Abstract
Electronmicroscopic study was carried out on the skin tumors of mouse treated with 20-methylcholanthrene (20 MC) and 4-nitroquinoline-N-oxide (4NQO) in order to elucidate the mechanism of tumorgenesis.
The results obtained were as follows ;
1) Intramitochondrial electron dense bodies were observed in the prickle cells of the animals treated with 20 MC on two months and after two months. The mitochondria containing these bodies were swollen and enlarged.
However, these bodies were not found in the 4 NQO-treated animals in spite that the degenerated change of mitochondria was seen.
2) The formation of the crown of thorn-like pattern, as described by Setälä, was observed in epidermal cells after three months' treatment with 20 MC and 4 NQO.
3) After 4 months' treatment with 4 NQO, two kinds of cells, i.e. clear and dark cells, were found in proliferating epidermal cells in addition to the changes of tonofilament mentioned above. However, both cells may rather be taken as an ultrastructural sign of degeneartion.
4) The finding observed above suggested to be precancerous changes of the epidermis. However, after 6 months' treatment with 4 NQO, the finding was almost disappeared and fibrosarcomatous change was developed. It was assumed that electron microscopic examination proved the specific tissue affinity of 4 NQO, as reported by Nakahara.
5) The spinalioma cells showed an increase of nuleo-cytoplasmic ratio, the irregularity nuclear shape together with an increase in volume and number of nucleoli. Although cytoplasmic organelles were generally numerous in the carcinomatious cells, tonofilaments and desmosomes were smaller in number than in normal epidermal cells.
6) The fibrosarcoma cells showed the irregularity of intrachromatic granules and the variety of nucleoli. The cytoplasmic filamentous structures were found in the majority of the tumor cells. They were delicate and slightly wavy in appearance. It was assumed that they were related to the collagen production.
