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PubMed1991

Human pupillary light reflex and reaction time at different intensity of light stimulation (a simple motor reaction to modify the human pupillogram).

The relations between the parameters of a pupillary light reflex and the reaction time to four intensities of light stimulation were studied in 13 normal volunteers (mean age 21.7 years). The consensual pupillary reactions to light were recorded at an infrared-reflecting pupillograph; the reaction time (RT) was recorded by a button pressed with the thumb. All subjects were tested at least twice in two blocks of trials: NO-RT-block, where only pupillograms (PGs) were recorded; and RT-block, where simple motor reactions were performed and recorded on a tape simultaneously with PGs. It was demonstrated that: (1) the intensity of light stimulation is a principal factor influencing the parameters of the human PG and is not a principal factor influencing the visuo-motor reaction time; and (2) A simple motor reaction exerts an inhibitory effect on the PG-amplitude and latency and on other PG-parameters. Some implications of probable mechanisms of the inhibitory influence of RT-processing on the PG-parameters are discussed.

Adult↗

PubMed1988

Photosensitization of leukemic cells and normal bone marrow cells by 514 nm laser light and effects of laser light on migration inhibition and lymphokine response.

In a model for ex-vivo purging of bone marrow grafts, leukemic cells and normal bone marrow cells were treated with merocyanine 540 and exposed to 514 nm laser light. With this treatment, 99.9999% of leukemic cells were killed while 55% of the normal bone marrow cells survived. The deleterious effects of laser light alone in the absence of photosensitizer were not observed as determined by cell viability, cell migration, and response of target cells to human migration inhibition factor. These results indicate that laser light induced photodynamic therapy can be useful for ex-vivo autologous bone marrow purging without regard to the deleterious effects of laser light alone.

Bone Marrow↗

PubMed2004

Influence of light fleck and low light on foliar injury and physiological responses of two hybrid poplar clones to ozone.

Five-month old hybrid poplar clones NE388 and NE359 were exposed to square-wave 30, 55, and 80 ppb O(3) (8 h/day, 7 day/week) under constant high light (HL) and light fleck (LF) during 28 May-29 June 1999, and exposed to 30 and 55 ppb O(3) under HL, LF, and constant low light (LL) during 22 May-28 June 2000 within Continuously Stirred Tank Reactors (CSTR) in a greenhouse. Ramets of these two hybrid clones received similar total photosynthetically active radiation (PAR) within the LF and LL treatments. Visible foliar symptoms, leaf gas exchange, and growth were measured. More severe O(3) induced foliar symptoms were observed on ramets within the LF and LL treatments than within the HL treatment for both clones. The LF treatment resulted in significantly greater foliar injury than the LL treatment for NE388. The LF and LL treatments generally resulted in lower photosynthetic rates (Pn) for both clones, but did not affect stomatal conductance (g(wv)); therefore, the ratios of g(wv)/Pn and the O(3) uptake/Pn were greatest in plants grown under the LF treatment, followed by those grown under LL treatment; plants grown under HL had the lowest ratios of g(wv)/Pn and O(3) uptake/Pn. Greater ratios of g(wv)/Pn and O(3) uptake/Pn were consistently associated with more severe visible foliar symptoms. The negative impacts of the LF treatment on growth were greater than those of the LL treatment. Results indicate that not only the integral, but also the pattern of photo flux density, may affect carbon gain in plants. Increased foliar injury may be expected under light fleck conditions due to the limited repair capacity as a result of continuity of O(3) uptake while photosynthesis decreases under LL conditions.

Adaptation, Physiological↗

PubMed1998

Complete primary sequences of two lambda immunoglobulin light chains in myelomas with nonamyloid (Randall-type) light chain deposition disease.

We herein report on the first two primary sequences (BOU and RAC) of monoclonal light chains of the lambda type responsible for nonamyloid lambda light chain deposition disease. Both patients were affected with severe forms of myeloma complicated with renal failure. The pathological presentation typically featured Congo red-negative deposits along tubular basement membranes but differed somewhat from the typical "Randall-type" kappa light chain deposition disease: they lacked the prominent glomerulosclerosis pattern often featuring nonamyloid kappa deposits and were associated with cylinders or myeloma casts. Both protein sequences were deduced from those of the corresponding complementary DNAs in the bone marrow plasma cells. For each chain, products of three independent amplifications by polymerase chain reaction were sequenced and found to be identical. BOU and RAC lambda mRNAs had a normal overall structure consisting of Vlambda2 segments rearranged to Jlambda2Clambda2 but displayed a number of unusual features within their primary sequences. These substitutions are likely responsible for changes in light chain conformation that promote their aggregation and deposition along renal tubule basement membranes.

Amino Acid Sequence↗

PubMed2004

In vitro evaluation of color change in maxillofacial elastomer through the use of an ultraviolet light absorber and a hindered amine light stabilizer.

STATEMENT OF PROBLEM: External prostheses composed of silicone elastomers exhibit an unwanted color change over time. PURPOSE: This study evaluated color stability when an ultraviolet light absorber and hindered amine light stabilizer were mixed in the maxillofacial elastomer containing either organic or inorganic pigments. MATERIAL AND METHODS: The materials used were an RTV silicone elastomer, 1 natural inorganic dry-earth pigment (burnt sienna) and 2 synthesized organic pigments (hansa yellow and alizarin red), ultraviolet light absorber (UVA) and hindered amine light stabilizer (HALS). Specimens (n=160) were fabricated in a custom mold and randomly assigned and exposed to weathering sites in Miami and Phoenix for approximately 3 months. Eight test groups (2 of each 4 material types with or without additives) of 10 specimens each were assigned to each site. L*, a*, b* readings were obtained before and after weathering from a spectrocolorimeter. Nonpigmented elastomers served as the control. Three-factor ANOVA was conducted to examine interaction effects between weathering sites, specimen type, and the presence of additive (alpha=.05). Overall color change (Delta E) and change in color coordinates (Delta L*, Delta a*, Delta b*) of specimen groups with and without additive were analyzed with independent sample t tests. RESULTS: In specimen groups with the additives (UVA and HALS), color change decreased significantly (P<.05) in burnt sienna and hansa yellow in Phoenix and in the control and hansa yellow in Miami. Additives did not affect color change in the alizarin red group. CONCLUSION: UVA and HALS were shown to be effective in retarding color change in some circumstances.

Absorption↗

PubMed1996

Effects of different patterns of light adaptation on cellular and synaptic plasticity in teleost retina: comparison of flickering and steady lights.

The importance of the pattern of light stimulus in inducing light-adaptive morphological (cellular and sub-cellular) changes in the outer retina of the carp was assessed. Thus, the effects of steady and flickering backgrounds (of the same intensity) on cone photomechanical movements (PMMs) and horizontal cell (HC) spinules were compared by quantitative measurements. For both phenomena, flickering stimuli had a significantly greater effect than steady, although the number of photons delivered by the former was one-half. The results demonstrate clearly that the pattern of light stimulus is indeed an important parameter in determining the extent of adaptation in the outer retina. The effects are discussed in relation to possible neurochemical bases of light-adaptive neural control mechanisms.

Adaptation, Physiological↗

PubMed2001

Very high light resistant mutants of Chlamydomonas reinhardtii: Responses of Photosystem II, nonphotochemical quenching and xanthophyll pigments to light and CO(2).

We have isolated very high light resistant nuclear mutants (VHL (R)) in Chlamydomonas reinhardtii, that grow in 1500-2000 mumol photons m(-2) s(-1) (VHL) lethal to wildtype. Four nonallelic mutants have been characterized in terms of Photosystem II (PS II) function, nonphotochemical quenching (NPQ) and xanthophyll pigments in relation to acclimation and survival under light stress. In one class of VHL (R) mutants isolated from wild type (S4 and S9), VHL resistance was accompanied by slower PS II electron transfer, reduced connectivity between PS II centers and decreased PS II efficiency. These lesions in PS II function were already present in the herbicide resistant D1 mutant A251L (L (*)) from which another class of VHL (R) mutants (L4 and L30) were isolated, confirming that optimal PS II function was not critical for survival in very high light. Survival of all four VHL (R) mutants was independent of CO(2) availability, whereas photoprotective processes were not. The de-epoxidation state (DPS) of the xanthophyll cycle pigments in high light (HL, 600 mumol photons m(-2) s(-1)) was strongly depressed when all genotypes were grown in 5% CO(2). In S4 and S9 grown in air under HL and VHL, high DPS was well correlated with high NPQ. However when the same genotypes were grown in 5% CO(2), high DPS did not result in high NPQ, probably because high photosynthetic rates decreased thylakoid DeltapH. Although high NPQ lowered the reduction state of PS II in air compared to 5% CO(2) at HL in wildtype, S4 and S9, this did not occur during growth of S4 and S9 in VHL. L (*) and VHL (R) mutants L4 and L30, also showed high DPS with low NPQ when grown air or 5% CO(2), possibly because they were unable to maintain sufficiently high DeltapH due to constitutively impaired PS II electron transport. Although dissipation of excess photon energy through NPQ may contribute to VHL resistance, there is little evidence that the different genes conferring the VHL (R) phenotype affect this form of photoprotection. Rather, the decline of chlorophyll per biomass in all VHL (R) mutants grown under VHL suggests these genes may be involved in regulating antenna components and photosystem stoichiometries.

Journal Article↗

PubMed2003

Determination of DNA by Rayleigh light scattering enhancement of molecular "light switches".

Base on the enhancement of Rayleigh light scattering signals of molecular "light switches" by DNA under acidic condition, a sensitive and convenient method for DNA determination was proposed. The experiments indicated that, under optimum conditions, good linear relationships were obtained between the Rayleigh light scattering intensity and the concentration of nucleic acids. The detect limits of calf thymus DNA (ctDNA) were 13.0 ng ml(-1), 4.2 ng ml(-1), 51.5 ng ml(-1) and 3.0 ng ml(-1) with four "light switches", respectively. Plasmid DNA extracted from Bacillus subtilis were determined by the proposed method with satisfactory results, and the recovery rates of calf thymus DNA were in the range of 94.6-110.7%.

Animals↗

PubMed1983

Isolation of cDNA clones for the light subunit of rat liver ferritin: evidence that the light subunit is encoded by a multigene family.

The shell of the iron-storage protein ferritin consists of two types of subunit (heavy, Mr = 21,000; light, Mr = 19,000). To study the structure and expression of the ferritin subunit genes, recombinant plasmids containing ferritin cDNA have been isolated. A cDNA library was constructed in the vector pBR322 from rat liver polysomal mRNA and screened by using I125-labeled antibody to rat liver ferritin. Six positive clones were identified and were shown to contain cDNA inserts ranging in length from 800 to 950 base pairs. When these cDNA clones were used for hybrid selection of rat liver mRNA and the selected mRNAs were translated in vitro, the products from each clone migrated on denaturing gels in a position similar to that of the light subunit of ferritin. No evidence of translation of the heavy subunit was obtained, indicating that the two subunits are encoded by separate mRNAs. RNA blot analysis gave a length of 1,100 nucleotides for the light-subunit mRNA. One of the cDNA inserts was fractionated into four fragments by using the restriction enzyme Sau3A. When the fragments were hybridized with Southern blots of rat spleen DNA, each fragment yielded similar patterns of hybridization to that obtained with the intact cDNA. Therefore, all regions of the cDNA sequence contain homologous sequences to similar genomic restriction fragments. This is consistent with the existence of a family of genes that encode the light subunit of rat ferritin.

Animals↗

PubMed1986

Structural differences in a single gene encoding the V kappa Ser group of light chains explain the existence of two mouse light-chain genetic markers.

Two phenotypic markers of mouse immunoglobulin kappa light chains, the IB-peptide marker and the Ef1a isoelectric focusing marker, are expressed by the C58/J, AKR/J, RF/J, and PL/J strains (called expressor strains) but not by BALB/c and most inbred strains. Expression is linked to the kappa light-chain locus and the Lyt-2/Lyt-3 genes on chromosome 6. Light chains bearing these markers belong to a group of variable region kappa chain (V kappa) regions called V kappa Ser, which has a serine amino terminus and a framework 1 region not observed to date among BALB/c light chains. Southern hybridization of genomic DNA with a V kappa Ser-specific cDNA probe has demonstrated a single strongly hybridizing DNA fragment in all strains of mice tested. Characteristic restriction enzyme polymorphisms define the V kappa Ser alleles of expressor (Igk-VSera) and nonexpressor (Igk-VSerb) strains. In the present study, the unrearranged V kappa Ser gene and its flanking regions from an expressor (C.C58) and nonexpressor (BALB/c) strain have been cloned and their nucleotide sequences determined. The C.C58 V kappa Ser gene isolated (the Igk-VSera allele) was shown to code for the two phenotypic markers described. While the nucleotide sequence of the BALB/c coding region (the Igk-VSerb allele) shows 97% identity with the C.C58 gene, single nucleotide substitutions lead to structural changes in the encoded protein which render it IB-negative and Ef1a-negative. These differences alone can explain the failure of strains containing the BALB/c allele to express these kappa-chain phenotypic markers. Also, the BALB/c gene contains a single substitution in a conserved octamer sequence approximately equal to 100 nucleotides upstream of the coding region, which could affect its expression. Finally, the C.C58 allele contains a BAM5/R repetitive DNA element approximately equal to 1200 nucleotides upstream of the coding regions that is not present in BALB/c. This element gives rise to the EcoRI and BamHI restriction enzyme polymorphisms, which distinguish the Igk-VSera and Igk-VSerb alleles.

Amino Acid Sequence↗

PubMed2006

Removal of Cu(II)-EDTA complex using TiO2/solar light: the effect of operational parameters and feasibility of solar light application.

The photocatalytic oxidation (PCO) of Cu(II)-ethylene diamine tetra acetic acid (EDTA) was investigated at 38 degrees latitude, using natural sunlight instead of artificial UV light. In order to investigate the optimum conditions for the PCO of Cu(II)-EDTA, the effects of several parameters, such as the type and angle of solar collector, solar light intensity, area of the solar reactor and flow rate, on the removals of Cu(II) and dissolved organic carbon (DOC) were examined with 20 L of 10(-4) M Cu(II)-EDTA at pH 4 in a circulating reactor. The removals (%) of Cu(II) and DOC were favorable with the use of a hemispherical collector, with a 38 degrees tilt angle when flat, on a sunny day, and a solar collector with a high area, in a TiO(2) slurry system. On the basis of these experimental results, PCO with solar light irradiation could be used as a feasible technique in the treatment of Cu(II)-EDTA. In addition, PCO with solar light irradiation is regarded as a potential technique in the treatment of real electroplating wastewater when considering the quite similar removal efficiency of Cu(II)-EDTA, with the subsequent removal of the liberated Cu(2+) by adsorption onto the TiO(2) compared to that of synthetic wastewater.

Adsorption↗

PubMed2002

Three days of novel wheel access diminishes light-induced phase delays in vivo with no effect on per1 induction by light.

The mammalian circadian clock, located in the hypothalamic suprachiasmatic nuclei, synchronizes endogenous behavioral and physiological rhythms to a 24 h period through responses to two types of stimuli: photic (light) and nonphotic (behaviorally induced arousal and/or increases in activity). Photic stimuli can block nonphotic effects and vice versa, although the mechanisms and levels of interactions between these two stimuli types are unknown. Here, we investigated whether 3 d of access to a novel running wheel alters the phase shift to light in vivo, and whether this effect could be seen on induction by light of the circadian gene per1. Through measurement of running wheel activity of golden hamsters, access to a new wheel for 3 d was shown to diminish photic phase delays with no effect on phase advances. As seen using in situ hybridization, however, there was no effect on levels of light-induced per1 mRNA. This study indicates a possible role for this paradigm as a model of interactions between photic and nonphotic stimuli.

Animals↗

PubMed2003

Solar light induced degradation of trichloroethylene (TCE) using TiO2: effects of solar light intensity and seasonal variations.

The feasibility of the trichloroethylene (TCE) degradation using solar light was investigated. With both solar light and TiO2 present, TCE was more effectively degraded than either with solar light or TiO2 alone. The rate of photocatalytic degradation under a clear sky was about five and 18 times higher than that of photocatalytic degradation under cloudy and thick cloudy skies, respectively. The optimization of the degradation rates was strongly dependent on the solar light intensity. All experimental data were fit to a first-order rate equation. Summer showed faster degradation rate than winter. From the mass balance, this study showed that over 80% of chloride in clear and partly cloudy skies was mineralized from TCE degradation.

Kinetics↗

PubMed2005

Effectiveness of photodynamic therapy with topical 5-aminolevulinic acid and intense pulsed light versus intense pulsed light alone in the treatment of acne vulgaris: comparative study.

BACKGROUND: Photodynamic therapy (PDT) involves the activation of a photosensitizing agent by light to produce oxygen intermediates that destroy target tissues. Topical 5-aminolevulinic acid (ALA) is converted to protoporphyrin IX, a very potent photosensitizer, which accumulates in human skin, particularly in the epidermis and its appendages. OBJECTIVE: To study the effect of PDT in acne vulgaris using topical ALA and intense pulsed light (IPL). METHODS: Thirteen individuals with varying degrees of acne were treated after a 3-week washout period. Twenty percent ALA hydrochloride (DUSA Pharmaceuticals, Wilmington, MA, USA) was applied to half of the face, and after 3 hours, the whole face was exposed to intense pulsed light (Quantum SR, Lumenis, Santa Clara, CA, USA) using a 560 nm cutoff filter starting at a fluence of 26 J/cm. The procedure was done twice at 2-week intervals, and the patients were clinically evaluated on the second, fourth, and eighth weeks. RESULTS: All patients had no apparent improvement on the second week on both facial halves. In fact, some of the patients developed acute acneiform eruptions on the side treated with ALA. By the fourth week, however, most of the patients had visible improvement of facial acne that was more significant on the ALA-treated side of the face. This persisted until the eighth week post-treatment. On the other hand, the facial half treated with intense pulsed light only showed a return to baseline of their facial acne. CONCLUSION: ALA-IPL are beneficial in the management of acne vulgaris and may be used in combination with other forms of acne treatment or may be an alternative treatment for patients who do not want to take systemic retinoids.

Acne Vulgaris↗

PubMed2002

Hadronic light-by-light scattering contribution to the muon g - 2: an effective field theory approach.

The hadronic light-by-light contribution to a(mu), the anomalous magnetic moment of the muon, is discussed from the point of view of an effective low-energy theory. As an application, the coefficient of the leading logarithm arising from the two-loop graphs involving two anomalous vertices is computed, and found to be positive. This corresponds to a positive sign for the pion-pole contribution to the hadronic light-by-light correction to a(mu), and to a sizable reduction of the discrepancy between the present experimental value of a(mu) and its theoretical counterpart in the standard model.

Journal Article↗

PubMed1998

Induction of acclimative proteolysis of the light-harvesting chlorophyll a/b protein of photosystem II in response to elevated light intensities

Most plants have the ability to respond to fluctuations in light to minimize damage to the photosynthetic apparatus. A proteolytic activity has been discovered that is involved in the degradation of the major light-harvesting chlorophyll a/b-binding protein of photosystem II (LHCII) when the antenna size of photosystem II is reduced upon acclimation of plants from low to high light intensities. This ATP-dependent proteolytic activity is of the serine or cysteine type and is associated with the outer membrane surface of the stroma-exposed thylakoid regions. The identity of the protease is not known, but it does not correspond to the recently identified chloroplast ATP-dependent proteases Clp and FtsH, which are homologs to bacterial enzymes. The acclimative response shows a delay of 2 d after transfer of the leaves to high light. This lag period was shown to be attributed to expression or activation of the responsible protease. Furthermore, the LHCII degradation was found to be regulated at the substrate level. The degradation process involves lateral migration of LHCII from the appressed to the nonappressed thylakoid regions, which is the location for the responsible protease. Phosphorylated LHCII was found to be a poor substrate for degradation in comparison with the unphosphorylated form of the protein. The relationship between LHCII degradation and other regulatory proteolytic processes in the thylakoid membrane, such as D1-protein degradation, is discussed.

Journal Article↗

PubMed1999

Light-induced changes in hydrogen, calcium, potassium, and chloride ion fluxes and concentrations from the mesophyll and epidermal tissues of bean leaves. Understanding the ionic basis of light-induced bioelectrogenesis

Noninvasive, ion-selective vibrating microelectrodes were used to measure the kinetics of H+, Ca2+, K+, and Cl- fluxes and the changes in their concentrations caused by illumination near the mesophyll and attached epidermis of bean (Vicia faba L.). These flux measurements were related to light-induced changes in the plasma membrane potential. The influx of Ca2+ was the main depolarizing agent in electrical responses to light in the mesophyll. Changes in the net fluxes of H+, K+, and Cl- occurred only after a significant delay of about 2 min, whereas light-stimulated influx of Ca2+ began within the time resolution of our measurements (5 s). In the absence of H+ flux, light caused an initial quick rise of external pH near the mesophyll and epidermal tissues. In the mesophyll this fast alkalinization was followed by slower, oscillatory pH changes (5-15 min); in the epidermis the external pH increased steadily and reached a plateau 3 min later. We explain the initial alkalinization of the medium as a result of CO2 uptake by photosynthesizing tissue, whereas activation of the plasma membrane H+ pump occurred 1.5 to 2 min later. The epidermal layer seems to be a substantial barrier for ion fluxes but not for CO2 diffusion into the leaf.

Journal Article↗

PubMed1978

Light Penetration and Light-induced Seed Germination in Soil.

Light penetration through a Drummer silty clay loam and a Broomfield sand was measured spectrophotometrically and biologically. The spectrophotometric measurements showed that less than 1% of the incident light penetrated 2.2 millimeters at any wavelength between 350 and 780 nanometers for ped sizes up to 1 millimeter. Biological measurements with light-sensitive lettuce (Lactuca sativa) seeds in soil showed that an exposure to light equivalent to about 1 sunny day induced some germination of seeds which were 2 millimeters below the surface, but did not affect seeds 6 millimeters below the surface.

Journal Article↗