R C Dai

Central South University, Changsha, Hunan, China

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Publications (6)8.46 Total impact

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    ABSTRACT: Little research exists on the dynamic effects of glucocorticoids on bone mineral density (BMD) and microarchitecture of trabecular bones of rats assessed by micro-computed tomography (micro-CT). To investigate time-related changes in the BMD and microarchitecture of trabeculae in rats exposed to glucocorticoid. Female Sprague-Dawley rats were recruited into a baseline group, glucocorticoid-treated groups, or control groups. Glucocorticoid-treated rats were given daily subcutaneous injections of methylprednisolone at a dosage of 3.5 mg/kg for 1 or 9 weeks. A high-resolution micro-CT was used to identify the densitometric and microarchitectural properties of trabeculae in both the proximal metaphysis of tibiae and the sixth lumbar vertebrae (L6). Compared with baseline rats, volumetric BMD, tissue BMD, bone volume fraction, trabecular number, and degree of anisotropy of trabeculae from tibiae or L6 increased in control rats and glucocorticoid-treated rats with time; however, changes in the latter group were smaller. Compared with control rats at each time point, a decrease occurred in volumetric BMD, tissue BMD, bone volume fraction, trabecular number, degree of anisotropy, and trabecular connectivity density in trabecular bones from tibiae or L6 in glucocorticoid-treated rats. The decrease was greater in week 9 compared to week 1. Contrarily, an increase was noted in trabecular thickness, trabecular separation, and structure model index in glucocorticoid-treated rats. A time-related analysis within glucocorticoid-treated groups in both skeletal regions showed a decline in bone volume fraction, trabecular connectivity density, trabecular number, and degree of anisotropy with time, but trabecular thickness and trabecular separation were elevated. Methylprednisolone can inhibit bone mineralization and bone mass gain with growth in rats. It can also deteriorate microarchitecture of trabeculae in a time-dependent or an accumulative dose-dependent manner. Further, the remaining trabeculae appear to thicken in order to adapt to altered stress.
    Acta Radiologica 01/2009; 50(1):93-100. · 1.33 Impact Factor
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    ABSTRACT: Bone mineral density (BMD) and microstructural variations have been extensively investigated in recent years; however, the compensation for bone loss between different regions is still unclear. To fully characterize regional variations in bone mineral density (BMD) as well as the microstructure and dynamic changes of rat tibial trabeculae that occur with bone loss associated with estrogen deficiency. Female Sprague-Dawley rats were ovariectomized (OVX), sham-operated (sham), or left unoperated (baseline control). The left tibiae were harvested at baseline, and at postoperative weeks 3 and 15. High-resolution micro-computed tomography (microCT) was used to identify the densitometric and microstructural properties of trabeculae in the proximal ends of the rat tibia, specifically the epiphysis and metaphysis. Volumetric BMDs at the organ (organ BMD) and tissue (tissue BMD) levels were significantly higher for trabeculae at the epiphysis than metaphysis. Moreover, trabeculae at the epiphysis were thicker, and fewer in number and connectivity than those at the metaphysis, which were more rod like. Trabeculae at the metaphysis were more susceptible to bone loss induced by estrogen deprivation than at the epiphysis, and the regions varied greatly in their adaptation to this loss. At the metaphysis, trabecular tissue BMD and thickness were unexpectedly higher at postoperative week 15 than week 3 or baseline. In contrast, at the epiphysis, tissue BMD did not change with time, but trabecular thickness significantly increased at week 15 compared to baseline and was also greater in OVX compared to sham rats. Metaphyseal and epiphyseal trabeculae show regionally specific variations in BMD and microstructure. The former are more susceptible to bone loss induced by estrogen deficiency and would be strengthened by either hypertrophy or hypermineralization, while epiphyseal trabeculae are mainly strengthened by thickening.
    Acta Radiologica 07/2007; 48(5):531-9. · 1.33 Impact Factor
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    ABSTRACT: Ascorbic acid (AA) plays a key role in the regulation of differentiation and activation of osteoclast (OCL). It was reported that AA might induce the formation of OCL in cocultures of mouse bone marrow cells and ST2 cells, but it is not clear whether AA has a direct impact on the OCL precursors. The purpose of this study was to examine the effect of AA on the differentiation of OCL precursor RAW264.7 cells, cultured with receptor-activated nuclear factor kappaB ligand (RANKL). The results showed that AA remarkably inhibited the cell proliferation at a higher concentration and RANKL alone is sufficient for osteoclastogenesis. The expression of carbonic anhydrase (CAII) mRNA and protein, the number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells (MNCs), and the percentage area of resorption lacunae induced by RANKL were decreased when AA was added to the cultures. The results demonstrate that AA inhibits RANKL-induced differentiation of OCL precursor cells into mature OCL and reduces the formation of bone resorption pits in vitro.
    Journal of endocrinological investigation 04/2005; 28(3):253-60. · 1.65 Impact Factor
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    ABSTRACT: Our previous study showed that estrogen stimulates membrane-type matrix metalloproteinases-1 (MT1-MMP) production in osteoblastic cells culture, but has no effect on MMP-2 and TIMP-2 synthesis. Osteoblast-derived MT1-MMP have been recently implied to play a role in bone metabolism by degrading tumor necrosis factor-alpha (TNF-alpha), resolving extracellular matrix and activating proMMP-2, which requires the process of activation mediated by MT1-MMP/tissue inhibitor of metalloproteinase (TIMP-2) complex on the cell surface. To investigate the mechanism of bone loss following estrogen deficiency, we examined the effects of estrogen on osteoblast synthesis of MT1-MMP, MMP-2 and TIMP-2. In situ hybridization and immunohistochemistry of rat bone samples were used to document the synthesis of MT1-MMP, MMP-2, and TIMP-2 mRNA and protein. Osteoblasts from distal femoral head showed an increase in the pattern of MT1-MMP mRNA and protein production in sham-operated controls and 17beta-estradiol (E2)-treated rats, compared with the ovariectomized group; the synthesis of MMP-2 and TIMP-2 mRNA and protein was unaffected. Our data show a down-regulation of MT1-MMP synthesis by osteoblast in vivo following estrogen withdrawal, and treatment with E2 resulted in induced MT1-MMP expression in vivo. There is evidence suggesting a role for MT1-MMP in the process of bone loss during the pathogenesis of osteoporosis.
    Journal of endocrinological investigation 02/2004; 27(1):1-5. · 1.65 Impact Factor
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    ABSTRACT: To understand the differences among reference curves for bone mineral density (BMD) for Chinese, Japanese, and American Caucasian women, we measured the BMD at the anteroposterior (AP) lumbar spine (L1-L4), lateral lumbar spine (L2-L4), hip (including the femoral neck, trochanter, intertrochanter, Ward's triangle, and total hip), and ultradistal forearm by the dual-energy X-ray absorptiometry (DXA) in a total of 2728 healthy Chinese women, aged 5-96 years. Documented BMD data for Japanese women and device manufacturer's BMD new reference databases (including the NHANES III dataset) for American Caucasian women were also used in this study. The cubic regression model was found to fit best in analyzing the age-associated variations of BMD at various sites in Chinese women, i.e., the equations had the largest coefficient of determination (R2). At the AP/Lat spine, trochanter, intertrochanter, and Ward's triangle, BMD reference curves for Chinese women were lower than those for Japanese or Caucasian women, while at the femoral neck, total hip, and ultradistal forearm, the reference curves for Chinese women were higher than those for Japanese women, with overlaps and crossing of the curves for some age spans in comparing the Chinese and Caucasian women. There were significant differences in the peak BMD (PBMD) at various sites among the Chinese, Japanese, and Caucasian women (P = 0.000). The PBMDs for Chinese women at the lumbar spine and various sites of the hip were 5.7% +/- 2.1% (mean +/- SD, range, 2.7-7.9%) lower than those for Japanese women and 5.1% +/- 2.7% (range, 0.5-7.2%) lower than those for Caucasian women; however, the PBMDs for Chinese women were 26.2% higher than those for Japanese women and 10% higher than those for Caucasian women at the ultradistal forearm. After the PBMD, average T-scores of Chinese women for losses at the AP lumbar spine with increasing age were nearly identical to those for Japanese women, but both were greater than those for Caucasian women. The average T-scores for BMD loss at various sites in Chinese women were higher than those for both Japanese and Caucasian women except at the femoral neck, where the T-scores of Chinese women were exceeded by those of both Japanese and Caucasian women. Estimated from the T-score curve of BMD loss, the age of osteoporosis occurrence at the femoral neck in Chinese women was about 10 years later than that in Japanese or Caucasian women; at the AP spine, Chinese women were similar to Japanese women; at the other sites, the age for occurrence of osteoporosis in Chinese women was about 5-15 years earlier than that in either Japanese or Caucasian women. There are differences in prevalence or odds ratio (OR) of osteoporosis at the same skeletal region for Chinese, Japanese, and Caucasian women aged > or = 50 years or at different skeletal regions in women of the same race. The prevalences of osteoporosis at various regions of the hip in Chinese women are 10.1-19.8% and ORs are 22.0-32.3, of which prevalence at the femoral neck is the lowest (10.1%); the prevalences of osteoporosis in Japanese women are 11.6-16.8% and ORs are 21.1-26.3, of which prevalence at the femoral neck is the lowest (11.6%); and the prevalences of osteoporosis in Caucasian women are 13.0-20.0% and ORs are 19.4-48.9, of which prevalence at the femoral neck is the highest (20%). In conclusion, racial differences in BMD reference curves, prevalences, and risks of osteoporosis at various skeletal sites exist among native Chinese, Japanese, and American Caucasian women.
    Calcified Tissue International 08/2003; 73(2):122-32. · 2.50 Impact Factor
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    ABSTRACT: The laser scanning confocal microscope(LSCM) is the new high distinguishing microscope, which can be used in observation on fluorescence, since 1990. The bone morphometry is an important way to study metabolic bone diseases. Our study on research combination of LSCM with bone morphometry in observing microarchitecture of bone found that LSCM could make the photo of bone trabecula distinctly and its location accurately. Because of its technical advantages, LSCM could link histochemical or immunohistochemical method for the bone morphometry and bone cells at the same time and obserrate the thick-slide. It is a new method and way to study and diagnose metabolic bone diseases.
    Hunan yi ke da xue xue bao = Hunan yike daxue xuebao = Bulletin of Hunan Medical University 09/2000; 25(4):413-5.