Cell death in the embryonic brain of Gallotia galloti (Reptilia; Lacertidae): a structural and ultrastructural study.

In the striatum, thalamus and cerebellum of a Lacertid reptile, we have found three types of cellular death during embryonic development, both at the light and electron microscopic level. The first affects the undifferentiated neuro-epithelial cells and is commonest during the early stages (E. 32-E. 36). The second corresponds to the type of 'nuclear' death described in the bibliography and reaches a maximum in the middle embryonic period (E. 37-E. 39); nevertheless important variations were observed in different zones. The third is the same as the 'cytoplasmic' death type and appears in the perinatal stages. Phagocytosis involved in the elimination of dead cells is of two types. One is associated with early death and is carried out by undifferentiated neuro-epithelial cells. The other is carried out by microglial cells which appear around Stage 37. Much cellular debris was observed in the intermediate zone and this was associated with the second type of phagocytosis. In both cases lipid production was associated with the degenerative process. Comparison of the temporal cellular death pattern with synaptogenesis, gliogenesis and maturation of neuronal processes is consistent with the view that the various types of cellular death found by us had different causes.

Cell death in the normal development of Gallotia galloti mesencephalon (Reptilia Lacertidae). An ultrastructural study.

We have studied the development of the mesencephalon of Gallotia galloti and we have observed two classes of cellular death: 'nuclear' or 'Type I' and 'cytoplasmatic' or 'Type II'. The first appears in stages around E-34 and the second one is observed from stages around hatching to the adult lizard. The degenerative cells have been observed in the profundus, torus semicircularis, the 5th pair of the trigeminal nerve nuclei as well as the 4th and 5th layers of the optic tectum where this last nucleus mentioned is situated.

Neuronal cilia in the embryonic thalamus and striatum of Gallotia galloti (Reptilia, Lacertidae).

Cilia are a common characteristic of the embryonic neurons of the thalamus and striated centers of Gallotia galloti from E.35. The ciliogenesis process occurs around the stages E.33 and E.34. The ciliary morphology shows no substantial variations between the different stages and the ciliary structure in the embryonic period is 8 + 1. On the other hand, the adult cilia has a 9 + 2 arrangement of microtubules. We do not rule out the possibility of other axonemes.