Complex oscillations in simple neural systems.

One of the goals of this workshop is to explore how research on aquatic plants and animals can improve our understanding of the basic mechanisms underlying the effects of gravity on biological processes. In general, the focus of “gravitational biology” has been to investigate gravitational effects at the organismal level rather than at the cellular, subcellular, or molecular levels. Indeed, previous theoretical studies have indicated that the effects of gravity would be minuscule at the subcellular level (Albrecht-Buehler, 199 1; Nate, 1983; Pollard, 1965, 197 1; Todd, 1989). However, recent spaceflight and ground-based experiments have demonstrated that a broad range of basic cellular properties can be influenced by gravity, including cytoskeletal structure and cell morphology, cell-cell interactions, cellular metabolism, exocytosis and endocytosis, concentrations of electrolytes, voltage-gated channels, intracellular levels of second messengers, and enzymatic activities (Cogoli et al., 1990; Cogoli and Gmiinder, 1991; Edgerton and Roy, 1994; Gruener and Hoeger, 1990, 199 1; HughesFulford, 199 1; Hymer et al., 1994; Krasnov, 1994; Morrison, 1994; Reitstetter et al., 199 1; Rijken et al., 1994; Sato et al., 1992; Schatz et al., 1994; Sibonga et al., 1989; Todd, 1989). Thus, perturbations in the gravitational environment can induce modifications in cellular activities, which in turn may contribute to gravity-dependent changes at the organismal level. How is it possible to resolve the theoretical and empirical findings? An intriguing explanation for the influence of gravity on cells was derived, in part, from nonlinear