Carcinogenesis and aging. IV. Effect of low-molecular-weight factors of thymus, pineal gland and anterior hypothalamus on immunity, tumor incidence and life span of C3H/Sn mice

The low-molecular-weight polypeptide factors were obtained from bovine thymus (TF), pineal gland (PF) and anterior hypothalamus (AHF). Both TF and PF administration enhanced the rejection of skin allograft and stimulated the immunological response to sheep erythrocytes in adult CBA mice. Treatment of CBA mice with AHF increased the graft survival and inhibited antibody formation to sheep erythrocytes. Chronic TF or PF administration decreased spontaneous tumor development and prolonged the life span of female C3H/Sn mice. Administration of AHF failed to influence the life span and the tumor incidence of female C3H/Sn mice. The role of immunity and hormonometabolic shifts in mechanisms of both aging and the age-associated increase in cancer incidence are discussed.

[Effect of thymic polypeptide factor on the cyclic nucleotide system of immunocompetent cells]

Thyramine, a polypeptide factor from thymus, at wide range of concentrations increased the cAMP content in rat thymocytes. Increase in the cAMP content was less distinct in spleen lymphoid cells. Thyramine decreased the cGMP content in thymocytes; minimal nucleotide level was found within 15 min of incubation. The data obtained suggest that the rate of lymphocyte maturation is important for response of the cells to the effect of immunoregulating agents.

[Effect of polypeptide factors of the thymus and epiphysis on radiation carcinogenesis]

Three-month-old female rats were exposed to a single x-ray irradiation (400 rad). Beginning from week 3 after irradiation the animals were treated with 0.2 mg of thymic factor (thymarin) or pineal factor (epithalamine) dissolved in 0.2 ml of normal saline. Meanwhile the control rats were given the same amount of the solvent. The treatment was carried out for 10 days monthly during the lifespan. Application of epithalamine reduced the incidence of all the tumors and that of malignant tumors 1.3- and 2.7-fold, respectively. The preparation suppressed the development of mammary adenocarcinomas, tumors of the thyroid gland, leukemias, and malignant tumors of the uterus. Administration of thymarine decreased the incidence of malignant tumors (1.9-fold) mainly that of mammary adenocarcinomas. It is suggested that normalization of hormonal and metabolic shifts and related immunity disorders that develop as a result of exposure to ionizing radiation prevents the development of tumorous process more effectively than application of specific immunity stimulants.

[Effect of the thymic factor on blood coagulation and fibrinolysis in thymectomized rats]

Hypercoagulation and fibrinolysis inhibition are seen in adult rats 6 to 6 1/2 months after thymectomy. Hemocuagulation accelerating is caused by the shortened 1st phase of the blood coagulation process. Fibrinolysis delay is partially produced by a decrease in the fibrinalytic agent concentration and smooth elevation of the antiplasmin level. The most part of the coagulogram indices and fibrinolysis activation returns to normal in operated animals following the injection of a low-molecular polypeptide thymic factor within 5 days.

[Effect of thymalin on the cyclic nucleotide system in the mouse spleen]

The effect of the thymus preparation thymalin (1000 micrograms/mouse, i.p.) on the system of cyclic nucleotides in the spleen has been studied. The preparation produced two-phasic changes in the content of cAMP and cGMP, as well as in the activity of cAMP phosphodiesterase. The changes in the spleen cAMP content are consequent on those in the activity of phosphodiesterase.

[Regulation of the functional activity of the stem cell precursors of granulo- and monopoiesis by polypeptide factors of the thymus and bone marrow]

Effect of polypeptide thymic and bone marrow factors on functional activity of stem cells was studied with the use of two-layer agar system containing human bone marrow hemopoietic cells. Unlike bone marrow factor, thymic factor appreciably increased the cluster- and colony-forming abilities of cells - precursors of granulomonopoiesis. The results indicate that thymic and bone marrow factors regulate different stages of stem cell differentiation.

[Role of the thymus in regulating blood coagulation and fibrinolysis]

Within 2-6 months after thymectomy the rats developed hypercoagulation and their fibrinolysis became suppressed. Administration of low-molecular polypeptide factor of the thymus to the thymectomized animals restored the initial indices of blood coagulation and fibrinolysis. The adequate response of the blood coagulating system and fibrinolysis to adrenaline or heterogenic blood is disturbed in the thymectomized animals.

[Isolation, purification and identification of an immunomodulating polypeptide from human and calf thymus]

A comparison of human and calf thymus extracts was carried out. The thymus extracts and the fractions isolated from them differ in their physico-chemical properties, amino acid composition and biological activity. The extracts tested contain different amounts of the thymus factor, which stimulates the reactions of cellular and humoral immunity. The results obtained suggests that calf and human thymus contain only one immunomodulating factor, namely thymarin, a component of thymus extracts from various sources, in particular of thymosin. In some of its physico-chemical properties thymarin is similar to histone H1 from calf thymus, thus suggesting an essential role of this histone in the formation and differentiation of T-lymphocytes. A possibility of quantitative estimation and identification of the immunomodulating polypeptide in thymus extracts obtained by various methods is postulated.

[Development of an experimental tuberculous process in the presence of immune deficiency and immunostimulation]

The effects were studied of the degree of immunodeficiency produced by thymectomy of one-month-old rats on the course of experimental tuberculosis induced 3, 6 and 9 months after thymectomy. Subject to study was also the effect of immunodeficiency correction with thymalin on the tuberculous process. It was established that the lungs of thymectomized rats infected 9 months after the thymectomy were damaged more severely as compared with control or thymalin-treated animals. In thymectomized rats treated with thymalin, the absolute content of medium-sized and big lymphocytes in peripheral blood was found to be lower, the content of small lymphocytes being unchanged throughout all observation periods. The time course of migration activity (spontaneous and in response to PPD) in rats treated with thymalin corresponded with the time course in controls in contrast to thymectomized rats which did not receive the treatment. The results indicate that tuberculosis severity depends on the degree of immunodeficiency and that the functional properties of immunocompetent cells may be corrected with thymalin.

[Effect of thymalin on blood coagulation and fibrinolysis]

Experiments were made on 20 cats to show that within the first minutes intravenous administration of thrombin led to the enhancement of blood coagulation, an abrupt lowering in fibrinogen concentration, growth of antithrombin III activity and inhibition of fibrinolysis. 30-60 minutes after thrombin injection there developed a secondary hypocoagulation accompanied by the increment of the level of natural anticoagulants and by drastic enhancement of fibrinolysis. In animals given timalin in a dose of 2 mg for 5 days, the injection of thrombin produced a more remarkable increase in blood fibrinolytic activity.

[Effect of substances of a polypeptide nature isolated from the thymus and cerebral cortex on the primary immune response of mice to thymus-dependent and thymus-independent antigen]

The study of the effect of low molecular polypeptides on the primary immune response induced in CBA mice by the injection of thymus-dependent antigen (SRBC) and thymus-independent Vi-antigen showed that the injection of the preparation obtained from the cerebral cortex (cortexin) or the thymus (thymarin) for 5 days before and for 3 days after SRBc immunization stimulated the production of both direct (IgM) and indirect (IgG) antibody-producing cells, as well as the production of hemagglutinins. At the same time the production of antibody-producing cells and antibodies to Vi-antigen was suppressed. The preparations of white cerebral tissue and red bone marrow produced no effect on immune response in the animals.