Biomedical subjects

C Y Hong

Publications and source records attributed to C Y Hong.

At least 109 records · Page 6Linked to original sources

PubMed1995

The inhibitory effect of tannins on lipid peroxidation of rat heart mitochondria.

We induced lipid peroxidation in rat heart mitochondria with ferrous sulphate (FeSO4) and compared the inhibitory effect of various tannins on the peroxidation. Oxygen consumption and malondialdehyde (MDA) formation were used to quantitate the amount of lipid peroxidation, and the free radical scavenger activity of tannins was measured with a diphenyl-p-picryl hydrazyl (DPPH) method. Of 25 tannins and related compounds tested, catechin benzylthioether and procyanidin B-2 benzylthioether were the most potent in inhibiting lipid peroxidation, with inhibitory effects stronger than that of trolox, a water soluble analogue of vitamin E. The concentrations (IC50) required for catechin benzylthioether and procyanidin B-2 benzylthioether to inhibit oxygen consumption to 50% of control values were 0.85 and 2.0 microM, respectively, while their IC50 values from the inhibition of MDA formation were 0.9 and 1.70 microM, respectively. The IC50 values for catechin, and procyanidin B-2 to inhibit oxygen consumption were 34.0 and 11.0 microM. Both compounds were less potent than their benzylthioether derivatives. However, the ability of catechin and procyanidin B-2 to scavenge DPPH were similar to that of their benzylthioether derivatives. We conclude that conjugation with a benzylthioether group enhances the inhibitor effect of tannins on lipid peroxidation, and that the mechanism is not an increase in its scavenger activity.

Animals↗

PubMed1995

Decreased vascular contractile and inositol phosphate responses in portal hypertensive rats.

The purpose of this study was to investigate the vascular contractile and inositol phosphate responses in portal hypertensive rats. Portal hypertension was induced by partial portal vein ligation (PVL) in Sprague-Dawley rats. Sham-operated rats served as controls. Pressures, vasoconstrictor responses, and inositol phosphate responses were determined at 14 days after surgery. The portal venous pressure was significantly higher, while systemic arterial pressure and heart rate were lower, in PVL rats. Dose-dependent contractile responses were observed for both norepinephrine (1 x 10(-8) - 3 x 10(-6) M) and vasopressin (3 x 10(-10) - 3 x 10(-8) M) in the tail artery of both groups. The contractile response to norepinephrine was significantly decreased in PVL rats compared with controls at all doses. The contractile response to vasopressin was significantly decreased in PVL rats at higher doses. After myo-[3H]inositol incorporation in tail artery, the levels of 3H-labelled phosphatidylinositols (cpm/mg) were similar between the two groups. Norepinephrine (10(-7) - 10(-5) M) and vasopressin (10(-10) - 10(-8) M) dose dependently stimulated the 3H-labelled inositol phosphate production in the tail artery of both PVL and sham-operated rats. However, the response was significantly lower in PVL rats. The results suggested that the attenuation of vascular contractile responses in portal hypertension was reflected in the phosphoinositide messenger system.

Animals↗

PubMed1995

Change in vascular cAMP and cGMP contents in portal hypertensive rats.

The purpose of this study was to investigate the possible changes of cyclic nucleotide contents in portal hypertensive rats. Portal hypertension was induced by partial portal vein ligation (PVL) in Sprague-Dawley rats. Sham-operated rats served as controls. Hemodynamic and cyclic nucleotide measurements were performed at 14 days after surgery. The portal venous pressure was significantly higher, while systemic arterial pressure and heart rate were lower in PVL rats than those in controls. Basal cAMP (PVL, 10.91 +/- 0.98, vs. sham, 8.08 +/- 0.81 pmol/mg protein) and cGMP (PVL, 0.91 +/- 0.12, vs. sham, 0.59 +/- 0.05 pmol/mg protein) contents in the tail artery were significantly higher in PVL rats. Isobutyryl methylxanthine (10(-5) M), a nonspecific phosphodiesterase inhibitor, exerted similarly stimulating effects on the tissue cGMP (PVL, 158 +/- 10, vs. sham, 178 +/- 20%) and cGMP (295 +/- 28 vs. 316 +/- 71%) levels in both PVL and control rats; so did forskolin (10(-6) M) on the cAMP (184 +/- 20 vs. 197 +/- 66%) content in both groups. Our results showed that the arterial cAMP and cGMP contents were higher in PVL rats, which may contribute to the reduction of peripheral resistance in portal hypertension.

1-Methyl-3-isobutylxanthine↗

PubMed1995

Trilinolein reduces infarct size and suppresses ventricular arrhythmias in rats subjected to coronary ligation.

Trilinolein, a triacylglycerol with linoleic acid as the only fatty acid residue in all esterified positions of glycerol, was previously found to improve erythrocyte deformability in vitro. In this study, the in vivo antiarrhythmic and anti-ischemic effects of trilinolein in coronary ligated rats were investigated. Male Sprague-Dawley rats were anaesthetized with urethane. Trilinolein, at dosages ranging from 10(-11) to 10(-7) g/kg, was administered intravenously 15 min before ligation of coronary artery. Also, the effect of trilinolein on arrhythmia was studied by ligating the coronary artery for 30 min, then reperfusing myocardium for 10 min. During the 30-min ischemia, trilinolein reduced not only the number of ectopic beats but also the incidence rate and duration of ventricular tachycardia. At 10(-7) g/kg, trilinolein completely suppressed all ventricular arrhythmias. Ventricular arrhythmias during 10 min reperfusion were also reduced by trilinolein at similar dosages. Furthermore, the effect of trilinolein on infarct size was evaluated by occluding the coronary artery for 4 h before the infarct zone was stained and weighed. In rats subjected to 4 h coronary ligation, pretreatment with 10(-7) g/kg trilinolein at 15 min prior to the coronary ligation significantly reduced infarct size. Trilinolein may protect myocardium against ischemic injury and suppress arrhythmia during ischemia and reperfusion.

Animals↗

PubMed1994

Trilinolein inhibits epinephrine-induced human platelet aggregation.

At concentrations ranging from 10(-9) to 10(-6) M, trilinolein inhibited epinephrine-induced platelet aggregation. This inhibition was accompanied by reduced ATP release and thromboxane B2 formation. However, concentration-response curves for the interaction between trilinolein and epinephrine showed that trilinolein was unlikely a competitive antagonist of epinephrine. Platelet aggregation induced by collagen, thrombin, ADP or arachidonic acid was not inhibited. This study supported the theory that this type of triglyceride may have therapeutic potential but the definite mechanism for its effect remains to be answered.

Epinephrine↗

PubMed1994

Magnolol and honokiol isolated from Magnolia officinalis protect rat heart mitochondria against lipid peroxidation.

In isolated rat heart mitochondria lipid peroxidation was induced with ADP and ferrous sulfate (FeSO4). Oxygen consumption and malondialdehyde (MDA) production were measured to quantitate lipid peroxidation. The antioxidant effects of magnolol and honokiol purified from Magnolia officinalis were 1000 times higher than that of alpha-tocopherol. The IC50 values of magnolol and honokiol for inhibition of oxygen consumption were 8.0 x 10(-8) M and 1.0 x 10(-7) M, respectively, while that of alpha-tocopherol was 1.0 x 10(-4) M. Magnolol at 0.5 microM inhibited 71.4 +/- 9.4% of oxygen consumption and 59.3 +/- 4.6% MDA production. At the same concentration, honokiol inhibited 78.1 +/- 4.7% of oxygen consumption and 86.9 +/- 4.0% of MDA production. Of conjugated diene formation 48.4 +/- 4.6% and 53.1 +/- 3.4% were inhibited by 0.5 microM magnolol and honokiol, respectively. Also both magnolol and honokiol exhibited free radical scavenging activities as shown by the diphenyl-p-picrylhydrazyl assay, but they were less potent than alpha-tocopherol.

Animals↗

PubMed1994

Risks of asthma associated with occupations in a community-based case-control study.

The aim of this study was to identify occupational risk groups which might usefully be targeted for occupational asthma surveillance and control, using a community-based case-control approach. Data on previous and current occupations held by subjects were analyzed for 787 adult patients with bronchial asthma and 1591 nonasthmatic patient controls, aged 20-54 years, belonging to the three major races (Chinese, Malays, and Indians) in five outpatient primary care polyclinics. Odds ratios (OR) and 95% confidence intervals (95% CI) of association were adjusted for sex, age, race, smoking, and clinical atopy. No associated risks of asthma were found for clerical or sales workers in general. Significantly reduced risks of association with asthma were found for professional, technical, administrative, and managerial occupations (OR, 0.62; 95% CI, 0.47-0.82). The associated risks of asthma were generally elevated for service workers (OR, 1.35; 95% CI, 1.04-1.74) and manufacturing production and related workers (OR, 1.49; 95% CI, 1.23-1.81). Among them, increased risks were observed for cleaners, particularly municipal cleaners and sweepers (OR, 1.91; 95% CI, 1.22-2.99), textile workers (OR, 5.83; 95% CI, 1.93-17.57), garment markers (OR, 1.61; 95% CI, 1.01-2.58), electrical and electronic production workers (OR, 1.36; 95% CI, 1.06-1.75), printers (OR, 2.24; 95% CI, 1.17-4.31), and construction/renovation workers (OR, 2.24; 95% CI, 1.30-3.85). The odds ratio of association of asthma with exposures in service and production-related occupations overall, relative to the "nonexposed" reference group of nonmanual professional/technical, administrative/managerial, clerical, and sales occupations, was estimated to be 1.72 (95% CI, 1.36-2.19); the estimated population attributable risk was 0.33 (95% CI, 0.22-0.44).

Adult↗

PubMed1994

Trilinolein improves erythrocyte deformability during cardiopulmonary bypass.

The in vitro effect of trilinolein, a triglyceride with linoleic acid as the major fatty acid residue in the esterified positions of glycerol, on erythrocyte deformability was studied in blood samples collected from 12 patients before and after cardiopulmonary bypass (CPB). Erythrocyte deformability was measured with a filtration method and expressed as red cell filtration rate (RFR). RFR was reduced after CPB and the reduction was time dependent. Trilinolein at a concentration of 10(-7) M significantly reversed the CPB-induced reduction of RFR when it was mixed with blood samples collected 30, 60 and 90 min from the start of CPB. This study confirmed the effect of CPB on erythrocyte deformability and showed that this damage could be significantly improved by mixing blood with trilinolein.

Cardiopulmonary Bypass↗

PubMed1994

Astragalus membranaceus and Polygonum multiflorum protect rat heart mitochondria against lipid peroxidation.

We isolated rat heart mitochondria and induced lipid peroxidation with ADP and FeSO4. Oxygen consumption and MDA formation were measured for quantitating the amount of lipid peroxidation. Using these methods, we screened the water extracts of 14 Chinese medicinal herbs for their effect on lipid peroxidation. It was found that Astragalus membranaceus inhibited 42.1 +/- 3.4% of oxygen consumption and 39.8 +/- 3.2% of MDA production at concentration of 2 mg dried herb/ml mitochondrial suspension. At the same concentration, Polygonum multiflorum inhibited 52.1 +/- 7.3% of oxygen consumption and 50.9 +/- 5.3% of MDA production. Other herbs did not inhibit lipid peroxidation to 50% of control at concentration up to 6 mg dried herb/ml mitochondrial suspension. Purification and identification of the active component(s) in Astragalus membranaceus and Polygonum multiflorum as well as their clinical application await further studies.

Adenosine Diphosphate↗

PubMed1994

Effect of flavan-3-ol tannins purified from Camellia sinensis on lipid peroxidation of rat heart mitochondria.

We induced lipid peroxidation in rat heart mitochondria with FeSO4 and compared the inhibitory effect of various flavan-3-ol tannins on it. These tannins were purified from Chinese tea (Camellia sinensis). Oxygen consumption and malondialdehyde formation were used to quantitate the amount of lipid peroxidation. The free radical scavenger activity of tannins was then measured with a diphenyl-p-picrylhydrazyl method. These tannins significantly inhibited lipid peroxidation at micromolar concentration. Their potencies were higher than that of Trolox, a water soluble analogue of vitamin E. Since epicatechin-3-O-gallate, epigallocatechin-3-O-gallate and gallocatechin-3-O-gallate were more potent than other flavan-3-ol tannins in these assays, we considered that a galloyl group in 3-O-position increased the scavenger activity of flavan-3-ol tannins as well as their potency in inhibiting lipid peroxidation.

Animals↗

PubMed1994

Understanding asthma: patient survey.

Eight hundred and two adult patients attending five randomly selected polyclinics in Singapore were interviewed to assess their understanding of asthma. Knowledge of asthma mechanism and its medications was poor with a mean score of 1.4 (median: 1) out of a total score of 6. About a third knew that asthma is due to narrowing of airways and a quarter knew the action of bronchodilators. Only 4.4% (27) knew that steroids decrease airway swelling or inflammation. The best knowledge score was associated with subjects who had the highest education, who had a family history and who had been exposed to pamphlets and books. Incorrect use of prophylaxis was also evident with only one-third (37%) using steroid inhalers regularly as prescribed. Only half (54.5%) of those with no schooling used the correct inhaler technique. Doctors were a source of information for only 49.9% (400) of the patients and it was those with the highest education who were most likely to get information from the doctors. Pamphlets were a source of information for less than one-fifth (16.2%) of the subjects. Greater emphasis should be given to patient education by doctors to help patients understand asthma and its treatment. Important target groups are the older, lesser educated and the moderate or severe patients on steroid inhalers.

Adult↗

PubMed1994

Outpatient adult bronchial asthma in Singapore.

OBJECTIVES: To describe the clinical pattern and drug use in adult bronchial asthma seen in Government polyclinics (primary health care centres). DESIGN: A cross-sectional study using a structured questionnaire. SETTING: The five largest Government polyclinics in Singapore. SUBJECTS: Eight hundred and two subjects aged between 21-58 years drawn from the register of outpatient attendances. The response rate was 63%. RESULTS: The mean age of the study subjects was 37.4 years and the mean age of onset was 19.2 years. Thirty-three percent had onset of asthma under 10 years old. The most commonly reported trigger factors were cold drinks (67%), a change of temperature or humidity (65%), influenza or colds (65%), house dust (58%) and cigarette smoke (37%). In 27%, the work environment was a provoking factor. One-fifth had attacks every night or every day. About half of the patients had FEV1 under 80% of predicted. In the past year, 10% had 4 or more acute attacks requiring emergency attendance, 18% had one or more hospital admissions and 21% had sickness absence from asthma for one week or more. Of the 186 subjects who needed bronchodilators/inhalers 3 times or more a day, only 19.3% were on inhaled steroids. CONCLUSIONS: Considerable morbidity existed amongst outpatient asthmatics. Inhaled steroids appeared to be under-used.

Adult↗

PubMed1994

Lifestyle and behavioural risk factors associated with asthma morbidity in adults.

We studied the association between morbidity and personal lifestyle/behavioural factors that predispose to exposure to known environmental precipitants of asthma, in a group of asthmatics (n = 787) in primary-care clinics. Clinical severity of asthma was determined by questions regarding the frequency of daytime or nocturnal attacks, the number of visits to primary care or hospital emergency departments for treatment of acute attacks, and the number of hospitalizations, as well as the amount of sick leave in the past year. Questions concerning risk factors included ethnicity, clinical atopic status (current rhinitis/eczema), smoking, occupation, keeping of pets, rugs and carpets, use of brooms, burning of mosquito coils or incense, and outdoor air pollution, as well as the patient's knowledge of asthma care. The most significant independent predictors of asthma morbidity, identified from multivariate logistic regression analyses, were current keeping of either pets or rugs/carpets (OR 1.49; 95% CI 1.12-1.99), and current high-risk occupations (OR 0.59, 95% CI 0.40-0.89). A multiplicity of interacting factors and behavioural responses appear to influence the effects of allergens and other environmental precipitants on asthma morbidity in patients.

Adult↗

PubMed1993

Low prevalence of hepatitis C virus infection among dentists in Taiwan.

To evaluate whether hepatitis C virus (HCV) infection is an occupational hazard in the dental environment, serum samples collected in 1990-1991 from 461 dentists were tested for the antibody to HCV (anti-HCV) with first- and second-generation HCV enzyme-linked immunoassays (EIAs). Five of the 363 (1.38%) serum samples were reactive by the first-generation (C100-3) HCV EIA. Of the same 363 samples and the other 98 samples, 3 (0.65%) were reactive by the second-generation test. Of the 5 first-generation EIA reactive samples, only the 2 samples showing an absorbance of greater than 2.0 were also reactive to the second-generation EIA. The other 3 low-absorbance samples became negative and were regarded as false positives. Among the 358 samples negative by the first-generation EIA, 1 was reacted by the second-generation EIA. Those samples positive by the first- and/or second-generation HCV EIA were analyzed further by cDNA/polymerase chain reaction (PCR) to detect the presence of HCV RNA. Only 1 of the 5 first-generation EIA reactive samples was positive by PCR, but 2 of the 3 second-generation EIA reactive samples were PCR positive. These results are comparable to the anti-HCV prevalence of healthy blood donors (0.95% by C100-3 assay) and pregnant women (0.63% by recombinant immunoblot assay). We conclude that the prevalence of HCV infection among dentists in Taiwan is low, and there is no increased risk of HCV infection through the practice of dentistry, at least in our area.

Adult↗

PubMed1993

Increased aortic endothelial death and enhanced transendothelial macromolecular transport in streptozotocin-diabetic rats.

Hypertension, cigarette smoking and diabetes mellitus are well-known risk factors for atherosclerosis and coronary heart disease. Repeated endothelial cell injury and increased lipid entry have been suggested as initiating events in atherogenesis. Our previous studies have demonstrated that the frequency of endothelial cell death and associated endothelial permeability were significantly increased in the aorta of spontaneously hypertensive rats and chronic oral nicotine-treated rats. In the present investigation, we examined the hypothesis that diabetes also increases the frequency of arterial endothelial cell death and hence transendothelial macromolecular transport, which may have some implications in increasing lipid entry and thus accelerating atherogenesis. Diabetes was induced in 15 male Sprague-Dawley rats by intraperitoneal injection of 60 mg streptozotocin per kg body weight. The duration of diabetes was 6 weeks. A group of 15 age-matched rats, injected only with the buffer and maintained over the same time period, served as the controls. In en face preparations of the thoracic aorta, IgG-containing dead endothelial cells were identified by an indirect immunoperoxidase method, and endothelial leakage to Evans blue-albumin complexes was quantified by fluorescence microscopy. Diabetic rats, compared to control rats, had significantly higher values for the frequency of endothelial cell death (0.77 +/- 0.10% vs 0.38 +/- 0.04%; p < 0.005 by two-tailed, unpaired Student's t-test) and the number density of Evans blue-albumin leaky foci (4.33 +/- 0.48/mm2 vs 2.99 +/- 0.38/mm2; p < 0.05 by two-tailed, unpaired t-test) in the aorta.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Effect of an extract from Phyllanthus amarus on hepatitis B surface antigen gene expression in human hepatoma cells.

It has been suggested that Phyllanthus amarus may be helpful in the treatment of hepatitis B virus infection. We studied the effect of an aqueous extract of P. amarus on the cultured hepatoma cell line HepA2. This cell line had been transfected with tandemly arranged HBV DNA and continued to synthesize and secrete both HBsAg and HBeAg. Extract of P. amarus reversibly inhibited cellular proliferation and suppressed HBsAg production but not HBeAg production in HepA2 cells. We also found that P. amarus suppressed HBsAg gene expression at mRNA level in a time-dependent manner, and selectively abolished the HBsAg gene promoter driven CAT activity. Our results demonstrate that P. amarus contains some active components which can suppress the HBsAg gene expression in human hepatoma cells. Such suppression may contribute the antiviral activity of P. amarus in vivo.

Animals↗

PubMed1993

Effect of pravastatin on fatty acid profile of low density lipoprotein in patients with hypercholesterolemia.

We gave pravastatin, an HMG-CoA reductase inhibitor, to 21 hypercholesterolemic patients for 12 weeks after they had been on dietary therapy for 12 weeks. In addition to inducing a significant reduction of total cholesterol and LDL-cholesterol, pravastatin significantly decreased the proportion of linoleic acid (18:2) and increased that of saturated (FA) (16:0 and 18:0) in the cholesterol ester of LDL. Linoleic acid was also reduced in the triglyceride of LDL. Besides, monounsaturated FA (16:1 and 18:1) were increased in the cholesterol ester, triglyceride and phospholipid of LDL, but the changes in monounsaturated FA were not statistically significant. The effect of pravastatin on the FA profile of LDL was similar to that of fibric acid derivatives. The mechanism as well as the clinical implication of these changes await further investigation.

Adult↗

PubMed1993

Effect of triacylglycerols on erythrocyte deformability in vitro.

With Reid's filtration technique as a bioassay for evaluating red blood cell (RBC) deformability, we found that tripalmitolein, triolein and trilinolein improved the deformability of calcium-loaded RBC while glycerol, linoleic acid, dilinoleoyl phosphatidyl choline, trilpalmitin, tristearin, trilinolenin and triarachidonin did not. Maximal effect of tripalmitolein, triolein and trilinolein was achieved at 10(-9), 10(-10) and 10(-8) M respectively. We propose that only those triacylglycerols which contain fatty acids with one or two double bonds could modify RBC membrane fluidity and improve RBC deformability.

Dose-Response Relationship, Drug↗