Laboratory Animals

Bacillus pilifarmis antigens were demonstrated in smear preparations from infected mouse livers by direct immunofluorescence technique. Mouse serum antibodies against B. pilifarmis were demonstrated by indirect immunofluorescence technique. The test was employed quantitatively both on sera from experimentally infected mice and on sera from clinically healthy mice from colonies infected with B. pilifarmis, and could be used for the quantitative demonstration of antibodies in sera from a stock of rabbits with Tyzzer's disease. It was found very useful for the detection of subclinical infection.

Mice from a colony with subclinical Tyzzer's disease were treated with prednisolone in order to activate a Bacillus piliformis infection. From the livers of these mice the organism was isolated and serially passaged in embryonated eggs. It resisted heating at 75°C for 20 minutes and was still infective after storage at -80°C for 24 days, but not for 52 days or more. Infectivity was maintained for more than a year by storing infectious liver tissue at -190°C. B. piliformis was also isolated from the liver of a mouse with naturally-occurring Tyzzer's disease and maintained for more than 300 passages. Mice inoculated with different egg passages developed fatal Tyzzer's disease and B. piliformis was reisolated from their livers.

Testicular development to 9 months of age has been studied. Seminiferous tubule diameter increased in a linear manner between 13 and 65 days of age, and there was a steep increase in testicular weight with age. At about 9 months the animals weighed 400-500 g and total testicular weight was about 10 g. This relatively large testicular size was correlated with high sperm density in the semen.

Spermatogenesis commenced at about 21-25 days of age, when the first spermatids were found. Spermatozoa appeared in a small proportion of seminiferous tubules by 31-35 days of age, and were seen in the epididymides of an animal of 31 and another of 34 days. Epididymal spermatozoa were consistently present in large numbers after 60 days and this correlated with the increased frequency of mature seminiferous tubules.

Leydig cell size increased rapidly from 13 to about 60 days, then remained constant. Inferences have been drawn from this and the study of spermatogenesis about the level of testosterone secretion.

The results indicate that the male cuis is almost fully grown and sexually mature by about 90 days of age.

Sera from 37 rabbits were assayed for antibodies against Encephalitozoon cuniculi (Nosema cuniculi) by the india-ink immunoreaction and the indirect fluorescent antibody tests: all animals seropositive to the former were also positive to the latter test. 27 of the rabbits were also tested for skin hypersensitivity and then autopsied. Animals positive to the skin test were also positive to the serological tests. At autopsy 18 of 22 rabbits positive in the immunological tests showed lesions typical of encephalitozoonosis.

Sera from 200 rabbits originating from 6 institutes were assayed by the india-ink test: seropositive rabbits were found from all institutes (9·1 to 81·9% incidence), with serum titres ranging from 1:125 to 1:5000.

The india-ink test appears to be a rapid and convenient method for diagnosis of encephalitozoonosis in rabbits.

In 4-week-old chicks that had been maintained on 3 different diets, caecal weights were lower in germ-free than in conventional birds eating practical but not semipurified diets. There were no consistent differences in total sodium, potassium and chloride ions in the contents of the small intestine. In germ-free chicks the caecal wall muscle appeared lacking in tone and there was a lower concentration of chloride ions in the contents, but there was no caecal enlargement comparable to that in germ-free rodents.

The haemoglobin types of 27 inbred strains of mice have been determined. Besides the common types, Hbb-s and Hbb-p, 2 strains were found with Hbb-p. Affinity between strains with the Hbb-p type and asiatic mice seems likely. The influence of storage on the polymerisation of Hbb-d and Hbb-p, the possibility of distinguishing between homo- and heterozygote Hbb types, and the possible existence of a 4th haemoglobin type, are discussed.

A hitherto unrecognised lipoprotein liver-cell inclusion is described in elderly mice. The significance of these inclusions is unknown.

Disorganization of muscle structures such as fragmentation of myofilaments with a loss of contrast in the Z bands, swelling of mitochondria and glycogenic infiltration, was seen in ascorbic acid deficient guinea-pigs. Vacuolar degeneration of external and internal endothelial cell membranes with accompanying dystrophic changes of the surrounding muscle and lack of collagen formation were consistent findings. Chondroblasts showed a marked dissolution of the matrix vesicle and a lack of hyaline droplets.

The historical and present role of lower (non-mammalian) vertebrates in biomedical research is discussed. Examples are given of disease problems and experimental studies. It is suggested that lower vertebrates may prove of increasing value in this field in the future.

A 2 year old pet male hamster died with spontaneously occurring ocular melanoma. Metastasis occurred in the lung.

An apparatus easily manufactured in the laboratory is described for the continuous infusion of substances into the stomach of the unanaesthetised rat.

A pen to hold individual miniature pigs during long-term radiation exposure studies has been designed and used. Wooden construction results in low cost and minimizes radiation scatter problems associated with higher density materials. An automatic water system is provided.