Experimental cryptococcosis in guinea pigs

A guinea pig model was used to evaluate immune response to Cryptococcus neoformans. This model shared characteristics with cryptococcosis in humans. Twenty five guinea pigs injected intraperitoneally with 10(7) viable C. neoformans cells developed disseminated disease. Forty days after infection all guinea pigs were killed and autopsy performed. C. neoformans growth in the lungs, brains, livers and spleen of the infected animals were determined. Furthermore, the immune response was characterized by moderate degree of delayed-type hypersensitivity and humoral response. In some organs was observed neutrophil and lymphocyte infiltration with presence of cryptococci cells. The infiltration observed in the organs was probably a consequence of an immune reaction.     

Normal electrocardiogram in guinea pig

For establishing normal mean values of the parameters of the electrocardiographic curve and their standard deviations 50 male guinea pigs were studied. The directions of temporary vectors of atrial (AP) and ventricular (AQRS) depolarization times, and ventricular repolarization time (AT) were determined, and the position of the heart was evaluated. In all animals limb leads I, II, III, aVR, aVL, aVF were used, and in 38 animals additionally the precordial leads V1, V2, V3, V4, V5, V6 were applied. The investigations were done by a non-invasive method with a specially designed plate making possible immobilization of the animals in supine position under general anaesthesia with urethane. In 10% of the animals abnormalities were detected in the ECG curve and these guinea pigs were eliminated from further analysis. The investigations showed that, after consideration given to the differences in the ECG curves in relation to man, guinea pigs might be used for preclinical cardiological studies.     

Pathogenesis of cytomegalovirus-associated labyrinthitis in a guinea pig model

Cytomegalovirus infects fetuses through the placenta, resulting in various congenital disorders in newborns, including hearing loss. We developed a monoclonal antibody to guinea pig cytomegalovirus (GPCMV) that was available for immunohistochemistry, and investigated the expression of the GPCMV antigen in animal models of direct and congenital infections. Injection of GPCMV, directly to the inner ear, increased the sound pressure level and resulted in labyrinthitis with severe inflammation. Immunohistochemistry detected GPCMV-infected cells mainly in the scala tympani, scala vestibule and spinal ganglion, but rarely in the cochlear duct. Injection of GPCMV to 5-week pregnant guinea pigs resulted in severe labyrinthitis in fetuses. Immunohistochemistry detected GPCMV-infected cells in the perilymph area and spinal ganglion, but not in the endolymph area, including hair cells. These data suggest that the virus spreads via the perilymph and neural routes in the inner ear of both models of direct and congenital infections.