J. T. Van Bruggen

Acetate metabolism: effects of tracer concentration.

Abstract A study of the role of tracer acetate concentration in CO 2 − , fatty acid-, and cholesterol-forming systems has been made. By evaluating the specific activity response, i.e., increase, with increasing tracer concentrations, it has been established that the amount of tracer used in in vitro studies may be critical and that this critical concentration may be different for various systems. It appears necessary to determine, for each system using labeled tracers, the amount of the tracer that will trace existing reactions at their normal rate or in situ rate of reaction.

Hydroxylamine and reactive acyls

Abstract Conditions for the selective and complete reactivity of thiol esters with hydroxylamine are described, and conditions hazardous to the successful isolation of hydroxamates are presented. The R f values of a series of biological compounds are tabulated.

Fatty acid and cholesterol synthesis rates in the intact rat.

Abstract An approach to the determination of lipide synthesis rates in the individual intact rat using single tracer injection, short-term experiments is described. Use is made of respiratory C 14 O 2 data to evaluate the carbon flux through the precursor stages. Fatty acid and cholesterol synthesis rates determined in this manner are reported as mg. lipide synthesized/ hr./100 g. animal weight for total animal, liver, and carcass of normal, chow-fed Sprague-Dawley rats in the postprandial, postabsorptive, and 18-hr. fasted states.

In vitro studies on oxidative and lipid metabolism in the immature macaque monkey

Summary The effects of diets differing qualitatively in fatty acid composition on blood and tissue lipids and upon oxidative and lipid biosynthetic pathways in monkeys ( Macaca mulatta ) have been followed. The milk-fat diet, as compared with the vegetable-fat diet, led to higher serum cholesterol, serum total lipid and liver cholesterol values. Adrenal cholesterol was lower in the milk-fat group, but kidney cholesterol values were higher. [1- 14 C]Acetate and [2- 14 C]mevalonate incorporation into cholesterol in the liver was lower in the milk-fat group, so that the hypercholesterolemia observed in the latter group is not attributable to increased cholesterol synthesis. Other metabolic changes are described for the two groups.

Multiple Labeling to Determine Metabolic Pathways: Use of Labeling Ratios

The story of the metabolism of ethanol in man has been of interest to many people and to many kinds of research workers. Problems in physiology, pharmacology, biochemistry, psychology, and sociology are involved.

Hydroxamates of tissue-activated acyls: Preparation and separation

Abstract To determine the amount of reactive acyl present in tissue with the aid of hydroxylamine, it is necessary to heat inactive (10 min, 70°) the enzymes responsible for the enzymic formation of hydroxamates. Such heat treatment is shown to leave intact the thiol acyl forms of the monobasic acids studied but to destroy the succinyl derivative. Extraction and fractionation of formed hydroxamates, prior to chromatography, is done with butanol.

Metabolism of NaHC14O3: Effects of Anesthesia and Route of Dosage.

Summary The time-course of respiratory C14O2 has been followed after intraperitoneal and intravenous dosage of NaHC14O3 into anesthetized and non-anesthetized rats. Nembutal has been shown to affect the turnover of injected bicarbonate through its depression of respiration. The anesthetic did not slow peritoneal absorption. The multiple bicarbonate dosage used did not lead to appreciable labeling in tissue lipids, and the contribution of C14O2 to secondary labeling reactions can under these conditions be ignored. Liver glycogen “fixed” a small but measurable amount of the C14 label.SummaryThe time-course of respiratory C14O2 has been followed after intraperitoneal and intravenous dosage of NaHC14O3 into anesthetized and non-anesthetized rats. Nembutal has been shown to affect the turnover of injected bicarbonate through its depression of respiration. The anesthetic did not slow peritoneal absorption. The multiple bicarbonate dosage used did not lead to appreciable labeling in tissue lipids, and the contribution of C14O2 to secondary labeling reactions can under these conditions be ignored. Liver glycogen “fixed” a small but measurable amount of the C14 label.