Sunlight is a primary source of energy for life. However, its UV component causes DNA damage. We suggest that the strong UV component of sunlight contributed to the selective pressure for the evolution of the specialized photoreceptor cryptochrome from photolyases involved in DNA repair and propose that early metazoans avoided ...

PURPOSE: To determine the accuracy and reproducibility of scotopic pupil measurements with a slitlamp-based cobalt blue light. SETTING: University of Texas Health Science Center-San Antonio, San Antonio, Texas, USA. METHODS: In a prospective experimental study, 2 independent observers measured 16 subjects' pupils with a standard slitlamp-based cobalt blue light. In ...

To explore the possibility of using blue light for extracorporeal circulation therapy in patients with leukemia, the effects of blue light on cell growth in vitro and in extracorporeally circulated blood of rats with leukemia were evaluated. When HL60 cells circulated extracorporeally using a peristaltic pump were exposed to blue ...

In the Purkinje shift, the dark adapted eye becomes more sensitive to blue than to red as the retinal rods take over from the cones. A striking demonstration of the Purkinje shift, suitable for classroom use, is described in which a small change in viewing distance can reverse the perceived ...

A current model suggests that magnetoreception of compass information starts with light-dependent primary processes. Light-dependency of magnetoreception is supported by behavioral experiments with homing pigeons and caged migratory birds. Three passerine species showed normal orientation under dim monochromatic light from the blue-green range of the spectrum, while they were disoriented ...

PURPOSE: Less accommodation was found when human subjects read in blue (peak at about 440 nm) than when they read in red light (above 600 nm; [Kroger & Binder, British Journal of Ophthalmology 84 (2000) 890]). On the other hand, emmetropization in chickens did not appear to compensate for the ...

Anoxygenic photosynthetic proteobacteria exhibit various light responses, including changing levels of expression of photosynthesis genes. However, the underlying mechanisms are largely unknown. We show that expression of the puf and puc operons encoding structural proteins of the photosynthetic complexes is strongly repressed by blue light under semi-aerobic growth in Rhodobacter ...

Blue light is the primary entrainment signal for a number of developmental and morphological processes in the lower eucaryote Neurospora crassa. Blue light regulates photoactivation of carotenoid synthesis, conidiation, phototropism of perithecia and circadian rhythms. Changes in the electrical properties of the plasma membrane are one of the fastest responses ...

In the fungus Neurospora crassa, the blue light photoreceptor(s) and signaling pathway(s) have not been identified. We examined light signaling by exploiting the light sensitivity of the Neurospora biological clock, specifically the rapid induction by light of the clock component frequency (frq). Light induction of frq is transcriptionally controlled and ...

The plasma membrane-associated NADH oxidase (NOX) of spinach leaf disks is characterized by oscillations in activity with a regular period length of ca. 24 min. Within a single population of plants exposed to light at the same time, NOX activities of all plants function synchronously. Exposure of plants transferred from ...

Guard cells of the orchid genus, Paphiopedilum have been reported to lack developed chloroplasts and detectable chlorophyll a autofluorescence. Paphiopedilum stomata lack a photosynthesis-dependent opening response but have a blue light-specific opening. The present study found that low fluence rate green and red light elicited stomatal opening in Paphiopedilum and ...

We analysed the effects of inactivation of the phytochrome genes cph1 and cph2 on the phototactic migration of the cyanobacterium Synechocystis sp. PCC 6803 under different light qualities. Motility towards white, green, red and far red light was not altered in several independently raised cph1, cph2 and cph1/cph2 double mutants. ...

Solar-reflective roofs remain cooler than absorptive roofs and thus conserve electricity otherwise needed for air conditioning. A currently controversial aspect of solar-reflective cool roofing is the extent to which an initially high solar reflectance decreases with time. We present experimental data on the spectral absorption of deposits that accumulate on ...

We have synthesized a series of symmetrical phenothiazines in which the methyl groups of methylene blue have been substituted by longer alkyl chains. Intrinsic photosensitizing ability was not altered by increasing the chain length. However, in vitro phototoxicity after 2 h incubation of RIF-1 murine fibrosarcoma cells followed the order ...

Changes in photosynthetic capacity of the seaweed Gracilaria tenuistipitata Zhang et Xia acclimated to monochromatic blue light were studied. For this purpose, affinity for external inorganic carbon, light use efficiency, carbonic anhydrase (CA; EC 4.2.1.1) activity and content of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) were determined in thalli acclimated to ...

A diaheliotropic response of sunflower, Helianthus annuus, following a short pulse of low intensity blue light to a small area of leaf surface was examined with the application of the very low-force-measurements technique (the order of magnitude of 10(-5) N). One leaf from a pair was illuminated with a low ...

Blue light regulates processes such as the development of plants and fungi and the behaviour of microbes. Two types of blue-light receptor flavoprotein have been identified: cryptochromes, which have partial similarity to photolyases, and phototropins, which are photoregulated protein kinases. The former have also been found in animals with evidence ...

This paper describes the design, realization and characterization of a micromachined light detection cell. This light detection cell is designed to meet the specifications needed for a micro total analysis system in which ammonia is converted to indophenol blue. The concentration of indophenol blue is measured in a light detection ...

Based on quantitative data on nutrients, light penetration, phytoplankton, zooplankton and zoobenthos obtained in the period 1992-1994 the relations between trophic levels were studied by means of statistical analysis. The two lakes are distinguished by relatively high transfer efficiency between phytoplankton and zooplankton, which depends on the size distribution among ...

Blue light inhibits the formation of asexual cycle spores (conidia) and stimulates the development of the sexual (female) reproductive structures (protoperithecia) in the nitrogen-starved mycelium of Neurospora crassa. The DNA methylation inhibitor, 5-azacytidine (3-300 microM), opposed the effect of light by suppressing the protoperithecia formation and stimulating a conidiation. The ...

The stomatal pores of higher plants allow for gaseous exchange into and out of leaves. Situated in the epidermis, they are surrounded by a pair of guard cells which control their opening in response to many environmental stimuli, including blue light. Opening of the pores is mediated by K(+) accumulation ...

Blue light was found to induce shrinkage of the protoplasts isolated from first-leaf lamina pulvini of 18-day-old Phaseolus vulgaris. The response was transient following pulse stimulation, while it was sustainable during continuous stimulation. No apparent difference was found between flexor and extensor protoplasts. Protoplasts of the petiolar segment located close ...

The blue-blindness (tritanopia) of the human foveola normally goes unnoticed but can be directly visualized by having observers view a flickering, monochromatic, short-wavelength field. The blue scotoma appears as a tiny dark spot in central vision, the visibility of which depends upon the wavelength of the field and the temporal ...

To investigate how magnetoreception is affected by the wavelength and intensity of light, we tested European robins, Erithacus rubecula, under monochromatic lights of various wavelengths at two intensities using oriented behaviour as an indicator of whether the birds could derive directional information from the geomagnetic field. At a quantal flux ...

European robins tested under monochromatic green light with a peak wavelength of 565 nm at an intensity of 2.1 mW m-2 in the local geomagnetic field preferred their migratory direction, heading southward in autumn and northward in spring. Inverting of the vertical component of the magnetic field caused the robins ...

The present study aimed to test the effects of blue, green or white light on the stress response of the Nile tilapia, Oreochromis niloticus (L.). Each color was tested on two groups of isolated adult Nile tilapia (8 replicates each): one being subjected to confinement stress, and the other not ...

Luminescent lures, counter-shading in the dark blue sea, flashes of light intensive enough to temporarily blind a predator, love fireworks in the night to impress a mate, and toadstools that glow to attract parasitic wasps--these are just some of the many examples of bioluminescence at work in Nature. But how ...

Lutein and zeaxanthin are the predominant carotenoids in the human macula lutea. Epidemiological data suggest that an increased intake of a lutein-rich diet correlates with a diminished risk for age-related macular degeneration, a major cause of impaired vision in the elderly. Filtering of blue light has been proposed as a ...

Observations were made of the reflective properties of the iridophore stripes of the squid Alloteuthis subulata and Loligo vulgaris, and the likely functions of these stripes are considered in terms of concealment and signalling. In both species, the mantle muscle is almost transparent. Stripes of iridophores run along the length ...

We investigated the blur tolerance of human observers for stimuli modulated along the isoluminant red-green, the isoluminant yellow-blue, and the luminance (black-white) direction in color space. We report the following results: (i) Blur difference thresholds for red-green and luminance stimuli (of equal cone contrast) are very similar and as low ...

Researchers studying plant growth under different lamp types often attribute differences in growth to a blue light response. Lettuce plants were grown in six blue light treatments comprising five blue light fractions (0, 2, 6% from high-pressure sodium [HPS] lamps and 6, 12, 26% from metal halide [MH] lamps). Lettuce ...

PURPOSE: Acute white-light damage to rods depends on the amount of rhodopsin available for bleaching during light exposure. Bleached rhodopsin is metabolically regenerated through the visual cycle involving the pigment epithelium, or photochemically by deep blue light through photoreversal of bleaching. Because photoreversal is faster than metabolic regeneration of rhodopsin ...

Although many fundamental blue light responses have been identified, blue light dose-response curves are not well characterized. We studied the growth and development of soybean, wheat and lettuce plants under high-pressure sodium (HPS) and metal halide (MH) lamps with yellow filters creating five fractions of blue light. The blue light ...

BACKGROUND AND OBJECTIVE: Studies on the photobactericidal efficacy of methylene blue (MB) and toluidine blue (TB) have shown inconsistent results in the literature. This study evaluated the bactericidal efficacy of MB and TB against different bacteria under light and dark conditions to determine the most effective bactericidal dye. STUDY DESIGN/MATERIALS ...

We investigated the temporal properties of the red - green, blue-yellow, and luminance mechanisms in a contour-integration task which required the linking of orientation across space to detect a 'path'. Reaction times were obtained for simple detection of the stimulus regardless of the presence of a path, and for path ...

Studies using a variety of investigative methods, including functional brain imaging and electroencephalography (EEG), have suggested that changes in central nervous system (CNS) dopamine function result in altered visual system processing. The discovery of abnormal retinal blue cone, but not red cone, electroretinogram in association with cocaine withdrawal and Parkinson's ...

PURPOSE: To determine whether blue light induces photoreversal of rhodopsin bleaching in vivo. METHODS: Eyes of anesthetized albino rats were exposed to either green (550 nm) or deep blue (403 nm) light, and the time course of rhodopsin bleaching was determined. Rhodopsin was isolated from whole retinas by detergent extraction ...

A fiber-ribbon-based coupling method is presented as a practical way to enhance light sensitivity in spectroscopic and similar systems employing a multialkali photomultiplier tube as a detector. The sensitivity enhancement is achieved by an increase in absorption in the photocathode through multiple total internal reflection in the photomultiplier entrance window. ...

We analysed how the assembling behaviour of Triatoma infestans is modulated by the convergence of chemical cues released by their faeces and the spectral quality of the light associated with refuges. Second-instar larvae were confronted with refuges associated with a visual stimulus (either blue, green or red lights having the ...

BACKGROUND: A variety of protocols exist for the treatment of Bowen's disease by photodynamic therapy (PDT) using topical 5-aminolaevulinic acid (5-ALA). OBJECTIVE: To determine the optimal wavelength (red or green light) for this treatment. METHODS: A randomized comparison study of ALA-PDT using red (630 +/- 15 nm) or green (540 ...

The tubular eye of scopelarchids contains a lens pad, derived from cornea, lateral to the lens and opposite a gap in the iris. The pad, transparent in life, is formed of optically dense lamellae arranged at ca. 45 degrees to the sagittal plane of the fish. The lamellae are ca. ...

Experiments on the integration of blue and orange stimuli in Halobacterium salinarum were performed by using different combinations of blue and orange steps. The results show that the prevalence of the blue stimulus over the orange one depends on both the blue and the orange light intensities. A quantitative analysis ...

The effects of light on gravitaxis and velocity in the bi-flagellated green alga Chlamydomonas reinhardtii were investigated using a real time automatic tracking system. Three distinct light effects on gravitaxis and velocity with parallel kinetics were found. Photosynthetically active continuous red light reversibly enhances the swimming velocity and increases or ...

The plant photoreceptor phototropin is an autophosphorylating serine-threonine protein kinase activated by UV-A/blue light. Two domains, LOV1 and LOV2, members of the PAS domain superfamily, mediate light sensing by phototropin. Heterologous expression studies have shown that both domains function as FMN-binding sites. Although three plant blue light photoreceptors, cry1, cry2, ...

The sensitivity of positive phototactic orientation of cells of the ciliated protozoan Ophryoglena flava has been measured for white light, broad-band blue and red light, and narrow-band monochromatic light, using a laboratory-developed computer aided system. The white-light fluence rate-response curve shows that there is no negative phototaxis in the fluence ...

Chimeric proteins were produced using the green light-emitting luciferase of Phrixothrix vivianii (PxGr: lambda max = 548 nm) and the red light-emitting luciferase of Phrixothrix hirtus (PxRe: lambda max = 623 nm). Constructs containing residues 1-344 of the red light-emitting luciferase with residues 345-545 of the green light emitting one ...

Protoplasts isolated from Cuscuta reflexa exhibited a higher rate of exogenous NADH oxidation as compared to NADPH in the dark. NAD(P)H oxidation was monitored by measuring the rate of oxygen consumption and this oxidase system was sensitive to blue light. Both NADH oxidase and its blue light sensitivity were inhibited ...

Photobleaching of bacteriorhodopsin (BR) by continuous light has recently been demonstrated. This bleaching consists of at least two subsequent product states. One of them is absorbing maximally in the blue spectral region. Our present study shows that upon illumination of the bleached sample with blue light a back photoprocess appears, ...

Blue-light-induced repellent and demethylation responses, characteristic of behavioral adaptation, were observed in Rhodobacter sphaeroides. They were analyzed by computer-assisted motion analysis and through the release of volatile tritiated compounds from [methyl-(3)H]methionine-labeled cells, respectively. Increases in the stop frequency and the rate of methanol release were induced by exposure of cells ...

Larval release and photobehavior were studied in the colonial ascidian Polyandrocarpa zorritensis. The test hypothesis was that if larval release is induced by light, then larvae should be attracted to settlement areas where light is sufficient for larval release. Light induced larval release but the time course varied with light ...