Biomedical subjects

B M Chan

Publications and source records attributed to B M Chan.

42 records · Page 3Linked to original sources

PubMed1989

IgE receptors from rat intestinal mucosal and peritoneal mast cells show mast cell subtype-specific differences.

High- (alpha chain) and low-affinity IgE receptors from purified populations of rat intestinal mucosal (IMMC) and peritoneal mast cells (PMC) were characterized by SDS-PAGE. Receptor expression and molecular weight were compared. IMMC yielded 59-kilodalton (kDa) alpha chains of the high-affinity receptors and two forms (58, 50 kDa) of low-affinity receptors, whereas PMC possessed only 51-kDa alpha chains and 56-kDa low-affinity receptors. These differences extend the evidence for functional diversity between mast cell subtypes.

Animals↗

PubMed1988

Factor-independent tissue cultured mast cells: establishment from rat peritoneal mast cells.

We report here that extended culture of purified rat peritoneal mast cells (RpMC), typical of the connective tissue-type (CTMC), gives rise to continuously proliferative cell lines without the requirement of exogenous growth factors such as IL-3 and IL-4 or accessory cells. Two of the cell lines established, RCMC1 and RCMC2, are described here. Both cell lines have been maintained in continuous culture in vitro for over a year. Although these cell lines were derived from CTMC, they exhibit phenotypic characteristics of mucosal-type mast cells, i.e., they contain rat mast cell protease II (RMCP II), low levels of histamine and stain alcian blue+/safranin-. Previous studies have identified both high and low affinity receptors for IgE, designated Fc epsilon RI and Rc epsilon RII, respectively, on RpMC and rat basophilic leukemia (RBL) cells. At the early stages of cell culture, RCMC1 expressed predominantly Fc epsilon RI and a gradual increase in the expression of Fc epsilon RII has been observed with time in culture. By comparison, RCMC2 expressed predominantly Fc epsilon RII throughout its entire period of cell culture.

Animals↗

PubMed1987

Mycoplasma-induced degradation of IgE bound by Fc epsilon receptors of rat basophilic leukemia cells.

Previous studies from this laboratory have shown that Mycoplasma hyorhinis interacts with some unoccupied, high-affinity 45-kDa receptors for IgE on rat basophilic leukemia (RBL) cells to induce the formation of 71-kDa receptors for IgE. The present study demonstrates that when IgE is bound to the high-affinity receptors, exposure of RBL cells to mycoplasma leads to a time-dependent degradation of the cell-bound IgE into fragments of 186 kDa, 158 kDa and 115 kDa, all of which remain bound to the receptors. Upon reduction, these fragments yield 67-kDa and 55-kDa epsilon chain-derived polypeptides. The degradation appears to start at the N-terminus of the IgE, leading eventually to a complete loss of L chains. In the absence of mycoplasma, the IgE remains relatively intact throughout the same time period with a molecular mass of 210 kDa. The observed degradation of receptor-bound IgE by mycoplasma, should it also occur in vivo, could have important consequences as far as the IgE-dependent mediator release is concerned.

Animals↗

PubMed1986

Effects of mycoplasma infection on Fc receptors for IgE of rat basophilic leukemia cells.

Earlier studies from this laboratory had shown that rat basophilic leukemia cells carry two major receptors for IgE, named R and H, and a third minor receptor, designated 71K. It is now apparent that 71K is induced by the action of Mycoplasma hyorhinis, a common contaminant of tissue cultures. This induction is reversible. Decontamination either in in vitro or in vivo leads to a disappearance of 71K and re-infection causes its reappearance. The 71K receptor appears to be induced by the action of the mycoplasma on a surface molecule, most likely R, present on the cells at the time of infection. When receptors are occupied by IgE, 71K induction is inhibited. Other effects of mycoplasma infection include the significant reduction in the expression of transferrin receptors and increased histamine content of infected cells.

Animals↗

PubMedDate not supplied

Degradation of adsorbed fibrinogen by surface-generated plasmin.

An investigation of the physical status of fibrinogen that has been adsorbed to glass and then eluted has been conducted. Exposure of Kabi fibrinogen to glass was carried out using a glass bead column experiment. The fibrinogen was eluted sequentially, first by 1 M Tris and then by SDS. The initially eluted fibrinogen showed considerable degradation (SDS polyacrylamide gel electrophoresis) while the later fractions were less degraded. Fibrinogen purified by chromatography on either DEAE-cellulose or Sepharose-lysine to remove plasminogen was less degraded. When purified plasminogen was added to fibrinogen, degradation of column eluates was very extensive in all eluted fractions. These results are interpreted in terms of a surface-mediated activation of plasminogen to plasmin followed by fibrinogenolysis. Although such an effect remains to be demonstrated as a general property of surfaces, it is speculated that surfaces may vary in their activation of fibrinolysis as well as their activation of clotting, and that maximization of fibrinolysis is a worthwhile goal in the development of blood-compatible surfaces.

Adsorption↗

PubMedDate not supplied

Vinorelbine tartrate.

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Agranulocytosis↗