ISSN:
1040-452X
Keywords:
Cooling
;
[Ca2+]i transients
;
Activation
;
Fertilization
;
Egg
;
Rat
;
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
Notes:
In mammalian eggs, activation by sperm that leads to resumption of meiosis is characterized by an explosive transient increase in intracellular calcium ion concentration ([Ca2+]i), followed by [Ca2+]i oscillations. In addition to the spermatozoon, various treatments can induce parthenogenetic activation, accompanied by an elevation of [Ca2+]i. It has been reported that cooling can induce egg activation, yet the mechanism of this phenomenon has not been elucidated. In the present study we followed changes in egg [Ca2+]i (measured by Fura-2 fluorescence ratio imaging) during activation by cooling, using conditions that ensure a low rate of spontaneous activation.Our present findings demonstrate that cooling induces egg activation as manifested by [Ca2+]i transient(s) and second polar body extrusion. Seventy-eight of 104 eggs responded to cooling with increased [Ca2+]i. Thirty-five percent of the responding eggs displayed a single [Ca2+]i transient, while 65% exhibited at least two [Ca2+]i transients within the time window of the experiment (30-40 min). Twenty-two percent of these eggs displayed high-frequency oscillations (intervals of 3.5-5.9 min). In these eggs, the overall pattern of calcium dynamics was similar to that observed in eggs activated by sperm, as judged by the transient's intervals, duration, and a gradual increase in the amplitude of successive transients. The amplitudes of [Ca2+]i transients, however, were 2-3 times lower. We propose that cooling affects [Ca2+]i homeostasis to produce fertilization-like changes in [Ca2+]i, possibly associated with parthenogenetic activation. Moreover, great care should be exercised to prevent temperature changes during egg handling. © 1995 wiley-Liss, Inc.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrd.1080420116
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