| signal sequence | A peptide present on proteins that are destined either to be secreted or to be membrane components. It is usually at the N terminus and normally absent from the mature protein. Normally refers to the sequence (ca 20 amino acids) that interacts with signal recognition particle and directs the ribosome to the endoplasmic reticulum where co translational insertion takes place. Could also refer to sequences that direct post translational uptake by organelles. Signal peptides are highly hydrophobic but with some positively charged residues. The signal sequence is normally removed from the growing peptide chain by signal peptidase, a specific protease located on the cisternal face of the endoplasmic reticulum. See: signal recognition particle. (18 Nov 1997) |
|---|---|
| signal-to-noise ratio | <microscopy> Also sometimes used as an abbreviation for serial number, can be somewhat confusing in the case of electronic equipment. (05 Aug 1998) |
| 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) |
| 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) |
| anterior tibial node | A small inconstant lymph node in front of the interosseous membrane along the upper part of the anterior tibial vessels. Synonym: nodus tibialis anterior, anterior tibial node. (05 Mar 2000) |
| artery to atrioventricular node | The atrioventricular branches or the nodal branches, the small arteries supplying the atrioventricular node; they usually arise from the right coronary artery where it starts to descend the posterior interventricular sulcus. Synonym: ramus nodi atrioventricularis, atrioventricular nodal branch, branch to atrioventricular node. (05 Mar 2000) |
| artery to the sinuatrial node | Ascending atrial branch, usually (55%) arising from the anterior stem of the right coronary artery (but 35-45% arising from the circumflex branch of the left coronary artery), which runs around the base of the superior vena cava to reach the sinuatrial node. Synonym: ramus nodi sinuatrialis arteriae coronaria dextra, branch to sinuatrial node, sinuatrial nodal branch of right coronary artery, sinuatrial node artery. (05 Mar 2000) |
| atrioventricular node | <cardiology> The location in the heart's conduction system, between the atria and the ventricles, which conducts the normal electrical impulse from the atria to the ventricles. (27 Sep 1997) |
| A-V node | <cardiology> The location in the heart's conduction system, between the atria and the ventricles, which conducts the normal electrical impulse from the atria to the ventricles. (27 Sep 1997) |
| axillary node | <anatomy> The lymph nodes in the axilla (underarm) that are cut out and examined during surgery to see if the cancer has spread past the breast. The number of nodes in this area varies. (09 Oct 1997) |
| branch to atrioventricular node | The atrioventricular branches or the nodal branches, the small arteries supplying the atrioventricular node; they usually arise from the right coronary artery where it starts to descend the posterior interventricular sulcus. Synonym: ramus nodi atrioventricularis, atrioventricular nodal branch, branch to atrioventricular node. (05 Mar 2000) |
| branch to sinuatrial node | Ascending atrial branch, usually (55%) arising from the anterior stem of the right coronary artery (but 35-45% arising from the circumflex branch of the left coronary artery), which runs around the base of the superior vena cava to reach the sinuatrial node. Synonym: ramus nodi sinuatrialis arteriae coronaria dextra, branch to sinuatrial node, sinuatrial nodal branch of right coronary artery, sinuatrial node artery. (05 Mar 2000) |
| buccal node | One of the chain of facial lymph nodes located superficial to the buccinator muscle. Synonym: nodus buccinatorius, buccinator node, buccal node. (05 Mar 2000) |
| malar node | One of the facial lymph nodes located near the zygomatic minor muscle. Synonym: nodus malaris, malar node. (05 Mar 2000) |