| DNA, circular | Any of the covalently closed DNA molecules found in bacteria, many viruses, mitochondria, plastids, and plasmids. Small, polydisperse circular DNA's have also been observed in a number of eukaryotic organisms and are suggested to have homology with chromosomal DNA and the capacity to be inserted into, and excised from, chromosomal DNA. It is a fragment of DNA formed by a process of looping out and deletion, containing a constant region of the mu heavy chain and the 3'-part of the mu switch region. Circular DNA is a normal product of rearrangement among gene segments encoding the variable regions of immunoglobulin light and heavy chains, as well as the T-cell receptor. (12 Dec 1998) |
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| after-nystagmus | Nystagmus occurring after the abrupt cessation of rotation in the opposite direction of the rotatory nystagmus. (05 Mar 2000) |
| amaurotic nystagmus | The pendular or, rarely, jerky nystagmus seen in severely reduced vision. Synonym: amaurotic nystagmus. (05 Mar 2000) |
| Bruns' nystagmus | A fine, jerking (vestibular) nystagmus on horizontal gaze in one direction, together with a slower, larger amplitude (gaze, paretic) nystagmus on looking in the opposite direction; due to lateral brainstem compression, usually by a cerebellar-pontine angle mass such as an acoustic neuroma. (05 Mar 2000) |
| caloric nystagmus | Jerky nystagmus induced by labyrinthine stimulation with warm or cold water injected into the ear canal. (27 Sep 1997) |
| galvanic nystagmus | Nystagmus involving galvanic stimulation of the labyrinth. (05 Mar 2000) |
| palatal nystagmus | A clonic spasm of the levator palati muscle, causing an audible click. (05 Mar 2000) |
| railroad nystagmus | Nystagmus induced by looking at moving visual stimuli. Synonym: opticokinetic nystagmus, railroad nystagmus. (05 Mar 2000) |
| gaze paretic nystagmus | A nystagmus occurring in partial gaze paralysis when an attempt is made to look in the direction of the gaze paresis. (05 Mar 2000) |
| vertical nystagmus | An up-and-down oscillation of the eyes. (05 Mar 2000) |
| vestibular nystagmus | Nystagmus resulting from physiological stimuli to the labyrinth that may be rotatory, caloric, compressive, or galvanic, or due to labyrinthal lesions. See: Barany's sign. Synonym: labyrinthine nystagmus. (05 Mar 2000) |
| voluntary nystagmus | Pendular nystagmus in which the individual causes an extremely fine and rapid horizontal oscillation of the eyes. The nystagamus consists of back-to-back saccades and is seldom done for more than a few seconds at a time. (05 Mar 2000) |
| pendular nystagmus | A nystagmus that, in most positions of gaze, has oscillations equal in speed and amplitude, usually arising from a visual disturbance. (05 Mar 2000) |
| cervical nystagmus | Nystagmus arising from a lesion of the proprioceptive mechanism of the neck. (05 Mar 2000) |
| rotational nystagmus | Jerky nystagmus arising from stimulation of the labyrinth by rotation of the head around any axis and induced by change of motion. (05 Mar 2000) |