Biomedical subjects

X Dong

Publications and source records attributed to X Dong.

At least 73 records · Page 4Linked to original sources

PubMed2001

Constitutive disease resistance requires EDS1 in the Arabidopsis mutants cpr1 and cpr6 and is partially EDS1-dependent in cpr5.

The systemic acquired resistance (SAR) response in Arabidopsis is characterized by the accumulation of salicylic acid (SA), expression of the pathogenesis-related (PR) genes, and enhanced resistance to virulent bacterial and oomycete pathogens. The cpr (constitutive expressor of PR genes) mutants express all three SAR phenotypes. In addition, cpr5 and cpr6 induce expression of PDF1.2, a defense-related gene associated with activation of the jasmonate/ethylene-mediated resistance pathways. cpr5 also forms spontaneous lesions. In contrast, the eds1 (enhanced disease susceptibility) mutation abolishes race-specific resistance conferred by a major subclass of resistance (R) gene products in response to avirulent pathogens. eds1 plants also exhibit increased susceptibility to virulent pathogens. Epistasis experiments were designed to explore the relationship between the cpr- and EDS1-mediated resistance pathways. We found that a null eds1 mutation suppresses the disease resistance phenotypes of both cpr1 and cpr6. In contrast, eds1 only partially suppresses resistance in cpr5, leading us to conclude that cpr5 expresses both EDS1-dependent and EDS1-independent components of plant disease resistance. Although eds1 does not prevent lesion formation on cpr5 leaves, it alters their appearance and reduces their spread. This phenotypic difference is associated with increased pathogen colonization of cpr5 eds1 plants compared to cpr5. The data allow us to place EDS1 as a necessary downstream component of cpr1- and cpr6-mediated responses, but suggest a more complex relationship between EDS1 and cpr5 in plant defense.

Arabidopsis↗

PubMed2001

Preliminary results from an EIT breast imaging simulation system.

An electrical impedance tomography (EIT) simulation system for breast imaging has been developed using impedance data from a previous study and a finite-element model (FEM). This system has the functionality to construct various models of the breast, image the boundary voltages developed from any injection schema and provide parametric Cole-Cole modelling. Simulations indicate that breast carcinoma can be imaged and multi-frequency Cole-Cole dispersion data can be extracted. This is intended as the first stage towards providing an artificial intelligence based system capable of producing clinically relevant analytical data.

Algorithms↗

PubMed2001

Activation of an EDS1-mediated R-gene pathway in the snc1 mutant leads to constitutive, NPR1-independent pathogen resistance.

The Arabidopsis NPR1 protein is an essential regulatory component of systemic acquired resistance (SAR). Mutations in the NPR1 gene completely block the induction of SAR by signals such as salicylic acid (SA). An Arabidopsis mutant, snc1 (suppressor of npr1-1, constitutive 1), was isolated in a screen for suppressors of npr1-1. In the npr1-1 background, the snc1 mutation resulted in constitutive resistance to Pseudomonas syringae maculicola ES4326 and Peronospora parasitica Noco2. High levels of SA were detected in the mutant and shown to be required for manifestation of the snc1 phenotype. The snc1 mutation was mapped to the RPP5 resistance (R) gene cluster and the eds1 mutation that blocks RPP5-mediated resistance suppressed snc1. These data suggest that a RPP5-related resistance pathway is activated constitutively in snc1. This pathway does not employ NPR1 but requires the signal molecule SA and the function of EDS1. Moreover, in snc1, constitutive resistance is conferred in the absence of cell death, which is often associated with R-gene mediated resistance.

Arabidopsis↗

PubMed2001

New approach to phylogenetic analysis of the genus Bifidobacterium based on partial HSP60 gene sequences.

The partial 60 kDa heat-shock protein (HSP60) genes of 36 Bifidobacterium strains representing 30 different Bifidobacterium species and subspecies and of the type strain of Gardnerella vaginalis were cloned and sequenced using a pair of universal degenerate HSP60 PCR primers. The HSP60 DNA sequence similarities were determined for the taxa at various ranks as follows: 99.4-100% within the same species, 96% at the subspecies level, and 73-96% (mean 85%) at the interspecies level (and 98% in the case of two groups of closely related species, Bifidobacterium animalis and Bifidobacterium lactis, Bifidobacterium infantis, Bifidobacterium longum and Bifidobacterium suis, whose 165 rRNA sequence similarities are all above 99%). The HSP60 DNA sequence similarities between different Bifidobacterium species and G. vaginalis, a closely related bacterium according to 16S rRNA analysis, ranged from 71 to 79% (mean 75%). Although the topology of the phylogenetic tree constructed using the HSP60 sequences determined was basically similar to that for 16S rRNA, it seemed to be more clear-cut for species delineation, and the clustering was better correlated with the DNA base composition (mol% G+C) than that of the 16S rRNA tree. In the HSP60 phylogenetic tree, all of the high-G+C (55-67 mol%) bifidobacteria were grouped into one cluster, whereas the low-G+C species Bifidobacterium inopinatum (45 mol %) formed a separate cluster with G. vaginalis (42 mol%) and Bifidobacterium denticolens (55 mol%); a Bifidobacterium species of intermediate G+C content formed another cluster between the two. This study demonstrates that the highly conserved and ubiquitous HSP60 gene is an accurate and convenient tool for phylogenetic analysis of the genus Bifidobacterium.

Animals↗

PubMed2001

Functional conservation of plant secondary metabolic enzymes revealed by complementation of Arabidopsis flavonoid mutants with maize genes.

Mutations in the transparent testa (tt) loci abolish pigment production in Arabidopsis seed coats. The TT4, TT5, and TT3 loci encode chalcone synthase, chalcone isomerase, and dihydroflavonol 4-reductase, respectively, which are essential for anthocyanin accumulation and may form a macromolecular complex. Here, we show that the products of the maize (Zea mays) C2, CHI1, and A1 genes complement Arabidopsis tt4, tt5, and tt3 mutants, restoring the ability of these mutants to accumulate pigments in seed coats and seedlings. Overexpression of the maize genes in wild-type Arabidopsis seedlings does not result in increased anthocyanin accumulation, suggesting that the steps catalyzed by these enzymes are not rate limiting in the conditions assayed. The expression of the maize A1 gene in the flavonoid 3' hydroxylase Arabidopsis tt7 mutant resulted in an increased accumulation of pelargonidin. We conclude that enzymes involved in secondary metabolism can be functionally exchangeable between plants separated by large evolutionary distances. This is in sharp contrast to the notion that the more relaxed selective constrains to which secondary metabolic pathways are subjected is responsible for the rapid divergence of the corresponding enzymes.

Acyltransferases↗

PubMed2001

Treatment of fungal keratitis by penetrating keratoplasty.

AIM: To study the use of penetrating keratoplasty (PKP) for the treatment of severe fungal keratitis that could not be cured by antifungal medication. METHODS: A retrospective analysis of 108 cases of severe fungal keratitis in which PKP was performed served as the basis for this study. Fungal keratitis was diagnosed by KOH staining of corneal scrapings or by confocal microscopic imaging of the cornea. All patients received a combination of topical and oral antifungal medicines without steroids as the first course of therapy. Patients whose corneal infection was not cured or in whom the infection progressed during antifungal treatment were given a PKP. After surgery, the patients continued to receive antifungal therapy with gradual tapering of the dose over a 1-2 month period. Cyclosporine was used to prevent graft rejection beginning 2 weeks after PKP. Topical steroid only was administered to the patient whose donor graft was over 8.5 mm and with a heavy iris inflammation 2 weeks after PKP. The surgical specimens were used for microbiological evaluation and examined histopathologically. The patients were followed for 6-24 months after PKP. Graft rejection, clarity of the graft, visual acuity, and surgical complications were recorded. RESULTS: Corneal grafts in 86 eyes (79.6%) remained clear during follow up. There was no recurrence of fungal infection and the visual acuity ranged from 40/200 to 20/20. Complications in some patients included recurrent fungal infection in eight eyes (7.4%), corneal graft rejection in 32 eyes (29.6%), secondary glaucoma in two eyes (1.9%), and five eyes (4.6%) developed cataracts. 98 of 108 of the recipient corneas had PAS positive fungal hyphae in tissue sections; 97 of 108 were culture positive for various fungi, including Fusarium (63), Aspergillus (14), Candida (9), Penicillium (4), and seven cases in which septate hyphae were seen but identification of the organism was not conclusive. CONCLUSIONS: PKP is an effective treatment for fungal keratitis that does not respond to antifungal medication. Early surgical intervention before the disease becomes advanced is recommended. It is critical that the surgical procedure remove the infected tissue in its entirety in order to effect a cure.

Adult↗

PubMed2001

Genomic structure, chromosome mapping and expression analysis of the human AXIN2 gene.

Conductin is a Wnt signalling protein and serves as a negative regulator of beta-catenin stability. We have previously isolated the human homolog (AXIN2) of the murine conductin gene and shown that it is mutated in colorectal cancer (CRC) with defective mismatch repair (MMR). Here we report the detailed genomic structure of this gene by analysis of cDNA and genomic clones. The gene spans > or =25 kb containing ten exons ranging from 96 bp to 904 bp. All splice donor and acceptor sites conform to the GT/AG rule. FISH (Fluorescence in situ Hybridization) analysis localized this gene to human chromosome band 17q24 and showed that it exists as a single copy in the human genome. Northern blot analysis from different human organs demonstrated that the AXIN2 gene is highly expressed in human thymus, prostate, testis, small intestine and ovarian tissues but expressed at a lower level in colon. The data reported here provides a framework for further analysis of this important Wnt signalling protein in vertebrate development and tumorigenesis.

Axin Protein↗

PubMed2001

Superparamagnetic properties of carbon-encapsulated Ni nanoparticle assemblies.

Carbon-encapsulated Ni nanoparticles [Ni(C)] were synthesized using a modified arc-discharge reactor under methane atmosphere. The average particle size was revealed to be typically 10.5 nm with a spherical shape. The intimate and contiguous carbon fringe around these Ni nanoparticles is good evidence for complete encapsulation by carbon shell layers. Superparamagnetic property studies indicate that the blocking temperature (TB) is around 115 K at 1000 Oe applied field. Below TB, the temperature dependence of the coercivity is given by Hc = Hci[1 -(T/TB)1/2], with Hci approximately 500 Oe. Above TB, the magnetization M(H, T) can be described by the classical Langevin function L using the relationship M/Ms(T = 0) = coth(microH/kT)-kT/microH. The particle size can be inferred from the Langevin fit (particle moment mu) and the blocking temperature theory (TB), with values slightly larger than the high-resolution transmission electron microscopy observations. It is suggested that these assemblies of carbon-encapsulated Ni nanoparticles have typical single-domain, field-dependent superparamagnetic relaxation properties.

Carbon↗

PubMed2001

[Simulation study of electrode configurations for cardiac stroke volume calculation by 3-dimensional finite element method].

This is a research in Kubicek electrode configurations for cardiac stroke volume calculation from the angle of Kubicek model simulation by 3-dimensional finite element method. In the process of computer simulation, we have studied, respectively, the effect of the width, thickness, and material property (specific resistance) of potential electrode band on cardiac stroke volume calculation in order to guide the choice of electrode configurations in the clinic. The simulation results showed that in Kubicek electrode configurations, its all properties of the potential electrode band affected the impedance results for cardiac stroke volume calculation, one main factor of which is the choice of the material property. Therefore, we have to attend to the choice of Kubicek electrode configurations while calculating SV by Kubicek method in order to improve the accuracy of SV calculation.

Electrodes↗

PubMed2001

5-HT1B receptor augmented 5-HT vasoconstrictor response of pulmonary artery in monocrotaline-induced pulmonary hypertensive rats.

AIM: To study the relationship between the vasoconstrictor effect to 5-hydroxytryptamine (5-HT) and the expression of 5-HT1B-and 5-HT1D)-receptors in pulmonary arteries (PA) from normal and pulmonary hypertensive (PHT) rats. METHODS: Monocrotaline (MCT)-treated rats were used as a model for chronic PHT. Concentration-response curves of 5-HT induced pulmonary vasoconstriction were established and semiquantitative RT-PCR was performed to identify mRNA expression of 5-HT1B- and 5-HT1D-receptors in rat PA. RESULTS: 5-HT induced vasoconstrictor response of PA from MCT rats was enhanced (Emax) 50 % +/- 20 % vs control 38 % +/- 21 %, P < 0.05). A significantly higher level of 5 -HT1B receptor mRNA expression was detected in PA from MCT rats. The ratio of the PCR products of 5-HT1B receptor gene to those of beta-actin gene was much higher in MCT rats than that in control rats (0.43 +/- 0.14 vs control 0.27 +/- 0.15, P < 0.05). CONCLUSION: 5-HT1B receptor is involved in pulmonary vasoconstriction and the enhanced level of 5-HT1B receptor mRNA expression is closely related to the augmentation of 5-HT induced pulmonary vasoconstriction in PHT rats.

Animals↗

PubMed2001

[Effect of hormone replacement therapy on hemorheology in postmenopausal women].

OBJECTIVE: Our study is to observe the effects of conjugated equine estrogen (CEE) combined with medroxyprogesterone acetate (MPA) on hemorheology in postmenopausal women in order to evaluate mechanism responsible for the increase in the incidence of cardiovascular disease after menopause and also to provide proper instruction and advice of hormone replacement therapy (HRT) for postmenopausal women. METHODS: 60 healthy postmenopausal women were assigned to 3 groups randomly, 20 cases in each group. Group A: CEE 0.625 mg/d + MPA 2 mg/d + calcium carbonate co. (Ca-D) 600 mg/d. Group B: CEE 0.3 mg/d + MPA 2 mg/d + Ca-D 600 mg/d. Group C: Ca-D 600 mg/d only served as control. Measurements of hemorheological parameters were performed before and 6 months after treatment. RESULTS: After 6 months of HRT, group A: blood viscosity under the shear rate of 94.5 s-1 dropped from (5.23 +/- 0.37) mPa.s to (5.03 +/- 0.43) mPa.s (P < 0.05), plasma viscosity dropped from (1.66 +/- 0.19) mPa.s to (1.58 +/- 0.15) mPa.s (P < 0.05), erythrocyte deformability dropped from (4.76 +/- 0.32) mPa.s to (4.54 +/- 0.34) mPa.s (P < 0.05). Group B: blood viscosity under the shear rate of 94.5 s-1 dropped from (5.10 +/- 0.30) mPa.s to (4.87 +/- 0.30) mPa.s (P < 0.05), erythrocyte deformability dropped from (4.65 +/- 0.34) mPa.s to (4.43 +/- 0.29) mPa.s (P < 0.05). No change was found in the control group. After treatment, the levels of plasma viscosity and fibrinogen in group A were much lower than that in group C (P < 0.05). The whole blood viscosity and plasma viscosity in group B were much lower than that in group C (P < 0.05). Thrombelastogram study demonstrated no change regardless HRT or not (P > 0.05). CONCLUSION: Both different dosages of CEE have favor effects on blood viscosity and erythrocyte deformabillity, which could play the role in preventing cardiovascular disease in postmenopausal women.

Blood Viscosity↗

PubMed2001

[Geographic distribution and feature of Yersinia pestis plasmid isolated from Yunnan province].

OBJECTIVE: To analysis the molecular-epidemiological feature of Yersinia pestis plasmid isolated from Yunnan. METHODS: One thousand and twenty strains of Y. pestis isolates from 44 counties of Yunnan province in China and the border of China-Myanmar using Kado and Liu method and detected by agrose gel electrophoresis. RESULTS: Results showed that these strains from Yunnan province carried 9 kinds of plasmids with molecular weights about 3.93, 6.05, 22.97, 35.65, 45.35, 64.82, 74.59, 111.36 and 129.55 x 10(6). Of these, three kinds of 3.93, 35.65 and 111.36 x 10(6) were found very specific, only reported in Yunnan. The plasmid profile could be divided into 10 types according to the plasmid content. Type I-V were common and had a clustering nature in geographic distribution. CONCLUSION: Based on the plasmid profile, the epidemic districts of plague could be divided into several independent plague foci, suggesting that the resurgence of domestic rat caused plague epidemics might have several hidden plague foci as the result of epidemics since 1982 in Yunnan.

Animals↗

PubMed2001

[Association between dopamine transporter gene polymorphism and Parkinson's disease].

OBJECTIVE: To detect the association between dopamine transporter gene polymorphism and Parkinson's disease (PD). METHODS: The authors analyzed the difference in the distribution of the variable number tandem repeat (VNTR ) polymorphism within the 3' untranslated region of the DAT gene between 85 normal controls and 128 PD patients that were further divided into the senile subgroup (aged >50 years at onset of PD ) and the early-onset subgroup (aged </=50 years). RESULTS: There were significant differences in genotypic and allelic distribution between the control group and the PD group. The senile PD was strongly associated with the 7-copy allele and weakly with the 10-copy allele, and the early onset PD was mainly associated with the 9-copy allele. CONCLUSION: The findings not only support an association between DAT gene and PD but also suggest the relationship of the 3'VNTR polymorphism of DAT gene with the age at the onset of PD.

Adolescent↗

PubMed2001

[Clinico-pathologic study on extended radical resection for rectal cancer].

OBJECTIVE: To justify clinico-pathologically the extended radical resection for rectal cancer. METHODS: Resected lymphatic specimens obtained by the triple approach in the radical resection for advanced rectal cancer was studied by routine pathological method. The outcome of this extended radical resection, guided by the route of lymphatic metastasis are presented in the justification. RESULTS: The incidence of lymphatic metastasis in advanced rectal cancer in the Chinese was 45.0%, with 44.0%, 14.0%, 10.0% and 9.0% in the upper 1, 2, 3 and the lateral third groups. Lymphatic metastasis from rectal cancer was related to the extent, depth and pathological type. The 5- and 10-year survival rates were 68.0% and 47.0%, which are much higher than those of the conventional radical resection. CONCLUSION: Extended radical resection for the rectal cancer, removing all the lymphatics, is able to prevent possible metastasis, thereby improving the survival rate significantly, This extended radical resection is an optimal type of operation.

Humans↗

PubMed2001

[Changes of microarousal in OSAS patients during CPAP].

OBJECTIVE: To study the mechanism of microarousal, its clinical meaning and value in the diagnosis and treatment of sleep apnea-hypopnea syndrome (SAHS). METHODS: 270 snorers (218 men, 58 women) mean aged 48 years underwent standard polysomnography (PSG), from which AHI, sleep latency (SL), number of oxygen desaturation >/= 4% per hour (ODI(4)) and microarousal index (MAI) were calculated. The overnight PSG recordings were also repeated during nCPAP in 28 patients, who have filled in the Epworth Sleep Score (ESS) before and after the treatment to evaluate the improvement of daytime sleepiness. RESULTS: Of the 270 snorers, there were 247 SAHS patients. Their AHI, ODI(4), MAI and SL were (43 +/- 27)/h, (44 +/- 23)/h, (29 +/- 16)/h and (12 +/- 17) min, respectively. AHI and MAI, ODI(4) and MAI were both positively correlated (r = 0.38, both P < 0.001). MAI and SL were negatively correlated (r = -0.15, P = 0.02), while AHI and SL, ODI(4) and SL were not correlated (r = -0.09, -0.02, P > 0.1). Of the 28 patients after CPAP, ODI(4) decreased from (48 +/- 25)/h to (4 +/- 9)/h, MAI decreased from (27 +/- 18)/h to (15 +/- 9)/h. The ESS and SL indicated that subjective and objective sleepiness improved. CONCLUSIONS: Microarousals with at least 3 seconds EEG changes can be scored by computerized EEG analysis. MAI can reflect the severity of daytime sleepiness. MAI is complementary to AHI in the diagnosis and treatment of SAHS. After nCPAP, the patients' MAIs decreased and daytime sleepiness improved.

Adult↗

PubMed2001

[Penetrating keratoplasty in active herpes simplex stromal keratitis].

OBJECTIVE: To evaluate the efficacy of penetrating keratoplasty (PKP) in treating active herpes simplex stromal keratitis. METHODS: PKP was performed on 59 patients with quiescent and 66 patients with active herpes simplex stromal keratitis. The results and complications of herpes simplex keratitis (HSK) in the quiescent group were compared with that of the HSK active group. RESULTS: No clinical or statistical significant differences in visual outcome, graft transparent rate and recurrent rate of HSK after operation were identified between the active and quiescent groups. CONCLUSION: When the pre- and intra-operative managements of PKP are properly performed on active HSK, the same results as that performed on quiescent HSK can be obtained, and it can reduce the complications and shorten the duration of the disease.

Acyclovir↗

PubMed2001

[Analysis and applications of a PrP antibody elicited by synthesized human PrP peptides].

BACKGROUND: To further study the immuno-reactivity and specificity of a PrP antibody elicited by synthesized human PrP peptides. METHODS: Construction of a plasmid which expresses a N-terminus deleted human PrP protein and purification of this truncated protein. The prepared PrP antibody was tested for reaction with various prokaryotic expressed human PrP proteins,including the full-length protein,the N-terminus-and C-terminus-truncated proteins with Western blot. The antibody was also used in the immunofluorescence assays to identify the PrP proteins expressed from the cell lines transfected with human PrP genes. Moreover,the brain tissues from scrapie agents-infected hamsters and a CJD patient were extracted and the proteinase K-resistant PrP-res were analyzed with the prepared antibody. RESULTS: The PrP-peptide elicited antibody could recognize both prokaryotic and eukaryotic expressed human PrP proteins, as well as the PrP-res proteins in the brain tissues both from the scrapie-infected hamsters and CJD patient. CONCLUSIONS: The tested antibody possesses eligible immuno-reactivity and specificity and can be used for diagnosis of CJD in the clinical work.

Animals↗

PubMed2001

[Characterization and phylogenetics of a new species of genus Methanobacterium].

A strain of methanogenic bacterium Px1 was isolated from an anaerobic digester in the department of environmental sciences, TsingHua University, which treated the wastewater from Beijing Beer Factory. The isolate is curved rod, light-yellow colony, uses only H2 + CO2 as the substrate for CH4 formation. On the basis of physiology, morphology, structural characteristics and phylogenetic analysis, it is turned out that strain Px1 is a new species of the genus Methanobacterium, the name Methanobacterium curvum sp. nov. is proposed.

DNA, Bacterial↗