Biomedical subjects

J L Wang

Publications and source records attributed to J L Wang.

At least 19 recordsLinked to original sources

PubMed2006

QTL analysis for rice grain length and fine mapping of an identified QTL with stable and major effects.

Grain length in rice plays an important role in determining rice appearance, milling, cooking and eating quality. In this study, the genetic basis of grain length was dissected into six main-effect quantitative trait loci (QTLs) and twelve pairs of epistatic QTLs. The stability of these QTLs was evaluated in four environments using an F7 recombinant inbred line (RIL) population derived from the cross between a Japonica variety, Asominori, and an Indica variety, IR24. Moreover, chromosome segment substitution lines (CSSLs) harboring each of the six main-effect QTLs were used to evaluate gene action of QTLs across eight environments. A major QTL denoted as qGL-3a, was found to express stably not only in the isogenic background of Asominori but also in the recombinant background of Asominori and IR24 under multiple environments. The IR24 allele at qGL-3a has a positive effect on grain length. Based on the test of advanced backcross progenies, qGL-3a was dissected as a single Mendelian factor, i.e., long rice grain was controlled by a recessive gene gl-3. High-resolution genetic and physical maps were further constructed for fine mapping gl-3 by using 11 simple sequence repeat (SSR) markers designed using sequence information from seven BAC/PAC clones and a BC4F2 population consisting of 2,068 individuals. Consequently, the gl-3 gene was narrowed down to a candidate genomic region of 87.5 kb long defined by SSR markers RMw357 and RMw353 on chromosome 3, which provides a basis for map-based cloning of this gene and for marker-aided QTL pyramiding in rice quality breeding.

Alleles↗

PubMed2005

Effect of celecoxib on Ca2+ fluxes and proliferation in MDCK renal tubular cells.

The effect of celecoxib on renal tubular cells is largely unexplored. In Madin Darby canine kidney (MDCK) cells, the effect of celecoxib on intracellular CaCa2+ concentration ([Ca2+]i) and proliferation was examined by using the Ca(2 +)-sensitive fluorescent dye fura-2 and the viability detecting fluorescent dye tetrazolium, respectively. Celecoxib (> or =1 micro M) caused an increase of [CaCa2+]i in a concentration-dependent manner. Celecoxib-induced [CaCa2+]i increase was partly reduced by removal of extracellular CaCa2+. Celecoxib-induced CaCa2+ influx was independently suggested by MnCa2+ influx-induced fura-2 fluorescence quench. In Ca(2 +)-free medium, thapsigargin, an inhibitor of the endoplasmic reticulum Ca(2 +)-ATPase, caused a monophasic [CaCa2+]i increase, after which celecoxib only induced a tiny [CaCa2+]i increase; conversely, pretreatment with celecoxib completely inhibited thapsigargin-induced [CaCa2+]i increases. U73122, an inhibitor of phospholipase C, abolished ATP (but not celecoxib)-induced [CaCa2+]i increases. Overnight incubation with 1 or 10 micro M celecoxib decreased cell viability by 80% and 100%, respectively. These data indicate that celecoxib evokes a [CaCa2+]i increase in renal tubular cells by stimulating both extracellular CaCa2+ influx and intracellular CaCa2+ release and is highly toxic to renal tubular cells in vitro.

Animals↗

PubMed2004

Local atomic structures of palladium nanowire.

In this paper, investigation of the structure of palladium nanowire has been performed by using genetic algorithm simulation based on the molecular dynamics. Our calculation employs a well-fitted, tight-binding many-body potential for Pd atoms. Some local atomic structures and defects in nanowires have been reported. The melting behavior of palladium nanowire has also been investigated. An interesting result is that the diffusion of the central atoms results in the beginning of the melting. The moving central atoms build up a monostrand atomic chain during the melting process. The single atomic chain is very stable which can exist in a wide temperature region (800-950 K). The formation of the single atomic chain causes some new defects in the nanowire. And the new defects result in the decrease of the thermal stability of the nanowire. Interestingly, the liquid from the nanowire melting has a supercooled feature because the splitting of the second peak of pair correlation function is observed. The curves of the internal energy and the local cluster are used to monitor the phase transition. The melting of the nanowire is not only due to the single atomic diffusion, but also the diffusion of the local clusters.

Journal Article↗

PubMed2004

Biofidelic whole cervical spine model with muscle force replication for whiplash simulation.

Whiplash has been simulated using volunteers, whole cadavers, mathematical models, anthropometric test dummies, and whole cervical spines. Many previous in vitro whiplash models lack dynamic biofidelity. The goals of this study were to (1) develop a new dynamic whole cervical spine whiplash model that will incorporate anterior, lateral and posterior muscle force replication, (2) evaluate its performance experimentally and (3) compare the results with in vivo data. To evaluate the new model, rear-impact whiplash simulations were performed using the incremental trauma approach at maximum measured T1 horizontal accelerations of 3.6 g, 4.7 g, 6.6 g, and 7.9 g. The kinematic response of the new model, e.g., peak head-T1 extension and peak intervertebral rotations, were compared with the corresponding in vivo data. The average peak head-T1 extension was within the in vivo corridor during the 3.6 g whiplash simulation (9.1 kph delta V). The peak in vivo intervertebral rotations obtained during a 4.6 g whiplash simulation of a young volunteer were within, or only marginally in excess of, the 95% confidence limits of the average peak intervertebral rotations measured during the 4.7 g whiplash simulation of the present study. Thus, the new whole cervical spine model with muscle force replication produced biofidelic dynamic responses to simulated whiplash. The new model is capable of generating important biomechanical data that may help improve our understanding of whiplash injuries and injury mechanisms.

Acceleration↗

PubMed2004

CD44 and tenascin play critical roles in growth and vascular development of the chick chorioallantoic membrane and are targets of cigarette smoke.

Chorioallantoic membranes (CAMs) were used to determine which extracellular matrix molecules play essential roles in growth and vascular development in vivo and whether expression of critical molecules is affected by cigarette smoke exposure. Treatment of CAMs on day 5 of development with antibodies to CD44 or tenascin, but not to other matrix molecules, inhibited CAM growth and affected various aspects of blood vessel development including normal growth and branching of vessels, migration of vessels, and formation and differentiation of the capillary plexus. DNA synthesis was inhibited by antibodies to both C44 and tenascin which probably accounted for many of the phenotypic changes observed in treated CAMs. CD44 was located on all cells in day 5 CAMs, and tenascin, while present throughout the CAM, was especially abundant around large, non-migratory mesodermal blood vessels and endodermal cells that were positioned away from the direction of blood vessel migration. These data suggest that while tenascin is required for normal blood vessel migration, high levels of tenascin inhibit migration. The different distributions of CD44 and tenascin in CAMs and the observation that antibodies to either CD44 or tenascin produced similar phenotypes indicate that CD44 and tenascin were not functionally redundant. Mainstream smoke solutions, which produce a phenotype similar to that seen with anti-tenascin and anti-CD44, inhibited expression of CD44 mRNA and increased tenascin mRNA expression. 3-Ethylpyridine, a chemical in cigarette smoke that produced changes in CAM development similar to anti-CD44 and anti-tenascin treatment, also increased tenascin mRNA expression, but did not affect CD44. Together these data show that tenascin and CD44 play critical roles in early growth and vascular development of the CAM and support the idea that 3-ethylpyridine in mainstream smoke impairs CAM growth and vascular development by targeting expression of tenascin. 3-Ethylpyridine is generally regarded as safe and is used in many consumer products including food and tobacco.

Animals↗

PubMed2004

Melting behavior of one-dimensional zirconium nanowire.

In this paper, we analyze the melting behavior of zirconium nanowire using the results of a series of molecular dynamics simulations. Our calculation employs a well-fitted, tight-binding many-body potential for zirconium atoms. The melting point of the nanowire is predicted by the root-mean-square displacements for inner and outer shells. Our simulations predict two melting behaviors: one is the inner melting and the other is the outer melting. Our results reveal that the melting of nanowire starts from the inner shell atoms. The melting point of zirconium nanowire is lower than the bulk value (2125 K). Moreover, the melting point of the inner shell is lower than that of the outer shell. A coexistence of crystal and liquid units is observed in the melting process of nanowire. An investigation of local clusters is carried out to further analyze the melting mechanism of the nanowire. The presence of the local clusters 1331, 1321, 1211, etc. is an indication of disordered structures. The pair and angular correlation functions are also presented for the analysis of the melting behavior. It is not only the diffusion of single atom but the diffusion of clusters result in the occurrence of the melting.

Journal Article↗

PubMed2004

Effect of strain rate on tensile properties of sheep disc anulus fibrosus.

We investigated the effect of loading rate on tensile properties of sheep bone-anulus-bone specimens in axial direction. Disc anulus Samples with adjacent bone attachments were prepared from lateral, posterior and anterior regions of sheep lumbar spinal segments. The specimens were then tested at different strain rates under non-destructive cyclic tensile loading followed by destructive tensile loading. Each specimen was prepared by embedding the bony parts in the polymethylmetacrylate (PMMA) exposing the anulus portion to support tension. The results of non-destructive cyclic tests indicated a decrease in the hysteresis energy loss as strain rate increased. In the destructive tests, no significant differences in ultimate stress, ultimate strain and strain energy density were observed at different strain rates or annulus locations. However, there was a significant increase in the modulus at linear region as strain rate increased. Two major modes of failure were observed; rupture in the anulus mid-substance and at the anulus-endplate junction. The former failure was more frequent with no clear pattern across strain rates and locations, while the latter failure at anulus-endplate junction occurred primarily at slow strain rates.

Animals↗

PubMed2001

The cortical shell architecture of human cervical vertebral bodies.

STUDY DESIGN: An anatomic study of cervical vertebral bodies. OBJECTIVES: To provide quantitative information on the cortical shell architecture of the middle and lower cervical vertebral bodies. SUMMARY OF BACKGROUND DATA: Some external dimensions have been measured, but little quantitative data exists for the cortical shell architecture of the vertebral bodies of the cervical spine. METHODS: Twenty-one human cervical vertebral bodies (C3-C7) were sectioned along parasagittal planes into five 1.7-mm thin slices for each vertebra. Radiographs of each slice were digitized, and external and internal dimensions were measured. Averages and standard deviations were computed. Single factor analysis of variance was used to determine significant (P < 0.05) differences between the vertebral levels. RESULTS: The superior endplate was thickest in the posterior region (range 0.74-0.89 mm) and thinnest in the anterior region (range 0.44-0.56 mm). The inferior endplate was thickest in the anterior region (range 0.61-0.81 mm) and thinnest in the posterior region (range 0.49-0.62 mm). In the central region, the superior endplate (range 0.42-0.58 mm) was thinner than the inferior endplate (range 0.53-0.64 mm). Variation with vertebral level was dependent on the dimension studied. CONCLUSIONS: Comprehensive quantitative anatomic data of the middle and lower cervical vertebral bodies have been obtained. This may be useful in improving the understanding of the three-column and other vertebral-fracture theories, the fidelity of the finite element models of cervical spine, and the designs of surgical instrumentation.

Cadaver↗

PubMed2001

Event history graphs for censored survival data.

A compact graphical device for combining survival and time-varying covariate information is proposed. The proposed graph contains the Kaplan-Meier estimator for right-censored data and a simultaneous display of the behaviour of time-dependent covariate(s) and the lifetime for each subject in the sample. The observed levels of time-dependent covariates are possibly subjected to an initial dimension reduction or smoothing step to produce a continuous covariate function. Values of this function are plotted on a horizontal bar for the length of the lifetime of the subject. Covariate information for censored data is also incorporated. The union of the horizontal bars forms the Kaplan-Meier estimator of the survival function. Our graphical method is implemented with a new S-plus function and demonstrated in several applications.

Age Factors↗

PubMed2001

Development of a system for in vitro neck muscle force replication in whole cervical spine experiments.

STUDY DESIGN: An in vitro biomechanical study. OBJECTIVES: To develop and evaluate a new in vitro whole cervical spine model that provides to the specimen, in vivo-like mechanical characteristics. SUMMARY OF BACKGROUND DATA: In vitro studies of kinematics, kinetics, and trauma using isolated spine specimens (head-T1 vertebra) have usually applied upward force to the head, resulting in tensile spine forces, contrary to the physiological compressive forces present in vivo. Further, the in vitro load-displacement curves have never been compared with the corresponding in vivo data. METHODS: A novel muscle force replication (MFR) system is presented. It consists of a set of compressive forces applied to the various vertebrae and occiput of a whole cervical spine specimen. Two protocols, with and without MFR, were evaluated using standardized flexibility testing. Ranges of motion (ROM) and load-displacement curves were documented, and contrasted with similar in vivo data. RESULTS: Results for the MFR were found to be similar to the in vivo measurements, with respect to the intersegmental and whole neck motions as well as the load-displacement curves, thus validating the MFR approach. CONCLUSIONS: The new model advances the in vitro testing, which uses whole cervical spine specimens.

Adult↗

PubMed2001

Association of galectin-1 and galectin-3 with Gemin4 in complexes containing the SMN protein.

In previous studies we showed that galectin-1 and galectin-3 are factors required for the splicing of pre-mRNA, as assayed in a cell-free system. Using a yeast two-hybrid screen with galectin-1 as bait, Gemin4 was identified as a putative interacting protein. Gemin4 is one component of a macromolecular complex containing approximately 15 polypeptides, including SMN (survival of motor neuron) protein. Rabbit anti-galectin-1 co-immunoprecipitated from HeLa cell nuclear extracts, along with galectin-1, polypeptides identified to be in this complex: SMN, Gemin2 and the Sm polypeptides of snRNPs. Direct interaction between Gemin4 and galectin-1 was demonstrated in glutathione S-transferase (GST) pull-down assays. We also found that galectin-3 interacted with Gemin4 and that it constituted one component of the complex co-immunoprecipitated with galectin-1. Indeed, fragments of either Gemin4 or galectin-3 exhibited a dominant negative effect when added to a cell-free splicing assay. For example, a dose-dependent inhibition of splicing was observed in the presence of exogenously added N-terminal domain of galectin-3 polypeptide. In contrast, parallel addition of either the intact galectin-3 polypeptide or the C-terminal domain failed to yield the same effect. Using native gel electrophoresis to detect complexes formed by the splicing extract, we found that with addition of the N-terminal domain the predominant portion of the radiolabeled pre-mRNA was arrested at a position corresponding to the H-complex. Inasmuch as SMN-containing complexes have been implicated in the delivery of snRNPs to the H-complex, these results provide strong evidence that galectin-1 and galectin-3, by interacting with Gemin4, play a role in spliceosome assembly in vivo.

Alternative Splicing↗

PubMed2001

An in vitro model for evaluation of vaporous toxicity of trichloroethylene and tetrachloroethylene to CHO-K1 cells.

Toxicokinetics of trichloroethylene (TCE) and tetrachloroethylene (PER) in culture medium and their toxicity to CHO-K1 cells were investigated by employing an in vitro vapor exposure system. Cells were cultured in a 60 mm petri dish with a 25 mm glass dish glued in the central area. TCE or PER was added to the central glass dish so that it would evaporate and dissolve in the surrounding medium in which cells were growing. The results showed that the concentration of TCE or PER in medium increased significantly within 20 min and then decreased very rapidly with time. After a 24 h incubation, the residual of TCE or PER in the medium was very low, but was displayed in a dose-dependent manner. Treatment of cells with either TCE or PER resulted in a dose- and time-dependent inhibition of cell growth. A significantly increase in the frequency of micronuclei (MN) was also observed with either TCE or PER treatment. Low doses of TCE (5-20 microl) or PER (1-5 microl) significantly enhanced the intracellular glutathione (GSH) level. However, the level of GSH rapidly decreased with higher doses of TCE (40-80 microl) or PER (10-20 microl). Depletion of cellular GSH showed no effect on the sensitivity of cells to TCE or PER treatment. GSH-conjugation has been proposed as an activation mechanism to account for the nephrotoxicity of TCE and PER, however the toxicity of TCE and PER to CHO-K1 cells is probably mediated through a distinct mechanism.

Animals↗

PubMed2001

Construction and validation of automated purge-and-trap-gas chromatography for the determination of volatile organic compounds.

An automated purge-and-trap chromatographic system for the determination of dissolved volatile organic compounds in aqueous samples was built in the laboratory with minimum cost both in the construction and routine operation. This system was built upon a commercial gas chromatograph with full automation capability using self-developed hardware and software. The use of a multi-sorbent bed quantitatively trapped a wide range of volatile organic compounds at ambient temperature, including the extremely volatile ones such as dichlorofluoromethane (CFC-12). Flash heating for rapid desorption and adequate plumbing for minimizing dead volume resulted in excellent chromatographic separation at above-ambient temperatures, which eliminated the need for cryogen for cooling at the head of the column, a second refocusing stage, or entire GC oven for refocusing. This cryogen-free system was tested with standard solutions and environmental samples for determining hydrocarbons with flame ionization detection, and halogenated compounds with electron-capture detection. An innovative method was also developed for validating the system's linearity for extremely volatile compounds. By introducing ambient air, which usually contains constant levels of anthropogenic halocarbons, e.g., CFC-12 and CFC-11 (CCl3F), the need to prepare aqueous standards containing extremely volatile compounds is avoided, hence providing a convenient method for evaluating a purge-and-trap system.

Automation↗

PubMed2001

CP55,940 increases intracellular Ca2+ levels in Madin-Darby canine kidney cells.

The effect of CP55,940, a presumed CB1/CB2 cannabinoid receptor agonist, on intracellular free Ca2+ levels ([Ca2+]i) in Madin-Darby canine kidney cells was examined by using the fluorescent dye fura-2 as a Ca2+ indicator. CP55,940 (2-50 microM) increased [Ca2+]i concentration-dependently with an EC50 of 8 microM. The [Ca2+]i signal comprised an initial rise and a sustained phase. Extracellular Ca2+ removal decreased the maximum [Ca2+]i signals by 32+/-12%. CP55,940 (20 microM)-induced [Ca2+]i signal was not altered by 5 microM of two cannabinoid receptor antagonists, AM-251 and AM-281. CP55,940 (20 microM)-induced [Ca2+]i increase in Ca2+-free medium was inhibited by 86+/-3% by pretreatment with 1 microM thapsigargin, an endoplasmic reticulum Ca2+ pump inhibitor. Conversely, pretreatment with 20 microM CP55,940 in Ca2+-free medium for 6 min abolished thapsigargin-induced [Ca2+]i increases. CP55,940 (20 microM)-induced intracellular Ca2+ release was not inhibited when inositol 1,4,5-trisphosphate formation was abolished by suppressing phospholipase C with 2 microM U73122. Collectively, this study shows that CP,55940 induced significant [Ca2+]i increases in canine renal tubular cells by releasing stored Ca2+ from the thapsigargin-sensitive pools in an inositol 1,4,5-trisphosphate-independent manner, and also by causing extracellular Ca2+ entry. The CP55,940's action appears to be dissociated from stimulation of cannabinoid receptors.

Animals↗

PubMed2001

Concentration variability of halocarbons over an electronics industrial park and its implication in compliance with the Montreal protocol.

This work investigated fugitive emissions of anthropogenic halocarbons in a semiconductor and electronics industrial park in Taiwan using both flask and in-situ measurement methods. Large concentration variabilities in methylchloroform, trichloroethene, and tetrachloroethene suggested substantial usage and emissions in the industrial park. While the variability of CFC-113, CCl4, and CFC-11 was rather small using the flask sampling technique, the in-situ method with its higher frequency, however, showed significantly larger variability arising from observing periodic emission episodes, which were highly correlated with wind direction and topography of the park.

Air Pollutants↗

PubMed2001

Evolution of digital organisms at high mutation rates leads to survival of the flattest.

Darwinian evolution favours genotypes with high replication rates, a process called 'survival of the fittest'. However, knowing the replication rate of each individual genotype may not suffice to predict the eventual survivor, even in an asexual population. According to quasi-species theory, selection favours the cloud of genotypes, interconnected by mutation, whose average replication rate is highest. Here we confirm this prediction using digital organisms that self-replicate, mutate and evolve. Forty pairs of populations were derived from 40 different ancestors in identical selective environments, except that one of each pair experienced a 4-fold higher mutation rate. In 12 cases, the dominant genotype that evolved at the lower mutation rate achieved a replication rate >1.5-fold faster than its counterpart. We allowed each of these disparate pairs to compete across a range of mutation rates. In each case, as mutation rate was increased, the outcome of competition switched to favour the genotype with the lower replication rate. These genotypes, although they occupied lower fitness peaks, were located in flatter regions of the fitness surface and were therefore more robust with respect to mutations.

Biological Evolution↗

PubMed2001

Mechanisms of diethylstilbestrol-induced calcium movement in MG63 human osteosarcoma cells.

The effect of the estrogen diethylstilbestrol (DES) on cytosolic free Ca(2+) levels ([Ca(2+)](i)) in MG63 human osteoblasts was explored by using fura-2 as a Ca(2+) indicator. DES at concentrations between 5--20 microM induced an immediate increase in [Ca(2+)](i) in a concentration-dependent manner with an EC(50) of 10 microM. Removing extracellular Ca(2+) reduced the Ca(2+) signal by 70%. Pretreatment with 50 microM La(3+) or 10 microM of nifedipine, verapamil and diltiazem did not change 20 microM DES-induced [Ca(2+)](i) increases. Addition of 3 mM Ca(2+) increased [Ca(2+)](i) in cells pretreated with 20 microM DES in Ca(2+)-free medium. Pretreatment with 1 microM thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor) to deplete the endoplasmic reticulum Ca(2+) store partly inhibited 20 microM DES-induced Ca(2+) release, but addition of carbonylcyanide m-chlorophenylhydrazone (CCCP; a mitochondrial uncoupler) and thapsigargin together abolished DES-induced Ca(2+) release. Conversely, pretreatment with 20 microM DES abrogated CCCP- and thapsigargin-induced Ca(2+) release. Inhibition of phospholipase C activity with 2 microM U73122 did not alter 20 microM DES-induced Ca2+ release. Another estrogen 17beta-estradiol also increased [Ca(2+)](i) in a concentration-dependent manner with an EC50 of 7 microM. Together, the data indicate that in human osteoblasts, DES increased [Ca(2+)](i) via causing Ca(2+) release from both mitochondria and the endoplasmic reticulum in a phospholipase C-independent manner, and by causing Ca(2+) influx.

Calcium↗

PubMed2001

Clomiphene, an ovulation-inducing agent, causes [Ca2+]i increases in human osteoblast-like cells.

The effect of clomiphene, an ovulation-inducing agent, on cytosolic free Ca2+ levels ([Ca2+]i) in MG63 human osteosarcoma cells was explored by using fura-2 as a Ca2+ indicator. Clomiphene at concentrations between 5-75 microM increased [Ca2+]i in a concentration-dependent manner with an EC50 of 50 microM. The [Ca2+]i signal consisted of an initial rise and a sustained phase. Ca2+ removal reduced the Ca2+ signal by 40+/-10%. The [Ca2+]i increase induced by 50 microM clomiphene was inhibited by 80+/-5% by 10 microM nifedipine, but was insensitive to 50 microM La3+ or 10 microM verapamil. In Ca2+-free medium, pretreatment with 50 microM brefeldin A (to disrupt the Golgi complex Ca2+ store), 1 microM thapsigargin (to inhibit the endoplasmic reticulum Ca2+ pump), and carbonylcyanide m-chlorophenylhydrazone (CCCP; to uncouple mitochondria) inhibited 51+/-3% of 50 microM clomiphene-induced Ca2+ release; conversely, pretreatment with 50 microM clomiphene abolished the [Ca2+]i increase induced by thapsigargin, CCCP, and brefeldin A. The Ca2+ release-induced by 50 pM clomiphene was unchanged by inhibition of phospholipase C with 2 microM 1-(6-((17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122). Collectively, the results suggest that clomiphene increased [Ca2+]i, in osteoblast-like cells, by releasing intracellular Ca2+ in a phospholipase C-independent manner and by causing nifedipine-sensitive Ca2+ influx.

Calcium↗