J Gravit Physiol. 2002 Jul;9(1):P267-8.

Variable acceleration influences cyclic AMP levels in Paramecium biaurelia.

Journal of gravitational physiology : a journal of the International Society for Gravitational Physiology

Ruth Hemmersbach, Manuela Wilczek, Christiane Stieber, Richard Braucker, Krassimira Ivanova

PMID: 15002574

Abstract

Paramecium is used as a model system to analyse the gravity signal transduction pathway, that leads to gravitaxis and gravikinesis. In order to prove whether gravistimulation is coupled with second messenger production (cyclic AMP: hyperpolarization, cyclic GMP: depolarization) Paramecium was fixated under variable accelerations (1 x g, 9 x g and 10(-4) x g) on a centrifuge and during a sounding rocket flight (TEXUS 39). The analysis of cAMP and cGMP levels revealed an acceleration-dependent change in cAMP, while cGMP-levels showed gravity-independent variations. Hypergravity did not only induce an amplification of gravitaxis and gravikinesis, but also an increase in cAMP compared to the 1 x g-data. We conclude that the increased pressure of the cytoplasm on the lower membrane of upward swimming cells enhance the number of open K+(-)channels, thus causing hyperpolarization and change in cAMP concentration. Consequently, transition to microgravity declines gravitaxis and gravikinesis, and decreases cAMP concentration due to the loss of pressure on the cell membrane.

Publication Types

• Journal Article
• Research Support, Non-U.S. Gov't