Biomedical subjects
Publications and source records attributed to Yi Zhang.
In the experimental study on the electrophysiology and functions of heart in the animal, the thorax should be opened to expose the heart, at the same time natural breathing is maintained instead of artificial breathing. The key procedure of this new method is to avoid injuring the pleural cavity, so pneumothorax can be prevented. By means of this new method some subject studies have been finished.
BACKGROUND: Many forms of hypertension are associated with increased oxidative stress. This study investigated the effects of Tempol, a superoxide scavenger, on prevention and reversal of hypertension induced by the synthetic glucocorticoid dexamethasone (Dex) in the rat. METHODS: Male Sprague-Dawley rats (n = 10 in each group) were treated with saline or Dex (10 microg/kg/day subcutaneously) for 13 days. Tempol (1 mmol/L) was given in drinking water from 4 days before treatment (prevention) or from treatment day 8 (T8) (reversal). Systolic blood pressure (SBP) was measured by the tail-cuff method. Plasma F(2)-isoprostane concentrations were measured as a highly specific marker of oxidative stress. Thymus weight was measured as a marker of glucocorticoid activity. RESULTS: Dex treatment increased SBP (122 +/- 5 to 136 +/- 3 mm Hg, P <.05) and plasma F(2)-isoprostane concentrations (P =.005). Tempol alone did not alter SBP, but Tempol pretreatment prevented Dex-induced hypertension compared with that in rats treated with Dex alone (128 +/- 4 and 144 +/- 7 mm Hg respectively, P' <.05). Tempol partially reversed Dex-induced hypertension (122 +/- 5 and 136 +/- 3 mm Hg, respectively, P' =.057). Thymus weight was decreased in Dex-treated rats compared with saline treated rats (157 +/- 10 saline and 105 +/- 6 mg/100 g body weight Dex, P <.0005). Tempol affect neither thymus weight nor F(2)-isoprostane concentrations. CONCLUSIONS: Chronic Dex treatment increased SBP and tended to increase oxidative stress shown as increased plasma F(2)-isoprostane concentrations. Tempol prevented and partially reversed Dex-induced hypertension, independent of improvement in systemic oxidative stress measured by F(2)-isoprostane concentrations.
BACKGROUND: This study was designed to investigate the effects of adrenocorticotropic hormone (ACTH) on systolic blood pressure (BP) and serum erythropoietin (EPO) concentrations in two strains of rats. We hypothesized that ACTH-induced hypertension in the rat is characterized by increased EPO production. METHODS: Male Sprague-Dawley (SD) and Wistar out-bred (Wistar) rats were treated with saline or ACTH (0.2 mg/kg/d). Systolic BP was measured using the tail-cuff method. Serum EPO concentrations were assayed using an ELISA kit for human EPO, which cross-reacts with but underestimates rat EPO. Thymus weight was used as a marker of glucocorticoid activity. RESULTS: In SD rats, ACTH increased systolic BP (from 109 +/- 4 to 142 +/- 5 mm Hg, P <.0005), significantly greater than in saline-treated rats (P <.01). Systolic BP in ACTH-treated Wistar increased from 120 +/- 3 to 133 +/- 4 mm Hg (P <.05), but was not significantly different from saline-treated Wistar rats. The ACTH-induced increase in systolic BP was greater in SD than in Wistar rats (P <.05). Serum EPO levels were 5.6 +/- 0.4 in SD and 5.9 +/- 0.3 IU/L in Wistar rats, and decreased to undetectable levels with ACTH treatment in 10 of 10 SD and 7 of 10 Wistar rats. The ACTH treatment increased hemoglobin and hematocrit, and decreased thymus weight in both strains. CONCLUSIONS: 1) ACTH decreased serum EPO concentrations in both strains; 2) EPO is inversely related to ACTH-induced hypertension in the rat; and 3) Wistar rats are relatively resistant to the BP raising effects of ACTH treatment but not to the ACTH-induced decrease in thymus weight. These data suggest that EPO is not causal in ACTH-induced hypertension.
OBJECTIVE: Allogeneic transplantation with umbilical cord blood (UCB) in adult recipients is limited mainly by a low CD34+ cell dose. To overcome this shortcoming, human placenta as a novel source of human mesenchymal progenitor cell (MPC) was incorporated in an attempt to expand CD34+ cells from UCB in vitro. MATERIALS AND METHODS: Human placenta MPC was isolated and characterized by morphologic, immunophenotypical, and functional analysis. UCB CD34+ cells were expanded by coculture with placental MPC. Suitable aliquots of cells were used to monitor cell production, clonogenic activity, and long-term culture-initiating culture (LTC-IC) output. Finally, the immunoregulatory effect of placental MPC was evaluated by T-cell proliferation assay. RESULTS: In its undifferentiated state, placental MPC displayed fibroblastoid morphology; was CD73, CD105, CD29, CD44, HLA-ABC, and CD166 positive; produced fibronectin, laminin, and vimentin; but was negative for CD14, CD31, CD34, CD45, HLA-DR, and alpha-smooth muscle actin. Functionally, it could be induced into adipocytes, osteocytes, and chondrocytes. In vitro expansion of UCB hematopoietic cells, when cocultured with placental MPC in the presence of cytokines, was significantly enhanced: CD34+ cells by 14.89 +/- 2.32 fold; colony-forming cell (CFC) by 36.73 +/- 5.79 fold; and LTC-IC by 7.43 +/- 2.66 fold. Moreover, placental MPC could suppress T-cell proliferation induced by cellular stimuli. CONCLUSION: These results strongly suggest that human placental MPC may be a suitable feeder layer for expansion of hematopoietic progenitors from UCB in vitro.
Polycomb group (PcG) proteins are important for maintaining the silenced state of homeotic genes. Biochemical and genetic studies in Drosophila and mammalian cells indicate that PcG proteins function in at least two distinct protein complexes: the ESC-E(Z) or EED-EZH2 complex, and the PRC1 complex. Recent work has shown that at least part of the silencing function of the ESC-E(Z) complex is mediated by its intrinsic activity for methylating histone H3 on lysine 27. In addition to being involved in Hox gene silencing, the complex and its associated histone methyltransferase activity are important in other biological processes including X-inactivation, germline development, stem cell pluripotency and cancer metastasis.
AIMS: Early definition of treatment outcomes, including coronary patency and infarct size, after reperfusion therapy for myocardial infarction (MI) is desirable to identify patients requiring further intervention. METHODS AND RESULTS: Patients receiving reperfusion therapy for a first MI had continuous 12-lead ST segment monitoring to document reperfusion and ischaemia time. Infarct size was measured by 12-lead QRS score and radionuclide scintigraphy ((201)Tl single-photon emission computed tomography, SPECT) at 1 week, and left ventricular function by echocardiography at 1 week and 1 month. Resolution of ST elevation accurately detected TIMI 2 or 3 reperfusion (predictive accuracy 93%) in 55 patients undergoing immediate angioplasty, but ST recovery was delayed (17+/-14min) after angiographic reperfusion. A multivariate model, including risk region and ischaemia time, accurately predicted MI size (R(2)=0.80, P<0.00001) in these patients. The same model, prospectively applied on Day 1 to 154 patients receiving thrombolytic therapy, accurately predicted MI size, measured by QRS score (R(2)=0.88, P<0.0000001) and (201)Tl SPECT (R(2)=0.75, P<0.000001) at 1 week for individual patients. Regional myocardial wall motion at 1 month was directly correlated with MI size predicted by the model on Day 1 (r=0.73, P<0.0001). CONCLUSIONS: Use of ST segment monitoring during reperfusion therapy facilitates early prediction of treatment outcomes, including coronary reperfusion, infarct size and ventricular function.
OBJECTIVE: To evaluate the use of hematocrit as a surrogate end point for survival among end-stage renal disease (ESRD) patients treated with epoetin. STUDY DESIGN AND SETTING: Using United States Renal Data System (USRDS) data, we conducted an observational prospective study to analyze the relationships among epoetin dose, hematocrit, and survival for 31,301 facility-based hemodialysis patients incident to ESRD therapy in 1998. To address our objective, we used criteria developed by Prentice based on results from a Cox regression model. RESULTS: Results indicate that hematocrit is inversely associated with epoetin dose. For the same epoetin treatment-related achieved hematocrit levels, there were widely varying treatment-related survival outcomes, thereby challenging a central criterion required to empirically validate a surrogate end point. CONCLUSION: Our results support earlier clinical trial and epidemiological data suggesting that hematocrit may not be a valid surrogate for survival among the epoetin-treated renal failure population. We hypothesize that hematocrit may not be in the causal pathway or that epoetin may have important mechanisms of action apart from increasing hematocrit. Effective treatment for anemia may therefore not be simply a matter of increasing hematocrit. This study has potential implications for revising the existing treatment guidelines for anemia management and selecting an appropriate treatment regimen.
Annexin B1 is a novel member of the annexin family of Ca2+- and phospholipid-binding proteins from Cysticercus cellulosae. To obtain high quality annexin B1 for biochemical and biophysical analyses, its cDNA was cloned into the prokaryotic expression vector pJLA503 and the translation initiation codon was immediately under the control of the inducible bacteriophage lambda promoters P(R) and P(L). After induction by shifting temperature, large amounts of non-fusion protein were produced in Escherichia coli in a soluble form. The recombinant protein was purified to homogeneity by means of two subsequent ion-exchange chromatographic steps. The final yield was about 25 mg/L bacterial culture. Western blot analysis showed that recombinant annexin B1 was specifically recognized by serum of pigs infected with cysticercosis. Secondary structure predictions from circular dichroism spectroscopy indicated that alpha-helix is the main secondary structure of the protein. In anticoagulant assays, the recombinant non-fusion protein exhibited dose-dependent effects in modified kaolin partial thromboplastin time (KPTT) prolongation and doubled the clotting time of control human plasma at 60 microg/ml. The expression, purification, and initial characterization of annexin B1 set an important stage for further characterization of the protein.
A highly efficient cell-free translation system has been combined with suppressor tRNA technology to substitute nor-Tyr and 3-fluoro-Tyr in place of Tyr183 at the DNA polymerase active site of p66 of human immunodeficiency virus type 1 reverse transcriptase (HIV-1 RT). Supplementing the wild-type HIV-1 p51 RT subunit into this translation system permitted reconstitution of the biologically relevant p66/p51 heterodimer harboring Tyr analogs exclusively on the catalytically competent p66 subunit. Addition of an affinity tag at the p66 C-terminus allowed rapid, one-step purification of reconstituted and selectively mutated heterodimer HIV-1 RT via strep-Tactin-agarose affinity chromatography. The purified enzyme was demonstrated to be free of contaminating nucleases, allowing characterization of the DNA polymerase and ribonuclease H activities associated with HIV-1 RT. Preliminary characterization of HIV-1 RT(nor-Tyr) and HIV-1 RT(m-fluoro-Tyr) is presented. The success of this strategy will facilitate detailed molecular analysis of structurally and catalytically critical amino acids via their replacement with closely related, unnatural analogs.
OBJECTIVES: to demonstrate that nitric oxide (NO) contributes to free radical generation after epicardial shocks and to determinethe effect of a nitric oxide synthase (NOS) inhibitor, N(G)-nitro-L-arginine (L-NNA), on free radical generation. BACKGROUND: Free radicals are generated by direct current shocks for defibrillation. NO reacts with the superoxide (O2*-) radical to for peroxynitrite (O = NOO-), which is toxic and initiates additional free radical generation. The contribution of NO to free radical generation after defibrillation is not fully defined. METHODS AND RESULTS: Fourteen open chest dogs were studied. In the initial eight dogs, 40 J damped sinusoidal monophasic epicardial shocks was administered. Using electron paramagnetic resonance, we monitored the coronary sinus concentration of ascorbate free radical (Asc*-), a measure of free radical generation (total oxidative flux). Epicardial shocks were repeated after L-NNA, 5 mg/kg IV. In six additional dogs, immunohistochemical staining was done to identify nitrotyrosine, a marker of reactive nitrogen species-mediated injury, in post-shock myocardial tissue. Three of these dogs received L-NNA pre-shock. After the initial 40 J shock, Asc*- rose 39 +/- 2.5% from baseline. After L-NNA infusion, a similar 40 J shock caused Asc*- to increase only 2 +/- 3% form baseline (P < 0.05, post-L-NNA shock versus initial shock). Nitrotyrosine staining was more prominent in control animals than dogs receiving L-NNA, suggesting prevention of O = NOO- formation. CONCLUSION: NO contributes to free radical generation and nitrosative injury after epicardial shocks; NOS inhibitors decrease radical generation by inhibiting the production of O = NOO-.
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Proof of concept was obtained that nitrobenzene can be reduced to aniline by a mixed reductive microbial culture using H2 as the sole electron donor source. In a continuous-flow anaerobic bioreactor, both pH and temperature affected nitrobenzene reduction with optima of pH 6.5-6.8 and 30 degrees C. The efficiency of nitrobenzene degradation increased with H2 up to 10% (v/v). An increase in sulfate concentration decreased the removal rate of nitrobenzene.
Adrenocorticotrophic hormone (ACTH) elevates systolic blood pressure (SBP) and lowers plasma reactive nitrogen intermediates in rats. We assessed the ability of NO donation from isosorbide dinitrate (ISDN) to prevent or reverse the hypertension caused by ACTH. In the prevention study, male Sprague Dawley rats were treated with ACTH (0.2 mg/kg/day) or saline control for 8 days, with either concurrent ISDN (100 mg/kg/day) via the drinking water or water alone. Animals receiving ISDN via the drinking water were provided with nitrate-free water for 8 hours every day. In the reversal study ISDN (100 mg/kg) or vehicle was given as a single oral dose on day 8. SBP was measured daily by the indirect tail-cuff method in conscious, restrained rats. ACTH caused a significant increase in SBP compared with saline (P < 0.0015). In the prevention study, chronic administration of ISDN (100 mg/kg/day) did not affect the SBP in either group. In the reversal study, ISDN significantly lowered SBP in ACTH-treated rats at 1 and 2.5 hours (132 +/- 3 mmHg (1 h) and 131 +/- 2 mmHg (2.5 h) versus 143 +/- 3 mmHg (0 h), P < 0.002), but not to control levels. It had no effect in control (saline treated) rats. In conclusion, the lowering of SBP by NO donation is consistent with the notion that ACTH-induced hypertension involves an impaired bioavailability or action of NO in vivo.
(Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETA/NO) is a recently synthesized member of NO-releasing, polyamine zwitterions, the so-called NONOates, that spontaneously liberate NO in aqueous solutions. The aim of this study was to determine the hemodynamic effects of DETA/ NO in normotensive and hypertensive mice. Male Swiss Outbred mice were implanted with TA11PA-C20 blood pressure devices (Data Sciences International, USA). After recovery (7-10 days), blood pressure was monitored for 10 days while mice were receiving saline (0.1 ml/20 g/day, s.c.). Mice were then treated every four hours for 1 day with either DETA/NO 60 mg/kg i.p. or the inactive metabolite, diethylenetriamine 38 mg/kg (molar equivalent) i.p. After a 2 week wash-out period, mice were treated with adrenocorticotrophic hormone (ACTH: 500 microg/kg/day, s.c.) for 10 days and re-challenged with DETA/NO or diethylenetriamine. Results were expressed as mean +/- SEM. After 10 days of saline treatment, baseline systolic and diastolic blood pressure (BP) were similar for animals subsequently receiving DETA/NO or the amine (123 +/- 1/95 +/- 3 and 124 +/- 1/92 +/- 0.2 mmHg) respectively. DETA/NO induced a profound fall in BP [Systolic: 74 +/- 4 mmHg (-40 +/- 3%); Diastolic: 46 +/- 4 mmHg (-52 +/- 4%)] and an increase in heart rate [729 +/- 33 bpm (32 +/- 2%)] within the first 80 minutes. Diethylenetriamine had no effect. ACTH treatment increased BP in both groups (137 +/- 16/108 +/- 12 and 161 +/- 1/142 +/- 1 mmHg) respectively. DETA/ NO induced a profound fall in blood pressure [Systolic: 92 +/- 11 mmHg (-32 +/- 7%); Diastolic: 68 +/- 10 mmHg (-35 +/- 10%)] and an increase in heart rate [613 +/- 36 bpm (18 +/- 6%)] within the first 80 minutes. Again diethylenetriamine had no significant effect. There was no significant effect on body weight with any treatment. Thus DETA/NO has potent blood pressure lowering effects in both normotensive and hypertensive mice.
To produce a thrombi-targeting plasminogen activator, low molecular weight single-chain urokinase gene (scuPA32k) was spliced with the full-length cDNA of annexin B1 gene (anxB1) by overlap extension method. The fused gene anxB1scuPA was ligated into pET28a vector, transformed into E. coli BL21-RIL, and then induced to express under the control of T7 promoter. The AnxB1ScuPA protein expressed amounted to 22% of the total bacterial proteins. The product was refolded, and then purified by using DEAE Sepharose fast flow ion-exchange column and Superdex S-200 gel-filtration column. HPLC analysis revealed that the final purity is about 95%. The specific activity of AnxB1ScuPA, measured as amidolytic activity, reached 100,000 IU/mg. It had a similar S2444 catalytic efficiency (kcat/Km) to ScuPA32k, and also showed high activated-platelet membrane-binding activity and anticoagulant activity, indicating that the chimera fully retained the components of enzymatic and membrane-binding activities of the parent molecules. In vivo test revealed that, the dogs administered with AnxB1ScuPA had less reperfusion time, higher reperfusion ratio, and less bleeding effects than those with urokinase. These findings indicated that AnxB1ScuPA might have advantages over current available thrombolytic agents.
The aim of the present study was to investigate the putative role of endothelin (ET) in mediating ischemia/hypoxia-induced ANP release utilizing exogenous ET-1 or ET receptor antagonists (BQ-123 or Bosentan). Isolated rat hearts with non-distended atria were perfused using a Langendorff apparatus and heart rate maintained constant via atrial pacing. Global ischemia was induced either by direct reduction in perfusion or by infusion of exogenous ET-1 (5 x 10(-10) M) for 30 minutes. Perfusion with the ET receptor antagonists, BQ-123 (10(-6) M) or Bosentan (10(-5) M) was initiated 10 minutes before onset of ischemia. Moderate or severe ischemia was induced by reduction (52-61% and 70-82%, respectively) in perfusate flow. Thirty minutes of ischemia/hypoxia (5% O2) was followed by 30 minutes of reperfusion/re-oxygenation. Both moderate and severe ischemia increased ANP release. BQ-123 and Bosentan did not affect basal or ischemia-induced ANP release. Exogenous ET-1 perfusion induced a late increase in ANP release (P < 0.01) that did not exceed the increase in ANP release associated with equivalent direct flow reduction. Hypoxia induced an 8-fold increase in ANP release rate. The ANP release rate returned toward basal levels after re-oxygenation. Bosentan, but not BQ-123, significantly attenuated (P < 0.01) hypoxia-induced ANP release. In conclusion, in this system, ANP release is stimulated by moderate (or severe) ischemia and severe hypoxia independent of change in atrial distension; endogenous ET does not mediate basal and ischemia-induced ANP release; and hypoxia-induced ANP release is partially modulated via interaction with endogenous ET.
Triphasic shocks have been evaluated for endocardial defibrillation but not for open-chest epicardial defibrillation. The purpose of this study was to compare the efficacy and safety of biphasic versus triphasic shocks for epicardial defibrillation in a porcine model. Twenty-two adult swine (18-28 kg) were deeply anesthetized and intubated. After 30 seconds electrically induced VF, each pig received truncated exponential biphasic (7.2-ms positive pulse duration and 7.2-ms negative pulse duration, total waveform duration 14.4 ms) and triphasic (4.8/4.8/4.8 ms, total waveform duration 14.4 ms) epicardial shocks. Pigs in group 1 (n = 11) received epicardial biphasic and triphasic shocks from large hand held paddle electrodes (44.2 cm2); pigs in group 2 (n = 11) received shocks from small paddle electrodes (15.9 cm2). Shocks were given at five selected energy levels (3-30 J) in random sequence. Four shocks were delivered at each energy level to construct an energy versus percentage of success curve. In group 1 (large paddle electrodes), percentage of shock success was significantly higher for triphasic shocks at the energy levels of 3, 5, 10, and 20 J compared to biphasic shocks. In group 2 (small paddle electrodes), triphasic shocks yielded a significantly higher percentage of shock success than biphasic shocks at the energy levels of 5, 10, and 20 J). Shock induced ventricular tachycardia was similar for both waveforms; asystole was rare. For open-chest defibrillation, triphasic waveform shocks were superior to biphasic waveform shocks for VF termination at energy levels of 3-20 J and were as safe as biphasic shocks.