18 results on '"Sen, Partha"'
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2. Metal-free regioselective bromination of imidazo-heteroarenes: the dual role of an organic bromide salt in electrocatalysis.
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Sen, Partha Pratim, Roy, Vishal Jyoti, and Raha Roy, Sudipta
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BROMINATION , *ELECTROCATALYSIS , *BROMIDES , *TRANSITION metals , *SALT , *WATER chlorination - Abstract
This paper represents an electrochemical transformation by demonstrating the dual role of an organic bromide salt, i.e., tetra-n-butylammonium bromide (TBAB), as a brominating agent and as an electrolyte for the regioselective bromination of several imidazo heteroaromatic motifs. Instead of using a transition metal/external oxidant, this methodology utilized electron holes and electrons by means of anodic oxidation and cathodic reduction to form the desired products in good to excellent yields at ambient temperature. The method is simple, environment friendly and compatible with various functional groups. The significance of this sustainable greener bromination technique relies on the fact that the readily available cost-effective electrodes (C(+)/C(−)) can be reused up to forty times without loss of any electrochemical activities. The electro-oxidative method could efficiently be scaled up and can be extended to chlorination as well. Moreover, this electro-synthetic strategy was extrapolated to the domino organo-electrochemical bromination technique for the synthesis of a brominated imidazo heteroaromatic moiety directly starting from substituted 2-bromoacetophenone and 2-aminopyridine by using catalytic amounts of electrolyte. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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3. Uncertain lifetimes and convergence in a two-country Heckscher–Ohlin model.
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Sen, Partha
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STOCHASTIC convergence , *HECKSCHER-Ohlin principle , *INFINITY (Mathematics) , *FACTORS of production , *PROBABILITY theory , *SET theory - Abstract
In a two-country infinite-horizon model, with two traded goods and two factors of production and no international borrowing and lending, there is no convergence of incomes if there is factor-price equalization. With factor-price equalization, the Euler equations of the two economies become identical. I show that in such a set-up if agents have a non-zero probability of death, then we do get convergence. In the steady state the two economies have identical capital–labor ratios and revert to autarky. [ABSTRACT FROM AUTHOR]
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- 2015
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4. Phenotypic screening and molecular analysis of blast resistance in fragrant rice for marker assisted selection.
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Khan, Mohammad Ashik Iqbal, Sen, Partha Pratim, Bhuiyan, Rejwan, Kabir, Enamul, Chowdhury, Abul Kashem, Fukuta, Yoshimichi, Ali, Ansar, and Latif, Mohammad Abdul
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PHENOTYPES , *RICE blast disease , *GENETIC markers , *MICROBIAL virulence , *PLANT germplasm ,RICE genetics - Abstract
Abstract: Experiments were conducted to identify blast-resistant fragrant genotypes for the development of a durable blast-resistant rice variety during years 2012–2013. The results indicate that out of 140 test materials including 114 fragrant germplasms, 25 differential varieties (DVs) harbouring 23 blast-resistant genes, only 16 fragrant rice germplasms showed comparatively better performance against a virulent isolate of blast disease. The reaction pattern of single-spore isolate of Magnaporthe oryzae to differential varieties showed that Pish, Pi9, Pita-2 and Pita are the effective blast-resistant genes against the tested blast isolates in Bangladesh. The DNA markers profiles of selected 16 rice germplasms indicated that genotype Chinigura contained Pish, Pi9 and Pita genes; on the other hand, both BRRI dhan50 and Bawaibhog contained Pish and Pita genes in their genetic background. Genotypes Jirakatari, BR5, and Gopalbhog possessed Pish gene, while Uknimodhu, Deshikatari, Radhunipagol, Kalijira (3), Chinikanai each contained the Pita gene only. There are some materials that did not contain any target gene(s) in their genetic background, but proved resistant in pathogenicity tests. This information provided valuable genetic information for breeders to develop durable blast-resistant fragrant or aromatic rice varieties in Bangladesh. [Copyright &y& Elsevier]
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- 2014
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5. Comparative Analyses of Lung Transcriptomes in Patients with Alveolar Capillary Dysplasia with Misalignment of Pulmonary Veins and in Foxf1 Heterozygous Knockout Mice.
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Sen, Partha, Dharmadhikari, Avinash V., Majewski, Tadeusz, Mohammad, Mahmoud A., Kalin, Tanya V., Zabielska, Joanna, Ren, Xiaomeng, Bray, Molly, Brown, Hannah M., Welty, Stephen, Thevananther, Sundararajah, Langston, Claire, Szafranski, Przemyslaw, Justice, Monica J., Kalinichenko, Vladimir V., Gambin, Anna, Belmont, John, and Stankiewicz, Pawel
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COMPARATIVE studies , *DYSPLASIA , *PULMONARY vein abnormalities , *KNOCKOUT mice , *DEVELOPMENTAL disabilities , *LUNG diseases , *PATIENTS - Abstract
Alveolar Capillary Dysplasia with Misalignment of Pulmonary Veins (ACDMPV) is a developmental disorder of the lungs, primarily affecting their vasculature. FOXF1 haploinsufficiency due to heterozygous genomic deletions and point mutations have been reported in most patients with ACDMPV. The majority of mice with heterozygous loss-of-function of Foxf1 exhibit neonatal lethality with evidence of pulmonary hemorrhage in some of them. By comparing transcriptomes of human ACDMPV lungs with control lungs using expression arrays, we found that several genes and pathways involved in lung development, angiogenesis, and in pulmonary hypertension development, were deregulated. Similar transcriptional changes were found in lungs of the postnatal day 0.5 Foxf1+/− mice when compared to their wildtype littermate controls; 14 genes, COL15A1, COL18A1, COL6A2, ESM1, FSCN1, GRINA, IGFBP3, IL1B, MALL, NOS3, RASL11B, MATN2, PRKCDBP, and SIRPA, were found common to both ACDMPV and Foxf1 heterozygous lungs. Our results advance knowledge toward understanding of the molecular mechanism of ACDMPV, lung development, and its vasculature pathology. These data may also be useful for understanding etiologies of other lung disorders, e.g. pulmonary hypertension, bronchopulmonary dysplasia, or cancer. [ABSTRACT FROM AUTHOR]
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- 2014
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6. A familial case of alveolar capillary dysplasia with misalignment of pulmonary veins supports paternal imprinting of FOXF1 in human.
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Sen, Partha, Gerychova, Romana, Janku, Petr, Jezova, Marta, Valaskova, Iveta, Navarro, Colby, Silva, Iris, Langston, Claire, Welty, Stephen, Belmont, John, and Stankiewicz, Pawel
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DYSPLASIA , *PULMONARY veins , *RARE diseases , *GENETIC mutation , *HUMAN genetic variation , *HAPLOTYPES , *DISEASES - Abstract
Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) is a rare developmental lung disorder that is uniformly lethal. Affected infants die within the first few weeks of their life despite aggressive treatment, although a few cases of late manifestation and longer survival have been reported. We have shown previously that mutations and deletions in FOXF1 are a cause of this disorder. Although most of the cases of ACD/MPV are sporadic, there have been infrequent reports of familial cases. We present a family with five out of six children affected with ACD/MPV. DNA analysis identified a missense mutation (c.416G>T; p.Arg139Leu) in the FOXF1 gene that segregated in the three affected siblings tested. The same variant is also present as a de novo mutation in the mother and arose on her paternally derived chromosome 16. The two tested affected siblings share the same chromosome 16 haplotype inherited from their maternal grandfather. Their single healthy sibling has a different chromosome 16 haplotype inherited from the maternal grandmother. The results are consistent with paternal imprinting of FOXF1 in human. [ABSTRACT FROM AUTHOR]
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- 2013
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7. Short-term administration of rhGH increases markers of cellular proliferation but not milk protein gene expression in normal lactating women.
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Maningat, Patricia D., Sen, Partha, Rijnkels, Monique, Hadsell, Darryl L., Bray, Molly S., and Haymond, Morey W.
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Growth hormone is one of few pharmacologic agents known to augment milk production in humans. We hypothesized that recombinant human GH (rhGH) increases the expression of cell proliferation and milk protein synthesis genes. Sequential milk and blood samples collected over four days were obtained from five normal lactating women. Following 24 h of baseline milk and blood sampling, rhGH (0.1 mg/kg/day) was administered subcutaneously once daily for 3 days. Gene expression changes were determined by microarray studies utilizing milk fat globule RNA isolated from each milk sample. Following rhGH administration, DNA synthesis and cell cycle genes were induced, while no significant changes were observed in the expression of milk synthesis genes. Expression of glycolysis and citric acid cycle genes were increased by day 4 compared with day 1, while lipid synthesis genes displayed a circadian-like pattern. Cell cycle gene upregulation occurred after a lag of ∼2 days, likely explaining the failure to increase milk production after only 3 days of rhGH treatment. We conclude that rhGH induces expression of cellular proliferation and metabolism genes but does not induce milk protein gene expression, as potential mechanisms for increasing milk production and could account for the known effect of rhGH to increase milk production following 7-10 days. [ABSTRACT FROM AUTHOR]
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- 2011
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8. Genomic and Genic Deletions of the FOX Gene Cluster on 16q24.1 and Inactivating Mutations of FOXF1 Cause Alveolar Capillary Dysplasia and Other Malformations.
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Stankiewicz, Pawel, Sen, Partha, Bhatt, Samarth S., Storer, Mekayla, Zhilian Xia, Bejjani, Bassem A., Zhishuo Ou, Wiszniewska, Joanna, Driscoll, Daniel J., Bolivar, Juan, Bauer, Mislen, Zackai, Elaine H., McDonald-McGinn, Donna, Nowaczyk, Malgorzata M. J., Murray, Mitzi, Shaikh, Tamim H., Martin, Vicki, Tyreman, Matthew, Simonic, Ingrid, and Willatt, Lionel
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DYSPLASIA , *GENETIC mutation , *CHROMOSOMES , *GENES , *GENOMICS - Abstract
Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) isa rare, neonatally lethal developmental disorder of the lung with defining histologic abnormalities typically associated with multiple congenital anomalies (MCA). Using array CGH analysis, we have identified six overlapping microdeletions encompassing the FOX transcription factor gene cluster in chromosome 16q24.1q24.2 in patients with ACD/MPV and MCA. Subsequently, we have identified four different heterozygous mutations (frameshift, nonsense, and no-stop) in the candidate FOXF1 gene in unrelated patients with sporadic ACD/MPV and MCA. Custom-designed, high- resolution microarray analysis of additional ACD/MPV samples revealed one microdeletion harboring FOXF1 and two distinct microdeletions upstream of FOXF1, implicating a position effect. DNA sequence analysis revealed that in six of nine deletions, both breakpoints occurred in the portions of Alu elements showing eight to 43 base pairs of perfect microhomology, suggesting replication error Microhomology-Mediated Break-Induced Replication (MMBIR)/Fork Stalling and Template Switching (FoSTeS) as a mechanism of their formation. In contrast to the association of point mutations in FOXF1 with bowel malrotation, microdeletions of FOXF1 were associated with hypoplastic left heart syndrome and gastrointestinal atresias, probably due to haploinsufficiency for the neighboring FOXC2 and FOXL1 genes. These differences reveal the phenotypic consequences of gene alterations in cis. [ABSTRACT FROM AUTHOR]
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- 2009
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9. Gene expression in the human mammary epithelium during lactation: the milk fat globule transcriptome.
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Maningat, Patricia D., Sen, Partha, Rijnkels, Monique, Sunehag, Agneta L., Hadsell, Darryl L., Bray, Molly, and Haymond, Morey W.
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The molecular physiology underlying human milk production is largely unknown because of limitations in obtaining tissue samples. Determining gene expression in normal lactating women would be a potential step toward understanding why some women struggle with or fail at breastfeeding their infants. Recently, we demonstrated the utility of RNA obtained from breast milk fat globule (MFG) to detect mammary epithelial cell (MEC)-specific gene expression. We used MFG RNA to determine the gene expression profile of human MEC during lactation. Microarray studies were performed using Human Ref-8 BeadChip arrays (Illumina). MFG RNA was collected every 3 h for 24 h from five healthy, exclusively breastfeeding women. We determined that 14,070 transcripts were expressed and represented the MFG transcriptome. According to GeneSpring GX 9, 156 ontology terms were enriched (corrected P < 0.05), which include cellular (n = 3,379 genes) and metabolic (n = 2,656) processes as the most significantly enriched biological process terms. The top networks and pathways were associated primarily with cellular activities most likely involved with milk synthesis. Multiple sampling over 24 h enabled us to demonstrate core circadian clock gene expression and the periodicity of 1,029 genes (7%) enriched for molecular functions involved in cell development, growth, proliferation, and cell morphology. In addition, we found that the MFG transcriptome was comparable to the metabolic gene expression profile described for the lactating mouse mammary gland. This paper is the first to describe the MFG transcriptome in sequential human samples over a 24 h period, providing valuable insights into gene expression in the human MEC. [ABSTRACT FROM AUTHOR]
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- 2009
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10. SKP1 connects cell cycle regulators to the ubiquitin proteolysis machinery through a novel motif...
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Bai, Chang and Sen, Partha
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CELL cycle - Abstract
Identifies the yeast gene, SKP1, that is required for two critical phases of the cell cycle. SKP1 gene as a cyclin F-binding protein; SKPQ as a link between cell cycle regulators and the ubiquitin-mediated proteolysis mechanism.
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- 1996
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11. The maltase-glucoamylase gene: Common ancestry to sucrase-isomaltase with complementary starch digestion activities.
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Nichols, Buford L., Avery, Stephen, Sen, Partha, Swallow, Dallas M., hahn, Dagmar, and Sterchi, Erwin
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GENETICS , *STARCH , *BIOLOGICAL evolution , *DIET , *GLUCOSE - Abstract
Brush-border maltase-glucoamylase (MGA) activity serves as the final step of small intestinal digestion of linear regions of dietary starch to glucose. Brush-border sucrase-isomaltase (SI) activity is complementary, through digestion of branched starch linkages. Here we report the cloning and sequencing of human MGA gene and demonstrate its close evolutionary relationship to SI. The gene is ≈82,000 bp long and located at chromosome 7q34. Forty-eight exons were identified. The 5' gene product, when expressed as the N-terminal protein sequence, hydrolyzes maltose and starch, but not sucrose, and is thus distinct from SI. The catalytic residue was identified by mutation of an aspartic acid and was found to be identical with that described for SI. The exon structures of MGA and SI were identical. This homology of genomic structure is even more impressive than the previously reported 59% amino acid sequence identity. The shared exon structures and peptide domains, including proton donors, suggest that MGA and SI evolved by duplication of an ancestral gene, which itself had already undergone tandem gene duplication. The complementary human enzyme activities allow digestion of the starches of plant origin that make up two-thirds of most diets. [ABSTRACT FROM AUTHOR]
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- 2003
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12. Photocatalysis in Dual Catalysis Systems for Carbon‐Nitrogen Bond Formation.
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Singh, Swati, Roy, Vishal Jyoti, Dagar, Neha, Sen, Partha Pratim, and Roy, Sudipta Raha
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CATALYSIS , *PHOTOCATALYSIS , *SUSTAINABLE chemistry , *CATALYSTS - Abstract
The development of versatile methods for the formation of carbon‐nitrogen bonds has significant impact on the synthetic chemistry community. However, it remains challenging owing to the utilization of costly catalyst systems and harsh reaction conditions. Compared to conventional methods, photoredox catalysis which harnesses the energy from light has emerged as an environmentally benign and cost‐effective strategy for promoting challenging C−N bond constructions. Furthermore, the synergistic action of photoredox catalysis with another catalytic process has a profound impact on the reactivity profiles of many traditional synthetic routes. Over the recent years, immense progress has been made towards expediting photocatalysis in dual‐catalysis for achieving various industrially important C−N bond formation processes under milder conditions. This review highlights the advancement of the state‐of‐the‐art achieved in these dual‐catalytic platforms for the construction of C−N bonds over the last decade. [ABSTRACT FROM AUTHOR]
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- 2021
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13. Alveolar capillary dysplasia with misalignment of pulmonary veins with a wide spectrum of extrapulmonary manifestations.
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Nguyen, Lananh, Riley, Melissa M., Sen, Partha, and Galambos, Csaba
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PULMONARY veins , *NEONATAL diseases , *PANCREATIC acinar cells , *PULMONARY blood vessels , *PATHOLOGISTS , *LUNG diseases , *HISTOLOGY - Published
- 2013
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14. Neck blast disease influences grain yield and quality traits of aromatic rice.
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Ashik Iqbal Khan, Mohammad, Rejwan Bhuiyan, Md, Hossain, Md Shahadat, Pratim Sen, Partha, Ara, Anjuman, Abubakar Siddique, Md, and Ansar Ali, Md
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RICE blast disease , *CROP yields , *RICE quality , *RICE varieties , *STERILITY in plants - Abstract
A critical investigation was conducted to find out the effect of neck blast disease on yield-contributing characters, and seed quality traits of aromatic rice in Bangladesh. Both healthy and neck-blast-infected panicles of three aromatic rice cultivars (high-yielding and local) were collected and investigated at Plant Pathology Division, Bangladesh Rice Research Institute (BRRI), Gazipur, Bangladesh. All of the tested varieties were highly susceptible to neck blast disease under natural conditions, though no leaf blast symptoms appear on leaves. Neck blast disease increased grain sterility percentages, reduced grain size, yield and quality traits of seeds. The degrees of yield and seed quality reduction depended on disease severity and variety's genetic make-up. Unfilled grains were the main source of seed-borne pathogen, especially for blast in the seed lot. Transmission of blast pathogen from neck (panicle base) to seed was very poor. These findings are important, especially concerning the seed certification programme in which seed lots are certified on the basis of field inspection. Finally, controlled experiments are needed to draw more critical conclusions. [ABSTRACT FROM AUTHOR]
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- 2014
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15. Doxorubicin-intercalated nano-hydroxyapatite drug-delivery system for liver cancer: An animal model.
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Kundu, Biswanath, Ghosh, Debasree, Sinha, Mithlesh Kumar, Sen, Partha Sarathi, Balla, Vamsi Krishna, Das, Nirmalendu, and Basu, Debabrata
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LIVER cancer , *DOXORUBICIN , *HYDROXYAPATITE in medicine , *DRUG delivery systems , *ANIMAL models in research , *CANCER-related mortality - Abstract
Abstract: Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related death worldwide, and satisfactory treatment is unavailable. Doxorubicin (DOX) is commonly used for HCC treatment with very limited success and serious side-effects such as cardiotoxicity and non-cancer cell cytotoxicity. Methods: In the present investigation, a new nano-sized hydroxyapatite (HAp)-based drug-delivery system was successfully developed with nano-sized hydroxyapatite (HAp) (sizes 5–30nm) and synthesised with a Ca/P molar ratio of 1.67. After thorough in vitro characterisation, these nano-HAP particles were loaded/intercalated with DOX (50–60% encapsulation efficiency), and thorough characterisation of the size, shape and morphology of the particles was performed. Results: The average drug-loaded nanoparticles had a spherical morphology with a size range of 40–60nm. The in vitro drug-elution kinetics were examined under different pH conditions to account for the actual pH conditions found in the body environment. The kinetics were observed to be ideal for IV therapy to treat HCC. In vivo experiments using animal models demonstrated very promising results in terms of relative liver weight changes and histopathology. Ultimately, ‘high-dose’ HAp-DOX produced maximum suppression of hyperplastic nodules and a minimum number of preneoplastic lesions. In summary, our results indicate that this new formulation is an efficient, safe and reliable treatment method for HCC. [Copyright &y& Elsevier]
- Published
- 2013
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16. A Novel Mutation in FOXF1 Gene Associated with Alveolar Capillary Dysplasia with Misalignment of Pulmonary Veins, Intestinal Malrotation and Annular Pancreas.
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Miranda, Joana, Rocha, Gustavo, Soares, Paulo, Morgado, Hélder, Baptista, Maria João, azevedo, Inês, Fernandes, Susana, Brandão, Otília, Sen, Partha, and Guimarães, Hercília
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DYSPLASIA , *ALVEOLAR nerve , *GENETIC mutation , *PANCREATIC diseases , *INTESTINAL diseases , *PULMONARY veins , *CONGENITAL disorders , *GENETICS , *DISEASES - Abstract
Alveolar capillary dysplasia with misalignment of pulmonary veins (ACD/MPV) is a rare, fatal, neonatal developmental lung disorder, which usually presents as persistent pulmonary hypertension unresponsive to treatment. The authors report the case of a neonate with persistent pulmonary hypertension, associated with duodenal stenosis secondary to annular pancreas and intestinal malrotation. Support treatment, inhaled nitric oxide, oral sildenafil and nebulized iloprost were used with no clinical improvement. The neonate presented an overwhelming course, with hypoxemia refractory to treatment. At autopsy lung histology showed the characteristic features of ACD/MPV. DNA sequence analysis revealed a heterozygous nonsense mutation c.539C>A;p.S180X, in the first exon of FOXF1. FOXF1 has been identified as one of the genes responsible for ACD/MPV associated with multiple congenital malformations. This clinical case is the first report of a heterozygous nonsense mutation c.539C>A;p.S180X in the first exon of FOXF1, in a patient with ACD/MPV associated with annular pancreas and intestinal malrotation. Copyright © 2013 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]
- Published
- 2013
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17. Contribution of mucosal maltase-glucoamylase activities to mouse small intestinal starch alpha-glucogenesis.
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Quezada-Calvillo, Roberto, Robayo-Torres, Claudia C, Opekun, Antone R, Sen, Partha, Ao, Zihua, Hamaker, Bruce R, Quaroni, Andrea, Brayer, Gary D, Wattler, Sigrid, Nehls, Michael C, Sterchi, Erwin E, and Nichols, Buford L
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ACARBOSE , *ANIMAL experimentation , *COMPARATIVE studies , *GENES , *GLUCANS , *GLUCOSE , *GLYCOSIDASES , *INTESTINAL mucosa , *JEJUNUM , *RESEARCH methodology , *MEDICAL cooperation , *MICE , *RESEARCH , *SWEETENERS , *EVALUATION research , *PHARMACODYNAMICS - Abstract
Digestion of starch requires activities provided by 6 interactive small intestinal enzymes. Two of these are luminal endo-glucosidases named alpha-amylases. Four are exo-glucosidases bound to the luminal surface of enterocytes. These mucosal activities were identified as 4 different maltases. Two maltase activities were associated with sucrase-isomaltase. Two remaining maltases, lacking other identifying activities, were named maltase-glucoamylase. These 4 activities are better described as alpha-glucosidases because they digest all linear starch oligosaccharides to glucose. Because confusion persists about the relative roles of these 6 enzymes, we ablated maltase-glucoamylase gene expression by homologous recombination in Sv/129 mice. We assayed the alpha-glucogenic activities of the jejunal mucosa with and without added recombinant pancreatic alpha-amylase, using a range of food starch substrates. Compared with wild-type mucosa, null mucosa or alpha-amylase alone had little alpha-glucogenic activity. alpha-Amylase amplified wild-type and null mucosal alpha-glucogenesis. alpha-Amylase amplification was most potent against amylose and model resistant starches but was inactive against its final product limit-dextrin and its constituent glucosides. Both sucrase-isomaltase and maltase-glucoamylase were active with limit-dextrin substrate. These mucosal assays were corroborated by a 13C-limit-dextrin breath test. In conclusion, the global effect of maltase-glucoamylase ablation was a slowing of rates of mucosal alpha-glucogenesis. Maltase-glucoamylase determined rates of digestion of starch in normal mice and alpha-amylase served as an amplifier for mucosal starch digestion. Acarbose inhibition was most potent against maltase-glucoamylase activities of the wild-type mouse. The consortium of 6 interactive enzymes appears to be a mechanism for adaptation of alpha-glucogenesis to a wide range of food starches. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
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18. Contribution of Mucosal Maltase-Glucoamylase Activities to Mouse Small Intestinal Starch α-Glucogenesis.
- Author
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Quezada-CaIvilIo, Roberto, Robayo-Torres, Claudia C., Opekun, Antone R., Sen, Partha, Zihua Ao, Hamaker, Bruce R., Quaroni, Andrea, Brayer, Gary D., Wattler, Sigrid, Nehls, Michael C., Sterchi, Erwin E., and Nichols, Buford L.
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STARCH synthesis , *SMALL intestine , *GENE expression , *NUCLEOTIDE sequence , *AMYLASES , *OLIGOSACCHARIDES , *ACARBOSE , *DEXTRINS , *LABORATORY mice - Abstract
Digestion of starch requires activities provided by 6 interactive small intestinal enzymes. Two of these are luminal endoglucosidases named α-amylases. Four are exoglucosidases bound to the luminal surface of enterocytes. These mucosal activities were identified as 4 different maltases. Two maltase activities were associated with sucrase-isomaltase. Two remaining maltases, lacking other identifying activities, were named maltase-glucoamylase. These 4 activities are better described as α-glucosidases because they digest all linear starch oligosaccharides to glucose. Because confusion persists about the relative roles of these 6 enzymes, we ablated maltase-glucoamylase gene expression by homologous recombination in Sv/129 mice. We assayed the α-glucogenic activities of the jejunal mucosa with and without added recombinant pancreatic α-amylase, using a range of food starch substrates. Compared with wild-type mucosa, null mucosa or α-amylase alone had little α-glucogenic activity. α-Amylase amplified wild-type and null mucosal α-glucogenesis. α-Amylase amplification was most potent against amylose and model resistant starches but was inactive against its final product limit-dextrin and its constituent glucosides. Both sucrase-isomaltase and maltase-glucoamylase were active with limit-dextrin substrate. These mucosal assays were corroborated by a 13C-limit-dextrin breath test. In conclusion, the global effect of maltase-glucoamylase ablation was a slowing of rates of mucosal α-glucogenesis. Maltase-glucoamylase determined rates of digestion of starch in normal mice and α-amylase served as an amplifier for mucosal starch digestion. Acarbose inhibition was most potent against maltase-glucoamylase activities of the wild-type mouse. The consortium of 6 interactive enzymes appears to be a mechanism for adaptation of α-glucogenesis to a wide range of food starches. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
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