Read by QxMD icon Read


Daniel S Joyce, Beatrix Feigl, Graham Kerr, Luisa Roeder, Andrew J Zele
Parkinson's disease (PD) is characterised by non-motor symptoms including sleep and circadian disruption. Melanopsin-expressing intrinsically photosensitive Retinal Ganglion Cells (ipRGC) transmit light signals to brain areas controlling circadian rhythms and the pupil light reflex. To determine if non-motor symptoms observed in PD are linked to ipRGC dysfunction, we evaluated melanopsin and rod/cone contributions to the pupil response in medicated participants with PD (n = 17) and controls (n = 12)...
May 17, 2018: Scientific Reports
Marina Saito, Kentaro Miyamoto, Yusuke Uchiyama, Ikuya Murakami
The natural blind spot in the visual field has been known as a large oval region that cannot receive any optical input because it corresponds to the retinal optic disk containing no rod/cone-photoreceptors. Recently, stimulation inside the blind spot was found to enhance, but not trigger, the pupillary light reflex. However, it is unknown whether blind-spot stimulation also affects visual perception. We addressed this question using psychophysical brightness-matching experiments. We found that a test stimulus outside the blind spot was judged as darker when it was accompanied by a consciously unexperienced blue oval inside the blind spot; moreover, the pupillary light reflex was enhanced...
May 15, 2018: Scientific Reports
Jessica Rodgers, Steven Hughes, Carina A Pothecary, Laurence A Brown, Doron G Hickey, Stuart N Peirson, Mark W Hankins
Melanopsin (OPN4) is an opsin photopigment expressed within intrinsically photosensitive retinal ganglion cells (ipRGCs) that mediate non-image forming (NIF) responses to light. Two single nucleotide polymorphisms (SNPs) in human melanopsin (hOPN4), Pro10Leu and Thr394Ile, have recently been associated with abnormal NIF responses to light, including Seasonal Affective Disorder. It has been suggested these behavioural changes are due to altered melanopsin signalling. However, there is currently no direct evidence to support this...
April 30, 2018: Human Molecular Genetics
Dinesh Kankanamge, Kasun Ratnayake, Saroopa Samaradivakara, Ajith Karunarathne
Melanopsin (Opn4), a ubiquitously expressed photoreceptor in all classes of vertebrates, is crucial for both visual and non-visual signaling. Opn4 supports visual functions of the eye by sensing radiance levels and discriminating contrast and brightness. Non-image forming (NIF) functions of Opn4 not only regulate circadian behavior, but also control growth and development processes of the retina. Nevertheless, it is unclear how a single photoreceptor governs such a diverse range of physiological functions. While genetic hardwiring of host cells is thought to be a source, molecular and mechanistic justifications for the prominent functional diversity of Opn4 are lacking...
April 30, 2018: Journal of Cell Science
Jessica Rodgers, Stuart N Peirson, Steven Hughes, Mark W Hankins
Melanopsin is a blue light-sensitive opsin photopigment involved in a range of non-image forming behaviours, including circadian photoentrainment and the pupil light response. Many naturally occurring genetic variants exist within the human melanopsin gene (OPN4), yet it remains unclear how these variants affect melanopsin protein function and downstream physiological responses to light. Here, we have used bioinformatic analysis and in vitro expression systems to determine the functional phenotypes of missense human OPN4 variants...
April 26, 2018: Cellular and Molecular Life Sciences: CMLS
Ranjay Chakraborty, Lisa A Ostrin, Debora L Nickla, P Michael Iuvone, Machelle T Pardue, Richard A Stone
PURPOSE: Despite extensive research, mechanisms regulating postnatal eye growth and those responsible for ametropias are poorly understood. With the marked recent increases in myopia prevalence, robust and biologically-based clinical therapies to normalize refractive development in childhood are needed. Here, we review classic and contemporary literature about how circadian biology might provide clues to develop a framework to improve the understanding of myopia etiology, and possibly lead to rational approaches to ameliorate refractive errors developing in children...
May 2018: Ophthalmic & Physiological Optics: the Journal of the British College of Ophthalmic Opticians (Optometrists)
Anders Tolstrup Christiansen, Jens Folke Kiilgaard, Kristian Klemp, David Paul Drucker Woldbye, Jens Hannibal
Neuropeptide Y (NPY) is a peptide neurotransmitter abundantly expressed in the mammalian retina. Since its discovery, NPY has been studied in retinas of several species, but detailed characterization of morphology, cell-type, and connectivity has never been conducted in larger mammals including humans and pigs. As the pig due to size and cellular composition is a well-suited animal for retinal research, we chose to compare the endogenous NPY system of the human retina to that of pigs to support future research in this field...
April 17, 2018: Journal of Comparative Neurology
Marija Zivcevska, Shaobo Lei, Alan Blakeman, Herbert C Goltz, Agnes M F Wong
Purpose: To develop an objective psychophysical method to quantify light-induced visual discomfort, and to measure the effects of viewing condition and stimulus wavelength. Methods: Eleven visually normal subjects participated in the study. Their pupils were dilated (2.5% phenylephrine) before the experiment. A Ganzfeld system presented either red (1.5, 19.1, 38.2, 57.3, 76.3, 152.7, 305.3 cd/m2) or blue (1.4, 7.1, 14.3, 28.6, 42.9, 57.1, 71.4 cd/m2) randomized light intensities (1 s each) in four blocks...
March 1, 2018: Investigative Ophthalmology & Visual Science
Diego García-Ayuso, Johnny Di Pierdomenico, Wahiba Hadj-Said, Mélanie Marie, Marta Agudo-Barriuso, Manuel Vidal-Sanz, Serge Picaud, María P Villegas-Pérez
Purpose: To examine if light exposure exacerbates retinal neuronal loss induced by taurine depletion. Methods: Albino rats received β-alanine in the drinking water to induce taurine depletion. One month later, half of the animals were exposed to white light (3000 lux) continuously for 48 hours and the rest remained in normal environmental conditions. A control group of animals nontreated with β-alanine also was prepared, and half of them were exposed to light using the same protocol...
March 1, 2018: Investigative Ophthalmology & Visual Science
Qi Lu, Tushar H Ganjawala, Samer Hattar, Gary W Abrams, Zhuo-Hua Pan
Purpose: To develop an animal behavioral assay for the quantitative assessment of the functional efficacy of optogenetic therapies. Methods: A triple-knockout (TKO) mouse line, Gnat1-/-Cnga3-/-Opn4-/-, and a double-knockout mouse line, Gnat1-/-Cnga3-/-, were employed. The expression of channelrhodopsin-2 (ChR2) and its three more light-sensitive mutants, ChR2-L132C, ChR2-L132C/T159C, and ChR2-132C/T159S, in inner retinal neurons was achieved using rAAV2 vectors via intravitreal delivery...
March 1, 2018: Investigative Ophthalmology & Visual Science
Dingcai Cao, Adam Chang, Shaoyan Gai
Current models of human color vision only consider cone inputs at photopic light levels, yet it is unclear whether the recently discovered melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) contribute to color perception. Using a lab-made five-primary photostimulator that can independently control the stimulations of rods, cones, and ipRGCs in human retina, we determined the observer's unique white perception, an equilibrium point for signals arising from the opponent mechanisms of color vision, under different levels of melanopsin activation...
April 1, 2018: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
Andrew J Zele, Prakash Adhikari, Beatrix Feigl, Dingcai Cao
We determined the contributions of cone and melanopsin luminance signaling to human brightness perception. The absolute brightness of four narrowband primary lights presented in a full-field Ganzfeld was estimated in two conditions, either cone luminance-equated (186.7-1,867.0  cd·m-2 ) or melanopsin luminance-equated (31.6-316.3  melanopsin cd·m-2 ). We show that brightness estimations for each primary light follow an approximately linear increase with increasing cone or melanopsin luminance (in log units), but are not equivalent for primary lights equated with either cone or melanopsin luminance...
April 1, 2018: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
Peter B Detwiler
The mammalian retina contains a small number of retinal ganglion cells that express melanopsin, a retinal based visual pigment, and generate a depolarizing response to light in the absence of rod and cone driven synaptic input; hence they are referred to as intrinsically photosensitive retinal ganglion cells (ipRGCs). They have been shown to be comprised of a number of sub-types and to provide luminance information that participates primarily in a variety of non-imaging forming visual functions. Here I review what is currently known about the cascade of events that couple the photoisomerization of melanopsin to the opening of a non-selective cation channel...
March 2018: Yale Journal of Biology and Medicine
Raymond P Najjar, Sourabh Sharma, Eray Atalay, Annadata V Rukmini, Christopher Sun, Jing Zhan Lock, Mani Baskaran, Shamira A Perera, Rahat Husain, Ecosse Lamoureux, Joshua J Gooley, Tin Aung, Dan Milea
PURPOSE: To evaluate the ability of chromatic pupillometry to reveal abnormal pupillary responses to light in patients with early-stage primary open-angle glaucoma (POAG) and to test whether the degree of pupillometric impairment correlates with structural hallmarks of optic nerve damage in the disease. DESIGN: Cross-sectional study. PARTICIPANTS: Forty-six patients with early-stage POAG (63.4±8.3 years, 63% male, 87% ethnic-Chinese) and 90 age-matched healthy controls (61...
March 21, 2018: Ophthalmology
Shi-Jun Weng, Jordan M Renna, Wei-Yi Chen, Xiong-Li Yang
Intrinsically photosensitive retinal ganglion cells (ipRGCs) are a special subset of retinal output neurons capable of detecting and responding to light via a unique photopigment called melanopsin. Melanopsin activation is essential to a wide array of physiological functions, especially to those related to non-image-forming vision. Since ipRGCs only constitute a very small proportion of retinal ganglion cells, targeted recording of melanopsin-driven responses used to be a big challenge to vision researchers...
2018: Methods in Molecular Biology
Seul Ki Lee, Tiffany M Schmidt
Melanopsin-expressing, intrinsically photosensitive retinal ganglion cells (ipRGCs) are a relatively recently discovered class of photoreceptor. ipRGCs can be subdivided into at least five subtypes (M1-M5), each of which has a distinct complement of morphological and physiological properties. ipRGC subtypes can be identified morphologically based on a combination of dendritic morphology and immunostaining for a cell-type specific marker. In this chapter, we describe methods for conclusively identifying each of the five ipRGC subtypes through a combination of patch clamp electrophysiology, Neurobiotin filling, visualization of ipRGC dendrites, and immunostaining for the marker SMI-32...
2018: Methods in Molecular Biology
Liju Luan, Chaoran Ren, Wenyao Wang, Yan Nan, Jie Gao, Mingliang Pu
The amygdala is a limbic structure that is involved in many brain functions, including emotion, learning and memory. It has been reported that melanopsin-expressing retinal ganglion cells (ipRGCs) innervate the medial amygdala (MeA). However, whether conventional RGCs (cRGCs) project to the MeA remains unknown. The goal of this study was to determine if cRGCs project to the MeA and to determine the morphological properties of MeA-projecting RGCs (MeA-RGCs). Retrogradely labeled RGCs in whole-mount retinas were intracellularly injected to reveal their dendritic morphologies...
March 19, 2018: Science China. Life Sciences
Shakoor Ba-Ali, Rigmor Højland Jensen, Line Sofie Larsen, Henrik Lund-Andersen, Steffen Hamann
Previously, it has been reported that melanopsin-mediated pupillary light response (PLR), measured with pupillometry, is reduced in patients with idiopathic intracranial hypertension (IIH), indicating the clinical utility of the tool in the diagnosis of IIH. In the current study, the authors aimed to measure the PLR in 13 treatment-naive patients with new-onset IIH and 13 healthy controls. In contrast to the previous report, which was based on patients with longstanding IIH ( n = 13), the authors found no significant difference in the melanopsin-mediated PLR ( p = 0...
April 2018: Neuro-ophthalmology
Donna Hermawati, Farid Agung Rahmadi, Tanjung Ayu Sumekar, Tri Indah Winarni
Prevalence autism spectrum disorders (ASD) has been on rise, but many studies suggests over-diagnosed. Currently, children have more access to electronic media on the daily basis than those of previous generation. Some studies suggest that increases screen time is associated with melanopsin-expressing neurons and decreasing gamma-aminobutyric acid (GABA) neurotransmitter, and thus results aberrant behavior, decreased cognitive, and language development. Early exposure of electronic media in early life (< 2 years old) gives an impact on language, but it still inconclusive...
February 2018: Intractable & Rare Diseases Research
Andrew J Zele, Beatrix Feigl, Prakash Adhikari, Michelle L Maynard, Dingcai Cao
The visual consequences of melanopsin photoreception in humans are not well understood. Here we studied melanopsin photoreception using a technique of photoreceptor silent substitution with five calibrated spectral lights after minimising the effects of individual differences in optical pre-receptoral filtering and desensitising penumbral cones in the shadow of retinal blood vessels. We demonstrate that putative melanopsin-mediated image-forming vision corresponds to an opponent S-OFF L + M-ON response property, with an average temporal resolution up to approximately 5 Hz, and >10x higher thresholds than red-green colour vision...
March 1, 2018: Scientific Reports
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"