bluuebunny/crossref_metadata_2025 huggingface dataset:
Alkali absorption and citrate excretion in calcium nephrolithiasis
Authors: Sakhaee Khashayar , Williams Russel H. , Oh Man S. , Padalino Paulette , Adams-Huet Beverley , Whitson Peggy , Pak Charles Y.C.
Published: February 2010

The role of net gastrointestinal (GI) alkali absorption in the development of hypocitraturia was investigated. The net GI absorption of alkali was estimated from the difference between simple urinary cations (Ca, Mg, Na, and K) and anions (Cl and P). In 131 normal subjects, the 24 h urinary citrate was positively correlated with the net GI absorption of alkali (r = 0.49, p < 0.001). In 11 patients with distal renal tubular acidosis (RTA), urinary citrate excretion was subnormal relative to net GI alkali absorption, with data from most patients residing outside the 95% confidence ellipse described for normal subjects. However, the normal relationship between urinary citrate and net absorbed alkali was maintained in 11 patients with chronic diarrheal syndrome (CDS) and in 124 stone-forming patients devoid of RTA or CDS, half of whom had “idiopathic” hypocitraturia. The 18 stone-forming patients without RTA or CDS received potassium citrate (30–60 mEq/day). Both urinary citrate and net GI alkali absorption increased, yielding a significantly positive correlation (r = 0.62, p < 0.0001), with the slope indistinguishable from that of normal subjects. Thus, urinary citrate was normally dependent on the net GI absorption of alkali. This dependence was less marked in RTA, confirming the renal origin of hypocitraturia. However, the normal dependence was maintained in CDS and in idiopathic hypocitraturia, suggesting that reduced citrate excretion was largely dietary in origin as a result of low net alkali absorption (from a probable relative deficiency of vegetables and fruits or a relative excess of animal proteins).
Passive immunization with anti-parathyroid hormone-related protein monoclonal antibody markedly prolongs survival time of hypercalcemic nude mice bearing transplanted human PTHrP-producing tumors
Authors: Sato Kanji , Yamakawa Yukiko , Shizume Kazuo , Satoh Tomoko , Nohtomi Kyoko , Demura Hiroshi , Akatsu Takuhiko , Nagata Naokazu , Kasahara Tadashi , Ohkawa Hiroyuki , Ohsumi Kazuoki
Published: February 2010

Malignancy-associated hypercalcemia is mainly caused by excessive production of parathyroid hormone-related protein (PTHrP) by the tumor. Using anti-PTHrP-(1–34) monoclonal murine antibody (anti-PTHrP MoAb), we studied whether repeated injection of the homologous antibody would continuously decrease the serum calcium concentration in hypercalcemic nude mice bearing transplanted human PTHrP-producing tumors, leading to prolongation of their survival time. Daily SC injections of anti-PTHrP MoAb decreased the serum calcium concentration almost to within the normal range in nude mice bearing transplanted human PTHrP-producing tumors (T3M-1, EC-GI, PC-3, and FA-6) but not in a nude mouse bearing a transplanted parathyroid carcinoma. The antibody did not affect FA-6 tumor growth either in vitro or in vivo. Pancreatic carcinoma cells (FA-6), which caused the most severe hypercalcemia, were inoculated into 6-week-old nude mice. When severe hypercalcemia (˜19 mg/dl) had developed, daily SC injection of anti-PTHrP MoAb was started. Within 18 days of this time point, all untreated tumor-bearing mice (n = 10) died of hypercalcemia and cachexia, whereas all the treated mice (n = 10) showed an increase in body weight and survived for at least 25 days. Histologic examination of the treated mice revealed a marked decrease in osteoclastic bone resorption, without toxicologic findings in the kidney and liver. These results suggest that passive immunization against PTHrP can continuously ameliorate the hypercalcemia and markedly prolong the survival time of severely hypercalcemic, tumor-bearing mice. If a human monoclonal antibody against PTHrP-(1–34) could be developed, then passive immunization would be potentially one of the most effective therapies for patients with malignancy-associated hypercalcemia due to excessive production of PTHrP.
Effect of age and osteoarthritis on bone mineral in rhesus monkey vertebrae
Authors: Grynpas Marc D. , Huckell C.B. , Reichs K.J. , Derousseau C.J. , Greenwood C. , Kessler M.J.
Published: February 2010

We have used vertebrae of free-ranging rhesus macaques to study the effect of age and osteoarthritis on bone mineralization and bone density and to relate these findings to weight, sex, parity, and mineral chemistry. Bone mineralization was determined using the density fractionation technique and bone density using dual-photon absorptiometry. Arthritis was determined osteologically. We found a relationship between mineralization, age, and osteophytes, such that mineralization rose with age in nonarthritics and decreased with age in arthritics. This could also be seen when the females were examined separately. In males, only an increase in mineralization with age could be seen. In females mineralization decreases with parity. Also in females, DPA density decreases with age and increases with parity. No relationships with DPA density could be seen using males and females together or males alone. In conclusion, we have shown that normal skeletal aging in rhesus monkeys is accompanied by an increase in mineralization similar to that in other species, but this is not true in the presence of osteoarthritis. In the females parity has an important effect because it seems to build up bone mass even though the bone present may be undermineralized.
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

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 (>50%) and C1 (>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

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

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

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 < 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

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

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

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 < 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

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

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

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 < 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 < 0.03) for the eroded perimeter, and 0.315 ± 0.064 versus 0.561 ± 0.23 μm3/μm2/day in NW (p < 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

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

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

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.
Journal of Bone and Mineral Research
Authors: Avioli Louis V.
Published: February 2010

Hormonal control of skeletal growth, modeling, and remodeling is characterized by a complex interaction between the calciotropic hormones (25-hydroxycholecalciferol, 1,25-dihydroxycholecalciferol, parathyroid hormone, and calcitonin), growth, and thyroid hormones in addition to the estrogenic and androgenic gonadal hormones. Although both growth and thyroid hormones are essential for normal skeletal growth and modeling and also can produce detrimental skeletal effects in adults when circulating in excess concentrations, these hormones assume a minor role in the day-to-day bone remodeling of the mature skeleton. Following the attainment of the peak bone mass, bone mineral content begins to decline in the fourth and fifth decades of life, accelerating in females in the first 5–7 years after the menopause as a result of estrogen deficiency. Associated with this age-dependent loss in skeletal mass are decreases in calcitonin reserve primarily in the 5–7 years following the menopause, decreases in circulating 25-hydroxycholecalciferol, intestinal resistance to 1,25-dihydroxycholecalciferol, and a gradual progressive rise in blood parathyroid hormone. These changes in calciotropic hormone profiles, together with poor nutritional habits, anticonvulsant, glucocorticoid, and thyroid medications, diseases such as type I diabetes, immobilization, or decreased physical activity all serve to weaken the aging skeleton. The result is a gradual and subtle change in skeletal anatomy, which progresses to alterations in vertebral structure, such as kyphosis, scoliosis, and pseudospondylolisthesis, and a variety of sciatic and nerve entrapment syndromes. Vertebral, forearm, and hip fractures and edentulism ultimately comprise the syndrome of age-related bone loss, resulting in lifestyle disabilities, extensive morbidity, analgesic drug abuse, hospitalization, and escalating annual health care expenditures.
Journal of Bone and Mineral Research
Authors: Teitelbaum Steven L.
Published: February 2010

Bone remodeling is a process initiated by the osteoclast, and thus, its understanding is prerequisite to regulation of bone turnover. The last decade has witnessed major advances in our understanding of osteoclast biology, specifically as relates to the ontogeny of the cell and the mechanisms by which it degrades bone. It is now possible to isolate and generate osteoclasts and maintain them in relative purity. Using these models, a number of laboratories have shown that ion transport by the osteoclast plays a major role in its ability to resorb bone. Furthermore, osteoclast–bone matrix attachment, mediated at least in part by integrins, is pivotal to the resorptive process. These discoveries are likely to lead to insight into control of the remodeling process.
Absence of paramyxovirus RNA in cultures of pagetic bone cells and in pagetic bon
Authors: Dr. Birch M.A. , Taylor W. , Fraser W.D. , Ralston S.H. , Hart C.A. , Gallagher J.A.
Published: February 2010

It has been proposed that Paget's disease of bone is caused by the infection of bone cells with one or several paramyxoviruses. In this study we used the polymerase chain reaction (PCR), which allows the detection of very low levels of a target nucleic acid sequence, to study cultures of pagetic bone cells and samples of pagetic bone. Oligonucleotide primers were designed to flank a sequence of the nucleocapsid genome of measles virus and canine distemper virus (CDV). Within this fragment there were contrasting restriction endonuclease sites specific to measles or CDV that allowed identification of the original template. We were unable to detect paramyxovirus RNA in four strains of human bone cells outgrown from pagetic bone and one strain derived from an uninvolved site of a patient with Paget's disease. Furthermore, paramyxovirus sequences were not detected in cDNA prepared from six samples of pagetic bone biopsies. The work presented here further questions the role of measles and CDV in the abnormal remodeling observed in Paget's disease.
Regulation of insulin-like growth factor binding protein 4 by a specific insulin-like growth factor binding protein 4 proteinase in normal human osteoblast-like cells: Implications in bone cell physiology
Authors: Durham Susan K. , Kiefer Michael C. , Riggs Lawrence B. , Conover Cheryl A.
Published: February 2010

Insulin-like growth factor binding protein 4 (IGFBP-4) is secreted by normal human osteoblast-like cells (hOB) and is a potent inhibitor of insulin-like growth factor (IGF) action in vitro. In previous studies, IGF treatment of hOB in culture led to markedly reduced medium levels of IGFBP-4 as detected by western ligand blotting. In the present study, incubation of hOB-conditioned medium (hOB-CM) with IGF under cell-free conditions resulted in a similar loss of IGFBP-4. Both IGF-I and IGF-II were capable of inducing a decrease in IGFBP-4; however, IGF-II was more effective. When the six characterized IGFBP were added to hOB-CM, only IGFBP-4 disappeared in response to IGF-II addition. This IGF-regulated loss of IGFBP-4 was inhibited by metalloproteinase inhibitors and appeared to be due to a proteinase that cleaved IGFBP-4 in 18 and 14 kD fragments identified by western immunoblotting. Conditioned media from eight of eight different donor hOB lines tested exhibited IGFBP-4 proteinase activity. To assess the biologic consequences of IGF-II-induced IGFBP-4 proteolysis, we treated hOB with IGF-II for 5 h, which decreased medium IGFBP-4 by 70%, and then measured IGF-I and insulin stimulation of [3H]thymidine incorporation. IGF-II itself was not mitogenic and had no effect on insulin-stimulated [3H]thymidine incorporation. However, pretreatment of cultured hOB with IGF-II enhanced IGF-I-stimulated [3H]thymidine incorporation threefold. In conclusion, these data indicate that (1) regulation of IGFBP-4 availability can occur via an IGF-dependent, IGFBP-4 proteinase secreted by normal hOB, and (2) IGF-II-induced IGFBP-4 proteolysis is associated with enhanced hOB response to IGF-I. The IGFBP-4/IGFBP-4 proteinase system may be involved in local regulation of IGF action in bone.
Accuracy, precision, and utility of spine and whole-skeleton mineral measurements by dxa in rats
Authors: Dr. Mitlak Bruce H. , Schoenfeld David , Neer Robert M.
Published: February 2010

We evaluated the precision and accuracy of dual-energy x-ray bone densitometry (DXA) in 38 male and female rats aged 1–10 months. The coefficients of variation (CV) estimated from same-day paired measurements of bone mineral content (BMC) were 1.26% at the lumbar spine and 0.69% at the whole skeleton, and the corresponding CV for BMC corrected for projected bone area (i.e., bone mineral density, BMD) were 0.57 and 0.66%. BMC, measured in vivo, correlated closely with the subsequently determined ash weights (spine r2 = 0.94, whole-skeleton r2 = 0.97). The long-term CV for BMC measurements, assessed by measuring a frozen animal daily for 4 weeks, were 1.28% for the spine and 1.03% for the whole skeleton; for BMD the corresponding CV were 0.88 and 1.15%. To examine the utility of serial DXA measurements we followed female rats subjected to ovariectomy (OVX) or sham operation at 10 months of age and male rats given daily subcutaneous injections of hPTH-(1–34) or vehicle starting at 10 months of age every 3 weeks for 15 weeks. In the OVX rats a progressive decrease in spine BMC was observed that was most rapid during the first 6 weeks. By 15 weeks the mean spine BMC decreased by 17% in the OVX rats (p < 0.007 versus sham operation). OVX did not affect the accuracy of DXA measurements as assessed by comparison with the ash weight at the end of the 15 week study. PTH treatment increased spine BMC by a mean of 32% and increased whole-skeleton BMC by a mean of 19% within 15 weeks. The long-term in vivo variation was estimated by fitting a model for BMC and BMD in the vehicle-treated male rats and sham-operated female rats, assuming a linear rate of change over the 15 weeks and a different slope and intercept for each animal; the residual root mean squared error was taken as an estimate of variability. Defined in this manner, the long-term variation for BMC measurements in vivo is 5% for the spine and 3% for the whole skeleton; for BMD the corresponding figures are 3 and 2%. This variability is significantly greater than that attributable to instrumental variation and/or same-day repositioning and must be considered when designing experiments requiring serial measurements.XS
Monitoring bone resorption in early postmenopausal women by an immunoassay for cross-linked collagen peptides in urine
Authors: Gertz B.J. , Shao P. , Hanson D.A. , Quan H. , Harris S.T. , Genant H.K. , Chesnut C.H. , Eyre D.R.
Published: February 2010

A new immunoassay using an ELISA approach for measuring urinary excretion of cross-linked N-telopeptides of type 1 collagen was evaluated as a specific measure of bone resorption. The assay was applied to 65 early postmenopausal women who participated in a placebo-controlled trial of the aminobisphosphonate, alendronate sodium. Eight blood and urine samples were collected over a 9 month interval. Baseline cross-linked peptide excretion varied from 26 to 216 pmol BCE (bone collagen equivalents)/μmol Cr. Within-subject variability (CV) for cross-linked peptide excretion was 20.2% over the 9 months in placebo-treated subjects, substantially less than that observed for other biochemical markers of bone resorption: 45, 53, and 63% for fasting urinary calcium and hydroxyproline and 24 h urinary lysylpyridinoline (HPLC assay), respectively. Baseline cross-linked peptide excretion correlated significantly (p < 0.001) with baseline total urine lysylpyridinoline and serum osteocalcin, but not with the other biochemical markers. Initial peptide excretion also correlated inversely with lumbar spine bone mineral density at entry (r = −0.26, p < 0.05). Treatment for 6 weeks with alendronate produced a dose-dependent suppression of cross-linked peptide excretion (0 ± 8, 29 ± 6, 56 ± 5, and 64 ± 3% for 0, 5, 20, and 40 mg, respectively, p < 0.01 versus placebo for treatment effect), with a return toward pretreatment values during follow-up. Measurement of the urinary cross-linked N-telopeptides of type I collagen by this new ELISA approach appears promising as a simple and reliable method to assess overall bone resorption. It may prove especially useful in monitoring the treatment of osteoporotic women with antiresorptive therapy. Its utility in identifying those women in the high resorption range at menopause who may be at greater risk for osteoporosis should also be assessed in future studies.
Effect of long-term tamoxifen therapy on cancellous bone remodeling and structure in women with breast cancer
Authors: Wright C.D.P. , Garrahan N.J. , Stanton M. , Gazet J.-C. , Mansell R.E. , Dr. Compston J.E.
Published: February 2010

The effects of long-term tamoxifen therapy on bone remodeling were studied in 41 women with breast cancer, 22 treated with tamoxifen for a minimum of 15 months (mean 33) and 19 untreated. Transiliac crest bone biopsies were obtained and a comprehensive histomorphometric analysis performed using a semiautomatic image analysis system. There were no statistically significant differences between the two groups in bone area, osteoid perimeter and area, or osteoid width. Mineral appositional rate, adjusted appositional rate, and mineralization lag time were also similar in the two groups; however, tissue-based bone formation rate was significantly lower in the tamoxifen-treated women (p = 0.05) and the remodeling period significantly longer (p < 0.05). Mean and maximum resorption cavity depth and cavity area were significantly reduced in the tamoxifen-treated patients compared to the untreated patients (p < 0.01, p < 0.01, and p < 0.03, respectively). Calculated and directly measured indices of cancellous bone structure were similar in the two groups, although the data indicated a trend toward greater connectedness in the tamoxifen-treated group. These data indicate that tamoxifen does not exert an antiestrogenic effect on bone remodeling in the human and are consistent with a weak estrogenic effect.
Dietary boron modifies the effects of vitamin D3 nutrition on indices of energy substrate utilization and mineral metabolism in the chick
Authors: Hunt Curtiss D. , Herbel Jo L. , Idso Joseph P.
Published: February 2010

An experiment was designed to test part of the hypothesis that physiologic amounts of dietary boron enhance utilization of or, alternatively, compensate for, inadequate concentrations of active vitamin D metabolites to normalize energy substrate utilization and mineral metabolism. Day-old cockerel chicks were fed a ground corn, high-protein casein, corn oil-based diet (<0.18 mg B/kg) supplemented with physiologic amounts of boron (as orthoboric acid) at 0 (non-PSB) or 1.4 (PSB) mg/kg and vitamin D3 (as vitamin D3 powder in corn endosperm carrier) at 3.13 (inadequate, IVD) or 15.6 (adequate, AVD) μg/kg. After 26 days, IVD decreased food consumption and plasma calcium concentrations and increased plasma concentrations of glucose, β-hydroxybutyrate, triglycerides, triiodothyronine, cholesterol, and alkaline phosphatase activity. In the IVD chicks, PSB returned plasma glucose and triglycerides to concentrations exhibited by the AVD chicks and increased food consumption in both IVD and AVD chicks. Histologic findings suggested that PSB enhanced maturation of the growth plate. A ninefold increase in dietary boron yielded only a twofold increase in plasma boron concentration and no increase in femur boron concentration, which suggests that boron is under homeostatic control. The findings suggest that boron acts on at least three separate metabolic sites because it compensates for perturbations in energy substrate utilization induced by vitamin D3 deficiency, enhances major mineral content in bone, and, independently of vitamin D3, enhances some indices of growth cartilage maturation.
Bone response to alternate-day mechanical loading of the rat tibia
Authors: Raab-Cullen D.M. , Akhter M.P. , Kimmel D.B. , Recker R.R.
Published: February 2010

Mechanical loading of the living skeleton influences bone formation, mass, and strength. The primary purpose of the present study was to examine the influence of different loading schedules (days/week) on the bone response to external loading using an in vivo rat tibia four-point bending model. Three studies were conducted to (1) characterize the loaded region, (2) examine the variation of the response within the loaded region, and (3) test the response to different loading schedules. In all studies adult female retired breeder Sprague-Dawley rats were used (6 months, 285 g). First, the location of the loaded region during four-point bending was determined by radiogrammetry of 7 rats. Second, 5 rats were externally loaded for 8 of 10 days at 31 N, 36 cycles, and 2 Hz (1349 ± 244 μϵ). The extent of labeled (forming) periosteal and endocortical surface in the loaded region was compared both among four serial sections from the same tibia and between the loaded and the contralateral tibiae. Finally, 50 rats were randomized into five groups: two nonloaded, control and sham, and three loaded, alternate day, Monday, Wednesday, and Friday, and daily. The rats were externally loaded for 3 weeks at 35 N, 36 cycles, and 2 Hz (1533 ± 308 μϵ). The tibia and fibula were studied for labeled surfaces and mineral apposition rate. For adult female rats with tibial length 39 mm, the loaded region was located 3.5–14 (±0.7) mm proximal to the tibia-fibula junction (TFJ). With multiple repositionings in the same rat, the location of the distal inner pad varied from 3.2 to 3.8 mm proximal to the TFJ (95% confidence interval). The response to loading was consistent within the loaded region and reliably sampled by two cross sections from the loaded region. The bone response under the loading pads was not different from that at other points within the loaded region. There were no differences in the response to external mechanical loading among the three loading schedules (daily, alternate day, and Monday-Wednesday-Friday). Loading created greater formation surface on the medial periosteum of the tibia (70%) and on the fibula (92%) of externally loaded legs than in nonloaded legs. Loading had no effect on the lateral periosteal formation surface or on the endocortical surface of the tibia. Loading created greater mineral apposition rate in loaded than nonloaded tibia (28–72% greater) at all periosteal surfaces. The pattern of response to loading was the same in both studies 2 and 3. In an adult rat, this model produces a predictable bone response to external mechanical loading in a defined region of the tibial diaphysis. External loading 3 or 4 days/week is as effective as daily loading for increasing periosteal bone formation surface and mineral apposition rate.
Loss of parathyroid hormone-stimulated 1,25-dihydroxyvitamin D3 production in aging does not involve protein kinase A or C pathways
Authors: Friedlander Jason , Janulis Mark , Tembe Vrishali , Ro Heung Kyu , Wong Man-Sau , Dr. Favus Murray J.
Published: February 2010

Intestinal calcium absorption declines with aging as a result of decreased renal 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] biosynthesis. At least part of the decline in 1,25-(OH)2D3 may be due to acquired resistance to parathyroid hormone (PTH) stimulation of renal 25-hydroxyvitamin D1-hydroxylase (1-OHase) activity. To test whether aging rats can increase 1,25-(OH)2D3 production in response to PTH, male rats of the same litter were fed a normal Ca diet and were sacrificed at 175–225 g (young rats) or 3 months later at 350–425 g (aging rats). At sacrifice, basal serum 1,25-(OH)2D3 levels (88 ± 16 versus 49 ± 8 pg/ml, P < 0.05) and in vitro renal proximal tubule 1-OHase activity (178 ± 15 versus 77 ± 5 pmol/mg protein/5 minutes, n = 6, P < 0.001) were lower in aging animals. rPTH-(1–34) (10−11 or 10−11 M) increased in vitro 1,25-(OH)2D3 secretion by perifused renal proximal tubules from young but not aging rats. For young and aging rats, rPTH-(1–34) (10−7 M) increased proximal tubule cAMP-dependent protein kinase (PKA) activity, and lower concentrations (10−11 M) stimulated translocation of protein kinase C (PKC) activity from cytosolic to soluble membrane proximal tubule cell fractions. The results of this study show that PTH activation of 1,25-(OH)2D3 production may involve both signaling pathways, with the PKC pathway responsive to lower concentrations of the hormone. The acquired resistance to PTH stimulation of 1,25-(OH)2D3 production in aging appears not to involve the hormonal activation of PKA or PKC.
Bone loss accompanying voluntary weight loss in obese humans
Authors: Jensen Lars Bjørn , Quaade Flemming , Sørensen Ole Helmer
Published: February 2010

Dual-energy x-ray absorptiometry was performed in 51 obese patients before and after 15 weeks on a low-calorie diet. Of these patients 39 were scanned 6 months later. Total and regional body bone mineral, fat mass, and fat free mass were measured. In the control group, 9 normal volunteers were scanned with up to 23 kg lard distributed anteriorly, and 9 volunteers were scanned with 15 kg lard posteriorly. The lard was then gradually removed to simulate the fat loss found in the patient group. In the patient group the mean weight loss was 12,273 g, the mean fat loss was 11,014 g, and the mean bone mineral loss was 171.6 g after 15 weeks. Close correlation between the fat loss and the bone loss was found and calculated to be 16.5 g bone mineral per kg fat in the patient group, in contrast with 0.5 g bone mineral per kg fat in the control group. In the control group, 15 kg lard placed posteriorly had no statistically significant effect on the bone measurements. If weight and fat were regained at the scanning time 6 months later, the bone mineral was regained as well. Patients with further weight loss continued to lose bone mineral. One patient lost 754 g bone mineral in 9 months. Her weight loss was 45 kg in that period, and the bone mineral content remained within the range for normal women at her age. Methodologic and pathogenetic problems are discussed. It is concluded that the observed bone loss should be regarded as physiologic normalization accompanying a diet-induced weight loss in the obese.