Biomedical subjects

X Zhang

Publications and source records attributed to X Zhang.

At least 433 records · Page 24Linked to original sources

PubMed2001

Apoptotic cell death and Smad4 expression in transitional cell carcinoma of the renal pelvis and ureter.

PURPOSE: To investigate the frequency of apoptosis and the expression of Smad4 protein as well as their roles in transitional cell carcinoma (TCC) of the renal pelvis and ureter. METHODS: Apoptosis was detected by using terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL) technique in 34 formalin-fixed and paraffin-embedded specimens of renal pelvic and ureteral TCC. The expression of Smad4 was immunohistochemically studied. RESULTS: The incidence of apoptosis ranged from 1.10 to 3.75% with a median of 2.50% in TCC of the renal pelvis and ureter. The incidence of apoptosis was noted to be closely related to histologic grade but not to pathologic stage of the cancer. The expression of Smad4 was detected in six of 34 cases (17.6%). Regarding subcellular distribution, Smad4 protein was localized both in cytoplasm and nucleus of the cancer cells. In comparing the incidence of apoptosis with the expression of Smad4, no significant associations were seen between them. The expression of Smad4 was not related to the tumor grade nor stage of the cancer. CONCLUSIONS: The present study demonstrated close association of the incidence of apoptosis with the tumor grade of TCC of the renal pelvis and ureter. Significance of Smad4 expression was not noted in the study. It suggests that apoptotic cell death may play an important role in the tumor progression of renal pelvic and ureteral TCC.

Adult↗

PubMed2001

Clinical predictors and efficacy of antitachycardia pacing in patients with implantable cardioverter defibrillators: the importance of the patient's sex.

The ICD has become accepted as primary therapy for malignant ventricular arrhythmias. The incorporation of antitachycardia pacing into ICDs has provided a better tolerated alternative to shocks but has the potential disadvantage of delaying definitive therapy. Accordingly, we sought to delineate the characteristics of patients likely to experience unsuccessful termination of pacing and to identify ineffective pacing strategies. Of 519 patients who received ICDs, 11 clinical and tachycardia characteristics in the 162 who received antitachycardia pacing therapy for sustained ventricular arrhythmias were evaluated. Tachycardia episodes were grouped according to outcome of pacing (successful, unsuccessful, acceleration). Of 1,946 episodes, 1,502 (77.2%) were successfully reverted with pacing, 322 (16.5%) were unsuccessful, and 121 (6.2%) were accelerated. Antitachycardia pacing was less successful in women, patients with a history of myocardial infarction, those with more severe left ventricular dysfunction, those who received antiarrhythmic drugs, and those programmed to ramp pacing. Tachycardia acceleration was inversely related to tachycardia cycle length and was more frequent in patients programmed to more aggressive ramp pacing protocols. Women had an almost threefold incidence of tachycardia acceleration compared with men (14% vs 5%, P < 0.001). Antitachycardia pacing is generally successful in terminating ventricular tachycardia and has a low incidence of tachycardia acceleration. Caution should be used with rapid tachycardias and aggressive ramp pacing protocols because of an increased risk of acceleration. Antitachycardia pacing appears less successful and has a higher incidence of complications in women.

Cardiac Pacing, Artificial↗

PubMed2001

Use of stable isotopes to identify benzoate as a metabolite of benzene degradation in a sulphidogenic consortium.

An enriched sulphidogenic consortium capable of mineralizing benzene was used to study the metabolic pathway of anaerobic benzene degradation. Benzoate was detected in active cultures and benzene was confirmed to be the source of this benzoate by the addition of deuterated benzene (D6) and subsequent detection of deuterated benzoate (D5) in active cultures but not in autoclaved controls. Benzoate was utilized by this culture at 1/12 the rate of benzene, while its presence did not inhibit benzene utilization. The benzene utilization rate was reduced, however, in the presence of 2-fluorobenzoate. When the culture was supplemented with [(13)C]-bicarbonate, the carboxyl group on benzoate was not labelled with [(13)C]-carbon, suggesting that this transformation relies on a more complex set of reactions than simple addition of carbonate.

Bacteria↗

PubMed2001

Primary transanal rectosigmoidectomy for Hirschsprung's disease: Preliminary results in the initial 33 cases.

PURPOSE: The authors describe their newly developed technique-primary transanal rectosigmoidectomy for Hirschsprung's disease (HD) and its preliminary results in neonates and infants. METHODS: Thirty-four consecutive patients (26 boys) with biopsy-proven rectosigmoid HD, aged 18 days to 4 years, underwent this new procedure. Rectal mucosectomy started 1 to 1.5 cm posteriorly and 2 to 3 cm anteriorly proximal to the dentate line. The rectal muscular sleeve below the peritoneal reflection was resected to the level of the striated muscle complex, leaving a shorter muscular cuff, into which a partial internal sphincterotomy was made posteriorly. An oblique anastomosis was constructed between the pull-through ganglionic colon and the anus canal. RESULTS: The mean time for the operation was 160 minutes, and the average length of bowel resected was 29.5 cm (range, 12.5 to 41 cm). Two children (6.06%, 2 of 33) had 2 to 5 episodes of postoperative enterocolitis (EC). One was cured by rectal irrigation and dilation, and the another by Lynn's myectomy. Eighty-four percent of patients had 1 to 6 bowel movements per day during a 6- to 18-month follow-up period. CONCLUSIONS: Primary transanal rectosigmoidectomy for HD is logical and associated with excellent early results. A long-term follow-up is required to determine bowel functions. J Pediatr Surg 36:1816-1819.

Anal Canal↗

PubMed2001

Generation and mapping of expressed sequence tags from virus-infected swine macrophages.

In an effort to identify genes that have a major effect on macrophage function during viral infection, we employed differential display reverse transcription (DDRT)-PCR to capture expressed sequence tags (ESTs) of swine alveolar macrophages infected by the porcine reproductive and respiratory syndrome virus (PRRSV). Sequence analyses showed that approximately 60% of these ESTs had significant similarity (> or =93%) to known pig ESTs or genes or matched sequences from other species with homology > or =80%. To determine chromosomal localization, PCR-based mapping was performed across either swine somatic cell hybrid or radiation hybrid panels. A total of 48 porcine viral response ESTs were mapped via the swine somatic cell panel or the INRA-Minnesota porcine Radiation Hybrid (IMpRH) panel (LOD > 6.0). Northern blot analyses confirmed PRRSV-induced altered transcript expression for several ESTs, including a 2'-5' oligoadenylate synthetase and a putative dual-specificity phosphatase. These virus-response ESTs represent good candidate genes for understanding PRRSV pathogenesis and for dissecting host genes which may have major effect on disease resistance.

2',5'-Oligoadenylate Synthetase↗

PubMed2001

Formation and evolution of haloacetic acids in drinking water of Beijing City.

The formation and evolution of haloacetic acids (HAAs) in drinking water were examined in five water treatment plants in Beijing City, China. It was found that HAAs in water increased due to prechlorination and postchlorination. The conventional treatment processes removed the HAAs in less than 20%. By comparison, activated carbon bed removed 49-86% of HAAs and was considered to be an effective treatment unit for HAAs removal. The HAAs concentration in distribution system was associated with water sources, especially the total organic carbon in raw water, while its fluctuation appeared small.

Acetates↗

PubMed2001

Allosteric regulation of BK channel gating by Ca(2+) and Mg(2+) through a nonselective, low affinity divalent cation site.

The ability of membrane voltage to activate high conductance, calcium-activated (BK-type) K(+) channels is enhanced by cytosolic calcium (Ca(2+)). Activation is sensitive to a range of [Ca(2+)] that spans over four orders of magnitude. Here, we examine the activation of BK channels resulting from expression of cloned mouse Slo1 alpha subunits at [Ca(2+)] and [Mg(2+)] up to 100 mM. The half-activation voltage (V(0.5)) is steeply dependent on [Ca(2+)] in the micromolar range, but shows a tendency towards saturation over the range of 60-300 microM Ca(2+). As [Ca(2+)] is increased to millimolar levels, the V(0.5) is strongly shifted again to more negative potentials. When channels are activated by 300 microM Ca(2+), further addition of either mM Ca(2+) or mM Mg(2+) produces similar negative shifts in steady-state activation. Millimolar Mg(2+) also produces shifts of similar magnitude in the complete absence of Ca(2+). The ability of millimolar concentrations of divalent cations to shift activation is primarily correlated with a slowing of BK current deactivation. At voltages where millimolar elevations in [Ca(2+)] increase activation rates, addition of 10 mM Mg(2+) to 0 Ca(2+) produces little effect on activation time course, while markedly slowing deactivation. This suggests that Mg(2+) does not participate in Ca(2+)-dependent steps that influence current activation rate. We conclude that millimolar Mg(2+) and Ca(2+) concentrations interact with low affinity, relatively nonselective divalent cation binding sites that are distinct from higher affinity, Ca(2+)-selective binding sites that increase current activation rates. A symmetrical model with four independent higher affinity Ca(2+) binding steps, four voltage sensors, and four independent lower affinity Ca(2+)/Mg(2+) binding steps describes well the behavior of G-V curves over a range of Ca(2+) and Mg(2+). The ability of a broad range of [Ca(2+)] to produce shifts in activation of Slo1 conductance can, therefore, be accounted for by multiple types of divalent cation binding sites.

Action Potentials↗

PubMed2001

Establishment of hybridoma cell lines producing monoclonal antibodies against hepatitis B virus surface antigens (a, d, and r) and development of sensitive ELISA diagnostic test.

A new treble-coated enzyme-linked immunoadsorbent assay (ELISA) kit of detecting Hepatitis B virus (HBV) surface antigen subtypes a, d and r (HBsAg-a, -d, -r) was developed by using four established hybridoma cell lines, of which two specifically secrete monoclonal antibodies (MAbs) against HBsAg-a (anti-HBsAg-a), one against -d (anti-HBsAg-d), and one against -r (anti-HBsAg-r). The approach of hybridoma cell lines' establishment were by fusing myeloma cells (SP2/0) with splenocytes from BALB/c mice immunized with a mixture of HBsAg-a, -d, -r. The ascitic MAb productivity of the four cell lines was at the titres of 1:10(6)-1:10(8). A treble-coated ELISA based HBV diagnostic kit was developed for detecting all of the three responding subtypes of HBsAgs. A 96-well ELISA microplate was coated with anti-HBSAg-a, -d, -r at a ratio of 3: 1: 0.5, with a horseradish peroxidase (HRP) conjugated anti-HBsAg-a as the labelled antibody. For clinical application, the new developed diagnostic kit detected HBsAgs of adr, adw, ayr, and ayw at a rate of lower than 0.25, 0.25, 0.5, and 0.5 ng/mL, respectively. Results indicated that this kit was more rapid and sensitive than that other current ELISA-based kits coated with a single MAb (e.g., anti-HBsAg-a).

Animals↗

PubMed2001

Production of cloned goats from enucleated oocytes injected with cumulus cell nuclei or fused with cumulus cells.

This study was designed to produce cloned goats from cumulus cells. Cloning donor nuclei were from cumulus cells either freshly isolated or cultured in vitro. Enucleated oocytes were either injected with cumulus cell nuclei without piezo-driven manipulator (injection method) or fused with cumulus cells (fusion method). The survival rate of cloned embryos, obtained by injection, was higher than that derived from fusion (62.7 and 45.9%, respectively). Two cloned goats were derived by fusion with in vitro cultured cumulus cells without starvation, but died shortly after natural birth, from respiratory difficulties. Their birth weights (2.23 kg and 2.03 kg) were within the normal range (2.0-2.7 kg) and postmortem analysis revealed no morphological abnormalities. The third cloned goat, derived by injection of nuclei from freshly isolated cumulus cells, weighed 3.3 kg at birth, and was 37% overweight compared with the average weight of the same species. This goat is healthy and well as this paper is being prepared. Nested PCR-RFLP analysis confirmed that all the cloned goats were derived from the donor cells.

Animals↗

PubMed2001

The leucine-rich repeat domain can determine effective interaction between RPS2 and other host factors in arabidopsis RPS2-mediated disease resistance.

Like many other plant disease resistance genes, Arabidopsis thaliana RPS2 encodes a product with nucleotide-binding site (NBS) and leucine-rich repeat (LRR) domains. This study explored the hypothesized interaction of RPS2 with other host factors that may be required for perception of Pseudomonas syringae pathogens that express avrRpt2 and/or for the subsequent induction of plant defense responses. Crosses between Arabidopsis ecotypes Col-0 (resistant) and Po-1 (susceptible) revealed segregation of more than one gene that controls resistance to P. syringae that express avrRpt2. Many F(2) and F(3) progeny exhibited intermediate resistance phenotypes. In addition to RPS2, at least one additional genetic interval associated with this defense response was identified and mapped using quantitative genetic methods. Further genetic and molecular genetic complementation experiments with cloned RPS2 alleles revealed that the Po-1 allele of RPS2 can function in a Col-0 genetic background, but not in a Po-1 background. The other resistance-determining genes of Po-1 can function, however, as they successfully conferred resistance in combination with the Col-0 allele of RPS2. Domain-swap experiments revealed that in RPS2, a polymorphism at six amino acids in the LRR region is responsible for this allele-specific ability to function with other host factors.

Alleles↗

PubMed2001

Predominance of a novel splenic B cell population in mice expressing a transgene that encodes multireactive antibodies: support for additional heterogeneity of the B cell compartment.

We generated IgHmudelta transgenic mice using a V(H) gene that in A/J mice encodes multireactive BCR in the preimmune B cell compartment and is predominantly expressed by a memory B cell subpopulation. Most primary splenic B cells in these mice have a size, cell-surface phenotype and in vitro response profile distinct from mature follicular (B2), marginal zone (MZ) or B1 B cells, but are long-lived and appear to be slowly cycling. They reside in conventional B cell areas of the spleen and mount robust foreign antigen-driven germinal center responses, but do not efficiently differentiate to secretory phenotype. We propose that these qualities result from ongoing, low-avidity BCR-self-ligand interactions and promote entry into the memory pathway. Given these data, and the enormous diversity and characteristic multireactivity of the preimmune antibody repertoire, we also suggest that it may be more appropriate to view the primary B cell compartment as a continuum of functional and phenotypic 'layers', rather than as a group of discrete B1, B2 and MZ subsets.

Animals↗

PubMed2001

Citalopram distribution in postmortem cases.

This is a report of the analytical findings in 13 cases investigated by either the Office of the Chief Medical Examiner, State of Maryland or the Bexar County (San Antonio, TX) Medical Examiner's Office in which citalopram, a highly selective serotonin reuptake inhibitor used therapeutically as an antidepressant, was identified. In 8 of the 9 cases in which both blood and urine specimens were received, the urine citalopram concentration exceeded the blood concentration, indicating that urine is an appropriate specimen for screening citalopram use. The average liver to blood citalopram concentration ratio was 6.5 (range 3.1-13, n = 6). Three cases had blood concentrations less than 0.24 mg/L, which is in the reported antemortem therapeutic range of the drug. Eleven cases had blood concentrations less than 1.3 mg/L; in each of these cases, citalopram was determined to be an incidental finding to the ultimate cause of death. Quantitation of citalopram and the metabolite desmethylcitalopram in these cases yielded an average parent-to-metabolite ratio of 6.4.

Autopsy↗

PubMed2001

Mechanisms of alcohol-nicotine interactions: alcoholics versus smokers.

This article represents the proceedings of a symposium at the 2000 ISBRA Meeting in Yokohama, Japan. The chairs were Toshio Narahashi and Bo Söderpalm. The presentations were (1) Nicotinic mechanisms and ethanol reinforcement: Behavioral and neurochemical studies, by Bo Söderpalm, M. Ericson, P. Olausson, and J. A. Engel; (2) Chronic nicotine and ethanol: Differential regulation in gene expression of nicotinic acetylcholine receptor subunits, by X. Zhang and A. Nordberg; (3) Nicotine-ethanol interactions at neuronal nicotinic acetylcholine receptors, by Toshio Narahashi, William Marszalec, and Gary L. Aistrup; (4) Relapse prevention in alcoholics by cigarette smoking? Treatment outcome in an observational study with acamprosate, by L.G. Schmidt, U. Kalouti, M. Smolka, and M. Soyka; and (5) Effect of nicotine on voluntary ethanol intake and development of alcohol dependence in male rats, by L. Hedlund and G. Wahlström.

Acamprosate↗

PubMed2001

Multivariate matching and bias reduction in the surgical outcomes study.

BACKGROUND: Outcomes studies often need a level of detail that is not present in administrative data, therefore requiring abstraction of medical charts. Case-control methods may be used to improve statistical power and reduce abstraction costs, but limitations of exact matching often preclude the use of many covariates. Unlike exact matching, multivariate matching may allow cases to be matched simultaneously on hundreds of covariates. OBJECTIVES: To develop multivariate matched case-control pairs in a study of death after surgery in the Medicare population. RESEARCH DESIGN: Using 830 randomly selected index cases of patients who died within 60 days from admission, controls were found who did not die within that time period, matching on risk for death and other patient characteristics with up to 173 variables used simultaneously in the matching algorithms. SUBJECTS: General and orthopedic Medicare surgical cases in Pennsylvania from 1995 to 1996. Controls were either selected from across the entire state (108,765 possible subjects), or from within the same hospital as the case. MEASURES: Percent bias reduction and the average difference between cases and controls in units of standard deviations. RESULTS: Matched controls were far more similar to cases (deaths) upon admission to the hospital than typical patients, both in statewide and within hospital matches. Bias reduction was usually greater than 50% and often approached 100%. The difference between cases and matched controls for most variables was usually below 0.2 SD. CONCLUSIONS: Multivariate matching methods may aid in conducting studies with Medicare claims records by improving the quality of matches, thereby achieving a better understanding of the etiology of outcomes.

Aged↗

PubMed2001

Gastric choriocarcinoma shows characteristics of adenocarcinoma and gestational choriocarcinoma: a comparative genomic hybridization and fluorescence in situ hybridization study.

The authors report two cases of the rare primary gastric choriocarcinoma. These tumors showed an overwhelming predominance of cytotrophoblast- and syncytiotrophoblast-like tumor cells that were positive for beta-human chorionic gonadotrophin, with small foci of glandular differentiation. Beta-human chorionic gonadotrophin was also detected serologically in one patient. Comparative genomic hybridization study was performed on one specimen. Copy number gains of chromosomes 12, 17, 20, 22, and X, together with losses on 18q, were the major findings. Except for the gain of chromosome 12, which is known to be uncommon in primary gastric adenocarcinoma but frequently associated with choriocarcinoma, the remaining genomic imbalances were among the most common comparative genomic hybridization findings reported in primary gastric adenocarcinoma. Fluorescence in situ hybridization on paraffin sections of both specimens confirmed the presence of polysomy 17 and trisomy 12. These results suggest that primary gastric choriocarcinoma genetically possesses characteristics of both adenocarcinoma and gestational choriocarcinoma. The authors believe this is the first interphase cytogenetics study on this rare tumor, and that the results support the theory that gastric choriocarcinoma arises from alternate differentiation pathways of adenocarcinoma.

Adenocarcinoma↗

PubMed2001

Hydrogen peroxide is involved in abscisic acid-induced stomatal closure in Vicia faba.

One of the most important functions of the plant hormone abscisic acid (ABA) is to induce stomatal closure by reducing the turgor of guard cells under water deficit. Under environmental stresses, hydrogen peroxide (H(2)O(2)), an active oxygen species, is widely generated in many biological systems. Here, using an epidermal strip bioassay and laser-scanning confocal microscopy, we provide evidence that H(2)O(2) may function as an intermediate in ABA signaling in Vicia faba guard cells. H(2)O(2) inhibited induced closure of stomata, and this effect was reversed by ascorbic acid at concentrations lower than 10(-5) M. Further, ABA-induced stomatal closure also was abolished partly by addition of exogenous catalase (CAT) and diphenylene iodonium (DPI), which are an H(2)O(2) scavenger and an NADPH oxidase inhibitor, respectively. Time course experiments of single-cell assays based on the fluorescent probe dichlorofluorescein showed that the generation of H(2)O(2) was dependent on ABA concentration and an increase in the fluorescence intensity of the chloroplast occurred significantly earlier than within the other regions of guard cells. The ABA-induced change in fluorescence intensity in guard cells was abolished by the application of CAT and DPI. In addition, ABA microinjected into guard cells markedly induced H(2)O(2) production, which preceded stomatal closure. These effects were abolished by CAT or DPI micro-injection. Our results suggest that guard cells treated with ABA may close the stomata via a pathway with H(2)O(2) production involved, and H(2)O(2) may be an intermediate in ABA signaling.

Abscisic Acid↗

PubMed2001

Radiation impedance of a finite circular piston on a viscoelastic half-space with application to medical diagnosis.

In a recent study a new analytical solution was developed and validated experimentally for the problem of surface wave generation on a linear viscoelastic half-space by a rigid circular disk located on the surface and oscillating normal to it. The results of that study suggested that, for the low audible frequency range, some previously reported values of shear viscosity for soft biological tissues may be inaccurate. Those values were determined by matching radiation impedance measurements with theoretical calculations reported previously. In the current study, the sensitivity to shear viscoelastic material constants of theoretical solutions for radiation impedance and surface wave motion are compared. Theoretical solutions are also compared to experimental measurements and numerical results from finite-element analysis. It is found that, while prior theoretical solutions for radiation impedance are accurate, use of such measurements to estimate shear viscoelastic constants is not as precise as the use of surface wave measurements.

Elasticity↗

PubMed2001

A phenomenological model for the responses of auditory-nerve fibers: I. Nonlinear tuning with compression and suppression.

A phenomenological model was developed to describe responses of high-spontaneous-rate auditory-nerve (AN) fibers, including several nonlinear response properties. Level-dependent gain (compression), bandwidth, and phase properties were implemented with a control path that varied the gain and bandwidth of tuning in the signal-path filter. By making the bandwidth of the control path broad with respect to the signal path, the wide frequency range of two-tone suppression was included. By making the control-path filter level dependent and tuned to a frequency slightly higher than the signal-path filter, other properties of two-tone suppression were also included. These properties included the asymmetrical growth of suppression above and below the characteristic frequency and the frequency offset of the suppression tuning curve with respect to the excitatory tuning curve. The implementation of this model represents a relatively simple phenomenological description of a single mechanism that underlies several important nonlinear response properties of AN fibers. The model provides a tool for studying the roles of these nonlinearities in the encoding of simple and complex sounds in the responses of populations of AN fibers.

Audiometry, Pure-Tone↗