Sea urchin eggs and those of most other deuterostomes are activated at fertilization by an increase in cytoplasmic free calcium concentration ([Ca2+]i) that triggers the onset of the embryonic cell division cycles. We can image the calcium wave using fluorescent calcium indicator dyes and confocal microscopy. There are two components to the [Ca2+]i increase at fertilization. The first is due to a rapid calcium influx caused by a calcium action potential; this leads to a small increase in [Ca2+]i just beneath the plasma membrane with spherical symmetry. After a latent period of some 15 s, there is a second large and rapid increase in [Ca2+]i localized to the region of sperm-egg contact: during the latent period [Ca2+]i does not change but within 1 s of the end of the latent period [Ca2+]i reaches 2 micromolar. The calcium wave then spreads across the egg with a velocity of 5 micrometre s-1. Behind the advancing wavefront, the calcium concentration is uniformly high, even within the egg nucleus, though there are no indications that intranuclear calcium concentration differs from [Ca2+]i. [Ca2+]i falls uniformly towards resting levels over the next 500 s. In cases where there is an apparent inhomogeneity in [Ca2+]i in either the cortex or the nucleus, we find that the calcium indicator dye is inhomogeneously distributed. This appears to be due to uptake of the indicator dye (Fluo-3), probably into mitochondria. The artefact can be avoided by using a dextran-conjugated dye.
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JOURNAL ARTICLE| 01 November 1993
IMAGING CALCIUM WAVES IN EGGS AND EMBRYOS
Online Issn: 1477-9145
Print Issn: 0022-0949
© 1993 by Company of Biologists
J Exp Biol (1993) 184 (1): 213–219.
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I Gillot, M Whitaker; IMAGING CALCIUM WAVES IN EGGS AND EMBRYOS. J Exp Biol 1 November 1993; 184 (1): 213–219. doi: https://doi.org/10.1242/jeb.184.1.213
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