Ontogenetical study of the chick embryo subcommissural organ by lectin-histofluorescence and electronmicroscopy.

The secretory activity of the subcommissural organ (SCO) was studied during embryogenesis of the chick (Gallus gallus) using two lectins labelled with fluorescein isothiocyanate, concanavalin A (Con A) and wheat-germ agglutinin (WGA). While WGA labels the apical or ventricular border of the organ, Con A labels both, the apical and vascular poles of the cells. Glycoproteinaceous secretory products, visualized by Con A appear early, at 5 days, in the ependymal epithelium and expand progressively in a rostrocaudal direction. A correlation is established between histofluorescence and the ultrastructural aspects of the ependymocytes. This throws light on the role of the endoplasmic reticulum in the synthesis, storage and transport of the material produced by the SCO, and points to the existence of two poles of exchange between the secretory cells and the extracellular medium, i.e., the ventricular and the vascular one. WGA reactivity at the apical border is linked up with the formation of Reissner's fibre and shows that the secretory product of the SCO cells undergoes at least partly modifications during its intracytoplasmic transport preceding apical discharge.

[Ultrastructure and cytochemistry of primordial germ cells involved in migration in dichlorvos-treated quail embryos]. / Etude ultrastructurale et cytochimique des cellules germinales primordiales et des tissus impliqués dans leur migration chez des embryons de Caille après traitement au dichlorvos.

In dichlorvos-treated quail embryos, the ultrastructural cytochemistry of gonads reveals perturbations in the glycoconjugate distribution. The modifications observed concern the surface and matricial glycoconjugates of tissues involved in the primordial germ cells (PGC) migration. In treated embryos, these cytochemical alterations could explain a delayed migration of PGC to germinal anlage and their disturbed settling into gonads.

[Embryotoxic and teratogenic action of dichlorvos (organophosphate insecticide) on the development of the quail embryo]. / Action embryotoxique et tératogène du dichlorvos (insecticide organophosphoré) sur le développement de l'embryon de caille.

Incubation of quail embryos in a DDVP-enriched atmosphere (0,002 18 mg dichlorvos/m3 air) reveals both embryotoxic and teratogenic effects of this pesticide. The embryos surviving beyond the 5th day were affected with multiple malformations associated to those ascribed to an anticholinesterase action: lordosis, scoliosis... Although incubation chambers were ventilated twice a day, the results can be modulated according to the nature (aluminium, plastic, cardboard) of the boxes which were used.

[Effects of an organophosphorous pesticide, dichlorvos, on germ cells of the undifferentiated gonads of young quail embryos]. / Action d'un pesticide organophosphoré, le dichlorvos, sur les cellules germinales des gonades indifférenciées de jeunes embryons de caille.

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.