| 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) |
| channel transport |
<radiobiology> In inertial fusion research using light ion drivers, describes the use of current-carrying plasma channels (which are magnetically confined to the channel) to transport electron or ion beams between the ion diode and the fusion target. This allows the ion source to stand back from the target.
(09 Oct 1997) |
| chloride channel |
Ion channels selective for chloride ions. Various types including ligand activated Cl channels at synapses (the GABA and glycine activated channels), as well as voltage gated Cl channels found in a variety of plant and animal cells.
See: CFTR, MDR.
(18 Nov 1997) |
| ryanodine receptor calcium release channel |
Protein complexes that mediate the release of calcium from the sarcoplasmic reticulum in both skeletal and cardiac muscle cells by forming tetrametric complexes. These complexes each then act as a calcium channel. There are three isoforms of the ryr: ryr1, ryr2, and ryr3. Ryr1 is specifically expressed in skeletal muscles and ryr2 in cardiac muscles. Ryr3 is yet another isoform found in non-muscle cells such as neuronal cells.
(12 Dec 1998) |
| single channel recording |
Variant of patch clamp technique.
(18 Nov 1997) |
| slow channel-blocking agent |
calcium channel-blocking agent |
| sodium channel |
<neurology, physiology> The protein responsible for electrical excitability of neurons. A transmembrane ion channel, containing an aqueous pore around 0.4nm diameter, with a negatively charged region internally (the selectivity filter) to block passage of anions.
The channel is voltage gated: it opens in response to a small depolarisation of the cell (usually caused by an approaching action potential), by a multistep process.
Around 1000 sodium ions pass in the next millisecond, before the channel spontaneously closes (an event with single step kinetics). The channel is then refractory to further depolarisations until returned to near the resting potential.
There are around 100 channels per square micron in unmyelinated axons, in myelinated axons, they are concentrated at the nodes of Ranvier. The sodium channel is the target of many of the deadliest neurotoxins.
(18 Nov 1997) |
| delayed rectifier channel |
<physiology> The potassium selective ion channels of axons, so called because they change the potassium conductance with a delay after a voltage step.
The name is used to denote any axon like K channel. Various roles for example regulation of pacemaker potentials, generation of bursts of action potentials or generation of long plateaus on action potentials.
(18 Nov 1997) |
| double-channel catheter |
A catheter with two lumens, allowing irrigation and aspiration.
Synonym: two-way catheter.
(05 Mar 2000) |
| ion channel |
<cell biology> A transmembrane pore that presents a hydrophilic channel for ions to cross a lipid bilayer down their electrochemical gradients.
Some degree of ion specificity is usually observed and typically a million ions per second may flow. Channels may be permanently open, like the potassium leak channel or they may be voltage gated, like the sodium channel or ligand gated like the acetylcholine receptor.
(27 Oct 1998) |
| ion channel gating |
The opening and closing of ion channels due to a stimulus. The stimulus can be a change in membrane potential (voltage-gated), drugs or chemical transmitters (ligand-gated), or a mechanical deformation. Gating is thought to involve conformational changes of the ion channel which alters selective permeability.
(12 Dec 1998) |
| transnexus channel |
A hexagonal 15-20A |
| ligand-gated channel |
A class of ion channel's whose ionic permeability is regulated by cell membrane receptors that respond to specific extracellular chemical signals.
(05 Mar 2000) |
| ligand gated ion channel |
A transmembrane ion channel whose permeability is increased by the binding of a specific ligand, typically a neurotransmitter at a chemical synapse. The permeability change is often drastic, such channels let through effectively no ions when shut, but allow passage at up to 10exp7 ions sexp 1 when a ligand is bound. Recently, the receptors for both acetylcholine and GABA have been found to share considerable sequence homology, implying that there may be a family of structurally related ligand gated ion channels.
(18 Nov 1997) |
