. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 280 H. SCHUEL + 50,. -75 I sec Figures 3-6. Electrical recordings of fertilization potentials in Lytechinus variegatus eggs. Abscissa: time (see scales); ordinate: {upper) current in pA; (lower) membrane potential in mV. Vertical arrow: start of depolarization in inseminated egg; horizontal bracket: interval during which fertilization membrane (FM) elevation occurred. Temp. = 22°C. From Chambers and DeArmendi (1979), reprinted with permission of Academic Press, Inc. Figure 3. Action potential and fertilization potential reco
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 280 H. SCHUEL + 50,. -75 I sec Figures 3-6. Electrical recordings of fertilization potentials in Lytechinus variegatus eggs. Abscissa: time (see scales); ordinate: {upper) current in pA; (lower) membrane potential in mV. Vertical arrow: start of depolarization in inseminated egg; horizontal bracket: interval during which fertilization membrane (FM) elevation occurred. Temp. = 22°C. From Chambers and DeArmendi (1979), reprinted with permission of Academic Press, Inc. Figure 3. Action potential and fertilization potential recorded in an egg cultured in sea water. A: Oscillograph record of unfertilized egg {left) injected with pulses of depolarizing current. An action potential was elicited by 20 pA pulse of 2 s duration. The pulse was cut off during the rising phase of the action potential. The same egg (right) after insemination. For segments (a) and (/?), see text. Break in curve represents 10 min period when membrane potential repolarized steadily to -70 mV. B: Same oscillograph records as A. wath time scale expanded 8X. The steep rising limb of the action potential ( ) and the fertilization potential ( ) are superimposed. C Same record as B. but time scale expanded 4X (32x scale of A). capable of excluding sperm (Jaffe, 1976) within 100 m s (Fig. 3c). Repolarization of the fertilized egg is completed in 10 min, and is associated with increased potassium conductance (Steinhardt et al, 1971). Damaged eggs have leaky membranes and show a resting potential of -10 to -20 mV (Fig. 4). They can not be excited electrically. Upon insemination, the sharp early peak of the fertilization potential (segment a) is missing. The membrane potential slowly rises to positive levels (segment b) within about 15 s. Such eggs lack a voltage sensitive mechanism to generate a rapid spike depolarization, which can be triggered only if the egg's membrane potential is more negative than -40 mV. Eggs with leaky membranes c
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