Human essential hypertension is generally recognized as a multifactorial disease involving the interplay of environmental factors based on genetic diathesis. Spontaneously hypertensive rats (SHR) and Dahl rats are widely used as animal models for human essential hypertension and salt-sensitive hypertension, respectively. The definitive genetic factor ruling the development of hypertension in these strains remains unclear, but recently advances in embryonic engineering and molecular biological techniques may make it possible for transgenic mice and gene-targeted mice to become important pathological models defined genetically and functionally for human disease. The author developed two types of genetically engineered mice that may serve as such models: a transgenic mouse with hypertension caused by enhancing the renin-angiotensin system and a gene-targeted mouse with hypotension caused by disrupting the renin-angiotensin system.

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The number of ovulated oocytes in the adult house musk shrews was examined by natural mating. The positive rate of ovulation was 83.3%, and the mean number of ovulated oocytes was 4.4 ± 1.9 (Mean ± SD). The induction of superovulation was examined by administering either pregnant mare's serum gonadotropin (PMSG) or human chorionic gonadotropin (hCG), exogenous gonadotropin, to house musk shrews. As a result, the number of ovulated oocytes were within the number of oocytes ovulated spontaneously. The method of superovulation induction by administering both PMSG and hCG to house musk shrews was investigated. In the group injected intraperitoneally with 7.5 iu of PMSG followed by 7.5 iu of hCG 48 hr later, the positive rate of ovulation was as high as 94.6% and the mean number of ovulated oocytes was 11.7 ± 13.4. Moreover, in 15 out of these 35 animals positive for ovulation,10 oocytes or more were observed and the mean number of ovulated oocytes was 21.0 ± 16.5, showing the superovulatory response. In the group of 5.0 iu PMSG and 5.0 iu hCG injected at an interval of 72 hr, every animal was induced to ovulate and the mean number of ovulated oocytes was 41.3 ± 19.9. Thus, the injection of PMSG and hCG at a longer interval increased the number of superovulated oocytes. Furthermore, 97.5% of eggs recovered from superovulating animals contained cumulus cells.

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Carmellose sodium (1.5%), dissolved in physiological saline, was given for 4 days via oral, subcutaneous or intraperitoneal routes. In the rats treated with carmellose sodium by the parenteral route, hepatic sinusoidal component cells and free macrophages were swollen. The degree of the swelling was more severe in the rats treated by the intraperitoneal route than by the subcutaneous route. The swollen sinusoidal component cells which engulfed the carmellose sodium-related substance were classified as Kupffer's cells or Ito cells by immunohistochemical reaction. Ito cells were isolated from a 5-week-old rat and were cultured in Dulbecco's modified Eagle's medium (DMEM). Some of the Ito cells which were cultured in DMEM containing 0.3% carmellose sodium showed phagocytic properties; vesicles in their cytoplasm and other Ito cells which were cultured in DMEM containing India ink contained some carbon particles.

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Povidone-iodine solution is widely used to disinfect the skin surface or prevent suppuration during human and animal surgery. Using radioisotope ¹²⁵I, we examined whether iodine may be absorbed and then concentrated in the thyroid gland when povidone-iodine solution is applied to the skin of rats or mice. The competition for ¹²⁵I uptake was examined in mice and rats after the application of povidone iodine to the skin. We also traced the process of absorbed ¹²⁵I in the thyroid gland during the fixation for tissue preparations. Povidone-iodine applied to the skin significantly reduced the uptake of ¹²⁵I both in mice and rats. Significant flux of ¹²⁵I from the thyroid gland in povidone-iodine treated animals was noted during the thyroid fixation of tissue preparations. From these results, povidone-iodine application to the skin instead of stable KI administration may be practical for preventing the uptake of ¹²⁵I by the thyroid gland during ¹²⁵I compound administration for medical therapy. In animal experiments concerning thyroid functions, careful attention must be paid when povidone-iodine is used for disinfection in animal surgery.

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Immunohistochemical study was carried out on D-galactosamine hydrochloride (GalN)-induced subacute hepatitis in rats of JCL: Wistar-TGN (ARGHGEN) 1Nts strain (Mini rats), in which the expression of growth hormone gene is suppressed by the presence of an antisense transgene. Mini rats were given 1000 mg/kg of GalN once a week for 4 consecutive weeks and killed at 1, 2, 3 and 4 weeks after the first administration. At 1 week after the first administration, proliferation of small epithelial cells positive for both a-fetoprotein and cytokeratin 7, i.e. so-called oval cells, was observed in the whole area of each hepatic lobule, and prominent deposition of fibronectin, laminin and type IV collagen was detected around these oval cells. Together with these extracellular matrix components, many activated Ito cells positive for both desmin and α-smooth muscle actin were obsereved. With time, most of the oval cells formed duct-like structures and lost their positive stainability for α-fetoprotein, and many Ito cells became inactive. Deposition of fibronectin decreased rapidly from 2 weeks after the first administration. At 4 weeks after the first administration, deposition of laminin was detected only around the duct-like structures, where that of type IV collagen was also still prominent. These results suggest that a large population of oval cells differentiated into bile duct epithelial cells and that Ito cells and extracellular matrix components might play a role in this process.

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This study was performed to examine mouse age-dependent changes in susceptibility to MHV-2-CC-infection and participation of macrophages in such changes in BALB/c mice. One-week-old mice were fully susceptible (mortality, 100%), 2-week-old semi-susceptible (36%), and 3- and 4-week-old fully resistant (0%) to MHV-2-CC, respectively. Such age-dependent differences corresponded well with the differences in the virus titers in the liver, spleen and blood and in the severity of liver lesions. In 1-week-old mice with peritoneal exudate cells (PEC) transferred from 4-week-old mice and infected with MHV-2-CC, a slight prolongation of survival time was recorded, although there was no difference in mortality. In 3-week-old mice infected with MHV-2-CC after silica-treatment to suppress macrophages, there was no significant change in susceptibility. In macrophages infected with MHV-2-CC in vitro, the virus replicated better in macrophages obtained from younger mice. These results suggest that macrophages may play a small role in the age-related development of resistance to MHV-2-CC infection in BALB/c mice.

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In this experiment, we examined the protective effects of a novel quinone derivative, E3330, on MHV-2cc-induced chronic hepatitis in athymic nude mice for up to 3 weeks after virus infection. The daily dose of 25 mg/kg b.w. suppressed the viral replication in the liver and the progression of hepatic lesions. The expansion of small focal lesions at 1 week after viral inoculation (WAI) was suppressed at 2 WAI, and the lesions were still small at 3 WAI in E3330-administered group, whereas small focal lesions at 1 WAI were expanded at 2 WAI to fuse with each other at 3 WAI in the control group. E3330 therefore showed protective effects on MHV-2cc-induced chronic hepatitis in athymic nude mice, but further studies are needed to analyze the mechanism.

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A naturally occurring epizootic of dermatitis involved all the mice, provisionally designated as DS-Nh, housed under conventional conditions, regardless of age or sex. The disease primarily attacked the lateral aspect of the face, neck and shoulders. The histopathologic features of the dermatitis varied in severity, but all affected regions showed signs of chronic dermatitis, including infiltration of inflammatory cells, parakeratosis and amyloidosis, and contained Gram-positive cocci clusters. Bacteriologically, coagulase-positive Staphylococcus aureus (S. aureus) was recovered in pure culture from the skin lesions. The disease experimentally induced with the S. aureus isolates was indistinguishable from those observed in naturally occurring cases. The results suggested that S. aureus may be causally associated with the disease.

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Mouse pronuclear oocytes and 2-cell embryos derived from in vitro fertilization were cryopreserved by a novel simple vitrification procedure. Most cryopreserved oocytes/embryos were morphologically normal after warming, and 89-92% of them developed to the blastocyst stage during the culture. Moreover, the rate of morphologically normal pronuclear oocytes after being repeatedly cooled and warmed three times was as high as that of oocytes cooled and warmed only once, and 85% of them developed to the blastocyst stage. In addition, 43-57% of the cryopreserved oocytes/embryos transferred to recipients had developed normally to live fetuses observed on day 18.5 of pregnancy.

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TM rats have a light brown hooded coat pattern resembling that of Fawn hooded (FH) rats which are a model of platelet storage pool deficiency (SPD). We examined whether the TM strain has the same platelet SPD as the FH strain. TM rats had a prolonged bleeding time and a low blood serotonin level, although their blood coagulation time and platelet counts were normal. The light coat color of the TM strain was judged to be associated with the red-eyed dilution gene as in the FH strain, but not pink eye dilution as in the RCS rat strain. Platelet SPD seen in TM rats may be a pleiotropic effect of the red-eyed dilution gene proposed in FH rats. Despite these similarities, the genetic background of the TM strain was obviously different from that of the FH strain. The TM strain, developed independently of the FH strain, will therefore be used as a model of platelet SPD.

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The inactivation efficacy of eight disinfectants commonly used in laboratories and animal rooms to inactivate Pneumocystis carinii cysts was estimated by experimental infection in C.B-17-scid mice. The disinfectants examined in this study were 70% ethyl alcohol, 10% iodoform, 0.5% hypochlorous acid, two 1% quanternary ammonium salts, 3% hydrogen peroxide, sodium chlorite and 1% cresol soap. The lung homogenates from P. carinii infected C.B-17-scid mice were treated with each disinfectant for 15 min at room temperature, washed with saline, and inoculated into C.B-17-scid mice. Eight weeks after inoculation, lungs from these mice were examined by staining with toluidine blue O to detect P. carinii cysts. PCR amplifying 346 bp of P. carinii specific mitochondrial ribosomal RNA large segments was also performed using DNA extracted from the lungs of the mice. As a result, seven disinfectants, excepting for 0.5% hypochlorous acid, were effective in the inactivation of P. carinii cysts. These results suggest that P. carinii cysts were sensitive to chemical disinfectants even though they have been commonly considered as insensitive.

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The present study was to clarify the relationship between voluntary exercise and follicular growth or ovulation. Rats kept for 4 weeks in a rotating drum with free access to the wheel, food and water ran 2-12 km per day. The number of ova shed after superovulation treatments and the number of non-atretic follicles were not influenced by voluntary exercise. These experiments demonstrate that spontaneous voluntary exercise does not affect either the number of ova shed or the number of non-atretic follicles in superovulating rats or control rats.

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