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Biomedical subjects

C T Jones

Publications and source records attributed to C T Jones.

At least 145 records · Page 8Linked to original sources
PubMed1976

Lipid biosynthesis in liver slices of the foetal guinea pig.

Lipid synthesis as measured by the incorporation of acetate or 3H2O into slices of foetal liver, is much higher than in slices of adult liver and shows a peak at about two-thirds of gestation. At this time the synthesis from glucose was low and reached a peak 10 days later. The changes in the activity of ATP citrate lyase, which mirrored acetate incorporation, and the effect of glucose and pyruvate on acetate corporation into lipid suggests that some of the lipid synthesis occurs via intramitochondrial acetyl-CoA production from acetate. Despite this, lipid synthesis was not inhibited by (-)-hydroxycitrate. The low rate of synthesis from glucose at two-thirds of gestation is ascribed to the low activity of pyruvate carboxylase at this time and a role for a phosphoenolpyruvate carboxykinase in providing oxaloacetate for lipogenesis is proposed. The activity of fatty acid synthetase broadly agreed with the changes in lipid synthesis, whereas the activity of acetyl-CoA carboxylase was barely sufficient to account for the rates of lipid synthesis in vivo. Acetate and short-chain fatty acids are likely to be the major precursors for lipid synthesis in vivo.

ATP Citrate (pro-S)-Lyase↗
PubMed1976

Lipid synthesis in vivo by tissues of the maternal and foetal guinea pig.

The rate of lipid biosynthesis in vivo was determined in pregnant guinea pigs after maternal and foetal injections of 3H2O. Synthesis in the maternal tissues was low and in the foetal liver and adipose tissues relatively high. In the foetal liver it reached a peak at about two-thirds of gestation, whereas that in the foetal adipose tissue occurred later. These results were used to support the view that lipid synthesis in the foetal guinea-pig liver at two-thirds of gestation is largely from short-chain fatty acids, whereas in foetal adipose tissue glucose is probably the major substrate.

Adipose Tissue↗
PubMed1976

The distribution and clearances of hormones and metabolites in the circulation of the foetal sheep.

Plasma hormone and metabolite concentrations have been measured in the plasma of blood collected simultaneously from the femoral artery, umbilical vein and carotid artery of the exteriorized foetal sheep. The concentration of vasopressin and catecholamines was consistently lower and of glucose, lactate and corticosteroids consistently higher in the umbilical vein compared with the femoral artery. ACTH concentrations showed no consistent pattern and fluctuated widely at each site, but during synacthen infusion the concentration in the umbilical vein was consistently lower than in the femoral artery. For corticosteroids the concentration in the carotid artery was much lower than that in the umbilical vein; the converse was true for catecholamines. Concentrations in the carotid and femoral artery were similar for all compounds investigated. These results indicate that the placenta is a major site of vasopressin, catecholamine and ACTH clearance and of glucose, lactate and corticosteroid production. The foetal liver is probably a major site of corticosteroid and catecholamine clearance.

Adrenocorticotropic Hormone↗
PubMed1976

Endocrine and metabolic changes associated with periods of spontaneous hypoxia in fetal sheep.

Periods of spontaneously occurring hypoxia have been observed in fetal sheep. These were associated with increases in the fetal plasma concentration of glucose, lactate, free fatty acids, ACTH and corticosteroids (for a fetus close to term). These changes are similar to those observed during experimentally induced hypoxia. Hypoxia may be a mechanism by which plasma metabolites and ACTH are increased in fetal sheep under physiological conditions, particularly during labour.

Adrenal Cortex Hormones↗
PubMed1975

Plasma catecholamines in foetal and adult sheep.

1. Foetal and maternal plasma catecholamine concentrations were measured during and after hypoxia (mean maternal Pa,02 44mmHg) in chronically catheterized sheep, 118-141 days pregnant. 2. In most foetuses the initial plasma catecholamines were smaller than 0.07 ng/ml. During hypoxia plasma adrenaline and noradrenaline always rose; there was a rise in arterial pressure and a fall in heart rate. 3. The initial catecholamine concentration in the ewes was smaller than 0.05-2.3 ng/ml. During hypoxia there was no consistent change; the maternal plasma concentrations were less than the foetal. 4. Infusion of adrenaline at 0.3 mug kg(-1) min(-1) to the ewe resulted in plasma catecholamine concentrations higher than those observed during hypoxia. There was a rise in heart rate but no consistent change in arterial pressure. 5. Infusion of adrenaline 0.4 mug kg(-1) min(-1) into the foetal jugular vein caused a rise in plasma concentration similar to that seen during hypoxia. There was a rise in heart rate but no significant change in arterial pressure. 6. The half-life of adrenaline and of noradrenaline in the maternal and foetal circulation was 0.25-1 min. There was no evidence of transfer of labelled catecholamine across the placenta.

Animals↗
PubMed1975

The clearance of ACTH from the plasma of adult and fetal sheep.

The disappearance of 125-I-ACTH from the circulation of 4 pregnant and fetal sheep has been followed after a single injection to the ewe or fetus. The mean metabolic clearance rate for the fetus and the ewe was 55 and 34 ml/min/kg respectively, giving a half-life in each case of about 1 min. The higher fetal than maternal arterial plasma ACTH concentration has been ascribed to a higher rate of secretion rather than a reduced rate of clearance compared with the ewe. There was no evidence of placental transfer of immunologically reactive ACTH.

Adrenocorticotropic Hormone↗