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Biomedical subjects

X Peng

Publications and source records attributed to X Peng.

At least 55 records · Page 3Linked to original sources

[Accurate diagnosis of stages of hepatic fibrosis by measuring levels of serum hyaluronic acid, procollagen type III, and collagen type IV].

OBJECTIVE: To study the accurate diagnosis of various stages of hepatic fibrosis by measuring serum hyaluronic acid (HA), procollagen type III (PC III), and collagen type IV (CIV). METHODS: The concentrations of serum HA, PC III, CIV in 253 patients with chronic liver disease were measured by radioimmunoassay. Liver biopsies were performed in all of the patients at the same time. According to the results of liver pathological diagnosis, we assessed the ability of serum HA, PC III and CIV to identify correctly patients with hepatic fibrosis (staging >or=S(2)) or cirrhosis (S(4)). RESULTS: The cutoff value of HA, PC III and C IV to identify correctly patients with hepatic fibrosis was 90 microg/L, 90 microg/L, 75 microg/L respectively. The sensitivity (Se) was 80.4%, 82%, 63.1%; the specificity (Spe) was 70.2%, 60.8%, 83.8%; the positive prediction value (PPV) was 86.7%, 83.5%, 90.4%; the negative prediction value (NPV) was 59.8%, 58.4%, 48.4%, respectively. The cutoff value to identify patients with cirrhosis was: HA 210 microg/L, Se 96.2%, Spe 85.3%, PPV 65.4%, NPV 98.8%; PC III 150 microg/L, Se 76.4%, Spe 68.7%, PPV 40.4%, NPV 91.3%; C IV 90 microg/L, Se 80%, Spe 75.8%, PPV 47.8%, NPV 93.2%, respectively. CONCLUSIONS: The determination of serum HA, PC III and C IV can make relatively accurate diagnosis to various stages of hepatic fibrosis. HA is the best for diagnosis of liver cirrhosis.

Biopsy↗

[Modulation of human small cell lung cancer cell line GLC4/ADR multidrug resistance in the inhibition of multidrug resistance-associated protein and its antisense].

OBJECTIVE: To study the effect of antisense multidrug resistance-associated protein (MRP) RNA on multidrug resistance (MDR) in the human small cell lung cancer (SCLC) cell line GLC4/ADR, in which the overexpression of MRP gene is discovered. METHODS: In using the plasmid pRC/RSV-MRP1 containing complete ORF of MRP as a template, two antisense recombinants targeting at the 5' and 3' regions were constructed with the application of the polymerase chain reaction (PCR) technique. Lipofectamine was conducted to transduce these antisense MRPs into the GLC4/ADR cells. Three clones (the GLC4/ADR-pcDNA3, MO; GLC4/ADR-MRP-5' region, Ma; GLC4/ADR-MRP-3' region, Mb) of transfectants after the selection of G418 were obtained. The expression of MRP protein was detected by the use of the Western blot and the MTT method for determination of chemosensitivity to ADR was used. RESULTS: The antisense MRPs was found to be effectively expressed in the clones, being transfected with two different antisense MRPs. The MRP expression in these transfectants were inhibited at the rates of 14.0% (GLC4/ADR Ma) and 83.0% (GLC4/ADR Mb), respectively. Moreover, decrease in the ADR resistance was observed in the Ma and Mb at the rates of 9.5% and 28.4%. Although the intracellular ADR concentration was increased in these transfectants, the proliferation and cell cycle and their early apoptosis induced by the ADR, indicated no difference between the transfectants and parental cells. CONCLUSION: It is possible to obtain the effective expression of the MRP antisense structures for the blocking of the mRNA translation in GLC4/ADR cell line and the fragment complementary to the 3'-region of MRP is more effective for the inhibition of the MRP than that related to the 5'-region of MRP. The antisense RNA may be a useful treatment in combination with the conventional chemotherapy for SCLC, in which the MRP overexpression usually occurs.

ATP Binding Cassette Transporter, Subfamily B↗

[The relationship between postburn enterogenic hypermetabolism and decontamination of intestine].

OBJECTIVE: To explore whether postburn enterogenic hypermetabolism exists. METHODS: Eighty -- eight Wistar rats inflicted by 30% TBSA III degree burns were randomly divided into two groups, i,e. burn (B) and burn with gut decontamination (D) groups. The change in resting energy expenditure (REE) was observed during 0 to 10 postburn day (PBDs) in rats. The plasma contents of lipopolysaccharide (LPS), tumor necrosis factor (TNF) and interleukin-1 (IL-1) were determined on 1, 3, 5, 7 and 10 PBDs and their correlations were analyzed. RESULTS: The postburn REE and plasma contents of TNF, LPS and IL-1 were much higher in both groups than those before injury. When compared between the two groups, the above data in D group were lower in varying degrees than those in B group. It was shown by correlation analysis that REE was postively correlated to LPS, TNF and IL-1, respectively (gamma = 0.77 similar 0.9, P < 0.05 similar 0.01). CONCLUSION: Postburn hypermetabolism in rats could be ameliorated by gut decontamination, and the postburn plasma inflammatory mediators in rats could also be lowered by gut decontmination. This suggests that enterogenic hypermetabolism does exist after burn injury.

Animals↗

Kinetics of inactivation of Ulva pertusa Kjellm alkaline phosphatase by ethylenediaminetetraacetic acid disodium.

Ulva pertusa Kjellm alkaline phosphatase (EC 3.3.3.1) is a metalloenzyme, the active site of which contains a tight cluster of two zinc ions and one magnesium ion. The kinetic theory described by Tsou of the substrate reaction during irreversible inhibition of enzyme activity has been employed to study the kinetics of the course of inactivation of the enzyme by EDTA. The kinetics of the substrate reaction at different concentrations of the substrate p-nitrophenyl phosphate (PNPP) and inactivator EDTA indicated a complexing mechanism for inactivation by, and substrate competition with, EDTA at the active site. The inactivation kinetics are single phasic, showing that the initial formation of an enzyme-EDTA complex is a relative rapid reaction, following by a slow inactivation step that probably involves a conformational change of the enzyme. The presence of Zn2+ apparently stabilizes an active-site conformation required for enzyme activity.

Alkaline Phosphatase↗

[Detection of TTV DNA from high background nuclear acid samples using specific nuclear acid captured-polymerase chain reaction].

OBJECTIVE: To improve the amplification of non-specificity of TTV DNA detection using PCR from high background nuclear acids because of its low level in samples. METHODS: Specific nuclear acid captured PCR(SNAC-PCR) was established through capturing TTV DNA onto microplate with specific nuclear acid by means of avidin-biotin system, then amplifying captured TTV DNA as usual. Its specificity was evaluated by comparing with the detection of routine extraction samples using nested-PCR with or without subsequent DNA sequencing in 10 samples of sera and liver tissues in pairs. RESULTS: Positive results were obtained using routine protocol in 4 and 9 out of 10 samples of the sera and the liver tissues respectively. The PCR products were proved to be specific using RFLP analysis with Kpn I. However, positive results were found in only 2/10 and 3/10 of samples of sera and liver tissue using DNA sequencing. The results of SNAC-PCR were the same as those of routine protocol with subsequent DNA sequencing. Furthermore, sharper electrophoresis bands were obtained. CONCLUSION: SNAC-PCR could dramatically increase the specificity of the detection of TTV DNA, especially in high background nuclear acid samples. It can be widely used in the detection of other pathogens with low seral level or in high background nuclear acid samples. The level of TTV infection might be over-evaluated by currently used TTV DNA detection when the PCR products were not confirmed by DNA sequencing.

Base Sequence↗

[The binding characteristics of insulin-MTX to insulin receptor].

OBJECTIVE: It has been reported that several kinds of tumors express increased insulin receptor and the molecules of insulin can be internalized in cells and may thence enter into the nuclei mediated by insulin receptor. In this study, we investigated the receptor binding characteristics of insulin-MTX for the possibility of using insulin as a carrier for carcinoma targeted therapy by receptor mediation. METHODS: MTX(methotrexate) was covalently linked to insulin directly. The insulin-MTX conjugate was purified by polyacrylamine agarose gel electrophoresis and analysed by high performance liquid chromatography and SDS- polyacrylamine agarose gel electrophoresis. Histologically confirmed human hepatocellular carcinoma specimens were obtained from patients at surgery and immediately frozen under -80 degrees C. Cell membrane fractions were isolated by sucrose density gradient centrifugation. Competitive displacement of 125I-insulin with insulin and insulin-MTX binding to insulin receptor were carried out and the values of IC50 and Ki were calculated so as to observe the characteristics of insulin-MTX binding to insulin receptor. RESULTS: Insulin-MTX competed as effectively as insulin with 125I-insulin for insulin receptor. The values of IC50 and Ki for insulin-MTX were 93.82 +/- 19.32 nmol/L and 91.88 +/- 16.86 nmol/L respectively, while the values of IC50 and Ki for insulin were 5.01 +/- 1.24 nmol/L and 4.85 +/- 1.12 nmol/L respectively. CONCLUSION: Insulin-MTX could bind with insulin receptor with high affinity. The result demonstrates us that there is a possibility of using insulin as a carrier for carcinoma targeted therapy by receptor mediation.

Antimetabolites, Antineoplastic↗

[The role of YIGSR and RGD peptides in regulating fenestrae of sinusoidal endothelial cells].

OBJECTIVE: To investigate the effects of Tye-Ile-Gly-Ser-Arg (YIGSR) and Arg-Gly-Asp (RGD) polypeptides on the fenestrae of the liver sinusoidal endothelial cells (SECs). METHODS: By in situ collagenase perfusion and two-step percoll gradient centrifugation, SECs were isolated from normal Wistar rats and cultured on collagen type I or laminin-coated coverslips. The population of SECs fenestrae and their diameters were observed using scanning electron microscopical technique; and the synthesis of collagen type IV in SECs was assessed by radio-immunoassay (RIA). RESULTS: The average number of fenestrae and their diameter in the SECs cultured on laminin-coated coverslips were significantly lower than those on collagen type I-coated coverslips. After the treatment with YIGSR pentapeptides (50 micrograms/ml) and RGD tripeptides (50 micrograms/ml) together for 48 hrs, the number and diameters of fenestrae in the SECs that grew on laminin-coated coverslips increased markedly. Meanwhile, the YIGSR and RGD peptides could significantly decrease the synthesis of collagen type IV in SECs that grew on laminin-coated coverslips. CONCLUSION: The results suggested that the YIGSR and RGD polypeptides may have an important role in regulating the morphology and function of SECs.

Animals↗

[Determination of intestinal trefoil factor in burned rats by reversed-phase high performance liquid chromatography].

A reversed-phase high performance liquid chromatographic method was established for determination of intestinal trefoil factor (ITF) in burned rats. The analysis was carried out on a Hypersil C4 column (30 nm, 5 microns, 4.6 mm i.d. x 250 mm) with gradient elution of acetonitrile-trifluoroacetic acid-water solution at a flow rate of 1 mL/min and detected by a UV detector at 214 nm. The volume proportion of trifluoroacetic acid in water is 0.1% and the volume proportion of acetonitrile in mobile phase ranged from 19.5% to 42.0%. The linear range of the method was 1 mg/L-100 mg/L with relative coefficient of 0.9989. The minimum detection limit was 0.5 mg/L. The recovery of ITF added ranged between 93.95% and 105.90%. The intra-day and inter-day RSD of ITF were less than 5.33% and 6.10% respectively. This method is precise, accurate and can be used for the determination of ITF in intestinal mucosal of burned rats. Therefore, it is helpful in the research of comparing the effects of enteral feeding and parenteral nutrition on ITF expression.

Animals↗

Evolution of the family of pRN plasmids and their integrase-mediated insertion into the chromosome of the crenarchaeon Sulfolobus solfataricus.

Plasmid pHEN7 from Sulfolobus islandicus was sequenced (7.83 kb) and shown to belong to the archaeal pRN family, which includes plasmids pRN1, pRN2, pSSVx and pDL10 that share a large conserved sequence region. pHEN7 is most closely related to pRN1 in this conserved region. It also shares a large variant region containing several homologous genes with pDL10, which is absent from the other plasmids. The variant region is flanked by the sequence motif TTAGAATGGGGATTC and similar duplicated motifs occur in plasmids pRN1 and pRN2, separated by a few bases. It is inferred that recombination at these sites produces the main genetic variability in the plasmid family. The conserved region of the plasmid, and duplicated copies of the motif, are also present in the genome of Sulfolobus solfataricus P2. Moreover, they are bordered by a partitioned integrase gene (int) and by a 45 bp perfect direct repeat corresponding to the downstream half of a tRNA(Val) gene. The integrase and the direct repeat are highly similar in sequence to the integrase and the chromosomal integration site (att), respectively, of the SSV1 virus, which integrates into the chromosome of Sulfolobus shibatae. Recombination at the att repeats in S. solfataricus would produce a novel plasmid, pXQ1, which carries both an intact integrase gene and a single integration site (att). This strongly suggests that the same mechanism of site-specific integration at a tRNA gene is used for both viruses and plasmids in Sulfolobus.

Attachment Sites, Microbiological↗

Morphine increases susceptibility to oral Salmonella typhimurium infection.

This study examined the effect of morphine on oral infection with virulent Salmonella typhimurium. Animals were treated with a 75-mg slow-release morphine pellet followed by inoculation with salmonellae. Morphine markedly sensitized mice to oral infection, as assessed by survival, mean survival time, and colony culture. By 24 h after Salmonella inoculation, morphine-treated mice had a 105-fold difference in number of organisms in the Peyer's patches, compared with controls. The opioid antagonist naltrexone significantly blocked Salmonella colonization in Peyer's patches and reduced Salmonella burden in other organs, indicating that morphine acts at least in part via an opioid receptor-mediated pathway. The data show that morphine markedly potentiates Salmonella infection at the gastrointestinal portal of entry and enhances subsequent dissemination of Salmonella organisms. The results have implications for potentiating gastrointestinal opportunistic infections in intravenous drug abusers and in opioid-medicated postsurgical patients.

Animals↗

Interleukin-4 mediates cell growth inhibition through activation of Stat1.

Interleukin-4 (IL-4) activates Stat6 (signal transducer and activator of transcription 6) and plays multiple roles in regulation of the immune system. IL-4 also triggers phosphorylation of insulin receptor substrate (IRS), leading to stimulation of cell growth. Moreover, IL-4 inhibits proliferation of a variety of cells, but the molecular mechanism of its growth inhibitory effect is not understood. In this study, we demonstrated that IL-4 inhibited cell growth of colon carcinoma cell lines (HT29 and WiDr) but promoted cell growth of Burkitt's lymphoma cell lines (BL30 and BL41) in a dose-dependent manner. The growth inhibition was not dependent on Stat6 activation, because Stat6 was activated at similar levels in all cell lines in response to IL-4. Strikingly, IL-4 activated Stat1 in colon carcinoma cell lines but not in Burkitt's lymphoma cell lines. Therefore, these results suggest that IL-4 induced Stat1 activation, resulting in growth inhibition of colon carcinoma cell lines. Importantly, we present evidence that Stat1 is necessary for IL-4-mediated growth inhibition using Stat1-deficient and Stat1-reconstituted cells. The growth inhibitory effect of IL-4 was diminished in Stat1-deficient cells, whereas it was restored in Stat1-reconstituted cells. In addition, the expression of dominant-negative Stat1 in HT29 cells led to the loss of growth inhibition in response to IL-4. Taken together, our data suggest that IL-4 activates Stat1, leading to cell growth inhibition in colon cancer cells. Thus, this study demonstrates, for the first time, a molecular mechanism by which IL-4 inhibits cell growth.

Animals↗

Shape control of CdSe nanocrystals

Nanometre-size inorganic dots, tubes and wires exhibit a wide range of electrical and optical properties that depend sensitively on both size and shape, and are of both fundamental and technological interest. In contrast to the syntheses of zero-dimensional systems, existing preparations of one-dimensional systems often yield networks of tubes or rods which are difficult to separate. And, in the case of optically active II-VI and III-V semiconductors, the resulting rod diameters are too large to exhibit quantum confinement effects. Thus, except for some metal nanocrystals, there are no methods of preparation that yield soluble and monodisperse particles that are quantum-confined in two of their dimensions. For semiconductors, a benchmark preparation is the growth of nearly spherical II-VI and III-V nanocrystals by injection of precursor molecules into a hot surfactant. Here we demonstrate that control of the growth kinetics of the II-VI semiconductor cadmium selenide can be used to vary the shapes of the resulting particles from a nearly spherical morphology to a rod-like one, with aspect ratios as large as ten to one. This method should be useful, not only for testing theories of quantum confinement, but also for obtaining particles with spectroscopic properties that could prove advantageous in biological labelling experiments and as chromophores in light-emitting diodes.

Journal Article↗

Interaction of the poliovirus receptor with poliovirus.

The structure of the extracellular, three-domain poliovirus receptor (CD155) complexed with poliovirus (serotype 1) has been determined to 22-A resolution by means of cryo-electron microscopy and three-dimensional image-reconstruction techniques. Density corresponding to the receptor was isolated in a difference electron density map and fitted with known structures, homologous to those of the three individual CD155 Ig-like domains. The fit was confirmed by the location of carbohydrate moieties in the CD155 glycoprotein, the conserved properties of elbow angles in the structures of cell surface molecules with Ig-like folds, and the concordance with prior results of CD155 and poliovirus mutagenesis. CD155 binds in the poliovirus "canyon" and has a footprint similar to that of the intercellular adhesion molecule-1 receptor on human rhinoviruses. However, the orientation of the long, slender CD155 molecule relative to the poliovirus surface is quite different from the orientation of intercellular adhesion molecule-1 on rhinoviruses. In addition, the residues that provide specificity of recognition differ for the two receptors. The principal feature of receptor binding common to these two picornaviruses is the site in the canyon at which binding occurs. This site may be a trigger for initiation of the subsequent uncoating step required for viral infection.

Amino Acid Sequence↗

Quantification of the selective retention of palladium octabutoxynaphthalocyanine, a potential photothermal drug, in mouse tissues.

Palladium octabutoxynaphthalocyanine (PdNc(OBu)8) is a potential photothermal therapy (PTT) agent, absorbing strongly in the near-infrared region with no ability to induce photodynamic-type sensitisation (unlike many related napthalocyanines). We report here on the application of high pressure liquid chromatography (HPLC) with near-infrared absorption detection for the determination of the tissue accumulation and clearance of PdNc(OBu)8 in a tumour-bearing mouse model (Balb/c mice with EMT6 carcinoma tumour). Due to its insolubility in aqueous-based solvents, the drug was delivered intraperitoneally in a Cremophor-containing vehicle. Good selective accumulation of the drug into the tumour versus muscle or skin is observed, with the best combination of selectivity and tumour concentration occurring at 24-72 h after drug administration. Clearance times are quite long. Comparison with other similar drugs as reported in the literature indicates that the Cremophor-containing vehicle is likely in large part responsible for the observed pharmacokinetic behaviour. This drug shows potential for PTT and will be investigated further for therapy in this animal model.

Animals↗

Whole grain foods and heart disease risk.

Coronary heart disease (CHD) is the leading cause of death in most developed nations and is rapidly increasing in prevalence in developing countries. Death rates from cardiovascular disease exceed 1 million annually in the United States and account for the largest disease-related cost to health with total costs estimated to exceed $120 billion per annum. Many dietary factors, including total and saturated fat consumption, fruit and vegetable intake and dietary fiber, have been shown to contribute to risk for CHD. We have systematically reviewed literature from the past 20 years evaluating an association between dietary fiber and CHD. Foods that are rich in dietary fiber, including fruits, vegetables, legumes and whole grain cereals, also tend to be a rich source of vitamins, minerals, phytochemicals. antioxidants and other micronutrients. Each of these factors may be independently contributing to the cardiovascular protective effects of fiber-rich foods.

Coronary Disease↗

The ntrB and ntrC genes are involved in the regulation of poly-3-hydroxybutyrate biosynthesis by ammonia in Azospirillum brasilense Sp7.

Azospirillum brasilense Sp7 and its ntrA (rpoN), ntrBC, and ntrC mutants have been evaluated for their capabilities of poly-3-hydroxybutyrate (PHB) accumulation in media with high and low ammonia concentrations. It was observed that the ntrBC and ntrC mutants can produce PHB in both low- and high-C/N-ratio media, while no significant PHB production was observed for the wild type or the ntrA mutant in low-C/N-ratio media. Further investigation by fermentation analysis indicated that the ntrBC and ntrC mutants were able to grow and accumulate PHB simultaneously in the presence of a high concentration of ammonia in the medium, while little PHB was produced in the wild type and ntrA (rpoN) mutant during active growth phase. These results provide the first genetic evidence that the ntrB and ntrC genes are involved in the regulation of PHB synthesis by ammonia in A. brasilense Sp7.

Ammonia↗

DNA vaccination prevents and/or delays carcinoma development of papillomavirus-induced skin papillomas on rabbits.

Malignant progression is a life-threatening consequence of human papillomavirus-associated lesions. In this study, we tested the efficacy of papillomavirus early-gene-based vaccines for prevention of carcinoma development of papillomavirus-induced skin papillomas on rabbits. Rabbit skin papillomas were initiated by infection with cottontail rabbit papillomavirus (CRPV). The papillomas were allowed to grow for 3 months without any treatment intervention. Rabbits were then immunized by gene gun-mediated intracutaneous administration of four DNA plasmids encoding CRPV E1, E2, E6, and E7 genes, respectively. All eight control rabbits receiving vector alone developed invasive carcinoma within 8 to 13 months. In contrast, only two of eight vaccinated rabbits developed carcinoma at 12 and 15 months, respectively. Papilloma growth was suppressed in the majority of vaccinated rabbits but not completely eradicated. These results indicate that gene gun-mediated immunization with papillomavirus early genes may be a promising strategy for prevention of malignant progression of human papillomavirus-associated lesions in humans.

Animals↗

Gene content and organization of a 281-kbp contig from the genome of the extremely thermophilic archaeon, Sulfolobus solfataricus P2.

The sequence of a 281-kbp contig from the crenarchaeote Sulfolobus solfataricus P2 was determined and analysed. Notable features in this region include 29 ribosomal protein genes, 12 tRNA genes (four of which contain archaeal-type introns), operons encoding enzymes of histidine biosynthesis, pyrimidine biosynthesis, and arginine biosynthesis, an ATPase operon, numerous genes for enzymes of lipopolysaccharide biosynthesis, and six insertion sequences. The content and organization of this contig are compared with sequences from crenarchaeotes, euryarchaeotes, bacteria, and eukaryotes.

Amino Acid Sequence↗