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Sperm nuclear decondensation in Barnea candida (mollusca, pelecypoda) oocytes does not require germinal vesicle
Abstract:
Barnea candida oocytes, submitted to D-600 (100 microM) 15-20 seconds after insemination in order to inhibit Ca++ uptake but not acid release, fail to exhibit germinal vesicle breakdown (GVBD) whereas penetrated spermatozoa are able to decondense normally. Oocytes transferred in 100 mM Na-acetate seawater at pH 6.3, 1 minute after insemination, in order to inhibit acid release, fail to undergo GVBD and sperm nuclear decondensation. Upon return of these oocytes to normal seawater and treatment with an excess of KCl, they exhibit GVBD and decondensed sperm nuclei are seen within their cytoplasm. These results show that sperm nuclear decondensation does not require GVBD or Ca++ uptake but may be related to an intracellular pH increase.
Insights
Sperm nuclear decondensation in Barnea candida oocytes occurs independently of germinal vesicle breakdown (GVBD) and calcium uptake. Intracellular pH increase appears crucial for this process, not GVBD or Ca++ uptake.
Area of Science:
- Marine biology
- Developmental biology
- Cellular biology
Background:
- Fertilization triggers complex cellular events in oocytes.
- Germinal vesicle breakdown (GVBD) and calcium (Ca++) uptake are typically associated with fertilization.
- The precise roles of GVBD, Ca++ uptake, and pH changes in sperm nuclear decondensation are not fully understood.
Purpose of the Study:
- To investigate the role of Ca++ uptake and acid release in Barnea candida oocyte fertilization.
- To determine if germinal vesicle breakdown (GVBD) is required for sperm nuclear decondensation.
- To explore the relationship between intracellular pH and sperm nuclear decondensation.
Main Methods:
- Barnea candida oocytes were treated with D-600 to inhibit Ca++ uptake.
- Oocytes were exposed to Na-acetate seawater to inhibit acid release.
- Oocytes were subsequently returned to normal seawater and treated with KCl.
- Changes in GVBD and sperm nuclear decondensation were observed.
Main Results:
- Inhibition of Ca++ uptake did not prevent sperm nuclear decondensation, but blocked GVBD.
- Inhibition of acid release prevented both GVBD and sperm nuclear decondensation.
- Restoration of normal conditions and KCl treatment induced GVBD and sperm decondensation.
Conclusions:
- Sperm nuclear decondensation in Barnea candida oocytes does not require GVBD or Ca++ uptake.
- Intracellular pH increase is likely involved in sperm nuclear decondensation.
- Acid release plays a critical role in initiating fertilization events, including GVBD and sperm decondensation.