MORPHOLOGICAL ASPECTS OF THE VASCULARIZATION IN INTRAVENTRICULAR NEURAL TRANSPLANTS FROM EMBRYO TO EMBRYO

Intraventricular transplants of neural tissues were performed in ovo f rom embryo to embryo. Fragments of the nervous wall. of the optic lobe (tectum) from 14-day chick or 12-day quail embryos (donor) were inser ted into the ventricle of the right optic lobe of 6-day chick or 5-day quail embryos (host). Chick-to-chick, chick-to-quail and quail-to-chi ck grafts were carried out. The vascularization changes occurring in t he host tectum and in the grafted neural tissues were analysed under l ight, transmission, and scanning electron microscopes and by morphomet ric methods. In the host embryo tectum, the neural graft stimulates a statistically significant increment in vessel density and a vessel spr outing into the ventricle of the optic lobe. The vascular sprouts reac h the transplanted tissue and establish connections with its native mi crovasculature. The chick-to-quail and quail-to-chick grafts, submitte d to immunoreaction with a quail-specific antibody which recognizes an antigen (MB1) present on endothelial cells, indicate that re-establis hment of the circulation in the graft depends upon anastomoses between host and donor vasculatures and the rapid new growth of host-derived and donor-native vessels. The presence of macrophage-like cells escort ing the new-growing vessels suggests that these cells are involved in the host and donor tissue angiogenesis.