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S S Desser

Publications and source records attributed to S S Desser.

At least 37 records · Page 2Linked to original sources
PubMed1995

The life history, ultrastructure, and experimental transmission of Hepatozoon catesbianae n. comb., an apicomplexan parasite of the bullfrog, Rana catesbeiana and the mosquito, Culex territans in Algonquin Park, Ontario.

Gametogenesis and sporogonic development of a haemogregarine parasite of bullfrogs (Rana catesbeiana) was observed in cells of the Malpighian tubules of laboratory-reared Culex territans that had fed on naturally infected bullfrogs. Mature oocysts, which varied considerably in size, were multisporocystic with ellipsoidal sporocysts that contained 4 sporozoites. Sporogonic development was completed in about 20 days. Mature meronts were observed in the liver and merozoites in erythrocytes of laboratory-reared bullfrogs that had been fed sporocysts 19 days previously. Similar attempts to infect laboratory-reared green and northern leopard frogs experimentally were unsuccessful, suggesting rather narrow specificity for this parasite in ranids. Gametogenesis and sporogonic stages of this parasite were ultrastructurally similar to those described for Hepatozoon species. The parasite appears to be transmitted directly between bullfrogs and mosquitoes in the study area where Cx. territans feeds avidly on bullfrogs, which in turn were observed to naturally ingest these mosquitoes. Based on data presented in this study and the earlier description by Stebbins in 1903, the haemogregarine parasite of bullfrogs was designated as a new combination, Hepatozoon catesbianae.

Animals↗
PubMed1995

Karyotype analysis of anuran trypanosomes by pulsed-field gradient gel electrophoresis.

The chromosomes of 12 species and isolates of anuran trypanosomes were investigated by pulsed-field gradient gel electrophoresis. Twelve to 16 chromosomes ranging from 0.45 to 2.2 megabase pairs were found in each of these trypanosomes. Minichromosomes were not observed in any of the examined isolates. Results indicate that different species of anuran trypanosomes display distinct karyotype patterns, and that isolates from the same region are similar. Our findings also reveal that most chromosome profiles of these trypanosomes are in accordance with isoenzyme and random amplified polymorphic DNA analysis data.

Animals↗
PubMed1995

The demise of a phylum of protists: phylogeny of Myxozoa and other parasitic cnidaria.

The notion that members of the phylum Myxozoa Grassé, 1970 do not properly belong in classifications of protists has frequently been suggested because the infective spores of these parasites are not unicellular. Systematists have failed to be decisive about myxozoan phylogenetic affinities, either finding the suggestion of a cnidarian connection to be preposterous or considering the recent suggestion of a relationship with nematodes to be an obvious failure of molecular phylogenetics. Thus, the group has remained in classifications as a protistan phylum in its own right. The ultrastructure of the development of myxozoans was critically re-examined in order to more fully explore the possibility of morphological synapomorphies with metazoan taxa. These morphological characters, in combination with small ribosomal subunit gene sequences, were used in a phylogenetic analysis in order to assess myxozoan origins. The results unequivocally support the inclusion of myxozoans as a clade of highly derived parasitic cnidarians, and as sister taxon to the narcomedusan Polypodium hydriforme. Reassessment of myxozoans as metazoans reveals terminal differentiation, typical metazoan cellular junctions, and collagen production. Their "polar capsules" are redescribed as typical nematocysts bearing atrichous isorhiza. Insofar as taxa cannot be contained within other taxa of equal rank, the phylum Myxozoa is abandoned and it is recommended that the group as a whole be removed from all protistan classifications and placed in a more comprehensive cnidarian system.

Animals↗
PubMed1994

The development of Hepatozoon sipedon sp. nov. (Apicomplexa: Adeleina: Hepatozoidae) in its natural host, the Northern water snake (Nerodia sipedon sipedon), in the culicine vectors Culex pipiens and C. territans, and in an intermediate host, the Northern leopard frog (Rana pipiens).

The life cycle of Hepatozoon sipedon sp. nov. was studied in two snake species, the Northern water snake and the Eastern garter snake, in its mosquito hosts Culex pipiens and C. territans, and in the Northern leopard frog. Gametogenesis, fertilization and sporogony occurred within fat body cells in the haemocoel of mosquitoes that had fed on infected water snakes. Mature oocysts averaging 263 microns in diameter and containing more than 500 sporocysts were observed in mosquitoes 28 days post-feeding. Each sporocyst enclosed eight sporozoites. Dizoic cysts were found in the liver of frogs that had been fed infected mosquitoes seven days previously. Two rounds of merogony in various internal organs and intraerythrocytic gamonts were observed in snakes that had been fed frogs which had been orally inoculated with infected mosquitoes. Developmental stages were not seen in snakes that were fed infected mosquitoes directly. A comparison of this life cycle with those described for other Hepatozoon species infecting snakes is presented with reference to the different modes of transmission featured by these parasites.

Animals↗
PubMed1994

Morphology, ultrastructure and taxonomic status of Toddia sp. in northern water snakes (Nerodia sipedon sipedon) from Ontario, Canada.

Inclusions characteristic of an infection caused by Toddia sp. were found in the erythrocytes and erythroblasts of 15 of 26 northern water snakes (Nerodia sipedon sipedon) collected near Kingston, Ontario, Canada. Erythrocytes contained translucent inclusions, small acidophilic bodies, and square-shaped crystalloid structures. Erythrocytes infected with Toddia sp. were more rounded than uninfected erythrocytes and had pycnotic nuclei. We observed icosahedral virus particles measuring 195 to 210 nm formed from a membrane-bounded viral assembly site in the cytoplasm of the host erythrocyte. As a result of the viral identity of this parasite, we recommend that the etiologic agent of Toddia sp. infections from this and other species of North American snakes be renamed Snake Erythrocytic Virus.

Animals↗
PubMed1994

Light and electron microscopic examination of so-called piroplasms of fishes from Atlantic Canada and systematic revision of the Haemohormiidae (Incertae sedis).

Haemohormidium terranovae infections in American plaice and infections with a similar parasite in oceanpout were examined by light and electron microscopy. All plaice were infected at the time of capture and remained infected for over 2 yr. Prevalence in oceanpout varied seasonally between 0% and 80%. Uninucleate, binucleate, and tetranucleate forms were found in both species. In addition, octonucleate stages were observed in some erythrocytes of infected plaice. The presence of DNA in parasite nuclei was confirmed. There was no evidence of any ultrastructural feature characteristic of the phylum Apicomplexa. It is proposed that the genus Haemohormidium Henry, 1910 be considered incertae sedis and the senior synonym to Haematractidium Henry, 1910.

Animals↗
PubMed1993

Cytopathological changes induced by Haemogregarina myoxocephali in its fish host and leech vector.

The cytopathological effects of infection with Haemogregarina myoxocephali were investigated by light and electron microscopy in its fish host, Myoxocephalus octodecemspinosus, and in its leech vector, Malmiana scorpii. Gamont-infected erythrocytes in fish appeared vacuolated and exhibited shrinkage and altered shape consistent with loss of cytoskeletal integrity. Infected intestinal epithelial cells in leeches showed changes suggestive of recruitment of host metabolic functions by the developing parasite, including hypertrophied mitochondria and accumulations of endoplasmic reticulum and secretory vesicles next to the parasitophorous vacuole.

Animals↗
PubMed1992

Ultrastructure of the development of a species of Encephalitozoon cultured from the eye of an AIDS patient.

Human fibroblast cell cultures inoculated with microsporidia-infected corneal scrapings from an AIDS patient were fixed in situ and examined by scanning and transmission electron microscopy. The parasite grew prolifically and all developmental stages were observed. Meronts underwent binary fission and the daughter cells transformed into elongate, chain-like sporonts that eventually separated into sporoblasts. The formation of components of the mature spores is described. The parasite, a species of Encephalitozoon, underwent development both in the cytoplasm and within a parasitophorous vacuole, distinguishing it from the morphologically similar species E. cuniculi and E. hellem, both of which have been described from lesions in the human eye and have been reported to develop exclusively within a parasitophorous vacuole.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Alterations to the cytoskeleton of erythrocytes infected with frog erythrocytic virus: a fluorescence and electron microscopic study.

Erythrocytes of bullfrogs (Rana catesbeiana) infected with frog erythrocytic virus are spheroid and their nucleus is displaced. In contrast, uninfected cells are ellipsoid and have a centralized nucleus. Fluorescent staining revealed that these changes are correlated with alterations to components of the erythrocyte cytoskeleton. Uninfected erythrocytes contained a broad, continuous marginal band of microtubules, which appeared thinner and interrupted in infected cells. The described disruption of microtubules was associated with an inability to polymerize the tubulin pool with the addition of 12 microM taxol. The arrangement of submembranous microfilaments in uninfected erythrocytes was not significantly altered in infected cells. Vimentin filaments were distributed throughout the cytoplasm and around the nucleus of uninfected cells, and concentrated at the cell and nuclear peripheries. Cytoplasmic pockets that did not contain vimentin filaments were associated with the viral assembly site(s) in infected cells. These data suggest that the distortion of viral-infected erythrocytes could be due, in part, to an irreversible depolymerization of microtubules of the marginal band and a reorganization of the vimentin filament network.

Actin Cytoskeleton↗
PubMed1992

Cytoplasmic localization of the DNA virus frog erythrocytic virus.

In situ hybridization, using a biotinylated clone of frog erythrocytic virus (FEV), was conducted to determine the location of viral sequences in bullfrog erythrocytes. FEV-specific hybridization signals were found to correspond to mature cytoplasmic viral particles and assembly sites. These data are consistent with electron microscopic observations of viral assembly in the erythrocyte cytoplasm. Although FEV has morphological and biochemical properties similar to frog virus 3, our data suggest that the site of DNA replication and assembly of FEV is more similar to that of the poxviruses.

Amino Acid Sequence↗
PubMed1992

Cytopathological observations and epizootiology of frog erythrocytic virus in bullfrogs (Rana catesbeiana).

A 5 yr survey (1985 to 1989) revealed that the prevalence of frog erythrocytic virus (FEV) was significantly higher in juveniles than in adult bullfrogs (Rana catesbeiana) in Algonquin Park, Ontario (Canada). The prevalence of infection in juveniles declined during May and June and increased in early August, persisting until late September. Tadpoles were not infected naturally with FEV, but were susceptible to experimental infection. Experimental data indicate that FEV is neither waterborne, nor transmitted by the oral route, nor by the leech Desserobdella picta. The virus may be transmitted mechanically by the mosquito Culex territans, or the midge Forcipomyia (Lasiohelea) fairfaxensis. Nine percent recapture of marked uninfected frogs versus 4% recapture of infected animals suggests that FEV contributes to mortality of juvenile bullfrogs. Infected erythrocytes were transformed from ellipsoidal to spheroidal cells, some of which contained flattened elongate, trapezoidal inclusions. There was no evidence of denatured hemoglobin or significant change in the hemoglobin content of infected cells. Anemia recorded in heavily infected animals was not attributable to an increased osmotic fragility of infected erythrocytes.

Animals↗
PubMed1992

Allozyme comparison of three Trypanosoma species (Kinetoplastida: Trypanosomatidae) of toads and frogs by starch-gel electrophoresis.

Six metabolic enzymes, glucose-6-phosphate dehydrogenase, glucosephosphate isomerase, isocitrate dehydrogenase, malate dehydrogenase, phosphoglucomutase, and purine nucleoside phosphorylase, from clonal isolates of 3 presumptive species of Trypanosoma (T. fallisi, T. ranarum, and T. rotatorium) from 3 anuran hosts (Bufo americanus, Rana clamitans, and Rana catesbeiana) were compared using starch-gel electrophoresis. Although bands were shared among the different zymodemes of isolates of the same host genus, low genetic polymorphism of the enzyme loci was observed with few apparent shared bands between samples isolated from frogs and toads. A distance value calculated between toad and frog trypanosome isolates suggests the likelihood of long-time separation of species. Cluster analysis based on overall similarity distinguished the trypanosomes of toads and frogs as separate taxa, suggesting that host specificity and observed morphological differences are consistent with heritable allozyme differences.

Alleles↗
PubMed1992

Alternative leech vectors for frog and turtle trypanosomes.

Trypanosoma pipientis infections were achieved by exposing laboratory-raised bullfrog tadpoles (Rana catesbeiana) to the leech Desserobdella picta that had fed on infected frogs. Likewise, a laboratory-raised snapping turtle (Chelydra serpentina) was infected with Trypanosoma chrysemydis following exposure to infected Placobdella ornata. Transmission of the trypanosomes by these leeches constitutes new vector records for the parasites. The biology of D. picta and P. ornata suggests that they are more important in transmitting these flagellates than the species of leech previously reported as vectors.

Animals↗
PubMed1991

Development of Trypanosoma fallisi in the leech, Desserobdella picta, in toads (Bufo americanus), and in vitro. A light and electron microscopic study.

The development of Trypanosoma fallisi of Bufo americanus from Algonquin Park, Ontario was studied by light and electron microscopy in blood culture, in its leech vector Desserobdella (= Batracobdella) picta, and in its toad host. In culture, bloodstream trypomastigotes transformed within one day to elongate epimastigotes which divided into rosettes. These gave rise to amastigotes, spheromastigotes, stumpy and elongate epimastigotes, and slender metacyclic trypomastigotes over a 4- to 6-day period. Development in the leech crop was similar to that in culture, with fewer amastigotes and no spheromastigotes observed. The stages in the leech were similar in size to their culture counterparts, except for metacyclic trypomastigotes, which were larger in culture. Culture and leech stages possessed a well developed cytostome-cytopharyngeal complex and prominent reservosomes. The kinetoplast of crop stages was small with a rectangular profile, but became larger and basket-like in the proboscis forms. Migration of trypanosomes to the proboscis appeared to depend on the rate of digestion of the bloodmeal. Flagellates in the leech were also characterized by the presence of intracellular microorganisms. Development of culture forms to mature stages in the toad was completed within 8 days postinoculation, with the organisms transforming into the typical "C"-shape with a large square kinetoplast. Natural infection of B. americanus was detected at 3 days postfeeding by D. picta and the resulting bloodstream trypomastigotes developed more slowly than inoculated cultured stages.

Animals↗
PubMed1991

Infectivity of cultured Trypanosoma fallisi (Kinetoplastida) to various anuran species and its evolutionary implications.

Trypanosoma fallisi, a hemoflagellate infecting Bufo americanus from Ontario, was grown in vitro, and metatrypanosomes from the primary culture were inoculated into 4 uninfected test groups from 3 anuran families: Bufonidae, Hylidae, and Ranidae. In vitro-cultured T. fallisi was found to infect B. americanus and to induce transient infections in Bufo valliceps and Hyla versicolor. The flagellate was not infective to Rana clamitans. Trypanosoma ranarum was uninfective to the bufonids and hylids tested. These data suggest that the potential for host-switching decreases with increased evolutionary distance of the potential anuran host.

Animals↗
PubMed1990

Ultrastructural observations on the developmental stages of Lankesterella minima (Apicomplexa) in experimentally infected Rana catesbeiana tadpoles.

During May to August 1988, the prevalence of Lankesterella minima in bullfrog tadpoles and adults in the vicinity of Lake Sasajewun, Algonquin Park, Ontario, was 54.8% and 29.4%, respectively. The parasite was transmitted to laboratory-reared tadpoles through the bite of experimentally infected, laboratory-reared leeches (Batracobdella picta). Intraerythrocytic sporozoites were observed in the experimentally infected tadpoles 36 days postexposure (PE) to leech bites. Sporogonic stages in these tadpoles were examined by light and electron microscopy. Oocysts developed in vascular endothelial cells of several organs. Multinucleate oocysts at 29 days PE lay in a parasitophorous vacuole and contained several large inclusions. Mature oocysts, observed 32 days PE, contained about 70 sporozoites that exhibited typical apicomplexan features. In the posterior region of the sporozoites, 12 helically arranged chains of electron-lucent intrapellicular extended anteriorly from a dense terminal ring.

Animals↗