[Preventive effect of domestic, synthetic beta-carotene on the development of rat mammary tumors induced by DMBA].

Preventive effects of artificial beta-carotene on the development of rat mammary gland adenocarcinomas induced by DMBA were studied in rats maintained on a diet containing beta-carotene at a dose of 2.5 mg per animal within 10 weeks, which was initiated after the carcinogen administration. The carotenoid treatment course caused the following effects: manifestation of adenocarcinomas induced by DMBA was decreased, latent period of neoplasm development as well as the rate of tumor differentiation were increased and metastatic spreading into the regional lymph nodes was inhibited.

[Modeling of differentiation and physiological involution in the tissues of induced cancer of the mammary gland].

The experiments used rats with mammary tumors induced by intravenous injection of DMBA. The animals were treated with alternating courses of estrogen and anti-estrogen (tamoxifen). The former was given in combination with papaverin and low doses of vitamin A.

[Epithelial-stromal interrelations in mammary gland tumors induced by 7,12-dimethylbenzanthracene in rats].

DMBA-induced mammary tumours in rats are mixed adenocarcinomas with various growth rate (rapid, slow and stabilized). The electron-microscopic study has shown that ultrastructure of tumours and their growth rate depend on a degree of the parenchyma cell differentiation and on the maturity of connective tissue being the result of their specific interaction.

[Involution of rat mammae after abortion, cessation of lactation and vitamin A exposure].

Structural changes in the mammary gland cells have been studied in rats electron microscopically during pregnancy and involution process after cessation of lactation, as well as at initiation processes by means of abortion at various time of pregnancy (on the 8th, 13th, 20th days). The involutional processes are demonstrated to depend on differentiation degree of the mammary gland cells: intensity of autolytic processes is essentially higher at abortion performed at late stages and at cessation of lactation. Stages of physiological death of the cells are followed.

[Effect of ionizing radiation on the sensitivity to hormonal inducers of differentiation in induced mammary cancer in rats].

gamma-Irradiated rat mammary tumours induced by DMBA are likely to enhance the level of differentiation and to lose their malignant properties when stimulated to differentiation by neuroendocrine factors.