Hidemaro Takeyama

Antihypertensive effect of ACE inhibitory oligopeptides from chicken egg yolks.

Oligopeptides of 1 KDa or less were obtained by hydrolysis of chicken egg yolks with a crude enzyme, and by dialysis with a semipermeable membrane filter. Since the extracted peptides had an inhibitory action on the activity of angiotensin I-converting enzyme (ACE) in vitro, they were orally administered at 20, 100 and 500 mg/kg body weight to spontaneously hypertensive rats (SHR) for 12 weeks to analyze the physiological role on cardiovascular functions. The administered oligopeptides suppressed the development of hypertension at all dosages. After 12 weeks at 500 mg/kg body weight, the values for systolic, mean, and diastolic blood pressure were approximately 10% less in SHRs administered than controls. Furthermore, serum ACE activity of the peptide-administered groups was significantly lower than that of the control group in a dose-related manner. Our results imply that oligopeptides extracted from hens egg yolks could potentially suppress the development of hypertension in SHR, and this effect might be induced by the inhibition of ACE activity.

Effects of shift schedules on fatigue and physiological functions among firefighters during night duty.

To examine the effects of shift schedules on fatigue and physiological functions among firefighters a 17-day field study at a fire station was carried out. Eleven firefighters, who were engaged in firefighting emergency services, participated in this study. At the fire station, night duty (22:00–07:00) was divided into 5 periods (P1: 22:00–00:00; P2: 23:45–01:45; P3: 01:30–03:30; P4: 03:15–05:15; P5:0 5:00–07:00). The participants were assigned to one of these 5 periods and awakened to answer calls from the citys central information centre. They took naps in individual rooms during night duty, except when on night shift or when called out on an emergency. Subjective complaints of fatigue, critical flicker fusion frequencies, 3-choice reaction times, and oral temperature were measured before and after work and following breaks during their 24 working hours. Heart rate variability was also recorded to evaluate autonomic nerve activity. The results show that during P3 and P4, participants who had to wake up at midnight took shorter naps. The rates of subjective complaints regarding P3 and P4 tended to be higher than those for P1, P2, and P5. The ratios of the low frequency component of heart rate variability to the high frequency component during P4 were significantly lower than those during P5. It is assumed that such an irregular sleeping pattern causes many complaints of subjective fatigue, and adversely affects physiological functions. A night-duty shift schedule ensuring undisturbed naps should be considered.

Effects of the length and timing of nighttime naps on task performance and physiological function

OBJECTIVE To examine the effects of the length and timing of nighttime naps on performance and physiological functions, an experimental study was carried out under simulated night shift schedules. METHODS Six students were recruited for this study that was composed of 5 experiments. Each experiment involved 3 consecutive days with one night shift (22:00-8:00) followed by daytime sleep and night sleep. The experiments had 5 conditions in which the length and timing of naps were manipulated: 0:00-1:00 (E60), 0:00-2:00 (E120), 4:00-5:00 (L60), 4:00-6:00 (L120), and no nap (No-nap). During the night shifts, participants underwent performance tests. A questionnaire on subjective fatigue and a critical flicker fusion frequency test were administered after the performance tests. Heart rate variability and rectal temperature were recorded continuously during the experiments. Polysomnography was also recorded during the nap. RESULTS Sleep latency was shorter and sleep efficiency was higher in the nap in L60 and L120 than that in E60 and E120. Slow wave sleep in the naps in E120 and L120 was longer than that in E60 and L60. The mean reaction time in L60 became longer after the nap, and faster in E60 and E120. Earlier naps serve to counteract the decrement in performance and physiological functions during night shifts. Performance was somewhat improved by taking a 2-hour nap later in the shift, but deteriorated after a one-hour nap. CONCLUSIONS Naps in the latter half of the night shift were superior to earlier naps in terms of sleep quality. However performance declined after a 1-hour nap taken later in the night shift due to sleep inertia. This study suggests that appropriate timing of a short nap must be carefully considered, such as a 60-min nap during the night shift.

HOW DO THE TIMING AND LENGTH OF A NIGHT-SHIFT NAP AFFECT SLEEP INERTIA?

Napping is one strategy that may assist night shiftworkers to cope with sleepiness and fatigue. However, one potential disadvantage of napping is that awakening from naps is disturbed by sleep inertia, which has also been found to impair performance and/or mood, transiently. The authors examined the effects of the timing and length of a night-shift nap on sleep inertia in a laboratory setting. Twelve male university students (mean ± SD: 21.6 ± 2.8 yrs) participated in this 3-day experiment, during which included a simulated night shift (22:00–08:00 h) and subsequent day (11:30–17:30 h) and night sleep (00:00–07:00 h). The simulated night shift was designed to include one of five (four nap/one no-nap) conditions. The napping conditions differed by their timing and duration: 00:00–01:00 h (Early 60 min; E60), 00:00–02:00 h (Early 120 min; E120), 04:00–05:00 h (Late 60 min; L60), 04:00–06:00 h (Late 120 min; L120). Participants completed all the experimental conditions in a counterbalanced order. Rectal temperature (RT) was recorded throughout the simulated shift and polysomnography (PSG) was recorded during the nap period. Immediately before and after each nap, participants were required to complete a visual analogue scale (VAS) to assess sleepiness and a visual vigilance test (VVT). During the simulated night shift, a set of tasks (an English transcription task, a performance test battery, and a break) was repeated hourly, except during the periods of napping. For each nap condition, the VAS and VVT (reaction time [RT]; lapses >5 s) results were analyzed by two-way, repeated-measures analysis of variance (ANOVA) (nap [nap versus no-nap] × time point [pre-nap versus post-nap]). PSG and RT data were analyzed with one-way repeated-measures ANOVA. Marginally significant interactions were observed for RTs and lapses in VVT for the L60 nap condition (p = .071 and p = .070, respectively). However, those effect sizes were moderate (partial η2 = 0.266, 0.268, respectively). Post hoc analyses showed significantly longer RTs (p < .05) and more lapses (p < .05) following the L60 nap compared with no nap. In contrast, there was no significant difference in sleepiness between the L60, or any of the other nap conditions, and the no-nap condition. Our findings suggest the effect of sleep inertia on VVT performance was profound in the L60 condition, although no significant effects on sleepiness were self-reported by VAS. The dissociation between performance and sleepiness might reflect an unstable state where participants cannot perceive decline in their performance. The present findings are significant in terms of occupational safety; the practical implication is that great care is needed when taking a 1-h nap between 04:00 and 05:00 h on the night shift. (Author correspondence: kubo@h.jniosh.go.jp)

Effects of a Modified Ambulance Night Shift System on Fatigue and Physiological Function among Ambulance Paramedics

Effects of a Modified Ambulance Night Shift System on Fatigue and Physiological Function among Ambulance Paramedics: Hidemaro Takeyama, et al. Faculty of Human Wellness, Department of Registered Dietitians, Tokaigakuen University

Estimation of Energy Expenditure during Sedentary Work with Upper Limb Movement

Estimation of Energy Expenditure during Sedentary Work with Upper Limb Movement: Kunio Tsurumi, et al. Health Sciences of Life, Work and Environment, Department of Environmental Health Science and Health Promotion, Graduate School of Medical Sciences, Nagoya City University—This study aims to evaluate the availability of surface‐ electrode electromyogram (EMG) and acceleration to predict energy expenditure during sedentary work with upper limb movement. The following variables were measured in 12 female subjects: oxygen consumption (VO2), heart rate, EMG from the medial and anterior part of the deltoid muscle, and acceleration of wrist movement. The subjects were requested to perform four different sedentary tasks. In tasks 1, 2 and 3, subjects touched two points on a table (height 70 cm) alternatively. The distance between the two points was 50 cm in tasks 1 and 3, and 100 cm in task 2. The frequency of the movement was 100 touches per minute in tasks 1 and 2, and 152 touches in task 3. In task 4, the points were located vertically on a wall, so they had to move their upper limb vertically in this task. The height of the points was 10 cm below and 40 cm above the acromion height of the subject, and task frequency was 100 touches per minute. The correlation coefficient was 0.285, 0.581 and 0.676, between VO2 and heart rates, VO2 and acceleration, and VO2 and EMG from the deltoid, respectively. The coefficient of determination was 0.648, when employing multiple regression analysis, with acceleration and EMG as independent variables. These results suggest that energy expenditure during sedentary work with upper limb movement can be well estimated by using the data from acceleration of wrist movement and the EMG of the deltoid.

Psycho-Physiological Effects of Naps during Night Shifts on Morning Types and Evening Types

Psycho‐Physiological Effects of Naps during Night Shifts on Morning Types and Evening Types: Hidemaro Takeyama, et al. Department of Hygiene and Occupational Health, Nagoya City University, Medical School—An experimental study was carried out under simulated shift‐work schedules to examine the effects of a nighttime nap on task performances and psycho‐physiological functions on morningness (M‐types) and eveningness (E‐types) subjects. Sixty male students, classified as M‐types or E‐types by the Japanese version morningness‐eveningness questionnaire, were recruited for this study. Five moderate M‐types and eight moderate E‐types were selected. Their MEQ scores were 32‐41 (average 36.9) in E‐types and 60‐64 (average 62.4) in M‐types, respectively. Experiment periods were simulated shift schedules of 9 consecutive days consisting of 2 d shifts (working 8:00‐16:00), 3 night shifts (working 22:00‐8:00) and 3 d shifts. They carried out two series of experiments. In one series the subjects took a nap from 2:00 to 4:00. In the other series they did not take a nap during the night shift. In order to minimize the effect of the previous experiments, a rest period of more than one week was inserted between the nap‐condition and the no‐nap condition experiments. During the shifts, the subjects repeatedly performed two kinds of tasks: typing figures listed randomly on sheets into a computer for 20 min; and after a 5 min break performing mental arithmetic with two adjacent figures, listed randomly on the sheets, for 15 min. During the breaks, psycho‐physiological functions and questionnaires on subjective feelings of fatigue and index of the state of anxiety were examined. Throughout the experiments, heart rate variability was also recorded with a portable recorder to evaluate autonomic nerve activity. Task performances decreased and subjective feelings of fatigue and anxiety scores increased in proportion to the length of time worked in both M‐types and E‐types who had no nap. In M‐types, these changes were significantly suppressed by the nap on the first night of duty. Parasympathetic nerve activity for M‐types estimated from heart rate variability between 4:00 and 6:00 under nap conditions decreased significantly compared with that under no‐nap conditions. Overall changes for E‐types, however, were smaller than those for M‐types in terms of task performance and psycho‐physiological parameters. The present study suggested that taking a nighttime nap was an effective way to reduce adverse effects due to first nocturnal work, especially for M‐types.

Balance of Magnesium Positively Correlates with That of Calcium

Background and Objective: In a prior study [1], we showed no significant relationship between intake and balance of magnesium (Mg). Subsequent further investigation [2] disclosed that intakes of both Ca and P were positively correlated with their respective balances, whereas intake of Mg did not show any significant correlation with Mg balance. In this paper, we show positive correlations between intake of Mg and balances of both Ca and P. Methods and Results: Using these correlations, the mean value and upper limit of the 95% confidence interval (from the regression equation between Mg intake and either the balances of Ca or that of P, when each balance is equal to zero) were 4.584 and 4.802 (against Ca balance), 4.554 and 4.785 (against P balance) mg/kg BW/d, respectively. Balances of Mg and Ca correlated with each other.

Magnesium Requirement and Affecting Factors

We performed 11 balance studies to learn the estimated average requirement (EAR) of magnesium (Mg). Magnesium intake was not correlated with Mg balance when all data was used (n = 109). However, Mg intake was correlated with calcium (Ca) and phosphorus (P) balances. During the analysis, we found a correlation between sodium intake and Ca and Mg balances. After excluding the data of the highest sodium (Na) intake study, Mg intake turned out to be correlated with Mg balance.