Dies used were caspase 3 and caspase 8 (Santa Cruz, Biotecnologies, USA). Immunohistochemistry was performed according to the manufacturer’s instructions. Sections were SR-3029 visualized by treating the slides with diamino-benzidine-tetrahydrochloride. To determine the levels of apoptotic marker expression, the tumor tissues were assessed in 10 fields by the point-counting technique, using a 100-point grid with a known area (62500 mm2 at a 4406 magnification) attached to the ocular lens of the microscope [18]. At 4006 magnification, the tumor area in each field was calculated according to the number of points hitting theconnective tissue as a proportion of the total grid area. Afterward, the number of positive cells within the tumor area was counted [19]. The cell area fraction was determined as the number of positive cells in each field divided by the tumor area. The final results were expressed as percentage mean 6 standard deviation (s.d.) of the tumor tissue, with non-coincident microscopic fields. Information about the used immunohistochemical antibodies is in Table S2.Optical Microscopy (Hematoxylin/Eosin)A longitudinal sample of the tumor was selected from each group, processed for paraffin embedding, sectioned (three microns) and stained with hematoxylin-eosin for light microscopy, using an Axiostar plus microscope (Carl Zeiss 
do Brasil Ltda.). The slides were evaluated by a pathologist with no prior knowledge of the group they belonged to.Electron MicroscopySmall fragments of different areas of the tumor from each group were washed and fixed in phosphate-buffered 1 paraformaldehyde and 2 glutaraldehyde (pH 7.3) overnight at 4uC. After fixation, the samples were washed in the same buffer, embedded in molten 2 agar (Merck, Darmstad, Germany) and post-fixed inApoptosis in Melanoma Cells after BNCTFigure 7. Hematoxylin and eosin-stained sections of malignant melanoma in control, irradiated control, BNCT 1 and BNCT 7 days groups. In the control and irradiated groups, malignant melanoma cells were preserved and composed of large cells with atypical nuclei and 115103-85-0 web abundant cytoplasm. Normal mitosis (blue arrows) and aberrant mitosis (yellow arrows) were both observed. Necrosis was absent in both groups of melanoma. By contrast, extensive necrosis (nec), pycnotic nuclei (black arrows) and acidophilic cytoplasm (green arrows) were present in the malignant melanoma of BNCT 1 and BNCT 7 day groups. Furthermore, the BNCT groups also presented aberrant mitosis. doi:10.1371/journal.pone.0059639.ga mixture of 1 phosphate-buffered osmium tetroxide and 1.5 potassium ferrocyanide for 1 h prior to dehydration in a graded ethanol series and infiltration and embedding in a propylene oxide-Epon sequence (PolyBed 812, Polysciences, Warrington, PA, USA). Thin sections were cut using a diamond knife on an ultramicrotome (Sorvall MT2, Newton, MA, USA) and mounted on uncoated 200-mesh copper grids (Ted Pella, Redding, CA, USA) before staining with uranyl acetate and lead citrate. The samples were viewed using a transmission electron microscope (TEM) (EM 10, Zeiss, Germany) at 60 kV.In situ Detection of Apoptotic CellsFor the in situ detection of apoptosis at the level 1313429 of a single cell, we used an apoptotic assay of the deoxynucleotidyl transferase (TdT) method of end labeling (TUNEL) (Boehringer Mannheim, Mannheim, Germany) [20,21]. Thick paraffin sections (4 to 6 mm)were layered on glass slides, deparaffinized with xylene, and rehydrated with graded dilutions.Dies used were caspase 3 and caspase 8 (Santa Cruz, Biotecnologies, USA). Immunohistochemistry was performed according to the manufacturer’s instructions. Sections were visualized by treating the slides with diamino-benzidine-tetrahydrochloride. To determine the levels of apoptotic marker expression, the tumor tissues were assessed in 10 fields by the point-counting technique, using a 100-point grid with a known area (62500 mm2 at a 4406 magnification) attached to the ocular lens of the microscope [18]. At 4006 magnification, the tumor area in each field was calculated according to the number of points hitting theconnective tissue as a proportion of the total grid area. Afterward, the number of positive cells within the tumor area was counted [19]. The cell area fraction was determined as the number of positive cells in each field divided by the tumor area. The final results were expressed as percentage mean 6 standard deviation (s.d.) of the tumor tissue, with non-coincident microscopic fields. Information about the used immunohistochemical antibodies is in Table S2.Optical Microscopy (Hematoxylin/Eosin)A longitudinal sample of the tumor was selected from each group, processed for paraffin embedding, sectioned (three microns) and stained with hematoxylin-eosin for light microscopy, using an Axiostar plus microscope (Carl Zeiss do Brasil Ltda.). The slides were evaluated by a pathologist with no prior knowledge of the group they belonged to.Electron MicroscopySmall fragments of different areas of the tumor from each group were washed and fixed in phosphate-buffered 1 paraformaldehyde and 2 glutaraldehyde (pH 7.3) overnight at 4uC. After fixation, the samples were washed in the same buffer, embedded in molten 2 agar (Merck, Darmstad, Germany) and post-fixed inApoptosis in Melanoma Cells after BNCTFigure 7. Hematoxylin and eosin-stained sections of malignant melanoma in control, irradiated control, BNCT 1 and BNCT 7 days groups. In the control and irradiated groups, malignant melanoma cells were preserved and composed of large cells with atypical nuclei and abundant cytoplasm. Normal mitosis (blue arrows) and aberrant mitosis (yellow arrows) were both observed. Necrosis was absent in both groups of melanoma. By contrast, extensive necrosis (nec), pycnotic nuclei (black arrows) and acidophilic cytoplasm (green arrows) were present in the malignant melanoma of BNCT 1 and BNCT 7 day groups. Furthermore, the BNCT groups also presented aberrant mitosis. doi:10.1371/journal.pone.0059639.ga mixture of 1 phosphate-buffered osmium tetroxide and 1.5 potassium ferrocyanide for 1 h prior to dehydration in a graded ethanol series and infiltration and embedding in a propylene oxide-Epon sequence (PolyBed 812, Polysciences, Warrington, PA, USA). Thin sections were cut using a diamond knife on an ultramicrotome (Sorvall MT2, Newton, MA, USA) and mounted on uncoated 200-mesh copper grids (Ted Pella, Redding, CA, USA) before staining with uranyl acetate and lead citrate. The samples were viewed using a transmission electron microscope (TEM) (EM 10, Zeiss, Germany) at 60 kV.In situ Detection of Apoptotic CellsFor the in situ detection of apoptosis 
at the level 1313429 of a single cell, we used an apoptotic assay of the deoxynucleotidyl transferase (TdT) method of end labeling (TUNEL) (Boehringer Mannheim, Mannheim, Germany) [20,21]. Thick paraffin sections (4 to 6 mm)were layered on glass slides, deparaffinized with xylene, and rehydrated with graded dilutions.
