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Do cellular slime molds form intercellular junctions?
| Content Provider | Semantic Scholar |
|---|---|
| Author | Johnson, Gary M. Johnson, R. Miller, M. Borysenko, Joan Z. Revel, Jean Paul |
| Copyright Year | 1977 |
| Abstract | Intercellular contact specializations such as gap junctions have been thought to play a role in growth and differentiation in many systems. This idea is based on the observation that small molecules can pass directly between the cytoplasms of adjacent cells and on the strong circumstantial evidence that gap junctions may provide for this intercellular permeability (1). Gap junctions are found in a wide variety of organisms, and it is reasonable to ask whether they could be associated with the process of differentiation in the cellular slime mold Dictyostelium discoideum. In this organism small molecules, such as adenosine 3',5'-monophosphate (cyclic AMP), play a role in the cell movements which occur during aggregation. In addition, differentiating cells bear antigenic determinants not found on vegetative cells (2), and a particular size of intramembranous particles (IMP's) has been implicated in the differentiation process (3). These observations suggest a role for cell surface components. However, several studies carried out over a number of years in our laboratories have failed to provide evidence for the existence of gap junctions or, for that matter, any other junctions (occluding, septate, or adhering) in D. discoideum. In our studies we used a variety of fixation procedures at different stages of cell development. The cells were fixed with glutaraldehyde-formaldehyde or osmium [including osmium vapors, see (4)], or both. Both fixative concentration and buffer composition were varied. We investigated the cells and slugs with both thin-section and freeze-fracture techniques. Although small gap junctions (less than 0.1 um in diameter) would be difficult to identify in sections, those involving as few as five to ten IMP's have been convincingly identified in freeze-fracture replicas of other cell systems. We sought evidence for the presence of intercellular junctions at various times during differentiation, from aggregating streams of amoebas to early slug stages; at no time were junctions observed. Because we are reporting a negative result, we have explored in 4itail the possibility that junctions do exist in D. discoideum but were not detected. A conceivable argument is that typical gap junctions exist in slime molds but did not withstand the various preparative procedures that were used. This hypothesis is not very likely, as the morphology of gap junctions in other systems has been shown to be fairly insensitive to treat- |
| Starting Page | 1300 |
| Ending Page | 1300 |
| Page Count | 1 |
| File Format | PDF HTM / HTML |
| DOI | 10.1126/science.561442 |
| Alternate Webpage(s) | http://science.sciencemag.org/content/sci/197/4310/1300.1.full.pdf |
| PubMed reference number | 561442 |
| Alternate Webpage(s) | https://doi.org/10.1126/science.561442 |
| Journal | Medline |
| Volume Number | 197 |
| Issue Number | 4310 |
| Journal | Science |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
