Higher Bone Concentrations Research Articles

A characteristic signature of insulin-like growth factor (IGF) axis expression during osteogenic differentiation of human dental pulp cells (hDPCs): Potential co-ordinated regulation of IGF action

The IGF axis is represented by two growth factors (IGF1 and IGF2), two cognate cell surface receptors (IGF1R and IGF2R), six soluble high affinity IGF binding proteins (IGFBP1-6) and several IGFBP proteases. IGF1 and IGF2 are present at high concentrations in bone and play a crucial role in the maintenance and differentiation of both foetal and adult skeleton. In order to understand the role of the IGF axis in bone and other tissues it is necessary to profile the expression and activity of all genes in the axis together with the activity of relevant ancillary proteins (including IGFBP proteases). In the current report we used differentiating human dental pulp cells (hDPC) to examine the expression and activity of the IGF axis during osteogenic differentiation of these cells. We found that, with the exception of IGF1 and IGFBP1, all components of the IGF axis are expressed in hDPCs. IGFBP-4 is the most abundantly expressed IGFBP species at both mRNA and protein levels under both basal and osteogenic conditions. Although we found no difference in IGFBP-4 expression under osteogenic conditions, we report increased expression and activity of pregnancy associated plasma protein-A (PAPP-A - an IGFBP-4 proteinase) leading to increased IGFBP-4 proteolysis in differentiating cell cultures. Further to this we report increased expression of IGF-2 (an activator of PAPP-A), and decreased expression of stanniocalcin-2 (STC2- a recently discovered inhibitor of PAPP-A) under osteogenic conditions. We also demonstrate that STC2 and PAPP-A are able to form complexes in hDPC conditioned medium indicating the potential for regulation of IGFBP-4 proteolysis through this mechanism. We suggest that these changes in the expression and activity of the IGF axis may represent part of an osteogenic signature characteristic of differentiating hDPCs.

불레기말 추출물이 난소를 절제한 갱년기 장애 모델의 혈청 지질 변화 및 골 형성에 미치는 영향

In this study, the effects of Colpomenia sinuosa (CS) extract on serum lipid level and bone formation in an ovariectomized animal model were investigated. Twenty four nine-week old female Sprague-Dawley rats were randomly assigned to four groups: sham-operated rats (SHAM), ovariectomized control rats (OVX-CON), and ovariectomized rats supplemented with CS extract at 50 mg/kg bw (OVX-CS50) or 200 mg/kg bw (OVX-CS200). Three OVX groups were surgically ovariectomized while the SHAM group was sham-operated. CS extract was orally administrated at 1 mL per day. Analysis of serum lipid contents found that the total cholesterol, triglyceride, and low density lipoprotein cholesterol levels in the OVX-CON group were higher than those in the SHAM group. Notably, upon administration of CS extract after ovariectomy, triglyceride levels tended to significantly decrease. In addition, platelet aggregation ability decreased in groups treated with CS extract compared to the OVX-CON group. Serum alkaline phosphatase activity as an indicator of bone formation was lower in the CS extract group compared to the OVX-CON group. Collagen contents in bone and cartilage were reduced by ovariectomy, whereas the CS extract-supplemented groups exhibited higher concentrations in bone. According to these results, CS extract improved serum lipid parameters and osteogenesis in ovariectomized rats.

The late Pleistocene Pilauco site, Osorno, south-central Chile

Paleontological and archaeological sites have frequently been found in open locations of the Intermediate Depression of south-central Chile. This paper presents the results of two field sampling seasons carried out at the Pilauco Site (ca. 39°S) and compares them with those of three well known sites in Chile: Quereo, Tagua-Tagua and Monte Verde, ca. 32°, 34° and 41°S, respectively. Stratigraphic data collected at Pilauco and the resulting radiocarbon age model suggest that before 12,540 ± 90 BP the old Damas River eroded an older volcaniclastic hill, which was followed by a bog formation in an ox-bow lake. The site was developing up to 11,004 ± 186 BP, the date of the youngest vertebrate fossil. Two younger peat beds seal the site. As in Tagua-Tagua and Monte Verde, Gomphotheres are the most represented megafauna. Fossils of Equidae, Camelidae, Cervidae, Mephitidae, Muridae, Myocastoridae and Xenarthra are also found in Pilauco. As a whole, 718 bones, 30 teeth and 11 coprolites represent the extinct and extant vertebrates. Preliminary taphonomic results suggest action of various agents in the bones, i.e. trampling, root etching, abrasion, and carnivore gnawing. The spatial analysis suggests the transfer of smaller anatomical units (e.g. bones of camelids and horses) and the rearrangement of some pieces comparatively large (e.g. gomphothere bones). Similar to the present day north Patagonian landscape, the area where Pilauco site is located had a variety of animal resources, plants and stones in an ecotone between hills, floodplains and wetlands. A total of 101 lithics were recorded: basalt and quartzite were collected from nearby fluvial deposits and dacitic obsidian from the local volcaniclastic deposits. Debitage is the most represented lithic item (75%); cores and marginal edge-trimmed artifacts represented 12 and 13%, respectively. Artifacts and flakes are spatially and temporality associated in the same PB-7 bed with high bone concentrations in some specific areas, between 361 and 424 cm of local altitude. This industry is characterized by a recurrent lithic expedite technology with production of flakes and chips which mastered marginal retouches over the bifacial trimming. This seems to be connected to strategic conditions of high resource diversity, especially of human groups with a high or medium mobility across land. Pilauco represents a site contemporaneous to Monte Verde related as well to the first human occupation in the southern cone of South America, but with higher mammal diversity.

High bone concentrations of homocysteine are associated with altered bone morphology in humans

Accumulation of homocysteine and S-adenosylhomocysteine in bone has been shown to be associated with reduced bone quality in rats. The aim of the present study was to investigate whether high bone concentrations of homocysteine and S-adenosylhomocysteine as well as a low methylation capacity are related to an impaired bone morphology in humans. Concentrations of homocysteine and its precursors S-adenosylhomocysteine and S-adenosylmethionine were measured in femoral bone samples of eighty-two males and females (age 71 (SD 8) years) who underwent elective hip arthroplasty. Cancellous bone structure was analysed by histomorphometry. In addition, blood was sampled to measure serum concentrations of homocysteine. Results of bone and serum analyses were grouped for individuals with high or low bone concentrations of homocysteine, S-adenosylhomocysteine and S-adenosylmethionine, as well as for individuals with a high or a low methylation capacity, which is indicated by a low or a high S-adenosylhomocysteine:S-adenosylmethionine ratio (n 41, each). Histomorphometry showed a higher trabecular separation and a lower trabecular thickness, trabecular number and trabecular area in individuals with high bone concentrations of homocysteine and S-adenosylhomocysteine compared with individuals with low bone concentrations of homocysteine and S-adenosylhomocysteine. There was no association between the S-adenosylhomocysteine:S-adenosylmethionine ratio and bone morphology. It was found that 48 % of bone homocysteine was bound to the collagen of the extracellular bone matrix. Blood analyses demonstrated a significant correlation between serum and bone homocysteine. The results of the present study indicate an association between altered bone morphology and elevated bone concentrations of homocysteine and S-adenosylhomocysteine, but not between altered bone morphology and methylation capacity.

Penetration of Moxifloxacin into Bone Evaluated by Monte Carlo Simulation

Moxifloxacin is a fluoroquinolone with a broad spectrum of activity and good penetration into many tissues, including bone. Penetration of moxifloxacin into bone has not yet been studied using compartmental modeling techniques. Therefore, we determined the rate and extent of bone penetration by moxifloxacin and evaluated its pharmacodynamic profile in bone via Monte Carlo simulation. Twenty-four patients (10 males, 14 females) undergoing total hip replacement received 400 mg moxifloxacin orally 2 to 7 h prior to surgery. Blood and bone specimens were collected. Bone samples were pulverized under liquid nitrogen by a cryogenic mill, including an internal standard. Drug concentrations were analyzed by high-performance liquid chromatography. We used ADAPT II (results reported), NONMEM, and WinBUGS for pharmacokinetic analysis. Monte Carlo simulation was performed to reverse engineer the necessary area under the free concentration-time curve fAUC(SERUM)/MIC in serum and total AUC(BONE)/MIC in bone for a successful clinical or microbiological outcome. The median (10% to 90% percentile for between-subject variability) of the AUC in bone divided by the AUC in serum (AUC(BONE)/AUC(SERUM)) was 80% (51 to 126%) for cortical bone and 78% (42 to 144%) for cancellous bone. Equilibration between serum and bone was rapid. Moxifloxacin achieved robust (> or = 90%) probabilities of target attainment (PTAs) in serum, cortical bone, and cancellous bone up to MICs of < or = 0.375 mg/liter based on the targets fAUC(SERUM)/MIC > or = 40 and AUC(BONE)/MIC > or = 33. Moxifloxacin showed high bone concentrations and a rapid equilibrium between bone and serum. The favorable PTAs compared to the 90%-inhibitory MIC of Staphylococcus aureus warrant future clinical trials on the effectiveness of moxifloxacin in the treatment of bone infections.

Glycopeptide Bone Penetration in Patients with Septic Pseudoarthrosis of the Tibia

In the treatment of bone infections, a major determinant of the clinical response is the active drug concentration at the infected site. Because of the high prevalence of meticillin (methicillin)-resistant staphylococci and enterococci, glycopeptides are widely used for the treatment of bone and joint infections, but data on their penetration into human bone are lacking. The aim of our study was to measure vancomycin and teicoplanin concentrations in infected human bone under steady-state conditions and verify their relationship with inflammatory markers, patient demographic characteristics and pharmacodynamic microbiological markers. Twenty-seven adult orthopaedic patients undergoing surgical debridement for septic pseudoarthrosis of the tibia and receiving either intravenous vancomycin (Vancocina) 1 g twice daily) or teicoplanin (Targosid) 10 mg/kg/day) were studied from January 2004 to January 2008. Plasma and bone specimens were simultaneously collected during surgery for pharmacokinetic and microbiological assays at a variable interval after antimicrobial administration. Bone samples were dissected into cortical and cancellous bone, cleaned of soft tissues, crushed and eluted into phosphate buffer. Necrotic samples and sequestra were not analysed.Plasma and bone antimicrobial concentrations were measured by a validated method of high-performance liquid chromatography with UV detection, and bone/plasma concentration ratios were calculated. Cortical and cancellous bone area under the concentration-time curve (AUC) over 24 hours (AUC(24)) values were measured by the linear-log trapezoidal rule, using WinNonlin) software, and were compared with the minimum inhibitory concentrations (MICs) of the infecting agents. For vancomycin, the mean +/- SD concentrations were 2.66 +/- 1.2 mg/L in cortical bone and 11.53 +/- 7.8 mg/L in cancellous bone (corresponding to 20.67% and 89.39% of intraoperative plasma concentrations), and the mean +/- SD tissue AUC(24) values were 55.15 +/- 25.26 h . mg/L for cortical bone and 299.16 +/- 299.54 h . mg/L for cancellous bone. For teicoplanin, the mean +/- SD concentrations were 2.01 +/- 1.7 and 7.51 +/- 7.0 mg/L in cortical and cancellous bone, respectively (12.35% and 48.6% of intraoperative plasma concentrations), and the mean +/- SD teicoplanin tissue AUC(24) values were 34.08 +/- 23.6 h . mg/L and 155.17 +/- 132.8 h . mg/L for cortical bone and cancellous bone, respectively. The mean vancomycin AUC(24)/MIC ratios were 215.02 for plasma, 47.14 for cortical bone and 268.95 for cancellous bone. The mean teicoplanin AUC(24)/MIC ratios were 336.48, 36.27 and 197.21 for plasma, cortical bone and cancellous bone, respectively. Bone penetration of both glycopeptides ranged from poor (<15%) to satisfactory (15-30%) in the cortical compartment, while it was far higher into the highly vascularized cancellous tissue. Vancomycin bone penetration was slightly higher than with teicoplanin, but the difference was not statistically significant. Higher bone concentrations were observed with higher inflammatory markers, possibly as a result of increased vascularization and vascular permeability under inflammatory conditions. Bone concentrations over the MIC and AUC/MIC ratios suggested that both glycopeptides achieve a satisfactory pharmacokinetic exposure in the cancellous bone, as far as Gram-positive pathogens are concerned. On the other hand, cortical bone exposure was suboptimal in most patients. Furthermore, as antimicrobial penetration may be affected by impaired blood supply, the role of radical surgical removal of purulent and necrotic tissues appears to be essential in order to shorten treatment duration and to reduce the risk of treatment failure.

An open-label clinical evaluation of tigecycline (TGC) concentrations in selected tissues and fluids

Background/Aims TGC, an expanded spectrum glycylcycline in development for the treatment of skin and skin structure infections and intraabdominal infections, has a large volume of distribution (Vss≈600 L). TGC concentrations were measured in serum, lung, colon, gallbladder, bone, bile, and synovial fluid. Methods Serum TGC was determined (by LC/MS/MS) predose, at end of 30-minute infusion of the single 100-mg TGC dose, and at tissue collection (during scheduled elective surgery). Results At the time of this analysis, data from 54 subjects (of 120 planned) were available. Serum samples from 52 and tissue/fluid samples from 49 subjects were analyzed. Median TGC serum concentrations were 1425 ng/mL, 198 ng/mL, and 60 ng/mL at end of infusion, 4 hours, and 24 hours, respectively. Gallbladder, lung, and colon had the highest TGC concentrations; synovial fluid and bone had the lowest. One (1) death, the only serious adverse event (AE), occurred after the study; it was not related to TGC. Treatment-related AEs of nausea (23, 43%) and vomiting (7, 13%) were most frequently reported. No subject withdrew because of AEs. Conclusions Based on this analysis, a 100-mg TGC dose distributes into gallbladder, lung, and colon at or above MICs shown by in vitro data to be efficacious, and into bone tissue and synovial fluid. In animal studies, labeled TGC achieved high concentrations in bone. Tight TGC-bone binding, with poor extraction for assay, may have occurred in this study, rather than low bone uptake. The study is ongoing. (See Table). Clinical Pharmacology & Therapeutics (2005) 77, P98–P98; doi: 10.1016/j.clpt.2005.01.005 Table 1. Concentration Mean±SD tissue/serum ratios a 1 subject at each time point; NA=data not available; BQL=below quantitation limit. Range (ng/g) 4 hrs 8 hrs 12 hrs 24 hrs Gallbladder (n=17) 238–20,700 39±40 15±19 85±79 38±42 Lung (n=2) 653–1890 8.6a NA NA 14.6a Colon (n=11) 87–995 2.1±1.9 1.7±2.3 2.1±2.5 NA Bone (n=19) BQL-269 0.35±0.16 NA 1.10±1.25 NA Synovial fluid (n=15) 26–181 0.58±0.24 NA 0.89±0.49 0.71±0.15

A Non-Invasive Quarry Mapping System

Abstract The meter-grid system, using spikes hammered into the quarry floor as grid nodes, is a common way to map paleontological and archaeological excavations. This method is invasive to the fossil-bearing horizon and can damage or even destroy buried specimens. This potential is greatest when the site is characterized by high bone concentrations, and/or specimen/matrix friability. A new portable mapping system based on a floating-grid was developed to circumvent these problems. This system also is well suited for excavations with uneven quarry floors. The floating-grid system extends over a quarry using retractable wires and mobile posts. It employs a mapping square that hangs from wires extended from a back wall or rebar posts.

Cortisol enhances the transcription of insulin-like growth factor-binding protein-6 in cultured osteoblasts.

Previous work indicate that glucocorticoids inhibit the synthesis of insulin-like growth factor I (IGF-I) and IGF-binding protein-3 (IG-FBP-3), -4, and -5, but not IGFBP-6, in osteoblast cultures. IGFBP-6 binds IGF-II with high affinity and prevents IGF-II-mediated effects. As IGF-II is present at high concentrations in bone, we postulate that glucocorticoids may regulate IGF-II by altering IGFBP-6 synthesis. We tested the expression of IGFBP-6 in cultures of osteoblast-enriched cells from 22-day-old fetal rat calvariae (Ob cells). Treatment of Ob cells with cortisol caused a time- and dose-dependent increase in IGFBP-6 messenger RNA levels, as determined by Northern blot analysis. The effect was maximal after 48 h of treatment and observed with cortisol concentrations of 10 nM to 1 microM. Treatment with cortisol also increased IGFBP-6 polypeptide levels in the medium, as determined by Western immunoblot analysis. Cycloheximide at 3.6 microM decreased IGFBP-6 transcripts and prevented the stimulatory effect of cortisol. Cortisol did not modify the decay of IGFBP-6 messenger RNA in transcriptionally arrested Ob cells. In addition, cortisol increased the rate of IGFBP-6 transcription, as determined by nuclear run-on assays. In conclusion, cortisol stimulates IGFBP-6 expression in Ob cells by transcriptional mechanisms. As IGFBP-6 binds to and prevents the effect of IGF-II, its increased synthesis could be relevant to the inhibitory actions of cortisol in bone.

TGF-β and PDGF Act Synergistically in Affecting the Growth of Human Osteoblast-Enriched Cultures

Transforming growth factor beta (TGF-beta) is a polypeptide found in high concentrations in bone and is produced by and acts on primary adult human derived osteoblast-enriched cultures (PHO cells). Receptors for TGF-beta are present on PHO cells and TGF-beta is mitogenic for these cells. Results of these studies in conjunction with those of others suggest that TGF-beta may have an important therapeutic role in orthopaedic surgery; however, with respect to its mitogenic actions, further studies were needed to establish whether TGF-beta was acting directly to stimulate the growth of PHO cells. TGF-beta has been found in other systems to act as an indirect mitogen, stimulating growth via secretion of another growth factor, platelet-derived growth factor (PDGF). In an effort to determine whether the TGF-beta growth stimulation was mediated directly or indirectly, we have examined the growth stimulation of PHO cells by PDGF alone and in combination with TGF-beta. These studies revealed that TGF-beta in combination with either PDGF-AA or BB led to stimulation greater than that observed with either growth factor alone. TGF-beta in combination with PDGF-BB led to a synergistic stimulatory response while that observed with the AA isoform was more nearly additive. Further studies demonstrated that TGF-beta was capable of up-regulating the protein levels of the PDGF alpha (alpha) receptor within thirty minutes of TGF-beta pretreatment. Thus, TGF-beta appears to have both direct and indirect mechanisms of action as a mitogen in the PHO system. Finally, we showed that both the positive and negative alkaline phosphatase staining PHO cells were responsive to the mitogenic effects of both growth factor singly and in combination.

Bone metal content in patients with chronic renal failure

Bone accumulation of metals, other than aluminum (Al), in patients with chronic renal failure (CRF) has rarely been studied. We report the bone and blood levels of iron (Fe), vanadium (V), lead (Pb), Al and calcium (Ca) in 18 CRF patients on longterm hemodialysis and in 14 controls (C). Significant increments in mean blood Al (1,300%), V (160%) and Fe (60%) and decrease in blood Pb (−50%) were found in the patients with CRF. Renal subjects had higher bone concentrations (mean ± S.E.M.; μg/g of bone) of Al ( CRF = 129.1 ± 16.9; C = 12.6 ± 2.9; P < 0.0001), Fe ( CRF = 940.4 ± 133.4; C = 263.4 ± 49.0; P < 0.0001) and V ( CRF = 2.55 ± 0.43; C = 1.39 ± 0.36; P = 0.0308) and lower Ca ( CRF = 268.2 ± 11.1 mg/ g; C = 377.2 ± 28.1; P = 0.0017). A positive correlation was found between bone Al and V ( r = 0.355, P < 0.05). Results indicated that a significant bone accumulation of Al, Fe and V, but not Pb, occurred in the hemodialyzed azotemic individuals.

Bone concentrations of cefuroxime and cefamandole in the femoral head in 96 patients undergoing total hip replacement surgery.

Ninety-six patients undergoing total hip replacement surgery received chemoprophylaxis with either cefuroxime (51 patients) or cefamandole (45 patients). The dosage with cefuroxime was either 750 mg given intramuscularly with the premedication (18 patients) or l·5 g given intravenously with induction of anaesthesia (33 patients). The remaining 45 patients received 1 g of cefamandole intravenously with anaesthetic induction. Bone concentrations depended on the time interval between the antibiotic injection and the removal of the femoral head. These ranged from 0·6 to 7·l mg/kg (mean 2 mg/kg) for the 750 mg dose of cefuroxime 85 to 150 mm after the dose. For the 1·5 g dose of cefuroxime the concentrations varied between 2·9 and 49·8 mg/kg (mean 19·4 mg/kg) 15 to 125 mm following the injection. With cefamandole the levels measured in cancellous bone ranged from 2·4–38·5 mg/kg (mean 12·6 mg/kg) 20 to 70 mm after the injection. The bone/serum concentration ratio was higher for cefamandole (0·36) than for cefuroxime (0·14 and 0·23). Cefuroxime and cefamandole achieve high concentrations in bone and are suitable as prophylactic agents in patients having total hip replacement.

Post-mortem migration of bone-seeking radionuclides in the rat and rabbit and its effect on estimates of bone uptake.

1. The continued uptake of 18F, 85Sr and 47Ca by bone after death has been studied in rats and rabbits after aortic injection followed by quick killing, a period of recirculation of tracer before death, and perfusion of the carcase. In each case an approximately linear increase of bone radioactivity was observed during a period of 1 h at about the same rate. The proportionate increase depended on the initial concentration of bone-seeking nuclide, ranging from a factor of 1.5 to 4.5. Boiling the carcase did not increase the migration rate. 2. Delay between death and dissection may therefore lead to spuriously high bone concentrations of these radionuclides, leading to over-estimates of bone uptake, extraction ratio or bone blood flow.