. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. I A2. A4 o o o I V2 IV3 Ref. V< 000 'v, Iv, Iv, I Figure 3A-B. Current density profiles at the vegetal (V) and at the animal (A) pole of individual Lvm- naea eggs measured in CFTW + 2 mA/CaCl:. (A) Anaphase (VI) through telophase (V2 an V3) to com- plete extrusion of first polar body (V4). (B) Current trace is shown of another egg from metaphase (VI) through anaphase (V2) and telophase (V3) to complete extrusion (V4) of second polar body. The dotted line connects the reference measurements and is not the actual measuremen
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. I A2. A4 o o o I V2 IV3 Ref. V< 000 'v, Iv, Iv, I Figure 3A-B. Current density profiles at the vegetal (V) and at the animal (A) pole of individual Lvm- naea eggs measured in CFTW + 2 mA/CaCl:. (A) Anaphase (VI) through telophase (V2 an V3) to com- plete extrusion of first polar body (V4). (B) Current trace is shown of another egg from metaphase (VI) through anaphase (V2) and telophase (V3) to complete extrusion (V4) of second polar body. The dotted line connects the reference measurements and is not the actual measurement of the reference level. In Figure 3B. the probe was moved to a reference position Rl. typically 200 ^m away, about 8 min before the maximal current density at V3 was measured and again to R2 about 6 minutes thereafter. Note that the current is outward (downward) at the vegetal pole (V), and inward (downward) at the animal pole (A), with highest densities at telophase. than 50 nA/cm2 were measured at the animal pole (data not shown). Discussion We have measured current densities ranging in indi- vidual eggs from 200 to 600 nA/cm- at both poles of the Lymnaea egg. These currents are rather weak as com- pared with other known developmental currents (Nucci- telli, 1986) and often approach the detection limit of the technique. However, the results clearly show an animal- vegetal difference in current pattern and density. In addi- tion, current pattern and density vary during the cell cycle. It has been shown, using techniques other than the vi- brating probe, that cell cycle-dependent changes in membrane ion permeabilities occur (Boonstra et a/., 1982; Rodeau and Vilain, 1987). Changes in intracellu- lar ion concentrations have been reported particularly for protons (Busa and Nuccitelli, 1984) and for calcium ions (Poenie et ai. 1985). In view of these intracellular ionic changes it would not be surprising if the cell cycle were to be associated with extracellular ionic currents.
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
