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Biochemical aspects of bovine ketosis.

ABSTRACT: 1. The concentrations of acetoacetate, beta-hydroxybutyrate and metabolites related to gluconeogenesis were determined in biopsy samples of the livers of ketotic, normal lactating and normal non-lactating cows. Key enzymes of gluconeogenesis in the liver were also assayed. 2. Significant decreases were found in the ketotic liver in the concentrations of glucogenic amino acids (glutamate, glutamine, alanine) and of glucogenic oxo acids (alpha-oxoglutarate, pyruvate, oxaloacetate). 3. The beta-hydroxybutyrate/acetoacetate concentration ratios were generally much higher than in rat liver. 4. The concentration of total fat was sevenfold higher in the ketotic liver, and that of glucose plus glycogen fourfold lower than in normal liver. 5. The blood of ketotic cows showed a marked rise in the concentration of free fatty acids. 6. The activities of pyruvate carboxylase, propionyl-CoA carboxylase, phosphopyruvate carboxylase and fructose 1,6-diphosphatase showed no clear-cut differences between normal and ketotic animals. 7. Glucose injection promptly relieved the ketotic condition with respect to both the clinical and biochemical signs. The fall in the concentrations of the ketone bodies in the blood was preceded by a fall in the concentrations of free fatty acids and glycerol. 8. The findings are taken to be consistent with the concept that an increased rate of gluconeogenesis, causing a decrease in the concentration of oxaloacetate, is a major causal factor in ketogenesis.

SUBMITTER: Baird GD

PROVIDER: S-EPMC1198721 | biostudies-other | 1968 May

REPOSITORIES: biostudies-other

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Project description:Experiments were designed to determine whether DNA synthesis ceases in terminally differentiating cardiac muscle of the rat because the activity of the putative replicative DNA polymerase (DNA polymerase alpha) is lost or whether the activity of this enzyme is lost because DNA synthesis ceases. DNA-template availability and 3'-hydroxyl termini in nuclei and chromatin, isolated from cardiac muscle at various times during the developmental period in which DNA synthesis and the activity of DNA polymerase alpha are decreasing, were measured by using Escherichia coli DNA polymerase I, Micrococcus luteus DNA polymerase and DNA polymerase alpha under optimal conditions. Density-shift experiments with bromodeoxyuridine triphosphate and isopycnic analysis indicate that DNA chains being replicated semi-conservatively in vivo continue to be elongated in isolated nuclei by exogenous DNA polymerases. DNA template and 3'-hydroxyl termini available to exogenously added DNA polymerases do not change as cardiac muscle differentiates and the rate of DNA synthesis decreases and ceases in vivo. Template availability and 3'-hydroxyl termini are also not changed in nuclei isolated from cardiac muscle in which DNA synthesis had been inhibited by administration of isoproterenol and theophylline to newborn rats. DNA-template availability and 3'-hydroxyl termini, however, were substantially increased in nuclei and chromatin from cardiac muscle of adult rats. This increase is not due to elevated deoxyribonuclease activity in nuclei and chromatin of the adult. Electron microscopy indicates that this increase is also not due to dispersal of the chromatin or disruption of nuclear morphology. Density-shift experiments and isopycnic analysis of DNA from cardiac muscle of the adult show that it is more fragmented than DNA from cardiac-muscle cells that are, or have recently ceased, dividing. These studies indicate that DNA synthesis ceases in terminally differentiating cardiac muscle because the activity of a replicative DNA polymerase is lost, rather than the activity of this enzyme being lost because DNA synthesis ceases.

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Biochemical aspects of bovine ketosis.

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