Biomedical subjects

Z Zhang

Publications and source records attributed to Z Zhang.

At least 361 records · Page 20Linked to original sources

PubMed2001

[Design of multi-channel EEG collection system for stereoscopic VEP and study of the VEP evoked by binocular disparity].

A multi-channel EEG collection system has been constructed for visual evoked potentials (VEP) studies, using IBM compatible PC and clinical EEG amplifier. The collection system not only is suitable for investigative and clinical use, but also works perfectly in the EEG collection and signal processing of stereoscopic VEP. The characters of the depth related VEP evoked by binocular disparity were identified after analysing and comparing the VEP superposition results. The partial results of the VEP extraction are in accord with the previous studies. The system serves as a helpful tool in studies of stereoscopic cognition and brain function.

Adult↗

PubMed2001

[Preparation and identification of activity of antiplatelet-derived growth factor receptor beta subunit hammerhead ribozyme in vitro].

OBJECTIVE: To study the preparation and cleavage activity of ribozyme directed against platelet-derived growth factor (PDGF) receptor beta subunit gene transcript in vitro. METHODS: PDGF receptor B subunit gene fragments were cloned into T-vector under the control of T7 promotor. 32P-labeled PDGF receptor beta subunit transcripts as target-RNAs were transcribed in vitro and purified by PAGE. Ribozyme gene designed by computer targeting the extracellular domain was cloned into vector P1.5 between 5'-cis ribozyme and 3'-cis ribozyme. 32P-labeled ribozyme transcripts was gel-purified, incubated with target-RNAs at different conditions and autoradiographed after denaturing gel-electrophoresis. RESULTS: The preparation of ribozyme was correct. It was active at 37 degrees C. The optimal temperature was 50 degrees C, Km=13,20 nm, Kcat=0.28 min-1. The cleavage efficiency was up to 78.3%. CONCLUSIONS: Ribozyme prepared in vitro possesses specific catalytic activity.

Animals↗

PubMed2001

Elevated interleukin-13 in patients with active lupus nephritis.

OBJECTIVE: To investigate the significance of interleukin-13 (IL-13) in patients with active lupus nephritis (LN). METHODS: Ten healthy volunteers and 16 patients with active LN were included in this study. The protein level of IL-13 in plasma was examined by enzyme linked immunosorbent assay (ELISA), and gene expression of IL-13 in peripheral blood mononuclear cells (PBMCs) by reverse transcription polymerase chain reaction (RT-PCR). Expression of IL-13 mRNA in renal tissue was studied by in situ hybridization (ISH) techniques. RESULTS: The level of IL-13 in plasma and the expression of IL-13 mRNA in PBMCs were significantly higher in LN patients than those in the controls (P < 0.001). Increased expression of IL-13 mRNA was detected in renal tissue of active LN patients compared to those in the controls (P < 0.001). Analysis of the linear correlation indicated that the level of IL-13 mRNA in the tubulointerstitial area in patients with active LN correlated with the concentration of serum creatinine (Scr), the glomerular activity index (GAI), the activity index of tubulointerstitium, and the level of serum C3 (P < 0.05 for each). CONCLUSION: The elevation of IL-13 may play an important role in the molecular pathogenesis of active LN.

Adult↗

PubMed2001

Cr (VI) increases tyrosine phosphorylation through reactive oxygen species-mediated reactions.

While Cr (VI)-containing compounds are well established carcinogens, the mechanisms of their action remain to be investigated. In this study we show that Cr (VI) causes increased tyrosine phosphorylation in human lung epithelial A549 cells in a time-dependent manner. N-acetyl-cysteine (NAC), a general antioxidant, inhibited Cr (VI)-induced tyrosine phosphorylation. Catalase, a scavenger of H2O2, sodium formate and aspirin, scavengers of hydroxyl radical (*OH), also inhibited the increased tyrosine phosphorylation induced by Cr (VI). SOD, an inhibitor of superoxide radical (O2*-), caused less inhibition. ESR study shows that incubation of Cr (VI) with the A549 cells generates *OH radical. The generation of radical was decreased by addition of catalase and sodium formate, while SOD did not have any inhibitory effect. Oxygen consumption measurements show that addition of Cr (VI) to A549 cells resulted in enhanced molecular oxygen consumption. These results indicate that Cr (VI) can induce an increase in tyrosine phosphorylation. H2O2 and *OH radicals generated during the process are responsible for the increased tyrosine phosphorylation induced by Cr (VI).

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2001

On the mechanism of Cr (VI)-induced carcinogenesis: dose dependence of uptake and cellular responses.

Cr (VI) compounds are widely used industrial chemicals and are recognized human carcinogens. The mechanisms of carcinogenesis associated with these compounds remain to be investigated. The present study focused on dose-dependence of Cr (VI)-induced uptake and cellular responses. The results show that Cr (VI) is able to enter the cells (human lung epithelial cell line A549) at low concentration (< 10 microM) and that the Cr (VI) uptake appears to be a combination of saturable transport and passive diffusion. Electron spin resonance (ESR) trapping measurements showed that upon stimulation with Cr (VI), A549 cells were able to generate reactive oxygen species (ROS). The amount of ROS generated depended on the Cr (VI) concentration. ROS generation involved NADPH-dependent flavoenzymes. Cr (VI) affected the following cellular parameters in a dose-dependent manner, (a) activation of nuclear transcription factors NF-kappaB, and p53, (b) DNA damage, (c) induction of cell apoptosis, and (d) inhibition of cell proliferation. The activation of transcription factors was assessed by electrophoretic mobility shift assay and western blot analysis, DNA damage by single cell gel electrophoresis assay, cell apoptosis by DNA fragmentation assay, and cell proliferation by a non-radioactive ELISA kit. At the concentration range used in the present study, no thresholds were found in all of these cell responses to Cr (VI). The results may guide further research to better understand and evaluate the risk of Cr (VI)-induced carcinogenesis at low levels of exposure.

Antioxidants↗

PubMed2001

Cr (VI) induces cell growth arrest through hydrogen peroxide-mediated reactions.

Cr (VI) compounds are widely used in industries and are recognized human carcinogens. The mechanism of carcinogenesis associated with these compounds is not well understood. The present study focused on Cr (VI)-induced cell growth arrest in human lung epithelial A549 cells, using flow cytometric analysis of DNA content. Treatment of the cells with Cr (VI) at 1 microM caused a growth arrest at G2/M phase. An increase in Cr (VI) concentration enhanced the growth arrest. At a concentration of 25 microM, Cr (VI)-induced apoptosis became apparent. Superoxide dismutase (SOD) or sodium formate did not alter the Cr (VI)-induced cell growth arrest. While catalase inhibited growth, indicating H2O2 is an important mediator in Cr (VI)-induced G2/M phase arrest. Electron spin resonance (ESR) spin trapping measurements showed that incubation of cells with Cr (VI) generated hydroxyl radical (*OH). Catalase inhibited the *OH radical generation, indicating that H2O2 was generated from cells stimulated by Cr (VI), and that H2O2 functioned as a precursor for *OH radical generation. The formation of H2O2 from Cr (VI)-stimulated cells was also measured by the change in fluorescence of scopoletin in the presence of horseradish peroxidase. The mechanism of reactive oxygen species generation involved the reduction of molecular oxygen as shown by oxygen consumption assay. These results support the following conclusions: (a) Reactive oxygen species are generated in Cr (VI)-stimulated A549 cells through reduction of molecular oxygen, (b) Among the reactive oxygen species generated, H2O2 played a major role in causing G2/M phase arrest in human lung epithelial cells.

Antioxidants↗

PubMed2001

Molecular genetic profiling of Gleason grade 4/5 prostate cancers compared to benign prostatic hyperplasia.

PURPOSE: Because Gleason grade 4/5 cancer is the primary cause of failure to cure prostate cancer, we examined the molecular profiles of this high grade cancer in search of potentially new therapeutic interventions as well as better serum markers than prostate specific antigen. MATERIALS AND METHODS: We compared the gene expressions in fresh frozen tissues from 9 men with Gleason grade 4/5 cancer to 8 men with benign prostatic hyperplasia (BPH) treated with radical retropubic prostatectomy. Labeled complementary RNA from each of the 17 tissues was applied to HuGeneFL probe arrays representing approximately 6,800 genes (Affymetrix, Inc., Santa Clara, California). After removing all genes undetectable in BPH and grade 4/5 cancers, and transforming the data into a parametric distribution, we chose only those up and down-regulated genes with a p difference in fluorescence between grade 4/5 cancer and BPH of p <0.0005. This value reduced the data set to 40 up-regulated and 111 down-regulated genes. We then eliminated all genes that were not expressed in all 8 BPH and 9 grade 4/5 tissues, which produced a final set of 86 genes, of which 22 were up-regulated and 64 were down-regulated. RESULTS: Cluster analysis cleanly separated men with grade 4/5 cancers from those with BPH. Only 17 of the 86 candidate genes (20%) were known to be prostate cancer related and 42 (49%) were related to other cancers. The most up-regulated gene is Hepsin, a trypsin-like serine protease with its enzyme catalytic domain oriented extracellularly. Prostate specific membrane antigen is the second most up-regulated gene (all other reports on prostate specific membrane antigen have been at the protein level). The genes for prostate specific antigen (hK3) and human glandular kallikrein2 (hK2) showed equivalent expression levels 10 times the average of other genes. Complete lists of all 22 up-regulated genes and 64 down-regulated genes, together with their locus on the chromosome, are presented in rank order. CONCLUSIONS: We characterize for the first time 64 down-regulated and 22 up-regulated genes in Gleason grade 4/5 cancer, using the gene profile from BPH as control tissue. A number of interesting new genes, previously undescribed in prostate cancer, are presented as possibilities for further study.

Aged↗

PubMed2001

[Ovarian carcinoma presents as distant metastases without detectable tumors of the origin disease at the first presentation].

OBJECTIVE: To study the characteristics, therapies and prognosis of the patients with epithelial ovarian cancer (EOC) that are initially categorized as extra-abdominal adenocarcinoma of unknown primary. METHODS: Twenty-five patients with EOC, who were treated in the Cancer Hospital of Fudan University from Jan. 1986 to Dec. 1997, and manifesting as extra-peritoneal or liver parenchyma metastases at the time of presentation, without detectable ovarian tumors, were retrospectively studied. RESULTS: Supraclavicular and inguinal lymph node metastases were common in this group of patients, with 6 and 5 cases respectively, and 6 patients with more than two sites metastases simultaneously. 16 patients (64%) were optimally surgical debulked. 20 patients with stage IV EOC initially presenting as extra-abdominal metastases experienced a better prognosis, with an estimated median survival of 24 months. Of whom the median survival was 30 months in patients presenting with pleural effusion or supraclavicular lymph node metastases Vs. 19 months in those with other sites spread (P = 0.0264). CONCLUSIONS: The prognosis of such cases, particularly for those with supraclavicular lymphadenopathy or malignant pleural effusion, is a lot better than other stage IV EOC patients, probably because of most of the patients initially presenting with distant metastases being generally in a good condition competent for aggressive surgery or multi-cycle chemotherapy.

Adult↗

PubMed2001

[Location expression of human telomerase reverse transcriptase in lung cancer, benign lesion and normal lung tissue].

OBJECTIVE: To evaluate the diagnostic role of telomerase in benign and malignant lesion of lung and its biological significance in normal lung tissues. METHODS: Tissues studied consisted of 38 specimens of lung cancer, 35 adjacent non-neoplastic tissue and 7 benign parenchymatous lesion. Telomerase activity was determined using a semiquantitative polymerase chain reaction-based telomeric repeat amplification protocol (TRAP) assay. Localization of telomerase reverse transcriptase (hTERT) expression was examined by in situ hybridization and immunohistochemistry. RESULTS: Telomerase activity was detected in 31 out of 38 lung cancer, 7 of 35 adjacent non-neoplastic lung tissue and 3 of 7 benign parenchymatous lesions (P < 0.001). Both hTERT protein and mRNA were detected in cancer cells, lymphocytes, fibroblasts, macrophages in benign parenchymatous tissue, epithelial cells of small airways, bronchiole, alveoli as well as lymph nodule germinal center of the adjacent normal tissues. There was no significant difference in the expression intensity of hTERT protein among different kinds of cells. There was a tendency that the expression intensity of hTERT protein was higher in squamous carcinoma than those in adenocarcinoma and stronger at TNM stage III with poorly differentiated than those at TNM stage I-II with well-differentiated squamous carcinomas and adenocarcinomas (P > 0.05). CONCLUSIONS: (1) Telomerase is involved in the pathogenesis of both lung cancer and benign parenchymatous lesion. (2) Telomerase expression may be of biological significance in maintaining the normal function of airway epithelial cells, alveolar macrophage and lymphocytes. (3) It is suggested that telomerase might be used as a proliferative marker, rather than a specific malignant marker. False positive response may occur using telomerase as a diagnostic marker.

Adult↗

PubMed2001

[Significance of vascular endothelial growth factor expression in colorectal cancer].

OBJECTIVE: To investigate the expression of vascular endothelial growth factor (VEGF) mRNA in colorectal cancer (CRC) and its relation with the clinicopathologic features and explore new approaches to prevent and inhibit recurrence and metastasis of CRC. METHODS: Surgical samples of 68 patients with CRC were studied using reverse transcription-polymerase chain reaction (RT-PCR). The relative level of VEGF mRNA expression was measured by determining a ratio of PCR products of VEGF to that of beta-actin gene. RESULTS: (1) Expression of VEGF mRNA in tumor tissue was found in 67.6% (46/68) of the sample, whereas it was seen in 32.4% (22/68) of the surrounding nontumorous colorectal tissue. (2) The level of VEGF mRNA expression in tumors with serosal invasion, lymph node metastasis, distant metastasis or Dukes' D stage was higher than that without serosal invasion, lymph node metastasis, distant metastasis or Dukes' A and B and C stage (P < 0.01). (3) There was no significant difference in the expression of VEGF mRNA between large CRC (diameter > 5 cm) and small CRC (diameter < or = 5 cm) (P > 0.05) or histologic types (P > 0.05). CONCLUSION: VEGF may play an important role in the invasion and metastasis of CRC. It is thus show that angiogenesis in tumor correlates with the progression of CRC.

Adult↗

PubMed2001

Myocardial protection of immature rabbits with an ATP-sensitive K+ channel opener pinacidil.

OBJECTIVE: To investigate the effectiveness of pinacidil, an opener of ATP-sensitive K+ channels, in protecting the myocardium of immature rabbit hearts from ischemic reperfusion injury. METHODS: Rabbit hearts underwent 30 min of global normothermic ischemia followed by 30 min of reperfusion on the modified Langendorff apparatus. Fifty-two isolated hearts of 3-4 week-old immature rabbits were divided into 4 groups randomly. During ischemia, 3 different cardioplegic solutions were administered intermittently by infusion every 15 min (20-25 ml each time in all groups). Group 1: control group (n = 13); group 2: Krebs-Henseleit (K-H) solution with potassium (16 mmol/L) (n = 13); group 3: K-H solution with potassium (16 mmol/L) and pinacidil (50 mumol/L) (n = 13); group 4: K-H solution with potassium (16 mmol/L), pinacidil (50 mumol/L) and glibenclamide (10 mumol/L) (n = 13). The pre-ischemic and post-ischemic myocardial functions were assessed by the percentage recovery of the left ventricular developed pressure (LVDP); the left ventricular end-diastolic pressure (LVEDP); both the positive peak and negative peaks of the first derivative of the left ventricular pressures (+/- dp/dtmax); coronary flow; the level of creatine kinase (CK), lactic dehydrogenase (LDH) and aspartate transcarbamoylase (AST) in coronary sinus venous effluent; and by myocardial ultrastructural changes. RESULTS: Before myocardial ischemia, there were no significant differences among the four groups in any of the parameters mentioned above. Post-ischemic recovery of LVDP, LVEDP, +/- dp/dtmax, coronary flow, the level of CK, LDH and AST, and myocardial ultrastructural changes were better in group 3 than those in the three other groups. CONCLUSIONS: As a new and effective composition, pinacidil can significantly improve myocardial protection from cardioplegia for immature rabbit hearts.

Animals↗

PubMed2001

Identification of the peroxisomal beta-oxidation enzymes involved in the biosynthesis of docosahexaenoic acid.

DHA (C22:6n-3) is an important PUFA implicated in a number of (patho)physiological processes. For a long time, the exact mechanism of DHA formation has remained unclear, but now it is known that it involves the production of tetracosahexaenoic acid (C24:6n-3) from dietary linolenic acid (C18:3n-3) via a series of elongation and desaturation reactions, followed by beta-oxidation of C24:6n-3 to C22:6n-3. Although DHA is deficient in patients lacking peroxisomes, the intracellular site of retroconversion of C24:6n-3 has remained controversial. By making use of fibroblasts from patients with defined mitochondrial and peroxisomal fatty acid oxidation defects, we show in this article that peroxisomes, and not mitochondria, are involved in DHA formation by catalyzing the beta-oxidation of C24:6n-3 to C22:6n-3. Additional studies of fibroblasts from patients with X-linked adrenoleukodystrophy, straight-chain acyl-CoA oxidase (SCOX) deficiency, d-bifunctional protein (DBP) deficiency, and rhizomelic chondrodysplasia punctata type 1, and of fibroblasts from l-bifunctional protein and sterol carrier protein X (SCPx) knockout mice, show that the main enzymes involved in beta-oxidation of C24:6n-3 to C22:6n-3 are SCOX, DBP, and both 3-ketoacyl-CoA thiolase and SCPx. These findings are of importance for the treatment of patients with a defect in peroxisomal beta-oxidation.

Acetyl-CoA C-Acetyltransferase↗

PubMed2001

Efficient down-regulation of the major vegetative storage protein genes in transgenic soybean does not compromise plant productivity.

Soybean (Glycine max L. Merr.) contains two related and abundant proteins, VSP alpha and VSP beta, that have been called vegetative storage proteins (VSP) based on their pattern of accumulation, degradation, tissue localization, and other characteristics. To determine whether these proteins play a critical role in sequestering N and other nutrients during early plant development, a VspA antisense gene construct was used to create transgenic plants in which VSP expression was suppressed in leaves, flowers, and seed pods. Total VSP was reduced at least 50-fold due to a 100-fold reduction in VSP alpha and a 10-fold reduction in VSP beta. Transgenic lines were grown in replicated yield trials in the field in Nebraska during the summer of 1999 and seed harvested from the lines was analyzed for yield, protein, oil, and amino acid composition. No significant difference (alpha = 0.05) was found between down-regulated lines and controls for any of the traits tested. Young leaves of antisense plants grown in the greenhouse contained around 3% less soluble leaf protein than controls at the time of flowering. However, total leaf N did not vary. Withdrawing N from plants during seed fill did not alter final seed protein content of antisense lines compared with controls. These results indicate that the VSPs play little if any direct role in overall plant productivity under typical growth conditions. The lack of VSPs in antisense plants might be partially compensated for by increases in other proteins and/or non-protein N. The results also suggest that the VSPs could be genetically engineered or replaced without deleterious effects.

Down-Regulation↗

PubMed2001

[Phosphorus behavior in soil-water system of paddy field and its environmental impact].

A field experiment with rice showed that P fertilizer application increased the concentrations of resin P in soil and total P in soil surface water, and both of them declined subsequently over time. Compared with applying mineral P fertilizer only, the integrated application of mineral-P and manure resulted in a higher resin P level within 20 days after P application. The total P concentration in soil surface water in the treatment of integrated application of mineral-P and manure was 3.4 times higher than that in the treatment of mineral-P fertilizer application only after 7 days of P application, and also, was 2.8 times higher than that in the treatment where P application rate was doubled. The potential of Ploss from surface water in the treatment of integrated application with manure was more than that in the treatment of applying-P fertilizer only. The effect of applied P sorts on P concentration in soil surface water could be ignored after 33 days of P application. Two drainages were conducted for rice growth, which caused the net P loss loading and its apparent P loss ratio in range of -0.038-0.076 kg.m-2 and 0.034-0.100%, respectively. To minimize P loss from rice production area, field drainage should be avoided in the initial week of P-fertilizer application or field harrowing.

Environment↗

PubMed2001

[Effect of silver carp stocking and fertilization on plankton community in enclosures in saline-alkaline ponds].

The effect of silver carp (Hypophthalmichthys molitrix) stocking and fertilization on plankton community of enclosures ecosystem in saline-alkaline ponds were studied. After stocking silver carp in enclosures, the abundance, chlorophyll-a content and primary productivity of phytoplankton increased, and the biomass of phytoplankton was mainly composed by small species, such as diatom and green algae. Moreover, Euglnophyta and Chrysophyta were also subdominant species. The biomass of zooplankton decreased with fish stocking, and that of Cladocera was greater in control than in fish-culture enclosures. Zooplankton community was dominated by larger species such as Daphnia carinata in control enclosures. Fertilization, especially applying inorganic fertilizer, significantly increased the abundance and primary productivity of phytoplankton and the biomass of zooplankton. Although the biomass of plankton in the enclosures applied organic fertilizer was greater than that of control enclosures, the primary productivity and chlorophyll-a content of phytoplankton, the diversity index of plankton, and the P/R ratio were very low, and thus, silver carp grew slowly. The effect of filter feeding fish and applying fertilizer on the structure of plankton community was also discussed.

Animals↗

PubMed2001

[The assay of beta-lactamase activity in Pseudomonas aeruginosa biofilm].

OBJECTIVE: To analyze the resistance mechanism of Pseudomonas aeruginosa biofilm bacteria. METHODS: An in vitro model of Pseudomonas aeruginosa bacterial biofilm was established in silicon disk with modified flat-board method and a rapid staining procedure of AgNO3 was used to verify it. Biofilm was observed under scanning electron microscopy. The test was carried out in three groups. Group A was planktonic bacteria of Pseudomonas aeruginosa, group B biofilm bacteria of Pseudomonas aeruginosa and group C biofilm bacteria induced by imipenem. The activity of beta-lactamase was quantitated with a spectrophotometric assay method and beta-lactamase quantitation was determined by using Bio-Rad protein assay. RESULTS: The activity and protein content of beta-lactamase in group B was higher than that in group A by 4.67 and 2.09 times. The activity of group C was 21.86 times as much as that in group A and 4.68 times as much as that in group B. The quantitation in group C was 6.28 times as much as that in group A and 3.00 times as much as that in group B. The activity and quantitation of the three groups were different significantly from each other (P < 0.01). CONCLUSION: The production of beta-lactamase in Pseudomonas aeruginosa biofilm bacteria is one of the main reasons of its resistance.

Anti-Bacterial Agents↗

PubMed2001

[Effect of rare earth elements on the seedling ratio of crops].

The effects of rare earth elements(REEs) on the relative seedling ratio of three crops(rice, rape and soybean) in three soil(red soil, yellow fluvo-aquic soil and yellow cinnamon soil) were studied according to OECD method, and the LC50 were obtained. Toxicity effect of REEs on rice was minimum among the crops tested. The toxicity on crops in yellow cinnamon soil was lower, whereas on soybean in yellow fluvo-aquic soil and on rape in red earth were higher.

Crops, Agricultural↗

PubMed2001

[N2O emission by trees under natural condition].

The sources of N2O, one of the major greenhouse gases in the atmosphere, are still unclear till now. It was previously thought that only soil microbial process produced N2O. The aim of this study was to provide evidences that plant can emit N2O under the natural condition. The measurement of aboveground vertical profiles of N2O concentrations were conducted within coniferous-deciduous mixed forests in Changbai Mountain, China. Significant high N2O concentrations were found at or near the height of canopy. High concentrations in profiles were 3.03% to 64.9% higher than the "normal concentrations". Differences between the high concentrations and the "normal concentrations" were statistically significant. The simultaneous occurrence of high concentrations at/nearby the canopy height and normal concentrations at the trunk space height indicated an efflux of N2O from foliage to atmosphere. This study afforded evidences supporting that plant per se, besides forest soil, was an important source of atmospheric N2O in a forest ecosystem.

Air↗