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Biomedical subjects

E Schein

Publications and source records attributed to E Schein.

At least 55 records · Page 3Linked to original sources
PubMed1986

Application of chemi- and bioluminescence in studies of immunological reactions against protozoa.

The opsonization and lysis of different protozoa by antibodies and/or complement was followed using luminol-dependent chemiluminescence and bioluminescence. The addition of immune serum to variable antigen type populations of Trypanosoma evansi led to the specific opsonization of trypanosomes resulting in an intense metabolic activation and chemiluminescence response of phagocytic cells. In comparison to those of uninfected control mice, the phagocytosis of coccidia merozoites by spleen cells from mice infected with Eimeria falciformis was enhanced during the acute stage of a primary infection. Opsonizing activity was demonstrated in phosphate-buffered saline extracts of gut contents of mice infected for 10 days. The incubation of E. falciformis merozoites together with guinea-pig complement resulted in slow lysis of the cells. The addition of mouse serum collected greater than 6 days after an infection led to an accelerated lysis of the merozoites, indicating the appearance of complement-fixing antibodies in the serum. Heat-inactivated immune serum alone had no lysing activity on merozoites. In the presence of complement, bovine lymphoblastoid cells infected with Theileria annulata were lysed by anti-lymphoblastoid cell serum raised in mice but not by serum from cattle which had developed immunity to Theileria annulata.

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PubMed1983

Ultrastructural study on the development of Babesia equi (Coccidia: Piroplasmia) in the salivary glands of its vector ticks.

The formation of Babesia equi sporozoites in the salivary glands of three tick species (Hyalomma anatolicum anatolicum, H. a. excavatum, Rhipicephalus turanicus) was studied by electron microscopy. The development was identical in all three vectors. On the 8th day post repletionem kinetes of B. equi had invaded alveoli of the nymphal salivary glands and were transformed to sporonts bounded by a single membrane. The sporonts were polymorphous bodies each with a highly lobed nucleus and numerous mitochondria. These stages persisted during ecdysis of the tick nymph to the adult stage. After attachment of these newly molted adults to a new host the formation of sporozoites was completed within five days. The sporonts occupied most of the infected alveolus and were extensively divided into cytoplasmic portions of various size. On the 4th day after attachment of the tick, sporozoite-anlagen, into each of which a nucleus and a mitochondrion were incorporated, appeared at the periphery of the sporonts. An apical complex with a polar ring, rhoptries, and micronemes was formed at the tip of each protruding anlage. Finally thousands of pyriform sporozoites (3.0 X 1.2 microns) filled the hypertrophied alveolus. This development is similar to sporogony in the genus Theileria.

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PubMed1983

Fine structure of Babesia equi Laveran, 1901 within lymphocytes and erythrocytes of horses: an in vivo and in vitro study.

The development of Babesia equi (Piroplasmia) in the vertebrate host was studied by electron microscopy. The tick-borne sporozoites initiated an exoerythrocytic schizogony in lymphocytes in vivo and in vitro. In lymphocyte cultures the schizonts of B. equi lay as fissured bodies directly within the host cell forming numerous cytomeres. These cytomeres were bordered by a single membrane and contained polymorphous nuclei. Merozoite differentiation was initiated at several places by protrusions appearing at the periphery of the cytomeres. The cytoplasm of the schizont merged progressively into the young merozoites. The mature merozoites were pear-shaped (2.0 X 1.5 microns), bounded by a pellicle and had an apical complex without conoid. Numerous merozoites were observed entering erythrocytes in vitro. In vivo, lymphocytes containing B. equi schizonts were seen in capillaries within lymph nodes from the 12th day onwards after attachment of infected ticks. At the same time some erythrocytes were found that contained B. equi merozoites. Development of B. equi in the vertebrate host shows many similarities to the corresponding development of Theileria parasites. This makes a new discussion of the taxonomic position of B. equi necessary.

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PubMed1981

Immunological aspects of Theileria annulata infection in calves. 1. E., EA, and EAC rosette forming cells in calves infected with T. annulata.

Peripheral blood lymphocytes (PBLs) from normal and Theilaria annulata-infected calves were assayed for E, EA, and EAC rosette formation. The E rosette forming cells showed the first increase on day 8 of the infection. This continued in all animals till day 14 the maximum increase was recorded. After that they showed reduced percentages of E rosettes, reaching normal values (as obtained before the infection) on day 24 to 30. When the recovered animals were challenged 64 days after the first infection, an increase in the percentage of E rosette formation was again observed. Although a moderate increase in the percentage of EAC rosette formation was recorded the tendency was the same as for E rosettes in regard to the course of the infection. In contrast to E rosettes, EAC rosettes remained constant during the challenge infection. The EA rosette forming cells generally had the same tendency as E rosettes during both the first and the challenge infection.

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PubMed1981

Immunological aspects of Theileria annulata infection calves. 2. Production of macrophage migration inhibition factor (MIF) by sensitized lymphocytes from Theileria annulata-infected calves.

Peripheral blood lymphocytes (PBLs) from calves infected experimentally with a stabilate of Theileria annulate, produced a factor which inhibited the migration of macrophages. This was first demonstrated against schizont antigen in some animals on day 8 post infection while in the others on day 12. The highest activity of the macrophage migration inhibition factor (MIF) was recorded on day 12 in some of the infected animals and on day 16 in the others, whereas on day 30 or more MIF was demonstrable. The MIF was also demonstrated against piroplasm antigen. 64 days after the first infection, the recovered calves were challenged with the homologous strain. It was found that PBLs from all challenged calves were able to produce MIF against both, schizont and piroplasm antigen. These results indicate occurrence of sensitized lymphocytes as effector cells of cell-mediated immunity to T. annulata infection.

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PubMed1981

Electron microscopical study on the effect of halofuginone on Theileria parva.

The effect of halofuginone (Stenorol) on schizonts of Theileria parva was studied by means of the electron microscope. After administration of 1,2 mg halofuginone per kg, it was observed that infected lymphocytes burst apart, whereas the intracellular parasites were at first little affected, showing some expansion of the perinuclear spaces. Once they were released from the cells, the schizonts degenerated completely. Apparently they are not capable of surviving outside the host cells. Probably this is due to the lack of a pellicle, which is characteristic for motile (i.e. normally extracellular) stages. The destruction of parasitized host cells occurred very rapidly, so that no infected cells could be observed 126 h after treatment. Uninfected lymphocytes were not affected by the drug.

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PubMed1981

Babesia equi (Laveran 1901) 1. Development in horses and in lymphocyte culture.

The vertebrate development of Babesia equi from infected Hyalomma marginatum in Morocco was investigated in vitro and in vivo. It was demonstrated that the sporozoites of B. equi initiate a phase of exo-erythrocytic schizogony in lymphocytes both in vitro and in vivo. On the other hand, sporozoites did not invade erythrocytes in vitro. The complete vertebrate life cycle of B. equi was simulated in vitro, from the invasion of lymphocytes by sporozoites, to the development of macro- and microschizonts, the invasion of erythrocytes by merozoites, and the subsequent intra-erythrocytic schizogony. In the equine host, macro- and microschizonts were detected in lymph node biopsies during the febrile phase on days 12 to 14 after application of ticks. As a result, the taxonomic position of B. equi appears to be uncertain.

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PubMed1980

Development of Theileria mutans (Theiler, 1906) in the gut and the haemolymph of the tick Amblyomma variegatum (Fabricius, 1794).

The development of Theileria mutans in the gut and haemolymph of its tick vector, Amblyomma variegatum, was studied by Giemsa-stained smears after the nymphal tick had completed engorgement on parasitaemic calves. Sexual stages occurred in the gut between five and seven days after repletion. The zygotes were observed in the gut from day 29 and the kinetes from day 30, i.e. three and four days after the nymphs moulted to adults. From day 34 kinetes were observed in the haemolymph. The developmental stages of T. mutans in the tick were compared with those of other Theileria spp. of cattle.

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PubMed1980

The development of Theileria=Cytauxzoon taurotragi (Martin and Brocklesby, 1960) from eland in its tick vector Rhipicephalus appendiculatus.

The sexual cycle of Theileria taurotragi was identified in the gut lumen of replete Rhipicephalus appendiculatur nymphs maintained at 28 degrees C which had fed on eland with rising parasitaemias. Macro- and micro-gametes developed from ring-form piroplasms within 24 h after repletion. The microgamonts were elongate with 2 or more lateral projections. The nuclei of the microgamonts divided into 4 and the microgamonts differentiated into 4 thread-like microgametes each with a central nucleus. Round macrogametes developed at the same time and stages indicative of the fusion of the macro- and microgametes were observed after 48 h. The resultant zygotes were detected in the gut wall cells by day 4, many being rounded and vacuolated with a peripheral nucleus. By day 7 the zygote cytoplasm became dense and they lay in clusters still within the cells. Binucleate zygotes were observed at this stage. The zygotes increased in size and by day 12 began to transform into kinetes by invagination. By the time the nymphs moulted into adults (about day 14), the kinete straightened to a broad anterior end and a tapering posterior with a mean length of 22.1 micrometer. Kinetes were detected in the haemolymph by day 16. By day 20 the kinetes had penetrated the salivary gland acinar cells where they underwent schizogony until the infected acinar cells were filled with multinucleated sporoblasts. The nuclei of the infected acinar cells became greatly enlarged soon after penetration of the kinete. Division of the sporoblast nuclei was stimulated by feeding of the adult ticks. From the 2nd day of attachment of the ticks to rabbits the sporoblasts underwent a process of schizogony to produce cytomeres. Each nucleus of the cytomere divided to produce several small nuclei which differentiated into uninucleated sporozoites.

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PubMed1980

Light and electron microscopic study on developmental stages of Babesia canis within the gut of the tick Dermacentor reticulatus.

The initial developmental stages of Babesia canis within the gut of the vector tick, Dermacentor reticulatus, were studied by means of light and electron microscopy. Large quantities of varying "spiky-rayed" stages and few ovoid stages without any protrusions were observed after lysis of the engorged canine erythrocytes. The transformation of spherical erythrocytic stages into "spiky-rayed" forms was initiated inside the intact erythrocytes. The significance of all developmental stages in a hypothetical life cycle of Babesia species is discussed.

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PubMed1979

Electron-microscopic studies on Theileria ovis Rodhain, 1916: development of kinetics in the gut of the vector tick, Rhipicephalus evertsi evertsi Neumann, 1897, and their transformation within cells of the salivary glands.

Gamogony of Theileria ovis Rodhain occurs within the gut of nymphs of the tick Rhipicephalus evertsi evertsi Neumann. After molting, spherical and ovoid parasites are found within the intestinal cells of the ticks. These stages are thought to be zygotes, because they undergo a transformation process leading ultimately (in 3 days) to the formation of a motile stage, the kinete, the fine structure of which is very similar to that of the ookinetes of the hemosporidia. The kinete leaves the gut cells of the tick and penetrates the salivary gland cells where it produces infective stages (the sporozoites). These stages may be transmitted to sheep during the next blood meal of the tick. The developmental processes of T. ovis are compared to those of Hemosporina.

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