Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Apicomplexa”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,207 records · Page 67Linked to original sources
PubMed1989

Improved characterization of Theileria parva isolates using the polymerase chain reaction and oligonucleotide probes.

Theileria parva DNA was purified from piroplasms isolated from cattle infected with 5 different East African isolates of the parasite, including the East Coast fever reference stock T. p. parva Muguga. Total cellular DNA was prepared from T. parva schizont-infected bovine lymphoblastoid cell cultures (11 isolates). Two probes, previously isolated from T. p. parva Muguga repetitive genomic DNA, were hybridized to restriction digests; closely similar restriction fragment length polymorphism (RFLP) patterns were produced, and no two isolates had the same RFLP pattern. The DNA sequences of probe PMB3, two further copies of the repeated sequence from T. p. parva Muguga, and homologous regions from T. p. parva Kiambu 4 and T. p. lawrencei 3081, were determined. Oligonucleotides were synthesized corresponding to two conserved sections flanking a region which varied between isolates. These oligonucleotides were used as primers in the polymerase chain reaction to amplify the variable region. Further oligonucleotides corresponding to sequences in this variable region were able to distinguish between isolates and no sample hybridized to both oligonucleotides. This is the first unequivocal plus/minus discrimination between groups of isolates to be achieved for T. parva.

Animals↗
PubMed1989

Protein changes in bovine lymphoblastoid cells induced by infection with the intracellular parasite Theileria parva.

Protein and glycoprotein changes induced in bovine lymphoblasts by infection with Theileria parva were analyzed by high-resolution two-dimensional gel electrophoresis. Uninfected and infected cloned bovine T and B lymphoblasts were biosynthetically labeled with [35S]methionine and their two-dimensional autoradiographic patterns were compared with each other and with the pattern obtained using purified labeled schizonts. Ten proteins were found in infected cells which were not present in uninfected cells, and seven of these were detected in preparations of purified schizonts. Four glycoproteins were detected on the surface of infected cells labeled with [3H]borohydride while a major glycoprotein present on uninfected cells disappeared or was reduced in infected cells. Other minor changes in protein and glycoprotein patterns were also observed.

Animals↗
PubMed1990

Characterisation of the gene encoding a 104-kilodalton microneme-rhoptry protein of Theileria parva.

A neutralizing antiserum, C16, raised against sporozoites of Theileria parva parva was used to screen a lambda gt11 expression library of T. parva parva (Muguga) genomic DNA fragments. Proteins encoded by one phage clone, lambda TpS-17, were reactive with the C16 antiserum. Detailed characterisation of the DNA insert showed it to encode determinants found on four theilerial antigens of approximately 104, 90, 85 and 35 kDa. The sequence encoded by the clone is expressed during sporogony as a single RNA transcript of about 3000 nucleotides. On sequencing a portion of the 5000-bp insert, an open reading frame of 2772 bp was revealed that encoded a 104-kDa protein. Immunoscreening a library of subfragments of the DNA insert with the original antiserum localised sequences encoding the dominant antigenic determinants to an 800-bp stretch of DNA at the 3' end of the open reading frame. Sequence data from three subclones spanning this region show portions of the antigenic domains to be unusually rich in proline residues which are repeated every three amino acids. These repeats often take the form X-S(T)-P or X-K(R)-P. Antibodies directed against each of the three subclones recognize the 104- and 35-kDa antigens and different combinations of the 90- and 85-kDa kDa antigens, suggesting that the smaller proteins are derived from the 104-kDa antigen by limited proteolysis occurring at the carboxyl terminus end of the protein. In immunoelectron micrographs the antigen is associated with the microneme/rhoptry complexes of the sporozoite.

Amino Acid Sequence↗
PubMed1990

Characterisation of an extrachromosomal DNA element from Theileria annulata.

Extrachromosomal nucleic acid elements are found in all organisms, commonly as organelle, viral or plasmid genomes. In this paper we describe the initial characterisation of a novel 6.5-kb linear, double-stranded extrachromosomal element from Theileria annulata, and a 2.6-kb RNA species. The DNA element is present in different stages of the life cycle and in different stocks of the parasite. Northern blots of total RNA isolated from different stages of the parasite, probed with the purified element, detect three major transcripts, of 1.45, 1.05 and 0.24 kb, present in all life-cycle stages examined. The possible origin and function of this element is discussed, together with its possible use as a transfection vector for the introduction of genes into protozoan cells.

Animals↗
PubMed1990

SfiI and NotI polymorphisms in Theileria stocks detected by pulsed field gel electrophoresis.

DNAs of Theileria parva parva, T. p. lawrencei, T. p. bovis and Theileria mutans stocks, from Kenya, Uganda, Zanzibar and Zimbabwe were digested with either SfiI or NotI and analysed using contour-clamped homogeneous electric field (CHEF) and field-inversion gel electrophoresis (FIGE). The SfiI-digested T. parva genomic DNA resolved into approximately 30 fragments while the NotI digestion produced between 4-7 bands. The summation of the sizes of SfiI fragments gave an estimate of 9-10 X 10(6) base pairs for the size of the T. parva genome. Heterogeneity within T. p. parva Muguga, Pemba/Mnarani and Mariakani stocks was detected. All the T. parva stocks analysed showed SfiI and NotI restriction fragment length polymorphisms (RFLP). Hybridisation of 5 SfiI-digested T. parva DNAs with a Plasmodium berghei telomeric repeat probe suggested that most of the polymorphisms and heterogeneity occurred in the telomeric or sub-telomeric regions of the genome. The recognition by the Plasmodium telomeric probe of 7-8 strongly hybridising SfiI bands indicates that the T. parva genome may possess at least 4 chromosomes. The T. mutans genome was cut frequently with the above enzymes resulting in large numbers of fragments predominantly below 50 kb, thus suggesting either a much higher G + C content than T. parva or the presence of highly reiterated G + C-rich regions.

Animals↗
PubMed1990

Developmental expression of a Theileria annulata merozoite surface antigen.

Culture of a lymphoblastoid cell line infected with the macroschizont stage of the protozoan parasite Theileria annulata at 41 degrees C induces differentiation to the next stage, the merozoite. We have demonstrated that this development results in the loss of monoclonal antibody epitopes associated with the macroschizont stage, and the appearance of epitopes associated with the piroplasm (the intra-erythrocytic stages). One of the monoclonals (5E1) was shown by immunoelectron microscopy to bind to the surface of heat-induced culture forms which had size and structural characteristics of the merozoite. The monoclonal was found to detect two polypeptides of 30 kDa and 25 kDa in extracts of piroplasms. The 30-kDa polypeptide was also detected in a merozoite extract, but was not detected in an extract derived from macroschizont-infected lymphoblastoid cells. We conclude that the heat-induced differentiation of T. annulata in vitro results in the expression of a 30-kDa molecule which is located at the surface of the merozoite, and discuss the potential of this molecule as a component in a subunit vaccine.

Animals↗
PubMed1986

Eicosanoid regulation of oosporogenesis by Lagenidium giganteum.

Cell proliferation is inhibited in many biological systems by lipid peroxides and related products derived from polyunsaturated fatty acids. Using developmentally synchronized cultures of Lagenidium giganteum (Oomycetes: Lagenidiales), a facultative parasite of mosquito larvae, it has been documented that oxidative lipid metabolism is necessary for the induction and subsequent maturation of its sexual stage, the oospore. Addition of lipoxygenase inhibitors to liquid cultures of the fungus results in the stage-specific disruption of antheridial induction, gametangial fusion, induction of meiosis and spore cell wall formation. Oosporogenesis is inhibited by these compounds at concentrations which have no discernible effect on mycelial viability or asexual reproduction. Cyclooxygenase inhibition had comparable effects using ibuprofen and to a lesser extent with indomethacin. Phenylbutazone and the salicylates affected oosporogenesis only at concentrations which decreased asexual reproduction or mycelial viability. The inhibitory effects of NDGA on oosporogenesis could be reversed using partly purified eicosanoid extracts from growth media.

Apicomplexa↗
PubMed1978

Protist classification and the kingdoms of organisms.

Traditional classification imposed a division into plant-like and animal-like forms on the unicellular eukaryotes, or protists; in a current view the protists are a diverse assemblage of plant-, animal- and fungus-like groups. Classification of these into phyla is difficult because of their relatively simple structure and limited geological record, but study of ultrastructure and other characteristics is providing new insight on protist classification. Possible classifications are discussed, and a summary classification of the living world into kingdoms (Monera, Protista, Fungi, Animalia, Plantae) and phyla is suggested. This classification also suggests groupings of phyla into superphyla and form-superphyla, and a broadened kingdom Protista (including green algae, oomycotes and slime molds but excluding red and brown algae). The classification thus seeks to offer a compromise between the protist and protoctist kingdoms of Whittaker and Margulis and to combine a full listing of phyla with grouping of these for synoptic treatment.

Animals↗
PubMed1978

Problems in the development of an explicit hypothetical phylogeny of the lower eukaryotes.

A semi-explicit arrangement of the lower eukaryotes is provided to serve as a basis for phyletic discussions. No single character is used to determine the position of all the groups. The tree provides no ready separation of protozoa, algae and fungi, groups assigned to these traditional assemblages being considered to be for the most part inextricably interwoven. Photosynthetic forms, whose relationships seem to be more readily discernable, are considered to have given rise repeatedly to nonphotosynthetic forms. The assumption that there are primitive "preflagellar" eukaryotes (red algae, non-flagellated fungi) is adopted. The potential value of mitochondrial features as indicators of broad affinities is emphasised, particularly in determining the probable affinities of non-photosynthetic forms, and this criterion is contra-indicative of a ciliate ancestry for the Metazoa. In the arrangement provided the distributions of chloroplast, mitochondrial and flagellar features match one another well, suggesting their probable co-evolution.

Animals↗
PubMed1988

Nuclear division and chromosome cycle in microsporidia.

Nuclear division and chromosome cycle of microsporidia are reviewed in the light of recent speculation that the group diverged as an early branch in the eukaryotic line of descent. Microsporidia are primitive eukaryotes with simple cytoplasmic organisation, lacking mitochondria, peroxisomes and a classical Golgi apparatus. The ribosomes resemble prokaryotic ribosomes in size and in having sequences complementary to the eukaryotic 5.8S rRNA contained within their large (23S) ribosomal subunit, rather than a separate 5.8S molecule. Nuclei may be isolated or closely appressed as a diplokaryotic pair which divide synchronously. Mitosis is intranuclear: there are no centrioles but spindle termini are electron dense plaques in pores in the nuclear envelope. Some genera have isolated nuclei throughout the life cycle, while others have diplokaryotic nuclei throughout: meiosis is not known in either of these categories of genera. In contrast, certain polymorphic species, which are transmitted horizontally between copepods and mosquitoes and vertically between generations of mosquitoes, alternate between stages with isolated nuclei and stages with diplokaryotic nuclei. Haploid spores in copepods are infective to mosquito larvae, in which gametogenesis and plasmogamy occur to give diplokaryotic (diploid) stages. Stages remain diplokaryotic through transovarial transmission to the next generation, when an unusual form of meiosis is initiated in both nuclei of the diplokaryon (as indicated by synaptonemal complexes), and mingling of chromosomes occurs when the two nuclei fuse during pachytene.

Animals↗
PubMed1981

Kinetics of infection with Theileria parva (East Coast fever) in the central lymph of cattle.

During the course of a lethal infection with Theileria parva in susceptible cattle, the dissemination of the parasite was examined in central lymph efferent from superficial lymph nodes in the thoracic duct. From the regional node, lymphocytes containing macroschizonts of T. parva were detected in efferent lymph 8 days after challenge where their appearance coincided with a dramatic increase in the output of lymphoblasts. The number of infected cells reached a maximum around Day 14, when 60-65% of efferent lymphocytes were parasitized. A severe reduction in the total cell output occurred after Day 14, at the time when widespread lymphocytosis was observed in the parent lymph node. A similar pattern of cellular kinetics was observed in the thoracic duct and in lymph efferent from lymph nodes distant from the site of challenge, although in the latter, the parasitosis reached only 10% of total cells. There was no selective depletion of parasitized cells from central lymph during the third week of infection, although the comparative parasitosis between lymph and lymph node cells indicated that infected cells entered central lymph less readily during this period. Macroschizonts appeared in cultures of lymphatic lymphocytes sampled between 5-9 days after challenge. These results, together with the failure of ablation of the regional lymph node 2, 3 or 5 days after challenge to delay the onset of the disease, indicated that dissemination of the infection from the site of challenge occurred within the first 2-3 days after the inoculation T. parva.

Animals↗
PubMed1981

Immunization of sheep against Theileria hirci infection with schizonts propagated in tissue culture.

Two experiments were carried out. In the first, three groups of lambs were inoculated subcutaneously with 3 X 10(6) schizonts of different passages (3, 30 and 63) of Theileria hirci propagated in tissue culture. Severe reactions were observed in lambs inoculated with organisms derived from the 3rd passage. In the second experiment, four groups were inoculated with 5 X 10(5), 3 X 10(6), 1 X 10(7) and 5 X 10(8) schizonts of the 63rd passage. No clinical reactions or parasites were detected in lambs inoculated with 5 X 10(5) schizonts. Mild reactions were observed in lambs inoculated with 3 X 10(6), 1 X 10(7), and 5 X 10(7) schizonts. Lambs inoculated with 3 X 10(6) schizonts were resistant to challenge with a virulent strain. The indirect fluorescent antibody (IFA) test was used to determine the antibody titre.

Animals↗
PubMed1982

Relative infectivity of Theileria annulata (Dchunkovsky and Luhs, 1904) stabilates derived from female and male Hyalomma excavatum (Koch, 1844) ticks.

Partially engorged female and male Hyalomma excavatum ticks infected with Theileria annulata were triturated separately in Eagle's minimum essential medium complemented with fetal calf serum. Glycerol was added to the supernatant obtained after centrifugation and the material was frozen at -79 degrees C. Infectivity of the stabilate was titrated by inoculating susceptible calves with dilutions of the material. Stabilate prepared from female ticks was considerably more infective on a per tick basis than stabilate from males. All calves inoculated with an estimated equivalent of 0.1 or more female ticks, or 3.3 or more male ticks, became infected. Time to fever, prepatent period, and mortality did not appear to be dose-dependent in the range of tick equivalents employed.

Animals↗
PubMed1983

Ultrastructural characteristics of in vitro parasite-lymphocyte behaviour in invasions with Theileria annulata and Theileria parva.

Host-parasite relationships have been studied by electron microscopy using glutaraldehyde-OsO4-fixed pellets of lymphoid cultures infected in vitro by Theileria annulata and T. parva. Intracellular presence of the parasite resulted in a progressive and marked lymphoblastoid transformation. The schizont stage periodically provoked the formation of, and adopted an intimate association with, cytoplasmic annulate lamellae in the interphase cell. Annulate lamellae developed from the outer nuclear membrane of the host cell by a delamination process and were taken into the cytoplasmic matrix of the schizont by phagotrophy through the cytostome. Schizont nuclei themselves were seen to divide at the prometaphase stage of host cell mitosis, the division being characterized by the development of intranuclear spindle microtubules anchored in spindle pole bodies. A hypothesis is propounded that Theileria parasites, consequent on interiorization, provoke the blastoid transformation and the formation of annulate lamellae through the influence of components of their genomic material on host cell deoxyribonucleic acid (DNA) and that the annulate lamellae represent a species of messenger ribonucleic acid (mRNA) and serve as a monitoring device for the schizont, facilitating the accurate timing of the host cell cyclical events.

Animals↗
PubMed1983

The early events of infection with Theileria parva in cattle: infectivity for cattle of leukocytes incubated in vitro with sporozoites.

Leukocytes were isolated from bovine blood and, after short periods of incubation in vitro with sporozoites of Theileria parva, were washed thoroughly, and their infectivity tested in autologous and allogeneic hosts. Using a standard inoculum of 10(6) viable cells, it was found that, after incubation in vitro for either 1 or 24 h, the cells initiated lethal infections in autologous cattle, but failed to infect allogeneic animals. Autologous and allogeneic erythrocytes and mouse lymphocytes similarly incubated with sporozoites failed to infect cattle. The supernatant from bovine lymphocyte suspensions incubated with sporozoites for 1 h produced lethal infections whereas after 24 h of incubation the supernatant was non-infective. All cattle which did not develop detectable infection were fully susceptible to subsequent challenge with a stabilate of sporozoites. By inoculating cattle with graded doses of autologous blood leukocytes which had been incubated for 24 h with sporozoites, it was found that as few as 2 X 10(3) cells gave rise to infection. The results indicate that this approach can be used to evaluate different cell populations as targets for infection and transformation by sporozoites of T. parva.

Animals↗
PubMed1983

The maturation of Theileria annulata in Hyalomma anatolicum anatolicum stimulated by incubation or feeding to produce sporozoites.

Adult Hyalomma anatolicum anatolicum ticks infected with Theileria annulata (Hissar strain) were incubated at 36 degrees C or fed on rabbits. Tick salivary glands were stained whole with methyl green pyronin or ground up and deposited on microscope slides and stained with Giemsa's solution. Separate batches of ticks from both treatments were ground up, centrifuged and filtered to produce sporozoite suspensions. The suspensions were examined as deposits on microscope slides stained with Giemsa's solution. The Theileria in the salivary glands of the fed ticks matured more completely and rapidly than in the incubated ticks. The peak numbers of sporozoites from the fed ticks was greater by at least tenfold than the peak from the incubated ticks. This peak was on the third day of feeding or on the fourth day of incubation. It was confirmed that fed ticks will be more suitable for sporozoite production for infection of cattle and production of stabilates.

Animals↗
PubMed1983

Preparation of suspensions of Hyalomma excavatum ticks infected with Theileria annulata.

Partially engorged adult Hyalomma excavatum ticks infected with Theileria annulata were reared for the preparation of an infective suspension. About 6000 partially engorged infected adults were obtained from 420 non-infective adult ticks. The entire cycle required about 4 months. Six rabbits were used for the production of the fully engorged females. The larvae were fed on 180 gerbils, the nymphs on 17 infected calves and the partially fed adults on 22 goats, 7 sheep and 7 rabbits The adult ticks did not show any host preference.

Animals↗