bluuebunny/crossref_metadata_2025 huggingface dataset:
Frequency‐Dependent Electrophysiologic Effects of d,1‐Sotalol and Quinidine and Modulation by Beta‐Adrenergic Stimulation
Authors: SAGER PHILIP T. , BEHBOODIKHAH MAHNAZ
Published: May 2007

Frequency‐Dependent Effects of Sotalol and Quinidine. Introduction: Frequency‐dependent electrophysiologic actions of oral quinidine and oral sotalol may be clinically important, but these properties and their modulation by beta‐adrenergic sympathetic stimulation have not been determined.

Methods and Results: The frequency‐dependent effects of oral quinidine (n = 17) and oral d,I‐sotalol (n = 17) were determined at: (1) drug‐free baseline; (2) during steady‐state drug dosing; and (3) during isoproterenol infusion to patients receiving quinidine or d,I‐sotalol. The monophasic APD90 and RVKRP were prolonged 12% to 17% (P < 0.001) during pharmacologic therapy, and frequency‐dependent effects were only observed for the RVERP during sotalol. In both drug groups, isoproterenol significantly reduced the sinus cycle length and reduced the RVERP to a greater extent at longer than at shorter paced cycle lengths. While isoproterenol fully reversed quinidine's effects on the APD90 and RVERP, sotalol‐induced APD90 prolongation was reduced by only 2% to 4%, and the RVERP was unaffected. Isoproterenol attenuated the frequency‐dependent effects of quinidine on QRS duration by a relatively fixed amount of 7% to 10%. Isoproterenol fully reversed quinidine‐induced, but did not affect sotalol‐ induced, prolongation in the sustained VT cycle length.

Conclusions: (1) Over the range of examined cycle lengths, oral quinidine and d,I‐sotalol did not exert frequency‐dependent effects on ventricular repolarization. (2) Isoproterenol fully reversed quinidine's effects on refractoriness, repolarization, and prolongation of VT cycle length, whereas d,I‐sotalol effects were largely preserved, despite significant reductions in sinus cycle length. (3) These results suggest that beta‐blockade is important in preventing reversal of antiarrhythmic drug effects by augmented sympathetic nervous system tone.
Atrial Natriuretic Peptide and Cardiac Electrophysiology: Autonomic and Direct Effects
Authors: CLEMO HENRY F. , BAUMGARTEN CLIVE M. , ELLENBOGEN KENNETH A. , STAMBLER BRUCE S.
Published: May 2007

ANP and Cardiac Electrophysiology. Atrial natriuretic peptide (ANP) has varied effects on cardiac electrophysiologic parameters including heart rate, intraatrial conduction time, and refractory period. ANP's vagoexcitatory and sympathoinhibitory actions as well as its direct actions on cardiac ion currents may be responsible for some of these effects. This review discusses the role of ANP in cardiac electrophysiology, its interactions with the autonomic nervous system and baroreceptor reflex, and its effects on cardiac ion currents.
Myocardial Vulnerability to T Wave Shocks: Relation to Shock Strength, Shock Coupling Interval, and Dispersion of Ventricular Repolarization
Authors: FABRITZ C. LARISSA , KIRCHHOF PAULUS F. , BEHRENS STEFFEN , ZABEL MARKUS , FRANZ MICHAEL R.
Published: May 2007

Myocardial Vulnerability to T Wave Shocks. Introduction: Induction of ventricular fibrillation (VF) by T wave shocks is of clinical interest due to the correlation between the upper limit of vulnerability (ULV) and the defibrillation threshold (DFT). However, the ULV bas not yet been defined precisely in reference to the entire “area of vulnerability” (AOV), which is defined bifunctionally by both shock strengths and shock coupling intervals, nor has it been related to the dispersion of ventricular repolarization, considered to be an important determinant of vulnerability.

Methods and Results: In 11 isolated perfused rabbit hearts immersed in a tissue bath containing a 3‐lead ECG recording system and two opposite plate electrodes for field shock administration, 7 monophasic action potentials (MAPs) were recorded simultaneously from different epicardial and endocardial regions of the right and left ventricles. An average of 90 ± 25 monophasic waveform shocks of varying shock strengths and coupling intervals were delivered to each heart to determine the horizontal and vertical boundaries of the AOV. The AOV approximated a rhomboid with homogenous VF inducibility. The ULV and lower limit of vulnerability (LLV) represented discrete corners of the AOV with significant changes in VF inducibility if either shock coupling intervals or shock strength were changed by only 10 msec or 10 V. respectively (P < 0.001). The ULV occurred at 7 ± 10 msec shorter coupling intervals than the LLV (P < 0.05), and VF‐inducing shock strengths at the left corner of the AOV were 50 ± 67 V higher as compared to the right corner (P < 0.01). The maximal range of VF‐inducing coupling intervals coincided (within < 2 msec) with the dispersion of MAPs at 70% repolarization, and the ULV coupling interval coincided (within < 4 msec) with the longest repolarization at 50%.

Conclusions: (1) VF vulnerability to monophasic T wave shocks is defined by an AOV that bas the shape of a leftward tilted rhomboid. (2) Both the ULV and LLV are sharply defined upper and lower corners of the AOV rhomboid. (3) The width of the AOV corresponds to the dispersion of ventricular repolarization at the 70% level. (4) Considering the dispersion of ventricular repolarization may yield more precise ULV determinations and a better understanding of the correlation between the ULV and DFT.
Effects of Heating with Radiofrequency Power on Myocardial Impulse Conduction: Is Radiofrequency Ablation Exclusively Thermally Mediated?
Authors: SIMMERS TIMOTHY A. , de BAKKER JACQUES M.T. , WITTKAMPF FRED H.M. , HAUER RICHARD N.W.
Published: May 2007

Impulse Conduction During Radiofrequency Ablation. Introduction: Although it is generally accepted that radiofrequency (RF) ablation causes exclusively thermally mediated effects, it has never been proved.

Methods and Results: In a previous report, temperatures required to induce conduction block in superfused canine epicardial ventricular myocardium were identified by exposure to heated superfusate: 50.3°± 1.1°C and 53.6°± 0.6°C for transient and permanent block, respectively. In the present study, heating was performed using RF power in an otherwise identical model. Nine preparations from four dogs were used. A 1‐cm diameter electrode was placed beneath the center of each preparation for RF delivery. Incisions were made to create a conductive Isthmus over the ablation electrode. Preparations were paced to one side of the isthmus and electrograms recorded from the center of the isthmus and to either side. Temperature was measured using a miniature thermocouple located just below the epicardial surface, adjacent to the recording electrode in the heated zone. RF was delivered for 30 seconds at 5‐minute intervals with increments in power per episode causing increments in temperature of approximately 2°C. Temperature during pulses at which transient block occurred was 50.7°± 3.0° C; temperature at 30 seconds of heating in pulses leading to permanent block was 58.0°± 3.4°C.

Conclusion: These findings provide evidence suggesting that the electrophysiologic effects of RF ablation are exclusively thermally mediated and are otherwise unrelated to the dissipation of high‐frequency current.
Epicardial Sock Mapping Following Monophasic and Biphasic Shocks of Equal Voltage with an Endocardial Lead System
Authors: USUI MASAHIRO , CALLIHAN RICHARD L. , WALKER ROBERT G. , WALCOTT GREGORY P. , ROLLINS DENNIS L. , WOLE PATRICK D. , SMITH WILLIAM M. , IDEKER RAYMOND E.
Published: May 2007

Mapping After Monophasic and Biphasic Shocks. Introduction: The reason for the increased defibrillation efficacy of biphasic shocks over monophasic shock is not definitely known.

Methods and Results: In six anesthetized pigs, we mapped the epicardium after transvenous defibrillation shocks to compare the activation patterns following successful biphasic shocks with unsuccessful monophasic shocks of the same voltage. The heart was exposed and a 510‐electrode sock with approximately 4‐mm interelectrode spacing was pulled over the entire ventricular epicardium and sutured to the pericardium. Defibrillation catheters were placed in the right ventricular apex and in the superior vena cava. Paired monophasic 12 msec and biphasic 6/6 msec defibrillation shocks were given using an up‐down protocol to keep shock strength between the defibrillation thresholds for the two waveforms so that the biphasic shock was successful while the monophasic shock was not. Activation fronts immediately following 60 paired shocks were recorded and analyzed by animated maps of the first derivative of the electrograms. The ventricles were divided into apical (I), middle (II), and basal (III) thirds, and early sites, i.e., the sites from which activation fronts first appeared on the epicardium following the shock, were grouped according to their location. Postshock intervals, i.e., the time from the shock until earliest epicardial activation occurred, were also determined. No ectopic activation fronts followed the shock in 20 biphasic episodes. In the other 40 paired episodes, the number of early sites was smaller after biphasic shocks than after monophasic shocks (monophasic: 198 (total), 3.3 ± 0.9 (mean ± SD) per shock episode; biphasic: 67, 1.1 ± 1.0, P < 0.05]. For biphasic but not monophasic shocks, early sites were less likely to arise from the middle (II) and basal (III) thirds than from the apical third (I) [monophasic: I: 84 (42%), II: 68 (34%), III: 46 (23%); biphasic: I: 49 (73%), II: 10 (15%), III: 8 (12%), P < 0.05]. Postshock intervals were significantly shorter for monophasic shocks (54 ± 14 msec) than for biphasic shocks (75 ± 23 msec, P < 0.05).

Conclusion: The decreased number of activation fronts and the longer delay following the shock for the earliest epicardial appearance of those activation fronts that do occur may be responsible for the increased defibrillation efficacy for biphasic shocks.
Effects of Azimilide Dihydrochloride on Circus Movement Atrial Flutter in the Canine Sterile Pericarditis Model
Authors: RESTIVO MARK , HEGAZY MAHA , CAREF EDWARD B. , AVITABLE MATTHEW J. , ASSADI MAHSHID A. , EL‐HAMAMI MOUSTAEA , YIN HONG , PIRACHA MUHAMMAD , BROOKS ROBERT R. , EL‐SHERIE NABIL
Published: May 2007

Azimilide and Atrial Flutter. Introduction: The effects of a Class III agent, azimilide di‐hydrochloride, on atrial flutter circuits were studied in a functional model of single loop reentrant atrial flutter using dogs, 3 to 5 days after production of sterile pericarditis.

Methods and Results: A computerized mapping system was used to construct activation maps from 138 to 222 epicardial sites in the right atrium. Doses of 3, 10, and 30 mg/kg IV azimilide dihydrochloride were analyzed in 8 dogs in which sustained atrial flutter lasting more than 30 minutes was induced by burst pacing. Atrial flutter was always due to a single loop circus movement reentry in the lower right atrium. At 3 mg/kg, azimilide dihydrochloride terminated atrial flutter in 2 dogs; however, atrial flutter was reinduced. At 10 mg/kg, atrial flutter was terminated in all 8 dogs but was reinduced in 4 dogs with slower rate. At 30 mg/kg, atrial flutter was terminated in the remaining 4 dogs and could not be reinduced. Atrial flutter cycle length always increased prior to termination. Isochronal activation maps showed that the increase in cycle length was due to additional conduction delays in the slow zone of the reentrant circuit. The site of termination was always located within the slow conduction zone situated in the lower right atrium between the line of functional conduction block and the AV ring. effective refractory periods (ERPs) were measured at selected sites in the slow zone and normal zone at twice diastolic threshold for the 10 mg/kg dose. Azimilide preferentially prolonged ERP in the slow zone (42.4 ± 20.l msec, mean ± SD) compared with (he normal zone (23.3 ± 15.4 msec, P < 0.0001). The increase in cycle length corresponded with the increase in ERP in the slow zone.

Conclusions: In a functional model of circus movement atrial flutter, azimilide dihydrochloride terminates and prevents reinduction of atrial flutter by a preferential increase in refractoriness leading to further conduction delay and conduction block in the slow zone of the functional reentrant circuit.
Persistence of Single Echo Beat Inducibility After Selective Ablation of the Slow Pathway in Patients with Atrioventricular Nodal Reentrant Tachycardia:
Authors: TONDO CLAUDIO , BELLA PAOLO DELLA , CARBUCICCHIO CORRADO , RIVA STEFANTA
Published: May 2007

Residual Slow Pathway Conduction Effects on AVN Function. Introduction: Residual slow pathway conduction with or without reentrant echo beats has been reported in 25% to 30% of patients undergoing ablation for AV nodal reentrant tachycardia (AVNRT).

Methods and Results: Fifty‐eight consecutive patients (aged 45 ± 12 years) with slow‐fast AVNRT underwent radiofrequency catheter ablation of the slow AV nodal pathway (SP). Residual slow‐fast echo beat was documented in 21 (36%) of 58 patients (group A). The pre‐and postablation AH intervals triggering the echo beats were similar (346 ± 8 msec vs 352 ± 6 msec, P = NS), as were the pre‐and postablation echo zones (55 ± 6 msec vs 52 ± 5 msec, P = NS) and functional refractory period of the SP. A consistent prolongation of the AV nodal effective refractory period (AVN‐ERP; from 265 ± 28 msec to 340 ± 50 msec, P < 0.001) and the Wenckebach cycle length (WBCL; from 298 ± 41 msec to 438 ± 43 msec, P < 0.001) was observed in all patients with abolition of SP conduction (group B). In group A patients, the prolongation of WBCL was less (285 ± 33 msec preablation, and 334 ± 41 msec postablation, P < 0.001). Additional pulses abolished the residual echo in 16 of 21 patients, and further prolongation of the AVN‐ERP and WBCL comparable to those found in patients without a residual echo beat was observed. During 19 ± 8 months follow‐up, no patient had clinical recurrence of AVNRT.

Conclusion: Residual single echo beat after SP ablation for AVNRT reflects the persistence of some portion of the SP with unchanged functional conduction properties whose prognostic significance is uncertain. A consistent increase of WBCL can be a reliable marker of complete abolition of slow pathway conduction and termination of AVNRT.
Electrophysiologic Effects of the New Class III Antiarrhythmic Drug Dofetilide Compared to the Class IA Antiarrhythmic Drug Quinidine in Experimental Canine Atrial Flutter:
Authors: CHA YONGMEI , WALES ALAN , WOLF PAUL , SHAHROKNI SHAHIN , SAWHNEY NEIL , FELD GREGORY K.
Published: May 2007

Effects of Dofetilide in Canine Atrial Flutter. Introduction: Previous studios that Class III antiarrhythmic drugs are more effective in reentrant arrhythmias because they prolong refractoriness (ERP) and wavelength and reduce dispersion of refractoriness compared to Class IA antiarrhythmic drugs, which slow conduction velocity (CV) in addition to their effects on refractoriness.

Methods and Results: To test this hypothesis, the Class III drug dofetilide and the Class IA drug quinidine were studied in the experimental canine crush‐injury model of atrial flutter, utilizing right atrial multipoint programmed stimulation and activation mapping. In seven dogs dofetilide prolonged ERP by 23%, slowed CV by 9% at 200‐msec cycle length (P < 0.001) and by 39% at 150‐msec cycle length (P < 0.001), and increased wavelength by 11% (P < 0.02). Dofetilide reduced dispersion of ERP by 20% (P = 0.003) and adjacent electrodes with ERP difference ≥: 20 msec by 76% (P < 0.001). Dofetilide slowed atrial flutter by 37% (P = 0.003) prior to terminating and suppressing it in all dogs. In eight dogs quinidine prolonged ERP by 14% (P < 0.001), slowed CV by 14% at 200‐msec cycle length (P < 0.00) and by 19% at 150‐msec cycle length (P < 0.001), and reduced wavelength by 2% (P = NS). Quinidine did not reduce dispersion of refractoriness. Quinidine slowed atrial flutter by 57% (P < 0.001), terminating and suppressing it in only three dogs. Efficacy of dofetilide was greater than quinidine (P = 0.026) and correlated with reduced dispersion of ERP (r = ‐0.653, P = 0.01), reduced adjacent electrodes with ERP difference ≥ 20 msec (r = ‐0.637, P = 0.012), and prolonged wavelength (r = 0.61, P = 0.018). Dofetilide and quinidine terminated atrial flutter by similar mechanisms. Myocardial fiber orientation was nonuniform around the crush injury.

Conclusions: Antiarrhythmic efficacy of dofetilide was greater than that of quinidine and correlated with drug‐induced prolongation of wavelength and reduction in dispersion of refractoriness, effects produced only by dofetilide.
Amiodarone Therapy for Atrial Rhythm Control: Insights Gained From a Single Center Experience
Authors: CHANDHOK SHEETAL , SCHWARTZMAN DAVID
Published: May 2007

Introduction: Amiodarone has been advocated as an effective “long‐term” therapy for atrial rhythm control in patients with atrial fibrillation (AF). We sought to assess the sustainability of this therapeutic strategy.

Methods and Results: Retrospective analysis of a consecutive, single‐center cohort (n = 168) with symptomatic AF who were treated with amiodarone and followed for 3 years. The incidence of amiodarone cessation was evaluated at 1, 2, and 3 years and attributed principally to drug inefficacy, intolerance, or toxicity. A gradual diminution in the number of patients on therapy was observed, such that by 3 years, only 45% remained. This was attributable to inefficacy (25%), intolerance (12%), or toxicity (18%). Pulmonary toxicity was surprisingly common, occurring in at least 7% of patients.

Conclusions: These data challenge the notion of amiodarone as a reasonable “destination” therapy for AF.
Can Late Supraclavicular Echo Doppler Reliably Predict Angiographical String Sign of Lima to Lad Area Grafts?
Authors: Hartman Joost M. , Kelder Hans C. , Ackerstaff Rob G. A. , Swieten van Henry A. , Vermeulen Freddy E. E. , Bogers Ad J. J. C.
Published: May 2007

Objective: To investigate whether supraclavicular ultrasonography of left internal mammary artery (LIMA) to left anterior descending (LAD) area grafts can reliably predict (distal) string sign grafts on arteriography. Methods: Fifty‐five patients (42 M, 61 ± 7 years) with the LIMA to LAD area grafting were prospectively studied. Control arteriography was performed at 1.4 ± 0.8 years postoperatively. Angiography demonstrated in 46 patients (group I) functional grafts, in 4 patients (group II) sequential distal string sign grafts and in 5 patients (group III) total string sign grafts. Ultrasonography was performed at 1.8 ± 0.8 year postoperatively and compared with control angiography. Data were tested by unpaired t‐ and ANOVA tests. The diagnostic accuracy was assessed by the area under the curve of the Receiver Operator Characteristic. A formula was developed to predict the probability of (distal) string sign phenomena of sequential as well as single LIMA grafts. Results: Between the groups all duplex parameters showed a highly significant linear relation (p ≤ 0.004) and all parameters between group I and III are significantly different with high Area Under Curve values. The model for the probability of (distal) string sign grafts fitted best with diastolic and systolic peak velocities as the most discriminative factors for (distal) string sign grafts. Conclusions: Postoperative supraclavicular duplex as a method to assess the patency of LIMA to LAD area grafts allows discriminating functional grafts from (distal) string sign grafts.
Abdominal Aorta Screening during Transthoracic Echocardiography
Authors: Roshanali Farideh , Mandegar Mohammad Hossein , Yousefnia Mohammad Ali , Mohammadi Azam , Baharvand Babak
Published: May 2007

Objective: The purpose of this study was to investigate the use of a modified abdominal ultrasound examination, performed as an extension of a routine diagnostic transthoracic echocardiography. This modified examination is arguably a simple, safe, quick, and accurate way to identify patients with abdominal aortic aneurysm (AAA). Methods: This prospective study, conducted over a 6‐month period, sought to obtain the maximum diameter of the abdominal aorta through a routine transthoracic echocardiography. Results: In 1285 patients, 1175 abdominal aortas were visualized (91.4%). The prevalence of AAA was 3.8% (45/1175), which increased with age. Six patients, who had diameters more than 5 cm, were referred to a surgeon. In the patients with AAA, left ventricular hypertrophy and left ventricular dilatation were more frequent. Conclusion: Routine screening of the abdominal aorta during transthoracic echocardiography is recommended on account of the prevalence of AAA in unselected and, in particular, older patients.
Just‐Identified Versus Overidentified Two‐Level Hierarchical Linear Models with Missing Data
Authors: Shin Yongyun , Raudenbush Stephen W.
Published: May 2007

SummaryThe development of model‐based methods for incomplete data has been a seminal contribution to statistical practice. Under the assumption of ignorable missingness, one estimates the joint distribution of the complete dataforθ∈Θfrom the incomplete or observed datayobs. Many interesting models involve one‐to‐one transformations of θ. For example, withyi∼N(μ, Σ)fori= 1, … , nandθ= (μ, Σ), an ordinary least squares (OLS) regression model is a one‐to‐one transformation of θ. Inferences based on such a transformation are equivalent to inferences based on OLS using data multiply imputed fromf(ymis | yobs, θ)for missingymis. Thus, identification of θ fromyobsis equivalent to identification of the regression model. In this article, we consider a model for two‐level data with continuous outcomes where the observations within each cluster are dependent. The parameters of the hierarchical linear model (HLM) of interest, however, lie in a subspace of Θ in general. This identification of the joint distribution overidentifies the HLM. We show how to characterize the joint distribution so that its parameters are a one‐to‐one transformation of the parameters of the HLM. This leads to efficient estimation of the HLM from incomplete data using either the transformation method or the method of multiple imputation. The approach allows outcomes and covariates to be missing at either of the two levels, and the HLM of interest can involve the regression of any subset of variables on a disjoint subset of variables conceived as covariates.
Nonparametric Bayesian Estimation of Positive False Discovery Rates
Authors: Tang Yongqiang , Ghosal Subhashis , Roy Anindya
Published: May 2007

Summary We propose a Dirichlet process mixture model (DPMM) for the P‐value distribution in a multiple testing problem. The DPMM allows us to obtain posterior estimates of quantities such as the proportion of true null hypothesis and the probability of rejection of a single hypothesis. We describe a Markov chain Monte Carlo algorithm for computing the posterior and the posterior estimates. We propose an estimator of the positive false discovery rate based on these posterior estimates and investigate the performance of the proposed estimator via simulation. We also apply our methodology to analyze a leukemia data set.
The Occurrence of Hepatozoon in the Gray Squirrel (Sciurus carolinensis)*
Authors: HERMAN CARLTON M. , PRICE DONALD L.
Published: May 2007

SUMMARY. Hepatozoon sciuri (Coles, 1914) is reported from gray squirrels (Sciurus carolinensis) in Washington, D.C. and Maryland. Blood smears stained with Giemsa's stain revealed a parasitemia in 16 to 71% of the squirrels examined. A technique for laking the red cells and concentrating the white cells in blood samples demonstrated this protozoon to be present in every squirrel so tested.
The Effect of Antihistamines on the Pigments of Green Protista.
Authors: GROSS JEAN A. , JAHN THEODORE L. , BERNSTEIN EMIL
Published: May 2007

SUMMARY. A preliminary survey of the influence of a number of antihistamines on growth of several protozoa indicated that not only growth but also pigment formation in green forms was inhibited. Subsequently, it was demonstrated that molar concentrations of the drugs of less than 1 times 10−3 caused chlorosis of cultures of Euglena gracilis var. bacillaris, Chlamydomonas pseudococcum, and Chlorella vulgaris.

With the aid of one of the antihistamines, Pyribenzamine (CIBA), a permanently colorless culture of Euglena was obtained. This culture has been maintained in the chlorotic state in antihistamine‐free medium through eighteen serial transfers in constant light. Comparative spectro‐photometric studies were made of the pigments extracted from this new euglenid strain with those from normal green, dark‐grown and streptomycin‐bleached euglenas. Although the dark‐etiolated forms retained small amounts of chlorophylls, neither of the drug‐bleached cultures showed evidence of these pigments. Quantitatively, the carotenoid picture in dark‐bleached and streptomycin‐grown organisms was similar, but these pigments were greatly reduced in the Pyribenzamine‐treated strain. Further studies on the identity of the carotenoids in the new euglenid are in progress.
Certain Aspects of the Sexuality of Two Species of Chlamydomonas
Authors: BERNSTEIN EMIL , JAHN THEODORE L.
Published: May 2007

SUMMARY. When older cultures (18 days old) of Chlamydomonas eugametos were mated, zygote formation occurred under conditions similar to those devised for C. moewusii. Young (6 days old) cultures of the former did not mate when the nitrogen concentration of the medium was high (0.03% NH4NO3). In confirmation of the work of Sager and Granick, it was found that low nitrogen concentrations, produced by decreasing the concentration of NH4NO3 in the original medium, by increasing the intensity of the illumination, or by using old cultures, enhanced gametogenesis in C. eugametos. It has also been demonstrated that the two species are compatible with one another, even under conditions which are unfavorable for gametogenesis in C. eugametos alone.
Environmental Factors Affecting Growth and Chlorophyll Synthesis in Euglena.* I. Physical and Chemical. II. The Effectiveness of the Spectrum for Chlorophyll Synthesis.
Authors: WOLKEN J. J. , MELLON A. D. , GREENBLATT C. L.
Published: May 2007

SUMMARY. Light ⇌ dark reactions in the algal flagellate, Euglena gracilis, were studied.

When cultures are aged, dark‐adapted, or subjected to elevated temperatures, analysis of absorption spectra indicates the magnesium is removed from the chlorophyll molecule and the chlorophyll is transformed to pheophytin. It also appears from chemical analyses, that the dark‐adapted and heat‐treated organisms are similar. The kinetics in terms of activation‐energy for growth and chlorophyll synthesis can be evaluated by their effective response to temperature. The action spectrum for greening indicates that in Euglena protochlorophyll is probably the light‐acceptor, as has been found for higher plants.
Observations on the Morphology and Division of Eudiplodinium neglectum Dogiel (Ciliata Entodiniomorpha) from the Stomach of a Moose (Alces americana).*
Authors: KRASCHENINNIKOW SERHIJ
Published: May 2007

SUMMARY. The material containing the ciliate Eudiplodinium neglectum Dog. from the rumen of a moose was fixed with 4% formalin solution and studied both unstained and after staining with methylene blue or methyl green.

This ciliate is closely related to Eudiplodinium neglectum Dog. (1925) formae spectabile Dog. (1925) and impalae Dog. (1925), but differs from them in the presence of a transverse cuticular line. The form of the macronucleus of the investigated ciliates is regularly elongated clavate, the anterior end being wider than the posterior one. The following measurements were obtained from 14 specimens: length 81.3 μ (67.2–112 μ), width 66.2 μ (48.8–84 μ).

During division the anterior daughter gets the old skeletal plate and a new one arises de novo in the posterior daughter. The anlage of a new skeletal plate for the posterior daughter was observed in earlier and later telophases, first as an indistinct structure, later as a group of a variable number of granules, more often about 30. This anlage gradually grew into a typical skeletal plate. The anlage of the pharynx in the posterior daughter was seen in later telophases. A part of the distal end of the old skeletal plate (one, two or five rectangular prisms belonging to this organelle) and a part of the distal end of the old oesophagus are possibly cut off during division and dissolved in the protoplasm of the posterior daughter. A crossing of the distal end of the old skeletal plate by the division plane was observed only in those specimens in which this part consisted of one row of the rectangular skeletal prisms and was not found in the specimens with a shaft of the skeletal plate consisting of two rows of polygons. In later division stages a bending of the old skeletal plate takes place.

The morphological plasticity of the skeletal plate (loss of the distal part and subsequent bending of this organelle during the division of the ciliate) observed by the present writer and its dynamic reversibility (disappearing during starvation and thickening under satisfactory feeding conditions, reported by Westphal) confirm the assumption that the skeletal lamina functions primarily as a storage organelle. Some cases of destruction and defective development of the old skeletal plate were observed.

The presence of fat in some specimens of E. neglectum Dog. is noted.
Environmental Factors Affecting the Aggregation of the Cellular Slime Mold, Dictyostelium discoideum*†
Authors: Bradley S. G. , Sussman M. , Ennis H. L.
Published: May 2007

SUMMARY. The aggregative process of Dictyostelium discoideum is unaffected by most chemical and physical alterations of the environment. Such substances as vitamins, amino acids, catabolic intermediates, purines and pyrimidines, redox poising agents, enzyme inhibitors, and inorganic salts were added to the aggregative substrate. Of these, only a few exerted any influence on aggregation except at lethal concentrations. Histidine allowed the wild‐type myxamoebae to aggregate at lower population densities and accelerated the aggregative process as compared with controls on minimal agar. Brief exposure to histidine irreversibly conditioned the cells. No degradation of the imidazol skeleton was detected. A rise and fall of internal soluble histidine were demonstrable. The purine base, adenine, raised the population density required for maximal center formation.
A Molecular Morphology of Euglena gracilis var. bacillaris*
Authors: WOLKEN JEROME J.
Published: May 2007

SUMMARY. The structural morphology of Euglena gracilis, particularly the photoreceptors, has been studied by electron microscopy in order to arrive at some structural basis for function. The chloroplast, eye‐spot, and flagella are described and their relationship within the cell discussed. A molecular model for both the chloroplast and eye‐spot are proposed from the available structural and experimental data. The effects of darkness, elevated temperatures, metal depletion, and streptomycin on the cells and structure of the chloroplast are described. In all cases where structural changes occur in the chloroplast they are accompanied by spectral shifts in the absorption spectra of chlorophyll indicative of the appearance of pheophytin. The relationship of the eye‐spot and flagella was considered as a structural unit and the energy for excitation was roughly estimated.
Some Factors Affecting Alkaline Phosphatase Activity inTetrahymena pyriformisW.
Authors: Fennell R. A. , Degenhardt Eeward F.
Published: May 2007

SUMMARY.Objectives of the investigation were to: (1) ascertain whether, on the basis of enzyme inhibition, localization, and staining intensity, multiple phosphatases exist inTetrahymena pyriformisW; (2) show activity values for phosphatase in specimens ofT. pyriformisW from various ages and types of culture solutions; and (3) test the reliability of the Ca‐cobalt technique for demonstration of phosphatase in cell nuclei.

Complete inhibition of phosphatases (Ca‐cobalt) was obtained with semi‐carbazide, HCI and 0.2 m citrate buffer, pH 5.5. Potassium cyanide (0.01 m) tended to activate phosphatase with adenosinetriphosphate and inhibited phosphatase with Na‐glycerophosphate, adenosine‐5‐phosphate, adenosine‐3‐phosphate, glucose‐1‐phosphate, and creatine phosphate solutions. A differential inhibition of phosphatase was obtained with inhibitors other than KCN.

Phosphatase‐active areas were in essentially the same intracellular position in all substrate solutions with the exception of enzyme‐active areas in organisms from tryptone‐MgCl2‐citrate (0.01 m, pH 5.5) solutions; in the latter, both nuclear and cytoplasmic activity was evident. Organisms from tryptone‐MgCl2‐citratel (0.02 m), and vitamin‐enriched tryptone solutions exhibited abundant cytoplasmic phosphatase with the azo‐dye procedure. On the other hand, cytoplasmic phosphatase was not demonstrated with the Ca‐cobalt procedure.

Results obtained with enzyme inhibitors, various substrate solutions and evaluation of staining intensities suggest but do not demonstrate that 3 phosphomonoesterases, which hydrolyze glycero‐phosphate, adenosine‐5‐phosphate, and adenosinetriphosphate, exist inTetrahymena pyriformisW.

Nuclear reactions obtained with the Ca‐cobalt procedure were believed to be artifacts, with the exception of reactions obtained with cells from tryptone‐MgCl2‐citrate solutions subsequent to incubation in adenosinetriphosphate solution.
Long‐term Adaptation to Fatty Acids by the Phytoflagellate, Polytoma uvella
Authors: Cirillo Vincent P.
Published: May 2007

SUMMARY. The adaptation to fatty acids by Polytoma depends upon two mechanisms: 1. The induced synthesis of fatty acid oxidase which precedes growth. 2. A long‐term physiological adaptation spanning several cell generations which results in an increase of the initial rate of growth.

Analysis of the long‐term adaptation shows that the adaptation does not result from the selection of fast‐growing mutants. The generation time on butyrate of unadapted cells is initially ca. 24 hours and it is reduced to ca. 10 hours after the second subculture in butyrate medium. Adaptation to butyrate results in a simultaneous adaptation to caproate.
Purification, Axenic Cultivation, and Description of a Soil Amoeba, Acanthamoeba sp.
Authors: Neff Robert J.
Published: May 2007

SUMMARY. A small soil amoeba was purified by an agar‐surface migration method. The amoeba was grown axenicly in a liquid medium composed of 1% proteose peptone, 1% glucose, and inorganic salts. The amoeba was identified as a species of Acanthamoeba. A hypothesis on the mechanism of agar‐surface purification of amoebæ is proposed. The nutritional requirements of this isolate are discussed; it is concluded that this organism metabolizes glucose.
Studies on Trichomonads. I. The Metabolism of Tritrichomonas foetus and Trichomonads from the Nasal Cavity and Gecum of Swine
Authors: Doran David J.
Published: May 2007

SUMMARY. The metabolism of Tritrichomonas foetus (strain, BP‐1) and trichomonads from the nasal cavity and cecum of swine was studied manometrically under similar experimental conditions. At pH 6.4, quantitative and qualitative differences were observed. The cecal (probably T. suis) and nasal trichomonad used glucose, galactose, fructose, mannose, lactose, sucrose, raffinose, and trehalose. T. foetus used all except lactose and raffinose. All three were inhibited by iodoacetate and arsenite. T. foetus and the nasal form were significantly inhibited by fluoride and 8‐hydroxyquinoline, whereas the cecal trichomonad was not. At varied pH, all failed to oxidize Krebs' cycle intermediates. The amounts of oxygen consumed by T. foetus and the nasal trichomonad in the presence of lactate and pyruvate were at levels similar to those with disaccharides; the cecal trichomonad was indifferent toward both substances. Anaerobically, lactate and pyruvate increased the evolution of gas by all three trichomonads. Aerobic acid formation was demonstrated for all three forms. Anaerobically, metabolic CO2 and gas(es) that were not absorbed by KOH were evolved by all three. Pure oxygen was inhibitory to glucose utilization and stimulatory to the endogenous respiration of all trichomonads; the nasal form was affected the least.

The writer believes that the cecal trichomonad is different from T. foetus and the nasal trichomonad of swine. The relationship between the nasal trichomonad and T. foetus remains in doubt.
A New Vector of Haemoproteus colmubae in England
Authors: Baker J. R.
Published: May 2007

SUMMARY. Haemoproteus columbae of English wood pigeons (Columba palumbus palumbus L.) was found to undergo sporogony in Ornithomyia avicularia. It is suggested that this insect is a vector of H. columbae, in spite of the failure of six attempts to transmit the haemosporidian to uninfected domestic pigeons (C. livia var. domestica) by the bite, or injection, of infected O. avicularia.
Rhythmic Cell Division in Populations of Gonyaulax polyedra*†‡
Authors: SWEENEY BEATRICE M. , HASTINGS J. WOODLAND
Published: May 2007

SYNOPSIS. In cultures of the marine dinoflagellate Gonyaulax polyedra grown with alternating light and dark periods of 12 hours each, at least 85% of all cell divisions which occur in a day take place during a 5‐hour period spanning the end of the dark period and the beginning of the light period. A very distinct maximum in the number of recently divided cells occurs at about the time the light period begins.

This diurnal periodicity in cell division is lost after 4 to 6 days in continuous bright light, but will persist for at least 14 days in continuous dim light. The period of approximately 24 hours under constant conditions is only slightly altered by varying light intensity and temperature, both of which factors are known to affect markedly the generation time. The time at which cell division occurs is therefore postulated to be controlled by some sort of rhythmic or clock mechanism.

Similarities between the cell division rhythm and the endogenous rhythm of luminescence in this organism are discussed. The occurrence of a glow, or steady light emission of low intensity, at about the time of cell division, is described, and it is suggested that this glow may result from cellular changes accompanying certain stages of cell division.
The Activity of the Contractile Vacuole of Crithidia fasciculata*
Authors: COSGROVE WILLIAM B. , KESSEL RICHARD G.
Published: May 2007

SYNOPSIS. It has been shown that the output of the contractile vacuole of Crithidia fasciculata increases as the concentration of solute in the external solution decreases when NaCl is the solute. The increase in output is the result of increased rate of growth as well as increased maximum size, the latter being more important in the range 0.1M–0.01M. Solutions of penta‐erythritol produce the same effects as isosmolar solutions of NaCl. Body volume is not maintained constant but increases less than two‐fold between 0.1M and 0.0001M. The isotonic concentration of NaCl is estimated as 0.12M. It is not possible to demonstrate any effect of concentration of the external environment on the endogenous rate of oxygen consumption. A linear relationship between output and calculated osmotic gradient across the cell membrane has been shown in the concentration range 0.1M–0.01M. Absence of this relationship, and failure of body volume to increase as predicted, in solutions more dilute than 0.01M are interpreted as indications that other processes probably become predominant in these solutions. It is concluded that the contractile vacuole of this flagellate is incapable of maintaining absolute constancy of internal osmotic pressure and body volume but prevents much of the change expected on physical grounds.
Non‐axenic and Axenic Growth of Vorticella microstoma
Authors: FINLEY HAROLD E. , McLAUGHLIN DAVID , HARRISON DORIS M.
Published: May 2007

SYNOPSIS. Vorticella microstoma was grown non‐axenically and axenically at pH 6.4. Vorticellas were maintained indefinitely on Bacillus cereus in a medium composed of Proteose‐Peptone, Cerophyl, and the filtrate from boiled wheat kernels. Prolific growth occurred in 2‐membered cultures. A medium containing hydrolyzed gelatin, aqueous liver extract, yeast nucleic acid hydrolysate, glucose, and penicillin is recommended for axenic growth.

The potential value of vorticellids as research tools is discussed together with metabolic implications of supplementing sterile Proteose‐Peptone broth with natural substances in particle form. The ineffectiveness of adding tryptophan, thiamine, glycine, and chelating agents to the axenic medium was considered. Refinements of the axenic medium are on trial.
Elektronenmikroskopische Untersuchungen über das Nephridialsystem von Paramaecium.
Authors: SCHNEIDER L.
Published: May 2007

SYNOPSIS.

The structure of the excretory apparatus of Paramecium caudatum and P. aurelia was studied in electro‐micrographs of ultrathin sections. The so‐called nephridial plasma visible in light microscopy was revealed as a network of fine branching tubules (nephridial tubules), of average diameter about 200 Å, which surround the nephridial canals. The nephridial tubules are connected peripherally directly to branches of the endoplasmic reticulum, which extends throughout the organism. During diastole of the radial canals the nephridial tubules open into the nephridial canals, but this connection is broken during systole. Surrounding the nephridial plasma are bundles of larger tubular elements (about 500 Å diameter).

The osmiophile wall of the terminal nephridial canal continues without change in the walls of the ampulla, the injection canal and the contractile vacuole. Contractile fibrillar elements, arranged in fiat band‐like bundles and of tubular structure (about 150‐250 A diameter) without periodic cross‐striations, begin at the top of the ampulla and extend, along the surface facing the pellicle, over the injection canal and contractile vacuole to the excretory canal, which they surround as a spiral envelope.

The closing of the contractile vacuole to the excretory canal is effected by a relatively compact membrane without pores, so that the emptying of the vacuole must follow breaking of this membrane. The function of the excretory system is discussed in the light of these new observations.
Hydramoeba hydroxena (Entz), a Parasite on the Fresh‐water Medusa, Craspedacusta sowerbii Lankester, and its Pathogenicity for Hydra cauliculata Hyman
Authors: RICE NOLAN E.
Published: May 2007

SYNOPSIS.

An amoeba found on the fresh‐water medusa, Craspedacusta sowerbii Lankester, collected in the Southampton Quarry Pond at Richmond, Virginia, is described and found to be identical with Hydramoeba hydroxena (Entz) which occurs on various species of fresh‐water hydras. Transfer of the amoeba to Hydra cauliculata Hyman, and other experiments, show it to be a facultative parasite for this species. The pathogenicity of the amoeba is decreased by fouling of the culture medium; the resistance of the hydra is decreased by starvation. Hydramoeba is also capable of destroying adult fresh‐water medusae in six days. Its relation to young medusae is not known, but the amoeba apparently does not attack the polyps or other developmental stages.
The Inadequacy of Monobacterially‐fed Paramecium aurelia as Food for Didinium nasutum
Authors: BURBANCK W. D. , EISEN JAMES D.
Published: May 2007

SYNOPSIS.

Sterile Didinium nasutum were fed Paramecium Aurelia which had been grown on monofloral cultures of five different species of bacteria and on a wild mixed culture of bacteria. Didinia grown on monoflorally‐fed paramenia or starved paramecia maintained a low daily division rate (0.88‐2.06), and after 3 or 4 days died, frequently showing structural abnormalities before death. Didinia fed paramecia grown on a wild mixture of bacteria showed a higher division rate (4.96), did not die after 3 or 4 days, and encysted, when the food was exhausted. It is suggested that a diet consisting of monoflorally‐fed or starved paramecia is inadequate for Didinium. This may be due to the lack of some substance or substances related to the enzyme system of the predator, possibly proteolytic enzymes elaborated by paramecia. In the experiments of Gause on the destruction of one species by another, his failure to establish population oscillations between Didinium and Paramecium might have been due to an inadequate diet for the didinia which resulted in their lack, of encystment and death.
A Redescription of Cyclidium glaucoma O.F.M., 1786 (Ciliata:Hymenostomatida), with Particular Attention to the Buccal Apparatus*
Authors: BERGER JACQUES , THOMPSON JESSE C.
Published: May 2007

SYNOPSIS.

An accurate description of Cyclidium glaucoma O.F.M., 1786, is presented. Fixed specimens were treated with the Chatton‐Lwoff silver impregnation technique and the standard Feulgen nucleal reaction. Living material was examined by phase microscopy. Components of the infraciliature have been given special attention, particularly in the buccal area. In brief consideration of the systematic status of this species emphasis is placed upon the close relationship of the pleuronematine and tetrahymenine groups of hymenostome ciliates. Comparisons on structures found in C. glaucoma with corresponding structures in species belonging to quite closely related families are made, and the fundamental nature of the infraciliary tetrahymenal buccal apparatus and the polar basal granule‐complex is discussed.
The Problem of Homonyms among Generic Names of Ciliated Protozoa, with Proposal of Several New Names*
Authors: CORLISS JOHN O.
Published: May 2007

SYNOPSIS.

Over ninety genera of ciliated protozoa have been given names preoccupied by the generic names of other animal organisms. To date some sixty of these junior homonyms never have been corrected. In half of these cases the homonymous ciliate names have been buried as synonyms of one kind or another, however, and need be of no further practical concern. For the remaining genera, thirty in number, replacement names arc proposed in the present paper in accordance with provisions of the International Rules of Zoological Nomenclature. Such action is considered to be in the best interest of ultimate taxonomic stability among the groups of organisms involved. New names also have had to be proposed for five families or subfamilies whose type genera have lost their original names through homonymy.
Mode of Action of 3‐Amino‐l,2,4‐Triazole on Photosynthetic Microorganisms*
Authors: AARONSON S.
Published: May 2007

SYNOPSIS.

3‐Amino‐l,2,4‐triazole (AT) inhibits the multiplication and pigment synthesis of several photosynthetic pro‐tists, Ochromonas danica, 0. malhamensis, Euglena gracilis and Rhodopseudomonas palustris; it also inhibits the catalase activity of beef liver and O. malhamensis. Fe++, Fe+++ or lecithin annul the inhibition by AT of multiplication and pigment synthesis in O. danica. Chelation of iron is suggested as the main action of AT on Odanica,
Malayan Protozoa 4. Epistylis caldwelli n. sp. (Ciliata: Peritricha), from Freshwater Neuston*
Authors: LAIRD MARSHALL
Published: May 2007

SYNOPSIS.

Epistylis caldwelli n.sp., a β‐mesosaprobic epi‐biont, was collected from the surface zone of only two of 164 water bodies at Singapore. It is recorded from the neustonic mosquito larvae Anopheles (Anophele s) hyrcanus Pallas subsp., An. (Myzomyia) kochi Donitz and Culex (Lutzi a) fuscanus Wiedemann, also from corixids, Micronecta quadristrigata Bred‐din, copepods, Mesocyclops leuckarti aequatorialis Kiefer, and floating dragonfly exuviae. Subsurface and benthic organisms were not infested. The squat zooids (av, 57.6 ± 34.8 μwhen fully extended) have a median contractile vacuole and a long and sinuous macronucleus. Colonies consist of 2–16 individuals on a short and unusually massive stalk up to 50 μthick.
The Centrioles of Trichonympha from Termites and their Functions in Reproduction
Authors: CLEVELAND L. R.
Published: May 2007

SYNOPSIS.

The centrioles of Trichonympha from termites do not differ, either in structure or function, from those of Trichonympha in Crypiocercus. The previous claims of a difference are erroneous. The roles of the centrioles in the reproduction of new extranuclear organelles and in nuclear duplication are described. The centrioles are autonomous organdies. They are just as essential for a cell's existence as are chromosomes.