| CRD | carbohydrate-recognition domain; chronic renal disease; chronic respiratory disease; child restraint... |
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| LARC | leukocyte automatic recognition computer |
| MRT | magnetic resonance tomography; maximum relaxation time; median range score; median reaction time; me... |
| OCR | oculocardiac reflex; oculocerebrorenal [syndrome]; optical character recognition |
| PDRT | Portland Digit Recognition |
| signal peptides | Additional polypeptide sequence of 25 to 30 residues at the amino-terminal or carboxy-terminal end of proteins. The signal sequence signals the cellular fate or destination of a newly synthesised protein directing it to its ultimate destination in the cell. These leaders are recognised by the signal recognition particle and bound by specific receptor sites on the outer surface of the endoplasmic reticulum. They are then transported into the cisterna of the endoplasmic reticulum and from there directed to their ultimate destination in the cell. In prokaryotes, the signal peptides attach to the plasma membrane. These signal sequences are ultimately removed by specific peptidases. (12 Dec 1998) |
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| signal processing, computer-assisted | Computer-assisted processing of electric, ultrasonic, or electronic signals to interpret function and activity. (12 Dec 1998) |
| signal response coupling | 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 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) |
| alpha particle | <physics> A radioactive particle made up of two protons and two neutrons, these particles are created by the decay of a radioactive material or by nuclear bombardment, and they are the same as the nucleus of a helium-4 atom. (09 Oct 1997) |
| beta particle | <physics, radiobiology> An electron or positron emitted from a radioactive nucleus during beta decay. (09 Oct 1997) |
| genes, intracisternal a-particle | A family of retrovirus-like genetic elements coding for virus-like particles found regularly in early rodent embryos (2-cell to blastocyst stage), but which, under certain circumstances such as DNA hypomethylation, are transcribed in a wide variety of neoplasms, including plasmacytomas, neuroblastomas, rhabdomyosarcomas, teratocarcinomas, and colon carcinomas. (12 Dec 1998) |
| particle | <chemistry> A tiny mass of material. Origin: L. Particula, dim. Of pars = part (18 Nov 1997) |
| particle accelerators | Devices which accelerate electrically charged atomic or subatomic particles, such as electrons, protons or ions, to high velocities so they have high kinetic energy. (12 Dec 1998) |
| particle fluence | <chemistry, radiobiology> at a given point in space, the sum of energies, the number of particles or photons incident during a given time interval on a small sphere centreed at that point, divided by the cross-sectional area of that sphere. It is identical with the time integral of the particle flux density. (16 Dec 1997) |
| charged particle | <radiobiology> A particle which carries a positive or negative electrical charge. In plasma physics, this typically means an ionised atom or molecule, or an electron. (09 Oct 1997) |