CAMP waves

Computer simulations of Ca waves, 400,402,404 of cAMP waves, 232 of oscillations, see Limit cycle oscillations Concentric waves olCa 399 of cAMP, 232 Condition... 

The results (Fig. 5) show that the extracellular cAMP concentration profiles are approximately symmetric cAMP waves. The width at the base of the wave is about 1,600 pm. Since the wave travels at a speed of about 300 pm/min, the periodicity of the wave is approximately 5-6 min. The rising flank of the wave, as well as the width at half-maximal concentration, is about 450 pm or 1.5 min. The absolute spatial gradient of the wave, VC = dC/dx, increases during the rising flank of the wave and reaches a maximum of about 4 nM/pm at about 1 min after arrival... 

Fig. 5. Natural cAMP wave during cAMP aggregation.The cAMP concentration was deduced from fluorographs of released cAMP measured by (13). For calculations see part 4. Gradients Generated by Aggregating DIctyostellum Cells the wave of CAMP travels through a filed of cells at a rate of about 300 xm/min (5 xm/s).

The cAMP waves are propagated in the field of cells with a speed V = dx/dtof 300 pm/min (13). Therefore, the temporal gradient is given by dC/df = v VC Thus, the temporal gradient follows the spatial gradient and reaches a maximum value of about 17.5 nM/s at 1-min after arrival of the cAMP wave. In the Zigmond chamber the temporal gradient reaches a maximum of 3 nM/s at 2 min after application of cAMP (Fig. Ic). 

At the onset of development, Dictyostelium cells start to produce and respond to the small molecular chemoattractant cAMP [146]. The details of the inner workings of the oscillatory cAMP-signaling network are not directly relevant to the description of the chemotactic response and will only be touched on briefly. In a field of cells, periodic cAMP waves emerge which coordinate the formation of centers towards which the cells move by chemotaxis. On the level of an individual cell, the... 

Sanders Did you ever look to see whether indomethacin (i.e. prostaglandin inhibition) decreases coupling between these Ca2+ waves and activation of BK channels Perhaps this is your time delay. Production of prostaglandin should activate protein kinase A because of cAMP production, and this will increase BK open probability. 

Some of the main examples of biological rhythms of nonelectrical nature are discussed below, among which are glycolytic oscillations (Section III), oscillations and waves of cytosolic Ca + (Section IV), cAMP oscillations that underlie pulsatile intercellular communication in Dictyostelium amoebae (Section V), circadian rhythms (Section VI), and the cell cycle clock (Section VII). Section VIII is devoted to some recently discovered cellular rhythms. The transition from simple periodic behavior to complex oscillations including bursting and chaos is briefly dealt with in Section IX. Concluding remarks are presented in Section X. 

The three best-known examples of biochemical oscillations were found during the decade 1965-1975 [40,41]. These include the peroxidase reaction, glycolytic oscillations in yeast and muscle, and the pulsatile release of cAMP signals in Dictyostelium amoebae (see Section V). Another decade passed before the development of Ca " " fluorescent probes led to the discovery of oscillations in intracellular Ca +. Oscillations in cytosolic Ca " " have since been found in a variety of cells where they can arise spontaneously, or after stimulation by hormones or neurotransmitters. Their period can range from seconds to minutes, depending on the cell type [56]. The oscillations are often accompanied by propagation of intracellular or intercellular Ca " " waves. The importance of Ca + oscillations and waves stems from the major role played by this ion in the control of many key cellular processes—for example, gene expression or neurotransmitter secretion. 

D. Dormann, J. Y. Kim, P. Devreotes, and C. J. Weijer, cAMP receptor affinity controls wave dynamics, geometry and morphogenesis in Dictyostelium. J. Cell. Sci. 114, 2513-2523 (2001). 

H. Levine, I. Aranson, L. Tsimring, and T. V. Truong, Positive genetic feedback governs cAMP spiral wave formation in Dictyostelium. Proc. Natl. Acad. Sci. USA 93, 6382-6386 (1996). 

J. Lauzeral, J. Halloy, and A. Goldbeter, Desynchronization of cells on the developmental path triggers the formation of spiral waves of cAMP during Dictyostelium aggregation. Proc. Natl. Acad. Sci. USA 94, 9153-9158 (1997). 

T. Bretschneider, F. Siegert, and C. J. Weijer, Three-dimensional scroll waves of cAMP could direct cell movement and gene expression in Dictyostelium slugs. Proc. Natl. Acad. Sci. USA 92, 4387 391 (1995). 

We returned to our camp and mentioned to all present that Dennis had generated the wave of cold air that he had predicted from the theory. But it was all sufficiently ambiguous that no one felt drawn to comment. After dinner, Vanessa and Dave returned to the riverside house and Ev, Dennis, and I settled into our first night in the forest since arriving at La Chorrera. 

There recently had been much discussion of fire and the role it must have played in forming the mental world of archaic human beings. Once, as we sat staring into the camp fire, Dennis had remarked to me that, "People have been looking into fires like this for thousands and thousands of years. The squeal of these coals is the release of ionized plasma and in the flickering waves of free electrons thus created, one can see into the past and the future. The fire is the place where the ideas come from."... 

Occasionally Dennis would interrupt me to ask that I or Ev smoke a cigarette for him. Questioning uncovered his belief that in hyperspace the topology of all human bodies is continuous and so he could effortlessly absorb what he needed directly out of our bodies. For five days life went on in that mode, a waking dream of overkill by palindrome and pun. We sent amazingly few waves of interaction out into the "real world" around us. No one stopped to stare at us or our camp we seemed to have become invisible. The morning of the tenth of March changed that. 

WARNING Renal impair is the major tox foUow administration instructions Uses CMV retinitis w/ HIV Action Selective inhibition of viral DNA synth Dose Rx 5 mg/kg IV over 1 h once/wk for 2 wk w/ probenecid Maint 5 mg/kg IV once/2 wk w/ probenecid (2 g PO 3 h prior to cidofovir, then 1 g PO at 2 h 8 h after cidofovir) X in renal impair Caution [C, -] Contra Probenecid or sulfa allergy Disp Inj SE Renal tox, chills, fever, HA, NA /D, thrombocytopenia, neutropenia Interactions t Nephrotox W/ aminoglycosides, amphot icin B, foscar-net, IV pentamidine, NSAIDs, vancomycin t effects W/zidovudine EMS Monitor ECG for hypocalcemia (t QT int val) and hypokalemia (flattened T waves) OD May cause renal failure hydration may be effective in reducing drug levels/effects Cilostazol (Pletal) TAntiplatelet, Arterial Vasodilator/ Phosphodiesterase Inhibitor] Uses Reduce Sxs of intermittent claudication Action Phosphodiesterase in inhibitor t s cAMP in pits blood vessels, vasodilation inhibit pit aggregation Dose 100 mg PO bid, 1/2 h before or 2 h after breakfast dinner Caution [C, +/-] Contra CHE, hemostatic disorders. 

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