| off-road motor vehicles | Motorised, recreational vehicles used on non-public roads. They include all-terrain vehicles, dirt-bikes, minibikes, motorbikes, trailbikes, and snowmobiles. Excludes motorcycles, which are considered public road vehicles. (12 Dec 1998) |
|---|---|
| on-off phenomenon | A state in the treatment of Parkinson's disease by l-dopa, in which there is a rapid fluctuation of akinetic (off) and choreoathetotic (on) movements. (05 Mar 2000) |
| ordered on-random off mechanism | A scheme for substrate binding and product release for multisubstrate enzymes; for a two-substrate two-product enzyme with this mechanism, the individuals have to bind to the enzyme in a distinct order; however, once the products are formed they may dissociate from the enzyme in either order. It has been suggested that pyruvate kinase has such a mechanism. The random on-ordered off mechanism is simply the reverse of this mechanism. (05 Mar 2000) |