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Biomedical subjects

X L Wu

Publications and source records attributed to X L Wu.

At least 37 records · Page 2Linked to original sources
PubMed2003

Optical emission from excess Si defect centers in Si nanostructures.

Four groups of Si nanostructures with and without beta-SiC nanocrystals were fabricated for clarifying the origin of a blue emission with a double-peak structure at 417 and 436 nm. Spectral analyses and microstructural observations show that the blue emission is related to the existence of excess Si atoms in these Si nanostructures. The energy levels of electrons in Si nanocrystals with vacancy defects formed from the excess Si atoms are calculated and the characteristics of the obtained density of states coincide with the observed double-peak emission. The present work provides a possible mechanism of the blue emission in various Si nanostructures.

Journal Article↗
PubMed2002

Phosphorus removal and greenhouse gas N2O emission in a lime-induced aerobic sludge granule process.

Aerobic sludge granulation was achieved in an activated sludge process continuously fed with lime (Ca2+ 100 mg l(-1) influent) every other day. Eighteen days after lime addition, activated sludge granules with the size of 0.5-2.2 mm were formed, which occupied 10-25% of total sludge volume. Sludge volume index (SVI) was reduced to an average of 50 ml g(-1), which increased average sludge concentration to 3.6-5.0 g VSS l(-1), 1.6-2.1 times of that of control. Greenhouse gas N2O emission was also significantly reduced: N2O concentration from the lime-addition reactor was 5-15 ppmv, 47-61% of that of control, Effluent PO4-P concentration was generally lower than 1 mg l(-1) when average influent PO4-P concentration was 6.07-6.37 mg l(-1). Total phosphorus (TP) and total nitrogen (TN) removal efficiencies were around 89.6% and 14.5-16.1%, over 3.5 and 1 times higher than those of control, respectively. COD removal rate in the lime-addition reactor was 2.05-2.48 kg COD m(-3) d(-1), higher than 1.34-1.61 kg COD m(-3) d(-1) in the control.

Air Pollution↗
PubMed2001

Universal distribution of centers and saddles in two-dimensional turbulence.

The statistical properties of the local topology of two-dimensional turbulence are investigated using an electromagnetically forced soap film. The local topology of the incompressible 2D flow is characterized by the Jacobian determinant Lambda(x,y) = 1 / 4(omega(2)-sigma(2)), where omega(x,y) is the local vorticity and sigma(x,y) is the local strain rate. For turbulent flows driven by different external force configurations, P(Lambda) is found to be a universal function when rescaled using the turbulent intensity. A simple model that agrees with the measured functional form of P(Lambda) is constructed using the assumption that the stream function, psi(x,y), is a Gaussian random field.

Journal Article↗
PubMed2001

Spherical growth and surface-quasifree vibrations of Si nanocrystallites in Er-doped Si nanostructures.

Si-based Er-doped Si nanostructures were fabricated for exploring efficient light emission from Er ions and Si nanocrystallites. High-resolution transmission electron microscopy observations reveal that Si nanocrystallites are spherically embedded in the SiO2 matrix. Energy-dispersive x-ray analysis indicates that the Er centers are distributed at the surfaces of nanocrystallites surrounded by the SiO2 matrix. Low-frequency Raman scattering investigation shows that Lamb's theory can be adopted to exactly calculate the surface vibration frequencies from acoustic phonons confined in spherical Si nanocrystallites and the matrix effects are negligible.

Journal Article↗
PubMed2001

Functional patterns and temperature response of cellulose-fermenting microbial cultures containing different methanogenic communities.

The effect of microbial composition on the methanogenic degradation of cellulose was studied using two lines of anaerobic cellulose-fermenting methanogenic microbial cultures at two different temperatures: that at 15 degrees C being dominated by Methanosaeta and that at 30 degrees C by Methanosarcina. In both cultures, CH4 production and acetate consumption were completely inhibited by either 2-bromoethanesulfonate or chloroform, whereas H2 consumption was only inhibited by chloroform, suggesting that homoacetogens utilized H2 concomitantly with methanogens. Hydrogen was the intermediate that was consumed first, while acetate continued to accumulate. At 15 degrees C, acetoclastic methanogenesis smoothly followed H2-dependent CH4 production. Fluorescence in situ hybridization showed that populations of Methanosaeta steadily increased with time from 5 to 25% of total cell counts. At 30 degrees C, two phases of CH4 production were obtained, with acetate consumed after the abrupt increase of Methanosarcina from 0 to 45% of total cell counts. Whereas populations of Methanosaeta were able to adapt after transfer from 15 to 30 degrees C, those of Methanosarcina were not, irrespective of during which phase the cultures were transferred from 30 degrees C to 15 degrees C. Our results thus show that the community structure of methanogens indeed affects the function of a cellulose-fermenting community with respect to temperature response.

Archaea↗
PubMed2001

Role of PTCH and p53 genes in early-onset basal cell carcinoma.

Basal cell carcinoma (BCC) is the most common skin cancer in the Western world. Ultraviolet (UV) exposure, race, age, gender, and decreased DNA repair capacity are known risk factors for the development of BCC. Of these, UVB irradiation from sunlight is the most significant risk factor. The incidence of sporadic BCC increases in individuals older than age 55, with the greatest incidence reported in individuals who are older than 70, and is rare in individuals who are younger than 30. In this study, we analyzed 24 BCC samples from individuals who had BCC diagnosed by the age of 30. Fifteen single-stranded conformation polymorphism variants in the PTCH gene were identified in 13 BCC samples. Sequence analysis of these single-stranded conformation polymorphism variants revealed 13 single nucleotide changes, one AT insertion, and one 15-bp deletion. Most of these nucleotide changes (nine of 15) were predicted to result in truncated PTCH proteins. Fifteen p53 mutations were also found in 11 of the 24 BCC samples. Thirty-three percent (five of 15) and 60% (nine of 15) of the nucleotide changes in the PTCH and p53 genes, respectively, were UV-specific C-->T and CC-->TT nucleotide changes. Our data demonstrate that the p53 and PTCH genes are both implicated in the development of early-onset BCC. The identification of UV-specific nucleotide changes in both tumor suppressor genes suggests that UV exposure is an important risk factor in early onset of BCC.

Adolescent↗
PubMed2001

Functional and structural response of a cellulose-degrading methanogenic microbial community to multiple aeration stress at two different temperatures.

Two cellulose-fermenting methanogenic enrichment cultures originating from rice soil, one at 15 degrees C with Methanosaeta and the other at 30 degrees C with Methanosarcina as the dominant acetoclastic methanogen, both degraded cellulose anaerobically via propionate, acetate and H2 to CH4. The degradation was a two-stage process, with CH4 production mainly from H2/CO2 and accumulation of acetate and propionate during the first, and methanogenic consumption of acetate during the second stage. Aeration stress of 12, 24, 36 and 76 h duration was applied to these microbial communities during both stages of cellulose degradation. The longer the aeration stress, the stronger the inhibition of CH4 production at both 30 degrees C and 15 degrees C. The 72 h stressed culture at 30 degrees C did not fully recover. Aeration stress at 30 degrees C exerted a more pronounced effect, but lasted for a shorter time than that at 15 degrees C. The aeration stress was especially effective during the second stage of fermentation, when consumption of acetate (and to a lesser extent propionate) was also increasingly inhibited as the duration of the stress increased. The patterns of CH4 production and metabolite accumulation were consistent with changes observed in the methanogenic archaeal community structure. Fluorescence in situ hybridization showed that the total microbial community at the beginning consisted of about 4% and 10% archaea, which increased to about 50% and 30% during the second stage of cellulose degradation at 30 degrees C and 15 degrees C respectively. Methanosarcina and Methanosaeta species became the dominant archaea at 30 degrees C and 15 degrees C respectively. The first round of aeration stress mainly reduced the non-Methanosarcina archaea (30 degrees C) and the non-Methanosaeta archaea (15 degrees C). Aeration stress also retarded the growth of Methanosarcina and Methanosaeta at 30 degrees C and 15 degrees C respectively. The longer the stress, the lower was the percentage of Methanosarcina cells to total microbial cells after the first stress at 30 degrees C. A later aeration stress decreased the population of Methanosarcina (at 30 degrees C) in relation to the duration of stress, so that non-Methanosarcina archaea became dominant. Hence, aeration stress affected the acetotrophic methanogens more than the hydrogenotrophic ones, thus explaining the metabolism of the intermediates of cellulose degradation under the different incubation conditions.

Air↗
PubMed2001

PTCH mutations in squamous cell carcinoma of the skin.

Ultraviolet light exposure is the major risk factor for the development of squamous cell carcinoma in Caucasians. Mutations in the tumor suppressor gene p53 have been identified in both squamous cell carcinomas and basal cell carcinomas. The human homolog of the Drosophila patched gene, has been shown to be mutated in sporadic basal cell carcinomas; however, mutations in the patched gene have not been found in squamous cell carcinoma. In this study, we screened a total of 20 squamous cell carcinoma samples for mutations in the patched gene. Using polymerase chain reaction-single strand conformation polymorphism as an initial screening method, we identified one non-sense mutation, two mis-sense mutations and three silent mutations in five squamous cell carcinoma samples. In one squamous cell carcinoma sample, we identified a tandem GG-->AA transitional change at nucleotide 3152 in exon 18 of the patched gene that resulted in a premature stop codon at codon 1051. The three squamous cell carcinoma samples containing non-sense and mis-sense mutations were isolated from individuals with histories of multiple basal cell carcinoma. Sequence analysis of the p53 gene in these five squamous cell carcinoma samples identified one CC-->TT and three C-->T ultraviolet-specific nucleotide changes. Our study provides evidence that the patched gene is mutated in squamous cell carcinoma from individuals with a history of multiple basal cell carcinoma. The identification of ultraviolet-specific nucleotide changes in both tumor suppressor genes supports the notion that ultraviolet exposure plays an important part in the development of squamous cell carcinoma.

Aged↗
PubMed2001

[Association of microsatellite genomic heterozygosity with inbred pig performance under successive inbreeding].

Genomic scanning using microsatellites was carried out in a pig family that has undergone 5 successive generations of inbreeding. A total of 56 microsatellite markers were utilized, which were derived from swine chromosome 01, 02, 11, 13, 17, 18 and gave a considerable coverage of these chromosomes. Genomic heterozygosity was estimated as an average of marker heterozygosity over all 6 chromosomes. Analysis of variance using a generalized linear model indicated that genomic heterozygosity was positively and significantly associated with slaughter weight (SWT) and average daily slaughter gain (ADSG), but inconsistently and non-significantly associated with backfat depth (BFDP). Association effects of GH on SWT and ADSG increased from generation 1 to generation 2, and, then, reduced gradually with generations while levels of inbreeding accumulated. The maximum effect was observed in generation 2, which was estimated to be 22.43 kg for SWT and 0.132 kg/d for ADSG. The effect of marker heterozygosity on SWT and ASDG differed dramatically from chromosome to chromosome: the largest effect was observed with chromosome 13 (i.e. 6.306 kg for SWT and 0.032 kg/d for ADSG), followed by chromosome 01, 17, 18, 02 and 11. Marker heterozygosity was not found to be significantly associated with BFDP for all chromosomes. These results give rise to three implications. First, genes (e.g. QTL) contributing to traits of economic importance are not equally distributed among these chromosomes, which represents the difference in determination of quantitative traits across chromosomes or at DNA level. Second, the association of genomic or marker heterozygosity with pig performance varies from chromosome to chromosome, or with generations of inbreeding. This phenomenon provides an evidence that heterozygosity-performance association is not straight-forward, but rather complex as a result of complicated gene actions and interactions, and sometimes may even be much more complicated when confounded and misled by inabequate or improper markers utilized. Last, decreased heterozygous advantage or heterozygous disadvantage, in some cases, is very much likely as a result of the high linkage disequilibrium under high levels of inbreeding, where one or several deleterious alleles might be linked with neutural markers in much high probability.

Animals↗
PubMed2001

[Phylogenetic analysis of interspecies in genus Glycine through SSR markers].

The genetic diversity among 11 species of genus Glycine (altogether 37 accessions) was evaluated through SSR analysis. The number of alleles in different loci ranges from 6 to 29, averaging 15.9 per locus; alleles of subgenus soja account for 71.5% of those in subgenus Glycine, and the fingerprinting among subgenus Glycine is more divergent than that of subgenus soja. Principal factor analysis shows that the first and the second principal factor can classify genus Glycine into two groups which represent subgenus Glycine and subgenus soja. The results of UPGMA indicate that G. mas, G. soja and G. gracilis in subgenus soja are different species.

Alleles↗
PubMed2001

[Association of parameters of crossbreeding effect for traits of growth and meat-production with average band-sharing of RAPD markers in commercial crosses of Duroc, Landrace and large white pigs].

Parameters of crossbreeding effect have been estimated for average daily gain (ADG), dressing percentage (DRP), backfat thickness (BFT), percent of hind legs (HLP), and average band-sharing of RAPD markers, by using individual records of growth and meatproduction and genotypes of RAPD analysis in crosses of Duroc, Landrace and Large White pigs from 1996 through 1998. The results indicate that significant individual and maternal genetic effects exist for all the 4 traits of growth and meat-production (P < 0.05). Effects of individual heterosis and maternal heterosis have also been found to be significant for ADG (P < 0.05), but not significant for DRP, BFT, and HLP (P > 0.05). Maternal genetic effect is positive and the effects of individual heterosis and maternal heterosis are negative for RAPD-marker ABS. Correlation analysis reveals that the total correlation, which includes all parameters at a time, is low and not significant. The partial correlation, however, is more reasonable than total correlation, which consider 1 parameter each time, or 2 in case of heterosis. All 3 partial correlations between ADG and RAPD-marker ABS are significantly greater or smaller than zero (P < 0.05), among which the correlation for individual genetic effect is very significant (P < 0.01). It is therefore concluded that the efficiency of predicting heterosis is low by simply applying total correlation. Alternatively, estimation of parameters of crossbreeding effect for both economic traits and DNA markers provides a way of efficiently predicting heterosis for it dramatically increases the correlation between markers and traits of economical importance. Increasing QTL coverage (percent of markers linked to QTL) will as well contribute to improved accuracy of predicting heterosis. It is also implied from the partial correlations that, while genomic similarity of crosses increases, individual genetic effect would increase, but that of individual heterosis and maternal heterosis would decreases.

Animals↗
PubMed2001

[QTLs mapping of some agronomic traits of soybean].

A recombinant inbred population of soybean was developed from a intraspecies cross of Kefeng1 and Nannong 1138-2. A genetic linkage group of soybean genome was constructed, which composed of 22 linkage groups, included 302 loci, covered 2,363.8 cM. The interval mapping was used to identify quantitative trait loci (QLTs) associated with ten important agronomic traits in the RIL population. The results indicated that thirty-four QTLs were detected for the ten traits associated with yield and seed quality. We conclude that QTL analysis offers a useful tool for the genetic improvement of soybean cultivars.

Chromosome Mapping↗
PubMed2001

[Construction and analysis of a genetic linkage map of soybean].

A high-density genetic map was constructed with a RILs population (NJRIKY) from a cross of two cultivated soybean Kefeng 1 and Nannong 1138-2, using RFLP, SSR, RAPD and AFLP markers. The map consists of 24 linkage groups, which include 792 genetic markers, and covers 2,320.7 cM with an average genetic distance of 2.9 cM. The higher polymorphsims between two parents were identified with SSR markers. Due to its simplicity and stability, they could be used as anchored marker to integrate different maps constructed with different genetic markers. AFLP marker system is efficient for map construction while it easily form clusters to cause big gaps in the map. A total of 21.7% of markers was found with distorted segregation in the RILs population. The high-density molecular linkage map is fundamental for gene localization, comparative genomics, and QTL mapping of important agronomic traits.

Genetic Linkage↗
PubMed2001

[Separation and determination of scandium, tin and aluminum by reversed-phase ion pair high performance liquid chromatography].

The reversed-phase ion pair high performance liquid chromatographic determination of scandium, tin and aluminum with diammonium stilbene-4,4'-bis(1-azo)-3,4-dihydroxybenzene-2,2'-disulfate as precolumn chelating reagent on Spherex C18 column has been investigated with the detection wavelength of 500 nm. Various parameters such as pH, reagent concentration, ion pair reagents, interference of foreign ions have been studied. The mobile phase was methanol-water (40:60, V/V) containing 20 mmol/L acetate buffer of pH 6.0 and 10 mmol/L sodium dodecyl sulfonate. Three complexes could be completely separated within 17 min. The method has been successfully used for the determination of the three metals in mineral samples, with recoveries of 98%, 101%, 103% respectively, and RSD was less than 3.6%. Beer's Law was obeyed over the concentration range 0.01 mg/L-3.80 mg/L, 0.06 mg/L-4.50 mg/L and 0.04 mg/L-3.40 mg/L respectively. The detection limits were 0.9 microgram/L, 1.0 microgram/L and 1.2 micrograms/L for scandium, tin and aluminum when the ratio of signal to noise was 3. Most of other metals did not interfere with the determination. The present method is sensitive and selective.

English Abstract↗
PubMed2000

Cytoprotection by electromagnetic field-induced hsp70: a model for clinical application.

A unique approach to clinical application of cytoprotection is offered by electromagnetic (EM) field induction of stress proteins. EM fields are noninvasive and easily applied, as compared with the current hyperthermia protocols. Fertilized dipteran eggs and cultured rodent cardiomyocytes (H9c2 cells) were used as models to test EM fields for their ability to induce increased hsp70 levels for effective cytoprotection. Eggs preconditioned with an 8 microT 60Hz EM field for 30 min had 114% increase in hsp70 levels, and an average 82% increase in survival, following a lethal temperature of 36.5 degrees C. Thermal preconditioning at 32 degrees C was not nearly as effective in dipteran eggs, inducing only a 44% increase in survival. Preconditioning of cultured murine cardiomyocytes (H9c2 cells) with an 8 microT 60 Hz field induced a 77% average increase in hsp70 levels.

Animals↗
PubMed2000

Particle diffusion in a quasi-two-dimensional bacterial bath.

We study the effect of bacterial motion on micron-scale beads in a freely suspended soap film. Given the sizes of bacteria and beads, the geometry of the experiment is quasi-two-dimensional. Large positional fluctuations are observed for beads as large as 10 microm in diameter, and the measured mean-square displacements indicate superdiffusion in short times and normal diffusion in long times. Though the phenomenon is similar to Brownian motions of small particles, its physical origin is different and can be attributed to the collective dynamics of bacteria.

Bacterial Physiological Phenomena↗
PubMed1999

[A preliminary study of developmental genetics of polymorphic serum esterase in domestic fowls].

Polymorphism of serum esterase was examined in 3 Super-Y 2000 broiler breeding populations differing in developmental stages (i.e. day 120, 180 and 300) using vertical polyacrylamide gel electrophoresis. The results indicated that both Es-1 and Es-2 loci exhibited polymorphism. Two to three polymorphic enzyme bands were detected at zone Es-1, and one band at zone Es-2 after electrophoresis. It was first discovered in this work that obvious developmental difference in products of Es-1 alleles existed with female birds, polymorphic bands of which disappeared after onset of lay. An individual tracing experiment conducted in a Super-Y 380 commercial layer population and an extensive experiment carried out in 2 ISA B380 parent CD stocks supported the previous finding. It could thus be inferred that phenotype "O" (no band at Es-1) discovered in hens was not genetically controlled by the recessive allele Es-1(0), which itself did not exist, but might be an evidence of gene regulation at laying period. For female birds, expression of Es-1 alleles was active before sexual maturity, and depressed after onset of lay, to meet their physiological need of high level of blood esterase for laying. It could also be inferred that this developmental difference in serum esterase polymorphism might be a common phenomenon in all avian species. If this hypothesis were true, the synthesis of esterase inside avian bodies could be a desirable model for investigating expression, and regulation of expression, of genes in avian populations.

Animals↗