Showing papers in "Journal of Eukaryotic Microbiology in 1987"
TL;DR: The uptake of various host plasma proteins by the bloodstream form of Trypanosoma brucei was studied both biochemically, using radiolabeled proteins, and with the electron microscope, using colloidal gold particles as molecular tracers onto which plasma proteins had been adsorbed.
Abstract: The uptake of various host plasma proteins by the bloodstream form of Trypanosoma brucei was studied both biochemically, using radiolabeled proteins, and with the electron microscope, using colloidal gold particles as molecular tracers onto which plasma proteins had been adsorbed. Total plasma proteins and serum albumin were taken up by a mechanism of fluid endocytosis with low clearance (0.1 microliter [mg cell protein]-1 h-1), while low-density lipoprotein (LDL) and transferrin were taken up by a receptor-mediated process with a clearance of two to three orders of magnitude higher than that of serum albumin. Binding prior to uptake of LDL and transferrin was saturable, depended on the presence of Ca2+, and the labeled ligand could be displaced by the homologous but not by heterologous protein. Binding of gold-labeled proteins was seen only to the membrane of the flagellar pocket and not elsewhere on the plasma membrane. After 1 h of incubation at 30 degrees C with gold-labeled LDL and transferrin, labeled cellular structures represented respectively half and one-third of the total volume of all single-membrane bounded endocytotic and electron-dense vacuoles within the cell.
216 citations
TL;DR: The cytoskeleton of Toxoplasma gondii was studied by electron microscopy using whole mounts of detergent-extracted parasites and thin sections of routine preparations, tannic acid-stained organisms, and Detergent-Extracted parasites to postulate that as the conoid moves, the polar ring complex moves along the spiral pathway of the conoids subunits.
Abstract: The cytoskeleton of Toxoplasma gondii was studied by electron microscopy using whole mounts of detergent-extracted parasites and thin sections of routine preparations, tannic acid-stained organisms, and detergent-extracted parasites. In whole mounts, the spiral arrangement of the 22 pellicular microtubules closely corresponded to the pattern of surface ridges seen previously by scanning electron microscopy and reflected the torsion of the parasite body during locomotion. The microtubules had free posterior ends and were anchored anteriorly in the polar ring, presumed to be a microtubule organizing center (MTOC). The insertions of the microtubules were supported by blunt projections of the polar ring, forming a cogwheel pattern in transverse view. The internal microtubules had 13 protofilaments and were twice the length of the conoid. They extended through the conoid and ended at the anterior preconoidal ring, presumably a second MTOC. The subunits of the conoid were arranged in a counterclockwise spiral when traced from base to tip, as were the pellicular microtubules. We postulate that as the conoid moves, the polar ring complex moves along the spiral pathway of the conoid subunits. Retraction of the conoid would then rotate the polar ring, producing the torsion of the body we observed by SEM.
178 citations
TL;DR: In vitro excystation of Cryptosporidium parvum from calves showed that sporozoite yields were optimum when oocysts were treated with sodium hypochlorite, then incubated at 37 degrees C for 60 min in the presence of taurocholic acid solutions at pH about 7.0.
Abstract: Studies of in vitro excystation of Cryptosporidium parvum from calves showed that sporozoite yields were optimum when oocysts were treated with sodium hypochlorite, then incubated at 37 degrees C for 60 min in the presence of taurocholic acid solutions at pH about 7.0. Trypsin was not required for excystation and high concentrations were inhibitory. Studies using protease inhibitors and direct assays for proteolysis failed to implicate proteolytic enzymes as effectors of excystation. The results suggest that Cryptosporidium uses excystation mechanisms that are different from those used by Eimeria spp.
60 citations
TL;DR: The distribution of reaction product suggests the vacuoles are lysosome-like; however, their function and development remain in question.
Abstract: Numerous membrane-bounded vacuoles are found adjacent to the plasma membrane of the pathogenic protozoan Giardia lamblia. The function of these vacuoles has been discussed by several authors. Approximately 100-400 nm in diameter with a core of low electron density, they have been suggested to be mitochondria, mucocysts, lysosomes, and endocytotic vacuoles. Enzyme cytochemical localization for acid phosphatase activity using cerium as a capturing agent demonstrates reaction product in these vacuoles as well as in the endoplasmic reticulum and nuclear envelope cisternae. The distribution of reaction product suggests the vacuoles are lysosome-like; however, their function and development remain in question.
57 citations
TL;DR: The internal pH (pHi) of Toxoplasma gondii was estimated by measuring the accumulation of the weak base 9-aminoacridine in buffers with various ionic compositions and Nigericin, which is known to collapse pH gradients across the membrane, abolished motility.
Abstract: The internal pH (pHi) of Toxoplasma gondii was estimated by measuring the accumulation of the weak base 9-aminoacridine in buffers with various ionic compositions. The pHi of the metabolizing parasite increased when the extracellular K+ was elevated in alkaline medium or when the external pH (pHc) was substantially increased in medium employing high external K+ (90 mM). The parasite in mouse peritoneal fluid, or in potassium sulfate buffer (pH 8.2), where the pHi was demonstrated to be increased to 7.9, became motile when acidic buffer was substituted for the original suspension medium. This acid-induced independent movement subsided within 5 min but was repeatedly induced if the pHc was serially lowered to 6.0. Basic buffers, on the other hand, abolished motility when applied to the moving parasites. Nigericin, which is known to collapse pH gradients across the membrane, also abolished motility.
51 citations
TL;DR: The possible role of micronuclear defects in somatic karyonidal senescence is discussed in light of the precise macronuclear chromosome copy controls demonstrated within the 81-MAC family.
Abstract: The 81-MAC family consists of three sizes of macronuclear chromosomes in Oxytricha fallax. Clones of these and of micronuclcar homologs have been classified according to DNA sequence into three highly homologous (95.9–97.9%), but distinct versions. Version A is represented by a micronuclear clone and by clones of two different-sized macronuclear chromosomes, showing that alternate processing of micronuclear DNA is responsible for the variety of sizes of macronuclcar chromosomes. Three Internal Eliminated Sequences (IES's) are demonstrated in Version A micronuclcar DNA. Two have been sequenced and show short, flanking direct repeats but no inverted terminal repeats. Version C micronuclear DNA has interruptions in the macronuclear homology which correspond closely to the Version A IES's. Whether they are true IES's is unknown because no Version C macronuclear DNA has been demonstrated. Version C micronuclear DNA may be “macronuclear-homologous” but “micronucleus-limited” and not “macronucleusdestined.” Version B is represented by macronuclear DNA clones, but no micronuclear clones. Vegetative micronuclear aneuploidy is suggested. The possible role of micronuclear defects in somatic karyonidai senescence is discussed in light of the precise macronuclear chromosome copy controls demonstrated within the 81-MAC family. These controls apparently operate throughout karyonidai life to mairitain 1) a constant absolute amount of 81-MAC sequences in the macronuclcus and 2) a constant sioichiometry within the family, both according to version and chromosome size.
50 citations
TL;DR: An intranuclear microsporidium is described from hemoblastic cells of the chinook salmon, Oncorhynchus tshawytscha, and the absence of mature spores and other life cycle stages precludes determination of its precise taxonomic identity.
Abstract: An intranuclear microsporidium is described from hemoblastic cells of the chinook salmon, Oncorhynchus tshawytscha. The infection is associated with an acute anemia in the fish. Up to 47% of the hemoblast nuclei were infected in anemic fish. The organisms, found only in spleen and kidney tissues, were 1-2 microns in diameter and consisted of vegetative and early sporulation forms. This microsporidium differs from known species which parasitize fish in its tissue location; however, the absence of mature spores and other life cycle stages precludes determination of its precise taxonomic identity.
45 citations
43 citations
TL;DR: Tetrahymena pyriformis ingested Escherichia coli for 15–20 min and the fine structure of food vacuoles was analyzed 5, 15, 30, 60, 90, 120, and 180 min after uptake began, finding that bacterial lysis may occur during acidification of the vacuole prior to fusion with lysosomes.
Abstract: Tetrahymena pyriformis ingested Escherichia coli for 15–20 min and the fine structure of food vacuoles was analyzed 5, 15, 30, 60, 90, 120, and 180 min after uptake began. From this analysis, eight vacuolar stages could be defined, and three to four stages were found in each sample. Stage 1 represents forming and newly detached vacuoles with a random distribution of bacteria. Stage 2 is the “dehydration” vacuole in which the bacteria are compacted and a few may lyse. Stage 3, corresponding to the acid phosphatase-positive stage, has an electron-dense vacuolar matrix revealing components of lysed bacteria and the translucent coat of intact bacteria. Stage 4 is the “halo” stage where centrally located, intact bacteria are surrounded by lysed material being removed by pinocytic activity of the vacuolar membrane. Stage 5 represents lysis of bacteria remaining intact until this stage; the stage is apparently followed by a second stage 4. Stage 6 contains few bacterial profiles in a smeared homogeneous mass. Stage 7 contains numerous vesicular membranous structures which apparently become transferred to the cytoplasm as such. Stage 8 represents defecation vacuoles derived from fusion of smaller vacuoles. The main findings are as follows: I) Bacterial lysis may occur during acidification of the vacuole prior to fusion with lysosomes. II) Digestion of bacteria apparently occurs in “bursts” as indicated by the extended time that vacuoles in stages 4 and 5 are present. III) Bacterial membranous structures seem to be transferred directly to the cytoplasm of Tetrahymena. IV) Mass defecation occurs 2 h after uptake begins.
42 citations
TL;DR: In the non-Mendelian mutants, macronuclei have a specific antigen gene deleted and also are impaired in their ability to direct normal DNA processing at the next conjugation or autogamy, showing that this system of macronuclear control is a fundamental feature of ciliate genetics.
Abstract: Several genes for surface antigens of the Paramecium aurelia complex of species have been isolated. In addition to known deletions of the 51A gene, we have obtained deletions involving the 51B gene and have developed a procedure for obtaining deletions of additional genes. Both Mendelian and non-Mendelian deletions of both the A and B genes have been found. In the non-Mendelian deletions the genes are present in the micronuclei and absent in the macronuclei. Processing of micronuclear DNA into new macronuclear DNA at conjugation and autogamy is under the control of the old macronucleus, and newly forming macronuclei become exactly like the old. Thus in the non-Mendelian mutants, macronuclei have a specific antigen gene deleted and also are impaired in their ability to direct normal DNA processing at the next conjugation or autogamy. These cases, along with others, show that this system of macronuclear control is a fundamental feature of ciliate genetics. The sequence of the 51A and 51C genes is described and compared with the 156G and 51H genes obtained by others. The 51A and 156G genes are remarkably similar while 51C and 51H are rather different. No introns or pseudogenes have been observed. Some, possibly all, of the genes are on the ends of chromosomes. Characteristic upstream and downstream sequences adjacent to the coding portions of the genes are given. The sequences UAA and UAG are preferred over CAA and CAG for glutamine while UGA is the true stop codon.
40 citations
TL;DR: Observations on the stomatogenesis of Coleps amphacanthus Ehrenberg show that this “gymno”-stome ciliate has a well developed oral ciliature made of 19–23 “paroral dikinetids” and three “adoral organelles,” which may lead to a revision of the systematic position of the genus Coleps.
Abstract: Light and electron microscopical observations on the stomatogenesis of Coleps amphacanthus Ehrenberg, 1833, show that this “gymno”-stome ciliate has a well developed oral ciliature made of 19–23 “paroral dikinetids” and three “adoral organelles.” These structures were previously known as “circumoral ciliature” and “dorsal brosse,” and it was thought that they originated from the distal ends of all the 22–26 somatic kineties. Contrary to this view, only four stomatogenic kineties (K1, Kn, Kn-1, and Kn-2) are involved in stomatogenesis of the opisthe. All paroral dikinetids arise from one single kinetofragment (KF1) to the right of the oral anlage while the adoral organelles originate from the three left kinetofragments (KFn, KFn-1, and KFn-2). In particular, the future paroral dikinetids perform a complex morphogenetic movement that leads to a situation where the postciliary microtubules of the once posterior kinetosome of each oral dikinetid give rise to the cytopharyngeal microtubular ribbons. The postciliary origin of the cytopharyngeal ribbons which could only be detected by an EM study of stomatogenesis shows that the basket of Coleps belongs to the cyrtos-type and not to the rhabdos-type basket, where transverse microtubules accompany the basket-forming nematodesmata. The taxonomic implications of these observations, which may lead to a revision of the systematic position of the genus Coleps, are discussed.
TL;DR: A new genus and species of microsporidia, Ovavesicula popilliae n.
Abstract: A new genus and species of microsporidia, Ovavesicula popilliae n. g., n. sp., is described from the Japanese beetle, Popillia japonica, on the basis of studies by light and electron microscopy. Parasite development primarily occurs within the Malpighian tubules of larvae, and spores are formed in a sporophorous vesicle. Meronts have diplokaryotic nuclei, develop in direct contact with the host cell cytoplasm, and divide by binary fission. Sporonts have unpaired nuclei, develop within a thick sporophorous vesicle, and undergo synchronous nuclear divisions producing plasmodia with 2, 4, 8, 16, and 32 nuclei. Cytokinesis of sporogonial plasmodia does not occur until karyokinesis is complete with 32 nuclei. Intact sporophorous vesicles are ovoid, containing numerous secretory products, and are surrounded by a persistent two-layered wall. The uninucleate spores are regularly formed in groups of 32, and the polar tube in each has six coils.
TL;DR: The Vertical distributions of two pond-dwelling zoochlorellae-bearing ciliates were monitored over a 24-h period and the O2 tension appears to be the principal factor controlling the vertical distributions of both species.
Abstract: 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 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.
TL;DR: The cyst wall of Paraurostyla weissei consists of four morphologically distinct layers and shows an ultrastructure and composition similar to that of the previously described kinetosome-resorbing cysts, and its cytoplasm displays characteristics of “urostylid-type” cysts.
Abstract: The cyst wall of Paraurostyla weissei consists of four morphologically distinct layers. It shows an ultrastructure and composition similar to that of the previously described kinetosome-resorbing cysts, and its cytoplasm displays characteristics of “urostylid-type” cysts. Therefore it is possible to consider it a “transition ciliate” between Stichotrichina and Sporadotrichina.
TL;DR: Entosiphon sulcatum is a phagotrophic euglenoid, a tubular ingestion apparatus composed of three microtubular rods extending the length of the cell and four large striated vanes arranged much like the blades in a pinwheel.
Abstract: Entosiphon 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.
TL;DR: A wide variety of derivatives of the biogenic amines had no effect on phagocytosis, demonstrating the specificity of recognition mechanism for neurohormones in Tetrahymena.
Abstract: Stimulation of phagocytosis by serotonin and catecholamines in Tetrahymena grown in proteose-peptone medium proved to be concentration dependent, the optimal concentrations being approximately 0.1 to 1.0 microM. The serotonergic antagonists, spiperone, and metergoline, also stimulated the process, whereas the beta- and alpha-adrenergic antagonists, propranolol, alprenolol, and ergocryptine, had no effect or inhibited phagocytosis. A wide variety of derivatives of the biogenic amines had no effect on phagocytosis, demonstrating the specificity of recognition mechanism for neurohormones in Tetrahymena. Such hormones act by at least two independent mechanisms, one for adrenergic agonists, another for dopamine. Presumably, recognition mechanisms for hormones in protozoa resemble in some respects those in multicellular organisms, therefore bespeaking a common origin.
TL;DR: The enzymic constitution of these flagellates is compared from a taxonomic standpoint to that of previously studied trypanosomatids.
Abstract: Trypanosomatids recently isolated from the plants Euphorbia pinea, E. characias, E. hyssopifolia, Manihoi esculenta (cassava) and Lycopersicon sp. (tomato) plus the McGhee-Postell isolate of Phytomonas davidi have been examined for the presence of enzymes of ornithine-arginine metabolism. Arginase (EC 3.5.3.1) was not detected in the flagellates examined whereas arginine deiminase (EC 3.5.3.6) and citrullinehydrolase (EC 3.5.1.20) were present in all organisms. Phytomonas davidi and the isolate from E. hyssopifolia, besides these enzymes, also had ornithine carbamoyltransferase (EC 2.1.3.3). The enzymic constitution of these flagellates is compared from a taxonomic standpoint to that of previously studied trypanosomatids.
TL;DR: Although the two rodent- Adapted stocks retained their pathogenicity for goats, neither the original stocks nor their corresponding rodent-adapted stocks could be cyclically transmitted by tsetse flies.
Abstract: Two Trypanosoma vivax stocks from East Africa have been adapted to rats and mice. Adaptation was induced by rapid passage at two- to four-day intervals in sublethally irradiated rats. After 200 such passages, the two stocks gave rise to parasitemias of 10(9)-10(10) trypanosomes/ml in peripheral blood, and the infection was fatal in 90% of the rats. By passaging the rat-adapted T. vivax into normal mice at two- to three-day intervals for over 200 passages, the two stocks also became pathogenic to mice. One of the stocks was also capable of maintenance in non-irradiated rats. The two stocks displayed a marked degree of pleomorphism in irradiated and non-irradiated rats and mice. In the early rising parasitemia, the organisms were predominantly short, with a well formed undulating membrane, a pointed posterior end, and a large terminal kinetoplast. As parasitemia approached its peak, the organisms transformed into long, slender forms with an inconspicuous undulating membrane, an elongated posterior end, and a sub-terminal kinetoplast. The short forms associated with the early, rising parasitemia were more infective for mice than the long forms encountered at peak parasitemia. Although the two rodent-adapted stocks retained their pathogenicity for goats, neither the original stocks nor their corresponding rodent-adapted stocks could be cyclically transmitted by tsetse flies. The availability of these stocks will greatly facilitate investigations on East African T. vivax which would otherwise be difficult to carry out in experimental rodents.
TL;DR: In the water column, FLA populations were highest in a persistent detrital layer; however, few amoebae were isolated from a massive layer of Oscillatoria, and the only N. fowleri isolated in this study was from the detritAL layer.
Abstract: A quantitative study of the seasonal distribution of thermotolerant (37 degrees C and 45 degrees C), small free-living amoebae (FLA) was conducted in Lake Issaqueena, a warm, monomictic lake with steep, sloping banks and a maximum basin depth of 10 m in the Piedmont region of South Carolina. Naegleria and Vahlkampfia were the most frequently encountered FLA in littoral sediment and surface water samples whereas Acanthamoeba was most commonly isolated from profundal sediment, especially during late summer. In the water column, FLA populations were highest in a persistent detrital layer; however, few amoebae were isolated from a massive (approximately 1.5 m thick) layer of Oscillatoria. The only N. fowleri isolated in this study was from the detrital layer. Discussion of the influence of differences in watershed and basin morphology on variations in the size and generic composition of FLA populations for the aquatic ecosystems of Lake Issaqueena and Willard's Pond is included.
TL;DR: The nonphysiological conditions used for DEAE chromatography of the parasites result in changes in the ATP levels of the trypanosomes and an enhanced release from the parasites of proteins such as variable surface glycoprotein, peptidase, and phospholipase.
Abstract: Bloodstream forms of African trypanosomes are routinely purified from blood components by a combination of centrifugation and chromatography on DEAE cellulose at pH 80 Here we report that the nonphysiological conditions used for DEAE chromatography of the parasites result in changes in the ATP levels of the trypanosomes and an enhanced release from the parasites of proteins such as variable surface glycoprotein, peptidase, and phospholipase Some of these changes can be reduced by the addition of nucleosides to the elution buffer and, after the elution of the parasites, by immediate readjustment of the external pH to the normal physiological level of blood (pH 74)
TL;DR: Two new species of coccidia (Apicomplexa: Eimeriidae) are described from the Madagascar giant day gecko, Phelsuma madagascariensis grandis, and the Golddust day geko, P. laticauda, found to infect the anterior one-half of the small intestine.
Abstract: Two new species of coccidia (Apicomplexa: Eimeriidae) are described from the Madagascar giant day gecko, Phelsuma madagascariensis grandis, and the Golddust day gecko, P. laticauda. Both species of coccidia were found to infect the anterior one-half of the small intestine. Oocysts of Eimeria brygooi n. sp. are spherical or subspherical, 23.0 × 21.3 (18.8–25.2 × 16.4–23.2) μm; shape index (L/W) 1.1 (1.0–1.2). A micropyle, oocyst residuum, and polar granule are absent. Sporocysts are ovoid, 9.2 × 7.9 (8.0–10.0 × 7.2–8.8) μm; shape index 1.2 (1.0–1.3), with a Goussia-type suture; Stieda and substieda bodies are absent. A sporocyst residuum is present, 4.2 × 3.0 (3.2–6.4 × 2.4–4.0) μm. Sporozoites are elongate, with anterior and posterior refractile bodies. This coccidian was found to infect five of six (83%) P. m. grandis and one of five (20%) P. laticauda examined. Oocysts of Isospora gekkonis n. sp. are spherical or subspherical, 24.2 × 22.0 (21.6–26.4 × 20.0–23.6) μm; shape index 1.1 (1.0–1.2). A micropyle and oocyst residuum are absent; polar granule present. Sporocysts are ovoid, 12.2 × 9.4 (11.2–12.8 × 8.4–10.0) μm, with Stieda and substieda bodies; shape index 1.3 (1.2–1.4). A sporocyst residuum is present, cither compact, 5.1 × 4.2 (4.0–7.2 × 3.2–5.6) μm or diffuse. Sporozoites arc elongate, with anterior and posterior refractile bodies. Isospora gekkonis was found in two of six (33%) P. m. grandis and one of five (20%) P. laticauda. In addition, oocysts of Cryptosporidium sp. were found in the cloacas of two of six (33%) necropsied P. m. grandis.
TL;DR: The time required for recovery increased markedly with the duration of the preceding heat treatment, up to about 70 h for a 12-hHeat treatment of Leishmania braziliensis panamensis promastigotes.
Abstract: Raising the temperature of a log-phase culture of Leishmania braziliensis panamensis promastigotes from 26 degrees C to 34 degrees C resulted in formation of a culture containing 85% ellipsoidally shaped forms after 1.5 h. The temperature-induced ellipsoidal forms decreased in size but persisted in high proportion (85-95%) for at least 12 h at 34 degrees C. Recovery from the ellipsoidal forms to a culture containing 85-95% promastigotes was observed after returning the temperature to 26 degrees C. The time required for recovery increased markedly with the duration of the preceding heat treatment, up to about 70 h for a 12-h heat treatment.
TL;DR: Flow cytometry was used to analyze the population dynamics of Trypanosoma cruzi clone mixtures and found that there is no dynamic equilibrium with coexistence of clones with different growth rates; under all culture protocols, the faster growing clone will prevail.
Abstract: Utilizing the previously reported inter-clonal differences in total DNA/organism, flow cytometry was used to analyze the population dynamics of Trypanosoma cruzi clone mixtures growing in liquid medium or vertebrate cells. The growth of clone mixtures in liquid medium can be described by unique parameters reflecting exponential growth rate (r), stationary phase population density (1/k), and the interaction between the clones (h). The relative numbers of each clone in the population change rapidly with time and the results arc in quantitative agreement with mathematical models of competitive population growth. The relationship between the parameters for T. cruzi is such that, in general, there is no dynamic equilibrium with coexistence of clones with different growth rates; under all culture protocols, the faster growing clone will prevail. A computer simulation of the vertebrate cell cycle of T. cruzi suggests that clone mixtures grow relatively independently; the basic attributes of the model were substantiated experimentally. Although wide fluctuations in the proportion of each clone released occurred, the faster growing clone again predominated. Finally, these results underline the importance of working with well-defined clones in the laboratory to avoid inconsistencies and paradoxical results and stress the importance of the rapid isolation of single cell clones from clinical specimens when studying the relationship of the parasite to human disease.
TL;DR: Five polyamines which could be separated by high performance liquid chromatography were found in Acanthamoeba castellanii (strain Neff) and a scheme for polyamine biosynthesis in A. castellaniai is proposed.
Abstract: Five polyamines which could be separated by high performance liquid chromatography were found in Acanthamoeba castellanii (strain Neff). These included in order of decreasing abundance: 1,3-diaminopropane, spermidine, spermine, norspermidine, and putrescine. Only diaminopropane and norspermidine had been found previously. Spermine was present in cultures grown in broth, but not in defined medium. Radioactive substrates were used to establish that putrescine was synthesized by decarboxylation of ornithine, ornithine was synthesized from arginine or citrulline, and diaminopropane was synthesized from spermidine. The presence of ornithine decarboxylase (EC 4.1.1.17), arginase (EC 3.5.3.1), and urease (EC 3.5.1.5) and the absence of arginine decarboxylase (EC 4.1.1.19) were established. A scheme for polyamine biosynthesis in A. castellanii is proposed.
TL;DR: Establishment of rumen ophryoscolecid ciliates in the intestinal tract of non-ruminant herbivores has not been reported previously.
Abstract: Rumen ophryoscolecid protozoa were observed in feces obtained from two capybara (Hydrochoerus hydrochaeris) housed at the Columbus Zoo, Columbus, Ohio. Total numbers were 58.1 X 10(4) and 19.0 X 10(4) 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.
TL;DR: Morphological evidence is presented suggesting that proteins are transported between the erythrocyte surface and intracellular parasites via two routes: one associated with Maurer's clefts for transport of membrane-associated knob material and a second associated with caveolae in the host cell membrane for the import or export of host- or parasite-derived substances through the ersatz cytoplasm.
Abstract: This report describes the fine structure of the erythrocytic stages of Plasmodium malariae. Erythrocytic parasites from a naturally acquired human infection and an experimentally infected chimpanzee were morphologically indistinguishable and structurally similar to other primate malarias. New findings included observations of highly structured arrays of merozoite surface coat proteins in the cytoplasm of early schizonts and on the surface of budding merozoites and the presence of knobs in the membranes of Maurer's clefts. Morphological evidence is presented suggesting that proteins are transported between the erythrocyte surface and intracellular parasites via two routes: one associated with Maurer's clefts for transport of membrane-associated knob material and a second associated with caveolae in the host cell membrane for the import or export of host- or parasite-derived substances through the erythrocyte cytoplasm.
TL;DR: Results indicated that these compounds were metabolized via a functioning tricarboxylic acid cycle and that most of the label that entered the tricARboxy Lic acid cycle was oxidized to carbon dioxide.
Abstract: The metabolism of [1-14C]- and [6-14C]glucose, [1-14]ribose, [1-14C]- and [U-14C]alanine, and [1-14C]- and [5-14C]glutamate by the promastigotes of Leishmania braziliensis panamensis was investigated in cells resuspended in Hanks' balanced salt solution supplemented with ribose, alanine, or glutamate. The ratio of 14CO2 produced from [1-14C]glucose to that from [6-14C]glucose ranged from about two to six, indicating appreciable carbon flow through the pentose phosphate pathway. A functional pentose phosphate pathway was further demonstrated by the production of 14CO2 from [1-14C]ribose although the rate of ribose oxidation was much lower than the rate of glucose oxidation. The rate of 14CO2 production from [1-14C]glucose was almost linear with time of incubation, whereas that of [6-14C]glucose accelerated, consistent with an increasing rate of flux through the Embden-Meyerhof pathway during incubation. Increasing the assay temperature from 26°C to 34°C had no appreciable effect on the rates or time courses of oxidation of either [1-14C]- or [6-14C]glucose or of [1-14C]ribose. Both alanine and glutamate were oxidized by L. b. panamensis, and at rates comparable to or appreciably greater than the rate of oxidation of glucose. The ratios of 14CO2 produced from [1-14C]- to [U-14C]alanine and from [1-14C]- to [5-14C]glutamate indicated that these compounds were metabolized via a functioning tricarboxylic acid cycle and that most of the label that entered the tricarboxylic acid cycle was oxidized to carbon dioxide. Heating the cultures for 6 or 12 h at 34°C, which converts the promastigotes into an ellipsoidally shaped intermediate form, decreased the rates of oxidation of glucose, alanine, and glutamate. The oxidation of glutamate decreased by about 50% and 70% after a 6-h or 12-h heat treatment, respectively. Returning the heated cultures to 26°C initiated a reversion to the promastigote form and recovery of the rate of glucose oxidation, but glutamate oxidation did not return to control levels by 19 h at 26°C.
TL;DR: Changes in parasite and epithelium observed in induced exit were similar to those in spontaneous departure after five days residence, suggesting an active role for the parasite in exit.
Abstract: The first change in the sequence of morphological events occurring as fully developed Ichthyophthirius multifiliis trophonts spontaneously left gill epithelium or as younger trophonts departed, following experimentally induced death of the fish, was the separation of parasites from overlying host cells. Discharge of contractile vacuoles may have played a role in this process. Spaces then appeared between host cells, and individual epithelial cells became vacuolated. Finally, the epithelium ruptured and the parasites swam free. In induced exit after three days residence in the host, departure of the trophont was evident only after autolysis of epithelium had occurred. Induced departure of trophonts after four days residence was more rapid, suggesting an active role for the parasite in exit. Changes in parasite and epithelium observed in induced exit were similar to those in spontaneous departure after five days residence.
TL;DR: The morphology and the morphogenesis of the freshwater hypotrich ciliate Onychodromus quadricornutus n.
Abstract: The morphology and the morphogenesis of the freshwater hypotrich ciliate Onychodromus quadricornutus n. sp. have been investigated using living organisms, protargol impregnation, and scanning electron microscopy. Some preliminary and supplementary results about the morphogenesis of O. grandis and Laurentiella acuminata are included. The new species is unique among all described hypotrichs in having four dorsal horns, whose function is unknown. In addition, O. quadricornutus is probably the most voluminous hypotrich ciliate known (2 times 10-6-5 times 106μm3). Its morphogenetic pattern resembles the oxytrichids O. grandis and L. acuminata. The strongest apomorphic character, which unites these three species, is probably the multiple fragmentation of the dorsal primordia during morphogenesis. This fragmentation causes the characteristic high number and more or less irregular distribution of the dorsal kineties in the non-dividing individuals.