SEARCH · Search PubMed

Results for “Lighting”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5Linked to original sources

PubMed1993

Light-evoked modulation of basolateral membrane Cl- conductance in chick retinal pigment epithelium: the light peak and fast oscillation.

1. We studied the ionic mechanism of the light-peak voltage of the DC electroretinogram (DC ERG) in an in vitro preparation of chick neural retina-retinal pigment epithelium (RPE)-choroid. The light peak originates from a depolarization of the RPE basolateral (basal) membrane, associated with an increase in its conductance. Using conventional and Cl(-)-selective microelectrodes, we tested the hypothesis that the light-peak voltage is generated by an increase in Cl- conductance (gCl) of the basolateral (basal) membrane. 2. Perfusion of the RPE basal membrane with 4,4'-diisothiocyanostilbene-2,2'-disulfonate (DIDS), a known blocker of gCl in chick RPE, suppressed both the light-peak depolarization and the accompanying conductance increase of the basal membrane. 3. Using sustained transepithelial current to clamp the basal membrane potential at different levels, we estimated the reversal potential of the light peak. At membrane potentials above the equilibrium potential for Cl- (ECl = -40 +/- 10 mV mean +/- SE), light-peak polarity was reversed. Current-voltage (I-V) curves measured in the dark and at the peak of the light peak also gave a reversal potential in the same range as ECl. In addition, shifting ECl by changing intracellular Cl- (aCli) via passage of transepithelial current or perfusing the apical side of the RPE with the Cl- uptake blocker, furosemide, shifted the light-peak reversal potential in the same direction as the change in ECl. 4. The transference number for Cl-, TCl, was estimated from step decreases in basal Cl- and increased from 0.20 +/- 0.01 in the dark to 0.31 +/- 0.01 during the light peak. These results indicate an average increase of 55% in the relative conductance of the basal membrane for Cl-. 5. Light-evoked changes in aCli, measured with Cl(-)-selective microelectrodes, were too small to account for the change in basal membrane potential during the light peak. These data strongly support the hypothesis that the light peak originates from an increase in RPE basal membrane permeability to Cl-. 6. We also obtained support for the model of Joseph and Miller that the fast-oscillation trough of the DC ERG, generated by a delayed basal membrane hyperpolarization of the RPE, originates from light-evoked modulation of the Cl- transport pathway. Perfusing either the apical side of the RPE with furosemide or the basal side with DIDS suppressed the fast oscillation. The delayed basal hyperpolarization reversed polarity at membrane potentials positive to ECl.(ABSTRACT TRUNCATED AT 400 WORDS)

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed2003

Alleviation of constant-light-induced photoreceptor degeneration by adaptation of adult albino rat to bright cyclic light.

PURPOSE: To further test the hypothesis that light-adaptation-mediated photoreceptor protection works through inhibition of apoptosis by activation and/or upregulation of neuroprotective molecules. METHODS: Albino rats were born and raised in 5-lux cyclic light (12 hours OFF and ON). At 8 weeks of age, animals were adapted to 400-lux cyclic light for different periods. Light damage was induced by exposure to constant light for 1 day at an illumination of 1700 lux. Animals were killed, and their eyes were removed for morphometric and biochemical analysis. TUNEL assay was used to evaluate photoreceptor cell apoptosis and Western blot analyses were used to determine the levels of basic fibroblast growth factor (bFGF), neuronal nitric oxide synthase (nNOS), and caspase-3. RESULTS: Exposure of dim-reared rats to constant light for 1 day dramatically increased TUNEL-positive cells in the outer nuclear layer. Adaptation to 400-lux bright cyclic light for 4 days significantly reduced TUNEL-positive cells induced by exposure to constant light, which correlated with a significant increase in bFGF expression. Compared with control retinas, caspase-3 levels were not changed by exposure to constant light or after adaptation to 400 lux. There was a significant increase in nNOS level in the constant-light-exposed group, but not in the group adapted to 400-lux bright light before exposure to constant light. CONCLUSIONS: The retina of the adult rat can rapidly upregulate neuroprotective mechanisms when switched from dim to bright cyclic light. Identification of the molecules involved in this process may allow rational development of therapeutic approaches to treat retinal degenerative diseases.

Adaptation, Ocular↗

PubMed2006

Protective effect of crocin against blue light- and white light-mediated photoreceptor cell death in bovine and primate retinal primary cell culture.

PURPOSE: The present study was performed to investigate the effect of crocin on blue light- and white light-induced rod and cone death in primary retinal cell cultures. METHODS: Primary retinal cell cultures were prepared from primate and bovine retinas. Fifteen-day-old cultures were exposed to blue actinic light or to white fluorescent light for 24 hours. Cultures were treated by the addition of different concentrations of crocin for 24 hours before light exposure or for 8 hours after light exposure. Cultures kept in the dark were used as controls. Green nucleic acid stain assay was used to evaluate cell death. Rods and cones were immunolabeled with specific antibodies and counted. TUNEL labeling was used to detect fragmented DNA in fixed cells after light exposure. RESULTS: Primary retinal cell cultures contained a mixture of retinal cells enriched in photoreceptors, bipolar cells, and Müller cells. Twenty-four-hour exposure to blue and white light induced death in 70% to 80% of the photoreceptors in bovine and primate retinal cell cultures. Crocin protected the photoreceptors against blue light- or white light-mediated damage in a concentration-dependent manner with an EC50 of approximately 30 microM. TUNEL assays confirmed that crocin protected photoreceptors from light damage. CONCLUSIONS: These results show that blue and white light selectively induce rod and cone cell death in an in vitro model. Crocin protects retinal photoreceptors against light-induced cell death.

Animals↗

PubMed1991

Treatment of seasonal affective disorder with green light and red light.

OBJECTIVE: This study sought to determine whether an equal photon density of green light is superior to red light in treating seasonal affective disorder. METHOD: After recruitment through the media, 20 outpatients with seasonal affective disorder participated in a balanced-order crossover trial of 1 week of green light therapy compared with 1 week of red light therapy. Each treatment consisted of 2 hours of daily light treatment at home in the early morning. Ultraviolet light was excluded from both treatment conditions. The photon densities of the two treatments (2.3 x 10(15) photons/sec per cm2) were similar to those used in previous studies of therapy with 2500-lux white light. Fourteen patients completed the study. At least 1 week separated each treatment period to allow time for relapse. Effectiveness of treatment was assessed by analysis of variance of changes in ratings on the Hamilton Rating Scale for Depression. RESULTS: Although patients' expectations of the two treatments were similar, green light induced greater antidepressant effects than red light. A Sequence by Color interaction was also demonstrated. CONCLUSIONS: Green light provides a treatment effect superior to that of red light and similar to that seen in previous studies with white light. These results are consistent with the hypothesis that retinal photoreceptors mediate the antidepressant response in seasonal affective disorder. Identifying optimal wavelengths for light treatment is important in optimizing phototherapy efficacy.

Ambulatory Care↗

PubMed2002

Bright light exposure at night and light attenuation in the morning improve adaptation of night shift workers.

With practical applicability in mind, we wanted to observe whether nocturnal alertness, performance, and daytime sleep could be improved by light exposure of tolerable intensity and duration in a real work place. We also evaluated whether attenuating morning light was important in adaptation of real night shift workers. Twelve night shift nurses participated in this study. The study consisted of three different treatment procedures: Room Light (RL), Bright Light (BL), and Bright Light with Sunglasses (BL/S). In RL, room light exposure was given during the night shift and followed by 1 hr exposure to sunlight or 10,000 lux light the next morning (from 08:30 to 09:30). In BL, a 4-hour nocturnal light exposure of 4,000-6,000 lux (from 01:00 to 05:00) was applied and followed by the same morning light exposure as in RL. In BL/S, the same nocturnal light exposure as in BL was done with light attenuation in the morning. Each treatment procedure was continued for 4 days in a repeated measures, cross-over design. Nocturnal alertness was measured by a visual analog scale. Computerized performance tests were done. Daytime sleep was recorded with actigraphy. The most significant overall improvement of sleep was noted in BL/S. BL showed less improvement than BL/S but more than RL. Comparison of nocturnal alertness among the 3 treatments produced similar results: during BL/S, the subjects were most alert, followed by BL and then by RL. Real night shift workers can improve nocturnal alertness and daytime sleep by bright light exposure in their work place. These improvements can be maximized by attenuating morning light on the way home.

Adaptation, Physiological↗

PubMed2026

Blue light therapy delivered through light glasses improves sleep quality and daytime sleepiness in Parkinson's disease: A randomized trial.

BackgroundSleep disturbances, including excessive daytime sleepiness (EDS) and fragmented nocturnal sleep, are common in Parkinson's disease (PD) and significantly reduce quality of life. This pilot study evaluated the efficacy of a novel approach using blue light, delivered via dedicated glasses with integrated LED lights, to improve sleep and non-motor symptoms.MethodsRandomised, placebo-controlled, single-blind pilot study with a 2-week light intervention. Participants were assessed at baseline, two weeks, and five weeks. The study was designed to evaluate between- and within-group changes. Participants were randomly allocated to receive blue light therapy (n = 15) or red light placebo (n = 15), delivered via LED-integrated glasses for one hour, twice daily, given for a 2-week period. Primary outcome was improvement in sleep quality, assessed via the Pittsburgh Sleep Quality Index. Secondary outcomes included diary-based sleep outcomes, excessive daytime sleepiness, mood, anxiety, and motor symptoms.ResultsThere was a significant group × time effect with blue light therapy leading to better Pittsburgh Sleep Quality Index scores (p = 0.021). Between-group analyses showed that at two weeks a trend toward significance was observed (p = 0.065), while sleep quality significantly improved at five weeks compared to placebo (p = 0.029) with a large effect size (0.896). Excessive sleepiness improved in the blue light group (p < 0.001), with a reduction in clinically relevant sleepiness from 50.0% to 6.7% (p = 0.005).ConclusionsBlue light therapy delivered through dedicated glasses appeared to show an improvement in sleep quality and daytime sleepiness in individuals with PD. Blue light therapy offers a promising alternative to traditional light therapy utilising lower light intensities and eliminating the need for light boxes.

Aged↗

PubMed1979

Light-Dark Regulation of Starch Metabolism in Chloroplasts: I. Levels of Metabolites in Chloroplasts and Medium during Light-Dark Transition.

In Spinacia oleracea the kinetics of CO(2) fixation, of starch formation, and of changes in the levels of metabolites in chloroplasts and the surrounding medium has been investigated during light-dark and dark-light transitions with isolated intact chloroplasts.The internal level of orthophosphate stays constant throughout a light-dark-light cycle. The concentration of 3-phosphoglycerate in the chloroplasts is about 4 millimolar in the light and decreases in the dark within 3 minutes to about 1.6 millimolar. The level of the hexose monophosphates shows a reverse trend, increasing from about 2.2 millimolar in the light to 6 millimolar in darkness. In the subsequent light period both compounds reach their original levels within 2 minutes. The chloroplastic concentrations of dihydroxyacetone phosphate, of the pentose monophosphates, and of the hexose- and heptose bisphosphates remain constant at about 0.4 millimolar throughout the light-dark-light cycle.In the medium, the concentration of 3-phosphoglycerate increases and dihydroxyacetone phosphate decreases in the dark phase: this is due to an exchange of internal 3-phosphoglycerate for external dihydroxyacetone phosphate. Part of the reimported dihydroxyacetone phosphate is converted into hexose monophosphates via aldolase and fructose bisphosphatase during the first minutes of darkness. Due to the observed exchange transport reactions, the large difference between the transenvelope concentration gradients of 3-phosphoglycerate, dihydroxyacetone phosphate, and orthophosphate which exist in the light, is completely abolished after 2 to 3 minutes in the dark.The kinetics and the magnitudes of the changes of metabolite concentrations during the light-dark-light cycle are compared to the kinetics of starch formation, and their relevance for a possible light-dark regulation of starch synthesis is discussed.

Journal Article↗

PubMed2004

Lighting for the human circadian clock: recent research indicates that lighting has become a public health issue.

The hypothesis that the suppression of melatonin (MLT) by exposure to light at night (LAN) may be one reason for the higher rates of breast and colorectal cancers in the developed world deserves more attention. The literature supports raising this subject for awareness as a growing public health issue. Evidence now exists that indirectly links exposures to LAN to human breast and colorectal cancers in shift workers. The hypothesis begs an even larger question: has medical science overlooked the suppression of MLT by LAN as a contributor to the overall incidence of cancer? The indirect linkage of breast cancer to LAN is further supported by laboratory rat experiments by David E. Blask and colleagues. Experiments involved the implanting of human MCF-7 breast cancer cell xenografts into the groins of rats and measurements were made of cancer cell growth rates, the uptake of linoleic acid (LA), and MLT levels. One group of implanted rats were placed in light-dark (12L:12D) and a second group in light-light (12L:12L) environments. Constant light suppressed MLT, increased cancer cell growth rates, and increased LA uptake into cancer cells. The opposite was seen in the light-dark group. The proposed mechanism is the suppression of nocturnal MLT by exposure to LAN and subsequent lack of protection by MLT on cancer cell receptor sites which allows the uptake of LA which in turn enhances the growth of cancer cells. MLT is a protective, oncostatic hormone and strong antioxidant having evolved in all plants and animals over the millennia. In vertebrates, MLT is normally produced by the pineal gland during the early morning hours of darkness, even in nocturnal animals, and is suppressed by exposure to LAN. Daily entrainment of the human circadian clock is important for good human health. These studies suggest that the proper use and color of indoor and outdoor lighting is important to the health of both humans and ecosystems. Lighting fixtures should be designed to minimize interference with normal circadian rhythms in plants and animals. New discoveries on blue-light-sensitive retinal ganglion cell light receptors that control the circadian clock and how those receptors relate to today's modern high intensity discharge (HID) lamps are discussed. There is a brief discussion of circadian rhythms and light pollution. With the precautionary principle in mind, practical suggestions are offered for better indoor and outdoor lighting practices designed to safeguard human health.

Chronobiology Disorders↗

PubMed2004

Green-light supplementation for enhanced lettuce growth under red- and blue-light-emitting diodes.

Plants will be an important component of future long-term space missions. Lighting systems for growing plants will need to be lightweight, reliable, and durable, and light-emitting diodes (LEDs) have these characteristics. Previous studies demonstrated that the combination of red and blue light was an effective light source for several crops. Yet the appearance of plants under red and blue lighting is purplish gray making visual assessment of any problems difficult. The addition of green light would make the plant leave appear green and normal similar to a natural setting under white light and may also offer a psychological benefit to the crew. Green supplemental lighting could also offer benefits, since green light can better penetrate the plant canopy and potentially increase plant growth by increasing photosynthesis from the leaves in the lower canopy. In this study, four light sources were tested: 1) red and blue LEDs (RB), 2) red and blue LEDs with green fluorescent lamps (RGB), 3) green fluorescent lamps (GF), and 4) cool-white fluorescent lamps (CWF), that provided 0%, 24%, 86%, and 51% of the total PPF in the green region of the spectrum, respectively. The addition of 24% green light (500 to 600 nm) to red and blue LEDs (RGB treatment) enhanced plant growth. The RGB treatment plants produced more biomass than the plants grown under the cool-white fluorescent lamps (CWF treatment), a commonly tested light source used as a broad-spectrum control.

Biomass↗

PubMed1998

Ambient light working times of visible light-cured restorative materials. Does the ISO standard reflect clinical reality?

OBJECTIVES: The aim of this study was to determine whether a custom built light box could reliably reproduce clinical conditions and whether the current ISO standard test for the working time of visible light cured (VLC) materials (ISO. Dental Resin-based Restorative Materials. ISO:4049, 1991) reflected clinical reality. METHOD: The ISO test requires a VLC material to remain homogenous after exposure to an 8 kLux light source for 60 s. The relationship between the intensity of ambient lighting and the working times of visible light-cured (VLC) restorative materials was investigated by exposing 23 different VLC composite resin materials to a range of light intensities and measuring the working time in seconds: (a) under clinical operating conditions; (b) in a custom light box at 24 kLux; and (c) at 8 kLux in the light box. Working times were determined by placing 0.06 g samples between two glass plates and gently rotating until clefts or voids appeared. RESULTS: Clinical lighting conditions (24 kLux) gave a mean working time of 54 s (s.d. 14 s). In the light box at 24 kLux the mean working time was 54 s (s.d. 11 s). At 8 kLux (under otherwise identical conditions) the mean working time was 162 s (s.d. 49 s). SIGNIFICANCE: A 24 kLux illuminance in the laboratory gives an optimal correspondence to operative lighting conditions. This is three times the lighting level required for ISO purposes, and gives more realistic working times.

Analysis of Variance↗

PubMed2002

A comparison of shear bond strengths of orthodontic brackets using various light sources, light guides, and cure times.

The objective of this study was to evaluate the effects of different cure times, light sources, and light guides on shear bond strength of orthodontic brackets bonded with Transbond XT (3M Unitek, Monrovia, Calif) to bovine enamel. Specifically, the Power Slot (Reliance Orthodontic Products, Itasca, Ill) light guide was placed on 4 visible light sources to compare shear bond strengths and recommended cure times with the light guides provided with each light source. We randomly divided 240 bovine mandibular incisors into 16 groups; each group consisted of 15 teeth mounted in an acrylic block. Each group of teeth was polymerized with a specific light and light guide combination. Eight groups were sheared after 5 minutes and the remaining 8 groups after 24 hours. After bonding, all brackets were subjected to a shear force with a testing machine. Overall, there was a significant increase in bond strengths of the 24-hour groups compared with the 5-minute shearing groups. However, there were no statistical differences (P =.05) within the 24-hour test groups or the 5-minute test groups. The results of this study indicate that, compared with standard light guides, the Power Slot and the Turbo Tip (Ormco Sybron Dental Specialties, Orange, Calif) light guides can significantly reduce the curing times (10 seconds per bracket; 5 seconds each from mesial and distal) without affecting their shear bond strengths. Therefore, the Power Slot and the Turbo Tip light guides with their collimation of visible light to increase its intensity can be recommended as advantageous alternatives for curing composite resins for orthodontic bonding procedures.

Analysis of Variance↗

PubMed1989

Light-controlled adaptation kinetics in Phycomyces: evidence for a novel yellow-light absorbing pigment.

When sporangiophores of the fungus Phycomyces blakesleeanus adapt from high to low fluence rate, dark adaptation (sensitivity recovery) can be accelerated by dim subliminal light [Galland et al. (1989) Photochem. Photobiol. 49, 485-491]. We measured fluence rate-response curves for this acceleration under the following conditions. After sporangiophores were initially adapted symmetrically to a fluence rate of 1 W m-2 (447 nm), they were exposed to unilateral subliminal light (subthreshold for phototropism) of variable wavelength and fluence rate, and then to unilateral test light (447 nm) of fluence rate either 10(-3) or 10(-5) W m-2. The duration of the subliminal light was chosen so that phototropism would not occur during this period. Phototropic latencies could be shortened by subliminal light that was less intense than the test light by several orders of magnitude. In experiments with the final unilateral light of fluence rate 10(-3) W m-2, the 447 nm subliminal light had a threshold (for the acceleration effect) of about 10(-11) W m-2. Yellow light of wavelength 575 nm, which itself is extremely ineffective for phototropism was extremely effective in shortening phototropic latencies in response in response to the test light. At 575 nm, the threshold was about 2 x 10(-12) W m-2. Conversely, near-UV light of wavelength 347 nm, which is highly effective for phototropism, was relatively ineffective (threshold approximately 7 x 10(-8) W m-2) in shortening the phototropic latency. Our results suggest the presence of a novel yellow-light absorbing pigment in Phycomyces that specifically regulates dark adaptation.(ABSTRACT TRUNCATED AT 250 WORDS)

Dark Adaptation↗

PubMed1983

Effects of extracellular calcium and of light adaptation on the response to dim light in honey bee drone photoreceptors.

Light responses in honey bee drone photoreceptors were recorded with intracellular micro-electrodes in superfused slices of retina. The effects of changes in extracellular calcium on the size and the shape of the response to dim light were studied and compared with the effects of light adaptation. Dim light stimuli were used so that the amplitude of the response was linearly related to the number of the photons absorbed, the effects of voltage-dependent mechanisms were negligible and no detectable light adaptation was produced by the stimulus. Lowering the extracellular calcium concentration increased the amplitude and the duration of the response. Raising the extracellular calcium concentration produced the opposite effects. Changing the extracellular calcium concentration modified the response without altering either the linearity of the intensity--response relation or the resting membrane potential in the dark. Light adaptation decreased the amplitude and the duration of the response in a manner that could be quantitatively simulated, in the same photoreceptors, by an increase in the extracellular calcium concentration. Changing the extracellular calcium concentration, or light-adapting the preparation, modified the response without altering its early depolarizing phase. Lowering external calcium either did not affect, or slightly increased, the maximum rate of the light-induced depolarization; raising external calcium, or light-adapting the preparation, either did not affect, or slightly decreased, the maximum rate of the light-induced depolarization. The experimental data can be quantitatively described by a mathematical model with the basic assumption that calcium acts in the process of light adaptation by decreasing the mean open time of the light-activated channels.

Adaptation, Ocular↗

PubMed2003

Comparison of quartz-tungsten-halogen, light-emitting diode, and plasma arc curing lights.

PURPOSE: This study determined which light source was best at photopolymerizing five representative brands of resin composite. The hypothesis was that there would be no difference in the hardness of the composites when irradiated by any of the lights. MATERIALS AND METHODS: Six curing light/tip combinations were used to photopolymerize five resin composites. In accordance with the manufacturer's instructions, the PAC light was used for 3 s and the high intensity QTH light was used for 5 s. The other QTH and LED lights were used for 40 s. To represent the clinical environment, the samples were irradiated at a distance of 2 and 9 mm away from the tip of the light guide. The Knoop hardness was measured at the top and bottom of the composites after 15 min and again at 24 h. The hardness data were compared using a general linear model analysis with Sidak's adjustment for multiple comparisons with p < 0.01 as the level of significance. RESULTS: The 6 curing light/tip combinations had different effects on the hardness of the 5 composites (p < 0.01). The two LED lights could not cure the neutral shade of Pyramid Enamel in 40 s. As the distance increased from 2 to 9 mm, the decrease in hardness was not similar amongst the different light/tips and composite combinations (p < 0.0012). The curing light/tip combination which delivered the greatest total energy produced the hardest specimens. CONCLUSION: 1) The 6 curing light/tip combinations had different effects on the hardness of the 5 composites (p < 0.01). 2) Neither of the two LED lights used was able to adequately polymerize the five resin composites tested. 3) The QTH light, which delivered the greatest total energy, always produced the hardest resin composite. 4) When the distance of the composites from the light guides was increased, the effect on their hardness was not the same for all light/tip combinations. It is therefore not possible to predict the performance of a curing light at 9 mm based upon power density measurements or hardness data recorded when the tip of the light guide is 2 mm away.

Composite Resins↗

PubMed1989

Myosin light chains of guinea-pig striated muscles. Similarities and differences with rat myosin light chains.

1. Myosin light chains of guinea-pig striated muscles have been screened by two-dimensional gel electrophoresis and compared to rat myosin light chains. 2. The fast type light chains 1F and 3F, slow type light chains 1S and 2S, and embryonic type light chain 1E are shown to differ in the two rodents; only the fast type light chains 2F co-electrophorese on the gel. 3. In guinea-pig, as in rat, ventricle muscle light chains appear the same as the 1S and 2S light chains and atrial light chain type 1 the same as the 1E light chain. We show that this embryonic light chain of guinea-pig myosin is difficult to identify and may be confused with the adult 1F light chain.

Animals↗

PubMed2006

Bright cyclic light rearing-mediated retinal protection against damaging light exposure in adrenalectomized mice.

Previous studies have shown that albino rats and mice raised in bright cyclic light are protected from light-induced retinal damage. We tested if the stress response mediated by the adrenal grand is involved in the initiation of this neuroprotective phenomenon. Balb/c mice that were adrenalectomized (Adrex) or sham operated at 28 days of age were kept under dim (5 lux) or bright (400 lux) cyclic light (12h on/off) for 2 weeks. Thereafter, their electroretinogram (ERG), outer nuclear layer (ONL) thickness and area, and plasma corticosterone levels were measured in animals with (dim+light and bright+light groups) and without (dim and bright groups) damaging light exposure (3000 lux for 24 h). In the dim+light group, a- and b-wave amplitudes and the ONL thicknesses and areas were significantly higher in the Adrex animals than the sham animals, indicating that adrenalectomy itself yielded retinal protection. In the Adrex animals, the ONL areas were significantly larger in the bright+light group than the dim+light group, indicating that bright cyclic light rearing yielded further retinal tolerance, even in the absence of the adrenal gland. In sham animals, the plasma corticosterone concentration did not change between the dim and the light groups. Accordingly, glucocorticoid secreted from the adrenal gland is not likely to be required for the mechanisms of the light-adaptation neuroprotection phenomenon in mice.

Adaptation, Physiological↗

PubMed1999

Prophylactic treatment of seasonal affective disorder (SAD) by using light visors: bright white or infrared light?

BACKGROUND: Thirty-eight patients with SAD participated in a light visor study addressing two questions. 1. Can the development of a depressive episode be prevented by daily exposure to bright light started before symptom onset in early fall and continued throughout the winter? 2. Does the light have to be visible in order to have beneficial effects? METHODS: Three groups participated in the study: I (n = 14) received bright white light (2500 lux); II, (n = 15) received infrared light (0.18 lux); III (n = 9, control group) did not receive any light treatment at all. RESULTS: Infrared light is just as effective as bright white light. Both are more effective than the control condition. CONCLUSIONS: Light visors can be effectively used to prevent the development of SAD. The fact that exposure to infrared light was as effective as exposure to bright white light questions the specific role of visible light in the treatment of SAD.

Adult↗

PubMed1999

Differential responses to different light spectral ranges of violaxanthin de-epoxidation and accumulation of Cbr, an algal homologue of plant early light inducible proteins, in two strains of Dunaliella.

Unicellular green algae of the genus Dunaliella, similar to higher plants, respond to light stress by enhanced de-epoxidation of violaxanthin and accumulation of Cbr, a protein homologous to early light inducible proteins (Elips) in plants. These proteins belong to the superfamily of chlorophyll a/b binding proteins. Two Dunaliella strains, D. bardawil and D. salina, were compared for these two responses under light in the UVA, blue, green and red spectral ranges. In D. bardawil, the two stress responses were similarly induced under UVA, blue or red light and to a lesser extent under green light. In D. salina, a similar spectral range dependence was exhibited for violaxanthin de-epoxidation. However, Cbr accumulated only under UVA or blue light but not under green or red light. A strong synergistic effect of a low dose of blue light superimposed on red light resulted in Cbr accumulation. These results reveal strain-specific differences in spectral range requirements of the two light-stress responses. In the two strains, violaxanthin de-epoxidation is triggered under photosynthetically-active spectral ranges but at least in D. salina, Cbr accumulation appears to require a specific light signal additionally to a signal(s) generated by light stress.

Journal Article↗