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Biomedical subjects

C W Lam

Publications and source records attributed to C W Lam.

At least 145 records · Page 8Linked to original sources
PubMed1994

High-performance thin-layer chromatography of free porphyrins for diagnosis of porphyria.

In this simple high-performance thin-layer chromatographic technique for evaluating porphyrin excretion, porphyrins rapidly extracted from urine or feces are separated on reversed-phase octadecylsilyl (C18)-bonded silica thin-layer chromatography plates. We observed > 12 distinct bands of different porphyrins by viewing the plates under long-wave ultraviolet light. Positive screening tests can readily be characterized by the relative fluorescence of various free porphyrins. The two patients presented in this paper are possibly the first two cases of porphyria cutanea tarda reported in Hong Kong Chinese.

Adult↗
PubMed1993

Toxicokinetics of inhaled bromotrifluoromethane (Halon 1301) in human subjects.

Bromotrifluoromethane (CBrF3), commonly known as Halon 1301, is used as a fire extinguishant in the Space Shuttle. Several scenarios, such as a fire or a faulty alarm, could lead to its discharge resulting in a Halon 1301 concentration of up to 1% in the spacecraft cabin atmosphere. To examine the effects of Halon 1301 on mental performance and physiologic function, the National Aeronautics and Space Administration sponsored a human inhalation study. Four pairs of adult male subjects were each exposed in a double-blind fashion for 24 hr to 1% (10,000 ppm or 60,875 mg/m3) Halon 1301 and to air in two separate exposures approximately 1 week apart. Mental performance and physiologic function were assessed and the results are reported in a companion paper (D. S. Calkins, J. J. Degioanni, M. N. Tan, J. R. Davis, and D. L. Pierson. Fundam. Appl. Toxicol. 20, in press). Blood and breath samples from the exposed subjects were also collected to provide dosimetric and toxicokinetic information, which is presented here. Blood Halon 1301 levels increased rapidly and approached a steady state within 2 hr of beginning the exposure; the steady-state concentration was approximately 3-4.5 micrograms/ml. Breath samples collected during exposures closely reflected chamber concentrations. Analysis of postexposure blood samples revealed that Halon 1301 was eliminated biphasically with an average t1/2 alpha and t1/2 beta of 4.5 min (range 2.5-8.1 min) and 200 min (range 131-347 min), respectively. Halon 1301 concentrations in fat and soft tissues were also estimated. Subsequently, the end-tidal breath/blood/tissue/fat partition coefficients were calculated to be 17/1/0.5/33.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1993

Analysis of charge of kappa and lambda chain-containing serum immunoglobulin A by immunoblotting and densitometry.

A novel method for studying the charge distribution of different subclasses of serum immunoglobulin A (defined by the light chains) is described. Affinity-chromatography purified immunoglobulins were focused in polyacrylamide gel and were then transferred electrophoretically onto nitrocellulose membranes. The transferred immunoglobulins were detected by rabbit antiserum to human kappa (kappa) or lambda (lambda) chain, swine antirabbit IgG, rabbit anti-peroxidase antibodies and peroxidase, together with a substrate solution comprising H2O2 and diaminobenzidine. Finally, the developed membranes were made transparent with Triton-x 114, scanned at 485 nm with a densitometer to obtain quantitation of charge distribution.

Densitometry↗
PubMed1993

Postprandial changes in apolipoprotein(a) concentration of triglyceride-rich lipoproteins can be reproduced by in vitro incubation: implications for underlying mechanism.

We investigated the reciprocal changes in apolipoprotein(a) concentration in the lipoprotein of d > 1.006 and the triglyceride-rich lipoprotein (TRL) fractions of plasma which occur in vivo following fat ingestion. Twenty fasting subjects were studied before and 4 h after a fat-rich meal. In 75% of cases, in vitro incubation of the postprandial (4-h) TRL with autologous fasting (0-h) lipoproteins of d > 1.006 resulted in further substantial (> 5% total) reciprocal changes in apo(a) concentration of the 2 fractions. The increase in re-isolated postprandial TRL apo(a) was 25.1% +/- 5.1% of the total apo(a), compared to the insignificant increase (0.1% +/- 0.1%) in re-isolated fasting TRL. Most of the further increase in 4-h TRL apo(a) (94% +/- 4%) could be achieved by incubation with the corresponding 4-h chylomicron fraction (CM) alone. The re-isolated 4-h TRL apo(a) concentration correlated positively with 4-h plasma TG concentration (r = 0.65, P < 0.01) and other indices of postprandial lipaemia. In vitro incubation of pooled serum lipoproteins of d > 1.006 with serial dilutions of nascent CM obtained from chylous ascitic fluid revealed that the reciprocal changes in apo(a) concentration exhibit a curvilinear relationship with the concentration of CM triglyceride which plateaued round 7 mmol/l in this instance. We conclude that the reciprocal changes in apo(a) concentration between TRL and lipoproteins of d > 1.006 which occur in the postprandial phase are quantitatively significant and largely represent a redistribution process rather than de novo synthesis because they can be reproduced by in vitro incubation.

Adult↗
PubMed1993

Lipids, lipoproteins and other coronary risk factors in Chinese male survivors of myocardial infarction.

OBJECTIVE: To assess the importance of an abnormal lipid profile as a risk factor in relation to non-biochemical risk factors, and to define the risk levels for lipid, lipoprotein and apolipoprotein in a Chinese population. PATIENTS AND METHODS: Serum lipids, lipoproteins, apolipoproteins and other cardiovascular risk factors were studied in 89 Chinese men 3 months after acute myocardial infarction and 56 controls. RESULTS: Cases had higher mean total cholesterol (TC), LDL- and VLDL-cholesterol, triglycerides and apolipoprotein B (Apo B), and lower mean HDL-cholesterol and apolipoprotein AI (Apo AI). Mean BMI was also higher, as was the prevalence of smokers and subjects with a history of hypertension. In univariate analysis, the odds ratios for TG > or = 1.6 mmol/l, LDL-cholesterol > or = 4.1 mmol/l, VLDL-cholesterol > or = 0.73 mmol/l, Apo B > or = 104 mg/dl were of the same order of magnitude as being a current smoker, having a BMI > or = 24.3 kg/m2, and a history of hypertension. High HDL-cholesterol (> or = 1.39 mmol/l) and Apo AI (> or = 139 mg/dl) were protective factors. The odds ratios for successively higher quartile values of cholesterol were not statistically significant. Multiple logistic regression identified smoking habit, history of hypertension, obesity, high Apo B and low Apo AI concentrations as independent risk factors for myocardial infarction. CONCLUSIONS: In a Chinese population, low serum Apo AI and high Apo B are risk factors for myocardial infarction of a comparable magnitude to smoking, hypertension and obesity.

Apolipoprotein A-I↗
PubMed1993

Effect of lovastatin on serum lipid profile in the treatment of dyslipoproteinaemia in uraemic patients on continuous ambulatory peritoneal dialysis.

BACKGROUND: Dyslipoproteinaemia is an important risk factor for cardiovascular disease in uraemic patients on continuous ambulatory peritoneal dialysis (CAPD). Lovastatin is an HMG Coenzyme A reductase inhibitor which is useful in treating non-uraemic patients with hypercholesterolaemia. AIMS: We conducted a single blind cross-over study versus placebo in 10 CAPD patients to examine the effect of lovastatin (20-40 mg) on the serum lipid profile and its safety in uraemic patients. METHODS: Treatment phases were of eight weeks' duration. Each four weeks' measurements were made of serum total cholesterol (TC), triglyceride (TG), HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C), VLDL-cholesterol (VLDL-C), Apolipoprotein A1 & B (Apo A1 & Apo B) and Lipoprotein (a). After eight weeks, lovastatin significantly reduced TC by 29% from 6.7 +/- 0.3 (mean +/- S.E.M.) to 4.8 +/- 0.1 mmol/L, LDL-C by 41% from 4.6 +/- 0.3 to 2.7 +/- 0.1 mmol/L and Apo B by 32% from 116 +/- 7 to 78 +/- 3 mg/dl (p < 0.01). HDL-C increased by 8% from 1.2 +/- 0.1 to 1.3 +/- 0.2 mmol/L after eight weeks' therapy (p < 0.05). TG decreased by 18% from 1.9 +/- 0.4 to 1.6 +/- 0.3 mmol/L (p < 0.05). There was no significant difference in changes of other lipid profiles between placebo and drug. No adverse effects of the drug were noted during treatment and the liver function and muscle enzymes were not significantly altered by either drug therapy or placebo. RESULTS: Lovastatin appears to be a safe and useful drug in effectively treating dyslipoproteinaemia in CAPD patients.

Female↗
PubMed1993

Serum lipid profile and its association with some cardiovascular risk factors in an urban Chinese population.

The lipid profile of a Chinese population, which has a lower prevalence of coronary heart disease compared with Caucasians, is studied to determine whether lipid-modifying disease prevention programs are necessary. The study population consisted of 910 men (mean age 36.7 +/- 9.2 yrs) and 603 women (mean age 38.6 +/- 9.1 yrs), who were employees of a public utility company and non-medical staff of a district hospital. Indices of obesity, fasting cholesterol (TC), and its various subfraction, triglycerides (TG), apolipoprotein A-I (Apo A-I), and apolipoprotein B (Apo B) concentrations were measured. Glucose tolerance was also estimated by measuring fasting and 2 h glucose after a 75 g oral glucose load. The lipid profile was similar to that of the North American population, with an overall prevalence of low density lipoprotein cholesterol (LDL-C) > or = 4.1 mmol/L of 21% and 11% in men and women respectively. Similar variations with age, sex, smoking and glucose tolerance compared with Caucasian populations were observed. The high prevalence of subjects with "undesirable" lipid values in this Chinese population, which at present has a coronary artery disease prevalence of one-eighth to one-quarter compared with that in Caucasians, suggests that the incidence of the disease may well rise in the future to pose a similar problem to that in Caucasian populations. Cut off values of lipids conferring increased cardiovascular risks need to be determined in this population, so that public health strategies may be formulated.

Adult↗
PubMed1993

Lovastatin treatment of dyslipoproteinemia in patients on continuous ambulatory peritoneal dialysis.

We conducted a single, blinded cross-over placebo versus lovastatin study on 10 continuous ambulatory peritoneal dialysis (CAPD) patients with dyslipoproteinemia who failed to respond to diet control. They were given 8 weeks of lovastatin (20-40 mg) and placebo, respectively. After 8 weeks of lovastatin treatment, total cholesterol was significantly reduced by 28.6% (6.68 +/- 0.26 mmol/L, mean +/- SEM, to 4.77 +/- 0.12, p < 0.01); low-density lipoprotein cholesterol by 40.5% (4.57 +/- 0.27 mmol/L to 2.72 +/- 0.09, p < 0.01); apolipoprotein B by 32.4% (115.9 +/- 6.99 mg/dL to 78.3 +/- 2.9 mg/dL, p < 0.01); and triglyceride by 17.8% (1.92 +/- 0.38 mmol/L to 1.58 +/- 0.32, p < 0.05). Simultaneously high-density lipoprotein cholesterol increased by 7.6% from 1.24 +/- 0.13 mmol/L to 1.34 +/- 0.16, p < 0.05. There were no significant changes in other lipid profiles between placebo and drug treatment. No significant adverse effects were observed with lovastatin treatment. Lovastatin appears to be effective in treating dyslipoproteinemia in CAPD patients.

Adult↗
PubMed1991

Association of serum lipoprotein(a) concentration with other cardiovascular risk factors in a Chinese population.

The association between serum Lp(a) concentration, a risk factor for atherothrombotic disease, and other cardiovascular risk factors such as smoking, alcohol intake, hypertension, obesity, and indices of glycemic control is examined in a cohort of 313 elderly Chinese subjects (M = 160, mean age +/- SD = 68 +/- 11 year; F = 153, mean age +/- SD = 73 +/- 11). Although associations existed for the above risk factors and other serum lipid levels, there was no association with serum Lp(a) concentration in the overall population. Men with Lp(a) greater than or equal to 30 mg/dl had a higher mean age and blood pressure. A higher percentage of subjects with Lp(a) greater than or equal to 30 mg/dl had a family history of stroke, although the total number of those with a family history was too small to reach statistical significance. The lack of association with known modifiable cardiovascular risk factors is compatible with the conclusion that Lp(a) concentration is primarily under genetic control and therefore unlikely to be a modifiable risk factor.

Aged↗
PubMed1991

Light-chain ratio of serum IgA1 in IgA nephropathy.

Patients with primary IgA nephropathy have deposits of IgA1 in their kidneys and increased IgA1 in circulation. We had previously shown that IgA nephritic patients displayed a unique immunological response characterized by a predominance of IgA with lambda chain in glomerular deposits and in circulation. We have now studied the kappa/lambda (kappa/lambda) ratio of serum IgA1 in 21 IgA nephritic patients at quiescence, with 11 patients investigated during exacerbation as well. A novel enzyme-linked immunosorbent assay was used with monoclonal mouse anti-human IgA1 as the solid-phase capture antibody and peroxidase-labeled anti-human kappa and lambda antibodies as tracers. The ratio of serum IgA1 to total IgA (mean +/- SD) was significantly higher in patients (90.1 +/- 8.2% at quiescence, P less than 0.01; 88.7 +/- 8.1% during exacerbation, P less than 0.02) than in 20 healthy age- and sex-matched controls (80.0 +/- 9.8%). Furthermore, serum IgA1 kappa/lambda ratios were significantly lower in patients (1.02 +/- 0.27 at quiescence, P less than 0.01; 0.93 +/- 0.16 during exacerbation, P less than 0.01) than in controls (1.31 +/- 0.30). These findings indicate a predominance of lambda light-chain IgA1 in the serum of IgA nephritic patients. However, no difference in IgA1 kappa/lambda ratio was observed in these patients at quiescence and during exacerbation.

Adolescent↗
PubMed1991

Effect of cyclosporine A on circulating immune complexes in IgA nephropathy.

This work was undertaken to examine the effect of cyclosporine A (CyA) on the serum concentration of circulating immune complexes in 22 patients with IgA nephropathy during an infection-free period. They were randomly divided into 2 groups: 11 patients received oral cyclosporine A (5 mg/kg/day) for 12 weeks and 11 patients received placebo (0.05 ml/kg/day). A significant reduction of proteinuria was observed in patients on CyA therapy but not in those receiving placebo. IgG-circulating immune complexes (CIC) were determined by solid phase Clq enzyme immunoassay (Clq EIA) and radial immunodiffusion (RID) and IgA-CIC were determined by solid phase anti-C3 enzyme immunoassay (anti-C3 EIA) and radial immunodiffusion. There was no change in IgA-CIC measured by RID and anti-C3 EIA after 12 weeks of CyA therapy. Similarly, changes in IgG-CIC were not demonstrated with CyA therapy. No apparent decrease in IgG-CIC or IgA-CIC was observed with placebo treatment. Our study suggests that immunomodulation by CyA therapy does not affect the IgA-CIC and IgG-CIC levels in patients with IgA nephropathy.

Adult↗
PubMed1991

Light chain ratios of serum immunoglobulins in disease.

We have determined the individual kappa (kappa)/lambda (lambda) ratios of serum IgG, IgA, and IgM in normal subjects and patients with rheumatoid arthritis, systemic lupus erythematosus, hepatic cirrhosis and IgA nephropathy--40 in each group. Serum samples were first screened by agarose electrophoresis to exclude paraproteinaemia. Concentrations of IgG, IgA, and IgM were determined by enzyme-linked immunosorbent assay (ELISA). The kappa and lambda chain concentrations of each immunoglobulin class were assayed by an ELISA method first developed by us for the determination of kappa/lambda ratios. Our results showed that kappa/lambda ratios of serum IgA and IgM were significantly different from that of IgG in normal subjects and the 4 groups of patients studied (p less than 0.01). The kappa/lambda ratios of individual immunoglobulins in patients with rheumatoid arthritis, systemic lupus erythematosus and liver cirrhosis were similar to those of normal subjects. However, patients with IgA nephropathy displayed a distinctly lower IgA kappa/lambda ratio, suggesting a unique antibody response in the immunopathogenesis of this disease.

Antibodies↗
PubMed1991

Plasma lipoprotein distribution of apolipoprotein(a) in the fed and fasted states.

In order to quantitate the contribution of triglyceride-rich lipoprotein (TRL) apolipoprotein(a) to total plasma apo(a) concentration in the fed and fasted states, we have studied a group of 20 male subjects (age 49 +/- 3 years) with fasting apo(a) concentrations varying from 39 to 1385 U/l. After a 12-h overnight fast, each subject was given a fat-rich meal (1 g fat/kg body weight) and venous blood samples were obtained at hourly intervals for 10 h. TRL were isolated from bihourly plasma samples by ultracentrifugation (d less than 1.006 g/ml) and apo(a) was measured by radioimmunoassay. Total plasma apo(a) concentration did not change after the meal. However, TRL apo(a) increased significantly (0 h: 3 +/- 1, 4 h: 30 +/- 7 U/l; p less than 0.001) and 'd greater than 1.006' apo(a) decreased (0 h: 267 +/- 56, 4 h: 231 +/- 50 U/l; P less than 0.05). Similar postprandial changes were observed in apoB concentration (TRL apo B at 0 h: 10.3 +/- 1.5, 4 h: 13.6 +/- 1.7 g/l, P less than 0.001, 'd greater than 1.006' apoB at 0 h: 118 +/- 7, 4 h: 110 +/- 7 g/l, P less than 0.001). In the fasted state 2.0 +/- 1.0% and in the fed state (4 h postprandially) 16.0 +/- 4.6% of total plasma apo(a) was found in the TRL fraction. Eleven subjects had less than 10% of total apo(a) in TRL, 5 had 25% or more apo(a) in TRL in the fed state. Postprandial increase in TRL apo(a) was significantly correlated (r = 0.75, P less than 0.001) with increase in plasma triglycerides. TRL apo(a) concentration in the fed state was not correlated with total fasting cholesterol, triglyceride, apo(a) or HDL cholesterol concentration. We conclude that in some individuals, TRL apo(a) makes a significant contribution to total plasma apo(a) concentration in the fed state.

Adult↗
PubMed1991

Relationship between newborn and maternal iron status and haematological indices.

The haemoglobin, mean corpuscular volume, mean corpuscular haemoglobin, haematocrit, serum iron and total iron binding capacity, and serum ferritin concentrations in umbilical cord blood samples taken from 96 appropriate-for-gestational age infants delivered at term were measured and compared to the respective maternal values measured at 36 weeks' gestation. All the values were higher in cord blood. Only maternal mean corpuscular volume and mean corpuscular haemoglobin were correlated with cord serum iron. Cord blood haematological indices were not correlated with either gestation at delivery or birth weight. However, newborn serum ferritin was positively correlated with gestation at delivery, while the maternal:newborn ferritin ratio was inversely correlated with gestation and birth weight. The results suggest that maternal haematological and iron indices are not predictive of the haemoglobin or iron status of the newborn, and that the fetus continues to take up iron from the mother until delivery.

Adult↗
PubMed1991

Hypertension, lipoprotein(a), and apolipoprotein A-I as risk factors for stroke in the Chinese.

We analyzed the serum concentrations of lipids and lipoproteins and the prevalence of other risk factors in a case-control study of 304 consecutive Chinese patients with acute stroke (classified as cerebral infarction, lacunar infarction, or intracerebral hemorrhage) and 304 age- and sex-matched controls. For all strokes we identified the following risk factors: a history of ischemic heart disease, diabetes mellitus, or hypertension; the presence of atrial fibrillation or left ventricular hypertrophy; a glycosylated hemoglobin A1 concentration of greater than 9.1%; a fasting plasma glucose concentration 3 months after stroke of greater than 6.0 mmol/l; a serum triglyceride concentration 3 months after stroke of greater than 2.1 mmol/l; and a serum lipoprotein(a) concentration of greater than 29.2 mg/dl. We found the following protective factors: a serum high density lipoprotein-cholesterol concentration of greater than 1.59 mmol/l and a serum apolipoprotein A-I concentration of greater than or equal to 106 mg/dl. The patterns of risk factors differed among the three stroke subtypes. When significant risk factors were entered into a multiple logistic regression model, we found a history of hypertension, a high serum lipoprotein(a) concentration, and a low apolipoprotein A-I concentration to be independent risk factors for all strokes. The attributable risk for hypertension was estimated to be 24% in patients aged greater than or equal to 60 years. In this population, in which cerebrovascular diseases are the third commonest cause of mortality, identification of risk factors will allow further studies in risk factor modification for the prevention of stroke.

Apolipoprotein A-I↗
PubMed1991

Poems syndrome.

A 40 year old Chinese woman presented with anasarca and later developed features of POEMS syndrome. These are peripheral neuropathy (P), organomegaly (O), endocrine dysfunction (E), monoclonal gammopathy (M), and skin changes (S) which are usually associated with plasma cell dyscrasia. In our patient, monoclonal gammopathy was not detected on immunofixation electrophoresis and was revealed only after analysis of kappa/lambda light chain ratio of the raised serum IgA immunoglobulin. Needle liver biopsy of her grossly enlarged liver showed marked accumulation of glycogen and presence of giant mitochondria in the hepatocytes, a feature not previously reported.

Adult↗