An inbred strain of mice, DDD, was established at the Institute for Infectious Diseases (so-called Denken in Japanese; currently called Institute of Medical Science, The University of Tokyo: Jms) in 1962 (Table 1) . Many interesting characteristics including development of pregnancy-dependent mammary tumors, presence ofFv-2^s, a Friend leukemia virus-susceptible gene, high incidence of hydronephrosis and low level of natural killer (NK) cell activity have been reported in this strain of mice. Two congenic strains, DDD-Fv-2^rand DDD-Mtv-2⁺, have been produced. Inbreeding ofddmice maintained at Denken was commenced in 1957 and the resulting inbred strain was named DDD afterddatDenken (Table 1) . The ancestors ofddmice had come from Germany. The process of introduction to Japan and the history of these mice were surveyed in the literatures (Table 2), since the description concerning them had been confused. As a result, the following history was confirmed: the original colony of mice of an unknown size was introduced from the Hoechst Company, Frankfurt a. m. Main, Germany into the Kitasato Institute, Tokyo, Japan by Dr. Tsuneo Komatsu under the direction of Dr. Sahachiro Hata in autumn, 1928 (Table 3) . Dr. Hata and his colleagues bred these mice to use for medical researches and called them“deutsche Maus” (Table 2) . Their descendants (one male and one female) were shipped to the Health Institute of Manchuria Railway, Talien (currently called Dalian), China on demand of Dr. Koji Ando in 1934 (Table 3) . Two males and eight females from the Talien colony were shipped back to Dr. Saburo Kojima, the Institute for Infectious Diseases, Tokyo, Japan in 1943 (Table 3) . They had been maintained without crossing with another colony at the Institute, from which mice were distributed to many institutes throughout Japan between 1944 and 1960, and served as the starting nuclei of many inbred or outbred strains (Table 1) . The“deutsche Maus”was named dd mice after“deutscheMaus atDenken”in 1952 (Table 1) . Thus, the mouse strains connected withddmice usually have D, DD or dd at the head in their names.

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Pentatrichomonassp. from the feces of beagles was cultured axenically, and identified asP. hominis. The culture medium used was slightly modified Dimmond's medium supplemented with chicken liver extract and rifampicin. Based upon good proliferation after inoculating only a few organisms in this medium, a fecal examination method employing cultivation was developed. Resistance of the trichomonad against disinfectants and metrpnidazole was tested, and it was found that the protozoan was rather susceptible. After oral administration of the organism to mice and rats, all the treated animals were infected. Since two types of the trichomonad, moving and non-moving, were detected, the presence of any type resistant to standing or drying was ruled out. A possible route of trichomonad infection to beagles is discussed.

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Attempts were made to examine progesterone levels during pregnancy block, first initiated by pheromones and then by the injection of pregnant mare serum gonadotropin (PMSG) . The proximity of a strange male inhibits the usual increase in progesterone levels, resulting in no activation of the corpora lutea, from the estrous cycle to the pregnancy. Strain differences were observed in the imitation of pregnancy block by the injection of PMSG. The C 3 H and BALB/c strains required much smaller doses of PMSG for pregnancy block than the C 57 BL /6 strain did. The changes of progesterone observed in pregnancy block initiated by PMSG were slightly different from that caused by the proximity of the strange male : The progesterone levels temporally increased on the day following the injection of PMSG and then decreased on day 4 in the PMSG-treated group. These results suggest that PMSG imitates the effect of the proximate strange male in the pregnancy block.

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Using sperms of the transgenic mice carrying a human^Aγ /β -globin gene on Ychromosome, we attempted to separate X-and Y-bearing sperms by the Percoll density gradient centrifugation. The ratio of X- and Y-sperms was determined by DNA dot blot hybridization procedure with sperm DNA. Sperm suspension collected from cauda epididymidis was loaded on the gradient composed of 7 Percoll concentrations (35-84%) and was centrifuged at 300×g for 10, 15 or 20 minutes, respectively, at room temperature. After centrifugation, sperms were collected from each gradient fraction and washed with 0.85% saline solution. DNA was extracted from sperms, dotted and fixed on nitrocellulose filter, and was hybridized with the³²P-labeled DNA probe derived from the β-globin gene. Each DNA spot was cut out, immersed in the liquid scintillator and was counted for radioactivity. There was no difference among the radioactivities in the DNA spots, indicating that the ratio of X-and Y-sperms was the same in all the gradient fractions of three different centrifugal conditions. The result suggests to be difficult to separate X-and Y-sperms by Percoll density gradient centrifugation, at least, using sperms from cauda epididymidis of mouse.

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The sensitivity of spontaneously epileptic rats (SER), double homozygotes of zitter and tremor mutations, to external stimuli that induce seizures was studied in comparison with tremor (tm/tm) and zitter (zi/zi) rats, and with normal Kyo: Wistar and F 344/N rats. Touching their body, a blinking light (1200 lux, 1 sec interval) or a big sound (8 and 12 kHz, 95 dB) induced tonic extension only in the SER. The response frequency was 22 to 44% at 9 weeks of age and 75 to 100% at 13 weeks of age. Electric stimulusi at 30 mA induced tonic-clonic convulsions in all Kyo: Wistar and F 344/N rats. At 20 mA the incidence of seizures decreased with age, from 100% at 5 weeks of age to 33% at 13 weeks of age in Kyo: Wistar rats and from 100 to 71% in F344/N rats. In SER, 10-mA stimuli induced tonic extension at 9 and 13 weeks of age, and 20 and 30 mA induced tonic convulsions, generalized or partial convulsions, and wild jumping or running episodes at 5, 9 and 13 weeks of age. At 30 mA, the incidence of convulsive seizures decreased with age in both tremor (tm/tm) and zitter (zi/zi) rats. Apparently external stimuli acted as simple triggers in the induction of tonic extension, since characteristic tonic extension is induced in the SER by each of the stimuli used in the present study, and induced convulsions closely resembled spontaneously occurringconvulsions. The threshold of external stimuli in the induction of tonic extensionbecame lower with aging in the SER, indicating that they are appropriate modelsfor evaluating anticonvulsant drugs, as reported previously.

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To determine the chronic toxicity of diesel exhaust, 2, 150 F 344 rats were made to inhale various dilutions of exhaust under specific pathogen-free conditions for 16 hours a day, 6 days a week, for 30 months. Ten experimental groups, each with 120 male and 95 female 5 week-old rats, were set up and 14 males and 9 females were usually sacrificed for measurement of the 51 hematological and clinico-biochemical parameters at 7, 13, 19, and 25 months of age, respectively. These parameters were also examined in all surviving rats after 30 months of exhaust inhalation. In this experiment, no remarkable change in any of the parameters was observed in the periodic examinations. Therefore, tendencies of change in parameters were examined by comparing histograms for control and experimental groups. For the reference histograms, we used the values obtained from 144 males and 116 females aged 13-31 months. The first histogram was based on data from 1, 352 rats, and the range from the minimum to the maximum value was divided into eight parts. When almost all the values were centered on a peak in the first histogram, this peak was divided into a further eight parts in the second histogram. Histogram evaluation clarified the differences between the control and experimental groups better than general statistical methods such as Student's t-test.

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An ozonization method was used to inactivate the viral pathogens of laboratory animals. Ozone at a concentration of over 100 ppm with high humidity was highly virucidal against 4 RNA viruses: HVJ, Theiler's murine encephalomyelitis virus (TMEV), Reo type 3 virus (RV) and murine hepatitis virus (MHV) . For the ozone tests, 0.1 ml of a virus suspension in deionized water or saline and was placed in 35-mm dishes. The titer of 10⁶plaque-forming units of TMEV in a liquid-phase, which was highly stable against physical treatments, was reduced within lhr to a level of 0 by 300 ppm of ozone at 80% humidity and 22-25°C. HVJ and MHV were more susceptible than TMEV to the ozone treatment. RV was the most resistant of the 4 viruses. The ozonization method may be a good way to disinfect not only for the laboratory animal RNA-viruses (both of enveloped and unenveloped viruses) but also animal rooms, clean rooms and even safety cabinets.

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Using a data logger system, body temperature (dorsal subcutaneous temperature), heart rate, ingestive or ruminating behaviour and posture in adult Shiba goats tied to a stanchion were recorded automatically during 24 hours, to obtain basic information on the biological rhythms. A 600g of usual ration mixed with haycube, hay, beet pulp and wheat bran was fed twice a day (morning ; 9: 00-9: 30, evening ; 16: 00-16: 30) . Animals kept under an artificial photoperiod (12 L-12 D, light period ; 5: 30-17: 30) and about 10°C room temperature. 1) Diurnal patterns of the above-mentioned items were recorded (as shown in Fig. 2), mutual relationships between these items were revealed. 2) The heart rate was higher after morning feeding, or during a light period and decreased gradually from midnight to early morning. Twice feeding greatly increased the heart rate. 3) The body temperature was lower in the early morning and increased gradually after morning feeding and showed the highest level during 1 to 1. 5 hours after evening feeding. After that it decreased gradually till the early morning. 4) The numbers of jaw movement (bites/min) were a 70-90 bites in the ingestive behaviour and a 80-90 bites in the ruminating behaviour at dark period. 5) The total heart rate was a 110000 to 120000 beats/day, the total bitig time was a 9.5 hours/day, and the mean standing time was a 9.3 to 11.7 hours/day. The standing time during light period (12 hours) was a 7.3 to 9.9 hours and that during dark period (12 hours) was a 1.8 to 2 hours.

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Spontaneous histopathologic lesions were examined in 276 young beagle dogs (8 to 15 months old) used in toxicity studies. Mononuclear cell infiltration in the liver was observed with the highest incidence (more than 95%) . Calcium deposition in the kidney, mononuclear cell infiltration in the salivary glands, pigmentation in the spleen, and cortical atrophy in the thymus were seen with relatively high incidences (more than 30%) . The incidence of mononuclear cell infiltration in the gallbladder, vacuolization of the tubular epithelium in the kidney, and vacuolization of the zona glomerulosa cell in the adrenal gland showed differences between the sexes. No abnormalities were seen in the spinal cord, sternum, and femur. Although most lesions observed are considered to be age-related, several were considered to be due to congenital anomalies observed in some organs.

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Alveolar macrophages (AM) in bronchoalveolar lavage derived 6 species of laboratory animals (mouse, rat, Syrian hamster, Mongolian gerbil, guinea pig, and rabbit) were cultivatedin vitroand were infected with HVJ, parainfluenza virus type 1, for the purpose of studying virus reproduction in these cells. Using infectivity assay, fiuorescent antibodies and hemadsorption techniques, three categories were proposed depending on the potential of virus replication and antigen production. Category 1 (mouse, Syrian hamster, and guinea pig AM) was the most susceptible group to HVJ infection. All AM became antigen positive, and more than 10⁶ PFU/ml of virus infectivity in the culture fluids was noted at 4 days after the virus infection. Rat and Mongolian gerbil AM were grouped into Category 2. Their AM showed a moderate virus yield (average 10⁵PFU/ml of infetivity) and antigen production. On the other hand, Category 3 (rabbit AM), exhibited no production of an infectious virus. It was likely that the virus penetrated into the AM but did not replicate complete virus. However, antigen positive cells ranging from 10 to 50% depended on the multiplicity of the infection to the AM. These findings suggest that HVJ infection in the rabbit AM was abortive (incomplete virus replication), since trypsin treatment of the culture fluids, which may contain incomplete HVJ particles, did not induce infectivity.

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To estimate the immune function of the rat, the blastogenic response of rat lymphocytes in blood drawn from the vena cava was investigated. The recovery rate of lymphocytes from venous blood was 33.2±2.23% and their viability rate was 99.8±0.25%. Three kinds of mitogens (phytohemaggultinin-M, concanavalin A and pokeweed mitogen) at three different concentrations (high, middle and low) were added to lymphocyte suspensions, and the suspensions were cultured under 5% CO₂incubation. Cultured suspensions were served for glucose consumption test and values were calculated (glucose consumption test-stimulation ratio (GCT-SR) ) . Incidence of blast cells was also observed by morphology. In both the GCT-SR and blast cell incidence, the highest values, 41.2% and 50.8%, respectively, were obtained after stimulation with phytohemaggultinin-M at the concentration of 0.1 ml/ml. The results were statistically analyzed by the variance of means. On both the GCT-SR and blast cell incidence, values obtained in each condition (kind of mitogens on the concentration used) were all statistically significant (all P<0.01) . The correlation coefficient between the GCT-SR values and the blast cell incidence was 0.97 (P<0.01) . From these results, we concluded that the glucose consumption test using rat blood lymphocytes can be used as a safe and simple method to measure the immune function of rats.

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Specific pathogen free BALB/c mice from 3 commercial laboratory animal breeders in Japan were compared on the composition of caecal flora revealed by selective and nonselective cultivation as well as direct microscopical observation on smears, and relative caecal weight. Large differences were detected in viable counts of total bacteria and almost all bacterial groups, while direct microscopical counts which consisted mainly of fusifrom bacteria were almost equal, resulting in diverse recovery rates among 3 breeders.Eubacteriumand spiral shaped organisms were not detected from all breeders. There also existed variations within breeders, especially those in the number of Enterobacteriaceae. Relative caecal weight also differed among breeders, suggesting the participation of variety of caecal bacteria in determining this parameter. As these variations in bacteriological status of animals can influence experimental results. standardization of intestinal microbial flora is required.

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Two inbred strains from a foundation stock derived from Crj: CD-1 (ICR) mice were established after more than 20 generations of full-sib mating, and by simultaneous selective breeding for developing and not developing diabetes after alloxan administration (45mg/kg in males, 47mg/kg in females) . To elucidate the genetic background of the two inbred strains, i, e., alloxan-induced diabetes-susceptible (ALS) strain and alloxan-induced diabetes-resistant (ALR) strain, their biochemical genetic markers and immunogenetic markers were examined. 1) For both strains, investigation of biochemical genetic markers at 19 loci and immunogenetic markers at 11 loci revealed no variation in any gene within the same strain, showing to be homogeneous, thus indicating establishment of the inbred strains. 2) The two strains differed from each other at 2 loci of biochemical genetic markers and at 5 loci of immunogenetic markers. 3) The ALS and ALR strains can be regarded as new inbred strains derived from ICR mice. 4) The results show that the marker genes of the two strains are different at 7 loci, but it remains unclear whether or not these genes are involved in the difference between the two strains in susceptibility to alloxan.

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A survey for the prevalence ofHepatocystis sp. was done on 10 rhesus monkeys (M. mulatta) from Yunnan, China. Examinations were performed on blood smears to detect erythrocytic gametocytes of the parasite, and on livers to detect merocysts. In 6 out of 10 monkeys, Hepatocystis sp. infection was confirmed. The gametocytes took about 6 days to reach maturity. The fully grown macrogametocytes were about 8μm in diameter. The cytoplasm was stained pale lilac and the nucleus consisted of dense chromatin dots lying in an unstained zone. The microgametocytes had cytoplasm dyed a biscuit color and large nuclei dyed pink. In the pathological section of livers, the merocyst measured about 3 mm in diameter and had a smooth outline without any projecting limb. The characteristics of this protozoan species were very similar to those ofH. taiwanensis. However, more work should be done to clarify the relationship between this species andH. taiwanensis.

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Milk samples were collected from herbivorous voles (Microtus montebelli) and their compositions were analyzed. Total solids, fat, protein and ash concentrations of vole's milk were very higher than those of cow's milk. The lactose concentration was very lower than that of milk of cow or mouse. The electrophoretic patterns of milk casein of vole were different markedly from those of bovine, but resembled to those of mouse.

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Peripheral neuropathy associated with osteosarcoma of the humerus was reported in a Japanese monkey (Macaca fuscata) . The monkey developed osteosarcoma in the right humerus. Postmortem morphometric analyses on lower limb nerves revealed loss and size reduction of myelinated nerve fibers. Pathological findings including various demyelinative processes were found with electron microscopy. These findings were more predominant in the distal part than in the proximal part of the nerves, which is compatible with axonal degeneration of peripheral nerve fibers. This is the first case found in a monkey of dying-back neuropathy associated with malignancy, which is not infrequent in humans.

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This paper describes the rate of naturally occurring abortion and fetal death that were diagnosed by the use of an ultrasonographical device in 683 pregnant cynomolgus monkeys (Maraca fascicularis) of which 542 were wild-imported monkeys and 141 were colony-bred monkeys. All of these animals had become pregnant by the 3day timed mating system. The combined rate of abortion and fetal death was 7.0% in the wild-imported animals and 7.8% in the colony-bred animals. There were no significant differences in the rate with respect to different ages and to different period of feeding at Tsukuba Primate Center. Seventy-eight per cent (38 monkeys) of the total cases occurred during the first 5 to 9 pregnancy-weeks.

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A inbred strain, ICRF, which can be used as a model of both human cataract and epilepsy is described.The strain was bred from the ICR cataractous rat (Ihara, 1983) . The original ICR strain showed bilateral cataract on 11-12 weeks of age, but the cataractous syndrome frequently disappeared during life. In the new ICRF strain the cataractous syndrome continued through the life, as shown by primary investigation of 38 males and 32 females. Besides cataract, severe epilepsy-like seizures were observed in 90% of the males. Seizures were rare in females (3%) . The life span of the ICRF rats was short, 58% of the males and 6% of the females died before 52 weeks of age.

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Two-cell mouse embryos from four different inbred strains (BALB/c, C3H/He, C57BL/6 and DBA/2) and one closed colony (Slc: ICR) were frozen by direct placement into liquid nitrogen after a 10-15 sec exposure to a highly concentrated solution (DAP 213: 2 M dimethyl sulphoxde, 1 M asetamide, 3 M propylene glycol in PB 1), and later thawed in a 37°C waterbath. The percentages of morphologically normal embryos were 80.7-92.6% on thawing. Morphologically normal embryos were then transferrd to the oviducts of peudopregnant recepients, and 7.4-60.0% of the embryos developed into normal young (BALB/c ; 34.3%, C3H/He ; 30.6%, C57BL/ 6 ; 60.0%, DBA/2 ; 7.4%, and Slc : ICR ; 24.3%) .

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Unfertilized mouse oocytes from inbred strains (BALB/c, C 3 H/He and C 57 BL/6) were frozen ultrarapidly by direct plunging into liquid nitrogen, immediately after exposure to a highly-concentrated solution (DAP 213: 2 M dimethyl sulphoxide, 1 M acetamide, and 3 M propylene glycol in PB 1), and were later thawed in a 37°C waterbath. After thawing, 76.8-90.9 % of recovered oocytes were morphologically normal. Following fertilization in vitro of cryopreserved oocytes, the proportion of 2-cell embryos 24 h after insemination ranged from 70.7% to 83.4 %. Nearly all 2-cell embryos obtained from cryopreserved oocytes were transferred to the oviducts of pseudopregnant recipients and 31.0-43.0% of 2-cell embryos developed into normal young.

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Southern blot hybridization of EcoRI digests of DNAs from 13 rat strains using human cardiac actin gene as a proe revealed polymorphisms in actin-related sequences of rats. EcoRI fragments of 11 kb, 7 kb, 6 kb, 5 kb, 4.5 kb and 4 kb detected in several strains were absent in the remaining strains. The presence of these fragments was suggested to be due to presence of extra sequences homologous to the actin genes, such as processed pseudogenes, in the particular strains. The 13 strains were assigned to each of 7 specific patterns of the polymorphic EcoRI fragments. It was concluded that the polymorphisms of actin-related sequences should be useful for genetic monitoring of laboratory rats.

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