Long-term changes in bone metabolism, bone mineral density, quantitative ultrasound parameters, and fracture incidence after spinal cord injury: a cross-sectional observational study in 100 paraplegic men

To study the time course of demineralization and fracture incidence after spinal cord injury (SCI), 100 paraplegic men with complete motor loss were investigated in a cross-sectional study 3 months to 30 years after their traumatic SCI. Fracture history was assessed and verified using patients' files and X-rays. BMD of the lumbar spine (LS), femoral neck (FN), distal forearm (ultradistal part = UDR, 1/3 distal part = 1/3R), distal tibial diaphysis (TDIA), and distal tibial epiphysis (TEPI) was measured using DXA. Stiffness of the calcaneus (QUI.CALC), speed of sound of the tibia (SOS.TIB), and amplitude-dependent SOS across the proximal phalanges (adSOS.PHAL) were measured using QUS. Z-Scores of BMD and quantitative ultrasound (QUS) were plotted against time-since-injury and compared among four groups of paraplegics stratified according to time-since-injury (<1 year, stratum I; 1-9 years, stratum II; 10-19 years, stratum III; 20-29 years, stratum IV). Biochemical markers of bone turnover (deoxypyridinoline/creatinine (D-pyr/Cr), osteocalcin, alkaline phosphatase) and the main parameters of calcium phosphate metabolism were measured. Fifteen out of 98 paraplegics had sustained a total of 39 fragility fractures within 1,010 years of observation. All recorded fractures were fractures of the lower limbs, mean time to first fracture being 8.9 +/- 1.4 years. Fracture incidence increased with time-after-SCI, from 1% in the first 12 months to 4.6%/year in paraplegics since >20 years ( p<.01). The overall fracture incidence was 2.2%/year. Compared with nonfractured paraplegics, those with a fracture history had been injured for a longer time ( p<.01). Furthermore, they had lower Z-scores at FN, TEPI, and TDIA ( p<.01 to <.0001), the largest difference being observed at TDIA, compared with the nonfractured. At the lower limbs, BMD decreased with time at all sites ( r=.49 to.78, all p<.0001). At FN and TEPI, bone loss followed a log curve which leveled off between 1 to 3 years after injury. In contrast, Z-scores of TDIA continuously decreased even beyond 10 years after injury. LS BMD Z-score increased with time-since-SCI ( p<.05). Similarly to DXA, QUS allowed differentiation of early and rapid trabecular bone loss (QUI.CALC) vs slow and continuous cortical bone loss (SOS.TIB). Biochemical markers reflected a disproportion between highly elevated bone resorption and almost normal bone formation early after injury. Turnover declined following a log curve with time-after-SCI, however, D-pyr/Cr remained elevated in 30% of paraplegics injured >10 years. In paraplegic men early (trabecular) and persistent (cortical) bone loss occurs at the lower limbs and leads to an increasing fracture incidence with time-after-SCI.

Dose optimization approach to fast X-ray microtomography of the lung alveoli

A basic prerequisite for in vivo X-ray imaging of the lung is the exact determination of radiation dose. Achieving resolutions of the order of micrometres may become particularly challenging owing to increased dose, which in the worst case can be lethal for the imaged animal model. A framework for linking image quality to radiation dose in order to optimize experimental parameters with respect to dose reduction is presented. The approach may find application for current and future in vivo studies to facilitate proper experiment planning and radiation risk assessment on the one hand and exploit imaging capabilities on the other.

Visualization and stereological characterization of individual rat lung acini by high-resolution X-ray tomographic microscopy

The small trees of gas-exchanging pulmonary airways which are fed by the most distal purely conducting airways are called acini and represent the functional gas-exchanging units. The three-dimensional architecture of the acini has a strong influence on ventilation and particle deposition. Due to the difficulty to identify individual acini on microscopic lung sections the knowledge about the number of acini and their biological parameters like volume, surface area, and number of alveoli per acinus are limited. We developed a method to extract individual acini from lungs imaged by high-resolution synchrotron radiation based X-ray tomographic microscopy and estimated their volume, surface area and number of alveoli. Rat acini were isolated by semiautomatically closing the airways at the transition from conducting to gas-exchanging airways. We estimated a mean internal acinar volume of 1.148mm(3), a mean acinar surface area of 73.9mm(2), and a mean of 8470 alveoli per acinus. Assuming that the acini are similarly sized throughout different regions of the lung, we calculated that a rat lung contains 5470±833 acini. We conclude that our novel approach is well suited for the fast and reliable characterization of a large number of individual acini in healthy, diseased, or transgenic lungs of different species including humans.

Influence of rubber dam on objective and subjective parameters of stress during dental treatment of children and adolescents - a randomized controlled clinical pilot study

BACKGROUND Rubber dam is recommended for isolating the working field during adhesive dentistry procedures; however, dentists often omit rubber dam, particularly in paediatric dentistry, supposing that it would stress the patient. AIM The aim of this study was to evaluate stress parameters during a standardized dental treatment procedure performed with or without rubber dam. The treatment time was measured as a secondary outcome variable. DESIGN This study was designed as a randomized, controlled, clinical study with 72 patients (6-16 years; mean age, 11.1). During standardized fissure sealing procedures, objective parameters of stress (e.g., skin resistance, breath rate) were recorded. The operator's stress level was measured by pulse rate. Subjective pain (patients) and stress perception (operator) were evaluated by an interview. RESULTS The breath rate was significantly (P<0.05) lower and the skin resistance level was significantly higher during treatment with rubber dam compared to the control group. Subjective pain perception was significantly lower for the test group. The treatment time needed for the fissure sealing procedure was 12.4% less in the test group. CONCLUSION Isolation with rubber dam caused less stress in children and adolescents compared to relative isolation with cotton rolls if applied by an experienced dentist.

Synchrotron x ray induced axonal transections in the brain of rats assessed by high-field diffusion tensor imaging tractography

Since approximately two thirds of epileptic patients are non-eligible for surgery, local axonal fiber transections might be of particular interest for them. Micrometer to millimeter wide synchrotron-generated X-ray beamlets produced by spatial fractionation of the main beam could generate such fiber disruptions non-invasively. The aim of this work was to optimize irradiation parameters for the induction of fiber transections in the rat brain white matter by exposure to such beamlets. For this purpose, we irradiated cortex and external capsule of normal rats in the antero-posterior direction with a 4 mm×4 mm array of 25 to 1000 µm wide beamlets and entrance doses of 150 Gy to 500 Gy. Axonal fiber responses were assessed with diffusion tensor imaging and fiber tractography; myelin fibers were examined histopathologically. Our study suggests that high radiation doses (500 Gy) are required to interrupt axons and myelin sheaths. However, a radiation dose of 500 Gy delivered by wide minibeams (1000 µm) induced macroscopic brain damage, depicted by a massive loss of matter in fiber tractography maps. With the same radiation dose, the damage induced by thinner microbeams (50 to 100 µm) was limited to their paths. No macroscopic necrosis was observed in the irradiated target while overt transections of myelin were detected histopathologically. Diffusivity values were found to be significantly reduced. A radiation dose ≤ 500 Gy associated with a beamlet size of < 50 µm did not cause visible transections, neither on diffusion maps nor on sections stained for myelin. We conclude that a peak dose of 500 Gy combined with a microbeam width of 100 µm optimally induced axonal transections in the white matter of the brain.

Microstructural Parameters of Bone Evaluated Using HR-pQCT Correlate with the DXA-Derived Cortical Index and the Trabecular Bone Score in a Cohort of Randomly Selected Premenopausal Women.

BACKGROUND Areal bone mineral density is predictive for fracture risk. Microstructural bone parameters evaluated at the appendicular skeleton by high-resolution peripheral quantitative computed tomography (HR-pQCT) display differences between healthy patients and fracture patients. With the simple geometry of the cortex at the distal tibial diaphysis, a cortical index of the tibia combining material and mechanical properties correlated highly with bone strength ex vivo. The trabecular bone score derived from the scan of the lumbar spine by dual-energy X-ray absorptiometry (DXA) correlated ex vivo with the micro architectural parameters. It is unknown if these microstructural correlations could be made in healthy premenopausal women. METHODS Randomly selected women between 20-40 years of age were examined by DXA and HR-pQCT at the standard regions of interest and at customized sub regions to focus on cortical and trabecular parameters of strength separately. For cortical strength, at the distal tibia the volumetric cortical index was calculated directly from HR-pQCT and the areal cortical index was derived from the DXA scan using a Canny threshold-based tool. For trabecular strength, the trabecular bone score was calculated based on the DXA scan of the lumbar spine and was compared with the corresponding parameters derived from the HR-pQCT measurements at radius and tibia. RESULTS Seventy-two healthy women were included (average age 33.8 years, average BMI 23.2 kg/m(2)). The areal cortical index correlated highly with the volumetric cortical index at the distal tibia (R  =  0.798). The trabecular bone score correlated moderately with the microstructural parameters of the trabecular bone. CONCLUSION This study in randomly selected premenopausal women demonstrated that microstructural parameters of the bone evaluated by HR-pQCT correlated with the DXA derived parameters of skeletal regions containing predominantly cortical or cancellous bone. Whether these indexes are suitable for better predictions of the fracture risk deserves further investigation.

THE EFFECT OF RELAXIN ON BIOCHEMICAL AND MORPHOLOGICAL PARAMETERS OF RAT MYOMETRIAL CELLS IN CULTURE (CYCLIC-AMP, CELL SHAPE CHANGE)

Relaxin is able to inhibit spontaneous, oxytocin-and prostaglandin-driven uterine contractions. The intracellular mechanism of action of relaxin on uterine relaxation had previously been studied using isometrically suspended uterine strips. Since uterine strips contain stroma as well as myometrium, the changes in biochemical parameters induced by relaxin treatment may not occur in the same cell types responsible for the physical changes. In these studies, cultures of enriched populations of rat myometrial cells were used to investigate the effect of relaxin on biochemical and morphological parameters which are related to relaxation.^ Under optimal culture conditions (initial plating density 1 - 1.5 x 10('6)cells/ml, 3 ml/35 mm dish, 2 days culture), enzymatically isolated rat myometrial cells were able to respond to relaxin with cAMP elevation. Relaxin elevated cAMP levels in the presence but not the absence of 0.1 mM methylisobutylxanthine or 0.4 um forskolin in a time- and concentration-dependent manner. In contrast, isoproterenol was able to elevate cAMP levels in the presence and absence of 0.1 mM methylisobutylxanthine.^ Oxytocin treatment caused a decrease in mean cell length and area of myometrial cells in culture which could be considered analogous to contraction. Under optimal culture conditions, relaxin increased myometrial cell length and area (i.e. analogous to relaxation) of oxytocin-treated cells in a time- and concentration-dependent manner. Other relaxants such as isoproterenol and dibutyryl cAMP also increased cell length and area of oxytocin - treated myometrial cells in culture.^ Under optimal culture conditions, relaxin decreased myosin light chain kinase activity in a time-and concentration-dependent manner by increasing the K(,50) of the enzyme for calmodulin (CaM), i.e. decreasing the affinity of the enzyme for CaM. The decrease in the affinity of myosin light chain kinase for CaM may be due to the phosphorylation of the enzyme by cAMP-dependent protein kinase. Relaxin also decreased the Ca('2+)(.)CaM-independent myosin light chain kinase activity to a lesser extent than that of the Ca('2+)(.)CaM-dependent enzyme activity. This was not attributable to a decrease in the affinity of the enzyme for myosin in myometrial cells in culture, in contrast to the finding of such a change following relaxin treatment of uterine strips. Further studies are required to clarify this point.^ There was a temporal association between the effects of relaxin on elevation of cAMP levels in the presence of 0.4 uM forskolin, increase in cell length and decrease in myosin light chain kinase activity. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMI ^

Snow and ice surfaces on King George Island (Antarctic Peninsula) with high-resolution TerraSAR-X time series, with links to shapfiles and GeoTIFFs

Changes of glaciers and snow cover in polar regions affect a wide range of physical and ecosystem processes on land and in the adjacent marine environment. In this study, we investigate the potential of 11-day repeat high-resolution satellite image time series from the TerraSAR-X mission to derive glaciological and hydrological parameters on King George Island, Antarctica during the period Oct/25/2010 to Apr/19/2011. The spatial pattern and temporal evolution of snow cover extent on ice-free areas can be monitored using multi-temporal coherence images. SAR coherence is used to map glacier extent of land terminating glaciers with an average accuracy of 25 m. Multi-temporal SAR color composites identify the position of the late summer snow line at about 220 m above sea level. Glacier surface velocities are obtained from intensity feature-tracking. Surface velocities near the calving front of Fourcade Glacier were up to 1.8 ± 0.01 m/d. Using an intercept theorem based on fundamental geometric principles together with differential GPS field measurements, the ice discharge of Fourcade Glacier was estimated to 20700 ± 5500 m**3/d (corresponding to ~19 ± 5 kt/d). The rapidly changing surface conditions on King George Island and the lack of high-resolution digital elevation models for the region remain restrictions for the applicability of SAR data and the precision of derived products.

Mean dynamic topography and oceanographic parameters estimated from an inverse model and satellite geodesy, with link to model result in one single NetCDF file (392 MB), including the inverse data error covariance

Geostrophic surface velocities can be derived from the gradients of the mean dynamic topography-the difference between the mean sea surface and the geoid. Therefore, independently observed mean dynamic topography data are valuable input parameters and constraints for ocean circulation models. For a successful fit to observational dynamic topography data, not only the mean dynamic topography on the particular ocean model grid is required, but also information about its inverse covariance matrix. The calculation of the mean dynamic topography from satellite-based gravity field models and altimetric sea surface height measurements, however, is not straightforward. For this purpose, we previously developed an integrated approach to combining these two different observation groups in a consistent way without using the common filter approaches (Becker et al. in J Geodyn 59(60):99-110, 2012, doi:10.1016/j.jog.2011.07.0069; Becker in Konsistente Kombination von Schwerefeld, Altimetrie und hydrographischen Daten zur Modellierung der dynamischen Ozeantopographie, 2012, http://nbn-resolving.de/nbn:de:hbz:5n-29199). Within this combination method, the full spectral range of the observations is considered. Further, it allows the direct determination of the normal equations (i.e., the inverse of the error covariance matrix) of the mean dynamic topography on arbitrary grids, which is one of the requirements for ocean data assimilation. In this paper, we report progress through selection and improved processing of altimetric data sets. We focus on the preprocessing steps of along-track altimetry data from Jason-1 and Envisat to obtain a mean sea surface profile. During this procedure, a rigorous variance propagation is accomplished, so that, for the first time, the full covariance matrix of the mean sea surface is available. The combination of the mean profile and a combined GRACE/GOCE gravity field model yields a mean dynamic topography model for the North Atlantic Ocean that is characterized by a defined set of assumptions. We show that including the geodetically derived mean dynamic topography with the full error structure in a 3D stationary inverse ocean model improves modeled oceanographic features over previous estimates.

Physico-chemical parameters of sediment core PG1972-1 (09-Tik-03) from a Tundra Lake, Northeastern Siberia

Thermokarst lakes in the Siberian Arctic contain sediment archives that can be used for paleoenvironmental inference. Until now, however, there has been no study from the inner Lena River Delta with a focus on diatoms. The objective of this study was to investigate how the diatom community in a thermokarst lake responded to past limnogeological changes and what specific factors drove variations in the diatom assemblage. We analysed fossil diatom species, organic content, grain-size distribution and elemental composition in a sediment core retrieved in 2009 from a shallow thermokarst lake in the Arga Complex, western Lena River Delta. The core contains a 3,000-year record of sediment accumulation. Shifts in the predominantly benthic and epiphytic diatom species composition parallel changes in sediment characteristics. Paleoenvironmental and limnogeological development, inferred from multiple biological and sedimentological variables, are discussed in the context of four diatom zones, and indicate a strong relation between changes in the diatom assemblage and thermokarst processes. We conclude that limnogeological and thermokarst processes such as lake drainage, rather than direct climate forcing, were the main factors that altered the aquatic ecosystem by influencing, for example, habitat availability, hydrochemistry, and water level.

Geochemical and biogeochemical parameters of bottom sediments from the area of the Spitsbergen (Svalbard) Archipelago

Quantitative characteristics for rates of diagenetic processes in the upper (0-30 cm) layer of sedimentary deposits in the area of the Spitsbergen (Svalbard) Archipelago (78°-80°N) were obtained by lithologo-geochemical, radioisotope (35S, 14C), and stable isotope (d34S, d13C) studies. It was proved that rates of diagenetic processes in polar deposits at 123-395 m depth affected by the East Spitsbergen ''warm'' current are mostly determined by bioproductivity and are commensurate with rates of processes in shelf deposits of temperate latitudes. High contents of migratory methane (up to 263 ml/dm**3) and isotopically-light organic carbon (Corg, d13C = -30 per mil PDB) were found in the 1 m layer of shelf deposits (at 123 m sea depth) with low bacterial in situ production of methane. It was shown that methane is not utilized in the deposits by the methanotrophic bacterial community and it may be supplied to the water mass and, probably, to the atmosphere.

Dinoflagellate cyst assemblages, Mg/Ca based reconstructed temperatures, stable carbon isotopes, and geochemical parameters of sediment core GeoB9508-5

In order to investigate a possible connection between tropical northeast (NE) Atlantic primary productivity, Atlantic meridional overturning circulation (AMOC), and drought in the Sahel region during Heinrich Stadial 1 (HS1), we used dinoflagellate cyst (dinocyst) assemblages, Mg/Ca based reconstructed temperatures, stable carbon isotopes (d13C) and geochemical parameters of a marine sediment core (GeoB 9508-5) from the continental slope offshore Senegal. Our results show a two-phase productivity pattern within HS1 that progressed from an interval of low marine productivity between ~ 19 and 16 kyr BP to a phase with an abrupt and large productivity increase from ~ 16 to 15 kyr BP. The second phase is characterized by distinct heavy planktonic d13C values and high concentrations of heterotrophic dinocysts in addition to a significant cooling signal based on reconstructions of past sea surface temperatures (SST). We conclude that productivity variations within HS1 can be attributed to a substantial shift of West African atmospheric processes. Taken together our results indicate a significant intensification of the North East (NE) trade winds over West Africa leading to more intense upwelling during the last millennium of HS1 between ~ 16 and 15 kyr BP, thus leaving a strong imprint on the dinocyst assemblages and sea surface conditions. Therefore, the two-phase productivity pattern indicates a complex hydrographic setting suggesting that HS1 cannot be regarded as uniform as previously thought.