Ultrastructural analysis of the Krebs-2 ascites cancer cells treated with extracellular double-stranded DNA preparation.

Electron-microscopic analysis of the ultrastructure of the Krebs-2 carcinoma ascites cells in the first 90 min immediately after their exposure to fragmented double-stranded DNA has been performed. Morphological attributes of the treated cancer cells indicate the induction in these cells of destructive processes of presumably apoptotic type. The predominance of dystrophic-destructive changes in cells after the addition of DNA is supposed to be a consequence of the disturbance in metabolic processes caused by the experimental action.

Ascites tumor invasion of mouse peritoneum studied by high-voltage electron microscope stereoscopy.

Interaction of Krebs-2 and Ehrlich tetraploid cells with NYLR/Nya mouse peritoneum mesothelium and penetration of basal lamina and elastic reticulum were studied. Invasion of abdominal viscera was rare. Invading cells had a shrunken nucleus and cytoplasm like the "dark cells" of hyperplastic epithelia. High-voltage electron microscope stereoscopy showed that invasive cells pass through small holes in the elastic reticulum by adherence to the reticulum and by constriction of the cells. High voltage electron microscopy stereoscopy of collagen fibers near tumor cells indicated that fragmentation and loss of collagen is minimal. Rapid progression by ascites transfer appears to produce anchorage-independent cells adapted to ascites fluid growth, but new selection steps must be adopted to concentrate strongly invasive subpopulations.

Variation in microsomal subfractions obtained from normal animal tissues and transformed cells following cell disruption by nitrogen cavitation.

Microsomal membranes were obtained from MPC-11 cells, L-cells, Krebs II ascites cells and various normal animal tissues following cell disruption by nitrogen cavitation. Membrane preparations were applied to discontinuous sucrose gradients designed to separate three fractions--heavy rough (HR), light rough (LR) and smooth (S) microsomes. In each of the transformed cell lines all three fractions were found whilst in the normal tissues tested the HR fraction was absent. Of the normal tissues liver and pancreas were rich in both LR and S microsomes, the presence of large amounts of LR indicating a rich protein synthesizing activity on membrane-bound polysomes. Kidney also contained appreciable LR but much less than both liver and pancreas. Both heart and lung contained virtually only S microsomal material--a reflection of low protein synthetic activity on membrane-bound polysomes. Attempts to promote the appearance of the HR fraction in liver, kidney and pancreas by incubation in tissue culture medium, or, in the case of pancreas, by cholecystokinin/pancreozymin/secretin stimulation both in vivo and in vitro were unsuccessful.