bluuebunny/crossref_metadata_2025 huggingface dataset:
Responsiveness to 1,25-Dihydroxyvitamin D3 is reduced in lymphocytes from osteoporotic women
Authors: Dr. Koren R. , Ravid A. , Liberman U.A. , Narinsky R. , Maron L. , Weisman M. , Samuel R.
Published: February 2010

The purpose of this work was to test the hypothesis that reduced responsiveness of target organs to 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] is associated with osteoporosis. Peripheral blood mononuclear (PBM) cells have been previously shown to be a valid model for the action of 1,25-(OH)2D3 on its classic target organs in various pathologic and physiologic situations. The responsiveness of lymphocytes to the hormone can be assessed by the extent of inhibition it exerts on the proliferative response to mitogenic lectins. A group of 39 postmenopausal women, at least 10 years after the menopause, participated in the study. Osteoporosis, defined as the presence of at least one nontraumatic vertebral crush fracture, was diagnosed in 19 subjects. Mitogenesis of PBM cells stimulated by phytohemagglutinin and cultured for 72 h in the presence or absence of 1,25-(OH)2D3 (0.03–1 nmol/liter) was assessed by [3H]thymidine incorporation during a 4 h pulse. The maximal inhibitory effect of 1,25-(OH)2D3 at saturating concentration (1 nM/liter) was 74.6 ± 2.8% (mean ± SEM) for normal compared to 65.3 ± 2.9% for osteoporotic women (P = 0.015). The geometric mean of the ED50 values of 1,25-(OH)2D3 was 60% higher in the osteoporotic than in the normal group (P = 0.035). Our data are consistent with the notion that reduced responsiveness of target organs to 1,25-(OH)2D3 is associated with osteoporosis.
Site-matched calcaneal measurements of broad-band ultrasound attenuation and single X-ray absorptiometry: Do they measure different skeletal properties?
Authors: Glüer C.C. , Vahlensieck M. , Faulkner K.G. , Engelke K. , Black D. , Genant H.K.
Published: February 2010

Because of the differences in the interactions of ultrasound and x-ray waves with bone, quantitative ultrasound (QUS) techniques may yield information about skeletal status not accessible by regular bone densitometry (BD) techniques. However, relatively strong correlations have been reported between broad-band ultrasound attenuation (BUA) and several x-ray-based BD methods. We assessed the precision and association of single x-ray absorptiometry (SXA) and BUA of the calcaneus. We examined both BUA and SXA at the calcaneus using special software for matching the regions of interest. An algorithm was derived and applied to correct the observed correlation coefficients for the attenuation effect caused by the precision errors for BUA and SXA. In a group of 33 volunteers covering a wide range of age and calcaneal bone mineral densities, the site-matched and precision-adjusted correlation coefficient between BUA and SXA was r = 0.58, with a standard error of the estimate (SEE) of 14.41 dB/MHz, or 17.08%. For the subgroup of 25 women the correlation was stronger, with r = 0.72 and SEE = 11.53 dB/MHz, or 14.33%. SXA precision was 0.79% for the regular region of interest (ROI) and 1.22% for the site-matched ROI. BUA precision was 2.76% for the entire subject group and 1.63% for women of age 40 or older. The observed correlation coefficient between ultrasound and x-ray based techniques of the order of 0.7 is significant, but it leaves about 50% of the variability unexplained. It remains to be investigated to what extent the unexplained 50% is related to bone strength or structure or whether it reflects a variability unrelated to osteoporosis status.
Rapid publication: Hypocalcemic actions of amylin amide in humans
Authors: Wimalawansa Sunil J. , Gunasekera Ranjan D. , Datta Harish K.
Published: February 2010

Amylin (also known as islet amyloid polypeptide and diabetes-associated peptide) has recently been shown by us to have a potent hypocalcemic effect in rat and rabbit owing to inhibition of osteoclast-mediated bone resorption. The hypocalcemic potency of amylin was found to be second only to that of calcitonin (CT) and is 100-fold more potent than calcitonin gene-related peptide. Here we demonstrate that amylin has a hypocalcemic effect in patients with Paget's disease of bone. Both human CT (hCT) and amylin induced a maximum hypocalcemic effect 2 h following intravenous administration of the peptides (p < 0.001). Although on a molar basis amylin is less potent than CT, it exhibits a significantly prolonged hypocalcemic effect compared to hCT. Here we demonstrate for the first time a profound hypocalcemic effect of amylin in the human, despite sharing only 15% amino acid sequence identity with hCT.
Prostaglandin E2 stimulates synthesis of insulin-like growth factor binding protein-3 in rat bone cells in vitro
Authors: Schmid Christoph , Schläpfer Irene , Waldvogel Margaretha , Zapf Jürgen , Froesch E. Rudolf
Published: February 2010

Prostaglandin E2 is produced by bone cells and increases cyclic AMP in these cells. Like PTH and dibutyryl cyclic AMP, PGE2 is a potent stimulator of IGF-I synthesis in cultured rat osteoblasts and inhibits DNA synthesis and type I procollagen gene expression. In addition, PGE2 inhibits the response of the cells toward IGF-I after 1 day but not after 4 days of incubation. Rat calvaria osteoblasts constitutively release IGFBPs into the culture medium, in particular IGFBP-2 and IGFBP-3. Like growth hormone, PGE2 stimulates the accumulation of IGFBP-3. PGE2 rapidly increases IGF-I and IGFBP-3 mRNA expression in calvaria cells, with a time course clearly different from that observed in response to growth hormone. Thus, PGE2 modifies not only the synthesis of IGF-I but also that of IGFBP-3 in skeletal tissue.
Osteogenesis associated with bone gla protein gene expression in diffusion chambers by bone marrow cells with demineralized bone matrix
Authors: Dr. Dohi Yoshiko , Ohgushi Hajime , Tabata Shiro , Yoshikawa Takafumi , Dohi Kazuhiro , Moriyama Tadashige
Published: February 2010

Diffusion chambers with rat bone marrow cells and demineralized bone matrix (DBM) were implanted subcutaneously to syngeneic 8-week-old rats and were harvested every week 3–7 weeks after implantation, and histochemical examination, determination of alkaline phosphatase activity, total calcium and phosphorus, the bone-specific vitamin K-dependent gla-containing protein (BGP) content, and detection of BGP mRNA relative to mineralization were performed. Alkaline phosphatase in diffusion chamber implants reached the highest activity at 4 weeks and then decreased. Calcium and phosphorus deposits occurred at 4 weeks after implantation and were followed by marked increases until 7 weeks, which was comparable to the accumulation of BGP. The BGP gene within the diffusion chambers began to be expressed at 5 weeks, and its expression increased markedly at 7 weeks after implantation. At 4–5 weeks after implantation, new bone adjacent to the membrane filters and cartilage toward the center of the diffusion chamber were observed histochemically. Light microscopic and immunohistologic examinations of chambers with marrow cells and DBM revealed production of mineralized matrices, typical of bone characterized by the appearance of BGP and mineralized nodules. In contrast, bone marrow cells alone did not show extensive bone formation and yielded very low values for these biochemical parameters. The present experiments demonstrate the potential of bone marrow cells and DBM to produce not only cartilage formation but also membranous bone formation associated with increasing expression of BGP mRNA during the later stages of bone formation, as well as a marked accumulation of BGP.
Racial differences in pre- and postmenopausal bone homeostasis: Association with bone density
Authors: Meier Diane E. , Luckey Marjorie M. , Wallenstein Sylvan , Lapinski Robert H. , Catherwood Bayard
Published: February 2010

The disparity in fracture incidence and bone mass in women of European (white) and African (black) ancestry is of unknown etiology. To determine if racial differences in bone mass reflected racial differences in the mechanisms of bone turnover underlying bone mineral loss, we measured serum osteocalcin, serum alkaline phosphatase, fasting urinary calcium and hydroxyproline excretion, 24 h urinary excretion of calcium and sodium, and dietary intakes of calcium and vitamin D in 263 healthy pre-, peri-, and postmenopausal white and black women. In addition, radial and spinal bone density were measured cross-sectionally for comparison with biochemical measures of bone turnover. The biochemical parameters thought to reflect bone resorption (fasting urinary calcium and hydroxyproline excretions) were lower in black than in white women throughout the age and menopausal stages studied. The parameters thought to reflect bone formation (alkaline phosphatase and osteocalcin), were similar in the two racial groups among the premenopausal women, but osteocalcin was significantly lower among the peri- and postmenopausal blacks. Cross sectionally measured radial bone density increased with age in premenopausal black women, but it did not change with age in the white premenopausal subjects, a statistically significant difference. In peri- and postmenopausal women radial density declined significantly with years after menopause in both racial groups, but the rate of decline was significantly slower in the black women. Lumbar bone density in premenopausal white and black women did not change with age. After menopause lumbar bone density declined significantly and similarly in both racial groups. The biochemical findings and the densitometric data at the radial site are consistent, both suggesting lower bone resorption and lower rates of cortical bone loss in pre- and postmenopausal black women than in whites. Together these findings indicate that racial differences in bone density result, at least in part, from measurable racial differences in bone homeostasis and support the hypothesis of a more positive bone balance in both pre- and postmenopausal black women.
Prostaglandin E2 alleviates cyclosporin a-induced bone loss in the rat
Authors: Katz I.A. , Jee W.S.S. , Joffe I.I. , Stein B. , Takizawa M. , Jacobs T.W. , Setterberg R. , Lin B.Y. , Tang L.Y. , Ke H.Z. , Zeng Q.Q. , Berlin J. , Dr. Epstein S.
Published: February 2010

Cyclosporine A (CsA) administered to the male and female rat produces high-turnover osteopenia. Prostaglandins have both bone-resorbing and bone-forming properties, but administration of prostaglandin E2 (PGE2) to the rat in vivo produces a net increase in cancellous bone. To investigate the effects of PGE2 on CsA-induced alteration in bone mass, 43 male Sprague-Dawley rats (9 weeks old) were administered 15 mg/kg of CsA by oral gavage and/or 6 mg/kg of PGE2 by subcutaneous injection daily for 21 days according to the following protocol: group A was an age-matched control; group B received CsA only; group C received PGE2 only; and group D received CsA and PGE2. Serum was assayed on days 0, 7, 14, and 21 for bone gla protein (BGP), PTH, and 1,25-dihydroxyvitamin D [1,25-(OH)2D]. A computerized image analysis system was used for bone histomorphometry of the proximal tibial metaphysis after double tetracycline labeling. Compared to control animals (group A), treatment with CsA alone (group B) and PGE2 alone (group C) significantly elevated BGP levels. Combination therapy (group D) resulted in BGP levels that were significantly higher on days 7 and 14 than with either agent alone. 1,25-(OH)2D was significantly elevated in the CsA group only (group B). Therapy with CsA alone (group B) resulted in a significant osteopenia. The concurrent administration of PGE2 with CsA (group D) alleviated the altered bone mass induced by CsA alone by adding a significant amount of additional bone. This report confirms and extends the current knowledge of the different effects of CsA and PGE2 on bone mineral metabolism and demonstrates that PGE2 can alleviate the deleterious effects of CsA on bone.
β-Glycerophosphate-induced mineralization of osteoid does not alter expression of extracellular matrix components in fetal rat calvarial cell cultures
Authors: Lee Kui-Lai , Aubin Jane E. , Heersche Johan N. M.
Published: February 2010

When fetal rat calvarial cells are cultured in medium containing vitamin C, osteoid nodules develop after approximately 15 days of culture. Upon addition of an organic phosphate (β-glycerophosphate, βGP), these nodules mineralize. We have now used this system to explore the suggestion made by others that a negative feedback may exist between matrix mineralization on the one hand and the synthesis of alkaline phosphatase and bone matrix collagen on the other by analyzing the synthesis of these proteins and the levels of their mRNAs in mineralizing and nonmineralizing cultures. Our results indicate that in the osteoid nodule-bone nodule system, matrix mineralization did not affect the mRNA levels for osteopontin, type I collagen, bone sialoprotein, or osteocalcin. Synthesis of total protein and collagen and the osteocalcin content of culture media were also not different in the mineralizing and nonmineralizing cultures. However, alkaline phosphatase mRNA was increased in early mineralizing cultures and alkaline phosphatase activity in the cell layer was also increased in mineralizing cultures. Thus, the hypothesis that a direct negative feedback exists between mineralization and matrix protein synthesis is not supported by our experiments.
Diurnal variation in serum markers of type I collagen synthesis and degradation in healthy premenopausal women
Authors: Hassager Christian , Risteli Juha , Risteli Leila , Jensen Signe Birk , Christiansen Claus
Published: February 2010

There are several indications that the functions of human osteoblasts and osteoclasts have circadian rhythms with peak activities occurring at night. It is not known, however, whether the principal function of these cells, namely synthesis and degradation of the organic matrix of bone, of which about 90% is type I collagen, also has a circadian rhythm. This was therefore investigated for both the formation of type I collagen and the degradation of type I collagen in bone using two newly developed serum markers: the serum concentration of the carboxy-terminal propeptide of type I procollagen (PICP) as a marker of formation and the serum concentration of the carboxy-terminal pyridinoline cross-linked telopeptide of type I collagen (ICTP) as a marker of degradation. PICP and ICTP were measured by RIA in samples taken every 3 h over a 24 h period in 12 healthy premenopausal women (age 32 ± 5 years, mean ± SD). Both PICP (p = 0.003) and ICTP (p = 0.00003) showed a significant circadian rhythm, with about 20% higher values at night than in the afternoon. We conclude that serum markers of both the formation of new type I collagen and the degradation of old type I collagen in bone exhibit a clear circadian rhythm, with increased activity of both osteoblasts and osteoclasts at night. The etiology of this circadian rhythm is still unknown.
Effects of stem cell factor on osteoclast-like cell formation in long-term human marrow cultures
Authors: Demulder A. , Suggs S.V. , Zsebo K.M. , Scarcez T. , Roodman G.D.
Published: February 2010

Stem cell factor (SCF) is a newly described hematopoietic growth factor that stimulates the growth of primitive hematopoietic progenitors and mast cells. Since the osteoclast precursor is hematopoietic in origin, we tested SCF for its capacity to stimulate the formation of osteoclast-like multinucleated cells (MNC) in long-term human marrow cultures. These MNC express an osteoclast phenotype and form resorption lacunae on calcified matrices. Addition of SCF alone (0.1 pg/ml to 100 ng/ml) to long-term marrow cultures did not increase MNC formation. However, treatment of these cultures sequentially with SCF for 1 week followed by 1,25-(OH)2D3 for the second and third weeks of culture significantly enhanced MNC formation. [3H]Thymidine incorporation studies showed that SCF increased the proliferation of MNC precursors. These data suggested that SCF was acting on early MNC precursors. We then tested the capacity of SCF to stimulate the formation of colonies of committed precursors for osteoclast-like MNC. SCF (20 pg/ml to 20 ng/ml) enhanced osteoclast precursor formation in unfractionated bone marrow mononuclear cells but was unable to increase osteoclast precursor formation when a highly purified population of hematopoietic precursors was used as the target cells for SCF. These data suggest that SCF works in concert with other factors produced by nonhematopoietic marrow cells to increase the precursor pool for osteoclasts and that other factors, such as 1,25-(OH)2D3, complete the differentiation process to the mature osteoclast.
Effects of 4-amino-1-hydroxybutylidene bisphosphonate on bone biomechanics in rats
Authors: Toolan B.C. , Shea M. , Myers E.R. , Borchers R.E. , Seedor J.G. , Quartuccio H. , Rodan G. , Hayes W.C.
Published: February 2010

Bisphosphonates inhibit osteoclast-mediated bone resorption, but their effects on the mechanical behavior of bone remain uncertain. This study investigated the effects of 4-amino-1-hydroxybutylidene bisphosphonate (AHBuBP) on the biomechanical and morphologic properties of bone in ovariectomized rats. Sprague-Dawley rats (four groups, n = 6) were ovariectomized at 3 months of age. From 7 to 13 months, the groups received vehicle or 0.28, 2.8, or 28 μg/kg of AHBuBP twice weekly through subcutaneous injection. An additional group of control animals (n = 6) received neither surgery nor drug. We determined the stiffness, yield, and ultimate loads of the femoral midshaft, the sixth lumbar (L6) vertebra, and the femoral neck. Geometric properties of the cortical bone were measured from digitized images of the tibial diaphysis at the level of the synostosis. The area fraction of trabecular bone was determined through the midsagittal plane of the fifth lumbar (L5) vertebra. There were no significant differences in the structural properties of the femoral neck and midshaft, with the exception that the medium-dose group had a greater ultimate load than the vehicle group for the femoral midshaft in bending. Cross-sectional analysis of the tibia did not show significant differences in the inertial properties or area. Ovariectomy caused a significant reduction in the stiffness and ultimate load of L6 and in the area fraction of trabecular bone of L5. Using the Tukey method of pairwise comparisons, the mean ultimate load ± standard deviation of the L6 vertebrae from the ovariectomized vehicle group was 30% lower than that from the nonovariectomized control group (276 ± 35 versus 396 ± 63 N, p < 0.05). The mean stiffness was 46% lower (723 ± 206 versus 1327 ± 336 N/mm, p < 0.05), and the area fraction was 41% lower (17.8 ± 5.2 versus 30.0 ± 7.9%, p < 0.05). The high dose of AHBuBP maintained the structural properties of the vertebral bone; the ultimate load (424 ± 55 N), stiffness (1149 ± 145 N/mm), and area fraction (33.7 ± 5.5%) in the high-dose group were all significantly greater than those in the vehicle group but did not differ significantly from those in the control group. We conclude that long-term administration of AHBuBP in rats (started 4 months after ovariectomy) preserves the strength and area fraction of trabecular bone in the lumbar spine in a dose-dependent manner, without evidence of detrimental effects upon the biomechanical or morphologic properties of cortical bone.
Bone and mineral metabolism in the adult guinea pig: Long-term effects of estrogen and androgen deficiency
Authors: Vanderschueren D. , van Herck E. , Suiker A.M.H. , Allewaert K. , Visser W.J. , Geusens P. , Bouillon R.
Published: February 2010

The effects of androgen and estrogen deficiency on skeletal homeostasis were studied in the guinea pig. Male and female adult (7 months old) guinea pigs were either sham operated (9 females and 7 males) or gonadec-tomized [9 ovariectomized (OVX) females and 6 orchidectomized (ORX) males] and sacrificed 4 months later for evaluation of bone mass, bone turnover, and serum calcium homeostasis. Parameters of bone turnover, calcium homeostasis, and vitamin D metabolites were similar in all groups except for increased serum IGF-I concentrations (+30%) in males compared to females. Gonadectomy resulted in a 50% decrease in serum IGF-I concentrations in males only (p < 0.001). Volume, total calcium content, and cortical density of the tibia were significant higher in males than in females. Estrogen deficiency had no effect on bone volume or calcium content. Androgen deficiency resulted in a significant lower volume and calcium content of the tibia and in a lower calcium content of the distal lumbar vertebrae. Single-photon absorptiometry of the tibia showed that only cortical, not trabecular bone density of the tibia was decreased after ORX. Histomorphometric studies of the tibial metaphysis also did not show significant differences in trabecular bone volume between sham-operated and ORX males. We conclude that in adult male guinea pigs androgen deficiency results in a decrease in (cortical) bone volume and content concomitant with decreased IGF-I levels. In female guinea pigs of the same age, estrogen deficiency did not affect total or regional bone mass.
An indirect method of measuring widths suitable for automated bone histomorphometry
Authors: Huffer William E. , Lepoff Ronald B.
Published: February 2010

Orthogonal intercepts from random test lines (OIr), uniformly distributed intercepts (OIu), and areas and lengths (Ar/Le) were measured manually and by computer to determine individual profile and sample widths of artificial profiles and human osteoid seams. Individual widths were equal by Ar/Le and OIu methods. The means of individual profile widths (all methods), of all orthogonal intercepts (OIu and OIr), or of profile widths weighted in proportion to their lengths (Ar/Le) were also equal. Ar/Le and OIu had smaller variance than OIr. Discrepant individual OIu and Ar/Le widths in digitized images were corrected by thresholding and did not significantly affect sample means. Unweighted Ar/Le sample means were 15–44% lower than weighted means. Distributions of osteoid seam widths were not normal, and all but one had more than one mode. We conclude that the Ar/Le method is comparable to direct orthogonal intercept methods and suitable for automated histomorphometry.
A cruciate ligament injury produces considerable, permanent osteoporosis in the affected knee
Authors: Kannus Pekka , Sievänen Harri , Järvinen Markku , Heinonen Ari , Oja Pekka , Vuori Ilkka
Published: February 2010

Bone mineral density (BMD) and clinical status of 42 patients treated surgically 10–11 years earlier for an acute knee ligament injury were determined. The BMD was measured at the spine (L2–4) and the femoral neck, distal femur, patella, proximal tibia, and calcaneus of both lower extremities using dual-energy x-ray absorptiometric (DXA) scanner. The relative BMD results of the injured knee were correlated with sex, age, activity level, knee stability, and functional scores of the patient. In the 11 patients with moderate injury (isolated rupture of the medial collateral ligament), the BMDs of the injured and uninjured extremities were equal. In the 31 patients with severe injury (cruciate ligament rupture), the BMDs were significantly lower in the injured knee: distal femur, −6.0% (p = 0.0000); patella, −9.0% (p = 0.0000); and proximal tibia, −3.3% (p = 0.0012). Neither the femoral neck nor the calcaneus showed any differences. There were no significant differences either between men and women or between patients with different activity levels. The relative BMDs of the injured knee did not correlate with age or static knee stability but correlated significantly (r = 0.42–0.78, p < 0.01–0.001) with the functional scores of the same knee: the better the knee function in comparison with the healthy knee, the higher the relative BMD. The spinal BMDs corresponded with the age-adjusted reference values of the used densitometry. In conclusion, a severe knee ligament injury results in permanently decreased BMD in the injured knee. Other parts of the same extremity and lumbar spine are not affected. The observed decrease (3–9%) is clinically important with respect to age-related bone loss of 1%/year after the age of 35 years. Additional follow-up is needed to determine any increased risk of osteoporotic knee fracture.
Two hereditary defects related to vitamin D metabolism map to the same region of human chromosome 12q13–14
Authors: Labuda Malgorzata , Fujiwara T. Mary , Ross Michelle V. , Morgan Kenneth , Garcia-Heras Jaime , Ledbetter David H. , Hughes Mark R. , Dr. Glorieux Francis H.
Published: February 2010

We have localized the locus for the vitamin D receptor (VDR) responsible for hypocalcemic vitamin D-resistant rickets (HVDRR), close to the pseudovitamin D-deficient rickets (PDDR) locus, another disorder related to impaired vitamin D metabolism. PDDR (formerly vitamin D dependency type I, VDD1) was recently mapped to human chromosome 12q14 by linkage analysis. Here we report on the assignment of VDR to 12q13–14 by in situ hybridization and by linkage analysis. Linkage analysis between VDR, PDDR, and several RFLP markers show close linkage, with no recombination (θ = 0) between VDR and PDDR (Z = 1.94), a COL2A1 haplotype (Z = 4.03), ELA1 (Z = 0.98), and D12S15 (Z = 4.17). The analysis of extended haplotypes in one of the PDDR families provides evidence for recombination between VDR and PDDR and localizes VDR together with COL2A1 proximal to PDDR. Complete allelic association detected between VDR and COL2A1 loci on PDDR chromosomes and lower association between VDR and PDDR suggests a VDR location very close to COL2A1 and one more distant to PDDR. We propose the following order of loci: (VDR, COL2A1), (PDDR, ELA1, D12S15), D12S4, (D12S14, D12S17), D12S6. Thus, two clearly distinct loci involved in the control of vitamin D activity map close to each other in the region 12q13–14.
Bone resorption and formation on the periosteal envelope of the ilium: A histomorphometric study in healthy women
Authors: Balena Raffaella , Shih Mei-Shu , DR. Parfitt A. Michael
Published: February 2010

Continuation of net periosteal bone gain after cessation of longitudinal growth has been inferred from sequential radiographic morphometry. Accordingly, we performed histomorphometry of the periosteal surfaces of transilial bone biopsies from 57 healthy women aged 24–74 years, 29 premenopausal and 28 postmenopausal. Compared to the endocortical surface, the extents of eroded and osteoid surfaces were very similar, but the extents of osteoclast- and osteoblast-covered surfaces were 80–90% smaller, and both wall thickness and osteoid thickness were about 30% lower. Double tetracycline labels were present in only 11 cases. The second (demethylchlortetracycline) label was almost four times as long as the first (oxytetracycline) label, a much greater difference than on the endocortical surface, so that the extent of mineralizing surface was based only on the second label. Even so, adjusted apposition rates and bone formation rates were only about 20% of the endocortical values, and unlike the endocortical surface, formation rates were not higher in the postmenopausal than in the premenopausal women. Resorption, reversal, and formation periods were each much longer than on the endocortical surface. There was no correlation between periosteal and endocortical values for any variable. At least 54% of total cement line length was scalloped, implying reversal of remodeling direction from resorption to formation, and at least 18% of total cement line length was smooth, implying temporary arrest of bone formation. Convincing evidence of modeling, related to growth or mechanical stimulation, was not observed. We conclude (1) periosteal bone turnover occurs by remodeling rather than modeling; it is much slower than endosteal turnover and extends less far from the surface, (2) periosteal bone formation is probably discontinuous with long periods of interruption, and (3) periosteal bone cell recruitment and activity appear to be relatively uninfluenced by the hormonal changes of aging and menopause; presumably local factors, possibly biomechanical, are more important.
Journal of Bone and Mineral Research
Authors: Ypey Dirk L. , Weidema Adam F. , Höld Karin M. , Van Der Laarse Arnoud , Ravesloot Jan H. , Van Der Plas Arie , Nijweide Peter J.
Published: February 2010

Embryonic chick bone cells express various types of ionic channels in their plasma membranes for as yet unresolved functions. Chick osteoclasts (OCL) have the richest spectrum of channel types. Specific for OCL is a K+ channel, which activates (opens) when the inside negative membrane potential (Vm) becomes more negative (hyperpolarization). This is consistent with findings of others on rat OCL. The membrane conductance constituted by these channels is called the inward rectifying K+ conductance (GKi), or inward rectifier, because the hyperpolarization-activated channels cause cell-inward K+ current to pass more easily through the membrane than outward K+ current. Besides GKi, channels, OCL may express two other types of voltage-activated K+ channels. One constitutes the transient outward rectifying K+ conductance (GKto), which is activated upon making the membrane potential less negative (depolarization) but has a transient nature. This conductance favors transient K+ conduction in the cell-outward direction. The GKto also occurs in a small percentage of cells in osteoblast (OBL) and periosteal fibroblast (PFB) cultures. The other OCL K+ conductance, the GKCa, is activated by both membrane depolarization and a rise in [Ca2+]i. GKCa channels are also present in the other chick bone cell types, that is, OBL, osteocytes (OCY), and PFB. Furthermore, in excised patches of all bone cell types, channels have been found that conduct anions, including CI− and phosphate ions. These channels are only active around Vm = 0 mV. While searching for a membrane mechanism for adaptation of bone to mechanical loading, we found stretch-activated channels in chick osteoclasts; other investigators have found stretch-activated cation channels (K+ or aselective) in rat and human osteogenic cell lines. In contrast to other studies on cell lines or OBL from other species, we have not found any of the classic macroscopic voltage-activated calcium conductances (GCa) in any of the chick bone cells under our experimental conditions. However, our fluorescence measurements of [Ca2+]i in single cells indicate the presence of Ca2+ conductive pathways through the plasma membrane of osteoblastic cells and osteoclasts, consistent with other studies. We discuss possible roles for GKi, GKCa, and anion channels in acid secretion by OCL and for stretch-activated channels in OCL locomotion.
Journal of Bone and Mineral Research
Authors: Carter Dennis R. , Orr Tracy E.
Published: February 2010

The role of in vivo mechanical loading histories in normal skeletogenesis is related to the process of adaptive, stress-regulated bone remodeling in the adult. The results of many previous computer models for endochondral ossification and bone modeling and remodeling are reviewed. These studies support the view that simple stress-related mathematical algorithms or “construction rules” can be used to emulate normal skeletal development and architectural construction. Such mathematical rules presumably represent the net result of biophysical phenomena influencing cell metabolism and biosynthetic activity. These rules are also successful in describing the adaptation of adult bone to changes in tissue stresses. The findings suggest that stress-related functional adaptation in mature bones may be merely the adult manifestation of the same mechanical construction rules that guide and constrain normal development.
Journal of Bone and Mineral Research
Authors: Cordey Jacques , Schneider Marina , Belendez Christina , Ziegler Walter J. , Rahn Berton A. , Perren Stephan M.
Published: February 2010

Proximal femur fractures in the elderly lead to a high rate of hospitalization. In studying the operative treatment of such fractures, it is first necessary to understand the relationship between the morphologic properties of this part of the femur (related to both geometry and density) and its mechanical properties. Numerous investigations showed that femoral strength correlates with bone mass; however, the dimension of the bones was not taken into account. We measured the relationship between the stiffness of the proximal femur under physiologic load and its geometry and density. Conventional x-rays and quantitative computed tomography (QCT) were carried out on pairs of human cadaver femora. Eight pairs were instrumented with strain gauges. Bones were subjected to an eccentric load that simulates moderate weight bearing (single-leg stance), and the strain parallel to the bone axis was plotted as a function of the load applied. An apparent bone stiffness was calculated as the ratio between the strain gradient within the section and the load applied. Strong correlation was found between x-ray densitometry and QCT. The bone stiffness also correlates strongly with the geometry (area) and slightly with bone mass; however, an unexpectedly low correlation was found between stiffness and density. We chose stiffness as a mechanical parameter (not strength) because it describes the “normal” bone behavior under load. Our results clearly demonstrate that the cross-sectional size of the bones must be taken into account when establishing the relationship between the mechanical characteristics of the bone and its morphology. In accordance with previous predictions, our results support that bone loss due to osteoporosis is compensated for by an increase in bone diameter.
Cultured circulating mononuclear cells from osteopetrotic infants express the osteoclast-associated vitronectin receptor and form multinucleated cells in response to 1,25-dihydroxyvitamin D3
Authors: Cournot Giulia , Petrovic Milka , Trubert Claire-Lise , Cormier Catherine , Girault Danielle , Fischer Alain , Garabedian MichÈLe
Published: February 2010

Malignant osteopetrosis is characterized by impaired osteoclast activity. Osteoclasts derive from hematopoietic stem cells. In osteopetrosis, marrow cavities fail to develop, resulting in extramedullary hematopoiesis and the presence of stem cells in the bloodstream. Resistance to 1,25-(OH)2D3 may be involved in the pathogenesis of the disease. Sensitivity to 1,25-(OH)2D3, calcitonin sensitivity, and expression of the osteoclast-associated vitronectin receptor (VR) was examined in cultures of circulating mononuclear cells of seven osteopetrotic infants (1.5–6 months old). Since peripheral blood from age-matched children contains few stem cells, umbilical cord blood was used as control. Mononucleated cells were isolated by the Ficoll-Hypaque method and cultured (106 cells per ml) in α-MEM containing 20% horse serum in presence or absence of added 1,25-(OH)2D3. VR was identified by immunochemical staining with MAb 23C6. 1,25-(OH)2D3 at 10−8 M significantly stimulated the formation of multinucleated cells (MNC) in cultures from all osteopetrotic patients and cord blood samples. Cells from three of five patients responded to 10−9 M 1,25-(OH)2D3, the minimal stimulatory concentration for cord blood. Salmon calcitonin (100 ng/ml) partially inhibited the 10−8 M 1,25-(OH)2D3-induced MNC formation in cultures from three of six patients and in cultures of all cord blood samples. In both types of cultures mononuclear cells and MNC cross-reacted with MAb 23C6, and 1,25-(OH)2D3 concentration did not influence the number and percentage of these cells. This study does not support the hypothesis of 1,25-(OH)2D3 resistance in osteopetrotic infants and shows that mononuclear cells expressing VR, possibly osteoclast progenitors, develop in cultures of circulating mononuclear cells from these infants. 1,25-(OH)2D3 may not be closely involved in VR expression.
Collagen crosslinks and mineral crystallinity in bone of patients with osteogenesis imperfecta
Authors: Vetter Ulrich , Weis Mary Ann , Mörike Martin , Eanes Edward David , Eyre David Rodney
Published: February 2010

In cortical bone samples from patients with osteogenesis imperfecta (OI), the concentrations of hydroxy pyridinium cross-linking amino acids in collagen were measured by reversed-phase HPLC and the x-axis crystallinity of the apatite mineral phase was determined by x-ray diffraction. Bone samples from three patients with type I, nine patients with type III, and eight patients with type IV OI were analyzed and compared with human bone from nine controls. The concentration of the two chemical forms of the mature collagen cross-linking amino acids, hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP), and the ratio HP/LP were found to be alike in bone collagen of OI patients and healthy controls. However, the c-axis crystallinity of the apatite was found to be reduced in the type III and IV OI patients compared with controls. Regression analysis of crosslink concentrations and c-axis crystallinity in OI bones did not show any correlation. Therefore, collagen molecules deposited in the extracellular matrix of OI bone appear to fulfill the structural requirements for the action of the enzyme lysyl oxidase, such that a normal concentration of intermolecular crosslinks is formed compared with healthy bone. Consequently, crosslink formation and apatite crystal growth seem to be regulated independently in OI bone.
Early strain-related changes in cultured embryonic chick tibiotarsi parallel those associated with adaptive modeling in vivo
Authors: Dallas Sarah L. , Zaman Gul , Pead Matthew J. , Lanyon Lance E.
Published: February 2010

A model was developed for the application of cyclic mechanical loads to 17 day embryonic chick tibiotarsi in culture. A single 20 minute period of intermittent loading at 0.4 Hz, producing physiologic peak strains and strain rates, resulted in two peak strain magnitude-related responses that were previously reported in vivo: (1) a rapid increase in glucose 6-phosphate dehydrogenase activity in osteoblasts and osteocytes and (2) increased RNA synthesis, as shown by increased incorporation of [3H]uridine into extracted RNA. The RNA response was detectable 8 h following loading but was more pronounced by 24 h. Both responses were blocked by indomethacin (10−6 M). These results demonstrate that embryonic chick bones in organ culture exhibit cellular responses to loading similar to those previously identified in adult canine cancellous bone cultures in vitro and adult avian cortical bone in vivo. These findings are consistent with a sequence of events between loading and new bone formation that includes an immediate strain magnitude-related, prostanoid-dependent increase in activity of the pentose monophosphate shunt in osteoblasts and osteocytes, followed by a similarly strain magnitude-related increase in RNA synthesis over the subsequent 24 h.
Early loading-related changes in the activity of glucose 6-phosphate dehydrogenase and alkaline phosphatase in osteocytes and periosteal osteoblasts in rat fibulae in vivo
Authors: Dodds Robert A. , Ali Nadire , Pead Matthew J. , Lanyon Lance E.
Published: February 2010

The tibiae and fibulae of 14-week-old rats were subjected to a single 5 minutes period of cyclic longitudinal loading at 1 Hz. The activity of the enzymes glucose 6-phosphate dehydrogenase (G6PD) and alkaline phosphatase (ALP) in osteocytes and periosteal osteoblasts was measured immediately and 24 h after loading. In osteocytes G6PD activity was increased immediately after loading but returned to control values 24 h later. There was no detectable ALP activity in these cells regardless of loading history. In periosteal osteoblasts G6PD activity was raised immediately after loading and remained higher than controls 24 h later. ALP activity in periosteal cells was unaffected immediately after loading but 24 h later was substantially increased. These findings are consistent with osteocytes and periosteal cells both being immediately responsive to periods of intermittent loading in their adjacent matrices. In both cell types an early feature of this response is an increase in G6PD activity. In osteocytes this response is short-lived, suggesting that it is an early biochemical change associated with strain perception that does not progress to matrix synthesis. The increase in G6PD activity with unaffected ALP levels in periosteal cells immediately after loading is consistent with a similar response. In these cells the increase in G6PD accompanied by increased ALP levels 24 h after loading suggests that the loading-related response progresses to new bone formation.
Cross talk of dual-signal transduction systems in the regulation of DNA synthesis by parathyroid hormone in osteoblastic osteosarcoma cells
Authors: Kano Junichi , Sugimoto Toshitsugu , Fukase Masaaki , Chihara Kazuo
Published: February 2010

There has been recent evidence that calcium/protein kinase C (Ca/PKC) messenger system as well as adenylate cyclase are involved in the signal transduction stimulated by PTH. We therefore examined the role of these dual-signal transduction systems and the interaction of these systems in the regulation of DNA synthesis by PTH in the osteoblastic osteosarcoma cells, UMR-106. As recently reported, 10−4 M Sp-cAMPS, a direct activator of cAMP-dependent protein kinase (PKA), and 10−4 M dibutyryl-cAMP, as well as hPTH-(1–34), caused the significant inhibition of [3H]thymidine incorporation (TdR). Both A23187 and ionomycin (10−8-10−6 M) inhibited TdR in a dose-dependent manner, with a minimal effective dose at 10−7 M. Although 10−6 M phorbol 12-myristate 13-acetate (PMA) caused slight but significant stimulation of TdR by itself, it augmented not only dibutyryl-cAMP- but also Sp-cAMPS-induced inhibition of TdR. On the other hand, 4α-phorbol 12,13-didecanoate, incapable of activating PKC, failed to augment these cAMP analogs-induced effects. Pretreatment with 50 μM H-7, an inhibitor of PKC, not only abolished the PMA-induced augmentation of effect by cAMP analogs but also significantly blocked the PTH-induced inhibitory effect on TdR. Pretreatment with 10−6 M PMA, which downregulates PKC, significantly inhibited the PTH-induced suppression of TdR. Combined treatment with cAMP analog (dibutyryl-cAMP or Sp-cAMPS) and calcium ionophore (A23187 or ionomycin) caused additive effects on TdR, and PMA used in combination with both cAMP analog and calcium ionophore induced the further inhibition of TdR. The present study indicated that in addition to the PKA system, the Ca/PKC system also played a contributory role in the full expression of PTH response in the regulation of DNA synthesis in osteoblasts. The present data provided additional evidence for a dual pathway of target cell activation by PTH and the existence of interaction between the adenylate cyclase system and the Ca/PKC system.
Mechanism of action of estrogen on cancellous bone balance in tibiae of ovariectomized growing rats: Inhibition of indices of formation and resorption
Authors: Turner Russell T. , Evans Glenda L. , Wakley Glenn K.
Published: February 2010

Ovariectomy results in cancellous osteopenia in rat long bones, a condition that is prevented by treatment with estrogens. The purpose of these studies was to clarify the effects of estrogen on cancellous bone turnover using dynamic bone histomorphometry. Treatment of ovariectomized rats with diethylstilbestrol (DES) reduced the mineral apposition rate, double-label perimeter, osteoblast number, and osteoclast number, suggesting that the hormone had inhibitory effects on bone formation as well as bone resorption. However, we could not estimate the bone formation rate because of rapid resorption of tetracycline-labeled bone in the ovariectomized rat. The magnitude of loss was documented by a time course study: 58% of the tetracycline initially incorporated into the secondary spongiosa of the tibial metaphysis was resorbed after 11 days and 89% was resorbed after 22 days. Similarly, cancellous bone area was decreased by 67% after 11 days and by 88% after 22 days. Administration of either DES or tamoxifen (TAM) dramatically reduced resorption of tetracycline as well as the decrease in cancellous bone area. These results demonstrate that (1) estrogen prevents osteopenia in ovariectomized (OVX) rats, in part by inhibiting bone turnover, (2) TAM is an estrogen agonist on bone resorption, and (3) resorption of tetracycline-labeled bone leads to serious underestimation of the bone formation rate in OVX rats.
Age- and gender-related changes in body composition in Japanese subjects
Authors: Tsunenari Tohru , Tsutsumi Masaharu , Ohno Kyota , Yamamoto Yoshihiro , Kawakatsu Mitsuru , Shimogaki Kazuhisa , Negishi Hirokuni , Sugimoto Toshitsugu , Fukase Masaaki , Fujita Takuo
Published: February 2010

Age-dependent changes in body composition, namely a decrease in bone mass and lean mass and a reciprocal increase in fat mass, are often observed in normal populations. The recent development of dual-energy x-ray absorptiometry (DXA) made it possible to analyze bone mineral content (BMC), fat mass (fat), and lean body mass (LBM) more precisely and easily. We measured BMC, fat, and LBM in Japanese subjects by DXA to describe the changes in body composition with aging in the Japanese population. A total of 34 female (aged 20–74) and 34 male (aged 18–78) volunteers were divided into three groups according to their age: young (18–22 years), middle-aged (39–48 years), and old (61–78 years). Mean values for body height (BH), body weight (BW), and body mass index (BMI) of the subjects were very similar to Japanese normative values. The BMI of the middle-aged group was the highest of all groups of both sexes. BMC decreased significantly with aging in females but not in males. A decrease in LBM and a reciprocal increase in fat were found between young and middle-aged males but not in females. The correlation between BMC and LBM tends to be greater in males than in females. On the other hand, the correlation between BMC and fat was greater in females than males. These results demonstrate the age- and gender-related difference in body components in Japanese subjects. DXA may be useful for the analysis of body composition in different age and sex groups.
Expression of αv and β3 integrin subunits in rat osteoclasts in situ
Authors: Shinar Doron M. , Schmidt Azriel , Halperin Drora , Rodan Gideon A. , Weinreb Miron
Published: February 2010

Recent findings suggest that the vitronectin receptor, a member of the integrin family, plays an important role in the attachment of osteoclasts to bone matrix. We report here the localization by in situ hybridization of the mRNA for the α and β subunits of the vitronectin receptor in rat bone sections. To generate the rat-specific RNA probes used in this study, we cloned cDNA fragments of integrin chains αv, β3, and β5 by the polymerase chain reaction from rat cDNA. These fragments share 86–91% homology with the respective human sequences. In situ hybridization localized the αv and β3 mRNAs to regions undergoing extensive bone resorption. The histologic appearance and prestaining of bone sections for tartrate-resistant acid phosphatase (TRAP) indicated the presence of these mRNAs in osteoclasts. These observations support immunohis-tochemical findings that osteoclasts express high levels of the vitronectin receptor, confirm the identity of this receptor as integrin αv/β3, and suggest that osteoclasts may actively synthesize these molecules.