The Effects of Chorioallantoic Grafts on the Developing Chick Embryo:I. Studies on Weight and Histology of Homologous and Heterologous Tissues

Abstract

It was observed that following CAM grafts of adult chicken duodenum there was a marked decrease in the absolute weight of the host, a marked increase in the weight of the spleen, liver, and heart, and a relative weight increase in the duodenum. Further, following grafts of adult skin and brain the spleen and liver were significantly heavier. Following liver grafts the liver and heart showed a significant increase in weight. Adult chicken spleen grafts caused a marked increase in the weight of the spleen and heart. Further, it was observed that, regardless of what tissue was used for grafting, 9 days later the morphological integrity of the graft was destroyed and the area was replaced by a myeloid metaplastic centre. On the other hand, embryonic duodena retained their integrity and continued to differentiate. Grafting of adult duodenum caused acceleration of tissue differentiation of the host duodenum. The polysaccharides in the connective tissue and goblet cells of the duodenum differentiated at least 24 hours earlier than in control chicks. Following grafting of duodenum, spleen, and skin, the host spleen exhibited a marked increase in granuloblasts and granulocytes. The heart and liver following grafts were essentially like those in control embryos. Treatment of the adult duodenum prior to grafting with either 95 per cent, alcohol for 24 hours at —20°C., lyophilization, or heating at 80° C. for 20 minutes, resulted in inactivation, the host not being affected. When duodena of 15-, 16-, 17-, 18-, and 20-day embryos were grafted to the CAM, no changes in the weight of host spleen, liver, or heart were found. Following 20-day duodenal grafts the weight of the duodenum was significantly decreased. All embryos receiving adult duodenum, liver, and heart extracts into the yolk sac at 4 days of incubation, died within 72 hours after inoculation. The results are discussed in the light of organ-specific growth stimulation and graft-versus-host reaction, both of which fail to adequately explain all the results observed.