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Biomedical subjects

J C Chan

Publications and source records attributed to J C Chan.

At least 145 records · Page 8Linked to original sources
PubMed1997

Plasma fibrinogen concentration in a Chinese population.

Plasma fibrinogen concentration has been shown to be a predictor of major cardiovascular events. Information on plasma fibrinogen amongst Chinese has been scanty. We examined the relationships between plasma fibrinogen concentration and cardiovascular risk factors in 988 chinese subjects who underwent 75 g oral glucose tolerance test for screening for glucose intolerance. The study involved a selected sample with subjects who had an history of gestational diabetes, delivery of big babies (birth weight > or = 4 kg), equivocal plasma glucose concentrations and subjects who were family members of diabetic patients. This was mainly a non-smoking (96.6%), non-drinking (98%) and non-exercising (99%) population of which 87% (n = 855) were female. Among the 988 subjects (age +/- S.D. 36.8 +/- 10.2, range 16-79 years), plasma fibrinogen concentration ranged from 1.40 to 9.90 g/l with a mean of 3.26 +/- 0.93 g/l. On stratification of the subjects into 4 quartiles based on plasma fibrinogen concentrations, we found that increased plasma fibrinogen was associated with older age, higher body mass index (BMI), systolic and diastolic blood pressure (BP), fasting and 2 h plasma glucose (PG), prevalence of diabetes, glycated haemoglobin (HbA1c) and triglyceride (TG) level. After adjustment for age and sex, increased plasma fibrinogen concentration remained associated with higher BMI, systolic BP, 2 h PG and TG level. On multivariate analysis using age, BMI, BP, TG, HbA1c and PG as independent variables, plasma fibrinogen was independently related to plasma TG concentration and HbA1c. With 1 S.D. change in TG concentration and HbA1c, there were 3.7 and 5.2% changes in plasma fibrinogen concentration respectively. These findings emphasize the close relationships between plasma fibrinogen and cardiovascular risk factors, in particular abnormal lipid and glucose metabolism.

Adolescent↗
PubMed1997

Accuracy, precision and user-acceptability of self blood glucose monitoring machines.

The performance of six self-monitoring blood glucose (SMBG) machines (Accutrend, Reflolux S, Companion 2, Glucometer GX, Glucometer IV and One Touch II) were examined using venous blood samples from 88 patients. Whole blood glucose (BG) values were measured by four machines from each brand. Machine-generated whole blood glucose (BG) values were corrected before comparison with laboratory plasma glucose values, measured by a glucose oxidase method. Based on error grid analysis, most of the corrected machine-generated BG values were clinically acceptable. Accutrend, Glucometer IV and Companion 2 showed the greatest consistency between machines of the same brand. Over 80% of corrected BG values generated by Glucometer IV fell within +/-10% of the reference values. One Touch II yielded the most reproducible results with a mean CV of 2.7% and was considered the most user friendly machine. More studies are required to examine the performance of these machines in the hands of patients.

Analysis of Variance↗
PubMed1997

Simple anthropometric indexes and cardiovascular risk factors in Chinese.

OBJECTIVE: Obesity is a major public health problem due to its associations with multiple cardiovascular risk factors. Although there are sophisticated methods, such as imaging, to document total body fat and its distributions, anthropometric measurements remain important in clinical practice. We examined the relationships between cardiovascular risk factors and the three commonest anthropometric measurements for obesity, body mass index (BMI), waist-hip ratio (WHR) and waist circumference (WC), in Hong Kong Chinese subjects. DESIGN AND SETTING: The data are obtained from a prevalence survey for glucose intolerance and lipid abnormality in a representative Hong Kong Chinese working population. All employees from a public utility company and a regional hospital were invited to participate. SUBJECTS: There were 1513 subjects (910 men and 603 women, mean age +/- s.e.m.: 37.5 +/- 0.2 y). All of them had no significant past medical history. MEASUREMENTS: BMI, WHR and WC of the 1513 subjects were assessed for their relationships with various cardiovascular risk factors. These include blood pressure, fasting and 2 h plasma glucose and insulin, glycated haemoglobin, total cholesterol, triglyceride, high density and low density lipoprotein cholesterol, and urine albumin concentration. RESULTS: After age adjustment, all three anthropometric indexes were significantly correlated with the major cardiovascular risk factors in both men and women. When BMI, WHR and WC were analysed according to quartiles, there was a significant trend for blood pressure, plasma triglyceride, fasting and 2 h plasma glucose and insulin to increase, and high density lipoprotein cholesterol to decrease, with increasing obesity after adjustment for age and smoking. Using stepwise regression analysis with the three indexes as independent variables, most of the variance in blood pressure, plasma lipid, insulin, glucose and urinary albumin concentration were explained either by WC or WHR. In women, BMI was the main explanatory variable for reduced high density lipoprotein cholesterol. CONCLUSIONS: In Hong Kong Chinese, BMI, WHR and WC provide important information in assessing cardiovascular risks. In men, central adiposity as reflected by WC and to some extent, WHR, explained most of the variance in blood pressure, plasma glucose, lipid, insulin and albuminuria. In women, all three indexes reflecting general and central obesity contribute to the variance in these risk factors.

Adult↗
PubMed1997

A prescription survey in a hospital hypertension outpatient clinic.

AIMS: The objective of this study was to investigate drug utilization in the management of hypertension in Hong Kong. METHODS: We conducted a prescription survey to examine the use of antihypertensive drugs in a hypertension clinic in a regional hospital and the resulting expenditure incurred. The use of concurrent medications such as antidiabetic drugs and lipid-lowering agents was also examined. RESULTS: During a 7-week study period, 530 prescriptions were collected. All except 14 patients received antihypertensive drugs with 262 (50.8%) on monotherapy and 254 (49.2%) on combination therapy. Calcium channel blocking agents and beta-adrenoceptor blocking agents were the two most popular antihypertensive drugs used in both monotherapy (38% and 31%, respectively) and combination therapy (27% and 33%, respectively). Forty-nine patients (19%) received three antihypertensive drugs or more. The number of antihypertensive drugs showed a significant positive correlation with the duration of attendance at the clinic (r=0.88, P < 0.001). Of the total 530 prescriptions, 5.6% and 10% contained antidiabetic drugs and lipid-lowering agents, respectively. Calcium channel blocking agents, angiotensin converting enzyme (ACE) inhibitors and lipid lowering agents, accounted for 82% (HK$211,654; pounds sterling 1 approximately HK$12) of the total drug expenditure (HK$258,115). Seventy-nine percent of the lipid lowering agents prescribed were hydroxymethylglutaryl coenzyme A (HMG CoA) reductase inhibitors. Amlodipine accounted for 26% of usage but contributed to 41% of the overall costs of calcium channel blocking agents. Alpha1-adrenoceptor blocking agents were only used infrequently and were the most expensive class of drugs, due to the preferred use of doxazosin rather than prazosin which is far cheaper than the former. CONCLUSIONS: In view of the use of these often costly drugs for long-term therapy, monitoring of their use and its correlation with clinical outcomes and quality of life is essential to ensure the optimal use of health care resources.

Antihypertensive Agents↗
PubMed1997

Chinese herbs and warfarin potentiation by 'danshen'.

Drug interactions with warfarin can be dangerous and although common drug interactions are now well recognized those with Chinese herbs are not widely appreciated. 'Danshen' is a herbal medicine often used for various complaints, particularly cardiovascular, in the Chinese community. We report a case of danshen-induced overcoagulation with severe and dangerous abnormalities of clotting in a patient with rheumatic heart disease.

Anticoagulants↗
PubMed1997

A 4-year longitudinal study of the oral prevalence of enteric gram-negative rods and yeasts in Chinese children.

A 4-year longitudinal study of the oral prevalence of enteric gram-negative rods and yeasts in 116 Chinese primary school children in Hong Kong was conducted. The oral prevalence of enteric gram-negative rods for each consecutive year was 25.3%, 37.0%, 24.0% and 25.8% respectively, with a weighted mean of 27.9%. Enterobacteriaceae, which comprised 57% of all enteric gram-negative rods, were more common in children with no caries experience. The oral prevalence of yeasts for each consecutive year was 7.7%, 12.0%, 14.4% and 15.5% respectively, with a weighted mean of 12.5%. Candida albicans comprised 84% of all yeasts isolated. Oral yeast carriage was significantly associated with caries prevalence. While the oral prevalence of enteric gram-negative rods in primary school children in Hong Kong may be higher than in other parts of the world, repeated isolation of either enteric gram-negative rods or Candida spp. from individual children over the 4-year study period was rare, suggesting that carriage of these organisms is transient.

Candida↗
PubMed1997

A time domain binaural model based on spatial feature extraction for the head-related transfer function.

A complex-valued head-related transfer function (HRTF) can be represented as a real-valued head-related impulse response (HRIR). The interaural time and level cues of HRIRs are extracted to derive the binaural model and also to normalize each measured HRIR. Using the Karhunen-Loeve expansion, normalized HRIRs are modeled as a weighted combination of a set of basis functions in a low-dimensional subspace. The basis functions and the space samples of the weights are obtained from the measured HRIR. A simple linear interpolation algorithm is employed to obtain the modeled binaural HRIRs. The modeled HRIRs are nearly identical to the measured HRIRs from an anesthetized live cat. Typical mean-square errors and cross-correlation coefficients between the 1816 measured and modeled HRIRs are 1% and 0.99, respectively. The real-valued operations and linear interpolating in the model are very effective for speeding up the model computation in real-time implementation. This approach has made it possible to simulate real free-field signals at the two eardrums of a cat via earphones and to study the neuronal responses to such a virtual acoustic space (VAR).

Acoustic Stimulation↗
PubMed1997

Antihypertensive and anti-albuminuric effects of losartan potassium and felodipine in Chinese elderly hypertensive patients with or without non-insulin-dependent diabetes mellitus.

After a 4-week placebo baseline period, 29 Chinese elderly hypertensive patients were randomized, double-blind, to 12 weeks of treatment with either losartan potassium (n = 19), an angiotensin II antagonist at the AT1 receptor, or felodipine (n = 10), a calcium channel blocking agent. Of these 29 patients 12 had coexisting non-insulin-dependent diabetes mellitus. At week 12, the mean reductions (95% confidence intervals) in mean arterial pressure were similar in both groups: losartan -18 (range -22 to -14) mm Hg; felodipine -19 (range -25 to -11) mm Hg. In the whole group, the 24-hour urinary albumin excretion was reduced by 27% with losartan as compared with no change in the felodipine-treated group (p = 0.03; analysis of variance). In the diabetic group, losartan treatment reduced the urinary albumin excretion by 24% as compared with 11% in the felodipine-treated group. In the non-diabetic patients, the urinary albumin excretion fell by 29% in the losartan-treated group, but increased by 14% in the felodipine-treated group (p < 0.001; repeated-measures analysis of variance). Plasma sodium increased to a similar extent in both groups. The fasting plasma triglyceride level declined by 25% (p < 0.001 within group) with losartan, but was not significantly reduced in the felodipine-treated group. For comparable reductions in blood pressure, a greater reduction in albuminuria was seen with losartan than with felodipine treatment in Chinese hypertensive patients with or without non-insulin-dependent diabetes mellitus. Long-term studies are required to examine whether these antiproteinuric effects of losartan can be translated to renoprotection.

Aged↗
PubMed1997

IgA nephropathy: to treat or not to treat?

IgA nephropathy (Berger's disease) is thought to be the most common primary glomerulonephritis in the world. Characteristically, it presents with intermittent macroscopic hematuria in association with upper respiratory infections. The diagnosis is established by demonstrating predominant IgA deposits in the glomerular mesangium. One third of the cases progress slowly over 25 years to glomerulosclerosis and end-stage renal disease. This rate of disease progression has not been altered by any known treatment, including the use of corticosteroids or cyclosporine. The pathogenesis of this disease is unknown; however, recent data implicated oxygen free radicals in the development of IgA nephropathy. The recent controlled, double-blind, 2-year study from the Mayo Clinic showed that fish oil slowed the progression of IgA nephropathy. This contrasts with the previous studies where the use of fish oil either accelerated the rate of deterioration of renal function in patients with IgA nephropathy or showed no change compared to untreated subjects. Furthermore, in experimental uremia, marked renal functional deterioration with fish oil administration has been reported. Experimental models of IgA nephropathy have been developed in the past few years. In addition, molecular biology offers an unique opportunity to study kidney tissue obtained from patients and animals with IgA nephropathy. These advances will enable the identification of the critical sequence of events that result in renal injury and provide new insight into the pathogenesis and progression of IgA nephropathy. This will help clarify the role of free oxygen radical release on disease progression, and an understanding on the mechanisms of antioxidants, such as vitamin E, in preventing such renal injury.

Animals↗
PubMed1997

Flavobacterium indologenes keratitis.

Flavobacterium indologenes has recently been implicated in nosocomial or opportunistic infection. It has been isolated from lids, conjunctiva, and lacrimal system, and is resistant to most antibiotics. No previous cases of F. indologenes corneal ulcer have been reported in the literature. The natural habitat of Flavobacteria is soil, water, plants, and foodstuffs. In the hospital environment, these bacteria exist in water systems and on wet surfaces. They are not part of the normal ocular flora.

Administration, Topical↗
PubMed1997

Comparison of two oral evacuants (Citromag and Golytely) for bowel preparation before barium enema.

Oral regimens for bowel preparation before barium enema examination are routinely used because of their convenience and simplicity, rather than the traditional method of colonic wash-out. We performed a prospective study comparing the side-effects and efficacy of two commonly used oral bowel evacuants (Citromag and Golytely) for bowel preparation before barium enema examination in 102 patients. The side-effects associated with the agents were assessed by analysing a questionnaire completed by the patients. There was no significant difference in the side-effects between the two agents although more patients taking Golytely (45.5%) deemed its taste unacceptable than those taking Citromag (25.9%). The results of the bowel preparation were assessed by two independent radiologists giving scores on the amount of faecal residue and the quality of mucosal coating. The amount of faecal residue was less in the Golytely group (p < 0.05). The quality of mucosal coating by barium was also better in the Golytely group than the Citromag group (p < 0.05).

Adolescent↗
PubMed1997

Visceral fat and cardiovascular risk factors in Chinese NIDDM patients.

OBJECTIVE: The interrelations between obesity, glucose intolerance, hypertension, dyslipidemia, and insulin resistance are well recognized. These relationships are of particular interest in Hong Kong's Chinese population, in whom increasing affluence has coincided with a marked increase in the prevalence of NIDDM. We designed a pilot study to examine the relationships between visceral fat and cardiovascular risk factors in Chinese NIDDM patients. RESEARCH DESIGN AND METHODS: We studied 21 Chinese NIDDM patients whose visceral fat was quantified by magnetic resonance imaging. Cardiovascular risk factors including plasma lipids and 24-h ambulatory blood pressure (BP) were measured. In addition, insulin resistance was determined by a short insulin tolerance test (SITT). RESULTS: Increased visceral adiposity was significantly correlated with plasma triglycerides (r = 0.63, P = 0.004), the total cholesterol/HDL cholesterol ratio (r = 0.61, P = 0.008), the urinary albumin/creatinine ratio (r = 0.49, P = 0.04), and decreased insulin sensitivity as measured by the SITT (r = 0.47, P = 0.03). When the data were analyzed by tertiles, increasing visceral fat area was associated with higher plasma triglycerides, lower HDL cholesterol, and a smaller plasma glucose decrement during the SITT. In addition, the diurnal rhythm in BP and heart rate tended to be best preserved in those with the least visceral obesity. CONCLUSIONS: This pilot study demonstrates that visceral fat accumulation is associated with dyslipidemia, hypertension, insulin resistance, and albuminuria in Chinese patients with NIDDM.

Adipose Tissue↗
PubMed1997

Fasting plasma glucose as a screening test for diabetes and its relationship with cardiovascular risk factors in Hong Kong Chinese.

OBJECTIVE: To evaluate the use of fasting plasma glucose (FPG) in the diagnosis of diabetes and the relationship between FPG and various cardiovascular risk factors in a community-based Hong Kong Chinese population. RESEARCH DESIGN AND METHODS: The results of 1,470 oral glucose tolerance tests from a prevalence survey for glucose intolerance and lipid abnormality in a Hong Kong Chinese working population were examined. Our previous report showed that an FPG of 5.7 mmol/l corresponded to a 2-h plasma glucose (PG) of 11.1 mmol/l, and we used this value as a cutoff value and examined the relationship between FPG and various cardiovascular risk factors in nondiabetic subjects. RESULTS: An FPG cutoff value of 7.8 mmol/l gave a sensitivity of 20.0% and a specificity of 100% in the diagnosis of diabetes (defined as 2-h PG > or = 11.1 mmol/l). We divided the non-diabetic subjects (FPG < 7.8 mmol/l and 2-h PG < 11.1 mmol/l) into two groups: subjects with FPG < 5.7 mmol/l and those with FPG > or = 5.7 mmol/l and < 7.8 mmol/l. Subjects in the latter group were older, had higher blood pressure, BMI, waist-to-hip ratio, 2-h PG, fasting and 2-h insulin, fasting serum triglyceride, VLDL cholesterol, apolipoprotein B, and urinary albumin concentrations, as well as lower plasma HDL cholesterol and HDL2 cholesterol concentrations. CONCLUSIONS: These findings suggest that an FPG cutoff value of 7.8 mmol/l, as recommended by the World Health Organization, was too high when applied to Chinese populations. As in the case of hyperlipidemia, plasma glucose concentration should be viewed as a continuum in terms of its relationship with cardiovascular risk.

Adult↗
PubMed1997

Dexfenfluramine in obese Chinese NIDDM patients. A placebo-controlled investigation of the effects on body weight, glycemic control, and cardiovascular risk factors.

OBJECTIVE: To investigate the safety, efficacy, and metabolic effects of dexfenfluramine in obese Chinese NIDDM patients. RESEARCH DESIGN AND METHODS: Thirty-two patients, mean (+/- SD) body weight 76.2 +/- 8.5 kg with corresponding BMI 31.1 +/- 2.1 kg/m2, were randomized into a two-phase study, after a 2-week single-blind run-in period on placebo. Phase 1 was a randomized 3-month double-blind placebo-controlled trial during which either dexfenfluramine or placebo was added to the existing treatment regimens of diet plus or minus sulfonylureas without metformin. Phase 2 was a further 3-month single-blind trial during which the placebo group was given dexfenfluramine without patients' knowledge of changing to active medication, while the active group continued with dexfenfluramine. Body weight, glycemic control, blood pressure, lipids, and quality of life were assessed before and at 3 and 6 months after randomization. A total of 27 patients were also followed for an additional period of 6-12 months (215 +/- 53 days) after dexfenfluramine treatment was withdrawn. RESULTS: During the run-in period, both groups were comparable for all parameters measured. At 3 months, mean changes in BMI were -1.2 +/- 1.0 kg/m2 (dexfenfluramine) vs. -0.1 +/- 0.5 kg/m2 (placebo) (P < 0.001). The mean changes in fasting plasma glucose were -1.14 +/- 0.99 vs. 0.51 +/- 1.34 mmol/l (dexfenfluramine vs. placebo, P = 0.004). HbA(1c) also significantly improved in the dexfenfluramine group (-0.80 +/- 0.53 vs. 0.25 +/- 0.64%, P < 0.001). During the 3-month single-blind dexfenfluramine treatment in the ex-placebo group, there were similar improvements in body weight and glycemic indexes. After cessation of dexfenfluramine therapy at 6 months, significant increases in body weight and glycemic indexes, almost back to the baseline, were observed for both groups. CONCLUSIONS: Dexfenfluramine aids weight loss and improves glycemic control in obese Chinese NIDDM patients over a 3- to 6-month period. These effects are emphasized after withdrawal of treatment and further support the longer-term use of dexfenfluramine for chronic complicated obesity.

Adult↗
PubMed1997

Growth hormone and insulin-like growth factor in non-uremic acidosis and uremic acidosis.

Growth retardation is a cardinal feature of children with renal tubular acidosis. This is reversible by correcting the non-uremic acidosis with alkali therapy. Sodium bicarbonate solutions or citrate solutions have been used for this purpose. However, the odious taste of these medications almost invariably causes medical noncompliance. The persistent and often profound metabolic acidosis from medical noncompliance, precipitates hypercalciuria and hypocitraturia, and increases the risk of nephrocalcinosis. The mechanism of the growth retardation in renal tubular acidosis is thought to be related to a blunting of anterior pituitary growth hormone secretion. In experimental metabolic acidosis, the growth hormone secretory pulse areas are reduced. Just as importantly, hepatic growth hormone receptor expression and IGF-I mRNA were blunted in metabolic acidosis. In uremia, growth retardation is secondary to a host of factors including metabolic acidosis, renal osteodystrophy, and the side effects of treatment such as corticosteroids, which compound the growth retardation. Growth hormone secretion by individual pituitary cells was stimulated by corticosteroids but, paradoxically, the total number of somatotropes was suppressed. In uremia, the secretion of growth hormone was not different from controls at any level of growth-hormone-releasing hormone challenges. Hepatic IGF-I mRNA was markedly reduced in uremic rats. Growth hormone receptor expression was significantly reduced in uremic acidotic rats. The growth hormone and IGF-I expression on the growth plate of the long bone of uremic rats was reduced. IGF-I immunoreactivity was present in both the hypertrophic and proliferative zones. The lack of growth of the proliferative zones suggested growth hormone and IGF-I resistance in uremic chondrocytes.

Acidosis↗