Nívea Lopes de Souza

Hematological and biochemical profiles of rats (Rattus norvegicus) kept under microenvironmental ventilation system

Em estudos anteriores, demonstrou-se que ratos mantidos em sistema de Ventilacao Microambiental (VMA) apresentaram parâmetros de produtividade e padrao sanitario melhores do que aqueles mantidos em sistema de Ventilacao Geral Diluidora (VGD). Outra etapa dos experimentos foi determinar os parâmetros fisiologicos destes animais. O presente estudo foi realizado para avaliar os perfis hematologico e bioquimico de ratos mantidos sob o sistema de VMA. Para tanto, foram realizados dois experimentos diferentes, com ratos mantidos em VMA, quais sejam: Experimento 1 (E1), no qual foi avaliado o desempenho reprodutivo de machos e femeas, sob duas faixas de velocidade de ar (FV1 - de 0,03 a 0,26 m/s, e FV2 - de 0,27 a 0,80 m/s); Experimento 2 (E2), no qual foram avaliados diferentes intervalos de troca de cama (3, 5, 7 e 9 dias), para ratos machos mantidos a uma velocidade de ar constante de 0,5 m/s. Os valores do hemograma e de parâmetros bioquimicos destes animais foram comparados com os valores encontrados em ratos mantidos sob VGD. Os resultados obtidos demonstraram diferencas estatisticas em alguns dos parâmetros observados, tanto entre os sistemas VGD e VMA, como entre os diferentes grupos de VMA. Contudo, os valores encontrados em todos os parâmetros avaliados encontram-se dentro de faixas de variacao normal para a especie estudada, como e descrito na literatura. Isto indica que o emprego do sistema de VMA nao induz alteracoes relevantes nos parâmetros fisiologicos estudados.

Effects of an individually ventilated cage system on the airway integrity of rats (Rattus norvegicus) in a laboratory in Brazil

The ventilation method used in the management of laboratory rats is important in maintaining their health. Rats kept under general diluting ventilation (GDV) are exposed to high levels of pollutants present in the environment (dust, airborne bacteria, etc.) or those pollutants produced by animal metabolism and excretion inside the boxes (e.g. ammonia and carbon dioxide). These pollutants may contribute to respiratory pathologies. An alternative experimental ventilation system for laboratory animal housing using intracage ventilation technology (individually ventilated cage system, IVC) was developed. In this system, ammonia levels decreased and rats exhibited better reproductive performance and a lower incidence of pneumonia than rats maintained under GDV. Using two different levels of air speed (0.03–0.26 m/s: IVC1; 0.27–0.80 m/s: IVC2), the effects of IVC were compared with GDV (control) in Wistar rats in terms of respiratory mucus properties, on the nasal epithelium (as measured by quantitative morphometry) and on the lungs (as determined by the cellular composition obtained by bronchoalveolar lavage). Mucus of the respiratory system was evaluated using the following techniques: rheology (viscoelasticity) by microrheometer, in vitro mucociliary transportability (frog palate) and contact angle (an indicator of adhesivity). Also, membrane transepithelial potential difference was measured as a biomarker of airway integrity. After bedding was changed, ammonia concentrations inside the cages on day 3 were significantly higher for GDV than for IVC1 and IVC2. The potential-difference values for IVC1, IVC2 and GDV in the epiglottis and in the trachea also showed differences. Although some significant differences were observed across the three groups in counts of some cell types, the intragroup results were highly variable among individuals and inconsistent between sexes. No significant differences in the other parameters were found across groups. These results establish that rats maintained under GDV in relatively unregulated conditions are exposed to factors that can lead to deleterious effects on the ciliated epithelium of the airways, and that these effects can be prevented by the use of IVC.

Breeding system can affect the offspring sex ratio in Syrian hamsters

Nulliparous female Syrian hamsters were used to investigate the effect of two different breeding systems on the fertility of the female Syrian hamster. We hypothesized that females submitted to a harem system (HS) would deliver smaller and more female-biased litters than in a monogamic system. Ten female and 10 adult male hamsters housed individually (G1) were kept in a monogamic temporary breeding system, while 10 females and five males (G2) were submitted to HS with two females and a male permanently housed together since female weaning. Females from G1 and G2 delivered, respectively, 47 and 50 litters, and produced 364 (G1) and 383 (G2) weaned pups without any difference in litter size, mean weight of weaned pups and body condition of dams. Interparturition intervals were shorter and the percentage of male pups per litter was higher in the HS possibly as a result of different endocrine conditions provided by different breeding systems. Besides providing evidence that housing conditions can influence the sex of hamster offspring, our findings suggest a mechanism for the non-random distribution of male and female pups in hamster litters.

Influência da temperatura e do fluxo de ar sobre o consumo de ração e ganho de peso em ratos Wistar (Rattus norvegicus) mantidos em sistema microambiental

Ratos wistar foram mantidos individualmente, em gaiolas metabolicas de arame, sem abrigo, em sistema microambiental, sob fluxo direto de ar a 0,6 m/s, nas temperaturas de 22o, 24o, 26o, 28o e 30o C. O consumo de racao e o ganho de peso foram comparados do final de 5 dias (ANOVA; Tukey-Kramer). No total, sete grupos de 10 animais cada foram comparados. Para a faixa de 22oC foram utilizados tres grupos, sendo um grupo experimental e dois grupos controles. Um deles foi mantido em condicoes ambientais semelhantes a bioterios convencionais sob ventilacao geral diluidora (VGD) - C1. O outro grupo controle (C2) foi mantido no interior do equipamento de ventilacao microambiental, porem, sem o direcionamento de ar, simulando a VGD. Os resultados obtidos demonstram claramente que animais mantidos sob ventilacao microambiental direta a 26o, 28o e 30oC apresentam o mesmo ganho de massa corporea que animais do grupo C1. Os grupos de animais mantidos a 22o e 24oC, apresentaram menor ganho de massa corporea quando comparados a C1 (p<0,001 e p<0,01 respectivamente). O ganho de peso de todos os grupos experimentais, quando comparado ao C2, apresenta diferencas estatisticas, exceto o mantido a 30oC que apresentou indice de ganho de peso equivalente a C2. O consumo de racao de todos os grupos se manteve constante. Somente o grupo E5 apresentou uma reducao no consumo de racao quando comparado aos grupos C1 e C2 (p<0,05 para as duas comparacoes).