| M | 1. Symbol for mega-; morgan; moles per liter (also written M or m); myopia or myopic; methionine; 6-mercaptopurine ribonucleoside in a nucleic acid; molarity; L. Misce, mix. 2. Symbol for a blood factor.MNSs blood group, Blood Groups Appendix. Symbol for meter; milli-; minim; mass; magnetic dipole moment; molality. (05 Mar 2000) |
|---|---|
| M antigen | An antigen found in the cell of Streptococcus pyogenes; associated with virulence. See: beta-haemolytic streptococci. (05 Mar 2000) |
| M band | Central region of the A band of the sarcomere in striated muscle. (18 Nov 1997) |
| M cell | <cell biology> An autonomous self replicating unit (in principle) that may constitute an organism (in the case of unicellular organisms) or be a sub unit of multicellular organisms in which individual cells may be more or less specialised differentiated) for particular functions. The individual units from which tissues of the body are formed. All living organisms are composed of one or more cells. (26 Mar 1998) |
| M channels | Voltage sensitive K channels inactivated by acetylcholine. ACh acting at muscarinic AChR's produces an internal messenger that turns off this class of K channel. A mechanism for regulating the sensitivity of cells to synaptic input. (18 Nov 1997) |
| M concentration | The maximum number of bacterial cells which can be produced in a unit volume of growth medium. (05 Mar 2000) |
| M current | <physiology> Flow of potassium ions through M channels. (26 Mar 1998) |
| M line | <cell biology> Central part of the A band of striated muscle (and of the M band): contains M line protein (myomesin, 165 kD), creatine kinase (40 kD) and glycogen phosphorylase b (90 kD). Involved in controlling the spacing between thick filaments. (18 Nov 1997) |
| M phase | Mitotic phase of cell cycle of eukaryotic cells, as distinct from the remainder, which is known as interphase (and that can be further subdivided as G1, s and G2). Beginning of M is signalled by separation of centrioles, where present and by the condensation of chromatin into chromosomes. M phase ends with the establishment of nuclear membranes around the two daughter nuclei, normally followed immediately by cell division (cytokinesis). (18 Nov 1997) |
| M phase promoting factor | Protein whose levels rise rapidly just before and fall away just after, mitosis. Thought to be a trigger for mitosis. (18 Nov 1997) |
| M protein | 1. Galactoside carrier in E. Coli 2. Cell surface antigen of Brucella. 3. Structural protein in the M line of striated muscle (myomesin). (4) Cell wall protein of streptococci: antibody typing of the M protein is important in identification of different strains of Group A streptococci (at least 55 serotypes are known). The M protein confers antiphagocytic properties on the cell and is present as hair like fimbriae on the surface. M protein is an important virulence factor and antibodies directed against M protein are essential for phagocytic killing of the bacteria. (18 Nov 1997) |
| m proteins | Antibodies or parts of antibodies found in unusually large amounts in the blood or urine of multiple myeloma patients. (12 Dec 1998) |
| M ring | <biology, microbiology> Innermost (motor) ring of the bacterial flagellar base, located in the outer leaflet of the plasma membrane. It is this ring that is linked to the hook region (and thus to the flagellum itself) and that rotates. Composed of 16 or 17 subunits (one more or less than the S ring). (13 Nov 1997) |
| M'Dowel | Benjamin G., Irish anatomist, 1829-1885. See: frenulum of M'Dowel. (05 Mar 2000) |
| M'Naghten | Daniel, British criminal, tried in March, 1843. See: M'Naghten rule. (05 Mar 2000) |