Scanning Microscopy


Cell death is a normal feature within the chick chorioallantoic membrane, occurring principally between days 10 and 14 of incubation.

Samples of chorioallantoic membrane were obtained on days 6, 8, 10, 12 and 14 of incubation, after the creation of artificial air chambers on day 3. These were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM) after staining for acid phosphatase activity, and by light microscopy after demonstrating oxygen free radicals with nitro blue tetrazolium. On day 6, small defects in the plasmalemma, approximately 200 nm in diameter, could be seen by SEM. A sequence of events leading to complete destruction of the plasmalemma, with exposure of the nucleus and other cytoplasmic organelles, could be traced, and by day 8 the membrane was a mosaic of healthy cells and others in various stages of degeneration.

TEM revealed that acid phosphatase activity was confined to the golgi apparatus and associated vesicles even in advanced stages of degeneration. By comparison, oxygen free radicals were demonstrated in individual cells from day 6 onwards. Application of superoxide dismutase and catalase to the epithelium using a nebuliser spray significantly reduced the amount of cell death seen by scanning microscopy on day 12. It is concluded that oxygen free radicals may mediate cell death in the chorioallantoic membrane.

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