After hypophysectomy, behavioral circadian rhythmicities in the rat became indistinct and phase shift was observed. Therefore, it was thought that the suprachiasmatic neucleus (SCN), which is the circadian oscillator in mammals, was affected by hypophysectomy. We investigated the effects of hypophysectomy on SCN neurons using immunohistochemical staining. Wistar-Imamichi strain male rats were hypophysectomized at 60 days old. Their brains were fixed by acrolein perfusion at 10, 30 and 60 days after the operation, and then vasopressin (AVP) -, vasoactive intestinal polypeptide (VIP) - and somatostatin (SRIH) - neurons in the SCN were stained immunohistochemically. Ten days after the operation, SRIH-neurons were not found in the SCN. At 30 and 60 days after the operation, a few SRIH-positive cell bodies were recognized. In contrast, AVP-and VIP-neurons did not change in morphology in comparison with normal rats. These results suggest that hypophysectomy produces an essential change in SRIH neurons in the SCN, and that such change is responsible for the abnormal behavioral rhythms.

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Effects of the reproductive activity upon major organ weights and ovarian histology were examined in the inbred wild-colored mastomys (Praomys coucha), MWC. The liver, ovary and spleen weights increased during pregnancy and kept the increased levels until weaning of the young in the former 2, but not in the last. The most characteristic histological changes were observed in the corpora lutea and interstitial cells. The corpora lutea changed in both size and number according to the reproductive status. The interstitium was meagre in virgins as observed in other laboratory rodents, but expanded during pregnancy. It contained two types of interstitial cells. One was characterized by light cytoplasm and the other by dark cytoplasm. The latter increased in number during pregnancy and occupied the interstitium exclusively. These changes suggested that the interstitial (steroidogenic) cells in the mastomys might have a unique and distinctive turnover mechanism as did those constituting the zona reticularis and border zone in the female mastomys adrenal cortex.

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Athymic (nu/nu) and euthymic (nu/+) mice were intraperitoneally given doses of 0.25 to 1.5 mg/g body weight of urethan at the age of 14 to 16 days. Dose-response relationship and sequential changes in lung tumorigenesis induced by urethan in athymic mice were compared with those in euthymic littermates. The urethan dose-response relationship in lung tumorigenesis of the nu/nu mice was almost the same as that in the nu/+ mice. Incidence and multiplicity of the lung tumors were investigated sequentially 28 days to 12 months after urethan injection. They showed similar indexes in the two phenotypically different mice at varying periods after 0.5 mg/g body weight urethan treatment (incidences of 4.8 and 4.4 tumors/mouse and 96 and 97% for nu/nu and nu/+ mice, respectively, at 12 months after treatment) . This means that the length of the latent period is similar in these phenotypically different mice. It may be concluded that the immunosurveillance mechanism mediated by T-cells does not function in the present model.

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Changes in the visual function of the male WBN/Kob rat known as diabetic strain with increasing age were studied electrophysiologically. The measurements of electroretino-gram (ERG) and visual evoked potential (VEP) in male WBN/Kob rats were performed at 5, 9, 13, 17, 23, 27, 36, 45, 54, 67 and 80 weeks of age, and compared with those in male Wistar/ST rats used as control. The prolonged latencies and decreased amplitudes of a- and b- waves and oscillatory potentials of ERG in WBN/Kob rats aged over 17 or 27 weeks were recorded under the light or after 20 min dark adaptation. The visual abnormality as indicated by non-recordable ERG was obvious in WBN/Kob rats aged 67 and 80 weeks. No changes of N1, P and N2 peak latencies of VEP were recorded in WBN/ Kob rats with increasing age. The amplitudes between N1 peaks and P peaks decreased remarkably in WBN/Kob rats aged 54 weeks. The amplitudes of VEP in 67 or 80 weeks old rats in which ERG disappeared showed 26 or 28% of those in 5 weeks old rats. From these results, recording of ERG and VEP suggested that the visual abnormality occured in male WBN/Kob rats aged 67 or 80 weeks and the process of visual abnormality with increasing age was clarified.

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Spinal bone mineral density (BMD) of African green monkeys were measured by a dual-energy X-ray absorptiometry (DEXA) . The value determined in male was rather higher (0.674±0.068g/cm², Mean ± S. D.) than that in female (0.611±0.105g/cm²), while the coefficient of variance was larger in female (17%) than in male (10%) . Females were divided into two groups according to their diversity of BMD values. Serum biochemi-cal values were compared among three groups, one male group (n=37) and two groups of female (A: n=31, B: n=22), using a canonical discriminant analysis. As the result of the canonical discriminant analysis, closed relationship between serum biochemical properties and BMD was demonstrated. Lower BMD, lower serum protein concentration and higher serum inorganic phosphorus may be the reflection of malnutrition in this primate species. In conclusion, animals showing osteopenia were included in our breeding colony of the African green monkey judging by the value of bone measurements and serum biochemical measurements.

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Colonization pattern of Pasteurella pneumotropica (P. pneumotropica) in mice with latent pasteurellosis was examined with the original selective media, NKBT medium and TGN broth. In the mice of 0 to 15 weeks old, the organism was mainly isolated from the upper respiratory tract, lower intestinal tract, feces and vagina, with the highest isolation rate in the pharyngolarynx. In the pregnant and lactating mice, the organism was isolated from the same sites, but not from the uterus, fetus or mammary gland. In the neonates, the organism was isolated from the respiratory and intestinal tracts within 24hr after birth. The organism was constantly detected in the feces of the 0- to 20-week-old mice, with the highest viable count one week after birth. Through the monitoring of mouse colonies, the pharyngolarynx always showed higher isolation rate than the feces in several mouse strains. These results reveal that the pharyngolarynx is the primary colonization site of P. pneumotropica in mice, and the lower intestinal tract and vagina are also the main sites. Further, frequent isolation of the organism from the feces and vagina, and the results in neonates suggest the mode of the transmission to newborn mice in the colony, i. e., intravaginal infection at the partrition, and oro-nasal infection through the maternal feces and saliva.

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We examined seasonal changes in serum testosterone and LH, and investigated mechanisms of reduction of testicular function in non-mating season in male Japanese monkeys. Blood samples were collected monthly throughout one year in 5 males, and hCG and LH-RH were administered to 5 and 3 animals, respectively, in non-mating and mating season. Serum testosterone and LH were measured by RIA. Serum testosterone showed the obvious seasonal changes, being low in March to August and high in October to February. Also we found the seasonal changes in LH being low in May to August and high in September to February. When hCG was administered to 5 monkeys in mating season (January), serum testosterone levels increased markedly 30 to 180 min after single administration and showed further increases after continuous administrations for four days. However, in non-mating season (August), serum testosterone showed a little increase for the same treatment as in mating season. These data showed that the reserve ability of testosterone secretion in testis in non-mating season decreased obviously in contrast to mating season. The increase of serum LH and testosterone levels in 3 males in non-mating season (July) after LH-RH single administration were less than those in mating season (December) . In intermediate period (September) between non-mating season and mating season, LH showed higher level than that in mating season but the testosterone level was the same extent as in non-mating season. These data showed that the secretive functions of pituitary LH and testicular testosterone were low conditions in non-mating season, and that in intermediate period the secretive function of pituitary LH was getting to active, but that the secretive function of testicular testosterone remained in depressive condition yet. These findings suggested that one reason for the reduction in testicular function in non-mating season was a decline in secretive function of hypothalamic LH-RH.

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In an effort to explore a sensitive species-specific detection system using the polymerase chain reaction (PCR) for B. piliformis, we sequenced 16S ribosomal DNA (rDNA) of the organism (MSK strain) isolated from the mouse and compared it with known rDNA sequences of the RJ strain isolated from the rat. Sequence homology between the MSK strain and the RJ strain was over 97%, but homology between the MSK strain and other bacterial species was less (70-83%) . The results indicated that the sequences included B. piliformis species-specific regions. On the basis of the sequences, we designed a PCR primer set which amplifies B, piliformis rDNA specifically. The PCR with the primer set detected not only these two strains but also an HN strain of hamster origin, although it did not detect other organisms. Therefore, this primer set was considered to be specific for B. piliformis species. More than one organism (RJ strain) could be detected by the PCR method. Nine Jcl: Wistar rats were infected perorally with 2x10⁴ RJ strain organisms, and three rats each were sacrificed on days 1, 3 and 5 postinoculation (p. i.) to investigate the presence of the organism in the liver, heart, cecum, spleen and mesenteric lymph nodes by PCR and the immunofluorescence test. On days 1 and 3 p.i., B. piliformis was not detected in any tissues of the six rats, but B. piliformis was detected in two of the three rats sacrificed on day 5 p.i. The presence of the pathogen was seen in both liver and heart (1/ 3), or in the cecum (1/3) by both methods. The results of this study demonstrate that the 16S rDNA sequence of MSK strain is well conserved at the species level and the PCR with the primers selected is useful for the sensitive and specific species-identification of B. piliformis.

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Laboratory matings were attempted to establish breeding colonies of Northern grasshopper mice, Onychomys leucogaster (which were captured in New Mexico, U.S.A.), as experimental animals. The results were as follows. The rate of pregnancy was 75% with cohabitation for more than 30 days, and 4% with cohabitation from 1 to 7 days. Both cases were of monogamous mating. The mean litter size was 3.5±1.2, with a range of 1 to 6. The rate of weaning was 78.8% . The mean gestation period was 27.4±2.0 days, with a range of 25 to 31. The gestation period was achieved by the method of confirming sperm from smears. Further, it was possible to breed all year round in a rearing room with fixed temperature and humidity.

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Mastomys is a rodent with a intermediate size between mouse and rat, and classify as a subgenus of Praomys coucha. Our study determined the phylogenetic evolutional relationships of mastomys to mouse and rat deduced from satellite DNA sequences. Genomic DNA was extracted from each liver and digested by restriction enzymes (EcoRI and BglII) . After separation and purification, we obtained these EcoRI/BglII-0.5 Kbp repeated elements and determined the nucleotide sequences. The similarities and speed of evolution were 86.06% and 0.1578 between mastomys and mouse, 85.56% and 0.1671 between mastomys and rat, and 83.91% and 0.1863 between rat and mouse, indicating that mastomys was evolutionary classified between mouse and rat, and closely related with mouse.

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Changes in the visual organ with aging were investigated non-surgically in male WBN/Kob rats, in which spontaneous diabetic mellitus commonly occurs. Male Wistar/ST rats at the ages of 5, 9, 13, 17, 23, 27, 36, 45, 54, 67 and 80 weeks were examined for changes in the peri-orbital region, eyelid, lens, corpus vitreum and ocular fundus by macroscopic inspection and funduscopy. The area around the eyelid was stained with reddish-brown excretions from the Harderian gland. This stain was frequently observed in rats of both strains aged 54 weeks or over, showing no difference in frequency between WBN/Kob rats and Wistar/ST rats. Lens opacity was observed in male WBN/Kob rats aged 67 weeks or over, and narrowing of the retinal artery and vein in those aged 36 weeks or over. The occurrence of lens opacity was consistent with that of visual dysfunction as determined by a test of the ability to differentiate light from dark using a Y-shaped apparatus (Kiyosawa et al., 1993) .

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The polymerase chain reaction (PCR) and culture methods were used to detect Mycoplasma pulmonis in nasal, tracheal and oral swab samples of rats derived from 5 mycoplasma-contaminated and 2 mycoplasma-free facilities, and the results of both methods were compared. Thirty-four/54 and 30/54 in nasal samples, 31/54 and 28/54 in tracheal samples, and 12/39 and 30/39 in oral samples were positive in PCR and cultures, respectively. Agreements in the results of both tests were 48/54 (88.9%) in nasal samples and 49/54 (90.7%) in tracheal samples. This indicates that nasal and tracheal samples are useful for detecting M. pulmonis by PCR. The detection number for M. pulmonis from the oral cavity by PCR was remarkably lower than those of nasal and tracheal sites. These results show that the PCR method has significant potential as a rapid and sensitive method for detecting M. pulmonis in clinical samples collected from the nasal cavity and trachea.

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Two male laboratory beagle dogs used in toxicity studies, one 7 months old and the other 9 months old, showed the evidence of corneal dermoid. Grossly, the dermoid was observed in both cases as hair growth from the cornea. In one case, the hairs had been removed from the cornea, but regrowth was observed about 70 days later. Histopathologically, melanocytes, melanin granules, hairs, hair bulbs, adipose tissue and sebaceous and sweat glands were observed in the corneal epithelium and propria. According to the information obtained from 4 breeders, the incidence of corneal dermoid was extremely rare in laboratory beagle dogs.

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Hibernating pocket mice (Perognathus flavus) were obtained from the Department of Veterinary Medicine, Hokkaido University, in September 1990, and attempted to rear them in National Institute of Neuroscience, NCNP. Rearing of pocket mice was possible under the general conditions used for rearing mice. As a result of random mating of 4 females to 2 males for breeding, gestation was achieved in only one pair of animals, and parturition under artificial rearing conditions was observed for the first time. The animal gave birth to 3 offspring that had no body hair. Their eyes were closed. Each of the offspring weighed about 1.0g. The mean body weight of the females was 6.5g and that of males 5.6g at 3 weeks. Weaning was possible at this age. Subsequently the animals grew rapidly ; the body weight was almost equal to that of an adult animal (8.0g) at 5 weeks of age for the females and 7 weeks for the males. The gestation period was estimated to be 26 days. These findings indicate that pocket mice can be bred and reared under general laboratory conditions.

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Adult male rats received pituitary transplantations to induce hyperprolactinemia. Some of those had bromocriptine (CB-154) treatment, and the other had vehicle (saline) as control. The grafted animals with vehicle exhibited significantly more suppression than sham operated animals. While the hyperprolactinemic rats treated with CB-154 showed no significantly more suppression of copulatory behavior than sham operated control. In the grafted animal without CB-154 treatment, the concentration of serum PRL was significant-ly higher than in sham operated controls. There were no significant differences in adrenal weight and serum levels of gonadotropin between grafted and control groups. These results may imply that PRL has direct actions on central nerveous system (CNS) and inhibits copulatory behavior in hyperprolactinemic male rats.

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We developed a data acquisition system which measure the body weight, food and water consumption and spontaneous activity of a rat automatically. The correlation of body weight gain with other parameters obtained by this system were analysed. Each parameter showed rhythmic circadian changes. The multiple regression analysis with stepwise method brought the high coeffciency on the body weight gain with water consumption in the dark period, whereas only low correlation was observed among the body weight gain, food consumption and spontaneous activity in the light period. Since the body weight is affected by various factors, food and water consumption, spontaneous activity and/or other parameter (s) with body weight should be monitored simultaneously.

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Receptor levels of Interleukin-1 (IL-1) on bone marrow macrophages in ICR mouse and Wistar rat were measured chronologically using europium-labeled ligand assay. The IL-1α bound to high and low affinity sites but IL-1β bound only to low affinity site on the macrophages in both mouse and rat. The Kd values of IL-1α and IL-1β were gradually increased with age in both species, althought the binding capacities (receptor number) of IL-1α were low in young and aged mice. Binding capability of IL-1β decreased agedependently. These results suggested that receptors of IL-1 on bone marrow macrophages of these species might decrease with age in both quality and quantity.

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In vitrofertilized mouse eggs (C57BL/6N), followed by ultrarapid freezing were used for production of transgenic mice by microinjection of the chicken β-actin promoter-driven the firefly luciferase cDNA (βact-Luc) . Following micromanipulation, the survival rates of the cryopreserved eggs and of the freshin vitrofertilized eggs (control) were 70.8% (131/185) and 71.9% (159/221), respectively. After transferring them into oviducts of psudopregnant recipients on Day 1, 13.6% (17/125) of the cryopreserved eggs developed to live offspring and 14.1% (21/149) of fresh eggs did so. It was confirmed by Southern blotting analysis that each two transgenic mice were produced from the cryopreserved eggs (12%, 2/17) and the fresh eggs (10%, 2/21) . All of transgenic mice produced from both eggs showed the expression of the luciferase gene. These results indicate that thein vitrofertilized eggs cryopreserved by ultrarapid freezing, can be, easily and conveniently, used for generation of transgenic mice.

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IgE responses toFasciola hepaticaextract in 6 strains of mice (C3H/HeN, CBA/JN, DBA/2N, BALB/cAnN, C57BL/6N and NZBWF₁) were investigated. Serum anti-F. hepaticaIgE antibodies were determined by passive cutaneous anaphylaxis (PCA) . DBA/ 2N and BALB/cAnN mice showed higher IgE responses than other strains.

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