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At least 451 records · Page 25Linked to original sources
PubMed2006

Balancing the energy flow from captured light to biomass under fluctuating light conditions.

The balance of energy flow from light absorption into biomass was investigated under simulated natural light conditions in the diatom Phaeodactylum tricornutum and the green alga Chlorella vulgaris. The energy balance was quantified by comparative analysis of carbon accumulation in the new biomass with photosynthetic electron transport rates per absorbed quantum, measured both by fluorescence quenching and oxygen production. The difference between fluorescence- and oxygen-based electron flow is defined as 'alternative electron cycling'. The photosynthetic efficiency of biomass production was found to be identical for both algae under nonfluctuating light conditions. In a fluctuating light regime, a much higher conversion efficiency of photosynthetic energy into biomass was observed in the diatom compared with the green alga. The data clearly show that the diatom utilizes a different strategy in the dissipation of excessively absorbed energy compared with the green alga. Consequently, in a fluctuating light climate, the differences between green algae and diatoms in the efficiency of biomass production per photon absorbed are caused by the different amount of alternative electron cycling.

Acclimatization↗
PubMed2005

Light patch: preliminary report of a novel form of blue light delivery for the treatment of actinic keratosis.

OBJECTIVE: To evaluate a novel light patch formulated for blue light delivery and topical activation of gamma-aminolevulinic acid (ALA) during photodynamic therapy for the treatment of actinic keratosis (AK). MATERIALS AND METHODS: Ten volunteers with past unsuccessful treatment of AK were enrolled. Areas with AK lesions were treated with 20% ALA (Levulan) for an incubation period of 1 hour. Half of the area was treated with blue light patches (the patch emits 431 to 515 nm wavelength, 55.6 mJ/cm2 over 20 minutes), and the other half was left uncovered (control). The percentage of visible AK lesions cleared at the 3-month follow-up determined therapeutic efficacy. RESULTS: The mean lesion count for all treatment areas was decreased from 7.60 to 2.40 (p<.01). The subjects had slight burning or itching and mild to moderate erythema. One subject developed a blister at the treatment site. Controls had clearance of 30%, 17%, and 20% for the face, scalp, and hands, respectively. Patients were satisfied with the results and noticed an improvement in skin texture. CONCLUSION: Preliminary results show that the blue light patch is a potentially safe, effective, and alternative method for light delivery and topical ALA activation during photodynamic therapy of AK.

Aged↗
PubMed1984

Drosophila melanogaster has only one myosin alkali light-chain gene which encodes a protein with considerable amino acid sequence homology to chicken myosin alkali light chains.

A chimeric lambda DNA molecule containing the myosin alkali light-chain gene of Drosophila melanogaster was isolated. The encoded amino acid sequence was determined from the nucleic acid sequence of a cDNA homologous to the genomic clone. The identity of the encoded protein was established by two criteria: (i) sequence homology with the chicken alkali light-chain proteins and (ii) comparison of the two-dimensional gel electrophoretic pattern of the peptides synthesized by in vitro translation of hybrid-selected RNA to that of myosin alkali light-chain peptides extracted from Drosophila myofibrils. There is only one myosin alkali light-chain in D. melanogaster; its chromosomal location is region 98B . This gene is abundantly expressed during the development of larval as well as adult muscles. The Drosophila protein appears to contain one putative divalent cation-binding domain (an EF hand) as compared with the three EF hands present in chicken alkali light chains.

Amino Acid Sequence↗
PubMed1998

Light chain deposition disease detected by antisera to a variable region of the kappa1 light chain subgroup.

A 59-year-old male started maintenance hemodialysis, and 80 months later died of congestive heart failure. Just before death he had no urine, and no monoclonal immunoglobulin could be demonstrated in the serum on immunoelectrophoresis. An autopsy showed deposition of periodic acid-Schiff-positive and Congo red-negative material in the interstitium and vessel walls of almost all organs and tissues. In the glomeruli there was a multifocal nodular accumulation of the material. Electron microscopy showed finely granular, not fibrillar deposits. In spite of these impressive lesions on light microscopy, the material was not stained with commercially available antisera to light chains. However, the material was positive for antisera to the variable region of the kappa1 light chain subgroup. This is the first case with light chain deposition disease that showed positive staining only with antisera to the variable region of the light chain.

Amyloidosis↗
PubMed2004

High-definition imaging system based on spatial light modulators with light-scattering mode.

We have developed a prototype high-definition imaging system using polymer-dispersed liquid-crystal (PDLC) light valves, which can modulate unpolarized light with high spatial resolution and exhibit a high optical efficiency, based on the light-scattering effect. We fabricated high-definition light valves with a fine polymer-matrix structure in a PDLC film by controlling the curing conditions used during the photopolymerization-induced phase separation and formation process. This device has excellent characteristics, such as a high resolution, with 50 lp/mm for a limiting resolution and greater than 20 lp/mm at the 50% modulation transfer function point, and a reflectivity of greater than 60%. An optically addressable full-color projection display was designed, consisting of three PDLC light valves, a schlieren optical system based on shift-decentralization optics with a xenon lamp illumination and input-image sources with 1.5 million pixels, including electrical image compensation of the gamma characteristics. We succeeded in displaying pictures on a 110-inch screen with a resolution of 810 TV lines and a luminous flux of 1900-2100 American National Standards Institute lumens.

Journal Article↗
PubMed2006

Estimation method for the light extraction efficiency of light-emitting elements with a rigorous grating diffraction theory.

The light extraction efficiency of a light-emitting element with microstructured surface is analyzed with a rigorous grating diffraction theory. The grating theory reveals an improvement of extraction efficiency due to diffraction of light by the surface microstructure. The simulation results show that the improvement of extraction efficiency is due mainly to the reflected diffraction rather than to the transmitted diffraction. A part of total-internal-reflection light is diffracted into directions at less than the critical angle. Extraction efficiency is improved by multiple reflection and diffraction of light in a high-refractive-index layer. We propose a simple design method for an efficient surface microstructure from the viewpoint of reflected diffraction.

Journal Article↗
PubMed1975

[Effect of light deprivation and light stimulation on the RNA content of neurons in the adult rat visual analyzer].

By means of two-wavelength visual cytospectrophotometry, a content of nucleic acids per cell was determined in the gallocyanin chrome alum stained sections of the adult rat nervous system. Illumination of normal rats with constant or flashing light for 2 hr resulted in an accumulation of RNA in II--III layer neurons of the visual cortex and in the retina ganglionic neurons. After the rats had been kept for 30 days in a complete darkness the nucleic acid content in their visual cortex neurons was increased. Illumination of these animals with constant or flashing light for 2 hr gave rise to a return of the nucleic acid content in the cortex neurons to the normal. Under the effect of 30-day light deprivation, the nucleic acid content in the retina ganglionic neurons remained unchanged. Illumination of the light-deprived rats with flashing light for 2 hr also did not change RNA content in these retina neurons. The data obtained indicate the prolonged hypofunction in adult animals to induce marked changes in nucleic acid metabolism in the neurons of visual analyser. A relationship between the function and metabolism in adult neurons is emphasized; differences of the function-dependent metabolic responses in the cell structures of central and peripheral parts of the visual analyser are discussed.

Animals↗
PubMedDate not supplied

Treatment of sebaceous gland hyperplasia by photodynamic therapy with 5-aminolevulinic acid and a blue light source or intense pulsed light source.

Treatment of SGH by ALA-PDT with Blue Light Source or Intense Pulsed Light Activation. Sebaceous gland hyperplasia (SGH) lesions often present as a sign of photoaging and have proven difficult to treat. Photodynamic therapy (PDT) may be an effective treatment option. Twelve patients with SGH received PDT with 5-aminolevulinic acid (ALA, Levulan Kerastick, DUSA Pharmaceuticals, Inc) photosensitizing agent topically applied with a 30- to 60-minute drug incubation period. Patients received either 405-420 nm blue light (ClearLight PhotoClearing System, CureLight, Lumenis) for 15 minutes or intense pulsed light (IPL), 500-1,200 nm and 550 nm cut-off filter (VascuLight System, Lumenis) according to a randomization protocol. ALA-PDT was administered once per month for 4 consecutive months. Progress was evaluated at 4 and 12 weeks after the final treatment. More than a 50% reduction in the number of SGH lesions was achieved for patients in both treatment arms without lesional recurrence during the treatment and follow-up periods. All treatments were well-tolerated. Adverse effects were limited to mild, transient erythema (n = 2) and blisters (n = 1), which resolved without sequelae. ALA-PDT with either blue light or IPL photoactivation may provide therapeutic benefit without significant adverse effects in patients with SGH.

Administration, Cutaneous↗
PubMed1976

Light peak to dark trough ratio in clinical electro-oculography: influence of dark oscillations on the following light peak.

In the clinical standard EOG procedure the light rise potential is influenced by the preceding dark troughs oscillation. This is apparent in the different configuration of the light rise potential when following a dark trough instead of a steady state. Uninfluenced responses can be obtained only under steady-state conditions. Recording of the light peak potential in this manner may be used on a trial basis for clinical routine examination. Experimental and more detailed clinical studies require separate recording of light peak and dark trough potential, each preceded by a steady state. The evaluation of these responses, expressing them in percent of the steady state, should reveal more information than can be expected from the standard light peak to dark trough ratio.

Adult↗
PubMed2005

Thermo-optically induced reorganizations in the main light harvesting antenna of plants. I. Non-Arrhenius type of temperature dependence and linear light-intensity dependencies.

Thermo-optically induced structural reorganizations have earlier been identified in isolated LHCII, the main chlorophyll a/b light harvesting complexes of Photosystem II, and in granal thylakoid membranes [Cseh et al. (2000) Biochemistry 39: 15250-15257; Garab et al. (2002) Biochemistry 41: 15121-15129]. According to the thermo-optic mechanism, structural changes can be induced by fast, local thermal transients due to the dissipation of excess excitation energy. In this paper, we analyze the temperature and light-intensity dependencies of thermo-optically induced reversible and irreversible reorganizations in the chiral macrodomains of lamellar aggregates of isolated LHCII and of granal thylakoid membranes. We show that these structural changes exhibit non-Arrhenius type of temperature dependencies, which originate from the 'combination' of the ambient temperature and the local thermal transient. The experimental data can satisfactorily be simulated with the aid of a simple mathematical model based on the thermo-optic effect. The model also predicts, in good accordance with experimental data published earlier and presented in this paper, that the reorganizations depend linearly on the intensity of the excess light, a unique property that is probably important in light adaptation and photoprotection of plants.

Circular Dichroism↗
PubMed2004

Light-modulated exposure of the light-harvesting complex II (LHCII) to protein kinase(s) and state transition in Chlamydomonas reinhardtii xanthophyll mutants.

Reversible phosphorylation of chl a/b protein complex II (LHCII), the mobile light-harvesting antenna, regulates its association and energy transfer/dissipation to photosystem (PS) II or I (state transition). Excitation of LHCII induces conformational changes affecting the exposure of the phosphorylation site at the N-terminal domain to protein kinase(s) [Zer, H., et al. (1999) Proc. Natl. Acad. Sci. U.S.A. 96, 8277-8282; Zer, H., et al. (2003) Biochemistry 42, 728-738]. Thus, it was of interest to examine whether the pigment composition of LHCII affects the light-induced modulation of LHCII phosphorylation and state transition. To this end, we have used thylakoids of wild-type Chlamydomonas reinhardtii and xanthophyll deficient mutants npq1, lor1, npq2, npq1 lor1, and npq2 lor1. Phosphorylated protein bands P11, P13, and P17 are considered components of the mobile C. reinhardtii LHCII complex. The protein composition of these bands has been analyzed by mass spectrometry using Qtof-2 with a nanospray attachment. P11 and P13 contain C. reinhardtii light-harvesting chlorophyll a/b binding protein LhcII type I. P17 contains C. reinhardtii LhcII types III and IV. Illumination of isolated thylakoids inhibits the redox-controlled phosphorylation of polypeptide bands P13 and P17 and to a lower extent that of P11. The light-induced inhibition of LHCII phosphorylation and the state transition process are not influenced by extensive differences in the xanthophyll composition of the mutants. Thus, LHCII can be visualized as possessing two functionally distinct, independent domains: (i) the pigment binding transmembrane domain regulating the extent of energy transfer/dissipation and (ii) the surface-exposed phosphorylation site regulating the association of LHCII with PSII or PSI.

Animals↗
PubMed1997

A subset of protein kinase C phosphorylation sites on the myosin II regulatory light chain inhibits phosphorylation by myosin light chain kinase.

Protein kinase C (PKC) phosphorylates the regulatory light chains of smooth muscle and cytoplasmic myosin II at three known sites: S1, S2, and T9 [Ikebe, M., Hartshorne, D. J., & Elzinga, M. (1987) J. Biol. Chem. 262, 9569-9573]. Phosphorylation at these sites inhibits the actomyosin ATPase and inhibits phosphorylation of S19 on the regulatory light chain by myosin light chain kinase (MLCK) [Nishikawa, M., Sellers, J. R., Adelstein, R. S., & Hidaka, H. (1984) J. Biol. Chem. 259, 8808-8814]. To compare the effects of phosphorylation at a subset of PKC sites on the rate of MLCK phosphorylation, we substituted alanines for the known PKC phosphorylation sites in the Xenopus regulatory light chain (XRLC). PKC phosphorylation of S1A/S2A/T9A revealed secondary phosphorylation sites at T7 and T10, which are accessible both on isolated S1A/S2A/T9A and S1A/S2A/T9A-myosin hybrids. Apparent kinetic constants were determined for MLCK phosphorylation of WT XRLC and XRLC mutants: T9A, S1A/S2A, S1A/S2A/T9A, and T7A/T9A/T10A. PKC prephosphorylation of S1/2 had no effect on the rate of MLCK phosphorylation, while PKC prephosphorylation of T7/9/10 inhibited MLCK phosphorylation due to a 6-fold increase in Km. Our results suggest that phosphorylation of RLC S1/2 as observed in vivo may not be responsible for an inhibition of MLCK phosphorylation.

Amino Acid Sequence↗
PubMed1990

Effect of light sources and light intensity on growth performance and behaviour of female turkeys.

1. The effect of different light sources (incandescent, sodium vapour, daylight fluorescent and warm fluorescent) and light intensities (10.8 and 86.1 lux) on growth performance and behaviour of female turkeys was investigated in two experiments conducted at different times of the year. 2. Although light source influenced body weight and efficiency of food utilisation, there was no consistent effect between experiments in favour of any particular source. 3. Light intensity had no effect on body weight, efficiency of food utilisation or behaviour.

Animals↗
PubMed2005

[Study of luminescence ability of organic white light emitting diode by light conversion].

An organic luminescence material of white light was investigated. The organic luminescence film was made by heating and melting method. The film consists of riboflavin, anthrone derivative, and linear low-density polyethylene. The results show that the spectra of luminescence films were affected by weight ratio and heating time of the made films. The spectra were wide band from green light to red light. The organic white light emitting diodes made of this film have super performance.

Anthracenes↗
PubMed2006

The photochemistry of the light-, oxygen-, and voltage-sensitive domains in the algal blue light receptor phot.

Phot proteins are blue light photoreceptors in plants and algae that mainly regulate photomovement responses. They contain two light-, oxygen-, and voltage-sensitive (LOV) domains and a serine/threonine kinase domain. Both LOV domains noncovalently bind a flavin mononucleotide (FMN) as chromophore. Upon blue light illumination, the LOV domains undergo a photocycle, transiently forming a covalent adduct of the FMN moiety with a nearby cysteine residue. The presence of two light-sensitive domains in the photoreceptor raises the question about the differences in properties and function between LOV1 and LOV2. As a model system, the photocycles of the LOV1 and LOV2 domains from phot of the green alga Chlamydomonas reinhardtii have been studied in detail, both separately and in a tandem construct. Here we give an overview about the results on the individual behavior of the domains and their interaction. Furthermore, the current status in the understanding of the role of LOV1 in phot in general is presented.

Animals↗
PubMed1991

Light-inducible and constitutively expressed DNA-binding proteins recognizing a plant promoter element with functional relevance in light responsiveness.

Four cis-acting elements, designated as Boxes I, II, III and IV, have previously been identified as functionally relevant components of the light-responsive chalcone synthase (CHS) promoter in parsley (Petroselinum crispum). This paper describes the isolation of three cDNAs encoding proteins which bind specifically to Box II, one of two cis-acting elements found within a 52 bp CHS promoter region shown here to be sufficient for light responsiveness in parsley. The deduced amino acid sequences of all three proteins reveal conserved basic and leucine zipper domains characteristic of transcription factors of the bZIP class. Nucleotide sequences recognized by these factors contain an ACGT motif common to many cis-acting elements. Therefore, we have termed the proteins CPRF-1, -2 and -3 (Common Plant Regulatory Factor). The characteristics of CPRF-1 binding to Box II and the timing of transient CPRF-1 mRNA accumulation during light exposure of previously dark-grown parsley cells are consistent with the hypothesis that this factor participates in the light-mediated activation of the CHS gene in parsley.

Acyltransferases↗
PubMed1993

Light-independent and light-dependent protochlorophyllide-reducing activities and two distinct NADPH-protochlorophyllide oxidoreductase polypeptides in mountain pine (Pinus mugo).

Lower plants and gymnosperms synthesize chlorophyll and develop photosynthetically competent chloroplasts even when grown in the dark. In cell-free extracts of pine (Pinus mugo, Turra, ssp. mugo) seedlings, light-independent and light-dependent protochlorophyllide-reducing activities are present. Two distinct NADPH-protochlorophyllide-oxidoreductase (POR) polypeptides can be detected immunologically with an antiserum raised against the POR of barley. The subcellular localization and amounts of the two POR polypeptides are differentially affected by light: one of them is predominantly present in prolamellar bodies of etiochloroplasts and its abundance rapidly declines once the pine seedlings are exposed to light; the other is found in thylakoid membranes and its amount does not change during illumination of dark-grown seedlings. Two types of cDNA sequences are identified that encode two distinct POR polypeptides in pine. The relevance of these POR polypeptides for the two chlorophyll biosynthetic pathways active in gymnosperms is discussed.

Amino Acid Sequence↗
PubMed1989

Effect of photofrin II and light energy on retinoblastoma-like cells in vitro. Dose-response relationships, effect of light dose rate and recovery ratio.

A clonogenic survival assay on retinoblastoma-like cells (EXP-5 cells) was applied in vitro to assess the effect of photodynamic therapy at relative low concentrations of photofrin II and high doses of light energy. The cellular concentration of photofrin II was estimated by spectrofluorimetry. The cellular content of photofrin II increased with the concentration in the medium (up to 3 micrograms/ml) and the incubation time (up to 24 h) in cells first incubated in photofrin II for 24 h and then in photofrin-II-free medium for 24 h. There was an obvious dose-response relationship between cell damage and photodynamic therapy both for the cellular photofrin II content and the total amount of light energy delivered. The dose rate of light energy had no influence on the cell damage. The cells had a recovery factor of only 1.34, suggesting a low repair of sublethal damage. An approximately linear isoeffect curve at the 10% survival level was described as a function of photofrin II concentration and light energy, suggesting a predictable reversible relationship between them. The results suggest that retinoblastoma cells are very sensitive to photodynamic therapy.

Animals↗