Home About us Contact
|
Home About us Contact | ||
|
|
||
Physiological Regulator (physiological + regulator)
Selected AbstractsEvidence That Gonadotropin-Releasing Hormone II Is Not a Physiological Regulator of Gonadotropin Secretion in MammalsJOURNAL OF NEUROENDOCRINOLOGY, Issue 9 2003P. M. Gault Abstract Gonadotropin-releasing hormone (GnRH)-II stimulates luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion when administered at high doses in mammals, and this effect has been assumed to be mediated through the GnRH-II receptor expressed on gonadotropes. This study used two selective GnRH-I receptor antagonists to test the alternative hypothesis that GnRH-II acts through the GnRH-I receptor to elicit gonadotropin secretion. The antagonist, antide, was used to characterize the receptor-relay because it was a pure antagonist in vitro based on inositol phosphate responses in COS-7 cells transfected with either mammalian GnRH-I and GnRH-II receptors and, in vivo, potently antagonized the gonadotropin-releasing effect of a single injection of 250 ng GnRH-I in our sexually inactive sheep model. In a series of studies in sheep, antide (i) blocked the acute LH response to a single injection of GnRH-II (20 µg antide: 10 µg GnRH-II); (ii) blocked both the acute, pulsatile LH response and the FSH priming response to 2-hourly injections of GnRH-II over 36 h (100 µg antide/8 h: 4 µg GnRH-II/2 h); and (iii) chronically blocked both the pulsatile LH response and the marked FSH priming response to 4-hourly injections of GnRH-II over 10 days (75 µg antide/8 h: 4 µg GnRH-II/4 h). In two final experiments, the GnRH-I antagonist 135-18, shown previously to agonize the mammalian GnRH-II receptor, blocked the gonadotropin-releasing effects of GnRH-I (250 ng) but failed to elicit an LH response when given alone, and simultaneous administration of GnRH-II (250 ng) failed to alter the LH-releasing effect of GnRH-I (50,500 ng). These data thus support our hypothesis. Based on additional literature, it is unlikely that the GnRH-II decapeptide is a native regulator of the gonadotrope in mammals. [source] Retinoic acid is a negative physiological regulator of N-cadherin during early avian heart morphogenesisDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 9 2009Mahmoud Romeih The vitamin A-deficient (VAD) early avian embryo has a grossly abnormal cardiovascular system that is rescued by treating the embryo with the vitamin A-active form, retinoic acid (RA). Here we examine the role of N-cadherin (N-cad) in RA-regulated early cardiovascular morphogenesis. N-cad mRNA and protein are expressed globally in the presomite through HH14 normal and VAD quail embryos. The expression in VAD embryos prior to HH10 is significantly higher than that in normal embryos. Functional analyses of the N-cad overproducing VAD embryos reveal N-cad involvement in the RA-regulated cardiovascular development and suggest that N-cad expression may be mediated by Msx1. We provide evidence that in the early avian embryo, endogenous RA is a negative physiological regulator of N-cad. We hypothesize that a critical endogenous level of N-cad is needed for normal early cardiovascular morphogenesis to occur and that this level is ensured by stage-specific, developmentally regulated RA signaling. [source] Hypoxia-inducible factor as a physiological regulatorEXPERIMENTAL PHYSIOLOGY, Issue 6 2005Patrick H. Maxwell Hypoxia-inducible factor (HIF) is a transcription complex which responds to changes in oxygen, providing cells with a master regulator that coordinates changes in gene transcription. HIF operates in all mammalian cell types and is ancient in evolutionary terms, being conserved in C. elegans and D. melanogaster. This review summarizes recent insights into the molecular events that link reduced oxygenation to HIF activation and emerging insights into the extensive role of HIF in a broad range of physiological processes. [source] Carbon monoxide and oxidative stress in Desulfovibrio desulfuricans B-1388JOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 2 2004M. Davydova Abstract It has been shown that carbon monoxide (CO) in low concentration may be an active biochemical and physiological regulator of cell function. The bases of CO toxicity and cell protection are not clearly understood. To provide insights into these mechanisms, we measured superoxide production by D. desulfuricans B-1388 incubated anaerobically in Postgate medium with or without 5% CO. D. desulfuricans B-1388 growing with CO in the gas phase produced more superoxide radicals then control cells growing in Ar. When the cells were pregrown with CO, NADH oxidase and peroxidase activities were increased. The increase in peroxidase activities of cells growing under CO (particularly NADH peroxidase) suggested that H2O2 was accumulated in cells. Superoxide dismutase (SOD) activity of cells decreased in exponential growth phase and increased in stationary phase. This may be due to CO concentration fall during CO oxidation by CO dehydrogenase. Altogether, our data suggest that superoxide production is a possible mechanism of CO toxicity. © 2004 Wiley Periodicals, Inc. J Biochem Mol Toxicol 18:87,91, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20011 [source] A family of octapamine receptors that specifically induce cyclic AMP production or Ca2+ release in Drosophila melanogasterJOURNAL OF NEUROCHEMISTRY, Issue 2 2005Sabine Balfanz Abstract In invertebrates, the biogenic-amine octopamine is an important physiological regulator. It controls and modulates neuronal development, circadian rhythm, locomotion, ,fight or flight' responses, as well as learning and memory. Octopamine mediates its effects by activation of different GTP-binding protein (G protein)-coupled receptor types, which induce either cAMP production or Ca2+ release. Here we describe the functional characterization of two genes from Drosophila melanogaster that encode three octopamine receptors. The first gene (Dmoa1) codes for two polypeptides that are generated by alternative splicing. When heterologously expressed, both receptors cause oscillatory increases of the intracellular Ca2+ concentration in response to applying nanomolar concentrations of octopamine. The second gene (Dmoa2) codes for a receptor that specifically activates adenylate cyclase and causes a rise of intracellular cAMP with an EC50 of ,3 × 10,8 m octopamine. Tyramine, the precursor of octopamine biosynthesis, activates all three receptors at ,,100-fold higher concentrations, whereas dopamine and serotonin are non-effective. Developmental expression of Dmoa genes was assessed by RT,PCR. Overlapping but not identical expression patterns were observed for the individual transcripts. The genes characterized in this report encode unique receptors that display signature properties of native octopamine receptors. [source] ,-Adrenoceptor stimulation potentiates insulin-stimulated PKB phosphorylation in rat cardiomyocytes via cAMP and PKABRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2010Jorid T Stuenæs Background and purpose:, Genetic approaches have documented protein kinase B (PKB) as a pivotal regulator of heart function. Insulin strongly activates PKB, whereas adrenaline is not considered a major physiological regulator of PKB in heart. In skeletal muscles, however, adrenaline potentiates insulin-stimulated PKB activation without having effect in the absence of insulin. The purpose of the present study was to investigate the interaction between insulin and ,-adrenergic stimulation in regulation of PKB phosphorylation. Experimental approach:, Cardiomyocytes were isolated from adult rats by collagenase, and incubated with insulin, isoprenaline, and other compounds. Protein phosphorylation was evaluated by Western blot and phospho-specific antibodies. Key results:, Isoprenaline increased insulin-stimulated PKB Ser473 and Thr308 phosphorylation more than threefold in cardiomyocytes. Isoprenaline alone did not increase PKB phosphorylation. Isoprenaline also increased insulin-stimulated GSK-3, Ser9 phosphorylation approximately twofold, supporting that PKB phosphorylation increased kinase activity. Dobutamine (,1 -agonist) increased insulin-stimulated PKB phosphorylation as effectively as isoprenaline (more than threefold), whereas salbutamol (,2 -agonist) only potentiated insulin-stimulated PKB phosphorylation by approximately 80%. Dobutamine, but not salbutamol, increased phospholamban Ser16 phosphorylation and glycogen phosphorylase activation (PKA-mediated effects). Furthermore, the cAMP analogue that activates PKA (dibutyryl-cAMP and N6 -benzoyl-cAMP) increased insulin-stimulated PKB phosphorylation by more than threefold without effect alone. The Epac-specific activator 8-(4-chlorophenylthio)-2,-O-methyl-cAMP (007) increased insulin-stimulated PKB phosphorylation by approximately 50%. Db-cAMP and N6 -benzoyl-cAMP, but not 007, increased phospholamban Ser16 phosphorylation. Conclusions and implications:, ,-adrenoceptors are strong regulators of PKB phosphorylation via cAMP and PKA when insulin is present. We hypothesize that PKB mediates important signalling in the heart during ,-adrenergic receptors stimulation. [source] Peroxynitrite: just an oxidative/nitrosative stressor or a physiological regulator as well?BRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2006Péter Ferdinandy British Journal of Pharmacology (2006) 148, 1,3. doi:10.1038/sj.bjp.0706693 [source] Co-Culture of Mouse Epidermal Cells for Studies of PigmentationPIGMENT CELL & MELANOMA RESEARCH, Issue 2 2003Tae-Jin Yoon Interactions between melanocytes and keratinocytes in the skin suggest bi-directional interchanges between these two cell types. Thus, melanocytes cultured alone may not accurately reflect the physiology of the skin and the effects of physiological regulators in vivo, because they do not consider possible interactions with keratinocytes. As more and more pigment genes are identified and cloned, the characterization of their functions becomes more of a challenge, particularly with respect to their roles in the processing and transport of melanosomes and their transfer to keratinocytes. Immortalized melanocytes mutant at these loci are now being routinely generated from mice, but interestingly, successful co-culture of murine melanocytes and keratinocytes is very difficult compared with their human counterparts. Thus, we have now optimized co-culture conditions for murine melanocytes and keratinocytes so that pigmentation and the effects of specific mutations can be studied in a more physiologically relevant context. [source] | |||||||||||||