Biomedical subjects

L H Wang

Publications and source records attributed to L H Wang.

At least 55 records · Page 3Linked to original sources

PubMed2000

Activation of human T lymphocytes is inhibited by peroxisome proliferator-activated receptor gamma (PPARgamma) agonists. PPARgamma co-association with transcription factor NFAT.

T lymphocyte activation is highlighted by the induction of interleukin-2 (IL-2) gene expression, which governs much of the early lymphocyte proliferation responses. Peroxisome proliferator-activated receptor-gamma (PPARgamma) is a member of the nuclear receptor superfamily of ligand-activated transcription factors. PPARgamma mRNA expression was found in human peripheral blood T lymphocytes, raising the possibility of PPARgamma involvement in the regulation of T cell function. Here we show that PPARgamma ligands, troglitazone and 15-deoxy-Delta(12,14) prostaglandin J(2), but not PPARalpha agonist Wy14643, inhibited IL-2 production and phytohemagglutinin-inducible proliferation in human peripheral blood T-cells in a dose-dependent manner. This inhibitory effect on IL-2 was restricted to the PPARgamma2-expressing, not the PPARgamma-lacking, subpopulation of transfected Jurkat cells. The activated PPARgamma physically associates with transcriptional factor NFAT regulating the IL-2 promoter, blocking NFAT DNA binding and transcriptional activity. This interaction with T-cell-specific transcription factors indicates an important immunomodulatory role for PPARgamma in T lymphocytes and could suggest a previously unrecognized clinical potential for PPARgamma ligands as immunotherapeutic drugs to treat T-cell-mediated diseases by targeting IL-2 gene expression.

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PubMed2000

Targeted disruption of stat6 DNA binding activity by an oligonucleotide decoy blocks IL-4-driven T(H)2 cell response.

The transcription factor, signal transducer and activator of transcription (Stat) 6, regulates T(H)2-lymphocyte activity by controlling the expression and responsiveness to interleukin (IL)-4, which plays a key role in numerous allergic maladies. Therefore, we sought to use a phosphorothiolate cis-element decoy to target disruption of Stat6 transcriptional activity. Here we showed that the Stat6 decoy potently ablated the messenger RNA expression and production of IL-4, but not of several other cytokines. The Stat6 decoy functionally disrupted IL-4-inducible cell proliferation of murine T(H)2 cells and primary human CD4(+) T lymphocytes. Specificity of the decoy was demonstrated by its ability to directly block Stat6 binding to a cis-element probe and transactivation, but not affect Stat6 tyrosine phosphorylation or expression of the IL-4 receptor chains. Moreover, the decoy failed to inhibit non-Stat6-dependent signaling pathways since IL-2 was competent to induce cell proliferation and activation of Stats 1, 3, and 5a/b. With the use of laser scanning confocal microscopy, fluorescently tagged Stat6 decoy was detectable in the cytoplasm and nucleus; however, greater levels of oligonucleotide were present in the latter following IL-4 treatment. Taken together, these data suggest that IL-4-driven T(H)2 cell activity can be preferentially restricted via targeted disruption of Stat6 by a novel and specific decoy strategy that may possess gene therapeutic potential. (Blood. 2000;95:1249-1257)

Base Sequence↗

PubMed2000

Some observations on the use of cultured corneal endothelial cells as a model for intact corneal endothelium.

Major differences have been identified between corneal endothelial cells in situ and those grown in culture. Cells in intact porcine corneal endothelium were studied and compared with primary cultures of the same cells either in suspension or in monolayers which had been grown on plastic (Nunc, Permonax). Differences were identified in the organization of the cytoskeleton (filamentous actin) between the cells in situ and in monolayer culture. The ability to withstand exposure to cryoprotective concentrations of Me(2)SO also varied substantially depending on whether the cells were in situ or in culture. These results underline the need for caution in the use of cells in culture as a model for studying the nature of injury to cells during the freezing of whole tissues.

Animals↗

PubMed2000

Enhancing immunity by dietary consumption of a probiotic lactic acid bacterium (Bifidobacterium lactis HN019): optimization and definition of cellular immune responses.

OBJECTIVE: To define the cellular basis for immune enhancement by a probiotic lactic acid bacteria strain (Bifidobacterium lactis HN019); and to determine whether immune enhancement can be optimized by delivery in oligosaccharide-enriched low-fat milk. DESIGN: A double-blind, three-stage before-and-after intervention trial. SETTING: Taipei Medical College Hospital, Taipei, Taiwan. SUBJECTS: Fifty healthy Taiwanese citizens (age range 41-81; median 60) randomly allocated to two groups. INTERVENTIONS: In stage 1 (run-in control stage) all subjects consumed reconstituted low-fat milk (LFM) for 3 weeks; in stage 2 (probiotic intervention) subjects consumed B. lactis in LFM (group A) or B. lactis in lactose-hydrolysed LFM (group B) for 3 weeks; in stage 3 all subjects returned to non-supplemented LFM for a further 3 weeks (washout stage). The innate immune functions of two different leucocyte types (polymorphonuclear (PMN) cells and natural killer (NK) cells) were assessed at four time points via in vitro analyses on peripheral blood samples. RESULTS: While consumption of LFM alone had no significant effect on immune responses, stage 2 results indicated significantly enhanced PMN cell phagocytosis and NK cell tumour killing activity following consumption of milk containing B. lactis. These increases levelled off following cessation of B. lactis consumption, but remained above the pre-treatment values. Increases in PMN and NK cell activity were greatest among subjects who consumed B. lactis in lactose-hydrolysed LFM. CONCLUSIONS: Dietary consumption of the probiotic bacterium B. lactis HN019 enhanced immune function of two different types of leucocytes; the degree of enhancement was increased by consuming B. lactis in an oligosaccharide-rich substrate. SPONSORSHIP: Financial support was provided by the New Zealand Dairy Board.

Adult↗

PubMed2000

Effects of gonadal steroids on brain serotonergic and aromatase activity during the critical period of sexual differentiation in tilapia, Oreochromis mossambicus.

The effects of gonadal steroids on brain serotonin (5-HT) and aromatase activity during the critical period of sexual differentiation were investigated in tilapia, Oreochromis mossambicus. Treatment of tilapia with 17beta-oestradiol (E2) between days 7 and 10 posthatching resulted in a significant increase in the female : male ratio as determined at day 90, and a significant reduction in brain 5-HT content. Treatment between days 10 and 20, or between days 20 and 30, had no significant effect. Since the 5-HT system may influence sexual differentiation, we examined the effects of para-chlorophenylalanine (p-CPA), a 5-HT synthesis inhibitor. As with E2, treatment of tilapia with p-CPA between days 7 and 10 posthatching resulted in a significant increase in the female : male ratio. Again, treatment between days 10 and 20, or between days 20 and 30, had no significant effect. Both p-CPA and E2 significantly depressed brain aromatase activity when administrated between days 7 and 10, but not subsequently. In tilapia treated between days 7 and 10, the brain 5-HT content was lowered by E2 to an extent similar to that seen with p-CPA, which is consistent with the suggestion that the effect of E2 on sexual differentiation may be mediated by the 5-HT system. Treatment of tilapia with 17alpha-methyltestosterone (MT), by contrast, resulted in a reduction in the female : male ratio, and treatment was most effective when given between days 10 and 20. The period of maximal effect of MT upon sex ratio appears to coincide with the ability of MT to induce an increase in brain aromatase activity.

Aging↗

PubMed2000

Response properties of PMLS and PLLS neurons to simulated optic flow patterns.

The processing of optic flow information has been extensively investigated in the medial superior temporal area (MST) of the macaque. In the cat, the posteromedial area and the posterolateral area in the lateral suprasylvian cortex (PMLS and PLLS, respectively) have been suggested as likely participants according to their direction preferences to moving objects. In the present study, 203 PMLS and 123 PLLS neurons were tested with simulated optic flow patterns composed of random dots (including expansion and contraction, clockwise and counter-clockwise rotation, and translation) and moving bar stimuli. About 90% of the neurons were found to be excited by the optic flow stimuli and most of them were multiple-responsive to different flow patterns. Only 20-25% of the cells were selective to different optic flow modes, and in general, the direction preference was fairly modest. The selective cells showed stronger directionality to both flow field and moving bar than nonselective cells. However, the optic flow response properties in the PMLS and PLLS were not well correlated with the direction preference to moving bars. In accordance with previous findings, the PMLS was analogous to the middle temporal area of the macaque in many respects. As for the PLLS cells, they were sensitive to fewer types of stimuli, but responded better and more selectively to radial motion. All these results suggest that the two lateral suprasylvian areas are unlikely to be specialized for the analysis or discrimination of different flow patterns, but may play some kind of relay role in optic flow information processing.

Animals↗

PubMed2000

Vav3 mediates receptor protein tyrosine kinase signaling, regulates GTPase activity, modulates cell morphology, and induces cell transformation.

A recently reported new member of the Vav family proteins, Vav3 has been identified as a Ros receptor protein tyrosine kinase (RPTK) interacting protein by yeast two-hybrid screening. Northern analysis shows that Vav3 has a broad tissue expression profile that is distinct from those of Vav and Vav2. Two species of Vav3 transcripts, 3.4 and 5.4 kb, were detected with a differential expression pattern in various tissues. Transient expression of Vav in 293T and NIH 3T3 cells demonstrated that ligand stimulation of several RPTKs (epidermal growth factor receptor [EGFR], Ros, insulin receptor [IR], and insulin-like growth factor I receptor [IGFR]) led to tyrosine phosphorylation of Vav3 and its association with the receptors as well as their downstream signaling molecules, including Shc, Grb2, phospholipase C (PLC-gamma), and phosphatidylinositol 3 kinase. In vitro binding assays using glutathione S-transferase-fusion polypeptides containing the GTPase-binding domains of Rok-alpha, Pak, or Ack revealed that overexpression of Vav3 in NIH 3T3 cells resulted in the activation of Rac-1 and Cdc42 whereas a deletion mutant lacking the N-terminal calponin homology and acidic region domains activated RhoA and Rac-1 but lost the ability to activate Cdc42. Vav3 induced marked membrane ruffles and microspikes in NIH 3T3 cells, while the N-terminal truncation mutants of Vav3 significantly enhanced membrane ruffle formation but had a reduced ability to induce microspikes. Activation of IR further enhanced the ability of Vav3 to induce membrane ruffles, but IGFR activation specifically promoted Vav3-mediated microspike formation. N-terminal truncation of Vav3 activated its transforming potential, as measured by focus-formation assays. We conclude that Vav3 mediates RPTK signaling and regulates GTPase activity, its native and mutant forms are able to modulate cell morphology, and it has the potential to induce cell transformation.

3T3 Cells↗

PubMed2000

Differential activation of ERK 1/2 and JNK in normal human fibroblast-like cells in response to UVC radiation under different oxygen tensions.

The mechanisms by which mitogen-activated protein kinases (MAPK) respond to the input of UV-induced signal transduction pathways and the resulting biological functions are not well understood. We investigated whether the level of oxygen tension of culture was responsible for the differential activation of MAPK and different cellular outcomes in UVC-irradiated cells. The intracellular oxidative level of normal human fibroblast-like cells in a normal atmosphere (normoxic, 20% O2) was increased within 30 min after UVC irradiation. When cells were cultured at lower oxygen tension in the presence of an antioxidant N-acetyl-L-cysteine (NAC) or under physiologically hypoxic (5% O2) conditions, the elevation of the oxidative level by UV-irradiation was significantly reduced. Among MAPK, extracellular-signal related kinase (ERK) 1/2 was activated by UV regardless of the oxidative level, while c-Jun N-terminal kinase (JNK) activation was inhibited in NAC-treated and in hypoxic cultures. In addition, in cultures at lower oxygen tension, there was less apoptosis and cell survival was enhanced. These results suggest that UV-induced oxidative stress was responsible for intracellular signaling through the JNK pathway. Furthermore, the balance between ERK1/2 and JNK activities after UV irradiation under different oxygen tensions possibly modified cellular outcome in response to UV.

Apoptosis↗

PubMed2000

Lichen sclerosus et atrophicus, bullous morphea, and systemic lupus erythematosus: a case report.

Lichen sclerosus et atrophicus (LSA) rarely coexists with morphea, especially when bullae occur in lesions of morphea. Here we report the case of a 15-year-old girl with this condition, who also fulfilled four out of 11 diagnostic criteria for systemic lupus erythematosus (SLE). Tissue biopsy of different skin lesions showed LSA in the regions of bullous morphea, that has rarely been reported in the literature.

Adolescent↗

PubMed2000

Efficacy and safety of methotrexate therapy for juvenile rheumatoid arthritis.

BACKGROUND AND PURPOSE: Juvenile rheumatoid arthritis (JRA) can result in disability, growth disturbance, and systemic complications. This study investigated the efficacy and adverse effects of oral methotrexate (MTX) therapy in Taiwanese children with JRA. METHODS: The medical records of 52 Taiwanese children with JRA treated with oral MTX were retrospectively analyzed. The disease onset was polyarticular in 22 children, oligoarticular in 13, and systemic in 17. The indication for MTX therapy was lack of efficacy of previous drugs, including two or more nonsteroidal anti-inflammatory drugs, in all patients. In addition, three patients had received hydroxychloroquine and one had received sulfasalazine, without improvement. Corticosteroid dependency had developed in 27 patients prior to MTX therapy. The mean initial dose of MTX was 9.1 mg.m-2.wk-1 (range, 5-20 mg.m-2.wk-1), and the mean maximal dose was 10.2 mg.m-2.wk-1 (range, 5-20 mg.m-2.wk-1). The mean duration of treatment was 23 months (range, 6-96 mo), and the mean duration of follow-up was 52 months (range, 10-123 mo) from the start of MTX therapy. RESULTS: Thirty-six children (69%) showed clinical improvement and 25 children (48%) achieved clinical remission. The administration of MTX resulted in more than a 50% reduction in required corticosteroid dosage in six children, and complete discontinuation of corticosteroid in 10 children. MTX was discontinued in 18 patients following a mean of 8 months (range, 2-34 mo) of clinical remission. Relapse occurred in nine (50%) of these patients. Thirteen patients (25%) suffered from adverse effects associated with MTX treatment. All of these adverse effects resolved spontaneously, or subsided within 4 weeks following dosage reduction or discontinuation of MTX. CONCLUSIONS: Oral MTX therapy is effective and well-tolerated in Taiwanese children with JRA. It can serve as the first choice of second-line therapy in JRA.

Adolescent↗

PubMed2000

Propylthiouracil-induced antineutrophil cytoplasm antibody-positive anaphylactoid purpura-like vasculitis--a case report.

Propylthiouracil (PTU), a drug commonly used for treatment of hyperthyroidism, is associated with various rare side effects. Antineutrophil cytoplasm antibody (ANCA)-positive vasculitis is a relatively unusual complication among them. The pathogenesis of ANCA-positive vasculitis during PTU therapy is still obscure. We present the case of a 12-year-old boy who developed ANCA-positive vasculitis during PTU therapy for Graves' disease. His symptoms and signs were indistinguishable from anaphylactoid purpura, a common small-vessel vasculitis in children. The clinical manifestations improved after discontinuation of PTU and immunosuppressant treatment. He remained symptom-free at 11-months follow-up.

Antibodies, Antineutrophil Cytoplasmic↗

PubMed2000

Inhibition of mitogen-activated protein kinase kinase selectively inhibits cell proliferation in human breast cancer cells displaying enhanced insulin-like growth factor I-mediated mitogen-activated protein kinase activation.

Mitogen-activated protein (MAP) kinase mediates cell proliferation, cell differentiation, and cell survival by regulating signaling pathways activated by receptor protein tyrosine kinases (RPTKs), including the insulin-like growth factor 1 receptor (IGF-IR). We analyzed the upstream signaling components of the MAP kinase pathway, including RPTKs, in human breast cancer cell lines and found that some of those components were overexpressed. Importantly, signaling molecules such as IGF-IR, insulin receptor, and insulin receptor substrate 1, leading to the MAP kinase pathway, were found to be concomitantly overexpressed within certain tumor lines, i.e., MCF-7 and T-47D. When compared with the nonmalignant and other breast tumor lines examined, MCF-7 and T-47D cells displayed a more rapid, robust, and sustained MAP kinase activation in response to insulin-like growth factor I (IGF-I) stimulation. By contrast, IGF-I treatment led to a sustained down-regulation of MAP kinase in those lines overexpressing ErbB2-related RPTKs. Interestingly, blocking the MAP kinase pathway with PD098059 had the greatest antiproliferative effect on MCF-7 and T-47D among the normal and tumor lines tested. Furthermore, addition of an IGF-IR blocking antibody to growth medium attenuated the ability of PD098059 to suppress the growth of MCF-7 and T-47D cells. Thus, our study suggests that concomitant overexpression of multiple signaling components of the IGF-IR pathway leads to the amplification of IGF-I-mediated MAP kinase signaling and resultant sensitization to PD098059. The enhanced sensitivity to PD098059 implies an increased requirement for the MAP kinase pathway in those breast cancer cells, making this pathway a potential target in the treatment of selected breast malignancies.

Breast Neoplasms↗

PubMed2000

[Content and activity of the focal adhesion kinase in cultured vascular smooth muscle cells enhanced by urotensin II].

Urotensin II (U II) is the most potent vasoconstrictor identified in vivo, which plays an important role in the smooth muscle cell proliferation in atherosclerosis. All available information suggests that focal adhesion kinase (FAK) is at the crossroads of multiple signaling pathways and is essential for cell proliferation. But the effect of U II on the FAK mediated signal transduction pathway is unclear. In this study, FAK content and tyrosine phosphorylation were assessed by Western blot and immunoprecipitation in cultured rat vascular smooth muscle cells. Increased protein tyrosine phosphorylation was observed within 5 min of U II 10(-7) (mol/L) addition and was maximal by 30 min, while FAK protein content showed no change during the first 30 min but it increased at 2 h reaching a plateau by 4 h, and decreased after 6 h. In addition, the elevated phosphorylation of FAK was detected upon U II stimulation at 10(-8) mol/L, being maximal at 10(-7) mol/L, but decreased at 10(-6) mol/L. Treatment of the cells with cytochalasin B (50 micromol/L), which disrupted the organization of cytoskeleton, had no influence on the increased FAK tyrosine phosphorylation in response to U sti II mulation. In order to study the relationship between FAK and mitogen-activated protein kinase, calmodulin and protein kinase C, selective inhibitors PD98059 (50 micromol/L), W7 (50 micromol/L) and H7 (50 micromol/L) were added following U II treatment. Neither PD98059 nor W7 influenced the increased FAK tyrosine phosphorylation, but H7 further increased it. These findings indicate that FAK activation is independent of the integrity of cytoskeleton and closely related to protein kinase C, but had no relation with mitogen activated protein kinase and calmodulin.

Animals↗

PubMed2000

[Ultrastructure differences of in vitro cotton fiber and native cotton fiber].

Native cotton fiber and in vitro cotton fiber that was induced from cotton ovule callus by suspension culture were observed using transmission electron microscope and scanning electron microscope. The ovule surface on the first day preanthesis was quite smooth. On the anthesis, it had a lot of protuberances. Two kinds of callus, smooth and rough were found. The microfibrils of callus was vertical to the cell long axis and they changed their orientations with the development of the in vitro cotton fiber: from the vertical to shallow spiral and then to parallel to the cell long axis. So was the native cotton fiber. It suggests that in vitro cotton fiber and native cotton fiber have similar development process. Compared with the ovule surface cell, most callus cells had smaller nuclear. During the development of the fiber, the plasm of native cotton fiber was denser than that of in vitro fiber, and it has more cellular organ than in vitro fiber. The cell wall of native cotton fiber was thicker and denser than that of the in vitro cotton fiber too. It suggests that the physiological activity of in vitro cotton fiber was less active than native cotton fiber.

Cotton Fiber↗

PubMed2000

[Treatment of patients with chronic sinusitis by endoscopic and Caldwell-Luc approaches].

OBJECTIVE: To investigate the clinical effect of surgical procedures on patients with chronic sinusitis. METHOD: 104 patients with chronic sinusitis were treated by endoscopic and Caldwell-Luc's approaches. The lesions were cleared away completely. RESULT: The clinical cure rate was 96.1% after 6-12 months (average 9 months) follow up. CONCLUSION: It suggests that patients with severe maxillary sinus diseases might be cured by endoscopic and Caldwell-Luc's procedure.

Adolescent↗

PubMed1999

A point mutation of human p53, which was not detected as a mutation by a yeast functional assay, led to apoptosis but not p21Waf1/Cip1/Sdi1 expression in response to ionizing radiation in a human osteosarcoma cell line, Saos-2.

PURPOSE: The 123A point mutation of p53 showed increased radiosensitivity, whereas other mutations (143A, 175H, and 273H) were not affected. To determine the reason for increased radiosensitivity of the 123A mutation, the response of the transformant of 123A mutation to ionizing radiation (IR) was examined and compared to those of transformants with the wild type p53 or other point mutations (143A, 175H, and 273H). METHODS AND MATERIALS: Stable transformants with a mutant or wild type p53 made by introducing cDNA into the human osteosarcoma cell line, Saos-2, which lacks an endogenous p53 were used. The transcriptional activity of mutant p53 was examined using a yeast functional assay. The transformants were examined for the accumulation of p53, the induction of p21Waf1/Cip1/Sdi1 (hereafter referred to as p21), and the other response of p53-responsive genes (MDM2, Bax, and Bcl-2) by Western blotting. Apoptosis was analyzed by detection of DNA fragmentation. RESULTS: The 123A point mutation of p53 was detected as a wild type in the yeast functional assay. The 123A mutant accumulated p53 in response to IR. The 123A mutant did not induce p21, but normally responded to MDM2, Bax, and Bcl-2. The 123A mutant entered apoptosis earlier than the wild type p53 transformant, and induced Fas at earlier in response to IR. CONCLUSION: The 123A mutant led to apoptosis, but not p21 expression in response to IR. The occurrence of apoptosis, but not induction of p21, corresponded to the radiosensitivity in the transformant. The early occurrence of apoptosis in 123A transformants may depend on the early induction of Fas.

Apoptosis↗

PubMed1999

Plexin-neuropilin-1 complexes form functional semaphorin-3A receptors.

Class 1 and 3 semaphorins repulse axons but bind to different cell surface proteins. We find that the two known semaphorin-binding proteins, plexin 1 (Plex 1) and neuropilin-1 (NP-1), form a stable complex. Plex 1 alone does not bind semaphorin-3A (Sema3A), but the NP-1/Plex 1 complex has a higher affinity for Sema3A than does NP-1 alone. While Sema3A binding to NP-1 does not alter nonneuronal cell morphology, Sema3A interaction with NP-1/Plex 1 complexes induces adherent cells to round up. Expression of a dominant-negative Plex 1 in sensory neurons blocks Sema3A-induced growth cone collapse. Sema3A treatment leads to the redistribution of growth cone NP-1 and plexin into clusters. Thus, physiologic Sema3A receptors consist of NP-1/plexin complexes.

Animals↗

PubMed1999

Src kinases involved in hepatitis B virus replication.

Chronic infection by hepatitis B virus is a leading cause of human liver cancer and liver disease. The hepatitis B virus HBx protein is a regulatory factor that is essential for virus infection in mammals and is implicated in development of liver cancer and liver disease. Among the reported activities of HBx is the ability to stimulate Src tyrosine kinases, Ras-GTPases and transcriptional activation. We now demonstrate that HBx activation of Src tyrosine kinases, but not Ras, promotes a high level of viral replication in cell culture. HBx is shown to stimulate reverse transcription of the viral pregenomic mRNA into genomic DNA through a Src-mediated pathway in tissue culture cells. Targeted inhibition of Src tyrosine kinase activity, mutational inactivation of the HBx gene or retargeting of HBx to the nucleus to abolish cytoplasmic signal transduction activity, are shown to impair viral reverse transcription strongly. These studies implicate HBx stimulation of the Src family of tyrosine kinases in stimulation of viral polymerase activity.

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