Home About us Contact
|
Home About us Contact | ||
|
|
||
Distal Tip (distal + tip)
Selected AbstractsMorphogenesis of the node and notochord: The cellular basis for the establishment and maintenance of left,right asymmetry in the mouseDEVELOPMENTAL DYNAMICS, Issue 12 2008Jeffrey D. Lee Abstract Establishment of left,right asymmetry in the mouse embryo depends on leftward laminar fluid flow in the node, which initiates a signaling cascade that is confined to the left side of the embryo. Leftward fluid flow depends on two cellular processes: motility of the cilia that generate the flow and morphogenesis of the node, the structure where the cilia reside. Here, we provide an overview of the current understanding and unresolved questions about the regulation of ciliary motility and node structure. Analysis of mouse mutants has shown that the motile cilia must have a specific structure and length, and that they must point posteriorly to generate the necessary leftward fluid flow. However, the precise structure of the motile cilia is not clear and the mechanisms that position cilia on node cells have not been defined. The mouse node is a teardrop-shaped pit at the distal tip of the early embryo, but the morphogenetic events that create the mature node from cells derived from the primitive streak are only beginning to be characterized. Recent live imaging experiments support earlier scanning electron microscopy (SEM) studies and show that node assembly is a multi-step process in which clusters of node precursors appear on the embryo surface as overlying endoderm cells are removed. We present additional SEM and confocal microscopy studies that help define the transition stages during node morphogenesis. After the initiation of left-sided signaling, the notochordal plate, which is contiguous with the node, generates a barrier at the embryonic midline that restricts the cascade of gene expression to the left side of the embryo. The field is now poised to dissect the genetic and cellular mechanisms that create and organize the specialized cells of the node and midline that are essential for left,right asymmetry. Developmental Dynamics 237:3464,3476, 2008. © 2008 Wiley-Liss, Inc. [source] Glutathione Peroxidase-Based Amperometric Biosensor for the Detection of S -NitrosothiolsELECTROANALYSIS, Issue 21 2006Mustafa Musameh Abstract A new biosensor is described for the detection of S -nitrosothiols (RSNOs) based on their decomposition by immobilized glutathione peroxidase (GPx), an enzyme containing selenocysteine residue that catalytically produces nitric oxide (NO) from RSNOs. The enzyme is entrapped at the distal tip of a planar amperometric NO sensor. The new biosensor shows good sensitivity, linearity, reversibility, and response times towards various RSNO species in PBS buffer, pH,7.4 . In most cases, the response time is less than 5,min, and the response is linear up to 6 ,M of the tested RSNO species. The lowest detection limit is obtained for S -nitrosocysteine (CysNO), at approx. 0.2,,M. The biosensor's sensitivity is not affected by the addition of EDTA as a chelating agent; an advantage over other potential catalytic enzymes that contain copper ion centers, such as CuZn-superoxide dismutase and xanthine oxidase. However, lifetime of the new sensor is limited, with sensitivity decrease of 50% after two days of use. Nonetheless, the new amperometric GPx based RSNO sensor could prove useful for detecting relative RSNO levels in biological samples, including whole blood. [source] Sperm ultrastructure and spermiogenesis in two Exogone species (Polychaeta, Syllidae, Exogoninae)INVERTEBRATE BIOLOGY, Issue 4 2002Adriana Giangrande The spermatozoa of Exogone naidina and E. dispar are characterized by a prominent bell-shaped acrosome, a spheroidal nucleus, and a conventional flagellum. During spermiogenesis, the acrosomal vesicle undergoes conspicuous modifications leading to its final bell shape with a posterior opening. The subacrosomal material initially shows radiating filaments but in mature sperms it appears as a meshwork of electron-opaque material. The acrosomal axis is oblique with respect to the main longitudinal sperm axis. The chromatin is arranged in electron-opaque strands in the early spermatids, then becomes amorphous, and is finally organized in filaments in mature sperms. Centrioles are orthogonally arranged beneath the nucleus and fibers radiate from the distal centriole to contact the plasma membrane and the single mitochondrion. The latter is located eccentrically on the side of the nucleus opposite the acrosome. A disk-shaped structure is evident beneath the distal centriole. The flagellar axoneme has a 9+2 microtubule pattern. A conspicuous glycocalyx surrounds the flagellar plasma membrane, and an electron-lucent space is present between these two structures at the distal tip of the flagellum. We compare the sperm morphology of these two species of Exogone with that described in other members of the subfamily Exogoninae. The fine structure of these two species supports the occurrence of an ent-aquasperm type within Exogoninae, in accordance with the brood strategy present within this subfamily. The mode of reproduction is of taxonomic importance for defining subfamilies within Syllidae, and is likely also of phylogenetic significance. Because epitoky is probably plesiomorphic, the ent-aquasperm type found in Exogoninae can be considered a derived feature within Syllidae. [source] Measurement of the linear dynamics of the descent of the bovine fetal testisJOURNAL OF ANATOMY, Issue 1 2003M. J. Edwards Abstract Measurements were made on 86 male bovine fetuses collected from abattoirs in the vicinity of Sydney, Australia. The fetal body length was used to calculate the approximate day of gestational age (DGA); most fetuses were between 60 and 150 DGA. The distances from the caudal pole of the kidney (metanephros) to, respectively, the tip of the scrotum, the distal end of the testis and the internal ring of the inguinal canal were measured, as well as the dimensions of the testis and gubernaculum testis. Distances of (1) testis to inguinal canal, (2) inguinal canal to scrotum, (3) testis to scrotum and (4) gubernaculum to scrotum were calculated from these measurements, which were made on both left and right sides. The total length of the gubernaculum testis increased during transabdominal passage and during transinguinal passage of the testis. Furthermore, the gubernaculum appeared to maintain the testis at a relatively fixed distance from the scrotum during transabdominal passage so that the inguinal canal appeared to move towards the testis. The greatest distance between the testis and the tip of the scrotum was found during the transinguinal passage of the testis and was 2.8 cm for the left testis and 2.3 cm for the right. When located within the scrotum, each testis was still 1.6,1.7 cm from the tip of the scrotum, so the distance to be traversed was only 0.6,1.2 cm. Following passage of the testis through the inguinal canal, the gubernaculum became shorter and its distal tip was displaced toward the distal end of the scrotum. Traction by the gubernaculum could account for the final transposition of the testis from the external inguinal ring to the scrotum. Other factors involved in displacement of the testis include differential growth patterns as well as increases in the dimensions of the testis itself. [source] Combining the EndoFlex® tube with fiberoptic bronchoscopy in difficult intubationACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 7 2009K. SUGIYAMA We applied a combination technique using the EndoFlex® tube with fiberoptic bronchoscopy for a 69-year-old man presenting with limited mouth opening and neck movement. Awake nasotracheal intubation was performed under conscious sedation with propofol and fentanyl. After positioning the tip of the EndoFlex® tube in the oropharynx, the fiberoptic bronchoscope was inserted into the tube until the tip reached the bevel of the tube. Anterior flexion of the distal tip of the EndoFlex® tube facilitated uncomplicated insertion of the tube into the trachea without impingement on the arytenoids. Fiberoptic visualization confirmed that the distal-tip flexing mechanism of the EndoFlex® tube corrected the direction of the tube tip anteriorly, allowing entry into the trachea. We present a case where this technique proved valuable for tracheal intubation in a patient with limitations of mouth opening and neck movement. [source] Catheter-Based Transendocardial Myocardial Gene TransferJOURNAL OF INTERVENTIONAL CARDIOLOGY, Issue 1 2002CHRISTER SYLVÉNM.D. Ph.D. Background and Aim: Local modulation of myocardial function by gene transfer or cell depositions constitutes a potential method of cardiac treatment. This study tested the morphology of myocardial plasmid gene transfer by catheter-based transendocardial injection (NOGA). Methods: Left ventricular morphology and electrical and mechanical characteristics were mapped in three dimensions. In two pigs, 0.10 mL oftoluidine blue was injected at ten sites. In seven pigs, seven to ten injections of 0.10 mL saline containing 0.10 mg pCMV-LacZ expressing the enzyme ,-galactosidase and 0.10 mg phVEGF-A165 were given. The pigs were sacrificed after 3 days and gene expression was determined. Results: Macroscopically on the endocardial surface, all identified spots were located in the target area. However, along the transmyocardial axis, injections with color and plasmid were located randomly throughout the left ventricular wall from the endocardium to the epicardium. In each detected spot, gene expression of ,-galactosidase was observed in an approximate myocardial volume of 5 × 5 × 5 mm. Microscopically, the transfected cells were located typically at the tip of the injection scar. As a rule, 10 to 20 transfected cells were located at the end of the injection scar. In sections where expression of both transcripts was observed, 42% of the cells expressed both ,-galactosidase and vascular endothelial growth factors (VEGF), 32% only ,-galactosidase, and 26% only VEGF. Conclusions: Myocardial gene transfer following magnetic guidance can be located precisely on the left ventricular inner surface. Within the myocardium, gene expression is local around the distal tip of the injection scar and is located randomly at every level of depth of the left ventricular wall. [source] Continuous peripheral nerve block catheter tip adhesion in a rat modelACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 6 2006C. C. Buckenmaier III Background:, Continuous peripheral nerve block (CPNB) has been used effectively in combat casualties from Iraq and Afghanistan to provide surgical anesthesia and extended duration analgesia during evacuation and convalescence. Little information is available concerning catheter tip tissue reaction with prolonged use. Methods:, Forty-eight male Sprague-Dawley rats were assigned (12 per group) to one of four catheter tip designs provided by Arrow International: group A, 20-gauge catheter with three side-holes and a bullet-shaped tip; group B, 19-gauge StimuCathÔ catheter with coiled omni-port end with hemispherical distal tip; group C, 19-gauge catheter with single end-hole in conducting tip; group D, 19-gauge catheter with closed conducting tip with four side-holes. Following laparotomy, a randomly assigned catheter tip was sutured to the parietal peritoneal wall with the tip extending between experimental injuries created on the abdominal wall and cecum. After 7 days in situ, the catheter tips were removed from the adhesion mass using a force gauge, and the grams of force needed for removal were recorded. Results:, The mean force ± standard deviation values were 1.09 ± 1.21 g for group A, 21.20 ± 30.15 g for group B, 0.88 ± 1.47 g for group C and 1.60 ± 2.50 g for group D. The variation of each catheter group mean force compared with that of group B was significant (P < 0.05). There was no significant difference in adhesion force between groups A, C and D. Conclusions:, These results suggest that the manufactured design of a CPNB catheter tip can contribute to the adhesion of the tip in an intense inflammatory environment. This finding may have important clinical implications for CPNB catheters left in place for extended periods of time. [source] Thoracic epidural catheters via the caudal and lumbar approaches using styletted multiple port catheters in pediatric patients: a report of three casesACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 4 2006B. C. H. Tsui Advancing catheters from the lumbar and caudal epidural spaces to the thoracic level has been reported to be an alternative to the direct thoracic approach. However, as children grow, the threading of catheters in the epidural space becomes increasingly difficult. This report describes three cases of thoracic epidural placement using a multiport catheter threaded from the caudal and lumbar spaces using electrical stimulation guidance. In the first case, a multiport catheter was threaded 22 cm from the lumbar space to T8 following a failed attempt with a single-port catheter in a 9-year-old boy scheduled to undergo a right nephrectomy. In the second case, a multiport catheter was threaded 26 cm from the caudal space to T9 in a 3-year-old girl undergoing fundoplication. In the last case, a multiport catheter was inserted at the completion of a fundoplication in a 2-year-old girl after it had been confirmed that the single-port catheter inserted prior to surgery had not advanced to the desired thoracic level. The multiport catheter was threaded 17 cm without resistance from the caudal space to T9. In all cases, electrical stimulation was used to confirm the location of the catheter tip at the time of insertion. The position of the catheters was later confirmed by X-ray. The multiport catheter incorporates a stylet, which extends to a closed distal tip, within a catheter body that ejects fluid from three lateral holes in a direction perpendicular to the advancing catheter. These properties may facilitate the reliable advancement of catheters in the epidural space. [source] Diameter of paediatric sized flexible bronchoscopes: When size mattersPEDIATRIC PULMONOLOGY, Issue 8 2006Barry Linnane MD Abstract Background: A flexible bronchoscope typically gets its designated size from the diameter of the distal tip but this is not the maximum diameter of the insertion tube. Aim: The aim of this study was to determine the size and site of the maximum diameter of flexible bronchoscope insertion tubes and to compare standard bronchofiberscopes with newer bronchovideoscopes. Methods: We assessed 10 bronchoscopes ranging from 2.2 to 4.9 mm external diameter (Olympus®, Tokyo, Japan) using an electronic digital caliper. Investigators were blinded to the type and model of each scope. The median, minimum and maximum diameters of the bronchoscopes were calculated and the measured diameters were compared with the stated diameters of the distal tip and insertion tube. Results: The maximum and median measured diameters were wider than the stated diameter of the distal tip in all the scopes. The maximum discrepancy between the measured and stated diameters ranged from 0.19 mm (6.7%) to 0.66 mm (22.2%) with a mean of 0.41 mm (14.0%). There was no difference between bronchofiberscopes and bronchovideoscopes. Conclusion: The maximum diameter of the distal tip and insertion tube of pediatric sized flexible bronchoscopes is significantly greater than the manufacturer's specifications. This may impact on the choice of bronchoscope selected for procedures in children. Pediatr Pulmonol. 2006; 41: 787,789. © 2006 Wiley-Liss, Inc. [source] A prospective, randomised, cross-over trial comparing the EndoFlex® and standard tracheal tubes in patients with predicted easy intubationANAESTHESIA, Issue 11 2009W. H. L. Teoh Summary We aimed to determine if using the EndoFlex® tracheal tube on the first intubation attempt provided improved placement times and intubation success compared with a standard-type tracheal tube in 50 patients undergoing gynaecological surgery in a prospective, randomised, cross-over trial. We found that using the EndoFlex resulted in shorter intubation times (mean (SD) 14.8 (9.7) vs 30.1 (30.5) s), easier intubation (VAS, median (range) 10 (0,70) vs 20 (0,100)), and an increased rate of successful insertion at the first attempt; all p < 0.001. Flexing the distal tip of the EndoFlex was used in 18 patients. There were reductions in the use of external laryngeal pressure, advancement of laryngoscope blade and increased lifting force when intubating with the EndoFlex. Furthermore, patients with a grade 2 (19/50) or 3 (6/50) laryngoscopic view had shorter intubation times, easier intubation and reduced insertion attempts with the EndoFlex. The EndoFlex is a satisfactory alternative to a standard-type tracheal tube, even with an anterior larynx. [source] Delivery sheath tear after modification for ASD closureCATHETERIZATION AND CARDIOVASCULAR INTERVENTIONS, Issue 1 2006FSCAI, Mark H. Hoyer MD Abstract During transcatheter closure of an atrial septal defect with insufficient aortic rim, a standard delivery sheath was modified by cutting a bevel at the distal tip to improve device orientation. The sheath split longitudinally when attempting to recapture the closure device. Troubleshooting allowed a device to be implanted successfully. Pitfalls regarding our sheath modification and methods to overcome prolapse of the left atrial disk into the right atrium are discussed. © 2006 Wiley-Liss, Inc. [source] | |||||||||||||||||||||||||