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: IVC(1); 0.27-0.80 m/s: IVC(2)), 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 IVC(1) and IVC(2). The potential-difference values for IVC(1), IVC(2) 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.

Evaluation of reproductive indices in rats (Rattus norvegicus) housed under an intracage ventilation system.

A cabinet with an intracage ventilation system (ICV) was developed, and rats (Rattus norvegicus) were exposed to five air-speed levels (ICV 1, 0.03 to 0.12 m/s; ICV 2, 0.13 to 0.18 m/s; ICV 3, 0.19 to 0.33 m/s; ICV 4, 0.34 to 0.51 m/s, and ICV 5, 0.52 to 0.80 m/s) to evaluate optimal rates for ventilation and to assess whether reproductive performance differed at the various air speeds. Our results showed that rats housed under ICV conditions tolerate a continuous air flow into the cage. This condition did not impair the reproductive performance in any of the groups. In fact, air-speed levels ranging from 0.19 to 0.51 m/s (ICV3 and ICV4 conditions) led to a greater number of and more uniform litters with decreased mortality rates compared with those of the control group.

Role of lymphatic drainage on the development of Calmette-Guérin bacillus-induced granulomas in the hamster.

The influence of lymphatic drainage on Calmette-Guérin bacillus (BCG)-induced granulomas was investigated by comparing the time course of granuloma formation in two sites: the hamster footpad and the check pouch, an area deprived of lymphatic vessels. Typical epithelioid granulomas developed in both sites. Whereas in the footpad the size of granulomas increased and the volume of the lesion persisted, in the pouch the lesion decreased in volume. The inoculation of BCG into the footpad of animal with granulomas in the pouch, reactivated the pouch lesions. T lymphocytes were detected by an immunocytochemical technique at the edge of these lesions. Inoculation of the bacteria into the pouch induces suppressive mechanisms which hold down the volume of the lesions induced in the footpad. The cutaneous purified protein derivative (PPD) test, positive in animals inoculated in the footpad, was always negative in animals with granulomas in the pouch. The number of bacteria per microscopic field in pouch granulomas increased from 10 to 1,000 after PPD injection. Evidence that PPD has a direct effect on pouch granuloma cells is given.

[Behavior of the arterial wall of non-selected rats, old and young, subjected to potentially atherogenic dietary factors]. / Comportamento da parede arterial de ratos não selecionados, idosos e jovens, frente a fatores dietéticos potencialmente aterogênicos.

PURPOSE: To evaluate the arterial wall behaviour in old and young rats submitted to a ration containing atherogenic factors (cholesterol, dehydrocolic acid and vitamin D2). MATERIAL AND METHODS: 20 old male albino rats (approximately one year old) were grouped as follows: group 1, five control animals; group 2, five animals receiving a ration with cholesterol plus dehydrocolic acid; group 3, ten rats receiving an equivalent ration added to vitamin D2. Equivalent groups (4, 5 and 6), with an identical number, but younger animals (2 months old), were compared to the former. Groups 4, 5 and 6 were treated in the same way of groups 1, 2 and 3. After two months, all the groups were bled for cholesterol (CT), triglycerides and HDL dosage. Afterwards, they were sacrificed and the histopathological analysis of the aorta, heart, and lungs executed by the hematoxylin-eosin, Verhoeff and acetic orcein methods. RESULTS: Serum cholesterol (average) was 52 mg/dl in group 1 and 56.6 in group 4. Groups 3 and 6 presented about two times the serum cholesterol level observed in control groups and groups 2 and 5 three times control groups. When the old and young animals CT averages were compared, no significant differences were observed. However, when the influences of the atherogenic factors were analyzed, significant differences appeared; the simultaneous administration of dehydrocolic acid and cholesterol tripled the value of CT, and the use of vitamin D2, applied with other factors, raised CT only to the double. No atherosclerotic lesions were obtained but only Monckberg atherosclerosis lesions, sclerosis type (calcification of the medium stratum) in those animals who received vitamin D2. CONCLUSION: The arterial wall of non-selected old and young rats behaved equally when submitted to a ration containing cholesterol, dehydrocolic acid and vitamin D2. They developed calcified lesions of atherosclerotic type, in spite of a prolonged hypercholesterolemia.