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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 193 (1996), S. 43-51 
    ISSN: 1432-0568
    Keywords: Type II collagen ; Human embryo ; Non-radioactive in situ hybridization ; Vertebral column ; Cartilage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The role of extracellular matrix molecules in ontogenetic differentiation processes is a matter of increasing interest. In cartilage development, type II collagen is suspected of promoting chondrogenic differentiation, since its expression has been demonstrated in a range of precartilaginous tissues of vertebrate species. Up to now, no studies supplying a coherent description of type II collagen expression in the skeletogenesis of human embryos including early embryonic stages have been published. In this work, we examine the temporal and spatial distribution of type II collagen mRNA during vertebral column development in human embryos from 4 to 12 weeks of gestation using non-radioactive in situ hybridization. The onset of gene expression was demonstrable in the 5th week in precartilaginous mesenchymal cells and in notochordal cells. Additionally, we found a weaker hybridization signal in the mesenchymal precursors of the intervertbral discs. In the anlagen of the axial skeleton, type II collagen expression decreased during osteogenic reconstruction in the 11th/12th week, whereas expression continued in the notochordal remnants of the future nuclei pulposi. The results suggest a relatively late occurrence of type II collagen in human vertebral development compared with other vertebrate species. The distribution of gene expression is concordant with a possible role of this molecule in promoting differentiation of mesenchymal cells into chondrocytes. The mechanism of this influence remains to be established.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Surgical and radiologic anatomy 15 (1993), S. 131-137 
    ISSN: 1279-8517
    Keywords: Sacroiliac joint ; Computed tomography ; Secondary ossification centres ; Os sacrum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Résumé Des formations osseuses apparemment bilatérales, de formes et tailles différentes, localisées dans les parties antéro-supérieures et inférieures des articulations sacroiliaques, ont été observées sur les images de coupes axiales de la région pelvienne chez des patients jeunes. Aucune autre modification pathologique n'a été notée au niveau des articulations sacro-iliaques de ces individus. Chez l'un des patients, les structures osseuses pouvaient aussi être observées sur les radiographies standard. Nous avons aussi étudié cette articulation chez 3 sujets anatomiques juvéniles, par la radiographie, la TDM, l'étude macroscopique et histologique. Chez deux d'entre eux des formations osseuses semblables à celles observées chez les patients jeunes pouvaient être détectées sur les coupes TDM. Les recherches macroscopiques ont montré que ces structures étaient des points d'ossification secondaires localisés dans le cartilage articulaire de la partie latérale du sacrum en regard du 1er et du 3e segments sacrés. Si l'on se réfère à une littérature anatomique plus ancienne, ces points d'ossification épiphysaires contribuent à la surface auriculaire de la partie latérale du sacrum et à la surface libre latérale des parties caudales du sacrum. Ils peuvent être observés entre 12 et 25 ans et commencent à fusionner avec les parties latérales aux environs de la 18e année. Sur les bassins osseux provenant de pièces juvéniles conservées, les ossicules libres n'ont pas pu être décelés dans la région des articulations sacroiliaques. Les particularités histologiques du processus d'ossification observé sont discutés. Ces points d'ossification physiologiques doivent être distingués des altérations pathologiques apparaissant au scanner comme des structures osseuses ou assimilées.
    Notes: Summary Bilateral apparently bony structures of different forms and sizes located in the inferior and superior ventral parts of the sacroiliac joints were observed on axial CT images of the pelvic region of juvenile patients. No other pathological changes were noted in the sacroiliac joints of these individuals. In one patient the bony structures could also be seen on a conventional plain radiograph. We also examined 3 juvenile autopsy specimens of this joint using radiology, CT, macroscopical evaluation and histology. In two of them, structures could be detected on the CT scans which were similar to those observed in the young patients. Macroscopic investigations revealed the structures to be secondary ossification centres located in the articular cartilage of the lateral part of the os sacrum at the levels of the first and third sacral segments. According to older anatomical literature, these epiphysial ossification centres contribute to the auricular surface of the lateral part of the os sacrum and the free lateral surface of the inferior sacral parts. They can be observed between the ages of 12 and 25 years and begin to synostose with the lateral part around the age of 18 years. In macerated juvenile specimens of the bony pelvis, free ossicles were not detectable in the region of the sacroiliac joints. Histological peculiarities of the ossification process observed are discussed. These physiologically occurring ossification centres are to be differentiated from pathological alterations appearing as bony or bone-like structures on CT scans.
    Type of Medium: Electronic Resource
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