Broad-spectrum White Light Research Articles

Effect of spectral distribution on isomerization of bilirubin in vivo

The purpose of our study was to compare the effects of narrow-spectrum blue light and broad-spectrum white light on the production of bilirubin photo-isomers in human infants with jaundice. Twelve preterm infants were studied under both white and blue light. Irradiance at 450 nm was controlled at 12 microW/cm2/nm for both light sources. Each light condition (white or blue) was administered for 12 hours. Bilirubin isomers (4Z,15E-bilirubin and lumirubin) were measured before therapy and after 12 hours of each sequential light condition. The percentage of 4Z,15E-bilirubin was greater under blue light than under white light (P less than 0.01) phototherapy. There was no significant difference in percentage lumirubin under white or blue light therapy. Our data indicate that blue light is more effective than white light in producing 4Z,15E-bilirubin in vivo. Our study demonstrates that when irradiance in the bilirubin absorbance spectrum is constant, the color of light (spectral distribution) will determine the relative concentrations of photo-isomers produced.

Effects of selected wavelengths of light on reproductive development in cockerels

This study examined the effects of light from different portions of the spectrum on reproductive development in Leghorn cockerels. Chicks were distributed among six identical chambers. One was illuminated with broad spectrum white light; the other five were equipped with filter systems designed to provide approximately 100-nm bandwidths of light of similar intensity. All treatment groups were synchronized to a 14L:10D photoperiod. Plasma concentrations of LH and testosterone were measured by radioimmunoassay in 15- and 18-week-old cockerels. Body weights and testes weights were obtained from 18-week-old birds. Statistically significant ( P < 0.05) differences in plasma LH concentrations due to lighting could not be detected at either age. However, at 15 weeks, circulating testosterone levels were significantly higher in the groups exposed to red or white light. Three weeks later, testosterone was also elevated in cockerels grown under green light, while testes weights were heavier only in birds kept under white or red.

BILIRUBIN PHOTOISOMERIZATION UNDER GREEN LIGHT

Recent clinical studies have shown that green fluorescent light is more effective in reducing serum bilirubin (BR) than is broad-spectrum white fluorescent light. During phototherapy BR is converted to more polar isomeric structures which are excreted principally in the bile. The most rapidly formed photoproducts are configurational isomers, principally Z,E-BR, which accumulate in the serum and are slowly excreted with first-order kinetics. The other major photoproduct is a structural isomer of BR called lumirubin (LR) which is formed more slowly but excreted more rapidly than the configurational isomers. The relative contribution of these two photochemical reactions to the efficacy of phototherapy is not known. In this study, we measured the steady-state serum concentrations of these two classes of photoproducts in premature infants treated with either green or white fluorescent lamps. The concentration of Z,E-BR in the serum of infants treated with green light was significantly less than in infants exposed to white light. In contrast, the concentration of LR was greater in the serum of infants treated with green light. These data suggest the clinical efficacy of green phototherapy may be the result of increased production (and elimination) of lumirubin.

THE EFFECT OF SPECTRAL IRRADIANCE ON THE ISOMERIZATION OF BILIRUBIN IN VIVO

The initial event during phototherapy is the isomerization of native bilirubin to more polar configurational isomers (Z,E) and a structural isomer called lumirubin (LUM). The purpose of this study was to compare the effect of narrow spectrum blue light (B) versus broad spectrum white light (W) on the production of photoisomers in jaundiced infants. Thirteen preterm neonates (BW 1.68 ± .45 kg, GA 32 ± 2.3 wks) were studied under both B and W light. Irradiance at 450 nm was controlled at 12 uwatt/cm2/nm for both B and W. Infants were assigned to one of two study orders: B,W,B (n=4) or W,B,W (n=9). Each light condition (B or W) was administered for 12 hrs. Serum for Z,E and LUM were obtained before treatment and every 12 hours thereafter. Results were expressed as a percent of the total bilirubin. For all study infants % Z,E and LUM under B were compared with % under W for the two possible treatment sequences: W to B and B to W These data suggest that B is more effective than W in producing Z,E. The inability to demonstrate differences in % LUM may be due to more rapid excretion of this photoproduct.

The effects of light illuminance and wavelength on the growth of broiler chickens

SUMMARYThe effects of light illuminance and wavelength on the growth of male and female broiler chickens from day-old to 8 weeks of age were studied.Different coloured lights, at equal illuminance and peak wavelengths of 425, 525 and 610 nm and a broad-spectrum white light of median wavelength 560 nm had no significant effect on the growth rate or cumulative food intake of birds of either sex.The performance of male broilers was unaffected by light of different illuminances, equal to 0·7, 3·0, 15·0 and 46·5 lux. The weight gain of female broilers, adjusted for food intake, was progressively depressed at illuminances above 3 lux.There is probably no commercial advantage in using broad-spectrum white light at intensities above 3 lux.

Damage and repair in mammalian cells after exposure to non-ionizing radiations III. Ultraviolet and visible light irradiation of cells of placental mammals, including humans, and determinations of photorepairable damage in vitro

Cultured cells of placental mammals (including human skin fibroblasts) as well as fresh cornea tissue from oxen have been UV (254 nm)-irradiated and either kept dark or exposed to photoreactivating light (wavelengths >375 nm) only prior to extraction of their DNA. The latter was added to an in vitro photorepair system consisting of UV-irradiated DNA from Haemophilus influenzae and yeast-photoreactivating enzyme, illuminated with broad-spectrum white fluorescent light. The extent of competitive inhibition of the in vitro photorepair of Haemophilus-DNA, resulting from the addition of mammalian DNA, has been taken as a measure of mammalian DNA lesions capable of reacting with photoreactivating enzyme. In most cases the amount of these DNA lesions was reduced if the UV-irradiated mammalian cells had been light-exposed prior to DNA extraction, indicating photoenzymatic repair of up to 90% of the lesions. DNA damage by the photoreactivating light itself was observed at varying degrees in human cells, where this effect presumably masks some of the photorepair.