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W Engel

Publications and source records attributed to W Engel.

At least 235 records · Page 13Linked to original sources
PubMed1978

Appearance of hCG-receptor after conversion of newborn ovarian cells into testicular structures by H-Y antigen in vitro.

In a previous report (Zenzes et al., 1978b) it was shown that dissociated ovarian cells of newborn rats in vitro, if exposed to H-Y antigen, reorganize into testicular structures. The current study was designed to see whether this morphological conversion also results in a functional conversion. The LH/hCG receptor was used as a parameter characteristic for the newborn testis, but not for the newborn ovary. In the converted ovary, the LH/hCG receptor becomes detectable a few hours after onset of the culture and remains continuously present afterward. The appearance of this receptor may be due to a hormone-like action of H-Y antigen.

Animals↗
PubMed1978

DNA sequence organisation in avian genomes.

By means of renaturation kinetics of DNA of the three avian species Cairina domestica, Gallus domesticus and Columba livia domestica the following major DNA repetition classes were observed: a very fast reannealing fraction comprising about 15% of the DNA, a fast or intermediate reannealing fraction that makes up 10%, and a slow reannealing fraction of about 70%, which apparently renatures with single copy properties. --Comparing the reassociation behaviour of short (0.3 kb) and long (greater than 2 kb) DNA fragments of duck and chicken it becomes apparent that only 12% (duck) and 28% (chicken) of the single copy DNA are interspersed with repetitive elements on 2 to 3 kb long fragments. The lengths of the repetitive sequences were estimated by optical hyperchromicity measurements, by agarose A-50 chromatography of S1 nuclease resistant duplexes and by electron microscopic measurements of the S1 nuclease resistant duplexes. It was found that in the case of the chicken DNA the single copy sequences alternating with middle repetitive ones are at least 2.3 kb long; the interspersed moderate repeats have a length average of at least 1.5 kb. The sequence length of the moderate repeats in duck DNA is smaller. The results show that the duck and the chicken genomes do not follow the short period interspersion pattern of genome organisation, characteristic of the eucaryotic organisms studied so far.

Animals↗
PubMed1978

Organization in vitro of ovarian cells into testicular structures.

While it has been shown previously (Zenzes et al., 1978; Ohno et al., 1978) that when dissociated testicular cells are exposed to anti H-Y antiserum in vitro they are prevented from reorganizing into testicular structures, forming ovarian follicular structures instead, the most conclusive evidence for the action of H-Y antigen would be the conversion of ovarian cells into testicular organization. Testing for H-Y antigen of the medium collected from cultivated testicular cells revealed a positive reaction. Dissociated ovarian cells of newborn rats cultivated in this medium reorganize into testicular structures. It is concluded that H-Y antigen is responsible for this histomorphologic change.

Animals↗
PubMed1978

Studies on the function of H-Y antigen: dissociation and reorganization experiments on rat gonadal tissue.

On circumstantial evidence, H-Y antigen is assumed to be responsible for the differentiation of the undetermined gonadal anlage into a testis. A direct approach to test the function of H-Y antigen is provided by Moscona-type experiments. Applying a modified technique of in vitro reassociation of cell suspensions, we obtained the following results: (1) dissociated newborn rat gonads, both testis and ovary, reorganize into histotypic structures; (2) under exposure to anti-H-Y antiserum, testicular cells reassociate into ovarian follicular-like organization; (3) anti-H-1 antiserum by itself does not prevent the testicular cells from forming tubular structures. It is concluded that H-Y antigen acts as a differentiation between preferably or exclusively on the cell elements participating in the formation of the seminiferous cords.

Animals↗
PubMed1978

Ageing of the female gamete. 2 Lactate dehydrogenase activity in fragmented oocytes and ova of the rat.

LDH enzyme activities were determined in atretic and fragmented oocytes. The enzymatic activities in fragmented oocytes and ova were compared to those already known in early rat cleavage stages. Atretic oocytes are totally devoid of LDH activity. However, fragmented oocytes and ova exhibit nearly identical LDH activities to early cleavage stages. This result supports our earlier assumption that fragmentation and cleavage are homologus processes, induced by the same maternally transmitted factors in the oocyte cytoplasm.

Animals↗
PubMed1977

Adrenalectomy, ovarian HCG-binding and the onset of female puberty in the rat.

The delay of puberty onset in female rats adrenalectomized before the 25th day of age is due neither to changes in the number of ovarian HCG-receptors nor to an altered hormone affinity of these receptors. It is assumed that glucocorticoids act on an intracellular level in the ovarian cells, possibly by alterations of cyclic AMP-dependent phosphodiesterase activity.

Adrenal Glands↗
PubMed1977

Ovarian HCG-binding in hemicastrated immature female rats.

Hemigonadectomy in 9-day-old female rats results in a drastic increase in the weight and the number of HCG-binding sites of the remaining ovary during further development. However, on a per mg basis of ovarian weight, the number of HCG-receptors is identical in hemicastrated and control rats.

Animals↗
PubMed1977

Evidence for postmeiotic expression of ribosomal RNA genes during male gametogenesis.

Pre- and postmeiotic stages of male gametogenesis of 10 different vertebrate species belonging to mammals, birds, amphibians, and fishes were subjected to the Ag-AS staining technique (Goodpasture and Bloom, 1975). A uniform pattern of silver-staining is observable during spermatogenesis of the different vertebrate species. Silver-staining is present in spermatogonia and during the whole period of meiotic prophase, but totally absent during diakinesis and metaphase II of meiosis. In early spermatids silver-staining reappears and only disappears around the beginning of elongation of the spermatid nucleus. Since the Ag-AS technique is believed to stain only transcriptionally active nucleolus organizer regions, our findings indicate that ribosomal RNA genes become reactivated in the haploid spermatid.

Animals↗
PubMed1977

Activation of mouse ribosomal RNA genes at the 2-cell stage.

The Ag-AS method, developed by Goodpasture and Bloom (1975) strains transcriptionally active nucleolus organizer regions (NORs) on the chromosomes and in the interphase nuclei. Metaphases and interphase nuclei of early mouse embryos (unfertilized eggs, pronucleus stages, 2-, 4-, 8-cell stages, and morulae) were subjected to silver-staining. First staining of a single chromosome bearing an NOR was observed at the 2-cell stage. At the 4-cell stage 4--6 chromosomes, and at the 8-cell stage invariably all the 6 chromosomes known to bear NORs, respond positively to silver-staining. These results indicate that during mouse embryogenesis ribosomal RNA genes start to function at the 2-cell stage. The polar body does not respond to silver-staining, which supports the view that the polar body genome remains inactive.

Animals↗
PubMed1977

Ovarian HCG-binding capacity during the oestrous cycle of the rat.

Binding in 125I-labelled HCG to rat ovary varies during the oestrus cycle. The highest amount of binding was found in dioestrous-II rats (7.33 X 10(-15) mol of HCG per mg wet weight), while the lowest binding was observed in oestrous rats (1.67 X 10(-15) mol of HCG per mg wet weight) of circulation LH. It is concluded that the low binding capacity of the rat ovary in the oestrous stage is due to masking of the specific receptors by the excessively high LH hormone secretion in pro-oestrus.

Animals↗