Cell and Tissue Research

, Volume 162, Issue 2, pp 235–252

Freeze-fracture replication of junctional complexes in unincubated and incubated chick embryos

  • R. Bellairs
  • A. S. Breathnach
  • M. Gross
Article

DOI: 10.1007/BF00209209

Cite this article as:
Bellairs, R., Breathnach, A.S. & Gross, M. Cell Tissue Res. (1975) 162: 235. doi:10.1007/BF00209209

Summary

Junctional complexes have been investigated in the epiblast of young chick embryos by examination of freeze-fracture replicas and of sections of comparable specimens stained with lanthanum nitrate. By means of freeze-fracture, tight junctions were shown to be present in the unincubated embryo (stage 1 of Hamburger and Hamilton). The number of ridges or grooves was found to vary between 2 and 10 near the dorsal border, whereas isolated ridges were found more ventrally. Lanthanum was unable to penetrate between the cells in the region of the dorsally situated tight junctions. Similar tight junctions were found in incubated embryos (stage 3) examined by both techniques. Tight junctions were also seen in cleavage (pre-laying) embryos examined in section.

Gap junctions were extremely uncommon in unincubated embryos, though occasional aggregates of gap junction particles were seen on the lateral cell membranes close to the dorsal surface. In only one instance were associated pits visible. By contrast, gap junctions were more frequently encountered by stage 3, and these junctions possessed both pits and particles. Desmosomes were never seen in the freeze-fracture replicas at either stages 1 or 3, though structures which might be developing desmosomes were visible in sections.

The functions of both the tight and gap junctions in the young chick embryo are discussed. The results are also considered in relation to recent theories about the way in which gap junctions are formed.

Key words

Junctions (gap, tight) Chick embryo Freeze-fracture Lanthanum Unincubated, incubated 

Copyright information

© Springer-Verlag 1975

Authors and Affiliations

  • R. Bellairs
    • 1
    • 2
  • A. S. Breathnach
    • 1
    • 2
  • M. Gross
    • 1
    • 2
  1. 1.Department of Anatomy and EmbryologyUniversity College LondonUK
  2. 2.Department of AnatomySt. Mary's Hospital Medical SchoolLondon
  3. 3.Dept. of Anatomy and EmbryologyUniversity CollegeGower St.UK