bluuebunny/crossref_metadata_2025_split huggingface dataset:
Selective Inhibition of Flagellar Activity in Chlamydomonas by Nickel
Authors: BEAN BARRY , HARRIS ALAN 
Published: May 2007

SYNOPSISFlagellar activity in the biflagellate chlorophyte Chlamydomonas reinhardtii is selectively inhibited by Ni2+ or by treatment with Ca2+‐chelating agents. Inhibitions of swimming speed, geotaxis, phototaxis, and pattern swimming result from qualitative and quantitative losses in the activity of individual flagella and in the coordination of activity beween the 2 flagella of each cell. Addition of Ca2+ (a) prevents inhibition and (b) restores normal flagellar activity in inhibited cells. Mg2+ is partially effective in reversal of inhibition. Other ions do not cause similar inhibition or reversal of nickel inhibition. The characteristics of inhibition and reversal suggest that the prmary target for nickel is a component of the flagellar apparatus, and that this component uses Ca2+ to perform its normal function in the regulation of flagellar activity. A 2nd target for nickel is a Carequiring process specific to phototaxis (and not involved in the photophobic response).
Microplankton Patchiness in the Northwest Altantic Ocean
Authors: FORNSHELL JOHN A. 
Published: May 2007

SYNOPSISPlankton samples were collected in the Northwest Atlantic on the Grand Banks of Newfoundland in August 1976 and on Flemish Cap in March 1977. The samples were taken using a Hardy Continuous Plankton Recorder towed at a depth of 9.1 m. On the Grand Banks the following species were found: Ceratium arcticum (Ehrenberg), C. longipes (Ehrenberg), C. lineatum (Ehrenberg), C. macroceros (Ehrenberg), C. fusus (Ehrenberg). C. tripos (Müller) and Ceratium spp. Other microplankton found in the samples included Radiolaria, Globigerina humilis (Brady), and the tintinnid ciliates Tintinnopsis cylindrica (Daday) and Tintinnopsis spp. In the samples from Flemish Cap only a single species of diatom was found in small numbers. The paucity of individuals in these samples is most probably related to the season of the survey, winter. The population density of C. arcticum had a patchiness with a length scale on the order of 104 m. The plankton tow on the Grand Banks was parallel to the north‐south axis of the Labrador Current. This patchiness scale on the order of 104 m may reflect a meandering of the Labrador Current.
Freeze‐Fracture Study of Malaria Sporozoites: Antibody‐Induced Changes of the Pellicular Membrane*
Authors: AIKAWA MASAMICHI , COCHRANE ALAN H. , NUSSENZWEIG RUTH S. , RABBEGE JOHN 
Published: May 2007

SYNOPSISPlasmodium cynomolgi, Plasmodium knowlesi, and Plasmodium berghei sporozoites, before and after incubation with immune serum, were studied after freeze‐fracture by electron microscopy. There were evenly distributed numerous intramembranous particles (IMP) on the P face of the outer membrane. The E face of the plasma membrane had fewer IMP than its P face. The E face of the intermediate membrane had few IMP and also linear arrays of slightly raised ridges running the length of the parasite. The P face of the intermediate membrane had many IMP aligned along the long axis of the sporozoite. On the P face of the inner membrane. IMP were arranged in very distinct rows conforming to the long axis of the parasite; the E face of this membrane had a few randomly distributed IMP.A prominent change in the sporozoite incubated in immune serum was the appearance of a layer of aggregated particles around the parasite. The P face of the plasma membrane had several clear areas devoid of IMP and IMP aggregates. No changes were seen in the other fractured faces of the pellicle. These observations suggest that immune serum acts only on the P face of the plasma membrane.
Myxosoma funduli Kudo (Myxosporida) in Fundulus kansae: Ultrastructure of the Plasmodium Wall and of Sporogenesis*
Authors: CURRENT WILLIAM L. , JANOVY JOHN , KNIGHT STEPHEN A. 
Published: May 2007

SYNOPSISUltrastructure of the plasmodium wall and of sporogenesis were studied in Myxosoma funduli Kudo infecting the gills of Fundulus kansae (Garman). Plasmodia were located within the lamellar tissues adjacent to sinuses and capillaries. The plasmodium wall consisted of a single unit membrane which was continuous with numerous pinocytic canals extending into the parasite ectoplasm. The plasmodium membrane was covered by a surface coat of almost uniform thickness which prevented direct parasite‐host cell contact. Numerous generative cells and cell aggregates, representing early stages of spore development, were seen in immature plasmodia. Later stages of spore development, including mature spores, were observed in older plasmodia. Sporogenesis was initiated by envelopment of one generative cell, the sporont, by a 2nd, nondividing cell, the envelope cell. The sporont and its progeny proceeded through a series of divisions until there were 10 cells, all compartmentalized within the envelope cell. Subsequently, the 10 cells became structurally differentiated and arranged into two 5‐celled spore‐producing units, each consisting of 1 binucleate sporoplasm and 2 capsulogenic cells, all surrounded by 2 valvogenic cells. Observations of later developmental stages revealed the major events of capsulogenesis, valvogenesis, and sporoplasm maturation, which occurred concomitantly during spore construction.
The Methylated Purines of Tetrahymena pyriformis Transfer Ribonucleic Acid*
Authors: KEEGAN FRANK P. , BERECH JOHN 
Published: May 2007

SYNOPSIS. By phenol extraction and DEAE cellulose column chromatography, tRNA was isolated from Tetrahymena pyriformis strain GL. Following acid hydrolysis of the tRNA, the methylated purine content was determined by Dowex 50 column chromatography and paper chromatography.The most abundant methylated guanine derivative was found to be N2‐DMG. Also present were 1‐MG, N2‐MG, and 7‐MG. The most abundant methylated adenine was found to be 1‐MA; no 2‐MA was detected. Small amounts of the N6‐methyladenines were detected.
Development and Ultrastructure of First‐Generation Meronts of Sarcocystis cruzi in Calves Fed Sporocysts from Coyote Feces*
Authors: DUBEY J. P. , SPEER CLARENCE A. , DOUGLASS THOMAS G. 
Published: May 2007

SYNOPSIS. The development of Sarcocystis cruzi Hasselmann (syn. S. fusiformis Railliet) meronts was studied in seven 7‐ to 10‐day‐old calves killed 4, 7, 11, 15, 22, 25 and 28 days postinoculation (DPI) with 5 × 107 sporocysts from feces of coyotes. No meronts were found 4 and 7 DPI. Young and intermediate meronts with 1–16 nuclei were found in endothelial cells of arteries in mesenteric lymph nodes, but not in kidneys 11 DPI.Mature meronts were noted in endothelial cells of arteries, arterioles, or capillaries of many organs of calves killed 15 to 25 DPI. No first‐generation meronts were found 28 DPI. By electron microscopy, all stages of the first‐generation merogony were found free within the host cell cytoplasm and not within a parasitophorous vacuole. The appearance of intranuclear spindles preceded the formation of merozoites by endopolygeny. Mature meronts measured 41.0 × 17.5 (34–50 × 15–24) μm, contained ∼ 100–350 merozoites, and had 2 to 4 relatively small residual bodies, 2.8 μm in diameter. Merozoites measured 6.3 × 1.5 (5.5–7 × 1 μm) and contained most of the organelles characteristically found in coccidian merozoites. Micropores were observed in merozoites, but not in young and intermediate meronts. Merozoites were seen free in the lumen of blood vessels, in intracellular areas, and free within the host cell cytoplasm.
Chemotherapy and the Immune Response in Protozoal Infections1
Authors: HANSON WILLIAM L. 
Published: May 2007

ABSTRACTAvailable evidence indicates that many of the antiprotozoal drugs currently in use significantly modify the immune response of the host. The effect depends on both the drug and the host. Some drugs enhance the immune response, some are immuno‐suppressants, and others enhance some types of immune mechanisms while suppressing others. Future efforts in the development of antiprotozoal drugs should consider their effects on both the parasite and the immune response of the host. Also in the chemotherapy of protozoal infections consideration should be given to the combined usage of immunoenhancing agents and antiprotozoal drugs.
Pathogenic and Nonpathogenic Acanthamoeba spp. in Thermally Polluted Discharges and Surface Waters1
Authors: DE JONCKHEERE JOHAN F. 
Published: May 2007

ABSTRACTDuring spring and autumn, the total number of amoebae and the number of Acanthamoeba species able to grow at 37°C were determined in six thermally polluted factory discharges and the surrounding surface waters. The isolated Acanthamoeba strains were studied for growth in axenic medium, cytopathic effect in Vero cell cultures, and virulence in mice. Although more amoebae were isolated in autumn, the number of Acanthamoeba species was lower than in spring, when the percent of pathogenic strains among the isolates was highest. Higher concentrations of amoebae were found in warm discharges, and more virulent strains occurred in thermal discharges than in surface waters.
A Light‐ and Electron‐Microscopical Study of Protacanthamoeba caledonica n. sp., Type‐Species of Protacanthamoeba n. g. (Amoebida, Acanthamoebidae)1
Authors: PAGE FREDERICK C. 
Published: May 2007

ABSTRACTIn its amoeboid stage, Protacanthamoeba caledonica n. g., n. sp. closely resembles the genus Acanthamoeba, on both light‐ and electron‐microscopical levels, including possession of a centrosphere with a plaque‐shaped centriole‐like body. The cyst wall differs from that of Acanthamoeba in lack of preformed exit pores and in fine structure; the occasional apparent division into exocyst and endocyst is due to irregular splitting. The strain isolated from a Scottish estuary did not grow at 37°C and did not grow normally on agar made with 25% sea water, but cysts remained viable after a week in full‐strength sea water. Protacanthamoeba n. g. is distinguished from Acanthamoeba on the basis of cyst structure, but it is assigned to the family Acanthamoebidae.
Nuclear Roles in the Post‐Conjugant Development of the Ciliate Euplotes aediculatus II. Experimentally Induced Regeneration of Old Macronuclear Fragments1
Authors: KLOETZEL JOHN A. 
Published: May 2007

ABSTRACTFollowing conjugation in ciliates, the usual fate of the old pre‐conjugant macronucleus is resorption. In some species, however, old macronuclei, or their fragments, have the ability to reform functional vegetative macronuclei when new macronuclear anlagen are defective. The present work on Euplotes shows that if anlagen are allowed to carry out their essential roles in early exconjugant development, including influence on cortical reorganization such that feeding can resume, they can then be permanently damaged by UV‐microbeam irradiation and regeneration of old macronuclear fragments can occur. E. aediculatus exconjugants were anlage‐irradiated at 40–60 hr of development and the irradiated cells cultured individually and fed. Squashes revealed enlargement and anteriorward migration of the persistent (posterior) macronuclear fragments. The first post‐conjugant fission of such cells was delayed (times ranged 6–43 days) and did not seem to involve the damaged anlagen, which remained rudimentary, did not divide along with the cells, and were subsequently resorbed. It appeared that cell fission was supported by the fragments of the old macronuclei, which either divided or partitioned themselves between the two daughter cells. Mating tests performed on early clones derived from irradiated exconjugants revealed ample conjugation competence; intraclonal conjugation in such clones was also apparent. The absence of the immature period seen in normal exconjugants provides further evidence that the clones arose from cells with regenerated macronuclei.
Partial Purification of a Species‐Specific Lethal Factor from Amoeba indica1
Authors: LEITH A. , KAUFMAN M. C. 
Published: May 2007

ABSTRACTThe species‐specific lethal factor obtained from Amoeba indica, a freeliving mononucleate amoeba, can be partially purified by differential centrifugation, gel exclusion chromatography, and elution from Cibacron blue‐agarose. The factor is unstable in the partially purified form, but activity is correlated with a heat‐labile protein having an apparent molecular weight of 186,000. The factor causes inhibition of division and death when injected into A. proteus. Purification of the lethal factor indicates that aggregation of the factor with amoebal proteins is not a hindrance to further investigation. The natural role of the factor is discussed.
Leptomonas lactosovorans n. sp., a Lactose‐Utilizing Trypanosomatid: Description and Nutritional Requirements1
Authors: MANAIA ARMANDO DA COSTA , SOUZA MARIA DO CARMO MOREIRA DE , LUSTOSA ÉDIA DE SENA , ROITMAN ISAAC 
Published: May 2007

ABSTRACTLeptomonas lactosovorans n. sp. is described from the gut of the reduviid hemipteran Zelurus martinsi. It can be grown in a defined medium. The requirements for amino acids, vitamins, purine, and heme were similar to those established for Crithida fasciculata. Growth is stimulated by aeration. Generation time is longer than for any other insect trypanosomatid described; its utilization of lactose as a carbon source is a unique feature among trypanosomatids.
The Relation of Concanavalin A Receptor Distribution to the Conjugation Process in Tetrahymena thermophila
Authors: WATANABE S. , TOYOHARA A. , SUZAKI T. , SHIGENAKA Y. 
Published: May 2007

ABSTRACTBy using fluorescent isothiocyanate‐conjugated concanavalin A (FITC‐Con A), cell surface events were examined under a light microscope during the early period of the conjugation process in Tetrahymena thermophila. Until the two complementary mating types (D‐III and IV) were mixed, Con A‐binding activities were hardly detected on the cell surface of ciliates. After mixing, however, the FITC‐Con A (25 μg/ml) bound especially to the anterior cell surface at the early stage of conjugation, followed by characteristic changes of the Con A‐binding pattern and, subsequently, by formation of a bright fluorescent ring around the area of contact between conjugants. Such alterations of FITC‐Con A‐binding pattern were found to be interrupted or eliminated by cycloheximide (2 μg/ml). These findings are related to the onset and subsequent conjugation in T. thermophila.
The Unique Position of the Degenerating Macronucleus in Tetrahymena tropicalis1
Authors: SIMON ELLEN M. , DOERDER F. PAUL 
Published: May 2007

ABSTRACTIn contrast to the situation in 13 other species of the Tetrahymena pyriformis complex, in which the condensed degenerating old macronucleus lies in the posterior end of the cell during the late stages of conjugation, in Tetrahymena tropicalis that nucleus is found in the anterior portion. This developmental characteristic may be useful for taxonomic purposes as well as being of value in investigations on nucleocytoplasmic interaction.
Parental Development of Eimerian Coccidia in Sandhill and Whopping Cranes1
Authors: NOVILLA MELITON N. , CARPENTER JAMES W. , SPRAKER TERRY R. , JEFFERS THOMAS K. 
Published: May 2007

ABSTRACTIn contrast with isosporoid species of coccidia that have established extraintestinal phases of development, the eimeriids, except for a few species, generally have been considered inhabitants of the intestinal tract. Eimeria infection in sandhill cranes (Grus canadensis) and whooping cranes (G. americana) may result in disseminated visceral coccidiosis. Nodules were observed in the oral cavity of 33% (n = 95) of the G. canadensis at the Patuxent Wildlife Research Center (PWRC) in Laurel, MD. Necropsy of six of the afflicted cranes revealed granulomatous nodules in many tissues and organs. Histologic studies disclosed protozoan organisms morphologically resembling schizonts in the granulomas, and endogenous stages of coccidia were present in the intestines of four birds. Fecalysis of three of four sandhill cranes yielded oocysts of E. reichenowi and E. gruis. Only E. reichenowi‐type oocysts were recovered from a dead whooping crane sample. Domestic broiler chicks each intubated with about 1 times 106 pooled sporulated oocysts of E. reichenowi and E. gruis were not infected. Exposure of six incubator‐hatched and hand‐reared sandhill crane chicks to oocysts artificially (two chicks) and naturally (four chicks) resulted in typical infection of intestinal epithelium with invasion of subepithelial tissues extending to the muscular layer and widespread extraintestinal development. Asexual and sexual stages occurred primarily in macrophages in the liver, spleen, heart, and lung. In the lung, oocysts were found in bronchial exudate and epithelial lining cells. Six of ten G. canadensis chicks, one adult G. americana, and three of five G. americana chicks that died naturally at PWRC had disseminated visceral coccidiosis.
Données Nouvelles sur Quelques Processus Morphogénétiques chez les Hypotriches, Notamment dans le Genre Euplotes: Leur Contribution à l'Approche Evolutionniste du Problème de la Régulation de l'Activité Morphogenétique chez les Ciliés1
Authors: FLEURY ANNE , FRYD‐VERSAVEL GHISLAINE 
Published: May 2007

RÉSUMÉL'étude, par le protargol, des phénomènes infraciliaires et de leur corrélation avec les phénomènes nucléaires au cours de l'autogamie dans le genre Euplotes montre, par comparaison avec la conjugaison, que les diverses étapes de la morphogenèse sont liées à la progression de l'état nucléaire. Par ailleurs, l'étude comparative des différents types de morphogenèse (bipartition, phénomena sexuel, réorganisation induite par le jeǔne) permet de supposer qu'il existe deux territoires morphogènes soumis à des systèmes de régulation bien distincts. La comparaison des séquences de morphogenèse chez divers hypotriches conduit à dresser un plan général d'évolution de la régulation de l'activité corticale en relation avec l'étendue des remaniements associés à la stomatogenèse.ABSTRACTThe changes in the arrangement of the infraciliature associated with autogamy in Euplotes are described and compared with similar events associated with conjugation. The successive steps of morphogenesis are strongly correlated with nuclear processes. The comparative study of different types of morphogenesis (binary fission, sexual phenomena, starvation‐induced reorganization) leads to the hypothesis that two morphogenetic fields (a ventral one and a dorsal one) depend on separate regulatory systems. From the viewpoint of evolution, the morphogenetic sequences of some hypotrichs have been compared. A general scheme of the evolution of cortical regulation is proposed, taking into account the extension of the area concerned with stomatogenic activity.
Histological and Ultrastructural Studies of the Interaction of Toxoplasma gondii Tachyzoites with Mouse Omentum in Experimental Infection1
Authors: KHAVKIN THEODOR 
Published: May 2007

ABSTRACTMouse omentum was studied after intraperitoneal challenge with tachyzoites of Toxoplasma gondii. Parasites inhabit omental histiocytes, fibroblasts, mesothelial cells, and free peritoneal macrophages. Recently infected cells showed enhanced metabolic and functional activity. Villous projections of the parasitophorous vacuole wall appeared, usually opposite the anterior pole of the parasite. In mesothelial cells, projections formed terminal swellings not observed in other infected cells. Activation of host cells was followed by reduction of the density of the cytoplasmic matrix, autophagosome formation, and intracellular edema, indicating the damage. The wall of the parasitophorous vacuole loses the supporting host cell endoplasmic reticulum that was attached to the vacuole just after entrance of the parasite into the cell. Then lysis of the parasitophorous vacuole and complete cell destruction occurs. The growth of parasites in undamaged cells does not coincide with the inflammatory response. Inflammation of the peritoneum develops only after the start of mass destruction of infected cells. Thus tachyzoites of Toxoplasma exert significant pathogenic effects by their ability to activate the host cell, causing lysis of the parasitophorous vacuole and subsequent destruction of the entire cell.
An Electron Microscopical Study of the Interaction of Monoclonal Antibodies with Gametes of the Malarial Parasite Plasmodium gallinaceum1
Authors: AIKAWA MASAMICHI , RENER JOAN , CARTER RICHARD , MILLER LOUIS H. 
Published: May 2007

ABSTRACTAnti‐malarial gamete antibodies prevent the fertilization of gametes in the mosquito midgut and prevent transmission of malaria. Recently, hybridoma cell lines secreting monoclonal antibodies (10G3 and 11C7) against gametes of the malarial parasite have been developed. These antibodies act synergistically to mediate 80–90% suppression of the infectivity of gametocytes, although neither monoclonal antibody alone has a significant effect on gametocyte infectivity. We performed immuno‐electron microscopy to characterize the interactions of these monoclonal antibodies with gametes of Plasmodium gallinaceum. Male gametes exposed to either 10G3 or 11C7 agglutinated into loose clusters, while those exposed to a mixture of 10G3 and 11C7 agglutinated into long, rope‐like bundles. This difference appears to be related to the distribution of the antibodies on the surface of the gametes. When 10G3 or 11C7 labeled with a ferritin‐conjugated anti‐mouse Ig were used singly, the ferritin particles were distributed in focal areas over the surface of the parasites. By contrast, when the male gametes were exposed to a mixture of 10G3 and 11C7, the ferritin particles were distributed over their entire surface. Female gametes reacted similarly to these antibodies. These observations indicate that combinations of antibody specificities that reduce fertilization efficiency coat the entire surface of the gametes. On the other hand, focal interactions resulting from a single antibody are unable to block fertilization.
Oral Apparatus Structure in the Carnivorous Macrostomal Form of Tetrahymena vorax
Authors: SMITH HARRIETT E. 
Published: May 2007

ABSTRACTThe structure of the oral apparatus in the carnivorous macrostomal form of Tetrahymena vorax has been investigated using serial thin sections and preparations of isolated oral apparatuses. The cilia of the oral apparatus are organized into an undulating membrane that borders the right and part of the posterior margin of the buccal cavity and three membranelles that project from plateaus on the anterior surface. Each membranelle consists of one short row and two longer rows of hexagonally packed kinetosomes. The organization of the microtubules of the oral ribs is identical to that in the T. vorax microstomal cell type. However, the first oral rib originates near the first kinetosome at the anterior end of the undulating membrane. The fine filamentous reticulum that underlies part of the oral ribs in the macrostomal cell type is not striated, unlike the reticulum in the microstomal form. A band of filaments similar to the fine filamentous reticulum extends around the anterior margin of the large cytostomal opening that occupies most of the posterior part of the oral cavity. The single row of microtubules along the left side of the oral cavity and cytostome also has filaments associated with it. A major difference between the microstomal and macrostomal forms in the structure of the oral apparatus is in the oral connectives. The macrostomal cell type contains only a single cross‐connective that joins the three membranelles and the anterior portion of the undulating membrane. The posterior or peripheral connective between the posterior ends of membranelles one and two and the posterior end of the undulating membrane is absent.