Browsing by Author "Schroepfer, George J."

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    Cholesterol biosynthesis. Metabolism of 14(alpha)-hydroxymethly-5-(alpha)-cholest-7-en-3(beta)-ol
    (1975) Lu, Yueh-Chin; Schroepfer, George J.
    [3a- H]-14a-Hydroxymethyl-5a-choiest-7-en-3B-ol, prepared by chemical synthesis, was incubated with rat liver homogenate preparations (1, x g supernatant fraction) . Efficient conversion to cholesterol was observed. Column chromatographic methods for the separation of sterols on silicic acid-Super-Cel columns, silica gel-Super-Celsilver nitrate columns and alumina-Super-Cel-silver nitrate columns were utilized during the course of the above studies. The metabolism of [32- H]-14a-hydroxymethyl-5acholest7-en-3&-ol, prepared by chemical synthesis, was also investigated. The incorporation of the radioactivity into tritiated water was demonstrated by the incubation of this labeled substrate with 1, x g supernatant fraction of rat liver homogenate. The fate of tritium labeled formate ( HCOONa) was investigated by incubation with 1, x g supernatant fraction also and most of the radioactivity recovered after incubation was in the form of tritiated water. The tritium labeled formate was also investigated by incubation with rat liver microsomal preparations in the presence of a TPNH generating system and the results showed that no metabolism of tritium labeled formate could be detected. Therefore, the incubation of the [32- H] labeled substrate with rat liver microsomes was carried out and the results showed that the label of [32- H]-14a-hydroxymethyl-5a-cholest-7-en36-ol was incorporated into formic acid.
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    The effect of an oral or intravenous nucleotide-free diet on selected enzyme activities in purine metabolism in rats
    (1982) Snyder, Sandra Lynn; Rudolph, Frederick B.; Berget, Susan M.; Schroepfer, George J.; Bennett, George; Storck, Roger L.
    Interrelationships between purine metabolism and immunity, cancer, and the diet have been considered. In studying trends of metabolic changes which occur in response to changes in the purine content of the diet, it has been hypothesized that when purines are lacking from the diet, there is a general shift from a catabolic to an anabolic state. In the present investigation, the activities of selected enzymes on purine metabolism in rats were studied with respect to an oral or intravenous nucleotide-free diet compared to the activities in rats fed normal chow. The intravenous nucleotide-free diet caused a decrease in purine nucleoside phosphorylase activity, an increase in adenine phosphoribosyl transferase, and no change in the activity of hypoxanthine-guanine phosphoribosyl transferase, with respect to a normal control diet. The orally fed nucleotide-free diet caused a decrease in the activity of purine nucleoside phosphorylase and xanthine oxidase and increase in pancreatic ribonucléase and no change in adenine phosphoribosyl transferase or hyphoxanthine-guanine phosphoribosyl transferase, with respect to a normal control diet. These observations support the predicted shift from catabolism to anabolism. They also augment the growing awareness of the interrelationships between diet and cancer as well as diet and the immune response.