ABSTRACT. To determine how to eliminate species difference in animal bone experiment, bone mineral content (BMC) was measured using dual energy X-ray absorptiometry (DXA) on the femurs of laboratory mice (Mus musculus) and rats (Rattus norvegicus), and common marmosets (Callithrix jacchus). Measures were taken on femurs in situ, detached from the body, skinned and defleshed, or dried completely. When the BMC of the bone measured in the intact limb attached to the trunk was set at 100%, the actual BMC of the dry bone was 58.7  11.5% in mice and 103.2  3.2% in rats. Similarly, the bone area (Area) and bone mineral density (BMD) of the dried femur was significantly lower in the mouse femurs than intact limb. Thus, soft limb tissue such as skin and muscle modified the BMC, Area, and BMD only in mouse but not in those from rats or marmosets. The bone mineral ratio (BMR; BMC divided by dry bone weight) was nearest to the human bone value in the rat femurs, whereas the mouse femur BMR was the most different. The BMR was proved to be a practical index in evaluating bone characteristics in laboratory animals, but the mouse femur might not be suitable as an animal model for research into the aging of human bone.KEY WORDS: bone mineral content, bone mineral density, bone mineral ratio, dual energy X-ray absorptiometry, femur.J. Vet. Med. Sci. 71(11): 1493-1497, 2009 Longevity sciences which consist of gerontology, geriatrics and sociogerontology require practical animal models of basic aging processes. Many animal models (e.g., Caenorhabditis elegans [4], Drosophila [17], rodents [15] and primates [6]) have been used for such studies. However, species-specific factors sometimes produce results that cannot be extrapolated to human beings, and although experimental animals are bred under special conditions, researchers sometimes forget this limitation. Therefore, we need to categorize the species-specific physiology of animals.The temporal measurement of human bone mass is very important for the diagnosis of osteoporosis [5,7,8]. Dual X-ray absorptiometry (DXA) is widely used in the world for the analysis of bone mineral content (BMC). The advantage of DXA is that it is noninvasive and uses low radiation dosage. Therefore, many bone analyses have been performed on experimental animals using DXA. However, bone characteristics and size differ between animals and humans. Above all, the bone mineral density (BMD) of the femur measured by DXA varies widely from about 30 mg/cm 2 in mice to about 830 mg/cm 2 in humans [14]. The present study was conducted to evaluate such differences and to test whether different preparation methods modify bone measurements. We report here on variations in animal bone content characteristics and on new methods for evaluating bone composition. MATERIALS AND METHODSA total of five C57BL/6CrSlc mice (Mus musculus) (9.8~12.8-month-old male) and five F344/NSlc rats (Rattus norvegicus) (12.7~13.2-month-old male) were used. Mice and rats were established at the Aging Farm of National Center for Geriatri...

ABSTRACT. The aim of this study was to determine whether the thickness of the adrenocortical zone is associated with age in virgin and parous female DDD mice. The zona reticularis and zona glomerulosa of parous mice tended to be thicker than those of virgin mice at all ages. The zona fasciculata lactating parous mice was significantly thicker than that of virgin mice at 20 weeks of age (P<0.01). Age did not affect the thickness of the three outer adrenocortical zones in either group. However, in virgin mice, the X zone consisted of vacuolated and nonvacuolated cells at 5 weeks of age and only of vacuolated cells at 10 weeks of age; the number of vacuolated cells and the thickness of the zone decreased at 40 weeks of age. In contrast, parous mice of all ages lacked an X zone. The decrease in X zone thickness with age was most evident when expressed relative to organ weight. In conclusion, the thickness of the outer three adrenocortical zones is affected by endocrine changes associated with pregnancy and lactation but not by age. The thickness of the X zone is an index of growth and maturation in nulliparous female DDD mice less than one year of age. KEY WORDS: adrenal cortex, age, DDD mouse, reproduction, X zone morphology.The adrenal cortex of most mammals consists of three zones. These zones play distinct roles in steroid hormone production [11]. The mineral corticoid of the zona glomerulosa regulates Na-K valance. The glucocorticoid of the zona fasciculata regulates multiple physiological metabolisms, and the adrenal androgen is mainly produced in the zona reticularis (exclude mice and rats [11]). In the mouse, a fourth zone, the X zone, is present in the innermost cortex of the adrenal. Masui and Tamura first described the characteristics of this zone in 1924 [12]. It was named the X zone by Howard-Miller in 1927 [8]. Many studies have shown that degeneration of this zone is induced by pregnancy and lactation [10]. Furthermore, in the absence of pregnancy, X zone degeneration is induced by the administration of androgen [6]. In male mice, degeneration of the X zone is induced by sexual maturation [3]; and regeneration of a second X zone is induced by castration of adult mice or androgen administration [4,7]. Thus, the endocrinological characteristics of these four adrenocortical zones are well known. But, little studies have been conducted on agerelated changes in the morphology of these adrenocortical zones [1].Strain differences in the morphology of X zone degeneration have been observed between A/Cam and CBA/FaCam mice [15], C57BL/6By and BALB/cBy mice [8], C57BL/ 6JJms and DDD mice [18], and A/J and SM/J mice [19,20].The main differences between strains involve the extent of vacuolation, which is an index of tissue lipid content [15,18,20,24]. Although it was recently reported that the agouti locus affects vacuolation [16,19], no statistical data were provided. As female DDD mice have a thicker and more vacuolated X zone than other strains of mice [18], we considered that the female DDD mice were suitable...

Abstract:The body and major organ weights of A/J-Chr 11 SM consomic mice were compared to those of the progenitor strains, A/J and SM/J. The weights of the body and organs, except for those of the brain and uterus, were significantly greater in A/J mice than in SM/J mice. However, those of consomic mice were highly variable. For example, the average body weight of consomic mice was significantly greater than that of SM/J mice and nearly equal to that of A/J mice. Chromosome 11 of SM/J mice induced various significant changes of the organ weights of A/J mice, especially those of the brain, lung, kidney, adrenal, and ovary, demonstrating the importance of this chromosome in determining the phenotypes.

No abstract