The high emetic response (HER) strain and low emetic response (LER) strain of musk shrews (Suncus murinus) markedly differ in the emetic reflex in adults. However, there have been no studies on young musk shrews. We gave a shaking stimulus to young musk shrews aged 10 days or more that were obtained by mating within each strain and observed emetic responses. In the HER strain, no animal aged 10 days vomited, but vomiting was observed in 1 of 5 animals each aged 12 and 14 days, 2 of 5 animals aged 16 days, and all animals aged 18 days or more. In the LER strain, no vomiting was observed until the age of 14 days, but at the age of 16 days or more, 1 or 2 of 5 animals at each age vomited. After stimulation, activated neurons of the dorsal vagal complex and the dorsal reticular formation of the nucleus ambiguus (Amb) were examined by Fos immunohistochemistry. This morphometric study demonstrated that the numbers of Fos-positive neurons in the nucleus of the solitary tract and the dorsal reticular formation of the Amb were significantly larger in the animals that vomited in the HER strain than animals that did not vomit in the LER strain. We suggest that neurons in these regions are involved in emetic responses, as is the case in adult animals.

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Relationships between the NO synthase inhibitor and gastric and pancreaticobiliary functions measured simultaneously in the digestive state have been little studied. The aim of this study was to estimate the effect of NO synthase inhibitor on integrated digestive function in conscious dogs. A strain gauge force transducer was implanted on the gastric antrum of 6 mongrel dogs to measure gastric contractile activity and two duodenal cannulas were inserted into the proximal and distal sites to measure the gastric emptying rate and the pancreaticobiliary output into the duodenum using our novel method. Postprandial pancreatic and biliary secretion were presented as amylase and bile acid activity, respectively. Furthermore, a cervical cannula was placed into the superior vena cava as a route for the administration of NO synthase inhibitor, N^ω-nitro-L-arginine (L-NNA), at a dose of 2.5 mg/kg-h. In a group given L-NNA, gastric contractile activity after ingestion was significantly enhanced, but the emptying rates of gastric solids and liquids were significantly suppressed in comparison with the control. The mean 0-1 h amylase integrated output was significantly (P<0.05) decreased in comparison with the control, and the mean bile acid integration of 0-1 h output was also significantly (P<0.01) decreased. A possible explanation for this observation is that smaller volumes of nutrient are delivered into the duodenum; however, it could also be that postprandial pancreaticobiliary secretion is inhibited by an alteration of blood flow or by a change in contractions of the sphincter of Oddi after the administration of L-NNA.

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In 183 male progeny derived from a backcross between the FGS/Kist strain, a new mouse model for focal glomerulosclerosis (FGS) in humans, and the standard normal strain, C57BL/6J, we performed a genome-wide scan for quantitative trait loci (QTLs) affecting the glomerulosclerosis index (GSI) based on histological observation as well as kidney and body weights. Two QTLs for GSI (Gsi1-2) located on chromosomes (Chrs) 8 and 10, a kidney weight QTL (Kdw1) on Chr 19, and a body weight QTL (Bdw1) on Chr 13 were detected at the genome-wide 5% or less level. The allele derived from FGS/Kist increased GSI at Gsi1, but decreased it at Gsi2. The mice homozygous for the FGS/Kist allele decreased body and kidney weights. The identified QTLs accounted for 5-8% of the phenotypic variance.

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A spontaneous mutant having small testes was found in a laboratory mouse strain of mixed origins. The testis size was 1/3-1/2 of normal size, but no significant difference was seen in body mass and weight of organs such as kidney and seminal vesicle, which are influenced by androgen. Small testis males were found to be infertile by the mating test, although formation of a vaginal plug was normally observed in their female partners. Histological and air-dried specimens revealed degeneration of zygotene or early pachytene spermatocytes and very few numbers of pachytene and diplotene spermatocytes, round and elongate spermatids and mature spermatozoa in the mutant testis. Therefore, it was concluded that spermatogenesis is disrupted at the zygotene to early pachytene stages of meiosis in the mutant males. Segregation ratios of normal and mutant males were in accord with the assumption that the small testis character is caused by an autosomal recessive mutation. This mutant may be useful for research that would contribute to the elucidation of genetic mechanisms controlling the process of spermatogenesis and as a model animal for male infertility in humans.

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We found a novel recessive mutation in an inbred strain, INT, that was derived from an ICR closed colony. Mice homozygous for this mutation are identified by severe anemia, dysgenesis and neonatal death. This mutation was tentatively named int. Intercrosses of int heterozygotes (+/int) and the flaky skin heterozygotes (+/fsn) resulted in abnormal mice (int/fsn heterozygotes) showing anemia and flaky skin with the expected frequency for autosomal recessive mutation. The int gene was therefore named fsn^Jic as an allele of the fsn locus on chromosome 17. We carried out phenotype analyses using B6.INT- fsn^Jic mice to observe phenotypes of blood and skin in the embryonic and neonatal stages. Discrimination of fsn^Jic embryos from normal embryos was performed by an indirect diagnosis of the fsn^Jic gene using the D17Mit130 microsatellite marker tightly linked to the fsn locus. The number of fetal nucleated RBC of normal embryos decreased gradually to 17.5 dpc, but that of the abnormal embryos decreased to 14.5 dpc followed by a gradual increase to 17.5 dpc. Skin of fsn^Jic embryos did not show any abnormalities and expressed cytokeratins normally as skin epithelial cell markers at each embryonic stage (15.5 dpc to 18.5 dpc). Time differences in the appearance of the different phenotypes observed in various tissue and organs of fsn homozygotes suggest they are caused by expression of the fsn gene at different developmental stages.

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Adult NMRI mice were superovulated using human menopausual chorionic gonadotropic hormones (hMG and hCG), and then some of them were daily injected with progesterone (1 mg/mouse). At 3.5 and 4.5 days after hCG injection scanning electron micrographs revealed that the hyperstimulated and progesterone-injected group had well-developed pinopodes while most of the hyperstimulated group without progesterone injection had no pinopodes 3.5 days after stimulation. The results suggest that the lifespan of pinopodes is short and changeable during hyperstimulation and that progesterone causes premature formation of the pinopodes and that implantation after ovarian stimulation might depend upon the timing of the pinopode expression.

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In the present study, embryo transfer was performed using frozen-thawed embryos to establish a SPF colony of human apolipoprotein (a) (apo(a)) transgenic rabbits. Apo(a) transgenic rabbits were kept under conventional condition and were infected with Bordetella bronchiseptica. Embryos at the morula stage were collected and stored in liquid nitrogen. After thawing, the in vitro survival rate was 84.6%, and 125 morphologically normal embryos were transferred to 6 SPF recipient rabbits. Four rabbits became pregnant and 23 live pups were born. PCR and Western blot analyses revealed that 9 of 23 pups were transgenic and expressed apo(a) protein. Microbiological tests showed all rabbits were free from infections. We succeeded in establishing a SPF colony of apo(a) transgenic rabbits. These rabbits are now maintained under a barrier system and are available for medical research.

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Mycoplasma pulmonis and Mycoplasma arthritidis were differentially identified using PCR-restriction fragment length polymorphism (RFLP). A genus-specific sequence of mycoplasma was amplified by PCR and the PCR products were digested with the restriction enzyme SmaI. Each PCR product from the four isolates of M. pulmonis was digested with SmaI into two fragments; however, there was no digestion in the PCR product from M. arthritidis. This method might be useful to differentiate infection of M. pulmonis from that of M. arthritidis.

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Syrian hamsters of the APA strain (APA hamsters) are known to show continuous diabetes accompanied by its complications, such as glomerulosclerosis and atherosclerosis, following a single injection of streptozotocin (SZ). Recently, we observed Stanford type B aortic dissection in three diabetic APA hamsters and histopathological analysis was performed. The histopathologic observations in the false lumen, such as proliferation of granulation tissues, neointima and pseudoneointima, corresponded to the non-thrombosed type of human aortic dissection, and blood clots of the thrombosed type were similar to the remodeling structures of aortic dissection found in human cases. Thus, this model may be useful for investigating the etiology and pathogenesis of aortic dissection accompanying diabetes mellitus in humans.

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This study investigated the lactating stage of rats to determine the effect on maternal behavior of a single exposure to general anesthetic. Lactating Wistar rats were treated with anesthetic doses of pentobarbital (PENT) or ketamine (KET) on day 3 or 9 of lactation, and their behavioral responses were evaluated during a 50-min nursing period, after a 4-h mother-pup separation, on day 12. Exposure to KET on day 9 led to a significantly longer latency to pup-retrieval than that of the control. Duration of pup-retrieval in mothers treated with KET on day 3 and 9 was significantly longer than in the control. Other components of maternal behavior did not differ between the groups. The present findings suggested that general anesthetics have an impact upon pup-retrieval activities, which indirectly represent maternal motivation.

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We attempted to determine the number of sperm cells required for genotyping of one microsatellite marker. The crude genomic DNA extracted from about 760 or more sperm cells gave sufficient quantity of PCR product using a 20 μl-scale PCR. We also studied the effects of non-ionic detergents on extraction of crude sperm genomic DNA. PCR products amplified with the crude sperm genomic DNA extracted using the lysis buffer supplemented with non-ionic detergents showed much clear bands. In conclusion, our results suggest that a small part of the frozen sperm, which is less than 1/10 of the original volume (10 μl), provides sufficient quantity of template DNA for genetic quality testing.

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