The legacy of the F344 rat as a cancer bioassay model (a retrospective summary of three common F344 rat neoplasms)

<p>The Fischer 344 (F344) rat was used by the National Toxicology Program (NTP) for over 5 decades for toxicity and carcinogenicity studies. However, in 2006, the NTP decided to switch to a different rat stock due largely to high background control incidences of Leydig cell tumors (LCTs) and mononuclear cell leukemia (MNCL), also known as large granular lymphocytic (LGL) leukemia. In the current review, we aim (1) to provide a summary of NTP bioassays with treatment-associated effects involving MNCL and LCTs in addition to male F344-specific tunica vaginalis mesothelioma (TVM); (2) to describe important pathobiological differences between these F344 rat tumor responses and similar target tissue-tumor response in humans; and (3) to present the NTP reasons for switching away from the F344 rat. We show that due to the highly variable background incidence of F344 MNCL, more reliance on historical control data than is usual for most tumor responses is warranted to evaluate potential effect of any chemical treatment in this rat strain. The high spontaneous incidence of LCTs in the testes of male F344 rats has made this tumor endpoint of little practical use in identifying potential testicular carcinogenic responses. TVM responses in F344 rats have a biological plausible relationship to LCTs unlike TVM in humans. Given their high spontaneous background incidence and species-specific biology, we contend that MNCL and LCT, along with TVM responses, in F344 rat carcinogenicity studies are inappropriate tumor types for human health risk assessment and lack relevance in predicting human carcinogenicity.</p

Comparative cardiopulmonary toxicity of exhausts from soy-based biofuels and diesel in healthy and hypertensive rats

<p>Increased use of renewable energy sources raise concerns about health effects of new emissions. We analyzed relative cardiopulmonary health effects of exhausts from (1) 100% soy biofuel (B100), (2) 20% soy biofuel + 80% low sulfur petroleum diesel (B20), and (3) 100% petroleum diesel (B0) in rats. Normotensive Wistar–Kyoto (WKY) and spontaneously hypertensive rats were exposed to these three exhausts at 0, 50, 150 and 500 μg/m³, 4 h/day for 2 days or 4 weeks (5 days/week). In addition, WKY rats were exposed for 1 day and responses were analyzed 0 h, 1 day or 4 days later for time-course assessment. Hematological parameters, <i>in vitro</i> platelet aggregation, bronchoalveolar lavage fluid (BALF) markers of pulmonary injury and inflammation, <i>ex vivo</i> aortic ring constriction, heart and aorta mRNA markers of vasoconstriction, thrombosis and atherogenesis were analyzed. The presence of pigmented macrophages in the lung alveoli was clearly evident with all three exhausts without apparent pathology. Overall, exposure to all three exhausts produced only modest effects in most endpoints analyzed in both strains. BALF γ-glutamyl transferase (GGT) activity was the most consistent marker and was increased in both strains, primarily with B0 (B0 > B100 > B20). This increase was associated with only modest increases in BALF neutrophils. Small and very acute increases occurred in aorta mRNA markers of vasoconstriction and thrombosis with B100 but not B0 in WKY rats. Our comparative evaluations show modest cardiovascular and pulmonary effects at low concentrations of all exhausts: B0 causing more pulmonary injury and B100 more acute vascular effects. BALF GGT activity could serve as a sensitive biomarker of inhaled pollutants.</p

Expression of Flag-Pol β in MEFs and tissues from Pol β Tg mice.

<p>(A) Specificity of mouse and human qRT-PCR analysis for Pol β expression: RNA was isolated from WT and Pol β KO MEFs and MEFs expressing the Flag-Pol β transgene, as described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0006493#s4" target="_blank">Methods</a> section. The relative level of expression of both the mouse (open bars) and human (filled bars) Pol β mRNA (normalized to mouse β-actin) was determined using mouse and human specific Taqman assays. Expression across samples was normalized to the expression level in the WT/Flag-Pol β MEF sample. (B) Expression of the human Pol β transgene in mouse tissues and tumors: RNA was isolated from the sample indicated in the plot, as described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0006493#s4" target="_blank">Methods</a> section. The relative level of expression of human Pol β mRNA (open bars; normalized to mouse β-actin) was determined using human specific Taqman assays as in panel A. Expression across samples was normalized to the expression level in the Tg Brain sample.</p

Incidence of non-neoplastic & neoplastic proliferative lesions in DNA polymerase β Tg mice.

*<p>Frequency defined as the number of animals with the lesion divided by the number of animals with the tissue examined histopathologically, multiplied by 100. Data derived from 15 males and 21 females except where noted. No neoplastic changes were detected in gallbladder, parathyroid, thymus, ileum, cecum, colon, pancreas, brain, eye, urinary bladder, testis, epididymis, prostate, seminal vesicle, oviduct, vagina, and mammary gland.</p

Incidence of macroscopic findings observed in DNA polymerase β Tg mice.

*<p>Frequency defined as the number of animals with the lesion divided by the number of animals with the tissue examined macroscopically, multiplied by 100.</p

Decreased expression of Pol β in human esophageal adenocarcinoma.

<p>(A) Photomicrograph of sections of esophageal adenocarcinoma and esophageal squamous mucosa stained for Pol β expression by immunohistochemistry. Top images reflect magnification×40 and the inserts depict magnification×100. (B) Bar graph representing relative expression level of Pol β in various tumors (stippled, open bars) and pathologically normal (grey bars) epithelial tissues. Immunoreactivity Score is the average of 5 different tumor samples each evaluated in two independent analyses.</p

Representative photomicrographs (H & E stain) of duodenal changes in Pol β Tg mice.

<p>(A) Normal duodenum. Note normal Brunner's glands (arrows) (magnification×20). (B) Diffuse hyperplasia of Brunner's glands (small arrows) and duodenal crypt epithelium (large arrow). Note markedly increased mucosal thickness due to glandular hyperplasia, compared to panel A (magnification×20). (C) Cystic dilatation of mucosal crypts and Brunner's glands with displacement of cystic glands into the tunica muscularis (magnification×200). (D) Focal proliferation of dysplastic glands in a mouse diagnosed with duodenal adenoma (magnification×400).</p

Incidence of non-neoplastic lesions observed in DNA polymerase β Tg mice.

*<p>Frequency defined as the number of animals with the lesion divided by the number of animals with the tissue examined histopathologically, multiplied by 100. Abnormal non-neoplastic changes were not detected in thyroid, parathyroid, thymus, stomach, jejunum, ileum, cecum, colon and pituitary.</p

sj-tif-5-tpx-10.1177_01926233231182115 – Supplemental material for Results of the European Society of Toxicologic Pathology Survey on the Use of Artificial Intelligence in Toxicologic Pathology

Supplemental material, sj-tif-5-tpx-10.1177_01926233231182115 for Results of the European Society of Toxicologic Pathology Survey on the Use of Artificial Intelligence in Toxicologic Pathology by Xavier Palazzi, Erio Barale-Thomas, Bhupinder Bawa, Jonathan Carter, Kyathanahalli Janardhan, Heike Marxfeld, Abraham Nyska, Chandrassegar Saravanan, Dirk Schaudien, Vanessa L. Schumacher, Robert H. Spaet, Simone Tangermann, Oliver C Turner and Enrico Vezzali in Toxicologic Pathology</p

sj-tif-29-tpx-10.1177_01926233231182115 – Supplemental material for Results of the European Society of Toxicologic Pathology Survey on the Use of Artificial Intelligence in Toxicologic Pathology

Supplemental material, sj-tif-29-tpx-10.1177_01926233231182115 for Results of the European Society of Toxicologic Pathology Survey on the Use of Artificial Intelligence in Toxicologic Pathology by Xavier Palazzi, Erio Barale-Thomas, Bhupinder Bawa, Jonathan Carter, Kyathanahalli Janardhan, Heike Marxfeld, Abraham Nyska, Chandrassegar Saravanan, Dirk Schaudien, Vanessa L. Schumacher, Robert H. Spaet, Simone Tangermann, Oliver C Turner and Enrico Vezzali in Toxicologic Pathology</p