| SGA | small for gestational age |
|---|---|
| SI | International System of Units [Fr. le Systeme International d'Unites]; sacroiliac; saline infusion; ... |
| SIG | small inducible gene |
| SISS | Sentinel Injury Surveillance System [for Gunshot and Stab Wounds] small inducible secreted substance... |
| SL | sarcolemma; sclerosing leukoencephalopathy; secondary leukemia; segment length; sensation level; sen... |
| direct nuclear division | <cell biology> An unusual form of nuclear division, in which the nucleus simply constricts, rather like a cell without chromosome condensation or spindle formation. Partitioning of daughter chromosomes is haphazard. Observed in some Protozoa. (18 Nov 1997) |
|---|---|
| indirect nuclear division | <cell biology> A method of indirect division of a cell, consisting of a complex of various processes, by means of which the two daughter nuclei normally receive identical complements of the number of chromosomes characteristic of the somatic cells of the species. Mitosis, the process by which the body grows and replaces cells, is divided into four phases. 1. Prophase: formation of paired chromosomes, disappearance of nuclear membrane, appearance of the achromatic spindle, formation of polar bodies. 2. Metaphase: arrangement of chromosomes in the equatorial plane of the central spindle to form the monaster. Chromosomes separate into exactly similar halves. 3. Anaphase: the two groups of daughter chromosomes separate and move along the fibres of the central spindle, each toward one of the asters, forming the diaster. 4. Telophase: the daughter chromosomes resolve themselves into a reticulum and the daughter nuclei are formed, the cytoplasm divides, forming two complete daughter cells. NOTE: the term mitosis is used interchangeably with cell division, but strictly speaking it refers to nuclear division, whereas cytokinesis refers to division of the cytoplasm. In some cells, as in many fungi and the fertilized eggs of many insects, nuclear division occurs within the cell unaccompanied by division of the cytoplasm and formation of daughter cells. (13 Nov 1997) |
| internal nuclear layer of retina | The intermediate layer of neurons in the retina composed largely of bipolar cells. Synonym: internal nuclear layer of retina, stratum ganglionare retinae, stratum nucleare internum retinae. (05 Mar 2000) |
| epstein-barr virus nuclear antigens | Nuclear antigens encoded by epstein-barr virus genes. at least six nuclear antigens have been identified but their mechanism of action and role in B-cell transformation is still unknown. (12 Dec 1998) |
| external nuclear layer of retina | The outermost layer of the cerebral layer of retina, composed of the primary receptor cells of the retina; the stratum consists of two sublayers: 1) an external layer made up of the rods and cones, the photosensitive processes of the receptor cells, and 2) the external nuclear layer containing the cell bodies of these cells; the external limiting membrane forms a perforated supporting plate between the two sublayers; the name refers to the fact that the retinal receptor cells are a specialised form of (epithelial) ependyma cell and thus, in a sense, are comparable to the neuroepithelial cells (e.g., hair cells) of other sense organs. Synonym: external nuclear layer of retina, stratum neuroepitheliale retinae, stratum nucleare externum retinae. (05 Mar 2000) |
| acceptor RNA | rNA |
| antisense RNA | <molecular biology> A complementary RNA sequence that binds to (and thus blocks the transcription of) a naturally-occuring (sense) messenger RNA molecule. These proteins can be used to selectively turn off production of certain proteins or block viral genetic instructions, by marking them for destruction by cellular enzymes, in order to prevent the building of new virus or the infection of new cells. (09 Oct 1997) |
| bacteriophage T3 RNA polymerase | <enzyme> Used for the rapid generation of strand-specific RNA molecules that can be used for the identification of genes in hybridization experiments Registry number: EC 2.7.7.- Synonym: t3 RNA polymerase (26 Jun 1999) |
| cap II RNA(nucleoside-2'-)methyltransferase | <enzyme> Converts cap i-terminated mRNA to cap II-terminated mRNA Registry number: EC 2.1.1.- Synonym: cap II methylase (26 Jun 1999) |
| cap I RNA (nucleoside-2'-)methyltransferase | <enzyme> Converts cap 0-terminated mRNA to cap i-terminated mRNA Registry number: EC 2.1.1.- Synonym: cap I methylase (26 Jun 1999) |
| p68 RNA helicase | <enzyme> An RNA helicase isolated from uv-induced tumours in mice; amino acid sequence has been determined Registry number: EC 2.7.7.- Synonym: dead box helicase p68 (26 Jun 1999) |
| masked messenger RNA | <molecular biology> Long lived and stable mRNA found originally in the oocytes of echinoderms and constituting a store of maternal information for protein synthesis that is unmasked (derepressed) during the early stages of morphogenesis. In these early stages the rate of cell division is so rapid that transcription from the embryonic genome cannot occur. Undoubtedly not restricted to oocytes and the term can be applied to any mRNA which is present in inactive form. (18 Nov 1997) |
| ribosomal RNA | <molecular biology> A nucleic acid found in all living cells. Plays a role in transferring information from DNA to the protein-forming system of the cell. (16 Dec 1997) |
| messenger-like RNA | An ill-defined form of RNA, of high molecular weight, that never leaves the nucleus and is thought to be the precursor of messenger RNA. (05 Mar 2000) |
| messenger RNA | <molecular biology> Single stranded RNA molecule that specifies the amino acid sequence of one or more polypeptide chains. This information is translated during protein synthesis when ribosomes bind to the mRNA. In prokaryotes, mRNA is normally formed by splicing a large primary transcript from a DNA sequence and protein synthesis starts while the mRNA is still being synthesised. Prokaryote mRNAs are usually very short lived (average t 1/2 is 5mins.). In contrast, in eukaryotes the primary transcripts (HnRNA) are synthesised in the nucleus and they are extensively processed to give the mRNA that is exported to the cytoplasm where protein synthesis takes place. This processing includes the addition of a 5' 5' linked 7 methyl guanylate cap at the 5' end and a sequence of adenylate groups at the 3' end, the poly A tail, as well as the removal of any introns and the splicing together of exons, only 10% of HnRNA leaves the nucleus. Eukaryote mRNAs are comparatively long lived with a half life ranging from 30minutes to 24 hours. (27 Jun 1999) |