On the survival probability of a slightly advantageous mutant gene with a general distribution of progeny size--a branching process model.
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Biomedical subjects
Publications and source records attributed to I Eshel.
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Conditions for the reproducible measurement of thymic hormonal effect on the functional activity of human peripheral blood lymphocytes (PBL) were determined using a mixed lymphocyte-tumor culture assay. Three thymic hormonal preparations (thymopoietin, thymic humoral factor and TP-1) were tested by this assay and found to have a significant enhancing effect on the blastogenic response. Essential for the demonstration of the hormonal effect was the selection of suboptimal stimulation conditions, with the appropriate cell lines, including the number of stimulating cells and the time in culture. The most reproducible results were achieved when 1 x 10(5) PBL were co-cultured for 4 days with 1 x 10(4) mitomycin-C treated Raji lymphoma cells, after 1 h preincubation with one of the thymic preparations. However, strong enhancing effects of the thymic preparations could also be demonstrated with other tumor cel lines, especially IgR3 melanoma cells.
The thymic extract TP-1 significantly enhanced the production of immune interferon (IF) by human peripheral blood mononuclear cells in Con A- or Raji- but not PHA-induced cultures. TP-1 effect was more pronounced under conditions of low IF production. The effect was evident before cell proliferation took place and without necessary concurrent effect of TP-1 on the blastogenic response. TP-1 had no detectable effect on nonactivated cultures. The enhancement of IF production by TP-1 to the degree demonstrated here necessitates consideration of its possible effects in every assay of thymic hormones that involves lectin or allogeneic stimulation of lymphocytes.
A unique automated sampling manifold designed to recover cells grown in standard 96 well microplates from their culture medium is described. Cells are recovered and washed on fiber glass filter discs. Incorporation of radioisotopes into cells, can then be measured by appropriate counting of the filter discs. Typical applications include termination of mixed lymphocyte cultures, assays of mitogen stimulation of lymphocytes and antigen-specific lymphocyte transformation and assays of interferon activity. The harvester can also be used in other biological systems where collection and washing of precipitates is desired.
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Deterministic selection forces operating at a modifier level within a population lead to the establishment of systems of sex-determination which, under a variety of natural conditions, induce sex-ratios close to 1 : 1.
When Moloney lymphoma (YAC) cells were freshly explanted from the tumor-bearing host into culture, two events occurred in the first 120 minutes: The cells lost their natural IgG coat, and their sensitivity to complement-dependent lysis (CdL) mediated by antibodies to Moloney lymphoma cells decreased or increased. An increasing sensitivity to CdL as a function of incubation time at 37 degrees C was likely to occur when the sensitivity to CdL was low at explantation. A decreasing sensitivity to CdL was probable in instances of a high sensitivity to CdL at explantation. Artifical coating of YAC cells with antibodies to Moloney lymphoma immediately after explantation moderated the alterations in their sensitivity to CdL. This occurred even though a functional antibody did not remain on the cells as evidenced from the gradual decreased sensitivity of these artifically coated cells to the addition of complement. Spent culture media in which freshly explanted cells grew for 60 or 120 minutes sometimes blocked CdL of YAC cells mediated by antibodies to Moloney lymphoma.
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