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Biomedical subjects

H Wu

Publications and source records attributed to H Wu.

At least 271 records · Page 15Linked to original sources
PubMed2000

Metallothionein inhibits myocardial apoptosis in copper-deficient mice: role of atrial natriuretic peptide.

Dietary copper restriction causes heart hypertrophy in animal models. Several studies have indicated that this cardiomyopathy is mediated by oxidative stress. Metallothionein (MT), a low molecular weight and cysteine-rich protein, functions in protecting the heart from oxidative injury. We therefore used a cardiac-specific MT-overexpressing transgenic mouse model to test the hypothesis that MT inhibits copper deficiency-induced heart hypertrophy. Dams of both transgenic pups and non-transgenic littermates were fed a copper-adequate or copper-deficient diet, starting on the fourth day post-delivery, and the weanling mice were continued on the dams' diets until they were killed. Heart hypertrophy developed in copper-deficient pups by the fourth week of the combined pre- and post-weaning feeding and aggressively progressed until the end of the experiment (6 weeks). MT overexpression did not prevent the occurrence of heart hypertrophy, but inhibited the progression of this cardiomyopathy, which correlated with its suppression of cardiac lipid peroxidation. Corresponding to the progression of heart hypertrophy, myocardial apoptosis and atrial natriuretic peptide (ANP) production in the left ventricle were detected in non-transgenic copper-deficient mice; these effects were significantly suppressed in transgenic copper-deficient mice. Measurement of apoptosis by TUNEL assay and Annexin V-FITC confocal microscopy in primary cultures of cardiomyocytes revealed that ANP was largely responsible for the myocyte apoptosis and that MT inhibited ANP-induced apoptosis. The data clearly demonstrate that elevation of MT in the heart inhibits oxidative injury and suppresses the progression of heart hypertrophy in copper deficiency, although it does not block its initiation. The results suggest that MT inhibits the transition from heart hypertrophy to failure by suppressing apoptosis through inhibition of both cardiac ANP production and its apoptotic effect.

Animals↗
PubMed2000

T cell lines specific for a synthetic Heymann nephritis peptide derived from the receptor-associated protein.

Pathogenic antigens involved in the induction of Heymann nephritis (HN), an experimental rat model of human membranous nephritis, have been identified in megalin (gp330) and the receptor-associated protein (RAP) [1,2]. A pathogenic epitope has been identified in RAP (amino acid 1-86) that plays a significant role in the formation of immune deposits in glomeruli in HN. A synthetic peptide (P31-53) derived from RAP1-86 contains a pathogenic epitope recognized by antibodies eluted from glomerular immune deposits and includes two putative RT-1B1 MHC class II-binding motifs. We have investigated whether RAP P31-53 can be recognized by T cells. Five peptide-specific T cell lines were generated from regional lymph node (LN) T cells from Lewis rats immunized with P31-53. The T cell lines were characterized by using a T cell proliferation assay for their specificity, FACS and MHC restriction assay for the phenotype, reverse transcription-polymerase chain reaction for TCR Vbeta repertoire and cytokine expression, and cloning and sequencing for the analysis of the CDR3 sequence of TCR. The helper function of the T cell line was confirmed by autoantibody production in vitro. In this study, we clearly identify that the synthetic pathogenic peptide P31-53 contains a T cell epitope recognized by CD4+ Th2 cells in Lewis rats. This recognition was restricted by MHC class II RT1.B1. These CD4+ Th2 cells were able to promote B cells to produce specific antibodies and used a restricted set of TCR Vbeta genes with preferential usage of Vbeta18. A charged amino acid motif at the CDR3 region of predominant TCR Vbeta subfamilies may contribute to the specific ability of these cells to recognize the immunogenic T cell epitope within RAP peptide P31-53.

Amino Acid Sequence↗
PubMed2000

Effect of intragastric pH on control of peptic ulcer bleeding.

BACKGROUND: We have performed series studies to investigate the effect of intragastric pH on control of peptic ulcer bleeding. In laboratory and animal studies, both platelet aggregation and gastric mucosal bleeding time were shown to be extremely sensitive to different pH levels. Platelet aggregation decreased significantly at pH > or = 6.8 and gastric mucosal bleeding time fell significantly at pH > or = 6.4. In a prospective clinical trial, primed infusions of different dosages of omeprazole (8 or 4 mg/h) after a bolus (40 mg) produced consistently high intragastric pH values in patients with bleeding duodenal ulcer. These results were not significantly different from that obtained from omeprazole 40 mg bolus treatment every 12 h (P > 0.05). However, primed injection with cimetidine (800 mg/12 h) was less effective (P < 0.05). METHODS: In a retrospective analysis, 303 patients with bleeding peptic ulcer who were treated with cimetidine and 326 patients who were treated with omeprazole were compared. RESULTS: The emergency surgery (4.91%) and mortality rates (1.84%) in the omeprazole group were not significantly different (P > 0.05) from those (7.28 and 1.99%) in the cimetidine group. However, the standardized emergency surgery rate of the omeprazole group (3.28%) was significantly lower than that (9.28%) of the cimetidine group (P < 0.05). CONCLUSION: We conclude that increased intragastric pH to at least 6.4 with omeprazole is helpful in controlling peptic ulcer bleeding. Chinese patients require a lower dose of omeprazole than their Western counterparts to control ulcer bleeding.

Adolescent↗
PubMed2000

Alterations in hypertrophic gene expression by dietary copper restriction in mouse heart.

Dietary copper (Cu) restriction causes a hypertrophic cardiomyopathy similar to that induced by work overload in rodent models. However, a possible change in the program of hypertrophic gene expression has not been studied in the Cu-deficient heart. This study was undertaken to fill that gap. Dams of mouse pups were fed a Cu-deficient diet (0.35 mg/kg diet) or a Cu-adequate control diet (6.10 mg/kg) on the fourth day after birth, and weanling mice continued on the dams' diet until they were sacrificed. After 5 weeks of feeding, Cu concentrations were dramatically decreased in the heart and the liver of the mice fed the Cu-deficient diet. Corresponding to these changes, serum ceruloplasmin concentrations and hepatic Cu,Zn-superoxide dismutase activities were significantly (P<0.05) depressed. The size of the Cu-deficient hearts was greatly enlarged as estimated from the absolute heart weight and the ratio of heart weight to body weight. The abundances of mRNAs for atrial natriuretic factor, beta-myosin heavy chain, and alpha-skeletal actin in left ventricles were all significantly increased in the Cu- deficient hearts. Furthermore, Cu deficiency activated the expression of the c-myc oncogene in the left ventricle. This study thus demonstrated that a molecular program of alterations in embryonic genes, similar to that shown in the work-overloaded heart, was activated in the hypertrophied heart induced by Cu deficiency.

Animals↗
PubMed2000

High-LET radiation-induced aberrations in prematurely condensed G2 chromosomes of human fibroblasts.

PURPOSE: To determine the number of initial chromatid breaks induced by low- or high-LET irradiations, and to compare the kinetics of chromatid break rejoining for radiations of different quality. MATERIAL AND METHODS: Exponentially growing human fibroblast cells AG1522 were irradiated with gamma-rays, energetic carbon (290MeV/u), silicon (490MeV/u) and iron (200 and 600 MeV/u). Chromosomes were prematurely condensed using calyculin A. Chromatid breaks and exchanges in G2 cells were scored. PCC were collected after several post-irradiation incubation times, ranging from 5 to 600 min. RESULTS: The kinetics of chromatid break rejoining following low- or high-LET irradiation consisted of two exponential components representing a rapid and a slow time constant. Chromatid breaks decreased rapidly during the first 10min after exposure, then continued to decrease at a slower rate. The rejoining kinetics were similar for exposure to each type of radiation. Chromatid exchanges were also formed quickly. Compared to low-LET radiation, isochromatid breaks were produced more frequently and the proportion of unrejoined breaks was higher for high-LET radiation. CONCLUSIONS: Compared with gamma-rays, isochromatid breaks were observed more frequently in high-LET irradiated samples, suggesting that an increase in isochromatid breaks is a signature of high-LET radiation exposure.

Cell Line↗
PubMed2000

Effect of zidovudine resistance mutations on virologic response to treatment with zidovudine-lamivudine-ritonavir: genotypic analysis of human immunodeficiency virus type 1 isolates from AIDS clinical trials group protocol 315.ACTG Protocol 315 Team.

The effect of baseline drug resistance mutations on response to zidovudine, lamivudine, and ritonavir was evaluated in zidovudine-experienced persons infected with human immunodeficiency virus type 1 (HIV-1). Presence of the K70R mutation was associated with significantly higher plasma HIV-1 RNA levels at baseline. However, presence of resistance mutations did not affect the increase in plasma HIV-1 RNA during a 5-week drug washout, nor was there any effect on first-phase virus decay rates after initiation of therapy or on the probability of having plasma HIV-1 RNA levels <100 copies/mL at week 48. Polymorphisms at protease codons 10, 36, and 71 were associated with significantly faster second-phase decay rates. Suppression of plasma HIV-1 RNA despite presence of zidovudine resistance mutations implies that the presence of these mutations does not preclude a durable response to treatment with a potent 3-drug regimen.

Adult↗
PubMed2000

The DNA segregation mechanism of Epstein-Barr virus nuclear antigen 1.

Latent Epstein-Barr virus (EBV) genomes are maintained in human cells as low copy number episomes that are thought to be partitioned by attachment to the cellular mitotic chromosomes through the viral EBNA1 protein. We have identified a human protein, EBP2, which interacts with the EBNA1 sequences that govern EBV partitioning. Here we show that, in mitosis, EBP2 localizes to the condensed cellular chromosomes producing a staining pattern that is indistinguishable from that of EBNA1. The localization of EBNA1 proteins with mutations in the EBP2 binding region was also examined. An EBNA1 mutant (delta325-376) disrupted for EBP2 binding and segregation function was nuclear but failed to attach to the cellular chromosomes in mitosis. Our results indicate that amino acids 325-376 mediate the binding of EBNA1 to mitotic chromosomes and strongly suggest that EBNA1 mediates EBV segregation by attaching to EBP2 on the cellular mitotic chromosomes.

Antineoplastic Agents, Phytogenic↗
PubMed2000

Resistance of helicobacter pylori to metronidazole, tetracycline and amoxycillin.

Resistance to metronidazole, tetracycline and amoxycillin, and beta-lactamase production were determined for 153 clinical isolates of Helicobacter pylori. Of these isolates, 77.8% were resistant to metronidazole (MIC > 8 mg/L), 58.8% to tetracycline (MIC > 16 mg/L) and 71.9% to amoxycillin (MIC > 0.5 mg/L); 39.2% were multiresistant. Resistance to metronidazole was more common in isolates from females than in those from males (P < 0.05). None of the isolates produced beta-lactamase, so the mechanism of amoxycillin resistance was not linked to production of beta-lactamase.

Amoxicillin↗
PubMed2000

Injection of sperm cytosolic factor into mouse metaphase II oocytes induces different developmental fates according to the frequency of [Ca(2+)](i) oscillations and oocyte age.

Intracellular calcium ([Ca(2+)](i)) rises are a hallmark of mammalian fertilization and are associated with normal activation of embryonic development. Injection of mammalian sperm cytosolic factor (SCF) into oocytes has been shown to trigger [Ca(2+)](i) rises similar to those observed during fertilization, and to initiate normal embryonic development. However, Ca(2+) release has also been shown to be associated with cell death, but the mechanisms of the detrimental effects of Ca(2+) stimulation on development have not yet been investigated. Thus, studies were undertaken using SCF to test the effects of [Ca(2+)](i) oscillations on oocyte activation in freshly ovulated and aged oocytes. Injections of 1 mg/ml SCF into freshly ovulated mouse metaphase II oocytes, which evoked Ca(2+) responses with low frequency and short duration, induced normal activation and cleavage to the two-cell stage. Conversely, injection of 15 mg/ml SCF, which triggered high-frequency and persistent Ca(2+) responses, induced abnormal activation that was characterized by abnormal chromatin configurations, inhibition of DNA synthesis, and lack of first mitotic spindle assembly. More importantly, fertilization-like Ca(2+) responses induced by injection of 1 mg/ml SCF triggered cell death, rather than activation, in in vitro-aged oocytes. These oocytes exhibited extensive cytoplasmic and DNA fragmentation that was accompanied by activation of protein caspases, all of which are signs of apoptotic cell death. Fewer similarly aged oocytes that were either unstimulated or activated with 7% ethanol underwent fragmentation. Together, these results suggest that [Ca(2+)](i) oscillations are required to activate freshly ovulated oocytes, but if initiated at abnormally high frequency and duration or if induced in aged oocytes, the [Ca(2+)](i) oscillations may trigger premature termination of embryonic development.

Animals↗
PubMed2000

Mycosis fungoides with CD30-positive cells in the epidermis.

Large numbers of CD30-positive tumor cells are not typically observed in mycosis fungoides (MF), but CD30 expression may occur on large cells of MF that have transformed into high-grade large cell lymphoma. Of 202 patch/plaque phase MF cases studied by immunohistochemistry, we encountered 4 patients with patch-phase MF at stage Ia or Ib, whose lesions contained a high proportion (greater than 50%) of CD30-positive tumor cells within the epidermis. The morphologic and immunohistochemical features of these four cases were otherwise similar to those of other patch-phase MF cases, and were different from those of pagetoid reticulosis. More importantly, the clinical behavior of these cases did not differ from that of other cases of early MF without CD30 expression. The mechanism underlying the high levels of CD30 expression by epidermotropic tumor cells is unknown. With increased use of the CD30 immunohistochemical stain in the diagnosis of cutaneous lymphomas, similar cases are likely to be encountered, and perhaps will be evaluated for their clinical behavior.

Adult↗
PubMed2000

Role of autocrine and endocrine gastrin-like peptides in colonic carcinogenesis.

Colon carcinogenesis is a multistep process that involves deletions, mutations, and changes in expression of genes that regulate growth, differentiation, and apoptosis. Hyperproliferation can initiate dysplastic growth, resulting in accumulation of genetic defects and progression of colon cancer. Although genetic instability, because of inheritance of specific genetic defects, plays a dominant role in familial cancers, in the majority of sporadic cancers hyperproliferation is likely to play a permissive role in initiation and progression of the disease. Thus factors that regulate growth, differentiation, and apoptosis are likely to play an important role in colon carcinogenesis. Autocrine gastrins, insulin-like growth factor-II, transforming growth factor-alpha, and endocrine gastrins have been implicated in the tumorigenic potential of colon cancer cells. In this article we focus on the role of endocrine and autocrine gastrins in colon cancer and review recent advances that suggest a role of processing intermediates of gastrin in colon carcinogenesis.

Journal Article↗
PubMed2000

Crystallization and preliminary X-ray crystallographic analysis of the 30 kDa membrane-binding domain of protein 4.1 from human erythrocytes.

The 30 kDa membrane-binding domain of protein 4.1 from human erythrocytes has been expressed in Escherichia coli and crystallized in a form suitable for X-ray crystallographic study. Crystals were grown using a salting-in technique. Crystals have a tetragonal plate shape and belong to the C2 space group, with unit-cell parameters a = 163.9, b = 106.5, c = 93.5 A, beta = 95.5 degrees. The crystals diffract to 2.8 A resolution.

Crystallization↗
PubMed2000

A comparison study of models and fitting procedures for biphasic viral dynamics in HIV-1 infected patients treated with antiviral therapies.

The study of HIV dynamics is one of the most important developments in recent AIDS research. It has led to a new understanding of the pathogenesis of HIV infection. But, although important findings in HIV dynamics have been published in prestigious scientific journals in the last 5 years, the model-fitting procedures used in these publications have not been studied in any detail. In this paper, we evaluate the performance of four model-fitting procedures proposed and used in biphasic HIV dynamic data analysis via extensive Monte Carlo simulations. We propose some guidelines for practitioners to select an appropriate method for their own data analysis. Real data examples from an AIDS clinical trial are provided as illustrations.

Anti-HIV Agents↗
PubMed2000

Regulation of cathelicidin gene expression: induction by lipopolysaccharide, interleukin-6, retinoic acid, and Salmonella enterica serovar typhimurium infection.

Cathelicidins are a family of antimicrobial peptides prominent in the host defense mechanisms of several mammalian species. In addition to their antimicrobial activities, these peptides have been implicated in wound healing, angiogenesis, and other innate immune mechanisms. To investigate the regulatory mechanisms of cathelicidin gene expression, we conducted in vitro experiments evaluating the bone marrow cell expression of two porcine cathelicidins, PR-39 and protegrin, and cloned and evaluated the promoter sequence of PR-39. In addition, we evaluated in vivo kinetics of cathelicidin gene expression in pigs during an infection with Salmonella enterica serovar Typhimurium. Lipopolysaccharide (LPS) increased PR-39 and protegrin mRNA expression, which was ameliorated by polymyxin B. Concentrations of PR-39 in supernatants from bone marrow cell cultures were increased 10-fold after LPS stimulation. Similarly, interleukin-6 (IL-6) and all-trans retinoic acid (RA) markedly induced cathelicidin gene expression. To verify the transcriptional activation of the PR-39 gene by these agents, we made a PR-39 promoter-luciferase construct containing the full-length PR-39 promoter driving luciferase gene expression and transiently transfected PK-15 epithelial cells. RA and IL-6 increased luciferase activity in PK-15 cells transfected with the PR-39 promoter-luciferase reporter. Similarly, Salmonella-challenged pigs showed increased expression of PR-39 and protegrin mRNA in bone marrow cells at 6 and 24 h postchallenge. Taken together, these findings show that bacterial products (LPS), IL-6, RA, and Salmonella infection enhance the expression of the cathelicidins, PR-39 and protegrin, in bone marrow progenitor cells, and we suggest that extrinsic modulation of this innate host defense mechanism may be possible.

Amino Acid Sequence↗
PubMed2000

Cloning of porcine NRAMP1 and its induction by lipopolysaccharide, tumor necrosis factor alpha, and interleukin-1beta: role of CD14 and mitogen-activated protein kinases.

The gene for natural resistance-associated macrophage protein 1 (NRAMP1) plays a dominant role in controlling the resistance of inbred mice to infection with intracellular bacteria, such as Mycobacteria, Salmonella, and Leishmania. NRAMP1 is a membrane protein with a consensus transport motif present in one of the intracellular loops. Although its functions remain unclear, recent clues suggest that NRAMP1 protein plays a potential role in ion transport, which presumably accounts for the ability of this single protein to regulate the intraphagosomal replication of several species of antigenically unrelated intracellular pathogens. Expression of NRAMP1 in mice can be induced by lipopolysaccharide (LPS) or bacterial infection; however, little is known about the mechanisms of induction. Here, we report the cloning of the full-length cDNA for porcine NRAMP1, which had over 85% identity in amino acid sequence to its congeners from humans, mice, cattle, and sheep. As for its mammalian congeners, expression of porcine NRAMP1 mRNA was cell and tissue specific and was highest in macrophages. Investigation of the molecular mechanisms by which NRAMP1 is induced showed that LPS-induced expression in macrophages, neutrophils, and peripheral blood mononuclear cells was time and dose dependent and was mediated primarily through CD14. Induction of NRAMP1 required de novo protein synthesis, and mitogen-activated protein kinases (MAPK) were essential. Blockage of either p38 or p42/44 MAPK pathways suppressed the expression of NRAMP1 to basal levels. These findings suggest that bacterial infection and proinflammatory mediators induce NRAMP1 expression via activation of MAPK pathways.

Amino Acid Sequence↗
PubMed2000

Identification and characterization of two chemotactic transducers for inorganic phosphate in Pseudomonas aeruginosa.

Two chemotactic transducers for inorganic phosphate (P(i)), designated CtpH and CtpL, have been identified in Pseudomonas aeruginosa. The corresponding genes (ctpH and ctpL) were inactivated by inserting kanamycin and tetracycline resistance gene cassettes into the wild-type genes in the P. aeruginosa PAO1 genome. Computer-assisted capillary assays showed that the ctpH single mutant failed to exhibit P(i) taxis when the concentration of P(i) in the capillary was higher than 5 mM. Conversely, the ctpL single mutant could not respond to P(i) at the concentration of 0.01 mM. The ctpH ctpL double mutant was defective in P(i) taxis at any concentration ranging from 0.01 to 10 mM. To investigate regulation of P(i) taxis, the ctpH and ctpL genes were also disrupted individually in the P. aeruginosa phoU and phoB single mutants. The ctpH phoU and ctpH phoB double mutants were defective in P(i) taxis, regardless of whether the cells were starved for P(i). The ctpL phoU double mutant was constitutive for P(i) taxis, whereas the ctpL phoB double mutant was induced by P(i) limitation for P(i) taxis. The region upstream of ctpL, but not ctpH, contained a putative pho box sequence. Expression of ctpL::lacZ was induced by P(i) limitation in PAO1, while it was constitutive in the phoU mutant. In contrast, the phoB mutant showed only background levels of ctpL::lacZ expression. These results showed that ctpL is involved in the pho regulon genes in P. aeruginosa. The ctpH phoU mutant, which failed to exhibit P(i) taxis, was constitutive for ctpL::lacZ expression, suggesting that the P(i) detection by CtpL requires PhoU. Like PAO1, the phoB and phoU single mutants were constitutive for expression of ctpH::lacZ. Thus, the evidence that the ctpL phoU mutant, but not the ctpL phoB mutant and PAO1, was constitutive for P(i) taxis raised the possibility that PhoU exerts a negative control on P(i) detection by CtpH at the posttranscriptional level.

Bacterial Proteins↗
PubMed2000

NH(4)Cl inhibition of acid secretion: possible involvement of an apical K(+) channel in bullfrog oxyntic cells.

This study was undertaken to determine the mechanism by which ammonium chloride (NH(4)Cl) inhibits stimulated acid secretion in the bullfrog gastric mucosa. To this end, four possible pathways of inhibition were studied: 1) blockade of basolateral K(+) channel, 2) blockade of ion transport activity, 3) neutralization of secreted H(+) in the luminal solution, or 4) ATP depletion. Addition of nutrient 10 mM NH(4)Cl (calculated NH(3) concentration = 92.5 microM and NH(4)(+) concentration = 9.91 mM) inhibited acid secretion within 30 min. Inhibition of acid secretion did not occur by blockade of basolateral K(+) channel activity or ion transport activity or by neutralization of the luminal solution. Although ATP depletion occurred in the presence of NH(4)Cl, the magnitude of ATP depletion in 30 min was not sufficient to inhibit stimulated acid secretion. By comparing the effect of NH(4)Cl on the resistance of inhibited or stimulated tissues, we demonstrate that NH(4)Cl acts specifically on stimulated tissues. We propose that NH(4)Cl blocks activity of an apical K(+) channel present in stimulated oxyntic cells. Our data suggest that the activity of this channel is important for the regulation of acid secretion in bullfrog oxyntic cells.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗