Preparation of High-quality Hematoxylin and Eosin–stained Sections from Rodent Mammary Gland Whole Mounts for Histopathologic Review

Identifying environmental exposures that cause adverse mammary gland outcomes in rodents is a first step in disease prevention in humans and domestic pets. ‘Whole mounts’ are an easy and inexpensive tissue preparation method that can elucidate typical or abnormal mammary gland morphology in rodent studies. Here we propose procedures to facilitate the use of whole mounts for histological identification of grossly noted tissue alterations. We noted lesions in mammary whole mounts from 14 month old CD-1 mice that were not found in the contralateral gland hematoxylin and eosin (H&E)-stained section. Whole mounts were removed from the slide and carefully processed to produce high quality histological sections that mirrored the quality of the original H&E-stained section in order to properly diagnose the unidentified gross abnormalities. Incorporation of this method into testing protocols which focus on low-dose human relevant chemicals and endocrine disruptors will increase the chances of identifying lesions in the gland and reduce the risk of false negative findings. This method can be especially invaluable when lesions are not always palpable during the course of the study or visible at necropsy, or when a single cross-section of the mammary gland is otherwise used for detecting lesions

Immunotoxic and hepatotoxic effects of perfluoro-n-decanoic acid (PFDA) on female Harlan Sprague–Dawley rats and B6C3F1/N mice when administered by oral gavage for 28 days

Poly- and perfluoroalkyl substances (PFAS) are chemically and thermally stable, hydrophobic, lipophobic compounds used in stain repellants and water and oil surfactants, and associated with immunosuppression and peroxisome proliferator activity. Perfluoro-n-decanoic acid (PFDA, (CF3(CF2)8COOH), a fluorinated straight chain fatty acid compound, is reported to induce thymic atrophy and reversible bone marrow hypocellularity in rodent models. The objective of this study was to assess potential immunotoxicity of PFDA, due to its structural similarity to other immunosuppressive PFASs. Female Harlan Sprague–Dawley rats were exposed to 0–2.0 mg PFDA/kg by oral gavage daily for 28 d. Female B6C3F1/N mice were exposed once/week to 0–5.0 mg PFDA/kg by gavage for 4 weeks. Animals were evaluated for effects on immune cell populations in spleen and bone marrow, and innate, humoral-, and cell-mediated immunity. Mice were also evaluated for resistance to Influenza virus. Treatment-related hepatocyte necrosis and hepatomegaly were observed in rats treated with 0.5 mg PFDA/kg/d. In mice, hepatomegaly (26–89%) was observed following exposure to ≥0.625 mg PFDA/kg/week, while splenic atrophy (20%) was observed at 5.0 mg PFDA/kg/week. At 5.0 mg PFDA/kg/week, total spleen cells, and Ig + and NK + cells were decreased (17.6–27%). At ≥ 1.25 mg PFDA/kg/week the numbers of splenic CD3+, CD4+, CD8+, and Mac3+ cells were decreased (10.5–39%). No changes were observed in leukocyte subpopulations in PFDA-exposed rats. Phagocytosis by fixed-tissue macrophages was decreased in liver (specific activity, 24–39%) at ≥0.25 mg PFDA/kg/d in rats. PFDA-induced effects on humoral- and cell-mediated immunity, host resistance, and bone marrow progenitor cells were limited. These data suggest that exposure to PFDA may induce adverse effects in rat liver in a manner consistent with the PFAS class, and may also alter the balance of immune cell populations in lymphoid tissues in mice

Immunotoxic and hepatotoxic effects of perfluoro-<i>n</i>-decanoic acid (PFDA) on female Harlan Sprague–Dawley rats and B₆C₃F₁/N mice when administered by oral gavage for 28 days

<p>Poly- and perfluoroalkyl substances (PFAS) are chemically and thermally stable, hydrophobic, lipophobic compounds used in stain repellants and water and oil surfactants, and associated with immunosuppression and peroxisome proliferator activity. Perfluoro-<i>n</i>-decanoic acid (PFDA, (CF₃(CF₂)₈COOH), a fluorinated straight chain fatty acid compound, is reported to induce thymic atrophy and reversible bone marrow hypocellularity in rodent models. The objective of this study was to assess potential immunotoxicity of PFDA, due to its structural similarity to other immunosuppressive PFASs. Female Harlan Sprague–Dawley rats were exposed to 0–2.0 mg PFDA/kg by oral gavage daily for 28 d. Female B₆C₃F₁/N mice were exposed once/week to 0–5.0 mg PFDA/kg by gavage for 4 weeks. Animals were evaluated for effects on immune cell populations in spleen and bone marrow, and innate, humoral-, and cell-mediated immunity. Mice were also evaluated for resistance to <i>Influenza</i> virus. Treatment-related hepatocyte necrosis and hepatomegaly were observed in rats treated with 0.5 mg PFDA/kg/d. In mice, hepatomegaly (26–89%) was observed following exposure to ≥0.625 mg PFDA/kg/week, while splenic atrophy (20%) was observed at 5.0 mg PFDA/kg/week. At 5.0 mg PFDA/kg/week, total spleen cells, and Ig + and NK + cells were decreased (17.6–27%). At ≥ 1.25 mg PFDA/kg/week the numbers of splenic CD3⁺, CD4⁺, CD8⁺, and Mac3⁺ cells were decreased (10.5–39%). No changes were observed in leukocyte subpopulations in PFDA-exposed rats. Phagocytosis by fixed-tissue macrophages was decreased in liver (specific activity, 24–39%) at ≥0.25 mg PFDA/kg/d in rats. PFDA-induced effects on humoral- and cell-mediated immunity, host resistance, and bone marrow progenitor cells were limited. These data suggest that exposure to PFDA may induce adverse effects in rat liver in a manner consistent with the PFAS class, and may also alter the balance of immune cell populations in lymphoid tissues in mice.</p