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D Xu

Publications and source records attributed to D Xu.

At least 73 records · Page 4Linked to original sources
PubMed2001

Performance characteristics of the COBAS AmpliScreen HIV-1 test, version 1.5, an assay designed for screening plasma mini-pools.

BACKGROUND: The COBAS AmpliScreen HIV-1 test, version 1.5 (v1.5) (Roche Molecular Systems), is designed for screening pools composed of samples from 24 individual units of blood or plasma. A specimen-processing procedure (Multiprep) simultaneously concentrates and extracts HIV-1, HCV, and HBV particles from plasma and incorporates an HIV-1 internal control (IC) RNA. Processed samples are amplified by RT-PCR using HIV-1-specific primers and detected by hybridization of the amplified products to HIV-1- and IC-specific oligonucleotide probes. STUDY DESIGN AND METHODS: Plasma samples containing known quantities of HIV-1 were used to evaluate analytical sensitivity and precision and to validate a pool testing algorithm. Analytical specificity was evaluated by adding various viruses and bacteria to HIV-1-negative plasma. Seroconversion panels were tested to estimate the window-period reduction achieved by RNA testing. RESULTS: The analytical sensitivity of the test (concentration that yields > or = 95% positive results in a set of replicate tests) was 25 copies of HIV-1 RNA per mL of pooled plasma. Representative strains from all HIV-1 group M subtypes were reproducibly detected (> 95% positive results) at concentrations of 20 to 200 viral particles per mL. The test did not cross-react with a set of 31 viral and 5 bacterial isolates, and it yielded negative results on a panel of 500 blood samples from HIV-1-seronegative donors. Plasma samples containing abnormally high levels of Hb, albumin, triglycerides, or bilirubin did not interfere with the test. HIV-1 RNA was detected 2 to 14 days before HIV-1 antibody and 0 to 28 days before p24 antigen. The test specifically detected pools containing a single positive unit with 2400 HIV-1 RNA copies per mL and correctly identified the positive unit. CONCLUSION: The COBAS AmpliScreen HIV-1 test, v1.5, has sufficient sensitivity to detect a single infected unit containing 600 copies of HIV-1 per mL in a pool with 23 uninfected units and should reduce the window period between infection and seroconversion by at least 2 to 14 days.

Acquired Immunodeficiency Syndrome↗
PubMed2001

Steroidal saponins from Tribulus terrestris.

Three new steroidal saponins were isolated from the fruits of Tribulus terrestris, and their structures were elucidated as (25R,S)-5 alpha-spirostane-12-one-3 beta-ol-3-O-beta-xylopyranosyl(1-->2)- [beta-xylopyranosyl(1-->3)]-beta-glucopyranosyl(1-->4)-[alpha-rhamno- pyranosyl(1-->2)]-beta-galactopyranoside; 26-O-beta-glucopyranosyl-(25S)-5 alpha-furostane-12-one-3 beta,22 alpha,26-triol-3-O-beta-glucopyranosyl(1-->2)-beta-galactopyranoside; 26-O-beta-glucopyranosyl-(25S)-5 alpha-furostane-12-one-3 beta,22 alpha,26-triol-3-O-beta-glucopyranosyl(1-->4)-[alpha- rhamnopyranosyl(1-->2)]-beta-galactopyranoside, respectively, by spectroscopic analysis and color reaction.

Carbohydrate Sequence↗
PubMed2001

In vivo staphylococcal superantigen-driven polyclonal Ig responses in mice: dependence upon CD4(+) cells and human MHC class II.

Staphylococcal enterotoxin (SE) B and seven other staphylococcal superantigens (SAg), despite promoting vigorous Ig production in human peripheral blood mononuclear cell cultures, are exceedingly poor at eliciting Ig responses in cultures of spleen cells from C57BL/10J (B10) or C3H/HeJ mice. In contrast, SEB elicits Ig responses in cultures of spleen cells from human MHC class II-transgenic mice. Whereas i.p. administration of SEB (0.2-20 microg) to non-transgenic B10 mice elicits very weak in vivo Ig responses, identical treatment of CD4(+) cell-intact (but not CD4(+) cell-depleted) human MHC class II-transgenic mice elicits dramatic increases in both splenic Ig-secreting cells and serum Ig levels. Over a 2-week period, the SEB-induced in vivo Ig responses peak and then plateau or fall in association with a preferential increase in splenic CD8(+) cells. Nevertheless, in vivo depletion of CD8(+) cells has no sustained effect on SEB-driven Ig responses. Taken together, these observations demonstrate that the effects of SAg on in vivo humoral immune responses are highly CD4(+) cell dependent, are substantially CD8(+) cell independent and can be successfully investigated using human MHC class II-transgenic mice. This model system may be useful in investigating the polyclonally activating effects of microbial products (prototypic environmental insults) on the development of systemic autoimmunity.

Animals↗
PubMed2001

Muscle strength in knee varus and valgus.

PURPOSE: The purpose of this study was to investigate the lower-limb muscle strength in knee varus-valgus and its dependence on knee varus-valgus position. The hypothesis was that humans could differentially contract the medial and lateral muscles crossing the knee and generate significant moments in knee valgus-varus. METHODS: The subjects sat with the knee at full extension and secured from the medial, lateral, anterior, and posterior sides. Both hips were clamped from the lateral sides. The subjects adducted (abducted) the ipsilateral hip during the knee valgus (varus) maximal voluntary contraction with EMG signals recorded from muscles crossing the knee and knee joint moments measured using a six-axis force sensor. Frontal plane tibiofemoral movement was evaluated using a fluoroscope. RESULTS AND CONCLUSIONS: The subjects differentially contracted the medial and lateral muscles, and fluoroscope images showed the corresponding tibiofemoral movement. The subjects showed considerable strength in knee varus and valgus. The active knee varus strength increased significantly with increasing knee valgus angle, and the valgus strength was significantly higher when the knee was in varus position (P < 0.039). Active valgus muscle strength at 5 degrees knee varus was significantly higher than the active varus strength at 5 degrees valgus (P = 0.002). The passive resistance moment increased linearly with increasing knee valgus and varus angles, and it accounted for 28% and 35% of the total (active plus passive) moment at the 5 degrees varus and 5 degrees valgus, respectively. The significant varus-valgus muscle strength demonstrated in this study may play important roles in performing various functional tasks, maintaining joint stability, and preventing potential injuries, whether the major load and motion at the knee is in the frontal plane or not.

Adult↗
PubMed2001

Transcatheter closure of secundum atrial septal defect with a new self-expanding nitinol double disk device (Amplatzer device): experience in Nanjing.

PURPOSE: Various devices have been developed for the transcatheter closure of secundum atrial septal defect (ASD II) to avoid the morbidity, discomfort, and thoracotomy scar associated with surgical closure. The purpose of this study was to evaluate the safety and efficacy of the Amplatzer septal occluder for transcatheter closure of ASD II. PATIENTS AND METHODS: Only patients who were clinically diagnosed with ASD II were selected. The anatomy of ASD had to meet certain echocardiographic criteria. Under the guidance of echocardiography and fluoroscopy, the implantation of the device was accomplished as recommended by the manufacturer. RESULTS: Thirty patients (median age 18.4 years) with an ASD II underwent transcatheter closure. Procedure time ranged from 30-200 minutes and fluoroscopy time from 10-50 minutes. The diameter of the ASD measured by echocardiography ranged from 13-25 mm, while both the stretched diameters of the ASDs and the sizes of the devices ranged from 18-34 mm. The successful placement rate was 100%. The residual shunt rate was 100% immediately after device implantation and 10% after 24 hours. After 3 months, 3.3% of the patients had a (trivial) residual shunt. The device did not affect the surrounding structures of ASD. No embolization of the device occurred. CONCLUSION: The Amplatzer device designed for the closure of ASD II can be implanted easily and also is retrievable. Due to a low ratio of residual shunt and few complications, this device is a good choice for transcatheter closure of ASD II. Long-term follow-up will be required for widespread clinical use.

Adolescent↗
PubMed2001

Influence of vector-encoded cytokines on anti-Salmonella immunity: divergent effects of interleukin-2 and tumor necrosis factor alpha.

Attenuated Salmonella strains are of interest as new vaccine candidates and as vectors of cloned genes of other organisms. Attenuated strains expressing specific cytokines were constructed as a means of manipulating the immune response in various disease settings. In the present study, interleukin-2 (IL-2)-expressing (GIDIL2) or tumor necrosis factor alpha (TNF-alpha)-expressing (GIDTNF) strains were compared with the parent strain (BRD509) for the effect of cytokines on anti-Salmonella immunity. Expression of IL-2 resulted in a rapid clearance of the organism soon after vaccination. The reduction in GIDIL2 CFU was 50- to 300-fold higher than that of BRD509 and correlated with a markedly decreased splenomegaly. Furthermore, no evidence for any significant activation, including upregulation of surface markers and production of nitric oxide (NO), was observed in spleens of GIDIL2-injected mice. In contrast, the host response to GIDTNF was marked by an early, strong, splenic cellular influx, but surprisingly, the degree of induced splenomegaly and NO secretion was only 50% of that observed in BRD509-treated mice. Despite this, bacterial colonization of the spleen in GIDTNF-immunized animals was either slightly decreased from or equivalent to that of the BRD509-treated group, suggesting the induction of additional antimicrobial mechanisms by TNF-alpha. In vivo protection studies demonstrated that, at limiting doses, GIDIL2 was inferior to GIDTNF and BRD509 in its capacity to protect against virulent challenge. At high doses, however, all three strains exhibited equal protective efficacy. These results demonstrate that the immune response against intracellular bacteria can be manipulated by pathogen-expressed cytokines and open the way for further fine tuning of immune responses not only to Salmonella strains themselves but also to the heterologous gene(s) carried by them.

Animals↗
PubMed2001

Splicing factor slt11p and its involvement in formation of U2/U6 helix II in activation of the yeast spliceosome.

Slt11p is a new splicing factor identified on the basis of synthetic lethality with a mutation in the 5' end of U2 snRNA, a region that is involved in intermolecular U2/U6 helix II interaction. Slt11p is required for spliceosome assembly. Our genetic results suggest that Slt11p is involved in the base-pairing interaction of U2/U6 helix II in vivo. We showed that the recombinant protein binds to RNAs with some degree of structural specificity. Slt11p also anneals RNA and binds to the resulting duplexes, which contain two separated helical regions. These RNA structures are reminiscent of U2/U6 helix II, which is formed concomitantly with U4/U6 stem II, and suggest that Slt11p facilitates the cooperative formation of helix II in association with stem II in the spliceosome. We show that Slt11p and Slu7p, a second-step factor, interact with each other both in vivo and in vitro and that the binding of Slu7p to Slt11p impairs the RNA-binding activity of the latter. These results suggest that the function of Slt11p is regulated by Slu7p in the spliceosome.

Amino Acid Sequence↗
PubMed2001

Human airway smooth muscle expresses 7 isoforms of adenylyl cyclase: a dominant role for isoform V.

Adenylyl cyclases are a nine-member family of differentially regulated enzymes responsible for the synthesis of cAMP. cAMP is an important second messenger that contributes to the regulation of airway smooth muscle tone. However, little is known regarding the expression and regulation of adenylyl cyclase isoforms in airway smooth muscle cells. Nondegenerate specific primers were designed for all nine known isoforms of human adenylyl cyclase. RT-PCR experiments were performed using total RNA extracted from whole human brain (positive control), whole rat brain (negative control), whole human trachea, human airway smooth muscle, and primary cultures of human airway smooth muscle cells. Seven of the nine known isoforms of adenylyl cyclase (isoforms I, III-VII, and IX) were expressed at the mRNA level in both human airway smooth muscle and primary cultures of human airway smooth muscle cells. Immunoblot and adenylyl cyclase functional assay indicated that isoform V is likely among the functionally predominant isoforms of adenylyl cyclase in human airway smooth muscle. These results suggest that multiple isoforms of adenylyl cyclase enzymes are coexpressed in human airway smooth muscle cells and that isoform V is among the functionally important isoforms.

Adenylyl Cyclases↗
PubMed2001

Force patterns of heel strike and toe off on different heel heights in normal walking.

This study investigated the changes of force patterns of the heel strike and toe off phases at different heel heights during normal walking. Ten healthy female college students wore running shoes, flat leather shoes and high heeled shoes while walking on a Kistler force platform at their self-comfortable paces. It was found that the high heeled shoes and the leather shoes generated significantly greater vertical impact forces and anterior-posterior forces in the toe off phase than those in the heel strike phase. Accumulated impulses did not show significant increase while the heel heights increased and total support time while wearing the high heeled shoes was significantly longer than while wearing the running shoes.

Adult↗
PubMed2001

Asymmetrical response of p38 kinase activation to volume changes in primary rat astrocytes.

Activation of p38 kinase by osmotic stress has been documented in many cells; however, no report has distinguished the effects of cell volume on p38 activity from the effects of the altered osmotic condition per se. Here we report asymmetrical activation of astrocyte p38 mitogen-activated protein (MAP) kinase in response to volume increases and volume decreases. We separate effects of cell volume changes from the effects of osmotic exposure on p38 activation. Exposure to 400, 500, or 600 mOsm phosphate-buffered saline (PBS) caused cell shrinkage and an osmolality-dependent increase in p38 activity to 175%, 409%, or 518%, respectively, compared with cells maintained in control conditions (290 mOsm). Likewise, hyposmotic conditions ranging from 250 to 57 mOsm PBS caused the same activation of p38 (approximately 300% of the control value within 10 min). The activity in hyposmotic conditions did not diminish over 30 min despite cell volume recovery, indicating a dependence of extracellular osmolality or ionic strength rather than cell volume. Cells that were returned to isosmotic conditions following 30 min in 250, 150, or 57 mOsm PBS shrunk to 73%, 39%, or 26% of the control cell volume, respectively. In these cells, the activity of p38 increased further from approximately 300% of the control values in each hyposmotic condition to as much as 500% of the control activity as a function of the degree of cell shrinkage. Thus, p38 may be activated by cell shrinkage in hyperosmotic or in isoosmotic conditions, indicating reduced cell volume is a more important determinant of this enzyme activity than extracellular osmolality. Our results indicate distinct mechanisms of p38 activation in astrocytes exposed to hyperosmotic or hyposmotic PBS.

Animals↗
PubMed2001

Real-time quantitative telomeric repeat amplification protocol assay for the detection of telomerase activity.

BACKGROUND: Telomerase is a ribonucleoprotein enzyme associated with immortalization and transformation of human cells. The telomeric repeat amplification protocol (TRAP) is widely used for the detection of telomerase activity. The TRAP method, although highly sensitive and specific because it includes PCR amplification, is laborious and does not provide precise quantitative information. METHODS: We developed a real-time quantitative TRAP (RTQ-TRAP) system by combining a real-time PCR technique with the conventional TRAP method. Telomerase activity in human tumor cell lines and in 13 lymphoma samples was measured using the RTQ-TRAP assay, and the results obtained from the samples using the RTQ-TRAP method were compared with the conventional TRAP method. RESULTS: The RTQ-TRAP method was both accurate and reproducible in measuring telomerase activity in a dilution series of protein extracts from HL60 cells. Telomerase activity in 13 lymphoma samples, as determined by the RTQ-TRAP method, was ninefold lower than that measured by the conventional TRAP method. The half-life of telomerase activity in human tumor cells, as determined using RTQ-TRAP, was much shorter than the half-life reported previously. CONCLUSIONS: Our results suggest that the conventional TRAP assay frequently overestimates telomerase activity in tumor samples. The RTQ-TRAP method is thus a useful tool to rapidly and precisely quantify telomerase activity.

Enzyme-Linked Immunosorbent Assay↗
PubMed2001

[A prospective study on histological and serological changes after interferon alpha-2b treatment in patients with chronic hepatitis B infection].

OBJECTIVE: To investigate the histological changes in liver biopsies and HBV DNA changes in sera induced by 18 weeks of interferon alpha-2b therapy in patients with chronic hepatitis B infection. METHODS: Twenty-two patients were enrolled into this prospective study. All patients had a liver biopsy within 1 week before starting interferon therapy. Interferon alpha-2b was given at a dose of 3MU thrice a week for 18 weeks. A second liver biopsy was taken for comparison at the end of week 18. Blinded biopsies were scored according to Knodell's histology activity index (HAI), and examined for HBsAg, HBeAg, HBcAg and alpha - SMA by immunohistochemistry. The serum samples corresponding with liver biopsies were collected and HBV DNA, e-antigen were measured. RESULTS: Histological assessment revealed a significant improvement in intralobular inflammation and periportal necrosis after treatment(P<0.01). Fifty-five percent (12/22) patients had a reduction of hepatic necroinflammatory HAI score at the end of 18 weeks of interferon alpha-2b therapy compared to pretreatment values, but periportal inflammation and fibrosis failed to show improvement. HBeAg disappeared from liver tissues in 7 from 13 cases(53.8%)and a significant reduction of activated liver stellate cells was demonstrated in biopsies performed after suspending the interferon treatment(P=0.0004). Serum HBV DNA levels decreased significantly after treatment (P<0.01). The clearance rate of HBeAg was 42.9% after treatment. There was no significant difference between HBeAg positive and negative patients either in liver histological improvements or declining level of serum HBV DNA. CONCLUSIONS: Interferon alpha-2b may decrease the level of serum HBV DNA in the patients with chronic hepatitis B infection, and improve their necroinflammation in liver tissues.

Adult↗
PubMed2001

[Establishment and characterization of a cell line derived from human ovarian mucinous cystadenocarcinoma].

OBJECTIVE: To establish a cell line of human ovarian cancer, and study its characterization. METHODS: The cell line was established by the cultivation of subsides walls, and kept by freezing. The morphology was observed by microscope and electromicroscope. The authors studied its growth and propagation, the agglutination test of phytohemagglutinin (PHA), the chromosome analysis, heterotransplanting, immuno-histochemistry staining, the analysis of hormone, the pollution examination and the test of sensitivity to virus etc. RESULTS: A new human ovarian carcinoma cell line, designated ovarian mucinous cystadenocarcinoma 685 (OMC685), was established from mucinous cystadenocarcinoma. This cell line had subcultured to 91 generations, and some had been frozen for 8 years and revived, still grew well. This cell line possessed the feature of glandular epithelium cancer cell. The cells grew exuberantly, and the agglutinating test of PHA was positive. Karyotype was subtriploid with distortion. Heterotransplantations, alcian blue periobic acid-schiff (AbPAS), mucicarmine, alcian blue stainings, estradiol (E2) and progesterone were all positive. Without being polluted, it was sensitive to polivirus-I, adenovirus 7 and measles virus. CONCLUSIONS: OMC685 is a distinct human ovarian tumous cell line.

Cell Count↗
PubMed2001

Genotypes and polymorphisms of mutant CCR5-delta 32, CCR2-64I and SDF1-3' a HIV-1 resistance alleles in indigenous Han Chinese.

OBJECTIVE: To evaluate the frequencies and polymorphisms of CCR5-delta 32, CCR2-64I and SDF1-3' A alleles conferring resistance to HIV-1 infection in Chinese population from Han ethnic origin. METHODS: This cohort was comprised of 1251 subjects (915 men and 336 women) aged 15-80 years and none was HIV-1 positive. Genotyping of allelic CCR5-delta 32, CCR2-64I and SDF1-3' A variants was performed using PCR or PCR/RFLP assay, and further confirmed by direct DNA sequencing. RESULTS: Our finding shows that the delta 32 deletion mutation in the CCR5 gene does occur in this population and can be inherited in a Mendelian fashion in indigenous Han Chinese at a very low frequency of 0.00119 (n = 1254). The frequencies of mutant CCR2-64I and SDF1-3' A alleles were 0.20023 (n = 1251) and 0.2873 (n = 893), in this population, which are higher than those found in American Caucasians. Furthermore the polymorphisms of CCR2-64I and SDF1-3' A alleles in the Han Chinese population were different from those in American Caucasians. Statistical analysis showed that the genotype distribution of CCR5-delta 32, CCR2-64I and SDF1-3' A alleles was in equilibrium according to the Hardy-Weinberg equation. CONCLUSION: The CCR5-delta 32 mutation may not be a major resistant factor against HIV-1 infection in indigenous Han Chinese. The significance of higher frequencies of CCR2-641 and SDF1-3' A alleles (0.20023 and 0.2791) in the Han population remains to be clarified in HIV-1-positive carriers and AIDS patients.

Acquired Immunodeficiency Syndrome↗
PubMed2001

Comparison of CT virtual endoscopy with electronic colonoscopy in 30 colonic carcinoma patients.

OBJECTIVE: To evaluate the clinical application of CT virtual endoscopy (CTVE) in the diagnosis and treatment of colonic carcinoma. METHODS: We collected 30 patients pathologically proven to have colonic carcinomas as examined by CTVE and electronic colonoscopy (EC), correlating the CTVE and EC images respectively with surgical pathology in three aspects: tumor morphological features, degree of circumferential bowel wall involvement and longitudinal extent of tumor. RESULTS: CTVE imaging of colonic carcinomas showed morphological features: polypoid pattern (11 patients), ulcerative pattern (11), and infiltrative pattern (8); degree of circumferential bowel wall involvement: less than 1/2 (4 patients), from 1/2 to 3/4 (6), and more than 3/4 (20); and their longitudinal extent: 1.0-3.0 cm (7 patients), 31-5.0 cm (10), and 5.1-11.0 cm (13). Correlation of CTVE and EC with surgical pathology was found. Comparison of CTVE with surgical pathology showed tumor morphological features: concordant (26 patients), and disconcordant (4); degree of circumferential bowel wall involvement: concordant (25), disconcordant (5); and longitudinal extent of the tumor: concordant (23), disconcordant (7). Comparison of EC with surgical pathology showed tumor morphological features: concordant (22 patients), disconcordant (8); degree of circumferential bowel wall involvement: concordant (28), disconcordant (2); and longitudinal extent of the tumor: concordant (14), disconcordant (3), and undefined by EC (13). CONCLUSIONS: The images obtained by CTVE in colonic carcinoma are similar to those obtained by EC. CTVE is an excellent alternative to EC for patients who cannot tolerate EC and for cases with incomplete EC.

Adult↗
PubMed2001

Urinary excretion of aquaporin-2 water channel protein in chronic heart failure rats.

OBJECTIVE: To study the urinary excretion of aquaporin-2 (AQP2) water channel protein, and the relationship between urine AQP2 concentration and renal AQP2 gene expression in chronic heart failure (CHF) rats. METHODS: Male Sprague-Dawley rats (200 g-250 g) underwent either a left coronary artery ligation, a model of CHF, or a sham-operation. Nine weeks after surgery, urinary AQP2 concentrations and renal AQP2 protein levels were measured by Western blot. RESULTS: The urinary concentration of AQP2 water channel protein increased significantly in CHF rats as compared with sham-operated rats (365.6% +/- 102.9% vs 98.5% +/- 47.6%, P < 0.01). There was positive correlation between urinary AQP2 concentration and renal AQP2 protein expression (r = 0.89, P < 0.01). CONCLUSION: The urinary concentration of AQP2 water channel protein increases significantly in chronic heart failure rats.

Animals↗
PubMed2001

Minimum spanning trees for gene expression data clustering.

This paper describes a new framework for microarray gene-expression data clustering. The foundation of this framework is a minimum spanning tree (MST) representation of a set of multi-dimensional gene expression data. A key property of this representation is that each cluster of the expression data corresponds to one subtree of the MST, which rigorously converts a multi-dimensional clustering problem to a tree partitioning problem. We have demonstrated that though the inter-data relationship is greatly simplified in the MST representation, no essential information is lost for the purpose of clustering. Two key advantages in representing a set of multi-dimensional data as an MST are: (1) the simple structure of a tree facilitates efficient implementations of rigorous clustering algorithms, which otherwise are highly computationally challenging; and (2) as an MST-based clustering does not depend on detailed geometric shape of a cluster, it can overcome many of the problems faced by classical clustering algorithms. Based on the MST representation, we have developed a number of rigorous and efficient clustering algorithms, including two with guaranteed global optimality. We have implemented these algorithms as a computer software EXCAVATOR. To demonstrate its effectiveness, we have tested it on two data sets, i.e., expression data from yeast Saccharomyces cerevisiae, and Arabidopsis expression data in response to chitin elicitation.

Algorithms↗