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 language | English (US) |
|---|---|
| Title of host publication | Proceedings of SPIE - The International Society for Optical Engineering |
| Editors | Steven L. Jacques |
| Pages | 460-467 |
| Number of pages | 8 |
| Volume | 2681 |
| State | Published - 1996 |
| Event | Laser-Tissue Interaction VII - San Jose, CA, USA Duration: Jan 29 1996 → Feb 1 1996 |
Other
| Other | Laser-Tissue Interaction VII |
|---|---|
| City | San Jose, CA, USA |
| Period | 1/29/96 → 2/1/96 |
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ASJC Scopus subject areas
- Engineering(all)
Cite this
Photodisruption increases the free-radical reactivity of melanosomes isolated from retinal pigment epithelium. / Glickman, Randolph D.; Jacques, Steven L.; 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 proceeding › Conference contribution
}
TY - GEN
T1 - Photodisruption increases the free-radical reactivity of melanosomes isolated from retinal pigment epithelium
AU - Glickman, Randolph D.
AU - Jacques, Steven L.
AU - Schwartz, Jon A.
AU - Rodriguez, Tom
AU - Lam, Kwok Wai
AU - Buhr, Gwen
PY - 1996
Y1 - 1996
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=0029728076&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0029728076&partnerID=8YFLogxK
M3 - Conference contribution
AN - SCOPUS:0029728076
SN - 0819420557
SN - 9780819420558
VL - 2681
SP - 460
EP - 467
BT - Proceedings of SPIE - The International Society for Optical Engineering
A2 - Jacques, Steven L.
ER -