Intraspecific variation in reproductive physiology and egg quality in the European Starling Sturnus vulgaris

Egg mass shows large intraspecific variation in birds and is repeatable within individuals. The mechanisms underlying this variation are unknown. We hypothesized that measures of egg quality (the mass of yolk protein, yolk lipid, and albumen protein) would be positively correlated with the plasma pools of the yolk precursor vitellogenin, and the masses of the oviduct, metabolic machinery (liver, heart, lungs, kidneys, gizzard, small intestine and pancreas), and endogenous stores of protein and lipid. We tested these predictions in European Starlings Sturnus vulgaris collected at the peak of egg production effort. In contrast to our predictions, both yolk protein and yolk lipid were negatively correlated with plasma vitellogenin levels. Albumen protein was positively related to oviduct mass, but other aspects of body composition failed to explain variation in egg quality. Hence, while we observed correlations between egg composition and peripheral systems (circulating precursor pools and the oviduct), we found no evidence that egg quality is determined by more general processes, i.e., the supply and processing of nutrients.     

Alterations in lipid-linked oligosaccharide metabolism in human melanoma cells concomitant with induction of stress proteins

Challenge of human A375 melanoma cells with sodium arsenite induced the synthesis of stress proteins and stimulated [3H]mannose incorporation into a novel component migrating on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an apparent molecular mass of 14 kDa (designated M14). Enhanced M14 expression was elicited by heavy metals (zinc, copper, cadmium, and nickel), thiol-reactive agents (iodoacetamide and auranofin), and hyperthermia. The kinetics of M14 induction and recovery from stress were similar to those of the stress proteins, but M14 half-life was only 15 min. Incorporation of [3H]mannose into M14 was inhibited by tunicamycin but not by cycloheximide or actinomycin D. M14 was metabolically labeled with [32P]orthophosphate but not by [35S] methionine or [3H]asparagine. Further studies revealed that M14 was selectively soluble in chloroform/methanol/water (10:10:3) and sensitive to both endo-beta-N-acetylglucosaminidase H digestion and mild acid hydrolysis. The latter released a water-soluble mannose-labeled moiety which eluted from Bio-Gel P-6 in a manner similar to Glc3Man9GlcNAc2. Together, these data suggest that M14 is a lipid-oligosaccharide intermediate of N-linked protein glycosylation and that enhanced expression of this class of molecule in response to chemical insults and hyperthermia is a newly described cellular reaction to stress.     

Stimulation of anchorage independent proliferation of human adrenocortical carcinoma cells by inhibition of cholesterol biosynthesis

Proliferation of SW13 human adrenocortical carcinoma cells under anchorage independent conditions was stimulated in a dose-dependent manner by treatment with the cholesterol biosynthesis inhibitor mevinolin. Induction of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity was observed in mevinolin treated cultures. The growth stimulatory effect of mevinolin, but not that of epithelial transforming growth factor, a polypeptide growth factor for SW13 cells, was reversed by exogenous mevalonic acid. However, neither dolichol nor low density lipoprotein supplementation affected the response of SW13 cells to mevinolin. The results suggest that mevalonic acid metabolites may participate in the regulation of anchorage independent growth of SW13 cells.     

Analysis of the Escherichia coli glycogen gene cluster suggests that catabolic enzymes are encoded among the biosynthetic genes

The nucleotide sequences of the Escherichia coli genome between the glycogen biosynthetic genes glgB and glgC, and 1170 bp of DNA which follows glgA have been determined. The region between glgB and glgC contains an open reading frame (ORF) of 1521 bp which we call glgX. This ORF is capable of coding for an M_r 56 684 protein. The deduced amino acid (aa) sequence for the putative product shows significant similarity to the E. coli glycogen branching enzyme, and to several different glucan hydrolases and transferases. The regions of sequence similarity include residues which have been reported to be involved in substrate binding and catalysis by taka-amylase. This suggests that the proposed product may catalyze hydrolysis or glycosyltransferase reactions. The cloned region which follows glgA contains an incomplete ORF (1149 bp), glgY, which appears to encode 383 aa of the N terminus of glycogen phosphorylase, based upon sequence similarity with the enzyme from rabbit muscle (47% identical aa residues) and with maltodextrin phosphorylase from E. coli (37% identical aa residues). Results suggest that neither ORF is required for glycogen biosynthesis. The localization of glycogen biosynthetic and degradative genes together in a cluster may facilitate the regulation of these systems in vivo.