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Biomedical subjects

Li Zhang

Publications and source records attributed to Li Zhang.

At least 325 records · Page 18Linked to original sources
PubMed2005

Inhibition of Qi site of mitochondrial complex III with antimycin A decreases persistent and transient sodium currents via reactive oxygen species and protein kinase C in rat hippocampal CA1 cells.

Hypoxia-induced inhibition of Qi site of mitochondrial complex III under hypoxia has received attention, but its downstream pathways remain unclear. In this paper, we used Qi site inhibitor antimycin A to mimic the inhibition of the Qi site of mitochondrial complex III and studied the effects of the inhibition of this site on persistent sodium currents, transient sodium currents, and neuronal excitability in rat hippocampal CA1 cells with whole cell patch-clamp methods. The results showed that antimycin A decreased the amplitude of both persistent and transient sodium currents; antioxidant 2-mercaptopropionylglycine or 1,10 phenanthroline abolished the effect of antimycin A; the complex III Qo site inhibitor stigmatellin, the protein kinase C inhibitor chelerythrine, but not the protein kinase A inhibitor H89, canceled the effect of antimycin A; antimycin A decreased the amplitude of both persistent and transient sodium currents only at more depolarized membrane potentials and the decrease percentage of both persistent and transient sodium currents after antimycin A at potentials above -50 mV increased with the change in potentials toward more depolarized direction; exogenous application of H2O2 inhibited the amplitude of both persistent and transient sodium currents; the amount of current required to trigger spikes was increased and the number of spikes produced by varying levels of currents was decreased by antimycin A. These results suggest that the inhibition of Qi site of mitochondrial complex III decreases both persistent and transient sodium currents via reactive oxygen species and protein kinase C in rat hippocampal CA1 cells.

Action Potentials↗
PubMed2005

Inaccurate electrocardiographic interpretation of long QT: the majority of physicians cannot recognize a long QT when they see one.

BACKGROUND: Physicians in all fields of medicine may encounter patients with long QT syndrome (LQTS). It is important to define the percentage of physicians capable of distinguishing QT intervals that are long from those that are normal because LQTS can be lethal when left untreated. OBJECTIVES: The purpose of this study was to define the percentage of physicians in the different disciplines of medicine who can recognize a long QT when they see one. METHODS: We presented the ECGs of two patients with LQTS and two healthy females to 902 physicians (25 world-renowned QT experts, 106 arrhythmia specialists, 329 cardiologists, and 442 noncardiologists) from 12 countries. They were asked to measure the QT, calculate the QTc (the QT interval corrected for the heart rate), and determine whether the QT is normal or prolonged. RESULTS: For patients with LQTS, >80% of arrhythmia experts but <50% of cardiologists and <40% of noncardiologists calculated the QTc correctly. Underestimation of the QTc of patients with LQTS and overestimation of the QTc of healthy patients were common. Interobserver agreement was excellent among QT experts, moderate among arrhythmia experts, and low among cardiologists and noncardiologists (kappa coefficient = 0.82, 0.44, and < 0.3, respectively). Correct classification of all QT intervals as either "long" or "normal" was achieved by 96% of QT experts and 62% of arrhythmia experts, but by only <25% of cardiologists and noncardiologists. CONCLUSIONS: Most physicians, including many cardiologists, cannot accurately calculate a QTc and cannot correctly identify a long QT.

Cardiology↗
PubMed2005

Immobilized carbon nanotubes as matrix for MALDI-TOF-MS analysis: applications to neutral small carbohydrates.

In this work, we reported on the advantages of immobilized carbon nanotubes as a novel MALDI-matrix. Recently, carbon nanotubes have been reported to be an effective MALDI matrix for small molecules (Anal. Chem.2003, 75, 6191), as it can eliminate the interfering matrix peaks as well as form a web morphology to fully disperse the analyte and allow strong ultraviolet absorption for enhanced pulsed laser desorption and ionization. In our study, to overcome the problem that the carbon nanotube matrix may fly off from the target, a type of polyurethane adhesive, NIPPOLAN-DC-205, is introduced to immobilize carbon nanotubes on the target, which enables widespread application of carbon nanotubes as matrix for MALDI-MS analysis. At the same time, the properties of the carbon nanotubes as an efficient matrix remained after immobilization. The presence of NIPPOLAN-DC-205 increases the time for analysis at a particular desorption spot by minimizing the time-consuming search for "hot spots" and facilitating experiments such as post source decay (PSD) which need longer-lasting signals. Moreover, NIPPOLAN-DC-205 produces no interference peaks and can easily be cleaned with acetone. Fast evaporation technology may be used to enhance signal reproducibility in MALDI analysis using carbon nanotubes as matrix. Consequently, the applicability of the carbon nanotube as matrix for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis of low molecular mass analytes is highly improved. The feasibility of the method employing polyurethane is demonstrated by comparison of the results produced from the carbon nanotube matrix with and without immobilization. In addition, neutral small carbohydrates, which are difficult to be ionized normally, can be cationized with high efficiency by MALDI-TOF-MS using the immobilized carbon nanotube matrix. The method was further applied to analyze peptides and detect urine glucose successfully.

Carbohydrates↗
PubMed2005

Preparation of fluorescent polyvinyl alcohol keto-derivatives nanoparticles and selective determination of chromium(VI).

A novel fluorescent polyvinyl alcohol keto-derivatives nanoparticle (PVAK) has been prepared in one-step method. The nanoparticles has excitation and emission maxima at 349 and 462 nm, respectively. Based on the fluorescence quenching of PVAK by Cr(VI), we established a simple and selective fluorimetric method for the determination of Cr(VI) without separation of Cr(III) in water. The reaction conditions between Cr(VI) and PVAK were investigated in detail. Furthermore, the reaction mechanism between PVAK and Cr(VI) was also discussed. Under optimal experimental conditions, a limit of detection of 0.02 microg mL(-1) was achieved. The calibration curve was linear over the concentration range 0.1-13.2 microg mL(-1) with a correlation coefficient of 0.9987. The proposed method has been applied to the selective quantification of Cr(VI) in synthetic samples and waste-water samples with the satisfactory results.

Carboxylic Acids↗
PubMed2005

Differential expression of interleukin-8 and its receptors in the neuroendocrine and non-neuroendocrine compartments of prostate cancer.

Hormonal therapy (androgen ablation and/or inhibition of androgen action) is the treatment of choice for advanced prostate cancer. After an initial response in most patients, tumors invariably progress to an androgen-independent state. It is unclear how prostate cancer cells proliferate without androgen. Recent studies suggest that interleukin-8 may promote androgen-independent proliferation, but the source of interleukin-8 in the prostate is unknown. Using immunohistochemistry, we show that interleukin-8 was expressed by the neuroendocrine tumor cells in human prostate cancer tissue. Expression of the interleukin-8 receptor CXCR1 was negative or low in benign prostatic tissue and was frequently increased in malignant cells of high-grade prostatic intraepithelial neoplasia and prostate cancer; however, CXCR1 was not detected in the neuroendocrine tumor cells, suggesting a paracrine mechanism by which interleukin-8 produced by neuroendocrine tumor cells stimulates androgen-independent proliferation of prostate cancer. Neuroendocrine tumor cells expressed another type of interleukin-8 receptor, CXCR2, suggesting an autocrine mechanism by which interleukin-8 regulates the differentiation or function of the neuroendocrine cells. These results, combined with previous reports that neuroendocrine differentiation is induced by hormonal therapy, suggest that neuroendocrine cells play an important role in promoting androgen-independent growth of prostate cancer through interleukin-8 signaling.

Carcinoma, Neuroendocrine↗
PubMed2005

Terpenoids from the roots and rhizomes of Nardostachys chinensis.

A new diterpene, 10-isopropyl-2,2,6-trimethyl-2,3,4,5-tetrahydronaphtha[1,8-bc]oxocine-5,11-diol (1), and a new monoterpene, 6-hydroxy-7-(hydroxymethyl)-4-methylenehexahydrocyclopenta[c]pyran-1(3H)-one, together with four known sesquiterpenes, delta1(10)-aristolene-9beta-ol, debilon, nardosinone, and kanshone A, were isolated from the roots of Nardostachys chinensis. The structures of the new compounds were established on the basis of their spectroscopic data, and the structure of 1 was confirmed by X-ray crystallographic analysis.

Diterpenes↗
PubMed2005

Analysis of combined treatment of embolic stroke in rat with r-tPA and a GPIIb/IIIa inhibitor.

Suppression of platelet activation improves the efficacy of thrombolytic therapy for stroke. Thus, combination treatment with recombinant tissue plasminogen activator (r-tPA) and 7E3 F(ab')2, a GPIIb/IIIa inhibitor that binds the platelet to fibrin, may improve the efficacy of thrombolytic therapy in embolic stroke. Magnetic resonance imaging (MRI) was used to monitor treatment response in rats subjected to embolic middle cerebral artery (MCA) occlusion (MCAo). Animals were randomized into treated (n=12) and control (n=10) groups and received intravenous combination therapy or saline, respectively, 4 hours after MCAo. Magnetic resonance imaging (MRI) measurements performed 1 hour after MCAo showed no difference between groups. However, an increased incidence (50%) of MCA recanalization was found in the treated group at 24 hours compared with 20% in the control group. The area of low cerebral blood flow at 24 and 48 hours was significantly smaller in the combination treatment group, and the lesion size, as indicated from the T2 and T1 maps, differed significantly between groups. Fluorescence microscopy measurements of cerebral microvessels perfused with fluorescein isothiocyanate-dextran and measurements of infarct volume revealed that the combination treatment significantly increased microvascular patency and reduced infarct volume, respectively, compared with the control rats. The efficacy of combination treatment 4 hours after ischemia is reflected by MRI indices of tissue perfusion, MCA recanalization, and reduction of lesion volume. The treatment also reduced secondary microvascular perfusion deficits.

Animals↗
PubMed2005

Quantitative evaluation of BBB permeability after embolic stroke in rat using MRI.

We sought to identify magnetic resonance imaging (MRI) parameters that can identify as well as predict disruption of the blood-brain barrier (BBB) after embolic stroke in the rat. Rats subjected to embolic stroke with (n=13) and without (n=13) rt-PA treatment were followed with MRI using quantitative permeability-related parameters, consisting of: transfer constant (K(i)) of Gd- DTPA, the distribution volume (V(p)) of the mobile protons, and the inverse of the apparent forward transfer rate for magnetization transfer (k(inv)), as well as the apparent diffusion coefficient of water (ADC(w)), T2, and cerebral cerebral blood flow (CBF). Tissue progressing to fibrin leakage resulting from BBB disruption and adjacent tissue were then analyzed to identify MRI markers that characterize BBB disruption. Animals were killed after final MRI measurements at 24 h after induction of embolic stroke and cerebral tissues were perfused and stained to detect fibrin leakage. K(i), V(p), and k(inv) were the most sensitive early (2 to 3 h) indices of the cerebral tissue that progresses to fibrin leakage. Cerebral blood flow was not significantly different between ischemic tissue with a compromised and an intact BBB. Our data indicate that compromise of the BBB can be sensitively predicted using a select set of MR parameters.

Animals↗
PubMed2005

The prevalence of celiac disease in average-risk and at-risk Western European populations: a systematic review.

Until recently, celiac disease (CD) was felt to be a rare disease in the United States. The aim of this study was to conduct a systematic review of the prevalence of CD in general Western populations and in populations at high risk for CD. Standard systematic review methodology was used. A literature search was conducted in MEDLINE (1966 to October 2003) and EMBASE (1974 to December 2003) databases. Qualitative and quantitative prevalence estimates were produced after assessing study heterogeneity. The prevalence of CD in general Western populations is close to 1% and is somewhat higher in certain Western European populations. The prevalence of CD in populations at risk for CD is as follows: 3%-6% in type 1 diabetic patients, up to 20% in first-degree relatives, 10%-15% in symptomatic iron-deficiency anemia (IDA), 3%-6% in asymptomatic IDA, and 1%-3% in osteoporosis. The prevalence of CD in patients suspected of having CD varied depending on the reasons for suspecting CD and on whether the study was conducted in a referral center. In general, the prevalence ranged from 5% to 15%, but was up to 50% in symptomatic patients evaluated in a tertiary referral center. CD is a common medical condition. The prevalence is higher still in high-risk groups. Clinicians in a variety of specialties should have a high index of suspicion for the diagnosis of CD and in particular need to pay close attention to the identified high-risk groups.

Adult↗
PubMed2005

Consequences of testing for celiac disease.

Population screening studies have identified that up to two thirds of celiac disease (CD) cases are asymptomatic. The aim of this study was to conduct a systematic review of the expected consequences of testing for CD in the following populations: (1) patients with symptoms suggestive of CD, (2) asymptomatic at-risk populations, and (3) general population. Standard systematic review methodology was used. A comprehensive literature search was conducted in MEDLINE (1996-2003), EMBASE (1974-2003), CAB (1972 forward), PsychINFO (1840-2003), AGRICOLA (1970-2003), and Sociological Abstracts (1963 forward); searches were conducted in December 2003. Pooled summary estimates were not calculated. The majority of the included studies were before-after studies, case control, or retrospective cohorts. The quality of evidence for the before-after studies is weaker. The overall strength of the evidence for this issue was fair to good. This area of research is relatively new, and further high-quality studies are required. The consequences of testing for celiac disease in symptomatic individuals appears to have a positive impact on patient-relevant outcomes. The data are less clear for those with silent CD or those with lower grade histologic lesions in small bowel biopsy. The literature suggests that compliance is less than ideal in these individuals, especially if diagnosed when adults. Long-term outcomes have not been extensively studied in those with silent CD.

Adult↗
PubMed2005

The diagnostic accuracy of serologic tests for celiac disease: a systematic review.

Clinicians are increasingly utilizing noninvasive serologic tests for the diagnosis and screening of celiac disease (CD). The aim of this study was to conduct a systematic review of the diagnostic performance of serologic tests for the diagnosis and screening of CD. Standard systematic review methodology was used. A literature search was conducted in MEDLINE (1966 to October 2003) and EMBASE (1974 to December 2003) databases. A weighted mean of the sensitivity and specificity along with 95% confidence intervals and summary receiver operating characteristic (ROC) curves were calculated. The pooled specificity of endomyseal antibody (EMA)-monkey esophagus (ME) or EMA-human umbilical cord (HU) was close to 100% in adults and children. The pooled specificity of transglutaminase antibody (tTG)-guinea pig (GP) and tTG-human recombinant (HR) were between 95% and 99%. IgA-EMA-ME demonstrated sensitivities of 96% and 97% in children and adults, respectively. EMA-HU demonstrated a similar sensitivity of 97% in children but 90% in adults. The pooled sensitivity of tTG-GP in adults and children was 90% and 93%, respectively. The sensitivity of tTG-HR was 98% and 96%, respectively. The performance of antigliadin antibody was inferior to that of EMA and tTG. EMA and tTG offer high sensitivity and specificity. The sensitivity of these tests appears to be lower than reported when milder histologic grades are used to define CD (below 90%). If true, the nearly perfect negative predictive value of these tests would drop. The positive predictive value of these tests is likely lower than reported when the tests are applied in low-prevalence populations.

Antibodies↗
PubMed2005

Genetic engineering of human embryonic stem cells with lentiviral vectors.

Human embryonic stem (hES) cells present a valuable source of cells with a vast therapeutic potential. However, the low efficiency of directed differentiation of hES cells remains a major obstacle in their uses for regenerative medicine. While differentiation may be controlled by the genetic manipulation, effective and efficient gene transfer into hES cells has been an elusive goal. Here, we show stable and efficient genetic manipulations of hES cells using lentiviral vectors. This method resulted in the establishment of stable gene expression without loss of pluripotency in hES cells. In addition, lentiviral vectors were effective in conveying the expression of an U6 promoter-driven small interfering RNA (siRNA), which was effective in silencing its specific target. Taken together, our results suggest that lentiviral gene delivery holds great promise for hES cell research and application.

Cell Differentiation↗
PubMed2005

Derivation of adipocytes from human embryonic stem cells.

Human embryonic stem (hES) cells are undifferentiated and pluripotent cells that hold great therapeutic potential, but are hampered by our limited knowledge to promote specific cell differentiation. Here we provide the first report of the directed differentiation of hES cells into adipocytes. Embryoid bodies (EBs) derived from hES cells are shown to respond to factors that promote adipogenesis. Differentiated cells were observed that displayed the key features of adipocytes, i.e., expression of specific molecular markers, such as peroxisome proliferator-activated receptor gamma2 (PPARgamma2), adipocyte fatty acid binding protein (aP2) and adiponectin, the secretion of leptin, and the accumulation of lipid droplets in cytoplasm. Taken together, our results demonstrate that adipocytes derived from hES cells in vitro can provide a novel model system to study human adipogenesis and obesity.

Adipocytes↗
PubMed2005

High-density lipoprotein cholesterol levels increase with age, body mass index, blood pressure and fasting blood glucose in a rural Uygur population in China.

OBJECTIVES: To investigate the distribution of the serum high-density lipoprotein cholesterol (HDLC) levels and its relationship with obesity, hypertension and diabetes in a Uygur case-control study on hypertension. DESIGN: A case-control (339 hypertensive cases, 272 normotensive controls) study on hypertension was conducted, and obesity, hypertension, lipid profiles and fasting blood glucose were analyzed. METHODS: The demographic data, history of disease and lifestyles, including diet, smoking and salt intake, were recorded and three measurements of blood pressure were obtained by trained observers. The fasting serum lipid profiles and glucose were determined. RESULTS: The HDLC levels of hypertensive participants were significantly higher than normotensive participants after adjustment for age and gender (1.145 versus 1.117 mmol/l, P = 0.001, power = 0.867). After adjustment for related variables, the HDLC levels slightly increased with age, body mass index and fasting glucose (all P = 0.001, power > 0.80) in normotensive participants and only increased with age among hypertensive participants (P = 0.0001, power = 0.971). CONCLUSIONS: The serum HDLC levels in Uygur normotensive participants increased with age, body mass index, blood pressure and fasting glucose levels. This was inconsistent with the previous studies and the reason remained unclear. Further study is needed to elucidate both the environmental and genetic determinants of the novel distribution of the HDLC levels and their association with coronary heart disease in the Uygur population.

Adolescent↗
PubMed2005

Circulating level of vascular endothelial growth factor in differentiating hemangioma from vascular malformation patients.

BACKGROUND: The majority of vascular anomalies can be diagnosed accurately based on natural history and physical examination; however, there is no convenient, noninvasive, and objective method to (1) differentiate hemangioma from vascular malformation; (2) determine whether a hemangioma is in the proliferating or involuting phase; (3) tell whether or not corticosteroids or interferon alfa-2a is effective for hemangioma; or (4) follow up hemangioma. Although the differences in endothelial cell, protein, and mRNA expression levels of some positive and negative angiogenic factors in the lesions can help to solve these problems, these methods (pathological section, immunohistochemical analysis, and in situ hybridization techniques) necessitate that a biopsy be performed, and the procedures are complicated. A nonsurgical and convenient method would have significant clinical applications. METHODS: Fifty-nine patients with proliferating hemangiomas, 38 with involuting hemangiomas, 18 with vascular malformations, and 12 negative control subjects were examined for serum levels of vascular endothelial growth factor using enzyme-linked immunosorbent assays. RESULTS: The serum level of vascular endothelial growth factor in proliferating hemangiomas was significantly higher than that in involuting hemangiomas, vascular malformations, and negative controls, while differences among involuting hemangiomas, vascular malformations, and negative controls were not statistically significant. In addition, after systemic steroid therapy, the serum level of vascular endothelial growth factor was significantly reduced compared with pretreatment levels in six patients with proliferating hemangiomas. CONCLUSIONS: The serum level of vascular endothelial growth factor may be useful in differentiating hemangioma from vascular malformations, staging hemangiomas, judging the efficacy of steroid therapy, and evaluating follow-up criteria for hemangiomas. The results probably shed new light on the pathogenesis of hemangiomas.

Blood Vessels↗
PubMed2005

Design of ultrasonic transmitters with defined frequency characteristics for wireless pressure sensing in injection molding.

This paper describes a new mechanical wireless data transmission technique using ultrasonic waves as the information carrier for on-line injection mold cavity pressure measurement. Ultrasonic transmitters with specific frequency characteristics were designed, modeled, simulated, and prototyped for pressure data retrieval from an enclosed machine environment, as well as for sensor identification in a sensor matrix configuration. The effects of the front layer and bonding layer of the transmitter on the overall sensor frequency characteristics were investigated, using an equivalent circuit model. The optimal layer thickness was determined for the design of transmitters with specific dominant resonant frequency and narrow bandwidth. Experimental results were in good agreement with the analysis, thus confirming the design approach.

Journal Article↗
PubMed2005

Correlation between a gene polymorphism of tumor necrosis factor and inflammatory bowel disease.

OBJECTIVES: To analyze polymorphism of the tumor necrosis factor (TNF) gene in inflammatory bowel disease (IBD) patients from the Han Chinese ethnic group, and to investigate the role of polymorphism in the pathogenesis of IBD. METHODS: Polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) techniques were used to analyze gene polymorphisms in the TNF-alpha and TNF-beta genes in 131 patients with IBD. RESULTS: The genotype frequency and allelic frequency of TNF-alpha-308 in patients with ulcerative colitis (UC) were 15.5% and 8.7%, respectively, significantly higher than the control population (4.1% and 2.0%, respectively; P < 0.001). There was no significant difference between patients with Crohn's disease (CD) and the normal population with regard to the genotype frequency and allelic frequency of TNF-alpha-308, and neither were there any differences with regard to TNF-beta+252 in patients with IBD (UC and CD) and the normal population. The TNF-alpha-308 polymorphism and the TNF-beta+252 loci did not correlate with age, gender, disease activity or lesion site for IBD patients. CONCLUSIONS: The TNF-alpha-308 allele may be related to susceptibility to UC. The TNF-alpha-308 gene polymorphism is not involved in pathogenesis of CD. No correlation was found between the TNF-beta+252 polymorphism and IBD. Polymorphisms of the TNF-alpha-308 and TNF-beta+252 loci do not correlate with age, gender, disease activity or lesion site.

Adult↗