The L-type calcium channel (LTCC) provides trigger Ca2+ for sarcoplasmic reticulum Ca2+-release and LTCC function is influenced by interacting proteins including the LTCC Distal Carboxyl-terminus (DCT) and calmodulin. DCT is proteolytically cleaved, and re-associates with the LTCC complex to regulate calcium channel function. DCT reduces LTCC barium current (IBa,L) in reconstituted channel complexes, yet the contribution of DCT to ICa,L in cardiomyocyte systems is unexplored. This study tests the hypothesis that DCT attenuates cardiomyocyte ICa,L. We measured LTCC current and Ca2+ transients with DCT co-expressed in murine cardiomyocytes. We also heterologously co-expressed DCT and CaV1.2 constructs with truncations corresponding to the predicted proteolytic cleavage site, CaV1.2Δ1801, and a shorter deletion corresponding to well-studied construct, CaV1.2Δ1733. DCT inhibited IBa,L in cardiomyocytes, and in HEK 293 cells expressing CaV1.2Δ1801 and CaV1.2Δ1733. Ca2+-CaM relieved DCT block in cardiomyocytes and HEK cells. The selective block of IBa,L combined with Ca2+-CaM effects suggested that DCT-mediated blockade may be relieved under conditions of elevated Ca2+. We therefore tested the hypothesis that DCT block is dynamic, increasing under relatively low Ca2+, and show that DCT reduced diastolic Ca2+ at low stimulation frequencies but spared high frequency Ca2+-entry. DCT reduction of diastolic Ca2+ and relief of block at high pacing frequencies, and under conditions of supraphysiological bath Ca2+ suggests that a physiological function of DCT is to increase the dynamic range of Ca2+ transients in response to elevated pacing frequencies. Our data motivates the new hypothesis that DCT is a native reverse use-dependent inhibitor of LTCC current.

The discovery that bile acids act as endogenous ligands of the membrane receptor TGR5 and the nuclear receptor FXR increased their significance as regulators of cholesterol, glucose and energy metabolism. Activation of TGR5, expressed on enteroendocrine L cells, by bile acids caused secretion of GLP-1, which stimulates insulin secretion from pancreatic β cells. Expression of TGR5 on pancreatic islet cells and the direct effect of bile acids on the endocrine functions of pancreas, however, are not fully understood. The aim of this study was to identify expression of TGR5 in pancreatic islet cells and determine the effect of bile acids on insulin secretion. Expression of TGR5 was identified by quantitative PCR and western blot in islets from human and mouse, and in α (αTC1-6) and β (MIN6) cells. Release of insulin, glucagon and GLP-1 were measured by ELISA. The signaling pathways coupled to TGR5 activation were identified by direct measurements such as stimulation of G proteins, adenylyl cyclase activity, PI hydrolysis and intracellular Ca2+ in response to bile acids; and confirmed by the use of selective inhibitors that block specific steps in the signaling pathway. Our studies identified expression of TGR5 receptors in β cells and demonstrated that activation of these receptors by both pharmacological ligands (oleanolic acid (OA) and INT-777) and physiological ligand (lithocholic acid, LCA) induced insulin secretion. TGR5 receptors are also expressed in α cells and, activation of TGR5 by OA, INT-777 and LCA at 5 mM glucose induced release of glucagon, which is processed from proglucagon by the selective expression of prohormone convertase 2 (PC2). However, under hyperglycemia, activation of TGR5 in α cells augmented the glucose-induced increase in GLP-1 secretion, which in turn, stimulated insulin secretion. Secretion of GLP-1 from α cells reflected TGR5-mediated increase in PC1 promoter activity and PC1 expression, which selectively converts proglucagon to GLP-1. The signaling pathway activated by TGR5 to mediate insulin and GLP-1 secretion involved Gs/cAMP/Epac/PLC-ε/Ca2+. These results provide insights into the mechanisms involved in the regulation of pancreatic α and β cell function by bile acids and may lead to new therapeutic avenues for the treatment of diabetes.

Mitochondrial diseases encompass a broad range of devastating disorders that typically affect tissues with high-energy requirements. These disorders have been difficult to diagnose and research because of the complexity of mitochondrial genetics, and the large variability seen among patient populations. We have devised and carried out a mechanistic study to generate a cell based model for Leigh’s disease caused by mitochondrial DNA mutation 8993 T>G. Leigh’s disease is a multi-organ system disorder that depends heavily on the mutation burden seen within various tissues. Using new reprogramming and sequencing technologies, we were able to show that Leigh’s disease patient fibroblasts reprogrammed to induced pluripotent stem cells maintain the same level of mutation burden seen in the original patient cell line. Mutation burden was maintained through several passages and spontaneous differentiation. This cell based model could be useful for future pathogenesis studies, or therapeutic drug screenings in a patient and tissue specific manner.

Many fish face low oxygen concentrations (hypoxia) in their natural environments, and they respond to hypoxia through a variety of behavioral, physiological, and cellular mechanisms. Some of these responses involve changes in gene expression. In mammals, the hypoxia inducible factor (HIF) family of transcription factors are the “master regulators” of gene expression during hypoxia, but the study of HIF in fish has been hampered by the lack of reagents to detect this protein in non-mammalian vertebrates. The goals of this thesis are to affinity purify antibodies against HIF from the killifish Fundulus heteroclitus and use them to recover and quantify HIF from killifish cells and tissues. The purified, validated antibodies represent a critical reagent for future studies of the role of HIF in the molecular response of this and other fish to fluctuations in oxygen in their natural environments.

Formé auprès de Gaston Bonnier (1853-1922) à Paris à la fin des années 1880, Henri Devaux (1862-1956) s’impose comme l’un des botanistes prometteurs de sa génération en travaillant sur les échanges gazeux chez les plantes aquatiques. De 1906 à 1932, il occupe la chaire de physiologie végétale de la Faculté des sciences de Bordeaux. Bien que ce ne soit pas son domaine de prédilection, il s’intéresse progressivement à la physico-chimie des lames (ou couches) minces et devient l’une des figures de l’école française qui émerge dans les années 1910 autour de ces questions. Tout au long du premier tiers du XXe siècle, ses travaux sur les effets de surface vont faire autorité, y compris outre-Atlantique, et lui ouvrir les portes de l’Académie des sciences. Les lames minces sont aussi un moyen pour lui de comprendre la structure et le fonctionnement des membranes cellulaires et in fine ceux du vivant à l’échelle moléculaire. En nous appuyant sur près de 10 000 pages de notes de laboratoire inédites, nous avons reconstruit l’essentiel de son cheminement intellectuel dans ce domaine.Ancré dans la foi réformée, Devaux cherche par ailleurs à montrer dans des écrits de vulgarisation que les savoirs scientifiques et la Bible concordent. Il y défend notamment une vision créationniste et fixiste du monde. Devaux lie régulièrement science et religion dans ses carnets de laboratoire et affirme même sa foi dans un article du Journal de physique. / Trained by Gaston Bonnier (1853-1922) in Paris at the end of the 1880s, Henri Devaux (1862-1956) was numbered among the most promising botanists of his generation due to his work on gaseous exchanges of aquatic plants. Between 1906 and 1932, he was professor of plant physiology at the Faculty of sciences of Bordeaux. Even though it was not his primary field of study, he slowly developed an interest in the physico-chemistry of thin films (or layers) and became one of the most prominent figures of the French school that emerged on this topic in the 1910s. Throughout the first third of the 20th century, his works on surface were considered as a reference in this field, also in the United States, and opened him the doors of the Académie des sciences. Thin layers were also for him a way to understand the structure and functions of cellular membranes and, consequently, of the life on the molecular scale. Having worked on almost 10 000 pages of his unexplored laboratory notebooks, we have reconstructed the salient points of his investigative pathway in this field.Rooted in a protestant faith, Devaux also tried to show with science popularization writings that scientific knowledge and the Bible are in harmony. He defended a fixist creationist vision of the world. Devaux regularly linked science and religion in his laboratory notebooks and even claimed his faith in an article published in the Journal de physique.

Foi realizado o pirossequenciamento de duas bibliotecas de cDNA do intestino médio de Tenebrio molitor e as sequências foram submetidos à montagem através do programa Newbler. Visando sanar alguns questionamentos a respeito de muitos tipos de transportadores que pudessem estar envolvidos com funções presumíveis em tamponamento luminal, absorção de nutrientes, envolvimento em mecanismos de secreção de enzimas como a α-manosidases e secreção e absorção de água, foram analisadas sequências de interesse que pudessem esclarecer os fenômenos fisiológicos em questão. O pirossequenciamento revelou 19 sequencias de α-manosidases. Após alinhamentos múltiplos, desconfiou-se que o contig 12 era a continuação da sequência original da α-manosidase. Utilizando-se de iniciadores apropriados, a suspeita foi confirmada e uma sequência completa foi obtida e denominada de TmMan1. Através de cladogramas gerados com as sequências de todos os contigs obtidos, assim como de sequências representativas das famílias 38 e 47 das glicosídeos hidrolases, mostrou que todas a nossas sequências, exceto o contig 6 e 7, pertencem à família 38. Todas as sequências com mais de 100 reads (exceto o contig 9) tiveram a sua expressão tecidual avaliada por RT-PCR. Os resultados mostraram que só são expressos no intestino ou intestino e túbulo de Malpighi, implicando na possibilidade de serem digestivas. Dessas sequências, as únicas com peptídeo sinal são a TmMan1 (contig 12) e o contig 14 e, portanto, devem corresponder às atividades Man1 e Man2. Levando em conta o número de reads, TmMan1 deveria corresponder a Man2 e o contig 14 à Man1. É possível, embora necessite de confirmação, que os contigs 8 e 15 sejam de expressão lisossômica. Um peptídeo sintetizado que correspondia a sequencia única da TmMan1 foi usado para gerar anticorpos, que reconheceram a Man2, mas não a Man1, confirmando a identificação de TmMan1 com a Man2. Esse anticorpo foi também utilizado para imunolocalizar a TmMan1 nas células intestinais de T. molitor. Os resultados mostraram que a TmMan1 é secretada de forma apócrina pela região anterior de intestino de T. molitor. Esse trabalho é o primeiro que mostra a ocorrência de α-manosidases com especificidade similar àquelas lissossômicas, mas que são secretadas apócrinamente para fora da célula, devendo agir no lúmen intestinal, removendo resíduos de manoses de oligossacarídeos manosilados. Foram identificados 10 tipos diferentes de transportadores e na elaboração dos modelos fisiológicos só foram levados em conta aqueles expressos exclusivamente no intestino médio ou no intestino médio e túbulos de Malpighi. A V-ATPase em T.molitor parece ser uma bomba usada para energizar muitos dos transportes ao longo do intestino médio como, por exemplo, o de oligopeptídeos. Já as bombas de Na+ e K+ são responsáveis pelo equilíbrio de cargas e, portanto estão presentes na maioria dos tipos celulares. Duas sequências de cotransportadores de oligopeptídeos/H+ foram encontradas no pirossequenciamento e sua expressão é maior na região posterior, uma vez que ali é a última possibilidade de absorção dos oligopeptídeos que ainda estiverem no lúmen, remanescentes da digestão final de proteínas. Foi demonstrado que T.Molitor absorve aminoácidos e açúcares ao longo de todo o intestino médio, pois estes tipos de transportadores possuem uma expressão uniforme ao longo do intestino médio. Já a expressão dos transportadores de NH3/NH4+ em T.molitor, encontra-se confinada ás regiões onde o pH do intestino médio do inseto é mais ácida. Também há uma expressão de transportadores de cloreto que se manifesta mais intensamente na região anterior. Podemos visualizar que a distribuição dos contigs dos transportadores de bicarbonato encontra-se mais expressiva na região posterior do intestino médio. Os resultados sugerem que a acidificação na região anterior do intestino de T.molitor pode resultar da secreção de NH4+ acompanhado do íon cloreto e a alcalinização na região posterior do lançamento no lúmen de bicarbonato. A importância dos canais de cloreto é que o mesmo balanceia as cargas e desta forma pode ser útil juntamente com o transporte de NH4+, que gera uma carga no lado onde é transportado. Há absorvição de água (junto com glicose) ao longo de todo o intestino médio, enquanto que a secreção de água ocorreria apenas nos dois terços finais do intestino médio com o auxílio de aquaporinas complementado por transportadores de íons, teria como consequência a abosorção líquida de água na região anterior e uma secreção líquida no final do intestino médio. Isso esclarece qual a base molecular para a ocorrência do contrafluxo intestinal evidenciado por experimentos fisiológicos. / Pyrosequencing was performed with two cDNA libraries in the midgut of Tenebrio molitor and the sequences were subjected to assembly with the Newbler program. In order to tackle questions concerning proteins which may be involved in midgut buffering, nutrient absorption, in the secretion of enzymes such as α-mannosidases , and water absorption and secretion, sequences of interest were analyzed in order to clarify those physiological phenomena. The pyrosequencing revealed 19 sequences of α- mannosidases . After multiple alignments, it was suspected that the contig 12 was the continuation of the original sequence of the α-mannosidase. Using appropriate primers, the hypothesis was confirmed and a complete sequence was obtained and named TmMan . Through cladograms generated from the sequences of the contigs obtained, as well as of sequences representing families 38 and 47 of glycoside hydrolases, it was showed that all sequences except the contig 6 and 7 belong to family 38. All sequences with over 100 reads (except contig 9) had their tissue expression assessed by RT-PCR. The results showed that they are expressed only in the midgut or midgut and Malpighian tubules, implying the possibility of having a digestive function. Among these sequences, the only ones with a signal peptide are TmMan1 (contig 12) and contig 14 and therefore they should correspond to the activities Man1 and Man2. Taking into account the number of reads, TmMan1 should correspond to Man2 and contig 14 to Man1. It is possible, though it requires confirmation, that the contigs 8 and 15 are lysosomal. A peptide corresponding to the unique sequence TmMan1 was synthesized and used to generate antibodies that recognized Man2 , but not Man1, confirming the identification of TmMan1 with Man2. This antibody was also used to immunolocalyze TmMan1 in the midgut cells of T. molitor. The results showed that TmMan1 is secreted in an apocrine way by the anterior region of T. molitor midgut. This is the first study that shows the occurrence of α-mannosidases with similar specificity to those lysosomal, but that are secreted in an apocrine way, acting in the midgut lumen, removing mannoses from mannosylated oligosaccharides. We identified 10 different types of carriers and in the development of physiological models it was only taken into account those expressed exclusively in the midgut or midgut and Malpighian tubules . The V- ATPase in T.molitor appears to be a pump used for powering many transports along the midgut, as of oligopeptides. The Na+ and K+ pumps are responsible for charge load balancing and therefore are present in most cell types. Two sequences of oligopeptide / H+ cotransporters were found in the transcriptome and their expression is higher in the posterior region. This agrees with the fact that there is the last possibility of oligopeptides remaining in the lumen to be absorbed. It is highly probable that T.molitor absorbs amino acids and sugars throughout the midgut, once these types of carriers have a uniform expression throughout the midgut . The expression of NH3/NH4+ transporters in T.molitor is confined to the regions where the pH of the insect midgut is more acidic. There is also chloride transporter expression there. The expression of bicarbonate transporters is more significant in the posterior midgut. The results suggest that acidification in the anterior T.molitor midgut may result from the secretion of NH4+ and chloride ions together, whereas the alkalization in the posterior midgut results from bicarbonate release. There is water absortion (along with glucose) throughout the midgut , while the water secretion occurs only in the final two-thirds of the midgut with the aid of aquaporins, complemented by ion transporters. It would result in the net absorption and net secretion of water in the anterior and postertior midgut, respectively. This clarifies the molecular basis of the midgut countercurrent fluxes evidenced by physiological experiments.

Na gravidez, o aumento da resistência à insulina é compensado por alterações morfo-funcionais na ilhota pancreática, como o aumento da proliferação e da secreção de insulina. Após o parto ocorre retorno do pâncreas às condições basais e aumento simultâneo da sensibilidade periférica à insulina. Neste trabalho estudamos os mecanismos moleculares responsáveis pelo remodelamento da ilhota no período perinatal. Os resultados mostram que a fosforilação em serina do STAT3 regula a expressão de SERCA2 e assim, modula a primeira fase da secreção de insulina. A fosforilação do STAT3 é dependente da ativação da ERK1/2. No início da lactação, ocorre redução da fosforilação das ERK1/2 devido ao aumento da expressão da fosfatase MKP1. A ação dos glicocorticóides é essencial para este fenômeno, e depende da expressão diferencial de 11<font face=\"symbol\">b-HSD1 e 11<font face=\"symbol\">b-HSD2. O aumento da sensibilidade periférica à insulina ocorre especificamente em músculos oxidativos no início da lactação, e depende do aumento da expressão de Glut4, IR, da via IRS2-PI3K-AKT e da diminuição da PTP1B. / During pregnancy, the increase in insulin resistance is compensated by morfofunctional adaptations of the pancreatic islets, as seen by an increase in cell proliferation and insulin secretion. After delivery, the endocrine pancreas returns to basal conditions, simultaneously to an increase in peripheral insulin sensitivity. In this work we studied the molecular mechanisms involved in islets remodeling during the peripartum period. Our results show that STAT3 serine phosphorylation regulates SERCA2 expression, thus modulating first phase of insulin secretion. STAT3 serine phosphorylation is dependent on ERK1/2 activation. At the beginning of lactation, ERK1/2 phosphorylation is downregulated by the overexpression of the phosphatase MKP1. The action of glucocorticoids is essential in this mechanism, which depends on the differential expression of 11<font face=\"symbol\">b-HSD1 and 11<font face=\"symbol\">b-HSD2. The increase in peripheral insulin sensitivity occurs specifically on oxidative skeletal muscles, which involves an increase in Glut4 and IR expression, IRS2-PI3K-AKT pathway, and a decrease in PTP1B.

One hypothesis explaining the numerous independent evolutionary transitions from oviparity to viviparity among squamates (snakes and lizards) proposed that squamate embryonic development is independent of eggshell calcium. Recent research showed at least 25% of the calcium in hatchling oviparous squamates is extracted from the shell. Though not a direct test, these results are inconsistent with the hypothesis. To directly test the hypothesis, we removed eggshell calcium (through peeling) early in development of Pantherophis guttatus (corn snake) eggs. Survivorship to hatching did not differ between peeled and intact eggs. Yet hatchlings from peeled eggs were shorter (273.6 ± 3.4 vs. 261.0 ± 3.7 mm, p=0.0028, n=16), lighter (6.36 ±0.22 vs. 5.75 ± 0.23 g, p=0.0158, n=16), and had reduced calcium (40.8 ± 1.7 vs. 30.5 ± 1.8 mg, p

Improvement of feeding regimens for production animals has been hindered by a lack of fundamental knowledge about how the capacity to regulate nutrient absorption across cell membranes affects the function of nutrient metabolizing enzymes. The objective is to determine if the activities and protein content of system X-AG glutamate transporter, its regulatory protein (GTRAP3-18 and ARL6IP1), glutamine synthetase (GS) and glutathione (GSH) content, changes in liver (Experiment 1), longissimus dorsi (LM) and subcutaneous adipose tissue (SF) (Experiment 2) as beef steers transitioned from predominantly-lean (growing) to -lipid (finished) tissue accretion phases. In liver (Experiment 1), system X-AG activity in canalicular membranes was abolished as steers developed from growing to finished stages but did not change in basolateral membranes. EAAC1 protein content in liver homogenates decreased in finished vs. growing steers, whereas GTRAP3-18 and ARL6IP1 content increased and GLT-1 content did not change. Concomitantly, hepatic GS activity decreased in finished steers whereas GS protein content did not differ. Hepatic GSH content did not differ in finished vs. growing steers. These results demonstrate a negative functional relationship between GTRAP3-18 and system X-AG activity with glutamine synthesis capacity in livers of fattened cattle. In addition to liver, skeletal muscle and adipose tissues play important roles in maintaining whole-body glutamate and nitrogen homeostasis. In Experiment 2, Western blot analysis of LM homogenates showed decreased EAAC1 and GS content, whereas GTRAP3-18 and ARL6IP1 did not differ in finished vs. growing steers. GSH content in LM was increased in finished vs. growing steers in concomitance with increased mRNA expression of GSH-synthesizing enzymes. In SF, GTRAP3-18 and ARL6IP1 content was increased, whereas EAAC1 and GS content did not differ. Concomitantly, GSH content in SF was decreased in finished vs. growing steers in parallel with decreased mRNA expression of GSH-metabolizing enzymes. These results demonstrate that the negative regulatory relationship between GTRAP3-18 and ARL6IP1 with EAAC1 and GS expression, which exists in liver, does not exist in LM and SF of fattened cattle; and antioxidant capacity in LM and SF changes and differs as steer compositional gain shifts from lean to lipid phenotype. To further explore the upstream regulatory machinery of EAAC1, transcriptome analysis (Experiment 3) was conducted to gain a greater understanding of hepatic metabolic shifts associated with the change in whole-body compositional gain of growing vs. finished beef steers. The expression of upstream regulators of EAAC1 was decreased in a manner consistent with the decreased EAAC1 activity in Experiment 1. Bioinformatic analysis found that, for amino acid metabolism, finished steers had increased capacities for ammonia, arginine, and urea production, and shunting of amino acid carbons into pyruvate. For carbohydrate metabolism, capacity for glycolysis was inhibited, whereas glycogen synthesis was stimulated in finished steers. For lipid metabolism, finished steers showed decreased capacity for fatty acid activation and desaturation, but increased capacity for fatty acid b-oxidation and lipid storage. In addition, redox capacity and inflammatory responses were decreased in finished steers. Collectively, these data describe novel regulatory relationships of system X-AG in liver and peripheral tissues, and the metabolic mechanisms that control nutrient use efficiency, as beef steers develop from lean to lipid phenotypes.

The ketogenic diet is commonly used to control epilepsy, especially in cases when medications cannot. The diet typically consists of high fat, low carb, and adequate protein and produces a metabolite called acetoacetate. Seizure activity is characterized by glutamate excitotoxicity and therefore glutamate regulation is a point of research for control of these disorders. Acetoacetate is heavily implicated as the primary molecule responsible for decreasing glutamate in the synapse; it is believed that acetoacetate interferes with the transport of glutamate into the synaptic vesicles. The effects on synaptic transmission at glutamatergic synapses was studied in relation to the ketogenic diet in Drosophila larvae for this thesis. Various measures of synaptic transmission were conducted. Acetoacetate decreased neurotransmission at the synapse. It was also found that acetoacetate has direct effects on the postsynaptic membrane, which indicates a novel role for the metabolite.