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J R Barta

Publications and source records attributed to J R Barta.

At least 37 records · Page 2Linked to original sources
PubMed1998

A new Isospora sp. from Carduelis tristis (Aves: Fringillidae) from Ontario, Canada.

Isospora gryphoni n. sp. is described from oocysts found in the feces of the American goldfinch, Carduelis tristis, from Guelph, Ontario, Canada. The oocysts are spherical to subspherical, with a double-layered, smooth, colorless oocyst wall, 29.2 x 30.7 microm (25-33 x 28-34; n = 30) with 2-4 rice-grain-shaped polar bodies; no micropyle or residuum. Sporocysts are ovoid, 22.2 x 13.4 microm (15-25 x 12-14.5; n = 30) with a small Stieda body, indistinct substiedal body, and prominent sporocyst residuum. Sporozoites are vermiform, each with a large refractile body at the posterior end. Forty-nine of 52 (94%) wild-caught adult C. tristis and 1 juvenile bird (minimum 12 days old) were excreting oocysts of I. gryphoni. None of 36 nestlings (maximum 10 days old) was excreting oocysts. Fecal encrustations from 7 of 10 used nests were found to contain oocysts of I. gryphoni.

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PubMed1998

Cellular dynamics and cytokine responses in BALB/c mice infected with Eimeria papillata during primary and secondary infections.

BALB/c mice were infected with the intestinal intracellular parasite Eimeria papillata to characterize lymphocyte responses and cytokine profiles throughout primary and secondary infections. Lymphocytes from the mesenteric lymph node (MLN) and the gastrointestinal tract (GIT) of infected mice were phenotypically analyzed using flow cytometry and immunofluorescence microscopy, respectively. Lymphocytes isolated from the MLN during primary infections of BALB/c mice with E. papillata do not proliferate, compared to day 0 uninfected controls, when stimulated in vitro with conconavalin A and express TH2-type cytokines (interleukin [IL]-4 and IL-10) on day 3 PI followed by the release of TH1-type cytokines (IL-2 and interferon-gamma) during patency. In the small intestine, significantly more T cells and their subsets were observed during primary infection. During secondary infections, IL-2 was the only 1 of the 4 cytokines that was expressed earlier and at higher levels in the MLN when compared to primary infections. In the small intestine, significantly more alphabeta+ and CD8+ T lymphocytes were observed in mice during secondary infection. Oocyst antigens did not induce cellular proliferation at any time point during primary or secondary infections. We conclude that primary oral infection of BALB/c mice with E. papillata is associated with localized immunosuppression that may be mediated, in part, by early TH2-type cytokines. Immunity to secondary infection may be mediated by intestinal alphabeta+ CD8+ T lymphocytes through an IL-2-dependent mechanism.

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PubMed1997

Investigating phylogenetic relationships within the Apicomplexa using sequence data: the search for homology.

Whether stated explicitly or not, all molecular studies that seek to infer "homologies" among sequences or that attempt to determine the "relatedness" of taxa based on sequence comparisons are evolutionary studies. The generation of a reliable evolutionary hypothesis based on molecular sequences is dependent almost exclusively on the ability to align sequences such that bases or amino acids in the same position of two sequences are positionally homologous (i.e., they share the same position in the gene under study). The selection of suitable gene targets (commonly 18S small subunit rRNA gene sequences in the Apicomplexa) and appropriate ingroup and outgroup taxa will affect the ability to align sequences unambiguously. Mathematically derived alignments based on local sequence similarity have been shown to be less reliable than alignments based on conserved secondary structures coupled with an analysis of compensatory base changes. Use of staggered sequence alignments through hypervariable regions of 18S small subunit rRNA gene sequences in which subsets of taxa are aligned independently may permit inclusion of more of the primary sequences with an associated increase in information content in the data set. The use of these highly variable regions is critical for determining the branching order of closely related terminal taxa in the phylum Apicomplexa.

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PubMed1997

Analysis of immunological cross-protection and sensitivities to anticoccidial drugs among five geographical and temporal strains of Eimeria maxima.

Two laboratory strains (USDA strain No. 68 isolated from the eastern shore of Maryland 15 years ago and a University of Guelph strain isolated from an Ontario broiler house 23 years ago) and 3 recent field strains of Eimeria maxima [isolated in Maryland (MD), North Carolina (NC) and Florida (FL)] were tested for their ability to induce cross-protective immunity and their sensitivities to a variety of anticoccidial compounds. To assess immunological cross-protection, 1-day-old chicks were inoculated and subsequently challenged at 10 days of age, testing all possible combinations of initial inoculating (immunizing) and subsequent challenge strain. Six days post-challenge, chicks were killed and weight gains and lesion scores were determined and compared to sham inoculated and challenged, and sham challenged age-matched controls. The 2 laboratory strains and the NC strain were fully cross-protective against each other by both these measures. In contrast, the MD and FL strains induced complete protection only against the homologous strain. Reciprocally, no other strains protected chicks completely against the FL and MD strains. Drug sensitivity studies using 10 different anticoccidial formulations at prescribed drug levels showed significant differences between the 2 laboratory strains and the 3 recently isolated field strains; more recent isolates from commercial broiler houses demonstrated complete or partial resistance to a wider range of anticoccidial compounds. No correlation was seen between cross-protection and sensitivities to anticoccidials.

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PubMed1997

Vitamin E-deficient diets enriched with fish oil suppress lethal Plasmodium yoelii infections in athymic and scid/bg mice.

Mice fed vitamin E-deficient diets containing omega-3 fatty acids survive infection with lethal Plasmodium yoelii. The current study sought to determine if antimalarial T- and B-cell responses were required for such dietary-mediated protection. In the first set of experiments, nu/nu mice (which lack alphabeta T-cell-receptor-positive T cells and do not produce antimalarial antibody) and nu/+ mice were fed casein-based diets containing 4% menhaden oil, with or without vitamin E supplementation, for 4 weeks prior to infection with lethal P. yoelii. All mice fed diets containing vitamin E developed fulminating parasitemias and quickly died, whereas both nu/nu and nu/+ mice fed diets deficient in vitamin E controlled their parasitemias for the first 18 days of infection. Thereafter, the nu/nu mice became anemic and died, whereas the nu/+ mice produced antimalarial antibodies and survived. In the second set of experiments, scid/scid.bg/bg mice (which lack B cells and alphabeta and gammadelta T cells and have reduced NK-cell activity) were fed the experimental diet for 6 weeks and then infected with the less virulent 17XNL strain of P. yoelii. Mice fed vitamin E-containing diets quickly died, whereas those fed the vitamin E-deficient diet survived without developing detectable parasitemias. Results from these experiments show that under prooxidant dietary conditions, mice were able to control and even survive malaria in the absence of malaria-primed T cells and antimalarial antibody. These results emphasize the importance of cellular oxidative processes in parasite elimination.

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PubMed1997

Nonspecific immune responses and mechanisms of resistance to Eimeria papillata infections in mice.

Severe combined immunodeficient (SCID)-beige mice inoculated with the intracellular parasite Eimeria papillata produced significantly more oocysts during primary infections than inoculated immunodeficient SCID mice. Therefore, the addition of the beige mutation, which detrimentally affects neutrophil and natural killer (NK) cell functions, enhanced the parasites' ability to reproduce within the small intestine. To identify which of these two cell types is responsible for a protective immune response during primary infection, the following groups of mice were inoculated: (i) SCID mice depleted of neutrophils with antigranulocyte monoclonal antibody (RB6-8C5), (ii) C57BL/6 mice depleted of NK cells with the anti-NK-1.1 monoclonal antibody (PK136), and (iii) transgenic Tg epsilon26++ mice (T and NK cell deficient). To identify the mechanisms of immunity during primary and secondary infections, gamma interferon (IFN-gamma) knockout and perforin knockout mice were inoculated. Oocyst output was found to be significantly higher during primary infection for mice depleted of NK cells by administration of anti-NK-1.1 antibodies, for Tg epsilon26++ mice, and for IFN-gamma knockout mice. During secondary infections, only perforin knockout mice produced significantly more oocysts compared to control mice. Our observations suggest that NK cells inhibit E. papillata oocyst output during primary infection by the production of IFN-gamma and that this inhibition is independent of perforin. Immunity to reinfection does not require IFN-gamma but appears to be mediated, at least in part, by a perforin-dependent mechanism.

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PubMed1997

Phylogenetic relationships among eight Eimeria species infecting domestic fowl inferred using complete small subunit ribosomal DNA sequences.

Complete 18S ribosomal RNA gene sequences were determined for 8 Eimeria species of chickens and for Eimeria bovis of cattle. Sequences were aligned with each other and with sequences from 2 Sarcocystis spp., Toxoplasma gondii, Neospora caninum, and 4 Cryptosporidium spp. Aligned sequences were analyzed by maximum parsimony to infer evolutionary relationships among the avian Eimeria species. Eimecia bovis was found to be the sister taxon to the 8 Eimeria species infecting chickens. Within the avian Eimeria species, E. necatrix and E. tenella were sister taxa: this clade attached basally to the other chicken coccidia. The remaining Eimeria spp. formed 3 clades that correlated with similarities based on oocyst size and shape. Eimeria mitis and Eimeria mivati (small, near spherical oocysts) formed the next most basal clade followed by a clade comprising Eimeria praecox. Eimeria maxima, and Eimeria brumetti (large, oval oocysts), which was the sister group to Eimeria acervulina (small, oval oocysts). The 4 clades of avian Eimeria species were strongly supported in a bootstrap analysis. Basal rooting of E. necatrix and E. tenella between E. bovis and the remaining Eimeria species and the apparent absence of coccidia that infect the ceca of jungle fowl all suggest that E. necatrix and E. tenella may have arisen from a host switch, perhaps from the North American turkey, Meleagris gallopavo.

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PubMed1996

Detection of Cryptosporidium parvum in raw milk by PCR and oligonucleotide probe hybridization.

Cryptosporidium spp. are potential contaminants of food. Suspected cases of food-borne cryptosporidiosis are rarely confirmed because of the limited numbers of oocysts in the samples and the lack of sensitive detection methods adaptable to food. PCR was investigated as a means of overcoming this problem. A PCR assay was designed for the specific amplification of a previously sequenced portion of an oocyst protein gene fragment of Cryptosporidium parvum (N. C. Lally, G. D. Baird, S. J. McQuay, F. Wright, and J. J. Oliver, Mol. Biochem. Parasitol. 56:69-78, 1992) and compared with the primer set of Laxer et al. (M. A. Laxer, B. K. Timblin, and R. J. Patel, Am. J. Trop. Med. Hyg. 45:688-694, 1991). The PCR products were hybridized with digoxigenin-labeled internal probes and detected by chemiluminescence to enhance sensitivity. The two sets of primers were compared with regard to their sensitivity and specificity by using a variety of human and animal isolates of C. parvum and related parasites. Both assays enabled the detection of 1 to 10 oocysts in 20 ml of artificially contaminated raw milk. The assay based on the PCR set and probe of Laxer et al. detected DNAs from Eimeria acervulina and Giardia intestinalis. The new assay has good specificity for C. parvum bovine isolates and hence has a better potential for monitoring the prevalence of C. parvum in raw milk and other environmental samples.

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PubMed1996

Comparison of four murine Eimeria species in immunocompetent and immunodeficient mice.

Factors associated with immune-mediated protection against coccidial parasites were examined in a series of experiments utilizing immunocompromised scid/scid(SCID) and scid/scid.beige/beige(SCID/Bg) mice, as well as immunocompetent BALB/c mice. Number of oocysts produced per g feces each day and prepatent and patent periods were assessed for 4 eimerian parasites (Eimeria papillata, Eimeria vermiformis, Eimeria falciformis, and Eimeria ferrisi) using the 3 murine strains. The number of infections required to elicit a protective immune response was also determined for each coccidial species in BALB/c mice. We report the first description of patent infections in inbred immunocompetent and immunodeficient mice infected with E. papillata. Results indicate that during primary infections, parasite replication is under partial immunological control for all Eimeria species. However, the control is mechanistically different for E. papillata because the adaptive immune response does not contribute to the control of primary infections. Both coccidial species infecting intestinal villar epithelial cells (E. papillata and E. ferrisi) were affected by the beige mutation using parasite output as an indicator, whereas E. falciformis, which infects intestinal crypt cells, is not. BALB/c mice were more resistant to challenge infections with upper intestinal parasites (E. papillata and E. vermiformis) in comparison to challenge infections with lower intestinal and cecal parasites (E. falciformis and E. ferrisi).

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PubMed1996

Establishment of Demodex canis on canine skin engrafted onto scid-beige mice.

A small animal model of canine demodicosis is described. Normal canine skin was engrafted onto scid (severe combined immunodeficient)-beige mice, which lack functional B and T lymphocytes and have reduced natural killer cell activity. The xenografts were later infected with Demodex canis collected from a dog with demodicosis. At 30-112 days following infection, mites were seen histologically in the canine hair follicles of the engrafted skin. Demodex canis adults, nymphs, larvae, and eggs were present in samples macerated in sodium hydroxide. Mite infestations could not be demonstrated in the mouse skin, nor were mites passed from the infected graft to uninfected skin grafts on in-contact mice. This model may be utilized to assess the efficacy of miticidal treatments, to evaluate the importance of specific components of the immune response, and to study the biology of D. canis.

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PubMed1995

Monoclonal antibodies raised against coccidia and malarial parasites recognize antigenic epitopes found in lankesterellid and adeleorin parasites.

Three murine monoclonal antibodies (MAbs) raised against poultry coccidia or murine malarial parasites were tested for cross-reactivity with 2 sporozoan parasites with different life histories and hosts: Lankesterella minima (Eimeriorina), an intraerythrocytic parasite of frogs that is transmitted by leeches; and Heptazoon catesbianae (Adeleinorina) that infects the red blood cells of frogs and is transmitted by mosquitoes. MAb 1209 recognized both refractile bodies of sporozoites of L. minima, using the indirect fluorescent antibody (IFA) technique and immunoelectron microscopy, and recognized antigens with relative rates of migration (M(r)) of 17, 23, 26, 43, and 48 kDa on a chemiluminescent western blot of L. minima sporozoite antigens. MAbs C(3)4F1 and E12 demonstrated spotty cytoplasmic staining and labeling of the anterior pellicle of L. minima sporozoites, respectively. Gamonts of H. catesbianae labeled with only MAb E12, using IFA. These gamonts exhibited staining similar to that observed with the L. minima sporozoites. The presence of the cross-reactive epitopes recognized by these MAbs in the same conserved locations suggests that these antigens are homologous.

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PubMed1994

In vitro and in vivo immunolabeling of sporozoites, schizonts, and sexual stages of Eimeria acervulina and E. tenella by a species- and stage-cross-reactive monoclonal antibody.

A cross-reactive monoclonal antibody (mAb), designated 1205, was used to study redistribution, parasitophorous vacuole (PV) incorporation, and in situ antigen production during the intracellular parasite development of Eimeria acervulina and E. tenella. Western-blot analysis of sporozoite preparations showed that the mAb recognized antigenic bands at 55 and 80 kDa. Indirect immunofluorescent antibody (IFA) labeling of sporozoites produced an internal dot pattern. Immunogold electron microscopy (IM) showed labeling of dense granules within sporozoites. The IFA pattern changed to a general-internal label in immature schizonts followed by a surface-tip pattern in mature merozoites both in vitro and in vivo. IM of the asexual stages revealed the same labeling pattern for the in vivo development of both species, and labeling of rhoptries was seen. In vitro, the PV membrane together with amorphous material within the PV was labeled by IFA during schizont development for E. tenella. No IM labeling of either the PV membrane or material within the PV was observed. Sexual stages seen in vivo for both species had the general-internal IFA pattern.

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PubMed1993

Species and strain differentiation of Eimeria spp. of the domestic fowl using DNA polymorphisms amplified by arbitrary primers.

Eimeria spp. from the domestic fowl were examined for genetic relatedness by the random amplified polymorphic DNA (RAPD) assay. Nine different oligonucleotide decamers with arbitrary DNA sequences were tested as primers to amplify DNA from six Eimeria species infecting chickens. Two strains each of E. acervulina and E. tenella were used. Depending on the species/strain-primer combination, between 1 and 12 DNA segments ranging in size from 0.16 to 4.95 kb were amplified. The two strains of E. acervulina showed minor and major differences in their amplified DNA patterns, giving a similarity coefficient of 61%. The two strains of E. tenella seemed to be more closely related, yielding a similarity coefficient of 98%. The differences observed between species were greater than those found between strains with every primer used, indicating that the RADP assay could be a useful tool for the study of relationships among these coccidia. The results obtained in this study also indicate the presence of unique, species-specific, amplified DNA segments that could be exploited to identify Eimeria species of the chicken.

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PubMed1993

Spontaneous and experimental infections in scid and scid/beige mice.

Severe combined immunodeficient (scid) mice are valuable animals to study a variety of physiologic and disease processes. Their capacity to support multiple tissue xenografts permits these mice to be used as intermediate models for host-specific, fastidious organisms for which a small animal model has not been available previously. However, because they are unable to mount a normal immune response, they are very susceptible to a variety of primary and opportunistic microbial pathogens. Fatal, naturally occurring infections with bacteria such as Proteus mirabilis, Streptococcus viridans, and Escherichia coli have been observed. In addition, based on observations after experimental or naturally occurring viral infections, scid and scid/beige mice have been shown to be very susceptible to infections with viruses such as mouse hepatitis virus, Sendai virus, and murine respiratory virus, with resulting mortality. Of the parasitic infections, Pneumocystis carinii is a relatively common contaminant of the respiratory tracts of scid mice and may complicate research projects, particularly experimental respiratory tract infections. In view of the enhanced susceptibility of these mice to infections of this type, it is essential that they be housed under optimal conditions, which include implementing stringent management practices and a functional barrier system.

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PubMed1992

Characterization of anti-Neospora caninum hyperimmune rabbit serum by western blot analysis and immunoelectron microscopy.

The antigens recognized by hyperimmune rabbit serum raised against tachyzoites of the NC-1 isolate of Neospora caninum were characterized using chemiluminescent Western blotting, immunogold-silver staining and immunoelectron microscopy. Approximately 20 immunodominant antigens whose relative rates of migration were 16-80 kDa were recognized by the serum in Western blots using reduced or nonreduced parasite antigen preparations. The nonreduced parasite antigens were more strongly recognized by the serum than were the reduced antigen preparations. Immunoelectron microscopy revealed that the rabbit-serum-labeled antigens were localized to some organelles of N. caninum tachyzoites and to the parasitophorous vacuole surrounding them. In particular, antigens found in the dense granules, in the micronemes, and in the posterior portion of the rhoptries were strongly labeled by an indirect immunogold-labeling technique.

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PubMed1992

Localization of a low molecular weight antigen of Eimeria tenella by use of hybridoma antibodies.

Three monoclonal antibodies (Mabs), found by western blot analysis to recognize 10-kDa bands of Eimeria tenella sporozoite preparations, were used with immunoelectron (IE) microscopy, immunogold-silver staining (IGSS), and indirect immunofluorescent antibody (IFA) light microscopy to determine the location and distribution of the antigens in or on extra- and intracellular parasites. All 3 of the Mabs (designated C3, E5, and 1231) were found by IE microscopy to label amylopectin granules of extracellular sporozoites. Additionally, these Mabs extensively gold-labeled the sporocyst wall. In cultured primary chicken kidney cells inoculated with sporozoites of E. tenella, IGSS showed surface labeling of the parasite and intense labeling of the infected host cells by 6 hr postinoculation (PI). At 24 hr PI, host cell vacuoles in infected and uninfected cells were labeled by the 3 Mabs by IFA. The E5 and C3 Mabs also were seen to label the host cell membrane of newly infected cells. The C3 and 1231 Mabs showed little label of the host cells by 48 hr PI, but the parasites still were labeled up to 96 hr PI. The E5 Mab had intense IFA labeling of infected host cells at 48 hr PI. The results of this study indicate that parasites apparently release antigenic material during the early stages of parasite development and that this material is found internally and/or on the surface of the infected host cells.

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PubMed1991

Development of resistance to coccidiosis in the absence of merogonic development using X-irradiated Eimeria acervulina oocysts.

Sporulated oocysts of the protozoan Eimeria acervulina were subjected to 0, 10, 15, 20, or 30 krad of X-irradiation and inoculated into susceptible outbred chickens to determine if radioattenuated coccidia could induce protection against parasite challenge. Irradiation treatment had an appreciable dose-dependent effect on parasite development. Insignificant numbers of oocysts were produced by chickens inoculated with parasites that had been exposed to greater than 10 krad X-irradiation. Sporozoites exposed to 15 or 20 krad irradiation conferred significant protection against the appearance of intestinal lesions after parasite challenge. Sporozoites subjected to the highest dose level (30 krad) did not produce any significant level of protection. To investigate this phenomenon further and assess intracellular parasite development, susceptible outbred strains of chickens were administered either nonirradiated (0 krad) oocysts or oocysts that were exposed to an optimal dose (15 krad) or a high dose (30 krad) of X-irradiation. Immunofluorescence staining of tissue sections from each treatment group at various intervals after the initial administration of irradiated parasites indicated that sporozoites exposed to 15 krad irradiation were as capable of invading the host intestinal epithelium as nonirradiated sporozoites. However, at 48, 60, 72, and 96 hr, there was a marked reduction in merogonic development in groups receiving irradiated sporozoites compared to those inoculated with nonirradiated parasites. The latter parasites underwent profuse merogonic development; in contrast, irradiated parasites demonstrated little (15 krad) or no (30 krad) merogonic development. These results suggest that induction of a protective immune response occurs during a critical period early in intracellular development of E. acervulina.

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