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Insights into the means by which osteoclasts (OC) are activated to resorb bone may benefit the development of novel therapies for bone loss disorders. Extracellular protons are the most powerful direct activator of mammalian OC known to date; small shifts in extracellular pH can effectively act as an on-off switch for rat OC in vitro. We investigated the effects of pertussis toxin (PT, 5nM),...
Reliable results of quantitating serum osteocalcin can be obtained by measuring the stable N-terminal-mid fragment (N-MID region) of osteocalcin. In this study we present a new immuno radiometric assay (IRMA) based on two monoclonal antibodies specific for the osteocalcin N-terminal and mid region respectively. The assay used a simple one-step three hours procedure, and provides accurate measures...
Although skeletal unloading causes a rapid loss of bone, the precise mechanism whereby mechanical unloading causes bone loss is as yet unclear. Using a tail suspension model in rats, we have previously shown that mechanical unloading of hind limbs causes a rapid increase in bone resorption at trabecular bone areas, which is followed by a sustained reduction in bone formation mainly at cortical bone...
Aim of the trial was estimation of clodronate efficacy in the therapy of steroid secondary osteoporosis. Bronchial asthma was the reason of of steroid administration. 38 women were evaluated. First group (n=13) was treated by Clodronate 0,4 g daily 6 months + 1,0 g of elemental calcium +1200 U.vitamin D; second (n=15) and third (n=10) groups obtained only calcium and vitamin D. Women in groups...
Bisphosponates are potent inhibitors of osteoclastic bone resorption both in vivo and in vitro, but the mechanism by which these compounds exert their effect remains to be clarified. In particular data on human systems in vitro are lacking. The aim of this study was to assess the effect of alendronate (ALN), one compound of bisphosphonates family, on bone resorption in human system, using as experimental...
Heterotopic ossification (HO) occurs as a complication of several diseases and is frequently found in patients with neurologic injury. The histogenesis of this type of soft tissue ossification and involved osteogenic precursor cells are still unclear. Local factors like osteogenic protein 1 (OP-1, BMP-7) were found to be potent regulators of bone and cartilage formation in vitro and in vivo.Applying...
Annexin II has previously been implicated in osteoclastic bone resorption (Nesbitt, S.A. and Horton, M.A. (1995). J. Bone. Min. Res. 10: S221). The mechanism of action of annexin II in the mature osteoclast was explored using human osteoclasts derived from giant cell tumours of bone (osteoclastomas). The calcium-dependent binding of soluble type I collagen to osteoclastoma-derived annexin II was...
We have investigated bone disease in mice bearing a transgene encoding mature porcine TGF-β1, under the control of the murine promoter and enhancer (Sanderson et al, PNAS 92:2972, 1995). In five lines, transgene expression is confined to the liver. One line, designated line 25, has the highest TGF-β1 transgene expression and the highest TGF-β1 plasma levels, with a peak of 8-fold elevation at three...
Hypercalcemia due to primary hyperparathyroidism (pHPT) can sometimes develop into a life threatening condition (hypercalcemic crisis). Surgical removal of the hyperfunctioning gland (s) is the only effective method to cure such patients. In the critically ill patient preoperative medical treatment of the hypercalcemia is necessary to reduce the risk during anesthesia and surgery. The aim of this...
Growth plate histomorphometry of rats after spaceflight or on-Earth unloading showed marked alterations in cell organization (D. Montufar-Solis et al., J. Appl. Physiol., 73, 19S, 1992; D. Montufar-Solis and J. Duke, Am. Soc. Gravitational Space Biol., 1, 34, 1988). The regulation of longitudinal bone growth (LBG) is complex, as it includes among others nutritional and endocrine factors. However,...
Platelet-derived growth factors (PDGF), are potent bone cell mitogens which exist in three isoforms, PDGF-AA, -BB and -AB. PDGF-BB and AB are the most prevalent circulating forms whereas in normal bone PDGF-AA is most readily detected. In vitro osteoblast-like cells express the PDGF-A but not the -B gene. Using biopsies of heterotopic bone and osteophytes we investigated the expression of PDGF-A...
Tartrate resistant acid phosphatase (TRAP) is a widely used histochemical marker to identify osteoclasts but does not differentiate between circulating TRAP and the specific type V isoform. We have developed three monoclonal antibodies (mabs) specific to the type V isoform, each with distinct epitopes and have investigated their immunolocalisation in human heterotopic bone.Cryosections were fixed...
Interleukin-11 (IL-11) is a stromal cell derived cytokine which may be important for osteoclast development triggered by 1,25(OH)2D3 and other osteotropic factors. We prepared osteoclast-like multinucleated cells (OCL's) by maintaining cultures of murine bone marrow cells, or co-cultures of bone marrow and primary osteoblastic cells in the presence of 10nM 1,25 (OH)2D3 for up to 10 days. In order...
A fracture takes many weeks to heal even under optimal conditions, hence there is much interest in the possibility that growth factors might be used to accelerate the rate of healing. Bone morphogenetic proteins are known to induce bone and cartilage formation in ectopic sites in vivo, and their availability makes them ideal agents for this purpose.Fractures were made in the left tibiae of adult...
Fractures healing is generally reliable, but delay or failure of union may occur and is often associated with severe morbidity. Normal fracture healing has been exhaustively investigated both in animal models and (to a lesser extent) in man, but nonunion has received less attention. A principal feature of bone repair is elaboration of collagens in a sequential fashion giving gradual restitution...
Extracellular nucleotides elevate [Ca 2+ ] i and induce c-fos expression in bone cells through an interaction with purinoceptors. We have studied the signal transduction pathways that link calcium mobilization to c-fos expression in Saos-2 cells, following nucleotide stimulation. Here, we begin to explore the possible interactions of nucleotide agonists with parathyroid hormone...
Bisphosphonates seem to have distinct effects on inflammatory action of macrophages in vitro. We have shown that, in vitro, clodronate inhibits endotoxin induced secretion of inflammatory cytokines (IL-1, IL-6, TNF) from macrophages, especially when encapsulated in liposomes, while aminobisphosphonates sensitize the cells to enhanced production of these mediators. Also in vivo, clodronate exerts...
GM-CSF is an important modulator of hematopoietic cells. However, the role of GM-CSF in non-hematopoietic cells remains unclear. In this study, we have determined whether GM-CSF is an autocrine mitogenic factor for human osteoblastic (hOB) cells. We found by RT-PCR on total cellular RNA that quiescent hOB cells express both GM-CSF and the α and β receptor chains for GM-CSF in basal culture conditions...
Nitric oxide (NO), a free radical gas, is a messenger molecule with diverse functions throughout the body. NO is produced by constitutive and inducible isoforms of NO synthase (NOS) both of which have been reported in cultured osteoblast-like cells. (J.A. inducible isoform (iNOS) has been shown to be upregulated by Riancho et. al. JBMR. 10, 439, 1995). NO production via the inducible isoform (iNOS)...
Most fracture gaps are bridged initially by a cartilaginous (soft) callus which is later replaced by bony trabeculae (hard callus). This involves capillary invasion, cartilage resorption and deposition of bone onto the unresorbed cartilage struts similar to the endochondral ossification at the growth plate. So far little attention has been paid to the role of the chondrocytes during this process...
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