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Biomedical subjects

Wei Lin

Publications and source records attributed to Wei Lin.

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

A two-stage linkage analysis of Chinese schizophrenia pedigrees in 10 target chromosomes.

We performed a two-stage linkage scan involving 25 Chinese schizophrenia families, focusing on 10 target chromosomes which have already been the subject of considerable research. We initially genotyped 237 individuals with 186 markers, five candidate regions were then chosen for fine mapping and 49 additional markers were genotyped. In region 1q21-23, a maximum multipoint HLOD (HLOD=2.38) was observed between D1S484 and D1S2705, under the dominant model. In region 5q35, dominant HOLD of 2.36, 2.04, and 2.31 were found at marker D5S2030, D5S408, and D5S2006, respectively. Consistent multipoint results also supported linkage to this region under the same dominant model, with a highest HOLD of 2.47. Furthermore, single-point HLODs (HLOD=1.95 at D22S274, and HLOD=1.91 at D22S1157) were found in region 22q13, under the dominant model. Evidence from these three regions satisfied the criteria for suggestive linkage and should help in identifying schizophrenia susceptibility genes.

China↗
PubMed2006

Structural characterizations and electronic properties of Ti-doped SnO2(110) surface: a first-principles study.

The Ti-doped SnO2(110) surface has been investigated by using first-principles method with a slab model. The geometrical optimizations and band-structure calculations have been performed for four possible doping models. Our results indicate that the substitution of Ti for sixfold-coordinated Sn atom at the top layer is most energetically favorable. Compared to the undoped surface, those Sn and O atoms located above Ti atom tend to move toward the bulk side. Besides the surface relaxations, the doping of Ti has significant influences on the electronic structures of SnO2(110) surface, including the value and position of minimum band gap, the components of valence and conduction bands, the distributions of the charge densities, and the work function of the surface. Furthermore, the effects introduced by the substitution of Ti atom observed in the experiments can be well explained when the sixfold-coordinated Sn atom at the first layer is replaced by Ti atom.

Journal Article↗
PubMed2006

Heteroaggregation in binary mixtures of oppositely charged colloidal particles.

Heteroaggregation (or heterocoagulation) rate constants have been measured in mixtures of well-characterized colloidal particles of opposite charge with multiangle static and dynamic light scattering. This technique permits routine measurements of absolute heteroaggregation rate constants, also in the presence of homoaggregation. Particularly with multiangle dynamic light scattering, one is able to estimate absolute heteroaggregation rate constants accurately in the fast aggregation regime for the first time. Heteroaggregation rate constants have also been measured over a wide range of parameters, for example, ionic strength and different surface charge densities. Amidine latex particles, sulfate latex particles, and silica particles have been used for these experiments, and they were well characterized with respect to their charging and homoaggregation behavior. It was shown that heteroaggregation rate constants of oppositely charged particles increase slowly with decreasing ionic strength, and provided the surface charge is sufficiently large, the rate constant is largely independent of the surface charge. These trends can be well described with DLVO theory without adjustable parameters.

Journal Article↗
PubMed2006

Studying the mechanosensitivity of voltage-gated channels using oocyte patches.

The mechanosensitivity of voltage-gated (VG) channels is of biophysical, physiological. and pathophysiological interest. Xenopus oocytes offer a critical advantage for investigating the electrophysiology of recombinant VG channels subjected to membrane stretch, namely, the ability to monitor macroscopic current from membrane patches. High-density channel expression in oocytes makes for macroscopic current in conventional-size, mechanically sturdy patches. With the patch configuration, precisely the same membrane that is voltage-clamped is the membrane subjected to on-off stretch stimuli. With patches, meaningful stretch dose responses are possible. Experimental design should facilitate within-patch comparisons wherever possible. The mechanoresponses of some VG channels depend critically on patch history. Methods for minimizing and coping with interference from endogenous voltage-dependent and stretch-activated endogenous channels are described.

Animals↗
PubMed2006

Identification of norharman as the cytotoxic compound produced by the sponge (Hymeniacidon perleve)-associated marine bacterium Pseudoalteromonas piscicida and its apoptotic effect on cancer cells.

Marine invertebrates harbour a wealth of micro-organisms in their bodies. Most of these micro-organisms can catabolize antibiotic compounds as chemical-defence compounds. These compounds not only play an important protective role for their producer and for their hosts, but also have high potential in medicinal applications. In order to discover natural anticancer products, 29 marine bacterial strains have been isolated from the sponge Hymeniacidon perleve, samples of which were collected from the intertidal zone during low tide off Nanji island in Eastern China. By means of a cytotoxicity bioassay, one strain, NJ6-3-1, with significant cytotoxic activity, was selected for culture in a 30-litre fermentation tank. The major cytotoxic compound in the metabolites of NJ6-3-1, separated by means of a bioassay-guided fractionation process, has been identified as norharman (a beta-carboline alkaloid) by electron-impact MS and NMR analyses. Norharman showed cytotoxicity towards both the HeLa cervical-cancer cell line and the BGC-823 stomach-cancer cell line, with an IC(50) of 5 microg/ml. Several methods were used to study the mechanism by which norharman is cytotoxic to HeLa cells. By means of an Acridine Orange/ethidium bromide dual-staining assay, condensation of chromatin was observed. A TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling) assay showed degradation of DNA. Flow-cytometric analysis indicated that norharman could arrest cells at the G(2)/M phase of the cell cycle. These results demonstrate the cytotoxic mechanism of norharman involves the induction of apoptosis in HeLa cells.

Animals↗
PubMed2006

Using white noise to enhance synchronization of coupled chaotic systems.

In the paper, complete synchronization of two chaotic oscillators via unidirectional coupling determined by white noise distribution is investigated. It is analytically proved that chaos synchronization could be achieved with probability one merely via white-noise-based coupling. The established theoretical result supports the observation of an interesting phenomenon that a certain kind of white noise could enhance chaos synchronization between two chaotic oscillators. Furthermore, numerical examples are provided to illustrate some possible applications of the theoretical result.

Journal Article↗
PubMed2006

Determination of ultrasound phase velocity in trabecular bone using time dependent phase tracking technique.

Ultrasound velocity is one of the key acoustic parameters for noninvasive diagnosis of osteoporosis. Ultrasound phase velocity can be uniquely measured from the phase of the ultrasound signal at a specified frequency. Many previous studies used fast Fourier transform (FFT) to determine the phase velocity, which may cause errors due to the limitations of FFT. The new phase tracking technique applied an adaptive tracking algorithm to detect the time dependent phase and amplitude of the ultrasound signal at a specified frequency. This overcame the disadvantages of FFT to ensure the accuracy of the ultrasound phase velocity. As a result, the new method exhibited high accuracy in the measurement of ultrasound phase velocity of two phantom blocks with the error less than 0.4%. 41 cubic trabecular samples from sheep femoral condyles were used in the study. The phase velocity of the samples using the new method had significantly high correlation to the bulk stiffness of the samples (r = 0.84) compared to the phase velocity measured using fast Fourier transform FFT (r = 0.14). In conclusion, the new method provided an accurate measurement of the ultrasound phase velocity in bone.

Algorithms↗
PubMed2006

[Application of three-dimensional contrast-enhanced magnetic resonance angiography in renal artery angiography].

OBJECTIVE: To increase the probability of successful renal artery angiography with a three-dimensional contrast-enhanced magnetic resonance angiography (3D CE-MRA). METHODS: 3D CE-MRA was performed in 33 patients with hypertension. To calculate the scan delay time, a testing contrast agent bolus of 2 ml was injected for single sagittal slice real-time scanning, followed by oblique coronal 3D Fast TOF SPGRE. With maximum intensity projection, a set of images was acquired. RESULTS: Exact scan delay time was obtained in all the cases from which clear images were acquired with the exception of two cases in which failure of breath-holding occurred during the scanning. CONCLUSION: This examination enhances the performance by adopting elliptical-centric k-space recording for data acquisition for the center in k-space at the beginning of acquisition, and utilizing preceding testing bolus injection and signal intensity/time curve for determining the scan delay time, using slice selection and multiview image reconstruction.

Adolescent↗
PubMed2005

A theoretical study on the electronic structures of TiO2: Effect of Hartree-Fock exchange.

The effects of the Fock exchange on the geometries and electronic structures of TiO2 have been investigated by introducing a portion of Hartree-Fock (HF) exchange into the traditional density functional. Our results indicate that the functional with 13% HF exchange can correctly predict the band gap and the electronic structures of rutile TiO2, and such an approach is also suitable to describe the structural and electronic properties of anatase and brookite phases. For the TiO2 (110) surfaces, although the surface relaxations are insensitive to the variation of HF exchange, there are larger effects on the positions of the occupied surface-induced states. When 13% HF exchange is employed, the predicted band gap of the perfect surface and position of defect state of the reduced surface are consistent with the experimental values. Moreover, the electronic structures of TiO2 (110) surface are carefully reexamined by using this hybrid density functional method.

Journal Article↗
PubMed2005

Light-scattering form factors of asymmetric particle dimers from heteroaggregation experiments.

Measurements of form factors of asymmetric particle dimers composed of oppositely charged polystyrene latex particles are presented. These measurements are based on time-resolved static and dynamic light scattering on dilute aggregating aqueous suspensions. The experimental form factors are compared with independent calculations based on the superposition T-matrix method and Rayleigh-Debye-Gans (RDG) approximation. While the RDG approximation is found to be reliable only up to particle diameters of about 250 nm, the superposition T-matrix method is very accurate for all types of dimers investigated. The present results show clearly the appropriateness of the superposition T-matrix method to estimate the optical properties of colloidal particles in the micrometer range reliably.

Journal Article↗
PubMed2005

Allelic variation in gene expression identified through computational analysis of the dbEST database.

Differential expression between the two alleles of an individual and between people with different genotypes has been commonly observed. Quantitative differences in gene expression between people may provide the genetic basis for the phenotypic difference between individuals and may be the primary cause of complex diseases. In this paper, we developed a computational method to identify genes that displayed allelic variation in gene expression in human EST libraries. To model allele-specific gene expression, we first identified EST libraries in which both A and B alleles were expressed and then identified allelic variation in gene expression based on the EST counts for each allele using a binomial test. Among 1107 SNPs that had a sufficient number of ESTs for the analysis, 524 (47%) displayed allelic variation in at least one cDNA library. We verified experimentally the allelic variation in gene expression for 6 of these SNPs. The frequency of allelic variation observed in EST libraries was similar to the previous studies using the SNP chip and primer extension method. We found that genes that displayed allelic variation were distributed throughout the human genome and were enriched in certain chromosome regions. The SNPs and genes identified in this study will provide a rich source for evaluating the effects of those SNPs and associated haplotypes in human health and diseases.

Alleles↗
PubMed2005

Design, synthesis and bioactivities of TAR RNA targeting beta-carboline derivatives based on Tat-TAR interaction.

A series of new beta-carboline derivatives 3-14 bearing guanidinium group or amino group-terminated side chain targeting the TAR RNA were designed and synthesized. Molecular modeling studies indicated that the minimal interaction energy was obtained for compound 11, which contained the optimal linker of three methylene groups and the terminal guanidinium group interacted with the three-base bulge of TAR element by hydrogen bonds, which were the main contributor to the stability of drug-TAR RNA complex. To evaluate the ability of compounds 3-14 to block Tat-TAR interaction, we established a rapid, sensitive quantitative bioassay based on transient cotransfection of a Tat expression vector and a long terminal repeat region-chloramphenicol acetyltransferase (LTR-CAT) reporter construct in eukaryotic cells, monitoring the influence of the compounds on CAT expression levels with ELISA. Compounds 11 and 12 were the most active compounds of all in inhibiting Tat-TAR interaction bearing the terminal guanidinium group, and the optimal linker of the three methylene groups. Both compounds also exhibited anti-HIV-1 activity in MT4 cells, and their LD50 values of intraperitoneal acute toxicity for mice were 320.0 and 104.3 mg/kg, respectively. Furthermore, the results of capillary electrophoresis (CE) suggest that it is through targeting TAR RNA that this series of compounds block the Tat-TAR interaction.

Animals↗
PubMed2005

[Therapeutic effects of chemotherapeutic regimens containing pirarubicin on the treatment of high-risk or refractory and relapsed acute leukemia in adults].

OBJECTIVE: To evaluate the therapeutic effects of chemotherapeutic regimen containing pirarubicin (THP) on the treatment of high-risk or refractory and relapsed acute leukemia (AL) in adults. METHODS: Forty patients with high-risk or refractory and relapsed AL, 26 males and 14 females, aged 33 (14-63) received treatment regimens with THP: TA regimen [THP + cytosine-arabinoside (Ara-C)] for acute myeloid leukemia (AML) and TAOP regimen [THP + Ara-C + vincristine (VCR) + prednisone (Pred)] for acute lymphocytic leukemia (ALL) or biphenotype-AL. Forty matched patients received mitoxantron (MIT) + Ara-C for AML or MIT + Ara-C + VCR + Pred for ALL and biphenotype AL as controls. The therapeutic effects were observed. RESULTS: The complete remission (CR) rate was 47.5% vs 45% (P > 0.05), partial response (PR) rate was 25% vs 20% (P > 0.05), and overall response (OR) rate was 72.5% vs 65% (P > 0.05) in the treatment group and control group. The continuous CR time was 528 days in the treatment group, significantly longer than in the control group (463 days, P < 0.05). Marrow suppression was more serious in the treatment group. The patients in the treatment group had higher incidence of infections (P < 0.05). The time with sustained recovery of platelet number was 13.9 days in the treatment group, significantly longer than in the control group (P < 0.05). CONCLUSION: Regimens with THP are more effective on treatment of high-risk or refractory and relapsed AL in adults, however, with more serious marrow suppression and higher incidence of infection.

Adolescent↗
PubMed2005

The Genomes of Oryza sativa: a history of duplications.

We report improved whole-genome shotgun sequences for the genomes of indica and japonica rice, both with multimegabase contiguity, or almost 1,000-fold improvement over the drafts of 2002. Tested against a nonredundant collection of 19,079 full-length cDNAs, 97.7% of the genes are aligned, without fragmentation, to the mapped super-scaffolds of one or the other genome. We introduce a gene identification procedure for plants that does not rely on similarity to known genes to remove erroneous predictions resulting from transposable elements. Using the available EST data to adjust for residual errors in the predictions, the estimated gene count is at least 38,000-40,000. Only 2%-3% of the genes are unique to any one subspecies, comparable to the amount of sequence that might still be missing. Despite this lack of variation in gene content, there is enormous variation in the intergenic regions. At least a quarter of the two sequences could not be aligned, and where they could be aligned, single nucleotide polymorphism (SNP) rates varied from as little as 3.0 SNP/kb in the coding regions to 27.6 SNP/kb in the transposable elements. A more inclusive new approach for analyzing duplication history is introduced here. It reveals an ancient whole-genome duplication, a recent segmental duplication on Chromosomes 11 and 12, and massive ongoing individual gene duplications. We find 18 distinct pairs of duplicated segments that cover 65.7% of the genome; 17 of these pairs date back to a common time before the divergence of the grasses. More important, ongoing individual gene duplications provide a never-ending source of raw material for gene genesis and are major contributors to the differences between members of the grass family.

Base Sequence↗
PubMed2005

Crystal structure of the virulence gene activator AphA from Vibrio cholerae reveals it is a novel member of the winged helix transcription factor superfamily.

AphA is a member of a new and largely uncharacterized family of transcriptional activators that is required for initiating virulence gene expression in Vibrio cholerae, the causative agent of the frequently fatal epidemic diarrheal disease cholera. AphA activates transcription by an unusual mechanism that appears to involve a direct interaction with the LysR-type regulator AphB at the tcpPH promoter. As a first step toward understanding the molecular basis for tcpPH activation by AphA and AphB, we have determined the crystal structure of AphA to 2.2 angstrom resolution. AphA is a dimer with an N-terminal winged helix DNA binding domain that is architecturally similar to that of the MarR family of transcriptional regulators. Unlike this family, however, AphA has a unique C-terminal antiparallel coiled coil domain that serves as its primary dimerization interface. AphA monomers are highly unstable by themselves and form a linked topology, requiring the protein to partially unfold to form the dimer. The structure of AphA also provides insights into how it cooperates with AphB to activate transcription, most likely by forming a heterotetrameric complex at the tcpPH promoter.

Amino Acid Sequence↗
PubMed2005

Study on the interactions between anti-HIV-1 active compounds with trans-activation response RNA by affinity capillary electrophoresis.

The study on the interactions between two anti-human immunodeficiency virus type 1 (anti-HIV-1) active compounds with trans-activation response (TAR) RNA by affinity capillary electrophoresis (ACE) with UV absorbance detection is presented. The results showed that the novel active molecules could interact with TAR RNA and inhibit the reproduce process of HIV-1. The binding constants were estimated by the change of migration time of the analytes through the change of concentrations of TAR RNA in the buffer solution. The yielded binding constants of 8.87 x 10(3)M(-1) for active compound C(3) and 8.42 x 10(3)M(-1) for MC(3) at 20.0 degrees C, 0.626 x 10(3)M(-1) and 0.644 x 10(3)M(-1) at 37.0 degrees C, respectively. The thermodynamic parameters Delta H and DeltaS were obtained and shown that both hydrophobic and electrostatic interaction played roles in the binding processes. The results showed that the presented method was an easy and simple method to evaluate the interaction of small molecules with some bioactive materials.

Anti-HIV Agents↗
PubMed2005

Synergistic activity of Sef and Sprouty proteins in regulating the expression of Gbx2 in the mid-hindbrain region.

Sef and Sprouty proteins function as feedback antagonists of fibroblast growth factor (Fgf) signaling in zebrafish embryos. To study the role of Sef in mice, we generated Sef homozygous mutant animals. These animals are viable and show normal expression of mid-hindbrain genes at embryonic days 8.5 and 9.5. To investigate the possibility of functional synergism between Sef and Sprouty proteins, we electroporated Sprouty2(Y55A), which functions in a dominant-negative manner in tissue culture cells into the mid-hindbrain region of wildtype and Sef mutant embryos. The expression pattern of Gbx2, a downstream target of Fgf signaling, was expanded or shifted in electroporated embryos, and this effect was significantly enhanced in the Sef mutant background. Altogether, our results demonstrate that Sef and Sproutys function synergistically to regulate Gbx2 expression in the anterior hindbrain.

Adaptor Proteins, Signal Transducing↗