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Qun Chen

Publications and source records attributed to Qun Chen.

At least 19 recordsLinked to original sources

A novel phage vB_VhaM_HVS-1 inhibits host cell associated Vibrio harveyi.

INTRODUCTION: Vibrio harveyi is a major pathogen causing skin ulceration syndrome and mass mortality in sea cucumber Apostichopus japonicus aquaculture. METHODS: In this study, a pathogenic strain NB-3 was isolated from diseased A. japonicus and identified as V. harveyi based on morphological, physiological, and genomic analyses. A novel lytic phage vB_VhaM_HVS-1 belonging to the family Straboviridae (class Caudoviricetes) was isolated from A. japonicus breeding pond silt. RESULTS: The phage exhibited a latent period of 50 min and a burst size of approximately 168 PFU/cell, and its genome lacked lysogeny-related genes, suggesting a lytic nature. Phage treatment significantly reduced the number of cell-associated bacteria, decreasing the association rate from 2.3% to nearly 0. Flow cytometry revealed that phage infection protected coelomocytes from V. harveyi-induced damage, increasing the proportion of viable cells from 78.17% to 88.54%. CONCLUSION: These findings demonstrate that phage vB_VhaM_HVS-1 effectively reduces V. harveyi association with coelomocytes and alleviates host cell apoptosis. The phage shows strong potential as an alternative biocontrol agent against V. harveyi infection in sea cucumber aquaculture.

aquaculture disease↗

Renal function measurements from MR renography and a simplified multicompartmental model.

The purpose of this study was to determine the accuracy and sources of error in estimating single-kidney glomerular filtration rate (GFR) derived from low-dose gadolinium-enhanced T1-weighted MR renography. To analyze imaging data, MR signal intensity curves were converted to concentration vs. time curves, and a three-compartment, six-parameter model of the vascular-nephron system was used to analyze measured aortic, cortical, and medullary enhancement curves. Reliability of the parameter estimates was evaluated by sensitivity analysis and by Monte Carlo analyses of model solutions to which random noise had been added. The dominant sensitivity of the medullary enhancement curve to GFR 1-4 min after tracer injection was supported by a low coefficient of variation in model-fit GFR values (4%) when measured data were subjected to 5% noise. These analyses also showed the minimal effects of bolus dispersion in the aorta on parameter reliability. Single-kidney GFR from MR renography analyzed by the three-compartment model (4.0-71.4 ml/min) agreed well with reference measurements from (99m)Tc-DTPA clearance and scintigraphy (r = 0.84, P < 0.001). Bland-Altman analysis showed an average difference of 11.9 ml/min (95% confidence interval = 5.8-17.9 ml/min) between model and reference values. We conclude that a nephron-based multicompartmental model can be used to derive clinically useful estimates of single-kidney GFR from low-dose MR renography.

Computer Simulation↗

High-fat diet postinfarction enhances mitochondrial function and does not exacerbate left ventricular dysfunction.

Lipid accumulation in nonadipose tissue due to enhanced circulating fatty acids may play a role in the pathophysiology of heart failure, obesity, and diabetes. Accumulation of myocardial lipids and related intermediates, e.g., ceramide, is associated with decreased contractile function, mitochondrial oxidative phosphorylation, and electron transport chain (ETC) complex activities. We tested the hypothesis that the progression of heart failure would be exacerbated by elevated myocardial lipids and an associated ceramide-induced inhibition of mitochondrial oxidative phosphorylation and ETC complex activities. Heart failure (HF) was induced by coronary artery ligation. Rats were then randomly assigned to either a normal (10% kcal from fat; HF, n = 8) or high saturated fat diet (60% kcal from saturated fat; HF + Sat, n = 7). Sham-operated animals (sham; n = 8) were fed a normal diet. Eight weeks postligation, left ventricular (LV) function was assessed by echocardiography and catheterization. Subsarcolemmal and interfibrillar mitochondria were isolated from the LV. Heart failure resulted in impaired LV contractile function [decreased percent fractional shortening and peak rate of LV pressure rise and fall (+/-dP/dt)] and remodeling (increased end-diastolic and end-systolic dimensions) in HF compared with sham. No further progression of LV dysfunction was evident in HF + Sat. Mitochondrial state 3 respiration was increased in HF + Sat compared with HF despite elevated myocardial ceramide. Activities of ETC complexes II and IV were elevated in HF + Sat compared with HF and sham. High saturated fat feeding following coronary artery ligation was associated with increased oxidative phosphorylation and ETC complex activities and did not adversely affect LV contractile function or remodeling, despite elevations in myocardial ceramide.

Animals↗

Reversible blockade of electron transport during ischemia protects mitochondria and decreases myocardial injury following reperfusion.

Cardiac mitochondria sustain damage during ischemia and reperfusion, contributing to cell death. The reversible blockade of electron transport during ischemia with amobarbital, an inhibitor at the rotenone site of complex I, protects mitochondria against ischemic damage. Amobarbital treatment immediately before ischemia was used to test the hypothesis that damage to mitochondrial respiration occurs mainly during ischemia and that protection of mitochondria during ischemia leads to decreased cardiac injury with reperfusion. Langendorff-perfused Fischer-344 rat hearts were treated with amobarbital (2.5 mM) or vehicle for 1 min immediately before 25 min of global ischemia. Both groups were reperfused for 30 min without additional treatment. Subsarcolemmal (SSM) and interfibrillar (IFM) populations of mitochondria were isolated after reperfusion. Ischemia and reperfusion decreased state 3 and increased state 4 respiration rate in both SSM and IFM. Amobarbital treatment protected oxidative phosphorylation measured following reperfusion and improved the coupling of respiration. Cytochrome c content measured in SSM and IFM following reperfusion decreased in untreated, but not in amobarbital-treated, hearts. H(2)O(2) release from SSM and IFM isolated from amobarbital-treated hearts during reperfusion was markedly decreased. Amobarbital treatment before ischemia improved recovery of contractile function (percentage of preischemic developed pressure: untreated 51 +/- 4%, n = 12; amobarbital 70 +/- 4%, n = 11, p < 0.01) and substantially reduced infarct size (untreated 32 +/- 2%, n = 7; amobarbital 13 +/- 2%, n = 7, p < 0.01). Thus, mitochondrial damage occurs mainly during ischemia rather than during reperfusion. Reperfusion in the setting of preserved mitochondrial respiratory function attenuates the mitochondrial release of reactive oxygen species, enhances contractile recovery, and decreases myocardial infarct size.

Amobarbital↗

Modulation of electron transport protects cardiac mitochondria and decreases myocardial injury during ischemia and reperfusion.

Mitochondria are increasingly recognized as lynchpins in the evolution of cardiac injury during ischemia and reperfusion. This review addresses the emerging concept that modulation of mitochondrial respiration during and immediately following an episode of ischemia can attenuate the extent of myocardial injury. The blockade of electron transport and the partial uncoupling of respiration are two mechanisms whereby manipulation of mitochondrial metabolism during ischemia decreases cardiac injury. Although protection by inhibition of electron transport or uncoupling of respiration initially appears to be counterintuitive, the continuation of mitochondrial oxidative phosphorylation in the pathological milieu of ischemia generates reactive oxygen species, mitochondrial calcium overload, and the release of cytochrome c. The initial target of these deleterious mitochondrial-driven processes is the mitochondria themselves. Consequences to the cardiomyocyte, in turn, include oxidative damage, the onset of mitochondrial permeability transition, and activation of apoptotic cascades, all favoring cardiomyocyte death. Ischemia-induced mitochondrial damage carried forward into reperfusion further amplifies these mechanisms of mitochondrial-driven myocyte injury. Interruption of mitochondrial respiration during early reperfusion by pharmacologic blockade of electron transport or even recurrent hypoxia or brief ischemia paradoxically decreases cardiac injury. It increasingly appears that the cardioprotective paradigms of ischemic preconditioning and postconditioning utilize modulation of mitochondrial oxidative metabolism as a key effector mechanism. The initially counterintuitive approach to inhibit mitochondrial respiration provides a new cardioprotective paradigm to decrease cellular injury during both ischemia and reperfusion.

Aging↗

The amino terminus of the human multidrug resistance transporter ABCC1 has a U-shaped folding with a gating function.

Multidrug resistance is a serious problem in successful cancer chemotherapy. Studies using model cell lines have demonstrated that overexpression of some members of the ATP-binding cassette (ABC) transporter superfamily, such as ABCC1, causes enhanced efflux and, thus, decreased accumulation of multiple anticancer drugs, which leads to increased cell survival. Unlike most other ABC transporters, ABCC1 has an additional membrane-spanning domain (MSD0) with a putative extracellular amino terminus of 32 amino acids. However, the function of MSD0 and the role of the extracellular amino terminus are largely unknown. In this study, we examined the structural folding and the function of the amino terminus. We found that it has a U-shaped folding with the bottom of the U-structure facing cytoplasm and both ends in extracellular space. We also found that this U-shaped amino terminus probably functions as a gate to regulate the drug transport activity of human ABCC1.

Amino Acid Sequence↗

Gravity-dependent signal gradients on MR images of the lung in supine and prone positions: a comparison with isogravitational signal variability.

PURPOSE: To investigate the tendency of proton MR signal intensity (SI) gradients to be steeper in the supine than in the prone body position, and to quantify the relation between gravity-related and isogravitational changes of SI on proton MR images of the lung. MATERIALS AND METHODS: In eight healthy volunteers, MR images were obtained in the supine and prone positions using a multiple inversion recovery turbo spin-echo (TSE) sequence. The variation in SI along the gravity-dependent direction and within isogravitational planes was measured on a pixel-by-pixel basis. Ratios of slopes were calculated for comparisons among volunteers. Comparisons of ratios were made using Fisher's exact test. Isogravitational variability was compared with the mean SI, the signal-to-noise ratio (SNR), and the image noise. RESULTS: The average ratios of slopes showed that the overall SI gradient was steeper in the supine than the prone position, with a substantial difference in the supine/prone ratios between inspiration (1.21) and expiration (1.72). In both the supine and prone positions, gravity-dependent gradients were steeper in expiration than in inspiration (P = 0.001). The SI variability along the gravitational direction was larger than the isogravitational variability. The isogravitational variability in turn was larger than the image noise but smaller than the mean SI of the MR images. CONCLUSION: Gravity-dependent gradients in proton MR SI are steeper in the supine than in the prone position. The magnitudes of these gradients were larger than the isogravitational signal variability, showing that MRI is sensitive to gravitationally induced effects.

Adult↗

Magnetic resonance imaging of myocardial infarction using a manganese-based contrast agent (EVP 1001-1): preliminary results in a dog model.

PURPOSE: To investigate the MRI characteristics of an intracellular manganese-based contrast agent, EVP 1001-1 (Eagle Vision Pharmaceutical Corp.), in a canine model of myocardial infarction. MATERIALS AND METHODS: Three dogs were imaged 14-37 days following permanent ligation of the left anterior descending coronary artery (LAD). Measurements of the longitudinal relaxation rate R(1) were made prior to EVP 1001-1 administration (20 micromol/kg i.v.) and for one hour thereafter. Triphenyl tetrazolium chloride (TTC) staining was used to document infarction. RESULTS: In normal myocardium, EVP 1001-1 produced a substantial increase in the longitudinal relaxation rate, which remained fairly constant over the postcontrast imaging period (DeltaR1= 1.47 +/- 0.58 sec(-1) (mean +/- SD) at 35 minutes, P < 0.05). In the infarct, the response to EVP 1001-1 was small or negligible (DeltaR1= 0.27 +/- 0.28 sec(-1)). This resulted in a significant postcontrast difference in relaxation rate between normal and infarcted tissue (R1(normal) - R1(infarct) = 1.08 +/- 0.26 sec(-1), P < 0.05). The infarct remained clearly delineated in all animals throughout the steady-state imaging period, and qualitatively matched TTC results. CONCLUSION: The persistent enhancement pattern revealed by MRI following EVP 1001-1 administration may be beneficial for identifying and characterizing myocardial infarction.

Animals↗

Magnetic resonance imaging correlated with the histopathological effect of Pd-bacteriopheophorbide (Tookad) photodynamic therapy on the normal canine prostate gland.

BACKGROUND AND OBJECTIVE: To determine the optimal magnetic resonance imaging (MRI) methodology to assess photodynamic therapy (PDT)-induced histopathological responses in the prostate. STUDY DESIGN/MATERIALS AND METHODS: Laparotomy was performed in five healthy dogs. Cylindrical diffuser was placed in the prostates to deliver light of 50-300 J/cm at 150 mW/cm and 763 nm to activate IV-injected Tookad (1 mg/kg b.w.). Fast spin echo (FSE) T2-weighted, post-contrast-enhanced T1-(CE-T1) and diffusion weighted images (DWI) were obtained pre- and 2 days, 7 days, and 1 month post-PDT. Radiological-histopathological correlation was performed at 7 days (n = 4) and 1 month (n = 1) after PDT. A qualitative assessment of signal changes and apparent diffusion coefficient (ADC) mapping was performed. RESULTS: At 2 or 7 days post-PDT, there was good spatial correlation between PDT-induced hemorrhagic necrosis and unenhanced regions on CE-T1 images. There was a rapidly and persistently enhancing rim corresponding to edema and inflammation. FSE T2 and DWI showed altered signal but did not clearly define necrosis in all cases. At 1 month, it was hard to correlate MR images to histopathologic changes as they represented a mixture of necrosis and developing fibrosis, which led to a mixed signal intensity and less demarcated contrast enhancement. CONCLUSIONS: At 7 days after PDT, gadolinium DTPA contrast-enhanced MRI is superior to DWI and T2 imaging in assessing the boundary of Tookad PDT-induced tissue necrosis in the normal canine prostate.

Animals↗

Sensitizing hormone-refractory prostate cancer cells to drug treatment by targeting 14-3-3sigma.

Advanced and hormone-refractory prostate cancer has long been considered as a chemoresistant disease. Recently, it was found that 14-3-3sigma expression increases as prostate tumor progresses, and that 14-3-3sigma contributes significantly to drug resistance in breast cancers. We, thus, hypothesized that advanced and hormone-refractory prostate cancers may have an increased level of 14-3-3sigma, which in turn may contribute to drug resistance in advanced and hormone-refractory prostate cancers. In this study, we tested this hypothesis and found that, indeed, the expression level of 14-3-3sigma in androgen-independent prostate cancer cell lines DU145, PC3, and CWR22RV are much higher than that in the androgen-dependent cell line LNCaP, and that the androgen-independent cells are more resistant to mitoxantrone and Adriamycin than the androgen-dependent cells. Depleting 14-3-3sigma expression in DU145 and CWR22RV by RNA interference significantly sensitized these cells to mitoxantrone and Adriamycin by abrogating G2-M checkpoint and increasing apoptosis, whereas restoring 14-3-3sigma expression in LNCaP cells enhanced drug resistance. We also showed that 14-3-3sigma deficiency caused nuclear localization of Cdc2 and dephosphorylation of the Tyr15 residue upon DNA damage. Based on these studies, we propose that therapeutic intervention targeting 14-3-3sigma may be useful for sensitizing hormone-refractory prostate cancers to chemotherapy by both G2-M checkpoint abrogation and apoptosis enhancement.

14-3-3 Proteins↗

Effect of protein kinase C on T lymphocyte proliferation and apoptosis in acute idiopathic thrombocytopenic purpura.

Previous studies have shown that T lymphocyte proliferation and apoptosis are abnormal in idiopathic thrombocytopenic purpura (ITP) children; however, the underlying regulated mechanisms in signal transductions remain unknown. In this paper, we investigated the changes of protein kinase C (PKC) activity in peripheral blood T lymphocytes and the effect of PKC on the peripheral blood T lymphocyte proliferation and apoptosis in ITP children. We demonstrated that T lymphocytes from ITP children were more susceptible to the activator (phorbol myristate acetate) and the inhibitor (H-7) of PKC. In ITP children, phorbol myristate acetate and H-7 dramatically affected T lymphocyte proliferation and apoptosis, but altered little in healthy children. Compared with healthy children, PKC activity was significantly enhanced in ITP children, increasing the expressions of Fas ligand on CD3+, CD4+ and CD8+ T cells, indicating positive correlations between PKC activity and the expressions of Fas ligand on T cells, while the relations between PKC activity and platelet count showed negative correlations. Taken together, our findings suggest that PKC signal transductions may participate in the procedure of T lymphocyte proliferation and apoptosis in ITP children. PKC activation may enhance T lymphocyte activity, suppress T cell apoptosis, and be involved in thrombocyte damage, which can be related to the immunity pathogenesis of ITP.

Acute Disease↗

[Analysis of protein kinase C activity of peripheral blood T lymphocytes in children with acute idiopathic thrombocytopenic purpura].

OBJECTIVE: Acute idiopathic thrombocytopenic purpura (AITP) is a common autoimmune disease in children. Thrombocytes decrease extremely in serious patients, its pathogenesis involves abnormal activation of T lymphocytes and T cell-dependent production of autoantibody. The aim of the present study was to investigate changes of protein kinase C (PKC) activity in peripheral blood T lymphocytes in children with AITP and the relationships between PKC activity and T lymphocytes activation and thrombocytopenia. METHODS: Peripheral blood specimens were collected from children with acute ITP (n = 35) and healthy children (n = 30), and T lymphocytes were isolated and purified by using T cells Segregation Enrichment Column. PKC activity was detected by using PepTag Assay, a non-radioactive detection method. The reaction mixture, in a final volume of 25 microl, consisted of 5 microl reaction buffer, PepTag C1 5 microl (0.4 microg/microl), PKC activator solution (DG) 5 microl, peptide protection solution 1 microl and sample 9 microl. Phosphorylation reaction was allowed to continue for 30 minutes, then 25 microl reaction mixture was subjected to electrophoresis on a 0.8% agarose gel at 100 V for about 20 minutes. After electrophoresis, the PepTag C1 peptides which were phosphorylated and non-phosphorylated were separated, phosphorylated PepTag C1 peptide with negative electricity migrated toward the anode (+), but nonphosphorylated PepTag C1 peptide with positive electricity migrated toward cathode (-), the gel was photographed. Electrophoresis bands on anode represented PKC activity and were analyzed quantitatively. FasL, which is T cell activation marker, was determined by flow cytometer and platelet was counted by cell counting meter. RESULTS: Compared with healthy children, children with AITP had significantly higher PKC total activity [(0.97 +/- 0.21) nmol/(min.ml) vs. (0.55 +/- 0.13) nmol/(min.ml), (P < 0.05)]. Expression of FasL on T cell subpopulation in children with AITP was significantly higher [Th FasL: (32.7 +/- 3.4) vs. (14.7 +/- 4.2); Tc FasL: (17.3 +/- 9.7) vs. (11.6 +/- 8.5)%, (P < 0.05)]. Besides, relationships between the changes of PKC activity, Th FasL and Tc FasL had positive correlation (r(1) = 0.68, r(2) = 0.53, P < 0.05). However, PKC activity and platelet count had a significantly negative correlation (r = -0.75, P < 0.05). CONCLUSION: Increased PKC activity was seen in children with AITP, which can cause damage to thrombocytes and reduction of thrombocytes. PKC signal transduction pathway might play an important role in the immunopathogenesis of AITP.

Acute Disease↗

[Clinical analysis of the treatment of reserving limb for patients with malignant bone tumor].

OBJECTIVE: To investigate the curative effect of the treatment of reserving limb for patients with malignant bone tumor. METHODS: Forty patients with bone neoplasms underwent the operation of reserving limbs. The neoadjuvant chemotherapy was given to all the patients before the operation. After the ablation of the tumor we used the artificial prosthetic replacement,tumor tissue deactivation and reimplant, variant bone and joint transplantation to reserve the limb. RESULTS: All the patients were followed up. The average follow-up time was 34.8 months. Eight patients got complications. And the fineness rate was 72.5% according to functional evaluation standard of Enneking after surgical treatment of bone tumor. CONCLUSION: The operation of reserving limb was an ideal method to cure the malignant bone tumor. The proper operative treatment with neoadjuvant chemo-therapy is helpful to extend the life of the patients and increase the quality of life.

Adolescent↗

Ischemia-reperfusion injury changes the dynamics of Ca2+-contraction coupling due to inotropic drugs in isolated hearts.

Positive inotropic drugs may attenuate or exacerbate the deleterious effects of ischemia and reperfusion (IR) injury on excitation-contraction coupling in hearts. We 1) quantified the phase-space relationship between simultaneously measured myoplasmic Ca2+ concentration ([Ca2+]) and isovolumetric left ventricular pressure (LVP) using indexes of loop area, orientation, and position; and 2) quantified cooperativity by linearly modeling the phase-space relationship between [Ca2+] and rate of LVP development in intact hearts during administration of positive inotropic drugs before and after global IR injury. Unpaced, isolated guinea pig hearts were perfused at a constant pressure with Krebs-Ringer solution (37 degrees C, 1.25 mM CaCl2). [Ca2+] was measured ratiometrically by indo 1 fluorescence by using a fiber-optic probe placed at the left ventricular free wall. LVP was measured by using a saline-filled latex balloon and transducer. Drugs were infused for 2 min, 30 min before, and for 2 min, 30 min after 30-min global ischemia. IR injury worsened Ca2+-contraction coupling, as seen from decreased orientation and repositioning of the loop rightward and downward and reduced cooperativity of contraction and relaxation with or without drugs. Dobutamine (4 microM) worsened, whereas dopamine (8 microM) improved Ca2+-contraction coupling before and after IR injury. Dobutamine and dopamine improved cooperativity of contraction and relaxation after IR injury, whereas only dopamine increased cooperativity of relaxation before IR injury. Digoxin (1 microM) improved Ca2+-contraction coupling and cooperativity of contraction after but not before ischemia. Levosimendan (1 microM) did not alter Ca2+-contraction coupling or cooperativity, despite producing concomitant increases in contractility, relaxation, and Ca2+ flux before and after ischemia. Dynamic indexes based on LVP-[Ca2+] diagrams (area, shape, position) can be used to identify and measure alterations in Ca2+-contraction coupling during administration of positive inotropic drugs in isolated hearts before and after IR injury.

Adrenergic beta-Agonists↗

Depletion of cardiolipin and cytochrome c during ischemia increases hydrogen peroxide production from the electron transport chain.

Mitochondrial electron transport is a major source of reactive oxygen species (ROS) during cardiac ischemia and reperfusion. In the isolated rabbit heart, 30 and 45 min of ischemia decrease the contents of cardiolipin and cytochrome c in subsarcolemmal mitochondria (SSM) located beneath the plasma membrane. In contrast, interfibrillar mitochondria (IFM) in the interior of the myocyte do not sustain a decrease in cardiolipin. We proposed that the depletion of cardiolipin and the accompanying cytochrome c loss during ischemia were critical events that amplified ROS production by mitochondria. The total production of H2O2 was measured in submitochondrial particles (SMP) prepared from rabbit heart SSM and IFM after 0, 15, 30, and 45 min of ischemia. With NADH as substrate, total H2O2 production was increased only in SMP from SSM after 30 and 45 min ischemia, when ischemia decreased the content of cardiolipin and cytochrome c. In contrast, ischemia did not augment H2O2 generation in SMP from IFM with preserved cardiolipin and cytochrome c content. Thus, during the evolution of ischemic injury, H2O2 production from the electron transport chain increased after depletion of cardiolipin and the loss of cytochrome c.

Animals↗

Blockade of electron transport before cardiac ischemia with the reversible inhibitor amobarbital protects rat heart mitochondria.

Cardiac ischemia damages the mitochondrial electron transport chain. Irreversible blockade of electron transport at complex I by rotenone decreases ischemic damage to cardiac mitochondria by decreasing the loss of cytochrome c and preserving respiration through cytochrome oxidase. Therapeutic intervention to protect myocardium during ischemia and reperfusion requires the use of a reversible inhibitor that allows resumption of oxidative metabolism during reperfusion. Amobarbital is a reversible inhibitor at the rotenone site of complex I. We asked whether amobarbital administered immediately before ischemia protected respiratory function. Isolated rat hearts were perfused for 15 min followed by 25-min global ischemia at 37 degrees C. Amobarbital-treated hearts received drug for 1 min before ischemia. Subsarcolemmal (SSM) and interfibrillar (IFM) populations of mitochondria were isolated after ischemia, and oxidative phosphorylation was measured. Amobarbital protected oxidative phosphorylation, including through cytochrome oxidase, in both SSM and IFM in a dose-dependent manner, with an optimal dose of 2 to 2.5 mM. Amobarbital also preserved cytochrome c content in both SSM and IFM. Thus, reversible blockade of the electron transport chain during ischemia protects mitochondrial respiration.

Amobarbital↗