Biomedical subjects

Gang Hu

Publications and source records attributed to Gang Hu.

At least 55 records · Page 3Linked to original sources

PubMed2005

Relaxation to equilibrium in few-particle adiabatic piston systems.

A Hamiltonian system with few particles and a heavy adiabatic piston is studied. With ensemble averages based on proper classification of slow and fast variables, a nonequilibrium state is defined and the relaxation from nonequilibrium to equilibrium is investigated. Coherent oscillation, dissipative oscillation damping, and anti-intuition energy transfer of the adiabatic piston are observed by numerical simulations. Noise-driven thermodynamic equations of slow variables are derived, based on the assumption of local equilibrium and the fluctuation-dissipation theorem, to understand and quantitatively reproduce all the above few-body nonequilibrium relaxation features.

Journal Article↗

PubMed2005

Activation of mitochondrial ATP-sensitive potassium channels improves rotenone-related motor and neurochemical alterations in rats.

Our previous studies revealed that activation of mitochondrial ATP-sensitive potassium channels exerted protective effects on rotenone-treated rats and cultured cells. The aim of the present study is to examine the potential therapeutic effects of iptakalim, an ATP-sensitive potassium-channel opener, and diazoxide, a selective mitochondrial ATP-sensitive potassium-channel opener, on Parkinsonian symptoms in rats induced by rotenone. Rats were treated with rotenone (2.5 mg/kg s.c.) daily for 4 wk. This treatment caused a depletion of dopamine in the striatum and substantia nigra. Behaviourally, rotenone-infused rats exhibit Parkinsonian symptoms. Catalepsy was estimated by a 9-cm bar test. Treatment with L-dopa (10 mg/kg.d p.o.), iptakalim (0.75, 1.5, 3.0 mg/kg.d p.o.) and diazoxide (3.0 mg/kg.d p.o.) for 2 wk improved behavioural dysfunction and elevated dopamine contents in the striatum and substantia nigra of rotenone-treated rats. Studies also found that iptakalim and diazoxide could reduce the enzymic activities and mRNA levels of inducible nitric oxide synthase elicited by chronic administration of rotenone. All neurorestorative effects by both iptakalim and diazoxide were abolished by 5-hydroxydecanoate, a selective mitochondrial ATP-sensitive potassium-channel blocker. Collectively, the data suggested that mitochondrial ATP-sensitive potassium channels play a key role in improving both Parkinsonian symptoms and neurochemistry alterations of rotenone model rats, and selective activation of mitochondrial ATP-sensitive potassium channels may provide a new therapeutic strategy for treatment of early Parkinson's disease.

Animals↗

PubMed2005

Suppress Winfree turbulence by local forcing excitable systems.

The occurrence of Winfree turbulence is currently regarded as one of the principal mechanisms underlying cardiac fibrillation. We develop a local stimulation method that suppresses Winfree turbulence in three-dimensional excitable media. We find that Winfree turbulence can be effectively suppressed by locally injecting periodic signals to only a very small subset (around some surface region) of total space sites. Our method for the first time demonstrates the effectiveness of local low-amplitude periodic excitations in suppressing turbulence in 3D excitable media and has fundamental improvements in efficiency, convenience, and turbulence suppression speed compared with previous strategies. Therefore, it has great potential for developing into a practical low-amplitude defibrillation approach.

Animals↗

PubMed2005

The gender-specific impact of diabetes and myocardial infarction at baseline and during follow-up on mortality from all causes and coronary heart disease.

OBJECTIVES: The goal of this study is to compare the magnitude of diabetes and myocardial infarction (MI) at baseline and during follow-up on cause-specific and all-cause mortality. BACKGROUND: History of both MI and diabetes are strong predictors of coronary heart disease (CHD) death. However, gender-specific data on the joint effect of diabetes and MI, and particularly on the effect of incident diabetes and MI developed during the follow-up, on CHD mortality are scarce. METHODS: The baseline cohort study included 2,416 patients with prior diabetes or MI at baseline; the follow-up cohort study included 4,315 patients with incident diabetes or MI diagnosed during the follow-up. RESULTS: In the baseline cohort study, men with prior MI had a 20% to 80% increased risk of CHD or total mortality, but women with prior MI had a 43% to 45% decreased risk of CHD or total mortality in comparison with men and women with prior diabetes. In the follow-up cohort study, men and women with incident MI had a higher risk of CHD mortality (hazard ratio [HR] 2.15 in men and 1.65 in women), and an almost similar risk of total mortality (HR 0.95 in men and 1.02 in women) in comparison with men and women with incident diabetes. CONCLUSIONS: In men, MI at baseline or during follow-up confers a greater risk on CHD mortality than diabetes does. In women, prior MI at baseline confers a lower risk on CHD mortality than prior diabetes does, but incident MI during follow-up confers a greater risk than incident diabetes does. In both men and women, total mortality is similar for incident MI and diabetes.

Cohort Studies↗

PubMed2005

Systematic administration of iptakalim, an ATP-sensitive potassium channel opener, prevents rotenone-induced motor and neurochemical alterations in rats.

Our previous studies revealed that iptakalim, a novel ATP-sensitive potassium channel opener, has a significant neuroprotective function against ischemia in vivo or rotenone-induced neurotoxicity in vitro. To investigate the potential pharmaceutical benefit of ATP-sensitive potassium channel openers on neurodegenerative diseases, we studied the effects of iptakalim and diazoxide, a selective mitochondrial ATP-sensitive potassium channel opener, on the rotenone-induced nigrostriatal degeneration in rats. Iptakalim (1.5 mg/kg/day, orally) or diazoxide (1.5 mg/kg/day, orally) alone was administered to rats for 3 days, and then for 4 weeks was used daily with an injection of rotenone (2.5 mg/kg/day, subcutaneously) 1 hr later each time. The results showed that rotenone-infused rats exhibited parkinsonian symptoms and had dopamine depletion in the striatum and substantia nigra. Pretreatment with iptakalim or diazoxide prevented rotenone-induced catalepsy and the reduction of striatum dopamine contents. Moreover, iptakalim and diazoxide reduced the enzymatic activities and mRNA levels of inducible nitric oxide synthase elicited by chronic administration of rotenone. These neuroprotective effects of iptakalim and diazoxide were abolished by 5-hydroxydecanoate, a selective mitochondrial ATP-sensitive potassium channel blocker. In conclusion, our data suggested that mitochondrial ATP-sensitive potassium channels might play a key role in preventing both parkinsonian symptoms and neurochemistry alterations induced by rotenone in rats. The selective activation of mitochondrial ATP-sensitive potassium channels may provide a new therapeutic strategy for prevention and treatment of neurodegenerative disorders such as Parkinson's disease.

ATP-Binding Cassette Transporters↗

PubMed2005

Crystallization and preliminary X-ray crystallographic analysis of yeast NAD+-specific isocitrate dehydrogenase.

NAD+-specific isocitrate dehydrogenase (IDH; EC 1.1.1.41) is a complex allosterically regulated enzyme in the tricarboxylic acid cycle. Yeast IDH is believed to be an octamer containing four catalytic IDH2 and four regulatory IDH1 subunits. Crystals of yeast IDH have been obtained and optimized using sodium citrate, a competitive inhibitor of the enzyme, as the precipitating agent. The crystals belong to space group R3, with unit-cell parameters a = 302.0, c = 112.1 A. Diffraction data were collected to 2.9 A from a native crystal and to 4.0 A using multiwavelength anomalous diffraction (MAD) methods from an osmium derivative. Initial electron-density maps reveal large solvent channels and the molecular boundaries of the allosteric IDH multimer.

Allosteric Site↗

PubMed2005

Anti-proliferating effect of iptakalim, a novel KATP channel opener, in cultured rabbit pulmonary arterial smooth muscle cells.

ATP-sensitive potassium (K(ATP)) channels of pulmonary arterial smooth muscle cells (SMCs) have been implicated in pulmonary hypertension. Iptakalim, designed and synthesized by ourselves, is a newly selective K(ATP) channel opener. Here, we explored the effects of iptakalim on the rise of cytoplasmic free Ca(2+) concentration ([Ca(2+)](cyt)) induced by endothelin-1 (ET-1) and on the proliferation of cultured rabbit pulmonary arterial SMCs. The results showed that iptakalim inhibited the [Ca(2+)](cyt) increase. The enhanced [(3)H]thymidine incorporation was inhibited and the transition of cells from static phase (G(0)/G(1)) to DNA synthesis (S) and mitotic phase (G(2)/M) was held back by iptakalim in a concentration-dependent manner. Glyburide abolished the inhibitory effect of iptakalim. In conclusion, we have shown that iptakalim had an inhibitory effect on [Ca(2+)](cyt) increase and the proliferation of pulmonary arterial SMCs induced by endothelin-1 through activation of K(ATP) channels. These findings suggest that iptakalim might be a promising candidate for the treatment of pulmonary arterial remodeling in pulmonary hypertension.

ATP-Binding Cassette Transporters↗

PubMed2005

The distribution of neural nitric oxide synthase-positive cerebrospinal fluid-contacting neurons in the third ventricular wall of male rats and coexistence with vasopressin or oxytocin.

The detailed distribution of neural nitric oxide synthase (nNOS)-positive cerebrospinal fluid-contacting neurons (CSF-CN) was studied in the wall of the third ventricle of rats by anti-nNOS immunohistochemistry. The coexistence of nNOS and 8-arginine vasopressin (AVP) or oxytocin (OT) was also investigated in the CSF-CN using double labeling immunohistochemistry. The results demonstrated a widespread occurrence of nNOS-CSF-CN throughout the wall of the hypothalamic third ventricle. The vast majority of nNOS-CSF-CN cell bodies were of magnocellular type, commonly classified as oval, fusiform, multipolar, and inverted pear shape. These cell bodies were located in the ependyma, the subependyma, or the parenchyma, and their processes inserted in the ependymal layer or directly contacted with the CSF space. Electron microscopy demonstrated many nNOS-immunoreactive somas, dendrites, and/or axons that were situated at the subependyma, the ependyma, or the supraependyma. Generally, the distribution of OT-CSF-CN in the third ventricular wall was similar to the nNOS-CSF-CN and the ratio of NOS/OT co-expression was approximately 88%. In comparison, the distribution of AVP-CSF-CN was mainly restricted to the rostral part of the third ventricle and the ratio of nNOS/AVP co-expression was only about 6%. The widespread presence of nNOS-CSF-CN-expressing OT in the third ventricular region suggests that NO is an important messenger in the CSF-hypothalamo-hypophyseal neuroendocrine regulation that may in part act in concert with OT.

Animals↗

PubMed2005

Educational inequalities in the metabolic syndrome and coronary heart disease among middle-aged men and women.

BACKGROUND: Previous studies have shown socioeconomic inequalities in the metabolic syndrome and coronary heart disease (CHD), but it is not known whether educational disparities in the metabolic syndrome explain educational inequalities in CHD. We investigated this question in a prospective study of middle-aged men and women. METHODS: Baseline data were collected in 1992 in Finland from 864 men and 1045 women aged 45-64 years without history of CHD. A total of 113 new CHD cases were identified by the end of 2001. Logistic and Cox regression models were used in data analysis. RESULTS: The metabolic syndrome defined by NCEP criteria was less prevalent in subjects with university education (21% in men and 14% in women) compared with basic level education (41% and 27%, respectively). Adjusting for health behavioural factors had only a slight effect on the educational gradient in the metabolic syndrome. An educational gradient in CHD incidence was clear [hazard ratio (HR) = 0.67 95% confidence interval (CI) 0.48-0.94, men and women combined]. Adjustment for the metabolic syndrome attenuated this gradient only slightly, but when individual components of the metabolic syndrome were included as covariates the attenuation was more substantial (HR = 0.73 95% CI 0.52-1.04). CONCLUSIONS: Educational differences in the metabolic syndrome and CHD incidence are clear. Metabolic risk factors explain the gradient in CHD incidence partly, but only when they are treated as independent risk factors. Screening for the metabolic syndrome alone is not sufficient to account for socioeconomic inequalities in cardiovascular disease.

Coronary Disease↗

PubMed2005

Enhancing chaoticity of spatiotemporal chaos.

In some practical situations strong chaos is needed. This introduces the task of chaos control with enhancing chaoticity rather than suppressing chaoticity. In this paper a simple method of linear amplifications incorporating modulo operations is suggested to make spatiotemporal systems, which may be originally chaotic or nonchaotic, strongly chaotic. Specifically, this control can eliminate periodic windows, increase the values and the number of positive Lyapunov exponents, make the probability distributions of the output chaotic sequences more homogeneous, and reduce the correlations of chaotic outputs for different times and different space units. The applicability of the method to practical tasks, in particular to random number generators and secure communications, is briefly discussed.

Journal Article↗

PubMed2005

Differential gene expression by Metarhizium anisopliae growing in root exudate and host (Manduca sexta) cuticle or hemolymph reveals mechanisms of physiological adaptation.

Like many other fungal pathogens Metarhizium anisopliae is a facultative saprophyte with both soil-dwelling and insect pathogenic life-stages. In addition, as M. anisopliae traverses the cuticle and enters the hemolymph it must adapt to several different host environments. In this study, we used expressed sequence tags and cDNA microarray analyses to demonstrate that physiological adaptation by M. anisopliae to insect cuticle, insect hemolymph, bean root exudate (a model for life in the soil), and nutrient rich Sabouraud dextrose broth (SDB) involves different subsets of genes. Overall, expression patterns in cuticle and hemolymph clustered separately from expression patterns in root exudates and SDB, indicative of critical differences in transcriptional control during pathogenic and saprophytic growth. However, there were differences in gene expression between hemolymph and cuticle and these mostly involved perception mechanisms, carbon metabolism, proteolysis, cell surface properties, and synthesis of toxic metabolites. These differences suggest previously unsuspected stratagems of fungal pathogenicity that can be tested experimentally. Examples include the switch-off of cuticle-degrading proteases and a dramatic cell wall reorganization during growth in hemolymph.

Adaptation, Physiological↗

PubMed2005

Studies of ATP-sensitive potassium channels on 6-hydroxydopamine and haloperidol rat models of Parkinson's disease: implications for treating Parkinson's disease?

In the present study, we first investigated the effects of unilateral 6-hydroxydopamine (6-OHDA) lesioning of the substantia nigra pars compacta (SNc) on the expression of subunits of ATP-sensitive potassium channels (KATP channels) in the prefrontal cortex (PFC), striatum and hippocampus of adult rats by utilizing semiquantitative reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry techniques. The results show that Kir6.2 and SUR2 expression in the PFC, Kir6.1, Kir6.2 and SUR1 expression in the striatum, and Kir6.1 and Kir6.2 expression in the hippocampus of injured side increased significantly after unilateral 6-OHDA lesioning of the SNc in rats. Afterward, we studied the effects of iptakalim (Ipt), a novel ATP-sensitive potassium channel opener (KCO), on parkinsonian symptoms, which were induced by acute injection of haloperidol. The results indicate that intraperitoneal injection of Ipt (0.125 mg/kg, 0.25 mg/kg or 0.5 mg/kg) partially alleviated haloperidol-induced catalepsy and hypolocomotion. Even though the observed effects (0.5 mg/kg) are better than those of l-3,4-dihydroxyphenylalanine (L-DOPA) (100 mg/kg), Ipt (0.25 mg/kg) failed to enhance the anti-parkinsonian actions of L-DOPA (100 mg/kg). Our results suggest that KATP channels might be involved in the pathogenesis of Parkinson's disease (PD) induced in an animal model and conceptually support the idea that KATP channels may be new therapeutic targets for PD.

Adenosine Triphosphate↗

PubMed2005

Eyelid disease.

Explore the source record for details and available documents.

Corneal Diseases↗

PubMed2005

Visual orientation in a mirror world tilted 90 degrees.

Previously, we showed that many supine observers in a furnished room tilted 90 degrees perceive themselves and the room as upright. We called this the "levitation illusion" because the arms feel weightless when held out from the body. We now report that a familiar scene viewed by supine observers through a mirror at 45 degrees appears vertical when, optically, it is horizontal and above the head. However, the body feels pitched upright only partially. This visual-righting effect, like the levitation illusion, is due to the polarity axis of the scene being accepted as vertical even in the presence of conflicting information from the gravity sense organs. In experiment 1 we tested the potency of objects containing either intrinsic polarity (due to familiar tops and bottoms) or extrinsic polarity (due to support relationships) to generate a visual-righting illusion. To almost all observers, a blank surface seen in the mirror appeared like a ceiling. A scene containing an object with intrinsic polarity, such as a chair or person, seen in the mirror appeared vertical to almost all observers. A scene containing a pair of objects with only extrinsic polarity, such as a ball on a shelf (but not a ball under a shelf), also appeared vertical to most observers. In experiment 2 we found that a polarised scene was more likely to produce a visual-righting illusion when it was arranged as a view through a window rather than as a picture inside a room.

Adolescent↗

PubMed2005

Low physical activity as a predictor for antihypertensive drug treatment in 25-64-year-old populations in eastern and south-western Finland.

OBJECTIVE: To determine whether low leisure-time physical activity, occupational physical activity and commuting activity independently increase the risk of hypertension when adjusted for most risk factors for hypertension and for different forms of physical activity. DESIGN: Population-based prospective cohort study. SETTING: Eastern and south-western Finland. PARTICIPANTS: Men (n = 5935) and women (n = 6227) aged 25-64 years. MAIN OUTCOME MEASURE: Initiation of free-of-charge medication for hypertension during a mean follow-up time of 11.3 years. RESULTS: Men with high leisure-time physical activity had a reduced risk of hypertension when adjustment had been made for age, area and year of survey, education, smoking, alcohol intake, baseline systolic blood pressure (SBP), body mass index (BMI), commuting activity and occupational physical activity [hazard ratio (HR) 0.79; 95% confidence interval (CI) 0.63 to 0.99]. Women with high leisure-time physical activity had a reduced risk of hypertension when adjusted for age, area and time of survey (HR 0.65; 95% CI 0.46 to 0.91). This association was no longer significant when further adjustments were made for other covariates (HR 0.73; 95% CI 0.52 to 1.03). High occupational physical activity reduced the risk of hypertension only among men and women combined when adjustment was made for age, area and time of survey, education, smoking and alcohol intake, in addition to baseline SBP, BMI, commuting activity and leisure-time physical activity (HR 0.83; 95% CI 0.72 to 0.96). Commuting activity was not associated with risk of hypertension in multivariate models. CONCLUSION: High levels of leisure-time physical activity are associated with a reduced risk of hypertension, independently of most common risk factors for hypertension, occupational physical activity and commuting activity. Promoting leisure-time physical activity is essential to prevent hypertension.

Adult↗

PubMed2005

The validity of the Finnish Diabetes Risk Score for the prediction of the incidence of coronary heart disease and stroke, and total mortality.

BACKGROUND: Cardiovascular disease shares several risk factors with type 2 diabetes. We tested whether the Finnish Diabetes Risk Score (FINDRISC), recently developed in a Finnish population to estimate the future risk of diabetes, would also identify individuals at high risk of coronary heart disease (CHD) and stroke, and total mortality in this same population. DESIGN: Independent risk factor surveys were conducted in 1987, 1992, and 1997 in Finland, comprising 8268 men and 9457 women aged 25-64 years and free of CHD and stroke at baseline. During the follow-up until the end of 2001, 699 incident acute CHD events, 324 acute stroke events, and 765 deaths occurred. METHODS: The data were analysed by using receiver operating characteristic (ROC) curves and the Cox-regression model. RESULTS: The areas under the ROC curves (AUC) were 71% for CHD, 73% for stroke, and 68% for total mortality in men and 78, 68, and 72% in women, respectively. The addition of systolic and diastolic blood pressures, total and high-density lipoprotein cholesterol, and smoking increased the AUC values modestly (the change of the absolute values from 2.6 to 6.5%), but the additional use of plasma glucose had only a slight effect on the AUC values for CHD and stroke. CONCLUSIONS: The FINDRISC is a reasonably good predictor of CHD, stroke and total mortality.

Adult↗

PubMed2005

Variation in gene expression patterns as the insect pathogen Metarhizium anisopliae adapts to different host cuticles or nutrient deprivation in vitro.

Metarhizium anisopliae infects a broad range of insects by direct penetration of the host cuticle. To explore the molecular basis of this process, its gene expression responses to diverse insect cuticles were surveyed, using cDNA microarrays constructed from an expressed sequence tag (EST) clone collection of 837 genes. During growth in culture containing caterpillar cuticle (Manduca sexta), M. anisopliae upregulated 273 genes, representing a broad spectrum of biological functions, including cuticle-degradation (e.g. proteases), amino acid/peptide transport and transcription regulation. There were also many genes of unknown function. The 287 down-regulated genes were also distinctive, and included a large set of ribosomal protein genes. The response to nutrient deprivation partially overlapped with the response to Man. sexta cuticle, but unique expression patterns in response to cuticles from another caterpillar (Lymantria dispar), a cockroach (Blaberus giganteus) and a beetle (Popilla japonica) indicate that the pathogen can respond in a precise and specialized way to specific conditions. The subtilisins provided an example of a large gene family in which differences in regulation could potentially allow virulence determinants to target different hosts and stages of infection. Comparisons between M. anisopliae and published data on Trichoderma reesei and Saccharomyces cerevisiae identified differences in the regulation of glycolysis-related genes and citric acid cycle/oxidative phosphorylation functions. In particular, M. anisopliae has multiple forms of several catabolic enzymes that are differentially regulated in response to sugar levels. These may increase the flexibility of M. anisopliae as it responds to nutritional changes in its environment.

Adaptation, Physiological↗

PubMed2005

Enhancement of glutamate uptake mediates the neuroprotection exerted by activating group II or III metabotropic glutamate receptors on astrocytes.

We investigated whether the activation of astroglial group II and III metabotropic glutamate receptors (mGluRs) could exert neuroprotective effects and whether the neuroprotection was related to glutamate uptake. Our results showed that the activation of astroglial group II or III mGluRs exerted neuroprotection against 1-methyl-4-phenylpyridinium (MPP+) astroglial conditioned medium-induced neurotoxicity in midbrain neuron cultures. Furthermore, MPP+ decreased glutamate uptake of primary astrocytes and C6 glioma cells, which was recovered by activating group II or III mGluRs. Specific group II or III mGluRs antagonists completely abolished the neuroprotective effects and the enhancement of glutamate uptake of their respective agonists. Our results showed that the primary cultured rat astrocytes and C6 glioma cells expressed receptor proteins for group II mGluR2/3, group III mGluR4, mGluR6 and mGluR7. C6 glioma cells expressed mRNA for group II mGluR3, group III mGluR4, mGluR6, mGluR7 and mGluR8. In conclusion, we confirmed that the activation of astroglial mGluRs exerted neuroprotection, and demonstrated that the mechanism underlying this protective role was at least partially related to the enhancement of glutamate uptake.

1-Methyl-4-phenylpyridinium↗