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Emys orbicularis is a freshwater turtle with temperature-dependent sex determination. Estrogens play a major role in gonadal differentiation; when they are produced at high levels during the thermosensitive period (TSP), ovaries differentiate; when their synthesis is very low, testes differentiate. Estrogens are synthesized from androgens through the activity of aromatase. We examine here two aspects of gonadal differentiation, intersexuality and growth, in E. orbicularis. For gonadal intersexuality, we studied the relationship between gonadal aromatase activity and gonadal structure at 28.5 degrees C (pivotal temperature), from the beginning of TSP to hatching, and compared results to those obtained at 30 degrees C (producing 100% females) and 25 degrees C (producing 100% males). At 28.5 degrees C, both males and females are obtained. However, histological differentiation of gonads is delayed compared to that at 25 degrees C and 30 degrees C, and an ovarian-like cortex of various thicknesses often develops at the surface of the male gonads; thus, several individuals display ovotestes at hatching. Despite important individual variations, the aromatase activity in ovaries differentiating at 28.5 degrees C increases during development as in ovaries differentiating at 30 degrees C. In most cases, however, activity is slightly lower than at 30 degrees C, and at the end of embryonic life, it becomes similar to that at 30 degrees C. In testes or ovotestes differentiating at 28.5 degrees C, aromatase activity remains low but is generally slightly higher than in testes at 25 degrees C; however, at the end of embryonic development, it becomes similar to that at 25 degrees C. Oocytes in the cortex of ovotestes begin to degenerate around hatching and continue to degenerate after hatching. Therefore, ovotestes evolve as testes. However, some oocytes may persist at the surface of testes up to the adult age. To estimate gonadal growth, the protein content was measured at different embryonic stages at 25 degrees C and at 30 degrees C. Testis growth is fast during TSP, somewhat slower after TSP, and decreases around hatching. Ovary growth is much slower than testis growth during TSP and then accelerates up to the end of embryonic development. This differential growth is well correlated with gonadal aromatase activity--much higher at 30 degrees C than at 25 degrees C--and can be explained by the fact that during TSP, testicular cords develop at 25 degrees C whereas they are inhibited at 30 degrees C; the ovarian cortex begins to form during this period but grows chiefly after TSP. Both inhibition of testicular cord development and stimulation of cortex development are under the control of endogenous estrogens. In the case of ovotestes, slight increases in estrogen synthesis, compared to that in typical testes, are sufficient to induce the transient formation of an ovarian-like cortex although they do not inhibit the development of testicular cords.

Emys orbicularis is a turtle with temperature-dependent sex determination. The thermosensitive period (TSP) lies between embryonic stages 16 and 22. Gonadal differentiation begins during this period involving oestrogens. Treatment with oestrogens during TSP results in the differentiation of ovaries at a male-producing temperature (25 degrees C), whereas treatment with an antioestrogen (tamoxifen) or with nonsteroidal aromatase inhibitors results in gonadal masculinization at a female-producing temperature (30 degrees C). The present study examines the effects on the ovary of inhibiting aromatase activity after TSP. Eggs of E. orbicularis incubated at 30 degrees C were given five or seven applications of 10 micrograms aromatase inhibitor Letrozole (CGS 20267) in ethanol, between stages 22+ and 24-25 when ovarian aromatase activity strongly increases. Individuals which received five applications were sacrificed at stages 24(+)-25. Those which received seven applications were sacrificed either at stage 25+ (close to hatching), or 34-36 days after hatching. Gonadal aromatase activity and related gonadal structure were studied in each individual. In the three series, the gonadal aromatase activity in individuals treated with Letrozole varied from similar or close to that in controls to much lower, and the gonadal structure varied from ovary-like to ovotestis. Ovotestes had the lowest levels of aromatase activity, under 4 fmoles/h/gonad, close to testis levels. They were found in 7 out of 26 individuals given Letrozole. Besides ovotestes, gonads presenting various degrees of masculinization, with enlarged epithelial cords and lacunae in the medulla, were found. Therefore, by inhibiting aromatase activity and thus estrogen synthesis, we were able to obtain the differentiation of testis-like cords or tubes in ovaries of E. orbicularis, after the period of temperature sensitivity. These results show that the ovary retains male potential after this period. Thus, besides their implication during the critical embryonic period for gonadal sex differentiation, oestrogens play a role in maintaining the ovarian structure after this period. A decrease in oestrogen levels could explain some other cases of ovarian masculinization known in vertebrates.

In embryos of Emys orbicularis, the sexual differentiation of gonads is influenced by the incubation temperature of eggs. Estrogens administered during the thermosensitive period result in the feminization of gonads at 25 degrees (male-producing temperature), whereas an antiestrogen or aromatase inhibitors masculinize the gonads at 30 degrees (female-producing temperature). The nonsteroidal aromatase inhibitor Letrozole induces gonads with different degrees of masculinization, from ovary-like to testis-like. The present study examines the endocrine function of such masculinized gonads, at the end of embryonic life. Aromatase activity (which is involved in estrogen synthesis in ovary) and the status of Müllerian ducts (the regression of which reflects the secretion of a putative anti-Müllerian hormone by the Sertoli cells) were examined. One month after treatment with Letrozole, the gonads of embryos presented various levels of aromatase activity. There was a strong correlation among aromatase activity, gonadal structure, and Müllerian duct status; high levels of aromatase (similar or close to those in control females) were found in ovary-like gonads; intermediate levels were found in gonads (masculinized ovaries or ovotestes?) exhibiting a cortex and a composite medulla containing a mixture of ovarian lacunae and testicular cord-like structures; low levels (similar or close to those in control males) were found in strongly masculinized gonads (testis-like or ovotestes). Müllerian ducts were regressing in the majority of embryos with gonads containing low levels of aromatase activity. In these individuals, gonads functioned as embryonic testes. These results confirm the implication of estrogens in gonadal differentiation. The origin of these hormones is controversial, so that the aromatase activity was compared in gonads, in the undissociated adrenal-mesonephric complex (AM), and in different parts of this complex during the thermosensitive period. At the female-producing temperature, the aromatase activity per unit of tissue increased in differentiating ovaries but it was low in AM and similar to that found in AM at male-producing temperature. In embryos whose gonads had been masculinized by early treatment with Letrozole, aromatase activity was unchanged in AM. These results suggest that the main source of estrogens involved in ovarian differentiation is the gonad itself.

From a medium in which Daudi cells had been grown, we isolated by HPLC a protein that caused ovarian abnormalities in adult females of Drosophila melanogaster when injected into preblastoderm embryos. This protein, whose apparent M(r) is between 30,000 and 50,000, was found to be a moderately polar compound which is heat stable and whose activity is destroyed by acidification. The protein is characteristic of medium conditioned from Daudi cells.

The sex, age, occupation and residence of 251 patients with aplastic anaemia in adults have been analyzed, and compared to those of the french population. The following observations have been done: excess of males at each age beyond the 20th year; excessive frequency after the 50th year; excessive frequency in the rural population and the inhabitants of villages and little towns; but no excess in the industrial workers. These observations lead to minimize the aetiological responsibility of industrial toxics in aplastic anaemia; at the reverse they invite to look for a possible responsibility of one or several agents used in the rural world.

Cauterization of pole cells in embryos of the Colorado beetle does not prevent organogenesis of the gonads. So, pole cells do not govern to the differentiation of the gonadal mesoderm (this latter is limited to abdominal segments 6, 7 and 8). Moreover, this mesoderm develops into testis or ovary even without any innitial germ cells.

Drosophila melanogaster embryos were injected before the blastoderm stage with conditioned media from several male Burkitt's lymphoma human cell lines and the Daudi cell line. Such injections do not have any effect on the male genital apparatus or on the female tract. The Daudi conditioned medium modifies the ovarian morphogenesis of the flies and the rudimentary ovaries obtained look like nymphal gonads. Moreover, they have a drastically reduced number of germ cells. The ovaries that looked functional contain numerous necrotic germ cells and the mean number of ovarioles per fly is significantly smaller than that of the controls. The abnormalities observed resemble the results of experimental and genetic lack of germ cells. They disappear at very high dilution (1×10 -6 ).

During the last 12 years, 86 apparently primary polycythemias have been observed in subjects less than 40 years old. In twelve of them a non-suspected cause has been found (seven abnormalities of the hemoglobin function). In 43 cases, all males, the erythrocytosis (red cell volume more than 36 ml/kg) was pure and stable, without any complication; this "benign erythrocytosis" probably depicts extreme values of the normal distribution of the red cell mass. In 31 cases, the disease had criteria similar to those of polycythemia vera observed in older patients; in 12 of these cases, severe thrombo-embolic complications have been observed at the very beginning of the disease; however no further complication has been seen, when the patients were actively treated (phlebotomies or 32P); at the present time, no one of these cases did show transformation into acute leukemia, but the long-term prognosis (beyond 15 years) cannot yet been precisely drawn.