Ultrastrukturelle Untersuchungen zur ungeschlechtlichen Vermehrung von Frenkelia in der Leber der R�telmaus

Abstract

Bank voles (Clethrionomys glareolus) were infected by stomach tube with Frenkelia sporocysts from the faeces of buzzards (Buteo buteo). The voles were sacrificed at regular intervals and their livers examined electronmicroscopically. Seven days p.i. developmental stages of Frenkelia could be detected in liver parenchymal cells. The youngest schizonts detected are enveloped by a pellicle consisting of two membranes. This pellicle, which is in direct contact with the host cell mitochondria, shows marked invaginations which increase with the development of the schizont. A parasitophorous vacuole is not detectable. In developing schizonts numerous sections through nuclei with nucleic spindles and merozoite anlagen (dome-shaped) structures) are visible. It is not clear whether there are several nuclei or a section through one large and lobed nucleus. Within the merozoite anlagen the conoid and the subpellicular microtubules are formed first. By the prolongation of the dome-shaped structures towards the posterior pole, the nucleus and the other newly formed cell organelles are incorporated into the forming merozoite. The posterior pole of the merozoite still remains open at this stage of development. With increasing differentiation the merozoites become lancet-shaped, their apical poles bing always directed towards the periphery of the schizont. The outer membrane of the pellicle of the schizont forms the outer part of the pellicle of the merozoites by invaginating around them. At this stage of development the inner membrane of the pellicle of the schizont is no longer detectable. Thus the typical pellicle of the motile stages of sporozoaonsisting of three membranes is formed. In the centre of the merozoites which lie freely in the liver cell a residual body is present. The host cell reacts against the parasites by forming a thick border of mitochondria and distinct endoplasmic reticulum.

An Ultrastructural Study of First‐ and Second‐Generation Merogony in the Coccidian Sarcocystis tenella1

“…At 19, 21, and 25 DPI, second-generation meronts (Figs. [8][9][10][11][12][13][14] were found free in the cytoplasm of host cells in glomerular capillaries as well as in capillaries associated with convoluted tubules. In glomerular capillaries, the host cell was completely surrounded by a basal lamina, on the other side of which was a typical endothelial cell or foot processes of podocytes and the urinary space (Figs.…”

“…In glomerular capillaries, the host cell was completely surrounded by a basal lamina, on the other side of which was a typical endothelial cell or foot processes of podocytes and the urinary space (Figs. [8][9][10][12][13][14].…”

Sarcocystis neurona n. sp. (Protozoa: Apicomplexa), the Etiologic Agent of Equine Protozoal Myeloencephalitis

“…species name is derived from neural (Greek) and refers to the location of the parasite.RemarksStructurally, schizonts of S. neurona closely resemble the schizonts of other species of Sarcocystis and Frenkelia(Krampitz et al 1976;Gobel et al, 1978;Geisel et al 1979; Dubey, Speer, and Fayer, 1989). Also the merozoites of S. neurona lack rhoptries, are located free in the host cell cytoplasm and divide by endopolygeny.…”