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Biomedical subjects

G L Fletcher

Publications and source records attributed to G L Fletcher.

At least 55 records · Page 3Linked to original sources
PubMed1984

Accumulation of winter flounder antifreeze messenger RNA after hypophysectomy.

The effect of hypophysectomy (hypex) on winter flounder antifreeze mRNA accumulation in the liver was examined. Hypophysectomy resulted in a significant decrease in serum freezing temperature, and increases in liver weights, total liver poly(A)+ RNA and antifreeze polypeptides (AFP) mRNA accumulation. The identity of the AFP mRNA in hypex animals was confirmed by gel electrophoresis, cell-free translation, and Northern blot hybridization techniques. Cytoplasmic dot hybridization analysis indicated that the AFP mRNA level in hypex fish approximated that observed in winter animals actively synthesizing AFP. An increase in AFP mRNA was detectable as early as the first day after hypophysectomy and by Day 7 reached 25% of the level found in fish actively synthesizing AFP mRNA during the winter months. Since AFP mRNA is found at very low levels in the control flounder, we suggest that its accumulation after hypophysectomy depends on accelerated transcription. The pituitary gland appears to regulate the liver AFP mRNA level by a negative transcriptional control mechanism.

Animals↗
PubMed1982

Liver hypertrophy in winter flounder following exposure to experimentally oiled sediments.

1. Male winter flounder were exposed to sediments contaminated with Venezuelan crude oil in 3 laboratory experiments of 4-5 months duration. 2. Oil exposure resulted in significant increases in liver weight. This was particularly evident in fish weighing less than 400 g. 3. The enlarged livers of the oil-exposed flounder had reduced concentrations of DNA, protein, Na+ and Zn2+, and increased concentrations of lipid and phospholipid. 4. The reduced DNA and Na+ concentrations suggested liver hypertrophy rather than hyperplasia. 5. The increased phospholipid concentrations suggested growth of membrane structures such as endoplasmic reticulum.

Animals↗
PubMed1981

Antifreeze proteins from the sea raven, Hemitripterus americanus. Further evidence for diversity among fish polypeptide antifreezes.

The antifreeze proteins of the sea raven, Hemitripterus americanus, were isolated and compared with other fish antifreeze proteins. The sea raven contains one major protein of molecular weight 14,000-16,000 with little or no carbohydrate. Except for its similar seasonal appearance, the sea raven antifreeze protein differs from other polypeptide antifreeze in its amino acid composition, secondary structure, and immunological specificity. Amino acid analysis of sea raven antifreeze showed that it contains a high amount of half-cystine, hydrophilic amino acids, and only an average amount of alanine. In contrast, all other fish antifreeze proteins contain approximately 60% alanine and no half-cystine residues. Furthermore, the sea raven antifreeze protein is sensitive to sulfhydryl reagents. The antifreeze activity was decreased by 67% in the presence of 0.01 M dithiothreitol. Circular dichroism studies indicated the absence of significant amounts of alpha-helix and the possible presence of beta-structure. Antibodies raised against the antifreeze protein did not cross-react with the known polypeptide antifreeze from the winter flounder and shorthorn sculpin (Hew, C. L., Fletcher, G. L., and Ananthanarayanan, V. S. (1980) Can. J. Biochem. 58, 377-383). A specific radioimmunoassay was developed for the sea raven antifreeze protein and was used to quantitate the protein concentration in the fish. The seasonal profile obtained by radioimmunoassay was compatible with the antifreeze activity determined with a freezing point osmometer.

Amino Acids↗
PubMed1980

Antifreeze proteins from the shorthorn sculpin, Myoxocephalus scorpius: isolation and characterization.

The antifreeze proteins (AFP) of the shorthorn sculpin, Myoxocephalus scorpius, were isolated and compared with the AFP of the winter flounder. The shorthorn sculpin was found to contain one major and one minor antifreeze protein with an approximate molecular weight of 10 000--11 000 in the winter. The major AFP was isolated and characterized. It had many characteristics in common with the flounder AFP studied in our laboratories. These characteristics included its seasonal appearance, size, amino acid composition, the abundance of alanine in the composition, the extent of antifreeze activity, and the nature of the secondary structure. It is suggested that both the sculpin and flounder AFP are structurally homologous and belong to the same type of polypeptide antifreeze.

Alanine↗
PubMed1979

The binding of zinc to the soluble proteins of intestinal mucosa in winter flounder (Pseudopleuronectes americanus).

1. The binding of Zn2+ to soluble proteins of intestinal mucosa of winter flounder was examined using an equilibrium dialysis technique. 2. There appeared to be more than one binding system present for Zn2+ in the mucosal cytosol. 3. It required four times the normal endogenous Zn2+ level found in the mucosal cytosol to saturate the highest affinity (K1 = 2.42 x 10(7] binding system. 4. Of 10 metals tested Cu2+ was the only one which interfered with Zn2+ binding to the mucosal cytosol proteins. 5. It is postulated that binding proteins in the mucosal cytosol of winter flounder may play a role in the transport of Zn2+.

Animals↗