David Kritchevsky

Detection of steroids in paper chromatography

Summary o 1. Methods for the detection of steroids in paper chromatography have been described and evaluated for 31 compounds. 2. A new method of detection of steroids involving phosphomolybdic acid has been reported. 3. A method using silicotungstic acid has been extended to cover many new compounds.

Observations on the Fate of Ingested Cholesterol in Man

Tritium-labeled Cholesterol has been used to study several aspects of exogenous cholesterol metabolism in man. The rate and magnitude of the appearance of ingested cholesterol in the various blood compartments has been followed. Fecal excretion of the labeling material was measured. Cholesterol of dietary origin was demonstrated in a human atherosclerotic aorta.

Observations with Radioactive Hydrogen (H3) in Experimental Atherosclerosis

Tritium has been used to study certain aspects of endogenous and exogenous cholesterol metabolism in normal and hypercholesterolemic rabbits. Special attention is given to turnover studies on aortic cholesterol. Labeled cholesterol has been used for feeding experiments and the subsequent rise of serum cholesterol specific activity has been investigated.

The effect of Δ7-cholestenol feeding on the cholesterol and lipoproteins of rabbit serum.

Abstract 1. 1.When Δ 7 -cholestenol is fed to rabbits there is produced a rise in the various classes of low-density serum lipoproteins. The lipoprotein “pattern” is qualitatively the same as that observed after feeding cholesterol. 2. 2. Δ 7 -Cholestenol produces a striking rise in serum cholesterol, and about the same levels are reached as are observed on feeding cholesterol itself. The sterols of the serum after this feeding show a maximum of about 12% of Δ 7 -cholestenol. 3. 3. Δ 7 -Cholestenol and cholesterol produce an additive effect on the levels of serum lipoproteins when fed simultaneously. 4. 4. Five per cent of the serum sterols is Δ 7 -cholestenol at the end of 1 week of feeding both this sterol and cholesterol. At the end of 2 weeks the Δ 7 -cholestenol falls almost to zero in spite of continued feeding of both sterols.

Detection of Tritiated Compounds in Paper Chromatography

A windowless tube has been developed which can be used to detect tritium activity on paper, glass, or aluminum. The tube is of glass, with a nichrome anode and a copper sulfide coated copper cathode, and utilizes a stream of helium saturated with alcohol. This device is convenient for detection of tritiated compounds in paper chromatography.

Biosynthesis of cholesterol from isobutyrate.

Es wird der Beweis erbracht, daß die Methyl-Gruppen der Isobuttersäure in das Cholesterin der Ratte einverleibt werden.

Distribution of Radioactivity in the Egg after Feeding Sodium Acetate-1-C14

Summary The data indicate that upon feeding of carboxyl-labeled sodium acetate, the activity is rapidly incorporated into all portions of the egg. The acetate is utilized immediately and a comparatively small percentage of radioactivity is diverted to the metabolic pool. Steady feeding of labeled material is required in order to maintain a high specific activity in all portions of the egg.

RADIOACTIVE EGGS. II. DISTRIBUTION OF RADIOACTIVITY IN THE YOLKS

Summary (1) The distribution of radioactivity in the yolks of eggs laid by a hen fed sodium acetate-1-C14 has been determined. (2) The radioactivity appears in all fractions of all yolks in the following order of increasing specific activity: protein, glycerol, phospholipids, fatty acids, cholesterol.

OBSERVATIONS ON THE SUITABILITY OF TRITIUM-LABELED CHOLESTEROL FOR THE STUDY OF CHOLESTEROL METABOLISM

Abstract Following the feeding of cholesterol doubly labeled with radioactive hydrogen and carbon, the ratio of tritium specific activity to C14 specific activity in the serum cholesterol over a 10-day period was found to correspond to the ratio of tritium specific activity to C14 specific activity in the material fed. These results show that tritium-labeled cholesterol is a suitable tracer compound for biological investigations of many aspects of cholesterol absorption and turnover.

Radioactive eggs. III. Degradation of yolk glycerol

Abstract 1. 1. The labeled glycerol obtained from the eggs of a hen continuously fed sodium acetate-1-C 14 for 7 days has been degraded by two methods. 2. 2. The general pattern of activity distribution is 86–88% in the terminal carbon atoms and 12–14% in the middle carbon atom. 3. 3. A mechanism that might explain these results has been suggested.