bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Mitochondrial Protein Synthesis Inhibitors on the Incorporation of Isoleucine into Plasmodium falciparum In Vitro1
Authors: BLUM J. J. , YAYON A. , FRIEDMAN S. , GINSBURG H. 
Published: May 2007

ABSTRACTPlasmodium falciparum was grown in human erythrocytes in vitro and the effect of chloramphenicol, erythromycin, and tetracycline on growth and maturation of the parasites and on their ability to incorporate [3H]isoleucine into protein was observed. Exposure of rings to high concentrations of chloramphenicol had little effect on subsequent maturation of the rings whereas brief (4 h) exposure of trophozoites caused a dose‐dependent inhibition of subsequent ring formation. Incorporation of [3H]isoleucine into protein was not affected during at least 6 h of exposure to high concentration of the three drugs examined, but appreciable inhibition was observed after 21 h, with chloramphenicol being the least effective inhibitor. These results suggest that there is a stage‐specific effect of inhibition of mitochondrial protein synthesis on subsequent development and that the mitochondria are essential for growth and development even though they lack a functional Krebs cycle.
Localizing Surface‐Related Proteins in Ciliates by Indirect Immunofluorescence Microscopy1
Authors: WILLIAMS NORMAN E. 
Published: May 2007

ABSTRACTResults obtained in immunofluorescence localization studies involving three antisera, six species of ciliates, and a variety of fixation procedures suggest that superior results can often be obtained by fixing cells in 35–70% ethanol. Formaldehyde fixation appeared to induce redistributions of epiplasmic proteins and surface antigens which were not observed in ethanol‐fixed cells. In addition, background fluorescence was significantly lower in ethanol‐fixed cells than it was in cells fixed in aldehydes.
Paramecium Phagosome Membrane: From Oral Region to Cytoproct and Back Again1
Authors: ALLEN RICHARD D. 
Published: May 2007

ABSTRACTTen years of research on digestive vacuoles (phagosomes) of Paramecium caudatum have revealed sequential changes both within the vacuole lumen as well as within the surrounding membrane. Four vacuole stages can be recognized by a combination of thin section and freeze‐fracture ultrastructural features. Three sets of vesicles (discoidal vesicles, acidosomes, and lysosomes) fuse with the vacuole, each at a predetermined stage, to bring about these membrane and physiological changes. At various times membrane is removed as vesicles from the vacuole surface, which has the effect of regulating vacuole size. Membrane recycling, membrane replacement, and specific membrane to membrane recognition all appear to be operating during the digestive cycle. Details of these events are summarized in this address and a number of unanswered questions suggest areas for future research.
Two New Species of Myxozoa, Myxobolus inaequus sp. n. and Henneguya theca sp. n. from the Brain of a South American Knife Fish, Eigemannia virescens (V.)
Authors: KENT MICHAEL L. , HOFFMAN GLENN L. 
Published: May 2007

ABSTRACTTwo new species of Myxozoa from the brain of the green knife fish Eigemannia virescens are described: Myxobolus inaequus sp. n. has an unusually large spore body and extremely unequal polar capsules, and Henneguya theca sp. n. has an attenuated spore encased in a sheath not previously described in other Myxozoa. Only spores of the two species were observed, and infections caused no obvious pathological changes in the brain.
Membrane Protein Differences Correlated with the Development of Mating Competence in Tetrahymena thermophila1
Authors: BELL CRAIG T. VAN , WILLIAMS NORMAN E. 
Published: May 2007

ABSTRACTInitiation is the contact‐independent phase of sexual conjugation which occurs when mature cells of Tetrahymena thermophila are shifted from growth medium to a low‐salt starvation buffer. Immaturity, like high‐salt starvation, restricts the ability of cells to conjugate; immature cells do not conjugate in either low‐ or high‐salt buffers. Comparisons between sexually mature cells starved in initiation‐restrictive and initiation‐permissive buffers, and between immature and mature cells starved in an initiation‐permissive buffer permitted the analysis of membrane protein expression correlated with mating competence. No polypeptides identified by lactoperoxidase‐catalyzed iodination were found to be specific to mating‐competent cells; however, several polypeptides not present in initiated cells were found to be common to the cell surfaces of immature and non‐initiated cells which suggests that (1) initiation involves the removal of specific proteins from the cell surface, and (2) immaturity may be due to an inability to initiate.
Enzymes of Carbohydrate Metabolism in Leishmania donovani Amastigotes1
Authors: MEADE JOHN C. , GLASER THERESA A. , BONVENTRE PETER F. , MUKKADA ANTONY J. 
Published: May 2007

ABSTRACTA method for the isolation of Leishmania donovani amastigotes from infected hamster spleen and liver tissues is described. Over 85% of the isolated amastigotes were viable as judged by acridine orange‐ethidium bromide staining and in vitro transformation to the promastigote form. A comprehensive survey of the enzymes of carbohydrate metabolism in L. donovani amastigotes and promastigotes was conducted. Amastigotes and promastigotes possess all of the enzymes of the Embden‐Meyerhof pathway, hexose monophosphate shunt, and tricarboxylic acid cycle. Cell‐free extracts of both forms show pyruvate dehydrogenase activity which permits entry of pyruvate into the tricarboxylic acid cycle. Both forms demonstrate an active glutamate dehydrogenase, thus linking amino acid metabolism with carbohydrate metabolism. Pyruvate carboxylase, the enzyme responsible for replenishment of C4 acids by heterotrophic CO2 fixation into pyruvate, was also demonstrable in the tissue and insect forms. In general, activities of promastigote enzymes are higher than the amastigote enzymes. Differences between the vertebrate (amastigote) and invertebrate (promastigote) forms in their potential to utilize carbohydrates as substrates would appear to be quantitative rather than qualitative.
Fine Structural Alterations in Trypanosoma rhodesiense Grown In Vitro, Treated with WR 1635771
Authors: BERMAN J. D. , OKA M. , AIKAWA M. 
Published: May 2007

ABSTRACTFine‐structural alterations in Trypanosoma rhodesiense trypomastigotes exposed to WR 163577, a prophylactic agent against animal African trypanosomiasis, were determined from cells grown in vitro. Exposure of trypomastigotes to a low concentration of drug resulted only in condensation of kinetoplast DNA fibrils. Exposure to higher drug concentrations caused clumping of nuclear chromatin and of cytoplasmic contents. Although alteration of kinetoplast DNA is the first detectable drug‐induced change, the function of the kinetoplast in mammalian forms of African trypanosomes is unclear, and the secondary changes in the nucleus and cytoplasm may constitute the functionally significant alterations caused by WR 163577.
Etude ultrastructurale comparée du processus de dégradation de l'hémoglobine par P. berghei (Vincke et Lips, 1948) en fonction de l'état de maturité de la cellule hǒte1
Authors: Slomianny C. , Prensier G. , Charet P. 
Published: May 2007

ABSTRACTBy serial sectioning and 3D reconstruction we have been able to demonstrate that the type of system for hemoglobin digestion in two strains of Plasmodium berghei, N and RC, is dependent on the maturity of the host cell. In parasites growing in erythrocytes, both systems for the endocytosis of hemoglobin—micropinocytosis and the cytostomal system (i.e. a cytostome budding a cytostomal tube that releases food vacuoles)—are fully functional and produce a great quantity of residual pigment. Parasites growing in reticulocytes have a disrupted cytostomal system; no tube is formed and only food vacuoles are visible in their cytoplasm. Residual pigment is smaller in size and in quantity. The reduced quantity of pigment in reticulocytes is explained by our observation of the exocytosis of pigment. We propose a hypothesis that relates the process of degradation of hemoglobin to the maturity of the host cell and a possible mechanism of protection against chloroquine, a drug known for its affinity for malarial pigment.
S‐Adenosylhomocysteine Hydrolase Deficiency in Cysteine Auxotrophs of Tetrahymena thermophila1
Authors: Murphy Sharon E. , Fall Ray 
Published: May 2007

ABSTRACTThe biochemical lesion in two cysteine auxotrophs of Tetrahymena thermophila has been established as a defect in S‐adenosylhomocysteine hydrolase, an enzyme of the transsulfuration pathway. As a result, these mutants require cysteine (or cystathionine or homocysteine) for growth in a denned medium. Cell‐free extracts of the mutants contained < 5% of the level of the enzyme seen in the wild type. One of the mutant strains accumulated intracellular levels of S‐adenosylhomocysteine as high as 1380 üM, a level 200 times normal. When both mutant strains were maintained in defined medium without cysteine, growth occurred after a long lag; this phenomenon was termed “adaptation.” Adaptation was a) reversed by passage through rich medium, b) was not a recovery of S‐adenosylhomocysteine hydrolase, and c) was probably linked to induction of an alternate pathway for cysteine biosynthesis, involving a lysosomal S‐adenosylhomocysteine nucleosidase activity.
Purification of Tissue Forms (Amastigotes) of Trypanosoma cruzi by Immunoaffinity Chromatography1
Authors: Campos‐Neto Antonio , Lima Fernanda W. M. , Andrade Arnaldo F. B. 
Published: May 2007

ABSTRACTA rapid and simple method for the purification of amastigotes of Trypanosoma cruzi from spleens of infected mice is described. A protein A‐Scpharose 4B immunoadsorbent column bound with antisera to epimastigotes of T. cruzi was used to purify the tissue forms of this parasite. Host cells and debris are not retained, and parasites can be eluted in high yields and purity. Studies of surface glycoproteins and glycolipids of the purified amastigotes with 18 lectins of various specificities revealed the presence on the parasites of receptors for N‐acetylglucosamine, N‐acetylgalactosamine, D‐galactose, and D‐mannose binding lectins.
An in Vitro Assay for Sequestration: Binding of Plasmodium falciparum‐Infected Erythrocytes to Formalin‐Fixed Endothelial Cells and Amelanotic Melanoma Cells1
Authors: Udeinya Iroka J. , Leech James , Aikawa Masamichi , Miller Louis H. 
Published: May 2007

ABSTRACTErythrocytes infected with Plasmodium falciparum bind specifically to cultured endothelial cells and to a line of amelanotic melanoma cells. We have fixed endothelial cells and amelanotic melanoma cells in various ways and determined whether the fixed cells were still able to bind infected erythrocytes. Only cells fixed with 1.0‐2.5% formalin in phosphate‐buffered saline continued to bind infected erythrocytes as well as unfixed cells. The mechanism of binding to fixed and unfixed cells appeared to be identical for the following reasons. First, erythrocytes infected by parasite strains that bound to unfixed cells also bound to fixed cells while those that did not bind to unfixed cells did not bind to fixed cells. Second, immune serum that inhibited binding to unfixed cells also inhibited binding to fixed cells. Third, electron microscopy showed that knobs were the points of attachment between infected erythrocytes and both fixed and unfixed melanoma cells. Fixed cells gave reproducible results over at least 2 months. Thus, we have developed a simplified, reproducible assay for measuring binding of P. falciparum‐infected erythrocytes to target cells.
Vertical Distribution of Potentially Pathogenic Free‐Living Amoebae in Freshwater Lakes1
Authors: Kyle Dennis E. , Noblet Gayle Pittman 
Published: May 2007

ABSTRACTThe vertical distribution of thermotolerant (37°C and 45°C) free‐living amoebae (FLA) in warm monomictic lakes was determined in relation to the onset of thermal stratification and associated physical and chemical changes. The position of abiotic or biotic paniculate layers in the water column was located by using a submersible horizontal beam transmissometer that measures attenuance, or the absorption and scattering of light by participates in the water column. During mixis, the vertical distribution of amoebae was sporadic with significant numbers of FLA only occurring in clay layers caused by runoff after heavy rains. With the onset of thermal stratification in the lakes, phytoplankton layers began to form. Few amoebae were isolated from layers containing flagellated phytoplankton; however, significant (P < 0.005) numbers of FLA were isolated from two paniculate layers dominated by the filamentous blue‐green algae Aphanizomenon and Lyngbya, respectively. By late June, a persistent detrital or decomposition layer formed in the lower metalimnion, as well as a hypolimnetic iron layer where the Fe2+ state was predominant. In this midsummer period, 13 Naegieria fowleri were isolated, with three from the detrital layer and seven from the iron layer. The presence of attenuation zones was found to be the best indicator of the vertical distribution of FLA in the water column, and such layers represent an important, previously undescribed habitat for potentially pathogenic FLA.
Cytopathogenicity of Naegleria fowled for Cultured Rat Neuroblastoma Cells1
Authors: Fulford D. E. , Bradley S. G. , Marciano‐Cabral F. 
Published: May 2007

ABSTRACTThe cytopathogenicity of Naegleria fowleri strain LEE (ATCC‐30894) for cultured rat neuroblastoma cells (B‐103) has been investigated. Both live N. fowleri amoebae and Naegleria lysates added to 51Cr‐labeled B‐103 cells caused release of radiolabel, which was dependent upon the ratio of amoebae to target cells or to the lysate concentration. Lysates of N. fowleri strains LEE, NF‐66, NF‐69, and HB‐4 were equally injurious to B‐103 target cells whereas lysates of strains 6088 and KUL were less cytotoxic. Highly pathogenic mouse‐passaged strain LEE were less cytotoxic than axenically grown amoebae. Maximum cytotoxicity was observed in lysates from amoebae in late exponential or early stationary phase of growth. Cytopathogenicity of lysates was reduced after heating at 44°C for 60 min or at 60°C for 30 min. Cytotoxicity was stable during storage at 4°C or at −20°C for 26 h. Neither live amoebae nor lysates injured B‐103 target cells at 4°C. Live amoebae and lysates injured B‐103 by a time, temperature, and concentration dependent process.
Cryptolembus gongi n. gen., n. sp., a Philasterine Scuticociiiate from the Intestine of the Tunicate Ascidia ceratodes (Huntsman, 1912)1
Authors: Gunderson John 
Published: May 2007

ABSTRACTA philasterine scuticociiiate 82‐133 μm in length and 29‐51 μm in width is described from the intestine of the solitary tunicate Ascidia ceratodes. It has 44 somatic kineties, an anterior dorsal bald spot, and a triangular scutico‐vestige which lies above recessed posterior oral polykinetids.
Coccidia in Camels (Camelus dromedarius) in Saudi Arabia1
Authors: Kasim Ahmed A. , Hussein Hussen S. , Shawa Yaser R. Al 
Published: May 2007

ABSTRACTSaudi Arabian camels {Camelus dromedarius) are infected with three species of Eimeria: E. dromedarii (28.4%), E. rajasthani < 22.2%), and E. cameli (19.2%); 41.6% of the animals examined were positive. The highest prevalence of infection was reported in the western region of the country. Mixed infection with two Eimeria species is most common; E. dromedarii was most frequently and generally the most predominant species. Eimeria dromedarii and E. rajasthani are described for the first time from Saudi Arabian camels.
Fluorescein‐Conjugated Folate as an Indicator of Specific Folate Binding to Paramecium1
Authors: VAN HOUTEN J. L. , SMITH R. , WYMER J. , PALMER B. , DENARO M. 
Published: May 2007

ABSTRACTNormal Paramecium tetraurelia cells stained with fluorescein‐conjugated folate show intense fluorescence that can be reduced to near background autofluorescence with excess K2‐folate, but not with excess KCl. Mutant d4–534, which is not attracted to folate and does not specifically bind 3H‐folate, shows reduced fluorescence when stained. This method of monitoring specific folate binding to cells can be adapted to a microscale for rapid screening of clones since cells are routinely fixed and stained in microtiter wells.
Subcellular Distribution of Hydrolases in Naegleria fowleri1
Authors: DAVID M. LOWREY  , JOHN McLAUGHLIN  
Published: May 2007

ABSTRACTThe presence and particle association of various hydrolytic enzymes in Naegleria fowleri has been studied in whole cell extracts of trophozoites in an effort to establish authentic markers for surface membrane and lysosomal components. Evidence from the experiments reported here indicates that in N. fowleri a) acid proteinase, N‐acetylglucosaminidase, and acid phosphatase are associated with cytoplasmic granules closely resembling lysosomes; b) 5'‐nucleotidase is associated with the surface membrane, probably on the external surface; c) aspartate aminotransferase is associated with mitochondria; d) a‐D‐glucosidase and an aminopeptidase have bimodal distributions, activity being associated with both the surface membrane and lysosomal particles.
Enzyme Variation in Paramecium caudatum
Authors: KHADEM N. , GIBSON I. 
Published: May 2007

ABSTRACTStocks of four “syngens” (syngens 1, 3, 12, 13) of Paramecium caudatum could not be distinguished on the basis of isozymic variations of six enzymes. Using the most common enzyme form as the standard for the syngen, we found a higher coefficient of identity between syngens (>90%) than within syngens (73%). These observations, combined with evidence for fertile matings among the groups, suggest that the groups do not warrant the status of syngens. True syngenic variation in P. caudatum is, however, clearly established on the basis of isozymic and breeding studies of wild stocks collected from various places. Some stocks from England have a close affinity with those from Japan, but stocks from Scotland and California must be placed in separate syngenic sets. Thus, P. caudatum is indeed a species complex, within which evolutionarily distinct groups (species = syngens) are identifiable. The definition of syngens on the basis of initial agglutination response is, however, unjustified.
Action of the Organophosphorous Insecticide Parathion on the Free‐Living Marine Dinoflagellate Prorocentrum micans Ehrbg.
Authors: PREVOT P. , SOYER M.‐O. 
Published: May 2007

ABSTRACTGrowth of cultures of the dinoflagellate Prorocentrum micans Ehrbg. was slowed by parathion >1 ppm. Parathion also decreased chlorophyll content and perturbed cellular ultrastructure, eliciting especially plastoglobuli in their chloroplasts. Toxicity of this organophosphorous insecticide is unlikely to be due to its anticholinesterase activity since P. micans appears not to contain cholinesterase. Fluorescence kinetics show that parathion affects the photosynthetic system, particularly photosystem II.
Flagellar Morphology in Stumpy‐Flagella Mutants of Chlamydomonas reinhardtii1
Authors: JARVIK JONATHAN W. , CHOJNACKI BONNIE 
Published: May 2007

ABSTRACTSixteen new mutants of the biflagellate green alga Chlamydomonas reinhardtii with either stumpy‐flagella or no flagella at all were examined by electron microscopy. Four of the mutants were found to carry short bulbous flagella containing amorphous electron‐dense material which may represent unassembled flagellar protein. Basal bodies of normal ultrastructure were present in all mutants. Dikaryon dominance tests indicated that the stumpy mutations were recessive to wild‐type in all cases tested. Stumpy mutations also conferred a measure of detergent resistance to Chlamydomonas, apparently by affecting the detergent‐solubility of the flagellar membrane.
Cytolytic Activity Released from Tetrahymena1
Authors: FLORIN‐CHRISTENSEN J. , FLORIN‐CHRISTENSEN M. , KNUDSEN J. , RASMUSSEN L. 
Published: May 2007

ABSTRACTUsing a hemolytic assay system, we have detected cytolytic activities in extracellular medium from Tetrahymena thermophila and T. pyriformis. In addition, we have identified two phospholipase activities (types A and C) from the same source by thin layer chromatography analysis of the breakdown products of a phospholipid preparation. The hemolytic activity peaks at low pH values. It is inhibited by egg lecithin, supporting the view that a phospholipase activity is involved in the cytolytic processes. Cytolytic activities may play important roles in Tetrahymena, both in nutrition, especially in parasitic and scavenger forms, and in defense against predators. Tetrahymena is probably partly protected from its own released cytolytic phospholipase by having a high proportion of phosphonolipids on its surface membrane.
Phagocytic Activity of Three Naegleria Strains in the Presence of Erythrocytes of Various Types1
Authors: ALONSO PILAR , ZUBIAUR ELENA 
Published: May 2007

ABSTRACTThe phagocytic activities of N. lovaniensis (Aq/9/1/45D) and N. gruberi (1518/1f and 1518/1e) were studied in the presence of erythrocytes of various species: chicken, rabbit, goat, and human (A+, B+, and AB+ were tested). The percentage of amoebae with ingested red cells, the phagocytic index (PhI), can be considered as an expression of phagocytic activity. Under given conditions (erythrocyte concentration, incubation time, age of amoebic cultures) each strain of Naegleria prefers one erythrocyte type. Thus, for 72‐h cultures, N. lovaniensis ingested more A+ type erythrocytes than did N. gruberi strains but had very low affinity for rabbit red cells except when very high concentrations were tested. Naegleria gruberi 1f was the most active of the three strains towards rabbit and B+ and AB+ human erythrocytes, but very low PhIs were obtained with goat erythrocytes. Naegleria gruberi le exhibited high phagocytic activity for every erythrocyte type except for rabbit red cells.
Fine Structure of Exoerythrocytic Merozoite Formation of Plasmodium berghei in Rat Liver1
Authors: MEIS JACQUES F. G. M. , VERHAVE JAN PETER , JAP PAUL H. K. , MEUWISSEN JOSEPH H. E. T. 
Published: May 2007

ABSTRACTThe fine structure of exoerythrocytic merogony of Plasmodium berghei was studied after perfusion‐fixation of rat livers from 51 h post‐inoculation onwards. Meroblast formation was effected by clefts originating from the parasite plasmalemma and by fusion of vacuoles with each other. Invaginations at the periphery resulted in labyrinthine structures providing the parasites with an enormous increase in surface area, which might facilitate exchange of metabolites. When the parasitophorous vacuole membrane collapsed, the newly formed merozoites were lying free in the hepatocytic cytoplasm, which degenerated until the merozoites were sticking together by a stroma, obviously a remnant of the host hepatocyte. Groups of merozoites, still kept together by the spongy stroma, were subsequently released in the bloodstream. At 53 h most of the developmental stages leading to the release of merozoites could be found and thereafter parasite numbers decreased while large granulomas became apparent.
Population Growth in Stationary and Suspension Culture of Paramoeba pemaquidensis Page (Amoebida, Paramoebidae)1
Authors: MARTIN RONALD E. 
Published: May 2007

ABSTRACTParamoeba pemaquidensis Page requires attachment to a substrate in order for population growth to occur. Populations of amoebae suspended in bacterized culture media on a roller tube apparatus did not increase in size whereas amoebae maintained in stationary control tubes multiplied in number. Amoebae maintained in suspension for as long as three weeks attached and multiplied in culture when allowed to settle. This suggests that Paramoeba found suspended in the surface microlayer of the ocean may be in a “dormant” state. Implications for the survival and geographic distribution of the genus are discussed.