Biomedical subjects

Zhi Chen

Publications and source records attributed to Zhi Chen.

At least 127 records · Page 7Linked to original sources

PubMed2002

Effect of nonstationarities on detrended fluctuation analysis.

Detrended fluctuation analysis (DFA) is a scaling analysis method used to quantify long-range power-law correlations in signals. Many physical and biological signals are "noisy," heterogeneous, and exhibit different types of nonstationarities, which can affect the correlation properties of these signals. We systematically study the effects of three types of nonstationarities often encountered in real data. Specifically, we consider nonstationary sequences formed in three ways: (i) stitching together segments of data obtained from discontinuous experimental recordings, or removing some noisy and unreliable parts from continuous recordings and stitching together the remaining parts-a "cutting" procedure commonly used in preparing data prior to signal analysis; (ii) adding to a signal with known correlations a tunable concentration of random outliers or spikes with different amplitudes; and (iii) generating a signal comprised of segments with different properties-e.g., different standard deviations or different correlation exponents. We compare the difference between the scaling results obtained for stationary correlated signals and correlated signals with these three types of nonstationarities. We find that introducing nonstationarities to stationary correlated signals leads to the appearance of crossovers in the scaling behavior and we study how the characteristics of these crossovers depend on (a) the fraction and size of the parts cut out from the signal, (b) the concentration of spikes and their amplitudes (c) the proportion between segments with different standard deviations or different correlations and (d) the correlation properties of the stationary signal. We show how to develop strategies for preprocessing "raw" data prior to analysis, which will minimize the effects of nonstationarities on the scaling properties of the data, and how to interpret the results of DFA for complex signals with different local characteristics.

Computer Simulation↗

PubMed2002

High-efficiency gene transfer to primary T lymphocytes by recombinant adenovirus vectors.

Recombinant, replication-deficient adenoviruses are efficient vectors for gene transfer to a wide range of cell types, with the exception of T lymphocytes. Here, we show that primary T lymphocytes from peripheral blood, cord blood, and the Jurkat T cell line are efficiently transduced by recombinant adenovirus. Nearly 100% infection efficiency of primary T cells is obtained with high multiplicity of infection (MOI) (5000) of recombinant adenovirus coding for lacZ. Similar infection efficiency by adenovirus-mediated gene transfer was obtained at lower MOI (3000) by activating primary T cells with PHA and PMA. Addition of cationic liposomes together with RAdlacZ markedly enhanced the infection efficiency at lower MOI (1000) resulting in over 90% infection efficiency. Primary T cells express low levels of coxsackievirus and adenovirus receptor (CAR), a cell surface receptor for adenovirus fiber attachment, as well as alpha(v)beta(3) and alpha(v)beta(5) integrins, cellular receptors for adenovirus internalization. This suggests that adenovirus entry to T cells at high MOI is mediated by other mechanisms. In conclusion, these results demonstrate that genes can be efficiently transferred to primary lymphocytes by adenovirus vectors at high MOI or in combination with cationic liposomes.

Adenoviridae↗

PubMed2002

Birth characteristics, maternal reproductive history, hormone use during pregnancy, and risk of childhood acute lymphocytic leukemia by immunophenotype (United States).

OBJECTIVE: To investigate the associations of birth characteristics and maternal reproductive factors with risk of childhood acute lymphoblastic leukemia (ALL) by immunophenotypic subtypes. METHODS: Data collected from a case-control study including 1842 ALL cases (age < 15 years) and 1986 individually matched controls were analyzed. Exposure information was obtained through telephone interviews of parents. RESULTS: Factors associated with risk of ALL from all subgroups combined included high birth weight (OR = 1.4, 95% CI = 1.1-1.8), high birth order (OR = 2.0, 95% CI = 1.3-3.0 for fourth-born child compared to first-born child). young maternal age (<20 compared to 25-29, OR = 1.4, 95% CI = 1.1-1.9), advanced paternal age (>39 compared to 25-29, OR = 1.4, 95% CI = 1.0-1.9), induced abortion prior to the index pregnancy (OR = 1.2, 95% CI = 1.0-1.4), and oral contraceptive use during the index pregnancy (OR = 1.5, 95% CI = 1.0-2.2) with children under the age of 2 (OR = 5.1, 95% CI = 1.0-24.7) being the predominantly affected group. Risk of early pre-B-cell ALL increased with advanced paternal age (OR = 1.7, 95% CI = 1.1-2.7) and high birth order (OR = 2.0, 95% CI = 1.1-3.6), while risk of pre-B-cell ALL increased with both younger (OR = 3.4, 95% CI = 1.4-8.4) and advanced maternal age (OR = 2.6, 95% CI = 1.1-5.9). T-cell ALL was associated with high birth weight (OR = 2.4, 95% CI = 1.1-5.5) and history of induced abortion (OR = 2.4, 95% CI = 1.3-4.5). CONCLUSION: This study suggests that the association of ALL with birth characteristics and maternal reproductive factors varies with the immunophenotype of the ALL. Future studies are needed to better understand the effect of maternal hormone in the development of subtype of childhood ALL.

Abortion, Spontaneous↗

PubMed2002

Fabrication and characterization of vertically aligned carbon nanotubes on silicon substrates using porous alumina nanotemplates.

An ethylene-air laminar diffusion flame successfully provided silicon substrates of anodic aluminum oxide (AAO) template with vertically oriented well-aligned carbon nanotubes. Field emission scanning electron microscopy (SEM) showed that open-tipped carbon nanotubes consisting of tube elements with the same length and diameter uniformly coated the template. High-resolution transmission electron microscopy (TEM) analyses revealed these nanotubes to be multiwalled carbon nanotubes, some well graphitized. It was found that cobalt catalyst particles, but not the porous aluminum templates, helped the growth of carbon nanotubes through graphitization and bonding of carbon nanotubes to the silicon substrates.

Anisotropy↗

PubMed2002

[Express of human papillomavirus, P53 and H-ras gene in laryngeal cancer]

OBJECTIVE: To study the abnormality of p53 and H-ras gene in laryngeal cancer cells and their relation to the infection of human papillomavirus(HPV) subtypes. METHODS: The HPV subtypes, P53 and H-ras gene were examined in 28 cases of laryngeal cancer by polymerase chain reaction (PCR), single strand conformation polymorphism(SSCP), restriction fragment length polymorphism (RFLP) and DNA sequencing. RESULTS: P53 gene mutation existed in 50%cases of laryngeal cancer and DNA sequencing showed base substitution, insertion or deletion in 4 cases; The positive rate of the H-ras oncogene mutation was only 3.57% All high risk HPV infections (HPV-16 or-18) were distinctly seen in the cancer cases, especially in cases with P53 mutation. CONCLUSION: The high risk HPV subtype infection and P53 gene abnormality may play an important role in laryngeal cancer progression and these two factors may be correlated to each other.

Journal Article↗

PubMed2002

[Construction of HBV S gene recombinant and its immunity induced in mice]

OBJECTIVE: To investigate the feasibility of HBV DNA vaccines. METHODS: HBV S gene was obtained by PCR and the PCR product was cloned into pcDNA3. The recombinant was screened by antibiotics, identified by digestion and confirmed by sequencing. The plasmid was then transfected into mammalian cell COS-7 for transient expression. Then the recombinant was injected into mice and the immune responses induced in mice were investigated. RESULTS: The sequence of HBV S gene was correct and HBsAg could be detected in cells transfected with pcDNA3-S. After immunization, the positive rate in mice immunized with pcDNA3-S and pCMV-S was 70%(7/10) and 80% (8/10). The mean levels of anti-HBs were (32.14+/-13.79)mIU/ml and (28.50+/-11.87)mIU/ml respectively. There was no statistically significant difference between them P 0.05 . The mean levels of anti HBs in the control group and blank groups were both less than 10 mIU/ml. In mice immunized with pcDNA3-S and pCMV-S the results were (35.40+/-4.85)% and (38.20+/-7.69)% when E/T was 20:1, or (23.95+/-3.98)% and (24.55+/-3.59)% when E/T was 10:1, again showing no difference statistically (P>0.05). The specific CTL cytotoxicity rate of control and blank groups was both less than 5%. CONCLUSION: A specific humoral and cellular immune response can be induced in mice by intramuscular injection of pcDNA3-S.

Journal Article↗

PubMed2002

[DNA vaccine encoding Streptococcus mutans surface protein protected gnotobiotic rats from caries].

OBJECTIVE: Protein of Streptococcus mutans is considered as one of the virulence factors due to its ability to mediate the initial attachment of Streptococcus mutans to tooth surface. In this study, an anticaries DNA vaccine pCIA-P was used to immunize rats. The expression of PAc in different tissues in vivo, specific immune response and protection effects against dental caries were observed. METHODS: Plasmid pCIA-P was injected into rats by two different routs: intramuscular injection (i.m.) and targeted salivary gland immunization (TSG). Immunohistochemistry technique was used to detect the expression of PAc. Gnotobiotic rats were vaccinated with pCIA-P by three different approaches: TSG, intramuscular injection and buccal mucosal injection (i.o.). The specific immune responses were evaluated by ELISA and their anticaries effects were evaluated by Keyes caries scores. RESULTS: PAc was expressed in the sarcoplasm and sarcolemma of muscle fibers and submandibular glands, especially strongly positive in duct regions. The levels of serum specific anti-PAc IgG and salivary specific anti-PAc IgA in TSG immunization and buccal mucosal immunization group were significantly higher than those of other groups. The Keyes caries scores of those two groups were significantly lower than those of other groups. CONCLUSION: The plasmid pCIA-P could provoke specific immune responses as a novel immunogen. Mucosal immunization with pCIA-P appears to be an effective genetic immunization method against dental caries.

Animals↗

PubMed2002

[Study on production of acrylamide by microbial method (I)--Culture of bacterium cells and expression of high activity of nitrile hydratase].

The cultural conditions for the growth of Norcardia cell were studied in this paper. Controlling pH value, adding nutrient and optimizing the quantity of inducer during cultivation, the activity of nitrile hydratase reached 6567 u/mL (culture medium), which was the highest value appeared in native journals. In the farther hydratase experiments, no by-product, crylic acid, was detected. It showed that the activity of amidase was not promoted obviously while the activity of nitrile hydratase was increased greatly. The results set a strong foundation for the industrial application and the research on new technology.

Acrylamides↗

PubMed2002

[Study on production of acrylamide by microbial method (II)--enzyme catalytic kinetics and de-active dynamics of nitrile hydratase].

The hydration reaction by microbial method is the crisis of the procedure of acrylamide production from acrylonitrile. This research studied the enzyme catalytic kinetics and de-active kinetics of nitrile hydratase in the type of free cell. Firstly, the effects of the concentration of cells, the temperature, pH value, the concentration of acrylonitrile and the concentration of acrylamide on the activity of nitrile hydratase was investigated. The result is that the temperature and the concentration of acrylamide are the most important among these factors. The activity of the nitrile hydratase was 5659 u/mL (broth) at 28 degrees C; the counterpart was only 663 u/mL (broth) at 5 degrees C. And the activity of NHase in solution of 45% acrylamide was just about half of that in solution of 5% acrylamide. After study on the relation of temperature and the reaction speed, It was found that the activation energy of the hydration of NHase was 65.57 kJ.mol-1. This paper studied the effects of concentration of cells, temperature, pH value, concentrations of acrylonitrile and acrylamide on the deactivation of Nhase, as well as the related enzyme de-active kinetics. The result also showed that the temperature and the concentration of acrylamide are the most important among these factors. In solution of 35% acrylamide, the residual activity was about 0% of the original value after 55 h; but in solution of 10% acrylamide, after the same period of time, the residual activity was 50% of the original one. It was also found that the concentration of acrylonitrile had little effect on the stability of NHase. The coefficient of deactivation at 28 degrees C was 21.77 times of the one at 5 degrees C. Correlating the temperature and the coefficient of deactivation, the activation energy of the de-active reaction was found to be 92.28 kJ.mol-1.

Acrylamide↗

PubMed2002

The crystallographic properties of the mineral phases of enamel and dentin in normal deciduous and permanent teeth.

OBJECTIVE: To investigate the crystallographic properties of the mineral phases of normal enamel and dentin (dental apatite) in deciduous and permanent teeth. METHODS: Three kinds of physical methods including X-ray diffraction (XRD), infrared absorption spectroscope (IR) and electron probe micro-analysis (EPMA) were utilized in this study. RESULTS: Dental apatite was not uniphase, but multiphase, which could be described as carbonate-substituted hydroxyapatite. Compared to dentin apatite, the higher crystallinity and expanded a-axis lattice parameters were found in enamel. Chemical analyses demonstrated that higher concentrations of Mg and CO(3)(2-) were found in dentin than those of enamel. But enamel had higher Cl content. CONCLUSIONS: The differences among enamel and dentin, in terms of lattice parameter and crystallinity may be partially attributed to the incorporation of Mg, CO(3)(2-) and Cl minor elements.

Dental Enamel↗

PubMed2002

Polymerase chain reaction analysis of the clonality of Porphyromonas gingivalis and collagenase gene.

OBJECTIVE: To investigate the genotypic characterization of Porphyromonas gingivalis (Pg) and the heterogeneity of a potential virulence factor-PrtC. METHODS: Arbitrarily primed polymerase chain reaction (AP-PCR) was applied to 80 Pg strains isolated from 24 unrelated Chinese periodontitis patients. PCR reaction was used to detect a fragment of the collagenase gene (PrtC gene). To evaluate the sequence heterogeneity of the Pg PrtC genes, sequence analysis of four PrtC gene of clinical isolates was performed. RESULTS: Random primer OPA-05 and OPA-17 distinguished 7 AP-PCR profiles (I through VII). The majority of the strains belonged to type VII which accounted for 25.8%. A 548bp fragment of PrtC gene was detected from 24 clinical strains. The PCR products were verified by the restriction endonucleases PstI and PvuI. Sequence analysis showed 4 PrtC genes were heterogeneous in their nucleotide composition and differed from reference strain Pg 53977. CONCLUSIONS: The results demonstrated genetic diversity existed among these clinical strains isolated from Chinese periodontitis patients and the PrtC genes are heterogeneous in their nucleotide sequence.

Adult↗

PubMed2002

Extract and identify ingredient from Ligustrum Lucidum Ait and study its effect to periodontal pathogen.

OBJECTIVE: To extract the effective ingredient (crystal I) from effective section (saponin) of Ligustrum Lucidum Ait, identify the chemical structure of crystal I, study the effect of crystal I on P. gingivalis, B. forsythus and P. intermedia. METHODS: Isolated crystal I from saponin using the silica gel column chromatograph. Identified crystal I with IR spectra, (1)H-NMR and (13)C-NMR. Measured the minimal inhibitory concentration (MIC) and the minimal bactericidal concentration (MBC) through micro-liquid dilution. Studied the killing curve of ursolic acid on B. forsythus and P. intermedia. RESULTS: The crystal I was identified as ursolic acid; its MIC and MBC to P. gingivalis, B. forsythus and P. intermedia were 0.740 and 0.295 microg/L respectively. The killing curve indicated that 0.800 microg/L ursolic acid could kill P. intermedia and B. forsythus in 3 and 6 hours respectively. CONCLUSION: Ursolic acid has obvious effect to inhibit periodontal pathogen.

Bacteroides↗

PubMed2002

[Study of immunological indicators in peripheral blood for nasopharyngeal carcinoma].

OBJECTIVE: To find reliable diagnostic immunological indicators in peripheral blood for nasopharyngeal carcinoma, and to evaluate the possibility of cancer screening and early diagnosis of the malignancies in the future. METHODS: Plasma samples were obtained from 83 patients with nasopharyngeal carcinoma and from 105 patients with benign diseases. Nine cytokines were selected as the candidates for the indicators and their quantity in the plasma samples determined by enzyme-linked immunosorbent assay, the result of which was analyzed statistically. RESULTS: Interleukin (IL)-4 level was obviously increased, while IL-6, IL-12, transforming growth factor (TGF)-beta, interferon (IFN)-gamma levels significantly reduced (P<0.05) in the plasma from patients with nasopharyngeal carcinoma. CONCLUSION: These cytokins may serve as the indicators in the diagnosis of nasopharyngeal carcinoma.

Biomarkers, Tumor↗

PubMed2002

[Study on the characteristics of antisense oligodeoxy-neucleotides-liposomes complex and cellular uptake].

AIM: To investigate factors affecting the properties of antisense oligodeoxy nucleotides (ASON)-liposomes complex and their cellular uptake. METHODS: Three types of blank liposomes were prepared by reverse-phase evaporation vesicles, and the complex were obtained through physical absorption. The light microscope was used to observe morphology characteristics of the complex. Drug loading capacity was analyzed by agarose gel electrophoresis. The transfected cell percentage and means fluorescence intensity were determined by flow cytometric analysis using M3 myeloma cell as a model. RESULTS: The neutral liposome showed no aggregation while the cationic liposomes appeared some different extent aggregation in different medium when associated antisense oligodeoxynucleotides. The drug loading capacity depended on the ratio of +/- and the cationic charge density on the lipid membrane. The two kinds of cationic liposomes appeared different principles of loading ASON. As far as cellular uptake, The neutral liposomes showed no improvement of cellular uptake of ASON. However, the cationic liposomes were shown to enhance the cellular uptake of ASON if the appropriate +/- charge ratio was used. The optimal cellular uptake was achieved when +/- charge ratio was at 0.5:1 and 1:1 for SA-I liposome and SA-II liposomes, respectively. CONCLUSION: The cationic liposomes improved the loading capacity and cell uptake of antisense oligodeoxynucleotides, which was determined by +/- charge ratio and charge density.

Amines↗

PubMed2002

Dynamic changes in the collagen metabolism of liver fibrosis at the transcription level in rabbits with Schistosomiasis japonica.

OBJECTIVE: To study the role of the synthesis and degradation of collagen at the transcription level during liver fibrogenesis due to schistosomiasis japonica in rabbits. METHODS: New Zealand rabbits challenged by cercariae of Schistosoma japonicum (S. japonicum) were served as animal models for liver fibrosis. Liver specimens were collected through operations at 4, 6, 8, 10, 12, 16, 20, 24 and 28 wks after challenge. Type I collagen, type III collagen, type IV collagen, MMP-1 and MMP-9 mRNA levels of liver tissue were detected by RT-PCR + Dot blot. The size of egg granulomas and the degree of liver fibrosis were measured by histopathological examinations. RESULTS: Type I collagen, type III collagen, type IV collagen, MMP-1 and MMP-9 mRNA levels increased simultaneously in the early stage after challenge. Most of them reached their peak at 10 weeks, and compared with normal controls, type I collagen, type III collagen, type IV collagen, MMP-1 and MMP-9 mRNA levels increased by 12.0-, 11.0-, 6.6-, 10.0- and 11.0-fold, respectively, coinciding with the change of egg granulomas, i.e., the change in the inflammatory process. Then both collagen and collagenase mRNA levels decreased. Type I, III and IV collagen mRNA levels declined to 2-fold to 3-fold as compared with normal controls (P < 0.05), while MMP-1 and MMP-9 mRNA levels declined close to normal levels (P > 0.05) at 28 wks. This study shows that the synthesis and degradation of collagen keep a dynamic balance at the early stage of schistosomiasis japonica challenge, while at the later stages the quantity of collagen synthesis was higher than that of collagen degradation. CONCLUSIONS: It was confirmed at transcription level that when the quantity of collagen synthesis was higher than that of collagen degradation liver fibrogenesis may be resulted in.

Animals↗

PubMed2002

[Construction and cellular expression of GTF-PAc fusion anti-caries DNA vaccine].

OBJECTIVE: To construct a fusion anti-caries DNA vaccine pGLUA-P carrying GLU fragment from gtfB gene of Streptococcus mutans GS-5 and A-P fragment including the A region and P region of PAc protein from a DNA anti-caries vaccine pCIA-P, and to investigate its expression in prokaryotic and eukaryotic cells. METHODS: The sequence of GLU fragment in pGLU plasmid was testified by DNA sequencing. The fusion anti-caries DNA vaccine was constructed by ligating A-P fragment from pCIA-P to pGLU. The expression of GLUA-P fusion protein in E. coli BL21 (DE3) was induced by IPTG and checked by SDS-PAGE electrophoresis. pGLUA-P was transfected in vitro to cultured rat primary muscle cells by cation liposome Dosper, and immunohistochemical method was used to test the expression of GLUA-P fusion protein in cells. RESULTS: GLU sequence was identical with relative sequence of GTF-I (GS-5 strain) in Gene Bank. Recombinant eukaryotic expression plasmid pGLUA-P was confirmed to have both GLU and A-P fragment. After pGLUA-P was transferred into E. coli (DE3), it could express a new 115 000 protein by the induce of IPTG. Specific brown products could be found in the cytoplasm of cultured rat primary muscle cells transfected by pGLUA-P. CONCLUSIONS: Fusion anti-caries DNA vaccine pGLUA-P is successfully constructed and confirmed by sequencing and enzymes digestion. Fusion GLUA-P protein can be correctly expressed in prokaryotic and eukaryotic cells.

Animals↗

PubMed2002

Cytomegalovirus infection in liver transplant recipients.

OBJECTIVE: To explore cytomegalovirus (CMV) infection in recipients of liver transplantation (LT). METHODS: 30 recipients of LT were screened for the appearance of CMV infection by using ELISA to test anti-CMV-Ab from serum samples and using immunohistochemistry method to test CMV antigen expression and nested-PCR to amplify CMV-DNA from blood samples. RESULTS: Four of 243 samples taken from 30 recipients came out positive of anti-CMV IgG and anti-CMV IgM with a positive rate of 100% and 1.6% respectively. 85 samples resulted in CMV antigen expression (35.0%) with the average antigen index being 4.2+/-3.1/5 X 10(4) WBC. Besides, 99 samples were found to be positive by nested-PCR with a positive rate of 40.7%. 61 samples were found to be simultaneously positive in test of CMV antigen and DNA, with a rate of 25.1%. CONCLUSIONS: Infection of CMV is common in recipients of LT. Simultaneous screening of anti-CMV-Ab, CMV-Ag and CMV-DNA after liver transplantation is very important for early diagnosis of CMV infection.

Adult↗

PubMed2002

Mutations in precore and core promoter region of HBV in patients with hepatic failure.

OBJECTIVE: To clarify the association of hepatitis B virus mutants in precore and core promoter regions in patients with hepatic failure and HBeAg state. METHODS: Precore and core promoter regions of 25 HBV isolates from the patients with hepatic failure were analyzed by polymerase chain reaction (PCR) direct sequencing approach. RESULTS: Precore G-to-A(1896) mutants were identified in 16 (64%) of the 25 isolates. The "hot spot" mutations at A-to-T(1762) and G-to-A(1764) were present together in 19 (76%) of the 25 isolates, while C-to-T(1653) and T-to-C(1753) existed in a mutually exclusive manner and more frequently in hepatic failure with liver cirrhosis group than in hepatic failure with chronic hepatitis group (100% vs 50%). Both A(1896) and T(1762)-A(1764) could be found frequently in HBeAg-positive subjects (77.8% and 88.9%), whereas T(1653)/C(1753) was more prevalent in anti-HBe-positive subjects than in HBeAg-positive subjects (93.8% vs 33.3%). CONCLUSIONS: The whole frequency of mutations in precore and core promoter gene will become more frequent as HBV infection is to be persistent. Mutation to T(1653)/C(1753) may be useful as a marker for hepatic failure. It requires further study whether the mixed infection of mutants and wilds will develop and affect the condition of HBeAg in serum along the progression of liver disease.

Base Sequence↗