Search results for "light"
showing 10 items of 3575 documents
Light-dependent CK2-mediated phosphorylation of centrins regulates complex formation with visual G-protein.
2008
AbstractCentrins are Ca2+-binding EF-hand proteins. All four known centrin isoforms are expressed in the ciliary apparatus of photoreceptor cells. Cen1p and Cen2p bind to the visual G-protein transducin in a strictly Ca2+-dependent way, which is thought to regulate light driven movements of transducin between photoreceptor cell compartments. These relatively slow motile processes represent a novel paradigm in light adaptation of photoreceptor cells.Here we validated specific phosphorylation as a novel regulator of centrins in photoreceptors. Centrins were differentially phosphorylated during photoreceptor dark adaptation. Inhibitor treatments revealed protein kinase CK2 as the major protein…
Subjective photic phenomena with refractive multifocal and monofocal intraocular lenses. results of a multicenter questionnaire.
2001
Abstract Purpose To compare the incidence and severity of photic phenomena after the implantation of the Array® (Allergan) refractive multifocal intraocular lens (MIOL) and a monofocal IOL. Setting Multicenter study at Kiel, Mainz, Karlsruhe, and Bremerhaven, Germany. Methods The study comprised 231 randomly selected patients from 4 study centers. The patients had had uneventful phacoemulsification with implantation of a refractive MIOL (n = 138) or a monofocal IOL (n = 93). By questionnaire, patients were asked whether they experienced light sensations postoperatively (light streaks, halos, flare, flashes, or glare) that had not been noticed preoperatively. Additional questions evaluated w…
Color stimuli perception in presence of light scattering.
2006
Perception of different color contrast stimuli was studied in the presence of light scattering: in a fog chamber in Clermont-Ferrand and in laboratory conditions where light scattering of similar levels was obtained, using different light scattering eye occluders. Blue (shortest wavelength) light is scattered in fog to the greatest extent, causing deterioration of vision quality especially for the monochromatic blue stimuli. However, for the color stimuli presented on a white background, visual acuity in fog for blue Landolt-C optotypes was higher than for red and green optotypes on the white background. The luminance of color Landolt-C optotypes presented on a LCD screen was chosen corresp…
Spatio-temporal Contrast Sensitivity in the Cardinal Directions of the Colour Space. A Review
2010
AbstractWe review the psychophysics of the spatio-temporal contrast sensitivity in the cardinal directions of the colour space and their correlation with those neural characteristics of the visual system that limit the ability to perform contrast detection or pattern-resolution tasks. We focus our attention particularly on the influence of luminance level, spatial extent and spatial location of the stimuli - factors that determine the characteristics of the physiological mechanisms underlying detection. Optical factors do obviously play a role, but we will refer to them only briefly. Contrast sensitivity measurements are often used in clinical practice as a method to detect, at their early …
Phytoplankton in the physical environment: beyond nutrients, at the end, there is some light
2009
This article summarizes the outcomes of the 15th Workshop of the International Association for Phytoplankton Taxonomy and Ecology. Four major issues dealing with the role of physical factors in phytoplankton ecology were addressed in the articles of this special volume: global change and its likely impacts on phytoplankton, the role of physical factors in the autecology of particular species, impacts on the inocula for the following years, and the role of light in shaping phytoplankton dynamics. Case studies from different types of aquatic environments (rivers, deep and shallow lakes, floodplain lakes, wetlands, oxbows, and even the deep ocean) and from diverse geographical locations (not o…
Tracking migration of black‐headed buntings Emberiza melanocephala reveals the Iranian Plateau as an ecological barrier along the Indo‐European flyway
2021
The black-headed bunting is one of the few species that migrate along the Indo-European flyway, and its migration routes and phenology are poorly understood. We provide the first individual-based year-round tracking study describing route choice and timing of black-headed buntings migrating from a breeding site in Croatia to a 6000 km distant non-breeding region in Maharashtra, central India. To evaluate landscapes important for the black-headed bunting migration, we quantified land covers and climates along the migration corridor. Stopover areas during the post-breeding migration were concentrated in four distinct regions: the Balkan Peninsula, central Anatolia, along with the Zagros mount…
Lightning-induced weathering of Cascadian volcanic peaks
2020
Abstract The process of meteorological lightning-induced modification of coherent volcanic rocks is examined by geochemical, textural, and experimental analysis of fulgurites from South Sister volcano, Oregon Cascades, USA. Lightning's effects on volcanic target rocks was simulated with an arc-welding device in order to reproduce the geochemical and textural features of natural fulgurites and to constrain temperatures of melting and devolatilization behavior during lightning strikes. Melting of volcanic target rocks produces melts of exceptional compositional diversity, ranging from those with pure mineral compositions (e.g., diopside and plagioclase), resulting from congruent melting react…
Origin of methane and light hydrocarbons in natural fluids emissions: A study from Greece.
2018
Abstract Greece, a country characterised by intense seismic and volcanic activity, has a complex geodynamic and geological setting that favours the occurrence of many gas manifestations. In this study, we address the origin of CH 4 and light hydrocarbons in cold and thermal emissions discharging along the Hellenic territory. Also, we investigate their possible relationship with the main geochemical composition of the gases and the different geological settings of the sampling sites. For this purpose we collected 101 new samples that were analysed for their chemical (O 2 , N 2 , CH 4 , CO 2 , He, Ne, Ar, H 2 , H 2 S and C 2 -C 6 hydrocarbons) and isotopic (R/R A , δ 13 C-CO 2 , δ 13 C-CH 4 a…
Laminar Micrite Crusts and Associated Foreslope Processes, Red Sea
1991
ABSTRACT Forereef slopes in the Red Sea of Sudan exhibit a uniform biozonation that is independent from the topography of the slopes. Below - 120 m, ledges protrude horizontally from sleep cliffs of barrier reefs and atolls as well as from patches of in situ lithified slope sediment on inclined fringing reef slopes. Free surfaces and cavities within these ledges are partly covered by laminar micrite crusts of 7-20 mm thickness. The ledges are formed by an organic framework of living azooxanthellate corals, bryozoans, serpulids and fossil red algae. They are affected by repeated episodes of boring, infilling, and cementation which obliterate much of the original fabric. Concomitant cementati…
Tyramine Actions on Drosophila Flight Behavior Are Affected by a Glial Dehydrogenase/Reductase
2017
The biogenic amines octopamine (OA) and tyramine (TA) modulate insect motor behavior in an antagonistic manner. OA generally enhances locomotor behaviors such as Drosophila larval crawling and flight, whereas TA decreases locomotor activity. However, the mechanisms and cellular targets of TA modulation of locomotor activity are incompletely understood. This study combines immunocytochemistry, genetics and flight behavioral assays in the Drosophila model system to test the role of a candidate enzyme for TA catabolism, named Nazgul (Naz), in flight motor behavioral control. We hypothesize that the dehydrogenase/reductase Naz represents a critical step in TA catabolism. Immunocytochemistry rev…