Ultrastructure of the spermatozoon of the digenean Lecithocladium excisum (Rudolphi, 1819) (Hemiuroidea: Hemiuridae), a parasite of marine teleosts in Senegal

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.

Spermiogenesis and spermatozoon of the liver fluke Mediogonimus jourdanei (Microphalloidea: Prosthogonimidae), a parasite of Myodes glareolus (Rodentia: Cricetidae)

Spermatological characters of the liver fluke Mediogonimus jourdanei Mas-Coma et Rocamora, 1978 were studied by means of transmission and scanning electron microscopy. Spermiogenesis begins with the formation of the differentiation zone containing two centrioles associated with striated rootlets and an intercentriolar body. These two centrioles originate two free flagella that undergo a 90 degrees rotation before fusing with the median cytoplasmic process. Both nuclear and mitochondrial migrations toward the median cytoplasmic process occur before the proximodistal fusion of flagella. Finally, the constriction of the ring of arched membranes gives rise to the young spermatozoon. The mature sperm of M. jourdanei measures about 260 microm and presents two axonemes of different lengths with the typical pattern of the Trepaxonemata, two bundles of parallel cortical microtubules, one mitochondrion, a nucleus and granules of glycogen. An analysis of all the microphalloidean species studied to date emphasised some differences in certain characters found in Maritrema linguilla Jägerskiöld, 1908 and Ganeo tigrinum Mehra et Negi, 1928 in comparison to those in the remaining microphalloideans. The presence and variability of such ultrastructural characters according to family, superfamily or order have led several authors to propose their use in the analysis of trematode relationships and phylogeny. Therefore, apart from producing new data on the family Prosthogonimidae, the present study also compares the spermatological organization of M jourdanei with other available ultrastructural studies focusing on the Microphalloidea.

Ultrastructure of the spermatozoon of the digenean Lecithocladium excisum (Rudolphi, 1819) (Hemiuroidea: Hemiuridae), a parasite of marine teleosts in Senegal

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.

Bilateral deep brain stimulation: the placement of the second electrode is not necessarily less accurate than that of the first one.

BACKGROUND: Deep brain stimulation (DBS) is recognized as an effective treatment for movement disorders. We recently changed our technique, limiting the number of brain penetrations to three per side. OBJECTIVES: The first aim was to evaluate the electrode precision on both sides of surgery since we implemented this surgical technique. The second aim was to analyse whether or not the electrode placement was improved with microrecording and macrostimulation. METHODS: We retrospectively reviewed operation protocols and MRIs of 30 patients who underwent bilateral DBS. For microrecording and macrostimulation, we used three parallel channels of the 'Ben Gun' centred on the MRI-planned target. Pre- and post-operative MRIs were merged. The distance between the planned target and the centre of the implanted electrode artefact was measured. RESULTS: There was no significant difference in targeting precision on both sides of surgery. There was more intra-operative adjustment of the second electrode positioning based on microrecording and macrostimulation, which allowed to significantly approach the MRI-planned target on the medial-lateral axis. CONCLUSION: There was more electrode adjustment needed on the second side, possibly in relation with brain shift. We thus suggest performing a single central track with electrophysiological and clinical assessment, with multidirectional exploration on demand for suboptimal clinical responses.

Spermiogenesis and spermatozoon of the liver fluke Mediogonimus jourdanei (Microphalloidea: Prosthogonimidae), a parasite of Myodes glareolus (Rodentia: Cricetidae)

Spermatological characters of the liver fluke Mediogonimus jourdanei Mas-Coma et Rocamora, 1978 were studied by means of transmission and scanning electron microscopy. Spermiogenesis begins with the formation of the differentiation zone containing two centrioles associated with striated rootlets and an intercentriolar body. These two centrioles originate two free flagella that undergo a 90 degrees rotation before fusing with the median cytoplasmic process. Both nuclear and mitochondrial migrations toward the median cytoplasmic process occur before the proximodistal fusion of flagella. Finally, the constriction of the ring of arched membranes gives rise to the young spermatozoon. The mature sperm of M. jourdanei measures about 260 microm and presents two axonemes of different lengths with the typical pattern of the Trepaxonemata, two bundles of parallel cortical microtubules, one mitochondrion, a nucleus and granules of glycogen. An analysis of all the microphalloidean species studied to date emphasised some differences in certain characters found in Maritrema linguilla Jägerskiöld, 1908 and Ganeo tigrinum Mehra et Negi, 1928 in comparison to those in the remaining microphalloideans. The presence and variability of such ultrastructural characters according to family, superfamily or order have led several authors to propose their use in the analysis of trematode relationships and phylogeny. Therefore, apart from producing new data on the family Prosthogonimidae, the present study also compares the spermatological organization of M jourdanei with other available ultrastructural studies focusing on the Microphalloidea.

Ultrastructural study of spermiogenesis and the spermatozoon of the proteocephalidean cestode Barsonella lafoni de Chambrier et al., 2009, a parasite of the catfish Clarias gariepinus (Burchell, 1822) (Siluriformes, Clariidae)

Spermiogenesis in the proteocephalidean cestode Barsonella lafoni de Chambrier et al., 2009 shows typical characteristics of the type I spermiogenesis. These include the formation of distal cytoplasmic protrusions forming the differentiation zones, lined by cortical microtubules and containing two centrioles. An electron-dense material is present in the apical region of the differentiation zone during the early stages of spermiogenesis. Each centriole is associated to a striated rootlet, being separated by an intercentriolar body. Two free and unequal flagella originate from the centrioles and develop on the lateral sides of the differentiation zone. A median cytoplasmic process is formed between the flagella. Later these flagella rotate, become parallel to the median cytoplasmic process and finally fuse proximodistally with the latter. It is interesting to note that both flagellar growth and rotation are asynchronous. Later, the nucleus enlarges and penetrates into the spermatid body. Finally, the ring of arching membranes is strangled and the young spermatozoon is detached from the residual cytoplasm. The mature spermatozoon presents two axonemes of the 9 +"1" trepaxonematan pattern, crested body, parallel nucleus and cortical microtubules, and glycogen granules. Thus, it corresponds to the type II spermatozoon, described in almost all Proteocephalidea. The anterior extremity of the gamete is characterized by the presence of an apical cone surrounded by the lateral projections of the crested body. An arc formed by some thick and parallel cortical microtubules appears at the level of the centriole. They surround the centriole and later the first axoneme. This arc of electron-dense microtubules disorganizes when the second axoneme appears, and then two parallel rows of thin cortical microtubules are observed. The posterior extremity of the male gamete exhibits some cortical microtubules. This type of posterior extremity has never been described in proteocephalidean cestodes. The ultrastructural features of the spermatozoon/spermiogenesis of the Proteocephalidea species are analyzed and compared.

Spermiogenesis and ultrastructure of the spermatozoon of Wardula capitellata (Digenea, Mesometridae), an intestinal parasite of the sparid teleost Sarpa salpa in Senegal

The spermiogenesis process in Wardula capitellata begins with the formation of a differentiation zone containing two centrioles associated with striated rootlets and an intercentriolar body. Each centriole develops into a free flagellum orthogonal to a median cytoplasmic process. Later these flagella rotate and become parallel to the median cytoplasmic process, which already exhibits two electron-dense areas and spinelike bodies before its proximodistal fusion with the flagella. The final stage of the spermiogenesis is characterized by the constriction of the ring of arched membranes, giving rise to the young spermatozoon, which detaches from the residual cytoplasm. The mature spermatozoon of W. capitellata presents most of the classical characters reported in digenean spermatozoa such as two axonemes of different lengths of the 9 + '1' trepaxonematan pattern, nucleus, mitochondrion, two bundles of parallel cortical microtubules and granules of glycogen. However, some peculiarities such as two lateral expansions accompanied by external ornamentation of the plasma membrane and spinelike bodies characterize the mature sperm. Moreover, a new spermatological character is described for the first time, the so-called cytoplasmic ornamented buttons.

Ultrastructural study of spermiogenesis and the spermatozoon of the proteocephalidean cestode Barsonella lafoni de Chambrier et al., 2009, a parasite of the catfish Clarias gariepinus (Burchell, 1822) (Siluriformes, Clariidae)

Spermiogenesis in the proteocephalidean cestode Barsonella lafoni de Chambrier et al., 2009 shows typical characteristics of the type I spermiogenesis. These include the formation of distal cytoplasmic protrusions forming the differentiation zones, lined by cortical microtubules and containing two centrioles. An electron-dense material is present in the apical region of the differentiation zone during the early stages of spermiogenesis. Each centriole is associated to a striated rootlet, being separated by an intercentriolar body. Two free and unequal flagella originate from the centrioles and develop on the lateral sides of the differentiation zone. A median cytoplasmic process is formed between the flagella. Later these flagella rotate, become parallel to the median cytoplasmic process and finally fuse proximodistally with the latter. It is interesting to note that both flagellar growth and rotation are asynchronous. Later, the nucleus enlarges and penetrates into the spermatid body. Finally, the ring of arching membranes is strangled and the young spermatozoon is detached from the residual cytoplasm. The mature spermatozoon presents two axonemes of the 9 +"1" trepaxonematan pattern, crested body, parallel nucleus and cortical microtubules, and glycogen granules. Thus, it corresponds to the type II spermatozoon, described in almost all Proteocephalidea. The anterior extremity of the gamete is characterized by the presence of an apical cone surrounded by the lateral projections of the crested body. An arc formed by some thick and parallel cortical microtubules appears at the level of the centriole. They surround the centriole and later the first axoneme. This arc of electron-dense microtubules disorganizes when the second axoneme appears, and then two parallel rows of thin cortical microtubules are observed. The posterior extremity of the male gamete exhibits some cortical microtubules. This type of posterior extremity has never been described in proteocephalidean cestodes. The ultrastructural features of the spermatozoon/spermiogenesis of the Proteocephalidea species are analyzed and compared.

Spermiogenesis and ultrastructure of the spermatozoon of Wardula capitellata (Digenea, Mesometridae), an intestinal parasite of the sparid teleost Sarpa salpa in Senegal

The spermiogenesis process in Wardula capitellata begins with the formation of a differentiation zone containing two centrioles associated with striated rootlets and an intercentriolar body. Each centriole develops into a free flagellum orthogonal to a median cytoplasmic process. Later these flagella rotate and become parallel to the median cytoplasmic process, which already exhibits two electron-dense areas and spinelike bodies before its proximodistal fusion with the flagella. The final stage of the spermiogenesis is characterized by the constriction of the ring of arched membranes, giving rise to the young spermatozoon, which detaches from the residual cytoplasm. The mature spermatozoon of W. capitellata presents most of the classical characters reported in digenean spermatozoa such as two axonemes of different lengths of the 9 + '1' trepaxonematan pattern, nucleus, mitochondrion, two bundles of parallel cortical microtubules and granules of glycogen. However, some peculiarities such as two lateral expansions accompanied by external ornamentation of the plasma membrane and spinelike bodies characterize the mature sperm. Moreover, a new spermatological character is described for the first time, the so-called cytoplasmic ornamented buttons.

Radio Imaging of the Very-High-Energy γ-Ray Emission Region in the Central Engine of a Radio Galaxy

The accretion of matter onto a massive black hole is believed to feed the relativistic plasma jets found in many active galactic nuclei (AGN). Although some AGN accelerate particles to energies exceeding 1012 electron volts and are bright sources of very-high-energy (VHE) γ-ray emission, it is not yet known where the VHE emission originates. Here we report on radio and VHE observations of the radio galaxy Messier 87, revealing a period of extremely strong VHE γ-ray flares accompanied by a strong increase of the radio flux from its nucleus. These results imply that charged particles are accelerated to very high energies in the immediate vicinity of the black hole.

Ultrastructural characters of the spermatozoon of the digenean Hypocreadium caputvadum Kacem et al., 2011 (Lepocreadioidea: Lepocreadiidae), an intestinal parasite of Balistes capriscus in Tunisia

The ultrastructural organization of the spermatozoon of the digenean Hypocreadium caputvadum (Lepocreadioidea: Lepocreadiidae) is described. Live digeneans were collected from Balistes capriscus (Teleostei: Balistidae) from the Gulf of Gabès, Tunisia (Eastern Mediterranean Sea). The mature spermatozoon of H. caputvadum shows several ultrastructural characters such as two axonemes of different lengths exhibiting the classical 9 +"1" trepaxonematan pattern, a nucleus, two mitochondria, granules of glycogen, external ornamentation of the plasma membrane and two bundles of parallel cortical microtubules. Moreover, in the anterior extremity, the second axoneme is partly surrounded by a discontinuous and submembranous layer of electron-dense material. Our study provides new data on the spermatozoon of H. caputvadum in order to improve the understanding of phylogenetic relationships in the Digenea, particularly in the superfamily Lepocreadioidea. In this context, the electron-dense material surrounding one of the axonemes in the anterior spermatozoon extremity constitutes the unique distinguishing ultrastructural character of lepocreadioideans, and it is present in spermatozoa of lepocreadiids, aephnidiogenids and gyliauchenids.

Ultrastructural characters of the spermatozoon of the digenean Hypocreadium caputvadum Kacem et al., 2011 (Lepocreadioidea: Lepocreadiidae), an intestinal parasite of Balistes capriscus in Tunisia

The ultrastructural organization of the spermatozoon of the digenean Hypocreadium caputvadum (Lepocreadioidea: Lepocreadiidae) is described. Live digeneans were collected from Balistes capriscus (Teleostei: Balistidae) from the Gulf of Gabès, Tunisia (Eastern Mediterranean Sea). The mature spermatozoon of H. caputvadum shows several ultrastructural characters such as two axonemes of different lengths exhibiting the classical 9 +"1" trepaxonematan pattern, a nucleus, two mitochondria, granules of glycogen, external ornamentation of the plasma membrane and two bundles of parallel cortical microtubules. Moreover, in the anterior extremity, the second axoneme is partly surrounded by a discontinuous and submembranous layer of electron-dense material. Our study provides new data on the spermatozoon of H. caputvadum in order to improve the understanding of phylogenetic relationships in the Digenea, particularly in the superfamily Lepocreadioidea. In this context, the electron-dense material surrounding one of the axonemes in the anterior spermatozoon extremity constitutes the unique distinguishing ultrastructural character of lepocreadioideans, and it is present in spermatozoa of lepocreadiids, aephnidiogenids and gyliauchenids.

Electron scattering in isotonic chains as a probe of the proton shell structure of unstable nuclei

Electron scattering on unstable nuclei is planned in future facilities of the GSI and RIKEN upgrades. Motivated by this fact, we study theoretical predictions for elastic electron scattering in the N=82, N=50, and N=14 isotonic chains from very proton-deficient to very proton-rich isotones. We compute the scattering observables by performing Dirac partial-wave calculations. The charge density of the nucleus is obtained with a covariant nuclear mean-field model that accounts for the low-energy electromagnetic structure of the nucleon. For the discussion of the dependence of scattering observables at low-momentum transfer on the gross properties of the charge density, we fit Helm model distributions to the self-consistent mean-field densities. We find that the changes shown by the electric charge form factor along each isotonic chain are strongly correlated with the underlying proton shell structure of the isotones. We conclude that elastic electron scattering experiments on isotones can provide valuable information about the filling order and occupation of the single-particle levels of protons.

Spermiogenesis and spermatozoon ultrastructure of the dilepidid cestode Molluscotaenia crassiscolex (von Linstow, 1890), an intestinal parasite of the common shrew Sorex araneus

Spermiogenesis in Molluscotaenia crassiscolex begins with the formation of a differentiation zone containing two centrioles. One of the centrioles develops a flagellum directly into the cytoplasmic extension. The nucleus elongates and later migrates along the spermatid body. During advanced stages of spermiogenesis, a periaxonemal sheath appears in the spermatid. Spermiogenesis finishes with the appearance of a single helicoidal crested body at the base of the spermatid and, finally, the narrowing of the ring of arched membranes causes the detachment of the fully formed spermatozoon. The mature spermatozoon of M. crassiscolex exhibits a partially detached crested body in the anterior region of the spermatozoon, one axoneme, twisted cortical microtubules, a periaxonemal sheath, and a spiralled nucleus. The anterior spermatozoon extremity is characterized by the presence of an electron-dense apical cone and a single spiralled crested body, which is attached to the sperm cell in the anterior and posterior areas of region I, whereas in the middle area it is partially detached from the cell. This crested body is described for the first time in cestodes. The posterior extremity of the male gamete exhibits only the disorganizing axoneme. Results are discussed and compared particularly with the available ultrastructural data on dilepidids sensu lato.

Spermiogenesis and spermatozoon ultrastructure of the diphyllidean cestode Echinobothrium euterpes (Neifar, Tyler and Euzet 2001) Tyler 2006, a parasite of the common guitarfish Rhinobatos rhinobatos

Spermiogenesis and the ultrastructural characters of the spermatozoon of Echinobothrium euterpes are described by means of transmission electron microscopy, including cytochemical analysis for glycogen. Materials were obtained from a common guitarfish Rhinobatos rhinobatos caught in the Gulf of Gabès (Tunisia). Spermiogenesis in E. euterpes is characterized by the orthogonal development of two unequal flagella followed by the flagellar rotation and the proximodistal fusion of these flagella with the median cytoplasmic process. The most interesting pattern characterizing the diphyllidean cestodes is the presence of a triangular body constituted by fines and dense granules without visible striation and assimilated at the striated rootlets. This pattern, only related in the Diphyllidea cestodes may be a synapomorphy of this order. Spermiogenesis is also characterized by the presence of a very short flagellum (around 1 μm long), observed in all the stages of spermiogenesis. This type of flagellum has never been commented in the diphyllidean cestodes and should be considered as an evolved character in this group. In the latest stage of spermiogenesis, this short axoneme probably degenerates. Thus, the mature spermatozoon of E. euterpes possesses only one axoneme of 9 + '1' trepaxonematan pattern. It also exhibits a single helical electron-dense crested body, a spiraled nucleus, few parallel cortical microtubules, and α-glycogen granules. Similitudes and differences between spermatozoa of diphyllideans are discussed.