Zeitschrift für vergleichende Physiologie

, Volume 71, Issue 3, pp 295–310 | Cite as

The properties and propagation of a cardiac-like impulse in the skin of young tadpoles

  • Alan Roberts
  • Charles A. Stirling
Article

Summary

The contact relationships of skin cells in late embryos and young larvae of Xenopus laevis are described. Superficial cells are joined by ‘tight’ or ‘gap’ junctions at their outer periphery but elsewhere ‘simple appositions’ are found. All-or-none impulses are evoked in the skin by electrical or mechanical stimuli (Fig. 3). Evidence is presented in favour of the view that these impulses are generated by the majority of skin cells and not by some neuronal element in the skin. The impulse propagates throughout the skin from any stimulated point (at average speed of 7.7 cm/sec) even when the animal is in distilled water. However, removal of Na+ from solutions bathing the inner skin surface or treatment with Tetrodotoxin abolishes the impulse indicating that it is Na+ dependent. Current injected into skin cells spreads to others so it is suggested that the impulse propagates by direct current flow from cell to cell. The ‘neuroid’ conduction system in the skin of Xenopus tadpoles is compared to similar systems in coelenterates and to the propagation of the vertebrate cardiac impulse.

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References

  1. Bennet, M. V. L., Trinkaus, J. P.: Electrical coupling between embryonic cells by way of extracellular space and specialized junctions. J. Cell Biol. 44, 592–610 (1970).Google Scholar
  2. Brightman, M. W., Reese, T. S.: Junctions between intimately apposed cell membranes in the vertebrate brain. J. Cell Biol. 40, 648–677 (1969).Google Scholar
  3. Fahmy, A.: An extemporaneous lead citrate stain for electron microscopy. Proc. Electron Microscopy Soc. Am., p. 148–149. Baton Rouge: Claitor's Book Store 1967.Google Scholar
  4. Farquhar, M. G., Palade, G. E.: Junctional complexes in various epithelia. J. Cell Biol. 17, 375–412 (1963).Google Scholar
  5. Fatt, P., Ginsburg, B. L.: The ionic requirements for the production of action potentials in crustacean muscle fibres. J. Physiol. (Lond.) 142, 516–543 (1958).Google Scholar
  6. Furshpan, E. J., Potter, D. D.: Low resistance junctions between cells in embryos and tissue culture. Curr. Top. Develop. Biol. 3, 95–127 (1968).Google Scholar
  7. Goodenough, D. A., Revel, J. P.: A fine structural analysis of intercellular junctions in the mouse liver. J. Cell Biol. 45, 272–290 (1970).Google Scholar
  8. Hagiwara, S., Nakajima, S.: Differences in Na and Ca spikes as examined by application of tetrodotoxin, procaine, and manganese ions. J. gen. Physiol. 49, 793–806 (1966).Google Scholar
  9. Kelly, D. E.: Fine structure of desmosomes, hemidesmosomes, and an adepidermal globular layer in developing newt epidermis. J. Cell Biol. 28, 51–72 (1966).Google Scholar
  10. Loewenstein, W. R.: Permeability of membrane junctions. Ann. N. Y. Acad. Sci. 137, 441–472 (1966).Google Scholar
  11. Mackie, G. O.: Conduction in the nerve-free epithelia of siphonophores. Amer. Zool. 5, 439–453 (1965).Google Scholar
  12. -Neuroid conduction and the evolution of conducting tissues. Quart. Rev. Biol. (in press, 1971).Google Scholar
  13. —, Passano, L. M.: Epithelial conduction in hydromedusae. J. gen. Physiol. 52, 600–622 (1968).Google Scholar
  14. Muntz, L.: Neuro-muscular foundations of behaviour in embryonic and larval stages of the Anuran, Xenopus laevis. Dissertation, Univ. Bristol. 1964.Google Scholar
  15. Nieuwkoop, P. D., Faber, J.: Normal tables of Xenopus laevis (Daudin). Amsterdam: North-Holland Publishing Co. 1956.Google Scholar
  16. Orkand, R. K., Niedergerke, R.: Heart action potential: dependence on external calcium and sodium ions. Science 146, 1176–1177 (1964).Google Scholar
  17. Parker, G. H.: The elementary nervous system. Philadelphia and London: Lippincott 1919.Google Scholar
  18. Roberts, A.: Conducted impulses in the skin of young tadpoles. Nature (Lond.) 222, 1265–1266 (1969).Google Scholar
  19. Schroeder, T. E.: Neurulation in Xenopus laevis. An analysis and model based upon light and electron microscopy. J. Embryol. exp. Morph. 23, 427–462 (1970).Google Scholar
  20. Steinman, R. M.: An electron microscopic study of ciliogenesis in developing epidermis and trachea in the embryo of Xenopus laevis. Amer. J. Anat. 122, 19 (1968).Google Scholar
  21. Williams, J. A.: Origin of transmembrane potentials in non-excitable cells. J. theor. Biol. 28, 287–297 (1970).Google Scholar

Copyright information

© Springer-Verlag 1971

Authors and Affiliations

  • Alan Roberts
    • 1
  • Charles A. Stirling
    • 1
  1. 1.Department of ZoologyUniversity of BristolUK

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