PubMed · 4688754
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K E Jolles. 1973-02-15. Biorhythmics.. https://pubmed.ncbi.nlm.nih.gov/4688754/
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Ligation of the T-cell receptor/CD3 complex results in global Ca(2+) signals that are essential for T-cell activation. We have recently reported that these global Ca(2+) signals are preceded by localized pacemaker Ca(2+) signals. Here, we demonstrate for the first time for human T cells that an increase in signal frequency of subcellular pacemaker Ca(2+) signals at sites close to the plasma membrane, in the cytosol and in the nucleus depends on the type 3 ryanodine receptor (RyR) and its modulation by cyclic ADP-ribose. The spatial distribution of D-myo-inositol 1,4,5-trisphosphate receptors and RyRs indicates a concerted action of both of these receptors/Ca(2+) channels in the generation of initial pacemaker signals localized close to the plasma membrane. Inhibition or knockdown of RyRs resulted in significant decreases in (1) the frequency of initial pacemaker signals localized close to the plasma membrane, and (2) the frequency of localized pacemaker Ca(2+) signals in the inner cytosol. Moreover, upon microinjection of cyclic ADP-ribose or upon extracellular addition of its novel membrane-permeant mimic N-1-ethoxymethyl-substituted cyclic inosine diphosphoribose, similarly decreased Ca(2+) signals were observed in both type 3 RyR-knockdown cells and in control cells microinjected with the RyR antagonist Ruthenium Red. Taken together, our results show that, under physiological conditions in human T cells, RyRs play crucial roles in the local amplification and the spatiotemporal development of subcellular Ca(2+) pacemaker signals.
We propose a technique to control coherent collective oscillations in ensembles of globally coupled units (self-sustained oscillators or maps). We demonstrate numerically and theoretically that a time delayed feedback in the mean field can, depending on the parameters, enhance or suppress the self-synchronization in the population. We discuss possible applications of the technique.
We demonstrate experimentally and theoretically the existence of canard orbits and excitable quasiharmonic limit cycles in the thermo-optical dynamics of semiconductor optical amplifiers. We also observe the phase locking of the noise-induced spikes to the small-amplitude Hopf quasiharmonic oscillations, recently predicted by Makarov, Nekorkin, and Velarde [Phys. Rev. Lett. 86, 3431 (2001)]].