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S Tang

Publications and source records attributed to S Tang.

At least 19 recordsLinked to original sources
PubMed2006

Role of acetylcholine transmission in nucleus accumbens and ventral tegmental area in heroin-seeking induced by conditioned cues.

The involvement of cholinergic transmission in heroin self-administration and the reinstatement of heroin-seeking was examined in rats trained to nose-poke for i.v. heroin. Systemic treatment with physostigmine, an inhibitor of acetylcholinesterase, modestly reduced the acquisition and rate of heroin self-administration, and this suppression of heroin intake was reversed by pretreatment with scopolamine but not by mecamylamine. Following 10-14 days of self-administration, rats were left in the home environment for 14 days. Subsequently, rats were evaluated for extinction of nose-pokes during the first hour after being returned to the self-administration apparatus. One hour later a conditioned stimulus (house light, light in the nose-poke hole, sound of the infusion pump) was presented to initiate cue-induced reinstatement. Physostigmine produced a dose-dependent inhibition of cue-induced reinstatement, but only the dose of 0.5 mg/kg significantly decreased nose-poke responding in the extinction test. Chronic treatment with physostigmine (0.1 mg/kg) did not impair performance during acquisition of heroin self-administration. However, during a subsequent reinstatement test conducted in the absence of physostigmine pretreatment, heroin seeking was significantly below that of rats chronically pretreated with saline. To evaluate brain regions mediating the effects of systemic drug treatment on reinstatement, physostigmine was microinjected into the nucleus accumbens (NAc) or ventral tegmental area (VTA). Microinjection of physostigmine into the NAc prior to presenting conditioned cues inhibited the reinstatement of heroin-seeking, without affecting extinction responding. In contrast, microinjection of physostigmine into the VTA augmented the reinstatement induced by conditioned cues and extinction responding. Inactivation of either NAc or VTA by microinjecting tetrodotoxin blocked both extinction responding and cue-induced reinstatement. These data demonstrate that cholinergic transmission influences heroin self-administration and reinstatement. Moreover, cue-induced reinstatement was inhibited by physostigmine in the NAc and potentiated by cholinergic stimulation in the VTA.

Acetylcholine↗
PubMed2006

Observation and simulation of net primary productivity in Qilian Mountain, western China.

We modeled net primary productivity (NPP) at high spatial resolution using an advanced spaceborne thermal emission and reflection radiometer (ASTER) image of a Qilian Mountain study area using the boreal ecosystem productivity simulator (BEPS). Two key driving variables of the model, leaf area index (LAI) and land cover type, were derived from ASTER and moderate resolution imaging spectroradiometer (MODIS) data. Other spatially explicit inputs included daily meteorological data (radiation, precipitation, temperature, humidity), available soil water holding capacity (AWC), and forest biomass. NPP was estimated for coniferous forests and other land cover types in the study area. The result showed that NPP of coniferous forests in the study area was about 4.4 tCha(-1)y(-1). The correlation coefficient between the modeled NPP and ground measurements was 0.84, with a mean relative error of about 13.9%.

Altitude↗
PubMed2006

LAI inversion algorithm based on directional reflectance kernels.

Leaf area index (LAI) is an important ecological and environmental parameter. A new LAI algorithm is developed using the principles of ground LAI measurements based on canopy gap fraction. First, the relationship between LAI and gap fraction at various zenith angles is derived from the definition of LAI. Then, the directional gap fraction is acquired from a remote sensing bidirectional reflectance distribution function (BRDF) product. This acquisition is obtained by using a kernel driven model and a large-scale directional gap fraction algorithm. The algorithm has been applied to estimate a LAI distribution in China in mid-July 2002. The ground data acquired from two field experiments in Changbai Mountain and Qilian Mountain were used to validate the algorithm. To resolve the scale discrepancy between high resolution ground observations and low resolution remote sensing data, two TM images with a resolution approaching the size of ground plots were used to relate the coarse resolution LAI map to ground measurements. First, an empirical relationship between the measured LAI and a vegetation index was established. Next, a high resolution LAI map was generated using the relationship. The LAI value of a low resolution pixel was calculated from the area-weighted sum of high resolution LAIs composing the low resolution pixel. The results of this comparison showed that the inversion algorithm has an accuracy of 82%. Factors that may influence the accuracy are also discussed in this paper.

Algorithms↗
PubMed2006

The LRRK2 Gly2385Arg variant is associated with Parkinson's disease: genetic and functional evidence.

Evidence of LRRK2 haplotypes associated with Parkinson's disease (PD) risk was recently found in the Chinese population from Singapore, and a common LRRK2 missense variant, Gly2385Arg, was independently detected as a putative risk factor for PD in the Chinese population from Taiwan. To test the association between the Gly2385Arg variant in a large case-control sample of Chinese ethnicity from Singapore, and to perform functional studies of the wild type and Gly2385Arg LRRK2 protein in human cell lines. In a case-control study involving 989 Chinese subjects, the frequency of the heterozygous Gly2385Arg genotype was higher in PD compared to controls (7.3 vs. 3.6%, odds ratio = 2.1, 95% CI: 1.1-3.9, P = 0.014); these values yield an estimated population attributable risk (PAR) of approximately 4%. In a multivariate logistic regression analysis with the disease group (PD vs. controls) as the dependent variable and the genotype as an independent factor with adjustments made for the effect of age and gender, the heterozygous Gly2385Arg genotype remained associated with an increased risk of PD compared to wild type genotype (odds ratio = 2.67, 95% CI: 1.43-4.99, P = 0.002). The glycine at position 2385 is a candidate site for N-myristoylation, and the Gly2385Arg variant replaces the hydrophobic glycine with the hydrophilic arginine, and increases the net positive charge of the LRRK2 WD40 domain. In transfection studies, we demonstrated that both the wild type and Gly2385Arg variant LRRK2 protein localize to the cytoplasm and form aggregates. However, under condition of oxidative stress, the Gly2385Arg variant was more toxic and associated with a higher rate of apoptosis. Our study lends support to the contention that the Gly2385Arg is a common risk factor for PD in the Chinese population. Our bioinformatics and in-vitro studies also suggest that the Gly2385Arg variant is biologically relevant and it might act through pro-apoptotic mechanisms.

Aged↗
PubMed2006

Short-term induction and long-term suppression of HPV16 oncogene silencing by RNA interference in cervical cancer cells.

RNA interference-mediated gene silencing has the potential to block gene expression. A synthetic double-stranded small interfering RNA (siRNA) based on a sequence motif of 21 nucleotides from human papillomavirus 16 (HPV16) E6E7 bicistronic RNA was found to be a potent siRNA that suppresses expression of both the E6 and E7 oncogenes in HPV16+ CaSki and SiHa cells. When stably expressed as a short hairpin RNA in these cells, however, siRNA silencing of E6 and E7 expression was efficient only at early cell passages, but became inefficient with increased cell passages despite the continued expression of the siRNA at the same level. The loss of the siRNA function was duplicable in stable p53 siRNA cells, but not in stable lamin A/C siRNA cells, suggesting that it is gene selective. The cells resistant to siRNA function retained normal siRNA processing, duplex unwinding and degradation of the unwound sense strand and RNA-induced silencing complex formation, suggesting that loss of the siRNA function occurred at a later step. Surprisingly, the siRNA-resistant cells were found to express notably a cytoplasmic protein of approximately 50 kDa that specifically and characteristically interacted with the unwound, antisense strand E7 siRNA. Altogether, our data indicate that a potent siRNA targeting to an essential or regulatory gene might induce a cell to develop siRNA-suppressive function.

Base Sequence↗
PubMed2006

Highly purified CD44+ prostate cancer cells from xenograft human tumors are enriched in tumorigenic and metastatic progenitor cells.

CD44 is a multifunctional protein involved in cell adhesion and signaling. The role of CD44 in prostate cancer (PCa) development and progression is controversial with studies showing both tumor-promoting and tumor-inhibiting effects. Most of these studies have used bulk-cultured PCa cells or PCa tissues to carry out correlative or overexpression experiments. The key experiment using prospectively purified cells has not been carried out. Here we use FACS to obtain homogeneous CD44(+) and CD44(-) tumor cell populations from multiple PCa cell cultures as well as four xenograft tumors to compare their in vitro and in vivo tumor-associated properties. Our results reveal that the CD44(+) PCa cells are more proliferative, clonogenic, tumorigenic, and metastatic than the isogenic CD44(-) PCa cells. Subsequent molecular studies demonstrate that the CD44(+) PCa cells possess certain intrinsic properties of progenitor cells. First, BrdU pulse-chase experiments reveal that CD44(+) cells colocalize with a population of intermediate label-retaining cells. Second, CD44(+) PCa cells express higher mRNA levels of several 'stemness' genes including Oct-3/4, Bmi, beta-catenin, and SMO. Third, CD44(+) PCa cells can generate CD44(-) cells in vitro and in vivo. Fourth, CD44(+) PCa cells, which are AR(-), can differentiate into AR(+) tumor cells. Finally, a very small percentage of CD44(+) PCa cells appear to undergo asymmetric cell division in clonal analyses. Altogether, our results suggest that the CD44(+) PCa cell population is enriched in tumorigenic and metastatic progenitor cells.

Animals↗
PubMed2005

Identification and validation of QTL for Sclerotinia midstalk rot resistance in sunflower by selective genotyping.

Midstalk rot, caused by Sclerotinia sclerotiorum (Lib.) de Bary, is an important cause of yield loss in sunflower (Helianthus annuus L.). Objectives of this study were to: (1) estimate the number, genomic positions and genetic effects of quantitative trait loci (QTL) for resistance to midstalk rot in line TUB-5-3234, derived from an interspecific cross; (2) determine congruency of QTL between this line and other sources of resistance; and (3) make inferences about the efficiency of selective genotyping (SG) in detecting QTL conferring midstalk rot resistance in sunflower. Phenotypic data for three resistance (stem lesion, leaf lesion and speed of fungal growth) and two morphological (leaf length and leaf length with petiole) traits were obtained from 434 F3 families from cross CM625 (susceptible) x TUB-5-3234 (resistant) under artificial infection in field experiments across two environments. The SG was applied by choosing the 60 most resistant and the 60 most susceptible F3 families for stem lesion. For genotyping of the respective F2 plants, 78 simple sequence repeat markers were used. Genotypic variances were highly significant for all traits. Heritabilities and genotypic correlations between reMidstalk rot, caused by Sclerotinia sclerotiorum (Lib.) de Bary, is an important cause of yield loss in sunflower (Helianthus annuus L.). Objectives of this study were to: (1) estimate the number, genomic positions and genetic effects of quantitative trait loci (QTL) for resistance to midstalk rot in line TUB-5-3234, derived from an interspecific cross; (2) determine congruency of QTL between this line and other sources of resistance; and (3) make inferences about the efficiency of selective genotyping (SG) in detecting QTL conferring midstalk rot resistance in sunflower. Phenotypic data for three resistance (stem lesion, leaf lesion and speed of fungal growth) and two morphological (leaf length and leaf length with petiole) traits were obtained from 434 F3 families from cross CM625 (susceptible) x TUB-5-3234 (resistant) under artificial infection in field experiments across two environments. The SG was applied by choosing the 60 most resistant and the 60 most susceptible F3 families for stem lesion. For genotyping of the respective F2 plants, 78 simple sequence repeat markers were used. Genotypic variances were highly significant for all traits. Heritabilities and genotypic correlations between resistance traits were moderate to high. Three to four putative QTL were detected for each resistance trait explaining between 40.8% and 72.7% of the genotypic variance (PTS). Two QTL for stem lesion showed large genetic effects and corroborated earlier findings from the cross NDBLOSsel (resistant) x CM625 (susceptible). Our results suggest that SG can be efficiently used for QTL detection and the analysis of congruency for resistance genes across populations.

Ascomycota↗
PubMed2005

Glomerular pathology of allograft kidneys in Hong Kong.

AIMS: Our goal was to define the spectrum of glomerular diseases in allograft kidneys and to correlate them with clinical parameters. METHODS: Eight hundred ninety-one renal graft biopsies and 43 graft nephrectomies from 1980 to 2004 were obtained from 442 allografts transplanted to 425 patients. RESULTS: Glomerular diseases were diagnosed in 33% of kidney grafts. Indications for biopsy were baseline assessment (23 biopsies, 2.5%); renal dysfunction (790 biopsies, 88.7%); proteinuria (154 biopsies, 17.3%); hematuria (11 biopsies, 1.2%); and study protocol (four biopsies, 0.4%). The median time to take a biopsy was less than 8 months posttransplant. The mean time posttransplant when the biopsy diagnosis was made was 70 months for IgA nephropathy (IgAN); 66 months for transplant glomerulopathy (TG); 65 months for focal segmental glomerulosclerosis (FSG); 55 months for mesangiocapillary glomerulonephritis (MCGN); 45 months for membranous glomerulonephritis (GN); 49 months for mesangial proliferative GN; and 101 months for diabetic nephropathy. Recurrent glomerular disease was documented in 31 (7.0%) grafts. Specific glomerular diseases were diagnosed by biopsies in 106 (89.1%) of 119 proteinuric allografts. CONCLUSIONS: Glomerulopathy was common in allografted kidneys. IgAN, TG, FSG, mesangial proliferative GN, and membranous GN were the majority. A higher proportion of grafts from donors related to the recipients than from unrelated donors showed IgAN (P < .05), suggesting that genetic factors might play a role in the pathogenesis of IgAN. Recurrence of glomerulopathy underlying ESRD was frequent for IgAN, FSG, and MCGN, but this was rarely seen in membranous GN.

Biopsy↗
PubMed2005

Factors affecting delays in tuberculosis diagnosis in rural China: a case study in four counties in Shandong Province.

Improving case detection is an urgent and serious challenge for tuberculosis (TB) control in China. We investigated the extent to which TB patients delayed seeking TB care and health services delayed reaching a diagnosis, and socio-economic factors associated with the delays. Standard questionnaires were administered to 190 new smear-positive TB patients who had completed treatment at TB dispensaries in four counties of Shandong Province in 2001. Multivariate analysis using Cox Regression showed that old age, lack of education and distance from home to a township health centre were significantly associated with delay in seeking care from service providers. In examining the delay between first contact with a service provider and diagnosis, we found that women experienced longer delays than men, and that the higher the level of facility patients first visited, the less time was needed to achieve a diagnosis. These two factors were statistically significant in multivariate Cox Regression analysis. We concluded that the elderly, the less educated, women, and those living far from health facilities face the longest delays in reaching TB services and achieving diagnosis.

Adult↗
PubMed2005

Angiotensin inhibition or blockade for the treatment of patients with quiescent lupus nephritis and persistent proteinuria.

Angiotensin-converting enzyme inhibitor (ACEI) or angiotensin II receptor blocker (ARB) reduces proteinuria and the rate of renal function deterioration in diabetic nephropathy and other glomerular diseases, but its role in quiescent lupus nephritis has not been established. We conducted a retrospective study to investigate the effects of ACEI/ARB on proteinuria and renal function in patients with persistent proteinuria (>1 g/day) despite resolution of acute lupus nephritis following immunosuppressive treatment. Fourteen out of 92 patients were included. The duration of treatment with ACEI/ARB was 52.1 +/- 35.7 months. The levels of proteinuria, serum albumin, serum creatinine, systolic and diastolic blood pressure were 1.10 to 6.90 g/day, 35.8 +/- 3.6 g/L, 102.54 +/- 34.48 micromol/L, 137.6 +/- 10.9 and 81.9 +/- 9.2 mmHg at baseline. Proteinuria and serum albumin showed significant sustained improvements after 6 and 24 months of treatment. Comparison of slopes for serial proteinuria, albumin and reciprocal of serum creatinine before and after treatment showed significant improvements in six (43%), eight (57%) and two patients, respectively. At last follow-up proteinuria remained significantly lower (0.36 g/day, P = 0.043) and albumin higher (41.3 +/- 2.2 g/L, P = 0.023). Eleven (78.6%) patients had proteinuria improved by >50%, and five had insignificant proteinuria at last follow-up. Systolic blood pressure was significantly reduced from 6 months onwards, but this did not correlate with proteinuria reduction. Diastolic blood pressure, serum creatinine, creatinine clearance, anti-dsDNA, C3 and haemoglobin were not altered. We conclude that ACEI/ARB effectively reduces proteinuria and improves serum albumin in patients with persistent proteinuria despite quiescent lupus nephritis.

Adult↗
PubMed2004

QTL mapping of Sclerotinia midstalk-rot resistance in sunflower.

In many sunflower-growing regions of the world, Sclerotinia sclerotiorum (Lib.) de Bary is the major disease of sunflower (Helianthus annuus L.). In this study, we mapped and characterized quantitative trait loci (QTL) involved in resistance to S. sclerotiorum midstalk rot and two morphological traits. A total of 351 F3 families developed from a cross between a resistant inbred line from the germplasm pool NDBLOS and the susceptible line CM625 were assayed for their parental F2 genotype at 117 codominant simple sequence repeat markers. Disease resistance of the F3 families was screened under artificial infection in field experiments across two sowing times in 1999. For the three resistance traits (leaf lesion, stem lesion, and speed of fungal growth) and the two morphological traits, genotypic variances were highly significant. Heritabilities were moderate to high (h2=0.55-0.89). Genotypic correlations between resistance traits were highly significant (P<0.01) but moderate. QTL were detected for all three resistance traits, but estimated effects at most QTL were small. Simultaneously, they explained between 24.4% and 33.7% of the genotypic variance for resistance against S. sclerotiorum. Five of the 15 genomic regions carrying a QTL for either of the three resistance traits also carried a QTL for one of the two morphological traits. The prospects of marker-assisted selection (MAS) for resistance to S. sclerotiorum are limited due to the complex genetic architecture of the trait. MAS can be superior to classical phenotypic selection only with low marker costs and fast selection cycles.

Analysis of Variance↗
PubMed2004

Neurally mediated hypotension in systemic lupus erythematosus patients with fibromyalgia.

OBJECTIVE: Fibromyalgia (FM) is a major determinant of poor health status in systemic lupus erythematosus (SLE). FM has been shown to be associated with neurally mediated hypotension (NMH) in the general population, in which effective treatments exist. We explored whether NMH was more common in SLE patients with FM than those without. METHODS: Seventy-six SLE patients (4 male, 72 female; 1 ethnic Indian, 28 African American, 47 Caucasian; mean age 40.2 +/- 9.4 yr) were recruited and their FM status ascertained using American College of Rheumatology (ACR) classification criteria. Patients who were pregnant or deconditioned were excluded. A two-stage tilt-table test was used to detect NMH. All patients completed the SF-36 Heath Status Inventory (SF-36) and the Krupp Fatigue Severity Scale (KFSS) to evaluate their quality of life. Serological markers and the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) were recorded. Medications that might interfere with testing were temporarily withheld before the tilt-table test. RESULTS: The prevalence of NMH (first stage) in SLE patients was 47.9%. Seven patients had both NMH and postural orthostatic tachycardia syndrome. Two patients had borderline results with symptoms reproduced but an inadequate drop in systolic blood pressure by definition (a drop of at least 25 mmHg defines an abnormal response). Eighteen (23.7%) SLE patients had FM and 51 (67.1%) had at least one tender point (TP). The frequency of NMH (first or second stage) in SLE with FM was 58.3% compared with 69.4% in SLE without FM (odds ratio 0.62, 95% CI 0.16-2.37). SF-36 and KFSS scores were not significantly different in SLE patients with and without NMH. However, both scores were found to be associated with FM status (P<0.001 and P = 0.014), reflecting poor health status in the FM group. No confounding variable was found to be significantly associated with both NMH and FM. CONCLUSION: NMH is common in SLE patients with a high prevalence rate. The large increase in NMH, a form of autonomic neuropathy, in SLE, has not been explained. However, NMH has no impact on quality of life above that determined by FM, and has no statistically significant association with FM status. Identification of NMH may be important in selected patients with SLE who have chronic fatigue, but NMH cannot explain the increased prevalence of FM in SLE.

Adult↗
PubMed2004

Phenylpropanoid NF-kappaB inhibitors from Bupleurum fruticosum.

Two phenylpropanoids from Bupleurum fruticosum (Apiaceae/Umbelliferae) were shown to inhibit the transcriptional activity induced by PMA or TNFalpha of an NF-kappaB-controlled reporter gene. Western blot experiments indicated that the phenylpropanoids did not prevent IkappaBalpha degradation, suggesting that their molecular target is at a post-IKB degradation level. Both compounds prevented cytokine (IL-1, IL-6, TNF, IL-8) release and prostaglandin E2 synthesis.

Apiaceae↗
PubMed2004

Regulation of complement C3 and C4 synthesis in human peritoneal mesothelial cells by peritoneal dialysis fluid.

Although complement is activated in the peritoneal cavity during chronic peritoneal dialysis (PD), little is known about its role in peritoneal defence and injury related to long-term PD. We examined the impact of glucose and commercial peritoneal dialysis solutions on complement expression in HPMCs obtained by primary culture from omental tissues of consented patients undergoing elective abdominal surgery. Constitutive expression of C3 and C4 mRNA in HPMCs was up-regulated upon exposure to 75 mm glucose in a time-dependent manner. C3 and C4 protein was secreted in both apical and basolateral directions. Glucose doses beyond 100 mm markedly down-regulated C3 and C4 expression, and stimulated LDH release dose-dependently. Such cytotoxic effects were attenuated using equivalent doses of mannitol instead of glucose. Treatment with conventional lactate-buffered dialysis solution gave rise to down-regulation of C3 and C4 expression, and heightened LDH release in HPMCs. These effects correlated with the glucose strength of the solution, persisted despite replacement with a bicarbonate-buffered solution, aggravated by glycated albumin, and were partially abrogated by supplementation with 10% fetal bovine serum in the culture system. Our findings suggest that the artificial conditions imposed by PD lead to alterations in local complement synthesis that have implications for the role of the peritoneal mesothelium in both inflammation and defence.

Cell Membrane Permeability↗
PubMed2003

Experimental verification of anticipated and retarded synchronization in chaotic semiconductor lasers.

Experimental observation of both anticipated and retarded synchronization is demonstrated using unidirectionally coupled semiconductor lasers with delayed optoelectronic feedback. Depending on the difference between the transmission time and the feedback delay time, the lasers fall into either the anticipated or the retarded synchronization regime, where the driven receiver laser leads or lags behind the driving transmitter laser. The two regimes are observed to have the same stability of chaos synchronization in the presence of small perturbations by noise and parameter mismatches. In both regimes the observed time shift between the synchronized chaotic waveforms is found to be equal to the difference between the transmission time and the feedback delay time.

Journal Article↗