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Biomedical subjects

J Woo

Publications and source records attributed to J Woo.

At least 163 records · Page 9Linked to original sources
PubMed1996

G/C-modified oligodeoxynucleotides with selective complementarity: synthesis and hybridization properties.

Modified oligodeoxyribonucleotides (ODNs) that have unique hybridization properties were designed and synthesized for the first time. These ODNs, called selective binding complementary ODNs (SBC ODNs), are unable to form stable hybrids with each other, yet are able to form stable, sequence specific hybrids with complementary unmodified strands of nucleic acid. To make SBC ODNs, deoxyguanosine (dG) and deoxycytidine (dC) were substituted with deoxyinosine (dI) and 3-(2'-deoxy-beta-D-ribofuranosyl)pyrrolo-[2,3-d]-pyrimidine-2-(3H)-one (dP), respectively. The hybridization properties of several otherwise identical complementary ODNs containing one or both of these nucleoside analogs were studied by both UV monitored thermal denaturation and non-denaturing PAGE. The data showed that while dI and dP did form base pairs with dC and dG, respectively, dI did not form a stable base pair with dP. A self-complementary ODN uniformly substituted with dI and dP acquired single-stranded character and was able to strand invade the end of a duplex DNA better than an unsubstituted ODN. This observation implies that SBC ODNs should effectively hybridize to hairpins present in single-stranded DNA or RNA.

Base Sequence↗
PubMed1996

Albuminuria, insulin resistance and dyslipidaemia in Chinese patients with non-insulin-dependent diabetes (NIDDM).

In order to examine relationships between albuminuria, insulin resistance, and dyslipidaemia in non-insulin-dependent diabetes (NIDDM), we studied 164 Chinese patients (68 men, 96 women), treated with diet or oral hypoglycaemic agents, on three occasions during a 6-week period. Antihypertensive treatment, if previously prescribed, was withdrawn for at least 2 weeks before the study period. Insulin resistance was calculated from simultaneous fasting plasma glucose and insulin concentrations using the homeostasis model assessment (HOMA) method. Based on two of three 24 h urinary collections, 87 (53%) patients had normoalbuminuria, 46 (28%) microalbuminuria, and 31 (19%) macroalbuminuria. Despite similar glycaemic control, patients with abnormal albuminuria had higher mean arterial pressure, fasting plasma total cholesterol, triglyceride and serum apo B concentrations and were more insulin resistant than normoalbuminuric patients. Albuminuria correlated with mean arterial pressure (r = 0.31, p < 0.001), triglyceride (r = 0.36, p < 0.001), total cholesterol (r = 0.28, p = 0.001), apolipoprotein B (apo B) (r = 0.25, p = 0.003), and insulin resistance (r = 0.25, p < 0.002). These close associations may contribute to the increased cardiovascular risk in Chinese NIDDM patients with abnormal albuminuria.

Albuminuria↗
PubMed1996

Normal ranges for vertebral height ratios and prevalence of vertebral fracture in Hong Kong Chinese: a comparison with American Caucasians.

We have established the normal ranges for vertebral height ratios and studied the prevalence of vertebral fracture in 481 Chinese women aged 70-79. Our results were compared with those of an American study with a similar methodology. Lateral spine radiographs centered at T8 and L3 were taken, and the anterior, middle, and posterior vertebral heights of each vertebra from T5 to L4 were measured. The means and standard deviations (SDs) of the anterior to posterior, middle to posterior, and posterior to posterior vertebral height ratios were derived after trimming the extreme values from the distribution. The Chinese had smaller vertebral size than the American Caucasians at all levels. Moreover, the anterior to posterior vertebral height ratios were consistently smaller in the Chinese than in the Americans from T10 onward. The means of other vertebral height ratios in the Chinese were similar to the American Caucasians, but the SDs were greater in the Chinese. The prevalence of vertebral fracture was 29% in the Chinese and 25% in the American Caucasians if a cut-off of 3 SD below the mean for vertebral height ratios was used. We conclude that population-specific means and SD should be used for defining vertebral fracture and that the prevalence of vertebral fracture is similar in Hong Kong Chinese and American Caucasians.

Aged↗
PubMed1996

Dietary calcium intake, physical activity and the risk of vertebral fracture in Chinese.

To study the relationship between dietary calcium intake, load-bearing activity, reproductive factors, anthropometric factors and vertebral fracture in Chinese, a case-control study was carried out on 481 women (aged 70-79 years) who lived in three housing blocks under the Geriatric Priority Housing Scheme in Shatin, Hong Kong. Lateral spine radiographs were taken from the T4 to L4 level. Definite and doubtful vertebral fractures were diagnosed when any of the three vertebral height (anterior to anterior, middle to posterior and posterior to posterior) ratios was 3 SD and 2-2.99 SD below the mean respectively. Women with one or more definite fractures were classified as definite cases, those with one or more doubtful fractures were classified as doubtful cases, and the rest as controls. The mean dietary calcium intake and load-bearing activities were obtained by interview, using a structured questionnaire. Detailed information on cigarette smoking, alcohol consumption and reproductive factors was also obtained. The grip strength, body weight and height were measured. Doubtful cases were found to differ little from the controls in their lifestyle and anthropometric factors. The odds ratio (OR) for being a definite case was 2.1 (95% CI = 1.1-3.9) when the dietary calcium intake was in the lowest quartile. The OR was 1.8 (95% CI = 0.8-4.4) for subjects who walked or exercised outdoors for less than an hour a day. Giving birth to or breast-feeding three children or more was protective against definite fracture. The definite cases were significantly lighter and shorter than controls; they also had a weaker grip strength. It is concluded that a low dietary calcium intake was significantly associated with an elevated risk of vertebral fracture, while the effect of infrequent load-bearing activity was uncertain. Giving birth to or breast-feeding three or more children was protective against vertebral fracture in our population.

Aged↗
PubMed1996

Body composition and bone mineral density of Chinese women with vertebral fracture.

This study was designed to compare the body composition and bone mineral density measurements (BMD) in Chinese women with vertebral fracture and normal controls. A total of 400 community dwelling Chinese women aged 70-79 years old were studied. Vertebral height ratios were calculated from lateral thoracic and lumbar spine X-rays and subjects were classified into definite cases (n = 122), doubtful cases (n = 138) and normal controls (n = 140). Bone mineral density and body composition measurements were made by dual X-ray densitometry. The height, fat mass, lean mass, and BMD at all sites were significantly lower in patients with definite fracture than normal controls. Nevertheless, BMD at the hip was more predictive of vertebral fracture than BMD at the spine, the odds ratio in the lowest quartile of hip BMD being 3.8 (95% C.I. = 1.3 to 10.9). Finally, the extent of spinal deformity was poorly predicted by a combination of the anthropometric and BMD measurements, as only 12% of the total variance in TD1 was accounted for.

Absorptiometry, Photon↗
PubMed1996

Suppression of TRH-stimulated TSH secretion by glucose-induced hypothalamic somatostatin release.

To determine whether the combined glucose-thyrotropin-releasing hormone (TRH) test can be a useful method for the evaluation of the hypothalamic somatostatinergic activity, we investigated whether TRH-induced thyroid stimulating hormone (TSH) secretion can be suppressed by the oral glucose administration that stimulates the hypothalamic somatostatin (SRIH) secretion. Six tests were performed in ten healthy young men. Test 1: 1 ml of normal saline was intravenously administered at 0 min. Test 2: TRH was administered intravenously at 0 min. Test 3: Glucose, 75 g, was administered orally at -60 min. Test 4: Glucose and TRH were administered as above. Test 5: Pyridostigmine (PST), 120 mg, was given orally at -90 min followed by the administration of GH and TRH as above. Basal TSH levels were suppressed slightly, but significantly. In Test 3 compared to those observed in Test 1. The oral glucose administration also significantly suppressed TRH-stimulated TSH response by 27-35% between 40 min and 80 min in Test 4. In contrast, the pretreatment with PST completely reverted the suppressive effect of glucose on TRH-stimulated TSH response in Test 5. These data suggest that the increased hypothalamic SRIH secretion induced by oral glucose administration can suppress TRH-stimulated TSH response in normal men, and the combined glucose-TRH test can be a useful method to evaluate the hypothalamic somatostatinergic activity.

Adult↗
PubMed1996

Risk factors for falls in the Chinese elderly population.

BACKGROUND: Besides being the major cause of hip fracture, falls also have important consequences in injuries and mortality, especially in the elderly population. This study investigated the occurrence of and the correlates of falls in a cohort of Hong Kong Chinese elderly aged 70 years and above. METHODS: The research was based on the baseline cross-sectional study of an age- and sex-stratified cohort consisting of 1,947 ambulatory subjects. The occurrence of falls was based on the previous 12 months. Logistic regression analysis was used to test the effect of each independent variable, adjusting for age and sex. Multivariate logistic regression analysis based on the backward elimination procedure was used for the final model. RESULTS: Previous white-collar employment, poor self-perceived health, dizziness, slow gait velocity, difficulties in activities of daily living, non-practice of "morning walk," body mass index in the range of 20-24, use of local skin preparation, and presence of cerebrovascular disease were independently associated with falls. Smokers were found to have an independent decreased risk of falls. Neither age nor sex was significantly associated with falls after adjusting for the other explanatory variables. CONCLUSIONS: The results from this population-based cross-sectional study form a basis for further prospective study on falls in the Chinese elderly population. Both intrinsic and extrinsic factors including circumstances and consequences of falls are important considerations in the strategy for the prevention of falls.

Accidental Falls↗
PubMed1996

Tuberculosis among elderly Chinese in residential homes: tuberculin reactivity and estimated prevalence.

Objectives of this study were to determine the prevalence of positive tuberculin reactivity and associated factors among elderly nursing home residents in a population with a relatively high tuberculosis notification rate, to estimate the prevalence of active tuberculosis, and to assess tuberculin reactivity as a screening tool. A stratified, disproportional, randomized cluster sample of residents was selected and the Mantoux test (using 0.1 ml of 5 tuberculin units of purified protein derivative of tuberculin) carried out. All subjects with a positive test had a chest X-ray followed by sputum smear and culture if the X-ray was abnormal. Sputum examination was also carried out in a random sample of controls, matched for age and gender, drawn from subjects with a negative Mantoux test. Information regarding medical history, tobacco smoking habits, symptoms related to tuberculosis, and communal eating habits were gathered. Also anthropometric data were collected. Sixteen nursing homes in the catchment area of a major district hospital in Hong Kong comprising 587 residents (136 men, 451 women, mean age 80 +/- 8 years) participated in this study. The weighted prevalence of tuberculin reactivity was 43.8%. It was higher in men, among those who took their meals in a common area, in the younger age group, and in those with no previous history of hospitalization. No association was found between prevalence and duration of residence, smoking, skinfold thickness, past medical history, or any relevant symptoms. Following radiological and sputum examination, the estimated prevalence of active tuberculosis ranged from 1.2 to 2.6%. The sensitivity of the tuberculin test was 86, the specificity 30%. The prevalence of active tuberculosis in nursing homes in Hong Kong is high, but it is unclear whether cross-infection or poor health of the residents is the major contributing factor. Tuberculin skin testing does not appear to be a useful screening method in this population.

Aged↗
PubMed1996

Serum bilirubin and cardiovascular risk factors in a Chinese population.

BACKGROUND: Many risk factors for cardiovascular disease (CVD) have been identified. Recently an association between low concentration of serum bilirubin and increased risk of CVD has been reported. However, information on this topic remains scarce. METHODS: We examined the relationships between serum bilirubin and CVD risk factors in 1508 Hong Kong Chinese. We divided the subjects into four quartiles based on serum bilirubin concentrations. Cardiovascular risk factors studied include age, sex, smoking, obesity glycaemic status and lipid indices. RESULTS: Decreasing serum bilirubin concentration was associated with older age, increased prevalence of smoking, higher body mass index and systolic blood pressure, increased glycated haemoglobin, fasting and 2 h insulin, triglyceride, very-low-density lipoprotein and apolipoprotein B concentrations, and lower high-density lipoprotein concentration. Women had lower bilirubin concentrations than men. After adjustment for age, sex, smoking and insulin levels as covariates, the associations between serum bilirubin concentration and glycated haemoglobin, triglyceride, high-density lipoprotein and very-low-density lipoprotein persisted. The prevalence rates of abnormal glucose tolerance (impaired glucose tolerance or diabetes) were similar amongst the four quartiles of bilirubin concentrations. However, the mean bilirubin concentration was significantly lower in subjects with abnormal glucose tolerance (9.3 +/- 3.5 mumol/l, n = 178) than in normal subjects (10.1 +/- 5.2 mumol/l, n = 1330, P = 0.039). When analysed as a continuous variable by age-adjusted partial correlation coefficients, serum bilirubin concentration was inversely correlated with fasting insulin, triglyceride, very-low-density lipoprotein and glycated haemoglobin level. CONCLUSIONS: There were close associations between low serum bilirubin concentration and increased CVD risk factors. Subjects with abnormal glucose tolerance also had lower serum bilirubin concentration than normal subjects. Some of these associations (body mass index, systolic blood pressure) could be explained by differences in insulin level. These relationships between bilirubin and CVD risk factors require further clarification, although abnormal intermediary metabolism and antioxidant deficiency may be possible linking factors.

Adult↗
PubMed1996

Apolipoprotein E genotype and Alzheimer's disease in Hong Kong elderly Chinese.

We studied the apolipoprotein E (apoE) allele frequencies in 65 Chinese patients with late-onset Alzheimer's disease (AD) and 82 age- and sex-matched controls. The apoE epsilon 4 allele frequency was significantly higher in the AD group than in the control group (0.169 versus, p < 0.01). There were five homozygotes for epsilon 4 in the AD group but none among the controls. The odds ratio for AD was 1.6 for epsilon 4 heterozygotes. The age at onset was lower in the presence of the epsilon 4 allele and higher with the epsilon 2 allele, although neither of these differences reached statistical significance. The association between apoE alleles and AD previously reported in Caucasian populations was also present in this reports of lower prevalence of AD compared with the prevalence of multi-infarct dementia.

Aged↗
PubMed1996

Characteristics of gsp-positive growth hormone-secreting pituitary tumors in Korean acromegalic patients.

A subset of human growth hormone (GH)-secreting pituitary tumors contains the gsp oncogene that encodes an activation mutation of the alpha-subunit of the stimulatory GTP-binding protein (G(S) alpha). This study was undertaken to investigate the frequency of the gsp oncogene in GH-secreting pituitary tumors in Korean acromegalic patients and to elucidate the clinical characteristics of these patients to endocrine testing. Direct polymerase chain reaction sequencing revealed the gsp oncogene mutation in 9 out of 21 tumors (43%) at amino acid 201 of the G(S) alpha protein. A single nucleotide mutation in the tumors carrying the gsp oncogene was observed, which replaced an arginine (CGT) in the normal protein with cysteine (TGT) in eight tumors and serine (AGT) in one tumor. The patients with the gsp oncogene mutation (group 1) were older (54 +/- 10 vs 41 +/- 11 years, p = 0.0085) than those without the mutation (group 2). Sex, tumor size and grade, basal GH and prolactin levels, the GH response to oral glucose loading, the GH fluctuation and the paradoxical response to thyrotropin-releasing hormone or gonadotropin-releasing hormone did not differ between the groups. The gsp oncogene was found mostly in somatotroph adenomas. The octreotide-induced GH suppression was significantly higher in group 1 than in group 2 (95 +/- 5% vs 81 +/- 17%, p = 0.0335). The GH response to bromocriptine did not differ between the groups. These results suggest that the G(S) alpha mutations of GH-secreting tumor are observed in Korean acromegalic patients with similar frequency to those of western countries. The patients with gsp oncogene are likely to be older than those without the oncogene, and show excellent response of GH suppression to octreotide.

Acromegaly↗
PubMed1996

Helicobacter pylori infection increases the risk of peptic ulcers in chronic users of non-steroidal anti-inflammatory drugs.

The objective was to study the gastrointestinal complications in chronic NSAID users with Helicobacter pylori infection. Eighty-two Chinese patients on long-term NSAID or aspirin treatment were studied for the occurrence of H. pylori infection and gastroduodenal mucosal injuries by upper endoscopy. H. pylori infection was confirmed by CLO test, histology and bacteriological cultures. Frequency and severity of symptoms of dyspepsia were also assessed. Thirty-three (40%) patients were diagnosed to have H. pylori infection and 49 (60%) patients were not infected. The two groups were comparable in age, sex, smoking and drinking habit and the use of anti-ulcer drags. Twenty-four out of 33 (72.7%) H. pylori-positive patients and 31 out of 49 (63%) of H. pylori-negative patients were found to have macroscopic lesions by endoscopy. The overall incidence of gastroduodenal lesions in the H. pylori positive patients was not significantly different from the H. pylori-negative patients (p = 0.34). However a higher incidence of duodenal ulcers in the H. pylori-infected group than the H. pylori-negative group (33% vs 6%, p = 0.0001) was found. The difference in severity and frequency of dyspeptic symptoms between the two groups did not reach statistical significance. H. pylori infected chronic NSAID users is associated with a higher rate of duodenal ulcer.

Adult↗
PubMed1996

An estimation of the functional disability burden in elderly Chinese age 70 years and over.

A cross-sectional survey of functional status among elderly Hong Kong Chinese aged 70 years and over was carried out to estimate the current burden of disability. Two thousand and thirty-two subjects (999 men, 1033 women) were recruited by random sampling of the old age and disability allowance schemes covering over 90% of the elderly population, stratified by sex and 5-year age groups. Functional ability was administered using the Barthel Index. The duration of disability, if any, was also noted. The prevalence of disability for different activities of daily living varied from 0.8% to 26% (lowest for feeding and highest for climbing stairs and bathing). The prevalence was higher for women than men, and higher in the older age group for both sexes. Men in the 80+ age group had shorter duration of disability compared with those in the 70-79 age group, and compared with women. Using disability years (estimated number of elderly with disability in the population x median duration of disability) as an estimate of disability burden, the number ranges from approximately 19,000 (inability to feed) to 100,000 (inability to climb stairs). This estimate may be useful in the planning of service provisions for the formal and informal care sector.

Activities of Daily Living↗
PubMed1996

Both L- and D-isomers of allotrap 2702 prolong cardiac allograft survival in mice.

BACKGROUND: Peptides derived from a conserved region of the human leukocyte antigen class I heavy chain (a.a. 75-84) have been shown to have immunomodulatory activity. The peptide 07.75-84, derived from HLA-B7, prolonged Lewis 1.W cardiac allograft survival in Lewis 1.A recipients. In combination with cyclosporine A, permanent heart allograft acceptance was induced in the Lewis to ACI donor/recipient combination. In mice, 2702.75-84, derived from HLA-B2702, prolonged the survival of C57B1/6 skin allograft in CBA recipients. In vitro, 2702.75-84 inhibited NK and cytotoxic T cells. To further evaluate the immunomodulatory activity of both L- and D-isoforms of 2702.75-84, we studied their effects in a mouse cardiac allograft model. METHODS: Peptides consisting of L- and D-amino acids were synthesized and administered to CBA (H-2k) recipients of a C57B1/6 (H-2b) cardiac allografts. In addition to peptide monotherapy, combinations of peptide with cyclosporine A and azathioprine were evaluated. Graft survival was monitored by palpation. Breakdown products of 2702.75-84 were identified by a combination of high-performance liquid chromatography and mass spectrometry. RESULTS: Daily administration of 2702.75-84 to CBA (H-2k) recipients of a C57B1/6 (H-2b) cardiac allograft prolonged graft survival to 11.4 +/- 2.6 days compared with 7.5 +/- 1.2 days in untreated control animals (n = 8; p = 0.0003, Mann-Whitney U Test). Other major histocompatibility complex class I-derived peptides including HLA-G.75-84, HLA-07.75-84, HLA-2705.75-84, H-2Kk.75-84, H-2Dk.75-84, H-Kb.75-84, and H-2Db.75-84 had no effect. In combination with a subtherapeutic dose of cyclosporine A (days 0 to 4), 2702.75-84 prolonged graft survival to at least 70 days (five of eight grafts still beating, p = 0.0002) compared with a median graft survival of 14 days in animals that received cyclosporine A monotherapy. Like other peptides consisting of L-amino acids, 2702.75-84 is subject to degradation by serum proteases. Breakdown products of 2702.75-84 were identified by a combination of high-performance liquid chromatography and mass spectrometry. These compounds were found to be inactive when tested in vivo. In contrast to peptides consisting of L-amino acids, peptides consisting of D-amino acids are resistant to proteolytic degradation. When D2702.75-84 was administered to graft recipients at 5 to 10 mg/kg/day (days 0 to 10), graft survival was prolonged to more than 50 days (5 of 13 grafts still beating, p = 0.0001). In combination with azathioprine, administration of D2702.75-84 induced graft acceptance (> 100 days) in 100% of animals (all grafts still beating). CONCLUSIONS: This study shows that administration of 2702.75-84 consisting of L- or D-amino acids will prolong graft survival in mice. In addition, the data suggest that the D2702 isomer is more potent than the L-isomer in vivo and may allow reduced dosage or frequency of administration.

Adjuvants, Immunologic↗