Remarkable individual variations were seen in experimentally induced atherosclerosis in male Japanese white rabbits from a closed colony of JW/CSK fed on 1 % cholesterol diet. Correlation analyses revealed that the severity of gross atheromatous lesions was paralleled with aortic cholesterol content and that individual variations in both of these parameters were mainly dependent upon individual variations in the changes of serum cholesterol levels. A genetic effect was suggested as a factor for these variations. Thus, inter-litter differences in aortic cholesterol contents and serum cholesterol levels were highly significant (p<0.01) and it was estimated that inter-litter variances constituted 760 of the inter-individual variances in both parameters. However, an attempt to isolate a pedigree resistant to cholesterol feeding by consanguinity analysis and subsequent mating did not result in success.

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Deta are presented on lifetime reproductive performance (number of fertile matings, litters and mice born and weaned) and lifespan of C3Hf/HeMsNrs reared under specific pathogen free conditions. Thirty pairs of mice were mated at the age of 64±5 days and maintained under a single pair mating system until either of pair died. No mice died before termination of their reproductive life, therefore, the data of reproductive performance ara based on 30 monogamous pairs. Twenty four pairs out of 30 pairs could produce at least the 6th litters. In relation to the age of females, 82 % of a total of 210 litters and 87 % of a total of 1, 226 offsprings were produced until the age of 250 days. The females gave a maximum litter size, 6.9 at the age between 101 and 150 days. Sex ratio of offsprings did not vary with the age of the females at littes and the parity. It is, however, noteworthy that, when the sex ratio is calculated on mating pair basis it significantly differs from expected ratio of one to one in 5 pairs out of 30 pairs. Among mating pairs, a total number of litters per pair ranged from 3 to 10 litters and a mean total number of offsprings was 41 mice. The ages of females at the last litter born ranged from 128 to 352 days (mean 261 days) . The mean lifespan for females and males were 737 and 731 days, respectively. It was not found that there is any correlation between lifespan and lifetime reproductive performance.

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The nematodes were found at a high percentage (66.7%) in the lung tissue by histopathological examination of beagle dogs imported from U. S. A. to Japan as laboratory animals. Although these infected dogs did not display abnormal respiratory signs, postmortem examination revealed the presence of adults and larvae of the lungworms in the alveolar spaces, and in many cases terminal and respiratory bronchioles with slight inflammatory reaction by adult worms and marked gronulomatous inflammation by larva. Degenerated larvae were also found in the liver and lymph nodes evoking a focal granulomatous reaction. Accordingly the dogs infected with these worms are unsuitable as laboratory animals, and the importations of these infected animals may result in prevalence of filaroidiasis in our country. These lungworms are readily distinguished fromFilaroides osleri (Osler, 1877) by the location in lung and by much smaller body size and spicules. These lungworms are most similar toF. milksiWhitlock, 1956, but can be distinguished by smaller size and slightly stouter spicuter spicules. They are identified asF. hirthiGeorgi and Anderson, 1975

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[in Japanese]

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