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941.
U. Müller Maria Teresa Zenzes T. Bauknecht U. Wolf J. W. Siebers W. Engel 《Human genetics》1978,45(2):203-207
Summary In a previous report (Zenzes et al., 1978 b) 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. 相似文献
942.
Summary Various cell types of the rat testis during pubescence, including germ, Sertoli, and Leydig cells, were partially enriched. The fractions were tested for the presence, binding, and secretion of H-Y antigen. The main results are: Immature germ cells are H-Y antigen-negative until the late diploid stages, and late primary spermatocytes or spermatids become positive; the somatic cells of the gonad are positive at all ages examined (18 days old to adulthood). Secretion of H-Y antigen is restricted to the Sertoli cell fraction. Binding of externally supplied antigen takes place on Leydig cells; the Sertoli cell surface will be saturated because of active secretion; there is no binding to germ cells. Thus, immature germ cells seem to be the only H-Y antigen-negative cells of the male organism, and the Sertoli cells seem to be the only ones to secrete H-Y antigen. 相似文献
943.
The effect of chlorous salts of cesium, lithium, and rubidium on the analgetic action of morphine (according to the vocalization test) and also on the pattern of the dependence on it (according to the so-called "two-bottle test") was studied. As shown, the salts under investigation decreased both the algesic reaction threshold and the duration of morphine-induced analgesia; cesium chloride proved most active in this respect. All the compounds studied decrease the morphine preference coefficient. The greatest effect was found in cesium chloride which decreased the morphine preference coefficient 40-fold as compared to the control. 相似文献
944.
An electron microscopical investigation of the cell walls in young antheridia ofPolypodium crassifolium andPlatycerium alcicorne confirms the classical developmental model as postulated byStrasburger and byKny. The structure of the basal cell walls, both of the funnel cell and of the operculum, and especially the evidence of plasmodesmata in those walls, disprove the widely accepted interpretation presented 1951 byDavie.
相似文献
945.
946.
Several observations suggest an increased RNA synthesis in livers of protein-deprived rats, though the RNA/DNA ratio is decreased. A number of hormones may be involved in these changes. Therefore, we studied in RNA metabolism in isolated perfused livers taken from protein-fed and protein-deprived rats. (3H)-orotic acid was given to the rats 2 h before liver explantation, and (14C)-orotic acid was added to the perfusate. Other rats, called controls in vivo, whose livers were not transplanted were also given (3H)-orotic acid followed by (14C)-orotic acid. The livers of these rats, which were not hormone supplemented, were labelled for the same length of times as the livers in vitro. The ratio specific RNA radioactivity/specific nucleotide radioactivity x RNA/DNA was determined and taken as a measure of the RNA synthesis per liver cell. In the controls in vivo, this ratio was significantly higher for protein-deprived than for protein-fed rats. In livers from the protein-fed rats, labelling in vitro increased significantly when growth hormone, hydrocortisone, insulin and tri-iodothyronine were added to the perfusate. Labelling was also significantly higher in these livers than in the controls in vivo. In livers from protein-deprived rats, the ratio in question was the same whether the hormones were added to the perfusate or not, and was significantly lower than in the controls in vivo. Differences in RNA labelling are thus obtained in our in vitro system. Gel electrophoresis of RNA demonstrated normal RNA labelling, showing that the system is suitable for studying liver RNA synthesis. Further refinement can be made by studying the labelling of UTP and CTP. The results might suggest that the liver from a protein-fed rat, explanted in vitro, may increase its RNA synthesis under the influence of the four hormones in question, and that the RNA synthesis of the liver of a protein-deprived rat is high in-vivo and that it might decrease, when it is explanted to in vitro conditions. 相似文献
947.
948.
949.
cGMP and db-cGMP administered for 20–24 h to neonatal rat hepatocytes in primary culture stimulated their DNA synthesis and proliferation only at concentrations higher than the physiological one, whereas at concentrations equal to or lower than the physiological concentration they were ineffective or inhibitory for both activities. Induction of DNA synthesis to be effected by cGMP required 15 h of treatment, preceded, however, by inhibition of the same process between the 6th and the 14th hour of exposure. In contrast, cAMP and db-cAMP stimulated the flow of cultivated hepatocytes into the S and M stages of their mitotic cycle when administered at very wide concentration range, including the physiological for cAMP and the sub-physiological for db-cAMP. cAMP was effective after 12–14 h of treatment. Equimolar mixtures of cGMP with cAMP and of db-cGMP with db-cAMP also stimulated the proliferative activity of primary hepatocytes, but only at very low doses, which induced a first peak of DNA synthesis between the 2nd and the 6th hour of treatment and a second peak at about the 18th hour. These actions of the cyclic compounds, employed singly or in equimolar combination, were shown to be specific, since they could not be reproduced by their main metabolites. The present results strengthen the view that cAMP plays a pre-eminent role in the positive regulation of hepatocyte proliferation. Contrary to the postulate of the dualistic doctrine, cGMP by itself is not proliferogenic in the physiological range; in fact, cGMP acts as an ancillary, possibly dispensable, compound whose physiological role may be to help, in cooperation with cAMP, liver cells to cross the G1/S boundary of their growth-division cycle. 相似文献
950.