Properties of the organic matrix of bone as well as its function in the microstructure could be the key to the remarkable mechanical properties of bone. Previously, it was found that on the molecular ...level, calcium-mediated sacrificial bonds increased stiffness and enhanced energy dissipation in bone constituent molecules. Here we present evidence for how this sacrificial bond and hidden length mechanism contributes to the mechanical properties of the bone composite, by investigating the nanoscale arrangement of the bone constituents and their interactions. We find evidence that bone consists of mineralized collagen fibrils and a non-fibrillar organic matrix, which acts as a 'glue' that holds the mineralized fibrils together. We believe that this glue may resist the separation of mineralized collagen fibrils. As in the case of the sacrificial bonds in single molecules, the effectiveness of this mechanism increases with the presence of Ca2+ ions.
Abstract Background Falls are common among older adults and can lead to serious injuries, including fractures. We aimed to determine associations between anxiety disorders and falls in older adults. ...Methods Participants were 487 men and 376 women aged ≥60 years enrolled in the Geelong Osteoporosis Study, Australia. Using the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Non-patient edition (SCID-I/NP), lifetime history of anxiety disorders was determined. Falls were determined by self-report. In men, a falls-risk score (Elderly Falls Screening Test (EFST)) was also calculated. Results Among fallers, 24 of 299 (8.0%) had a lifetime history of anxiety disorder compared to 36 of 634 (5.7%) non-fallers (p=0.014). Examination of the association between anxiety and falls suggested differential relationships for men and women. In men, following adjustment for psychotropic medications, mobility and blood pressure, lifetime anxiety disorder was associated with falling (OR 2.96; 95%CI 1.07–8.21) and with EFST score (OR 3.46; 95%CI 1.13–10.6). In women, an association between lifetime anxiety disorder and falls was explained by psychotropic medication use, poor mobility and socioeconomic status. Limitations Sub-group analyses involving types of anxiety and anxiety disorders over the past 12-months were not performed due to power limitations. Conclusion Although anxiety disorders were independently associated with a 3-fold increase in likelihood of reported falls and high falls risk among men, an independent association was not detected among women. These results may aid in prevention of falls through specific interventions aimed at reducing anxiety, particularly in men.
Purpose
The aim of the study was to investigate two single nucleotide polymorphisms (SNP) in
PTK2
for associations with human muscle strength phenotypes in healthy men.
Methods
Measurement of maximal ...isometric voluntary knee extension (MVC
KE
) torque, net MVC
KE
torque and vastus lateralis (VL) specific force, using established techniques, was completed on 120 Caucasian men (age = 20.6 ± 2.3 year; height = 1.79 ± 0.06 m; mass = 75.0 ± 10.0 kg; mean ± SD). All participants provided either a blood (
n
= 96) or buccal cell sample, from which DNA was isolated and genotyped for the
PTK2
rs7843014 A/C and rs7460 A/T SNPs using real-time polymerase chain reaction.
Results
Genotype frequencies for both SNPs were in Hardy–Weinberg equilibrium (
X
2
≤ 1.661,
P
≥ 0.436). VL specific force was 8.3% higher in rs7843014 AA homozygotes than C-allele carriers (
P
= 0.017) and 5.4% higher in rs7460 AA homozygotes than T-allele carriers (
P
= 0.029). No associations between either SNP and net MVC
KE
torque (
P
≥ 0.094) or peak MVC
KE
torque (
P
≥ 0.107) were observed.
Conclusions
These findings identify a genetic contribution to the inter-individual variability within muscle specific force and provides the first independent replication, in a larger Caucasian cohort, of an association between these
PTK2
SNPs and muscle specific force, thus extending our understanding of the influence of genetic variation on the intrinsic strength of muscle.
Titin provides a molecular blueprint for muscle sarcomere assembly, and sarcomere length can vary according to titin isoform expression. If variations in sarcomere length influence muscle fascicle ...length, this may provide an advantage for running performance. Thus, the aim of this study was to investigate whether the titin (TTN) rs10497520 polymorphism was associated with muscle fascicle length in recreationally active men (RA; n=137) and marathon personal best time in male marathon runners (MR; n=141). Fascicle length of the vastus lateralis was assessed in vivo using B‐mode ultrasonography at 50% of muscle length in RA. All participants provided either a whole blood, saliva or buccal cell sample, from which DNA was isolated and genotyped using real‐time polymerase chain reaction. Vastus lateralis fascicle length was 10.4% longer in CC homozygotes, those carrying two copies of the C‐allele, than CT heterozygotes (P=.003) in RA. In the absence of any TT homozygotes, reflective of the low T‐allele frequency within Caucasian populations, it is unclear whether fascicle length for this group would have been smaller still. No differences in genotype frequency between the RA and MR groups were observed (P=.500), although within the MR group, the T‐allele carriers demonstrated marathon personal best times 2 minutes 25 seconds faster than CC homozygotes (P=.020). These results suggest that the T‐allele at rs10497520 in the TTN gene is associated with shorter skeletal muscle fascicle length and conveys an advantage for marathon running performance in habitually trained men.
Abstract
Delayed gastric conduit emptying (DGCE) after esophagectomy for cancer is associated with adverse outcomes and troubling symptoms. Widely accepted diagnostic criteria and a symptom grading ...tool for DGCE are missing. This hampers the interpretation and comparison of studies. A modified Delphi process, using repeated web-based questionnaires, combined with live interim group discussions was conducted by 33 experts within the field, from Europe, North America, and Asia. DGCE was divided into early DGCE if present within 14 days of surgery and late if present later than 14 days after surgery. The final criteria for early DGCE, accepted by 25 of 27 (93%) experts, were as follows: >500 mL diurnal nasogastric tube output measured on the morning of postoperative day 5 or later or >100% increased gastric tube width on frontal chest x-ray projection together with the presence of an air–fluid level. The final criteria for late DGCE accepted by 89% of the experts were as follows: the patient should have ‘quite a bit’ or ‘very much’ of at least two of the following symptoms; early satiety/fullness, vomiting, nausea, regurgitation or inability to meet caloric need by oral intake and delayed contrast passage on upper gastrointestinal water-soluble contrast radiogram or on timed barium swallow. A symptom grading tool for late DGCE was constructed grading each symptom as: ‘not at all’, ‘a little’, ‘quite a bit’, or ‘very much’, generating 0, 1, 2, or 3 points, respectively. For the five symptoms retained in the diagnostic criteria for late DGCE, the minimum score would be 0, and the maximum score would be 15. The final symptom grading tool for late DGCE was accepted by 27 of 31 (87%) experts. For the first time, diagnostic criteria for early and late DGCE and a symptom grading tool for late DGCE are available, based on an international expert consensus process.
This paper reports deuteron vector and tensor beam polarization measurements taken to investigate the systematic variations due to geometric beam misalignments and high data rates. The experiments ...used the In-Beam Polarimeter at the KVI-Groningen and the EDDA detector at the Cooler Synchrotron COSY at Jülich. By measuring with very high statistical precision, the contributions that are second-order in the systematic errors become apparent. By calibrating the sensitivity of the polarimeter to such errors, it becomes possible to obtain information from the raw count rate values on the size of the errors and to use this information to correct the polarization measurements. During the experiment, it was possible to demonstrate that corrections were satisfactory at the level of 10
−5 for deliberately large errors. This may facilitate the real time observation of vector polarization changes smaller than 10
−6 in a search for an electric dipole moment using a storage ring.
We derive depth‐age relationships across the ice divide between the Ross and Amundsen Seas by tracking radar‐detected layers from the Byrd ice core and a dated 105‐m core near the divide. The ...depth‐age relationships and an ice‐flow model are used to establish histories of accumulation and ice sheet dynamics over the past 8000 years. Results show that accumulation was approximately 30% higher than today from 5000 to 3000 years ago. Antarctic climate variability today is dominated by periodic fluctuations in strength of the circumpolar vortex, which raises the possibility that the vortex was systematically weaker during the period of high accumulation. Accumulation today decreases almost linearly across the divide. It is unlikely that this pattern has changed through the Holocene. The radar‐detected stratigraphy shows no evidence of the arched layers that are expected beneath a stable divide that is frozen to its bed, implying that the divide has also been migrating and/or the basal ice has been sliding through the Holocene. We cannot rule out the possibility of sliding because the basal ice is near its pressure melting point. Other evidence indicates that divide migration is likely. The Ross Sea sector is now near steady state, but it had a strong negative imbalance 200 years ago when Kamb Ice Stream was active. In contrast, recent speedups of Pine Island and Thwaites Glaciers have likely caused the mass balance of the Amundsen Sea sector to become negative. The divide is likely migrating toward the Ross Sea today.
In recent years, the important role of the organic matrix for the mechanical properties of bone has become increasingly apparent. It is therefore of great interest to understand the interactions ...between the organic and inorganic constituents of bone and learn the mechanisms by which the organic matrix contributes to the remarkable properties of this complex biomaterial. In this paper, we present a multifaceted view of the changes of bone's properties due to heat-induced degradation of the organic matrix. We compare the microscopic fracture behavior (scanning electron microscopy; SEM), the topography of the surfaces (atomic force microscopy; AFM), the condition of bone constituents X-ray diffraction (XRD), thermogravimetric analysis (TGA), and gel electrophoresis), and the macromechanical properties of healthy bovine trabecular bone with trabecular bone that has a heat-degraded organic matrix. We show that heat treatment changes the microfracture behavior of trabecular bone. The primary failure mode of untreated trabecular bone is fibril-guided delamination, with mineralized collagen filaments bridging the gap of the microcrack. In contrast, bone that has been baked at 200°C fractures nondirectionally like a brittle material, with no fibers spanning the microcracks. Finally, bone that has been boiled for 2 h in PBS solution fractures by delamination with many small filaments spanning the microcracks, so that the edges of the microcracks become difficult to distinguish. Of the methods we used, baking most effectively weakens the mechanical strength of bone, creating the most brittle material. Boiled bone is stronger than baked bone, but weaker than untreated bone. Boiled bone is more elastic than untreated bone, which is in turn more elastic than baked bone. These studies clearly emphasize the importance of the organic matrix in affecting the fracture mechanics of bone.
The passive properties of the muscle–tendon unit are regularly assessed in individuals with cerebral palsy (CP). However, no information is available on the passive properties of adult muscle, and ...whether any differences exist between the paretic and control muscles. Eleven ambulant male athletes with spastic hemiplegic CP (21.2 ± 3.0 years) and controls without neurological impairment (age = 21.8 ± 2.2 years) completed two and one passive stretch session, respectively. During each session, the ankle was passively dorsiflexed until end range of motion (ROM), whilst recording passive ankle angle, torque and gastrocnemius medialis (GM) myotendinous junction (MTJ) displacement. In addition, GM cross-sectional area (CSA) and length were measured. Subsequently, in vivo stress and strain were determined to calculate elastic modulus. Passive stiffness, MTJ displacement and ROM of the paretic GM were not different from the control muscles. However, the elastic modulus of the paretic GM was two times stiffer than the control GM muscles. In conclusion, athletes with CP exhibit absolute passive muscle stiffness similar to the controls; however, the elastic modulus of the CP muscle was significantly greater. Therefore, throughout the same ROM a smaller GM CSA in CP athletes has to dissipate larger relative torque compared to the control muscles, consequently causing the muscle to elongate to the same extent as the non-paretic muscle under stretch.
Summary
There are no internationally recognized criteria available to determine preparedness for hospital discharge after esophagectomy. This study aims to achieve international consensus using ...Delphi methodology. The expert panel consisted of 40 esophageal surgeons spanning 16 countries and 4 continents. During a 3-round, web-based Delphi process, experts voted for discharge criteria using 5-point Likert scales. Data were analyzed using descriptive statistics. Consensus was reached if agreement was ≥75% in round 3. Consensus was achieved for the following basic criteria: nutritional requirements are met by oral intake of at least liquids with optional supplementary nutrition via jejunal feeding tube. The patient should have passed flatus and does not require oxygen during mobilization or at rest. Central venous catheters should be removed. Adequate analgesia at rest and during mobilization is achieved using both oral opioid and non-opioid analgesics. All vital signs should be normal unless abnormal preoperatively. Inflammatory parameters should be trending down and close to normal (leucocyte count ≤12G/l and C-reactive protein ≤80 mg/dl). This multinational Delphi survey represents the first expert-led process for consensus criteria to determine ‘fit-for-discharge’ status after esophagectomy. Results of this Delphi survey may be applied to clinical outcomes research as an objective measure of short-term recovery. Furthermore, standardized endpoints identified through this process may be used in clinical practice to guide decisions regarding patient discharge and may help to reduce the risk of premature discharge or prolonged admission.
PDF
