Wyniki wyszukiwania - Biblioteka Nauki

1

The effect of time and temperature on the infective activity of oncospheres of Fimbriaria czaplinskii Grytner-Ziecina, 1994

100%

Grytner-Ziecina B.

Acta Parasitologica

|

1994

|

tom 39

|

nr 3

2

Morphological studies on envelopes of oncospheres of the hymenolepidid cestode, Fimbriaria fasciolaris [Pallas, 1781]

75%

Chomicz L. , Grytner-Ziecina B. , Walski M.

Acta Parasitologica

|

1995

|

tom 40

|

nr 1

EN

The envelopes of oncospheres of Fimbriaria fasciolaris, found in the distal part of the strobila or free, were the subject of scanning electron microscope (SEM) and light microscope (LM) studies. The oncospheres inside the strobila were in close apposition to the uterine wall and showed morphological ties suggesting metabolic interactions. SEM studies allowed us to discern 3 stages of uterine development: early - with a continuous, tubular, and branched uterus; intermediate - with bulging parts of the uterus forming uterine capsules packed with oncospheres; late - with the uterus discontinuous, breaking down into uterine capsules, either individual or connected into chains of different lengths, containing 1 to 12 oncospheres. The uterine epithelium within uterine capsules was structurally heterogeneous, closely connected with the oncospheres, constituting a common uterine envelope. Infective eggs outside the strobila were deprived of the uterine envelope, and were joined together by separate external envelopes, easily visible in the LM. Live oncospheres observed over a 24 h period after liberation from the strobila exhibited alterations in taxonomically important features, such as dimensions and shape of the external envelope. The possible roles of different envelopes are discussed.

3

Ultrastructure of oncospheral hook formation in the cestode Mosgovoyia ctenoides [Railliet, 1890] Beveridge, 1978 [Cyclophyllidea, Anoplocephalidae]

63%

Mlocicki D. , Swiderski Z. , Conn D. B. , Eira C. , Miquel J. , Baranowska-Korczyc A.

Acta Parasitologica

|

2005

|

tom 50

|

nr 2

EN

The ultrastructure of oncospheral hook formation in the anoplocephalid cestode Mosgovoyia ctenoides (Railliet, 1890) Beveridge, 1978, is described. The hook morphogenesis takes place inside the six symmetrically arranged hook-forming cells, the oncoblasts. They show characteristic large nuclei of semilunar shape, localized at one pole of the embryo. At the beginning of the hook formation, the "hook-forming centre" appears in the cytoplasmic part of each oncoblast. It consists of numerous free ribosomes and polyribosomes surrounded by several mitochondria and Golgi complexes. The hook-forming centre is involved in synthesis of an electron-dense, undifferentiated hook primordium, which undergoes progressive differentiation and elongation into the fully developed hook. A fully formed oncospheral hook consists of the three parts: blade, shank, and base. Each hook, at the site of its protrusion from the oncosphere, is surrounded by two electron-dense rings interconnected by a circular septate junction. The hook material consists of two or three layers that differ in electron density: (1) a moderately electron-dense core, (2) a middle layer of low electron density, and (3) a highly osmiophilic cortex. Wide bands of hook muscles are attached to the basal and collar parts of the hook. The hook blades project outside of the oncospheral body into a large cavity delimited by the hook region membrane attached at this pole directly to the oncospheral surface. In the fully developed oncosphere of M. ctenoides, the three pairs of oncospheral hooks and their muscles form a complex "hook muscle system", responsible for coordinated hook action. The differentiation and ultrastructure of oncospheral hooks in the oncospheres of M. ctenoides are compared to those described in other cestode species.

4

Ultrastructural study of the embryonic development of the anoplocephalid cestode Anoplocephaloides dentata, an intestinal parasite of Arvicolidae rodents. II. Differentiation and cellular organisation of the oncosphere

51%

Swiderski Z. , Ndiaye P. I. , Miquel J. , Tkach V. , Marchand B. , Chomicz L. , Grytner-Ziecina B. , Sereda M. J.

Acta Parasitologica

|

2001

|

tom 46

|

nr 4

5

Ultrastructure of embryonic development of Inermicapsifer madagascariensis [Cestoda, Anoplocephalidae] with emphasis on the cellular organisation of the infective eggs

51%

Swiderski Z. , Tkach V. V.

Acta Parasitologica

|

2002

|

tom 47

|

nr 2

EN

The cellular organisation of the infective eggs of I. madagascariensis has been reconstructed at light (LM) and electron microscopy (EM) level from serial semithin (LM) and ultrathin sections (EM). The oncospheres are surrounded by parenchymatic capsules. The total number of oncospheral cells' is about 44 (50 nuclei). Among them, five major cell types have been distinguished. These consisted of: (1) a six-nucleate, U-shaped penetration gland; (2) a bi-nucleate medullary centre (= sunken perikaryon of oncospheral tegument); (3) two nerve cells of neurosecretory type; (4) about 30 somatic cells (= myocytons of hook and somatic musculature); and (5) about 12 germinative cells (two groups of 6 cells), localised in the posterior pole of the hexacanth. The functional ultrastructure of hook-muscle system and penetration gland and their role in host tissue penetration are discussed.

6

Ultrastructure of oncospheral envelopes and their differentiation in the cestode, Dicranotaenia coronula [Dujardin, 1845] [Cyclophyllidea, Hymenolepididae]

51%

Chomicz L. , Swiderski Z. , Grytner-Ziecina B.

Acta Parasitologica

|

1995

|

tom 40

|

nr 1

EN

Studies of the ultrastructure of oncospheral envelopes and their differentiation in the hymenolepidid cestode Dicranotaenia coronula in utero revealed four main envelopes: (1) capsule, (2) outer envelope, (3) inner envelope with a thin, electron-dense embryophore, and (4) oncospheral membrane. An additional hemispherical calotte, the hook region membrane covers one pole of the oncosphere and is attached to its surface. Both the outer and inner envelope represent syncytial layers which contain large, flattened nuclei of blastomeres which participated in their formation: nuclei of macromeres in the outer, and nuclei of mesomeres in the inner envelope. The granular cytoplasm of the both envelopes contains a large amount of free ribosomes, numerous mitochondria and several lipid droplets. The primary inner envelope of the early embryo forms in the later stage of embryogenesis its two derivatives: the embryophore and the oncospheral membrane. The hook region membrane oryginates from a syncytial binucleate complex by delamination of its cytoplasmic plate. Both the ultrastructural features of oncospheral envelopes and mode of their differentiation are compared with those described previously in the other hymenolepidids with aquatic and terrestrial life cycles. The ultrastructure of the oncospheral envelopes in D. coronula is discussed in relation to its life cycle and to environmental conditions in which the infective eggs remain for a certain period of time, until eaten by benthal ostracods, the intermediate hosts of D. coronula.

7

Ultrastructural studies on the cellular organisation of the oncospheres of the nematotaeniid cestode, Nematotaenia dispar [Goeze, 1782]

44%

Swiderski Z. , Tkach V. V.

|

tom 42

|

nr 3

EN

A complete reconstruction of the constituents of the mature egg of N. dispar has been attempted at the light microscope level based on serial semithin sections, and results have been correlated with partial reconstruction from ultrathin sections. The outer coat of the oncosphere consists of an anucleate cytoplasmic layer of tegument, a basal lamina, and two layers of peripheral, somatic musculature. The oncospheral hooks and their associated muscle system, situated in the anterior pole of the larvae, together with penetration gland secretion appear to play an important role in host tissue penetration. The bases of each lateral hook pair are joined by a common zone of “connective” material whereas the medial hook bases are embedded in individual cups of this material. Five major types of oncospheral cells have been distinguished. These consisted of: (1) a bi-nucleate medullary centre (= subtegumental cell); (2) a bi-nucleate, U-shaped penetration gland; (3) two nerve cells of neurosecretory type; (4) about 34 somatic cells (= cell bodies of somatic and hook muscles); and (5) about 12 germinative cells, arranged in two groups of six cells, situated in the posterior pole of the hexacanth. The position of oncospheral structures remains fixed in relation to one another but at the same time is somewhat arbitrary due to the high plasticity of the hexacanth during movements.

8

Electron microscopical studies on the cellular organisation of the oncospheres of the hymenolepidid cestode, Staphylocystoides stefanskii [Zarnowski, 1954]

44%

Swiderski Z. , Tkach V. V.

Acta Parasitologica

|

1999

|

tom 44

|

nr 1

EN

The cellular organisation of the oncospheres of S. stefanskii has been examined by means of light and transmission electron microscopy. The reconstruction of hexacanth larvae was based on serial semithin sections and its results have been correlated with partial reconstruction from ultrathin sections. The surface of the oncospheres was covered by a thin layer of oncospheral tegument. Five major cell types have been distinguished in mature oncospheres of S. stefanskii: (1) about 10 germinative cells, situated in the posterior pole of the oncosphere; (2) about 36 somatic cells (= myocytons of somatic and hook muscles); (3) a bi-nucleate medullary centre representing a perikaryon of oncospheral tegument; (4) a bi-nucleate, U-shaped penetration gland and (5) two nerve cells containing characteristic dense-core vesicles. The total number of cells in mature oncospheres was thus about 50, while the number of nuclei was about 52. The hook-muscle system of oncospheres, composed of peripheral and hook muscles, is similar to that described in other cyclophyllideans. The oncospheral hooks were formed in specialised hook-forming cells or oncoblasts. The oncoblasts are retained in mature oncospheres only as a thin layer of anucleated cytoplasm around the hook handle region, which seems to be a common feature for the mammalian hymenolepidids. The data on the oncospheral cell types and their number are in agreement with formerly proposed hypothesis (Swiderski 1972, 1983), assuming that the progressive reduction in number of oncospheral cells is one of the characteristic features in cestode evolution.