Alkaline phosphatase activity in normal and scorbutic bones.
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Alkaline Phosphatase↗
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Discrimination of phytochrome dependent light inducible from non-light inducible plant genes. Prediction of a common light-responsive element (LRE) in phytochrome dependent light inducible plant genes.
We aligned 14 5'-leading sequences of small subunit ribulose-1,5-bisphosphate carboxylase (rbcS) genes. A strong consensus sequence ("CCTTATCAT") was located directly upstream of the TATA-box. The occurrence of this motif in other light dependent phytochrome regulated plant genes led to the calculation of two consensus matrices. With these two matrices we are able to distinguish almost all known light induced plant genes which are phytochrome regulated from non-light induced plant genes indicating, that all these genes share a common light-responsive element (LRE). The results obtained by computer analysis are discussed with regard to experimental data.
Base Sequence↗
Effect of light-tip distance on the shear bond strengths of resin-modified glass ionomer cured with high-intensity halogen, light-emitting diode, and plasma arc lights.
INTRODUCTION: The purpose of this study was to assess the effect of light-tip distance on the shear bond strength and the failure site of brackets cured with 3 light-curing units (high-intensity halogen, light-emitting diode, and plasma arc). METHODS: One hundred thirty-five bovine mandibular permanent incisors were randomly allocated to 9 groups of 15 specimens each. Stainless steel brackets (Victory Series, Unitek/3M, Monrovia, Calif) were bonded with a resin-modified glass-ionomer (Fuji Ortho LC, GC Europe, Leuven, Belgium) to the teeth, and each curing light was tested at 3 distances from the bracket: 0, 3, and 6 mm. After bonding, all samples were stored in distilled water at room temperature for 24 hours and subsequently tested for shear bond strength. RESULTS: When the 3 light-curing units were compared at a light-tip distance of 0mm, they showed no significantly different shear bond strengths. At a light-tip distance of 3 mm, no significant differences were found between the halogen and plasma arc lights, but both lights showed significantly higher shear bond strengths than the light-emitting diode light. At a light-tip distance of 6 mm, no significant differences were found between the halogen and light-emitting diode lights, but both showed significantly lower bond strengths than the plasma arc light. When the effect of the light-tip distance on each light-curing unit was evaluated, the halogen and light-emitting diode lights showed no significant differences among the 3 distances. However, the plasma arc light produced significantly higher shear bond strengths at a greater light-tip distance. No significant differences were found among the adhesive remnant index scores of the various groups, except with the LED light at a distance of 3 mm. CONCLUSIONS: In hard-to-reach areas, the plasma arc curing light is suggested for optimal curing efficiency.
Acrylic Resins↗
Retinal light damage in rats exposed to intermittent light. Comparison with continuous light exposure.
Visible light-induced photoreceptor cell damage resulting from exposure to multiple intermittent light-dark periods was compared with damage resulting from continuous light in albino rats maintained in a weak cyclic-light environment or in darkness before light treatment. The time course of retinal damage was determined by correlative measurements of rhodopsin and visual cell DNA at various times after light exposure, and by histopathological evaluation. The effect of intense light exposures on rhodopsin regeneration and on the level of rod outer segment docosahexaenoic acid was also determined. For rats previously maintained in weak cyclic light, 50% visual cell loss was measured 2 weeks after 12 1 hr light/2 hr dark periods, or following 24 hr of continuous light. A comparable 50% loss of visual cells was found in dark-reared rats after only 5 hr of continuous illumination or 2-3 hr of intermittent light. As judged by histology, cyclic-light-reared rats incurred less retinal pigment epithelial cell damage than dark-reared animals. In both experimental rat models intermittent light exposure resulted in greater visual cell damage than continuous exposure. Visual cell damage from intermittent light was found to depend on the duration of light exposure and on the number of light doses administered. Measurements of rhodopsin and DNA 2 hr and 2 weeks after light exposure of up to 8 hr duration revealed that visual cell loss occurs largely during the 2 week dark period following light treatment. The loss of docosahexaenoic acid from rod outer segments was also greater in rats exposed to intermittent light than in animals treated with continuous light. It is concluded that intermittent light exposure exacerbates Type I light damage in rats (involving the retina and retinal pigment epithelium) and the schedule of intense light exposure is a determinant of visual cell death.
Animals↗
The effect of distance from light source on light intensity from curing lights.
PURPOSE: To investigate how light intensity changes as the distance increases from the tip of the light guide. MATERIALS AND METHODS: Ten different curing light/light guide combinations were used. Light intensity was measured at 0, 3, 6, and 10 mm from the tip of the light guide with a radiometer. Measurements were repeated in five separate trials and the mean light intensity +/- standard deviation was calculated. The fiber density was measured at the entrance and exit of all ten light guides and the light dispersion patterns were recorded. RESULTS: Light intensity decreased as distance increased for all lights tested; however, the rate and extent of this decrease was not similar for all lights (p < 0.0001). Turbo light guides exhibited a more rapid decrease in intensity as the distance increased than standard light guides. At 10 mm, all the turbo light guides had lost over 80% of their intensity recorded at 0 mm. CONCLUSION: 1. The rate and extent of the decrease in intensity is not similar among curing lights (p < 0.0001). 2. It is not possible to predict light intensity at 10 mm from measurements made at 0 mm. 3. Curing light manufacturers should state intensity over clinically relevant distances (0 to 10 mm).
Analysis of Variance↗
The effect of delayed light exposure on bond strength: light-cured resin-reinforced glass ionomer cement vs light-cured resin.
Under clinical situations, the intervals between material mixing and light exposure during bracket bonding using light-cured resin-reinforced glass ionomer cement may vary for each individual bracket. This study evaluates the bond strength of light-cured resin-reinforced glass ionomer cement subjected to various time intervals between material mixing and subsequent light exposure. This investigation was conducted in two parts. The first part consisted of measuring the enamel surface temperature to define the conditions under which the second part of the study was carried out. One hundred fifteen subjects, 63 males and 52 females, participated in this study. The over-all mean temperature as measured with a noncontact infrared thermometer was 31.9 degrees C. The second part of this study assessed tensile and shear bond strengths of light-cured resin-reinforced glass ionomer cement subjected to immediate light exposure (time interval, 5 minutes) and bond strengths subjected to light exposure at 10, 20, and 40 minutes after material mixing. Light-cured resin-reinforced glass ionomer cement was then compared with light-cured composite resin. Mean tensile and shear bond strengths of light-cured resin-reinforced glass ionomer cement exposed after 40 minutes were 4.5 MPa and 20.5 MPa, respectively. This represented a reduction of approximately 20% when compared with the 5-minute group. Scheffé test showed no statistically significant differences between any two time intervals. Mean bond strengths of the light-cured resin decreased with time. Tensile and shear bond strengths of light-cured resin indicated high statistical significance within groups across time. It could therefore be concluded that the bond strength of light-cured resin-reinforced glass ionomer cement was not affected by the timing of visible light exposure; whereas, the bond strength of light-cured resin decreased as time intervals increased. Light-cured resin-reinforced glass ionomer cement may thus serve as an advantageous alternative to composite resin for bracket bonding.
Adolescent↗
Isolation of cardiac myosin light-chain isotypes by chromatofocusing. Comparison of human cardiac atrial light-chain 1 and foetal ventricular light-chain 1.
Cardiac myosin light chain isotypes have been resolved using chromatofocusing, a new preparative column chromatographic technique. The method relies on production of narrow-range, shallow and stable pH gradients using ion-exchange resins and buffers with even buffering capacity over the required pH range. Light chains were resolved in order of decreasing isoelectric point in the pH range 5.2-4.5. Gradients of delta pH = 0.004-0.006/ml elution volume were achieved which were capable of resolving light chains with isoelectric point differences of only 0.03. Analytical isoelectric focusing of light chains in polyacrylamide gels could be used to predict the results of preparative chromatofocusing for method development. Chromatofocusing was capable of resolving human and bovine cardiac light chain 1 and 2 subunits, atrial (ALC) and ventricular (VLC) light chain isotypes and homologous VLC-2 and VLC-2* light chains. The technique was used to purify and resolve the human foetal ventricular light chain 1 (FLC-1) from adult ventricular light chain 1 (VLC-1) present in foetal ventricles and the atrial light chain 1 (ALC-1) in adult atria. Comparative peptide mapping studies and amino acid analyses were carried out on FLC-1 and ALC-1. No differences were detected between FLC-1 and ALC-1 using three different proteases and amino acid compositions were similar with the exception of glycine content. The studies indicate that FLC-1 and ALC-1 are homologous, and possibly identical, light chains. Comparison of human FLC-1/ALC-1 with VLC-1 suggested marked structural and chemical differences in these light chain isotypes, in particular in the contents of methionine, proline, lysine and alanine residues. Differences in the contents of these residues were also apparent in the corresponding bovine atrial and ventricular light chains [Wikman-Coffelt, J. & Srivastava, S. (1979) FEBS Lett. 106, 207-212]. The latter three residues are known to be rich in the N-termini of cardiac and skeletal light chain 1 isotypes, an area that has been implicated in actin binding, suggesting that atrial and ventricular light chains may differ functionally in this region.
Amino Acids↗
Blue light, green light, white light, more light: treatment of neonatal jaundice.
This article reviews the current understanding of how phototherapy, the most widely used treatment of neonatal jaundice, uses light energy to pump bilirubin out of a jaundiced infant. It provides a framework for understanding the often conflicting results of clinical comparisons of various phototherapeutic regimens, and stresses the importance of light intensity in the overall effectiveness of phototherapy.
Bilirubin↗
[Retinal light damage: I. The influences of light intensity and exposure duration at moderate and low intensities of cyclic light].
PURPOSE: To study the influences of moderate- and low intensity of cyclic light exposure on the light damage of rat retina and its relationship with light intensity and exposure duration. METHODS: Twenty five 8-10 weeks old of female Sprague-Dawley rats were divided into 5 groups randomly. One group were as controls reared in dark-room, others were exposured to 12 hour light: 12 hour dark cyclic white xenon light from 3 to 28 days. The light intensities were 90-115 Lux(100 Lux), 400-650 Lux(500 Lux), 800-1,150 Lux(1,000 Lux), 1,400-1,650 Lux(1,500 Lux) separately. After various duration of exposure, the retina were evaluated with light microscopy, electron microscopy and morphometric study. RESULTS: Except for the intensity of 100Lux group, all of the other exposure intensities can induce the light damage of rat retina. The photoreceptor cells were affected most early. The higher of light intensity and the longer of exposure duration, the severer of the photoreceptor cell loss. In the severely damaged eye, RPE were also damaged. CONCLUSIONS: For the light damage of rat retina which is induced by moderate- or low intensity of cyclic light, the damage degree was both affected by light intensity and exposure duration.
Animals↗
The unbearable lightness of "light" cigarettes: a comparison of smoke yields in six varieties of Canadian "light" cigarettes.
BACKGROUND: Labelling cigarettes as "light" or "mild" is claimed to be one of the biggest marketing scams in Canadian history. Arguably, such labelling implies that these varieties of cigarettes are less harmful than "regular" cigarettes. In Canada, a food product can be labelled "light" if there is a 25% reduction from the "reference food" and if the constituent being reduced is clearly identified (e.g., light in fat). Cigarette labelling does not comply with these regulations, however. To examine whether or not some tobacco constituents meet the 25% reduction criterion, we compared yields of 41 toxic and/or carcinogenic smoke constituents in six varieties of "light" cigarettes to the yields of "regular" cigarettes. We selected cigarettes from the two most popular Canadian brands, Du Maurier and Players. METHODS: Using a set of data provided by Imperial Tobacco Canada and made available to the public by the Government of British Columbia, we compared yields measured under a laboratory protocol (modified ISO) that was designed to provide a more rigorous evaluation of the differences between varieties of cigarettes and a more accurate assessment of smokers' potential smoke intake than the traditional protocol (standard ISO). FINDINGS: For all six varieties of "light" cigarettes, the yields of nicotine were higher by an average of 5% (range: 1% to 13%). The 25% reduction criterion was not met for any variety of "light" cigarettes concerning yields of tar. For all cigarettes tested, yields of tar were reduced on average by only 16% (range: 5% to 22%). For carbon monoxide (CO), only Player's Smooth Light had an over 25% reduction (30%) compared with Player's Regular. Conversely, yield of CO was 24% higher for Du Maurier Lights compared with Du Maurier Regular. As for the other smoke constituents, the majority (75%) were not reduced by 25% or more in "light" cigarettes, and a sizeable proportion of yields (e.g., acrylonitrile, benzene, chromium, m+p cresol, mercury, nickel, toluene) were larger in these varieties of cigarettes. Only yields of formaldehyde, crotonaldehyde, 1-aminonaphtalene, and proprionaldehyde were systematically reduced in all varieties of "light" cigarettes. CONCLUSION: The six varieties of "light" cigarettes examined in this study do not differ substantially from "regular" cigarettes in terms of smoke yields. We argue that the modified ISO protocol should be implemented for a more valid comparison of potential smoke yields in all varieties of cigarettes and that labelling based on this protocol should be promoted.
Advertising↗
Effect of light guide tip diameter of LED-light curing unit on polymerization of light-cured composites.
OBJECTIVE: The aim of this study was to investigate the influence of the diameter of the light guide tip on the polymerization of light cured composites when light guide tips of different diameters were used with an light-emitting diode (LED)-unit. METHODS: An LED-unit was used with three light guide tips of 4, 8 and 10 mm diameter. Variations of light illuminance with irradiation time of each light guide tip were measured with a lux meter. Two Composites were exposed for 10, 20, 30 or 40 s. Thereafter, the depths of cure of the specimens were measured by the scraping method, and Knoop hardness was measured at 0.5 mm intervals. RESULTS: The relative light illuminances from the 8 mm tip and 10 mm tip were 45 and 32% of that of the 4 mm tip. The depth of cure for the 4 mm tip was significantly greater than the others. At a depth of 2.0 mm, the 4 mm tip produced significantly greater hardness than the others. The depth of cure of composite irradiated for 10 s using the 4 mm tip corresponded to those of composites irradiated for 20 s using the 8 mm tip and for 30 s using the 10 mm tip. Thus, when the irradiation time was extended, Knoop hardness of the 4 mm tip was not significantly different from the others. SIGNIFICANCE: This study showed that the polymerization of light cured composite was affected by the diameter of the light guide tip of the LED-unit.
Analysis of Variance↗
Light-induced structural changes in a putative blue-light receptor with a novel FAD binding fold sensor of blue-light using FAD (BLUF); Slr1694 of synechocystis sp. PCC6803.
The sensor of blue-light using FAD (BLUF) domain is the flavin-binding fold categorized to a new class of blue-light sensing domain found in AppA from Rhodobacter sphaeroides and PAC from Euglena gracilis, but little is known concerning the mechanism of blue-light perception. An open reading frame slr1694 in a cyanobacterium Synechocystis sp. PCC6803 encodes a protein possessing the BLUF domain. Here, a full-length Slr1694 protein retaining FAD was expressed and purified and found to be present as an oligomeric form (trimer or tetramer). Using the purified Slr1694, spectroscopic properties of Slr1694 were characterized. Slr1694 was found to show the same red-shift of flavin absorption and quenching of flavin fluorescence by illumination as those of AppA. These changes reversed in the dark although the rate of dark state regeneration was much faster in Slr1694 than AppA, indicating that Slr1694 is a blue-light receptor based on BLUF with the similar photocycle to that of AppA. The dark decay in D(2)O was nearly four times slower than in H(2)O. Light-induced Fourier transform infrared (FTIR) difference spectroscopy was applied to examine the light-induced structure change of a chromophore and apo-protein with deuteration and universal (13)C and (15)N isotope labeling. The FTIR results indicate that light excitation induced distinct changes in the amide I modes of peptide backbone but relatively limited changes in flavin chromophore. Light excitation predominantly weakened the C(4)=O and C(2)=O bonding and strengthened the N1C10a and/or C4aN5 bonding, indicating formational changes of the isoalloxazine ring II and III of FAD but little formational change in the isoalloxazine ring I. The photocycle of the BLUF is unique in the sense that light excitation leads to the structural rearrangements of the protein moieties coupled with a minimum formational change of the chromophore.
Bacterial Proteins↗
Lack of efficacy of light reduction in preventing retinopathy of prematurity. Light Reduction in Retinopathy of Prematurity (LIGHT-ROP) Cooperative Group.
BACKGROUND: Hospital-nursery lighting has been suggested as a factor in causing retinopathy of prematurity. Despite ongoing debate, a causal relation has not been established. METHODS: We conducted a prospective, randomized, multicenter study of the effects of light reduction on 409 premature infants with birth weights of less than 1251 g and gestational ages of less than 31 weeks. Two hundred five infants were exposed to reduced light, and 204 to typical nursery lighting. The amount of light reaching the infants' eyes was reduced within 24 hours after birth by placing goggles on the infants that reduced visible-light exposure by 97 percent and ultraviolet-light exposure by 100 percent. The babies wore the goggles until 31 weeks' postconceptional age or 4 weeks after birth, whichever was longer. Once the goggles were removed, ophthalmologists masked to the treatment assignments assessed the infants for retinopathy of prematurity at least biweekly for up to 13 weeks. RESULTS: There were 188 infants in the group that wore goggles and 173 in the control group who survived and were available for follow-up. The mean birth weights were 906 g in the goggles group and 914 g in the control group; the mean gestational ages were 27.4 weeks and 27.2 weeks, respectively. The mean ambient-light level adjacent to the infants' faces was 399 lux for the goggles group and 447 lux for the control group. Retinopathy of prematurity was diagnosed in 102 infants (54 percent) in the goggles group and 100 (58 percent) in the control group (relative risk, 0.9; 95 percent confidence interval, 0.8 to 1.1; P=0.50). CONCLUSIONS: A reduction in ambient-light exposure does not alter the incidence of retinopathy of prematurity.
Eye Protective Devices↗
Light-dependent magnetoreception in birds: analysis of the behaviour under red light after pre-exposure to red light.
In previous experiments, migratory birds had been disoriented under 635 nm red light, apparently unable to use their magnetic compass. The present study with European robins, Erithacus rubecula, confirms these findings for red light at the levels of 6 x 10(15) quanta s(-1) m(-2) and 43 x 10(15) quanta s(-1) m(-2), suggesting that the disorientation under red light was not caused by the test light being below the threshold for magnetoreception. However, pre-exposure to red light for 1 h immediately before the critical tests under red light of 6-7 x 10(15) quanta s(-1) m(-2) enabled robins to orient in their seasonally appropriate migratory direction in spring as well as in autumn. Pre-exposure to darkness, by contrast, failed to induce orientation under red light. Under green light of 7 x 10(15) quanta s(-1) m(-2), the birds were oriented in their migratory orientation after both types of pre-exposure. These findings suggest that the newly gained ability to orient under red light might be based on learning to interpret a novel pattern of activation of the magnetoreceptors and hence may represent a parallel to the previously described enlargement of the functional window to new magnetic intensities. Mechanisms involving two types of spectral mechanisms with different absorbance maxima and their possible interactions are discussed.
Animal Migration↗
Measurement of stray light and glare: comparison of Nyktotest, Mesotest, stray light meter, and computer implemented stray light meter.
AIM: To evaluate the properties of devices for measuring stray light and glare: the Nyktotest, Mesotest, "conventional" stray light meter and a new, computer implemented version of the stray light meter. METHODS: 112 subjects, divided in three groups: (1) young subjects without any eye disease; (2) elderly subjects without any eye disease, and (3) subjects with (early) cataract in at least one eye. All subjects underwent a battery of glare and stray light tests, measurement of visual acuity, contrast sensitivity, refraction, and LOCS III cataract classification. Subjects answered a questionnaire on perceived disability during driving. RESULTS: Repeatability values were similar for all glare/stray light tests. Validity (correlation with LOCS III and questionnaire scores), discriminative ability (ability to discriminate between the three groups), and added value (to measurement of visual acuity and contrast sensitivity) were all superior for both stray light meters. Results of successive measurements are interrelated for the conventional but not the new stray light meter. This indicates a better resistance to fraud for the latter device. CONCLUSIONS: The new computer implemented stray light meter is the most promising device for future stray light measurements.
Adaptation, Ocular↗
Comparative treatment of psoriasis with UV-light, trioxsalen plus UV-light, and coal tar plus UV-light.
Areas within psoriasis plaques have been treated with UV-light alone, trioxsalen plus UV-light, and coal tar (liquid carbonis detergens) plus UV-light, using the 313, 365 and 405 nm wavelength bands in various doses. With the 313 nm band, the same degree of healing was obtained with all three types of treatment. With the 365 nm band, no healing was achieved with UV-light alone, but healing did occur with UV-light when the skin was sensitized with trioxsalen. Coal tar itself has a certain healing effect on psoriasis but the effect is so markedly enhanced by light of the 365 nm band that the healing is comparable to that obtained with the 313 nm band. No healing was seen with light of the 405 nm band. The patients who were healed with the 313 nm band alone, also healed with trioxsalen or coal tar plus UV-light of the 365 nm band. With each method there is an individual optimal light dose of 1--2 MED that gives healing.
Coal Tar↗
Analysis of serum free light chains by crossed immunoelectrophoresis: comparison with urinary light chains in light chain disease.
We investigated the relationship between serum free light chain levels measured by crossed immunoelectrophoresis in ten patients with light chain disease and traditional 24-hour urinary light chains in the same patients. The crossed immunoelectrophoresis test requires only a venipuncture for specimen acquisition, can be completed within 24 hours, and has a reproducibility (+/- 14%) comparable with that of other immunoprecipitin techniques. Twenty-eight serum-urine pairs, representing 18 discrete intervals, were analyzed. There was a close relationship between changes in serum and urine light chain levels, with a correlation coefficient of .77 or .93, depending on the method of calculation. This suggests that serum light chain levels measured by crossed immunoelectrophoresis would be equivalent to urinary light chain levels as indicators of tumor burden. Monitoring serum levels would have the advantage of greatly simplified specimen acquisition. In patients with renal failure, serum light chain levels should be a superior indicator of light chain synthesis.
Blood Protein Electrophoresis↗
Early light-inducible protein in pea is stable during light stress but is degraded during recovery at low light intensity.
The nuclear-encoded, thylakoid-bound early light-inducible protein (ELIP) reported to be related to the initial stages of chloroplast differentiation is synthesized in substantial amounts in leaves of mature plants exposed to light stress conditions (Adamska, I., Ohad, I., and Kloppstech, K. (1992b) Proc. Natl. Acad. Sci. U.S.A. 89, 2610-2613). Increase in ELIP content correlates with the photoinactivation of PSII, degradation of D1 protein, and changes in the level of pigments. Inhibition of phytoene desaturase and/or zeta-carotene desaturase during light stress drastically increases accumulation of the protein. ELIP mRNA is short-lived (t1/2 = 1 h). The thylakoid bound protein is stable in high light exposed leaves and is degraded only during recovery from light stress at low light intensity (40 microE/m2s). The lifetime of the protein during the recovery process increases with the extent of initial light stress condition. We propose that ELIP synthesis and degradation is related to the process of the plant response to light stress and recovery from photoinhibition.
Arabidopsis Proteins↗