The binding of fibrinogen and fibrin to platelets is important in normal hemostasis. The extent of platelet-fibrin interaction can be measured as the viscoelastic strength of clot by rotational ...thromboelastometry (ROTEM). In this study, we investigated the effect of fibrinogen concentration and its relative contribution to overall clot strength using ROTEM.
Blood samples were collected from healthy volunteers. The effects of platelet count on clot strength, determined by maximum clot elasticity (MCE), were evaluated on ROTEM using platelet-rich plasma (PRP) adjusted with autologous plasma to generate a range of platelet counts. PRPs were adjusted to 10 x 10(3) mm(-3), 50 x 10(3) mm(-3), and 100 x 10(3) mm(-3) and spiked with fibrinogen concentrates at 550 and 780 mg/dL. The effect of fibrin polymerization on clot strength, independent of platelet attachment, was analyzed by the cytochalasin D-modified thromboelastometry (FIBTEM) method. Additional retrospective analysis of clot strength (MCE) in two groups of thrombocytopenic patients was conducted.
Clot strength (MCE) decreased at a platelet count below 100 x 10(3) mm(-3), whereas increases in MCE peaked and reached a plateau at platelet counts from 400 x 10(3) mm(-3). Increasing fibrinogen concentrations in PRP increased clot strength in a concentration-dependent manner, even at low platelet counts (10 x 10(3) mm(-3)). The positive correlation between clot strength and plasma fibrinogen level was also confirmed in the analysis of the data obtained from 904 thrombocytopenic patients.
These in vitro and clinical data indicate that the clot strength increases in a fibrinogen concentration-dependent manner independent of platelet count, when analyzed by ROTEM. The maintenance of fibrinogen concentration is critical in the presence of thrombocytopenia. EXTEM (extrinsic activation) and FIBTEM may be useful in guiding fibrinogen repletion therapy.
Using a combination of quantum Monte Carlo simulations, functional renormalization group calculations and mean-field theory, we study the Hubbard model on the Bernal-stacked honeycomb bilayer at ...half-filling as a model system for bilayer graphene. The free bands consisting of two Fermi points with quadratic dispersions lead to a finite density of states at the Fermi level, which triggers an antiferromagnetic instability that spontaneously breaks sublattice and spin rotational symmetry once local Coulomb repulsions are introduced. Our results reveal an inhomogeneous participation of the spin moments in the ordered ground state, with enhanced moments at the threefold coordinated sites. Furthermore, we find the antiferromagnetic ground state to be robust with respect to enhanced interlayer couplings and extended Coulomb interactions.
We studied the effect of re‐exposure to Earth's gravity on the proximal femoral BMD and structure of astronauts 1 year after missions lasting 4–6 months. We observed that the readaptation of the ...proximal femur to Earth's gravity entailed an increase in bone size and an incomplete recovery of volumetric BMD.
Introduction: Bone loss is a well‐known result of skeletal unloading in long‐duration spaceflight, with the most severe losses occurring in the proximal femur. However, there is little information about the recovery of bone loss after mission completion and no information about effect of reloading on the structure of load‐bearing bone. To address these questions, we carried out a study of the effect of re‐exposure to Earth's gravity on the BMD and structure of the proximal femur 1 year after missions lasting 4–6 months.
Materials and Methods: In 16 crew members of the International Space Station (ISS) making flights of 4.5–6 months, we used QCT imaging to measure the total, trabecular, and cortical volumetric BMD (vBMD) of the proximal femur. In addition to vBMD, we also quantified BMC, bone volume, femoral neck cross‐sectional area (CSA), and femoral neck indices of compressive and bending strength at three time‐points: preflight, postflight, and 1 year after mission.
Results: Proximal femoral bone mass was substantially recovered in the year after spaceflight, but measures of vBMD and estimated bone strength showed only partial recovery. The recovery of BMC, in the absence of a comparable increase in vBMD, was explained by increases in bone volume and CSA during the year after spaceflight.
Conclusions: Adaptation of the proximal femur to reloading entailed an increase in bone size and an incomplete recovery of vBMD. The data indicate that recovery of skeletal density after long‐duration space missions may exceed 1 year and supports the evidence in the aging literature for periosteal apposition as a compensatory response for bone loss. The extent to which this compensatory effect protects against fracture remains to be seen.
Because of inconsistencies in the field of attentional bias to food cues in eating behavior, this study aimed to re-examine the assumption that hungry healthy weight individuals have an attentional ...bias to food cues, but satiated healthy weight individuals do not. Since attentional engagement and attentional disengagement have been proposed to play a distinct role in behavior, we used a performance measure that is specifically designed to differentiate between these two attentional processes. Participants were healthy weight women who normally eat breakfast. In the satiated condition (n = 54), participants were instructed to have breakfast just before coming to the lab. In the fasted condition (n = 50), participants fasted on average 14 h before coming into the lab. Satiated women showed no stronger attentional engagement or attentional disengagement bias to food cues than to neutral cues. Fasted women did show stronger attentional engagement to food cues than to neutral cues that were shown briefly (100 ms). They showed no bias in attentional engagement to food cues that were shown longer (500 ms) or in attentional disengagement from food cues. These findings are in line with the assumption that healthy weight individuals show an attentional bias to food cues when food stimuli are motivationally salient. Furthermore, the findings point to the importance of differentiating between attentional engagement and attentional disengagement.
We measured cortical and trabecular bone loss using QCT of the spine and hip in 14 crewmembers making 4‐ to 6‐month flights on the International Space Station. There was no compartment‐specific loss ...of bone in the spine. Cortical bone mineral loss in the hip occurred primarily by endocortical thinning.
Introduction: In an earlier study, areal BMD (aBMD) measurements by DXA showed that cosmonauts making flights of 4‐ to 12‐month duration on the Soviet/Russian MIR spacecraft lost bone at an average rate of 1%/month from the spine and 1.5%/month from the hip. However, because DXA measurements represent the sum of the cortical and trabecular compartments, there is no direct information on how these bone envelopes are affected by spaceflight.
Materials and Methods: To address this, we performed a study of crewmembers (13 males and 1 female; age range, 40‐55 years) on long‐duration missions (4‐6 months) on the International Space Station (ISS). We used DXA to obtain aBMD of the hip and spine and volumetric QCT (vQCT) to assess integral, cortical, and trabecular volumetric BMD (vBMD) in the hip and spine. In the heel, DXA was used to measure aBMD, and quantitative ultrasound (QUS) was used to measure speed of sound (SOS) and broadband ultrasound attenuation (BUA).
Results and Conclusions: aBMD was lost at rates of 0.9%/month at the spine (p < 0.001) and 1.4‐1.5%/month at the hip (p < 0.001). Spinal integral vBMD was lost at a rate of 0.9%/month (p < 0.001), and trabecular vBMD was lost at 0.7%/month (p < 0.05). In contrast to earlier reports, these changes were generalized across the vertebrae and not focused in the posterior elements. In the hip, integral, cortical, and trabecular vBMD was lost at rates of 1.2‐1.5%/month (p < 0.0001), 0.4‐0.5%/month (p < 0.01), and 2.2‐2.7%/month (p < 0.001), respectively. The cortical bone loss in the hip occurred primarily by cortical thinning. Calcaneal aBMD measurements by DXA showed smaller mean losses (0.4%/month) than hip or spine measurements, with SOS and BUA showing no change. In summary, our results show that ISS crewmembers, on average, experience substantial loss of both trabecular and cortical bone in the hip and somewhat smaller losses in the spine. These results do not support the use of calcaneal aBMD or QUS measurements as surrogate measures to estimate changes in the central skeleton.
Theoretically, concomitant therapy with parathyroid hormone and alendronate might be synergistic, increasing bone formation while simultaneously reducing resorption. In this study, 238 postmenopausal ...women with osteoporosis were randomly assigned to receive daily parathyroid hormone (1–84), alendronate, or both for 12 months. Bone mineral density increased in all groups, with no significant differences between those receiving parathyroid hormone and those receiving both drugs. Bone formation increased markedly with parathyroid hormone therapy but not with combined therapy.
No evidence of synergy with PTH plus alendronate.
The prevention of osteoporotic fractures with the use of antiresorptive drugs represents an established therapeutic approach for patients with osteoporosis.
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The results of double-blind, randomized, placebo-controlled trials have indicated that nitrogen-containing bisphosphonates such as alendronate and risedronate, which work principally by suppressing bone resorption, reduce the risk of fracture and increase bone mineral density.
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Unlike bisphosphonates, parathyroid hormone is anabolic when it is administered intermittently for osteoporosis. Both parathyroid hormone (1–34) and parathyroid hormone (1–84) increase bone density by stimulating bone formation rather than by reducing bone resorption.
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Recently, the 34-amino-acid fragment, parathyroid hormone (1–34), was shown . . .
Background: Aging skeletal muscle is characterized not only by a reduction in size (sarcopenia) and strength but also by an increase in fatty infiltration (myosteatosis). An effective countermeasure ...to sarcopenia is resistance exercise; however, its effect on fatty infiltration is less clear. Objective: To examine in resistance-trained older persons whether muscle attenuation, a noninvasive measure of muscle density reflecting intramuscular lipid content, is altered with training status. Methods: Thirteen healthy community-dwelling men and women aged 65–83 years (body mass index 27.0 ± 1.2, mean ± SE) had computed-tomography scans of the mid-thigh performed following 24 weeks of training, 24 weeks of detraining, and 12 weeks of retraining. Training and retraining were undertaken twice weekly for several upper- and lower-body muscle groups. Skeletal muscle attenuation in Hounsfield units (HU) as well as mid-thigh muscle volume was obtained for the quadriceps and hamstrings. Muscle strength was assessed by 1-repetition maximum and physical function by a battery of tests. Results: The average change in muscle strength following training, detraining and retraining was 48.8 ± 2.9%, –17.6 ± 1.3%, and 19.8 ± 2.0%, respectively. Strength changes were accompanied by significant alterations in muscle density (p < 0.001), with the quadriceps HU decreasing by 7.7 ± 1.0% following detraining and increasing by 5.4 ± 0.5% with retraining. For the hamstrings HU measure, detraining and retraining resulted in an 11.9 ± 1.4% loss and a 5.5 ± 1.8% gain, respectively. There was no significant change in muscle volume. Conclusion: Cessation of resistance exercise in trained older persons increases the fatty infiltration of muscle, while resumption of exercise decreases it. Monitoring changes in both muscle size and fat infiltration may enable a more comprehensive assessment of exercise in combating age-related muscular changes.
Electronic states at the ends of a narrow armchair nanoribbon give rise to a pair of nonlocally entangled spins. We propose two experiments to probe these magnetic states, based on magnetometry and ...tunneling spectroscopy, in which correlation effects lead to a striking, nonlinear response to external magnetic fields. On the basis of low-energy theories that we derive here, it is remarkably simple to assess these nonlinear signatures for magnetic edge states. The effective theories are especially suitable in parameter regimes where other methods such as quantum Monte Carlo simulations are exceedingly difficult due to exponentially small energy scales. The armchair ribbon setup discussed here provides a promisingly well-controlled (both experimentally and theoretically) environment for studying the principles behind edge magnetism in graphene-based nanostructures.
The structure of the femoral neck contributes to hip strength, but the relationship of specific structural features of the hip to hip fracture risk is unclear. The objective of this study is to ...determine the contribution of structural features and volumetric density of both trabecular and cortical bone in the proximal femur to the prediction of hip fracture in older men. Baseline QCT scans of the hip were obtained in 3347 men ≥65 yr of age enrolled in the Osteoporotic Fractures in Men Study (MrOS). All men were followed prospectively for an average of 5.5 yr. Areal BMD (aBMD) by DXA was also assessed. We determined the associations between QCT‐derived measures of femoral neck structure, volumetric bone density, and hip fracture risk. Forty‐two men sustained incident hip fractures during follow‐up: an overall rate of 2.3/1000 person‐years. Multivariable analyses showed that, among the QCT‐derived measures, lower percent cortical volume (hazard ratio HR per SD decrease: 3.2; 95% CI: 2.2–4.6), smaller minimal cross‐sectional area (HR: 1.6; 95% CI: 1.2–2.1), and lower trabecular BMD (HR: 1.7; 95% CI: 1.2–2.4) were independently related to increased hip fracture risk. Femoral neck areal BMD was also strongly related to hip fracture risk (HR: 4.1; 95% CI: 2.7–6.4). In multivariable models, percent cortical volume and minimum cross‐sectional area remained significant predictors of hip fracture risk after adjustment for areal BMD, but overall prediction was not improved by adding QCT parameters to DXA. Specific structural features of the proximal femur were related to an increased risk of hip fracture. Whereas overall hip fracture prediction was not improved relative to aBMD, by adding QCT parameters, these results yield useful information concerning the causation of hip fracture, the evaluation of hip fracture risk, and potential targets for therapeutic intervention.
Twisted double- and mono-bilayer graphene are graphene-based moiré
materials hosting strongly correlated fermions in a gate-tunable
conduction band with a topologically non-trivial character. Using
...unbiased exact diagonalization complemented by unrestricted Hartree-Fock
calculations, we find that the strong electron-electron interactions
lead to a non-coplanar magnetic state, which has the same symmetries as
the tetrahedral antiferromagnet on the triangular lattice and can be
thought of as a skyrmion lattice commensurate with the moiré scale,
competing with a set of ferromagnetic, topological charge density waves
featuring an approximate emergent O(3) symmetry, “rotating” the
different charge density wave states into each other. Direct comparison
with exact diagonalization reveals that the ordered phases are
accurately described within the unrestricted Hartree-Fock approximation.
Exhibiting a finite charge gap and Chern number
|C|=1,
the formation of charge density wave order which is intimately connected
to a skyrmion lattice phase is consistent with recent experiments on
these systems.
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