Cytochemical Ca2+ Distribution in Activated Discoglossus pictus Eggs: A Gradient in the Predetermined Site of Fertilization |
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Authors: | Roberto Gualtieri Chiara Campanella Piero Andreuccetti |
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Affiliation: | Dipartimento di Biologia Evolutiva e Comparata, Universitàdegli Studi di Napoli "Federico II", Via Mezzocannone 8, 80134 Napoli, Italy. |
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Abstract: | The K-pyroantimonate/OsO4 (PA) cytochemical method coupled with EGTA and X-ray microanalytical controls has been used to localize Ca2+ at egg activation in Discoglossus pictus eggs. The results show that: 1) the PA method is able to selectively localize Ca2+ pools mobilized by activating stimuli; 2) the smooth endoplasmic reticulum (SER) elements located in the animal dimple region, i.e. in the predetermined site of fertilization, are the first egg components labeled by precipitates; 3) a decreasing gradient of precipitates is present from the center beyond the boundaries of the dimple region; 4) precipitates are lacking in the remainder of the egg even at late times after activation. The possibilities are discussed that a) SER is the major Ca2+-releasing store at activation in Discoglossus , and b) the observed gradient of pyroantimonate-detected Ca2+ reflects an ionic Ca2+ gradient. |
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Keywords: | (amphibians calcium/egg activation/K-pyroantimonate |
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