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T Kwok

Publications and source records attributed to T Kwok.

At least 19 recordsLinked to original sources
PubMed2006

Crystal structure of the N-terminal domain of the TyrR transcription factor responsible for gene regulation of aromatic amino acid biosynthesis and transport in Escherichia coli K12.

The X-ray structure of the N-terminal domain of TyrR has been solved to a resolution of 2.3 A. It reveals a modular protein containing an ACT domain, a connecting helix, a PAS domain and a C-terminal helix. Two dimers are present in the asymmetric unit with one monomer of each pair exhibiting a large rigid-body movement that results in a hinging around residue 74 of approximately 50 degrees . The structure of the dimer is discussed with reference to other transcription regulator proteins. Putative binding sites are identified for the aromatic amino acid cofactors.

Amino Acids, Aromatic↗
PubMed2006

Nutrient intake and psychological health in an elderly Chinese population.

BACKGROUND: Associations between nutrition and cognitive impairment, and nutrition and depression, have been observed. Elderly people are at risk of under nutrition, and also have higher prevalence of cognitive impairment and depression. OBJECTIVE: To examine the relationship between nutrient intake and psychological health in the elderly, adjusting for confounding factors. SUBJECTS: Three thousand nine hundred and ninety-nine men and women aged 65 years and over living in the community, with approximately equal numbers in three age groups: 65-69, 70-74, 75+ years. METHODS: Dietary intake was assessed using a 7-day food frequency questionnaire. Cognitive function was assessed by the cognitive part of the Community Screening Instrument for Dementia (CSID). Depression was assessed using the Geriatric Depression Scale (GDS). Information was also collected for confounding factors: demographics, educational level, socioeconomic status, medical history, smoking, alcohol intake, and physical activity. Logistic regression analyses were carried out to examine associations between lifestyle and dietary variables, and CSID and GDS, controlling for confounders. RESULTS: Both CSID and GDS scores were associated with co-morbidity, demographic and socioeconomic factors. Few associations between lifestyle factors and CSID score were observed. Dietary factors inversely associated with GDS score include total fat intake, vitamins A, B2, B3, C, fibre, and vegetables. In terms of nutrient density, iron and isoflavone intake were additional factors. CONCLUSION: Association exists between intake of various nutrients and psychological health independent of other confounding factors in the elderly population. A follow-up study of this cohort or interventional studies are needed to elucidate cause effect relationship.

Aged↗
PubMed2006

Evaluation of the effect of energy conservation techniques in the performance of activity of daily living tasks.

OBJECTIVE: To determine whether energy conservation techniques during common activity of daily living tasks actually result in lower energy expenditure, and to document subjective comments regarding any differences in the perceived level of effort. DESIGN: Descriptive study comparing energy expenditure in three tasks with and without energy conservation techniques, taking into account the effect of age. SETTING: Occupational therapy department of a rehabilitation hospital in Hong Kong. SUBJECTS: One hundred and eight subjects (30 < 60 years; 78 > or = 60 years) were recruited from staff and members of an elderly social centre in the community. MEASUREMENTS: Energy expenditure was measured using a portable indirect calorimetry system for three tasks (shopping, washing clothes and hanging laundry) with and without energy conservation techniques. Dyspnoea, fatigue and perceived exertion were measured using visual analogue scales. RESULTS: Reduction in energy expenditure using energy conservation techniques for shopping and hanging laundry was documented in younger subjects only (O2 consumption fell from 13.8 +/- 3.7 to 12.2 +/- 3.8 mL/min per kg for shopping, P < 0.001 and 5.9 +/- 1.2 to 5.0 -/+ 1.2 mL/min per kg, P < 0.001 for hanging laundry), although the older subjects experienced less perceived exertion with the energy conservation techniques. For washing clothes, no reduction in energy expenditure was observed in either age groups. CONCLUSION: Measurable benefits were observed with use of labour-saving equipment and avoidance of overhead reaching in younger subjects only.

Activities of Daily Living↗
PubMed2005

Angiotensin converting enzyme inhibitor use is associated with higher bone mineral density in elderly Chinese.

Hypertension and osteoporosis are two major chronic diseases affecting the elderly. A cross-sectional study of 3887 Chinese men (n = 1958) and women (n = 1929) was used to explore the association between angiotensin converting enzyme inhibitor (ACEI) use and bone mineral density (BMD). The participants were aged 65 years and above, and were recruited using a combination of private solicitation and public advertising from community centers, housing estates, and the general community in Hong Kong. Demographic, medical, and lifestyle information was obtained from face to face interviews using standardized questionnaire, and physical examination measurements included anthropometry, tibial, and brachial systolic blood pressures, femoral neck, total hip, and lumbar spine BMD. In multiple regression analyses, after adjusting for age, weight, height, thiazide, beta-blocker, calcium channel blocker, statin, corticosteroid, and calcium supplement use, history of diabetes, heart disease, peripheral vascular disease, cigarette smoking, alcohol intake, and physical activity level, ACEI use was associated with higher femoral neck BMD (+0.015 g/cm2, P = 0.035) in women, and higher femoral neck (+0.015 g/cm2, P = 0.017), total hip (+0.016 g/cm2, P = 0.021), and lumbar spine (+0.043 g/cm2, P < 0.001) BMD in men. Thiazide use was associated with higher BMD at all three sites in general, although associations with BMD increase at the total hip (P = 0.07) and femoral neck (P = 0.09) were weak in men. Calcium channel blocker use was only significantly associated with BMD increase at the lumbar spine (P = 0.03) in women, and beta-blocker use did not have significant associations with BMD at any site. This study suggests that in addition to thiazide diuretics ACEI may have possible benefits in treating not only hypertension but also osteoporosis among older Chinese.

Aged↗
PubMed2005

The determinants of bone mineral density in Chinese men--results from Mr. Os (Hong Kong), the first cohort study on osteoporosis in Asian men.

Mr. Os (Hong Kong) is the first study to address the risk factors for osteoporosis in Asian men. A standardized, structured interview and dual X-ray densitometry (DEXA) were performed on 2,000 Chinese men aged 65-92. By multiple regression, the following factors were found to be positively associated with BMD at both the total hip and the spine: body weight, grip strength and a history of diabetes mellitus. The following factors were found to be negatively associated with BMD at both the total hip and spine: cigarette smoking, a history of gastrectomy or bowel resection, current use of inhaled steroid and a history of fracture after 50 years. Moreover, a history of chronic obstructive pulmonary disease (COPD) was negatively associated with BMD at the total hip, and age, the use of an alpha-blocker, thiazide diuretic and nitrate were associated with a higher BMD at the spine. A total of 21.8% of the variance in total hip and 31.5% of the variance in total spine BMD was accounted for in the multivariate analysis.

Absorptiometry, Photon↗
PubMed2005

Bone mineral density and the risk of peripheral arterial disease in men and women: results from Mr. and Ms Os, Hong Kong.

Previous population studies have demonstrated an association between peripheral vascular disease and bone mineral density in women, but not in men. In a large prospective cohort of 3,998 Chinese men and women aged 65 to 92 years of age in Hong Kong, the association between peripheral vascular disease and bone mineral density was explored. Demographic and lifestyle information was obtained from face to face interviews using a standardized questionnaire. This included demographic information, medical history and lifestyle factors. Physical examination measurements included anthropometry and tibial and brachial systolic blood pressures. The ratio of the posterior tibial and brachial systolic blood pressures, the ankle/arm index, was used as a measure of peripheral arteriosclerosis in the lower extremities. Bone mineral density (BMD) at the total hip and spine (L1-L4) was measured by Hologic QDR-4500 W densitometers (Hologic, Inc., Waltham, Mass.). In this cross-sectional analysis, the ankle brachial index (ABI) was positively correlated with hip BMD (correlation coefficient=0.27; P<0.001). However, after adjustment for confounders, the correlation became much weaker (correlation coefficient=0.03; P<0.05). This showed that much of the relationship between ABI and BMD could be explained by other confounders. In multiple regression analysis, an increase in ABI of 1 SD of ABI was associated with an increase of 0.5% (95% CI: 0.02%, 0.9%) in hip BMD after adjusting for age, sex, body weight, smoking status, history of diabetes, cardiovascular diseases, use of thiazide diuretics, grip strength and physical activity. Although our study shows that peripheral vascular disease in the lower extremities may be associated with decreased bone mineral density, the association is weak especially after adjustment was made for confounders. This indicates that other factors may be contributing to the association between peripheral vascular disease and osteoporosis.

Aged↗
PubMed2004

Use of fasting urinary methylmalonic acid to screen for metabolic vitamin B12 deficiency in older persons.

OBJECTIVES: We sought to determine the cutoffs of fasting urinary methylmalonic acid (MMA) indicating elevated and mildly elevated serum MMA concentrations in older persons. METHODS: We studied 113 female Chinese vegetarians older than 55 y with normal renal function. Fasting serum samples were obtained for measurement of vitamin B12, MMA, and folate and tests of renal function. A fasting urine sample was collected for MMA measurement by the stable-isotope dilution method. The correlation between serum and urinary MMA levels was examined. The optimal cutoffs of urinary MMA for predicting elevated and mildly elevated serum MMA were estimated by use of receiver operating characteristic curves. RESULTS: Fasting urinary and serum MMA levels were linearly correlated. Pearson's correlation coefficient was 0.94. The cutoff of fasting urinary MMA of 2 microM/mM of creatinine had a sensitivity of 79%, a specificity of 85%, and a positive predictive value of 93% for elevated serum MMA (> 0.4 microM/L). A cutoff of 1.5 microM/mM of creatinine had a sensitivity of 86%, a specificity of 85%, and a positive predictive value of 95% for mildly elevated serum MMA (> 0.3 microM/L). Both cutoffs had high positive predictive values for subnormal vitamin B12 concentrations. CONCLUSION: Overnight fasting urinary MMA concentrations have a strong linear relation to serum MMA in older vegetarians without renal impairment. Urinary MMA is potentially useful as a screening tool for metabolic vitamin B12 deficiency in older persons.

Aging↗
PubMed2004

The standard oxygen consumption value equivalent to one metabolic equivalent (3.5 ml/min/kg) is not appropriate for elderly people.

In epidemiological studies, estimation of total energy expenditure can only be carried out from using metabolic equivalent (MET) units calculated physical activity questionnaires, where 1 MET is generally assumed to be 3.5 ml/min/kg resting oxygen consumption (VO2 resting). Since the basal metabolic rate varies with age, the energy expenditure equivalent to 1 MET is likely to vary with age. The objective of this study was to determine the energy value for 1 MET in elderly Chinese people compared with younger subjects, using a cross-sectional study. The participants were 138 young adults (88 female, 50 male) aged 16-64 years and 70 elderly adults (35 female, 35 male) aged 65-89 years. VO2 resting was determined by indirect calorimetry (Deltatrac; Datex Division Instrumentraium Corp, Helsinki, Finland). The height and weight were measured. The body fat percentage and lean mass was estimated by body mass index, tricep and bicep skinfold thickness and Bio-impedance analysis. Both VO2 resting and VO2 resting/kg body weight were significantly lower in elderly than young subjects in both gender groups (P<0.01). The significant age difference in VO2 resting remained after adjustment for weight, height and lean mass in both the male group (P<0.001) and the female group (P<0.01). In conclusion, age had an independent effect on VO2 resting, independent of the change of body composition. The present study suggested that the assumption of 1 MET=3.5 ml/min/kg VO2 resting may over-estimate energy expenditure when apply to elderly people.

Adolescent↗
PubMed2004

Cognitive impairment and functional outcome after stroke associated with small vessel disease.

OBJECTIVES: Although stroke associated with small vessel disease (SSVD) can induce both motor and cognitive impairment, the latter has received less attention. We aimed to evaluate the frequency of the varying severity levels of cognitive impairment, the determinants of severe cognitive impairment, and the association of cognitive impairment with functional outcome after SSVD. METHODS: Consecutive patients admitted to hospital because of SSVD were assessed at 3 months after stroke. We performed a semi-structured clinical interview to screen for cognitive symptoms. Severity of cognitive symptoms was graded according to the Clinical Dementia Rating Scale (CDR). Performance on psychometric tests (Mini-Mental State Examination, Alzheimer's Disease Assessment Scale (cognition subscale), Mattis Dementia Rating Scale (initiation/perseverence subscale; MDRS I/P)) of patients of different CDR gradings was compared with that of 42 healthy controls. Basic demographic data, vascular risk factors, stroke severity (National Institute of Health Stroke Scale; NIHSS), pre-stroke cognitive decline (Informant Questionnaire on Cognitive Decline in the Elderly; IQCODE), functional outcome (Barthel index; BI), Instrumental Activities Of Daily Living; IADL), and neuroimaging features (site of recent small infarcts, number of silent small infarcts, white matter changes) were also compared among the groups. Regression analyses were performed to find predictors of severe cognitive impairment and poor functional outcome. RESULTS: Among the 75 included patients, 39 (52%) complained of cognitive symptoms. The number of patients in each CDR grading was as follows: 39 (52%) had a CDR of 0, 26 (34.7%) had a CDR of 0.5, 10 (13.3%) had a CDR of > or =1. Pre-stroke IQCODE and previous stroke predicted CDR> or =1. The NIHSS was associated with more impaired BI. The NIHSS and MDRS I/P contributed most to impaired IADL. CONCLUSIONS: Half of the patients with SSVD complained of varying severity of cognitive problems 3 months after stroke. Pre-stroke cognitive decline and previous stroke predict severe cognitive impairment post stroke. Stroke severity and executive dysfunction contribute most to a poor functional outcome.

Activities of Daily Living↗
PubMed2004

Nutritional status of older Tibetans in rural Sichuan China.

OBJECTIVE: To examine the nutritional status of older Tibetans in rural China. DESIGN: Cross sectional study. SETTING: Remote mountainous region of Sichuan province of Western China. SUBJECTS AND METHOD: Forty four male and forty six female Tibetans, over 60 years old were recruited. Body weight, standing height, triceps and bicep skinfold thicknesses (TSF, BSF), mid arm circumference (MAC) and waist circumference (WC) were measured. Dietary intakes were assessed by a twenty-four hour dietary recall. Based on skinfold thicknesses and MAC, total body fat and corrected arm muscle area (CAMA) were calculated by published equations. Their nutritional status and dietary intakes were compared with those of normal older people in Hong Kong and a rural area near Tianjin in the east coast of China. RESULTS: Compared with Hong Kong older women, the Tibetan older women had similar BMI and total body fat, but their CAMA was significantly greater (p<0.01). The Tibetan older men had lower BMI, total body fat (p<0.05), and higher CAMA than the Hong Kong older men (p<0.05). The average calorie intake in the Tibetans was lower than that of older people in Hong Kong and rural Tianjin. Intakes of protein, vitamins and minerals were the lowest in Tibetans and the highest in older people in Hong Kong. CONCLUSIONS: Older Tibetans had more lean mass than Hong Kong older Chinese despite having lower caloric and protein intakes. Older Tibetan women were fatter than their male counterparts, and they were as fat as the older people in Hong Kong, despite having low caloric intakes.

Aged↗
PubMed2002

Independent effect of vitamin B12 deficiency on hematological status in older Chinese vegetarian women.

We have examined the independent effect of vitamin B(12) deficiency on hematological indices in older Chinese vegetarian women using a cross-sectional study design: 119 women older than 55 years who had been vegetarian for more than 3 years were studied. Fasting blood samples were taken for complete blood count, serum iron, total serum iron binding capacity, serum iron saturation, serum vitamin B(12), serum folate, serum methylmalonic acid levels (MMA), and renal function test. Subjects with iron deficiency (iron saturation <15%) and those with serum creatinine >150 mmol/L were excluded. The prevalence of definite vitamin B(12) deficiency (vitamin B(12) level < 150 pmol/L and MMA >or= 0.4 micromol/L) was 42%. Another 32.8% had possible vitamin B(12) deficiency (either criterion). The prevalence of iron deficiency was 10%. After exclusions, 96 subjects were further analyzed. Vitamin B(12) deficiency defined by serum vitamin B(12) and MMA was associated with a decrease in hemoglobin concentrations by up to 0.9 g/dL, but it was not associated with an increase in mean corpuscular volume (MCV). Serum MMA but not vitamin B(12) levels correlated inversely with hemoglobin and platelet counts and positively with MCV, after adjustment of confounding factors. However, the percentage of subjects with anemia did not increase significantly until serum MMA became >1.0 micromol/L. In conclusion, vitamin B(12) deficiency was associated with a significant decrease in hemoglobin concentration. However, anemia associated with vitamin B(12) deficiency was seldom macrocytic. We recommend that older vegetarians should be given vitamin B(12) supplements routinely.

Aged↗
PubMed2001

Prediction of body fat by anthropometry in older Chinese people.

OBJECTIVE: To derive regression equations for fat percentage by using simple anthropometric measurements applicable in normal and immobile (cannot stand or walk) older people. RESEARCH METHODS AND PROCEDURES: The study population comprised 352 females and 261 males, apparently well and community-dwelling, aged 69 to 82 years. Fifty-one females and 27 males were recruited for external validation. Body weight, standing height, arm span, triceps and biceps skinfold thicknesses (SFTs), and midarm circumference were measured. The reference method of total body fat percentage was dual-energy X-ray densitometry. Predictive equations for fat percentages were derived by stepwise multiple linear regression on anthropometric indices and gender. RESULTS: Upper-limb SFTs, body mass index, and gender yielded the more predictive equation. The SEE was 4.1% weight. There was a significant trend of underestimation in overweight subjects, especially in females. The equation using SFTs and midarm circumference was less reliable but more applicable to older immobile people and those with significant kyphoscoliosis. CONCLUSIONS: The combination of body mass index and upper-limb SFTs gives reliable prediction of fat percentages in older Chinese people, except in the obese.

Absorptiometry, Photon↗
PubMed2001

Does low lactose milk powder improve the nutritional intake and nutritional status of frail older Chinese people living in nursing homes?

BACKGROUND: Malnutrition is prevalent among nursing home residents in Hong Kong. Nutrient dense oral supplements and yoghurt are unpopular among the Chinese older people because of their unfamiliar tastes and relatively high costs. Vitamin and mineral supplements do not address the problem of protein calorie undernutrition. Milk powder may be a suitable alternative supplement, but diarrhoea resulting from lactase deficiency is common in Chinese people. OBJECTIVE: We hypothesized that a low lactose milk powder would be better tolerated in Chinese nursing home residents and result in improvement in nutritional intake without reducing habitual intake. DESIGN: Forty-seven residents were randomized to receive milk powder twice daily, or no supplement for seven weeks. Twenty-four hour food record, body weight, upper limb skinfold thicknesses and midarm circumference, grip strength, Barthel Index, and abbreviated mental test score were carried out at baseline and at seven weeks. RESULTS: The overall compliance was nearly 100%, and no subjects developed diarrhoea. Compared with controls, milk supplementation increased intake of calcium, vitamin D, vitamin A, riboflavin and potassium. There was no significant reduction in habitual dietary intake in supplemented subjects. There was a trend of weight gain in supplemented subjects, though this did not reach statistical significance. There was no change in handgrip strength, mental function and disability level. CONCLUSION: The study shows that low lactose milk powder is a well-accepted nutritional supplement without reducing habitual dietary intake.

Aged↗
PubMed2000

Experimental analysis of chaotic neural network models for combinatorial optimization under a unifying framework.

The aim of this paper is to study both the theoretical and experimental properties of chaotic neural network (CNN) models for solving combinatorial optimization problems. Previously we have proposed a unifying framework which encompasses the three main model types, namely, Chen and Aihara's chaotic simulated annealing (CSA) with decaying self-coupling, Wang and Smith's CSA with decaying timestep, and the Hopfield network with chaotic noise. Each of these models can be represented as a special case under the framework for certain conditions. This paper combines the framework with experimental results to provide new insights into the effect of the chaotic neurodynamics of each model. By solving the N-queen problem of various sizes with computer simulations, the CNN models are compared in different parameter spaces, with optimization performance measured in terms of feasibility, efficiency, robustness and scalability. Furthermore, characteristic chaotic neurodynamics crucial to effective optimization are identified, together with a guide to choosing the corresponding model parameters.

Algorithms↗
PubMed1999

Crystallization of the N-terminal domain of the Escherichia coli regulatory protein TyrR.

The N-terminal domain of the regulatory protein TyrR from Escherichia coli forms a dimer in solution and has been purified and crystallized. The crystals belong to space group C2 with unit-cell parameters a = 134.5, b = 72.1, c = 96.7 A, beta = 98.5 degrees. The crystals diffract to 2.8 A. Assuming a molecular weight of 23219 Da, a V(m) of 2.5 A(3) Da(-1) is obtained for two dimers in the asymmetric unit.

Bacterial Proteins↗
PubMed1999

Geriatric screening in acute care wards--a novel method of providing care to elderly patients.

OBJECTIVE: To assess a nurse-implemented geriatric screening system. DESIGN: Descriptive study. SETTING: University teaching hospital, Hong Kong. PATIENTS: All (5080) elderly patients admitted between 1 January 1996 and 31 December 1996. MAIN OUTCOME MEASURES: Patient characteristics such as disease, prior admission, living quarters, and regular medications; interventions taken; and morbidity and mortality. RESULTS: The most common interventions were referral to a convalescent hospital, patient education, and carer contact. The overall death rate was 8.5% and the diseases with the highest mortality rates were renal failure, liver cirrhosis, and cancer. Approximately one quarter of patients had been admitted to hospital in the previous month. The death rate was higher among women than men (10.8% versus 6.7%, P<0.001; odds ratio=1.68; 95% confidence interval, 1.38-2.05), as was the percentage of those with a history of admission in the previous month (32.8% versus 20.0%, P<0.001; odds ratio=1.95; 95% confidence interval, 1.71-2.21). Patients with multiple pathologies and polypharmacy had a greater frequency of previous 1-month admission compared with those who did not have these features (37.5% versus 20.0%, P<0.001; odds ratio=2.37; 95% confidence interval 2.0-2.7). Patients living in old-age homes had a higher death rate and more previous 1-month admissions than home dwellers, and patients living in private old-age homes had a higher death rate but lower number of previous 1-month admissions than those living in subsidised old-age homes. CONCLUSIONS: This study has collected important data from one form of integrated geriatric practice, which can be used for future service provision.

Journal Article↗