The Spleen and Haemolytic Disorders

Vascular pathways in nonsinusal red pulp--an electron microscope study of the cat spleen

The red pulp of the cat spleen, including terminal segments of arterial capillaries, pulp venules, and the reticular meshwork, was studied by transmission electron microscopy. Splenic congestion and contraction were produced by barbiturate anesthetic and norepinephrine. Terminal segments of arterial capillaries were ampullary and flared. Blood escaped into surrounding pulp spaces through interendothelial gaps. Pulp venules originated as open-ended vessels in the reticular meshwork near trabeculae and drained into trabecular veins. Venule walls were thin and composed of squamous endothelial cells, a continuous basement membrane, and reticular cells. Venules in congested spleens had many mural apertures, but venules in contracted spleens had few. The interstices of the reticular meshwork in congested spleens contained large amounts of blood, which often was concentrated, many macrophages, lymphocytes, and plasma cells. Fewer blood cells and scant plasma were present in contracted spleens. The vascular arrangements are anatomically open. Blood takes pathways through the reticular meshwork from arterial terminations to pulp venules. Some pathways through the reticular meshwork probably function as closed vascular channels conveying rapidly flowing blood. Other pathways are functionally open and probably contain slowly moving blood that constitutes a reservoir of red cells. Macrophages formed associations with mature red cells and with reticulocytes. Mature red cells were attached to macrophages in a manner indicating erythrophagocytosis. Reticulocyte attachment had a different appearance and likely resulted in reticulocyte sequestration. Platelets bore pseudopodia which would impede their passage through irregular and cell-filled pulp spaces. The change in platelet shape probably is responsible for the formation of the splenic pool of platelets.

Hereditary haemolytic anaemia due to red cell pyrimidine 5'-nucleotidase deficiency in two Irish families with a note on the benefit of splenectomy

Hereditary haemolytic anaemia with basophilic stippling caused by pyrimidine 5'-nucleotidase deficiency is described in three members of two unrelated Irish families. In one family, the disease was moderately severe and the patient's condition was improved by splenectomy. In the other family the haemolytic anaemia was well compensated. In neither family was there a marked elevation of reduced glutathione. The implications are that pyrimidine 5'-nucleotidase deficiency is a heterogeneous disorder, both clinically and biochemically. In more severe forms splenectomy may be beneficial.