Different Wavelengths Of Visible Light Research Articles

Cells, bilirubin and light: formation of bilirubin photoproducts and cellular damage at defined wavelengths.

Cultured cells from one human and one murine cell line were treated with bilirubin and irradiated with visible light of different wavelengths, either from phototherapy lamps or from a Xenon/Mercury lamp equipped with a monochromator. Bilirubin bound to human serum albumin was also irradiated with light. After irradiation, the bilirubin and its photoisomers were extracted and analysed with High Pressure Liquid Chromatography. The formation of single strand breaks in the DNA of treated cells was studied using a fluorescence marker. Cytotoxicity in the mouse skin cell line was measured by loss of the ability to form visible colonies in vitro. Green light exposure favours the production of lumirubin, while blue light causes more DNA damage and cytotoxicity. Green light may be more efficient and safer than shorter wavelength exposure when treating jaundiced newborns with phototherapy.

Bilirubin bound to cells does not form photoisomers.

Cultured cells from one human and one murine cell line were incubated with bilirubin by different methods that allowed bilirubin to be bound to cells. The cells were irradiated with visible light of different wavelengths. Bilirubin bound to human serum albumin was also irradiated with light. After irradiation, bilirubin and its photoisomers were extracted and analyzed by HPLC. No photoisomers were found in samples of irradiated cells, while the types and amounts of photoisomers that were expected from the literature were found in samples of irradiated bilirubin/albumin mixtures. We conclude that the formation of therapeutically active photoisomers during phototherapy most probably does not take place in skin cells, but most likely in bilirubin bound to albumin in the vessels or in the interstitial space.

Photosensitized production of hydrogen by water-soluble tetraphenanthroporphyrazine in micellar solutions

The use of water soluble H2TPPSO3Na as a photosensitizer for the photoreduction of methyl viologen in micellar solutions at pH = 5 and pH = 6, has been investigated. The dye collects a large fraction of solar energy in the spectral region (330–730 nm). Illumination of solutions consisting of EDTA/MV2+/H2TTPSO3Na/Cetyl trimethyl ammonium chloride (CTAC) at pH = 5 and pH = 6 with visible light of different wavelengths, gave at (395 nm) and at (602 nm) an action spectrum of methyl viologen radical (MV+), similar to the absorption spectrum of the dye itself. No photosensitization was observed in the absence of cationic micelles. Irradiation of micellar solutions with visible light gave rise to a build up of methyl viologen radical, and in the presence of colloidial platinum in the system at pH = 6, led to hydrogen evolution. As the pH was lowered to 5 the quantity of hydrogen evolved was also lowered. For this process the quantum yield was very low compared to processes involving porphyrins, but there are indications that a more finely divided platinum may result in improved yields.

Influence of visible light on the ethyl methane sulfonate induced mutation frequencies in H. vulgare Linn.

Although light is an important constituent of environment, it has not being taken into consideration by mutation breeders while applying mutagenic treatments. Hence, in the studies being reported here, the effect of different wave-lengths of visible light on ethyl methane sulfonate (EMS) treatments in barley (Hordeum vulgare L.) was investigated. The visible light wave-lengths falling in the range of 450 to 670 nm were observed to induce mitotic as well as meiotic chromosomal aberrations, besides modifying the effectiveness of EMS in the M, generation. The wave-lengths were also found to enhance and broaden the EMS induced mutation frequencies in the M2 generation. Further, these light conditions also broadened the mutation spectrum or eliminated certain types of chlorophyll-deficient mutations. From the data, it may be seen that visible light influence the EMS induced muta-genicity.

A spectrum response study on single strand DNA breaks, sister chromatid exchanges, and lethality induced by phototherapy lights.

Little information is available on the effect of visible light from commercial fluorescence lamps, commonly used in the treatment of neonatal hyperbilirubinemia, on parameters related to genetic damage in eucaryotic cells. The present study was undertaken to determine whether or not visible light of different wavelengths had any differential effects on the frequency of DNA breaks (frank breaks plus alkaline labile lesions), DNA replication, frequency of sister chromatid exchanges, and survival in cultured Chinese hamster cells. The results revealed that the "blue" spectral band (420 to 500 nm) is mainly responsible for DNA breaks, sister chromatid exchanges, and lethality induced by fluorescent light. This band is precisely that which bilirubin heavily absorbs and, hence, is the most efficient for the decomposition of this metabolite. These results were obtained with the use of light doses of 5 to 30 X 10(4) J/m3 versus the light doses of the order of 100 X 10(4) J/m2 being received by infants undergoing phototherapy treatments.