In vitro studies have indicated that reactive oxygen species modifying cellular redox status are involved in hypoxia-induced erythropoietin (EPO) production. However, the effects of redox balance on hypoxia-induced EPO production in vivo are still not fully understood. To investigate the effect of the change in cellular redox status on EPO generation, we determined whether glutathione (GSH) depletion has a significant influence on hypoxia-induced EPO production in rats. For the inhibition of GSH synthesis, DL-buthionine-[S,R]-sulfoximine (BSO) was employed by intraperitoneal injection. Twenty male rats were assigned to one of four experimental groups: (1) normoxic placebo, (2) normoxic BSO, (3) hypoxic placebo, and (4) hypoxic BSO. Hypoxic groups were exposed to a simulated normobaric hypoxic condition (4,500 m above sea level) for 12 hours. BSO treatment resulted in a significant depletion of total GSH levels in kidney and plasma in both conditions. However, the hypoxia-induced elevation in serum EPO concentration was not completely affected by the inhibition of GSH synthesis. These data demonstrate that GSH depletion in the kidney is not involved in the increase in serum EPO concentration in response to systemic hypoxia. It is also conceivable that the cellular redox changes could not function as a primary regulator of hypoxia-induced renal erythropoietin formation in vivo.

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Light elicits non-visual effects on a wide range of biological functions and behavior. These effects are mediated by a melanopsin-based photoreceptor system that is very sensitive to blue light (440–480 nm) relative to the three-cone visual photopic system. The aim of the current study was to assess the time-of-day-dependent effects of two different wavelength monochromatic lights at 458 nm and 550 nm on human cognitive function. We conducted an experiment in the daytime and nighttime on different days. Twelve subjects were selected, none of whom was either morning-type or evening-type, as assessed by a translated version of the morningness/eveningness questionnaire. The cognitive function was measured by event-related potential (ERP) using an oddball task, and arousal level was measured by the Alpha Attenuation Test (AAT). We found that 458 nm light exposure caused a significantly larger P300 amplitude than occurred with 550 nm light. There was a significant interaction among wavelength, time of day, and electrode site. Exposure to 458 nm light induced a larger P300 amplitude at nighttime than in the daytime at the Fz electrode site. The Alpha Attenuation Coefficient (AAC) at nighttime was higher than in the daytime. Our results suggest that short wavelength monochromatic light can affect the circadian rhythms of cognitive functions, and indicate that these effects are mediated by a melanopsin-based photoreceptor system. This study has extended previous findings in terms of time of day, and higher cognitive function by using an endogenous ERP component, P300.

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The effects of paced breathing (PB) on the reproducibility of heart rate variability (HRV) measurements were examined in 55 male subjects (age range: 20–54 years). Spectral components of HRV were measured under a combination of two respiratory conditions (spontaneous and 4s PB) and two postures (standing and supine). The procedures were repeated 3 weeks after the first measurement. Log-transformed low-frequency (lnLF) and high-frequency (lnHF) components of HRV were calculated from a 205s electrocardiography (ECG) recording. The coefficients of interindividual variations of lnHF and lnLF (ca. 13–16%) and the intraindividual variations of the frequency components (5–6%) were not significantly affected by PB. The coefficients of intraindividual variation of heart rate, ln HF and ln LF did not correlate with age in either posture. Effect sizes of PB on the intraindividual variation ranged from −0.04 to 0.13. Although intraclass correlation coefficients (ICCs) were slightly improved by PB in some cases, the differences were negligible. The above results suggest that PB provides a limited improvement in the reproducibility of HRV measurements, and metronome-guided respiration is not necessarily required for HRV measurement if subjects are reminded to avoid irregular respiration.

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This study aimed to clarify the sex-, age-, and obesity-level-specific regional subcutaneous fat characteristics and their relationships with total and visceral fat in 302 Japanese adults (mean age: 41.8±15.7 yr; range: 20.0 to 82.6 yr). Subcutaneous fat thickness at 14 sites (right cheek, chin, chest (2 sites), abdomen, suprailiac, triceps, subscapular, back (2 sites), thigh (2 sites), knee, and calf), percent body fat (%BF) and visceral fat area (VFA) were measured by B-mode ultrasound, dual-energy x-ray absorptiometry and computed tomography, respectively. The results of 3-way ANOVA (2 sex groups, 5 age groups, 2 obesity-level groups) for each subcutaneous fat thickness at 14 sites indicated that the characteristics of sex-specific differences differed by age groups and obesity levels, and these differences are more apparent in the obese group and the 30- to 50-year-old groups. Subcutaneous fat accumulation progressed toward the central body with increased age and obesity. The relationships between subcutaneous fat, total fat, and visceral fat differed with sex and obesity level. The significant relationship between abdominal subcutaneous fat thickness and VFA was found in the nonobese (BMI<25 kg/m²) and nonviscerally obese (VFA<100 cm²) groups (male: r=.474; female: r=.417), but not in the nonobese and viscerally obese males (r=−.068) and in the obese and viscerally obese subjects (males: r=.291; females: r=−.327). There may be a close relationship between subcutaneous fat accumulation capacity and visceral fat accumulation.

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Tryptophan (Trp) intake at breakfast promotes morning-typed circadian typology and higher sleep quality in Japanese children aged 0–6 yrs (Harada et al., 2007). This effect may be accelerated by morning exposure to sunlight, which has not yet been tested. This study aimed to investigate such an effect in Japanese children. In May, 2006, an integrated questionnaire was administered to 0–6-year-old children attending one of 12 kindergartens. 906 parents answered the questionnaire for their children and themselves (response rate: 67.4%). The integrated questionnaire included the revised version for children of the Morningness-Eveningness (M-E) Questionnaire and questions on sleep, nutritional balance, mental health, and sunlight exposure. Analysis was made on data from 744 children aged 2–6 (385 girls, 359 boys) whose average M-E score was 20.6±3.46. Children who had breakfast at regular times tended to be more morning-typed and were less frequently angry (p=0.001) and depressed (p=0.007). Children who had nutritionally well-balanced breakfasts tended to be more morning-typed (p<0.001), and woke up and fell asleep at earlier times (p<0.001). Children with higher protein intake tended to have higher M-E scores (p<0.001) and earlier bedtime and wake-up time (p=0.003). Children exposed to sunlight for 30–60 min on their way to kindergarten showed more distinctive shifting-effects to morning-type with protein intake than those exposed to sunlight for less than 20 min (p=0.006). A well-balanced breakfast might be a strong zeitgeber for circadian oscillators of children, and the morning-type driving effect of protein intake could be accelerated by morning exposure to sunlight.

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A one-legged training model was adopted to assess the influence of moderate-intensity exercise training on subcutaneous adipose tissue, especially focusing on the trained limb. Eight young sedentary Japanese women (ages 21–23 yr) participated in a 12-week training program. The leg was assigned randomly to trained or untrained limb. Each subject performed a supervised 60-min one-legged cycle ergometer training session three times a week. The exercise intensity was set at approximately 40% of peak VO₂ (“moderate” intensity, i.e., below the estimated lactate threshold), which was determined before training. Each subject performed a one-legged incremental cycle exercise test until exhaustion to determine the peak VO₂ of each leg (the trained and untrained legs being investigated separately). The areas of subcutaneous fat and the remaining nonfat tissues of the thigh were evaluated by our novel visualized measuring system based on ultrasonography. The fat cross-sectional areas of the trained and untrained thigh were not different after training (trained: 68.6±17.8 vs. untrained: 68.3±18.5 cm²). The non-fat (muscle and bone) area was also similar between the trained and untrained limb. In addition, there was no systematic influence of the training on the total and lean body mass. After training, the duration time of the one-legged cycle incremental exercise test by the trained leg was significantly improved unilaterally (trained: 1049±122 vs. untrained: 930±109 s, p<0.05) without any difference of peak VO₂. The results indicate that moderate one-legged aerobic training did not induce any compositional change in the trained thigh; rather, what did improve were certain peripheral factor alone relating to endurance.

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