Odontogenic fibroma in Sprague-Dawley rats: a report of 2 cases.

Two cases of odontogenic fibroma occurring in aged Sprague-Dawley rats are described. Both neoplasms were associated with a maxillary incisor and had identical histomorphological features. They were composed of solid proliferations of primitive, dental pulp-like mesenchyme separated by areas of collagenization. Small strands and islands of mainly undifferentiated odontogenic epithelium immunostaining for keratins were scattered throughout both tumours. As a further characteristic, the lesions contained small foci of mineralization which were either cementum-like or resembled dysplastic dentin. The odontogenic fibroma represents a further type of odontogenic tumour in rats, which due to its typical histomorphology, can easily be differentiated from other odontogenic tumours such as ameloblastic odontoma or ameloblastoma.

Experimental genital tract infection with Chlamydia psittaci (GPIC agent) in male rats.

The course of experimental chlamydial infection of the male genital tract was studied. Inoculation of the Chlamydia psittaci agent of guinea pig inclusion conjunctivitis (GPIC agent) into the vas deferens of rats resulted in chlamydial infection of the epididymis, testis and the prostate gland. The inflammatory response was most prominent at 14 days after infection. Chlamydiae were recovered from the epididymides and the prostate glands for up to 90 and 60 days post inoculation, respectively. Histopathological changes associated with chlamydial infection of the epididymis or prostate gland were characterized by intratubular and interstitial purulent inflammation. Chlamydia-specific IgM- and IgG-antibodies were found in sera of nearly all infected animals. Results of this study indicate that this animal model may be useful to study the pathogenesis, immune responses and sequelae of chlamydial infections of the male genital tract.