bluuebunny/crossref_metadata_2025_split huggingface dataset:
Macrophage Activation by Tetrahymena pyriformis. I. Active Subcellular Fractions of Tetrahymena
Authors: Makioka Asao , Kobayashi Akio 
Published: May 2007

ABSTRACTExperiments were carried out to determine what subcellular fractions of Tetrahymena pyriformis could, after inoculation into mice, activate macrophages to kill Toxoplasma gondii in vitro. Peritoneal macrophages from mice inoculated intraperitoneally with cilia, pellicles, mitochondria, and microsomes exhibited strong toxoplasmacidal activity and had an enhanced capacity to release hydrogen peroxide (H2O2) by stimulation of a membrane‐active agent as compared with resident macrophages. In contrast, macrophages from mice inoculated with macronuclei and postmicrosomal supernatant showed no toxoplasmacidal activity and a low level of H2O2 release. Similar dose response was observed on the active subcellular fractions with regard to the degree of macrophage activation. Treatment of the active subcellular fractions with heating and trypsin markedly reduced their activity.
Biochemical Identification and Phylogenetic Relationships in Free‐Living Amoebas of the Genus Naegleria1
Authors: PERNIN PIERRE , CARIOU MARIE‐LOUISE , JACQUIER ARLETTE 
Published: May 2007

ABSTRACTUsing isoelectric focusing, the zymograms of 23 pathogenic and nonpathogenic Naegleria strains were studied for the activity of 16 enzymes. Certain enzymes (lactate dehydrogenase, L‐threonine dehydrogenase, superoxide dismutase, acid phosphatase, malic enzyme, and leucine aminopeptidase) proved particularly useful from a practical point of view as they allow easy and reliable identification of pathogenic N. fowleri and N. australiensis as well as nonpathogenic N. lovaniensis strains. Genetic interpretation of these zymograms gave estimates of genetic distances that largely confirmed the taxonomic position of the Naegleria species. In addition, the genetic data suggest that there are two main phylogenetic groups in the genus Naegleria.
Pleiotropic Effects of a Temperature‐Sensitive Mouthless Mutation in Tetrahymena thermophila on the Excretion of Extracellular Enzymes
Authors: NIELSEN TORBEN , VILLADSEN INGRID S. 
Published: May 2007

ABSTRACTThe mode of enzyme excretion was investigated during balanced growth in wild type Tetrahymena thermophila and in a temperature‐sensitive mutant that did not form a mouth and food vacuoles at the restrictive temperature. The mutant was used to determine which of the extracellular enzymes are normally excreted by defecation. During balanced growth at the permissive temperature the excretion of enzymes was constant, and maximal in complex medium. No protease activity against azocasein was detected. Changes in the growth temperature of the wild type cells only affected the release of 3′‐nucleotidase. For the mutant, however, the excretion changed markedly with increasing temperature: (a) ribonuclease, deoxyribonuclease, α‐glucosidase, and β‐glucosidase were detected in 0–10% of normal amounts; (b) 3′‐ and 5′‐nucleotidase, not measured previously in Tetrahymena, were found in 10‐ to 14‐fold of normal amounts; (c) excretion of acid phosphatase was unaffected. We therefore conclude that the extracellular enzymes (a) are released by defecation, that 3′‐ and 5′‐nucleotidase are secreted through the membrane system, and that acid phosphatase is released by lysosomes emptied through pinocytosis. It is proposed that the lysosomes used for the formation of digestive vacuoles are different from those used for the formation of pinocytotic vacuoles and for autophagic vacuoles.
Interactions of Giardia lamblia with Human Intestinal Mucus: Enhancement of Trophozoite Attachment to Glass1
Authors: ZENIAN ASADOUR , GILLIN FRANCES D. 
Published: May 2007

ABSTRACTGiardia lamblia trophozoites frequently are associated with mucus in vivo. We investigated the effects of human intestinal mucus on parasite attachment and survival in vitro. All samples of mucus from the duodenum and ileum (from four humans and two rabbits) enhanced attachment at 100 μm/ml. Attachment increased with mucus concentrations from 1 to 1000 μg/ml but declined toward the unstimulated level at concentrations above 1000 μg/ml. Mucus from the small intestine also promoted the survival of the parasites during the 2‐h incubation. In contrast, colonic mucus promoted survival, but inhibited attachment. Fractionation of mucus from the human small intestine by cesium chloride equilibrium density gradient ultracentrifugation revealed that both attachment‐ and survival‐promoting activities were in the low density, protein‐rich fraction. The high density fractions containing the mucins were devoid of activity. Thus, a non‐mucin fraction of mucus from the human small intestine may promote colonization by G. lamblia.
Development of the Swine Coccidium Eimeria debliecki Douwes, 1921 in Mammalian Cell Cultures1
Authors: LINDSAY DAVID S. , BLAGBURN BYRON L. , CURRENT WILLIAM L. , ERNST JOHN V. 
Published: May 2007

ABSTRACTSporozoites of Eimeria debliecki entered human fetal lung and porcine kidney cells grown in cultures and underwent one merogenous cycle, terminating in the production of second‐generation trophozoites. Sporozoites were intracellular 1 h post‐inoculation (PI) and developed into sporozoite‐shaped meronts at 40 h PI. These meronts, one of which was motile, had from two to ten nuclei. Sporozoite‐shaped meronts then developed into elongate or spheroidal meronts with 10 to 24 nuclei by two days PI. Ten to 26 first‐generation merozoites were formed by budding from the meront surface. Mature first‐generation merozoites were most numerous three days PI. Most meronts had ruptured and released nonmotile merozoites into the culture medium by four days PI. Merozoites that were not released became rounded and developed into second‐generation trophozoites. Refractile bodies were present in all developmental stages. No further development was observed five through eight days PI.
An Ultrastructural and Cytochemical Study of the Cell Surface of a Suctorian Ciliate1
Authors: SUNDERMANN CHRISTINE A. , PAULIN JEROME J. 
Published: May 2007

ABSTRACTThe surfaces of the main cell body, tentacle shaft, and knob of Discophrya collini, a freshwater suctorian ciliate, were characterized using various cytochemical techniques. Cells prepared for conventional transmission electron microscopy exhibited a 50–60 nm thick fuzzy layer over the cell body surface; this layer was absent from the tentacle knob. A thick (240 nm), two‐layered surface coat surrounding the main cell body was stained with ruthenium red. This heavy coat was absent from the surface of the knob where a thin, dense, ruthenium red‐positive layer and projecting filaments were present. Freeze‐etched material revealed a “particle region” (150–250 nm in thickness) closely associated with the outer cell surface of the suctorian. Fixed specimens were treated with four different lectins and analyzed with electron microscopy in order to obtain information about the carbohydrate composition of the outer surface of D. collini. Concanavalin A bound to the surface of the cell body and tentacle shaft as a dense, particulate layer (80 nm thick) but thinned to 13–16 nm over the surface of the knob. Wheat germ agglutinin‐treated cells also displayed a heavy, electron‐dense layer (128 nm thick) that surrounded the main cell body and tentacle shaft, but only scattered patches of bound wheat germ agglutinin were observed on the surface of the knob. Discophrya treated with Helix agglutinin or peanut agglutinin appeared similar to control cells. Suctorians were treated with lectins in vivo in an attempt to inhibit capture and ingestion of their prey, Tetrahymena pyriformis, by masking prey receptor sites on the knob. Concanavalin A and, to a lesser degree, wheat germ agglutinin, successfully inhibited attachment of the prey organism. Helix agglutinin and peanut agglutinin had little effect on prey capture.
Cellulose Detected in the Stalk of Protostelium irregularis (Eumycetozoea)1
Authors: BLANTON R. L. , CHANZY H. D. 
Published: May 2007

ABSTRACTThe stalk of Protostelium irregularis (Eumycetozoea) has been studied with light and electron microscopy and selected‐area electron diffraction. The stalk is positively birefringent and fibrillar. Diffraction patterns obtained from stalks indicate that crystalline cellulose I is one component of the stalk.
Identification of the Meiotic Division of Malarial Parasites
Authors: SINDEN R. E. , HARTLEY R. H. 
Published: May 2007

ABSTRACTZygotes of Plasmodium berghei were cultured 15–25 h in vitro to yield mature infective ookinetes. Samples taken in the first 5 h of culture were examined by electron microscopy. Meiotic figures were detected in the nuclei of the zygotes. Threadlike leptotene chromatids (chromosomes) condensed from attachment plaques on the nuclear envelope; chromatid pairing followed (zygotene), with synaptonemal complexes subsequently appearing (pachytene). These complexes persisted into metaphase but dissociated when the chromatids rapidly decondensed during anaphase. At telophase of the first meiotic division the kinetochores were retracted toward two small spindle complexes, which were found at widely separated poles in the nuclear envelope. The observations are consistent with a haploid genome of 8–10 chromosomes.
Symposium on “Symbiosis in Protozoa”: Introductory Remarks1,2
Authors: LEE JOHN J. , CORLISS JOHN O. 
Published: May 2007

ABSTRACT.Attention, perhaps overdue, is drawn to the extent and significance of endosymbionts (xenosomes sensu lato) in the cytoplasm and nuclei of many protozoa from diverse taxonomic groups. Even more importantly, recent advances in the study of such intimate associations are reviewed and discussed and their impact on broader problems of cell biology and evolution are stressed. Workers inside and especially outside the fields of protozoology and parasitology have often neglected such data, failing to appreciate their relevance to significant problems in their own fields of investigation. The major topics covered by speakers in the Symposium (to which this paper serves only as an introduction) include the following, in order of their presentation: terminology for the symbiont‐host relationship and a brief overview of the field; the evolutionary problem of the origin of contemporary associations, including cell organelles such as mitochondria and plastids; the adaptive value of endosymbionts to their protozoan hosts; mechanisms of establishment, maintenance, and integration of such foreign bodies/invaders in their unicellular eukaryotic host cells; and the extent of algal and bacterial endosymbioses in diverse protozoan groups. In all papers, the principal relatively well studied complexes used as examples are the following: various kinds of algae in the larger foraminifera and in ciliates, radiolarians, and acantharians; the several types of bacteria in the cytoplasm of Amoeba and of Pelomyxa; the endonuclear bacterial symbionts of Paramecium; the cytoplasmic prokaryotes in Paramecium and in Parauronema; and the methanogenic bacteria of certain ciliates.
Establishment, Maintenance, and Integration Mechanisms of Endosymbionts in Protozoa1
Authors: REISSER WERNER , MEIER RENATE , GÖRTZ HANS‐DIETER , JEON KWANG W. 
Published: May 2007

ABSTRACT.Important progress has been made in recent years towards better understanding of the establishment and maintenance of endosymbiosis in protozoa and of the eventual integrative mechanisms involved. Still, many problems remain to be investigated more thoroughly. In this paper, while treating and reviewing the subject broadly, particular and more detailed attention is given to three selected systems: endonuclear symbiosis by Holospora bacteria in Paramecium; algal (Chlorella) relationships with the “green”Paramecium (P. bursaria) as host; and the rod‐shaped bacteria found in the cytoplasm of Amoeba proteus. Data concerning the physiology of food vacuoles, membrane transport, photobehavior, recognition specificity, enzyme activity, and the like are presented and reviewed and discussed in light of the growing literature on the overall subject of “endocytobiology.” Emphasized is the complicated network of interactions between symbiotic partners and the importance of the development of integrative mechanisms in the evolution of the many intimate associations known at the cellular level today.
Morphogenesis in the Heterotrich Ciliate Climacostomum virens. II. Oral Development During Regeneration1
Authors: FAHRNI JOSÉ F. 
Published: May 2007

The regeneration (RG) of the oral apparatus (OA) by Climacostomum virens (Ciliophora, Heterotrichida) is examined by estimation of the ability of live cells to ingest food as well as by Nomarski interference contrast microscopy, bright field microscopy of protargol‐stained specimens, and by scanning electron microscopy. When placed in a 6% (w/v) urea solution for ∼ 2 min 10 sec, populations of 10,000–100,000 cells shed a large part of their OA. In more than 90% of the cells that shed, the discarded segment is comprised of the apical membranelles, most of the adoral membranelles, and of a variable part of the buccal tube. After washing and incubation at 26°C, 50% of the cells regenerate a functional OA in 4 h 47 min, and after 5 h 26 min, 90% of the cells are able to ingest food. At any given moment during the process, 50–90% of the cells are morphologically in the same stage of RG.Seven stages (among which three are divided into two substages) of RG are defined. The process begins by the disorganization of the remnant oral structures. Concomitantly, kinetosomes multiply along the kineties of the zone of discontinuity and form the longitudinally oriented oral primordium. The latter gives rise to the adoral primordium, which rapidly produces the adoral zone of membranelles (AZM), and to the paroral primordium, which subsequently forms the apical membranelles, the buccal peristomial kineties, and the paroral kinety. Morphogenetic movements lead to incurvation of the AZM and the frontal field and to invagination of the buccal tube.
Structural Aspects of Digestion of Escherichia coli in Tetrahymena1
Authors: NILSSON JYTTE R. 
Published: May 2007

ABSTRACTTetrahymena pyriformis ingested Escherichia coli for 15–20 min and the fine structure of food vacuoles was analyzed 5, 15, 30, 60, 90, 120, and 180 min after uptake began. From this analysis, eight vacuolar stages could be defined, and three to four stages were found in each sample. Stage 1 represents forming and newly detached vacuoles with a random distribution of bacteria. Stage 2 is the “dehydration” vacuole in which the bacteria are compacted and a few may lyse. Stage 3, corresponding to the acid phosphatase‐positive stage, has an electron‐dense vacuolar matrix revealing components of lysed bacteria and the translucent coat of intact bacteria. Stage 4 is the “halo” stage where centrally located, intact bacteria are surrounded by lysed material being removed by pinocytic activity of the vacuolar membrane. Stage 5 represents lysis of bacteria remaining intact until this stage; the stage is apparently followed by a second stage 4. Stage 6 contains few bacterial profiles in a smeared homogeneous mass. Stage 7 contains numerous vesicular membranous structures which apparently become transferred to the cytoplasm as such. Stage 8 represents defecation vacuoles derived from fusion of smaller vacuoles. The main findings are as follows: I) Bacterial lysis may occur during acidification of the vacuole prior to fusion with lysosomes. II) Digestion of bacteria apparently occurs in “bursts” as indicated by the extended time that vacuoles in stages 4 and 5 are present. III) Bacterial membranous structures seem to be transferred directly to the cytoplasm of Tetrahymena. IV) Mass defecation occurs 2 h after uptake begins.
Seasonal Distribution of Thermotolerant Free‐Living Amoebae. II. Lake Issaqueena1
Authors: KYLE DENNIS E. , NOBLET GAYLE PITTMAN 
Published: May 2007

ABSTRACTA quantitative study of the seasonal distribution of thermotolerant (37°C and 45°C), small free‐living amoebae (FLA) was conducted in Lake Issaqueena, a warm, monomictic lake with steep, sloping banks and a maximum basin depth of 10 m in the Piedmont region of South Carolina. Naegleria and Vahlkampfia were the most frequently encountered FLA in littoral sediment and surface water samples whereas Acanthamoeba was most commonly isolated from profundal sediment, especially during late summer. In the water column, FLA populations were highest in a persistent detrital layer; however, few amoebae were isolated from a massive (∼1.5 m thick) layer of Oscillatoria. The only N. fowleri isolated in this study was from the detrital layer. Discussion of the influence of differences in watershed and basin morphology on variations in the size and generic composition of FLA populations for the aquatic ecosystems of Lake Issaqueena and Willard's Pond is included.
Intestinal Mucus Protects Giardia lamblia from Killing by Human Milk1
Authors: ZENIAN ASA J. , GILLIN FRANCES D. 
Published: May 2007

ABSTRACTWe have previously shown that nonimmune human milk kills Giardia lamblia trophozoites in vitro. Killing requires a bile salt and the activity of the milk bile salt‐stimulated lipase. We now show that human small‐intestinal mucus protects trophozoites from killing by milk. Parasite survival increased with mucus concentration, but protection was overcome during longer incubation times or with greater milk concentrations. Trophozoites preincubated with mucus and then washed were not protected. Protective activity was associated with non‐mucin CsCl density gradient fractions. Moreover, it was heat‐stable, non‐dialyzable, and non‐lipid. Whereas whole mucus inhibited milk lipolytic activity, protective mucus fractions did not inhibit the enzyme. Furthermore, mucus partially protected G. lamblia trophozoites against the toxicity of oleic acid, a fatty acid which is released from milk triglycerides by lipase. These studies show that mucus protects G. lamblia both by inhibiting lipase activity and by decreasing the toxicity of products of lipolysis. The ability of mucus to protect G. lamblia from toxic lipolytic products may help to promote intestinal colonization by this parasite.
Isospora elmahalensis n. sp. (Apicomplexa, Eimeriidae), a Parasite of the White‐Cheeked Bulbul (Pycnonotus leucogenys) in Saudi Arabia
Authors: AMOUDI MIKKY A. 
Published: May 2007

ABSTRACTIsospora elmahalensis n. sp. is described from the Saudi Arabian bird, Pycnonotus leucogenys, from the Elmahala valley. Sporulated oocysts of I. elmahalensis were spherical or nearly subspherical, 19.5–22.5 × 18.5–20 (21.34 ± 0.4 × 19.06 ± 0.5) μm. Oocysts lacked a micropyle, residuum, and polar granule. Sporocysts were ovoid, 14–17.5 × 7–12 (16.08 ± 1.05 × 9.9 ± 1.55) μm, and had a Stieda body and sporocyst residuum, but lacked a substiedal body. Sporozoites were elongated with a clear globule at one end. The host bird belongs to the order Passeriformes.
The Ultrastructure of Vampyrellidium perforans Surek & Melkonian and Its Taxonomic Position Among the Naked Filose Amoebae1
Authors: PATTERSON DAVID J. , SUREK BARBARA , MELKONIAN MICHAEL 
Published: May 2007

ABSTRACTAn account of the fine structure of Vampyrellidium perforans is given. The organism has filose pseudopodia, mitochondria with flattened cristae, and cytoplasmic microtubules, some of which arise from a perinuclear cytoplasmic sheath. Microtubules were observed within nuclei presumed to be at an early stage of division. Relatively massive (non‐filose) pseudopodia are formed by cells feeding by engulfment. The cytoplasm of these pseudopodia has a fibrillar consistency with local aggregations of material. Despite sharing aspects of feeding behavior with vampyrellid filose amoebae, Vampyrellidium perforans is ultrastructurally more similar to Nuclearia, and it is here assigned to nucleariid filose amoebae.
Partial Purification and Characterization of Naegleria fowleriβ‐Glucosidase1
Authors: DAS SIDDHARTHA , SAHA ASISH K. , NERAD THOMAS A. , MARTINEZ A. JULIO , LAMARCO KAREN L. , BASU ALAKANANDA , LEGLER GUNTER , GLEW ROBERT H. 
Published: May 2007

ABSTRACTNaegleria fowleri cells, grown axenically, contain high levels of β‐D‐glucosidase which catalyzes the hydrolysis of 4‐methylumbelliferyl‐β‐D‐glucopyranoside (4MUGlc) (Km, 0.9 mM), octyl‐β‐D‐glucoside (Km, 0.17 mM), and p‐nitrophenyl‐β‐D‐glucopyranoside at relative rates of 1.00, 2.88, and 1.16, respectively (substrate concentration, 3.0 mM). When the amebae are subjected to freeze‐thawing, sonication, and centrifugation (100,000 g, 1 h), 85% of the β‐glucosidase activity appears in the supernatant fraction. The β‐glucosidase was purified 40‐fold (34% yield) using a combination of chromatographic steps involving DE‐52 cellulose, concanavalin A‐Sepharose, and hydroxylapatite followed by isoelectric focusing. The predominant soluble β‐D‐galactosidase activity in the Naegleria extract copurifies with the β‐D‐glucosidase; the two activities have the same isoelectric point (pI, 6.9), similar heat stabilities, are both inhibited by lactobionic acid (Ki, 0.40 mM), and exhibit optima at pH 4.5, indicating that they are probably the same enzyme. The Naegleriaβ‐D‐glucosidase has an apparent molecular weight of 66,000, a Stokes radius of 25 Å, and a sedimentation coefficient of 4.2S. The β‐glucosidase is not inhibited by conduritol β‐epoxide or galactosylsphingosine but is completely inhibited by 1.25 mM bromo conduritol β‐epoxide. The latter compound, when present in the growth medium, inhibits the growth of the organism and profoundly alters its ultrastructure, the main effect being the apparent inhibition of cytokinesis and the generation of multinucleate cells. The issue of the role of the β‐glucosidase in the metabolism of the ameba and its possible role in pathogenic mechanisms are discussed.
Genetic Heterogeneity in a Natural Population of Acanthamoeba polyphaga from Soil, an Isoenzyme Analysis1
Authors: JACOBSON LISA M. , BAND R. NEAL 
Published: May 2007

ABSTRACTAcanthamoeba polyphaga, a free‐living, bacterial feeder found in freshwater and soil, reproduces asexually and is morphologicaly distinguishable from other acanthamoebae. Isoenzyme analyses were done on 15 random, clonal isolates from soil. Electrophoretic patterns indicated that enzyme bands occurred in clusters consistent with that of a diploid organism. The data indicates that natural populations of A. polyphaga have a greater genetic diversity than laboratory isolates of other amoebae, resembling the heterogeneity observed for natural populations of bacteria.
Freeze‐Fracture Localization of Filipin‐Sterol Complexes in Plasma‐ and Cyto‐Membranes of Pneumocystis carinii1
Authors: YOSHIKAWA HISAO , MORIOKA HIROYUKI , YOSHIDA YUKIO 
Published: May 2007

ABSTRACTThe polyene antibiotic, filipin, was used as the probe for demonstrating sterols in the freeze‐fractured plasma‐ and cytomembranes of Pneumocystis carinii. The distribution of filipin‐sterol complexes was homogeneous on the plasma membrane throughout all developmental stages from trophozoite to cyst; however, the density of the complexes gradually decreased with the progress of development. In the trophozoite, the density of the complexes was 485 ± 42/μm2 on the P face and 341 ± 27/μm2 on the E face. It was 249 ± 50 on the P face and 132 ± 48 on the E face in the precyst and 138 ± 24 and 59 ± 20, respectively, in the cyst. The membranes of nucleus, mitochondria, and small round bodies showed more or fewer complexes while no complexes were found in the membranes of one endoplasmic reticulum. In nuclear and mitochondrial membranes, some small scattered clusters of complexes were observed. Two types of vacuoles were distinguished: one having many complexes in its membrane and the other having none at all.