Osteopetrotic (op/op) mice show severe osteosclerosis caused by an inherited deficiency of osteoclast and resultant failure of tooth eruption, which can be cured by the injection of macrophage colony-stimulating factor (M-CSF). The present study revealed that concecutive injections of M-CSF in these mutant mice brought about a recovery of bone resorption resulting in the resumption of growth of tooth root and periodontal ligament. Bone resorption at the inner surface of bony crypts was noted on the 5th day after the start of M-CSF injections. This activity was reduced with the progress of root and periodontal ligament formation, being confined to the basal and crestal portion of bony crypts by the 15th day of the experiment. Second molars emerged into the oral cavity on the 15th day, but no eruption of first molars was observed until the 20th day. Throughout the experiment, first molars exhibited appreciable root deformity, which was less severe in second molars. Delayed eruption of first molars was thought to be related to the severity of the distubance of root formation.

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IQI/Jic mice showed a high incidence of subcapsular spindle cell hyperplasia (SCH) in the adrenal cortex accompanied by prominent mast cell infiltration. SCH-positive animals appeared as early as at 3 months of age, with an incidence of 18% in males and 20% in females. Except for one mouse, all females older than 6 months had the lesion. In males, the incidence increased gradually until 9 months, and was then stable at 75-88% thereafter. The severity of SCH increased with age in both sexes, and the lesions were more prominent in females. Mast cells infiltrated mainly at the sites of spindle cell hyperplasia, and their density was associated with the severity of the lesion. A quantitative morphometric study confirmed a significant correlation between the severity of SCH and the density of mast cells. A histochemical study demonstrated that these mast cells were of the connective tissue-type. These observations indicate that IQI/Jic mice may be a useful strain to elucidate the pathogenesis of SCH in the adrenal cortex in association with mast cell function.

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In-vivo viability of frozen-thawed embryos derived from transgenic rats, as well as the transmission and the expression of transgenes in the resultant newborn rats, was investigated. Three strains of transgenic rats, carrying human growth hormone gene connected downstream to the promoter region of the bovine a-lactalbumin gene (αLA/hGH), bovine β-casein gene (βCN/hGH) or bovine α-S1 casein gene (αS1CN/hGH), were used. Two-cell stage embryos (non-transgenic Wistar female × heterozygous transgenic male) were placed in 10% (v/v) dimethylsulfoxide (DMSO) solution and cooled from -7 to -30°C at -0.5°C/min before being plunged into liquid nitrogen. After 2 to 4 years storage, the embryos were thawed by rapid warming. The intact embryos were transferred into the oviducts of Day 1 pseudopregnant recipients. The postthaw survival rate of frozen embryos was high in all 3 transgenic strains (88 to 92%), which was similar to that of control (non-transgenic) frozen embryos (95%). Development to newborn rats following transfer of embryos derived from the 3 strains (64 to 68%) was also similar to that of control embryos (60%). These transgenes (αLA/hGH, βCN/hGH and αS1CN/hGH) were detected in the DNA extracts from tail tissue of the newborn rats, but the transmission rates (41, 23 and 32%, respectively) were lower than 50% which is expected in the Mendelian fashion. In a transgenic line carrying αS1CN/hGH, hGH levels of secretion into the milk of transgenic newborn rats derived from frozen-thawed embryos and her transgenic offspring were the same mg/ml-level as that of their founder rat. Two-step freezing of embryos derived from transgenic rats was therefore an effective method for the long-term cryopreservation of transgene.

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Female ICR:CD-1 mice orally treated with 10 mg/kg b.w. of T-2 toxin were killed at 1, 3, 6, 9, 12, 24 and 48 hr after treatment (HAT) and subjected to examination of the process of the development of T-2 toxin-induced apoptosis in the thymus and spleen. The early ultrastructural changes in lymphocytes characterized by shrinkage of the cell body and condensation of nuclear chromatin were detected at 3HAT in the thymus. The number of apoptotic lymphocytes observed by the in situ detection method for fragmented DNA increased drastically from 9 to 24 HAT in the thymus while it began to increase at 12 HAT in the spleen. The DNA ladder was first detected by agarose gel electrophoresis at 9 HAT and became clearer at 12 and 24 HAT in the thymus but was not clearly detected in the spleen throughout the observation period. Thus T-2 toxin-induced apoptosis developed earlier and was apparently severer in the thymus than in the spleen. Apoptois was first detected by electron microscopy, then by the in situ detection method for fragmented DNA, and finally by DNA agarose gel electrophoresis.

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It is well known that the Brown Norway (BN) rat strain exhibits airway hyperresponsiveness to exposure to allergens or some chemicals. We investigated the histological characteristics of the trachea and lungs of this strain (10-week-old and retired animals) and compared them with those of age-matched Fischer 344 (F344) rat strain. No histological differences between two strains in tracheal epithelial cells were detected, but differences in the distribution and development of submucosal glands were clarified by the observation of serial sections cut at intervals of 100 μm. Submucosal glands of BN strain were larger in the number and better-developed than those of F344 strain, especially in the middle and lower trachea. Similar results were also obtained in scanning electron microscopic observation of resin casts. There were no significant differences between two strains in the lectin histochemical characteristics of the cytoplasm of glandular epithelial cells. No age-related changes in these morphological characteristics in the two strains were observed. These results suggest that mucin from submucosal glands is quantitatively different but qualitatively similar in the two strains. In addition, microgranuloma mainly composed of histiocytes and eosinophils was observed in the lungs of the BN strain rats.

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In an IDDM model mouse which was inoculated with a diabetogenic variant, DK-27, of encephalomyocarditis (EMC) virus, the relation between a stable glycated hemoglobin A_1c (St-HbA_1c) level and plasma glucose level (PGL) in the progress of diabetes was studied. The St-HbA_1c level and PGL were examined every 2 weeks for 10 weeks in normal male DBA/2 and IDDM-onset mice. PGLs of normal control mice did not change, but their St-HbA_1c levels were slightly increased by 0.52 to 1.03%. On the other hand, in IDDM mice, their PGLs were greatly increased (>400 mg/dl) and hyperglycemia was maintained throughout this observation period, with their St-HbA _1c noticeably increased to 3.8% according to the progress of diabetes for 10 weeks. A highly significant correlation between St-HbA_1c levels and averaged PGLs for the past weeks was found in IDDM mice. To examine the reflection of St-HbA_1c levels to delicately varied PGLs, we also estimated both values in IDDM mice which were treated with insulin at a minimal effective dose once a day for 4 weeks. The St-HbA_1c levels in insulin-injected IDDM mice were significantly lower than those in control IDDM mice. These findings suggest that the estimation of the St-HbA_1c level is useful in following up blood glucose control in a long-term therapeutical study with small laboratory animals.

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In normal rats, 24-hr water-deprivation was found to cause a significant increase in the plasma concentration of arginine vasopressin (AVP), and marked induction of Fos in the AVP-positive magnocellular neurons in the paraventricular nucleus (PVN) and the supraoptic nucleus (SON) of the hypothalamus. On the other hand, 24-hr water-deprivation also caused a significant increase in the plasma AVP concentration in hereditary microphthalmic rats, but much less than in normal rats. Consistent with this, the extent of induction of Fos in the nuclei of the PVN and SON of these rats was lesser than in normal rats. These results suggest that hereditary microphthalmic rats have a defect or decrease in the response to water-deprivation of vasopressinergic magnocellular neurons in the PVN and SON.

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Light and electron microscopic examinations were carried out on the dorsal skin to which hydrogen peroxide (HPO) (3, 6, and 10%) was topically applied for 7 consecutive days in Wistar rat-derived inbred WBN/Kob-Ht rats which have an autosomal dominant gene responsible for their characteristics of hypotrichosis. In addition to focal epidermal thickening, keratinocyte necrosis, dermal mononuclear cell infiltration and focal detachment of the epidermis from the dermis by fluid-filled spaces were detected. This is thought to be brought about by edema due to prominent capillary endothelial damage in the superficial dermis. The damage to keratinocytes and capillary endothelial cells was thought to be induced by HPO itself and free radicals generated by HPO. In addition, these changes were apparently more severe in WBN/Kob-Ht rats than in Wistar rats used as controls.

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Sensitivities to antitumor drugs of human tumor xenografts (HTXs) implanted in C.B-17-scid and in BALB/cA-nu were compared to examine whether genetic backgrounds of immune deficiency of the host mice influenced the chemotherapeutic profiles of implanted tumors. In a total of 25 pairs of corresponding experiments with each host mouse strain (5 HTXs × 5 drug treatment groups), we obtained consistent results in 23 (92.0%) experiments consisting of 10 which were both significantly effective and 13 which were both ineffective, although the remaining two (8.0%) experiments showed inconsistent results. A human T-cell lymphoma cell line, LM-2-JCK, implanted in nude mice, was resistant to treatment with 65 mg/kg of cyclophosphamide, but this tumor showed sensitivity to the same treatment when implanted in either SCID mice or mice with a recombination activating gene 2 defect [BALB/cA-TgH(Rag2)], suggesting that the genetic immune background of the host mouse should not be overlooked as a factor affecting tumors.

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Plasma progesterone (P₄) concentrations during pregnancy and lactation in Mongolian gerbils were measured by enzymeimmunoassay (EIA). The P₄ concentration was found to increase rapidly after mating and reach a peak on day 6 of pregnancy. The maximum level (166.0 to 184.8 ng/ml) was maintained to day 12 and then decreased to a plateau at a moderate level until day 21. The P₄ concentration declined to its lowest level on day 24 of pregnancy, one day before parturition. The P₄ concentration on the first day of lactation was similar to that on the last day of pregnancy. The concentration then increased to a significantly higher level on day 4 of lactation, remained relatively stable until day 19, and then significantly dropped on day 22. The present study in gerbils showed that the plasma P₄ concentration during pregnancy was higher in the first half than in the second half of gestation and that the P₄ level during lactation was fairly constant. The pattern of changes in the P₄ level during pregnancy and lactation is therefore quite different from that of other rodent species, such as rats, mice and hamsters.

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To quarantine human tumor samples for transplantation into immune deficient mice or tumor xenograft lines established and introduced from other institutions, we performed isolated implantation and passaging of tumors in a vinyl isolator, and microbiological examinations of sentinel mice kept together with tumor bearing mice. We examined 105 pairs of sentinel mice used to quarantine 907 tumors, and found six cases of contamination or infection with Staphylococcus aureus, 20 cases with Pseudomonas aeruginosa and one case with mouse hepatitis virus (MHV). It was, however, possible that Mycoplasma pulmonis contamination was overlooked because the microbe had been isolated from tumors passaged after quarantine, even though the results of the quarantine of these tumors showed no sign of pathogens. Direct culture of tumors for the microbe was recommended to improve the quarantine system.

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The effects of anti-rheumatic drugs (dexamethasone 0.1 mg/kg and naproxen 5 mg/kg) were evaluated immunologically and histopathologically on type II collagen-induced arthritis in Lewis rats. Increased paw volume in the hind limbs was significantly suppressed in the groups treated with dexamethasone or naproxen, but noticeable retardation of body weight gain was observed in the group treated with dexamethasone. Serum anti-type II collagen IgG was significantly suppressed in the group treated with dexamethasone but not naproxen. Histopathological evaluation by our grading system, classification of the stages in arthritic lesion development, revealed suppression of the inflammatory changes in the tarsal joints of the animals treated with dexamethasone or naproxen. From our results, histopathological evaluation is considered to be more suitable for assessment of the efficacy of anti-rheumatic drugs on type II collagen-induced arthritis, an animal model for human rheumatoid arthritis.

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