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Aporocotyle simplex
No full text<i>3.1. The anterior foregut of A. simplex</i> <p> With SEM, the anterior extremity of the <i>A. simplex</i> body has an anterior depression opening into the mouth cavity (Fig. 1A). In LM</p> <p>Fig. 1B and C the long esophagus surrounded by the compact cellular masses, which extend up to the bifurcation of the H-shaped caecum, may be clearly seen, with shorter right and left anterior caeca and longer right and left posterior caeca, which end near the posterior extremity (Fig. 1B). In TEM longitudinal sections, the mouth cavity is funnelshaped (Fig. 1D–F), and the ciliated sensory endings are located around the mouth cavity (Fig. 1E). The syncytial lining of the anterior foregut is continuous with the distal syncytial tegumental cytoplasm of the body and both have similar cytoplasmic inclusions, electron-dense tegumental bodies and vesicular inclusions (Fig. 1E and H). The syncytial lining of the body and anterior foregut is surrounded by thin basal lamina and a thick extracellular basal matrix separates the syncytial cytoplasm from the underlying muscle fibres; their luminal surface bears irregular knob-like outgrowths (Fig. 1E and H). Behind the mouth cavity, the foregut syncytial lining (about 15–22 μm in the length) is surrounded by circular and radial muscle fibres (Fig. 1D, F, G). Directly beneath the extracellular matrix surrounding this foregut region (muscular anterior foregut), circular muscle fibres are arranged into 8–10 isolated bands on each canal side (Fig. 1D–G). Radial muscle fibres appear to run between the circular bands (Fig. 1E, F, I). These radial fibres represent the branchings of two powerful radial bands of antero-lateral orientation situated on both sides of this foregut region (Fig. 1D F, G). The distal margins of the radial muscles are attached by hemidesmosomes to the canal extracellular matrix (Fig. 1I). The muscle fibres of the anterior foregut are supplied with nerve fibres (Fig. 1F). Some deep lateral folds of the distal epithelial layer may be observed along the anterior foregut (Fig. 1E, F, G).</p>Published as part of <i>Poddubnaya, Larisa G., Hemmingsen, Willy & MacKenzie, Ken, 2023, Digestive system of the marine blood fluke, Aporocotyle simplex (Odhner, 1900) (Digenea: Aporocotylidae) with consideration of the digenean digestive morphology, pp. 11-22 in Zoologischer Anzeiger 305</i> on page 12, DOI: 10.1016/j.jcz.2023.05.003, <a href="http://zenodo.org/record/10376067">http://zenodo.org/record/10376067</a>
Aporocotyle simplex
No full text<i>3.2. The anterior esophagus of A. simplex</i> <p>The long unbranched esophagus leads directly from the muscular anterior foregut (Fig. 1D, G and 2A). The esophageal epithelial lining is a prolongation of the anterior foregut epithelium with sunken cell bodies (Fig. 2C). The epithelial syncytial lining of the short anterior esophageal portion projects its cytoplasm into the lumen, possessing luminal irregular, broad and angular cytoplasmic protrusions variable in shape and size (Fig. 2B, C, E). Due to these cytoplasmic protrusions, the esophageal cytoplasmic lining varies in thickness from 0.2 to 6.5 μm and contains a number of electron-dense bodies, which are similar to those that fill the body syncytial tegumental cytoplasm and anterior foregut epithelium (Fig. 2B, C, E). Besides tegumental dense bodies, numerous rounded vesicles (about 0.2–0.3 μm in diameter), with moderately dense content or empty-looking, fill the cytoplasmic matrix (Fig. 2B, C, E). These vesicles may liberate their contents into the esophageal lumen (Fig. 2B, C, E). An extensive system of regularly arranged tubular structures is present in the moderately dense cytoplasm of the esophageal lining (Fig. 2E). The luminal surface of the epithelial lining is smooth, the basal plasma membrane is surrounded by a thin electron-dense basal lamina and a thick layer of extracellular matrix, below which are thick bands of circular and longitudinal myofibrils (Fig. 2B and C). Sunken cell body processes connect to the epithelial lining and open into the epithelial cytoplasm (Fig. 2C). The distal portion of these processes contains numerous longitudinally oriented microtubules and electron-dense bodies in their cytoplasmic matrix (Fig. 2C). Electron-dense membranous whorls may be present within the anterior foregut as well as within the anterior esophageal lumen (Fig. 2B).</p>Published as part of <i>Poddubnaya, Larisa G., Hemmingsen, Willy & MacKenzie, Ken, 2023, Digestive system of the marine blood fluke, Aporocotyle simplex (Odhner, 1900) (Digenea: Aporocotylidae) with consideration of the digenean digestive morphology, pp. 11-22 in Zoologischer Anzeiger 305</i> on page 12, DOI: 10.1016/j.jcz.2023.05.003, <a href="http://zenodo.org/record/10376067">http://zenodo.org/record/10376067</a>
Glandular cell products in adult cestode: A new tale of tapeworm interaction with fish innate immune response
No full textThe caryophyllidean tapeworm Caryophyllaeus brachycollis (Janiszewska, 1953) is indigenous to the Lake Blidinje in the west-central part of Bosnia-Herzegovina where it infects chub Squalius tenellus (Heckel, 1843). Of 22 chubs examined, 45% were infected with C. brachycollis and a total of 912 specimens of this worm were counted. Histopathological and ultrastructural investigations were conducted on interface region between chub intestine and cestode scolex. Different sizes of lipid droplets in cestode tegument, in interface region and in chub enterocytes were observed. C. brachycollis lacks any specialized attachment organs and with an expanded, flattened scolex goes deep in mucosal folds and firmly attaches to them. In the epithelium of fish intestine, near the site of worm attachment, a high number of mucous cells and several rodlet cells were noticed. Indeed, within the intestinal tunica propria-submucosa, beneath the site of scolex attachment, numerous neutrophils and mast cells were encountered. Transmission electron microscopy of the apical part of the scolex of C. brachycollis showed the occurrence of a multicellular, syncytial glandular complex, the scolex produced membrane-bound secretory granules and their fibrillar contents discharged by merocrine and apocrine secretion onto the host-parasite interface. Our results are among the first to provide evidence on the sophisticated relationship between fish intestine and amorphous-undefinable substance produced by scolex glandular complex
Aporocotyle simplex
No full text<i>3.4. Gastrodermis of A. simplex</i> <p> Along its entire length, the syncytial epithelial lining of the caecum is composed of a morphologically uniform, syncytial layer, possessing considerable variation in the thickness of the epithelial lining from 0.5 to 15.0 μm, without marked differences between its anterior and posterior regions (Fig. 4A and B). Most of the luminal volume of the caecum is filled with moderately dense amorphous finely dispersed material (Fig. 4A, B, I, K). In addition, there are both dark inclusions of different shape and different kinds of residual bodies within the caecal lumen (Fig. 4A and K). The gastrodermal luminal surface is increased by numerous thin, flexible lamellae, which project a short distance into the lumen and range in length from 0.9 to 2.5 μm (Fig. 4B and K). The basal plasma membrane of the gastrodermal syncytial lining is thrown into numerous basal invaginations, which may be confined to the lower haft of the gastrodermis, but may extend to the luminal membrane (Fig. 4C). The gastrodermal lining is underlain by a thin basal lamina and thicker layer of fibrous extracellular matrix (Fig. 4B). Thin fibres of circular muscles are embedded in the surrounding extracellular matrix (Fig. 4C and D). The syncytial cytoplasm contains elongated oval or irregularly shaped nuclei with dense patches of heterochromatin, which usually occupy the central or basal positions within the epithelial lining (Fig. 4A and B). The dense cytoplasmic matrix of the gastrodermis contains cisternae of granular endoplasmic reticulum, which are usually located in the proximity of the nuclear areas (Fig. 4B and H). Golgi bodies give rise to ovoid membrane-bound rounded vesicles ranging from 0.1 to 0.3 μm in diameter, which may occur throughout the syncytial layer (Fig. 4B, G, H, insert, K). These vesicles contain an agglomeration of finely dispersed, flocculent and moderately dense material (Fig. 4G and H insert, I). Regularly arranged tubular arrays are scattered throughout the gastrodermal syncytial lining (Fig. 4E, H, I, J). Occasionally, multivesiculate bodies (about 0.4 μm in diameter) are dispersed in the upper portion of the syncytial cytoplasm (Fig. 4G). Different kinds of residual bodies are scattered throughout the cytoplasm (Fig. 4C D, F, H, I, J). Some bodies show a combination of alternate electron-dense glandular and moderately dense finely dispersed material (Fig. 4F, H, I, J). The membrane-bound Golgi vesicles appear to fuse with residual bodies (Fig. 4F and I). Occasionally, there are large residual bodies (from 2.0 to 2.6 μm in diameter) containing heterogeneous, flocculent and moderately dense material, within which are scattered clumps of electron dense material (Fig. 4C and D). In Fig. 4H three stages of development of such bodies may be observed in the gastrodermal cytoplasm. The nascent body (<i>nb</i>) is about 0.4 μm in diameter containing moderately dense flocculent, loosely packed material with a few pinpoint clumps of dense material and, a short way off it, the network of tubular structures and Golgi vesicles (Fig. 4H). As such bodies develop, their diameter begins to increase from 0.9 μm (<i>dlb1</i>) to 1.5 μm (<i>dlb2</i>) and the amount of both flocculent moderately dense and clumpy dense material increases (Fig. 4H). In the worms studied, along the entire length of the caecum there are areas in a secretory-absorptive phase possessing a highly vacuolated luminal surface, where the lamellae may be of various configurations and appear to be recurved to form loops (Fig. 4B, I, J). In such gastrodermal areas the percentage of the granular endoplasmic reticulum and the Golgi complexes increases and the amount of Golgi vesicles begins to increase in the gastrodermal cytoplasm (Fig. 4B and K). The numerous vesicular-like surface depressions are filled with trapped material from the gastrodermal lumen, demonstrating the subsequent stages of their endocytosis into the gastrodermis (Fig. 4I–K). Also, between flattened lamellae an agglomeration of residual material is entrapped (Fig. 4I and J).</p>Published as part of <i>Poddubnaya, Larisa G., Hemmingsen, Willy & MacKenzie, Ken, 2023, Digestive system of the marine blood fluke, Aporocotyle simplex (Odhner, 1900) (Digenea: Aporocotylidae) with consideration of the digenean digestive morphology, pp. 11-22 in Zoologischer Anzeiger 305</i> on page 16, DOI: 10.1016/j.jcz.2023.05.003, <a href="http://zenodo.org/record/10376067">http://zenodo.org/record/10376067</a>
Aporocotyle simplex
No full text<i>4.4. Gastrodermal ultrastructural features of A. simplex</i> <p> As shown in the present investigation, the lumen of four ramifications of the caecum in all studied specimens of <i>A. simplex</i> is filled with moderately dense amorphous finely dispersed material, in which dark inclusions and residual bodies are embedded. In <i>A. simplex</i> the luminal amplification of the syncytial gastrodermal lining is flexible lamellae, ranging in length from about 0.9 to 2.5 μm. A single cell type constitutes the digenean cellular or syncytial lamellated caecal epithelial lining (gastrodermis), the cytological nature of which changes with each phase of the digestive activity for both secretory and absorptive functions (Davis et al., 1968; Robinson and Threadgold, 1975). As shown in our study, in the case of <i>A. simplex</i>, the secretory and absorptive functions in the gastrodermal syncytial epithelium may be observed along different regions of the caecum, performing both functions simultaneously. As noted by Robinson and Threadgold (1975), every gastrodermal cell (or gastrodermal syncytial region) shows an alternation in phases of its activity and the ability of the gastrodermis to perform some function. Robinson and Threadgold (1975) suggested that the various organelles of each gastrodermal region may reflect the physiological state of the particular region. Moreover, Davis et al. (1968) noted that secretory and nonsecretory digestive cycles exist in the cellular gastrodermis of the plagiorchiid, <i>Heamatoechus medioplexus</i>, and it is highly probable that both functions are performed simultaneously whenever food is present in the caecal lumen. The presence of a secretory cycle in the cellular gastrodermis of the plagiorchiid <i>P. epiclitum</i> was indicated by Mattison et al. (1992). In another plagiorchiid feeding on blood, <i>Fellodistomum fellis</i>, as in polyopisthocotylidean monogeneans, the digestive caeca consists of a layer of digestive cells overlain by a syncytial layer of connective tissue (Halton, 1997). In contrast to polyopisthocotylideans, digestive cells possessing intracellular hemoglobin degradation (Konstanzov´a et al., 2015; Poddubnaya et al., 2015; Cable and El-Naggar, 2021) in <i>F. fellis</i> haemoglobin is not degraded within digestive cells, but is entrapped and digested within pockets formed by luminal lamellae, in which contents of zymogen-like granules are released with subsequent formation of residual haematin bodies. Such a type of digestion is called extracellular (Halton, 1997). It should be emphasized that for the digeneans Bogitsh (1993) assumed the absence of intracellular digestion of exogenous food in the gastrodermis, but the presence of extracellular digestion in the caecal lumen, in so-called ‘superficial digestive vacuoles’ formed by the luminal lamellae. However, in other studies of blood flukes, the schistosomes demonstrated the acidic contents of their gastrodermis, suggesting that it is a site of hemoglobinolytic action and the enzymes secreted by the gastrodermis (Bogitsh and Davenport, 1991). Distribution of acid phosphatase activity was associated with the luminal surface of the gastrodermis, gastrodermal lysosome-like structures such as the multivesiculate bodies, a variety of cytoplasmic vesicles and bodies in the schistosome gastrodermis (Bogitsh and Shannon, 1971). Acid phosphatase was established as a marker for lysosomes and related organelles such as food vacuoles and may reflect the presence of a lysosome system in the digenean gastrodermis (Ernst, 1975; Bogitsh and Ryckman, 1982). Moreover, the proteolytic pathway of hemoglobin digestion in the schistosome gastrodermis may indicate endopeptidase, as asparaginil, which has a pivotal role in haemoglobin digestion (Dalton et al., 1995). In the gastrodermal cytoplasm of <i>A. simplex</i> there are extensive GER and Golgi complexes producing rounded vesicles (0.1–0.3 μm in diameter) containing an agglomeration of finely dispersed substance. In addition, the occurrence of multivesiculate bodies (0.4 μm in diameter), different kinds of residual bodies (2.0–2.6 μm in diameter), and large residual bodies (0.9–1.5 μm in diameter) may indicate the gastrodermal pathways of haemoglobin digestion in the studied marine aporocotylid species. The presence of protein synthesis in the gastrodermis is indicated by the observation that the enzymes enclosed within the Golgi vesicles are primary lysosomes (Bogitsh and Davenport, 1991). As shown our investigation, haematin accumulates in the gastrodermal lumen of <i>A. simplex</i>. The fact that haematin occurs both intracellularly (within residual bodies) and within the gastrodermal lumen between lamellae may suggest the possibility that it is being moved across the membrane. As Morris (1968) postulated for schistosomes, and we assume it is true for the aporocotylid blood fluke, <i>A. simplex,</i> a combination of extra- and intracellular digestion occurs. Extracellular digestive enzymes produced by the esophagus initiate the digestion of hemoglobin, and the digestive process may then be completed after uptake by the gastrodermis, in which ‘an intermediate is phagocytosed and broken down to simple end products’ (see Morris, 1968, p. 482). Moreover, the presence of a number of regularly arranged tubular arrays in the gastrodermal cytoplasm of <i>A. simplex</i> may support a transport system of host proteins from the gastrodermal lumen to the intracellular reticular system of channels of gastrodermal cytoplasm.</p> <p> Another aporocotylid species, the freshwater blood fluke <i>S. inermis</i>, has five, short, reduced intestinal outgrowths, the luminal surface of which lacks lamellae (McMichael et al., 1994a). In the brief description of the <i>S. inermis</i> intestine by McMichael et al. (1994a), the expanded cisternae of GER and Golgi complexes and electron-dense granules are restricted to some gastrodermal areas. However, these authors assumed that this is likely to facilitate food transport across the external tegument and might account for the reduction of the intestine and apical gastrodermal projections in the genus <i>Sanguinicola</i>. It is pertinent to note here that the previously published ultrastructural studies on the tegumental structure of the aporocotilid digeneans, <i>A. simplex</i> and <i>S. inermis</i>, have revealed no morphological evidence, which may reflect the physiological state for blood feeding through the tegument (Poddubnaya et al., 2019; 2020b). Moreover, the distal cytoplasmic layer of these two aporocotylid digeneans is poor in organoids and vesicular inclusions. Further, using nucleotide pulse-chase, Lee (2023) noted that a large proportion of stem cells produce tegument precursors in schistosomula/juveniles. ‘Such continuous replenishment of stem cell-driven tegument cell production likely contributes to the schistosome’ s ability to evade host immunity’ (Lee, 2023, p. 4). We may assume that the presence of short intestinal caeca in species of the genus <i>Sanguinicola</i> is a result of miniaturization of both body size and organs in the species of this genus. In any case, for freshwater species of the genus <i>Sanguinicola,</i> additional studies of the digestive system are required.</p>Published as part of <i>Poddubnaya, Larisa G., Hemmingsen, Willy & MacKenzie, Ken, 2023, Digestive system of the marine blood fluke, Aporocotyle simplex (Odhner, 1900) (Digenea: Aporocotylidae) with consideration of the digenean digestive morphology, pp. 11-22 in Zoologischer Anzeiger 305</i> on pages 19-20, DOI: 10.1016/j.jcz.2023.05.003, <a href="http://zenodo.org/record/10376067">http://zenodo.org/record/10376067</a>
Aporocotyle simplex
No full text<i>4.3. Esophageal ultrastructural features of A. simplex</i> <p> Thirdly, our ultrastructural data allowed us to subdivide the long esophagus of <i>A. simplex</i> into two morphologically different parts - a short anterior and a long middle - posterior esophagus. The anterior esophageal portion resembles that of the body tegument and retains morphologically similar cytoplasmic inclusions and sunken perikarya, but differs in the absence of knob-like surface outgrowths and the presence of irregular, broad and angular cytoplasmic protrusions along the esophageal cytoplasmic lining. However, the middle-posterior esophageal portion retains only the basic tegumental cytoarchitecture and possesses considerable morphological modifications of the syncytial cytoplasmic lining by variations in the shape of long, bunched, extensive cytoplasmic protrusions, forming a reticular network through the esophageal lumen, and the sunken epithelial bodies are modified into well-developed esophageal glands. In <i>A. simplex,</i> however, based on a light microscopical description by Thulin (1980), the length of the esophagus in adult specimens is about 1/6 of the total body length and it may be divided into two parts, the first of which occupies 2/3 of the total esophageal length. Our TEM data supported another kind of esophageal morphological division, which corresponds to the data observed for schistosomatid blood flukes. As in <i>A. simplex</i>, the anterior portion of the esophagus in <i>S. mansoni</i> has tegumental inclusions identical to those of the external tegument, while in the middle and posterior portions the folded projections contain other cytoplasmic inclusions and the esophageal nucleated cell bodies form so-called esophageal glands (Morris and Threadgold, 1968; Ernst, 1975). Besides, in the freshwater adult aporocotylid blood fluke, <i>S. inermis</i>, the esophagus is divided into three regions, distinguished by the morphology and arrangement of the apical cytoplasmic lining (McMichael-Phillips et al., 1994a, b). In the three abovementioned blood flukes, the esophageal epithelial cytoplasm consists of a number of morphological characters, which are unique for each studied species (Morris and Threadgold, 1968, Ernst, 1975; McMichael-Phillips et al., 1994a; Present study). Generally, in the Trematoda the esophagus varies in the fine morphology from group to group. In the trematode <i>Aspidogaster conchicola,</i> the short esophagus has tegumental traits with a number of uniciliate sensory endings (Halton, 1972). In a plagiorchiid digenean of the family Paramphistomatidae, <i>Paramphistomum epiclitum</i>, the esophageal lining has irregular corrugations with flattened ridges and secretory esophageal cytons (Mattison et al., 1992). Another plagiorchiid digenean of the family Gyliauchenidae, <i>Gyliauchen nahaensis</i>, has three morphologically distinguishable esophageal parts ornamented with rugae-like surface projections and secretory esophageal sunken cytons (Jones et al., 2000). Aporocotylids have a diet of dissolved matter in the blood fluid surrounding them. Interestingly, in the case of plagiorchiid gyliauchenids and paramphistomids with fluid diet (see Mattison et al., 1992; Jones et al., 2000), Jones et al. (2000) suggested that there has been a succession of innovations in the evolution of the feeding of gyliauchenids. Their oral sucker was lost first as a change to a fluid-based diet occurred, and the esophagus lengthened and adopted a major role in the digestion of the food (Jones et al., 2000). The above suggestion by Jones et al. (2000) may also be true for aporocotylid digeneans. As mentioned above, the absence of an oral sucker is not characteristic of all members of the family Aporocotylidae. Some adult fish blood flukes retain the cercarial anterior sucker, but seemingly lack a pharynx (Bullard and Overstreet, 2003; 2004; McVay et al., 2011).</p> <p> For schistosomatid blood flukes, it has been suggested that the digestion of host erythrocytes commences in the esophageal region of the digestive tract, and that the final phases of digestion occur in the lumen of the intestine (Morris, 1968; Ernst, 1975). Schistosomes have a glandular esophagus, and secretory cells are modified sunken epithelial bodies, which are a source of digestive enzymes, and digestion of blood cells begins in the esophagus (Ernst, 1975; Halton, 1997). Present data on the <i>A. simplex</i> esophagus are in complete agreement with those obtained for schistosomes. As shown in our study, the esophageal morphological features of <i>A. simplex</i> might suggest a digestive-absorptive function for the middle-posterior esophageal region surrounded by compact cellular complex, in which sunken glandular perikarya of different development stages and their cytoplasmic processes mix with muscle cells as well as with extensive nerve fibres. In <i>A. simplex</i> each esophageal secretory granule has heterogeneous content with a dense thin outer halo and less dense inner core. Such granules are surrounded by the lucent or moderately dense matrix of the vacuole, within which each granule is embedded. Such a glandular appearance shows morphological similarity with digestive vacuoles described in the gastrodermal digestive cells of polyopisthocotylean monogeneans (Poddubnaya et al., 2015; Cable and El-Naggar, 2021). In the cercaria of the freshwater aporocotylid, <i>S. inermis</i>, the esophageal secretory granules are similar to those of <i>A. simplex</i>, but there is no information on their vacuolar appearance (McMichael-Phillips et al., 1994a, b). However, in schistosomatid <i>S. mansoni,</i> esophageal secretory granules of varied shape display a highly structured morphology, each granule consisting of a dark substance with crystalline structure (Morris and Threadgold, 1968) or with rays of tubules (Bogitsh and Carter, 1977). Usually, particular attention has been concentrated on the cytochemical composition of the esophageal secretory product in <i>S. mansoni</i> (Ernst, 1975; Bogitsh and Carter, 1977). Ernst (1975) indicated that the posterior esophageal portion of <i>S. mansoni</i> contains substantial acid phosphatase activity both in the lining of the esophageal lumen and in the sunken perikarya connected to this lining. The reaction product in this region occurs in some membrane-bound vesicles and in the basal infoldings of the cytoplasmic lining. These acid-phosphatase-positive vesicles are found in the esophageal cell bodies and in the Golgi complexes and granular endoplasmic reticulum, suggesting that these proteins are being synthesized and packaged in the cell bodies and then transported to the esophageal cytoplasmic lining. Also, the cytochemical results of Bogitsh and Carter (1977) have shown that esophageal granules contain carbohydrate-containing endopeptidase, which is capable of digesting hemoglobin. Biochemical and molecular data indicated proteolytic pathways of haemoglobin digestion in schistosomes (Halton, 1997). Immunocytochemistry has shown that the complex of hydrolytic proteinases (cysteine endopeptodases) is involved in the sequential degradation of haemoglobin to readily absorbable peptides, all of which are expressed in the schistosome gastrodermis (Dalton et al., 1995).</p> <p> The abovementioned cytochemical data for <i>S. mansoni</i> is supported by our morphological data on the <i>A. simplex</i> esophagus. In studied specimens of <i>A. simplex</i>, clots of host blood cells in various stages of decay were found in close proximity to epithelial cytoplasmic protrusions within the lumen of the posterior esophagus. As a result of blood cell disintegration, the conglomerations of moderately dense substance, in which small vesicles and dense formless inclusions are embedded, may be seen in the esophageal lumen.</p> <p> Additional data by Ernst (1975) shows that, like the tegument, the anterior portion of the esophagus contains negligible cytochemically demonstrable acid phosphatase activity. Contrary data by Cesari (1974) show that most of the acid phosphatase activity in <i>S. mansoni</i> males is located in the epidermis, but in the opinion of Ernst (1975) the techniques employed by Cesari (1974) do not allow the determination of the original cytological site of the soluble enzyme activity measured in the supernatant fractions. Also, Pappas (1988) suggested that it is basically correct that the tegument is the primary source of nutrients for adult digeneans during short-term <i>in vitro</i> incubations, but that “trematodes do not readily feed under artificial (<i>in vitro</i>) conditions, so the value of such experiments remains questionable” (see Pappas, 1988, p. S110).</p> <p> Additionally, besides differentiated esophageal secretory perikarya, there are undifferentiated cells, cells at the beginning stage of their differentiation and disintegrated cells in the compact cellular masses surrounding the middle and posterior esophagus of <i>A. simplex</i>. Taking into account that esophageal glandular cells are considered to be an initial site of blood processing, with blood cells being lysed as they pass through the esophagus, the new esophageal glandular cells should be produced prior to the initiation of blood feeding and be accompanied by apoptosis of utilized esophageal glands. The presence of extensive nerve fibres supporting the foregut of <i>A. simplex</i> suggests that such processes are controlled by the nervous system.</p>Published as part of <i>Poddubnaya, Larisa G., Hemmingsen, Willy & MacKenzie, Ken, 2023, Digestive system of the marine blood fluke, Aporocotyle simplex (Odhner, 1900) (Digenea: Aporocotylidae) with consideration of the digenean digestive morphology, pp. 11-22 in Zoologischer Anzeiger 305</i> on pages 18-19, DOI: 10.1016/j.jcz.2023.05.003, <a href="http://zenodo.org/record/10376067">http://zenodo.org/record/10376067</a>
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Chub enteric tapeworm: Cestode glandular products - a sign of parasite defence mechanism against fish immune response?
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