[Helminth fauna in a semi-arid host species - scaled quail (Callipepla squamata)].

Helminths were examined from 145 scaled quail (Callipepla squamata) collected during the 2012-2013, 2013-2014 and 2014-2015 hunting seasons from a semi-arid region of Texas that spans four ecoregions. Helminth infracommunities were species poor, averaging 1.7 (range 1-4) species. Six species occurred within the component community of which one (Oxyspirura petrowi) is known to be pathogenic to quail. Aulonocephalus pennula was most abundant (9991 individuals, 95% of total) followed by O. petrowi (391 individuals, 4%). Each of the remaining four species was rare (≤21% prevalence) and contributed few individuals (<1%). In the High Plains ecoregion, prevalence of O. petrowi was higher in host collections made during the 2013-2014 hunting season than either hunting seasons 2012-2013 or 2014-2015 and was higher in the High Plains ecoregion than the Edwards Plateau ecoregion during the 2013-2014 hunting season. Mean abundance of A. pennula and O. petrowi was higher in scaled quail from the High Plains ecoregion than the Edwards Plateau ecoregion. Our results provide new information about helminth fauna in scaled quail, persistence of indirect lifecycle helminth species within a semi-arid region, and the occurrence of pathogenic helminth species within this host species.

Helminth community and host dynamics in northern bobwhites from the Rolling Plains Ecoregion, U.S.A.

One hundred and sixty-one northern bobwhites (Colinus virginianus; hereafter 'bobwhite') were examined from the Rolling Plains ecoregion of Texas and western Oklahoma from 2011 to 2013. Complete necropsies yielded 13 species, of which two are new host (Gongylonema phasianella) and region (Eucoleus contortus) records and three (Dispharynx nasuta, Tetrameres pattersoni and Oxyspirura petrowi) are known to cause morbidity and mortality. Of the species found, Aulonocephalus pennula commonly occurred, Oxyspirura petrowi was intermediate in prevalence, and the remaining species were rare. Species richness was similar compared to studies from the southeastern U.S., but higher than studies from the same region. In addition, 12 of the 13 species were heteroxenous helminths, supporting the theory that heteroxenous helminths in semi-arid regions are more successful than monoxenous helminths. Prevalence and abundance of A. pennula and O. petrowi were higher in adult bobwhites than in juveniles. Abundance of A. pennula and O. petrowi was higher at southern locations compared to northern locations in the study area. Our study is the first to provide a current assessment of the bobwhite helminth community across the Rolling Plains ecoregion of the U.S.

Infection levels of the eyeworm Oxyspirura petrowi and caecal worm Aulonocephalus pennula in the northern bobwhite and scaled quail from the Rolling Plains of Texas.

Northern bobwhite (Colinus virginianus) and scaled quail (Callipepla squamata) have experienced chronic declines within the Rolling Plains ecoregion of Texas. Parasitic infection, which has long been dismissed as a problem in quail, has not been studied thoroughly until recently. A total of 219 northern bobwhite and 101 scaled quail from Mitchell County, Texas were captured and donated from 2014 to 2015, and examined for eyeworm (Oxyspirura petrowi) and caecal worm (Aulonocephalus pennula) infections. In 2014, bobwhites averaged 19.6 ± 1.8 eyeworms and 98.6 ± 8.2 caecal worms, and 23.5 ± 2.1 eyeworms and 129.9 ± 10.7 caecal worms in 2015. Scaled quail averaged 4.8 ± 1.0 eyeworms and 50 ± 6.8 caecal worms in 2014, and 5.7 ± 1.3 eyeworms and 38.1 ± 7.1 caecal worms in 2015. This study expands the knowledge of parasitic infection in quail inhabiting the Rolling Plains of Texas. A significant difference was documented in O. petrowi infection between species but there was no significant difference in A. pennula between quail species. No significant difference was detected in parasite infection between the sexes of both northern bobwhite and scaled quail. This study also documented the highest reported O. petrowi infection in both species of quail. Additional research is needed on the life history and infection dynamics of O. petrowi and A. pennula infections to determine if there are individual- and/or population-level implications due to parasitic infection.

Protein-Derived Acetaminophen-Cysteine Can Be Detected After Repeated Supratherapeutic Ingestion of Acetaminophen in the Absence of Hepatotoxicity.

UNLABELLED: Generation of protein-derived acetaminophen-cysteine (APAP-CYS) is reported after ingestion of large and therapeutic dosages of acetaminophen in healthy and in liver-damaged patients. The incidence of protein-derived APAP-CYS adducts in repeated supratherapeutic dosages of APAP is not known. METHODS: for 12 months, a standardized and comprehensive questionnaire was used to interview every consecutive patient at a pain management clinic. Patients found to ingest more than 4 g of APAP per day for a minimum of 14 consecutive days at the time of the encounter were invited to have blood drawn for hepatic transaminases and APAP-CYS adduct levels. Twelve subjects out of 990 interviewees met inclusion criteria. Ten of the 12 had measurable protein-derived APAP-CYS, none had evidence of liver injury. Patients that ingest repeated supratherapeutic amounts of APAP over several weeks may generate APAP-CYS protein adducts in the absence of hepatic injury.

Live eyeworm (Oxyspirura petrowi) extraction, in vitro culture, and transfer for experimental studies.

Northern bobwhite ( Colinus virginianus ) have experienced a dramatic decline in West Texas over the last 3 yr, and investigations are underway to evaluate the role of parasites in this decline. One of the key parasites being investigated is the eyeworm (Oxyspirura petrowi). Live eyeworms were extracted from both live and dead northern bobwhites, and in vitro survival was tested using 10 liquid media. Eyeworms placed in an egg white and physiological saline solution lived for at least 36 days. Live O. petrowi placed into the eyes of uninfected pen-raised bobwhites were monitored for 21 days to demonstrate successful transfer. Eyeworm behavior during feeding, mating, and development were monitored. This study is important to research that requires "banking" of live O. petrowi from wild-captured definitive hosts for life history studies and assessing the impact of O. petrowi on host individuals.

Differential enamel and osteogenic gene expression profiles in odontogenic tumors.

Odontogenic tumors occur within the jaw bones and may be derived from odontogenic epithelium or ectomesenchyme or contain active components of both tissue types. We investigated the gene expression profile of enamel matrix proteins (EMPs), genes related to osteogenesis, and the mineralization process in odontogenic tumor cell populations focusing on an ameloblastoma (AB-1), a keratocystic odontogenic tumor (KCOT-1), and a calcifying epithelial odontogenic tumor (CEOT-1). All cell populations were shown to be epithelial in origin by CK14 expression. All tested EMPs were expressed by all odontogenic tumor cell types, with higher transcript levels seen in the AB-1 population especially for AMEL, AMBN, and ODAM. CEOT-1 cell populations showed a greater content of ALP-positive cells as well as higher ALP mRNA levels. Using qRT-PCR, we found a higher expression of 8 genes in the CEOT-1 compared to the AB-1 and KCOT-1. In this study we demonstrated the establishment of AB-1, KCOT-1 and CEOT-1 cell populations. The unique gene expression profiles of AB-1, KCOT-1, and CEOT-1 cells and their interactions with the surrounding microenvironment may support their unique tumor development, progression, and survival.

Comparison of the temperature profile and pathological effect at unipolar, bipolar and phased radiofrequency current configurations.

With a multi-electrode catheter, phased radiofrequency (RF) delivers current between each electrode and a backplate as well as between adjacent electrodes. This study compared the tissue heating and lesion dimensions created by phased and standard RF. Ablation was performed on the in vivo thigh muscles in 5 pigs. Six lesions were created on each thigh muscle using phase angle 0 degrees RF, 127 degrees RF, 180 degrees RF with and without a backplate, and standard RF in bipolar and sequential unipolar configurations. Two plunge needles, each with 6 thermocouples 1 mm apart, were inserted into the tissue with one needle beside an electrode and the other midway between electrodes for tissue temperature measurement. The 0 degrees RF created lower tissue temperatures and smaller lesions between electrodes than those beside electrode. With 127 degrees and 180 degrees RF, tissue temperature and lesion dimensions between electrodes were similar to beside electrode, while the 127 degrees RF created higher tissue temperature and deeper lesions than 180 degrees RF (both with and without a backplate) at both sites. Standard RF bipolar ablation created similar tissue temperatures and lesion depths at both sites, but required greater power than the 127 degrees RF. Standard RF sequential unipolar ablation created only a slight temperature increase and no lesions between electrodes 3 and 4. As judged by tissue temperature, lesion depth and uniformity, and RF power requirement, 127 degrees RF may be a better energy configuration for linear ablation than the other RF modalities tested.

Knowledge, attitudes and practices regarding evidence-based medicine and outcome assessment: a survey of British Columbia cataract surgeons.

BACKGROUND: While the advantages of practising evidence-based medicine are well-documented, it is frequently suggested that doctors' attitudes are a major roadblock to its implementation. We carried out a survey to determine the knowledge, attitudes and practices of British Columbia cataract surgeons regarding evidence-based medicine and outcome assessment. METHODS: The survey was conducted in the spring of 1999. The study population was drawn from the directory of the British Columbia College of Physicians and Surgeons. A 16-item questionnaire designed to elicit the knowledge of, attitudes toward and use of evidence-based medicine and outcome assessment was sent to all surgeons performing cataract surgery in British Columbia. RESULTS: Of the 103 eligible participants, 70 (68%) returned completed questionnaires. Surgeons affiliated with the University of British Columbia were more likely to respond than those not affiliated with the university (81% vs. 58%) (p < 0.05). Most surgeons (89%) viewed the responsibility of monitoring quality of care as primarily their own. Although 79% of the respondents felt that outcome assessment is an effective method for determining quality of care, less than half (49%) reported that they routinely include some form of outcome assessment in their clinical practice. There was wide variation in the respondents' understanding of the nature of outcome assessment and evidence-based medicine. Respondents professed little inclination or motivation to committing time or resources to an outcome program. They also expressed concerns over the use of outcome data for external management activities. INTERPRETATION: Cataract surgeons in British Columbia clearly appreciate the advantages of outcome assessment, but translation of this understanding into practice is limited. There appears to be a need for further education on outcome assessment and evidence-based medicine through academic bodies and professional societies.

Effect of four laboratory decontamination procedures on the quantitative determination of cocaine and metabolites in hair by HPLC-MS.

The testing for drugs of abuse in hair is increasingly used to detect illicit substances. Laboratories have implemented various decontamination, or washing, procedures in order to eliminate concerns regarding potential contamination of the hair with drug from the environment. However, the effect of these decontamination procedures on drug incorporated into the hair shaft via systemic exposure is unknown. This study evaluated the effect of four simple laboratory wash procedures on the quantitative measurement of cocaine and its metabolites in hair from rats administered cocaine by intraperitoneal injection. Washes included (1) methanol only; (2) 0.1 M phosphate buffer, pH 6.0; (3) 0.1 M phosphate buffer, pH 8.0; and (4) isopropanol and phosphate buffer, pH 5.5. Cocaine and its major metabolites, benzoylecgonine, norcocaine, ecgonine methyl ester, and cocaethylene, were analyzed using high-performance liquid chromatography coupled to atmospheric pressure electrospray ionization mass spectrometry. All four washes resulted in significant differences from unwashed hair controls (p < or = 0.05) for some or all of the detectable analytes. Because different wash procedures lead to significant differences in the measured concentrations of analytes in hair known to contain drug, quantitative data must be interpreted cautiously based on the wash procedures employed.

Interpreting physical evidence of predation on hoofstock and management alternatives for coping with predators.

Predation on domestic and wild hoofstock is a serious management constraint, especially for small ruminants and neonates. Diagnosis of the species of predator responsible for livestock losses relies on the ability to interpret direct and indirect evidence of predation. This article summarizes the physical evidence associated with depredation events and includes the most common species of predators encountered in North America. Management alternatives for coping with predators are discussed.

Amphetamine and N-acetylamphetamine incorporation into hair: an investigation of the potential role of drug basicity in hair color bias.

To elucidate the role of drug basicity in the preferential incorporation of certain drugs into dark hair rather than light hair, Long-Evans rats were dosed with amphetamine or its non-basic analogue N-acetylamphetamine (N-AcAp) and their hair evaluated for drug content. Rats were shaved prior to dosing. On the 14th day after dosing, hair from the same area that was shaved prior to dosing was shaved and collected. After the addition of amphetamine-d3 or N-AcAp-d3 as an internal standard, hair samples (20 mg) were digested in 1M NaOH at 37 degrees C. Digested solutions were then extracted with n-butyl chloride/chloroform (4:1, v/v). After drying and reconstituting, samples were injected onto a ThermoQuest TSQ liquid chromatography-tandem mass spectrometry instrument for analysis. Black hair from rats dosed with amphetamine (n = 8) was found to contain 6.44 +/- 1.31 (SD) ng amphetamine/mg hair. White hair from the same rats contained 2.04 +/- 0.58 ng amphetamine/mg hair. In contrast, no difference in N-AcAp content was found between black hair (0.87 +/- 0.08 ng N-AcAp/mg hair) and white hair (0.83 +/- 0.15 ng N-AcAp/mg hair) from rats dosed with N-AcAp (n = 8).

Relationship of melanin degradation products to actual melanin content: application to human hair.

Methods not only for characterizing but also for quantitating melanin subtypes from the two types of melanin found in hair--eumelanin and pheomelanin--have been established. In relation to testing for drugs of abuse in hair, these methods will allow for correction of drug binding to specific melanin subtypes and will serve to improve drug measurement in hair. 5,6-Dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) make up the majority of the eumelanin polymer while benzothiazene units derived from 2-cysteinyl-S-Dopa (2-CysDopa) and 5-cysteinyl-S-Dopa (5-CysDopa) compose the majority of the pheomelanin polymer. Our results show that: (1) pyrrole-2,3-dicarboxylic acid (PDCA) and pyrrole-2,3,5-tricarboxylic acid (PTCA), markers for DHI and DHICA units, respectively, are produced in 0.37 and 4.8% yields, respectively, when melanins are subjected to alkaline hydrogen peroxide degradation, (2) 3-aminotyrosine (3AT) and 4-amino-3-hydroxyphenylalanine (AHP), markers for 2-CysDopa and 5-CysDopa, respectively, are produced in 16 and 23% yield, respectively, when subjected to hydriodic acid hydrolysis, and (3) that black human hair contains approximately 99% eumelanin and 1% pheomelanin, brown and blond hair contain 95% eumelanin and 5% pheomelanin; and red hair contains 67% eumelanin and 33% pheomelanin. These data will allow deeper investigation into the relationship between melanin composition and drug incorporation into hair.

Pacing during ventricular fibrillation: factors influencing the ability to capture.

INTRODUCTION: Recent studies showed that pacing atrial and ventricular fibrillation (VF) is possible. The studies presented here determined which parameters influence the efficacy of a pacing train to capture fibrillating ventricular myocardium. Electrode type, current strength, order of pacing trains, polarity, and VF morphology preceding the pacing trains were investigated. METHODS AND RESULTS: A 504-electrode recording plaque sutured to the right ventricle of pig hearts was used to record the activations of VF and those resulting from the pacing stimulation. Capture of VF by pacing was determined by observing an animated display of the first temporal derivative of the electrograms. A series of electrodes in a line captured the heart more frequently during VF than did a point electrode. Increasing the current strength to 10 x diastolic pacing threshold increased the incidence of capture, but increasing this strength further did not. The second or third train of 40 stimuli had greater capture rates than did the first train during the same VF episode. Anodal and cathodal unipolar, and bipolar stimulation were equally efficacious in capturing VF. VF activation during the 1-second interval preceding pacing was more organized for pacing trains that captured than those that did not. The highest incidence of capture, 46% to 61% of pacing trains, occurred with a line of electrodes at 10 x diastolic pacing threshold delivered by the second or third train. CONCLUSION: The probability of a pacing train capturing fibrillating myocardium can be influenced by the pacing protocol parameters.

The incorporation of cocaine and metabolites into hair: effects of dose and hair pigmentation.

The relationship between xenobiotic concentrations in hair and the degree of systemic xenobiotic exposure is poorly defined. The purpose of this study was to evaluate the effect of dose, time, and pigment on the hair incorporation of cocaine (COC) and its metabolites, benzoylecgonine (BE), ecgonine methyl ester (EME), and norcocaine (NCOC). COC was administered by the i.p. route to male Long-Evans (LE) rats at three doses (5, 10, and 20 mg/kg) once daily for 5 days. Fourteen days after the initial injection, the hair was collected and analyzed by gas chromatography/mass spectrometry for the compounds of interest. COC, EME, and NCOC were preferentially incorporated into pigmented hair in a dose-dependent manner. None of the analytes were detected in nonpigmented hair. The plasma pharmacokinetic profile of each analyte was determined at each dose. After normalizing for the plasma concentrations, the incorporation of COC into pigmented hair was 2 orders of magnitude greater than BE. The time course of COC and metabolite distribution into hair was also investigated from 1 h to 14 days after a single dose. After COC disappears from plasma, there is a 3-day delay before maximal hair concentrations are reached in pigmented hair. In nonpigmented hair, concentrations of BE and COC did not exceed 0.25 ng/mg and were undetectable after 4 h and 2 days, respectively. This study demonstrates that the pigment-mediated differences in the incorporation of COC and its metabolites noted at 14 days after dosing are also evident a few hours after drug administration.

Effects of intrathecal morphine on the ventilatory response to hypoxia.

BACKGROUND: Intrathecal administration of morphine produces intense analgesia, but it depresses respiration, an effect that can be life-threatening. Whether intrathecal morphine affects the ventilatory response to hypoxia, however, is not known. METHODS: We randomly assigned 30 men to receive one of three study treatments in a double-blind fashion: intravenous morphine (0.14 mg per kilogram of body weight) with intrathecal placebo; intrathecal morphine (0.3 mg) with intravenous placebo; or intravenous and intrathecal placebo. The selected doses of intravenous and intrathecal morphine produce similar degrees of analgesia. The ventilatory response to hypercapnia, the subsequent response to acute hypoxia during hypercapnic breathing (targeted end-tidal partial pressures of expired oxygen and carbon dioxide, 45 mm Hg), and the plasma levels of morphine and morphine metabolites were measured at base line (before drug administration) and 1, 2, 4, 6, 8, 10, and 12 hours after drug administration. RESULTS: At base line, the mean (+/-SD) values for the ventilatory response to hypoxia (calculated as the difference between the minute ventilation during the second full minute of hypoxia and the fifth minute of hypercapnic ventilation) were similar in the three groups: 38.3+/-23.2 liters per minute in the placebo group, 33.5+/-16.4 liters per minute in the intravenous-morphine group, and 30.2+/-11.6 liters per minute in the intrathecal-morphine group (P=0.61). The overall ventilatory response to hypoxia (the area under the curve) was significantly lower after either intravenous morphine (20.2+/-10.8 liters per minute) or intrathecal morphine (14.5+/-6.4 liters per minute) than after placebo (36.8+/-19.2 liters per minute) (P=O.003). Twelve hours after treatment, the ventilatory response to hypoxia in the intrathecal-morphine group (19.9+/-8.9 liters per minute), but not in the intravenous-morphine group (30+/-15.8 liters per minute), remained significantly depressed as compared with the response in the placebo group (40.9+/-19.0 liters per minute) (P= 0.02 for intrathecal morphine vs. placebo). Plasma concentrations of morphine and morphine metabolites either were not detectable after intrathecal morphine or were much lower after intrathecal morphine than after intravenous morphine. CONCLUSIONS: Depression of the ventilatory response to hypoxia after the administration of intrathecal morphine is similar in magnitude to, but longer-lasting than, that after the administration of an equianalgesic dose of intravenous morphine.

Reduction of atrial defibrillation threshold with an interatrial septal electrode.

BACKGROUND: The standard lead configuration for internal atrial defibrillation consists of a shock between electrodes in the right atrial appendage (RAA) and coronary sinus (CS). We tested the hypothesis that the atrial defibrillation threshold (ADFT) of this RAA-->CS configuration would be lowered with use of an additional electrode at the atrial septum (SP). METHODS AND RESULTS: Sustained atrial fibrillation was induced in 8 closed-chest sheep with burst pacing and continuous pericardial infusion of acetyl-ss-methylcholine. Defibrillation electrodes were situated in the RAA, CS, pulmonary artery (PA), low right atrium (LRA), and across the SP. ADFTs of RAA-->CS and 4 other lead configurations were determined in random order by use of a multiple-reversal protocol. Biphasic waveforms of 3/1-ms duration were used for all single and sequential shocks. The ADFT delivered energies for the single-shock configurations were 1.27+/-0.67 J for RAA-->CS and 0. 86+/-0.59 J for RAA+CS-->SP; the ADFTs for the sequential-shock configurations were 0.39+/-0.18 J for RAA-->SP/CS-->SP, 1.16+/-0.72 J for CS-->SP/RAA-->SP, and 0.68+/-0.46 J for RAA-->CS/LRA-->PA. Except for CS-->SP/RAA-->SP versus RAA-->CS and RAA-->CS/LRA-->PA versus RAA+CS-->SP, the ADFT delivered energies of all of the configurations were significantly different from each other (P:<0. 05). CONCLUSIONS: The ADFT of the standard RAA-->CS configuration is markedly reduced with an additional electrode at the atrial SP.

The effects of collection methods on oral fluid codeine concentrations.

The use of a variety of alternative biological specimens such as oral fluid for the detection and quantitation of drugs has recently been the focus of considerable scientific research and evaluation. A disadvantage of drug testing using alternative specimens is the lack of scientific literature describing the collection and analyses of these specimens and the limited literature about the pharmacokinetics and disposition of drugs in the specimen. Common methods of oral fluid collection are spitting, draining, suction, and collection on various types of absorbent swabs. The effect(s) of collection techniques on the resultant oral fluid drug concentration has not been thoroughly evaluated. Reported is a controlled clinical study (using codeine) that was designed to determine the effects of five collection techniques and devices on oral fluid codeine concentrations. The collection techniques were control (spitting), acidic stimulation, nonacidic stimulation, and use of either the Salivette or the Finger Collector (containing Accu-Sorb) oral fluid collection devices. Preliminary data were collected from two subjects using the Orasure device. The in vitro drug recovery was also evaluated for the Salivette and the Finger Collector devices. With the exception of a single time point, codeine concentrations in specimens collected by the control method (spitting) were consistently higher than concentrations in specimens collected by the other methods. The control collection concentrations averaged 3.6 times higher than concentrations in specimens collected by acidic stimulation and 1.3 to 2.0 higher than concentrations in specimens collected by nonacidic stimulation or collection using either the Salivette or the Finger Collector devices. When calculated using oral fluid codeine concentrations from the clinical study, the elimination rate constant, t(1/2), AUC and the peak oral fluid concentrations demonstrated device differences. The slope of the elimination curve for codeine using the acidic collection method exceeded that of the other four methods. As a result, the t(1/2) for the acidic method was significantly less than that of the control method (1.8 vs. 3.0 h, respectively). Oral contamination contributed to the control method having higher AUC than that calculated using the other methods. There was considerable variation in peak codeine concentrations between devices and between individuals within each collection method. When samples were collected simultaneously with the Salivette and the Finger Collector, the mean codeine concentrations were similar. We were able to recover > or = 500 microL of oral fluid from 81.8% of the clinical samples collected with the Salivette. However, we were able to recover this volume from only 25.5% of the samples collected with the Finger Collector. In addition, the in vitro drug recoveries were lower using the Finger Collector. When oral fluid was collected nearly simultaneously by the control method and by use of the Salivette, mean control codeine concentrations were 2.3 times higher, but the duration of detection was similar for both methods.

Three-dimensional mapping of spontaneous ventricular arrhythmias in a canine thrombotic coronary occlusion model.

INTRODUCTION: Ventricular tachycardia (VT) and ventricular fibrillation (VF) induced by thrombotic coronary occlusion were mapped in three dimensions in ten dogs. METHODS AND RESULTS: Thrombotic occlusion was induced using a wire to deliver current to the proximal left circumflex artery (LCX). In nine dogs, nonsustained VT (NSVT) arose from numerous focal sites. Sustained VT was initiated in six dogs (VT group) by a focus near or in the ischemic region. VT was maintained by a focus in the ischemic border in three dogs and by macroreentry that involved both the ischemic and nonischemic regions in the other three dogs. In five dogs, VT degenerated into VF due to intramural reentry in different locations. Mean total activation time (AT), the time for activation to traverse the ventricles, for a sinus beat when LCX current was first applied was 40 +/- 4 msec. In the four dogs in which VT occurred 3 to 7 minutes after total occlusion, sinus AT increased to 98 to 146 msec just before VT. Sinus AT in the four dogs without VT was always <98 msec. Mean AT of the first ten cycles of VT was significantly longer in those VTs that degenerated into VF (169 +/- 29 msec) than in those that did not (81 +/- 12 msec). CONCLUSION: Thrombotic LCX occlusion induced NSVT in 90%, VT in 60%, and VF in 50% of dogs. Focal mechanisms caused most NSVTs and VT initiation. VT was maintained by a focus near or in the ischemic region or by macroreentry involving both the ischemic and nonischemic regions. AT identified animals in which VT occurred soon after LCX occlusion and in which VT progressed to VF.

A telemetry system for the study of spontaneous cardiac arrhythmias.

The characteristics of spontaneous cardiac arrhythmias leading to sudden cardiac death are largely unknown. To study arrhythmias in animal models, an eight-channel implantable radio telemetry system has been developed to record continuously cardiac electrograms over a period of weeks to months, with maintenance restricted to changing batteries. The inputs are connected in a unipolar manner. Each channel has a gain of fifty and is AC coupled, band limited to 0.07-260 Hz. The signals are digitized with 12 bits resolution at 1000 samples/s. The amplifiers, analog-to-digital converter, and control logic are packaged in an implantable unit. An umbilical cable is passed through the skin to an external backpack unit for power and data transmission. A custom serial interface card, a PC/104 form factor 25-MHz 80386-based single-board computer with a PCMCIA wireless local area network (WLAN) card, and battery power supply make up the backpack. Data are read into the parallel port of the computer, buffered, then transmitted over the WLAN to the laboratory network where it can be analyzed and archived. Approximately 12 h of 14,000 bytes/s data can be collected with each set of batteries. The system is suitable for continuous monitoring of animal models of spontaneous arrhythmias and sudden cardiac death.