bluuebunny/crossref_metadata_2025_split huggingface dataset:
Purification and fragmentation of nondenatured bone sialoprotein: Evidence for a cryptic, RGD-resistant cell attachment domain
Authors: Mintz Keith P. , Grzesik Wojciech J. , Midura Ronald J. , Robey Pamela Gehron , Termine John D. , Fisher Larry W. 
Published: February 2010

Abstract
Bone sialoprotein (BSP), a small (˜80,000 Mr) integrin binding, RGD-containing bone matrix glycoprotein, has been purified in milligram quantities from the serum-free medium of the rat osteosarcoma cell line UMR-106-BSP using nondenaturing conditions. Routine protein purification without serine protease inhibitors or reducing agents consistently resulted in three major fragments. The largest fragment (E1) started at amino acid 117 and did not bind to antibodies made to the RGD region of the protein. Furthermore, the smallest fragment (E3), was shown by sequencing to contain the RGD region of the protein. Digestion of intact BSP with highly purified chymotrypsin also resulted in a large fragment (C1) with properties nearly identical to those of E1. The large, non-RGD-containing fragments, E1 and C1, as well as the intact BSP, supported attachment by normal human bone cells and human skin fibroblasts in vitro. Attachment to the intact BSP was totally blocked by 0.4 mM GRGDS peptide. Both preparations of skin fibroblasts and approximately half of the preparations of normal human bone cells, however, also would not attach to the E1 and C1 fragments in the presence of 0.4 mM GRGDS peptide. In contrast, half of the bone cell preparations had significant attachment activity to E1 (&gt;50%) and C1 (&gt;25%) in the presence of 0.4 mM GRGDS peptide. These data suggest that cleavage of the BSP results in either (1) the exposure of a previously unavailable or cryptic cell attachment site or (2) a conformational change that increases the affinity of the complex between a non-RGD-encoded binding region of the E1 and C1 fragments and at least one receptor. The possible homology of the second, non-RGD-suppressible site of BSP with the second cell attachment site on the gamma chain of fibrinogen is discussed.
Biologic activity of dihydroxylated 19-nor-(pre)vitamin D3
Authors: Bouillon Roger , Sarandeses Luis A. , Allewaert Katrien , Zhao Jie , Mascareñas Luis J. , Mouriño Antonio , Vrielynck Sara , De Clercq Pierre , Vandewalle Maurits 
Published: February 2010

Abstract
Vitamin D3 and its hydroxylated metabolites are normally in thermal equilibrium with their previtamin D isomers. To evaluate the biologic activity of 1α,25-dihydroxyprevitamin D3, we synthesized 19-nor analogs of 1α,25-dihydroxy(pre)vitamin D3 because the absence of a C19 methylene group prevents the isomerization of these analogs. The affinity of 1α,25-(OH)2D3-19-nor-D3 for the intestinal vitamin D receptor and plasma vitamin D binding protein was mildly decreased [30 and 20% of the affinity of 1α,25-(OH)2D3, respectively], but the affinity of 1α,25-(OH)2-19-nor-previtamin D3 was only 1 and 6% of that of 1α,25-(OH)2D3 for the receptor and DBP, respectively. The in vitro effects on human promyeloid leukemia (HL-60 cell) differentiation and osteocalcin secretion by human osteosarcoma (MG-63) cells by 1α,25-(OH)2-19-nor-D3 were nearly identical to those of 1α-25-(OH)2D3, whereas 19-nor-previtamin D3 showed poor activity (2%). The in vivo calcemic effects of both analogs, studied in vitamin D-deficient chicks treated for 10 consecutive days with the analogs, showed no activity of the previtamin D3 analog and reduced calcemic effects (≤ 10%) of 1α,25-(OH)2-19-nor-D3. We conclude that the previtamin D form of 1α,25-(OH)2D3 has lost most of its biologic activity in vitro and in vivo.
Reduced creatinine clearance in primary osteoporosis in women
Authors: Dr. Yendt Edmund R. , Cohanim Moussa , Jarzylo Stanley , Jones Glenville , Rosenberg Gilbert 
Published: February 2010

Abstract
We determined the relationship between bone mass and age, anthropometric variables, and serum and urine biochemical variables in 77 normal white women and 37 women with primary osteoporosis, 25 of whom had one or more vertebral compression fractures. Skeletal status was assessed by radiography of the hands with measurement of combined cortical thickness of the second metacarpal bones (CCT) or measurement of radial and lumbar bone density, or by both methods. Radial bone mineral content (RBMC) was measured by single-photon absorptiometry (SPA) and lumbar bone mineral density by dual-photon absorptiometry (DPA). Serum and urine biochemical variables were measured on days 6 and 7 of a controlled diet. In this mixed population of normal and osteoporotic women, we confirmed the strong positive correlation between creatinine clearance (Ccr) and bone mass that we previously reported in normal women. Multiple regression analysis showed that the relationship between Ccr and bone mass of the radius and lumbar spine was independent of age and body stature. Ccr was significantly lower in the 25 osteoporotic women with vertebral crush fractures than in age-matched normal women, and Ccr had predictive value for bone mass in individual subjects. The basis for the relationship between Ccr and bone mass has not been established. We excluded diminished production of 1,25-dihydroxyvitamin D as a result of declining renal function as a possible mechanism.
Training increases the in vivo strength of the lower leg: An experimental study in the rat
Authors: Nordsletten Lars , Kaastad Trine Sand , Skjeldal Sigmund , Kirkeby Ole J. , Reikerås Olav , Ekeland Arne 
Published: February 2010

Abstract
The effect of training on bone strength has been investigated in rats. After 7 weeks of training, fracture strength of the tibia in vivo during muscle contraction and after resection was assessed. A group of 30 male rats 11 weeks old were randomized to exercise on a treadmill, sedentary (ordinary caging), and inactivity (right-sided patellar tendonectomy) groups. The training group ran on a treadmill with a 10% inclination for 1 h per day. After 4 weeks the animals in all groups were anesthetized and the right lower legs loaded in three-point ventral bending until fracture during electrically induced muscle contraction. The contralateral tibiae were tested correspondingly after resection. Ultimate bending moment, energy absorption to failure, bending stiffness, and deflection were assessed for the in vivo and the resected tibiae. The body weight gain was 37% higher in the sedentary and 57% higher in the inactive animals than in the training group (P &lt; 0.05), indicating a physiologic effect of the training. In the dissected tibiae there were no significant group differences in any of the mechanical parameters, indicating that neither training nor inactivity changed the structural capacity of the tibiae per se. In contrast, there were significant differences between the in vivo tibiae. Ultimate bending moment was 12% higher in the training group than in the sedentary and inactive groups (P = 0.03). Energy absorption in the training group was 11 and 12% higher (not significant) than in the sedentary and inactivity groups, respectively. Bending stiffness was 7 and 17% higher in the training group compared to sedentary and inactivity groups (P = 0.018). These results indicate that muscle training protects against fracture in vivo.
Demonstration of a difference in urinary calcium, not calcium absorption, in black and white adolescents
Authors: Dr. Bell Norman H. , Yergey Alfred L. , Vieira Nancy E. , Oexmann Mary Joan , Shary Judith R. 
Published: February 2010

Abstract
Bone mineral density (BMD) of the forearm, lumbar spine, and femoral neck is greater in black than in white children. Studies were performed to determine whether differences in intestinal absorption of calcium or urinary calcium or both account for an assumed more positive calcium balance and greater bone mass in black children. Normal black and white boys and girls were admitted to a metabolic ward and given a constant daily diet containing 1000 mg calcium, 60% as calcium carbonate, for 2½ days (study I) or 3½ days (study II). Fasting blood and 24 h urine collections were obtained, and in study II, unidirectional fractional absorption of calcium (α) was determined with stable isotopes of calcium. It was found that (1) serum 25-hydroxyvitamin D (25-OHD) and urinary calcium were lower and serum 1,25-dihydroxyvitamin D [1,25-(OH)2D] was higher in black than in white children, and (2) α was higher in boys than in girls with no racial difference, and (3) there were significant positive correlations between α and urinary calcium in the blacks and in the black and white children together. It is concluded that (1) α is higher in boys than in girls and (2) a lower urinary calcium, not increased intestinal absorption of calcium, is the means for a more positive calcium balance in blacks that accounts for the racial difference in BMD.
Osteoblast-Specific Expression of the α2(I) Collagen Promoter in Transgenic Mice: Correlation with the Distribution of TGF-β1
Authors: D'Souza Rena N. , Niederreither Karen , de Crombrugghe Benoit 
Published: February 2010

Abstract
To begin to assess the transcriptional mechanisms that regulate type I collagen gene expression in differentiating osteoblasts, we have sought to determine the minimal promoter sequences that confer osteoblast-specific expression to the α2(I) collagen gene during murine development. Transgenic mice were generated harboring DNA constructs in which the −2000, −500, and −350 to +54 regions located upstream of the start of transcription were linked to the Escherichia coli β-galactosidase reporter gene (LacZ). Histochemical staining using X-gal indicated that the −2000 lacZ transgene was strongly expressed in newly differentiated and fully functional osteoblasts at intramembranous and endochondral sites of ossification. The promoter was also active in osteocytes in regions of bone remodeling within alveolar bone. The temporal and spatial activity of this region of the promoter closely resembled the developmental patterns of expression of the endogenous α2(I) collagen gene as determined by in situ hybridization. The cis-acting elements within the 500 and 350 bp segments of the α2(I) collagen promoter also drove reporter gene expression in forming osteoblasts, although levels of transgene expression were not as marked as that seen with the 2000 bp promoter. Furthermore, the synthesis and secretion of TGF-β1 in osteogenic zones coincided with areas where the α2(I) collagen promoter constructs were transcriptionally active. Since a nuclear factor 1 binding site present at −300 has been shown to mediate the effects of TGF-β1 on the α2(I) collagen promoter, these data support a role for TGF-β, in the control of this gene during development.
Stimulation by interleukin-1 of renal calcium reabsorption in thyroparathyroidectomized rats
Authors: Dr. Caverzasio J. , Rizzoli R. , Vallotton M.B. , Dayer J.M. , Bonjour J.-P. 
Published: February 2010

Abstract
Recombinant human interleukin-1 (rhIL-1) can induce an elevation in calcium that has been ascribed exclusively to the stimulation of bone resorption. In the present study, we investigated whether rhIL-1 could also enhance the renal tubular reabsorption of calcium. The chronic influence of recombinant human rhIL-1 on renal calcium transport was investigated in thyroparathyroidectomized rats. Administration of rhIL-1 at the dose of 1.5 μg/day sc for 6 days induced a significant elevation in plasma calcium that was associated with a slight but significant decrease in the urinary excretion of calcium. Recording of the urinary calcium excretion expressed per ml glomerular filtrate at various plasma calcium levels, as achieved by acutely infusing calcium gluconate, indicates that rhIL-1 enhanced the tubular reabsorption of calcium. The calculated index of the tubular reabsorption of calcium (TRCal) was significantly increased by rhIL-1 (2.18 ± 0.14 versus 1.79 ± 0.07 mmol/l GFR, p &lt; 0.05, in vehicle-treated rats). The change in the renal handling of calcium was not associated with stimulation of the tubular reabsorption of magnesium. Acute administration of a large dose (24 μg given in a bolus IV injection) of rhIL-1 enhanced within minutes the urinary excretion of prostaglandin E2. This effect was followed by a significant increase in urinary cAMP excretion and associated with a lower urinary calcium excretion. In conclusion, the results presented in this study indicate that rhIL-1 administered chronically selectively stimulated the tubular reabsorption of calcium. Experimental evidence suggests that this effect is mediated by prostaglandin-induced cAMP generation. These data strongly suggest that changes in the tubular handling of calcium could contribute to rhIL-1-induced hypercalcemia.
Altered cartilage phenotype expressed during intramembranous bone formation
Authors: Ting Kang , Petropulos Lee Ann , Iwatsuki Masaru , Dr. Nishimura Ichiro 
Published: February 2010

Abstract
The sequential phenotypic expression occurring during intramembranous bone formation was investigated using the tooth extraction socket created in rat alveolar bone in vivo. The differential expression of bone extracellular matrix genes, such as collagen I and osteocalcin, was confirmed by RNA transfer blot analysis and in situ hybridization during the active healing period of the bony socket. To clarify the possible involvement of the chondrogenic phenotype during the process of intramembranous bone formation, the expression of cartilage collagen II and IX was further examined in this model. It was found that both α1(II) and α1(IX) mRNAs were present, but the α1(IX) mRNA was a transcript from the downstream start site/promoter, which is a different site in the α1(IX) gene from that used in hyaline cartilage. In situ hybridization indicated that the α1(IX) message was expressed by cells associated with bone matrix in the early formation stage. This finding led to the investigation of type IX collagen expression by osteogenic cells isolated from newborn rat calvariae, in which only the truncated form of α1(IX) mRNA was indicated by RNA transfer analysis. The expression of collagen II and a truncated form of collagen IX may represent an early phenotypic feature of osteoblast differentiation.
Interrelationships between densitometric, geometric, and mechanical properties of rat femora: Inferences concerning mechanical regulation of bone modeling
Authors: Prof. Ferretti José Luis , Capozza Ricardo Francisco , Mondelo Nélida , Zanchetta José Rubén 
Published: February 2010

Abstract
A compensation for differences in bone material qualtiy by bone geometric properties in femora from two different strains of rats was previously shown by us. A feedback mechanism controlling the mechanical properties of the integrated bones was then proposed, in accordance with Frost's mechanostat theory. Evidence of such a system is now offered by the finding of a negative correlation between the modeling-dependent cross-sectional architecture (moment of inertia) and the mineral-dependent stiffness (elastic modulus) of bone material in the femoral diaphyses of 45 normal Wistar rats of different sexes, ages, and sizes. The strength and stiffness of the integrated diaphyses were found to depend on both cross-sectional inertia and body weight, not on bone mineral density. These findings are interpreted as supporting the hypothesis that the architectural efficiency of diaphyseal cross-sectional design resulting from the spatial orientation of bone modeling during growth is optimized as a function of the body weight-dependent bone strain history, within the constraints imposed by bone stiffness. Results suggest a modulating role of biomass, related to the system set point determination, and explain the usually observed lack of a direct correlation between mineral density and strength or stiffness of long bones in studies of geometrically inhomogeneous populations.
Osteopenia and bone-remodeling abnormalities in warfarin-treated lambs
Authors: Pastoureau P. , Vergnaud P. , Meunier P.J. , Pr. Delmas P.D. 
Published: February 2010

Abstract
The physiologic role of osteocalcin (OC), a vitamin K-dependent protein specific to bone, remains elusive. It has been shown that rats maintained on chronic treatment with vitamin K1 and its antagonist warfarin exhibit a marked decrease in bone osteocalcin because noncarboxylated osteocalcin does not bind to bone hydroxyapatite. To assess the role of OC in bone remodeling, we applied the warfarin model to growing lambs. We analyzed the bone changes after 3 months of concurrent warfarin and vitamin K1 treatment. Four groups of four lambs were constituted at birth and received daily a saline solution (control group, CT), 4 mg/kd/day of vitamin K1 (vitamin K group), 4 mg/kg/day of vitamin K1 + 75 or 150 mg/kg/day of warfarin (W75 and W150 group, respectively). In warfarin-treated animals, bone osteocalcin levels were decreased, both in the metaphysis (9% compared to controls) and the diaphysis (30% compared to controls) of the metacarpals. The fraction of noncarboxylated osteocalcin measured every month in the serum was significantly higher in warfarin-treated lambs than in controls at each timing point (37.6 ± 2.6% in W75 and 48.7 ± 5.2% in W150 versus 14.4 ± 3.8% in controls at 3 months). Compared to non-warfarin-treated animals (NW), the main histomorphometric parameters measured on the iliac crest after tetracycline double labeling were significantly reduced in the warfarin-treated lambs: 12.2 ± 5.2 versus 18.6 ± 4.7% in NW (p &lt; 0.03) for the cancellous bone area, which reflects the trabecular bone density; 14.7 ± 6.1 versus 21.0 ± 3.6% in NW (p &lt; 0.03) for the eroded perimeter, and 0.315 ± 0.064 versus 0.561 ± 0.23 μm3/μm2/day in NW (p &lt; 0.02) for the tetracycline-based bone formation rate. In conclusion, the depletion of osteocalcin in the bone of lambs induced within 3 months a marked osteopenia that resulted from a decrease in resorption and a more pronounced decrease in bone formation. Our data suggest that the presence of osteocalcin, the major gla-containing protein of bone, may be important for the maintenance of a normal bone mass and remodeling of trabecular bone.
1,25-dihydroxyvitamin D3 potentiates fluoride-stimulated collagen type I production in cultures of human bone marrow stromal osteoblast-like cells
Authors: Kassem Moustapha , Mosekilde Leif , Dr. Eriksen Erik Fink 
Published: February 2010

Abstract
In this study we tested the effects of sodium fluoride (NaF) in serum-free cultures of human marrow stromal osteoblast-like [hMS(OB)] cells. NaF (10−5 M) stimulated hMS(OB) cell proliferation up to 220% of control cultures. NaF alone did not increase type I collagen production, but in the presence of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] (10−9 M), NaF enhanced type I collagen production in a dose-dependent way to 300% of 1,25-(OH)2D3-treated control cultures. The production of alkaline phosphatase (ALP) and osteocalcin (bone gla protein, BGP) was also enhanced in the presence of 1,25-(OH)2D3 to 170 and 200%, respectively, of 1,25-(OH)2D3-treated controls. Our results suggest that 1,25-(OH)2D3 potentiates fluoride-mediated anabolism in hMS(OB) cell cultures and suggest that osteoblast precursors in bone marrow are targets for fluoride action.
Journal of Bone and Mineral Research
Authors: Jeffcoat Marjorie K. 
Published: February 2010

Abstract
Bone loss in the oral cavity may occur due to many causes, including infection, systemic or local alterations in the host response, or multifactorial causes. The purpose of this article is to review our present understanding of the major causes of oral bone loss in adults, with special emphasis on two major oral diseases: periodontitis and residual ridge resorption. Periodontitis is characterized by resorption of the alveolar bone as well as loss of the soft tissue attachment to the tooth. Progressive periodontitis will result in continued alveolar bone loss and may result in tooth mobility, abscesses, and ultimately tooth loss. Although the reported prevalence may vary according to the epidemiologic study design, the 1985 National Survey of Oral Health of United States Adults indicated that 94% of female senior citizens examined demonstrated at least one site with at least 2 mm loss of attachment. Resorption of alveolar bone that occurs following tooth extraction is termed residual ridge resorption. In many cases, the denture will loosen because of the inability of the resorbed ridge to stabilize the prosthesis. In the most severe cases, the denture may impinge on the exposed mandibular nerve, resulting in pain or total inability to tolerate the prostheses. Although clear statistics on the prevalence of residual ridge resorption are not available, this boss loss may result in the need for new dentures to replace ill-fitting prostheses.
Journal of Bone and Mineral Research
Authors: Reddi A. Hari , Cunningham Noreen S. 
Published: February 2010

Abstract
The presence of growth and differentiation factors in bone has been demonstrated by subcutaneous implantation of demineralized bone matrix that initiates new cartilage and bone morphogenesis. The genes for bone morphogenetic proteins (BMPs) have been cloned and expressed. Recombinant BMPs induce endochondral bone formation in vivo. The multistep sequential developmental cascade consists of chemotaxis, mitosis, and differentiation of cartilage and bone. The pleiotropic response has been well characterized. BMPs stimulate osteogenic and chondrogenic phenotypes. Natural bovine osteogenin (BMP-3) and recombinant BMP-4 are equipotent in chemotaxis, limb bud chondrogenesis, cartilage maintenance, and in vivo bone induction. There are multiple isoforms of BMPs, raising the biologic relevance of the redundancy. The mode of action and second messengers are not clear. BMPs appear to have cognate receptors as demonstrated by iodinated BMP-2B (BMP-4). Other novel members of the BMP family include osteogenic protein 1 (BMP-7) and osteogenic protein 2 (BMP-8). Bone morphogenetic proteins are members of the transforming growth factor-β superfamily and include three distinct subfamilies: BMP-2, BMP-3, and BMP-7. Native BMP-3 and recombinant BMP-4 bind type IV collagen of the basement membrane. This novel connection may be the long elusive mechanistic explanation for the requirement of angiogenesis and vascular invasion for bone morphogenesis. BMPs may have a role in fracture repair, periodontal regeneration, and alveolar ridge augmentation.