Pathway of cholesterol biosynthesis in the brain of the neonatal rat

Suckling rats were killed at various intervals after intraperitoneal injection of acetate-1-(14)C and their brain sterols were analyzed by column, thin-layer, paper, and gas-liquid chromatography. The crude sterol (to which carrier zymosterol was added) was separated by column chromatography into cholesterol, desmosterol, and zymosterol fractions, and the specific activities of the recovered digitonides were determined. The zymosterol fraction, mainly carrier, was not uniformly labeled, in that the trailing half of the peak had a higher specific activity than the leading half. Evidence obtained suggests that this carbon activity was present in one or more sterols resembling zymosterol (Delta(8,24)-cholestadienol), Delta(7,24)-cholestadienol, and Delta(7,5.24)-cholestatrienol. The desmosterol and cholesterol were also carbon-labeled. The time course of the distribution of carbon activity among the above fractions indicated that the zymosterol fraction is a precursor of the desmosterol and that the desmosterol is, in turn, a precursor of the cholesterol. The data suggest that, in the developing brain of the rat, the course of the transformation of cholesterol precursors into cholesterol is influenced by the presence of at least two slow steps, one involving the conversion of Delta(7)- and Delta(8)-compounds to Delta(5)-compounds and the other, the reduction of the Delta(24)-unsaturation.     

<Emphasis Type="Italic">Coccinia</Emphasis> (Cucurbitaceae) gains two new species from East Africa,three new synonyms,and one new combination

We describe and illustrate Coccinia pwaniensis Holstein from eastern Tanzania and southeast Kenya, and C. samburuensis Holstein from the Samburu area in Kenya. The new species were already recognised by Charles Jeffrey in 1967 and are now known from eight and four collections, respectively. Ongoing monographic work also revealed three new synonyms and the need for a new combination, Coccinia heterophylla (Hook. f.) Holstein.     

Putative intermediates in the nerve cell differentiation pathway in hydra have properties of multipotent stem cells

We have investigated the properties of nerve cell precursors in hydra by analyzing the differentiation and proliferation capacity of interstitial cells in the peduncle of Hydra oligactis, which is a region of active nerve cell differentiation. Our results indicate that about 50% of the interstitial cells in the peduncle can grow rapidly and also give rise to nematocyte precursors when transplanted into a gastric environment. If these cells were committed nerve cell precursors, one would not expect them to differentiate into nematocytes nor to proliferate apparently without limit. Therefore we conclude that cycling interstitial cells in peduncles are not intermediates in the nerve cell differentiation pathway but are stem cells. The remaining interstitial cells in the peduncle are in G1 and have the properties of committed nerve cell precursors (Holstein and David, 1986). Thus, the interstitial cell population in the peduncle contains both stem cells and noncycling nerve precursors. The presence of stem cells in this region makes it likely that these cells are the immediate targets of signals which give rise to nerve cells.     

Dissociated centriole development as a cause of spermatid malformation in man

Ultrastructural study of a testicular biopsy from an infertile man with decapitated spermatozoa revealed a hitherto undescribed type of malformation. It was caused by a dissociation between the proximal and distal centrioles during the first steps of spermatid differentiation. The disconnection probably occurred because of the lack of striated columns in the connecting piece. Up to 40% of the separately developed and released tails showed a normal motility in the ejaculate.     

Acacipetalin from six species of Acacia of Mexico and Texas

Acacipetalin is the principal cyanogenic glycoside in Acacia chiapensis, A. cochliacantha, A. hindsii, A. macracantha, A. schaffneri var. schaffneri (all from Mexico) and A. schaffneri var. bravoensis (Texas).     

Morphological analysis of tissue components in the tunica dartos of man

Cell and Tissue Research - The human tunica dartos has been investigated by light, fluorescence and electron microscopy. It consists of solid bundles of smooth musculature in the subcutis, and...