Graduate Thesis Or Dissertation
 

Sea urchin eggs

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Calcium and magnesium flux in dividing sea urchin eggs

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/gb19f9289

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  • This study was initiated to determine the concentration of magnesium and calcium in dividing eggs of the sea urchin Stroncavocentrotus purpuratus and to explore the relationship between these ions and mitotic events. Samples of developing eggs, maintained at 15°C, were taken at ten-minute intervals from fertilization through the second cleavage, cytologically monitored, and analyzed for magnesium and calcium content. The analytical procedure was spectrophotometric, utilizing a modification of the method of Lamkin and Williams which employs Arsenazo (= 0- [(1,8-dihydroxy-3,6-disulfo-2-naphthyl)-azo] benzene arsonic acid) and EGTA (= [ethylene bis (oxyethylenenitrilo)] tetraacetic acid). Each division cycle was characterized by fluctuations in cellular content of magnesium and calcium which showed for each ion two peaks of uptake and release. The first magnesium and calcium uptakes occurred at very early prophase and mid-prophase, respectively. These peaks were interpreted to be related to the gelation of the 3.5 S soluble protein component of the mitotic apparatus prior to the actual assembly of the apparatus. The second magnesium and calcium uptakes occurred at meta-anaphase and anaphase-cleavage, respectively. These peaks were interpreted to be related to the gelation of the proteins associated with cleavage furrowing and the increase of blastomeric cell surface.. At fertilization, the base levels of magnesium and calcium rose to approximately twice the amounts characteristic of the unfertilized egg, i.e., from 11.0 to 22.2 mM for magnesium and 4.0 to 8.0 mM for calcium per Kg of water in the egg. At peak levels during mitosis, the magnesium and calcium concentrations reached 35.0 and 14.0 mM/Kg, respectively, approximately 1.5 times the post fertilization base levels.
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