| signal transduction | The cascade of processes by which an extracellular signal (typically a hormone or neurotransmitter) interacts with a receptor at the cell surface, causing a change in the level of a second messenger for example calcium or cyclic AMP) and ultimately effects a change in the cells functioning (for example: triggering glucose uptake or initiating cell division). Can also be applied to sensory signal transduction, for example of light at photoreceptors. (18 Nov 1997) |
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| signal void | In magnetic resonance imaging, a region emitting no radiofrequency signal, either because there are no activated protons in the region (such as flowing blood) or because a different element predominates, particularly calcium. (05 Mar 2000) |
| nuclear localization signal | Short, predominantly basic amino acid sequences identified as nuclear import signals for some proteins. These sequences are believed to interact with specific receptors at nuclear pores. (12 Dec 1998) |
| calcium channel | <physiology> A membrane channel that is specific for calcium. It is a voltage-dependent cell membrane glycoproteins selectively permeable to calcium ions. They are categorised as l, t, n, or p types based on the activation and inactivation kinetics, ion specificity, and sensitivity to drugs and toxins. (12 May 2002) |
| calcium channel agonist | <pharmacology> Agents that increase calcium influx into calcium channels of excitable tissues. This causes vasoconstriction in vascular smooth muscle and/or cardiac muscle cells as well as stimulation of insulin release from pancreatic islets. Therefore, tissue-selective calcium agonists have the potential to combat cardiac failure and endocrinological disorders. They have been used primarily in experimental studies in cell and tissue culture. (12 Dec 1998) |
| calcium channel antagonist | <pharmacology> A class of drugs that act by selective inhibition of calcium ion influx through or across cell membranes or on the release and binding of calcium in intracellular pools. Calcium channel blockers are used primarily in the treatment of certain heart conditions and stroke. As they are inducers of vascular and other smooth muscle relaxation, they are also used in the treatment of hypertension and cerebrovascular spasms, as myocardial protective agents, and in the relaxation of uterine spasms. Synonym: calcium antagonist, calcium channel-blocker, slow channel-blocking agent. (12 May 2002) |
| calcium channel-blocker | <pharmacology> A class of drugs that act by selective inhibition of calcium ion influx through or across cell membranes or on the release and binding of calcium in intracellular pools. Calcium channel blockers are used primarily in the treatment of certain heart conditions and stroke. As they are inducers of vascular and other smooth muscle relaxation, they are also used in the treatment of hypertension and cerebrovascular spasms, as myocardial protective agents, and in the relaxation of uterine spasms. Synonym: calcium antagonist, calcium channel-blocker, slow channel-blocking agent. (12 May 2002) |
| gated ion channel | <physiology> Transmembrane proteins of excitable cells, that allow a flux of ions to pass only under defined circumstances. Channels may be either voltage gated, such as the sodium channel of neurons or ligand gated such as the acetylcholine receptor of cholinergic synapses. Channels tend to be relatively ion specific and allow fluxes of typically 1000 ions to pass in around 1ms, they are thus much faster at moving ions across a membrane than transport ATPases. (05 May 1997) |
| voltage-gated channel | A class of ion channel's that open and close in response to change in the electrical potential across the plasma membrane of the cell; voltage-gated Na+ c.'s are important for conducting action potential along nerve cell processes. (05 Mar 2000) |
| voltage gated ion channel | <physiology> A transmembrane ion channel whose permeability to ions is extremely sensitive to the transmembrane potential difference. These channels are essential for neuronal signal transmission and for intracellular signal transduction. See: sodium channel. (18 Nov 1997) |
| channel | A furrow, gutter, or groovelike passageway. See: canal. Origin: L. Canalis (05 Mar 2000) |
| channel forming ionophore | <chemistry> An ionophore that makes an amphipathic pore with hydrophobic exterior and hydrophilic interior. most known types are cation selective. (18 Nov 1997) |
| channel gating | <physiology> Small currents in the membrane just prior to the increase in ionic permeability, due to the movement of charged particles within the membrane. So called because they open the gates for current flow through ion channels. (20 Mar 1998) |
| channel islands | A group of four british islands and several islets in the english channel off the coast of france. They are known to have been occupied prehistorically. They were a part of normandy in 933 but were united to the british crown at the time of the norman conquest in 1066. Guernsey and jersey originated noted breeds of cattle. (12 Dec 1998) |
| channel protein | <chemistry, physiology> A protein that facilitates the diffusion of molecules/ions across lipid membranes by forming a hydrophilic pore. most frequently multimeric with the pore formed by subunit interactions. (18 Nov 1997) |