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Rats were exposed to low-frequency electromagnetic field, adequate to the natural background, with Gaussian energy distribution, spectrum width 15 kHz, and field intensity 5 V/cm. Electric fluctuations were shown to have an inhibitory action on the normal growth of the animals and on blastoma development. This action reaches maximum with the greatest build-up gradient. As the frequency band of the field of action increase, the inhibitory effect declines.

Studies with the use of intact inbred albino mice showed that in intravenous administration the acute toxicity of antibiotic No. 6270 and echinomycin in complexes with DNA increased 3--4 times as compared to the toxicity of the same antibiotics used without the complex. Under the experimental conditions with 3-fold intravenous administration at 72-hour intervals in doses equivalent by their acute toxicity, the antitumor activity of the echinomycin complex with DNA against the solid form of lymphosarcoma L10-1 was approximately 4 times lower than the activity of the antibiotic used alone. Like echinomycin, antibiotic No. 6270 in complex with DNA used according to the same administration scheme in doses equivalent by their acute toxicity had a lower inhibitory effect on growth of lymphosarcoma L10-1 and sarcoma 180 as compared to its use alone.

Intertesticular inoculation to rats of 1 ml of sarcoma suspension was accompanied by a rapid growth of the tumour at the site of inoculation and the spread of the tumour nodes to the omentum majus, porta hepatis, mesentery and the abdominal walls. After intraperitoneal inoculation the spread of the tumour nodes was similar. In these experiments animals died in 13-15 days. One month after the intratesticular inoculation of 0.2 ml of the tumour suspension-lung metastases were revealed in 74% of the animals with sarcoma-45 and in 90% of those with sarcoma-536. It was shown that tumour cells appeared in the blood stream already during the inoculation. However, laying of lung metastases occurred only after the formation of a primary tumour node at the site of transplantation. A conclusion was drawn that this system was a suitable experimental model for the study of the lung metastases development in rats.

The three-dimension growth -- spheroidoformation of tumor cells of the primary MX-induced sarcoma in mice BALB/c, C57BL, and C3H/Sn, was studied. The tumor cells were cultured on millipore filters of the diffusion chambers implanted into the peritoneal cavity of normal syngeneic mice.

A comparative cytochemical investigation for alpha-glycerophosphate dehydrogenase (alpha-GPhD) activity in transplanted cellular line of mouse glioblastoma (EPNT-5) and KOX-1 was performed under normal conditions and under hydrocortisone effect. In glioblastoma EPNT-5 cells a high alpha-GPhD activity was revealed. The enzymatic activity was found to correspond to the dynamics of cell multiplication. Under the effect of hydrocortisone, alpha-GPhD activity demonstrated a two-fold increase, while alpha-GPhD activity in KOX-1 cells was very low, and hydrocortisone did not induce its increase. The data obtained supported the view on the glial nature of the transplanted ćpHT-5 line and demonstrated that the glial elements preserved their specific peculiarities at a prolonged cultivation.

While using different methods of skeletal investigation, definite alterations were revealed in frequency of osteosarcomas under plutonium exposure (2.5 muC/Kg). The ratio of the corresponding values is 1:1,2:1,27:1,47. The highest incidence of osteosarcomas was noted in the complex roentgeno-morphological study (according to an extensive scheme of procurement of the osteomaterial) -- 39.8% In separate application of different methods of skeletal investigation the roentgenological method seems to be prefered: it determines more precisely the number of tumor nodes and the number of tumor-bearing rats, accordingly.

Serologically active preparations of soluble H-2 antigens were obtained by 3 M KCl extraction from the ascitic cells of leukemia L 1210 (H-2d) and sarcoma MX-11 (H-2b). These preparations had no specific influence in vitro on the cytotoxic effect of immune lymphocytes on target cells, and did not inhibit the lymphocyte adsorption on the monolayer of the corresponding target cells.

A survey of the latest data associated with the analysis of the mechanisms of cancerogenesis with the help of hybridization of somatic cells is presented. Results of the investigations showing that malignization is not a dominant feature are discussed. A possible role of hybridization of cells in vivo in the genesis of tumours is indicated.