Biology subjects

Eto, T.

Publications and source records attributed to Eto, T..

3 recordsLinked to original sources

bioRxiv2026

Light-induced melatonin suppression in school-aged children before and during camping: associations with circadian phase and daytime light exposure

Prior light exposure can influence the magnitude of melatonin suppression in response to evening light, even within the same individual. We examined whether light-induced melatonin suppression in school-aged children differed before and during a camp with approximately two weeks of exposure to a natural light-dark cycle. We also explored interindividual variation in melatonin suppression and its associations with circadian phase, habitual sleep timing, and daytime light exposure. Twenty-one healthy children aged 9--14 years underwent evening light experiments at the start of camp (Pre-camp session) and approximately two weeks later (Camp session). Melatonin suppression was calculated by comparing the area under the melatonin concentration curve between the evening light condition (200 {+/-} 30 lx, 5000 K) and the dim light condition (< 30 lx, incandescent lamps), with integration starting at dim light melatonin onset (DLMO). We assessed sleep habits from 14-day sleep diaries before camping and measured wrist-level illuminance during camping. We examined associations using Spearman correlations and compared Pre-camp and Camp melatonin suppression using a paired t-test. Melatonin suppression did not differ significantly between Pre-camp and Camp sessions (p = 0.21). Greater suppression in the Pre-camp session was associated with later DLMO (rho = 0.49, p = 0.028), but not with habitual sleep variables. In the Camp session, higher same-day geometric mean illuminance was associated with lower suppression (n = 15; rho = -0.58, p = 0.024), whereas 7-day light-exposure metrics were not. Mean melatonin suppression did not significantly change across the camping period. Meanwhile, children showed large interindividual variation in melatonin suppression, and circadian phase and recent daytime light exposure are candidate correlates of this variation in the responsiveness to the evening light.

physiology↗

bioRxiv2025

Light stimulation system for measuring pupillary light responses based on Maxwellian view optical system using a retina presentation type viewfinder

BackgroundMelanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGC) contribute predominantly to non-image-forming effects of light, such as light-induced circadian phase shift, melatonin suppression, and pupillary light reflex. Post-illumination pupil response (PIPR) has been well-used for the evaluation of ipRGC sensitivity for humans since it is able to detect ipRGC function independently from conventional cones. However, pharmacological mydriasis or a specialized light stimulation system, such as the Maxwellian view (MV) optical system, is required to avoid dynamic pupil constriction in the stimulated eye for effective PIPR measurements, which makes these approaches less practical and difficult to implement in standard experimental settings. In this context, we propose the application of a retinal projection viewfinder based on the MV system as a practical approach for measuring PIPR, and evaluate the feasibility of this approach by comparing its performance with a typical LED-based optical system. MethodsTwenty-two healthy participants underwent pupillometry using both the MV-based viewfinder and a typical LED-based system. Monochromatic red and blue light stimuli were presented for durations of 1 and 10 seconds. Pupil responses, including maximum constriction, PIPR amplitude after 6 seconds from the light offset, area under the curve (AUC) values of PIPR, and sustained slopes, were analyzed using a linear mixed-effects model to assess the differences between the two systems. ResultsThe MV-based viewfinder significantly enhanced net PIPR amplitude (p < 0.05) and sustained slope (p < 0.01) during 10-second light stimulation compared to the LED system, demonstrating its capability to effectively measure ipRGC-driven responses. In contrast, no significant differences were observed in the net AUC values. These results highlight that the MV-based viewfinder enables effective PIPR measurements by delivering constant and controlled light stimulation directly to the retina, minimizing the effects of dynamic pupil constriction during light stimulation. ConclusionsThe MV-based viewfinder showed feasibility as an effective method for measuring PIPR without requiring pharmacological dilation or complex optical instrumentation. This approach has strong potential for advancing the assessment of human ipRGC function using pupillary responses.

neuroscience↗

bioRxiv2022

Strategy for selective acquisition of transgenic marmosets using the piggyBac transposon system

Transgenic (Tg) nonhuman primates (NHPs) are excellent potential models due to their physiological similarities with humans. In NHPs, the lentiviral vector is the only available transgenesis method, but transgene sizes are limited. The piggyBac (PB) transposon system is a DNA element sandwiched between two terminal inverted repeats (TRs) that allows transposases to introduce larger genes than lentiviral vectors. However, embryos with integrated transgenes are difficult to distinguish using this system. To address this issue, we placed the Enhanced Green Fluorescent Protein (EGFP) gene inside the TRs and the humanized kusabira orange 1 (hKO1) fluorescent protein gene with the proteolysis-promoting sequence d2PEST outside the TRs to create an indicator for gene integration using fluorescent protein expression. In HEK293T cells, hKO1 and EGFP co-expression after transfection gradually changed to decay of hKO1 expression and enhancement of EGFP expression by transposase within five days. In mouse and marmoset embryos, hKO1 expression was attenuated, while only EGFP expression was observed at the blastocyst stage. All offspring obtained through embryo transfer of EGFP-expressing embryos were Tg; thus, we established a new PB system capable of determining Tg embryos and successfully produced Tg marmosets, for the first time, in NHPs.

molecular biology↗