DOES THE PARAXIAL MESODERM OF THE AVIAN EMBRYO HAVE HEMANGIOBLASTIC CAPACITY

In a previous study of the hemangioblastic capacity of lateral plate m esoderm, we showed that the endoderm-associated splanchnopleural layer is capable of giving rise to both endothelial and hemopoietic cells w hile the ectoderm-associated somatopleural layer is not (Pardanaud and Dieterlen-Lievre 1993a). In order to complete the inventory of territ ories able to produce these two cell lineages, we assayed the paraxial mesoderm, and report the results here. Quail somites or segmental pla tes were treated with mab QH1+complement in order to eliminate attache d aortic endothelial cells, which cling to the ventral aspects of thes e structures. They were grafted in the limb bud or the coelom of chick host, since these sites promote the differentiation of endothelial an d hemopoietic cells, respectively. Vascular development and hemopoieti c cell emergence were analyzed using QH1 immunocytology. Segmental pla te and somites both produced abundant endothelial cells. In addition, the segmental plate gave rise to small groups of hemopoietic cells whe n grafted in the coelom.