Invited Symposium: Photodynamic Therapy
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Portnoy, M (Photonics Research Ontario and Department of Medical Biophysics, University of Toronto, Canada)
Wilson, BC (Photonics Research Ontario and Department of Medical Biophysics, University of Toronto, Canada)
Abstract
The apoptotic response of normal brain and brain tumour following Photodynamic Therapy using five different photodynamic photosensitizers, Photofrin, 5-aminolevulinic acid (ALA)-induced Protoporphyrin IX (PpIX), chloroaluminium phthalocyanine (AlClPc), Tin Ethyl Etiopurpurin (SnET2) and meta-Tetra(hydroxyphenyl)clorin (mTHPC), was evaluated. Free DNA ends, produced as a result of internucleosomal DNA cleavage in apoptotic cells, were stained using a terminal deoxynucleotidyl transferase (TdT) assay, which allowed for quantification and determination of the spatial distribution of apoptotic cells using confocal laser-scanning microscopy (CLSM). The incidence of apoptosis was confirmed by a histopathological study, which demonstrated cell shrinkage, pyknosis, and karyorrhexis. At 24 hours post PDT, AlClPc did not cause any apoptosis, while the other photosensitizers tested produced minimal apoptotic effects, with varying numbers of apoptotic cells localized near the region of frank coagulative necrosis. The apoptotic effect does not appear to be related to photosensitizer dose for any of the drugs and doses tested. These results suggest that at 24 hours after PDT, a minimal and localized apoptotic effect is produced, the extent of which appears to depend largely on the particular photosensitizer chosen.
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Presentation Number SAlilge0757
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