RESUMO
Glucagon, the counter-regulatory hormone to insulin, is secreted from pancreatic alpha cells in response to low blood glucose. To examine the role of glucagon in glucose homeostasis, mice were generated with a null mutation of the glucagon receptor (Gcgr(-/-)). These mice display lower blood glucose levels throughout the day and improved glucose tolerance but similar insulin levels compared with control animals. Gcgr(-/-) mice displayed supraphysiological glucagon levels associated with postnatal enlargement of the pancreas and hyperplasia of islets due predominantly to alpha cell, and to a lesser extent, delta cell proliferation. In addition, increased proglucagon expression and processing resulted in increased pancreatic glucogen-like peptide 1 (GLP-1) (1-37) and GLP-1 amide (1-36 amide) content and a 3- to 10-fold increase in circulating GLP-1 amide. Gcgr(-/-) mice also displayed reduced adiposity and leptin levels but normal body weight, food intake, and energy expenditure. These data indicate that glucagon is essential for maintenance of normal glycemia and postnatal regulation of islet and alpha and delta cell numbers. Furthermore, the lean phenotype of Gcgr(-/-) mice suggests glucagon action may be involved in the regulation of whole body composition.
Assuntos
Glicemia/metabolismo , Glucagon/sangue , Ilhotas Pancreáticas/patologia , Receptores de Glucagon/genética , Receptores de Glucagon/fisiologia , Animais , Peso Corporal , Calorimetria , Divisão Celular , AMP Cíclico/metabolismo , Epididimo/metabolismo , Epinefrina/farmacologia , Glucose/metabolismo , Hormônios/metabolismo , Hiperplasia , Imuno-Histoquímica , Insulina/metabolismo , Fígado/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Microscopia de Fluorescência , Fenótipo , Fatores de TempoRESUMO
Viable bovine nasal cartilage was examined with magnetic resonance (MR) spectroscopy. Digestion of the proteoglycan matrix by papain or trypsin was accompanied by substantial changes in carbon-13, sodium-23, and hydrogen-1 MR spectra and relaxation parameters, with C-13 MR spectra showing the most pronounced changes. These results indicate the potential of MR spectroscopy (and imaging) for noninvasive evaluation of cartilage disease and monitoring of patients with degenerative joint diseases.
Assuntos
Espectroscopia de Ressonância Magnética , Septo Nasal/metabolismo , Animais , Doenças das Cartilagens/diagnóstico , Bovinos , Técnicas In Vitro , Imageamento por Ressonância Magnética , Septo Nasal/efeitos dos fármacos , Septo Nasal/patologia , Papaína/farmacologia , Tripsina/farmacologiaRESUMO
We have employed 31P nuclear magnetic resonance (NMR) spectroscopy to examine the relationship between cytosolic free Mg2+ ([Mg2+]in), intracellular pH, high energy phosphates, and genetic hypertension using the Wistar-Kyoto rat (WKY) as a control and the spontaneously hypertensive rat (SHR) as a model for essential hypertension. The mean systolic blood pressures (measured using the tail cuff method) of control and hypertensive rats (aged 7 to 12 weeks) were 113 +/- 4 mm Hg (mean +/- 2 SE, n = 14) and 162 +/- 5 mm Hg (mean +/- 2 SE, n = 17), respectively. Intracellular free Mg2+ levels were significantly depleted in the isolated Langendorff perfused hypertensive rat hearts (452 +/- 39 mumol/L, mean +/- 2 SE, n = 17) compared to control hearts (756 +/- 52 mumol/L, n = 14); however, intracellular pH did not differ in the SHR hearts (7.02 +/- 0.03, mean +/- 2 SE, n = 7) compared with controls (7.03 +/- 0.03, n = 7). Although we could not demonstrate a statistically significant difference in the levels of P-creatine or ATP, intracellular Pi was two-fold higher (5.71 +/- 2.28 mmol/L v 2.92 +/- 0.66 mmol/L, n = 4) and the phosphorylation potential, [MgATP]/[MgADP][Pi], was correspondingly lower (3.0 X 10(4) +/- 1.6 x 10(4) v 8.3 X 10(4) +/- 1.4 X 10(4) (mol/L)-1, n = 4) in SHR compared to WKY hearts. These data demonstrate free magnesium depletion in heart muscle and indicate an alteration in cardiac bioenergetics in essential hypertension.
Assuntos
Trifosfato de Adenosina/análise , Hipertensão/metabolismo , Magnésio/análise , Miocárdio/química , Trifosfato de Adenosina/metabolismo , Animais , Pressão Sanguínea/fisiologia , Creatina/análise , Creatina/metabolismo , Concentração de Íons de Hidrogênio , Hipertensão/fisiopatologia , Magnésio/metabolismo , Espectroscopia de Ressonância Magnética/métodos , Masculino , Miocárdio/metabolismo , Fosfatos/análise , Fosfatos/metabolismo , Fósforo , Fosforilação , Ratos , Ratos Endogâmicos SHR , Ratos Endogâmicos WKYRESUMO
Proton and phosphorus-31 nuclear magnetic resonance (1H and 31P NMR) studies of the interaction between a tridecapeptide pheromone, the alpha-factor of Saccharomyces cerevisiae, and sonicated lipid vesicles are reported. 31P NMR studies demonstrate that there is interaction of the peptide with the phosphorus headgroups, and quasielastic light scattering (QLS) studies indicate that lipid vesicles increase in size upon addition of peptide. Previous solution (aqueous and DMSO) studies from this laboratory indicate that alpha-factor is highly flexible with only one long-lived identifiable structural feature, a type II beta-turn spanning the central portion of the peptide. Two-dimensional (2D) 1H nuclear Overhauser effect spectroscopy (NOESY) studies demonstrate a marked ordering of the peptide upon interaction with lipid, suggesting a compact N-terminus, in addition to a stabilized beta-turn. In contrast to our results in both solution and lipid environment, Wakamatsu et al. [Wakamatsu, K., Okada, A., Suzuki, M., Higashijima, T., Masui, Y., Sakakibara, S., & Miyazawa, T. (1986) Eur. J. Biochem. 154, 607-615] proposed a lipid environment conformation, on the basis of one-dimensional transferred NOE studies in D2O, which does not include the beta-turn.
Assuntos
Peptídeos/metabolismo , Feromônios/metabolismo , Fosfolipídeos/metabolismo , Sítios de Ligação , Lipossomos , Espectroscopia de Ressonância Magnética , Fator de Acasalamento , Conformação Proteica , Saccharomyces cerevisiae/metabolismoRESUMO
The conformation of the tridecapeptide alpha-factor of the yeast Saccharomyces cerevisiae was examined in both solution and in the presence of lipid vesicles. CD, differential scanning calorimetry, and phosphorus nmr all indicate that this mating pheromone interacts with lipid vesicles. In both aqueous and organic solution the alpha-factor is a flexible molecule that exhibits features of a type II beta-turn spanning the center of the peptide. Two-dimensional Nuclear Overhauser enhancement spectroscopy gives evidence that the beta-turn is stabilized on interaction of the peptide with lipid vesicles. Our current belief is that the beta-turn may play an important role in the biologically active conformation of the alpha-factor.