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Biomedical subjects

Y T Wang

Publications and source records attributed to Y T Wang.

At least 73 records · Page 4Linked to original sources
PubMed2000

Production of tumour necrosis factor alpha by primary cultured rat alveolar epithelial cells.

Tumour necrosis factor alpha(TNF-alpha) is one of the most important pro-inflammatory cytokines, which plays an important role in host defense and acute inflammation related to tissue injury. The major source of TNF-alpha has been shown to be immune cells such as macrophages and neutrophils. In the present study, we demonstrated that LPS-treatment on alveolar epithelial cells isolated from adult rat lungs also induced a dose- and time-dependent release of TNF-alpha. The purity and identity of these cells were examined by immunofluorescent staining and confocal microscopy with antibodies for cytokeratin and pro-surfactant protein C, markers for epithelial cells and type II pneumocytes respectively. Positive staining of TNF-alpha was observed throughout the cell layer and localized intracellularly. LPS-induced TNF-alpha production from alveolar epithelial cells was blocked not only by cycloheximide, an inhibitor of protein translation, but also by actinomycin D, an inhibitor of gene transcription. The mRNA of TNF-alpha rapidly increased within 1 h of LPS stimulation. These data suggest that LPS-induced TNF-alpha production from alveolar epithelial cells is primarily regulated at the transcriptional level, which is different from that of macrophages and neutrophils. TNF-alpha produced by alveolar epithelial cells may function as an alert signal in host defense to induce production of other inflammatory mediators.

Animals↗
PubMed2000

Intracellular trafficking of AMPA receptors in synaptic plasticity.

Modification of ligand-gated receptor function at the postsynaptic domain is one of the most important mechanisms by which the efficacy of synaptic transmission in the nervous system is regulated. Traditionally, these types of modifications have been thought to be achieved mainly by altering the channel-gating properties or conductance of the receptors. However, recent evidence suggests that AMPA (alpha-amino-3-hydroxyl-5-methyl-4-isoxayolepropionic acid)-type ligand-gated glutamate receptors are continuously recycling between the plasma membrane and the intracellular compartments via vesicle-mediated plasma membrane insertion and clathrin-dependent endocytosis. Regulation of either receptor insertion or endocytosis results in a rapid change in the number of these receptors expressed on the plasma membrane surface and in the receptor-mediated responses, thereby playing an important role in mediating certain forms of synaptic plasticity. Thus, controlling the number of postsynaptic receptors by regulating the intracellular trafficking and plasma membrane expression of the postsynaptic receptors may be a common and important mechanism of synaptic plasticity in the mammalian central nervous system.

Cell Line↗
PubMed2000

Expression of cerebellar long-term depression requires postsynaptic clathrin-mediated endocytosis.

Cerebellar long-term depression (LTD) is a cellular model system of information storage that may underlie certain forms of motor learning. While cerebellar LTD is expressed as a selective modification of postsynaptic AMPA receptors, this might involve changes in receptor number/distribution, unitary conductance, kinetics, or glutamate affinity. The observation that GluR2-containing synaptic AMPA receptors could be internalized by regulated clathrin-mediated endocytosis suggested that this process could underlie LTD expression. To test this hypothesis, we postsynaptically applied dynamin and amphiphysin peptides that interfere with the clathrin endocytotic complex and found that they blocked LTD expression in cultured Purkinje neurons. In addition, induction of LTD and attenuation of AMPA responses by stimulation of clathrin-mediated endocytosis occluded each other. These findings suggest that the expression of cerebellar LTD requires clathrin-mediated internalization of postsynaptic AMPA receptors.

Animals↗
PubMed2000

Regulation of AMPA receptor-mediated synaptic transmission by clathrin-dependent receptor internalization.

Redistribution of postsynaptic AMPA- (alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid-) subtype glutamate receptors may regulate synaptic strength at glutamatergic synapses, but the mediation of the redistribution is poorly understood. We show that AMPA receptors underwent clathrin-dependent endocytosis, which was accelerated by insulin in a GluR2 subunit-dependent manner. Insulin-stimulated endocytosis rapidly decreased AMPA receptor numbers in the plasma membrane, resulting in long-term depression (LTD) of AMPA receptor-mediated synaptic transmission in hippocampal CA1 neurons. Moreover, insulin-induced LTD and low-frequency stimulation-(LFS-) induced homosynaptic CA1 LTD were found to be mutually occlusive and were both blocked by inhibiting postsynaptic clathrin-mediated endocytosis. Thus, controlling postsynaptic receptor numbers through endocytosis may be an important mechanism underlying synaptic plasticity in the mammalian CNS.

Adaptor Protein Complex alpha Subunits↗
PubMed2000

Molecular spectroscopy study of the reaction of nucleic acids with brilliant cresol blue.

The interaction of brilliant cresol blue (BCB) with nucleic acids in aqueous solution has been studied by spectrophotometry and Rayleigh light scattering (RLS) spectroscopy. Under suitable conditions, the RLS spectra of BCB changed significantly due to the presence of nucleic acids. RLS intensity of BCB at 364 nm is greatly enhanced with the addition of nucleic acids, and a new RLS peak is observed at 552 nm. This peak is about half the intensity of that at 364 nm. The results of this study show that BCB interacts with DNA possibly due to the cooperative effect of electrostatic attraction, intercalation, coordination and hydrophobic effect. Under optimum conditions, the increase of RLS at 364 nm of a BCB solution is proportional to the concentration of nucleic acids added. This result is the basis for a new RLS method for determination of nucleic acids. The linear range of ctDNA, fsDNA and yRNA is 0.12-4.70, 0.11-4.64 and 0.43-7.07 microg ml(-1), respectively.

Hydrogen-Ion Concentration↗
PubMed2000

Distinct molecular mechanisms and divergent endocytotic pathways of AMPA receptor internalization.

Internalization of postsynaptic AMPA receptors depresses excitatory transmission, but the underlying dynamics and mechanisms of this process are unclear. Using immunofluorescence and surface biotinylation, we characterized and quantified basal and regulated AMPA receptor endocytosis in cultured hippocampal neurons, in response to synaptic activity, AMPA and insulin. AMPA-induced AMPA receptor internalization is mediated in part by secondary activation of voltage-dependent calcium channels, and in part by ligand binding independent of receptor activation. Although both require dynamin, insulin- and AMPA-induced AMPA receptor internalization are differentially dependent on protein phosphatases and sequence determinants within the cytoplasmic tails of GluR1 and GluR2 subunits. AMPA receptors internalized in response to AMPA stimulation enter a recycling endosome system, whereas those internalized in response to insulin diverge into a distinct compartment. Thus, the molecular mechanisms and intracellular sorting of AMPA receptors are diverse, and depend on the internalizing stimulus.

Animals↗
PubMed2000

Respiratory monitoring using an air-mattress system.

This paper describes a non-invasive respiratory monitoring system using an air mattress. The air-mattress system features multiple air compartments to monitor movements of the thorax and the abdomen separately. To evaluate the performance of the air-mattress system, four subjects were selected for the study and their separate ribcage and abdominal movements were monitored simultaneously by respiratory inductive phlethysmography belts and the air-mattress system. The sensitivity and accuracy indices of the air-mattress system for the detection of hypopnoeas scored remarkably well (above 90%). In addition, it was noted that the mean error in the measurement of the respiratory rate between the two systems was very small. This paper shows that the air-mattress system can be a reliable non-invasive respiratory monitoring system to detect simple abnormalities in breathing, such as respiration rate and hypopnoeas.

Abdomen↗
PubMed2000

Patient and disease characteristics, and outcome of treatment defaulters from the Singapore TB control unit--a one-year retrospective survey.

SETTING: The Singapore Tuberculosis Control Unit. OBJECTIVES: 1) To identify any demographic, social, disease or treatment-related characteristics which may be predictive of patients defaulting from treatment; 2) to assess the effectiveness of home visits as a means of defaulter recall; 3) to ascertain outcome in these patients. DESIGN: A retrospective, case-controlled study of TB treatment defaulters, defined as patients who missed their scheduled appointments and required a home visit to recall for treatment. Controls were randomly selected, non-defaulting patients who started treatment on the same dates as the defaulters. RESULTS: Forty-four patients required home visits in 1996. Compared to controls, defaulters were more likely to be non-Chinese, and to live on their own or with friends. There was no significant association of defaulting with age, sex, marital or employment status, disease characteristics, or treatment-related factors. Seventy per cent defaulted during the continuation phase of treatment. Home visits did not result in contact with the patient (or any other person) 41% of the time. Although 48% of the defaulters remained lost to follow-up at the time of the survey, all but one of the sputum-positive patients had bacteriologically converted by the time of default. CONCLUSION: Non-Chinese ethnicity and lack of family support were found to be factors strongly predictive of default. Age, sex, marital and employment status, treatment-related factors and disease characteristics were not significant in distinguishing those at risk for defaulting.

Case-Control Studies↗
PubMed2000

[Inheritance of resistance to Heterodera glycines race 14 in Huibuzhi black bean].

Heterodera glycines is the most serious disease in the world soybean (Glycine max) production. Huibuzhi black bean from Xing County in Shanxi Province, China is one of the most important resistant resources. Using a set of host differentials for soybean cyst nematode and criterion of race classification as well as method of manual inoculation, race 14 was identified as a prevalent one in the soil population of the Experiment Station, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing. A sensitive variety #7 Jidou as a female donor crossed with Huibuzhi black bean. Their offsprings were investigated for resistance to race 14. Two of F1 seedlings demonstrated their resistant. Two populations in F2 including 116 seedlings and 78 seedlings in each one appeared their own separate ratio that was in common: 43R:21S. A genetic hypothesis was proposed that resistance to SCN race 14 in Huibuzhi black bean was controlled by three gene pairs arose. Gene reciprocity existed among them: one recessive epistasis gene pair and two dominant complementary gene pairs. Random 30 families in F3 including 10-15 tested seedlings in each family were screened for resistance to SCN race 14. The segregate ratio, 19R:38Seg.:7S, among F3 families confirmed that the presented genetic hypothesis was correct.

Animals↗
PubMed2000

A complex containing both trypsin inhibitor and dehydroascorbate reductase activities isolated from mitochondria of etiolated mung bean (Vigna radiata L. (Wilczek) cv. Tainan no. 5) seedlings.

A complex containing trypsin inhibitor (TI) activity was extracted with 0.1 M TRIS buffer (pH 7.9) from trypsin-treated mitochondria of etiolated mung bean seedlings, and further purified with a Superdex 200 FPLC column. This partially purified complex with an M(r) about 820 kDa exhibited additional dehydroascorbate (DHA) reductase activity with specific activities of 0.21, 1.53 and 1.54 mumol ascorbate formed min-1 mg-1 protein at pH 6.0, 6.5 and 7.0, respectively, when glutathione was added. Much lower DHA reductase activity (0.013 and 0.026 mumol ascorbate formed min-1 mg-1 protein at pH 6.5 and 7.0, respectively) was found when glutathione was omitted. The isolated complex gave positive results when it was tested by TI activity staining after SDS-PAGE, and could be recognized by a polyclonal antibody which was raised against 38 kDa sweet potato Kunitz-type TI, one of the root storage proteins of sweet potato. The possible physiological functions of this complex with both TI and DHA reductase activities were discussed.

Chromatography↗
PubMed2000

Fumes from meat cooking and lung cancer risk in Chinese women.

Chinese women are recognized to have a high incidence of lung cancer despite a low smoking prevalence. Several studies have implicated domestic exposure to cooking fumes as a possible risk factor, although the exact carcinogens have yet to be identified. Heterocyclic amines are known carcinogens, which have been identified in cooked meat, and also in fumes generated during frying or grilling of meats. We conducted a case-control study of 303 Chinese women with pathologically confirmed, primary carcinomas of the lung and 765 controls to examine the association between exposure to meat cooking and lung cancer risk. Data on demographic background, smoking status, and domestic cooking exposure, including stir-frying of meat, were obtained by in-person interview while in hospital. The response rates among eligible cases and controls were 95.0 and 96.9%, respectively. The proportion of smokers (current or ex-smokers) among cases and controls was 41.7 and 13.1%, respectively. Adenocarcinomas comprised 31.5% of cancers among smokers and 71.6% among nonsmokers. When cases were compared with controls, the odds ratio (OR) for lung cancer (all subtypes) among ex-smokers was 4.3 [95% confidence interval (CI) 2.7-6.8] and that among current smokers was 5.0 (95% CI, 3.4-7.3). Among smokers, women who reported that they stir-fried daily in the past had a significantly increased risk of lung cancer (adjusted OR, 2.0; 95% CI, 1.0-3.8) and among these women, risk was enhanced for those who stir-fried meat daily (OR, 2.7; 95% CI, 1.3-5.5). Women who stir-fried daily but cooked meat less often than daily did not show an elevated risk (OR, 1.0. 95% CI, 0.5-2.4). Risk was further increased among women stir-frying meat daily who reported that their kitchen was filled with oily fumes during cooking (OR, 3.7; 95% CI, 1.8-7.5). These cooking practices on their own did not increase risk among nonsmokers in our study population. Our results suggest that inhalation of carcinogens, such as heterocyclic amines generated during frying of meat, may increase the risk of lung cancer among smokers. Further studies in different settings are warranted to examine this possibility, which may also help to explain the higher risk observed among women smokers compared with men.

Adenocarcinoma↗
PubMed2000

Questionnaire survey on management of spontaneous pneumothorax.

INTRODUCTION: Management of spontaneous pneumothorax (SP) is variable and the initial management of SP is often undertaken by frontline junior medical staff. OBJECTIVES: To assess if medical education in the principles of SP management is adequate and to determine if practice variability exists among different disciplines. METHODS: A validated questionnaire survey on the knowledge and practice of the junior medical staff posted to a general hospital from May to December 1998 was performed. 138 doctors posted to the various departments: medical (n = S9), surgical (n = 46) and emergency (n = 33) were surveyed. RESULTS: The response rate was 95%. 73% surveyed had experience inserting chest tubes (CT). Of the 27% (n = 37) who had never inserted CT, 41% were medical officers. Our results showed adequate knowledge pertaining to initial management of primary SP (PSP). The preferred site and method for CT insertion was the 5th intercostal space, anterior axillary line and open method. There was significant practice variability in the CT size, method of insertion and CT removal sequence among the disciplines (p < 0.05). However a significant proportion of staff (49%) chose to observe or aspirate an acutely breathless patient with a 10% secondary SP (SSP) instead of CT insertion. CONCLUSION: While knowledge in PSP appears adequate, management of SSP and practical training in CT insertion must be emphasized as it is a simple procedure that is potentially life-saving.

Attitude of Health Personnel↗
PubMed1999

DT-diaphorase protects against menadione-induced oxidative stress.

To study the role of DT-diaphorase in menadione-mediated cytotoxicity, menadione-resistant cells were selected from P19 cells by stepwise increasing concentrations of menadione from 10 to 60, 120 or 300 microM without mutagenic pretreatment. Three isolated clones, K60, K120 and K300, were maintained in media containing 60, 120 or 300 microM menadione, respectively. The resistance of these cells to menadione, in order, was: K300 > K120 > K60 > P19 cells. K300 cells were the most resistant. Acquisition of resistance was associated with elevation in DT-diaphorase activity. Pretreatment of the resistant cells with 30 microM dicumarol at 37 degrees C for 30 min sensitized the resistant cells to menadione. When the resistant cells were maintained in the absence of menadione for 28 days, the resistance of K60 and K120 cells was lost. The lower degree of resistance was accompanied by a decrease in DT-diaphorase activity in the revertant cells. However, the resistance and the activity of DT-diaphorase in K300 cells were quite stable in the same period. These results support strongly that DT-diaphorase protects against menadione-induced oxidative stress.

Animals↗
PubMed1999

Selective modulation of membrane currents by hypoxia in intact airway chemoreceptors from neonatal rabbit.

1. We previously described voltage-dependent ionic currents and hypoxia chemosensitivity in cultured pulmonary neuroepithelial body (NEB) cells isolated from fetal rabbit. Here we use fresh neonatal rabbit lung slices (200-400 micrometer thick) to characterize the electrophysiological properties of 'intact' NEBs with patch-clamp, whole-cell recording. 2. Under voltage clamp, outward currents were partially inhibited by TEA (20 mM), 4-amino pyridine (4-AP; 2 mM) and cadmium (Cd2+; 100 micrometer), suggesting the presence of both Ca2+-dependent (IK(Ca)) and Ca2+-independent (IK(V)) components. 3. Inward currents, carried by voltage-dependent Ca2+ channels and also, in occasional cells (approximately 11%), by TTX-sensitive Na+ channels, were also detected in intact NEB cells. 4. Hypoxia (PO2 = 15-20 mmHg) reduced the outward K+ current by approximately 34% during voltage steps from -60 to +30 mV, while inward Ca2+ or Na+ currents were not affected by hypoxia. Hypoxia suppressed roughly equally both IK(Ca) and IK(V) components of outward current, and no further inhibition of K+ currents was seen with either TEA and 4-AP + hypoxia. 5. Diphenylene iodonium (DPI; 1 microM) suppressed outward K+ current by approximately 42%, and DPI + hypoxia had no additional effect on the K+ current. 6. Direct application of H2O2 augmented outward K+ current; for a voltage step from -60 mV to +30 mV, 0.25 mM H2O2 increased K+ current by approximately 37%. 7. These results indicate that intact neonatal NEB cells express hypoxic chemosensitivity and introduce the rabbit lung slice preparation as an new model for investigating the role of airway O2 chemoreceptors.

4-Aminopyridine↗
PubMed1999

Methacholine-induced fall in forced vital capacity as a marker of asthma severity.

The dose of methacholine causing a 20% fall in forced expiratory volume in 1 sec (FEV1) from baseline (PD20) has been used as an index of asthma severity. The aim of this study was to determine if the percentage fall in forced vital capacity (FVC) from baseline at the PD20 (dFVC%) is an independent marker of asthma severity. We first retrospectively studied the dFVC% and PD20 obtained from 149 consecutive newly diagnosed asthmatics with a positive methacholine-challenge test (MCT). We then performed MCT on 20 normal subjects and 35 stable asthmatics. The 'milder' asthmatics (n = 20) and 'more severe' asthmatics (n = 15) were on regular inhaled corticosteroids: 200 micrograms or less and 800 micrograms or more daily, respectively. A dosimeter technique was used, and normal subjects were given a cumulative dose of 2400 micrograms. The PD20 and dFVC% were calculated using log-linear interpolation of the last two points. Student's unpaired t-tests and linear regression analyses were used for comparison and correlation of results. There was no significant correlation between dFVC% and PD20 among the 149 newly diagnosed asthmatics (r = 0.1), or among the 35 known stable asthmatics (r = 0.008). The more severe asthmatics had a larger dFVC% compared with the milder asthmatics (15.8% vs. 9.6%; P = 0.0005). In addition, inhaled corticosteroid usage correlated better with dFVC% (r = 0.56) than with PD20 (r = 0.36). The normal subjects had a mean fall in FVC of only 4.8%. The percentage fall in FVC at PD20 (dFVC%) may be a useful index of asthma severity which is independent of PD20. This index is potentially complementary to the PD20 in the assessment of asthma severity.

Adrenal Cortex Hormones↗
PubMed1999

NAT2 slow acetylator genotype is associated with increased risk of lung cancer among non-smoking Chinese women in Singapore.

Among non-smokers, the factors resulting in lung carcinogenesis are poorly understood. We conducted a hospital-based case-control analysis of 294 Chinese women, of whom 217 were non-smokers, to evaluate the role of polymorphic N-acetyltransferase (NAT2) as a susceptibility factor for the disease. The proportion of slow acetylator genotypes among non-smoking cases (n = 92) and controls (n = 125) was 38.0 and 24.0%, respectively [odds ratio (OR) 2.0, 95% confidence interval (CI) 1.1-3.7]. No effect of NAT2 genotype was seen among smokers. Among non-smokers, the effect was marked for adenocarcinomas (OR 2.1, 95% CI 1.1-4.0). As NAT2 activity is known to modify risk of arylamine-induced carcinogenesis, our results suggest that exposure to arylamines in the environment may play a role in risk of lung cancer among non-smokers.

Acetylation↗