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Biomedical subjects

C C Chow

Publications and source records attributed to C C Chow.

At least 55 records · Page 3Linked to original sources
PubMed2000

Outcomes of screening for diabetes in high-risk Hong Kong Chinese subjects.

OBJECTIVE: To examine the significance of individual risk factors on the development of diabetes in subjects who underwent screening for diabetes. RESEARCH DESIGN AND METHODS: A total of 1,649 Chinese subjects underwent screening for diabetes. They were asymptomatic but had known risk factors for diabetes, including a positive family history of diabetes, a past history of gestational diabetes, obesity, hypertension, and/or dyslipidemia. Another 799 age-matched subjects from the community who had no risk factors for diabetes were used as the comparison group. RESULTS: Of the 1,649 subjects who underwent screening, 241 (14.6%) had diabetes. In these subjects, 989 (60.0%) had 1 risk factor, 502 (30.4%) had 2 risk factors, 141 (8.6%) had 3 risk factors, and 17 (1.0%) had 4 or 5 risk factors for diabetes. Of the 799 control subjects, 29 (3.6%) had diabetes. Compared with the comparison group, the odds ratio (95% CI) of having diabetes after adjustment for age was 5.2 (3.5-7.7) in the 1,649 subjects with known risk factors. The odds ratio of having diabetes increased from 3.7 in subjects with 1 risk factor to 28.4 in subjects with 4 or 5 risk factors. CONCLUSIONS: In men, age, BMI, family history of diabetes, and dyslipidemia, and in women, age, BMI, hypertension, dyslipidemia, total cholesterol, and history of gestational diabetes are associated with increased odds of developing diabetes. These risk factors have additive effects on the odds of having diabetes. Early and regular screening for diabetes and other cardiovascular risk factors is essential in these high-risk individuals.

Adult↗
PubMed2000

Diabetes in Hong Kong Chinese: evidence for familial clustering and parental effects.

OBJECTIVE: To investigate transmission patterns of diabetes and their relationships with clinical characteristics in Hong Kong Chinese patients with late-onset (age > or =35 years) type 2 diabetes. RESEARCH DESIGN AND METHODS: This study involved 2,310 patients consecutively selected from a hospital clinic-based diabetes registry. These patients all reported the diabetes status of their parents as well as siblings. RESULTS: Approximately 36% of the 2,310 patients reported at least 1 affected parent or sibling (25 and 21% reported at least 1 diabetic parent and sibling, respectively). These patients, irrespective of their sex, were more likely to have a diabetic mother than a diabetic father (17 vs. 13% of the male patients and 18 vs. 9% of the female patients, P<0.01). The male patients were more likely than the female patients to have a diabetic father (13 vs. 9%, P<0.01). The female patients with a diabetic mother were found to have higher levels of plasma total cholesterol compared with the female patients with a diabetic father in multiple comparisons with adjustment for significance (5.56+/-1.30 vs. 5.09+/-0.95 mmol/l, P<0.05). In 2-group comparisons, there was also evidence that the male patients with a diabetic father had higher BMI values than the male patients with a diabetic mother (25.9+/-3.5 vs. 25.0+/-3.5 kg/m2, P<0.05). CONCLUSIONS: We found familial clustering of diabetes in the Hong Kong Chinese population as well as a significant maternal influence and a male sex-specific paternal effect. We suggest that both maternal and paternal factors may be implicated in the development of type 2 diabetes in the Chinese population.

Adult↗
PubMed1999

Noise shaping in populations of coupled model neurons.

Biological information-processing systems, such as populations of sensory and motor neurons, may use correlations between the firings of individual elements to obtain lower noise levels and a systemwide performance improvement in the dynamic range or the signal-to-noise ratio. Here, we implement such correlations in networks of coupled integrate-and-fire neurons using inhibitory coupling and demonstrate that this can improve the system dynamic range and the signal-to-noise ratio in a population rate code. The improvement can surpass that expected for simple averaging of uncorrelated elements. A theory that predicts the resulting power spectrum is developed in terms of a stochastic point-process model in which the instantaneous population firing rate is modulated by the coupling between elements.

Mathematics↗
PubMed1999

Assessing muscle stiffness from quiet stance in Parkinson's disease.

In previous studies, we developed a postural stiffness measure that is extracted from foot center-of-pressure (COP) trajectories from quietly standing individuals and is based on an analytical mechanical model of posture control. Here we apply this measure to patients with Parkinson's disease (PD). We correlated the postural stiffness measure with different clinical rating scales, obtained from patients. Kendall's rank correlation was highly significant between the stiffness measure and rigidity, bradykinesia, posture impairment, gait, and leg agility, respectively, as rated by the Unified Parkinson's Disease Rating Scale. These results provide further evidence that a higher intrinsic muscle stiffness may contribute to the aforementioned clinically defined symptoms. From a clinical standpoint, this work indicates that the proposed postural stiffness measure may be useful as an assessment tool for the evaluation of PD patients subsequent to pharmacological and surgical treatment.

Disability Evaluation↗
PubMed1999

Effects of fatigue on the temporal neuromuscular control of vastus medialis muscle in humans.

The effects of muscle fatigue on the temporal neuromuscular control of the vastus medialis (VM) muscle were investigated in 19 young male subjects. The electromyogram (EMG) activities of VM and the force generation capacities of the quadriceps muscle were monitored before and after a fatigue protocol. In response to light signals, which were triggered randomly, the subjects made three maximal isometric knee extensions. This was then followed by the fatigue protocol which consisted of 30 isometric maximal voluntary contractions at a sequence of 5-s on and 5-s off. Immediately after the exercise to fatigue, the subjects performed another three maximal isometric contractions in response to the light signals. The effects of fatigue on the temporal neuromuscular control were then investigated by dividing the total reaction time (TRT) into premotor time (PMT) and electromechanical delay (EMD). The TRT was defined as the time interval between the light signal and the onset of the knee extension force. The PMT was defined as the time from the light signal to the onset of EMG activities of VM, and EMD as the time interval between onset of EMG activities to that of force generation. Following the contractions to fatigue there was a significant decrease in peak force (Fpeak, P = 0.016), an increase in the root mean square (rms)-EMG: Fpeak quotient (P = 0.001) but an insignificant change in the median frequency (P = 0.062) and rms-EMG (P = 0.119). Significant lengthening of mean EMD was found after the fatigue protocol [0.0396 (SD 0.009) vs. 0.0518 (SD 0.016) s P<0.001]. The lengthening of EMD in VM would affect the stabilizing effect of the patella during knee extension. The faster mean PMT [0.2445 (SD 0.093) vs. 0.2075 (SD 0.074) s, P = 0.042] following the fatigue protocol might have compensated for the lengthened EMD and contributed to the insignificant change in the mean TRT [0.284 (SD 0.09) vs. 0.259 (SD 0.073) s, P = 0.164]. This was probably related to the low level of fatigue (15% decrease in force) and the stereotyped nature of the action such that the effects of the fatigue on neuromuscular control were likely to have been attributable to peripheral processes.

Adult↗
PubMed1999

Molecular genetics of diabetes mellitus in Chinese subjects: identification of mutations in glucokinase and hepatocyte nuclear factor-1alpha genes in patients with early-onset type 2 diabetes mellitus/MODY.

AIMS: To examine the prevalence of identified MODY-related genes in Chinese subjects with early onset Type 2 diabetes mellitus and a positive family history of diabetes and to look for possible associations between the gene mutations and the development of diabetes. METHODS: Ninety-two unrelated Chinese subjects with diabetes diagnosed before the age of 40 years who had a positive family history of diabetes were screened for mutations in hepatocyte nuclear factors (HNF-1alpha and HNF-4alpha) and glucokinase genes by direct sequencing. The family members of patients with mutations and 100 healthy controls were also examined. RESULTS: Mutations in the HNF-1alpha and the glucokinase genes were found in 5% and 3% of the diabetic subjects, respectively but no mutations were found in the coding region of the HNF-4alpha gene. Three mutations found in the glucokinase gene were novel missense mutations (I110T, A119D and G385V). The mutations in the HNF-1alpha gene were also new and included four missense mutations (G20R, R203H, S432C, I618M) and one splice acceptor site mutation (IVS2nt-1G-->A). Patients with mutations in these genes were clinically heterogeneous with respect to phenotype and basal pancreatic beta cell function. CONCLUSIONS: Genetic factors such as mutations in the HNF-1alpha and glucokinase genes may be important in the development of diabetes in Chinese people, especially when the disease is of early onset.

Adolescent↗
PubMed1999

Clinical characteristics of acromegaly in Hong Kong.

This study analyses the clinical characteristics of acromegalic patients in Hong Kong. All patients with acromegaly under follow up in Prince of Wales Hospital, Hong Kong between January 1984 and December 1992 were reviewed retrospectively. Detailed hospital notes were available for review in 28 out of 34. Of the 28 patients with full records available, 27 were Chinese and 1 was Nepalese. There were 8 (28.6%) males and 20 (71.4%) females. The mean age (+/- SD) at presentation was 51.2+/-16.8 years (range: 28 to 84 years) (male, 49.9+/-13.9 years [range: 28-66]; female, 51.7+/-18.1 years [range: 31-84]; p-value: NS). The commonest mode of presentation (n=22, 78.6%) was clinical suspicion by medical staff during consultation for other conditions, acromegaly being later confirmed. The estimated duration of symptoms, before diagnosis, was 14 years (range: 1 to 30 years). CT scan imaging of the pituitary gland showed that 12 patients (42.9%) had pituitary macro-adenomas (> or =1 cm), 3 (10.7%) had micro-adenomas (<1 cm), 6 (21.4%) had normal imaging, 1 (3.6%) had an empty sella and 6 (21.4%) had suspicious but inconclusive lesions in the pituitary gland. Surgery was offered as initial treatment to all patients. 4 to 6 weeks after surgery, if the maximal growth hormone response following glucose loading exceeded 10 microg/L, radiotherapy was offered. Of the 28 patients, 13 received surgery and radiotherapy, 2 surgery only, 4 radiotherapy only, 4 no treatment and 5 defaulted. At presentation, 50% had some abnormality of glucose tolerance. The mean early morning fasting baseline growth hormone was 52.8+/-37.0 microg/L (mean +/- SD, median: 48.1 microg/L) and the maximal growth hormone response during an extended oral glucose tolerance test was 63.2+/-34.9 microg/L (median: 61.3 microg/L). Forty five percents of patients had a maximal growth hormone response exceeding 60 microg/L. Of the 19 patients who underwent surgery and/or radiotherapy, 15 had their pituitary function reassessed 6 months after intervention. Their early morning fasting growth hormone and maximal growth hormone response in an extended oral glucose tolerance test were 21.3+/-25.8 and 35.4+/-37.5 microg/L, respectively. In conclusion, acromegaly in Hong Kong has an estimated annual incidence of 3.8 per million. There is a female preponderance, tendency to late presentation (>10 years) and low number of large tumors. Up to 80% were referred following observer suspicion.

Acromegaly↗
PubMed1999

Gynaecomastia as a presenting feature of thyrotoxicosis.

The association between gynaecomastia and thyrotoxicosis is well recognised. However, the reported frequency of the association is variable, partly depending upon the defining criteria used. Here we report two patients with thyrotoxicosis in whom gynaecomastia was the presenting feature. Both patients had other contributing factors, which are assumed to have predisposed to gynaecomastia. In both patients, the gynaecomastia resolved with successful treatment of the thyrotoxicosis. When gynaecomastia is a presenting, or prominent feature of thyrotoxicosis, the possibility of additional underlying pathology should be considered.

Adult↗
PubMed1999

Plasma insulin, growth hormone, cortisol, and central obesity among young Chinese type 2 diabetic patients.

OBJECTIVE: To examine the relationships between central obesity, insulin resistance index, plasma insulin, growth hormone (GH), and cortisol concentrations in 90 young Chinese type 2 diabetic patients (aged 33+/-5 years) and 104 age- and sex-matched control subjects (aged 32+/-9 years). RESEARCH DESIGN AND METHODS: Young Chinese diabetic patients (aged <40 years) were recruited from the Prince of Wales Hospital. Blood pressure, height, weight, and waist and hip circumferences were determined. Venous blood was sampled for measurements of fasting plasma glucose, HbA1c, lipids, creatinine, insulin, GH, and cortisol. A 24-h urine was assayed for urinary albumin excretion (UAE). General and central obesity was represented by BMI and waist circumference, respectively. Insulin resistance index was estimated as a product of fasting plasma insulin and glucose concentrations. RESULTS: Compared with control subjects, diabetic patients were more obese, hyperglycemic, and had worse lipid profile, higher blood pressures, UAE, insulin resistance index, plasma insulin, and cortisol concentrations (all P < 0.001) but lower GH concentrations (P < 0.05). When analyzed as a whole group (n = 194), increasing quartiles of waist circumference were associated with increasing trends of insulin resistance index, plasma insulin, and cortisol concentrations (all P < 0.01) but a decreasing trend of plasma GH concentration (P < 0.05). Using stepwise multiple regression analysis, waist circumference was only associated with sex variable (being higher in men) in the control subjects. In the diabetic group, 51% of waist circumference was independently related to male sex and increased plasma insulin and cortisol concentrations as well as reduced plasma GH levels. CONCLUSIONS: In young Chinese type 2 diabetic patients, hyperinsulinemia, hypercortisolemia, and reduced plasma GH levels were closely associated with central obesity. Based on these findings, we postulate that maladaptive hormonal responses to rapid changes in lifestyle may have led to obesity and type 2 diabetes in these young patients. Alternatively, lifestyle-related obesity may have given rise to these hormonal changes. More studies are required to delineate the nature of these relationships.

Adolescent↗
PubMed1998

Human dynamin-like protein interacts with the glycogen synthase kinase 3beta.

Members of the dynamin superfamily are implicated in vesicle trafficking. Using human glycogen synthase kinase 3 beta (Gsk-3 beta) as bait in the yeast two-hybrid system, we identified a novel human dynamin-like protein IV (HdynIV). When the full-length cDNA of HdynIV was sequenced, it showed that HdynIV's carboxyl terminal lacks a proline-rich domain that can bind to Gsk-3 beta. By Northern blot analysis and isoform-specific PCR, we found that HdynIV is expressed ubiquitously in all human tissues examined. Two transcripts of 2.4 and 4.4 kb are shown to be more abundant in heart, brain, and skeletal muscle. Interestingly, the 2.4-kb transcript is expressed more distinctly in the fetal liver than in the adult liver, suggesting that this protein might play a role during development. In the present report, we have demonstrated that HdynIV interacts with the Gsk-3 beta through its carboxyl-terminal region, implying than HdynIV may also be involved in cell signaling.

Adult↗
PubMed1998

It's a small world.

Explore the source record for details and available documents.

Games, Experimental↗
PubMed1998

Glycated haemoglobin and cardiovascular risk factors in Chinese subjects with normal glucose tolerance.

Increased plasma glucose concentration is a predictive factor for mortality in both diabetic and non-diabetic subjects. Although glycated haemoglobin (HbA1c) is a useful index of mean blood glucose concentrations over the preceding 1 to 3 months, there are few data regarding its relationship to cardiovascular risk. We have examined the relationship between HbA1c and cardiovascular risk factors in 1280 subjects with normal glucose tolerance. Based on HbA1c tertiles (tertile 1: n = 427, 262 men and 165 women, HbA1c level: 2.9-4.7% in men and 3.2-4.2% in women; tertile 2: n = 426, 261 men and 165 women, HbA1c level: 4.7-5.1% in men and 4.2-4.6% in women; tertile 3: n = 427, 262 men and 165 women, HbA1c level: 5.1-6.7% in men and 4.6-6.9% in women), increasing HbA1c was associated with increasing age, blood pressure, waist-hip ratio, fasting and 2-h plasma glucose, 2-h insulin, cholesterol, low-density lipoprotein cholesterol, apolipoprotein B and urate concentrations. When age and sex were included as covariates, increasing HbA1c remained associated with increasing fasting and 2-h plasma glucose, 2-h insulin, total cholesterol, and low-density lipoprotein cholesterol concentrations. These findings emphasize the importance of hyperglycaemia, as reflected by HbA1c, as a continuum in the evaluation of cardiovascular risk. Furthermore, these findings support the hypothesis that cardiovascular disease risk commences with rising glucose concentrations before 'conventionally-defined' glucose intolerance occurs.

Adult↗
PubMed1998

Short-term efficacy and tolerability of combination therapy with lovastatin and acipimox in Chinese patients with type 2 diabetes mellitus and mixed dyslipidemia.

In type 2 diabetes, it is not uncommon to find an elevated serum triglyceride and/or reduced high-density lipoprotein (HDL) cholesterol levels; elevated total cholesterol levels often occur as well. To evaluate the short-term efficacy and tolerability of combination therapy with lovastatin and acipimox in Chinese patients with type 2 diabetes who have mixed dyslipidemia, an open-label 6-month trial was conducted. All patients had type 2 diabetes (n = 33) with total cholesterol > or = 6.2 mmol/L and fasting triglyceride > or = 2.8 mmol/L, which had been confirmed twice and persisted for at least 12 weeks after introduction of diet control. After a 4-week run-in period, they were given lovastatin 40 mg daily at night for 12 weeks. Acipimox 250 mg three times a day was then added for a further 12 weeks. After 12 weeks of treatment with lovastatin alone, improvement was observed in total cholesterol (21% reduction), triglyceride (32% reduction), low-density lipoprotein (LDL) cholesterol (5.5% reduction), HDL cholesterol (11.6% elevation), apolipoprotein A-I (4.6% elevation), and apolipoprotein B (20.5% reduction). The addition of acipimox to lovastatin for an additional 12 weeks further reduced serum total cholesterol, triglyceride, LDL cholesterol, and apolipoprotein B, but this additional decrease was not statistically significant. However, HDL cholesterol and apolipoprotein A-I levels were significantly increased by the addition of acipimox (a 14.2% and 9.0% elevation, respectively). Serum creatine phosphokinase increased slightly after 12 weeks of lovastatin but decreased to a concentration similar to baseline after 12 weeks of combination treatment. No patients reported muscle pain or weakness or other side effects. Combination treatment with lovastatin and acipimox appears to be a safe and effective therapy in patients with type 2 diabetes and mixed dyslipidemia, and has particular benefit in elevating serum HDL cholesterol and apolipoprotein A-I levels.

Adult↗
PubMed1998

Childhood goitre and urinary iodine excretion in Hong Kong.

UNLABELLED: Goitre is common among growing children and adolescents. To define the aetiology of goitre in adolescents of Hong Kong and to examine their current level of iodine intake, this cross-sectional survey of goitre in high school students was performed and urine samples were collected for the analysis of iodine excretion. Screening examinations were carried out in 2439 secondary school students aged 12-18 years from ten randomly selected high schools in Hong Kong. Blood samples were obtained from all goitrous subjects for the determination of serum TSH, free T4 and thyroid antibodies. We obtained 476 random urine samples and 80 24-h urinary collections for the analysis of iodine excretion. Of these, 85 subjects (3.5%) had goitre, 70 had simple goitre. Chronic lymphocytic thyroiditis was found in ten subjects. Two had Graves' disease and three had nodular goitre. The median urinary iodine concentration for the random urine samples was 190 microg/l (1.50 micromol/l) or 158 microg/g creatinine. The median 24-h urinary excretion of iodine was 189 microg (1.49 micromol) per day. CONCLUSION: This cross-sectional study demonstrates the spectrum of thyroid disease in Chinese adolescents in Hong Kong. Their urinary iodine excretion was adequate and much higher than those of children from many European countries and coastal cities of China.

Adolescent↗
PubMed1998

Synchronization and oscillatory dynamics in heterogeneous, mutually inhibited neurons.

We study some mechanisms responsible for synchronous oscillations and loss of synchrony at physiologically relevant frequencies (10-200 Hz) in a network of heterogeneous inhibitory neurons. We focus on the factors that determine the level of synchrony and frequency of the network response, as well as the effects of mild heterogeneity on network dynamics. With mild heterogeneity, synchrony is never perfect and is relatively fragile. In addition, the effects of inhibition are more complex in mildly heterogeneous networks than in homogeneous ones. In the former, synchrony is broken in two distinct ways, depending on the ratio of the synaptic decay time to the period of repetitive action potentials (tau s/T), where T can be determined either from the network or from a single, self-inhibiting neuron. With tau s/T > 2, corresponding to large applied current, small synaptic strength or large synaptic decay time, the effects of inhibition are largely tonic and heterogeneous neurons spike relatively independently. With tau s/T < 1, synchrony breaks when faster cells begin to suppress their less excitable neighbors; cells that fire remain nearly synchronous. We show numerically that the behavior of mildly heterogeneous networks can be related to the behavior of single, self-inhibiting cells, which can be studied analytically.

Computer Simulation↗
PubMed1998

Frequency control in synchronized networks of inhibitory neurons.

We analyze the control of frequency for a synchronized inhibitory neuronal network. The analysis is done for a reduced membrane model with a biophysically based synaptic influence. We argue that such a reduced model can quantitatively capture the frequency behavior of a larger class of neuronal models. We show that in different parameter regimes, the network frequency depends in different ways on the intrinsic and synaptic time constants. Only in one portion of the parameter space, called phasic, is the network period proportional to the synaptic decay time. These results are discussed in connection with previous work of the authors, which showed that for mildly heterogeneous networks, the synchrony breaks down, but coherence is preserved much more for systems in the phasic regime than in the other regimes. These results imply that for mildly heterogeneous networks, the existence of a coherent rhythm implies a linear dependence of the network period on synaptic decay time and a much weaker dependence on the drive to the cells. We give experimental evidence for this conclusion.

Action Potentials↗