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Stentor and Blepharisma possess photoreceptor systems that render the cells capable of avoiding light. The observed photobehaviour is largely the result of a step-up photophobic response displayed by both ciliates. The photophobic response caused by a sudden increase in light intensity starts with a cessation of ciliary beating, then a period of ciliary reversal followed by renewed forward movement. Ciliary reversal correlates with the generation of an action potential, which is elicited by a photoreceptor potential as a result of light absorption by cellular pigments. The photochemical processes within the pigments lead in the case of Stentor, to internal cyclic GMP level changes that possibly result in changes of ionic conductance of cation channels gated by this cyclic nucleotide. In related Blepharisma cells, however, InsP3 seems to be responsible for the alterations in membrane potentials and induction of light avoiding response. This supposition is proved by a measured increase in the InsP3 levels in cells exposed to light and an identification of InsP3 receptor-like protein exclusively localized within the Blepharisma cell cortex.
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The Editorial Board
Andrzej Łukaszyk - przewodniczący, Zofia Bielańska-Osuchowska, Szczepan Biliński, Mieczysław Chorąży, Aleksander Koj, Włodzimierz Korochoda, Leszek Kuźnicki, Aleksandra Stojałowska, Lech Wojtczak

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