Archivos de biologia y medicina experimentales最新文献

Isolated cells from rat submaxillary gland bound 125I-labelled insulin in a time-dependent process that reached a maximum at 30-40 min at 25 degrees C. The radioactivity bound to cells could be dissociated by dilution of the binding site-hormone complex with the incubation buffer. The presence of unlabelled insulin in the incubation buffer inhibited 125I-labelled insulin degradation according to the amount of hormone added. After 10 min of incubation at at 25 degrees C, radioactivity associated to cells was almost exclusively identified as intact 125I-labelled insulin. With increasing times, a greater contribution of final products of degradation in total radioactivity bound to cells was observed; nevertheless, in the presence of unlabelled insulin the radioactivity associated to low molecular weight products markedly decreased. Equilibrium binding data analysis gave rise to a non-linear Scatchard plot, whose high affinity component showed a dissociation constant of 6.6 +/- 0.4 nM. These observations are consistent with the presence of insulin binding sites in rat submaxillary gland cells which are similar in their characteristics to those identified in other tissues.

Oxidative stress, as proposed by H. Sies, indicates a change in the prooxidant/antioxidant balance of a biologic system in favour of the former. It is related to oxidative reactions that occur in aerobic metabolism which can damage biomolecules through generation of reactive oxygen species. The oxidative deterioration of polyunsaturated fatty acids of membrane phospholipids (lipid peroxidation) is one of the consequences of oxidative stress, and has been observed in the liver cell under the influence of ethanol or lindane intoxication, associated with the calorigenic action of thyroid hormones, induced by the rupture of t-butyl hydroperoxide by cellular hemoproteins, or in the autoxidation of a disrupted tissue. Apart from noxious challenges, oxidative free-radical processes are important in numerous physiological reactions, such as NADPH oxidase in the function of macrophages, ribonucleotide reduction in DNA metabolism, or in eicosanoids production.

Three different methods have been applied to the prediction of secondary structure. The prediction that better fitted the chemical data was chosen. Two regions of the bovine growth hormone molecule (111-117 and 166-174) appear to be exposed to the solvent, according to hydropathic analysis but have several charged residues not reactive towards their specific reagents. Two molecular domains are postulated, each one bearing a region with charged residues on its surface and interacting with the other in the molecule by means of saline bridges. The hydrophobic core of the molecule is formed by the ensemble of the hydrophobic region predicted between residues 81 and 108, and the hydrophobic faces of the amphiphilic helices 109-127 and 9-33.

Studies on erythropoietin (Epo) are briefly reviewed in their historical perspective from mid 19th century until its identification as a product of genetic recombination and its clinical trials in 1987. Our own work throughout three decades deals mainly with Epo action on RNA biosynthesis in rat bone marrow. Results show that Epo participation as a fundamental compound in the erythropoietic process, inducing the biosynthesis of a giant RNA probably with hnRNA characteristics, which is processed to functional RNA with the participation of testosterone (Te). Despite the so many experimental data available at present, there is still no conclusive evidence allowing to define the specific molecular mechanisms of action of both hormones at transcriptional level. A model is postulated to explain the effects of Epo and Te on RNA biosynthesis. Finally, the implications of present knowledge for the conceptual approach and design of future work are discussed.

Over the past several years it has become possible to study some of the electrical properties of excitable and endocrine cells by measuring fluxes of radioactive tracer ions; 86Rb fluxes has been widely used to study potassium permeability. We have validated this approach in adrenal glomerulosa cells, in which we demonstrated the presence of a Ca-dependent K channel that is activated by angiotensin II, ATP, the ionophore A23187 and external K. Here, we present evidence that the steroidogenic response of the bovine adrenal glomerulosa cells is related, in the case of angiotensin II, to the inhibitory effect to the hormone on the coefficient rate of 86Rb efflux that occurs after the initial transient increase. This inhibition of the potassium permeability is probable responsible of the depolarization of the cells. Apamin, that blocks the initial transient raise on 86Rb efflux mediated by angiotensin II, has a minor stimulatory action on the hormone induce steroidogenesis; whereas the opposite is true for the steroidogenic action of potassium ions in the presence of apamin. The second groups of experiments examined the effect of angiotensin II on 86Rb fluxes when the Ca in the medium was increased from 0.6 to 1.25 mM in the case of bovine glomerulosa cells or angiotensin was assayed in rat glomerulosa tissue perifused with 0.6 mM Ca; in both conditions only the inhibitory effect in 86Rb efflux was observed. When the effect of external ATP on steroidogenesis was examined a significant increase on aldosterone secretion occurred probable by a similar mechanism. These results are indicative that Ca-mediated K efflux in adrenal glomerulosa cells may provide a modulatory mechanism for agonist action.

Tardive dyskinesia is described as a distinct neurological entity. Its probable etiology, pathophysiology and biochemical pharmacology are reviewed and discussed in the light of the latest findings.

Stable mammalian cell lines synthesizing and secreting Hepatitis B surface particles have been obtained through genetic engineering techniques. These particles show by electron microscopy a size of 22 nm, they are structurally and immunochemically similar to the particles present in the plasma from chronic hepatitis B patients. Therefore these particles are an excellent source for the preparation of a vaccine against the virus.