1. Electrophysiological measurements of Ca2+ influx using patch clamp methodology were combined with fluorescent monitoring of the free intracellular calcium concentration ([Ca2+]i) to determine mechanisms of Ca2+ regulation in isolated nerve endings from the rat neurohypophysis. 2. Application of step depolarizations under voltage clamp resulted in voltage-dependent calcium influx (ICa) and in...

Indirect evidence suggests that fluctuations, or oscillations, in the intracellular free calcium concentration [( Ca2+]i) can occur spontaneously in intact cardiac preparations, but such [Ca2+]i fluctuations have never been demonstrated directly. We used the bioluminescent Ca2+-sensitive protein aequorin to detect fluctuations in the [Ca2+]i in canine cardiac Purkinje fibers. Noise analysis of ...

Cardiac hypothermia alters contractility and intracellular Ca2+ concentration ([Ca2+]i) homeostasis. We examined how left ventricular pressure (LVP) is altered as a function of cytosolic [Ca2+]iover a range of extracellular CaCl2 concentration ([CaCl2]e) during perfusion of isolated, paced guinea pig hearts at 37°C, 27°C, and 17°C. Transmural LV phasic [Ca2+] was measured using the Ca2+ indicat...

Objective(s): Activation of acid-sensing ion channel 1a (ASIC1a) is responsible for tissue injury caused by acidosis in nervous systems. But its physiological and pathological roles in nucleus pulposus cells (NPCs) are unclear. The aim of this study is to investigate whether ASIC1a regulates the survival of NPCs in the acidic environment of degenerated discs. Materials and Methods: NPCs were i...

Sea urchin sperm motility is modulated by sperm-activating peptides. One such peptide, speract, induces changes in intracellular free calcium concentration ([Ca2+]i). High resolution imaging of single sperm reveals that speract-induced changes in [Ca2+]i have a complex spatiotemporal structure. [Ca2+]i increases arise in the tail as periodic oscillations; [Ca2+]i increases in the sperm head lag...

Individual unstimulated GH4C1 cells exhibited spontaneous dynamic fluctuations in cytosolic free Ca2+ concentration ([Ca2+]i). Either chelation of extracellular Ca2+ with EGTA or treatment with nifedipine inhibited spontaneous [Ca2+]i fluctuations, indicating that the [Ca2+]i profile was dependent on the entry of extracellular Ca2+ via voltage-operated Ca2+ channels (VOCC). Spontaneous [Ca2+]i ...

Insulin-like growth factor (IGF-I) stimulates thyroid cell proliferation. Using primary cultured porcine thyroid cells, we studied the intracellular pathways that mediate the action of IGF-I on thyroid cell proliferation. IGF-I stimulates inositol phosphate accumulation, a rise in cytoplasmic free calcium [( Ca2+]i), and cell proliferation. Exposure to IGF-I results in a time- and dose-dependen...

The mossy fiber synapse between dentate granule cells and CA3 pyramidal cells in the guinea pig hippocampus shows a robust short-term synaptic enhancement. We have simultaneously measured presynaptic residual free calcium ([Ca2+]i) and postsynaptic field potentials at this synapse to examine the role of [Ca2+]i in this enhancement. Single action potentials produced an increase in [Ca2+]i of 10-...

The induction of long-term potentiation (LTP) in hippocampal CA1 pyramidal cells requires a rise in postsynaptic intracellular Ca2+ concentration ([Ca2+]i). To determine the time for which Ca2+ must remain elevated to induce LTP, the photolabile Ca2+ buffer diazo-4 was used to limit the duration of the rise in postsynaptic [Ca2+]i following a tetanus. The affinity of diazo-4 for Ca2+ increases ...

This study examines the Ca2+ influx-dependent regulation of the Ca2+-activated K+ channel (KCa) in human submandibular gland (HSG) cells. Carbachol (CCh) induced sustained increases in the KCa current and cytosolic Ca2+ concentration ([Ca2+]i), which were prevented by loading cells with 1,2-bis(2-aminophenoxy)ethane- N, N, N', N'-tetraacetic acid (BAPTA). Removal of extracellular Ca2+ and addit...