. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. DEVELOPMENT 199. Figure 1. Response of aggregation-competent slime mold amoebae to 366-nm microbeam uncaging of caged c-AMP. The microbeam was positioned near the side ol this amoeba, and the IT flashes were sinned I ininule 27 seconds before I lie frame A. See le.\l. Time in minutes:seconds after A and headed towards their natural source, an aggregate formed by many amoebae located outside the induced territory. Early during aggregation, most amoebae remained in loose contact with each other and slowly spiralled around the
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. DEVELOPMENT 199. Figure 1. Response of aggregation-competent slime mold amoebae to 366-nm microbeam uncaging of caged c-AMP. The microbeam was positioned near the side ol this amoeba, and the IT flashes were sinned I ininule 27 seconds before I lie frame A. See le.\l. Time in minutes:seconds after A and headed towards their natural source, an aggregate formed by many amoebae located outside the induced territory. Early during aggregation, most amoebae remained in loose contact with each other and slowly spiralled around the center of the aggregate. Whether in a naturally formed aggregate made up of many scores of cells or in an artificially induced aggregate made up of only a few cells, the amoeba located in the center became stationary relative to the substratum. Through-focus observations indicated that such an amoeba anchored itself to the soft substrate by protruding knobby "feet" into the agar surface. In the artificially induced aggregate, the central amoeba generated and maintained its feet (small arrows in Fig. 1C; the UV micromirror is retracted and focus is now on the agar surface) so long as the c-AMP pulses (UV flashes) were continued. Once the UV flashes were turned off, the feet were gradually retracted (Fig. ID). If the UV flashes were restarted within a minute or so, the feet reformed, and the departing outer amoebae rejoined the aggregate. The process was completely reversible and could be repeated many times. Thus we have established a tool for investigating localized and reversible c-AMP-mediated modu- lation of chemotaxis and cell response. Supported by NIH grants R01 GM 39548 to YF and R37 GM 31617 to SI. Literature Cited 1- Bonner. J. T. 1971. Ann RevMicrolnol 25: 75-92. 2. Gerisch, G. 1987. Anmi. Rev Biochem. 56: 853-879. 3. Devreotes, P. 1989. Science IAS: 1054-1058. 4. Nerbonne, J. M., S. Richard, J. Nargcot and H. A. Lester. 1984. Nature 310: 74-76. 5. Fukui, V.
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