Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Lighting”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28Linked to original sources
PubMed1994

Effect of light intensity on polymerization of light-cured composite resins.

The depths of cure and the distributions of degree of conversion (DC), polymerization conversion (PC) and percent pendant double bonds (PDB) of light-cured composite resins cured under various intensities of light were investigated. When the total amount of exposure, represented by the product of the light intensity and the irradiation time, was kept constant, each of the depth of cure and the distributions of DC, PC and PDB were the same for each material regardless of the light intensity and irradiation time. The depth of cure could be expressed as a logarithmic function of the total amount of exposure. From regression analysis, the attenuation coefficient and the critical total amount of exposure capable of initiating polymerization of each composite resin could be determined.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1997

Effect of light wavelength on polymerization of light-cured resins.

Experimental light-cured composite resins were exposed to a narrow-band light at a constant quantum number using a narrow-band interference filter. The IR spectra of the cured resin specimens were measured before and after extraction of residual monomers. Degree of conversion (DC) and polymerization conversion (PC) were calculated from these IR spectra. The light in 410-550 nm could be polymerized. With a brief exposure (5 s), DC and PC were affected by the wavelength. The effect of wavelength between 410 and 490 nm decreased with increasing duration of exposure. The most efficient wavelength was 470 nm and the most adequate wavelength was in the 450-490 nm wavelength range. The absorbance of camphorquinone strongly affected polymerization, especially during the initial stage. However, from the relationship between DC or PC and exposure energy, polymerization depended not only on the wavelength of the light, but also on the exposure energy.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1998

[Clinical application of photodynamic therapy combined with non-coherent light (red light) for treatment of port-wine stains].

OBJECTIVE: This is to report the clinical application of photodynamic therapy (PDT) combined with non-coherent light (red light) for the treatment of port wine stains (PWS). METHODS: Eleven cases with PWS have been treated with PDT combined with non-coherent light since Dec. 1995. RESULTS: The facial lesions of PWS in the 11 cases disappeared completely without any scarring. CONCLUSION: PDT combined with red light that has strong skin-penetrating ability and irradiation just after intravenous injection of photosensitizing drugs are effective to embolize the malformative vasculature in pink lesions, especially in dark purple lesions and purple lesions with proliferation.

Adolescent↗
PubMedDate not supplied

Circadian phagocytic activity in rats under light-dark and constant light regimens.

The phagocytic function was proved to be a periodic, circadian process. Its acrophase appears to be differently timed in species with different activity type, occurring in the evening in diurnal species and at night in nocturnal ones. The main pineal hormone melatonin, whose secretion occurs strictly at dark, has been shown to play a role in the control of inflammation and to exert a certain stimulatory effect upon phagocytosis in vitro. The aim of the present study was to assess whether the phagocytic activity of neutrophils in the blood of rats exhibits a circadian rhythmicity similar to that of other nocturnal rodents (mice) and also if a constant light regimen alters its amplitude and/or chronostructure. Wistar rats were submitted to either an artificial light-dark 12/12 regimen (LD) or to constant light (LL), for 15 days. In vitro phagocytosis of the neutrophils in whole blood against E.coli was assessed at 10:00, 16:00, 22:00, and 04:00 hours. In LD, phagocytosis appears to be a rhythmical function, with statistically significant differences between the highest value at 04:00 hrs and the lowest at 10:00 hrs. Constant light induces a 30% depression of the phagocytic ability throughout the whole 24 hours cycle, without altering its oscillations. The darkness period appears to play the role of a synchronizer; in its absence the rhythm tends to free-run. It may be stated that rhythmical melatonin secretion is responsible only for maintenance of the phagocytic level, probably via the anterior hypothalamic area and thymus, while it cannot account directly for the nocturnal increase of phagocytosis.

Animals↗
PubMedDate not supplied

Neutrophil adherence in rats submitted to light-dark alternance and to constant light.

A good amount of experimental data suggests the existence of a circadian control of the inflammatory process. It was shown that migration of neutrophils in chemotactic gradient, ingestion of particles, vascular permeability etc. are rhythmical circadian functions. Melatonin, the pineal hormone secreted during the darkness phase, has been shown to be involved in the control of inflammation. The present study aims to assess whether neutrophil adherence to nylon fibers exhibits circadian rhythmicity and also if its amplitude and/or chronostructure are altered in a constant light regimen. Wistar rats were submitted to either an artificial light-darkness 12/12 regimen (LD) or to constant light (LL), for 15 days. Adherence of the neutrophils in whole blood was assessed at 10:00, 16:00, 22:00, and 04:00 hrs. In LD. neutrophil adherence appears to be a rhythmic, biphasic function, with the acrophase at 10:00, a secondary peak at 22:00 and trough values in the late dark hours. Constant light induces a depression of the adherence ability by about 10%, except for the 04:00 hrs point, where the value in LL is higher than in LD. The fact that adherence and phagocytic activity do not oscillate in phase suggests that the physiological relevance of neutrophil adherence goes beyond that of a first stage of the phagocytic process.

Animals↗
PubMed1989

[Effect of light exposure time on hardness of visible light cured composites].

In this article effect of light exposure time on hardness of visible light cured composites with different microfiller ratios were investigated. For this purpose specimens with heights 1, 2, 3 mm and 6 mm in diameter were prepared. During the preparation of the specimens, half of the specimens were cured with visible light for 40 seconds and the other half for 60 seconds. Surface hardness values were measured from the top and bottom of the specimens immediately after the light source was removed with Barcol Hardness tester. Surface hardness were also measured 24 hours and 7 days later. Results were statistically evaluated.

Composite Resins↗
PubMed1985

Chemical probing of the light-induced interaction between rhodopsin and G-protein. Near-infrared light-scattering and sulfhydryl modifications.

Near-infrared light scattering and gel electrophoresis were used to monitor the interaction between rhodopsin and G-protein at photoreceptor disc membranes. It is found that substitution of one SH hydrogen at the G alpha-subunit by N-ethylmaleimide or thionitrobenzoate still allows dark binding of the G-unit to the membrane but blocks its light binding to rhodopsin. Repair of the modification restores the interaction of the proteins. Evidence is provided that substitution by the less bulky cyanide is also able to remove the hindrance to light binding. The rhodopsin-G interaction is reduced in proportion to bound N-ethylmaleimide, and the interaction kinetics remain constant over the measurable range. GTP/GDP exchange at the G-protein after interaction with rhodopsin does not reduce the accessibility of the relevant SH group. In contrast to the effect of G-protein modification, even exhaustive modification of rhodopsin has no effect on the dark and light binding of G-protein.

Animals↗
PubMed1982

Light effects in yeast: relation between the respiratory deficiency and light sensitivity in yeast.

Visible light of 5,000 lux intensity has been shown to photokill yeast cells at 12 degrees C. In the present report some of isogenic respiratory deficient mit- and nuclear mutants were compared for their sensitivity to light. No close correlation between the cytochromes spectra and light resistance was observed. Although, the nuclear and rho- mutants which lack cytochromes a + a3 and b are as a rule light resistant. Photokilling effect in yeast seems to be dependent both on the sufficiency of respiratory chain and on protein synthesis probably on cytoplasmic level.

Culture Techniques↗
PubMed1981

Light-induced changes in H+ binding to the purple membrane. Effect of pH, light, temperature, and ionic strength.

Under continuous illumination, isolated planar sheets of purple membrane from Halobacterium halobium acidify the surroundings at alkaline pH. This light-induced change in H+ binding to the purple membrane (delta h) was studied by differential titration under varying conditions of pH, temperature, ionic strength, salt composition, light intensity, and wavelength. A maximum acidification was found between pH 9 and 10, with delta h less at neutral or more alkaline pH, consistent with a previously proposed three-state model. The light intensity and wavelength dependence also support this model. The temperature dependence of delta h, interpreted in terms of the three-state model, is anomalous. The apparent enthalpy of proton dissociation (delta H0) is -6 kcal/mol, a value of opposite sign to the expected delta H0 for a group of pK = 10. The apparent activation energy (Ea) for proton uptake is 14 kcal/mol in 15 mM NaCl and 18 kcal/mol in 3 M KCl, 5 to 10 times too large for a diffusion-limited proton transfer reaction from water. However, both delta H0 and Ea are consistent with conformational changes linked to light-independent proton dissociation and pump-dependent proton uptake. An increase in ionic strength increases delta h. This effect is shown to be quantitatively explained by a high negative electrostatic surface potential, which accumulates protons in a diffuse electrical double layer.

Bacteriorhodopsins↗
PubMed1999

Light chain shifting: identification of a human plasma cell line actively undergoing light chain replacement.

We identified an antibody-secreting human B-cell line (HTD8), which actively replaces the production of the original lambda light chain with a new lambda chain (light chain shifting) at a high rate. Loss of the original rearranged lambda light chain occurs by significantly reducing the amount of transcript expressed. Expression of the new lambda chain, which replaces the original lambda chain, occurs by rearranging new VJ segments on a previously excluded allele. V lambda gene usage of these new rearrangements are biased toward Vlambda4, Vlambda6, and Vlambda10 families, which are known to be the least frequently used. In striking contrast to the plasma cell phenotype, recombination activating genes, RAG-1 and RAG-2, were expressed in the HTD8 cells and were shown to be necessary, but insufficient for inducing expression of the new lambda chain. These results suggest that human plasma cells have the potential to actively undergo light chain replacement.

Alleles↗
PubMed1990

Human skeletal muscle myosin light chains analyzed by immobilized pH gradients during ontogenesis: identification of new phosphorylatable isoforms of light chain 2.

Previous studies using two-dimensional gel electrophoresis have described adult and fetal isoforms of skeletal muscle myosin light chains (MLC). They have also revealed an embryo-specific light chain (LC1emb), apparently absent in most adult skeletal muscles. In order to characterize more thoroughly the MLC family, we have analyzed the MLCs from human skeletal muscle at different developmental stages using a two-dimensional electrophoresis technique with an immobilized pH gradient in the first dimension. The high resolution of this novel technique, resolving components which in isoelectric points are less than or equal to 0.01 pH, combined with sensitive silver staining, has allowed us to identify four phosphorylatable isoforms of MLC2: two slow-myosin light chains (MLC2Sa and b), two fast myosin light chains (MLC2Fa and b), and their phosphorylated counterparts: MLC2SaP and bP, MLC2FaP and bP. The following major modifications during development were observed: (i) The embryonic LC (LC1emb) persists up to at least 26 weeks of fetal life. (ii) The polymorphism of LC2 is already evident at 10 weeks of development but only the nonphosphorylated forms of LC2S and LC2F seem to be present. The LC2Fa form is predominant. As early as 26 weeks of fetal life, the 4 phosphorylated forms are detected. In the adult, LC2Fb is a minor component. (iii) LC3F (fast) is already expressed at an early embryonic stage (10 weeks).

Blotting, Western↗
PubMed1984

Myosin light chains of avian and mammalian slow muscles: peptide mapping of 2S light chains.

The 2S light chains of mammalian and avian slow muscle myosin, indistinguishable by two-dimensional gel electrophoresis, have been examined by peptide mapping. The fragments obtained with S. aureus V8 protease were analysed either by gel electrophoresis or by reverse-phase high performance liquid chromatography. The peptide maps of avian 2S light chains contain fragments distinct from those of mammalian 2S light chains. Chicken and turkey LC2S appear to be more similar to each other than those from mammalian species (rat and rabbit). These results are in agreement with the relative phylogenetic distances among the four species studied here. The 2S light chain of slow muscle represent further examples of polypeptides which comigrate in two-dimensional gel electrophoresis in spite of their different peptide maps.

Animals↗
PubMed2002

Exposure of Porphyromonas gingivalis to red light in the presence of the light-activated antimicrobial agent toluidine blue decreases membrane fluidity.

Porphyromonas gingivalis, one of the etiological agents of periodontitis, can be killed by red light in the presence of toluidine blue. The purpose of this study was to determine whether this light-induced killing was accompanied by changes in the fluidity of the organism's cytoplasmic membrane. A suspension of the organism was exposed to red light in the presence of toluidine blue, and the membrane fluidity was monitored spectrofluorimetrically by using the membrane probe trimethylammonium diphenyl hexatriene. The fluidity of the organism's cytoplasmic membrane was found to decrease significantly during lethal photosensitization, and this was accompanied by membrane condensation and vacuolation of the cells. Although changes in membrane fluidity are often attributable to lipid peroxidation, malonaldehyde (a product of lipid peroxidation) was not detectable. The disruption of membrane functions associated with a decreased membrane fluidity may contribute to the bactericidal effect of light-activated toluidine blue.

Cell Membrane↗
PubMed2001

Tensile bond strength of light-cured resin-reinforced glass ionomer cement with delayed light exposure.

In the clinical situations, the time intervals between material mixing and light exposure during bracket bonding, using light-cured resin-reinforced glass ionomer cement (LCGIC), may vary for each individual bracket. This study determined the tensile bond strengths of LCGIC subjected to various time intervals, and evaluated the durability with thermocycling. Comparisons were made between LCGIC and light-cured composite resin (LCR). Two hundred and forty bovine teeth were chosen as specimens. Light exposure was performed 5, 10, 20, and 40 min after the commencement of powder/liquid mixing. The durability was evaluated by thermocycling for 2000 times at temperatures between 5 degrees C and 55 degrees C, with a 30-s dwell time. Tensile bond strengths of LCGIC and LCR after 5 min, representing the general condition in clinical use, equaled 5.7 +/- 1.5 MPa and 5.1 +/- 2.6 MPa, respectively. For the LCGIC groups, no significant differences were seen between bond strengths with and without thermocycling. Also, no significant differences were noted among any time intervals. For the LCR groups, there were also no significant differences with and without thermocycling. The tensile bond strength of LCR showed highly significant differences within groups across time. Compared with LCR, the failure sites for brackets bonded with LCGIC appeared to be predominantly at the bracket/adhesive interface. The standard deviations of LCR were high when compared with those of LCGIC. The bond strength of LCGIC with or without thermocycling surpassed the clinically required minimum. LCGIC may be an advantageous alternative to LCR for orthodontic bracket bonding.

Journal Article↗
PubMed1991

Formation and properties of smooth muscle myosin 20-kDa light chain-skeletal muscle myosin hybrids and photocrosslinking from the maleimidylbenzophenone-labeled light chain to the heavy chain.

Experimental conditions which permit the exchange of smooth muscle 20-kDa light chain into skeletal muscle myosin are described. The hybridization does not result in the regulation of actin-activated ATPase activity of the hybrid myosin by smooth light chain phosphorylation. Further, the KCl dependence of the Mg-ATPase activity of the hybrid was similar to that of skeletal muscle myosin. The dephosphorylation of the smooth light chain in the hybrid did not induce a conformational change in the hybrid from the 6 S to the 10 S state, thereby indicating that the conformational transition is dependent also on the nature of the heavy chain subunit. Exchange of the smooth light chain premodified at its Cys-108 by photolabile 4-(N-maleimido)benzophenone and photolysis resulted in crosslinking to the heavy chain subunit. Immunopeptide mapping using a monoclonal antibody against residues 1-23 at the N-terminus of the skeletal muscle myosin heavy chain identified the location of the photocrosslinking site to be beyond 92 kDa away from the N-terminus.

Actins↗
PubMed1990

Effects of sodium nitrite on ultraviolet light-induced relaxation and ultraviolet light-dependent activation of guanylate cyclase in bovine mesenteric arteries.

It was demonstrated that precontracted strips from different bovine mesenteric arteries showed variation in sensitivity to ultraviolet radiation (366 nm). Some strips relaxed when they were exposed to ultraviolet light, others showed no sensitivity at all and, finally, some showed contraction. However, all arteries relaxed when they were irradiated with UV-light in the presence of 10 microM NaNO2. Ultraviolet radiation (366 nm) increased the activity of guanylate cyclase in crude homogenate from bovine mesenteric arteries by about 20-fold in the presence of NaNO2, while UV-light in the absence of sodium nitrite had no effect on the guanylate cyclase activation. These results support the notion that nitrite may be essential for vascular smooth muscle relaxation by UV-light, possibly through the release of nitric oxide.

Animals↗
PubMed1995

Efferent projections of the olivary pretectal nucleus in the albino rat subserving the pupillary light reflex and related reflexes. A light microscopic tracing study.

The olivary pretectal nucleus is a primary visual centre sensitive to luminance changes. It is involved in the pupillary light reflex, the consensual pupillary light reflex and related reflexes, such as the lid closure reflex whereby pupillary constriction takes place. Since the olivary pretectal nucleus is a small nucleus, previous studies using degeneration, horseradish peroxidase and radioactive amino acid tracing were limited regarding to the exclusiveness of the projections from the olivary pretectal nucleus. In the present study the position of the olivary pretectal nucleus in the rat was first localized by physiological recording of the neurons upon luminance stimulation. Subsequently, an anterograde tracer Phaseolus vulgaris leucoagglutinin was injected iontophoretically. This allows a much more precise localization of the olivary pretectal nucleus projections. Ascending and descending pathways originating from the olivary pretectal nucleus were observed. Ascending fibres project bilaterally to the intergeniculate leaflet, the ventral part of the lateral geniculate nucleus and ipsilaterally to the anterior pretectal nucleus. In addition, contralateral projections were observed to the zona incerta and the fields of Forel. Descending fibres project bilaterally to the periaqueductal gray, the nucleus of Darkschewitsch, the interstitial nucleus of Cajal, the Edinger-Westphal nucleus and the intermediate gray layer of the superior colliculus. Also a contralateral projection to the oculomotor nucleus and an ipsilateral projection to the pontine nucleus and the nucleus of the optic tract were found. Furthermore, the contralateral olivary pretectal nucleus received a small projection. Retrograde tracing experiments using two fluorescent dyes revealed that the fibres projecting to the contralateral olivary pretectal nucleus and to the contralateral interstitial nucleus of Cajal are collaterals. The projection from the olivary pretectal nucleus to the facial nucleus which has been described to receive an input in cats could not be confirmed for the rat. The fact that the Edinger-Westphal nucleus, the interstitial nucleus of Cajal and the superior colliculus receive an input from the olivary pretectal nucleus suggests that this primary visual centre is not only involved in the pupillary light reflex, but also in controlling eye and head position and saccadic eye movements. Although visual acuity largely depends on receptive field sizes of retinal ganglion cells and their central connections, the stronger sympathetic influence during the pupillary light reflex in animals with frontally placed eyes compared to animals with laterally placed eyes may also contribute to the higher visual acuity in animals with frontally placed eyes.

Afferent Pathways↗
PubMed1984

Mutation induction by 365-nm radiation and far-ultraviolet light in Escherichia coli strains differing in near- and far-ultraviolet light sensitivity.

The his-4 locus derived from Escherichia coli strain AB1157 has been transduced into 4 E. coli strains that exhibit all 4 possible combinations of genes controlling sensitivity to near-ultraviolet light (nur versus nur+) and far-ultraviolet light (uvrA6 versus uvrA+). The 4 strains exhibited the predicted sensitivity to 254-nm radiation based on the sensitivity of the parent strains from which they were derived and the frequency of his+ mutations predicted from experiments with AB1157 from which the his-4 locus was derived. When the 4 strains were treated with 365-nm radiation, they exhibited the predicted sensitivity based on the near-ultraviolet light sensitivity of the strains from which they were derived while his+ mutations were undetectable with the 4 strains as well as with strain AB1157. When treated with 365-nm radiation, cells of a WP2s strain (a derivative of B/r transduced to his-4) plated on semi-enriched medium prepared with casamino acids did not yield induced mutations, whereas plating on semi-enriched medium prepared with nutrient broth did yield mutants at both the his-4 and trp loci at frequencies at least an order of magnitude lower than that observed with far-ultraviolet light. The induction of nutritionally independent mutants by 365-nm radiation is strongly dependent on the supplement used for semi-enrichment. When compared at equivalent survival levels, mutant frequencies are significantly less following 365-nm radiation when compared with far-ultraviolet radiation.

Cell Survival↗