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Biomedical subjects

G Wong

Publications and source records attributed to G Wong.

At least 73 records · Page 4Linked to original sources
PubMed1997

Propofol-induced ataxia and hypnosis in rat lines selected for differential alcohol sensitivity.

An alcohol-sensitive rat line, selectively bred for high sensitivity to ethanol-induced motor impairment, also exhibits greater sensitivity to gamma-aminobutyric acid type A (GABAA) receptor agonists, such as benzodiazepines and barbiturates, than an alcohol-insensitive rat line. We have investigated whether this difference was also maintained for the most recent intravenous anaesthetic, propofol. Propofol (100 mg/kg, intraperitoneally) induced similar sleep times and produced identical plasma propofol concentrations in alcohol-sensitive and alcohol-insensitive rat lines. At lower doses (50 and 75, but not 25 mg/kg), propofol produced a greater motor impairment in a tilting plane test in alcohol-sensitive than alcohol-insensitive rats shortly after the injection. Binding of a convulsant, [35S]t-butylbicyclophosphorothionate, to cerebellar and cerebrocortical GABAA receptors in the presence of 2 microM GABA was similarly affected by low micromolar propofol concentrations in both rat lines, while in the absence of GABA, propofol was slightly less potent in the alcohol-sensitive than alcohol-insensitive line. These data indicate that alcohol-sensitive rats show transiently enhanced sensitivity to an ataxic, but not to a hypnotic dose of propofol, which cannot be explained by sensitivity differences to propofol in GABAA receptors determined in a binding assay using brain membrane homogenates.

Alcohol Drinking↗
PubMed1997

Glucocorticoids induce beta2-adrenergic receptor function in human nasal mucosa.

Glucocorticoids are hypothesized to induce beta2-adrenergic receptors (beta2-R) and their functions. The ability of dexamethasone (DEX) in vitro and beclomethasone dipropionate (BDP) in vivo to induce beta2-R messenger RNA (mRNA) and function was investigated in human nasal mucosa. In this tissue, albuterol does not stimulate exocytosis either in vivo or in vitro (Mullol and coworkers, 1992). Therefore, induction of beta2-R-mediated glandular exocytosis by glucocorticoids was proposed as an unambiguous outcome measure. Human nasal mucosa was cultured for 3 d with and without 1 microM DEX, then challenged with media or 100 microM albuterol. Culture supernatants were collected for measurement of exocytosed glandular products. Explant mRNA was extracted for reverse transcriptase-polymerase chain reaction (RT-PCR), and in situ hybridization of beta2-R mRNA performed. In vivo, normal subjects received saline or BDP for 3 d before albuterol nasal provocation. Concentrations of exocytosed products were measured in nasal secretions. RNA was extracted from nasal epithelial scrapings for RT-PCR. In vitro, DEX treatment induced albuterol-mediated glandular exocytosis (p < 0.04), and increased the steady-state beta2-R/beta-actin mRNA ratio (p < 0.05), and expression of beta2-R mRNA in glands. In vivo, BDP increased the beta2-R/beta-actin mRNA ratio in epithelial scrapings (p < 0.04), but did not induce albuterol-mediated glandular secretion. We conclude that glucocorticoids increase steady-state beta2-R mRNA levels in vivo and in vitro, and can induce beta2-R function as assessed by submucosal gland exocytosis in vitro. While topical BDP induced epithelial beta2-R mRNA, it did not modulate exocytosis from the deeper submucosal glands.

Administration, Topical↗
PubMed1997

Prevalence of asthma and allergy in Hong Kong schoolchildren: an ISAAC study.

Asthma and allergic disease in children is increasing in many Western countries but such trend has not been well-defined in Chinese populations. This paper aims to determine the prevalence of asthma and allergic disease in Hong Kong schoolchildren and compare it with previous data to identify a changing trend. We studied 4,665 schoolchildren aged 13-14 yrs using the International Study of Asthma and Allergy in Childhood (ISAAC) protocol to determine prevalence rates for asthma, wheeze, respiratory symptoms, rhinitis and eczema in 1994-1995. Additional questions on education levels of the parents and smoking status were also asked. Concordance between responses to the written and video questionnaires was good (76% for wheeze ever, 80% for current wheeze). Prevalence rates for asthma ever, wheeze ever, and current wheeze were 11, 20 and 12%, respectively, and were greater in boys (p < 0.05). Rhinitis affected slightly over half of the subjects (52%), and eczema was reported by a sixth (15%), whilst current rhinitis and current eczema were present in 44% and 3.6% of children, respectively. In multiple logistic regression: odds ratio male sex (OR) 1.47; (95% confidence interval (95% CI) 1.15-1.86); current rhinitis (OR 3.00; 95% CI 2.36-3.81); current eczema (OR 2.34; 95% CI 1.40-3.93); and active smoking (OR 2.00; 95% CI 1.38-2.89) were associated with current wheeze; whilst severe wheezing attack was associated with: current rhinitis (OR 2.72; 95% CI 1.47-5.02); current eczema (OR 6.13; 95% CI 2.82-13.33); and active smoking (OR 4.62; 95% CI 2.43-8.76). Age, parental education and passive smoking were not important factors. When compared to previous epidemiological data obtained in 1992, the prevalence rates for asthma ever and wheeze ever had increased by 71 and 255%, respectively, in Hong Kong schoolchildren. The severity of asthma and respiratory symptoms showed a similar increasing trend. Further studies should aim to identify the role of the environment in the pathogenesis of asthma.

Adolescent↗
PubMed1997

Evaluation of two videotape instruction programmes on how to break bad news--for Cantonese-speaking medical students in Hong Kong.

OBJECTIVES: To evaluate a culture-specific videotape on how to 'break bad news' and another videotape produced by a western university, and to determine if the language of presentation influenced the students' perceived abilities to execute basic skills. SUBJECTS: Third year medical students at the Faculty of Medicine, the University of Hong Kong. DESIGN: Longitudinal study with experimental design. INTERVENTION: Two instructional tapes on breaking bad news; one using Chinese speaking role models and one using English. RESULTS: In both groups, self-efficacy summed scores increased from 26.8 (95% CI = 25.9-27.7) at the pre-test to 29.0 (95% CI = 28.4-29.6). The biggest changes occurred in perceived self-efficacy regarding specific skills. However, students using the Chinese tape rated skills as more useful than those using the English tape. CONCLUSION: The videotapes were useful in teaching communication skills. Culturally relevant audiovisual materials were more effective.

China↗
PubMed1997

Maternal postural challenge as a functional test for cervical incompetence.

We studied the effect of an upright maternal position on the cervix. Of 41 high risk patients (17 to 33 weeks' gestational age), 14 of 16 who had a greater than 33% decrease in cervical length in the upright position compared to supine position delivered their infants prematurely, compared to 1 of 25 patients who had a decrease of less than 33% (P < 0.0005). No change in the cervical length was noted in 24 low-risk patients, all of whom were delivered at term. When the finding of a cervical length of less than 2 cm was combined with a postural change, the sensitivity for prediction of preterm delivery was 100%. We conclude that for patients at high risk for incompetent cervix, maternal posture-related cervical shortening can assist in predicting those who will undergo premature delivery.

Adult↗
PubMed1997

The eye in diabetes. Key points for the general practitioner.

Diabetic retinopathy is a common complication in people with diabetes. General practitioners can arrange annual screening for diabetic eye disease to detect early changes and prevent severe damage. Due to an ageing population the number of people with type II diabetes will increased dramatically during the next 20 years. This article outlines how general practitioners can prevent progressive loss of vision in their patients.

Australia↗
PubMed1997

Comparison of the ISAAC video questionnaire (AVQ3.0) with the ISAAC written questionnaire for estimating asthma associated with bronchial hyperreactivity.

BACKGROUND: A standardized protocol is essential for international comparisons of asthma prevalence and severity. The International Study of Asthma and Allergies in Childhood (ISAAC) used a standardized written questionnaire (WQ) and a video questionnaire (AVQ3.0) to survey the prevalence and severity of asthma in 13-14-year-old schoolchildren in different countries. OBJECTIVE: To compare the effectiveness of WQ and AVQ3.0 in predicting bronchial hyperresponsiveness (BHR), defined as having a provocation dose of inhaled methacholine causing a 20% fall in baseline FEV1 of 7.8 mumol. METHODS: One hundred and eighty-nine Chinese schoolchildren completed a written questionnaire followed by a video questionnaire on asthma symptoms. They then underwent bronchial challenge to methacholine. RESULTS: Fair correlations were seen between the first two corresponding questions (moderate wheezing at rest and exercise wheeze) in the two questionnaires with Kapper indices of 0.44 and 0.43, respectively. The ability to predict BHR, as indicated by the Youden's index, was similar between the corresponding questions of the two questionnaires, except for 'severe wheeze' which had a significantly higher Youden's index in AVQ3.0 (0.44) than the corresponding question in WQ (0.11, P < 0.05). CONCLUSION: The ISAAC International video questionnaire is at least as effective as the ISAAC written questionnaire in predicting BHR. It therefore provides a simple and valid tool for international comparisons of asthma prevalence and severity.

Adolescent↗
PubMed1996

Effects of clozapine metabolites and chronic clozapine treatment on rat brain GABAA receptors.

Similarly to clozapine, a clozapine metabolite, N-desmethylclozapine, but not clozapine N-oxide, antagonized brain gamma-aminobutyric acid type A (GABAA) receptors at high micromolar concentrations. However, daily subcutaneous injections of clozapine (10 and 25 mg/kg) and haloperidol (0.5 mg/kg) for 14 days failed to alter the modulation by GABA of rat cerebrocortical and cerebellar benzodiazepine ([3H]flunitrazepam) or convulsant (t-[35S]bicyclophosphorothionate) binding sites of the GABAA receptor. The results thus suggest that the GABAA receptor antagonism exerted by chronic in vivo clozapine treatment is weak as compared to this treatment's actions on certain monoamine receptors and is unlikely to be involved in the therapeutic actions of clozapine.

Animals↗
PubMed1996

Stimulation of stress-activated protein kinase and p38 HOG1 kinase in murine keratinocytes following photodynamic therapy with benzoporphyrin derivative.

The activation state of the members of the mitogen-activated protein kinase family following photodynamic therapy (PDT) with benzoporphyrin derivative monoacid ring A was investigated using a naturally transformed murine keratinocyte cell line, Pam 212. PDT involves the use of photosensitizer molecules and a specific wavelength of visible light. The process of PDT generates singlet oxygen and other reactive oxygen intermediates (ROIs), and the cytotoxic effect of these ROIs is the basis for the use of PDT to treat cancer and psoriasis. PDT caused a strong dose- and time-dependent activation of both stress-activated protein kinase (SAPK) and p38 HOG1. The maximum activation of SAPK and p38 HOG1 occurred between 20 and 30 min following PDT treatment with 200 ng/ml benzoporphyrin derivative monoacid ring A and 2 J/cm2 of red light at 690 nm. In our system, PDT did not cause significant activation of extracellularly regulated kinase (ERK) 1 and ERK2. Under the same experimental conditions, ultraviolet light irradiation caused strong activation of SAPK and p38 HOG1 and minimum activation of ERK1 and ERK2 in Pam212 cells. A number of ROI scavengers were tested for their effect on PDT-induced SAPK and p38 HOG1 activation. Both L-histidine and N-acetyl-L-cysteine showed a significant inhibitory effect on PDT-induced SAPK and p38 HOG1 activation. This indicated that PDT-induced SAPK and p38 HOG1 activation may be partially mediated by ROI.

Animals↗
PubMed1996

Laboratory and field studies on the effects of the antibiotic tylosin on honey bee Apis mellifera L. (Hymenoptera: Apidae) development and prevention of American foulbrood disease.

Laboratory and field studies were conducted to determine the effectiveness of the antibiotic tylosin in preventing and controlling infections of American foulbrood disease (AFB) of honey bees. Studies conducted on immature worker bees maintained in the laboratory revealed that honey bee larvae could tolerate quite a range of doses of antibiotic in their diet. Intermediate doses of tylosin protected very young larvae from becoming infected by Bacillus larvae at a concentration of 1.5 x 10(8) spores/ml of diet. Antibiotic treatment had no measurable effects on larval or pupal developmental rates until the dose reached a lethal level. Bees in field colonies readily consumed tylosin in powered sugar, up to a level of 800 mg/7 g sugar. No negative colony effects were noted at any dosage rates. Protection against infection by American foulbrood was compared to results obtained with 200 mg Terramycin, the standard dose of the only substance currently registered for foulbrood control. Both 200 mg Terramycin and 100 mg tylosin protected the colonies for up to 3 weeks. A 200-mg dose of tylosin protected the colony for an additional week. Doses of 100 mg or more of tylosin were adequate to eliminate signs of AFB infection in overtly diseased colonies.

Animals↗
PubMed1996

Intracranial plasma cell granuloma.

We present a case of plasma cell granuloma involving the dura mater with infiltration of the adjacent brain parenchyma. The radiological and pathological features of this entity are described.

Brain Diseases↗
PubMed1996

Pharmacologic actions of subtype-selective and novel GABAergic ligands in rat lines with differential sensitivity to ethanol.

Alcohol-nontolerant (ANT) rats, produced by selective breeding for high sensitivity to motor-impairing effects of ethanol, have a point mutation in the cerebellar gamma-aminobutyric acid type A (GABAA) receptor alpha 6 subunit, which has been proposed to underlie enhanced sensitivity to benzodiazepine agonists as well. We compared ANT and alcohol-tolerant (AT) rats using behavioral and neurochemical methods to assess the significance of alpha 6- and non alpha 6-containing GABAA receptor subtypes. Motor performance in a tilting plane test was largely unaffected by a type I benzodiazepine receptor-preferring agonist, zolpidem [1-10 mg/kg, intraperitoneally (IP)], partial benzodiazepine agonists bretazenil and ZG-63 (both at 40 mg/kg, IP), and a novel broad-spectrum anticonvulsant loreclezole (40 mg/kg, IP) in both ANT and AT rats. In contrast, diazepam (10 mg/kg, IP) impaired performance of the ANT but not AT animals. These data, supported by results from brain regional autoradiography of [3H]Ro15-4513 and membrane binding of [3H]ZG-63 and [35S]TBPS as influenced by these ligands, strongly suggest that only ligands with full agonist actions on mutant (ANT) but not wild-type (AT) alpha 6-containing GABAA receptors are able to produce motor impairment in the ANT rats.

Animals↗
PubMed1996

The synthesis of fluorine-18 lomefloxacin and its preliminary use in human studies.

Lomefloxacin is a new fluorine-containing antibiotic that has recently been approved for general use. Fluorine-18 lomefloxacin has been prepared by fluoride exchange between fluorine-18 fluoride and lomefloxacin in DMSO. Both time and temperature of the reaction have been optimized and conditions developed for the isolation and purification of the labeled product in a form suitable for oral administration. The exchange reaction provides sufficient labeled material for human studies with pharmacologically relevant quantities of the drug. We have performed preliminary human studies with this compound using positron emission tomography to estimate the tissue distribution of the compound and show the distribution of the compound into the liver and lungs.

Animals↗
PubMed1996

Predictive value of flow cytometric analysis in DNA contents in patients with locally advanced head and neck carcinoma.

A retrospective study was performed on 61 eligible patients with stage III and IV (AJC/UICC Staging System) squamous carcinomas of the head and neck region who were treated with definitive radiotherapy with, or without, surgery. DNA contents were measured by flow cytometric analysis of archival paraffin blocks and were correlated with clinicopathological findings, tumour response and patient survival. Comparison of variables including treatment modality was performed for identification of significant prognostic factors. There were 28 diploid, 27 aneuploid tumours and the remaining six were questionable. All patients were followed-up for at least two years or until death. Aneuploid tumours had a significantly higher S-phase fraction (percentage S-phase) (p < 0.001). Neither ploidy nor percentage S-phase were found to have predictive value in tumour response or patient survival within the power of a sample size of 61. Twenty of the 27 (74 per cent) aneuploid tumours had a complete response (CR) whereas 19 out of 28 (68 per cent) diploid tumours achieved CR. Five-year survival by the Kaplan-Meier method was 33 per cent for both aneuploid and diploid tumours. However, nodal stage (N stage) was found to have significant predictive value in both tumour response and patient survival. The complete response for stage N0 patients was 96 per cent, N1 patients 61 per cent, N2 patients 60 per cent and 43 per cent for N3 patients (p < 0.002). Similarly, the five year survival for the N0 and N3 groups of patients was 53 per cent and 29 per cent respectively (p < 0.05).

Adult↗
PubMed1996

Brain regional pharmacology of GABA(A) receptors in alcohol-preferring AA and alcohol-avoiding ANA rats.

Compounds interacting with the GABA(A) receptor system modulate voluntary alcohol consumption in alcohol-preferring AA (Alko, Alcohol) rats. Therefore, we compared the central GABA(A) receptor pharmacology of the AA rats to that of their counterpart, alcohol-avoiding ANA (Alko, Non-Alcohol) rats with receptor autoradiography. Total flumazenil-sensitive [(3)H]Ro 15-4513 binding to the benzodiazepine site of GABA(A) receptor was slightly lower in the hippocampus, striate cortex and lateral hypothalamus of the AA than ANA rats. The proportions of zolpidem- and diazepam-sensitive components were similar in both rat lines. Basal picrotoxin-sensitive [(35)S]TBPS binding to the convulsant site of GABA(A) receptor was similar in most regions between the rat lines, but the up-modulation of the binding by 10 microM diazepam in the hippocampal, amygdaloid and entorhinal cortical areas was greater in the AA than ANA rats. These results do not reveal any general genetic defect in the GABA(A) receptors of AA or ANA rats, but the regional profile of the ligand binding differences between the lines, especially in the coupling of the benzodiazepine and chloride channel sites, suggests receptor subtype-specific changes in brain regions implicated in behavioural reward and anxiolysis.

Journal Article↗
PubMed1996

Behavioral and biochemical characterization of benzodiazepine receptor partial agonists in pigeons.

The ability of benzodiazepine receptor partial agonists to exhibit full efficacy in preclinical anxiolytic tests, in conjunction with initial clinical results, has suggested the possibility of a reduced clinical side-effect profile compared to benzodiazepine receptor full agonists like diazepam. Because punished behavior of pigeons has been useful in detecting effects of novel anxiolytic drugs, effects of imidazobenzodiazepine and beta-carboline benzodiazepine receptor partial agonists and some related compounds were evaluated in this species. The abilities of these compounds to substitute for the discriminative stimulus effects of the full agonists midazolam also was determined. Intrinsic efficacy was assessed by the degree to which gamma-aminobutyric acid increased ligand potency to displace [(3)H]Ro15-1788 (flumazinil) from membranes of pigeon cerebrum, and ranged from full agonist-like efficacy (Ro 19-5470; 7-(3-cyclopropyl-1,2,4-oxodiazol-5-yl)-5,6-dihydro-5-methyl-4H- imidazo[1,5a]-thieno[3,2-f]diazin-4-one) to minimal gamma-aminobutyric acid potentiations close to that of the antagonist flumazenil (abecarnil and Ro 41-7812; 7-chloro-4,5-dihydro-3-(3-hydroxy-1-propynyl)-5-methyl-6H-imidazo[1,5-a] -[1,4 ]benzodiazepine-6-one). Punished responding was increased markedly by midazolam and by all partial agonists, except Ro 41-7812 and Ro 42-8773 (7-chloro-3-[3-(cyclopropylmethoxy)-1-propynyl]-4,5-dihyro-5 -methyl-6H-imidaz o[1,5-a][1,4]benzodiazepine-6-one), at doses that did not affect nonpunished responding. In contrast to the full substitution generally observed in mammals, all of the partial agonists produced incomplete substitution (40-70%) in the midazolam drug discrimination procedure in pigeons. A positive relationship was observed between the degree of substitution and intrinsic efficacy. The benzodiazepine antagonists, flumazenil and ZK 93,426 (ethyl-5-isopropoxy-4-methoxymethyl-beta-carboline-3-carboxylate), neither increased punished responding nor substituted for midazolam. The results of the present study suggest that benzodiazepine receptor partial agonists and related compounds may provide full anxiolytic activity at doses that do not fully reproduce the subjective effect profile of full agonists.

Animals↗