title: A characterization of the preaggregative period of Dictyostelium discoideum.
abstract: The preaggregative period of Dictyostelium discoideum has been characterized by measuring the reduction in time for the onset of aggregation under conditions which hinder close cell-cell associations, inhibit protein synthesis, and/or include continuous high concentrations or pulsed low concentrations of exogenous cAMP. The results demonstrate that: the preaggregative period (normally 7 hr for cells from log phase cultures) can be dissected into two distinct components: an initial component which includes the first 4.5 hr, and a second component which includes the last 2.5 hr; the first component will progress at normal rate in the continuous absence of close cell-cell associations (as single amoebae in suspension) or in the continuous absence of de novo protein synthesis; the second component will not progress in the continuous absence of close cell-cell associations or de novo protein synthesis; high concentrations of cAMP continuously present in suspension cultures do not affect progress through the first component, nor do they support progress through the second component; however, if cells are allowed to form close cell-cell associations during progress through the first component, high concentrations of cAMP will support progress through the second component in the absence of close cell-cell associations; these associations, which render cells sensitive to cAMP, will occur in the absence of de novo protein synthesis and before the acquisition of contact sites A; these associations may be completely bypassed if suspended cells are continuously pulsed with low concentrations of cAMP; in this case, pulses of cAMP will support progress through the final component in continuous suspension cultures; and the acquisition of contact sites A will not occur in the absence of progress through the second component; in contrast, the acquisition of cAMP binding sites on the cell's surface will occur. These results are considered in terms of the complexity and regulation of the preaggregative period of Dictyostelium.
authors.forename: R E
authors.initials: RE
authors.lastname: Finney
authors.forename: C J
authors.initials: CJ
authors.lastname: Langtimm
authors.forename: D R
authors.initials: DR
authors.lastname: Soll
mesh_terms: D001665:Binding Sites; D002449:Cell Aggregation; D002450:Cell Communication; D003470:Culture Media; D000242:Cyclic AMP / Q000378:metabolism; D004023:Dictyostelium / Q000166:cytology*; D005656:Fungal Proteins / Q000096:biosynthesis; D011953:Receptors, Cyclic AMP / Q000378:metabolism; D013997:Time Factors
chemical_list: D003470:Culture Media; D005656:Fungal Proteins; D011953:Receptors, Cyclic AMP; D000242:Cyclic AMP