bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biochemical and Structural Analyses of Microtubules in the Pellicular Membrane of Leishmania tropica1
Authors: BORDIER CLEMENT , GARAVITO R. MICHAEL , ARMBRUSTER BARBARA 
Published: May 2007

ABSTRACTThe structure of the major protein of the pellicular membrane of Leishmania tropica was investigated. This protein is composed of two polypeptides, of ca. 50,000 d molecular weight, that were found to cross‐react immunologically with the α and β subunits of pig brain tubulin. The polypeptides and pig brain tubulin subunits were partially digested with S. aureus V8 protease, and the peptides obtained analysed by SDS‐polyacrylamide gel electrophoresis. A comparison of the patterns showed that the β subunits of Leishmania and pig tubulin have very similar primary structures, while the α subunits have evolved divergently. These experiments demonstrate that the major polypeptides found in the pellicular membrane of L. tropica are α and β subunits of tubulin. Immuno‐electron microscopy indicates that the tubulin is located in the microtubules associated with the pellicular membrane of Leishmania. Arrays of microtubules were prepared by nonionic detergent treatment of the cells and observed by electron microscopy after negative staining. Optical diffraction reveals a 5 nm spacing between protofilaments in the microtubule and a 4 nm axial periodicity corresponding to the tubulin subunits. The pitch of the shallow left‐hand three‐start helix is 12°. A distance of 47 nm separates each microtubule from the next. These data show that the dimensions and supramolecular organization of the tubulin subunits in the microtubules are identical in the pellicular membrane of L. tropica and in mammalian brain.
Unicapsula seriolae n. sp. (Myxosporea, Multivalvulida) from Australian Yellowtail Kingfish Seriola lalandi1
Authors: LESTER R. J. G. 
Published: May 2007

ABSTRACTUnicapsula seriolae n. sp. forms long plasmodia within the striated muscle fibers of Seriola lalandi off eastern Australia. Its spores are composed of three valves, only one of which contains a developed polar capsule. Within the capsule, the filament makes 2 1/2–3 turns, and this criterion can be used to separate U. seriolae from the two other members of the genus. The flesh of infected fish disintegrates during slow cooking.
Distribution of Members of the Crypthecodinium cohnii (Dinophyceae) Species Complex1
Authors: BEAM CARL A. , HIMES MARION 
Published: May 2007

ABSTRACTCrypthecodinium cohnii, a small marine heterotrophic homothallic dinoflagellate, has diversified into a complex of morphologically very similar breeding groups (biological species or sibling species), some of which have become widely dispersed. Membership of two clones in the same sibling species is shown by their sexual compatibility as determined by genetic complementation in zygotes formed from motility mutants derived from the two stocks. Membership in different sibling species may be inferrec when motility mutants of one strain do not complement those of another. Fifty‐six clones representing seaweed enrichments from *** geographic sites have been found to belong to 28 sibling species; 35 clones are members of seven wide‐ranging biological species, and 21 are single representatives of 21 other breeding groups within the ranges of the others. Of 174 clonal isolates in our possession, 168 conform in size and shape to C. cohnii. Six others which have smaller cells and only one‐fifth the standard DNA and chromosome number belong, we believe, to another species. The C. cohnii complex provides a unique opportunity for the study of evolutionary divergence and geographical dispersion of a dinoflagellate.
Development of Plasmodium chabaudi in Mouse Red Blood Cells: Structural Properties of the Host and Parasite Membranes1
Authors: WUNDERLICH FRANK , STÜBIG HELLA , KÖNIGK EBERHARD 
Published: May 2007

ABSTRACTThe structure of both the host and parasite membranes during stages in the asexual development of Plasmodium chabaudi in mouse red blood cells is examined by transmission electron microscopy of thin sections and freeze‐fracture preparations. The erythrocyte's plasma membrane, the membrane of the parasitophorous vacuole, and the plasma membrane of the parasite exhibit different structural properties in terms of membrane width and the frequency and diameter of the typical intramembrane‐particles (IMP) populating the membrane's fracture faces. The difference between the parasitophorous vacuolar membrane and host cell's plasma membrane is remarkable because the vacuolar membrane is formed from an invagination of the erythrocyte's plasma membrane. The vacuolar membrane has significantly reduced frequencies and diameters of IMP's on both faces and reveals a marked temperature response manifesting itself as large IMP‐devoid domains emerging on both faces on chilling to 4°C. In contrast, cooling induces only some very small IMP‐devoid patches on both faces of the host plasma membrane. Neither of these membranes changes significantly as parasite development progresses. In contrast, the parasite's plasma membrane shows local alterations during its development, forming compaction domains with the nuclear envelope in ca. 30% of the ring‐stages and trophozoites. These compaction domains disappear in late uninuclear trophozoites and schizonts. Furthermore, the plasma membrane of the host cell, the vacuolar membrane, and the parasite's plasma membrane do not respond to externally applied Ca2+, and their temperature‐response remains unaltered during the infection cycle. Thus, modification of these three membranes as a consequence of invasion and development of the parasites, as recently found in the primate malaria caused by P. knowlesi, can be detected neither directly nor indirectly via temperature‐ and/or Ca2+‐response in the rodent malaria caused by P. chabaudi.
In Vivo and In Vitro Activity by Diverse Chelators against Trypanosoma brucei brucei1
Authors: SHAPIRO ANNA , NATHAN H. C. , HUTNER S. H. , GAROFALO JOANNE , McLAUGHLIN SUSAN DITTUS , RESCIGNO DIANE , BACCHI C. J. 
Published: May 2007

ABSTRACTA system of prescreens and screen has been developed to select chelators as potential drugs against Trypanosoma brucei brucei EATRO 110. The chelators tested were nearly all commercially available, low molecular, and having moderate to high affinity for Fe(III). We prescreened 70 compounds showing heme‐sparing or inhibitory activity in a Crithidia fasciculata growth system having excess Fe and minimal hemin. Of these, 45 were highly trypanocidal for suspensions of bloodstream T. b. brucei; criteria of activity here were immobilization, lysis, and loss of infectivity. Eighteen of the chelators highly active in the suspension prescreen were tried in T. b. brucei‐infected mice. Thirteen of these chelators were curative in mice with 24‐h infections, that is, they allowed survival >30 days beyond the untreated controls. 3,4‐Dihydroxycinnamic acid (caffeic acid). 2,9‐dimethyl‐1, 10 phenanthroline (neocuproine), and 2‐pyridinecarboxaldehyde‐2‐pyridyl‐hydrazone cured five out of five mice after an i.v. dose of 100 mg/kg. Salicylaldehyde thiosemicarbazone cured five out of five mice at an i.p. dose of 500 mg/kg. Lesser activity was shown by several other chelators.
Characterization of the Proteins of Naegleria fowleri: Relationships between Subunit Size and Charge1
Authors: WOODWORTH T. W. , KEEFE W. E. , BRADLEY S. G. 
Published: May 2007

ABSTRACTProteins of whole cell extracts of Naegleria fowleri, precipitated with acetone, have been resolved by two‐dimensional polyacrylamide gel electrophoresis. Autoradiograms of the [35S]‐methionine‐labeled polypeptides were scanned and analyzed by a computer‐assisted program in order to determine whether there were correlations between selected attributes of proteins (e.g., subunit size and charge). The majority of the polypeptides had molecular sizes within the range of 20–60 kilodaltons. The mean amount of polypeptide was less for those with molecular sizes between 20 and 45 kilodaltons than for those larger than 45 kilodaltons. The mean amount of polypeptide was greater in the isoelectric focusing range of pH 5–6 than in the range of pH 6–7. Polypeptides in the size range of 20–40 kilodaltons had a median isoelectric point of 6.1, whereas polypeptides in the size range of 40–80 kilodaltons had a median pI of 5.6. Our data indicated that molecular size and charge were not entirely independent variables, and that the composition of a polypeptide might have an important influence on its steady state level in N. fowleri.
Adhesion and Interiorization of Trypanosoma cruzi in Mammalian Cells1
Authors: ANDREWS NORMA W. , COLLI WALTER 
Published: May 2007

ABSTRACTA quantitative method for experimentally separating the adhesion and interiorization phases of the interaction of Trypanosoma cruzi with mammalian cells was developed. Incubation of confluent monolayers of mammalian cells with epimastigotes or trypomastigotes at 4°C allowed the evaluation of the number of adhered parasites that do not become interiorized at this temperature. Quantification of interiorized parasites at 34°C was achieved by employing hypotonic lysis to eliminate the extracellularly adhered trypomastigotes. Both adhesion and interiorization were found to be proportional to the time of exposure of cells to parasites and to the multiplicity of infection. These phenomena occur normally for trypomastigotes in the absence of serum with LLC‐MK2 cells, HeLa cells, and 3T3 fibroblasts. Moreover, it was possible to obtain trypomastigotes that presented the same infectivity to LLC‐MK2 cells as did parasites obtained in the presence of 2% fetal calf serum after 10 serial passages in a medium devoid of serum. Inhibition of adhesion (of epimastigotes and trypomastigotes) and of interiorization (of trypomastigotes) was obtained with inactivated normal serum from several sources, a saturation effect being observed at a final concentration of 20%. Bovine serum albumin, at the concentrations present in the sera, had no inhibitory effect. Trypomastigotes that have been pre‐incubated with 40% FCS (45 min at 4°C) showed decreased adhesion and interiorization indices, effects that can be reversed by trypsinization of the parasites prior to exposure of the cells. A progressive internalization of previously attached trypomastigotes was observed on raising the temperature from 4°C to 34°C; no spontaneous detachment of parasites was detected up to 120 min. Approximately 75% of the adhered parasites were found inside the cells after 45 min at 34°C. The presence of normal inactivated calf serum during incubation at 34°C resulted in a certain degree of detachment and in a lower interiorization index.
Development of Caryospora bigenetica n. sp. (Apicomplexa, Eimeriidae) in Rattlesnakes and Laboratory Mice1
Authors: WACHA RICHARD S. , CHRISTIANSEN JAMES L. 
Published: May 2007

ABSTRACTDuring a survey of the coccidian parasites of reptiles from Iowa, three specimens of Crotalus horridus L., the Timber Rattlesnake, and one of Sistrurus catenatus (Rafinesque), the Massasauga Rattlesnake, were found to be passing oocysts of a Caryospora, here described as C. bigenetica n. sp. Since these snakes (family Crotalidae) are known to subsist mainly on small mammals, oocysts from one of the Timber Rattlesnakes were fed to laboratory white mice (Mus musculus L.) to determine if mammals might be involved as alternate hosts in the life cycle. At necropsy, tissues of the tongue and dermis of the mice revealed a sequence of stages which included mature male and female gamonts, fully sporulated sporocysts, “excysted” sporozoites, and “resting” sporozoites that lay individually in solitary, cyst‐like host cells termed “caryocysts.” A coccidia‐free Massasauga that was fed an infected mouse, at a time when caryocysts in the mouse would have been present, later passed oocysts similar to those of the original inoculum. These results, along with the discovery of endogenous stages (asexual and sexual) in the intestine of the Timber Rattlesnake and the experimentally infected Massasauga, suggest that this parasite has a heteroxenous life cycle pattern, with sexual stages occurring both in the ophidian and the mammalian hosts.
Generation of Mechanical Forces in Phagocytosing Amoebae: Light and Electron Microscopic Study1
Authors: JEON K. W. , JEON M. S. 
Published: May 2007

ABSTRACTCells of Amoeba proteus and Chaos carolinensis that were in the process of phagocytosing large prey organisms were studied to find a structural basis for the generation of mechanical forces exerted by newly forming food cups. It was found that the food‐cup walls facing prey organisms have a more prominent network of thin filaments inside the plasmalemma and that the glycocalyx covering the area is more condensed than usual.
Uptake of Ferritin‐labeled Antibodies by Tetrahymena1
Authors: WILLIAMS NORMAN E. 
Published: May 2007

ABSTRACTExperiments with Tetrahymena thermophila using ferritin probes revealed that these cells take up ferritin conjugated to antibodies (not directed against Tetrahymena) much more readily than they do ferritin or cationized ferritin. The massive and rapid uptake of antibody‐ferritin offers certain advantages for studies of endocytosis and membrane flow in cells of this type, and the method may be applicable to other types of protozoa as well.
Myxosoma cerebralis (Myxozoa: Myxosporea) Etiologic Agent of Salmonid Whirling Disease Requires Tubificid Worm (Annelida: Oligochaeta) in its Life Cycle
Authors: MARKIW MARIA E. , WOLF KEN 
Published: May 2007

ABSTRACTStudies of the life cycle of Myxosoma cerebralis showed that development of infectivity did not occur endogenously but that the spore “aging” process required participation of an aquatic tubificid oligochaete. Data suggestive of such involvement were derived from trials in which spores were “aged” in an array of inert, sterilized, pasteurized, or natural aquatic substrates and from examination of aquatic soils from trout hatcheries in which whirling disease was epizootic. The role of the aquatic oligochaete was confirmed two ways. First, signs of whirling disease developed, and M. cerebralis spores were produced in young rainbow trout (Salmo gairdneri) that had been fed oligochaetes harvested from pond soil taken from two hatcheries where whirling disease was epizootic. Second, when containers of pasteurized soil were populated with four genera of oligochaetes–Aeolosoma, Dero, Stylaria, or Tubifex– from a biological supply house, or with tubificid worms from trout hatcheries free of whirling disease, and then seeded with M. cerebralis spores and “aged” for 4 months, whirling disease occurred only in trout held with Tubifex and with hatchery tubificids.
Divalent Cation‐dependent ATPase Activities Associated with Cilia and Other Subcellular Fractions of Paramecium: An Electrophoretic Characterization on Triton‐polyacrylamide Gels1
Authors: DOUGHTY MICHAEL J. , KANESHIRO EDNA S. 
Published: May 2007

ABSTRACTSeveral divalent cation‐dependent ATP phosphohydrolases associated with cilia, ciliary axonemes, ciliary membranes, pellicles, trichocysts, nuclei, mitochondria, microsomes, and soluble peripheral cell surface fractions of Paramecium tetraurelia were resolved in this study. Fifteen different activity bands were detected in whole cell sonicates or subcellular fractions by Triton polyacrylamide gel electrophoresis and ATPase activity staining. The ciliary surface membrane contained two major ATPase activities that were distinct from the enzymes associated with all other cell fractions.
Defined Minimal Growth Medium for Acanthamoeba polyphaga
Authors: INGALLS CONNIE S. , BRENT MORGAN M. 
Published: May 2007

ABSTRACTNutritional requirements of Acanthamoeba polyphaga (strain PD) were compared to those reported for A. castellanii. Although A. polyphaga and A. castellanii have essentially the same minimal amino acid requirements–arginine, methionine, leucine, isoleucine, and valine–A. polyphaga cannot utilize acetate as sole carbon source, but A. castellanii can if the medium is supplemented with glycine.
Macromolecular Syntheses During the Quick‐Change Act of Naegleria1,2
Authors: FULTON CHANDLER 
Published: May 2007

ABSTRACTThe rapid, synchronous differentiation of N. gruberi from amoebae to flagellates is a useful paradigm to study aspects of cell differentiation, including regulation of the synthesis of proteins that are related to the changes in cell shape and motility, which occur during differentiation. The differentiation requires synthesis of new RNA and protein molecules to accomplish defined morphogenetic events. Specific new proteins, including the tubulins that form the flagellar microtubules, are synthesized at various times during differentiation, and particular mRNA species appear and disappear. The time course of the synthesis of the α and β subunits of flagellar tubulin is paralleled by the programmed appearance and disappearance of flagellar tubulin mRNAs. The evidence supports the hypothesis that the synthesis of flagellar tubulin is regulated by the transcription, and subsequent disappearance, of flagellar tubulin mRNA. Translatable mRNAs for two calmodulin‐like calcium‐binding proteins appear and disappear contemporaneously with those for flagellar tubulin. During differentiation the synthesis of actin, the major protein of amoebae, is selectively shut down, and translatable actin mRNA rapidly disappears. This description of the orderly appearance, utilization, and disappearance of the mRNAs for actin, calcium‐binding proteins, and flagellar tubulin during differentiation provides means and motivation to investigate the mechanisms that regulate these events.
Analysis of Mitochondrial DNA Variation as an Approach to Systematic Relationships in the Genus Acanthamoeba1
Authors: BYERS THOMAS J. , BOGLER SUSANA A. , BURIANEK LINDA L. 
Published: May 2007

ABSTRACTClassification at the species level has been difficult in the genus Acanthamoeba. The taxonomic designations of a number of strains are in doubt and new approaches to classification are needed. We describe the use of electrophoretic patterns obtained with restriction enzyme digests of mitochondrial DNA as a basis for one new approach. Results from analysis of ten strains of A. castellanii, two of A. polyphaga and one of A. astronyxis are discussed. Examples both of nucleotide sequence diversity and of sequence conservation have been found among strains with the same species designation. Five strains from Europe, North America and New Zealand had identical digestion phenotypes with five enzymes; consequently, very similar nucleotide sequences are predicted. All are pathogenic to humans or mice. The mtDNA sequences of eight remaining strains are predicted to differ from this cluster and, in most cases, from each other at least as much as in sibling species of Paramecium aurelia.
Control of Protein Synthesis in Acanthamoeba castellanii
Authors: JANTZEN HELGA , SCHULZE INGRID , HORSTMANN ULRIKE , CHRISTOFORI GERHARD 
Published: May 2007

ABSTRACTDuring development of Acanthamoeba castellanii in a non‐nutrient medium, the pattern of synthesis of proteins changes. Comparison of in vivo and in vitro patterns of protein synthesis reveals concomitant relative increases of five proteins, indicating a control of synthesis of these proteins at the level of the RNA content. The decrease in the overall rate of protein synthesis and relative decreases in the synthesis of actin and ribosomal proteins during development, not accompanied by equivalent changes in the content of mRNA, suggest control mechanisms also at the level of translation. Patterns of ribosomal proteins do not change qualitatively during encystation, indicating that the inhibition in the overall rate of protein synthesis and the formation of inactive monosomes is not controlled by this mechanism; however, phosphorylation of one ribosomal protein, S 3, is observed occasionally during encystation. Phosphorylation of S 3 is also detected after transfer of stationary phase cells into fresh nutrient medium. It was found that only such cells having RNA of aberrant properties are able to phosphorylate S 3 after transfer into fresh nutrient medium. Since these changes in the property of RNA are never observed in cysts, in which phosphorylation of S 3 sometimes occurs, it is concluded that either other alterations in the properties of RNA than those detected or other parameters are responsible for changes in phosphorylation of S 3.
Incubation in Mice Provides a Signal for the Differentiation of Trypanosoma cruzi Epimastigotes to Trypomastigotes1
Authors: SHER ALAN , CRANE MARK ST. J. , KIRCHHOFF LOUIS V. 
Published: May 2007

ABSTRACTThe differentiation of Trypanosoma cruzi epimastigotes into trypomastigotes was studied in diffusion chambers sub‐cutaneously implanted in mice. Using epimastigotes of the Tulahuén strain, transformation was first evident at 16 h after implantation and reached its maximum (92% trypomastigotes) by 24 h. Shortly before their differentiation into trypomastigotes, epimastigotes were found to develop resistance to lysis by the alternative pathway of complement. Furthermore, implantation of stationary‐phase (as opposed to log‐phase) parasites resulted in the accumulation of large numbers of complement‐resistant epimastigotes in the chambers. These observations suggest that epimastigotes pass through a complement‐resistant transitional stage before differentiating into trypomastigotes and that transformation may require cell division. In a further series of experiments, epimastigotes recovered 7 h after implantation in mice were found to differentiate into trypomastigotes when cultured in vitro for an additional 17 h at 37°C. This observation indicates that the events which trigger the morphologic transformation of epimastigotes into trypomastigotes can be dissociated operationally from the differentiation process itself.
Freshwater Euplotes Species with a 9 Type 1 Cirrus Pattern Depend upon Endosymbionts1,2
Authors: HECKMANN KLAUS , HAGEN RUDOLF TEN , GÖRTZ HANS‐DIETER 
Published: May 2007

ABSTRACTThe hypothesis is advanced that all freshwater Euplotes species with a 9 type 1 fronto‐ventral cirrus pattern (E. patella type) depend upon bacteria‐like endosymbionts. Aposymbiotic cells of these species are unable to divide. The hypothesis is based on the investigation of 40 different freshwater Euplotes stocks collected in Germany, France, the USA, and Japan. No symbionts were found in E. crenosus and E. palustris, freshwater species with 10 fronto‐ventral cirri, nor in E. muscicola, a representative of the freshwater Euplotes group with a 9 type 2 fronto‐ventral cirrus pattern (E. affinis type). Characteristic for the essential endosymbionts are multiple nucleoids, a feature described earlier for omikron, an indispensable symbiont of E. aediculatus. Although the symbionts differ from omikron and among each other in size, shape, and their average number per host, they are believed to be related to omikron. In two stocks a different type of bacterium was found in which no defined nucleoids can be detected. Transfer of this symbiont into aposymbiotic cells, originally carrying omikron, revealed that it can restore the ability to multiply. Similarly, omikron was also able to restore the ability to divide in cells freed of this symbiont. It is assumed that this different type of symbiont is a secondary invader of Euplotes which displaced the original omikron‐like endosymbiont. Some of the stocks were found to carry, in addition to omikron‐like symbionts, other symbiotic bacteria; E. daidaleos carries in addition an alga. The findings suggest that the freshwater Euplotes species with a 9 type 1 cirrus pattern are closely related to each other and evolved from an ancestor (probably of cirrotype 10) which already was dependent upon endosymbionts of the omikron type. It supports the view that the two subgroups of freshwater Euplotes forms with a cirrotype of 9 have evolved independently from each other from species with 10 fronto‐ventral cirri by losing a cirrus at different positions.