bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of a Class III Antiarrhythmic Drug and Biphasic Shocks on the Postdefibrillation Refractory Period of Relatively Refractory Myocardium
Authors: MURAKAWA YUJI , YAMASHITA TAKESHI , AJIKI KOHSUKE , SEZAKI KAZUNORI , OMATA MASAO 
Published: May 2007

Refractory Period and Defibrillation. Introduction: This study was designed to test whether the refractory state of nondepolarized myocardium is a major determinant of electrical defibrillation. Methods and Results: Postshock recovery interval (PSRI) was estimated by measuring the residual refractory period after an appropriately timed field stimulus (1 to 16 V). The PSRI and transcardiac defibrillation threshold (DFT) were compared before and during the administration of E‐4031, a new Class III antiarrhythmic drug (group I, n = 10), or between monophasic and biphasic shocks (group 2, n = 14) in anesthetized open chest dogs. Group 1: E‐4031 reduced the DFT from 2.6 ± 0.6 J to 1.8 ± 0.6 J (P < 0.01). The PSRI increased with the increase of the applied voltage and was almost always greater during K‐4031 Infusion than at baseline. There was an inverse correlation between the changes of DFT and PSRI measured with a 14‐V stimulus (r =−0.80, P < 0.01) and a 16‐V stimulus (r =−0.80, P < 0.01). Group 2: Mean DFTs were not statistically different between the two waveforms (3.3 ± 1.0 J vs 2.9 ± 1.4 J). However, there also was an inverse correlation between the differences in individual PSRIs and DFTs of the two waveforms (10‐V stimulus: r =−0.62, P < 0.05; 16‐V stimulus: r =−0.75, P < 0.01). Conclusions: Modulation of defibrillation efficiency by E‐4031 infusion or by changes of the shock waveform was related to the effect of these interventions on PSRI. These results suggest an independent role for the refractoriness of nondepolarized myocardium in the mechanism of defibrillation.
Strength‐Interval Curves for Cardiac Tissue Predicted Using the Bidomain Model
Authors: ROTH BRADLEY J. 
Published: May 2007

Cardiac Strength‐Interval Curves. Introduction: Strength‐interval curves are predicted for unipolar anodal and cathodal stimulation of cardiac muscle. Methods and Results: Cardiac tissue is represented by the bidomain model, and the active properties of the membrane are described by the Beeler‐Reuter model. Two successive stimuli (S1 and S2) are delivered through a single extracellular electrode. The S2 threshold is determined as a function of the S1‐S2 interval, for anodal and cathodal S2 stimuli with 2‐, 5‐, 10‐, and 20‐msec durations. Each of the resulting cathodal and anodal strength‐interval curves is divided into two parts: one section corresponding to make stimulation (long intervals) and the other section corresponding to break stimulation (short intervals). Generally, the cathodal strength‐interval curves are decreasing functions of interval, except for an anomalous section of the 20‐msec duration cathodal curve in the interval range from 310 to 318 msec. At short intervals, the anodal strength‐interval curve contains a deep dip, which is more prominent for longer S2 durations. The cathodal threshold is less than the anodal threshold for all intervals except those corresponding to the end of the refractory period. Conclusion: The bidomain model predicts complex anodal and cathodal strength‐interval curves, with the anodal curve containing a dip (supernormal stimulation). These results resemble the experimental observations of Dekker.
Reorganisation du Type Endomixique chez les Loxodidae et chez les Centrophorella
Authors: FAURE‐FREMIET E. 
Published: May 2007

New investigations of the nuclear cycle in the gymnostome ciliate Loxodes rostrum verify the long‐neglected hypothesis proposed by Bütschli that in this multinucleated ciliate the macronuclei never divide. The consequences of this “caryosterose” are compensated for by a process of endomixis, that is, by the transformation of a certain number of the micronuclei, during vegetative multiplication, into new macronuclei.The nuclear cycle in the gymnostome Centrophorella fistulosa does not show any aspect of nuclear division. Interpretation of this supposes the existence of polyenergid nuclei which fragment, during the interdivisional period, into subnuclei; among these some evolve in the somatic and macronuclear direction, before disappearance by karyolysis; others, corresponding to the micronuclei, grow by endomitosis, and reconstitute the polyploid and polyenergid nuclei. Thus the very particular nuclear cycle of C. fistulosa is believed to exhibit a new aspect in the endomictic process of nuclear reorganization.
The Oxidative Metabolism of a Cryptomonad Flagellate, Chilomonas paramecium*
Authors: HOLZ GEORGE G. 
Published: May 2007

Tests based on respirometric and population growth methods for the analysis of oxidizable substrates for Chilomonas paramecium revealed that only those substances tested which are intermediates in terminal cyclic respiratory mechanisms (pyruvate, lactate, acetate, α‐ketoglutarate, succinate, fumarate, L‐malate, oxalacetate, but not citrate, cis‐aconitate or DL‐isocitrate) were attacked. These organic acids, and the fatty acids and alcohols earlier known to be used, n‐butyric, n‐caproic and n‐caprylic acids, ethyl, n‐butyl and n‐hexyl alcohols, were the only carbon compounds oxidized by C. paramecium under the test conditions employed.Utilization of acid substrates was found to be pH‐dependent. Reproductive and respiratory rates were related to the pKa values of the compounds. Oxidation of acetate, lactate, and pyruvate, however, was observed at pH values where their molecular form was present in exceedingly small amounts.Naturally‐occurring α‐amino acids, amines, glycolysis intermediates (3‐phosphoglyceric acid, glucose‐1‐phosphate, hexose diphosphate) and degraded intermediates of glycolysis (glyceric acid, glycerol, dihydroxyacetone, glucose), two‐carbon compounds more oxidized than acetic acid (oxalic, glycolic, glyoxylic acids, glyoxal, ethylene glycol), and formic, tartaric, malonic, and glutaric acids, were not used.Respiration in the presence of single members of the group of oxidizable substrates was sensitive to malonate and fluoroacetate. Malonate inhibition of succinate oxidation could be reversed by an increase in succinate concentration, but the relationship was not competitive; possibly because of permeability differences between the substrate and inhibitor. Fluoroacetate inhibition was accompanied by the accumulation of citric acid.The experiments on substrate oxidation, and the effects of inhibitors on the respiratory metabolism of the flagellate, are considered to provide evidence for the operation of the Krebs tricarboxylic acid cycle as a terminal respiratory mechanism in C. paramecium.
The Literature on Tetrahymena: Its History, Growth, and Recent Trends*
Authors: CORLISS JOHN O. 
Published: May 2007

The literature involving the genus Tetrahymena has become so voluminous in recent years that some consolidation of it appears advisable. Through 1953 well over 500 papers, scattered through more than 100 scientific journals, have been devoted in whole or in part to studies in which species and strains of this genus, under a variety of names, have been employed as one of the experimental animals. Nearly half of these works are cited directly in the present paper. The major areas of research in which these ciliates have been used to advantage include physiology and biochemistry, containing nearly 60% of all the papers, cytology and taxonomy, and three smaller fields arbitrarily designated as cytogenetics, morphogenesis, and parasitism.Tetrahymena's sustained popularity as an object of research may be considered as due primarily to its ability to thrive axenically in a chemically defined nutrient medium and secondarily to such factors as its ubiquity in nature, its ready adaptability to a variety of ecological situations (including endoparasitism), its possession of a relatively primitive and fundamental type of buccal ciliature of considerable phylogenetic significance, and its exhibition of the sexual phenomena of conjugation and autogamy.
The Metabolism of Trichomonas vaginalis: The Glycolytic Pathway*
Authors: WIRTSCHAFTER SAMUEL , JAHN THEODORE L. 
Published: May 2007

SUMMARY. Three enzymes of the glycolytic pathway, hitherto not identified in Trichomonas vaginalis, have been studied: phosphoglucomutasse, α‐glycerophosphate dehydrogenase, and lactic dehydrogenase.The identification of seven phosphorylated glycolytic intermediates is reported.The operation of glycolysis in T. vaginalis is postulated from enzymatic as well as chemical studies.
The Metabolism of Trichomonas vaginalis: The Oxidative Pathway*†
Authors: WIRTSCHAFTER SAMUEL , SALTMAN PAUL , JAHN THEODORE L. 
Published: May 2007

SUMMARY. Washed intact cell preparations of T. vaginalis oxidize pyruvate and malate. They are unable to utilize other intermediates of the Krebs cycle. Homogenates of these cells show the same pattern of enzymatic dehydrogenase activity toward the Krebs cycle organic acids. Attempts to inhibit pyruvate oxidation with such Krebs cycle blocking agents as malonate, arsenite, parapyruvate, and fluoroacetate were unsuccessful.Isotopic tracer studies with 2‐C14 pyruvate showed that although several, as yet unidentified, compounds incorporated activity during the course of pyruvate metabolism, none of these labeled compounds corresponded to any of the Krebs cycle intermediates.It is concluded that the Krebs cycle is not the pathway for the oxidation of pyruvate in T. vaginalis.
Adaptation by Tetrahymena pyriformis to Potassium Cyanide II. Adaptation Against Respiratory Inhibition*
Authors: MCCASHLAND B. W. 
Published: May 2007

SUMMARY. Cells from a clonal culture of Tetrahymena pyriformis W were cultured in the presence of 10‐4 M KCN for a prolonged time until they became “adapted” to cyanide. The effect of 10‐3 M KCN upon respiration in the “adapted” cells was compared with the effect upon “normal” cells of the same clone grown in the absence of cyanide. The direct method of Warburg was employed.Adapted cells are more resistant against respiratory inhibition than are normal cells. Resistance is due both to a factor or factors retained within the cell and the extracellular factor(s) released into the medium by the adapted cells during their growth. The intracellular factor is acid labile, and apparently may be developed within a short time. The extracellular factor is heat labile and may cause normal cells to be more resistant against respiratory inhibition by KCN.Resistance to respiratory inhibition is lost if adapted cells are cultured in the absence of KCN. It is proposed that changes involved in gain or loss of cyanide resistance are due to physiological adaptation and not to the usual genetic influences.
Macro nuclear Morphogenesis during Division of Blepharisma undulans*
Authors: McLoughlin Donald K. 
Published: May 2007

SUMMARY. The division cycle was followed in four strains of Blepharisma undulans. Animals were fixed and stained at regular intervals from the end of one division through completion of the next.A comparative study of the present findings and those in the literature shows that in all strains in which the macronucleus is nodulated there is a similarity in the events that occur during division. These include a loss of some of the chromatin material, a fusion of macronuclear nodes into two masses, and a subsequent fusion of these two masses into one large, centrally located mass. This, in turn, elongates and divides into two daughter nuclei which either are nodulated at the time of separation or become so shortly after the division into daughter nuclei.Great variation exists, among different strains, in the number of macronuclear nodes present. This fact, coupled with knowledge of nuclear morphogenesis during the division cycle, renders macronuclear form of little taxonomic value at infrageneric levels.
Achromatic Figure Formation by Multiple Centrioles of Barbulanympha
Authors: Cleveland L. R. 
Published: May 2007

SUMMARY. The role of centrioles in achromatic figure production is considered when the number present varies from 1–8. Each centriole after it becomes elongate produces astral rays from its distal end. Some of these rays remain free; some, by joining centromeres, become chromosomal fibers; and some, by joining and growing along those produced by one or more other centrioles, produce the central spindle portion of the achromatic figures. Thus, one centriole may function cooperatively with one to several others in the production of central spindles. But at least two centrioles must be present, and in the proper spacial relation to each other, to form a central spindle; one by itself can form only free astral rays, no central spindle or chromosomal fibers.The flagellated areas (to which the centrioles are anchored anteriorly) play an important role in determining the position of the distal ends of the centrioles with respect to one another, and the position of these ends, in turn, in a large measure, determines the types of achromatic figures produced, particularly the number of central spindles.
The Biology of Trypanosoma diemyctyli, Tobey. III. Factors influencing the cycle of Trypanosoma diemyctyli in the vertebrate host Triturus v. viridescens.
Authors: BARROW JAMES H. 
Published: May 2007

SYNOPSIS. The effects of some environmental influences on the cycle of Trypanosoma diemyctyli in Triturus v. viridescens are described. Bleeding of the host produced a reduction in the number of trypanosomes but did not affect their growth rate. The temperature at which the host was maintained affected the cycle of the trypanosomes. The length of the post‐inoculation latent stage increased from 24 hours at 25°C. to an indefinitely long time at 5°C. The trypanosomes were found to be dimorphic. Adult parasites of the short form had a range of 45–75 μ and those of the long form of 76–116 μ. Growth rate of the trypanosomes was inhibited or greatly retarded at temperatures of 10°C. or lower and was greatest at 25°C. The size attained by the parasites and the number of parasites were greatest at 15°C. At this temperature the infection was pathogenic and the dimorphic parasites were in their long form. At the higher temperatures (20–25°C.) the infection was non‐pathogenic with the trypanosomes in their short form.The infection is primarily one of adult newts. Experiments indicated that the larvae were resistant to the trypanosomes at all temperatures while the red efts were not. The latter are usually free from the trypanosomes because they are not exposed to them. Attempts to infect other newts and to locate any cryptic stages by the injection of blood and tissues from infected newts gave negative results.Starvation, sodium salicylate, and treatments used to control fungus infection of the newts had no detectable effects on the trypanosomes.
On the Parasitic Protozoa of Liberia. II. The Malaria Parasites of Agamid Lizards.
Authors: BRAY R. S. 
Published: May 2007

SYNOPSIS. 45% of the agamid lizards captured in the Harbel area of Liberia harboured haemosporidia. These were Haemamoeba (=Plasmodium) agamae, H. giganteum and a Haemoproteus.A full description of H. agamae and H. giganteum blood forms is made and the discovery is reported of exo‐erythrocytic forms of H. agamae in the spleen and of H. giganteum in the brain and liver. One oöcyst of H. agamae is reported in Aedes aegypti.
Carbon Nutrition and Metabolism of Polytomella caeca*
Authors: WISE DONALD L. 
Published: May 2007

SYNOPSIS. Polytomella caeca utilizes as sole carbon sources in chemically defined media: acetate, propionate, butyrate, valerate, pyruvate, succinate, ethyl, butyl, amyl, and hexyl alcohols. Glyceraldehyde and α‐ketoglutarate sustain very small populations. Caproate, caprylate, fumarate, malate, propyl, heptyl, and octyl alcohols and the iso‐compounds iso‐butyrate, iso‐butyl and iso‐hexyl alcohols are inadequate.Acetate is not assimilated <pH 5.0, propionate and butyrate <pH 6.0, and valerate <pH 7.0. Optimum for utilization of succinate is pH 3.0, for pyruvate pH 4.0, utilized also at pH 2.0 Fatty acids are utilized dissociated; succinate and pyruvate are utilized undissociated. Alcohols are assimilated throughout pH 4.0–7.4, except hexanol at pH 7.4. Alcohol availability is proportional to molecular length‐1.pH after growth of fatty acid media is 8.4 ± 0.4; stable in pH 2.0 pyruvate and pH 3.0 succinate media; 3.5 ± 0.3 in alcohol media with initial pH <6.0. Longer alcohols cause less pH decrease during growth.Acetate concentrations <0.2% do not support maximum populations; concentrations of 0.2–1.0% do. pH after growth increases in these media to pH 8.5 with maximum populations.Malate, fumarate, α‐ketoglutarate, and lactate seem not to penetrate the cell, but are metabolized by homogenates. Methylene blue reduction by homogenates indicates the presence of lactic, malic, succinic and α‐ketoglutaric dehydrogenases, fumarase and glutamic transaminase. Extracts contain Embden‐Meyerhof phosphate esters, ATP, and ADP.
Macronuclear Changes in a Strain of Blepharisma undulans during the Divisional Cycle*
Authors: HELSON LAWRENCE , PECORA PAULINE , HIRSHFIELD HENRY I. 
Published: May 2007

SYNOPSIS. Specimens of Blepharisma undulans were transferred from young clone cultures to a rotocompressor with 3 mm3 of culture medium. The organisms were slightly compressed and photographed at various intervals with dark field illumination. The sequence of macronuclear and cytoplasmic changes was compared with similarly followed Feulgen preparations.The cycle falls into several phases: (1) an interphase (12–24 hr.) in which the organism increases in size while cytoplasmic and macronuclear appearances remain unchanged. During this phase, the macronucleus consists of 3 to 5 nodes of various sizes connected by strands. (2) a pre‐condensation phase (1 hr.) in which a new posterior peristome and cytopyge appear without visible macronuclear change. (3) a condensation phase (10–20 min.) in which the macronuclear nodes coalesce into a round mass without dissolution of the central nodes or strands. (4) a postcondensation phase (1 hr.) characterized by: (a) elongation of the condensed macronucleus into a rod‐like shape followed by typical nodal formation; or (b) elongation of the condensed macronucleus into a form resembling the letter “J”, followed by nodal formation, and resulting in a double row of nodes in one daughter and a single row in the other. Separation occurs at this time, initiating the new interphase. The development of the j‐form macronucleus. the lack of obliteration of the central nodes, and the characteristic interphase condition distinguish this strain of B. undulans from others described elsewhere.
Studies on the Fine Structure of a Gregarine Parasitic in the Gut of the Grasshopper, melanoplus differentialis*
Authors: BEAMS H. W. , TAHMISIAN T. N. , DEVINE R. L. , ANDERSON EVERETT 
Published: May 2007

SYNOPSIS. Materials within the endoplasm of both the protomerite and deutomerite may be displaced and stratified by ultracentrifugation. Animals are not killed by this treatment, and in time a redistribution of stratified materials may occur. The electron microscope reveals numerous ultramicroscopic folds in the surface envelope which is composed of 3 membranes; the outer and middle cover the surface of the folds while the inner one continues as a smooth membrane over the ectoplasm. The contact surfaces of animals in syzygy do not show the small folds to be interlocked; instead, they are in fold‐to‐fold contact. Numerous relatively dense bodies which appear to be filamentous are sometimes observed immediately underneath or within the middle or inner membrane. Within the ectoplasm is an ultramicroscopic net‐like fibrillar structure much denser than the surrounding cytoplasm. This system of fibrils is composed of anastomosing elements varying from ∼ 50 to 200 Å in diameter. Certain of the larger fibrils are directly attached to the surface envelope at positions between the folds. A second filamentous structure within the ectoplasm appears to be tubular. Elements of this system also appear to join and penetrate the surface envelope by means of pores.A large amount of gelatinous secretion forms at the surface of the sporont; as it glides forward a trail of mucous is left behind. The actual mechanism involved in the gliding movement was unobserved, but evidence is lacking to support the view that the gliding movement is engendered by posteriorly directed “jets” of mucus.
Some Physiological Characteristics of the Mating Types and Varieties of Tetrahymena pyriformis*†
Authors: HOLZ GEORGE G. , ERWIN JOSEPH A. , DAVIS ROBERT J. 
Published: May 2007

SYNOPSIS. Differences in temperature‐tolerance, generation time, nutritional requirements, osmoresistance, pigment production, and sensitivity to high hydrogen or hydroxyl ion concentration have been observed among varieties, and among mating types within varieties of Tetrahymena pyriformis. The usefulness of these differences to taxonomists and geneticists is discussed.The nutrition of a temperature‐tolerant strain, mating type II, variety 1, was given special attention and a chemicallydefined medium devised to support rapid growth at 35d̀ C. At 40d̀, growth in this medium failed, but was good in a crude medium. Temperature factors are suggested. Permeability of this ciliate, as inferred by utilization of nucleotides, was high.
Studies on Trichomonads. III. Inhibitors, Acid Production, and Substrate Utilization by 4 Strains of Tritrichomonas foetus
Authors: DORAN DAVID J. 
Published: May 2007

SYNOPSIS. Inhibitors, acid production, and substrate utilization by 4 strains of Tritrichmonas foetus (BP‐3, BP‐4, A‐1, and A‐2) were studied manometrically. All used glucose, galactose, mannose, fructose, sucrose, maltose, trehalose, glycogen, starch, lactate, and pyruvate. Strain A‐1, with the highest aerobic and anaerobic endogenous rates, used these substrates less than did the others. Strain BP‐3 did not use lactose; strains BP‐4 and A‐2 did not use raffinose aerobically and only slightly anaerobically; strain A‐1 used both nearly as well as maltose and sucrose. All were strongly inhibited by iodoacetate and, if tested in the presence of glucose, aerobically or anaerobically, by fluoride, arsenite, hydroxylamine, and 8‐hydroxyquinoline. Aerobically, 2,4‐dinitrophenol produced stimulation which was greater in the presence of glucose; anaerobically, it produced inhibition which was, in some cases, comparable to the effects produced by the other inhibitors. Fluoride, arsenite, azide, and hydroxylamine, although producing insignificant inhibitory effects on endogenous O2 consumption, reduced and, in some cases, abolished motility of all strains. All 4 strains produced acid under anaerobic and aerobic conditions; strain A‐1 produced more than the others. Lactic acid accounted for 30–51% of the acid produced in all strains.Strain A‐1 more closely resembled the nasal trichomonad of swine (strain PN‐610) than did strain BP‐1. (Doran(3)). The writer believes that the swine nasal strain is a highly adapted strain of T. foetus.