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Biomedical subjects

M Gillberg

Publications and source records attributed to M Gillberg.

30 records · Page 2Linked to original sources
PubMed1984

The effects of two alternative timings of a one-hour nap on early morning performance.

The effect on performance and sleepiness of two alternative timings of a one-hour nap (2100h and 0430h, respectively) were compared with a control condition (no nap). Twelve healthy male subjects divided into three groups participated in a partly balanced repeated measurements design. At all three occasions the subjects slept 4 h during the preceding night, worked during the day and were then kept awake (except for naps) in the laboratory from 1700h to 0800h the following morning. Performance was measured through a 10-min single choice visual reaction time task administered at 1900h and 0700h. Sleepiness was measured through self-ratings and sleep latency tests at 2100h and 0600h. The results showed clear positive effects of naps (especially the 0430h nap) on performance. The sleep latency measurements showed similar, but less clear tendencies, while ratings of sleepiness did not differentiate between conditions. It was concluded that a one-hour nap could counteract the late night performance decrement.

Adult↗
PubMed1983

Comparison of urinary and plasma catecholamine responses to mental stress.

8 subjects were exposed to the Stroop mental performance test in a design with alternating hourly periods of rest and stress. During each period one urine sample and several venous plasma samples were obtained. Heart rate responded rapidly to initiation and termination of the stress exposure with increases and decreases respectively. Both urinary and plasma adrenaline increased significantly during stress. The plasma response was immediate and sustained. Neither urinary, nor plasma noradrenaline were significantly increased by the test. Plasma noradrenaline, however, increased significantly on termination of the exposure to stress. It was suggested that the latter effect may be due to muscle sympathetic nerve activity decreasing during stress and increasing following stress. The sample-to-sample variation was more than 20% of the mean for both catecholamines, indicating the need for frequent sampling to reliably reflect plasma levels. The mean intraindividual plasma/urine correlation was r = 0.70 (p less than 0.001) for adrenaline and r = 0.40 (p less than 0.05) for noradrenaline. When only resting periods were considered, no significant correlations remained, apparently due to a reduced range of variation and accompanying reduced signal-to-noise ratio. It is concluded that both urinary and plasma adrenaline may be useful in the evaluation of changes in sympatho-adrenal activity during stress.

Adult↗
PubMed1982

Body temperature and sleep at different times of day.

Six healthy male subjects were exposed to seven different bedtime conditions, one per week. Bedtimes were scheduled in 4-h intervals, resulting in times without sleep ranging from 16 h to 40 h. The influences of overt zeitgebers were minimized and the subjects were allowed to sleep until they felt they had slept enough. Rectal temperature was measured continuously and showed a circadian rhythm during both sleeping and waking. A fall in temperature immediately after sleep onset was noted at all bedtimes except at 0700 and 1900 h. In the majority of cases temperature rose toward the end of sleep, i.e., awakenings tended to occur during the rising phase of the circadian temperature rhythm. It was suggested that the phase of the body temperature rhythm is an important factor in determining sleep duration, mainly through terminating sleep during the high or rising parts of the rhythm.

Body Temperature↗
PubMed1982

The circadian covariation of fatigue and urinary melatonin.

Twelve healthy male subjects were kept under constant conditions (no sleep, isolation from time cues, controlled activity, etc.) for 64 hr. Urinary melatonin values, self-rated sleepiness, and vigilance performance scores were obtained every 3 hr. All variables showed a pronounced circadian rhythmicity. Vigilance performance and self-rated sleepiness showed, in addition, a gradual decrease and increase, respectively, with increasing sleep deprivation. The correlation of melatonin with performance and ratings was highly significant, high melatonin levels being associated with reduced performance and increased sleepiness. Aligning self-ratings and behavioral data with respect to the melatonin troughs and peaks showed that the former coincided with performance and alertness peaks and the latter with the troughs. It was concluded that under these conditions there is a strong circadian covariation between melatonin and indices of fatigue/sleepiness.

Adult↗
PubMed1981

The circadian variation of experimentally displaced sleep.

In a group of 6 male subjects sleep was displaced to seven different times of day (one displacement condition per week). The subjects were isolated from external time cues (daylight, clocks, noise) and sleep was allowed to terminate spontaneously. The results showed a pronounced time-of-day variation of total sleep time, stage 2, and rapid eye movement (REM) sleep. Maxima occurred after bedtimes at 1900 hr and 2300 hr, while the minima occurred after bedtimes at 0700 hr and 1100 hr. The latter also was the time of maximum propensity to wake up. Slow wave sleep showed a rapid decrease from high initial levels, irrespective of time of day. Ratings of sleepiness showed a highly significant circadian variation peaking between 0500 hr and 0700 hr. The lowest level of sleepiness coincided with the maximum tendency to wake up, and it was suggested that sleep termination may be closely related to the sleepiness/alertness rhythm.

Adult↗
PubMed1980

Adrenocortical and gonadal steroids during sleep deprivation.

Twelve healthy males were exposed to 48 hr of sleep deprivation under conditions of strictly controlled activity and of food and drink intake. During the experiment the subjects were isolated from external time cures, i.e. no daylight, clocks, etc. Plasma samples were obtained before and at the end of the vigil, as well as after 5 days of recovery. Samples were analyzed for adrenal and gonadal steroid hormones and for follicle-stimulating (FSH) and luteinizing hormones (LH). The levels of all unconjugated steroids studied (cortisol, 17-hydroxypregnenolone, 17-hydroxyprogesterone, androstenedione, dihydrotestosterone) were significantly lower at the end of the sleep deprivation period. Self-ratings of fatigue were significantly higher at the end of the deprivation period. After recovery, all values returned to base line. No changes were observed in the levels of FSH, LH, or most conjugated steroids. It was concluded that the results were not consistent with the view that sleep deprivation induces an emergency reaction with increased activation, but rather that it results in lower levels of both psychological and physiological activation.

17-alpha-Hydroxypregnenolone↗