A female mouse spontaneously exhibiting polyuria and glucosuria accompanied by rapid weight loss was found in one of two sublines derived from the CTS mice. Eight mating pairs were made using its offspring and selection was performed for both spontaneous diabetes and reproductive ability. After six generations of the selective breeding the diabetic (nod) and the control (non) lines were established.
A marked sex difference was observed in the incidence of diabetic symptoms in the nod mouse. The cumulative incidence of the onset up to 30 weeks of age was 80% in females and less than 20% in males. The onset of diabetes was abrupt in both sexes, and spontaneous remission was not observed. However, daily administration of insulin induced an increase of body weight and a prolongation of life span.
Diabetic symptoms are biochemically characterized by polyuria, polydipsia, hyperglycemia, glucosuria and hypercholesteremia. Pathological examination revealed a high frequency of lymphocyte infiltration around and/or into the Langerhans' islet. It was observed even at the prediabetic stage over five weeks of both sexes. The number and size of the islets were markedly reduced in the overt diabetic mice.
Although the mechanism of the pathogenesis is not clear yet, the nod mouse may be a useful animal model for investigating the human juvenile type diabetes.

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It has already been reported that the zona pellucida in the rodentia plays an important role in the mechanism of preventing polyspermatozoan fertilization. The implantation of the blastocyst is known to begin after the zona pellucida is taken off from the surface. The authors carried out a scanning electron microscopical observation on temporal changes in the zona pellucida after mating. After fertilization, a clear spongy structure having a double or triple construction was formed on the zonal surface. The structure was distinguishable until 2.5 days after mating, when it developed into the 2-cell stage. After that, it became indistinct and thinned increasingly as the ovum grew further. When the blastocyst was formed completely 4.5 days after mating, the zonal surface was hatched. It is assumed that the existence of active zonal reaction may physiologically convert almost all the zona pellucida as a fine spongy structure. In the present research observation was made on the implantation process and the implantation chamber with a scanning electron microscope. On the early morning of 5.5 days after mating, the blastocyst tended to adhere to the implantation chamber which had been formed previously in the endometrium by the secretion of mucoidal substances. After that, implantation proceeded. On the evening of 5.5 days after mating, however the implantation of blastocyst onto the endometrium progressed with interdigitation by microvilli.

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Rat ova in the early stage after fertilization were subjected to the double fixation with glutaraldehyde and osmium combined with critical point drying. Then they were observed by the scanning electron microscope. After that, they were soaked in QY-1 and embedded in epon. Ultrathin sections were prepared for them by means of MT-1 and observed by transmission electron microscopy.
These sections were potentially available for scanning and transmission electron microscopy to observe peripheral changes and inner development of the ovum with the lapse of time in the early stage after fertilization.

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An analbuminemic rat colony (NAR, Nagase Analbuminemia Rat) was established from Sprague-Dawley rats. The Analbuminemia was inherited as an autosomal recessive trait. The rate of growth or propagation of the mutant rats was not different from those of normal rats.
Biochemically the mutant was characterized by an extraordinarily low serum albumin and hyperlipidemia.
Total protein level of the serum in the mutant rat was similar to that of control Sprague-Dawley rats and globulin increased compensatorily.
Serum cholesterol concentration was inversely correlated with a decrease in albumin, its correlation coefficient was -0.92.
NAR may serve as a model of human familial analbuminemia. It should be also useful in elucidating the functional roles of albumin.

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Osteogenesis in the penial bone was observed in male rat: immature stromal cells of mesenchymal origin appeared in the penis on the 21st day of fetal age and developed to form mature bony structure with the bonemarrow on or before day 7 after birth; the bone was 1.41±0.12 mm in length. Neonatal castration caused maldevelopment of the genial bone, while prepuberal treatment with testosterone propionate stimulated the bony growth in castrated immature rat. These results suggest that the stromal cells in penile part of newborn male rats have already been destinated to develop into os penis by fetal exposure to androgen and they do not require androgens for further differentiation but for the bony growth after birth.

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Age-related kidney lesions were studied in male and female inbred strain Fischer-344/Yit rats of 4, 9, 25, 52 (male rats only) and 71 weeks of age. The lesions that represent probably early stage of chronic nephropathy were observed in 9-week-old rats, and also hyaline casts characteristic of chronic nephropathy occurred for the first time in 52-week-old male rats.
In males, degeneration of convoluted tubular epithelial cells, occurrence of hyaline droplets and eosinophilic bodies in proximal convoluted tubular epithelinm were already observed at 9 weeks. At 25 weeks, these lesions were most pronounced, with yellowish-brown epithelial cells in the proximal convoluted tubulus, and erythrocyte-like structure were observed occasionally in the lumen, in the epithelial cells or in the Bowman's spaces. Some of the eosinophilic bodies were positive with hemoglobin staining. In glomerulus, increase of mesangial cells and thickening of basement membrane were recognized. At 52 weeks, glomerular lesions were attended with mild fibrosis, and the hyaline casts were found in dilated tubulus of corticomedullary area. Hemosiderin deposits and appearance of brown pigment were seen in the proximal convoluted tubular epithelium. At 71 weeks, glomerular lesions, hyaline casts, hemosiderin deposits and increase of interstitial connective tissue became more severe, and also slight infiltration of lymphocytes were observed in the interstitial tissue.
Above-mentioned lesions found in male animals were also seen in females but the changes were very mild in females with the exception of the occurrence of brown pigment. In females, calcified casts were found in tubulus of corticomedullary area at 71 weeks.

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Reproductive ability of germfree and conventional female ICR mice was examined. Litter size and number of fetuses of germfree ICR mice kept in Facility A were smaller than those of Jcl^®: ICR mice. No difference was seen in oestrous cycle, pregnant rate, gestation period, weaning rate and number of corpora lutea between germfree and conventional mice. The small litter size of germfree mice seemed to be associated with early embryonic death before implantation. On the other hand, litter size of ex-germfree mice did not increase after conventionalization in Facility B.

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In order to determine heritability of accessory nipples, variations in the number of nipples were investigated in 13-week old female Wistar-Imamichi rats, maintained as a closed colony in the Institute for Animal Reproduction. Most of the females examined (93.32%) had six pairs of nipples; three in the pectoral and three in the abdomino-inguinal regions. Whereas, 229 out of 3606 rats had one accessory nipple each, 9 animals had 2 accessories, and 3 females were deficient of the pectoral nipple. Most of the accessory nipples were found either in the caudal and cranial regions of the third pectoral nipples or in the regions between the second and third abdomino-inguinal nipples. The frequencies for appearance of the accessory nipples were higher in the pectoral regions than those in the abdomino-inguinal ones, and also in the left side than in the right (p<0.01), respectively. In 208 out of 791 litters examined, 177 litters had only one sister-mate with accessory nipple, 29 litters had 2 sister-mates with accessories, and 2 litters had 3 sister-mates with accessories, respectively. The localization of accessory nipples of the sister mates within the litter was similar in most of the cases. Heritability of the appearance of accessory nipples was estimated to be 0.8074 by using the formula described by Falconer.

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The blood samples from the cephalic vein and the external jugular vein were compared hematologically and serum biochemically in 22 beagle dogs. No significant differences (p<0.05) between these two venous blood were observed in most of the items determined except MCV (mean corpuscular volume) and serum glucose level. The time required to collect 12 ml of blood was less than 30 seconds from the external jugular vein while two to eight minutes from the cephalic vein. From the result of this study the external jugular vein is shown more suitable region for collecting much volume of blood samples than the cephalic vein in dogs.

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A total of 248 strains of Escherichia coli, 132 of Staplylococcus epidermidis, 137 of Streptococcus faecalis and 89 of Str. faecium were collected from feces of 40 mice and 36 rats of 8 colonies in 1978, and drug resistance were examined by an agar dieution method using 23 antibiotics. The results indicated a positive relation between use of antibiotics and appearance of multiple drug resistant organisms.

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[in Japanese]

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