Biomedical subjects

Xiao-Ping Xu

Publications and source records attributed to Xiao-Ping Xu.

16 recordsLinked to original sources

PubMed2006

Efficient automatic noise reduction of electron tomographic reconstructions based on iterative median filtering.

A simple, fast and efficient noise-reduction protocol for three-dimensional electron tomographic reconstructions of biological material is presented. The approach is based on iterative application of median filtering and shows promise for automatic noise reduction as a pre-processor for automated data analysis tools which aim at segmentation, feature extraction and pattern recognition. The application of this algorithm produces encouraging results for a wide variety of experimental and synthetic electron tomographic reconstructions.

Algorithms↗

PubMed2005

Mechanism of filament nucleation and branch stability revealed by the structure of the Arp2/3 complex at actin branch junctions.

Actin branch junctions are conserved cytoskeletal elements critical for the generation of protrusive force during actin polymerization-driven cellular motility. Assembly of actin branch junctions requires the Arp2/3 complex, upon activation, to initiate a new actin (daughter) filament branch from the side of an existing (mother) filament, leading to the formation of a dendritic actin network with the fast growing (barbed) ends facing the direction of movement. Using genetic labeling and electron microscopy, we have determined the structural organization of actin branch junctions assembled in vitro with 1-nm precision. We show here that the activators of the Arp2/3 complex, except cortactin, dissociate after branch formation. The Arp2/3 complex associates with the mother filament through a comprehensive network of interactions, with the long axis of the complex aligned nearly perpendicular to the mother filament. The actin-related proteins, Arp2 and Arp3, are positioned with their barbed ends facing the direction of daughter filament growth. This subunit map brings direct structural insights into the mechanism of assembly and mechanical stability of actin branch junctions.

Actin-Related Protein 2↗

PubMed2005

Porcine acute liver failure model established by two-phase surgery and treated with hollow fiber bioartificial liver support system.

AIM: To establish a highly reproducible animal model of acute liver failure (ALF), for assessing the effect of bioartificial liver support system (BALSS). METHODS: A two-phase complete liver devascularization procedure was performed in eight loco-hybrid pigs. Blood biochemical index and liver biopsy were studied every 2 h after surgery, and survival time was recorded. The BALSS constructed with high volume recirculating technique was a hollow fiber circulating system consisting of a hepatocyte reactor-hollow fiber module inoculated with microcarrier-adhering hepatocytes, and a double pump, heparinized, thermostabilized, micro-capsulized activated carbon-adsorbing plasmapheresis system. Twelve pigs undergoing two-phase surgery were randomized into: control group (perfused without hepatocytes, n = 6) and treatment group (perfused with hepatocytes, n = 6). Intergroup liver biochemical indexes, survival time, and liver pathological changes were analyzed at regular intervals. RESULTS: Two-phase surgery was performed in all the experimental pigs, and there was no obvious difference between their biochemical indexes. After 3 h of phase II surgery, ammonia (Amm) increased to (269+/-37) micromol/L. After 5 h of the surgery, fibrinogen (Fib) decreased to (1.5+/-0.2) g/L. After 7 h of the surgery, ALT, AST, Tbil and PT were (7.6+/-1.8) nka/L, (40+/-5) nka/L, (55+/-8) micromol/L and (17.5+/-1.7) nka/L respectively. After 9 h of surgery, ALB and Cr were (27+/-4) g/L and (87+/-9) micromol/L. After 13 h of surgery, BUN was (3.5+/-0.9) micromol/L. All the above values were different from those determined before surgery. Survival time of pigs averaged 13.5+/-1.4 h. ALF pigs in the other group were treated with BALSS. The comparison analysis between the treated and control animals showed the changes of Tbil, PT, Alb, BUN, Cr, Fib, and Amm (P<0.01), but there was no change of ALT and AST. The survival time was statistically different (P<0.01), and there was no significant difference in histological changes. CONCLUSION: The porcine ALF model established by two-phase devascularized surgery is valid and reproducible. The hollow fiber BALSS can meet the needs of life support and is effective in treating ALF.

Alanine Transaminase↗

PubMed2005

Effects of Arp2 and Arp3 nucleotide-binding pocket mutations on Arp2/3 complex function.

Contributions of actin-related proteins (Arp) 2 and 3 nucleotide state to Arp2/3 complex function were tested using nucleotide-binding pocket (NBP) mutants in Saccharomyces cerevisiae. ATP binding by Arp2 and Arp3 was required for full Arp2/3 complex nucleation activity in vitro. Analysis of actin dynamics and endocytosis in mutants demonstrated that nucleotide-bound Arp3 is particularly important for Arp2/3 complex function in vivo. Severity of endocytic defects did not correlate with effects on in vitro nucleation activity, suggesting that a critical Arp2/3 complex function during endocytosis may be structural rather than catalytic. A separate class of Arp2 and Arp3 NBP mutants suppressed phenotypes of mutants defective for actin nucleation. An Arp2 suppressor mutant increased Arp2/3 nucleation activity. Electron microscopy of Arp2/3 complex containing this Arp2 suppressor identified a structural change that also occurs upon Arp2/3 activation by nucleation promoting factors. These data demonstrate the importance of Arp2 and Arp3 nucleotide binding for nucleating activity, and Arp3 nucleotide binding for maintenance of cortical actin cytoskeleton cytoarchitecture.

Actin-Related Protein 2↗

PubMed2005

[Effects of dexamethasone on arsenic trioxide induced apoptosis, NF-kappaB activation and gene expression in lymphoma cell line].

OBJECTIVES: To study the effect of dexamethasone (Dex) on the apoptosis and NF-kappaB activation in Raji cells as well as expression of MMP9 and VEGF induced by As2O3, and to observe the effect of inhibited activity of NF-kappaB by Dex on apoptosis. METHODS: Cell apoptosis was analysed by Annexin V. Fluctuation of NF-kappaB, MMP9 and VEGF was detected by semi-quantitative immunohistochemistry. RESULTS: The apoptosis and activation of NF-kappaB of Raji cells could be induced by As2O3. The percentage of apoptosis was (39.2 +/- 1.3)%. Dex significantly increased (77.5%) the apoptosis induced by As2O3 (P < 0.05). Dex suppressed the activation of NF-kappaB induced by As2O3 (a suppression rate of 28.0%, P < 0.05). There was a positive correlation between the changes of MMP9, VEGF and NF-kappaB. CONCLUSIONS: As2O3 could induce apoptosis, activate NF-kappaB and up-regulate expression of MMP9 and VEGF of Raji cells. The mechanism of enhanced apoptosis by Dex may be related to suppressing activation of NF-kappaB and down-regulating expression of MMP9 and VEGF.

Apoptosis↗

PubMed2005

[Arsenic trioxide induced leukemic cell apoptosis relative to NF-kappaB activation].

To investigate the relationship of As(2)O(3)-induced leukemic cell apoptosis with NF-kappaB activation and expression of VEGF, MMP9, apoptosis of K562-n cells induced by As(2)O(3) was analyzed by Annexin V, the dynamic changes of NF-kappaB, MMP9 and VEGF expressions were detected by immunohistochemistry. The results showed that activity of NF-kappaB could be increased, accompanied by higher level of expression of MMP9 and VEGF when apoptosis of K562-n cells was induced by As(2)O(3). Dexamethasome not only increased significantly the apoptotic rate, but also suppressed the activation of NF-kappaB of K562-n cells induced by As(2)O(3). Furthermore, there was a positive correlation between the expression of MMP9, VEGF and the activity of NF-kappaB. It is concluded that As(2)O(3) can induce apoptosis, in the meanwhile, activate NF-kappaB and up-regulate expression of MMP9 and VEGF in K562-n cell line. The mechanism of apoptosis of K562-n cells enhanced by dexamethasome may be related to suppression of the activation of NF-kappaB and expression of MMP9 and VEGF.

Antineoplastic Agents↗

PubMed2005

[Establishment of a mouse model for detecting multi-drug resistant minimal residual leukemia cells expressing green fluorescent protein].

This study aimed to investigate the pathophysiology and therapy of multi-drug resistant model of minimal residual leukemia in mice. The multi-drug resistant model of minimal residual leukemia was established by using P388/VCR-G cell line expressing enhanced green fluorescent protein (EGFP) and DBA mice. The results showed that P388/VCR-G were inoculated in the abdominal cavities of DBA mice, the incidence of leukemia was 100%. Any of these mice with leukemia could not obtain remission spontaneously. The model of leukemia was sensitive to cyclophosphamide (Cy) and the time of survival was related to the dose of Cy received. The logarithm of cells inoculated in mice correlated regressionally with the dose of Cy. So this model was ideal for research on minimal residual leukemia. The distribution of residual leukemia cells in complete remission was not uniform in different organs including liver, spleen, thymus and bone marrow. Minimal residual leukemia cells could be found by fluorescent microscopy in freezing tissue slice. It is concluded that the multi-drug resistant model of minimal residual leukemia expressing EGFP can be established by using P388/VCR-G cell line and DBA mice. The minimal residual leukemia cells can be observed by fluorescence microscopy in complete remission stage.

Animals↗

PubMed2005

[Pulmonary fungal infection in malignant hematological diseases: an analysis of 14 cases].

The objective of this study was to evaluate the etiological factors, diagnosis and therapy of pulmonary fungal infection in hematological malignancies, 14 cases of malignant hematological disease with pulmonary fungal infection were collected and analyzed. The results showed that 11 out of 14 cases had the respiratory manifestations, sputum was sticky and difficult to be expectorated in 7 cases, X rays in chests showed shadows with features of stigma and sheet in 11 cases, Candida albicans and aspergillus infection were observed in 10 and 2 cases respectively, the numbers of neutrophil were below 0.5 x 10(9)/L in 8 cases and below 1.0 x 10(9)/L in 3 cases respectively, fluconazole was used for 12 cases and clinical symptoms of 11 cases were improved within two weeks. In conclusion, the occurrence of pulmonary fungal infection in malignant hematological diseases is associated with intensive chemotherapy, decrease of neutrophil counts and using of broad-spectrum antibiotics, the diagnosis at early stage is difficult and clinicians should pay more attention to its clinical and laboratory examinations, and give them therapy in time.

Adolescent↗

PubMed2004

Protective effects of tumor necrosis factor alpha antibody and ulinastatin on liver ischemic reperfusion in rats.

AIM: To study the protective effects of tumor necrosis factor alpha (TNF alpha) antibody and ulinastatin on liver ischemic reperfusion in rats. METHODS: One hundred and twenty male SD rats were randomly divided into four groups: normal control group, ischemic group, TNF alpha antibody group and TNF alpha antibody + ulinastatin group. The animals were killed at 0, 3, 6, 9, 12 h after ischemia for 60 min and followed by reperfusion. Serum alanine aminotransferase (ALT), malondialdehyde (MDA) and liver histopathology were observed. RESULTS: After ischemic reperfusion, the serum ALT and MDA were remarkably increased, and the hepatic congestion was obvious. Treatment of TNF alpha antibody and ulinastatin could significantly decrease serum ALT and MDA levels, and relieve hepatic congestion. CONCLUSION: Ulinastatin and TNF alpha antibody can suppress the inflammatory reaction induced by hepatic ischemic reperfusion, and have protective effects on rat hepatic ischemic reperfusion injury.

Alanine Transaminase↗

PubMed2004

[Establishment of K562 cell lines resistant to STI571 and a preliminary biological study].

To produce leukemic STI571-resistant cell lines and to explore the molecular mechanism of STI571-resistance, cell lines K562-n and K562-n/VCR were induced by exposing cells to gradually increasing STI571 concentration of culture medium to have STI571-resistance and major biological characteristics between these subclones and the parent cells were compared. The results showed that a STI571-resistant cell line based on multidrug-resistance was established, which exhibited 23.41-fold resistance to STI571, 662.26-fold resistance to VCR and cross-resistance to HHT. K562-n/STI was generated from K562-n and had some characteristics of MDR. The intracellular accumulation of DNR in K562-n/STI and K562-n/VCR/STI were 33.24 and 18.76 respectively. Transcription of mdr-1 gene in both K562-n/STI and K562-n/VCR/STI was positive. Cell doubling time of K562-n/STI and K562-n/VCR/STI was significantly longer than that in their parent cells (P <0.05). And proliferation index was also higher than that in parent cells (P <0.05). It is conclusion that the tolerance of K562-n cells to STI571 can be augmented by adding low-dose of STI571 into the culture medium repeatedly. K562-n/STIs expressed MDR at some extent, and transcription of mdr-1 gene in K562-n/STIs was positive. As K562-n is a cell line used to develop human leukemia in nude mice, K562-n/STI and K562-n/VCR/STI 571 will contribute to the study of mechanism of STI571-resistance as in vitro and in vivo experimental models.

Antineoplastic Agents↗

PubMed2003

[Microsequencing, analysis of molecular weight and amino acid composition for pyrimidine 5'-nucleotidase I of human erythrocytes].

To further explore the mechanism of congenital pyrimidine 5'-nuleotidase I (P5'N-I) deficiency, on the basis of purification of the protein, the molecular weight and amino acid composition were analysed by mass-spectrograph and amino-acid analyzer, microsequencing and bioinformation analysis of P5'N-I were performed after it was hydrolysed by trypsin. The results showed that three fractions were found in the purified P5'N-I and their molecular weights were 26,952.9, 55,476 and 110,938, respectively. The sequence from one of the peptide fragments was I-E-G-P-T-I-R-Q-I-E. The homologous sequence was not found after comparision with the ten-amino-acid sequence in GenBank by blast procedure. Amino acid analysis indicated that P5'N-I was composed of 18 amino acids at least, and 243 amino acid residues. In conclusion, the enzyme might be an allosteric enzyme, there might be homologous dimer or tetramer in physiological status of normal human erythrocyte, the microsequence could be designed as the probe for fishing the genes of interest. The composition of amino acid might be an important information in determination of its protein primary structure.

5'-Nucleotidase↗

PubMed2003

[The reverse effect on drug-resistance against tyrosine kinase inhibitor STI571 in mdr1 and bcr-abl positive leukemic cells].

To explore the possibility of leukemia cell line of both bcr-abl and mdr-1 positive were cross-resistant to tyrosine kinase inhibitor STI571 and its reversal way, the inhibitory effect of STI571 on K562-n/VCR cells was detected with MTT method and reverse effects of CsA, TAM, IFN-alpha and CsA cominated with IFN-alpha were observed. The results showed that K562-n/VCR cell line expressing bcr-abl and mdr1 positive was resistant to STI571, and could be reversed by 5.18, 1.82 and 1.67-fold respectively, when treated with CsA, TAM, and IFN-alpha. It could be reversed by 34.87-fold with combination of half-dose CsA and IFN-alpha. In conclusion, amplification of mdr1 gene may contribute to drug-resistance of bcr-abl positive leukemic cells against STI571. The reversal agents, CsA, TAM and IFN-alpha show obviously reverse effects on drug-resistance. The combination of half-dose of both CsA and IFN-alpha display stronger effect than the full dose of either.

Antineoplastic Agents↗

PubMed2002

Probing multiple effects on 15N, 13C alpha, 13C beta, and 13C' chemical shifts in peptides using density functional theory.

We have used density functional calculations on model peptides to study conformational effects on (15)N, (13)C alpha, (13)C beta, and (13)C' chemical shifts, associated with hydrogen bonding, backbone conformation, and side-chain orientation. The results show a significant dependence on the backbone torsion angles of the nearest three residues. Contributions to (15)N chemical shifts from hydrogen bonding (up to 8 ppm), backbone conformation (up to 13 ppm), side-chain orientation and neighborhood residue effects (up to 22 ppm) are significant, and a unified theory will be required to account for their behavior in proteins. In contrast to this, the dependence on sequence and hydrogen bonding is much less for (13)C alpha and (13)C beta chemical shifts (<0.5 ppm), and moderate for carbonyl carbon shifts (<2 ppm). The effects of side-chain orientation are mainly limited to the residue itself for both nitrogen and carbon, but the chi(1) effect is also significant for the nitrogen shift of the following residue and for the (13)C' shift of the preceding residue. The calculated results are used, in conjunction with an additive model of chemical shift contributions, to create an algorithm for prediction of (15)N and (13)C shifts in proteins from their structure; this includes a model to extrapolate results to regions of torsion angle space that have not been explicitly studied by density functional theory (DFT) calculations. Crystal structures of 20 proteins with measured shifts have been used to test the prediction scheme. Root mean square deviations between calculated and experimental shifts 2.71, 1.22, 1.31, and 1.28 ppm for N, C alpha, C beta, and C', respectively. This prediction algorithm should be helpful in NMR assignment, crystal and solution structure comparison, and structure refinement.

Carbon Isotopes↗

PubMed2002

Effect of coenzyme I on apoptosis of liver cell line L02 induced by ischemia-reperfusion injury.

OBJECTIVE: To study the protective effect of coenzyme I (NADH) on normal liver cell line L02 against ischemia-reperfusion injury. METHODS: Cultured L02 cells was divided into 3 groups, namely ischemia-reperfusion group (I/R), ischemia-reperfusion group with NADH pretreatment (NADH+I/R) and control group. Assisted by flow cytometry (FCM), the apoptosis rate and the expression of apoptosis-related proteins (Bcl-2, p16, p21, p53) were detected in L02 cells in the 3 groups. Apoptotic L02 cells were also observed under transmission electron microscope. RESULTS: I/R significantly inhibited L02 cell proliferation and increased their apoptosis rate up to (31.53+/-8.27)% 12 h after I/R. In the presence of NADH, however, the apoptotic rate of the cells was significantly decreased to (12.61+/-2.34)% (P<0.05). FCM indicated that I/R down-regulated the expression of Bcl-2 and up-regulated the expression of p16, p21 and p53 proteins as compared with control group, but NADH acted to the reverse effect. Typical apoptotic features were observed by transmission electron microscope in the cells 12 h after I/R. CONCLUSION: I/R might induce apoptosis in L02 cells by up-regulating the expression of p16, p21, p53 and down-regulating the expression of Bcl-2, and the protective effect of NADH against I/R-induced apoptosis may lie in the expression regulation of the proteins concerned.

Apoptosis↗

PubMed2001

[Establishment of Quantitative Assay for Human Erythrocyte Pyrimidine 5'-Nucleotidase Content by Double Antibody Sandwich ELISA]

For exploring pathogenesis of pyrimidine 5'-nucleotidase (P5'N) deficiency, a quantitative assay method for human erythrocyte pyrimidine 5'-nucleotidase was established. The specific substrate uridine monophosphate (UMP) of P5'N was used as ligand. The UPM-ADH-Sepharose 4B affinity column was prepared. P5'N of human erythrocyte was purified by ammonium sulfate fractionation and precipitation, ion chromatography and affinity chromatography. Rabbit anti-human P5'N antibody was acquired by immunizing rabbits with purified P5'N. Using rabbit anti-human antibody as the coated anti-body and HRP-rabbit anti-human antibody as demonstrated anti-body, the double antitody sandwich ELISA for quantitative assay of human erythrocyte P5'N was established after square rank trial, antigen blocked trial and antigen substituted test. Results showed that the titer of rabbit anti-human erythrocyte was 1:4 and the sensitivity of double antibody sandwich ELISA was 5 ng/ml. Its blocking rate was more than 95% and the rate of substitution less than 30%. The content of P5'N was (71.77 + 10.98) ng/mg NHP in normal human erythrocyte. A new ELISA method for quantitative determination of human erythrocyte P5'N was first established. It not only had high specificity and sensitivity but also could assay the minimun content of P5'N as 5 - 20 ng/ml. It could be a suitable method for large sample in clinics.

Journal Article↗

PubMed1999

Cultivation of human liver cell lines with microcarriers acting as biological materials of bioartificial liver.

AIM:To improve the cultivation efficiency and yield of human liver cell line CL-1.METHODS:High-density cultivation of CL-1 on microcarriers was carried out with periodic observation of their growth and proliferation. The specific functions of human liver cell were also determined.RESULTS:Cells of CL-1 cell line grew well on microcarrier Cytodex-3 and on the 7th day the peak was reached. The amount of CL-1 cells was 2.13X10(8) and the total amount of albumin synthesis reached 71.23&mgr;g,urea synthesis 23.32mg and diazepam transformation 619.7ug respectively. The yield of CL-1 on microcarriers was 49.3 times that of conventional cultivation. The amounts of albumin synthesis, urea synthesis and diazepam transformation were 39.8 times, 41.6 times and 33.3 times those of conventional cultivation, respec-tively.CONCLUSION:The human liver cell line CL-1 can be cultivated to a high density with Cytodex-3 and has better biological functions. High-density cultivation of CL-1 on microcarriers can act as the biological material of bioartificial liver.

Journal Article↗