Abstract
Freeze-fracture techniques have been used to study gap junction formation between Novikoff hepatoma cells reaggregated for 0-60 min. Quantitative data have been obtained for the proportion of membrane "interfaces" containing formation plaques with and without gap junctions [FP(+)'s and FP(-)'s, respectively], for the areas and numbers of FP(+)'s and FP(-)'s, and for the numbers and densities of 9- to 11-nm particles in FPs. Methods have been devised to correct these data for FP(+)'s carried over from dissociation. Comparisons have also been made with undissociated Novikoff cells. The results show that new FP(-)'s and FP(+)'s first appear between 5 and 15 min of reaggregation, and increase gradually between 15 and 30 min. Interfaces with FP(-)'s develop more rapidly than those with FP(+)'s. Between 30 and 60 min, FP(-)'s begin to disappear while FP(+)'s continue to increase. The results suggest that many FP(-)'s are converted into FP(+)'s, but some FP(-)'s may "abort." The mean areas of FP(-)'s and FP(+)'s, either per plaque or per interface, show no significant changes with reaggregation time, although there is an increased average number of FPs per interface at later times. There is a progressive increase with time in the number of total 9- to 11-nm particles in FPs per plaque and per interface, with densities of 9- to 11-nm particles also generally increasing. However, FP(+)'s, especially in 15-min samples, have a relatively constant density of unaggregated 9- to 11-nm particles, in spite of a large variation in aggregated particle density. A number of related analyses have led us to suggest that the 9- to 11-nm particles in FP(+)'s behave as though they are in a saturated solution, with the aggregated particles being analogous to a precipitate. Particle aggregation in FP(-)'s is considered analogous to precipitation from a supersaturated solution. The relation of the results to previous physiological data is discussed.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 263-276 |
| Number of pages | 14 |
| Journal | Journal of Ultrasructure Research |
| Volume | 77 |
| Issue number | 3 |
| DOIs | |
| State | Published - Dec 1981 |
Bibliographical note
Funding Information:We thank Michael Atkinson for help in evaluating the data on particle aggregation and Victor Bloomfield for suggesting that "saturation" and "supersaturation" might be involved in the aggregation process. The authors also appreciate the assistance of Kris Kohn in preparing the graphic materials and of Janet McCallister in typing the manuscript. This work was supported by Grant CA 16335 from the National Institutes of Health.