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G Sbrana

Publications and source records attributed to G Sbrana.

8 recordsLinked to original sources
PubMed1988

Bilirubin photoconversion induced by monochromatic laser radiation. Comparison between aerobic and anaerobic experiments in vitro.

Structural and geometric photoisomerization of bilirubin bound to human serum albumin was investigated. Solutions were irradiated with monochromatic light emitted by an Ar ion laser, the 457.9, 488.0 and 514.5 nm wavelengths being selected. Photoproducts were separated and analysed by h.p.l.c. Visible-absorption spectra of pure ZZ-bilirubin, ZE-bilirubin and lumirubin in the eluent were registered in the 350-550 nm region by collecting single fractions by h.p.l.c. Wavelength-dependence of bilirubin photoconversion was studied within photoequilibrium and up to a large decrement of the total concentration. Experiments were performed in aerobic and anaerobic conditions in order to assess the contribution of the photo-oxidation to the overall process. The presence of O2 was found to increase the rate of bilirubin degradation and unexpectedly to favour lumirubin production. The ability of 514.5 nm irradiation to induce bilirubin cyclization was definitively confirmed.

Bilirubin↗
PubMed1987

Phototherapy in the management of neonatal hyperbilirubinemia: efficacy with light sources emitting more than 500 nanometers.

The clinical action of green fluorescent lamps, properly filtered to remove wavelengths of less than 500 nm, was investigated in a group of 23 newborns with different initial serum bilirubin concentrations. The serum bilirubin levels were measured at 6, 12, 24, and 48 hours after the beginning of phototherapy. These results are compared with those obtained, under the same experimental conditions, in a group exposed to commercial green lamps. Similar bilirubin decline rates were observed in the two experiments. In general, these data confirm the satisfactory clinical efficacy of the green light in phototherapy and prove, in particular, that the blue component present in the emission spectrum of the commercial green lamps has a negligible effect on the bilirubin degradation process.

Bilirubin↗
PubMed1986

Phototherapy for neonatal jaundice: clinical equivalence of fluorescent green and "special" blue lamps.

The relative efficacy of fluorescent green (Sylvania F20T12/G) and "special" blue (Westinghouse F20T12/BB) lamps in the phototherapy of jaundiced neonates was investigated. Two groups of low birth weight infants with a mean gestational age of 35 weeks and mean birth weight of 1930 gm, who developed hyperbilirubinemia within the first 5 days of life, were given green or blue lamp phototherapy under the same irradiation conditions. No statistically significant difference in plasma bilirubin concentrations was found between the two groups after 24 or 48 hours of treatment. Because recent measurements indicate that green lamps are much less efficient than special blue lamps for the production of Z, E isomers of bilirubin in vitro and in vivo, the clinical equivalence of these two types of lamps seems to support the hypothesis that production of structural photoisomers of bilirubin is the main mechanism of phototherapy in humans. Therefore, fluorescent green lamps provide an alternative to special blue lamps for treatment of neonatal hyperbilirubinemia.

Bilirubin↗
PubMed1985

Laser investigation of bilirubin-photobilirubin photoconversion.

The reversibility of the configurational photoisomerization process of bilirubin (BR) with laser lines in the blue-green spectral region is investigated. Photoisomerization efficiency of BR is found to depend strongly on wavelength, and to decrease when the excitation wavelength is increased from blue to green. Reversion of BR photoisomers (identical to photobilirubin, PBR) back to native BR is demonstrated for several laser lines by irradiating PBR/BR mixtures with wavelengths greater than the excitation wavelengths. Green lines turn out to be very efficient for PBR----BR reversion. The PBR concentrations at photoequilibrium, obtained from the spectrophotometric data, are in close agreement with the corresponding values measured with the high performance liquid chromatography technique in the case of 10 nm bandwidth filtered light reported in the literature. The 457 nm blue laser line produces 32% PBR concentration at photoequilibrium; only 14, 7, and 3% PBR concentrations are produced by the blue-green lines at 488, 501, 514 nm, respectively. The effect on the photostationary PBR/BR mixture of successive irradiations with different wavelengths, and the influence of the wavelength sequence are reported. In the case of blue lines our results support the assumption of the first-order kinetics for the BR in equilibrium PBR photoreaction. Departures are observed with green-lines (501, 514 nm). The present results, together with the i) good clinical efficiency reported for fluorescent green lamps; and ii) slow elimination of configurational photoisomers in infants, tend to confirm the lumirubin-pathway as the main mechanism for phototherapy, and call for clinical investigation of narrow-spectrum lamps with peak emission wavelength in the (biologically safer) 480 divided by 530 nm range.

Bilirubin↗
PubMed1983

Green light in phototherapy.

Photodegradation of bilirubin in vivo has been investigated by using green fluorescent sources according to the suggestions obtained in a previous study in vitro. Two groups of 50 jaundiced low-birth-weight infants were exposed to fluorescent light in phototherapy units under similar irradiant conditions. One group was exposed for 24 h to standard green tubes, the other, to daylight lamps. Newborns of the two groups were similar for gestational age, birthweight, and initial bilirubin concentration. A greater decrease in the serum concentration of bilirubin was found in subjects exposed to the green light when compared with infants exposed to daylight lamps. The use of green light is strongly suggested instead of the white, blue, and special blue lamps, because of the real efficiency, power and range of wave lengths.

Bilirubin↗
PubMed1981

Laser photolysis of bilirubin.

Photodegradation of bilirubin in vitro has been investigated by using monochromatic light supplied by an argon ion laser selecting the 457.9, 488.0 and 514.5 nm wavelengths. Bilirubin was examined in chloroform, in aqueous solutions and in human serum under different experimental conditions of concentration, laser power and time of irradiance. Photodecomposition was followed by optical density measurements on the absorption maximum of the electronic band at 460 nm. The rate of degradation of bilirubin was found to be only slightly affected by the wavelength of the exciting lines provided they fall within the absorption band. In particular it was shown that any wavelength, lambda, is equally effective if the corresponding absorbance, A lambda, exceeds a minimum value of 5-10%. In the aqueous solutions, light with lambda greater than 470 nm has been found to be largely effective in the photodegradation of bilirubin in vitro.

Bilirubin↗