bluuebunny/crossref_metadata_2025_split huggingface dataset:
Consequences of childhood-onset growth hormone deficiency for adult bone mass
Authors: de Boer H. , Blok G.J. , van Lingen A. , Teule G.J.J. , Lips P. , van der Veen E.A. 
Published: February 2010

Abstract
To assess the implications of prolonged growth hormone deficiency (GHD) for the acquisition and maintenance of bone mass, bone mineral density (BMD) was measured in 70 adult males (mean age 26.7 ± 4.5 years) with childhood-onset GHD, 7.4 ± 4.2 years after discontinuation of previous GH therapy. Because most of these patients were short (mean height 165.8 ± 6.6 cm), the influence of body height on standard BMD measurements, conventionally reported as the areal density (BMDarea, expressed in g/cm2), was analyzed in a group of age-matched healthy males. In GHD patients, BMDarea was significantly reduced at the lumbar spine (Z score -1.59 ± 1.08, p &gt; 0.001) as well as at the nondominant hip (Z score -1.18 ± 0.95, p &gt; 0.001). The reduction in BMDarea was similar for patients with isolated GHD (N = 25) and those with combined deficiencies of GH and luteinizing hormone (N = 40). In patients and controls, BMDarea was positively correlated with body height, a relation that was attributed to skeletal size. Bone dimensions were significantly smaller in patients than in controls, and therefore it was hypothesized that the difference in areal density between patients and controls might be confounded by differences in bone size. Measured bone mineral content corrected for the estimated bone volume (BMDvolume, expressed in g/cm3) remained significantly reduced (Z score: lumbar spine, -0.90 ± 1.08, p &gt; 0.001; femoral neck, -0.74 ± 1.00, p &gt; 0.001), but the differences between GHD patients and controls were less than indicated by BMDarea (p &gt; 0.01). We conclude that the low BMDarea in our patient population can be explained in part by their subnormal body height. However, after correction for the effect of body height-related differences in bone volume, bone density was still significantly reduced. This indicates that in adult males with childhood-onset GHD a moderate degree of osteopenia is present. Insufficient bone acquisition during childhood years is considered the primary cause of the observed reduction in bone density.
Effects of tiludronate on bone mass, structure, and turnover at the epiphyseal, primary, and secondary spongiosa in the proximal tibia of growing rats after sciatic neurectomy
Authors: Murakami Hiroshi , Nakamura Toshitaka , Tsurukami Hiroshi , Abe Mitsuhiro , Barbier Alain , Suzuki Katsumi 
Published: February 2010

Abstract
To evaluate the effects of tiludronate on the mass, structure, and turnover of cancellous bone regions in immobilized rat tibiae, we performed a 4 week dosing experiment. The right hindlimbs of 84 Sprague-Dawley rats (5 weeks old) were neurectomized or sham operated. Animals were assigned to seven groups (n = 12 each); group 1 was sham operated, and groups 2-7 were neurectomized. Groups 1 and 2 were given vehicle only (distilled water), and groups 3, 4, and 5 were given tiludronate orally at doses of 25, 50, and 100 mg/kg body weight (BW)/day, respectively, throughout the experimental period. Group 6 was given 100 mg/kg BW/day of the agent for the first 2 weeks only, and group 7 received vehicle only for the first 2 weeks and then 100 mg/kg BW/day of the agent for the last 2 weeks. After tetracycline labeling was performed, the right tibiae were removed from the animals and processed to yield undecalcified sections. Histomorphometry was performed in the epiphyseal, primary, and secondary spongiosa of the proximal tibia. In group 2, trabecular bone volume (BV/TV) and trabecular number (Tb.N) were significantly decreased in the primary and secondary spongiosae, but this did not occur in the epiphyseal spongiosa. Osteoid surface (OS/BS) was decreased and osteoclast surface (Oc.S/BS) was increased in the secondary spongiosa. Tiludronate increased BV/TV and Tb.N in the primary spongiosa by reducing the values for the parameters of osteoclast surface (Oc.S/BS) and osteoclast number (Oc.N/BS). Osteoid surface in this region was not decreased by the agent. In groups 4 and 5, tiludronate prevented bone loss in the secondary spongiosa by reducing both OS/BS and Oc.S/BS. In group 6, BV/TV in the primary spongiosa was maintained at the level of group 1, but Oc.S/BS and Oc.N/BS were elevated. In the secondary spongiosa, bone mass was preserved and the reduction in these parameters was maintained. In group 7, however, BV/TV was increased in the primary spongiosa as a result of a reduction in osteoclastic resorption; in the secondary spongiosa, however, BV/TV was decreased and trabecular turnover was not reduced at the end of the experiment in these growing animals. Mineral apposition rates were not reduced by tiludronate. This study clearly demonstrated that this agent prevented immobilization bone loss by inhibiting resorption. The histomorphometric data suggest that (1) tiludronate begins to act early after administration in the primary spongiosa and rather late in the secondary spongiosa, and (2) the bone matrix is involved in the antiresorbing action of this bisphosphonate.
Cancellous bone turnover in growing rats: Time-dependent changes in association between calcein label and osteoblasts
Authors: Turner Russell T. 
Published: February 2010

Abstract
Calcein was given to growing male rats to label mineralizing bone, and groups of animals were sacrificed from 6 h to 12 days later. Fluorochrome-labeled perimeter and osteoblast perimeter were determined in a growth-adjusted sampling site in the secondary spongiosa of the proximal tibial metaphysis. The best correspondence between calcein-labeled perimeter and osteoblast-lined perimeter was during the initial 24 h following administration of the label. This association decreased progressively thereafter because of (1) cessation of bone formation on fluorochrome-labeled surfaces and (2) initiation of new foci of bone formation. The time-dependent decline in osteoblast-lined trabeculae with adjacent calcein label exceeded the increase in osteoblast perimeter on nonfluorochrome-labeled trabeculae, indicating that there was a net decrease in osteoblast number. Fluorochrome-labeled perimeter and bone area showed parallel decreases with time after labeling, as a result of bone resorption. Interestingly, the decrease in cancellous bone was caused exclusively by a reduction in trabecular number. There was no change in trabecular thickness. The findings suggest that the decreased osteoblast number and progressive bone resorption resulted in complete erosion of trabeculae most distal to the growth plate. As a result of the nearly equal growth and destruction of trabeculae, there was no change in the length of the cancellous metaphysis with time. It is concluded that cancellous bone turnover in growing rats represents a maturation process that differs fundamentally from bone turnover in adults.
Structure-activity studies of the s-echistatin inhibition of bone resorption
Authors: DR. Sato Masahiko , Garsky Victor , Majeska Robert J. , Einhorn Thomas A. , Murray John , Tashjian Armen H. , Gould Robert J. 
Published: February 2010

Abstract
Synthetic Arg-Gly-Asp (RGD)-containing peptides were examined in bone resorption or attachment and detachment assays with isolated mammalian osteoclasts in an effort to elucidate the mechanistic and structural basis for the inhibition of bone resorption by s-echistatin. Bone resorption was the process most sensitive to inhibition by s-echistatin, with IC50 = 0.3 nM; inhibition of attachment to bone or detachment (lamellipodial retraction) was 30- to 70-fold less sensitive, with IC50 = 10 or 20 nM, respectively. Single amino acid substitutions within the 49-residue sequence of s-echistatin showed that although the efficacy of s-echistatin is dependent on the Arg24-Gly25-Asp26 sequence, additional residues, including Asp27, Met28, and Cys39, are also critical for potent inhibition of the resorbing activity of isolated rat osteoclasts. Because of the identification of the avβ3 as the primary integrin on rat osteoclasts interacting the RGD peptides (Helfrich et al.), we examined the possibility of modeling bone resorption with other β3-mediated processes. Specifically, avβ3 endothelial cell (human or rat) attachment to vitronectin and aIIbβ3 platelet aggregation were compared with bone resorption for sensitivity to s-echistatin analogs, linear RGD peptides, and cyclic RGD peptides. Essentially no similarity in sensitivity to RGD peptides were observed between bone resorption, platelet aggregation, or endothelial cell attachment. Because rat osteoclasts and human giant cell tumors (osteoclastomas) shared similar sensitivity to s-echistatin and rat and human endothelial cells showed a similar sensitivity profile to RGD peptides, the dissimilarity of bone resorption to other β3-mediated processes cannot be explained in terms of species differences. These data show that the osteoclast avβ3 integrin is functionally distinct, despite epitopic similarity to the vitronectin receptor on other cells. Laser scanning confocal and scanning electron micrographs of rat osteoclasts on bone supported the hypothesis that resorption differs from the processes of attachment or detachment from substrates and suggest that inhibition of a minority of integrin-bone interactions by s-echistatin is sufficient to inhibit bone resorption. s-Echistatin was also found to inhibit bone resorption in an organ culture system of neonatal mouse calvariae with IC50 = 1 μM. Taken together, these data show that although it may be possible to target the osteoclast avβ3 integrin for the development of pharmaceuticals, s-echistatin itself is not useful in this capacity.
Bone mineral density of total body, spine, and femoral neck in children and young adults: A cross-sectional and longitudinal study
Authors: DR. Lu Pei Wen , Briody Julie N. , Ogle Graham D. , Morley Kate , Humphries Ian R.J. , Allen Jane , Howman-Giles Robert , Sillence David , Cowell Christopher T. 
Published: February 2010

Abstract
Bone mineral density (BMD) of total body (TBMD), lumbar spine (L2-4), and femoral neck was measured in 266 normal subjects (136 males) aged 4-27 years (mean 13 years) using dual-energy x-ray absorptiometry (DXA). BMD of all sites increased significantly with age until 17.5 years in males and 15.8 years in females, except for femoral neck BMD in females, which peaked at age 14.1 years. Males had higher peak TBMD, which was attributed to greater weight and lean tissue mass. In contrast, despite a later timing, peak L2-4 BMD in males was not different from that in females. Before peak BMD, weight was the best predictor of TBMD and L2-4 BMD in both sexes (r2 ranged from 0.77 to 0.88), whereas femoral neck BMD was predicted equally by height and weight. Longitudinal information collected from 53 (25 boys) of these children, aged 4-16.9 years, showed that the average annualized gain in TBMD was 0.047 g/cm2 for boys and 0.039 g/cm2 for girls. No significant difference in the association between age and BMD (slopes) was found between cross-sectional and longitudinal data for either sex. We conclude that the timing for peak BMD was consistent for total body, lumbar spine, and femoral neck for each sex. The earlier peak BMD in females is most likely related to earlier puberty. The cross-sectional normative data of this study are useful in serving as a standard for serial assessment in health and disease states.
Analysis of type II and type X collagen synthesis in cultured growth plate chondrocytes by in situ hybridization: Rapid induction of type X collagen in culture
Authors: O'Keefe R.J. , Puzas J.E. , Loveys L. , Hicks D.G. , Rosier R.N. 
Published: February 2010

Abstract
Type X collagen is produced by hypertrophic chondrocytes and serves as a highly specific marker for chondrocyte maturation. This study was designed to compare the expression of type II and type X collagen in growth plate sections and in distinct populations of chondrocytes in culture by in situ hybridization. Growth plate sections were treated with type II and type X collagen cDNA probes. Type II collagen mRNA was present throughout the growth plate but greatest in the lower proliferating and upper hypertrophic regions. In contrast, type X collagen was expressed only in the hypertrophic region. Northern analysis confirmed the specificity of the probe for type X collagen mRNA. Chick growth plate chondrocytes were separated by countercurrent centrifugal elutriation into five distinct populations and plated in serum-containing medium. These cultures were examined at varying times after plating for the expression of type II and type X collagen mRNA. At 3 h, type II collagen was present in the majority of the cells in all fractions, and approximately 15–20% of the cells expressed type X collagen mRNA. The cells expressing type X were from the hypertrophic region. At 24 h, however, nearly all cells in culture expressed type X mRNA, and there was a decrease in expression of type II collagen mRNA. Similar results were obtained in cultures in the absence of serum, and SDS-PAGE analysis of collagen synthesis confirmed the expression of type X collagen in all populations of fractionated cells at 24 h at the protein level. Type X collagen is an important marker through which cellular matruation can be evaluated in culture. The rapid induction of type X collagen in culture and its evaluation through in situ hybridization permit the investigation of factors that enhance or delay the development of cell hypertrophy and maturation. This may have important implications for the understanding and study of endochondral ossification and fracture repair.
Isolation and localization of basic fibroblast growth factor-immunoreactive substance in the epiphyseal growth plate
Authors: Twal W.O. , Vasilatos-Younken R. , Gay C.V. , Leach R.M. 
Published: February 2010

Abstract
Previous research in our laboratory has shown basic fibroblast growth factor (bFGF) to be a permissive mitogen for isolated avian growth plate chondrocytes. The present study was conducted to determine whether bFGF is present in avian growth plate and, if present, to determine its localization within the tissue. Immunohistochemical studies revealed that bFGF is present in the resting proliferative and hypertrophic calcifying zones of the growth plate but is absent from the prehypertrophic zone. Basic FGF appears to be associated with the extracellular matrix of the proliferative zone, but it is predominantly intracellular in the hypertrophic and mineralizing zone chondrocytes. Partial purification of cartilage-derived bFGF was performed on crude extracts of cartilage using heparin-Sepharose affinity chromatography. The presence of bFGF in the heparin-Sepharose column fractions was confirmed by immunoblotting and radioimmunoassay. Furthermore, western blot analysis of the extracts showed multiple protein bands having bFGF immunoreactivity, in the molecular weight range 14.4–18 kD. The data support the hypothesis that bFGF has a dual role in the growth plate. In the proliferative zone it acts as a chondrocyte mitogen, whereas when released from terminal hypertrophic chondrocytes, bFGF may serve as a chemotactic signal for metaphyseal blood vessel proliferation.
Skeletal unloading induces resistance to insulin-like growth factor I
Authors: Bikle Daniel D. , Harris Jonathan , Halloran Bernard P. , Morey-Holton Emily R. 
Published: February 2010

Abstract
In previous studies with a hindlimb elevation model, we demonstrated that skeletal unloading transiently inhibits bone formation. This effect is limited to the unloaded bones (the normally loaded humerus does not cease growing), suggesting that local factors are of prime importance. IGF-I is one such factor; it is produced in bone and stimulates bone formation. To determine the impact of skeletal unloading on IGF-I production and function, we assessed the mRNA levels of IGF-I and its receptor (IGF-IR) in the proximal tibia and distal femur of growing rats during 2 weeks of hindlimb elevation. The mRNA levels for IGF-I and IGF-IR rose during hindlimb elevation, returning toward control values during recovery. This was accompanied by a 77% increase in IGF-I levels in the bone, peaking at day 10 of unloading. Changes in IGF binding protein levels were not observed. Infusion of IGF-I (200 μg/day) during 1 week of hindlimb elevation doubled the increase in bone mass of the control animals but failed to reverse the cessation of bone growth in the hindlimb-elevated animals. We conclude that skeletal unloading induces resistance to IGF-I, which may result secondarily in increased local production of IGF-I.
Fractal geometry and vertebral compression fractures
Authors: Weinstein Robert S. , Majumdar Sharmila 
Published: February 2010

Abstract
Cancellous bone in postmenopausal osteoporosis is characterized by widely spaced and disconnected trabeculae. These architectural changes may disproportionately increase bone fragility compared with the decrease in bone mass alone. To determine whether there is an independent architectural contribution to fracture risk, we applied fractal geometry to the cancellous bone in osteoporosis. Fractal objects have recurrent, branching patterns that are quantified by a fractal dimension D, that describes how the object fills space. Photomicrographs of transiliac bone biopsy specimens were digitized, and D was calculated from the negative of the straight portion of the slope of the log of the number of pixels containing boundary points versus the log of the pixel size over a range of pixel sizes. The results were compared with the cancellous bone histomorphometry in 31 individuals, aged 19–80 years, who were healthy before sudden death. D was inversely related to age (r = −0.72, p &lt; 0.0001) and trabecular spacing (r = −0.87; p &lt; 0.0001) and directly related to bone area (r = 0.86, p &lt; 0.0001) and trabecular number (r = 0.83, p &lt; 0.0001). We then examined 12 healthy volunteers and 12 patients with vertebral compression fractures as a result of osteoporosis who were matched for age and cancellous bone area. The patients with fractures had a 7.9% lower mean value for D (1.224 ± 0.085 SD versus 1.329 ± 0.125, p &lt; 0.026). Other markers of the cancellous architecture, such as trabecular width, separation, and number, were not different between the matched groups. D was more than 1 SD below the normal mean value in 50% of the fracture cases and in only 1 of the nonfracture cases (p &lt; 0.025). Applied to cancellous bone, fractal geometry may discriminate more effectively between fracture and nonfracture cases than measurement of bone area and help accent the impact of architecture on bone fragility. The single expression, D, greatly simplifies description of the spatial distribution of cancellous bone and thus has a potential role in the computer-assisted histologic investigation of osteoporosis.
Differential distribution of insulin-like growth factors and their binding proteins within bone: Relationship to bone mineral density
Authors: Dr. Benedict Mark R. , Ayers David C. , Calore James D. , Richman Robert A. 
Published: February 2010

Abstract
To evaluate the possibility that insulin-like growth factors (IGFs) and their binding proteins (BPs) in bone play a role in regulating cortical bone formation in growing animals, we compared changes in IGF and IGF BP levels with changes in bone mineral density (BMD) at three different regions (proximal, middle, and distal) along the rabbit femoral shaft. BMD measured by dual-energy x-ray absorptiometry decreased progressively from proximal to distal regions of the shaft, from 0.449 ± 0.005 to 0.354 ± 0.002 g/cm2 (mean ± SEM; n = 9), respectively; total protein concentrations also decreased toward the distal region. We extracted the IGFs and their BPs from bone by demineralization in 10% EDTA and 4 M guanidine-HCl (pH 4.5). The IGFs were then separated from their BPs by size exclusion HPLC. The pH of the extraction buffer profoundly influenced the recoveries of the IGFs and, to a lesser extent, the total protein; at least 100% more IGFs were recovered at acid (4.5) pH than at neutral (7.5) or basic (10.5) pH. The levels of IGF-I decreased markedly from proximal to distal regions, from 273 ± 27 to 100 ± 38 ng human IGF-I equivalent/g bone (or 103 ± 10 to 52 ± 11 ng human IGF-I equivalent/mg protein), respectively. IGF-II was uniformly distributed (385 ± 17 ng human IGF-II equivalent/g bone; mean of all three regions). Levels of the predominant 28–32 kD IGF BP doublet increased by about 100% from proximal to distal segments, regardless of whether the data were expressed per unit mass or protein. Thus, the differential distribution of bone-associated IGF-I paralleled that of BMD and total protein, whereas levels of the 28–32 kD bone IGF BP(s) were inversely related to cortical bone density.
Lack of evidence for rickets in the osteopetrotic rat mutation, toothless
Authors: Seifert Mark F. 
Published: February 2010

Abstract
A common, but paradoxic, feature among osteopetrotic human infants is the presence of rickets. This disorder of mineralization is manifested radiographically and histologically by increased growth plate cartilage and hypertrophic cell zone thickness and excess metaphyseal osteoid and biochemically by decreased serum calcium and phosphorus concentrations. Rickets has also been reported in two osteopetrotic animal mutations, the osteosclerotic (oc) mouse and the toothless (tl) rat. Although the phenotypic expression of the rachitic lesion in the oc mouse closely resembles that in affected humans, the results of the present study show that the lesion in the tl rat does not. Compared with normal littermates, histologic and morphometric analyses of tibial growth plate cartilage in tl rats up to 5 weeks of age showed age-related increases in thickness of the proliferative cell zone and decreases in thickness of the hypertrophic cell zone that were most apparent within the central, but not lateral, regions of the growth plate and areas of acellularity and failure of chondrocytes to transform synchronously from proliferative cell to hypertrophic cell phenotypes. Femoral ash content, composition, and accretion rates did not differ from those in normal rats during the first 5 weeks of life. These findings do not support the rachitic nature of the cartilage lesion in the tl rat. Rather, a chondrodysplastic disorder is suggested, which more closely resembles the cartilage defect present in this mutation.