Biomedical subjects

Wei Chen

Publications and source records attributed to Wei Chen.

At least 55 records · Page 3Linked to original sources

PubMed2006

Degenerated primer design to amplify the heavy chain variable region from immunoglobulin cDNA.

BACKGROUND: The amplification of variable regions of immunoglobulins has become a major challenge in the cloning of antibody genes, whether from hybridoma cell lines or splenic B cells. Using conventional protocols, the heavy-chain variable region genes often are not amplified successfully from the hybridoma cell lines. RESULTS: A novel method was developed to design the degenerated primer of immunoglobulin cDNA and to amplify cDNA ends rapidly. Polymerase chain reaction protocols were performed to recognize the VH gene from the hybridoma cell line. The most highly conserved region in the middle of the VH regions of the Ig cDNA was identified, and a degenerated 5'primer was designed, using our algorithms. The VH gene was amplified by both the 3'RACE and 5'RACE. The VH sequence of CSA cells was 399 bp. CONCLUSION: The new protocol rescued the amplifications of the VH gene that had failed under conventional protocols. In addition, there was a notable increase in amplification specificity. Moreover, the algorithm improved the primer design efficiency and was shown to be useful both for building VH and VL gene libraries and for the cloning of unknown genes in gene families.

Cell Line↗

PubMed2006

Noninvasive and three-dimensional imaging of CMRO(2) in rats at 9.4 T: reproducibility test and normothermia/hypothermia comparison study.

Ability to image cerebral metabolic rate of oxygen (CMRO(2)) is essential for studying the fundamental role of oxidative metabolism in brain function and disease. We have demonstrated recently that three-dimensional (3D) CMRO(2) images can be obtained in the rat brain during a 2-min (17)O(2) inhalation using the (17)O MR spectroscopic imaging (MRSI) approach at high field. The feasibility for establishing a completely noninvasive approach for imaging CMRO(2) has also been demonstrated. In this study, we further explored the feasibility of (17)O MRSI approach for performing repeated CMRO(2) measurements within a short period of time and evaluated the reproducibility of the repeated measurements. Subsequently, we applied the (17)O MRSI approach to measure CMRO(2) and cerebral blood flow (CBF) values at two brain temperatures in the alpha-chloralose anesthetized rat brain at 9.4 T. Finally, we tested the validity of simplified model for noninvasively determining CMRO(2) in normothermic and hypothermic rat brain. The results show (i) an excellent reproducibility among repeated measurements of 3D CMRO(2) images under the same physiologic condition; (ii) a 44% decrease of CMRO(2) across the rat brain at mild hypothermic (32 degrees C) condition as compared with normothermic (37 degrees C) condition; and (iii) a close correlation between CMRO(2) and CBF within a relatively wide physiologic range. This study demonstrates the capability of (17)O MRSI approach for noninvasively imaging CMRO(2) and its changes caused by physiologic perturbation. This approach, thus, should provide a promising neuroimaging modality for studying oxidative metabolism and bioenergetics associated with brain functions and diseases.

Animals↗

PubMed2006

Race (black-white) and gender divergences in the relationship of childhood cardiovascular risk factors to carotid artery intima-media thickness in adulthood: the Bogalusa Heart Study.

It has been established that childhood cardiovascular (CV) risk factors are predictive of adulthood vascular changes as measured by carotid intima-media thickness (IMT). However, whether this relationship is race- and gender-specific is not known. This aspect was examined in a black-white cohort of 868 adults (29% blacks, 42% males) aged 25-44 years who were examined at least twice in childhood for traditional CV risk factors with an average follow-up period of 26.4 years. The average value of the two earliest childhood measurements was used as the childhood value, standardized to age, race, and gender-specific z-score. Carotid IMT was measured by B-mode ultrasonography. The mean of the maximum carotid IMT readings of three right and three left far walls for common, bulb and internal segments was used. In univariate analysis, significant correlates of adulthood carotid IMT (standardized to age-, race- and gender-specific z-score) were, in the order of decreasing magnitude, triglyceride and LDL cholesterol in white males; systolic blood pressure, LDL cholesterol, and body mass index (BMI) in white females; systolic blood pressure in black males; BMI and systolic blood pressure in black females. In multivariate regression analysis, significant predictors of carotid IMT were triglycerides and LDL cholesterol in white males; systolic blood pressure and LDL cholesterol in white females; systolic blood pressure in black males; and BMI and LDL cholesterol in black females. In conclusion, the predictability of childhood CV risk factors for increased carotid IMT in adulthood varies by race and gender. The prevention implications of these findings need further investigation.

Adolescent↗

PubMed2006

Homozygosity mapping in consanguineous families reveals extreme heterogeneity of non-syndromic autosomal recessive mental retardation and identifies 8 novel gene loci.

Autosomal recessive gene defects are arguably the most important, but least studied genetic causes of severe cognitive dysfunction. Homozygosity mapping in 78 consanguineous Iranian families with nonsyndromic autosomal recessive mental retardation (NS-ARMR) has enabled us to determine the chromosomal localization of at least 8 novel gene loci for this condition. Our data suggest that in the Iranian population NS-ARMR is very heterogeneous, and they argue against the existence of frequent gene defects that account for more than a few percent of the cases.

Adult↗

PubMed2006

Spatial resolution of EEG cortical source imaging revealed by localization of retinotopic organization in human primary visual cortex.

The aim of the present study is to investigate the spatial resolution of electroencephalography (EEG) cortical source imaging by localizing the retinotopic organization in the human primary visual cortex (V1). Retinotopic characteristics in V1 obtained from functional magnetic resonance imaging (fMRI) study were used as reference to assess the spatial resolution of EEG since fMRI can discriminate small changes in activation in visual field. It is well known that the activation of the early C1 component in the visual evoked potential (VEP) elicited by pattern onset stimuli coincides well with the activation in the striate cortex localized by fMRI. In the present experiments, we moved small circular checkerboard stimuli along horizontal meridian and compared the activations localized by EEG cortical source imaging with those from fMRI. Both fMRI and EEG cortical source imaging identified spatially correlated activity within V1 in each subject studied. The mean location error, between the fMRI-determined activation centers in V1 and the EEG source imaging activation peak estimated at equivalent C1 components (peak latency: 74.8+/-10.6 ms), was 7 mm (25% and 75% percentiles are 6.45 mm and 8.4 mm, respectively), which is less than the change in fMRI activation map by a 3 degrees visual field change (7.8 mm). Moreover, the source estimates at the earliest major VEP component showed statistically good correlation with those obtained by fMRI. The present results suggest that the spatial resolution of the EEG cortical source imaging can correctly discriminate cortical activation changes in V1 corresponding to less than 3 degrees visual field changes.

Adult↗

PubMed2006

HP1 proteins are essential for a dynamic nuclear response that rescues the function of perturbed heterochromatin in primary human cells.

Cellular information is encoded genetically in the DNA nucleotide sequence and epigenetically by the "histone code," DNA methylation, and higher-order packaging of DNA into chromatin. Cells possess intricate mechanisms to sense and repair damage to DNA and the genetic code. However, nothing is known of the mechanisms, if any, that repair and/or compensate for damage to epigenetically encoded information, predicted to result from perturbation of DNA and histone modifications or other changes in chromatin structure. Here we show that primary human cells respond to a variety of small molecules that perturb DNA and histone modifications by recruiting HP1 proteins to sites of altered pericentromeric heterochromatin. This response is essential to maintain the HP1-binding kinetochore protein hMis12 at kinetochores and to suppress catastrophic mitotic defects. Recruitment of HP1 proteins to pericentromeres depends on histone H3.3 variant deposition, mediated by the HIRA histone chaperone. These data indicate that defects in pericentromeric epigenetic heterochromatin modifications initiate a dynamic HP1-dependent response that rescues pericentromeric heterochromatin function and is essential for viable progression through mitosis.

Cell Cycle Proteins↗

PubMed2006

Blockade of STAT3 by antisense oligonucleotide in TNBS-induced murine colitis.

BACKGROUND AND AIMS: The expression of signal transducers and activators of transcription 3 (STAT3) is increased in Crohn's disease (CD), and nuclear translocated STAT3 is also found in the disease. However, the role of STAT3 protein on the pathogenesis of CD is not clear. This study was executed to investigate the role of STAT3 protein on the pathogenesis of trinitrobenzene sulfonic acid (TNBS)-induced colitis, the pathogenesis of which is CD-like. METHODS: TNBS-induced colitis was produced, and STAT3 antisense oligonucleotide was administrated intracolonically during the early phase of colitis. The mice were killed 7 days later, and the expressions of STAT3 and phosphorylated STAT3 were identified by Western blot and immunofluorescence. The lamina propria mononuclear cells (LPMCs) were isolated freshly, and the percent of cell death and the expressions of Bcl-2 and Bax in LPMCs were evaluated. Colonic tissue damage and the production of inflammatory cytokines were measured also. RESULTS: Administration of STAT3 antisense oligonucleotide effectively inhibited STAT3 expression and phosphorylation in inflamed colonic mucosa of colitis. The mice that were administered STAT3 antisense oligonucleotide showed less colonic tissue damage with decreased production of inflammatory cytokines such as TNF-alpha and INF-gamma in mucosa compared with that of those TNBS-induced colitis. Administration of STAT3 antisense oligonucleotide successfully induced apoptosis of LPMCs and counteracted the unbalanced expressions of Bcl-2 and Bax in LPMCs from colitis. CONCLUSIONS: STAT3 activation may play an important role in the inflammatory process of TNBS-induced colitis, and inhibiting STAT3 activation during the early phase of the inflammatory response may have a beneficial effect on the colitis.

Animals↗

PubMed2006

C60 on SiC nanomesh.

A SiC nanomesh is used as a nanotemplate to direct the epitaxy of C60 molecules. The epitaxial growth of C60 molecules on SiC nanomesh at room temperature is investigated by in situ scanning tunneling microscopy, revealing a typical Stranski-Krastanov mode (i.e., for the first one or two monolayers, it is a layer-by-layer growth or 2-D nucleation mode; at higher thicknesses, it changes to island growth or a 3-D nucleation mode). At submonolayer (0.04 and 0.2 ML) coverage, C60 molecules tend to aggregate to form single-layer C60 islands that mainly decorate terrace edges, leaving the uncovered SiC nanomesh almost free of C60 molecules. At 1 ML C60 coverage, a complete wetting layer of hexagonally close-packed C60 molecules forms on top of the SiC nanomesh. At higher coverage from 4.5 ML onward, the C60 stacking adopts a (111) oriented face-centered-cubic (fcc) structure. Strong bright and dim molecular contrasts have been observed on the first layer of C60 molecules, which are proposed to originate from electronic effects in a single-layer C60 island or the different coupling of C60 molecules to SiC nanomesh. These STM molecular contrast patterns completely disappear on the second and all the subsequent C60 layers. It is also found that the nanomesh can be fully recovered by annealing the C60/SiC nanomesh sample at 200 degrees C for 20 min.

Journal Article↗

PubMed2006

Correction of aberrant imprinting of IGF2 in human tumors by nuclear transfer-induced epigenetic reprogramming.

Loss of genomic imprinting of insulin-like growth factor II (IGF2) is a hallmark of many human neoplasms. We attempted to correct this aberrant epigenotype by transferring nuclei from human tumor cells that showed loss of IGF2 imprinting into enucleated mouse and human fibroblasts that had maintained normal IGF2 imprinting. After nuclear transfer, the abnormal biallelic expression of IGF2 in tumor nuclei transiently converted to normal monoallelic imprinted expression in the reconstructed diploid cells. In tetraploid hybrid cells, however, normal IGF2 imprinting was permanently restored in the tumor genome. Inhibition of the synthesis of putative trans imprinting factors with cycloheximide led to loss of IGF2 imprinting in normal cultured fibroblasts, suggesting that normal cells produce proteins that act in trans to induce or maintain genomic imprinting. These data demonstrate that an abnormal tumor epigenotype can be corrected by in vitro reprogramming, and suggest that loss of imprinting is associated with the loss of activity of non-CTCF trans imprinting factor(s) that are either inactivated or mutated in tumors.

Animals↗

PubMed2006

Expression of MHC I and NK ligands on human CD133+ glioma cells: possible targets of immunotherapy.

Mounting evidence suggests that gliomas are comprised of differentiated tumor cells and brain tumor stem cells (BTSCs). BTSCs account for a fraction of total tumor cells, yet are apparently the sole cells capable of tumor initiation and tumor renewal. BTSCs have been identified as the CD133-positive fraction of human glioma, whereas their CD133-negative daughter cells have limited proliferative ability and are not tumorogenic. It is well established that the bulk tumor mass escapes immune surveillance by multiple mechanisms, yet little is known about the immunogenicity of the CD133-positive fraction of the tumor mass. We investigated the immunogenicity of CD133-positive cells in two human astrocytoma and two glioblastoma multiforme samples. Flow cytometry analyses revealed that the majority of CD133-positive cells do not express detectable MHC I or natural killer (NK) cell activating ligands, which may render them resistant to adaptive and innate immune surveillance. Incubating CD133-positive cells in interferon gamma (INF-gamma) significantly increased the percentage of CD133-positive cells that expressed MHC I and NK cell ligands. Furthermore, pretreatment of CD133-positive cells with INF-gamma rendered them sensitive to NK cell-mediated lysis in vitro. There were no consistent differences in immunogenicity between the CD133-positive and CD133-negative cells in these experiments. We conclude that CD133-posistive and CD133-negative glioma cells may be similarly resistant to immune surveillance, but that INF-gamma may partially restore their immunogenicity and potentiate their lysis by NK cells.

AC133 Antigen↗

PubMed2006

Sensitive amperometric immunosensing using polypyrrolepropylic acid films for biomolecule immobilization.

An electrochemical immunosensor was constructed using an electropolymerized pyrrolepropylic acid (PPA) film with high porosity and hydrophilicity. A high density of carboxyl groups of PPA was used to covalently attach protein probes, leading to significantly improved detection sensitivity compared with conventional entrapment methods. As a model, anti-mouse IgG was covalently immobilized or entrapped in the PPA film and used in a sandwich-type alkaline phosphatase-catalyzing amperometric immunoassay with p-aminophenyl phosphate as the substrate. With covalent binding, the detection limit for IgG in PBS buffer, pH 7.4, was 100 pg/mL with a dynamic range of 5 orders of magnitude. The covalent bonding mode in the carbonate-bicarbonate buffer, pH 9.6, further brought down the detection limit to 20 pg/mL with remarkable selectivity.

Biosensing Techniques↗

PubMed2006

Obligatory role of cardiac nerves and alpha1-adrenergic receptors for the second window of ischemic preconditioning in conscious pigs.

We tested the hypothesis that cardiac nerves may mediate ischemic preconditioning. Pigs were chronically instrumented to measure aortic, left atrial and left ventricular pressures, and regional myocardial function (wall thickening). Hemodynamic variables, area at risk, and tissue blood flows (radioactive microspheres) were similar among groups. Myocardial infarct size following 60 minutes coronary artery occlusion and 4 days reperfusion, expressed as a fraction of the area at risk, was 42+/-4.0%, in innervated pigs and similar in pigs with regional cardiac denervation (CD, 41+/-2.5%). Infarct size in innervated pigs during the first window of preconditioning (first window) was markedly reduced (6+/-1.8%, P<0.01), as it was in the second window of preconditioning (second window) (16+/-3.3%, P<0.01). Although infarct size was still reduced in pigs with CD and first window preconditioning (9+/-1.8%, P<0.01), the protective effects of second window were abrogated in pigs with CD resulting in an infarct size of 38+/-5.6%. In another group of innervated pigs during pharmacological alpha(1)-adrenergic receptor (AR) blockade, infarct size was also not reduced during the second window (48+/-3.2%). Additionally, Western blot analysis of inducible nitric oxide synthase and cyclooxygenase-2 proteins demonstrated significant (P<0.05) upregulation following the second window in innervated pigs, but not in pigs with CD or alpha(1)-AR blockade. Thus, the mechanism of protection during the second window, but not the first window, appears to be dependent on cardiac nerves and alpha(1)-AR stimulation.

Adrenergic alpha-1 Receptor Antagonists↗

PubMed2006

Dithiocarbamate-capped silver nanoparticles.

Nanometer-sized silver particles were synthesized by using didecylamine dithiocarbamates as the protecting ligands. With control of the initial ligand-metal feed ratios, the core diameter of the resulting particles was found to vary from about 5 to 2.5 nm, as determined by transmission electron microscopic measurements. The core size dispersity was also found to decrease with increasing feed ratio. In UV-visible spectroscopic studies, the particle surface plasmon resonance peak diminished in intensity as the particle core size decreased, whereas in electrochemical measurements, smaller sized particles gave rise to well-defined quantized charging voltammetric features, in contrast to the featureless responses with the larger particles. Such single electron-transfer behaviors were consistent with those observed in STM measurements involving individual nanoparticles. Overall, this study provides an effective approach to the synthesis of stable nanometer-sized silver nanoparticles with interesting electronic and electrochemical properties.

Journal Article↗

PubMed2006

In vivo 31P MRS of human brain at high/ultrahigh fields: a quantitative comparison of NMR detection sensitivity and spectral resolution between 4 T and 7 T.

The primary goal of this study was to establish a rigorous approach for determining and comparing the NMR detection sensitivity of in vivo 31P MRS at different field strengths (B0). This was done by calculating the signal-to-noise ratio (SNR) achieved within a unit sampling time at a given field strength. In vivo 31P spectra of human occipital lobe were acquired at 4 and 7 T under similar experimental conditions. They were used to measure the improvement of the human brain 31P MRS when the field strength increases from 4 to 7 T. The relaxation times and line widths of the phosphocreatine (PCr) resonance peak and the RF coil quality factors (Q) were also measured at these two field strengths. Their relative contributions to SNR at a given field strength were analyzed and discussed. The results show that in vivo 31P sensitivity was significantly improved at 7 T as compared with 4 T. Moreover, the line-width of the PCr resonance peak showed less than a linear increase with increased B0, which leads to a significant improvement in 31P spectral resolution. These findings indicate the advantage of high-field strength to improve in vivo 31P MRS quality in both sensitivity and spectral resolution. This advantage should improve the reliability and applicability of in vivo 31P MRS in studying high-energy phosphate metabolism, phospholipid metabolism and cerebral biogenetics in the human at both normal and diseased states noninvasively. Finally, the approach used in this study for calculating in vivo 31P MRS sensitivity provides a general tool in estimating the relative NMR detection sensitivity for any nuclear spin at a given field strength.

Adult↗

PubMed2006

Supercritical fluid chromatography reduction of hydrogen/deuterium back exchange in solution-phase hydrogen/deuterium exchange with mass spectrometric analysis.

The single biggest problem with solution-phase H/D exchange as a mass spectrometric probe of surface exposure in a protein (or protein complex) is back-exchange of H for D after the initial H/D exchange has been quenched. Back-exchange results in loss of pertinent data and also greatly hampers data analysis. Previously, very fast, cold (0-4 degrees C) HPLC was performed to help reduce back-exchange, but calculated back-exchange still averages approximately 30%. In this report, supercritical fluid chromatography replaces HPLC as the desalting/separation technique prior to mass analysis, providing a dramatic reduction in back-exchange compared to the fast, cold HPLC methods.

Amino Acid Sequence↗

PubMed2006

Electric field-induced changes in membrane proteins charge movement currents.

Our previous study showed that thermal effects induced by Joule heating did not play the pivotal role in damage of membrane proteins when cell membranes were shocked by a pulsed membrane potential up to 500 mV. Our analytical study of ion channel currents further indicated that a brief electric shock may cause protein conformational damage in the channel gating system, resulting in a reduction in the number of limiting gating charge particles. In this paper, we present the results of our study into electric shock-induced changes in the intramembrane charge movement currents. We found that a brief electric shock may significantly alter the characteristics of the charge movement currents of the membrane proteins, including reducing the magnitudes of two components Q(beta) and Q(gamma), broadening the hump shape of Q(gamma), and increasing its time delay. This study suggests that a brief intensive electric shock may cause proteins to structurally alter, reducing the amount of movable charge particles and therefore decreasing the protein functions. These results indicate that electro-coupled structural damage in membrane proteins is an important mechanism involved in electrical injury, especially in a field range not sufficient to cause thermal damage.

Animals↗

PubMed2006

[The clinical significance of expression and amplification of FGF3 in bladder transitional cell carcinoma].

OBJECTIVE: To investigate the amplification and expression of FGF3 in bladder transitional cell carcinoma (BTCC) and its clinical significance. METHODS: Immunohistochemistry (IHC) and Fluorescence In Situ Hybridization (FISH) methods were used to examine the protein expression and amplification of FGF3 in a tissue microarray (TMA) of 100 BTCCs and 30 adjacent normal bladder mucosas, so as to analyze their correlation and association with patient's clinico-pathological features. RESULTS: In this study, none of the normal bladder mucosas were detected FGF3 positivity, while in 89 informative BTCCs, 20 (22%) cases were observed positive expression of FGF3 protein, and it was significantly more frequently to occur in BTCCs of poor-differentiation (Grade 3), later clinical stage (T2-4) and tumor in >or= 3 cm in diameter (P < 0.05). In FISH study, 10 of the 63 (16%) informative BTCCs were observed amplification of FGF3 and it was significantly associated with BTCC's tumor size and clinical stage (P < 0.05). In addition, 10 BTCCs with amplification of FGF3 in this study were all detected positive expression of FGF3 protein, while in the remaining 53 BTCCs without amplification of FGF3, only 3 (6%) cases were observed FGF3 protein positivity. CONCLUSION: The up-regulated expression of FGF3 in BTCC was associated closely with tumor's malignant clinical phenotypes, and it might be involved in the malignant progression of parts of BTCC. The amplification of FGF3 gene might be a predominant mechanism of increased expression of FGF3 protein in BTCC.

Carcinoma, Transitional Cell↗

PubMed2006

Not polymorphism but methylation of class II transactivator gene promoter IV associated with persistent HBV infection.

BACKGROUND: Class II transactivator (CIITA) is the major rate-limiting regulator for expression of class II major histocompability complex (MHC-II). Human CIITA gene expression is controlled by four distinct promoters (pIto pIV). OBJECTIVE: To evaluate the relationship among polymorphism and methylation status of CIITA gene promoters and persistent hepatitis B virus (HBV) infection. METHODS: We recruited 21 patients with hepatocellular carcinoma (HCC), 45 liver cirrhosis (LC), 65 chronic hepatitis B (CHB), 26 acute hepatitis B (AHB) and 95 healthy blood donors. Polymorphism of CIITA gene promoters was assayed by PCR-SSCP-sequencing. Bioinformatics analysis was employed to predict the existence of CpG islands. Methylation-specific PCR (MSP) was used to detect the methylation status of CIITA gene pIV. RESULTS: No sequence differences were observed at CIITA genes pI, III and IV among HCC, LC, CHB, AHB patients and healthy controls. No CpG islands were found in the pI, pII and pIII sequences, but there was a CpG island in pIV. The frequency of methylated POV was not significantly different within persistent HBV infection groups (patients with HCC, LC or CHB). Significance was found between the persistent infection group and acute HBV infection or healthy controls. CONCLUSIONS: CIITA gene promoter sequences are conserved. PIV is highly methylated and associated with host susceptibility to HBV persistent infection.

DNA Methylation↗