Immunoradiometric assay for intact human osteocalcin(1-49) without cross-reactivity to breakdown products.
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BACKGROUND: Osteocalcin (Oc), a serum marker of bone turnover, circulates in several forms. We developed an assay for intact human Oc and investigated its clinical features. METHODS: We generated goat antibodies and N- and C-terminal Oc. The former was used on solid phase (polystyrene beads), and the latter was used as the tracer in an IRMA. RESULTS: The assay was linear with no cross-reactivity to Oc(1-43), total imprecision (CV) of <10%, and recovery of 100% +/- 10%. Assay values for intact Oc in EDTA plasma samples were unchanged at 18-25 degrees C for 6 h. Values for intact Oc in serum, EDTA plasma, and heparin plasma samples did not change after storage on ice for 8 h. Serum samples from patients with various conditions were stored at -70 or -135 degrees C for up to 5 years and yielded z-scores comparable to an Oc(1-43) IRMA for all conditions except for renal failure. In renal failure, the Oc(1-43) assay values were increased, whereas the intact assay values were in the reference interval. CONCLUSION: Decreases in Oc assay values are inhibited by calcium chelation, and slowed by reduced temperatures. The described assay for intact Oc allows improved specificity for bone compared with an assay for Oc(1-43). (+info)
Serum galactosyl hydroxylysine as a biochemical marker of bone resorption.
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BACKGROUND: Serum-based biochemical markers of bone resorption may provide better clinical information than urinary markers because direct comparison with serum markers of bone formation is possible and because the within-subject variability of serum markers may be lower. We describe a method for the measurement of free beta-1-galactosyl-O-hydroxylysine (Gal-Hyl) in serum. METHODS: The assay used preliminary ultrafiltration of serum, dansylation, and separation by reversed-phase HPLC with fluorescence detection. Healthy subjects were recruited from population-based studies of bone turnover. RESULTS: The within-run (n = 15) and between-run (n = 15) CVs were 7% and 14%, respectively, at a mean value of 48 nmol/L. In women and pubertal girls, serum free Gal-Hyl correlated with urine free Gal-Hyl (r = 0.84; P <0.001). Serum Gal-Hyl was higher during puberty and increased after menopause. The fractional renal clearance of free Gal-Hyl relative to that of creatinine was 0.90 (95% confidence interval, 0.82-0.98). Serum free Gal-Hyl decreased by 36% (SE = 4%) in 14 patients with mild Paget disease treated with an oral bisphosphonate, and this decrease was significantly (P <0. 001) greater than that seen for either serum tartrate-resistant acid phosphatase (9%; SE = 4%) or serum C-terminal telopeptide of collagen I (19%; SE = 8%). CONCLUSION: Serum free Gal-Hyl may be useful as a serum marker of bone resorption. (+info)
Physiology and pathophysiology of bone remodeling.
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The skeleton is a metabolically active organ that undergoes continuous remodeling throughout life. This remodeling is necessary both to maintain the structural integrity of the skeleton and to subserve its metabolic functions as a storehouse of calcium and phosphorus. These dual functions often come into conflict under conditions of changing mechanical forces or metabolic and nutritional stress. The bone remodeling cycle involves a complex series of sequential steps that are highly regulated. The "activation" phase of remodeling is dependent on the effects of local and systemic factors on mesenchymal cells of the osteoblast lineage. These cells interact with hematopoietic precursors to form osteoclasts in the "resorption" phase. Subsequently, there is a "reversal" phase during which mononuclear cells are present on the bone surface. They may complete the resorption process and produce the signals that initiate formation. Finally, successive waves of mesenchymal cells differentiate into functional osteoblasts, which lay down matrix in the "formation" phase. The effects of calcium-regulating hormones on this remodeling cycle subserve the metabolic functions of the skeleton. Other systemic hormones control overall skeletal growth. The responses to changes in mechanical force and repair of microfractures, as well as the maintenance of the remodeling cycle, are determined locally by cytokines, prostaglandins, and growth factors. Interactions between systemic and local factors are important in the pathogenesis of osteoporosis as well as the skeletal changes in hyperparathyroidism and hyperthyroidism. Local factors are implicated in the pathogenesis of the skeletal changes associated with immobilization, inflammation, and Paget disease of bone. (+info)
A case of a dog with thickened calvaria with neurologic symptoms: magnetic resonance imaging (MRI) findings.
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A 6-year-old female mongrel dog weighing 9.0 kg was presented ananastatic, with clouding of consciousness, bilateral loss of hearing and depressed reactivity of the eyes to light. Magnetic resonance imaging (MRI) examination showed that the calvaria was markedly thickened with compression to the cerebrum and cerebellum. The case of a dog with thickened calvaria with compression of the cerebrum and cerebellum which could not be diagnosed by conventional measures was amenable to diagnosis by MRI. With increased application of MRI examination, such canine cases might increase in number. (+info)
Controlled study of the prevalence of radiological osteoarthritis in clinically unrecognised juxta-articular Paget's disease.
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BACKGROUND: Paget's disease of bone is common and often undiagnosed in the population. The association of Paget's disease and osteoarthritis is well described but only in cases ascertained in secondary and tertiary care centres to which they have been referred largely because of pain. This study represents an attempt to confirm the association between Paget's disease and osteoarthritis in a population previously unknown to have Paget's disease. METHODS: Radiographs of people over 55 years that included the entire pelvis, sacrum, femoral heads and lumbar spine (mostly plain abdominal radiographs) were obtained from hospital records for the period 1993-95. Films were screened by a trained observer and the positive films were reviewed by a consultant radiologist who also examined a 1 in 10 sample of the negative films. A sub-sample of 153 confirmed positive cases were matched for age and sex using cases without Paget's disease and these pairs were assessed by two observers working in tandem. The hip joints were scored 0-5 using a modification of the original descriptive classification of Kellgren and Lawrence and minimum joint space of the hip was also measured. RESULTS: Not all cases were available for assessment. A total of 248 films were included (137 without Paget's, 89 with unilateral and 22 with bilateral disease). The mean age of the cases and controls was 78.4 years and 77.4 years respectively with 66/45 male/female cases and 78/59 male/female controls. One hundred and twenty nine affected hips were available for comparison with 352 unaffected hips. Median joint space narrowing for the affected hip was 3 mm (range, 0-5 mm) and for the unaffected hip 4 mm (range, 0-6 mm, Mann-Whitney U test, p=0.00001). Median Kellgren and Lawrence grade for both groups was 0, with no statistical difference between the groups (Mann-Whitney U test, p=0.74). In terms of severity of osteoarthritis, there were 19 instances of grades 2+ in the unaffected hips, and only five in the affected hips. CONCLUSIONS: Pagetic coxopathy is characterised by loss of joint space, which may represent a secondary chondropathy. Although joint failure may result from this secondary chondropathy progression may be dependent on non-Pagetic factors. It is also possible that the usual radiological features of osteoarthritis may be modified or obscured by the Paget's disease. (+info)
Stabilisation of acute femoral fractures in Paget's disease.
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Eleven cases of acute femoral fractures in patients with Paget's disease are presented following stabilisation with the solid AO femoral nail. In three cases with severe deformity of the femur, reaming was required to enable implant insertion. No corticotomies were required. The median operation time was 55 (35-65) min. There was no operative mortality and no patient developed signs of acute respiratory distress syndrome/fat embolism. Skeletal stability was achieved in all cases. The reconstruction proximal locking option (spiral blade) was utilised in ten of the eleven cases. In all cases a 9 mm nail was inserted. One patient (pagetic sarcoma) died 23 months after surgery. Ten of the eleven fractures healed uneventfully. The mean time to union was 32 (26-42) weeks. (+info)
Osteoclasts expressing the measles virus nucleocapsid gene display a pagetic phenotype.
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Osteoclasts (OCLs) in Paget's disease are markedly increased in number and size, have increased numbers of nuclei per multinucleated cell, and demonstrate increased resorption capacity and increased sensitivity to 1,25-(OH)(2)D(3), the active form of vitamin D. These cells also contain nuclear inclusions, reminiscent of those seen in paramyxovirus-infected cells, which cross-react with antibodies to measles virus nucleocapsid (MVNP) antigen. To elucidate the role of MV in the abnormal OCL phenotype of Paget's disease, we transduced normal OCL precursors with retroviral vectors expressing MVNP and the MV matrix (MVM) genes. The transduced cells were then cultured with 1,25-(OH)(2)D(3) for14 or 21 days to induce formation of OCL-like multinucleated cells. The MVNP-transduced cells formed increased numbers of multinucleated cells, which contained many more nuclei and had increased resorption capacity compared with multinucleated cells derived from empty vector-transduced (EV-transduced) and MVM-transduced or normal bone marrow cells. Furthermore, MVNP-transduced cells showed increased sensitivity to 1, 25-(OH)(2)D(3), and formed OCLs at concentrations of 1, 25-(OH)(2)D(3) that were 1 log lower than that required for normal, EV-transduced, or MVM-transduced cells. These results demonstrate that expression of the MVNP gene in normal OCL precursors stimulates OCL formation and induces OCLs that express a phenotype similar to that of pagetic OCLs. These results support a potential pathophysiologic role for MV infection in the abnormal OCL activity and morphology that are characteristic of pagetic OCLs. (+info)
Short- and long-term effects of ibandronate treatment on bone turnover in Paget disease of bone.
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BACKGROUND: In Paget disease of bone (PD), serum total alkaline phosphatase (TAP) is a valid marker of disease activity. The aim of the present longitudinal study was to compare TAP with new and potentially more specific markers of bone turnover in bisphosphonate-treated patients with PD. METHODS: Twenty patients with active PD were studied before and after treatment with 2 mg of intravenous ibandronate over a period of 12 months. TAP (by colorimetry), serum bone-specific alkaline phosphatase (BAP; by enzyme immunoassay), serum osteocalcin (OC; by ELISA), serum bone sialoprotein (BSP; by RIA), and urinary total pyridinoline (PYD; by HPLC) and deoxypyridinoline (DPD; by HPLC) were measured as markers of bone turnover. RESULTS: Before treatment, TAP, BAP, and BSP were increased in all 20 patients, whereas OC was increased in 10, PYD in 13, and DPD in 15 patients. Three months post treatment, nine patients showed normalized TAP values, and a >/=25% re-increase (i.e. , relapse) was observed in all patients after 12 months. A normalization of BAP was achieved in six patients only. No significant changes were found for OC. BSP was decreased significantly at 24 h, and DPD at 48 h post treatment. A normalization of BSP was found in 8, of PYD in 18, and of DPD in 16 cases. Both PYD and DPD increased significantly from 9 months post treatment onward. CONCLUSIONS: Most markers of bone turnover show similar long-term changes after treatment of active PD with ibandronate. With regard to cost-effectiveness and assay performance, TAP remains the marker of choice in therapeutic monitoring of PD. However, more specific markers may improve the biochemical assessment of PD in certain situations. (+info)