Akira Yasukouchi

Effects of short wavelength control in polychromatic light sources on nocturnal melatonin secretion

In this study, 12 healthy males were exposed to various light conditions (2300K, 3000K, 5000K and dim) for 1.5h at midnight. The conditions of 3000K and 5000K were created by commercial fluorescent lamps. The light at 2300K was achieved by fitting a 3000K fluorescent lamp with a special filter that absorbed short-wavelength light. The vertical illuminance level was kept at 200lx. Saliva samples were taken before and after the light exposure. The light at 5000K suppressed melatonin secretion acutely. The 2300K lamp condition appeared to have no effect on melatonin secretion as well as the dim condition, while melatonin secretion was measurably suppressed by the light at 3000K.

Sex Differences on Components of Mental Rotation at Different Menstrual Phases

Male (n = 18) and female (n = 16) subjects completed a three-dimensional mental rotation task (MRT). The hormonal and MRT data were collected from female subjects at low (menstruation) and high (ovulation) estrogen phases. Each subjects reaction time (RT) and error rate (ER) were plotted to give the slope and intercept of the functions, relating performance to angular disparity. Males showed faster RT and lower ER compared to females at each menstrual phase; the difference arises from the slope. These findings suggest that there is a sex difference in mental rotation at each menstrual phase.

Journal of Physiological Anthropology aims to investigate, how the speed of technological advance, experienced during the 21st century, is affecting mankind

Editorial Journal of Physiological Anthropology (JPA) covers a broad range of studies on humans living in modern society. Today’s highly technological environment has developed rapidly, when we consider the time scale of human history, and rapid advances in science and technology are thought to be exerting profound effects on the human community, in terms of not only lifestyle and culture, but also the physiological capabilities of the human body. Against this background, JPA presents research on humans in modern society, evaluating humankind mainly from a physiological perspective, in efforts to create truly healthy and adaptable living environments. Our general interest is focused on what it is that mankind seeks. What sorts of selective pressures are exerted upon modern humans, and what sorts of responses do these pressures elicit? What biological strategies do humans use to adapt flexibly to ever changing modern environments? In the discipline of physiological anthropology, which focuses on human adaptability to the environment and its diversity, our research is centered around the key concepts of physiological polytypism; the potential capabilities of physiological traits (functional potentiality); physiological coordination of the whole body (whole-body coordination); environmental adaptability and techno-adaptability. The maximum functional ability of mankind has both manifest and latent components and the boundary between these two components changes depending on the type, frequency and intensity of stress encountered in daily life, which are in turn dependent upon the behavioral history of individuals. The three basic concepts of physiological polytypism, functional potentiality and whole-body coordination can be briefly defined as follows. Physiological polytypism is a characteristic phenotype of the manifest component and it depicts a specific difference manifested by an individual. Although physiological polytypism is influenced by gene and environmental factors, the latter effects, especially, are of a more plasticizing nature. Functional potentiality defines the superficially non-apparent, or latent, component of maximum functional ability. In these terms a coordinated response is considered to involve the body’s functional adjustment system, which maintains homeostasis against certain stresses. The adjustment system is constructed and affected by the degree of the manifested function and the output distribution of various sub-system or element functions. These together mold the specific patterns of coordinated responses, and where the coordination system is systemic, it is known as wholebody coordination. We can use the three concepts of physiological polytypism, functional potentiality and whole-body coordination to discuss environmental adaptability and techno-adaptability from the viewpoint of the adaptability of groups, thereby allowing us to consider the nature of human diversity and its meaning. The elements affecting phenotype in polytypism include gene, physical environmental and culture related factors. The phenotype is affected by genes themselves as well as by the interactions of physical and/or cultural factors on the genes [1]. Since our lifestyles and the environments in which we live are consistently shifting and changing with the advances made in science and technology, we need to adapt to these changes in our living environment. Therefore, the factors influencing phenotype are more likely to be physical and cultural, and their interactions with genes are more likely to involve gene-environment interplay, Correspondence: yasukouc@design.kyushu-u.ac.jp Department of Physiological Anthropology, Faculty of Design, Kyushu University, Fukuoka, Japan Yasukouchi Journal of Physiological Anthropology 2012, 31:1 http://www.jphysiolanthropol.com/content/31/1/1

The ERG responses to light stimuli of melanopsin-expressing retinal ganglion cells that are independent of rods and cones

The mechanisms by which melanopsin-expressing retinal ganglion cells (mRGCs) regulate circadian rhythms in humans have not been established. To understand mRGC characteristics and their role independent of effects due to the rods and cones, mRGC responses should be induced or measured independent of cone and rod responses. In the present study, we obtained results from light stimuli which differentially induce only the mRGC response by using a receptor-silent substitution technique. The mRGCs responded linearly to contrast changes of light stimuli, whereas they showed complicated responses to frequency changes with regard to the latency of response time. These results suggest that mRGC behavior is not a simple response to the various frequencies found in solar light but may be related to intrinsic neural circuits with feedback connections in the mRGC pathway. The results in this study also demonstrated that the test stimuli affected only the mRGC response and that this could be successfully detected by using the electroretinogram (ERG).

Thermoregulatory effect in humans of suppressed endogenous melatonin by pre-sleep bright-light exposure in a cold environment

This study investigated the physiological function of suppressed melatonin through thermoregulation in a cold environment. Interactions between thermoregulation directly affected by exposure to a cold environment and indirectly affected by endogenous melatonin suppression by bright-light exposure were examined. Ten male subjects were exposed to two different illumination intensities (30 and 5000 lux) for 4.5 h, and two different ambient temperatures (15 and 27°C) for 2 h before sleep under dark and thermoneutral conditions. Salivary melatonin level was suppressed by bright light (p < 0.001), although the ambient temperature condition had no significant effect on melatonin. During sleep, significant effects of pre-sleep exposure to a cold ambient temperature (p < 0.001) and bright light (p < 0.01) on rectal temperature (Tre) were observed. Pre-sleep, bright-light exposure led to an attenuated fall in Tre during sleep. Moreover, Tre dropped more precipitously after cold exposure than thermoneutral conditions (cold: −0.54 ± 0.07°C/h; thermoneutral: −0.16 ± 0.03°C/h; p < 0.001). Pre-sleep, bright-light exposure delayed the nadir time of Tre under thermoneutral conditions (p < 0.05), while cold exposure masked the circadian rhythm with a precipitous decrease in Tre. A significant correlation between the Tre nadir and melatonin level (r = −0.774, p < 0.05) indicated that inter-individual differences with higher melatonin levels lead to a reduction in Tre after cold exposure. These results suggest that suppressed endogenous melatonin inhibits the downregulation of the body temperature set-point during sleep. (Author correspondence: ishibasi@design.kyushu-u.ac.jp)

Melanopsin gene polymorphism I394T is associated with pupillary light responses in a dose-dependent manner.

Background Melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs) play an important role in non-image forming responses to light, such as circadian photoentrainment, light-induced melatonin suppression, and pupillary light response. Although it is known that there are some single nucleotide polymorphisms (SNPs) in the melanopsin (OPN4) gene in humans, the associations of the SNPs with non-image forming responses to light remains unclear. In the present study, we examined the associations of melanopsin gene polymorphisms with pupillary light response. Methods Japanese university students (mean age: 21.0±1.7 years) with the genotypes of TT (n = 38), TC (n = 28) and CC (n = 7) at rs1079610 (I394T) located in the coding region participated in the present study. They were matched by age and sex ratio. Dark-adapted pupil size (<1 lx) was first measured. Then steady-state pupil size was measured during exposure to five lighting conditions (10 lx, 100 lx, 1000 lx, 3000 lx, 6000 lx in the vertical direction at eye level). Results Significant interaction between the genotype of I394T (TT versus TC+CC) and luminance levels was found in pupil size. Under high illuminance levels (1000 lx, 3000 lx and 6000 lx), pupil sizes in subjects with the C allele were significantly smaller than those in subjects with the TT genotype. On the other hand, pupil size in subjects with the C allele under low illuminance (<1 lx) was significantly larger than that in subjects with the TT genotype. Percentages of pupil constriction under high illuminance levels were significantly greater in subjects with the C allele than in subjects with the TT genotype. Conclusions Human melanopsin gene polymorphism I394T interacted with irradiance in association with pupil size. This is the first evidence suggesting a functional connection between melanopsin gene polymorphism and pupillary light response as an index of non-image forming response to light.

Distinct responses of cones and melanopsin-expressing retinal ganglion cells in the human electroretinogram

BackgroundThe discovery of the novel photoreceptor, melanopsin-expressing retinal ganglion cells (mRGCs), has raised researchers’ interest in photoreceptive tasks performed by the mRGC, especially in non-image-forming visual functions. In a prior study, we investigated the mRGC response to light stimuli independent of rods and cones with the four-primary illumination system, which modulates stimulus levels to the mRGC and cones independently, and mRGC baseline responses were recorded in the electroretinogram (ERG).MethodsIn the present study, we used the same illumination system to compare independent responses of the mRGC and cones in five subjects (mean ± SD age, 23.0 ± 1.7 years). The ERG waveforms were examined as direct measurements of responses of the mRGCs and cones to stimulation (250 msec). Implicit times (the time taken to peaks) and peak values from 30 stimuli given to each subject were analyzed.ResultsTwo distinct positive peaks appeared in the mRGC response, approximately 80 msec after the onset of the stimuli and 30 msec after their offset, while no such peaks appeared in the cone response. The response to the mRGC stimulus was significantly higher than that to the cone stimulus at approximately 80 msec (P < 0.05) and tended to be higher than the cone stimulus at approximately 280 msec (P = 0.08).ConclusionsImplicit time of the first peak was much longer than that to the b-wave and this delay might reflect mRGC’s sluggish responses. This is the first report of amplitudes and implicit time in the ERG from the response of the mRGC that is independent of rods and cones, and obtained using the four-primary illumination system.

Human variation : from the laboratory to the field

Factors and Forces Influencing Human Variation Alan H. Bittles and Michael L. Black Genetics of Body Weight and Obesity Paul Higgins, V. Saroja Voruganti, and Anthony G. Comuzzie Diversity of Human Adaptability to Environments: A Physiological Anthropology Perspective Akira Yasukouchi Tissue and Cell Adaptability to Physical and Chemical Factors Susumu Kudo and Kazuo Tanishita Human Adaptation to Natural and Artificial Light: Variation in Circadian Photosensitivity Shigekazu Higuchi Effect of Environmental Light on Human Gastrointestinal Activity: From Laboratory Study to Fieldwork Yoshiaki Sone Cold Tolerance and Lifestyle in Modern Society Takafumi Maeda Human Adaptability to Emotional and Intellectual Mental Stresses Koichi Iwanaga Impact of Pollution on Physiological Systems: Taking Science from the Laboratory to the Field Lawrence M. Schell Bridging the Gap between Laboratory Trials and the Reality of the Human in Context Neil J. Mansfield Geography, Migration, Climate, and Environmental Plasticity as Contributors to Human Variation Michael A. Little From a History of Anthropometry to Anthropometric History Stanley Ulijaszek and John Komlos Growth and Maturation: Interactions and Sources of Variation Robert M. Malina Bone Health and Body Composition Measurement in Older People: Challenges Imposed by Variability Katherine Brooke-Wavell Research Designs and Statistical Methods in Both Laboratory and Field Settings C.G. Nicholas Mascie-Taylor Impact of Natural Environmental Stressors on Physiological and Morphological Processes: Methodological Approaches in the Field and Laboratory Ralph M. Garruto and Charles A. Weitz

Changes in breathing pattern at loads near perceptual threshold at different work levels

SummaryFive subjects were tested to determine the threshold for detection of au added resistance to inspiration in three tests, one at rest and two with exercise (mild = 50 W; moderate = 100 W) on a cycle ergometer. Changes in the breathing pattern were examined at added resistances near the perceptual threshold. Added inspiratory resistances with a 50% probability of detection were very variable at rest; they decreased significantly from rest (250 Pa · l−1 · s−1) to moderate exercise (98 Pa · l−1 · s−1) in four subjects. It is suggested that physical exercise may cause discomfort even when workers wearing a respirator do not have any abnormal sensation during sedentary work. Breathing patterns were compared between resistance loaded and unloaded breathing during each test. Decreases in inspiratory peak flow and acceleration of flow early in inspiration were found in resistance loaded breathing in almost all tests and a tendency for tidal volume to decrease was found during moderate exercise only. The ratios of resistance loaded to unloaded breathing for inspiratory time (ti) and total time (tt) tended to be greater in the detected than in the undetected responses at rest and during mild exercise but not during moderate exercise. This would imply that further prolongation ofti andtt in the detected responses was attributable to conscious or subconscious aspects of the resistance loading responses; however, these adjustments in breathing, which reduce frequency, would be less likely to occur as the work rate increases.

Effect of reduced illumination on insomnia in office workers

Effect of Reduced Illumination on Insomnia in Office Workers: Tomoaki KOZAKI, et al. Faculty of Design, Kyushu University—