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Sheath
Kinds of Sheath Terms modified by Sheath Selected AbstractsEffect of Oscillating Sheath on Near-Wall Electron Current Profile in Hall ThrustersCONTRIBUTIONS TO PLASMA PHYSICS, Issue 9-10 2008D. R. Yu Abstract The radial profile of the axial electron current in Hall thrusters was measured; however, the significant decay of the current density peak in the near-wall region can't be explained effectively by the steady sheath theory. As the sheath exhibits an oscillating character when the thruster is in operation, its effect on the near-wall current profile has been studied in this paper. To obtain a comprehensive knowledge, we have considered a wide sheath oscillation frequency span which includes two asymptotic frequency cases at high and low ends. Based on the case studied, either an analytical treatment or a numerical simulation is applied. The results show that the current density peak has a fastest damping speed away from the wall at the asymptotic low frequency. With the increase of the frequency, both the decay and the spatial "wavelength" of the current profile decrease. The decay finally disappears at the asymptotic high frequency with a constant spatial "wavelength". Moreover, the sheath oscillation amplitude can enhance the decay and enlarge the spatial "wavelength". Taking into account of the realistic situation in Hall thrusters, the significant impact of the oscillating sheath on the near-wall electron current profiles can be anticipant. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Formulation of Boundary Conditions for the Unmagnetized Multi-Ion-Component Plasma SheathCONTRIBUTIONS TO PLASMA PHYSICS, Issue 7-9 2006D. Tskhakaya Abstract Boundary conditions are derived for the unmagnetized electrostatic multi-ion-component plasma sheath. Analytic results are supported by high-resolution numerical kinetic (particle-in-cell) simulations. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Sheath in Front of a Negatively Biased Collector that Emits Electrons and is Immersed in a Two Electron Temperature PlasmaCONTRIBUTIONS TO PLASMA PHYSICS, Issue 8 2005T. Gyergyek Abstract An extension of a recently published [Gyergyek T., ,er,ek M. Contrib. Plasma Phys., 45, (2005), 89] one dimensional fluid model of the sheath formation in front of a floating electrode (collector) that emits secondary electrons and is immersed in a two-electron temperature nonmagnetized, collisionless plasma is presented. The electron velocity distribution function is assumed to be a two-temperature maxwellian, while the singly charged positive ions and the emitted electrons are assumed to be monoenergetic. It is assumed that the electrons in the pre-sheath potential drop obey the Boltzmann relation, so that a larger fraction of the hot than of the cool electrons can penetrate to the sheath edge. Our model predicts that the collector can in some cases have 3 and in some cases, when the emission of electrons from the collector is critical, even 5 different floating potentials at the same hot to cool electron temperature and density ratios very far away from the collector. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Coaxial Metal Nano-/Microcables with Isolating Sheath: Synthetic Methodology and Their Application as InterconnectsADVANCED MATERIALS, Issue 17 2010Min-Rui Gao Abstract Synthesis of coaxial nano-/microcables has been an intensive research subject due to their heterogeneous structures, tuneable properties, and important applications in nano-/micrometer-scale electronic and optoelectronic devices. Research on the fabrication of nanocables via solution strategies has made great progress in the past few years. In this Research News article, rapidly emerging new solution strategies such as hydrothermal carbonization (HTC) and synergistic soft,hard templates (SSHTs) are highlighted. Unique and flexible coaxial nano-/microcables synthesized by those methods have obvious advantages such as long-term stability and their electrical transport properties, compared with bare counterparts, suggesting that they are potential candidates as interconnects in the future. [source] Intracardiac Ultrasound Detection of Thrombus on Transseptal Sheath: Incidence, Treatment, and PreventionJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 6 2005KATANEH MALEKI M.D. Background: Transseptal (TS) catheterization is used for left atrial (LA) ablation procedures and a major risk is thromboembolism. The purpose of this study was to assess (1) the value of intracardiac ultrasound (ICUS) monitoring during LA ablation procedures, and (2) a new technique to reduce the risk of thrombus formation. Methods and Results: One hundred and eighty consecutive patients underwent TS catheterization under ICUS guidance with two sheaths for atrial fibrillation ablation and one for other LA procedures. Group I included the initial 90 patients in whom TS sheaths were flushed with a standard 2 U/cc concentration of heparin; group II consisted of the next 90 patients in whom sheaths were flushed with 1,000 U/cc concentration. All patients received bolus and infusion of heparin to maintain ACT between 250,300 seconds. ICUS was monitored throughout. In group I, echodense material at the tip of the sheath consistent with thrombus was observed on ICUS in 8 of 90 patients (9%) within 5,15 minutes of entering the LA. In group II, only 1 of 90 patient (1%) demonstrated thrombus (P < 0.001). There were no significant clinical differences in group I patients with and without thrombus. In all nine patients, the clot was removed with vigorous aspiration. No patients suffered a neurological event. Conclusion: Thrombus formation on TS sheath, detected by ICUS, may be more common than expected despite adequate anticoagulation. Using a higher concentration of heparin for the TS system before deployment reduced the risk. The thrombus was retrieved with aspiration without the need to abort the procedure. [source] Use of a Long Preshaped Sheath to Facilitate Cannulation of the Coronary Sinus at Electrophysiologic StudyJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 12 2001CHRIS B. PEPPER B.Sc. CS Cannulation Using a Long Sheath. Introduction: Catheterization of the coronary sinus (CS) from the femoral vein can be challenging. We tested whether use of a long preshaped sheath facilitates CS cannulation. Methods and Results: One hundred four patients were randomized into two phases. In phase 1, consecutive patients were allocated to CS catheterization using the long sheath (n = 26) or standard 7-French 15-cm sheath (n = 25). If unsuccessful within 10 minutes, the alternative technique was used. Phase 2 assessed the utility of the long sheath in difficult cases. All patients initially were approached using the standard sheath. If cannulation failed after 10 minutes, patients were randomly allocated to the standard or long sheath approach. In phase 1, the standard approach failed in 4 (16%) of 25 cases. In each case, a long sheath proved successful (mean 3.2 min). The long sheath approach was successful within 10 minutes in all 26 cases. Catheter deployment was significantly quicker with the long sheath, but this was offset by the time required for sheath insertion. In phase 2, the standard approach was successful in 46 (87%) of 53 cases. Of 7 "failures," 3 were randomized to continue the standard approach, which was successful in 1; 4 were randomized to the long sheath approach, and success was achieved in all (mean 4.4 ± 1.5 min). Overall, the CS could not be promptly catheterized in 15% of cases within 10 minutes using the standard sheath, and no failures were seen using the long sheath. No complications arose from the use of either technique. Conclusion: The long sheath was uniformly successful in permitting catheterization of the CS from the femoral approach in both unselected and difficult cases. [source] Sheath of guidewire of ureteric stent as an aid to extubation; Wrong interpretationPEDIATRIC ANESTHESIA, Issue 5 2010Rajeev Sharma No abstract is available for this article. [source] Fetal Anatomy of the Human Carotid Sheath and Structures In and Around ItTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 3 2010Naritomo Miyake Abstract The aim of this study was to find basic rules governing the morphological development of the typical neurovascular sheath. We carried out histological examination of 15 paraffin-embedded mid-term fetuses at 9,25 weeks of gestation (three fetuses each at 9, 12, 15, 20, and 25 weeks). As the result, the vagus nerve showed a high propensity to change its topographical relationship with the common carotid artery (CCA) during 9,20 weeks of gestation: that is, from a primitive ventral course to a final dorsal course. The adventitia of the great arteries, which was distinct from other fascial structures, became evident by 15 weeks. The carotid sheath appeared at and after 20 weeks: it was clearly separated from the prevertebral lamina of the deep cervical fasciae, but fused with the pretracheal lamina covering the strap muscles. Thus the carotid sheath, as well as the topographical relationships of structures within it, seems to become established much later than the prevertebral and pretracheal laminae of the deep cervical fasciae. However, the adventitia of the cervical great arteries consistently becomes evident much earlier than the sheath, and it seems to be regarded as one of the basic components of the fetal deep cervical fasciae. Anat Rec, 293:438,445, 2010. © 2010 Wiley-Liss, Inc. [source] Cavernous Hemangioma of the Carotid SheathTHE LARYNGOSCOPE, Issue S1 2009Luc G.T. Morris MD No abstract is available for this article. [source] TEM, FISH and molecular studies in infertile men with pericentric inversion of chromosome 9ANDROLOGIA, Issue 4 2006G. Collodel Summary Pericentric inversions involving the secondary constriction (qh) region of chromosome 9 are considered to be normal variants of human karyotype. A number of investigators have suggested that chromosomal anomalies can contribute to human infertility causing spermatogenetic derangement. The present study was aimed at verifying the influence of chromosome 9 inversion on human spermatogenesis. Semen samples of 18 male carriers of chromosome 9 inversion, analysed by light microscopy, revealed that five patients were azoospermic. PCR analysis demonstrated that two of them also had Y microdeletions. The other 13 showed generally normal sperm concentrations and reduced motility. The morphological characteristics of sperm were studied by TEM and the data were elaborated by a mathematical formula. Sperm pathologies resulted more frequently in the studied group compared to controls, particularly apoptosis. Partial sequences of the A-kinase anchoring protein (Akap) 4 and 3 genes were performed in all patients, as a previous study by our group highlighted Dysplasia of Fibrous Sheath (DFS) defect in two men with inv 9 investigations. The possible effect of chromosome 9 inversion on meiotic chromosome segregation was investigated by FISH, which showed an increased incidence of diploidy. We hypothesized that this inversion could have variable effects on spermatogenesis, from azoospermia to severely altered sperm morphology, motility and meiotic segregation. [source] A quantitative study of the optic nerve in diabetic mutant, Otsuka Long-Evans Tokushima Fatty (OLETF) ratsCONGENITAL ANOMALIES, Issue 4 2001Kazuhiko Sawada ABSTRACT, Optic nerves of the Otsuka Long-Evans Tokushima Fatty (OLETF) rat, an animal model of non-insulin dependent diabetes mellitus, were examined using quantitative stereological procedures. At 67 weeks of age, OLETF rats showed a mild hyperglycemia: their blood glucose level was 196 ± 93 mg/dl, significantly higher than that of non-diabetic control Long-Evans Tokushima Otsuka (LETO) rats (110 ± 24 mg/dl). However, there were no differences in the cross sectional area of optic nerves (the mean minimum diameter), the total number and mean diameter of both myelinated and non-myelinated fibers, or the thickness of the myelin sheath between OLETF and LETO rats. The results suggested that a mild hyperglycemia in OLETF rats could not cause any morphological changes in the optic nerve. [source] Dynamics of Dislocations in a 2D Plasma CrystalCONTRIBUTIONS TO PLASMA PHYSICS, Issue 4-5 2009V. Nosenko Abstract Recent experimental results on the dislocation dynamics in a two-dimensional plasma crystal are reviewed. A single layer of micron-size microspheres was suspended in the sheath of a capacitively coupled rf discharge. The particles self-organized in a triangular lattice. Edge dislocations were created in pairs in this plasma crystal when the internal shear stress built up above a threshold, due to the crystal's slow differential rotation. Basic stages of dislocation nucleation were identified and studied, from gradual pile-up of shear strain in the crystal to eventual escape of free dislocations. After nucleation, dislocations moved supersonically with respect to the shear waves and generated shear-wave Mach cones (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of Oscillating Sheath on Near-Wall Electron Current Profile in Hall ThrustersCONTRIBUTIONS TO PLASMA PHYSICS, Issue 9-10 2008D. R. Yu Abstract The radial profile of the axial electron current in Hall thrusters was measured; however, the significant decay of the current density peak in the near-wall region can't be explained effectively by the steady sheath theory. As the sheath exhibits an oscillating character when the thruster is in operation, its effect on the near-wall current profile has been studied in this paper. To obtain a comprehensive knowledge, we have considered a wide sheath oscillation frequency span which includes two asymptotic frequency cases at high and low ends. Based on the case studied, either an analytical treatment or a numerical simulation is applied. The results show that the current density peak has a fastest damping speed away from the wall at the asymptotic low frequency. With the increase of the frequency, both the decay and the spatial "wavelength" of the current profile decrease. The decay finally disappears at the asymptotic high frequency with a constant spatial "wavelength". Moreover, the sheath oscillation amplitude can enhance the decay and enlarge the spatial "wavelength". Taking into account of the realistic situation in Hall thrusters, the significant impact of the oscillating sheath on the near-wall electron current profiles can be anticipant. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of Cathode and Anode Voltage on an Ion Sheath Thickness in a Magnetically Confined Diffusion PlasmaCONTRIBUTIONS TO PLASMA PHYSICS, Issue 10 2007M. Kr. Abstract This article reports about the ion sheath thickness variation occurring in front of a negatively biased plate immersed in the target plasma region of a double plasma device. The target plasma is produced due to the local ionization of neutral gas by the high energetic electrons coming from the source region (main discharge region). It is observed that for an increase in cathode voltage (filament bias voltage) in the source region, the ion flux into the plate increases. As a result, the sheath at the plate contracts. Again, for an increase in source anode voltage (magnetic cage bias), the ion flux to the plate decreases. As a result, the sheath expands at the plate. The ion sheath formed at the separation grid of the device is found to expand for an increase in cathode voltage and it contracts for an increase in the anode voltage of the main discharge region. One important observation is that the applied anode bias can control the Bohm speed of the ions towards the separation grid. Furthermore, it is observed that the ion current collected by the separation grid is independent of changes in plasma density in the diffusion region but is highly dependent on the source plasma parameters. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Formulation of Boundary Conditions for the Unmagnetized Multi-Ion-Component Plasma SheathCONTRIBUTIONS TO PLASMA PHYSICS, Issue 7-9 2006D. Tskhakaya Abstract Boundary conditions are derived for the unmagnetized electrostatic multi-ion-component plasma sheath. Analytic results are supported by high-resolution numerical kinetic (particle-in-cell) simulations. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fluid Model of a Sheath Formed in Front of an Electron Emitting Electrode Immersed in a Plasma with Two Electron TemperaturesCONTRIBUTIONS TO PLASMA PHYSICS, Issue 2 2005T. Gyergyek Abstract The formation of a sheath in front of a negatively biased electrode (collector) that emits electrons is studied by a one-dimensional fluid model. Electron and ion emission coefficients are introduced in the model. It is assumed that the electrode is immersed in a plasma that contains energetic electrons. The electron velocity distribution function is assumed to be a sum of two Maxwellian distributions with two different temperatures, while the ions and the emitted electrons are assumed to be monoenergetic. The condition for zero electric field at the collector is derived. Using this equation the dependence of electron and ion critical emission coefficients on various parameters - like the ratio between the hot and cool electron density, the ratio between hot and cool electron temperature and the initial velocity of secondary electrons - is calculated for a floating collector. A modification of the Bohm criterion due to the presence of hot and emitted electrons is also given. The transition between space charge limited and temperature limited electron emission for a current-carrying collector is also analyzed. The critical potential, where this transition occurs, is calculated as a function of several parameters like the Richardson emission current, the ratio between the hot and cool electron density, the ratio between hot and cool electron temperature and the initial velocity of secondary electrons. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Monte Carlo Simulations of the Electron Currents Collected by Electrostatic ProbesCONTRIBUTIONS TO PLASMA PHYSICS, Issue 7-8 2004D. Trunec Abstract We have carried out Monte Carlo simulation of the motion of electrons in the space charge sheath surrounding a cylindrical Langmuir (electrostatic) probe. The electron currents to the probe have been calculated from these simulations for different conditions (pressure of neutral gas, presence of magnetic field). The results of the simulations have been compared with recent Langmuir probe measurements made in cylindrical DC magnetron plasmas. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Diameter of Involved Nerves Predicts Outcomes in Cutaneous Squamous Cell Carcinoma with Perineural Invasion: An Investigator-Blinded Retrospective Cohort StudyDERMATOLOGIC SURGERY, Issue 12 2009AMY S. ROSS MD BACKGROUND Perineural invasion (PNI) has been associated with poor prognosis in cutaneous squamous cell carcinoma (CSCC), but it is unclear how different degrees of nerve involvement affect prognosis. OBJECTIVE To determine whether the diameter of nerves invaded by CSCC affects outcomes of recurrence, metastasis, and disease-specific and overall survival. METHODS A retrospective cohort study was conducted of patients with CSCC with PNI. Dermatopathologists blinded to subject outcomes determined the diameter of the largest involved nerve. RESULTS Data were obtainable for 48 patients. Small-caliber nerve invasion (SCNI) of nerves less than 0.1 mm in diameter was associated with significantly lower risks of all outcomes of interest. Disease-specific death was 0% in subjects with SCNI, versus 32% in those with large-caliber nerve invasion (LCNI) (p=.003). Other factors associated with significantly worse survival were recurrent or poorly differentiated tumors or tumor diameter of 2 cm or greater or depth of 1 cm or greater. On multivariate analysis, only tumor diameter and age predicted survival. CONCLUSIONS The individual prognostic significance of factors associated with poor survival remains uncertain. Small-caliber nerve invasion may not adversely affect outcomes. Defining PNI as tumor cells within the nerve sheath and routine recording of diameter of involved nerves, tumor depth, and histologic differentiation on pathology reports will facilitate further study. [source] Characterization and expression of AmphiBMP3,/3b gene in amphioxus Branchiostoma japonicumDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 2 2010Yi Sun Bone morphogenetic proteins (BMPs) are responsible for regulating embryo development and tissue homeostasis beyond osteogenesis. However, the precise biological roles of BMP3 and BMP3b remain obscure to a certain extent. In the present study, we cloned an orthologous gene (AmphiBMP3/3b) from amphioxus (Branchiostoma japonicum) and found its exon/intron organization is highly conserved. Further, in situ hybridization revealed that the gene was strongly expressed in the dorsal neural plate of the embryos. The gene also appeared in Hatschek's left diverticulum, neural tube, preoral ciliated pit and gill slit of larvae, and adult tissues including ovary, neural tube and notochordal sheath. Additionally, real-time quantitative polymerase chain reaction (RTqPCR) analysis revealed that the expression displayed two peaks at gastrula and juvenile stages. These results indicated that AmphiBMP3/3b, a sole orthologue of vertebrate BMP3 and BMP3b, might antagonize ventralizing BMP2 orthologous signaling in embryonic development, play a role in the evolutionary precursors of adenohypophysis, as well as act in female ovary physiology in adult. [source] Id2, Id3, and Id4 proteins show dynamic changes in expression during vibrissae follicle developmentDEVELOPMENTAL DYNAMICS, Issue 6 2008Nigel L. Hammond Abstract Id proteins are involved in the transcriptional control of many fundamental biological processes, including differentiation and lineage commitment. We studied Id2, Id3, and Id4 protein expression during different stages of rat vibrissa follicle development using immunohistochemistry. Id2 was highly expressed in the cytoplasm of specialized cells in the basal epidermis and outer root sheath during early stages of follicle development. These cells were identified as Merkel cells (MCs) by means of double-immunolabeling with synaptophysin and cytokeratin-20, and persisted in neonatal follicles. Id3 immunofluorescence was characterized by membrane-associated expression in basal epithelial cells of follicles early in development. Subsequently follicle epithelial cells switched to have strong nuclear labeling, also a feature of newly forming dermal papilla cells. Id4 expression was primarily associated with innervation of the developing follicle musculature. These observations illustrate dynamic expression patterns of Id2 and Id3 proteins in developing follicles and specifically link Id2 expression to Merkel cell specification. Developmental Dynamics 237:1653,1661, 2008. © 2008 Wiley-Liss, Inc. [source] ENDOSONOGRAPHY-GUIDED GALLBLADDER DRAINAGE FOR ACUTE CHOLECYSTITIS FOLLOWING COVERED METAL STENT DEPLOYMENTDIGESTIVE ENDOSCOPY, Issue 1 2009Osamu Takasawa Endosonography-guided biliary drainage (ESBD) is gaining acceptance as an effective treatment for obstructive jaundice. Only a few reports on the application of this technique to the gallbladder (endosonography-guided gallbladder drainage [ESGBD]) have been published in the literature. In order to relieve acute cholecystitis which developed in a patient with unresectable malignant biliary obstruction after deployment of a covered metal stent (CMS), we applied this technique. ESGBD was carried out by using an electronic curved linear array echoendoscope. After visualization of the gallbladder and determination of the puncture route, a needle knife papillotome was advanced with electrocautery to pierce the gastric and gallbladder walls. Under the guidance of a guidewire inserted through the needle sheath into the gallbladder, a 7.2 Fr, 30 cm-long, single pigtail plastic tube was placed to bridge the gallbladder and the stomach. No complications relevant to the procedure were encountered. ESGBD was quite effective in ameliorating the patient's acute cholecystitis and the drainage tube was removed after 10 days without sequelae. Acute cholecystitis following CMS deployment is considered to be a good indication for ESGBD. [source] SUCCESSFUL PLACEMENT OF SELF-EXPANDABLE METALLIC STENTS FOR DOUBLE COLORECTAL CANCERSDIGESTIVE ENDOSCOPY, Issue 4 2006Tsuyoshi Abe Stent placement for the palliation of unresectable colon cancer is an alternative to surgical treatment that has recently become popular. A dedicated stent for colorectal cancer is not available in Japan. We report a patient with two colonic obstructions who underwent a successful palliative treatment using two stents. He was admitted to Toho University Ohashi Medical Center because of ileus. A colonoscopy revealed two advanced lesions with stenosis in the sigmoid and transverse colon. Because he had multiple liver metastases and severe Alzheimer dementia, we selected palliative stent placement for the treatment of both strictures. We placed a covered stent in the sigmoid colon stricture and subsequently attempted to place a second stent in the transverse colon stricture. However, the second stent could not be placed in the transverse colon because the modified delivery system could not pass through the first stent in the sigmoid colon. This probably led to a twisting of the stent in the sigmoid colon. We next used the 24 F introducer sheath that is included in Keller-Timmermans Introducer Sets. This strategy allowed the modified delivery system to be easily passed through the initial stent in the sigmoid colon and then advanced into the transverse colon stricture, enabling both stents to be positioned properly. [source] THE TECHNICAL FUNDAMENTALS OF ENDOSCOPIC MUCOSAL RESECTION IN THE COLON: OUR METHODDIGESTIVE ENDOSCOPY, Issue 2004Yasushi Oda ABSTRACT Endoscopic mucosal resection (EMR) is the technique used to resect flat or depressed tumors or larger tumors such as laterally spreading tumors with marginal normal mucosa. Recently, endoscopic mucosal dissection technique has been rapidly accepted, mainly in early gastric cancer in Japan. We need to have firm knowledge of EMR technique in the colon for recovery as we advance this new technique. We describe our conventional EMR method practically. EMR should be performed to locate the target lesion at down side to perform sure EMR. The ideal shape of upheaval by saline injection is hemisphere. The needle sheath and snare should be taken out a little of the endoscopy to manipulate firmly. Another technique of secure EMR is the snare manipulation. We prefer that the shape of the snare is circular and the snare is hard. It is important while trapping to press the target lesion with both the whole snare circle and the end of the sheath. With these fundamental procedures we could resect the target lesions at will. [source] Ultrastructure of spermiogenesis and mature spermatozoon of Anonchotaenia globata (von Linstow, 1879) (Cestoda, Cyclophyllidea, Paruterinidae)ACTA ZOOLOGICA, Issue 2 2010Aneta Yoneva Abstract Yoneva, A., Georgieva, K., Mizinska, Y., Nikolov, P. N., Georgiev, B. B. and Stoitsova, S. R. 2010. Ultrastructure of spermiogenesis and mature spermatozoon of Anonchotaenia globata (von Linstow, 1879) (Cestoda, Cyclophyllidea, Paruterinidae). , Acta Zoologica (Stockholm) 91: 184,192 The ultrastructure of spermiogenesis and of the spermatozoon of a species of the family Paruterinidae is described for the first time. The spermiogenesis of Anonchotaenia globata starts with the formation of a differentiation zone with two centrioles associated with thin striated roots. One of the centrioles gives rise to a free flagellum followed by a slight flagellar rotation and a proximodistal fusion of the flagellum with the cytoplasmic protrusion. This pattern corresponds to Type III spermiogenesis in cestodes. The spermatozoon consists of five distinct regions. The anterior extremity possesses an apical cone and a single helically coiled crested body. The cortical microtubules are spirally arranged. The axoneme is surrounded by a periaxonemal sheath and a thin layer of cytoplasm filled with electron-dense granules in Regions I,V. The periaxonemal sheath is connected with the peripheral microtubules by transverse intracytoplasmic walls in Regions III and IV. The nucleus is spirally coiled around the axoneme. Anonchotaenia globata differs from Dilepididae (where paruterinids have previously been classified) in the type of spermiogenesis, the lack of glycogen inclusions and the presence of intracytoplasmic walls. The pattern of spermiogenesis is similar to that in Metadilepididae and Taeniidae, which are considered phylogenetically close to Paruterinidae. [source] Spermiogenesis and spermatozoon ultrastructure of the davaineid cestode Raillietina micracantha (Fuhrmann, 1909)ACTA ZOOLOGICA, Issue 2 2010Jordi Miquel Abstract Miquel, J., Torres, J., Foronda, P. and Feliu, C. 2010. Spermiogenesis and spermatozoon ultrastructure of the davaineid cestode Raillietina micracantha. , Acta Zoologica (Stockholm) 91: 212,221 The spermiogenesis and the ultrastructural organization of the spermatozoon of the davaineid cestode Raillietina micracantha are described by means of transmission electron microscopy. Spermiogenesis begins with the formation of a zone of differentiation containing two centrioles. One of the centrioles develops a free flagellum that later fuses with a cytoplasmic extension. The nucleus migrates along the spermatid body after the proximodistal fusion of the flagellum and the cytoplasmic extension. During advanced stages of spermiogenesis a periaxonemal sheath and intracytoplasmic walls appear in the spermatids. Spermiogenesis finishes with the appearance of two helicoidal crested bodies at the base of spermatids and, finally, the narrowing of the ring of arched membranes detaches the fully formed spermatozoon. The mature spermatozoon of R. micracantha is a long and filiform cell, tapered at both ends, which lacks mitochondria. It exhibits two crested bodies of different lengths, one axoneme of the 9 + ,1' pattern of trepaxonematan Platyhelminthes, twisted cortical microtubules, a periaxonemal sheath, intracytoplasmic walls, granules of glycogen and a spiralled nucleus. The anterior extremity of the spermatozoon is characterized by the presence of an electron-dense apical cone and two spiralled crested bodies while the posterior extremity of the male gamete exhibits only the axoneme and an electron-dense posterior tip. [source] Ultrastructure of spermatozoa of lizards in the genus Mabuya from Central BrazilACTA ZOOLOGICA, Issue 1 2009S. M. De Sá Mandel Abstract This is the first description of spermatozoal ultrastructure of Mabuya skinks. The spermatozoa of the species studied are filiform, consisting of a head region, a midpiece and a tail. The head is characterized by the following features: a depressed acrosome anteriorly, an acrosome vesicle divided into cortex and medulla, paracrystalline subacrosomal material, a pointed tip perforatorium, a circular perforatorium base plate inside the subacrosomal cone, an epinuclear lucent zone separated from the subacrosomal cone by a membrane, a large nuclear rostrum, and round nuclear shoulders. The midpiece presents a bilateral stratified laminar structure, a distal centriole, peripheral fibres 3 and 8 grossly enlarged, columnar mitochondria with linear cristae, dense body rings and a triangular annulus. Finally, the tail is composed of a principal piece and an end piece. An axoneme and a fibrous sheath characterize the principal piece, and the end piece is formed only by an axoneme, which loses its pattern in the last portion. Comparisons with members of Teiidae revealed differences in the numbers of dense rings. A well-developed epinuclear lucent zone in Mabuya is less prominent among teiids. In the spermatozoa of Mabuya, the first ring of dense bodies is very large, uniquely resembling the condition present in snakes. [source] Ultrastructure of the spermatozoon of Apus apus (Linnaeus 1758), the common swift (Aves; Apodiformes; Apodidae), with phylogenetic implicationsACTA ZOOLOGICA, Issue 4 2005Barrie G. M. Jamieson Abstract The spermatozoon of Apus apus is typical of non-passerines in many respects. Features shared with palaeognaths and the Galloanserae are the conical acrosome, shorter than the nucleus; the presence of a proximal as well as distal centriole; the elongate midpiece with mitochondria grouped around an elongate distal centriole; and the presence of a fibrous or amorphous sheath around the principal piece of the axoneme. The perforatorium and endonuclear canal are lost in A. apus as in some other non-passerines. All non-passerines differ from palaeognaths in that the latter have a transversely ribbed fibrous sheath whereas in non-passerines it is amorphous, as in Apus, or absent. The absence of an annulus is an apomorphic but homoplastic feature of swift, psittaciform, gruiform and passerine spermatozoa. The long distal centriole, penetrating the entire midpiece, is a remarkably plesiomorphic feature of the swift spermatozoa, known elsewhere only in palaeognaths. The long centriole of Apus, if not a reversal, would be inconsistent with the former placement of the Apodiformes above the Psittaciformes from DNA,DNA hybridization. In contrast to passerines, in A. apus the microtubules in the spermatid are restricted to a transient single row encircling the cell. The form of the spermatozoon fully justifies the exclusion of swifts from the passerine family Hirundinidae. [source] Fine structure of unusual spermatozoa and spermiogenesis of the mite Megisthanus floridanus Banks, 1904 (Acari: Gamasida: Antennophorina)ACTA ZOOLOGICA, Issue 4 2002Gerd Alberti Abstract The aflagellate spermatozoa of the gamasid mite Megisthanus floridanus are characterized by a large vacuole which contains a cytoplasmic column protruding into the vacuole from the region defined as the posterior part of the cell. The membrane of the column and the inner membrane of the posterior part of the cytoplasmic mantle (outer sheath) surrounding the vacuole bear numerous so-called cellular processes. However, most of the outer sheath is reduced and represented solely by a very thin membrane-like envelope. The posterior part of the cell bears extensive folds. The cell, or, more precisely, the column, shows a deep posterior invagination. This invagination contains extracellular material composed of thin filaments or strands. Peripheral folds emerging from the posterior rim of the cell form a thin-walled tube that contains the same material as the invagination. The elongated nucleus is attached to a peculiar acrosomal complex consisting of a flat acrosomal cisterna that parallels most of the cell membrane, an attachment cone, and a short acrosomal filament which is embedded in a narrow canal within the nucleus. The spermatozoa of M. floridanus represent a peculiar version of the vacuolated type of sperm known to be plesiomorphic within the anactinotrichid Acari. Some details of spermiogenesis are described and consequences for phylogenetic and systematic considerations are discussed. [source] Development of an identification system for location of free metallic particles in GIS based on analysis of Lamb wavesELECTRICAL ENGINEERING IN JAPAN, Issue 3 2009Masahiro Kozako Abstract We investigated propagation properties of Lamb waves in a gas-insulated switchgear (GIS) tank to diagnose insulation performance of GIS. The acoustic signals excited by a free metallic particle colliding with the tank sheath were measured using AE sensors. The wavelet transform was applied to decompose the wave data into its time,frequency components. As a result, difference of propagation properties of Lamb waves is clearly seen with different sizes of GIS tank. Based on the characteristics of Lamb waves, algorithms for location identification of a free metallic particle were examined in model GIS using two AE sensors. Herein, we propose a new system for location identification of a free metallic particle in GIS. Moreover, it is verified that the new identification system is suitable as a diagnostic technique for GIS. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(3): 28,35, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20676 [source] Histopathological alterations in the edible snail, Babylonia areolata (spotted babylon), in acute and subchronic cadmium poisoningENVIRONMENTAL TOXICOLOGY, Issue 2 2005P. Tanhan Abstract Histopathological alterations in 6- to 8-month-old juvenile spotted babylon, Babylonia areolata, from acute and subchronic cadmium exposure were studied by light microscopy. The 96-h LC50 value of cadmium for B. areolata was found to be 3.35 mg/L, and the maximum acceptable toxicant concentration (MATC) was 1.6 mg/L. Snails were exposed to 3.35 and 0.08 mg/L (5% of MATC) of cadmium for 96 h and 90 days, respectively. After exposure the gill, the organs of the digestive system (proboscis, esophagus, stomach, digestive gland, and rectum), and the foot were analyzed for cadmium accumulation. The results showed that most digestive organs had a high affinity for cadmium. The main target organ was the stomach, which could accumulate on average 1192.18 ,g/g dry weight of cadmium. Cadmium was shown to accumulate to a lesser extent in the digestive gland, gill, rectum, esophagus, proboscis, and foot. Histopathological alterations were observed in the gill and digestive organs (proboscis, esophagus, stomach, and rectum). The study showed that the stomach and gill were the primary target organs of both acute and subchronic exposure. Gill alterations included increased size of mucous vacuoles, reduced length of cilia, dilation and pyknosis of nuclei, thickening of basal lamina, and accumulation of hemocytes. The epithelial lining of the digestive tract showed similar alterations such as increased size of mucous vacuoles, reduced length of cilia, and dilation of nuclei. In addition, fragmentation of the muscle sheath was observed. © 2005 Wiley Periodicals, Inc. Environ Toxicol 20: 142,149, 2005. [source] | ||||||||||||||||||||||||||||||||||||||||