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5 mg of Geldanamycin, an inhibitor of stress protein HSP86 which express on mammalian germ cells, were administered to E8 pregnant mice. E17 embryos were removed, and a quantitative analysis of HSP90-immunoreactive cells in the gonad was performed, in comparison to control embryos. First, we observed that the number of germ cells is lower in male than in female embryos, as well in control and experimental embryos. External features of experimental and control embryos did not display any difference. Embryos exposed to geldanamycin exhibit a significant decrease of immunoreactive germ cells. In two embryos, we observed a group of ectopic immunoreactive cells in the pelvic area. We conclude that geldanamycin inhibits germ cells migration, and suggest that this inhibition can lead to ectopic germ cell populations, similar to teratomas.

Effects of epidermal growth factor (EGF) on pH transients in aggregates of Sertoli cells and germinal cells have been investigated with confocal microscopy using a fluorescent pH sensitive indicator. In some Sertoli cells EGF caused a rapid rise in the pH whereas other Sertoli cells did not respond to EGF. Some Sertoli cells showed a delayed response which coincidated with a similar pH change in neighbouring germinal cells. Since isolated germinal cells never showed a pH response after exposure to EGF, we have concluded that some Sertoli cells may communicate with germinal cells via gap junctions.

Colonization of the genital ridges by primordial germ cells was quantitatively studied, at stages 18-24, in Chick embryos issued from eggs treated with commercial DDT before incubation. The pesticide provokes, dating from the 4th day of development (stage 24), a significant reduction in the gonadal germ population. This deficit may be due to 3 different actions of DDT on the primordial gonocytes: an inhibition of their gonadic colonizing capacity, a failure of proliferation and, at last, an excessive rate of cell death. However, the DDT modifies neither the initial number of blastodermal germ cells nor their migratory capacity toward the gonadal region.

According to the date of treatment by DDT of chick and quail eggs, the germ population of embryonic gonads is more or less reduced. Administered before incubation, the pesticide provokes a strong decrease in the number of gonocytes: at a later stage (the beginning or the end of germ migration), the DDT does not exert a significant effect. On the other hand, in all the cases, the rate of degenerative germ cells is superior to the control one.

Effect of injection of Arachis hypogea (PNA) and Soybean (SBA) lectins on the migration of Xenopus primordial germ cells (PGCs) were investigated. PNA inhibited almost entirely the PGCs migration, more than SBA. Our results indicated that the inhibition of the migration could be a consequence of the lectin-induced alterations of cell surface properties.

In quail embryos, issued from eggs injected, before incubation, with oil solution of DDVP, the germ population was strongly reducted. However, at the 24 stage of embryonic development, the germ deficit is lower than at older stage (29). This deficit may be due to an inhibition of their gonadic colonizing capacity and an excessive rate of cell death.

The p, p'-DDT present in the composition of commercial DDT, is responsible for the germ deficit in the gonads of bird embryos. Administered into the vitellus or on the shell, before incubation, the pesticide exerts the same reduction of the Quail germ population. While, for the Chick, the germ decrease is less significant after injection than after immersion.

The seminiferous tubulars of rats testis, subject to the action of Misulban during their foetal life, contain only Sertoli cells and constitute a good model for their study. From the ultrastructural point of view, these cells present several important mitochondria of tubular crest from, an abundant smooth endoplasmic reticulum, a Golgi apparatus well developed, a cytoplasm rich in ribosomes, Lipids droplets and intercellular junctions whose number increases with age. The administration of diethylstilbestrol, which inhibits gonadotropic and androgenic secretions reduces the signs of activity in the Sertoli cells.

After a treatment of early embryos by AMPc, only 40% of the primordial germ cells are found in the gonads; the others are found in the dorsal mesentery and especially in the intestinal wall.

At stages 16 and 18, the germ cells counts, in the quail embryos' gonads from control and 2,4,5-T treated eggs, show no significative difference. On the contrary, at stage 20, the gonocyte numbers of the treated embryos are strongly decreased. Actually, this mechanism cannot be stage precisely.

After the treatment in toto of the embryos from various species of Anura by cAMP, the number of primordial germ cells (PGC) in genital ridges is strongly reduced; the most part of the PGC are found in the endoderm. A ventral implant of agar impregnated with a solution of cAMP attracts numerous PGC in the same way as grafted chordomesoderm. The chordomesoderm itself, incubated with 3'-5' cyclic nucleotide phosphodiesterase, then grafted on to the ventral area of normal embryos attracts very few PBC compared with the non-incubated chordomesoderm. The results are analyzed and discussed along the following hypothesis: the migration of the PGC of the Anura is guided by cAMP which, diffusing from the chordomesoderm, is distributed along a concentration gradient increasing in a ventrodorsal direction. The PGC go up the gradient by a chemiotactic mechanism and reach the dorsal parts of the embryo.

The gonadic germ deficit induced by DDT in Quail embryos issued from eggs only treated at the first generation, partially decreases at the second generation and completely at the third. When the DDT treatment is repeated for each generation, the reduced effect slightly increases.