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PubMed2000

Stylocephalus occidentalis n. sp. (Apicomplexa: Eugregarinida: Stylocephalidae) from Trimytis pruinosa (Coleoptera: Tenebrionidae) in the Nebraska Sandhills.

Stylocephalus occidentalis n. sp. (Apicomplexa: Eugregarinida) is described from Trimytis pruinosa (Coleoptera: Tenebrionidae) collected from Keith County in the Sandhills of western Nebraska. Measurements are means in micrometers. Developing trophozoites solitary; epimerite a complex of terminal epimerite and intercalating diamerite; epimerite shallowly ovoid to transversely elliptoid, with transverse basal constriction at junction with diamerite, length 0.5-1 times width, approximately 3-4 times that of diamerite; width approximately equal to that of diamerite; diamerite roughly cylindrical to spindle-shaped, without significant anterior taper, little or no evidence of longitudinal folds, length approximately twice width. Association late, frontal, isogamontic. Gamont protomerite depressed ovoid to very broadly ovoid, length 27.3, width 35.1, anterior distance to widest point 15.4. Protomerite-deutomerite septum clearly marked and constricted, width 34.6. Deutomerite often with distinct marginal crenulation, narrowly obovoid to very narrowly obovoid, length 356.5, maximum width 57.6, anterior distance to widest point 26.3, equatorial width 35.1, +/-12.5, 29. Total length 381.5. Nucleus ellipsoid, length 32.5, width 18.8; with 0 or 2 polysomal endosomes. Gametocysts roughly spherical; diameter 205.0; wall desiccating to become paper-like, slightly papillated, dehiscing by simple rupture, releasing oocysts in coiled chains, epispore packet absent, gametocyst residuum present. Oocysts dark brown to black, axially asymmetric, broadly deltoid, gibbous in lateral aspect, slightly keeled in dorsal aspect; length 9.8, height 7.9; with slight terminal protuberances and 2 central, spherical residua.

Animals↗
PubMed2000

Two new Aggregata species (Apicomplexa: Aggregatidae) infecting Octopus tehuelchus and Enteroctopus megalocyathus (Mollusca: Octopodidae) in Patagonia, Argentina.

During a long-term study carried out between 1981 and 1996 on the biological and fishery aspects of octopuses inhabiting the Gulfs of San Matías, San José, and Nuevo, Patagonia, Argentina, 2 new species of Aggregata (Apicomplexa: Aggregatidae) were found in the digestive tracts of Octopus tehuelchus d'Orbigny, 1834 (prevalence 72%) and Enteroctopus megalocyathus (Gould, 1852) (prevalence 77%). Both species can be distinguished from other congeners on the basis of their hosts, the diameters of sporocysts, and number and length of sporozoites. Despite overlap in the distributions of the two hosts species in the area covered in this study, both Aggregata new species exhibited high host specificity.

Animals↗
PubMed2001

The response of Gregarina niphandrodes (Apicomplexa: Eugregarinida: Septatina) to host starvation in Tenebrio molitor (Coleoptera: Tenebrionidae) adults.

Numerous studies of host starvation have emphasized pathological effects of parasites on their insect host, but little attention has been focused on the effects of host starvation on the parasites. This study addressed the possibility that parasite life-cycle events could be manipulated by withholding food from the host. The system used was Gregarina niphandrodes (Apicomplexa: Eugregarinida) in Tenebrio molitor (Coleoptera: Tenebrionidae) adults. Gregarine gametocyst formation and shedding ceased after 1 day in starved beetles but continued in fed controls. There were no statistically significant differences between total lengths of associated (3 of 5 trials) or unassociated (5 of 5 trials) gregarines found between experimental and control groups, but average numbers of the 2 life cycle events were generally higher in fed hosts than in starved ones. If infected, fed control beetles continued to form gametocysts throughout the 7-day trial periods, and gametocysts could be observed in the gut. Starved experimental beetles had no gametocysts in their guts. Refeeding of starved beetles after 4 days resulted in resumption of gametocyst formation and shedding. The studies demonstrated that the gregarine life cycle could be stopped and then started at the gametocyst formation stage like an off/on switch, simply by withholding food from, then refeeding, the host.

Analysis of Variance↗
PubMed2003

Biosynthetic pathways of plastid-derived organelles as potential drug targets against parasitic apicomplexa.

Apicomplexan parasites are a large phylum of unicellular and obligate intracellular organisms of great medical importance. They include the human pathogens Plasmodium spp., the causative agent of malaria, and Toxoplasma gondii, an opportunistic parasite of immunosuppressed individuals and a common cause of congenital disease, together affecting several hundred million people worldwide. The search for new and effective drugs against these pathogens has been boosted during the last years by an unexpected finding. Through molecular and cell biological analysis it was realized that probably most members of this phylum harbor a plastid-like organelle, called the apicoplast, which probably is derived from the engulfment of a red alga in ancient times. Although the apicoplast itself contains a small circular genome, most of the proteome of this organelle is encoded in the nuclear genome, and the proteins are subsequently transported to the apicoplast. It is assumed to contain a number of unique metabolic pathways not found in the vertebrate host, making it an ideal "playground" for those interested in drug targets. Recent reports have shown that the rationale of this approach is valid and that new drugs which are urgently needed especially for plasmodial infections, might be developed in the near future based on these targets. Amongst them are three enzymes of the plant-like fatty acid synthesis machinery and enzymes of the non-mevalonat isoprenoid biosynthesis pathway. From their presence in the apicoplast it can be concluded that fatty acid and lipid biosynthesis seems to be a major function of the apicoplast. Another recently described apicoplast enzyme, ferredoxin-NADP(+)-reductase and its redox partner, ferredoxin, points to another interesting organelle-specific biosynthetic pathway, namely [Fe-S] cluster biosynthesis. In the present review, the fundamental aspects of the apicoplast as drug target will be described, together with the specific pathways and their currently known inhibitors. Furthermore, based on the recent findings potentially new targets will be discussed. A short overview of the presently available high-throughput methods for Apicomplexa to evaluate the potency of new inhibitory substances will also be given.

Animals↗
PubMed1992

The red-tailed hawk, Buteo jamaicensis, a native definitive host of Frenkelia microti (Apicomplexa) in North America.

Oral inoculation of prairie voles, Microtus ochrogaster, with coccidian sporocysts isolated from the feces of a red-tailed hawk, Buteo jamaicensis, in Kansas, USA, resulted in formation of Frenkelia microti (Apicomplexa: Sarcocystidae) tissue cysts in the brains of the voles. Five additional isolates of morphologically similar sporocysts collected from red-tailed hawks or other Buteo spp. in Kansas failed to result in detectable infections in rodents. These results are the first to verify that red-tailed hawks are natural definitive host in North America for F. microti.

Animals↗
PubMed1999

Revision of the genus Xiphocephalus and description of Xiphocephalus ellisi n. sp. (Apicomplexa: Eugregarinida: Stylocephalidae) from Eleodes opacus (Coleoptera: Tenebrionidae) in the western Nebraska Sandhills.

Xiphocephalus is revised, clarifying diagnosis of the epimerite complex, gametocyst, and oocyst. Xiphocephalus ellisi n. sp. (Apicomplexa: Eugregarinida) is described from Eleodes opacus (Coleoptera: Tenebrionidae) collected from Keith County in the Sandhills of western Nebraska. Measurements are means in micrometers. Developing trophozoites solitary; epimerite a complex of terminal epimerite and intercalating diamerite: epimerite elongate, ensiform, with transverse basal tumidus, length 2-3 times width of basal tumidus; width approximately half that of basal tumidus; tumidus toroidal, concavoconcave in anterioposterior axis: diamerite roughly cylindrical, no longitudinal fold apparent, length approximately twice width. Association late, frontal, isogamontic. Protomerite depressed ovoid, length 84.1, width 114.9, anterior distance to widest point 50.8. Protomerite-deutomerite septum clearly marked and constricted, width 99.3. Deutomerite narrowly obovoid, length 1,094.0, maximum width 197.0, anterior distance to widest point 137.8, equatorial width 163.3. Total length 1,204.4. Nucleus ellipsoid, length 64.9, width 42.2; typically with 2-3 polysomal endosomes. Gametocysts roughly spherical, length 376.1, width 348.2, wall paperlike, papillated, dehiscing by simple rupture, releasing oocysts in coiled chains, epispore packet absent, gametocyst residuum present. Oocysts brown to black, broadly deltoid, gibbous in lateral aspect, slightly keeled in dorsal aspect, length 9.7, height 8.5; with terminal protuberances and a single, central, spherical residuum.

Animals↗
PubMed2006

Ditrypanocystis sp. (Apicomplexa, Gregarinia, Selenidiidae): the mode of survival in the gut of Enchytraeus albidus (Annelida, Oligochaeta, Enchytraeidae) is close to that of the coccidian genus Cryptosporidium.

A selenid gregarine Ditrypanocystis sp. (Apicomplexa, Gregarinia, Selenidiidae), harboring the gut lumen of the oligochaete Enchytraeus albidus, was studied by light and electron microscopy. The trophozoite of Ditrypanocystis sp. is attached to the gut wall with its apical end to be anchored eventually between enterocytes in the crypts. Simultaneously, between the surfaces of the parasite and the host cell a peculiar contact is formed made of membranous channels and vesicles of unknown origin, the host cell surface in the contact area lacking cilia. The trophozoite becomes progressively enclosed within a parasitophorous vacuole made of layers of fused ciliar membranes of enterocytes. The fused cilia may be a source of membranes lining channels and vesicles of the contact area. Such a mode of parasitophorous arrangements has never been described before for gregarines, however, it bears a some likeness with that of the coccidian genus Cryptosporidium (similarity and differences being discussed). With regard to some molecular phylogeny constructions, claiming the "sister" relationship between gregarines and the coccidian genus Cryptosporidium (Carreno et al., 1999; Leander et al., 2003), this common feature in host-parasite relationships enabled us to put forward an idea of a possible evolutionary route from extracellularity of gregarines to intracellularity of coccidia, as exemplified by species of Cryptosporidium.

Animals↗
PubMed1980

Ultrastructural demonstration of succinic dehydrogenase and cytochrome oxidase activity in sporozoites of Babesia ovis and Theileria annulata (Apicomplexa: Piroplasmea) in salivary glands of tick vectors (Rhipicephalus bursa, Hyalomma anatolicum excavatum).

Salivary gland stages ("sporozoites") of Babesia ovis and Theileria annulata (Apicomplexa: Piroplasmea) in female ixodid ticks were studied for ultracytochemical activity of the respiratory enzymes, succinic dehydrogenase (SDH), and cytochrome oxidase. Both SDH and cytochrome oxidase were demonstrated in the sporozoites and the mitochondria in these stages. Identified in this way the final reaction product of SDH was located mainly at the inner side of the mitochondrial boundary, though it was also visible in the internal space of the organelle. Cytochrome oxidase activity always was confined to the wall of mitochondria. This enzyme was demonstrated also in the erythrocyte stage of B. ovis. The cytochemical results indicate respiratory potential of the piroplasmean stages studied. Cristate or typical protozoan mitochondria have not been observed in sporozoites of Babesia or Theileria. This report is the first demonstration of mitochondria, or mitochondrialike activity in Babesia.

Animals↗
PubMed1995

Domadracunculus janovyi n. gen., n. sp. (Apicomplexa: Actinocephalidae) from adults of Ischnura verticalis (Odonata: Zygoptera) in Texas.

Domadracunculus janovyi n gen., n. sp. (Apicomplexa: Actinocephalidae) is described from trophozoites, gamonts, and oocysts collected from adult Ischnura verticalis (Odonata: Zygoptera) in Brazos County, Texas. Oocysts of the new species are axially asymmetric, smooth, and crescentic, features that unite the taxon with the Menosporinae. The new genus is distinguished from existing menosporid genera by an epimerite in the form of a distinctly pleated cup or sucker, without the anterior digitations of Hoplorhynchus or the crown of hooks diagnostic of Menospora.

Animals↗
PubMed1998

Revision of the genus Torogregarina and description of Torogregarina sphinx n. sp. (Apicomplexa: Eugregarinida) from a Missouri river bank beetle, Bembidion laevigatum (Coleoptera: Carabidae), in southeastern Nebraska.

Torogregarina is revised to clarify the nature of the epimerite-protomerite complex and the method of gametocyst dehiscence, removed from the family Gregarinidae, and placed among the Hirmocystidae. Torogregarina sphinx n. sp. (Apicomplexa: Eugregarinida) is described from Bembidion laevigatum (Coleoptera: Carabidae) collected along the Missouri River near Peru, Nemaha County, Nebraska. Measurements are means in micrometers. Association is precocious and caudofrontal. Primite epimerite depressed ovoid and persistent through syzygy; length 25.2, width 41.0. Protomerite a high toroid collar between epimerite and deutomerite; length 13.5, width 35.4. Deutomerite obovoid; length 137.3, width 90.7. Total length including epimerite 172.2. Satellite epimerite protomerite complex concentrically formed by a depressed ovoid epimerite within a transversely oblong protomerite, the protruding dome of the epimerite fitting into a posterior depression on the primite and the transverse anterior margin of the protomerite mating with the posterior margin of the primite to form the syzygial junction; length 25.0, width 48.8. Deutomerite obovoid; length 113.5, width 63.5. Total length 138.6. Gametocysts roughly spherical; diameter 142.9. Gametocysts mature and dehisce by simple rupture, extruding oocysts in a single mass without an epispore packet. Oocysts axially symmetric, dolioform in dorsal aspect, concavoconcave in transverse plane, uniform in size and shape; length 5.2, terminal width 2.4, equatorial width 3.1.

Animals↗
PubMed2005

Multi-membrane-bound structures of Apicomplexa: I. the architecture of the Toxoplasma gondii apicoplast.

Apicomplexan parasites carry a plastid-like organelle termed apicoplast. The previous documentation of four membranes bordering the Toxoplasma gondii apicoplast suggested a secondary endosymbiotic ancestry of this organelle. However, a four-membraned apicoplast wall could not be confirmed for all Apicomplexa including the malarial agents. The latter reportedly possesses a mostly tri-laminar plastid wall but also displays two multi-laminar wall partitions. Since these sectors apparently evolved from regional wall membrane infoldings, the malarial plastid could have lost one secondary wall membrane in the course of evolution. Such wall construction was however not unambiguously resolved. To examine whether the wall of the T. gondii apicoplast is comparably complex, serial ultra-thin sections of tachyzoites were analyzed. This investigation revealed a single pocket-like invagination within a four-laminar wall segment but also disclosed that four individual membranes do not surround the entire T. gondii apicoplast. Instead, this organelle possesses an extensive sector that is bordered by two membranes. Such heterogeneous wall construction could be explained if the inner two membranes of a formerly four-membraned endosymbiont are partially lost. However, our findings are more consistent with an essentially dual-membraned organelle that creates four-laminar wall sectors by expansive infoldings of its interior border. Given this architecture, the T. gondii apicoplast depicts a residual primary plastid not a secondary one as presently proposed.

Animals↗
PubMed1998

Amplification of genomic DNA fragments of Sarcocystis muris (Apicomplexa) cyst merozoites encoding a thiol (cysteine) proteinase.

Parasites of the phylum Apicomplexa (Sporozoa) cause diseases such as malaria, toxoplasmosis, or intestinal coccidiosis. Invasive stages possess typical apical organelles such as dense granules that harbor a broad range of polypeptides that are believed to take part in the parasite-host cell interaction. In previous studies a 26-kDa polypeptide of dense granules from Sarcocystis muris cyst merozoites (bradyzoites) was characterized as a thiol (cysteine) proteinase. In this paper a method is demonstrated to amplify DNA fragments from genomic DNA of S. muris cyst merozoites by polymerase chain reaction, which probably code for the 26-kDa antigen.

Amino Acid Sequence↗
PubMed1987

Rapid nucleotide sequence analysis of the small subunit ribosomal RNA of Toxoplasma gondii: evolutionary implications for the Apicomplexa.

A method for obtaining a large proportion of the nucleotide sequence of the small subunit ribosomal RNA (srRNA) was applied to the obligate intracellular protozoon Toxoplasma gondii. The method uses reverse transcription of as little as 8 micrograms of total cellular RNA. This fast, efficient method has numerous advantages over traditional gene cloning methods when nucleotide sequences are required for evolutionary studies. A phylogenetic analysis of the srRNA sequence data showed that T. gondii is not especially closely related to any other organism for which srRNA sequences are available, including another member of the Apicomplexa.

Animals↗
PubMed1996

Rhoptry organelles of the apicomplexa: Their role in host cell invasion and intracellular survival.

Members of the phylum Apicomplexa are obligate intracellular parasites that invade erythrocytes, lymphocytes, macrophages or cells of the alimentary canal in various vertebrate species. Organelles within the apical complex of invasive stages facilitate host cell invasion. Parasites in this phylum cause some of the most debilitating diseases of medical and veterinary importance. These include malaria, toxoplasmosis, babesiosis, theileriosis (East Coast fever), and coccidiosis in poultry and livestock. In recent years, opportunistic infections caused by Cryptosporidium parvum, and recrudescent Toxoplasma gondii infections in AIDS patients have prompted intensified efforts in understanding the biology of these parasites. In this review, Tobili Sam-Yellowe examines the unifying and variant molecular features of rhoptry proteins, and addresses the role of multigene families in organelle function: the biogenesis of the rhoptries will also be examined, in an attempt to understand the sequence of events leading to successful packaging, modification and processing of proteins within the organelle.

Journal Article↗
PubMed1991

The troublesome parasites--molecular and morphological evidence that Apicomplexa belong to the dinoflagellate-ciliate clade.

Large insertions and deletions in the variable regions of eukaryotic 16S-like rRNA relative to the archaebacterial structure have been defined as a marker for rapidly evolving taxa. Deletions in the rRNA occur in the diplomonad Giardia and the microsporidian Vairimorpha, whereas insertions occur in Euglenozoa (Euglena and the kinetoplastids), Acanthamoeba, Naegleria, Physarum, Dictyostelium, the apicomplexan Plasmodium, the ciliate Euplotes, and some metazoa. Except Acanthamoeba and Euplotes, all of these protists were previously placed at the base of the eukaryote phylogeny. A re-analysis of the 16S-like rRNA and 5S rRNA data with the neighborliness method revealed a close relationship of Apicomplexa to the dinoflagellate-ciliate clade, most probably closer to the dinoflagellates. Morphological evidence that supports this grouping is the layer of sacs underneath the plasma membrane in all three taxa and the identical structure of trichocysts in the apicomplexan Spiromonas and dinoflagellates. The remaining rapidly evolving organisms might still be misplaced in the 16S-like rRNA trees.

Animals↗
PubMed2005

Insights into unique physiological features of neutral lipids in Apicomplexa: from storage to potential mediation in parasite metabolic activities.

The fast intracellular multiplication of apicomplexan parasites including Toxoplasma and Plasmodium, requires large amounts of lipids necessary for the membrane biogenesis of new progenies. Hence, the study of lipids is fundamental in order to understand the biology and pathogenesis of these deadly organisms. Much has been reported on the importance of polar lipids, e.g. phospholipids in Plasmodium. Comparatively, little attention has been paid to the metabolism of neutral lipids, including sterols, steryl esters and acylglycerols. In eukaryotic cells, free sterols are membrane components whereas steryl esters and acylglycerols are stored in cytosolic lipid inclusions. The first part of this review describes the recent advances in neutral lipid synthesis and storage in Toxoplasma and Plasmodium. New potential pharmacological targets in the pathways producing neutral lipids are outlined. In addition to lipid bodies, Apicomplexa contain unique secretory organelles involved in parasite invasion named rhoptries. These compartments appear to sequester most of the cholesterol found in the exocytic pathway. The second part of the review focuses on rhoptry cholesterol and its potential roles in the biogenesis, structural organisation and function of these unique organelles among eukaryotes.

Acyltransferases↗
PubMed2004

Fluorescent protein tagging in Toxoplasma gondii: identification of a novel inner membrane complex component conserved among Apicomplexa.

Toxoplasma gondii is an obligate intracellular parasite, and its sub-cellular organization shows clear adaptations to this life-style. In addition to organelles shared among all eukaryotes, the organism possesses a number of specialized compartments with important roles in host cell invasion and intra-cellular survival. These unique aspects of the parasite's biology are also reflected in its genome. The ongoing genome sequencing efforts for T. gondii and related apicomplexans predict a high proportion of genes unique to the phylum, which lack homologs in other model organisms. Knowing the sub-cellular localization of these gene products will be an important first step towards their functional characterization. We used a library approach wherein parasite genomic DNA was fused to the yellow fluorescent protein (YFP) gene. Parasites transformed with this library were screened by flow cytometry and fluorescence microscopy. Clones tagged in a wide variety of sub-cellular compartments (nucleus, mitochondria, ER, dense granules (secreted), spliceosome, plasma membrane, apicoplast, inner membrane complex) were isolated and confirmed using compartment specific markers. Clones with tags in parasite-specific localizations were subjected to insert rescue and phenotypic verification using an in vitro recombination system. Among the genes identified is a novel inner membrane complex gene (IMC3) conserved among Apicomplexa.

Amino Acid Sequence↗
PubMed2000

SCID mice as a tool for evaluation of heteroxenous life cycle pattern of Caryospora (Apicomplexa, Eimeriidae) species.

Adult severe combined immunodeficient (SCID) mice were inoculated with oocysts of 13 different Caryospora (Protozoa, Apicomplexa) species isolated from the faeces of 10 reptilian and three raptorial bird hosts in attempt to test heteroxenous life cycle pattern. Only three reptilian isolates originated from viperid snakes, namely from Calloselasma rhodostoma, Atheris nitschei and Vipera ursinii induced lethal dermal caryosporosis in SCID mice. Neither clinical signs nor developmental stages were observed in mice infected with further nine caryosporan isolates originated from other reptilian and raptorial bird hosts. Results of this study confirmed that SCID mice represent a useful tool for evaluation of heteroxenous life cycle pattern of caryosporan coccidia and that only the Caryospora species from viperid and crotalid snakes produce dermal caryosporosis in mice

Animals↗