bluuebunny/crossref_metadata_2025 huggingface dataset:
IL-6 Mediates the Effects of IL-1 or TNF, but Not PTHrP or 1,25(OH)2D3, on Osteoclast-like Cell Formation in Normal Human Bone Marrow Cultures
Authors: Devlin Rowena D. , Reddy Sakamuri V. , Savino Rocco , Ciliberto Gennaro , Roodman G. David
Published: April 2006

A potent interleukin-6 (IL-6) antagonist (Sant 5), which binds tightly to the IL-6α receptor but has impaired gp130 heterodimerization, has been developed recently by site-directed mutagenesis of human IL-6. We report here that Sant 5 inhibits IL-6-stimulated osteoclast-like multinucleated cell (MNC) formation in human marrow cultures but also inhibits the stimulatory effects of IL-1 or tumor necrosis factor alpha (TNF-α in these cultures. We further show that a neutralizing antibody to IL-6 also inhibits the stimulatory effects of IL-1 or TNF-α in these cultures. In contrast, Sant 5 had no effect on parathyroid hormone related protein (PTHrP) or 1,25-dihydroxyvitamin D3 stimulated MNC formation in human marrow cultures. Transfection of a human marrow stromal cell line, which normally induces osteoclast formation through production of IL-6, with the Sant 5 cDNA driven by a cytomegalovirus (CMV) promoter blocked the capacity of these cells to stimulate osteoclast-like cell formation. These Sant 5 transfected cells and conditioned media from these cells also inhibited the stimulatory effects of the parent cell line on MNC formation. These data suggest that IL-6 mediates the effects of IL-1 and TNF on human osteoclast formation, but in contrast to murine systems, does not mediate the effects of PTHrP. These data further demonstrate that stromal cells transfected with the Sant 5 cDNA can constitutively produce high levels of the IL-6 antagonist and inhibit osteoclast formation in vitro.
Bone Mineral, Histomorphometry, and Body Composition in Adults with Growth Hormone Receptor Deficiency
Authors: Bachrach Laura K. , Marcus Robert , Ott Susan M. , Rosenbloom Arlan L. , Vasconez Oswaldo , Martinez Victor , Martinez Ana Lucia , Rosenfeld Ron G. , Guevara-Aguirre Jaime
Published: April 2006

Growth hormone (GH) and insulin-like growth factor I (IGF-I) deficiencies have been associated with osteopenia in both children and adults. To examine the effects of growth hormone resistance on bone mineral and body composition, we studied 11 adults (mean age 30 years) with growth hormone receptor deficiency (GHRD, Laron syndrome) and 11 age- and gender-matched controls from Southern Ecuador. Bone mineral and body composition were determined by dual-energy X-ray absorptiometry. Bone physiology was assessed with biochemical markers of bone turnover and dynamic bone histomorphometry. Bone size and body composition differed markedly between subjects with GHRD and controls. Affected adults were 40 cm shorter than controls, had significantly less lean body mass, and had increased percent body fat. Bone mineral content and density (BMD) at the spine, femoral neck, and whole body were significantly lower in adults with GHRD than in controls. Mean BMD Z scores were −1.5 to −1.6 at all sites in affected women and −2.2 to −2.3 in men with GHRD. Estimated volumetric bone density (BMAD) at the spine and femoral neck, however, was not reduced in GHRD. Spine BMAD was 0.210 ± 0.025 versus 0.177 ± 0.021 for affected women versus controls (p < 0.05) and 0.173 ± 0.018 versus 0.191 ± 0.025 for men with GHRD versus normals (p = 0.31). Urinary pyridinoline concentrations were significantly greater in adults with GHRD than in controls, while type I collagen C-telopeptide breakdown products and markers of bone formation did not differ. Differences in histomorphometry were limited to a reduction in trabecular connectivity; bone volume and formation rate were similar to controls. These data confirm the importance of the GH/IGF axis in regulating bone size and body composition. The contribution of these peptides to the acquisition and maintenance of bone mineral is less certain since volumetric bone density was preserved despite low levels of IGF-I and IGFBP-3 associated with GH resistance.
Expression of Type X Collagen and Matrix Calcification in Three-Dimensional Cultures of Immortalized Temperature-Sensitive Chondrocytes Derived from Adult Human Articular Cartilage
Authors: Oyajobi Babatunde O. , Frazer Astrid , Hollander Anthony P. , Graveley Robert M. , Xu Chi , Houghton Adam , Hatton Paul V. , Russell R. Graham G. , Stringer Bradley M. J.
Published: April 2006

Chondrocytes isolated from normal adult human articular cartilage were infected with a retroviral vector encoding a temperature-sensitive mutant of the simian virus 40 large tumor antigen and a linked geneticin (G418)-resistance marker. G418-resistant colonies were then isolated, ring-cloned, and expanded in serum-containing media. Several immortalized chondrocyte cell lines were established from the clones that survived, some of which have been maintained in continuous culture for over 2 years. Despite serial subcultures and maintenance as monolayers, these cells retain expression of markers specific for cells of the lineage, namely type II collagen and aggrecan, detected immunocytochemically. We also examined the phenotype of three of these immortalized cell lines (designated HAC [human articular chondrocyte]) using a pellet culture system, and in this report, we present evidence that a prototype of these lines (HAC-F cells) expresses markers normally associated with hypertrophic chondrocytes. When HAC-F cells were cultivated in centrifuge tubes, for periods of up to 63 days, at 39°C with mild and intermittent centrifugation they continued to express both lineage markers; total type II collagen/pellet remained stable, whereas there was a temporal decrease in cartilage-specific glycosaminoglycans content. In addition, in the presence of ascorbate but in the absence of a phosphate donor or inorganic phosphate supplement, the cells also begin to express a hypertrophic phenotype characterized by type X collagen synthesis and extensive mineralization of the extracellular matrix in late stage cultures. The mRNA encoding type X collagen was detected in the cell pellets by reverse transcriptase polymerase chain reaction as early as day 2, and anti-type X collagen immunoreactivity was subsequently localized in the matrix. The mineral was characterized by energy-dispersive X-ray microanalysis as containing calcium (Ca) and phosphorus (P) with a Ca:P peak height ratio close to that of mineralized bone tissue. The unexpected phenotype of this human chondrocyte cell line provides an interesting opportunity for studying chondrocyte maturation in vitro.
Initiation of the Bony Epiphysis in Long Bones: Chronology of Interactions Between the Vascular System and the Chondrocytes
Authors: Roach Helmtrud I. , Baker Janice E. , Clarke Nicholas M. P.
Published: April 2006

Many events occur concurrently during the initiation of the secondary ossification center in the cartilaginous epiphyses of long bones. We have investigated the chronology of interactions between the vascular system and epiphyseal chondrocytes by culturing explanted heads of femurs and humeri from pre- and neonatal rabbits on the chorioallantoic membrane (CAM) of growing chick embryos. We confirmed that, on the whole, the epiphyseal cartilage was resistant to vascular invasion, whereas the physeal growth plate was resorbed. However, new CAM-derived cartilage canals occasionally penetrated through the articular surface. This caused death of those chondrocytes in the immediate vicinity of the canal but no further reaction. If explants already contained a bony epiphysis and were halved prior to culture, CAM-derived vessels were attracted to the spongiosa. From there they pushed into the uncalcified cartilage, indicating that calcification was not a prerequisite for vascular invasion. Where at least two vessels were in apposition, a new pseudo-ossification center was initiated: chondrocytes became hypertrophic and the matrix calcified. This suggests that cumulative release of diffusible factors from more than one vessel was the trigger for chondrocyte hypertrophy, which, in turn, led to the initiation of the bony epiphysis. CAM cultures thus provide an experimental model for both the quiescent angiogenesis of cartilage canal formation and the reactionary angiogenesis associated with chondrocyte hypertrophy. By exploiting the different anatomy of CAM-derived vascularity, events that occur concurrently in vivo can be spacially separated in CAM culture.
The Role of Estrogen in the Control of Rat Osteocyte Apoptosis
Authors: Tomkinson A. , Gevers E. F. , Wit J. M. , Reeve J. , Noble B. S.
Published: April 2006

We have previously shown that estrogen withdrawal by gonadotrophin-releasing hormone analogs (GnRHa) induces osteocyte death via apoptosis in human bone. Although it is likely that the increase in osteocyte death via apoptosis was related to the loss of estrogen, these experiments could not rule out a direct role for the GnRHa. Therefore, in this study, we have used a rat model of ovariectomy (OVX) to determine whether the effect of estrogen withdrawal extends to other species and to clarify the role of estrogen in the maintenance of osteocyte viability. Twelve 9-week-old rats were divided into three treatment groups: sham operated (SHAM) (n = 4), OVX (n = 4), and OVX + estrogen (E2) (25 μg/day) (n = 4). At 3 weeks following the start of treatment, tibial bones were removed. The percentage of osteocytes displaying DNA breaks, using an in situ nick-translation method, was significantly higher in the OVX group compared with the SHAM control in both cortical bone (10.04% vs. 2.31%, respectively; p < 0.0001) and trabecular bone (6.44% vs. 1.58%, respectively; p = 0.003). Addition of estrogen in the OVX animals completely abrogated the increase in osteocyte apoptosis in cortical bone (0.78%) and trabecular bone (1.17%). The percentage of apoptotic osteocytes decreased with increasing distance from the primary/secondary spongiosa interface below the growth plate in the OVX model and the OVX + E2 model. Nuclear morphology and electrophoresis of DNA confirmed the presence of apoptotic cells in the samples. In conclusion, OVX in the rat results in an increase in osteocyte apoptosis as a direct or indirect result of E2 loss. Addition of estrogen in the OVX animals prevents this increase in osteocyte apoptosis. These data confirm an important role for estrogen in the control of osteocyte apoptosis and the maintenance of osteocyte viability. Estrogen deficiency might, through compromising the viability of osteocyte networks, reduce the ability of bone to respond appropriately to loading.
Novel Mutations in the 1α-Hydroxylase (P450c1) Gene in Three Families with Pseudovitamin D–Deficiency Rickets Resulting in Loss of Functional Enzyme Activity in Blood-Derived Macrophages
Authors: Smith S. J. , Rucka A. K. , Berry J. L. , Davies M. , Mylchreest S. , Paterson C. R. , Heath D. A. , Tassabehji M. , Read A. P. , Mee A. P. , Prof. Mawer E. B.
Published: April 2006

Pseudovitamin D–defiency rickets (PDDR) is an autosomal recessive disorder characterized by hypocalcemia, rickets (which are resistant to treatment with vitamin D), and low or undetectable serum levels of 1,25-dihydroxyvitamin D (1,25(OH)2D). The symptoms are corrected with 1,25(OH)2D treatment, and the disease is now believed to result from a defect in the cytochrome P450 component (P450c1; CYP27B1) of the renal 25-hydroxyvitamin D-1α-hydroxylase (1-OHase). We have studied genomic DNA from three families with PDDR and have identified the same homozygous mutation in the P450c1 gene in two of the index cases, causing a frameshift in exon 8, resulting in a premature stop codon in the heme-binding domain. The two cases in the third kindred were compound heterozygotes with missense mutations in exons 6 and 9. We have also identified a C/T polymorphism in intron 6 of the P450c1 genomic DNA. Interferon γ–inducible 1-OHase activity in blood-derived macrophages was shown by 1,25(OH)2D synthesis in all control cells tested (37–184 fmol/h/106 cells) and those from the PDDR family parents (34–116 fmol/h/106 cells) but was totally absent from the patients' cells, indicating a defect in their macrophage 1-OHase, similar to the presumed renal defect. The assumption of similarity between the renal and macrophage P450c1 was supported by our ability to clone a 514 bp sequence, including the heme-binding region of the macrophage P450c1 cDNA from controls, which was identical to that published for both the renal and keratinocyte P450c1 cDNAs.
Adenovirus-Mediated Gene Therapy of Osteoblasts In Vitro and In Vivo
Authors: Mehrara Babak J. , Saadeh Pierre B. , Steinbrech Douglas S. , Dudziak Matthew , Spector Jason A. , Greenwald Joshua A. , Gittes George K. , Longaker Michael T.
Published: April 2006

Modulation of biological pathways governing osteogenesis may accelerate osseous regeneration and reduce the incidence of complications associated with fracture healing. Transforming growth factor β1 (TGF-β1) is a potent growth factor implicated in the regulation of osteogenesis and fracture repair. The use of recombinant proteins, however, has significant disadvantages and has limited the clinical utility of these molecules. Targeted gene therapy using adenovirus vectors is a technique that may circumvent difficulties associated with growth factor delivery. In this study, we investigate the efficacy of replication-deficient adenoviruses containing the human TGF-β1 and the bacterial lacZ genes in transfecting osteoblasts in vitro and osseous tissues in vivo. We demonstrate that adenovirus-mediated gene therapy efficiently transfects osteoblasts in vitro with the TGF-β1 virus causing a marked up-regulation in TGF-β1 mRNA expression even 7 days after transfection. Increased TGF-β1 mRNA expression was efficiently translated into protein production and resulted in approximately a 46-fold increase in TGF-β1 synthesis as compared with control cells (vehicle- or B-galactosidase–transfected). Moreover, virally produced TGF-β1 was functionally active and regulated the expression of collagen IαI (5-fold increase) and the vascular endothelial growth factor (2.5-fold increase). Using an adenovirus vector encoding the Escherichia coli LacZ gene, we demonstrated that adenovirus-mediated gene transfer efficiently transfects osteoblasts and osteocytes in vivo and that transfection can be performed by a simple percutaneous injection. Finally, we show that delivery of the hTGF-β1 gene to osseous tissues in vivo results in significant changes in the epiphyseal plate primarily as a result of increased thickness of the provisional calcification zone.
Renal Phosphate Wasting in Fibrous Dysplasia of Bone Is Part of a Generalized Renal Tubular Dysfunction Similar to That Seen in Tumor-Induced Osteomalacia
Authors: Collins Michael T. , Chebli Caroline , Jones Janet , Kushner Harvey , Consugar Mark , Rinaldo Piero , Wientroub Shlomo , Bianco Paolo , Robey Pamela Gehron
Published: April 2006

Fibrous dysplasia (FD) of bone is characterized by focal replacement of normal bone and marrow with abnormal bone and fibrous tissue. It arises from postzygotic activating mutations of the GNAS1 gene. Hypophosphatemia due to renal phosphate wasting has been reported in association with FD as a part of the McCune-Albright Syndrome (MAS), which is characterized by FD, skin hyperpigmentation, and precocious puberty. To date, the prevalence and mechanism of phosphate wasting has not been well studied. We evaluated 42 patients with FD/MAS. Serum and urine samples were tested for indices of mineral metabolism, amino acid handling, and markers of bone metabolism. Twenty (48%) patients had some degree of renal phosphate wasting. Nephrogenous cyclic adenosine monophosphate (cAMP) was normal in FD patients, suggesting that the underlying cause of phosphate wasting is not the presence of activating GNAS1 mutations in the kidney. In addition, there was evidence of a more generalized renal tubulopathy as represented by the presence of abnormal vitamin D metabolism, proteinuria in 36 (86%) patients, and aminoaciduria in 39 (94%) patients. Renal phosphate wasting significantly correlated with the degree of bone involvement, as assessed by serum and urine markers of bone metabolism, suggesting that a circulating factor produced by FD bone and impacting on the kidney may be the mechanism. These data show that phosphaturia as part of a generalized renal tubulopathy represents the most common extraskeletal manifestation of FD and that the observed tubulopathy is similar to that seen in tumor-induced osteomalacia (TIO).
Risk Factors for Fractures of the Proximal Humerus: Results From the EPIDOS Prospective Study
Authors: Lee Sun H. , Dargent-Molina Patricia , Bréart Gérard
Published: April 2006

Fracture of the proximal humerus is one of the most frequent fractures attributable to osteoporosis; yet, it has seldom been studied. Two types of factors (related to bone fragility and falls) were evaluated to identify risk factors for proximal humerus fractures as well as to examine possible interactions between them. Subjects were 6901 white women aged ≥75 years and all participated in the EPIDOS study of risk factors for osteoporotic fractures (France, 1992-1998). The baseline examination included measurements of femoral neck bone mineral density (BMD) and calcaneal ultrasound parameters (speed of sound [SOS] and broadband ultrasound attenuation [BUA]), a functional clinical examination, and completing a questionnaire on health status and lifestyle. During a mean of 3.6 (0.8) years of follow-up, 165 women had a humeral fracture. Using multivariate Cox regression models, we identified three predictors related to bone fragility—low BMD (relative risk [RR] = 1.4; 95% CI, 1.1-1.7), low SOS (RR = 1.3; 95% CI, 1.0-1.6), and maternal history of hip fracture (RR = 1.8; 95% CI, 1.0-3.0)—and four fall-related predictors—a previous fall (RR = 3.0; 95% CI, 1.5-6.1), a low level of physical activity (RR = 2.2; 95% CI, 1.1-4.4), impaired balance (RR = 1.8; 95% CI, 1.1-2.9), and pain in lower limb extremity (RR = 1.4; 95% CI, 1.0-2.1). The effect of these fall-related predictors varied according to the BMD level; they were significantly associated with proximal humerus fractures in women with osteoporosis (BMD T score < −2.5) but not in nonosteoporotic women. The incidence of proximal humerus fracture in women with osteoporosis and a low fall risk score (5.1 per 1000 woman-years) was only slightly higher than in nonosteoporotic women (4.6 per 1000 woman-years) and similar to the incidence in women without osteoporosis but a high fall risk score (5.3 per 1000 woman-years). On the other hand, the incidence in women who had both types of risk factors was more than two times higher (12.1 per 1000 woman-years) than in women with only one of the two risk factors. These results suggest that women who have both types of risk factors should receive the highest priority for prevention.
Systemic Regulation of Distraction Osteogenesis: A Cascade of Biochemical Factors
Authors: Weiss S. , Baumgart R. , Jochum M. , Strasburger C. J. , Bidlingmaier M.
Published: April 2006

This study investigates the systemic biochemical regulation of fracture healing in distraction osteogenesis compared with rigid osteotomy in a prospective in vivo study in humans. To further clarify the influence of mechanical strain on the regulation of bone formation, bone growth factors (insulin-like growth factor [IGF] I, IGF binding protein [IGFBP] 3, transforming growth factor [TGF] β1, and basic FGF [bFGF]), bone matrix degrading enzymes (matrix-metalloproteinases [MMPs] 1, 2, and 3), human growth hormone (hGH), and bone formation markers (ALP, bone-specific ALP [BAP], and osteocalcin [OC]) have been analyzed in serum samples from 10 patients in each group pre- and postoperatively. In the distraction group, a significant postoperative increase in MMP-1, bFGF, ALP, and BAP could be observed during the lengthening and the consolidation period when compared with the baseline levels. Osteotomy fracture healing without the traction stimulus failed to induce a corresponding increase in these factors. In addition, comparison of both groups revealed a significantly higher increase in TGF-β1, IGF-I, IGFBP-3, and hGH in the lengthening group during the distraction period, indicating key regulatory functions in mechanotransduction. The time courses of changes in MMP-1, bone growth factors (TGF-β1 and bFGF), and hGH, respectively, correlated significantly during the lengthening phase, indicating common regulatory pathways for these factors in distraction osteogenesis. Significant correlation between the osteoblastic marker BAP, TGF-β1, and bFGF suggests strain-activated osteoblastic cells as a major source of systemically increased bone growth factors during callus distraction. The systemic increase in bFGF and MMP-1 might reflect an increased local stimulation of angiogenesis during distraction osteogenesis.
The Structural and Hormonal Basis of Sex Differences in Peak Appendicular Bone Strength in Rats
Authors: Kim Bom-Taeck , Mosekilde Lis , Duan Yunbo , Zhang Xin-Zhou , Tornvig Lise , Thomsen Jesper Skovhus , Seeman Ego
Published: April 2006

To identify the structural and hormonal basis for the lower incidence of fractures in males than females, sex differences in femoral mid-shaft geometry and breaking strength were studied in growth hormone (GH)-replete and -deficient male and female rats. Sexual dimorphism appeared during growth. Cortical thickening occurred almost entirely by acquisition of bone on the outer (periosteal) surface in males and mainly on the inner (endocortical) surface in females. By 8 months of age, males had 22% greater bone width and 33% greater breaking strength than females. Gonadectomy (Gx) at 6 weeks reduced sex differences in bone width to 7% and strength to 21% by halving periosteal bone formation in males and doubling it in females. Gx had no net effect on the endocortical surface in males but abolished endocortical bone acquisition in females. GH deficiency halved periosteal bone formation and had no net effect on the endocortical surface in males, but abolished bone acquisition on both surfaces in females, leaving males with 17% greater bone width and 44% greater breaking strength than females. Sex hormone deficiency produces greater bone fragility in males than females by removing a stimulator of periosteal growth in males and removing an inhibitor of periosteal growth in females. GH deficiency produces less bone fragility in males than females because males retain androgen-dependent periosteal bone formation while bone acquisition on both surfaces is abolished in females. Thus, periosteal growth is independently and additively stimulated by androgens and GH in males, inhibited by estrogen, and stimulated by GH in females. The hormonal regulation of bone surfaces establishes the amount and spatial distribution of bone and so the sexual dimorphism in its strength.
The Dynamic Mobility of Vertebral Compression Fractures
Authors: McKiernan Fergus , Jensen Ron , Faciszewski Tom
Published: April 2006

We have observed that some osteoporotic vertebral compression fractures (VCFs) are mobile. The purpose of this report was to document the existence of dynamic fracture mobility, estimate the frequency of dynamic mobility in patients referred for vertebroplasty, define the magnitude and nature of dynamic mobility, and consider the implications of the dynamic mobility of osteoporotic VCFs. This was a prospective radiographic analysis of 41 consecutive patients with 65 VCFs who underwent vertebroplasty. Preoperative standing lateral radiographs of the fractured vertebrae were compared with supine cross-table lateral radiographs to determine the presence or absence of dynamic mobility. Postoperative standing lateral radiographs were evaluated to document fracture mobility and assess final vertebral height restoration. Radiographs were manually digitized to calculate vertebral body morphometrics. Dynamic fracture mobility was demonstrated in 44% of patients (35% of treated vertebrae) who underwent vertebroplasty. Postoperatively, in mobile fractures, average anterior vertebral height increased 106% compared with initial fracture height (absolute increase, 8.41 ± 0.4 mm). Mean lateral vertebral area increased from 48% to 80% of normal, and kyphotic angle decreased 40%. Mobile fractures dominated at the thoracolumbar junction. Intravertebral clefts were defined and identified in every mobile fracture and were absent from every nonmobile (fixed) fracture. This radiographic series documents the previously unrecognized occurrence of dynamic fracture mobility in many osteoporotic VCFs. Fracture mobility can be substantial and clinically significant. Any intervention that claims vertebral height restoration must control for the occurrence of dynamic fracture mobility.
Trabecular Bone Tissue Strains in the Healthy and Osteoporotic Human Femur
Authors: Van Rietbergen B , Huiskes R , Eckstein F , Rüegsegger P
Published: April 2006

Quantitative information about bone tissue‐level loading is essential for understanding bone mechanical behavior. We made microfinite element models of a healthy and osteoporotic human femur and found that tissue‐level strains in the osteoporotic femoral head were 70% higher on average and less uniformly distributed than those in the healthy one.

Introduction: Bone tissue stresses and strains in healthy load‐adapted trabecular architectures should be distributed rather evenly, because no bone tissue is expected to be overloaded or unused. In this study, we evaluate this paradigm with the use of microfinite element (μFE) analyses to calculate tissue‐level stresses and strains for the human femur. Our objectives were to quantify the strain distribution in the healthy femur, to investigate to what extent this distribution is affected by osteoporosis, to determine if osteoporotic bone is simply bone adapted to lower load levels, and to determine the “safety factor” for trabecular bone.

Materials and Methods: μFE models of a healthy and osteoporotic proximal femur were made from microcomputed tomography images. The models consisted of over 96 and 71 million elements for the healthy and osteoporotic femur, respectively, and represented their internal and external morphology in detail. Stresses and strains were calculated for each element and their distributions were calculated for a volume of interest (VOI) of trabecular bone in the femoral head.

Results: The average tissue‐level principal strain magnitude in the healthy VOI was 304 ± 185 microstrains and that in the osteoporotic VOI was 520 ± 355 microstrains. Calculated safety factors were 8.6 for the healthy and 4.9 for the osteoporotic femurs. After reducing the force applied to the osteoporotic model to 59%, the average strain compared with that of the healthy femur, but the SD was larger (208 microstrains).

Conclusions: Strain magnitudes in the osteoporotic bone were much higher and less uniformly distributed than those in the healthy one. After simulated joint‐load reduction, strain magnitudes in the osteoporotic femur were very similar to those in the healthy one, but their distribution is still wider and thus less favorable.
TRACP as an Osteopontin Phosphatase
Authors: Andersson Göran , Ek-Rylander Barbro , Hollberg Karin , Ljusberg-SjÖLander Jenny , Lång Pernilla , Norgård Maria , Wang Yunling , Zhang Shi-Jin
Published: April 2006

TRACP is synthesized as a latent proenzyme requiring proteolytic processing to attain maximal phosphatase activity. Excision of an exposed loop domain abolishes the interaction between the loop residue Asp146 and a ligand to the redox-sensitive iron of the active site, most likely Asn91, providing a mechanism for the enzyme repression. Both cathepsin K and L efficiently cleave in the loop domain and activate the latent enzyme, and we propose that cathepsin K acts as a physiological activator of TRACP in osteoclasts, whereas cathepsin L might fulfill a similar role in different types of macrophages. Considering the rather broad substrate specificity of TRACP, a tight regulation of its activity in the cell appears warranted. Besides proteolytic cleavage, the enzyme should need a specific local environment with a slightly acidic pH and reducing equivalents to keep the enzyme fully active. Cellular subcompartments where these required conditions prevail are potential subcellular site(s) of TRACP action. Of bone phosphoproteins shown to be substrates for TRACP, both osteopontin and bone sialoprotein are colocalized with TRACP in the resorption lacuna of the osteoclasts, and dephosphorylation of OPN impair its ability to promote adhesion as well as migration of osteoclasts in vitro. A role for TRACP as an osteopontin phosphatase in bone is therefore suggested. The expression of TRACP as well as OPN in other tissues with possible interactions between the two could suggest a more general function for TRACP as a regulator of OPN phosphorylation and bioactivity.
Associations Among Disease Conditions, Bone Mineral Density, and Prevalent Vertebral Deformities in Men and Women 50 Years of Age and Older: Cross-Sectional Results From the Canadian Multicentre Osteoporosis Study
Authors: Hanley DA , Brown JP , Tenenhouse A , Olszynski WP , Ioannidis G , Berger C , Prior JC , Pickard L , Murray TM , Anastassiades T , Kirkland S , Joyce C , Joseph L , Papaioannou A , Jackson SA , Poliquin S , Adachi JD
Published: April 2006

This cross-sectional cohort study of 5566 women and 2187 men 50 years of age and older in the population-based Canadian Multicentre Osteoporosis Study was conducted to determine whether reported past diseases are associated with bone mineral density or prevalent vertebral deformities. We examined 12 self-reported disease conditions including diabetes mellitus (types 1 or 2), nephrolithiasis, hypertension, heart attack, rheumatoid arthritis, thyroid disease, breast cancer, inflammatory bowel disease, neuromuscular disease, Paget's disease, and chronic obstructive pulmonary disease. Multivariate linear and logistic regression analyses were performed to determine whether there were associations among these disease conditions and bone mineral density of the lumbar spine, femoral neck, and trochanter, as well as prevalent vertebral deformities. Bone mineral density measurements were higher in women and men with type 2 diabetes compared with those without after appropriate adjustments. The differences were most notable at the lumbar spine (+0.053 g/cm2), femoral neck (+0.028 g/cm2), and trochanter (+0.025 g/cm2) in women, and at the femoral neck (+0.025 g/cm2) in men. Hypertension was also associated with higher bone mineral density measurements for both women and men. The differences were most pronounced at the lumbar spine (+0.022 g/cm2) and femoral neck (+0.007 g/cm2) in women and at the lumbar spine (+0.028 g/cm2) in men. Although results were statistically inconclusive, men reporting versus not reporting past nephrolithiasis appeared to have clinically relevant lower bone mineral density values. Bone mineral density differences were −0.022, −0.015, and −0.016 g/cm2 at the lumbar spine, femoral neck, and trochanter, respectively. Disease conditions were not strongly associated with vertebral deformities. In summary, these cross-sectional population-based data show that type 2 diabetes and hypertension are associated with higher bone mineral density in women and men, and nephrolithiasis may be associated with lower bone mineral density in men. The importance of these associations for osteoporosis case finding and management require further and prospective studies.
Children and the Risk of Fractures Caused by Oral Corticosteroids
Authors: van Staa TP , Cooper C , Leufkens Hgm , Bishop N
Published: April 2006

Oral corticosteroids are known to increase the risk of fracture in adults, but their effects in children remain uncertain. The medical records of general practitioners in the United Kingdom (from the General Practice Research Database) were used to estimate the incidence rates of fracture of children ages 4-17 years taking oral corticosteroids (n = 37,562) and of control children taking nonsystemic corticosteroids (n = 345,748). Each child with a fracture (n = 22,846) was subsequently matched by age, sex, practice, and calendar time to one child without a fracture. The average duration of treatment was 6.4 days (median, 5 days). The risk of fracture was increased in children with a history of frequent use of oral corticosteroids; children who received four or more courses of oral corticosteroids had an adjusted odds ratio (OR) for fracture of 1.32 (95% CI, 1.03-1.69). Of the various fracture types, the risk of humerus fracture was doubled in children who received four or more courses of oral corticosteroids (adjusted OR, 2.17 [1.01-4.67]). Fracture risk was also increased among children using 30 mg prednisolone or more each day (adjusted OR for fracture, 1.24 [1.00-1.52]) and among those receiving four or more courses of oral corticosteroids (OR, 1.32 [1.03-1.69]). Children who stopped taking oral corticosteroids had a comparable risk of fracture to those in the control group. Our findings suggest that children who require more than four courses of oral corticosteroid as treatment for underlying disease are at increased risk of fracture. It is not entirely clear whether this relates directly to oral corticosteroid use or the underlying disease and its severity. Irrespective of these issues, this group of children is at increased risk of fracture.
Aging of Microstructural Compartments in Human Compact Bone
Authors: Akkus Ozan , Polyakova-Akkus Anna , Adar Fran , Schaffler Mitchell B
Published: April 2006

Composition of microstructural compartments in compact bone of aging male subjects was assessed using Raman microscopy. Secondary mineralization of unremodeled fragments persisted for two decades. Replacement of these tissue fragments with secondary osteons kept mean composition constant over age, but at a fully mineralized limit. Slowing of remodeling may increase fracture susceptibility through an increase in proportion of highly mineralized tissue.

In this study, the aging process in the microstructural compartments of human femoral cortical bone was investigated and related to changes in the overall tissue composition within the age range of 17-73 years. Raman microprobe analysis was used to assess the mineral content, mineral crystallinity, and carbonate substitution in fragments of primary lamellar bone that survived remodeling for decades. Tissue composition of the secondary osteonal population was investigated to determine the composition of turned over tissue volume. Finally, Raman spectral analysis of homogenized tissue was performed to evaluate the effects of unremodeled and newly formed tissue on the overall tissue composition. The chemical composition of the primary lamellar bone exhibited two chronological stages. Organic matrix became more mineralized and the crystallinity of the mineral improved during the first stage, which lasted for two decades. The mineral content and the mineral crystallinity did not vary during the second stage. The results for the primary lamellar bone demonstrated that physiological mineralization, as evidenced by crystal growth and maturation, is a continuous process that may persist as long as two decades, and the growth and maturation process stops after the organic matrix becomes “fully mineralized.” The average mineral content and the average mineral crystallinity of the homogenized tissue did not change with age. It was also observed that the mineral content of the homogenized tissue was consistently greater than the osteons and similar to the “fully mineralized” stage of primary bone. The results of this study demonstrated that unremodeled compartments of bone grow older through maturation and growth of mineral crystals in a protracted fashion. However, the secondary osteonal remodeling impedes this aging process and maintains the mean tissue age fairly constant over decades. Therefore, slowing of remodeling may lead to brittle bone tissue through accumulation of fully mineralized tissue fragments.
T-Cells Mediate an Inhibitory Effect of Interleukin-4 on Osteoclastogenesis
Authors: Mirosavljevic Danijela , Quinn Julian Mw , Elliott Jan , Horwood Nicole J , Martin T John , Gillespie Matthew T
Published: April 2006

IL-4 is an important cytokine that can influence bone. We identified two distinct actions of IL-4 to inhibit osteoclast formation: one direct on osteoclast progenitors and the second through the production of a novel T-cell surface-associated molecule(s). These data show a new link between the immune system and bone.

The Th2 cytokine interleukin (IL)-4 inhibits osteoclast formation in vitro but also acts on other cell types found in bone, including T-cells and macrophages. Because some osteoclastogenesis inhibitors (e.g., IL-12) act indirectly through T-cells, we investigated IL-4 action on osteoclastogenesis in the presence of T-cells. Osteoclast formation from murine spleen cells treated with RANKL and macrophage colony-stimulating factor (M-CSF) was blocked by IL-4 even when spleen cells were depleted of T-cells (Thy 1.2+) and/or B-cells (B220+). Also, IL-4 inhibited osteoclastogenesis in RANKL/M-CSF-stimulated adherent spleen cells, Rag1−/− (lymphocyte-deficient) spleen cells, and bone marrow macrophages, indicating an action on myelomonocytic cells to block osteoclastogenesis. In contrast, IL-4 did not inhibit osteoclastogenesis in cells from IL-4 receptor null mice (IL-4R−/−). However, when wildtype T-cells were added to IL-4R−/− spleen cell cultures, IL-4 inhibited osteoclast formation, indicating a T-cell-dependent action. Osteoclast formation in RANKL-stimulated RAW 264.7 cells was not inhibited by IL-4 unless T-cells were added to the culture. Separation of RAW 264.7 cells and T-cells by semipermeable membrane ablated this action of IL-4, suggesting the induction of a membrane-associated osteoclastogenesis inhibitor. However, membrane-bound inhibitors thymic shared antigen-1 (TSA-1) and osteoclast inhibitory lectin (OCIL) were not regulated by IL-4. In summary, at least two mechanisms of IL-4-mediated osteoclastogenesis inhibition exist, including a direct action on myelomonocytic progenitors (from which osteoclasts derive) and an indirect action through T-cells that may involve novel anti-osteoclastic factors.
Cortical and Trabecular Load Sharing in the Human Vertebral Body
Authors: Eswaran Senthil K , Gupta Atul , Adams Mark F , Keaveny Tony M
Published: April 2006

The biomechanical role of the vertebral cortical shell remains poorly understood. Using high-resolution finite element modeling of a cohort of elderly vertebrae, we found that the biomechanical role of the shell can be substantial and that the load sharing between the cortical and trabecular bone is complex. As a result, a more integrative measure of the trabecular and cortical bone should improve noninvasive assessment of fracture risk and treatments.

Introduction: A fundamental but poorly understood issue in the assessment of both osteoporotic vertebral fracture risk and effects of treatment is the role of the trabecular bone and cortical shell in the load-carrying capacity of the vertebral body.

Materials and Methods: High-resolution μCT-based finite element models were developed for 13 elderly human vertebrae (age range: 54–87 years; 74.6 ± 9.4 years), and parameter studies—with and without endplates—were performed to determine the role of the shell versus trabecular bone and the effect of model assumptions.

Results: Across vertebrae, whereas the average thickness of the cortical shell was only 0.38 ± 0.06 mm, the shell mass fraction (shell mass/total bone mass)—not including the endplates—ranged from 0.21 to 0.39. The maximum load fraction taken by the shell varied from 0.38 to 0.54 across vertebrae and occurred at the narrowest section. The maximum load fraction taken by the trabecular bone varied from 0.76 to 0.89 across vertebrae and occurred near the endplates. Neither the maximum shell load fraction nor the maximum trabecular load fraction depended on any of the densitometric or morphologic properties of the vertebra, indicating the complex nature of the load sharing mechanism. The variation of the shell load-carrying capacity across vertebrae was significantly altered by the removal of endplates, although these models captured the overall trend within a vertebra.

Conclusions: The biomechanical role of the thin cortical shell in the vertebral body can be substantial, being about 45% at the midtransverse section but as low as 15% close to the endplates. As a result of the complexity of load sharing, sampling of only midsection trabecular bone as a strength surrogate misses important biomechanical information. A more integrative approach that combines the structural role of both cortical and trabecular bone should improve noninvasive assessment of vertebral bone strength in vivo.
Preconditioning Doses of NMDA Promote Neuroprotection by Enhancing Neuronal Excitability
Authors: Soriano Francesc X. , Papadia Sofia , Hofmann Frank , Hardingham Neil R. , Bading Hilmar , Hardingham Giles E.
Published: April 2006

Neuroprotection can be induced by low doses of NMDA, which activate both synaptic and extrasynaptic NMDA receptors. This is in apparent contradiction with our recent findings that extrasynaptic NMDA receptor signaling exerts a dominant inhibitory effect on prosurvival signaling from synaptic NMDA receptors. Here we report that exposure to low preconditioning doses of NMDA results in preferential activation of synaptic NMDA receptors because of a dramatic increase in action potential firing. Both acute and long-lasting phases of neuroprotection in the face of apoptotic or excitotoxic insults are dependent on this firing enhancement. Key mediators of synaptic NMDA receptor-dependent neuroprotection, phosphatidylinositol 3 kinase-Akt (PI3 kinase-Akt) signaling to Forkhead box subgroup O (FOXO) export and glycogen synthase kinase 3β (GSK3β) inhibition and cAMP response element-binding protein-dependent (CREB-dependent) activation of brain-derived neurotrophic factor (BDNF), can be induced only by low doses of NMDA via this action potential-dependent route. In contrast, NMDA doses on the other side of the toxicity threshold do not favor synaptic NMDA receptor activation because they strongly suppress firing rates below baseline. The classic bell-shaped curve depicting neuronal fate in response to NMDA dose can be viewed as the net effect of two antagonizing (synaptic vs extrasynaptic) curves: via increased firing the synaptic signaling dominates at low doses, whereas firing becomes suppressed and extrasynaptic signaling dominates as the toxicity threshold is crossed.
Development of an Anthropomorphic Telemanipulation System (Entwicklung eines anthropomorphen Telemanipulationssystems)
Authors: Stanczyk Bartlomiej , Buss Martin
Published: April 2006

This article describes the development of a dual arm robotic manipulator with anthropomorphic kinematics. The goal of this work is mimicking the functionality of the human arms for the purpose of teleoperation. Two main issues are discussed. First, the kinematic control of the manipulators, including redundancy resolution and singularity robust inverse kinematics, is presented. Second issue is the comparative study of compliant control methods aiming at securing stable contact with unknown environments. As a practical benchmark an assembly experiment for a case of a negligible time delay was successfully performed.
Molly Mooching on Bradley Mountain: The Aesthetic Ecology of Appalachian
Authors: hufford mary
Published: April 2006

Morel mushrooms (morchella sp.) are a prized delicacy wherever they can be found in the world’s temperate zone. Among English speakers they go by a variety of names, related to their appearance and habitat, such as Honeycombs, Dryland Fish, and Orchard mushrooms. Only in Central Appalachia are they referred to as “molly moochers.” This article explores the relationship of molly moochers to the idea and practice of the community forest. The community forest exemplifies Gregory Bateson’s notion of the thinking system, which is the organism plus its environment, as the minimal unit required for any organism’s survival. Viewed in isolation from human communities, forests are in part the expression of mycorrhizal associations (from the Greek mykes meaning fungus and rhiza meaning root). Viewed as a medium for and expression of community life, the community forest becomes in part the expression of homomycorrhizal associations. The intelligence circulating through the community forest implicates memory and the senses in a deep aesthetic ecology. This aesthetic ecology forms the context for the renewal of the community forest through such annual events as the springtime hunt for molly moochers.
Clarissa; or, Rake Versus Usurer
Authors: BATSAKI YOTA
Published: April 2006

ABSTRACT This paper applies “interest,” as a dominant eighteenth-century model of human nature, to Richardson's Clarissa; it proceeds to explore the construction of a new ethics of sexual relationship in the novel by focusing on the homology between usury and libertinism as two kinds of speculation judged immoral due to absence of risk. Clarissa's economic language reveals her to be an astute exegete of her culture's politics and enables her to redress the sexual imbalance of risk; Lovelace, by contrast, troubles the assumptions of the “interest” paradigm by subscribing to an aristocratic economy of expenditure that is at odds with the economic prudence of the bourgeoisie.
Interrelationships among Agronomic and Seed Quality Traits in an Interspecific Soybean Recombinant Inbred Population
Authors: Cicek Mine S. , Chen Pengyin , Saghai Maroof M. A. , Buss Glenn R.
Published: April 2006

The objectives of this study were to evaluate soybean [Glycine max (L.) Merr.] agronomic and quality traits and to examine correlations among traits in an interspecific soybean population. The agronomic traits included maturity, plant canopy height, canopy spread, leaflet length, leaflet width, seed yield, and seed size. The seed quality traits were sucrose, raffinose, and stachyose content. A total of 308 recombinant inbred lines (RIL) were developed from the cross between a large‐seeded Glycine max breeding line (V71‐370) and a small‐seeded Glycine soja Sieb. & Zucc. accession (PI 407162). Normal distribution was observed for most of the traits with a slight skewness towards the G. soja parent. Most correlation coefficients were highly significant, such as the positive correlation between yield and sucrose and between seed size and sucrose. Genotype × environment interaction was significant for all of the agronomic traits but not for sugar contents. Maturity, seed size, and sucrose content were highly heritable, whereas plant height, canopy spread, leaflet length, leaflet width, yield, stachyose content, and raffinose content had relatively low broad‐sense heritabilities. Our findings suggest that the lack of genotype × location effects on sugar content favors progress through selection, but the strong correlation among the sugars may hinder progress in selecting lines that are high in sucrose but low in raffinose and stachyose over different environmental conditions. The information on heritabililty and interrelationships among the agronomic and seed quality traits will be helpful to breeders in constructing their breeding populations and implementing selection strategies.