Sleep is regulated by complex biological systems and environmental influences, neither of which is fully clarified. This study demonstrates differential effects of partial sleep deprivation (SD) on sleep architecture and psychomotor vigilance task (PVT) performance using two different protocols (sequentially) that each restricted daily sleep to 3 hours in healthy adult men. The protocols differed only in the period of sleep restriction; in one, sleep was restricted to a 3-hour block from 12:00 AM to 3:00 AM, and in the other, sleep was restricted to a block from 3:00 AM to 6:00 AM. Subjects in the earlier sleep restriction period showed a significantly lower percentage of rapid-eye-movement (REM) sleep after 4 days (17.0 vs. 25.7 %) and a longer latency to the onset of REM sleep (L-REM) after 1 day (78.8 vs. 45.5 min) than they did in the later sleep restriction period. Reaction times on PVT performance were also better (i.e. shorter) in the earlier SR period on day 4 (249.8 vs. 272 ms). These data support the view that earlier-night sleep may be more beneficial for daytime vigilance than later-night sleep. The study also showed that cumulative declines in daytime vigilance resulted from loss of total sleep time, rather than from specific stages, and underscored the reversibility of SR effects with greater amounts of sleep., H. Wu ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
We analyzed human postural responses to muscle vibration applied at four different frequencies to lower leg muscles, the lateral gastrocnemius (GA) or tibialis anterior (TA) muscles. The muscle vibrations induced changes in postural orientation characterized by the center of pressure (CoP) on the force platform surface on which the subjects were standing. Unilateral vibratory stimulation of TA induced body leaning forward and in the direction of the stimulated leg. Unilateral vibration of GA muscles induced body tilting backwards and in the opposite direction of the stimulated leg. The time course of postural responses was similar and started within 1 s after the onset of vibration by a gradual body tilt. When a new slope of the body position was reached, oscillations of body alignment occurred. When the vibrations were discontinued, this was followed by rapid recovery of the initial body position. The relationship between the magnitude of the postural response and frequency of vibration differed between TA and GA. While the magnitude of postural responses to TA vibration increased approximately linearly in the 60-100 Hz range of vibration frequency, the magnitude of response to GA vibration increased linearly only at lower frequencies of 40-60 Hz. The direction of body tilt induced by muscle vibration did not depend on the vibration frequency., A. Polónyová, F. Hlavačka., and Obsahuje bibliografii
Addiction to tobacco results in an imbalance of endocrine homeostasis in both sexes. This can also have impacts on fertility problems. The male reproductive system is less susceptible than that of females, with a worsening spermiogram in smokers, the most cited effect in the literature. However, the literature is inconsistent as to the effects of smoking on steroid hormone levels in men, and there is very little data on the effects of quitting smoking in men. In this study we followed 76 men before quitting smoking, and then after 6, 12, and 24 weeks and 1 year of abstinence. We measured basic anthropomorphic data and steroid hormone levels along with steroid neuroactive metabolites using GC-MS. We demonstrate lower androgen levels in men who smoke, and these changes worsened after quitting smoking. There was a drop in SHBG already in the first week of non-smoking, and levels continued to remain low. Male smokers have lower androgen levels compared to non-smokers. The lower the initial level of androgen, the lower the likelihood of success in quitting smoking. Changes in steroid hormones proved to be a promising marker for the prediction of success in quitting smoking., H. Jandikova, M. Duskova, K. Simunkova, B. Racz, M. Hill, E. Kralikova, K. Vondra, L. Starka., and Obsahuje bibliografii