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At least 253 records · Page 14Linked to original sources
PubMed1988

Phosphorylation of the 20,000-Da myosin light chain isoforms of arterial smooth muscle by myosin light chain kinase and protein kinase C.

Phosphorylation of myosin light chain (LC) isoforms in arterial actomyosin can be induced by endogenous kinases upon addition of Mg2+ and ATP. The extent of phosphorylation in the presence of 2 mM ethylene glycol bis(beta-aminoethyl ether)N,N'-tetraacetic acid (EGTA), 0.2 mM Ca2+, or 0.2 mM Ca2+ plus calmodulin is 1.6, 2.1, and 2.3 mol phosphate/mol LC, respectively. Two-dimensional gel electrophoresis of actomyosin shows that the LC isoforms may be mono-, di-, and triphosphorylated. Tryptic phosphopeptide mapping of LC indicates that the radioactive phosphate is distributed to six peptides referred to as A through F. Phosphoamino acid analyses and the phosphopeptide maps of isolated LC, phosphorylated by either purified myosin light chain kinase or protein kinase C, reveal that myosin light chain kinase phosphorylates a serine residue in peptides A and B, and threonine plus serine residues in peptides C and D. Peptides E and F are phosphorylated by protein kinase C in serine and threonine residues, respectively. In actomyosin, with EGTA, phosphorylation of peptides E and F proceeds while phosphorylation of peptides A, B, C, and D is inhibited. Ca2+ and calmodulin enhance the phosphorylation of peptides A, B, C, and D, while phosphorylation of peptides E and F is decreased. In isolated LC, myosin light chain kinase preferentially phosphorylates the peptides A and B over C and D. Phosphorylation of peptides E and F in LC by protein kinase C promotes additional phosphorylation of peptides C and D by myosin light chain kinase, whereas phosphorylation of peptides A and B is diminished. The present data suggest that the phosphorylation of distinct sites in arterial myosin light chain by myosin light chain kinase and protein kinase C is interrelated.

Adenosine Triphosphate↗
PubMed1989

Effect of unit and operatory lights on the consistency of light-activated composites.

The extent to which the flow of composite resin is reduced when exposed to dental lights was studied. Samples were exposed to operating lights of various intensities for varying periods of time. After exposure each sample was placed under a fixed load and the resulting average diameter was calculated. Data from the testing of samples exposed to dental lights were analyzed by a two-way analysis of variance with subsequent Tukey multiple comparison test. Diameter comparisons were significant (p less than 0.05) between the controls and samples exposed to the 960 fc light at 6 minutes, the 1920 fc light at 4 minutes, the 2880 fc light at 2 minutes, and the 5120 and 7680 fc lights at 1 minute. The smaller diameters observed with respect to increased intensity and time of exposure show that either variable or the combination of both variables will alter the consistency of composite resin.

Chemical Phenomena↗
PubMed1990

The induction of chromosomal aberrations and SCEs by visible light in combination with dyes. II. Cell cycle dependence, and the effect of hydroxyl radical scavengers during light exposure in cultures of Chinese hamster ovary cells sensitized with acridine orange.

Chinese hamster ovary (CHO) cells were synchronized by mitotic shake-off, treated with the fluorochrome acridine orange (AO; 0.5 micrograms/ml), washed free of excess dye and subsequently exposed to visible light (2 X 40 W/8 Wm-2). The light exposure was performed on cells in the G1, G1/S, S or G2 phase of the cell cycle. AO + light induced high frequencies of aberration in the S phase and even higher in the G1 phase. The aberrations observed were all of the chromatid type. The chromosome-type aberrations (dicentrics, rings) obtained when cells in the G1 phase were exposed to X-rays were not found after corresponding treatments with AO + light. With the exception of an increased frequency of gaps, no chromosomal aberrations were induced in G2-phase cells. Sister-chromatid exchanges were efficiently produced by the photodynamic system in the G1, G1/S and S phase of the cell cycle. In other experiments, AO-treated unsynchronized CHO cells were exposed to light in the presence of the hydroxyl radical scavengers mannitol (100 mM) and 5-dimethyl thiourea (100 mM). In parallel experiments these scavengers were found to reduce markedly the chromosome breaking effects by X-rays but had no influence on the photodynamic induction of chromosomal alterations. The results presented show that the visible light-induced chromosomal alterations in CHO cells sensitized with the fluorochrome AO are obtained by an S-dependent mechanism. Furthermore, the results indicate that the hydroxyl free radical does not play a major role in the production of chromosomal alterations by AO + light.

Acridine Orange↗
PubMed1988

Light spread and scatter from some common adapting stimuli: computations based on the point-source light profile.

A point source of light is not so imaged on the photoreceptor mosaic. The light is distributed over the retina by diffraction, imperfections in the optics of the eye, and scatter. The spatial distribution of light is specified quantitatively by the point-source light profile, which can be used in convolution to determine light spread from more complex visual stimuli. We use the Vos, Walraven and van Meeteren [Vision Res. 16, 215-219 (1976)] light profile to determine spread light in specific regions within the spared area of an illuminated surround, and within a thin spared ring in an otherwise uniformly illuminated circular field. Surrounds of different sizes and rings of various widths and diameters are evaluated.

Adaptation, Ocular↗
PubMed1989

Arabidopsis thaliana mutant that develops as a light-grown plant in the absence of light.

The signal transduction pathways that lead to chloroplast biogenesis in plants are largely unknown. We describe here the identification and initial characterization of a novel genetic locus which fits the criteria of a regulatory gene located in a central pathway controlling light-mediated development. In the absence of light, these Arabidopsis thaliana mutants, designated det1 (de-etiolated 1), constitutively display many characteristics that are light-dependent in wild-type plants, including leaf and chloroplast development, anthocyanin accumulation, and accumulation of mRNAs for several light-regulated nuclear and chloroplast genes. The switch between dark and light growth modes thus appears to be a programmed step in a developmental pathway that is defined by det1. We suggest a model where the primary role of light on gene expression is mediated by the activation of leaf development. Further, the recessive nature of the det1 mutation implies that there is negative growth control on leaf development in dicotyledonous plants in the absence of light.

Anthocyanins↗
PubMed1987

Effect of light history on retinal antioxidants and light damage susceptibility in the rat.

Albino rats were born and raised to 12 weeks of age in 12L:12D light regimes of 5, 300 or 800 lx. Upon killing, the activities of the following glutathione enzymes were measured in the neuroretina: (1) glutathione peroxidase; (2) glutathione-S-transferase; and (3) glutathione reductase. Also measured were vitamin E, ascorbic acid, and the levels of oxidized and reduced glutathione. Animals raised in 800-lx cyclic light have a significant increase in the retinal activities of the three glutathione enzymes over activities measured in animals raised in the two dimmer regimes. The retinal level of vitamin E, measured per nmol of lipid phosphorus, is directly and significantly correlated with rearing illuminance (P less than 0.05). The same is true of retinal ascorbic acid, which shows a 30% increase in the 800-lx-reared rats over the level of those raised in the intermediate light regime (300 lx). Some of the animals from each group were exposed to 2000 lx for 24 hr to determine if correlations existed between the levels of retinal antioxidants listed above and susceptibility to light damage. Animals raised in 5-lx cyclic light lost almost all of their photoreceptors as a result of the exposure. Rats raised in 300-lx cyclic light lost a small but significant number (ca. 20%), while those raised in 800 lx sustained no light damage. Electroretinographic evaluation supports these morphometrical findings.

Animals↗
PubMed1999

Five-year color changes of light-cured resin composites: influence of light-curing times.

OBJECTIVES: The purpose of this study was to investigate the influence of light-curing times on the color changes of light-cured resin composites, over specified periods of time. METHODS: Silux Plus (3M Dental Products) light-cured resin composite disks (shades: U, Y, DY, L, G, UO, YO), 10 mm in diameter and 1 mm in thickness were prepared with 20, 40, and 120 s of light exposure through a 1 mm thick glass plate. The specimens were stored in artificial saliva at 37 degrees C. Colorimetric values of the specimens immediately after curing and after every 6 months for 5 years were measured backed by a light trap, and a white colored plate using a fast spectrophotometer. The CIE 1976 L*a*b* color system was used for the determination of the color difference. RESULTS: For specimens backed by a white colored plate, the delta E*ab of all shades increased for 3 years and 6 months to 5 years, to the time elapsed during all curing times. However, the a*b* values to the time elapsed differed among the shades and light curing times. In the 20 and 120 s curing time groups, the opacity% of all shades increased for 4 or 5 years to the time elapsed. SIGNIFICANCE: The modes of color changes of Silux Plus resins differed among the shades and light curing times.

Analysis of Variance↗
PubMed2002

Two light-responsive elements of pea chloroplastic fructose-1,6-bisphosphatase gene involved in the red-light-specific gene expression in transgenic tobaccos.

The pea chloroplast fructose-1,6-bisphosphatase (FBPase) gene was cloned from a pea genomic library and sequenced. The gene contained three introns and four exons. Both in vitro and in vivo analyses of the promoter region of the gene were carried out simultaneously to elucidate the mechanisms of light-mediated gene expression. Two light-responsive elements were identified in gel mobility shift assays: a GT-1-like sequence for the binding of a GT-1-like factor (termed pea factor 1; PF1) and a binding site for a dark-specific factor (termed pea factor 2; PF2). The binding affinity of PF1 was higher in light-grown peas than in dark-grown peas and was affected by phosphorylation. The binding site was located at nucleotides (nt) -326 to -341. PF2 binding was dark-specific and the binding region was located upstream of the PF1-binding site (nt -492 to -412). In vivo experiments with transgenic tobacco plants suggested that the region between nt -411 and -272 contained a PF1-binding site that promoted light-mediated expression of the pea chloroplast FBPase. In contrast, the 81-bp region between nt -492 and -412, which is located further upstream than the PF1-binding site, negatively regulated light-mediated expression of FBPase. Moreover, activation of gene expression by the region (nt -411 to -272) contained a PF1-binding site that was sensitive to red-light irradiation, suggesting that the expression of the chloroplast FBPase was regulated by the phytochrome system. Interestingly, the binding region for the dark-specific factor (PF2; nt -492 to -412) not only repressed gene expression in the dark, but also acted as a light-dependent activating element of the chloroplast FBPase gene.

Base Sequence↗
PubMed1986

Light- and nucleotide-dependent binding of phosphodiesterase to rod disk membranes: correlation with light-scattering changes and vesicle aggregation.

Under conditions in which large guanosine cyclic 3',5'-phosphate (cGMP)- and phosphodiesterase (PDE)-dependent changes in near-infrared transmission and vesicle aggregation and disaggregation occur, we have observed a striking change in the binding of PDE to rod disk membranes. The change in PDE binding is nucleotide and light dependent as are the light-scattering changes. The cGMP- and PDE-dependent light-scattering signal can be produced by a 500-nm light flash which bleaches 1/(1 X 10(7] rhodopsin molecules. Mg ions are an essential cofactor for the nucleotide-dependent PDE binding and light-scattering changes. 3-Isobutyl-1-methylxanthine and other competitive inhibitors of PDE hydrolytic activity support increased PDE binding to the disk membrane, vesicle aggregation, and the light-scattering signal. However, treatments which block GTP-dependent activation of PDE hydrolytic activity (colchicine, GDP, or ethylenediaminetetraacetic acid) also block these phenomena. Thus, GTP-dependent activation of PDE rather than its hydrolytic activity appears to be correlated with the light-scattering signal.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2005

Light-induced structural changes of apoprotein and chromophore in the sensor of blue light using FAD (BLUF) domain of AppA for a signaling state.

AppA is a new class blue-light receptor controlling photosynthesis gene expression in the purple bacterium Rhodobacter sphaeroides and retains a characteristic flavin adenine dinucleotide (FAD)-binding domain named the "sensor of blue light using FAD" (BLUF). AppA functions as an antirepressor controlling transcription of photosynthesis genes through the direct association with a transcriptional repressor PpsR in a blue-light-dependent manner [Masuda and Bauer (2002) Cell 110, 613-623]. Illumination of AppA induces a red shift in the UV-visible absorption of FAD, which results in a signaling state of AppA. Light-induced Fourier transform infrared (FTIR) difference spectrum of the AppA BLUF domain showed relatively simple features, which were mainly composed of two sets of derivative-shaped sharp bands at 1709(-)/1695(+) and 1632(+)/1619(-) cm(-)(1). We have developed an in vitro reconstitution method, by which a fully functional BLUF domain was reconstituted from free FAD and an apoprotein for the BLUF domain of AppA. An AppA BLUF domain that consisted of an apoprotein isotopically labeled with (13)C and unlabeled FAD was constituted using this method, and hydrated and deuterated samples were applied to FTIR spectroscopic analyses. When the spectra for the reconstituted domain were compared with those for uniformly (15)N- and (13)C-labeled or deuterated domains as well as for the unlabeled domain, the IR bands responsible for the light-induced changes in the FAD chromophore and apoprotein were identified. Unexpectedly, the light-induced spectrum of the unlabeled BLUF domain of AppA was predominantly composed of multiple apoprotein bands, while a C(4)=O stretching of an isoalloxazine ring was the only band exclusively assigned to FAD. The results showed that relatively large structural changes occur in the protein backbone of the BLUF domain of AppA upon illumination. These changes were discussed in relation to the mechanistic role of the BLUF domain in the process of blue-light perception by AppA.

Apoproteins↗
PubMed1997

Further investigation of the light chain shifting phenomenon: light chain replacement through secondary rearrangement induced by lectin stimulation in the hybridoma cell line HB4C5.

We found that when the hybridoma cell line HB4C5 was stimulated with wheat germ agglutinin (WGA), loss of production of the original lambda light chain occurred, followed by production of new light chain, which mirrored the reaction when stimulated with concanavalin A (ConA). We previously reported that the RAG genes are expressed not only in HB4C5 and its ConA-treated variant subclones, but also in the in the parental Namalwa cells, which are known to be in the plasma state. However, the new lambda light chains were expressed only in the HB4C5 cells and not in the parental Namalwa cells. Here we found that the RAG genes are expressed in HB4C5 cells after continuous stimulation with WGA. To further investigate the mechanism of this loss of original lambda light chain production by stimulation with lectins in HB4C5 cells, which leads to a sIg-negative subpopulation, we analyzed the differences between HB4C5 and Namalwa cells. In this present study, we found that a 70 kDa phosphorylated protein in HB4C5 cells became undetectable after stimulation with lectins (WGA and ConA), and was not detected in Namalwa cells before or after lectin stimulation. It has been believed that the RAG genes and loss of original lambda light chain production are required to induce expression of a new lambda light chain in the HB4C5 cells. We suggested that the phosphorylated 70 kDa protein in HB4C5 cells play important roles in regulating the production of new lambda light chains which is induced by lectins.

Amino Acid Sequence↗
PubMed2001

Useful polyclonal antibodies against synthetic peptides corresponding to immunoglobulin light chain constant region for immunohistochemical detection of immunoglobulin light chain amyloidosis.

For the immunohistochemical detection of immunoglobulin (Ig) light chain amyloidosis on formalin-fixed, paraffin-embedded tissue sections, we prepared polyclonal antibodies against synthetic peptides corresponding to positions 118-134 of Ig lambda light chain and positions 116-133 of Ig kappa light chain. Nineteen cases of systemic Ig lambda light chain amyloidosis (Alambda amyloidosis), 10 cases of systemic Ig kappa light chain amyloidosis (Akappa amyloidosis), one case of immunohistochemically unclassified systemic amyloidosis and five cases of localized Alambda amyloidosis were tested with these antibodies. Anti-lambda (118-134) antiserum and the affinity-purified antibody both reacted with 18 of the 19 cases of systemic Alambda amyloidosis and all cases of localized Alambda amyloidosis, although the immunoexpression was somewhat variable in intensity in different areas within the same specimen in both systemic and localized amyloidosis. The signal intensities in plasma cells and serum reacted for anti-lambda (118-134) antiserum were weaker than signals obtained with commercially available anti-Ig lambda light chain antibodies. Anti-kappa (116-133) antiserum and the affinity-purified antibody reacted with nine of the 10 cases of systemic Akappa amyloidosis. We conclude that these antibodies against synthetic peptides corresponding to the Ig light chain constant region are useful for the classification of amyloidosis on formalin-fixed, paraffin-embedded tissue sections.

Amyloidosis↗
PubMed2001

[Vitamins C and E protect cultures of bovine lens epithelium from the damaging effects of blue light (430 nm) and UVA light (300-400 nm)].

BACKGROUND: In 1992 Radlmaier showed that catalase can protect bovine lens epithelial cultures from blue light. The following experiments have the aim to examine, if vitamin C and E have protective functions, also. MATERIAL AND METHODS: 367 cultures of bovine lens epithelial cells were incubated in Medium 199 added by 20% foetal calf serum FCS, by 125 I.U./ml penicillin, by 125 mg/ml Streptomycin, by 0.31 microgram/ml amphotericin B, by 2% L-Glutamin (200 mM), and by 1.25% Hepesbuffer. The incubation temperature was kept at 36 degrees C at a pCO2 of 5%. In order to avoid secondary morphologic alterations, we experimented only on the second to the third subculture. Light exposure followed three days after addition of the substances such as Cebion 500 (R) ad injection (6 mg/dl) and E-Vicotrat (R) ad injection (0.5 mg/dl). The blue light (420-430 nm, Draeger) was applied in a baby bed at 36 degrees C for four hours (1.1 mW/cm). The UV-A lamp was constructed and described by Heller [7]; at a wave length of 300-400 nm, the irradiation time was 10 minutes at 100 mW/cm2. In morphologic evaluation we looked for criteria such as cell diameter, cellular wall alterations, cellular inclusions and vacuoles. The cell count was done after staining with the vital dye trypan-blue in Neubauer's chamber. In statistic evaluation we used the pair comparison of Tuckey and Kruskall-Wallis-Test. RESULTS: After addition of 0.5 mg/ml vitamin E: In 89 cultures, morphologic evaluation and cell count showed a significant protection against light toxicity: After Uv-A-irradiation we counted 50% more living cells and after blue light 30% more. After addition of 6 mg/ml Cebion vitamin C: Morphologic evaluation and cell count of 223 cultures showed them also to be significantly protected: after irradiation by UV-A we counted 25% more and after exposition to blue light 15% more living cells. CONCLUSION: The demonstrated experiments significantly showed, that vitamin C and vitamin E can protect lens epithelial cultures from toxic stress by blue and by UV-A light and might delay cataract formation in man.

Animals↗
PubMed2003

Functional conservation of light, oxygen, or voltage domains in light sensing.

In Neurospora, the flavin adenine dinucleotide-containing protein WHITE COLLAR-1 is the blue-light photoreceptor for the circadian clock and other light responses. The putative chromophore-binding domain of WC-1, its light, oxygen, or voltage (LOV) domain, is similar to the LOV domains found in the plant phototropins, the Neurospora VIVID (VVD) protein, and the Arabidopsis FKF1 and its related proteins. Studies of the plant phototropins have identified 11 flavin-contacting residues that are also conserved in the LOV domains of WC-1, VVD, and FKF1. In this study, by mutating the putative WC-1 flavin-binding sites, we show that these sites are important for the light function of the protein, suggesting that the WC-1 LOV domain adapts a structure similar to that of the phototropin LOV domains. By creating a Neurospora strain in which the LOV domain of WC-1 is swapped with that of VVD, we show that the LOV domain of VVD partially replaces the function of the WC-1 LOV domain, suggesting that VVD is a wc-dependent photoreceptor in Neurospora. Furthermore, we show that the Neurosporastrains containing a chimeric WC-1 protein with the LOV domain from FKF1 or phot1 can also sense light, suggesting that FKF1 and its related proteins are light sensors in Arabidopsis. Taken together, our data suggest that these LOV domains are structurally similar protein modules involved in blue-light sensing.

Amino Acid Sequence↗
PubMed2005

A comparison of tungsten-quartz-halogen, plasma arc and light-emitting diode light sources for the polymerization of an orthodontic adhesive.

This study investigated whether there were differences between the debond stress and adhesive remnant index (ARI) of an adhesive cured with three different orthodontic light sources. Sixty sound premolar teeth were divided into three groups of 20. A standard pre-adjusted edgewise premolar bracket (Victory Series) was bonded to each tooth using a light-cured orthodontic adhesive, Transbond X. Group 1 (control) specimens were cured with an Ortholux XT (tungsten-quartz-halogen bulb) light for 20 seconds, group 2 with an Ortho lite (plasma arc) for 6 seconds and group 3 with an Ortholux LED light-emitting diode for 10 seconds. The specimens were debonded 24 hours later using a universal mechanical testing machine, operating at a crosshead speed of 0.5 mm minute(-1). The Weibull modulus and a Logrank test showed no statistically significant differences between the three groups for debond stress. The ARI was assessed at x10 magnification. The ARI scores for group 2 were significantly different (P < 0.01) from those of groups 1 and 3 (between which there was no significant difference). For group 2 there was a greater tendency for failure to occur at the adhesive/tooth interface than for the other two groups. There appears to be no reason why any of the three types of light source cannot be used in orthodontics. Polymerization, as effective as that produced by conventional bulb light sources, was obtained with the short exposure times recommended for the plasma arc or light-emitting diode sources.

Bicuspid↗
PubMed2004

Photosynthetic characteristics of rice leaves grown under red light with or without supplemental blue light.

In rice plants grown under red light supplemented with blue light (red/blue-light PPFD ratio was 4/1), photosynthetic rates per unit leaf area measured under white light at 1,600 and 250 micromol m-2) s-1 were higher than those in the plants grown under red light alone. The higher photosynthetic rates were associated with higher total N content of leaves, which was accompanied by larger amounts of key components of photosynthesis-limiting processes, including Rubisco, Cyt f, Chl and LHCII. These results suggested that the increase in total N content of leaves induced by supplemental blue light enhanced both light-saturated and light-limited photosynthesis.

Chlorophyll↗
PubMed1999

Ahemeral lighting of turkey breeder hens. 3. Temporary application and early age at lighting.

Ahemeral (non-24 h) light-dark cycles are known to increase egg size but when applied continuously have adverse effects on egg production. The purpose of this experiment was to determine whether temporary application of ahemeral light-dark cycles (AH) can overcome the adverse effects of continuous AH and provide improved reproductive performance of turkey hens photostimulated at an early age. Of particular interest was the effect of temporary AH on increasing egg weight at the start of lay because decreased egg weight is a major problem associated with early lighting of turkey hens. The AH treatments started at 26 wk of age and were given for 2 wk, 5 wk, or continuously. Each consisted of 15 h of light per cycle with a cycle length of 28 h duration, that is, 15 h light (L):13 h dark (D). The experiment was started in the winter season and continued for 28 wk. 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. It was clear that 5 wk or more of AH followed by standard lighting (15L:9D) increased initial egg weights from those of 26-wk controls and were similar to those of 30-wk controls. This effect was temporary, as it was absent by 8 wk of photostimulation. Also, cumulative eggs per hen to 54 wk of age were increased by 5 wk of AH treatment as compared to those of controls photo-stimulated at 30 wk of age. These eggs had normal fertility, hatchability, and poults per hen in two evaluation periods. A high incidence of AH floor eggs was reduced to that of the controls following a shift to standard light-dark cycles. We concluded that temporary use of AH at the start of photostimulation is better than continuous use of AH throughout lay and resulted in improved reproductive performance of hens photostimulated at an early age.

Age Factors↗
PubMed2003

Stray light of spectacle lenses compared with stray light in the eye.

Stray light in spectacle lenses may affect the overall vision. It may also affect the measurement of ocular stray light, contrast sensitivity, or glare sensitivity. This article describes common stray light characteristics for glass and plastic spectacle lenses and compares this to the stray light characteristics of the eye, which are well known from the literature. Stray light is described by the skirts of the point-spread function (PSF), which were measured for angles from 4 degrees to 30 degrees. The PSF of spectacle lenses appears to follow the equation PSF = a(10). (theta/10)b, with a(10) and b representing fitting parameters and theta representing the stray light angle. The slope b is on average -2, which similar to that of the eye. For clean spectacle lenses, the PSF is usually at least an order of magnitude lower than that of the eye, whereas "as worn" (uncleaned) spectacle lenses may approach the PSF of the eye. To reach the PSF of the eye, the spectacle lens needs to be contaminated by as much as one or two fingerprints. The article also shows that plastic spectacle lenses degrade much faster than glass spectacle lenses when looking at the amount of stray light.

Eye↗