Biomedical subjects

J A Reig

Publications and source records attributed to J A Reig.

42 records · Page 3Linked to original sources

PubMed1983

Reconstitution of a hormone-sensitive adenylate cyclase with membrane extracts from Neurospora and avian erythrocytes.

Adenylate cyclase activity associated to wild type Neurospora membranes is highly dependent on Mn2+ and insensitive to fluoride, guanyl nucleotides, and cholera toxin. These membranes are able to interact with components of detergent extracts from turkey erythrocyte ghosts. The reconstituted cyclase system is catalytically active in the presence of Mg2+ and it is activated by guanyl-5'-yl imidodiphosphate plus isoproterenol and fluoride. When detergent extracts were prepared from avian erythrocyte membranes treated with cholera toxin, the reconstituted system was stimulated by guanyl-5'-yl imidodiphosphate in the absence of isoproterenol and cyclase activities were higher than those observed with extracts from membranes not treated with the toxin. Dose-response curves for isoproterenol and fluoride in the reconstituted system were similar to those reported for avian erythrocyte and liver membranes, respectively.

Adenylyl Cyclases↗

PubMed1983

Monoclonal antibodies to Neurospora adenylate cyclase.

A monoclonal antibody against Neurospora soluble adenylate cyclase was obtained. The antibody inhibits cyclase activities from several lower eucaryotic organisms but not activities associated to testicular cytosol or turkey erythrocyte membranes.

Adenylyl Cyclase Inhibitors↗

PubMed1982

Soluble adenylate cyclase activity in Neurospora crassa.

A soluble form of adenylate cyclase was extracted from mycelia of Neurospora crassa wild-type strains. This enzyme activity was purified by chromatography on hexyl-amino-Sepharose, agarose and Blue Sepharose and preparative polyacrylamide-gel electrophoresis. On sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, peak fractions from the later purification steps showed a main polypeptide band with an apparent molecular weight of about 66 000. The following hydrodynamic and molecular parameters were established for the Neurospora soluble adenylate cyclase activity: sedimentation coefficient, 6.25 S; Stokes radius, 7.3 nm; partial specific volume, 0.74 ml/g; molecular weight, 202 000; frictional ratio, 1.65. The isoelectric point of this enzyme activity was 4.65. The enzyme was not activated by GTP, [beta gamma-imido]GTP, fluoride or cholera toxin.

Adenylyl Cyclases↗

PubMed1982

Purification and chemical characterization of a W2 protein from brain myelin.

Starting from a pellet of beef brain myelin insoluble in chloroform/methanol (2:1, vol/vol)(Wolfgram protein fraction), a pure W2 protein with apparent molecular weight of 52,000 was isolated by a simple preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis method. A comparative chemical analysis was carried out between purified W2 and a standard tubulin. Glutamic acid and arginine were the N-terminals detected. Similar peptide maps and amino acid composition were also found in both proteins. Immunological cross-reactivity was detected when W2 protein was tested against antitubulin serum. These results suggest that W2 protein could have a tubulin-like protein nature that is associated with the myelin membrane and could play a role in the myelination process.

Amino Acids↗

PubMedDate not supplied

Dihydropyridine BAY-K-8644 activates chromaffin cell calcium channels.

Douglas and Rubin suggested that "the role of acetylcholine as a transmitter at the adrenal medulla is to cause some brief change in medullary cells which allows Ca ions to penetrate them and trigger the catecholamine ejection process". The Ca2+-channel blocking agents, verapamil, nifedipine and nitrendipine, have been used widely to investigate the properties of slow Ca2+ channels in a variety of tissues, including the adrenomedullary chromaffin cell. Recently, small modifications to the nifedipine molecule produced a derivative, BAY-K-8644 (methyl-1,4-dihydro-2, 6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)-pyridine-5-carboxylate), that in contrast to the Ca2+-channel blocking agents, stimulated cardiac and vascular smooth muscle contractility. We have tested whether this compound behaves as a Ca2+-channel activator at the chromaffin cell membrane as shown by Schramm et al. in smooth muscle cells. The experiments described here strongly suggest that it does so.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗

PubMedDate not supplied

Insulin-producing cells derived from stem cells: recent progress and future directions.

Type 1 diabetes is characterized by the selective destruction of pancreatic beta-cells caused by an autoimmune attack. Type 2 diabetes is a more complex pathology which, in addition to beta-cell loss caused by apoptotic programs, includes beta-cell dedifferentiation and peripheric insulin resistance. beta-Cells are responsible for insulin production, storage and secretion in accordance to the demanding concentrations of glucose and fatty acids. The absence of insulin results in death and therefore diabetic patients require daily injections of the hormone for survival. However, they cannot avoid the appearance of secondary complications affecting the peripheral nerves as well as the eyes, kidneys and cardiovascular system. These afflictions are caused by the fact that external insulin injection does not mimic the tight control that pancreatic-derived insulin secretion exerts on the body's glycemia. Restoration of damaged beta-cells by transplantation from exogenous sources or by endocrine pancreas regeneration would be ideal therapeutic options. In this context, stem cells of both embryonic and adult origin (including beta-cell/islet progenitors) offer some interesting alternatives, taking into account the recent data indicating that these cells could be the building blocks from which insulin secreting cells could be generated in vitro under appropriate culture conditions. Although in many cases insulin-producing cells derived from stem cells have been shown to reverse experimentally induced diabetes in animal models, several concerns need to be solved before finding a definite medical application. These refer mainly to the obtainment of a cell population as similar as possible to pancreatic beta-cells, and to the problems related with the immune compatibility and tumor formation. This review will summarize the different approaches that have been used to obtain insulin-producing cells from embryonic and adult stem cells, and the main problems that hamper the clinical applications of this technology.

Adult Stem Cells↗