Publications by authors named "Terje Christensen"

14 Publications

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Violet-blue light exposure of the skin: is there need for protection?

Photochem Photobiol Sci 2021 May 24;20(5):615-625. Epub 2021 Apr 24.

Nordic Institute of Dental Materials (NIOM), Oslo, Norway.

Advocates of skin protection against blue light express concern about exposure to indoor lighting and electronic screens as well as natural outdoor exposure. However, the nature of adverse effects in skin is unclear and the doses to induce effects are unknown. We aimed to reveal whether there is a scientific basis for promoting skin protection against violet-blue light (400-500 nm, VBL). Based on published literature, we determined the time to reach a threshold dose that induced a biological response in human skin. In the absence of an action spectrum for effects on skin, we used a hand held probe with a defined spectral response and measurements of the unweighted exposure between 400 and 500 nm to estimate the exposure by a selection of artificial light sources and solar light. For comparison, an outdoor threshold erythemally weighted UV dose was set to 1 SED (standard erythema dose). Outdoor, weighted irradiances were obtained using a radiative transfer model. Induction of pigmentation in human skin tissue was the only consistently reported endpoint after VBL exposure of about 65 Jcm. This threshold dose was reached in 0.5 to 20 months of exposure to indoor lighting sources. In comparison, specialised medical sources reached this dose in 0.5 min to 45 h. The time outdoors to reach 1 SED was shorter than the time to reach a VBL threshold dose throughout all seasons. Skin protection against VBL is superfluous for exposures to domestic lighting sources or screens and for solar radiation; however, it may be advantageous for patients suffering from photosensitive diseases or taking photosensitising medication.
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http://dx.doi.org/10.1007/s43630-021-00043-9DOI Listing
May 2021

Sub-lethal UV radiation during early life stages alters the behaviour, heart rate and oxidative stress parameters in zebrafish (Danio rerio).

Ecotoxicol Environ Saf 2018 Dec 1;166:359-365. Epub 2018 Oct 1.

Centre for Environmental Radioactivity (CERAD CoE), NMBU, 1433 Ås, Norway; Norwegian Radiation Protection Authority, P.O. Box 329 Skøyen, 0213 Oslo, Norway.

Environmental UV radiation in sufficient doses, as a possible consequence of climate change, is potent enough to affect living organisms with different outcomes, depending on the exposure life stage. The aim of this project was to evaluate the potentially toxic effects of exposure to sub-lethal and environmentally relevant doses of UVA (9.4, 18. 7, 37.7 J/cm) and UVB radiation (0.013, 0.025, 0.076 J/cm) on the development and behaviour in early life stages (4.5-5.5 h post fertilization, hpf) of the zebrafish (Danio rerio). The used doses were all below the median lethal dose (LD) and caused no significant difference in survival, deformities, or hatching between exposed and control groups. Compared to controls, there were transient UVA and UVB exposure effects on heart rate, with dose dependent reductions at 50 hpf, and at 60 hpf for UVA only. The UVB exposure caused an increasing trend in reactive oxygen species (ROS) formation at the two highest doses, even though only significant at 120 hpf for the second highest dose. Both UVA and UVB caused an increasing trend in lipid peroxidation (LPO) at the highest doses tested at 72 hpf. Furthermore, UVA exposure led to significant reductions in larval movement following exposure to the two highest doses of UVA, i.e., reduction in the time spent active and the total distance moved compared to control at 100 hpf, while no effect on the swimming speed was observed. The lowest dose of UVA had no effect on behaviour. In contrast, the highest dose of UVB led to a possible increase in the time spent active and a slower average swimming speed although these effects were not significant (p = 0.07). The obtained results show that UV doses below LD levels are able to cause changes in the behaviour and physiological parameters of zebrafish larvae, as well as oxidative stress in the form of ROS formation and LPO. Further testing is necessary to assess how this type of radiation and the effects observed could affect fish population dynamics.
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http://dx.doi.org/10.1016/j.ecoenv.2018.09.082DOI Listing
December 2018

Dose-dependent effects of gamma radiation on the early zebrafish development and gene expression.

PLoS One 2017 19;12(6):e0179259. Epub 2017 Jun 19.

Norwegian University of Life Sciences (NMBU), CERAD CoE, Faculty of Veterinary Medicine and Biosciences, Oslo, Norway.

Ionizing radiation from natural sources or anthropogenic activity has the potential to cause oxidative stress or genetic damage in living organisms, through the ionization and excitation of molecules and the subsequent production of free radicals and reactive oxygen species (ROS). The present work focuses on radiation-induced biological effects using the zebrafish (Danio rerio) vertebrate model. Changes in developmental traits and gene expression in zebrafish were assessed after continuous external gamma irradiation (0.4, 3.9, 15 and 38 mGy/h) with corresponding controls, starting at 2.5 hours post fertilization (hpf) and lasting through embryogenesis and the early larval stage. The lowest dose rate corresponded to recommended benchmarks at which adverse effects are not expected to occur in aquatic ecosystems (2-10 mGy/day). The survival observed at 96 hours post fertilization (hpf) in the 38 mGy/h group was significantly lower, while other groups showed no significant difference compared to controls. The total hatching was significantly lower from controls in the 15 mGy/h group and a delay in hatching onset in the 0.4 mGy/h group was observed. The deformity frequency was significantly increased by prolonged exposure duration at dose rates ≥ 0.4 mGy/h. Molecular responses analyzed by RNA-seq at gastrulation (5.5 hpf transcriptome) indicate that the radiation induced adverse effects occurred during the earliest stages of development. A dose-response relationship was found in the numbers of differentially regulated genes in exposure groups compared to controls at a total dose as low as 1.62 mGy. Ingenuity Pathway Analysis identified retinoic acid receptor activation, apoptosis, and glutathione mediated detoxification signaling as the most affected pathways in the lower dose rate (0.54 mGy/h), while eif2 and mTOR, i.e., involved in the modulation of angiogenesis, were most affected in higher dose rates (5.4 and 10.9 mGy/h). By comparing gene expression data, myc was found to be the most significant upstream regulator, followed by tp53, TNF, hnf4a, TGFb1 and cebpa, while crabp2b and vegfab were identified as most frequent downstream target genes. These genes are associated with various developmental processes. The present findings show that continuous gamma irradiation (≥ 0.54 mGy/h) during early gastrula causes gene expression changes that are linked to developmental defects in zebrafish embryos.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0179259PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5476279PMC
September 2017

Ultraviolet-B radiation mobilizes uranium from uranium-dissolved organic carbon complexes in aquatic systems, demonstrated by asymmetrical flow field-flow fractionation.

J Chromatogr A 2017 May 21;1496:105-114. Epub 2017 Mar 21.

Centre of Environmental Radioactivity CoE, Department of Environmental Sciences, Norwegian University of Life Sciences (NMBU), P. O. Box 5003, 1432, Ås, Norway.

Humic substances have a tendency to form complexes with metal ions in aquatic medium, impacting the metal mobility, decreasing bioavailability and toxicity. Ultraviolet-B (UV-B) radiation exposure degrades the humic substance, changes their molecular weight distribution and their metal binding capacity in aquatic medium. In this study, we experimented the effect of UV-B radiation on the uranium complexed with fulvic acids and humic acids in a soft water system at different pH, uranium concentrations and radiant exposure. The concentration and distribution of uranium in a complexed form were investigated by asymmetrical flow field-flow fractionation coupled to multi detection technique (AsFlFFF-UV-ICP-MS). The major concentration of uranium present in complexes was primarily associated with average and higher molecular weight fulvic and humic acids components. The concentration of uranium in a complexed form increased with increasing fulvic and humic acid concentrations as well as pH of the solution. The higher molecular weight fraction of uranium was degraded due to the UV-B exposure, transforming about 50% of the uranium-dissolved organic carbon complexes into low molecular weight uranium species in complex form with organic ligands and/or free form. The result also suggests AsFlFFF-UV-ICP-MS to be an important separation and detection technique for understanding the interaction of radionuclides with dissolved organic matter, tracking size distribution changes during degradation of organic complexes for understanding mobility, bioavailability and ecosystem transfer of radionuclides as well as metals.
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http://dx.doi.org/10.1016/j.chroma.2017.03.042DOI Listing
May 2017

Methacrylate monomers lower the level of reduced glutathione and increase the in vitro sensitivity of cells to optical radiation.

Photochem Photobiol Sci 2010 Dec 23;9(12):1597-600. Epub 2010 Sep 23.

NIOM - Nordic Institute of Dental Materials, P.O. Box 70, NO-1305, Haslum, Norway.

Induction of cell death by optical radiation in the wavelength range 350-500 nm was significantly increased by commonly used methacrylate monomers, not mediated by absorption of radiation by the methacrylate monomers, but through a mechanism involving rapid reduction in the level of glutathione (GSH).
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http://dx.doi.org/10.1039/c0pp00240bDOI Listing
December 2010

In vitro photosensitization initiated by camphorquinone and phenyl propanedione in dental polymeric materials.

J Photochem Photobiol B 2010 Sep 4;100(3):128-34. Epub 2010 Jun 4.

NIOM as - Nordic Institute of Dental Materials AS, NO-1305 Haslum, Norway.

Documentation is scarce on the photobiological effects of photoinitiators present in dental light curable materials. The aim of this study was to determine cellular effects of the photoinitiators camphorquinone (CQ) and phenyl propanedione (PPD) and to investigate whether these substances produced reactive oxygen species after low and high doses of optical radiation (between 0 and 17J/cm(2)). Rat salivary gland cells in vitro were exposed to visible blue light and/or UVA. Hematoporphyrin (HP), a photosensitizer used in medicine, and the UVA-filter 2-methoxy-4-hydroxy-benzophenone (B-3) were used as reference substances. It was found that PPD produced hydrogen peroxide, but not singlet oxygen, upon light irradiation. CQ produced neither hydrogen peroxide nor singlet oxygen. Cell death by necrosis and apoptosis was induced by irradiation in the presence of CQ, PPD and HP. Doses higher than 6J/cm(2) UVA and blue visible light from a source similar to clinically applied sources, induced apoptosis even in the absence of photosensitizers added. A reciprocity relationship was found between radiant exposure (at constant irradiance) and concentration of photoinitiators. In conclusion, the oral cells under investigation were light sensitive, and the sensitivity increased in presence of photoinitiators. PPD acted by mechanisms that included reactive oxygen species and CQ probably by formation of free radicals.
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http://dx.doi.org/10.1016/j.jphotobiol.2010.05.012DOI Listing
September 2010

Octyl methoxycinnamate modulates gene expression and prevents cyclobutane pyrimidine dimer formation but not oxidative DNA damage in UV-exposed human cell lines.

Toxicol Sci 2010 Apr 13;114(2):272-84. Epub 2010 Jan 13.

Department of Chemical Toxicology, Division of Environmental Medicine, Norwegian Institute of Public Health, Nydalen, NO-0403 Oslo, Norway.

Octyl methoxycinnamate (OMC) is one of the most widely used sunscreen ingredients. To analyze biological effects of OMC, an in vitro approach was used implying ultraviolet (UV) exposure of two human cell lines, a primary skin fibroblast (GM00498) and a breast cancer (MCF-7) cell lines. End points include cell viability assessment, assay of cyclobutane pyrimidine dimers (CPDs) and oxidated DNA lesions using alkaline elution and lesion-specific enzymes, and gene expression analysis of a panel of 17 DNA damage-responsive genes. We observed that OMC provided protection against CPDs, and the degree of protection correlated with the OMC-mediated reduction in UV dose. No such protection was found with respect to oxidative DNA lesions. Upon UV exposure in the presence of OMC, the gene expression studies showed significant differential changes in some of the genes studied and the expression of p53 protein was also changed. For some genes, the change in expression seemed to be delayed in time by OMC. The experimental approach applied in this study, using a panel of 17 genes in an in vitro cellular system together with genotoxicity assays, may be useful in the initial screening of active ingredients in sunscreens.
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http://dx.doi.org/10.1093/toxsci/kfq005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2840218PMC
April 2010

In vitro efficacy and risk for adverse effects of light-assisted tooth bleaching.

Photochem Photobiol Sci 2009 Mar 16;8(3):377-85. Epub 2009 Jan 16.

Nordic Institute of Dental Materials (NIOM), NO-1305, Haslum, Norway.

The use of optical radiation in the so-called light-assisted tooth bleaching procedures has been suggested to enhance the oxidizing effect of the bleaching agent, hydrogen peroxide. Documentation is scarce on the potential adverse effects of bleaching products and on optical exposure risks to eyes and skin. The efficacy of seven bleaching products with or without simultaneous use of seven different bleaching lamps was investigated using extracted human teeth. The bleaching effect was determined immediately after treatment and one week later. Tooth surfaces were examined for adverse alterations after bleaching using a scanning electron microscope. Source characteristics of eight lamps intended for tooth bleaching were determined. International guidelines on optical radiation were used to assess eye and skin exposure hazards due to UV and visible light emission from the lamps. Inspection of teeth one week after bleaching showed no difference in efficacy between teeth bleached with or without irradiation for any of the products. Scratches, probably from the cleaning procedure were frequently seen on bleached enamel irrespective of irradiation. Maximum permissible exposure time (t(max)) and threshold limit values were exceeded for about half the bleaching lamps investigated. One lamp exceeded t(max) even for reflected blue light within the treatment time. This lamp also exceeded t(max) values for UV exposure. The lamps were classified as "low risk" and as borderline to "moderate risk" according to a relevant lamp standard.
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http://dx.doi.org/10.1039/b813132eDOI Listing
March 2009

Evaluation of eye protection filters for use with dental curing and bleaching lamps.

J Occup Environ Hyg 2007 Jun;4(6):432-9

Nordic Institute of Dental Materials, Haslum, Norway.

Exposure to intense radiation sources in a dental clinic necessitates the use of eye protective filters to avoid blue-light photochemical retinal hazard. We have investigated the filtering quality and assessed whether the filters protect sufficiently against retinal hazards throughout the workday. Visible light transmittance of 18 protective filters was measured. These products consisted of spectacles, stationary lamp shields, and a hand-held shield intended for use in dental clinics. Nine of the 18 tested filters had adequate filtering capacity according to today's lamp technology and exposure limit values. These filters transmitted less than 0.1% of the radiation at any wavelength between 400 nm and 525 nm. Seven of the nine filters showed transmission values below the detection limit (approximately 10(-3)%) in the wavelength band between 400 nm and 500 nm. Filters of inferior quality may prove inadequate if the use and radiation intensity of the lamps further increase. Lack of protection may also occur if a filter is used to protect against emission from a lamp with properties other than the lamp for which the filter has been intended. It is of major importance that the spectacles/shields accommodate the emission from the lamp source. The suppliers of dental radiation sources should be responsible for information on the need for and proper use of eye protectors. In addition, the filters should be marked according to testing procedures appropriate for the specific use.
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http://dx.doi.org/10.1080/15459620701354218DOI Listing
June 2007

Formation of photoproducts and cytotoxicity of bilirubin irradiated with turquoise and blue phototherapy light.

Acta Paediatr 2005 Oct;94(10):1448-54

Norwegian Radiation Protection Authority, Østerås, Norway.

Aim: To compare a new turquoise ("green") fluorescent phototherapy lamp (490 nm) with a conventional blue phototherapy lamp (450 nm) with respect to cytotoxicity and photochemical effects of bilirubin.

Methods: Mouse lymphoma cells (L5178Y-R) in the presence of bilirubin solutions were exposed to phototherapy light. Occurrence of necrosis and apoptosis, reduction of mitotic index and inhibited cell growth was assayed by appropriate methods. The presence of bilirubin and its photoisomers was measured by high-pressure liquid chromatography analysis and absorption spectroscopy.

Results: At constant and equal light irradiances, the cytotoxic effects in the presence of bilirubin bound to human serum albumin showed that the green lamp caused significantly less necrosis (n = 4, p < 0.05) and less inhibition of cell multiplication (n = 3, p < 0.05) than the blue lamp. A slightly lower apoptotic fraction, although not statistically significant, was observed in cells exposed to the blue lamp. Photo-oxidation of bilirubin was more prominent with blue light irradiation. The photoequilibria between geometric isomers of bilirubin were different for the two lamps; more geometric photoisomers were formed by blue irradiation (n = 6, p < 0.05). The amounts of the most water-soluble isomers (presumably mainly lumirubin) were rather similar for the two lamps.

Conclusion: The two lamps were similar in the formation of therapeutically relevant photoproducts, but the blue lamp showed potential in forming more photo-oxidation products and in causing more severe cellular damage in the presence of bilirubin.
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http://dx.doi.org/10.1111/j.1651-2227.2005.tb01819.xDOI Listing
October 2005

Effects of bilirubin and phototherapy on osmotic fragility and haematoporphyrin-induced photohaemolysis of normal erythrocytes and spherocytes.

Acta Paediatr 2005 Oct;94(10):1443-7

Norwegian Radiation Protection Authority, Østerås, Norway.

Aim: To study the effects of phototherapy on erythrocyte haemolysis in vitro and to determine possible differences in sensitivity to phototherapy between normal erythrocytes and spherocytes.

Methods: Erythrocytes from four normal healthy donors and two donors with hereditary spherocytosis were treated with bilirubin (160 microM) in the presence of human serum albumin in the molecular ratio bilirubin/albumin 0.8. Treated cells were maintained either in the dark or in blue light (450 nm, 8 mW/cm2, 30 min). The experimental light dose was comparable to 2 h of clinical phototherapy. The osmotic fragility of the treated cells was measured by scoring haemolysis in hypo-osmolar solutions (0.10-0.90% NaCl). The sensitivity to photohaemolysis of cells pre-treated with bilirubin (BR) and/or phototherapy was tested by exposing the cell suspensions to haematoporphyrin and UVA radiation. The delayed (18 h) photohaemolysis was measured by spectrophotometry.

Results: Osmotic fragility, expressed as percentage haemolysis, of normal erythrocytes was more than doubled in the presence of BR combined with phototherapy (n = 6, p < 0.05). In contrast, osmotic fragility of spherocytes was unaffected by either treatment (n = 8, p < 0.05). Increased photohaemolysis was seen in spherocytes treated with BR (n = 13, p < 0.05), phototherapy (n = 13, p < 0.05) and a combination of the two agents (n = 13, p < 0.05) compared with spherocytes without BR in the dark (n = 6).

Conclusion: Bilirubin may make the plasma membrane of normal erythrocytes more fragile. Newborns with hereditary spherocytosis may be sensitive to phototherapy.
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http://dx.doi.org/10.1111/j.1651-2227.2005.tb01818.xDOI Listing
October 2005

The digital photobiology compendium: perspectives on a web-based teaching tool from learners and developers.

Photochem Photobiol Sci 2004 Aug 14;3(8):788-94. Epub 2004 Apr 14.

Istituto di BioFisica, Consiglio Nazionale delle Richerche, Pisa, Italy.

The DPC offers many benefits for learners, teachers and developers involved in creation of teaching materials in photobiology. Modifications and additions can be made relatively easily. Anonymous peer review of modules, allowing them to be cited as peer reviewed publications, is likely to encourage new submissions.
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http://dx.doi.org/10.1039/b316118hDOI Listing
August 2004

Zinc octa-n-alkyl phthalocyanines in photodynamic therapy: photophysical properties, accumulation and apoptosis in cell cultures, studies in erythrocytes and topical application to Balb/c mice skin.

Photochem Photobiol Sci 2003 Jun;2(6):660-7

Gentian AS, Belsetsvingen 39, 1348 Rykkinn, Norway.

Two octa-substituted phthalocyanines, namely 1,4,8,11,15,18,22,25-octakis(decyl)phthalocyaninato zinc(II) (ZnODPc) and 1,4,8,11,15,18,22,25-octakis(pentyl)phthalocyaninato zinc(II) (ZnOPPc), were investigated for their use in photodynamic therapy (PDT) after topical application. Both substances exhibited favourable properties as photosensitisers in vitro: absorption maxima around 700 nm with absorption coefficients of about 190000 (M(-1) cm(-1)), a singlet oxygen quantum yield of 0.47 +/- 0.02 (ZnODPc), and good accumulation in keratinocytes and fibroblasts. Cell death after phthalocyanine-photosensitisation appeared to occur mainly via apoptosis. The in vivo experiments demonstrated a good accumulation of the phthalocyanines after topical application in a tetrahydrofuran-azone formulation onto the dorsal skin of Balb/c mice: [(4.6-4.7) +/- 1.0]% of deposited dye could be recovered after 3 h from deposition. ZnODPc showed significantly better skin-photosensitising properties than ZnOPPc and is therefore a potential candidate for the treatment of psoriasis.
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http://dx.doi.org/10.1039/b211348aDOI Listing
June 2003
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