Biomedical subjects

Xun Li

Publications and source records attributed to Xun Li.

32 records · Page 2Linked to original sources

PubMed2005

[Management of urinary obstruction following renal transplantation: report of 16 cases].

OBJECTIVE: To explore the diagnosis and treatment of urinary obstruction involving the transplanted kidney. METHODS: A retrospective analysis was performed in 16 cases of urinary obstruction involving the transplanted kidney, including 5 cases of ureteral calculi, 6 vesicoureteral anastomotic stricture, 2 pyeloureteral junction stricture after transplantation, 1 ureter necrosis due to graft rejection, and 2 infection surrounding the renal graft and ureter end necrosis. RESULTS: Only one patient had the renal graft removed due to massive hemorrhage in an open surgery for correction of urinary obstruction, and the renal function of the graft was preserved in all the other cases after endoscopic or open surgeries. In the follow-up for 0.5 to 3 years after the second surgery, serum creatinine of the patients were maintained within the range of 90-150 micromol/L, without further renal enlargement or exacerbation of renal retention shown by B-mode ultrasonography. CONCLUSION: Urinary obstruction after renal transplantation is a difficult surgical complication, which can be managed by endoscopic or open surgeries depending on the causes of the obstruction.

Adult↗

PubMed2004

Redox regulation of Ito remodeling in diabetic rat heart.

Oxidative stress and the resulting change in cell redox state are proposed to contribute to pathogenic alterations in ion channels that underlie electrical remodeling of the diseased heart. The present study examined whether K(+) channel remodeling is controlled by endogenous oxidoreductase systems that regulate redox-sensitive cell functions. Diabetes was induced in rats by streptozotocin, and experiments were conducted after 3-5 wk of hyperglycemia. Spectrophotometric assays of ventricular tissue extracts from diabetic rat hearts revealed divergent changes in two major oxidoreductase systems. The thioredoxin (TRX) system in diabetic rat heart was characterized by a 52% decrease in TRX reductase (TRXR) activity from control heart (P < 0.05), whereas TRX activity was 1.7-fold greater than control heart (P < 0.05). Diabetes elicited similar changes in the glutaredoxin (GRX) system: glutathione reductase was decreased 35% from control level (P < 0.05), and GRX activity was 2.5-fold greater than in control heart (P < 0.05). The basal activity of glucose-6-phosphate dehydrogenase, which generates NADPH required by the TRX and GRX systems, was not altered by diabetes. Voltage-clamp studies showed that the characteristically decreased density of the transient outward K(+) current (I(to)) in isolated diabetic rat myocytes was normalized by in vitro treatment with insulin (0.1 microM) or the metabolic activator dichloroacetate (1.5 mM). The effect of these agonists on I(to) was blocked by inhibitors of glucose-6-phosphate dehydrogenase. Moreover, inhibitors of TRXR, which controls the reducing activity of TRX, also blocked upregulation of I(to) by insulin and dichloroacetate. These data suggest that K(+) channels underlying I(to) are regulated in a redox-sensitive manner by the TRX system and the remodeling of I(to) that occurs in diabetes may be due to decreased TRXR activity. We propose that oxidoreductase systems are an important repair mechanism that protects ion channels and associated regulatory proteins from irreversible oxidative damage.

Animals↗

PubMed2004

Computational analysis of responsible dipeptides for optimum pH in G/11 xylanase.

A bioinformatics method was used to search the responsible dipeptides for optimum pH in the G/11 xylanase, for dipeptides can provide position information of the related residues for rational protein design. The responsible dipeptides were found as negative YS and positive SY, GR, MR, and KR. The minimum and maximum optimum pH was calculated as 2.33 and 14.29, respectively. Compared with the known crystal structures of the G/11 xylanase, YS was found mostly in the turn area of beta-strands of S/T surface; and SY was found in the inner part of beta-strands of the S/T area near to the active site of proton donor; and the GR, MR, and KR in the coil region connecting "finger" to the alpha-helix. The result clearly explained the success of shifting of pH 0.5 U to alkaline by the introduction of arginines into S/T area of a xylanase. The result would be useful for xylanase engineering, and the adaptation mechanism to high alkaline was also discussed.

Aspergillus↗

PubMed2004

Effects of tetracycline operator element insertion on Plasmodium falciparum glycophorin binding protein 130 gene promoter activity.

OBJECTIVE: To construct tetracycline operator (TetO) modified glycophorin binding protein 130 gene (GBP130) promoter of Plasmodium falciparum and investigate the position effect of insertion of TetO on the promoter activity. METHODS: Cloning of 7-copy of TetO (7cot) sequence into 4 points relative to transcriptional initiation site of GBP130 promoter in pGBPCATdelta2 plasmid (2 upstream and 2 downstream), respectively, produced 4 derivative plasmids, pG/7T (-5), pG/7T (-2), pG/7T (+2) and pG/7T (+5). After transient transfection, the expression level of reporter gene CAT in both pGBPCATdelta2 and its derivative plasmids was detected and analysed by CAT ELISA. RESULTS: Identification by enzyme restrictions and PCR amplifications, as well as DNA sequencing confirmed that the plasmids were successfully constructed. Transfection of these plasmids and CAT detection suggested that insertion of 7cot into each point of GBP130 promoter enhanced the promoter activity, and downstream location of 7cot in the promoter showed higher promoter activity than those located upstream, with the strongest effect in Ins 4 (point +5). CONCLUSION: Plasmid pG/7T (+5), in which 7cot was inserted into +5 point of GBP130 promoter, can be chosen as the responsive plasmid in establishing tetracycline-controlled transgenic expression system of malarial parasites.

Animals↗

PubMed2004

[Endoscopic management of bilateral ureteral obstruction after radiotherapy].

BACKGROUND & OBJECTIVE: It is difficult to stent the obstructed ureters cystoscopically in patients with renal failure caused by radiotherapy for abdominal or pelvic tumors. Commonly draining the kidney with nephrostomy is the only method for the patients. However, external nephrostomy impacts on life quality of the patients. We reported our experience in stenting the obstructed ureters using minimally invasive percutaneous nephrostomy combined with ureteroscopy, and investigated viability of endoscopic treatment for bilateral ureteral strictures following radiotherapy. METHODS: Indwelling double pigtail stents in ureter by minimally invasive percutaneous nephrostomy combined with ureteroscopy was carried out in 19 patients with bilateral ureteral strictures following radiotherapy. The clinical outcomes including ureteral drainage and renal function were reviewed. RESULTS: Bilateral retrograde placement of double pigtail stent was performed in 2 cases. Indwelling different size double pigtail stents in unilateral ureters were carried out in 17 cases. The patients were followed-up for 1-24 months. Renal function was improved excellently in 17 cases, with serum creatinine level of 45 micromol/L to 113 micromol/L. Two patients had poor renal function improvement after ureteral stenting and were converted to percutaneous nephrostomy for draining the kidney. CONCLUSION: Indwelling different size double pigtail stents simultaneously in unilateral ureter by minimally invasive percutaneous nephrostomy is safe, simple, and effective in treating bilateral ureteral obstruction following radiotherapy.

Adult↗

PubMed2004

[Treatment of upper urinary calculi with the PCNL technique (Experience of 20 years)].

OBJECTIVE: To sum up experience of 20 years for treating upper urinary calculi with percutaneous nephrolithotomy (PCNL) at our institute and assess the safety, feasibility and superiority of the technique. METHODS: We retrospectively investigated 4,014 patients suffering from upper urinary calculi, who were treated with PCNL of 4,014 cases, traditional PCNL was performed in 358, two stage "mini perc" technique in 520 and minimally invasive PCNL in 3,136. RESULTS: The success rates were 90%, 95% and 98%, the stone free rates were 82%, 86% and 91%. Major complications rates were 5.3%, 1.2% and 0.5%, respectively,with single tract in 3,027 cases and multiple tracts in 987 cases. A total of 5,571 PCNLs were performed in 4,014 patients. CONCLUSION: By improvement and innovation of this technique, percutaneous nephrolithotomy can reach the high success rate and stone free rate, with less morbidity and wide clinical indications.

Adolescent↗

PubMed2004

[Preliminary study on regulable DNA vaccines against Plasmodium falciparum].

AIM: To construct regulable DNA vaccine against Plasmodium falciparum by using tetracycline(Tet) regulable system. METHODS: Eukaryotic expression vectors pTL-8/apical membrane antigen 1 (AMA-1) (tTA) and pTL-8/AMA-1(rtTA) gene which express trans-activator (tTA) or reverse trans-activator(rtTA), respectively, and AMA-1 gene of Plasmodium falciparum were constructed. BALB/c mice were immunized with these plasmids and doxycycline (dox) was administered to regulate the expression of AMA-1. For some mice immunized with pTL-8/AMA-1(rtTA), pUHS6-1, a plasmid containing trans-silencer (tTS) to suppress basal expression of AMA-1 from pTL-8/AMA-1(rtTA), was injected into these mice together with pTL-8/AMA-1(rtTA). The sera of the mice were isolated at 2,4,6 and 8 weeks post-immunization and the antibodies specific to AMA-1 were measured by ELISA. RESULTS: pTL-8/AMA-1 and pTL-8/AMA-1(rtTA) were constructed successfully. The mice immunized by pTL-8/AMA-1(tTA) with dox or by pTL-8/AMA-1(rtTA) without dox (at these conditions, AMA-1 was expressed at basal level)developed significant antibodies against AMA-1. Mice immunized by pTL-8/AMA-1(rtTA) and pUHS6-1 without dox did not develop significantly antibodies against AMA-1. In contrast, the mice immunized by pTL-8/AMA-1(rtTA) and pUHS6-1 with dox produced high level of antibodies. CONCLUSION: pTL-8/AMA-1(rtTA) combined with pUHS6-1 is a good regulable DNA vaccine candidate against Plasmodium falciparum.

Animals↗

PubMed2004

[Effects of ureteral stents on rabbit upper urinary tract urodynamics].

OBJECTIVE: To explore the effects of ureteral stent placement on ureteral peristalsis and the time course of renal pelvic pressure changes. METHOD: Forty rabbits were randomized equally into 8 groups, including a control group without placement of ureteral stents. The other 7 groups received ureteral stent placement, which were retained for 0, 1, 2, 3, 4, 7, and 12 weeks respectively. When the rabbits were bred for the specified time periods, ureteral peristalsis was observed and renal pelvic pressure measured. RESULT: The renal pelvic pressure was initially increased after the stent placement, but then followed by gradual decreases. Ureteral peristalsis was not observed after the stent placement. CONCLUSION: Ureteral stent is a factor for causing obstruction in normal ureter.

Animals↗

PubMed2004

[Modulation of immune response to Plasmodium falciparum apical membrane antigen 1 DNA vaccine by cytokine plasmids].

OBJECTIVE: To explore the effect of cytokine encoding plasmids on DNA immunization in mice. METHODS: Prototype DNA vaccine VR1020/E which contain Plasmodium falciparum apical membrane antigen 1 (AMA1) ectodomain was constructed, and eukaryotic expression vectors pcDNA3/GM-CSF, pcDNA3.1(-)/IL-4, pIL-12 and pGM-CSF/pTPA-E were also built. BALB/c mice were immunized with VR1020/E alone or with VR1020/E plus different cytokine plasmids. Serum IgG and its subtype were determined by ELISA and in vitro splenocyte proliferation assay was done. RESULTS: GM-CSF, IL-4 and IL-12 encoding plasmids all promoted mice immune response to VR1020/E, the antibody level increased 7 to 10 times and splenocyte proliferation was enhanced too. Plasmid pcDNA3/GM-CSF induced much more IgG1 whereas plasmid pIL-12 induced much more IgG2a. CONCLUSION: Cytokine encoding plasmids might be used as adjuvant in AMA1 DNA immunization.

Adjuvants, Immunologic↗

PubMed2004

[Study on the spectroscopy and electrochemistry of the combination between samarium (III) ion probe and bovine serum albumin].

The synthesis of solid compound of bovine serum albumin (BSA) with samarium (III) ion was studied. The FTIR spectrum shows that samarium (III) ion forms high sensitivity compound with BSA's oxygen in hydroxyl and nitrogen in amidocyanogen or amide groups. The ultraviolet spectrum shows that samarium (III) ion binds directly with residue of tyrosine. The character of the combination between samarium (III) ion and BSA was studied under simulated physiology conditions. The fluorescence spectrum shows that the molar ratio of samarium (III) ion to BSA is 2.5:1, with apparent complex constant lgK = 11.00. By cyclic voltammetry, the paper reports the stability of compound of BSA with samarium (III) ion and the effect pH on the of combination between samarium (III) ion and BSA.

Animals↗

PubMed2004

Effect of sodium citrate based anticoagulants on the growth activity of malaria parasites.

OBJECTIVE: To study the effect of anticoagulants based on sodium citrate on the growth activity of malaria parasites. METHODS: The parasites were treated with 3 anticoagulants (ACD, CD and SC), respectively, and the parasitemia was determined to measure the effect of the anticoagulants on the growth of the parasites. Unsynchronized Plasmodium falciparum was treated with the anticoagulants at different concentrations for 3 h at 37 degrees C. Treated erythrocytes were mixed with normal parasites or treated parasites with normal erythrocytes, which was followed by parasitemia determination of the two cultures to determine the cell target of the anticoagulants. Stage-synchronized parasites (ring, trophozoite and schizont) were treated as above to investigate the stage target. P. berghei was also treated with anticoagulants and inoculated in mice to detect the effect of anticoagulants on the animal malaria parasite by counting the parasitemia. RESULTS: All 3 anticoagulants inhibited falciparum parasite growth and ACD had the strongest potency. The treatments of the erythrocyte and the parasite with anticoagulants respectively showed that the anticoagulants targeted the parasites rather than normal erythrocytes. Stage-synchronized parasite treatment suggested anticoagulants primarily inhibited schizonts. The effect of anticoagulants on P. berghei was similar to that on P. falciparum. CONCLUSION: ACD showed the most significant inhibitive effect on the growth of malaria parasites and SC was the best anticoagulant based on sodium citrate for malarial experiments.

Animals↗

PubMed2003

Regulation of glutathione in cardiac myocytes.

Reduced glutathione (GSH) is an essential, multifunctional tripepetide that controls redox-sensitive cellular processes, but its regulation in the heart is poorly understood. The present study used a pharmocological model of GSH depletion to examine cellular mechanisms controlling cardiac GSH. Inhibition of GSH metabolism was elicited in normal rats by daily injections of buthionine sulfoximine (BSO), a blocker of gamma-glutamylcysteine synthetase, plus 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU), an inhibitor of glutathione reductase. After 3 d of BSO/BCNU treatment, intracellular [GSH] was measured in isolated-ventricular myocytes by fluorescence microscopy using the probe monochlorobimane. Basal [GSH] in left-ventricular myocytes from BSO/BCNU-treated rats (2.0 +/- 0.05 amol/microm(3), n = 146) was 50% less than control (4.0 +/- 0.13 amol/microm(3), n = 116; P < 0.05). Incubation of myocytes from BSO/BCNU rats with 0.1 microM insulin normalized [GSH] after a delay of 3-4 h (3.6 +/- 0.29 amol/microm(3), n = 66). This effect of insulin was blocked by pre-treating myocytes with cycloheximide. A protein tyrosine phosphatase inhibitor, bis-peroxovanadium-1,10-phenanthroline (bpV(phen), 1 microM), elicited a similar effect as insulin, while neither agent altered [GSH] in myocytes from control rats. Moreover, the effect of insulin and bpV(phen) to up-regulate GSH was blocked by inhibitors of PI 3-kinase (wortmannin, LY294002), MEK (PD98059) and p38 MAP kinases (SB203580). These data suggest that the insulin-signaling cascade regulates [GSH] in ventricular myocytes by a coordinated activation of PI 3-kinase and MAP kinase pathways. These signaling mechanisms may play essential roles in controlling intracellular redox state and normal function of cardiac myocytes.

Animals↗

PubMed2003

[Protective antibody response to recombinant fragments of Plasmodium falciparum apical membrane antigen 1].

OBJECTIVE: To determine the role of putative apical membrane antigen (AMA)1 domains in inducing protective immunity and to provide basis for selection of vaccine applicable segments. METHODS: Encoding gene segments of AMA1 were amplified and cloned into pET prokaryotic expression vectors. Recombinant proteins were expressed and purified. Groups of BALB/c mice were immunized by using recombinant protein in Freund's adjuvant, and the IgG titer and specificity of the immune sera were analyzed by IFA and Western blotting. Efficiency of the immune sera in inhibiting Plasmodium falciparum in vitro growth was evaluated. RESULTS: Recombinant AMA1 fragments including the entire ectodomain E and subdomain I + II, I, II and III were successfully expressed and purified. Different levels of antibody were induced in mice by individual proteins and all the immune sera recognized native antigen in the parasites. Sera from protein E and I + II immunized mice inhibited the growth of parasites. CONCLUSION: The integrality of the ectodomain of AMA1 determines the conformation of the protective antibody epitopes, and these protective epitopes distribute mainly in the subdomain I.

Animals↗

PubMed2002

Functional characterization of the 5' proximal flanking fragment of Plasmodium falciparum GBP130 gene.

OBJECTIVE: To identify the putative regulation elements with strength- and stage-specificity in 5' proximal flanking sequence of P. falciparum GBP130 gene. METHODS: Plasmids containing different deletions of upstream of the GBP130 promoter were constructed. For strength-specific analysis, pGBPCAT delta 2, pGBP delta 2/400 and pGBP delta 2/800 were electroporated into ring-stage P. f. respectively, and the expression level of CAT in each plasmid was detected by liquid scintillation counts(LSC). For stage-specific analysis, transfectants with pGBP delta 2/400 and pGBP delta 2/800 were harvested at 5 hours post-transfection(h), 15 h and 46 h respectively, and the CAT expression levels were detected. RESULTS: In strength-specific analysis, the expression level of CAT in pGBP delta 2/800 and pGBPCAT delta 2 was similar, down-regulated significantly in pGBP delta 2/400. The CAT level showed significant difference between pGBP delta 2/400 and the control. In stage-specific analysis, the CAT level of pGBP delta 2/400 was higher than that of pGBP delta 2/800 at the time point of 5 h, and lower at 15 h and 46 h. CONCLUSION: This strength-specific promoter activity was due to the difference of 5'UTR length: the longer the 5'UTR the higher the promoter strength, and two poly (dA:dT) tracts in the proximal sequence could enhance the promoter activity. The length of 5'UTR regulated the promoter activity in a stage-specific manner. The shorter 5'UTR was functional at ring stage, while the longer one prompted transcription at trophozoite and schizont stage. The functional role of poly (dA:dT) tracts in stage-specific regulation of GBP130 remains unclear.

5' Flanking Region↗