RESUMEN
Syndesmotic sutures of the skull are formed by dense connective tissue and called "open"; they are "closed" by formation of a synostosis between adjacent bones. Open sutures are considered as areas of growth and as hinges. The importance of open sutures during the period of skull growth is reflected by pathological situations in which premature closure of the sutures occurs. As alterations of the FGF receptor have been reported in genetical disorders accompanied by premature suture closure (Bellus et al. 1996), the role of fibroblasts and connective tissue in the development of the sagittal suture of mice has been investigated by light and electron microscopy. Morphological changes of the sagittal suture at the following stages are reported: at embryonic day 18, days 1, 5, 9, 14, 20, 26, 28 after birth and in adult mice. Two skulls per stage were investigated. Early osteogenesis appeared in a thin plate, followed by a second plate underneath the first one. Both were separated by blood vessels. In general, vascularization preceded desmoid mineralization; the space around blood vessels was occupied by non-bone-forming cells leaving cavities for the presumptive bone marrow. Mineralization of the collagen-rich osteoid at the mineralizing rim of the bone plates was accompanied by apoptoses and cell disintegration. Newly formed bone was immediately covered by osteoblasts forming a sheet of bone-lining cells. At day 9, the double-layered bone plates of both sides reached the median area of the skull but were separated by non-mineralizing, collagen-rich connective tissue. From day 14 onwards, the bone plates thickened. Bone apposition, recognizable by the formation of collagen-rich osteoid and proceeding from day 14 pp onwards, occurred mainly at the outer and inner surfaces of the calvariae, but neither at bone marrow surfaces nor at the medial edges of the parietal bones. These opposite bone faces showed fewer osteoblasts and bone-lining cells, but an increased number of fibroblasts. Tendon-like collagen bundles connected both bone plates of the open suture of day 26 pp as well as in the adult mice, whereby synostotically closed areas alternated. Formation of an open, syndesmotic suture can, therefore, be described as a transition of bone-forming tissue into a bone-tendon junction. The results indicate the importance of the replacement of osteoblasts by fibroblasts at the sutural front of the bone plates in order to prevent a premature suture closure.
Asunto(s)
Suturas Craneales/crecimiento & desarrollo , Suturas Craneales/ultraestructura , Osteogénesis/fisiología , Hueso Parietal/crecimiento & desarrollo , Hueso Parietal/ultraestructura , Animales , Animales Recién Nacidos , Femenino , Ratones , EmbarazoRESUMEN
This study is the first presentation of three-dimensional computed tomography (3D-CT) for the in vitro evaluation of the prenatal human cranium. The study was based on CT examinations from 26 aborted normal fetuses between 10 and 25 weeks gestational age. Incremental coronal and transverse CT slices of 1 mm thickness and a threshold segmentation algorithm were used to generate 3D-CT reconstructions (surface-shaded display, SSD) of the cranial bones similar to their anatomical appearance. The threshold of the segmentation algorithm was selected after comparison of the 3D-CT images generated with varying thresholds and graphically reconstructed histological serial sections of particular sutures in five specimens. The variation of the segmentation threshold resulted in alterations of the bone sizes and suture widths. However, 3D-CT images allowed sensitive identification of the cranial ossification centers and accurate evaluation of the bone topography. Cutting and rotating procedures made it possible to evaluate all imaged bones in arbitrary views without disturbing superpositions, thus making isolated examinations of particular macroscopic sections of the specimens unnecessary. In conclusion, 3D-CT of the fetal cranium promises to be of considerable help in the evaluation of prenatal cranial development.
Asunto(s)
Huesos Faciales/embriología , Cráneo/embriología , Algoritmos , Anatomía Transversal , Desarrollo Embrionario y Fetal , Huesos Faciales/diagnóstico por imagen , Edad Gestacional , Humanos , Osteogénesis/fisiología , Cráneo/diagnóstico por imagen , Tomografía Computarizada por Rayos X/métodosRESUMEN
A rare case of subcutaneous granuloma annulare of the eyelid is reported. A diabetic patient developed a unilateral periorbital tumorous mass. Biopsy revealed subcutaneous palisading granuloma. By microscopy and immunohistology, other granulomatous reactions including necrobiosis lipoidica could be ruled out. Since treatment with dapsone was without effect, the tumor was surgically excised. The differential diagnosis and the literature are briefly discussed.
Asunto(s)
Enfermedades de los Párpados/patología , Granuloma Anular/patología , Adulto , Dapsona/uso terapéutico , Diagnóstico Diferencial , Enfermedades de los Párpados/tratamiento farmacológico , Enfermedades de los Párpados/cirugía , Neoplasias de los Párpados/diagnóstico , Femenino , Granuloma Anular/tratamiento farmacológico , Granuloma Anular/cirugía , Humanos , Necrobiosis Lipoidea/diagnósticoRESUMEN
According to a new technology in the planning of endo-osseous implantation, based on a new CT-software for evaluation of the bone structure of the jaws, anatomico-morphological changes after the loss of teeth are measured much more accurately than with conventional methods like the panoramic intraoral x-ray or conventional tomography. 30 mandibles and 22 maxillae of 36 patients were examined. Besides the topographic course of the mandibular canal and the location of the foramen mentale, the anatomic structures as the important aspects for planning endo-osseous implants are seen more accurately. It is now possible to recognise morphological changes with paraxial reconstructions in a very short time more clearly and precisely than with former techniques.