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2 results

  • 4 - Revisiting the Embryo

  • Alessandro Minelli
  • Book:
    Understanding Development
    Published online:
    29 April 2021
    Print publication:
    20 May 2021, pp 54-75

  • Summary

    The traditional notion of the embryo as the developmental phase in which, starting from an undisputable origin (egg, seed) the outline of the bodily architecture of a multicellular organism is shaped, deserves critical discussion. Development does not necessarily have a recognizable starting point. Some of the cells deriving from the zygote may not contribute to the embryo. There are significant differences between the early developmental stages of animals and plants. In animals, at the end of embryonic development the entire structure of the organism is almost always delineated. In plants, the seedling formed during the so-called embryonic development contains only the shoot with the first leaves and the radicle, while the entire structure of the plant, including almost all the leaves and all the flowers, will form from groups of stem cells generated through the entire life of the plant. Development does not necessarily produce an increasing division of labour. Development is not necessarily irreversible. Individual organs are not the products of a distinct developmental process. Differences between species do not always increase progressively from the egg on.

  • Specialised cell types in the chorioallantoic membrane express carbonic anhydrase during chick embryogenesis

  • M. GABRIELLA GABRIELLI, GIOVANNI MATERAZZI, JOHN V. COX, GIOVANNA MENGHI
  • Journal:
    The Journal of Anatomy / Volume 198 / Issue 2 / February 2001
    Published online by Cambridge University Press:
    26 March 2001, pp. 229-238
    Print publication:
    February 2001

  • The expression of carbonic anhydrase in the chorioallantoic membrane (CAM) of the chick embryo was investigated by means of the histochemical localisation of the enzyme catalytic sites and the immunohistochemical identification of its isoenzymatic forms. The results show that carbonic anhydrase is developmentally expressed in a subset of cells both in the ectodermal and the endodermal epithelium. The distribution patterns from both methodological approaches indicated that carbonic anhydrase is a marker of the villus cavity cells and the mitochondria-rich cells in the ectodermal and the endodermal epithelium, respectively. Such a cell-specific pattern of the enzyme expression provides a further contribution to characterising the heterogeneous cell population of the chick CAM and supports specific functional involvement for the distinct cell types in CAM-mediated processes, such as calcium transport, maintenance of acid-base balance and water and electrolyte reabsorption, during chick embryogenesis.