| sympathectomy, chemical | Sympathectomy using chemicals (e.g., 6-hydroxydopamine or guanethidine) which selectively and reversibly destroy adrenergic nerve endings while leaving cholinergic nerve endings intact. (12 Dec 1998) |
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| evolution, chemical | Chemical and physical transformation of the biogenic elements from their nucleosynthesis in stars to their incorporation and subsequent modification in planetary bodies and terrestrial biochemistry. It includes the mechanism of incorporation of biogenic elements into complex molecules and molecular systems, leading up to the origin of life. (12 Dec 1998) |