Effects of evening light conditions on salivary melatonin of Japanese junior high school students

BACKGROUND: In a previous study, when adult subjects were exposed to a level of 400 lux light for more than 30 min or a level of 300 lux light for more than 2 hours, salivary melatonin concentration during the night dropped lower than when the subjects were exposed to dim illumination. It was suggested that such light exposure in adolescents or children during the first half of subjective night in normal life might decrease the melatonin level and prevent the falling into sleep. However, there has been no actual study on the effects of light exposure in adolescents. METHODS: Effects of exposure to the bright light (2000 lux) from fluorescent light bulbs during a period of three hours from 19:30 to 22:30 in one evening were examined on evening salivary melatonin concentrations from 19:45 to 23:40. The control group was exposed to dim light (60 lux) during these three hours. Both the dim light control group [DLCG] and the bright light experimental group [BLEG] consisted of two female and three male adolescent participants aged 14–15 y. RESULTS: The salivary melatonin level increased rapidly from 3.00 pg/ml at 21:45 to 9.18 pg/ml at 23:40 in DLCG, whereas it remained at less than 1.3 pg/ml for the three hours in BLEG. Melatonin concentration by BLEG at 22:30 of the experimental day was lower than that at the same time on the day before the experimental day, whereas it was significantly higher in the experimental day than on the day before the experimental day in DLCG. CONCLUSIONS: Bright lights of 2000 lux and even moderate lights of 200–300 lux from fluorescent light bulbs can inhibit nocturnal melatonin concentration in adolescents. Ancient Japanese lighting from a traditional Japanese hearth, oil lamp or candle (20–30 lux) could be healthier for children and adolescents because rapid and clear increase in melatonin concentration in blood seems to occur at night under such dim light, thus facilitating a smooth falling into night sleep

Salivary Melatonin at Night: Responding to the Night Lighting and Cow’s Milk Consumption at Breakfast in Japanese Junior High and University Students

(1) In junior high school students aged 14–15 years old, the salivary melatonin level increased rapidly from 3.00 pg/ml at 21:45 to 9.18 pg/ml at 23:40 under orange light from light bulb, whereas it remained at less than 1.3 pg/ml under white light from fluorescent lamp. (2) In 3 weeks of intervention on university athlete students, the salivary melatonin concentration at 23:00 of G3 (protein-rich breakfast and following sunlight exposure and orange light from the light bulb at night) after intervention was significantly higher than that of G1 (protein-poor breakfast and not following exposure to sunlight and white light from the fluorescent lamp at night) and G2 (protein-rich breakfast and following exposure to sunlight and white lights from the fluorescent lamp at night). (3) This study evaluates the effects of cow’s milk intake (Group 1: G1) for 20 days at breakfast on saliva melatonin concentration at 22:00 and 23:00 on 0, 10, and 21 days of the intervention period in Japanese university male athletes attending a university soccer club. In the intervention group (G1), salivary melatonin concentration increased at 22:00 in comparison with that before intervention, but there was no significant change in the control group (Group 2: G2). On the other hand, there were no significant differences in the melatonin at 23:00 between the both groups just after 21 days of intervention. Intake of cow’s milk at breakfast might make the circadian phase in advance in the soccer athletes

Transport Properties of Steam Curing Concrete Using Mineral Admixtures

Steam curing has been used widely in the precast concrete industry. However, investigations on steam curing concrete focused mainly on their strength development. Research on durability of steam curing concrete, particularly on mixes using mineral admixtures, is somewhat limited. In this study, transport properties and mechanical properties of concretes using mineral admixtures under different steam curing conditions were measured. Normal Portland cement, high early strength Portland cement, ground granulated blast-furnace slag and fly ash were used. Steam curing conditions were varied by changing the preliminary curing time, temperature drop rate and curing method after steam curing. Transport properties, such as oxygen gas diffusion coefficient and water diffusion coefficient were measured. Moreover, mechanical properties, such as compressive strength, static elastic modulus and dynamic elastic modulus were measured. From the experimental result, the degree of the influence that the differences in steam curing conditions give to transport properties varies according to the types of binder. It was confirmed that transport properties might decrease remarkably in comparison with the case of a standard steam curing condition

Photoresponse in the Ciliated Protozoan Colpoda cucullus

Kawano, Noriyuki, Funadani, Ryoji, Arikawa, Mikihiko, Harada, Tetsuo, Suizu, Futoshi, Matsuoka, Kou, Matsuoka, Tatsuomi (2017): Photoresponse in the Ciliated Protozoan Colpoda cucullus. Acta Protozoologica 56 (1): 1-7, DOI: 10.4467/16890027AP.17.001.6965, URL: https://www.mendeley.com/catalogue/0cd0b706-68e1-3ba9-9e25-c545a0f41b65