Streamer F mutants have been found to be useful tools for studying the pathway of signal transduction leading to chemotactic cell movement. The primary defect in these mutants is in the structural gene for the cyclic GMP specific phosphodiesterase. This defect allows a larger and prolonged peak of cyclic GMP to be formed in response to the chemotactic stimulus, cyclic AMP. This characteristic aberrant pattern of cyclic GMP accumulation in the streamer F mutants has been correlated with similar patterns of (...) changes in the influx of calcium from the medium, myosin II association with the cytoskeleton, myosin phosphorylation and a decrease in speed of movement of the amoebae. From these studies a sequence of events can be deduced that leads from cell surface cyclic AMP stimulation to cell polarization prior to movement of the amoebae in response to the chemotactic stimulus. (shrink)

A very rapid cellular event that follows chemotactic stimulation of leucocyte and cellular slime mould amoebae is a massive polymerization of G to F actin and its association with the cytoskeleton. In the cellular slime moulds this event occurs within 3–5 sec of cell surface binding of chemoattractants. It is correlated with rapid pseudopodium extension and may be a cell orientation mechanism. Curiously, before an amoebae moves away in the direction of its new pseudopodium it rounds up or “cringes” for (...) 10–20 sec, an event correlated with a massive actin depolymerization. Transduction of the chemotactic signal involves Ca2+ release from internal stores by inositol trisphosphate. (shrink)

Recalling past transformations, this book examines what makes the current challenge different, and especially urgent. It analyses how green transformations must take place in the context of the particular moments of capitalist development, and in relation to particular alliances. The book emphasises the role of the state and the role of citizens, as innovators, entrepreneurs, green consumers and members of social movements. Green transformations must be both 'top-down', involving elite alliances between states and business, but also 'bottom up', pushed by (...) grassroots innovators and entrepreneurs, and part of wider mobilisations among civil society. (shrink)