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Biomedical subjects

J R David

Publications and source records attributed to J R David.

279 records · Page 16Linked to original sources
PubMed1965

Suppression of delayed hypersensitivity in vitro by inhibition of protein synthesis.

Peritoneal cells from guinea pigs exhibiting delayed hypersensitivity are inhibited from migrating in vitro by specific antigen. This inhibition is prevented by the addition of puromycin to the culture medium. The amount of puromycin necessary to prevent the inhibition by antigen also suppressed the incorporation of C(14)-leucine into peritoneal cell protein. Additional evidence that the action of puromycin is due to its inhibition of protein synthesis has been obtained with analogues of puromycin; those that inhibit protein synthesis also prevent the action of antigen on the cells, while those analogues that do not inhibit protein synthesis have no effect. Actinomycin also prevents the inhibition of sensitive cells by antigen while chloramphenicol has no effect. The data indicate that the inhibition of sensitive cell migration by antigen requires active protein synthesis. The possible mechanisms by which inhibition of protein synthesis may influence the in vitro reactions of delayed hypersensitivity are discussed.

Animals↗
PubMed1965

In vitro demonstration of cellular sensitivity in allergic encephalomyelitis.

Peritoneal cells obtained from animals exhibiting delayed hypersensitivity are inhibited from migrating in vitro by specific sensitizing antigen. This test for the detection of delayed hypersensitivity was applied to the problem of cellular sensitivity in allergic encephalomyelitis (AE). The migration of peritoneal cells obtained from guinea pigs with AE was inhibited specifically by nervous tissue antigens. The specificity of this reaction was further studied. Neonatal rat nervous tissue, which was shown to lack the encephalitogenic antigen, i.e. did not produce AE when injected with complete adjuvant into guinea pigs and rats, did not inhibit the migration of cells from animals with AE. Adult rat nervous tissue, which readily produces AE, and thus contains the encephalitogenic antigen did inhibit the migration of such cells. The finding that cells from animals with AE display hypersensitivity which appears to be directed specifically to the encephalitogenic antigen strongly supports the view that such cells could play an important role in the pathogenesis of this disease.

Animals↗
PubMedDate not supplied

Developmental constraints on an adaptive plasticity: reaction norms of pigmentation in adult segments of Drosophila melanogaster.

Variation of dark pigmentation according to developmental temperature was investigated in two geographic populations (France and India) with the isofemale line technique (20 lines for each population). The response curves called the reaction norms, were established in females for seven different segments: the mesothorax and abdomen segments 2-7 (Abd 2-7). In all cases the response curves were non-linear and had to be described either by a quadratic convex polynomial for thorax and Abd 2-5, or by a cubic polynomial for Abd 6 and 7. Among abdomen segments, increasing antero-posterior gradients were observed for several traits, including average pigmentation, overall phenotypic plasticity, the temperature of minimum pigmentation, and the curvature parameter of quadratic norms. Genetic correlations between abdomen segments were high when adjacent segments were considered, but became nil when more distant segments were correlated, suggesting that different pigmentation genes are expressed in the anterior and the posterior part of the abdomen. Characteristic values of reaction norms provided information either on trait value (i.e., the extension of pigmentation) or on plasticity. Correlations between plasticity and pigmentation were generally low and non-significant, suggesting their genetic independence. The overall darker pigmentation which is observed at low temperatures is assumed to be an adaptive plasticity. However, the differences which are evidenced among segments reveal strong interactions with developmental genes. These interactions are less likely to be a consequence of natural selection and are better interpreted as developmental constraints. The reaction norms analysis reveals the complexity of these interactions and should help, in the future, in the identification of the responsible thermosensitive genes.

Adaptation, Physiological↗
PubMedDate not supplied

A cloned DNA fragment for identification of Mycobacterium tuberculosis.

The identification of Mycobacterium tuberculosis is a lengthy process. Attempts were made to develop a more rapid, specific, and sensitive assay for identifying tubercle bacilli in biologic specimens by differentially screening plasmid libraries of Sau3AI-digested M. tuberculosis H37Rv (ATCC 25618) DNA with homologous and heterologous DNA for clones that hybridized strongly with M. tuberculosis DNA alone. Three clones, pMTB1, pMTb2, and pMTb3, were selected for further study. Southern analysis indicated that these clones reacted strongly with DNA from strains of M. tuberculosis isolated in different parts of the world, weakly with DNA from other mycobacterial species, and not at all with Escherichia coli or human DNA. Smaller fragments of mycobacterial DNA contained in plasmid pMTb3 were subcloned into pBR322 (pMTb4) or pUC12 (pMTb5). These recombinant plasmids hybridized with DNA from M. tuberculosis, Mycobacterium bovis, and Mycobacterium bovis BCG (bacille Calmette-Guérin) Montreal and may provide the reagents needed for the development of new methods for rapid diagnosis of M. tuberculosis infections.

Blotting, Southern↗