Mechanisms of Plutonium Redox Reactions in Nitric Acid Solutions.

Plutonium (Pu) exhibits a complex redox behavior in aqueous solutions. This is due to the ability of the element to adapt a wide range of oxidation states typically from +3 to +6 and the tendency for dynamic interconversion between the oxidation states that primarily depend upon acid concentration and presence of coordinating ligands. This work interrogates the Pu redox behavior in aqueous nitric acid via a combination of voltammetry and in situ vis-NIR spectroelectrochemistry under controlled potentials to map the interconversion between the various Pu oxidation states. The NIR-spectroelectrochemistry studies used to complement the visible spectroscopy bring a new and more complete perspective into the plutonium redox transformations. This allows elucidation of the mechanisms of the involved redox reactions facilitating an in-depth understanding of the relative stability of the Pu oxidation states as a function of redox potentials and nitric acid concentrations. It is observed that oxidation of Pu(III) results in generation of Pu(IV) and Pu(VI) (the latter as PuO22+), bypassing the Pu(V) oxidation state. Further, with increasing acid concentrations, the formation of the Pu(VI) species progressively decreases so that the dynamic equilibrium between the Pu(III) and Pu(IV) oxidation states dominates. These findings have significant implications for developing separation processes for used nuclear fuel reprocessing and treatment.

Highly Selective Colorimetric and Luminescence Response of a Square-Planar Platinum(II) Terpyridyl Complex to Aqueous TcO4(-).

Molecular recognition of an aqueous pertechnetate (TcO4(-)) anion is fundamentally challenging partly due to the charge-diffuse nature of this anion, which hampers design of new technologies for its separation and detection. To address this gap, simple salts of transition metal complexes that undergo a distinct spectroscopic change upon exposure to aqueous anions were explored. The Pt(II) complex [Pt(tpy)Br]SbF6 (tpy = 2,2';6',2″-terpyridine) undergoes a dramatic color change and intense luminescence response upon TcO4(-) uptake due to concomitant enhancement of Pt···Pt interactions. The spectroscopic response was highly selective and quantitative for aqueous TcO4(-) among other competing anions. Complementary Raman spectroscopy and microscopy techniques, structural determination, and theoretical methods were employed to elucidate the mechanism of this response at the molecular level.

Effects of Age and Estrogen on Skeletal Gene Expression in Humans as Assessed by RNA Sequencing.

UNLABELLED: Precise delineation of the specific genes and pathways altered with aging and estrogen (E) therapy may lead to new skeletal biomarkers and the development of novel bone therapeutics. Previous human bone studies, however, have been limited by only examining pre-specified genes and pathways. High-throughput RNA sequencing (RNAseq), on the other hand, offers an unbiased approach to examine the entire transcriptome. Here we present an RNAseq analysis of human bone samples, obtained from iliac crest needle biopsies, to yield the first in vivo interrogation of all genes and pathways that may be altered in bone with aging and E therapy in humans. 58 healthy women were studied, including 19 young women (mean age ± SD, 30.3 ± 5.4 years), 19 old women (73.1 ± 6.6 years), and 20 old women treated with 3 weeks of E therapy (70.5 ± 5.2 years). Using generally accepted criteria (false discovery rate [q] < 0.10), aging altered a total of 678 genes and 12 pathways, including a subset known to regulate bone metabolism (e.g., Notch). Interestingly, the LEF1 transcription factor, which is a classical downstream target of the Wnt/ß-catenin signaling pathway, was significantly downregulated in the bones from the old versus young women; consistent with this, LEF1 binding sites were significantly enriched in the promoter regions of the differentially expressed genes in the old versus young women, suggesting that aging was associated with alterations in Wnt signaling in bone. Further, of the 21 unique genes altered in bone by E therapy, the expression of INHBB (encoding for the inhibin, beta B polypeptide), which decreased with aging (by 0.6-fold), was restored to young adult levels in response to E therapy. In conclusion, our data demonstrate that aging alters a substantial portion of the skeletal transcriptome, whereas E therapy appears to have significant, albeit less wide-ranging effects. These data provide a valuable resource for the potential identification of novel biomarkers associated with age-related bone loss and also highlight potential pathways that could be targeted to treat osteoporosis. TRIAL REGISTRATION: ClinicalTrials.gov NCT02349113.

Electron ionization mass spectrum of tellurium hexafluoride.

The electron ionization mass spectrum of tellurium hexafluoride (TeF6) is reported for the first time. The starting material was produced by direct fluorination of Te metal or TeO2 with nitrogen trifluoride. Formation of TeF6 was confirmed through cryogenic capture of the tellurium fluorination product and analysis through Raman spectroscopy. The eight natural abundance isotopes were observed for each of the set of fragment ions: TeF5(+), TeF4(+) TeF3(+), TeF2(+), TeF1(+), and Te(+), Te2(+). A trend in increasing abundance was observed for the odd fluoride bearing ions, TeF1(+) < TeF3(+) < TeF5(+), and a decreasing abundance was observed for the even fragment series, Te(F0)(+) > TeF2(+) > TeF4(+) > TeF6(+), with the molecular ion TeF6(+) not observed at all. Density functional theory based electronic structure calculations were used to calculate optimized ground state geometries of these gas phase species, and their relative stabilities explain the trends in the data and the lack of observed signal for TeF6(+).

Development of Online Spectroscopic pH Monitoring for Nuclear Fuel Reprocessing Plants: Weak Acid Schemes.

In nuclear fuel reprocessing, separating trivalent minor actinides and lanthanide fission products is extremely challenging and often necessitates tight pH control in TALSPEAK (Trivalent Actinide-Lanthanide Separation by Phosphorus reagent Extraction from Aqueous Komplexes) separations. In TALSPEAK and similar advanced processes, aqueous pH is one of the most important factors governing the partitioning of lanthanides and actinides between an aqueous phase containing a polyaminopolycarboxylate complexing agent and a weak carboxylic acid buffer and an organic phase containing an acidic organophosphorus extractant. Real-time pH monitoring would significantly increase confidence in the separation performance. Our research is focused on developing a general method for online determination of the pH of aqueous solutions through chemometric analysis of Raman spectra. Spectroscopic process-monitoring capabilities, incorporated in a counter-current centrifugal contactor bank, provide a pathway for online, real-time measurement of solution pH. The spectroscopic techniques are process-friendly and can be easily configured for online applications, whereas classic potentiometric pH measurements require frequent calibration/maintenance and have poor long-term stability in aggressive chemical and radiation environments. Raman spectroscopy discriminates between the protonated and deprotonated forms of the carboxylic acid buffer, and the chemometric processing of the Raman spectral data with PLS (partial least-squares) regression provides a means to quantify their respective abundances and therefore determine the solution pH. Interpretive quantitative models have been developed and validated under a range of chemical composition and pH conditions using a lactic acid/lactate buffer system. The developed model was applied to new spectra obtained from online spectral measurements during a solvent extraction experiment using a counter-current centrifugal contactor bank. The model predicted the pH of this validation data set within 11% for pH > 2, thus demonstrating that this technique could provide the capability of monitoring pH online in applications such as nuclear fuel reprocessing.

Cortical porosity identifies women with osteopenia at increased risk for forearm fractures.

Most fragility fractures arise among the many women with osteopenia, not the smaller number with osteoporosis at high risk for fracture. Thus, most women at risk for fracture assessed only by measuring areal bone mineral density (aBMD) will remain untreated. We measured cortical porosity and trabecular bone volume/total volume (BV/TV) of the ultradistal radius (UDR) using high-resolution peripheral quantitative computed tomography, aBMD using densitometry, and 10-year fracture probability using the country-specific fracture risk assessment tool (FRAX) in 68 postmenopausal women with forearm fractures and 70 age-matched community controls in Olmsted County, MN, USA. Women with forearm fractures had 0.4 standard deviations (SD) higher cortical porosity and 0.6 SD lower trabecular BV/TV. Compact-appearing cortical porosity predicted fracture independent of aBMD; odds ratio (OR) = 1.92 (95% confidence interval [CI] 1.10­3.33). In women with osteoporosis at the UDR, cortical porosity did not distinguish those with fractures from those without because high porosity was present in 92% and 86% of each group, respectively. By contrast, in women with osteopenia at the UDR, high porosity of the compact-appearing cortex conferred an OR for fracture of 4.00 (95% CI 1.15­13.90). In women with osteoporosis, porosity is captured by aBMD, so measuring UDR cortical porosity does not improve diagnostic sensitivity. However, in women with osteopenia, cortical porosity was associated with forearm fractures.

Effects of estrogen on bone mRNA levels of sclerostin and other genes relevant to bone metabolism in postmenopausal women.

CONTEXT: Studies in postmenopausal women have shown that estrogen reduces circulating sclerostin levels, but effects of estrogen on skeletal sclerostin mRNA levels are unknown. OBJECTIVE: The objective of the study was to evaluate the effects of short-term estrogen treatment on bone mRNA levels of sclerostin and other genes relevant to bone metabolism. DESIGN, SETTING, AND PATIENTS: Needle bone biopsies were obtained from 20 postmenopausal women treated with transdermal estrogen for 3 weeks and 20 untreated controls. Quantitative PCR analyses were used to examine the expression of sclerostin and other genes related to bone metabolism, including 71 additional genes linked to bone density/fracture from genome-wide association studies. RESULTS: Estrogen treatment was associated with lower bone sclerostin mRNA levels (by 48%, P<.05) and with lower (by 54%, P<.01) mRNA levels of the sclerostin-related protein, sclerostin domain-containing protein 1 (SOSTDC1), which is also a Wnt/bone morphogenetic protein inhibitor. Consistent with studies in mice showing that ovariectomy increased nuclear factor-κB (NF-κB) activation, we found that estrogen treatment was associated with a significant reduction in inflammatory genes as a group (P=.028), with bone mRNA levels of NFKB2 and RELB (both encoding proteins in the NF-κB transcription factor complex) being significantly reduced individual genes. Eight of the 71 genome-wide association study-related genes examined were modulated by estrogen (P<.05, false discovery rate<0.10). CONCLUSION: In humans, estrogen-induced decreases in two key inhibitors of Wnt/bone morphogenetic protein signaling, sclerostin and SOSTDC1, along with reductions in NF-κB signaling, may be responsible for at least part of the protective effects of estrogen on bone.

Effects of age on bone mRNA levels of sclerostin and other genes relevant to bone metabolism in humans.

Although aging is associated with a decline in bone formation in humans, the molecular pathways contributing to this decline remain unclear. Several previous clinical studies have shown that circulating sclerostin levels increase with age, raising the possibility that increased production of sclerostin by osteocytes leads to the age-related impairment in bone formation. Thus, in the present study, we examined circulating sclerostin levels as well as bone mRNA levels of sclerostin using quantitative polymerase chain reaction (QPCR) analyses in needle bone biopsies from young (mean age, 30.0years) versus old (mean age, 72.9years) women. In addition, we analyzed the expression of genes in a number of pathways known to be altered with skeletal aging, based largely on studies in mice. While serum sclerostin levels were 46% higher (p<0.01) in the old as compared to the young women, bone sclerostin mRNA levels were no different between the two groups (p=0.845). However, genes related to notch signaling were significantly upregulated (p=0.003 when analyzed as a group) in the biopsies from the old women. In an additional analysis of 118 genes including those from genome-wide association studies related to bone density and/or fracture, BMP/TGFß family genes, selected growth factors and nuclear receptors, and Wnt/Wnt-related genes, we found that mRNA levels of the Wnt inhibitor, SFRP1, were significantly increased (by 1.6-fold, p=0.0004, false discovery rate [q]=0.04) in the biopsies from the old as compared to the young women. Our findings thus indicate that despite increases in circulating sclerostin levels, bone sclerostin mRNA levels do not increase in elderly women. However, aging is associated with alterations in several key pathways and genes in humans that may contribute to the observed impairment in bone formation. These include notch signaling, which represents a potential therapeutic target for increasing bone formation in humans. Our studies further identified mRNA levels of SFRP1 as being increased in aging bone in humans, suggesting that this may also represent a viable target for the development of anabolic therapies for age-related bone loss and osteoporosis.

Water O-H stretching Raman signature for strong acid monitoring via multivariate analysis.

A distinct need exists for real time information on an acid concentration of industrial aqueous streams. Acid strength affects efficiency and selectivity of many separation processes, including nuclear fuel reprocessing. Despite the seeming simplicity of the problem, no practical solution has been offered yet, particularly for the large-scale schemes involving toxic streams such as highly radioactive nuclear wastes. The classic potentiometric technique is not amiable for online measurements due to the requirements of frequent calibration/maintenance and poor long-term stability in aggressive chemical and radiation environments. Therefore, an alternative analytical method is needed. In this work, the potential of using Raman spectroscopic measurements for online monitoring of strong acid concentration in solutions relevant to dissolved used nuclear fuel was investigated. The Raman water signature was monitored for solution systems containing nitric and hydrochloric acids and their sodium salts of systematically varied composition, ionic strength, and temperature. The trivalent neodymium ion simulated the presence of multivalent f metals. The gaussian deconvolution analysis was used to interpret observed effects of the solution nature on the Raman water O-H stretching spectrum. The generated Raman spectroscopic database was used to develop predictive multivariate regression models for the quantification of the acid and other solution components, as well as selected physicochemical properties. This method was validated using independent experiments conducted in a flow solvent extraction system.

Relationship of adiposity to bone volumetric density and microstructure in men and women across the adult lifespan.

Recent evidence suggests that adipose tissue may negatively impact bone health, challenging the traditional paradigm that increased fat mass, through mechanical loading or endogenous estrogen production, is beneficial to the skeleton. We hypothesized that it is primarily the visceral compartment of body fat that is detrimental to bone metabolism, resulting in impaired bone density and architecture. In an age-stratified population sample of 218 women and 291 men (age 20-97 years), we assessed visceral (VAT) and subcutaneous (SAT) adipose tissue areas at the L2-L3 interspace level by single slice quantitative computed tomography (QCT) and measured total body fat mass (TBF) by dual-energy X-ray absorptiometry. We then correlated these findings with volumetric bone mineral density (vBMD) at the femoral neck (FN) and lumbar spine (LS) assessed by central QCT, and with vBMD and microstructural parameters at the ultradistal radius (UDR) by high resolution peripheral QCT (HRpQCT). In unadjusted analyses in postmenopausal women, TBF and SAT were positively correlated with total, trabecular, and cortical vBMD at the FN, LS, and UDR and with trabecular microstructure at the UDR. By contrast, VAT was not correlated with vBMD at the FN or LS but was positively correlated with UDR total and trabecular vBMD but not cortical vBMD. Adjustment for age or for bioavailable estradiol and testosterone levels reduced these correlations, while adjustment for body weight eliminated most positive associations. Assessment of the VAT/SAT ratio, however, demonstrated a negative relationship with vBMD at the FN and LS in postmenopausal women, a relationship eliminated when adjusted for age. Correlations between skeletal parameters and adipose measurements in pre-menopausal women and older men were weaker and mostly non-significant. In younger men, VAT was negatively associated with vBMD, cortical thickness, and trabecular microstructure at the UDR, and with LS vBMD and FN cortical vBMD. These associations generally remained after adjustment, with some negative associations (e.g., UDR cortical area) being accentuated. Similar results were found when the VAT/SAT ratio was correlated with FN vBMD in younger men; in contrast, VAT/SAT was positively correlated with FN vBMD in older men and this relationship was strengthened by age-adjustment. Together, our data suggest that adiposity has associations with bone that are age-, gender-, menopausal status-, adipose depot-, and bone compartment-specific. These novel observations warrant further investigations to establish any causal relationships.

Separating and stabilizing phosphate from high-level radioactive waste: process development and spectroscopic monitoring.

Removing phosphate from alkaline high-level waste sludges at the Department of Energy's Hanford Site in Washington State is necessary to increase the waste loading in the borosilicate glass waste form that will be used to immobilize the highly radioactive fraction of these wastes. We are developing a process which first leaches phosphate from the high-level waste solids with aqueous sodium hydroxide, and then isolates the phosphate by precipitation with calcium oxide. Tests with actual tank waste confirmed that this process is an effective method of phosphate removal from the sludge and offers an additional option for managing the phosphorus in the Hanford tank waste solids. The presence of vibrationally active species, such as nitrate and phosphate ions, in the tank waste processing streams makes the phosphate removal process an ideal candidate for monitoring by Raman or infrared spectroscopic means. As a proof-of-principle demonstration, Raman and Fourier transform infrared (FTIR) spectra were acquired for all phases during a test of the process with actual tank waste. Quantitative determination of phosphate, nitrate, and sulfate in the liquid phases was achieved by Raman spectroscopy, demonstrating the applicability of Raman spectroscopy for the monitoring of these species in the tank waste process streams.

Characterization of mesenchymal progenitor cells isolated from human bone marrow by negative selection.

Studies on the pathogenesis of osteoporosis and other metabolic bone diseases would be greatly facilitated by the development of approaches to assess changes in gene expression in osteoblast/osteoprogenitor populations in vivo without the potentially confounding effects of in vitro culture and expansion of the cells. While positive selection to identify a progenitor population in human marrow can be used to select for cells capable of osteoblast differentiation, each of the markers that have been used to identify marrow mesenchymal populations (alkaline phosphatase [AP], Stro-1, CD29, CD49a, CD73, CD90, CD105, CD166, CD44, CD146 and CD271) may be expressed on distinct subsets of marrow mesenchymal cells. Thus, positive selection with one or more of these markers could exclude a possibly relevant cell population that may undergo important changes in various clinical conditions. In the present report, we describe the isolation and characterization of human osteoprogenitor cells obtained by depletion of bone marrow cells of all hematopoietic lineage/hematopoietic stem cells and endothelial/endothelial precursor cells (lin-/CD34/CD31-). The yield of lin-/CD34/CD31- cells from ~10 mL of bone marrow (~80 million mononuclear cells) was ~80,000 cells (0.1% of mononuclear cells). While not selected on the basis of expression for the mesenchymal marker, Stro-1, 68% of these cells were Stro-1+. Using linear whole transcriptome amplification followed by quantitative polymerase chain reaction (QPCR) analysis, we also demonstrated that, compared to lin- cells (which are already depleted of hematopoietic cells), lin-/CD34/31- cells expressed markedly lower mRNA levels for the endothelial/hematopoietic markers, CD34, CD31, CD45, and CD133. Lin-/CD34/31- cells were also enriched for the expression of mesenchymal/osteoblastic markers, with a further increase in runx2, osterix, and AP mRNA expression following in vitro culture under osteogenic conditions. Importantly, lin-/CD34/31- cells contained virtually all of the mineralizing cells in human marrow: while these cells displayed robust calcium deposition in vitro, lin-/CD34/31+ cells demonstrated little or no mineralization when cultured under identical osteogenic conditions. Lin-/CD34/31- cells thus represent a human bone marrow population highly enriched for mesenchymal/osteoblast progenitor cells that can be analyzed without in vitro culture in various metabolic bone disorders, including osteoporosis and aging.

Evaluation of Cuprimine® and Syprine® for decorporation of radioisotopes of cesium, cobalt, iridium and strontium.

Cuprimine® and Syprine® are therapeutics approved by the USFDA to treat copper overload in Wilson Disease (a genetic defect in copper transport) by chelation and accelerated excretion of internally-deposited copper. These oral therapeutics are based on the respective active ingredients D-penicillamine (DPA) and N,N'-bis (2-aminoethyl) -1,2-ethanediamine dihydrochloride (Trien). Cuprimine is considered the primary treatment, although physicians are increasingly turning to Syprine as a first-line therapy. Both drugs exhibit oral systemic activity and low toxicity; their biological effects and safety are established. Previous in vivo studies using a rodent animal model established the decorporation potential of Cuprimine and Syprine for (60)Co and (210)Po. Currently these studies are being expanded to evaluate the in vivo decorporation efficacy of these drugs for several additional radionuclides. In this report, results of this investigation are discussed using the radionuclides (137)Cs, (60)Co, (192)Ir and (85)Sr. Short-term 48-h pilot studies were undertaken to evaluate DPA and Trien for their in vivo decorporation potential using male Wistar-Han rats. In these studies, a radionuclide solution was administered to the animals by intravenous (IV) injection, followed by a single IV dose of either DPA or Trien. Control animals received the radionuclide alone. Results show effective decorporation of (60)Co by DPA within the time frame evaluated. DPA and Trien were also modestly effective in decorporation of (137)Cs and (85)Sr, respectively. The study did not find DPA or Trien effective for decorporation of (192)Ir. Based on these encouraging findings, further studies to evaluate the dose-response profiles and timing of the chelator administration post exposure to radionuclides are warranted.

Effects of intermittent parathyroid hormone treatment on osteoprogenitor cells in postmenopausal women.

Intermittent parathyroid hormone (PTH) 1-34 treatment stimulates bone formation, but the molecular mechanisms mediating this effect have not been previously studied in humans. Thus, we used magnetic activated cell sorting to isolate hematopoietic lineage negative (lin-)/alkaline phosphatase positive (AP+) osteoprogenitor cells from bone marrow of 20 postmenopausal women treated with PTH (1-34) for 14 days and 19 control subjects. Serum PINP and CTX increased in PTH-treated subjects (by 97% and 30%, respectively, P<0.001). Bone marrow lin-/AP+ cells from PTH-treated subjects showed an increase in the RANKL/OPG mRNA ratio (by 7.5-fold, P=0.011) and in the mRNAs for c-fos (a known PTH-responsive gene, by 42%, P=0.035) and VEGF-C (by 57%, P=0.046). Gene Set Enrichment Analysis (GSEA, testing for changes in pre-specified pathways) demonstrated that PTH had no effect on osteoblast proliferation, apoptosis, or differentiation markers. However, PTH treatment resulted in a significant decrease (GSEA P-value, 0.005) in a panel of BMP target genes in the lin-/AP+ cells. Our findings thus identify several future directions for studying mechanisms of PTH action in humans. First, given the increasing evidence that PTH induces angiogenesis, the role of increased VEGF-C production by bone marrow osteoprogenitor cells in mediating this effect and the anabolic response to PTH warrants further study. Second, while the observed inhibition of BMP target gene expression by PTH is not consistent with the anabolic effects of PTH on bone and requires further validation, these data do generate the hypothesis that an inhibition of BMP signaling by PTH may, over time, limit the availability of mature osteoblasts on bone surfaces and thereby contribute to the observed waning of the anabolic response to PTH.

Effects of estrogen on osteoprogenitor cells and cytokines/bone-regulatory factors in postmenopausal women.

Decreases in estrogen levels contribute not only to early postmenopausal bone loss but also to bone loss with aging. While estrogen is critical for the maintenance of bone formation, the mechanism(s) of this effect remain unclear. Thus, we assessed the effects of 4months of transdermal estradiol treatment (0.05mg/day) of postmenopausal women as compared to no treatment (n=16 per group) on the expression of genes in pre-specified pathways in freshly isolated bone marrow osteoprogenitor cells (hematopoietic lineage [lin]-/Stro1+). We also evaluated whether estrogen treatment modulated peripheral blood or bone marrow plasma levels of the Wnt antagonists, sclerostin and DKK1, as well as serotonin, OPG, RANKL, adiponectin, oxytocin, and inflammatory cytokines (TNFα, IL-1ß, and IL-6), as each of these molecules have recently been shown to play an important role in regulating osteoblast function and/or being responsive to estrogen. We observed a significant decrease in the expression of several proliferation markers (cyclin B1, cyclin E1, E2F1) and increase in adhesion molecules (N-cadherin) in bone marrow lin-/Stro1+ cells from estrogen-treated compared to control women. None of the peripheral blood or bone marrow plasma marker levels differed between the two groups, with the exception of sclerostin levels, which were significantly lower in the estrogen-treated as compared to the control women in peripheral serum (by 32%, P=0.009) and in bone marrow plasma (by 34%, P=0.017). There were significant differences in bone marrow versus peripheral plasma levels of several factors: sclerostin and OPG levels were higher in bone marrow as compared to peripheral plasma, whereas serotonin and adiponectin levels were higher in peripheral as compared to bone marrow plasma. In summary, our data directly assessing possible regulation by estrogen of osteoprogenitor cells in humans indicate that, consistent with previous studies in mice, estrogen suppresses the proliferation of human bone marrow lin-/Stro1+ cells, which likely represent early osteoprogenitor cells. Further animal and human studies are needed to define the role of the changes we observed in mRNAs for adhesion molecules in these cells and in local sclerostin production in bone in mediating the effects of estrogen on bone metabolism in humans.

Regulation of circulating sclerostin levels by sex steroids in women and in men.

Sex steroids are important regulators of bone turnover, but the mechanisms of their effects on bone remain unclear. Sclerostin is an inhibitor of Wnt signaling, and circulating estrogen (E) levels are inversely associated with sclerostin levels in postmenopausal women. To directly test for sex steroid regulation of sclerostin levels, we examined effects of E treatment of postmenopausal women or selective withdrawal of E versus testosterone (T) in elderly men on circulating sclerostin levels. E treatment of postmenopausal women (n = 17) for 4 weeks led to a 27% decrease in serum sclerostin levels [versus +1% in controls (n = 18), p < .001]. Similarly, in 59 elderly men, we eliminated endogenous E and T production and studied them under conditions of physiologic T and E replacement, and then following withdrawal of T or E, we found that E, but not T, prevented increases in sclerostin levels following induction of sex steroid deficiency. In both sexes, changes in sclerostin levels correlated with changes in bone-resorption, but not bone-formation, markers (r = 0.62, p < .001, and r = 0.33, p = .009, for correlations with changes in serum C-terminal telopeptide of type 1 collagen in the women and men, respectively). Our studies thus establish that in humans, circulating sclerostin levels are reduced by E but not by T. Moreover, consistent with recent data indicating important effects of Wnts on osteoclastic cells, our findings suggest that in humans, changes in sclerostin production may contribute to effects of E on bone resorption.

Biomaterials for the decorporation of (85)Sr in the rat.

Although four stable isotopes of strontium occur naturally, Sr is produced by nuclear fission and is present in surface soil around the world as a result of fallout from atmospheric nuclear weapons tests. It can easily transfer to humans in the event of a nuclear/radiological emergency or through the plant-animal-human food chain causing long-term exposures. Strontium is chemically and biologically similar to calcium, and is incorporated primarily into bone following internal deposition. Alginic acid (alginate) obtained from seaweed (kelp) extract selectively binds ingested strontium in the gastrointestinal tract blocking its systemic uptake and reducing distribution to bone in rats, while other natural polysaccharides including chitosan and hyaluronic acid had little in vivo affinity for strontium. Alginate exhibits the unique ability to discriminate between strontium and calcium and has been previously shown to reduce intestinal absorption and skeletal retention of strontium without changing calcium metabolism. In our studies, the effect of commercially available alginate on intestinal absorption of strontium was examined. One problem associated with alginate treatment is its limited solubility and gel formation in water. The aqueous solubility of sodium alginate was improved in a sodium chloride/sodium bicarbonate electrolyte solution containing low molecular weight polyethylene glycol (PEG). Furthermore, oral administration of the combined alginate/electrolyte/PEG solution accelerated removal of internal strontium in rats when compared to treatment with individual sodium alginate/electrolyte or electrolyte/PEG solutions. Importantly, both alginate and PEG are nontoxic, readily available materials that can be easily administered orally in case of a national emergency when potentially large numbers of the population may require medical treatment for internal depositions. Our results suggest further studies to optimize in vivo decorporation performance of engineered alginate material via modification of its chemical and physicochemical properties are warranted.

Effects of parathyroid hormone treatment on circulating sclerostin levels in postmenopausal women.

CONTEXT: Intermittent PTH treatment stimulates bone formation, but the mechanism(s) of this effect remain unclear. Sclerostin is an inhibitor of Wnt signaling, and animal studies have demonstrated that PTH suppresses sclerostin production. OBJECTIVE: The objective of the study was to test whether intermittent PTH treatment of postmenopausal women alters circulating sclerostin levels. DESIGN: Prospective study. SETTING: The study was conducted at a clinical research unit. PARTICIPANTS AND INTERVENTIONS: Participants included 27 postmenopausal women treated with PTH (1-34) for 14 d and 28 control women. MAIN OUTCOME MEASURES: Serum sclerostin levels were measured. RESULTS: Circulating sclerostin levels decreased significantly in the PTH-treated subjects, from (mean ± SEM) 551 ± 32 to 482 ± 31 pg/ml (-12.7%, P < 0.0001) but did not change in the control women (baseline, 559 ± 34 pg/ml; end point, 537 ± 40 pg/ml, P = 0.207; P = 0.017 for difference in changes between groups). Bone marrow plasma was obtained in a subset of the control and PTH-treated subjects (n = 19 each) at the end of the treatment period, and marrow plasma and peripheral serum sclerostin levels were significantly correlated (R = 0.64, P < 0.0001). Marrow plasma sclerostin levels were 24% lower in PTH-treated compared with control women, but perhaps due to the smaller sample size, this difference was not statistically significant (P = 0.173). CONCLUSIONS: Circulating sclerostin levels correlate with bone marrow plasma levels and are reduced by intermittent PTH therapy in postmenopausal women. Further studies are needed to assess the extent to which decreases in sclerostin production contribute to the anabolic skeletal response to PTH.

Effects of chronic estrogen treatment on modulating age-related bone loss in female mice.

While female mice do not have the equivalent of a menopause, they do undergo reproductive senescence. Thus, to dissociate the effects of aging versus estrogen deficiency on age-related bone loss, we sham-operated, ovariectomized, or ovariectomized and estrogen-replaced female C57/BL6 mice at 6 months of age and followed them to age 18 to 22 months. Lumbar spines and femurs were excised for analysis, and bone marrow hematopoietic lineage negative (lin-) cells (enriched for osteoprogenitor cells) were isolated for gene expression studies. Six-month-old intact control mice were euthanized to define baseline parameters. Compared with young mice, aged/sham-operated mice had a 42% reduction in lumbar spine bone volume/total volume (BV/TV), and maintaining constant estrogen levels over life in ovariectomized/estrogen-treated mice did not prevent age-related trabecular bone loss at this site. By contrast, lifelong estrogen treatment of ovariectomized mice completely prevented the age-related reduction in cortical volumetric bone mineral density (vBMD) and thickness at the tibial diaphysis present in the aged/sham-operated mice. As compared with cells from young mice, lin- cells from aged/sham-operated mice expressed significantly higher mRNA levels for osteoblast differentiation and proliferation marker genes. These data thus demonstrate that, in mice, age-related loss of cortical bone in the appendicular skeleton, but not loss of trabecular bone in the spine, can be prevented by maintaining constant estrogen levels over life. The observed increase in osteoblastic differentiation and proliferation marker gene expression in progenitor bone marrow cells from aged versus young mice may represent a compensatory mechanism in response to ongoing bone loss.

Characterization of conserved bases in 4.5S RNA of Escherichia coli by construction of new F' factors.

To more clearly understand the function of conserved bases of 4.5S RNA, the product of the essential ffs gene of Escherichia coli, and to address conflicting results reported in other studies, we have developed a new genetic system to characterize ffs mutants. Multiple ffs alleles were generated by altering positions that correspond to the region of the RNA molecule that interacts directly with Ffh in assembly of the signal recognition particle. To facilitate characterization of the ffs mutations with minimal manipulation, recombineering was used to construct new F' factors to easily move each allele into different genetic backgrounds for expression in single copy. In combination with plasmids that expressed ffs in multiple copy numbers, the F' factors provided an accurate assessment of the ability of the different 4.5S RNA mutants to function in vivo. Consistent with structural analysis of the signal recognition particle (SRP), highly conserved bases in 4.5S RNA are important for binding Ffh. Despite the high degree of conservation, however, only a single base (C62) was indispensable for RNA function under all conditions tested. To quantify the interaction between 4.5S RNA and Ffh, an assay was developed to measure the ability of mutant 4.5S RNA molecules to copurify with Ffh. Defects in Ffh binding correlated with loss of SRP-dependent protein localization. Real-time quantitative PCR was also used to measure the levels of wild-type and mutant 4.5S RNA expressed in vivo. These results clarify inconsistencies from prior studies and yielded a convenient method to study the function of multiple alleles.