Biomedical subjects

Wei Li

Publications and source records attributed to Wei Li.

At least 253 records · Page 14Linked to original sources

PubMed2005

Simultaneous determination of amoxicillin and ranitidine in rat plasma by high-performance liquid chromatography.

A high-performance liquid chromatography method using ultraviolet detection at 230 nm for the simultaneous determination of amoxicillin and ranitidine in rat plasma has been validated. Plasma samples after pretreatment with acetonitrile to effect deproteinization were dried under N2 and reconstituted with water. The standard calibration curves for amoxicillin and ranitidine were linear (r2=0.9999) over the concentration range of 0.2-20 microg ml-1 and 0.03-6 microg ml-1 in rat plasma, respectively. The intra- and inter-day assay variability range for amoxicillin was 2.4-8.5% and 3.2-11.7%, and for ranitidine was 1.7-9.0% and 4.5-10.1%, respectively. This method has been successfully applied to a pharmacokinetic study after oral coadministration of amoxicillin and ranitidine to rats.

Amoxicillin↗

PubMed2005

Myocardial tissue Doppler and long axis function in the fetal heart.

UNLABELLED: Current echocardiographic assessment of fetal ventricular function uses relatively crude measures and this has led to inconsistencies in assessment of diastolic function. Long axis parameters may be more insightful. OBJECTIVE: To describe fetal long axis cardiac function and construct reference ranges. DESIGN: 159 normal fetuses were studied cross-sectionally using long axis M-mode to measure displacement of the atrioventricular ring and pulsed wave Doppler ultrasound to record myocardial tissue Doppler velocities at the base of the heart. RESULTS: There was a strong, almost linear gestational relationship for all but late left basal myocardial velocities. Systolic amplitude of the atrioventricular ring increased significantly. Wall thickness increased with gestation and heart rate reduced. Late diastolic mitral and tricuspid flow velocities showed no age-dependence. Right ventricular filling (p<0.0001) and myocardial lengthening (p<0.0001) and shortening velocities (p<0.0001) were higher than left. Aortic velocities were higher than pulmonary (p<0.0001). Right ventricular long axis amplitude was greater than left (p<0.0001). There were no significant differences in right (RV) and left (LV) ventricular and septal thicknesses (RV 2.5 mm [1.2-4.1]; LV (2.4 mm [1.0-4.0] and septum 2.6 mm [1.0-4.3]). Left and right myocardial tissue Doppler velocities showed similar maturation in systole (LV 0.14 vs. RV 0.10 cm/s/week) and early diastole (LV 0.16 vs. RV 0.14 cm/s/week). CONCLUSIONS: This study demonstrates maturational changes occur in both fetal systolic and diastolic ventricular function and moreover the maturational rate of myocardial tissue velocities is similar in both ventricles, despite differential loading conditions.

Blood Flow Velocity↗

PubMed2005

The role of microRNA genes in papillary thyroid carcinoma.

Apart from alterations in the RET/PTC-RAS-BRAF pathway, comparatively little is known about the genetics of papillary thyroid carcinoma (PTC). We show that numerous microRNAs (miRNAs) are transcriptionally up-regulated in PTC tumors compared with unaffected thyroid tissue. A set of five miRNAs, including the three most up-regulated ones (miR-221, -222, and -146), distinguished unequivocally between PTC and normal thyroid. Additionally, miR-221 was up-regulated in unaffected thyroid tissue in several PTC patients, presumably an early event in carcinogenesis. Tumors in which the up-regulation (11- to 19-fold) of miR-221, -222, and -146 was strongest showed dramatic loss of KIT transcript and Kit protein. In 5 of 10 such cases, this down expression was associated with germline single-nucleotide changes in the two recognition sequences in KIT for these miRNAs. We conclude that up-regulation of several miRs and regulation of KIT are involved in PTC pathogenesis, and that sequence changes in genes targeted by miRNAs can contribute to their regulation.

Base Sequence↗

PubMed2005

Ablation of the Sam68 RNA binding protein protects mice from age-related bone loss.

The Src substrate associated in mitosis of 68 kDa (Sam68) is a KH-type RNA binding protein that has been shown to regulate several aspects of RNA metabolism; however, its physiologic role has remained elusive. Herein we report the generation of Sam68-null mice by homologous recombination. Aged Sam68-/- mice preserved their bone mass, in sharp contrast with 12-month-old wild-type littermates in which bone mass was decreased up to approximately 75%. In fact, the bone volume of the 12-month-old Sam68-/- mice was virtually indistinguishable from that of 4-month-old wild-type or Sam68-/- mice. Sam68-/- bone marrow stromal cells had a differentiation advantage for the osteogenic pathway. Moreover, the knockdown of Sam68 using short hairpin RNA in the embryonic mesenchymal multipotential progenitor C3H10T1/2 cells resulted in more pronounced expression of the mature osteoblast marker osteocalcin when differentiation was induced with bone morphogenetic protein-2. Cultures of mouse embryo fibroblasts generated from Sam68+/+ and Sam68-/- littermates were induced to differentiate into adipocytes with culture medium containing pioglitazone and the Sam68-/- mouse embryo fibroblasts shown to have impaired adipocyte differentiation. Furthermore, in vivo it was shown that sections of bone from 12-month-old Sam68-/- mice had few marrow adipocytes compared with their age-matched wild-type littermate controls, which exhibited fatty bone marrow. Our findings identify endogenous Sam68 as a positive regulator of adipocyte differentiation and a negative regulator of osteoblast differentiation, which is consistent with Sam68 being a modulator of bone marrow mesenchymal cell differentiation, and hence bone metabolism, in aged mice.

Adaptor Proteins, Signal Transducing↗

PubMed2005

Effect of oral Lactococcus lactis containing endostatin on 1, 2-dimethylhydrazine-induced colon tumor in rats.

AIM: To investigate the effects of oral Lactococcus lactis (L lactis) containing endostatin on 1, 2-dimethylhydrazine (DMH)-induced rat colorectal cancer. METHODS: Recombinant endostatin was produced by the expression of L lactis NZ9000. Sixty male Wistar rats were injected with DMH (40 mg/kg body weight) subcutaneously once a week for 10 wk to induce colorectal cancer. The rats were gavaged with 1 mL of endostatin at a dose of 1 x 10(8)/d and fed with the basal diet. The animals were killed after 22 wk for histopathological examination. The total time of experimental observation was 58 wk. RESULTS: Rat endostatin protein was expressed in L lactis. Recombinant endostatin exhibited a significant effect on colorectal cancer (P<0.05). Furthermore, the mean survival time of the rats treated with endostatin was longer than that of the animals treated with DMH. There was no statistically significant difference between the rats treated with endostatin and those treated with DMH. The results showed that endostatin could not result in complete cure.

1,2-Dimethylhydrazine↗

PubMed2005

[Effect of surgical treatment of tricuspid regurgitation late after valve replacement of left heart].

OBJECTIVE: To investigate the appropriate methodology and outcome of surgical treatment of tricuspid regurgitation late after valve replacement of left heart. METHODS: Eighteen patients with tricuspid insufficiency, with the diagnosis conformed by echocardiogram and in New York Heart Association (NYHA) class III to IV, were treated surgically 3 to 14 years after left heart valve replacement, including 13 mitral valve replacements and 5 double valve replacements, from January 1995 to May 2004. DeVega was used in 5 patients. The ages at the time of tricuspid surgery ranged from 35 to 65 years (median 50 years). The patients were followed up for 36.7 months (12-114 months). RESULTS: There was no death from hemorrhage because of re-open. Tricuspid repair was performed in 8 patients, tricuspid replacement was done in 10 patients, 5 bioprostheses and 5 mechanical valves were implanted. The hospital mortality was 16.7%. Among the survivors, the three-year survival rate was 78.8%. Twelve patients showed improvement of symptoms, while there was no improvement in 3 patients who needed medical therapy. CONCLUSION: The pathophysiology of tricuspid regurgitation is associated with delayed left heart operation, implement of tricuspid repair in the first operation or progressive right ventricular failure. The surgical intervention should be earlier before the onset of severe right ventricular failure Tricuspid valve repair is the procedure of choice, while tricuspid valve replacement is also acceptable.

Adult↗

PubMed2005

Mechanism of the cardioprotection of rhEPO pretreatment on suppressing the inflammatory response in ischemia-reperfusion.

Erythropoietin (EPO), originally known for its role in stimulation of erythropoiesis, has recently been shown to have a dramatic protective effect in animal models of myocardial ischemia-reperfusion (I-R) injury. However, the precise mechanisms remain unclear. We tried to study the anti-inflammatory properties of recombinant human erythropoietin (rhEPO) using an in vivo myocardial I-R rat model, which was established by 30 min ligation of left descending coronary and 3 h reperfusion. rhEPO or saline solution was intraperitoneally injected 24 h before I-R insult. The infarct size was measured by triphenyltetrazolium chloride (TTC)-Evans blue technique. Myeloperoxidase (MPO) activity and tissue neutrophil infiltration were studied. Ultrastructural organizations were observed and semiquantitatively evaluated. Tumor necrosis-alpha (TNF-alpha), interleukin-6 (IL-6), and IL-10 concentrations of left ventricle were analyzed by enzyme-linked immunosorbance assays; intercellular adhesion molecule-1 (ICAM-1) by reverse-transcription polymerase chain reaction; and nuclear factor-kappa B (NF-kappaB) and activator protein 1 (AP-1) by electrophoretic mobility shift assay, respectively. We found that a single bolus injection of 5000 units/kg of rhEPO 24 h before insult remarkably reduced infarct size and neutrophil infiltration. It greatly attenuated I-R-induced NF-kappaB and AP-1 activation with decreased TNF-alpha, IL-6, and ICAM-1 production, but enhanced IL-10 production. In conclusion, the cardioprotection of EPO may be due in part to the suppression of the inflammatory response via down-regulation of NF-kappaB and AP-1 induced by I-R. IL-10 was also suggested to play a protective role through another independent mechanism involved in cardioprotection of rhEPO.

Animals↗

PubMed2005

Effect of phosphate on the adsorption of Cu and Cd on natural hematite.

Interactions between anions and cations are important to understand the chemical processes of pollutants in environment. In this study, batch experiments were carried out to investigate the simultaneous adsorption of Cu and Cd on hematite as affected by phosphate. Phosphate pretreatment suppressed the maximum adsorption of Cu and Cd on hematite and moved the adsorption pH edges to a higher pH range. Phosphate application time had a marked impact on Cu and Cd adsorption and longer contact time resulted in more reduction of Cu and Cd adsorption. Results of back-titration, Fourier transform infrared (FTIR) spectroscopy study and ionic strength effect on the adsorption revealed that Cu and Cd were adsorbed on hematite mainly through the inner-sphere complex formation mechanism and phosphate treatment reduced the inner-sphere adsorption sites, thus decreasing Cu and Cd adsorption on hematite.

Adsorption↗

PubMed2005

A beta-galactose-specific lectin isolated from the marine worm Chaetopterus variopedatus possesses anti-HIV-1 activity.

A 30 kDa beta-galactose-specific lectin named CVL was isolated from the polychaete marine worm Chaetopterus variopedatus (Annelida) and its anti-HIV-1 activity in vitro was determined. Results showed that CVL inhibited cytopathic effect induced by HIV-1 and the production of viral p24 antigen. The EC(50) values were 0.0043 and 0.057 microM, respectively. Time-of-addition analysis of anti-HIV-1 activity indicated its action was at the early stage of virus replication. CVL could blocked the cell-to-cell fusion process of HIV infected and uninfected cells with an EC(50) of 0.073 microM. The inhibition of HIV-1 entry into host cells was demonstrated by using fluorescence-based real-time quantify PCR. At CVL concentration of 0.33 microM and 0.07 microM, 86% and 21% virus attachment were blocked, respectively. The anti-HIV-1 action of CVL might relate to blockade of HIV-1 entry into cells.

Animals↗

PubMed2005

Analysis of mass transport models for protein adsorption to cation exchanger by visualization with confocal laser scanning microscopy.

The mass transfer of bovine serum albumin (BSA) to a cation exchanger, SP Sepharose FF, has been studied by finite batch adsorption experiments. The uptake curve was simulated with three mass transport models (i.e., effective pore diffusion model, surface diffusion model and Maxwell-Stefan model) incorporating the particle size distribution of the adsorbent particles. All the three models can simulate the uptake curves reasonably well. However, how well these models could simulate the real concentration profile within the adsorbent particle cannot be verified by the fitness of the models to the uptake curve. Thus, confocal laser scanning microscopy (CLSM) was used to visualize protein uptake to the porous adsorbent particles during the batch experiments. Using a fluorescent dye-labeled bovine serum albumin (BSA) for the dynamic adsorption experiments, the radial concentration profiles of the labeled BSA molecules into individual adsorbent particles at different times were obtained from the CLSM images. The protein distribution profiles within various particle diameters at different time were compared with the radial protein distributions predicted from the models. It reveals that surface diffusion model describes the intraparticle protein concentration profiles better than the other two models.

Adsorption↗

PubMed2005

[A multi-central, randomized, controlled clinical trial of glucosamine hydrochloride/sulfate in the treatment of knee osteoarthritis].

OBJECTIVE: To evaluate the efficacy and safety of glucosamine hydrochloride (GH) in the treatment of patients with knee osteoarthritis (OA) comparing with glucosamine sulfate (GS). METHODS: A multi-central, randomized, parallel-controlled clinical trial of GH vs GS was performed. 142 patients suffering from knee OA were randomized into 2 groups, treated with GH and GS for 480 mg and 500 mg one time respectively. Patients received medicine 3 times daily with total 1440 mg per day for GH group and 1500 mg for GS group, orally for 4 weeks and were assessed for drug efficacy and safety for 2 more weeks. Knee pain at rest, at movement and at pressure, knee swelling, morning stiffness and walking ability were recorded at 1, 2, 3, 4 and 6 week according to Lequesne's criteria. Other features such as therapeutic efficacy, adverse events and laboratory parameters were also recorded. RESULTS: A considerable improvement in OA symptoms and a reduce of total Lequesne's score were observed in both groups after the 4-week treatment. The Lequesne's score decreased to 3.4 +/- 1.9 (P < 0.05) and 3.4 +/- 1.8 (P < 0.05) after 4-week treatment comparing to 0-week in the GH (9.4 +/- 1.8) group and GS (9.5 +/- 1.4) group respectively. There was no significant difference between 2 groups in decreasing the Lequesne's score (P > 0.05). The symptomatic improvement rates in patients were 91.4% and 90.0% at 4-week treatment in the GH and GS group respectively (P > 0.05). There was a remnant therapeutic effect in both groups at 2 weeks after discontinuation of the treatment. And 4.2% (3/71) of patients on GH reported adverse events, vs 7.0% (5/71) adverse events with GS group (P > 0.05), mainly mild stomach discomfort and constipation. CONCLUSION: There were no significant differences in efficacy and safety between GH and GS groups in the treatment of knee OA. Glucosamine hydrochloride is as effective and safe as glucosamine sulfate.

Administration, Oral↗

PubMed2005

Synthesis and SAR of highly selective MMP-13 inhibitors.

The structure-based design and synthesis of a series of novel biphenyl sulfonamide carboxylic acids as potent MMP-13 inhibitors with selectivity over MMP-1, MMP-2, MMP-3, MMP-7, MMP-8, MMP-9, MMP-14, Aggrecanase 1, and TACE are described.

Amination↗

PubMed2005

Crystal structure of wild-type human thrombin in the Na+-free state.

Regulation of thrombin activity is critical for haemostasis and the prevention of thrombosis. Thrombin has several procoagulant substrates, including fibrinogen and platelet receptors, and essential cofactors for stimulating its own formation. However, thrombin is also capable of serving an anticoagulant function by activating protein C. The specificity of thrombin is primarily regulated by binding to the cofactor TM (thrombomodulin), but co-ordination of Na+ can also affect thrombin activity. The Na+-free form is often referred to as 'slow' because of reduced rates of cleavage of procoagulant substrates, but the slow form is still capable of rapid activation of protein C in the presence of TM. The molecular basis of the slow proteolytic activity of thrombin has remained elusive, in spite of two decades of solution studies and many published crystallographic structures. In the present paper, we report the first structure of wild-type unliganded human thrombin grown in the absence of co-ordinating Na+. The Na+-binding site is observed in a highly ordered position 6 A (1 A=0.1 nm) removed from that seen in the Na+-bound state. The movement of the Na+ loop results in non-catalytic hydrogen-bonding in the active site and blocking of the S1 and S2 substrate-binding pockets. Similar, if more dramatic, changes were observed in a previous structure of the constitutively slow thrombin variant E217K. The slow behaviour of thrombin in solutions devoid of Na+ can now be understood in terms of an equilibrium between an inert species, represented by the crystal structure described in the present paper, and an active form, where the addition of Na+ populates the active state.

Binding Sites↗

PubMed2005

Beneficial effects of exercise and its molecular mechanisms on depression in rats.

Exercise showed the beneficial effects on mental health in depressed sufferers, whereas, its underlying mechanisms remained unresolved. This study utilized the chronic unpredictable stress (CNS) animal model of depression to evaluate the effects of exercise on depressive behaviors and spatial performance in rats. Furthermore, we tested the hypothesis that the capacity of exercise to reverse the harmful effects of CNS was relative to the hypothalamo-pituitary-adrenal (HPA) system and brain-derived neurotrophic factor (BDNF) in the hippocampus. Animal groups were exposed to CNS for 4 weeks with and without access to voluntary wheel running. Stressed rats consumed significantly less of a 1% sucrose solution during CNS and exhibited a significant decrease in open field behavior. On the other hand, they showed impaired spatial performance in Morris water maze test 2 weeks after the end of CNS. Further, CNS significantly decreased hippocampal BDNF mRNA levels. However, voluntary exercise improved or even reversed these harmful behavioral effects in stressed rats. Furthermore, exercise counteracted a decrease in hippocampal BDNF mRNA caused by CNS. In addition, we also found that CMS alone increased circulating corticosterone (CORT) significantly and decreased hippocampal glucocorticoid receptor (GR) mRNA. At the same time, exercise alone increased CORT moderately and did not affect hippocampal GR mRNA levels. While, when both CNS and exercise were combined, exercise reduced the increase of CORT and the decrease of GR caused by CMS. The results demonstrated that: (1) exercise reversed the harmful effects of CNS on mood and spatial performance in rats and (2) the behavioral changes induced by exercise and/or CNS might be associated with hippocampal BDNF levels, and in addition, the HPA system might play different roles in the two different processes.

Animals↗

PubMed2005

Adventitial inversion technique without the aid of biologic glue or Teflon buttress for acute type A aortic dissection.

OBJECTIVE: This study was performed to evaluate the clinical usefulness of the adventitial inversion technique in acute type A aortic dissection, with special attention to the impact of this procedure on the postoperative status of false lumen evaluated by computed tomographic scan. METHODS: From March 2001 to November 2004, 18 consecutive patients underwent emergent surgery for acute type A aortic dissection. Supracoronary graft replacement was performed in all the patients (ascending aorta/hemiarch replacement: 13/18=72%, total arch replacement: 5/18=28%). The adventitial inversion technique was used for both the proximal and the distal stump constructions of the dissected aortic wall without the aid of Teflon felt or biologic glue. Aortic regurgitation was treated with resuspension of the aortic commissures. RESULTS: There were two hospital deaths and the overall hospital mortality rate was 11.1%. The mean postoperative blood loss was 635+/-214 ml and no reexploration was required in any of the patients. Postoperative computed tomography showed closure of the false lumen in aortic root, aortic arch, and proximal descending thoracic aorta in all of the surviving patients. Postoperative echocardiography demonstrated no aortic regurgitation in any of the patients. Two patients died late postoperatively from unrelated causes to aortic dissection. The remaining 14 patients are doing well without a second-stage operation for aortic root or distal aortic lesions during the follow-up period of 7-51 months (mean: 28+/-14 months). CONCLUSIONS: The adventitial inversion technique provides an excellent immediate hemostasis and facilitates thrombotic closure of the proximal and the distal false lumen in the treatment for acute type A aortic dissection.

Acute Disease↗

PubMed2005

More tea for septic patients?--Green tea may reduce endotoxin-induced release of high mobility group box 1 and other pro-inflammatory cytokines.

Despite recent advances in antibiotic therapy and intensive care, sepsis remains widespread problems in critically ill patients. The high mortality of sepsis is in part mediated by bacterial endotoxin, which stimulates macrophages/monocytes to sequentially release early (e.g., TNF, IL-1, and IFN-gamma) and late (e.g., HMGB1) pro-inflammatory cytokines. In light of our recent discovery of HMGB1 as a late mediator of lethal systemic inflammation, and the observation that green tea (Camellia sinensis) dose-dependently attenuated bacterial endotoxin-induced HMGB1 release, we propose that regular tea intake might decrease the incidence of and mortality rates from lethal endotoxemia and sepsis.

Animals↗

PubMed2005

Effect of carbamate esters on neurite outgrowth in differentiating human SK-N-SH neuroblastoma cells.

Carbamate esters are widely used as pesticides and can cause neurotoxicity in humans and animals; the exact mechanism is still unclear. In the present investigation, the effects of carbamates at sublethal concentration on neurite outgrowth and cytoskeleton as well as activities of acetylcholinesterase (AChE) and neuropathy target esterase (NTE) in differentiating human SK-N-SH neuroblastoma cells were studied. The results showed that 50 microM of either aldicarb or carbaryl significantly decreased neurite length in the retinoic acid-induced differentiation of the neuroblastoma cells, compared to cells treated with vehicle. Western blot analyses revealed that neither carbamate had significant effects on the levels of actin, or total neurofilament high molecular proteins (NF-H). However, increased NF-H phosphorylation was observed following carbamate treatment. These changes may represent a useful in vitro marker of carbamate neurotoxicity within a simple model of neuronal cell differentiation. Furthermore, activity of AChE, but not NTE, was significantly inhibited by aldicarb and carbaryl in differentiating cells, which suggested that cytoskeletal protein changes induced by carbamate esters in differentiating cells was associated with inhibition of AChE but not NTE.

Acetylcholine↗

PubMed2005

Archaeal proteasomes and other regulatory proteases.

Numerous proteases have been shown to catalyze the precisely-timed and rapid turnover of key cellular proteins. Often these regulatory proteases are either energy-dependent or intramembrane-cleaving. In archaea, two different types of energy-dependent proteases have been characterized: 20S proteasomes associated with proteasome-activating nucleotidases and membrane-associated Lon proteases. Interestingly, homologs of all three mechanistic classes of intramembrane-cleaving proteases are widely distributed in archaea. Similar to their eucaryal and bacterial counterparts, members of these uncharacterized proteases might promote the controlled release of membrane-anchored regulatory proteins or liberate small peptide reporters and/or effectors that function in cell signaling.

Amino Acid Sequence↗