bluuebunny/crossref_metadata_2025_split huggingface dataset:
Temperature‐Dependent Spore Dimorphism in Burenella dimorpha (Microspora: Microsporida)
Authors: JOUVENAZ D. P. , LOFGREN C. S. 
Published: May 2007

ABSTRACTBurenella dimorpha, a microsporidian parasite of the tropical fire ant, Solenopsis geminata, produces two morphologically distinct types of spores. The binucleate free spores (spores not bound by a pansporoblast membrane) develop normally at temperatures at least as low as 20°C and as high as 32°C. The uninucleate octospores (spores bound in octets by a pansporoblast membrane), however, develop in a restricted range of temperature. Octospores constituted 35.9%± 2.6 of the spores in 25 pupae held at 28°C. Raising the temperature to 30°C reduced octospores to < 1% of the total spore population. Lowering the temperature to 25° or 22°C reduced the octospore population to 8.5%± 6.5 or 0.4 ± 0.5, respectively. Inhibition of octospore development was complete at 20°C. In contrast, the octospores of Vairimorpha necatrix and Vairimorpha plodiae are reported to be abundant at 16°C and 21°C, respectively. The critical event blocked in octospore development may be meiosis, as evidenced by an abundance of binucleate sporonts in the octospore sequence of development, and absence of more advanced sporogonic stages in hosts held at inhibitory temperatures. Free spore size is not affected by temperature although yield may be slightly reduced at elevated temperature.
The Death of an Amoeba1
Authors: LEITH A. G. 
Published: May 2007

ABSTRACTA geneological study shows that about 4% of the cells in healthy, adequately fed Amoeba proteus cultures are inviable. Two different categories of inviability are distinguished. About 44% of all inviability involves twin sisters formed at a division. Another 39% involves single cells with viable sisters and nieces. The inviable singles usually die more rapidly and show fewer visible abnormalities than the twins. The mothers of inviable twins show an increased interdivision time compared to mothers of inviable singles. Both categories of death are more rapid than starvation. The 17% of the deaths which involve aunt‐niece pairs appear to be special cases of twin sister or single cell deaths. There is no evidence for stem line division where a cell forms only one viable daughter for several generations. It is proposed that death is a normal occurrence in amoeba populations. It occurs regardless of culture conditions and may be a measure of accumulated lethal mutations in an asexual polyploid organism.
Parasitic Protozoa of the Blood of Rodents VI. Two New Hemogregarines of the Pygmy Flying Squirrel Idiurus macrotis (Rodentia: Theridomyomorpha: Anomaluridae) in West Africa
Authors: KILLCK‐KENDRICK R. 
Published: May 2007

ABSTRACT. Descriptions are given of two new species of Hepatozoon Miller, 1908 found in the pygmy squirrel, Idiurus macrotis, in the Ivory Coast. Gamonts of both are parasites of monocytes.The size and shape of the gamonts of one, H. normani n. sp., are similar to those of a number of gamonts of other species of rodent hemogregarines and the separate identity of the parasite is based on the host restriction of mammalian hemogregarines. The gamonts of the other species, H. dolichomorphon n. sp., are remarkably long and slender and are unlike those of any other known hemogregarine of mammals. Schizonts of this species were found in a smear prepared from heart blood.
Nonvariant Antigens Limited to Bloodstream Forms of Trypanosoma brucei brucei and Trypanosoma brucei rhodesiense1
Authors: BEAT DAVID A. , STANLEY HAROLD A. , CHOROMAŃSKL LESZEK , MacDONALD A. BRUCE , HONIGBERG B. M. 
Published: May 2007

ABSTRACT. The presence of nonvariant antigens (NVAs) limited to bloodstream forms of Trypanosoma brucei brucei and Trypanosoma brucei rhodesiense was demonstrated for the first time by immunodiffusion and Immunoelectrophoresis. Noncloned and cloned populations were employed in preparation of polyclonal antisera in rabbits and of antigens to be used in the immunologic reactions. The NVAs could be shown best in systems in which hyperimmune rabbit sera (adsorbed with procyclic forms to eliminate antibodies against antigens common to bloodstream form and procyclic stages) were reacted with trypanosomes characterized by heterologous variant‐specific antigens (VSAs).The NVAs demonstrated in this study are very likely different from the common parts of VSAs. As has been suggested by experiments with living trypanosomes, at least a part of the NVAs appears to be located on the surface of the bloodstream forms. In these experiments involving the quantitative indirect fluorescent antibody test, the amount of fluorescence recorded for the heterologous system, i.e. ETat 5 trypanosomes incubated with anti‐AmTat 1.1 serum, equalled ∼3.0% of the fluorescence emitted by the AmTat 1.1 bloodstream forms treated with their homologous antiserum. Evidently, only small amounts of NVAs are present on the surfaces of T. brucei bloodstream forms.In addition to the NVAs, the electrophoresis results suggested the presence of antigenic differences between procyclic stages belonging to different T. brucei stocks.
Processing of Digestive Vacuoles in Tetrahymena and the Effects of Dichloroisoproterenol1
Authors: Fok Agnes K. , Shockley Brenda U. 
Published: May 2007

ABSTRACTThe digestive‐lysosomai system in Telrahymena has been extensively studied; however, the various vacuole stages and the existence of a required processing period prior to defecation have not been clearly denned, in this study the presence of such a required processing period and the rate of DV defecation in Tetrahymena thermophila were determined. Like the cycle in Paramecium. a digestive cycle in Tetrahymena consisted of two periods: the processing period was 45 min and the defecation period was ˜2 h, making the complete cycle ˜3 h. During the defecation period vacuole egestion followed the kinetics of a first‐order rate reaction and had a rate constant of 0.0187/min and a t1/2 of 37 min (82 min into the cycle). Using the naphthol AS‐TR phosphate‐hexazotized rosanilin method to visualize acid phosphatase activity at the light microscopic level, DVs became positive beginning at 10 min. The number of positive DVs increased to a maximum of 13% when DVs were 20‐min old and declined to 5‐7% beyond 30 min. Although dichloroisoproterenol (DCI) has been reported by others to stimulate vacuole defecation, we found it inhibited the defecation rate. The extent of inhibition depended on the age of the DVs when exposed to DCI. Vacuole formation was completely blocked in cells pre‐exposed to 40 μ DCI for only 10 min; however, upon further exposure, cells could recover from this inhibition. The time required for complete recovery increased with increasing DCI concentrations. If DCI was given to cells simultaneously with latex beads, it was found to exert a dose‐dependent inhibitory effect on DV formation. These results showed the heterophagic pathway of the digestive‐lysosomal system in Telrahymena to be similar to that of Paramecium, though it was less efficient in the former cell.
Isolation and Properties of Macronuclei from Tetrahymena thermophila1
Authors: Corr Reinhard , Eichler Wolfgang 
Published: May 2007

ABSTRACTA simple and efficient method is described for the isolation of macronuclei from Tetrahymena thermophila (7B). The steps involved are deciliation and removal of the mucocysts’ contents by dibucaine treatment, digitonin mediated lysis, differential centrifugations, and finally isopyenic sucrose density gradient centrifugation. Judging from the distribution of marker enzymes and electron microscopy, the macronuclei obtained were free of cytoplasmic and paniculate contamination and were highly active in endogenous RNA‐synthesis (1.5 pmol UTP incorporation/ng DNA min at 30°C). The ratio of protein: RNA: DNA was 2.0:0.33:1.0 (weight) and each macronucleus contained an average of 17 pg DNA. The average yield of isolation was 50%.
Isolation and Partial Characterization of Mutants of the Trypanosomatid Crithidia fasciculata and Their Use in Detecting Genetic Recombination1
Authors: Glassberg J. , Miyazaki L. , Rifkin M. R. 
Published: May 2007

ABSTRACTCrithidia fasciculata was used as a model trypanosomatid to study the possible existence of genetic recombination in this group of protozoa. The approach was based on the ability to select a variety of mutants on agar plates. Following mutagenesis of wild type cells by nitrosoguanidine or ethylmethanesulfonate, stable mutant phenotypes were obtained. These included mutants resistant to the drugs actinomycin D, 6‐azauracil, 6‐azauridine, and 5‐fluorouracil, auxotrophs and colony morphology mutants. Following mixed growth of pairs of drug‐resistant mutants on selective media, isolates exhibiting stable recombinant phenotypes were obtained. The data presented suggest that 1) Crithidia undergoes some type of genetic recombination and 2) Crithidia must be diploid at some time during this process.
Entamoeba histolytica and E. invadens: Sulfhydryl‐Dependent Proteolytic Activity1
Authors: Vila Eva E. A. , SÁnchez‐Garza Mireya , Calderón Jesús 
Published: May 2007

ABSTRACTSodium dodecyl sulfate (SDS) and 2‐mercaptoethanol (2‐ME) activated proteolytic enzymes present in extracts of Entamoeba histolytica and E. invadens; SDS (0.5%) and 2‐ME (1.4 and 715 mM) doubled the enzymatic activity when assayed on a stained insoluble substrate. Urea (4 M) did not reduce this activity, suggesting that amebic proteases are stable in the above denaturant conditions. Specific reagents for sulfhydryl (‐SH) groups completely inhibited proteolytic activity regardless of pH. Inhibition with alkylating agents, such as N‐ethylmaleimide and iodoacetamide, was reversed with 715 mM 2‐ME as was also observed with papain. We conclude from these results that the main proteolytic enzymes contained in extracts of E. histolytica and E. invadens are dependent on free thiol groups.
Structural Bases of the Cytolytic Mechanisms of Entamoeba histolytica1
Authors: Martinez‐Palomo Adolfo , Gonzalez‐Robles Arturo , Chavez Bibiana , Orozco Esther , Fernandez‐Castelo Silvia , Cervantes Arnulfo 
Published: May 2007

ABSTRACTThe cellular bases of the powerful cytolytic activity of the human protozoan parasite Entamoeba histolytica were explored by studying the effect of the virulent strain HM1:IMSS on epithelial monolayers of MDCK cells using a combination of time‐lapse microcinematography and transmission and scanning electron microscopy. Early alterations of the epithelial cell membranes were detected by measuring changes in the transepithelial electrical resistance of MOCK monolayers mounted in Ussing chambers. The aggressive mechanism of E. histolytica trophozoites was found to be a complex, multifactorial phenomenon that included hit‐and‐run damage to the plasma membrane of effector cells mediated through contact, phagocytosis of lysed or apparently intact, but detached, MDCK cells, and inlracellular degradation of ingested cells. Following contact with amebas, the epithelial monolayers showed a pronounced lowering of transepithelial resistance, opening of tight junctions, distortion of microvilli, surface blebbing, and the presence of minute focal discontinuities in the plasma membrane. There was no evidence of amebic exocytosis, membrane fusion, or junction formation between the parasite and host plasma membranes. Although modifications in the epithelial cell membranes usually preceded lysis, the cytolytic activity of the parasite did not exclusively involve damage to the plasma membrane of the cultured host cells but also was mediated by avid phagocytosis, the displacement and separation of neighboring cells by means of pseudopodial activity, and the “pinching‐off” of the peripheral cytoplasm of epithelial cells.
Isolation of Naegleria australiensis from an Oklahoma Lake1
Authors: JOHN D. T. , DE JONCKHEERE J. F. 
Published: May 2007

ABSTRACTEight isolates of Naegleria australiensis were obtained from a small lake in Tulsa, Oklahoma. The eight strains were isolated during the hot summer months of July through September, when water temperatures ranged from 27 to 33°C. All eight isolates were pathogenic for mice. The mean time to death for mice was 10 days (range 6–13 days). This pathogenic free‐living ameba has not before been reported from the United States or the Western Hemisphere.
Isospora dawadimiensisn. sp. (Protozoa: Eimeriidae) from the Jerboa (Jaculus jaculus) in Saudi Arabia
Authors: KASIM AHMED A. , SHAWA YASER R. AL 
Published: May 2007

ABSTRACTIsospora dawadimiensisn. sp. is described from the jerboa,Jaculus jaculus, from Dawadimi, Saudi Arabia. Sporulated oocysts ofI. dawadimiensisn. sp. were ovoidal or nearly subspherical 22–26.5 times 20.5–22 μm (24.4 times 21.4 μm). Oocyst wall had one layer. Micropyle, oocyst residuum, and polar granule were absent. Sporocysts were ellipsoid 12–16.5 times 9–10.5 μm (14.6 times 9.9 μm). Sporocyst residuum was present. The sporocysts lack a Stieda body. Sporozoites 8–11 times 2–3 μm (10 times 2.6 μm) were sausage‐shaped, slightly curved, and tapered at one end.
Nutritional Requirements of Plasmodium falciparum in Culture. III. Further Observations on Essential Nutrients and Antimetabolites1
Authors: GEARY TIMOTHY G. , DIVO ALAN A. , BONANNI LINDA C. , JENSEN JAMES B. 
Published: May 2007

ABSTRACTIn a semi‐defined minimal medium for cultivation of Plasmodium falciparum, ribose, mannose, fructose, galactose, and maltose could not replace glucose. Hypoxanthine was the preferred purine source for the parasite over adenine, guanine, inosine, adenosine and guanosine although all supported growth equally. Inhibitors of nucleoside uptake had low potency in killing the parasites but depressed incorporation of [3H]adenosine more than [3H]hypoxanthine. Glutamate could not be replaced by 5‐oxoproline, indicating that the γ‐glutamyl transferase pathway for amino acid uptake is probably not found in this organism. Adenine, nicotinamide, and orotic acid could not supplement glutamine‐deficient medium. The pyridoxine antagonists isoniazid and 4‐deoxypyridoxine were reversed by amino acid supplementation, suggesting that transaminases may be targets of these drugs. Orotic acid, but not glutathione or its amino acid components, partially reversed the effects of 8‐methylamino‐8‐desmethyl riboflavin. Thus, the flavin enzyme, dihydroorotic acid dehydrogenase, but not glutathione reductase, appears to be a target of this riboflavin antagonist. Five biotin antagonists had no significant activity. The choline antagonist 2‐(tert‐butylamino)ethanol and thiamin uptake inhibitors had nonspecific inhibitory effects, which were not reversed by the respective target vitamin. Buthionine sulfoximine and methionine sulfoximine, inhibitors of glutathione synthesis, had significant oxygen‐dependent toxicity. Six sulfonamides showed marked variation in potency and efficacy. Sulfathiazole and sulfadoxine were reversed differentially by p‐aminobenzoic acid, folic acid, and folinic acid. Folinic acid was more effective than folic acid at reversing the toxicity of the dihydrofolate reductase inhibitors aminopterin and pyrimethamine; p‐aminobenzoic acid had no effect.
RNA and Protein Synthesis During Meiotic Prophase in Tetrahymena thermophila1
Authors: MARTINDALE DUANE W. , ALLIS C. DAVID , BRUNS PETER J. 
Published: May 2007

ABSTRACTTetrahymena is one of the few organisms from which large amounts of precisely staged meiotic material can be obtained. We took advantage of this fact to monitor RNA and protein synthesis during meiosis. The rate of total protein synthesis as well as the synthesis of the majority of heavily labeled conjugation‐specific polypeptides (monitored by high resolution two‐dimensional gel electrophoresis) was maximal during meiotic prophase. We therefore cloned cDNAs corresponding to genes active during this time. The mRNA levels of three conjugation‐specific genes (pC1, pC2, and pC7) and one conjugation‐induced gene (pC3) were followed by using the corresponding labeled cDNAs to probe RNA isolated from different times during mating that was also followed cytologically. Synthesis of the conjugation‐specific mRNAs was maximal just prior to maximum crescent stage (pachytene). Evidence is presented for transcription by the normally inactive micronucleus just prior to the maximum crescent stage, confirming an earlier report. The significance of these results is discussed.
Morphology of Giardia agilis: Observation by Scanning Electron Microscopy and Interference Reflexion Microscopy1
Authors: FEELY DENNIS E. , ERLANDSEN STANLEY L. 
Published: May 2007

ABSTRACTThe flagellated protozoan, Giardia agilis, was isolated from tadpole small intestine and examined by scanning electron microscopy and interference reflexion microscopy. The general morphology of the G. agilis trophozoite is similar to G. muris and G. duodenalis, but with modifications that reflect its elongated form. Interference reflexion microscopic analysis of attachment of G. agilis reveals a pattern of focal contacts by the lateral crest of the ventral disc, the ventrolateral flange, the lateral shield, and by numerous microvillus‐like appendages found along the lateral border of the trophozoite. The pattern of focal contacts was observed to be dynamic; trophozoites were observed to make and break the focal contacts in a relatively short time and to glide along the surface of the substratum without breaking focal contacts.
Ultrastructure of Cryptosporidium parvum Oocysts and Excysting Sporozoites as Revealed by High Resolution Scanning Electron Microscopy1
Authors: REDUKER DAVID W. , SPEER C. A. , BLIXT JOHN A. 
Published: May 2007

ABSTRACTCryptosporidium parvum oocysts isolated from calf feces were examined by scanning electron microscopy during excystation. Intact C. parvum oocysts were spheroid to ellipsoid, ≅3.5 × 4.0 μm, with length: width ratio = 1.17. The oocyst wall had a single suture at one pole, which spanned 1/3 to 1/2 the circumference of the oocyst. During excystation the suture dissolved, resulting in a slit‐like opening, which the sporozoites used to exit the oocyst. Sporozoites were 3.8 times 0.6 μm and had a rough outer surface.
Holospora elegans‐Infected Micronuclei of Paramecium caudatum Still Serve a Function During Vegetative Life1
Authors: MIKAMI KAZUYUKI , GÖRTZ HANS‐DIETER 
Published: May 2007

ABSTRACTThe fission rate of Paramecium caudatum cells infected with the micronucleus‐specific bacterium Holospora elegans was examined before and after elimination of the micronucleus. Uninfected cells, micronucleate and amicronucleate, were used as controls. Emicronucleation of Holospora elegans‐infected cells causes a decrease of fission rates, as is observed after emicronucleation of uninfected cells. This is taken as an argument that infected micronuclei still serve a function for the vegetative life of P. caudatum.
Inclusion Bodies in Xenosomes Purified on Percoll Gradients as Revealed by Electron Microscopy
Authors: SOLDO A. T. , BRICKSON S. A. , CASTIGLIONE G. A. 
Published: May 2007

ABSTRACTA method is described for the isolation and purification of xenosomes, intracytoplasmic bacterial symbionts of the marine hymenostome Parauronema acutum, using percoll gradients. Xenosomes isolated by this procedure retained both their ability to kill susceptible Uronema strains and to infect homologous and heterologous P. acutum strains. Unexpectedly, both killer and non‐killer xenosomes were found to contain inclusion bodies, heretofore unseen in fixed whole cell preparations, in the form of double helices, which we have termed H‐bodies. The nature and function of these bodies is unknown.
Structure and Operation of the Feeding Apparatus in a Colorless Euglenoid, Entosiphon sulcatum1
Authors: TRIEMER RICHARD E. , FRITZ LAWRENCE 
Published: May 2007

ABSTRACTEntosiphon sulcatum is a phagotrophic euglenoid. The tubular ingestion apparatus, called a siphon, is composed of three microtubular rods extending the length of the cell. Within the tube are four large striated vanes arranged much like the blades in a pinwheel. The vanes arise from the microtubular rods and curve towards the center of the feeding apparatus. Sheets of endoplasmic reticulum are positioned adjacent to each of the vanes and surround the perimeter of the apparatus. A cap, supported by a scaffold and anchored into the cytoplasm, covers the opening of the siphon. An elongate invagination of the plasma membrane is positioned adjacent to the edge of the cap and extends downward into the siphon forming the opening. The vanes converge at the anterior end of the siphon and surround the invagination. During feeding, the siphon protrudes from the cell. As the apparatus protrudes the cap is withdrawn to the side, opening the siphon. The vanes spread apart expanding the invagination of the plasma membrane into a large cavity into which ingested food particles are taken.
Transmission of Megatrypanum Trypanosomes to Cervus dama by Tabanidae1
Authors: BÖSE REINHARD , FRIEDHOFF KARL T. , OLBRICH SYLVIA 
Published: May 2007

ABSTRACTFour fallow deer, Cervus dama, became infected with Trypanosoma (Megatrypanum) sp. by oral application of triturated guts from tabanids collected in an area with deer but without any cattle; four control calves remained negative. Upon challenge with triturated guts from tabanids from an area with pastured cattle, the four calves became infected with Trypanosoma (M.) theileri. The prepatent period in deer was five days or less. Haematopota spp. and Tabanus spp. were identified as vectors of the deer trypanosomes. It is concluded that the trypanosomes of C. dama belong to a Megatrypanum species that is not identical with T. theileri.
Chemotaxis by Naegleria fowleri for Bacteria1
Authors: MARCIANO‐CABRAL FRANCINE , CLINE MICHAEL 
Published: May 2007

ABSTRACTNaegleria fowleri amebae demonstrated a chemotactic and chemokinetic response toward live cells and extracts of Escherichia coli and other bacterial species when experiments were performed using a blind‐well chemotaxis chamber. The peptide N‐formyl‐methionyl‐leucyl‐phenylalanine acted as a chemokinetic rather than a chemotactic factor for N. fowleri amebae. Competition experiments in which nerve cell extracts or bacteria were placed on either side of the filter in chemotaxis chambers resulted in increased movement towards bacteria. A scanning electron microscopy study of the interaction of N. fowleri with different bacterial species confirmed that when the amebae were near ingestible bacteria they moved toward the bacteria by pseudopod formation. Naegleria fowleri appeared to respond to bacteria by three interrelated but distinct processes: (a) chemokinesis, (b) chemotaxis, and (c) formation of food cups.
Rumen Ophryoscolecid Protozoa in the Hindgut of the Capybara (Hydrochoerus hydrochaeris)1
Authors: DEHORITY BURK A. 
Published: May 2007

ABSTRACTRumen ophryoscolecid protozoa were observed in feces obtained from two capybara (Hydrochoerus hydrochaeris) housed at the Columbus Zoo, Columbus, Ohio. Total numbers were 58.1 times 104 and 19.0 times 104 per gram of wet feces in a male and female capybara, respectively. Four common rumen species of Entodinium were observed in the feces from both animals, with low numbers of Eudiplodinium maggii and Elytroplastron bubali also occurring in the male. Establishment of rumen ophryoscolecid ciliates in the intestinal tract of non‐ruminant herbivores has not been reported previously.