Structural Characteritics Of Zebrafish Thymus And Head Kidney And The Process Of Sample Preparation

Zebrafish(Danio rerio)is a kind of tropical freshwater teleosts which has meaningful features of its small size,prolific reproduction,and the transparent embryo.As a new experimental model animal,it has been widely used in genetics,cancer biology,development biology,environmental monitoring and so on.For the past few years,zebrafish has drawn more and more attention in immunology research.As important immune and hematopoietic organs of zebrafish,respectively,thymus and head kidney becomes more and more important in morphological study.However,on account of its small size,taking samples of thymus and head kidney is difficult.And there has been few reports about thymus and head kidney of zebrafish in morphology so far.In the present study,we expound its organization structure,cellular ultrastructure and the age-related changes.As reference data of public welfare,establishing and enriching physiological information database of zebrafish viscera,is conductive to the networked sharing of experimental animals characteristics.Meanwhile,histomorphological research of thymus and head kidney in normal zebrafish,can provide morphological reference for pathological experiments.Experiment I Microstructure and ultrastructure of zebrafish thymusThymus could divide into two parts roughly with the help of light microscopy,the cortex and the medullary.The out cortex is consist of many epithelial cell,however,the in cortex is full of lymphocyte.The quantity of the lymphocyte in the medullary is less than cortex,but the reticular epithelial cell is plentiful.Melano-macrophage centre,myoid cell,epithelial-cyst,capillary,mucous cell and adipocyte are observed in thymus.According to the morphologic transformation during the growth of zebrafish,learn the mode of the degeneration of the thymus of zebrafish.Under the TEM,we can observe the ultrastructure of different kind of epithelial cells,lymphocytes and debris-laden cell.Epithelial divide into two types by their different shape:Type I is irregular,vertical of cell is long,fully contact with lymphocytes.Type ? is much bigger than lymphocytes,and big nucleus is located at centre.Experiment ? Microstructure and ultrastructure of zebrafish head kidneywe can observe the head kidney of zebrafish is surrounded by a mount of collagen fibers.A lot of lymphocyte,blood cells,nephrocyte and few thyroid follicle with the follicular epithelial cell are observed in the head kidney of young zebrafish.At the head kidney of zebrafish which is 1-year-old,we found the adrenal cell and a lot of nephrocyte.Using the IHC,we compare the quantity of the hemopoietic stem cell in different growth stage,analyse the age-related change of hematopoiesis.In order to understand zebrafish head kidney more deeply,we observed ultrastructure of macrophages and granulocytes in the head kidney.The cytoplasm of eosinophil granulocytes is full of rod-granules and the neutrophilic granulocytes full of round granule.The degeneration of granulocytes is abvious.Experiment ? Sample taking of thymus and head kidney of zebrafish for microstructure and ultrastructure abservation.Taking samples of thymus and head kidney in zebrafish is difficult owing to its small size.Detailed description of the methods how we take and process samples,will provide standardized operating procedures for the research of zebrafish viscera(such as,thymus,head kidney and so on).The process of TEM includes:taking samples and staining.The process of light microscope experiments includes:taking samples,H-E staining,PAS staining,Gorden Sweets staining and so on.It is helpful for the standardizing of the operation of morphology study of thymus,head kidney and other organs of zebrafish.And it provide the procedure for the widely use of the zebrafish in the environmental monitoring field.