Theiler's murine encephalomyelitis virus in nonbarrier rat colonies.

Theiler's murine encephalomyelitis virus (TMEV), a member of the genus Cardiovirus, is an enteric pathogen of mice that causes acute encephalomyelitis followed by persistent central nervous system infection with chronic inflammation and demyelination after intracerebral inoculation. Although TMEV is a mouse pathogen, antibodies against TMEV strain GDVII have been detected in conventional rat colonies. Natural infection of rats by Cardiovirus has not yet been described. The purpose of this study was to demonstrate TMEV infection of rat colonies by using serologic assays, reverse transcription-polymerase chain reaction (RT-PCR) analysis, and clinical characterization. Indirect immunofluorescence assay of rat serum samples demonstrated antibodies against TMEV-GDVII in 86.3% of samples analyzed, and 77.2% of the antibody-positive samples had neutralizing antibodies. To determine whether rats can be infected experimentally with TMEV-GDVII, specific pathogen-free newborn mice and rats were inoculated intracerebrally with intestinal suspensions from seropositive rats. Both species showed the typical clinical signs of TMEV infection in mice, which is characterized by flaccid hindlimb paralysis and tremor. RT-PCR in brain tissue of experimentally infected animals detected RNA sequences corresponding to the 5' noncoding region of Cardiovirus known as the 'internal ribosome entry site.' These results suggest that rats can be naturally infected with TMEV and related Cardiovirus. Therefore, continued health monitoring for TMEV infection should be included in rat colonies mainly because these animals are used for various experimental purposes.

Respostas inflamatorias em ratos wistar submetidos a atividade fisica / Inflamatory response in wistar rats submitted to the physical activity

Os principais objetivos deste estudo foram investigar os efeitos da atividade fisica sobre os leucocitos circulantes e sobre os leucocitos presentes no exsudato resultante da reacao inflamatoria induzida por implante de esponja de PVC em ratos Wistar.Os animais foram distribuidos em sedentarios (S) e treinados(T).O treinamneto consistiu em natacao diaria,com carga de 5 por cento,1 hora por dia 5 dias por semana durante 30 dias.Aos 10 dias do inicio do experimeto,sofreram implante subcutaneo de esponja de PVC,na regiao dorsal.Apos 20 dias de implante,foram sacrificados e retirados amostras de sangue para glicemia e musculo soleo para dosagem de glocogenio e proteinas totais.Aliquotas de sangue e de exsudato da esponja implantada foram coletadas para contagem total e diferencial de leucocitos.O treinamento fisico aumentou as reservas de glicogenio(T=0,205+ ou -0,02;S=0,143+ ou -0,04,pmenor0,01)e proteinas musculares(T=4,85+ou-0,48;S=3,74+ ou -0,41,pmenor0,01)mas reduziu a porcentagem de eosinofilos circulantes(T=8,5+ou-2,3;S=12,9+ou-3,0 por cento,p menor 0,0007) e de monocitos no exsudato do implante (T=10,1+ ou -3,9;S=15,3+ ou-4,5 por cento,,p>0,02)Nao foram encontrados diferencas na glicemia,leucocitos totais,neutrofilos e linfocitos.Esses dados sugerem que a atividade fisica regular realizada simultaneamente ao processo de inflamacao,preserva as reservas musculares,mas atenua a resposta inflamatoria,podendo interfirir na recuperacao tecidual

Effect of time of exposure to rat coronavirus and Mycoplasma pulmonis on respiratory tract lesions in the Wistar rat.

The effects of time of exposure on the progression of pulmonary lesions in rats inoculated with Mycoplasma pulmonis and the rat coronavirus, sialodacryoadenitis virus (SDAV) were studied, using six groups of 18 SPF Wistar rats (n = 108). Rats were inoculated intranasally as follows: Group 1, sterile medium only; Group 2, sterile medium followed one week later by 150 TCID50 SDAV; Group 3, sterile medium followed by 10(5.7) colony forming units of M. pulmonis; Group 4, SDAV followed one week later by M. pulmonis; Group 5, M. pulmonis followed one week later by SDAV; Group 6, M. pulmonis followed two weeks later by SDAV. Six rats from each group were euthanized at one, two and three weeks after the final inoculation. In a separate experiment, six additional animals were inoculated in each of groups 3, 5 and 6 (n = 18) and were sampled at five weeks after they had received M. pulmonis. Bronchoalveolar lavage and quantitative lung mycoplasma cultures were conducted on two-thirds of the rats. Histopathological examination and scoring of lesion severity were performed on all animals. Based on the prevalence and extent of histopathological lesions, bronchoalveolar lavage cell numbers, neutrophil differential cell counts and the isolation of M. pulmonis, the most severe disease occurred in the groups that received both agents. There was no significant difference in lesion severity between the groups receiving both agents other than in those examined during the acute stages of SDAV infection. Based on these results, it is evident that SDAV enhances lower respiratory tract disease in Wistar rats whether exposure occurs at one week prior to or at various intervals following M. pulmonis infections.