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Biomedical subjects

J H Chang

Publications and source records attributed to J H Chang.

At least 127 records · Page 7Linked to original sources
PubMed1995

c-Src regulates the simultaneous rearrangement of actin cytoskeleton, p190RhoGAP, and p120RasGAP following epidermal growth factor stimulation.

Analysis of C3H10T1/2 murine fibroblasts overexpressing wild type and dominant negative variants of c-Src has demonstrated a requirement for c-Src in EGF-induced mitogenesis. Correlating with the ability of c-Src variants to potentiate or inhibit EGF-dependent DNA synthesis is the phosphotyrosine content of multiple cellular proteins, including p190-RhoGAP, a protein thought to regulate growth factor-induced actin cytoskeleton remodeling by modulating the activity of the small GTP binding protein, Rho. Because the in vivo phosphotyrosine content of p190 varies with the level of active c-Src and not with EGF treatment, p190 is considered to be a preferred substrate of c-Src. To determine whether tyrosyl phosphorylation of p190 (by c-Src) could influence EGF-dependent actin remodeling, we used conventional and confocal immunofluorescence microscopy to examine the intracellular distribution of p190, actin, and p120RasGAP in EGF-stimulated or unstimulated 10T1/2 Neo control cells and cells that stably overexpress wild-type (K+) or kinase-defective (K-) c-Src. We found that in all cell lines, EGF induced a rapid and transient condensation of p190 and RasGAP into cytoplasmic, arclike structures. However, in K+ cells the rate of appearance and number of cells exhibiting arcs increased when compared with control cells. Conversely, K- cells exhibited delayed arc formation and a reduction in number of cells forming arcs. EGF-induced actin stress fiber disassembly and reassembly occurred with the same kinetics and frequency as did p190 and RasGAP rearrangements in all three cell lines. These results, together with the documented Rho-GAP activity intrinsic to p190 and the ability of Rho to modulate actin stress fiber formation, suggest that c-Src regulates EGF-dependent actin cytoskeleton reorganization through phosphorylation of p190.

Actins↗
PubMed1995

Tyrosine 807 of the v-Fms oncogene product controls cell morphology and association with p120RasGAP.

Expression of the v-fms oncogene of feline sarcoma virus in fibroblasts causes surface exposure of an activated receptor tyrosine kinase, v-Fms, that is autophosphorylated at multiple sites within its cytoplasmic domain. Cellular proteins interacting with this part of v-Fms modulate the mitogenic activity and morphology of the cells. We show here that the tyrosine residue in position 807 (Y-807) of the v-Fms molecule constitutes a major autophosphorylation site. The replacement of this residue by phenylalanine (Y807F mutation) allowed us to functionally dissect v-Fms-specific mitogenic and morphogenic cascades. Cells expressing the mutant v-Fms molecule resembled wild-type (wt) v-Fms-transformed (wt-v-Fms) cells in terms of [3H]thymidine uptake rates and activation of the Ras/Raf-1 mitogenic cascade. Such cells showed, however, a flat morphology and contained intact actin cables and fibronectin network. Our studies indicate that the v-Fms molecule controls cell morphology by a cascade that involves a direct interaction with p120RasGAP and p190RhoGAP: (i) in contrast to wt v-Fms molecules, the Y807F v-Fms protein failed to associate with and phosphorylate p120RasGAP; (ii) tight complexes between p120RasGAP and p190RhoGAP as well as detectable RhoGAP activity were present exclusively in wt-v-Fms cells; and (iii) p190RhoGAP was dispersed throughout the cytoplasm of wt-v-Fms cells, whereas its distribution was restricted to perinuclear regions of cells expressing the mutant v-Fms gene.

3T3 Cells↗
PubMed1995

AL072, a novel anti-Legionella antibiotic produced by Streptomyces sp.

AL072 is a potent anti-Legionella antibiotic produced by Streptomyces strain AL91. The compound was isolated from the fermentation broth with 1 volume of isopropyl alcohol, followed by an ethyl acetate extraction and subsequent concentration under reduced pressure. Purification was performed on an octadecyl silica gel column followed by preparative HPLC. AL072 purified as mentioned above showed extremely specific activity only towards Legionella pneumophila. No antibacterial activity against any other bacteria tested was demonstrable. Its molecular weight was determined by FAB-MS (m/z 648) and the compound was identified as a novel 1,3-diacyl glycerol with the molecular formula C41H76O5. One of the two acyl groups is linoleyl and the other is 3,5-dimethyl octadecanoyl.

Anti-Bacterial Agents↗
PubMed1995

The susceptibility of five stains mice to infections with Angiostrongylus cantonensis.

The susceptibility to the infection of Angiostrongylus cantonensis was studied in five inbred stains of mice including four H-2 haplotypes. Three weeks after infection, C57 BL/10J (H-2b) and C57BL/6J (H-2b) stains of mice showed the lowest, CBA (H-2k) and A/J (H-2a) stains showed intermediate, and the BALB/cJ (H-2d) mice showed the greatest susceptibility to infection. BALB/cJ mice also displayed the most body weight loss, the highest number of worms and showed the least number of days of survival. The s susceptibility of C57BL/6J (H-2b) and C57BL/10J (H-2b) strains of mice sharing same H-2 haplotype was the same despite their different genetic backgrounds. These data suggested that the H-2 gene might influence the susceptibility of mice to A. cantonensis.

Angiostrongylus cantonensis↗
PubMed1995

[Results of school children with enterobiasis in Tainan city, treated with mebendazole].

There were 2,471 school children suffering from enterobiasis in six primary schools of Tainan city. The infected children in five primary schools, Po-Ai, Yung-Hua, Fu-Hsiao, Pao-Jeng and Hsin-Nan, were treated with one single dosage of 100 mg mebendazole. In Shih-Men primary school, the sixth, the students were given placebos as a control group. Negative conversion rates of infected children were examined after three weeks of chemotherapy and school children in the six primary schools were surveyed for enterobiasis two months after chemotherapy to obtain infection rates. The method of examination was two consecutive-day adhesive cellophane perianal swabs. With the purpose of evaluating the efficiency of treatment, positive reduction rates were used and calculated according to the infection rates of school children gained before and after chemotherapy. Those rates in Pao-Jeng, Fu-Hsiao, Yung-Hua, Po-Ai and Hsin-Nan were 62.1%, 47.8%, 41.8%, 37.1% and 3.3%, respectively, and in Shih-Men 3.9%. Judging the data obtained from each grade or each class of schools showed that the efficacy of chemotherapy in reducing the rate of infection was variable. Hence, one single dose of mebendazole and education on personal hygiene were not sufficient to reduce the prevalence of enterobiasis in primary schools. This was because the cycle of E. vermicularis was relatively short, cutting out the routes of transmission was very difficult, and the factors involved were very complex. Overall, though the positive reduction rate presented in Hsin-Nan primary school showed nearly no success in reducing the infection, the other four schools showed valuable rates. Whether continue a treatment, of about three-months in duration, can inhibit the prevalence of enterobiasis among children in primary schools or not will need further study.

Child↗
PubMed1994

Palliative fetal surgery for diaphragmatic hernia.

Congenital diaphragmatic hernia is associated with a poor prognosis in spite of advances in antenatal detection and newborn care. Open fetal surgery has been suggested as a strategy for salvaging selected fetuses at high risk for pulmonary hypoplasia as a result of this lesion. We report a strategy for palliative fetal surgery with definitive repair postponed to the newborn period.

Adult↗
PubMed1994

A protein that is highly related to GTPase-activating protein-associated p62 complexes with phospholipase C gamma.

p62 is a highly tyrosyl phosphorylated protein that was first identified in immunoprecipitates of the GTPase-activating protein (GAP) of p21ras from cells transformed by oncogenic nonreceptor tyrosine kinases or stimulated through tyrosine kinase receptors (C. Ellis, M. Moran, F. McCormick, and T. Pawson, Nature 343:377-381, 1991). In this article we describe a highly related 62-kDa protein that becomes tyrosyl phosphorylated and associated with phospholipase C gamma (PLC gamma) in C3H10T1/2 cells stimulated with epidermal growth factor (EGF) or transformed by v-src. GAP-associated and PLC gamma-associated p62 comigrated in one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and exhibited nearly identical phosphotryptic peptide patterns. That the association of p62 with PLC gamma was direct and not mediated through binding of GAP-p62 to PLC gamma or to the EGF receptor (and coprecipitation of the receptor with PLC gamma) was demonstrated by (i) the inability to detect GAP in PLC gamma immunocomplexes or PLC gamma in GAP immunocomplexes, (ii) the association of p62 with PLC gamma in v-src-transformed cells in the absence of EGF stimulation, and (iii) in vitro solution binding and direct blotting of p62 with a glutathione S-transferase fusion protein containing the Src homology 2 (SH2) domains of PLC gamma. Unlike GAP, whose N-terminal SH2 mediates the interaction between GAP and p62, PLC gamma was found to require both its N- and C-terminal SH2 regions for p62 binding. These studies demonstrate that a protein identical to or highly related to GAP-associated p62 binds PLC gamma and suggest a means by which "cross-talk" between PLC gamma- and GAP-mediated signalling may occur.

Animals↗
PubMed1993

Identification of the peptide binding domain of hsc70. 18-Kilodalton fragment located immediately after ATPase domain is sufficient for high affinity binding.

Recombinant hsc70, a purified glutathione S-transferase (GST) fusion protein containing the C-terminal domain of hsc70 (GST-Ct), and an internal 18-kDa polypeptide located immediately after the 44-kDa ATPase domain of hsc70 were investigated for their peptide binding properties. The dissociation constants of the S-peptide for native hsc70 (Kd = 5-8 microM), GST-Ct (Kd = 6.5 microM), and the 18-kDa fragment (Kd = 8.1 microM) are virtually identical. In addition, polylysine and (Pro-Pro-Gly)5 do not show high affinity toward hsc70, GST-Ct, and the 18-kDa fragment, whereas peptide GT4 and P3a show comparably high affinity toward these polypeptides. These observations indicate that the peptide binding domain of hsc70 is confined in the internal 18-kDa fragment.

Adenosine Triphosphatases↗
PubMed1993

Evaluation of multiple drug resistance in human bladder cancer cell lines.

We evaluated multidrug resistance (MDR) in human bladder cancer cell lines UM-UC-2, UM-UC-6, UM-UC-9 and the UM-UC-6dox subline induced to doxorubicin resistance by in vitro doxorubicin exposure. We compared the profile of multidrug resistance in these cell lines with that of the UM-UC-3 human renal cancer cell line. Of these cell lines, UM-UC-2 was most sensitive to both doxorubicin and etoposide, while UM-UC-6, UM-UC-9 and UM-UC-3 showed 1.5-, 2.1-, and 5.4-fold more resistance to doxorubicin than UM-UC-2 cells. These cell lines were also more resistant to etoposide than UM-UC-2. Addition of verapamil at 10 microM. reduced the doxorubicin resistance in UM-UC-6 and UM-UC-6dox cells, but UM-UC-9 cells showed little change in doxorubicin sensitivity in the presence of verapamil. In a model of intravesical (short-term) treatment verapamil increased the doxorubicin sensitivity of UM-UC-6dox but not that of UM-UC-6 cells. This effect in UM-UC-6dox cells was enhanced by continuously treating with verapamil after doxorubicin had been removed. Western blot analysis with rabbit anti-human P-glycoprotein polyclonal antibody demonstrated a distinct increase in P-glycoprotein in the resistant cell lines as compared with UM-UC-2. P-glycoprotein expression was roughly proportional to the degree of resistance to both doxorubicin and etoposide, but did not always correlate with the effect of verapamil on decreasing doxorubicin resistance. These results suggest that multidrug resistance is an important phenomenon in bladder cancer and that more than one pathway of multidrug resistance may be present in human bladder cancer cell lines.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Suture to limbus distances in eyes with a posterior chamber intraocular lens implanted by scleral fixation.

This study used linear regression to analyze the correlation between the location of transscleral sutures and the postoperative visual acuity, refraction, and anterior chamber depth in eyes with posterior chamber intraocular lenses implanted by scleral fixation. The suture-to-limbus distance at the 12 o'clock and 6 o'clock positions averaged 2.4 mm and 1.7 mm, respectively. Suture location had no statistically significant relationship with postoperative acuity, spherical equivalent, astigmatism, or anterior chamber depth.

Adult↗
PubMed1993

Non-steroidal anti-inflammatory drug and endotoxin induced uveitis.

Suprofen eye drop was instilled into one eye of 10 pigmented rabbits and then anterior uveitis was induced by intraperitoneal injection of endotoxin of Shigella flexneri serotype 1A to evaluate the effects of non-steroidal anti-inflammatory drug on endotoxin induced uveitis. The pupillary diameters were measured, and aqueous cell and flare gradings were recorded in 20 eyes of 10 rabbits for one week at an interval of 12 hours for the first 24 hours and then every 24 hours for a week. A difference between the treated and control groups were investigated. All the above parameters showed greatest changes at 12 or 24 hours after injection and became normal by one week. The two groups demonstrated statistically significant difference at 12 hours, day 1 and day 2 as for pupillary diameter, at day 1 and day 2 as for cell and at 12 hours and day 1 as for flare. Thus, it can be concluded that prostaglandins play a role in miosis, in the appearance of inflammatory cells and flare in endotoxin induced uveitis and the topical administration of non-steroidal anti-inflammatory drug can alleviate signs of anterior uveitis. Specific relationship between leukotriene B4 and aqueous cell was not demonstrated.

Administration, Topical↗
PubMed1993

Increased levels of p21ras-GTP and enhanced DNA synthesis accompany elevated tyrosyl phosphorylation of GAP-associated proteins, p190 and p62, in c-src overexpressors.

While examining the role of pp60c-src in cellular proliferation, we found that overexpression of c-src in C3H10T1/2 murine fibroblasts results in an augmented mitogenic response to epidermal growth factor (EGF) [Luttrell, D.K., Luttrell, L.M. & Parsons, S.J. (1988). Mol. Cell. Biol., 8, 497-501; Wilson, L.K., Luttrell, D.K., Parsons, S.J. (1989). Mol. Cell. Biol., 9, 1536-1544] and enhanced tyrosyl phosphorylation of specific cellular proteins [Wilson, L.K. & Parsons, S.J. (1990). 5, 1471-1480]. Here we identify two of these proteins as the GAP (GTPase-activating protein of p21ras)-associated proteins, p190 and p62. Evidence is presented to support the notion that, in 10T1/2 fibroblasts, p190 is a preferred substrate of pp60c-src, while p62 is preferentially phosphorylated by the EGF receptor. First, the phosphotyrosine content of p190 in quiescent cells is three- to fivefold higher in c-src overexpressors than in control cells and is not altered by growth factor treatment. In contrast, tyrosyl phosphorylation of p62 is undetectable in quiescent cells and transiently observable upon EGF addition. Second, the phosphotyrosine content of p190 in cells overexpressing defective pp60c-src is reduced in comparison with wild-type (wt) c-src overexpressors, while that of p62 is significantly less affected. Further studies revealed that tyrosyl phosphorylation of p190 and p62 is not required for GAP complex formation, as equal amounts of p190 and p62 proteins could be detected in GAP complexes from wt and variant c-src overexpressors both before and after EGF stimulation. However, analysis of GTP-bound p21ras revealed higher basal and EGF-stimulated levels in c-src overexpressors than in control cells. Taken together, these results suggest that one mechanism by which pp60c-src may contribute to early events in the EGF-induced mitogenic pathway in 10T1/2 fibroblasts is by increasing the level of GAP-associated p190 and p62 tyrosyl phosphorylation, which in turn results in higher levels of p21ras-GTP.

Animals↗
PubMed1993

Nucleolar protein B23: bacterial expression, purification, oligomerization and secondary structures of two isoforms.

Protein B23 is an abundant nucleolar phosphoprotein and putative ribosome assembly factor. Two forms of the protein, B23.1 and B23.2, contain 292 and 257 amino acids, respectively, and differ only in their C-terminal sequences. The two B23 isoforms have been produced in Escherichia coli using the pKK223-3 expression vector and purified to near homogeneity. The purification utilized ammonium sulfate fractionation followed by chromatography on DEAE-cellulose, heparin-Sepharose and Bio-Rad Q. By combined gel filtration and sedimentation analyses, both B23.1 and B23.2 formed multimers of Mr 210 to 255 kDa (apparent hexamers), suggesting that the differences in C-terminal ends of of the isoforms do not affect oligomerization. The oligomerization was not dependent on disulfide bond formation. The circular dichroism spectra of recombinant proteins B23.1 and B23.2 were similar suggesting that the carboxyl-terminal difference in the two proteins does not markedly influence overall secondary structure. Using routines for fitting the CD spectra to those of basis vectors the recombinant B23 isoforms appeared to be composed predominantly of beta-sheet and beta-turn secondary structures. Protein B23 from HeLa cell nuclei was recently shown to have a high affinity for the HIV-1 Rev protein. Using sucrose density gradient centrifugation it was shown that both recombinant proteins B23.1 and B23.2, as well as B23.1 isolated from Novikoff hepatoma nucleoli, were capable of binding the Rev protein.

Cell Nucleus↗
PubMed1992

Possible mechanism of immunosuppressive effect of scoparone (6,7-dimethoxycoumarin).

The possible mechanism of the immunosuppressive effect of scoparone (6,7-dimethoxycoumarin) was investigated. Human peripheral blood mononuclear cells (10(6) cells/ml) were stimulated with 0.25% phytohemagglutinin (PHA) and the proliferative response was determined from the uptake of tritiated thymidine. Scoparone (10(-6) to 3 x 10(-4) M) reduced the proliferative response in a dose-dependent manner. The proliferative response of mononuclear cells to mixed lymphocyte reaction was also reduced by scoparone (10(-5) to 10(-4) M). Interleukin-1, interleukin-2 production and interleukin-2 receptor expression were all reduced in the presence of scoparone. Scoparone (10 and 30 microM) significantly reduced the suppression elicited by the diabetogenic drug, alloxan (10 mM). The suppressive activity of scoparone was significantly reduced by quinacrine (a phospholipase A2 inhibitor), indomethacin (a cyclooxygenase inhibitor) and nordihydroguaiaretic acid (a lipoxygenase inhibitor). The levels of prostaglandin E2, prostaglandin F2 alpha, leukotriene B4 and 2,3-dinor-thromboxane B2 in culture medium of PHA-stimulated mononuclear cells, measured with an enzyme immunoassay, were elevated by scoparone treatment. We compared the effect of scoparone on the mononuclear cell response to genistein, a specific inhibitor of protein tyrosine kinase and demonstrated the non-additivity and cross-desensitization of the two compounds. Our results suggest that the immunosuppressive effect of scoparone may be exerted in part through inhibition of protein tyrosine kinase and release of arachidonic acid metabolites.

Alloxan↗
PubMed1992

Immunosuppressive effect of emodin, a free radical generator.

The possible mechanism of immunosuppressive effect of emodin (1,3,8-trihydroxy-6-methylanthraquinone) was investigated in this study. Human mononuclear cells (10(6) cells/ml) were stimulated with 0.25% phytohemagglutinin for 24, 48 and 72 h, and the proliferative response was determined by the uptake of tritiated thymidine. In the presence of emodin (10(-6) to 3 x 10(-5) M), the proliferative response was reduced in a dose-dependent manner. Emodin (3 x 10(-7) to 3 x 10(-5) M) also dose dependently reduced the proliferative response to mixed lymphocyte reaction. After 72 h exposure to emodin (10 microM), interleukin-1 (IL-1), interleukin-2 (IL-2) production and IL-2 receptor expression were all reduced. The structure-activity relationship of emodin and 10 other anthraquione derivatives indicates that the free hydroxyl group at the beta-position of the anthraquinone nucleus plays an important role in the immunosuppressive effect. The suppressive activity of emodin was significantly inhibited by catalase (a scavenger of hydrogen peroxide), but little affected by superoxide dismutase (a scavenger of superoxide radical) and mannitol (a scavenger of hydroxyl radical). Methylene blue and hemoglobin, guanylate cyclase inhibitors, did not significantly affect the suppressive activity of emodin. Nordihydroguaiaretic acid (a lipoxygenase inhibitor) significantly potentiated the suppressive activity whereas quinacrine (a phospholipase A2 inhibitor) and indomethacin (a cyclooxygenase inhibitor) did not significantly affect it. The results suggest that the immunosuppressive effect of emodin may be partly mediated through hydrogen peroxide generated from semiquinone and regulated by arachidonic acid metabolites or byproducts.

Anthraquinones↗
PubMed1992

Antibodies of different immunoglobulin isotypes in serum and bile of patients with clonorchiasis.

Specimens of serum and bile from patients were assayed by an enzyme-linked immunosorbent assay to reveal antibodies specific to antigens from adult Clonorchis sinensis. Antibodies of the IgG isotype showed the greatest elevation during infection (Student's t-test, P < 0.001), whereas serum IgA and IgE and secretory IgA in bile were moderately elevated (P < 0.05). Major differences in the distribution of antibodies among the IgG subclasses were observed between patients who were and those who were not infected. IgG4 antibody levels were elevated in the serum and bile of infected patients, and there were significant correlations between the levels of IgG and IgG4 antibodies and the intensity of infection.

Adult↗
PubMed1992

Fatty acid composition and fatty acid elongase and stearoyl-CoA desaturase activities in tissues of steers fed high oleate sunflower seed.

The effects of a high oleate sunflower seed diet on tissue composition and on fatty acid elongation and desaturation enzyme activities were investigated. Three Simmental calves were fed a standard corn-based diet (2.6% fat); three others were fed the corn-based diet containing 20% high oleate sunflower seed (10.4% fat). Blood samples and perianal adipose tissue samples were obtained at 7, 90 and 180 d on trial. Samples of liver, longissimus dorsi muscle and intestinal mucosa were obtained at the termination of the experiment (195 d on trial). Plasma oleate was higher (P < 0.05) in the cattle fed the sunflower seed, and oleate, myristate (P < 0.05) and stearate (P < 0.06) were elevated in perianal adipose tissue in response to the greater lipid content of the dietary sunflower seed. Dietary sunflower seed decreased the concentration of stearate (P < 0.05) in liver. The high oleate diet significantly (P < 0.05) increased the activity of stearoyl-CoA desaturase activity in muscle, and numerical increases in desaturase activity were observed in liver, adipose and small intestine samples. Elongase activity was unaffected by diet. Because stearate is the primary fatty acid available for absorption in ruminants, elevated oleate in plasma and depressed stearate in liver of cattle fed sunflower seed may have reflected an adaptive response of stearoyl-CoA desaturase in their tissues.

Acetyltransferases↗