across the Escherichia coli inner membrane via the SecYEG translocon. Although dimeric in solution, SecA associates monomerically with SecYEG during secretion according to several crystallographic and cryo-EM structural studies. The steps SecA follows from its dimeric cytoplasmic state to its active SecYEG monomeric state are largely unknown. We have previously shown that dimeric SecA in solution dissociates into monomers upon electrostatic binding to negatively charged lipid vesicles formed from E. coli lipids. Here we address the question of the disposition of SecA on the membrane prior to binding to membrane embedded SecYEG. We mutated to cysteine, one at a time, 25 surface-exposed residues of a Cys-free SecA. To each of these we covalently linked the polarity-sensitive fluorophore NBD whose intensity and fluorescence wavelength-shift change upon vesicle binding report on the the local membrane polarity. We established from these measurements the disposition of SecA bound to the membrane in the absence of SecYEG. Our results confirmed that SecA is anchored in the membrane interface primarily by the positive charges of the N terminus domain. But we found that a region of the nucleotide binding domain II is also important for binding. Both domains are rich in positively charged residues, consistent with electrostatic interactions playing the major role in membrane binding. Selective replacement of positively charged residues in these domains with alanine resulted in weaker binding to the membrane, which allowed us to quantitate the relative importance of the domains in stabilizing SecA on membranes. Fluorescence quenchers inside the vesicles had little effect on NBD fluorescence, indicating that SecA does not penetrate significantly across the membrane. Overall, the topology of SecA on the membrane is consistent with the conformation of SecA observed in crystallographic and cryo-EM structures of SecA-SecYEG complexes, suggesting that SecA can switch between the membrane-associated and the translocon-associated states without significant changes in conformation., Competing Interests: Declaration of interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)
- Published
- 2022
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20. A hydrophilic microenvironment in the substrate-translocating groove of the YidC membrane insertase is essential for enzyme function.
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Chen Y, Sotomayor M, Capponi S, Hariharan B, Sahu ID, Haase M, Lorigan GA, Kuhn A, White SH, and Dalbey RE
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- Bacillus subtilis enzymology, Cell Membrane metabolism, Escherichia coli chemistry, Escherichia coli enzymology, Hydrophobic and Hydrophilic Interactions, Structure-Activity Relationship, Escherichia coli Proteins chemistry, Escherichia coli Proteins metabolism, Membrane Transport Proteins chemistry, Membrane Transport Proteins metabolism
- Abstract
The YidC family of proteins are membrane insertases that catalyze the translocation of the periplasmic domain of membrane proteins via a hydrophilic groove located within the inner leaflet of the membrane. All homologs have a strictly conserved, positively charged residue in the center of this groove. In Bacillus subtilis, the positively charged residue has been proposed to be essential for interacting with negatively charged residues of the substrate, supporting a hypothesis that YidC catalyzes insertion via an early-step electrostatic attraction mechanism. Here, we provide data suggesting that the positively charged residue is important not for its charge but for increasing the hydrophilicity of the groove. We found that the positively charged residue is dispensable for Escherichia coli YidC function when an adjacent residue at position 517 was hydrophilic or aromatic, but was essential when the adjacent residue was apolar. Additionally, solvent accessibility studies support the idea that the conserved positively charged residue functions to keep the top and middle of the groove sufficiently hydrated. Moreover, we demonstrate that both the E. coli and Streptococcus mutans YidC homologs are functional when the strictly conserved arginine is replaced with a negatively charged residue, provided proper stabilization from neighboring residues. These combined results show that the positively charged residue functions to maintain a hydrophilic microenvironment in the groove necessary for the insertase activity, rather than to form electrostatic interactions with the substrates., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)
- Published
- 2022
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21. Corrigendum to: "The effect of animal-assisted therapy on nursing student anxiety: A randomized control study" [Nurse Educ. Pract. 52 (2021) 103042].
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Anderson D, White SH, Ohm R, Brown S, and Poggio JP
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- 2021
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22. The SecA ATPase motor protein binds to Escherichia coli liposomes only as monomers.
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Roussel G and White SH
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- Cell Membrane metabolism, Escherichia coli metabolism, Escherichia coli Proteins metabolism, Liposomes, Protein Binding, Protein Multimerization, SecA Proteins metabolism, Cell Membrane chemistry, Escherichia coli chemistry, Escherichia coli Proteins chemistry, SecA Proteins chemistry
- Abstract
The essential SecA motor ATPase acts in concert with the SecYEG translocon to secrete proteins into the periplasmic space of Escherichia coli. In aqueous solutions, SecA exists largely as dimers, but the oligomeric state on membranes is less certain. Crystallographic studies have suggested several possible solution dimeric states, but its oligomeric state when bound to membranes directly or indirectly via the translocon is controversial. We have shown using disulfide crosslinking that the principal solution dimer, corresponding to a crystallographic dimer (PDB 1M6N), binds only weakly to large unilamellar vesicles (LUV) formed from E. coli lipids. We report here that other soluble crosslinked crystallographic dimers also bind weakly, if at all, to LUV. Furthermore, using a simple glutaraldehyde crosslinking scheme, we show that SecA is always monomeric when bound to LUV formed from E. coli lipids., Competing Interests: Declaration of competing interest The authors declare no conflicts of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)
- Published
- 2020
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23. Submaximal exercise training, more than dietary selenium supplementation, improves antioxidant status and ameliorates exercise-induced oxidative damage to skeletal muscle in young equine athletes.
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White SH and Warren LK
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- 2020
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24. Correlations of Calf Muscle Macrophage Content With Muscle Properties and Walking Performance in Peripheral Artery Disease.
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Kosmac K, Gonzalez-Freire M, McDermott MM, White SH, Walton RG, Sufit RL, Tian L, Li L, Kibbe MR, Criqui MH, Guralnik JM, S Polonsky T, Leeuwenburgh C, Ferrucci L, and Peterson CA
- Subjects
- Adaptation, Physiological, Aged, Biomarkers analysis, CD11b Antigen analysis, Case-Control Studies, Cross-Sectional Studies, Extracellular Matrix pathology, Female, Humans, Macrophages immunology, Male, Membrane Glycoproteins analysis, Microvascular Density, Middle Aged, Muscle, Skeletal physiopathology, Observational Studies as Topic, Peripheral Arterial Disease diagnosis, Peripheral Arterial Disease physiopathology, Phenotype, Randomized Controlled Trials as Topic, Receptors, Immunologic analysis, Satellite Cells, Skeletal Muscle pathology, Macrophages pathology, Muscle, Skeletal pathology, Peripheral Arterial Disease pathology, Walking
- Abstract
Background Peripheral artery disease (PAD) is a manifestation of atherosclerosis characterized by reduced blood flow to the lower extremities and mobility loss. Preliminary evidence suggests PAD damages skeletal muscle, resulting in muscle impairments that contribute to functional decline. We sought to determine whether PAD is associated with an altered macrophage profile in gastrocnemius muscles and whether muscle macrophage populations are associated with impaired muscle phenotype and walking performance in patients with PAD. Methods and Results Macrophages, satellite cells, and extracellular matrix in gastrocnemius muscles from 25 patients with PAD and 7 patients without PAD were quantified using immunohistochemistry. Among patients with PAD, both the absolute number and percentage of cluster of differentiation (CD) 11b+CD206+ M2-like macrophages positively correlated to satellite cell number ( r =0.461 [ P =0.023] and r =0.416 [ P =0.042], respectively) but not capillary density or extracellular matrix. The number of CD11b+CD206- macrophages negatively correlated to 4-meter walk tests at normal ( r =-0.447, P =0.036) and fast pace ( r =-0.510, P =0.014). Extracellular matrix occupied more muscle area in PAD compared with non-PAD (8.72±2.19% versus 5.30±1.03%, P <0.001) and positively correlated with capillary density ( r =0.656, P <0.001). Conclusions Among people with PAD, higher CD206+ M2-like macrophage abundance was associated with greater satellite cell numbers and muscle fiber size. Lower CD206- macrophage abundance was associated with better walking performance. Further study is needed to determine whether CD206+ macrophages are associated with ongoing reparative processes enabling skeletal muscle adaptation to damage with PAD. Registration URL: https://www.clinicaltrials.gov; Unique identifiers: NCT00693940, NCT01408901, NCT0224660.
- Published
- 2020
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25. Planning for patient-reported outcome implementation: Development of decision tools and practical experience across four clinics.
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Nelson TA, Anderson B, Bian J, Boyd AD, Burton SV, Davis K, Guo Y, Harris BA, Hynes K, Kochendorfer KM, Liebovitz D, Martin K, Modave F, Moses J, Soulakis ND, Weinbrenner D, White SH, Rothrock NE, Valenta AL, and Starren JB
- Abstract
Introduction: Many institutions are attempting to implement patient-reported outcome (PRO) measures. Because PROs often change clinical workflows significantly for patients and providers, implementation choices can have major impact. While various implementation guides exist, a stepwise list of decision points covering the full implementation process and drawing explicitly on a sociotechnical conceptual framework does not exist., Methods: To facilitate real-world implementation of PROs in electronic health records (EHRs) for use in clinical practice, members of the EHR Access to Seamless Integration of Patient-Reported Outcomes Measurement Information System (PROMIS) Consortium developed structured PRO implementation planning tools. Each institution pilot tested the tools. Joint meetings led to the identification of critical sociotechnical success factors., Results: Three tools were developed and tested: (1) a PRO Planning Guide summarizes the empirical knowledge and guidance about PRO implementation in routine clinical care; (2) a Decision Log allows decision tracking; and (3) an Implementation Plan Template simplifies creation of a sharable implementation plan. Seven lessons learned during implementation underscore the iterative nature of planning and the importance of the clinician champion, as well as the need to understand aims, manage implementation barriers, minimize disruption, provide ample discussion time, and continuously engage key stakeholders., Conclusions: Highly structured planning tools, informed by a sociotechnical perspective, enabled the construction of clear, clinic-specific plans. By developing and testing three reusable tools (freely available for immediate use), our project addressed the need for consolidated guidance and created new materials for PRO implementation planning. We identified seven important lessons that, while common to technology implementation, are especially critical in PRO implementation., (© The Association for Clinical and Translational Science 2020.)
- Published
- 2020
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26. Binding of SecA ATPase monomers and dimers to lipid vesicles.
- Author
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Roussel G and White SH
- Subjects
- Escherichia coli Proteins chemistry, Glutamic Acid metabolism, Liposomes chemistry, Protein Binding, Protein Multimerization, SecA Proteins chemistry, Escherichia coli Proteins metabolism, Liposomes metabolism, SecA Proteins metabolism
- Abstract
The Escherichia coli SecA ATPase motor protein is essential for secretion of proteins through the SecYEG translocon into the periplasmic space. Its function relies upon interactions with the surrounding lipid bilayer as well as SecYEG translocon. That negatively charged lipids are required for bilayer binding has been known for >25 years, but little systematic quantitative data is available. We have carried out an extensive investigation of SecA partitioning into large unilamellar vesicles (LUV) using a wide range of lipid and electrolyte compositions, including the principal cytoplasmic salt of E. coli, potassium glutamate, which we have shown stabilizes SecA. The water-to-bilayer transfer free energy is about -7.5 kcal mol
-1 for typical E. coli lipid compositions. Although it has been established that SecA is dimeric in the cytoplasm, we find that the most widely cited dimer form (PDB 1M6N) binds only weakly to LUVs formed from E. coli lipids., (Copyright © 2019 Elsevier B.V. All rights reserved.)- Published
- 2020
- Full Text
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27. Evaluation of dietary trace mineral supplementation in young horses challenged with intra-articular lipopolysaccharide.
- Author
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Millican AA, Leatherwood JL, Coverdale JA, Arnold CE, Bradbery AN, Larson CK, Lamprecht ED, White SH, Paulk CB, Welsh TH Jr, and Wickersham TA
- Abstract
Sixteen weanling Quarter Horses (255 ± 22 kg) were utilized in a 56-d trial to evaluate the effects of trace mineral (TM) source on intra-articular inflammation following a single acute inflammatory insult. Horses were stratified by age, sex, and BW and then randomly assigned to dietary treatment: concentrate formulated with Zn, Mn, Cu, and Co as inorganic sources (CON; n = 8) or complexed TMs (CTM; n = 8). Added TM were formulated at iso-levels across treatments and intakes met or exceeded NRC requirements. Horses were offered 1.75% BW (as-fed) of treatment concentrate and 0.75% BW (as-fed) coastal Bermudagrass hay. Growth measurements were collected on days 0, 28, and 56, and plasma was collected biweekly for determination of Mn, Cu, Zn, and Co concentrations. On day 42, carpal joints were randomly assigned to receive injections of 0.5 ng lipopolysaccharide (LPS) or sterile lactated Ringer's solution (LRS; contralateral control). Synovial fluid was collected at preinjection hours (PIH) 0, and 6, 12, 24, 168, and 336 h post-injection and analyzed for TM concentration, prostaglandin E
2 (PGE2 ), carboxypeptide of type II collagen (CPII), collagenase cleavage neopeptide (C2C), and aggrecan chondroitin sulfate 846 epitope (CS846). Data were analyzed using the MIXED procedure of SAS. Results showed a TM source × LPS × h effect for synovial fluid Co, Cu, and Se ( P < 0.05); concentrations of TM peaked at hour 6 and decreased to preinjection values by hour 168 in both CON and CTM-LPS knees. A delayed peak was observed at hour 12 for CTM-LRS. Peak synovial fluid Cu and Se concentrations were higher in LPS knees, and Co was highest in CTM-LPS. A TM source × h interaction was observed for Zn ( P < 0.05); concentrations peaked at hour 6 in CON vs. hour 12 for CTM. An LPS × h interaction was observed for Mn ( P < 0.01); synovial concentration peaked at hour 6 in LPS knees compared with hour 24 in LRS. Synovial PGE2 , C2C, CPII, and CS846 concentrations were greater with LPS ( P ≤ 0.01), and C2C was greater ( P < 0.01) in CTM compared with CON. Concentrations of CPII and PGE2 were unaffected by diet. A TM source × h × LPS interaction was observed for CS846 ( P = 0.02). Concentrations of CS846 in CTM peaked at 12 h, whereas CON peaked at a lower concentration at 24 h ( P < 0.05). Data indicate sufficient intake of a complexed TM source may support cartilage metabolism through increased aggrecan synthesis and type II collagen breakdown following an intra-articular LPS challenge in growing horses., (© The Author(s) 2020. Published by Oxford University Press on behalf of the American Society of Animal Science.)- Published
- 2020
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28. Altered TAOK2 activity causes autism-related neurodevelopmental and cognitive abnormalities through RhoA signaling.
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Richter M, Murtaza N, Scharrenberg R, White SH, Johanns O, Walker S, Yuen RKC, Schwanke B, Bedürftig B, Henis M, Scharf S, Kraus V, Dörk R, Hellmann J, Lindenmaier Z, Ellegood J, Hartung H, Kwan V, Sedlacik J, Fiehler J, Schweizer M, Lerch JP, Hanganu-Opatz IL, Morellini F, Scherer SW, Singh KK, and Calderon de Anda F
- Subjects
- Adult, Animals, Anxiety genetics, Autism Spectrum Disorder genetics, Autism Spectrum Disorder pathology, Autism Spectrum Disorder psychology, Child, Cognitive Dysfunction genetics, Cognitive Dysfunction metabolism, Cognitive Dysfunction pathology, Cognitive Dysfunction psychology, Dendrites metabolism, Dendrites pathology, Female, Humans, Interpersonal Relations, Male, Mice, Mice, Inbred C57BL, Mice, Knockout, Neurodevelopmental Disorders genetics, Neurodevelopmental Disorders pathology, Neurodevelopmental Disorders psychology, Neurogenesis, Phenotype, Phosphorylation, Protein Serine-Threonine Kinases genetics, Signal Transduction, Synaptic Transmission, Exome Sequencing, Autism Spectrum Disorder metabolism, Neurodevelopmental Disorders metabolism, Protein Serine-Threonine Kinases metabolism, rhoA GTP-Binding Protein metabolism
- Abstract
Atypical brain connectivity is a major contributor to the pathophysiology of neurodevelopmental disorders (NDDs) including autism spectrum disorders (ASDs). TAOK2 is one of several genes in the 16p11.2 microdeletion region, but whether it contributes to NDDs is unknown. We performed behavioral analysis on Taok2 heterozygous (Het) and knockout (KO) mice and found gene dosage-dependent impairments in cognition, anxiety, and social interaction. Taok2 Het and KO mice also have dosage-dependent abnormalities in brain size and neural connectivity in multiple regions, deficits in cortical layering, dendrite and synapse formation, and reduced excitatory neurotransmission. Whole-genome and -exome sequencing of ASD families identified three de novo mutations in TAOK2 and functional analysis in mice and human cells revealed that all the mutations impair protein stability, but they differentially impact kinase activity, dendrite growth, and spine/synapse development. Mechanistically, loss of Taok2 activity causes a reduction in RhoA activation, and pharmacological enhancement of RhoA activity rescues synaptic phenotypes. Together, these data provide evidence that TAOK2 is a neurodevelopmental disorder risk gene and identify RhoA signaling as a mediator of TAOK2-dependent synaptic development.
- Published
- 2019
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29. RAPID COMMUNICATION: Differential skeletal muscle mitochondrial characteristics of weanling racing-bred horses1.
- Author
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Latham CM, Fenger CK, and White SH
- Abstract
Responses of equine skeletal muscle characteristics to growth and training have been shown to differ between breeds. These differential responses may arise in part because muscle fiber type and mitochondrial density differ between breeds, even in untrained racing-bred horses. However, it is not known when these breed-specific differences manifest. To test the hypothesis that weanling Standardbreds (SB) and Thoroughbreds (TB) would have higher mitochondrial measures than Quarter Horses (QH), gluteus medius samples were collected from SB (mean ± SD; 6.2 ± 1.0 mo; n = 10), TB (6.1 ± 0.5 mo; n = 12), and QH (7.4 ± 0.6 mo; n = 10). Citrate synthase (CS) and cytochrome c oxidase (CCO) activities were assessed as markers of mitochondrial density and function, respectively. Mitochondrial oxidative (P) and electron transport system (E) capacities were assessed by high-resolution respirometry (HRR). Data for CCO and HRR are expressed as integrated (per mg protein and per mg tissue wet weight, respectively) and intrinsic (per unit CS). Data were analyzed using PROC MIXED in SAS v 9.4 with breed as a fixed effect. Mitochondrial density (CS) was higher for SB and TB than QH (P ≤ 0.0007). Mitochondrial function (integrated and intrinsic CCO) was higher in TB and QH than SB (P ≤ 0.01). Integrated CCO was also higher in TB than QH (P < 0.0001). However, SB had higher integrated maximum P (PCI+II) and E (ECI+II) than QH (P ≤ 0.02) and greater integrated and intrinsic complex II-supported E (ECII) than both QH and TB (P ≤ 0.02), whereas TB exhibited higher integrated P with complex I substrates (PCI) than SB and QH (P ≤ 0.003) and higher integrated PCI+II and ECI+II than QH (P ≤ 0.02). In agreement, TB and QH had higher contribution of complex I (CI) to max E than SB (P ≤ 0.001), whereas SB had higher contribution of CII than QH and TB (P ≤ 0.002). Despite having higher mitochondrial density than QH and TB, SB showed lower CCO activity and differences in contribution of complexes to oxidative and electron transport system capacities. Breed differences in mitochondrial parameters are present early in life and should be considered when developing feeding, training, medication, and management practices., (© The Author(s) 2019. Published by Oxford University Press on behalf of the American Society of Animal Science.)
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- 2019
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30. Stabilization of SecA ATPase by the primary cytoplasmic salt of Escherichia coli.
- Author
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Roussel G, Lindner E, and White SH
- Subjects
- Cytoplasm metabolism, Dose-Response Relationship, Drug, Enzyme Stability, Glutamic Acid chemistry, Salts chemistry, Salts pharmacology, Structure-Activity Relationship, Temperature, Cytoplasm chemistry, Escherichia coli metabolism, Escherichia coli Proteins metabolism, Glutamic Acid pharmacology, SecA Proteins metabolism
- Abstract
Much is known about the structure, function, and stability of the SecA motor ATPase that powers the secretion of periplasmic proteins across the inner membrane of Escherichia coli. Most studies of SecA are carried out in buffered sodium or potassium chloride salt solutions. However, the principal intracellular salt of E. coli is potassium glutamate (KGlu), which is known to stabilize folded proteins and protein-nucleic acid complexes. Here we report that KGlu stabilizes SecA, including its dimeric state, and increases its ATPase activity, suggesting that SecA is likely fully folded, stable, and active in vivo at 37°C. Furthermore, KGlu also stabilizes a precursor form of the secreted maltose-binding protein., (© 2019 The Protein Society.)
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- 2019
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31. Dropping Out and Other Fates of Transmembrane Segments Inserted by the SecA ATPase.
- Author
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Lindner E and White SH
- Subjects
- Amino Acid Sequence, Escherichia coli Infections microbiology, Humans, Hydrogen chemistry, Hydrophobic and Hydrophilic Interactions, Lipid Bilayers chemistry, Protein Domains, Escherichia coli K12 chemistry, Escherichia coli Proteins chemistry, SecA Proteins chemistry
- Abstract
Type II single-span membrane proteins, such as CadC or RodZ, lacking a signal sequence and having a far-downstream hydrophobic segment, require the SecA secretion motor for insertion into the inner membrane of Escherichia coli. Using two chimeric single-span proteins containing a designed hydrophobic segment H, we have determined the requirements for SecA-mediated secretion, the molecular distinction between TM domains and signal peptides, and the propensity for hydrophobic H-segments to remain embedded within the bilayer after targeting. By means of engineered H-segments and a strategically placed SPase I cleavage site, we determined how targeting and stability of the chimeric proteins are affected by the length and hydrophobicity of the H-segment. Very hydrophobic segments (e.g., 16 Leu) are stably incorporated into the inner membrane, resulting in a C-terminal anchored membrane protein, while a 24L construct was not targeted to the membrane by SecA and remained in the cytoplasm. However, a construct carrying preMalE at the N-terminus led to SecA targeting to SecYEG via the native signal sequence and stable insertion of the downstream 24L H-segment. We show that the RseP intramembrane protease degrades weakly stable H-segments and is a useful tool for investigating the borderline between stable and unstable TM segments. Using RseP
- cells, we find that moderately hydrophobic sequences (e.g., 5Leu + 11Ala) are targeted to SecYEG by SecA and inserted, but subsequently drop out of the membrane into the cytoplasm. Therefore, the free energy of transfer from translocon to bilayer is different from the transfer free energy from membrane to water., (Copyright © 2019 Elsevier Ltd. All rights reserved.)- Published
- 2019
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32. Erratum: Evaluating equine feeding behavior utilizing GrowSafe Systems: a pilot study.
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Dickson EC, Kayser WC, Latham CM, Leatherwood JL, Daigle CL, and White SH
- Abstract
[This corrects the article DOI: 10.1093/tas/txz002.]., (© The Author(s) 2019. Published by Oxford University Press on behalf of the American Society of Animal Science.)
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- 2019
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33. CNTN5 - /+ or EHMT2 - /+ human iPSC-derived neurons from individuals with autism develop hyperactive neuronal networks.
- Author
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Deneault E, Faheem M, White SH, Rodrigues DC, Sun S, Wei W, Piekna A, Thompson T, Howe JL, Chalil L, Kwan V, Walker S, Pasceri P, Roth FP, Yuen RK, Singh KK, Ellis J, and Scherer SW
- Subjects
- Adolescent, Adult, Cells, Cultured, Child, Contactins deficiency, Contactins genetics, Electrophysiological Phenomena, Female, Heterozygote, Histocompatibility Antigens genetics, Histone-Lysine N-Methyltransferase deficiency, Histone-Lysine N-Methyltransferase genetics, Humans, Kinesins genetics, Kinesins metabolism, Male, Middle Aged, Models, Theoretical, Nerve Tissue Proteins genetics, Nerve Tissue Proteins metabolism, Patch-Clamp Techniques, Ubiquitin-Conjugating Enzymes genetics, Ubiquitin-Conjugating Enzymes metabolism, Young Adult, Zinc Finger Protein Gli3 genetics, Zinc Finger Protein Gli3 metabolism, Autistic Disorder physiopathology, Contactins metabolism, Histocompatibility Antigens metabolism, Histone-Lysine N-Methyltransferase metabolism, Induced Pluripotent Stem Cells physiology, Nerve Net physiology, Neurons physiology
- Abstract
Induced pluripotent stem cell (iPSC)-derived neurons are increasingly used to model Autism Spectrum Disorder (ASD), which is clinically and genetically heterogeneous. To study the complex relationship of penetrant and weaker polygenic risk variants to ASD, 'isogenic' iPSC-derived neurons are critical. We developed a set of procedures to control for heterogeneity in reprogramming and differentiation, and generated 53 different iPSC-derived glutamatergic neuronal lines from 25 participants from 12 unrelated families with ASD. Heterozygous de novo and rare-inherited presumed-damaging variants were characterized in ASD risk genes/loci. Combinations of putative etiologic variants ( GLI3/KIF21A or EHMT2/UBE2I ) in separate families were modeled. We used a multi-electrode array, with patch-clamp recordings, to determine a reproducible synaptic phenotype in 25% of the individuals with ASD (other relevant data on the remaining lines was collected). Our most compelling new results revealed a consistent spontaneous network hyperactivity in neurons deficient for CNTN5 or EHMT2. The biobank of iPSC-derived neurons and accompanying genomic data are available to accelerate ASD research., Editorial Note: This article has been through an editorial process in which authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter)., Competing Interests: ED, MF, SW, DR, SS, WW, AP, TT, JH, LC, VK, SW, PP, FR, RY, KS, JE No competing interests declared, SS Serves on the Scientific Advisory Committees of Population Bio and Deep Genomics, and intellectual property originating from his research and held at the Hospital for Sick Children is licensed to Lineagen, and separately Athena Diagnostics., (© 2019, Deneault et al.)
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- 2019
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34. Complete Disruption of Autism-Susceptibility Genes by Gene Editing Predominantly Reduces Functional Connectivity of Isogenic Human Neurons.
- Author
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Deneault E, White SH, Rodrigues DC, Ross PJ, Faheem M, Zaslavsky K, Wang Z, Alexandrova R, Pellecchia G, Wei W, Piekna A, Kaur G, Howe JL, Kwan V, Thiruvahindrapuram B, Walker S, Lionel AC, Pasceri P, Merico D, Yuen RKC, Singh KK, Ellis J, and Scherer SW
- Published
- 2019
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35. Evaluating equine feeding behavior utilizing GrowSafe Systems: a pilot study.
- Author
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Dickson EC, Kayser WC, Latham CM, Leatherwood JL, Daigle CL, and White SH
- Abstract
Equine research and management is limited to single-housing systems if individual animal intake is to be precisely recorded. Even then, dry forage intake is difficult to quantify accurately due to stomping or mixing hay with fecal matter and bedding. In cattle management, GrowSafe Systems (GrowSafe) is a commonly used tool to closely monitor individual animal feeding data using radio frequency identification (RFID) tag technology. Animals are equipped with a unique RFID tag that is read by the feed bunks each time the animal lowers its head into the bunk to consume feed. The objectives of this pilot study were 1) to test the feasibility of use of the GrowSafe system with horses by measuring intake of dry hay and 2) to characterize feeding behaviors of horses in an individually housed (without competition) or group-housed (with competition) setting. To test the hypothesis that horses would consume more hay when individually (NOCOMP) compared to group-housed (COMP), 10 mature Quarter Horses (14 ± 1.5 yr) were placed in one of four pens containing GrowSafe feed bunks in a 4-wk crossover design consisting of two 2-wk treatment periods. Pen 1 contained five horses with access to two GrowSafe bunks (Period 1: n = 4 mares, n = 1 gelding; Period 2: n = 5 geldings); pens 2, 3, and 4 contained one horse each with access to one bunk. Horses were individually fed 0.25% body weight (BW; dry matter [DM] basis) of a commercial concentrate once per day and were allowed Coastal bermudagrass hay in the GrowSafe bunks ad libitum. Although five horses were used in the group-housed (COMP) pen to more closely mimic a true group environment, only data from horses that experienced both housing systems ( n = 3 mares and n = 3 geldings) were used for statistical analyses. Hourly ( P = 0.008) and daily ( P = 0.003) durations of hay feeding were higher for NOCOMP compared to COMP horses, and total daily intake (g DM/kg BW) of NOCOMP horses tended to be greater ( P = 0.09) than COMP horses. Conversely, eating rate (g DM/kg BW/min) was greater ( P = 0.04) for COMP compared to NOCOMP mares but was unaffected by housing in geldings. The GrowSafe system may provide an opportunity for efficient and effective monitoring of individual horse feed intake and feeding behavior in group-housing situations in horses., (© The Author(s) 2019. Published by Oxford University Press on behalf of the American Society of Animal Science.)
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- 2019
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36. Structural Relaxation Processes and Collective Dynamics of Water in Biomolecular Environments.
- Author
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Capponi S, White SH, Tobias DJ, and Heyden M
- Subjects
- Hydrogen Bonding, Molecular Dynamics Simulation, Nanopores, Pyrococcus furiosus chemistry, Temperature, Archaeal Proteins chemistry, SEC Translocation Channels chemistry, Water chemistry
- Abstract
In this simulation study, we investigate the influence of biomolecular confinement on dynamical processes in water. We compare water confined in a membrane protein nanopore at room temperature to pure liquid water at low temperatures with respect to structural relaxations, intermolecular vibrations, and the propagation of collective modes. We observe distinct potential energy landscapes experienced by water molecules in the two environments, which nevertheless result in comparable hydrogen bond lifetimes and sound propagation velocities. Hence, we show that a viscoelastic argument that links slow rearrangements of the water-hydrogen bond network to ice-like collective properties applies to both, the pure liquid and biologically confined water, irrespective of differences in the microscopic structure.
- Published
- 2019
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37. A feasibility study of indocyanine green fluorescence mapping for sentinel lymph node detection in cutaneous melanoma.
- Author
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Lo MCI, White SH, Nunney I, Skrypniuk J, Heaton MJ, and Moncrieff MDS
- Subjects
- Adult, Aged, Feasibility Studies, Fluorescence, Humans, Lymphatic Metastasis, Middle Aged, Multimodal Imaging, Neoplasm Staging, Radiopharmaceuticals, Sensitivity and Specificity, Sentinel Lymph Node diagnostic imaging, Sentinel Lymph Node Biopsy methods, Technetium Tc 99m Aggregated Albumin, Coloring Agents, Indocyanine Green, Melanoma pathology, Skin Neoplasms pathology
- Published
- 2019
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38. The importance of the membrane interface as the reference state for membrane protein stability.
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Ulmschneider JP, Smith JC, White SH, and Ulmschneider MB
- Subjects
- Amino Acids chemistry, Hydrophobic and Hydrophilic Interactions, Lipid Bilayers, Membranes metabolism, Molecular Dynamics Simulation, Peptides chemistry, Protein Structure, Secondary, Thermodynamics, Membrane Proteins chemistry, Protein Stability
- Abstract
The insertion of nascent polypeptide chains into lipid bilayer membranes and the stability of membrane proteins crucially depend on the equilibrium partitioning of polypeptides. For this, the transfer of full sequences of amino-acid residues into the bilayer, rather than individual amino acids, must be understood. Earlier studies have revealed that the most likely reference state for partitioning very hydrophobic sequences is the membrane interface. We have used μs-scale simulations to calculate the interface-to-transmembrane partitioning free energies ΔG
S→TM for two hydrophobic carrier sequences in order to estimate the insertion free energy for all 20 amino acid residues when bonded to the center of a partitioning hydrophobic peptide. Our results show that prior single-residue scales likely overestimate the partitioning free energies of polypeptides. The correlation of ΔGS→TM with experimental full-peptide translocon insertion data is high, suggesting an important role for the membrane interface in translocon-based insertion. The choice of carrier sequence greatly modulates the contribution of each single-residue mutation to the overall partitioning free energy. Our results demonstrate the importance of quantifying the observed full-peptide partitioning equilibrium, which is between membrane interface and transmembrane inserted, rather than combining individual water-to-membrane amino acid transfer free energies., (Copyright © 2018 Elsevier B.V. All rights reserved.)- Published
- 2018
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39. Genetic engineering a large animal model of human hypophosphatasia in sheep.
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Williams DK, Pinzón C, Huggins S, Pryor JH, Falck A, Herman F, Oldeschulte J, Chavez MB, Foster BL, White SH, Westhusin ME, Suva LJ, Long CR, and Gaddy D
- Subjects
- Alkaline Phosphatase genetics, Animals, Bone Development genetics, Female, Humans, Hypophosphatasia genetics, Phenotype, Point Mutation, Sheep, Time Factors, Alkaline Phosphatase metabolism, Disease Models, Animal, Genetic Engineering methods, Hypophosphatasia metabolism
- Abstract
The availability of tools to accurately replicate the clinical phenotype of rare human diseases is a key step toward improved understanding of disease progression and the development of more effective therapeutics. We successfully generated the first large animal model of a rare human bone disease, hypophosphatasia (HPP) using CRISPR/Cas9 to introduce a single point mutation in the tissue nonspecific alkaline phosphatase (TNSALP) gene (ALPL) (1077 C > G) in sheep. HPP is a rare inherited disorder of mineral metabolism that affects bone and tooth development, and is associated with muscle weakness. Compared to wild-type (WT) controls, HPP sheep have reduced serum alkaline phosphatase activity, decreased tail vertebral bone size, and metaphyseal flaring, consistent with the mineralization deficits observed in human HPP patients. Computed tomography revealed short roots and thin dentin in incisors, and reduced mandibular bone in HPP vs. WT sheep, accurately replicating odonto-HPP. Skeletal muscle biopsies revealed aberrant fiber size and disorganized mitochondrial cristae structure in HPP vs. WT sheep. These genetically engineered sheep accurately phenocopy human HPP and provide a novel large animal platform for the longitudinal study of HPP progression, as well as other rare human bone diseases.
- Published
- 2018
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40. Complete Disruption of Autism-Susceptibility Genes by Gene Editing Predominantly Reduces Functional Connectivity of Isogenic Human Neurons.
- Author
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Deneault E, White SH, Rodrigues DC, Ross PJ, Faheem M, Zaslavsky K, Wang Z, Alexandrova R, Pellecchia G, Wei W, Piekna A, Kaur G, Howe JL, Kwan V, Thiruvahindrapuram B, Walker S, Lionel AC, Pasceri P, Merico D, Yuen RKC, Singh KK, Ellis J, and Scherer SW
- Subjects
- Cell Line, Electrodes, Gene Knockout Techniques, HEK293 Cells, Humans, Induced Pluripotent Stem Cells metabolism, Mutagenesis, Insertional genetics, Phenotype, Autistic Disorder genetics, Autistic Disorder physiopathology, Gene Editing, Genetic Predisposition to Disease, Neurons metabolism, Neurons pathology
- Abstract
Autism spectrum disorder (ASD) is phenotypically and genetically heterogeneous. We present a CRISPR gene editing strategy to insert a protein tag and premature termination sites creating an induced pluripotent stem cell (iPSC) knockout resource for functional studies of ten ASD-relevant genes (AFF2/FMR2, ANOS1, ASTN2, ATRX, CACNA1C, CHD8, DLGAP2, KCNQ2, SCN2A, TENM1). Neurogenin 2 (NGN2)-directed induction of iPSCs allowed production of excitatory neurons, and mutant proteins were not detectable. RNA sequencing revealed convergence of several neuronal networks. Using both patch-clamp and multi-electrode array approaches, the electrophysiological deficits measured were distinct for different mutations. However, they culminated in a consistent reduction in synaptic activity, including reduced spontaneous excitatory postsynaptic current frequencies in AFF2/FMR2-, ASTN2-, ATRX-, KCNQ2-, and SCN2A-null neurons. Despite ASD susceptibility genes belonging to different gene ontologies, isogenic stem cell resources can reveal common functional phenotypes, such as reduced functional connectivity., (Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.)
- Published
- 2018
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41. Correction to: Computed Free Energies of Peptide Insertion into Bilayers are Independent of Computational Method.
- Author
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Gumbart JC, Ulmschneider MB, Hazel A, White SH, and Ulmschneider JP
- Abstract
The original version of the article unfortunately contained an error in NIH support grant number RO1-GM74639 in the Acknowledgements section. The correct grant number is RO1-GM74637. This has been corrected with this erratum.
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- 2018
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42. Computed Free Energies of Peptide Insertion into Bilayers are Independent of Computational Method.
- Author
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Gumbart JC, Ulmschneider MB, Hazel A, White SH, and Ulmschneider JP
- Subjects
- Hydrophobic and Hydrophilic Interactions, Molecular Dynamics Simulation, Temperature, Thermodynamics, Computational Biology methods, Lipid Bilayers chemistry, Peptides chemistry
- Abstract
We show that the free energy of inserting hydrophobic peptides into lipid bilayer membranes from surface-aligned to transmembrane inserted states can be reliably calculated using atomistic models. We use two entirely different computational methods: high temperature spontaneous peptide insertion calculations as well as umbrella sampling potential-of-mean-force (PMF) calculations, both yielding the same energetic profiles. The insertion free energies were calculated using two different protein and lipid force fields (OPLS protein/united-atom lipids and CHARMM36 protein/all-atom lipids) and found to be independent of the simulation parameters. In addition, the free energy of insertion is found to be independent of temperature for both force fields. However, we find major difference in the partitioning kinetics between OPLS and CHARMM36, likely due to the difference in roughness of the underlying free energy surfaces. Our results demonstrate not only a reliable method to calculate insertion free energies for peptides, but also represent a rare case where equilibrium simulations and PMF calculations can be directly compared.
- Published
- 2018
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43. The twin peg Oxford knee - Medium term survivorship and surgical principles.
- Author
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White SH, Roberts S, and Kuiper JH
- Subjects
- Adult, Aged, Aged, 80 and over, Bone Cements, Cohort Studies, Female, Humans, Male, Middle Aged, Osteoarthritis, Knee surgery, Reoperation, Treatment Outcome, Arthroplasty, Replacement, Knee instrumentation, Arthroplasty, Replacement, Knee methods, Knee Prosthesis
- Abstract
Background: A multicentre study of single peg Oxford knees reported failure associated with osteoarthritis progression, femoral component loosening, unexplained pain and meniscal bearing dislocation. Suboptimally positioned femoral components and intraoperative MCL damage could explain these problems. We hypothesised that modifying implantation technique to optimise femoral component positioning and MCL preservation, and introducing the twin peg Oxford knee would address these problems and improve longer term survival. Moreover, its better congruency in high flexion could reduce wear. This study aims to investigate this hypothesis by asking 1) Is the 98% survivorship up to nine years found in an earlier study sustained at longer term (up to 13 years)? 2) What are the remaining causes of failure?, Methods: We described our modified implantation technique. A cohort of all patients treated by the senior author using this modified technique and the Oxford twin peg cemented knee replacement between September 2003 and August 2013 was investigated. A survival analysis was performed and the causes of failure were analysed., Results: The cohort consisted of 468 patients with 554 medial cemented implants. In all, 16 implants were revised and the 12-year survivorship was 95%. Patients with extended indications had a lower survivorship than those with anteromedial osteoarthritis (10-year survival rate 78% vs 97%, p<0.001). There were no failures due to femoral loosening., Conclusions: Using our surgical principles the cemented twin peg Oxford knee can result in good medium to long-term implant survival, comparable to those obtained by the originating centre for the single peg Oxford knee., (Copyright © 2018 Elsevier B.V. All rights reserved.)
- Published
- 2018
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44. Tyrosine Phosphorylation Determines Afterdischarge Initiation by Regulating an Ionotropic Cholinergic Receptor.
- Author
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White SH, Sturgeon RM, Gu Y, Nensi A, and Magoski NS
- Subjects
- Acetylcholine metabolism, Acetylcholine pharmacology, Animals, Aplysia, Calcium metabolism, Cations, Divalent metabolism, Cells, Cultured, Genistein pharmacology, Membrane Potentials drug effects, Neurotransmitter Agents pharmacology, Patch-Clamp Techniques, Phosphorylation drug effects, Protein Kinase C metabolism, Protein Kinase Inhibitors pharmacology, Protein-Tyrosine Kinases antagonists & inhibitors, Protein-Tyrosine Kinases metabolism, Sphingosine analogs & derivatives, Sphingosine pharmacology, Tissue Culture Techniques, Membrane Potentials physiology, Receptors, Cholinergic metabolism, Tyrosine metabolism
- Abstract
Changes to neuronal activity often involve a rapid and precise transition from low to high excitability. In the marine snail, Aplysia, the bag cell neurons control reproduction by undergoing an afterdischarge, which begins with synaptic input releasing acetylcholine to open an ionotropic cholinergic receptor. Gating of this receptor causes depolarization and a shift from silence to continuous action potential firing, leading to the neuroendocrine secretion of egg-laying hormone and ovulation. At the onset of the afterdischarge, there is a rise in intracellular Ca
2+ , followed by both protein kinase C (PKC) activation and tyrosine dephosphorylation. To determine whether these signals influence the acetylcholine ionotropic receptor, we examined the bag cell neuron cholinergic response both in culture and isolated clusters using whole-cell and/or sharp-electrode electrophysiology. The acetylcholine-induced current was not altered by increasing intracellular Ca2+ via voltage-gated Ca2+ channels, clamping intracellular Ca2+ with exogenous Ca2+ buffers, or activating PKC with phorbol esters. However, lowering phosphotyrosine levels by inhibiting tyrosine kinases both reduced the cholinergic current and prevented acetylcholine from triggering action potentials or afterdischarge-like bursts. In other systems, acetylcholine receptors are often modulated by multiple signals, but bag cell neurons appear to be more restrictive in this regard. Prior work finds that, as the afterdischarge proceeds, tyrosine dephosphorylation leads to biophysical alterations that promote persistent firing. Because this firing is subsequent to the cholinergic input, inhibiting the acetylcholine receptor may represent a means of properly orchestrating synaptically induced changes in excitability., (Copyright © 2018 IBRO. Published by Elsevier Ltd. All rights reserved.)- Published
- 2018
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45. OTUD7A Regulates Neurodevelopmental Phenotypes in the 15q13.3 Microdeletion Syndrome.
- Author
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Uddin M, Unda BK, Kwan V, Holzapfel NT, White SH, Chalil L, Woodbury-Smith M, Ho KS, Harward E, Murtaza N, Dave B, Pellecchia G, D'Abate L, Nalpathamkalam T, Lamoureux S, Wei J, Speevak M, Stavropoulos J, Hope KJ, Doble BW, Nielsen J, Wassman ER, Scherer SW, and Singh KK
- Subjects
- Animals, Autism Spectrum Disorder genetics, Chromosome Deletion, Chromosomes, Human, Pair 15 enzymology, Chromosomes, Human, Pair 15 genetics, Dendritic Spines metabolism, Deubiquitinating Enzymes genetics, Endopeptidases metabolism, Female, Gene Deletion, Genetic Association Studies, Humans, Male, Mice, Phenotype, Prosencephalon pathology, Chromosome Disorders enzymology, Chromosome Disorders genetics, Deubiquitinating Enzymes physiology, Endopeptidases genetics, Intellectual Disability enzymology, Intellectual Disability genetics, Neurodevelopmental Disorders enzymology, Neurodevelopmental Disorders genetics, Seizures enzymology, Seizures genetics
- Abstract
Copy-number variations (CNVs) are strong risk factors for neurodevelopmental and psychiatric disorders. The 15q13.3 microdeletion syndrome region contains up to ten genes and is associated with numerous conditions, including autism spectrum disorder (ASD), epilepsy, schizophrenia, and intellectual disability; however, the mechanisms underlying the pathogenesis of 15q13.3 microdeletion syndrome remain unknown. We combined whole-genome sequencing, human brain gene expression (proteome and transcriptome), and a mouse model with a syntenic heterozygous deletion (Df(h15q13)/+ mice) and determined that the microdeletion results in abnormal development of cortical dendritic spines and dendrite outgrowth. Analysis of large-scale genomic, transcriptomic, and proteomic data identified OTUD7A as a critical gene for brain function. OTUD7A was found to localize to dendritic and spine compartments in cortical neurons, and its reduced levels in Df(h15q13)/+ cortical neurons contributed to the dendritic spine and dendrite outgrowth deficits. Our results reveal OTUD7A as a major regulatory gene for 15q13.3 microdeletion syndrome phenotypes that contribute to the disease mechanism through abnormal cortical neuron morphological development., (Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.)
- Published
- 2018
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- View/download PDF
46. Skeletal muscle from aged American Quarter Horses shows impairments in mitochondrial biogenesis and expression of autophagy markers.
- Author
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Li C, White SH, Warren LK, and Wohlgemuth SE
- Subjects
- Age Factors, Aging genetics, Aging pathology, Animals, Autophagosomes metabolism, Autophagosomes pathology, Autophagy-Related Proteins genetics, DNA, Mitochondrial genetics, DNA, Mitochondrial metabolism, Female, Gene Expression Regulation, Horses genetics, Lysosomes metabolism, Lysosomes pathology, Male, Mitochondria, Muscle genetics, Mitochondria, Muscle pathology, Muscle, Skeletal pathology, Signal Transduction, Aging metabolism, Autophagy, Autophagy-Related Proteins metabolism, Horses metabolism, Mitochondria, Muscle metabolism, Muscle, Skeletal metabolism, Organelle Biogenesis
- Abstract
Aging is associated with decreased mitochondrial content and function in skeletal muscle, possibly due to compromised biogenesis and autophagic removal of dysfunctional mitochondria. The aim of this study was to compare markers of mitochondrial content and biogenesis and of autophagy between skeletal muscle from young and aged American Quarter Horses. Citrate synthase protein and mtDNA copy number were decreased in triceps brachii (TB) muscle (P<0.05) from aged horses, suggesting an age-related decline in mitochondrial content. Concomitantly, mRNA expression of PGC-1α and TFAM, regulators of mitochondrial biogenesis, was lower in aged compared to young TB (P<0.05). Expression of autophagy markers suggested an age-associated decline of autophagy. The autophagosomal cargo protein SQSTM/p62 accumulated with age in both muscles (P<0.05). Expression of Autophagy-related protein Atg5 (P<0.05) and the autophagosome-bound form of Microtubule-associated protein light chain 3 (LC3-II; P<0.05) were lower in aged compared to young TB. While LC3 transcript level was elevated in aged compared to young GM (P<0.001), protein expression of LC3-II was unaffected. Gene expression of Lysosomal Membrane-Associated Protein 2 (LAMP2) was not affected by age in either muscle. However, LAMP2 protein expression declined with age (P<0.05), suggesting a decline in autophagosome-lysosome fusion. Taken together, our data indicate that equine skeletal muscle mitochondrial content and biogenesis were impaired with age. Further, autophagosome formation and lysosomal degradation were negatively affected in aged TB and GM, respectively. Future research needs to explore whether interventions targeting these cellular processes can prolong health and performance of aging American Quarter Horses., (Copyright © 2017 Elsevier Inc. All rights reserved.)
- Published
- 2018
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47. Starring or Supporting Role? Satellite Cells and Skeletal Muscle Fiber Size Regulation.
- Author
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Murach KA, Fry CS, Kirby TJ, Jackson JR, Lee JD, White SH, Dupont-Versteegden EE, McCarthy JJ, and Peterson CA
- Subjects
- Animals, Extracellular Matrix physiology, Humans, Hypertrophy physiopathology, Muscle Fibers, Skeletal physiology, Muscle, Skeletal growth & development, Satellite Cells, Skeletal Muscle physiology
- Abstract
Recent loss-of-function studies show that satellite cell depletion does not promote sarcopenia or unloading-induced atrophy, and does not prevent regrowth. Although overload-induced muscle fiber hypertrophy is normally associated with satellite cell-mediated myonuclear accretion, hypertrophic adaptation proceeds in the absence of satellite cells in fully grown adult mice, but not in young growing mice. Emerging evidence also indicates that satellite cells play an important role in remodeling the extracellular matrix during hypertrophy., (Copyright © 2018 Int. Union Physiol. Sci./Am. Physiol. Soc.)
- Published
- 2018
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48. Submaximal exercise training improves mitochondrial efficiency in the gluteus medius but not in the triceps brachii of young equine athletes.
- Author
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White SH, Warren LK, Li C, and Wohlgemuth SE
- Subjects
- Animals, Athletes, Buttocks, Electron Transport, Female, Forelimb, Male, Mitochondria metabolism, Muscle, Skeletal physiology, Organelle Biogenesis, Oxidation-Reduction, Thigh, Horses physiology, Physical Conditioning, Animal methods, Physical Conditioning, Animal physiology
- Abstract
We tested the hypothesis that, similar to humans and rodents, exercise training would enhance mitochondrial (Mt) biogenesis and function in skeletal muscle of young horses. Twenty-four Quarter Horse yearlings were randomly assigned to either submaximal exercise training or no forced exercise (untrained). Biopsies were collected from the gluteus medius and triceps brachii before and after 9 wk of treatment. Citrate synthase activity was lower (P < 0.0001) and cytochrome c oxidase activity per Mt unit was higher (P < 0.0001) in gluteus compared to triceps, but neither changed over the trial period. From wk 0 to 9, intrinsic Mt respiration (P
CI , PCI+II ; P = 0.008) and electron transport capacity (ECI+II ; P = 0.01) increased, and LEAK-related flux control factor (FCFL ; P = 0.02) decreased in both muscles. After 9 wk of training, gluteus muscle exhibited higher (P < 0.05) intrinsic PCI , PCI+II , ECI+II , and FCFCI and FCFCI+II , and lower FCFL (P = 0.0002). Mitochondrial content did not change from wk 0 to 9, and also not in response to submaximal exercise training. Improvements in Mt function were most directly related to ongoing growth of horses independent of muscle group, and training further enhanced Mt function in the gluteus medius.- Published
- 2017
- Full Text
- View/download PDF
49. Transmembrane helices containing a charged arginine are thermodynamically stable.
- Author
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Ulmschneider MB, Ulmschneider JP, Freites JA, von Heijne G, Tobias DJ, and White SH
- Subjects
- Amino Acid Sequence, Protein Conformation, alpha-Helical, Protein Stability, Thermodynamics, Arginine chemistry, Lipid Bilayers chemistry, Membrane Proteins chemistry, Membrane Proteins metabolism, Molecular Dynamics Simulation
- Abstract
Hydrophobic amino acids are abundant in transmembrane (TM) helices of membrane proteins. Charged residues are sparse, apparently due to the unfavorable energetic cost of partitioning charges into nonpolar phases. Nevertheless, conserved arginine residues within TM helices regulate vital functions, such as ion channel voltage gating and integrin receptor inactivation. The energetic cost of arginine in various positions along hydrophobic helices has been controversial. Potential of mean force (PMF) calculations from atomistic molecular dynamics simulations predict very large energetic penalties, while in vitro experiments with Sec61 translocons indicate much smaller penalties, even for arginine in the center of hydrophobic TM helices. Resolution of this conflict has proved difficult, because the in vitro assay utilizes the complex Sec61 translocon, while the PMF calculations rely on the choice of simulation system and reaction coordinate. Here we present the results of computational and experimental studies that permit direct comparison with the Sec61 translocon results. We find that the Sec61 translocon mediates less efficient membrane insertion of Arg-containing TM helices compared with our computational and experimental bilayer-insertion results. In the simulations, a combination of arginine snorkeling, bilayer deformation, and peptide tilting is sufficient to lower the penalty of Arg insertion to an extent such that a hydrophobic TM helix with a central Arg residue readily inserts into a model membrane. Less favorable insertion by the translocon may be due to the decreased fluidity of the endoplasmic reticulum (ER) membrane compared with pure palmitoyloleoyl-phosphocholine (POPC). Nevertheless, our results provide an explanation for the differences between PMF- and experiment-based penalties for Arg burial.
- Published
- 2017
- Full Text
- View/download PDF
50. YidC Insertase of Escherichia coli: Water Accessibility and Membrane Shaping.
- Author
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Chen Y, Capponi S, Zhu L, Gellenbeck P, Freites JA, White SH, and Dalbey RE
- Subjects
- Alkylation, Cell Membrane metabolism, Crystallography, X-Ray, Cysteine chemistry, Escherichia coli chemistry, Models, Molecular, Molecular Dynamics Simulation, Protein Stability, Protein Structure, Secondary, Escherichia coli enzymology, Escherichia coli Proteins chemistry, Escherichia coli Proteins metabolism, Membrane Transport Proteins chemistry, Membrane Transport Proteins metabolism, Water metabolism
- Abstract
The YidC/Oxa1/Alb3 family of membrane proteins function to insert proteins into membranes in bacteria, mitochondria, and chloroplasts. Recent X-ray structures of YidC from Bacillus halodurans and Escherichia coli revealed a hydrophilic groove that is accessible from the lipid bilayer and the cytoplasm. Here, we explore the water accessibility within the conserved core region of the E. coli YidC using in vivo cysteine alkylation scanning and molecular dynamics (MD) simulations of YidC in POPE/POPG membranes. As expected from the structure, YidC possesses an aqueous membrane cavity localized to the membrane inner leaflet. Both the scanning data and the MD simulations show that the lipid-exposed transmembrane helices 3, 4, and 5 are short, leading to membrane thinning around YidC. Close examination of the MD data reveals previously unrecognized structural features that are likely important for protein stability and function., (Copyright © 2017 Elsevier Ltd. All rights reserved.)
- Published
- 2017
- Full Text
- View/download PDF
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