Differences in susceptibility of female mice among 10 strains to Corynebacterium kutscheri infection were studied pathologically and bacteriologically. Twenty mice of each strain were inoculated orally with 4×10^5.0 CFU of the bacteria. The gross lesions were observed in 60.0% of BALB/c-nu/nu mice, 25.0% of CBA/N mice, 10.0% of MPS mice, and 5.0% of A/J and C3H/He mice, while BALB/cCr, C57BL/6Cr, B10. BR/SgSn, ddY and ICR mice showed neither clinical signs nor gross lesions. Six BALB/c-nu/nu, two CBA/N and one MPS mice died within 15 days after inoculation. C. kutscheri was recovered from 95.0% of BALB/c-nu/nu mice, followed by 75.0% of A/J mice, 65.0% of CBA/N mice, 55.0% of MPS and BALB/cCr mice, and 30% of C3H/He mice. On the other hand, from C57BL/6Cr, B10. BR/SgSn and ddY mice, the bacteria were recovered at less than 15.0% of the mice. No bacteria were recovered from ICR mice. C. kutscheri colonized most frequently in the cecum, colon and rectum. Number of mice having agglutinating antibodies were less than 20% and their antibody titers ranged from 1: 10 to 1: 80. These results indicated that there were differences in susceptibility of mice among the strains to oral infection of C. kutscheri. Namely, BALB/c-nu/nu, A/J, CBA/N, MPS and BALB/cCr mice appeared to be susceptible, and C3H/He mice intermediate, while C57BL/6Cr, B10. BR/SgSn, ddY and ICR resistant. BALB/c-nu/nu mice were most susceptible and exhibited markedly severe disease by the infection.

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A forced air ventilation system for small laboratory animals was developed. The system consists of an air handling unit with air supply and exhaust funs, a rack, hard cage covers with a large diameter air inlet and an outlet, and shoe box cages. Air flow from the supply duct, to the exhaust duct and within the cage were observed. Variations in air flow among cages was minimal. The optimal air exchange rate of the cages in this system was determined to be 60 times per hour based on the results obtained in the present study. At this air exchange rate, air flow at the base of the cages had a velocity of less than 0.09m/sec, which was within the range of recommended values for humans. The observed results show that the system developed is capable of sustaining a laboratory animal micro-environment well in terms of air flow, without too much energy cost.

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Pancreatic islets of C57BL/6J-ob mice were microscopically examined at the ages of 5, 13, and 21 days, to clarify the time of the increase in number of A-cells, which appears to lead to diabetic symptoms in Small-ob mice (C57BL/6J-ob/ob) . The findings of islet in 5-day-old C57BL/6J-ob mice were the same as those of C57BL/6J-+/+ mice. At 13 days of age, changes in islet of C57BL/6J-ob mice were classified into 3 groups. They were no significant changes (putative normal), hypertrophic B-cells with clear cytoplasm (Ob mice), and an increase of A-cells (Small-ob mice), respectively. Electron microscopically, a tendency toward dilatation of endoplasmic reticulum was found in the hypertrophic B-cells. In the islets that had an increase in number of A-cells, only a few vacuoles, which were suggestive of degranulation, were found in the cytoplasm of B-cells, and premature secretory granules were seen in the A-cells. In part of the A-cells, development of rough-surfaced endoplasmic reticulum was also seen. Mild hypertrophy of the islets and the B-cells were observed in more non-diabetic Ob mice at the age of 21 days than nonobese mice at the same age, and only 2 of 6 mice had the increase in number of A-cells.In Small-ob mice, the increase in number of A-cells was more obvious than in the diabetic Ob mice, while other islet findings were similar to those of non-obese mice in extent. These observations disclosed that the changes in islet of Small-ob mice appear between 6 and 12 days of age.

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We examined an application of in vitro fertilization-embryo culture-embryo trans-fer system for reproductive and developmental study on the drug safety evaluation in mice. The male mice at 10 weeks of age were administered intravenously with a single dose of 75 mg/kg of the anticancer platimun complex (DWA 2114R) which inhibits DNA synthesis. Four to six weeks after administration, the males were mated with the superovulated females. Fertilization rates were significantly lower than the controls at each weeks after the administration. Furthermore, delayed formation of pronucleus was observed as compared with the control. Four weeks after administration, the preimplantation development to blastocyst stage of those embryos in vitro and the survival rates on the day 17 of gestation after embryo transfer suggested that a DNA synthesis in germ cells during maturation was inhibited and/or prevented by DWA 2114R. The results of in vitro fertilization reflected its sperm concentration rather than the administration of DWA 2114R. Thus, an analysis of the delayed formation of pronucleus observed fertilization in vivo could not done in detail. To use for the drug safety evaluation, there exist plenty of room for improvement in this system. These results have showed that the embryo culture and the embryo transfer are useful techniqes as the reproductive and developmental study on the drug safety evaluation. These techniges bring additional imformations on the pre- and post -implantation development in vivo.

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This study evaluates the reliability of the equation, metabolizable energy (ME) = digestible energy (DE) -1.25×digestible crude protein (DCP), as a means of estimating the energy value of non-purified diets for laboratory dogs. To do this, five digestion and nitrogen-balance (NB) trials and determination of the energy value of a diet were conducted using five diets and four mature, male Beagles for each experiment. The resulting digestibility of crude protein, acid ether extract, and nitrogen-free extract of these diets were 79.5%, 91.6%, and 84.8%, respectively. The NB in every diet was positive: 1.4-8.6mg/g dry matter of ingested diet. Of the nitrogen (N) ingested, 21% was excreted into feces, 66% was excreted into urine, and 13% was retained. In terms of dietary gross energy (GE), 18% was lost in feces and 5% was excreted into urine leaving 77% as ME. Retained energy in the body was only 1%, and N-corrected metabolizable energy (MEn) was 76% of GE. The average urinary energy (UE) loss per gram of urinary N was 7.84kcal. The correlation between UE/DCP and NB values is statistically significant: UE/DCP=1.24-0.03NB, r=0.798, P<0.001. Therefore, UE/DCP is 1.24kcal/g at N-equilibrium, almost the same as the factor in the above equation. The ME value calculated by the equation is identical to the MEn value, and both are significantly lower (P<0.05) than the empirically determined ME value. We conclude that this equation should be expressed as MEn=DE-1.25DCP, and is a reliable and convenient means of estimating the MEn of diets. Also, this study demonstrates that this revised equation can be applied, in the case of dogs, not only at N-equilibrium but also when N is retained in the body.

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It is known that suppression of copulatory behavior observed in aged male animals is due to elevated prolactin levels, the so-called hyperprolactinemia, found in these animals. The present study was done to determine whether hyperprolactinemia can modify the copulatory behavior of young adult male rats. Hyperprolactinemia was induced by grafting one or two pituitary glands of adult males of the same strain under the kidney capsules of each sexually experienced male. Grafted animals exhibited suppressed copulatory behavior patterns when tested one month after pituitary transplantation. The animals given two pituitary grafts differed from the sham-operated controls in latency to intromit (P<0.05), as well as in the numbers of intromission (P<0.05) and ejaculation (P<0.01) . After tests of copulatory behavior, serum concentrations of LH, FSH, prolactin and testosterone were measured by radioimmunoassay. Serum levels of prolactin were significantly increased (P<0.05) in the animals given 2 grafts, compared with sham-operated controls. From these results, suppression of copulatory behavior in the young adult animals grafted was similar to that in aged adults. The findings suggest that decline of copulatory behavior with increasing age results from chronic elevation of prolactin.

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The relationship between body weight gain and food intake was examined using 3 strains of mice, C3H/He, C57BL/6 and A/J mice, that were fed 4 kinds of diets differing in crude protein contents. Body weight gain of the mice fed the diet containing 3% protein was extremely small, while that of the mice fed the diet containing 40% protein was smaller than that of the mice fed the diet containing 10% or 20% protein. Mice were shown to possess a characteristic ability to intake an almost constant amount of calories irrespective of crude protein contents in diets, with some exceptions. These experimental results indicate that crude protein intake plays an important role for body weight gain. It was also assumed that energy consumption in C57BL/6 mice fed the 40% protein diet was accelerated because of excessive protein intake. Normal NK activity and antibody responses to SRBC were maintained at the age of 12 weeks in all the strains of mice fed the different diets.

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A detailed knowledge of the vascular system of tumors is requisite to a clear understanding of tumor physiology and pathology. Accordingly, in this study, examination was made of the vascular architecture of rat fibrosarcomas induced by 3-methyl choranthrene by scanning electron microscopy of resin casts to observe the three-dimensional vascular pattern of the sarcoma. The results were compared with those of corresponding serial sections of India ink-injected tissue. The major arteries in and around tumors appeared devoid of intra-arterial cushions which regulate blood flow. The arterial lining of resin casts was smooth just at the site where it entered the tumor. This may possibly be indication of degeneration and loss of the smooth muscle layer in the vascular wall. Casts of capillaries were very thin from 4 to 6 μm in diameter and very few sprouts could be seen. Capillaries, frequently present in superficial regions of the tumor, formed a rich irregular fine polygonal network. In fibrous tissue in deeper regions of the tumor, this network was coarse. The absence of intra-arterial cushions and degeneration of muscle cells may thus possibly be the reason for the characteristic haemodynamics of tumors.

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Development of the pronephros and mesonephros of Xenopus laevis was morphologically studied in the larvae immediately after hatch (stage 35/36) to the end of metamorphosis (stage 66) together with the appearance of renin-immunopositive cells. The pronephros consisted of 3 pairs of pronephric tubules at stage 35/36 and became functional at stage 37/38 with the opening of the pronephric ducts to the cloaca. It increased thereafter in volume, but became degenerative at stage 56, lost a part of the pronephric ducts at stage 60, and completely disappeared at stage 64. The mesonephros displayed its anlage at stage 42, and gained the immature renal corpuscles at stage 48. At stage 49, it was equipped with the matured nephrons. The mesonephric tubules differentiated into the neck, proximal, intermediate and distal parts. The collecting tubules and ducts were also observed at this stage. At stage 56, a part of the mesonephric tubules degenerated and were displaced by newly formed tubules. Reorganization of the mesonephros was not completed at the end of metamorphosis. Renin-immunopositive cells did not appear in the pronephros, but were observed at the diverging part of the renal artery from the dorsal aorta, and in the walls of arteries and afferent arterioles within the mesonephros in a low frequency of appearance.

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The rabbit is a representative animal species that conducts coprophagy, i. e. the production and reingestion of soft feces. We, however, encountered a maternal rabbit eating its own hard feces. A detailed investigation was performed on coprophagy in the rabbit to elucidate whether rabbits actually reingest their own hard feces. It was found that young adult Japanese White rabbits reingested their hard, as well as soft, feces directly from the anus. It has been reported that rabbits reingest only soft feces because of their high nutritive content, but the present study domonstrates that rabbits also reingest their hard feces despite their low nutritive content. It seems possible that coprophagy may be initiated by the colonic or rectal wall expanding effects of the fecal material itself.

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The presence of the scent glands were examined macroscopically and histologically in the Japanese vole, Microtus montebelli and the Hungarian vole, Microtus arvalis. A pair of scent glands were observed on the buttocks of the Japanese vole as the oval nodules with yellowish colored skin. The size of the glands was larger in males than in females. Histologically, the glands were composed of the aggregation of many acini of sebaceous glands. The epidermis above the scent glands were thicker than that in the other areas. In the Hungarian vole, no such gland could be detected with macroscopical and histological examinations.

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A method of long-term bile collection from unrestrained dogs was developed. A steel needle was passed subcutaneously from the animal's right side into the abdomen. A catheter, threaded through this needle, was inserted from the side and brought out below the abdomen. The catheter was introduced into the common bile duct and a vest was then fitted on the dog. The external catheter tip was placed in a collection bottle in the pocket of the vest. This method allows the animal to move freely in its cage. The bile of an unrestrained dog weighing 10kg was collected for 3 weeks at an output rate of 4.2-4. 6ml per hour.

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Female mice of the IVCS strain (ddN origin), aged 90, 180, 240, 270 and 300 days, were used in this experiment. The percentages of fertilized ova per ova collected from the oviducts, on Day 1 of pregnancy, of mice aged 90 and 180 days were 100% and 91.1%, respectively. Significantly decreased rates of fertilized ova were observed in mice aged 240 to 300 days as compared to 90-day-old controls (P<0.05) . Almost all two-cell embryos collected from 90-to 270-day-old mice developed into blastocysts or expanded blastocysts, and the developmental rate from 2-cell embryo to hatched blastocyst then decreased significantly (P<0.05) . The developmental rate from 2-cell embryo to hatched blastocyst also decreased significantly in 300-day-old mice (P<0.05) . These results demonstrate differences in the viability of mouse embryos collected from mice of different ages.

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The usefulness of alpha 1 acid glycoprotein (αl-AG) levels in selecting pound dogs from animal shelters for experimental use, was assessed in 1, 013 dogs. The mean (±SD), minimum, and maximum α1-AG values were 375.9 (±244.8), 20, and 1, 650μg/ml. The α1-AG value exceeded 500μg/ml, the cut-off value for the normal range, in 219 dogs. There was little correlation between αl-AG values and any of 15 blood chemistry parameters or with hematocrit values. Of the 176 dogs that died within 2 weeks after arrival at our institution, the α1-AG concentration was abnormal in one-third. These findings confirm that measurement of α1-AG is extremely useful in identifying desperate dogs and in confirming of the prognosis.

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Spontaneous mammary tumour potential was compared between virgins and breeders of a high mammary tumour strain of SHN mice. Virgins were essentially similar to breeders in both the cumulative and the monthly incidences of mammary tumours. DNA synthesizing enzyme activities and the number and the weight of mammary tumours also differed little between groups. While the number of preneoplastic mammary hyperplastic alveolar nodules (HAN) was significantly higher in breeders than in virgins, little difference was observed between groups in the end-bud formation and the duct growth of normal glands and the growth of HAN. These results indicate that in SHN mice virgins have similar mammary tumour potential to breeders, which is much advantageous for practical use of this strain as an animal model for human breast and other types of cancers.

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The body surface areas (BSAs) of 42 cotton rats (21 females weighing 29.08 to 169.60g, and 21 males weighing 18.93 to 168.03g) were measured. From these areas and body weights (BW), the equation, BSA (cm²) 47.66+2.476×BW (g) -0.006×BW (g) ², was derived. To verify the applicability of the equation, the BSAs of another 19 animals (12 females weighing 29.08 to 169.60g, and 7 males weighing 19.27 to 167.32g) were calculated and the values compared with the measured BSAs. The correlation between calculated and measured BSAs was significant (r=0.995, P<0.01) . Therefore, this equation can be used to calculate cotton rat BSA.

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The rhino mouse, so called because of its characteristic rhinocerous-like skin cannot raise its young. Although the animal has rudimentary mammary glands, these are thought to be defective due to their impossibility to raise their young. Morphological observations of the female mammary glands of rhino mice (hr^rh/hr^rh) were carried out and the results were compared with those of their normal litter mates (hr^rh/+) at various ages from 1 month to 1 year. No morphological differences in mammary gland development was seen between the rhino mice and their normal litter mates, and normal secretory changes were observed in the rhino mice after delivery. Mouse mammary tumor virus (MMTV) expression and the occurrence of hyperplastic alveolar nodule (HAN) were analogous to these features in phenotypically normal hr^rh/+ mice. Further, the sweat glands in the rhino mouse were normal. Thus, anomalies in the rhino mouse appeared to be limited to the skin and pilosebaceous apparatus.

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Cytokine levels of interleukin-lα (IL-lα), interleukin-1β (IL-1β), interleukin-3 (IL-3), interleukin-6 (IL-6), erythropoietin (EPO) and tumor necrosis factorα (TNFα) in bone marrow of Wistar rat were measured with immunofluorescent assay. The levels of IL-lα, IL-1β, IL-3, IL-6 and EPO were high in young (4 weeks old), and gradually decreased thereafter. In contrast, TNFα level in bone marrow was low by 18 weeks old and high at 26 and 52 weeks old. These results indicated that age-associated changes of bone marrow cell composition in rat are well correlated with the levels of cytokine related to bone marrow cell differentiation.

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Changes in visual function with increasing age were studied in male WBN/Kob rats, a new diabetic strain. In order to detect visual abnormalities in WBN/Kob rats, 5 WBN/Kob and 5 Wistar/ST (control) rats from each group were examined at 5, 9, 13, 17, 23, 27, 36, 45, 54, 67 and 80 weeks of age using dark and light distinction and open-field tests. The rates at which WBN/Kob rats selected the dark area were 85.0 to 100%, 58.8% and 52.6% at 5 to 54, 67 and 80 weeks of age, respectively, while those for Wistar/ST rats were 85.0 to 100% in each age group. Visual abnormality was obvious in WBN/Kob rats aged 67 and 80 weeks, compared with Wistar/ST rats (P<0.05) . There were no significant signs of visual abnormality in the open-field test. Detection of visual abnormality seems to be possible from 67 weeks of age.

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The purpose of this study is to establish reference data on several hematological parameters in the cotton rat. Eight hematological values were measured in 28 males and 29 females at 16 to 18 weeks of age. Females showed significantly lower RBC, Ht and MCV values than males. Female Hb and PLT values tended to be lower than male values, although differences did not reach a conventional level of significance. WBC and PLT values varied widely in both sexes.

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[in Japanese]

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