Regulation of liver metallothionein and plasma zinc by the glucocorticoid dexamethasone.
Explore the source record for details and available documents.
Adrenalectomy↗
Biomedical subjects
S G Shapiro
Publications and source records attributed to S G Shapiro.
Cell-free synthesis of metallothionein directed by rat liver polyadenylated messenger ribonucleic acid.
Total RNA was isolated from rat liver polyribosomes and fractionated by oligo(dT)-cellulose chromatography to obtain polyadenylated mRNA. The mRNA was translated in a wheat-germ cell-free protein-synthesizing system containing [3H]glycine, [3H]lysine and [3H]serine. Most of the newly synthesized 3H-labelled polypeptides were removed from the cell-free products by precipitation at pH 4.0. 3H-labelled thionein chains, which were soluble at pH 4.0, were purified by activated-thiol-Sepharose 4B chromatography or by gel-filtration chromatography. Polyribosomal thionein mRNA was found to increase by at least 3-fold after parenteral administration and by 20 h thereafter the ratio of thionein mRNA to total mRNA approached that found in controls. Actinomycin D administration in vivo blocked the Zn2+-induced increase in polyribosomal thionein mRNA content. These data strongly suggest that metallothionein is an inducible protein. The mechanism of regulation appears to involve changes in the synthesis de novo of thionein mRNA and hence the pool of thionein mRNA available for translation.
Animals↗
Platelet membrane fluidity and aggregation of rabbit platelets.
Aggregation of rabbit platelets from citrated plasma in response to ADP was directly correlated with platelet plasma membrane fluidity as determined by fluorescence depolarization measurements with the probe diphenylhexatriene. Rabbits were maintained for periods of 200 and 400 days on potentially hyperlipidemic diets (20% fat by weight) with varying levels of saturated and polyunsaturated fatty acids. Dietary variations were effective in modulating the mole percentage distribution patterns of the platelet phospholipid fatty acids. The major chemical control of membrane fluidity was the actual mass of unsaturated lipid in the cells and not simply the relative percentage distributions of such unsaturated fatty acids. Substantially higher phospholipid/protein ratios were observed upon analysis of platelets and platelet membranes from rabbits after 200- than after 400-day diet periods. Accordingly lipid structures were significantly more fluid in either whole platelets or membrane isolates at the end of the shorter diet period. The observations pertaining to the extent of aggregation and membrane fluidity are in consonance with the general role of membrane fluidity in controlling biological activity and support the concept that platelet aggregation is a membrane-associated phenomenon.
Adenosine Diphosphate↗