Biomedical subjects

L Wang

Publications and source records attributed to L Wang.

At least 199 records · Page 11Linked to original sources

PubMed2004

Stress and dysmenorrhoea: a population based prospective study.

BACKGROUND: Dysmenorrhoea is the most common gynaecological disorder in women of reproductive age. Despite the association between stress and pregnancy outcomes, few studies have examined the possible link between stress and dysmenorrhoea. AIMS AND METHODS: Using a population based cohort of Chinese women, the independent effect of women's perceived stress in the preceding menstrual cycle on the incidence of dysmenorrhoea in the subsequent cycle was investigated prospectively. The analysis included 1160 prospectively observed menstrual cycles from 388 healthy, nulliparous, newly married women who intended to conceive. The perception of stress and the occurrence of dysmenorrhoea in each menstrual cycle were determined from daily diaries recorded by the women. RESULTS: After adjustment for important covariates, the risk of dysmenorrhoea was more than twice as great among women with high stress compared to those with low stress in the preceding cycle (OR = 2.4; 95% CI 1.4 to 4.3). The risk of dysmenorrhoea was greatest among women with both high stress and a history of dysmenorrhoea compared to women with low stress and no history of dysmenorrhoea (OR = 10.4, 95% CI 4.9 to 22.3). Stress in the follicular phase of the preceding cycles had a stronger association with dysmenorrhoea than stress in the luteal phase of the preceding cycles. CONCLUSION: This study shows a significant association between stress and the incidence of dysmenorrhoea, which is even stronger among women with a history of dysmenorrhoea.

Adult↗

PubMed2004

[Quantification of gender specific thermal sensory and pain threshold before and after laser needle stimulation].

Quantitative thermal sensory and pain threshold testing (QST) was performed in 29 adult healthy volunteers (mean age 24.2 +/- 2.7 years; range: 18-29 years; 20 females, 9 males) using the Thermal Sensory Analyser TSA-II (Medoc Advanced Medical Systems, Ramat Yishai, Israel, and Minneapolis, Minnesota, USA) before and after laser needle acupuncture and placebo stimulation, respectively. Significant (p < or = 0,001; t-test) gender-specific differences were seen on cold pain threshold analysis. No significant changes in parameters of thermal sensory and pain thresholds were found before and after laser needle or placebo stimulation at acupuncture points for acute pain. However, a trend towards change in the median value of cold pain sensation after laser needle stimulation (p = 0.479; paired t-test; n.s.) was seen within the group of healthy females. The influence of stimulation of acupuncture points for chronic pain on the various parameters needs to be clarified in future studies.

Acupuncture↗

PubMed2003

Labeled cortical mantle distance maps of the cingulate quantify differences between dementia of the Alzheimer type and healthy aging.

The cingulate gyri in 37 subjects with and without early dementia of the Alzheimer type (DAT) were studied by using MRI at 1.0 mm3 isotropic resolution. Groups were segregated into young controls (n = 10), age-matched normal controls (n = 10), very mild DAT (n = 8), and mild DAT (n = 9). By using automated Bayesian segmentation of the cortex and gray matter/white matter (GM/WM) isosurface generation, tissue compartments were labeled into gray, white, and cerebrospinal fluid as a function of distance from the GM/WM isosurface. Cortical mantle distance maps are generated profiling the GM volume and cortical mantle distribution as a function of distance from the cortical surface. Probabilistic tests based on generalizations of Wilcoxon-Mann-Whitney tests were applied to quantify cortical mantle distribution changes with normal and abnormal aging. We find no significant change between young controls and healthy aging as measured by the GM volume and cortical mantle distribution as a function of distance in both anterior and posterior regions of the cingulate. Significant progression of GM loss is seen in the very mild DAT and mild DAT groups in all areas of the cingulate. Posterior regions show both GM volume loss as well as significant cortical mantle distribution decrease with the onset of mild DAT. The "shape of the cortical mantle" as measured by the cortical mantle distance profiles manifests a pronounced increase in variability with mild DAT.

Adult↗

PubMed2003

Modulation of rabbit corneal epithelial cell proliferation by growth factor-regulated K(+) channel activity.

We characterized the dependence of the mitogenic response by rabbit corneal epithelial (RCE) cells to serum containing growth factors on K(+) channel activation. Using both cell-attached and nystatin-perforated patch-clamp configurations, a K(+) channel was identified whose current-voltage relationship is linear with a single-channel conductance of 31 pS. Its activity was barely detectable following 24 h serum starvation. Exposure of starved cells to either 10% FBS, 5 ng/ml epidermal growth factor (EGF) or 2 n M endothelin-1 (ET-1) continuously increased its activity within 30 min by 40%, 54% and 29%, respectively. EGF and ET-1 in combination had additive effects on such activity. Application of 100 micro M 4-aminopyridine (4-AP), a K(+) channel blocker, inhibited serum-stimulated K(+) channel activity by 85%. DNA synthesis was markedly stimulated by serum, whereas incubation with either 4-AP (200 micro M) or Ba(2+) (1 m M) suppressed this increase by 51% and 23%, respectively, whereas 5 m M tetra ethyl ammonium (TEA) had no effect. Taken together, growth factor-induced increases in proliferation are dependent on K(+) channel stimulation. As the increases in K(+) channel activity induced by ET-1 and EGF were additive, these mitogens may stimulate K(+) channel activity through different signaling pathways linked to their cognate receptors.

4-Aminopyridine↗

PubMed2003

Osteoblasts generate an osteogenic microenvironment when grown on surfaces with rough microtopographies.

Osteoblasts respond to microarchitectural features of their substrate. On smooth surfaces (tissue culture plastic, tissue culture glass, and titanium), the cells attach and proliferate but they exhibit relatively low expression of differentiation markers in monolayer cultures, even when confluent. When grown on microrough Ti surfaces with an average roughness (Ra) of 4-7 mum, proliferation is reduced but differentiation is enhanced and in some cases, is synergistic with the effects of surface microtopography. In addition, cells on microrough Ti substrates form hydroxyapatite in a manner that is more typical of bone than do cells cultured on smooth surfaces. Osteoblasts also respond to growth factors and cytokines in a surface-dependent manner. On rougher surfaces, the effects of regulatory factors like 1alpha,25(OH)2D3 or 17beta-estradiol are enhanced. The response to the surface is mediated by integrins, which signal to the cell through many of the same mechanisms used by growth factors and hormones. Studies using PEG-modified surfaces indicate that increased differentiation may be related to altered attachment to the surface. When osteoblasts are grown on surfaces with chemistries or microarchitectures that reduce cell attachment and proliferation, and enhance differentiation, the cells tend to increase production of factors like TGF-beta1 that promote osteogenesis while decreasing osteoclastic activity. Thus, on microrough Ti surface, osteoblasts create a microenvironment conducive to new bone formation.

Calcium↗

PubMed2003

Medicago truncatula EST-SSRs reveal cross-species genetic markers for Medicago spp.

Expressed sequence tags (ESTs) are important resources for gene discovery and molecular marker development. From over 147,000 ESTs of Medicago truncatula, we have identified 4,384 ESTs containing perfect simple sequence repeats (EST-SSR) of di-, tri-, tetra- or pentanucleotides. Six hundred sixteen primer pairs (PPs) were designed and screened over a panel of eight genotypes representing six Medicago spp. and subspecies. Nearly, 74% (455) of the PPs produced characteristic SSR bands of expected size length in at least one Medicago species. Four hundred six (89%) of these 455 PPs produced SSR bands in all eight genotypes tested. Only 17 PPs were M. truncatula -specific. High levels of polymorphism (>70%) were detected for these markers in alfalfa, M. truncatula, and other annual medics. About 48% of the reported markers are part of gene transcripts linked to putative functions. Our results indicate that the SSR markers developed from M. truncatula ESTs are valuable genetic markers for the Medicago genus. These markers will be useful in establishing the genomic relationships of M. truncatula to important forage legume crops such as alfalfa and other annual medics.

Alleles↗

PubMed2003

Grating-enhanced through-wafer optical microprobe for microelectromechanical system high-resolution optical position feedback.

We present modeling and experimental results from the use of a 1310-nm-wavelength through-wafer optical microprobe in conjunction with a microstructure grating to monitor the motion of a lateral comb resonator stage. The optical signal that results from shuttle interaction with the microprobe beam exhibits a peak-to-valley dynamic range that corresponds to 2-microm microstructure displacement, facilitating submicrometer positional resolution on digitization. This signal was used to achieve microstructure positional feedback and effective microsystem model parameter extraction, which are essential for structure control and model-based fault detection.

Journal Article↗

PubMed2003

Evidence for expression of a single distinct form of mammalian cysteine dioxygenase.

Cysteine dioxygenase (CDO) plays a critical role in the regulation of cellular cysteine concentration. Because multiple forms of CDO ( approximately 23 kDa, approximately 25 kDa, and approximately 68 kDa) have been claimed based upon separation and detection using SDS-PAGE/western blotting (with antibodies demonstrated to immunoprecipitate CDO), we further investigated the possibility of more than one CDO isoform. Using either rabbit antibody raised against purified rat liver CDO or against purified recombinant his(6)-tagged CDO (r-his(6)-CDO) and using 15% (wt/vol) polyacrylamide for the SDS-PAGE, we consistently detected the approximately 25 kDa band, but never detected a approximately 68 kDa band, in rat liver, kidney, lung and brain. Nondenatured gel electrophoresis of r-his(6)-CDO yielded a molecular mass estimate of 25.7 kDa and no evidence of dimerization. Mass spectrometry of r-his(6)-CDO yielded two peaks with molecular masses of 24.1 kDa and 24.3 kDa. Anion-exchange FPLC of r-his(6)-CDO also gave two peaks, with the first containing CDO that was 7.5-times as active as the more anionic form that eluted second. When the two peaks recovered from FPLC were run on SDS/PAGE, the first (more active) CDO fraction yielded two bands (perhaps as an artifact of SDS/PAGE), whereas the second (less active) CDO fraction yielded only the approximately 23 kDa band. We conclude that the physiologically active form of CDO is the approximately 25 kDa (i.e., 23.5 kDa based on mass spectrometry) monomer and that this active form is probably derived by post-translational modification of the 23 kDa gene product.

Animals↗

PubMed2003

Fluorescence resonance energy transfer between donor-acceptor pair on two oligonucleotides hybridized adjacently to DNA template.

We use fluorescein as the energy donor and rhodamine as the acceptor to measure the efficiency of fluorescence resonance energy transfer (FRET) in a set of hybridized DNA constructs. The two fluorophores are covalently attached via linkers to two separate oligonucleotides with fluorescein at the 3' end of one oligonucleotide and rhodamine at the 5' end or in the middle of another nucleotide. For the FRET analysis both fluorophore-labeled oligonucleotides are hybridized to adjacent sections of the same DNA template to form a three-component duplex with a one base gap between the two labeled oligonucleotides. A similar configuration is implemented for a quantitative real-time polymerase chain reaction (PCR) with LightCycler technology, where a 1-5 base separation between donor and acceptor is recommended to optimize energy transfer efficiencies. Our constructs cover donor-acceptor separations from 2 to 17 base pairs (approximately 10-70 A). The results show that, when the two fluorophores are located at close distances (less than 8 base separation), FRET efficiencies are above 80%, although there may be ground-state interactions between fluorophores when the separation is under about 6 bases. Modeling calculations are used to predict the structure of these three-component constructs. The duplex mostly retains a normal double helical structure, although slight bending may occur near the unpaired base in the DNA template. Stable and reproducible energy transfer is also observed over the distance range investigated here in real-time thermal cycling. The study identifies important parameters that determine FRET response in applications such as real-time PCR.

Base Sequence↗

PubMed2003

Candidate-gene association studies with pedigree data: controlling for environmental covariates.

Case-control studies provide an important epidemiological tool to evaluate candidate genes. There are many different study designs available. We focus on a more recently proposed design, which we call a multiplex case-control (MCC) design. This design compares allele frequencies between related cases, each of whom are sampled from multiplex families, and unrelated controls. Since within-family genotype correlations will exist, statistical methods will need to take this into account. Moreover, there is a need to develop methods to simultaneously control for potential confounders in the analysis. Generalized estimating equations (GEE) are one approach to analyze this type of data; however, this approach can have singularity problems when estimating the correlation matrix. To allow for modeling of other covariates, we extend our previously developed method to a more general model-based approach. Our proposed methods use the score statistic, derived from a composite likelihood. We propose three different approaches to estimate the variance of this statistic. Under random ascertainment of pedigrees, score tests have correct type I error rates; however, pedigrees are not randomly ascertained. Thus, through simulations, we test the validity and power of the score tests under different ascertainment schemes, and an illustration of our methods, applied to data from a prostate cancer study, is presented. We find that our robust score statistic has estimated type I error rates within the expected range for all situations we considered whereas the other two statistics have inflated type I error rates under nonrandom ascertainment schemes. We also find GEE to fail at least 5% of the time for each simulation configuration; at times, the failure rate reaches above 80%. In summary, our robust method may be the only current regression analysis method available for MCC data.

Case-Control Studies↗

PubMed2003

Cystathionine beta-synthase deficiency in Georgia (USA): correlation of clinical and biochemical phenotype with genotype.

Cystathionine beta-synthase (CBS) deficiency is a rare autosomal recessive disorder that is the most frequent cause of clinical homocystinuria. Patients not treated in infancy have multi-systems disorders including dislocated lenses, mental deficiency, osteoporosis, premature arteriosclerosis, and thrombosis. In this paper, we examine the relationship of the clinical and biochemical phenotypes with the genotypes of 12 CBS deficient patients from 11 families from the state of Georgia, USA. By DNA sequencing of all of the coding exons we identified mutations in the CBS genes in 21 of the 22 possible mutant alleles. Ten different missense mutations were identified and one novel splice-site mutation was found. Five of the missense mutations were previously described (G307S, I278T, V320A, T353M, and L101P), while five were novel (A226T, N228S, A231L, D376N, Q526K). Each missense mutation was tested for function by expression in S. cerevisiae and all were found to cause decreased growth rate and to have significantly decreased levels of CBS enzyme activity. The I278T and T353M mutations accounted for 45% of the mutant alleles in this patient cohort. The T353M mutation, found exclusively in four African American patients, was associated with a B(6)-nonresponsive phenotype and detection by newborn screening for hypermethioninemia. The I278T mutation was found exclusively in Caucasian patients and was associated with a B(6)-responsive phenotype. We conclude that these two mutations occurred after ethnic socialization and that the CBS genotype is predictive of phenotype.

Black or African American↗

PubMed2003

Analysis of RHD genes in Taiwanese RhD-negative donors by the multiplex PCR method.

The determination of the RhD phenotype is important in transfusion medicine. However, due to the complexity of D antigen expression, the routine serological method cannot differentiate all RhD variants. In addition, the induction of the anti-D antibody is still the major cause of severe hemolytic disease of the newborn (HDN). Therefore, it is important to understand RHD gene profiles. To analyze the RHD gene profiles of Taiwanese RhD-negative donors, the multiplex PCR method was applied to amplify RHD specific exons 3, 4, 5, 7, and 9. Based on the PCR results, the 156 RhD-negative donors were divided into 12 groups according to the different expression patterns of the RHD gene. These 12 groups were further divided into three categories: type I=Rh D(el) (21.8%); type II = partial D, containing some exons (9.0%); and type III = true RhD-negative (69.2%). The results indicated that 21.8% of RhD-negative donors in Taiwan were RhD(el), and 9% carried a part of the RHD gene. Six defined RhD variants were found in this study: four R(O) (Har), one D(Va), and two D(IVb). However, no true RhD-negative or RhD(el) donor with the CcdEe phenotype was found in this analysis.

Blood Grouping and Crossmatching↗

PubMed2003

Adaptive approximation of the boundary surface of a neuron in confocal microscopy volumetric images.

In biomedical visualisation, the isosurface is usually used to represent (approximate) the boundary surface of the structure within biomedical volumetric images. However, in many confocal microscopy volumetric images of neurons, the grey values of the object and/or background are usually uneven. Therefore a fixed isosurface is not suitable for use in approximating the boundary surface of the neuron. A method is proposed to construct the adaptively approximating surface of the boundary surface of the neuron. In this method, the boundary surface of the neuron could be locally and adaptively approximated with different surface patches in different local regions. Consequently, the approximation accuracy has been considerably improved.

Algorithms↗

PubMed2003