| peripheral membrane protein | <protein> Membrane proteins that are bound to the surface of the membrane and not integrated into the hydrophobic region. Usually soluble and were originally thought to bind to integral proteins by ionic and other weak forces (and could therefore be removed by high ionic strength, for example). However, it is now clear that some peripheral membrane proteins are covalently linked to molecules that are part of the membrane bilayer (see acylated proteins and glypiation) and that there are others that fit the original definition but are perhps more appropriately considered proteins of the cytoskeleton (e.g. Band 4.1 and spectrin) or extracellular matrix (e.g. Fibronectin). (18 Nov 1997) |
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| Rivinus' membrane | Triangular loose part of tympanic membrane between the malleolar folds. Synonym: pars flaccida membranae tympani, flaccid membrane, membrana flaccida, Rivinus' membrane, Shrapnell's membrane. (05 Mar 2000) |
| chorioallantoic membrane | Extraembryonic membrane formed in birds and reptiles by the apposition of the allantois to the inner face of the chorion. The chorioallantoic membrane is highly vascularised and is used experimentally as a site upon which to place pieces of tissue in order to test their invasive capacity. (18 Nov 1997) |
| ruptured membrane | <obstetrics> A term used to define the rupture of the amniotic sac, releasing the amniotic fluid and heralding the onset of labour. (17 Dec 1997) |
| circular layer of tympanic membrane | Circular fibres deep to the radiate layer of the membrane that are more abundant near the periphery; not present in the pars flaccida. Synonym: circular layer of tympanic membrane. (05 Mar 2000) |
| Ruysch's membrane | The internal layer of the choroidea of the eye, composed of a very close capillary network. Synonym: lamina choroidocapillaris, choriocapillaris, entochoroidea, lamina choriocapillaris, membrana choriocapillaris, Ruysch's membrane. (05 Mar 2000) |
| phosphatidylglycerol - membrane-oligosaccharide glycerophosphotransferase | <enzyme> Transfers phosphoglycerol residues from phosphatidylglycerol to membrane-derived oligosaccharides of E coli Registry number: EC 2.7.8.20 Synonym: phosphoglycerol transferase I, phosphoglyceroltransferase, phosphoglycerol transferase (26 Jun 1999) |
| cloacal membrane | A transitory membrane in the caudal area of the ventral wall of the embryo, separating the endodermal from the ectodermal cloaca; it is divided into anal and genitourinary membrane's that break down during the eighth to ninth week to establish the external opening for the alimentary and genitourinary tracts. (05 Mar 2000) |
| mitochondrial membrane | The double biomembrane surrounding the mitochondrion. (05 Mar 2000) |
| Wachendorf's membrane | Remnants of the central portion of the anterior layer of the iris stroma (the iridopupillary lamina) which occludes the pupil in foetal life, and normally atrophies about the seventh month of gestation. Persistent strands usually stretch across the pupil from one iris collarette to the other, without touching the pupillary margin. Failure to regress is a rare cause of congenital blindness. Synonym: membrana pupillaris, Wachendorf's membrane. (05 Mar 2000) |
| coated pits, cell-membrane | Specialised regions of the cell membrane composed of pits coated with a bristle covering made of the protein clathrin. These pits are the entry route for macromolecules bound by cell surface receptors. The pits are then internalised into the cytoplasm to form the coated vesicles. (12 Dec 1998) |
| pial-glial membrane | The dual outer lining of the brain and spinal cord, composed of the glial limiting membrane and the pia mater. (05 Mar 2000) |
| pituitary membrane | The mucous membrane lining the nasal cavity. (12 Dec 1998) |
| placental membrane | The semipermeable layer of foetal tissue separating the maternal from the foetal blood in the placenta; composed of: 1) endothelium of the foetal vessels in the chorionic villi, 2) stromata of the villi, 3) cytotrophoblast (negligible after the fifth month of gestation), and 4) syncytial trophoblast covering the villi; the placental membrane acts as a selective membrane regulating passage of substances from the maternal to the foetal blood. Synonym: placental barrier. (05 Mar 2000) |
| complement membrane attack complex | The assembly of complement plasma glycoproteins c5b, c6, c7, c8, and polymeric c9 as a group on biological membranes. The complex forms transmembrane channels which displace lipid molecules and other constituents, thus disrupting the phospholipid bilayer of target cells leading to cell lysis by osmotic leakage. The formation of the membrane attack complex is the terminal step in the complement cascade. (12 Dec 1998) |