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Biomedical subjects

R Leung

Publications and source records attributed to R Leung.

At least 73 records · Page 4Linked to original sources
PubMed1994

Physical activity and personal characteristics associated with depression and suicide in American college men.

Among Harvard alumni aged 35-74 in 1962 or 1966, incidence rates of physician-diagnosed depression, together with suicide rates, were examined during a 23-27-year follow-up period, by antecedent physical activity habits and other personal characteristics. A total of 387 first attacks of depression developed among 10,201 alumni who survived through 1988; 129 suicides occurred among 21,569 alumni during follow-up through 1988. Depression rates were lower among the physically active and sports players, higher among cigarette smokers, unrelated to alcohol consumption, and higher among alumni reporting such personality traits as insomnia, exhaustion, cyclothymia, and self-consciousness. Suicide rates were largely unrelated to antecedent physical activity and alcohol consumption, higher among smokers, and substantially higher among men reporting the personality traits that predicted increased rates of depression.

Adult↗
PubMed1994

Asthma, allergy, and atopy in three south-east Asian populations.

BACKGROUND: Whilst many recent reports have suggested a rise in the prevalence of asthma and allergic disease in Western countries, little is known about the epidemiology of these common conditions in south-east Asia. This study compared the prevalence of asthma and allergic disease amongst secondary school students in three south-east Asian populations--Hong Kong, Kota Kinabalu in Malaysia, and San Bu in China--and investigated the associations with atopy and family history. METHODS: Secondary school students were given standard questionnaires on respiratory and allergic symptoms for completion by parents with response rates of 89.2% in Hong Kong (611 male, 451 female; mean (SD) age = 13.9 (1.8 years), 87.6% in Kota Kinabalu (134 male, 275 female; 15.5 (2.1) years), and 98.6% in San Bu (492 male, 245 female; 16.4 (1.8) years). Skin tests were performed in a subsample of students to determine atopic status. RESULTS: The respective prevalence (and 95% CI) for hayfever, eczema, and wheeze or asthma were 15.7% (13.5, 17.9), 20.1% (17.7, 22.5), 11.6% (9.3, 13.9) in Hong Kong, 11.2% (8.2, 14.3), 7.6% (5.0, 10.1), 8.2% (5.5, 10.9) in Kota Kinabalu, and 2.1% (1.2, 3.1), 7.2% (5.4, 9.1), 1.9% (0.7, 3.1) in San Bu. Atopy was common and was present in 49.0-63.9% of subjects in the three populations. Dust mite and cockroach were the commonest allergens that gave positive reactions in 42.8-60.5% and 25.7-35.9% of students respectively. A higher proportion of students in Hong Kong had severe degree of reactivity on skin test than the other two populations. Family history was associated with asthma and allergic symptoms in the three populations conferring a 3-80-fold increase in risk to family members and was a stronger predictor for asthma and allergy than atopy. CONCLUSIONS: Prevalence of asthma and allergic disease is low compared with Western countries, but considerable differences exist between the three south-east Asian populations despite similar rates of atopy. Asthma and allergic disease are more strongly associated with family history than atopy, which suggests that genetic and environmental factors common to the family, other than aeroallergen sensitisation, are important in the pathogenesis of asthma and allergy in the region.

Adolescent↗
PubMed1994

Prevalence of asthma and wheeze in Hong Kong schoolchildren: an international comparative study.

Comparison of asthma prevalence between populations is difficult because of lack of uniformity of methodology and agreement on the definition. This study aims to determine and compare the prevalence of wheeze and respiratory symptoms in Hong Kong schoolchildren with that in Melbourne children by using identical questionnaires. Schools were randomly selected in different regions of Hong Kong and three age groups (7, 12 and 15 yrs) were chosen for the study. The Chinese version of the questionnaire used in a recent Melbourne survey was distributed to children for completion by their parents. A total of 1,800 questionnaires was issued and 1,689 returned (response rate = 94%). The prevalence of wheeze in the past 12 months was 7 (5.1-8.0), 5 (3.0-6.7) and 4 (1.7-5.6) % for 7, 12 and 15 year olds, respectively. The prevalence of a history of asthma in the respective age groups was 10 (7.1-12.9), 8 (7.5-9.2) and 7 (5.0-9.6) %, respectively. Whilst a history of wheeze ever was more common in boys than in girls and 12 yr olds (14% vs 5%), wheeze in the past 12 months was more common in boys than in girls aged 7 yrs (9 vs 4%). We conclude that the prevalence of wheeze and asthma in school children was low in Hong Kong compared to Melbourne. Environmental differences between the two regions may be important in the pathogenesis.

Adolescent↗
PubMed1994

Intracranial tuberculoma and hydrocephalus developing during treatment of tuberculous meningitis.

A 3 1/2-year-old boy with tuberculous meningitis is described. He developed hydrocephalus and subsequently an intracranial tuberculoma while receiving appropriate antituberculous therapy. Such a paradoxical response is thought to be due to a hypersensitivity reaction to the infection during antituberculous therapy. Both hydrocephalus and tuberculomata should be looked for if any patient develops new neurological signs or symptoms during treatment of tuberculous meningitis.

Antitubercular Agents↗
PubMed1992

Immunohistochemical and ultrastructural correlates of muscle-actin expression in pleomorphic adenomas and myoepitheliomas based on comparison of formalin and methanol fixation.

The degree and range of differentiation of the cells referred to as myoepithelial-like in pleomorphic adenomas and the tumour cells of myoepitheliomas are not definitely established. This type of information is critical for establishing reliable diagnostic criteria, such as expression of muscle-specific actin and ultrastructural identification of myofilaments, in these and other salivary gland tumours. Pleomorphic adenomas (18) and myoepitheliomas (5), of which 10 cases were fixed only in formalin and 13 cases where tissues were fixed in both formalin and methanol/acetic acid, were studied. Each tumour and normal accompanying parotid was immunostained with two monoclonal antibodies for smooth muscle actin, HHF35 and MSA. Staining of myoepithelial cells was absent in certain samples of normal gland with both HHF35 (15%) and MSA (69%) when formalin-fixed tissue was used. Using formalin-fixed tissue from 15 pleomorphic adenomas/myoepitheliomas, 2 (14%) had focal positivity with HHF35, while 8 cases (57%) were positive with MSA. However, a certain degree of false positivity was suspected since in samples of normal parotid, both acinar and duct cells were frequently stained, particularly with MSA. With methanol/acetic acid-fixed tissue only 4 of 13 cases (31%) were positive with either MSA or HHF35 and 2 of these only had a minor proportion of the tumour cells expressing muscle-specific actin. Using alcohol-fixed tissue, myoepithelial cells were strongly stained in all examples of normal parotid gland with both anti-actin antibodies. In 5 cases examined by electron microscopy, there was no apparent correlation between immunohistochemical results and the presence or absence of cytoplasmic filament accumulation. The results indicate considerable tumour cell heterogeneity in muscle-specific actin expression and suggest that non-luminal cells in pleomorphic adenomas and the tumour cells in myoepitheliomas may differentiate as classical myoepithelial cells, as partially differentiated (i.e. modified myoepithelial cells) or as the counterpart of basal cells present in the intra- and interlobular ducts of normal salivary gland.

Actins↗
PubMed1992

Paracetamol anaphylaxis.

We describe four cases of anaphylaxis to paracetamol without co-existing aspirin intolerance and review the Australian experience in paracetamol anaphylaxis. Paracetamol sensitivity may differ in the mechanism from sensitivity to aspirin and other non-steroidal anti-inflammatory drugs as previously believed.

Acetaminophen↗
PubMed1991

A primary determinant for lipoxygenase positional specificity.

The three mammalian lipoxygenases are named according to the carbon position (5, 12 or 15) at which they catalyse the oxygenation of arachidonic acid; they are implicated in inflammatory disorders, for example 15-lipoxygenase is induced in atherosclerosis and can oxidize low-density lipoprotein to its atherogenic form. To identify what determines this positional specificity, we have exchanged conserved differences in the isoforms of 12- and 15-lipoxygenases. Substitution of methionine with valine at position 418 of human 15-lipoxygenase results in an enzyme that performs 12- and 15-lipoxygenation equally. This effect can be mimicked by incubating wild-type 15-lipoxygenase with a synthetically altered substrate which has its doubly allylic methylene carbons shifted by one carbon relative to arachidonic acid. Other mutations at the neighbouring amino acids 416 and 417 give an enzyme which performs 12- and 15-lipoxygenation in a ratio of 15:1. These results indicate that this region might position the substrate in the active site.

Amino Acid Sequence↗
PubMed1991

Metabolic and cardiorespiratory responses to the performance of Wing Chun and T'ai Chi Chuan exercise.

The primary purpose of this study was to examine the metabolic and cardiorespiratory responses to the continuous performance of Wing Chun and T'ai Chi Chuan exercise. No significant differences in VO2max or HRmax obtained during treadmill exercise were found between the practitioners of the two styles. Average values for oxygen uptake (VO2) were 23.3 +/- 7.5 ml.kg-1.min-1 (6.6 METS) and 16.0 +/- 3.9 ml.kg-1.min-1 (4.6 METS) for Wing Chun and T'ai Chi Chuan exercise, respectively. Mean heart rates obtained during exercise were 137 +/- 25 beats.min-1 for Wing Chun and 116 +/- 22 beats.min-1 for T'ai Chi Chuan exercise. These exercise values corresponded to 52.4% of VO2max and 70.5% of HRmax for Wing Chun and only 36.4% of VO2max and 59.8% of HRmax for T'ai Chi Chuan exercise. Thus, only the continuous performance of Wing Chun exercise elicited VO2 and HR responses that would be expected to bring about a cardiorespiratory training effect in subjects with a relatively low initial VO2max. The ventilatory equivalent for oxygen (VE/VO2) obtained during T'ai Chi Chuan exercise (21.7) was significantly lower than for Wing Chun exercise (24.2), suggesting that T'ai Chi practitioners utilize efficient breathing patterns during exercise. Both Wing Chun and T'ai Chi Chuan styles may have a small static component that produces a slightly elevated heart rate relative to metabolic load when compared to traditional aerobic activities. However, the effect was not severe and these forms of exercise should not be considered dangerous for individuals at high risk for cardiovascular disease.

Adult↗
PubMed1990

Ultrastructural study of acinar and intercalated duct organization of submandibular and parotid salivary gland.

According to some current hypotheses, the morphology and organization of the intercalated duct/acinar interface of salivary gland have implications for the induction of tumors in this organ. However, this region has received limited detailed investigation. To study the organization of the terminal ductal segments of salivary gland, conventional transmission electron microscopy of human parotid and submandibular glands and canine submandibular gland was combined with 3-dimensional observations of polymer casts of the canine submandibular ductal system; the latter were prepared by retrograde injection of acrylic resin via the main excretory duct with subsequent digestion of the gland tissue. The division of intercalated ducts, into first- and second-order branches, and acinar arrangement is more complex than previously suggested. The entire surface of each elongated second-order intercalated duct is covered with acini projecting in all directions. In the human gland, some acini abut directly on the intercalated duct surface, whereas others are connected by a short stalk of intercalated duct cells; in comparison with canine submandibular gland, the latter may be a modification producing a third-order of the intercalated duct unit. All of these features combine to produce a highly efficient secretory apparatus with a large proportion of acinar cells to each intercalated duct.

Animals↗
PubMed1987

Listeria brain abscess associated with steroid therapy: successful non-surgical treatment.

A patient is reported who developed a brain abscess due to Listeria monocytogenes while on long-term steroid therapy and who was successfully treated medically without surgical intervention. The literature on listeria brain abscess is reviewed, and the importance of early recognition of this infection in any immunocompromised patient who develops focal cerebral dysfunction is emphasised.

Adult↗
PubMed1984

A novel approach for scanning electron microscopy of colloidal gold-labeled cell surfaces.

A method is described for the use of scanning electron microscopy on the surface of gold-labeled cells. It includes the use of 45- or 20-nm colloidal gold marker conjugated with Staphylococcal protein A. The marker is best recognized on the basis of its atomic number contrast by using the backscattered electron imaging mode of the scanning electron microscope. When the backscattered electron signal is mixed with the secondary electron signal, an optimum correlation between the distribution of the labeled sites and the cell surface structures is demonstrated. The method is illustrated by its application to the identification of human circulating granulocytes. Its good resolution, high contrast, and good labeling efficiency offers a promising approach to the specific localization of cell surface antigenic sites labeled with particles of colloidal gold.

Erythrocytes↗
PubMed1984

Effects of backing reflectance and mold size on polymerization of photo-activated composite resin.

The in vitro depth of cure of a visible-light-activated microfilled composite, as influenced by backing reflectance and mold size, was investigated using microhardness measurements. More extensive polymerization was obtained with higher values of backing reflectance. Mold size larger than the cross-sectional area of the photo-activating beam also increased the degree of polymerization. Backing reflectance and mold size are influential factors and need to be defined in depth-of-cure evaluations if in vitro measurements are to be valid predictors of clinical performance.

Chemical Phenomena↗
PubMed1982

Human myometrial adrenergic receptors: identification of the beta-adrenergic receptor by [3H]dihydroalprenolol binding.

The radioactive beta-adrenergic antagonist [3H] dihydroalprenolol (DHA) binds to particulate preparations of human myometrium in a manner compatible with binding to the beta-adrenergic receptor. The binding of DHA is rapid (attaining equilibrium in 12 minutes), readily reversible (half time = 16 minutes), high affinity (KD = 0.50 nM), low capacity (Bmax = 70 fmoles/mg of protein), and stereoselective ([-]-propranolol is 100 times as potent as [+]-ipropranolol in inhibiting DHA binding). Adrenergic agonists competed for DHA binding sites in a manner compatible with beta-adrenergic interactions and mirrored beta 2 pharmacologic potencies: isoproterenol greater than epinephrine much greater than norepinephrine. Studies in which zinterol, a beta 2-adrenergic agonist, competed for DHA binding sites in human myometrial particulate indicated that at least 87% of the beta-adrenergic receptors present are beta 2-adrenergic receptors. Binding of DHA to human myometrial beta-adrenergic receptors provides a tool which may be used in the examination of gonadal hormonal modification of adrenergic response in human uterus as well as in the analysis of beta-adrenergic agents as potentially useful tocolytic agents.

Adrenergic beta-Agonists↗