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Biomedical subjects

M A Bach

Publications and source records attributed to M A Bach.

At least 127 records · Page 7Linked to original sources
PubMed1979

Respective influence of extrinsic and intrinsic factors on the age-related decrease of thymic secretion.

The serum level of a circulating thymic factor (FTS) described in our laboratory diminishes in mice after adult thymectomy and with age. However, thymuses from old mice, when grafted into young adult thymectomized recipients lacking circulating FTS, can still partially restore the circulating FTS level of the recipients, whereas newborn thymuses are less efficient in restoring the serum level of FTS in old recipients than in young adult thymectomized recipients. Taken together, our results suggests that in addition to an intrinsic deficiency of the thymic secretion, "environmental" factors play a role in the disappearance of circulating FTS with age, the more so since we observed in old mouse sera factors inhibiting the in vitro biologic activity of FTS, factors that are absent from young mouse sera.

Aging↗
PubMed1977

Lymphocyte-mediated cytotoxicity: effects of ageing, adult thymectomy and thymic factor.

Adult thymectomy, as well as ageing, depressed splenic lymphocyte-mediated cytotoxicity (LMC) in the mouse. Ageing depressed significantly LMC as early as 19 weeks of age, independently of the number of cells used for immunization. Thymectomy affected LMC only when supoptimal numbers of immunizing allogeneic cells were used. This effect peaked at 6 to 12 weeks after thymectomy. No difference between thymectomized and normal mice was observed when LMC was tested 16 to 20 weeks after thymectomy, at an age when normal control mice themselves already showed a lowered LMC due to ageing. The effect of in vivo treatment with a circulating thymic factor (TF), which was shown to disappear with ageing as well as after adult thymectomy, has been tested in adult thymectomized mice and normal young and ageing mice. TF treatment prevented LMC depression in adult thymectomized mice, whereas it depressed paradoxically splenic LMC in normal young and old mice. The possible mechanisms of the effects of adult thymectomy, ageing, and thymic factor on the different T cell subsets involved in allogeneic killer cell generation are discussed.

Aging↗
PubMed1976

Differences in effect of isoproterenol stimulation on levels of cyclic AMP in human B and T lymphocytes.

The level of cyclic AMP (cAMP) in human lymphocytes in the presence or absence of isoproterenol stimulation was studied in various lymphocyte subpopulations containing different proportions of B and T lymphocytes. Lymphocytes from thymus and peripheral blood (which contain a majority of T cells) were more sensitive to isoproterenol action than lymphocytes from tonsils or adenoids (where B cells are predominant). Using purified B or T lymphocytes from peripheral blood, tonsils or adenoids, we observed an absence of B lymphocyte response to isoproterenol, whereas T lymphocytes, which had a lower basal c-AMP level than B cells, exhibited in all experiments a significant increase in cAMP content after isoproterenol stimulation. The intensity of the response varied in the different T lymphocyte subpopulations.

Adenoids↗
PubMed1976

Thymic function in NZB mice. II. Regulatory influence of a circulating thymic factor on antibody production against polyvinylpyrrolidone in NZB mice.

Administration of a circulating thymic factor isolated from normal pig blood prevented the development of the exaggerated production of anti-polyvinyl pyrrolidone (PVP) antibody in young NZB mice. However, treatment was ineffective if initiated after the 4th week of life at a time when endogenous serum thymic factor (TF) normally disappears in these mice. These data suggest that circulating TF is necessary for the survival of short-lived suppressor T cells normally implicated in the regulation of the production of antibodies against PVP, a thymus-independent antigen. In older NZB mice, TF treatment increased paradoxically anti-PVP antibody production, which suggests that "amplifier" T cell activity could also be under TF influence.

Age Factors↗
PubMed1975

Regulation of theta-antigen expression by agents altering cyclic AMP level and by thymic factor.

Thymic factor, cyclic AMP, and products increasing its cellular level, such as Prostaglandin E1, induce the appearance of the theta-antigen on T-cell precursors whether assessed by a rossette-inhibition assay or a cytotoxic assay after cell fractionation on BSA discontinuous gradiet. Synergism has been demonstrated between cyclic AMPT and TF for that effect. Conversely, decrease of theta expression has been obtained by altering cyclic AMP level in theta-positive cells either increasing it by dibutyryl cAMP treatment or decreasing it by indomethacin treatment. Finally, these data suggest the involvement of cyclic AMP in the regulation of theta expression under thymic hormone control.

Acetylcholine↗
PubMed1975

Differences in Cyclic AMP Changes after Stimulation by Prostaglandins and Isoproterenol in Lymphocyte Subpopulations.

Various lymphocyte populations have been studied for their content in cyclic adenosine 3',5'-monophosphate (cAMP) before and after stimulation by isoproterenol and prostaglandin E(1) (PGE(1)). Basal cAMP levels vary among lymphocytes according to their origin: peripheral blood lymphocytes show high cAMP level while spleen and lymph node cells and thymocytes show lower levels. Thymocytes are extremely sensitive to the stimulating effects of isoproterenol and PGE(1), much more than spleen and lymph node or peripheral blood cells. Corticoresistant thymocytes are less sensitive to isoproterenol stimulation than normal thymocytes, but are significantly more sensitive than peripheral thymus-derived (T)-cells. Studies using bone-marrow-derived (B) or T cell depletion with anti-immunoglobulin-coated columns and antitheta serum (AthetaS) indicate that lymph node B cells synthesize more cAMP in the presence of isoproterenol than T cells. However, this difference between T and B cells has not been found in spleen cells.

Journal Article↗