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Biomedical subjects

Q Chen

Publications and source records attributed to Q Chen.

At least 37 records · Page 2Linked to original sources
PubMed2006

High-frequency promoter hypermethylation of the deleted in liver cancer-1 gene in multiple myeloma.

BACKGROUND: Deleted in liver cancer-1 (DLC-1) is a tumour suppressor gene that is inactive in liver carcinogenesis. It encodes a rho-guanosine triphosphatase-activating protein (rho-GAP) and maps to one of the deleted regions (8p21.3-22). Little is known, however, about the methylation status of the DLC-1 promoter in myeloma cells. AIM: To identify whether methylation of DLC-1 was associated in pathogenesis of multiple myeloma. METHODS: Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect DLC-1 transcripts in RPMI 8226, U266, OPM-2 and XG-2 cell lines. The methylation status was determined by methylation-specific PCR followed by bisulphite DNA sequencing in these four cell lines and in the bone marrow of 14 patients with multiple myeloma and 4 normal patients. DLC-1 mRNA expression in cells with or without treatment with 5-aza-deoxycytidine (5-aza-CdR) or trichostatin A (TSA) was investigated by real-time RT-PCR. RESULTS: RPMI 8226 and U266 showed complete methylation and XG-2 showed partial methylation. DLC-1 was expressed only in OPM-2 cell lines that showed no methylation. DLC-1 methylation was shown in 11 of 14 (78%) patients with multiple myeloma and none of the normal controls. The exposure of cell lines to 5-aza-CdR or TSA resulted in the up regulation of DLC-1 gene expression. CONCLUSIONS: DLC-1 methylation is often present in multiple myeloma and has a key role in DLC-1 silencing.

Azacitidine↗
PubMed2006

Single breath-hold T1 measurement using low flip angle TrueFISP.

A method for estimating T1 using a single breath-hold, segmented, inversion recovery prepared, true fast imaging with steady-state precession (sIR-TrueFISP) acquisition at low flip angle (FA) was implemented in this study. T1 values measured by sIR-TrueFISP technique in a Gd-DTPA-doped water phantom and the human brain and abdomen of healthy volunteers were compared with the results of the standard IR fast spin echo (FSE) technique. A good correlation between the two methods was observed (R2=0.999 in the phantom, and R2=0.943 in the brain and abdominal tissues). The T1 values of the tissues agreed well with published results. sIR-TrueFISP enables fast measurements of T1 to be obtained within a single breath-hold with good accuracy, which is particularly important for chest and abdominal imaging.

Algorithms↗
PubMed2006

Serum deprivation induced apoptosis in macrophage is mediated by autocrine secretion of type I IFNs.

Apoptosis can be triggered by different forms of cellular stress. We here show that serum deprivation induces the expression and secretion of type I interferons and results in apoptosis in RAW 264.7 cell in a caspase dependent manner. Administration of either IFN-alpha or IFN-beta antibody partially inhibits apoptosis while the two antibodies used together totally prevents RAW264.7 cell from apoptosis. GM-CSF, but not M-CSF and IL-3, protects serum deprivation induced apoptosis. Inhibition of JAKs also prevents macrophages from apoptosis. Activation of MAPKs is not required for serum deprivation induced apoptosis. Our results are the first to demonstrate that serum deprivation-induced apoptosis acts through autocrine secretion of type I interferons.

Animals↗
PubMed2006

Characterization of HLA-B*5516, -B*1313, -B*9512, and -DRB1*1457 alleles identified in a southwest Chinese population.

The human leukocyte antigen (HLA)-B*5516 allele differs from the B*5502 by a single 97 T --> C substitution (His to Tyr at position 33) in exon 2. The B*1313 allele results from 419 T --> A and 420 A --> C substitutions, encoding a Leu to Tyr substitution at 140 in exon 2 of the B*1301 allele. The B*9512 allele differs from B*1502 by a single 360 G --> C substitution (Gln to His at 120) in exon 3. The DRB1*1457 allele appears to be a hybrid molecule generated by recombination between the DRB1*13 and DRB1*14 alleles. The serological equivalents of these new alleles are HLA-B22, -B13, -B15, and DR13, respectively. Family studies detected two rare haplotypes: A*11, B*9512, DRB1*14 and A*24, B*52, Cw*07, DRB1*1457, DRB3*020201, DQB1*050301. The gene frequencies of these alleles in the Chinese population are less than 0.0001.

Alleles↗
PubMed2005

High-quality ultralong Sb2S3 nanoribbons on large scale.

Large-scale, ultralong, single-crystalline Sb2S3 nanoribbons were prepared by directly reacting SbCl3 and Na2S2O3 solutions, without any organics used in the experiment. The nanoribbons were analyzed by a range of methods. The nanoribbons are usually several millimeters in length, typically 200-500 nm in width and 30-80 nm in thickness. The structure of the nanoribbons is determined to be of the orthorhombic phase. The growth mechanism of the nanoribbons was investigated based on high-resolution transmission electron microscopy observations. Optical absorption experiment shows that the nanoribbon is a semiconductor with a bandwidth Eg approximately 1.5 eV, near to the optimum for photovoltaic conversion, suggesting that Sb2S3 nanoribbons could be used in solar energy and photoelectronic applications.

Journal Article↗
PubMed2005

Development and comparison of five site-specific biosphere models for safety assessment of radioactive waste disposal.

This paper describes the development and application of site-specific biosphere models that might be used for assessment of potential exposures in the framework of performance assessment studies of nuclear waste disposals. Model development follows the Reference Biosphere Methodology that has been set up in the framework of the BIOMASS study. In this paper, the application is to real sites at five European locations for which environmental and agricultural conditions have been described and characterised. For each of the sites a biosphere model has been developed specifically assuming a release of radionuclides to waters that are used by humans, for example as drinking water for humans and cattle and as irrigation water. Among the ingestion pathways, the intakes of drinking water, cereals, leafy vegetables, potatoes, milk, beef and freshwater fish are included in all models. Annual individual doses were calculated, and uncertainties in the results were estimated by means of stochastic calculations. To enable a comparison, all results were normalised to an activity concentration in groundwater of 1 Bq m(-3) for each of the radionuclides considered ((36)Cl, (79)Se, (99)Tc, (129)I, (135)Cs, (226)Ra, (231)Pa, (230)Th, (237)Np, (239)Pu, and (238)U), i.e. those that are usually most relevant in performance assessment studies of nuclear waste disposals. Although the results do not give answers in absolute terms on potential future exposures, they indicate the spectrum of exposures that might occur in different environments and specify the interaction of environmental conditions, human habits and potential exposure.

Animals↗
PubMed2005

A comparative radiological assessment of five European biosphere systems in the context of potential contamination of well water from the hypothetical disposal of radioactive waste.

In the framework of the BioMoSA project for the development of biosphere assessment models for radioactive waste disposal the Reference Biosphere Methodology developed in the IAEA programme BIOMASS was applied to five locations, situated in different European countries. Specific biosphere models were applied to assess the hypothetical contamination of a range of agricultural and environmental pathways and the dose to individuals, following contamination of well water. The results of these site-specific models developed by the different BioMoSA partners, and the individual normalised dose to the exposure groups were compared against each other. Ingestion of drinking water, fruit and vegetables were found to be among the most important pathways for almost all radionuclides. Stochastic calculations revealed that consumption habits, transfer factors, irrigation rates and distribution coefficients (Kd(s)) were the most important parameters that influence the end results. Variations in the confidence intervals were found to be higher for sorbing elements (e.g. (36)Cl, (237)Np, (99)Tc, (238)U, (129)I) than for mobile elements (e.g. (226)Ra, (79)Se, (135)Cs, (231)Pa, (239)Pu). The influence of daughter products, for which the distribution into the biosphere was calculated individually, was also shown to be important. This paper gives a brief overview of the deterministic and stochastic modelling results and the parameter sensitivity. A screening methodology was introduced to identify the most important pathways, simplify a generic biosphere tool and refine the existing models.

Adult↗
PubMed2005

Measurement of the local 1H spin-diffusion coefficient in polymers.

Proton spin diffusion is widely used to determine domain sizes in heterogeneous organic solids. For an accurate analysis, spin diffusion coefficients are required. However, in most cases they are not directly measured, but instead derived from model systems. The effects of magic-angle spinning (MAS), mobility, or spin-lock fields on spin-diffusion coefficients have also been difficult to quantify. In this work, direct measurement of local (1)H spin-diffusion coefficients in any rigid polymer is achieved in experiments with heteronuclear dephasing of the (1)H magnetization, a mixing time for (1)H spin diffusion, and (13)C detection after cross-polarization. In the presence of (1)H homonuclear decoupling and (13)C 180 degrees-pulse recoupling, each (13)C spin dephases a significant number (3-20) of protons, depending on the dephasing time. For (13)C and other sufficiently dilute heteronuclei, the dephasing of the protons is described by simple spin-pair REDOR curves. As a result, every (13)C nucleus will "burn" a spherical hole of known diameter and profile into the proton magnetization distribution. (1)H spin diffusion into the hole during the mixing time can be monitored and simulated accurately for every resolved (13)C site, with the spin-diffusion coefficient as the only significant unknown parameter. By varying the dephasing time, holes with diameters of 0.4-0.8 nm can be burned into the proton magnetization profile and thus the dependence of the local spin-diffusion coefficients on the proton density or partial mobility can be explored. The effects of transverse or magic-angle spin-lock fields on spin diffusion can be quantified conveniently by this method. Analytical and numerical fits yield short-range spin-diffusion coefficients of 0.2-0.5 nm(2)/ms on the 0.5-nm scale, which is smaller than the value of 0.8 nm(2)/ms for organic solids previously measured on the 10-nm scale.

Algorithms↗
PubMed2005

High-quality ultralong Bi2S3 nanowires: structure, growth, and properties.

A simple one-step hydrothermal method for large-scale synthesis of ultralong single-crystalline Bi2S3 nanowires was reported, and the nanowires were comprehensively characterized. The diameters of the nanowires are about 60 nm, and their lengths range from tens of microns to several millimeters. The structure of the nanowires was determined to be of the orthorhombic phase, the growth direction was along [001], and the growth mechanism was investigated based on extensive high-resolution transmission electron microscopy observations. Optical absorption experiments revealed that the Bi2S3 nanowires are narrow-band semiconductors with a band gap E(g) approximately 1.33 eV. Electrical transport measurements on individual nanowires gave a resistivity of about 1.2 ohms cm and an emission current of 3.5 microA at a bias field of 35 V/microm. This current corresponds to a current density of about 10(5) A/cm2, which makes the Bi2S3 nanowire a potential candidate for applications in field-emission electronic devices.

Journal Article↗
PubMed2005

Spatially resolved measurement of rock core porosity.

Density weighted, centric scan, Conical SPRITE MRI techniques are applied in the current work for local porosity measurements in fluid saturated porous media. The methodology is tested on a series of sandstone core samples. These samples vary in both porosity and degree of local heterogeneity due to bedding plane structure. The MRI porosity measurement is in good agreement with traditional gravimetric measurements of porosity. Spatially resolved porosity measurements reveal significant porosity variation in some samples. This novel MRI technique should have applications to the characterization of local porosity in a wide variety of porous media.

Journal Article↗
PubMed2005

Field-effect characteristics and screening in double-walled carbon nanotube field-effect transistors.

Field-effect transistors (FETs) have been fabricated using double-walled carbon nanotubes (DWCNTs), and electrical transport measurements have been carried out on 125 DWCNT FETs. Among these devices, 52 were found to show basically semiconducting field-effect characteristics, 44 show metallic characteristics, and 29 show neither pure semiconducting nor metallic characteristics. These 3 distinct types of field-effect characteristics were identified as resulting from the semiconducting (S)-S, metallic (M)-M or M-S, and S-M combinations of the two shells of the DWCNT. While the S-S and M-M or M-S DWCNT devices exhibit similar field-effect characteristics to those by single-walled carbon nanotube (SWCNT) devices, the S-M device responds uniquely to the external gate voltage. In particular, it was found that free charges in the inner metallic shell may screen the outer semiconducting shell from the gate effect and that the screening is directly related to the intershell interaction, which increases with increasing temperature and tube diameter. The screening is disadvantageous to the performance of DWCNT FETs, and a similar effect is expected to occur in MWCNTs.

Journal Article↗
PubMed2005

Failure to find association between TRAR4 and schizophrenia in the Chinese Han population.

The TRAR4 gene locates in SCZD5 (MIM 603175), which a number of studies have linked with schizophrenia. One recent study suggested that three TRAR4 variants (M1: rs4305745, P=0.0014; M2: rs6903874, P=0.0026; M3: rs6937506, P=0.0052) in the 3'-UTR were associated with schizophrenia. To replicate these findings, we conducted a family-based association study within a sample of 235 Chinese Han trios. However, we didn't find significant evidence of preferential transmission of the three variants across all the trios (all P values>0.2). Thus, we conclude that TRAR4 is not a major or independent determinant in the occurrence of schizophrenia in the Chinese Han population.

Adult↗
PubMed2005

Investigating the binding interaction of azur A with hyaluronic acid via spectrophotometry and its analytical application.

The interaction between azur A (AA) and hyaluronic acid (HA) at AA concentrations from 3.430 x 10(-5) to 8.575 x 10(-5) M and sodium chloride concentrations from 0 to 0.01 M was investigated spectrophotometrically at 620 nm at temperatures from 0 to 50 degrees C. AA was shown to be a useful spectroscopic probe for detecting carboxyl groups in HA macromolecules. The interaction between AA and HA was temperature sensitive and little AA-HA interaction was observed at temperatures higher than 30 degrees C. The interaction of HA with AA was seen to be electrostatic in nature. The maximum binding number decreased with decreasing NaCl concentration, and the absorbance sensitivity decreased with increasing NaCl concentration in aqueous solution. Self-interference from the AA in the AA-HA interaction caused an overestimate of the molar mass of hyaluronic acid. An improved method was proposed to estimate the molar mass of HA, and a molar mass of 1.219 x 10(6) Da was obtained with this improved method for HA.

Azure Stains↗
PubMed2005

Possible association of the MAG locus with schizophrenia in a Chinese Han cohort of family trios.

Neurotransmitter-based hypotheses have so far led to only moderate success in predicting new pathogenetic findings in etiology of schizophrenia. On the other hand, the more recent oligodendroglia hypotheses of this disorder have been supported by an increasing body of evidence. For example, the expression level of the myelin associated glycoprotein (MAG) gene has been shown to be significantly lower in schizophrenia patient groups compared to control groups. Such an effect might be a result of genetic variations of the MAG gene. In order to test this hypothesis, we genotyped four markers within the MAG locus in 413 trios sample of the Han Chinese using allele-specific PCR. None of the four markers revealed noticeable allelic significance. However, the four-marker and two-marker haplotypes covering components rs720309 and rs720308 were observed to be significantly associated with schizophrenia (P < 0.0001) in this study. In addition, we identified one common risk haplotype TA (rs720309-rs720308, present in 78.5% of the general population) that showed increased evidence of overtransmission from parents to affected offspring (P = 0.0001). The results demonstrated MAG might play a role in genetic susceptibility to schizophrenia. Furthermore, our finding of a possible association between the MAG locus and schizophrenia is in agreement with the hypotheses of oligodendrltic and myelination dysfunction.

Adult↗
PubMed2005

Evidence of increased oxidative damage in subjects with mild cognitive impairment.

OBJECTIVE: To determine if increased levels of oxidative damage are present in the brains of persons with mild cognitive impairment (MCI), a condition that often precedes Alzheimer disease (AD). METHODS: The authors assessed the amount of protein carbonyls, thiobarbituric acid-reactive substances (TBARS), and malondialdehyde in the superior and middle temporal gyri (SMTG) and cerebellum of short postmortem interval and longitudinally evaluated normal subjects and those with MCI and early AD. RESULTS: Elevated levels of protein carbonyls (approximately 25%), malondialdehyde (approximately 60%), and TBARS (approximately 210%) were observed in the SMTG of individuals with MCI and early AD vs normal control subjects. The elevation in TBARS was associated with the numbers of neuritic but not diffuse plaques. Levels of protein carbonyls increased as delayed verbal memory performance declined. CONCLUSION: Oxidative damage occurs in the brain of subjects with mild cognitive impairment, suggesting that oxidative damage may be one of the earliest events in the onset and progression of Alzheimer disease.

Aged↗
PubMed2005

Bulk motion of granular matter in an agitated cylindrical bed.

Experimental results are reported for the bulk motion induced in a bed of granular matter contained in a cylindrical pan with a flat bottom subjected to simultaneous vertical and horizontal vibrations. The motion in space of the moving pan is quantified. A number of distinct bulk dynamical modes are observed in which the particle bed adopts different shapes and motions. At the lowest pan excitation frequency omega , the bed forms a "heap," and rotates about the cylinder axis. As omega is increased, a more complex "toroidal" mode appears in which the bed takes the shape of a torus; in this mode, circulation occurs both about the cylinder axis, and also radially, with particles moving from the outer edge of the pan to the center on the top surface of the bed, and back to the outer edge along the pan bottom. At the highest omega , surface modulations ("surface waves" and "sectors") of the toroidal mode occur. The origin of this family of behavior in terms of the pan motion is discussed.

Journal Article↗
PubMed2005

Electron field emission characteristics and field evaporation of a single carbon nanotube.

Direct transmission electron microscope (TEM) observations of the field emission and evaporation process of emitting carbon nanotubes (CNTs) shown that the tip structure of the CNT is in general composed of irregular shaped graphitic sheets which extend typically more than 10 nm from the end of the CNT. It is found that the irregular shaped graphitic sheets at the tip of the CNT may greatly enhance the field emission characteristics of the CNT when compared with that having an ideal circular edge. The field evaporation of the CNT proceeds typically via the removal of the irregular shaped graphitic sheets from the tip of the CNT, and field emission characteristics of a CNT depend far more sensitively on the tip structure than on the geometric length of the CNT.

Microscopy, Electron, Transmission↗