Normal Light Conditions Research Articles

A Study of Reading Fatigue

Compared to traditional printed books, digital e-book readers may cause consumers to read overtime and reading fatigue or even vision injury. Therefore, it is needed to study on reading fatigue based on different reading illuminants, i.e. under brighter, normal, dim, and LED lighting conditions, and different book content carriers, i.e. printed bond paper, Kindle, and iPad, to evaluate degrees of reading fatigue. Overall, the results showed that the reading illuminants are critical and highly affect vision fatigue; especially the LED light resulted in greater reading fatigue. Printed paper can cause less degree of fatigue or even no vision fatigue at all as long as with sufficient illuminant.

TAC7, an essential component of the plastid transcriptionally active chromosome complex, interacts with FLN1, TAC10, TAC12 and TAC14 to regulate chloroplast gene expression in Arabidopsis thaliana

Transcriptionally active chromosome (TAC) is a fraction of protein/DNA complexes with RNA polymerase activity in the plastid. However, the function of most TAC proteins remains unknown. Here, we isolated two allelic mutants of the gene for a TAC component, TAC7, and performed functional analysis in plastid gene expression and chloroplast development in Arabidopsis. tac7-1 is a mutant with a premature translation termination isolated from a population treated with ethyl methane sulfonate, and tac7-2 is a transfer-DNA tagging mutant. Both of them showed an albino phenotype when grown under normal light conditions, and a few appressed membranes were observed inside the defective chloroplasts. These data indicate that TAC7 is important for thylakoid biogenesis. The TAC7 gene encodes an uncharacterized 161 amino acids polypeptide localized in chloroplast. The transcriptional levels of plastid-encoded polymerase (PEP)-dependent genes were downregulated in tac7-2, suggesting that PEP activity was decreased in the mutant. Yeast two-hybrid assay shows that TAC7 can interact with the four TAC components including FLN1, TAC10, TAC12 and TAC14 which are involved in redox state changes, phosphorylation processes and phytochrome-dependent light signaling, respectively, These data indicate that TAC7 plays an important role for TAC to regulate PEP-dependent chloroplast gene expression and chloroplast development.

Analysis of the light‐sensitivity of the photoreceptor cells of the ataxia and male sterility (AMS) mouse, an Nna1 mutant

We confirmed retinal degeneration in the ataxia and male sterility (AMS) mouse, a mutant of the Nna1 gene, and examined the photosensitivity of the photoreceptors to determine how closely related the intrinsic and extrinsic factors were in triggering photoreceptor cell death. The AMS mice reared in a dark environment did not show atrophy of the outer nuclear layer (ONL) before 4 weeks of age, but in the older mice, retinal atrophy progressed in the same manner as in the AMS mice housed under normal light conditions. Examining the sensitivity to intentional light stimulation revealed the atrophy of the AMS retina to be exacerbated by a weak light. After administering strong light irradiation, equally severe ONL atrophy occurred in both the wild-type and AMS mice. These results indicate that in addition to functional loss of Nna1, another injurious stimulation is necessary to trigger death signals in photoreceptor cells during the postnatal period, but the cells die gradually and autonomously in older age, and that the mutation makes the cells vulnerable to a weak light, but does not increase the number of cells sensitive to strong light stimulation. Thus, these two factors are mutually independent death triggers in AMS photoreceptor cells.

Inactivation of the conserved open reading frame ycf34 of Synechocystis sp. PCC 6803 interferes with the photosynthetic electron transport chain

Ycf34 is a hypothetical chloroplast open reading frame that is present in the chloroplast genomes of several non-green algae. Ycf34 homologues are also encoded in all sequenced genomes of cyanobacteria. To evaluate the role of Ycf34 we have constructed and analysed a cyanobacterial mutant strain. Inactivation of ycf34 in Synechocystis sp. PCC 6803 showed no obvious phenotype under normal light intensity growth conditions. However, when the cells were grown under low light intensity they contained less and smaller phycobilisome antennae and showed a strongly retarded growth, suggesting an essential role of the Ycf34 polypeptide under light limiting conditions. Northern blot analysis revealed a very weak expression of the phycocyanin operon in the ycf34 mutant under light limiting growth in contrast to the wild type and to normal light conditions. Oxygen evolution and P700 measurements showed impaired electron flow between photosystem II and photosystem I under these conditions which suggest that the impaired antenna size is most likely due to a highly reduced plastoquinone pool which triggers regulation on a transcriptional level. Using a FLAG-tagged Ycf34 we found that this protein is tightly bound to the thylakoid membranes. UV–vis and Mössbauer spectroscopy of the recombinant Ycf34 protein demonstrate the presence of an iron–sulphur cluster. Since Ycf34 lacks homology to known iron–sulphur cluster containing proteins, it might constitute a new type of iron–sulphur protein implicated in redox signalling or in optimising the photosynthetic electron transport chain.

Antioxidative response of Golden Agave leaves with different degrees of variegation under high light exposure

Variegated mutants are spotted rare in wild, and especially in the high light (HL) conditions. In addition, these plants are cultivated by a growing number of horticulturists due to their high economic value. In this experiment, the antioxidative response of both albino and green tissues from a mutant plant Golden Agave, which possesses leaves with different degrees of variegation, was investigated under normal or HL exposure, respectively. Severe oxidative stress was observed in green tissues of high albinism leaves (30–40 % albino tissues, muy) over low albinism counterparts (less than 10 % albino tissues, mug). Compared with green tissues, low oxidative damage (relative electrolyte leakage and protein damage) and antioxidant enzyme (SOD, CAT, APX, and GR) activities were observed in the albino than in the adjacent green tissues. Photoinactivation of the CAT and the APX enzyme activities were observed in the albino tissues to a significantly level under HL exposure. In addition, lower redox values (ASC/DHA and GSH/GSSG) and higher levels of reactive oxygen species (ROS) were monitored in the green tissues of the muy over mug mutant even under normal light conditions. This work could help us to understand the HL sensitivity of variegated mutant plants better and allow us to improve variegated mutant plant cultivation skills. At last, the “oxidative stress hypothesis” was introduced to illustrate the reduced evolutionary advantage of plant variegation phenomenon in the discussion.

Characterization of different isoforms of the light-harvesting chlorophyll a/b complexes of photosystem II in bamboo

The major light-harvesting chlorophyll (Chl) a/b complexes of photosystem II (LHCIIb) play important roles in energy balance of thylakoid membrane. They harvest solar energy, transfer the energy to the reaction center under normal light condition and dissipate excess excitation energy under strong light condition. Many bamboo species could grow very fast even under extremely changing light conditions. In order to explain whether LHCIIb in bamboo contributes to this specific characteristic, the spectroscopic features, the capacity of forming homotrimers and structural stabilities of different isoforms (Lhcb1-3) were investigated. The apoproteins of the three isoforms of LHCIIb in bamboo are overexpressed in vitro and successfully refolded with thylakoid pigments. The sequences of Lhcb1 and Lhcb2 are similar and they are capable of forming homotrimer, while Lhcb3 lacks 10 residues in the N terminus and can not form the homotrimeric structure. The pigment stoichiometries, spectroscopic characteristics, thermo- and photostabilities of different reconstituted Lhcbs reveal that Lhcb3 differs strongly from Lhcb1 and Lhcb2. Lhcb3 possesses the lowest Qy transition energy and the highest thermostability. Lhcb2 is the most stable monomer under strong illumination among all the isoforms. These results suggest that in spite of small differences, different Lhcb isoforms in bamboo possess similar characteristics as those in other higher plants.

Arabidopsisplants grown in the field and climate chambers significantly differ in leaf morphology and photosystem components

BackgroundPlants exhibit phenotypic plasticity and respond to differences in environmental conditions by acclimation. We have systematically compared leaves of Arabidopsis thaliana plants grown in the field and under controlled low, normal and high light conditions in the laboratory to determine their most prominent phenotypic differences.ResultsCompared to plants grown under field conditions, the "indoor plants" had larger leaves, modified leaf shapes and longer petioles. Their pigment composition also significantly differed; indoor plants had reduced levels of xanthophyll pigments. In addition, Lhcb1 and Lhcb2 levels were up to three times higher in the indoor plants, but differences in the PSI antenna were much smaller, with only the low-abundance Lhca5 protein showing altered levels. Both isoforms of early-light-induced protein (ELIP) were absent in the indoor plants, and they had less non-photochemical quenching (NPQ). The field-grown plants had a high capacity to perform state transitions. Plants lacking ELIPs did not have reduced growth or seed set rates, but their mortality rates were sometimes higher. NPQ levels between natural accessions grown under different conditions were not correlated.ConclusionOur results indicate that comparative analysis of field-grown plants with those grown under artificial conditions is important for a full understanding of plant plasticity and adaptation.

Compensatory Head Movements in Blowflies Walking Freely on Differently Structured Substrates

Event Abstract Back to Event Compensatory Head Movements in Blowflies Walking Freely on Differently Structured Substrates Daniel Kress1, 2* and Martin Egelhaaf1, 2 1 Bielefeld University, Neurobiology, Germany 2 CITEC Center of Excellence Cognitive Interaction Technology, Germany Many insects such as flies and bees rely heavily on visual signals in order to obtain functionally relevant information about their environment. This is especially true for goal directed behaviors like the approach to an object of interest. The quality of these visual signals may deteriorate in walking animals as a consequence of the kinematic properties of the locomotor apparatus, which may lead to movements of the eyes contingent on the walking cycle. Moreover, locomotion on a rough terrain can cause huge unintended retinal image shifts. Consequently, various species evolved strategies to compensate for these unintended image shifts and, thus, to support visual information processing. An example are compensatory head movements, which stabilize the gaze and, thus, the orientation of the visual reference system by counterbalancing changes in body attitude during self-movement. Up to now, it is still unclear to what extent walking insects are able to stabilize their gaze when walking on structured ground. Furthermore, due to the complex multimodal control of head movements, it is unknown to what extent the visual system is involved in controlling potential stabilizing movements. To tackle these open questions, we analyzed by stereo high-speed video compensatory head movements of blowflies walking freely on differently structured substrate types. We found that even pronounced asperities of the ground structure with bumps of almost the size of the animal were largely compensated by the walking machinery of the blowfly. As a consequence, body roll and pitch movements are not much, but significantly larger than those on even ground. Pitch and roll fluctuations of the head were even smaller than those of the body on all tested substrates, emphasizing the significance of compensatory head/body coordination in flies when walking across difficult terrain. To assess the influence of the visual system on this compensatory performance, we filmed blowflies walking on different substrates in darkness (under unperceivable infrared illumination). Interestingly, blowflies changed their walking style in the dark and seemed to use their forelegs as tactile probes to get mechanosensory information. Nonetheless, head and body fluctuations were similar to those under normal light conditions, indicating that the control system mediating compensatory head movements during walking works fine without visual input. As the gaze of freely walking blowflies is apparently never completely rotationally stabilized even during walks on flat ground, we are currently analyzing how these residual fluctuations affect the spatial vision and fixation behavior during goal directed tasks in which the blowflies approach an attractive object. Figure 1 Keywords: Blowfly, Compensation, gaze, head movement, insect, stabilization, Vision, Walking Conference: Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012. Presentation Type: Poster (but consider for student poster award) Topic: Sensory: Vision Citation: Kress D and Egelhaaf M (2012). Compensatory Head Movements in Blowflies Walking Freely on Differently Structured Substrates. Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00079 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 30 Mar 2012; Published Online: 07 Jul 2012. * Correspondence: Mr. Daniel Kress, Bielefeld University, Neurobiology, Bielefeld, 33615, Germany, daniel.kress@uni-bielefeld.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract Supplemental Data The Authors in Frontiers Daniel Kress Martin Egelhaaf Google Daniel Kress Martin Egelhaaf Google Scholar Daniel Kress Martin Egelhaaf PubMed Daniel Kress Martin Egelhaaf Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Room temperature synthesis of PbSe quantum dots in aqueous solution: stabilization by interactions with ligands

An aqueous route of synthesis is described for rapid synthesis of lead selenide quantum dots (PbSe QDs) at room temperature in an attempt to produce water-soluble and stable nanocrystals. Several thiol-ligands, including thioglycolic acid (TGA), thioglycerol (TGC), 3-mercaptopropionic acid (MPA), 2-mercaptoethylamine hydrochloride (MEA), 6-mercaptohexanoic acid (MHA), and l-cysteine (l-cys), were used for capping/stabilization of PbSe QDs. The effects of the ligands on the stability of PbSe QDs were evaluated for a period of two months at room temperature under normal light conditions and at 4 °C in the dark. The TGA- and MEA-capped QDs exhibited the highest stability prior to purification, almost two months when kept in the dark at 4 °C. However, the stability of TGA-capped QDs was reduced substantially after purification to about 5 days under the same conditions, while MEA-capped QDs did not show any significant instability. The stabilization energies of Pb-thiolate complexes determined by theoretical DFT simulations supported the experimental results. The PbSe QDs capped with TGA, MPA and MEA were successfully purified and re-dispersed in water, while those stabilized with TGC, MHA and l-cys aggregated during purification attempts. The purified PbSe QDs possess very susceptible surface resulting in poor stability for about 30-45 min after re-dispersion in water. In the presence of an excess of free ligand, the stability increased up to 5 days for TGA-capped QDs at pH 7.19, 9-12 days for MPA-capped QDs at pH 7.3-7.5 and 45-47 days for MEA-capped QDs at pH 7.35. X-Ray diffraction (XRD) results showed that the QDs possess a cubic rock salt structure with the most intense peaks located at 2θ = 25.3° (200) and 2θ = 29.2° (100). TEM images showed that the size of the QDs ranges between 5 and 10 nm. ICP-MS results revealed that Pb : Se ratios were 1.26, 1.28, 3.85, 1.18, and 1.31 for the QDs capped with TGA, MPA, MEA, l-cys, and TGC, respectively. The proposed method is inexpensive, simple and utilizes environmentally friendly chemicals and solvents.

The membrane-tethered transcription factor ANAC089 serves as redox-dependent suppressor of stromal ascorbate peroxidase gene expression

The stromal ascorbate peroxidase (sAPX) functions as central element of the chloroplast antioxidant defense system. Its expression is under retrograde control of chloroplast signals including redox- and reactive oxygen species-linked cues. The sAPX promoter of Arabidopsis thaliana was dissected in transient reporter assays using mesophyll protoplasts. The study revealed regulatory elements up to –1868 upstream of the start codon. By yeast-one-hybrid screening, the transcription factor ANAC089 was identified to bind to the promoter fragment 2 (–1262 to –1646 bp upstream of translational initiation). Upon mutation of the cis-acting element CACG, binding of ANAC089 was abolished. Expression of a fused fluorescent protein version and comparison with known endomembrane markers localized ANAC089 to the trans-Golgi network and the ER. The transcription factor was released upon treatment with reducing agents and targeted to the nucleus. Transactivation assays using wild type and mutated versions of the promoter showed a partial suppression of reporter expression. The data indicate that ANAC089 functions in a negative retrograde loop, lowering sAPX expression if the cell encounters a highly reducing condition. This conclusion was supported by reciprocal transcript accumulation of ANAC089 and sAPX during acclimation to low, normal, and high light conditions.

Sponge Transgenic Mouse Model Reveals Important Roles for the MicroRNA-183 (miR-183)/96/182 Cluster in Postmitotic Photoreceptors of the Retina

MicroRNA-183 (miR-183), miR-96, and miR-182 comprising the miR-183/96/182 cluster are highly expressed in photoreceptor cells. Although in vitro data have indicated an important role for this cluster in the retina, details of its in vivo biological activity are still unknown. To observe the impact of the miR-183/96/182 cluster on retinal maintenance and light adaptation, we generated a sponge transgenic mouse model that disrupted the activities of the three-component microRNAs simultaneously and selectively in the retina. Although our morphological and functional studies showed no differences between transgenic and wild type mice under normal laboratory lighting conditions, sponge transgenic mice displayed severe retinal degeneration after 30 min of exposure to 10,000 lux light. Histological studies showed that the outer nuclear layer thickness was dramatically reduced in the superior retina of transgenic mice. Real time PCR experiments in both the sponge transgenic mouse model and different microRNA stable cell lines identified Arrdc3, Neurod4, and caspase-2 (Casp2) as probable downstream targets of this cluster, a result also supported by luciferase assay and immunoblotting analyses. Further studies indicated that expression of both the cluster and Casp2 increased in response to light exposure. Importantly, Casp2 expression was enhanced in transgenic mice, and inhibition of Casp2 partially rescued their light-induced retinal degeneration. By connecting the microRNA and apoptotic pathways, these findings imply an important role for the miR-183/96/182 cluster in acute light-induced retinal degeneration of mice. This study demonstrates a clear involvement of miRs in the physiology of postmitotic cells in vivo.

Leucocyte Infiltration in Lymphoid Organs and Peritoneal Cavity upon Immunization: Dependence on Circadian Rhythmicity and Melatonin 24-H Profile

Circadian rhythmicity and melatonin secretion influence many functions in mammals, including the immune system function. The aim of our study is to investigate the effect of suppression of melatonin synthesis (caused by constant lighting) on the quantity of leucocytes in immunized BALB/c mice. The mice were kept under different lighting conditions: (1) customary environmental lighting; (2) constant exposure to light; (3) exposure to light and daily melatonin treatment. The disrupted melatonin synthesis had no effect on the number of cells in the thymus, bone marrow, spleen, lymph nodes and Peyer's patches of immunized mice. However, the mice kept under constant light had an increased number of leucocytes in the peritoneal cavity when immunizations were performed in the evening. Melatonin treatment normalized the cell number. When the immunizations were performed in the morning, the numbers of cells in peritoneum of mice kept under constant lighting conditions were lower compared to mice exposed to normal lighting conditions. The number of cells of mice kept in normal light/dark conditions was significantly higher when the immunizations were performed in the morning. The number of peritoneal cells, however, did not depend on the immunization time when mice were kept under constant lighting. In conclusion, the amount of peritoneal cells in mice immunized with T cell-dependent antigens seems to be related to circadian rhythmicity, melatonin production and immunization timing.

Interleukin-1β Inhibition Prevents Choroidal Neovascularization and Does Not Exacerbate Photoreceptor Degeneration

The pro-inflammatory cytokine IL-1β has been shown to promote angiogenesis. It can have a neurotoxic or neuroprotective effect. Here, we have studied the expression of IL-1β in vivo and the effect of the IL-1 receptor antagonist on choroidal neovascularization (CNV) and retinal degeneration (RD). IL-1β expression significantly increased after laser injury (real time PCR) in C57BL/6 mice, in the C57BL/6 Cx3cr1(-/-) model of age-related macular degeneration (enzyme-linked immunoabsorbent assay), and in albino Wistar rats and albino BALB Cx3cr1(+/+) and Cx3cr1(-/-) mice (enzyme-linked immunoabsorbent assay) after light injury. IL-1β was localized to Ly6G-positive, Iba1-negative infiltrating neutrophils in laser-induced CNV as determined by IHC. IL-1 receptor antagonist treatment significantly inhibited CNV but did not affect Iba1-positive macrophage recruitment to the injury site. IL-1β significantly increased endothelial cell outgrowth in aortic ring assay independently of vascular endothelial growth factor, suggesting a direct effect of IL-1β on choroidal endothelial cell proliferation. Inhibition of IL-1β in light- and laser-induced RD models did not alter photoreceptor degeneration in Wistar rats, C57BL/6 mice, or RD-prone Cx3cr1(-/-) mice. Our results suggest that IL-1β inhibition might represent a valuable and safe alternative to inhibition of vascular endothelial growth factor in the control of CNV in the context of concomitant photoreceptor degeneration as observed in age-related macular degeneration.

High Survival Rates of Sutchi Catfish, Pangasianodon hypophthalmus, Larvae Reared under Dark Conditions

The sutchi catfish, Pangasianodon hypophthalmus is an important species for aquaculture in Southeast Asia. However, the larvae demonstrate a low survival rate due to their strong cannibalism during rearing. The aim of the present study was to reduce their cannibalism and improve larval rearing methods. Larval rearing experiments were conducted under normal light conditions (following a diel rhythm) and continuous dark conditions with larval densities of 10, 20 and 40 individuals L-1 from hatching day to 20 days old. The trial with 10 individuals L-1 under dark conditions had the highest survival rate. The dark conditions with lower individual densities tended to produce higher survival rates than the light conditions with higher individual densities. Fish body weight on the final day of larval rearing showed that rearing larvae under dark conditions resulted in steady growth similar to growth under light conditions. It seemed that the feeding behavior of sutchi catfish depended on chemo-sense rather than visual sense. This study showed that the cannibalism of sutchi catfish larvae can be reduced by rearing under dark conditions at low densities with adequate access to food. Therefore, it was concluded that rearing under dark conditions is a method for reducing cannibalism and increasing survival rates. © 2011 Academic Journals Inc.

Larval Rearing and Feeding Behavior of African Catfish, Clarias gariepinus under Dark Conditions

The present study was conducted to elucidate the relationship between the larval feeding behavior of African catfish, Clarias gariepinus and their sensory organs. We also sought to reduce the cannibalism and improve larval rearing methods for this species. The feeding behavior of intact and streptomycin-treated larvae was examined under light and dark conditions using Artemia nauplii. The ingestion rates under light versus dark conditions did not vary significantly; furthermore, no difference was observed between intact and streptomycin-treated larvae. These results showed that the feeding behavior of C. gariepinus depends on chemo-sensory senses rather than visual or mechanical senses. In addition, the larvae were reared under normal light conditions (following a diurnal cycle) and continuous dark conditions from the hatching day until they were 20 days old. Although, there was no significant difference, the trials under continuous dark conditions tended to have higher survival rates than those under light conditions. Moreover, the larvae reared under dark conditions showed the same growth rate as those under light conditions. The observations of larval behavior in the present study showed that larval activity increased under dim light conditions; the number of fish resting on the bottom of the aquaria decreased and fewer larvae were bitten by other individuals than under light conditions. The results of this study suggest that higher activity of C. gariepinus under dark conditions reduced the rate of cannibalism and resulted in higher rates of survival compared to light conditions. This study suggests that the survival rate of C. gariepinus larvae can be improved under dark or dim light conditions with low larval densities and adequate access to food. © 2011 Academic Journals Inc.

The conserved factor DE-ETIOLATED 1 cooperates with CUL4-DDB1DDB2to maintain genome integrity upon UV stress

Plants and many other eukaryotes can make use of two major pathways to cope with mutagenic effects of light, photoreactivation and nucleotide excision repair (NER). While photoreactivation allows direct repair by photolyase enzymes using light energy, NER requires a stepwise mechanism with several protein complexes acting at the levels of lesion detection, DNA incision and resynthesis. Here we investigated the involvement in NER of DE-ETIOLATED 1 (DET1), an evolutionarily conserved factor that associates with components of the ubiquitylation machinery in plants and mammals and acts as a negative repressor of light-driven photomorphogenic development in Arabidopsis. Evidence is provided that plant DET1 acts with CULLIN4-based ubiquitin E3 ligase, and that appropriate dosage of DET1 protein is necessary for efficient removal of UV photoproducts through the NER pathway. Moreover, DET1 is required for CULLIN4-dependent targeted degradation of the UV-lesion recognition factor DDB2. Finally, DET1 protein is degraded concomitantly with DDB2 upon UV irradiation in a CUL4-dependent mechanism. Altogether, these data suggest that DET1 and DDB2 cooperate during the excision repair process.

Characterization of photosystem II in transgenic tobacco plants with decreased iron superoxide dismutase

Iron superoxide dismutases (FeSODs) play an important role in preventing the oxidative damage associated with photosynthesis. To investigate the mechanisms of FeSOD in protection against photooxidative stress, we obtained transgenic tobacco ( Nicotiana tabacum) plants with severely decreased FeSOD by using a gene encoding tobacco chloroplastic FeSOD for the RNAi construct. Transgenic plants were highly sensitive to photooxidative stress and accumulated increased levels of O 2 •− under normal light conditions. Spectroscopic analysis and electron transport measurements showed that PSII activity was significantly reduced in transgenic plants. Flash-induced fluorescence relaxation and thermoluminescence measurements revealed that there was a slow electron transfer between Q A and Q B and decreased redox potential of Q B in transgenic plants, whereas the donor side function of PSII was not affected. Immunoblot and blue native gel analyses showed that PSII protein accumulation was also decreased in transgenic plants. PSII photodamage and D1 protein degradation under high light treatment was increased in transgenic plants, whereas the PSII repair was not affected, indicating that the stability of the PSII complex was decreased in transgenic plants. The results in this study suggest that FeSOD plays an important role in maintaining PSII function by stabilizing PSII complexes in tobacco plants.

Room-temperature red emission from light-emitting diodes with Eu-doped GaN grown by organometallic vapor phase epitaxy

We obtained room-temperature red emission from GaN-based light-emitting diodes (LEDs) using a Eu-doped GaN (GaN:Eu) as an active layer. The bright emission was observed under normal lighting condition, which is associated with the intra-4f shell transition of Eu 3+ ions. The LED properties depends on the growth condition of GaN:Eu layer. Since the high-quality GaN can be grown at higher growth pressure, the intense electroluminescence (EL) was observed in the LED with a GaN:Eu active layer grown at atmospheric pressure, which is due to the enhancement of the energy transfer efficiency from the GaN host material to the Eu ions. At a d.c. current of 20 mA, the light output power and external quantum efficiency were 17 μW and 0.04%, respectively. These results indicate the feasibility of GaN:Eu to realize a GaN-based red emitter for fabrication of nitride-based monolithic optical devices.

The effect of bright light on sleepiness among rapid-rotating 12-hour shift workers

About 20% of workers in industrialized countries are shift workers and more than half of them work on night or rotating shifts. Most night workers complain of sleepiness due to lack of adjustment of the circadian rhythm. In simulated night-work experiments, scheduled exposure to bright light has been shown to reduce these complaints. Our study assessed the effects of bright light exposure on sleepiness during night work in an industrial setting. In a cross-over design, 94 workers at a ceramic factory were exposed to either bright (2500 lux) or normal light (300 lux) during breaks on night shifts. We initiated 20-minute breaks between 24.00 and 02.00 hours. Sleepiness ratings were determined using the Stanford Sleepiness Scale at 22.00, 24.00, 02.00 and 04.00 hours. Under normal light conditions, sleepiness peaked at 02:00 hours. A significant reduction (22% compared to normal light conditions) in sleepiness was observed after workers were exposed to bright light. Exposure to bright light may be effective in reducing sleepiness among night workers.

Influence of light and time on bilirubin degradation in CSF spectrophotometry for subarachnoid haemorrhage

Aim. Investigation of the influence of light on bilirubin degradation over time in cerebrospinal fluid (CSF) specimens from patients with computed tomography (CT) positive subarachnoid haemorrhage (SAH).Methods. Twenty-nine CSF samples were analysed from 23 patients with CT-positive SAH. Samples were divided into two cohorts – one half being stored in the dark, the other in normal room light conditions. Samples were assayed by spectrophotometry 0, 1, 2, 6, 19, 24 and 48 h post-storage. Net bilirubin absorbance (NBA) was measured in absorbance units (AU) by determining the optical density at 476 nm.Results. In 27 of 28 (96%) samples stored in light conditions and 21 of 29 (72%) samples stored in dark, a decline in the amount of bilirubin detected in CSF over time was observed. The rate of bilirubin degradation over 24 h for CSF samples stored in the light ranged from 0.0001 to 0.0048 AU/h (mean 0.0020 AU/h), and was significantly greater (p < 0.01) than the rate of degradation in the dark, which ranged from 0 to 0.0024 AU/h (mean 0.0005 AU/h).Conclusion. CSF bilirubin samples are susceptible to the same photodegradation as shown in serum bilirubin samples. The rate of degradation is not predictable or consistent. This photodegradation may potentially produce false-negative results in the diagnosis of SAH. If spectrophotometry cannot be carried out immediately, all such CSF samples should at least be centrifuged immediately, the supernatant protected from light as soon as possible and the collection and analysis times provided in the report.