Showing papers in "Calcified Tissue International in 1990"
TL;DR: Comparison of the FTIR spectra of biological apatites with those of synthetic, nonapatitic-containing phosphate minerals shows that the presence of these bands does not arise from nonapAtitic, well-defined phases; they are due to the local environment of phosphate ions which may possibly be loosely related or perhaps unrelated to the phosphate groups present in the well-crystallized nonap atitic calcium phosphates.
Abstract: In order to investigate the possible existence in biological and poorly crystalline synthetic apatites of local atomic organizations different from that of apatite, resolution-enhanced, Fourier transform infrared spectroscopy studies were carried out on chicken bone, pig enamel, and poorly crystalline synthetic apatites containing carbonate and HPO4
2− groups. The spectra obtained were compared to those of synthetic well crystallized apatites (stoichiometric hydroxyapatite, HPO4
2−-containing apatite, type B carbonate apatite) and nonapatitic calcium phosphates which have been suggested as precursors of the apatitic phase [octacalcium phosphate (OCP), brushite, and β tricalcium phosphate and whitlockite]. The spectra of bone and enamel, as well as poorly crystalline, synthetic apatite in thev
4 PO4 domain, exhibit, in addition to the three apatitic bands, three absorption bands that were shown to be independent of the organic matrix. Two low-wave number bands at 520–530 and 540–550 cm−1 are assigned to HPO4
2−. Reference to known calcium phosphates shows that bands in this domain also exist in HPO4
2−-containing apatite, brushite, and OCP. However, the lack of specific absorption bands prevents a clear identification of these HPO4
2− environments. The third absorption band (610–615 cm−1) is not related to HPO4
2− or OH− ions. It appears to be due to a labile PO4
3− environment which could not be identified with any phosphate environment existing in our reference samples, and thus seems specific of poorly crystalline apatites. Correlation of the variations in band intensities show that 610–615 cm−1 band is related to an absorption band at 560 cm−1 superimposed on an apatite band. All the nonapatitic phosphate environments were shown to decrease during aging of enamel, bone, and synthetic apatites. Moreover, EDTA etching show that the labile PO4
3− environment exhibited a heterogeneous distribution in the insoluble precipitate.
438 citations
TL;DR: It is suggested that the formation of the CO3 apatite crystals associated with the implanted Ca−P ceramic is due to dissolution/precipitation and secondary nucleation involving an epitatic growing process and not to an osteogenic property of the ceramic.
Abstract: The aims of this study were (1) to determine at the crystal level, the nonspecific biological fate of different types of calcium phosphate (Ca−P) ceramics after implantation in various sites (osseous and nonosseous) in animals and (2) to investigate the crystallographic association of newly formed apatitic crystals with the Ca−P ceramics. Noncommercial Ca−P ceramics identified by X-ray diffraction as calcium hydroxylapatite (HA), beta-tricalcium phosphate (β-TCP), and biphasic calcium phosphates (BCP) (consisting of β-TCP/HA=40/60) were implanted under the skin in connective tissue, in femoral lamellar cortical bone, articular spine bone, and cortical mandibular and mastoidal bones of animals (mice, rabbits, beagle dogs) for 3 weeks to 11 months. In humans, HA or β-TCP granules were used to fill periodontal pockets, and biposies of the implanted materials were recovered after 2 and 12 months. Results of this study demonstrated the following: (1) the presence of needle-like microcrystals (new crystals) associated with the Ca−P ceraiic macrocrystals in the microporous regions of the implants regardless of the sites of implantation (osseous or nonosseous), type of Ca−P ceramics (HA, β-TCP, BCP), type of species used (mice, rabbits, dogs, humans), or duration of implantation; (2) decrease in the area occupied by the ceramic crystals and the subsequent filling of the spaces between the ceramic crystals by the new crystals; (3) these new crystals were identified as apatite by electron diffraction and as carbonate-apatite by infrared absorption spectroscopy; (4) high resolution transmission electron microscopy (Hr TEM) revealed one family of apatite lattice fringes in the new crystals in continuity with the lattice planes of the HA of β-TCP ceramic crystals; (5) Hr TEM also demonstrated the presence of linear dislocations at the junction of the new apatite crystals and ceramic crystals. It is suggested that the formation of the CO3 apatite crystals associated with the implanted Ca−P ceramic is due to dissolution/precipitation and secondary nucleation involving an epitatic growing process and not to an osteogenic property of the ceramic.
372 citations
TL;DR: Calcium had a consistent prevention effect on the rate of bone loss in the 12 studies of calcium supplements in postmenopausal women and was greatest in studies in which the baseline calcium was low, supporting the idea of a threshold beyond which the effect of calcium is reduced.
Abstract: The relationship between calcium intake and bone mass remains controversial. In this paper, the published research on this association is reviewed using the quantitative technique of meta-analysis. Selection of studies was based on defined eligibility criteria, and information relating to study design was recorded. Study results were converted, where necessary, to similar outcome measures so that direct comparison among studies was possible. A total of 37 eligible papers, representing 49 separate studies or parts of studies, were identified in the literature. Calcium had a consistent prevention effect on the rate of bone loss in the 12 studies of calcium supplements in postmenopausal women. This effect was greatest in studies in which the baseline calcium was low, supporting the idea of a threshold beyond which the effect of calcium is reduced. Cross-sectional studies showed a small but consistent positive correlation between calcium intake and bone mass. This association was greater in studies of premenopausal women. Some caution is needed in interpreting the results of this meta-analysis because of the poor quality of many of the studies reviewed. Nevertheless, the consistency of findings suggests that women in their early postmenopausal years will benefit from a high calcium intake.
319 citations
TL;DR: It is concluded that more emphasis should be given to the results of prospective studies, and that more attention should be paid to subject selection in all investigations, to reduce the level of confusion in the field and provide more clinically relevant information.
Abstract: The usefulness of various bone mineral measurement techniques is a subject of current controversy. In order to explore whether disparate conclusions may have arisen from differences in analytic methodology, data from published reports of bone mass and nonviolent fractures have been reanalyzed in terms of fracture risk. In the large majority of studies, reduced bone mass was associated with an increased risk of fractures. However, the magnitude of the relationship varied much more among cross-sectional studies than among prospective studies, suggesting that bias related to subject selection and/or postfracture bone loss may have strongly influenced the cross-sectional findings. We conclude that more emphasis should be given to the results of prospective studies, and that more attention should be paid to subject selection in all investigations. Analyzing and presenting results in terms of fracture risk would probably reduce the level of confusion in the field and provide more clinically relevant information. These issues are also applicable to studies of potential fracture risk factors other than bone mass, such as bone structure and bone quality.
260 citations
TL;DR: Findings suggest that even under controlled, chemically defined conditions, solubility of a source has very little influence on its absorbability; and absorbability of calcium from food sources is determined mainly by other food components.
Abstract: Fractional absorption of seven chemically defined calcium sources was measured in normal adult women under standardized load conditions. Solubility of the sources in water at neutral pH ranged from a low of 0.04 mM to a high of 1500 mM. The relationship of solubility to absorbability was weak. In the range from 0.1 to 10 mM, within which most calcium supplement sources fall, there was no detectable effect of solubility on absorption. Data from four food sources are presented for comparison. Absorbability of food calcium was not clearly related to absorbability of the dominant chemical form in the food concerned. These findings suggest that (1) even under controlled, chemically defined conditions, solubility of a source has very little influence on its absorbability; and (2) absorbability of calcium from food sources is determined mainly by other food components.
187 citations
TL;DR: It is possible that PGE2 stimulates the osteogenesis caused by increased functional demands, and initiates the remodeling caused by bone damage, as any cell type, any mediator, and any strain pattern or parameter can be individually studied.
Abstract: A new method of investigating the mechanisms of strain-induced bone remodeling has been developed. Bone cells were subjected to cyclical strainsin vitro by computer-controlled stretching of the plastic substrate on which they were cultured, enabling both physiological and pathological strains to be investigated. Physiological strains have not previously been investigatedin vitro. The prostaglandin E2 (PGE2) released by the cells was found to depend on the strain magnitude. It was independent of cycle time, and 5 hours after straining had ceased, it had returned to control levels. These results are similar to thein vivo findings that bone remodeling is dependent on strain magnitude and not strain frequency, indicating that PGE2 may play an important role in strain-induced bone remodeling. The relationship between PGE2 release and strain magnitude was biphasic, with particularly high levels being released at strains that would be associated with either abnormally strenuous activity or microstructural bone damage. It is therefore possible that PGE2 stimulates the osteogenesis caused by increased functional demands, and initiates the remodeling caused by bone damage. This new method of investigating strain-induce remodeling is useful, as any cell type, any mediator, and any strain pattern or parameter can be individually studied.
147 citations
TL;DR: The results indicate that aged chicken cartilage and its accompanying thin and spongy osteoporotic bone offer a favorable host environment for embryonal cell implants.
Abstract: Partial and full thickness defects were created mechanically in articular cartilage and subchondral bone of the tibiotarsal joint condyles of 3-year-old chickens. The wounds were then repaired using embryonal chick chondrocytes embedded in a new biocompatible, hyaluronic acid-based delivery substance. Controls were similarly operated on but received either no treatment or implants of the delivery substance only. Animals were killed from 1 week to 6 months postoperatively. Sections from the two groups were examined and compared macroscopically, histologically, and histochemically. Results of 6-month follow-up showed that only the defects of the experimental chickens were completely filled with reparative hyaline cartilage tissue, with no signs of inflammation or immunologic rejection. Initially the entire defect cavity, whether partial thickness or full thickness up to the deep regions in the subchondral bone, was filled with cartilaginous reparative tissue. Relatively rapid maturation occurred under the tidemark; chondrocytes hypertrophied, were invaded with vascular elements and ossified. In the superficial areas, the reparative tissue remained cartilaginous and matured as typical hyaline cartilage tissue. These results indicate that aged chicken cartilage and its accompanying thin and spongy osteoporotic bone offer a favorable host environment for embryonal cell implants.
132 citations
130 citations
TL;DR: This culture system offers a potentially powerful model for bone formationin vitro and for investigating the osteogenic potential of bone-derived cells.
Abstract: Cells of the clonal osteogenic cell line MC3T3-E1 were seeded onto a three-dimensional matrix of denatured collagen type 1 and cultured for a period of up to 8 weeks. Specimens were analyzed by histological, enzyme histochemical, immunocytochemical, and ultrastructural methods and byin situ hybridization between day 7 and day 56 after seeding. In 56-day cultures, the MC3T3-E1 cells were arranged in a three-dimensional network and formation of bone-like tissue was indicated by calcification of a newly synthesized collagen type I matrix resembling osteoid and surrounding osteocyte-like cells. The differentiating culture showed high expression of osteocalcin and alkaline phosphatase activity. NIH3T3 fibroblasts used as control cells passed through the network of the substrate forming a confluent monolayer underneath. This culture system offers a potentially powerful model for bone formationin vitro and for investigating the osteogenic potential of bone-derived cells.
127 citations
TL;DR: The developmental similarities between decapentaplegic in the fly and FOP in man suggest a useful model for the study of FOP, and it is believed that FOP is a genetic disorder characterized by a disturbed developmental expression of this endochondral program and may represent a mutation resulting in a dominant gain of function.
Abstract: Fibrodysplasia (myositis) ossificans progressiva (FOP) is a rare autosomal dominant disorder characterized by symmetrical congenital malformations of the blastemal anlage of the hands and feet and by progressive heterotopic chondrogenesis and ossification of the soft connective tissues. There is neither an established pathogenesis nor an effective treatment for this disabling disorder. We reevaluated the published data on the natural history of FOP and discovered an array of developmental gradients (characteristic patterns of disease expression) similar to developmental anomalies induced by pleiotropic mutations of thedecapentaplegic (dpp) locus inDrosophila melanogaster. The protein encoded by thedpp locus is a member of the transforming growth factor-beta (TGF-β) family of molecules. It shares 75% sequence homology with the c-terminal region of two recently cloned human bone morphogenetic proteins (BMP-2A, BMP-2B), also members of the TGF-β family. The striking sequence identity across so large an evolutionary distance suggests that the BMP-2 genes in man and thedpp gene in the fly may be derived from a common ancestral gene. BMP is the only molecule discovered thus far that is capable of inducing endochondral ossificationin vivo. Expression of endochondral bone formation is the basis for limb formation in embryogenesis, longitudinal bone growth in postnatal life, and local bone regeneration (fracture healing) following injury. We believe that FOP is a genetic disorder characterized by a disturbed developmental expression of this endochondral program and may represent a mutation resulting in a dominant gain of function. The developmental similarities between decapentaplegic in the fly and FOP in man suggest a useful model for the study of FOP. The use of such a model might be especially fruitful in suggesting a molecular basis for FOP.
107 citations
TL;DR: The Z score, which expresses the difference between the measured calcium absorption and that predicted from the 1,25(OH)2D3 level, was significantly reduced in the osteoporotic group, and analysis by VMD yielded similar conclusions.
Abstract: We have examined the relation between radiocalcium absorption and serum 1,25-dihydroxy-vitamin D [1,25(OH)2D3] levels in a set of 60 postmenopausal women on corticosteroid therapy (29 with and 31 without vertebral compression fractures) and compared these results with those from 31 normal postmenopausal women age-matched with the “normal” corticosteroid-treated women. Radiocalcium absorption was a function of serum 1,25(OH)2D3 in both corticosteroid-treated groups and in the set as a whole, but the impaired calcium absorption in the corticosteroid-treated patients with osteoporosis was not accounted for by their slightly reduced serum 1,25(OH)2D3 levels. This apparent resistance to the intestinal action of 1,25(OH)2D3 was quantified by a Z score which expresses, in standard deviation units, the difference between the measured calcium absorption and that predicted from the 1,25(OH)2D3 level. The Z score was significantly reduced in the osteoporotic group. Vertebral mineral density (VMD) was measured by quantitative computed tomography in 43 of the corticosteroid-treated cases and in all the normal postmenopausal women; analysis by VMD yielded similar conclusions.
TL;DR: Not enough precision exists to monitor the development of relative osteopenia in OX rats, but its self-limiting nature suggests the existence of an estrogen-dependent quantum of cancellous bone in female rats.
Abstract: One hundred ninety-eight rats were ovariectomized (OX) or sham-ovariectomized (shOX) at 100 days of age. Groups were killed at 35, 70, 100, 125, 180, 270, 360, and 540 days postsurgery. Bone mineral content (BMC) of the right femur was assayed on a dual photon absorptiometer (DPA) optimized for human spine and whole body measurements. Three regions were studied: the distal measuring 0.8 cm, the proximal measuring 0.88 cm, and the diaphysis, the remainder. The DPA technique accurately showed the ash content (r=0.96), with a precision error of 3–5%. Whole femoral BMC was 4.3–11.1% lower in OX than shOX rats, with significant differences from 35–180 days. By 35 days, distal femoral BMC declined 6% in OX rats and rose 12% in shOX rats. Distal femoral BMC was 11.3–17.5% lower in OX than shOX rats, with significant differences at all times except 540 days. Femoral diaphyseal BMC of OX and shOX rats did not differ at any time. The relative distal femoral osteopenia which appeared by 35 days in OX rats did not worsen during the next 17 months. A DPA suited for human BMC studies is also accurate for BMC determination in bones with 250–500 mg of mineral It is less precise for this purpose than dedicated instruments using single photon absorptiometry. However, enough precision exists to monitor the development of relative osteopenia in OX rats. Osteopenia in OX rats is confined to a region containing appreciable cancellous bone. Its self-limiting nature suggests the existence of an estrogen-dependent quantum of cancellous bone in female rats. The adult rat model is accurate for cancellous bone of the adult human, but inaccuare for cortical bone.
TL;DR: The overall decline in bone and serum osteocalcin in men and women, and the increase in serum osteoccin in the sixth decade in women, indicate that aging is associated with a decrease in bone formation and turnover and that osteoblastic activity and bone turnover are stimulated at the menopause.
Abstract: We measured bone osteocalcin concentrations in EDTA extracts from iliac crest cortical bone specimens obtained postmortem from 63 men and 71 women (age range 19–90 years), and serum osteocalcin levels in healthy blood donors, 49 men and 49 women (age range 21–65 years). Bone and serum osteocalcin concentrations were higher in men than in women, and an age-related decline was observed in both sexes. In women, however, a temporary increase in serum (P<0.05) osteocalcin was seen in the sixth decade. This study shows sex- and age-related changes in bone osteocalcin consistent with changes in serum osteocalcin, confirming that serum measurement of osteocalcin reflects bone levels. As osteocalcin reflects osteoblastic activity and thus bone formation, the overall decline in bone and serum osteocalcin in men and women, and the increase in serum osteocalcin in the sixth decade in women, indicate that aging is associated with a decrease in bone formation and turnover and that osteoblastic activity and bone turnover are stimulated at the menopause.
TL;DR: Marrow fat volume was significantly positively correlated with serum osteocalcin, rib trabecular bone porosity, rib cross-sectional area, and gains in body weight, and it was negatively correlation with serum estrogen concentrations and the extent of rib trABecular surfaces labeled with tetracycline.
Abstract: It was previously shown that 11 months after ovariectomy the volume fraction of trabecular bone in the spine and 11th rib medullary canal of Beagle dogs (6 control, 9 ovariectomized) was significantly reduced. In this paper it is shown that these changes are accompanied by increased marrow fat volume in the 11th rib (59.0±9.5% vs. 44.3 ±10.0%). Conversely, the volume fraction of functional (hematopoietic) cells in the marrow was reduced by ovariectomy. Additionally, variations in marrow fat volume were tested for correlation with 22 other variables pertinent to bone physiology. Marrow fat volume was significantly positively correlated with serum osteocalcin, rib trabecular bone porosity, rib cross-sectional area, and gains in body weight. It was negatively correlated with serum estrogen concentrations and the extent of rib trabecular surfaces labeled with tetracycline.
TL;DR: Osteonectin is a product of chondrocytes in each zone of growth cartilage but accumulates only in the mineralizing zone, suggesting that the high affinity of the protein for calcium could favor its retention in calcifying matrix.
Abstract: Osteonectin is a calcium-binding matrix protein thought to play a role in regulating calcium distribution in a variety of biologic processes. To examine its role in endochondral bone formation, we examined the distribution of the protein during mineralization of the chicken tibial growth cartilage, using immunohistochemistry and immunoelectron microscopy. The synthesis of osteonectin was also determined in chondrocyte populations isolated from premineralizing and mineralizing regions of growth cartilage and assayed in short-term culture. The resuls show that a very low level of osteonectin is detectable in the resting, proliferating, and early hypertrophic zones of growth cartilage; in these zones, osteonectin is largely cell-associated. In contrast, a large amount of osteonectin is present in the mineralizing zone where it is associated with the matrix. Biosynthetic data from short-term culture experiments indicate, however, that osteonectin is synthesized and secreted by chondrocytes from both premineralizing and mineralizing zones. As indicated by immunoprecipitation, Northern hybridization,in vitro translation of hybrid-selected messenger RNA (mRNA), and electrophoretic analysis, osteonectin synthesized by chondrocytes of the premineralizing zones is not obviously different in structure from that synthesized by chondrocytes of the mineralizing zone. We conclude that osteonectin is a product of chondrocytes in each zone of growth cartilage but accumulates only in the mineralizing zone. The high affinity of the protein for calcium could favor its retention in calcifying matrix.
TL;DR: Salmon calcitonin is effective and safe in the management of acute hypercalcemia and may be used in conjunction with other hypocalcemic agents such as mithramycin, the bisphosphonates, or gallium nitrate to prolong the clinical response to more than 1 week.
Abstract: Salmon calcitonin has been used for the management of acute hypercalcemia for the past several years. Unlike other hypocalcemic agents, it is effective within 2 hours after first dosing. This pharmacologic agent shows peak effect at 24-48 hours and has a duration of action of 4-7 days in most cases. Its effectiveness may diminish thereafter despite continuous administration (the so-called "escape phenomenon"). Salmon calcitonin has been shown to be effective in the management of acute hypercalcemia due to a variety of causes, and, because of its low toxicity profile, it may be administered to patients with congestive heart failure or azotemia. Salmon calcitonin is also an analgesic agent in patients with pain associated with bone metastases and may be used in conjunction with other hypocalcemic agents such as mithramycin, the bisphosphonates, or gallium nitrate to prolong the clinical response to more than 1 week. Salmon calcitonin is therefore effective and safe in the management of acute hypercalcemia.
TL;DR: The overall results may reflect changes in the composition of the medium in which precipitation of enamel carbonatoapatite occurs, initial formation of an acid phosphate such as octacalcium phosphate-like mineral, or modifications of the precipitating phase induced byChanges in the kinetics of the mineral formation.
Abstract: The present study was undertaken to investigate changes in the crystalline structure and composition of procine enamel mineral during amelogenesis. Special attention was given to the carbonate location in the forming apatite crystal. Enamel samples were obtained from the outer (young) secretory, inner (old) secretory, maturation, and mature (hard) enamel of the permanent incisors of slaughtered piglets. The crystalline structure and composition of these enamel samples were studied using Fourier transform infrared spectroscopy, X-ray diffraction, and chemical analyses. The initial enamel mineral in the outer secretory enamel was rich in acid phosphate and carbonate. The carbonate was mainly substituted for phosphate groups in the apatite crystals of the early (outer) secretory enamel. Developmental advancement from the outer secretory to the inner secretory (as well as early maturation) stages brought about significant changes in crystal parameters, namely, shrinkage and expansion of thec anda unit cell dimensions, respectively, and the shift of av3 PO4 band to higher wavenumbers in the FTIR spectrum. X-ray diffraction patterns indicated that mineralization during the tissue maturation was characterized by a gradual growth of enamel crystals parallel to thea-axis direction. A most prominent finding was that, with developmental advancement, a decrease in CO3 per unit mass of P (or Ca) in the tissue, and a concomitant increase in the CO3 occupying OH sites in the crystalline lattice became apparent. The overall results may reflect (1) changes in the composition of the medium in which precipitation of enamel carbonatoapatite occurs, (2) initial formation of an acid phosphate such as octacalcium phosphate-like mineral, or (3) modifications of the precipitating phase induced by changes in the kinetics of the mineral formation.
TL;DR: The results obtained support the view that amelogenetic mineralization is regulated by the presence of various organic matter and, importantly, that their efficacy as inhibitors of mineralization may be modulated through their degradation.
Abstract: Enamel proteins were isolated from specific locations of permanent porcine incisors at various developmental stages, namely, the outer (young) and inner (old) secretory, and maturing (chalk-like in appearance) enamel. The selective adsorption of these matrix proteins onto hydroxyapatite (HA) crystals was investigated in the presence of dissociative agents. The results showed that the proteins with the highest adsorption affinity were present at the highest concentration in the vicinity of the ameloblasts, i.e., in the outer enamel layer; a substantial reduction of these proteins was observed in the older (inner) secretory enamel and in the tissue in the maturing stage. An interesting finding was that a group of proteins having molecular masses of 32 kd present only in the inner secretory enamel, adsorbed strongly onto the HA crystals and were potent inhibitors of HA crystal growth. This 32 kd group contains phosphorylated glycoproteins; they are rich in Pro, Glu, Gly, and Asp and the N-terminal sequence was LXQVPGRIPPGYGRPPTP-, having no resemblance to the reported sequences of amelogenins. It was also found that the 32 kd moieties remained only as trace constituents in the maturing enamel, suggesting that most of them were removed as soluble constituents in the tissue fluid or further degraded by enzymatic activity during the late secretory stage. The results obtained support the view that amelogenetic mineralization is regulated by the presence of various organic matter and, importantly, that their efficacy as inhibitors of mineralization may be modulated through their degradation.
TL;DR: The diurnal pattern for serum OC under well-defined experimental conditions is not altered by age, sex, season, or smoking habits, however, the S-OC(I) varies with age, height, gender, and season.
Abstract: In the present study we examined whether the diurnal pattern and the 24-hour integrated serum concentration of osteocalcin (S-OC(I)) showed any variation due to age, sex, season, or smoking habits in 31 normal subjects, aged 23–47 years. Blood samples were drawn every 60 minutes from 4 p.m. until 6 p.m. the following day. Serum osteocalcin showed diurnal variation as described earlier but no influence of age or sex on the diurnal variation could be demonstrated. Ten subjects were smokers, all consuming more than 10 cigarettes daily, but the diurnal variation in OC with time was not different from an age-, sex-, and height-matched group of strictly nonsmokers. Sixteen of the subjects were initially examined in March and 15 in November. Eight subjects were examined during a period in both November and March, and 5 of these went through an additional study period in July. These seasonal studies showed that the diurnal time course pattern during different seasons of the year were statistically indistinguishable from each other. The S-OC(I) was significantly higher in subjects below 29 years of age compared with subjects aged 30–40 years (P<0.01). Men had higher values than women (P<0.05). Moreover, S-OC(I) was higher in November compared to March (P<0.05). There was no effect of smoking on S-OC(I). A significant correlation existed between S-OC(I) and age (r= 0.50,P<0.005). Multiple regression showed that among age, height, and weight, only age and height were significant determinants for S-OC(I) (r=0.50,P=0.02). In conclusion, the diurnal pattern for serum OC under well-defined experimental conditions is not altered by age, sex, season, or smoking habits. However, the S-OC(I) varies with age, height, gender, and season.
TL;DR: The present study is the first to report that the rate of BGP secretion at times beyond 48 hours declines to that of control cultures despite the continued administration of 1,25(OH)2D3, and that MGP synthesis is induced in ROS 17/2 cells by 48 hours of 1-25-dihydroxyvitamin D3 treatment.
Abstract: The synthesis of matrix Gla protein (MGP) and bone Gla protein (BGP) have been shown to be mutually exclusive in all osteosarcoma cell lines investigated. In the cell lines that produce the respective proteins, synthesis is stimulated by 1,25-dihydroxyvitamin D3(1,25(OH)2D3) within the first several hours of hormone treatment. In the present studies we have investigated the effects of longer-term treatment with 1,25(OH)2D3 in the ROS 17/2 cell line, a cell line that synthesizes BGP constitutively but does not synthesize MGP. In agreement with earlier studies, the rate of BGP synthesis increases within 8 hours of hormone treatment, is maximal by 24 hours, and remains at the maximal rate through 48 hours of 1,25(OH)2D3 treatment. The present study is the first to report that the rate of BGP secretion at times beyond 48 hours declines to that of control cultures despite the continued administration of 1,25(OH)2D3, and that MGP synthesis is induced in ROS 17/2 cells by 48 hours of 1,25(OH)2D3 treatment. At this time, MGP mRNA could be detected by northern blot analysis and MGP secretion could be demonstrated by radioimmunoassay of culture medium. Both the level of MGP message per unit total RNA and the rate of MGP secretion into culture medium increased steadily between 2 and 6 days of 1,25(OH)2D3 treatment. The MGP synthesized by the 1,25(OH)2D3-treated ROS 17/2 cells was identical to that found in bone by northern blot analysis of message and by western blot analysis of the media antigen. Halfmaximal induction of MGP synthesis was obtained with 0.3 nM 1,25(OH)2D3, a 60-fold higher dosage than was required for the half maximal stimulation of BGP synthesis in these cells. Treatment of ROS 17/2 cells with 24,24-F21,25(OH)2D3 suggests that the observed difference in dose dependence is not due to an increased rate of hormone catabolism.
TL;DR: It is proposed that osteoclasts engulf and destroy osteocytes during bone degradation, and the following sequence of events takes place when a lacuna is opened up by an osteoclast.
Abstract: It is generally accepted that osteoclasts are responsible for the breakdown and removal of bone matrix constituents. However, very little is known about the fate of osteocytes during bone resorption. In the present study we have examined sites of bone destruction in calvaria of young rats aged 4–9 days in the hope of obtaining information on the fate of osteocytes. Decalcified glutaraldehyde-formaldehyde-fixed specimens were prepared for ultrathin section electron microscopy. When sequentially arranged, the images obtained suggest that osteoclasts engulf and destroy osteocytes during bone degradation. We propose that the following sequence of events takes place when a lacuna is opened up by an osteoclast: (1) When the osteoclast comes in contact with an osteocyte, the villi of the ruffled border become flat and broad. (2) Long osteoclastic extensions surround the osteocyte. (3) The osteocyte is subsequently internalized with apparent degradation.
TL;DR: The results suggest that the deleterious effects of the HFS diet may be more related to changes in the material properties of the cortical bone rather than to osteoporoticChanges in the bone.
Abstract: High fat-sucrose (HFS) diets can reportedly produce glucose intolerance and hyperinsulinemia that may indirectly have deleterious effects on bone. The effects of a high-fat diet on calcium absorption, bone calcium content, and bone mechanical properties, however, remain controversial. Thus, we examined the morphological and biomechanical adaptations in limb bones of rats that were fed a HFS diet. Female Sprague-Dawley rats (8 weeks old) were randomly assigned to two groups, either a control group (n = 9) fed a standard diet (low-fat complex-carbohydrate) or an experimental group (n = 9) fed a HFS diet for 10 weeks. The right tibia and second metatarsus (MT) were fractured in three-point bending, and contralateral bones were used for morphological and histological analyses. HFS tibias had significantly lower maximum load and failure energy, and tensile stress at the proportional limit for both HFS tibia and MT was significantly less than controls. In addition, the elastic modulus and density of the HFS MT was significantly lower than controls. Geometry of the tibial mid-diaphysial cross section did not differ for the two diets, but the cortical cross-sectional area of HFS MT increased significantly compared to control MT. The total number of osteons in the mid-diaphysis of HFS MT decreased, but tibial and MT porosities did not change with the HFS diet. Our results suggest that the deleterious effects of the HFS diet may be more related to changes in the material properties of the cortical bone rather than to osteoporotic changes in the bone.
TL;DR: Spurious rates of loss of spine BMD are likely to be found in subjects with calcification of the aorta, osteophytes or other abnormalities in the spine scan field, and should be kept in mind when serial spine scans are being considered in these subjects.
Abstract: When measured by dual-photon absorptiometry (DPA), the adjusted annual rate of change in bone mineral density (BMD) of the lumbar spine was 0.11±0.51 (SE) % in 44 healthy postmenopausal women with radiographic abnormalities in the scan field and −0.97±0.26% in 249 women with normal lateral lumbar radiographs (p=0.046). Rates of loss of BMD from the radius were similar in the 2 groups. Spurious rates of loss of spine BMD are likely to be found in subjects with calcification of the aorta, osteophytes or other abnormalities in the spine scan field. This should be kept in mind when serial spine scans are being considered in these subjects.
TL;DR: The results lend support to the hypothesis of a progesterone-glucocorticoid competitive antagonism at the bone level, though other possibilities can be entertained, and suggest MPA as an effective therapy for glucocortICoid-induced osteoporosis in men.
Abstract: The effect of long-acting medroxyprogesterone acetate (MPA) on the trabecular bone density in patients with glucocorticoid-induced osteoporosis (GCO) was evaluated. Thirteen steroid-dependent asthmatic male patients with GCO were administered 200 mg MPA intramuscularly at 6-week intervals and 1 g of elemental calcium daily for a period of 1 year. Ten additional matched steroid-dependent asthmatic male patients received 1 g of elemental calcium daily (controls). All 23 patients involved in the study had vertebral trabecular bone densitometry (TBD) by quantitative computed tomography (QCT) at baseline and at 6 and 12 months into the study. A 17% increase in TBD was found in the MPA-treated patients at 1 year (from 68.5±5 to 80.2±4 mg K2HPO4/cc) in contrast to the control group who experienced a 21% decrease in TBD during the same period of time (from 80.5±7 to 63.7±8 mg K2HPO4/cc) (T=6.90,P=0.0001 df=21). There were no significant changes in other parameters followed during the study in the MPA-treated group (serum calcium, phosphorus, magnesium, PTH, alkaline phosphatase, triglycerides, total and HDL cholesterol, urinary excretion of calcium, phosphate, creatinine) except for a decrease in the serum luteinizing hormone (LH) and testosterone (P<0.01) as well as of the hydroxyproline-creatinine ratio (P<0.01). The results lend support to the hypothesis of a progesterone-glucocorticoid competitive antagonism at the bone level, though other possibilities can be entertained, and suggest MPA as an effective therapy for glucocorticoid-induced osteoporosis in men.
TL;DR: It is concluded that 3–4 drinks of alcohol taken over 45 minutes decreases serum osteocalcin in a dose-dependent way and the time lag between changes in serum osteoccin and cortisol indicates that the decrease in serum bone formation is not related to the increase in serum cortisol.
Abstract: The acute effect of 25 and 50 g of alcohol on the variation in serum osteocalcin, a specific and sensitive marker of bone formation, and on serum cortisol and serum parathyroid hormone (PTH)(1–84) was calculated in 6 normal young adults. They were studied during three periods, each lasting from 4 p.m.–7:30 a.m. Alcohol was ingested between 4:15 and 5 p.m. during period two and three. Blood was taken at 4 p.m. and every 15 minutes from 4:30 til 6 p.m., followed by hourly sampling until 12 p.m. The last blood sample was taken after an overnight fast at 7:30 a.m. Initial and end values before and after alcohol ingestion did not differ significantly from control values. Repeated measures analysis of variance showed that 50 g of ethanol decreased serum osteocalcin significantly (P<0.02) and increased serum cortisol (P<0.05) during the 4–12 p.m. interval. The interaction of 50 g of ethanol on the variation in serum osteocalcin was already significant during the first 2 hours (P<0.02), where no significant effect on serum cortisol could be detected. Although insignificant, the same pattern was observed after 25 g of alcohol. There was no significant change in the variation of serum iPTH(1–84) during the 4–6 p.m. after alcohol intake. We conclude that 3–4 drinks of alcohol taken over 45 minutes decreases serum osteocalcin in a dose-dependent way. The time lag between changes in serum osteocalcin and cortisol indicates that the decrease in serum osteocalcin is not related to the increase in serum cortisol.
TL;DR: It is concluded that a habitual calcium intake exceeding 800 mg/day (the current Recommended Daily Allowance for adults) is ineffective in preventing cortical bone loss during early menopause.
Abstract: During an 8-year follow-up study, the effect of habitual dietary calcium intake on cortical bone loss in 154 healthy perimenopausal women was examined Dietary calcium intake, determined by the cross-check dietary history method, and cortical bone mineral content of the radius were measured annually Habitual dietary calcium intake was calculated as the mean of the estimated daily dietary calcium intake during the follow-up period The women were classified according to their habitual calcium intake: those with an intake below 800 mg/day (n = 28), between 800 and 1350 mg/day (n = 95), and above 1350 mg/day (n = 31) The results show a continuous significant loss of cortical bone in all groups, amounting yearly to 13 +/- 025, 15 +/- 010, and 19 +/- 023% (mean +/- SE) for the groups with a low, medium, and high habitual calcium intake, respectively (P less than 001) The differences among the three groups did not reach statistical significance (P = 011) Body mass index was found to be positively correlated with the negative changes in cortical bone mineral density (r = 032, P less than 001), even after adjustments had been made for confounding factors It is concluded that a habitual calcium intake exceeding 800 mg/day (the current Recommended Daily Allowance for adults) is ineffective in preventing cortical bone loss during early menopause Body mass index is of major importance for the perimenopausal bone loss
TL;DR: Results show that prophylactic administration of salmon CT in ovariectomized women prevent estrogen deficiency-induced bone loss, inhibiting skeletal resorption and allowing osteogenesis to occur normally.
Abstract: We present the results of a 12-month clinical study assessing the effects of synthetic salmon calcitonin (sCT) on a group of fertile white women who had undergone ovariectomy for uterine fibromatosis. The study was performed to verify whether CT can prevent the loss of bone mass and the changes in calcium-phosphorus metabolism associated with acute estrogen deficiency. The study consisted of an initial double-blind phase of 6 months, followed by a 6-month open period. Treated patients were given 100 MRC U of synthetic salmon CT injected i.m. in the morning, every other day, starting on the 7th day after the operation and continued for 12 months. Control patients received a placebo injection for the first 6 months; subsequently, they too were treated with sCT i.m. every other day for 6 months at the same dose as the 12 month-treated group. All patients received 500 mg of elementary calcium p.o., b.i.d. Bone mineral content (BMC) was measured at the extreme distal radius of the nondominant arm by a dual photon bone densitometer which utilizes two radio nuclides, 241 Am and 125 I, with energies of about 60 and 30 KeV. Biochemical parameters of the calcium-phosphorus metabolism were also measured. After 12 months of study, no significant changes of BMC were observed in the 12 months sCT treated group, while control patients, treated 6 months after the ovariectomy, showed a significant decrease in BMC values. Total hydroxyproline/ creatinine (OHPr/Cr) ratio, which increased after ovariectomy, returned to normal after the first month of sCT administration in the continuously treated group whereas it remained high in the control group up to the 6th month of observation, declining thereafter in coincidence with sCT treatment. The behavior of Bone GLA-protein (BGP), like that of the nondializable OHPr/Cr ratio, was substantially similar in both treated and control groups for the entire period of observation. These results show that prophylactic administration of salmon CT in ovariectomized women prevent estrogen deficiency-induced bone loss, inhibiting skeletal resorption and allowing osteogenesis to occur normally.
TL;DR: It is suggested that bone death, in addition to osteoporosis, may sometimes contribute to hip fracture in the elderly.
Abstract: We examined femoral head bone from 50 cadavers and from 21 patients who had suffered pathologic fracture of the femoral neck. We used a histochemical technique for lactate dehydrogenase (LDH) activity to demonstrate osteocyte viability. The femoral heads were removed within 36 hours of death or fracture, as LDH activity persists in the cytoplasm of viable cells for this time at 37° after interruption of the blood supply. In the controls, there was an age-related reduction in mean osteocyte viability, from 88±7% (mean±SD) at age 10–29 years to 58±12% at age 70–89 years. In the hip fracture patients, mean osteocyte viability was 58±21% but there was much variability in both osteocyte viability and bone mass. In 5 fracture patients, there was extensive osteocyte death, suggesting that most of the femoral head bone was nonviable; these patients had little microfracture callus. Others had predominantly viable bone which was usually osteoporotic, and their bone frequently showed microfracture callus. Osteomalacia was not seen in any patient. It is suggested that bone death, in addition to osteoporosis, may sometimes contribute to hip fracture in the elderly.
TL;DR: These studies demonstrate that changes in Ca influx and efflux are metabolite specific and may be a mechanism by which vitamin D metabolites directly regulated chondrocytes in culture.
Abstract: Vitamin D3 metabolites have been shown to affect proliferation, differentiation, and maturation of cartilage cells. Previous studies have shown that growth zone chondrocytes respond primarily to 1,25(OH)2D3 whereas resting zone chondrocytes respond primarily to 24,25(OH)2D3. To examine the role of calcium in the mechanism of hormone action, this study examined the effects of the Ca ionophore A23187, 1,25(OH)2D3, and 24,25(OH)2D3 on Ca influx and efflux in growth zone chondrocytes and resting zone chondrocytes derived from the costochondral junction of 125 g rats. Influex was measured as incorporation of45Ca. Efflux was measured as release of45Ca from prelabeled cultures into fresh media. The pattern of45Ca influx in unstimulated (control) cells over the incubation period was different in the two chondrocyte populations, whereas the pattern of efflux was comparable. A23187 induced a rapid influx of45Ca in both types of chondrocytes which peaked by 3 minutes and was over by 6 minutes. Influx was greatest in the growth zone chondrocytes. Addition of 10−8–10−9 M 1,25(OH)2D3 to growth zone chondrocyte cultures results in a dose-dependent increase in45Ca influx after 15 minutes. Efflux was stimulated by these concentrations of hormone throughout the incubation period. Addition of 10−6–10−7 M 24,25(OH)2D3 to resting zone chondrocytes resulted in an inhibition in ion efflux between 1 and 6 minutes, with no effect on influx during this period. Efflux returned to control values between 6 and 15 minutes.45Ca influx was inhibited by these concentrations of hormone from 15 to 30 minutes. These studies demonstrate that changes in Ca influx and efflux are metabolite specific and may be a mechanism by which vitamin D metabolites directly regulated chondrocytes in culture.
TL;DR: It is concluded that disturbed carbohydrate metabolism such as insulin hypersecretion and insulin resistance, in patients with PHPT is an early finding in this disease and that these early disturbances in glucose metabolism are, however, fully reversible.
Abstract: Glucose tolerance, insulin secretion, and insulin sensitivity were evaluated in 8 asymptomatic patients with primary hyperparathyroidism (PHPT) before and at least 8 weeks after surgical correction of PHPT by means of the hyperglycemic clamp technique. In addition, 15 sex- and agematched control subjects were investigated for comparative reasons by the same technique. Glucose metabolized (M) during the hyperglycemic clamp was not significantly (NS) different between patients with PHPT and controls (7.9±2.3 vs. 6.3±1.9 mg/kg/min). However, insulin secretion (I) was significantly elevated in patients with PHPT compared to controls (87±17 vs. 45±12 μU/ml,P<0.05). The calculated insulin sensitivity index, (M/I) was significantly reduced in PHPT compared to controls (11.0±2.1 vs. 15.2±1.4 mg/kg/min per μU/ml×100,P<0.05). Comparing patients with PHPT before and after surgery, the M value, which is a measure of glucose tolerance, was not significantly different (7.9±2.3 vs. 7.8±1.5 mg/kg/min). However, insulin secretion was significantly lower after surgical correction of PHPT compared to the preoperative situation (48±9 μU/ml vs. 87±17 μU/7 ml,P<0.01). The calculated M/I rose significantly after surgery compared to the preoperative value (11±2.1 vs. 17.6±2.7 mg/kg/min per μU/ml ×100,P<0.001). We conclude that disturbed carbohydrate metabolism such as insulin hypersecretion and insulin resistance, in patients with PHPT is an early finding in this disease and that these early disturbances in glucose metabolism are, however, fully reversible. Correction of disturbed carbohydrate metabolism in PHPT might be a distinct argument for early surgical intervention in this disease.