Dynamic muscle quality of the plantar flexors is impaired in claudicant patients with peripheral arterial disease and associated with poorer walking endurance

Objective Peripheral arterial disease and intermittent claudication (PAD-IC) negatively affects physical activity and function. There is evidence for plantarflexor muscle dysfunction and weakness; however, the extent to which this dysfunction can be attributed to reduced muscle size or quality, or both, is not yet known. This study investigated whether in vivo plantarflexor muscle quality during static and dynamic contractions is altered by PAD-IC and whether such changes are associated with impaired walking endurance according to initial and absolute claudication distances. Methods The study recruited 22 participants, consisting of 10 healthy controls and 12 claudicant patients with occlusion of the superficial femoral artery (seven unilateral and five bilateral). Muscle quality of the combined gastrocnemius muscles during static contractions was calculated by normalizing the estimated maximal potential muscle force to the physiological cross-sectional area of the lateral and medial gastrocnemius. Muscle quality during dynamic contractions of the combined plantarflexor muscles was calculated as the ratio of peak voluntary concentric plantarflexor power and the summed volume of lateral and medial gastrocnemius. Results Dynamic muscle quality was 24% lower in the claudicating-limb and asymptomatic-limb groups compared with controls (P = .017 and P = .023). The differences were most apparent at the highest contraction velocity (180°/s). Dynamic muscle quality was associated with reduced walking endurance (R = 0.689, P = .006 and R = 0.550, P = .042 for initial and absolute claudication distance, respectively). The claudicating-limb group demonstrated a trend toward reduced static muscle quality compared with controls (22%, P = .084). The relative contribution of the soleus muscle to plantarflexion maximum voluntary contraction was significantly higher in the claudicating-limb and asymptomatic-limb groups than in controls (P = .012 and P = .018). Conclusions The muscle strength of the plantarflexors in those with PAD-IC appears to be impaired at high contraction velocities. This may be explained by some reduction in gastrocnemii muscle quality and a greater reliance on the prominently type I-fibered soleus muscle. The reduced dynamic capability of the plantarflexor muscles was associated with disease severity and walking ability; therefore, efforts to improve plantarflexor power through dynamic exercise intervention are vital to maintain functional performance

Biomechanical demands of the 2-step transitional gait cycles linking level gait and stair descent gait in older women

Stair descent is an inherently complex form of locomotion posing a high falls risk for older adults, specifically when negotiating the transitional gait cycles linking level gait and descent. The aim of this study was to enhance our understanding of the biomechanical demands by comparing the demands of these transitions. Lower limb kinematics and kinetics of the 2-step transitions linking level and descent gait at the top (level-to-descent) and the bottom (descent-to-level) of the staircase were quantified in 36 older women with no falls history. Despite undergoing the same vertical displacement (2-steps), the following significant (p<.05) differences were observed during the top transition compared to the bottom transition: reduced step velocity; reduced hip extension and increased ankle dorsiflexion (late stance/pre-swing); reduced ground reaction forces, larger knee extensor moments and powers (absorption; late stance); reduced ankle plantarflexor moments (early and late stance) and increased ankle powers (mid-stance). Top transition biomechanics were similar to those reported previously for continuous descent. Kinetic differences at the knee and ankle signify the contrasting and prominent functions of controlled lowering during the top transition and forward continuance during the bottom transition. The varying musculoskeletal demands encountered during each functional sub-task should be addressed in falls prevention programmes with elderly populations where the greatest clinical impact may be achieved. Knee extensor eccentric power through flexion exercises would facilitate a smooth transition at the top and improving ankle plantarflexion strength during single and double limb stance activities would ease the transition into level gait following continuous descent

Assessment of available anatomical characters for linking living mammals to fossil taxa in phylogenetic analyses

ORCID: 0000-0003-4919-8655© 2016 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited. The file attached is the published version of the article

FROM ON-PREMISES TO ON-DEMAND: LEARNING FROM TWO CASES OF TRANSFORMATION OF SOFTWARE COMPANIES

The software industry is facing a fundamental change from On-premises to On-demand software. To survive, well-established companies have to adjust strategies and governance. One of the most difficult challenges is to shift the focus from the (still) profitable On-premises market to an, as yet unprofitable, On-demand market. This requires a major rethink for managers as well as for company structuring. Based on our case studies and Christensen´s theory for managing disruptive innovations, we wish to learn from software companies and their transformation strategies to discover to what extent the theory´s recommendations are applicable for software companies. We have seen that a company needs an effective strategy in order to survive market changes. From our two cases we learned that a successful transformation strategy consists of the combination of Christensen´s recommendations, its individual adjustments as well as some additional strategies. We were able to develop seven propositions for software providers to give ideas in order to better cope with the transformation process

On the creep ringing behavior of semi-dilute polyacrylamide and polyethylene oxide solutions

Aqueous polyacrylamide solutions (PAAm) and polyethylene oxide solutions (PE) of 5, 10, and 15 wt% were characterized under creep measurements. To the best of our knowledge it is the first time that the creep ringing method is used to study these types of polymeric materials. The rheometric measurements were carried out using an Anton Paar MCR 502 rheometer, equipped with a parallel plate measuring geometry with sandblasted surfaces. By performing a stepwise adjustment of the gap, it was possible to keep the maximum normal force during the loading procedure below 5 N. In addition, after each step the time evolution of the relaxation was recorded. In this way, the measurements could be carried out on fully relaxed samples. Systematic creep measurements showed that the initial response correlates to the moment of inertia of the instrument and the geometry. All samples exhibited dumping oscillations. For both PAAm and PE, a profound effect of the polymer concentration on the characteristic ringing frequency and amplitude of oscillations was found. Although, the results are qualitatively comparable, PE exhibits much higher storage and loss moduli. Independent of the magnitude of the applied stress, the initial ringing data coincide until the end of the ringing behavior. However, the long-term creep behavior is significantly affected by the magnitude of the applied stress. In addition, we studied the impact of NaCl and the molecular weight of the polymer on the viscoelasticity of the PAAm solutions. We found that the ionic strength affects both the frequency and duration of ringing. In addition, we found that decreasing the molecular weight of PAAm decreases the amplitude of oscillation and ringing frequency. If the instrument inertia is taken into account, the Jeffreys model provides a satisfying fit to the creep data. All values of the viscoelastic parameters presented here were obtained by fitting this model to the creep compliance curve. The present study shows that the creep ringing method is an extremely helpful since the short- and long-term creep compliance can be simultaneously obtained. Please click Additional Files below to see the full abstract

A novel Arabidopsis pathosystem reveals cooperation of multiple hormonal response-pathways in host resistance against the global crop destroyer Macrophomina phaseolina.

Dubbed as a "global destroyer of crops", the soil-borne fungus Macrophomina phaseolina (Mp) infects more than 500 plant species including many economically important cash crops. Host defenses against infection by this pathogen are poorly understood. We established interactions between Mp and Arabidopsis thaliana (Arabidopsis) as a model system to quantitatively assess host factors affecting the outcome of Mp infections. Using agar plate-based infection assays with different Arabidopsis genotypes, we found signaling mechanisms dependent on the plant hormones ethylene, jasmonic acid and salicylic acid to control host defense against this pathogen. By profiling host transcripts in Mp-infected roots of the wild-type Arabidopsis accession Col-0 and ein2/jar1, an ethylene/jasmonic acid-signaling deficient mutant that exhibits enhanced susceptibility to this pathogen, we identified hundreds of genes potentially contributing to a diverse array of defense responses, which seem coordinated by complex interplay between multiple hormonal response-pathways. Our results establish Mp/Arabidopsis interactions as a useful model pathosystem, allowing for application of the vast genomics-related resources of this versatile model plant to the systematic investigation of previously understudied host defenses against a major crop plant pathogen

Sec6 mutations and the Drosophila exocyst complex

To allow a detailed analysis of exocyst function in multicellular organisms, we have generated sec6 mutants in Drosophila. We have used these mutations to compare the phenotypes of sec6 and sec5 in the ovary and nervous system, and we find them to be similar. We also find that Sec5 is mislocalized in sec6 mutants. Additionally, we have generated an epitope-tagged Sec8 that localized with Sec5 on oocyte membranes and was mislocalized in sec5 and sec6 germ-line clones. This construct further revealed a genetic interaction of sec8 and sec5. These data, taken together, provide new information about the organization of the exocyst complex and suggest that Sec5, Sec6 and Sec8 act as a complex, each member dependent on the others for proper localization and function