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Biomedical subjects

Yu Zhang

Publications and source records attributed to Yu Zhang.

At least 109 records · Page 6Linked to original sources
PubMed2006

Sensitive isotope dilution liquid chromatography/electrospray ionization tandem mass spectrometry method for the determination of acrylamide in chocolate.

Isotope dilution liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-MS/MS) was applied to the quantification of acrylamide in chocolate matrixes (dark chocolate, milk chocolate, chocolate with nuts, chocolate with almonds, and chocolate with wheat best element). The method included defatting with petroleum ether, extracting with aqueous solution of 2 mol l(-1) sodium chloride and clean-up by solid-phase (SPE) with OASIS HLB 6 cm3 cartridges. Acrylamide was detected with an Atlantis dC18 5 microm 210 x 1.5 mm column using 10% methanol/0.1% formic acid in water as the mobile phase. The analytical method was in-house validated and good results were obtained with respect to repeatability (RSD < 3.5%) and recovery (86-93%), which fulfilled the requirements defined by European Union legislation. The acrylamide levels in chocolate were 23-537 microg kg(-1). Therefore, the method was successfully used for the quantitative analysis of acrlyamide in various chocolate products.

Acrylamide↗
PubMed2006

Alignment of optical maps.

We introduce a new scoring method for calculation of alignments of optical maps. Missing cuts, false cuts, and sizing errors present in optical maps are addressed by our alignment score through calculation of corresponding likelihoods. The size error model is derived through the application of Central Limit Theorem and validated by residual plots collected from real data. Missing cuts and false cuts are modeled as Bernoulli and Poisson events, respectively, as suggested by previous studies. Likelihoods are used to derive an alignment score through calculation of likelihood ratios for a certain hypothesis test. This allows us to achieve maximal descriminative power for the alignment score. Our scoring method is naturally embedded within a well known DP framework for finding optimal alignments.

Algorithms↗
PubMed2006

Simulation of vocal fold impact pressures with a self-oscillating finite-element model.

Vocal fold impact pressures were studied using a self-oscillating finite-element model capable of simulating vocal fold vibration and airflow. The calculated airflow pressure is applied on the vocal fold as the driving force. The airflow region is then adjusted according to the calculated vocal fold displacement. The interaction between airflow and the vocal folds produces a self-oscillating solution. Lung pressures between 0.2 and 2.5 kPa were used to drive this self-oscillating model. The spatial distribution of the impact pressure was studied. Studies revealed that the tissue collision during phonation produces a very large impact pressure which correlates with the lung pressure and glottal width. Larger lung pressure and a narrower glottal width increase the impact pressure. The impact pressure was found to be roughly the square root of lung pressure. In the inferior-superior direction, the maximum impact pressure is related to the narrowest glottis. In the anterior-posteriorfirection, the greatest impact pressure appears at the midpoint of the vocal fold. The match between our numerical simulations and clinical observations suggests that this self-oscillating finite-element model might be valuable for predicting mechanical trauma of the vocal folds.

Air Pressure↗
PubMed2006

Differentiation of Escherichia coli pathotypes by oligonucleotide spotted array.

To accurately determine the pathotypes of Escherichia coli strains, a comprehensive assessment of each strain that targets multiple genes is required. A new approach to the identification and characterization of E. coli pathotypes was developed by constructing gene-specific probes (70-mers) for not only the virulence genes associated with each E. coli pathotype but also the O157-, CFT073-, and K-12-specific and common genes of each pathotype. Analysis of oligonucleotide probes with reference and clinical isolates of E. coli pathotypes indicated that the array could differentiate the pathotypes on the basis of their virulence and specific gene patterns. Probes targeting common genes of E. coli were present in all the reference and clinical strains. Salmonella enterica subsp. enterica-specific genes and Salmonella core genes were used as negative controls. The entire E. coli pathotype showed reactivity to only 4 of the 81 Salmonella-specific gene probes. Characterization of the genetic and virulence profiles of a single strain by using probes for virulence factors and specific and common genes in the spotted array is an ideal diagnostic tool for determination of E. coli pathotypes and could also have a significant impact on the epidemiological analysis of E. coli infections.

DNA, Bacterial↗
PubMed2006

Resistance imparted by vitamin C, vitamin E and vitamin B12 to the acute hepatic glycogen change in rats caused by noise.

The effects of vitamin C, vitamin E and vitamin B12 on the noise-induced acute change in hepatic glycogen content in rats were investigated. The exposure of rats to 95 dB and 110 dB of noise acutely reduced their hepatic glycogens. Vitamin C (ascorbic acid) and vitamin E (alpha-tocopherol) attenuated the noise-induced acute reduction in the hepatic glycogen contents. This result suggests that antioxidants could reduce the change via reactive oxygen species. Vitamin B12 (cobalamin) delayed the noise-induced change, a finding that suggests that vitamin B12 could postpone the acute change via compensating for vitamin B12 deficiency.

Animals↗
PubMed2006

Tachykinins in the immune system.

Until recently, the mammalian tachykinins included substance P, neurokinin A and neurokinin B. Following the discovery of the fourth member of this family, hemokinin 1, a diverse group of novel tachykinins and tachykinin gene-related peptides have been identified in mammals. These newly identified members are preferentially expressed in peripheral tissues. Currently, the impact of these new tachykinin peptides on the immune system remains unclear. Some data imply an important role for hemokinin 1 in the generation of lymphocytes. Tachykinins are traditionally viewed as neuropeptides with well-defined functions as neurotransmitters. Many studies however, indicate that they may also be produced by non-neuronal cells, and exert profound influence on inflammatory responses by affecting multiple aspects of immune cell function. It is of great importance to determine whether the new tachykinin peptides have similar effects. A more detailed understanding of the interactions between tachykinins and immune cells may provide the basis for the development of new therapies for inflammatory and immune-mediated diseases.

Amino Acid Sequence↗
PubMed2006

[Expression and significance of C-kit and platelet-derived growth factor receptor-beta (PDGFRbeta) in esophageal carcinoma].

BACKGROUND & OBJECTIVE: Some researches have showed that STI-571 could inhibit tyrosine kinase of Bcr-Abl, C-kit, and platelet-derived growth factor receptor-beta (PDGFRbeta), therefore, inhibit cell differentiation and proliferation and accelerate cell apoptosis. This study was to examine the expression of tyrosine kinase receptor C-kit and PDGFRbeta, which is correlated to STI-571, in esophageal carcinoma. METHODS: The expression of C-kit and PDGFRbeta in tumor tissue, para-tumor tissue, and normal tissue of 50 specimens of esophageal carcinoma was examined by immunohistochemistry. RESULTS: The strong expression rate of C-kit was low in tumor, para-tumor, and normal tissues (4%, 4%, and 12%, respectively), with no significant difference (P=0.220). The strong expression rate of PDGFRbeta was significantly higher in tumor tissues than in para-tumor and normal tissues (68% vs. 28% and 28%, P=0.001). Logistic regression analysis revealed that the strong expression rate of C-kit and PDGFRbeta had no correlation to sex, age, differentiation degree, infiltrative depth, position, lymph node metastasis, and stage of esophageal carcinoma. CONCLUSIONS: The strong expression rate of PDGFRbeta is significantly higher in tumor tissues than in para-tumor and normal tissues. The strong expression rate of C-kit in normal esophageal tissues is low, and it is lower in para-tumor and tumor tissues.

Adult↗
PubMed2006

[Measurement of setup error in conformal radiotherapy for nasopharyngeal carcinoma].

BACKGROUND & OBJECTIVE: Setup error is the key factor in determining the margin of planning target volume (M(PTV)) for conformal radiotherapy of nasopharyngeal carcinoma (NPC). This study was to establish a method using radiopaque fiducial markers which were embedded in occlusal splint ("occlusal splint method") to acquire setup errors to calculate M(PTV) in CRT for NPC. METHODS: The occlusal splint method was performed in 22 NPC patients who received CRT. Setup errors were calculated by comparing the coordinates of 3 fiducial markers read from portal images with those read from computed tomography (CT) data. According to the formulation, the size of MPTV with or without consideration of organ motion was also calculated. RESULTS: The standard deviations of systematic errors (Sigma) were 1.13 mm, 1.47 mm, and 1.31 mm in X (medio-lateral), Y (antero-posterior) and Z (cranio-caudal) axes, respectively; the standard deviations of random errors were 0.81 mm, 0.45 mm, and 0.80 mm in X, Y, and Z axes, respectively. Without consideration of organ motion, the sizes of M(PTV) were 3.40 mm, 3.98 mm, and 3.83 mm in X, Y, and Z axes, respectively; with consideration of organ motion, the sizes of M(PTV) were 3.75 mm, 4.35 mm, and 4.16 mm in X, Y, and Z axes, respectively. CONCLUSION: Using the "occlusal splint method", each institution can precisely calculate setup error data, and stipulate the size of M(PTV) adequate to one's own situation.

Adult↗
PubMed2006

[Changes in renal cell apoptosis and inflammatory cytokines in early stage of sepsis in rats].

OBJECTIVE: To investigate the relationship between changes in renal cell apoptosis and inflammatory cytokines in sepsis rats. METHODS: Sepsis was produced in rats by cecal ligation and puncture. Changes in tumor necrosis factor-alpha (TNF-alpha) and monocyte chemotactic protein-1 (MCP-1) levels in renal tissues were determined by enzyme-linked immunoadsorbent assay (ELISA), respectively. Meanwhile, apoptosis rate was also assessed by Annexin V/PI staining and flow cytometry and terminal deoxynucleotidyl transferase-mediated dUTP biotin nick end labeling (TUNEL) methods. RESULTS: TNF-alpha and MCP-1 levels in renal tissues were significantly increased in rats with sepsis in the early stage. Apoptosis rate of renal cells increased and reached the highest level at 3 hours after sepsis was established and decreased after 6 hours, and the differences were significant (P<0.05 or P<0.01). CONCLUSION: TNF-alpha and MCP-1 are cytokines which are activated in early stage of sepsis. The increase in renal cell apoptosis in the early stage of sepsis is related with the release of cytokines.

Animals↗
PubMed2006

[Noise image segmentation based on generalized fuzzy Gibbs random field].

In order to segment the blurred image with large noise, the authors propose a new Bayesian image segmentation method based on generalized fuzzy Gibbs random field. Based on the generalized fuzzy set, the new method introduces generalized fuzzy membership into Gibbs potential function and the potential function is redefined to obtain the new segmentation model. The optimal processing is executed through iterative conditional modes (ICM). The experiment results showed that the new approach could effectively segment the degenerated images.

Algorithms↗
PubMed2006

[Human inward rectifying potassium current and Kir2.1 mRNA expression in myocytes isolated from patients with chronic atrial fibrillation].

OBJECTIVE: To compare the changes of both inward rectifying K(+) (Kir) current(I(k1)) density and mRNA expression level of Kir2.1, a major subfamily of Kir in chronic human atrial fibrillation (CAF) with those in normal sinus rhythm (NSR). METHODS: I(k1) density was measured with whole-cell patch clamp technique in single myocyte isolated by an enzymatic dissociation method from right atrial appendages in patients with CAF (n = 8) and those with NSR (n = 12). The mRNA expression levels of Kir2.1 was determined in right atrial appendages from CAF (n = 19) and NSR (n = 18) by semiquantitative reverse-transcription polymerase chain reaction (RT-PCR). RESULT: The average resting membrane potentials were similar between CAF and NSR (-78.95 mV +/- 4.67 mV and -70.22 mV +/- 11.08 mV, P>0.05). I(k1) density in single myocyte significantly increased at hyperpolarized potential level (-100 mV) in CAF compared to that in NSR (-9.59 pA/pF +/- 2.47 pA/pF vs. -5.58 pA/pF +/- 2.52 pA/pF, P<0.01). The mRNA level of Kir2.1 was also significantly higher in CAF than that of NSR (0.50+/-0.16 vs. 0.34+/-0.09, P<0.05). CONCLUSION: The data suggest that Kir2.1 up-regulation and I(k1) current increase might contribute to the electrical remodeling in CAF patients.

Atrial Fibrillation↗
PubMed2006

[Synthesis and immunosuppressive activity of new artemisinin derivatives containing polyethylene glycol group].

AIM: To search for new artemisinin derivatives with higher immunosuppressive activity. METHODS: Two kinds of new artemisinin derivatives containing polyethylene glycol group were synthesized from dihydroartemisinin via condensation and esterification. These compounds were assayed for their inhibitory activity on ConA-induced T cell proliferation and LPS-induced B cell proliferation. RESULTS: Twenty three new compounds (2a - 2f, 3a - 3d, 4a - 4f, 6a, 6b and 7a - 7g) were synthesized and identified by 1H NMR and elemental analysis. CONCLUSION: These compounds had immunosuppressive activity in vitro. Among them, the symmetrical substituted compound 2 and 6 had higher activity than mono-substituted compound 3, 4 and 7. Especially, compounds 2a - 2f remarkably exhibited higher inhibition in comparison with artemisinin and artesunate.

Animals↗
PubMed2006

[Comparison of hydroxyl radical production rates in H2O2 solution under homogeneous catalysis of Fe3+ or Fe2+].

The production of *OH radicals was investigated by using the electron spin resonance (ESR) method with 5,5-dimethyl-1-lpyrroline-1-oxide (DMPO) as spin trap reagent. ESR signals composed of 4 lines with a 1:2:2:1 intensity ratio indicated the formation of *OH radicals in the Fenton-like reaction. For both systems, the production rates of hydroxyl radicals in the initial stage were considerably high, and increased with increasing concentrations of H2O2 and Fe2+ or Fe3+. However, the radical production rate in Fenton reaction system was markedly higher than that in Fenton-like reaction under similar dosing conditions. The differences of radical production rates between the reaction systems remained even in the slow reaction stage. The optimum pH ranges of the production of *OH radicals in Fenton process and Fenton-like process were 2.5 to approximately 3.5 and 2.8 to approximately 3.0 respectively. The above results demonstrate that the Fenton system and Fenton-like system are possibly based on different reaction mechanisms.

Catalysis↗
PubMed2006

Effect of tea polyphenol on cytokine gene expression in rats with alcoholic liver disease.

BACKGROUND: Oxidative stress plays a pathogenetic role in initiation and progression of hepatic damage caused by alcohol. Recently, antioxidants have received considerable attention. Green tea polyphenols have both antioxidant and antiinflammatory properties. This study was designed to evaluate the effect of tea polyphenol (TP) on alcohol-induced liver injury in rats. METHODS: The rats were divided randomly into 3 groups: group A gastrically infused with alcohol for 12 weeks, group B fed with alcohol plus TP (250 mg/kg.d) simultaneously, and group C (control group) gastrically infused with normal saline. At the end of 12 weeks, the rats were sacrificed. The liver specimen of each rat was taken for histological examination. All data were statistically analyzed in quantum and semi-quantum. Gene expression of cytokines of each group was determined. RESULTS: At the end of 12 weeks, hepatic injury of different degrees developed in group A and group B compared to group C. The degree of hepatic injury was attenuated in group B, with slight steatosis, liver cellular swelling in small areas; less spot and focal necrosis, no bridging necrosis, less mega-bubble steatosis and less collagen deposition in contrast to group A. Gene expressions of IL-3, IL-4, IL-1R2, IL-6R, IL-7R2 were up-regulated in group B compared with group A, but those of IL-3Ra, IL-1R1 were down-regulated. Gene expressions of IL-13, IL-1R1, IL-7R2, EPO-R, LIFR were up-regulated in group A compared with group C, but those of IL-1R2, IL-5R2, CSF1, CD27, IL-6R were down-regulated. CONCLUSION: TP is able to attenuate alcoholic liver damage. Cytokine may contribute to alcoholic liver disease.

Animals↗
PubMed2006

[In vivo distribution and pharmacokinetics of dexamethasone sodium phosphate thermosensitive in situ gel following intratympanic injection].

OBJECTIVE: To investigate the absorption and distribution of DSP (Dexamethasone sodium phosphate)-loaded thermosensitive in situ gel following IT (intratympanic injection) in guinea pig and provide rationale for clinical application. METHODS: DSP-loaded thermosensitive in situ gel was prepared by using poloxamer 407 as matrix. The HPLC assays for the determination of DSP and dexamethasone (Dex) in perilymph (PL), cerebrospinal fluid (CSF) and plasma were developed, respectively. DSP-loaded gel and solution were administered after IT or IV (intravenous injection). PL, CSF and plasma were collected periodically. The concentrations of DSP and Dex were measured by HPLC, and were used to estimate in vivo distribution and pharmacokinetic parameters of Dex in the inner ear. RESULTS: The AUC (area under curve) and t1/2 of Dex in PL following IT DSP-loaded gel were 593.7- and 28.6-fold higher than those following IV DSP solution. Moreover, DSP-loaded gel following IT extended the mean residence time (MRT) by nearly 5 times, compared with the solution. After IT, the concentration levels of Dex in CSF and plasma were much lower than that in PL. CONCLUSION: DSP thermosensitive in situ gel following IT has significant cochlea-oriented and sustained-release effect.

Administration, Topical↗
PubMed2006

[Expression of heparanase and angiopoietin-2 mRNA in endometriosis].

OBJECTIVE: To investigate the relationship between heparanase (Hpa) and angiopoietin-2 (Ang-2) gene expression and the development of endometriosis (EM). METHODS: Expression of Hpa gene and Ang-2 mRNA in the eutopic and ectopic endometrium collected from 86 patients with endometriosis (EM group) and the normal endometrium from 30 women without endometriosis (control group) was determined by RT-PCR. RESULTS: (1) Hpa gene expression was detected in 53 ectopic endometrium and 47 eutopic endometrium specimens in the EM group and 8 normal endometrium specimens in the control group. There was no significant difference in Hpa gene expression between ectopic and eutopic endometrium in the EM group (P > 0.05). However, the Hpa gene expression in normal endometrium in the control group was significantly lower than that in ectopic and eutopic endometrium in the EM group (P < 0.05). (2) Ang-2 gene expression was detected in 61 ectopic endometrium and 56 eutopic endometrium specimens in the EM group and 10 normal endometrium specimens in the control group. There was no significant difference in Ang-2 gene expression between ectopic and eutopic endometrium in the EM group (P > 0.05), however, the Ang-2 positive rate in normal endometrium in the control group was significantly lower than that in ectopic and eutopic endometrium in the EM group (P < 0.05). (3) The expression of Hpa gene in stage III-IV endometriosis was significantly higher than that in stage I-II endometriosis (P < 0.05). (4) The difference of Ang-2 mRNA expression between stage III-IV and stage I-II endometriosis was not significant (P > 0.05). (5) The expression of Hpa gene was shown to be significantly correlated to the expression of Ang-2 gene in ectopic endometrium specimens from patients with endometriosis (P < 0.05). CONCLUSION: Hpa and Ang-2 genes are highly expressed in both ectopic and eutopic endometrium of patients with endometriosis. Over-expression of these two genes may play a role in the development and progression of endometriosis.

Adult↗
PubMed2006

[Study on preparation of konjac glucomannan-hydroxypropyl methyl cellulose compression coated tablets for colonic delivery and in vitro release].

OBJECTIVE: Prepare konjac glucomannan-hydroxypropyl methyl cellulose (HPMC) compression coated tablets and study the effects of the formulation, technics and in vitro dissolution condition on drug release behavior to elevate the colon-specific effects of preparation. METHOD: Berberine hydrochloride core tablets were prepared by wet granulation technique and konjac glucomannan-HPMC mixture as the coating layer were used with compression coated technique. The effects of the formulation and technics on drug release behavior were investigated by dissolution test. The erosion of coat layer during dissolution test was investigated. RESULT: Drug almost not released in dissolution medium stimulating gastric and intestinal condition, and released completely by coating layer erosion and rupture by enzyme in stimulating colonic condition. Drug release decreased with decreasing the ratio of konjac glucomannan-HPMC and increasing coat weight (P < 0.05), compression force was not found to be a significant factor on drug release. Drug release increased with increasing the concentration of beta-mannase in dissolution medium (P < 0.05), rotation speed has no effect on drug release. The release of drug was correlative with erosion of coat layer. The mechanism of drug release were diffusion and erosion. CONCLUSION: The konjac glucomannan-HPMC compression coated tablets was a promising delivery system for drugs to be delivered to the colon.

Administration, Oral↗