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30662. Ultrastructure of the ovarian follicles, oviducts and oocytes of Gyrocotyle urna (Neodermata: Gyrocotylidea)
- Creator:
- Poddubnaya, Larisa G., Kuchta, Roman, Scholz, Tomáš, and Xylander, Willi E.R.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- Platyhelminthes, comparative morphology, TEM, ovary, oocapt, ovarian receptacle, and fertilisation canal
- Language:
- English
- Description:
- An ultrastructural study of the ovarian follicles and their associated oviducts of the cestode Gyrocotyle urna Grube et Wagener, 1852, a parasite from the spiral valve of the rabbit fish, Chimaera monstrosa L., was undertaken. Each follicle gives rise to follicular oviduct, which opens into one of the five collecting ducts, through which pass mature oocytes. These collecting ducts open into an ovarian receptacle which, in turn, opens via a muscular sphincter (the oocapt) to the main oviduct. The maturation of oocytes surrounded by the syncytial interstitial cells within the ovarian follicles of G. urna follows a pattern similar to that in Eucestoda. The ooplasm of mature oocytes contain lipid droplets (2.0 × 1.8 µm) and cortical granules (0.26 × 0.19 µm). The cytoplasm of primary and secondary oocytes contains centrioles, indicating the presence of the so-called ''centriole cycle'' during oocyte divisions. A morphological variation between different oviducts was observed. The luminal surface of the follicular and the collecting oviducts is smooth. The zones of the septate junctions are present within the distal portion of the net-like epithelial wall of the collecting ducts close to the ovarian receptacle. The syncytial epithelial lining of the ovarian receptacle, oocapt and main oviduct is covered with lamellae and cilia. Cortical granules secreted from mature oocytes occur freely within the lumen of the main oviduct that functions as a fertilisation canal. A division of the ovary into separated parts with their own collecting ducts as that typical of Gyrocotyle has been observed in neodermates, basal monogenean family Chimaericolidae, and Neoophora (some Proseriata and Fecampiidae). Ultrastructural data thus reveal several unique morphological characteristics of gyrocotylideans, the most basal taxon of tapeworms (Cestoda).
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
30663. Ultrastructure of the secondary osmoregulatory canals in the scolex and neck region of Silurotaenia siluri (Batsch, 1786) (Cestoda: Proteocephalidae)
- Creator:
- Žďárská, Zdeňka and Nebesářová, Jana
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Language:
- English
- Description:
- The secondary osmoregulatory canals in the scolex and neck region of Silurotaenia siluri, a parasite of the catfish Silurus glanis (L.), terminate below the tegument basal plasma membrane. The basal plasma membrane of the osmoregulatory canal syncytium is in tight contact with the tegument basal plasma membrane.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
30664. Ultrastructure of the spermatozoon of the digenean Lecithocladium excisum (Rudolphi, 1819) (Hemiuroidea: Hemiuridae), a parasite of marine teleosts in Senegal
- Creator:
- Ndiaye, Papa Ibnou, Diagne, Papa Mbagnick, Sène, Aminata, Bakhoum, Abdoulaye J. S., and Miquel, Jordi
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- Lecithocladium excisum, Hemiuridae, Digenea, spermatozoon, ultrastructure, Scomber japonicus, Scombridae, fish, and Senegal
- Language:
- English
- Description:
- The present study describes the ultrastructure of the mature spermatozoon of Lecithocladium excisum (Rudolphi, 1819) (Digenea: Hemiuroidea: Hemiuridae) from the stomach of the marine teleost Scomber japonicus Houttuyn (Scombridae) captured in the Atlantic Ocean, off Dakar (Senegal). The ultrastructural organization of the spermatozoon of L. excisum follows the general model described in most digeneans. It presents two axonemes of the 9+'1' pattern of the Trepaxonemata, nucleus, mitochondrion and parallel cortical microtubules, among other characters. However, some particularities of the spermatozoon of L. excisum are (i) the presence of a membranous ornamentation not associated with cortical microtubules in its anterior extremity, (ii) the presence of a very reduced number of cortical microtubules located only in the ventral side of the spermatozoon and (iii) the absence of several structures described in most digeneans such as spine-like bodies and cytoplasmic expansions.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
30665. Ultrastructure of the surface structures and secretory glands of the rosette attachment organ of Gyrocotyle urna (Cestoda: Gyrocotylidea)
- Creator:
- Poddubnaya, Larisa G., Scholz, Tomáš, Kuchta, Roman, Levron, Céline, and Gibson, David I.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- Cestoda, Gyrocotylidea, Gyrocotyle urna, rosette organ, adhesive secretion, secretory glands, and ultrastructure
- Language:
- English
- Description:
- The surface structures and gland cells of the posterior rosette organ of Gyrocotyle urna Grube et Wagener, 1852, a member of the group presumed to be the most basal of the tapeworms (Cestoda: Gyrocotylidea), was studied by scanning electron and transmission electron microscopy. Surface structures on the outer (oriented away from the intestinal wall) and inner (in contact with the intestinal wall) rosette surfaces differ from each other and represent a transitional form between microvilli and microtriches typical of tapeworms (Eucestoda). The inner surface of the rosette possesses numerous glands. On the basis of the size and electron-density of their secretory granules, three types of unicellular gland cells can be distinguished. The least common type (Type I) is characterized by the production of small, round, electron-dense granules of about 0.3 µm in diameter, whereas another type of secretion (Type II) is formed from homogenous, moderately electron-dense, spheroidal granules of about 0.7 µm in diameter. The most common type of glands (Type III) is recognized by a secretion comprising large, elongate, electron-dense granules of about 1 µm long and 0.5 µm broad. The secretory granules of the three types of the glands are liberated by an eccrine mechanism and the gland ducts open via small pores on the inner rosette surface. The complex of secretory glands of the posterior rosette of G. urna is similar to those in the anterior attachment glands of monogeneans (as opposed to the types of glands present in other helminth groups). However, the tegumental surface structures of Gyrocotyle are supporting evidence for the relationship between the Gyrocotylidea and Eucestoda.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
30666. Ultraviolet spectra of Algol binaries
- Creator:
- Plavec, Mirek J.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- astronomy, ultraviolet spectra, and Algol-binaries
- Language:
- Czech
- Description:
- A systematic study of the ultraviolet spectra of the Algol-like semidetached binary stars is described. Revision of the traditionally accepted spectral types has been found necessary in most cases toward earlier spectral types. Superionized emission lines seen at total eclipses show interesting differences in intensities.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
30667. Ultraviolet spectroscopy of the symbiotic star AG Pegasi
- Creator:
- D., Komárek, Z., and Vittone, A.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- observations, ultraviolet spectroscopy, and star AG Pegasi
- Language:
- Czech
- Description:
- High resolution UV spectroscopic observations of the binary symbiotic star AG Peg obtained with the IUE satellite in the periode 1978-81 are analyzed. The variability of the fluxes and the radial velocities of emission lines accordingto orbital phase are presented, The observaions support a binary model with mass transfer from a hot rotationaly unstable subdvarf to a cool M giant.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
30668. Ultraviolet-B induced changes in ultrastructure and D1/D2 proteins in cyanobacteria synechococcus sp. PCC 7942
- Creator:
- Chauhan, Sanjay, Pandey, Ritu, and Singhal, Gauri S.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- carotenoids, cell shape, chlorophyll, phycocyanin, and thylakoid
- Language:
- Multiple languages
- Description:
- Effects of ultraviolet-B (UV-B) irradiation on ultrastructure, total cellular protein, and PS2 proteins D1 and D2 of Synechococcus sp. PCC 7942 cells was studied. The scanning electron micrographs showed UV-B radiation induced bending of the cells. The transmission electron micrographs revealed disorganization and shift in thylakoid lamellar structure to one side of the cell. The cellular phycocyanin/chlorophyll ratio decreased with increasing UV-B treatment and due to this the colour of cells turned light-green. No apparent change in total cellular proteins was evident, but the contents of two major proteins of PS2, D1 and D2, showed decline due to UV-B irradiation, although to different extent. and Sanjay Chauhan, Ritu Pandey, Gauri S. Singhal.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
30669. Ultraviolet-B radiation (280-315 nm) invoked antioxidant defence systems in Vigna unguiculata (L.) Walp. and Crotalaria juncea L.
- Creator:
- Selvakumar, V.
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- ascorbate-glutathione cycle, ascorbate oxidase and peroxidase, catalase, dehydroascorbate reductase, glutathione transferase, monodehydroascorbate reductase, oxidative stress, peroxidase, and superoxide dismutase
- Language:
- Multiple languages
- Description:
- A crop legume Vigna unguiculata L. (Walp.) and a wild legume Crotalaria juncea L. were evaluated for their relative responses to the oxidative stress injury induced by various doses of UV-B radiation (UV-B, 280-315 nm; 0, 1.0, 1.4, 4.7, and 6.0 kJ m-2 d-1). A dose-dependent damage in lipid peroxidation was determined as an index of membrane injury caused by UV-B. The impact was significantly higher in V. unguiculata than in C. juncea. The specific activities of superoxide dismutase, ascorbate peroxidase, monodehydroascorbate reductase, and dehydroascorbate reductase increased directly proportional to UV-B doses. However, the activities of these enzymes were significantly higher in V. unguiculata than in C. juncea indicating that V. unguiculata was inflicted with more severe oxidative stress injury under UV-B. In C. juncea the glutathione reductase and ascorbate oxidase activities were 35 and 40 % greater than in V. unguiculata, respectively. Further, the non-enzymatic antioxidants ascorbate and glutathione, and their reduced/oxidizes ratios in C. juncea were much greater than V. unguiculata indicating C. juncea has an inherently greater antioxidative potential than V. unguiculata. Thus C. juncea is better adapted to oxidative stress than V. unguiculata by means of efficient cellular antioxidant mechanisms helping to combat the photooxidative stress injury elicited by UV-B.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
30670. Ultraviolet-B radiation or heat cause changes in photosynthesis, antioxidant enzyme activities and pollen performance in olive tree
- Creator:
- Koubouris, G. C., Kavroulakis, N., Metzidakis, I. T., Vasilakakis, M. D., and Sofo, A.
- Format:
- print, bez média, and svazek
- Type:
- model:article and TEXT
- Subject:
- fotosyntéza, klimatické změny, ozon, olivovník evropský, photosynthesis, climate changes, ozone, Olea europaea, Kréta (Řecko : ostrov), Crete (Greece), abiotic stress, lipid peroxidation, pollen germination, 2, and 581
- Language:
- Multiple languages
- Description:
- The present study attempts to determine how some physiological and reproductive functions of olive tree (Olea europaea L., cv. Koroneiki) respond to enhanced UV-B radiation or heat. Enhanced UV-B radiation was applied to (1) three-year-old potted plants in an open nursery (corresponded to ca. 16% ozone depletion), and (2) in vitro cultured pollen samples (220 μmol m-2 s-1, PAR = 400-700 nm + UV-B at 7.5, 15.0, or 22.5 kJ m-2 d-1). Potted olive plants were also subjected to high temperature (38 +- 4°C) for 28 h to mimic heat levels regularly measured in olive growing areas. A significant effect of UV-B on photosynthetic rate was observed. However, enhanced UV-B radiation did affect neither chlorophyll nor carotenoid content, supporting previous reports on hardiness of the photosynthetic apparatus in olive. Increased superoxide dismutase activity was observed in UV-B-treated olive plants (+ 225%), whereas no effect was found in the plants under heat stress. Neither UV-B and nor heat did affect H2O2 accumulation in the plant tissues. However, the same treatments resulted in enhanced lipid peroxidation (+ 18% for UV-B and + 15% for heat), which is likely linked to other reactive oxygen species. The increased guaiacol peroxidase activity observed in both treatments (+ 32% for UV-B and + 49% for heat) is related to the defense against oxidative membrane damage. The observed reduction in pollen germination (20-39%) and tube length (11-44%) could have serious implications on olive yields, especially for low fruit-setting cultivars or in years and environments with additional unfavorable conditions. UV-B and heat effects described here support the hypothesis that plant response to a given stressor is affected by the overall context and that a holistic approach is necessary to determine plant strategies for climate change adaptation., G. C. Koubouris, N. Kavroulakis, I. T. Metzidakis, M. D. Vasilakakis, A. Sofo., and Obsahuje bibliografii
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public