Photoactivated hypericin produces singlet oxygen and superoxide anion radical; however, the intracellular events contributing to toxicity are unknown. Clonogenic assays of oxygen-dependent hypericin phototoxicity to EMT6 cells have previously shown that 0.5 microM hypericin + 1.5 J cm(-2) fluorescent light is non-toxic and that 1.0 microM hypericin + 1.5 J ...

The ability to perceive the 3-D shape of objects solely from motion cues is referred to as structure-from-motion perception. Recent experiments indicate how this remarkable perceptual attribute is computed by the brains of primates. This computation proceeds in at least two stages, one in which motion measurements are made and ...

We demonstrated that fluorescence anisotropy can be effectively decreased or increased in the presence of light quenching, depending on relative polarizations of excitation and quenching pulses. For parallel light quenching, anisotropy decreases to 0.103 and z-axis symmetry is preserved. In the presence of perpendicular light quenching, the steady-state anisotropy of ...

In working environments all over the world, fluorescent tubes are by far the dominating light source. Still, there have been very few studies on the impact of the non-visible flicker from fluorescent tubes. The purpose of the study was to compare the impact on subjective well-being, performance and physiological arousal ...

Effects of ascorbic acid (0.025, 0.05, and 0.1%, w/v) on the light-induced riboflavin degradation and color changes in whole and skim milks were studied during 10 h fluorescent light illumination at 7 +/- 2 degrees C. As the time of light illumination increased, the riboflavin content in milks greatly decreased, ...

Malignant gliomas accumulate fluorescing protoporphyrin IX intracellularly after exposure to 5-aminolevulinic acid, a metabolic precursor of haem. This phenomenon has been exploited for intraoperative identification of residual tumour to enable greater completeness of tumour removal. The present report describes the necessary modifications to the operating microscope to enable microsurgical, fluorescence-guided ...

The high-resolution FTIR spectrum of FNO has been recorded and the rovibrational structure of the essentially unperturbed nu3, 2nu3, and nu1 + nu3 cold bands and the 2nu3 <-- nu3, nu2 + nu3 <-- nu3, and nu1 + nu2 + nu3 <-- nu3 hot bands has been analyzed. The perturbed ...

Artificial visual stimuli in the form of photographs, video sequences and computer-generated images are increasingly being used to explore the visual world of birds but their use is controversial as it is still not clear whether birds see them in the same way that humans do. While differences between bird ...

We present an intensity based sensor designed for on-line monitoring of green fluorescent protein, a revolutionary marker of protein expression. The device consisted of a blue light emitting diode as the excitation source. A band pass excitation filter cut off light longer than 490 nm. The light was directed into ...

When barley leaves were suddenly exposed to strong white light, the rate of thermal de-excitation of the absorbed light energy, measured with a photoacoustic device, increased by around 12% within a few minutes. This phenomenon was paralleled by a quenching of chlorophyll fluorescence. Simultaneous measurements of the heat emission increase ...

Under many environmental conditions, plants are exposed to levels of sunlight in excess of those required for photosynthesis. Then, a regulated increase in the rate of nonradiative dissipation of excess excitation energy in the thylakoid membrane correlates with the conversion of the carotenoid violaxanthin into zeaxanthin and provides protection from ...

Photosynthetic O(2) evolution at high irradiances (approximately 600-1000 micro mol m(-2) s(-1)) and O(2) uptake in darkness were measured in needles of control, irrigated and irrigated-fertilized trees of Norway spruce (Picea abies (L.) Karst.). Measurements were made at 20 degrees C and at high CO(2) concentrations. The results suggest that, ...

A two-monochromator reference spectrofluorimeter has been developed at the National Research Council of Canada in accordance with International Commission on Illumination and American Society for Testing and Materials colorimetry standards to permit high-accuracy total spectral radiance factor measurements of fluorescent materials. This fully automated instrument employs a xenon-arc light source, ...

The ability of honeybees to gauge the distances of short flights was investigated under controlled laboratory conditions where a variety of potential odometric cues such as flight duration, energy consumption, image motion, airspeed, inertial navigation and landmarks were manipulated. Our findings indicate that honeybees can indeed measure short distances travelled ...

An increasing number of people in Sweden are claiming that they are hypersensitive to electricity. These patients suffer from skin as well as neurological symptoms when they are near computer monitors, fluorescent tubes, or other electrical appliances. Provocation studies with electromagnetic fields emitted from these appliances have, with only one ...

A novel method for performing color image recognition by the use of the coherent joint-transform correlator is introduced. The input plane of the proposed method is a spatial rearrangement of the separation into color channels of both the color input scene and the color target. This input plane is gray ...

7,12-Dimethylbenz[a]anthracene (DMBA), which is widely used in mutagenesis and experimental carcinogenesis, is activated to a mutagen by white fluorescent light. A 40 min exposure to white fluorescent light of Salmonella typhimurium TA98 plates treated with DMBA, in the absence of exogenous metabolism, resulted in an approximately 30-fold increase in the ...

We describe a new scheme for extending the bandwidth of IR detectors by the employment of a reticle that shifts the higher spatial-frequency content of the scene onto the lower-frequency region. Then all the spatial-frequency information can pass through the bandwidth of the detector system, so that a high-resolution image ...

An application of fluorescence photography to demonstrate wear of the articulating surfaces of prosthetic hip joints. The physical nature and design of the hip prosthesis present considerable lighting difficulties when using conventional lighting methods to record fine abrasions on the articular surface--in particular, specular reflections from the light source. A ...

We have designed, fabricated, and tested a compact, transportable, excitation-emission spectrofluorimeter with optical-fiber light delivery and collection for use in rapid analysis of tissues in a clinical setting. This system provides up to eleven different excitation wavelengths, permitting collection of all the corresponding emission spectra in approximately 600 ms. It ...

The photosystem II (PSII) reaction center in higher plants is susceptible to photoinhibitory molecular damage of its component pigments and proteins upon prolonged exposure to excess light in air. Higher plants have a limited capacity to avoid such damage through dissipation, as heat, of excess absorbed light energy in the ...

We have used confocal fluorescence microscopy and fluorescent calcium indicators to investigate the relationship between light-induced elevation of intracellular calcium ion concentration (Cai) and depolarization in small volumes of cytosol close to the microvillar plasma membrane of the ventral photoreceptor of Limulus polyphemus. We prolonged the latency of the light ...

Fluorescence changes attributed to state transitions have been shown to exist in phycobilisome-containing organisms. Contradictory conclusions have been derived from studies about the mechanism of state transitions carried out either in cyanobacteria or in red algae. In this paper, fluorescence changes induced by light 1 and light 2 are reinvestigated ...

In this paper, we show that stacked lamellar aggregates of the purified chlorophyll a/b light-harvesting antenna complexes (LHCII) and granal thylakoid membranes are capable of undergoing light-induced reversible changes in the chiral macroorganization of the chromophores as well as in the photophysical pathways. In granal thylakoids, the light-induced reversible structural ...

Greenland ice core records provide clear evidence of rapid changes in climate in a variety of climate indicators. In this work, rapid climate change events in the Northern and Southern hemispheres are compared on the basis of an examination of changes in atmospheric circulation developed from two ice cores. High-resolution ...

Total internal reflection aqueous fluorescence has been shown to be capable of achieving spatial resolution in surface contours of about 1 nm. When used with highly structured objects, errors in measurements can arise from light scattered either by the object or within the body of the microscope. We describe how ...

Steady-state fluorescence polarization measurements provide a relatively simple method for investigating the orientation of molecular components in ordered biological systems. However, the observed fluorescence polarization ratios also depend on any mobility of the fluorophores on the time scale of the fluorescence lifetime. Such mobility commonly arises from incomplete immobilization of ...

In a confocal theta fluorescence microscope, two objective lenses with circular apertures are used, one to illuminate the sample and the other to detect the emitted light at an angle to the illumination axis. We show that annular illumination and detection apertures lead to a reduction in the extent of ...

A simple approach to quantitative determination of antioxidant capacity of rat liver homogenate is proposed. It consists of measuring chemiluminescence generated by a suitable system "detector" for .OH radicals produced from sodium perborate. The system generating the light signal contained luminol and compounds producing enhancement of light emission, such as ...

Use of near infrared instead of visible light would markedly improve tissue penetration, making larger tumors candidates for photochemotherapy. Because common photesensitizers exhibit virtually no absorption in this wavelength region, conditions are required where the simultaneous action of two photons is possible. Healthy tissue (rat ears), sensitized by hematoporphyrin derivative, ...

A diaminobenzidine posttreatment employing osmium tetroxide and potassium ferrocyanide was successfully used to intensify the diaminobenzidine stain formed by photoconversion of immunofluorescent labelling. Lactoferrin labelled granules became visible following the photoconversion process. Adequate diaminobenzidine staining was obtained after irradiating the cytospin preparations with ultraviolet light for 30-40 min. The diaminobenzidine ...

1. The objective of this study was to develop a physiologically based method to evaluate the neurotoxic potential of drug candidates in vitro. Rat embryo midbrain cells were grown in micromass culture, and the movement of mitochondria labelled with the fluorescent dye rhodamine 123 was quantified in fasciculated neurites, using ...

The role of superoxide in the mechanism of photoinactivation of the secondary donors of the reaction center of photosystem II membranes depleted of Mn by extraction with NH2OH plus EDTA (NH2OH/EDTA-PSII) was assessed. EPR analyses (g = 2 region) in continuous light, optical kinetic spectrophotometric analyses of P680+ and Car+, ...

The most difficult impediments to transcutaneous optical sensing are the absorbance and scatter of light caused by skin and the lack of fluorescent sensing probes which can be excited at wavelengths over 600 nm. Furthermore, current optical sensing techniques rely on absorbance or fluorescence intensity measurements, both of which are ...

Several Ca-sensitive fluorescent dyes (fura-2, mag-fura-2 and Calcium Green-5N) were used to measure intracellular calcium ion concentration, Cai, accompanying light-induced excitation of Limulus ventral nerve photoreceptors. A ratiometric procedure was developed for quantification of Calcium Green-5N fluorescence. A mixture of Calcium Green-5N and a Ca-insensitive dye, ANTS, was injected in ...

A video technique is described which uses a fluorescent dye as a tracer to quantify dermal deposition of chemicals such as pesticides. The subject stands inside a dodecahedral arrangement of ultraviolet (u.v.) strip-lights, which cause a given area of dye to fluoresce with a consistent intensity over a range of ...

The mesophyll of sugar beet (Beta vulgaris L.) leaves emits red (chlorophyll a) fluorescence and blue-green fluorescence when excited with ultraviolet light. The intensity of blue-green fluorescence was increased in mesophylls affected by iron deficiency. This increase was large and progressive. It was concomitant with a decrease of photosynthetic pigments ...

Fluorescence studies of NADH and various dyes in tissue are complicated by changes in light absorption, causing spurious results. Methods were developed to reduce and compensate for changes in light absorption in perfused rat hearts, subjected to normoxia and hypoxia. Isosbestic wavelengths were determined (i.e., absorption independent of oxygenation) in ...

A bench specular microscope, modified to perform as a scanning microfluorometer, was used to make simple and precise measurements of the absorption of visible light by the isolated rabbit cornea. The tissue was scanned while identical FITC dextran solutions were perfused over both the surfaces, and the measured fluorescence levels ...

We report the first time-resolved studies of quenching of fluorescence by light, i.e., "light quenching". The dye 4-(dicyanomethylene)-2-methyl-6-(p-dimethamino)-4H-pyrane (DCM) was excited in the anti-Stokes region from 560-600 nm. At high illumination power the intensities of DCM were sub-linear with incident power. The extent of light quenching was proportional to the ...

The application of chlorophyll fluorescence measurements to screening barley (Hordeum vulgare L.) genotypes for salinity tolerance has been investigated. Excised barley leaves were cut under water and incubated with the cut end immersed in water or in a 100-mM NaCl solution, either in the dark or in high light. Changes ...

Edam type cheese was exposed to sunlight at ambient temperature and to fluorescent light at 5 degrees C. The loss of vitamin B2 (riboflavin) and vitamin A was monitored in both the surface and inner layers of the cheese and the results compared with control samples kept in the dark. ...

It was reported that the significant spectral difference of autofluroescence induced by laser light between cancer and normal tissue. A fluorescence bronchoscope system with simple light source and light filter was newly developed. In this paper, the detection of autofluorescence from bronchogenic dysplasia with this system was reported.

PURPOSE: To document quantitatively the fluorescence in the human lens relevant to its interference with visual function. To explain quantitatively the experimental findings relative to loss of visual function. To study the relation between the fluorescence and the light transmission of the lens. METHODS: Three normal lenses, from 22-, 28-, ...

The Hadamard transform is an example of a matrix transform that allows images to be represented in terms of orthogonal basis functions with binary-valued matrix elements. Such basis functions can be displayed on binary amplitude modulating ferroelectric-liquid-crystal-over-silicon spatial light modulators, permitting novel, real-time, and high-speed implementation of the transform on ...

A micro-fiberoptic methodology has been developed for non-invasive, real time measurement of endogenous pyridine nucleotide fluorescence from the surface of the visceral yolk sac (VYS) in intact, viable rat conceptuses. Gestational day (GD) 10-12 conceptuses are maintained in a customized perifusion system, which allows for control of oxygenation, as well ...

The technique of 10 GHz frequency-domain fluorometry was used to resolve the complex picosecond intensity and anisotropy decays of the tyrosyl emission of [Leu5] enkephalin. Enhanced resolution of anisotropy decay was obtained by using acrylamide quenching of the tyrosyl fluorescence and global analysis of the frequency-domain anisotropy data obtained with ...

Glycerol stabilizes cyanocob(III)alamin (vitamin B12) against anaerobic photolysis by a high-intensity UV light source or a low-intensity fluorescent light source. The likely mechanism for stabilization by viscosigens is a decrease in diffusion and an enhancement of radical-pair recombination. Glycerol (25% or greater) stabilizes therapeutic doses of vitamin B12 in single-dose ...

When spinach (Spinacia oleracea) leaf discs were incubated in a dark anaerobic environment, the chlorophyll fluorescence yield was much increased relative to the aerobic control. Occasionally, the fluorescence yield of the darkened anaerobic samples approached 80% of the maximum fluorescence. The anaerobic incubation period also induced in a leaf disc ...

1. The influence of fluorescent and incandescent artificial lighting in a 16L:8D day/night schedule on number and intensity of movements, and on total, resting and activity-related energy expenditure was investigated. 2. Fluorescent light showed the same positive correlation between light intensity and physical activity at all activity levels as was ...