Cytological and biochemical alterations in Carassius auratus hepatocytes from exposure to sediment containing dioxins and related compounds

Cytological and biochemical alterations of crucial carp (Carassius auratus) hepatocytes were characterized after exposure to sediments from a lake contaminated with dioxins and other industrial chemicals. Carp were exposed in 20 L water containing 25, 50, or 100 g of contaminated sediment for 2 and 4 weeks. Ultrastructural changes in the liver were characterized by severe enlargement of hepatocytes. Alterations in the cell. included formation of condensed and irregular cell nucleus, polynuclei, dispersed heterochromatin, enlargement of the nucleolus, and degeneration of the nucleus. Mitochondrial numbers were reduced and cristae were deformed. Myelin figures and lysosomes were increased, and sometimes cell organelles and cell matrix were totally lost after 4 weeks of exposure. The ultrastructural alterations were correlated with exposure time and sediment concentrations. Hepatosometic index was significantly increased in experimental groups at 2 and 4 weeks as compared with the control group. EROD enzyme activities were strongly induced in liver. A trend from rough endoplasmic reticulum (RER) to SER was observed. Our results suggest that the dioxin-like compounds bound by sediment were bioavailable to C. auratus and cause sublethal effects.

Cytological Mechanism on the Integration of Heterologous Genome or Chromosomes in the Unique Gynogenetic Carassius auratus gibelio

银鲫（ＣａｒａｓｉｕｓａｕｒａｔｕｓｇｉｂｅｌｉｏＢｌｏｃｈ）是行天然雌核发育生殖的两性型三倍体鱼类，与普通两性融合生殖鱼类相比，具有独特的育种优势。八十年代以来，异育银鲫、复合四倍体异育银鲫的发现表明，雌核发育卵子不但具有保持自身全部染色体的能力，还能整合异源精子的部分遗传物质或整个基因组，影响雌核发育后代的性状。因此，搞清楚异源基因组的整合机制对于进一步弄清其发育模式以及诱导复合多倍体银鲫均具有十分重要的作用。两性融合发育鱼类的精子入卵后，精核在促精核活化因子的诱导下，可以逐渐解凝并形成雄性原核；而在

Histological and cytological studies on the developing thymus of mandarin fish Siniperca chuatsi (Perciformes : Teleostei)

The thymus of the mandarin fish, Siniperca chuatsi, was examined by light and transmission electron microscopy to understand its formation and cellular composition. Larvae of the mandarin fish were collected and sectioned from 1 to 35 days post-hatching (dph). On dph 7 the thymus was packed with lymphocytes. From 12 dph onward, mucous cells were observed on the epithelial layer; from 23 dph, three zones could be differentiated in the thymic parenchyma. The thymus was connected with the extension of the third, fourth and fifth branchial pouches throughout early development, remaining in a superficial position in the adult S. chuatsi. In the thymus of the adult fish, thymic epithelial cells (TECs) characteristic of tonofilaments were observed, with limiting TECs (LECs) found in subcapsular, subseptal, perivascular and nurse-like TECs containing viable intact lymphocytes inside their vacuoles. In addition, three kinds of granulocytes were observed throughout the thymus, and an incomplete blood-thymus barrier was found in the inner zone. Other cell components such as cystic cells, macrophages and plasma cells, were also described in the thymus of the adult S. chuatsi. The thymus development in mandarin fish agrees, to some extent, with the ontogenetic patterns observed in other fish species.