Effects of Exposure to Intermittent versus Continuous Red Light on Human Circadian Rhythms, Melatonin Suppression, and Pupillary Constriction

Exposure to light is a major determinant of sleep timing and hormonal rhythms. The role of retinal cones in regulating circadian physiology remains unclear, however, as most studies have used light exposures that also activate the photopigment melanopsin. Here, we tested the hypothesis that exposure to alternating red light and darkness can enhance circadian resetting responses in humans by repeatedly activating cone photoreceptors. In a between-subjects study, healthy volunteers (n = 24, 21–28 yr) lived individually in a laboratory for 6 consecutive days. Circadian rhythms of melatonin, cortisol, body temperature, and heart rate were assessed before and after exposure to 6 h of continuous red light (631 nm, 13 log photons cm−2 s−1), intermittent red light (1 min on/off), or bright white light (2,500 lux) near the onset of nocturnal melatonin secretion (n = 8 in each group). Melatonin suppression and pupillary constriction were also assessed during light exposure. We found that circadian resetting responses were similar for exposure to continuous versus intermittent red light (P = 0.69), with an average phase delay shift of almost an hour. Surprisingly, 2 subjects who were exposed to red light exhibited circadian responses similar in magnitude to those who were exposed to bright white light. Red light also elicited prolonged pupillary constriction, but did not suppress melatonin levels. These findings suggest that, for red light stimuli outside the range of sensitivity for melanopsin, cone photoreceptors can mediate circadian phase resetting of physiologic rhythms in some individuals. Our results also show that sensitivity thresholds differ across non-visual light responses, suggesting that cones may contribute differentially to circadian resetting, melatonin suppression, and the pupillary light reflex during exposure to continuous light

Complex Coacervate-based Materials for Biomedicine

There has been increasing interest in complex coacervates for deriving and trans- porting biomaterials. Complex coacervates are a dense, polyelectrolyte-rich liq- uid that results from the electrostatic complexation of oppositely charged macroions. Coacervates have long been used as a strategy for encapsulation, par- ticularly in food and personal care products. More recent efforts have focused on the utility of this class of materials for the encapsulation of small molecules, pro- teins, RNA, DNA, and other biomaterials for applications ranging from sensing to biomedicine. Furthermore, coacervate-related materials have found utility in other areas of biomedicine, including cartilage mimics, tissue culture scaffolds, and adhesives for wet, biological environments. Here, we discuss the self- assembly of complex coacervate-based materials, current challenges in the intel- ligent design of these materials, and their utility applications in the broad field of biomedicine

EFFECTS OF CLASS START TIMES AND CHRONOTYPE ON SLEEP AND LEARNING IN UNIVERSITY STUDENTS

Ph.DDOCTOR OF PHILOSOPHY (DUKE

A targeted e-learning approach for keeping universities open during the COVID-19 pandemic while reducing student physical interactions

10.1371/journal.pone.0249839PLoS ONE164 Aprile024983

Assembly of photoluminescent [CunIn] (n = 4, 6 and 8) clusters by clickable hybrid [N,S] ligands

© the Partner Organisations 2015.Three new 1,2,3-triazole-based NS ligands, 2-((4-((benzylthio)methyl)-1H-1,2,3-triazol-1-yl)methyl)pyridine (L1), 2-((4-(2-(cyclopentylthio)ethyl)-1H-1,2,3-triazol-1-yl)methyl)pyridine (L2) and 2-((4-(2-(cyclopentylthio)ethyl)-1H-1,2,3-triazol-1-yl)methyl)quinoline (L3) and the corresponding copper(i)-iodide complexes [Cu4I4(L1)2] (1), [Cu6I6(L2)2] (2) and [Cu6I6(L3)2] (3A) have been prepared and characterized by single-crystal X-ray diffraction (XRD), powder XRD, photoluminescence spectroscopy and thermogravimetric analysis. Complexes 1, 2 and 3A exhibit stair-step [CunIn] (n = 4 and 6) cluster structures with supporting ligands L1, L2 and L3, respectively. Ligand L1 coordinates with a bidentate/monodentate binding mode in the [Cu4I4] cluster complex 1 using the pyridyl-triazole moiety and with a pendant -CH2SCH2Ph group. Increasing the length of the bridge from -CH2- in L1 to -C2H4- in L2 and L3 engages the S donor and these ligands coordinate using a bidentate/monodentate/monodentate mode supporting larger [Cu6I6] cluster complexes 2 and 3A. A kinetic product [Cu8I8(L3)2(CH3CN)2] (3B) was isolated from the reaction of L3 with CuI in CH3CN and the single-crystal X-ray structure indicates a rare discrete stair-step [Cu8I8] core supported by two L3 and two coordinated CH3CN solvates. The structure is further stabilized by intermolecular π⋯π stacking interactions in the lattice. Isolation of 1-3 provides a good demonstration of the use of multidentate and multifunctional hybrid ligands in supporting [CunIn] clusters of different sizes (n = 4, 6, 8). Ligands L1-L3 are blue emissive molecules. The corresponding complexes display strong blue (1 and 2) or remarkable yellow (3A) emissions between 500 and 700 nm in the solid state. The structures of sulfur-containing ligands and their copper-iodide complexes are described and discussed.Link_to_subscribed_fulltex

Early morning university classes are associated with impaired sleep and academic performance

10.1038/s41562-023-01531-xNATURE HUMAN BEHAVIOUR74502-

Circadian phase shift responses to light (h ± SEM).

<p>Circadian phase shift responses are shown for 6 h of exposure to continuous red light, intermittent red light and darkness, or bright white light near the onset of melatonin secretion. By convention, negative values indicate phase delay shifts. Using a linear mixed-effects model for comparing phase resetting responses, bright white light elicited a larger response than either red light condition (<i>P</i><0.003). Phase shifts were similar in response to continuous versus intermittent red light (<i>P</i> = 0.69), and did not differ across physiologic measures (<i>P</i> = 0.35). Data were also analyzed using one-way ANOVA, whereby asterisks (*) indicate significant differences in response to bright white light versus continuous red light, and daggers (^†) indicate significant differences in response to bright white light versus intermittent red light. Phase resetting did not differ between red light conditions.</p

Protocol for assessing circadian phase shift responses and melatonin suppression.

<p>(<b>A</b>) Subjects took part in a 6-day laboratory study. Circadian rhythms were assessed using constant routine (CR) procedures before and after an experimental light exposure session. During the CR procedure, subjects were exposed to <5 lux of ambient light. During the light exposure session, subjects were exposed to 6 h of continuous red light (631 nm, 13 log photons cm⁻² s⁻¹), intermittent red light and darkness (∼1 min on, 1 min off), or bright polychromatic white light (2,500 lux; 4000K) starting 1 h before habitual bedtime. (<b>B</b>) The narrow-bandwidth red light stimulus was generated using a light-emitting diode and delivered to subjects' eyes using a modified Ganzfeld dome. The spectral emission of the LED stimulus is shown.</p

Melatonin levels and pupillary constriction during nocturnal light exposure.

<p>(<b>A</b>) Melatonin profiles are shown for participants exposed to 6 h of continuous red light (left), intermittent red light and darkness (center), or bright white light (right) near the onset of melatonin secretion. Black traces show the melatonin rhythm on the day prior to light exposure, and gray traces show melatonin on the day of the light exposure session. Melatonin concentrations during light exposure were individually adjusted using Z-score values obtained during the first constant routine procedure. Vertical dotted lines indicate the onset and offset of the light exposure session. (<b>B</b>) The area under the curve (AUC) of the melatonin profile during light exposure is shown for each subject, expressed as a percentage of his AUC measured in dim light. Values less than 100% therefore indicate light-induced melatonin suppression, whereas values that exceed 100% indicate that the AUC was higher during the light exposure session relative to the AUC measured in dim light on the previous day. The open circles show responses for subjects <i>crl30</i> and <i>irl31</i>, who exhibited substantial resetting of circadian rhythms, as shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096532#pone-0096532-g003" target="_blank">Figure 3</a>. (<b>C</b>) The pupillary light reflex is shown during the first 50 min of exposure to continuous red light (left), alternating red light and darkness (center), and bright white light (right). (<b>D</b>) The median pupillary light response is shown for individual subjects during the 50-min fixed gaze period, expressed relative to the dark pupil. Horizontal dotted lines in <b>C</b> and <b>D</b> indicate pupil diameter in darkness, and data in <b>C</b> are binned at intervals of 15.625 s, corresponding to one-quarter of an intermittent lights-on pulse. In <b>A</b> and <b>C</b>, the mean ± SEM is shown. In <b>B</b> and <b>D</b>: crl, continuous red light; irl, intermittent red light; bwl, bright white light.</p