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Biomedical subjects

C Huang

Publications and source records attributed to C Huang.

At least 217 records · Page 12Linked to original sources
PubMed1999

Identification of inhibitor specificity determinants in a mammalian phosphodiesterase.

Mammalian phosphodiesterase types 3 and 4 (PDE3 and PDE4) hydrolyze cAMP and are essential for the regulation of this intracellular second messenger in many cell types. Whereas these enzymes share structural and biochemical similarities, each can be distinguished by its sensitivity to isozyme-specific inhibitors. By using a series of chimeric enzymes, we have localized the region of PDE4 that confers sensitivity to selective inhibitors. This inhibitor specificity domain lies within a short sequence at the carboxyl terminus of the catalytic domain of the protein, consistent with the competitive nature of inhibition by these compounds. Surprisingly, the identified region also includes some of the most highly conserved residues among PDE isoforms. A yeast-based expression system was used for the isolation and characterization of mutations within this area that confer resistance to the PDE4-specific inhibitor rolipram. Analysis of these mutants indicated that both conserved and unique residues are required for isoform-specific inhibitor sensitivity. In some cases, combined point mutations contribute synergistically to the reduction of sensitivity (suppression of IC50). We also report that several mutations display differential sensitivity changes with respect to distinct structural classes of inhibitors.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1999

Persistent membrane association of activated and depalmitoylated G protein alpha subunits.

Heterotrimeric signal-transducing G proteins are organized at the inner surface of the plasma membrane, where they are positioned to interact with membrane-spanning receptors and appropriate effectors. G proteins are activated when they bind GTP and inactivated when they hydrolyze the nucleotide to GDP. However, the topological fate of activated G protein alpha subunits is disputed. One model declares that depalmitoylation of alpha, which accompanies activation by a receptor, promotes release of the protein into the cytoplasm. Our data suggest that activation of G protein alpha subunits causes them to concentrate in subdomains of the plasma membrane but not to be released from the membrane. Furthermore, alpha subunits remained bound to the membrane when they were activated with guanosine 5'-(3-O-thio)triphosphate and depalmitoylated with an acyl protein thioesterase. Limitation of alpha subunits to the plasma membrane obviously restricts their mobility and may contribute to the efficiency and specificity of signaling.

Animals↗
PubMed1999

Modulation by cytokines of induction of oral tolerance to type II collagen.

OBJECTIVE: To determine whether the simultaneous administration of drugs and/or cytokines such as transforming growth factor beta (TGFbeta) can render oral tolerance to type II collagen (CII) more effective in causing resistance to collagen-induced arthritis (CIA) in mice, and to investigate whether oral tolerance can still be induced when high levels of anti-CII are present. METHODS: Tolerance was induced by intragastric feeding of low-dose CII to DBA/1 mice during a 2-week period, either before immunization with CII in Freund's complete adjuvant or after initiation of arthritis. Some mice were simultaneously injected with TGFbeta1 or with the H2 receptor agonist dimaprit. RESULTS: Both TGFbeta1 and dimaprit increased the degree of oral tolerance obtained. TGFbeta1 augmented the induction of immunoregulatory CD8 T cells, which transferred the resistance to CIA induction to normal recipients. Feeding of CII for 2 weeks, starting after the onset of arthritis, still significantly ameliorated the course of CIA. CONCLUSION: Administration of TGFbeta1 or dimaprit, both of which are believed to promote the development of immunoregulatory T cells, may reinforce induction of oral tolerance, even after the onset of arthritis.

Adjuvants, Immunologic↗
PubMed1999

The changes of plasma endothelin in oleic acid-induced acute lung injury and their implication.

The changes of pulmonary arterial and pulmonary venous plasma endothelin (ET) level in oleic acid (OA)--induced lung injury (ALI) rats were observed. After the ALI model of rats was established by intravenous injection of OA, blood samples were taken from a right cardiac catheter inserted via the right external jugular vein into the pulmonary artery to determine the plasma ET levels by using radioimmunoassay before OA injection, and 2 h and 4 h after OA injection. At the same time, arterial oxygen pressure (PaO2) and mean pulmonary arterial pressure (mPAP) were measured to evaluate the role of ET in acute lung injury. The results showed that the plasma ET levels after OA injection were significantly increased in OA group rats as compared with those in the controls, positively correlated with mPAP and negatively with PaO2. The plasma ET level in pulmonary vein was higher than in pulmonary artery, but no significant difference was found. It was concluded that ET, as a local or circulating hormone, might play an important role in pathophysiology of ALI.

Animals↗
PubMed1999

Effect of astragalus on the endothelin in rats with acute lung injury.

The effect of astragalus on the endothelin in serum and lung of the rats with acute lung injury was studied. The results demonstrated that the concentration of endothelin in the lung of the rats in therapy group was lower than that of the injured rats (64.36 +/- 5.37 ng/L vs 103.32 +/- 4.99 ng/L, P < 0.001), and level of serum endothelin was also lower than that of the injured rats (85.35 ng/L vs 113.35 ng/L, P < 0.01). PaO2, serum SOD, lung coefficient, ratio of lung wet weight/dry weight in two groups were also significantly different (P < 0.01) respectively, and the lung pathological injury in the treatment group were less than that of injury group. So it is concluded that astragalus could inhibit the increase of serum and lung endothelin, thereby playing a protective role in the rats with acute lung injury.

Animals↗
PubMed1999

Overexpression of bax associated with mutations in the loop-sheet-helix motif of p53.

Recent investigations have revealed that mutations of the loop-sheet-helix motif of p53 is a significant factor for a poor prognosis in patients with non-small-cell lung cancer (NSCLC). To clarify this mechanism, bcl-2 and bax expression were evaluated in relation to mutations of p53. Tumor tissues of 203 patients with NSCLC were analyzed. Immunohistochemistry was performed to evaluate bcl-2 and bax expression, and polymerase chain reaction single-strand conformation polymorphism following direct sequencing was performed to investigate p53 status. A total of 79 carcinomas were bcl-2 positive, 146 carcinomas were bax positive, and 72 carcinomas had missense mutations of p53. There was no difference in bcl-2 expression in relation to p53 status. On the other hand, tumors with structural mutations of p53 had significantly lower expression of bax than those with wild-type p53 (P = 0.0026). In contrast, tumors with mutations of the loop-sheet-helix motif of p53 had significantly higher expression of bax than those with wild-type p53 (P = 0.0236). The frequency of a bcl-2/bax ratio of >/=1 was significantly lower in tumors with mutations of the loop-sheet-helix motif than that in tumors with wild-type p53 (P = 0.0240). The bcl-2/bax ratio status was a significant factor for a prognosis in patients with NSCLC (P = 0.0083). Mutations of the loop-sheet-helix motif of p53 were correlated with overexpression of bax, while other mutations of p53 were correlated with low levels of bax expression. This variation in pattern of bax expression in relation to mutant p53 might reflect the biological behavior of tumors in patients with bcl-2-positive NSCLC.

Adenocarcinoma↗
PubMed1999

Sequence comparisons of medium RNA segment among 15 California serogroup viruses.

The complete nucleotide sequences have been determined for the M segment of 12 California (CAL) serogroup bunyaviruses. A method is described here of long reverse transcription-polymerase chain reaction (RT-PCR) that yields the full-length medium (M) RNA genomic segment. A phylogenetic tree was constructed by comparison of the open reading frames (ORFs) in the M RNA segment of 15 CAL serogroup viruses. Three distinct branches were identified and they are represented by the California encephalitis (CE), Melao (MEL), and Trivittatus (TVT) complexes. These groups correspond to those previously established by small (S) RNA genomic sequences. In addition, except for Inkoo virus, the predicted relationship among these viruses agreed with those found by serology.

Encephalitis Virus, California↗
PubMed1999

Differences in health characteristics between native Japanese and Japanese-Americans.

Health characteristics were compared among 1193 Japanese in Hiroshima, and 2306 Japanese-Americans in Hawaii. Japanese women experienced later menarche, earlier menopause, and a shorter interval between menarche and menopause than Japanese-Americans. Japanese men and women were shorter and lighter and the men bad lower body mass index than Japanese-Americans. Differences between populations were also found for the prevalence of artificial menopause, number of live births, lactation period, smoking, and alcohol consumption. Within one or both populations, significant trends with birth year were found for age at menarche, age at menopause, interval between menarche and menopause, lactation period, height, weight, and body mass index, suggesting the existence of cohort effects. Some of these trends may also reflect age-related changes. Environmental factors likely contribute to the differences in physique and reproductive factors, which may explain differences in frequency of osteoporosis, cardiovascular diseases, and cancer between the two populations.

Journal Article↗
PubMed1999

The role of hydroxyl radical as a messenger in the activation of nuclear transcription factor NF-kappaB.

Although it is generally believed that reactive oxygen species activate NF-kappaB, a primary oxidative stress-responsive transcription factor, it is unclear which one among these species causes NF-kappaB activation. Our hypothesis is that hydroxyl radical (*OH) functions as a messenger for the activation of NF-kappaB. Jurkat cells, macrophages and JB6 cells were used to test this hypothesis. Cr(VI), silica and ZnO were used as sources of *OH radicals. None of these *OH generating systems involves exogenous H2O2. Cr(VI) expressed enhanced activity in induction of NF-kappaB in Jurkat cells. This activation of NF-kappaB was decreased by a metal chelator, diethylene triaminepentaacetic acid or a H2O2 scavenger, catalase, but was increased by superoxide dismutase. Mn(II), which reacts with Cr(IV) to inhibit this metal ion-mediated *OH generation, decreased the NF-kappaB activation. Sodium formate, an *OH radical scavenger, also inhibited the NF-kappaB activation. Electron spin resonance measurements show that Cr(VI) was reduced by Jurket cells to Cr(IV) and Cr(V). During the reduction process, molecular oxygen was reduced to O2 and then to H2O2, which reacted with Cr(IV) and Cr(V) to generate *OH radical. The *OH generation correlated with the Cr(VI)-induced NF-kappaB activation. Similarly, silica caused NF-kappaB activation in macrophages via the *OH radical-mediated reaction. This radical was generated via metal mediated reaction from H2O2, which was generated by the reduction of molecular oxygen via O2- as an intermediate during the silica-stimulated 'respirable burst'. Silica particles did not cause *OH generation either in Jurket or in JB6 cells and thus did not cause any observable NF-kappaB activation in these cells. ZnO induced NF-kappaB activation in JB6 cells through the generation of *OH resulting from light irradiation of ZnO which was measured by electron spin resonance. The results thus show that *OH radical functions as a messenger for NF-kappaB activation. Antioxidants, which scavenge *OH radical or its precursors, inhibit NF-kappaB activation. Metal chelators, which make metal ions incapable of generating *OH from H2O2, inhibit activation of this transcription factor.

Animals↗
PubMed1999

An allelic non-histocompatibility antigen with wide tissue distribution as a marker for chimerism in pigs.

It is frequently useful in studies of transplantation to have available an antibody to a cell surface antigen, which is not itself responsible for transplant rejection. In this paper, we identify and describe such an antibody/antigen system in miniature swine. The monoclonal antibody, 1038H-10-9, was found to react to a pig allelic antigen (called PAA), found on a variety of pig cells and tissues, including peripheral blood mononuclear cells (PBMC), thymocytes, lymph node, bone marrow, and skin. Analysis for recipient sensitization against PAA was performed by in vitro cell-mediated lympholysis (CML) assay, mixed lymphocyte reaction (MLR) assay, antibody binding studies, and skin graft rejection patterns were examined. No evidence was found to indicate detection of PAA by any of these assays of alloreactivity. We therefore conclude that PAA is an allelic swine cell surface antigen, with wide tissue distribution, and that it is not a histocompatibility antigen. It should provide a powerful tool for studies of transplantation biology in miniature swine, such as identification and quantification of chimerism following organ transplantation.

Animals↗
PubMed1999

Prognostic significance of angiogenesis in human pancreatic cancer.

To evaluate whether angiogenic factors are of clinical relevance to actual human pancreatic cancers, we studied the intratumoral microvessel density (IMD), and PD-ECGF, VEGF protein expression in 40 pancreatic cancers using immunohistochemistry. We also investigated PD-ECGF and VEGF gene expression using reverse transcriptase-PCR (RT-PCR). Of the 40 pancreatic cancers studied, 30 carcinomas (75.0%) were evaluated to be PD-ECGF-positive and 10 carcinomas (25.0%) were determined to be PD-ECGF-negative. In contrast, 27 carcinomas (67.5%) were evaluated to be VEGF-positive, whereas 13 carcinomas (32.5%) were VEGF-negative. VEGF gene expression was moderately associated with an increase in the IMD (r2 = 0.181, P = 0.006), but no significant relationship was found between PD-ECGF gene expression and the IMD (r2 = 0.093, P = 0.059). However, tumours with positive expression for both PD-ECGF and VEGF had a higher IMD (P = 0.027). The results of the immunohistochemistry agreed well with the results of the quantitative RT-PCR. The median survival time of the hypervascular group was significantly shorter than that of the hypovascular group (P < 0.0001). In comparing the survival according to PD-ECGF and VEGF gene expression, the median survival time of the patients with positive PD-ECGF expression was significantly shorter than those with negative PD-ECGF expression (P = 0.040). Furthermore, the median survival time of the patients with positive VEGF expression was significantly shorter than those with negative VEGF expression (P = 0.048). However, the Cox multivariate analysis indicated that the IMD and VEGF expression were independent prognostic factors of the various clinicopathologic variables in pancreatic cancer patients (P = 0.0021 and P = 0.0443, respectively).

Aged↗
PubMed1999

Tacrolimus vs. cyclosporine immunosuppression: results in advanced-stage disease compared with historical controls treated exclusively with cyclosporine.

A phase HI comparative trial of tacrolimus- vs. cyclosporine-based graft-vs.-host disease (GVHD) prophylaxis for human leukocyte antigen (HLA)-identical sibling bone marrow transplantation showed less GVHD but poorer survival in the tacrolimus arm. To test the comparability of the two treatment arms with respect to baseline survival prognosis, a matched control study using exclusively cyclosporine-treated patients from the International Bone Marrow Transplant Registry (IBMTR) database was performed. Controls were matched (2:1) based on age (within 5 years), disease, and pretransplant disease status. Two-year survival for tacrolimus-treated clinical trial patients was similar to that of their cyclosporine-treated matched controls (27 and 24%, respectively), and 2-year survival of the cyclosporine-treated clinical trial patients was similar to that of their cyclosporine-treated matched IBMTR controls (42 and 45%, respectively). Consistent with the clinical trial results, the cyclosporine-treated IBMTR controls matched to the tacrolimus group had significantly poorer 2-year survival than the cyclosporine-treated IBMTR controls matched to the cyclosporine group (24 and 45%, respectively; p < 0.01). No significant difference was seen in GVHD between the cyclosporine-treated clinical trial patients and their matched controls; however, the tacrolimus-treated clinical trial patients had significantly less GVHD than their cyclosporine-treated IBMTR controls (p < 0.01). These results support the hypothesis that the survival difference in the phase III trial resulted from an imbalance in the underlying risk factors for death in the two groups rather than from the randomized immunosuppressive regimen.

Adolescent↗
PubMed1999

Increased TNF-alpha, IL-1 beta and IL-6 levels in the bronchoalveolar lavage fluid with the upregulation of their mRNA in macrophages lavaged from patients with active pulmonary tuberculosis.

SETTING: We hypothesized that patients with active pulmonary tuberculosis (TB) have tubercular pneumonitis and that alveolar macrophages at these sites release proinflammatory cytokines, resulting in high levels of cytokines in alveolar epithelial lining fluid. OBJECTIVE: To measure cytokine levels in bronchoalveolar lavage fluid (BALF) and to confirm the source of any cytokines by examination of alveolar macrophage cytokine mRNA. DESIGN: Seventeen active pulmonary TB patients and 15 healthy controls were prospectively studied. Bronchoalveolar lavage (BAL) was performed, proinflammatory cytokine levels were determined and alveolar macrophages isolated from BALF were prepared for RNA extraction and Northern blot analysis. RESULTS: Compared with healthy controls, TNF-alpha, IL-1 beta and IL-6 in BALF were all significantly higher in patients with active pulmonary TB, 298.7 +/- 85.9 vs. 8.9 +/- 2.7 (P = 0.0001); 164.4 +/- 67.5 vs. 8.9 +/- 2.7 (P = 0.003); 969.2 +/- 214.2 vs. 86.4 +/- 17.0 (mean +/- SE pg/ml) (P = 0.0001), respectively. Only TNF-alpha and IL-6 levels were significantly higher in sera of active pulmonary TB patients, 92.3 +/- 28.7 vs. 3.5 +/- 1.2; 15.2 +/- 5.4 vs. 2.1 +/- 2.1, respectively. Northern blot analysis revealed increased gene expression of these alveolar macrophage cytokines in patients with active pulmonary TB compared healthy controls. CONCLUSION: Significantly higher levels of TNF-alpha, IL-1 beta and IL-6 were found in BALF from patients with active pulmonary TB, and were released by alveolar macrophages in the TB lesions.

Adult↗
PubMed1999

Existence of multiple novel Gs alpha splice variants in acute leukemia patients.

The alpha subunit of the stimulatory G protein, Gs alpha, is involved in stimulation of the adenylate cyclase pathway of signal transduction. In this study, we investigated the status of the Gs alpha gene in 29 acute leukemia patients and identified three novel splice variants (designated Gs alpha L-1, Gs alpha L-2, and Gs alpha L-3), possibly derived from aberrant splicing. All of the splice variants have in-frame deletions, removing the functional domain responsible for GTPase activity of Gs alpha, and would encode truncated proteins of 160(Gs alpha L-1), 90(Gs alpha L-2) and 70(Gs alpha L-3) amino acids, respectively. The data suggest that these novel products may be implicated in an as-yet-unidentified signal transduction pathway in hematopoietic cells.

Acute Disease↗
PubMed1999

Rhmod syndrome: a family study of the translation-initiator mutation in the Rh50 glycoprotein gene.

Rhmod syndrome is a rare genetic disorder thought to result from mutations at a "modifier" but not at the suppressor underlying the regulator type of Rhnull disease. We studied this disorder in a Jewish family with a consanguineous background and analyzed RH and RHAG, the two loci that control Rh-antigen expression and Rh-complex assembly. Despite the presence of a d (D-negative) haplotype, no other gross alteration was found at RH, and cDNA sequencing showed a normal structure for D, Ce, and ce Rh transcripts in family members. However, analysis of RHAG transcript, which encodes Rh50 glycoprotein, identified a single G-->T transversion in the initiation codon, causing a missense amino acid change (ATG[Met]-->ATT[Ile]). This point mutation also occurred in the genomic region spanning exon 1 of RHAG, and its genotypic status in the mother and two children was confirmed by analysis of single-strand conformation polymorphism. Although blood typing showed a very weak expression of Rh antigens, immunoblotting barely detected the Rh proteins in the Rhmod membrane. In vitro transcription-coupled translation assays showed that the initiator mutants of Rhmod-but not those of the wild type-could be translated from ATG codons downstream. Our findings point to incomplete penetrance of the Rhmod mutation, in the form of "leaky" translation, leading to some posttranslational defects affecting the structure, interaction, and processing of Rh50 glycoprotein.

Base Sequence↗
PubMed1999

Diagnosis of Jamestown Canyon encephalitis by polymerase chain reaction.

In recent years, polymerase chain reaction (PCR) has been under study as a potential technique to improve the accuracy of diagnosis of suspected central nervous system viral infections. We describe a case of severe encephalitis in a previously healthy 20-year-old woman from New York who presented with headache, fever, and photophobia. Her illness was characterized by progressive worsening of her neurological status, leading to confusion, delirium, and status epilepticus. The diagnosis of Jamestown Canyon encephalitis was established by positive reverse transcriptase (RT)-PCR and nucleic acid sequencing of the band from both cerebrospinal fluid and brain tissue. The nucleotide sequence and the deduced amino acid sequence of the Jamestown Canyon virus from this patient were very similar to Jamestown Canyon virus isolates from mosquito pools in New York. This report suggests that RT-PCR assays could be important tools in the diagnostic workup of cases of encephalitis.

Adult↗
PubMed1999

Resveratrol suppresses cell transformation and induces apoptosis through a p53-dependent pathway.

Resveratrol, a plant constituent enriched in the skin of grapes, is one of the most promising agents for the prevention of cancer. However, the mechanism of the anti-carcinogenic activity of resveratrol is not well understood. Here we offer a possible explanation of its anti-cancer effect. Resveratrol suppresses tumor promoter-induced cell transformation and markedly induces apoptosis, transactivation of p53 activity and expression of p53 protein in the same cell line and at the same dosage. Also, resveratrol-induced apoptosis occurs only in cells expressing wild-type p53 (p53+/+), but not in p53-deficient (p53-/-) cells, while there is no difference in apoptosis induction between normal lymphoblasts and sphingomyelinase-deficient cell lines. These results demonstrate for the first time that resveratrol induces apoptosis through activation of p53 activity, suggesting that its anti-tumor activity may occur through the induction of apoptosis.

Animals↗