bluuebunny/crossref_metadata_2025_split huggingface dataset:
Selective modifiers of glutathione prevent restoration of photorelaxations in mouse gastric fundus
Authors: Ergün Yusuf , Öğülener Nuran 
Published: July 2005

Abstract S‐nitrosoglutathione (GSNO) has previously been shown to have a role in ultraviolet (UV) light‐elicited relaxations and proposed to account for the photosensitive store in the mouse gastric fundus. Furthermore, the depletion of this photosensitive store and its replenishment via long‐term electrical field stimulation were demonstrated in the same tissue. In relation to these results, the aim of the present study was to investigate the putative role of S‐nitrosothiols in the restorative effect of long‐term electrical field stimulation on the reduced photosensitive store. Two series of UV light‐elicited relaxations (photorelaxations) were obtained, and the magnitudes of the responses were 53 ± 6 and 26 ± 3%, respectively. The second series of photorelaxations attenuated statistically when compared with those in the first series. Ethacrynic acid (1 μm), diamide (1 μm) and glutathione (1 μm) had no effect on the photorelaxations occurred in the second series of responses. Electrical field stimulation (4 Hz, 25 V, 1 ms, 60 min), applied between two series of photorelaxations, revealed a complete recovery of the attenuated photorelaxations appeared in the second series. NG‐monomethyl‐l‐arginine (100 μm), ethacrynic acid (1 μm) and diamide (1 μm) extensively prevented the restorative effect of electrical field stimulation on photorelaxations. In addition, glutathione (1 μm) reversed the prevention achieved by ethacrynic acid and diamide. The conclusion is that the restoration accomplished by electrical field stimulation is because of the activation of nitric oxide synthase, which in turn brings about the regeneration of GSNO proposed to be the photodegradable material store.
Centrin Protein and Genes in Trichomonas vaginalis and Close Relatives
Authors: BRUGEROLLE GUY , BRICHEUX GENEVIEVE , COFFE GERARD 
Published: July 2005

ABSTRACT. Anti‐centrin monoclonal antibodies 20H5 and 11B2 produced against Chlamydomonas centrin decorated the group of basal bodies as well as very closely attached structures in all trichomonads studied and in the devescovinids Foaina and Devescovina. Moreover, these antibodies decorated the undulating membrane in Trichomonas vaginalis, Trichomitus batrachorum, and Tritrichomonas foetus, and the cresta in Foaina. Centrin was not demonstrated in the dividing spindle and paradesmosis. Immunogold labeling, both in pre‐ and post‐embedding, confirmed that centrin is associated with the basal body cylinder and is a component of the nine anchoring arms between the terminal plate of flagellar bases and the plasma‐membrane. Centrin is also associated with the hook‐shaped fibers attached to basal bodies (F1, F3), the X‐fiber, and along sigmoid fibers (F2) at the pelta‐axostyle junction, which is the microtubule organizing center for pelta‐axostyle microtubules. There was no labeling on the striated costa and parabasal fibers nor on microtubular pelta‐axostyle, but the fibrous structure inside the undulating membrane was labeled in T. vaginalis. Two proteins of 22–20 kDa corresponding to the centrin molecular mass were recognized by immunoblotting using these antibodies in the three trichomonad species examined.By screening a T. vaginalis cDNA library with 20H5 antibody, two genes encoding identical protein sequences were found. The sequence comprises the 4 typical EF‐hand Ca++ ‐binding domains present in every known centrin. Trichomonad centrin is closer to the green algal cluster (70% identity) than to the yeast Cdc31 cluster (55% identity) or the Alveolata cluster (46% identity).
The Role of Unconventional Myosins in Dictyostelium Endocytosis
Authors: TITUS MARGARET A. 
Published: July 2005

ABSTRACT. Dictyostelium discoideum is a simple eukaryote amenable to detailed molecular studies of the endocytic processes phagocytosis and macropinocytosis. Both the actin cytoskeleton and associated myosin motors are well‐described and a range of mutants arc now available that enable characterization of the role of the cytoskeleton in a range of cellular functions. Molecular genetic studies have uncovered roles for two different classes of Dictyostelium unconventional myosins in endocytosis. The class I myosins contribute to both macropinocytosis and phagocytosis by playing a general role in controlling actin‐dependent manipulations of the actin‐rich cortex. A class VII myosin has been shown to be important for phagocytosis. This brief review summarizes what is known about the role of these different myosins in both fluid and particle uptake in this system.
Is Leishmania (Viannia) peruviana a Distinct Species? A MLEE/RAPD Evolutionary Genetics Answer
Authors: BAÑULS ANNE‐LAURE , DUJARDIN JEAN‐CLAUDE , GUERRINI FRANCOISE , DE DONCKER SIMONNE , JACQUET DIANE , AREVALO JORGE , NOËL SEBASTIEN , LE RAY DOMINIQUE , TIBAYRENC MICHEL 
Published: July 2005

ABSTRACT.A set of 38 Leishmania stocks from the Andean valleys of Peru was characterized by both Multilocus Enzyme Electrophoresis (MLEE) and Random Amplified Polymorphic DNA (RAPD). Data were analyzed in terms of taxonomy and evolutionary genetics. Synapomorphic MLEE and RAPD characters, clear‐cut clustering, and strong agreement between the phylogenies inferred from either MLEE or RAPD supported the view that Leishmania (Viannia) peruviana and Leishmania (Viannia) braziliensis correspond to two closely related, but distinct monophyletic lines (clades) and can therefore be considered as “discrete typing units” (DTUs). The question whether the L. (V.) peruviana DTU deserves species status is dependent upon the desirability of it, in terms of epidemiological and medical relevance. A previous Orthogonal Field Alternating Gel Electrophoresis (OFAGE) analysis of the same L. (V.) peruviana isolates was published by Dujardin et al. (1995b). The data from the different markers (i.e. MLEE, RAPD and OFAGE) were compared by population genetics analysis. RAPD and OFAGE provided divergent results, since RAPD showed a strong linkage disequilibrium whereas OFAGE revealed no apparent departure from panmictic expectation. MLEE showed no linkage disequilibrium. Nevertheless, contrary to OFAGE, this is most probably explainable by the limited variability revealed by this marker in L. (V.) peruviana (statistical type II error). RAPD data were consistent with the hypothesis that the present L. (V.) peruviana sample displays a basically clonal population structure with limited or no genetic exchange. Disagreement between RAPD and OFAGE can be explained either by accumulation of chromosomal rearrangements due to amplification/deletion of repeated sequences, or by pseudo‐recombinational events.
Confusing Selective Feeding with Differential Digestion in Bacterivorous Nanoflagellates
Authors: BOENIGK JENS , MATZ CARSTEN , JÜRGENS KLAUS , ARNDT HARTMUT 
Published: July 2005

ABSTRACT.Food selectivity and the mechanisms of food selection were analyzed by video microscopy for three species (Spumella, Ochromonas, Cafeteria) of interception‐feeding heterotrophic nanoflagellates. The fate of individual prey particles, either live bacteria and/or inert particles, was recorded during the different stages of the particle‐flagellate‐interaction, which included capture, ingestion, digestion, and egestion. The experiments revealed species‐specific differences and new insights into the underlying mechanisms of particle selection by bacterivorous flagellates. When beads and bacteria were offered simultaneously, both particles were ingested unselectively at similar rates. However, the chrysomonads Spumella and Ochromonas egested the inert beads after a vacuole passage time of only 2–3 min, which resulted in an increasing proportion of bacteria in the food vacuoles. Vacuole passage time for starved flagellates was significantly longer compared to that of exponential‐phase flagellates for Spumella and Ochromonas. The bicosoecid Cafeteria stored all ingested particles, beads as well as bacteria, in food vacuoles for more then 30 min. Therefore “selective digestion” is one main mechanism responsible for differential processing of prey particles. This selection mechanism may explain some discrepancies of former experiments using inert particles as bacterial surrogates for measuring bacterivory.
Encystation in Acanthamoeba castellanii: Development of Biocide Resistance1
Authors: LLOYD D. , TURNER N. A. , KHUNKITTI W. , HANN A. C. , FURR J. R. , RUSSELL A. D. 
Published: July 2005

ABSTRACT. Since the early 1960s, axenic culture and the development of procedures for the induction of encystation have made Acanthamoeba spp. superb experimental systems for studies of cell biology and differentiation. More recently, since their roles as human pathogens causing keratitis and encephalitis have become widely recognized, it has become urgent to understand the parameters that determine differentiation, as cysts are much more resistant to biocides than are the trophozoites.Viability of trophozoites of the soil amoeba Acanthamoeba castellanii (Neff), is conveniently measured by its ability to form plaques on a lawn of Escherichia coli. Use of confocal laser scanning microscopy with Calcofluor white, Congo Red or the anionic oxonol dye, DiBAC4(3) or flow cytometry with propidium iodide diacetate and fluorescein or oxonol provides more rapid assessment. For cysts, the plaque method is still the best, because dye exclusion does not necessarily indicate viability and therefore the plate count method has been used to study the sequence of development of biocide resistance during the differentiation process. After two hours, resistance to HC1 was apparent. Polyhexamethylene biguanide, benzalkonium chloride, propamidine isethionate, pentamidine isethionate, dibromo‐ propamine isethionate, and H2O2 and moist heat, all lost effectiveness at between 14 and 24 h after trophozoites were inoculated into encystation media. Chlorhexidine diacetate resistance was observed at between 24 and 36 h. The molecular biology and biochemistry of the modifications that underlie these changes are now being investigated.
Immunohistochemistry Based Assay to Determine the Effects of Treatments on Cryptosporidium parvunt Viability
Authors: PHELPS KALMIA K. , LINDSAY DAVID S. , SUMNER SUSAN S. , PAYER RON 
Published: July 2005

SUMMARYCell culture infectivity assays can provide an accurate means of detecting viable Cryptosporidium parvum oocysts from environmental samples or to test the effects of various treatments on oocyst infectivity. Cell culture assays can also be used to test candidate chemotherapeutic agents. The use of a human cell line provides a situation close to human infection. The present assay uses an anti‐Cryptospordium primary antibody, combined with a biotinylated secondary antibody, and an immunoperoxidase detection system. Cryptosporidium parvum oocysts excysted in vitro when placed on monolayers of HCT‐8 cells and developmental stages including schizonts and merozoites were visualized using light microscopy of the immunoperoxidase stained slides and by transmission electron microscopy of infected HCT‐8 cell cultures. Because the immunoperoxidase system used gives a permanent preparation, the cell cultures can be retained and examined later. Dose titration of oocysts indicated that as few as 50 inoculated oocysts could be detected. The activity of paromomycin was evaluated in this system and 500 μg/ml produced a 97.8% reduction in infection.
A Marine Dinoflagellate, Amphidinium eilatiensis n. sp., from the Benthos of a Mariculture Sedimentation Pond in Eilat, Israel
Authors: LEE JOHN J. , OLEA RAUL , CEVASCO MEGAN , POCHON XAVIER , CORREIA MARIA , SHPIGEL MUKI , PAWLOWSKI JAN 
Published: July 2005

ABSTRACT. A species of Amphidinium bloomed in a mariculture sedimentation pond that was used to grow bivalves near the Gulf of Eilat, Israel. Its overall length averaged 13 μm, the hypocone was 11 μm, and its width was 8μm. It has a ventral ridge. The sulcus begins at the longitudinal flagellar pore and does not project forward in the apex toward the transverse flagellar pore and left margin of the cingulum. The sulcus is a very shallow groove that projects variably about a third of the body length toward the antapex. The cingulum is a deep groove as it circles the cell from the left ventral side to the dorsal side and then becomes very shallow on the right ventral side as it arches posterior toward the longitudinal flagellar pore. Using a modified method for studying dinoflagellate chromosomes in the SEM, we observed 31 chromosomes. The plastid is dorsal and peripheral with 6 ventrally projecting peripheral digital lobes that wrap around the sides of the ventral and posterior nucleus. Amphidinium eilatiensis n. sp. is morphologically closest to Amphidinium carterae and Amphidinium rhynchocephalum, but it does not have the obvious thecal plates or polygonal units described for the former species. Instead, it has a series of spicules, bumps, and ridges on its surface. It differs from A. rhynchocephalum by two morphological characters: surface morphology and gross plastid architecture.The amplified fragments of the rDNA from A. eilatiensis n. sp. isolated from 2 separate sedimentation ponds in Eilat include the 3′‐end of the SSU rDNA (about 100 nt), the whole ITS region (ITS1 + 5. 8S + ITS2) and the 5′‐end of the LSU rDNA (about 900 nts). The total length of the sequences ranged from 1,460 nt. (A. eilatiensis isolate #1) to 1,461 nts. (A. eilatiensis isolate #2). The latter sequences are identical, the difference in length being due to three insertions. Amphidinium eilatiensis is genetically more closely related to A. carterae than to A. klebsii, with respectively 2. 36% and 6. 93% of sequence divergence.
Introductory Remarks: Bacterial Endosymbionts or Pathogens of Free‐Living Amebae1
Authors: MARCIANO‐CABRAL FRANCINE 
Published: July 2005

ABSTRACTFree‐living amebae are ubiquitous in the environment and can be isolated from a variety of habitats including water, soil, air, hospital water systems, dental units, contact lens cases, and cooling towers. The interaction of amebae with other microorganisms in their environment is varied. Bacteria are a major food source for free‐living amebae. However, some bacteria have established a stable symbiotic relationship with amebae. Recent reports indicate an association of amebae with intracellular bacterial pathogens. Such amebae may serve as reservoirs for maintaining and dispersing pathogenic bacteria in the environment or as vectors of bacterial disease in humans.
Genetic and Physiological Interactions in the Amoeba‐Bacteria Symbiosis1
Authors: JEON KWANG W. 
Published: July 2005

ABSTRACTAmoebae of the xD strain of Amoeba proteus that arose from the D strain by spontaneous infection of Legionella‐like X‐bacteria are now dependent on their symbionts for survival. Each xD amoeba contains about 42,000 symbionts within symbiosomes, and established xD amoebae die if their symbionts are removed. Thus, harmful infective bacteria changed into necessary cell components. As a result of harboring X‐bacteria. xD amoebae exhibit various physiological and genetic characteristics that are different from those of symbiont‐free D amoebae. One of the recent findings is that bacterial symbionts control the expression of a host's house‐keeping gene. Thus, the expression of the normal amoeba sams gene (sams1) encoding one form of S‐adenosylmethionine synthetase is switched to that of sams2 by endosymbiotic X‐bacteria. Possible mechanisms for the switching of sams genes brought about by endosymbionts and its significance are discussed.
Bacterial Endosymbionts of Free‐living Amoebae1
Authors: HORN MATTHIAS , WAGNER MICHAEL 
Published: July 2005

ABSTRACTThe occurrence of bacterial endosymbionts in free‐living amoebae has been known for decades, but their obligate intracellular lifestyle hampered their identification. Application of the full cycle rRNA approach, including 16S rRNA gene sequencing and fluorescence in‐situ hybridization with 16S rRNA‐targeted oligonucleotide probes, assigned the symbionts of Acanthamoeba spp. and Hartmannella sp. to five different evolutionary lineages within the Proteobacteria, the Bacteroidetes, and the Chlamydiae, respectively. Some of these bacterial symbionts are most closely related to bacterial pathogens of humans, and it has been suggested that they should be considered potential emerging pathogens. Complete genome sequence analysis of a chlamydia‐related symbiont of Acanthamoeba sp. showed that this endosymbiont uses similar mechanisms for interaction with its eukaryotic host cell as do the well‐known bacterial pathogens of humans. Furthermore, phylogenetic analysis suggested that these mechanisms have been evolved by the ancestor of these amoeba symbionts in interplay with ancient unicellular eukaryotes.
Modulation of a “CD59‐like” Protein in Naegleria fowleri Amebae by Bacteria1
Authors: FRITZINGER ANGELA E. , MARCIANO‐CABRAL FRANCINE 
Published: July 2005

ABSTRACTFound in soil and freshwater habitats, Naegleria fowleri are free‐living amebae that cause a fatal disease in humans called Primary Amebic Meningoencephalitis. In the natural environment, amebae feed on bacteria. In the infected host, the amebae lyse and ingest nerve tissue. Recently, we have established that N. fowleri expresses a “CD59‐like” surface protein, but the function of this protein in the ameba has not been elucidated. In mammalian cells, CD59 is a complement‐regulatory protein that inhibits complement‐mediated lysis of cells expressing this protein. In the present study, expression of the “CD59‐like” protein in response to bacteria and bacterial toxins was investigated by Western immunoblot analysis. Co‐culture of N. fowleri with log phase Escherichia coli or Pseu‐domonas aeruginosa resulted in differential expression of the “CD59‐like” protein. Co‐cultures of amebae and bacteria were examined by electron microscopy. The results of our study implicate a possible protective role of the “CD59‐like” protein in response to bacterial predators and bacterial toxins, because amebae remained intact after co‐culture with bacteria.
Plastid‐Targeting Peptides from the Chlorarachniophyte Bigelowiella natans
Authors: ROGERS MATTHEW B. , ARCHIBALD JOHN M. , FIELD MATTHEW A. , LI CATHERINE , STRIEPEN BORIS , KEELING PATRICK J. 
Published: July 2005

ABSTRACTChlorarachniophytes are marine amoeboflagellate protists that have acquired their plastid (chloroplast) through secondary endosymbiosis with a green alga. Like other algae, most of the proteins necessary for plastid function are encoded in the nuclear genome of the secondary host. These proteins are targeted to the organelle using a bipartite leader sequence consisting of a signal peptide (allowing entry in to the endomembrane system) and a chloroplast transit peptide (for transport across the chloroplast envelope mem branes). We have examined the leader sequences from 45 full‐length predicted plastid‐targeted proteins from the Chlorarachniophyte Bigelowiella natans with the goal of understanding important features of these sequences and possible conserved motifs. The chemical characteristics of these sequences were compared with a set of 10 B. natans endomembrane‐targeted proteins and 38 cytosolic or nuclear proteins, which show that the signal peptides are similar to those of most other eukaryotes, while the transit peptides differ from those of other algae in some characteristics. Consistent with this, the leader sequence from one B. natans protein was tested for function in the apicomplexan parasite, Toxoplasma gondii, and shown to direct the secretion of the protein.
Assessing the Effectiveness of Coding and Non‐coding Regions in Antisense Ribosome Inhibition of Gene Expression in Tetrahymena
Authors: JACOBS MARY ELLEN , CORTEZZO DONNAMARIE E. , KLOBUTCHER LAWRENCE A. 
Published: July 2005

ABSTRACTIn Tetrahymena thermophila, an “antisense ribosome” technology has been developed for inhibiting gene expression and generating novel mutants. Short segments of genes are inserted in antisense orientation into an rDNA vector in a region corresponding to an external loop of the folded rRNA. DNA segments derived from the 5′‐ends of genes have proven most effective in reducing cognate gene expression. To investigate the efficacy of other genie regions, we generated Tetrahymena cell lines with antisense ribosome constructs containing 100‐bp DNA segments derived from the 5′‐ends, 3′‐ends, and internal coding regions of two non‐essential genes, granule lattice protein 1 and macronuclear histone H1. The 5′‐ and 3′‐end constructs inhibited gene expression, but antisense ribosomes derived exclusively from coding regions had little effect.
Identification of Amoebae Implicated in the Life Cycle of Pfiesteria and Pfiestena‐Like Dinoflagellates
Authors: PEGLAR MICHAEL T. , NERAD THOMAS A , ANDERSON O. ROGER , GILLEVET PATRICK M. 
Published: July 2005

ABSTRACTThis study was undertaken to assess whether amoebae commonly found in mesohaline environments are in fact stages in the life cycles of Pfiesteria and Pfiesteria‐like dinoflagellates. Primary isolations of amoebae and dinoflagellates were made from water and sediment samples from five tributaries of the Chesapeake Bay. Additional amoebae were also cloned from bioassay aquaria where fish mortality was attributed to Pfiesteria. Electron microscopy and small subunit (SSU) rRNA gene sequence analysis of these isolates clearly demonstrated that the commonly depicted amoeboid form of Pfiesteria is very likely a species of Korotnevella and is unrelated to Pfiesteria or Pfiesteria‐like dinoflagellates. We have determined that the Pfiesteria and Pfiesteria‐like dinoflagellates examined in this study undergo a typical homothallic life cycle without amoeboid stages. Furthermore, we have demonstrated that cloned amoebae sharing morphological characteristics described for stages in the life cycle of Pfiesteria do not transform into dino7.oites. The strict clonal isolation and cultivation techniques used in this study substantially support the conclusion that the amoebae and some of the flagellates depicted in the life cycle of Pfiesteria are environmental contaminants of the Pfiesteria culture system and that the Ambush Predator Hypothesis needs to be rigorously reevaluated.
Irreversible UV Inactivation of Cryptosporidium spp. Despite the Presence of UV Repair Genes1
Authors: ROCHELLE PAUL A. , FALLAR DAFFODIL , MARSHALL MARILYN M. , MONTELONE BETH A. , UPTON STEVE J. , WOODS KEITH 
Published: July 2005

ABSTRACTUltraviolet light is being considered as a disinfectant by the water industry because it appears to be very effective for inactivating pathogens, including Cryptosporidium parvum. However, many organisms have mechanisms for repairing ultraviolet light‐induced DNA damage, which may limit the utility of this disinfection technology. Inactivation of C. parvum was assessed by measuring infectivity in cells of the human ileocecal adenocarcinoma HCT‐8 cell line, with an assay targeting a heat shock protein gene and using a reverse transcriptase polymerase chain reaction to detect infections. Oocysts of five different isolates displayed similar sensitivity to ultraviolet light. An average dosage of 7.6 mj/cm2 resulted in 99.9% inactivation, providing the first evidence that multiple isolates of C. parvum are equally sensitive to ultraviolet disinfection. Irradiated oocysts were unable to regain pre‐irradiation levels of infectivity, following exposure to a broad array of potential repair conditions, such as prolonged incubation, pre‐infection excystation triggers, and post‐ultraviolet holding periods. A combination of data‐mining and sequencing was used to identify genes for all of the major components of a nucleotide excision repair complex in C. parvum and Cryptosporidium hominis. The average similarity between the two organisms for the various genes was 96.4% (range, 92–98%). Thus, while Cryptosporidum spp. may have the potential to repair ultraviolet light‐induced damage, oocyst reactivation will not occur under the standard conditions used for storage and distribution of treated drinking water.