Laboratory Animals

Trials of different drug combinations for use in rabbits, guinea-pigs, rats, hamsters and mice are described in detail and experience over a 5-year period evaluated. Combinations of fentanyl citrate, fluanisone and diazepam provided exceptionally good anaesthesia in each species and were considered superior to other injectable agents.

Questionnaires on research activities, mortality rates observed in various age groups, extent of examination of dead hamsters, and natural disease conditions and their relative importance were returned by 24 of 43 organisations surveyed in the United States. The average preweaning mortality rate due to all causes was 11·9%. Comparative data from 6 organisations that raised 87880 hamsters in the calendar year 1971 indicated that 97·5% of total preweaning mortality was due to cannibalism. 13·7% of all animals died before use for experiments. 'Wet-tail' was the most frequently recognized disease (71%), and it was also listed as the most important. Pneumonia was recognized by 43% of the respondents and was most commonly listed as second in importance. A selective review of the literature is presented on those diseases recognized by more than one survey respondent.

Pasteurella pneumotropica was isolated from cases of clinical conjunctivitis in mice. No isolates were obtained from normal mice.

Upper jejunum and terminal ileum were examined in specified-pathogen-free (SPF), conventional and conventional after SPF rearing (ex-SPF) rats. The effect of 2 different diets on the last 2 groups was examined.

Ex-SPF rats had taller villi and deeper crypts than SPF rats, but similar crypt to villus ratios and cell production rates. Ex-SPF rats had similar crypt depth and jejunal villus height to conventional rats on the same diet, but taller ileal villi and a lower cell production rate. Even after 6-8 weeks in a conventional environment, ex-SPF rat intestine was still not identical with conventional rat intestine.

Diet had a significant effect on mucosal architecture, and a smaller effect on cell production rate.

It is concluded that diet, microbiological status of colony of origin, and environment after weaning, can all affect mucosal architecture and epithelial cell production, and should be properly controlled in experimental studies.

Ampicillin was included (25 mg/litre) in the drinking water supplied to growing rats over periods of 2, 3, 4, 5, 6, 7 or 8 weeks. 32 rats were used in each experimental period, half being given the antibiotic and half being left as controls. The antibiotic increased the liveweight gain in each period, the results being significant after the 2- and 4-week feeding periods. Significant decreases were observed in the average percentage weights of the spleens of the rats given the antibiotic at the end of all the feeding periods except one. The few other significant changes in the percentage weights of other organs were, with one exception, noted at or before the end of the 4th week.

The disease was characterized by loss of hair, initially occurring at the tip of the nose and spreading throughout the body. Lesions appeared as circular, scaley alopecia with occasional scarring. Although spread of the infection in the colony was random, the most severe infection occurred in an inbred line with light coat colour. The unusually high temperature and humidity, and the open type of outdoor management, appear to have contributed to the high incidence and severity of infection. Electron microscopic observation indicated that the organism multiplied in the keratin layer of the skin. The hyphae as well as chlamydospores were readily demonstrable by electron microscopy.

Both skin and kidney allografts were at least partially protected from rejection by daily treatment with 1·0 mg/kg of prednisolone acetate. Azathioprine, cyclophosphamide, antilymphocytic serum, and attempts to produce a tolerant state with prior grafting of specific donor antigen, all failed to alter the course of rejection.

In contrast to the findings in newly caught baboons in Africa, the leading cause of death in captivity in America was a pneumonia and enteritis complex. Bacterial species such as Proteus morgani, Proteus mirabilis, Clostridium sp., Pseudomonas paracolon, pathogenic Escherichia coli and cocci have been isolated in association with a pneumoenteric syndrome of 35 newborn baboons, including neonates. The majority of these animals died with pulmonary factors such as anoxia and pneumonia.