Search Results (9)

Light is a major environmental factor that regulates circadian rhythms and pineal melatonin synthesis. While the influence of nighttime light exposure on melatonin suppression has been extensively investigated, much less is known about the impact of photophase light wavelength on pineal function. The aim of the study was to determine the influence of monochromatic light during the photophase on diurnal changes in melatonin-related indoles in the rat pineal gland. Wistar rats were exposed for 7 days to 150 lx of monochromatic blue (463 ± 10 nm), green (523 ± 10 nm), or red (623 ± 10 nm) LED light, or to white fluorescent light (control), under a 12:12 light–dark cycle. Pineal glands were collected every 3 h over 24 h, and the indole content was analyzed by high-performance liquid chromatography. The results demonstrated that both the timing and course of N-acetylserotonin (NAS) and melatonin (MLT) rhythms were significantly affected by light wavelength. Blue light most effectively preserved the normal rhythmicity observed under full-spectrum white light, whereas green—and particularly red light—delayed nocturnal NAS and MLT synthesis. These changes were accompanied by concurrent alternations in rhythms of serotonin, its precursors, and metabolites. The data strongly suggest that spectral light composition during the photophase influences pineal indole metabolism via melanopsin-mediated phototransduction and possibly other retinal mechanisms. These findings may have implications for the design of artificial lighting environments in human life and animal housing. Full article

We investigated the transcription of circadian clock genes in publicly available datasets of gene expression in medulloblastoma (MB) tissues using the R2 Genomics Analysis and Visualization Platform. Differential expression of the core clock genes among the four consensus subgroups of MB (defined in 2012 as Group 3, Group 4, the SHH group, and the WNT group) included the core clock genes (CLOCK, NPAS2, PER1, PER2, CRY1, CRY2, BMAL1, BMAL2, NR1D1, and TIMELESS) and genes which encode proteins that regulate the transcription of clock genes (CIPC, FBXL21, and USP2). The over-expression of several clock genes, including CIPC, was found in individuals with the isochromosome 17q chromosomal aberration in MB Group 3 and Group 4. The most significant biological pathways associated with clock gene expression were ribosome subunits, phototransduction, GABAergic synapse, WNT signaling pathway, and the Fanconi anemia pathway. Survival analysis of clock genes was examined using the Kaplan–Meier method and the Cox proportional hazards regression model through the R2 Genomics Platform. Two clock genes most significantly related to survival were CRY1 and USP2. The data suggest that several clock proteins, including CRY1 and USP2, be investigated as potential therapeutic targets in MB. Full article

Visible light refers to the frequencies within the electromagnetic spectrum that humans can see, encompassing radiation with wavelengths falling between 380 nm to 760 nm. The energy of a single photon increases with its frequency. In the retina, photoreceptor cells contain light-sensitive pigments that absorb light and convert it into electrical stimuli through a process known as phototransduction. However, since the absorption spectrum of photoreceptors closely aligns with blue light (ranging from 400 to 500 nm), exposure to high light intensities or continuous illumination can result in oxidative stress within these cells, leading to a loss of their functionality. Apart from photoreceptor cells, the retina also houses photosensitive ganglion cells, known as intrinsically photosensitive retinal ganglion cells (ipRGCs). These cells relay information to the suprachiasmatic nucleus in the brain, playing a crucial role in modulating melatonin secretion, which in turn helps in synchronizing the body’s circadian rhythms and responses to seasonal changes. Both, ipRGCs and skin possess a peak sensitivity to blue wavelengths, rendering them particularly susceptible to the effects of excessive blue light exposure. This study delves into the consequences of excessive illumination and/or prolonged exposure to blue light on retinal function and explores its implications for human health. Full article

cAMP is a key regulatory molecule that controls many important processes in the retina, including phototransduction, cell development and death, growth of neural processes, intercellular contacts, retinomotor effects, and so forth. The total content of cAMP changes in the retina in a circadian manner following the natural light cycle, but it also shows local and even divergent changes in faster time scales in response to local and transient changes in the light environment. Changes in cAMP might also manifest or cause various pathological processes in virtually all cellular components of the retina. Here we review the current state of knowledge and understanding of the regulatory mechanisms by which cAMP influences the physiological processes that occur in various retinal cells. Full article

The visual characteristics of animals with different circadian habits, especially colubrid snakes, exhibit highly variable photoreceptor morphology. While studies have reported on the diversity in retinal cell morphology among snakes with different circadian patterns, few studies have examined the expression of genes related to vision. To explore gene expression patterns in the eyes between diurnal and nocturnal snakes, we carried out RNA sequencing of six tissues (eye, heart, liver, lung, kidney, and muscle) in two colubrids with disparate circadian activities, i.e., diurnal Ahaetulla prasina and nocturnal Lycodon flavozonatum, followed by weighted gene co-expression network analysis (WGCNA). The genes in the two most correlated modules were primarily enriched in different functional pathways, thus suggesting different biological functions. Three opsin genes (RH1, LWS, and SWS) were differentially expressed between the two species. Moreover, in the phototransduction pathway, different genes were highly expressed in the eyes of both species, reflecting specific expression patterns in the eyes of snakes with different circadian activity. We also confirmed the dominance of cone- and rod-related genes in diurnal and nocturnal adaptation, respectively. This work provides an important foundation for genetic research on visual adaptation in snakes and provides further insight into the adaptive evolution of such species. Full article

Diapause is one of the survival strategies of insects for confronting adverse environmental conditions. Bombyx mori displays typical embryonic diapause, and offspring diapause depends on the incubation environment of the maternal embryo in the bivoltine strains of the silkworm. However, the molecular mechanisms of the diapause induction process are still poorly understood. In this study, we compared the differentially expressed miRNAs (DEmiRs) in bivoltine silkworm embryos incubated at diapause- (25 °C) and non-diapause (15 °C)-inducing temperatures during the blastokinesis (BK) and head pigmentation (HP) phases using transcriptome sequencing. There were 411 known miRNAs and 71 novel miRNAs identified during the two phases. Among those miRNAs, there were 108 and 74 DEmiRs in the BK and HP groups, respectively. By the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of the predicted target genes of the DEmiRs, we found that aside from metabolism, the targets were also enriched in phototransduction-fly and insect hormone biosynthesis in the BK group and the HP group, respectively. Dual luciferase reporter assay illustrated that bmo-miR-6497-3p directly regulated Bmcycle and subsequently regulated the expression of circadian genes. These results imply that microRNAs, as vitally important regulators, respond to different temperatures and participate in the diapause induction process across species. Full article

Spectral power distribution (SPD) is an essential element that has considerable implications on circadian energy and the perception of lit environments. The present study assessed the potential influences of SPD on energy consumption (i.e., considering circadian energy), visual comfort, work performance and mood. Two lighting conditions based on light-emitting diode (LED) and organic light-emitting diode (OLED) were used as proxies for SPDs of different spectral content: dominant peak wavelength of 455 nm (LED) and 618 nm (OLED). Using measured photometric values, the circadian light (CL), melatonin suppression (MS), and circadian efficacy (CE) of the two lighting sources were estimated via a circadian-phototransduction model and compared. Additionally, twenty-six participants were asked to evaluate the said lit environments subjectively in terms of visual comfort and self-reported work performance. Regarding circadian lighting and the associated energy implications, the LED light source induced higher biological actions with relatively less energy than the OLED light source. For visual comfort, OLED lighting-based conditions were preferred to LED lighting-based conditions, while the opposite was true when considering work performance and mood. The current study adds to the on-going debate regarding human-centric lighting, particularly considering the role of SPD in energy-efficient and circadian lighting practices. Full article

Night-time lights interact with human physiology through different pathways starting at the retinal layers of the eye; from the signals provided by the rods; the S-, L- and M-cones; and the intrinsically photosensitive retinal ganglion cells (ipRGC). These individual photic channels combine in complex ways to modulate important physiological processes, among them the daily entrainment of the neural master oscillator that regulates circadian rhythms. Evaluating the relative excitation of each type of photoreceptor generally requires full knowledge of the spectral power distribution of the incoming light, information that is not easily available in many practical applications. One such instance is wide area sensing of public outdoor lighting; present-day radiometers onboard Earth-orbiting platforms with sufficient nighttime sensitivity are generally panchromatic and lack the required spectral discrimination capacity. In this paper, we show that RGB imagery acquired with off-the-shelf digital single-lens reflex cameras (DSLR) can be a useful tool to evaluate, with reasonable accuracy and high angular resolution, the photoreceptoral inputs associated with a wide range of lamp technologies. The method is based on linear regressions of these inputs against optimum combinations of the associated R, G, and B signals, built for a large set of artificial light sources by means of synthetic photometry. Given the widespread use of RGB imaging devices, this approach is expected to facilitate the monitoring of the physiological effects of light pollution, from ground and space alike, using standard imaging technology. Full article

The daily expression of genes and the changes in gene expression after silencing the heme oxygenase (ho) gene were examined in the retina of Drosophila using microarray and SybrGreen qPCR (quantitative polymerase chain reaction) methods. The HO decrease in the morning upregulated 83 genes and downregulated 57 genes. At night, 80 genes were upregulated and 22 were downregulated. The top 20 genes downregulated after ho silencing in the morning modulate phototransduction, immune responses, autophagy, phagocytosis, apoptosis, the carbon monoxide (CO) response, the oxidative stress/UV response, and translation. In turn, the genes that upregulated at night were involved in translation—the response to oxidative stress, DNA damage, and phototransduction. Among the top 20 genes downregulated at night were genes involved in phototransduction, immune responses, and autophagy. For some genes, a low level of HO had an opposite effect in the morning compared to those at night. Silencing ho also changed the expression of circadian clock genes, while the HO decrease during the night enhanced the expression of immune system genes. The results showed that the cyclic expression of HO is important for controlling several processes in the retina, including neuroprotection and those involved in the innate immune system. Full article