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Biomedical subjects

M Schlesinger

Publications and source records attributed to M Schlesinger.

At least 271 records · Page 15Linked to original sources
PubMed1975

The association of H-2 antigens and EAC receptors on the surface of peritoneal cells.

The exposure of murine peritoneal cells to anti-H-2 sera results in a diminished expression of H-2 antigen on the cell surface. Concomitant with this "H-2 modulation" the capacity of macrophages to bind sheep red blood cells coated with antibody and complement (EAC) was markedly diminished. In contrast, there was no change in the capacity of modulated macrophages to bind sheep red blood cells coated with antibody alone (EA). Antibodies to K end H-2 specificities were more effective in reducing the binding of EAC than antibodies to D end H-2 specificities. Exposure of peritoneal cells to O or Ly antisera had no effect on the formation of EAC rosettes. Exposure of peritoneal cells to anti-H-2 sera, under conditions which would not allow modulation of H-2 antigens, also prevented the reduction of EAC binding. Thus, the EAC receptors and H-2 antigenic specificities seem to be closely related on the surface of peritoneal cells, but constitute distinct cell surface structures. Preliminary evidence indicates that vinblastine, a microtubule depolymerizing agent, may disrupt the close association of EAC receptors and H-2 antigens. It is suggested that the association of EAC receptors and K end H-2 determinants on the membrane of macrophages may have implications for the regulation of the immune response by H-2-linked Ir genes.

Animals↗
PubMed1975

Initiation sites for translation of sindbis virus 42S and 26S messenger RNAs.

Sindbis virus 26S RNA is the principal species of virus-specific RNA found in the infected cell; it is derived from a one third segment of virion 42S RNA. When translated in cell-free extracts from mouse ascites cells or rabbit reticulocytes, 26S RNA directed the synthesis primarily of the 33,000 dalton virus capsid protein, and the protein products were in the form of free peptides rather than peptidyl-tRNA. In contrast, the polypeptides synthesized in either extract in response to Sindbis virus 42S RNA were heterogeneous, ranging in molecular weight from 33,000 to 190,000, and were largely in the form of peptidyl-tRNA. The number of independent initiation sites on the 26S and 42S RNAs was determined by analyzing a tryptic digest of reaction products labeled with yeast N-formyl-35S-methionyl-tRNAFmet. The 26S RNA appeared to contain a single initiation site, and this site could also be found in varying amounts in different preparations of 42S RNA. However, a second initiation site, distinct from that of 26S RNA, was the major site in 42S virion RNA. These results suggest that 42S virion RNA contains two potential sites for initiation of protein synthesis. Only one of these may be active, however, and it is postulated that the second site functions primarily, if not exclusively, in the subgenomic 26S RNA species. In this regard, Sindbis virus 42S RNA may represent a novel form of a eucaryotic messenger RNA.

Binding Sites↗
PubMed1975

Subpopulations of human thymus cells differing in their capacity to form stable E-rosettes and in their immunologic reactivity.

The majority of human thymus cells from young donors form stable E-rosettes with sheep red blood cells (SRBC) that do not distintegrate after prolonged incubation at 37 degrees C. With advancing age the proportion of thymus cells forming such rosettes decreases gradually. The thymus of a patient receiving prednisone treatment was found to contain only a few cells that formed stable E-rosettes. The minor population of thymus cells that fails to form stable E-rosettes (non-rosetting or NR cells) was isolated and tested for its cell surface markers and immunologic reactivity in vitro. Most of the NR-cells were capable of forming regular E-rosettes with SRBC at room temperature. Like the majority of human thymus cells they were sensitive to the cytotoxic effect of normal constituted less than 0.2% of the original thymus cell suspensions, but about 1 to 3% of the NR-population. Thymus cells from donors over the age of 36 and from a prednisone-treated child responded in vitro to stimulation with either phytohemagglutinin (PHA) or concanavalin A (Con A). Unfractionated thymus cells from children up to the age of 14 failed to react to either PHA or Con A, but their NR-population responded vigorously to both lectins. In contrast to unfractionated thymus cell suspensions from children, the NR fraction showed a significant reactivity in mixed lymphocyte cultures with mitomycin-C treated allogeneic lymphocytes. It is concluded that like the thymus of other species, the human thymus contains a minor population of cortisone-resistant cells endowed with many of the immunologic properties characteristic for periperal T lymphocytes.

Adolescent↗