A free calcium wave traverses the activating egg of the medaka, Oryzias latipes
Journal Article
·
· J. Cell Biol.; (United States)
Aequorin injected eggs of the medaka (a fresh water fish) show an explosive rise in free calcium during fertilization, which is followed by a slow return to the resting level. Image intensification techniques now show a spreading wave of high free calcium during fertilization. The wave starts at the animal pole (where the sperm enters) and then traverses the egg as a shallow, roughly 20/sup 0/-wide band which vanishes at the antipode some minutes later. The peak free calcium concentration within this moving band is estimated to be about 30 ..mu..M (perhaps 100 to 1,000 times the resting level). Eggs activated by ionophore A23187 may show multiple initiation sites. The resulting multiple waves never spread throuh each other, rather, they fuse upon meeting so as to form spreading waves of compound origin. The fertilization wave is nearly independent of extracellular calcium because it is only slightly slowed (by perhaps 15%) in a medium containing 5mM ethylene glycol-bis(..beta..-aminoethyl ether)N,N'-tetraacetic acid (EGTA) and no deliberately added calcium. It is also independent of the large cortical vesicles, which may be centrifugally displaced. Normally, however, it distinctly precedes the well-known wave of cortical vesicle exocytosis. We conclude that the fertilization wave in the medaka egg is propagated by calcium-stimulated calcium release, primarily from some internal sources other than the large cortical vesicles. A comparison of the characteristics of the exocytotic wave in the medaka with that in other eggs, particularly in echinoderm eggs, suggests that such a propagated calcium wave is a general feature of egg activation.
- Research Organization:
- Purdue Univ., West Lafayette, IN
- OSTI ID:
- 5101184
- Journal Information:
- J. Cell Biol.; (United States), Journal Name: J. Cell Biol.; (United States) Vol. 76:2; ISSN JCLBA
- Country of Publication:
- United States
- Language:
- English
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