bluuebunny/crossref_metadata_2025_split huggingface dataset:
Amelin: An enamel-related protein, transcribed in the cells of epithelial root sheath
Authors: Fong Cheng Dan , Slaby Ivan , Hammarström Lars 
Published: February 2010

Abstract
Since 1974, when Slavkin and his collaborators proposed the epithelial origin of cementum, many experiments have been carried out to provide evidence for deposition of enamel-related proteins along the root surface. However, neither amelogenin nor other proteins have fully satisfied expectations. In previous studies, we have identified a novel mRNA coding for an extracellular-like protein which we called amelin. It was expressed at high levels in secretory and postsecretory ameloblasts in rat molars and incisors. In situ hybridization experiments described in the present study also localized the amelin message to epithelial cells adjacent to the peripheral surface of newly deposited dentin in the root end and to cells embedded in cellular cementum in molars. In incisors, the amelin RNA positive cells were detected in the area where cementum formation had been initiated. No amelogenin RNA signal was found in the cells at the root surface. We postulate that the epithelial cells of the root sheath as well as the ameloblasts are synthesizing amelin which might be one of the key proteins coupled to the process of cementogenesis. (J Bone Miner Res 1996;11:892-898)
Direct effect of phosphorus on PTH secretion from whole rat parathyroid glands in vitro
Authors: Almaden Yolanda , Canalejo Antonio , Hernandez Alexis , Ballesteros Evaristo , Garcia-Navarro Socorro , Torres Armando , Rodriguez Mariano , Rodriguez Mariano 
Published: February 2010

Abstract
Phosphorus retention is an important factor in the development of hyperparathyroidism secondary to renal failure. In vivo manipulation of phosphorus is associated with changes in serum calcium and calcitriol levels which in turn can modify parathyroid hormone synthesis and secretion. The present in vitro study evaluates whether high extracellular phosphorus has a direct effect on parathyroid hormone secretion. Fresh rat parathyroid glands were incubated in a media with phosphorus concentrations of 1, 2, 3, and 4 mM and subsequently exposed to calcium levels ranging from 0.4 to 1.35 mM. In 1.25 mM calcium, the parathyroid hormone secretion rate was similar in 1 and 2 mM phosphorus; however, a phosphorus concentration of 3 and 4 mM produced a 3- and 4-fold increase in the parathyroid hormone secretion, respectively, as compared with 1 mM phosphorus. While in 1 or 2 mM phosphorus an increase in calcium from 0.6 to 1.35 mM reduced parathyroid hormone secretion to 37%, in 4 mM phosphorus the same increase in calcium only inhibited parathyroid hormone secretion to 75%. Furthermore, the addition of arachidonic acid 20 μM, a substrate for inhibitory intracellular signal pathway, to the 4 mM phosphorus-1.35 mM calcium incubation media reduced the parathyroid hormone secretion to 34.5% (p &lt; 0.05). In conclusion, our results indicate that in vitro, high phosphorus directly increases parathyroid hormone secretion. (J Bone Miner Res 1996;11:970-976)
Dual-energy X-ray absorptiometry studies of bone mineral status in newborn infants
Authors: Dr. Koo Winston W. K. , Walters Jocelyn , Bush Andrew J. , Chesney Russell W. , Carlson Susan E. 
Published: February 2010

Abstract
We studied bone mineral status using dual-energy X-ray absorptiometry (DXA) on 150 singleton newborn infants with birth weights 1002–3990 g and gestational ages (GA) 27–42 weeks. Eighty-five infants were preterm (&lt;38 weeks), and 79 infants were low birth weight (≤2500 g). In addition, we aimed to determine the predictive value of anthropometric measurements, race, and gender on variability in bone mineral status. Data were acquired using a whole body DXA scanner with a pediatric platform. Scan analyses were performed with software version V5.64P. Results showed a highly significant (p &lt; 0.001 for all comparisons) correlation among the continuous independent variables, gestational age, birth weight, study weight, study bare weight, and study length, and between independent and each of the dependent variables, total body bone mineral content (TB BMC), TB area, and TB bone mineral density (TB BMD). The best single determinant of bone mineral status is body weight, accounting for 95% of TB BMC and TB area and for 86% of TB BMD variation. Body length was the only additional significant predictor of TB area. Inclusion of postnatal age (during the first week after birth), race, gender, or season, either individually or in combination, failed to improve bone mineral status explanation. By term (GA 38–42 weeks, birth weight 2700–3990 g), the mean TB BMC was 68.2 g, TB area 307.6 cm2, and TB BMD 0.221 g/cm2. We conclude that DXA can be performed even in small preterm infants during the newborn period. Our results can be used as a basis for further studies in physiologic and pathologic situations that might affect bone mineralization in infants. (J Bone Miner Res 1996;11:997-1002)
Low bone mineral content is common but osteoporotic fractures are rare in elderly rural Gambian women
Authors: Dr. Aspray Terence J. , Prentice Ann , Cole Timothy J. , Sawo Yankuba , Reeve Jonathon , Francis Roger M. 
Published: February 2010

Abstract
Osteoporosis is reported to be rare in Black Africa. The low fracture incidence among North American black women is explained by a high peak bone mass and preservation of bone mineral into old age. To assess whether this is the case among Black African women, we measured bone mineral content (BMC) and bone mineral density (BMD), using single- and dual-photon absorptiometry, in 195 rural Gambian women aged over 44 years and 391 white women of comparable age from three centers in the U.K. Measurements were made at the midshaft of the radius, distal radius, lumbar spine, and femoral neck. The influence of height, weight, and nationality on BMC and BMD was analyzed. BMC and BMD decreased with age at all sites. Age, decreasing weight, but not height were independently associated with lower BMC at all sites. BMC in Gambian women was lower than in British women by 31% at the lumbar spine and 16% at the midshaft of the radius. After adjustment for age, height, and weight, BMC among Gambian women remained 24% lower at the lumbar spine and 10% lower at the radius. In women aged over 64 years, BMC at the lumbar spine was 42% lower and BMD was 31% lower in The Gambia (for all comparisons, p &gt; 0.005). We conclude that bone mineral mass is not preserved in elderly Gambian women. However, minimal trauma fractures are rare in this population. These results challenge the concept of BMC as a primary determinant of fracture risk. (J Bone Miner Res 1996;11:1019–1025)
Vertebral fractures and other predictors of back pain among older women
Authors: Dr. Huang Chun , Ross Philip D. , Wasnich Richard D. 
Published: February 2010

Abstract
We examined the prevalence and predictors of back pain (BKP) among 645 postmenopausal Japanese-American women in Hawaii with a mean age of 73.9 years (ranging from 55 to 93 years) and serial spine radiographs during the preceding 12 years. The overall prevalence of BKP was 32.9% and appeared to be constant up to age 80, with an increase thereafter. At most ages, pain in the lower back was the most common, upper BKP was less so, and mid-BKP was the least common. The overall prevalence of BKP among Japanese-American women in Hawaii was about half of that reported for U.S. Caucasians. Vertebral fractures were divided into three categories based on the length of time since the fracture was identified on radiographs. BKP was only associated with recent vertebral fractures (during the previous 4 years, on average) and increased progressively with the number and severity of fractured vertebrae. A history of a single recent fracture was associated with a 2.8-fold increase in the odds of BKP; two recent fractures with a 7.8-fold increase and three recent fractures with a 21.7-fold increase in the odds of BKP. In addition, self-reported disk problems, body mass index, and the number of other painful joints also showed independent associations with BKP. Height, spine bone mineral density (BMD), calcaneus BMD, smoking, and number of live births were not significantly associated with BKP. (J Bone Miner Res 1996;11:1026–1032)
Single cell enzyme activity and proliferation in the growth plate: Effects of growth hormone
Authors: Dr. Gevers E.F. , Milne J. , Robinson I.C.A.F. , Loveridge N. 
Published: February 2010

Abstract
Longitudinal growth is a result of proliferation and differentiation of chondrocytes in the growth plate. Growth hormone (GH) stimulates longitudinal growth, and GH receptors have been shown on growth plate chondrocytes, but the effects of GH on chondrocytes of different cell layers are not clear. To study the effect of GH on chondrocyte activity, in situ biochemical techniques were used to measure enzyme activities, which are associated with cell differentiation (alkaline phosphatase [ALP]) and osteoclast activity (tartrate-resistant acid phosphatase [TRAP]), within single cells of the growth plate. Uptake of bromodeoxyuridine (BrdU) was used as a parameter for proliferative activity. In addition, glucose-6-phosphate dehydrogenase (G6PD) was measured since increased proliferation has been associated with increased G6PD activity. The role of GH was studied in a model of isolated GH deficiency (dwarf rat) and complete pituitary deficiency (hypophysectomized rat). Groups of GH-deficient dwarf rats were infused with recombinant human GH in either a continuous or a pulsatile manner, since the pattern of GH secretion is an important regulator of growth in the rat. After 7 days, G6PD activity in proliferative chondrocytes and TRAP activity in osteoclasts was increased, while ALP activity in hypertrophic chondrocytes was decreased. GH not only increased the number of chondrocytes that incorporated BrdU but also the total number of chondrocytes in the proliferative zone; therefore, its ratio, the labeling index (an indicator of proliferative rate), was not increased. The widths of the proliferative and hypertrophic zones were increased by both patterns of GH administration. The width of the resting zone was unaffected by continuous GH but decreased by pulsatile GH. ALP and TRAP activities were, respectively, higher and lower in hypophysectomized rats compared with the GH-deficient animals. Hypophysectomized rats had smaller growth plates than dwarf rats with a disproportionally wide resting zone, which, like BrdU uptake, was not affected by GH. GH treatment resulted in increased TRAP and decreased ALP activity. These results indicate that GH stimulates the commitment of chondrocytes within the resting/germinal layer to a proliferative phenotype (as opposed to stimulating the rate of chondrocyte proliferation) but only in the presence of other pituitary hormones. Furthermore, this study shows that enzyme activities within single chondrocytes and osteoclasts are GH-sensitive. The extent to which these effects are direct or mediated by systemic or local growth factors remains to be clarified.
Ultrastructural, enzyme-, lectin-, and immunohistochemical studies of the erosion zone in rat tibiae
Authors: Nakamura Hiroaki , Ozawa Hidehiro 
Published: February 2010

Abstract
To clarify the process of endochondral ossification, we used ultrastructural, enzyme-, lectin-, and immunohistochemical techniques to study perivascular cells located in the erosion zones of rat tibiae. In growth plate erosion zones, perivascular cells directly connected to blood capillaries were seen invading cartilage. These cells contained a well-developed rough endoplasmic reticulum and Golgi apparatus in their cytoplasm and formed finger-like cytoplasmic processes toward uncalcified transverse cartilage walls. These processes were seen to stretch as far as the degenerated chondrocytes located in the calcified layer of the growth plate. Interestingly, these perivascular cells showed neither alkaline phosphatase activity nor tartrate-resistant acid phosphatase activity. Lectin histochemistry revealed specific staining by Dolichos Biflorus agglutinin (DBA) on the perivascular cells. No reactivity for DBA was detected on either endothelial cells, osteoblasts, chondroclasts, or osteoclasts. In addition, immunohistochemical studies showed that the perivascular cells neither expressed CD44, which was localized on the plasma membrane of chondroclasts, osteoclasts, and osteocytes, nor were surrounded by laminin. These results suggest that the perivascular cells in the erosion zone are distinct from endothelial cells, osteoblasts, chondroclasts, and osteoclasts; that they may resorb uncalcified cartilage matrix and degenerated chondrocytes; and that perivascular cells may play an important role in the capillary invasion during the process of endochondral ossification.
Hysteresis of the PTH-calcium curve during hypocalcemia in the dog: Effect of the rate and linearity of calcium decrease and sequential episodes of hypocalcemia
Authors: Aguilera-Tejero E. , Sánchez J. , Almadén Y. , Mayer-Valor R. , Rodríguez M. , Felsenfeld A. J. 
Published: February 2010

AbstractSeveral studies have shown the presence of hysteresis of the parathyroid hormone (PTH)-calcium relationship in both normal humans and hemodialysis patients; for hypocalcemia, hysteresis is defined as a lower PTH level for the same serum calcium during the recovery from than the induction of hypocalcemia. However, some have questioned whether hysteresis is only a function of the rate and/or direction of change in calcium, and others have proposed that hysteresis is due to depletion of PTH stores. To address these issues, two groups of dogs were studied. To induce hypocalcemia, sodium EDTA (50 mg/kg) was infused either over 60 (termed slow) or 30 (termed fast) minutes; immediately after the cessation of the ethylenediamine tetracetate (EDTA) infusion, calcium chloride (0.75 mEq/kg) was infused over 60 or 30 minutes, respectively, to correct the hypocalcemia. The EDTA infusion produced a linear decrease in serum calcium by progressively increasing the infusion rate at regular intervals. A second cycle of hypocalcemia and recovery using the same protocol was started immediately after the completion of the first cycle. To determine whether a nonlinear decrease in the serum calcium affected the PTH response to hypocalcemia, a third group of dogs, termed superfast, was studied; in this group, EDTA was infused for 30 minutes at a constant rate of 50 mg/kg. The hysteretic loops of PTH produced by the two sequential slow and fast cycles and the superfast cycle during the induction of and recovery from hypocalcemia were similar. Moreover, the maximal PTH level for the two sequential slow and fast cycles and the superfast cycle was not different even though the rates of calcium decrease varied and the calcium decrease was nonlinear in the superfast cycle. In conclusion, (1) since hysteresis was reproducible and the maximal PTH was not different during two sequential cycles of hypocalcemia, hysteresis is not due to PTH depletion; (2) the PTH-calcium curve is not affected by the rate at which hypocalcemia is induced: and (3) the maximal PTH level is not influenced by either the rate or linearity of the reduction in serum calcium.
A large-scale population-based study of the association of vitamin D receptor gene polymorphisms with bone mineral density
Authors: Dr. Uitterlinden André G. , Pols Huibert A. P. , Burger Huibert , Huang Qiuju , van Daele Paul L. A. , van Duijn Cornelia M. , Hofman Albert , Birkenhäger Jan C. , van Leeuwen Johannes P. T. M. 
Published: February 2010

Abstract
Conflicting results have been reported on the association between restriction fragment length polymorphisms (RFLPs) at the vitamin D receptor (VDR) gene locus (i.e., for BsmI, ApaI, and TaqI) and bone mineral density (BMD). We analyzed this association in a large population-based sample (n = 1782) of men and women aged 55–80 years using a novel direct haplotyping polymerase chain reaction (PCR) test to monitor the three polymorphic sites simultaneously. The direct haplotyping test we developed demonstrated a larger degree of genetic polymorphism at the VDR gene locus than described until now. None of the individual RFLPs were associated with BMD at the proximal femur. By analyzing allele dose effects, we identified a VDR haplotype allele weakly associated with low BMD. This allele, as one representative of the group of b alleles, is different from the BsmI allele previously reported by other groups to be associated with low BMD. This suggests allelic heterogeneity at the VDR locus in relation to BMD. Our results indicate at most a small effect of the VDR genotype on BMD in this elderly population. Since anonymous polymorphisms were analyzed, alternative explanations for our results include linkage to another nearby bone-metabolism related gene.
Prediction of fracture load at different skeletal sites by geometric properties of the cortical shell
Authors: Augat P. , Reeb H. , Claes L. E. 
Published: February 2010

Abstract
Quantitative bone assessment today is primarily based on the analysis of bone mineral density (BMD). The geometric properties of bone, which are an important parameter for skeletal strength, are generally not considered in the routine clinical assessment of osteoporosis. This study combined the geometric properties and the BMD values determined by peripheral quantitative computed tomography (pQCT) at the distal radius and at the femoral neck to predict fracture loads of the radius, femur, and lumbar vertebrae of 20 cadavers. Generalized osteopenia reduced the fracture loads at all three sites (p &lt; 0.001). The strength of the radius and the femoral neck could best be predicted by considering either the second moment of inertia and trabecular BMD (R = 0.93) or the moment of inertia and the cortical BMD (R = 0.91). The geometric properties at the distal radius were highly correlated with the fracture load at the same skeletal site (R = 0.89) and were also used to estimate the fracture risk at the lumbar vertebrae (R = 0.75) and at the femoral neck (R = 0.87). We conclude that both geometry and density contribute substantially to the strength of the skeleton. The screening for osteoporosis and the prediction of fracture risk can be improved, therefore, by an additional consideration of the geometric properties of the cortex.
Effects of progesterone on serum levels of IGF-1 and on femur IGF-1 mRNA in ovariectomized rats
Authors: Barengolts E.I. , Kouznetsova T. , Segalene A. , Lathon P. , Odvina C. , Kukreja S.C. , Unterman T.G. 
Published: February 2010

Abstract
Local and systemic insulin-like growth factors (IGFs) may be involved in the regulation of bone formation by sex hormones. The present studies describe the in vivo effects of estradiol, progesterone, or both on IGF-1 mRNA abundance in bone, serum IGF-1 levels, and bone formation. Rats were sham-operated (SHAM) or ovariectomized (OVX) at 12 weeks of age and used a week later in three experiments. First, OVX rats were treated with vehicle, estradiol, and/or medroxyprogesterone (MPA) for 3 weeks, and bone formation was assessed in the tibial metaphysis. Second, OVX rats were treated in the same manner and serum IGF-1 levels measured. Third, OVX rats were treated with an injection of vehicle, estradiol, and/or progesterone, and 24 h later, levels of IGF-1 mRNA in the femur were analyzed. The mineralized surface, mineral apposition rate, and bone formation rate (BFR) were higher in OVX than in SHAM rats. The BFR was decreased in estrogen-treated but increased in MPA-treated rats compared with vehicle-treated OVX rats. Circulating levels of IGF-1 were higher in OVX than in SHAM rats but were not affected by sex hormones in a 3-week experiment, whereas these levels were not different among groups in a 24-h experiment. Northern analysis detected 7.5 and 0.8 kb IGF-1 mRNA transcripts. The abundance of IGF-1 mRNA was higher in OVX than in SHAM rats. IGF-1 transcripts 7.5 and 0.8 kb were decreased by 72 and 29%, respectively, in estrogen-treated and increased by 44 and 43%, respectively, in progesterone-treated rats compared with vehicle-treated OVX rats. We conclude that in the short term, estrogen lowers and progesterone raises bone IGF-1 mRNA and these changes are followed by coordinated changes in bone formation rate.
Dissociation of binding and antiresorptive properties of hydroxybisphosphonates by substitution of the hydroxyl with an amino group
Authors: van Beek Ermond , Löwik Clemens , Que Ivo , Papapoulos Socrates 
Published: February 2010

AbstractThe purpose of this study was to examine the role of the R1 moiety of bisphosphonates in binding to bone mineral and for antiresorptive action. For this, the R1 chain of three clinically useful hydroxybisphosphonates (etidronate, pamidronate, and olpadronate) was substituted with an amino group. The effects of the aminosubstituted bisphosphonates were compared with those of their hydroxy counterparts in a crystal growth assay and in fetal mouse long bone cultures which are representative of bisphosphonate actions in vivo. It was found that all three aminosubstituted compounds and their hydroxy analogs bound with similar affinity to bone mineral and inhibited the growth of calcium oxalate crystals to the same extent. Surprisingly, the antiresorptive effect of olpadronate was totally abolished by the amino substitution of the hydroxyl group while that of pamidronate was reduced by about six-fold and that of etidronate did not change. These studies demonstrate the involvement of the entire bisphosphonate molecule in the cellular mechanism of antiresorptive action. In addition, the aminosubstituted analog of olpadronate, which lacks any antiresorptive action but retains all other properties of olpadronate, provides an excellent tool for the study of specific cellular effects involved in bisphosphonate action.
Bisphosphonates clodronate and etidronate in the prevention of ovariectomy-induced osteopenia in growing rats
Authors: Lepola Vesa T. , Kippo Katriina , Hannuniemi Ritva , Laurén Leena , Virtamo Teija , Österman Thua , Jalovaara Pekka , Sellman Raija , Väänänen H. Kalervo 
Published: February 2010

Abstract
The aim of this study was to evaluate the ability of the bisphosphonate compounds clodronate and etidronate to prevent ovariectomy-induced bone changes. Three-month-old Sprague-Dawley rats were either ovariectomized (OVX) or sham-operated (SHAM) and further divided into groups receiving either vehicle (n = 30), 25 mg/kg/week of clodronate (n = 25) or 25 mg/kg/week of etidronate (n = 25). The subcutaneous drug administration was started immediately after the surgery and was continued for 12 weeks. OVX rats had accelerated bone turnover rates compared with the SHAM animals, as indicated by the results of dynamic histomorphometry and biochemical markers in serum and urine. Femoral and vertebral mineralized trabecular bone volume and maximum loads in compressions of the femoral neck and lumbar vertebra were lower after OVX compared with the SHAM operation. Both clodronate and etidronate prevented the decrease in trabecular bone volume and suppressed the increase in the bone turnover rate. Clodronate and etidronate also blocked the loss of bone strength in the femoral neck and lumbar vertebra of OVX rats. Both compounds resulted in an absence of double fluorochrome labels on the endocortical surface of the femoral metaphysis, which seemed, however, to be a dose-dependent response. Furthermore, etidronate also lowered serum osteocalcin and diaphyseal endocortical bone formation below the vehicle level both in the OVX and SHAM rats. In conclusion, clodronate and etidronate were effective in preventing the estrogen deficiency-induced decreases in trabecular bone volume and bone strength in rats. Treatment with a high dose of clodronate induced minor signs of abnormally low bone formation but not any impairment of bone mineralization, whereas both of these events were seen with high-dose etidronate administration.