The relationship between developing oligodendrocyte units and maturing axons during myelinogenesis in the anterior medullary velum of neonatal rats

Myelinogenesis was investigated in whole-mounted anterior medullary vela from rats aged postnatal day (P) 10–12, using double immunofluorescence labelling with Rip and anti-neurofilament 200 (NF200) antibodies, to identify oligodendrocytes and axons, respectively. A number of discrete phases of maturation of oligodendrocyte units were recognised. (1) Promyelinating oligodendrocytes co-expressed Rip and Myelin basic Protein and formed axonal associations, prior to ensheathment. (2) Transitional oligodendrocytes contained both ensheathing and non-ensheating processes. (3) Myelinating oligodendrocytes were established after a period of remodelling (in which non-ensheathing processes were lost), appearing as oligodendrocyte unit morphological phenotypes with a definitive number of incipient myelin sheaths. (4) Maturation of myelinating oligodendrocytes was defined as the establishment of internodal sheath lengths and the redistrubution of myelin basic protein from the cell somata and radial processes into the myelin sheaths only. Myelination was probably related to the maturational state of the axons, since it was initiated when the latter had attained a critical diameter of between ～0.2 and 0.4 μm, coincident with the expression of NF200. Oligodendrocyte differentiation and myelination of the AMV were asynchronous and multifocal, and at P10: (1) axons which were destined to be of the largest calibre in the adult AMV were already myelinated by early developing oligodendrocytes, whilst those which were destined to be the smallest calibre in the adult were unmyelinated, but ultimately became ensheathed by late developing oligoendrocytes; (2) axons were sequentially ensheathed by early developing myelinating oligodendrocytes and late developing promyelinating oligodendrocytes; (3) all axons were small calibre; (4) oligodendrocyte units exhibited polymorphism. Thus, the development of oligodendrocyte morphological phenotypes was not related solely to either the physical dimension of axon calibre at the time of ensheathment, nor oligodendrocyte birth dates.     

Shape‐shift: Semicircular canal morphology responds to selective breeding for increased locomotor activity

Variation in semicircular canal morphology correlates with locomotor agility among species of mammals. An experimental evolutionary mouse model was used to test the hypotheses that semicircular canal morphology (1) evolves in response to selective breeding for increased locomotor activity, (2) exhibits phenotypic plasticity in response to early‐onset chronic exercise, and (3) is unique in individuals possessing the minimuscle phenotype. We examined responses in canal morphology to prolonged wheel access and selection in laboratory mice from four replicate lines bred for high voluntary wheel‐running (HR) and four nonselected control (C) lines. Linear measurements and a suite of 3D landmarks were obtained from 3D reconstructions of μCT‐scanned mouse crania (μCT is microcomputed tomography). Body mass was smaller in HR than C mice and was a significant predictor of both radius of curvature and 3D canal shape. Controlling for body mass, radius of curvature did not differ statistically between HR and C mice, but semicircular canal shape did. Neither chronic wheel access nor minimuscle affected radius of curvature or canal shape These findings suggest that semicircular canal morphology is responsive to evolutionary changes in locomotor behavior, but the pattern of response is potentially different in small‐ versus large‐bodied species.     

An anatomic atlas of the medulla oblongata of the adult goat.

An anatomic atlas of the goat brain stem was developed for use in studies that analyze medullary neuronal groups, and factors that influence variability in the location of neuronal groups were determined. The medullas of 31 adult goats (weight, 17-88 kg) were fixed, harvested, frozen, serially sectioned, stained with 0.5% neutral red, and examined with a light microscope. Obex, the point at which the central canal opens into the fourth ventricle, was taken as the zero reference point from which the rostrocaudal and mediolateral coordinates of medullary neuronal groups were determined, whereas dorsoventral coordinates were calculated from the medullary surface. Histological variations with goat body weight were quantified, and linear regression analysis provided adjustment factors for weight in all three dimensions. Similar analysis of percentage of shrinkage on fixation and processing provided adjustment factors for precise coordinates of medullary neuronal groups. For accurate location of neuronal groups, body weight and histological procedure should be taken into account. The present study provided adjustment factors for body weight and standard histological processing to locate most major medullary neuronal groups in the adult goat.     

Correction of pincer-nail deformity using dermal grafting

Pincer-nail syndrome has been described as distortion in the shape of the nails with excessive transverse curvature of the plate that increases from proximal to distal, leading to pinching and loss of soft tissue in the affected digit, resulting in severe pain. Many treatments have been recommended, but an effective long-term method that preserves the nail matrix has not been described. A method of dermal grafting under the nail matrix is described, and the results of treatment of six digits are reported. Five women and one man with an average age of 52 were treated. The affected digit was the thumb in four patients and the great toe in two patients. Follow-up averaged 25 1/2 months. The results were good in all cases with only one side of one nail remaining slightly curved. Pain was relieved in all cases, and complete adherence of the new nail plate occurred. Dermal grafting seems to provide excellent long-term treatment of the pincer-nail deformity with preservation of the nail matrix.     

Intraspecific variation in the domestic cat bony labyrinth revealed by different measurement techniques

The knowledge of intraspecific variation is important to make assumptions on an interspecific level. To study intraspecific variation in the bony labyrinth morphology of the domestic cat, eleven specimens of Felis silvestris catus and two additional subspecies (F. s. lybica, F. s. ornata) were investigated. The sample comprises skulls of adult males and females, as well as juvenile cats. Each bony labyrinth endocast was virtually reconstructed based on µCT scans. To estimate the radius of curvature of each inner ear semicircular canal, three different approaches were tested. The comparison of the different methods resulted in different absolute values for the measured radii. The assumed best structure to precisely characterize the size of a semicircular canal is the inner perimeter. Within the tested sample, the anterior semicircular canal is always the largest, while the posterior semicircular canal is the second largest and the lateral semicircular canal the smallest in most cases. The coefficient of variation lies below 10% for all bony labyrinth measurements within the sample. The inner perimeter values of each semicircular canal are similar within all investigated specimens, even though the skull length of adult cats is twice as long as that of juvenile cats. Thus, inner ear biometry of the domestic cat seems stable throughout growth series and can therefore be used for systematic and ecological studies and the inclusion of juvenile individuals is reasonable. It is noteworthy that the inner perimeter values of the semicircular canals do not vary as much as the values of the angles spanned between the three canals within the sample. The inner ear within the cat skull is oriented about 25° to 31° to the palate (angle between the plane anchored to the lateral semicircular canals (SC) and the plane anchored to the palate). The cochlea coils between 3.00 and 3.25 turns in the investigated sample.     

The fixion proximal femur nailing system: biomechanical properties of the nail and a cadaveric study

The treatment of choice for early mobilization of hip fracture is surgery, which traditionally employs side plates and screws or intramedullary nails. We examined the biomechanical properties of a new proximal femoral nail system. The new expandable Fixion proximal femur nailing (PFN) system, made of stainless-steel alloy, consists of a nail, a peg and an anti-rotation pin. Upon positioning, the nail and peg are expanded to their maximal diameter. The current biomechanical study investigated: nail bending strength and stiffness, fatigue properties and hip peg strength. A cadaveric study that determined the effect of the expandable peg on the femoral head included subsidence testing, pull and torsion testing and intra-osseous pressure (IOP) measurements before and after expansion. Biomechanical properties of the new nail met ASTM F384 guideline requirements. The cadaver study yielded equivalent results for the pullout test between the peg and the hip screw, but found the peg superior in the torsion strength test. IOP during peg insertion and expansion was substantially lower than the threshold pressure that causes avascular necrosis. The biomechanical tests found the new system to be safe and able to provide good abutment of the nail to the bone. We conclude that the Fixion PFN system proved to be an effective proximal femur fracture fixation device.     

Fixation of a human rib by an intramedullary telescoping splint anchored by bone cement

A novel concept for rib fixation is presented that involves the use of a bioresorbable polymer intramedullary telescoping splint. Bone cement is used to anchor each end of the splint inside the medullary canal on each side of the fracture site. In this manner, rib fixation is achieved without fixation device protrusion from the rib, making the splint completely intramedullary. Finite element analysis is used to demonstrate that such a splint/cement composite can preserve rib fixation subjected to cough-intensity force loadings. Computational fluid dynamics and porcine rib experiments were used to study the anchor formation process required to complete the fixation.     

The unique organization of filamentous actin in the medullary canal of the medulla oblongata

In the central canal, F-actin is predominantly localized in the apical region, forming a ring-like structure around the circumference of the lumen. However, an exception is found in the medulla oblongata, where the apical F-actin becomes interrupted in the ventral aspect of the canal. To clarify the precise localization of F-actin, the fluorescence signals for F-actin were converted to the peroxidase/DAB reaction products in this study by a phalloidin-based ultrastructural technique, which demonstrated that F-actin is located mainly in the microvilli and terminal webs in the ependymocytes. It is because the ventrally oriented ependymocytes do not possess well-developed microvilli or terminal web that led to a discontinuous labeling of F-actin in the medullary canal. Since spinal motions can change the shape and size of the central canal, we next examined the cytoskeletons in the medullary canal in both rats and monkeys, because these two kinds of animals show different kinematics at the atlanto-occipital articulation. Our results first demonstrated that the apical F-actin in the medullary canal is differently organized in the animals with different head-neck kinemics, which suggests that the mechanic stretching of spinal motions is capable of inducing F-actin reorganization and the subsequent cell-shape changes in the central canal.     

Personnel real time dosimetry in interventional radiology

Interventional radiology and hemodynamic procedures have rapidly grown in number in the past decade, increasing the importance of personnel dosimetry not only for patients but also for medical staff. The optimization of the absorbed dose during operations is one of the goals that fostered the development of real-time dosimetric systems. Indeed, introducing proper procedure optimization, like correlating dose rate measurements with medical staff position inside the operating room, the absorbed dose could be reduced. Real-time dose measurements would greatly facilitate this task through real-time monitoring and automatic data recording. Besides real-time dose monitoring could allow automatic data recording. In this work, we will describe the calibration and validation of a wireless real-time prototype dosimeter based on a new sensor device (CMOS imager). The validation measurement campaign in clinical conditions has demonstrated the prototype capability of measuring dose-rates with a frequency in the range of few Hz, and an uncertainty smaller than 10%.     

Reconstruction of fingertip amputations with full-thickness perionychial grafts from the retained part and local flaps.

The treatment of fingertip amputations distal to the distal interphalangeal joint when the amputated part is saved is difficult and controversial. Both reattachment of the amputated portion as a composite graft and microvascular anastomosis are prone to failure in this distal location. The authors have evolved a reconstructive plan that uses the nail matrix, perionychium, and hyponychium of the amputated fingertip as a full-thickness graft when the amputation is between the midportion of the nail bed andjust proximal to the eponychial fold. Various flaps are used to lengthen and augment the finger pulp, and skeletal pinning is carried out as necessary. The charts of 15 patients who underwent this procedure over a 38 month period were evaluated retrospectively. Seven returned to the office for examination at least 1 year after the fingertip reconstruction described above; four others were interviewed by telephone. Nail deformity, fingertip sensation, and joint range of motion were evaluated, and the reconstructed fingertips were photographed in standardized views. In six of the seven patients seen in the office, aesthetic and functional results were judged as good by both patient and physician; one of the six had minimal nail curvature. The seventh patient had no nail growth, although finger length was retained and there was no functional disability. The four patients interviewed by phone reported normal fingertip use with no dysesthesias or cold intolerance; all had nail growth, although three patients described slight nail curvature that required care in trimming. The authors favor salvage of all perionychial parts when a distal fingertip amputation occurs. Reconstruction of the fingertip with grafting of the hyponychium, perionychium, and nail matrix from the amputated part combined with local flaps can provide a very satisfactory functional and aesthetic result.     

后磨牙模拟根管模型制备与研究

目的:制备后磨牙模拟根管模型。方法:依照预实验中测试的牙本质和树脂根管模型材料的布氏硬度值(牙本质HB72,树脂块HB54)选取纯铜质铜管为材料(纯铜HB58)同时利用预实验中确认的后磨牙模拟根管模型弯曲角度的范围(70°-60°)并参照树脂根管模型相关数据,设计不同弯曲角度(70°,64°,60°)的纯铜质根管模型,将20套镍钛根管锉随机分为4组,其中3组根管锉分别预备相应角度的10个纯铜质后磨牙根管模型,另一组在临床预备10个后磨牙根管作为对照组。所有镍钛根管锉均在疲劳寿命测试装置中测试疲劳寿命。结果:选用根管长度为16mm±1mm,弯曲半径为5mm,内径为0.70mm的纯铜质铜管制作后磨牙根管模型。其中在弯曲角度为70°的后磨牙根管模型中有33%(2/6)近似临床;在弯曲角度为64°的后磨牙根管模型中有67%(4/6)近似临床;在弯曲角度为60°的后磨牙根管模型中有33%(2/6)近似临床。结论:弯曲角度为64°的纯铜制后磨牙模拟根管模型更接近于临床实际,可为体外研究镍钛根管锉各项指标提供一个较为理想的模型。     

后磨牙模拟根管模型制备与研究

目的：制备后磨牙模拟根管模型。方法：依照预实验中测试的牙本质和树脂根管模型材料的布氏硬度值（牙本质HB72,树脂块HB54）选取纯铜质铜管为材料（纯铜HB58）同时利用预实验中确认的后磨牙模拟根管模型弯曲角度的范围（70°-60°）并参照树脂根管模型相关数据,设计不同弯曲角度（70°,64°,60°）的纯铜质根管模型,将20套镍钛根管锉随机分为4组,其中3组根管锉分别预备相应角度的10个纯铜质后磨牙根管模型,另一组在临床预备10个后磨牙根管作为对照组。所有镍钛根管锉均在疲劳寿命测试装置中测试疲劳寿命。结果：选用根管长度为16mm±1mm,弯曲半径为5mm,内径为0.70mm的纯铜质铜管制作后磨牙根管模型。其中在弯曲角度为70°的后磨牙根管模型中有33%（2/6）近似临床;在弯曲角度为64°的后磨牙根管模型中有67%（4/6）近似临床;在弯曲角度为60°的后磨牙根管模型中有33%（2/6）近似临床。结论：弯曲角度为64°的纯铜制后磨牙模拟根管模型更接近于临床实际,可为体外研究镍钛根管锉各项指标提供一个较为理想的模型。     

Biomechanical studies and finite element analysis of a bone-implant interface]

In the present study, the fixation system of a femoral medullary nail connection was investigated. In surgical treatment of fractured femurs, the fracture is bridged by a medullary nail that is fixed by interlocking screws in the bone. Bone failure around these screws is the most common complication associated with the treatment of fractures of osteoporotic bone. The present study analyses the stresses present in the region of the implant/bone system. Three-dimensional finite element models were generated, a nonlinear structure analysis performed, and the stresses at material interfaces investigated. The highest concentration of stresses is to be found in the middle of the interlocking screws and the holes drilled in the bone. This is in agreement with the results of experimental investigations.     

Geometry of human ribs pertinent to orthopedic chest-wall reconstruction

Orthopedic reconstruction of blunt chest trauma can aid restoration of pulmonary function to reduce the mortality associated with serial rib fractures and flail chest injuries. Contemporary chest wall reconstruction requires contouring of generic plates to the complex surface geometry of ribs. This study established a biometric foundation to generate specialized, anatomically contoured osteosynthesis hardware for rib fracture fixation. On human cadaveric ribs three through nine, the surface geometry pertinent to anatomically conforming osteosynthesis plates was characterized by quantifying the apparent rib curvature C(A), the longitudinal twist alpha(LT) along the diaphysis, and the unrolled curvature C(U). In addition, the rib cross-sectional geometry pertinent to intramedullary fixation strategies was characterized in terms of cross-section height, width, area, and cortex thickness. The rib surface exhibited a curvature C(A) ranging from 3.8 m(-1) in the anteromedial section of rib seven to 17.3 m(-1) in the posterior section of rib three. All ribs had in common a longitudinal twist alpha(LT), ranging from 41-60 degrees. The unrolled curvature C(U) decreased gradually from ribs three to five, and increased gradually with reversed orientation from rib six to nine. The cross-sectional area remained constant along the rib diaphysis. However, the medullary canal increased in size from 29.9 mm(2) posteriorly to 41.2 mm(2) in anterior rib segments. Results of this biometric rib characterization describe a novel strategy for intraoperative plate contouring and provide a foundation for the development of specialized rib osteosynthesis strategies.     

Cement flow during impaction allografting: a finite element analysis

Cement intrusion into cancellous or impacted bone is not well understood. We adopted an engineering mechanics approach to predict the effect of surgical variables on the cement intrusion into impacted cancellous bone, used for the revision of failed total hip replacement with the impaction allografting technique. Specifically, a three-dimensional finite element model was used to determine the effects of cement viscosity, the magnitude and duration of pressurization, and the distribution of the porosity along the femur on cement intrusion. The overall averaged mean intrusion depth difference between the finite element model prediction and the cadaveric measurements was 1.1mm. The depth of penetration increased with higher pressurization pressure, duration of pressurization, and earlier stem insertion (lower viscosity), but maintained a similar profile. The distribution of the porosity along the femur determined the intrusion profile. Cement viscosity, the applied pressure or the duration of the pressurization can be adjusted to limit the cement volume injected into the medullary canal and therefore prevent the cement from reaching the endosteal surface.     

Biomechanics of Schlemm's canal endothelial cells: influence on F-actin architecture

Aqueous humor drains from the eye through Schlemm's canal, a small endothelial-lined collecting duct. Schlemm's canal endothelial cells may be important in controlling the pressure within the eye (and hence are of interest in glaucoma), and are subject to an unusual combination of shear stress and a basal-to-apical pressure gradient. We sought to characterize this biomechanical environment and determine its effects on F-actin architecture in situ. A theoretical model of flow in Schlemm's canal was used to estimate shear stresses applied to endothelial cells by flowing aqueous humor. Alignment of Schlemm's canal endothelial cells in human eyes was quantified by scanning electron microscopy. F-actin architecture was visualized by fluorescent labeling and compared for closely adjacent cells exposed to different biomechanical environments. We found that, despite the relatively low flow rate of aqueous humor, shear stresses experienced by Schlemm's canal endothelial cells could reach those in the arterial system. Schlemm's canal endothelial cells showed a statistically significant preferential alignment, consistent with a shear-mediated effect. Schlemm's canal endothelial cells subjected to a basal-to-apical pressure gradient due to transendothelial flow showed a prominent marginal band of F-actin with relatively few cytoplasmic filaments. Adjacent cells not subject to this gradient showed little marginal F-actin, with a denser cytoplasmic random network. We conclude that Schlemm's canal endothelial cells experience physiologically significant levels of shear stress, promoting cell alignment. We speculate that this may help control the calibre of Schlemm's canal. F-actin distribution depends critically on the presence or absence of transendothelial flow and its associated pressure gradient. In the case of this pressure gradient, mechanical reinforcement around the cell periphery by F-actin seems to be critical.     

Ontogenesis of the human fetal nails. I. Observations using the scanning electron microscope

The development of the nail apparatus of the human foetuses from 6th to 18th weeks of pregnancy, was studied by Scanning Electron Microscopy. The main results can be summarized as follows: 1) first structure to appear is nail field defined by continuous shallow grooves; 2) the shape of the nail field is firstly ovoidal and it extends beyond the tip of the finger; later it becomes flat as in the adult nail plate; 3) the globular blebs of periderm cells accumulate mostly in the tip of the finger; 4) the surface of the nail field is first uniform, then it becomes irregular for the increasing of the process of keratinization.     

A new reconstruction of the Le Moustier 1 skull and investigation of internal structures using 3-D-μCT data

Using the non-destructive technique of 3-D micro computed tomography (3-D-μCT), we present a new, virtual reconstruction of the Le Moustier 1 Neandertal skull. This new reconstruction corrects defects found in earlier reconstruction attempts by repositioning misaligned cranial fragments, addressing the problem of asymmetry caused by pressure during the fossilization process, and placing the basioccipital in its proper anatomical position. Metric comparisons between Le Moustier 1 and juvenile and adult Neandertals demonstrate that facial height proceeded at a faster rate of growth than facial prognathism at the beginning of the adolescent period. They also confirm the anterior placement of the basioccipital. A compound painted to match the colour of the fossilized bone was used in previous reconstruction attempts and the aim of this analysis was to remove the false material to reveal to what extent the fossilized bone was preserved. The areas with the most artificial material and glue include the palate, areas around the mandibular teeth, the left frontal, and parts of the right parietal and temporal bones. The μCT data were also used to examine internal structures of the skull including the frontal sinus and the labyrinth of the inner ear. An investigation of the frontal sinus reveals morphology similar to that found in adult Neandertals, although the structure does not extend to mid-orbit. The dimension of the radius of curvature of the lateral semicircular canal falls within one standard deviation, and the anterior and posterior canals within two standard deviations, of the published Neandertal mean. As in other Neandertals, the posterior semicircular canal is in an inferior position relative to the plane of the lateral canal.     

A new reconstruction of the Le Moustier 1 skull and investigation of internal structures using 3-D-μCT data

Using the non-destructive technique of 3-D micro computed tomography (3-D-μCT), we present a new, virtual reconstruction of the Le Moustier 1 Neandertal skull. This new reconstruction corrects defects found in earlier reconstruction attempts by repositioning misaligned cranial fragments, addressing the problem of asymmetry caused by pressure during the fossilization process, and placing the basioccipital in its proper anatomical position. Metric comparisons between Le Moustier 1 and juvenile and adult Neandertals demonstrate that facial height proceeded at a faster rate of growth than facial prognathism at the beginning of the adolescent period. They also confirm the anterior placement of the basioccipital. A compound painted to match the colour of the fossilized bone was used in previous reconstruction attempts and the aim of this analysis was to remove the false material to reveal to what extent the fossilized bone was preserved. The areas with the most artificial material and glue include the palate, areas around the mandibular teeth, the left frontal, and parts of the right parietal and temporal bones. The μCT data were also used to examine internal structures of the skull including the frontal sinus and the labyrinth of the inner ear. An investigation of the frontal sinus reveals morphology similar to that found in adult Neandertals, although the structure does not extend to mid-orbit. The dimension of the radius of curvature of the lateral semicircular canal falls within one standard deviation, and the anterior and posterior canals within two standard deviations, of the published Neandertal mean. As in other Neandertals, the posterior semicircular canal is in an inferior position relative to the plane of the lateral canal.     

Curvature and tortuosity of the superficial femoral artery: a possible risk factor for peripheral arterial disease.

Atherosclerosis in the superficial femoral artery (SFA) resulting in peripheral arterial disease is more common in men than women and shows a predilection for the region of the adductor canal. Blood flow patterns are related to development of atherosclerosis, and we investigated if curvature and tortuosity of the femoral artery differed between young men and women and if differences resulted in adverse flow patterns. Magnetic resonance imaging (MRI) and computational fluid dynamics (CFD) were combined in 18 young adult volunteers (9 men) to assess the relationship of flow features to likely sites of future atherosclerosis formation. Subjects underwent MRI of the right SFA, three-dimensional vascular geometry was reconstructed, and measures of tortuosity and curvature were calculated. Tortuosity and curvature were significantly greater for men than women, and this was related to increased body surface area, body mass index, or weight in men. In both sexes, "tortuosity" increased from the midthigh to the popliteal fossa. The greatest curvature was found within the distal quarter of the SFA. CFD modeling was undertaken on MRI-based reconstructions of the SFA. Wall shear stresses (WSS) were extracted from the computations. WSS showed greater spatial variation in the men than in the women, and the men exhibited lower mean WSS. These data indicate that sex differences related to body size and anatomical course of the femoral artery may contribute to the enhanced risk of focal atherosclerosis in the adductor canal.