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Biomedical subjects

W Engel

Publications and source records attributed to W Engel.

At least 253 records · Page 14Linked to original sources
PubMed1977

HCG-binding capacity of the rat ovary during pregnancy.

During pregnancy, binding of 125I-labelled HCG to the rat ovary increases markedly from the 3rd to the 17th day of pregnancy but is reduced drastically at the end of pregnancy and after delivery. At the 17th day of pregnancy the HCG-binding capacity of the rat ovary is raised 76-fold in comparison to oestrous rats (17th day of pregnancy: 128 X 10(-15) mol/mg wet weight; oestrus: 1.67 X 10(-15) mol/mg wet weight). It is assumed that only LH receptors not occupied by endogenous hormone are covered by our assay. The high number of "free" ovarian HCG receptors during pregnancy apparently represents "Spare" receptors, the functional significance of which remains unclear. It is suggested that the metabolic activity of the ovarian luteal cells during pregnancy is not restricted by the number of HCG receptors present, but through the level of the endogenous gonadotrophic hormone and/or some unknown factors residing in the luteal cell.

Animals↗
PubMed1977

Binding of human chorionic gonadotrophin to rat ovary during development.

Ovarian tissue of prenatal, newborn, and 5-day-old rats does not specifically bind 125I-labelled HCG. Specific binding of HCG was first observed in ovaries of 10-day-old animals and binding increased with age. These results indicate that, contrary to rat testis, the HCG receptor in the rat ovary is not present during foetal and early postnatal development. Thus, the insensitivity of the ovary to endogenous and exogenous LH or HCG during this developmental period is due to the lack of specific receptors.

Age Factors↗
PubMed1976

Gene action in fish of tetraploid origin. IV. Ribosomal DNA amount in clupeoid and salmonoid fish.

Phylogenetically tetraploid species of the fish order Isospondyli generally have twice the mean ribosomal gene content as closely related species on the phylogenetically diploid level. Considerable intraspecific variation of rDNA amount was observed. These findings are discussed in view of the hypothesis that selective loss of ribosomal genes may account for diminishing genic activity in phylogenetically tetraploid organisms.

Animals↗
PubMed1976

Gene action in fish of tetraploid origin. III. Ribosomal DNA amount in cyprinid fish.

Phylogenetically diploid and tetraploid cyprinid fish species have cells of very similar volumes and protein contents. This finding has prompted us to postulate a regulatory system established during the evolution of the tetraploids leading to a diploid state of genic expression. It was proposed that this might be accounted for by a selective loss of ribosomal genes. RNA-DNA hybridization experiments, however, reveal a clear-cut 1:2 relationship of ribosomal DNA amounts between the diploid and the tetraploid species.

Animals↗
PubMed1976

Gene action in fish of tetraploid origin. V. Cellular RNA and protein content and enzyme activities in cyprinid, clupeoid, and salmonoid species.

The ratio of cellular RNA and protein content is about 1:1 between phylogenetically diploid and tetraploid species of the teleost family Cyprinidae, but is roughly in proportion to ploidy in species of the teleost order Isospondyli. Enzyme activities do not unequivocally comply with this scheme. These findings are discussed in view of the hypothesis that a regulatory mechanism which reduces genic activity has evolved in the tetraploid cyprinids but not in the tetraploid species of the order Isopondyli.

Animals↗
PubMed1975

Gene action in fish of tetraploid origin. II. Cellular and biochemical parameters in clupeoid and salmonoid fish.

By use of cell size, protein and hemoglobin content, and enzyme activities as markers, it becomes apparent that in the course of evolution the gene expression of anciently tetraploid fish of the order Ostariophysi was diploidized, but no such regulatory mechanism has evolved in the phylogenetically tetraploid species of the order Isospondyli. This finding is discussed in terms of possible selective neutrality of tetraploid expression and the phylogenetic age of Isospondyli.

Animals↗
PubMed1975

Binding of human chorionic gonadotrophin by rat testis: effect of sexual maturation, cryptorchidism and hypophysectomy.

The specific binding of 125I-labelled human chorionic gonadotrophin (HCG) by rat testicular homogenate as compared with isolated Leydig cells differs with respect to total binding capacity but not to the dissociation constant (Kd) as revealed by Scatchard analysis. The maximal binding capacity for [125I]HCG of crude testicular homogenate was 95 ng/g rat testis. Hypophysectomy causes a decline in binding capacity within the first three days but on the 20th and 30th day after hypophysectomy the relative binding capacity no longer differs from that of controls. Binding capacity is enhanced in cryptorchid testes relative to normal, and increases during sexual maturation to a peak shortly before puberty.

Age Factors↗