Photodisruption increases the free-radical reactivity of melanosomes isolated from retinal pigment epithelium

Randolph D. Glickman, Steven Jacques, Jon A. Schwartz, Tom Rodriguez, Kwok Wai Lam, Gwen Buhr

Research output: Chapter in Book/Report/Conference proceedingConference contribution

16 Citations (Scopus)

Abstract

Melanin in vivo is usually packaged in melanosomes with protein coats that restrict direct interaction of the melanin with the surrounding medium. We found that disruption of the melanosomes by exposure to a pulsed laser increased the ability of the melanin radicals to oxidize NADPH in a photochemical reaction. Retinal pigment epithelial (RPE) melanosomes were prepared from fresh bovine eyes in 0.25 M sucrose. A reaction mixture of 7 mM NADPH, approximately 7500 RPE melanosomes, and 80 mM Tris buffer, pH 7.2, was prepared in a volume of 60 μl. Of the two 25-μl aliquots taken from this mixture, one was pre-exposed to the 2nd-harmonic output of a Q-switched Nd:YAG laser (532 nm, 1800 10-nsec pulses at 10 Hz), and then was exposed to an Argon ion continuous wave (CW) laser (488.1 and 514.5 nm) for five minutes. The other aliquot was exposed only to the Argon laser. The CW exposure excited the melanin radicals to a reactive state that oxidized NADPH, as assayed by the loss of absorbance at 340 nm. Native melanosomes oxidized less NADPH during Ar + laser pumping than did melanosomes pre-exposed to the YAG laser. The YAG laser's stimulatory effect on melanosomes reactivity increased as the total energy it delivered rose above 3.5 J (0.14 J/cm 2/pulse × 1800 pulses), up to a maximum NADPH oxidation at about 20 J (0.2 J/cm 2/pulse × 1800 pulses, beam broadened at higher pulse energy). Electron microscopic analysis of the melanosomes confirmed the progressive physical disruption of melanosomes as the YAG pulse energy increased.

Original languageEnglish (US)
Title of host publicationProceedings of SPIE - The International Society for Optical Engineering
EditorsSteven L. Jacques
Pages460-467
Number of pages8
Volume2681
StatePublished - 1996
Externally publishedYes
EventLaser-Tissue Interaction VII - San Jose, CA, USA
Duration: Jan 29 1996Feb 1 1996

Other

OtherLaser-Tissue Interaction VII
CitySan Jose, CA, USA
Period1/29/962/1/96

Fingerprint

Melanin
Free radicals
Pigments
Lasers
Argon lasers
Pumping (laser)
Continuous wave lasers
Photochemical reactions
Sugar (sucrose)
Pulsed lasers
Argon
Laser pulses
Proteins
Oxidation
Electrons
Ions

ASJC Scopus subject areas

  • Engineering(all)

Cite this

Glickman, R. D., Jacques, S., Schwartz, J. A., Rodriguez, T., Lam, K. W., & Buhr, G. (1996). Photodisruption increases the free-radical reactivity of melanosomes isolated from retinal pigment epithelium. In S. L. Jacques (Ed.), Proceedings of SPIE - The International Society for Optical Engineering (Vol. 2681, pp. 460-467)

Photodisruption increases the free-radical reactivity of melanosomes isolated from retinal pigment epithelium. / Glickman, Randolph D.; Jacques, Steven; Schwartz, Jon A.; Rodriguez, Tom; Lam, Kwok Wai; Buhr, Gwen.

Proceedings of SPIE - The International Society for Optical Engineering. ed. / Steven L. Jacques. Vol. 2681 1996. p. 460-467.

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Glickman, RD, Jacques, S, Schwartz, JA, Rodriguez, T, Lam, KW & Buhr, G 1996, Photodisruption increases the free-radical reactivity of melanosomes isolated from retinal pigment epithelium. in SL Jacques (ed.), Proceedings of SPIE - The International Society for Optical Engineering. vol. 2681, pp. 460-467, Laser-Tissue Interaction VII, San Jose, CA, USA, 1/29/96.
Glickman RD, Jacques S, Schwartz JA, Rodriguez T, Lam KW, Buhr G. Photodisruption increases the free-radical reactivity of melanosomes isolated from retinal pigment epithelium. In Jacques SL, editor, Proceedings of SPIE - The International Society for Optical Engineering. Vol. 2681. 1996. p. 460-467
Glickman, Randolph D. ; Jacques, Steven ; Schwartz, Jon A. ; Rodriguez, Tom ; Lam, Kwok Wai ; Buhr, Gwen. / Photodisruption increases the free-radical reactivity of melanosomes isolated from retinal pigment epithelium. Proceedings of SPIE - The International Society for Optical Engineering. editor / Steven L. Jacques. Vol. 2681 1996. pp. 460-467
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