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Biomedical subjects

F R Singer

Publications and source records attributed to F R Singer.

At least 37 records · Page 2Linked to original sources
PubMed1996

Detection of measles virus nucleocapsid transcripts in circulating blood cells from patients with Paget disease.

Paget disease of bone is characterized by abnormalities in all phases of bone remodeling, but the fundamental cellular abnormality resides in the osteoclast (OCL). Osteoclasts in bone involved by Paget disease contain viral-like nuclear and cytoplasmic inclusions that react with antibodies directed against paramyxovirus nucleocapsid proteins, such as measles virus, respiratory syncytial virus, or canine distemper virus. However, the identity of the virus or the mechanisms responsible for its persistence or pathologic role in Paget disease is unclear. Furthermore, although Paget disease persists for many years, it remains a highly localized process with new lesions rarely if ever developing in previously unaffected bones. Since osteoclasts are formed by fusion of mononuclear precursors derived from colony forming unit-granulocyte macrophage (CFU-GM), the granulocyte-macrophage progenitor, we used reverse transcriptase polymerase chain reaction (RT-PCR) analysis to determine if CFU-GM, more differentiated osteoclast precursors, and peripheral blood cells derived from CFU-GM express measles virus nucleocapsid (MV-N) transcripts. We found that osteoclast precursors, as well as peripheral blood mononuclear cells, express MV transcripts in 9 of 13 patients. Sequence analysis of the PCR amplified products confirmed nucleotide identity of MV-N transcripts expressed in peripheral blood and bone marrow-derived cells from the same patient. In contrast, MV-N transcripts were not detected in OCL precursors or the peripheral blood from 10 normal subjects. In situ hybridization studies using 35S-labeled antisense riboprobes to MV-N transcripts further confirmed the expression of MV transcripts in these cells. Sequence analysis of the PCR amplified product from one of these patients also identified a novel mutation that converted lysine441 to glutamic acid441 in the MV-N transcript. These data demonstrate that OCL precursors and circulating peripheral blood cells also express MV transcripts in patients with Paget disease and suggest that the pagetic marrow microenvironment plays a critical role in maintaining the highly localized nature of the lesions in Paget disease.

Aged↗
PubMed1996

Medical management of nonparathyroid hypercalcemia and hypocalcemia.

In this article the differential diagnosis and management of non-parathyroid hypercalcemia and hypocalcemia are outlined. A differentiation is made between the acute management of symptomatic hypercalcemia and hypocalcemia and the chronic control of these relatively common states of abnormal electrolyte homeostasis. The use of newer agents such as bisphosphonates for hypercalcemia and calcitrol for hypocalcemia is emphasized.

Acute Disease↗
PubMed1995

Alendronate treatment of the postmenopausal osteoporotic woman: effect of multiple dosages on bone mass and bone remodeling.

BACKGROUND: The effects of the aminobisphosphonate alendronate sodium on bone mass and markers of bone remodeling were investigated. PATIENTS AND METHODS: In a multicenter, randomized, double-blind, placebo-controlled, 2-year study, 188 postmenopausal women, aged 42 to 75 years, with low bone mineral density (BMD) of the lumbar spine were randomly assigned to 1 of 6 daily treatment groups: placebo for 2 years, alendronate 5 or 10 mg for 2 years, alendronate 20 or 40 mg for 1 year followed by placebo for 1 year, or alendronate 40 mg for 3 months followed by 2.5 mg for 21 months. All subjects were given 500 mg/d of elemental calcium as calcium carbonate. RESULTS: At each dose, alendronate produced significant reductions in markers of bone resorption and formation, and significantly increased bone mass at the lumbar spine, hip, and total body, as compared with decreases (significant at lumbar spine) in subjects receiving placebo. In the 10-mg group, mean urinary deoxypyridinoline/creatinine had declined by 47% at 3 months, and mean serum osteocalcin by 53% at 6 months. Mean changes in BMD over 24 months with 10 mg alendronate were +7.21% +/- 0.49% for the lumbar spine, +5.27% +/- 0.70% for total hip, and +2.53% +/- 0.68% for total body (each P < 0.01) compared to changes of -1.35% +/- 0.61%, -1.20% +/- 0.64% and -0.31% +/- 0.44% at these sites, respectively, with placebo treatment. Progressive increases in BMD of both lumbar spine and total hip were observed in the second year of treatment with 10 mg alendronate (both P < 0.05). CONCLUSION: Alendronate, a potent inhibitor of bone resorption, reduces markers of bone remodeling and significantly increases BMD at the lumbar spine, hip, and total body, and is well tolerated at therapeutic doses (5 or 10 mg daily) in the treatment of osteoporosis in postmenopausal women.

Adult↗
PubMed1995

Bone marrow mononuclear cells from patients with Paget's disease contain measles virus nucleocapsid messenger ribonucleic acid that has mutations in a specific region of the sequence.

Ultrastructural, immunocytochemical, and in situ hybridization studies have suggested that paramyxoviruses, such as measles virus (MV), are present in Pagetic osteoclasts and may contribute to the abnormality in osteoclast function. However, little additional information is known about potential viruses present in Pagetic osteoclasts. As there are increased numbers of osteoclast precursors among the marrow mononuclear cells of Paget's patients, we used the reverse transcriptase-polymerase chain reaction to amplify the nucleocapsid sequence of MV from freshly isolated bone marrow-derived mononuclear cells to examine the potential role of these viruses in cells in the osteoclast lineage. We detected MV nucleocapsid transcripts in 5 of 6 individual Paget's patients' marrow samples. MV transcripts were not detected in marrow samples from 10 normal subjects. Sequence analysis of the PCR products revealed that 1 patient had the same sequence as the Edmonston strain of MV. The remaining 4 patients had point mutations clustered between position 1360-1371 base pairs. Two of the patients exhibited identical mutations at this region. In total, 3 different point mutations were identified that resulted in amino acid substitutions. These data show that 1) unlike those from normal subjects, marrow mononuclear cells from Paget's patients express MV nucleocapsid messenger ribonucleic acid; and 2) mutations of a specific region of the MV nucleocapsid gene were present in 4 of 5 patients and suggest a persistent MV infection in Pagetic osteoclast precursors. These data further suggest that osteoclasts are infected by fusion with infected precursors.

Amino Acid Sequence↗
PubMed1995

Bisphosphonates in the treatment of disorders of mineral metabolism.

Bisphosphonates are analogues of inorganic pyrophosphate, a naturally occurring chemical in bone. In vitro and animal experiments demonstrated that these agents were effective inhibitors of bone resorption. Subsequently they were applied to a variety of clinical problems in which increased bone resorption was an underlying feature of the pathology. In 1971 etidronate became the first bisphosphonate shown to inhibit bone resorption in humans when it was given to patients with Paget's disease. Subsequently this agent was also found to be useful in treating the hypercalcemia of malignancy. At the present time cyclic etidronate therapy is also used for the prevention of bone loss in patients with osteoporosis and for the prevention of heterotopic ossification in spinal cord-injured patients and in patients after hip replacement. Newer bisphosphonates are generally more potent than etidronate and do not produce a severe mineralization defect as do higher doses of etidronate. Pamidronate and clodronate are highly effective in the management of Paget's disease, hypercalcemia due to malignancy and immobilization, metastatic bone disease, and hematologic malignancies affecting bone. They are also promising agents for the prevention of osteoporosis. Alendronate, risedronate, and CGP 42446 are highly potent bisphosphonates that look very promising for the treatment of all disorders of bone resorption. It is fortunate that adverse reactions are not a prominent feature of bisphosphonate use. The main side effects are nausea and abdominal discomfort, mainly with oral use, a transient increase in bone pain in patients with Paget's disease, and an acute-phase reaction (fever, myalgia, mild leukopenia) in patients receiving aminobisphosphonates. The evolution of bisphosphonate therapy should be considered one of the major therapeutic events of the past 25 years. Future research should define the optimum use of these agents.

Diphosphonates↗
PubMed1993

Abnormalities in osteoclast precursors and marrow accessory cells in Paget's disease.

Paget's disease of bone is characterized by increased numbers of abnormal osteoclasts. To determine if osteoclast precursors were increased or abnormal in this disease, we examined CFU-GM, the committed granulocyte-macrophage progenitor and the most likely precursor for osteoclasts. In cultures of unfractionated marrow mononuclear cells, CFU-GM colony formation was significantly increased in Paget's marrow cultures compared to that in normal cells (356 +/- 44 vs. 271 +/- 15/10(5) cells; P < 0.05). However, when we enriched hematopoietic precursors from Paget's and normal marrow samples using an antibody that recognizes the CD34 antigen present on most hematopoietic precursors, we found that similar numbers of CFU-GM colonies were formed (87 +/- 13/10(4) cells plated vs. 83 +/- 13). Coculture experiments with highly purified hematopoietic precursors (CD34+ cells) and nonhematopoietic marrow accessory cells (CD34- cells) revealed that the growth of Paget's precursors was significantly enhanced above expected levels by normal or Pagetic CD34- cells (P < 0.05). CFU-GM colony formation was also significantly enhanced when normal CD34+ cells were cocultured with Pagetic, but not with normal, CD34- cells. In addition, CFU-GM colony-derived cells from Paget's patients were hyperresponsive to 1,25-dihydroxyvitamin D3 and could form osteoclast-like multinucleated cells with 1,25-dihydroxyvitamin D3 concentrations one tenth of that required for normal multinucleated formation (10(-11) vs. 10(-10) M). These data suggest that osteoclast precursors may be abnormal in Paget's disease, and other cells in the Pagetic marrow microenvironment may further enhance the growth and differentiation of these abnormal precursors.

Antigens, CD↗
PubMed1993

Biochemical assessment of bone formation and resorption in acromegaly.

The effects of chronic GH and insulin-like growth factor-I (IGF-I) excess on bone metabolism were examined by measuring serum markers of bone formation and urine markers of bone resorption as well as vertebral bone densities in patients with active acromegaly. Fasting serum GH levels were elevated in all 27 patients (31 +/- 11 micrograms/L). Serum calcium levels were within the normal range, except in 3 of 27 (10%) patients with mild hypercalcemia. Urinary calcium excretion, however, was increased in 6 (22%) patients despite mainly normal serum PTH and 1,25-dihydroxyvitamin D levels, suggesting a direct renal GH and/or IGF-I-mediated calciuric effect. Urinary hydroxyproline/creatinine excretion was increased in all except 1 patient and correlated with plasma IGF-I levels (r = 0.49; P < 0.02; n = 22). A more specific indicator of bone collagen turnover, urinary type I collagen cross-linked N-telopeptide, was elevated in all except 1 patient and correlated with serum GH (r = 0.47; P < 0.02), IGF-I (r = 0.60; P < 0.005), and urinary hydroxyproline/creatinine excretion (r = 0.62; P < 0.001). Serum bone Gla protein (osteocalcin), a specific marker of osteoblastic activity, was also increased in 50% of the patients and correlated with urinary N-telopeptide (r = 0.47; P < 0.02), but not with serum GH or IGF-I concentrations. Trabecular bone density, as determined by quantitative computerized tomography of the lumbar spine, was increased in only 1 patient; 13 others had subnormal bone density. The results suggest that in long-standing acromegaly, osteoblastic and osteoclastic activities are increased. Vertebral trabecular bone mass is usually reduced. Urinary collagen cross-links may serve as a more specific marker of bone resorption in acromegaly.

Acromegaly↗
PubMed1993

Giant cell tumor arising in Paget's disease of bone. Recurrences after 36 years.

A 96-year-old woman had both Paget's disease and a giant cell tumor of the same bone, the left scapula. Despite five surgical procedures, a full course of radiation therapy, and treatment with salmon calcitonin, human calcitonin, and finally disodium etidronate, the tumor has recurred over a 36-year period. The characteristic viral-like nuclear and cytoplasmic inclusions found in the osteoclasts of Paget's disease were found in the tumor giant cells, in specimens excised over an eight-year period, and in specimens obtained during orthopedic procedures on her other pagetic bone lesions over 12 years.

Aged↗
PubMed1992

A specific immunoassay for monitoring human bone resorption: quantitation of type I collagen cross-linked N-telopeptides in urine.

Peptides of low molecular weight that contain pyridinoline cross-links were isolated from adolescent human urine. A fraction was selected that was enriched in the N-telopeptide-to-helix intermolecular cross-linking domain of bone type I collagen. Mouse monoclonal antibodies were generated against these urinary peptides conjugated to a carrier protein as immunogen. A high-affinity antibody was identified that specifically bound to the trivalent peptides derived from the N-telopeptide-to-helix pyridinoline cross-linking site in type I collagen of human bone. This was confirmed by the direct isolation from human bone collagen of similar fragments recognized selectively by the antibody. A sensitive inhibition ELISA was established on microtiter plates that could quantify the bone-derived peptides in human urine. The assay, which can be run directly on untreated urine, was thoroughly tested against samples from normal subjects and from patients with metabolic bone disease. For example, strong correlations with urinary hydroxyproline and total pyridinoline cross-links were found in patients with Paget's disease of bone. The method shows considerable promise as a rapid and specific index of human bone resorption rates, with greatly improved specificity and convenience over total pyridinoline analysis. Potential applications include the study of normal metabolism, the diagnosis and monitoring of bone disease, and evaluating the effectiveness of antiresorption therapies.

Adolescent↗
PubMed1992

Effect of salmon calcitonin and etidronate on hypercalcemia of malignancy.

Hypercalcemia of malignancy is a commonly encountered serious clinical problem that often requires aggressive therapy. In order to combine the rapid hypocalcemic effects of calcitonin with the more delayed effect of a bisphosphonate, we administered etidronate, 7.5 mg/kg/day intravenously and salmon calcitonin, 100 IU subcutaneously, every 12 hours for 3 days in 9 patients with hypercalcemia associated with malignancy. The mean serum calcium concentration fell from 3.33 +/- 0.1 mmol/liter (mean +/- SEM) to 2.88 +/- 0.1 mmol/liter within 24 hours (P less than 0.001). All patients had a fall in the serum calcium concentration of greater than 0.5 mmol/liter and it returned to normal in 7 of the 9 patients. We conclude that the combination of salmon calcitonin with etidronate more effectively lowers the serum calcium concentration in patients with hypercalcemia of malignancy then the use of either agent alone.

Animals↗
PubMed1992

Interleukin 6. A potential autocrine/paracrine factor in Paget's disease of bone.

Pagetic osteoclasts are greatly increased in number and size and have increased numbers of nuclei per cell compared to normal osteoclasts. The mechanisms responsible for enhanced osteoclast formation in Paget's disease are unknown. We have used our recently described model system for pagetic osteoclast formation to evaluate culture media conditioned by these atypical multinucleated cells (MNC) to determine if pagetic osteoclasts produce an autocrine or paracrine factor that enhances osteoclast formation. Conditioned media from long-term bone marrow cultures from patients with Paget's disease stimulated osteoclast-like MNC formation in normal marrow cultures. At least part of this activity could be ascribed to interleukin 6 (IL-6). In contrast, conditioned media from normal marrow cultures contained lower levels of IL-6 and did not stimulate formation of osteoclast-like MNC. 7 of 8 bone marrow plasma samples taken from involved bones and 18 of 27 peripheral blood serum samples from Paget's patients had high levels of IL-6. Normal marrow plasma and peripheral blood serum had no or very low levels of IL-6. These results suggest that IL-6 produced by marrow and/or bone cells in patients with Paget's disease may be an autocrine/paracrine factor for pagetic osteoclasts.

Biological Assay↗
PubMed1992

Bone-resorption markers galactosyl hydroxylysine, pyridinium crosslinks, and hydroxyproline compared.

We compared the clinical performances of four bone-resorption (BR) assays (hydroxyproline, HYP; galactosyl hydroxylysine, GHYL; deoxypyridinoline, DPD; and pyridinoline, PYD) in subjects with different BR rates: normal (adult men and premenopausal women), mildly increased (postmenopausal osteoporotic women), high (Paget disease patients), and very high (children). The discrimination power (Z score) and the accuracy (estimated by receiver-operating characteristic analysis) for GHYL, DPD, and PYD were compared with those for HYP. Discrimination power and accuracy were similar for high- and very-high-BR groups for all four assays. However in the mildly increased-BR group, DPD, GHYL, and PYD showed a higher discrimination power and accuracy than did HYP. The clinical performances of HYP, DPD, GHYL, and PYD are comparable for large changes in BR. For modest changes, DPD, GHYL, and PYD are more accurate and have a higher discrimination power than does HYP.

Adult↗