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Biomedical subjects

J Xu

Publications and source records attributed to J Xu.

At least 145 records · Page 8Linked to original sources
PubMed2002

Chronic neuropathic pain is accompanied by global changes in gene expression and shares pathobiology with neurodegenerative diseases.

Neuropathic pain is induced by injury or disease of the nervous system. Studies aimed at understanding the molecular pathophysiology of neuropathic pain have so far focused on a few known molecules and signaling pathways in neurons. However, the pathophysiology of neuropathic pain appears to be very complex and remains poorly understood. A global understanding of the molecular mechanisms involved in neuropathic pain is needed for a better understanding of the pathophysiology and treatment of neuropathic pain. Towards this end, we examined global gene expression changes as well as the pathobiology at the cellular level in a spinal nerve ligation neuropathic pain model using DNA microarray, quantitative real-time PCR and immunohistochemistry. We found that the behavioral hypersensitivity that is manifested in the persistent pain state is accompanied by previously undescribed changes in gene expression. In the DRG, we found regulation of: (1) immediate early genes; (2) genes such as ion channels and signaling molecules that contribute to the excitability of neurons; and (3) genes that are indicative of secondary events such as neuroinflammation. In addition, we studied gene regulation in both injured and uninjured DRG by quantitative PCR, and observed differential gene regulation in these two populations of DRGs. Furthermore, we demonstrated unexpected co-regulation of many genes, especially the activation of neuroinflammation markers in both the PNS and CNS. The results of our study provide a new picture of the molecular mechanisms that underlie the complexity of neuropathic pain and suggest that chronic pain shares common pathobiology with progressive neurodegenerative disease.

Animals↗
PubMed2002

Edible dates (Phoenix dactylifera), a potential source of Cladosporium cladosporioides and Sporobolomyces roseus: implications for public health.

Edible dates (Phoenix dactylifera) were examined for the presence of endogenous yeasts and filimentous fungi. Mean counts of fungi were 530 colony forming units (cfu) per gram of fruit, representing a mixture of two phenotypic colony types. Subsequent DNA extraction and PCR amplification of these two morphotypes yielded an amplicon of approximately 350 bp with the 5.8S-28S rRNA ITS region. Sequence analysis identified these to be Cladosporium cladosporioides (230 cfu/g) and Sporobolomyces roseus. Both organisms have been previously reported in opportunistic infections involving skin or in immunocompromised patients. This is the first report of edible dates being a source of these organisms and we emphasize the importance of the common practice of washing hands following the consumption of these fruits by hand.

Arecaceae↗
PubMed2002

Matrix metalloproteinase-2 from bronchial epithelial cells induces the proliferation of subepithelial fibroblasts.

BACKGROUND: In bronchial asthma, subepithelial fibrosis in the conducting airways is associated with increased numbers of subepithelial fibroblasts. OBJECTIVE: This study examined the hypothesis that MMP-2 from airway epithelial cells induces the proliferation of subepithelial fibroblasts. METHODS: Using primary bronchial epithelial cells MMP-2, MT1-MMP and TIMP-2 mRNA expression were assessed by Northern blotting and RT-PCR. Primary bronchial epithelial cells transfected with constructs encoding pro-MMP-2 and MT1-MMP (MMP-14). RESULTS: Transfected cells showed enhanced expression of the appropriate mRNA species by RT-PCR and enhanced MMP-2 or MT1-MMP activity by zymography. Active MMP-2 levels in epithelial supernatants were increased most by cotransfection with pro-MMP-2 and MT1-MMP encoding constructs. By measuring tritiated thymidine incorporation, supernatants from transfected cells were found to enhance DNA synthesis of primary airway fibroblast cultures compared with controls. There was a strong correlation (r = 0.9, P < 0.01) between MMP-2 levels in epithelial cell conditioned media and fibroblast proliferation as indicated by DNA synthesis. The MMP inhibitor 1,10-phenanthroline attenuated the increased proliferation, while the addition of exogenous purified MMP-2 alone also increased fibroblast proliferation. CONCLUSIONS: Our results support a role for MMP-2 in mediating cross-talk between epithelial cells and myofibroblasts.

Bronchi↗
PubMed2002

Genotypic subgrouping of clinical isolates of Candida albicans and Candida dubliniensis by 25S intron analysis.

AIMS: To determine the frequency, distribution and association of genotypes of Candida albicans and C. dubliniensis in invasive and noninvasive clinical isolates. METHODS: Twenty-one invasive and 18 noninvasive isolates were examined by PCR amplification of a transposable intron region in the 25S rRNA gene. Isolates were genotyped following analysis of the size of resulting DNA amplicons. The isolates could be subdivided into four genotypes (A-D). RESULTS: There was no significant difference between the frequency and genotype distribution of the invasive and noninvasive Candida isolates. IMPACT OF THE STUDY: Therapeutic prophylaxis against candidal infections remains an area of controversy. Any diagnostic markers that reflect the potential of isolates to become invasive should be fully explored, so that more focused antifungal intervention should be targeted at these patients with these potential invasive markers. This study demonstrated that analysis of the transposable intron region in the 25S rRNA gene may be useful in helping to differentiate C. albicans from C. dubliniensis isolates, without the need for sequence analysis, which may not be readily available at primary diagnostic laboratories. However, employment of this genotypic assay is not a suitable locus to determine invasiveness and other more reliable markers of invasiveness should be sought.

Candida↗
PubMed2002

Mycobacterium triplex pulmonary infection in an immunocompetent patient.

We present the case of a 47-year-old immunocompetent patient with clinical evidence of pulmonary mycobacterial disease which was found to be due to Mycobacterium triplex. This novel organism is an uncommon, emerging, pathogen for which few reports of clinical infection exist in the medical literature.

Bronchoalveolar Lavage Fluid↗
PubMed2002

Trends in the epidemiology of Candida bloodstream infections in Northern Ireland between January 1984 and December 2000.

OBJECTIVE: To describe the epidemiology of Candida bloodstream infections (BSI) in Northern Ireland. METHODS: Retrospective collation of data relating to all clinically significant BSI in a university teaching hospital, which had been recorded prospectively, between 1984 and 2000. RESULTS: One hundred and forty five episodes of candidaemia occurred in 144 patients (of mean age 56.6 years). The contribution of Candida spp. towards all significant BSI increased from 2.0% to 2.5%. C. albicans was the most frequently isolated species, however, its incidence fell from 70% to 53% during the study period. The greatest increase in incidence was seen with C. glabrata which was the most common non-albicans species. Twenty-nine per cent of isolates occurred in patients from an intensive care unit and, surprisingly, a further 25.5% occurred in patients from a surgical service. CONCLUSION: There appears to be several subtle differences in the epidemiology of candidal BSI between Northern Ireland and other countries.

Adolescent↗
PubMed2002

Observation of radiation-specific damage in human cells exposed to depleted uranium: dicentric frequency and neoplastic transformation as endpoints.

Depleted uranium (DU) is a dense heavy metal used primarily in military applications. Published data from our laboratory have demonstrated that DU exposure in vitro to immortalised human osteoblast cells (HOS) is both neoplastically transforming and genotoxic. DU possesses both a radiological (alpha-particle) and chemical (metal) component. Since DU has a low specific activity in comparison to natural uranium, it is not considered to be a significant radiological hazard. The potential contribution of radiation to DU-induced biological effects is unknown and the involvement of radiation in DU-induced biological effects could have significant implications for current risk estimates for internalised DU exposure. Two approaches were used to address this question. The frequency of dicentrics was measured in HOS cells following DU exposure in vitro. Data demonstrated that DU exposure (50 microM, 24 h) induced a significant elevation in dicentric frequency in vitro in contrast to incubation with the heavy metals, nickel and tungsten which did not increase dicentric frequency above background levels. Using the same concentration (50 microM) of three uranyl nitrate compounds that have different uranium isotopic concentrations and therefore, different specific activities, the effect on neoplastic transformation in vitro was examined. HOS cells were exposed to one of three-uranyl nitrate compounds (238U-uranyl nitrate, specific activity 0.33 microCi.g-1; DU-uranyl nitrate, specific activity 0.44 microCi.g-1; and 235U-uranyl nitrate, specific activity 2.2 microCi.g-1) delivered at a concentration of 50 microM for 24 h. Results showed, at equal uranium concentration, there was a specific activity dependent increase in neoplastic transformation frequency. Taken together these data suggest that radiation can play a role in DU-induced biological effects in vitro.

Cell Transformation, Neoplastic↗
PubMed2002

Models for improving cataract surgical rates in southern China.

BACKGROUND/AIMS: Unoperated cataract is the main challenge to blindness reduction in China. This demonstration project in Guangdong Province was designed to test various strategies to improve the cataract surgical rate. METHODS: Two strategies (reduction of the cataract surgical fee and training of country doctors in the detection of cataract blindness) were implemented in each of two counties. Both interventions were introduced in a third county. RESULTS: The cataract surgery rate (CSR) per million was 366 in the county where training took place, 588 where the fee was lowered, and 1140 where both interventions took place. The improvement in CSR was highly significant (p<0.001). CONCLUSIONS: In southern China, CSR can be increased with community based measures. Sustainability for such measures will be the major future challenge.

Aged↗
PubMed2002

A new, simple, and accurate method for non-invasive estimation of pulmonary arterial pressure.

OBJECTIVE: To develop and validate a new non-invasive method for the estimation of pulmonary arterial pressure (PAP) based on advanced signal processing of the second heart sound. DESIGN: Prospective comparative study. SETTING: Referral cardiology centre. PATIENTS: This method was first tested in 16 pigs with experimentally induced pulmonary hypertension and then in 23 patients undergoing pulmonary artery catheterisation. METHODS: The heart sounds were recorded at the surface of the thorax using a microphone connected to a personal computer. The splitting time interval between the aortic and the pulmonary components of the second heart sound was measured using a computer assisted spectral dechirping method and was normalised for heart rate. RESULTS: The systolic PAP varied between 14-73 mm Hg in pigs and between 20-70 mm Hg in patients. The normalised splitting interval was measurable in 97% of the recordings made in pigs and 91% of the recordings made in patients. There was a strong relation between the normalised splitting interval and the systolic PAP (pigs: r = 0.94, standard error of the estimate (SEE) = 5.3 mm Hg; patients: r = 0.84, SEE = 7.8 mm Hg) or the mean pulmonary pressure (pigs: r = 0.94, SEE = 4.1 mm Hg; patients: r = 0.85, SEE = 5.8 mm Hg). CONCLUSIONS: This study shows that this new non-invasive method based on advanced signal processing of the second heart sound provides an accurate estimation of the PAP.

Blood Pressure↗
PubMed2002

Comparison of API20C with molecular identification of Candida spp isolated from bloodstream infections.

A study was carried out to compare the API20C technology with polymerase chain reaction amplification and direct sequencing of the short internal transcribed spacer region 2 (ITS2) for the identification of 58 isolates of invasive candida species obtained from patients with bloodstream infections over the seven year period 1994 to 2000. Overall, there was only one disagreement between the phenotypic and genotypic identification, where the API scheme identified the isolate as C albicans but the molecular method identified it as C dubliniensis. This study demonstrated that the API20C method is useful in the identification of Candida spp isolated from blood culture and that molecular methods do not enhance identifications made using the API20C scheme. However, for correct reporting of C dubliniensis, an emerging bloodborne pathogen, it is recommended that all isolates identified as C albicans by the API20C scheme are further examined phenotypically and/or genotypically.

Candida↗
PubMed2002

Misidentification of a genomovar of Burkholderia cepacia by recA restriction fragment length polymorphism.

An 8 year old girl with cystic fibrosis presented with a pulmonary exacerbation from which Burkholderia cepacia was cultured. Subsequent polymerase chain reaction restriction fragment length polymorphism analysis of the recA gene suggested the presence of B cepacia Genomovar V (Burkholderia vietnamiensis); however, on subsequent sequence typing, this isolate was confirmed as B cepacia Genomovar IIIb. This report outlines the potential difficulties in the correct characterisation of the various genomovars within the B cepacia complex of organisms, which has particularly important implications for patient segregation and infection control.

Bacterial Typing Techniques↗
PubMed2002

Rab3D: a regulator of exocytosis in non-neuronal cells.

Rab3D, a small Ras-like GTPase, is a key regulator of intracellular vesicle transport during exocytosis. It has been shown that Rab3 GTPases are abundant in cells with regulated secretory pathways and are thought to confer the specificity of docking and fusion during regulated exocytosis. Unlike other Rab3 isoforms, Rab3D is enriched in a number of non-neuronal tissues and is localised to secretory granules in the cytoplasm of these cells. The structure of Rab3D exhibits all of the conserved domains from the Rab family and also contains hypervariable N- and C-terminal regions. Rab3D undergoes post-translational isoprenylation and cycles between GDP- and GTP-bound forms. Apart from the factors involved in the Rab activation cycle, few Rab3D effector proteins have been identified to date. Nevertheless, it has long been suggested that Rab3D plays a role in regulated exocytotic processes as well as apically directed transcytosis. This review summarises the recent work on the biological function, structural integrity and molecular interactions of Rab3D in non-neuronal cells.

Amino Acid Sequence↗
PubMed2002

Linkage analysis using direct and indirect counting and relative efficiencies for codominant and dominant loci.

A method based on direct and indirect counting is developed for rapid and accurate linkage analysis for codominant and dominant loci. Methods for estimating gender-specific recombination frequencies are available for cases where at least one of the two loci is multiallelic and for biallelic loci with mixed parental linkage phases where at least one locus is codominant. Most of the estimates of gender-average and gender-specific recombination frequencies required iterative solutions. The new method makes use of the full data set, yields exact estimates of the recombination frequencies when the observed and expected genotypic frequencies are equal, and are computationally efficient. Relative efficiency of various data types is affected by the inheritance mode and by parental linkage phases of biallelic loci, but unaffected by the locus polymorphism when using the full data set for linkage analysis. The ability to determine parental linkage phases is affected by the locus polymorphism as well as inheritance mode. Intercross (or F-2 design) is more efficient for mapping codominant loci, whereas backcross is more efficient if dominance is involved. Mixed parental linkage phases of biallelic loci are less efficient than coupling or repulsion linkage phases. Ignoring noninformative offspring results in biased estimates of recombination frequency for biallelic loci only and reduced LOD scores for all cases.

Animals↗
PubMed2002

Selection of phage-display peptides that bind specifically to the outer coat protein of Rice black streaked dwarf virus.

Several peptides that could bind specifically to the outer coat protein encoded by the S10 gene of Rice black streaked virus (RBSDV) were isolated from a phage-display random 12-mer peptide library. The sequence analysis showed that the amino acid motif (K)K**(*)P, the asterisk denoting any amino acid, might be the core sequence by which the peptides bind to the target protein. The peptide 1 that had a high affinity to RBSDV outer coat protein was synthesized by a chemical method and its fusion protein with glutathione-S-transferase (GST) was produced in an Escherichia coli expression system. The dot and Western blot analyses indicated that RBSDV could be detected with a high sensitivity in crude extracts of diseased plant leaves using a purified GST fusion protein. The circular dichroism (CD) spectroscopy revealed that the synthesized binding peptide but not a nonbinding peptide could bring about a marked change in the conformation of outer coat RBSDV protein. Since the protein functions only when it has correct conformation, the peptides binding specifically to it could possibly disturb the function of the virus outer coat protein and might be used to block the transmission pathway of the virus. Summing up, as these peptides showed a high specificity and sensitivity and diagnostic potential for RBSDV, they may represent the basis of a novel strategy for development of resistance to RBSDV.

Artificial Gene Fusion↗
PubMed2001

Homologous phases built by boron clusters and their vibrational properties.

We have found a series of new rare earth boron-rich solids in REBC(N) (RE: Y, Ho, Er, Tm, and Lu), systems and their structures are solved from single crystal and/or powder X-ray diffraction data. Structure analysis results show that they are homologous with B(4)C and also show trigonal symmetry. As the two basic structural units, boron icosahedra and octahedra in the new phases form in layers and stack in different sequences which form different phases. With increasing number of icosahedral layers stacking between two neighboring octahedral layers, the c-axis of the unit cell is increased and the other two edges of the unit cell are only changed slightly. Three monophases of the series have been synthesized both in powders and as single crystals. The vibrational modes of the homologous phases are analyzed from the Raman spectra and compared with that of B(4)C.

Journal Article↗
PubMed2001

[Identification of high-pathogenicity island-harboring Escherichia coli from children with diarrhea disease].

OBJECTIVE: To investigate the etiological status of high-pathogenicity island-harboring Escherichia coli (HPIEC) in diarrhea diseases among children. METHODS: Escherichia coli was Isolated and identified from the stool specimens of 1,032 children with diarrhea diseases by culturing, serotyping, PCR, and colony hybridization. RESULTS: 652 strains of E. coli were isolated from the 1,032 stool specimens and confirmed by colony hybridization out of which 225 were identified as diarrheagenic E. coli, including 20 EPEC, 81 ETEC, 47 SLTEC, 74 ESIEC, and 3 EIEC strans. 112 (17.2%) irp2 virulent gene positive E. coli strains were detected from the 652 strains, out of which 24 were from the 74 ESIEC strans and 17 from the 47 SLTEC stranis. The typical clinical symptoms of diarrhea caused by HPI-haboring E. coli included anorexia (87.5%), abdominal pain (58.0%), diarrhea (75.9%, over 6 episodes, mostly of mucous stool a day, 75.9%), and fever (50.9%). CONCLUSION: High-pathogenicity island-harboring E. coli is one of the important pathogens of diarrhea diseases in children.

Adolescent↗