ISSN:
1432-072X
Keywords:
Hypericin
;
Ionophores
;
Light-induced membrane potential
;
Photophobic response
;
Stentor
;
Uncouplers
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The avoidance by Stentor coeruleus of a light trap is caused by a step-up photophobic response. The phobic response invariably consists of a delay of about 200 ms, a stop response, a turn to one side, and resumption of swimming in the new direction. After this the cells enter a refractory period of 1–3 s following a phobic response, during which they will not give a second response. Phobic responses can be elicited by spatial and temporal increases in light intensity. The action spectrum for the step-up photophobic response resembles the absorption spectrum of stentorin, the proposed photoreceptor pigment, and of its chromophore, hypericin. The phobic response is specifically inhibited by the protonophorous uncouplers TPMP+ and FCCP but not by the ionophores gramicidin and A23187. Since the uncouplers block light-induced membrane potential changes at the same concentrations, it has been proposed that the primary photoreception causes a light-induced potential change, which in turn, induces a motor response.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00511225
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