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Biomedical subjects

D Yaffe

Publications and source records attributed to D Yaffe.

At least 73 records · Page 4Linked to original sources
PubMed1978

Synthesis of tropomyosin in myogenic cultures and in RNA-directed cell-free systems: qualitative changes in the polypeptides.

The synthesis of polypeptides with the properties of alpha and beta tropomyosin was investigated in differentiating cultures of a myogenic cell line and in a wheat germ cell-free system directed by purified RNA extracted at different stages of differentiation. The polypeptides co-migrate with tropomyosin in isoelectric focusing and SDS two-dimensional gel electrophoresis and SDS-urea/SDS two-dimensional gels. Like authentic tropomyosin, these polypeptides change their mobility greatly in the presence of urea and do not become labeled with proline. The beta tropomyosin synthesized in the intact cells and in the cell-free system can be separated by isoelectric focusing into at least two components. One component (designated beta1) is present in a small amount at all developmental stages examined, and a more basic component (beta2) is specific for differentiated cultures. The synthesis of beta2 in the intact cells and the capacity of purified RNA to direct its synthesis in a cell-free system become detectable and increase greatly during the period of fusion of the mononucleated cells into multinucleated fibers. The results suggest that the beta1 and beta2 tropomyosins are coded for by different genes.

Cell Differentiation↗
PubMed1977

A myogenic cell line with altered serum requirements for differentiation.

Dfferentiation properties of a cell line, L84, which originated from a non-fusing clone isolated from the myogenic line L8, are described. In nutritional medium supplemented with 10% serum used routinely with L8 cells, L84 cells continue to proliferate to very high densities and fail to form multinucleated fibres. When grown in medium supplemented with 2% horse serum of 2% horse serum plus 0.1% microng/ml insulin, L84 cells behave very similarly to L8 cells grown in medium supplemented with 10% horse serum: when the cultures reach confluency, proliferation decreases and cells start to fuse and form a dense network of fibres. Large increases in creatine kinase activity and synthesis of myosin are associated with cell fusion. Under conditions in which L84 cells do not fuse the increase in these synthetic activities is not observed, even after extremely high cell densities are reached. The data show that L84 cells retain the programme for their differentiation into muscle fibres. The difference between L84 and its progenitor line L8 lies in the sensitivity to the environmental conditions which trigger the expression of this programme.

Animals↗
PubMed1976

Snythesis of polypeptides with the properties of myosin light chains direct by RNA extracted from muscle cultures.

Polyadenylylated RNA, extracted from differentiating primary cultures of rat muscle and the myogenic cell line L8, directs the synthesis of polypeptides in the wheat germ cell-free system which comigrate with myosin light chains under several electrophoretic conditions. The peptides also associate specifically with heavy myosin subunits during dissociation-reassociation treatment. Intact cells of primary skeletal muscle cultrues and of the myogenic line synthesize predominantly two ligh chains. RNA extracted from primary muscle cultures directs the synthesis of a third polypeptide in the cell-free system, similar to the third light chain found in myosin extracted from adult rat thigh muscle. Products of cell-free systems directly by RNA extracted from fibroblasts, reticulocytes, and myeloma cells did not contain detectable amounts of similar polypeptides.

Animals↗
PubMed1974

Determination of actin messenger RNA in cultures of differentiating embryonic chick skeletal muscle.

Cytoplasmic polyadenylylated messenger RNA from differentiated muscle cultures, when incubated in a wheat germ cell-free system, directed the synthesis of a polypeptide indistinguishable from authentic chicken skeletal muscle actin, as judged by mobility on sodium dodecyl sulfate-polyacrylamide gels, tryptic peptide analyses, and biological activity. The synthesis of actin in the cell-free system was used to assay levels of translatable actin mRNA in cultures of fibroblasts, pre- and post-fusion myoblasts, and myoblasts grown under conditions that prevent fusion. In all cases the amount of actin polypeptide synthesized in the cell-free system was proportional to the rate of actin synthesis in the cultures from which the RNA was extracted. It is suggested that actin synthesis is regulated by the actin mRNA content of the cell and that an increase in the cytoplasmic level of translatable actin messenger RNA is mediated by cell fusion rather than by the terminal round of DNA synthesis.

Actins↗