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Biomedical subjects

J R David

Publications and source records attributed to J R David.

At least 217 records · Page 12Linked to original sources
PubMed1977

Increased responsiveness to macrophage-activating factor (MAF) after alteration of macrophage membranes.

Guinea pig macrophages pretreated with the esterase inhibitor, antithrombin III (AT III) show increased responsiveness to macrophage-activating factor (MAF) as demonstrated by their enhanced cytotoxicity for tumor cells. Other proteins that are not esterase inhibitors did not enhance the effect of MAF on the macrophage. Enhancement of MAF activity was also obtained when macrophages were preincubated with the cell surface reactant, diazotized sulfanilic acid (DSA). These studies indicate that the effect of MAF can be enhanced by chemical modifications of the macrophage membrane. They also provide further evidence to support the hypothesis that an esterase on the macrophage membrane modulates this cell's responsiveness to lymphocyte mediators.

Animals↗
PubMed1977

Partial purification of antigens from eggs of Schistosoma mansoni that elicit delayed hypersensitivity.

Schistosoma mansoni egg antigens that elicit delayed hypersensitivity in appropriately sensitized guinea pigs were partially characterized by using ion exchange chromatography and preparative electrophoresis. At least three skin-reactive antigens were found, one of which was purified to homogeneity, as analyzed by polyacrylamide gel electrophoresis (PAGE). This antigen was not adsorbed to CM cellulose, migrated cathodal to guinea pig albumin on electrophoresis, and was adsorbed to DEAE cellulose. A second pool of antigenic activity was obtained by adsorption to CM cellulose and subsequent elution. DEAE cellulose chromatography and preparative electrophoresis of this pool indicated the presence of more than one antigen.

Animals↗
PubMed1976

Maternal-fetal relation. Absence of an immunologic blocking factor from the serum of women with chronic abortions.

We investigated an immunologic mechanism that might explain the apparent "tolerant" state of the mother during pregnancy. Cellular-immune reactivity in vitro to paternal alloantigens was demonstrated in multigravid women by production of lymphocyte migration inhibitory factor. Serum from normal multigravid women contained a factor that blocked production of migration inhibitory factor by maternal lymphocytes to paternal antigens in a specific manner. The blocking factor was an IgG antibody whose activity was removed by absorption with paternal lymphocytes but not with pooled human platelets. We tested the biologic importance of this blocking factor in women who have difficulty maintaining a normal term pregnancy. Our observations indicate that women who experience idiopathic spontaneous abortions produce lymphocyte migration inhibitory factor to paternal alloantigens, but their serums lack the blocking factor. The presence of the serum blocking factor during pregnancy may contribute to the success of the fetus as an allograft.

Abortion, Habitual↗
PubMed1976

Deleterious effects of copulation in Drosophila females as a function of growth temperature of both sexes.

In Drosophila females, copulation always results in a reduction of longevity but the gravity of the phenomenon varies according to growth temperature. The harmful effect of adult males, or aggressiveness, is maximum when growth took place at a middle temperature. Female sensitivity, on the other hand, is at a maximum when larvae were reared at exteme, low or high, temperatures.

Aggression↗
PubMed1976

Biological role of alcohol dehydrogenase in the tolerance of Drosophila melanogaster to aliphatic alochols: utilization of an ADH-null mutant.

The toxicity of the first eight primary alcohols and of four secondary alcohols was compared in a wild-type strain (having active ADH) and an ADH-negative mutant. Differences between LC50 measured in the two strains allowed an evaluation of the biological activity of the enzyme. In vitro, ADH is mainly active on secondary alcohols, while in vivo its main role is the detoxification and metabolism of ethanol. These observations suggest that originally ADH was involved in unknown metabolic pathways and that its utilization in ethanol metabolism could be a recent event.

Alcohol Oxidoreductases↗
PubMed1976

Partial characterization of murine migration inhibitory factor (MIF).

These studies describe the production of murine migration inhibitory factor (MIF)3 in sufficient quantities to allow its partial characterization by physiochemical and enzymatic methods. MIF was obtained from murine spleen cell cultures (C57BL/6 strain) stimulated with concanavalin A (Con A). Characterization of murine MIF was performed using Sephadex G-100 gel chromatography, isopycnic centrifugation in a CsCl density gradient, polyacrylamide disc electrophoresis, heat stability, and enzymatic treatment. MIF-containing and control fractions were assayed on normal C57BL/6 peritoneal exudate cells by using a microcapillary tube assay. Peak MIF activity was found in a Sephadex G-100 fraction containing molecules the size of albumin and slightly smaller, molecular weight 67,000 to 48,000. Murine MIF was stable to heating at 56 degrees C for 30 min but lost its activity at 80 degrees C for 30 min. Incubation of G-100 fractions containing MIF with water insoluble chymotrypsin destroyed the activity of MIF, indicating its protein nature. CsCl density gradient centrifugation revealed that murine MIF had a buoyand density greater than protein, consistent with its being a glycoprotein. Further, when subjected to disc electrophoresis on polyacylamide gels, murine MIF migrated in a region cathodal to albumin. Thus, mitogen stimulation of murine spleen cells produced MIF in quantities which allowed its partial characterization and purification, and its comparison with human and guinea pig MIF; this makes it feasible to analyze the role of murine MIF in cellular immunity and in its relationship to lymphocyte mediators which regulate humoral immune responses.

Animals↗
PubMed1976

Biological expressions of lymphocyte activation. V. Characterization of a soluble immune response suppressor (SIRS) produced by concanavalin A-activated spleen cells.

Supernatant fluids from murine spleen cell cultures incubated with concanavalin A for 48 hr contain a factor(s), soluble immune response suppressor (SIRS), which suppresses plaque-forming cell responses to sheep erythrocytes by murine spleen cells in vitro. In the present studies, some of the biochemical and biophysical properties of SIRS were investigated. SIRS was non-dialysable; the suppressive activity was stable at 56 degrees C for 30 min, but was destroyed by treatment at 70 degrees C for 30 min, 80 degrees C for 10 min, or at pH 2. The suppressive activity was not absorbed by the stimulating antigen, SRBC, or antisera against murine IgG or mu-chain, suggesting that SIRS does not contain immunoglobulin determinants. Murine spleen and thymus, but not kidney cells, however, absorbed SIRS activity. Enzyme treatments revealed that SIRS was resistant to DNase and RNase, but was destroyed by trypsin and chymotrypsin. In gel filtration with Sephadex G-100, SIRS activity eluted in the fraction corresponding to m.w. in the range between 48,000 and 67,000. With polyacrylamide gel electrophoresis, SIRS activity migrated in the region cathodal to albumin. Isopycnic centrifugation in a cesium chloride gradient suggested that SIRS is a glycoprotein. These supernatant fluids with SIRS activity were also found to contain macrophage migration inhibitory factor (MIF). In the experiments using gel filtration, polyacrylamide gel electrophoresis, and isopycnic centrifugation to fractionate supernatant fluids, SIRS and MIF activity were found in the same fractions, and to date we have been unable to dissociate definitively SIRS activity from MIF activity.

Absorption↗
PubMed1975

Two stages in lymphocyte mediator production by differential susceptibility to blockade using niridazole.

Sera from guinea pigs given niridazole, an anti-schistosomal compound, have been shown to reversibly block the production of antigen-induced migration inhibitory factor by sensitized guinea pig lymph node cells. Since niridazole itself has no effect in vitro, the blockade of production of migration inhibitory factor is probably due to drug metabolites in the serum. We report here further studies on the mechanism of this drug-induced suppression of cellular hypersensitivity; the data show that niridazole active serum does not block the production of migration inhibitory factor once it has been initiated. Indeed, if niridazole active serum is added a little as 60 sec after the addition of antigen, the lymphocytes will produce migration inhibitory factor. These results suggest the presence of at least two stages in production of migration inhibitory factor after the addition of antigen to lymphocytes. The first, lasting less than 60 sec, is susceptible to blockade by niridazole active serum; the second is not. The elucidation of the mechanism of this blockade should lead to further understanding of the early events after antigen triggering of sensitized lymphocytes.

Animals↗