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Biomedical subjects

M Shearer

Publications and source records attributed to M Shearer.

At least 55 records · Page 3Linked to original sources
PubMed1984

Complex kinetics of binding of human alpha-2 interferon to human, but not bovine cells.

Human alpha-2 interferon (HuIFN-alpha 2) is an effective antiviral agent for bovine cells, but does not inhibit the proliferation of these heterologous cells. A comparison of the kinetics of binding of 125I-HuIFN-alpha 2 at 4 degrees C to several bovine and human cells, shows that the kinetics of the initial receptor interactions are very different in the two species. Binding of HuIFN-alpha 2 to bovine cells follows the simple kinetics predicted for one species of ligand interacting with one type of high-affinity receptor. The kinetics of binding to human cells showing a range of sensitivities to the antigrowth effect are complex and indicate that receptor occupancy increases the rate of association of ligand. It is suggested that dimers of HuIFN-alpha 2 may be formed on the human, but not the bovine receptor, and where these occur between receptors, their formation may relate to the inhibition of cell growth.

Animals↗
PubMed1984

Monoclonal antibodies that distinguish between subspecies of human interferon-alpha and that detect interferon oligomers.

Monoclonal antibodies to human interferons (HuIFN) of the alpha-class have been prepared by screening against 125I-labeled IFN in a rapid liquid-phase radioimmunoassay. All of the six antibodies produced react with HuIFN-alpha 2 and with some components of HuIFN-alpha N (Namalwa); three of the antibodies also bind HuIFN-alpha 1, and these either do not bind or bind very weakly the 25K component of Namalwa. Reaction of the antibodies with IFN components blotted onto nitrocellulose after separation on reducing gels suggests that two of the antibodies are against conformational determinants, whereas the epitopes recognized by the other antibodies are not destroyed by reduction or SDS treatment; these antibodies can be used to detect the presence of oligomers in IFN preparations. From the reaction of the antibodies with different alpha-IFN in immunoblots, in an antiviral assay, and in an ELISA, it was concluded that at least five different epitopes are recognized by the six antibodies, only one of which is non-neutralizing.

Animals↗
PubMed1982

Effects of HuIFN-alpha 2 and HuIFN-alpha (Namalwa) on breast cancer cells grown in culture and as xenografts in the nude mouse.

The activity of HuIFN-alpha 2 produced in bacteria has been compared with that of HuIFN-alpha from Namalwa cells (HuIFN-alpha N) as an antiviral (against EMC virus) and antiproliferative agent in normal and malignant cultured human breast cells. The IFN preparations show the same spectrum of antiviral and antiproliferative activity in the human cell strains and lines examined, and are equally effective, when comparable amounts of IFN protein are used. Both interferon preparations inhibit virus growth (EMC) in four types of bovine cells but neither inhibit the growth of these cells. HuIFN-alpha 2 and HuIFN-alpha N can also be shown to effectively inhibit the growth of a transplantable human breast cancer, grown as xenografts in the nude mouse, although the amounts of IFN protein required may not be the same for both preparations.

Animals↗
PubMed1981

Anchorage-independent growth of normal calf lens epithelial cells and effect of SV40 transformation on their growth properties.

Calf lens epithelial cells cultured in vitro show growth properties usually associated with virally transformed fibroblasts. The lens cells are anchorage independent, forming colonies in agar, and show a low requirement for added mitogens. In dense culture they form multilayers and maintain a constant cell number by proliferation and shedding. Strains of lens cells transformed by SV40 virus have been obtained that show similar growth properties to the normal lens epithelium. The major effect of SV40 transformation is to increase the growth rate, final cell density and in vitro life-span of the lens cells and to inhibit the increase in size that occurs after 2-3 weeks of culturing the untransformed cells.

Animals↗
PubMed1981

Inhibitory effect of interferon on cellular DNA synthesis: modulation by pure mitogenic factors.

Quiescent Swiss 3T3 cells can be stimulated to synthesize DNA by combinations of polypeptide hormones, retinoids and tubulin-disrupting agents. Low doses of mouse interferon are effective in inhibiting DNA synthesis induced by one, two or three factors. When more growth factors are added DNA synthesis is not further stimulated, although the dose response curve for interferon is shifted dramatically to the right. Even when added before the mitogenic stimulus, up to 2000 units of interferon have no effect on DNA synthesis stimulated by five factors. A change in the dose-response curve for interferon as an antiviral agent is also observed when the mitogenic stimulation is increased, but the effect is less dramatic than that observed on its function as an inhibitor or DNA synthesis.

Animals↗
PubMed1978

Growth requirements of calf lens epithelium in culture.

The in vitro life span and rate of growth of calf lens cells cultured in serum-supplemented 199 medium can be markedly increased by growing the cells with a layer of mitomycin -killed 3T6 feeders. In the absence of feeders, the epithelial cells are partially blocked in the S period of the cell cycle but show a normal distribution of cells in G1 and G2 when grown with fibroblasts. Increased growth rates and division potential can also be achieved by growing the lens in 199 medium containing 10(-5) M thymidine, and cells grown under these conditions show a normal growth cycle. Our results suggest that lens epithelial cells cultured in medium 199 show a deficient endogenous synthesis of thymidylic acid, and fibroblast feeders or exogenously added thymidine enable them to overcome this deficiency. When grown in the presenct of 10(-5) M thymidine, the lens epithelial cells show a very low serum requirement for cell division in short term culture.

Animals↗
PubMed1977

Growth requirements of human mammary epithelial cells in culture.

Colony-forming epithelial cells can be separated from the non-dividing "foam cells" in human milk by differential adhesion to glass and freezing. The growth of such partially purified mammary epithelial cells is stimulated by co-culture with non-dividing feeder cells. Foam cells, mitomycin-treated mouse fibroblast lines and human mammary fibroblasts and calf lens epithelial cells are all effective in promoting mammary epithelial cell growth. Contact between epithelial cells and feeders is not required for the growth-promoting effect. The mitogenic effect of epidermal growth factor on mammary epithelial cells also requires feeder cell activity.

Animals↗
PubMed1977

Some properties of cells cultured from early-lactation human milk.

Cells that can be cultured from pools of early-lactation milk were studied. Under the culture conditions used, the majority of cells attached to collagen-coated dishes; most of these remained single, did not divide, and in their adhesiveness, phagocytic ability, and ultrastructure resembled macrophages or histiocytes. On a plate seeded with approximately 3 X 10(5) cells, however, 10-100 colonies of dividing cells developed. These cells had the junctional complexes typical of epithelial cells and grew well in a medium supplemented with human serum and hydrocortisone for 16-20 days after seeding. After removal of serum from the medium, some cells continued to traverse the cell cycle, and the colonies containing these cells were morphologically distinct from those which became quiescent. The nondividing cells in milk could be separated from the milk epithelial cells and were able to stimulate the growth of epithelial cultures from benign mammary dysplasias.

Breast Neoplasms↗
PubMed1976

Cardiac amyloidosis, contrictive pericarditis and restrictive cardiomyopathy.

Cardiac amyloidosis is not characterized by a single hemodynamic pattern. Some of the cases present the clinical findings of restrictive cardiomyopathy and in these differentiation from constrictive pericarditis remains difficult in spite of the introduction of techniques designed to assess myocardial contractility and ventricular diastolic compliance. The clinical features and the demonstration of left ventricular diastolic pressure greater than right remain the most useful means of distinguishing restrictive cardiomyopathy from constrictive pericarditis. In other cases of cardiac amyloidosis the diastolic pressure is elevated throughout diastole and ventricular ejectile ability is lost. These cases do not simulate constrictive pericarditis and should not be classified as restrictive cardiomyopathy.

Amyloidosis↗