bluuebunny/crossref_metadata_2025 huggingface dataset:
Computation of Heart Surface Potentials Using the Surface Source Model
Authors: SIMMS HOWARD D. , GESELOWITZ DAVID B.
Published: May 2007

Heart Surface Source Model. Introduction: The bidomain model of the heart leads to the result that the volume density of cardiac current source moment is proportional to the gradient of the macroscopic transmembrane action potential distribution. If the anisotropy ratios of the inner and outer domains (syncytia) of the myocardium are equal, then the volume distribution of cardiac sources can be replaced by an appropriate double layer on the heart surface. The double layer source distribution (heart surface source model) provides a basis for calculating heart surface potentials from cardiac sources.

Methods and Results: The heart surface model was used to calculate epicardial potentials for the normal heart as well as for a case of ischemia and of infarction. The model was also used to determine the effect of insulating the heart surface. Insulating the heart surface caused an almost fourfold increase in peak‐to‐peak amplitude of simulated electrograms, with little change in waveshape. Simulated electrograms showed good agreement with recorded electrograms reported in the literature.

Conclusion: The heart surface source model appears to provide a basis for relating heart surface potentials to the distribution of cellular action potential.
Reperfusion Arrhythmias: Role of Early Afterdepolarizations Studied by Monophasic Action Potential Recordings in the Intact Canine Heart During Autonomically Denervated and Stimulated States
Authors: VERA ZAKAUDDIN , PRIDE HARALD P. , ZIPES DOUGLAS P.
Published: May 2007

Reperfusion Arrhythmias and Afterdepolarizations. Introduction: The precise mechanism of reperfusion arrhythmias is not established. The role of early afterdepolarizations (EADs) and triggered activity in the genesis of reperfusion ventricular arrhythmia was investigated.

Methods and Results: Monophasic action potentials (MAPs) were recorded in the canine heart using Ag‐AgCl contact electrodes from the left and right ventricular endocardium and the left ventricular epicardial border zone during 10 minutes of occlusion of the proximal left anterior descending coronary artery followed by 2 minutes of reperfusion. Ventricular arrhythmias during ischemia and reperfusion were studied in three autonomically varied groups. Group 1 (n = 8) had intact autonomic neural innervation; group 2 (n =8) had bilateral transection of ansae subclavii and vagi; and group 3 (n =8) underwent bilateral transaction of ansae subclavii and vagi with bilateral ansae subclavii stimulation during reperfusion. Ventricular fibrillation (VF) on reperfusion occurred in 2, 3, and 5 animals in the innervated, denervated, and sympathetically stimulated groups, respectively. Rapid ventricular tachycardia during ansae subclavii stimulation, antecedent to VF, occurred in 4 of 5 episodes in the sympathetically stimulated group. The frequency of premature ventricular complexes, couplets, and triplets on reperfusion was not significantly different among the three groups. Phase 2 or phase 3 EADs were noted during the acute ischemic phase in 6 of 8, 7 of 8, and 7 of S animals in the three groups, respectively (and persisted during reperfusion in the majority). Thus, these EADs were not a de novo phenomenon during reperfusion. Of the 72 MAP recording sites, only one demonstrated de novo phase 2 EADs during reperfusion. EADs disappeared during reperfusion in 6 animals (prior to the onset of VF in 4), and 5 dogs developed reperfusion VF without EADs being recorded. There was no direct correlation between tbe presence of EADs during repertusion and the development of VF. The prevalence and onset of reperfusion VT was not significantly different in tbe presence of sympathetic stimulation.

Conclusion: This study demonstrates that EADs can be recorded in the majority of dogs during both ischemia and reperfusion and do not appear to be a major mechanism responsible for reperfusion ventricular tachycardia and VF.
Determination of Impulse Conduction Characteristics at a icroscopic Scale in Patterned Growth Heart Cell ultures Using Multiple Site Optical Recording of Transmemhrane Voltage
Authors: ROHR STEPHAN
Published: May 2007

MSORTV in Patterned Growth Heart Cell Cultures. It is well established that impulse propagation in cardiac tissue is determined by the interaction between active membrane properties and the passive electrical characteristics of the network formed by individual myocytes. In the past, the intricate microarchitecture of intact cardiac tissue and the limited spatial resolution of available recording techniques had rendered a systematic evaluation of the influence of the cellular microarchitecture on impulse propagation difficult. Recently, however, successful efforts have been undertaken to: (1) simplify the cellular arrangement by designing cardiac structures with defined two‐dimensional geometries; and (2) measure impulse propagation in these preparations at the cellular/subcellular scale using optical techniques. This short review considers both of these developments, i.e., patterned growth of heart cells in culture and multiple site optical recording of transmembrane voltage (MSORTV), and summarizes first results obtained with the combination of both techniques.
A Quantitative Fluoroscopic Comparison of the Coronary Sinus Ostium in Patients With and Without AV Nodal Reentrant Tachycardia
Authors: HUMMEL JOHN D. , STRICKBERGER S. ADAM , MAN K. CHING , DAOUD EMILE , NIEBAUER MARK , MORADY FRED
Published: May 2007

Coronary Sinus Ostium. Introduction: The purpose of this study was to perform a quantitative fluoroscopic analysis of the coronary sinus ostium and its relationship to the His bundle in patients with and without AV nodal reentrant tachycardia. Sites of slow pathway ablation are often near the coronary sinus ostium, which can be located within a few millimeters of the His bundle. Whether such close proximity of the coronary sinus ostium to the His bundle is unique to patients with AV nodal reentrant tachycardia is unknown.

Methods and Results: Fifty consecutive patients (mean age 39 ± 14 years) with no structural heart disease underwent electrophysiologic testing and radiofrequency ablation. The study group consisted of 28 patients with inducible AV nodal reentrant tachycardia or dual AV nodal physiology and 22 patients in the control group. A coronary sinus venogram was performed in each patient. The coronary sinus ostium was similar in size in the study group (11.4 ± 4.5 mm) and in the control group (10.5 ± 3.6 mm, P = 0.2). The coronary sinus ostium was funnel shaped in half of the study patients and in half of the control patients (P = 1.0). The mean distance from the upper lip of the coronary sinus ostium to the tip of the His bundle catheter was 9.7 ± 5.5 mm in the study group and 10.4 ± 5.1 mm in the control group (P = 0.7). The mean distance from the lower lip of the coronary sinus ostium to the tip of the His‐bundle catheter in the study group was 20.1 ± 6.1 mm and 19.5 ± 5.6 mm in the control group (P =0.7).

Conclusion: This study demonstrates a wide range of normal coronary sinus ostium diameters, morphology, and anatomic relationships with surrounding structures, with no demonstrable correlation to the presence or absence of dual AV node physiology or AV nodal reentrant tachycardia.
Slowing of the Ventricular Rate During Atrial Fibrillation by Ablation of the Slow Pathway of AV Nodal Reentrant Tachycardia
Authors: TEBBENJOHANNS JÜRGEN , PFEIFFER DIETRICH , SCHUMACHER BURGHARD , JUNG WERNER , MANZ MATTHIAS , LÜDERITZ BERNDT
Published: May 2007

Influence of Slow Pathway Ablation on Atrial Fibrillation. Introduction: The mechanisms whereby radiofrequency catheter modification of AV nodal conduction slows the ventricular response are not well defined. Whether a successful modification procedure can be achieved by ablating posterior inputs to the AV node or by partial ablation of the compact AV node is unclear. We hypothesized that ablation of the well‐defined slow pathway in patients with AV nodal reentrant tachycardia would slow the ventricular response during atrial fibrillation.

Methods and Results: In 34 patients with dual AV physiology and inducible AV nodal reentrant tachycardia, atrial fibrillation was induced at baseline and immediately after successful slow pathway ablation and at 1‐week follow‐up. The minimal, maximal, and mean RR intervals during atrial fibrillation increased from 353 ± 76,500 ± 121, and 405 ± 91 msec to 429 ± 84 (P < 0.01), 673 ± 161 (P < 0.01), and 535 ± 98 msec (P < 0.01), respectively. These effects remained stable during follow‐up at 1 week. The AV block cycle length increased from 343 ± 68 msec to 375 ± 60 msec (P < 0.05) immediately and to 400 ± 56 msec (P < 0.01) at 1‐week follow‐up. The effective refractory period of the AV node prolonged from 282 ± 83 msec to 312 ± 89 msec and to 318 ± 81 msec after 1 week (P < 0.05), respectively.

Conclusion: This study shows a decrease in ventricular response to pacing‐induced atrial fibrillation after ablation of the slow pathway in patients with AV nodal reentrant tachycardia. Since the AV nodal conduction properties could be defined, this study supports the hypothesis that the main mechanism of AV nodal modification in chronic atrial fibrillation is caused by ablation of posterior inputs to the AV node.
Temperature Monitoring in Radiofrequency Catheter Ablation of Atrial Flutter Using the Linear Ablation Technique
Authors: WEN ZU‐CHI , CHEN SHIH‐ANN , TAI CHING‐TAI , CHIANG CHERN‐EN , LEE SHIH‐HUANG , CHEN YI‐JEN , YU WEN‐CHUNG , HUANG JIN‐LONG , CHANG MAU‐SONG
Published: May 2007

Temperature Monitoring of Ablation. Introduction: Information about temperature and impedance monitoring during radiofrequency catheter linear ablation of atrial flutter bas not been reported. We proposed that a radiofrequency catheter ablation system using a closed‐loop temperature control model could decrease the incidence of coagulum formation and shorten the radiation exposure and procedure times compared with those found in a power control model.

Methods and Results: Forty patients (8 women and 32 men; mean age 64 ± 7 years) with atrial flutter were referred for radiofrequency ablation. The patients were randomized into two groups: group I patients underwent radiofrequency catheter linear ablation of atrial flutter using a power control of energy output model; and group II patients underwent the closed‐loop temperature control model with a target electrode temperature of 70°C. As compared with group II, group I patients bad a higher incidence of coagulum formation (12% vs 2%, P < 0.05), temperature shutdown (11% vs 0%, P < 0.01), and impedance shutdown (16% vs 3%, P < 0.01), more radiofrequency applications (7 ± 3 vs 4 ± 2, P < 0.01), and longer procedure time (100 ± 25 vs 75 ± 23 minutes, P < 0.05) and radiation exposure time (31 ± 10 vs 20 ± 7 minutes, P < 0.05) required for successful ablation. Larger deviations of temperature (9.0°± 2.4°C vs 5.0°± 1.2°C, P < 0.0001) and impedance (9.2 ± 2.6 ω vs 5.3 ± 1.6 ω, P < 0.0001) were also found in group I patients compared with those in group II.

Conclusions: This study demonstrated that a closed‐loop temperature control model could facilitate the effects of radiofrequency catheter ablation of the atrial flutter circuit by decreasing coagulum formation, temperature and impedance shutdown, and procedure and radiation exposure times.
Alteration of Human Placental Vascular Tone by Antiarrhythmic Medications In Vitro
Authors: OMAR HATIM A. , RHODES LARRY A. , RAMIREZ ROLANDO , ARSICH JELICA , EINZIG STANLEY
Published: May 2007

Antiarrhythmic and Placental Vessels. Introduction: Antiarrhythmic medications are commonly used during pregnancy for treatment of maternal or fetal arrhythmias, but little is known about their effect on human placental vascular tone and, consequently, placental blood flow. The objective of this study was to evaluate the tone responses caused by antiarrhythmic medications in human placental vessels from normal term pregnancies in vitro.

Methods and Results: Isolated human placental arteries and veins from uncomplicated term pregnancies incubated in Krebs'‐bicarbonate under 5% oxygen/5% carbon dioxide/balance nitrogen (PO2 35 to 38 torr) were exposed to cumulative doses of quinidine, procainamide, lidocaine, flecainide, propranolol, amiodarone, verapamil, digoxin, and adenosine after submaximal contraction with 5‐hydroxytryptamine. The study was conducted both in the presence and absence of endothelium. The addition of the tested medications caused a significant, dose‐dependent relaxation of human placental arteries and veins except for adenosine, which induced a sustained, dose‐dependent contraction of human placental vessels regardless of the presence or absence of tone. Removal of the endothelium did not alter these responses.

Conclusions: Based on these results, the medications tested should have no decremental effect on placental blood flow, with the possible exception of adenosine, which causes significant. dosedependent contraction of human placental vessels in vitro. Should similar contraction be present in vivo, it may have an adverse effect on the fetus when administering adenosine to pregnant women at term or during labor.
Origin of the Sinus Impulse
Authors: SCHUESSLER RICHARD B. , BOINEAU JOHN P. , BROMBERG BURT I.
Published: May 2007

Origin of the Sinus Impulse. It was generally accepted that the site of normal impulse origin within the atria was a single static focus within the sinus node. This review will examine how this model of impulse origin came about and has evolved. Early on, conflicting data suggested that the sinus node focus was not static and changed with interventions that changed heart rate, such as vagal stimulation. Furthermore, even with removal of the sinus node, a normal atrial rhythm was generated. High‐resolution mapping in humans and dogs showed that the initiation of the impulse was dynamic and could be multicentric, with more than one focus initiating a single beat. Shifts in the site of origin correlated with changes in rate and were consistent with P wave changes routinely observed in the standard ECG. These studies suggested multiple pacemakers were responsible for impulse initiation. However, it was not clear how these widespread pacemakers were coordinated to function synchronously. Recent canine data suggest that the node may be partially insulated from the surrounding atrium, resulting in multicentric origin starting from a single site within the node. What has evolved is a model of impulse origin with a sinus node having discrete exit sites and a dominant pacemaker within the node that can shift to other nodal sites. Complex and changing conduction out of the node, coupled with extranodal pacemakers, which can assume dominance over the node, combine with the autonomic nervous system to control heart rate and the pattern of impulse origin within the atria.
Safety of Nurse‐Administered Deep Sedation for Defibrillator Implantation in the Electrophysiology Laboratory
Authors: NATALE ANDREA , KEARNEY MARGARET M. , JOA BRANDON M. , KENT VIRGINIA , WASE ABDUL , NEWBY KEITH H. , PISANO ENNIO , GEIGER MARY J.
Published: May 2007

ICD and Sedation. Implantation of implantable cardioverter defibrillators (ICDs) in the electrophysiology (EP) laboratory has been shown to be safe. However, general endotracheal anesthesia and/or administration of sedatives is mostly performed by anesthesiologists. In 53 patients undergoing ICD implantation in the EP laboratory, we prospectively assessed whether deep sedation without endotracheal intubation can be administered by nursing personnel under medical supervision. The mean patient age was 67 ± 7 years, and the mean ejection fraction was 32 ± 8%. All ICDs were placed in the abdomen requiring lead tunneling. Patients were monitored with pulse oximetry and noninvasive blood pressure recordings. The level of consciousness and vital signs were evaluated at 5‐minute intervals. Deep sedation was induced with phenergan and midazolam and maintained with either meperidine or fentanyl. The mean doses given were as follows: phenergan 0.33 ± 0.15 mg/kg, midazolam 0.05 ± 0.03 mg/kg, meperidine 0.46 ± 0.10 mg/kg per hour, and fentanyl 1.94 ± 0.71 μg/kg per hour. None of the patients required intubation during or after the procedure. No death occurred and no patient had any recollection of the procedure. In three patients, O2 desaturation was easily managed by transient reversion of the effects of meperidine or fentanyl with naloxone. No patient experienced prolonged hospitalization after the implant (mean 2.4 ± 0.5 days). In conclusion: (1) adequate sedation for ICD implantation and testing can be administered safely by nursing staff in the EP lab; (2) optimum sedation protocols should include drugs easy to reverse in case of excessive respiratory depression; and (3) this may represent a more cost‐effective approach to ICD implantation.
Plateau Waveform Shape Allows a Much Higher Patient Shock Energy Tolerance in AF Patients
Authors: BORIANI GIUSEPPE , EDVARDSSON NILS , BIFFI MAURO , SILVESTRI PAOLO , MARTIGNANI CRISTIAN , VALZANIA CINZIA , DIEMBERGER IGOR , CHRISTOPHER MOULDER J. , MOUCHAWAR GABRIEL , POCI DRITAN , BRANZI ANGELO , KROLL MARK W.
Published: May 2007

Objectives: To evaluate the possible pain reduction of the plateau waveform in atrial fibrillation (AF) patients.

Background: Previous studies have indicated that reduced amplitude waveforms would be less painful than a conventional (65/65% tilt) biphasic waveform. Computer modeling suggested that a moderately long (10–12 msec) plateau (flat topped) shock waveform would deliver equivalent effectiveness with the lowest possible peak amplitude.

Methods: We enrolled 27 patients at two sites with persistent AF with a total of 220 shocks delivered during internal atrial cardioversion using an interleaved crossover design. Patient response was scored in three ways: (1) a verbally reported discomfort score, (2) visual analog scale (VAS), and (3) a blinded observer reporting a contraction score.

Results: All scores were significantly reduced (P < 0.0001) by the plateau waveform with impressive statistics: Verbal discomfort (3.51 ± 0.13 to 2.89 ± 0.12), VAS (7.00 ± 0.56 to 5.91 ± 0.36), and contraction scores (1.94 ± 0.12 to 1.62 ± 0.12). The average pain threshold shift (TS) for the Verbal score was 2.34, while that for the VAS score was 2.30. (This means that the patient typically could tolerate 2.34 times as much energy with the plateau waveform for the same level of verbally reported discomfort.) The contraction TS was less at 1.57. Response scores were also corrected for the shock sequence number to control for the sensitization effect from multiple shocks. This increased the TS for the Verbal score to 3.58, but the shock number was not significant for the VAS. A pulmonary artery electrode return was associated with lower pain compared with a coronary sinus position.

Conclusion: A plateau shaped biphasic waveform resulted in significantly increased shock energy pain tolerances. Controlling for session sensitization, patients tolerated over three times as much energy for the same verbally reported discomfort score.
Randomized Comparison Between Open Irrigation Technology and Intracardiac‐Echo‐Guided Energy Delivery for Pulmonary Vein Antrum Isolation: Procedural Parameters, Outcomes, and the Effect on Esophageal Injury
Authors: MARROUCHE NASSIR F. , GUENTHER JENS , SEGERSON NATHAN M , DACCARETT MARCOS , RITTGER HARALD , MARSCHANG HARALD , SCHIBGILLA VOLKER , SCHMIDT MARTIN , RITSCHER GUIDO , NOELKER GEORG , BRACHMANN JOHANNES
Published: May 2007

Introduction:
We performed a prospective study to compare efficacy and safety of both open irrigation tip (OIT) technology with intracardiac echo (ICE)‐guided energy delivery in patients presenting for PVAI.

Methods and Results:
Fifty‐three patients presenting for PVAI were randomized to ablation using an OIT catheter (Group 1, 26 patients; temperature and power were set at 50° and 50 W, respectively, with a saline pump flow rate of 30 mL/min) or radiofrequency (RF) energy delivery under ICE guidance (Group 2, 27 patients; energy was titrated based on microbubbles formation). The mean procedure time and fluoroscopy exposure were lower in Group 1 (164 ± 42 min and 7,560 ± 2,298 μGraym2 vs 204 ± 47 min and 12,240 ± 4,356 μGraym2; P = 0.005 and 0.008, respectively). Moreover, the durations of RF lesions applied per PV antrum was lower in Group 1 compared with Group 2 (5.1 ± 2.2 min vs 9.2 ± 3.2 min, P = 0.03, respectively). Within 24 hours after PVAI in 35.7% (all erythema) of Group 1 and 57.1% (21.4% erythema and 35.7% necrosis) of Group 2, patients' esophageal wall changes were documented. After 14 ± 2 months of follow up, recurrences were documented in 19.2% of Group 1 and 22.2% of Group 2 patients.

Conclusion:
Although both OIT and ICE‐guided energy delivery possess a similar effect in treating AF, OIT seems to be superior in terms of achieving isolation and shortening fluoroscopy exposure. Moreover, a lower incidence of esophageal wall injury was observed utilizing OIT for PVAI.
Risk Stratification and Prognosis in Octogenarians Undergoing Stress Echocardiographic Study
Authors: Chaudhry Farooq A. , Qureshi Ehtasham A. , Yao Siu‐Sun , Bangalore Sripal
Published: May 2007

Background: The prognostic value of stress echocardiography (SE) for the diagnosis and risk stratification of coronary artery disease in octogenarians is not well defined. Methods: Follow‐up of 5 years (mean 2.9 ± 1.0 years) for confirmed nonfatal myocardial infarction (n = 17) and cardiac death (n = 37) was obtained in 335 patients, age ≥80 years (mean age 84 ± 3 years, 44% male), undergoing SE (33% treadmill, 67% dobutamine). Left ventricular (LV) regional wall motion was assessed by a consensus of two echocardiographers and scored as per standard five‐point scale, 16‐segment model of wall motion analysis. Ischemic LV wall segment was defined as deterioration in the thickening and excursion during stress (increase in wall‐motion score index (WMSI) ≥1). Results: By univariate analysis, inducible ischemia (chi‐square = 38.4, P < 0.001), left ventricular ejection fraction (chi‐square = 41.2, P < 0.001), a history of previous myocardial infarction (chi‐square = 22.3, P < 0.01), hypertension (chi‐square = 33, P < 0.01), and age (chi‐square = 27.7, P < 0.01) were significant predictors of future cardiac events. WMSI, an index of inducible ischemia, provided incremental prognostic information when forced into a multivariable model where clinical and rest echocardiography variables were entered first. WMSI effectively stratified octogenarians into low‐ and high‐risk groups (annualized event rates of 1.2 versus 5.8%/year, P < 0.001). Conclusions: Stress echocardiography yields incremental prognostic information in octogenarians and effectively stratifies them into low‐ and high‐risk groups. Precise therapeutic decision making in very elderly patients should incorporate combined clinical and stress echocardiography data.
Effect of Obesity on Left Ventricular Structure and Myocardial Systolic Function: Assesment by Tissue Doppler Imaging and Strain/Strain Rate Imaging
Authors: Murat Tumuklu Mustafa , Etikan Ilker , Kisacik Bunyamin , Kayikcioglu Meral
Published: May 2007

Background: Obesity is associated with heart failure, cardiovascular morbitity, and mortality. A direct effect of weight on left ventricle (LV) structure and myocardial function is not well‐established. Aim: The aim of our study is to determine the effect of obesity on LV morphology and systolic function by using LV standard Doppler echocardiographic indices, myocardial Doppler imaging and strain/strain rate imaging indices. Methods: We studied 33 obese and 34 age, sex‐adjusted control subjects who had no other pathological conditions. Standard transthorasic Doppler echocardiographical measurements, reconstructed spectral pulsed wave tissue Doppler velocities, strain and strain rate imaging of six different myocardial regions were obtained. Peak systolic velocity (SR), peak systolic strain (Î), peak systolic strain rate (SR) for each region and as a global systolic longitidunal LV function mean of peak systolic strain of six myocardial regions (glsca) were compared. Results: Age, body surface area, blood pressure, and heart rate were comparable between the two groups. Obese subjects had significantly increased LV end‐diastolic volume, septal wall thickness, left atrial diameter, and decreased transmitral early to late diastolic velocity ratio. In obese subjects, reconstructed spectral pulsed‐wave tissue Doppler analysis showed significantly decreased basal lateral peak systoic (Sm) velocity (6.68 ± 1.89 vs. 8.08 ± 2.50, P < 0.05), mid lateral Sm (5.01 ± 2.17 vs. 6.78 ± 3.22, P < 0.05). Differences in regional strain rate (mid septal SR, 1.45 ± 0.23 vs. 1.63 ± 0.18, P < 0.05), regional strain (basal septum Î, 19.13 ± 3.83 vs. 22.09 ± 4.60, P < 0.05; mid‐septum Î, 18.03 ± 2.91 vs. 20.25 ± 4.77, P < 0.05; radial Î, 27.50 ± 7.32 vs. 35.53 ± 9.48, P < 0.05), and global strain (glsca, 19.38 ± 1.34 vs. 21.24 ± 2.82, P < 0.05) were identified between obese and the referent subjects. Conclusions: Obesity is associated with morphologic alterations in left ventricle and left atrium and subclinical changes in left ventricle systolic function which can be detected by strain and strain rate imaging even without overt heart disease.
A Nomogram for Measurement of Mitral Valve Area by Proximal Isovelocity Surface Area Method
Authors: Uzun Mehmet , Baysan Oben , Genc Celal , Yokusoglu Mehmet , Karaeren Hayrettin , Isik Ersoy
Published: May 2007

Introduction: Although its accuracy has been documented in many studies, the proximal isovelocity surface area (PISA) method is not used widely for mitral valve area (MVA) measurement. In this study, we prepared a new nomogram and tested its use in MVA assessment. Material and Methods: The study included 23 patients (age: 27 ± 5 years) with mitral stenosis, of whom 7 were in atrial fibrillation. The MVA was measured by four methods: planimetry (PL) (reference method), pressure‐half time (PHT), conventional PISA (CP), and nomogram (Nomo) methods. The nomogram included two unknowns: (1) r; the radius of the first PISA section; (2) a; the length of the border opposite to the PISA angle in the triangle with both adjacent borders of 1 cm. The nomogram was also tested for its popularity potential by eight echocardiographers, none of whom were included in the author list. Results: Mean MVAPL was 1.85 ± 0.53 cm2 (range: 0.72–2.99), mean MVAPHT was 1.72 ± 0.56 cm2 (range: 0.91–3.30), mean MVACP was 1.69 ± 0.45 cm2 (range: 0.97–2.54), and MVANomo was 1.70 ± 0.44 cm2 (0.96–2.49). The nomogram correlated with planimetry (r = 0.87; P < 0.001), pressure half‐time (r = 0.71; P < 0.001) and conventional PISA (r = 0.99; P = 0.000) methods. The nomogram method also correlated with planimetry in patients with atrial fibrillation (r = 0.81; P = 0.026). The echocardiographers found that the nomogram is superior to the planimetry and conventional PISA methods but inferior to the pressure half‐time method in terms of simplicity. Conclusion: The new nomogram is potentially helpful in measurement of MVA. It may be used as an additional method in assessing severity of mitral stenosis.
Trichodina myicola n. sp., a Peritrichous Ciliate from the Marine Bivalve Mya arenaria L.
Authors: UZMANN J. R. , STICKNEY A. P.
Published: May 2007

A new ciliate from the marine clam Mya arenaria is described and figured. The form is designated Trichodina myicola with specific characters as follows: Bell‐shaped to discoidal; length 31–86 microns; diam. 62–103 microns; diam. denticulate ring 29–46 microns; 26–36 denticles; diam. of basal disk 42–79 microns; adoral ciliary spiral performs slightly more than one turn; posterior ciliature in three closely applied, concentric tiers: an anterior circlet of marginal cilia, a middle circlet of overlapping membranelles, and a posterior circlet of inner cilia; macronucleus C‐shaped; micronucleus small, round, lying near outer curvature of left arm of macronucleus; large contractile vacuole present near end of left arm of macronucleus.

Taxonomy in the genus Trichodina is discussed and outlined. Special attention is given to details of the oral ciliature. T. myicola is compared with other members of the genus. A checklist of Trichodina species is presented.
Trypanosomes in American Ground Squirrels
Authors: NOBLE ELMER R. , SHIPMAN DONALD
Published: May 2007

SYNOPSIS. California ground squirrels (Citellus beecheyi) were found to be infected with trypa‐nosomes whose most striking morphological features are an unusually large kinetoplast and a long, tapering posterior end. The total length is 25.2 μ, and body length is 18.0 μ. This “lewisi”‐type species is compared with other trypanosomes reported from American ground squirrels, but a specific diagnosis is not made because the life cycle has not been observed and because morphological features of trypanosomes are known to vary widely under differing environmental conditions.
Evaluation of Some Trypanostatic Agents by Means of Herpetomonas culicidarum
Authors: GROSSOWICZ NATHAN , RASOOLY GOORY
Published: May 2007

SYNOPSIS. A rapid quantitative method for measuring trypanostatic activity by means of the nonpathogenic flagellate Herpetomonas culicidarum is described. Of the known trypanocidal agents tested, pentamidine was the most active; stilbamidine and propamidine somewhat less active. H. culicidarum is more resistant to these agents than are some pathogenic hemoflagellates. Two new antifungal antibiotics, nystatin and heptamycin (a candicidin‐like antibiotic), had powerful trypanostatic activity in vitro. The potential trypanostatic activity of antifungal agents is noted.
The Effect of Lowered Temperatures of the Host on the Reproductive Activity of Plasmodium cathemerium*
Authors: McGHEE R. BARCLAY
Published: May 2007

SYNOPSIS. Experiments were carried out to determine if the course of infection with Plasmodium cathemerium was changed when the temperature of incubation of the duck embryo host was lowered. At 30° C. the infection developed more slowly and never reached the peak seen in infected embryos incubated at 37° C. If infected embryos at 30° were returned to 37° C. the resultant parasitemia developed similarly to that usually seen in this host at the latter temperature. Studies of the periodic behavior of the parasite at 30° C. and 38° C. revealed no differences in the time of segmentation. Merozoite counts were unchanged. The reduced parasitemia in embryos at 30° C. may result from reduced ability of the parasite to penetrate new host cells.
Device for Facilitating the Inoculation of Screw‐cap Tubes
Authors: BURKE J. M. , MARCHISOTTO J. J.
Published: May 2007

SYNOPSIS.

A small reversible A.C. motor is utilized in the construction of a device to tighten and loosen the caps of screw‐cap test tubes.
Hypotrichomonas acosta (Moskowitz) Gen. nov. from Reptiles. I. Structure and Division.*
Authors: LEE JOHN J.
Published: May 2007

SYNOPSIS.

Hypotrichomonas gen nov., with a feeble undulating membrane but lacking a costa, is placed in the family Monocercomonadidae Kirby of the order Trichomonadida Kirby. H. acosta (Moskowitz) from squamate reptiles is designated as the type species. It has 3 unequal anterior flagella. The proximal part of its recurrent flagellum is attached to the surface of the body along an accessory filament. A low membrane with typically a few undulations extends between the accessory filament and the body surface. The membrane, which varies greatly in length in relation to the length of the body among strains of the species, is not supported by a costa. The recurrent flagellum continues as a free posterior flagellum beyond the end of the undulating membrane and terminates in an acroneme. The capitulum of the axostyle, spatulate or scoop‐shaped, is closely applied to the anteriorly located nucleus. The capitulum extends anteriorly into a crescent‐shaped pelta. The relatively stout trunk of the axostyle is straight or twisted. It projects for some distance from the posterior body surface, and the terminal segment of the projecting part tapers gradually to a point. The parabasal apparatus consists of a rod‐ or shaped body and of a filament or filaments.

In division, the full complement of flagella in each of the mastigonts is restored relatively late during division but before cytokinesis. One of the daughter individuals retains the parental undulating membrane; the other develops a new organelle. The development of the new membrane is first marked by the appearance of an acroneme, presumably recurrent flagellum, early in division. The proximal part of this flagellum becomes progressively attached to the body surface. The process of attachment is paralleled by differentiation of the accessory filament and is followed by the appearance of the undulating membrane. The parental axostyle is resorbed during division, and each daughter individual develops this organelle de wove. In the very early stages of division the parabasal consisted of two arms and in all more advanced stages of a single rod‐shaped body applied to a single filament.

The significance of Hypotrichonionas in the evolution of trichomonads is discussed. Its morphology and morphogenesis suggest that this genus may represent an important step in the evolution of Trichomonadidae from Monocercomonadidae.
Obtaining the Slime Mold Fuligo septica in Pure Culture*
Authors: LAZO WALDO R.
Published: May 2007

The slime mold Fuligo septica has been grown bacteria‐free in a pure 1.5% agar and oats at a temperature of 25°C. The Plasmodium was also grown under water.
Conditions for Mating and Inheritance of Mating Type in Variety Seven of Tetrahymena pyriformis*
Authors: OUTKA DARRYLL E.
Published: May 2007

Induction of conjugation in clones of variety 7 of Tetrahymena pyriformis required more precise control than was necessary for the classical variety 1 clones, WH‐6 and WH‐14. Axenic methods are herein described which were successful in eliciting the mating response; especially important was a period of growth under optimal nutritional conditions, and use of animals in the logarithmic phase of growth.

Three cases of presumptive age‐induced selfing are reported, along with the discovery of new mating types III and IV. The isolation of a stage intermediate between a “pure” marine type and a selfing condition offers additional evidence for mating type instability. An analysis of the system of mating‐type inheritance shows a pattern similar to that seen in Paramecium aurelia (Group B), and variety 9 of Tetrahymena pyriformis.
The Biology and Morphology of Crithidia acanthocephali n. sp., Leptomonas leptoglossi n. sp., and Blastocrithidia euschisti n. sp.*
Authors: HANSON WILLIAM L. , McGHEE R. BARCLAY
Published: May 2007

Three new species of Trypanosomatidae were isolated from three species of bugs: Leptomonas leptoglossi from Leptoglossus phyllopus, Crithidia acanthocephali from Acanthocephala femorata, and Blastocrithidia euschisti from Euschistus servus. All were cultured axenically and on avian embryo membranes. In addition to differences in morphology the three organisms displayed different growth rates in the chorio‐allantoic fluids of duck and chick embryos incubated at 30°C. L. leptoglossi grew most abundantly. B. euschisti barely maintained itself while C. acanthocephali occupied an intermediate position.

When the temperature of incubation was raised to 37°C, there was continued multiplication of L. leptoglossi and C. acanthocephali, but there was no growth of B. euschisti in either duck or chick embryos.

It is suggested that the criteria of morphology, cultural characteristics in vitro and in vivo, plus physiological characters be used as future aids in classification of the Trypanosomatidae.
The Role of the Cytoplasm during Reproduction in a Malarial Parasite (Plasmodium lophurae) as Revealed by Electron Microscopy*
Authors: RUDZINSKA MARIA A. , TRACER WILLIAM
Published: May 2007

An electron microscope study of Plasmodium lophurae maintained in vivo and in vitro provided information concerning the sequence of events during reproduction, and the role of the cytoplasm in this process.

Contrary to the generally held opinion that nuclear fissions precede cytoplasmic division, it was found that the last nuclear fission takes place during advanced stages of cytoplasmic segmentation. This study also supplied evidence that in addition to repeated nuclear divisions, a number of changes occur in all major components of the cytoplasm. These changes are considered as preparatory for reproduction. The cytoplasm continues to be active during the formation of merozoites. At this stage a segregation of cytoplasmic components takes place resulting in the incorporation into the offspring of a condensed cytoplasm containing all the organelles. The watery part of the cytoplasm with the lipids and food vacuoles is withheld and at the end of reproduction forms the residual body, a separate structure bound by a membrane.
Morpho‐Physiological Study of Ameboid Movement. 3. Invisible gel structures in the endoplasm of an ameba of the verrucosa type
Authors: ABE TOHRU H.
Published: May 2007

SYNOPSIS. A small ameba of the verrucosa type has a flattened and fan‐shaped body, at the broadest front of which there is formed a distinct hyaline zone. Along the lateral borders thereof there is a thin optically indistinct but rigid body wall, which can be determined by means of cine‐micrographic analysis of the positions of granules in and near it, and their movements. Its caudal portion is well differentiated from the rest of the body and was identified as a region of complicated conditions, manifesting solating activity, contractility, ejection, formation of caudal pseudopods, and continuous shifting of its minute components. The tracks of moving endoplasmic granules were plotted to determine their individual irregularities in velocity and direction of movement. These tracks suggest the existence in the endoplasm of small to large motionless gel structures derived from the frontal hyaline zone, which is therefore postulated to be heterogeneously gelate as a whole. Judging from the fact that granules carried by the protoplasmic matrix passed through these so‐called gel areas, it is proposed that the source of the motive force of ameboid movement may be in the advancing edge of the clear frontal zone where gelation is vigorously taking place.
Formation of Ciliature in Excystment and Induced Re‐encystment of Oxytricha fallax Stein
Authors: HASHIMOTO KANEJI
Published: May 2007

SYNOPSIS. In excystment the primordium of adoral membranelles (AZM) arises as one granular row stretching meridionally toward the cortical axial poles, growing to several rows. Then the AZM's primordial granules become compactly aggregated with a leaf‐like form. A separate primordium for the undulating membrane also appears as well as cirral primordia, all in arrangement similar to that in dividers and regenerators of the present species. Though it is difficult clearly to decide from where all these primordia are derived, their formation seems to have a morphogenetic relation to the thickening of certain fibrillar structures appearing only in resting cystic stages.

Re‐encystment is induced when the excysting cysts after the appearance of a contractile vacuole are transferred to Osterhout's solution from hay infusion employed for excystment induction. Re‐encystment follows after the final step of excystment differentiation is accomplished but with aborted rupture of cyst walls. In the resulting re‐encysted cyst, the secondary cyst walls are enclosed within the original ones. Repeated treatment can produce cysts with further supernumerary cyst walls by additional formation of third walls.

Protoplasts in re‐encystment show characteristics similar to animals prior to and after precystic stages. When their original cyst walls are removed, the naked protoplasts obtained take any one of the following courses: 1. recovery of normal form; 2. physiological regeneration; 3. irreversible encystment. Case (1) occurs in naked protoplasts from early stages of re‐encystment; case (2), in those prior to the extrusion of excretory granules seen in the course of re‐encystment; and the case (3), in those after their extrusion. From these results, presumably the removal of an incipient state of physiological regeneration in the course of re‐encystment may be essential for dedifferentiation of the ciliature that redifferentiated fully in the preceding excystment without escapement.
The Transmission of Crithidia fasciculata Leger 1902 in Culiseta incidens (Thomson)*
Authors: CLARK TRUMAN B. , KELLEN WILLIAM R. , LINDEGREN JAMES E. , SMITH THEODORE A.
Published: May 2007

SYNOPSIS. It has been shown that larva‐to‐larva transmission effected by means of free‐living Crithidia can account for the incidence of this flagellate in natural populations of adult mosquitoes. Larval infections lost at molting were reacquired early in subsequent instars. Infections of pupae came about by contamination of the midgut of the prepupa with nectomonads while the peritrophic membrane was being shed prior to pupation. By the time pupation was completed the flagellates had become immotile and continued to multiply in the pupal midgut; they again became motile in the midgut of the newly emerged adult. Adult‐to‐larva transmission was effected through water contaminated by adult mosquitoes infected with flagellates.
Pinocytotic Uptake and the Digestion of Hemoglobin in Malaria Parasites*†
Authors: RUDZINSKA MARIA A. , TRAGER WILLIAM , BRAY R. S.
Published: May 2007

SYNOPSIS. Electron micrographs of sections of Plasmodium falciparum, P. vivax schwetzi and P. ovale in chimpanzees, and of P. gonderi in mangabeys and P. coatneyi in rhesus monkeys showed that all these malaria parasites feed on their host cell by pinocytosis. As in P. lophurae and P. berghei droplets of host cytoplasm are engulfed by the parasites through invaginations of the plasma membrane with the subsequent formation of food vacuoles. Digestion of the content of the food vacuoles follows two patterns. In P. falciparum as in P. lophurae digestion takes place within the food vacuoles, in which hemozoin, the residue of hemoglobin digestion, accumulates. In P. vivax schwetzi, P. ovale, P. gonderi and P. coatneyi vesicles are pinched off from the food vacuoles and digestion takes place in these small vesicles. As in P. berghei hemozoin is not present in the food vacuole proper but only in the small vesicles, indicating that they are the site of hemoglobin digestion.

Malaria parasites are surrounded by two membranes, and they contain all the major nuclear and cytoplasmic organelles present in other cells with the exception of mitochondria, which were found only in P. lophurae and possibly in P. falciparum. All other plasmodia possess instead a structure composed of concentric double membranes. It is assumed that this structure performs mitochondrial functions.
Endogenous Bud Formation in Histriculus vorax, a New Asexual Reproductive Process In the Hypotrichida
Authors: CURDS COLIN R.
Published: May 2007

SYNOPSIS. Histriculus vorax (Stokes) Corliss, a hypotrichous ciliate, has been separated from activated sludge and cultured monoxenically in the laboratory. The asexual life cycle has been observed and the stages of development photographed. There are large variations in shape and size of cells within clonal cultures. Both large (190–250 μ long) and small (70–140 μ long) cells are capable of normal asexual binary fission but only the large cells are able to grow endogenous buds, which, when mature, are extruded through the body wall of the mother cell. Newly deposited buds can either develop directly into an embryonic form, or, if unfavorable conditions prevail, first encyst. Similar embryonic stages bearing caudal and frontal cirri are produced both by direct development and by excystment of the encysted bud. Embryos develop rapidly into trophic forms which finally grow into small adults capable of asexual binary fission. During binary fission the nuclei behave as described previously for other members of the Oxytrichidae. A reorganization band forms at the outer end of each macronucleus, and these bands move along the macronuclei towards each other, finally disappearing at the inner ends. A fusion nucleus is then formed which splits into 4 pieces, 2 of which pass to the proter and 2 to the opisthe. During bud formation the reorganisation bands form and move as in binary fission. No fusion nucleus is formed, but the macronuclei divide immediately after reorganization, and the anterior macronucleus of each pair so produced migrates to the budding region. The infraciliature of H. vorax resembles that of Opisthotricha monspessulana.‘Erratic’ kinetosomes, which are present in the adult, divide during binary fission and so produce the infraciliature of the proter and opisthe. During bud formation the budding region receives a number of these ‘erratic’ kinetosomes from the mother cell, and these divide to form the infraciliature of the bud.
A Preliminary Electron Microscopic Study of East Coast Fever (Theileria parva Infection)
Authors: JARRETT W. F. H. , BROCKLESBY D. W.
Published: May 2007

SYNOPSIS. The fine structure of various stages in the life cycle of Theileria parva is described. The appearance of the parasites suggests that there may be a double macroschizogony cycle. Micromerozoites are produced by a process of budding off from the body, known in light microscopy preparations as the residual body.
Macronuclear Cytology of Synchronized Tetrahymena pyriformis*
Authors: CAMERON I. L. , PADILLA G. M. , MILLER O. L.
Published: May 2007

SYNOPSIS. Heat shock and stationary‐phase conditions both cause fusion of nucleoli. In both cases the process is reversed when the cell is returned to normal physiological growth conditions. Fusion of nucleoli during the cell cycle of logarithmically growing cells was not observed. Likewise, fusion of nucleoli was not observed when the Padilla and Cameron(8) method of synchronization was used. The macronuclei of cells synchronized by the 1 cold‐shock per cycle method(8) more closely resembled macronuclei of log‐phase cells than did the macronuclei of cells synchronized by the Scherbaum and Zeuthen(12) heat‐shock method.
An Analysis of Macrostome Production in Tetrahymena vorax Strain V2S‐Type*
Authors: BUHSE HOWARD E.
Published: May 2007

SYNOPSIS. Tetrahymena vorax is a small polymorphic holotrichous ciliate capable of transforming to macrostomes when microstomes are washed and suspended with prey in distilled water.

Extrinsic factors having an effect on this transformation were examined; maximum yields of macrostomes (in excess of 90%) were obtained under the following conditions: populations of both prey, T. pyriformis, and potential predator, T. vorax microstomes, were grown on Loefer's medium for 48 hours prior to washing in distilled water. The density of the prey was adjusted to 300,000 cells/ml and the predator density to 2,000–3,000 cells/ml. Five ml of prey suspension and 5 ml of T. vorax microstome suspension were mixed together in a large petri dish because a high surface‐volume ratio is important for high yields of macrostomes. The pH was adjusted to 6.0 and the petri dish was placed at 20 C for 12 hr. Macrostomes then appeared about 6 hr after addition of the prey.

A dialyzable, heat stable substance released by the prey which can induce the microstome‐macrostome transformation was isolated. This material was effective after being stored for weeks in the cold; its activity was not affected by the protein digesting enzymes pepsin or trypsin. This factor was called stomatin because its first visible effect in producing microstome‐macrostome transformation appeared to be to incite reorganization of the oral structures.