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Focal granulomatous inflammation developed in the livers of five 10-week-old male
Sprague-Dawley rats. The characteristic features of this lesion were the
presence of foreign body multinucleated giant cells engulfing calcium deposits
and site-specific development in a fissure formed in a sub-lobation in the left
lobe or interlobar fissure of the medial lobe of the liver. To clarify the
pathogenesis of this lesion, rat livers showing abnormal sub-lobation or lobar
atrophy, rat livers in an acute dermal toxicity study and guinea pig livers in a
skin sensitization test were also examined histologically. Consequently, the
present lesion was considered to be a reactive change against calcium that was
dystrophically deposited in the area of hepatocellular necrosis due to delayed
circulatory disturbance caused by external pressure or extension force.
Granulomatous lesions like in the present cases should be differentiated from
those caused by evident exogenous pathogens such as chemicals or
microorganisms.
-Any devices used in toxicity studies should be validated. In the present study, the physiological conditions of rats implanted with a new micro-infusion pump, iPRECIO ® , were examined to evaluate its availability for toxicity studies. Five or six animals/group of 6-week-old male CD(SD) rats received either sham surgery or the implantation surgery for either the iPRECIO ® (iP) pump or a standard osmotic infusion pump (OSM) under the back skin. This was followed by 4 weeks (experiment I) or 13 weeks (experiment II) of observation. During the observation period, the iP-and OSM-animals received a continuous infusion of 2.0 or 2.5 μL/hr of saline via the external jugular vein. In experiment I, standard hematologic and blood chemical parameters used in toxicity studies were measured at weeks 1, 2, and 4. The iP-animals showed no abnormal changes in any parameters at any point when compared with the OSM-/SHAM-animals. In experiment II (only iP-and SHAM-animals), necropsy and histopathological examination were performed at weeks 1, 2, 4, and 13. The histopathological examination revealed foreign material-induced inflammatory changes in the dorsal subcutaneous tissue (implantation site) of the iP-animals, including the infiltration of polymorphonuclear or mononuclear cells, edema, granulation and fibrous capsule formation. However, the abnormalities were limited to the implantation site. These results suggest that the implantation of iPRECIO ® exerted no significant impact on the physiological condition of the rats. Therefore, we concluded that iPRECIO ® is applicable for toxicity studies.
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