The level of natural killer (NK) activity was found to vary considerably among several mouse strains. In vivo and in vitro, interferon (IFN) and IFN inducers have been shown to augment mouse NK activity. C3H/He mice showed high NK activity, DDD/1 and A/J mice low NK activity, and C57BL/6, BALB/c and DBA/2 mice intermediate NK activity after injection with polyinosinic polycytidylic acid (poly I. C.) . The same NK activity correlation was obserbed in nontreated mice, but the NK activities were lower compared with the poly I. C. - injected mice. Moreover, the DDD/1 and A/J mice showed almost no augmentation of NK activity on injection with poly I. C. In vivo, C3H/He, BALB/c and C57BL/6 mice injected with IFN showed augmented NK activity, but DDD/1 mice showed no such reaction. In vitro, C3H/He, BALB/c and C57BL/6 mouse spleen cells treated with IFN also showed augmented NK activity, but DDD/1 mouse spleen cells showed almost none. Fl hybrids between high (C3H/He) and low (DDD/1) NK-activity strains showed high NK activity. Thus, activity is dominant over low activity. The segregation of (DDD/1x C3H/He) Flx DDD/1 back-cross mice suggested that the strain differences in NK activity are under polygenic control.

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Degenerative osteoarthrosis was observed in the thoracic vertebrae in specific pathogen-free Sprague-Dawley rats at the ages of eight and 19 weeks. Histological changes seen in the lesions were degenerated matrix intermixed with collagen fibers, erosion or ulceration, and formation of cysts in the articular cartilage, and degeneration and necrosis in the subchondral bone.

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We carried out a histological examination of the implantation traces in delivered rats. 1. The implantation traces could be identified more than 500 days after delivery on the mesometrial side as black and brown spots. 2. The implantation traces were recognizable as a cicatrix remaining in the parametrium, mesometrial triangle, which was formed by repair of injury caused by placental desquamation. In this area, metrial gland cells which were laid down through pregnancy were recognized for about two months after delivery. 3. The implantation traces consisted of cicatrix tissue associated with collagen production and hemosiderin. It was possible to distinguish old and new traces by the size of the siderophile cells and by the degree of hemosiderin present. It was also possible to discriminate new traces as yellowish-brown areas, covered with a yellowish-white mass of degenerated metrial gland, in cleared uteri stained with 2% NaOH solution. 4. Siderophile cells on the implantation traces were derived from giant cells which persisted around the peripheral region of the placental desquamation site, and these giant cells were considered to be identifiable with metrial gland cells. 5. It was considered that formation of the cicatrix is essentially the same in abortion, stillbirth and normal delivery. However, it was found that the implantation traces had different histological appearances depending on the degree of injury to the endometrium and myometrium and time of placental desquamation. 6. The iron content of the implantation traces corresponded quantitatively with the hemosiderin observed in the histological investigations. The iron content decreased rapidly up to 21 days after delivery, decreasing gradually thereafter. The iron in the implantion traces could, however, be analyzed quantitatively by atomic absorption spectroscopy until day 365 after delivery.

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In order to establish the genetic relatedness of the inbred mouse strains kept in Nara, genetic marker patterns were determined in conjunction with a study on endogenous mammary tumor viral genes in these strains. Isoenzyme patterns combined with patterns of other genetic markers, show that the unrelatedness between various inbred strains of the dd stock is as high or even higher as between strains of known different origin and geneology. Based on endogenous viral gene patterns the dd stock derived mice can be subdivided into three group, (1) DDD, DDN, DDO, (2) KF and (3) DD/ Tbr. The DD/Tbr and its foster-nursed substrain (DD/Tbrf) have the lowest number of endogenous viral genes, i. e. two, while the other strains carry 4-6 such genes.
The SLN and SHN strains, derived from a Swiss stock, have a similar pattern of viral genes different that of all other strains studied, also strains of Swiss origin from other sources, such as the NFS and the GR.

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The effects of body weight and population density on the number of ova shed were examined in the superovulation-treated adult rat in order to clarify the variation of the number of ova shed. Twelve-week-old female rats, weighing 182-277 g, were injected with 40 i. u. of PMSG on metestrus, with sodium pentobarbital on diestrus (“critical period”), and with 40 i. u, of hCG, on estrus. Twenty hours after the injection, the number of ova shed in an ampulla was observeld. There was no correlation between body weight and the number of ova shed (r=0.004) . The rats were kept in at three, six or nine rats per cage (260×380×180mm) from weaning at 30 days old to 12 weeks, with superovulation treatment. There was no significant difference in the number of ova shed among the various population densities.

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An enzyme-linked immunosorbent assay system combined with microcomputer data analysis was established as a quantitative assay method of immunoglobulins. The assay system was applied to measure IgG and IgM levels of anti-microbe antibodies in animals, especially mouse and rat. And now the measurement of IgG and IgM levels (ng/ml) of anti-Sendai virus (HVJ) antibodies in naturally infected mice is available. The assay system could improve serodiagnosis in the specificity and sensitivity and in the rapid treatment of many serum samples. The operation of this system was performed by a microcomputer, FM 8 connected Titertek Multiskan MC. The limited sensitivity of this assay for IgG and IgM was 10 ng/ml and 30 ng/ml, respectively. Ninety-one of serum samples were positive for IgG and/or IgM (45 samples for IgG and IgM, 44 samples for IgG, 2 samples for IgM) to Sendai virus in the tested 279 mouse sera, and serum titers were ranged from 1: 10 to 1: 12, 800 in the IgG, and from 1: 20 to 1: 160 in the IgM. In these titers, serum IgG and IgM amounts were estimated to be 0.1 to 154 μg/ml and 0.5 to 4.8 μg/ml, respectively. Relationshipe of serum titers and antibody amounts were almost consisted, being judged like that approximately 10 μg/ml is 1: 400, 30 μg/ml is 1: 1, 600 in IgG, and 2.4 μg/ml is 1: 80, 4 μg/ml is 1: 160 in IgM.

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The filter efficiency of seven kinds of commercial face mask for particles and airborne bacteria was tested in the wash room of a laboratory animal facility. The filter efficiency of the masks was 19 to 50%, as measured by the weight of particles with diameters below 10μm, 22 to 71% for particles of the 0.3μm level, 47 to 906 for the 1μm level, and 90 to 99.606 for the 5 1μm level. The filter efficiency for airborne bacteria was 35 to 81%. Among thes even masks tested, glasswool surgery masks, three-sheet synthetic fiber masks with and without charcoal, and 28-sheet gauze masks with glass filter showed generally high efficiency, and single-sheet synthetic fiber masks, 18-sheet of gauze masks and gas masks showed low efficiency.

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Histopatholoical examinations on nephlocalcinosis of the Fischer 344 (F344) rats were carried out. As the results of comparison on its appearance among F344, Wistar and SD strains of rats, F344 female rats showed the most severe nephrocalcinosis.
Nephrocalcinosis developed between 4 weeks and 8 weeks and was likely to keep its appearance through 108 weeks of the survival period of the rats. Histologically, mineral deposit was always observed at cortico-medullary junction. It seemed to locate at the outer portion of the basement membrane of the tubular epithelium, adjacent to the capillary wall in the connective tissue. Four weeks after ovariectomy at 4 weeks of age, the rats showed a decrease in degree of nephrocalcinosis. In contrary, the rats treated with estorone following ovariectomy revealed an increase in degree of nephrocalcinosis. It was suggested that the oestrogen-type sex hormone appeared to give a role in nephlocalcinosis

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The population movements of thyroid follicles in young and aged mice subjected to acute fasting and refeeding were analyzed by a morphometric method. After fasting for three days, the size distribution of thyroid follicles from young mice did not change, while the follicles from aged mice became significantly bigger than in the control group. Subsequent refeeding for four days caused a decrement in follicular sizes in both young and aged thyroid. The activity of follicular epithelia was decreased by fasting, but accelerated by refeeding. The equation describing the relationship between epithelial cell numbers and follicle diameters from a young control mouse agreed well with the theoretical one, especially in small follicles. However, the equation for an aged mouse differed from the theoretical one. This suggests that the older the mouse, the greater the deviation of the constituent factor, e. g, that of follicle size or cell number in thyroid. The extent of deviation would be one of the characteristics of aging in mul-ticellular organisms.

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A statistical survey was performed in 1982 to ascertain the incidence of various diseases, especially trauma, in the cynomolgus monkey colony at Tsukuba Primate Center for Medical Science. In total, 1, 029 cases of disease, occurred of which 866, 89 and 74 were surgical, internals and reproductive disease cases, respectively (Table 1) . Among the 866 surgical cases, trauma (746 cases) was most often observed (Table 2) . It was shown that trauma occurred most frequently during the group feeding of juvenile monkeys (Table 3) . Analysis of the factors influencing the incidence of trauma during group feeding was carried out. As a result, it was revealed that the number of days after beginning group feeding and the age at which group feeding was begun had marked influences on the incidence of trauma (Figs. 1 and 2) . However, there was no significant relationship between the incidence of trauma and the number of animals per group or the sex-ratio in a group (Tables 4 and 5) . From the present survey results, a prospective rearing system should be established to reduce the incidence of trauma in the cynomolgus breeding and rearing colony.

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A joint study was undertaken in three testing facilities to evaluate cumulative background data of Himalayan rabbits. All litters were derived from control does. The conception rate was high (84.0-95.1%) but the average numbers of corpora lutea (7.9-8.7), implantation sites (6.5-7.5) and viable fetuses (5.8-6.9) were somewhat lower than that of most other strains of rabbit. Altogether 90 malfomed fetuses (1.12 %) and 425 fetuses with variations (5.270) occurred among 8, 060 virable fetuses.

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Blood samples were collected from 1000 or more apparently healthy cynomolgus monkeys of different ages. All the monkeys had been bred and reared under uniform environmental conditions at the Tsukuba Primate Center for Medical Science, NIH, Japan. Biochemical and hematological data were determined with these samples. The calculated arithmetic means and standard deviations were listed for each item of measurement performed (Tables 3, 4 and 5) . The correlation between the obtained value and the age was analyzed using a statistical significance level of 0.10 (Table 6) . It was revealed that hemoglobin concentration, mean corpuscular volume, alubuminglobulin ratio and triglyceride concentration increased with age, whereas red blood cell count and serum alkaline phosphatase activity decreased with age in both sexes.

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A system of predicting the time of parturition in the chimpanzee was developed to assure care of the newborn as soon as possible after delivery. To quantify activity, the number of times that a parturient chimpanzee crossed a sensor marker of a TV monitor was recorded by a videosensor on the market for crime prevention.The amount of activity increased remarkably just prior to parturition. A system using a personal pocket alarm (“beeper”), which rang automatically when the number of crossings by the chimpanzee exceeded a selected level within a certain period of time, was tested. In the present study, the threshold for sounding the alarm was set at 50 crossings within 10minutes. As a result, the pocket alarm began to ring at about 40 minutes before parturition. This enabled us to be present at parturition and to tend to a newborn abandoned by its mother in one case. The present system could be useful to predict the time of parturition in the chimpanzee.

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Interstitial pneumonia was observed in 12 male guinea pigs. Grossly, the lung showed clear white areas in the parenchyma. Histological changes in the lung consisted of interstitial pneumonia and formation of granulomas accompanied by bacterial clumps. It was thought that this disorder might have occurred as a bacterial infection.

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Own experiences with the identification of mice and rats using ear tags, ear punching, toe clipping (for newborns only) and ear tattooing are given and compared with methods presented in literature. By far, ear tattooing by the newly developed pincers is the most suitable method for marking adult rodents for life. Tattooing is easy to apply, easy to read and not harmful to the animals. For newborn pups on day 4 p. p., the s. c, injection of India ink into the palm of paw is recommended.

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Cardiac puncture through the anterior thoracic aperture, which was originally reported by Frankeberg, was improved. The improved method involved the use of a restraining board instead of manual holding. A mouse anesthetized with ether was fixed in a dorsal position on the restraining board, and then a needle of 26G×1/2 was inserted through the skin just in front of the anterior thoracic aperture, keeping the syringe parallel to the long axis of the animal. A blood volume of 0.6-0.9 ml could be obtained even by an inexperienced collector, and the blood collection was usually completed within 10-20 s. The potential for repeated blood collection of 0.4-0.6 ml was facilitated by use of the present method at intervals of 7 days or more.

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The circadian rhythm of air-borne bacteria and dust particles in a mice breeding room was studied at 1-hour intervals on the first, third and fifth day after accommodation of the animals. The numbers of air-borne bacteria in the room increased day by day after accommodation, and showed a circadian rhythm which went down at about noon and rose with three peaks at about 20: 00, 1: 00 and 8: 00. The numbers of dust particles tended to decrease from day to day, and they showed almost the same circadian rhythm as the air-borne bacteria. Correlations between air-borne bacteria and dust particles were not significant for each particle level on the first day, but were significant for all the particle levels of 0. 3, 1, 2, and 5μm at the third day, and were also significant at particles levels of 0.5μm or more on the fifth day.

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