1,720,961 research outputs found
PHYSICAL AND BIOLOGICAL ASPECTS OF THE CELLULAR REACTION OF FOREIGN BODY PARTICLES IN ORTHOPAEDIC IMPLANTS
No full textpoly-epiphyseal overgrowth: description of a previously unreported skeletal dysplasia
No full textA skeletal dysplasia with previously unreported features is presented. Its evolution was characterized by growth abnormalities of bones without involvement of other organs. Advanced bone age, increased stature and irregular epiphyseal ossification with stippling of the main long bones were documented. Physeal overgrowth was massive in the left proximal humerus and femur. Furthermore, the hip joint appeared fused with an abundant mass of pathological calcific tissue extending from the femur to the ilium. Pathological epiphyses were characterized by anarchic cartilaginous proliferation with multiple ossification centres, while lamellar bone apposition and remodelling were normal. The observed bone changes were different from those in any previously reported syndrome, metabolic defect or bone dysplasia. However, they clearly indicated a defect of endochondral ossification with some resemblance to phenotypes observed in dysplasia epiphysealis hemimelica
bone malformations in proteus sindrome. an analysis of bone structural changes and their evolution during growth.
No full textThe radiographic follow-up of a patient with Proteus syndrome is presented. Review of radiographs obtained at 3 years 10 months, 10 years, and 17 years 8 months indicated that the rate of growth in length of the oversized tubular bones of the hands was similar to that of the normal bones of the same hand. This observation supports the view that the primary lesion occurs in the early embryonic period, when the limb bud mesenchyme cells condense and cartilage differentiates producing oversized cartilage anlages, rather than being a defect of bone cell-mediated apposition and modelling processes of bone. Additional radiographs of the pelvis and spine were obtained at age 4 years 10 months and head CT at 8 years 10 months. This pathogenetic mechanism fits well with the hypothesis of somatic mosaicism, which is at present the most credible explanation for the aetiology of Proteus syndrome. Other skeletal malformations recognized as typical of the syndrome can be interpreted as secondary adaptations to the altered mechanical conditions induced by overgrowth of bone
A model of the intracortical vascular system of long bonesand of its organization: an experimental study in rabbitfemur and tibia
No full textThe vascular anatomy of the cortical bone and the canal system are highly correlated, and the former has an important bearing on shape and microscopic lamellar structure, as it is established in the progression of the remodelling process. The classical description of a longitudinal system of canals (Havers') connected by the transversal Volkmann's canals is the generally acknowledged model of the structural organization of the cortex. However, it is remarkably difficult to study the circulation inside the compact bone in detail owing to its hard, calcified matrix, and the methods thus far applied have represented either the bone morphology and the architecture of the canal system or the injected vessel network. In the present study, the intracortical vessel network was injected with black China ink and evidenced by transillumination of full-thickness, decalcified hemicortices. By making use of the depth of field of the microscope objective, the three-dimensional architecture of the network was highlighted and the morphometry of vessel size measurements and a classification of the network nodes according to the number of arms was made possible. These observations were integrated with data obtained by routine histology on decalcified sections relevant to the connections of the intracortical canal system with the outer environment, with regard to the direction of advancement of new canals and with regard to the mode of formation of the system nodes. The formation of the intracortical vessels network involved two processes: the incorporation of the periosteal network and osteonal remodelling, the latter occurring through the advancement of cutting cones followed by their own vascular loop and by concentric lamellar apposition. The two systems could be distinguished by the diameter of the vessels (the former were significantly larger) and by the network architecture (the former convoluted, and the latter longitudinally orientated and straight). Longitudinal vessels could form branches or create connections with the periosteal derived vessels that occasionally meet on the line of their advancement. They were observed entering from either inside the cortex from the metaphyses or from the endosteal surface of the marrow cavity. The combined observations from different methods of study documented a model of intracortical canal and vessel networks formed by two initially independent systems: one derived from the external, periosteal vessels, and one from metaphyseal and marrow vessels. Connections between the two were established with the advancing of cutting cones from the extremities of the diaphysis. Analysis of the system architecture and the modalities of its progressive organization suggested that the direction of advancement of a forming canal does not necessarily correspond to the final blood flow direction of its central vessel
Cyclosporine-A delays the end-plate degeneration in denerved rat muscles
No full textWhen an adult skeletal muscle is denerved, its end-plates degenerate and their acethylcholinesterase (ACHE) activity gradually decreases. However, if the proximal segment of the nerve is sutured to the distal segment, or if the nerve is implanted in a previous denerved muscle the axons regenerate and reconstitute new end-plates over a variable period. This period depends on the time passed between the nerve cutting and the reimplantation suggesting that the degenerative processes are closely correlated to regeneration. It has been shown that cyclosporine-A (CsA) is useful in nerve regeneration but their role in nerve degeneration is not well understand. We evaluated, using AChE histochemistry, the effects of CsA, on the degeneration of the end-plates in an experimental model of gastrocnemius muscle denervation in the rat. CsA at a dose of 15 mg/kg/day did not cause any quantitative or qualitative alterations in the end-plates on normal rat muscles. Moreover, our findings showed that CsA reduced the end-plate degeneration and loss in the denerved rat muscles
Design, morphometry and development of the secondary osteonal system in the femoral shaft of the rabbit.
No full textThe architecture of the diaphyseal bone is closely correlated with the cortical vessel network, whose pattern
develops in the course of growth. Various methods have been applied to clarify the three-dimensional anatomy
of the cortical canal system, but there is still disagreement about the geometry, blood supply, flux dynamics and
factors controlling canal geometry during bone growth and remodeling. A modification of the currently employed
dye-injection method was applied to study the vessel network of the whole hemi-shaft of the rabbit femur in
mature bones (8-month-old rabbits) and growing bones (1.5-month-old rabbits). The cortical vascular tree of the
hemi-shaft of the femur was injected with black China ink and observed in full-thickness specimens of the cortex.
The same specimens were then processed for histology. A comparative study of the middle diaphysis (mid-shaft)
with the distal extremity (distal shaft) was performed in both young and old rabbit femurs. The longitudinally
oriented pattern of the vessel network was seen to develop in the diaphysis of mature femurs, while at the
extremity of the shaft of the same specimen the network showed a reticular organization without a dominant
polarization. The vessels were significantly higher in the mid-shaft than in the distal shaft of the old femurs
(
P
< 0.0001), as was their diameter (
P
< 0.05). In the group of young rabbits at mid-shaft level the longitudinally
oriented pattern of the vessel network was not yet completely developed, without their being significant differences
in length and diameter between the mid-shaft and distal shaft. The differentiation of the mid-shaft from
the distal shaft was confirmed histologically by the presence, in the latter, of longitudinal calcified cartilage septa
between osteons. This pattern of structural organization and development of the intracortical vascular network
has not been previously reported. The cells primarily involved in polarization of the remodeling process were the
osteoclasts at the top of the cutting cones advancing from the proximal and distal metaphyses toward the midshaft.
This suggests, first, a relationship with the longitudinally oriented structures already present in the
cortex near the metaphysis (the calcified cartilage septa) and then with the columns of interosteonic breccia, which
were formed as a secondary effect of the longitudinal polarization of the remodeling process. Our observations
did not enable us to substantiate the model of two different systems, one of longitudinal vessels (Havers) and the
other of connecting transversal vessels (Volkmann), but suggested instead that there is a network whose loops
lengthen in the direction of the major bone axis in the course of growth and secondary modeling. The associated
morphology supported the view that the type of structural organization of the tubular bone cortex is primarily
determined by an inherited constitutional factor rather than by mechanical strains.
Key words
bone architecture; cortical bone; cortical vessel network; Havers’ and Volkmann’s canals
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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