Kinetics of particle uptake and clearance in fish

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1) Fluorescent latex beads were administered to 3-10 g rainbow trout by bath immersion, followed by time series sampling and histological examination. When the live fish exposed to the beads was dipped in 0.05% trypan blue before sampling, the patches of beads were observed at the skin area stained with trypan blue. In the skin examined histologically, there were the beads adhering to the superficial epithelial cells at the edge of wounds. During healing from wounds, the damaged cells and the beads sloughed together from the surface. However, the migrating epithelial cells which would repair the wounds displayed intensive phagocytosis of the beads at the edge of the wounds. The beads were also found in the intracellular gap in the dermis scaled with the migrating epithelium. Thus the microinjury in the skin are implicated as sites of particle uptake during bath immersion.2) Sevcral fluorescent labeling techniques were developed to track infectious organisms on fish hosts. Standardized … More staining methods of Uvitex2B and CFSE were applied for microsporidian and actinospore, respectively. In transmission experiments with labeled spores suggested that micro-sporidian (G.plecoglossi) invaded fish passively through microinjury on the body surface, and that actinospores (T.hovorkai, M.arcticus) invaded actively through gills and/or skin.3) G.plecoglossi spores had lectin-reactive components. Phagocytosis of the spores by ayu head kidney macrophages was significantly inhibited after ConA treatment. Percentage phagocytosis was significantly reduced when the spores were treated with ConA.Hydrogen peroxide production was suppressed by ConA treatment of spores. In the experimental infection of ayu, the number of cysts was smaller in ConA-treated spore administrated group than in untreated control group. It was suggested that ConA could block the binding of G.plecoglossi s spore with ayu macrophages and that their phagocytosis of the spores played an important role in migration of the spore in the infected fish. Less