ISSN:
1432-1424
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary A sensitive method for assaying aggregation of dissociated cells has been developed which allows the determination of the mean number of cells per aggregate of a cell population. We have demonstrated that exposure of dissociated 6- or 7-day chick embryo neural retinal cells to trypsin in calcium-free solution renders them unable to aggregate for a half hour in stirred cell suspensions. Aggregation was noticeable first at 30 to 40 minutes and, progressed to the formation of massive compact aggregates. Because the half-hour aggregation lag occurred both in the absence of serum and in medium reclaimed from aggregated preparations, the possibilities were excluded that it was due either to an inhibitor of aggregation in the serum, or was the time required for release into the medium of soluble aggregation-promoting materials emanating from the cells themselves. Cells dissociated by divalent cation withdrawal (Ca++, Mg++-free saline with EDTA) aggregated without a lag. The trypsin-induced lag does not appear to be the result of trypsin adsorbed to the, surfaces of dissociated cells, as the lag is not abolished by addition of trypsin inhibitors to the aggregation medium. Microelectrophoresis of dissociated cells did not reveal changes in surface charge density during recovery from trypsinization. A variety of proteins and calcium ion, if present during trypsinization, protect the cells against the trypsin-induced aggregation lag. If the temperature was reduced from 37 to 6°C, aggregation of fully adhesive cell populations came to a complete halt within 2 to 3 minutes. Aggregation resumed with a 5 to 10 minute delay when the temperature was returned to 37°C. The rapidity of onset and reversal of inhibition of aggregation by low temperature treatment militates against the hypothesis that the low-temperature inhibition of aggregation acts by suppressing the synthesis of cell surface components necessary for adhesion. The abolition of the aggregation lag in trypsinized cells was also shown to be temperature-dependent; a 20-minute cold, pulse administered in the middle of the lag period extended the length of the lag by exactly 20 minutes.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01868223
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