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Biomedical subjects

N Freinkel

Publications and source records attributed to N Freinkel.

At least 127 records · Page 7Linked to original sources
PubMed1969

Carbohydrate metabolism in pregnancy. VI. Plasma fuels, insulin, liver composition, gluconeogenesis, and nitrogen metabolism during late gestation in the fed and fasted rat.

The effects of late pregnancy on metabolic fuels, liver composition, gluconeogenesis, and nitrogen metabolism have been examined in fed and fasted rats. Plasma free fatty acid (FFA) and immunoreactive insulin (IRI) are greater and glucose and ketones are lower in fed 19-day pregnant than they are in agematched virgin rats. A 48 hr fast elicits greater increases in FFA and ketones and more profound reductions in glucose in the pregnant rats and obliterates the differences in IRI. Fetal weight is not modified by such fasting but maternal weight losses exceed that of the nongravid rats. Livers from rats 19 days pregnant contain more and larger hepatocytes. Per mumole hepatic deoxyribonucleic acid (DNA)-phosphorus, water and protein are more abundant, whereas glycogen is unaffected. Livers from fed pregnant rats contain more lipid phosphorus and less neutral lipid fatty acid. After a 48 hr fast, hepatic steatosis supervenes in gravid animals due to accumulated neutral fat. The contents of hepatic acetyl-coenzyme A (CoA) and citric acid are not different in fed pregnant and virgin rats but are greater in the pregnant rats after fasting. Formation of glucose-(14)C and glycogen-(14)C from administered pyruvate-(14)C are the same in fed pregnant and virgin rats, but greater in the pregnant ones after a 24 or 48 hr fast. Pregnancy does not affect creatinine excretion, and urinary urea is not different in fed pregnant, virgin, and postpartum animals. Contrariwise, more nitrogen, potassium, and phosphorus are excreted by the pregnant animals during a 2 day fast. The increment in urinary nitrogen is due largely to urea on the 1st day, whereas heightened ammonia accounts for half the increase on the 2nd and correlates with the enhanced ketonuria. Muscle catabolism, gluconeogenesis, and diversion to fat are activated more rapidly and to a greater degree when food is withheld during late gestation in the rat. These catabolic propensities are restrained in the fed state. The capacity for "accelerated starvation" may confer survival benefit upon an intermittently eating mother in the presence of a continuously feeding fetus.

Animals↗
PubMed1968

The mechanism of thyrotrophin action in relation to lipid metabolism in thyroid tissue.

1. The effects of thyrotrophin in vitro on the incorporation of [(14)C]-glucose, -glycerol, -palmitate and -oleate into the lipids of thyroid tissue were examined. 2. Thyrotrophin increased the incorporation of these (14)C-labelled precursors into phosphatidylinositol specifically. 3. Thyrotrophin also increased the proportion of (14)C radioactivity from labelled glucose, glycerol, palmitate and oleate incorporated into the 1,2-diglycerides. 4. The addition of thyrotrophin to thyroid slices for 10min., after 2hr. of prelabelling with [(14)C]glycerol, also increased the proportion of (14)C radioactivity incorporated into the 1,2-diglyceride fraction. 5. After incubation of thyroid tissue with [1-(14)C]palmitate, thyrotrophin caused a two- to three-fold increase in the specific radioactivity of palmitate isolated from phosphatidylinositol and 1,2-diglycerides. In contrast, the specific radioactivity of palmitate isolated from the choline and ethanolamine phosphoglycerides, 1,3-diglycerides and triglycerides was not increased by thyrotrophin.

Animals↗
PubMed1967

Internal standards in the estimation of acetyl-CoA in liver extracts.

The necessity for adding an internal standard to liver extracts during fluorimetric estimation of acetyl-CoA by the malic dehydrogenase-citrate synthase reaction is demonstrated. Addition of acetyl-CoA completely compensates for the inhibitory action of some tissue components. Values for hepatic acetyl-CoA in fed and fasted rats are given.

Animals↗
PubMedDate not supplied

Lipid deposition and metabolism in rat placenta during gestation.

Changes in placental lipid content in rats at the 15th and 20th days of pregnancy were investigates. It was found that progress of gestation is accompanied by a significant increase in triglycerides per mg placental DNA. Maternal starvation caused additional increase in the placental triglyceride content. By incubation with 14C-oleic acid, it was shown that placenta at term possesses an increased capacity to esterify fatty acids at a wide range of medium oleic acid concentrations. Increase in free fatty acid concentration caused a linear increase of their incorporation into placental lipids. Oxidation of oleic acid into CO2 was also increased with the duration of gestation, but to a lesser degree and over a narrower range of concentration than esterification, suggesting an increased channelling of fatty acids into glycerides.

Animals↗
PubMedDate not supplied

Transplacental arteriovenous gradients for glucose, insulin, glucagon and placental lactogen during normoglycaemia in human pregnancy at term.

The potential contributions of placental extraction and degradation to glucoregulatory hormone turnover in late pregnancy were assessed by measuring arteriovenous differences for glucose, insulin, glucagon and human placental lactogen (hPL) across the uterine and fetal circulation in ten pregnant women at the time of elective caesarean section. The observations were made during stable conditions of euglycaemia; values for maternal arterial glucose, insulin, glucagon and hPL were 78.8 +/- 5.0 mg/dl, 10.1 +/- 2.1 microU/ml, 72.0 +/- 8.5 pg/ml and 5.18 +/- 0.59 micrograms/ml, respectively. The glucose decrements observed consistently across the uterus and fetus indicated uptake by the placenta and fetus, and in the maternal circulation the arterial-uterine vein increment for hPL was 2.10 +/- 0.44 micrograms/ml. However, within the limits of analytical accuracy, no significant gradient could be demonstrated for insulin across the uterine (maternal) or umbilical (fetal) circulations. A small (8.5 per cent) but significant arteriovenous difference for glucagon was observed across the uterus but none was found on the fetal side of the placenta. The findings indicate that detectable gradients for insulin cannot be demonstrated under basal conditions of metabolism and at normal rates of placental blood flow. The results do not exclude the possibility of more significant extraction ratios under other physiological conditions or at higher concentrations of glucoregulatory hormones.

Adult↗