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Biomedical subjects

Jun Xu

Publications and source records attributed to Jun Xu.

At least 199 records · Page 11Linked to original sources
PubMed2003

[Secretory expression of an antifungal protein in the mold Trichoderma viride].

AFP (antifungal protein) secreted by the filamentous fungi Aspergillus giganteus MDH18894 is a strong basic protein (pI>10.65). Its mRNA has an 430 bp open reading frame encoding the 94 amino acids' precursor of AFP. The precursor of AFP is processed to form the mature AFP of 51 amino acids by a putative two-step processing. A 285 bp AFP-like gene (i.e. AFP cDNA) lacking introns was reported to exist in the genome of Trichoderma viride, another species of filamentous fungi, but the gene was silent. In order to investigate whether the genomic AFP gene from A. giganteus could be expressed in T. viride, an expression plasmid with the open reading frame of AFP gene fused between the promoter and terminator of trpC gene was constructed and was transformed into T. viride. SDS-PAGE and Western blot analysis showed that AFP was expressed and secreted into the culture supernatant of the transformant of T. viride. Our study provides a basis for further secretory expression of heterologous eukaryotic genes of important value in the system of T. viride.

Aspergillus↗
PubMed2003

NF-kappaB/I-kappaB pathway during ischemia reperfusion injury of rat liver.

OBJECTIVE: To determine the role of the NF-kappaB/I-kappaB pathway during ischemia reperfusion (I/R) injury to rat liver. METHODS: A group of rats underwent partial hepatic ischemia and reperfusion. The left and median lobe of the liver was subjected to ischemia for 90 minutes followed by reperfusion for previously specified periods. NF-kappaB activity was analyzed by electrophoretic mobility shift assay (EMSA). The protein level of I-kappaB was assessed using Western blot analysis. A semiquantitative reverse transcriptase polymerase chain reaction was used to analyze TNF-alpha and ICAM-1 mRNA levels. RESULTS: During liver I/R injury, NF-kappaB activation was induced in a time-dependent fashion. NF-kappaB was activated within 1 hour and 2 hours after the initiation of reperfusion and decreased afer 4 hours. The I-kappaB protein level was decreased in the cytoplasm after 2 hours, and the messenger RNA expression of TNF-alpha and ICAM-1 were increased simultaneously. CONCLUSIONS: The data suggest that I-kappaB protein was degraded during hepatic I/R injury, NF kappaB was released and bound to special sequence in the promoters of budget genes, which regulated the expression of TNF-alpha and ICAM-1 mRNA. This provides evidence that the NF-kappaB/I-kappaB pathway plays an important modulating role in the expression of proinflammatory genes relevant to the development of ischemia reperfusion injury.

Animals↗
PubMed2003

[Survey of self-rated health status of troop members stationing in the South China Sea islands].

OBJECTIVE: To conduct a survey of the self-rated health status of the troops stationing in the islands of the South China Sea. METHODS: Altogether 290 members of the selected troops were investigated by means of self-rated health evaluation sale (SRHMS 1.0), and the factors affecting the health status were analyzed. RESULTS: No significant difference was noted in the physical and psychosocial health between the troops in the isolated islands, but the social health and self-rated health significantly differed (P<0.05). The individual identity, dwelling place or education background did not significantly affect self-rated health status as the marital status did (P<0.05). CONCLUSIONS: The self-rated health of the troop members differ to some degree, especially the social health condition, and is affected by marital status in stead of the individual identity, dwelling place, and education background.

Adult↗
PubMed2003

[The regulatory effect of the supernatant of human airway epithelial cells transfected with DNA vaccine of 30-kilodalton major secretory protein of mycobacterium tuberculosis on the Th1/Th2 balance in mite allergic asthmatics].

OBJECTIVE: To investigate the regulatory effect of the supernatant of human airway epithelial cells transfected with DNA vaccine of 30-kilodalton major secretory protein of Mycobacterium tuberculosis (Ag85B) on the Th1/Th2 balance in peripheral blood mononuclear cells (PBMCs) from mite allergic asthmatics. METHODS: Eukaryocytes expressing vectors of pMG-Ag85B were constructed. After sequential analysis, the DNA vaccine was transfected into human airway epithelial cells (16HBE) with lipofectin. By the use of reverse transcription-polymerase chain reaction (RT-PCR), expression of Ag85B mRNA was detected in 16HBE cells. PBMCs were separated from 18 asthmatic patients who were allergic to house dust mites and from 13 non-allergic normal subjects. PBMCs were cocultured with mites, or the supernatant of 16HBE cells transfected with pMG-Ag85B or the combination of both. After 96 hours incubation, levels of IL-5 and IFN-gamma released in the culture medium were determined by enzyme-linked immunoabsorbent assay. RESULTS: The sequential analysis showed that the gene fragment was homogenous as that of original Ag85B gene. The plasmids of pMG-Ag85B had been successfully transfected into 16HBE cells and there was expression of Ag85B mRNA in 16HBE cells. Without any stimulus, no significant difference in IL-5 or IFN-gamma levels in PBMC culture medium was found between the patients and normal individuals. In the asthmatic group, there was an significant increase of IL-5 level after stimulation with mites as compared with control (17.8 +/- 1.9) pg/ml vs (11.9 +/- 0.9) pg/ml, P < 0.05. Level of IFN-gamma showed no difference after the stimulation by either mites or Ag85B transfected culture supernatant alone, but increased significantly by co-stimulation with mites plus Ag85B supernatant in comparison with the mites alone (111.5 +/- 15.9) pg/ml vs (58.8 +/- 7.8) pg/ml, P < 0.05. There were no difference in IL-5 or IFN-gamma levels among the four groups after above stimulation in normal subjects. CONCLUSIONS: In the presence of mites, PBMCs from mite allergic asthmatics demonstrated Th2 predominant reaction, and the culture medium from human airway epithelium cells transfected with Ag85B DNA vaccine upregulated Th1 response and the Th1/Th2 balance to some extent in asthmatics. As a subunit of DNA vaccine, Ag85B may play a role in the preventive management of allergic asthma in the future.

Acyltransferases↗
PubMed2003

Microstructural and ultrastructural changes in the healing process of bile duct trauma.

OBJECTIVE: To explore the mechanism of benign biliary stricture caused by bile duct trauma. METHODS: A model of trauma of the common bile duct was established in 28 dogs and then repaired. The anastomotic tissues were taken on 3 days, 1 week, 3 weeks, 3 months, and 6 months respectively after operation and examined by using light microscopy and electromicroscopy. Macrophage, transforming growth factor beta 1 (TGF-beta1) and alpha-smooth muscle actin (alpha-SMA) were studied immunohistochemically. RESULTS: The mucosal epithelium of the common bile duct restored poorly, chronic inflammation lasted for a long time, fibroblasts proliferated actively, extracellular matrix overdeposited, and myofibroblasts functioned actively during the whole healing process. Immunohistochemical test showed a high expression of macrophage, TGF-beta1 and alpha-SMA during the healing process lasting a long duration. Macrophages were found in the lamina propria under mucosa, TGF-beta1 in the granular tissue, fibroblasts and endothelial cells of blood vessels, while alpha-SMA in the myofibroblasts and smooth muscle tissue. CONCLUSIONS: The healing of the bile duct is in the mode of overhealing. Myofibroblast is the main cause for contracture of scar and stricture of the bile duct. The high expression of macrophage, TGF-beta1 and alpha-SMA is closely related to active proliferation of fibroblasts, extracellular matrix overdeposition and scar contracture of the bile duct.

Actins↗
PubMed2003

Analysis and prevention of factors predisposing to infections associated with severe acute pancreatitis.

OBJECTIVE: To analyze factors predisposing to the infections associated with severe acute pancreatitis (SAP) and work out ways for their prevention. METHODS: 208 patients with SAP treated at our hospital from January 1986 to December 2001 were retrospectively analyzed. RESULTS: Statistical difference in the incidence of the infections was found between the following pairs: the groups of bloody or non-bloody ascites, paralytic ileus lasting shorter or longer than 5 days, Ranson's scores lower or higher than 5, hematocrit lower or higher than 45%, CT Balthazar scores lower or higher than 7, and between January 1986-June 1992 or July 1992-December 2001 admissions (chi2>7.58, P<0.05), while no statistical difference established between the groups of biliogenic and non-biliogenic pancreatitis, serum amylase <200 U/L and >/=200 U/L, serum calcium <2 mmol/L and >/=2 mmol/L or groups of total parenteral nutrition shorter or longer than 7 days (chi2<1.61, P>0.05). CONCLUSIONS: Occurrence of infection in patients with SAP is closely related with bloody ascites, paralytic ileus (>/=5 days), Ranson's scores (>/=5), hematocrit (>/=45%) and CT Balthazar scores (>/=7), but not with pathogenesis, serum calium or total parenteral nutrition. Comprehensive prevention of pancreatic infection and individualized therapy may reduce the incidence of infection.

Acute Disease↗
PubMed2003

[cDNA cloning and sequence analysis of major allergen of Dermatophagoides farinae (Der f 2) in south China].

OBJECTIVE: To clone and analyze the cDNA of major allergen Der f 2 of Dermatophagoides farinae in south China. METHODS: cDNA of Der f 2 was cloned by RT-PCR, screened and their sequences were analyzed. RESULTS: cDNA of Der f 2 was cloned. The sequence of the cloned Der f 2 was different with that published (D10448) in GenBank, with 87 additional nucleotides inserted into the 62th nucleotide of the original one. According to the original ORF, the deduced amino acids that were located prior or after the inserted 29 amino acid sequence showed no changes. CONCLUSION: The cDNA of Der f 2 was cloned from Dermatophagoides farinae and its sequence showed significant difference with that reported in the GenBank.

Amino Acid Sequence↗
PubMed2003

[Comparison of hepatitis B virus serotype and genotype among HBsAg positive hepatitis B patients in a northern and a southern city of China].

OBJECTIVE: To understand HBV serotypes and genotypes epidemiology in a northern city and a southern city in China. METHODS: Using polymerase chain reaction (PCR) and direct sequencing of HBV DNA PCR products, the serotypes and genotypes of HBV in 530 from HBsAg positive samples. The enrolled patients were from Harbin, a northern city and Lianjiang, a southern city in China. RESULTS: Comparison of the serotypes and genotypes of HBV between Harbin and Lianjiang showed that adrq+ was the most predominant hepatitis B virus serotype in both Harbin and Lianjiang (87.2% and 73.5%,respectively), adw2 was the next (12.0% and 25.7%, respectively); genotype C was the most frequent in Harbin and Lianjiang (87.8% and 73.2%, respectively), and genotype B was the next (12.2% and 26.1%, respectively) only 1 patient was infected by genotype D, and 1 patient was found to be co-infected by genotype B and C in Lianjiang. CONCLUSION: The results suggest that the percentage of HBV serotypes and genotypes between Harbin and Lianjiang was significantly different (P less than 0.001), but the main HBV serotype and genotype of the two cities were similar.

China↗
PubMed2003

[A new method of processing quantitative PCR data].

Today standard PCR can't satisfy the need of biotechnique development and clinical research any more. After numerous dynamic research, PE company found there is a linear relation between initial template number and cycling time when the accumulating fluorescent product is detectable.Therefore,they developed a quantitative PCR technique to be used in PE7700 and PE5700. But the error of this technique is too great to satisfy the need of biotechnique development and clinical research. A better quantitative PCR technique is needed. The mathematical model submitted here is combined with the achievement of relative science,and based on the PCR principle and careful analysis of molecular relationship of main members in PCR reaction system. This model describes the function relation between product quantity or fluorescence intensity and initial template number and other reaction conditions, and can reflect the accumulating rule of PCR product molecule accurately. Accurate quantitative PCR analysis can be made use this function relation. Accumulated PCR product quantity can be obtained from initial template number. Using this model to do quantitative PCR analysis,result error is only related to the accuracy of fluorescence intensity or the instrument used. For an example, when the fluorescence intensity is accurate to 6 digits and the template size is between 100 to 1,000,000, the quantitative result accuracy will be more than 99%. The difference of result error is distinct using same condition,same instrument but different analysis method. Moreover,if the PCR quantitative analysis system is used to process data, it will get result 80 times of accuracy than using CT method.

English Abstract↗
PubMed2002

A new approach to finding natural chemical structure classes.

In modern drug discovery, large compound libraries need to be compared and the diversity of compound libraries needs to be analyzed. Classification algorithms are important tools for accomplishing these tasks. In this paper, a chemical structural scaffold based classification approach is reported. The goals of the approach are to find natural structure families from a large (millions of entries) compound library within a feasible time period and to view the library in two-dimensional data space using chemically meaningful methods.

Algorithms↗
PubMed2002

Imaging as-grown [60]fullerene nanotubes by template technique.

In this contribution we have developed a useful and experimentally easy way to use C60 powder to directly fabricate C60 nanotubes with a mondisperse size distribution and uniform orientation. The structure of C60 nanotubes was confirmed by SEM, TEM, and FT-IR.

Journal Article↗
PubMed2002

Peroxisome proliferator-activated receptor alpha (PPARalpha) influences substrate utilization for hepatic glucose production.

The hypoglycemia seen in the fasting PPARalpha null mouse is thought to be due to impaired liver fatty acid beta-oxidation. The etiology of hypoglycemia in the PPARalpha null mouse was determined via stable isotope studies. Glucose, lactate, and glycerol flux was assessed in the fasted and fed states in 4-month-old PPARalpha null mice and in C57BL/6 WT maintained on standard chow using a new protocol for flux assessment in the fasted and fed states. Hepatic glucose production (HGP) and glucose carbon recycling were estimated using [U-(13)C(6)]glucose, and HGP, lactate, and glycerol turnover was estimated utilizing either [U-(13)C(3)]lactate or [2-(13)C]glycerol infused subcutaneously via Alza miniosmotic pumps. At the end of a 17-h fast, HGP was higher in the PPARalpha null mice than in WT by 37% (p < 0.01). However, recycling of glucose carbon from lactate back to glucose was lower in the PPARalpha null than in WT (39% versus 51%, p < 0.02). The lack of conversion of lactate to glucose was confirmed using an [U-(13)C(3)]lactate infusion. In the fasted state, HGP from lactate and lactate production were decreased by 65 and 55%, respectively (p < 0.05) in PPARalpha null mice. In contrast, when [2-(13)C]glycerol was infused, glycerol production and HGP from glycerol increased by 80 and 250%, respectively (p < 0.01), in the fasted state of PPARalpha null mice. The increased HGP from glycerol was not suppressed in the fed state. While little change was evident for phosphoenolpyruvate carboxykinase (PEPCK) expression, pyruvate kinase expression was decreased 16-fold in fasted PPARalpha null mice as compared with the wild-type control. The fasted and fed insulin levels were comparable, but blood glucose levels were lower in the PPARalpha null mice than in controls. In conclusion, PPARalpha receptor function creates a setpoint for a metabolic network that regulates the rate and route of HGP in the fasted and fed states, in part, by controlling the flux of glycerol and lactate between the triose-phosphate and pyruvate/lactate pools.

Animals↗
PubMed2002

The role of Asp-462 in regulating Akt activity.

Protein kinase Akt, an important downstream target of phosphatidylinositol 3-kinase, is one of the major survival factors in mammalian cells. It has been shown that phosphorylation of the C-terminal hydrophobic motif is required for Akt activation. The activated Akt then phosphorylates several pro-apoptotic proteins and prevents apoptosis mediated by caspases and the mitochondria. Interestingly, Akt has also been implicated to be a direct substrate of caspases in apoptotic cells induced by Fas (Widmann, C., Gibson, S., and Johnson, G. L. (1998) J. Biol. Chem. 273, 7141-7147) and anoikis (Bachelder, R. E., Wendt, M. A., Fujita, N., Tsuruo, T., and Mercurio, A. M. (2001) J. Biol. Chem. 276, 34702-34707). In this study we showed that cytokine withdrawal resulted in Akt degradation by caspases as well. Furthermore, we demonstrated residue Asp-462 of Akt1 which is just upstream of the hydrophobic motif to be the primary cleavage site. The Akt1 mutant (D462N) that prevented caspase cleavage was more stable during factor withdrawal and enhanced cell survival. The Akt truncation mutant mimicking the caspase cleavage product lost its kinase activity and functioned as a dominant negative to promote cell death. Our results suggest that the balance between Akt and caspase activity controls cell survival. In particular, caspases are able to render Akt inactive and dominantly inhibit the Akt pathway by cleaving off the C-terminal hydrophobic motif. Consequently, the survival signal is quickly down-regulated to allow apoptosis to occur.

Amino Acid Sequence↗
PubMed2002

The biosynthetic gene cluster of the maytansinoid antitumor agent ansamitocin from Actinosynnema pretiosum.

Maytansinoids are potent antitumor agents found in plants and microorganisms. To elucidate their biosynthesis at the biochemical and genetic level and to set the stage for their structure modification through genetic engineering, we have cloned two gene clusters required for the biosynthesis of the maytansinoid, ansamitocin, from a cosmid library of Actinosynnema pretiosum ssp. auranticum ATCC 31565. This is a rare case in which the genes involved in the formation of a secondary metabolite are dispersed in separate regions in an Actinomycete. A set of genes, asm22-24, asm43-45, and asm47, was identified for the biosynthesis of the starter unit, 3-amino-5-hydroxybenzoic acid (AHBA). Remarkably, there are two AHBA synthase gene homologues, which may have different functions in AHBA formation. Four type I polyketide synthase genes, asmA-D, followed by the downloading asm9, together encode eight homologous sets of enzyme activities (modules), each catalyzing a specific round of chain initiation, elongation, or termination steps, which assemble the ansamitocin polyketide backbone. Another set of genes, asm13-17, encodes the formation of an unusual "methoxymalonate" polyketide chain extension unit that, notably, seems to be synthesized on a dedicated acyl carrier protein rather than as a CoA thioester. Additional ORFs are involved in postsynthetic modifications of the initial polyketide synthase product, which include methylations, an epoxidation, an aromatic chlorination, and the introduction of acyl and carbamoyl groups. Tentative functions of several asm genes were confirmed by inactivation and heterologous expression.

Actinomycetales↗
PubMed2002

Sex differences in sex chromosome gene expression in mouse brain.

A major question is whether genes encoded on the sex chromosomes act directly in non-gonadal tissues to cause sex differences in development or function, or whether all sex differences in somatic tissues are induced by gonadal secretions. As part of this question we asked whether mouse X-Y homologous gene pairs are expressed in brain in a sex-specific fashion. Using RT-PCR and northern blot analysis, we assessed mRNA expression in brain of eight Y-linked genes as well as their X-linked homologues, at three ages: 13.5 days post coitum, the day of birth (P1) and adult. Transcripts of six Y genes were expressed at one or more ages: Usp9y, Ube1y, Smcy, Eif2s3y, Uty and Dby. Their expression also occurred in XY female brain, and therefore does not require testicular secretions. Six X-linked homologues (Usp9x, Ube1x, Smcx, Eif2s3x, Utx and Dbx) were also expressed in brain, and in adulthood all of these transcripts were expressed at significantly higher levels in brains of females than in brains of males, irrespective of their X-inactivation status. For five of these gene pairs, the expression of the Y-linked homologue in males was not sufficient to compensate for the female bias in X gene expression. Three X-Y gene pairs, Usp9x/y, Ube1x/y and Eif2s3x/y, appeared to be differentially regulated (expressed in brain in a different age- or tissue-dependent pattern), and hence may not be functionally equivalent. These sex differences in X-Y gene expression suggest several mechanisms by which these genes may participate in sex differences in brain development and function.

Animals↗
PubMed2002

Inhibition of mitochondrial protein synthesis results in increased endothelial cell susceptibility to nitric oxide-induced apoptosis.

Mutations in mitochondrial DNA, affecting the activity of respiratory complexes, have been implicated in many chronic degenerative diseases. Mitochondrial proteins coded for by both the mitochondrial and nuclear genes are known to have important signaling roles in apoptosis. However, the impact of the inhibition of mitochondrial protein synthesis on apoptosis is largely unknown. This inhibition is particularly important in NO-dependent cytotoxicity, which is believed to have a significant mitochondrial component and depend on other factors such as glycolysis. In this study we have examined whether the inhibition of mitochondrial protein synthesis by chloramphenicol increases the susceptibility of endothelial cells to undergo NO-dependent apoptosis in glucose-free media. Bovine aortic endothelial cells were treated with chloramphenicol, which resulted in a decreased ratio of mitochondrial complex IV to cytochrome c and increased oxidant production in the cell. Inhibition of mitochondrial protein synthesis was associated with a greater susceptibility of the cells to apoptosis induced by NO in glucose-free medium.

Adenosine Triphosphate↗
PubMed2002

Quantum antidot formation and correlation to optical shift of gold nanoparticles embedded in MgO.

Quantum antidots are subnanometer scale vacancy clusters, the localized electronic structure of which can significantly alter the properties of a nanomaterial. We use positron spectroscopy to study vacancy clusters generated during the formation of gold nanoparticles via ion implantation in an MgO matrix. We observed that quantum antidots are associated with the nanoparticle surfaces after annealing in an O2 atmosphere, but not after annealing in a H2 atmosphere. In the former case, the presence of quantum antidots bound to the gold nanoparticles correlates with the redshift of the gold surface plasmon resonance, thus allowing an explanation for the redshift based on the transfer of electrons away from the metal particles.

Journal Article↗