. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. vm StK / \ ventral side RECORDING OF CURRENT ©©npyfii^ SCANNING CONTROL ' J" ',v dorsal side f: /\y 1mm Figure 1. Scanning of extracellular currents in the blastoderm. Left: the experimental set up. The blas- toderm attached to vitelline membrane is spread over the ring at the bottom of the chamber (stippled). The electrode (bent needle) vibrates in parallel or vertically to the plane of the preparation. Right top: photograph of the blastoderm of stage 4 of Hamburger and Hamilton. Right bottom: currents recorde
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. vm StK / \ ventral side RECORDING OF CURRENT ©©npyfii^ SCANNING CONTROL ' J" ',v dorsal side f: /\y 1mm Figure 1. Scanning of extracellular currents in the blastoderm. Left: the experimental set up. The blas- toderm attached to vitelline membrane is spread over the ring at the bottom of the chamber (stippled). The electrode (bent needle) vibrates in parallel or vertically to the plane of the preparation. Right top: photograph of the blastoderm of stage 4 of Hamburger and Hamilton. Right bottom: currents recorded using vibrations parallel (Ix), transversal (ly). and vertical (Iz) to the direction of scanning. These profiles correspond to the level indicated on the photograph by the two arrows. done to adjust and memorize a constant distance (mostly 125 ^m) from the preparation to the electrode tip. A pro- file interpolated from these measurements was used to control the height of the table during the scan done at 6 mm/min. Visual control and photographs of the prepa- ration were done using a binocular microscope. The electrode was made of a bent tungsten wire insu- lated with glass and the tip (about 5 yum) was plated with gold. The electrode was inserted into a miniature ampli- fier fixed on the oscillating arm of an ECG scriptor. The frequency of driving oscillation (around 180 Hz) was ad- justed to produce a stable resonance of the vibrating elec- trode and the amplitude of vibration was held at 250 /jm. The potential difference between the extreme positions of the electrode tip was detected by using a lock-in ampli- fier with a time-constant of s. The calibrations were done in the Tyrode solution between two square parallel electrodes generating a sinusoidal current of ^A/cm:. Each scan was done twice with the vibration parallel and, after 90° rotation of the probe, transversal to the direction of scanning. The corresponding currents were labelled Ix and ly. The vectori
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
