Biomedical subjects

Yu Zhang

Publications and source records attributed to Yu Zhang.

At least 181 records · Page 10Linked to original sources

PubMed2005

Ab initio studies on vibrational spectra of Ni(II), Pd(II), and Pt(II) complexes of M'X4(2-) and M'OS3(2-) (M' = Mo, W; X = O, S).

The vibrational spectra of MM'2X8(2-) and trans-MM'2S6O2(2-) (M = Ni(II), Pd(II), Pt(II); M' = Mo, W; X = O, S) are calculated using ab initio method at RHF/LanL2DZ level. The calculated vibrational frequencies of MM'2S8(2-) and trans-MM'2O2S6(2-) are evaluated via comparison with experimental data. The results obtained by this method have the deviation <5% for M'S and MS stretching vibrational frequencies, however, relatively higher deviation is obtained for M'O stretching vibrational frequencies. Some vibrational frequencies of these complexes that have not been experimentally reported are also predicted and some of the experimental values are assigned.

Models, Molecular↗

PubMed2005

Studying vocal fold vibrations in Parkinson's disease with a nonlinear model.

A nonlinear model is applied to study pathologic vocal vibratory characteristics and voice treatments of Parkinson's disease. We find that a number of pathologic vocal characteristics commonly observed in Parkinson's disease, including reduced vibratory intensity, incomplete vocal closure, increased phonation threshold pressure, glottal tremor, subharmonics, and chaotic vocal fold vibrations, can be studied with this nonlinear model. We also find that two kinds of clinical voice treatments for Parkinson's disease, including respiratory effort treatment and Lee Silverman voice treatment can be studied with this computer model. Results suggest that respiratory effort treatment, in which subglottal pressure is increased, might aid in enhancing vibratory intensity, improving glottal closure, and avoiding vibratory irregularity. However, the Lee Silverman voice treatment, in which both subglottal pressure and vocal fold adduction are increased, might be better than respiratory effort treatment. Increasing vocal fold thickness would be further helpful to improve these pathologic characteristics. The model studies show consistencies with clinical observations. Computer models may be of value in understanding the dynamic mechanism of disordered voices and studying voice treatment effects in Parkinson's disease.

Computer Simulation↗

PubMed2005

c-Fos antisense oligodeoxynucleotide offsets behavioral nociceptive responses and both up-regulations of c-Fos protein and dynorphin a (1-8) in dorsal horn: a study using the formalin test in rats.

The formalin test was used to elicit acute and chronic pain in rats, and antisense oligodeoxynucleotide (AS-ODN) was used as a tool to modulate the expression of nociceptive behavioral and neurochemical responses. AS-ODN complementary to c-Fos mRNA was administered intrathecally (i.t.) 4 h before formalin injection in the experimental group. Normal saline or reverse AS-ODN was pre-administered i.t. at the same time in two control groups (saline and reverse AS-ODN). The results showed that the acute phase of nociceptive behavior showed no change by AS-ODN administration, whereas the tonic phase of nociceptive licking and biting behavior was significantly suppressed by AS-ODN as compared with the saline or the reverse AS-ODN group, respectively (p < .05 and p < .01). At the same time, both Fos-like immunoreactive (FLI) neurons and density of dynorphin-like immunoreactivities (DLI) were decreased significantly (p < .05 and p < .01) in the AS-ODN group as compared with that in two control groups. The results indicate that the long-lasting nociceptive responses elicited by sustained noxious inputs are based on the up-regulation of c-Fos gene expression, which in turn induces the upregulation of Dyn A production. It is proposed that intensified Dyn A production in the dorsal horn may be pivotal for the appearance of chronic pain.

Animals↗

PubMed2005

Serial analysis of gene expression study of a hybrid rice strain (LYP9) and its parental cultivars.

Using the serial analysis of gene expression technique, we surveyed transcriptomes of three major tissues (panicles, leaves, and roots) of a super-hybrid rice (Oryza sativa) strain, LYP9, in comparison to its parental cultivars, 93-11 (indica) and PA64s (japonica). We acquired 465,679 tags from the serial analysis of gene expression libraries, which were consolidated into 68,483 unique tags. Focusing our initial functional analyses on a subset of the data that are supported by full-length cDNAs and the tags (genes) differentially expressed in the hybrid at a significant level (P<0.01), we identified 595 up-regulated (22 tags in panicles, 228 in leaves, and 345 in roots) and 25 down-regulated (seven tags in panicles, 15 in leaves, and three in roots) in LYP9. Most of the tag-identified and up-regulated genes were found related to enhancing carbon- and nitrogen-assimilation, including photosynthesis in leaves, nitrogen uptake in roots, and rapid growth in both roots and panicles. Among the down-regulated genes in LYP9, there is an essential enzyme in photorespiration, alanine:glyoxylate aminotransferase 1. Our study adds a new set of data crucial for the understanding of molecular mechanisms of heterosis and gene regulation networks of the cultivated rice.

Chromosome Mapping↗

PubMed2005

Stochastic frequency signature for chemical sensing using noninvasive neuronelectronic interface.

The detection of chemical agents is important in many areas including environmental pollutants, toxins, biological and chemical pollutants. As "smart" cells, with strong information encoding ability, neurons can be treated as independent sensing elements. A hybrid circuit of a semiconductor chip with dissociated neurons formed both sensors and transducers. Stochastic frequency spectrum was used to differentiate a mixture of chemical agents with effect on the opening of different ion channels. The frequency of spike trains revealed the concentration of the chemical agent, where the characteristic tuning curve revealed the identity. "Fatigue" experiment was performed to explore the "refreshing" ability and "memory" effect of neurons by cyclic and cascaded sensing. "Neuronelectronic noses" such as this should have wide potential applications, most notably in environmental and medical monitoring.

Action Potentials↗

PubMed2005

Microembolic signal characterization using adaptive chirplet expansion.

The adaptive chirplet expansion (ACE) is proposed to characterize high-intensity, transient signals from circulating microemboli. The nonnegative adaptive spectrogram based on the ACE gives a compact representation of the microembolic signal (MES) in joint-time, frequency domain. The mean instantaneous power (MIP) and mean instantaneous frequency (MIF) of MES are estimated from the adaptive spectrogram. Then, several important characteristics of MES, such as embolus-to-blood ratio (EBR), half width maximum (HWM), and embolic signal onset (ESO), are computed from the MIP, and the frequency modulation is examined in the MIF. To validate the new method, we improved the simulation model of the audio Doppler ultrasound signal. Some MESs together with a Doppler ultrasound signal from carotid blood flow are simulated in the simulation study. As a comparison, the adaptive Gabor expansion (AGE) also is implemented on these simulated signals. The experimental results of the simulation study show that the new method, based on the ACE, outperforms the AGE-based method in MES characterization. The consistent conclusion has been confirmed by the clinical study on some clinical MESs.

Algorithms↗

PubMed2005

Doppler ultrasound spectral enhancement using the Gabor transform-based spectral subtraction.

Most of the important clinical indices of blood flow are estimated from the spectrograms of Doppler ultrasound (US) signals. Any noise may degrade the readability of the spectrogram and the precision of the clinical indiCes, so the spectral enhancement plays an important role in Doppler US signal processing. A new Doppler US spectral enhancement method is proposed in this paper and implemented in three main steps: the Gabor transform is used to compute the Gabor coefficients of a Doppler US signal, the spectral subtraction is performed on the magnitude of the Gabor coefficients, and the Gabor expansion with the spectral subtracted Gabor coefficients is used to reconstruct the denoised Doppler US signal. The different analysis and synthesis windows are examined in the Gabor transform and expansion. The signal-to-noise ratio (SNR) improvement together with the overall enhancement of spectrograms are examined on the simulated Doppler US signals from a femoral artery. The results show the denoising method based on the orthogonal-like Gabor expansion achieves the best denoising performance. The experiments on some clinical Doppler US signals from umbilical arteries confirm the superior denoising performance of the new method.

Algorithms↗

PubMed2005

Intrinsic versus environmental influences on T-cell responses in aging.

A decline in T-cell responses and a switch to memory T-cell predominance occur with aging. We have used the T-cell receptor (TCR) transgenic mouse model to study age-associated changes in T-cell responses that are a consequence of shifts in subset representation versus changes intrinsic to T cells versus changes in the 'aged' microenvironment. We found that naive transgene-expressing (Tg(+)) CD4(+) T cells from aged mice respond to antigen with reduced interleukin-2 (IL-2) production, decreased cell expansion, and limited differentiation to effectors. Comparable to the characteristic accumulation of memory phenotype T cells in aged humans and conventional rodents, Tg(+) CD4(+) T cells from old OTII and 6.5 TCR transgenic mice acquire a memory phenotype without immunization and become hyporesponsive. The naive Tg(+) CD8(+) T cells from aged 2C mice expressed activation markers, produced IL-2, proliferated, and differentiated into cytotoxic T lymphocytes as efficiently as their young counterparts. Responses by adoptive transferred Tg(+) cells from young mice, immunized in young and old conventional hosts, indicated that the host age influences the onset of cell division, level of cell expansion, and number of cytokine-producing cells. Co-transfer of dendritic cells (DCs) from young and less so from aged conventional mice partially restored responses. Furthermore, DCs and T-cell migration to draining lymphoid organs was reduced due to deficiencies intrinsic to aged cells and the aged environment. Thus, alterations in T-cell responses in aging are attributable to intrinsic and environmental influences.

Aging↗

PubMed2005

Genetic analysis of Arabidopsis GATA transcription factor gene family reveals a nitrate-inducible member important for chlorophyll synthesis and glucose sensitivity.

The Arabidopsis GATA transcription factor family has 30 members, the biological function of most of which is poorly understood. Homozygous T-DNA insertion lines for 23 of the 30 members were identified and analyzed. Genetic screening of the insertion lines in defined growth conditions revealed one line with an altered phenotype, while the other lines showed no obvious change. This line, SALK_001778, has a T-DNA insertion in the second exon of At5g56860 which prevents the expression of the GATA domain. Genetic analysis of the mutant demonstrated that the phenotypic change is caused by a single gene effect and is recessive to the wild-type allele. In wild-type plants, the expression of At5g56860 is shoot-specific, occurs at an early stage of development and is inducible by nitrate. Loss of expression of At5g56860 in the loss-of-function mutant plants resulted in reduced chlorophyll levels. A transcript profiling experiment revealed that a considerable proportion of genes downregulated in the loss-of-function mutants are involved in carbon metabolism and At5g56860 is thus designated GNC (GATA, nitrate-inducible, carbon metabolism-involved). gnc mutants with no GNC expression are more sensitive to exogenous glucose, and two hexose transporter genes, with a possible connection to glucose signaling, are significantly downregulated, while GNC over-expressing transgenic plants upregulate their expression and are less sensitive to exogenous glucose. These observations suggest a function for GNC in regulating carbon and nitrogen metabolism.

Arabidopsis↗

PubMed2005

A biochemical and functional characterization of diet-induced brain insulin resistance.

While considerable research has examined diminished insulin responses within peripheral tissues, comparatively little has been done to examine the effects of this metabolic disruption upon the CNS. The present study employed biochemical and electrophysiological assays of acutely prepared brain slices to determine whether neural insulin resistance is a component of the metabolic syndrome observed within the fructose-fed (FF) hamster. The tyrosine phosphorylation levels of the insulin receptor (IR) and insulin receptor substrate 1 (IRS-1) in response to insulin were significantly reduced within FF hamsters. Also, insulin-mediated phosphorylation of both residues necessary for activation of the serine-threonine kinase Akt/PKB, a key effector of insulin signaling, was markedly decreased. Elevated levels of the protein tyrosine phosphatase 1B, which dephosphorylates the IR and IRS-1, were also observed within the cerebral cortex and hippocampus of FF hamsters. Examination of whether a nutritionally induced compromise of neural insulin signaling altered synaptic function revealed a significant attenuation of insulin-induced long-term depression, but no effect upon either paired-pulse facilitation or electrically induced long-term potentiation. Collectively, our results demonstrate, for the first time, that nutritionally induced insulin resistance significantly affects the neural insulin signaling pathway, and suggest that brain insulin resistance may contribute to cognitive impairment.

Animals↗

PubMed2005

A novel artemisinin derivative, 3-(12-beta-artemisininoxy) phenoxyl succinic acid (SM735), mediates immunosuppressive effects in vitro and in vivo.

AIM: To study the immunosuppressive activity of SM735 {[3-(12-beta-artemisininoxy)] phenoxyl succinic acid}, a synthetic artemisinin derivative with nonsteroidal anti-inflammatory drug structure, with the aim of finding potential immunosuppressive agents. METHODS: Concanavalin A (ConA), lipopolysaccharide (LPS), and mixed lymphocyte reaction (MLR), were used to induce the proliferation of splenocytes, and [3H]-thymidine incorporation was used to evaluate the proliferation of splenocytes. Cytokine production was promoted with ConA, LPS, or PMA plus ionomycin, and was detected with the enzyme-linked immunosorbent assay. Dinitrofluorobenzene (DNFB) and sheep red blood cells (SRBC) were used to induce delayed-type hypersensitivity and quantitative hemolysis of SRBC (QHS) mouse models, as criteria for the evaluation of in vivo immune activity. RESULTS: SM735 strongly inhibited the proliferation of splenocytes induced by ConA, LPS, or MLR, with IC(50) values of 0.33 micromol/L, 0.27 micromol/L, and 0.51 micromol/L, respectively. When compared with a CC(50) value of 53.1 micromol/L, SM735 had a favorable safety range. SM735 dose-dependently inhibited proinflammatory cytokine production [including interleukins (IL)-12, interferon (IFN)-gamma and IL-6] induced by LPS or PMA plus ionomycin. Upon ConA stimulation, SM735 suppressed IFN-gamma in a dose-dependent manner, but did not affect IL-2 secretion. SM735 also strongly suppressed both T-cell-mediated delayed-type hypersensitivity (DTH) and B-cell-mediated QHS reactions. CONCLUSION: SM735 had strong immunosuppressive activity in vitro and in vivo, suggesting a potential role for SM735 as an immunosuppressive agent, and established the groundwork for further research on SM735.

Animals↗

PubMed2005

Comparison of nonlinear dynamic methods and perturbation methods for voice analysis.

Nonlinear dynamic methods and perturbation methods are compared in terms of the effects of signal length, sampling rate, and noise. Results of theoretical and experimental studies quantitatively show that measurements representing frequency and amplitude perturbations are not applicable to chaotic signals because of difficulties in pitch tracking and sensitivity to initial state differences. Perturbation analyses are only reliable when applied to nearly periodic voice samples of sufficiently long signal lengths that were obtained at high sampling rates and low noise levels. In contrast, nonlinear dynamic methods, such as correlation dimension, allow the quantification of chaotic time series. Additionally, the correlation dimension method presents a more stable analysis of nearly periodic voice samples for shorter signal lengths, lower sampling rates, and higher noise levels. The correlation dimension method avoids some of the methodological issues associated with perturbation methods, and may potentially improve the ability for real time analysis as well as reduce costs in experimental designs for objectively assessing voice disorders.

Adult↗

PubMed2005

Antimicrobial activities and structures of two linear cationic peptide families with various amphipathic beta-sheet and alpha-helical potentials.

Many naturally occurring antimicrobial peptides comprise cationic linear sequences with the potential to adopt an amphipathic alpha-helical conformation. We designed a linear 18-residue peptide that adopted an amphipathic beta-sheet structure when it was bound to lipids. In comparison to a 21-residue amphipathic alpha-helical peptide of equal charge and hydrophobicity, this peptide possessed more similar antimicrobial activity and greater selectivity in binding to and inducing leakage in vesicles composed of bacterial membrane lipids than vesicles composed of mammalian membrane lipids (J. Blazyk, R. Weigand, J. Klein, J. Hammer, R. M. Epand, R. F. Epand, W. L. Maloy, and U. P. Kari, J. Biol. Chem. 276:27899-27906, 2001). Here, we compare two systematically designed families of linear cationic peptides to evaluate the importance of amphipathicity for determination of antimicrobial activity. Each peptide contains six lysine residues and is amidated at the carboxyl terminus. The first family consists of five peptides with various capacities to form amphipathic beta-sheet structures. The second family consists of six peptides with various potentials to form amphipathic alpha helices. Only those peptides that can form a highly amphipathic structure (either a beta sheet or an alpha helix) possessed significant antimicrobial activities. Striking differences in the abilities to bind to and induce leakage in membranes and lipid vesicles were observed for the two families. Overall, the amphipathic beta-sheet peptides are less lytic than their amphipathic alpha-helical counterparts, particularly toward membranes containing phosphatidylcholine, a lipid commonly found in mammalian plasma membranes. Thus, it appears that antimicrobial peptides that can form an amphipathic beta-sheet conformation may offer a selective advantage in targeting bacterial cells.

Anti-Bacterial Agents↗

PubMed2005

Therapeutic effect of Fe2O3 nanoparticles combined with magnetic fluid hyperthermia on cultured liver cancer cells and xenograft liver cancers.

The therapeutic effect of Fe2O3 nanoparticles combined with magnetic fluid hyperthermia (MFH) on human hepatocarcinoma SMMC-7721 cells in vitro and xenograft liver cancer in nude mice is studied. We examined growth and apoptosis of SMMC-7721 cells treated with MFH containing Fe2O3 nanoparticles at various concentrations (2, 4, 6, and 8 g/liter) for 30-60 min by using MTT, flow cytometry (FCM), and transmission electron microscopy (TEM). We also observed weight and volume inhibitory rates of the tumors of SMMC-7721-bearing nude mice by using animal experiments. The results showed that Fe2O3 nanoparticles combined with MFH could significantly inhibit the proliferation and increase the ratio of apoptosis of SMMC-7721 cells, and the effect was dose-dependent. The inhibitory rate was 26.5%, 33.53%, 54.4%, and 81.2%, respectively, and the apoptosis rate was 30.26%, 38.65%, 50.28%, and 69.33%, respectively. Animal experiments showed that tumors became small. The weight inhibitory ratio was 42.10%, 66.34%, 78.5%, and 91.46%, and the volume inhibitory ratio was 58.77%, 80.44%, 93.40%, and 98.30%, respectively. Compared with the control and experimental groups, each group had statistically significant difference (p < 0.05). So, Fe2O3 nanoparticles combined with MFH could inhibit the proliferation and induce apoptosis of SMMC-7721 cells and also has a significant inhibitory effect on the weight and volume of xenograft liver cancer. However, the mechanism remains to be further investigated.

Animals↗

PubMed2005

BJ-TSA-9, a novel human tumor-specific gene, has potential as a biomarker of lung cancer.

Using bioinformatics, we have identified a novel tumor-specific gene BJ-TSA-9, which has been validated by Northern blot analysis and reverse transcription-polymerase chain reaction (RT-PCR). BJ-TSA-9 mRNA was expressed in 52.5% (21 of 40) of human lung cancer tissues and was especially higher in lung adenocarcinoma (68.8%). To explore the potential application of BJ-TSA-9 for the detection of circulating cancer cells in lung cancer patients, nested RT-PCR was performed. The overall positive detection rate was 34.3% (24 of 70) in peripheral blood mononuclear cells (PBMCs) of patients with various types of lung cancers and was 53.6% (15 of 28) in PBMCs of lung adenocarcinoma patients. In combination with the detection of two known marker genes SCC and LUNX, the detection rate was increased to 81.4%. A follow-up study was performed in 37 patients after surgical removal of tumor mass. Among nine patients with persistent detection of two to three tumor marker transcripts in PBMCs, six patients had recurrence/metastasis. In contrast, 28 patients with transient detection of one tumor marker or without detection of any tumor marker were all in remission. Thus, BJ-TSA-9 may serve as a marker for lung cancer diagnosis and as a marker, in combination with two other tumor markers, for the prediction of the recurrence and prognosis of lung cancer patients.

Antigens, Neoplasm↗

PubMed2005

[Three-dimensional reconstruction of human organs based on magnetic resonance imaging data].

OBJECTIVE: To build proper three-dimensional models of human organs for radiation dose calculation. METHOD: Human organ models were built by contour reconstruction algorithm conforming to 4 criteria. The contours of the organs were extracted based on the contours of the reconstructed organ surfaces, and the three-dimensional models with smooth surface, exact structure and good visibility were completed by computer graphic techniques such as lighting, smoothing, and normal average. RESULT AND CONCLUSION: Several organ models were successfully reconstructed, suggesting that this method is suitable for building three-dimensional digital human organ models which can meet the need for dose calculation.

Humans↗

PubMed2005

[Effect of tea polyphenols on alcoholic liver injury].

OBJECTIVE: To reproduce an experimental model of alcoholic liver disease in rats and to investigate the preventive and treatment effects of tea polyphenols on alcoholic liver disease. METHODS: 68 male Sprague-Dawley rats were randomly divided into 3 groups: alcohol group (gastrically infused with 56% of ethanol once a day with a dose of 7 g/kg body weight for 4, 12 and 24 weeks), tea polyphenols group (gastric infusion with alcohol same as in the alcohol group and with tea polyphenols at 0.25 g/kg bw) and control group (gastric infusion with normal saline). At the end of 4, 12 and 24 weeks, blood samples were collected and then the rats were sacrificed. Liver samples were obtained for routine histological examination and the degree of hepatic steatosis and alcoholic hepatitis were examined. Blood specimens were used for evaluation of alanine transaminase (ALT) and aspartate aminotransferase (AST). RESULTS: (1) The levels of the two transaminases were elevated with the increase of the duration of ethanol feeding and the difference is significant. TP significantly mitigated the increase of ALT and AST activities induced by the alcohol. (2) Histological changes of the liver injury indicated that piecemeal or focal necrosis of hepatocytes was present in the centrilobular area. As fibrosis advanced, broader septa were formed with central-central and centra-portal bridging necrosis. In the TP infusion group, the severity of the pathological changes was significantly milder. CONCLUSION: The results of this study revealed that TP mitigated the development of alcoholic liver disease, and TP may be a potential drug for treatment of alcoholic liver disease.

Animals↗

PubMed2005

Ritodrine in the treatment of preterm labour: a meta-analysis.

BACKGROUND & OBJECTIVES: Results on the effect of ritodrine in the treatment of preterm labour are different all over the world. Therefore, a concrete conclusion cannot be drawn from a single randomized control trial (RCT). In this study, we selected a large number of RCTs worldwide on the treatment of preterm labour comparing ritodrine and placebo or magnesium sulfate and by applying meta-analysis, evaluated the effect of ritodrine in the treatment of preterm labour. METHODS: We searched and identified 20 RCTs about ritodrine versus placebo, and ritodrine versus magnesium sulphate in the main medical data resources (MEDLINE, PubMed, CBMdisc, Cochrane Library and EMBASE) from January 1970 to December 2001 published in English and Chinese literature. We abstracted data about delay of gestation, gestational age at delivery, birth weight, severe neonatal respiratory system diseases, perinatal deaths, and administration to contraction-ceased interval, etc. RESULTS: The odds ratio (OR) of 1 day (d) delay in 10 RCTs on ritodrine in preterm labour versus placebo was 2.95 (95%CI 2.15, 4.04), and OR of 2d delay was 1.91 (95%CI 1.49, 2.45), both differences were statistically significant. There were no significant difference on the OR of birth > or =37 wk, birth weight > or =2500 g, severe respiratory morbidity and perinatal mortality. The OR of 2d delay of four RCTs from abroad on ritodrine versus magnesium sulphate was 1.56 (95%CI 0.62, 3.94), and OR of 7d delay was 1.45 (95%CI 0.80, 2.62), both without significant difference. But the combined estimated rate difference (CERD) of side effects interruption rate was 12 per cent with significant difference. There were six Chinese RCTs on ritodrine and magnesium sulphate. The OR of 1d delay was 3.95 (95%CI 1.98, 7.88), and OR of neonatal death was 0.45 (95%CI 0.22, 0.93), both with significant difference. The average administration to contractionceased interval were 2.5 and 6.3 h, respectively, with CERD being -4.2 h. INTERPRETATION & CONCLUSION: In treating preterm labour, ritodrine can significantly prolong a short interval more quickly but with relatively more side effects than magnesium sulphate. Stratified RCTs for different gestational ages and different labour stages should be designed for further study.

Adrenergic beta-Agonists↗