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Biomedical subjects

H Wu

Publications and source records attributed to H Wu.

At least 37 records · Page 2Linked to original sources
PubMed2006

Inactivation of DNA adenine methyltransferase alters virulence factors in Actinobacillus actinomycetemcomitans.

DNA adenine methyltransferase (DAM) plays critical roles in diverse biological pathways in gram-negative bacteria, and specifically in regulating the expression of virulence genes in several organisms. Actinobacillus actinomycetemcomitans plays an important role in the pathogenesis of juvenile and adult periodontal disease, yet little is known about its mechanisms of gene regulation. DAM is shown here to directly or indirectly affect well-known A. actinomycetemcomitans virulence factors. A mutant A. actinomycetemcomitans strain lacking the dam gene was created by homologous recombination and shows normal growth phenotypes when grown exponentially. This mutant strain has four sixfold increased levels of extracellular leukotoxin, altered cellular levels of leukotoxin, and significant changes in bacterial invasion of KB oral epithelial cells. These results provide a basis for further characterization of regulatory mechanisms that control A. actinomycetemcomitans virulence.

Aggregatibacter actinomycetemcomitans↗
PubMed2006

Immunohistochemical expression of Mdm2 and p53 in canine cutaneous mast cell tumours.

The objective of this study was to evaluate by immunohistochemical means nuclear reactivity for Mdm2 and p53 proteins in 71 canine cutaneous mast cell tumours. Detectable reactivity for Mdm2 was observed in 17 of 23 grade I tumours, 19 of 27 grade II tumours, and 14 of 21 grade III tumours, the grading method used was that by Patnaik et al. [Vet. Pathol., vol. 21, 1984, p. 469]. Increased reactivity for Mdm2 was detected in grade III tumours compared with grade I tumours. In contrast to Mdm2, detectable reactivity for p53 was observed in 17 tumours. Of 39 cases with moderate or marked Mdm2, 34 showed mild or no detectable p53, although only five showed moderate or marked p53. The results suggest that Mdm2 overexpression plays a crucial role in canine mast cell tumorigenesis and is consistent with the histologic grade, and its expression may be induced without p53 overexpression.

Animals↗
PubMed2006

Interleukin-18 affects local cytokine expression but does not impact on the development of kidney allograft rejection.

Interleukin-18 is predominantly a macrophage-derived cytokine with a key role in inflammation and cell-mediated immunity. Having previously demonstrated IL-18 upregulation in a rat model of kidney rejection, here we examined IL-18 in a fully MHC-mismatched murine model of acute kidney rejection using IL-18-deficient recipients (IL-18-/-) and animals administered neutralizing IL-18 binding protein (IL-18BP). Gene expression of IL-18 and its receptor were significantly upregulated in allografts compared to isografts, as was the cellular infiltrate (T cells and macrophages) (p < 0.001). Allografts developed kidney dysfunction (p < 0.05) and tubulitis (p < 0.01) not observed in controls. There was a significant reduction in gene expression of IL-18 downstream pro-inflammatory molecules (iNOS, TNFalpha and IFNgamma) in IL-18-/- recipients (p < 0.01), and IL-18BP-treated animals. The CD4+ infiltrate and IL-4 mRNA expression was greater in the IL-18-/- recipients than wild-type (WT) allografts and IL-18BP-treated animals (p < 0.05), suggesting a Th2-bias which was supported by IFNgamma and IL-4 ELISPOT data and an increased eosinophil accumulation (p < 0.001). Neither IL-18 deficiency nor neutralization prevented renal dysfunction or tubulitis. This study demonstrates increased production of IL-18 in murine kidney allograft rejection and provides evidence that IL-18-induced pathways of inflammation are active. However, neither IL-18 deficiency nor neutralization was protective against the development of allograft rejection.

Animals↗
PubMed2006

Ectopic cartilage formation induced by mesenchymal stem cells on porous gelatin-chondroitin-hyaluronate scaffold containing microspheres loaded with TGF-beta1.

The study aimed to produce a novel porous gelatin-chondroitin-hyaluronate scaffold in combination with a controlled release of TGF- beta1 and to evaluate its potentials in ectopic cartilage formation. The gelatin-chondroitin-hyaluronate scaffold was developed to mimic the natural extra cellular matrix of cartilage. Gelatin microspheres loaded with TGF- beta1 (MS-TGF beta1) showed a fast cytokine release at initial phase (37.4%) and the ultimate accumulated release was 83.1% by day 18. Then MS-TGF beta1 were incorporated into scaffold. The MSCs seeded on scaffold with or without MS-TGF beta1 were incubated in vitro or implanted subcutaneously in nude mice. In vitro study showed that, compared to the scaffold, the scaffold/MS-TGF beta1 significantly augmented the proliferation of MSCs and GAG synthesis. Three weeks postoperatively histology observation showed that in MSCs/scaffold/MS-TGF beta1 implantation group, cells of newly formed ectopic cartilage were located within typical lacunae and demonstrated morphological characteristics of chondrocytes. Six weeks later the ectopic cartilage grew more and islands of cartilage were observed. The matrix was extensively metachromatic by safranin-O/Fast green staining. Immunohistochemical staining also indicated ectopic cartilage was intensely stained for type II collagen. Instead, in the MSCs/scaffold implantation group, no cartilage-like tissue formed and matrix showed negative or weak positive staining. The percentage of positive staining area was significantly larger in MSCs/scaffold/MS-TGF beta1 group (p<0.05) at each time point. The results indicated that the novel gelatin-chondroitin-hyaluronate scaffold with MS-TGF beta1 could induce the chondral differentiation of MSCs to form cartilage and might serve as a new way to repair cartilage defects.

Animals↗
PubMed2006

Induction of micronuclei in human fibroblasts across the Bragg curve of energetic heavy ions.

The space environment consists of a varying field of radiation particles including high-energy ions, with spacecraft shielding material providing the major protection to astronauts from harmful exposure. Unlike low-LEpsilonTau gamma or X rays, the presence of shielding does not always reduce the radiation risks for energetic charged-particle exposure. The dose delivered by the charged particle increases sharply as the particle approaches the end of its range, a position known as the Bragg peak. However, the Bragg curve does not necessarily represent the biological damage along the particle path since biological effects are influenced by the track structures of both primary and secondary particles. Therefore, the "biological Bragg curve" is dependent on the energy and the type of the primary particle and may vary for different biological end points. Here we report measurements of the biological response across the Bragg curve in human fibroblasts exposed to energetic silicon and iron ions in vitro at two different energies, 300 MeV/nucleon and 1 GeV/nucleon. A quantitative biological response curve generated for micronuclei per binucleated cell across the Bragg curve did not reveal an increased yield of micronuclei at the location of the Bragg peak. However, the ratio of mono- to binucleated cells, which indicates inhibition of cell progression, increased at the Bragg peak location. These results confirm the hypothesis that severely damaged cells at the Bragg peak are more likely to go through reproductive death and not be evaluated for micronuclei.

Cell Line↗
PubMed2005

Development of a physiologically based pharmacokinetic model for propylene glycol monomethyl ether and its acetate in rats and humans.

Propylene glycol monomethyl ether (PM), along with its acetate, is the most widely used of the propylene glycol ether family of solvents. The most common toxic effects of PM observed in animal studies include sedation, very slight alpha(2u)-globulin mediated nephropathy (male rats only) and hepatomegally at high exposures (typically > 1000 ppm). Sedation in animal studies usually resolves within a few exposures to 3000 ppm (the highest concentration used in subchronic and chronic inhalation studies) due to the induction of metabolizing enzymes. Data from a variety of pharmacokinetic and mechanistic studies have been incorporated into a PBPK model for PM and its acetate in rats and mice. Published controlled exposure and workplace biomonitoring studies have also been included for comparisons of the internal dosimetry of PM and its acetate between laboratory animals and humans. PM acetate is rapidly hydrolyzed to PM, which is further metabolized to either glucuronide or sulfate conjugates (minor pathways) or propylene glycol (major pathway). In vitro half-lives for PM acetate range from 14 to 36 min depending upon the tissue and species. In vivo half-lives are considerably faster, reflecting the total contributions of esterases in the blood and tissues of the body, and are on the order of just a few minutes. Thus, very little PM acetate is found in vivo and, other than potential portal of entry irritation, the toxicity of PM acetate is related to PM. Regardless of the source for PM (either PM or its acetate), rats were predicted to have a higher Cmax and AUC for PM in blood than humans, especially at concentrations greater than the current ACGIH TLV of 100 ppm. This would indicate that the major systemic effects of PM would be expected to be less severe in humans than rats at comparable inhalation exposures.

Acetates↗
PubMed2005

Epidemiological study of hepatitis B virus infection in Manitoba, Canada, 1992-2003.

In comparison with other Canadian provinces and most Western countries, the province of Manitoba maintains a different vaccination policy for hepatitis B. This policy provides selective antenatal screening for hepatitis B in women and an inoculation program for hepatitis B vaccination for fourth-grade pupils. There has been increasing concern for this policy with regard to its influence on secular trends of acute hepatitis B incidence in Manitoba. This created a need to summarise the epidemiological characteristics of hepatitis B virus (HBV) infection in Manitoba and to allocate finances and human resources for future prevention programs. The Cadham Provincial Laboratory in Winnipeg, a Canadian Public Health Laboratory, is responsible for testing all specimens for diagnosis of various common infectious diseases in Manitoba. During the period from 1 January 1992 to 31 December 2003, a total of 285,946 clinical specimens were submitted to this laboratory, which confirmed 310 cases of acute HBV and 7,556 cases of chronic HBV infection. A total of 18,168 individuals were identified as having vaccine-induced immune status. The incidence rate of acute HBV infection has significantly decreased from 6.52/100,000 person-years in 1996 to 0.86/100,000 person-years in 2003. Annual prevalence rates of chronic HBV infection in Manitoba increased slightly from 42.96 cases/100,000 population in 1992 to 71.47 cases/100,000 population in 2003. Incidence rates were generally higher in men than in women at all age groups, with values of 2.65 and 1.65 per 100,000 population, respectively (chi-square=15.768, p value <0.001). The highest incidence rate for both males and females was observed in the age group 30-34 years. The North Eastman and Winnipeg Regional Health Authorities showed significantly higher incidence rates of acute hepatitis B compared with the other nine Regional Health Authorities. Selective hepatitis B vaccination programs for children in Manitoba had achieved the greatest success in the prevention of vertical and horizontal transmission. There is an urgent need to develop cost-effective harm-reduction strategies for hepatitis B prevention among adults (aged 30-34) and groups at risk in Manitoba.

Adolescent↗
PubMed2005

High LET-induced H2AX phosphorylation around the Bragg curve.

We investigated the spatial distribution of the induction of the phosphorylated form of the histone protein H2AX (gamma-H2AX), known to be activated by DSBs. Following irradiation of human fibroblast cells with 600 MeV/nucleon silicon and 600 MeV/nucleon iron ions we observed the formation of gamma-H2AX aggregates in the shape of streaks stretching over several micrometers in an x/y plane. Polyethylene shielding was used to achieve a Bragg curve distribution with beam geometry parallel to the monolayer of cells. We present data that highlights the formation of immunofluorescent gamma-H2AX tracks showing the ion trajectories across the Bragg peak of irradiated human fibroblast cells. Qualitative analyses of these distributions indicated potentially increased clustering of DNA damage before the Bragg peak, enhanced gamma-H2AX distribution at the peak, and provided visual evidence of high-linear energy transfer particle traversal of cells beyond the Bragg peak in agreement with one-dimensional transport approximations. Spatial assessment of gamma-H2AX fluorescence may provide direct insights into DNA damage across the Bragg curve for high charge and energy ions including the biological consequences of shielding and possible contributors to bystander effects.

Bystander Effect↗
PubMed2005

Comparison of genotoxic damage in monolayer cell cultures and three-dimensional tissue-like cell assemblies.

Assessing the biological risks associated with exposure to the high-energy charged particles encountered in space is essential for the success of long-term space exploration. Although prokaryotic and eukaryotic cell models developed in our laboratory and others have advanced our understanding of many aspects of genotoxicity, in vitro models are needed to assess the risk to humans from space radiation insults. Such models must be representative of the cellular interactions present in tissues and capable of quantifying genotoxic damage. Toward this overall goal, the objectives of this study were to examine the effect of the localized microenvironment of cells, cultured as either 2-dimensional (2D) monolayers or 3-dimensional (3D) aggregates, on the rate and type of genotoxic damage resulting from exposure to Fe-charged particles, a significant portion of space radiation. We used rodent transgenic cell lines containing 50-70 copies of a LacI transgene to provide the enhanced sensitivity required to quantify mutational frequency and type in the 1100-bp LacI target as well as assessment of DNA damage to the entire 45-kbp construct. Cultured cells were exposed to high energy Fe charged particles at Brookhaven National Laboratory's Alternating Gradient Synchrotron facility for a total dose ranging from 0.1 to 2 Gy and allowed to recover for 0-7 days, after which mutational type and frequency were evaluated. The mutational frequency was found to be higher in 3D samples than in 2D samples at all radiation doses. Mutational frequency also was higher at 7 days after irradiation than immediately after exposure. DNA sequencing of the mutant targets revealed that deletional mutations contributed an increasingly high percentage (up to 27%) of all mutations in cells as the dose was increased from 0.5 to 2 Gy. Several mutants also showed large and complex deletions in multiple locations within the LacI target. However, no differences in mutational type were found between the 2D and the 3D samples. These 3D tissue-like model systems can reduce the uncertainty involved in extrapolating risk between in vitro cellular and in vivo models.

Animals↗
PubMed2005

Pleiotrophin expression correlates with melanocytic tumor progression and metastatic potential.

BACKGROUND: Gene expression profiling of melanoma and nevic tissue has demonstrated that pleiotrophin (PTN) is significantly overexpressed in human melanomas. METHODS: To further evaluate PTN expression in melanocytic lesions, protein immunohistochemistry was performed on the spectrum of melanocytic lesions. RESULTS: Melanocytic nevi were consistently negative (n=58). In contrast, the great majority of metastatic melanomas were positive (33/34, 97%). The analysis of 34 primary melanomas demonstrated PTN positivity in 20 lesions while 14 lesions were negative. Within the primary melanomas, PTN immunoreactivity was associated with metastasis (p=0.0004) and decreased melanoma-related survival (p=0.0444). Univariate analysis of PTN immunoreactivity predicted an increased risk for metastasis (relative risk 9.1, p=0.003). CONCLUSIONS: The results of this study confirm previous gene profiling data showing differential PTN expression between melanocytic nevi and melanomas. In addition, lesional PTN expression is associated with metastatic potential and may be a prognostic factor for melanomas.

Adult↗
PubMed2005

Acquired but reversible loss of erythrocyte complement receptor 1 (CR1, CD35) and its longitudinal alteration in patients with severe acute respiratory syndrome.

This longitudinal study investigates the change of erythrocyte complement receptor (E-CR1) expression in patients with severe acute respiratory syndrome (SARS). Circulating E-CR1 expression was semiquantified by flow cytometric analyses in 54 SARS patients and in 212 healthy individuals as a control. Since E-CR1 expression is influenced by the genetic polymorphisms in the CR1 gene, a major genetic polymorphism located within intron 27 of the CR1 gene was simultaneously analysed by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). The results showed that the expression level of E-CR1 (referred to as net fluorescence intensity values, NFI) was statistically correlated with the relevant genetic genotypes among the Chinese population including the healthy individuals (NFI: 5.14 +/- 0.82, 3.57 +/- 0.66 and 2.67 +/- 0.32 for HH, HL and LL genotypes, respectively) and SARS patients (NFI: 3.52 +/- 0.91 and 2.63 +/- 0.70 for HH and HL genotypes, respectively). Interestingly, the expression density of E-CR1 was found to fall significantly during the initiation and progressive phases (weeks 1 and 2 after the disease onset) and gradually returned close to normal through their whole convalescent phase (beginning from weeks 2 or 3 to weeks 7 or 8) in SARS patients irrespective CR1 genotype. In conclusion, our findings, at least, suggest that E-CR1 is likely involved in immune pathogenesis of SARS disease.

Adolescent↗
PubMed2005

Identification of a new HLA-A*0201-restricted CD8+ T cell epitope from hepatocellular carcinoma-associated antigen HCA587.

For the development of peptide-based cancer immunotherapies, we aimed to identify specific HLA-A*0201-restricted CTL epitopes in hepatocellular carcinoma (HCC) associated antigen HCA587, which has been identified as a member of the cancer/testis (CT) antigens highly expressed in HCC. We first combined the use of an HLA-A*0201/peptide binding algorithm and T2 binding assays with the induction of specific CD8(+) T cell lines from normal donors by in vitro priming with high-affinity peptides, then IFN-gamma release and cytotoxicity assays were employed to identify the specific HLA-A*0201 CD8(+) T cell epitope using peptide-loaded T2 cells or the HCA587 protein(+) HCC cell line HepG2. In the six candidate synthesized peptides, two peptides showed higher binding ability in T2 binding assays. No. 2 peptide, encompassing amino acid residues FLAKLNNTV (HCA587(317-325)), was able to activate a HCA587-specific CD8(+) T-cell response in human lymphocyte cultures from two normal donors and two HCC patients, and these HCA587-specific CD8(+) T cells recognized peptide-pulsed T2 cells as well as the HCA587 protein(+) HCC cell line HepG2 in IFN-gamma release and cytotoxicity assays. The results indicate that no. 2 peptide is a new HLA-A*0201-restricted CTL epitope capable of inducing HCA587-specific CTLs. Our data suggest that identification of this new HCA587/HLA-A*0201 peptide FLAKLNNTV may facilitate the design of peptide-based immunotherapies for the treatment of HCA587-bearing HCC patients.

Antigens, Neoplasm↗
PubMed2005

Demented flies? Using Drosophila to model human neurodegenerative diseases.

The success of biomedical research in the past few decades has led to dramatic improvements in human health and, as a result, increased life expectancy. An unexpected consequence, however, has been an increase in the number of age-related diseases and, in particular, neurodegenerative diseases. Despite their prevalence, a therapeutic void exists in part due to an incomplete understanding of the biochemical pathogenesis of these diseases. A powerful method that can be used to understand the basic mechanisms underlying neurodegenerative diseases is to generate animal models based on manipulating the expression of single genes that are disease causative. This approach has been facilitated by the fact that many neurodegenerative diseases are inherited as autosomal dominant traits such that expression of the mutant gene in a model organism might be expected to recapitulate the disease. During the past few years, the fruit fly, Drosophila melanogaster, has emerged as a powerful tool to model human neurodegenerative diseases. Here, we describe the various approaches utilized to create fly models of human neurodegenerative disease, and how they can aid in our understanding of disease pathogenesis and facilitate drug discovery and testing.

Animals↗
PubMed2005

Yeast-derived sigma C protein-induced immunity against avian reovirus.

Avian reoviruses (ARVs) can result in disease and economic losses in the poultry industry. Vaccines against ARV may not provide full protection and can cause adverse reactions. The coding sequence of the sigma C protein from strain S1133 of avian reovirus was expressed in Schizasaccharomyces pombe. Sigma C protein expression was demonstrated by Western blotting, and the protein was evaluated for its ability to protect specific-pathogen-free (SPF) chickens against challenge with the virulent S1133 strain. Serologic and challenge-infection data showed the efficacy of the recombinant vaccine administered orally each week for 3 consecutive wk. Sigma C protein induced antibody, as determined by enzyme-linked immunosorbent assay. Percentage (%) protection induced by the low dose (125 microg purified yeast-expressed sigma C protein/chicken) or the high dose (250 microg purified yeast-expressed sigma C protein/chicken) was 64 and 91, respectively. The commercial vaccine administered once or twice provided 82% protection. Results supported the feasibility of a plant-derived vaccine for use in poultry immunization schemes.

Animals↗
PubMed2005

Immunofluorescence detection of clustered gamma-H2AX foci induced by HZE-particle radiation.

We studied the spatial and temporal distributions of foci of the phosphorylated form of the histone protein H2AX (gamma-H2AX), which is known to be activated by double-strand breaks after irradiation of human fibroblast cells with high-energy silicon (54 keV/microm) and iron (176 keV/microm) ions. Here we present data obtained with the ion path parallel to a monolayer of human fibroblast cells that leads to gamma-H2AX aggregates in the shape of streaks stretching over several micrometers in an x/y plane, thus enabling the analysis of the fluorescence distributions along the ion trajectories. Qualitative analyses of these distributions provide insights into DNA damage processing kinetics for high charge and energy (HZE) ions, including evidence of increased clustering of DNA damage and slower processing with increasing LET.

Cells, Cultured↗
PubMed2005

Concentration and detection of SARS coronavirus in sewage from Xiao Tang Shan Hospital and the 309th Hospital of the Chinese People's Liberation Army.

A worldwide outbreak of severe acute respiratory syndrome (SARS) had been reported. Over 8439 SARS cases and 812 SARS-related deaths were reported to the World Health Organization from 32 countries around the world up to 5 July 2003. The mechanism of transmission of SARS-CoV has been limited only to close contacts with patients. Attention was focused on possible transmission by the sewage system because laboratory studies showed that patients excreted coronavirus RNA in their stools in Amoy Gardens in Hong Kong. To explore whether the stool of SARS patients or the sewage containing the stool of patients would transmit SARS-CoV or not, we used a style of electropositive filter media particle to concentrate the SARS-CoV from the sewage of two hospitals receiving SARS patients in Beijing, as well as cell culture, semi-nested RT-PCR and sequencing of genes to detect and identify the viruses from sewage. There was no live SARS-CoV detected in the sewage in these assays. The nucleic acid of SARS-CoV was found in the sewage before disinfection from both hospitals by PCR. After disinfection, SARS-CoV RNA could be detected from some samples from the 309th Hospital of the Chinese People's Liberation Army, but not from Xiao Tang Shan Hospital after disinfection. In this study, we found that the virus can survive for 14 days in sewage at 4 degrees C, 2 days at 20 degrees C, and its RNA can be detected for 8 days though the virus had been inactivated. In conclusion, this study demonstrates that the RNA of SARS-CoV could be detected from the concentrates of sewage of both hospitals receiving SARS patients before disinfection and occasionally after disinfection though there was no live SARS-CoV; thus much attention should be paid to the treatment of stools of patients and the sewage of hospitals receiving SARS patients.

Bacteriophages↗
PubMed2004

Synthetic furanones inhibit quorum-sensing and enhance bacterial clearance in Pseudomonas aeruginosa lung infection in mice.

INTRODUCTION: Antibiotics are used to treat bacterial infections by killing the bacteria or inhibiting their growth, but resistance to antibiotics can develop readily. The discovery that bacterial quorum-sensing regulates bacterial virulence as well as the formation of biofilms opens up new ways to control certain bacterial infections. Furanone compounds capable of inhibiting bacterial quorum-sensing systems have been isolated from the marine macro alga Delisea pulchra. OBJECTIVES: Two synthetic furanones were tested for their ability to attenuate bacterial virulence in the mouse models of chronic lung infection by targeting bacterial quorum-sensing without directly killing bacteria or inhibiting their growth. METHODS: Study I. Mice with Escherichia coli MT102 [luxR-PluxI-gfp(ASV)] lung infection were injected intravenously with N-acyl homoserine lactones with or without furanones to test the interference of furanones with quorum-sensing. Study II. Mice with lung infection by Pseudomonas aeruginosa PAO1 [dsred, lasR-PlasB-gfp(ASV)] were injected intravenously with furanones to evaluate their inhibiting effects on quorum-sensing. Study III. Mice with P. aeruginosa PAO1 lung infection were treated with different doses of furanones to evaluate the therapeutic effects of furanones on the lung infection. RESULTS: Furanones successfully interfered with N-acyl homoserine lactone and suppressed bacterial quorum-sensing in lungs, which resulted in decreases in expression of green fluorescent protein. Furanones accelerated lung bacterial clearance, and reduced the severity of lung pathology. In a lethal P. aeruginosa lung infection, treatment with furanone significantly prolonged the survival time of the mice. CONCLUSION: Synthetic furanone compounds inhibited bacterial quorum-sensing in P. aeruginosa and exhibited favourable therapeutic effects on P. aeruginosa lung infection.

Alginates↗