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At least 199 records · Page 11Linked to original sources
PubMed1994

Characterization of a light-responding trans-activator responsible for differentially controlling reaction center and light-harvesting-I gene expression in Rhodobacter capsulatus.

The purple nonsulfur photosynthetic bacterium Rhodobacter capsulatus regulates synthesis of its photosystem in response to two environmental stimuli, oxygen tension and light intensity. Here we describe the identification and characterization of the trans-acting regulatory gene hvrA, which we show is involved in differentially controlling reaction center and light-harvesting gene expression in response to alterations in light intensity. An hvrA mutant strain is shown to lack the capability to trans-activate light-harvesting-I and reaction center gene expression but retain normal light-harvesting-II and photopigment regulation, in response to a reduction in light intensity. As a consequence of altered expression, hvrA mutant strains exhibit reduced photosynthetic growth capabilities under dim-light conditions. The results of this study and additional studies indicate that regulated synthesis of the photosystem involves complex sets of overlapping regulatory circuits that differentially control photosystem gene expression in response to environmental stimuli such as oxygen tension and light intensity.

Amino Acid Sequence↗
PubMed2006

Effect of flashing light from blue light emitting diodes on cell growth and astaxanthin production of Haematococcus pluvialis.

To conserve energy in the production of astaxanthin by the green alga Haematococcus pluvialis, we utilized intermittent flashing light from blue light emitting diodes (LEDs) and investigated the effects of the incident light intensity (2-12 micromol m(-2) s(-1)), duty cycle (17-67%) and frequency (25-200 Hz) of flashing on the cell growth and astaxanthin production. In the above ranges, the final astaxanthin concentration under illumination by flashing light was significantly higher than that obtained under illumination with continuous light at the same incident intensity. For example, flashing light at an incident intensity of 8 micromol m(-2) s(-1) gave the same final astaxanthin concentration that was obtained under continuous light illumination at 12 micromol m(-2) s(-1), thus reducing energy consumption by 1/3. We therefore conclude that flashing light from blue LEDs is a promising illumination method for indoor algal cultivation using photobioreactors.

Bioreactors↗
PubMed2001

Improving spinach, radish, and lettuce growth under red light-emitting diodes (LEDs) with blue light supplementation.

Radish (Raphanus sativus L. cv. Cherriette), lettuce (Lactuca sativa L. cv. Waldmann's Green), and spinach (Spinacea oleracea L. cv. Nordic IV) plants were grown under 660-nm red light-emitting diodes (LEDs) and were compared at equal photosynthetic photon flux (PPF) with either plants grown under cool-white fluorescent lamps (CWF) or red LEDs supplemented with 10% (30 micromoles m-2 s-1) blue light (400-500 nm) from blue fluorescent (BF) lamps. At 21 days after planting (DAP), leaf photosynthetic rates and stomatal conductance were greater for plants grown under CWF light than for those grown under red LEDs, with or without supplemental blue light. At harvest (21 DAP), total dry-weight accumulation was significantly lower for all species tested when grown under red LEDs alone than when grown under CWF light or red LEDs + 10% BF light. Moreover, total dry weight for radish and spinach was significantly lower under red LEDs + 10% BF than under CWF light, suggesting that addition of blue light to the red LEDs was still insufficient for achieving maximal growth for these crops.

Biomass↗
PubMed1988

[The effect of the light intensity under daylight and artificial light conditions in supply centers on the fertility of breeding sows].

The influence of light intensity in service areas on fertility of breeding sows under daylight as well as artificial light conditions has been confirmed. Under conditions of confinement, which are necessary for epidemic reasons too, the improvement of lighting is possible in two ways: 1. By increasing daylight coefficients to at least 1.0% (300 Lx at overcast sky) using natural light more efficiently (window: floor ratio greater than 1:20 and/or south direction of windows, S-S-E, resulting in higher light intensities) during sunshine. These measures require some investment, but do not add to running expenses. 2. By additional artificial lighting with current-saving light bulbs (fluorescent lightings) and their fitting next to animals, which should result in at least 300 Lx. The additional expenses seem to be acceptable versus improvement of sows fertility and better working conditions for staff.

Animals↗
PubMed1983

Serum-free light chain analysis by crossed immunoelectrophoresis: correlation with plasmapheresis in light chain disease nephropathy.

The technique of crossed immunoelectrophoresis (X-IEP) has been used to quantify free monoclonal light chains (LC) directly in the serum of patients with light chain disease, without preliminary gel or membrane filtration of serum to separate whole immunoglobulin. LC concentration is proportional to the area under an immunoprecipitin peak formed by LC in the patient's serum and an anti-LC antibody of appropriate specificity. Light chains of beta electrophoretic mobility can be processed in the standard X-IEP technique at pH 8.6. Light chains of gamma mobility must be processed in a modified technique using a pH of 5.0 and a carbamylated antiserum in the second dimension gel. Dose response curves obtained from the method in serial dilution experiments with sera from 18 patients gave correlation coefficients greater than or equal to 0.99. Replicate measurements of absolute LC concentration on the same specimens were within +/- 10%. The method can also detect polymerized light chains. Serum light chain levels were measured during the course of plasmapheresis therapy in three patients with light chain disease and renal failure. Light chain levels were shown to fall after plasmapheresis and to rise rather rapidly in the interval between treatments.

Acute Kidney Injury↗
PubMed1990

Light-stimulated cell expansion in bean (Phaseolus vulgaris L.) leaves. II. Quantity and quality of light required.

The quantity and quality of light required for light-stimulated cell expansion in leaves of Phaseolus vulgaris L. have been determined. Seedlings were grown in dim red light (RL; 4 micromoles photons m-2 s-1) until cell division in the primary leaves was completed, then excised discs were incubated in 10 mM sucrose plus 10 mM KCl in a variety of light treatments. The growth response of discs exposed to continuous white light (WL) for 16 h was saturated at 100 micromoles m-2 s-1, and did not show reciprocity. Extensive, but not continuous, illumination was needed for maximal growth. The wavelength dependence of disc expansion was determined from fluence-response curves obtained from 380 to 730 nm provided by the Okazaki Large Spectrograph. Blue (BL; 460 nm) and red light (RL; 660 nm) were most effective in promoting leaf cell growth, both in photosynthetically active and inhibited leaf discs. Far-red light (FR; 730 nm) reduced the effectiveness of RL, but not BL, indicating that phytochrome and a separate blue-light receptor mediate expansion of leaf cells.

Cell Division↗
PubMed2004

Penetration of light into carpet, and responses of the European house-dust mite (Dermatophagoides pteronyssinus) to varying light intensity and diurnal cycle.

This study examined the question of what effect exposure to light might play in determining the vertical distribution of house-dust mites in carpet, and the degree to which light penetrates worn and unworn carpets of different pile conformation (loop- versus cut-pile), height and colour. The effect on population increase of a diurnal lighting cycle versus continual darkness was also investigated. It was found that the penetration of light into carpets was largely unaffected by pile colour or conformation. Pile height was an important factor, however, and for a given height within the pile, light intensity was higher in carpets subjected to a greater degree of wear. This corresponded to the reduction in effective pile height that occurs with carpet use. Whilst the differences observed were sometimes large (up to two-fold for a given height within the pile), Petri dish studies suggested no mite preference for habitation of areas of low light intensity compared to high intensity. Additionally, culturing mites under a diurnal light cycle was shown to be no more efficient than culturing in complete darkness. These results suggest that exposure to light is not an important determinant of house-dust mite behaviour, or their ability to colonise textile substrates.

Animals↗
PubMed2006

Non-visual biological effect of lighting and the practical meaning for lighting for work.

The effects of good lighting extend much further than we used to think. Recent medical and biological research has consistently shown that light entering the human eyes has, apart from a visual effect, also an important non-visual biological effect on the human body. As a consequence, good lighting has a positive influence on health, well-being, alertness, and even on sleep quality. Our better understanding of the diversity in lighting effects teaches us that new rules governing the design of good and healthy lighting installations are required. Thanks to the recent discovery of a novel photoreceptor in the eye and its probable distribution within the eye we can now begin to define these new rules. These will guide us to dynamic lighting installations: that is to say dynamic in lighting level and dynamic in tint of whiteness of the lighting colour.

Adaptation, Ocular↗
PubMed2006

Light induced structural changes of a full-length protein and its BLUF domain in YcgF(Blrp), a blue-light sensing protein that uses FAD (BLUF).

Blue-light sensing proteins that use FAD (BLUF) are members of a blue-light receptor family that is widely distributed among microorganisms. The Escherichia coli YcgF protein is a BLUF protein consisting of the N-terminal FAD-binding hold (BLUF domain) and the C-terminal EAL domain. The EAL domain of YcgF is predicted to have cyclic-di-GMP phosphodiesterase activity. Light-induced structural changes for the signaling state formation were studied using the light-induced Fourier transform infrared (FTIR) difference spectroscopy of both the full-length YcgF protein (YcgF-Full) and its BLUF domain (YcgF-BLUF). YcgF-Full and YcgF-BLUF showed identical UV-visible absorption spectra of flavin in the dark state and a light-induced absorption red shift for the signaling state, which relaxed to the dark state showing identical kinetics. The light-induced FTIR difference spectrum of YcgF-Full, however, was markedly different from that of YcgF-BLUF. The spectrum of YcgF-BLUF lacked most of the IR bands that were induced in the YcgF-Full spectrum. These bands were assigned to the light-induced structural changes of the protein. However, the bands for the C4=O stretching of a FAD isoalloxazine ring were induced at the same frequency with the same band intensity in the spectra for YcgF-Full and YcgF-BLUF. Furthermore, the YcgF-Full spectrum resembled that of the YcgF-BLUF when illuminated at medium-low temperatures because of the selective suppression of protein bands. The possibility that full-length-specific protein bands are predominantly ascribed to structural changes of the C-terminal EAL domain in the signaling state as a consequence of light excitation of the N-terminal BLUF domain is discussed.

Bacterial Proteins↗
PubMed1987

Comparisons of time intervals and plasma LH concentrations during the ovulatory cycle of broiler breeder hens maintained under either a 24 h light:dark cycle or continuous light.

The possibility that egg production in broiler breeder hens may be increased by selection for reduced oviposition interval under continuous light was investigated by comparing the pattern of pre-ovulatory releases of plasma luteinising hormone (LH) and the associated ovipositions in the same broiler hens maintained under normal cycles (15.25 h light/d) or continuous light. The lighting conditions had no effect on plasma concentrations of LH before and at the pre-ovulatory LH peak in first, mid-sequence or terminal ovulatory cycles. Plasma LH concentrations were similar during first, mid-sequence and terminal ovulatory cycles. Mid-sequence oviposition intervals and the interval between a mid-sequence LH peak and its associated oviposition were longer under continuous light than under normal lighting. Pre-ovulatory releases of LH occurred during a restricted period of day in both lighting conditions. Under continuous lighting they were probably entrained by the daily pattern of restricted feeding. Any selection programme for reduced oviposition interval under continuous lighting in broiler breeder hens should take into account the entraining effects of the daily pattern of feeding.

Animals↗
PubMed2003

Visual strain and lighting preferences of VDT users under different lighting systems.

Lighting influences users' visual strain and well-being. Therefore creating lighting that ensures visual work conditions do not result in visual fatigue is a preventive activity. The aim of the study was to model different lighting systems for visual display terminal (VDT) work and to determine their influence on users' visual strain and preferences. The results of the study showed that visual fatigue was lowest for indirect and compound lighting systems. On the other hand, in general, direct lighting realized by "dark-light" luminaires was the most preferred lighting system. Some interesting differences related to age, gender, and VDT work experience were found. On the basis of the obtained results lighting designers can be provided with some guidance.

Adolescent↗
PubMed1998

Effects of read-out light sources and ambient light on radiochromic film.

Both read-out light sources and ambient light sources can produce a marked effect on coloration of radiochromic film. Fluorescent, helium neon laser, light emitting diode (LED) and incandescent read-out light sources produce an equivalent dose coloration of 660 cGy h(-1), 4.3 cGy h(-1), 1.7 cGy h(-1) and 2.6 cGy h(-1) respectively. Direct sunlight, fluorescent light and incandescent ambient light produce an equivalent dose coloration of 30 cGy h(-1), 18 cGy h(-1) and 0 cGy h(-1) respectively. Continuously on, fluorescent light sources should not be used for film optical density evaluation and minimal exposure to any light source will increase the accuracy of results.

Calibration↗
PubMed1997

Ahemeral lighting of turkey breeder hens. 2. Early age at lighting and reproductive performance.

An experiment was conducted to determine whether ahemeral lighting (AH) could be used to obtain increased egg weight and poult weight and otherwise normal reproductive performance in Large White turkey hens lit as early as 26 wk of age. The experimental design utilized a 2 x 2 factorial arrangement of treatments that evaluated two light cycle lengths (24 h, control and 28 h, ahemeral) at two hen ages (26 and 30 wk). Treatments were continued for 24 wk and the following variables were measured: BW, feed intake, onset and rate of lay, fertility, hatchability, incidence of floor eggs, egg weight, poult production, and poult weight. As compared to the response of hens in the control lighting treatment, ahemeral lighting increased egg weight and poult weight early in the lay period only and resulted in delayed onset of lay (+3.4 d) and depressed egg production (-7 eggs to 54 wk of age). Percentage fertility and hatchability were similar between ahemeral and control treatment groups. However, ahemeral lighting decreased the number of poults per hen when started at 26, but not 30, wk of age. Hens photostimulated early at 26 wk of age were delayed in onset of lay by 5.9 d but produced more eggs per hen to 54 wk of age (95.8) than hens photostimulated at 30 wk (89.7); however, during equivalent lay periods, egg production was similar between the two groups. Early lighting did not have an adverse effect on fertility, hatchability, or poults per hen but egg weight and poult weight were depressed. It was concluded that although ahemeral lighting increased egg weight and poult weight in turkey hens photostimulated early, continuous application of ahemeral lighting throughout the lay period had adverse effects on some components of reproductive performance.

Aging↗
PubMed2002

Light-intensity-dependent expression of Lhc gene family encoding light-harvesting chlorophyll-a/b proteins of photosystem II in Chlamydomonas reinhardtii.

Excessive light conditions repressed the levels of mRNAs accumulation of multiple Lhc genes encoding light-harvesting chlorophyll-a/b (LHC) proteins of photosystem (PS)II in the unicellular green alga, Chlamydomonas reinhardtii. The light intensity required for the repression tended to decrease with lowering temperature or CO(2) concentration. The responses of six LhcII genes encoding the major LHC (LHCII) proteins and two genes (Lhcb4 and Lhcb5) encoding the minor LHC proteins of PSII (CP29 and CP26) were similar. The results indicate that the expression of these Lhc genes is coordinately repressed when the energy input through the antenna systems exceeds the requirement for CO(2) assimilation. The Lhc mRNA level repressed under high-light conditions was partially recovered by adding the electron transport inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea, suggesting that redox signaling via photosynthetic electron carriers is involved in the gene regulation. However, the mRNA level was still considerably lower under high-light than under low-light conditions even in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea. Repression of the Lhc genes by high light was prominent even in the mutants deficient in the reaction center(s) of PSII or both PSI and PSII. The results indicate that two alternative processes are involved in the repression of Lhc genes under high-light conditions, one of which is independent of the photosynthetic reaction centers and electron transport events.

Algal Proteins↗
PubMed2000

Differential effects of methyl jasmonate on the expression of the early light-inducible proteins and other light-regulated genes in barley.

The effects of methyl jasmonate (JA-Me) on early light-inducible protein (ELIP) expression in barley (Hordeum vulgare L. cv Apex) have been studied. Treatment of leaf segments with JA-Me induces the same symptoms as those exhibited by norflurazon bleaching, including a loss of pigments and enhanced light stress that results in increased ELIP expression under both high- and low-light conditions. The expression of both low- and high-molecular-mass ELIP families is considerably down-regulated by JA-Me at the transcript and protein levels. This repression occurs despite increased photoinhibition measurable as a massive degradation of D1 protein and a delayed recovery of photosystem II activity. In JA-Me-treated leaf segments, the decrease of the photochemical efficiency of photosystem II under high light is substantially more pronounced as compared to controls in water. The repression of ELIP expression by JA-Me is superimposed on the effect of the increased light stress that leads to enhanced ELIP expression. The fact that the reduction of ELIP transcript levels is less pronounced than those of light-harvesting complex II and small subunit of Rubisco transcripts indicates that light stress is still affecting gene expression in the presence of JA-Me. The jasmonate-induced protein transcript levels that are induced by JA-Me decline under light stress conditions.

Abscisic Acid↗
PubMed1993

Effects of light stress on the expression of early light-inducible proteins in barley.

Treatment of six-day-old barley leaves with white light of high intensity, 250-2000 W/m2, leads to a linear increase in the steady-state concentrations of early light-inducible protein (ELIP) mRNA followed by an accumulation of the protein. Accumulation of ELIP mRNA, under light stress, is highest in the basal third of the leaf and declines to approximately 50% of this level in the apical segment. The amount of the accumulated protein decreases more steeply towards the tip than would be expected from mRNA levels. This finding, as well as the fact that during greening a massive accumulation of the protein starts only at a time when the steady-state concentrations of ELIP mRNA have declined to 10% of the maximal value, indicate post-transcriptional control. Accumulation is presumably achieved by stabilization of the protein. ELIP mRNA and protein levels, induced by a 2-h period of high-light stress, are lowest in the afternoon and highest at midnight and during the morning. The inducibility of ELIP by high light is therefore under diurnal control. An increase of light stress, due to application of the carotenoid-biosynthesis inhibitor norfluorazon, results in a considerable induction of ELIP mRNA and protein. The plant hormone abscisic acid exerts only a small effect on the mRNA level. In all cases studied, the light-induced increase in the amount of ELIP mRNA was accompanied by a corresponding decline in the mRNA levels for the apoprotein of the chlorophyll-a/b-binding protein. Steady-state concentrations of mRNA for the small subunit of ribulose-1,5-bisphosphate carboxylase were hardly affected under all investigated light intensities.

Abscisic Acid↗
PubMed1998

Transcriptional and translational regulation of photosystem I and II genes in light-dark- and continuous-light-grown cultures of the unicellular cyanobacterium Cyanothece sp. strain ATCC 51142.

Cyanothece sp. strain ATCC 51142, a unicellular, diazotrophic cyanobacterium, demonstrated extensive metabolic periodicities of photosynthesis, respiration, and nitrogen fixation when grown under N2-fixing conditions. This report describes the relationship of the biosynthesis of photosynthesis genes to changes in the oligomerization state of the photosystems. Transcripts of the psbA gene family, encoding the photosystem II (PSII) reaction center protein D1, accumulated primarily during the light period, and net transcription reached a peak between 2 to 6 h in the light in light-dark (LD) growth and between 4 to 10 h in the subjective light when grown under continuous light (LL). The relative amount of the D1 protein (form 1 versus form 2) appeared to change during this diurnal cycle, along with changes in the PSII monomer/dimer ratio. D1 form 1 accumulated at approximately equal levels throughout the 24-h cycle, whereas D1 form 2 accumulated at significantly higher levels at approximately 8 to 10 h in the light or subjective light. The psbD gene, encoding the reaction center protein D2, also demonstrated differences between the two copies of this gene, with one copy transcribed more heavily around 6 to 8 h in the light. Accumulation of the PSI reaction center proteins PsaA and PsaB was maximal in the dark or subjective-dark periods, a period during which PSI was primarily in the trimeric form. We conclude that photosystem organization changes during the diurnal cycle to favor either noncyclic electron flow, which leads to O2 evolution and CO2 fixation, or cyclic electron flow, which favors ATP synthesis.

Bacterial Proteins↗
PubMed1990

Growth of cultured RPE and endothelial cells is inhibited by blue light but not green or red light.

Blue light, but not green or red light, inhibited growth of retinal pigment epithelial (RPE) cells, aortic endothelial cells, and fibroblasts in vitro. Significant inhibition was observed in all 3 cell types exposed for 18 hr to blue light (425-500 nm) at 42 J/cm2. Damage was prevented by inclusion of superoxide dismutase (SOD) and catalase, providing evidence for a photooxidative mechanism. Dopa (100 microM) also caused oxidative damage that suppressed growth of all 3 cell types. A synergism of dopa and light effects was observed in endothelial cells and fibroblasts, but the agents caused additive effects on RPE cells. Endothelial cells were the most sensitive to dopa, light, and the two combined. Fibroblasts were the only cell type that exhibited greater sensitivity to light than to dopa. These data suggest that oxygen-mediated damage to the growing blood vessels in the retina of a premature infant may be exacerbated by exposure to blue light. A further implication is that restriction of RPE melanogenesis to the prenatal period of darkness and lower oxygen protects the retina from simultaneous oxidative challenge by light and by reactive species generated during oxidation of dopa released to the extracellular environment.

Analysis of Variance↗