Search PubMed⌕ Search

Biomedical subjects

H J Nicholas

Publications and source records attributed to H J Nicholas.

35 records · Page 2Linked to original sources
PubMed1969

Sterol biosynthesis in sub-cellular particles of higher plants.

Mevalonic acid-2-(14)C was administered to cut stems of bean seedlings (Phaseolus vulgaris L.) for time intervals varying from 20 min to 24 hr. The plants were homogenized in a pH 7.8 tris-sucrose buffer and the homogenates separated into chloroplast, mitochondrial, microsomal, and supernatant fractions by means of differential centrifugation. The distribution of radioactivity into non-saponifiable material in each of the fractions was then determined. After short incubation periods labeled squalene was localized in the supernatant fraction. Labeled sterol was limited at all incubation periods to the microsomal and supernatant fractions. The data presented clearly implicate the microsomal and supernatant fractions in sterol biosynthesis in higher plants.

Journal Article↗
PubMed1969

Biosynthesis of squalene and cholesterol by cell-free extracts of adult rat brain.

Cell-free extracts of adult rat brain incubated with mevalonic acid-2-(14)C synthesize (14)C-labeled nonsaponifiable fractions consisting largely of squalene-(14)C. If the cofactor concentrations of the incubation medium are adjusted, much of the squalene can be induced to undergo turnover, with a resultant increase in (14)C-labeled digitonin-precipitable sterols, which include a small amount of cholesterol. The synthesis of labeled sterols is markedly increased in the presence of Mg(++) and depressed by nicotinamide. ATP, NADH, GSH, and glucose-6-phosphate are required for optimal synthesis of digitonin-precipitable material but, unlike Mg(++), are not essential. The cofactor-adjusted extracts also synthesize a complex ester mixture containing, in addition to cholesterol-(14)C, several compounds less polar than cholesterol. The biosynthesis of cholesterol in the extracts is a slow process; at least 12 hr of incubation is required for maximal sterol biosynthesis. A complex mixture of hydrocarbons accompanies squalene in the incubated extracts.

Adenosine Triphosphate↗
PubMed1969

Detection of monohydroxy "bile" acids in the brains of guinea pigs afflicted with experimental allergic encephalomyelitis.

3alpha-Hydroxy-5-cholanoic acid (lithocholic acid) and some unidentified acids (one of them perhaps 3-hydroxy-cholest-5-en-26-oic acid) have been detected in the brains of guinea pigs afflicted with experimental "allergic" encephalomyelitis. None of the acids could be identified in comparable amounts of brain tissue from normal guinea pigs. Thin-layer chromatography of the free acids, and thin-layer and gas-liquid chromatography combined with mass spectrometry of the methyl esters were used for identification. The occurrence of these acids may possibly be the result of cholesterol oxidation in the brain. The acids, or compounds related to them, may play a role in development of demyelination in experimental allergic encephalomyelitis.

Animals↗