This study was conducted to examine the relationship between dietary nitrogen (N)-corrected metabolizable energy (MEn) and dietary digestible energy (DE) in cats, in order to verify the reliability of the present metabolizable energy (ME) system for cats. Four adult female cats were fed diets containing four different levels of crude protein (CP) (24, 35, 49, and 62% as fed) 4 hours a day in a 4 × 4 Latin square design to determine energy-and N-balance. Dietary CP levels had hardly any effect on daily food intake, but acid-ether extract (AEE) intake tended to increase and carbohydrate (CHO) intake tended to decrease, in response to increases in dietary CP levels. Apparent CP and AEE digestibility did not change, regardless of the experimental diet. In contrast, CHO digestibility tended to diminish as dietary CP levels increased. Although the ratio of urinary energy (UE) to urinary N (UN) was higher in cats fed the lowest CP diet, it was still much lower than in other mammals. Regression between UE/digestible crude protein (DCP) and N-balance indicated that dietary ME at N-equilibrium (i.e., MEn) could be expressed as DE -0.47 × DCP. MEn could also be estimated as DE -0.62 × DCP by using the average ratio of UE/(UN × 6.25). Both DCP coefficients were much lower than in other mammals, including dogs and pigs, suggesting a unique form of N metabolism in cats. Because ME values applied to practical feline feed ingredients have been either estimated in pigs or calculated according to the equation, DE -1.25 × DCP, similar to the method used for dogs, the present ME values for cats are believed to have been underestimated.

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The effects of dietary protein levels on food and water intake, and urinary excretion of magnesium (Mg) and phosphorus (P) were examined in cats fed dry-type diets. Four adult female cats were used for trials in a 4 × 4 Latin square design, and fed diets with increasing protein content (25.9, 38.3, 51.4 or 65.2% in dry matter) daily from 9:00 to 13:00. While daily food intake was almost constant regardless of the dietary protein level, water intake and urine volume increased with increasing the dietary protein. Daily urinary excretion of P increased in response to the increase in dietary protein level. The urinary concentration of P was positively related to nitrogen (N)-intake. In contrast, daily urinary excretion of Mg was not affected by the dietary protein level, and the urinary concentration of Mg was negatively related to N intake. A dry-type diet with a high protein content might be effective in preventing the deposition of Mg salts in the urinary tract of cats under the meal-fed condition without affecting food intake because of both the lower concentration of urinary Mg resulting from the increase in urine volume and, probably, urinary acidification.

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An equation to estimate the metabolizable energy (ME) content of practical dry canine diets, [metabolizable energy (ME_NRC, kcal/g)=3.50 × crude protein + 8.46 × acid ether extract + 3.50 × nitrogen-free extract] has been recommended by the National Research Council (NRC), which assumes fixed digestibility for each nutrient. This estimation method is much more convenient than that of nitrogen-corrected metabolizable energy (MEn) following the equation MEn=digestible energy-1.25 × digestible crude protein. This study aimed to assess the validity of ME_NRC through a comparison with MEn determined by using 11 diets with 4 mature male Beagle dogs. The relation between ME_NRC and MEn was expressed as a quadratic equation (ME_NRC=0.83MEn²-5.43MEn + 12.36, r²=0.956, P<0.01), suggesting that MEn is overestimated when the NRC method was applied to lower energy diets. It was also suggested that the strict estimation of MEn by means of fixed digestibility coefficients was impossible, because of the relatively wide variation in digestibility among dry canine diets.

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M.MOL-MSM (MSM) mice derived from Mus musculus molossinus progenitors showed extreme resistance to the induction of lymphomas following whole-body X-irradiation with four doses of 1.7 Gy. (BALB/cHeA × MSM) F₁ mice between a high lymphoma strain, BALB/cHeA and the MSM showed a high incidence of radiation-induced lymphomas which was quite similar to that in BALB/cHeA mice, but the latent period was prolonged in the hybrids. Susceptibility in incidence was dominant over resistance in these crosses. Incidences of (BALB/cHeA × MSM)F₁ hybrids irradiated with four doses of 2.5 Gy X-rays were 77% in females and 88% in males. F1 hybrids between BALB/cHeA and another resistant strain STS/A, (BALB/cHeA × STS/A) F₁, also showed a high level of susceptibility, that is, lymphoma incidence was 64% in females and 63% in males. The mean latent period in the (BALB/cHeA × STS/A) F₁ hybrids was similar to that in (BALB/cHeA × MSM) F₁ hybrids. As all cases of tumors developed in F₁ hybrids are informative concerning the detection of the loss of heterozygosity in the loci depending on the combination of two parental strains, the radiation-induced lymphomas obtained from (BALB/cHeA × MSM) F₁ and (BALB/cHeA × STS/A) F₁ hybrids could be useful for fine analysis of the genetic alterations involved in lymphomagenesis.

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This study was undertaken to evaluate the sedative effect of medetomidine, an α₂-adrenoceptor agonist, and the counteractive effect of atipamezole, an antagonist to medetomidine, in house musk shrews (Suncus murinus). Two hundred, 300, 400, or 600 μg/kg of medetomidine was intraperitoneal injected into 89 house musk shrews. A sedative effect was produced in one to two minutes after injection. The dose-dependent prolongation of the sedative duration and the dose-dependent appearance of a hypothermic effect were demonstrated. With 200 μg/kg of medetomidine, the sedative effect obtained was not adequate in some of the animals. With 300 μg/kg and above, a stable sedative state was induced in all the animals. The duration of sedation in the house musk shrews was much longer (p<0.01) in males than in females. This suggested the higher susceptibility of male house musk shrews to this drug. The sedative effect and hypothermia obtained with 400 μg/kg of medetomidine were completely counteracted by more than 2.0 mg/kg of atipamezole. With 0.5 and 1.0 mg/kg of atipamezole, only a partial antagonistic action was produced. Transient vomiting appeared in 4.5% of the house musk shrews at approximately one minute after injection of medetomidine. This side-effect had occurred before the sedative effect was obtained, and was not serious enough to be a problem. None of the 89 house musk shrews died in this experiment. The above results show that the combination of medetomidine and atipamezole is a highly effective and safe anesthetic treatment which permits easy handling of house musk shrews.

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Age-related thyroid changes, such as those in weight, histology, morphometry, and hormonal concentrations were evaluated in 460 male and 460 female F344 rats from 9 to 109 weeks of age. The absolute weight of the thyroid increased with age in both sexes, but the relative weight was unaffected by age. Ectopic thymus and ultimobranchial cyst were observed in rats of both sexes from 9 to 109 weeks of age. The incidence of both congenital anomalies decreased with age. The incidence of follicular cyst, which was first observed in rats at 20 weeks of age, increased at 109 weeks. Hyperdistention of the follicle with infiltration of macrophages in the lumen and deposition of brown pigments in the cytoplasm of epithelial cells were observed in a few rats at 59 weeks of age. These follicular lesions were found in 29% of the males and 7% of the females at 109 weeks. The first thyroid tumor was seen at 59 weeks of age. In 109-week-old rats, 5% of males had follicular tumors, and 18% of males and 10% of females had C-cell tumors. At 82 weeks of age, the follicular area and the area of the follicular lumen increased, and the height of follicular epithelial cells decreased. Serum T₃, T₄ and TSH concentrations decreased with age and were significantly reduced at 82 weeks. These results suggest that in F344 male rats the thyroid structural and functional changes occurred with age, and thyroid function decreased after 82 weeks of age.

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11Lewis rats were immunized with an intradermal injection of type II collagen to study the time course of arthritic lesions. Serum type II collagen antibody was detected 9 days after immunization. Increased paw volume in the hind limbs was noted on day 11. Histopathologically, proliferation of synovial lining cells was observed on day 11 and typical lesions similar to those of human rheumatoid arthritis were noted on day 18.

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A behavioral profile of hereditary bilateral anophthalmic mutant rat was studied in different light: dark schedules. The control and mutant rats were acclimatized to either a) a 12h light:12h dark cycle or b) continuous darkness or c) continuous illumination. The measurements of spontaneous motor activity with Opto Varimex and behavioral despair in a swim test were conducted. The daily food consumption and plasma glucose levels were also measured. The study indicated that, unlike the control rats, mutants did not exhibit any time dependent change in the spontaneous motor activity in any of the three different lighting conditions. A strong biphasic feeding burst was also not affected by anophthalmia in mutant rats. Our findings on spontaneous motor activity and the feeding pattern are contrary to those in the existing literature.

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Male ICR mice were intraperitoneally injected with a single dose (100 mg/kg BW) of streptozotocin (STZ). The pancreas and testis were excised at 1, 2 or 4 weeks after STZ administration and observed by light and electron microscopy. At 2 weeks after injection (p.i.), the islets of Langerhans in the pancreas showed severe atrophy, indicating a diabetic state. In the testis, although no conspicuous morphological changes were detected at 2 weeks p.i., noticeable changes had occurred in the Leydig cells at 4 weeks p.i. In the cells, lipid droplets increased in number, whereas smooth endoplasmic reticulum (sER) decreased. Giant whorl-like sER appeared frequently at this time. These findings indicate the declined secretory activity of Leydig cells in STZ diabetic mice.

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Entire seminiferous tubules of laboratory rodents can be removed, separated into individual portions in physiological saline, fixed in Bouin’s solution and embedded in gyoza skin. After histological processing, microscopic examination of the entire length of the tubules is then possible.

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