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Biomedical subjects

P Chan

Publications and source records attributed to P Chan.

At least 73 records · Page 4Linked to original sources
PubMed2000

Antioxidant effects of Chinese traditional medicine: focus on trilinolein isolated from the Chinese herb sanchi (Panax pseudoginseng).

It is thought that oxygen-derived free radicals (OFR) cause lipid peroxidation, which contributes to the process of atherosclerosis, and they are also involved in the myocardial damage seen with ischemia and reperfusion. Antioxidants could potentially ameliorate such harmful effects. Many natural plant products have been shown to have antioxidant effects. Trilinolein, a triacylglycerol purified from Panax pseudoginseng, which is commonly used in Chinese traditional medicine, has been found to have pharmacological effects, including antioxidant activity that may explain the benefits in treating circulatory disorders perceived from the use of the herb over the centuries.

Animals↗
PubMed2000

Changes in superoxide dismutase activity and mRNA in vivo after short-term supplementation with trilinolein in rats.

BACKGROUND: Oxidative damage plays a central role in atherogenesis and antioxidation defense mechanisms may prevent atherosclerosis. This study evaluated the effect of short-term supplementation of the natural lipophilic antioxidant trilinolein on superoxide dismutase (SOD) activity and SOD-mRNA gene expression in vivo in rat vital organs. METHODS: Male Wistar rats (n = 8) were injected intraperitoneally with trilinolein (1 mM/ml/kg/day in 0.5% ethanol) daily for three consecutive days. Two control groups (n = 8) were administered saline or 0.5% ethanol in saline, respectively, for three days. RESULTS: Assay of SOD activity and SOD-mRNA by Northern blotting in rat liver, spleen and brain showed significant increases in SOD activity and increased SOD-mRNA gene expression. CONCLUSIONS: The natural lipophilic antioxidant trilinolein potentiates the SOD antioxidation defense mechanism and increases gene expression of SOD-mRNA after short-term supplementation in rats.

Animals↗
PubMed2000

Ticlopidine-induced severe cholestatic hepatitis.

We report a case study of an 86-year-old female patient with severe cholestatic hepatitis who was undergoing treatment with oral ticlopidine 250 mg daily for coronary artery disease. The patient had nausea and vomiting and was jaundiced after taking ticlopidine for 6 weeks. She was admitted to the hospital for further evaluation. Ultrasound and endoscopic retrograde cholangiopancreatography eliminated the presence of biliary obstruction. Results from a liver biopsy showed a histopathologic picture consistent with cholestatic hepatitis. Ticlopidine-induced cholestatic hepatitis has been reported 32 times in the foreign literature. This is the first reported severe cholestatic hepatitis (total bilirubin up to 43 mg/dl) case in Taiwan. Ticlopidine-related blood dyscrasia is a renowned adverse drug effect; liver function should be monitored in patients receiving ticlopidine therapy.

Aged↗
PubMed2000

Undergraduate medical education: comparison of problem-based learning and conventional teaching.

OBJECTIVE: To review the literature on studies comparing all aspects of problem-based learning with the conventional mode of teaching. DATA SOURCES: Medline literature search (1980 through 1999) and the references cited in retrieved articles. DATA SELECTION: Studies and meta-analyses that compared the newer problem-based learning curriculum and the conventional lecture-based mode of teaching undergraduate medical students. Areas of comparison included the academic process; programme evaluation; academic achievement; graduates' performance, specialty choices, and practice characteristics; and the attitude of students and teachers towards the programmes. DATA EXTRACTION: Data were extracted independently by multiple authors. DATA SYNTHESIS: Students of the problem-based learning curriculum found learning to be "more stimulating and more humane" and "engaging, difficult, and useful", whereas students of the conventional curriculum found learning to be "non-relevant, passive, and boring". Students who used the problem-based learning method showed better interpersonal skills and psychosocial knowledge, as well as a better attitude towards patients. Students using the conventional model, however, performed better in basic science examinations. Teachers tended to enjoy teaching the newer curriculum. Although the two curricula encourage different ways of learning, there is no convincing evidence of improved learning using the problem-based learning curriculum. CONCLUSION: A combination of both the conventional and newer curricula may provide the most effective training for undergraduate medical students.

Attitude of Health Personnel↗
PubMed2000

Evaluation of absorbed radiation dose to working staff during cardiac catheterization procedures.

BACKGROUND: Cardiac catheterization has been used frequently for the evaluation and treatment of patients with heart diseases. The working staff, particularly cardiologists who perform these procedures, have the highest potential risk of receiving high radiation doses due to close contact with patients. The purpose of this study was to measure and evaluate the accumulated radiation dosage of the cardiologists while they were performing clinical procedures in the cardiac catheterization laboratory. The working environment of the catheterization laboratory was also monitored for radiation. METHODS: Thermoluminescent dosimeters (TLDs) with very high sensitivity were employed for dose evaluations. They were taped to various parts of the body of the cardiologists during catheterization procedures. For environmental monitoring, TLDs were also distributed at several sites of the catheterization rooms for a period of 2 to 4 weeks. RESULTS: The study showed that the left wrist of the cardiologists received the highest radiation dose (338 microsieverts [microSv]/procedure) and the left lens received the second highest dose (149 microSv/procedure) during the procedures. The dose to the knees was unexpectedly high (92 microSv/procedure), partly due to radiation leakage from the lead curtain shielding under the patient couch. On average, the effective radiation dose per year was 37 mSv/y for a cardiologist who performs 10 catheterization procedures per week. Compare this to the occupational exposure limit of 50 mSv/y. The estimated accumulated equivalent dose to the lens was 152 mSv/y, which exceeded the regulatory limit for occupational exposure. CONCLUSIONS: Using proper lead shielding and increasing the distance from the radiation source are good strategies for reducing the radiation dose in medical staff. The work area outside the catheterization room was considered safe because the radiation level was essentially equivalent to the background radiation level.

Cardiac Catheterization↗
PubMed1999

Uniform risk of clinical progression despite differences in utilization of highly active antiretroviral therapy: Swiss HIV Cohort Study.

OBJECTIVE: To compare the initiation of highly active antiretroviral therapy (HAART) in HIV-infected patients according to sex, route of HIV acquisition and education, and to assess the impact of differences in utilization on the probability of progression to AIDS. DESIGN AND SETTING: Swiss HIV Cohort Study, a national prospective multi-centre study. PARTICIPANTS: A total of 3342 patients, including 1007 (30%) women. HIV was acquired through injection drug use in 1155 (35%) cases and through sex between men in 1172 (35%). Twenty-eight per cent (957) of participants had attained only the minimum level of schooling. At baseline, the median CD4 cell count was 269x10(6)/l cells, median HIV-1 RNA was 4.3 log10 copies/ml and 2917 (87%) were free of AIDS. METHODS: Kaplan-Meier life tables and Cox proportional hazards regression. RESULTS: During 7007 person-years of follow-up 2285 (69%) patients started HAART and 318 (10%) developed a new AIDS event. In multivariable analysis controlling for CD4 cell count, viral load and disease stage at baseline, the probability of starting HAART was lower in injection drug users compared with men who have sex with men, hazard ratio 0.63 (95% confidence intervals 0.56-0.70) and in patients with minimum schooling compared with those with vocational training, hazard ratio 0.82 (0.75-0.91). The risk of progression to AIDS was similar among men and women, patients with a history of injecting drug use, and patients with lower educational attainment in both univariable and multivariable analysis. CONCLUSION: HIV-infected injecting drug users and those with lower levels of educational attainment start HAART later than other patient groups. The deferred initiation of therapy in these patients does not, however, appear to translate into an increased risk of clinical disease progression. This observation has important implications for treatment policy and the design of future clinical trials.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Effect of trilinolein on the activity and gene expression of superoxide dismutase in cultured rat brain astrocytes.

Cerebrovascular disease is one of the major causes of morbidity and mortality in recent. Oxygen free radicals produced during cerebral infarction increases the damage to neurons. Superoxide dismutase (SOD) is the endogenous antioxidant enzyme that can effectively scavenge superoxide radicals. Trilinolein is a lipophilic antioxidant purified from the herb of Panax pseudoginseng. In the cultured rat brain astrocytes (RBA), the activity of SOD (both Cu,Zn-SOD and Mn-SOD subtypes) was markedly increased by incubation with trilinolein at low concentration (0.1 microM) for 2 days. This stimulatory effect of trilinolein was not related to the incubating concentration. However, long-term (7 days) incubation with trilinolein at same concentration decreased the activity. Similar changes were also observed in the gene expression of SOD in RBA; short-term (2 days) incubation of RBA by 0.1 microM trilinolein increased the mRNA level that was lowered in RBA received a long-term incubation with 0.1 microM trilinolein. This result shows that trilinolein is an effective antioxidant to increase the activity of SOD in RBA which would be beneficial to neurons subjected to oxygen free radical damage. However, long-term medication of antioxidant shall be concerned.

Animals↗
PubMed1999

Peptide nucleic acid (PNA) binding-mediated induction of human gamma-globin gene expression.

Peptide nucleic acids (PNAs) can bind to homopurine/homopyrimidine sequences of double-stranded DNA targets in a sequence-specific manner and form [PNA]2/DNA triplexes with single-stranded DNA D-loop structures at the PNA binding sites. These D-loop structures have been found to have a capacity to initiate transcription in vitro. If this strategy can be used to induce transcription of endogenous genes, it may provide a novel approach for gene therapy of many human diseases. Human [beta] globin disorders such as sickle cell anemia and beta-thalassemia are very common genetic diseases that are caused by mutations in the beta-globin gene. When gamma-globin genes are highly expressed in sickle cell patients, the presence of high levels of fetal hemoglobin (HbF, alpha2gamma2) can compensate for the defective beta-globin gene product and such patients have much improved symptoms or are free of disease. However, the gamma-globin genes are developmentally regulated and normally expressed at very low levels (>1%) in adult blood cells. We have investigated the possibility of inducing gamma-globin gene expression with PNAs. Using PNAs designed to bind to the 5' flanking region of the gamma-globin gene, induction of expression of a reporter gene construct was demonstrated both in vitro and in vivo. More importantly, PNA-mediated induction of endogenous gamma-globin gene expression was also demonstrated in K562 human erythroleukemia cells. This result suggests that induction of gamma-globin gene expression with PNAs might provide a new approach for the treatment of sickle cell disease. PNA-induced gene expression strategy also may have implications in gene therapy of other diseases such as genetic diseases, cancer and infectious diseases.

Anemia, Sickle Cell↗
PubMed1999

Population requirement for primary hip-replacement surgery: a cross-sectional study.

BACKGROUND: There has been a long-standing failure in many countries to satisfy the demand for several elective surgical treatments, including total hip replacement. We set out to estimate the population requirement for primary total hip replacement in England. METHODS: We undertook a cross-sectional study of a stratified random sample of 28,080 individuals aged 35 and over from 40 general practices in inner-city, urban, and rural areas of Avon and Somerset, UK. Prevalent disease was identified through a two-stage process: a self-report screening questionnaire (22,978 of 26,046 responded) and subsequent clinical examination. Incident disease was estimated from the point prevalence by statistical modelling. The requirement for total hip replacement surgery was estimated on the basis of pain and loss of functional ability, with adjustment for evidence of comorbidity and patients' treatment preferences. FINDINGS: 3169 people reported hip pain on the screening questionnaire. 2018 were invited for clinical examination, and 1405 attended. The prevalence of self-reported hip pain was 107 per 1000 (95% CI 101-113) for men and 173 per 1000 (166-180) for women. The prevalence of hip disease severe enough to require surgery was 15.2 (12.7-17.8) per 1000 aged 35-85 years. The corresponding annual incidence of hip disease requiring surgery was estimated as 2.23 (1.56-2.90), which suggests an overall requirement in England of 46,600 operations per year for patients who expressed a preference for, and were suitable for, surgery; the recent actual provision in England was about 43,500. INTERPRETATION: This research suggests that the satisfaction of demand for total hip replacement, given agreed criteria for surgery, is a realistic objective.

Adult↗
PubMed1999

Parkinson disease in twins: an etiologic study.

CONTEXT: The cause of Parkinson disease (PD) is unknown. Genetic linkages have been identified in families with PD, but whether most PD is inherited has not been determined. OBJECTIVE: To assess genetic inheritance of PD by studying monozygotic (MZ) and dizygotic (DZ) twin pairs. DESIGN: Twin study comparing concordance rates of PD in MZ and DZ twin pairs. SETTING AND PARTICIPANTS: A total of 19842 white male twins enrolled in the National Academy of Sciences/National Research Council World War II Veteran Twins Registry were screened for PD and standard diagnostic criteria for PD were applied. Zygosity was determined by polymerase chain reaction or questionnaire. MAIN OUTCOME MEASURE: Parkinson disease concordance in twin pairs, stratified by zygosity and age at diagnosis. RESULTS: Of 268 twins with suspected parkinsonism and 250 presumed unaffected twin brothers, 193 twins with PD were identified (concordance-adjusted prevalence, 8.67/1000). In 71 MZ and 90 DZ pairs with complete diagnoses, pairwise concordance was similar (0.129 overall, 0.155 MZ, 0.111 DZ; relative risk, 1.39; 95% confidence interval, 0.63-3.1). In 16 pairs with diagnosis at or before age 50 years in at least 1 twin, MZ concordance was 1.0 (4 pairs), and DZ was 0.167 (relative risk, 6.0; 95% confidence interval, 1.69-21.26). CONCLUSIONS: The similarity in concordance overall indicates that genetic factors do not play a major role in causing typical PD. No genetic component is evident when the disease begins after age 50 years. However, genetic factors appear to be important when disease begins at or before age 50 years.

Adult↗
PubMed1999

Effects of pulsed magnetic stimulation of GFAP levels in cultured astrocytes.

The present study evaluates the physiological effects of magnetic stimulation on astrocyte cultures. Cell cultures were exposed to pulsed magnetic stimulation (10 Hz, 10 sec) at the following levels: 0.10 tesla (T; Group A); 0.21 T (Group B); 0.42 T (Group C); and 0.63 T (Group D). Glial fibrillary acidic protein (GFAP) levels from immunoblots, total protein concentrations, and cellular morphology were analyzed at 0, 1, 3, 5, 7, 13, and 20 days poststimulation. Significantly higher GFAP levels were observed in Group D at day 3 (P = 0.0114). The change was transient as the GFAP levels quickly returned to control levels by day 5. No other significant changes in GFAP levels were observed. In comparison to control protein levels at day 0, concentrations from Groups B, C, and D were significantly lower (P < 0.006), whereas at day 3, Groups C and D were significantly higher (P < 0.02). Differences in astrocyte morphology due to magnetic stimulation were not observed. This study demonstrated that high intensity magnetic stimulation for only 10 sec induced a transient biological response.

Animals↗
PubMed1999

DA1 receptor activity opposes anorectic responses to amino acid-imbalanced diets.

The serotonin3 (5-HT3) receptor plays an important role in the aminoprivic feeding model. Other neurochemical systems, including cholecystokinin (CCK) and dopamine (DA), are known to affect food intake. We pretreated rats systemically with tropisetron, a 5-HT3 receptor antagonist, alone and combined with antagonists of DA1 and DA2 receptors, and measured intake of an amino acid-imbalanced diet (IMB). As expected, tropisetron significantly increased intake of IMB. SCH-23390, a DA1 antagonist, increased IMB anorexia. When combined with tropisetron, DA2 antagonism with eticlopride reduced short-term intake of both the basal diet (BAS) and IMB. In the IMB model, specificity of 5-HT3-DA2 interactions, and of 5-HT3-CCK(A) interactions from previous studies, prompted investigation of CCK(A)-DA2 interactions; there appeared to be none. SKF-38393, a DA1 agonist, combined with the CCK(A) receptor antagonist, devazepide, increased BAS and tended to increase IMB intake. Thus, CCK(A)-DA1 interactions were not specific for IMB. These data suggest that DA1 receptor activity opposes IMB anorexia, possibly via an interaction with the 5-HT3 receptor.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1999

Aortoiliac stenting, determinants of clinical outcome.

OBJECTIVES: To determine predictors of clinical outcome in stenting aortoiliac disease. DESIGN: Prospective/retrospective study. MATERIALS AND METHODS: One hundred and forty patients (163 limbs) underwent iliac artery stenting in the period 1994-1997. Ninety-eight occlusions and 65 stenoses were treated, either with primary stenting (n = 129) or after failed angioplasty (n = 34). Median follow-up 18 months (1-66). Factors analysed for their effect on outcome were: gender, age, Fontaine stage, ABI, lesion type/length/site, primary or secondary stenting, stent type, BP, smoking, diabetes, aspirin, cholesterol, residual gradient, overhanging and run-off. RESULTS: The immediate success was 95%. The primary successful clinical outcome was 90% at 12 months and 84% at 36 months; the primary-assisted successful clinical outcome was 95% at 12 months and 91% at 36 months and the secondary successful clinical outcome was 92% at 12 months and 87% at 36 months. Adverse factors affecting outcome were: residual pressure gradient (> 10 mmHg) and no treatment with aspirin (p < 0.05). Major complications occurred in 18% of patients with a re-intervention in 8%. The 30-day mortality was 5.5%. CONCLUSIONS: Stenting for aortoiliac occlusive disease has good short and long term clinical success, with low morbidity and mortality. Factors that might improve results further are ensuring that patients are taking aspirin and any residual pressure gradient is abolished.

Aged↗
PubMed1999

Calcium influx inhibition: possible mechanism of the negative effect of tetrahydropalmatine on left ventricular pressure in isolated rat heart.

The active ingredient dl-tetrahydropalmatine (THP) isolated from the traditional Chinese herb Corydalis racemosa has been found to have antihypertensive effects. However, severe cardiac and neurological toxic effects were reported from using this herb for the treatment of pain. In an isolated perfused rat heart model, THP at the concentration of 100 microM was found to have a negative effect (-45%) on left ventricular pressure and this effect was produced concentration-dependently from concentrations lower than 50 microM. In isolated cardiomyocytes, radioactive calcium influx was also inhibited significantly by THP at the concentration of 100 microM and this effect was also in a concentration-dependent manner (-39%). In a patient with latent heart disease, the use of Corydalis should probably be detrimental, the toxic effect was probably due to calcium influx inhibition.

Animals↗
PubMed1999

Inducibility of atrial fibrillation during atrioventricular pacing with varying intervals: role of atrial electrophysiology and the autonomic nervous system.

INTRODUCTION: Patients receiving VVI pacemakers have a higher incidence of paroxysmal atrial fibrillation (AF) than those receiving DDD pacemakers. However, the mechanism behind the difference is not clear. The purpose of this study was to investigate whether atrial electrophysiology and the autonomic nervous system play a role in the occurrence of AF during AV pacing. METHODS AND RESULTS: The study population consisted of 28 patients who had (group I, n = 15) or did not have (group II, n = 13) AF induced by a single extrastimulus during pacing with different AV intervals. Atrial pressure, atrial size, atrial effective refractory periods, and atrial dispersion were evaluated during pacing with different AV intervals. Twenty-four-hour heart rate variability and baroreflex sensitivity also were examined. Atrial pressure, atrial size, effective refractory periods in the right posterolateral atrium and distal coronary sinus, and atrial dispersion increased as the AV interval shortened from 160 to 0 msec. During AV pacing, group I patients had greater minimal (52+/-17 vs 25+/-7 msec; P < 0.005) and maximal (76+/-16 vs 36+/-9 msec; P < 0.005) atrial dispersion than group II patients. The differences in atrial size and atrial dispersion among different AV intervals were greater in patients with AF than in those without AF. Baroreflex sensitivity (6.6+/-1.7 vs 3.9+/-1.0; P < 0.00005), but not heart rate variability, was higher in patients with AF than in those without AF. CONCLUSION: Abnormal atrial electrophysiology and higher vagal reflex activity can play important roles in the genesis of AF in patients receiving pacemakers.

Atrial Fibrillation↗