Actin and lamin comprised filaments in the nuclei of Chinese hamster ovary cells affected with Clostridium difficile enterotoxin A.

The major change in the ultrastructure of Chinese hamster ovary (CHO) cells treated with Clostridium difficile enterotoxin A was the formation of bundles of filaments in the nucleoplasm. The filaments appeared after 2.5 h and disappeared by the fourth hour of incubation with the toxin. To partially characterize these filaments, laser diffractometry and ultrastructural immunocytochemistry were employed. The bundles consist of coiled filaments of about 11 nm and 16 nm diameter and a main long axial periodicity of about 26 nm. Postembedding immunogold labelling with monoclonal antibodies demonstrated that these intranuclear filaments are comprised mainly of actin, but also contain lamin and vinculin. Between 2.5 and 3 h of incubation with enterotoxin A, the lamins were located close to the nuclear envelope, but they were also consistently found scattered in the cytoplasm and nucleoplasm. Such an unusual distribution of lamins might mediate the adverse effects of enterotoxin A on nuclear organization and function and thus cause the eventual death of CHO cells.

Corneal endothelial autoradiography with the scanning electron microscope.

A new technique for performing corneal endothelial cell autoradiography with the scanning electron microscope is presented. The scanning electron microscope is able to detect silver grains deposited over tritiated thymidine--labeled nuclei of regenerating corneal endothelium.