In the apical glandular region of the adult Proteocephalus torulosus (Batsch, 1786), two types of eccrine gland cells are present. The first type of unicellular gland produces large electron-dense granules of various sizes. The second type contains small electron-dense granules. Most cells form glands with large granules; glands with small granules are infrequent. The secretion of both types of gland cells is concentrated in the apical parts of the cyton and in the ducts opening to the exterior. On the scolex of P. torulosus, there are regional structural differences of the microthrix border. The apical glandular region bears filamentous microtriches only. On the remaining frontal part, surrounding the glandular region, there are blade-like and filamentous microtriches. The lateral parts of the scolex and suckers bear blade-like microtriches. Possible functions of both types of gland cells and different parts of the scolex microthrix border are discussed. The unique structure of the frontal part of the scolex of P. torulosus and its differences from Proteocephalus macrocephalus, P. longicollis and P. percae correlate well with the putative basal phylogenetic position of P. torulosus among European species of Proteocephalus.
The forebody and foregut of Crepidostomum metoecus Braun, 1900 are invested with a tegument bearing regularly arranged surface tubercles comparable with the aspidogastrean surface structures. The tegument of the ventrolateral lobes and of the prepharynx is penetrated by ducts of eccrine gland cells. The frontal and prepharyngeal gland cells, localised in the parenchyma, discharge electron-dense granules. Their ducts are lined by peripheral microtubules and fixed to the tegument plasmalemma by a septate junction. The functional roles of these glands are discussed.
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).
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.
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.
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.
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.
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.
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