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Biomedical subjects

C G Jones

Publications and source records attributed to C G Jones.

26 records · Page 2Linked to original sources
PubMed1993

Effect of dexamethasone on gluconeogenesis, pyruvate kinase, pyruvate carboxylase and pyruvate dehydrogenase flux in isolated hepatocytes.

Treatment of 18 h-starved rats with dexamethasone and subsequent isolation and incubation of the hepatocytes in the presence of the steroid increased gluconeogenic flux with both 1.0 mM pyruvate and 1.0 mM lactate plus 0.2 mM pyruvate as the substrate. The magnitude of stimulation was comparable with both substrates. The increase in glucose output was accompanied by an increased flux through pyruvate carboxylase, although the absolute flux and magnitude were considerably less in the presence of the more reduced substrate. The effect of the steroid on the flux through pyruvate dehydrogenase was substrate-dependent, an inhibition occurring with the more oxidized substrate. There was no effect of steroid treatment on [1-14C]lactate or pyruvate oxidation or on tricarboxylic-acid-cycle flux as measured by [3-14C]pyruvate oxidation. Dexamethasone treatment resulted in a parallel increase in both pyruvate kinase flux and glucose synthesis with both substrates employed, indicating that the steroid had no effect on the partitioning of phosphoenolpyruvate between pyruvate and lactate formation and gluconeogenesis. Similarly there was no effect of the steroid on either the activity ratio or the total pyruvate kinase activity in the cells. It is suggested that the acute effect of the dexamethasone to increase gluconeogenesis resides at the level of phosphoenolpyruvate formation, i.e. pyruvate carboxylase and possibly phosphoenolpyruvate carboxykinase.

Animals↗
PubMed1993

The effect of treatment of the rat with bacterial endotoxin on gluconeogenesis and pyruvate metabolism in subsequently isolated hepatocytes.

The effect of treatment of rats with bacterial endotoxin on gluconeogenesis and the flux through pyruvate kinase, phosphoenolpyruvate carboxykinase (PEPCK), pyruvate carboxylase and pyruvate dehydrogenase (PDH) was measured in isolated hepatocytes, prepared from animals starved for 18 h, incubated in the presence of 1 mM pyruvate. The lipopolysaccharide reduced gluconeogenesis by 50% and lowered the flux through pyruvate kinase, PEPCK and pyruvate carboxylase by comparable amounts. There was no effect of endotoxaemia on PDH flux, indicating that the lowered rate of gluconeogenesis is not the result of a redistribution of pyruvate metabolism between oxidation and carboxylation. The results confirm that a stimulation of pyruvate kinase activity following treatment with lipopolysaccharide is not involved in the inhibition of gluconeogenesis, but that the effect resides at the level of phosphoenolpyruvate formation. The most favoured mechanism for the inhibition of glucose synthesis is via an inhibition of PEPCK and subsequent feedback inhibition of pyruvate carboxylase, although a secondary effect at the level of the mitochondria and pyruvate carboxylase cannot be excluded.

Animals↗
PubMed1985

Mechanism of dye response and interference in the Bradford protein assay.

Bradford Coomassie brilliant blue G-250 protein-binding dye exists in three forms: cationic, neutral, and anionic. Although the anion is not freely present at the dye reagent pH, it is this form that complexes with protein. Dye binding requires a macromolecular form with certain reactive functional groups. Interactions are chiefly with arginine rather than primary amino groups; the other basic (His, Lys) and aromatic residues (Try, Tyr, and Phe) give slight responses. The binding behavior is attributed to Van der Waals forces and hydrophobic interactions. Assay interference by bases, detergents, and other compounds are explained in terms of their effects upon the equilibria between the three dye forms.

Hydrogen-Ion Concentration↗
PubMed1983

Is sequestration structure-specific in the milkweed bug, Oncopeltus fasciatus?

Extracts of Oncopeltus fasciatus adults, fed from the first instar on sunflower seed diets impregnated with bufadienolides-cardenolide analogs, contained no detectable bufadienolides or polar steroid metabolites on TLC. O. fasciatus did sequester cardenolides from host and non-host sources, and bufadienolides were recovered from extracts of impregnated seeds. Possible reasons for the absence of detectable bufadienolides in these insects are suggested.

Animals↗
PubMed1980

The assessment of health in casualty birds of prey intended for release.

There are legal implications in deciding when a sick or injured bird or prey is able to be released. Important considerations are the health of the bird, its relationship with man and the locality in which it is to be released. Recommendations are made in order to help veterinary surgeons tackle this problem. Criteria for assessing health are outlined and discussed.

Animals↗