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Biomedical subjects

K D Brown

Publications and source records attributed to K D Brown.

At least 127 records · Page 7Linked to original sources
PubMed1984

Characterization of an epithelioid cell line derived from rat small intestine: demonstration of cytokeratin filaments.

A cell line (RIE-1) of epithelioid morphology was established from rat small intestine. RIE-1 cells possess the normal rat diploid number of chromosomes (42) up to at least passage 20. Both early (less than 10) and late (greater than 20) passage cells are non-tumourigenic and do not form colonies in soft agarose. RIE-1 cells bind two epithelial-specific monoclonal antibodies. In addition, the cells exhibit a network of cytoskeletal filaments which are labelled by an antiserum to keratin. These findings provide strong evidence for an epithelial origin of the RIE-1 cell line.

Animals↗
PubMed1983

Inhibition of the binding of 125I-labelled epidermal growth factor to mouse cells by a mitogen in goat mammary secretions.

Pre-colostrum and colostrum from goats cause a marked inhibition of the binding of 125I-labelled epidermal growth factor (125I-EGF) to Swiss 3T3 cells. The ability of these secretions to inhibit 125I-EGF binding is closely correlated with the ability to stimulate DNA synthesis in quiescent 3T3 cell cultures, suggesting that goat mammary secretions may contain an EGF-related mitogen. However, the material in colostrum which inhibits 125I-EGF binding to Swiss 3T3 cells is a basic protein with Mr greater than 20000 and is thus quite different from mouse and human EGF. Furthermore, the colostral-mediated inhibition of 125I-EGF binding, although rapid and apparently competitive, differs from the inhibition of binding induced by native, unlabelled EGF. Thus, the inhibitory effect of colostrum is markedly decreased when the assay temperature is shifted from 37 degrees C to 4 degrees C whereas unlabelled EGF is an effective competitive inhibitor at both 37 degrees C and 4 degrees C. Incubation of cells with EGF causes a reduction in cell surface EGF receptors whereas exposure to colostrum does not induce down-regulation of the EGF receptor. Our results suggest that the colostral factor does not bind directly to EGF receptors but inhibits 125I-EGF binding by an indirect mechanism which involves a temperature-sensitive step.

Animals↗
PubMed1983

Inhibition of epidermal growth factor binding to Swiss 3T3 cells by human platelet release-products.

Human platelet ionophore release-products (IRP) inhibit the binding of 125I-labelled epidermal growth factor (125I-EGF) to its receptors on Swiss 3T3 cells. The inhibition appears to be caused by platelet-derived growth factor (PDGF) in the IRP and results from a decrease in the apparent affinity of cellular receptors for 125I-EGF. However, our results indicate that PDGF does not bind directly to EGF receptors, since (1) PDGF does not down-regulate EGF receptors; (2) the PDGF-mediated inhibition of 125I-EGF binding is temperature-dependent; (3) cells which possess EGF receptors but lack PDGF receptors do not exhibit a PDGF-mediated inhibition of 125I-EGF binding.

Animals↗
PubMed1982

Inhibition of epidermal growth factor binding to mouse cultured cells by fibroblast-derived growth factor. Evidence for an indirect mechanism.

Fibroblast-derived growth factor (FDGF), a basic, heat- and acid-stable polypeptide partially purified from the serum-free conditioned medium of BHK cells transformed by simian virus 40, is a potent mitogen for Swiss 3T3 cells and causes a marked reduction in 125I-labeled epidermal growth factor (125I-EGF) binding to these cells. The activity which inhibits EGF binding coelutes with the growth-stimulating activity after gel filtration, ion exchange chromatography, and sodium dodecyl sulfate polyacrylamide gel electrophoresis. Both cellular responses are elicited by the same range of FDGF concentration in several murine cell types. The inhibition of EGF binding is rapid and results from a decrease in the apparent affinity of cellular receptors for 125I-EGF. FDGF does not affect the rate of cell-mediated 125I-EGF degradation. Several lines of evidence suggest that FDGF does not bind directly to EGF receptor. First, the effect of FDGF is dependent on the temperature of the assay; furthermore, treatment of cells with EGF results in loss of EGF receptors while exposure to FDGF for up to 24 h does not induce "down-regulation" of EGF receptors. Further, in A431 cells which display a large number of specific EGF receptors, 125I-EGF binding is not sensitive to FDGF. Finally, the effect of FDGF on 125I-EGF binding is not observed with isolated plasma membranes. Taken together, these findings suggest that FDGF binds to sites which are separate from EGF receptors. The results show a novel mechanism whereby a growth-promoting factor produced by a tumor cell line can rapidly modulate the affinity of the cellular receptors for EGF in an indirect manner.

Animals↗
PubMed1980

Colchicine inhibits epidermal growth factor degradation in 3T3 cells.

Colchicine (2 microM) did not affect the initial rate of association of 125I-labeled epidermal growth factor (125I-EGF) to Swiss 3T3 cells but continued incubation (up to 24 hr) led to an increase in cell-associated radioactivity. The effect is also produced by Colcemid, vinblastine, and podophyllotoxin but not by lumicolchicine. Disruption of microtubules with colchicine does not alter the rate of "down regulation" of EGF receptors, suggesting the binding and internalization of the factor proceed unchanged. However, colchicine markedly decreases the rate of appearance of acid-soluble radioactivity from cells either incubated continuously with 125I-EGF for 24 hr or exposed to the radioactive peptide for only 1 or 3 hr. The results indicate that colchicine decreases the rate of degradation of internalized 125I-EGF. Because antitubulin agents enhance the mitogenic effect of EGF our results suggest that peptide degradation can be dissociated from the long-term biological effect.

Ammonium Chloride↗
PubMed1979

Epidermal growth factor and the control of proliferation of Balb 3T3 and benzo[a]pyrene-transformed Balb 3T3 cells.

Benzo[a]pyrene-transformed Balb 3T3 cells (BP3T3) exhibit "normal" growth controls at low concentrations of serum. Epidermal growth factor (EGF) stimulates DNA synthesis and cell division in both Balb 3T3 and BP3T3 cells at physiological concentrations. The growth response of BP3T3 cells to EGF is qualitatively the same as that of 3T3 cells, however, the transformed cells have a lower quantitative requirement. Both 3T3 and BP3T3 cells show a density-dependent response to EGF, but the shift in the dose response curve for BP3T3 cells at high cell density is smaller than that seen for 3T3 cells. One cause of the restricted growth of 3T3 cells at high cell density compared with BP3T3 cells is the increased concentration of growth factor needed for stimulation of 3T3 cells at higher cell densities. A lower rate of depletion of other growth factory by BP3T3 cells may also explain the smaller effect of cell density on the EGF response of these cells.

Animals↗
PubMed1979

Binding, internalization, and degradation of epidermal growth factor by balb 3T3 and BP3T3 cells: relationship to cell density and the stimulation of cell proliferation.

Epidermal growth factor (EGF) stimulates the growth of both benzo[a]pyrene-transformed Balb 3T3 cells (BP3T3) and untransformed Balb 3T3 cells. We describe here the binding, internalization, and degradation of [125I]-EGF by BP3T3 cells and 3T3 cells. Binding of [125I]-EGF reaches a maximum after 45 to 90 minutes incubation at 37 degrees C. In both BP3T3 and 3T3 cells the extent of EGF binding required to stimulate DNA synthesis is density dependent; sparse cultures require a 15-30% occupancy to elicit a maximal response whereas dense cultures require a 70-85% occupancy. At physiological concentrations the total binding of [125I]-EGF to 3T3 cells is higher than to BP3T3 cells, and this difference increases at higher cell densities. The rate of degradation of [125I]-EGF is directly proportional to the total [125I]-EGF binding in each cell type. This supports the hypothesis that one cause of the diminished serum requirement of BP3T3 cells is a reduced rate of utilization of serum growth factors.

Animals↗
PubMed1978

An altered response of virally transformed 3T3 cells to ouabain.

The effect of ouabain on K+ transport was examined in 3T3 and virally transformed 3T3 cells. A 10 min exposure to ouabain (10(-3) M) produced approximately 40% inhibition of the unidirectional K+ influx in all cell lines. In 3T3 cells the response was not significantly altered by up to 70 min exposure to the drug. In contrast, the continued exposure of transformed cells to ouabain produced a time-dependent increase in the K+ influx. This increased influx was shown to be accompanied by an increase in the K+ efflux. The results suggest that, in transformed cells, ouabain produces both an inhibition of Na+-K+ exchange and a stimulation of K+-K+ exchange. The latter was shown to be more readily reversible than the former.

Cell Line↗