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Biomedical subjects

J Xu

Publications and source records attributed to J Xu.

At least 109 records · Page 6Linked to original sources
PubMed2004

Identification of novel eubacteria from spent mushroom compost (SMC) waste by DNA sequence typing: ecological considerations of disposal on agricultural land.

A small study was undertaken to examine the microbiological characteristics of spent mushroom compost (SMC), which is the major waste by-product of the mushroom industry and which is regularly disposed off by application to agricultural land. The primary aim of this study was to examine SMC for the presence of faecal bacterial pathogens, including Campylobacter spp., Salmonella spp. and Listeria monocytogenes. Secondly it was desirable to quantify bacterial and fungal populations within SMC, and also qualitatively identify the diversity of bacterial populations within SMC, through employment of rDNA PCR and direct sequencing techniques on the culturable microflora. Conventional microbiological analyses of SMC material (n=30) from six commercial operations in both Northern Ireland and the Republic of Ireland, failed to detect Salmonella spp, Listeria spp. or Campylobacter spp. in any of the SMC material examined. Total aerobic plate counts gave a mean count of log10 7.01 colony forming units (cfu) per gram SMC material (range: log10 6.53-7.52 cfu/g). Fungal counts gave a mean count of log(10) 4.57 cfu per gram SMC material (range: log10 3.93-4.98 cfu/g). From a total of greater than 50 colony picks, a total of 12 bacterial morphotypes were identified and were further examined by employment of partial 16S rRNA gene amplification and sequencing techniques, yielding several genera and species, including Bacillus licheniformis, Bacillus subtilis, Klebsiella/Enterobacter sp. Microbacterium sp. Paenibacillus lentimorbus, Pseudomonas mevalonii, Sphingobacterium multivorum and Stenotrophomonas sp. This is the first preliminary report on the microbial diversity of SMC waste and demonstrates the presence of several species that have not been previously described in SMC, in addition to two potentially novel species within the genera Microbacterium and Stenotrophomonas. It is thereby important to examine the ecological microbe-microbe and plant-microbe interactions that are occurring between the native bacterial soil flora and those added annually (theoretically estimated at approximately 10(18) cells) through the application of SMC. Such studies would be beneficial in helping to ascertain the ecological consequences involved in the disposal of SMC waste on agricultural land.

Agaricales↗
PubMed2004

Insulin-like growth factor-1 receptor signaling in 3T3-L1 adipocyte differentiation requires lipid rafts but not caveolae.

Previously, we have found that lipid rafts/caveolae were essential for insulin-like growth factor-1 (IGF-1) receptor signaling during 3T3-L1 preadipocytes differentiation induction. However, it was not identified as to which of the membrane lipid-ordered microdomains mediates the receptor signal. Using small double-stranded RNA-mediated interference (RNAi), we successfully suppressed the caveolin-1 protein expression. In cells stably transfected with vector expressing small interfering RNA (siRNA) fragment, no caveolin-1 protein or caveola was detected. On the other hand, removal of caveolin-1 did not affect the caveolinless lipid rafts or the localization of IGF-1 receptor in lipid rafts on plasma membrane. IGF-1 receptor signal transduction and induced cellular differentiation were normal in RNAi cells with only lipid rafts. Furthermore, these IGF-1 receptor signaling events were still sensitive to the cholesterol-binding reagents. Thus, our results suggest that lipid rafts are sufficient for IGF-1 receptor signaling and the recruitment of signal molecules by caveolin-1 is not essential for IGF-1 receptor signaling.

3T3-L1 Cells↗
PubMed2004

Skin concentrations of thromboxane synthetase inhibitor after topical application with bioelastic membrane.

Elevated thromboxane levels are associated with a number of disease states, including dermal pressure ulcers. When dazmegrel was orally administered to greyhound dogs wearing leg casts, it resulted in a sparring effect on the skin areas of potential pressure ulcer development. The objective of this research was to determine if bioelastic matrices could provide controlled release of thromboxane A2 synthetase inhibitor (dazmegrel) at tissue concentrations sufficient for inhibition of thromboxane synthesis. The animal used for these studies was the greyhound, which has thin skin, angular conformation, limited body fat and is predisposed to pressure ulcers similar to those occurring in humans. In vivo skin penetration studies showed that epidermal exposure to bioelastic thromboxane synthetase inhibitor (TSI) matrix resulted in local tissue concentrations of TSI sufficient for thromboxane synthetase inhibition. There were no significant differences between dazmegrel in the skin layers (epidermis, dermis and subcutaneous layers) on 1, 7 and 14-day exposures.

Administration, Cutaneous↗
PubMed2004

Culture-negative Bartonella endocarditis in a patient with renal failure: the value of molecular methods in diagnosis.

Members of the genus Bartonella are increasingly recognised as a cause of culture-negative endocarditis, particularly in those patients with underlying risk factors (e.g., homelessness and alcoholism (B. quintana) or valvulopathy and cat ownership (B. henselae). The aortic and mitral-valves are most commonly involved. Here, a case is reported of culture-negative right-sided endocarditis, without any of the above risk factors, due to Bartonella sp. in a 69-year-old man who presented with acute renal failure. The diagnosis was made using a broad-range 16S rRNA polymerase chain reaction (PCR) technique and direct automated sequencing on a peripheral blood sample, which was subsequently confirmed serologically. A review of the literature on Bartonella endocarditis is also presented. Molecular laboratory methods using peripheral blood or blood cultures may be very useful in the diagnosis of causal agents in culture-negative endocarditis and add further support to the recently inclusion of molecular (PCR) diagnosis, as a major Duke's criterion, for the diagnosis of infective endocarditis.

Acute Kidney Injury↗
PubMed2004

Primary care, infant mortality, and low birth weight in the states of the USA.

STUDY OBJECTIVE: The study tests the extent to which primary care physician supply (office based primary care physicians per 10 000 population) moderates the association between social inequalities and infant mortality and low birth weight throughout the 50 states of the USA. DESIGN: Pooled cross sectional, time series analysis of secondary data. Analyses controlled for state level education, unemployment, racial/ethnic composition, income inequality, and urban/rural differences. Contemporaneous and time lagged covariates were modelled. SETTING: Eleven years (1985-95) of data from 50 US states (final n = 549 because of one missing data point). MAIN RESULTS: Primary care was negatively associated with infant mortality and low birth weight in all multivariate models (p<0.0001). The association was consistent in contemporaneous and time lagged models. Although income inequality was positively associated with low birth weight and infant mortality (p<0.0001), the association with infant mortality disappeared with the addition of sociodemographic covariates. CONCLUSIONS: In US states, an increased supply of primary care practitioners-especially in areas with high levels of social disparities-is negatively associated with infant mortality and low birth weight.

Black or African American↗
PubMed2004

Interaction between osteoblast and osteoclast: impact in bone disease.

The intercellular communication between osteoblasts and osteoclasts is crucial to bone homeostasis. Since Rodan and Martin proposed the control of osteoclasts by osteoblasts in the 1980s, many factors have been isolated from osteoblasts and shown to regulate the differentiation and function of osteoclasts. However, the mechanism by which osteoblasts regulate osteoclasts during bone remodelling is still unclear. On the other hand, it is well accepted that many metabolic bone diseases are associated with the disruption of the communication between osteoblast and osteoclasts. Thus, this review focuses on the cross-talk between osteoblasts and osteoclasts and its impact in bone disease.

Animals↗
PubMed2004

Molecular characterisation of chondrocytes in autologous chondrocyte implantation.

Autologous chondrocyte implantation (ACI) relies on the use of cultured cells. However, the biosynthetic profile of cultured chondrocytes is shown to be altered during in vitro expansion. The purpose of this study therefore, was to examine the cellular phenotype of chondrocytes cultured for ACI and to determine the apoptotic index of cells implanted into patients. Using electron microscopy, immunohistochemistry, RT-PCR and flow cytometry analyses, we have investigated protein and gene expression of several chondrocyte-specific, or associated markers in cultured cells used for implantation in patients. They included S-100, type I and II collagen, aggrecan, transforming growth factor beta, glucocorticoid receptor alpha and beta and vitamin D3 receptor. We have also examined the apoptotic index of chondrocytes. Our results demonstrated that cultured cells for ACI display the characteristics of chondrocytes. These cells are round in shape, contain numerous small surface processes of cytoplasmic membrane and have an accumulation of glycogen within the cytoplasm. They express S-100, aggrecan TGF-beta, glucocorticoid receptor alpha and vitamin D3 receptor as evidenced by either immunohistochemistry or RT-PCR, however, there is variation in the expression of type I, type II collagen glucocorticoid receptor beta between cases. Chondrocyte used for implantation has relatively low level of apoptosis (<11%). In conclusion, although there was variation in the level of expression of these genetic markers, our data indicate that cultured cells used for ACI were of chondrocytic lineage cells and have low level of apoptotic cells.

Adult↗
PubMed2004

Evaluation of a synthetic bone defect test model to aid in the selection of materials for use in vertebral body compression fracture repair.

A synthetic test model was developed to assist in screening injectable cements with a focus on mechanical strength for vertebral body compression fracture repair. The two-part defect model consisted of a polyurethane foam cube to simulate trabecular bone and a defect to which various injectable cements could be introduced. In addition, a finite element analysis model was developed and the results were compared to laboratory testing. Agreement was found between the finite element analysis and test results. Once the finite element analysis model was validated with experimental data, an additional finite element analysis was conducted to study various parameters affecting mechanical performance such as simulated bone and cement stiffness. Finite element analysis models were also created using orthotropic bone properties typical of healthy trabecular bone and were compared to various foam stiffnesses. The foam model was a good in vitro representation of actual trabecular bone found in vertebral bodies and is a valid model to evaluate the mechanical strength of injectable cements for percutaneous vertebral body fracture repair.

Bone Cements↗
PubMed2003

Atomic force microscopy and nanoindentation characterization of human lamellar bone prepared by microtome sectioning and mechanical polishing technique.

Surface topography, microstructure, and micromechanical properties of human lamellar bone were characterized by atomic force microscopy and nanoindentation. The lamellar bone surfaces were prepared by two different methods: microtome sectioning and mechanical polishing. The lamellar bone surfaces prepared by mechanical polishing revealed that thin lamellae formed depressions approximately 200 nm deep, whereas the surfaces prepared by microtome sectioning were flat. Atomic force microscopy surface topographic images at higher magnification showed differences between thick and thin lamellae in polished samples, but these differences were less pronounced in microtomed samples. Roughness measurements confirmed that there was a significant difference between thick (21.0 nm) and thin lamellae (8.3 nm) in polished samples (p < 0.001). The difference in surface roughness between thick (13.9 nm) and thin lamellae (12.7 nm) in microtomed sample was statistically insignificant (p = 0.74). Higher elastic modulus values were observed for thick lamella in microtomed samples compared with that of thin lamellae, whereas measured elastic modulus differences between thick and thin lamellae in polished samples were found to be statistically insignificant.

Biomechanical Phenomena↗
PubMed2003

Epidemiology and cause of severe acute respiratory syndrome (SARS) in Guangdong, People's Republic of China, in February, 2003.

BACKGROUND: An epidemic of severe acute respiratory syndrome (SARS) has been associated with an outbreak of atypical pneumonia originating in Guangdong Province, People's Republic of China. We aimed to identify the causative agent in the Guangdong outbreak and describe the emergence and spread of the disease within the province. METHODS: We analysed epidemiological information and collected serum and nasopharyngeal aspirates from patients with SARS in Guangdong in mid-February, 2003. We did virus isolation, serological tests, and molecular assays to identify the causative agent. FINDINGS: SARS had been circulating in other cities of Guangdong Province for about 2 months before causing a major outbreak in Guangzhou, the province's capital. A novel coronavirus, SARS coronavirus (CoV), was isolated from specimens from three patients with SARS. Viral antigens were also directly detected in nasopharyngeal aspirates from these patients. 48 of 55 (87%) patients had antibodies to SARS CoV in their convalescent sera. Genetic analysis showed that the SARS CoV isolates from Guangzhou shared the same origin with those in other countries, and had a phylogenetic pathway that matched the spread of SARS to the other parts of the world. INTERPRETATION: SARS CoV is the infectious agent responsible for the epidemic outbreak of SARS in Guangdong. The virus isolated from patients in Guangdong is the prototype of the SARS CoV in other regions and countries.

China↗
PubMed2003

Polymorphisms in the CYP1B1 gene are associated with increased risk of prostate cancer.

CYP1B1 has been evaluated as a candidate gene for various cancers because of its function in activating environmental procarcinogens and catalysing the conversion of oestrogens to genotoxic catechol oestrogens. To test the hypothesis that genetic polymorphisms in the CYP1B1 gene may associate with the risk for prostate cancer (CaP), we compared the allele, genotype, and haplotype frequencies of 13 single nucleotide polymorphisms (SNPs) of CYP1B1 among 159 hereditary prostate cancer (HPC) probands, 245 sporadic CaP cases, and 222 unaffected men. When each of the SNPs was analysed separately, marginally significant differences were observed for allele frequencies between sporadic cases and controls for three consecutive SNPs (-1001C/T, -263G/A, and -13C/T, P=0.04-0.07). Similarly, marginally significant differences between sporadic cases and controls in the frequency of variant allele carriers were observed for five consecutive SNPs (-1001C/T, -263G/A, -13C/T, +142C/G, and +355G/T, P=0.02-0.08). Interestingly, when the combination of these five SNPs was analysed using a haplotype approach, a larger difference was found (P=0.009). One frequent haplotype (C-G-C-C-G of -1001C/T, -263G/A, -13C/T, +142C/G, and +355G/T) was associated with an increased risk for CaP, while the other frequent haplotype (T-A-T-G-T) was associated with a decreased risk for CaP. These findings suggest that genetic polymorphisms in CYP1B1 may modify the risk for CaP.

Aryl Hydrocarbon Hydroxylases↗
PubMed2003

Acetylenic TACE inhibitors. Part 1. SAR of the acyclic sulfonamide hydroxamates.

The SAR of a series of potent sulfonamide hydroxamate TACE inhibitors, all bearing a butynyloxy P1' group, was explored. In particular, compound 5j has excellent in vitro potency against isolated TACE enzyme and in cells, good selectivity over MMP-1 and MMP-9, and oral activity in an in vivo model of TNF-alpha production and a collagen-induced arthritis model.

ADAM Proteins↗
PubMed2003

Prostaglandin E2 production in astrocytes: regulation by cytokines, extracellular ATP, and oxidative agents.

Upregulation and activation of phospholipases A2 (PLA2) and cyclooxygenases (COX) leading to prostaglandin E2(PGE2) production have been implicated in a number of neurodegenerative diseases. In this study, we investigated PGE2 production in primary rat astrocytes in response to agents that activate PLA2 including pro-inflammatory cytokines (IL-1beta, TNFalpha and IFNgamma), the P2 nucleotide receptor agonist ATP, and oxidants (H2O2 and menadione). Exposure of astrocytes to cytokines resulted in a time-dependent increase in PGE2 production that was marked by increased expression of secretory sPLA2 and COX-2, but not COX-1 and cytosolic cPLA2. Although astrocytes responded to ATP or phorbol ester (PMA) with increased cPLA2 phosphorylation and arachidonic acid release, ATP or PMA only caused a small increase in levels of PGE2. However, when astrocytes were first treated with cytokines, further exposure to ATP or PMA, but not H2O2 or menadione, markedly increased PGE2 production. These results suggest that ATP release during neuronal excitation or injury can enhance the inflammatory effects of cytokines on PGE2 production and may contribute to chronic inflammation seen in Alzheimer's disease.

Adenosine Triphosphate↗
PubMed2003

Direct measurement of the photoelectric response time of bacteriorhodopsin via electro-optic sampling.

The photovoltaic signal associated with the primary photochemical event in an oriented bacteriorhodopsin film is measured by directly probing the electric field in the bacteriorhodopsin film using an ultrafast electro-optic sampling technique. The inherent response time is limited only by the laser pulse width of 500 fs, and permits a measurement of the photovoltage with a bandwidth of better than 350 GHz. All previous published studies have been carried out with bandwidths of 50 GHz or lower. We observe a charge buildup with an exponential formation time of 1.68 +/- 0.05 ps and an initial decay time of 31.7 ps. Deconvolution with a 500-fs Gaussian excitation pulse reduces the exponential formation time to 1.61 +/- 0.04 ps. The photovoltaic signal continues to rise for 4.5 ps after excitation, and the voltage profile corresponds well with the population dynamics of the K state. The origin of the fast photovoltage is assigned to the partial isomerization of the chromophore and the coupled motion of the Arg-82 residue during the primary event.

Bacteriorhodopsins↗
PubMed2003

Isolation of Alternaria alternata from an emollient cream: implications for public health.

A specimen of emollient cream, which was observed to be contaminated peripherally with a filamentous fungus was examined for the presence of fungi and the resulting fungal colonies were examined phenotypically and genotypically. Subsequent DNA extraction and PCR amplification of the large internal transcribed spacer region [ITS1-5.8S-ITS2] yielded an amplicon of 512 bp. Sequence analysis identified this as Alternaria alternata at the 100% homology level with all 512/512 bases called. This organism has been previously reported as a cause of opportunistic infections involving skin and immunocompromised patients. This is the first report of an emollient cream as a source of this organism. It highlights the need for proper management of such preparations in order to minimize the potential spread of fungi to susceptible patient populations.

Alternaria↗
PubMed2003

Weighing the care: patients' perceptions of physician care as a function of gender and weight.

OBJECTIVE: To examine patients' reports of the level of care that they receive from their physicians, and determine the influence of weight and gender in these reports. DESIGN: : In a four-cell design, male and female, overweight and nonoverweight patients reported on the medical care that they received immediately following their appointment. SUBJECTS: A total of 125 patients affiliated to one of four large clinics in the Texas Medical Center of Houston completed this study. MEASUREMENTS: Patients reported the positivity of the care that they received, the time that physicians spent with them, and the extent to which physicians discussed weight-related topics with them. RESULTS: Overweight patients, as a whole, did not report poorer levels of care than did their thinner counterparts. Rather, the weight and gender of the patient significantly interacted across each of the measures to reveal some divergence between male and female patients' weight-based experiences. When significant differences in reported perceptions emerged, overweight men reported deficits in care relative to average weight men (eg, physicians spent less time), whereas overweight women reported enhanced care relative to average weight women (eg, better levels of care, more topics discussed). CONCLUSION: Based on patients' reports, this study reveals that physician care may not be as influenced by patient weight as previously thought. Yet, there is a discernable impact of patients' weight on physician behavior. Overweight men, who may comprise the most at-risk population, indicate that less time is spent with them than that indicated by average weight men. While this may be alarming, overweight women do not report reductions in care. We propose that not only might physicians respond to them differently, but overweight female patients may also be engaging in denial strategies or compensatory behaviors that assure them of quality care.

Adult↗
PubMed2003

Employment of broad-range 16S rRNA PCR to detect aetiological agents of infection from clinical specimens in patients with acute meningitis--rapid separation of 16S rRNA PCR amplicons without the need for cloning.

AIMS: The aim of this study was to develop a polyacrylamide gel electrophoresis (PAGE) method for the rapid separation of 16S rRNA PCR amplicons from aetiological agents of acute meningitis. METHODS AND RESULTS: Blood samples from 40 patients with suspected acute meningococcal meningitis were examined for the presence of causal agents, including Neisseria meningitidis employing two methods: (i) broad-range 16S rRNA PCR in conjunction with PAGE and automated sequencing and (ii) species-specific PCR employing ABI TaqMan technology for N. meningitidis. Analysis of clinical specimens employing 16S rRNA PCR yielded 33/40 (82.5%) positive for the presence of bacterial DNA. Species-specific PCR yielded 30/40 (75%) clinical specimens positive for N. meningitidis. Prior to separation by PAGE, only 6/33 (18.2%) amplicons were able to be identified by sequence analysis, the remaining amplicons (n=27) did not yield an identification due to the presence of mixed 16S rRNA PCR amplicons. Following separation, amplicons were re-amplified and sequenced, yielding 24/27 (88.9%) positive for N. meningitidis and three specimens positive for Acinetobacter sp., Staphylococcus aureus and Streptococcus pneumoniae. One specimen was positive for both N. meningitidis and Streptococcus spp. and another specimen was positive for N. meningitidis and Pseudomonas sp., by broad-range PCR. Seven clinical specimens were negative for N. meningitidis and other eubacteria using both detection techniques. CONCLUSIONS: Clinical specimens including blood and cerebrospinal fluid from patients with suspected acute bacterial meningitis, may become contaminated with commensal skin flora, resulting in difficulties in downstream sequencing of pathogen plus contaminant DNA. This study allows for the rapid separation of amplified pathogen from contaminant DNA. SIGNIFICANCE AND IMPACT OF STUDY: This study demonstrated the usefulness of the rapid separation of multiple 16S rRNA PCR amplicons using a combination of PAGE and automated sequencing, without the need of cloning. Adoption of this technique is therefore proposed when trying to rapidly identify pathogens in clinical specimens employing broad-range 16S rRNA PCR.

Acinetobacter↗