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M A Shirley

Publications and source records attributed to M A Shirley.

24 records · Page 2Linked to original sources
PubMed1977

Electron-microscopic visualization of transcriptionally active and less active chromatin fractions from the rat ventral prostate and their content of histones.

The content of histones in transcriptionally active (euchromatin-like (E)) and transcriptionally less active (heterochromatin-like (H)) fractions from the rat ventral prostate was determined. The absolute amount of total histone was less in the E fraction, which contained relatively more stained histone F2b and F3 and less histone F1 than either the H fraction or unfractionated chromatin. The phosphotungstic-acid-stained E fraction was composed predominantly of shorter (50-500 nm) and thinner (5-15 nm) structures. In some preparations, pieces estimated to be 500-1000 + nm in length were present. Spherical structures, from 10 to 20 nm in diameter, some of which were present as 'dimers,' trimers,' or higher-ordered ensembles were seen in the shadow-case E fraction. The stained or shadow-cast H fraction contained longer (200-2000 + nm) and thicker (congruent to 20 nm) fragments with a more complex substructure. When the shadow-cast H fraction was sufficiently dispersed, it had a nodular or 'beaded' appearance.

Animals↗
PubMed1976

The obstetrician's role in reducing the risk of aspiration pneumonitis. With particular reference to the use of oral antacids.

Aspiration of gastric contents is the commonest cause of maternal anesthetic death. If the pH of the contents is below 2.5, morbidity and mortality rates are likely to be higher than if the pH is above 2.5. A study of 146 patients in labor shows that one in four patients is "at risk" to acid aspiration. No time interval between last mean and either onset of labor or delivery can guarantee an empty stomach. The use of oral antacids during labor reduces the number at risk to 1 in 35. Other methods by which the obstetrician may contribute to reducing the risk are discussed.

Anesthesia, Obstetrical↗
PubMedDate not supplied

Stereochemical studies on the beta-oxidation of valproic acid in isolated rat hepatocytes.

Stereochemical aspects of the biotransformation of valproic acid (VPA) to four compounds believed to represent products of mitochondrial beta-oxidation, viz. delta 2(E)-VPA, delta 3-VPA, 3-hydroxy-VPA, and 3-oxo-VPA, were examined in freshly isolated rat hepatocytes. Following incubation of the individual enantiomers of [5-13C]VPA and analysis of products by GC/MS techniques, it was possible to determine for each metabolite the relative populations of molecules that had been formed by oxidation on the pro-R vs. the pro-S propyl group of the drug. Metabolism was found to exhibit a slight preference (approximately 1.3:1) for attack on the pro-S side-chain for all four compounds, consistent with the hypothesis that this group shares a common metabolic origin. In contrast, the hepatotoxic terminal olefin, delta 4-VPA, was formed with marked enantiotopic differentiation (approximately 3.8:1) favoring the pro-R side-chain. The reason for the surprisingly low stereo-selectivity displayed by the products of beta-oxidation was investigated with the aid of [3-2H] delta 2(E)-VPA as metabolic substrate. Following incubation with rat hepatocytes, 35% of the substrate remaining after 2 hr was found to have been isomerized to [3'-2H] delta 2(E)-VPA. Because delta 2(E)-VPA is known to be formed from VPA-CoA through the action of 2-methyl-branched-chain acyl-CoA dehydrogenase, it is proposed that the three-carbon side-chains of both parent drug and delta 2(E)-VPA are interconverted as a consequence of reversibility in the second half-reaction of this enzymatic process.

Animals↗