The purposes of the present study were to determine (a) whether changes of intracellular [Ca2+] (Cai) can account for the decrease of developed tension observed in rat heart muscle when stimulation rate is increased, and (b) whether the effect of stimulation rate on Cai is altered in conditions in which the rate of repriming of the sarcoplasmic reticulum (SR) is altered, as when perfusate [Ca2+...

Nutrient-stimulated insulin secretion is dependent upon the generation of metabolic coupling factors in the mitochondria of the pancreatic B cell. To investigate the role of Ca 2 1 in mitochondrial function, insulin secretion from INS-1 cells stably expressing the Ca 2 1 -sensitive photoprotein aequorin in the appropriate compartments was correlated with changes in cytosolic calcium ([Ca 2 1 ] ...

AIMS The aim of the study was to obtain further information regarding the modes of action of doxazosin, naftopidil and nifedipine on platelet function. METHODS We conducted an in vitro study of drug influences on adrenaline and collagen-induced mobilization of platelet calcium. RESULTS In the presence of fibrinogen (300 micrograms ml-1) both collagen (5 micrograms ml-1) and adrenaline (16 m...

Intracellular calcium ([Formula: see text]) and left ventricular (LV) function were determined in the coronary-perfused mouse heart to study[Formula: see text]-related mechanisms of injury from myocardial ischemia and reperfusion. Specifics for loading of the photoprotein aequorin into isovolumically contracting mouse hearts under constant-flow conditions are provided. The method allows detecti...

The genetic transformation of the higher plant Nicotiana plumbaginifolia to express the protein apoaequorin has recently been used as a method to measure cytosolic free calcium ([Ca2+]i) changes within intact living plants (Knight, M. R., A. K. Campbell, S. M. Smith, and A. J. Trewavas. 1991. Nature (Lond.). 352:524-526; Knight, M. R., S. M. Smith, and A. J. Trewavas. 1992. Proc. Natl. Acad. Sc...

We report here the in vitro characterization of 1-(2-chlorophenyl)-6-[(2R)-3,3,3-trifluoro-2-methylpropyl]-1,5-dihydro-4H-pyrazolo[3,4-d]pyrimidine-4-one (BAY 73-6691), the first potent and selective inhibitor of phosphodiesterase 9 (PDE9), which is currently under preclinical development for the treatment of Alzheimer's disease. This compound selectively inhibits human (IC50 = 55 nM) and murin...

The calcium-regulated photoproteins, of which aequorin is the best known, continue to be one of the most useful groups of intracellular Ca2+ indicators. They are self-contained bioluminescent systems that emit blue light in the presence of Ca2+ ions, can readily be purified intact, and are nontoxic when introduced into foreign cells. They have been used successfully as Ca2+ indicators in almost...

Aplysia central neurons were injected with the calcium-sensitive photoprotein aequorin and stimulated with trains of identical depolarizing voltage-clamp pulses. The light emissions grew and the outward currents declined in successive pulses. Tetraethylammonium (TEA) enhanced the light emissions to single depolarizing pulses and suppressed the outward current. The remaining net inward current i...

The precise regulation of the Ca2+ concentration in the endoplasmic reticulum ([Ca2+]er) is important for protein processing and signal transduction. In the pancreatic beta-cell, dysregulation of [Ca2+]er may cause impaired insulin secretion. The Ca2+-sensitive photoprotein aequorin mutated to lower its Ca2+ affinity was stably expressed in the endoplasmic reticulum (ER) of rat insulinoma INS-1...

It has been proposed that the release of intracellular ionic calcium may be the universal factor promoting activation of egg metabolism at fertilization. If this hypothesis is valid, then fertilization and all parthenogenetic agents which evoke the entire program of activation would necessarily involve an intracellular rise in ionic calcium. Fertilization or parthenogenetic activation of Lytech...