P04: Histopathological investigation of Wilson slices from developmental toxicity studies.

In developmental toxicity studies, the investigation of soft tissues from rat fetuses is routinely performed using Wilson''s free hand razor cross sectioning technique. The unstained slices are investigated with a stereomicroscope for developmental variations or malformations. However, for some findings the correlation with tissue structures or their categorization may remain equivocal based on this technique. Histopathology may then be used for further clarification since the slices are prefixed in a conventional fixative (e.g. Davidson''s solution) and thus give good technical results when paraffin histotechnique is applied. Examples of the usefulness of the combination of Wilson slices and histopathology are presented. A cyst-like structure at the mouth floor proved to be part of the oral cavity and was hence no abnormal finding. A case of enlarged laryngeal lumen could be traced back by histology to a differing section plane. In the eyes, retinal folding as a developmental anomaly could be distinguished from artificial retinal detachment and folding. These examples show that in developmental toxicity studies, histopathology may be valuable for the differentiation between technical artifacts and spontaneous or induced changes in soft tissues. [Copyright &y& Elsevier]