Catalase plays a major role in cellular antioxidant defense by decomposing hydrogen peroxide, thereby preventing the generation
of hydroxyl radical by the Fenton reaction. The degree of catalase ...deficiency in acatalasemic and hypocatalasemic mice varies
from tissue to tissue. They therefore may not be suitable for studying the function of this enzyme in certain models of oxidant-mediated
tissue injury. We sought to generate a new line of catalase null mice by the gene targeting technique. The mouse catalase
( Cat or Cas1 ) gene was disrupted by replacing parts of intron 4 and exon 5 with a neomycin resistance cassette. Homozygous Cat knockout mice, which are completely deficient in catalase expression, develop normally and show no gross abnormalities. Slices
of liver and lung and lenses from the knockout mice exhibited a retarded rate in decomposing extracellular hydrogen peroxide
compared with those of wild-type mice. However, mice deficient in catalase were not more vulnerable to hyperoxia-induced lung
injury; nor did their lenses show any increased susceptibility to oxidative stress generated by photochemical reaction, suggesting
that the antioxidant function of catalase in these two models of oxidant injury is negligible. Further studies showed that
cortical injury from physical impact caused a significant decrease in NAD-linked electron transfer activities and energy coupling
capacities in brain mitochondria of Cat knockout mice but not wild-type mice. The observed decrease in efficiency of mitochondrial respiration may be a direct result
of an increase in mitochondrion-associated calcium, which is secondary to the increased oxidative stress. These studies suggest
that the role of catalase in antioxidant defense is dependent on the type of tissue and the model of oxidant-mediated tissue
injury.
Intimal hyperplasia and resulting restenosis limit the efficacy of coronary stenting. We studied a coronary stent coated with the antiproliferative agent paclitaxel as a means of preventing ...restenosis.
We conducted a multicenter, randomized, controlled, triple-blind study to evaluate the ability of a paclitaxel-eluting stent to inhibit restenosis. At three centers, 177 patients with discrete coronary lesions (<15 mm in length, 2.25 to 3.5 mm in diameter) underwent implantation of paclitaxel-eluting stents (low dose, 1.3 microg per square millimeter, or high dose, 3.1 microg per square millimeter) or control stents. Antiplatelet therapies included aspirin with ticlopidine (120 patients), clopidogrel (18 patients), or cilostazol (37 patients). Clinical follow-up was performed at one month and four to six months, and angiographic follow-up at four to six months.
Technical success was achieved in 99 percent of the patients (176 of 177). At follow-up, the high-dose group, as compared with the control group, had significantly better results for the degree of stenosis (mean +/-SD, 14+/-21 percent vs. 39+/-27 percent; P<0.001), late loss of luminal diameter (0.29+/-0.72 mm vs. 1.04+/-0.83 mm, P<0.001), and restenosis of more than 50 percent (4 percent vs. 27 percent, P<0.001). Intravascular ultrasound analysis demonstrated a dose-dependent reduction in the volume of intimal hyperplasia (31, 18, and 13 mm3, in the high-dose, low-dose, and control groups, respectively). There was a higher rate of major cardiac events in patients receiving cilostazol than in those receiving ticlopidine or clopidogrel. Among patients receiving ticlopidine or clopidogrel, event-free survival was 98 percent and 100 percent in the high-dose and control groups, respectively, at one month, and 96 percent in both at four to six months.
Paclitaxel-eluting stents used with conventional antiplatelet therapy effectively inhibit restenosis and neointimal hyperplasia, with a safety profile similar to that of standard stents.
Patients with postural orthostatic tachycardia syndrome (POTS) present to outpatient dysautonomia clinics endorsing a wide range of symptoms. Dry eyes and mouth, or sicca complex are frequently ...reported. This retrospective study investigates the incidence and quantifies the severity of dry eye syndrome (DES) in patients with POTS.
This retrospective study compiles survey results, and dry eye clinical data from twenty-three POTS patients (22 females, average age 34.9 and st dev 14.0 years) surveyed during their initial or follow-up appointments. Patient's medication lists were documented to account for anticholinergics, antihistamines, and anticholinesterase use. Patients endorsing dry eye symptoms were tested with Schirmer's test strips to identify clinically dry eyes and stratified for severity.
Sixty-five percent of patients endorsed dry eye symptoms (15/23). Seventy-four percent of patients endorsed dry mouth symptoms (17/23). Among patients endorsing dry eyes, 81% of eyes had decreased tear production with Schirmer's strip wetting less than 10 mm/5 min (13/16).
DES is an additional and significant disease burden for the POTS patient population. Dry eye and exocrine gland function should be evaluated as part of the dysautonomia work up with referral to ophthalmology as appropriate. Patients with clinically dry eyes who report additional autonomic dysfunction should be further evaluated for widespread autonomic dysfunction.
One-year series of hourly average ozone observations, which were obtained from urban and national park air monitoring stations at Taipei (Taiwan), were analyzed by means of descriptive statistics and ...fractal methods to examine the scaling structures of ozone concentrations. It was found that all ozone measurements exhibited the characteristic right-skewed frequency distribution, cyclic pattern, and long-term memory. A mono-fractal analysis was performed by transferring the ozone concentration time series (OCTS) into a useful compact form, namely, the box-dimension (
D
B)–threshold (
T
h) and critical scale (
C
S)–threshold (
T
h) plots. Scale invariance was found in these time series and the box dimension was shown to be a decreasing function of the threshold ozone level, implying the existence of multifractal characteristics. To test this hypothesis, the OCTS were transferred into the multifractal spectra, namely, the
τ(
q)–
q plots. The analysis confirmed the existence of multifractal characteristics in the investigated OCTS. A simple two-scale Cantor set with unequal scales and weights was then used to fit the calculated
τ(
q)–
q plots. This model fitted remarkably well the entire spectrum of scaling exponents for the examined OCTS. Because the existence of chaos behavior in OCTS has been reported in the literature, the possibility of a chaotic multifractal approach for OCTS characterization was discussed.
Some statistical tools, including histogram, spectral analysis and fractal theory, were used on the daily Taiwan stock price index (TSPI) from 1987 to 2002 to examine the possible scale-invariant ...behavior and the clustering characteristics in Taiwan stock market. It was found that the TSPI data exhibited the characteristic of right-skewed frequency distribution. The long-term memory and the possibility of scale invariance were roughly identified through the analysis of autocorrelation and power spectrum, respectively. The monofractal analysis was then performed by the box-counting method. Scale invariance was clearly found in the time series and the box dimension was shown to be a decreasing function of the threshold index level, implying multifractal characteristics, i.e., the low and high regions scale differently. To test this hypothesis, the time series were transferred into a useful compact form through the multifractal formalism, namely, the
τ(
q)–
q and
f(
α)–
α plots. The analysis confirmed the existence of multifractal characteristics in the investigated time series. The origin of multifractal phenomena in Taiwan stock market might be interpreted in terms of the multiplicative cascade process of stock market information.
The scale-invariant behavior of air pollutant concentration (APC) time structure was investigated by applying the box counting method to APC time series. One-year series of hourly average APC ...observations, including O
3, CO, SO
2, NO, NO
2, and PM10 which were obtained from urban, traffic, and national park air monitoring station at Taipei (Taiwan), were transferred into a useful compact form through this method, namely, the box-dimension (
D
B)-threshold (
T
h) and critical scale (
C
S)-threshold (
T
h) plots. The validity of this approach was supported with the result that the practical implications of
D
B-
T
h (or
C
S-
T
h) plots could be interpreted in terms of traditional statistical parameters. Since the dependences of both
D
B and
C
S on the
T
h values were closely related to the variation of APC in time, they were used to characterize the temporal distribution of APC. The analysis confirmed the existence of scale invariance in those investigated APC time series. Moreover, the
D
B (
C
S) was shown to be a decreasing (increasing) function of the threshold level, implying multifractal characteristics, i.e. the weak and intense regions scale differently. Some practical applications based on the box counting method were also discussed.
Objective:
To determine the effect of chronic magnesium (Mg
2+) deficiency on the relative arrhythmogenicity of halothane and sevoflurane in the rat.
Design:
Prospective, randomized, nonblinded ...study.
Setting:
University laboratory.
Participants:
Male Sprague-Dawley rats (n = 48).
Interventions:
Rats were maintained on a Mg
2+-deficient or control diet for 14 days, at which time they were anesthetized with halothane or sevoflurane, a tracheostomy was performed, and the lungs were ventilated to maintain normocapnia. Catheters were inserted into a femoral vein and carotid artery. Lead II of the electrocardiogram was monitored to determine the threshold for epinephrine-induced arrhythmias.
Measurements and main results:
Chronic Mg
2+ deficiency significantly decreased the dose of epinephrine required for arrhythmias (ADE). The reduction in the ADE was approximately one third during halothane anesthesia (
p < 0.05) and one fifth during sevoflurane anesthesia (
p < 0.001). Infusion of magnesium sulphate completely reversed the reduction in ADE. In normomagnesemic rats, the halothane ADE was significantly less than the sevoflurane ADE (mean difference = 6.0 μg/kg, 95% confidence interval of the difference = 3.6 to 8.4 μg/kg) (
p < 0.005). Mg
2+ deficiency significantly attenuated the difference between the halothane ADE and the sevoflurane ADE (mean difference in the Mg
2+-deficient group = 0.6 μg/kg, 95% confidence interval of the difference = −0.2 to 1.5 μg/kg).
Conclusion:
Chronic Mg
2+ deficiency decreased the threshold for epinephrine-induced arrhythmias and attenuated differences between the arrhythmogenic potential of halothane and sevoflurane, suggesting that arrhythmias are as likely to develop with sevoflurane as with halothane in the presence of coexisting magnesium deficiency and elevated catecholamines.
Objectives. The purpose of this study was to examine the effects of varying basic cycle lengths in a programmed stimulation protocol if up to seven extrastimuli were available at each basic cycle ...length.
Background. There is no uniformly accepted protocol for induction of ventricular tachycardia. Most protocols limit the number of extrastimuli to two or three but use several basic cycle lengths.
Methods. Twenty-eight patients with coronary artery disease and documented spontaneous sustained ventricular tachycardia or ventricular fibrillation were studied. In the absence of antiarrhythmic drugs, each patient underwent three inductions of ventricular tachycardia/ventricular fibrillation using sinus rhythm or right ventricular pacing at 600 or 400 ms as the basic cycle length. Up to seven extrastimuli were allowed at each basic cycle length.
Results. The maximal yield of clinical tachycardia (96%) was identical for each basic cycle length and was achieved using a maximum of seven, five and four extrastimuli for sinus rhythm and 600 and 400 ms, respectively. A basic cycle length of 400 ms required fewer extrastimuli (2.4 ± 0.7) to induce ventricular tachycardia/ventricular fibrillation than did 600 ms (2.7 ± 1.1, p = 0.014) or sinus rhythm (3.4 ± 1.2, p < 0.001). There was no significant difference in the cycle lengths of the induced ventricular tachycardia, incidence of induced ventricular fibrillation or requirement for direct current countershock.
Conclusions. The use of an adequate number of extrastimuli obviates the need for multiple basic cycle lengths for induction of ventricular tachycardia and does not increase induction of unwanted ventricular fibrillation. If only one basic cycle length is used, the ease of inducibility can be quantified in terms of the number of extrastimuli required. Fewer extrastimuli were required for induction of ventricular tachycardia if a basic cycle length of 400 ms was used. These data favor the use of ventricular pacing at a basic cycle length of 400 ms with up to at least four extrastimuli as the standard stimulation protocol for induction of ventricular tachycardia.
Although the signal-averaged ECG (SAECG) is currently the best noninvasive test to identify patients with ventricular tachycardia (VT) following myocardial infarction (MI), it is still a relatively ...insensitive test. Body surface mapping has improved the sensitivity of ECG in detecting various cardiac diseases. This study applied body surface mapping to the SAECG in the form of a clinically practical, 28-lead optimal array and compared its sensitivity and specificity with those of an orthogonal array.
Two hundred twenty-three patients with previous MI (82 with inducible VT) underwent SAECG using 28 surface electrodes from which were obtained a three-lead orthogonal array and a 28-lead optimal array (optimal). From the orthogonal array, two QRS durations (QRSd) were obtained using the combined vector magnitude method (CVM) and the earliest onset to latest offset of the three individually filtered leads (individual). From the optimal array, 28 QRSd were obtained, each defined as the duration from the earliest onset of any of the 28 leads to the offset of each individually filtered lead. QRSd > 120 msec in > or = 3 leads was considered abnormal. For CVM and individual, QRSd of > 120 msec were considered abnormal. While the specificity of each method was comparable (84%, 86%, and 84% for CVM, individual, and optimal, respectively), the sensitivity of optimal (70%) was significantly greater than the sensitivity of CVM (54%) (p = 0.001) or individual (59%) (p = 0.004). The magnitude of improvement in sensitivity, 16% and 15%, respectively, was equal for anterior (n = 120) and inferior (n = 103) infarctions.
Body surface mapping using the 28-lead optimal array significantly improved the sensitivity of the SAECG without loss of specificity. The increased sensitivity was of equal magnitude for inferior and anterior infarctions. The superiority and practicality of the 28-lead optimal array make it worth pursuing as an option for further refinement in SAECG:
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