. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MECHANISM OF NERVE GALVANOTROPISM 137 Table 1 The effects of various treatments on the rates of growth (fiin/h), orientation response and distribution of filopodia on nerves exposed to a small electric field (70-110 in I '/mm) Orientation Filopodial distribution Rate of growth (^m/h) Turn to cathode (left) Turn to To To anode No cathode anode (right) response (left) (right) [n] Treatment Control Experimental [n] E alone 26 ±2 25 ±2 [85] 75% 5% 20% + * + [16] E + Cyto D 24 ±4 3±2 [54] 62% 2% 36% Not present E +
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MECHANISM OF NERVE GALVANOTROPISM 137 Table 1 The effects of various treatments on the rates of growth (fiin/h), orientation response and distribution of filopodia on nerves exposed to a small electric field (70-110 in I '/mm) Orientation Filopodial distribution Rate of growth (^m/h) Turn to cathode (left) Turn to To To anode No cathode anode (right) response (left) (right) [n] Treatment Control Experimental [n] E alone 26 ±2 25 ±2 [85] 75% 5% 20% + * + [16] E + Cyto D 24 ±4 3±2 [54] 62% 2% 36% Not present E + Con A 23 ±3 10 ±2 [18] 6% 6% 88% Not assessed E + Co++ 21±3 7± 1 [29] 21% 0% 79% ±* ± [19] E + A23187 35 ±9 3±6 [12] 92% 0% 8% ± + [8] E + CO++] + A23187] 22 ±4 7±2 [21] 5% 62% 33% 3. 5 ±* ± [35] * P< Control 30 ±3 24 ±4 [70] 22% 20% 58% + ± [35] Each individual nerve was selected from a particular culture and photographed repeatedly over time (see Methods). The number analysed (n) therefore does not represent the number of nerves per culture dish, but a random selection of nerves taken from many culture dishes. Drug concentrations used were cylochalasin D Mg/ml; con A 80 Mg/ml; neuraminidase 1 and 10 Mg/ml; Co 5 mAf/1; A23187 10 or 15M-W/1. Results Filopodia are not necessary for galvanotropi sin. Most neurites exposed to cytochalasin D (CD, - Mg/ml) rapidly lost all of their filopodia and ad- vanced much more slowly. Nevertheless, continued growth did occur, and in cells exposed to an applied elec- tric field (100 mV/mm), two thirds of neurites turned towards the cathode (Table I; Fig. 1). Thus, contrary to expectation, neurites were capable of galvanotropic re- sponses in the absence of growth cone filopodia. A role for the cell surface in galvanotropism'^ In confirmation of Patel and Poo (1982), pretreatment of neurones with con A inhibited orientation to an ap- plied elec
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
