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Biomedical subjects

C T Ting

Publications and source records attributed to C T Ting.

At least 19 recordsLinked to original sources
PubMed2001

Progressive action potential duration shortening and the conversion from atrial flutter to atrial fibrillation in the isolated canine right atrium.

OBJECTIVES: We sought to evaluate the effects of progressive shortening of the action potential duration (APD) on atrial wave front stability. BACKGROUND: The mechanisms of conversion from atrial flutter to atrial fibrillation (AF) are unclear. METHODS: Isolated canine right atria were perfused with 1 to 5 micromol/l of acetylcholine (ACh). We mapped the endocardium by using 477 bipolar electrodes and simultaneously recorded transmembrane potentials from the epicardium. The APD(90) was measured during regular pacing (S(1)) with cycle lengths of 300 ms. Atrial arrhythmia was induced by a premature stimulus (S(2)). RESULTS: At baseline, only short runs of repetitive beats (<10 cycles) were induced. After shortening the APD(90) from 124 +/- 15 ms to 72 +/- 9 ms (p < 0.01) with 1 to 2.5 micromol/l of ACh, S(2) pacing induced single, stable and stationary re-entrant wave fronts (307 +/- 277 cycles). They either anchored to pectinate muscles (5 tissues) or used pectinate muscles as part of the re-entry (4 tissues). When ACh was raised to 2.5 to 5 micromol/l, the APD(90) was further shortened to 40 +/- 12 ms (p < 0.01); S(2) pacing induced in vitro AF by two different mechanisms. In most episodes (n = 13), AF was characterized by rapid, nonstationary re-entry and multiple wave breaks. In three episodes with APD(90) <30 ms, AF was characterized by rapid, multiple, asynchronous, but stationary wave fronts. CONCLUSIONS: Progressive APD shortening modulates atrial wave front stability and converts atrial flutter to AF by two mechanisms: 1) detachment of stationary re-entry from the pectinate muscle and the generation of multiple wave breaks; and 2) formation of multiple, isolated, stationary wave fronts with different activation cycle lengths.

Acetylcholine↗
PubMed2001

Genetic variation in the human urea transporter-2 is associated with variation in blood pressure.

The kidney, by regulating the volume of fluid in the body, plays a key role in regulating blood pressure (BP). The kidney uses primarily sodium and, to a lesser extent, urea to maintain the appropriate volume of fluid. Genetic variation in proteins that determine sodium reabsorption and excretion is known to significantly influence BP. However, the influence of genetic variation in urea transporters on BP has not been examined. We determined therefore whether nucleotide variation in the kidney-specific human urea transporter, HUT2, is associated with variation in BP. After determining the genomic structure of the coding sequence, seven single nucleotide polymorphisms (SNPs) were identified. Two of the SNPs result in Val/Ile and Ala/Thr amino acid substitutions at positions 227 and 357 in the HUT2 open reading frame, respectively. Another SNP is silent and four others are in introns or the 3' untranslated region. Over 1000 hypertensive and low-normotensive individuals of Chinese origin were typed for five of these SNPs using a high-throughput genotyping method. The Ile227 and Ala357 alleles were associated with low diastolic BP in men but not women, with odds ratios 2.1 [95% confidence interval (CI) 1.5-2.7, P < 0.001] and 1.5 (95% CI 1.2-1.8, P < 0.001), respectively. There was a similar trend for systolic BP, and odds ratios for the Ile227 and Ala357 alleles were 1.7 (95% CI 1.2-2.3, P = 0.002) and 1.3 (95% CI 1.1-1.6, P = 0.007), respectively, in men.

Blood Pressure↗
PubMed2001

Incipient speciation by sexual isolation in Drosophila: concurrent evolution at multiple loci.

Drosophila melanogaster from Zimbabwe and nearby regions shows strong but asymmetric sexual isolation from its cosmopolitan counterparts. By creating stable chromosome-substitution lines, earlier studies were able to show that the two major autosomes have very large effects on both male mating success and female mating preference. In this study, we genetically dissect this sexual isolation by recombination analysis between a whole-chromosome substitution line (which carries a Zimbabwe-derived third chromosome) and a strain with seven visible markers on that chromosome. Four loci are responsible for male mating success and three others are found to control female mating preference. Because male and female traits are not closely linked, their strong association among isofemale lines is most likely a reflection of sexual selection in nature. The results suggest that a large number of behavioral loci may evolve concurrently in the incipient stage of speciation before other aspects of reproductive isolation (such as hybrid sterility) have become evident. The results shed light on the population genetic processes underlying the formation of nascent species, as well as modes of speciation.

Animals↗
PubMed2001

Pulmonary veins and ligament of Marshall as sources of rapid activations in a canine model of sustained atrial fibrillation.

BACKGROUND: In dogs, chronic rapid pacing may result in sustained atrial fibrillation (AF). However, activation patterns in pacing-induced sustained AF are unclear. METHODS AND RESULTS: We induced sustained AF (>48 hours) in 6 dogs by rapid pacing for 139+/-84 days. We then performed computerized atrial epicardial mappings and recorded the activations in the ligament of Marshall (LOM) and the pulmonary veins (PVs). During AF, mean activation cycle length in the right atrial free wall (126+/-17 ms) was significantly longer than that in the left atrial free wall (96+/-5 ms, P:=0.006). In addition, mean activation cycle length in the left atrial free wall was significantly longer than that in the LOM (84+/-5 ms, P:<0.001), the left inferior PV (81+/-4 ms, P:=0.001), and the left superior PV (85+/-7 ms, P:=0.003). Similarly, the dominant frequency was highest in the LOM and the PVs (range 11.2 to 13.3 Hz), followed by the left and right atria (P:<0.001). In all dogs studied, rapid and complicated electrograms were consistently observed at the LOM and the PVs. During AF, both wandering wavelets and organized reentry were present. There were more wave fronts in the left atrium than in the right atrium (P:<0.001). CONCLUSIONS: In chronic pacing-induced sustained AF, the LOM and the PVs are the sources of rapid activations. The mechanism by which the left atrium activates faster and has more wave fronts than the right atrium may relate to the fact that the left atrium is closer to the sources of rapid activations.

Analysis of Variance↗
PubMed2001

Relation between the rapid focal activation in the pulmonary vein and the maintenance of paroxysmal atrial fibrillation.

This case report describes a patient with drug refractory paroxysmal atrial fibrillation (PAF). Rapid focal activations with multiple sharp spikes were continuously identified inside the left superior pulmonary vein (PV) during sustained AF. Among seven episodes of AF, cessation of rapid focal activations coincided with the conversion of AF to flutter (n = 4) or immediate AF termination (n = 3). Guided by sharp spikes in the PV, abrupt termination of AF occurred during radiofrequency energy application. Conclusively, rapid focal activations inside the PV are critical in AF maintenance. Cessation of these rapid focal activations underlies the mechanism by which AF converts to flutter.

Adult↗
PubMed2001

Sex in Drosophila mauritiana: a very high level of amino acid polymorphism in a male reproductive protein gene, Acp26Aa.

Many genes pertaining to male reproductive functions have been shown to evolve rapidly between species, and evidence increasingly suggest the influence of positive Darwinian selection. The accessory gland protein gene (Acp26Aa) of Drosophila is one such example. In order to understand the mechanism of selection, it is often helpful to examine the pattern of polymorphism. We report here that the level of amino acid polymorphism in the N-terminal quarter of Acp26Aa is high in Drosophila melanogaster and is unprecedented in its sibling species Drosophila mauritiana. We postulate that (1) this N-terminal segment may play a role in sperm competition, and (2) D. mauritiana may have been under much more intense sexual selection than other species. Both postulates have important ramifications and deserve to be tested rigorously.

Amino Acid Sequence↗
PubMed2001

High-throughput genotyping with single nucleotide polymorphisms.

To make large-scale association studies a reality, automated high-throughput methods for genotyping with single-nucleotide polymorphisms (SNPs) are needed. We describe PCR conditions that permit the use of the TaqMan or 5' nuclease allelic discrimination assay for typing large numbers of individuals with any SNP and computational methods that allow genotypes to be assigned automatically. To demonstrate the utility of these methods, we typed >1600 individuals for a G-to-T transversion that results in a glutamate-to-aspartate substitution at position 298 in the endothelial nitric oxide synthase gene, and a G/C polymorphism (newly identified in our laboratory) in intron 8 of the 11-beta hydroxylase gene. The genotyping method is accurate-we estimate an error rate of fewer than 1 in 2000 genotypes, rapid-with five 96-well PCR machines, one fluorescent reader, and no automated pipetting, over one thousand genotypes can be generated by one person in one day, and flexible-a new SNP can be tested for association in less than one week. Indeed, large-scale genotyping has been accomplished for 23 other SNPs in 13 different genes using this method. In addition, we identified three "pseudo-SNPs" (WIAF1161, WIAF2566, and WIAF335) that are probably a result of duplication.

Alleles↗
PubMed2001

Successful resuscitation of patient with massive coronary air embolism occluding two vessels during coronary angiography--a case report.

Massive coronary air embolism is usually disastrous although successful resuscitation has been reported previously. To what extent a patient with coronary air embolism can be resuscitated is not known. The authors report a rare case of massive air embolism to the left coronary arteries and successful resuscitation by vigilantly maintaining an effective driving force to dissipate the air lock.

Aged↗
PubMed2001

Orbital adenocarcinoma of lacrimal gland origin in a dog.

A 13-year-old intact female mixed-breed dog was presented for a progressive enlargement of the right eye, which had been treated previously for conjunctivitis. A round, firm mass, approximately 4 cm in diameter, was protruding from the superotemporal aspect of the right orbit, displacing the eyeball anteriorly and ventromedially. The mass was encapsulated, distinct from the eyeball, and not associated with the eyelids. On cut surface, there was a pale multilobulated periphery, with a dark red, soft, and depressed core. Histologically, tumor cells formed cords and tubules, which were stained with mouse anti-human cytokeratin antibody AE1/AE3. Residual glands were serous, and the majority of tumor cells were negative for mucin. The supraorbital location, encapsulation, and residual serous glands suggest that this mass was a low-grade adenocarcinoma of the lacrimal gland.

Adenocarcinoma↗
PubMed2001

The incidence of coronary artery disease in patients with symptomatic bradyarrhythmias.

Symptomatic bradyarrhythmia occurs most often in aged patients. Most of these patients have multiple coronary risk factors and present with angina-like symptoms. The coexistence of CAD not only has major effects on their prognosis but also influences the long-term care. This study was designed to evaluate the incidence of coexistent CAD in patients with symptomatic bradyarrhythmias and its relationship to conventional coronary risk factors in Chinese people. From May 1996 to April 1998, we prospectively studied all consecutive patients admitted to our institution for symptomatic bradyarrhythmias requiring permanent pacemaker implantation. Coronary angiographies were performed non-selectively at the same session of pacemaker implantation. Based on the presence or absence of CAD, patients were divided into two groups for analysis. Multivariate logistic regression analysis was performed to determine independent predictors of CAD including sex, age, diabetes mellitus (DM), hypertension, hypercholesterolemia, and smoking. The odds-ratio (OR) and 95% confidence interval (CI) were determined. A total of 113 patients [68 males and 45 females, mean age 70.4+/-8.2 years old (range 45-86)] were included in our study. The diagnosis was sick sinus syndrome in 69 patients (61%) and atrioventricular block in 44 patients (39%). The incidence of CAD based on coronary angiography was 20%. The nodal-related artery was seldom involved among patients with coexistent CAD and symptomatic bradyarrhythmias (9%), and most patients had significant stenosis over LAD (74%). The baseline characteristics and presenting symptoms were not different statistically between patients with or without CAD. Hypercholesterolemia (OR 6.6, 95% CI 2.0-22.2, p=0.002) and DM (OR 4.7, 95% CI 1.3-17.2, p=0.020) were the two most significant independent predictors of CAD. In our patients with symptomatic bradyarrhythmias requiring permanent cardiac pacing, the incidence of CAD was 20% as determined by coronary angiography (CAG). Hypercholesterolemia and DM were the two most significant independent predictors for CAD in these patients. The nodal artery was seldom involved in patients with coexistent CAD and symptomatic bradyarrhythmias.

Aged↗
PubMed2001

A randomized, double-blind, placebo-controlled, 8-week study to evaluate the efficacy and safety of once daily atorvastatin (10 mg) in patients with elevated LDL-cholesterol.

Lowering of serum cholesterol levels by pharmacologic intervention with statins reduces the incidence of cardiovascular events in subjects with and without atherosclerotic manifestations. In an 8-week, randomized, double-blind study we compared the efficacy and safety of the new compound atorvastatin for reducing LDL-cholesterol (LDL-C) with placebo in an Asian patient cohort. Patients with LDL-C between 160 mg/dl and 250 mg/dl were randomly assigned to treatment with 10 mg atorvastatin or placebo once daily for 8 weeks. At the end of weeks 4 and 8 of the randomized phase, the serum concentrations of lipid parameters as well as safety parameters were determined. Fifty-four patients (32 males and 22 females) were enrolled. Twenty-six patients were assigned to the treatment group. The primary end-point, LDL-C, was reduced by 40% and 42% after 4 and 8 weeks of treatment in the atorvastatin treated patients (p<0.001). The reductions in total cholesterol and triglycerides were up to 31% and 23%, respectively. The HDL-C levels increased up to 11% (p=0.043). There were no significant adverse events. Transient increases in CPK levels (10 times) without myalgia were identified in 1 patient. Atorvastatin, 10 mg/day produced significant reductions in LDL-C, total cholesterol and triglycerides and an elevation of HDL-C levels when used as an adjunct to diet in hyperlipidemic patients. The majority of the clinical effects could be attained by week 4. The overall safety profile of atorvastatin was similar to that of placebo. Atorvastatin was considered to be well tolerated in this patient cohort.

Aged↗
PubMed2000

The phylogeny of closely related species as revealed by the genealogy of a speciation gene, Odysseus.

Molecular differentiation between races or closely related species is often incongruent with the reproductive divergence of the taxa of interest. Shared ancient polymorphism and/or introgression during secondary contact may be responsible for the incongruence. At loci contributing to speciation, these two complications should be minimized (1, 2); hence, their variation may more faithfully reflect the history of the species' reproductive differentiation. In this study, we analyzed DNA polymorphism at the Odysseus (OdsH) locus of hybrid sterility between Drosophila mauritiana and Drosophila simulans and were able to verify such a prediction. Interestingly, DNA variation only a short distance away (1.8 kb) appears not to be influenced by the forces that shape the recent evolution of the OdsH coding region. This locus thus may represent a test case of inferring phylogeny of very closely related species.

Animals↗
PubMed2000

Differential coronary hemodynamics and left ventricular contractility in patients with syndrome X.

The relationship between coronary hemodynamics and left ventricular contractility was studied in 20 patients with syndrome X. Among them, 10 patients with a resting left ventricular ejection fraction (LVEF, by radionuclide method) equal to or greater than the mean value of the whole group (58%) were defined as having relative increased left ventricular contractility (group H), and another 10 patients with relatively normal contractility (50%</=LVEF<58%) were in group N. Eight subjects with normal contractility, exercise test and coronary angiograms served as the control (group C). Baseline great cardiac venous flow (GCVF) was higher in group N than in group H (P<0.05) and C (P<0.05), but similar between group H and C. After dipyridamole infusion (0.56 mg/kg, i.v., for 4 min), maximum GCVF was less in group H than in group N (P<0.001) and C (P<0.001), but similar between group N and C. As compared to group C (3.09+/-0.35), coronary flow reserve was reduced in both group H (2.34+/-0.55, P=0. 004) and N (2.40+/-0.36, P=0.001). In all syndrome X patients, resting LVEF was negatively correlated to baseline GCVF (P=0.026) and tended to be positively correlated to baseline coronary vascular resistance (P=0.057). Thus, coronary hemodynamics was altered with left ventricular contractility in syndrome X patients. In these patients, coronary flow reserve was similarly reduced with different underlying mechanisms. The limited increase of GCVF after dipyridamole infusion suggests impaired coronary microvascular dilation capacity in patients with relatively increased left ventricular contractility and the increase of baseline GCVF in those with normal contractility is more likely due to an altered basal myocardial metabolism.

Adult↗
PubMed2000

Significantly higher levels of oxidized LDL autoantibody in coronary artery disease patients.

BACKGROUND: Increasing evidence shows that oxidized low-density lipoprotein (ox-LDL) might play an important role in the pathogenesis of atherosclerosis. Ox-LDL is immunogenic and induces an autoantibody, which we used as a tool for measuring the content of ox-LDL in vivo. METHODS: Patients who were admitted for diagnostic cardiac catheterization for typical or atypical angina pectoris were enrolled in this study. After fasting for 12 hours, a venous blood sample was drawn from the antecubital vein for testing triglyceride, total cholesterol, LDL cholesterol, high-density lipoprotein (HDL) cholesterol, and ox-LDL autoantibody. The ox-LDL autoantibody was quantified using an enzyme linked immunosorbent assay. All patients underwent coronary angiography. Those who had more than 50% angiographic coronary luminal stenosis, were grouped into the coronary artery disease (CAD) group. RESULTS: Sixty-four patients were enrolled in the study (male/female = 46/18; mean +/- standard deviation, age, 64 +/- 9 years). The CAD group had a significantly higher level of ox-LDL autoantibody than the non-CAD group (494.0 +/- 355.0 mU/ml vs 258.1 +/- 196.8 mU/ml, p = 0.004). However, the other lipid profiles including triglyceride, total cholesterol, LDL-cholesterol and HDL-cholesterol were not statistically different between the two groups. Forty-six patients in this study had an arterial blood sample taken from the femoral artery for testing ox-LDL autoantibody. There was no significant difference between the arterial and venous samples of ox-LDL autoantibody (385.2 +/- 333.3 mU/ml vs 399.3 +/- 339.5 mU/ml, n = 46, p = 0.530). CONCLUSIONS: Ox-LDL autoantibody was significantly higher in the CAD group. Ox-LDL may prove to play a key role in the pathogenesis of atherosclerosis. Further study of Ox-LDL and its role in the process of atherosclerosis is warranted.

Adult↗
PubMed2000

Catheter-induced coronary spasm--a view of mechanical factors and experience with selective left coronary arteriography.

BACKGROUND: Coronary spasm during cardiac catheterization is not unusual. The mechanism of spasm remains uncertain, but is considered to be multifactorial. Many researchers believe that coronary spasm that develops during catheterization is partly spontaneous and partly catheter-induced. Because catheter-induced spasm results from mechanical irritation, we tried to find the iatrogenic factors that predispose patients to coronary spasm during coronary angiography. METHODS: Retrospectively, we reviewed the records of 7,295 patients who underwent coronary angiography at our hospital from June, 1983 to November, 1997; coronary spasm was documented in 30 patients, who became the study group. We randomly selected 41 patients who had normal coronary arteries as the normal control group. After reviewing cine films of coronary angiography, we compared these two groups for several parameters. These parameters included the length and diameter of the left main coronary artery (LMC), the angle between the LMC and the aorta, the angle between the catheter tip and the LMC, whether the catheter tip came into contact with the vascular wall and whether there was vessel wall bulging, catheter size and catheter/LMC ratio. This angiographic data and the demographic features, including age, sex, history of hypertension, diabetes mellitus, smoking, previous myocardial infarction, family history of coronary artery disease, cholesterol and triglyceride levels and chest pain character (exertional or rest pain) were compared between the study patient group and the control group. RESULTS: The results disclosed that larger catheter size (7.1 +/- 0.6 mm vs 6.4 +/- 0.7 mm, p < 0.001), smaller LMC diameter (4.2 +/- 0.9 mm vs 4.9 +/- 1.0 mm, p = 0.004), larger catheter/LMC ratio (0.07 +/- 0.05 vs 0.05 +/- 0.03, p = 0.022), catheter contact with the vessel wall (27/30 vs 20/41, p < 0.001) and vessel bulging (18/30 vs 5/41, p < 0.001) were related to catheter-induced coronary spasm. We found that the catheter tip coming into contact with the vessel wall, vessel wall bulging and catheter/LMC ratio (odds ratio 8.92 x 10(14)) were statistically significant factors predisposing patients to catheter-induced coronary spasm. CONCLUSIONS: Multiple factors contribute to coronary spasm. Of those, mechanical or iatrogenic factors might predispose patients to spasm during coronary catheterization. These facts deserve our attention, because iatrogenically induced spasms may be avoided by meticulously selecting catheters and manipulating them gently.

Adult↗
PubMed2000

Randomized, double-blind comparison of irbesartan and enalapril for treatment of mild to moderate hypertension.

BACKGROUND: Irbesartan is a newly developed angiotensin II receptor antagonist. Its antihypertensive efficacy and safety in Taiwanese patients with mild to moderate hypertension remains to be determined. METHODS: This was a multicenter, double-blind, randomized, parallel group study. One hundred and sixteen patients from three centers were enrolled. After a placebo lead-in period of 14 days, 55 patients (24-75 years-of-age) who had a mean seated diastolic blood pressure of 95 to 110 mmHg were randomized to once-daily treatment with irbesartan 150 mg or enalapril 10 mg. Doses were doubled at week 4 if trough seated diastolic blood pressure was 90 mmHg or more. Trough blood pressure was measured at zero, two, four and eight weeks of treatment. RESULTS: Both treatments lowered blood pressure with no significant difference in efficacy between treatment groups. Irbesartan 150 mg to 300 mg provided reductions in trough seated systolic and diastolic blood pressures at week 8 of -16.5 mmHg and -7.2 mmHg, respectively, with 36% of patients having a favorable response. Similarly, enalapril 10 mg to 20 mg reduced systolic and diastolic blood pressure by -10.6 mmHg and -5.0 mmHg, respectively, with a response rate of 43%. Headache, malaise and dizziness were the major adverse reactions observed in both groups. The incidence of drug-related cough was significantly higher with enalapril (18%) than with irbesartan (0%). CONCLUSIONS: Irbesartan 150 mg to 300 mg once daily was as effective in lowering blood pressure as enalapril 10 mg to 20 mg once daily. Both irbesartan and enalapril were well tolerated, while there was a significantly lower incidence of cough with irbesartan compared with enalapril.

Adult↗