Articles: human.
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We examined the effects of cytidine (5?)-diphosphocholine (CDP-choline) on plasma levels of cytidine, choline, and unchanged CDP-choline among normal volunteers receiving the substance orally or intravenously, and rats receiving it intravenously. Two hours after a single oral dose (2g), plasma choline levels were increased by 48% and plasma cytidine by 136%. Among subjects receiving three doses (2g each) at two-hour intervals, plasma choline peaked (30% over baseline) 4 h after the initial CDP-choline dose, while plasma cytidine levels continued to increase for at lest 6 h, at which time they were five times basal levels (P < 0.01). ⋯ In rats given a bolus injection of CDP-choline, five minutes earlier, the unchanged compound was also undetectable in plasma, while plasma cytidine levels increased markedly and remained elevated for at least 60 min. These observations show that CDP-choline is converted to at least two major circulating metabolites, choline and cytidine. Since both of these compounds are used in the biosynthesis of phosphatidylcholine, both may be involved in the long-term effects of the CDP-choline.
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Journal of motor behavior · Sep 1984
Motor programming: does the choice of the limb which is to carry out the response imply a delay?
In many activities, the human being must quickly decide on the response to be produced following a change in the environment. In some of these situations, the limb that the individual chooses to carry out a response seems to be a significant element in performance. Thus, if the individual carries out the response with the limb closest to the target, the performance can improve because it will take less time to achieve the goal. ⋯ In order to do so, the subjects performed a two choice reaction-time task. For this task, some subjects knew beforehand which hand they had to use to carry out the response while other subjects were unaware of this fact. The results of two experiments indicated that the choice of the limb which is to carry out the response requires no particular delay when the movement to be produced is externally guided.