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D Wang

Publications and source records attributed to D Wang.

At least 217 records · Page 12Linked to original sources
PubMed2001

Synchronization in relaxation oscillator networks with conduction delays.

We study locally coupled networks of relaxation oscillators with excitatory connections and conduction delays and propose a mechanism for achieving zero phase-lag synchrony. Our mechanism is based on the observation that different rates of motion along different nullclines of the system can lead to synchrony in the presence of conduction delays. We analyze the system of two coupled oscillators and derive phase compression rates. This analysis indicates how to choose nullclines for individual relaxation oscillators in order to induce rapid synchrony. The numerical simulations demonstrate that our analytical results extend to locally coupled networks with conduction delays and that these networks can attain rapid synchrony with appropriately chosen nullclines and initial conditions. The robustness of the proposed mechanism is verified with respect to different nullclines, variations in parameter values, and initial conditions.

Animals↗
PubMed2001

Glucose transporter type 1 deficiency syndrome (Glut1DS): methylxanthines potentiate GLUT1 haploinsufficiency in vitro.

Methylxanthines such as caffeine and theophylline are known to inhibit glucose transport. We have studied such inhibition in the glucose transporter type 1 deficiency syndrome (Glut1DS) by erythrocyte glucose transport assays. Data from four patients with individual mutations in the GLUT1 gene are discussed: patient 1 (hemizygosity), 3 (S66F), 15 (368Ins23), and 17 (R333W). Zero-trans influx of (14)C-labeled 3-O-methyl glucose (3-OMG) into erythrocytes of patients is reduced (patient 1, 51%; 3, 45%; 15, 31%; 17, 52%) compared with maternal controls. Inhibition studies on patients 1, 3, 17, and maternal controls show an IC(50) for caffeine of approximately 1.5 mM both in controls (n = 3) and patients (n = 3) at 5 mM 3-OMG concentration. In the same two groups, kinetic studies show that 3 mM caffeine significantly decreases V(max) (p < 0.005), whereas the decrease in K(m) is significant (p < 0.01) only in the three controls and one patient (patient 3). Kinetic data from individual patients permit us to speculate that the interactions between caffeine and Glut1 are influenced by the mutation. Three mM caffeine also inhibits the transport of dehydroascorbic acid (DHA), another substrate for Glut1. The combined effects of caffeine (3 mM) and phenobarbital (10 mM) on glucose transport, as determined in patient 15 and the maternal control, show no additive or synergistic inhibition. These data indicate that caffeine and phenobarbital have similar Glut1 inhibitory properties in these two subjects. Our study suggests that Glut1DS patients may have a reduced safety margin for methylxanthines. Consumption of methylxanthine-containing products may aggravate the neurologic symptoms associated with the Glut1DS.

3-O-Methylglucose↗
PubMed2001

Genetic variations in human G protein-coupled receptors: implications for drug therapy.

Numerous genes encode G protein-coupled receptors (GPCRs)-a main molecular target for drug therapy. Estimates indicate that the human genome contains approximately 600 GPCR genes. This article addresses therapeutic implications of sequence variations in GPCR genes. A number of inactivating and activating receptor mutations have been shown to cause a variety of (mostly rare) genetic disorders. However, pharmacogenetic and pharmacogenomic studies on GPCRs are scarce, and therapeutic relevance of variant receptor alleles often remains unclear. Confounding factors in assessing the therapeutic relevance of variant GPCR alleles include 1) interaction of a single drug with multiple closely related receptors, 2) poorly defined binding pockets that can accommodate drug ligands in different orientations or at alternative receptor domains, 3) possibility of multiple receptor conformations with distinct functions, and 4) multiple signaling pathways engaged by a single receptor. For example, antischizophrenic drugs bind to numerous receptors, several of which might be relevant to therapeutic outcome. Without knowing accurately what role a given receptor subtype plays in clinical outcome and how a sequence variation affects drug-induced signal transduction, we cannot predict the therapeutic relevance of a receptor variant. Genome-wide association studies with single nucleotide polymorphisms could identify critical target receptors for disease susceptibility and drug efficacy or toxicity.

Drug Therapy↗
PubMed2001

Composition, characteristic and activity of rare earth element-bound polysaccharide from tea.

The compositions and structural characteristics of rare earth elements-bound polysaccharides from tea (REE-TPS) were studied with the methods of Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Gas Chromatography (GC) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. The results show that polysaccharide from tea (TPS) was a sort of glycoprotein and coordinated with Rare Earth Elements (REE) closely. The sugar fraction was composed of Rha, Ara, Xyl, Fuc, Glc, and Gal. There existed almost all natural amino acids with Glx, Asx, and Hyp as the major parts in the protein fraction. The REEs in REE-TPS were mainly composed of La, Ce, and Nd, especially, more than 75% of them was La. The coordination atom of the first coordination shell of La in REE-TPS was oxygen, the coordination number of which was 6, and the average distance between the atoms was 2.52 A. The second shell was formed from sulfur atoms, the coordination number and the average distance were 3 and 2.91 A, respectively. The bio-experiments show that REE-TPS could decrease the content of blood glucose in mice significantly.

Animals↗
PubMed2001

Flatland optics. II. Basic experiments.

In "Flatland optics: fundamentals" [J. Opt. Soc. Am. A 17, 1755 (2000)] we described the basic principles of two-dimensional (2D) optics and showed that a wavelength lambda in three-dimensional (3D) space (x,y,z) may appear in Flatland (x,z) as a wave with another wavelength, lambda = lambda/cosalpha. The tilt angle alpha can be modified by a 3D (Spaceland) individual who then is able to influence the 2D optics in a way that must appear to be magical to 2D Flatland individuals-in the spirit of E. A. Abbott's science fiction story [Flatland, a Romance of Many Dimensions, 6th ed. (Dover, New York, 1952)] of 1884. We now want to establish the reality or objectivity of the 2D wavelength lambda by some basic experiments similar to those that demonstrated roughly 200 years ago the wave nature of light. Specifically, we describe how to measure the 2D wavelength lambda by mean of five different arrangements that involve Young's biprism configuration, Talbot's self-imaging effect, measuring the focal length of a Fresnel zone plate, and letting light be diffracted by a double slit and by a grating. We also performed experiments with most of these arrangements. The results reveal that the theoretical wavelength, as predicted by our Flatland optics theory, does indeed coincide with the wavelength lambda as measured by Flatland experiments. Finally, we present an alternative way to understand Flatland optics in the spatial frequency domains of Flatland and Spaceland.

Journal Article↗
PubMed2001

Flatland optics. III. Achromatic diffraction.

In the previous two sections of "Flatland optics" [J. Opt. Soc. Am. A 17, 1755 (2000); 18, 1056 (2001)] we described the basic principles of two-dimensional (2D) optics and showed that a wavelength lambda in three-dimensional (3D) space (x, y, z) may appear in Flatland (x, z) as a wave with another wavelength Lambda=lambda/cos alpha. The tilt angle alpha can be modified by a 3D-Spaceland individual, who then is able to influence the 2D optics in a way that must appear to be magical to 2D-Flatland individuals-in the spirit of E. A. Abbott's science fiction story of 1884 [Flatland, a Romance of Many Dimensions, 6th ed. (Dover, New York, 1952)]. Here we show how the light from a white source can be perceived in Flatland as perfectly monochromatic, so diffraction with white light will be free of color blurring and the contrast of interference fringes can be 100%. The basic considerations for perfectly achromatic diffraction are presented, along with experimental illustration of Talbot self-imaging performed with broadband illumination.

Journal Article↗
PubMed2001

[Toxicokinetics of terephthalic acid].

In order to study the toxicokinetics of terephthalic acid(TPA) in rats, and provide scientific basis for its biological exposed index (BEI), the concentrations of urine TPA in rats after single oral administration in dose of 100 mg/kg BW were determined by high pressure liquid chromatography. The toxicokinetic parameters were computed by using 3P97 program. The results showed that the first-order kinetics and two-compartment model were noted on the elimination of TPA. The main toxicokinetic parameters were as follows: Ka = 0.51/h, T1/2ka = 0.488 h, T1/2 alpha = 2.446 h, Tpeak = 2.160 h, Ku = 0.143/h, T1/2 beta = 31.551 h, Xu(max) = 10.00 mg. The excretion rates of TPA in urine were about 50%, 52% and 53% in 0-24 h, 0-48 h and 0-72 h respectively after administration. TPA is well absorbed when given orally and rapidly eliminated via urine. Urine TPA at the end of work shift should be considered as a biomarker of exposure for the occupational workers.

Animals↗
PubMed2001

[Characterization of speciation distribution of IPF-PFSi].

The preparation and speciation distribution characteristic of a new kind of inorganic polymer flocculant(IPF)-PFSi were investigated in detail by the combination of direct and indirect speciation analysis methods. The experimental results show that the speciation distribution of PFSi is decided significantly with basicity, kinds of silica and Si/Fe ratio. Among them, the basicity is one of the main factors. SilicaA and silicaB exhibit a similar effect, while silicaC has limited effect on the hydrolysis of Fe(III). The typical speciation distribution and transformation property of PFCl changes limitedly with the introduction of silica species.

Chlorides↗
PubMed2001

[Study of susceptibility loci located within Xp11 in attention deficit hyperactivity disorder].

OBJECTIVE: To detect the genetic relationship between monoamine oxidase(MAO) A type gene and attention deficit hyperactivity disorder(ADHD) in Chinese. METHODS: The haplotype-based haplotype relative risk(HHRR) and the transmission disequilibrium test(TDT) methods were used to analyze the genetic association and linkage in 60 ADHD children and their parents. RESULTS: In this sample were found significant association (chi(2)=4.90, P<0.05) and linkage (chi(2)=4.84, P<0.05) between the MAOCA 114bp allele and DSM-III-R-diagnosed ADHD in trios composed of father, mother and affected offspring. CONCLUSION: The above results suggested that ADHD was associated and in linkage with MAO A gene, and the susceptibility loci might reside in chromosome Xp11 for ADHD.

Attention Deficit Disorder with Hyperactivity↗
PubMed2001

[Adsorption of p-chlorophenol by biofilm and its components].

The p-chlorophenol (4-cp) adsorption to biofilm components was investigated by the experiment. Biofilm components included modeling water particulate (kaolin) with biofilm coating, bacterial cell, exopolysaccharide, kaolin and kaolin with exopolysaccharide. The adsorption of 4-cp in these systems could be described by Langmuir and Freundlich isotherm equations except the system of kaolin with exopolysaccharide. Under the condition of 25 degrees C and pH of 6.1 in these reaction systems, bacterial cell and EPS adsorbed more 4-cp than kaolin. The biofilm coating of kaolin affected its adsorption to 4-cp. Kaolin with biofilm coating adsorbed more 4-cp than that without biofilm coating.

Adsorption↗
PubMed2001

[A gene analysis of the low density lipoprotein receptor in Chinese with homozygous familial hyperchol-esterolemia].

OBJECTIVE: To investigate low density lipoprotein receptor(LDLR) gene mutations in Chinese with familial hyperchol-esterolemia(FH). METHODS: Genomic DNA was extracted from five unrelated children with clinical diagnosis of homozygous FH, together with their family members. Promoter and all of the 18 exons of LDLR gene were amplified by polymerase chain reaction (PCR) and were analyzed by single strand conformation polymorphism (SSCP). The PCR products of abnormal patterns shown by SSCP were sequenced directly. RESULTS: Two point mutations (A606T, C263R) were found in two families respectively. The two mutations were only found in China, and C263R is a novel mutation. CONCLUSION: The two mutations of LDLR gene are the cause of FH and there may be LDLR gene mutations only carried by FH patients in China.

Asian People↗
PubMed2001

[No evidence for association between the alpha 2-macroglobulin polymorphism and Alzheimer's disease in the Han Chinese].

OBJECTIVE: To determine the effect of the pentanucleotide deletion polymorphism adjacent to a consensus splice site in intron 17 of alpha 2-macroglobulin(A2M) gene on the development of late-onset Alzheimer's disease (LOAD) in the Han Chinese in Guangzhou area. METHODS: A2M and apolipoprotein E genotypes were examined by polymerase chain reaction(PCR) and restriction fragment length polymorphism (RFLP) techniques in the patients(32 men and 65 women) with LOAD and age-matched healthy elderly Chinese subjects (57 men and 54 women). RESULTS: The A2M gene deletion allele frequency was 2.6% in the cases with LOAD and 2.7% in the controls. In the LOAD cases, the frequency of apoE-epsilon4 increased significantly (Z=3.32, P<0.01). ApoE-epsilon4 was associated with LOAD (RR=2.67, chi(2)=10.71, P<0.01) while the A2M deletion polymorphism was not associated with LOAD even the samples were stratified according to the presence of the apoE-epsilon4 allele. CONCLUSION: The above data demonstrate that there is no evidence for the association of A2M polymorphism with the development of LOAD in the Han Chinese population in Gaungzhou.

Alzheimer Disease↗
PubMed2001

Representation of clinical practice guidelines for computer-based implementations.

Representation of clinical practice guidelines is a critical issue for computer-based guideline development, implementation and evaluation. We studied eight types of computer-based guideline representation models. Typical primitives for these models include decisions, actions, patient states and execution states. Temporal constraints and nesting are important aspects of guideline structure representation. Integration of guidelines with electronic medical records can be facilitated by the introduction of formal models of patient data. Patient states and execution states are closely related to one another. Data collection, decision, patient state and intervention are four basic steps in a guideline's logic flow.

Artificial Intelligence↗
PubMed2001

CT virtual endoscopy of the auditory ossicular chain: clinical applications.

OBJECTIVE: To evaluate the clinical applications and limitations of CT virtual endoscopy (CTVE) in the auditory ossicular chain. METHODS: CTVE of the auditory ossicular chain was performed with 1.0 mm collimation at pitch 1.0, bone algorithm, 9.6 cm field of view, and 0.1-0.2 mm reconstruction interval in 40 patients with middle ear diseases. 30 cases were confirmed by surgery. Results were compared with the findings of axial high resolution CT (HRCT) and multiplanar reformation (MPR) images and surgery. RESULTS: The accuracy of CTVE images in detecting ossicular destruction was 92.6%, significantly higher than that of axial HRCT (83.9%) and multiplanar reformation (76.5%) images. CTVE could also clearly reveal the postoperative condition and congenital dysplasia of the auditory ossicular chain. CONCLUSIONS: CTVE can clearly demonstrate a three-dimensional image of the auditory ossicular chain and is useful in evaluating diseases of the ear, especially the auditory ossicles. CTVE could not clearly demonstrate abnormal soft tissue within the tympanic cavity, abnormal changes of the tympanic membrane and tympanic walls, and could be easily influenced by artificial factors.

Adolescent↗
PubMed2001

Effect and mechanism of electronic magnetic pulse on peripheral lymphocytes in dogs.

OBJECTIVE: To study the effects of electronic magnetic pulse (EMP) on peripheral lymphocytes in dogs and to explore the mechanisms of the biological effects of EMP. METHODS: T, TH and TS lymphocytes were estimated by acid phosphatase cytochemistry. Apoptotic lymphocytes and Bax and Bcl-2 proteins related to apoptosis were observed with in situ terminal labeling and immunocytochemistry. RESULTS: Peripheral T lymphocyte subpopulations decreased obviously after EMP irradiation with (2-12) x 10(4) V/m. Apoptotic percentages of lymphocytes increased with the elevation of EMP doses. Ten days after different intensity radiation, the Bax protein was found to be elevated in accord with the peak value of lymphocyte apoptosis. However, Bcl-2 protein decreased obviously. CONCLUSION: A definite field intensity EMP could induce injury to lymphocytes. Apoptosis induced by EMP is one of the main causes of peripheral lymphocyte death and leads to immunosuppression of the body. These results suggest that people should pay more attention to the injury caused by EMP, especially to the immunological functions of the body.

Animals↗
PubMed2001

[Chronic hypoxia altered the mRNA expression of cyclooxygenase in intrapulmonary artery smooth muscle cell].

OBJECTIVE: To elucidate the effect of chronic hypoxia on the cyclooxygenase-2 mRNA expression in pulmonary artery smooth muscle cells of rats. METHODS: The gene expressions of COX-1 and COX-2 during acute hypoxia were measured with semi-quantified RT-PCR in the 2nd, 4th and 6th subculture of intrapulmonary artery smooth muscle cells (PASMC) of wistar rats under normoxic and continuous hypoxic condition separately. RESULTS: In all three generations, the expressions of COX-1 had no significant changes in hypoxia, while the COX-2 mRNA expression was higher in chronic hypoxic group than that in normoxic group and elevated with the duration of hypoxia exposure. After exposure to acute hypoxia, the augmentation of COX-2 mRNA expression in PASMC was higher in chronic hypoxic group than in normoxic group in all three subcultures. CONCLUSION: Chronic hypoxia could enhance the mRNA expression of cyclooxygenase-2 caused by acute hypoxia in PASMC of rats. It might be responsible for the lower HPV under chronic hypoxia.

Animals↗
PubMed2001

[Effect of lead stress on the activity of antioxidant enzymes in wheat seedling].

The changes of the antioxidant enzyme activity, such as superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) were researched through nutrient solution culture. The results showed that the activity of SOD in shoot and root were significantly enhanced under lead stress. The activity of CAT in root was also improved, but the degree was not bigger than that of SOD activity. However, the MDA content in shoot and root was significantly higher than that of check group, it suggested that the membrane system were damaged by lead stress. The experiments also revealed that the shoot of wheat seedling was influenced by lead stress greatly stronger than that of root.

Catalase↗