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1

Ultrastructure of mucous areolae in the pig placenta

100%

Bielanska-Osuchowska Z.

Folia Histochemica et Cytobiologica

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1995

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tom 33

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nr 2

2

Ultrastructural characteristics of the uterine epithelium of aspidogastrean and digenean trematodes

80%

Poddubnaya L. G. , Levron C. , Gibson D. I.

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2011

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tom 56

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nr 2

EN

The ultrastructure of the uterus proper of the aspidogastrean Aspidogaster limacoides Diesing, 1835 and two digenean species, Phyllodistomum angulatum Linstow, 1907 (Plagiorchiida, Gorgoderidae) and Azygia lucii (Müller, 1776) (Strigeida, Azygiidae), was examined by transmission electron microscopy (TEM). The uterine epithelial lining of these species is thin, except for the perinuclear region of the epithelial cells. Septate junctions occur between adjacent epithelial cells within the uterine wall. The luminal surface of the cells is elevated into microlamellae, which project into the uterine lumen and cover the entire epithelial lining. Basally the uterine epithelium is attached to a basal matrix, and its supporting layers of muscle fibres are weak and composed of scattered circular muscles. Despite the marked similarity in the ultrastructural pattern of the aspidogastrean and two digeneans studied, there is some degree of variation in the secretory activity of their uterine epithelium. The high level of vesicular exocytotic activity in the epithelial cytoplasm of A. lucii may be associated with differences in egg emission and the subsequent life cycle involving a non-ciliated, non-swimming and non-free-living miracidium, as opposed to the free-swimming miracidium of P. angulatum. The similar nature of the uterine epithelium in all three species studied represents an ultrastructural marker possibly supporting a close phylogenetic relationship between the Aspidogastrea and the Digenea.

3

Ultrastructure of the embryonic envelopes and associated maternal structures of Distoichometra bufonis [Platyhelminthes, Cestoidea, Nematotaeniidae]

80%

Conn D. B.

Acta Parasitologica

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1999

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tom 44

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nr 1

EN

Eggs within paruterine capsules of gravid proglottids of Distoichometra bufonis were examined by light and transmission electron microscopy. The embryonic capsule was membranous, but was immediately underlain by a non-uniform subcapsular lamina that was an intracellular component of the outer embryonic envelope. The subcapsular lamina was thick and semi-rigid on anterior and posterior poles, but thin and membranous laterally, giving the entire egg a laterally oblong shape. In contrast, the embryophore was spherical and uniform in thickness. The paruterine capsule walls were derived from layers of flattened processes of medullary parenchyma cells lined internally with a layer of uterine epithelium. All these layers extended inward to form parenchyma-uterine partitions segregating each egg into an individual chamber. The uterine epithelium was very thin, syncytial, and contained numerous vesicles. Little uterine secretory product occurred in the uterine lumen or on the outer surface of the embryonic capsule. Except for the unique subcapsular lamina, most features of the eggs and paruterine capsule resembled those of other nematotaeniid species. The paruterine capsule wall was similar to that of Mesocestoides lineatus, a species whose paruterine organ lacks parenchyma-uterine partitions.

4

Late stages of egg maturation in the cestode Pseudhymenolepis redonica Joyeux et Baer, 1935 [Cyclophyllidea, Hymenolepididae], a parasite of shrews

70%

Tkach V. V. , Swiderski Z.

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tom 42

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nr 2

EN

Ultrastructural characteristics of developing eggs in the late preoncospheral and oncospheral stage and that of the uterine capsules in the hymenolepidid cestode, Pseudhymenolepis redonica Joyeux et Baer, 1935, are described. The uterus in this species breaks down very early into uniovular capsules. The uterine wall consisted of a syncytial flat uterine epithelium separated from the medullary parenchyma by a thin extracellular basal matrix. The uterine epithelium contained elongated nuclei with prominent nucleoli in the juxtalumenal cytoplasm. Its apical plasma membrane was folded into long microlamellae. The differentiating and mature oncosphere were surrounded by three envelopes: (1) an outer envelope, still containing the nuclei in the preoncospheral stage; (2) an inner envelope consisting of three layers - an extraembryophoral cytoplasmic layer, a thin and discontinuous embryophore, and intraembryophoral cytoplasmic layer; (3) a thin oncospheral membrane, closely surrounding the oncosphere. The relative thickness of the extraembryophoral and intraembryophoral layers of the inner envelope was changing during egg maturation. The numerous small mitochondria which were initially present only in the intraembryophoral layer, were concentrated later in the extraembryophoral layer and in many cases were observed in the embryophoral pores. The above data may suggest that these cytoplasmic organelles are pushed through the embryophoral pores as a result of the pressure of the developing oncosphere. The oncosphere surface was covered by the cytoplasmic oncospheral tegument, basal lamina and a layer of subtegumental somatic muscles. Several cell types were distinguished in the differentiating and mature oncospheres, namely: the germinative cells; somatic cells (= myocytons of somatic and hook muscles); the bi-lobed penetration gland with its secretory granules; the “neurosecretory” cells with their characteristic dense-cored membrane-bound vesicles. Each oncosphere had three pairs of embryonic hooks: one median, one dorso-lateral and one ventro-lateral pair. The degenerating hook-forming cells or oncoblasts remained visible around the hook handles. The details of the ultrastructure of the uterine capsules, oncospheral envelopes and different cell types of differentiating and mature oncospheres of P. redonica are discussed in comparison with literature data on other hymenolepidids, parasites of mammals and birds.