Spiral calcium wave propagation and annihilation in Xenopus laevis oocytes.
Intracellular calcium (Ca2+) is a ubiquitous second messenger. Information is encoded in the magnitude, frequency, and spatial organization of changes in the concentration of cytosolic free Ca2+. Regenerative spiral waves of release of free Ca2+ were observed by confocal microscopy in Xenopus laevis oocytes expressing muscarinic acetylcholine receptor subtypes. This pattern of Ca2+ activity is characteristic of an intracellular milieu that behaves as a regenerative excitable medium. The minimal critical radius for propagation of focal Ca2+ waves (10.4 micrometers) and the effective diffusion constant for the excitation signal (2.3 x 10(-6) square centimeters per second) were estimated from measurements of velocity and curvature of circular wavefronts expanding from foci. By modeling Ca2+ release with cellular automata, the absolute refractory period for Ca2+ stores (4.7 seconds) was determined. Other phenomena expected of an excitable medium, such as wave propagation of undiminished amplitude and annihilation of colliding wavefronts, were observed.
Lechleiter
J
J
Department of Pharmacology, Mayo Foundation, Rochester, MN 55905.
Girard
S
S
Peralta
E
E
Clapham
D
D
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002451:Cell Compartmentation; D008845:Microinjections; D009865:Oocytes / Q000502:physiology*; D012333:RNA, Messenger / Q000008:administration & dosage; D011976:Receptors, Muscarinic / Q000502:physiology*; D011994:Recombinant Proteins; D015398:Signal Transduction; D013997:Time Factors; D014982:Xenopus laevis
D012333:RNA, Messenger; D011976:Receptors, Muscarinic; D011994:Recombinant Proteins; D002118:Calcium