A fluence response study of lethality and mutagenicity of white, black, and blue fluorescent light, sunlamp, and sunlight irradiation in Chinese hamster ovary cells

Under a set of defined experimental conditions, the fluence response of Chinese hamster ovary (CHO) cells to various light sources was studied by measuring single-cell survival and mutation to 6-thioguanine (TG) resistance. Fluorescent white, black, and blue lights were sightly lethal and mutagenic. Sunlamp light was highly lethal and mutagenic, exhibiting these biological effects within 15 sec of exposure under conditions recommended by the manufacturer for human use. Lethal and mutagenic effects were observed after 5 min of sunlight exposure; responses varied with hourly and daily variations in solar radiation. Sunlight-induced TG-resistant variants possessed less than 5% of parental cellular hypoxanthine--guanine phosphoribosyl transferase (HGPRT) enzyme activity, suggesting that the mutation induction occurs at this locus. The cell survival and mutation-induction curves generated by exposure of cells to both sunlamp and sunlight were similar to those obtained by the use of a standard far-UV lamp.     

Toxicity and mutagenicity of X-rays and [125I]dUrd or [3H]TdR incorporated in the DNA of human lymphoblast cells

We measured the toxicity and mutagenicity induced in human diploid lymphoblasts by various radiation doses of X-rays and two internal emitters. [¹²⁵I]iododeoxyuridine ([¹²⁵I]dUrd) and [³H]thymidine ([³H]TdR), incorporated into cellular DNA. [¹²⁵I]dUrd was more effective than [³H]TdR at killing cells and producing mutations to 6-thioguanine resistance (6TG^R). No ouabain-resistant mutants were induced by any of these agents. Expressing dose as total disintegrations per cell (dpc), the D₀ for cell killing for [¹²⁵I]dUrd was 28 dpc and for [³H]TdR was 385 dpc. The D₀ for X-rays was 48 rad at 37°C. The slopes of the mutation curves were approximately 75 × 10⁻⁸ 6TG^R mutants per cell per disintegration for [¹²⁵I]dUrd and 2 × 10⁻⁸ for [³H]TdR. X-Rays induced 8 × 10⁻⁸ 6TG^R mutants per cell per rad. Normalizing for survival, [¹²⁵I]dUrd remained much more mutagenic at low doses (high survival levels) than the other two agents. Treatment of the cells at either 37°C or while frozen at −70°C yielded no difference in cytotoxicity or mutation for [¹²⁵I]dUrd or [³H]TdR, whereas X-rays were 6 times less effective in killing cells at −70°C.

Assuming that incorporation was random throughout the genome, the mutagenic efficiencies of the radionuclides could be calculated by dividing the mutation rate by the level of incorporation. If the effective target size of the 6TG^R locus is 1000–3000 base pairs, then the mutagenic efficiency of [¹²⁵I]dUrd is 1.0–3.0 and of [³H]TdR is 0.02–0.06 total genomic mutations per cell per disintegration. ¹²⁵I disintegrations are known to produce localized DNA double-strand breaks. If these breaks are potentially lethal lesions, they must be repaired, since the mean lethal dose (D₀) was 28 dpc. The observations that a single dpc has a high probability of producing a mutation (mutagenic efficiency 1.0–3.0) would suggest, however, that this repair is extremely error-prone. If the breaks need not be repaired to permit survival, then lethal lesions are a subset of or are completely different from mutagenic lesions.     

Relative effectiveness and interaction of ultraviolet-B, red and blue light in anthocyanin synthesis of apple fruit

The effect of light on anthocyanin production in apple ( Malus pumila Mill. cv. Jonathan) skin disks was investigated, with prolonged irradiation from different light sources. High fluence rates of white light provided from a xenon lamp were unable to produce large amounts of anthocyanin, and anthocyanin production became saturated at about 30 W m⁻². When UV-B light, provided by a fluorescent lamp which had an emission peak at 312 nm, was combined with the white light, anthocyanin production was synergistically stimulated and increased up to the highest fluence rates of white light tested (44 W m⁻²). This UV-B light was more effective than red and blue light provided from fluorescent lamps, but anthocyanin production became saturated at about 1.7 W m⁻². However, simultaneous irradiation with red and UV-B light had a synergistic effect. UV-B light was also effective in increasing anthocyanin production in whole fruit. Therefore this synergism seemed to have an important role in the development of the desirable red skin color under field light conditions. The results of aminoethoxyvinylglycine treatment suggested that ethylene was not involved in the stimulative effect of UV-B light.     

Mutagenicity of coolwhite fluorescent light for Salmonella

The most common fluorescent lamps in use today in homes and businesses in the United States, 'coolwhite' fluorescent lamps, emit light that is mutagenic for Salmonella. Strains that carry both a uvrB mutation and plasmid pKM101 are extremely susceptible to this light-induced mutation. Both base substitution and frameshift mutations can be induced without substantial lethal effects on the bacteria. Induced mutations accumulate essentially as a linear function of the time bacteria are exposed to illumination. Of Salmonella histidine-requiring strains with known nucleotide target sequences (Hartman et al., 1986; Cebula and Koch, 1989, 1990), strains either carrying one of the base substitution mutations, hisG428 and hisG46, or one of the frameshifts, hisC3076 and hisD6610, are most highly mutagenized whereas frameshift strains with hisD6580 and hisD3052 exhibit lower rates of mutagenesis. Mutagenicity does not appear to require the presence of oxygen. A filter blocking wavelengths below 370 nm eliminates mutagenesis. Polystyrene, cellulose acetate and, especially, mylar and glass filters reduce mutagenesis, indicating that at least some of the mutagenic effects can be attributed to leakage of radiations below 290 nm (far-ultraviolet light) from 'coolwhite' lamps. The more recently introduced fluorescent 'softwhite' lamps are roughly 10-fold less mutagenic at approximately equal light intensity. Incandescent light bulbs are much less mutagenic than are these fluorescent lamps. Our mutational data correlate closely with previous results in eukaryotic cells (Jacobson and Krell, 1982). A uvrB recA Salmonella double mutant is hypersensitive to the lethal effects of coolwhite fluorescent light, even when illuminated through the lids of glass Petri dishes. Thus, appropriate Salmonella strains would appear to be simple and useful screens for both the mutagenic and the lethal activities of fluorescent lamps. These systems are amenable to classroom laboratory use as relatively safe and effective means of demonstrating environmental mutagenesis.     

Improved light sources for induction of sister chromatid differentiation

Various light sources, including ultraviolet light, mercury, germicidal, fluorescent, and incandescent lamps, were studied for their ability to induce sister chromatid differentiation (SCD) in rat bone marrow cells. The light sources were used along with Hoechst 33258 and Giemsa stains for SCD induction. When those lamps which emit significant amounts of heat were used, 60 degrees C incubation in 2X SSC was found to be unnecessary for SCD induction. A high wattage lamp, a high ambient temperature, a short distance between the lamp and the slides, or a light with 360 nm wavelength, minimized the required exposure time to the light. The pH value of the mounting buffer was also a significant factor. Fluorescent black light and incandescent lamps were found to be ideal light sources for SCD induction.     

Effect of light on the formation of atypical fruiting structures inGanoderma lucidum

Ganoderma lucidum develops atypical fruiting structures (AFSs) with non-basidiocarpous basidiospores during the incubation under light on nutrient agar media. To examine the light quality effective in inducing AFSs, 17 isolates ofG. lucidum were incubated on agar media under light from different colored fluorescent lamps. Of the 17 isolates, 13 isolates produced AFSs and basidiospores under fluorescent lamps. Nine isolates formed AFSs in a broad light region from P-B (pure blue) to P-R (pure red) lamps. The remaining 4 isolates produced AFSs under different colored fluorescent lamps. No isolates formed AFSs in the dark or under BLB (black light blue) illumination. The mycelial growth was inhibited by light illumination, especially BLB light. Although the AFSs were induced at a very low light intensity such as 0.5µmol m^–2s^–1, the optimum light intensity for the AFS formation varied depending on the kind of fluorescent lamp and the isolate. The AFS formation inG. lucidum isolates was also tested under monochromatic light produced by the combination of interference filters and colored glass filters.G. lucidum isolates were separable into various types in the responses of AFS formation to monochromatic light, indicating thatG. lucidum is heterogeneous in its photo-response with regard to AFS formation.     

光质对水稻幼苗初级氮同化的影响

用滤光膜过滤蓝色或红色荧光灯,得到纯的蓝光和红光,以白光为对照,研究不同光质对水稻（Ｏｒｙｚａ ｓａｔｉｖａ Ｌ．）幼苗初级氮同化的影响。结果表明：蓝光促进水稻黄化幼苗吸收ＮＯ＾－３含量,并促进ＮＲ（硝酸还原酶）的诱导。在蓝光下生长５￣７ｄ的幼苗的ＮＲ、ＮＩＲ（亚硝酸还原酶）、ＧＳ（谷氨酰胺合成酶）和ＧＯＧＡＴ（谷氨酸合酶）活性均高于白光下生长的,但第１０天以后,白光下生长的幼苗酶活性最高。与白光     

Light effects on in vitro adventitious root formation in axillary shoots of mature Prunus serotina

Light effects on in vitro adventitious root formation in axillary shoots of a 95-year-old black cherry ( Prunus serotina Ehrh.) were examined using microcuttings derived from cultured vegetative buds. Three studies were performed: 1) complete darkness and 4 levels of continuous white light irradiance were tested at 70, 278, 555 and 833 μmol m⁻² s⁻¹; 2) white, red, yellow and blue light were tested to assess the importance of spectral quality; and 3) the effect of blue light at intensities of 7,15, 22 and 30 μmol m⁻² s⁻¹ was also studied, Measurements included rooting percentage, total number of roots per shoot, and shoot and root dry weight. There was a strong negative effect of white light intensity upon root formation. Blue light between 15 and 22 μmol m⁻²: s⁻¹ significantly retarded root formation and completely inhibited it at 36 μmol m⁻² s⁻¹. Shoots treated with yellow light exhibited the highest rooting percentage, mean number of roots per shoot, and root dry weight.     

Effects of blue pulsed light on human physiological functions and subjective evaluation

Background

It has been assumed that light with a higher irradiance of pulsed blue light has a much greater influence than that of light with a lower irradiance of steady blue light, although they have the same multiplication value of irradiance and duration. We examined the non-visual physiological effects of blue pulsed light, and determined whether it is sensed visually as being blue.

Findings

Seven young male volunteers participated in the study. We placed a circular screen (diameter 500 mm) in front of the participants and irradiated it using blue and/or white light-emitting diodes (LEDs), and we used halogen lamps as a standard illuminant. We applied three steady light conditions of white LED (F0), blue LED + white LED (F10), and blue LED (F100), and a blue pulsed light condition of a 100-μs pulse width with a 10% duty ratio (P10). The irradiance of all four conditions at the participant''s eye level was almost the same, at around 12 μW/cm². We measured their pupil diameter, recorded electroencephalogram readings and Kwansei Gakuin Sleepiness Scale score, and collected subjective evaluations. The subjective bluish score under the F100 condition was significantly higher than those under other conditions. Even under the P10 condition with a 10% duty ratio of blue pulsed light and the F10 condition, the participant did not perceive the light as bluish. Pupillary light response under the P10 pulsed light condition was significantly greater than under the F10 condition, even though the two conditions had equal blue light components.

Conclusions

The pupil constricted under the blue pulsed light condition, indicating a non-visual effect of the lighting, even though the participants did not perceive the light as bluish.     

光质对水稻幼苗初级氮同化的影响

Pure blue(BL) or red light (RL) were obtained by filtering blue or red fluorescent lamp light through plastic filters. With the same intensity of white light(WL) as control, the effects of light quality on the primary nitrogen assimilation of rice seedlings were studied. Irradiation for 2-6 h with BL promoted the uptake of NO-3, the induction of nitrate reductase (NR), and the increase of the NO-3 content in the etiolated seedlings.Seedlings grown under BL for 5-7 d had higher activities of NR, NIR (nitrite reductase) GOGAT (glutamate synthase) as well as GS (glutamine synthetase) than those under WL. However, for more than 10 days under BL, the levels of these enzymes became lower than those of the seedlings under WL. Compared with BL or WL, RL was less effective on the primary nitrogen assimilation.     

Pyrimidine dimers are not the principal pre-mutagenic lesions induced in lambda phage DNA by ultraviolet light

Experiments were performed to examine the role of cyclobutyl pyrimidine dimers in the process of mutagenesis by ultraviolet (u.v.) light. Lambda phage DNA was irradiated with u.v. and then incubated with an Escherichia coli photoreactivating enzyme, which monomerizes cyclobutyl pyrimidine dimers upon exposure to visible light. The photoreactivated DNA was packaged into lambda phage particles, which were used to infect E. coli uvr- host cells that had been induced for SOS functions by ultraviolet irradiation. Photoreactivation removed most toxic lesions from irradiated phage, but did not change the frequency of induction of mutations to the clear-plaque phenotype. This implies that cyclobutyl pyrimidine dimers can be lethal, but usually do not serve as sites of mutations in the phage. The DNA sequences of mutants derived from photoreactivated DNA showed that almost two-thirds (16/28) were transitions, the same fraction found for u.v. mutagenesis without photoreactivation. These results show that in this system, the lesion inducing transitions (the major type of u.v.-induced mutation) is not the cyclobutyl pyrimidine dimer; a strong candidate for a mutagenic lesion is the Pyr(6-4)Pyo photoproduct. On the other hand, photoreactivation of SOS-induced host cells before infection with u.v.-irradiated phage reduced mutagenesis substantially. In this case, photoreversal of cyclobutyl dimers serves to reduce expression of the SOS functions that are required in the process of targeted u.v. mutagenesis.     

DNA-protein crosslinking in normal and solar UV-sensitive ICR 2A frog cell lines exposed to solar UV-radiation

DNA-protein crosslinks (DPC) were measured following exposure to the solar UV wavelengths produced by a fluorescent sunlamp in ICR 2A frog cells and two solar UV-sensitive mutants derived from this cell line. Approx. 5-7 DPC per 10(10) dalton were induced in these cells by either 150 kJ/m2 of sunlamp UV greater than 315 nm plus photoreactivating light (PRL) or 10 kJ/m2 of sunlamp UV greater than 295 nm. The irradiated cells were then incubated for 0-24 h and the level of DPC measured using alkaline elution. It was found for the ICR 2A cells exposed to sunlamp UV greater than 315 nm that the level of DPC increased about 3-fold during a 2-h postirradiation incubation and then decreased. The mutant cell lines also showed an enhancement in the level of DPC following irradiation, although it was much less pronounced and the levels decreased much more rapidly. In a similar fashion, the level of DPC increased in ICR 2A cells exposed to sunlamp UV greater than 295 nm with more than a 5-fold enhancement after a 4-h incubation. Once again, the mutant cell lines showed an increase in the level of DPC that was smaller and more transient than the effect in the ICR 2A cells. These results suggests that this enhancement in DPC may be indicative of a process that plays a role in cellular survival following solar UV-irradiation.     

Tuning the white light spectrum of light emitting diode lamps to reduce attraction of nocturnal arthropods

Artificial lighting allows humans to be active at night, but has many unintended consequences, including interference with ecological processes, disruption of circadian rhythms and increased exposure to insect vectors of diseases. Although ultraviolet and blue light are usually most attractive to arthropods, degree of attraction varies among orders. With a focus on future indoor lighting applications, we manipulated the spectrum of white lamps to investigate the influence of spectral composition on number of arthropods attracted. We compared numbers of arthropods captured at three customizable light-emitting diode (LED) lamps (3510, 2704 and 2728 K), two commercial LED lamps (2700 K), two commercial compact fluorescent lamps (CFLs; 2700 K) and a control. We configured the three custom LEDs to minimize invertebrate attraction based on published attraction curves for honeybees and moths. Lamps were placed with pan traps at an urban and two rural study sites in Los Angeles, California. For all invertebrate orders combined, our custom LED configurations were less attractive than the commercial LED lamps or CFLs of similar colour temperatures. Thus, adjusting spectral composition of white light to minimize attracting nocturnal arthropods is feasible; not all lights with the same colour temperature are equally attractive to arthropods.     

Effect of different light qualities on the ultrastructure, thylakoid membrane composition and assimilation metabolism of Chlorella fusca

Chlorella fusca (Shihira et Krauss) strain C-1.1.10 was grown under three different light qualities (red, white or blue light) in homocontinuous cultures. Under electron microscopy, blue light cultures showed enlarged cells, thinner cell walls and lower starch content than red light cells. Under blue light, the degree of stacking of the thylakoid membranes was significantly lower than under white or red light conditions. Changing the light from blue to red the ratio of exposed to appressed membranes was doubled. Compared to red light cells, blue light cells exhibited higher photosynthetic rates per chlorophyll molecule and contained less chlorophyll per dry weight. Blue light stimulated the content of soluble protein as well as that of soluble carbohydrates. The dry weight productivity per unit time was enhanced under blue light conditions. The thylakoid protein complexes which are generally assumed to be localized in the exposed membranes were found in higher concentrations under blue light than under red light. In blue light, both the Photosystem II/Photosystem I ratio and the ratio of light-harvesting chlorophyll protein to P-700 chlorophyll a -protein were lower than in red light. Blue light cells contained twice the concentration of cytochrome f , which correlates well with their higher photosynthetic capacity. When altering the light quality, the degree of change in the reaction center complexes was much lower than expected given the corresponding degree of change in the ratio of exposed to appressed membranes. These results are discussed in light of the question as to whether the variation in the stoichiometry of the laterally distributed complexes can be explained by changes in the degree of stacking alone.     

The loci of perception for phytochrome control of internode growth in light-grown mustard: Promotion by low phytochrome photoequilibria in the internode is enhanced by blue light perceived by the leaves

Under continuous white light (WL), extension growth of the first internode in Sinapis alba L. was promoted by low red (R): far-red (FR) ratios reaching the stem and-or the leaves. Conversely, the growth promotion by end-of-day light treatments was only triggered by FR perceived by the leaves and cotyledons, while FR given to the growning internode alone was tatally ineffective. Continuous WL+FR given to the internode was also in-effective if the rest of the shoot remained in darkness. Both the background stem growth, and the growth promotion caused by either an end-of-day FR pulse or continuous WL+FR given to the internode, increased with increasing fluence rates of WL given to the rest of the shoot. The increase by WL of the growth-stimulatory effect of low phytochrome photoequilibria in the internode appears to be mediated by a specific blue-light-absorbing photoreceptor, as blue-deficient light from sodium-discharge lamps, or from filtered fluorescent tubes, promoted background stem growth similarly to WL but did not amplify the response to the R:FR ratio in the internode. Supplementing the blue-deficient light (94 mol·m^-2·s^-1) with low fluence rates of blue (<9 mol·m^-2·s^-1) restored the promotive effect of low R:FR reaching the internode.Abbreviations BL blue light - FR far-red light - PAR photosynthetically active radiation - Pfr/P ratio between the FR-absorbing form and total phytochrome - R red light - SOX low-pressure sodium lamp - WL white light Supported by the Consejo Nacional de Investigaciones Cientificas y Técnicas (República Argentina) and the ORS scheme (UK)     

Layer pullet preferences for light colors of light-emitting diodes

Light colors may affect poultry behaviors, well-being and performance. However, preferences of layer pullets for light colors are not fully understood. This study was conducted to investigate the pullet preferences for four light-emitting diode colors, including white, red, green and blue, in a lighting preference test system. The system contained four identical compartments each provided with a respective light color. The pullets were able to move freely between the adjacent compartments. A total of three groups of 20 Chinese domestic Jingfen layer pullets (54 to 82 days of age) were used for the test. Pullet behaviors were continuously recorded and summarized for each light color/compartment into daily time spent (DTS), daily percentage of time spent (DPTS), daily times of visit (DTV), duration per visit, daily feed intake (DFI), daily feeding time (DFT), feeding rate (FR), distribution of pullet occupancy and hourly time spent. The results showed that the DTS (h/pullet·per day) were 3.9±0.4 under white, 1.4±0.3 under red, 2.2±0.3 under green and 4.5±0.4 under blue light, respectively. The DTS corresponded to 11.7% to 37.6% DPTS in 12-h lighting periods. The DTV (times/pullet·per day) were 84±5 under white, 48±10 under red, 88±10 under green and 94±8 under blue light. Each visit lasted 1.5 to 3.2 min. The DFI (g/pullet·per day) were 27.6±1.7 under white, 7.1±1.6 under red, 15.1±1.1 under green and 23.1±2.0 under blue light. The DFT was 0.18 to 0.65 h/pullet·per day and the FR was 0.57 to 0.75 g/min. For most of the time during the lighting periods, six to 10 birds stayed under white, and one to five birds stayed under red, green and blue light. Pullets preferred to stay under blue light when the light was on and under white light 4 h before the light off. Overall, pullets preferred blue light the most and red light the least. These findings substantiate the preferences of layer pullets for light colors, providing insights for use in the management of light-emitting diode colors to meet pullet needs.     

Photosynthetic Performance and Pigment Composition of Leaves from two Tropical Species is Determined by Light Quality

Abstract: A suitable light quantity and quality is essential for optimal photosynthetic metabolism. Using combinations of three lamp types, the impact of the quality of artificial light conditions on the photosynthetic apparatus of leaves developed in growth chambers was analysed. The VIALOX‐Planta lamps are quite poor outside the green to orange (520 ‐ 620 nm) wavelength range, while the HQI‐BT lamps present a more uniform spectral intensity between 425 and 650 nm (blue to red). The halogen lamps are particularly rich in the red and far red range of the electromagnetic spectra. The lamps also differ in the red: far red ratio, which were 3.07 (VIALOX), 2.06 (HQI‐BT) and 1.12 (halogen). Clear positive effects were detected in most of the photosynthetic parameters in relation to light quality, both at stomatal and mesophyll levels. Despite some species‐dependent sensitivity to blue and red/far red wavelengths, observed among the studied parameters, the best photosynthetic performances of the test plants (Packyrhizus ahipa and Piatã, a hybrid of Coffea dewevrei×Coffea arabica) were obtained almost always with the reinforcement of blue (HQI‐BT lamps), red and far red (halogen lamps) wavelengths and with a red: far red ratio closer to that observed in nature. This suggests the involvement of more than one photoreceptor family in photosynthetic performance. Under such light conditions, increases in net photosynthesis and stomatal conductance were observed and, despite the moderate effects on photosynthetic capacity, strong effects were observed in the capture and transfer of light energy in the antennae pigments, photochemical efficiency of photosystem II and electron transport. This was related to the striking quantitative and qualitative impacts observed on total chlorophylls and carotenoids, which reached, in some cases, increases of 100 and 200 %, respectively. Among carotenoids, increases as high as 9‐fold for α‐carotene were observed (P. ahipa), with chlorophyll (a/b), total (chlorophyll/carotenoid) and carotene (α/β) ratios also strongly affected. This would have affected the structure and stability of photosynthetic membranes which, in turn, affected photosynthetic‐related processes (e.g., antennae pigments, photosystem II and electron transport efficiencies). This was particularly clear in the HQI + halogen treatment. The results unequivocally show that light quality could remain a clear limiting factor for leaf/plant development under artificial light conditions, which could be overcome using more than one lamp type, with complementary emission spectra.     

207-nm UV Light - A Promising Tool for Safe Low-Cost Reduction of Surgical Site Infections. I: In Vitro Studies

Background

0.5% to 10% of clean surgeries result in surgical-site infections, and attempts to reduce this rate have had limited success. Germicidal UV lamps, with a broad wavelength spectrum from 200 to 400 nm are an effective bactericidal option against drug-resistant and drug-sensitive bacteria, but represent a health hazard to patient and staff. By contrast, because of its limited penetration, ∼200 nm far-UVC light is predicted to be effective in killing bacteria, but without the human health hazards to skin and eyes associated with conventional germicidal UV exposure.

Aims

The aim of this work was to test the biophysically-based hypothesis that ∼200 nm UV light is significantly cytotoxic to bacteria, but minimally cytotoxic or mutagenic to human cells either isolated or within tissues.

Methods

A Kr-Br excimer lamp was used, which produces 207-nm UV light, with a filter to remove higher-wavelength components. Comparisons were made with results from a conventional broad spectrum 254-nm UV germicidal lamp. First, cell inactivation vs. UV fluence data were generated for methicillin-resistant S. aureus (MRSA) bacteria and also for normal human fibroblasts. Second, yields of the main UV-associated pre-mutagenic DNA lesions (cyclobutane pyrimidine dimers and 6-4 photoproducts) were measured, for both UV radiations incident on 3-D human skin tissue.

Results

We found that 207-nm UV light kills MRSA efficiently but, unlike conventional germicidal UV lamps, produces little cell killing in human cells. In a 3-D human skin model, 207-nm UV light produced almost no pre-mutagenic UV-associated DNA lesions, in contrast to significant yields induced by a conventional germicidal UV lamp.

Conclusions

As predicted based on biophysical considerations, 207-nm light kills bacteria efficiently but does not appear to be significantly cytotoxic or mutagenic to human cells. Used appropriately, 207-nm light may have the potential for safely and inexpensively reducing surgical-site infection rates, including those of drug-resistant origin.     

小型黑光灯治疗斑块型银屑病疗效观察

目的:观察小型黑光灯治疗斑块型银屑病疗效。方法:采用小型黑光灯(电压220V,电流0.34A,功率25.4W,主波峰长365nm,辐照度为1070μW/cm2)治疗76例斑块型银屑病患者,20次为一疗程。结果:小型黑光灯第一疗程和第二疗程临床显效率分别达72.37%和84.21%,未发现明显不良反应。结论:小型黑光灯治疗斑块型银屑病具有治疗方便、疗效好,不良反应小等优点。     

Red white and blue – bright light effects in a diurnal rodent model for seasonal affective disorder

Despite the common use of bright light exposure for treatment of seasonal affective disorder (SAD), the underlying biology of the therapeutic effect is not clear. Moreover, there is a debate regarding the most efficacious wavelength of light for treatment. Whereas according to the traditional approach full-spectrum light is used, recent studies suggest that the critical wavelengths are within the range of blue light (460 and 484 nm). Our previous work shows that when diurnal rodents are maintained under short photoperiod they develop depression- and anxiety-like behavioral phenotype that is ameliorated by treatment with wide-spectrum bright light exposure (2500 lux at the cage, 5000 K). Our current study compares the effect of bright wide-spectrum (3,000 lux, wavelength 420- 780 nm, 5487 K), blue (1,300 lux, wavelength 420-530 nm) and red light (1,300 lux, wavelength range 600-780 nm) exposure in the fat sand rat (Psammomys Obesus) model of SAD. We report results of experiments with six groups of sand rats that were kept under various photoperiods and light treatments, and subjected to behavioral tests related to emotions: forced swim test, elevated plus maze and social interactions. Exposure to either intense wide-spectrum white light or to blue light equally ameliorated depression-like behavior whereas red light had no effect. Bright wide-spectrum white light treatment had no effect on animals maintained under neutral photoperiod, meaning that light exposure was only effective in the pathological-like state. The resemblance between the effects of bright white light and blue light suggests that intrinsically photosensitive retinal ganglion cells (ipRGCs) are involved in the underlying biology of SAD and light therapy.