Biomedical subjects

Juan Cheng

Publications and source records attributed to Juan Cheng.

At least 19 recordsLinked to original sources

PubMed2006

The regulation of integrin-mediated osteoblast focal adhesion and focal adhesion kinase expression by nanoscale topography.

An important consideration in developing physical biomimetic cell-stimulating cues is that the in vivo extracellular milieu includes nanoscale topographic interfaces. We investigated nanoscale topography regulation of cell functions using human fetal osteoblastic (hFOB) cell culture on poly(l-lactic acid) and polystyrene (50/50 w/w) demixed nanoscale pit textures (14, 29, and 45nm deep pits). Secondary ion mass spectroscopy revealed that these nanotopographic surfaces had similar surface chemistries to that of pure PLLA because of PLLA component surface segregation during spin casting. We observed that 14 and 29nm deep pit surfaces increased hFOB cell attachment, spreading, selective integrin subunit expression (e.g., alphav relative to alpha5, beta1, or beta3), focal adhesive paxillin protein synthesis and paxillin colocalization with cytoskeletal actin stress fibers, and focal adhesion kinase (FAK) and phosphorylated FAK (pY397) expression to a greater degree than did 45nm deep pits or flat PLLA surfaces. Considering the important role of integrin-mediated focal adhesion and intracellular signaling in anchorage-dependent cell function, our results suggest a mechanism by which nanostructured physical signals regulate cell function. Modulation of integrin-mediated focal adhesion and related cell signaling by altering nanoscale substrate topography will have powerful applications in biomaterials science and tissue engineering.

Biocompatible Materials↗

PubMed2006

Surface and depth profiling investigation of a drug-loaded copolymer utilized to coat taxus express2 stents.

The surface of a styrene-b-isobutylene-b-styrene triblock copolymer, containing a solid-phase drug, was studied by time-of-flight secondary ion mass spectrometry employing 15-keV Ga+ and 20-keV C60+ ion sources. This polymer/drug system has direct application in the cardiac stent arena, where it has been used to treat restenosis or renarrowing of arterial walls after stent or angioplasty procedures. Overall, the results illustrate the successful use of a cluster ion beam for greatly enhancing the high-mass fragment ion and molecular ion intensities from the surface and bulk of the polymer system. The use of C60+ also established the ability to remove common overlayers like poly(dimethylsiloxane), which was not possible using a Ga+ ion source. Furthermore, the use of C60+ allowed depth profiles to be obtained using primary ion dose densities in excess of 6 x 1014 C60+/cm2. Resultant sputter craters reached depths of approximately 2 microm and possessed relatively flat bottoms without the need for sample rotation. AFM and profilometry studies support the relatively gentile removal of surface species via phase contrast and topographic imaging. In addition, the findings suggest that relatively high ion doses do not significantly alter the phase distribution or surface topography of the polymer surface; however, a slight increase in surface roughness was detected.

Cardiovascular Diseases↗

PubMed2006

Direct comparison of Au(3)(+) and C(60)(+) cluster projectiles in SIMS molecular depth profiling.

The sputtering properties of two representative cluster ion beams in secondary ion mass spectrometry (SIMS), C(60)(+) and Au(3)(+), have been directly compared. Organic thin films consisting of trehalose and dipalmitoylphosphatidylcholine (DPPC) are employed as prototypical targets. The strategy is to make direct comparison of the response of a molecular solid to each type of the bombarding cluster by overlapping the two ion beams onto the same area of the sample surface. The ion beams alternately erode the sample while keeping the same projectile for spectral acquisition. The results from these experiments are important to further optimize the use of cluster projectiles for SIMS molecular depth profiling experiments. For example, Au(3)(+) bombardment is found to induce more chemical damage as well as Au implantation when compared with C(60)(+). Moreover, C(60)(+) is found to be able to remove the damage and the implanted Au effectively. Discussions are also presented on strategies of enhancing sensitivity for imaging applications with cluster SIMS.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2006

Molecular depth profiling with cluster ion beams.

Peptide-doped trehalose thin films have been characterized by bombardment with energetic cluster ion beams of C60+ and Aux+ (x = 1, 2, 3). The aim of these studies is to acquire information about the molecular sputtering process of the peptide and trehalose by measurement of secondary ion mass spectra during erosion. This system is important since uniform thin films of approximately 300 nm thickness can be reproducibly prepared on a Si substrate, allowing detailed characterization of the resulting depth profile with different projectiles. The basic form of the molecular ion intensity as a function of ion dose is described by a simple analytical model. The model includes parameters such as the molecular sputtering yield, the damage cross section of the trehalose or the peptide, and the thickness of a surface layer altered by the projectile. The results show that favorable conditions for successful molecular depth profiling are achieved when the total sputtering yield is high and the altered layer thickness is low. Successful molecular depth profiles are achieved with all of the cluster projectiles, although the degree of chemical damage accumulation was slightly lower with C60. With C60 bombardment, the altered layer thickness of about 20 nm and the damage cross section of about 5 nm2 are physically consistent with predictions of molecular dynamics calculations available for similar chemical systems. In general, the model presented should provide guidance in optimizing experimental parameters for maximizing the information content of molecular depth profiling experiments with complex molecular thin film substrates.

Algorithms↗

PubMed2006

The antimalarial artemisinin synergizes with antibiotics to protect against lethal live Escherichia coli challenge by decreasing proinflammatory cytokine release.

In the present study artemisinin (ART) was found to have potent anti-inflammatory effects in animal models of sepsis induced by CpG-containing oligodeoxy-nucleotides (CpG ODN), lipopolysaccharide (LPS), heat-killed Escherichia coli 35218 or live E. coli. Furthermore, we found that ART protected mice from a lethal challenge by CpG ODN, LPS, or heat-killed E. coli in a dose-dependent manner and that the protection was related to a reduction in serum tumor necrosis factor alpha (TNF-alpha). More significantly, the administration of ART together with ampicillin or unasyn (a complex of ampicillin and sulbactam) decreased mortality from 100 to 66.7% or 33.3%, respectively, in mice subjected to a lethal live E. coli challenge. Together with the observation that ART alone does not inhibit bacterial growth, this result suggests that ART protection is achieved as a result of its anti-inflammatory activity rather than an antimicrobial effect. In RAW264.7 cells, pretreatment with ART potently inhibited TNF-alpha and interleukin-6 release induced by CpG ODN, LPS, or heat-killed E. coli in a dose- and time-dependent manner. Experiments utilizing affinity sensor technology revealed no direct binding of ART with CpG ODN or LPS. Flow cytometry further showed that ART did not alter binding of CpG ODN to cell surfaces or the internalization of CpG ODN. In addition, upregulated levels of TLR9 and TLR4 mRNA were not attenuated by ART treatment. ART treatment did, however, block the NF-kappaB activation induced by CpG ODN, LPS, or heat-killed E. coli. These findings provide compelling evidence that ART may be an important potential drug for sepsis treatment.

Animals↗

PubMed2006

[Measurement of time-dependent spectra excited by pulse laser using multi-fiber delayer and optical multi-channel analyzer].

A new method and technology for measuring time-dependent spectra excited by pulse laser was reported in the present paper, in which a multi-fiber delayer combined with a two dimensional CCD array detector was employed for collecting and processing the spectra. The multi-fiber delayer consists of five fibers with a length difference of 1-2 m (relative delay time 5-10 ns), and the optical multi channel analyzer is PARC OMA-4. The time-dependent spectra, i. e. the spectra of R6G dye laser, the SRS spectra of acetone, and the plasma emission spectra of metal Mo excited by a double frequency YAG pulse laser with a time resolution of 5 ns were obtained.

English Abstract↗

PubMed2006

[Possible association between polymorphisms of human leukocyte antigen-DQ genes and susceptibility to trichloroethylene-induced severe generalized dermatitis].

OBJECTIVE: To investigate the association between genetic polymorphisms of human leukocyte antigen-DQ (HLA-DQ) and susceptibility to trichloroethylene (TCE)-induced severe generalized dermatitis. METHODS: A case-control study was conducted which included 112 patients with TCE-induced severe generalized dermatitis and 142 healthy controls exposed to TCE in the same workshop. The DNA sequences in exon2 of HLA-DQA1 and HLA-DQB1 were performed by direct sequencing of polymerase chain reaction (PCR) products. The frequencies distribution of allelic genotypes and codon polymorphisms were compared. RESULTS: The frequencies of DQA1*0201 and 060101/0602 in cases [7.6% (17/224) and 16.1% (36/224)] were significantly higher than those of the exposed controls [3.5% (10/284) and 7.0% (20/284)], while frequencies of DQA1*0103 and 050101/0503/0505 in cases [5.8% (13/224) and 8.9% (20/224)] were significantly lower than those of exposed controls [10.9% (31/284) and 17.3% (49/284)]. In terms of codon polymorphisms, there were 5 codons of DQA1 (25, 41, 52, 54 and 69) showing significant differences between cases and controls. There were no significant differences in the frequencies of allelic genotypes of HLA-DQB1 between cases and exposed controls. CONCLUSION: The genetic polymorphisms of HLA-DQA1 might be one of the factors influencing the individual susceptibility to TCE-induced severe generalized dermatitis.

Adolescent↗

PubMed2006

[Association between methylenetetrahydrofolate reductase gene haplotypes and the susceptibility of chromosomal damage in coke-oven workers].

OBJECTIVE: To investigate the association between MTHFR gene variances and chromosomal damage levels in peripheral blood lymphocyte in coke-oven workers exposed to polycyclic aromatic hydrocarbons (PAHs). METHODS: One-hundred and forty coke-oven workers who exposed to a high level of PAHs and sixty-six non-exposed controls were selected as the study subjects. Chromosomal damage in peripheral lymphocyte was measured by the cytokinesis-block micronucleus (CBMN) assay. Urinary 1-hydroxypyrene (1-OHP) levels were measured as the internal dose of PAHs exposure. Two single nucleotide polymorphisms(SNPs) in MTHFR gene, including C677T, A1298C were detected by PCR-RFLP. The MTHFR haplotypes were estimated by Bayesian statistical method with the software of PHASE Version 2.1. The associations between haplotype pairs and CBMN were assessed by analysis of covariance in the coke-oven workers and controls. RESULTS: The variant allele frequencies for MTHFRC677T and A1298C were 0.56 and 0.16 respectively, which consistent with Hardy-Weinberg equilibrium. There was linkage disequilibrium between the two SNPs (D' = 0.99) in this study. Four haplotypes were calculated by PHASE, in terms of 677T - 1298A, 677C-1298A, 677C-1298C and 677T-1298C, the frequencies were 0.555,0.279,0.163 and 0.003 respectively. In coke-oven workers, the frequencies of total micronucleus of non-677C-1298A/677C-1298A haplotype pair was significantly higher than 677C-1298A/677C-1298A (1.00 +/- 0.67 vs 0.60 +/- 0.41, P = 0.04). The frequencies of total micronucleus of 677T-1298A/677T-1298A haplotype pair was significantly higher than 677C-1298A/677C-1298A (1.08 +/- 0.71 vs 0.60 +/- 0.41, P = 0.04). In coke-oven workers, the frequencies of total micronucleus among the different SNPs were not significant differences, either in the controls. CONCLUSION: The haplotypes of MTHFR gene might be one genetic susceptibility factors of PAH induced chromosomal damage in coke-oven workers.

Air Pollutants, Occupational↗

PubMed2006

[Measurement of NO2 concentration in atmosphere in Chengdu by solar spectra].

In the present paper, a new improved method for measuring NO2 concentration of atmosphere by using differential optical absorption spectroscopy of solar spectrum was reported. The sample solar spectra were collected in Chengdu city and Xiling Mountain respectively by a CCD optical multi-channel analyzer. With the upper atmosphere solar spectrum as the reference spectrum, by fitting the sample spectrum and the reference spectrum using least-square method in five spectrum ranges, the various NO2 concentrations (vertical column density) of 3.1 x 10(16) to 5.8 x 10(16) (molecule x cm(-2)) in Chengdu city and 0.7 x 10(16) to 1.0 x 10(16) (molecule x cm(-2)) in Xiling Mountain were obtained respectively. The NO2 concentrations of atmosphere showed an increasing tendency with the rising temperature.

English Abstract↗

PubMed2005

Depth profiling of peptide films with TOF-SIMS and a C60 probe.

A buckminsterfullerene ion source is employed to characterize peptide-doped trehalose thin films. The experiments are designed to utilize the unique sputtering properties of cluster ion beams for molecular depth profiling. The results show that trehalose films with high uniformity can be prepared on Si by a spin-coating technique. Bombardment of the film with C60+ results in high quality time-of-flight secondary ion mass spectrometry spectra, even during ion doses of up to 3 x 10(14) ions/cm2. This result is in contrast to atomic bombardment experiments in which the dose of incident ions must be kept below 10(12) ions/cm2 so as to retain mass spectral information. Moreover, since the films are of uniform thickness, it is possible to depth-profile through the film and into the Si substrate. This experimental protocol allows the yield of trehalose molecular equivalents and the degree of interface mixing to be evaluated in detail. When doped with a variety of small peptides up to a molecular weight of m/z 500, we find that the peptide molecular ion intensity remains stable under continuous C60+ bombardment, although some decrease in intensity is observed. The results are interpreted in terms of a model whereby the high trehalose yield and low damage depth of the C60 projectile combine to prevent damage accumulation. In general, the peptide-trehalose system provides a valuable model for evaluating the parameters that lead to effective 3-dimensional characterization of biomaterials.

Fullerenes↗

PubMed2005

The association of XRCC1 haplotypes and chromosomal damage levels in peripheral blood lymphocyte among coke-oven workers.

Theoretically, a haplotype has a higher level of heterozygosity than individual single nucleotide polymorphism (SNP) and the association study based on the haplotype may have an increased power for detecting disease associations compared with SNP-based analysis. In this study, we investigated the effects of four haplotype-tagging SNPs (htSNP) and the inferred haplotype pairs of the X-ray cross-complementing group 1 (XRCC1) gene on chromosome damage detected by the cytokinesis-block micronucleus assay. The study included 141 coke-oven workers with exposure to a high level of polycyclic aromatic hydrocarbons and 66 nonexposed controls. The frequencies of total MN and MNed cells were borderline associated with the Arg(194)Trp polymorphism (P = 0.053 and P = 0.050, respectively) but not associated with the Arg(280)His, Arg(399)Gln and Gln(632)Gln polymorphisms among coke-oven workers. Five haplotypes, including CGGG, TGGG, CAGG, CGAG, and CGGA, were inferred based on the four htSNPs of XRCC1 gene. The haplotype CGGG was associated with the decreased frequencies of total MN and MNed cells, and the haplotypes TGGG and CGAG were associated with the increased frequencies of total MN and MNed cells with adjustment for covariates among coke-oven workers. This study showed that the haplotypes derived from htSNPs in the XRCC1 gene were more likely than single SNPs to correlate with the polycyclic aromatic hydrocarbon-induced chromosome damage among coke-oven workers.

Adult↗

PubMed2005

[The immunological effects in guinea pig sensitized by trichloroethylene].

OBJECTIVE: To investigate the changes of certain immunological indexes in development of Guinea Pig allergic dermatitis induced by trichloroethylene (TCE). METHODS: The Guinea Pig model of TCE-induced allergic dermatitis was established by Guinea Pig Maximisation Test. IgG levels in serum were measured by sandwich enzyme immunoassay. The splenic T lymphocytes ConA-stimulated proliferation function and natural killer (NK) cell activity were detected by MTT assay and micro-LDH release assay, respectively. RESULTS: The sensitization rate of TCE was 66.7%. The IgG level in serum of TCE-sensitized animals was significantly higher than that in normal animals (P < 0.05). No obvious differences in Splenic T lymphocytes proliferation index and NK cell activity between TCE-sensitized and normal animals were found (P > 0.05). CONCLUSION: Humoral immunity may play an important role in development of allergic dermatitis induced by TCE.

Animals↗

PubMed2005

[Association of XRCC1 polymorphisms and chromosomal damage levels in coke-oven workers].

OBJECTIVE: To investigate the association of XRCC1 polymorphisms and chromosomal damage levels in peripheral blood lymphocyte in coke-oven workers. METHODS: The study included 141 coke-oven workers who exposed to a high level of polycyclic aromahaplotpetic hydrocarbon and 66 non-exposed controls. Urinary 1-hydroxypyrene and chromosome damage in peripheral lymphocyte were measured. Four -tagging single nucleotide polymorphisms in XRCC1 gene, including C26304T, G27466A, G28152A and G36189A, were detected and the XRCC1 haplotypes were estimated by using an extension of Clark algorithm. The associations between haplotype pairs and micronuclei data were assessed by analysis of covariance in the exposed and non-exposed groups. RESULTS: The geometric means of urinary 1-hydroxypyrene levels in coke-oven workers and the controls were 12.0 and 0.7 micromol/mol Cr respectively (P < 0.01). The cytokinesis-block micronucleus cytokinesis-block micronucleus frequencies (number of micronucleus per 1 000 binucleated lymphocytes) was significantly higher in coke-oven workers (0.95 +/- 0.66)% than in the controls (0.40 +/- 0.36)%, P < 0.01. The haplotype CGGG was associated with the decreased frequencies of total micronucleus, and the haplotypes TGGG (P = 0.01) and CGAG (P < 0.05) were associated with the increased frequencies of total micronucleus in the multivariate analysis with adjustment for covariates among coke-oven workers. CONCLUSIONS: The genetic polymorphisms of XRCC1 gene could influence the chromosome damage levels in coke-oven workers.

Adult↗

PubMed2005

[Association of metabolic and DNA repair enzyme gene polymorphisms and DNA damage in coke-oven workers].

OBJECTIVE: To investigate the association of polymorphisms of metabolic and DNA repair enzyme genes and DNA damage in peripheral blood lymphocytes in coke-oven workers. METHODS: One hundred and forty-four coke-oven workers and 50 controls were recruited in this study. Urinary 1-hydroxypyrene (1-OHP) levels were measured as the internal dose of polycyclic aromatic hydrocarbons exposure. DNA damage was detected by alkaline comet assay, and the value of 1.74 was used as the cut-off value to determine whether the individual's DNA damage was positive. The genotypes of CYP1A1, CYP2E1, GSTP1, NQO1, mEH and XRCC1 were determined by PCR-based methods. With adjustment for urinary 1-OHP, age, sex, multiple analysis of covariance was used to study the association between genotypes and the ln-transformed olive TM and multiple logistic regression was used to calculate the adjusted OR and the 95% CI for the risk of DNA damage. RESULTS: In 144 coke-oven workers, with adjustment for urinary 1-OHP, coking history and sex, the olive TM was significantly higher with XRCC1 280His allele than those with Arg allele (5.6 vs. 2.8, P < 0.01). The subjects with XRCC1 280His allele also have significantly higher risk for DNA damage than subjects with Arg allele (adjusted OR = 2.66, 95% CI = 1.00-7.14, P = 0.05) and the subjects with GSTP1 104Val allele have higher risk for DNA damage than subjects with Ile allele (adjusted OR = 1.90, 95% CI = 0.94-3.85, P = 0.07). CONCLUSION: XRCC1 and GSTP1 polymorphisms might influence the susceptibility of DNA damage in occupational PAH-exposed coke-oven workers.

Adult↗

PubMed2005

[Immunological mechanism in development of allergic dermatitis in guinea pig induced by trichloroethylene in vitro].

OBJECTIVE: To investigate the immunological mechanism of allergic dermatitis induced by trichloroethylene (TCE). METHODS: The guinea pig model of TCE-induced allergic dermatitis was established by Guinea pig Maximization Test. The effects of TCE and its metabolites on splenic lymphocytes of TCE-sensitized and non-sensitized guinea pig were detected by MTT assay. RESULTS: For TCE-sensitized guinea pig, the survival rate of lymphocytes cultured with TCE (+S9) was significantly higher than that cultured with TCE (-S9) (83.0% +/- 3.4% vs 75.9% +/- 7.9%, P < 0.01), while, for normal animals, the survival rate of lymphocytes cultured with TCE (+S9) was significantly lower than that cultured with TCE (-S9) (63.4% +/- 8.4% vs 77.0% +/- 7.2%, P < 0.01). The survival rate of lymphocytes cultured with TCE (+S9) in TCE-sensitized animals was higher than that in normal animals (83.0% +/- 3.4% vs 63.4% +/- 8.4%, P < 0.05), but no statistically significant difference was found for TCE (-S9) (75.9% +/- 7.9% vs 77.0% +/- 7.2%, P > 0.05). CONCLUSION: Cytotoxicity of TCE to normal lymphocytes and proliferation of sensitized lymphocytes were enhanced by metabolic activation. The metabolites of TCE may act as effective immune hapten to stimulate the proliferation of hapten-specific lymphocytes in TCE-sensitized animals.

Animals↗

PubMed2005

[Study on sodium lauryl sulfate (SDS) induced fluorescence enhancement of rhodamine 6G in water solution excited by 532 nm laser].

It is reported that the Rhodamine 6G fluorescence in water solution changes with different concentration SDS excited by a 532 nm laser. A small amount of SDS in Rhodamine 6G water solution will reduce the intensity of fluorescence. More SDS enhances R6G fluorescence. The enhancement ratio can reach up to 3.1 when SDS concentration is 6 x 10(-2) mol L(-1) in 5 x 10(-5) mol L(-1) R6G water solution. Dye laser threshold decreases when SDS concentration is 2 x 10(-2) mol x L(-1) in 1 x 10(-4) mol x L(-1) R6G water solution. The physical mechanism of the phenomena is analyzed by the absorption spectra of different concentration R6G water solutions and the fluorescence spectra of R6G water solutions adulterated with different concentration SDS.

Fluorescence↗

PubMed2004

Effects of genetic polymorphisms of metabolic enzymes on cytokinesis-block micronucleus in peripheral blood lymphocyte among coke-oven workers.

Exploring the associations between genetic polymorphisms of metabolic enzymes and susceptibility to polycyclic aromatic hydrocarbon (PAH)-induced chromosomal damage is of great significance for understanding PAH carcinogenesis. Cytochrome P450, glutathione S-transferase, microsomal epoxide hydrolase, NAD(P)H:quinone oxidoreductase, and N-acetyltransferase are PAH-metabolizing enzymes. In this study, we genotyped for the polymorphisms of these genes and assessed their effects on cytokinesis-block micronucleus (CBMN) frequencies in peripheral blood lymphocytes among 141 coke-oven workers and 66 non-coke-oven worker controls. The geometric means of urinary 1-hydroxypyrene levels in coke-oven workers and the controls were 12.0 and 0.7 micromol/mol creatinine, respectively (P < 0.01). The CBMN frequency (number of micronuclei per 1,000 binucleated lymphocytes) was significantly higher in coke-oven workers (9.5 +/- 6.6 per thousand) than in the controls (4.0 +/- 3.6 per thousand; P < 0.01). Among the coke-oven workers, age was positively associated with CBMN frequency; the mEH His113 variant genotype exhibited significantly lower CBMN frequency (8.5 +/- 6.5 per thousand) than did the Tyr113/Tyr113 genotype (11.3 +/- 6.4 per thousand; P < 0.01); the low mEH activity phenotype exhibited a lower CBMN frequency (8.6 +/- 6.8 per thousand) than did the high mEH activity phenotype (13.2 +/- 6.7 per thousand; P = 0.01); the GSTP1 Val105/Val105 genotype exhibited a higher CBMN frequency (15.0 +/- 5.8 per thousand) than did the GSTP1 Ile105/Ile105 or Ile105/Val105 genotypes (9.3 +/- 6.5 per thousand; P < 0.01); the joint effect of high mEH activity phenotype and GSTM1 null genotype on CBMN frequencies was also found. Gene-environment interactions between occupational PAH exposure and polymorphisms of mEH and/or GSTM1 were also evident. These results indicate that the mEH, GSTP1, and GSTM1 polymorphisms may play a role in sensitivity or genetic susceptibility to the genotoxic effects of PAH exposure in the coke-oven workers.

Acyltransferases↗

PubMed2004

[Double light beam multi-channel analysis for laser induced fluorescence spectroscopy].

The incident pulse intensity wave will cause the induced fluorescence wave, which will lead to the obvious error of experiment results. A double-light-beam correlation method between the incident laser and the fluorescence was used to decrease such error efficiently in the experiments. A good correlation factor over 0.9 was obtained by the method in the experiment of R6G fluorescence enhanced by SDS. The method is better than sampling-averaging method when the incident laser intensity has more waves.

Fluorescence↗