. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. LU 7 CO + 1 16 ^ 1 5 cc I— 5 4 o LU LO- LL = o 03 2 5 ' ^ •^ 0 CALCIUM BUFFERS ARREST FUCOID EGGS I Dimethyl BAPTA 11 Dibromo BAPTA. T \ 1 5,5'-<fifluoro \ BAPTA \ k V 10 100 (/JM) Figure 1. Critical inhibitory buffer concentration versus buffer dissociation constant, KD. Each data point is an average of the final cytosolic buffer concentrations within all (Pelretia) eggs that were still ungermmated on day 2. except for those injected with the apparently somewhat unstable 4,4'-difluoro BAPTA which were counted on day 1. T
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. LU 7 CO + 1 16 ^ 1 5 cc I— 5 4 o LU LO- LL = o 03 2 5 ' ^ •^ 0 CALCIUM BUFFERS ARREST FUCOID EGGS I Dimethyl BAPTA 11 Dibromo BAPTA. T \ 1 5,5'-<fifluoro \ BAPTA \ k V 10 100 (/JM) Figure 1. Critical inhibitory buffer concentration versus buffer dissociation constant, KD. Each data point is an average of the final cytosolic buffer concentrations within all (Pelretia) eggs that were still ungermmated on day 2. except for those injected with the apparently somewhat unstable 4,4'-difluoro BAPTA which were counted on day 1. The solid line is calculated from equation (1) with r = 1. C = 10 n.\I. DCa/DB = 17; the dotted ones with C = 5 or 20 \iM. From work in progress. Fuller results, including additional buffers, will be reported elsewhere. out bound calcium will initially extract calcium from sources within and without the cell; but thereafter it will just sit. unable to release its bound calcium and will thus remain inert as yolk. Because of their very high reaction rates (Quasi el al. 1984), we assume that a BAPTA-type buffer is every- where in near local equilibrium with free Ca2+. We may then ask how large the buffer-mediated or facilitated cal- cium flux, JB. is between any two points as compared to the direct flux, JCa, of free Ca++. Presumably the buffer will begin to effect the cell when these two fluxes become comparable. A quantitative analysis of this model (to be presented elsewhere) yields the following equation: = rC.(DCa/DB)-[(l +F)2/F] (1) where: B is the critical inhibitory buffer concentration; r is JB/Jca at this concentration; C is the average concentration of free Ca++ in the region containing the gradient needed for development; DCa and DB are the cytosolic diffusion constants of free Ca++ and buffer, respectively; and F = KD/C where KD is the buffer's cytosolic dissociation constant. In order to apply (1) to our data, we must assume that the fucoid egg is in a relatively
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
