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Biomedical subjects

N Trainin

Publications and source records attributed to N Trainin.

At least 127 records · Page 7Linked to original sources
PubMed1975

Increased reactivity of responding cells in the mixed lymphocyte reaction by a thymic humoral factor.

A thymic humoral factor (THF) induces competence in a certain sector of the lymphoid cell population. The target cell for THF activity was studied using the one-way mixed lymphocyte culture (MLC). Cells from various lymphoid tissues (responding cells) were preincubated in THF for 1 hour and then mixed with mitomycin-C-treated cells (stimulating cells). The results obtained indicate that THF increases MLC competence of lymphocytes from spleen and thymus origin of intact mice and that of spleen of thymus-deprived mice. In contrast, no enhancing effect in the MLC response by THF could be observed when bone marrow-derived spleen cells, cortisone-resistant thymocytes or lymph node cells were used as responding cells. These results confirm our hypothesis that THF leads to differentiation of young thymus-derived (T) cells, promoting them to maturation and thus to the acquisition of full immune competence.

Animals↗
PubMed1975

Inhibition of tumor growth in syngeneic chimeric mice mediated by a depletion of suppressor T cells.

Syngeneic chimeric (lethally irradiated and reconstituted with syngeneic bone marrow cells) mice manifested an increased resistance to the development of Lewis lung carcinoma. In addition, these mice had a higher response to polyvinylpyrrolidone and a reduced reactivity to T mitogens. The present findings suggest that syngeneic chimeric mice lack suppressor T cells shown to regulate the development of Lewis lung tumor and the response to polyvinylpyrrolidone. Other components of the T cell population, such as helper cells responding to sheep red blood cells or cells involved in allograft rejection, assayed in these syngeneic chimeras were found unaffected. The fact that chimeric mice are deficient in a certain suppressor T cell population whereas other T activities are normal suggests the existence of different cell lines within the T cell population.

Animals↗
PubMed1975

Impaired radioprotective capacity and reduced proliferative rate of bone marrow from neonatally thymectomized mice;.

The colony forming capacity of bone marrow from neonatally thymectomized mice is reduced in comparison with that of normal animalsmin addition to this quantitative change, we observed that the bone marrow of thymectomized animals has a reduced radioprotective effect upon inoculation into lethally irradiated recipient mice. It was also found that the cellularity of spleen colonies derived from bone marrow of thymectomized animals is lower than that of intact controls. In vitro uptake of 3H-thymidine into cells of spleen colonies, and rate of DNA synthesis measured in vitro were found to be reduced in cells derived from bone marrow of thymectomized donors; The initially observed reduction in colony forming capactiy of bone marrow from neonatally thymectomized mice could be reversed by thymus reimplantation=

Animals↗
PubMed1975

The role of a thymus humoral factor in the proliferation of bone marrow CFU-S from thymectomized mice.

The colony forming capacity of bone marrow cells from thymectomized mice was shown to be reduced as compared to that of bone marrow cells from normal donors. A further indication of changes in the proliferative capacity of colony forming cells (CFU-S), following thymectomy, was given by examination of the sensitivity of these cells to chlorambucil and by 3H-thymidine 'suicide' experiments; both showed that CFU-S from thymectomized mice were not cycling at the same rate as normals. It was also found that in late pregnancy of thymectomized females, there is an elevation in the number of bone marrow CFU-S and an increase in cell cycling. Such an increase could also be achieved by implantation, into thymectomized mice, of thymus lobes in closed diffusion chambers. Finally, in vitro administration of a thymus hormone (THF) reversed the suppressive effect of thymectomy on DNA synthesis in bone marrow CFU-S. Since the action of THF was restricted to bone marrow cells of thymectomized mice it is plausible that normal bone marrow contains at least two subpopulations of CFU-S, one of which is dependent upon a humoral product of the thymus.

Animals↗
PubMed1975

Hydantoin immunosuppression and carcinogenesis.

The immunological response of mice submitted to hydantoin treatment was determined. Hydantoin reduced the absolute number of spleen cells in treated animals and did not modify spleen cells reactivity to concanavalin A, although the response to SRBC challenge, as measured by the Jerne plaque-forming cell technique, was significantly decreased. Following these findings, the influence of hydantoin on carcinogenesis was evaluated by using the model of urethane-induced lung adenomas in SWR mice. Treatment with hydantoin significantly reduced the incidence of the induced adenomas. We confirmed that hydantoin modifies the immune response of the host mainly by depressing its humoral function and we have shown that this effect was associated with an inhibitory effect on tumour induction.

Adenoma↗
PubMed1975

Intracellular events involved in the induction of immune competence in lymphoid cells by a thymus humoral factor.

A humoral factor extracted from calf thymus (THF) restores the immunocompetence of spleen cells from neonatally thymectomized (NTx) mice to induce an in vitro graft-vs-host (GVH) response. This acquistion of immunocompetence consists of a series of biochemical events, the first of which involves an obligatory rapid increase in adenyl cyclase acitivity and in intracellular levels of cyclic AMP. Protein synthesis occurs as a further step in the events leading to induction of immunocompetence by THF and could be blocked by cycloheximide with the consequent abolishment of the immunocompetence of the lymphoid cells tested. The induction of competence by THF is accompanied by a simultaneous reduction in DNA synthesis resulting from the increase in intracellular cyclic AMP levels. These steps have been studied in the absence of antigenic stimulation which is not required for the induction of competence by THF. Spleen extracts prepared by a similar procedure as THF were found to be devoid of the properties described above.

Adenosine Triphosphate↗
PubMed1974

Hormone-like activity of a thymus humoral factor on the induction of immune competence in lymphoid cells.

Experiments reported here were performed to understand the mechanism by which THF increases the immunocompetence of spleen cells from NTx mice. Dibutyryl cAMP or substances which increase intracellular levels of cAMP in lymphocytes such as Poly(A:U), theophylline, or PGE(2) were shown to mimic the effect of THF and confer reactivity in an in vitro GvH response to spleen cells from NTx mice. Flufenamic acid, an antagonist to PGE(2), was shown to inhibit the induction of competence by this substance. It was found that THF induces competence by activating membranal adenyl cyclase which leads to a rise in intracellular cAMP in thymus-derived cells only. These biochemical changes occur before antigenic stimulation and are unrelated to antigenic challenge. These findings indicate that THF exerts its effect via cAMP and are in agreement with the concepts which permit to classify THF as a thymus hormone.

Adenylyl Cyclases↗