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Biomedical subjects

X Tang

Publications and source records attributed to X Tang.

At least 55 records · Page 3Linked to original sources
PubMed2001

Overexpression of Pti5 in tomato potentiates pathogen-induced defense gene expression and enhances disease resistance to Pseudomonas syringae pv. tomato.

The tomato Pti5 gene encodes a pathogen-inducible ethylene response element-binding protein-like transcription factor that interacts with the disease resistance gene product Pto. Overexpression of Pti5 or Pti5-VP16, a translational fusion with a constitutive transcriptional activation domain, in tomato enhanced resistance to Pseudomonas syringae pv. tomato. Constitutive expression of Pti5 or Pti5-VP16 did not affect the basal level of pathogenesis-related gene expression, but it accelerated pathogen-induced expression of GluB and Catalase. The results demonstrate a positive role of Pti5 in defense gene regulation and disease resistance and suggest that a pathogen-activated posttranscriptional regulatory step is necessary for the pathogen induction of the defense gene expression.

DNA-Binding Proteins↗
PubMed2001

Expression of 35S::Pto globally activates defense-related genes in tomato plants.

The tomato (Lycopersicon esculentum) resistance gene Pto confers resistance to the bacterial pathogen Pseudomonas syringae pv tomato carrying the avirulent gene avrPto. Overexpressing Pto under the control of the cauliflower mosaic virus 35S promoter constitutively activates defense responses in the absence of pathogen infection and nonspecifically enhances disease resistance. To elucidate the mechanisms underlying this resistance, we isolated cDNAs corresponding to transcripts that accumulated in 35S::Pto plants. By using suppression subtractive hybridization, we isolated 82 unique cDNA clones, most of which corresponded to differentially expressed transcripts. Most of the genes examined were also induced by pathogen inoculation. Sequence analysis showed that a large number of genes encode defense-related proteins, and most had not been previously isolated from tomato. The isolated cDNAs also include those with a putative role in the oxidative burst, proteolysis, the hypersensitive response, signal transduction, and a number of genes with unknown functions. The isolation of these cDNAs of diverse functions will assist in the characterization of defense pathways activated during disease resistance.

Bacterial Proteins↗
PubMed2001

Arabidopsis NHO1 is required for general resistance against Pseudomonas bacteria.

Nonhost interactions are prevalent between plants and specialized phytopathogens. Although it has great potential for providing crop plants with durable resistance, nonhost resistance is poorly understood. Here, we show that nonhost resistance is controlled, at least in part, by general resistance. Arabidopsis plants are resistant to the nonhost pathogen Pseudomonas syringae pv phaseolicola NPS3121 and completely arrest bacterial multiplication in the plant. Ten Arabidopsis mutants were isolated that were compromised in nonhost (nho) resistance to P. s. phaseolicola. Among these, nho1 is caused by a single recessive mutation that defines a novel gene. nho1 is defective in nonspecific resistance to Pseudomonas bacteria, because it also supported the growth of P. s. tabaci and P. fluorescens bacteria, both of which are nonpathogenic on Arabidopsis. In addition, the nho1 mutation also compromised resistance mediated by RPS2, RPS4, RPS5, and RPM1. Interestingly, the nho1 mutation had no effect on the growth of the virulent bacteria P. s. maculicola ES4326 and P. s. tomato DC3000, but it partially restored the in planta growth of the DC3000 hrpS(-) mutant bacteria. Thus, the virulent bacteria appear to evade or suppress NHO1-mediated resistance by means of an Hrp-dependent virulence mechanism.

Arabidopsis↗
PubMed2001

Cone beam volume CT image artifacts caused by defective cells in x-ray flat panel imagers and the artifact removal using a wavelet-analysis-based algorithm.

The application of x-ray flat panel imagers (FPIs) in cone beam volume CT (CBVCT) has attracted increasing attention. However, due to a deficient semiconductor array manufacturing process, defective cells unavoidably exist in x-ray FPIs. These defective cells cause their corresponding image pixels in a projection image to behave abnormally in signal gray level, and result in severe streak and ring artifacts in a CBVCT image reconstructed from the projection images. Since a three-dimensional (3-D) back-projection is involved in CBVCT, the formation of the streak and ring artifacts is different from that in the two-dimensional (2-D) fan beam CT. In this paper, a geometric analysis of the abnormality propagation in the 3D back-projection is presented, and the morphology of the streak and ring artifacts caused by the abnormality propagation is investigated through both computer simulation and phantom studies. In order to calibrate those artifacts, a 2D wavelet-analysis-based statistical approach to correct the abnormal pixels is proposed. The approach consists of three steps: (1) the location-invariant defective cells in an x-ray FPI are recognized by applying 2-D wavelet analysis on flat-field images, and a comprehensive defective cell template is acquired; (2) based upon the template, the abnormal signal gray level of the projection image pixels corresponding to the location-invariant defective cells is replaced with the interpolation of that of their normal neighbor pixels; (3) that corresponding to the isolated location-variant defective cells are corrected using a narrow-windowed median filter. The CBVCT images of a CT low-contrast phantom are employed to evaluate this proposed approach, showing that the streak and ring artifacts can be reliably eliminated. The novelty and merit of the approach are the incorporation of the wavelet analysis whose intrinsic multi-resolution analysis and localizability make the recognition algorithm robust under variable x-ray exposure levels between 30% and 70% of the dynamic range of an x-ray FPI.

Algorithms↗
PubMed2001

A cone beam filtered backprojection (CB-FBP) reconstruction algorithm for a circle-plus-two-arc orbit.

The circle-plus-arc orbit possesses advantages over other "circle-plus" orbits for the application of x-ray cone beam (CB) volume CT in image-guided interventional procedures requiring intraoperative imaging, in which movement of the patient table is to be avoided. A CB circle-plus-two-arc orbit satisfying the data sufficiency condition and a filtered backprojection (FBP) algorithm to reconstruct longitudinally unbounded objects is presented here. In the circle suborbit, the algorithm employs Feldkamp's formula and another FBP implementation. In the arc suborbits, an FBP solution is obtained originating from Grangeat's formula, and the reconstruction computation is significantly reduced using a window function to exclude redundancy in Radon domain. The performance of the algorithm has been thoroughly evaluated through computer-simulated phantoms and preliminarily evaluated through experimental data, revealing that the algorithm can regionally reconstruct longitudinally unbounded objects exactly and efficiently, is insensitive to the variation of the angle sampling interval along the arc suborbits, and is robust over practical x-ray quantum noise. The algorithm's merits include: only 1D filtering is implemented even in a 3D reconstruction, only separable 2D interpolation is required to accomplish the CB backprojection, and the algorithm structure is appropriate for parallel computation.

Algorithms↗
PubMed2001

Internal transcribed spacer regions of rRNA genes of Pneumocystis carinii from monkeys.

Analysis of sequence variations among isolates of Pneumocystis carinii f. sp. macacae from 14 Indian rhesus monkeys (Macaca mulatta) at the internal transcribed spacer (ITS) regions of the nuclear rRNA gene was undertaken. Like those from P. carinii f. sp. hominis, the ITS sequences from various P. carinii f. sp. macacae isolates were not identical. Two major types of sequences were found. One type of sequence was shared by 13 isolates. These 13 sequences were homologous but not identical. Variations were found at 13 of the 180 positions in the ITS1 region and 28 of the 221 positions in the ITS2 region. These sequence variations were not random but exhibited definite patterns when the sequences were aligned. According to this sequence variation, ITS1 sequences were classified into three types and ITS2 sequences were classified into five types. The remaining specimen had ITS1 and ITS2 sequences substantially different from the others. Although some specimens had the same ITS1 or ITS2 sequence, all 14 samples exhibited a unique whole ITS sequence (ITS1 plus ITS2). The 5.8S rRNA gene sequences were also analyzed, and only two types of sequences that differ by only one base were found. Unlike P. carinii f. sp. hominis infections in humans, none of the monkey lung specimens examined in this study were found to be infected by more than one type of P. carinii f. sp. macacae. These results offer insights into the genetic differences between P. carinii organisms which infect distinct species.

Animals↗
PubMed2001

Attenuation of hypertension and heart hypertrophy by adeno-associated virus delivering angiotensinogen antisense.

Angiotensinogen (AGT), one of the major components in the renin-angiotensin system, has been linked to hypertension in humans and animals. We have previously systemically administered antisense oligonucleotides and plasmid vectors with DNA that targeted AGT and attenuated hypertension in spontaneously hypertensive rats. The aim of the present study was to prolong the effect of antisense treatment by the use of a recombinant adeno-associated viral (rAAV) vector targeted to AGT. Using a model of lifelong hypertension in which 5-day-old spontaneously hypertensive rats are treated, a single intracardiac injection of rAAV-AGT-antisense (rAAV-AGT-AS) delayed the onset of hypertension for 91 days and significantly attenuated hypertension in adulthood for up to 6 months. Systolic blood pressure was always lower, by up to 23 mm Hg in the AS-treated group. The vector was stable and expressed a reporter gene in liver, kidney, and heart. The rAAV-AGT-AS treatment significantly decreased left ventricular hypertrophy (P=0.01) and also lowered levels of AGT in the liver (2.78+/-0.61 microgram/g tissue versus 5.23+/-0.41 microgram/g tissue for the sense-treated group, P<0.01). Measurement of liver transaminases showed no evidence for liver toxicity. We conclude that rAAV-AGT-AS offers a safe, stable approach for gene therapy of hypertension.

Adenoviridae↗
PubMed2001

[Mutation characteristic of STK].

OBJECTIVE: To identify the mutation characteristic of STK(11) gene in Chinese with Peutz-Jeghers syndrome(PJS) and establish the base of the gene diagnosis of PJS. METHODS: STK(11) germline mutation was analysed by DNA sequencing in 18 unrelation patients with PJS. RESULTS: Six novel mutations of STK (11) gene were detected in six unrelation patients. These mutations will lead to production of truncated protein. CONCLUSION: STK (11) gene mutation accounts for one third of the Chinese with PJS. The content of mutation includes single base substitution or deletion and one or two bases insertion. The mutations were widely found in different regions of the whole coding sequence, and 2/3 of those concentr ate in exon 1. Mutation frequency is 66.7% in the family suffering PJS in two or more generations, and 16.7% in the disseminated cases.

AMP-Activated Protein Kinase Kinases↗
PubMed2001

[Preparation and quality control of cross-linked agarose coated activated charcoal (CAAC-II) used as adsorbents for hemoperfusion in artificial liver support].

The preparation and the quality control of cross-linked agarose coated activated (CAAC-II) were described. The crosslinking reagent epichlorohydrin was removed. Investigations indicate that the trace elements such as Pb, Cd, As, Cr, Fe and heavy metals, the pH, NH4+, SO4(2-), and ultraviolet absorbance in sample have met the requirements in Chinese Pharmacopeia and some other relevant standard promulgated by the Ministry of Health. No epichlorohydrin was detected in CAAC-II.

Capsules↗
PubMed2001

[Induction and kinetic characterization of nitric oxide synthase in hepatocytes].

OBJECTIVE: To study the synergistic responses of nitric oxide synthase (NOS) induction in rat hepatocytes to LPS and various cytokines in vitro and the kinetic characteristics of iNOS. METHODS: The hepatocytes were isolated by in-situ pre-perfusion and collagenase circulatory perfusion of rat livers. The effects of LPS associated with IFN-r, TNF-alpha and IL-1beta or IL-6 on NOS activity, cGMP, and NO(2)(-)+NO(3)(-) were observed in hepatocytes, respectively. Also the kinetic characteristics of this enzyme and dose response of corticosteroids on the induction of iNOS were analyzed. RESULTS: The maximum induction of NOS activity was observed in hepatocytes treated by LPS in combination with IFN-r, TNF-alpha and IL-1beta or IL-6. The kinetic analysis of this iNOS demonstrated specific constants of Km=10.8 micromol/L, Vmax=263.2 pmol/min/mg protein(for L-Arg), and Ki of 0.56, 0.94 micromol/L for competitive inhibitor, L-NMMA and NNA, respectively. The time course of induction showed that iNOS activity peaked at 9 h; however, significant increase in release of NO(2)(-)+NO(3)(-) and cGMP sustained for at least 18 h. Dexamethasone and hydrocortisone dramatically inhibited the NOS induction in hepatocytes in vitro with IC50 of 3.5+/-10(-8)mol/L and 2.6+/-10(-6)mol/L, respectively. CONCLUSIONS: The expression of inductive NOS in hepatocytes requires specific synergetic action of cytokines, and the inducible characteristics may play an important pathogenesis in endotoxemia and septic shock.

Animals↗
PubMed2001

[Clinical implications of HCV quasispecies heterogeneity in patients with hepatitis C].

OBJECTIVE: To determine the heterogeneity of viral quasispecies and its clinical significance in patients with hepatitis C. METHODS: Quasispecies in the sera from 76 patients infected with hepatitis C virus were detected using single stranded conformational polymorphism (SSCP) analysis of the HCV E2 hypervariable region 1 (HVR1). RESULTS: HVR1 was amplified in 72 (94.7%) of the 76 patients. The average number of SSCP bands was 5.8, with a range from 2 to 11. The numbers of quasispecies in acute hepatitis, chronic hepatitis and liver cirrhosis and/or primary hepatocellular carcinoma were 3.1 +/- 1.2, 6.0 +/- 2.3 and 8.4 +/- 4.1, respectively. There was a statistically significant difference among them (P < 0.01). Patients with infection acquired by blood transfusion and i.v. drug use had greater number of quasispecies than those acquired by other transmission pathway (sporadic) (P < 0.05). Patients with genotype 1 a and 1 b infection had increased quasispecies compared with those infected with HCV type 2 and 3(P < 0.05). Increased quasispecies heterogeneity was significantly correlated with serum HCV RNA levels (P < 0.01). CONCLUSIONS: SSCP is a simple, rapid and reliable method for the analysis of HCV viral quasispecies heterogeneity. Quasispecies heterogeneity plays an important role in HCV persistent infection and in the progress of hepatitis C. The duration of HCV infection, HCV genotype and HCV viremia are important determinants for the evolution of HCV quasispecies heterogeneity.

Adolescent↗
PubMed2001

[Studies of a new adsorbent cross-linked agar beads entrapped attapulgite clay for hemoperfusion].

The preparation and properties of a new adsorbent cross-linked agar beads entrapped attapulgite clay (CAA) are reported in detail. Medicinal attapulgite clay made in China was encapsulated with agar, shaped in organic solvent, and cross-linked by epichlorohydrin. The products withstood autoclaving at 121 degrees C for half an hour with no breakage, and had a good selective adsorption ability for some model compounds and medicaments such as methylene blue and phenothiazine drugs. Preliminary investigations and SEM photographs indicate that the CAA as an adsorbent is relatively hemocompatible for hemoperfusion.

Agar↗
PubMed2001

[Characteristics of litter and its contained water in three succession communities in Dinghushan Mountain].

Studies on the characteristics of litter and its contained water in three succession communities in Dinghushan Mountain showed that the standing mass of litter was in the order of pine forest > mixed forest > broad-leaved forest, and the annual litterfall was broad-leaved forest > mixed forest > pine forest, indicating that the return rate of nutrients was lower in pine forest than in broad-leaved forest. The proportion of leaf litter decreased in the order of pine forest > mixed forest > broad-leaved forest, and that of branch, flower, and fruit litter was on the contrary, because the broad-leaved forest had the largest amount of branches and the biggest scope of canopy. The staturation water content of litter in pine forest, mixed forest and broad-leaved forest was 329.0%, 313.0% and 295.0%, respectively, showing no significant difference, but the water content of litter in three communities differed significantly, followed the order of broad-leaved forest > mixed forest > pine forest. The evaporation ratio of litter water to free water in broad-leaved forest, mixed forest and pine forest was 78.9%, 82.45% and 91.22%, respectively.

Biodegradation, Environmental↗
PubMed2001

[The diagnostic value and limitations of total serum bile acid determined enzymatically].

OBJECTIVE: To elucidate the diagnostic value of total serum bile acid. METHOD: Clinical data from 913 cases was statistically analyzed with SPSS for Windows and other statistical procedures reported previously. RESULTS: (1) The mean of TBA of healthy subjects was (4.0 +/- 3.2) micromol/L. The TBA level of liver disease group is significantly higher than other group(P < 0.01). (2) The mean of TBA of patients with acute hepatitis was (167.2 +/- 132.4) micromol/L, the highest value was 449.5 micromol/L, it was significantly higher than other groups. TBA was a sensitive mark reflecting acute hepatic injury. (3) The sensitivity of TBA in patients with cirrhosis was 85.8%, higher than routine liver function tests. TBA is a valuable mark reflecting collateral circulation. (4) The sensitivity of TBA in mild chronic hepatitis was only 30.5%, much lower than ALT and TBIL (P < 0.01). (4) There was a relationship between the level of TBA and the severity of patients' condition, but the value of TBA for evaluating the severity was not as good as TBIL. CONCLUSION: The specificity of TBA is quite high, the sensitivity is moderate, TBA is valuable for the diagnosis of liver disease, especially for acute hepatitis and cirrhosis, but it's sensitivity for mild chronic hepatitis is only 30.5%, it is not as good as TBIL for evaluating the condition of patients.

Acute Disease↗
PubMed2001

[Analysis of causes of death and YPLL on residents in the industrial pollution area in Chongqing from 1991 to 1998].

OBJECTIVE: To investigate the causes of death in residents living in the area of industrial pollution in Chongqing. METHODS: Mortality rate, sequence of causes of death, years of potential life lost (YPLL) and the valued years of potential life lost (VYPLL) were used to analyze causes of death in 1991 - 1998. Community not polluted by industry was chosen to serve as control. RESULTS: The annual average mortality rate of the residents was 7.34 per thousand (standard mortality rate 4.61 per thousand). The sequence of major causes of death was shown as below: malignant tumors (mortality rate 198.07/10(5), standard mortality rate 126.35/10(5)), cerebrovascular diseases (mortality rate 159.13/10(5), standard mortality rate 92.66/10(5)), respiratory system diseases (mortality rate 107.33/10(5), standard mortality rate 84.85/10(5)), cardiac diseases (mortality rate 95.36/10(5), standard mortality rate 59.37/10(5)) and accidental deaths (mortality rate 47.08/10(5), standard mortality rate 43.28/10(5)). Among malignant tumors, lung cancer took the lead with a mortality rate of 65.49/10(5) (standard mortality rate 45.27/10(5)). In both sequences of standard rates of YPLL and VYPLL for major causes of deaths, accidental death was always took the first place. CONCLUSION: In order to reduce mortality rate of the residents in the area, it is necessary to strengthen the administration of natural and social environment of the area.

Accidents↗