Biomedical subjects
Publications and source records attributed to A Guichard.
We have demonstrated an in vitro secretion of inhibin by human OCCC, not related to subsequent egg cleavage. A putative signal, released by OCCC, that could modulate inhibin secretion by granulosa cells has not been discovered. Inhibin secretion by OCCC has no predictive value concerning the further fertilization and cleavage of the oocytes.
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Quail embryos with a sex-linked eye pigmentation marker allowing sex identification at autopsy provided a biological model for radioimmunoassay of sex steroids in embryonic quail gonads at a very early stage (51/2 and 61/2 days). The purpose was to demonstrate a sex difference in hormonal potentialities of the gonads before any morphological indication of sexual differentiation. Evidence of early steroidogenesis by undifferentiated gonads could be obtained: estrogen synthesis characterized female gonads, while testosterone was produced by the gonads of both sexes. The sex hormonal production was concomitant with, or even preceded, the apparent beginning of sex differentiation of gonads.
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An early treatment of quail eggs with an antiestrogen (Tamoxifen = TAM) modifies the female gonads morphologically. In the left ovary, the proliferation of the germinal epithelium and formation of a cortex is markedly inhibited, while the medulla on both sides becomes more developed and keeps a cordal organization. The effects of TAM on the hormonal potentialities of 15-day embryo gonads have been investigated by radioimmunoassay. The data have been compared with those of normal gonads. The results indicate that the TAM treatment does not mainly modify the hormonal levels and patterns in the gonads of both sexes and does not inhibit the function of the hypothalamo-hypophyseal-gonadal axis. The reduced cortical development is thus not linked to an estrogen decrease but to competitive effects on receptors at the level of this tissue.
In vitro effects of factors such as testosterone or hCG on steroidogenesis by 12-day quail embryo gonads have been investigated by radioimmunoassays. The purpose was to compare the hormonal potentialities (estradiol, estrone, and dihydrotestosterone; E1, E2, DHT) of normal and diethylstilbestrol-treated gonads. The results demonstrate that the reduced steroid production by the treated ovaries does not result from their inability to respond to both factors, but reflects their weakened stimulation in vivo at the time of explantation. On the other hand, the secreting abilities of the DES-treated male gonads do not greatly differ from those of normal testes; even in the presence of favorable factors, and despite their feminization, the ovotestes are effectively unable to produce significative amounts of estradiol. These results are compared with others obtained elsewhere in quail and in chick embryos.
Attempts have been made to determine fetal sex early by a simultaneous study of H-Y antigen and testosterone in amniotic fluid. H-Y (male) antigen was serologically detected in the amniotic cells from both sexes, but the results obtained from 473 amniotic fluids showed no significant sex differences either in fresh cells or after culture. Testosterone assays done from 263 samples of liquor confirm that the results obtained in cases of male fetuses were significantly higher than in females. 55% of all males and 47% of females could thus be detected to a level of 100% certainty. The probability of having a girl decreases as an inverse function of testosterone levels and comes out at 85% for testosterone less than 200 pg/ml. On the other hand the probability of a male fetus is 95% when the values are above 240 pg/ml. The determination of the testosterone/DHA ratio in order to try to eliminate the influence of the variations in volume has not improved the accuracy of this diagnosis.
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In quails, H-Y antigen is induced by oestrogens in the gonads of the originally H-Y negative homogametic sex but not in non-gonadal tissues. This is consistent with the view that oestrogens act via H-Y antigen in the organization of the avian gonad.
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Fetal mice testes convert pregnenolone-16-3H and progesterone-4-14C to testosterone in organ culture. The 3H/14C ratio in progesterone and testosterone fractions isolated from culture media suggests the importance of the delta5-3 beta hydroxysteroid pathway in our experimental conditions. LH decreases radioactive testosterone production and increases the activity of the kelta4-3-ketosteroid pathway.
The study made by histochemistry shows that the delta5-3 beta-hydroxysteroid-dehydrogenase (delta5-3 beta-HSDH) activity which is positive in the fresh placental tissue disappears after 24 h of culture but is maintained much longer if culture medium is supplemented with human chorionic gonadotropin (15 UI of HCG). The biochemical study confirms the delta5-3 beta-HSDH activity decrease during the first 24 h of culture. The enzymatic activity is restored during the following six days and this phenomenon is stimulated by the addition of HCG in the culture medium.
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