Ultrastructural Observations on Renal Schizogony of Leucocytozoon dubreuili in the American Robin |
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Authors: | STEVE T. C. WONG SHERWIN S. DESSER |
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Affiliation: | Department of Microbiology and Parasitology, Faculty of Medicine, University of Toronto, Toronto, Canada M5S 1A1 |
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Abstract: | SYNOPSIS. The schizogonic development of Leucocytozoon dubreuili in the kidney proximal tubule cells of the American robin, Turdus migratorius , was studied by electron microscopy. Renal schizogony is initiated by the entry of certain hepatic merozoites into cells of the proximal tubules. Development of the schizont consists of a coordinated sequence of events including extensive mitotic nuclear division, multiplication of mitochondria, increase in endoplasmic reticulum and ribosomes, differentiation of membranes, microtubules, micronemes and rhoptries, and cytoplasmic segmentation (cytomere formation). Merozoites form by budding around numerous centers in the schizont and, when mature, are bounded by a single plasma membrane subtended by microtubules. Each merozoite contains a large nucleus, a mitochondrion, and a well developed apical complex consisting of 3 polar rings, paired rhoptries, and numerous micronemes. An atypical nuclear division observed in some maturing schizonts was characterized by the multiple fission of a nucleus within a persistent outer nuclear membrane and the absence of mitotic spindle apparatus. Alterations in infected renal cells consisted of disorganization and loss of cytoplasmic organelles and the accumulation of lipofuscin-like inclusions. |
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Keywords: | Leucocytozoon dubreuili American robin, Turdus migratorius renal schizogony electron microscopy |
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