Biomedical subjects

Gang Hu

Publications and source records attributed to Gang Hu.

At least 109 records · Page 6Linked to original sources

PubMed2003

Experimental investigation of partial synchronization in coupled chaotic oscillators.

The dynamical behavior of a ring of six diffusively coupled Rössler circuits, with different coupling schemes, is experimentally and numerically investigated using the coupling strength as a control parameter. The ring shows partial synchronization and all the five patterns predicted analyzing the symmetries of the ring are obtained experimentally. To compare with the experiment, the ring has been integrated numerically and the results are in good qualitative agreement with the experimental ones. The results are analyzed through the graphs generated plotting the y variable of the ith circuit versus the variable y of the jth circuit. As an auxiliary tool to identify numerically the behavior of the oscillators, the three largest Lyapunov exponents of the ring are obtained.

Models, Theoretical↗

PubMed2003

Expressed sequence tag (EST) analysis of two subspecies of Metarhizium anisopliae reveals a plethora of secreted proteins with potential activity in insect hosts.

Expressed sequence tag (EST) libraries for Metarhizium anisopliae, the causative agent of green muscardine disease, were developed from the broad host-range pathogen Metarhizium anisopliae sf. anisopliae and the specific grasshopper pathogen, M. anisopliae sf. acridum. Approximately 1,700 5' end sequences from each subspecies were generated from cDNA libraries representing fungi grown under conditions that maximize secretion of cuticle-degrading enzymes. Both subspecies had ESTs for virtually all pathogenicity-related genes cloned to date from M. anisopliae, but many novel genes encoding potential virulence factors were also tagged. Enzymes with potential targets in the insect host included proteases, chitinases, phospholipases, lipases, esterases, phosphatases and enzymes producing toxic secondary metabolites. A diverse array of proteases composed 36 % of all M. anisopliae sf. anisopliae ESTs. Eighty percent of the ESTs that could be clustered into functional groups had significant matches (E<10(-5)) in other ascomycete fungi. These included genes reported to have specific roles in pathogens with plant or vertebrate hosts. Many of the remaining ESTs had their best BLAST match among animal, plant and bacterial sequences. These include genes with plant and microbial counterparts that produce potent antimicrobials. The abundance of transcripts discovered for different functional groups varied between the two subspecies of M. anisopliae in a manner consistent with ecological adaptations of the two pathogens. By hastening gene discovery this project has enhanced development of improved mycoinsecticides. In addition, the M. anisopliae ESTs represent a significant contribution to the extensive database of sequences from ascomycetes that are saprophytes or plant and vertebrate pathogens. Comparative analyses of these sequences is providing important information about the biology and evolutionary history of this clade.

Animals↗

PubMed2003

EST analysis of genes expressed by the zygomycete pathogen Conidiobolus coronatus during growth on insect cuticle.

Conidiobolus coronatus (Zygomycota) is a facultative saprobe that is a pathogen of many insect species. Almost 2000 expressed sequence tag (EST) cDNA clones were sequenced to analyse gene expression during growth on insect cuticle. Sixty percent of the ESTs that could be clustered into functional groups (E<or=10(-5)) had their best BLAST hits among fungal sequences. These included chitinases and multiple subtilisins, trypsin, metalloprotease and aspartyl protease activities with the potential to degrade host tissues and disable anti-microbial peptides. Otherwise, compared to the ascomycete entomopathogen Metarhizium anisopliae, Con. coronatus produced many fewer types of hydrolases (e.g. no phospholipases), antimicrobial agents, toxic secondary metabolites and no ESTs with putative roles in the generation of antibiotics. Instead, Con. coronatus produced a much higher proportion of ESTs encoding ribosomal proteins and enzymes of intermediate metabolism that facilitate its rapid growth. These results are consistent with Con. coronatus having adapted a modification of the saprophytic ruderal-selected strategy, using rapid growth to overwhelm the host and exploit the cadaver before competitors overrun it. This strategy does not preclude specialization to pathogenicity, as Con. coronatus produces the greatest complexity of proteases on insect cuticle, indicating an ability to respond to conditions in the cuticle.

Animals↗

PubMed2003

Age- and sex-specific prevalence of diabetes and impaired glucose regulation in 11 Asian cohorts.

OBJECTIVE: To report the age- and sex-specific prevalence of diabetes and impaired glucose regulation (IGR) according to revised World Health Organization criteria for diabetes in Asian populations. RESEARCH DESIGN AND METHODS: We performed 11 studies of 4 countries, comprising 24,335 subjects (10,851 men and 13,484 women) aged 30-89 years who attended the 2-h oral glucose tolerance test and met the inclusion criteria for data analysis. RESULTS: The prevalence of diabetes increased with age and reached the peak at 70-89 years of age in Chinese and Japanese subjects but peaked at 60-69 years of age followed by a decline at the 70 years of age in Indian subjects. At 30-79 years of age, the 10-year age-specific prevalence of diabetes was higher in Indian than in Chinese and Japanese subjects. Indian subjects also had a higher prevalence of IGR in the younger age-groups (30-49 years) compared with that for Chinese and Japanese subjects. Impaired glucose tolerance was more prevalent than impaired fasting glycemia in all Asian populations studied for all age-groups. CONCLUSIONS: Indians had the highest prevalence of diabetes among Asian countries. The age at which the peak prevalence of diabetes was reached was approximately 10 years younger in Indian compared with Chinese and Japanese subjects. Diabetes and IGR will be underestimated in Asians based on the fasting glucose testing alone.

Adult↗

PubMed2003

Iptkalim inhibits cocaine challenge-induced enhancement of dopamine levels in nucleus accumbens and striatum of rats by up-regulating Kir6.1 and Kir6.2 mRNA expression.

AIM: To investigate the effect and mechanism of novel ATP-sensitive potassium channel opener (KCO) iptkalim (IPT) on acute and cocaine challenge-induced alterations in the levels of dopamine (DA) and glutamate (Glu) from nucleus accumbens (NAc), striatum, and prefrontal cortex (PFC) in rats. METHODS: The levels of DA and Glu were assayed using high performance liquid chromatography (HPLC) combined with amperometric and fluorescent detection, respectively. The mRNA levels of Kir6.1, Kir6.2, SUR1, and SUR2 were measured by semiquantitative reverse transcription polymerase chain reaction (RT-PCR). RESULTS: IPT did not affect acute cocaine (30 mg/kg, ip)-induced elevations in either DA levels from NAc and striatum or Glu levels from NAc and PFC. An acute cocaine challenge (30 mg/kg, ip) on d 21 after withdrawal caused an elevation in DA levels in NAc and striatum. Moreover, the same treatment also increased Glu levels in PFC and NAc of cocaine-pretreated rats. Repeated IPT injections reversed cocaine challenge-induced DA increase in NAc and striatum. Cocaine challenge increased Kir6.1 and Kir6.2 mRNA expression in striatum and NAc and only elevate Kir6.2 expression in PFC in both cocaine-pretreated rats and rats pretreated with IPT plus cocaine. Moreover, expression of Kir6.1 and Kir6.2 mRNA was augmented in rats pretreated with IPT plus cocaine compared to rats pretreated with cocaine alone. No significant change was found in the SUR1 and SUR2 expression of all four groups. CONCLUSION: IPT inhibited cocaine challenge-induced enhancement of DA levels in NAc and striatum by up-regulating Kir6.1 and Kir6.2 mRNA expression.

Animals↗

PubMed2003

Group I mGluR ligands fail to affect 6-hydroxydopamine- induced death and glutamate release of PC12 cells.

AIM: To study the effect of group I metabotropic glutamate receptor (mGluR) ligands on 6-hydroxydopamine (6-OHDA)-induced death and glutamate release of PC12 cells. METHODS: PC12 cells were exposed to 100 micromol/L of group I mGluR agonist (RS)-3,5-dihydroxy-phenylglycine (DHPG) or antagonist DL-2-amino-3-phosphonopropionic acid (DL-AP3) 1 h before addition of 6-OHDA 100 micromol/L. After incubation for 24 h, morphological alterations were observed with microscope, DNA fragmentation was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) method, cytotoxicity was measured by MTT assay, and glutamate release was assayed by high performance liquid chromatography. RESULTS: 6-OHDA decreased cell viability (P<0.01) and induced concentration- and time-dependent glutamate release from PC12 cells. Group I mGluR ligands did not affect 6-OHDA-induced death of PC12 cells and had no influence on glutamate levels. CONCLUSION: Group I mGluR ligands cannot protect PC12 cells from 6-OHDA-induced death.

Adrenergic Agents↗

PubMed2003

[Relationship between neurotoxicity of 6-hydroxydopamine and glutamate transport].

AIM: To study the relationship of neurotoxicity of 6-hydroxydopamine (6-OHDA) and the function of glutamate transporter. METHODS: Using in vivo microdialysis together with high performance liquid chromatography (HPLC) to detect the alteration of glutamate in the striatum and extracellular fluid of the PC12 cell. The rate of apoptosis and the activity of PC12 cells are read in a flow cytometer and a photometer for enzyme-labeled assays. The function of glutamate transporter is decided by detecting the ability of L-[3H]-glutamate uptake. RESULTS: 6-OHDA was shown to induce apoptosis and decrease the activity of PC12 cells. Increased release of glutamate was also found in PC12 cells and the injured striatum of the PD rats. But glutamate uptake in PC12 cells and rat striatum synaptosomes are inhibited obviously. CONCLUSION: The neurotoxicity of 6-hydroxydopamine is associated with declined function of glutamate transporters, which may be one important pathogenesis mechanisms of Parkinson's disease.

Amino Acid Transport System X-AG↗

PubMed2003

[Expression of amino terminal of nucleoprotein and glycoprotein G2 of Hantaan virus in insect cells in the form of fusion protein].

AIM: To express the glycoprotein G2 and amino terminal of nucleoprotein (NP) of Hantaan virus in Bac-to-Bac baculovirus expression system in the form of fusion protein. METHODS: The recombinant baculovirus expression vector pFBDHTa-G2S 0.7 was constructed. The chimeric gene was inserted into bacmid in E.coli DH10Bac with the help of Tn7 transposition system. Then the recombinant baculovirus was screened and the fusion protein was expressed in insect cells. The expression product was detected by ELISA, immunofluorescence assay and Western blot analysis. RESULTS: The recombinant baculovirus containing the chimeric gene G2S 0.7 had been constructed successfully and the fusion protein could be expressed in insect cells. The expressed protein could be recognized by the Hantaan virus NP-specific mAb and glycoprotein G2-specific mAb. CONCLUSION: The successful expression of fusion protein G2S 0.7 with biological activity in insect cells lays the foundation for further research on its immunological characteristic.

Animals↗

PubMed2002

Chaos-based secure communications in a large community.

One-way coupled map lattices are used for cryptography in secure communication, based on spatiotemporal chaos synchronization. The sensitivity of synchronization between the encryption and decryption systems can be adjusted by varying the system size. With a suitable parameter combination, the cryptosystem can reach optimal trade-off of security and performance, i.e., it shows high security (resistant against the public-structure and known-plaintext attacks) together with fast encryption (and decryption) speed. An experiment of duplex voice transmission through university network is realized, which confirms the above advantages of our approach.

Journal Article↗

PubMed2002

Determination of sugars in Chinese traditional drugs by CE with amperometric detection.

A simple, fast and reliable method, based on capillary zone electrophoresis with amperometric detection, for the separation and determination of sucrose, glucose, and fructose in Chinese traditional drugs, namely Astragalus Membranceus (Fish.) Bge, Angelica and Codonopsis pilosula (Franch.) Nannf. was described in this paper. A copper disk electrode was used as working electrode. The optimal conditions of separation and detection were 0.05 mol/l sodium hydroxide buffer (pH 12.7), 5 kV for the separation voltage and +0.65 V (vs. Ag/AgCl) for the detection potential. The linear ranges were from 5.0x10(-6) to 5.0x10(-4) mol/l for all three sugars. The all regression coefficients were more than 0.999. The detection limits were 1.0x10(-6) mol/l for glucose and fructose, and 4.0x10(-6) mol/l for sucrose. The method built in this paper was directly applied to the separation and determination of the three sugars in three Chinese traditional drugs without prior derivatization, and the content for every sugar in the drugs was first assayed. The assay results were satisfactory.

Angelica↗

PubMed2002

Estrogenicity of organophosphorus and pyrethroid pesticides.

Although organophosphorus and pyrethroid pesticides are considered environmental contaminants, their estrogenic potentials are still ubiquitous and unclear. The present study was undertaken to evaluate the estrogenic activities of nine pesticides (phoxim, malathion, monocrotophos, dimethoate, opunal, fenvalerate, cypermethrin, permethrin, and deltamethrin) using three in vitro methods [E-Screen assay, estrogen receptor (ER) competitive binding assay, and pS2 expression assay]. All the pyrethroid pesticides tested induced MCF-7 cell proliferation significantly, while organophosphorus pesticides did not. The estrogenic potency were ranked as permethrin > fenvalerate > cypermethrin > deltamethrin. The proliferation induced by cypermethrin, permethrin, and deltamethrin was blocked by ICI 182.780, while fenvalerate only partly inhibited it. In addition, pyrethroid pesticides inhibited the binding of [3H]estradiol to ER, while the organophosphorus failed to do so. Fenvalerate, permethrin, and cypermethrin induced pS2 mRNA expression with varying potency, while there were no significant effects in deltamethrin-treated groups. Our findings provide evidence to support the idea that pyrethroid pesticides tested produce an ER-specific, agonist response. Fenvalerate induced MCF-7 cell proliferation by a mechanism not involving ER-mediated pathway. Organophosphorus pesticides tested showed no estrogenic potential. Compared with the pS2 expression assay, E-Screen was a more sensitive and useful assay for screening of the xenoestrogenic chemicals.

Animals↗

PubMed2002

Turbulence control by developing a spiral wave with a periodic signal injection in the complex Ginzburg-Landau equation.

Turbulence control in the two-dimensional complex Ginzburg-Landau equation is investigated. An approach is proposed for the purpose of control. In the presence of a small spiral wave seed initiation, a fully developed turbulence can be completely annihilated by injecting a single periodic signal into a small fixed space area around the spiral wave tip. The control is achieved in a parameter region where the spiral wave of the uncontrolled system is absolutely unstable. The robustness, convenience, and high control efficiency of this method are emphasized, and the mechanism underlying these practical advantages is intuitively understood.

Journal Article↗

PubMed2002

Collective directed transport of symmetrically coupled lattices in symmetric periodic potentials.

A mechanism responsible for the directed transport of symmetrically coupled lattices in a symmetric periodic potential is proposed. Under the action of an external wave that breaks the spatiotemporal symmetry and introduces inhomogeneities of the lattice, a net unidirectional current can be observed, originating from a collaboration of the lattice (periodic potential and mutual interactions) and the wave (amplitude, frequency, and phase shifts). Mode-locking induced resonant steps are observed and predicted. The directed transport can be optimized and furthermore controlled by suitably adjusting the parameters of the system.

Journal Article↗

PubMed2002

Direct synthesis of uniform hollow carbon spheres by a self-assembly template approach.

Hollow carbon spheres (50-100 nm) have been synthesized by a self-assembly approach using hexachlorobenzene and Na. NaCl which generated during the reaction has been successfully exploited as a template for the direct synthesis of porous carbon materials, which can be subsequently removed from carbon product by annealing above 1400 degrees C.

Journal Article↗

PubMed2002

Intermembrane spacing and velocity profiling of a lamellar lyotropic complex fluid under flow using x-ray diffraction.

We report on the use of x-ray diffraction as a means of extracting velocity profiles from a non-Newtonian complex fluid under laminar flow. In particular, we applied this technique to a concentrated undulating membrane system flowing through a cylindrical capillary tube. The intermembrane separation d was measured as a function of simple shear using a Couette flow cell. A logarithmic dependence of d as a function of the shear rate was observed, while there was a linear relationship between the fractional intermembrane spacing and the shear stress. Subsequent measurement of the system's intermembrane spacing as a function of position within the cylindrical flow pipe allowed for the calculation of a shear-rate profile within the capillary. Simple numerical integration then yielded an accurate velocity profile of the fluid flowing through the pipe. Both shear thickening and plug flow shear thinning profiles were observed.

Journal Article↗

PubMed2002

Statistical mechanics of two hard disks in a rectangular box.

A system of two hard disks in a rectangular box is studied based on the exact partition function and equilibrium distribution functions of particles. Box-size dependence of some quantities of interest, such as pressure and the particle distribution functions, is investigated and in particular the negative compressibility of the van der Waals type and the corresponding phase transition are analyzed in detail. This system turns out to have rich structures that are related to the ergode-nonergode transitions in this system.

Journal Article↗

PubMed2002

Pattern formation of spiral waves in an inhomogeneous medium with small-world connections.

Pattern formation of spiral waves in an inhomogeneous excitable medium with small-world connections is investigated. In both cases, with completely local regular connections and with completely random connections, spiral waves cannot survive in the given inhomogeneous medium. It is found that with small-world connections (basically local connections plus a small number of random connections) a well behaved spiral wave can be formed against the destructive role of the inhomogeneous medium. There also exists an optimal fraction of random connections which can greatly enhance the probability of spiral wave formation; this resembles the behavior of stochastic resonance.

Journal Article↗

PubMed2002

Nonhypertensive cardiac effects of a high salt diet.

Dietary salt intake plays a major role in variation of blood pressure levels and cardiovascular conditions. High salt intake is associated with the occurrence of hypertension. The evidence that high salt intake increases risk of cardiovascular disease is inconsistent. Some studies indicate a significant and positive association between salt intake and risk of cardiovascular disease, whereas several other studies report that such an association may not exist and that low sodium may even be harmful. It is clear that left ventricular hypertrophy is closely related to salt intake. There is evidence indicating that high salt intake increases renal glomerular filtration rate and glomerular filtration fraction in salt-sensitive patients. The association of high salt intake, insulin resistance, and salt sensitivity, and the interaction between high salt intake, heart rate, and blood pressure are debated.

Blood Pressure↗