title: Ultrastructural and histochemical investigation of the terminal capillaries in the spleen of the carp (Cyprinus carpio L.).
abstract: In the spleen of the carp arterial capillaries of a highly differentiated structure have been studied by light and electron microscopy. These capillaries share various structural characteristics with the sheathed capillaries (ellipsoids of Schweigger-Seidel) of higher vertebrates. The long arterial capillaries of the carp spleen are provided with cuboidal endothelial cells containing filaments approximately 7 nm in diameter. There is no basal lamina. The endothelial cells form various types of cell junctions, but there are also extensive areas without any junctions. Here, a free passage is possible between the capillary lumen and the subendothelial space. The capillaries possess a single-layered sheath of macrophages. Characteristically, the sheath macrophages posses long and slender cell processes forming a loose framework, the meshes of which are filled with lymphocytes and spindle cells. The sheath macrophages show a zone of ectoplasm rich in filaments. The also contain numerous phagolysosomes rich in hydrolytic enzymes, as identified histochemically. The sheath is sharply limited against the pulp by a thick layer of collagen fibers.
mesh_terms: D000135:Acid Phosphatase / Q000097:blood; D000818:Animals; D001192:Arylsulfatases / Q000378:metabolism; D002196:Capillaries / Q000166:cytology / Q000648:ultrastructure; D002347:Carps; D005260:Female; D006651:Histocytochemistry; D008297:Male; D010088:Oxidoreductases / Q000097:blood; D013154:Spleen / Q000098:blood supply* / Q000648:ultrastructure
chemical_list: D010088:Oxidoreductases; D000135:Acid Phosphatase; D001192:Arylsulfatases