bluuebunny/crossref_metadata_2025_split huggingface dataset:
Immunofluorescent Localization of Myosin at the Anterior Pole of the Coccidian, Toxoplasma gondi1
Authors: SCHWARTZMAN JOSEPH D. , PFEFFERKORN E. R. 
Published: May 2007

ABSTRACTIndirect immunofluorescence using anti‐myosin rabbit sera showed myosin localized in a characteristic pattern at the anterior pole of Toxoplasma gondii. This polar fluorescent staining was abolished by pre‐absorption of the anti‐sera with myosin extracted from avian muscle. Both intracellular and extracellular T. gondii showed similar patterns when formaldehyde‐fixed, but neither showed polar fluorescence when acetone was used as the sole fixative. Immunofluorescent staining of live T. gondii revealed no polar fluorescence, suggesting that myosin is not present on the outer parasite membrane. Anti‐myosin serum did not prevent host cell invasion and plaque formation in the presence of human complement. Inhibition of contractile proteins with cytochalasin D inhibited T. gondii motility and infectivity in a plaque formation assay. The pattern of polar fluorescence described here resembles the IgM‐associated polar staining frequently detected in human sera, but we believe it is a different phenomenon because human sera that showed such staining retained their activity after pre‐absorption with avian myosin. The unusual localization of myosin at the anterior pole of T. gondii tachyzoites may play a role in the function of anterior organelles, which are thought to facilitate the invasion of host cells.
Actin in Tetrahymena paravorax: Ultrastructural Localization of HMM‐Binding Filaments in Glycerinated Cells1,2
Authors: MÉTÉNIER GUY 
Published: May 2007

ABSTRACTActin has been identified in the ciliated protozoon Tetrahymena paravorax on the basis of the ultrastructural detection of filaments typically decorated with heavy meromyosin (HMM) in glycerinated microstome cells. These filaments are widely distributed in endoplasmic and cortical regions and can form bundles. They are particularly numerous in elongating cells; HMM‐binding filaments run approximately parallel to rib microtubules in the ectoplasm of the right wall of the buccal cavity and seem to extend to the cytopharyngeal region, suggesting some role of actin in maintenance of the crest‐trough pattern of ribbed wall and/or in formation of food vacuoles. Extensive actin bundles are observed below some membranellar areas and are thought to follow the course of the microtubular “deep fiber bundle.” The “fine filamentous reticulum” underlying the oral ribs and the “apical ring” extending beneath kinetosomes of ciliary couplets display filaments that do not bind HMM and are ˜ 14 nm in diameter. No evidence for actin in these structures was obtained in the present study. The “specialized cytoplasm” of the cytostome‐cytopharyngeal region appears as an undecorated reticulum with 20 nm‐spaced nodes. Occasionally HMM‐binding filaments were found inside the macronucleus, just beneath its envelope. Actin is suggested to be involved in cell shaping and in control of the transport of food vacuoles.
Transmission Electron Microscopy of Meront Development of Eimeria vermiformis Ernst, Chobotar and Hammond, 1971 (Apicomplexa, Eucoccidiorida) in the Mouse, Mus musculus1
Authors: ADAMS JOHN H. , TODD KENNETH S. 
Published: May 2007

ABSTRACTFirst and second generation meronts of Eimeria vermiformis developed in epithelial cells of the crypts of Lieberkühn. They were usually between the host cell nucleus and the basement membrane. Sporozoite organelles dedifferentiated with the first generation meront's development except for the refractile body and the apical complex, which persisted. After several nuclear divisions, the apical complex dedifferentiated further until only micronemes remained attached by a duct system to the plasmalemma. The form of the apical complex was highly variable. Sometimes the duct system was absent and the micronemes were attached directly to the plasmalemma or a dense material on it. Crescent body‐like material was often present in the parasitophorous vacuole next to the microneme structure. The microneme structure was not present in second generation meronts but evaginations of the plasmalemma, cytoplasmic outpocketings, and cytoplasmic vesicles were associated with the round granular bodies in the parasitophorous vacuoles. During first generation merogenesis, invaginations from the parasitophorous vacuole formed channels into the meront along which merozoites budded. Micropores were often at the ends of these invaginations. These and other micropores of the meront had a dense U‐shaped band for a collar while those of the merozoites had a collar with a double band of dense material that connected to the inner membrane. First generation merozoites budded randomly from the meront, resulting in a residual body that was usually in the middle of the parasitophorous vacuole. Second generation merozoites budded in one direction, resulting in a peripheral residual body and merozoites that were parallel in an oblong parasitophorous vacuole.
In Vitro Excystation of Caryospora simplex (Apicomplexa: Eimeriorina)1
Authors: UPTON STEVE J. , CURRENT WILLIAM L. , BARNARD SUSAN M. , ERNST JOHN V. 
Published: May 2007

ABSTRACTIn vitro excystation of sporozoites of the heteroxenous coccidian Caryospora simplex Léger, 1904 (Apicomplexa: Eimeriorina) is described. Sporocysts freed mechanically from oocysts released a maximum of 51% of their sporozoites within 45 min at 25°C and a maximum of 74% within 20 min at 37°C when incubated in a 0.25% (w/v) trypsin–0.75% (w/v) sodium taurocholate (bile salt) excystation solution. At emergence from sporocysts, sporozoites were weakly motile then became highly active after about 2 min in excystation solution. Sporozoites within sporocysts exposed to bile salt only became highly motile within 25 min at 25°C and within 15 min at 37°C but did not excyst. When exposed only to trypsin at the above temperatures, the Stieda body dissolved; the substieda body remained intact, and the sporozoites exhibited only limited motility within sporocysts; only a few excysted. Intact, sporulated oocysts incubated at 25° or 37°C in 0.02 M cysteine‐HC1 and a 50% CO2 atmosphere for 18 h had no morphologic changes in the oocyst wall. Further incubation of these intact oocysts in excystation solution for 30 min at 37°C caused neither motility of sporozoites within sporocysts nor excystation. Grinding oocysts for 30 sec in a motor‐driven, teflon‐coated tissue grinder caused motility of some sporozoites within sporocysts but did not result in excystation.
Characteristics of Cytidine Aminohydrolase Activity in Trypanosoma cruzi and Crithidia fasciculata1
Authors: KIDDER GEORGE W. 
Published: May 2007

ABSTRACTCytidine deaminase (cytidine aminohydrolase, 3.5.4.5) is present in Crithidia fasciculata (a mosquito parasite) and in Trypanosoma cruzi (a human pathogen). The enzyme from C. fasciculata deaminated both cytidine and deoxycytidine, the affinity for the former being much lower than the latter. Affinities for both substrates are equal for the T. cruzi enzyme. The production of the enzyme in C. fasciculata was significantly stimulated by the addition of a number of pyrimidine nucleosides (cytidine, uridine, 5‐bromouridine, thymidine, orotidine) to the culture media. Only cytidine stimulated enzyme production in T. cruzi. The enzyme from both organisms was unstable in air, even in the frozen state. Stabilization was achieved under anaerobic conditions.
Inhibitory Effect of Rhodamine 123 on the Growth of the Rodent Malaria Parasite, Plasmodium yoelii1
Authors: TANABE KAZUYUKI 
Published: May 2007

ABSTRACTThe effect of the cationic permeant fluorescent dye, rhodamine 123 (R123), on the in vivo growth of Plasmodium yoelii was examined. Plasmodium yoelii‐infected mouse erythrocytes were incubated in vitro with R123 and injected intravenously into mice. Examination of daily parasitemias showed that R123 delayed parasite growth whereas rhodamine 110, a neutral compound, and fluorescein, a negatively charged fluorescent dye, did not. Infected erythrocytes treated with R123 were not cleared from the circulation even 7 h after injection. Quantitation of cell‐associated R123 by spectrophotometry revealed that infected cells with increased levels of R123 considerably prolonged the 2% prepatent period, the time required for the parasite to develop a 2% parasitemia. Degenerating parasites within and outside the host erythrocytes were observed on day 1 of infection in the mice. Thus it follows that R123, which accumulated in infected erythrocytes, inhibits the growth of P. yoelii; moreover, when R123‐labeled infected erythrocytes were treated with 1–10 μM carbonylcyanide m‐chlorophenylhydrazone (CCCP), a proton ionophore, to release R123 from the cells, the inhibitory effect on the growth rate of P. yoelii was partially reversed.
A Comparative Study of 14 Strains of Naegleria australiensis Demonstrates the Existence of a Highly Virulent Subspecies: N. australiensis italica n. spp.1
Authors: JONCKHEERE JOHAN F. DE , PERNIN PIERRE , SCAGLIA MASSIMO , MICHEL ROLF 
Published: May 2007

ABSTRACTFourteen strains of Naegleria australiensis, including the type strain, were compared for virulence for mice, maximum growth temperature, lectin agglutination, isoenzyme pattern, and total protein banding pattern. Their relation to other species of Naegleria also was compared by immunoelectrophoretic analysis. Strains with high virulence, comparable to that of N. fowleri, were found to be different in concanavalin A agglutination as well as with regard to zymograms and total protein patterns. Although serologically different from N. fowleri and reacting with N. australiensis antiserum in the fluorescent antibody test, these high‐virulence strains differed in number of immunoelectrophoretic precipitin bands. Because of these results, the high‐virulence strains are considered to be a subspecies of N. australiensis. The low‐virulence strains showed minor differences from the type strain. Thus, N. australiensis does not appear to be as homogenous a species as N. fowleri. Pathogenic N. australiensis also seems to be more widespread than previously thought.
Changes in Oral Apparatus Structure Accompanying Vacuolar Formation in the Macrostomal Form of Tetrahymena vorax. A Model for the Formation of Food Vacuoles in Tetrahymena1
Authors: SMITH‐SOMERVILLE HARRIETT E. , BUHSE HOWARD E. 
Published: May 2007

ABSTRACTThe large cytopharyngeal pouch of the macrostomal form of Tetrahymena vorax, following the addition of calcium, can form a sealed, empty vacuole. The open cytostomal region of this cell, which averages about 16 μ in diameter, is closed by an upward (ventral) movement of the right and posterior ribbed walls, both of which project into the cytostomal cavity. At the same time, the anterior and left walls of the cytostome‐cytopharyngeal complex move to the right, forming a diagonally (right to left) placed furrow in the floor of the buccal cavity as these walls meet. As a result of the movement, the edges of the single membrane‐bounded cytopharyngeal pouch are brought together and fuse, producing the closed vacuole. Elements of the cytoskeleton appear to participate in the closure process. Three major groups of ribbed wall microtubules support the open cytostome. The anterior ribbed wall microtubules pass laterally along the anterior (dorsal) portion of the cytopharyngeal pouch to the left where they end in the specialized cytoplasm. Middle oral rib microtubules terminate at the right and posterior margin of the cytopharynx while microtubules from the most posterior region of the ribbed wall pass to the left terminating in the specialized cytoplasm. The fine filamentous reticulum, a striated reticulum that borders the right, posterior, and anterior margins of the cytostome‐cytopharyngeal complex, is in an ideal position to participate in these movements. It is anchored anteriorly high up in the buccal cavity to the cross‐connective between the third membranelle and the undulating membrane complex. It courses beneath the right and posterior ribbed walls and runs laterally along the anterior margin of the cytopharynx to the left side. Contraction or pulling of this reticulum would act to bring the microtubule‐reinforced walls of the cytopharynx together permitting fusion of the cytopharyngeal pouch membranes to form a sealed vacuole.
Life Cycle of Culicosporella lunata (Hazard & Savage, 1970) Weiser, 1977 (Microspora) as Revealed in the Light Microscope with a Redescription of the Genus and Species1
Authors: HAZARD EDWIN I. , FUKUDA TOKUO , BECNEL JAMES J. 
Published: May 2007

ABSTRACTLight microscopy studies of Culicosporella lunata (Hazard & Savage), a parasite of the mosquito Culex pilosus (Dyar & Knab), revealed two sporogonial sequences. One sequence begins with diplokaryotic meronts that undergo repeated nuclear divisions to produce sporogonial plasmodia with nuclei in diplokaryotic arrangement. These plasmodia form rosette‐like clusters of sporoblasts during incomplete cytokinesis and, eventually, binucleate spores. These spores initiate infections in healthy larvae when they ingest spores. The second sequence begins with diplokaryotic meronts that undergo karyogamy and meiosis to form Thelohania‐like sporonts and haploid spores. Anomalies are often observed in these sporonts which result in aberrant spores, usually fewer than eight, in an accessory (pansporoblastic) membrane. Normal haploid spores are morphologically similar to those of species of Amblyospora. The genus and the type species are redefined based on new information presented here and it and the type species are placed in the family Amblyosporidae.
Sporogony in Pneumocystis carinii: Synaptonemal Complexes and Meiotic Nuclear Divisions Observed in Precysts1
Authors: MATSUMOTO YOSHITSUGU , YOSHIDA YUKIO 
Published: May 2007

ABSTRACTEvidence for meiosis was demonstrated electron microscopically for the first time in Pneumocystis carinii in rat alveoli by the observation of synaptonemal complexes followed by nuclear divisions. Synaptonemal complexes indicating meiotic nuclear divisions were observed in uninuclear precysts. Additionally, owing to the use of tannic acid as a fixative, spindle microtubules were also observed for the first time in the precyst. Based on these facts, a new life cycle of the organism is proposed. The precyst has generally been considered an intermediate form between the trophozoite and the cyst. The present paper proposes that the precyst is additionally defined as the cell in which eight intracystic bodies are produced through meiotic reduction. The most characteristic feature of the precyst is a clump of mitochondria in the cytoplasm. We divide the precyst phase into three forms, which are named early, intermediate, and late. Synaptonemal complexes were only observed in the early precyst, which is a uninuclear cell with a thin pellicle. In the intermediate precyst, nuclear divisions are observed as follows: meiosis I produces two haploid nuclei and each of these divides at meiosis II producing four nuclei. After that, another postmeiotic mitosis takes place, resulting in eight haploid nuclei. In the late precyst, a delimiting membrane originates from the mother plasmalemma and surrounds the daughter nuclei and a small portion of the adjacent cytoplasm. Finally, when the eight intracystic bodies are complete, the precyst changes to a cyst. Thus, we deduce that intracystic bodies resulting from meiotic nuclear division are haploid and, after excystation, they are haploid trophozoites. We consider that this process can be called sporogony. Although we could not distinguish between the haploid and the diploid trophozoite, it is quite plausible that copulation occurs, probably in host alveoli.
The Ultrastructure of the Freshwater, Colorless Dinoflagellate Peridiniopsis berolinense (Lemm.) Bourrelly (Mastigophora, Dinoflagellida)1,2
Authors: WEDEMAYER GARY J. , WILCOX LEE W. 
Published: May 2007

ABSTRACTThe ultrastructure of the freshwater, heterotrophic dinoflagellate Peridiniopsis berolinense (Lemm.) Bourrelly resembles other dinoflagellates in the structure of its nucleus, theca, flagella, and mitochondria. Other features less frequently reported in related organisms include fine sub‐sulcal fibers, collared pits in the flagellar base region, and unusual structures herein termed fibrillar lamellae. Numerous vesicles are present, some of whose contents are distinctly crystalline, while others contain what appears to be membranous material arranged in either whorls or parallel stacks; still other vesicles contain electron‐dense, granular spheres. Of particular interest is the transitional helix present in the longitudinal flagellum, this being the first report of such a structure among the dinoflagellates. Plastids of any kind are lacking, and a peduncle is present and is used during phagotrophy.
Cytochemical and Electrophoretic Studies on the Cyst Wall of a Ciliate, Histriculus muscorum Kahl
Authors: MATSUSAKA TADAO , HONGO FUMIKAZU 
Published: May 2007

ABSTRACTMThe localization of proteins and polysaccharides in the cyst wall of a ciliate, Histriculus muscorum, was examined by light and electron microscope cytochemistry and by using an enzyme digestion test on thin sections. The endocyst and ectocyst were digested by treatment with pepsin or protease VI. The endocyst was intensely PAS‐positive and alcian blue‐positive. The ectocyst was also PAS‐ and alcian blue‐positive, but the reaction was weaker than that of the endocyst. At the electron microscope level, an intensely positive reaction to methenamine silver was observed in the endocyst and a weak reaction in the ectocyst of the mature cyst. In the ectocyst of the encysting organism, however, the reaction to methenamine silver was more intense than that of the mature cyst. These results demonstrate the possible presence of glycoproteins in the ectocyst and endocyst. The mesocyst was negative to all cytochemical and enzyme digestion tests examined. The cyst wall, isolated by sonication, was analyzed by SDS‐polyacrylamide gel electrophoresis. Two bands, 190 and 140 kilodaltons, were specific for the cyst wall. The 190 kilodalton band was the only PAS‐positive band and its localization in the cyst was was discussed.
The Ecology of Antigenic Variation1,2
Authors: SEED JOHN R. , EDWARDS ROBERT , SECHELSKI JOHN 
Published: May 2007

ABSTRACTA detailed molecular analysis using recombinant DNA technologies is extremely important to our understanding of the phenomena of antigenic variation in the African trypanosomes; however, by itself, it may not completely explain antigenic variation as it occurs in vivo. Several laboratories have demonstrated the ability of one variant population to replace another in vivo as well as the presence of heterogeneous populations of trypanosomes within an individual animal. These two phenomena do not permit us to explain antigen variation solely on the basis of the molecular regulation of variant antigen expression. In addition to studies in molecular biology, it will be necessary to define clearly the differences in growth rates of variant populations and the role of competition between these variants in a single anatomical site. It will also be necessary to determine the influence of various physiological environments on growth rates and the competition between the different variants of a single repertoire. It is concluded that the phenomenon of antigenic variation is a complex problem in ecology and population dynamics as well as molecular regulation. This paper is designated to examine a variety of the ecological parameters presumably involved in antigenic variation.
Antigenic Similarity Between the Coccidian Parasites Toxoplasma gondii and Hammondia hammondi1
Authors: ARAUJO FAUSTO G. , DUBEY J. P. , REMINGTON JACK S. 
Published: May 2007

ABSTRACTThe antigens that are present in the coccidian parasites Toxoplasma gondii and Hammondia hammondi were demonstrated and defined by using SDS‐PAGE and immunoenzymatic techniques with 125I‐labeled and unlabeled antigens of T. gondii and sera of mice infected orally or intraperitoneally with H. hammondi. All cell surface antigens of T. gondii that were labeled with 125I were recognized by antibodies in the sera of the mice infected with H. hammondi except the antigen of approximate molecular weight of 21.5 Kd. This suggests that this antigen is specific for T. gondii. Various antigens in the T. gondii‐lysed antigen preparations were recognized by antibodies to H. hammondi. The number of recognized antigens increased as the infection of the mice with H. hammondi progressed. Oral infection with H. hammondi appeared to induce the formation of antibodies that recognized more T. gondii antigens than infection by intraperitoneal inoculation.
Complete Development of Isospora suis of Swine in Chicken Embryos1
Authors: LINDSAY DAVID S. , CURRENT WILLIAM L. 
Published: May 2007

ABSTRACTDevelopment of the swine coccidium, Isospora suis, in embryonated chicken eggs is described. The allantoic cavities of eight‐to‐ten‐day‐old white Leghorn embryos were inoculated with either 100,000 or 200,000 sporozoites. Developmental stages morphologically similar to those found in the intestines of piglets were present in the endodermal layer of the chorioallantoic membrane (CAM), beginning three days post inoculation (PI). No stages were found in the mesodermal or ectodermal layers of the CAM and none were observed in heart, lung, liver, or spleen. Type I meronts and merozoites were found on days 3 through 10 PI. Type II meronts and merozoites were found days 4 through 10 PI. Mature microgamonts, macrogamonts, and oocysts were found on days 7 through 10 PI. Oocysts appeared to be retained in the endodermal cells and in ovo sporulation did not occur. Attempts to sporulate CAM‐derived oocysts were not successful. Isospora suis was not pathogenic for embryos under the conditions of this study. This study represents the first fully documented report of complete development of a mammalian coccidium in chicken embryos.
Absence of α‐Ketoglutarate Dehydrogenase Activity and Presence of CO2‐Fixing Activity in Plasmodium falciparum Grown In Vitro in Human Erythrocytes1
Authors: BLUM J. J. , GINSBURG H. 
Published: May 2007

ABSTRACTPlasmodium falciparum‐infected human erythrocytes grown in vitro do not release 14CO2, when incubated in the presence of [1‐14C]glutamate, despite the presence of glutamate dehydrogenase, implying the absence of α‐ketoglutarate dehydrogenase activity and the lack of functional tricarboxylic acid cycle in the human malaria parasite. Cultures incubated with [14C]bicarbonate, however, fix CO2 into acid‐stable metabolites; CO2 fixation proceeds linearly for up to two hours after an initial brief lag and may contribute appreciably to the metabolism of the parasite.
Phytohemagglutinin Induces Delays in Oral Regeneration in the Ciliate Stentor coeruleus1
Authors: MALONEY MICHAEL S. 
Published: May 2007

ABSTRACTRegenerating Stentor, exposed to the plant lectin phytohemagglutinin, are significantly delayed in completing oral regeneration. All of the delays are restricted to the earliest stages of regeneration prior to stage 3. The effects of phytohemagglutinin are reversible once the drug is removed. The addition of the presumed sugar receptor for phytohemagglutinin, N‐acetylgalactosamine, at the start of oral regeneration could not reverse the effects of phytohemagglutinin, but the addition of excess (10 mM) extracellular calcium could. When the addition of the excess calcium was delayed for various times after phytohemagglutinin exposure, the effectiveness of the calcium in reversing the phytohemagglutinin‐induced delays was reduced. Based on the mechanism of action of PHA in other cells, these results suggest that membrane proteins may be involved in controlling oral regeneration, possibly through mechanisms involving Ca++.