bluuebunny/crossref_metadata_2025_split huggingface dataset:
Local Electrogram Changes in Response to a High‐Voltage Intracardiac Shock in Humans
Authors: SMITH JEFFREY R. , KADISH ALAN H. , INBAR SHMUEL , YE DINGZHONG , GOLDBERGER JEFFREY J. 
Published: May 2007

Electrogram Changes Following ICD Shocks. Introduction: Transvenous defibrillators may have difficulty sensing ventricular fibrillation following an unsuccessful shock. This study was undertaken to characterize the changes that occur in intracardiac electrograms following a defibrillator shock that may contribute to the failure to redetect arrhythmias. Methods and Results: Unipolar and bipolar electrogram recordings were made during sinus rhythm before and following monophasic and biphasic test shocks delivered in random order through a single lead defibrillator system in 15 patients. An additional 14 patients received only a biphasic shock. Electrogram amplitude, dV/dt, and activation recovery time were determined. Following biphasic shocks, unipolar electrogram amplitude decreased by a mean of 19.6% and the bipolar amplitude by a mean of 20.8% (P = NS). The mean dV/dt in the unipolar recordings decreased by 30.7% and in the bipolar recordings decreased by 33.0% (P = NS). Time constants for recovery were approximately 60 seconds. Reduction in dV/dt was greater when the shocking coil was closer to the distal sensing electrode. There was no significant influence of shock waveform (monophasic vs biphasic), recording type (unipolar vs bipolar), or clinical variables on the change in electrogram characteristics. Conclusion: Changes in intracardiac electrograms following defibrillator shocks through transvenous leads are seen with shocks delivered in sinus rhythm and may be related to the proximity of the shocking coil to the distal sensing electrode.
Recurrence of Conduction Following Radiofrequency Catheter Ablation Procedures:
Authors: CALKINS HUGH , PRYSTOWSKY ERIC , BERGER RONALD D. , SAUL J. PHILI , KLEIN LAWRENCE S. , BIN LIEM L. , STEPHEN HUANG S.K. , GILLETTE PAUL , YONG PATRICK , CARLSON MARK ,   THE ATAKR MULTICENTER INVESTIGATORS GROUP
Published: May 2007

Recurrence of Conduction Following RF Catheter Ablation. Introduction: More than 1 in 10 patients may develop recurrence of conduction after undergoing a successful radiofrequency catheter ablation procedure. The physiologic basis for recurrence following successful ablation procedures remains uncertain. The purpose of this study was to evaluate the role of electrode temperature as a predictor of recurrence following radiofrequency catheter ablation procedures. Methods and Results: The subjects of this study were 538 patients who underwent a successful attempt at radiofrequency catheter ablation of AV nodal reentrant tachycardia, an accessory pathway, and/or the AV junction. Patients were followed for a mean of 215 ± 138 days. Conduction recurred in 35 (6.5%) of the 538 patients. Recurrence of conduction occurred in 25 (9.3%) of 270 patients undergoing ablation of an accessory pathway, 7 (3.5%) of 201 patients undergoing ablation of AV nodal reentrant tachycardia, and in 3 (4.5%) of 67 patients undergoing ablation of the AV junction. The electrode temperature achieved at successful sites associated with recurrence was not different from the temperature achieved at successful sites without recurrence (61.1 ± 8.9 vs 61.6 ± 9.1; P = 0.8). The likelihood of developing a recurrence was higher following ablation of accessory pathways than following ablation of A V nodal reentrant tachycardia or the AV junction (P = 0.03). Patients experiencing a recurrence following ablation of an accessory pathway had longer procedure durations (P = 0.0001). Ablation of left free‐wall pathways was associated with a lower incidence of recurrence as compared with all other locations (P = 0.008). Conclusion: The results of this study suggest that electrode temperature at the successful ablation site cannot be used to identify patients at highest risk of recurrence.
Amiodarone Instilled Into the Canine Pericardial Sac Migrates Transmurally to Produce Electrophysiologic Effects and Suppress Atrial Fibrillation
Authors: AYERS GREGORY M. , RHO TAI H. , BEN‐DAVID JOSEPH , BESCH HENRY R. , ZIPES DOUGLAS P. 
Published: May 2007

Pericardial Sac as Amiodarone Reservoir. Introduction: We investigated whether amiodarone delivered into the pericardial sac exerted an effect on atrial and ventricular refractoriness, impulse generation, and conduction and on induced atrial fibrillation. Methods and Results: All animals were anesthetized with α‐chloralose. After a sternotomy, the pericardium was opened and cradled to produce a “container” of approximately 75 mL. Part 1 experimental animals received amiodarone, 0.5, 1.0, or 5.0 mg/mL, dissolved in 3 mL polysorbate 80 and 5% dextrose in water (D5W) instilled into their pericardial sac for 3‐hour intervals. Part II experimental animals received either 1.0 or 5.0 mg/mL of amiodarone. Control dogs received a pericardial solution of 3 mL polysorhate 80 in D5W. Pre‐ and postinstillation electrophysiologic studies were performed. In part I, the increase in sinus cycle length, 1:1 AV conduction, and effective refractory period (ERP) of atrium, right ventricular (RV) and left ventricular epicardium, and RV endocardium were significantly greater in animals receiving amiodarone compared with controls. Amiodarone concentrations in the tissue samples were highest in the superficial sites of the atria, sinoatrial node, and ventricular epicardial samples and lowest in the interventricular septum. Only trace concentrations of amiodarone and no desethylamiodarone were found in the blood samples. In part II, atrial ERP significantly increased in the animals receiving amiodarone, and the number of episodes of sustained atrial fibrillation that could he induced decreased. Conclusions: Amiodarone instilled into the pericardial sac migrates transmurally to produce significant electrophysiologic effects at superficial sites and appears to suppress electrically induced atrial fibrillation.
Randomized Comparison of Two Techniques for Titrating Power During Radiofrequency Ablation of Accessory Pathways
Authors: ADA STRICKBERGER S. , WEISS RAUL , KNIGHT BRADLEY P. , BAJU MARWAN , BOGUN FRANK , BRINKMAN KAREN , HARVEY MARK , GOYAL RAJIVA , DAOUD EMILE , MAN K. CHIN , MORADY FRED 
Published: May 2007

Impedance Versus Temperature Monitoring. Introduction: The purpose of this study was to prospectively compare the value of impedance and temperature monitoring during accessory pathway ablation. Temperature and impedance monitoring can be used during radiofrequency ablation of accessory pathways to titrate power to achieve adequate but not excessive tissue beating. Methods and Results: One hundred thirty‐two patients with a single accessory pathway were randomly assigned to undergo ablation using either impedance monitoring or temperature monitoring. During impedance monitoring, the endpoint for titration of power was a 5‐to 10‐Ω decrease in the measured impedance while for temperature monitoring the endpoint was to achieve a temperature of 58° to 62°C. Two protocols were used. In protocol 1 (90 patients), impedance monitoring was performed with a nonthermistor catheter and temperature monitoring was performed with a thermistor catheter. In protocol 2 (42 patients), a thermistor catheter was used in all patients. In protocol 1, the success rate (93% vs 93%; P = 1.0), ablation procedure duration (57 ± 56 vs 41 ± 41 min), fluoroscopy time (48 ± 29 vs 41 ± 23 min; P = 0.3), number of applications (6.2 ± 4.7 vs 5.7 ± 4.6; P = 0.8), and the number of applications associated with coagulum formation (0.1 ± 0.3 vs 0.3 ± 0.6; P = 0.1) were similar in the two groups. In protocol 2, as in protocol 1, there were no differences in the success rate (91% vs 95%; P = 1.0), ablation procedure duration (49 ± 37 vs 62 ± 55 min; P = 0.4), fluoroscopy time (46 ± 24 vs 49 ± 36 min; P = 0.8), number of applications (6.8 ± 7.0 vs 7.8 ± 12.1; P = 0.7), or number of applications associated witb coagulum formation (0.3 ± 0.6 vs 0.2 ± 0.7; P = 0.6) between the impedance and temperature monitoring groups. Conclusion: Temperature and impedance monitoring are equally effective in optimizing the results of accessory pathway ablation.
Changes in Plasma Epinephrine Concentration and in Heart Rate During Head‐Up Tilt Testing in Patients with Neurocardiogenic Syncope:
Authors: KLINGENHEBEN THOMAS , KALUSCHE DIETRICH , LI YI‐GANG , SCHÖPPERL MATTHIAS , HOHNLOSER STEFAN H. 
Published: May 2007

Sympathetic Activation in Neurocardiogenic Syncope. Introduction: Tilt table testing is widely used in the management of patients with neurocardiogenic syncope. However, the exact pathophysiologic mechanism of this disorder is still under debate. Likewise, therapy of these patients continues to represent a challenge in many cases. Therefore, the present study aimed to gain further insight into the pathophysiology of this syndrome and to examine easily accessible clinical parameters that can improve therapy selection. Methods and Results: In 16 patients with neurocardiogenic syncope, changes in endogenous catecholamine concentrations were determined during repeated tilt table testing before and during treatment with metoprolol. Tachycardia preceded syncope in 8 of 10 responders compared to only 1 of 6 nonresponders (P < 0.05). In responders, the relative increase in epinephrine levels averaged 197%± 51% during drug‐free tilting and 75%± 33% during repeated testing while on β‐blocker therapy (P < 0.05). In nonresponders, there was a smaller relative increase in epinephrine averaging 137%± 35% at baseline tilt. During repeated tilt testing, a similar increase was observed in these patients with recurrent syncope (156%± 104%; P = NS compared to baseline). Conclusion: In patients with neurocardiogenic syncope who show both an increase in epinephrine concentration during tilt test and sinus tachycardia prior to the onset of symptoms, β‐blocker treatment is very effective. These findings confirm the major role of sympathetic activation as a trigger of syncope. Particularly, heart rate changes at the onset of syncope may allow early identification of patients responding to antiadrenergic therapy.
Cure of Incessant Pacemaker Circus Movement Tachycardia by Radiofrequency Catheter Ablation
Authors: TIMMERMANS CARL , RODRIGUEZ LUZ‐MARIA , DEN NDULK KAREL , DIJKMAN BARBARA , SMEETS JOEP L.R.M. , WELLENS HEIN J.J. 
Published: May 2007

Ablation of Pacemaker Circus Movement Tachycardia. Introduction: Treatment of pacemaker circus movement tachycardia (PCMT) in patients with very long VA conduction times may present a problem. Methods and Results: PCMT occurred in a 46‐year‐old woman with an uncommon AV nodal reentrant tachycardia who developed 2:1 AV block after fast pathway radiofrequency catheter (RF) ablation performed at another institution. Due to the long VA conduction time, PCMT could not be prevented by reprogramming the pacemaker or by the addition of antiarrhythmic drugs. Cure of the PCMT was obtained after selective RF ablation of the slow AV nodal pathway. Conclusion: RF ablation of the retrograde conduction offers another alternative for treatment of PCMT.
Regional Entrainment of Atrial Fibrillation in Man
Authors: KALMAN JONATHAN M. , OLGIN JEFFREY E. , KARCH MARTIN R. , LESH MICHAEL D. 
Published: May 2007

Entrainment of Atrial Fibrillation. Introduction: The feasibility of entrainment of macroreentrant atrial arrhythmias such as atrial flutter is well documented. Recently, it has been shown that regional entrainment of atrial fibrillation is feasible in dogs. Methods and Results: Three patients with chronic atrial fibrillation underwent electrophysiologic evaluation with attempted entrainment of atrial fibrillation prior to successful endocardial atrial defibrillation. A 16‐pole catheter was positioned in the trabeculated right atrium, and in two patients a multipolar catheter was positioned along the septum. In addition, two large surface area defibrillation catheters were placed, one in the lateral right atrium and one in the coronary sinus. Regional entrainment was attempted in the right atrium and from the catheter in the coronary sinus. Entrainment was achieved in the right atrium in all three patients over a cycle length range of 28, 17, and 13 msec, respectively, and over a radius of atrial tissue of at least 2.8 cm. Regional entrainment was demonstrated from the coronary sinus in one patient during simultaneous right atrial entrainment. Termination of atrial fibrillation during entrainment was not observed. Conclusion: Regional entrainment of chronic atrial fibrillation is feasible in humans.
The Common Occurrence of Micronuclear Variation During Binary Fission in an Unusual Race of Paramecium caudatum
Authors: WICHTERMAN RALPH 
Published: May 2007

Unstable micronuclear behavior was investigated in an unusual race of Paramecium caudatum. Lines were begun, after isolating single vegetative specimens, to yield mass cultures. After study of living specimens in the precision micro‐compression chamber and permanent preparations stained with Feulgen and iron‐hematoxylin, most paramecia revealed a single micronucleus but many were observed with two micronuclei and fewer with more than two micronuclei—occasionally three, rarely four. Specimens measured 225 microns in length; the micronucleus about seven microns. Instead of normal cyclosis, the protoplasm exhibited great fluidity. Generally two contractile vacuoles were present but specimens with three vacuoles, even four, were not uncommon.The method of producing amicronucleate specimens and those with variable numbers of micronuclei was discovered by studying large numbers of actively dividing paramecia. Instead of a micronucleus passing to each daughter at the end of fission as in normal animals, the entire late telophase stage of the dividing micronucleus is passed to the anterior or posterior daughter cell at the time of constriction of the cell. The result is that one daughter is bimicronucleate and the other daughter amicronucleate. Bimicronucleate and amicronucleate animals are capable of dividing normally. In bimicronucleate specimens, division stages show two micronuclei in late telophase stages that result in four micronuclei, two passing to each daughter cell. However, aberrations may again occur in fission to produce variations in number of micronuclei. The irregularly shaped, atypical, macronucleus may extrude chromatin or may undergo complete fragmentation (hemixis, type D). Paramecia and macronuclei may be parasitized by a microorganism which may cause this derangement of normal micronuclear events. This possibility of induction of micronuclear variation in Paramecium by foreign microorganisms may be of considerable evolutionary significance in the genus.
Le Macronucleus Hétéromere de Quelques Ciliés
Authors: Fauré‐Fremiet E. 
Published: May 2007

SUMMARY. In ciliates belonging to the two gymnostome families Chlamydodontidae and Dysteriidae as well as to the order Chonotrichida the macronucleus is composed of two parts which are distinct but in very close juxtaposition. One part, here called “orthomerous,” contains granules or microsomes of desoxyribonucleoprotein and several nucleoli; it thus shows the normal structure of a macronucleus of the ordinary type. The other part, “paramerous,” contains desoxy‐ribonucleic acid diffused, apparently, throughout a homogeneous karyolymph and possesses, in addition, several nucleoli and an endosome of desoxyribonucleoprotein.The three groups of ciliates under discussion are closely related and constitute an assemblage of forms remarkably evolved. The “heteromerous” structure of their macronuclei must be considered as a secondary acquisition and a differentiation of the “homeomerous” type which characterizes the structure of the macronucleus in most other ciliates.
Studies of Tritrichomonas batrachorum I. The trophic organism*
Authors: Samuels Robert 
Published: May 2007

SUMMARY. High variability within cultures of Tritrichomonas batrachorum (from Bufo boreas halophilus, Rana catesbeiana, and Rana pipiens) casts doubt on the validity of length measurements for species designation.The morphology differs from that described previously. The axostylar capitulum is a complex structure with a preblepharoplastic portion and a perinuclear cup spreading laterally in curved membranes ending in filaments. The parabasal apparatus is Y‐shaped with a very short base.Two types of amoeboid activity occur. Filopodia are used for anchorage. Their bases migrate and the filopodia may fuse and reseparate as in foraminifers. Ingestion is an amoeboid process utilizing lobopodia. Food adherent to a lobopod is invested in a food cup at the surface. Ingrowth of the lip of the food cup forms the food vacuole, or in cases of cannibalism, constricts the prey and forms a food tube pushing a vacuole before it. Repeated, this produces an alternating series of vacuoles and tubes. There is a pseudo‐amoeboid degenerative process in which the flagella, withdrawn into the cytosome, continue to move and produce non‐functional lobopod‐like protrusions.An actual cytostome has not been observed, but there is a region of reduced staining intensity ventral to the axostylar capitulum.
Intracellular phagotrophy by malaria parasites: an electron microscope study of Plasmodium lophurae*
Authors: Rudzinska Maria A. , Trager William 
Published: May 2007

SUMMARY. An electron microscope study of thin sections of duck erythrocytes infected with Plasmodium lophurae revealed that the so‐called “residual body” is a food vacuole formed by invagination from the cytoplasm of the host cell. Several such food vacuoles may exist in a single parasite. Digestion of hemoglobin evidently proceeds only within these food vacuoles, since they are the only place in the parasite where the characteristic malarial pigment granules may be found. This finding changes the role ascribed to the residual body and gives a new concept of the feeding mechanisms in P. lophurae and other malaria parasites. The cytoplasm of the host is taken in by the parasite by phagotrophy and not only as previously assumed, by diffusion.The fine structure of P. lophurae shows all major components found in other protozoan and metazoan cells. Some of the organelles appear to have a much simpler structure connected probably with the highly specialized intracellular parasitic life.
An Eight‐day Method for Screening Compounds against Leishmania donovani in the Golden Hamster*
Authors: STAUBER LESLIE A. , FRANCHINO ELIZABETH M. , GRUN JOHN 
Published: May 2007

SYNOPSIS. Intracardial inoculation of 1–10 million L. donovani in 0.1 ml. of ground spleen suspension from an infected animal (hamster) results in a uniform rise of parasite numbers in the untreated animal over the first 8 days after the inoculation. This rise is highly consistent from experiment to experiment.Treatment is accomplished by parenteral injection of a compound for 6 successive days in this time interval, starting 24 hours after inoculation.No known active compound in proper dosage (sodium stibogluconate, pentamidine, fuadin) has failed to show a significant suppression of the expected rise in parasite numbers. No known inactive compound has had any effect on the course of the infection.The dosage‐response curve for the active compounds suggests that the method is a sensitive one. Since it takes only 8 days to complete, it is economical as well.
An Electron‐Microscope Study of the Cytology of the Protozoan Peranema trichophorum*
Authors: ROTH L. E. 
Published: May 2007

SYNOPSIS. The flagellate, Peranema trichophorum, has been studied in the electron microscope by thin‐sectioning techniques. The flagella have the fibrillar pattern typical of cilia and flagella, but accessory structures including tapered, intraflagellar rods, striated, layered material on the outside of the membrane, and mastigonemes are present. In the near basal region of the flagellum, there is a swelling of the shaft which is correlated with the absence of the two central flagellar fibrils. The basal portion of the intraflagellar material is structurally and locationally similar to the basal parts of the flagellar fibril bundle; this similarity suggests that the two structures originated from similar precursors and that two kinetosomes comprise the light microscopist's blepharoplast in this organism.The ridged pellicle is composed of 3 membranes, only two of which follow the contour of the ridges. Several filaments 21 mμ in diameter are localized under the low point of each ridge, and a single, larger fibril which has a periodic structure is often located beneath the high point of each ridge.The cytostome and structures associated with it are described and discussed in relation to food taking. The pharyngeal rods are cross‐connected and each is composed of numerous tubular elements surrounded by a denser, homogeneous layer. A system of membranes is attached to the rods and extends anteriorly.The nucleus contains two large nucleoli, numerous rod‐shaped, membrane‐limited bodies which appear similar in structure to bacteria, and a smaller granular component.Other organelles are briefly described including mitochondria, Golgi bodies, vacuoles, and endoplasmic reticulum.
Lankesterella corvi n. sp., a Blood Parasite of the English Rook, Corvus f. frugilegus L.*
Authors: BAKER J. R. , LAINSON R. , KILLICK‐KENDRICK R. 
Published: May 2007

SYNOPSIS. Lankesterella corvi n. sp. (Coccidia, Eimeriidae, Cryptosporidiinae) is described from the rook, Corvus f. frugilegus L. in England. It was found in 36 of 196 fledged rooks less than 1‐year old, but not in 25 nestlings or 38 adults. It was not found in 71 jackdaws (C. monedula spermologus) or in 110 other birds of 16 species.Mature sporozoites were found in the erythrocytes and occasionally in other blood cells. They were 6.2 times 2.5 μ, with a central, band‐like nucleus, and cytoplasm which failed to stain with Giemsa's stain. Gametogonic and sporogonic stages, found in the bone‐marrow of one bird, resembled corresponding stages of Eimeria.A fledgling rook was infected experimentally by inoculation of a blood and tissue suspension from an infected bird. Sporozoites appeared in its blood 4 days after inoculation. They appeared to increase slightly in size and their cytoplasm lost its initial affinity for Giemsa's stain during the next few days. Engorged mites (Ornithonyssus sylviarum) from the experimentally infected rock contained unchanged sporozoites but no developmental stages of the parasite. A canary could not be infected by intraperitoneal inoculation and feeding of such mites.
An Illustrated Key to the Higher Groups of the Ciliated Protozoa, with Definition of Terms*
Authors: CORLISS JOHN O. 
Published: May 2007

SYNOPSIS. A dichotomous, analytical key is offered for use in recognition and differentiation of the 26 orders and suborders belonging to the two subclasses of the single class Ciliata of the subphylum CILIOPHORA. The basic terminology employed in these brief characterizations, usable in systematic studies of ciliates in general, is defined first, and a plea is made for a more uniform vocabulary, especially in reference to structures which are without doubt homologous throughout the several higher ciliate taxa. Particular emphasis is placed on the all‐important features in the oral area; many of these are figured as well as being described in words.Both the key and the definitions are essentially the first to be offered since Kahl's monographic work on the ciliates published in 1930–1935. They are demanded by the great accumulation of new pertinent data in the protozoclogical literature of the past 25 years.