An attempt was made to eradicate respiratory diseases developed in about 1, 000 mice of 19 congenic inbred strains which were maintained in a mouse breeding room. The contagious diseases with respiratory signs were found to be caused by mixed infections withMycoplasma pulmonisand Sendai virus. The eradication of the diseases was mainly made by sanitary improvement in care of the mice such as intensive disinfection, culling some diseased mice and so on, instead of destroying all colonies. As the result, mycoplasma infection decreased gradually, resulting in a complete eradication about one and half years later and remarkable increases in litter size and weaning rate of mice were obtained. Sendai virus infection failed to be eradicated.

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Establishing of an efficient system for the judgement of an optimal mating time is an important prerequisite for the successful development of a large scale breeding of macaques as labolatory animals. In general, an optimal mating time has been judged on the basis of individual records of menstruation. The length of the previous menstrual cycle has usualy been used for the prediction of the next cycle length. In the present study, the lengths of 240 menstrual cycles of 60 Cynomolgus monkeys of our breeding colony were statistically analysed. The mean and the standard deviation of those cycle-lengths were 29.4 and 4.3 days, respectively. Correlationship between the length of a menstrual cycle and the length of its previous cycle was statistically significant (p<0.05) . However, practically the correlation was not meaningful because the correlation coefficient (r) was very small even if the length of the second one of two successive cycles (r=0.26) or the average length of three successive cycles (r=0.36) is selected as a reference length. In other words, a cycle length can not be predicted on the basis of the length of the previous menstrual cycle. However, a marked increase of serum follicle stimulating hormone (FSH) concentration was observed from 8 to 15 days after menstruation. In 60 per cent of the animals observed, FSH increased 10 to 11 days after menstruation. Ovulation was observed one or two days later than the day of FSH increase. Therefore, the optimal mating time is judged to be between 11 and 14 days after menstruation regardless of the menstrual cycle length.

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Microtus species are very useful as experimental small animals with herbivorous characteristics. In this report, to approach establishment of the use of Japanese field voles (M. montebelli) and Hungarian voles (M. arvalis) as experimental animals, the biological characteristics, breeding methods and reproductive performance of these animal species were comparatively investigated. The number of chromosomes of M. arvalis is 2n=46, differing from those of M. montebelli, 2n=30. The breeding and reproduction of the Microtus species were relatively easily accomplished in the laboratory, by giving high fiber-containing rations. These animals prove to be polyestrous and showed postpartum estrous on the day of parturition. In the breeding by the continuous mating of the same pairs, there was little or no delay in implantation due to lactation, especially in M. arvalis resulting in continuous birth at intervals of 20 to 21 days. On examination of vaginal smears, Japanese field voles (M. montebelli) did not show any definite pattern whereas 23 out of 30 voles from Hungary (M. arvalis) examined showed 6- to 18-day cycles. There were remarkable differences between the Japanese voles and the Hungarian voles, both biologically and reproductively.

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In August, 1979, one female and three male wild volcano rabbits (Romerolagus diazi) were obtained and attempts have been made to rear and breed them in the laboratory. Mating was attempted from the 3rd month after the volcano rabbits were obtained and the first birth (two offspring) occurred after about one year. Thereafter, the same female gave birth three times and a total of 10 offspring have been obtained. Four females and three males could be weaned. The period of gestation was estimated as 34-48 days. The body weights at birth were 25-27 g for females and 32 g for males, and after three weeks, the weights had increased to 80-130g for females and 95-128g for males. Weaning was possible at 3 weeks of age. Volcano rabbits are small with an adult body weight of 400-600g and they are also gentle animals. They should prove valuable if they can be established as laboratory animals in the future.

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Corynebacterium kutscheri invasiveness of the tissues of the gastrointestinal tract in mice was investigated by the fluorescent antibody technique. The invasion was clearly recognized in 3-week-old mice infected intragastrically along with gastric mucin and a subcutaneous dose of cortisone ; 10⁷ organisms caused a notable invasion of the gastric and duodenal tissues. Furthermore, marked bacterial invasion of the large intestine appeared in mice challenged perorally with 7×10⁷ organisms.

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The net protein ratio of protein of six kinds of revised stock diets for rats and mice were compared with purified whole-egg protein and milk casein in six weeks old male Sprague-Dawley strain rats for a ten day experimental period, and they were given ten percent crude protein diets. The ratios of protein of the revised stock diets were lower than those of purified whole-egg protein, but were almost the same or superior to those of milk casein.

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A linkage study of the analbuminemia (alb) with some coat color loci (a, b, c, h) has been carried out by crossing the analbuminemic random-bred mutant NAR strain with the abh tester strain of rats, the Agouti-Irish inbred ACI strain and the Agouti-Nonhooded inbred IS strain. The analbuminemia (alb) locus is not linked to a, b, and c loci but linked to hooded locus from F2 and backcross progeny of the F1 hybrids of abh x NAR, ACI x NAR and IS x NAR to NAR. Recombination value between alb and h was 16.4±2.3 per cent from the data of F2 and backcross progeny of (ACI x NAR) F1 and (IS × NAR) F1 to NAR. This is the third locus on the sixth linkage group of the rat.

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Effects of gaseous ammonia on Mycoplasma pulmonis infection in mice and rats were investigated with special reference to growth of the organism in the respiratory organs and formation of pneumonic lesions. Multiplication of the organism was enhanced in both mice and rats exposed to 50 and 100 ppm ammonia, but the growth enhancement of the organism was not evident in the animals exposed to 20 ppm ammonia. The enhanced multiplication of the organism was especially remarkable in the lung of mice, showing a difference of about 104 organisms/g lung tissue between the exposed and unexposed mice. However, no formation of pneumonic lesions was observed in exposed and unexposed groups of both species of animals.

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[in Japanese]

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