Membrane Potential and Resistance of the Starfish Egg Before and After Fertilization

Abstract

Unequal distribution of ions between the interior and exterior is characteristic of living cells. In many thus far studied the concentration of potassium is much higher in the interior while the concentrations of sodium and chloride are lower. This ionic asymmetry is associated with a potential difference across the plasma membrane which is approximately related to the relative concentration of potassium (Hober, 1945; Hodgkin, 1951) according to the Nernst equation:or at 20 C., E (in mv.) = -58 log (A + )o Membrane potentials have been recorded from many cells (Hodgkin, 1951 ;Grundfest, 1955), including some whose internal potassium concentration is known, by means of a fine, saline-filled, microcapillary (Gelfan, 1927(Gelfan, , 1931Ling and Gerard. 1949) inserted through the cell surface. The magnitude of this potential in different cells ranges from 50 to 100 mv., inside negative. This indicates an internal excess of potassium approximately 9 to 50 times the external concentration, and is in approximate accord with the observed values in specific cases in which potassium concentration has been determined.

Effects of Media of Different Ionic Composition on the Activation Potential of Anuran Egg Cells

“…On further insertion, the potential abruptly deflected to the negative side, attaining -40 mV, then levelled at about -20 mV, indicating the membrane potential of the unactivated egg (Fig.lA, C, r). A similar large negative potential change, followed by a decrease in membrane potential caused by electrical leakage at the penetration site of the ooplasmic membrane, has already been reported in echinoderm eggs ( TYLER et al, 1956) and was observed frequently in the present experiments in the various experimental media. Upon insemination, the membrane potential, overshooting zero potential, rose rapidly to its crest, as high as 32 mV positive, and then declined gradually, usually taking 1-2 minutes to reach a steady state, which was nearly zero (Fig.lA).…”

“…Although the spread of depolarization over the egg surface upon fertilization is still unproven (ROTHSCHILD, 1956), many investigators have confirmed the existence of a slow monophasic potential change* during fertilization, by intracellular recording (in echinoderm eggs by TYLER, MONROY, KAO and GRUNDFEST, 1956; * A slow monophasic potential change during activation was referred to as the "activation potential" (MAENO, 1959).…”

Electrical excitability in the egg cell membrane of the tunicate

“…2 a, it was -9 mV. Similarly the relatively low values of 0 to -60 mV in the resting potentials have been reported in the marine echinoderm eggs (Rothschild, 1938;Kamada & Kinosita, 1940;Scheer, Santagelo & Riccobono, 1954;Lundberg, 1955;Tyler, Monroy, Kao & Grundfest, 1956;Hiramoto, 1959a, b).…”

The Onset of Electrical Communication Between Cells in the Developing Starfish Embryo

“…1 ; cf. Tyler, Monroy, Kao, and Grundfest, 1956) on the stage of a binocular dissecting microscope . All manipulations were carried out at a magnification of 50 X .…”