Polla 1987  Title: Melanosomes are a primary target of
Q-switched ruby laser irradiation in guinea pig skin.
Authors: Polla LL, Margolis RJ, Dover JS, Whitaker
D, Murphy GF, Jacques SL, Anderson RR
Journal: J Invest Dermatol 1987 Sep;89(3):281-6
PMID: 3624901, UI: 87309893
Cited in: Dierickx
The specific targeting of melanosomes may allow
for laser therapy of pigmented cutaneous lesions. The mechanism
of selective destruction of pigmented cells by various lasers,
however, has not been fully clarified. Black, brown, and albino
guinea pigs were exposed to optical pulses at various radiant
exposure doses from a Q-switched, 40 nsec, 694 nm ruby laser.
Biopsies were analyzed by light and electron microscopy (EM).
Albino animals failed to develop clinical or microscopic evidence
of cutaneous injury after irradiation. In both black and brown
animals, the clinical threshold for gross change was 0.4 J/cm2,
which produced an ash-white spot. By light microscopy, alterations
appeared at 0.3 J/cm2 and included separation at the dermoepidermal
junction, and the formation of vacuolated epidermal cells with
a peripheral cytoplasmic condensation of pigment. By EM, enlarged
melanosomes with a central lucent zone were observed within affected
epidermal cells at 0.3 J/cm2. At 0.8 and 1.2 J/cm2, individual
melanosomes were more intensely damaged and disruption of melanosomes
deep in the hair papillae was observed. Dermal-epidermal blisters
were formed precisely at the lamina lucida, leaving basal cell
membranes and hemidesmosomes intact. Possible mechanisms for melanosomal
injury are discussed. These observations show that the effects
of the Q-switched ruby laser are melanin-specific and melanin-dependent,
and may be useful in the selective destruction of pigmented as
well as superficial cutaneous lesions.
Note: this paper was used as evidence to dismiss a patent infringement
suit brought by laser maker Mehl against Palomar
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