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Biomedical subjects

K Resch

Publications and source records attributed to K Resch.

At least 145 records · Page 8Linked to original sources
PubMed1983

Inhibition of mitogen-induced lymphocyte proliferation by ouabain: interference with interleukin 2 production and interleukin 2 action.

Since the discovery of IL 2 it has been possible to dissect the mitogenic activation of T lymphocytes into two steps: first, the production of IL 2; and second, the response of IL 2-dependent T cell blasts to IL 2. We investigated the influence of ouabain, a known inhibitor of T cell activation, on the production of and the response to IL 2 in mouse T lymphocytes. Ouabain dose-dependently inhibited DNA synthesis in Con A activated C57BL/6 spleen cells; inhibition below background levels occurred at a concentration of 5 X 10(-4) mol/liter. The action of IL 2 was assayed on a mouse T cell line, named M 2, derived from C57BL/6 spleen cells and maintained in continuous IL 2-dependent culture for more than 21 mo. Ouabain dose-dependently inhibited the response of these cells to mouse IL 2 with optimal inhibition at 10(-3) mol/liter ouabain. The production of IL 2 by Con A-stimulated C57BL/6 spleen cells was also totally inhibited by 10(-3) mol/liter ouabain; 10(-4) mol/liter ouabain inhibited IL 2 production partially, and 10(-5) mol/liter and 10(-6) mol/liter ouabain had no inhibitory effect. The ouabain-mediated inhibition of IL 2 production and of IL 2 action was not due to a nonspecific toxicity, because the preincubation of spleen cells with 10(-3) mol/liter ouabain for 24 hr did not impair their ability to produce IL 2, nor was the response of M 2 cells to exogenously added IL 2 abrogated by the preincubation of the cells with 10(-3) mol/liter ouabain. The data suggest that ouabain acts on two steps during the induction of T cell activation.

Animals↗
PubMed1982

Phospholipid metabolism of stimulated lymphocytes. Preferential incorporation of polyunsaturated fatty acids into plasma membrane phospholipid upon stimulation with concanavalin A.

Rabbit thymocytes were isolated and incubated for various lengths of time with concanavalin A. The cultures were pulsed for the last 12.5 min of incubation with equimolar mixtures of radioactively labelled fatty acids, either [3H]arachidonate and [14C]oleate or [3H]arachidonate and [14C]palmitate, and the uptake of each fatty acid into phospholipid of plasma membrane was determined. Upon binding of the mitogen, the fatty acids were incorporated at an increased rate with a new steady state being reached between 12.5 and 42.5 min after stimulation. Initially after 12.5 min, when the two fatty acids were added together, no preferential incorporation of the polyunsaturated fatty acid arachidonate was seen compared to the saturated or monounsaturated ones, palmitate or oleate. However shortly thereafter arachidonate, when compared to palmitate or oleate, started to be preferentially incorporated into plasma membrane phospholipid so that by 4 h after activation, only arachidonate was incorporated at an increased rate: the uptake of palmitate and oleate had reverted to that of unstimulated cells. In contrast, when palmitate or oleate were added alone, after 4 h of activation incorporation was increased similar to that of arachidonate, suggesting that all long chain fatty acids compete for the same activated enzyme(s). A detailed analysis of incorporation into phospholipid species showed that all fatty acids were taken up with the highest rate into phosphatidylcholine. After activation, fatty acid incorporation was increased by approx. 50% for phosphatidylcholine: the highest stimulation rates were observed with phosphatidylinositol (3-7-fold) and phosphatidylethanolamine (2-3-fold). The data suggest that shortly after stimulation with mitogens, the membrane phospholipids start to change by replacing saturated and monounsaturated fatty acids by polyunsaturated ones, thus creating a new membrane.

Acyl Coenzyme A↗
PubMed1981

Inhibition of lymphocyte activation by ouabain. Interference with the early activation of membrane phospholipid metabolism.

Activation of lymphocytes by antigens and mitogens can effectively be prevented by ouabain, a known inhibitor of (Na+ + K+)-ATPase. Recently it was shown that lowering of intracellular levels of monovalent cations is not involved in the inhibitory effect of ouabain. (Na+ + K+)-ATPase was found to be closely associated with acyl-CoA : lysophosphatidylcholine acyltransferase in the plasma membrane of lymphocytes. Both enzymes are activated as an immediate consequence of mitogen binding. Human peripheral lymphocytes were stimulated with concanavalin A. Ouabain suppressed the induction of RNA and DNA synthesis in a concentration-dependent way. Increase of RNA synthesis was suppressed only if the glycoside were added within the first hours of activation. If ouabain was added later, incorporation of uridine remained at the rate that was reached at the time of glycoside administration, pointing to an early event where ouabain may be operative. Ouabain, in a dose-dependent manner similar to that affecting RNA and DNA synthesis, inhibited the increase in the incorporation of oleate into phospholipids in stimulated lymphocytes, whereas the turnover of phospholipid fatty acids in resting lymphocytes was unaffected. Increasing extracellular K+ concentrations reversed the binding of ouabain to lymphocytes. Simultaneously, the inhibition of stimulated RNA synthesis was decreased and the inhibition of oleate incorporation was reversed. These results suggest that the suppression of lymphocyte activation by ouabain is due to the inhibition of membrane phospholipid metabolism mediated by (Na+ + K+)-ATPase.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1981

Microtubules: are they involved in the initiation of lymphocyte activation?

Purified human blood lymphocytes were stimulated with concanavalin A or phytohemagglutinin. DNA synthesis was measured with 2-h pulses of [3H]thymidine between 48 h and 73 h after stimulation. Colchicine, at concentrations between 0.1 muM and 10 muM, suppressed consequent DNA synthesis without affecting viability of the cells when added at any time up to 18 h before incorporation of [3H]thymidine was assessed. In concanavalin-A-stimulated lymphocytes, removal of the mitogen by methyl alpha-mannoside only prevented proliferation when added initially, but was without any effect when added after 20 h of stimulation, regardless of when DNA synthesis was measured. Thus, there was a period after 20 h of concanavalin A stimulation, when DNA synthesis was still sensitive to colchicine, but no longer required the presence of the mitogen. Colchicine also suppressed incorporation of [3H]leucine into protein, in resting as well as mitogen-stimulated lymphocytes. Similarly, colchicine decreased amino acid transport, as determined by uptake of alpha-amino-isobutyrate, which appeared to be the rate-limiting step in the incorporation of amino acids into protein in colchicine-treated cells. When the rate of protein synthesis was followed by the relative distribution of ribosomal particles, especially the increase of polysomes in activated lymphocytes, colchicine was without any detectable effect. The early increase in the incorporation of [14C]oleate into phospholipids was identical in the presence or absence of the microtubule-active drug. The data strongly suggest that microtubules are not involved in the initiation of lymphocyte growth or mitogenesis.

Biological Transport↗
PubMed1980

Mitogen-induced interferon production by normal and steroid-resistant mouse thymocytes.

We have investigated the proliferative response and interferon production in cultures of mouse thymocytes stimulated with two different mitogens, PHA (phytohemagglutinin), or Con A (concanavalin A). Normal thymocytes proliferated weakly and did not produce detectable interferon levels in response to both mitogens. Supplementing this cell population with macrophages or adding 2-mercaptoethanol to the culture medium strongly enhanced the proliferative response to both mitogens, but only in response to PHA marginal levels of interferon could be detected. When the steroid-resistant population was tested, both PHA and Con A induced strong proliferative responses; in this case significant interferon levels could be obtained after stimulation with PHA, but only borderline levels with Con A. Peripheral lymphocytes from the spleen responded identically to both mitogens with respect to interferon production as well as proliferation. The data suggest that distinct differentiation pathways may exist for T lymphocytes producing interferon in response to different mitogens.

Animals↗
PubMed1980

Induction of prostaglandin E release from macrophages by colchicine.

Rat peritoneal macrophages released high amounts of prostaglandin E (PGE) when treated in vitro with 10(-7) to 10(-4) M colchicine. PGE production occurred after a lag period of 4 hr and proceeded at a constant rate for more than 24 hr. Lymphocytes could not be stimulated to PGE release by colchicine. Disaggregation of microtubules appeared to be an essential event, since lumicolchicine was inactive and addition of heavy water (D2O) abolished colchicine-induced PGE formation. Cytochalasin B (5 microgram/ ml) did not interfere with PGE production by colchicine during the initial 12 hr, but thereafter it gave rise to an activity capable of degrading or converting newly synthesized PGE. Although details of the mechanisms by which colchicine in association with disrupted microtubules may induce PGE release remain unclear, these observations suggest that components of the cytoskeleton may efficiently influence the biosynthesis of prostaglandins.

Animals↗
PubMed1979

Cytotoxicity of human mononuclear cells against chicken and human red blood cells, induced by treatment of the effector cells with phospholipase C.

Human mononuclear cells from peripheral blood which were treated with phospholipase C (PLC), became cytotoxic against human or chicken red blood cells. PLC-induced cellular cytotoxicity against human red blood cells was further analyzed and compared to anti-D-mediated, antibody-dependent cellular cytotoxicity (ADCC), using the same target cells. ADCC, but not cytotoxicity of PLC-treated effector cells, was inhibited by free IgG. In addition, iodoacetate strongly enhanced PLC-induced cytotoxicity, but blocked ADCC completely. Addition of fetal calf serum or human AB serum impaired PLC-induced cytotoxicity. A similar inhibition was found by adding lecithin liposomes suggesting that the inhibitory effect of sera was also due to their phospholipid content. The data show that cytotoxicity of PLC-treated effector cells can be clearly distinguished from cellular cytotoxicity, occurring spontaneously or induced by target cell antibodies. We favor the notion that cytotoxicity of PLC-treated effector cells against human erythrocytes is due to the action of PLC, adsorbed to the effector cells.

Absorption↗