During an experiment of shaking in El mice, a strain which was less susceptible to convulsion was found out. In this strain (ASK), the mortality to anaphylactic shock and susceptibility to audiogenic seizure were compared with five other strains of mice. Six strains of mice (ASK, El, IDT, JCC-ICR, dd, C57BL/6J) were sensitized by two subcutaneous injections with 2 mg/head of crystalline egg albumin at five and six weeks of age, and then challenged by the intravenons injection of 0, 125, 1, 8, 64, 512 and 4096μg/head at seven weeks of age. In both sexes of ASK strain, the mortality was the maximum (75-95%) after the challenge of 8-4096μg egg albumin. The mortality of the female El and IDT and the both sexes of JCL-ICR strains was middle (55-70%) after the challenge with 64 pg egg albumin, while that of other strains (dd and C57BL/6J) was very low (0-20%) . The susceptibility of 3-weeks-old mice of ASK, El, IDT, JCL-ICR and dd strains was low (1.9-19.0%), whereas mice of DBA/2 strain showed a very high susceptibility (80%) to 110 phons.

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In the course of study on serous cholesterol of rabbit, we found a male mutant with remarkably high choleoterol level (HLR) . The characteristics of this mutant could be described as follows : (1) Serous chemical determination for the mutant's serum revealed extremely high levels of total lipids, and β-lipoprotein as total cholesterol, being 3011 mg/dl, 10.6 units and 447 mg/dl respectively. High cholesterol level continued these two years during observation, though some fluctuation has been observed. (2) Such hypercholesterolemia was heritable. Determinative gene for hypercholesterolemia seemed to be recessive and not sex-linked, because, while F₁generation did not show so high cholesterolemia, one female rabbit among twelve off-springs born by full-sib mating showed persisting hypercholesterolemia similar to orginal HLR. (3) HLR may serve as a model of human familial hyperlipemia Type II or III according to the classification by Fredrickson et al.

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Mycoplasmas were isolated from 35 (16 %) of 215 specimens collected from 20 crabeating monkeys (Macaca irus), 9 green monkeys (Cercopithecus aethiops) and from 9 common squirrel monkeys (Saimiri sciurea) . All these animals had been imported from South-East Asia, Africa and South America being apparently healthy. A total of 38 large and 20 small colony-mycoplasma strains were isolated from the nasal and oral cavity, urethra, vagina and rectal feces. The large colony-mycoplasmas could be differentiated into 5 groups on the basis of their biological and serological characteristcs. Six and 7 of them were identified asM. orale2 andM. salivarium, respectively. Twenty strains were clearly distinguished not only fromM. orale2 andM. salivarium, but also from such arginase positive species asM. orale1, M. fermentans, M. hominis, M. arthritidis, M. maculosumandM. gateae. These were divided into 2 groups, comprising 9 and 11 strains, respectively, by growth inhibition as well as various biological tests. The remaining 5 strains were not identified serologically. The small colony-mycoplasmas were found to be urease-positive and appeared to be T-mycoplasmas, while not examined serologically.

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Latent infection withCorynebaterium kutscheriin mice and its provocation by cortisone were studied with a rifampicin-resistant strain of the organism. Mice having been infected perorally began to excrete the organisms in feces within 6 hours, and most of them were found to be carrying the organisms in the intestine, especially in the cecum even 90 days after infection. In such state of latency, however, no organisms were detcted in other main organs, and neither visible lesions nor serum agglutinin was detectable. The latent infection with excretion of the organisms in feces after peroral infection was shown to become overt and fatal by cortisone treatment made even 90 days after infection. In infected mice excreting no organisms in feces and having bites on their skin, the wounds became severe ulcers after cortisone treatment resulting in septicemia.

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We determined that leaner gene (la) is located in the linkage group XVIII and closely linked toEs-1, which is known to be located closely to tottering gene (tg) . Double heterozygote (la/tg) produced by mating betweenlaheterozygote andtgheterozygote showed an intermediate syndrome between those seen in tottering (tg/tg) and leaner (la/la) mice. Both leaner and totterig mice showed neuromuscular disorders, but their clinical and pathological characteristics were different. Leaner mice were found to represent a socalled cerebellar mutant having the reduced size of cerebellum and severe cytoarchitectonic abnormalities with focal losses of Purkinje and granular layer cells. Tottering was, however, another mutation having epileptif orm seizures, and it was characterized pathologically by cellular losses and shrinkage as well as vesiculations of cytoplasmic membranous structures in the cerebellum. The double heterozygote was shown to have both pathologic characteristics seen in each homozygote, and also showed shrinkage of Purkinje cells and vesiculaton of the endoplasmic reticulum and Golgi apparatus. These clinical and pathological findings supported the genetic data suggesting thatlaandtgconstitute an allele.

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Efficiency of sterilization was shown to vary according to the type of autoclave, and this would be taken into consideration for preparing sterilized diet and water for laboratory animals. It seems necessary to sterilize diet and water for 60 and 150 minutes, respectively, at 120°C using the autoclave in the Laboratory Animal Center of the Nippon Veterinary and Zootechnical Collge.

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