These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Ionic mechanism of the fertilization potential of the marine worm, Urechis caupo (Echiura).
    Author: Jaffe LA, Gould-Somero M, Holland L.
    Journal: J Gen Physiol; 1979 Apr; 73(4):469-92. PubMed ID: 571895.
    Abstract:
    Microelectrode and tracer flux studies of the Urechis egg during fertilization have shown: (a) insemination causes a fertilization potential; the membrane potential rises from an initial level of -33 +/- 6 mV to a peak at +51 +/- 6 mV (n = 16), falls to a plateau of about +30 mV, then returns to the original resting potential 9 +/- 1 min (n - 10) later; (b) the fertilization potential results from an increase in Na+ permeability, which is amplified during the first 15 s by a Ca++ action potential; (c) the maximum amplitude of the fertilization potential, excluding the first 15 s, changes by 51 mV for a 10-fold change in external [Na+]; (d) in the 10 min period after insemination, both Na+ and Ca++ influxes increase relative to unfertilized egg values by factors of 17 +/- 7 (n = 6) and 34 +/- 14 (n = 4), respectively; the absolute magnitude of the Na+ influx is 16 +/- 6 times larger than that of Ca++; (e) in the absence of sperm these same electrical and ionic events are elicited by trypsin; thus, the ion channels responsible must preexist in the unfertilized egg membrane; (f) increased Na+ influx under conditions of experimentally induced polyspermy indicates that during normal monospermic fertilization, only a fraction of available Na+ channels are opened; we conclude that these channels are sperm-gated; (g) Ca++ influx at fertilization is primarily via the membrane potential-gated channel, because kinetics are appropriate, and influx depends on potential in solutions of varying [Na+], but is independent of number of sperm incorporations in normal sea water.
    [Abstract] [Full Text] [Related] [New Search]