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Biomedical subjects

R A Prough

Publications and source records attributed to R A Prough.

At least 109 records · Page 6Linked to original sources
PubMed1977

Initiation of human parturition. VI. Identification and quantification of progesterone metabolites produced by the components of human fetal membranes.

The fetal membranes play a central role in the initiation of human parturition, a role that may be subserved in part by quantitative changes in progesterone metabolism. In order to identify and to quantify the metabolites of progesterone produced by the components of the human fetal membranes, amnion and chorion laeve tissues and homogenates were incubated with [3H]progesterone in the presence of added NADPH. The radioactive metabolites, 20alpha-hydroxy-4-pregnen-3-one, 5alpha-pregnane-3,20-dione and 3beta-hydroxy-5alpha-pregnan-20-one, were isolated and identified by derivative formation, a combination of chromatographic techniques, and by crystallization to constant specific activity after addition of authentic standards. A simplified technique of metabolite quantification was developed that involves one thin layer chromatographic procedure and liquid scintillation assay of radioactivity. The accuracy of this method was established by comparison with data obtained using classical techniques. This study demonstrates the presence of human fetal membranes 5alpha-reductase, 20alpha-hydroxysteroid oxidoreductase, and 3beta-hydroxy-steroid oxidoreductase, and a qualitative difference between amnion and chorion laeve.

20-alpha-Dihydroprogesterone↗
PubMed1976

The direct spectrophotometric observation of benzo(a)pyrene phenol formation by liver microsomes.

Optical spectral repetitive scan analysis during the oxidative metabolism of benzo(a)pyrene by liver microsomal suspensions reveals the time-dependent formation of an intermediate(s) of which the visible spectra resemble those of several benzo(a)pyrene phenols. Liver microsomes from 3-methylcholanthrene-treated rats showed a greater rate of formation of the phenols than did microsomes from control animals; the rate of formation catalyzed by liver microsomes from phenobarbital-pretreated rats was intermediate. When 3-hydroxybenzo(a)pyrene was used as a standard for comparison of activity, the rates of formation of phenols were compared when measured by fluorometric, spectrophotometric, or high-pressure liquid chromatographic analytical techniques. An epoxide hydrase inhibitor, 1,1,1-trichloropropene-2,3-oxide, enhanced phenol formation regardless of the source of liver microsomes, and 7,8-benzoflavone inhibited control and 3-methylcholanthrene-induced microsomal metabolism of benzo(a)pyrene, 7,8-Benzoflavone did not effect benzo(a)pyrene metabolism by liver microsomes from phenobarbital-pretreated rats. The effect of inhibitors on the spectrophotometric assay correlates well with the results obtained from benzo(a)pyrene metabolite analysis using high-pressure liquid chromatography.

Adenosine Monophosphate↗
PubMed1975

Properties of the stable aerobic and anaerobic half-reduced states of NADPH-cytochrome c reductase.

The microsomal flavoprotein, NADPH-cytochrome c reductase, has been reexamined to determine: (1) the nature of the flavine bound to the enzyme and (2) the oxidation-reduction state of the "half-reduced" form of the flavoprotein. Iyanagi and Mason (Iyanagi, T., and Mason, H.S. (1973), Biochemistry 12, 2297) have recently proposed that NADPH-cytochrome c reductase contains both FAD and FMN as prosthetic groups in lieu of FAD as the sole constituent, as suggested by all previous studies of this enzyme. The data presented herein, utilizing the recently published fluorometric procedure of Faeder and Siegel (Faeder, E. J., and Siegle, L. M. (1973), Anal. Biochem. 53, 332) for the determination of FAD and FMN in mixtures, confirm the conclusions of Iyanagi and Mason for both rat and pig liver reductase preparations. Data for other flavoproteins are also presented. Iyanagi and Mason have also concluded that the air-stable "semiquinone" is a form of NADPH-cytochrome c reductase reduced by one electron per two falvines (F-FH). The present studies, however, do not agree with this conclusion, but instead support our previous results which indicate that both the aerobic and anaerobic half-reduced states of this flavoprotein exist in the two-electron reduced form (FH-FH). Removal of NADP+ does not affect the spectrum of the air-stable half-reduced form of the flavoprotein, nor does it affect the back titration of this intermediate by potassium ferricyanide. The possible implications of these observations on the catalytic cycle of the flavines of NADPH-cytochrome c reductase are discussed.

Animals↗