Scanning Electron Microscopy


This study was undertaken to examine the effects of varying levels of methyl mercury (MeHg) on the ultrastructure of the surface epithelium of the oviduct of ducks. Accordingly, Pekin ducks were maintained on feed containing varying doses of (0.0; 0.5; 5.0; 15.0 ppm) of MeHg (Group I - control to IV) for 12 weeks and sacrificed. Tissue from the magnum and the shell gland regions of the oviduct was processed for scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that the primary and secondary folds of these regions of the oviducts of the control and 0.5 ppm treatment group were densely populated with ciliated cells and that the cilia tend to cover the apical surfaces of the non-ciliated secretory cells. This unchanged ultrastructural morphology of the surface epithelium of 0.5 ppm treatment group was verified with TEM. The ciliated and nonciliated cells in surface epithelium appeared to be equal in frequency. The nuclei of ciliated cells were superficial in location compared to nonciliated secretory cells which had nuclei in the basal part of the cytoplasm. In the oviducal tissues from ducks fed 5.0 ppm MeHg isolated areas of ciliary loss, but minimal disruption of the apical plasma membrane were observed by SEM. In a few birds plasma membrane lesions, condensation of nuclear chromatin and very dilated rough endoplasmic reticulum were seen with TEM. In the oviducal tissues from ducks fed 15.0 ppm MeHg it could be seen that ciliary loss was much more extensive than hitherto observed, and disruption of the apex of cells could be seen. TEM showed degeneration of cytoplasmic organelles, more or less severely damaged ciliated cells, loss of ciliary extensions and formation of compound cilia. These observations indicate that methyl mercury at 5.0 and 15.0 ppm dose levels causes toxic injury to oviducal surface epithelium of Pekin duck that may cause reduced reproductive capability.

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