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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Anatomy and embryology 182 (1990), S. 401-408 
    ISSN: 1432-0568
    Keywords: Meckel’s cartilage ; Wound healing ; Dysmorphogenesis ; Mandible ; Chick
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The embryonic chick mandibular arch was surgically sectioned in ovo on day 7 of incubation and the subsequent wound healing of the arch, together with the response of Meckel’s cartilage to fracture, was examined. The repair process observed (in contrast to that in adults) was characterised by minimal haematoma formation or cell death and the absence of formation of either cellular blastema or fracture callus. Re-epithelisation was complete within 48 h with no scar tissue formed. Continuity of Meckel’s cartilage, together with restoration of its histological appearance and that of the surrounding soft tissues, was re-established within 24 h in 88% of cases. In the case of the cartilage this was due to fusion of the matrix followed apparently by chondrocytic and perichondrial proliferation. This differs from the repair of embryonic long bone cartilages. In 12% of cases, however, mal-union or non-union of the cartilage resulted in mandibular arch deviation. This observation suggests that mandibular arch growth and morphogenesis may parallel the development of Meckel’s cartilage. Where cartilaginous non-union occurred, some irregularities in the pattern of the developing mandibular bones were evident, and it is argued that deformity in the cartilage may ultimately affect the length and shape of the adult mandible.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0568
    Keywords: Vasculature ; Wound healing ; Limb bud ; Chick
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Experimental analyses examining pattern formation in the developing chick limb have concentrated on the skeleton, muscles and nerves, and have rarely considered blood vessels. To investigate the relationship between the vasculature and limb development, posterior amputations were performed on 3.5–4 day chick limb-buds. It has been shown that the removal of the posterior half alters the developmental fate of the anterior tissue: it becomes necrotic and fails to differentiate into the complement of skeletal parts predicted by fate maps. The possibility that this developmental failure results from interference with the future arterial supply was examined by Indian ink injection between 3–48 h after operation. Scanning electron microscopy (SEM) and resin histology were used to examine the wound repair at similar post-operative intervals. Results from the Indian ink injections showed that within 6 h of operation a collateral circulation was established by means of a branch from the truncated primary subclavian artery. The capillary density in the operated limbs appeared normal when compared to the contralateral limb. The results support the view that the poor developmental performance of the anterior half is due to removal of the zone of polarising activity (ZPA) rather than to experimentally-induced alteration to the vascular supply. Histological and SEM examination of the wound healing process showed that epithelialization of the cut surface occurred within 24 h, and that the peridermal cells of the bilayered ectoderm appeared to initiate the regrowth. The wound site was not visible 48 h after operation, showing that wound healing at these developmental ages occurs quickly, with no scar tissue formation. These results show that the vasculature in the developing limb is labile, and that the cell death resulting from posterior-half amputation is not due to vascular insufficiency or ischaemia. In addition, this study of wound healing demonstrates the role of the ectoderm in establishing an avascular margin in the subjacent mesenchyme.
    Type of Medium: Electronic Resource
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