This study examined the mental and physiological responses to degree of comfort in using sanitary napkins. During menstrual period two types of napkins (thin type, thick type) were used by 8 women each. The indexes were 5 point scale, heart rate (HR), ratio of low frequency and high frequency (LF/HF) of heart rate variability and salivary chromogranin A (CgA). The results of 5 point scale (subjective evaluation) showed the thin type napkins were more comfortable than the thick type napkins. The results of LF/HF and CgA (physiological evaluation) indicated that sympathetic activities were lower in the thin type napkin users than in the thick type napkin users. From these results we concluded that using comfortable napkins have less mental and physiological stress.
The purpose of this study was to inspect it what kind of influence it has on the development of the motor ability of the childhood period that growth speed of the body mass is relatively bigger than growth speed of the stature by the allometric analysis (y=bx^α). The materials used for this study were the longitudinal data of the stature, body mass, body composition, and the motor ability of 31 girls whose aged form 2.5 to 5.5 years old, taken in 2006-09. The results obtained were as follows; 1) Mean allometry coefficients of stature and body mass is 1.86. 2) The increase of the BMI of the high group was increase of the body fat ingredient. 3) It may be said that a low group can be superior to the motor ability than the high group where increase of the weight is remarkable when I evaluate an motor ability by the same stature and the same body mass. We suggested that it only promoted increase of the body fat to add body mass and body size for the childhood period, and possibility to obstruct the development of the motor ability.
This plan is drawn up by the lighting research group in JSPA in order to summarize the topics and outline of the research which includes the non-visual effect of light on human biological rhythm. It is expected that these feature articles will bring many researchers a lot of useful information.
In this decade, the research on non-visual effects of light on circadian system progressed dramatically thanks to the discovery of the novel photoreceptor and the action spectrum. Based on the action spectrum on depolarization of melanopsin-expressing ganglion cells and on melatonin suppression, some calculation methods to estimate the impact of non-visual effects of light have been proposed recently. DIN (German institute for standardization) has established the pre-standard which enables to calculate relative effectiveness of various light sources. Lighting Research Center in the US has proposed a unique calculation method which enables to estimate melatonin suppression rate. There still are many research challenges to tackle with including investigation on the difference of action mechanism in monochromatic and polychromatic light exposure.
Light has various effects such as effects on human circadian rhythm, sleep, endocrine hormone, alertness, and pupillary light reflex. These effects are called "non-visual effects" or "non-image forming effects", are induced by light signals projecting to the hypothalamus in the brain, not to the visual area. Human physiological functions adapt to the natural light-dark cycle. However, dynamic changes in natural sunlight have a negative effect on mood and circadian rhythm in high-latitude regions in winter. In modern society, it has been reported that artificial light at night has negative effects on human health via non-image forming pathways. Study on adaptation to natural light and artificial light is important topic for study in the field of physiological anthropology.
Recently, non-cone, non-rod photoreceptor was discovered in rat retinal ganglion cells (RGCs). These photosensitive RGCs are small percentage of RGCs with morphological and functional features. The photosensitive RGCs, cones, rods are necessary for photopic input to the non-image-forming effect: locomotor activity, pupil light reflex, melatonin suppression. An action spectrum for melatonin suppression has a peak wavelength sensitivity of 460nm. However it is suggested that additivity is not approved from melatonin suppression using polychromatic light, non-image-forming effect may be a complicated mechanism.
Over the last 20 years, researchers have tried to understand the photoreceptor mechanisms which regulate the circadian system. The discovery of the novel photoreceptor, melanopsin-expressing retinal ganglion cells (mRGCs), aroused researchers' interest in the role of the eye in non-image-forming visual functions such as circadian rhythm regulation and pupillary light reflex. The mechanisms by which the mRGC regulates non-visual/visual functions in humans have not been established, but some researchers have reported that these cells differ from rods and cones in many respects. In the present report, I overview prior studies for the mRGC, and discuss the role of the mRGC which contributes to non-visual/visual pathways with aspects of morphology, neurophysiology and biology.
Melatonin secretion is suppressed by light exposure at night. However, little is known about the effect of moderate light exposure under an actual indoor environment on nocturnal melatonin secretion. The aim of this study is to investigate the effect of moderate light exposure in the evening on melatonin secretion. In this study, thirteen healthy males were exposed to two lighting conditions from 8:00PM to 0:00AM. One is that color temperature was 5000K (fluorescent) and vertical illuminance at eye level was kept at 100lx. Another is that there was a little light emitted from LCD display (Dim condition). Saliva samples were taken every 30 minuets during the exposure. As results, significant elevation of melatonin in Dim condition was found in about half subjects (Responders). The moderate light exposure of 100lx significantly suppressed nocturnal melatonin secretion just in Responders. Although further research is needed to find out the factors creating the difference between Responders and non-Responders, the results suggests that moderate light exposure under an actual indoor environment surely suppresses melatonin in some proportion of people.
Light is a key factor for human non-visual forming system as well as visual forming system. For example, bright light exposures at nighttime delay circadian rhythm and suppress melatonin secretion. The effects are known to depend on light intensity (dose-response curve) and wavelength (action spectrum). On the other hand, bright light at daytime advance circadian rhythms and encourage melatonin secretion. The difference of the impact between at daytime and nighttime is known as a phase-response curve. The light also has impacts on subjective wakefulness, autonomic nervous activity, central nervous activity, and so on at night. This paper reviews about the non-visual forming effects of light.