. The Biological bulletin. Biology; Zoology; Marine biology. Figure 6. Light micrograph of isolated, detached nerve terminals (arrows). Unfixed washed electrocytes after collagenase treatment at 6°C for 4 days were resuspended in saline and examined with Nomarski optics. Loosely adherent nerve terminals become detached from the electrocytes and are seen as free-floating structures. They are readily identifiable by their size and content of intraterminal organelles of mi- tochondrial dimensions (see Fig. 5). A nucleated Schwann cell (arrow and S) is identified by the large nucleus. Calibration
. The Biological bulletin. Biology; Zoology; Marine biology. Figure 6. Light micrograph of isolated, detached nerve terminals (arrows). Unfixed washed electrocytes after collagenase treatment at 6°C for 4 days were resuspended in saline and examined with Nomarski optics. Loosely adherent nerve terminals become detached from the electrocytes and are seen as free-floating structures. They are readily identifiable by their size and content of intraterminal organelles of mi- tochondrial dimensions (see Fig. 5). A nucleated Schwann cell (arrow and S) is identified by the large nucleus. Calibration bar = ^m. Discussion In the present study we show that skate electric organs dissociate into their component cellular elements (elec- trocytes, Schwann cells, nerves, and nerve terminals) when incubated in saline solutions containing 1% collagenase at temperatures down to 6°C. In contrast, we have not been able to dissociate Torpedo nerve endings from their electrocytes. The maintenance of skate tissues at these lower temperatures has several important advantages. It is more physiological, because skates prefer cold water; it results in very stable electrocyte preparations (see Fig. 2); and it inhibits the movement of the Schwann cells and thus prevents encapsulation of detached nerve terminals during coUagenase-induced denervation of dissociated electrocytes (Figs. 5 and 6). Nerve terminals prepared us- ing collagenase at 6°C are therefore purer and probably in a better physiological state than corresponding prepa- rations derived from tissue incubated at room tempera- ture. The disadvantage of using lower temperatures is the relatively long digestion period. However, as judged by electrocyte viabihty, this does not compromise the phys- iological quality of subsequent preparations. Use of tem- peratures between 6° and 16°C might accelerate the digestion somewhat without compromising purity or physiological state, but this would require Figure 7. Miniature en
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