No comparative study about somatosensory evoked potentials (SEP) on different rat strains has been done yet. It is evident that comparative SEP studies are important since different rat strains have different physiological properties. We aimed to compare early latency SEP values from stimulation of sciatic nerve in Wistar (Wr) and Sprague-Dawley (SDr) rats which are frequently used rat strains in experimental studies. In Wr group, the mean of first far field potential (Ff1) latency was shorter and the mean Ff1 amplitude was lower than that of Sprague-Dawley rat group. Mean cortical potential latency in Wr group was longer than that of SDr group while amplitude was not different. Central conduction time (CCT) in Wistar rat group was found to be longer than that of SDr group. Shorter Ff1 latency in Wr group implies that afferent volley reaches cervical posterior fasciculus from sciatic nerve earlier than SDr group while longer CP latency implies that afferent volley reaches cortex later than SDr group. Similarity between the latencies of lumbar potentials implies that peripheral conduction velocity has no effect on the difference of Ff1 latencies.

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The aim of this study was to examine the effects of gonadotrophin treatments on estrus synchronization and superovulation in young Sprague-Dawley (SD) rats that had not yet exhibited defined estrus cycles (5 to 7 weeks old), and to produce transgenic rats using these females as embryo donors and recipients. In Experiment 1, female rats were injected with PMSG and hCG (12.5, 25, 50 and 100 IU/kg each) and were mated with stud males. The reproductive performance of young rats were highest when PMSG and hCG at doses of 25 IU/kg each were injected (delivery rate 87.5%, nursing rate 92.9%). In Experiment 2, female rats were injected with PMSG and hCG (100, 150 and 300 IU/kg each) to induce superovulation. More eggs were recovered from the rats injected with PMSG and hCG at 150 and 300 IU/kg than from those treated with 100 IU/kg (33.4 and 41.3 vs. 13.3 eggs per female, respectively; p<0.05). In Experiment 3, pronuclear-stage zygotes from 150 IU/kg PMSG/hCG-treated rats were used for microinjection of the fusion gene of bovine αS1-casein gene promoter and human growth hormone gene (2.8 kb), and the microinjected zygotes were transferred into the oviduct ampullae of the 25 IU/kg PMSG/hCG-treated rats. Seventeen transgenic rats were obtained from the 334 DNA-injected zygotes (5.1%). These results indicate that recipients and embryo donors for the production of transgenic rats can be prepared by the appropriate PMSG and hCG treatments of young SD rats, regardless of their estrus stages.

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Cough elicitation and major physiological factors influencing cough occurrence were investigated in congenitally bronchial-hypersensitive (BHS) and -hyposensitive (BHR) guinea pigs exposed to citric acid (0.3 M) aerosol for 10 min. The number of cough in BHS was significantly larger than in BHR, while the latency to cough in BHS was significantly shorter than in BHR. Pretreatment with atropine (0.2%), lidocaine (2%) or salbutamol (0.1%) aerosol and desensitization of C-fibers with capsaicin (100 mg/kg) decreased the cough numbers in both BHS and BHR. The salbutamol, atropine and capsaicin pretreatments prolonged the cough latency in BHS, but only salbutamol prolonged the latency in BHR. After salbutamol pretreatment all BHR guinea pigs exhibited cough, while 66.7% of BHS guinea pigs exhibited it. Vagal blocking by atropine suppressed coughing in both BHS and BHR. Only a small number (33.3%) of BHR guinea pigs and no BHR guinea pigs exhibited a cough response after capsaicin and lidocaine pretreatment whereas many BHS guinea pigs still produced cough after such pretreatment. The present study demonstrated that the cough responsiveness to citric acid aerosol was significantly higher in BHS than in BHR. It was revealed that airway smooth muscle contraction and functional and/or morphological development of airway nervous receptors, especially C-fiber endings, contributed to aggravation of coughing in BHS.

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Although isolation racks are superior to open-type racks in terms of securing breeding conditions for laboratory animals, the contingency-proofing capability of the former has yet to be determined. Therefore, from the view of risk management, we studied the environmental change in isolation racks by forcibly suspending ventilation and air-conditioning and confirming the maximal time length for complete recovery to the original condition after restarting their operations. The isolation racks were placed in a room that was equipped with an independent air-conditioning system. When the inside condition of the racks reached 22-24°C and 59-64% of relative humidity, the air-conditioning and ventilation were forcibly suspended and the subsequent temperature, relative humidity, ammonium and CO₂ concentrations in the racks were measured over time. We found that after suspending the air-conditioning and ventilation, it took 40-60 min for temperature, and about 10 min for relative humidity to exceed the maximum values (temperature and relative humidity) referred to in the Showa 58 Nenban Guideline Jikken Doubutsu Shisetsu no Kenchiku oyobi Setsubi (Guidelines of buildings and facilities for experimental animals in Japan; Year 1983 edition). After 17 hr 25 min of the suspension of air-conditioning and ventilation, two rats were found dead. Then, the air-conditioning and ventilation were restarted. It took about 2 hr for temperature, and 50 min for relative humidity to regain the guideline values. The ammonium concentration stayed within the guideline value with a maximum concentration of 2 ppm in the experimental period, whereas the CO₂ concentration was found to exceed 9% at the time of animal death.

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This study presents a histological examination of dextran sodium sulfate (DSS)-induced colitis in germ-free (GF) mice. A comparison of the pathology between GF and conventionalized mice (CVz) was made to determine the role that intestinal microflora play in DSS-induced colitis. To induce colitis, GF and CVz IQI/Jic mice were given either 5% or 1% DSS orally. Administration of 5% DSS, a common concentration used to induce colitis in mice, caused gross rectal bleeding and a marked decrease in hematocrit as early as day one in GF mice. These mice died on day three due to massive bleeding into the intestinal lumen. In contrast, CVz mice did not die during the seven-day experimental period. Histopathological examination three days after administration of 5% DSS did not reveal any colitis lesions in GF mice, but CVz mice had developed moderate colitis in the large intestine. Administration of a low concentration of DSS (1%), which only induces mild basal crypt loss in CVz mice, caused severe colitis in the distal colon in GF mice, and they died on day 14. These data suggest that intestinal microflora are not necessary for the induction of colitis. Furthermore, DSS may be highly toxic to GF mice, and when given at a concentration of 5% it causes massive bleeding into the intestinal lumen resulting in death prior to development of colitis.

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The Biosafety Committee of the Japanese Association of Laboratory Animal Facilities of National Universities (JALAN) investigated recent episodes of microbiological contamination in genetically modified mice (GMM), and the countermeasures taken when the contaminated GMM were introduced into animal facilities, by questionnaires addressed to 53 animal facilities belonging to JALAN and serological tests. Although almost all of the contaminated GMM were accepted with conditions such as rederivation after or before reception and housing in designated rooms, contamination with a spectrum of microorganisms was demonstrated in GMM transferred domestically and from abroad. In serological tests, Mycoplasma pulmonis, mouse parvovirus, and mouse encephalomyelitis virus were detected in GMM transferred from domestic facilities and from abroad. The present results of the questionnaires and serological tests suggest that GMM are highly and widely contaminated with microorganisms compared with mice from commercial breeders. Thus, we propose a microbiological requirement, including microbiological status - excellent, common, and minimum - as a guide for the transfer and procurement of mice and rats in Japan.

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We studied the characteristics of the rhythmicity of heart rate (HR), body temperature (BT), and locomotor activity (LA) in conscious and unrestrained guinea pigs using a telemetry system. HR and/or LA in some guinea pigs clearly showed circadian rhythms, but in others there were no significant daily patterns; BT did not show significant daily rhythms. These results suggest that guinea pigs might have different individual characteristics of rhythmicity, and we should, therefore, be careful when using guinea pigs in chrono-biomedical research. We believe that the results of this study may be useful for future biomedical studies using guinea pigs.

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We found a new inner ear mutant exhibiting abnormal behavior, such as circling and head shaking, in a breeding stock of SJL/J mice. The traits are inherited in a simple autosomal-recessive fashion. Animals homozygous for the responsible gene, designated cosa, show no startle response to sounds and an inability to swim. In the inner ears of cosa/cosa homozygous, but not +/cosa heterozygous adults, histopathological features of severe damage that are typical for `cochleo-saccular' or `spotting' mutants have been demonstrated. We suggest here that the abnormal mice carry a mutation of a gene that is developmentally switched on in the early stages of development and is involved in endolymph homeostasis.

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We performed a histopathological investigation on arteriosclerotic development in the influx and intravisceral arteries of the liver, kidney and lung of male WHHL rabbits. In the influx arteries of these organs, we observed severe atherosclerotic vascular lesions with high-grade luminal stenosis. In the intravisceral arteries of the liver and kidney, no arteriosclerotic lesions were observed. However, in the intrapulmonary arteries, we recognized severe atherosclerotic vascular changes with high-grade stenosis or total obstruction of the lumen in some middle to large sized pulmonary arteries. These observations indicate that the development of arteriosclerosis in parenchymatous organs differs, and that some organs are predisposed to arteriosclerosis formation.

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The EDS (early-onset diabetes in suncus) colony was developed as a new laboratory colony of the musk shrew and is characterized by a high incidence of early-onset spontaneous non-insulin dependent diabetes mellitus (NIDDM). We examined blood lipid (triglyceride [TG], total cholesterol [TC], phospholipid [PL], free fatty acid [FFA]) and liver lipid (TG, TC, PL) concentrations to investigate the features of lipid metabolism in these animals. All lipid concentrations examined both in blood and liver of the diabetic shrews had a tendency toward higher values than those in non-diabetic shrews. The PL concentration was the only parameter that barely showed a significant difference. Values for all blood lipid concentrations in diabetic shrews at 7-9 months tended to be higher than those of 2-month-old diabetic shrews, although the difference was not significant. These findings indicate that diabetic EDS shrews exhibit a much milder defect of lipid metabolism induced by NIDDM than other rodent models.

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The EDS colony, developed as a new laboratory colony of the musk shrew, is characterized by a high incidence of early-onset spontaneous non-insulin dependent diabates mellitus (NIDDM). In this colony, a few diabetic shrews exhibited a cataract at 1 month after the onset of diabetes, and all diabetic shrews had bilateral cataracts at 5 months after the onset of diabetes. In contrast, cataractous animals were never observed among non-diabetic shrews. These results suggest that the cataract in the EDS colony is a diabetic complication.

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An allele specific polymerase chain reaction (PCR-SSP) assay for genotyping the mouse leptin receptor (Lepr^db) mutation and its wild type (Lepr⁺) gene was developed using two different fluorescent dye-labeled primers. First, we determined the Lepr^db and Lepr⁺ allele by PCR-SSP assay with usual dye-unlabeled primers. However this method requires two separate PCR reactions because the amplified products specific for each allele are almost the same size. We further developed a simple and reliable two-color PCR-SSP method that uses a color complementation strategy to distinguish the Lepr ^db and Lepr⁺ alleles. Lepr^db/Lepr ^db, Lepr^db/Lepr⁺ and Lepr⁺/Lepr⁺ of mice (5 each ) were clearly genotyped by the two-color PCR-SSP. We also performed PCR-direct sequencing for the same samples and confirmed the accuracy of this method. This method makes it possible to reduce the number of PCR reactions because both alleles are amplified in the same reaction mixture.

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The temporary preservation of oocytes without freezing would be useful for some experiments. ICR mouse oocytes were kept in a preservation medium under mineral oil for 1, 2, 3, 4 or 7 days at 5°C, and 1 or 2 days at 37°C. In vitro fertilization was attempted on oocytes rinsed with TYH medium after preservation. More than 70% of morphologically normal oocytes were recovered from each preservation group. Fertilization rates of oocytes preserved for 1, 2, 3, 4 or 7 days at 5°C were 69.9, 66.5, 45.3, 26.7 and 8.8% respectively. Fertilization rates of oocytes preserved for 1 or 2 days at 37°C were 9.6 and 1.6%, respectively. Preservation of oocytes at 5°C has some capability as a method of short-term storage without freezing.

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We compared tyrosine hydroxylase immunoreactivity in the substantia nigra and hypothalamus of hereditary microphthalmic rats with that of normal rats. A considerable number of neuronal cell bodies expressing tyrosine hydroxylase were present in the substantia nigra of the microphthalmic mutant as well as normal rats. Neuronal cells positive for tyrosine hydroxylase in the hypothalamus were fewer than in the substantia nigra in both rats. The concentrations of monoamines (dopamine, noradrenaline, adrenaline, and serotonin) in the substantia nigra and hypothalamus in the microphthalmic mutant were approximately the same as those of normal rats, although the diurnal fluctuation of a few monoamines was observed in normal rats. These results suggest that the metabolic aspects of catecholamine in the substantia nigra and hypothalamus of the microphthalmic mutant rat do not markedly differ from those of normal rats.

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Adrenal glands of small smooth-tailed tree shrews (Dendrogale murina), four males and two females, caught and fixed in Thailand were observed macroscopically and histologically. They were located at the cranio-medial sides of the kidney. They were elongated in shape and consisted of a cortex and medulla. The cortex could be subdivided into three zones by the cell arrangement and the morphology of nuclei, cytoplasm and cell strands, like in other mammalian species. The tree shrew seemed to share more morphological characteristics with some laboratory rodents than some of non-human primates.

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