Effects of central sympathetic inhibition on heart rate variability during steady-state exercise in healthy humans.

The profound reduction in heart rate variability (HRV) that occurs during exercise is thought to be, at least in part, the result of sympathetic nervous system activation. Moxonidine is a centrally acting anti-sympathetic drug, which suppresses sympathetic nervous system outflow by stimulation of central imidazoline receptors located in the rostral ventro-lateral medulla. This study was designed to investigate the combined effects of central sympathetic inhibition with moxonidine and steady-dynamic exercise on HRV.

Light-induced variation in phenolic levels in foliage of rain-forest plants : II. Potential significance to herbivores.

The allelochemic activity of the polyphenolics isolated from the leaves of four west African rain-forest plants,Acacia pennata, Cynometra leonensis, Diospyros thomasii, andTrema guineensis, was examined by means of protein precipitation experiments to estimate their specific activity as precipitants. Results indicated that light-induced phenol synthesis in the more heavily insolated foliage of a species led to greater protein-precipitating capacity in these leaves. It is considered doubtful that this produced a quantitative difference in protein availability to an herbivore as, on average, even in the most shaded leaves there was sufficient tannin present to precipitate all the foliar protein.

Factors affecting levels of some phenolic compounds, digestibility, and nitrogen content of the mature leaves ofBarteria fistulosa (Passifloraceae).

Levels of total phenolics, condensed tannins, acid detergent fiber, pepsin/cellulase digestibility, and nitrogen in mature leaves of 26 individuals of the ant-plant,Barteria fistulosa, have been determined. Analysis of the results in terms of the presence or absence of ants and the position of the branch from which the leaves were collected showed no relationship with concentrations of phenolics or fiber and only a weak relationship with digestibility and nitrogen. By contrast, light intensity strongly influenced levels of phenolics, notably condensed tannins, so that mature leaves of individuals growing in direct sunlight were less digestible and appeared to be of lower quality as food for herbivores than did mature leaves of individuals in shaded positions.