Ultrastructural study of bone morrow-derived granulocytic colonies in diffusion chambers in rats.

An ultrastructural study of diffusion chamber granulocytic colonies is reported. The colonies were derived from normal rat bone marrow cells and the chambers were inserted into the peritoneal cavity of lethally irradiated rats. The colonies were processed en bloc for electron microscopy enabling observation of cellular relationship to be made. Ultrastructural analysis of colonies disclosed normal maturing cells at all stages of maturation, with the exception of occasional granulocytes on neutrophil type that presented narrow strips of chromatin ('nuclear blebs'). The cells in colonies generally occurred in close apposition to one another and to occasional macrophages. This organization possible enhanced transmission of factors of maturation. Advantages of diffusion chamber haematopoietic culture are discussed; among the most important are the occurrence of fibroblasts originating from implanted marrow cells and the local formation of fibrin within the chambers.