| O | 1. Symbol for oxygen; orotidine. 2. <abbreviation> In chemistry, the abbreviation for ortho-. 3. Symbol for a blood group in the ABO system. See ABO blood group, Blood Groups appendix. 4. An abbreviation derived from ohne Hauch (without a film), used as a designation for: 1) antigens that occur in the bacterial cell, in contrast to those in the flagella; 2) specific antibodies for such somatic antigens; 3) the agglutinative reaction between somatic antigen and its antibody. (05 Mar 2000) |
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| O 2A progenitor | Bipotential progenitor cells in rat optic nerve that give rise initially to oligodendrocytes and then to type 2 astrocytes. Production of type 2 astrocytes from O 2A progenitor cells in vitro is triggered by ciliary neurotrophic factor (CNTF). (18 Nov 1997) |
| O agglutinin | An agglutinin that is formed as the result of stimulation by, and that reacts with, the relatively thermostable antigen(s) in the cell bodies of microorganisms. Synonym: somatic agglutinin. See ABO blood group. (05 Mar 2000) |
| O antigen | Somatic antigen of enteric gram-negative bacteria. External part of cell wall lipopolysaccharide. See: H antigen. See ABO blood group, Blood Groups appendix. (05 Mar 2000) |
| O antigens | Tetra and penta saccharide repeat units of the cell walls of gram-negative bacteria. They are a component of lipopolysaccharide. (18 Nov 1997) |
| O colony | Growth of a nonmotile bacterium in discrete, compact colony's in contrast to a film of growth produced by some motile bacteria. Compare: H colony. Origin: Ger. Ohne Hauch, without breath (05 Mar 2000) |
| O'Beirne | James, Irish surgeon, 1786-1862. See: O'Beirne's sphincter. (05 Mar 2000) |
| O'Beirne's sphincter | <anatomy> A circular band of muscular fibres at the recto sigmoid junction. Synonym: O'Beirne's sphincter, O'Beirne's valve, pelvirectal sphincter. (05 Mar 2000) |
| O'Beirne's valve | <anatomy> A circular band of muscular fibres at the recto sigmoid junction. Synonym: O'Beirne's sphincter, O'Beirne's valve, pelvirectal sphincter. (05 Mar 2000) |
| O'Dwyer | Joseph P., U.S. Physician, 1841-1898. See: O'Dwyer's tube. (05 Mar 2000) |
| O'Dwyer's tube | A metal tube formerly used for intubation of the larynx in diphtheria. (05 Mar 2000) |
| O'Hara forceps | Two slender clamp forceps's held together by a serrefine, once used in intestinal anastomosis; now obsolete. (05 Mar 2000) |
| O'Hara, Michael Jr | <person> U.S. Surgeon, 1869-1926. See: O'Hara forceps. (05 Mar 2000) |
| o'nyong-nyong fever | A dengue-like disease caused by the o'nyong-nyong virus, a member of the family Togaviridae, and transmitted by a mosquito, characterised by joint pains and notable lymphadenopathy followed by a maculopapular eruption of the face which extends to the trunk and extremities but fades in several days without desquamation. (05 Mar 2000) |
| o'nyong-nyong virus | A virus of the genus Alphavirus, in the family Togaviridae, found in Uganda, Kenya, and Congo, which causes o'nyong-nyong fever. (05 Mar 2000) |