Effects of Chlorambucil on the Ultrastructure of Neuroepithelial Cells of Neurulating Mouse Embryos

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The effects of chlorambucil on the neuroepithelial cells of mouse embryos are described ultrastructurally. Pregnant ICR mice were treated with oral administration of 3mg/kg chlorambucil at 7th day of gestation. Embryos were collected 6,12,24,36,and 48 hours after treatment and used for ultrastructural study. At 6 hours after treatment, many pyknotic cells were observed in the neural fold, which were thought to be the result of the direct cytotoxic effect of chlorambucil. At 24 hours, electron-dense protrusions of cytoplasm into the lumen of neural tube, which we call cytoplasmic clump, were observed. Intranuclear inclusions, which seemed to originate from invagination of the inner membrane of the nuclear envelope, were also observed. They were thought to be the characteristic findings in hypermetabolic cells induced by chlorambucil. At 36-48 hours pyknotic cells had almost disappeared, indicating that repair had taken place.