The Structure Of Circulatory Sistem And Hematopoiesis Of Leiocassis Longirostris

From October, 2003 to October, 2004, the morphological and histological structure of the circulatory system of Leiocassis longirostris was studied using intravascular injection and vascular casting technique and by means of histology and histochemistry. The hematocyte and hematopoiesis were also studied. The peripheral blood cells were observed under the light microscope and transmission electron microscope to study the microstructure and ultrastructure. Also the erythrocyte was observed under the scanning electron microscope. The results suggest:The structure of the circulatory system of Leiocassis longirostris is similar to the others. But it has its particular characters: having carotid enlargement and subspinal arteries. The carotid enlargement is a part of external carotid artery. It likes a shuttle, which projects in middle part and tapers in two end. Its histological structure characters show that it is composed of conduit part and substantiality part. Maybe the carotid enlargement has a function of adjusting blood pressure. After further research, we find that having carotid enlargement is a proprietary character of Bagridae. The subspinal artery, which provides nourishment for spinal cord, lies under the spinal cord and comes from internal carotid artery.Examination of the Wright-Giemsa's stained smears of peripheral blood has revealed the following five major cell types: erythrocyte, neutrophilic granulocyte, monocyte, lymphocyte and thrombocyte. Eosinophilic granulocyte and basophilic granulocyte aren't found in peripheral blood smears. Among these cells the erythrocyte is the most abundant. The thrombocyte and the lymphocyte are the most abundant leucocytes. Monocyte is as much as the neutrophilic granulocyte and is the least encounted leucocyte. In addition, the immature, dividing, dissolved and "nuclear shadow" erythrocytes are also found. The dividing erythrocyte ( bilobed erythrocyte ) is a form of senescence. The bilobed morphology marks the process of apoptosis. The volume's reduction of erythrocyte during apoptosis process facilitates the disposal of end phases by phagocytosis. According to the shape of nucleus and the color of cytoplasm, the neutrophilic granulcytes are further classified into three types. The monocyte has a reniform or irregularly oval nucleus,which occupy from thirty percent to fifty percent of the cell. Some monocytes have vacuoles in the cytoplasm. The cytoplasm to nucleus surface ratio of lymphocyte is larger than one. By the size, the lymphocytes are devided into two types: large lymphocyte and small lymphocyte. Thrombocyte is always irregularly round to oval, tadpole-shaped and spindle-shaped, and also the dividing thrombocytes are found.Observed under the transmission electron microscope, erythrocyte, which is shuttle-shaped, has rarely organelles and some mitochondria can be found in it occasionally. The small lymphocyte is characterized by its long pseudopodia and the large lymphocyte processed abundant of endoplasmic reticulum. Some granules, which like lysosome, are seen in monocyte. Neutrophilic granulocyte is recognized by its many specific granules, and these granules have three types. Neutrophilic granulocyte has pseudopodia also but shorter than those of small lymphocyte.The blood smears of hematopoietic organs are observed under the light microscopy, and the result shows that the head kidney, body kidney and spleen are the principal hematopoietic organs. Erythrocytes, lymphocytes and granulocytes develop mainly in head kidney and body kidney, and some of them are developed in spleen. While most of monocytes develop in kidney and spleen, some of them in head kidney. No primitive blood cells are seen in liver smears, so liver isn't a hematopoietic organ probably.The erythroid lineage consists of proerythroblast, basophilic erythroblast, acidophilic erythroblast and erythrocyte. During maturation of the erythroid cells, two directions of trends in size are distinguished: two decreasing and one increasing. Due to the great changes of granulood cells in maturation, the granuloid lineages are devided into five stages: granuloblast, young granulocyte, progranulocyte, metagranulocyte and granulocyte. During the maturation of granuloid cells, the size of cells is from large to small. The peripheral blood is the final place for their development. Maybe the bilobed granulocytes are the old granulocytes; it is to say that the splitting of nucleus is a sign of becoming senile. The development of lymphoid cells is similar to its of monocytoid cells. They experienced three stages respectively: lymphoblast, prolymphocyte, lymphocte and monoblast, promonocyte, monocyte. The size of these two kinds of cells become small from large regularly. Macrophages develop from monocyte and they have phagocytosis.