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L Xiang

Publications and source records attributed to L Xiang.

At least 19 recordsLinked to original sources
PubMed2026

Invisible Threats, Relentless Hunters: Biosurveillance of Airborne Plant Pathogens.

Airborne dispersal enables plant pathogens to travel across fields, regions, and continents, fueling rapid epidemics and emerging disease threats. Biosurveillance, the systematic monitoring of airborne inoculum, offers the opportunity to detect pathogens before symptoms appear and informs timely, risk-based management. Recent advances in air sampling, molecular diagnostics, metagenomics, and imaging technologies have expanded the scale and resolution of pathogen monitoring, from single-species qPCR assays to community-level aerobiome surveys. Integration of biosurveillance data with decision-support systems, remote sensing, and artificial intelligence is transforming early-warning capabilities and providing novel insights into pathogen ecology, evolution, and fungicide resistance. Yet major challenges remain, including assay standardization, data interpretation, and translation into actionable tools for growers. This review synthesizes current approaches, highlights case studies in which biosurveillance has advanced disease management, and outlines future directions toward coordinated surveillance networks and precision agriculture applications.

Air Microbiology↗
PubMed2005

Roles of the polypyrimidine tract and 3' noncoding region of hepatitis C virus RNA in the internal ribosome entry site-mediated translation.

Hepatitis C virus (HCV) genome contains a 3'noncoding region (3'NCR) consisting of a variable region, a polypyrimidine tract (polyU/UC) and the X region. To examine the roles of 3'NCR and polyU/UC tract in the internal ribosome entry site (IRES)-mediated translation process, a variety of 3'NCRs containing different lengths of polyU/UC tract were obtained from HCV infected patients and cloned respectively to the downstream of the firefly luciferase coding gene linked to HCV 5'NCR and 30 nucleotides of core gene (containing IRES element). The results of in vitro translation in rabbit reticulocyte lysate (RRL) and cell transfection assay in mammalian cells showed that the IRES-mediated translation efficiency could be enhanced by the full-length of 3'NCR of HCV RNA. However, contradictory results were observed when the role of polyU/UC tract in the IRES-mediated translation was studied. While the IRES-mediated translation efficiency was inhibited by the presence of polyU/UC tract in in vitro translation experiments, transfection of these expression cassettes into hepatic cell line showed that polyU/UC tract enhanced IRES-mediated translation efficiency in vivo. Cellular-fraction complement experiments showed that cellular factors were required for the enhancement by the polyU/UC tract. Further antibody blocking assay and UV cross-linking assay suggested the correlation of IRES-mediated translation with host factors, including the La protein. The data above also indicated that the modulations of the IRES-mediated translation by the HCV 3'NCR and the polyU/UC tract were in a length-independent manner.

3' Untranslated Regions↗
PubMed2005

Change of nitric oxide in experimental colitis and its inhibition by melatonin in vivo and in vitro.

AIM: To investigate the change of nitric oxide (NO) in rat colitis and its inhibition by melatonin in vivo and in vitro. METHODS: In vivo, rat colitis was established intracolonically with trinitrobenzenesulphonic acid (TNBS) and ethanol. The animals were randomised into five groups: control group, model group, melatonin group (2.5, 5.0, 10.0 mg/kg), and treated intracolonically with saline, saline and melatonin respectively (once a day, from day 7 after colitis was established to day 28). After the end of the experiment, the mucosal damage index (CMDI) and histology score (HS) were evaluated and the level of myeloperoxidase (MPO) and malondiadehyde (MDA) and NO in the colon tissue were measured. In vitro, the co-culture model of the inflamed colon mucosa (from the colitis) with lipopolysaccharide (LPS), and the colonocytes oxidative injury model by hydroxyl radical, were designed respectively to elucidate the inhibition of NO by melatonin. RESULTS: After treated with TNBS/ethanol, the extent of CMDI and HS, the levels of MPO, MDA, and NO in the model group, were higher than that in the control group; melatonin ameliorated these parameters effectively. The stimulation of LPS increased the level of NO and MPO and MDA in the co-culture model of inflamed colon mucosa, and melatonin significantly reduced the level of MPO, MDA, and NO. In the coloncyte oxidative injury model by hydroxyl radical, the contents of LDH, MDA, and NO were increased; melatonin reversed this oxidative injury considerably. CONCLUSION: This study showed that TNBS/ethanol induced colitis was pharmacologically controlled by melatonin in vivo and in vitro.

Animals↗
PubMed2004

Bioleaching of heavy metals from anaerobically digested sewage sludge using FeS2 as an energy source.

The effect of using FeS2 as an energy source, on the bioleaching of heavy metals (Zn, Cr, Cu, Pb and Ni) and nutrients (nitrogen and phosphorus) from anaerobically digested sludge using isolated indigenous iron-oxidizing bacteria was investigated in this paper. Addition of FeS2 in the range of 0.5-4.0 g l(-1) accelerated the acidification of sludge and raised the oxidation-reduction potential of sludge medium with an inoculation of 15% (v/v) of active bacteria, thus resulting in an overall increase in metal dissolution efficiency. After 16 days of bioleaching at 28 degrees C and an initial pH of 3.0, up to 99% of Zn, 65% of Cr, 74% of Cu, 58% of Pb and 84% of Ni can be removed from the sludge. In contrast, only 94% of Zn, 12% of Cr, 21% of Cu, 32% of Pb and 38% of Ni were leached out in the control without inoculation of iron-oxidizing bacteria and the addition of FeS2. Less than 15% of nitrogen and 6% of phosphorous were lost after 16 days of bioleaching when using FeS2 as the energy source. Comparing to 39% and 45% loss respectively for these two nutrients when using FeSO4.7H2O as the energy source, FeS2 appears to be a more suitable energy source for preserving nutrients in sludge while removing heavy metals from sludge.

Acidithiobacillus↗
PubMed2003

Allopurinol inhibits CXC chemokine expression and leukocyte adhesion in endotoxemic liver injury.

OBJECTIVE: Leukocyte activation and recruitment are rate limiting steps in endotoxemic liver injury. We investigated the effect of allopurinol on the expression of CXC chemokines and leukocyte-endothelium interactions, microvascular perfusion failure, and cellular injury and apoptosis in endotoxemic liver injury. MATERIALS AND METHODS: Mice were treated with allopurinol prior to challenge with lipopolysaccharide (LPS) + D-Galactosamine (Gal). Intravital microscopy of the liver microcirculation and analysis of liver enzymes were conducted 6 h later. RESULTS: We observed that allopurinol pre-treatment reduced the number of firmly adherent leukocytes by more than 57% in postsinusoidal venules of endotoxemic mice. Indeed, endotoxin-induced liver injury enzymes were decreased by 76% and sinusoidal perfusion failure was reversed in mice pre-treated with allopurinol. Moreover, administration of allopurinol reduced LPS-induced hepatocyte apoptosis by 56%. Notably, it was found that allopurinol significantly decreased the levels of CXC chemokines (more than 83% reduction) in livers of endotoxemic mice. CONCLUSIONS: This study shows that allopurinol markedly protects against endotoxemic liver injury and indicates that reactive oxygen species (ROS) mediate synthesis of CXC chemokines and leukocyte adhesion in the liver in vivo.

Allopurinol↗
PubMed2003

T helper 2 immunity to hepatitis B surface antigen primed by gene-gun-mediated DNA vaccination can be shifted towards T helper 1 immunity by codelivery of CpG motif-containing oligodeoxynucleotides.

Gene-gun-mediated DNA immunization usually induces predominant T helper 2 (Th2) type immune response. As oligodeoxynucleotides (ODN)-containing unmethylated CpG motifs can activate the innate immune system in a Th1-biased way, the potential of codelivery of CpG motifs-containing ODN (CpG-ODN) with plasmid DNA to switch the gene-gun-mediated Th2 immune response was evaluated in this study. Here we show that codelivery of CpG-ODN with plasmid DNA at certain ratio (10/1) can enhance the Th1 humoral and cell-mediated immune responses in gene-gun-mediated DNA immunization in BALB/c mice, including increasing the hepatitis B surface antigen-specific total immunoglobulin G (IgG), IgG2a subclass, cytotoxic T-cell lymphocyte activity as well as interferon-gamma (IFN-gamma) secretion. Taken together, these results demonstrate that codelivery of CpG-ODN with recombinant plasmid DNA by gene gun can shift the gene-gun-mediated DNA immune response from Th2 towards Th1.

Adjuvants, Immunologic↗
PubMed2001

Inhibitory effects of the combination of HER-2 antisense oligonucleotide and chemotherapeutic agents used for the treatment of human breast cancer.

Poor response to chemotherapy in patients with breast cancer is often associated with overexpression of HER-2/neu. Interference with HER-2 mRNA translation by means of antisense oligonucleotides might improve the efficacy of chemotherapy. To test this hypothesis, eight breast cancer cell lines and a normal human fibroblast cell line were examined for their level of HER-2 expression, their sensitivity to phosphorothioate antisense oligonucleotides (AS HER-2 ODN), and to various chemotherapeutic agents, and the combination of the two. No correlation was found between the intrinsic HER-2 level and either the sensitivity to a particular chemotherapeutic agent alone, or the amount of growth inhibition observed with a specific AS HER-2 ODN concentration. Although sequence specificity and extent of AS HER-2 ODN inhibition of HER-2 synthesis were somewhat higher in the HER-2 overexpressing MDA-MB-453 and SK-BR-3 cells, we found that antisense treatment significantly sensitized all of the breast cancer cells, even MDA-MB-231 and MDA-MB-435 cells, with approximately basal levels of HER-2, to various chemotherapeutic agents. In addition, the combination of AS HER-2 ODN and taxol was shown to synergistically induce apoptosis in MDA-MB-435. These results demonstrate that overexpression of HER-2 would not be a prerequisite for the effective use of AS HER-2 ODN as a combination treatment modality for breast cancer and suggest that the use of AS HER-2 ODN, as part of a combination treatment modality, need not be limited to breast tumors that display elevated levels of HER-2.

Antineoplastic Agents↗
PubMed2001

[Non-anthraquinone constituents from Rheum sublanceolatum C. Y. Cheng et Kao].

OBJECTIVE: Study on the non-anthraquinone constituents from rhizoma and radix of Rheum sublanceolatum. METHOD: The constituents were isolated through column chromatography and identified on the basis of their physiochemical and spectral data. RESULT: Six non-anthraquinone constituents were isolated and identified as n-octacosanic acid, sitosterol, daucosterol, 2-methyl-5-carboxymethyl-7-hydroxychromone, piceatannol and 6-hydroxymusizin-8-O-beta-D-glucopyranoside. CONCLUSION: All these compounds were firstly isolated from R. sublanceolatum.

Plant Roots↗
PubMed2000

Removal of heavy metals from anaerobically digested sewage sludge by isolated indigenous iron-oxidizing bacteria.

The removal of heavy metals (Cr, Cu, Zn, Ni and Pb) from anaerobically digested sludge from the Yuen Long wastewater treatment plant, Hong Kong, has been studied in a batch system using isolated indigenous iron-oxidizing bacteria. The inoculation of indigenous iron-oxidizing bacteria and the addition of FeSO4 accelerated the solubilization of Cr, Cu, Zn, Ni and Pb from the sludge. pH of the sludge decreased with an increase in Fe2+ concentrations and reached a low pH of 2-2.5 for treatments receiving both bacterial inoculation and FeSO4. After 16 days of bioleaching, the following heavy metal removal efficiencies were obtained: Cr 55.3%, Cu 91.5%, Zn 83.3%, Ni 54.4%, and Pb 16.2%. In contrast, only 2.6% of Cr, 42.9% of Cu, 72.1% of Zn, 22.8% of Ni and 0.56% of Pb were extracted from the control without the bacterial inoculation and addition of FeSO4. The residual heavy metal content in the leached sludge was acceptable for unrestricted use for agriculture. The experimental results confirmed the effectiveness of using the isolated iron-oxidizing bacteria for the removal of heavy metals from sewage sludge.

Agriculture↗
PubMed2000

Progesterone inhibits glucocorticoid-induced murine thymocyte apoptosis.

Sex and sex hormones modulate immune development and responses. A primary target of their effects is the structure and cellularity of the thymus; therefore, we examined the effects of sex and sex steroids on thymocyte apoptosis. We demonstrate initially that male DBA mice have a significantly higher percentage of glucocorticoid-induced apoptotic thymocytes (46.1+/-3.8%) than their female counterparts (31.6+/-3.1%; P=0.012). We postulated that this gender difference was due to differential modulation of glucocorticoid-induced apoptosis by sex hormones such as estrogen, testosterone or progesterone. Both estrogen and testosterone increased in vitro thymocyte apoptosis. In contrast, progesterone not only inhibited spontaneous in vitro thymocyte apoptosis, but also prevented in vitro glucocorticoid-induced apoptosis. Progesterone administration also suppressed glucocorticoid-induced in vivo thymocyte apoptosis. These results suggest that anti-apoptotic effects of progesterone may influence T cell development and subsequent immune responses.

Animals↗
PubMed2000

Genetic localization and molecular characterization of the nonS gene required for macrotetrolide biosynthesis in Streptomyces griseus DSM40695.

The macrotetrolides are a family of cyclic polyethers derived from tetramerization, in a stereospecific fashion, of the enantiomeric nonactic acid (NA) and its homologs. Isotope labeling experiments established that NA is of polyketide origin, and biochemical investigations demonstrated that 2-methyl-6,8-dihydroxynon-2E-enoic acid can be converted into NA by a cell-free preparation from Streptomyces lividans that expresses nonS. These results lead to the hypothesis that macrotetrolide biosynthesis involves a pair of enantiospecific polyketide pathways. In this work, a 55-kb contiguous DNA region was cloned from Streptomyces griseus DSM40695, a 6.3-kb fragment of which was sequenced to reveal five open reading frames, including the previously reported nonR and nonS genes. Inactivation of nonS in vivo completely abolished macrotetrolide production. Complementation of the nonS mutant by the expression of nonS in trans fully restored its macrotetrolide production ability, with a distribution of individual macrotetrolides similar to that for the wild-type producer. In contrast, fermentation of the nonS mutant in the presence of exogenous (+/-)-NA resulted in the production of nonactin, monactin, and dinactin but not in the production of trinactin and tetranactin. These results prove the direct involvement of nonS in macrotetrolide biosynthesis. The difference in macrotetrolide production between in vivo complementation of the nonS mutant by the plasmid-borne nonS gene and fermentation of the nonS mutant in the presence of exogenously added (+/-)-NA suggests that NonS catalyzes the formation of (-)-NA and its homologs, supporting the existence of a pair of enantiospecific polyketide pathways for macrotetrolide biosynthesis in S. griseus. The latter should provide a model that can be used to study the mechanism by which polyketide synthase controls stereochemistry during polyketide biosynthesis.

Bacterial Proteins↗
PubMed2000

Population-specific gender-biased hybridization between Dryopteris intermedia and D. carthusiana: evidence from chloroplast DNA.

As has been shown for many kinds of organisms, barriers to interspecific hybridization may differ in strength between reciprocal crosses, resulting in a bias in the probability that one or the other species may be the maternal or paternal parent of hybrids. The fern Dryopteris Xtriploidea, the "backcross" hybrid between the diploid D. intermedia and the tetraploid D. carthusiana, occurs in large numbers in nature, providing an opportunity to investigate whether such a bias exists. Differences in the chloroplast genome distinguishing the two parental species were discovered in the sequence of the trnL region following amplification by polymerase chain reaction (PCR), including a Mse I restriction site. This allowed rapid identification of the donor of the chloroplast genome, and therefore the maternal parent of each hybrid, assuming chloroplast DNA to be maternally inherited in Dryopteris. Analysis was carried out on 127 hybrids, shown to be of independent origin using allozymes, occurring at three localities in Virginia and West Virginia. When samples from all localities were pooled, 91 possessed the D. carthusiana trnL genotype and 36 possessed the D. intermedia genotype, a ratio that is significantly different (P < 0.001) from the null hypothesis of no gender bias. The strength of the bias differed significantly among the three sites, however, with bias at the West Virginia site much stronger (5.6:1 carthusiana:intermedia; P < 0.001) than at either Virginia site (1.55:1 and 1.43:1 carthusiana:intermedia, respectively; P > 0.05 in both cases). The cause of the strong bias in the West Virginia sample is unknown, as is the cause of the population differences. Causes of bias could include differences between the parental species related to their ploidy difference, including sizes of gametes and/or gametangia, sperm motility, breeding system (D. intermedia is outcrossing while D. carthusiana is selfing), or the nature and strength of interspecific isolating mechanisms.

Journal Article↗
PubMed1999

Quantitative alleles of CR1: coding sequence analysis and comparison of haplotypes in two ethnic groups.

The quantitative expression of complement receptor type 1 (CR1) on erythrocytes is regulated by two CR1 alleles that differ in having genomic HindIII fragments of either 7.4 or 6.9 kb and that determine high (H allele) or low (L allele) CR1 expression, respectively, across a 10-fold range. To investigate whether the product of the L allele may contain amino acid substitutions that make it more susceptible to proteolysis, cDNA sequence spanning the CR1 coding region was analyzed in two donors who were homozygous for the H and L alleles and differed by 7-fold in their mean numbers of CR1 per erythrocyte. Sequence differences were detected at 10 nucleotide positions, including 6 that would cause amino acid substitutions. The HindIII RFLP and 3 of the latter 6 sites were analyzed in genomic DNA of 85 Caucasians and 75 African Americans; sites encoding the other amino acid substitutions were analyzed less extensively. Two major haplotypes defined prototypic H and L alleles in both ethnic groups, suggesting that these alleles existed before the African and European populations diverged. Decreased erythrocyte CR1 expression is associated with impaired clearance of immune complexes from blood. Persistence of the L allele in all populations that have been analyzed may suggest a compensatory survival advantage, perhaps related to malaria or another infectious disease.

Alleles↗
PubMed1999

Expression of transthyretin gene in Pichia pastoris.

Plasmid pSK-TTR was digested by BamHI and the DNA fragment containing Transthyretin gene was cloned into the BamHI site of vector pHIL-SI. The recombinant plasmid pHIL-SI-TTR was digested by BglII; the larger fragment was transformed into yeast Pichia pastoris. SDS-PAGE analysis showed that the yeast transformant can express and secrete TTR as a fusion protein, TTRF. To purify TTRF,the DEAE-Sepherose F.F. chromatography and Sephacryl S-200 chromatography were used. The in vitro test showed that TTRF could inhibit the growth of human hepatoma cells.

Antineoplastic Agents↗
PubMed1999

[Prevalence of blindness among adults aged 50 years or above in Shunyi county of Beijing].

OBJECTIVE: To estimate the prevalence of blindness among older adults aged >or= 50 years in Shunyi county of Beijing, China. METHODS: Cluster sampling was used in randomly selecting individuals aged >or= 50 years in 28 villages in Shunyi county in fall, 1996. The survey was preceded by a pilot study where operational methods were refined and quality assurance evaluation was carried out. RESULTS: 5,555 individuals were enumerated. The response rate was 91.5%. In this population, the prevalence of blindness was 1.7% defined as pinhole visual acuity < 0.05 in both eyes; or 2.8% were blind, defined as presenting visual acuity < 6/60 in both eyes. Blindness was associated with older age and female gender. The principal cause of blindness in eyes was cataract. CONCLUSIONS: The prevalence of blindness was decreased 35.8% after ten year active eye-care program in the survey area. However, cataract blindness continues as a significant problem among elderly, especially females, in this population sample of rural area.

Age Factors↗
PubMed1999

[Safety analysis of dust mite allergen for diagnosis and immunotherapy of asthma and rhinitis].

AIM: To make a retrieval investigation of safety in using Dermatophagoides farinae extract in diagnosis and immunotherapy with patients of asthma and rhinitis. METHODS: A questionnaire evaluation of the safety use of D. farinae extract (SMU-Df) during diagnosis and immunotherapy of patients from 1974 to 1995 was carried out. RESULTS: A total of 8,46,342 injections were statistically analysed, among whom 142 systemic adverse reactions occurred involving urticaria 0.82@10000, severe attack of asthma 0.77@10000, anaphylactic shock 0.07@10000 (CL = 1.4-12.0/million), and angioedma 0.02@10000. The time of onset of systemic reactions of immediate type was < 30 min in 32 cases-times, and 1 h and 2 h in 6 cases-times; the time to onset of late response type was 3 h-48 h in 23 cases-times with highest incidence of severe asthmatic attacks. The systemic reactions occurred in 18 subjects during skin test, in 96 cases-times during increasing dose phase, and in 14 cases-times during. Among them 6 cases were of anaphylactic shock, and none of it after emergency treatment. The major cause of manifestation of systemic reactions for 41 cases after immunotherapy with SMU-Df extract was due to over dosage errors. CONCLUSION: The application of SMU-Df extract in skin test and immunotherapy of asthma and rhinitis sensitive to mite for the past 22 years in this country indicated that the efficacy and safety have been high.

Allergens↗