. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. EXTRACELLULAR CALCIUM LEVELS 133 06-, 400 mV/mm 200 mV/mm. «- 50 150 time (minutes) Figure 2. The time course of the galvanotactic response. The aver- age cosine of the translocation distribution was measured at various times after field application for the four field strengths indicated. The rate of approach to the final average cosine is much steeper at the higher field strengths than at the lower ones. removed by the addition of the Ca2+ chelator, EGTA, because the cells promptly round up and stop moving. However, t
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. EXTRACELLULAR CALCIUM LEVELS 133 06-, 400 mV/mm 200 mV/mm. «- 50 150 time (minutes) Figure 2. The time course of the galvanotactic response. The aver- age cosine of the translocation distribution was measured at various times after field application for the four field strengths indicated. The rate of approach to the final average cosine is much steeper at the higher field strengths than at the lower ones. removed by the addition of the Ca2+ chelator, EGTA, because the cells promptly round up and stop moving. However, this is not due to the absolute requirement of Ca2+ for cell motility because the addition of Mg2+ (in- creasing from to 10 mA/) prevents the rounding up in the absence of Ca2+ and the cells move quite well. Therefore, we studied the galvanotaxis response under these conditions. When the Mg2+ is raised to 10 mM without changing the external Ca2+ level, the galvano- taxis response is no longer observed and the degree of translocation is reduced (Fig. 3B). This blockage of the galvanotaxis response by Mg2+ was a surprise because Mg:+ is not a very efficient Ca2+ channel blocker. How- ever, at these high levels where its concentration is 30- fold higher than that of Ca2+, it might be blocking calci- um's access to channels. In support of this interpretation, an identical result was obtained when only 100 nAI of the much more specific Ca2+ channel blocker, Gd3+, was added (Fig. 3C). Again the galvanotaxis response is blocked and the net translocation of most cells is reduced compared to controls. The response to the removal of external Ca2+ in the high Mg2 * medium (Fig. 3D) is perhaps the most surpris- ing result. Under these conditions, most cells move in the reverse direction toward the positive pole of the ap- plied field. This reversal of direction of migration is remi- niscent of the observation by Cooper and Schliwa (1986b) who found a reversed response when extracellu-
Size: 1275px × 1960px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
