Prevalence Rates of Borrelia burgdorferi (Spirochaetales: Spirochaetaceae), Anaplasma phagocytophilum (Rickettsiales: Anaplasmataceae), and Babesia microti (Piroplasmida: Babesiidae) in Host-Seeking Ixodes scapularis (Acari: Ixodidae) from Pennsylvania.

The etiological agents responsible for Lyme disease (Borrelia burgdorferi), human granulocytic anaplasmosis (Anaplasma phagocytophilum), and babesiosis (Babesia microti) are primarily transmitted by the blacklegged tick, Ixodes scapularis Say. Despite Pennsylvania having in recent years reported the highest number of Lyme disease cases in the United States, relatively little is known regarding the geographic distribution of the vector and its pathogens in the state. Previous attempts at climate-based predictive modeling of I. scapularis occurrence have not coincided with the high human incidence rates in parts of the state. To elucidate the distribution and pathogen infection rates of I. scapularis, we collected and tested 1,855 adult ticks statewide from 2012 to 2014. The presence of I. scapularis and B. burgdorferi was confirmed from all 67 Pennsylvania counties. Analyses were performed on 1,363 ticks collected in the fall of 2013 to avoid temporal bias across years. Infection rates were highest for B. burgdorferi (47.4%), followed by Ba. microti (3.5%) and A. phagocytophilum (3.3%). Coinfections included B. burgdorferi+Ba. microti (2.0%), B. burgdorferi+A. phagocytophilum (1.5%) and one tick positive for A. phagocytophilum+Ba. microti. Infection rates for B. burgdorferi were lower in the western region of the state. Our findings substantiate that Lyme disease risk is high throughout Pennsylvania.

Seasonal Activity, Density, and Collection Efficiency of the Blacklegged Tick (Ixodes scapularis) (Acari: Ixodidae) in Mid-Western Pennsylvania.

Although Pennsylvania has recently reported the greatest number of Lyme disease cases in the United States, with the largest increase for PA occurring in its western region, the population biology of the blacklegged tick (Ixodes scapularis Say) has not been adequately characterized in western PA. We studied the seasonal activity of host-seeking I. scapularis larvae, nymphs, and adults in mid-western PA over the course of a year, including a severe winter, and determined their absolute densities and collection efficiencies using replicated mark-release-recapture or removal methods. Our results are compared to those from similar studies conducted in the highly Lyme disease endemic Hudson Valley region of southeastern New York State. The seasonal activity of I. scapularis was intermediate between patterns observed in the coastal northeastern and upper Midwestern United States. Only one peak of larval activity was observed, which was later than the major peak in the Midwest, but earlier than in the northeast. Seasonal synchrony of larvae and nymphs was similar to the northeast, but the activity peaks were much closer together, although not completely overlapping as in the Midwest. Pre- and postwinter relative densities of questing adult I. scapularis were not significantly different from one another. The absolute densities and collection efficiencies of larvae, nymphs, and adults were comparable to results from classic research conducted at the Louis Calder Center in Westchester County, NY. We conclude that the population biology of I. scapularis in mid-western PA is similar to southeastern NYS contributing to a high acarological Lyme disease risk.

A Critical Review of All Known Published Records for Water Mite (Acari: Hydrachnidiae) and Mosquito (Diptera: Culicidae) Parasitic Associations From 1975 to Present.

All published records of water mite-mosquito parasitic associations since Gary R. Mullen's comprehensive review in the 1970s of the literature were critiqued to provide an up-to-date account on the identity of water mites parasitizing mosquitoes and their geographic distribution. In total, 321 records in 62 sources were identified, with each record representing an association specific to a state, province, or region within a country. The greatest number of records were from the United States (120), followed by India (106) and Canada (40). In all, 105 species of mosquitoes were parasitized, with the majority belonging to the genera Aedes sensu lato (30), Anopheles (30), and Culex (21). Records were biased toward mosquito genera with the greatest number of freshwater species and medical importance. Most water mites belonged to the genus Arrenurus, or were Parathyas barbigera (Viets 1908). Arrenurus water mites were often not identified to species, but 15 different Arrenurus species were determined in 119 records. All but one of the species (i.e., Arrenurus madaraszi Daday 1898) were only reported from Canada, Germany, or the United States. Although a greater proportion of sources reviewed by us compared with Mullen's review identified water mites down to the level of genus, to better understand the biological significance of mite and mosquito interactions, more of an effort is needed to identify the species of water mites. The availability of molecular techniques such as DNA barcoding will make this goal more attainable.

Modulation of Na+/alanine cotransport in liver sinusoidal membrane vesicles by internal divalent cations.

Rat liver basolateral plasma membrane (blLPM) vesicles resuspended in 5 mM Mg2(+)-, Ca2(+)-, Mn2(+)- or Co2(+)-containing media exhibited a markedly lower rate of Na(+)-stimulated L-alanine transport. Divalent cation inhibition of L-alanine uptake was dose dependent, and was observed only when the vesicles were pre-loaded with the divalent cations. The presence or absence of the metal ions in the extravesicular incubation media had no effect on L-alanine transport. Conversely, pretreatment of the vesicles with 0.2 mM of either EGTA or EDTA resulted in higher initial rates of L-alanine transport. This stimulation was overcome by addition of excess divalent cation to the vesicle suspension solution. Since these blLPM vesicles are primarily oriented right-side-out, the divalent cation inhibition of L-alanine transport appears to be a result of their interaction with cytosolic components of the cell membrane. Total Na+ flux as measured with 22Na+ was not affected by intravesicular 5 mM Mg2+ or Ca2+, indicating that the inhibition was not due to dissipation of the Na+ gradient. These observations suggest that intracellular divalent cations may serve to modulate L-alanine transport across the liver cell plasma membrane.

Radiofrequency catheter ablation for management of symptomatic ventricular ectopic activity.

OBJECTIVES: This study assessed the useful role of intracardiac mapping and radiofrequency catheter ablation in eliminating drug-refractory monomorphic ventricular ectopic beats in severely symptomatic patients. BACKGROUND: Ventricular ectopic activity is commonly encountered in clinical practice. Usually, it is not associated with life-threatening consequences in the absence of significant structural heart disease. However, frequent ventricular ectopic beats can be extremely symptomatic and even incapacitating in some patients. Currently, reassurance and pharmacologic therapy are the mainstays of treatment. There has been little information on the use of catheter ablation in such patients. METHODS: Ten patients with frequent and severely symptomatic monomorphic ventricular ectopic beats were selected from three tertiary care centers. The mean frequency +/- SD of ventricular ectopic activity was 1,065 +/- 631 beats/h (range 280 to 2,094) as documented by baseline 24-h ambulatory electrocardiographic (ECG) monitoring. No other spontaneous arrhythmias were documented. These patients had previously been unable to tolerate or had been unsuccessfully treated with a mean of 5 +/- 3 antiarrhythmic drugs. The site of origin of ventricular ectopic activity was accurately mapped by using earliest endocardial activation time during ectopic activity or pace mapping, or both. RESULTS: During electrophysiologic study, no patient had inducible ventricular tachycardia. The ectopic focus was located in the right ventricular outflow tract in nine patients and in the left ventricular posteroseptal region in one patient. Frequent ventricular ectopic beats were successfully eliminated by catheter-delivered radiofrequency energy in all 10 patients. The mean number of radiofrequency applications was 2.6 +/- 1.3 (range 1 to 5). No complications were encountered. During a mean follow-up period of 10 +/- 4 months, no patient had a recurrence of symptomatic ectopic activity, and 24-h ambulatory ECG monitoring showed that the frequency of ventricular ectopic activity was 0 beat/h in seven patients, 1 beat/h in two patients and 2 beats/h in one patient. CONCLUSIONS: Radiofrequency catheter ablation can be successfully used to eliminate monomorphic ventricular ectopic activity. It may therefore be a reasonable alternative for the treatment of severely symptomatic, drug-resistant monomorphic ventricular ectopic activity in patients without significant structural heart disease.

Relative importance of intracellular glutathione peroxidase and catalase in vivo for prevention of peroxidation to the heart.

The relative importance in vivo of catalase and the selenoenzyme glutathione peroxidase for protection against peroxidation was assessed in the rat heart. Each of these enzymes was modulated by feeding animals a low selenium diet either unsupplemented or supplemented with 0.5 parts per million of selenium, with or without the catalase inhibitor, 3-amino-1,2,4-triazole, in their drinking water. After 8 weeks, selenium deficient rats had 88% reductions in cytosolic and mitochondrial glutathione peroxidase activities. These reductions were accompanied by increased peroxidation in heart homogenates and mitochondrial suspensions. Since increased mitochondrial peroxidation only occurred when both the cytosolic and mitochondrial glutathione peroxidase activities were compromised, these selenoenzymes appear to work in tandem and reductions in both are a prerequisite for increased peroxidation in this organ. Peroxidation did not occur in aminotriazole treated animals even though cytosolic catalase activity was inhibited by 65-80%. Moreover, inhibition of catalase activity did not exacerbate the level of peroxidation in selenium deficient animals depleted of glutathione peroxidase activity. Because increased peroxidation was only associated with reductions in glutathione peroxidase activity irrespective of catalase activity, the selenoenzyme appears to be more important for detoxification of hydrogen peroxide in the heart.

Effect of ischaemia on overdrive suppression in isolated, blood-perfused atrial preparations of dogs.

The magnitude of overdrive suppression of the SA nodal pacemaker activity was markedly influenced by its ischaemia which was produced by occlusion of the perfusion tubing close to the sinus node artery in the in-situ and isolated canine sino-atrial node preparations. In all isolated preparations, postdrive suppression was significantly augmented after occlusion of the perfusion system for at least 120 seconds. It is concluded that total ischaemia depresses sino-atrial node function in the atropinized canine heart and that postdrive suppression is a good index of such impaired function.

The effect of selenium deficiency on peroxidative injury in the house fly, Musca domestica. A role for glutathione peroxidase.

Selenium-dependent glutathione peroxidase activity is documented for the first time in insects. Reduction in glutathione peroxidase activity in the cytosol of adult house flies by lowering selenium in the diet results in significant increases in peroxidative injury. Catalase activity, while higher in low-selenium flies than in selenium-supplemented flies, does not prevent lipid peroxidation. The discovery of glutathione peroxidase activity in insects eliminates an anomaly which partially limited the usefulness of these animals as models for the study of the antioxidant defense system.

Effects of atrial fibrillation and atrial flutter on the signal-averaged electrocardiogram.

In conclusion, atrial flutter can create significant errors in the automated time-domain analysis of the SAECG that are only apparent when the study is repeated in sinus rhythm, thus lowering the predictive accuracy of the technique in patients with atrial flutter. Atrial fibrillation rarely creates problems with time-domain analysis of the SAECG. These findings suggest that, unless the performance of a specific signal-averaging device has been evaluated in patients with atrial flutter and found to have acceptable error rates, patients with atrial flutter should not have SAECGs performed for postinfarction risk assessment.

Catheter ablation of the atrioventricular junction using radiofrequency energy and a bilateral cardiac approach.

Radiofrequency current catheter ablation was used successfully to create complete atrioventricular (AV) block in 60 of 61 patients (98%) with drug refractory supraventricular tachyarrhythmias. The remaining patient developed Mobitz I AV block and is clinically improved (clinical efficacy 100%). In 54 patients (89%), complete AV block was achieved using a right-sided approach. Patients aged > 60 years needed significantly fewer right-sided radiofrequency applications to produce complete AV block (5.3 +/- 5.3 vs 11.1 +/- 10.0; p = 0.009). In 6 of 7 patients with unsuccessful right-sided ablation, a left ventricular approach was used. In each case, 1 to 4 additional radiofrequency applications produced complete AV block. Patients with unsuccessful right-sided ablation were generally younger than those with successful ablation (50 +/- 16 vs 64 +/- 11; p = 0.007). It is concluded that catheter ablation using radiofrequency current is an extremely effective means of producing complete AV block. Older patients appear to be more susceptible to right-sided radiofrequency approaches. Left ventricular ablation easily produces complete AV block in patients refractory to right-sided attempts.

Polarity of hepatic glutathione and glutathione S-conjugate efflux, and intraorgan mercapturic acid formation in the skate.

Mechanisms of hepatic glutathione and glutathione S-conjugate efflux were investigated in isolated hepatocytes and perfused liver of the little skate (Raja erinacea). Glutathione was released by isolated skate hepatocytes at a rate of 0.12 +/- 0.03 nmol.hr-1.(mg protein)-1. In the perfused liver, glutathione concentrations in bile were high (approximately 0.7 mM) compared to hepatic tissue levels (0.61 +/- 0.11 mumol.g-1). During the first hour of perfusion, the biliary glutathione excretion rate was 3 nmol.hr-1.(g liver)-1, whereas glutathione accumulated in the recirculating perfusate at a rate of only 1.5 nmol.hr-1.(g liver)-1. Release of glutathione by isolated hepatocytes and perfused liver was not affected by the addition of acivicin, an inhibitor of gamma-glutamyltransferase (EC 2.3.2.2), to cell suspension medium or liver perfusate. 1-Chloro-2,4-dinitrobenzene (CDNB) was taken up by isolated hepatocytes, conjugated to glutathione, and released as S-(2,4-dinitrophenyl) (DNP)-glutathione. After infusion of 0.5 mumol CDNB in perfused liver, S-DNP-glutathione was concentrated in bile (0.5 mM) and was associated with choleresis. S-DNP-Conjugates of cysteinylglycine, cysteine and N-acetylcysteine, were also found in bile, suggesting intrahepatic breakdown of S-DNP-glutathione and subsequent acetylation of the resulting cysteine conjugate to form the mercapturic acid, S-DNP-N-acetylcysteine. This mercapturic acid accounted for 31% of the total S-DNP-conjugates collected in bile. In contrast, neither S-DNP-glutathione nor other S-DNP-conjugates were detected in the perfusate (less than 0.5 microM). These findings demonstrate that biliary excretion is the predominant route for efflux of glutathione and a glutathione S-conjugate from skate liver. The results also identify an intrahepatic pathway for mercapturic acid biosynthesis facilitated by biliary glutathione S-conjugate excretion.

Initial experience with the maze procedure for atrial fibrillation.

From January 1991 until May 1992, a total of 14 patients (mean age 48 years) underwent the maze procedure for refractory atrial fibrillation (mean duration, 7 years; mean number of antiarrhythmic medications, six). Three patients had had embolic events, one patient had had a cardiac arrest from flecainide, one had pulmonary fibrosis from amiodarone, and six of ten who were employed were temporarily disabled. Two patients underwent successful mitral valve repair in which the maze procedure was added as a secondary goal of the operation. Postoperative fluid retention was a problem in five patients (36%). Six patients (43%) were temporarily treated with an antiarrhythmic medication. Two patients (14%) with preoperative sick sinus syndrome required pacemakers. One patient was discharged from the hospital but died suddenly less than 1 month after the operation (7% operative mortality) of hyperkalemia caused by acute renal failure. All patients beyond 3 postoperative months (100% "cure") are receiving no antiarrhythmic medications, have sinus rhythm, or have p-wave tracking with ventricular pacing. Atrial contraction has been documented by cinegraphic magnetic resonance imaging studies and by Doppler echocardiography performed when sinus rhythm had resumed. The maze procedure is an extensive operation but is indicated for selected patients who have the severe sequelae of atrial fibrillation.

Catheter ablation for recurrent ventricular tachycardia.

A 78-year-old man had sustained ventricular tachycardia refractory to drug therapy. An antitachycardia pacemaker and a cardioverter-defibrillator were implanted. It was suspected that rate crossover was occurring between his sinus rhythm and his antitachycardia pacemaker detection rate. He also had frequent discharges from his implantable cardioverter-defibrillator. Because of these problems, he was considered a candidate for catheter ablation treatment of his ventricular tachycardia. The procedure was completed successfully and long-term follow-up has been uneventful. Catheter ablation is recommended as a treatment option for patients who have ventricular tachycardia that is refractory to drug therapy and combined-device therapy, and who have rate crossover.

Pacemaker and defibrillator combination therapy for recurrent ventricular tachycardia.

The judicious use of antitachycardia pacemakers can enhance the benefits of automatic implantable cardioverter defibrillators in certain patients. Both devices were implanted in 10 highly selected patients with drug-refractory pace-terminable sustained ventricular tachycardia. During the observation period of 8 +/- 4.8 months, the automatic pacemakers detected 1,542 episodes of ventricular tachycardia and appropriately managed 1,373. The automatic implantable defibrillator was activated at least once in every patient; on two documented occasions, the defibrillator discharged because the automatic pacemaker accelerated the tachycardia. Concomitant antiarrhythmic drugs could be reduced but not withdrawn. With meticulous device programming and testing, the two systems in combination can work synergistically to manage malignant ventricular arrhythmias in carefully selected patients.

Transcatheter electrical AV junction ablation: predictors of success.

The initial and long-term results of transcatheter electrical ablation in 29 patients with drug-refractory supraventricular tachyarrhythmias were analyzed. Ablation was immediately successful (defined as induction of chronic complete heart block) in 25 patients (86.2%). Among the group in whom ablation was unsuccessful, there were more patients with ectopic atrial tachycardia and a higher incidence of narrow QRS escape rhythm following the initial ablation. A His amplitude equal to or greater than 0.3 mV was correlated with success. Complications of ablation included deep venous thrombosis and ventricular arrhythmias. Post-ablation stress testing was superior to ambulatory monitoring in identifying early return of atrioventricular conduction.

Atrial pacemaker leads compared.

In order to analyze the impact of different polarity and electrode designs on the acute pacing and sensing characteristics of pacemaker leads, 80 patients with complete heart block or sinus node dysfunction undergoing pacemaker implantation received eight different leads from five manufacturers. Once the leads were positioned, volt and current thresholds, P wave, peak-to-peak, and slew rate were assessed prospectively. There was no statistically significant difference between acute pacing thresholds, sensing characteristics, or unipolar and bipolar pacing thresholds. Active fixation leads allow atrial mapping and lead placement in areas generally inaccessible to tined tip leads. This is an advantage, especially for patients with a history of open heart surgery.

The Maze procedure: surgical therapy for refractory atrial fibrillation.

Although atrial fibrillation is well tolerated by most patients, in some patients the consequences may be severe. The Maze procedure is a new open-heart operation that creates a carefully designed maze of incisions in the atrial myocardium; this maze then acts as an electrical conduit to channel atrial impulses from the sinoatrial node to the atrioventricular node. The Maze procedure has been shown to restore sinus rhythm and atrial systole (thus reducing the risk of thromboembolism), improve hemodynamics, alleviate palpitations, and eliminate the need for antiarrhythmic and anticoagulant drugs. We describe our first patient to undergo this operation.

Significance of alterations in hepatic antioxidant enzymes. Primacy of glutathione peroxidase.

The relative contributions of catalase and the selenoenzyme glutathione peroxidase (GSH-Px) were elucidated in the rat liver by selectively modulating the activities of these enzymes using dietary selenium (Se) and the catalase inhibitor 3-amino-1,2,4-triazole (3-AT). Increased peroxidation occurred only in Se-deficient rats with markedly reduced cytosolic and mitochondrial GSH-Px activities. Although 3-AT treatment resulted in a 75% reduction of hepatic catalase activity and also a 20% reduction of both cytosolic and mitochondrial superoxide dismutase (SOD) activity, no incremental increase in peroxidation was observed over that associated with Se deficiency. In Se-deficient animals, treatment with 3-AT resulted in a doubling of cytosolic GSH-Px. This was associated with a 49% elevation in hepatic Se suggesting that increased Se may have contributed to the enhanced GSH-Px activity. These results suggest that GSH-Px plays the pivotal role in preventing hepatic peroxidation. Furthermore, the effects of 3-AT in vivo are not restricted to inhibition of catalase activity insofar as it also affects cytosolic GSH-Px activity and cytosolic and mitochondrial SOD activities.

Computer-assisted ECG interpretation for confirmation of premature atrial complexes.

UNLABELLED: Current programs for computerized ECG analysis are not interactive. We developed custom software for computer-assisted ECG interpretation that functioned interactively with an observer directing the computerized process. The software was first used for recognition of PACs superimposed on ST-T waveforms. The interactive process included 6 steps. 1) The computer displayed the 12-lead ECG and the user selected the most frequent QRS-T waveforms for averaging. 2) The computer generated and displayed the averaged QRS-T waveform. 3) The user selected waveforms suspected to have PACs superimposed on the ST-T segments. 4) The computer generated and displayed the difference waveform by subtracting the average waveform from the suspect waveforms. 5) The user recognized and p-waves in the difference waveform and marked the onset and offset by positioning the cursor and clicking. 6) The computer then measured p-wave amplitudes, durations, and areas and displayed the recognized p-wave. The program was developed using digital data from 2 ECGs and tested on 39 ECGs with suspected PACs and 26 control ECGs. RESULTS: The software and user interaction recognized 79 PACs in the suspect group. Control ECGs were analyzed using 3 complexes with the same leads and onsets as the test group. Of the 79 PACs found in the suspect group, mean values included an area under the curve of 4.0 +/- 3.2 microV-s for the test group versus 0.4 +/- 0.4 microV-s for the control (P < 0.001) and peak-to-trough voltage amplitudes of 104 +/- 66 microV versus 15 +/- 7 microV for the control (P < 0.001). The average time of onset of the premature complexes was 282 +/- 120 msec, and their duration was 100 +/- 28 msec. CONCLUSION: Custom software combined the superior human pattern recognition with the digital signal processing of the computer. This enhanced recognition of ectopic atrial activity.