Biomedical subjects

Z Sun

Publications and source records attributed to Z Sun.

At least 37 records · Page 2Linked to original sources

PubMed2001

Clad polymer buffer rods for polymer process monitoring.

Clad polymer buffer rods consisting of a polyetheretherketone (PEEK) core and a cladding made of a heat resistance epoxy aluminum composite are presented. The core has a uniform diameter or a taper shape. Ultrasonic measurement results indicate that the ultrasonic signal strength and signal to noise ratio of these clad rods are better than those of the non-clad PEEK rods for both longitudinal and shear waves because of the improved ultrasonic wave guidance in the core. Comparisons of these rods with those made of polymide and high-density polyethylene are given. Applications of these buffer rods for ultrasonic monitoring of polymer extrusion at temperatures up to 200 degrees C and pressures up to 180 psi are demonstrated. The monitoring results also reveal that within certain operating temperature and pressure range, clad polymer buffer rods show advantages over clad steel buffer rods.

Benzophenones↗

PubMed2001

Determination of active component in silymarin by RP-LC and LC/MS.

Silybin, isosilybin, silydianin and silycristin in silymarin were separated and quantitatively determined by RP-HPLC. Two diastereoisomers of silybin and isosilybin were respectively separated by RP-HPLC and confirmed by LC/MS. Chromatographic condition consisted of column: Shim-pack VP-ODS (150 x 4.6mm i.d. 5 microm) and Pre-column (10 x 4.6 mm i.d. 5 microm); mobile phase: methanol and solvent mixture (water: dioxane=9:1) by gradient; flow rate: 1.5ml/min; column temp.: 40 degrees C; detector wavelength: 288 nm; The recovery of 99.66% for silycristin, 99.48% for silydianin, 100.0% for silybin and 98.72% for isosilybin was respectively obtained.

Antioxidants↗

PubMed2001

The strawberry FaMYB1 transcription factor suppresses anthocyanin and flavonol accumulation in transgenic tobacco.

Fruit ripening is characterized by dramatic changes in gene expression, enzymatic activities and metabolism. Although the process of ripening has been studied extensively, we still lack valuable information on how the numerous metabolic pathways are regulated and co-ordinated. In this paper we describe the characterization of FaMYB1, a ripening regulated strawberry gene member of the MYB family of transcription factors. Flowers of transgenic tobacco lines overexpressing FaMYB1 showed a severe reduction in pigmentation. A reduction in the level of cyanidin 3-rutinoside (an anthocyanin) and of quercetin-glycosides (flavonols) was observed. Expression of late flavonoid biosynthesis genes and their enzyme activities were adversely affected by FaMYB1 overexpression. Two-hybrid assays in yeast showed that FaMYB1 could interact with other known anthocyanin regulators, but it does not act as a transcriptional activator. Interestingly, the C-terminus of FaMYB1 contains the motif pdLNL(D)/(E)Lxi(G)/S. This motif is contained in a region recently proposed to be involved in the repression of transcription by AtMYB4, an Arabidopsis MYB protein. Our results suggest that FaMYB1 may play a key role in regulating the biosynthesis of anthocyanins and flavonols in strawberry. It may act to repress transcription in order to balance the levels of anthocyanin pigments produced at the latter stages of strawberry fruit maturation, and/or to regulate metabolite levels in various branches of the flavonoid biosynthetic pathway.

Amino Acid Sequence↗

PubMed2001

Activation of MKK6, an upstream activator of p38, in Alzheimer's disease.

Mitogen-activated protein kinase (MAPK) p38 has been implicated in the pathogenesis of Alzheimer's disease, but the upstream cascade leading to p38 activation has not been elucidated in the disease. In the present study, we focused on mitogen-activated protein kinase kinase 6 (MKK6), one of the upstream activators of p38 MAPK. We found that MKK6 was not only increased but also specifically associated with granular structures in the susceptible neurons in the hippocampus and cortex of Alzheimer's disease patients, but was only weakly diffuse in the cytoplasm in neurons in control cases. Immunoblot analysis demonstrated a significant increase of MKK6 level in Alzheimer's disease compared with age-matched controls. In this regard, in hippocampal and cortical regions of individuals with Alzheimer's disease, the activated phospho-MKK6 was localized exclusively in association with pathological alterations including neurofibrillary tangles, senile plaques, neuropil threads and granular structures, overlapping with activated p38 MAPK suggesting both a functional and mechanic link. By immunoblot analysis, phospho-MKK6 is also significantly increased in AD compared with control cases. Together, these findings lend further credence to the notion that the p38 MAPK pathway is dysregulated in Alzheimer's disease and also indicates an active role for this pathway in disease pathogenesis.

Adolescent↗

PubMed2001

Effects of inhibition of PAF, ICAM-1 and PECAM-1 on gut barrier failure caused by intestinal ischemia and reperfusion.

BACKGROUND: The role of cell adhesion molecules and transmigration of PMNs through the endothelial barrier is probably essential in intestinal ischemia and reperfusion (I/R)-induced gut barrier dysfunction. Although cytokines are released in I/R, it is unclear whether cytokines directly increase permeability or if this phenomenon requires both expression of cell adhesion molecules and PMN adhesion-activation. Endothelial barrier dysfunction plays an important role in the pathogenesis of multiple organ dysfunction syndrome, inducing gut barrier failure, but the mechanisms are not fully understood. The purpose of this study was to evaluate the potential therapeutic value of inhibition of platelet activating factor (PAF), intercellular adhesion molecule-1 (ICAM-1), and platelet endothelial cell adhesion molecule-1 (PECAM-1) in gut barrier dysfunction induced by intestinal I/R. METHODS: A PAF antagonist (lexipafant, BB-882) and monoclonal antibodies against rat ICAM-1 (anti-ICAM-1-MAb) and PECAM-1 (anti-PECAM-1-MAb) were used in a model of gut barrier dysfunction caused by intestinal ischemia for 40 min and concomitant reperfusion for 12 h in the rat, and endothelial permeability, myeloperoxidase activity, interleukin-1beta and protease inhibitor levels were evaluated. RESULTS: The endothelial permeability and tissue leukocyte recruitment in the distal small intestine significantly increased in rats with I/R treated with saline. Proteolytic activity in plasma was evident by low levels of the three measured plasma protease inhibitors. These changes were, to different degrees, reduced by treatment with lexipafant, anti-ICAM-1-MAb, or anti-PECAM-1-MAb. Alterations in systemic levels of interleukin-1beta paralleled the changes found in gut barrier permeability and leukocyte trapping. CONCLUSIONS: Our results suggest that treatment with the PAF inhibitor lexipafant and monoclonal antibodies against ICAM-1 or, seemingly most efficient, PECAM-1 reduces the severity of I/R-associated intestinal dysfunction, associated with a decrease in systemic concentrations of IL-1beta local leukocyte recruitment, and partly restoring plasma protease inhibitor levels.

Animals↗

PubMed2001

Effects of a National Cholesterol Education Program Step II Diet on apolipoprotein A-IV metabolism within triacylglycerol-rich lipoproteins and plasma.

BACKGROUND: Apolipoprotein (apo) A-IV is a major component of triacylglycerol-rich lipoprotein (TRL) apolipoproteins. OBJECTIVE: We investigated the effects of dietary saturated fat and cholesterol restriction on the metabolism of TRL and plasma apo A-IV. DESIGN: We assessed TRL and plasma apo A-IV kinetics in 16 and 4 subjects, respectively, consuming an average US (baseline) diet for 6 wk and a National Cholesterol Education Program Step II diet for 24 wk, respectively. At the end of each diet period, all subjects received a primed, constant infusion of deuterated leucine for 15 h with hourly feeding. Ratios of stable-isotope tracer to tracee were measured by using gas chromatography-mass spectrometry, and kinetic data were modeled by using SAAM II. RESULTS: Mean apo A-IV concentrations during the isotope infusion period were 6.9 +/- 2.6 mg/L in TRL and 2.2 +/- 3.2 mg/L in plasma with the baseline diet; these values were 37.7% (P < 0.001) and 19.4% (P < 0.01) lower with the Step II diet. Similar changes were observed in the fasting state between the 2 diets. The mean apo A-IV secretion rate decreased significantly from baseline by 59.6% in TRLs and by 40.2% in plasma. Significant correlations were observed between TRL apo A-IV concentrations and the secretion rate (r = 0.94, P < 0.001) and between TRL apo A-IV pool size and TRL-cholesterol concentrations (r = 0.48, P < 0.01). CONCLUSIONS: Our data indicate that the National Cholesterol Education Program Step II diet significantly decreases TRL and plasma apo A-IV concentrations compared with the average US diet and that this decrease is due to a decreased secretion rate.

Adult↗

PubMed2001

Support vector machine approach for protein subcellular localization prediction.

MOTIVATION: Subcellular localization is a key functional characteristic of proteins. A fully automatic and reliable prediction system for protein subcellular localization is needed, especially for the analysis of large-scale genome sequences. RESULTS: In this paper, Support Vector Machine has been introduced to predict the subcellular localization of proteins from their amino acid compositions. The total prediction accuracies reach 91.4% for three subcellular locations in prokaryotic organisms and 79.4% for four locations in eukaryotic organisms. Predictions by our approach are robust to errors in the protein N-terminal sequences. This new approach provides superior prediction performance compared with existing algorithms based on amino acid composition and can be a complementary method to other existing methods based on sorting signals. AVAILABILITY: A web server implementing the prediction method is available at http://www.bioinfo.tsinghua.edu.cn/SubLoc/. SUPPLEMENTARY INFORMATION: Supplementary material is available at http://www.bioinfo.tsinghua.edu.cn/SubLoc/.

Amino Acid Sequence↗

PubMed2001

Behavioral and emotional problems in Chinese adolescents: parent and teacher reports.

OBJECTIVE: This study examined behavioral and emotional problems in Chinese adolescents. METHOD: A sample of 1,694 adolescents aged 12 to 16 years participated in this study in 1997. Parents completed the Child Behavior Checklist (CBCL), and teachers completed the Teacher's Report Form (TRF). RESULTS: For both parent and teacher reports, internalizing syndromes were scored higher in girls and externalizing syndromes were scored higher in boys. Scores on most of the CBCL and TRF subscales were higher for the older adolescents. The overall prevalence rates of parent- and teacher-reported behavioral problems were 23.1% and 19.2%, respectively. The eight cross-informant syndromes were highly comorbid, with a significant association across syndromes (mean odds ratio = 16.1 for CBCL and 22.5 for TRF). Correlations between parent and teacher reports were 0.51 for eight subscales and 0.68 for Total Problems. CONCLUSIONS: These findings demonstrate that behavioral and emotional problems tend to increase with age and cluster in the same individuals. The prevalence rates of behavioral problems in Chinese adolescents are comparable to those reported in Western countries. In contrast to findings for Western samples, parent reports of behavioral problems were highly correlated with teacher reports.

Adolescent↗

PubMed2001

A noninvasive cross-correlation ultrasound technique for detecting spatial profile of laser-induced coagulation damage--an in vitro study.

A cross-correlation A-mode ultrasound technique is proposed for noninvasively detecting the spatial profile of coagulation damage in tissue being irradiated by laser. The basic assumption underlying this technique is that when coagulation is taking place in a tissue region, owing to thermally-induced structure changes in tissue, the waveform of echo signal scattered from that region should be changing accordingly. Our technique consists of four steps: 1) repeatedly sending the same acoustic signal to the tissue being heated; 2) tracking echo signals scattered from many small tissue regions using a cross-correlation echo-tracking technique; 3) quantifying waveform change of echo signal scattered from each region by means of cross-correlation coefficient between the currently acquired signal and a reference signal; 4) using the spatial profile of the degree of the waveform change to represent the tissue coagulation status at different depths. We carried out 23 heating experiments on fresh canine liver samples using a Nd:YAG laser (1,064 nm wavelength) at various light intensity (62 to 105 W/cm2) and exposure time (20 to 350 s). A 13-mm-diameter 10-MHz broadband single-element spherical focused ultrasound transducer was used. The spatial profiles of the degree of coagulation damage in the heated tissues, as determined by our technique, qualitatively agreed with the grossly inspected results. They also appeared to be consistent with the experimental and theoretical findings in the literature on laser-tissue interaction. Moreover, we developed an automatic procedure to compute the coagulation depth using the spatial profiles of the waveform change. We used the result as an indirect but quantitative means for evaluating the technique. Good overall agreement with a root mean square (rms) difference of only 0.81 mm was obtained between the computed and visually inspected final coagulation depths for the 23 experiments.

Animals↗

PubMed2001

5'TG3' interacting factor interacts with Sin3A and represses AR-mediated transcription.

Like other nuclear receptors, the AR exerts its transcriptional function by binding to cis elements upstream of promoters and interacting with other transcriptional factors (e.g. activators, repressors, and modulators). Among them, histone acetyltransferases (HATs) and histone deacetylases (HDACs) play critical roles in altering the acetylation state of core histones, thereby regulating nuclear hormone receptor-mediated transcription. The nuclear receptor corepressor can repress the TR and RAR in the absence of ligand through either a Sin3A-dependent or -independent manner by recruiting HDACs. AR and some other steroid hormone receptors cannot silence transcription through a similar mechanism in that they are located in the cytoplasm as complexes with heat-shock proteins before exposure to ligand. It has been shown that AR can bind to p160/SRC, cAMP response element-binding protein-binding protein (CBP)/P300 and other coactivators to increase the AR-mediated transcription. However, the molecular mechanism for turning AR from transcriptionally active into silent states is unknown. In this study, we demonstrated that the transcription repressor, 5'TG3' interacting factor (TGIF), selectively represses AR-mediated transcription from several AR-responsive promoters. The repression is mediated through binding of TGIF to the DNA binding domain of AR and is trichostatin sensitive. We also identified a direct protein-protein interaction between TGIF and a transcription corepressor, Sin3A, which suggests a novel pathway for TGIF recruiting HDAC1 to the repression complex. These results provide fresh insight into understanding the mechanism for repressing AR-, and perhaps other steroid hormone receptor-, mediated transcriptions.

Animals↗

PubMed2001

Cyclin D1 binds the androgen receptor and regulates hormone-dependent signaling in a p300/CBP-associated factor (P/CAF)-dependent manner.

The androgen receptor (AR) is a ligand-regulated member of the nuclear receptor superfamily. The cyclin D1 gene product, which encodes the regulatory subunit of holoenzymes that phosphorylate the retinoblastoma protein (pRB), promotes cellular proliferation and inhibits cellular differentiation in several different cell types. Herein the cyclin D1 gene product inhibited ligand-induced AR- enhancer function through a pRB-independent mechanism requiring the cyclin D1 carboxyl terminus. The histone acetyltransferase activity of P/CAF (p300/CBP associated factor) rescued cyclin D1-mediated AR trans-repression. Cyclin D1 and the AR both bound to similar domains of P/CAF, and cyclin D1 displaced binding of the AR to P/CAF in vitro. These studies suggest cyclin D1 binding to the AR may repress ligand-dependent AR activity by directly competing for P/CAF binding.

Acetyltransferases↗

PubMed2001

Development of extension kinematic corridors to validate a head/neck finite element model.

The objective of the current study was the development of experimental response corridors for the purpose of validating a finite element head-neck model in simulated vehicular rear impact. Six intact human head-neck cadaver complexes were used to understand and quantify the kinematics of the cervical spine secondary to low-speed rear impact. The first and second thoracic vertebrae were mounted in a fixative and attached to a minisled/pendulum apparatus. The specimens experienced live different input velocities applied to the first thoracic vertebral, created t),y the pendulum. The response of the specimen was digitally imaged at 1000 Hz from the right lateral side. Relative angles between vertebrae were analyzed in the sagittal plane at 100 ms after impact of the pendulum. Results correlated well with published physiologic range of motion data and dynamic full-body cadaver real impact experiments. Data obtained from this study will be used to validate the macroscopic motions of a finite element model, which will be used to understand the injury mechanisms involved in low-speed vehicular rear impacts.

Acceleration↗

PubMed2001

[The transference and distribution of tritium water in the soybean-soil system].

The isotope trace techniques of simulation contamination were applied to explore the rule of transference and distribution of tritium water in a simulated soybeam-soil ecosystem. The activity ratio of two forms of tritium in plant and soil sample were measured by 50 days simulation experiment. The results showed that when tritium water was entered the soil, it not only was transferred to other compartments in the system, but also vaporized into atmosphere rapidly. Both free water tritium and bound tritium were found in the soybean and the soil. The activity ratio of free water tritium reduced after reaching the maximum (19.4 Bq.g-1 in root, 12.3 Bq.q-1 in stem and leaf) at 6th hour in the soybean. The bound tritium increased slowly. The activity ratio of total tritium in soybean root was upper than those in stem and leaf in the earlier stage, they reach equipoise each other in the later stage. The activity ratio of two tritium in the surface soil reduced continuously. The compartment model of tracer kinetic was applied to imitate the experimental data. The activity ratio of soil Cs = 88.37e-11.847t + 7.38e-0.030t and the activity ratio of soybean Cb = 10.30(e-0.030t - e-11.847t) were gained.

Soil↗

PubMed2001

[Clinical study on the relationships between HBV C gene promotor gene mutation and immunological marker, HBV DNA concentration].

OBJECTIVE: To investigate the relationships between HBV infected patients immunological marker, HBV DNA concentration, and clinical symptoms. METHODS: PCR-microplate nucleotide acid hybridization-ELISA and FQ-PCR methods were applied in the analysis of HBV BCP gene mutation and HBV DNA concentration in 246 HBV infected patients. RESULTS: In patients with HBsAg+/HBeAg+/anti-HBc+, HBsAg+/anti-HBeAb+/anti-HBcAb+, and HBsAg+/anti-HBc+, the HBV DNA positive rate were 97.9% (48/49), 22.9% (25/109), 31.1% (14/45) respectively, with the overall positive rate 42.85% (98/203). And the HBV BCP gene mutation rate were 59.1% (29/49), 11% (12/109), 13.3% (6/45) respectively, with the overall mutation rate 23.15% (47/203). In HBV BCP gene mutation group HBV DNA concentration of each specimen was more than 10(6) cps/ml, which are significantly higher than other groups(P < 0.001). CONCLUSION: Re-evaluation of HBV infected patients with HBsAg+/anti-HBe+/anti-HBc+ and HBV BCP gene mutation is necessary. The immunological turnover of HBeAg indicates the immune clearance and rest of HBV only in part of HBV infected patients. The immunological marker should not be the sole factor upon which the HBV replication status, the diagnosis and prognosis of patients are determined.

Adolescent↗

PubMed2001

[Studies on cloning and expression of hepatitis B virus x gene].

OBJECTIVE: To express and purify the x gene of hepatitis B virus (HBV), and then the purity of the protein could specifically be analysed by the human antibodies against HBV x antigen (protein). METHODS: HBV x gene was amplified from the complete genome by PCR, and cloned in the pGEX-2T fused expression vector. After transforming the plasmid into E.coli, the recombinant with HBx gene was obtained. The fusion protein was generated with E.coli fused expression system and purified with affinity chromatography. RESULTS: The HBx protein could be applied to detecting specific antibody of hepatitis B virus patients. CONCLUSIONS: The purity of the HBx protein can specifically be recognized by the human antibodies against HBV x antigen.

Base Sequence↗

PubMed2001

[Study on the immunologic function of lymphocyte in cord blood].

OBJECTIVE: To explore immunologic function of T lymphocytes in human cord blood (HUCB) and provide theoretical basis for clinical application of HUCB. METHODS: Immunophenotype and co-stimulated molecules were detected by flow-cytometry using a panel of double labelled McAb, intracellular cytokines (interferon-gamma, interleukin-4) secreted by T lymphocytes by micro-culture of whole blood, and CD25 expression of T lymphocyte by PHA stimulation. T lymphocytes from adult peripheral blood (PB) were used as control. RESULTS: There are a higher CD4+/CD8+ ratio of T subset and a lower percentage of CD8+ lymphocytes in HUCB than that in adult PB (P < 0.01), and more than 90% of HUCB T-cells co-expressed CD45RA naive antigen which was significant higher than the percentage in adult PB (P < 0.01). The percentages of IFN-gamma and IL-4-producing CD4+ and CD8+ T cells from HUCB were lower than that of the control group. T cells in HUCB were able to be activated by PHA, but the phases of activation differed from adult PB T cells. CONCLUSIONS: It suggested that the low ability to secret cytokines and high percentage of naive T cells might be responsible for the decreased incidence of acute and chronic GVHD and provided possible explanation for the clinical result in HUCB transplantation. T cells in HUCB is a potential resource of adoptive immunotherapy.

Cytokines↗

PubMed2001

[Analysis of relationship between risk factors of malignant transformation of oral leukoplakia and the LSCP system].

OBJECTIVE: To explore the clinical significance of the LSCP (lesion size, site of lesion, clinical aspects, pathological aspects) classification and staging system through a comprehensive analysis of relationships between the risk factors of malignant transformation of 209 cases with oral leukoplakia and the LSCP classification and staging system. METHODS: Single factor Chi-square test was first performed to examine the associations between LSCP stages (I, II, III, IV) of oral leukoplakia and each of risk factors, including sex, site, size, numbers of lesion, alcohol and tobacco consumption, clinical classification and histopathological classification respectively, to select the most significant factors which influence the LSCP classification and staging. Then, the association of these selected factors with LSCP stages of oral leukoplakia (stage IV vs. I, II and III) was evaluated using multiple logistic regression analysis. RESULTS: Sex, site of lesions, clinical aspect and histopathological features of lesions were chosen as risk factors incorporated into the multiple logistic regression models. The results demonstrated that the risk of oral leukoplakia of the female patients classified as LSCP stage IV was 2.49 times as high as that of the male patients. The risk of lesions occurring in tongue and/or that floor of mouth was higher than that in other sites. Among the different clinical subtypes of lesions, the verrucous leukoplakia was the highest and 10.00 times as high as that of the homogeneous one. Among the different histopathological types, when hyperplasia and mild dysplasia were set as the basic level, the risk of severe dysplasia classified as LSCP stage IV was the highest and 499.55 times as high as the basic level, while that of moderate dysplasia was 276.48 times as high as the basic level. Pathological features with moderate and severe dysplasia were the most important contributory factors to the LSCP staging. CONCLUSIONS: The LSCP classification and staging system provides a comprehensive description of the features of oral leukoplakia, which is helpful in evaluating the overall risk of malignant transformation of oral lesion, and is valuable in clinical follow-up and developing the best treatment plan.

Adult↗

PubMed2001

Factor V Leiden mutation in one family of Chinese origin.

OBJECTIVE: To investigate the factor V Leiden mutation associated with activated protein C resistance (APCR) in Chinese. METHODS: Thirty "normal" individuals and twenty patients with thrombotic disease from Chinese Han Nationality were studied with APTT +/- APC, PCR followed by MnLI restriction enzyme analysis, PCR based direct sequence-specific primers (PCR-SSP) and DNA sequence analysis. RESULTS: In one healthy control, the activated protein C (APC) sensitivity ratio (SR) was found to be significantly lower (0.8) than that in other normal control (> 2.0). This individual was identified to be heterozygous for FV Leiden mutation (Arg506-Gln). His grand-uncle, father, brother and son were also identified to be heterozygous for FV Leiden. The APC resistance was found in 3 other cases of thrombotic diseases, but with no FV Leiden mutation. CONCLUSION: This is the first four generations family case of FV Leiden mutation associated with APCR reported within Chinese ethnic population. It is note-worthy that more FV Leiden or whether other gene defects may be associated with APC resistance and acquired APCR causing thrombosis in Chinese population.

Activated Protein C Resistance↗