The incidence and histopathology of the spontaneous tumors in over 2-year-old ddY strain mice, an outbred widely used in Japan, are described. The incidences of the total spontaneous tumors were 47.5% in males and 66.7% in females in actual numbers. These, however, could be corrected to 64.4% and 80.0%, respectively, when the accidental death are omitted from the results. The incidences of the pulmonary tumors were very high; 39.2% in males and 26.7% in females of the total spontaneous tumors, respectively. Other tumors which showed high incidences were, lymphoid tumors; 17.5% in males and 19.2% in females and mammary tumors; 26.7% exclusively in females. However, no strain-specific tumors were observed which are common in inbred strains such as leukemia in AKR or mammary tumors in C3H strains, partly suggesting broad genetic variation of the strains. Histopathological examination revealed prevailing types of the tumors to be papillary adenoma of pulmonary tumors, simple adenoma of mammary tumors and poorly differentiated lymphosarcoma of lymphatic tissues.

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A total of 153 female virgin Sic: SD rats aged 13 to 24 months were sacrificed for observation of various spontaneous changes in their pituitary glands. Macroscopic changes observed were swelling, congestion, cysts, and grayish white nodules. The incidence of swelling occuring without marked change decreased with age. Usually the swelling was accompanied by congestion in aged animals. Slight to moderate congestion appeared constantly in animals between the ages of 15 to 24 months, while severe congestion (hematoma) increased with age. The cysts and grayish white nodules rarely appeared. Changes observed under the microscope were diffuse proliferation, nodular hyperplasia and tumors (adenoma and adenocarcinoma) of chromophobe cells, cysts in the anterior lobe and hyperplastic pars intermedia. The incidence of diffuse proliferation decreased with age but that of nodular hyperplasia increased in rats over 21 months of age. Both changes seemed to be transitional to tumors. The tumors increased with age. Microscopically, pituitary tumors were found in 6% of macroscopically normal glands as well as in all of the glands with hematoma. All the rats with pituitary tumors had hyperplastic mammary glands, associated mostly with lactation. This suggests that spontaneous pituitary tumors have a hormonal effect on mammary glands.

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The biochemical components, enzymes, and other items from the sera and plasma of normal male and female Göttingen miniature pigs from 3 to 20 months of age were investigated. The data were compared with the normal biochemical values of rhesus monkeys, beagle dogs, and JCL: SD rats. The following characteristics were noted. 1. Activities of serum enzymes were higher and their normal ranges wider than in the other experimental animal sera. 2. Of lipid components measured, total cholesterol and phospholipid showed strikingly lower values than in the monkey and the dog. 3. The serum urea nitrogen levels were lower than in the other experimental animal sera. 4. Serum creatinine and potassium were present at relatively high levels, with wide normal ranges. 5. There was a tendency with advancing age toward lower alkaline phosphatase and higher total protein and creatinine. 6. Leucine aminopeptidase was higher while total cholesterol and phospholipid were lower, in the male than in the female. 7. The electrophoretic patterns of serum protein and lipoprotein differed markedly among the species.

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Basic experiments of methane fermentation of livestock excreta have been reported by many investigators, yet there has been no report of experiments of methane fermentation of experimental animal feces. We considered that it would be feasible to gasiby experimental animal feces by methane fermentation. In this report, methane gas fermentation of rat feces is studied. The results are summaried as follows: 1. Methane fermentation of rat feces yielded, under the conditions described, 220-4231 of gas per kg of organic matter. 2. Decomposition ratio of BOD removal volume in organic matter was 50-60% when the fermentation condition was optimum. 3. The volume of gas from BOD removal volume in organic matter was 500-600ml/g. 4. Methane gas contents in the gas generated from the feces ranged from about 55-60%. 5. COD removal ratio was above 80%, and BOD removal ratio above 90%. From these data, the authors conclude that under the optimum conditions, described sufficient methane gas can be obtained from rat feces by methane fermentation.

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The postnatal development of the heart was morphometrically followed in growing golden hamsters to obtain basic information on the development of cardiovascular system of the animal. Correlations among the body weight, heart weight, heart width and length, atrial weight, right ventricular weight and left ventricular (inclusive of ventricular septum) weight, and thicknesses of right and left ventricular free walls were examined. A linear correlation was observed consistently between width and length and between body weight and atrial weight throughout the observation period. On the other hand, the results indicated that in the correlations seen between thicknesses of right and left ventricular free walls, body weight and heart weight, body weight and ventricular weight, and right and left ventricular weights, an alteration point existed at 40 to 50 days of age, which coincided with the period of achieving sexual maturity. The data have shown that the various morphometric elements of the heart correlated linearly with the body weight during the early life till 40-50 days of age, and after wards only those concerned with the left ventricular chamber preponderated as the body weight increased.

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Ishibashi rats, a mutant strain with congental spinal malformation discovered by Ishibashi in 1968, are generally regarded as an animal model for a human inborn error of spinal malformation. Biochemical values in serum or plasma of Ishibashi rats were compared with those of Wistar-Imamichi rats, and the following results were obtained: 1) In Ishibashi rat sera, alkaline phosphatase activity was significantly lower than that in sera of controls, and an intestinal type of isozyme was hardly detected. 2) All other serum biochemical parameters examined showed no significant difference between Ishibashi and Wistar-Imamichi rats. 3) The data suggest that Ishibashi rats may serve as an animal model of hypophosphatasia in man.

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Endurance of the forelegs of the dystrophic mouse was found to be significantly less than that of the normal mouse as early as at 3 weeks of age. It decreased progressively with age although the forelegs seemed to function almost normally even after 2 months of age by which time the hindlegs became almost immobile. Thus, histological and biochemical studies to compare the fore- and hindleg muscles of the dystrophic mice were conducted. Morphological abnormalities similar to those observed in the hindleg muscle were also found in foreleg muscles of the young dystrophic mice. Their foreleg and hindleg muscles showed significantly higher hydroxyproline contents than those of the normal mice even at 2 weeks of age when clinical signs of the disease first became manifest in their hindlegs. The present findings appear to be the first evidence for concurrent involvement of the fore- and hindleg muscles in murine muscular dystrophy. This would raise an issue as to why forelegs with abnormal muscles can subserve somewhat normal function, whereas hindlegs in these adult dystrophic mice are immobile. This might yield clues to clarify the mechanism underlying the aggravation of the disease.

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Thyroid hypertrophy of unknown cause occurred in a colony of Xenopus laevis maintained at the Institute of Endocrinology, Gunma University, Maebashi, Japan. These animals were kept in small aquaria with well water and fed on minced pig liver. An etiologic investigation was made on the thyroid abnormality by assessing its occurrence and histopathologic features and rearing conditions of the animals in comparison with those of the colonies at Tokyo and Sendai. 1) The occurrence of abnormal thyroids was restricted within the colony of Maebashi. In the colonies at Tokyo and Sendai where animals were maintained in conditions similar to those at Maebashi, no such thyroid abnormality was noted. 2) Female animals tended to exhibit a slightly higher incidence of the thyroid hypertrophy than males. 3) Histological characteristics of the abnormal thyroid found in the colony of Xenopus closely resembled those of thyroid adenocarcinoma in man, i. e. occurrence of numerous small vesicles, multi-layered follicle cells, reduced tinctorial reaction and lowered ability to take up radioactive iodine. 4) Ever since feed replacement with pellets for trout fingerling, no individual with thyroid abnormality has been encountered in the colonies of Maebashi, suggesting that the feeding with pig liver might be a potent cause, besides water quality, for the development of abnormality described herein.

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The heart weight of germfree mice has been reported to be lighter than that of conventional mice. The difference in heart function between these mice, however, has not been well investigated. In the present study, we recorded ECGs of germfree, ex-germfree and conventional mice anesthetized with pentobarbitone sodium and weighed the hearts of these animals. On ECGs, there was no significant difference between germfree and conventional mice except QT and PP intervals, which were shorter in male germfree mice than those in male conventional mice. It was found that the heart weight of germfree mice was significantly lighter than that of conventional mice in both sexes. It was concluded that although the heart weight between germfree and conventional mice was different, the heart function evaluated using the ECG was not.

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When mature female rats having been showing at least 2 consecutive 4-day estrous cycles were raised in a room with continuous lighting (LL), their vaginal smear pattern became irregular by 7 to 9 days, and a persistent-estrus (P-E) appeared around 25 to 75 days of exposure. Ovaries from LL-exposed rats showing irregular cycles or P-E had signs of cystic follicles and anovulatory polycystic follicles, respectively. When P-E rats were placed again under the light-dark cycling condition (14L: 10D; Lights on 05: 00 h), the regular 4-day cycles were recovered soon and ovarian structures became normal after about 5 cycles. In P-E rats injected i.v. with 10μg LH/day at 4-day intervals under the LL condition, the regular estrous cycle reappeared and ovarian structures became normal after 5 administrations. These results suggest that the polycystic ovary of P-E rat induced by LL is reversible with cyclic stimulation by LH.

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Body weight and body temperature of JCL: ICR mice infected with Sendai virus decreased depending on the viral dose. In severely infected mice, there were significantly higher values of hemoglobin, hematocrit, red and white blood cell counts, and leucin aminopeptidase (LAP), and lower values of reticulocytes and lactic dehydrogenase (LDH) . The other values tested were comparable to those of the non-infected mice.

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The maturation process of the secondary ossification centers of the extremities was radiographically investigated in the Japanese white rabbit of both sexes aged 1 day to 78 weeks. The ossification centers appeared at 1 day of age in the proximal and distal epiphyses of humerus, the head of femur, the distal epiphysis of femur and the proximal epiphysis of tibia, at 1 week of age in the supraglenoid tubercle of scapula, the proximal and distal epiphyses of radius, the proximal and distal epiphyses of ulna, the greater trochanter of femur, the distal epiphysis of tibia and the distal epiphysis of fibula, and at 2 weeks of age in the proximal epiphysis of fibula. The ossification centers developed rapidly from the time of appearance to 8 weeks of age, and gradually thereafter until 32 weeks of age. By 78 weeks of age, the complete fusion with the diaphysis was observed in the supraglenoid tubercle of scapula, the proximal and distal epiphyses of humerus, the head and distal epiphysis of femur. Incomplete fusion, leaving an epiphyseal line, was found in the proximal and distal epiphyses of radius, ulna, tibia and fibula, respectively.

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An attempt to isolate Enterobacter cloacae, Serratia marcescens and Yersinia enterocolitica was made in a total of 931 laboratory animals (mice, rats and rabbits) from five representative commercial breeders in this country and from our laboratory colonies. E. cloacae organisms were isolated from feces and other specimens of 15 mice and 7 rats between November 1979 and July 1980. Neither S. marcescens nor Y. enterocolitica was detectable in any specimen of feces, fur and skin, nasal discharge, lungs, urinary bladder or urine from the animals examined.

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