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Biomedical subjects

G Lipkin

Publications and source records attributed to G Lipkin.

33 records · Page 2Linked to original sources
PubMed1977

Restoration of in vitro growth control to malignant cells.

A glycoprotein (molecular weight, ca. 160,000) from culture medium of contact-inhibited hamster melanocytes restores contact inhibition of growth to malignant melanocytes of man, mouse, and hamsters, and also effectively inhibits growth in vitro of a broad spectrum of malignant and normal cell types of ectodermal, mesodermal and endodermal origins, including human colon carcinomas. The melanocyte contact inhibitory factor (MCIF) produces G1 growth arrest in malignant melanocytes; inhibition of all cell types is reversible, does related, and nontoxic at concentrations below 200 microgram/ml, but selectively lethal to malignant cells at higher concentrations. An electrophoretically identical protein is present in culture media of contact-inhibited melanocytes, fibroblasts, and epidermal cells, but absent from those of colon carcinomas, HeLa cells and malignant melanomas. Nevertheless, an MCIF-like band is present in whole cell homogenates of human colon carcinomas and hamster melanomas. MCIF may permit normal surface interactions required for feedback inhibition of growth.

Animals↗
PubMed1975

[Restoration of growth contact inhibition in malignant melanocytes from man, mice, and hamsters].

Contact inhibition of growth is the in vitro property whose loss is most closely correlated with in vivo tumorigenicity. A contact inhibited line of hamster melanocytes produces a diffusible high molecular weight protein (melanocyte contact inhibitory factor, MCIF) which restores contact inhibition of growth to hamster malignant melanocytes. MCIF, extracted from culture medium of confluent contact-inhibited cultures, is now shown to restore the same capacity for in vitro growth regulation to malignant melanocytes of human and murine origins. In all 3 species MCIF produces characteristic changes in growth and morphology of cultures, with significant reductions of saturation densities. MCIF, the first protein identified which restores contact inhibition of growth to malignant cells, may be the prototype for a closely related class of surface-associated proteins concerned with regulation of normal cell-cell interactions leading to feedback inhibition of growth.

Animals↗
PubMed1974

A diffusible factor restoring contact inhibition of growth to malignant melanocytes.

Contact inhibition of growth is the property in vitro whose loss is most closely correlated with tumorigenicity in vivo. A contact-inhibited melanocytic cell line produces a diffusible protein-containing factor capable of restoring contact inhibition of cell division to highly malignant hamster melanocytes. Its addition to subconfluent cultures of the malignant cells is followed by the obligatory acquisition, at confluence, of the contact-inhibited state. Cultures are flat, oriented, and fibroblast-like, and show a 55% decrease in saturation density with no loss of viability. The effect is reversible. Present in conditioned media of cultures of the contact-inhibited melanocytic cell line, isolated by column chromatography on Sephadex G-200, the factor appears to be of high molecular weight. Activity is preserved in aqueous solutions at 4 degrees for at least 8 weeks, but is destroyed by repeated freezethawing or by treatment with Pronase. This newly recognized contact-inhibitory factor may be a prototype for a more general and fundamental mechanism for regulation of normal cell-cell interactions. It is the first cell-elaborated factor to be isolated that is capable of restoring the capacity for contact inhibition of growth to malignant cells.

Animals↗
PubMed1967

Lipogenesis from amino acids in perfused isolated dog skin.

Lipogenesis from amino acids has been studied in isolated perfused dog skin. Uniformly labeled alanine-(14)C, glycine-(14)C, isoleucine-(14)C, leucine-(14)C, phenylalanine-(14)C, and valine-(14)C are all incorporated into the cutaneous lipids, with significant incorporation into most of the isolated lipid fractions. Efficiency of lipogenesis has been expressed relative to the extent of incorporation of acetate under the same experimental conditions. This efficiency was highest for the three branched-chain amino acids. The accuracy, uses, and limitations of the perfusion technique for the study of cutaneous lipogenesis have been evaluated.

Acetic Acid↗