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physiology of vision

Kanishka Senarath, Dinesh Kankanamge, Saroopa Samaradivakara, Kasun Ratnayake, Mithila Tennakoon, Ajith Karunarathne
Heterotrimeric guanine nucleotide-binding proteins (G proteins) deliver external signals to the cell interior, upon activation by the external signal stimulated G protein-coupled receptors (GPCRs).While the activated GPCRs control several pathways independently, activated G proteins control the vast majority of cellular and physiological functions, ranging from vision to cardiovascular homeostasis. Activated GPCRs dissociate GαGDPβγ heterotrimer into GαGTP and free Gβγ. Earlier, GαGTP was recognized as the primary signal transducer of the pathway and Gβγ as a passive signaling modality that facilitates the activity of Gα...
2018: International Review of Cell and Molecular Biology
Joaquín Fernández, Manuel Rodríguez-Vallejo, Javier Martínez, Ana Tauste, David P Piñero
Purpose/Aim: To evaluate the impact of ocular parameters on the visual performance achieved with the multifocal intraocular lens (IOL) Bi-Flex M 677MY. MATERIALS AND METHODS: 26 subjects were included in the current study. Several physiological variables were retrieved from the 3-month follow-up visit, including pupil diameter and distance from pupil center to the vertex normal of the anterior cornea (µ). These variables were also obtained in the preoperative visit. Binocular and monocular visual acuity defocus curves were measured at 1 and 3 months after surgery, respectively...
May 18, 2018: Current Eye Research
Allison M McKendrick, Yu Man Chan, Bao N Nguyen
PURPOSE: The number of older adults is rapidly increasing internationally, leading to a significant increase in research on how healthy ageing impacts vision. Most clinical assessments of spatial vision involve simple detection (letter acuity, grating contrast sensitivity, perimetry). However, most natural visual environments are more spatially complicated, requiring contrast discrimination, and the delineation of object boundaries and contours, which are typically present on non-uniform backgrounds...
May 17, 2018: Ophthalmic & Physiological Optics: the Journal of the British College of Ophthalmic Opticians (Optometrists)
Mohammad Shamsul Ola, Dalia Al-Dosari, Abdullah S Alhomida
Diabetic retinopathy (DR) is one of the leading causes of decreased vision and blindness in developed countries. Diabetes-induced metabolic disorder is believed to increase oxidative stress in the retina. This results in deleterious changes through dysregulation of cellular physiology that damages both neuronal and vascular cells. Here in this review, we first highlight the evidence of potential metabolic sources and pathways which increase oxidative stress that contributes to retinal pathology in diabetes...
May 15, 2018: Current Pharmaceutical Design
Xiaomei Kang, Qingqun Kong, Yi Zeng, Bo Xu
Compared to computer vision systems, the human visual system is more fast and accurate. It is well accepted that V1 neurons can well encode contour information. There are plenty of computational models about contour detection based on the mechanism of the V1 neurons. Multiple-cue inhibition operator is one well-known model, which is based on the mechanism of V1 neurons' non-classical receptive fields. However, this model is time-consuming and noisy. To solve these two problems, we propose an improved model which integrates some additional other mechanisms of the primary vision system...
2018: Frontiers in Computational Neuroscience
Samir Hasanov, Elif Demirkilinc Biler, Ahmet Acarer, Cezmi Akkın, Zafer Colakoglu, Onder Uretmen
PURPOSE: To evaluate and follow-up of functional and morphological changes of the optic nerve and ocular structures prospectively in patients with early-stage Parkinson's disease. MATERIALS AND METHODS: Nineteen patients with a diagnosis of early-stage Parkinson's disease and 19 age-matched healthy controls were included in the study. All participants were examined minimum three times at the intervals of at least 6 month following initial examination. Pattern visually evoked potentials (VEP), contrast sensitivity assessments at photopic conditions, color vision tests with Ishihara cards and full-field visual field tests were performed in addition to measurement of retinal nerve fiber layer (RNFL) thickness of four quadrants (top, bottom, nasal, temporal), central and mean macular thickness and macular volumes...
May 9, 2018: International Ophthalmology
Mary L White, L Michael Verdusco
As people age, physiological changes can occur causing deterioration of one or more of the senses, including hearing, vision, taste, and smell. The loss of sensory function can decrease the extent to which older adults can communicate, especially with their healthcare providers. The purpose of this article is to examine communication between older adults and healthcare providers, focusing on best practices and devices that can enhance and benefit their health and well-being. One consideration is the use of digital technology, such as smart phones, electronic tablets, and computers, to help mitigate the effects of aging on communication...
May 2018: Home Healthcare Now
Glenn P Lobo, Gayle Pauer, Joshua H Lipschutz, Stephanie A Hagstrom
Vitamin A/retinol (ROL) and its metabolites (retinoids) play critical roles in eye development and photoreception. Short-term dietary vitamin A deficiency (VAD) manifests clinically as night blindness, while prolonged VAD is known to cause retinal pigment epithelium (RPE) and photoreceptor degeneration. Therefore, sustained uptake of dietary vitamin A, for ocular retinoid production, is essential for photoreceptor health and visual function. The mechanisms influencing the uptake, storage, and supply of dietary vitamin A, for ocular retinoid production, however, are not fully understood...
2018: Advances in Experimental Medicine and Biology
Soon K Cheong, Wenjun Xiong, Jennifer M Strazzeri, Constance L Cepko, David R Williams, William H Merigan
Adaptive optics retinal imaging of fluorescent calcium indicators is a minimally invasive method used to study retinal physiology over extended periods of time. It has potential for discovering novel retinal circuits, tracking retinal function in animal models of retinal disease, and assessing vision restoration therapy. We previously demonstrated functional adaptive optics imaging of retinal neurons in the living eye using green fluorescent calcium indicators; however, the use of green fluorescent indicators presents challenges that stem from the fact that they are excited by short-wavelength light...
2018: Advances in Experimental Medicine and Biology
Amit K Goyal, Ranjit Singh, Gaurav Chauhan, Goutam Rath
Science of drug delivery has achieved tremendous milestones in the last few decades. Emergence of novel drug delivery techniques and the most popular nanotechnology directed the drug delivery to another level. Without any doubt, present technology holds the proficiency to approach even the intercellular targets. Between all these success auras, there lies wads of giant challenges. One such challenge is delivering the molecule directly to the blood stream. Parenteral route is considered as the most effective route for delivering active pharmaceutical substances, but is associated with major disadvantages of painful drug delivery...
April 24, 2018: Artificial Cells, Nanomedicine, and Biotechnology
M Bach, K Rohrschneider
Light filters with wavelength-dependent transmission and in particular cut-off or step filters (steep dependence of transmission on wavelength) have a broad optical application and are relevant in ophthalmology. This article describes some physical and physiological principles of cut-off filters, discusses the physiological aspects of applications, specifically the not always relevant necessity of blue-reducing filters and the lack of efficacy of color filters with color vision deficiencies.
April 20, 2018: Der Ophthalmologe: Zeitschrift der Deutschen Ophthalmologischen Gesellschaft
Ratnesh Singh, Oscar Cuzzani, François Binette, Hal Sternberg, Michael D West, Igor O Nasonkin
The retina is a very fine and layered neural tissue, which vitally depends on the preservation of cells, structure, connectivity and vasculature to maintain vision. There is an urgent need to find technical and biological solutions to major challenges associated with functional replacement of retinal cells. The major unmet challenges include generating sufficient numbers of specific cell types, achieving functional integration of transplanted cells, especially photoreceptors, and surgical delivery of retinal cells or tissue without triggering immune responses, inflammation and/or remodeling...
April 19, 2018: Stem Cell Reviews
Kellie Cloney, Shelby L Steele, Matthew R Stoyek, Roger P Croll, Frank M Smith, Sergey V Prykhozhij, Mary M Brown, Craig Midgen, Kim Blake, Jason N Berman
CHARGE syndrome is linked to autosomal dominant mutations in the CHD7 gene and results in a number of physiological and structural abnormalities, including heart defects, hearing and vision loss and gastrointestinal (GI) problems. Of these challenges, GI problems have a profound impact throughout an individual's life, resulting in increased morbidity and mortality. A homologue of CHD7 has been identified in the zebrafish, the loss of which recapitulates many of the features of the human disease. Using a morpholino chd7 knockdown model complemented by a chd7 null mutant zebrafish line, we examined GI structure, innervation, and motility in larval zebrafish...
April 16, 2018: FEBS Journal
Tom Kamperman, Marcel Karperien, Séverine Le Gac, Jeroen Leijten
Single-cell-laden microgels effectively act as the engineered counterpart of the smallest living building block of life: a cell within its pericellular matrix. Recent breakthroughs have enabled the encapsulation of single cells in sub-100-μm microgels to provide physiologically relevant microniches with minimal mass transport limitations and favorable pharmacokinetic properties. Single-cell-laden microgels offer additional unprecedented advantages, including facile manipulation, culture, and analysis of individual cell within 3D microenvironments...
April 12, 2018: Trends in Biotechnology
Pierre Gilfriche, Véronique Deschodt-Arsac, Estelle Blons, Laurent M Arsac
Diverse indicators of postural control in Humans have been explored for decades, mostly based on the trajectory of the center-of-pressure. Classical approaches focus on variability, based on the notion that if a posture is too variable, the subject is not stable. Going deeper, an improved understanding of underlying physiology has been gained from studying variability in different frequency ranges, pointing to specific short-loops (proprioception), and long-loops (visuo-vestibular) in neural control. More recently, fractal analyses have proliferated and become useful additional metrics of postural control...
2018: Frontiers in Physiology
Sasha M Woods, Edward Mountjoy, Duncan Muir, Sarah E Ross, Denize Atan
In the mammalian retina, rods and a specialised rod-driven signalling pathway mediate visual responses under scotopic (dim light) conditions. As rods primarily signal to rod bipolar cells (RBCs) under scoptic conditions, disorders that affect rod or RBC function are often associated with impaired night vision. To identify novel genes expressed by RBCs and, therefore, likely to be involved in night vision, we took advantage of the adult Bhlhe23-/- mouse retina (that lacks RBCs) to derive the RBC transcriptome...
April 3, 2018: Scientific Reports
Lingying Luo, Dandan Guo, Guanghong Zhou, Kunjie Chen
Researchers nowadays have paid much attention to the relationships between tenderness and marbling, or physiological age. While the marbling was mainly evaluated qualitatively with scores or grades, and rarely related with physiological age. Present study was carried out to analyze the marbling features of longissimus dorsi muscle between the 12th and 13th ribs from 18, 36, 54 and 72 months old Simmental steers were quantitatively described with area and perimeter using computer vision technique. Relationship between Warner-Bratzler Shear force (WBSF), physiological age and the marbling features were examined performing regression analysis...
April 2018: Journal of Food Science and Technology
Susana Martinez-Conde, Stephen L Macknik, David J Heeger
In the late 1970s, key discoveries in neurophysiology, psychophysics, computer vision, and image processing had reached a tipping point that would shape visual science for decades to come. David Marr and Ellen Hildreth's 'Theory of edge detection', published in 1980, set out to integrate the newly available wealth of data from behavioral, physiological, and computational approaches in a unifying theory. Although their work had wide and enduring ramifications, their most important contribution may have been to consolidate the foundations of the ongoing dialogue between theoretical and empirical vision science...
April 2018: Trends in Neurosciences
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
Hsin-Hao Yu, Nafiseh Atapour, Tristan A Chaplin, Katrina H Worthy, Marcello G P Rosa
Lesions of striate cortex (V1) trigger massive retrograde degeneration of neurons in the lateral geniculate nucleus (LGN). In primates, these lesions also lead to scotomas within which conscious vision is abolished. Mediation of residual visual capacity within these regions (blindsight) has been traditionally attributed to an indirect visual pathway to the extrastriate cortex, which involves the superior colliculus and pulvinar complex. However, recent studies have suggested that preservation of the LGN is critical for behavioral evidence of blindsight, raising the question of what type of visual information is channeled by remaining neurons in this structure...
March 19, 2018: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
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