bluuebunny/crossref_metadata_2025 huggingface dataset:
Phénomènes Périodiques, Métaboliques et Structuraux Chez un Protiste, Euglena gracilis
Authors: LEDOIGT G. , CALVAYRAC R.
Published: May 2007

RESUME.

Des divisions synchrones chez Euglena gracilis Z peuvent ětre obtenues par différentes méthodes. Lorsque les cellules sont cultivées sur milieu contenant du lactate comme seule source de carbone, des divisions synchrones sont observables, indépen‐damment des conditions d'éclairement. Toutefois, il existe une relation entre la phase des divisions cellulaires et les périodes lumière‐obscurité appliquée à la culture.

Pendant le cycle cellulaire, nous montrons que les synthèses des macromolécules sont discontinues: c'est le cas pour les ADN nucléaire et mitochondrial, les ARN ribosomaux et non‐ribosomaux, ainsi que pour certaines protéines (cytochrome c 558). Des variations cycliques touchant la morphologie des mitochondries et des chloroplastes sont observées. Au cours du cycle cellulaire, les processus métaboliques séquentiels accompagnent les modifications de structure des organites. C'est ainsi qu'en début du cycle, au commencement de la phase G1, sont synthétisés les ribosomes cytoplasmiques et qu'ensuite, chez les euglènes vertes, les ARN non‐ribosomaux sont formés.

Ces synthèses d'ARN précèdent l'accroissement du chondriome et du plastidome dans la cellule. En milieu de phase G1, une nouvelle synthèse d'ARN non‐ribosomal commence et est observée avant la synthèse des ADN nucléaire et mitochondrial. En fin de phase G1, démarre la division des organites à partir du chondriome et du plastidome en réseau.

SYNOPSIS.

Synchronous divisions of Euglena gracilis strain Z can be obtained by various methods. When the cells are cultivated in a medium containing lactate as the sole carbon source, synchronous divisions are observed, independent of the conditions of illumination. Nevertheless, there exists a relationship between the phase of cell division and the periods of light and darkness applied to the culture.

During the cell cycle, the synthesis of macromolecules is discontinuous—this is true of nuclear and mitochondrial DNA, ribosomal and nonribosomal RNA, and certain proteins (cytochrome c 558). Cyclic variations in the structure of mitochondria and chloroplasts are also observed. In the course of the cell cycle, sequential metabolic processes accompany structural modifications of the organelles. Also, at the beginning of the cycle, at the start of phase G1, the cytoplasmic ribosomes are synthesized, and then, in green euglenids, nonribosomal RNAs are formed. These syntheses of RNA precede enlargement of the chondriome and plastids. In mid‐G1 phase, a new synthesis of RNA begins, which precedes synthesis of nuclear and mitochondrial DNA. At the end of G1 phase, division of organelles starts, beginning with the chondriome and plastids, arranged in a network.
Lectin Analysis of Surface Saccharides in Two Trichomonas vaginalis Strains Differing in Pathogenicity*
Authors: WARTOŃ ANDRZEJ , HONIGBERG B. M.
Published: May 2007

SYNOPSIS. Surface saccharides in 2 Trichomonas vaginalis strains, the moderately pathogenic, JH34A, and the mild, JH162A, were analyzed with the aid of plant lectins. Concanavalin A (Con A), wheat germ agglutinin (WGA), soybean agglutinin (SBA), castor bean agglutinin (CBA), and lectin from the garden pea (GPA) were employed in agglutination tests and in treatment of ultrathin sections for electron microscopy according to the horseradish peroxidase‐3,3′‐diaminobenzidine method. With Con A and WGA, small quantitative differences were noted between the 2 strains in the results of agglutination and in the reaction‐product deposits observed by electron microscopy. Distribution of the binding sites for the 2 lectins was also somewhat different in the JH34A and JH162A trichomonads. In general, the reactions with the more pathogenic strain were slightly stronger. Although the reactions with SBA and CBA lectins were weaker than those with Con A or WGA, they provided the means for qualitative differentiation between the 2 trichomonad strains. SBA alone agglutinated the JH34A strain and formed demonstrable deposits on the cell surfaces. On the other hand, only CBA reacted with JH162A flagellates. The garden pea lectin failed to bind to the surface of either strain. On the basis of results obtained with the control preparations incubated in the presence of specific inhibitors, it was concluded that both strains had α‐methyl‐D‐mannoside and/or α‐methyl‐D‐mannoside‐like as well as N‐acetyl‐D‐glucosamine residues on their surfaces. In addition, JH34A strain had D‐lactose‐containing residues while JH162A trichomonads had residues with D‐galactose. Neither strain appeared to possess residues containing N‐acetyl‐D‐galactosamine.
Resuscitation of amebae deprived of essential symbiotes: Micrurgical studies*
Authors: LORCH I. JOAN , JEON KWANG W.
Published: May 2007

SYNOPSIS. The effect of depletion and restoration of obligatory bacterial endosymbiotes on Amoeba proteus strain xD was studied. Removal of the symbiotes by culturing the amebae at 26.5 C resulted in loss of viability of the host cells, indicating that this strain is dependent on its endosymbiotes for survival. Amebae depleted of bacteria could initially be resuscitated by injection of isolated symbiotes, but prolonged deprivation led to irreversible changes. Nuclei of aposymbiotic amebae were viable when transplanted into the cytoplasm of normal cells, but the symbiote‐depleted cytoplasm of heat‐treated amebae could not be resuscitated by renucleation. No immediate ultrastructural changes were detected in aposymbiotic amebae except for clumping of nucleoli. Thus it appears that the symbiote performs an essential function as a cytoplasmic constituent.
Infectivity of Plasmodium gallinaceum Sporozoites from Oocysts
Authors: DAHER VALQIRIA R. , KRETTLI ANTONANA U.
Published: May 2007

SYNOPSIS. Infectivity of Plasmodium gallinaceum (Brumpt) sporozoites isolated from midguts and salivary glands of experimentally infected Aedes fluviatilis (Lutz) was studied. The 2 populations were compared at 7, 8, and 9 days postisolation from mosquitoes, which were maintained at 27 C ± 1C and ∼75% relative humidity. Infectivity of the parasites was evaluated by the length of the prepatent period of the infection in 2‐week‐old chicks inoculated intramuscularly. Infection was caused by 7‐day‐old sporozoites from salivary glands, but not from midguts. Older sporozoites induced infection in all the inoculated chicks. The results suggested a somewhat higher infectivity of the 8‐ and 9‐day salivary‐gland parasites than of the oocyst sporozoites. However, unlike sporozoites from mammalian malaria, oocyst sporozoites from avian malaria were highly infective at this age.
Intranuclear Parasitism of the Ciliate Euplotes by a Trypanosomatid Flagellate
Authors: WILLE JOHN J. , WEIDNER EARL , STEFFENS W. L.
Published: May 2007

A trypanosomatid flagellate, Leptomonas sp., develops and multiplies in the macronucleus (only) of natural and laboratory‐reared populations of the ciliate Euplotes. Up to 90% of the natural populations of Euplotes in our test pond had such nuclear infections. Laboratory infections were transmitted to this ciliate by feeding it liberated parasites. Paramecium resisted infections. All laboratory‐induced infections were lethal to Euplotes, while control clones of the uninfected ciliates remained viable. This leptomonad, unlike Leptomonas karyophilus (found in Paramecium), shows no leishmanial forms in its several ciliate hosts and shows a varied pattern of locomotion.
Spore Germination in the True Slime Mold Didymium nigripes1
Authors: KERR NORMAN S.
Published: May 2007

The morphology of spore germination in Didymium nigripes was studied using scanning electron microscopy and Nomarski phase optics. First, the outer spore wall splits, revealing a fibrillar inner wall. Remnants of the inner wall continue to cover the newly emerged amoeba. A single nucleus and a prominent vacuole are visible throughout germination. Germination is more rapid in glucose‐peptone‐yeast extract than in phosphate buffer. Germination is completely inhibited at 4°C, and is very slow at 18°C. Germination is most rapid at 26°C; at 21°C or 32°C it is slightly slower. Germination is reversibly inhibited by 20 μ/ml cycloheximide, but not by 200 μ/ml 5‐fluoro uracil or 200 μ/ml proflavin. It is completely inhibited by 10‐3 M Na azide.
The Germination of Vavraia culicis Spores1
Authors: UNDEEN ALBERT H.
Published: May 2007

Buffered solutions of KCl and NaCl were tested for their stimulatory effect on the germination of variously‐aged spores of Vavraia culicis. Germination was optimal in 0.2 M KCl, pH 6.5 for one isolate, and, for another isolate, peaks of germination occurred at pH 7.0 and 9.5. Spores incubated for several hours in suboptimal solutions became unable to germinate under optimal conditions. After being returned to water, they regained their ability to germinate. Calcium chloride, magnesium chloride, and ammonium chloride inhibited germination. After ingestion by mosquito larvae, spores germinated near the posterior end of the midgut.
Stage‐Dependent Toxicity of N‐Acetyl‐Glucosamine to Plasmodium falciparum1
Authors: Gupta Suresh K. , Schulman Seymour , Vanderberg Jerome P.
Published: May 2007

The effects of N‐acetyl‐glucosamine on growth of synchronized cultures of Plasmodium falciparum were assessed by morphological observations and by measurement of parasite incorporation of 3H‐hypoxanthine. Inhibition of 3H‐hypoxanthine incorporation was more marked during the later stages of the erythrocytic cycle. At concentrations of the sugar below 20 mM, however, the deleterious effects were mainly a result of failure of released merozoites to invade erythrocytes, rather than a failure of schizonts to mature or release merozoites. These results are compatible with the hypothesis that a lectin‐like substance on the merozoite interacts with a surface glycoprotein on the red cell and that sugar residues on this glycoprotein may be involved in this recognition.
Mating‐Type Polymorphic Variation in Euplotes minuta (Ciliophora: Hypotrichida)1
Authors: Dini Fernando , Luporini Pierangelo
Published: May 2007

An investigation was carried out to probe into the mating‐type structure of a local population of the marine ciliate, Euplotes minuta. From this population, nine different mating types belonging to a unique set were isolated. The nine type‐representative wild stocks analyzed were found to be heterozygous at the mating‐type (mat) locus and provided, together with their sexual progeny, a total of 15 pure mating types. In E. minuta, the high‐multiple nature of the basic mating system controlled by a series of peck‐order alleles at a single locus should be considered a virtual certainty. The relationships among the genetic economies of the similar bottom‐dwelling marine ciliates of the genus Euplotes, the E. vannus‐crassus‐minuta group, are discussed.
Formation of the Cyst Wall of the Ciliate Colpoda steinii
Authors: RUTHMANN AUGUST , KUCK ANGELIKA
Published: May 2007

After a thin membranous envelope surrounding the cell body and cilia of Colpoda steinii has been formed, the main mass of the proteinaceous cyst wall is deposited without exocytosis. It can be composed of two layers, the denser and wrinkled ectocyst and the smooth‐walled endocyst; however, the ectocyst may be missing. Evidence is presented that ecto‐ and endocyst are formed from vesicles derived from abundant rough endoplasmic reticulum which appears at the time of wall formation. The cilia are retained and become embedded in the peripheral cytoplasm. Synthesis of RNA and protein is required as actinomycin C and cycloheximide block cyst formation. Calcium is required during a sensitive phase prior to encystment.
Relevance of Hemin for in vitro Differentiation of Trypanosoma cruzi1
Authors: ARÉVALO JORGE , PANEBRA ALFREDO , CRUZ CARLOS SANTA
Published: May 2007

Simple culture conditions that allow good growth and high yields of trypomastigotes are described. The proportion of metacyclic trypomastigotes increases with the concentration of hemin in the culture medium, reaching a peak of 80% after 10 days with 20 mg hemin/liter.
An Immunofluorescent Study of the Microtubule Organization in Trichomonas vaginalis Using Antitubulin Antibodies1
Authors: JULIANO CLAUDIA , RUBINO SALVATORE , ZICCONI DONATELLA , CAPPUCCINELLI PIERO
Published: May 2007

ABSTRACT. The flagellated protozoon Trichomonas vaginalis, parasite of the human urogenital tract, possesses a well developed microtubule system organized in highly differentiated structures. We have shown by immunoblotting that monospecific anti‐sheep brain tubulin antibodies are able to react with the microtubular tubulin of T. vaginalis. These antibodies were used to study the microtubular system of T. vaginalis both in interphase and mitosis by indirect immunofluorescence. The interphase microtubular pattern, characterized by an axostyle, a pelta, four anterior flagella, and a recurrent flagellum, displayed remarkable changes at the onset of mitosis: the axostyle disappeared, and two pole bodies connected by a short spindle became evident; chromosomal fibers arose while pole‐to‐pole fibers elongated. The last phases of mitosis were marked by the disappearance of chromosomal fibers, the appearance of two small axostyles, and the depolymerization of the pole‐to‐pole bundle. At the end of mitosis, the normal interphase microtubule pattern was observed.
Herpetomonas dedonderi N. Sp. (Sarcomastigophora, Trypanosomatidae) from Haemagogus janthinomys Dyar, 1921 (Diptera, Culicidae)1
Authors: DEDET JEAN‐PIERRE , GEOFFROY BERNARD , BENICHOU JEAN‐CLAUDE
Published: May 2007

ABSTRACT. A new species of Herpetomonas was isolated from the intestinal tract of a mosquito, Haemagogus janthinomys, in French Guiana (South America). Ultrastructure, growth in various culture media, and morphological changes are presented. The name, Herpetomonas dedonderi, is proposed for this new species of lower trypanosomatid.
Some Factors Controlling the Distribution of Two Pond‐Dwelling Ciliates with Algal Symbionts (Frontonia vernalis and Euplotes daidaleos)1
Authors: Finlay B. J. , Berninger U.‐G. , Stewart L. J. , Hindle R. M. , Davison W.
Published: May 2007

The vertical distributions of two pond‐dwelling zoochlorellae‐bearing ciliates (Euplotes daidaleos Diller & Kounaris, 1966 and Frontonia vernalis Ehrenberg, 1838) were monitored over a 24‐h period. Both species maintained peak abundance at a low O2 level (usually < 1 mg/liter). They did not migrate in response to the changing light level. Experiments with laboratory cultures indicated that the characteristic distribution in an O2 gradient in the dark was largely controlled by the oxygen tension. The increased motility in anoxia and high pO2 was independent of large changes in pCO2 and pH. Ciliates living in anoxia or a very low pO2 would migrate out of the dark and into the dimly lit (10 μE m‐2 sec‐1) part of a glass cell because there they could photosynthesize, produce O2, and create a suitable oxygenated microenvironment; a further increase in the light level caused a slow migration out of the light. Similar migrations were observed when the light level remained low but the pO2 was artificially raised. Ciliates suspended in 1 μM DCMU (an inhibitor of photosynthetic O2 evolution) took longer to migrate into the light and they did not avoid high light levels (> 100, μE m‐2 sec‐1)‐ Frontonia suspended in water with a pO2 of 1% aggregated at a low light level (1 μE m‐2 sec‐1); peak daytime abundance in the pond occurred at about this light level. Frontonia vernalis tends to swim vertically upwards (anterior end up) when suspended in anoxic water. This apparent negative geotaxis compensates for the high sedimentation velocity (0.36 mm sec‐1) of this large ciliate and facilitates its aggregation at the metalimnion. The O2 tension appears to be the principal factor controlling the vertical distributions of both species. Occasional, enhanced convection within the metalimnion has a secondary influence. Light influences the vertical profile only if it promotes photosynthesis and increases the intracellular pO2.
Transmission and Ecology of Trypanosomatid Flagellates of Water Striders (Hemiptera: Gerridae)
Authors: TIESZEN KENNETH L. , MOLYNEUX DAVID H.
Published: May 2007

An investigation of transmission and ecology of the monogenetic trypanosomatids, Blastocrithidia gerridis and Crithidia flexonema, in Gerris is described. Motile free‐living flagellates of both species were found in the faeces of Gerris and in the water on which the bugs inhabited. Transmission of both trypanosomatid species occurred from naturally infected wild‐caught bugs to flagellate‐free laboratory‐bred bugs via water. Crithidia flexonema was also transmitted to laboratory‐bred bugs after being isolated in culture. Observations of experimentally infected bugs indicate that C. flexonema flagellates are imbibed and pass through the fore‐ and midgut to the hindgut where they become attached and multiply. There was no evidence to suggest transovarial transmission. In a 3‐yr investigation into the prevalence of trypanosomatids in a natural population of adult Gerris odontogaster, it was found that the infection rate varied between 19% and 100%. There was no significant difference in infection rates between females and males. The infection rate peaked for each year in late spring or early summer. The significance of these results is discussed in relation to the ecology and behaviour of Gerris. The results indicate that the infections are maintained in hibernating bugs over winter.
Flagellar Membrane and Paraxial Rod Proteins of Leishmania: Characterization Employing Monoclonal Antibodies
Authors: ISMACH RICHARD , CIANCI CATHERINE M. L. , CAULFIELD JOHN P. , LANGER PAMELA J. , HEIN ANN , McMAHON‐PRATT DIANE
Published: May 2007

Flagella‐specific proteins of Leishmania have been identified employing the monoclonal antibody technique. Six monoclonal antibodies recognized 3 different proteins. A doublet of protein of Mr 69,000 and 74,000 Da identified by monoclonal antibodies F‐3, F‐4 and F‐6 is continuously distributed along the flagellum by immunofluorescence. Immunocytochemical electron microscopic studies localize these molecules to the paraxial rod of the flagellum. A single protein of Mr 13,200 Da is recognized by monoclonal antibodies F‐1, F‐2 and F‐5. The distribution of the Mr 13,200 protein appears irregular, occurring in localized patches along the length of the flagellum, especially at the flagellar tip. Immunocytochemical electron microscopic experiments show that the Mr 13,200 molecule is associated with the membrane of the flagellum. Indirect immunofluorescence experiments demonstrated these monoclonal antibodies cross‐reacted with members of the Kinetoplastida family (Endotrypanum, Trypanosoma, Leishmania) suggesting that these molecules may be evolutionarily conserved.
Scanning Electron Microscopic Observation of Differentiation from the Reproductive Short Form to the Infectious Long Form of Holospora obtusa
Authors: FUJISHIMA MASAHIRO , SAWABE HISAHIRO , IWATSUKI KENJI
Published: May 2007

To identify the surface features of Holospora obtusa during its differentiation from the reproductive short form to the infectious long form, bacteria of four different buoyant densities were isolated by Percoll density gradient centrifugation of homogenates of host cells or isolated macronuclei, and examined with a scanning electron microscope. Bacteria of buoyant density 1.09 g/ml were reproductive short forms as well as cells at various stages in the elongation process including fully elongated ones. Bacteria of buoyant densities 1.11 g/ml and 1.13 g/ml were premature long forms and those of 1.16 g/ml were mature infectious long forms. Bacteria of buoyant density 1.09 g/ml had an entirely rough surface while those of buoyant densities 1.11 g/ml and 1.13 g/ml were smooth and had wale‐like stripes on their surface. A small tapered tip was observed at one end of the bacteria of buoyant density 1.13 g/ml. Bacteria of buoyant density 1.16 g/ml had an entirely smooth surface, but one end always showed a rough surface; this locally differentiated surface of the special tip of the infectious long form may be responsible for both the nuclear and species specificities of the infectivity of H. obtusa. These observations indicate that the surface of H. obtusa changes during differentiation and the special tip develops in bacteria of buoyant density 1.13 g/ml.
Endosymbiotic Methanogenic Bacteria In Anaerobic Ciliates: Significance For the Growth Efficiency of the Host
Authors: FENCHEL TOM , FINLAY BLAND J.
Published: May 2007

ABSTRACT Endosymbiotic methanogenic bacteria of three species of anaerobic ciliates (Plagiopyla frontata, Metopus conforms, and M. palaeformis) were inactivated with the specific methanogen inhibitor 2‐bromoethanesulfonic acid. the absence of endosymbiont methanogens reduced growth rate and growth yield by about 30% in P. frontata and M. contortus, while no significant change in fitness was observed in M. palaeformis. In Plagiopyla the growth rate constant is not affected by an artificially increased pH2 neither in normal nor in methanogen‐free ciliates. the energetic advantage conferred by endosymbiont methanogens in Plagiopyla and in Metopus contortus probably is due to excretion of organic material from the bacteria at the expense of bacterial reproduction. It is unlikely that the maintenance of a low pH2 within the cells due to H2‐consumption by the bacteria is important to the ciliates.
Mixotrophic Protists In Marine and Freshwater Ecosystems
Authors: SANDERS ROBERT W.
Published: May 2007

ABSTRACT Some protists from both marine and freshwater environments function at more than one trophic level by combining photosynthesis and panicle ingestion. Photosynthetic algae from several taxa (most commonly chrysomonads and dinoflagellates) have been reported to ingest living prey or nonliving particles, presumably obtaining part of their carbon and/or nutrients from phagocytosis. Conversely, some ciliates and sarcodines sequester chloroplasts after ingestion of algal prey. Plastid retention or “chloroplast symbiosis” by protists was first demonstrated < 20 years ago in a benthic foraminiferan. Although chloroplasts do not divide within these mixotrophic protists, they continue to function photosynthetically and may contribute to nutrition. Sarcodines and ciliates that harbor endosymbiotic algae could be considered mixotrophic but are not covered in detail here. the role of mixotrophy in the growth of protists and the impact of their grazing on prey populations have received increasing attention. Mixotrophic protists vary in their photosynthetic and ingestion capabilities, and thus, in the relative contribution of photosynthesis and phagotrophy to their nutrition. Abundant in both marine and freshwaters, they are potentially important predators of algae and bacteria in some systems. Mixotrophy may make a stronger link between the microbial and classic planktonic food webs by increasing trophic efficiency.
An Improved Medium For Plasmodium chabaudi In Vitro Erythrocyte Invasion Assays
Authors: O'DONOVAN SUSAN M. , DALTON JOHN P.
Published: May 2007

ABSTRACT. RPMI‐1640 is routinely used as the basal medium for the in vitro maintenance of malaria parasites. In this study we tested several commercially available nutritional media in a Plasmodium chabaudi chabaudi erythrocyte invasion assay and showed that three media, BME Basal Medium—modified, Dulbecco's Modified Eagle Medium, and William's Medium E, improved the level of merozoite invasion when compared with RPMI‐1640. These media improve the rate of maturation of newly invaded rings to young trophozoites. Radioisotope incorporation by trophozoites maintained in these three media was also improved when compared to trophozoites maintained in RPMI‐1640. BME Basal Medium—modified, or a combination of three parts BME Basal Medium—modified with one part William's Medium E, supported higher levels of erythrocyte invasion by merozoites. We suggest that either of these media replace the currently used RPMI‐1640 for in vitro studies on P. c. chabaudi.
Developmental Life Cycle of Leishmania—Cultivation and Characterization of Cultured Extracellular Amastigotes1
Authors: PAN ALFRED A. , DUBOISE S. MONROE , EPERON SIMONE , RIVAS LUIS , HODGKINSON VIRGINIA , TRAUB‐CSEKO YARA , MCMAHON‐PRATT DIANE
Published: May 2007

ABSTRACT. The biochemistry and immunology of Leishmania promastigotes has been extensively studied; this is due primarily to the facility with which this stage, in contrast to the amastigotes stage, can be maintained in axenic culture. Several attempts to axenically culture lines of Leishmania amastigotes have been reported in the literature. This paper summarizes methods of adaptation (low pH, elevated temperature and culture medium) and characterization of several axenic lines of Leishmania amastigotes. Based on morphological, biological, immunological and biochemical evidence, these organisms appear to resemble amastigotes from infected macrophages or tissue. The axenically cultured amastigotes appear to be distinct from shocked (heat, serum deprivation, stressed) Leishmania promastigotes in the plethora of proteins synthesized, growth (multiplication) in culture, and developmental regulation observed. These data suggest that Leishmania organisms have a significant developmental response to certain signals (pH, temperature) mimicking their in vivo macrophage milieu. The response to other environmental parameters characteristic of the host‐macrophage remain to be determined. These axenically cultured amastigotes should be of interest for further immunological, biochemical and developmental investigations of the disease‐maintaining stage of this parasite.
In Vitro Activity of Mitochondrial ATP Synthetase Inhibitors Against Plasmodium falciparum
Authors: BASCO LEONARDO K. , LE BRAS JACQUES
Published: May 2007

ABSTRACT. The mitochondrion appears to be essential for the growth of asexual, intraerythrocytic stages of Plasmodium falciparum and may thus be a suitable chemotherapeutic target. The in vitro activity of almitrine, a mitochondrial ATP synthetase inhibitor used for the treatment of hypoxemia, was compared with other mitochondrial inhibitors against chloroquine‐susceptible and chloroquine‐resistant P. falciparum using an isotopic semimicro drug susceptibility assay. The 50% inhibitory concentration (IC50) values of almitrine (range: 2.6–19.8 μM) were within similar range of values of other mitochondrial ATP synthetase inhibitors and doxycycline, a mitochondrial protein synthesis inhibitor. Almitrine was equally active against chloroquine‐susceptible and chloroquine‐resistant parasites. Drug combination studies showed no interaction between chloroquine and almitrine. Our results suggest that almitrine, a clinically safe drug, may represent a lead compound with a specific target against the mitochondrial ATP synthetase which may be useful for antimalarial chemotherapy.
Cloning of a Partial Length cDNA Encoding the C‐Terminal Portion of the 75‐77‐kDa Antigen of Trypanosoma cruzi
Authors: YANG SHUMIN , BERGMAN LAWRENCE W. , SCHOLL DAVID R. , ROWLAND EDWIN C.
Published: May 2007

ABSTRACT It has been suggested that several Trypanosoma cruzi antigens have possible protective epitopes which may be suitable vaccine candidates. We found previously that animals resistant to T. cruzi infection produced antibodies against the 75‐77‐kDa parasite antigen. To test the ability of the recombinant form of this antigen to protect animals from T. cruzi infection, the cDNA which encodes a portion of the 75‐77‐kDa antigen was cloned using a cDNA library constructed in an orientation‐specific bacteriophage expression vector (λgt11) from poly (A)+ RNA of Brazil strain epimastigotes. One clone, named SFS‐40, was selected by screening the library using affinity purified antibodies specific for the 75‐77‐kDa parasite antigen as probe. The cDNA corresponding to the 1.7‐kilobase insert of SFS‐40 was subcloned into plasmid vectors and characterized. The cDNA sequence encodes a polypeptide of about 40 kDa. The putative product of the cDNA was homologous to members of the 70‐kDa stress protein family. When epimastigotes were shifted from 29° C to 37° C, there was no change in the level of SFS‐40 mRNA. In contrast, the 70‐kDa heat shock protein mRNA of the parasite was increased about four fold by this treatment.
The Sequence of the Hartmannella vermiformis Small Subunit rRNA Coding Region
Authors: GUNDERSON JOHN H. , GOSS SUSAN J. , SOGIN MITCHELL L.
Published: May 2007

ABSTRACT The Hartmannella vermiformis small‐subunit rRNA coding region was amplified, and the amplified DNA was cloned and sequenced. The coding region is 1,840 nucleotides long, and is typical of eukaryotic rRNA genes in both size and composition. Different clones contained different nucleotides at three positions.
The Large, Free‐living Amoebae: Wonderful Cells for Biological Studies
Authors: JEON KWANG W.
Published: May 2007

The large, free‐living amoebae have been widely used as model cells for studying a variety of biological phenomena, including cell motility, nucleocytoplasmic interactions, membrane function, and symbiosis. Results of studies by our group on amoebae as moving cells, as material for micrurgical manipulations, and as hosts for intracellular symbionts are summarized here. In particular, our recent studies of the amoeba as a microcosm, in which spontaneously infecting foreign microbes have become integrated as necessary cell components, are described in some detail. These processes have involved an initial microbial infection, mutual adaptation by the host and symbionts, and development of obligatory symbiosis. Evidence is presented to show that symbiont‐derived macromolecules are involved in the protection of symbionts from digestion, the symbionts have acquired regulatory elements on their chromosomal genes to enhance production of beneficial gene products, and symbionts apparently utilize host‐derived macromolecules to their benefit. These studies involved morphological observations both at light and electron microscopic levels, physiological and genetic studies, production and use of poly‐ and monoclonal antibodies, and molecular‐biological approaches including gene cloning and sequencing. It is shown that amoebae are uniquely suited as model cells with which to study these phenomena.
Observations on an Intranuclear Microsporidian in Lymphoblasts from Farmed Atlantic Halibut Larvae (Hippoglossus hippoglossus L.)
Authors: NILSEN FRANK , NESS ASLAUG , NYLUND ARE
Published: May 2007

ABSTRACT. An intranuclear microsporidian was observed in lymphoblasts from the kidney of farmed Atlantic halibut larvae (Hippoglossus hippoglossus). In addition to spores, intranuclear pre‐spore stages were observed. Uninucleated stages with a slight thickening of the cell membrane were the most simple developmental stages observed. Multinucleated developmental stages contain electron‐lucent vesicles and electron‐dense discs. The spores are ovoid and measure 2.9 × 1.2 μm (mean). Sporophorous vesicles, diplokarya and mitochondria were not observed in any of the developmental stages. The developmental stages observed are similar to those of the family Enterocytozoonidae, genus Enterocytozoon. However, there are several differences between the present species and E. bieneusi from enterocytes in man. The relationship to the other species in the genus, E. salmonis can only be determined when all the developmental stages of the species from Atlantic halibut are identified.
Cloning and Identification of Arp1, an Actin‐Related Protein from Pneumocystis carinii
Authors: CHRISTOPHER LISA J. , FLETCHER LEAH D. , DYKSTRA CHRISTINE C.
Published: May 2007

ABSTRACT. The complete Pneumocystis carinii Arp1 gene has been sequenced from two cDNA clones. The gene encodes a protein 385 bp in length with an estimated size of 45,000 kD. The A + T% for the Arp1 gene and a 900‐bp sequence upstream of the gene were 63.7% and 70.3%, respectively. These values are consistant with A + T codon preference displayed by P. carinii and are similar to values reported for other P. carinii genes. The predicted amino acid sequence of the P. carinii Arp1 protein had a similarity of 87.6% with Neurospora crassa Arp1, 82.1% similarity with vertebrate centractin, and 71.2% similarity with the Saccharomyces cerevisiae Act5p. Expression of Arp1 mRNA in P. carinii was detectable via synthesis of cDNA and subsequent PCR amplification. Affinity purified antibodies against S. cerevisiae Act5p, and canine centractin recognized both the recombinantly expressed protein and a 45,000 kD protein in P. carinii nuclear extracts. The Arp1 gene is the second member of the actin multigene family that has been identified in P. carinii.
Competition Among Homologous Polypeptide Pheromones of the Ciliate Euplotes raikovi for Binding to Each Other's Cell Receptors
Authors: ORTENZI OLAUDIO , LUPORINI PIERANGELO
Published: May 2007

ABSTRACT. Purified preparations of the polypeptide pheromones Er‐1 and Er‐2 were obtained from type I and II cells of Euplotes raikovi, respectively, radiolabeled, and used to study their ability to compete with each other in binding to the same type I and II cells and to type × cells secreting Er‐10, another pheromone homologous to Er‐1 and Er‐2. It was shown that: 1) These radiolabeled pheromone preparations bind, with similar but not identical affinities, to cells from which they originate as well as to cells of the other types. 2) Every pheromone binding reaction can be completely inhibited by another homologous pheromone added in excess to cells. These results are discussed in relation to phenomena, common in ciliates, of instability of (homotypic) mating pairs formed between genotypically identical cells suspended with a foreign (nonself) pheromone.
Elucidation of the DNA Synthetic Cycle of Entamoeba Spp. Using Flow Cytometry and Mathematical Modeling
Authors: DVORAK JAMES A. , KOBAYASHI SEIKI , ALLING DAVID W. , HALLAHAN CLAIRE W.
Published: May 2007

ABSTRACT. We developed a method to study the DNA synthetic cycles of Entamoeba histolytica and Entamoeba invadens by flow cytometry (FCM) based on a preparative procedure to reduce both high levels of natural fluorescence and non‐specific adsorption of fluorochromes. We modeled G1, S, and G2 phases as a series of overlapping Gaussian curves. Both E. histolytica and E. invadens displayed G1, S, and G2 proportions that are consistent with eukaryotic cell populations in exponential or stationary growth phase. Exponential phase E. histolytica populations contained a hypodiploid subset with a mass of about 20% less than the diploid value which we estimate by FCM to be 24 × 10‐14 g DNA/cell. Exponential phase E. invadens populations contained a hypodiploid subset with a mass of about 6% less than the diploid value which we estimate by FCM to be 30 × 10‐14 g DNA/cell.
Lipid Requirements and Lipid Uptake by Giardia lamblia Trophozoites in Culture
Authors: LUJAN HUGO D. , MOWATT MICHAEL R. , NASH THEODORE E.
Published: May 2007

To better understand the lipid requirements of Giardia lamblia trophozoites and the mechanisms of lipid uptake, we supplemented serum‐free TYI‐S‐33 medium with lipids incorporated into different lipid carriers. We found that serum lipoproteins, β‐cyclodextrins, and bile salts are able to supply cholesterol and phospholipids to Giardia and to support the multiplication of the parasite in vitro. The growth rates obtained with different lipoproteins or bile salts and lipid mixtures were similar to that in standard culture medium containing serum. Pulse labelling experiments using fluorescent lipid analogs demonstrated that Giardia can take up lipids from lipoproteins, β‐cyclodextrins, or bile salt micelles, but with different kinetics, and that bile salts greatly facilitated lipid transfer from lipoproteins and cyclodextrins to the parasite surface. The binding of different radioiodinated lipoprotein classes to the trophozoite surface, inhibition of lipoprotein interiorization at 4°C or by cytochalasin D, and incorporation studies using fluorescent LDL suggested that a small component of lipid uptake by trophozoites was likely due to endocytosis of lipoproteins.
Chemosensory Responses of Acanthamoeba castellanii: Visual Analysis of Random Movement and Responses to Chemical Signals
Authors: SCHUSTER F. L. , LEVANDOWSKY M.
Published: May 2007

A visual assay slide chamber was used in conjunction with time‐lapse videomicroscopy to analyze chemotactic behavior of axenically grown Acanthamoeba castellanii. Data were collected and analyzed as vector scatter diagrams and cell tracks. Amebas responded to a variety of bacterial products or potential bacterial products by moving actively toward the attractant. Responses to the chemotactic peptide formyl‐methionyl‐leucyl‐phenylalanine (fMLP), lipopolysaccharide, and lipid A were statistically significant (P≤ 0.03), as was the response to fMLP benzylamide (P≤ 0.05). Significant responses to cyclic AMP, lipoteichoic acid, and N‐acetyl glucosamine were also found.

Chemotactic peptide antagonists, mannose, mannosylated bovine serum albumin, and N‐acetyl muramic acid all yielded nonsignificant responses (P > 0.05). There was no single optimal concentration for response to any of the attractants tested, and amebas responded equally over the range of concentrations tested. Pretreatment of amebas with chemotactic peptides, bacterial products, and bacteria reduced the directional response to attractants. Amebas that had been grown in the presence of bacteria appeared more responsive to chemotactic peptides. Treatment of amebas with trypsin reduced the response of cells to chemotactic peptides, though sensitivity was restored within a couple of hours. This suggests the ameba membrane may have receptors, sensitive to these bacterial substances, which are different from the mannose receptors involved in binding bacteria to the membrane during phagocytosis. The rate of movement was relatively constant (ca. 0.40 μm/s), indicating that the locomotor response to these signals is a taxis, or possibly a klinokinesis, but not an orthokinesis. Studies of the population diffusion rate in the absence of signals indicate that the basic population motility follows the pattern of a Levy walk, rather than the more familiar Gaussian diffusion. This suggests that the usual mathematical models of ameboid dispersion may need to be modified.
Kinetics of 2 Genetically Distinct Pneumocystis carinii Populations in Rat Colonies
Authors: CUSHION MELANIE T. , ORR SALLY
Published: May 2007

SUMMARY The natural history of prototype and variant Pneumocystis Corinii populations in several colonies of rats were monitored over time periods ranging from 1 to 4 yean. Karyotypic profiles of organism populations from individual rats were evaluated for the proportion of prototype: variant P. carinii and the number of animals harboring co‐infections were enumerated. Throughout the observation periods: (1) each P. carinii population retained its distinctive karyotype; (2) the proportions of prototype:variant within the lungs fluctuated; and (3) the number of rats co‐infected within a colony varied. These surveys suggest a competition between 2 similarly adapted populations.
Intraspecific Variation in Cryptocaryon irritans
Authors: DIGGLES BENJAMIN K. , ADLARD ROBERT D.
Published: May 2007

ABSTRACT. Intraspecific variation in the ciliate Cryptocaryon irritans was examined using sequences of the first internal transcribed spacer region (ITS‐1) of ribosomal DNA (rDNA) combined with developmental and morphological characters. Amplified rDNA sequences consisting of 151 bases of the flanking 18 S and 5.8 S regions, and the entire ITS‐1 region (169 or 170 bases), were determined and compared for 16 isolates of C. irritans from Australia, Israela and the USA. There was one variable base between isolates in the 18 S region nd 11 variables indicate that Australian C. irritans isolates from estuarine (Moreton Bay) and coral reef (Heron Island) environments are distinct. The Heron Island isolate was genetically closer to morphologically dissimilar isolates from Israel (1.8% divergence) and USA (2.3 % divergence) than it was to the Moreton Bay isolates. Three isolates maintained in our laboratory since February 1994 originated from the same source. During this time the sequence of the isolates from wild fish in Moreton Bay remained unchanged. These genetic differences indicate the existence of a founder effects in laboratorty populations of C. irritans. The genetic variation found here, combined with known morphological and developmental differences, is used to characterise four strains of C. irritans.
Evidence for Hybridization by Multilocus Enzyme Electrophoresis and Random Amplified Polymorphic DNA Between Leishmania braziliensis and Leishmania panamensis/guyanensis in Ecuador
Authors: BANULS ANNE‐LAURE , GUERRINI FRANCOISE , PONT FRANCOIS LE , BARRERA CESAR , ESPINEL IVAN , GUDERIAN RONALD , ECHEVERRIA RAMIRO , TIBAYRENC MICHEL
Published: May 2007

ABSTRACT. The taxonomic attribution of four Leishmania stocks isolated from humans in Ecuador has been explored by both multilocus enzyme electrophoresis and random amplified polymorphic DNA. For three loci, MLEE results showed patterns suggesting a heterozygous state for a diploid organism, while the corresponding homozygous states are characteristic of the Leishmania panamensis/guyanensis complex and Leishmania braziliensis. RAPD profiles exhibited for several primers a combination of the Leishmania panmensis/guyanensis complex and L. braziliensis characters. These data hence suggest that the four stocks are the results of hybridization between L. panamensis/guyanensis and L. braziliensis. MLEE data show that the results cannot be attributed to either mixture of stocks, or an F1 in the framework of a simple Mendelian inheritance.
Cell Invasion by the Microsporidium Encephalitozoon intestinalis
Authors: MAGAUD ANNE , ACHBAROU ABDERRAHIM , DESPORTES‐LIVAGE ISABELLE
Published: May 2007

The ultrastructural study of the invasion of cells (THP1 AND RK13) by E. intestinalis shown that infective stages enter host cells via a phagocytic process intitiated at the contact of the apical part of spores with host cell membrane. The polar tube is extruded within an invagination of the host cell membrane that extends inside a pseudopod containing microfilaments. These observations suggest that microsporidia as well as other intracellular pathogens can induce host cell alterations facilitating the invasio.
Molecular Changes in Entamoeba histolytica in Response to Bacteria1
Authors: Bhattacharya A. , Anand Monika T. , Paul Jayshree , Yadav Nagendra , Bhattacharya S.
Published: May 2007

Entamoeba histolytica, the protozoan parasite, is the causative agent of amoebiasis. The degree of virulence, as inferred from invasiveness, of potentially pathogenic strains may be regulated by both host and parasite factors that determine the gut environment. One such factor that plays an important role is the bacterial flora in the gut. Previous studies have clearly shown that bacterial flora is an important determinant of virulence in E. histolytica. However, the exact nature of changes induced in E. histolytica in response to bacteria and their role in virulence is not clear. In this study the levels of a number of molecules potentially important in virulence mechanisms were determined in E. histolytica cells grown with and without normal human bacterial flora, using enzyme‐linked immunosorbent assay. Significant changes were observed only after the E. histolytica cells had been adapted to grow with bacterial flora for a number of generations, and not in short term culture.
Molecular Phylogenetic Relatedness of Frenkelia spp. (Protozoa, Apicomplexa) to Sarcocystis falcatula Stiles 1893: Is the Genus Sarcocystis Paraphyletic?
Authors: Votypka Jan , Hypša Vaclav , Jirku Milan , Flegr Jaroslav , Vavra Jiri , Lukes Julius
Published: May 2007

ABSTRACT The coccidians Frenkelia microti and F. glareoli (Apicomplexa: Sarcocystidae) form tissue cysts in the brain of small rodents (intermediate hosts) while oocysts are formed in the intestine of final hosts, buzzards of the genus Buteo. The inclusion of the small subunit ribosomal RNA gene sequences (SSU rRNA) of both Frenkelia species into the SSU rRNA trees of other, tissue cyst‐forming coccidia strongly supports paraphyly of the genus Sarcocystis. Frenkelia spp. exhibit close relatedness to Sarcocystis falcatula Stiles 1893, a bird‐opossum parasite, recognized under its junior synonym S. neurona Dubey et al. 1991, as the causative agent of equine protozoan myeloencephalitis on the American continent. As the definition of the genus Frenkelia is based on a plesiomorphic character (affinity to the neural tissue) of supposedly low phylogenetic value, the synonymization of the genus Frenkelia with Sarcocystis is proposed. This renders the genus Sarcocystis monophyletic.
Population genetics of Scirtothrips perseae: tracing the origin of a recently introduced exotic pest of Californian avocado orchards, using mitochondrial and microsatellite DNA markers
Authors: Rugman‐Jones P.F. , Hoddle M.S. , Stouthamer R.
Published: May 2007

The Californian avocado industry has recently been impacted by the establishment of three exotic arthropod pests that are native to Mexico and Central America. Establishment of all three pests is thought to have resulted from illegal movement of host plants (avocado) into California. To identify likely sources and routes of entry of such pest invasions, we examined the population genetics of the most recent invader, avocado thrips [Scirtothrips perseae Nakahara (Thysanoptera: Thripidae)], using mitochondrial DNA (mtDNA) and microsatellite markers. The mtDNA sequences revealed three geographically distinct and divergent lineages, of which the mtDNA haplotypes of Californian individuals were most closely related to populations in the center of the pest's native range. Analysis of allele frequencies at four microsatellite loci added resolution, indicating Coatepec Harinas, Mexico, as the most likely source of the Californian population. Statistically, we did not detect any bottleneck in population size associated with the invasion of California. However, estimates of the effective population size of the invading population suggest that a severe bottleneck occurred, indicating that the quantity of host‐plant material entering California was small. Our findings implicate Coatepec Harinas, a large avocado germplasm and breeding center, as the most likely source of the introduced Californian population of S. perseae and as a likely source of previous and future avocado pest introductions. Efforts to identify natural enemies of S. perseae for biological control should focus on Coatepec Harinas and immediate surrounds. Moreover, identification of the source of invasive pests enables the establishment and enforcement of plant quarantine and free‐trade protocols.
Primary malignant myoepithelioma of the distal femur
Authors: ALBERGHINI M. , PASQUINELLI G. , ZANELLA L. , PIGNATTI G. , BENINI S. , BACCHINI P. , BERTONI F.
Published: May 2007

A 55‐year‐old male presented with a 1‐month history of localized pain caused by an osteolytic and destructive lesion in the right distal femur. Histologically, the tumour consisted of spindle cells intermingled with epithelioid eosinophilic cells arranged in small cords embedded in a hyalinized‐to‐chondromyxoid stroma. Electron microscopy and immunohistochemistry showed features of myoepithelial differentiation. RT‐PCR failed to demonstrate chimeric transcripts of extraskeletal myxoid chondrosarcoma. The final diagnosis was primary malignant myoepithelioma of bone. The patient is alive with lung metastases 13 months after surgery. Primary malignant myoepithelioma of bone is an exceptionally rare neoplasm that should be considered in the differential diagnosis with the more aggressive myxoid spindle cell sarcomas.