Biomedical subjects

D Zhang

Publications and source records attributed to D Zhang.

At least 37 records · Page 2Linked to original sources

PubMed2004

Assessing temporal changes in genetic diversity of maize varieties using microsatellite markers.

To quantify genetic diversity among modern and earlier maize cultivars, 133 varieties, representative of the maize grown in France during the last five decades, were fingerprinted using 51 SSR. The varieties were grouped into four periods. For each period, allelic richness, genetic diversity and genetic differentiation among periods were computed. A total of 239 alleles were generated. Allelic richness, in terms of number of alleles per locus, for each period was 4.5, 3.6, 3.9 and 3.6 respectively. Genetic diversity corresponding to Nei's unbiased heterozygosity was calculated, based on allelic frequencies. Values ranged from 0.56 to 0.61. Period I presented the highest genetic diversity, whereas the three other periods all presented a similar value. A great proportion of the total genetic diversity (H(T)=0.59) was conserved within all periods (H(S)=0.57), rather than among periods (G(ST)=0.04). The analysis of molecular variance showed that the variation among periods represented only 10% of the total molecular variation. However, the differentiation among periods, although low, was significant, except for the last two periods. Our results showed that the genetic diversity has been reduced by about 10% in the maize cultivars bred before 1976 compared to those bred after 1985. The very low differentiation (G(ST)=0.21%) observed among cultivars of the last two decades should alert French maize breeders to enlarge genetic basis in their variety breeding programmes.

Breeding↗

PubMed2004

Cardiac disease due to random mitochondrial DNA mutations is prevented by cyclosporin A.

Mice expressing an error-prone mitochondrial DNA polymerase rapidly accumulate random mutations in mitochondrial DNA. Expression of the transgene in the heart leads to dilated cardiomyopathy accompanied by a wave of apoptosis in cardiomyocytes, and a vigorous and persistent protective response, including upregulation of the anti-apoptotic protein, Bcl-2. To investigate the role of the mitochondrial permeability transition pore in the development of disease, we treated mice with cyclosporin A (CsA), an inhibitor of pore opening. Drug treatment prevented cardiac dilatation, transgene-specific apoptosis, and upregulation of Bcl-2. It also rescued hearts from the profound decrease in connexin 43, which characterizes the dilatated heart. Treatment with FK506, which like CsA inhibits cytoplasmic calcineurin but not the mitochondrial pore, did not affect disease development, suggesting that the relevant target of CsA was the mitochondrial pore. These data implicate breakdowns in the mitochondrial permeability barrier in pathogenesis of elevated frequencies of mtDNA mutations.

Animals↗

PubMed2004

Silica-nanoparticle-based interface for the enhanced immobilization and sequence-specific detection of DNA.

A biocompatible and uniform interface based on silica nanoparticles derivatized with amino groups has been constructed for the effective immobilization and sensitive sequence-specific detection of calf thymus DNA. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) results showed that a monolayer of silica nanoparticles can be formed on a gold electrode under our experimental conditions using cysteine self-assembly monolayer as binder medium. Electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy (XPS) verified the successful immobilization of DNA on silica-nanoparticle-modified gold electrodes. Quantitative results demonstrated that enhanced immobilization of single-strand DNA (ss-DNA) up to 1.6 x 10(-8) mol cm(-2) could be achieved owing to the larger surface area and the special properties of silica nanoparticles. In addition, hybridization experiments demonstrated that the immobilized ss-DNA on silica nanoparticles could specifically interact with complementary DNA in solutions.

Animals↗

PubMed2004

Treatment of the yeast Rhodotorula glutinis with AlCl(3) leads to adaptive acquirement of heritable aluminum resistance.

When aluminum (Al) was added to a culture, growth of Rhodotorula glutinis IFO1125 was temporarily arrested, showing longer lag phases, depending on the Al concentrations (50-300 microM) added, but the growth rates were not affected at all. Resistant strains obtained by one round of plate treatment containing Al reverted the resistance level to the wild-type level when cultivated without Al. Repeated Al treatments, however, induced heritable and stable Al resistance, the level of which was increased up to 4,000 microM by stepwise increments in Al concentrations. Thus, the heritable Al resistance adaptively acquired was due neither to adaptation nor to mutation, but to a mechanism which has yet to be studied. Heritable Al resistance seemed to release the Al inhibition of magnesium uptake.

Adaptation, Physiological↗

PubMed2004

1-3 connectivity piezoelectric ceramic-polymer composite transducers made with viscous polymer processing for high frequency ultrasound.

Potential applications of high frequency ultrasound exist because of the high spatial resolution consequent upon short wavelength. The frequencies of interest, typically from 25 MHz upwards, are easily supported by modern instrumentation but the capabilities of ultrasonic transducers have not kept pace and the transducers in high frequency commercial ultrasonic systems are still made with single-phase crystal, ceramic or piezopolymer materials. Despite potential performance advantages, the 1-3 connectivity piezoelectric ceramic-polymer composite materials now widely used at lower ultrasonic frequencies have not been adopted because of manufacturing difficulties. These difficulties are centred on fabrication of the 1-3 piezoceramic bristle-block comprising tall, thin pillars upstanding from a supporting stock. Fabrication techniques which have been explored already include injection moulding, mechanical dicing, and laser machining. Here, we describe an alternative technique based on viscous polymer processing (VPP) to produce net shape ceramic bristle-blocks. VPP produces green-state ceramic with rheological properties suitable for embossing. We outline how this can be created then report on our work to fabricate PZT bristle-blocks with lateral pillar dimensions of the order of 50 microm and height-to-width ratios of the order of 10. These have been backfilled with low pre-cure viscosity polymer and made into complete 1-3 piezocomposite transducer elements. We outline the performance of the transducers in terms of electrical impedance and pulse-echo behaviour and show that it corresponds well with computer modelling. We conclude that VPP is a promising technique to allow the established advantages of piezocomposite material to be exploited at higher frequencies than have been possible so far.

Journal Article↗

PubMed2004

The expression of osteoprotegerin and the receptor activator of nuclear factor kappa B ligand in human periodontal ligament cells cultured with and without 1alpha,25-dihydroxyvitamin D3.

The receptor activator of nuclear factor kappa B ligand (RANKL) and its decoy receptor, osteoprotegerin (OPG), are important bone metabolism molecules, which directly control osteoclastogenesis. Periodontal ligament (PDL) cells play a vital role in maintaining the homeostasis of periodontal tissues, releasing cytokines to affect bone metabolism. The purpose of this study was to investigate the expression of OPG and RANKL in cultured human periodontal ligament cells (hPDLCs) derived from permanent teeth and the expression change after stimulation by 1alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)vitD(3)), a kind of bone resorption promoter. HPDLCs were cultured in the presence or absence of 10(-8)M 1alpha,25(OH)(2)vitD(3) in vitro. The expression of mRNA for OPG and RANKL in hPDLCs during 6 days' culture was examined using semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). The level of secreted OPG protein in the culture medium during 6 days' culture was detected by enzyme-linked immunoabsorbent assay (ELISA). The result showed that OPG and RANKL were expressed by hPDLCs. OPG expression was down-regulated by 10(-8)M 1alpha,25(OH)(2)vitD(3) in a time-dependent manner, while RANKL mRNA was up-regulated. The ratio of OPG/RANKL was decreased. In conclusion, our findings suggest that hPDLCs may regulate the alveolar bone metabolism through the OPG/RANKL system.

Adolescent↗

PubMed2004

Pool of dust particles over the Asian continent: balloon-borne optical particle counter and ground-based lidar measurements at Dunhuang, China.

Measurements of aerosols were made in 2001 and 2002 at Dunhuang (40 degrees 00'N, 94 degrees 30'E), China to understand the nature of atmospheric particles over the desert areas in the Asian continent. Balloon-borne measurements with an optical particle counter suggested that particle size and concentration had noticeable peaks in super micron size range not only in the boundary mixing layer but also in the free troposphere. Super-micron particle concentration largely decreased in the mid tropopause (from 5 to 10 km; above sea level, a.s.l.). Lidar measurements made during August 2002 at Dunhuang suggested the possibility that mixing of dust particles occurred from near the ground to about 6 km even under calm weather conditions, and a large depolarization ratio of particulate matter was found in the aerosol layer. The top of the aerosol layer was found at heights of nearly 6 km (a.s.l.). It is strongly suggested that nonspherical dust particles (Kosa particles) frequently diffused in the free atmosphere over the Taklamakan desert through small-scale turbulences and are possible sources of dust particles of weak Kosa events that have been identified in the free troposphere not only in spring but also in summer over Japanese archipelago. Electron microscopic experiments of the particles collected in the free troposphere confirmed that coarse and nonspherical particles observed by the mineral particle were major components of coarse mode (diameter larger than 1 microm) below about 5 km over Dunhuang, China.

Aerosols↗

PubMed2004

GM1 ganglioside regulates the proteolysis of amyloid precursor protein.

Plaques containing amyloid beta-peptides (Abeta) are a major feature in Alzheimer's disease (AD), and GM1 ganglioside is an important component of cellular plasma membranes and especially enriched in lipid raft. GM1-bound Abeta (GM1/Abeta), found in brains exhibiting early pathological changes of AD including diffuse plaques, has been suggested to be involved in the initiation of amyloid fibril formation in vivo by acting as a seed. However, the role of GM1 in amyloid beta-protein precursor (APP) processing is not yet defined. In this study, we report that exogenous GM1 ganglioside promotes Abeta biogenesis and decreases sAPPalpha secretion in SH-SY5Y and COS7 cells stably transfected with human APP695 cDNA without affecting full-length APP and the sAPPbeta levels. We also observe that GM1 increases extracellular levels of Abeta in primary cultures of mixed rat cortical neurons transiently transfected with human APP695 cDNA. These findings suggest a regulatory role for GM1 in APP processing pathways.

Amyloid Precursor Protein Secretases↗

PubMed2004

Construction and evaluation of cDNA libraries for large-scale expressed sequence tag sequencing in wheat (Triticum aestivum L.).

A total of 37 original cDNA libraries and 9 derivative libraries enriched for rare sequences were produced from Chinese Spring wheat (Triticum aestivum L.), five other hexaploid wheat genotypes (Cheyenne, Brevor, TAM W101, BH1146, Butte 86), tetraploid durum wheat (T. turgidum L.), diploid wheat (T. monococcum L.), and two other diploid members of the grass tribe Triticeae (Aegilops speltoides Tausch and Secale cereale L.). The emphasis in the choice of plant materials for library construction was reproductive development subjected to environmental factors that ultimately affect grain quality and yield, but roots and other tissues were also included. Partial cDNA expressed sequence tags (ESTs) were examined by various measures to assess the quality of these libraries. All ESTs were processed to remove cloning system sequences and contaminants and then assembled using CAP3. Following these processing steps, this assembly yielded 101,107 sequences derived from 89,043 clones, which defined 16,740 contigs and 33,213 singletons, a total of 49,953 "unigenes." Analysis of the distribution of these unigenes among the libraries led to the conclusion that the enrichment methods were effective in reducing the most abundant unigenes and to the observation that the most diverse libraries were from tissues exposed to environmental stresses including heat, drought, salinity, or low temperature.

Expressed Sequence Tags↗

PubMed2004

Targeted degradation of proteins by small molecules: a novel tool for functional proteomics.

A novel strategy that targets protein for degradation has recently been developed by exploiting a protein-targeting chimeric molecule ('Protac'). Typically, the chimeric Protac is composed of a small-molecule ligand ('bait') on one end and a synthetic octapeptide on the other. This octapeptide is recognized by E3 ubiquitin ligase pVHL (von Hippel Lindau tumor suppressor protein), thereby recruiting a small molecule-bound protein ('prey') to pVHL for ubiquitination and degradation. Since selective degradation of a cellular protein generates a "loss of function" mutation, this protein knock-out strategy may be useful to study the function of a given protein or to evaluate whether a cellular protein is a potential target for drug intervention, in a manner reminiscent of gene knock-out or siRNA approaches. Herein, we show that a synthetic pentapeptide is sufficient to interact with pVHL E3 ligase, and that the pentapeptide-based Protac efficiently induces ubiquitination and degradation of target protein. Our results also demonstrate that the pentapeptide-based Protac can enter cells efficiently to exerts its biological activity effectively. These results suggest that the synthetic pentapeptide can be used either directly in the preparation of cell-permeable Protacs or as a template to develop peptidomimetic or non-peptide Protacs.

Blotting, Western↗

PubMed2004

Nitrogen removal from sludge reject water by a two-stage oxygen-limited autotrophic nitrification denitrification process.

Nitrogen removal from sludge reject water was obtained by oxygen-limited partial nitritation resulting in nitrite accumulation in a first stage, followed by autotrophic denitrification of nitrite with ammonium as electron donor (similar to anaerobic ammonium oxidation) in a second stage. Two membrane-assisted bioreactors (MBRs) were used in series to operate with high sludge ages and subsequent high volumetric loading rates, achieving 1.45 kg N m(-3) day(-1) for the partial nitritation MBR and 1.1 kg N m(-3) day(-1) for the anaerobic ammonium oxidation MBR. Biomass retention in the nitritation stage ensured flexibility towards loading rate and operating temperature. Nitrite oxidisers were out-competed at low oxygen and high free ammonia concentration. Biomass retention in the second MBR prevented wash-out of the slowly growing bacteria. Nitrite and ammonium were converted to dinitrogen gas in a reaction ratio of 1.05, thereby maintaining nitrite limitation to assure process stability. The anoxic consortium catalysing the autotrophic denitrification process consisted of Nitrosomonas-like aerobic ammonium oxidizers and anaerobic ammonium oxidizing bacteria closely related to Kuenenia stuttgartiensis. The overall removal efficiency of the combined process was 82% of the incoming ammonium according to a total nitrogen removal rate of 0.55 kg N m(-3) day(-1), without adding extra carbon source.

Bacteria, Anaerobic↗

PubMed2003

Genetic mapping in (Populus tomentosa x Populus bolleana) and P. tomentosa Carr. using AFLP markers.

The AFLP genetic linkage maps for two poplar cultivars were constructed with the pseudo-test-cross mapping strategy. The hybrids were derived from an interspecific backcross between the female hybrid clone "TB01" (Populus tomentosa x Populus bolleana) and the male clone "LM50" ( P. tomentosa). A total of 782 polymorphic fragments were obtained with a PCR-based strategy using 49 enzyme-nested ( EcoRI/ MseI) primer combinations. Six hundred and thirty two of these fragments segregated in a 1:1 ratio ( P<0.01), indicating that these DNA polymorphisms are heterozygous in one parent and null in the other. The linkage analysis was performed using Mapmaker version 3.0 with LOD 5.0 and a maximum recombination fraction (theta) of 0.3. Map distances were estimated using the Kosambi mapping function. In the framework map for "LM50" (P. tomentosa), 218 markers were aligned in 19 major linkage groups. The linked loci spanned approximately 2,683 cM of the poplar genome, with an average distance of 12.3 cM between adjacent markers. For "TB01" (P. tomentosa x P. bolleana), the analysis revealed 144 loci, which were mapped to 19 major linkage groups and covered about 1,956 cM, with an average distance of 13.6 cM between adjacent markers. These maps covered about 87% and 77% of the estimated genome size of parents "LM50" and "TB01", respectively. The maps developed in this study lay an important foundation for future genomics research in poplar, providing a means for localizing genes controlling economically important traits in P. tomentosa.

Chromosome Mapping↗

PubMed2003

Preimplantation genetic diagnosis.

Preimplantation genetic diagnosis (PGD) is an exciting new approach for the prevention of transmission of genetic disorders between generations. The use of genetically screened, healthy embryos to establish a pregnancy avoids the need for termination of an affected pregnancy, a procedure which can be traumatic physically and emotionally for potential patients, and is sometimes not available when needed. PGD usually follows the processes of ovarian hyperstimulation and in vitro fertilization (IVF). After carrying out appropriate genetic tests, only normal embryos are transferred to the patient's uterus to achieve an unaffected pregnancy and the birth of a healthy infant.

China↗

PubMed2003

Alpha-1-antitrypsin expression in the lung is increased by airway delivery of gene-transfected macrophages.

Inadequate antiprotease activity in the lungs due to alpha-1-antitrypsin (A1AT) deficiency is a factor of early-onset emphysema. We propose a new approach to gene therapy that involves the intratracheal delivery of macrophages expressing human A1AT (hA1AT). Recombinant adeno-associated virus (rAAV) plasmids encoding the hA1AT gene were packaged into virions using 293 cells, and transgenic progeny virus was purified from the cells. The murine macrophage cell line J774A.1 was infected in vitro with the recombinant hA1AT rAAV virus. The hA1AT-producing macrophages were delivered intratracheally into mechanically ventilated C57BL/6J mice, a strain with low endogenous levels of A1AT. Transcription of hA1AT mRNA was detected in the transfected cells by RT-PCR, and protein expression was verified by immunohistochemistry. Levels of hA1AT in the cell culture medium and in the bronchoalveolar lavage (BAL) were assayed by ELISA. The concentration of hA1AT in J774A.1 cell-conditioned medium increased from undetectable levels prior to transfection, to 60 mg/l at 24 h post-transfection. At 1, 3 and 7 days after intratracheal delivery of transfected macrophages, hA1AT protein in BAL from C57BL/6J mice increased from undetectable levels to 2.5+/-0.9, 2.6+/-1.1 and 2.2+/-0.8 mg/l, respectively. These results suggest that airway delivery of macrophages overexpressing hA1AT may be an effective approach to enhance alveolar protection in A1AT deficiency.

Administration, Inhalation↗

PubMed2003

Association study of neuregulin 1 gene with schizophrenia.

A number of studies have indicated that 8p22-p12 is likely to harbor schizophrenia susceptibility loci. In this region, the candidate gene of interest, neuregulin 1 (NRG1), may play a role in the pathogenesis of schizophrenia. Then in the present study, we performed the linkage disequilibrium to determine the association between three genetic variants (SNPs: rs3924999, rs2954041, SNP8NRG221533) on NRG1 gene and schizophrenia in 246 Chinese Han schizophrenic family trios using PCR-based restriction fragment length polymorphism method and denaturing high-performance liquid chromatography. The transmission disequilibrium test analysis for each variant showed a significant difference between two transmitted alleles even after Bonferroni correction (rs3924999, P=0.007752; rs2954041, P=0.0009309; SNP8NRG221533, P=0.012606). The global chi(2) test for haplotype transmission also revealed a strong association (chi(2)=46.068, df=7, P&<0.000001). Our results suggest that the NRG1 gene may play a role in conferring susceptibility to the disease.

Adult↗

PubMed2003

Immunocytochemistry versus molecular fingerprinting of metastases.

Examination of cytological samples of cancer to suggest a possible primary site of origin is one of the commonest and most difficult tasks of diagnostic cytopathologists. Currently, both cytomorphology and immunocytochemistry are the main approaches to this diagnostic dilemma. We report the application of microsatellite analysis in cytological samples in a patient with a primary colonic tumour and two subsequent lung nodules, which were suspected on CT scans of the chest, and compared the findings with those obtained with conventional immunocytochemistry. The molecular results were in agreement with the radiological impression and conflicted with the immunocytochemistry. We conclude that immunocytochemical and molecular biology approaches to the diagnosis of tumours may give rise to contradictory results.

Adenocarcinoma↗

PubMed2003

Substrate induction of isomaltulose synthase in a newly isolated Klebsiella sp. LX3.

AIMS: Production of isomaltulose by newly isolated Klebsiella sp. LX3. METHODS AND RESULTS: The bacterial isolate LX3, which transforms sucrose to isomaltulose and trehalulose, has been isolated from a soil sample in Singapore. Morphological and biochemical analysis, as well as 16s rRNA sequence demonstrated that the isolate could represent a new member of genus Klebsiella. The strain has several interesting features. The immobilized cells of Klebsiella sp. LX3 convert more than 99% of sucrose to products that consist of more than 87% of isomaltulose, 11.6% of trehalulose, and <1% of glucose. CONCLUSIONS: The production of isomaltulose synthase in isolate LX3 is inducible by its substrate sucrose and the sugars containing a fructofuranosyl group. SIGNIFICANCE AND IMPACT OF STUDY: It would be useful for future biotechnological applications to understand the structural features or motifs of the isomaltulose synthases that determine the sucrose conversion efficiency and the ratio of the conversion products.

Bacteriological Techniques↗

PubMed2003

The vibrio pathogenicity island of epidemic Vibrio cholerae forms precise extrachromosomal circular excision products.

The Vibrio pathogenicity island (VPI) in epidemic Vibrio cholerae is an essential virulence gene cluster. Like many pathogenicity islands, the VPI has at its termini a phage-like integrase gene (int), a transposase-like gene (vpiT), and phage-like attachment (att) sites, and is inserted at a tRNA-like locus (ssrA). We report that the VPI precisely excises from the chromosome and that its left and right ends join to form an extrachromosomal circular excision product (pVPI). Two-stage nested PCR analysis and DNA sequencing confirmed the int-att-vpiT junction and that the core attP of pVPI is identical to the chromosomal VPI attR site. Excision was independent of toxR and toxT. Excision was independent of recA, suggesting that it is mediated by site-specific recombination. Interestingly, while excision was detected in int and vpiT mutants, excision was abolished in a double (int vpiT) mutant and was restored by plasmids containing genes for either recombinase. Excision results in deletion of A361 in the ssrA locus, which flanks the right junction of the VPI. Since A361 encodes U70 in the critical G. U base pair in the acceptor stem of the ssrA RNA that is the determinant for aminoacylation with alanine, this deletion might have deleterious effects on ssrA function. Also, vpiT may have undergone interchromosomal translocation or may represent an independent integration event, as it was found downstream of hutA in some isolates. Our results provide new insight into the molecular biology of the VPI, and we propose that the process of excision and circularization is important in the emergence, pathogenesis, and persistence of epidemic V. cholerae.

Chromosomes, Bacterial↗