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Biomedical subjects

Li Zhu

Publications and source records attributed to Li Zhu.

141 records · Page 8Linked to original sources
PubMed2002

Hypoxic preconditioning triggers myocardial angiogenesis: a novel approach to enhance contractile functional reserve in rat with myocardial infarction.

A modern experimental strategy for treating myocardial ischemia is to induce neovascularization of the heart by the use of "angiogens", mediators that induce the formation of blood vessels, or angiogenesis. Studies demonstrated that coronary collateral vessels protect ischemic myocardium after coronary obstruction; therefore we sought to examine a novel method of stimulating myocardial angiogenesis through hypoxic preconditioning at both capillary (using anti-CD31) and arteriolar (using anti- alpha smooth muscle actin) levels and also investigate whether such treatments could preserve left ventricular contractile functional reserve and regional blood flow by increasing vascular endothelial growth factor (VEGF). Male Sprague-Dawley rats were randomly divided into four groups: normoxia+sham surgery (CS), normoxia+permanent left anterior descending coronary artery (LAD) occlusion (CMI), hypoxic preconditioning+sham surgery (HS) and hypoxic preconditioning+permanent LAD occlusion (HMI). Rats in the preconditioned groups were subjected to systemic hypoxemic hypoxic exposure (10+/-0.4% O(2)) for 4 h followed by a 24 h period of normoxic reoxygenation prior to undergoing LAD occlusion. Rats in the normoxia group were time matched with the preconditioned group and maintained under normoxic conditions for a 28 h period prior to LAD occlusion. Western blot analysis was performed to measure VEGF expression and TUNEL staining with endothelial cell-specific antibody, anti-VWF, was used to examine endothelial apoptosis. One, two and three weeks after the LAD occlusion, baseline left ventricular pressures were monitored and recorded. Pharmacological stress tests with dobutamine infusion in progressively increasing doses revealed significantly elevated contractile reserve at each dose point in the HMI group compared to the CMI group. The HMI group displayed statistically significant increases in capillary as well as arteriolar density after 1, 2 and 3 weeks post-operation. Blood flow was also significantly elevated in the HMI groups when compared to the CMI group. The extent of endothelial cell apoptosis was found to be inversely proportional to VEGF expression. It was concluded that hypoxic preconditioning stimulates myocardial angiogenesis to an extent sufficient to exert significant cardioprotection in a rat model of myocardial infarction progressing to heart failure as evidenced by increased capillary/arteriolar density and enhanced ventricular contractile functional reserve.

Animals↗
PubMed2002

Ethanol suppresses fast potentiation of glycine currents by glutamate.

Excitatory (glutamate) and inhibitory (GABA(A) and glycine) receptor/channels coexist in many neurons. To assess effects of ethanol on the interaction of glutamate and glycine receptors, glycine-induced current (I(Gly)) was recorded by a whole-cell patch-clamp technique from neurons freshly dissociated from the ventral tegmental area of rats. A conditioning prepulse of glutamate (1-3 s, 1 mM) significantly and reversibly potentiated responses to a pulse of glycine. This potentiation was increased when extracellular calcium was raised to 12 mM and reduced by including 10 mM 1,2-bis-(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid in the internal recording medium. It was not affected by 5 microM 1-N,O-bis-(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazine (KN-62), a selective inhibitor of calcium/calmodulin-dependent protein kinase II. In a concentration-response analysis, a conditioning pulse of glutamate significantly lowered the EC(50) for glycine and increased the maximal I(Gly). Kinetic analysis of the currents indicated that glutamate slowed deactivation of glycine-gated chloride channels; therefore, glutamate may increase the affinity of glycine receptors for glycine. When coapplied with glycine, ethanol (10 mM) potentiated I(Gly) in 35% of neurons from the ventral tegmental area. In contrast, when coapplied with glutamate and glycine, ethanol suppressed the glutamate-induced potentiation of I(Gly) in these neurons. This suppression was also observed when ethanol and glycine were coapplied after a glutamate prepulse. A similar effect was observed when ethanol alone did not potentiate I(Gly). These findings suggest that glutamate-induced calcium influx modulates glycine receptors by a mechanism that can be blocked by ethanol.

Animals↗
PubMed2002

Endocardial mapping and ablation of tachycardia guided by noncontact balloon catheter mapping system.

OBJECTIVE: To describe a new noncontact balloon catheter mapping system and to assess the clinical utility of this system for guiding endocardial mapping and ablation of tachycardia. METHODS: Five patients with tachycardia underwent endocardial mapping and radiofrequency ablation using the noncontact balloon catheter mapping system. A 9 French, 64-electrode balloon catheter and a conventional 7 French electrode catheter for mapping and ablation were positioned in the same ventricular chamber. Ventricular three-dimensional geometry was established by the computerized mapping system. Using a boundary element inverse solution, 3360 virtual endocardial electrograms were computerized and used to derive isopotential maps. The earliest endocardial activation site, the exit site and the activation sequence of tachycardia or the critical isthmus of the reentry circuit were identified. Radiofrequency ablation with circular or linear lesion was performed at the target sites guided by the locator system. RESULTS: Six clinical types of tachycardia, 5 of which were ventricular tachycardia and one was concealed fasciculoventricular fiber mediated tachycardia, were induced by programmed stimulation. The mean cycle length of these tachycardias was 336.6 +/- 42.69 msec. The earliest activation site and the exit site of 5 mapped tachycardias were all identified using the system. One type of ventricular tachycardia was hemodynamically unstable and difficult to terminate, and could not be mapped. Among the 6 types of tachycardias, radiofrequency ablation was successful in 4. There was no complication during and after the procedure. During the mean follow-up of 6 months, no tachycardia recurred in the patients with a successful ablation. CONCLUSIONS: The noncontact mapping system described in this study has advantage over conventional mapping techniques for refractory tachycardia. It is not only helpful for understanding the electrophysiologic mechanism of a complex case, but also suitable for mapping hemodynamically intolerated and nonsustained ventricular tachycardia.

Adult↗
PubMed2002

[The histological study of the capsules formed around the mammary prosthesis].

OBJECTIVE: To observe and analyze the pathohistological characteristics of capsules which formed around the mammary prosthesis with different contents. And to provide the selective basis for ideal and safe prosthesis in clinical practice. METHODS: 20 specimen of the capsules were taken from 20 cases who receive the operation of prothesis removal for different reasons. HE, Masson and Mallory staining were used to analyse the tissue structure and characteristics under the light microscope. RESULTS: The common structure including the collagen fibers accumulation, inflammatory cells infiltration and the capillary hyperplasia were found in all specimen. A layer of squamous epithelium-like cell was detected in some specimen. The specific characteristics were also found in different capsules formed around different prosthesis. In the capsules around vegetable oil prosthesis, there was excessive collagen fiber accumulation, and the capsules were much thicker. In the PVP (polyvinylpyrolidone) prosthesis capsules, there was severe inflammatory cell infiltration, and the number of eosinophilic granulocyte increased obviously. In the silicone gel and saline prosthesis capsule, the collagen fibers were well-arranged and the inflammatory cells were much less. Synovial metaplasia was detected in two cases. CONCLUSION: 1. The capsules form around the prosthesis in all cases after mammary augmentation. 2. There will be synovial metaplasis in some cases, for vegetable oil prosthesis, the collagen over-accumulated which lead the capsules become thicker and harder. So it is not a kind of ideal mammary prothesis. 4. The severe infiltration of the inflammatory cells especially the large quantity of eosinophilic granulocyte indicate the possibility of the delayed hypersensitive reaction mediated by eosinophilic granulocyte. Cautious attitude should be taken during application.

Adult↗
PubMed2002

[Soil catalase activity of main plant communities in Leymus chinensis grassland in northeast China].

The seasonal dynamics of soil catalase activity of three different plants communities in Leymus chinensis grassland in northeast China were in a parabolas shape. The seasonal variation of Chloris virgata community was greater than those of Leymus chinensis community and Puccinellia tenuiflora community, and "seed effect" might be the main reason. The correlation between the activity of soil catalase in different soil layers and environmental factors were analyzed. The results showed that the activity of soil catalase was decreased gradually with depth of soil layer. The activity of soil catalase was closely correlated with rainfall and air temperature, and it was affected by soil temperature, soil moisture, and their interactions. The correlation between the activity and aboveground vegetation was very significant, and the growing condition of plant communities could be reflected by the activity of soil catalase.

Catalase↗
PubMed2002

Oxidative stress-inducing carbonyl compounds from common foods: novel mediators of cellular dysfunction.

BACKGROUND: The general increase in reactive oxygen species generated from glucose-derived advanced glycation endproducts (AGEs) is among the key mechanisms implicated in tissue injury due to diabetes. AGE-rich foods could exacerbate diabetic injury, at least by raising the endogenous AGE. MATERIALS AND METHODS: Herein, we tested whether, prior to ingestion, diet-derived AGEs contain species with cell activating (TNFalpha), chemical (cross-linking) or cell oxidative properties, similar to native AGEs. Glutathione (GSH) and GSH peroxidase (GPx) were assessed after exposure of human umbilical vein endothelial cell (HUVECs) to affinity-purified food-AGE extracts, each exposed to 250 degrees C, for 10 min, along with synthetic AGEs. RESULTS: Animal product-derived AGE, like synthetic methylglyoxal-bovine serum albumin (MG-BSA), AGE-BSA, and AGE-low density lipoprotein (AGE-LDL), induced a dose- and time-dependent depletion of GSH (()60-75%, p, 0.01) and an increase in GPx activity (()500-600%, p < 0.01), consistent with marked TNFalpha and cross-link formation (p < 0.05); this contrasted with the low bioreactivity of starch/vegetable AGE-extracts, which was similar to that of control BSA and CML- BSA and BSA (p:NS). Anti-AGE-R1,2,3 and -RAGE IgG each inhibited cell-associated (125) I-dAGE by approximately 30-55%; GSH/GPx were effectively blocked by N-acetyl-cysteine (NAC, 800 uM, p < 0.01) and aminoguanidine-HCl (AG, 100 uM, p < 0.01). CONCLUSION: Thus, food-derived AGE, prior to absorption, contain potent carbonyl species, that can induce oxidative stress and promote inflammatory signals.

Acetylcysteine↗
PubMed2002

[A clinicopathological study of bizarre leiomyoma].

OBJECTIVE: To investigate the feature of histomorphology and biology of uterine bizarre leiomyoma from the clinical, pathological features as well as the immunohistochemical expression. METHODS: Totally 25 cases of leiomyomas were studied. Among them, immuno-histochemical staining (SP and ABC methods) for smooth muscle actin (SMA), proliferative cell nucleus antigen (PCNA), estrogen receptors (ER), and progesterone receptors (PR) were performed in 20 cases. The clinical features and follow-up records were analyzed. RESULTS: The main clinical findings were irregular vaginal bleeding, pain and pelvic tumor. One case was with immense amount of ascitis and the other two were with pregnancy. All the cases had no history of taking pregestine. Light microscopy showed that part of all the cell nuclei were bizarre, accompanying with double or multiple nuclei in which rather big and reddish staining inclusion bodies were obtained (D = 7 - 26 micro m), and the mitotic figures were 0 - 2/10 HPF. Among 20 cases with immunohistochemical staining, markers indicating muscle cells in origin were positive in the bizarre cells, 15 of which (75%) with negative or weak positive PCNA, and 18 of which (90%) with negative ER. There were significant difference between the studied and control groups (P = 0.027, P < 0.005 respectively) and in addition, PR was positive in both these two groups. A majority of the nucleus inclusion bodies was SMA positive. Follow-up records demonstrated so far no recurrence cases obtained. CONCLUSIONS: Uterine atypical leiomyoma belongs to benign tumor, although its shape is bizarre. In this group, the morphology changes are correlated with pregnancy, but not with pregestine. The expression of immunohistochemistry shows certain features, and is important to identify uterine bizarre leiomyoma with leiomyosarcoma and STUMP in pathological diagnosis.

Adult↗
PubMed2002

[Sonographic diagnosis of carotid body tumor].

OBJECTIVE: To analyse the features of gray scale and colour Doppler sonography for carotid body tumor, to improve the sonographic diagnostic accuracy. METHODS: A retrospective review was performed of sonographic material of 18 carotid body tumors by gray scale sonography and 11 by colour Doppler sonography, with comparison with other diseases which are frequently misdiagnosed as carotid tumor. RESULTS: Well-defined, even weakly hypoechoic masses were noted on gray scale ultrasonogram at the carotid bifurcation, commonly broadening the carotid bifurcation and often encasing the common, external and internal carotid arteries. Disorderly non-echoic channel- like structures in the tumor were sometimes observed. Colour Doppler sonography showed abundant flow in the tumor. The non-echoic channel- like structures were vascularities. Seventeen masses diagnosed by ultrasound were proved to be carotid body tumors. The other was confirmed as a neurogenic tumor, giving an accuracy rate of 94.4% for sonographic diagnosis. CONCLUSION: Sonographic examination of the carotid body tumor is highly accurate. It is safe and reliable.

Adult↗
PubMed2002

[A study on localization of an autosomal dominant retinitis pigmentosa gene].

OBJECTIVE: To report the localization of a gene for an autosomal dominant retinitis pigmentosa (ADRP) family. METHODS: We studied a large ADRP family, collected 3 - 5 ml of venous blood samples from some family members, and genomic DNA was extracted from the blood. Then two-point linkage analysis between the known markers and the disease locus was performed. RESULTS: Linkage analysis showed the maximum LOD score reaches 2.732852 at marker D3S1292 (at recombination fraction theta = 0.1). CONCLUSION: Since D3S1292 was localized at 3q21, we roughly localized the disease gene on 3q21. In the mean time, the rhodopsin gene had been reported as linked to 3q21 adjacent to D3S1292, thus we think the disease gene may be the rhodopsin gene.

Chromosome Mapping↗
PubMed2000

Protective effect of early enteral feeding on postburn impairment of liver function and its mechanism in rats.

AIM:To study the protective effect of early enteral feeding (EEF) on the postburn impairment of liver function and its mechanism.METHODS:Wistar rats with 30% of total body surface area (TBSA) full-thickness burn were employed. The effects of EEF on the postburn changes of gastric intramucosal pH, endotoxin levels in portal vein, water contents of hepatic tissue, blood concentrations of tumor necrosis factor (TNF-alpha), plasma activities of alanine aminotransferase (ALT) and asparate aminotransferase (AST), as well as the blood contents of total (TB) and direct bilirubin (DB), total protein (TP) and albumin (ALB) were serially determined within 48h postburn.RESULTS:EEF could significantly improve gastric mucosal acidosis, reduce portal vein endotoxin level and water content of hepatic tissue, as well as plasma concentrations of TNF-alpha at all timepoints after severe burns (P < 0.01); postburn elevation of the plasma activities of ALT, AST and the contents of TB, DB were effectively prevented, whereas the plasma concentrations of TP and ALB were markedly increased 24h and 48h posturn in EEF group compared with that of the burn without EEF group (P < 0.01 ).CONCLUSION:EEF has significant beneficial effects on the improvement of hepatic function in rats after severe burn, and is probably related with an increase in splanchnic blood flow, reduction of the absorption of gut-origin endotoxin and the consequent release of inflammatory mediators.

Journal Article↗
PubMed2000

Reduced gastric acid production in burn shock period and its significance in the prevention and treatment of acute gastric mucosal lesions.

AIM:To investigate the changes of gastric acid production and its mechanism in shock period of severe burn in rats.METHODS:A rat model with 30% TBSA full thickness burn injury was employed and the gastric acid production,together with gastric mucosal blood flow (GMBF) and energy charge (EC) were measured serially within 48h postburn.RESULTS:The gastric acid production in the acute shock period was markedly inhibited after severe burn injury.At the 3rd h postburn,the gastric juice volume, total acidity and acid output were already significantly decreased (P < 0.01 =, and reached the lowest point, 0.63mL/L ± 0.20mL/L, 10.81mmol/L ± 2.58mmol/L and 2.23mmol/h ± 0.73mmol/h respectively, at the 12th h postburn. Although restored to some degree 24h after thermal injury, the variables above were still statistically lower, compared with those of control animals at the 48th h postburn. The GMBF and EC were also significantly reduced after severe burns, consistent with the trend of gastric acid production changes.CONCLUSION:Gastric acid production, as well as GMBF and EC was predominantly decreased in the early postburn stage, suggesting that gastric mucosal ischemia and hypoxia with resultant disturbance in energy metabolism, but not gastric acid proper, might be the decisive factor in the pathogenesis of AGML after thermal injury, and that the preventive use of anti-acid drugs during burn shock period was unreasonable in some respects. Therefore, taking effective measures to improve gastric mucosal blood perfusion as early as possible postburn might be more preferable for the AGML prevention and treatment.

Journal Article↗
PubMedDate not supplied

Statistical correlation of spectroscopic analysis and enzymatic hydrolysis of poplar samples.

Spectroscopic characterization of poplar wood samples with different crystallinity indices, lignin contents, and acetyl contents was performed to determine changes in the biomass spectra and the effects of these changes on the hydrolysis yield. The spectroscopic methods used were X-ray diffraction for determining cellulose crystallinity (CrI), diffuse reflectance infrared (DRIFT) for changes in C-C and C-O bonds, and fluorescence to determine lignin content. Raman spectroscopy was also used to determine its effectiveness in the determination of crystallinity and C-C and C-O bond changes in the biomass as a complement to better-known methods. Changes in spectral characteristics and crystallinity were statistically correlated with enzymatic hydrolysis results to identify and better understand the fundamental features of biomass that influence enzymatic conversion to monomeric sugars. In addition, the different spectroscopic methods were evaluated separately to determine the minimum amount of spectroscopic data needed to obtain accurate predictions. The principal component regression (PCR) model with only the DRIFT data gives the best correlation and prediction for both initial rate of hydrolysis and also the 72-h hydrolysis yield. The factor that most affects both the initial rate and the 72-h conversion is the O-H bond content of the sample, which directly relates to the breakage of structural carbohydrates into smaller molecules.

Cellulose↗
PubMedDate not supplied

Role of insulin-induced reactive oxygen species in the insulin signaling pathway.

Oxidants, including hydrogen peroxide (H2O2), have been recognized for years to mimic insulin action on glucose transport in adipose cells. Early studies also demonstrated the complementary finding that H2O2 was elaborated during treatment of cells with insulin, suggesting that cellular H2O2 generation was integral to insulin signaling. Recently, reactive oxygen species elicited by various hormones and growth factors have been shown to affect signal transduction pathways in various cell types. We recently reported that insulin-stimulated H2O2 modulates proximal and distal insulin signaling, at least in part through the oxidative inhibition of protein tyrosine phosphatases (PTPases) that negatively regulate the insulin action pathway. Nox4, a homologue in the family of NADPH oxidase catalytic subunits, was found to be prominently expressed in insulin-sensitive cells. By various molecular approaches, Nox4 was shown to mediate insulin-stimulated H2O2 generation and impact the insulin signaling cascade. Overexpression of Nox4 also significantly reversed the inhibition of insulin-stimulated receptor tyrosine phosphorylation by PTP1B, a widely expressed PTPase implicated in the negative regulation of insulin signaling, by inhibiting its catalytic activity. These recent studies have provided insight into Nox4 as a novel molecular link between insulin-stimulated reactive oxygen species and mechanisms involved in their modulation of insulin signal transduction.

Animals↗
PubMedDate not supplied

Hyperglycemia potentiates H(2)O(2) production in adipocytes and enhances insulin signal transduction: potential role for oxidative inhibition of thiol-sensitive protein-tyrosine phosphatases.

Insulin signal transduction in adipocytes is accompanied by a burst of cellular hydrogen peroxide (H(2)O(2)) that facilitates insulin signaling by inhibiting thiol-dependent protein-tyrosine phosphatases (PTPs) that are negative regulators of insulin action. As hyperglycemia is associated with increased cellular reactive oxygen species, we postulated that high glucose conditions might potentiate the H(2)O(2) generated by insulin and modulate insulin-stimulated protein phosphorylation. Basal H(2)O(2) generation was increased threefold in differentiated 3T3-L1 adipocytes by growth in 25 mM glucose versus 5 mM glucose. High glucose increased the sensitivity of the insulin-stimulated H(2)O(2) signal to lower concentrations of insulin. Basal endogenous total PTP activity and the activity of PTP1B, a PTP implicated in the negative regulation of insulin signaling, were reduced in high glucose conditions, and their further reduction by insulin stimulation was more enhanced in high versus low glucose medium. Phosphorylation of the insulin receptor, IRS-1, and Akt in response to insulin was also significantly enhanced in high glucose conditions, especially at submaximal insulin concentrations. In primary rat adipocytes, high glucose increased insulin-stimulated H(2)O(2) production and potentiated the oxidative inhibition of total PTP and PTP1B activity; however, insulin signaling was not enhanced in the primary cells in high glucose apparently due to cross-regulation of insulin-stimulated protein phosphorylation by activation of protein kinase C (PKC). These studies indicate that high glucose can enhance insulin stimulated H(2)O(2) generation and augment oxidative PTP inhibition in cultured and primary adipocytes, but the overall balance of insulin signal transduction is determined by additional signal effects in high glucose, including the activation of PKC.

Adipocytes↗