Choon-Myung Koh

Differential expression, shedding, cytokine regulation and function of TNFR1 and TNFR2 in human fetal astrocytes.

Tumor necrosis factor (TNF)-α induces pleiotropic cellular effects through a 55kDa, type 1 receptor (TNFR1) and a 75kDa type 2 receptor (TNFR2). Moreover, it participates in the pathogenesis of several CNS diseases, including demyelinating diseases. TNF-α receptors are differentially expressed and are regulated in many cell types. However, data regarding the TNF-α receptor expression and regulation in human astrocytes is limited to date. We investigated TNF-α receptor expression, its regulation by cytokines, and its functional role in primary cultured human fetal astrocytes, which are the most abundant cellular population in the central nervous system and are known to be immunologically active. In this study, astrocytes were found to constitutively and predominantly transcribe, translate and shed TNFR1 rather than TNFR2, but TNFR2 expression was increased by adding TNF-α, IL-1, and IFN-γ, but not by adding LPS. To determine the functional roles of TNFR1 and TNFR2 on TNF induction, we investigated NF-κB activation and TNF-α induction after neutralizing TNFR1 and TNFR2 by an antibody treatment. We found that NF-kB activation and TNF-α induction are blocked by TNFR1 neutralizing antibody treatments.

Rapid differentiation of Candida albicans from other Candida species using its unique germ tube formation at 39° C

In this study, we found that no Candida species other than C. albicans is able to form germ tubes at 39° C in serum‐free YEPD (1% (w/v) yeast extract, 2% (w/v) peptone and 2% (w/v) dextrose) media, which makes it easy to identify C. albicans from other Candida species. When cultivated in rabbit serum for at least 2 h at 37° C, more than 60% of C. albicans cells generated germ tubes. In YEPD, however, germ tubes began to appear from C. albicans cells within 30 min at 39° C, and more than 60% of C. albicans cells formed the germ tubes after 1 h at 39° C. Standard Candida strains (ATCC, CBS), three C. albicans and two C. dubliniensis strains were cultured in serum at 37° C for 2 h and in YEPD at 39° C for 1 h. All of the three C. albicans formed germ tubes at 39° C. The two C. dubliniensis strains formed germ tubes in serum at 37° C, but grew as a yeast form in YEPD at 39° C. All of the clinically isolated C. albicans strains in our laboratory formed germ tubes in YEPD at 39° C for 1 h, and none of the clinically isolated Candida species other than C. albicans generated germ tubes in YEPD at 39° C. Thus, the unique germ tube formation of C. albicans induced by high temperature (39° C) in YEPD could be applied to a protocol for the rapid and convenient identification of C. albicans in clinical laboratories. Copyright

Effects of cytokines on VEGF expression and secretion by human first trimester trophoblast cell line

PROBLEM: The mechanism through which vascular endothelial growth factor (VEGF) regulation occurs at the feto‐maternal interface is poorly understood. The aim of this study was to investigate the effects of various cytokines on VEGF expression and secretion by trophoblast cells.

In Vitro chemosensitivity test of SK-302B on human colon carcinoma cell lines

SK-302B, an antibiotic purified from soilStreptomyces sp. 302, was structurally identified as echinomycin (C50H66N11S2). In the present experiment, the possibility of SK-302B as an anticolon cancer agent was investigated by using chemosensitivity system (MTT assay, clonogenic assay). Treatment of SK-302B on various colon cancer cell lines resulted in a significant cytotoxicity and tumor colony formation inhibition. These studies showed that SK-302B had a potent inhibition on colon cancer cells.