Scapular and humeral movement patterns of people with stroke during range-of-motion exercises

BACKGROUND AND PURPOSE: Range-of-motion (ROM) exercises may contribute to hemiparetic shoulder pain, but the underlying mechanisms are unknown. This study examined scapular and humeral movement patterns in people with hemiparesis post stroke as they performed commonly prescribed ROM exercises. METHODS: Using kinematic techniques, we studied 13 people with hemiparesis, both with and without pain, as they performed three commonly prescribed ROM exercises: person-assisted ROM, self-assisted ROM, and cane-assisted ROM. Their data were compared to a group of 12 matched control subjects performing scapular plane shoulder elevation using mixed model ANOVAs. Correlation analyses were used to examine the relationship between participants’ ratings of pain and kinematic data. RESULTS: The hemiparetic group had mild pain at rest that increased during the performance of the exercises. During shoulder elevation, humeral external rotation in the hemiparetic group was decreased in all three ROM exercises compared to the control group. Scapular upward rotation in the hemiparetic group was decreased for the person-assisted ROM exercise only. No differences in scapular tilt were found between groups. The extent of movement abnormalities was not related to pain severity. DISCUSSION AND CONCLUSIONS: People with hemiparesis had altered scapular and humeral movement patterns and increased shoulder pain when performing the ROM exercises. These data can assist clinicians in making decisions regarding which exercises to prescribe to preserve shoulder motion and prevent contractures in this population

Model-free and model-based reward prediction errors in EEG

Learning theorists posit two reinforcement learning systems: model-free and model-based. Model-based learning incorporates knowledge about structure and contingencies in the world to assign candidate actions with an expected value. Model-free learning is ignorant of the world’s structure; instead, actions hold a value based on prior reinforcement, with this value updated by expectancy violation in the form of a reward prediction error. Because they use such different learning mechanisms, it has been previously assumed that model-based and model-free learning are computationally dissociated in the brain. However, recent fMRI evidence suggests that the brain may compute reward prediction errors to both model-free and model-based estimates of value, signalling the possibility that these systems interact. Because of its poor temporal resolution, fMRI risks confounding reward prediction errors with other feedback-related neural activity. In the present study, EEG was used to show the presence of both model-based and model-free reward prediction errors and their place in a temporal sequence of events including state prediction errors and action value updates. This demonstration of model-based prediction errors questions a long-held assumption that model-free and model-based learning are dissociated in the brain

Ascl1 phospho-status regulates neuronal differentiation in a Xenopus developmental model of neuroblastoma.

Neuroblastoma (NB), although rare, accounts for 15% of all paediatric cancer mortality. Unusual among cancers, NBs lack a consistent set of gene mutations and, excluding large-scale chromosomal rearrangements, the genome seems to be largely intact. Indeed, many interesting features of NB suggest that it has little in common with adult solid tumours but instead has characteristics of a developmental disorder. NB arises overwhelmingly in infants under 2 years of age during a specific window of development and, histologically, NB bears striking similarity to undifferentiated neuroblasts of the sympathetic nervous system, its likely cells of origin. Hence, NB could be considered a disease of development arising when neuroblasts of the sympathetic nervous system fail to undergo proper differentiation, but instead are maintained precociously as progenitors with the potential for acquiring further mutations eventually resulting in tumour formation. To explore this possibility, we require a robust and flexible developmental model to investigate the differentiation of NB's presumptive cell of origin. Here, we use Xenopus frog embryos to characterise the differentiation of anteroventral noradrenergic (AVNA) cells, cells derived from the neural crest. We find that these cells share many characteristics with their mammalian developmental counterparts, and also with NB cells. We find that the transcriptional regulator Ascl1 is expressed transiently in normal AVNA cell differentiation but its expression is aberrantly maintained in NB cells, where it is largely phosphorylated on multiple sites. We show that Ascl1's ability to induce differentiation of AVNA cells is inhibited by its multi-site phosphorylation at serine-proline motifs, whereas overexpression of cyclin-dependent kinases (CDKs) and MYCN inhibit wild-type Ascl1-driven AVNA differentiation, but not differentiation driven by a phospho-mutant form of Ascl1. This suggests that the maintenance of ASCL1 in its multiply phosphorylated state might prevent terminal differentiation in NB, which could offer new approaches for differentiation therapy in NB.This work was supported by a grant from the UK Neuroblastoma Society (A.P., L.A.W. and T.D.P.). C.J.T. and L.A.W. are supported by the intramural research program of the National Cancer Institute, National Institutes of Health. L.A.W. is an NIH-OxCam Scholar. L.J.A.H. is supported by a UK Medical Research Council Doctoral Training Award.This is the final version of the article. It first appeared from The Company of Biologists via http://dx.doi.org/10.1242/dmm.01863

Antiapoptotic herpesvirus Bcl-2 homologs escape caspase-mediated conversion to proapoptotic proteins

The antiapoptotic Bcl-2 and Bcl-x(L) proteins of mammals are converted into potent proapoptotic factors when they are cleaved by caspases, a family of apoptosis-inducing proteases (E. H.-Y. Cheng, D. G. Kirsch, R. J. Clem, R. Ravi, M. B. Kastan, A. Bedi, K. Ueno, and J. M. Hardwick, Science 278:1966-1968, 1997; R. J. Clem, E. H.-Y. Cheng, C. L. Karp, D. G. Kirsch, K. Ueno, A. Takahashi, M. B. Kastan, D. E. Griffin, W. C. Earnshaw, M. A. Veliuona, and J. M. Hardwick, Proc. Natl. Acad. Sci. USA 95:554-559, 1998). Gamma herpesviruses also encode homologs of the Bcl-2 family. All tested herpesvirus Bcl-2 homologs possess antiapoptotic activity, including the more distantly related homologs encoded by murine gammaherpesvirus 68 (gammaHV68) and bovine herpesvirus 4 (BHV4), as described here. To determine if viral Bcl-2 proteins can be converted into death factors, similar to their cellular counterparts, five herpesvirus Bcl-2 homologs from five different viruses were tested for their susceptibility to caspases. Only the viral Bcl-2 protein encoded by gammaHV68 was susceptible to caspase digestion. However, unlike the caspase cleavage products of cellular Bcl-2, Bcl-x(L), and Bid, which are potent inducers of apoptosis, the cleavage product of gammaHV68 Bcl-2 lacked proapoptotic activity. KSBcl-2, encoded by the Kaposi's sarcoma-associated herpesvirus, was the only viral Bcl-2 homolog that was capable of killing cells when expressed as an N-terminal truncation. However, because KSBcl-2 was not cleavable by caspases, the latent proapoptotic activity of KSBcl-2 apparently cannot be released. The Bcl-2 homologs encoded by herpesvirus saimiri, Epstein-Barr virus, and BHV4 were not cleaved by apoptotic cell extracts and did not possess latent proapoptotic activities. Thus, herpesvirus Bcl-2 homologs escape negative regulation by retaining their antiapoptotic activities and/or failing to be converted into proapoptotic proteins by caspases during programmed cell death

Comment on "A centrosome-independent role for gamma-TuRC proteins in the spindle assembly checkpoint"

Müller et al. (Reports, 27 October 2006, p. 654) showed that inhibition of the γ-tubulin ring complex (γ-TuRC) activates the spindle assembly checkpoint (SAC), which led them to suggest that γ-TuRC proteins play molecular roles in SAC activation. Because γ-TuRC inhibition leads to pleiotropic spindle defects, which are well known to activate kinetochore-derived checkpoint signaling, we believe that this conclusion is premature

Bifurcations and chaos in semiconductor superlattices with a tilted magnetic field

We study the effects of dissipation on electron transport in a semiconductor superlattice with an applied bias voltage and a magnetic field that is tilted relative to the superlattice axis.In previous work, we showed that although the applied fields are stationary,they act like a THz plane wave, which strongly couples the Bloch and cyclotron motion of electrons within the lowest miniband. As a consequence,the electrons exhibit a unique type of Hamiltonian chaos, which creates an intricate mesh of conduction channels (a stochastic web) in phase space, leading to a large resonant increase in the current flow at critical values of the applied voltage. This phase-space patterning provides a sensitive mechanism for controlling electrical resistance. In this paper, we investigate the effects of dissipation on the electron dynamics by modifying the semiclassical equations of motion to include a linear damping term. We demonstrate that even in the presence of dissipation,deterministic chaos plays an important role in the electron transport process. We identify mechanisms for the onset of chaos and explore the associated sequence of bifurcations in the electron trajectories. When the Bloch and cyclotron frequencies are commensurate, complex multistability phenomena occur in the system. In particular, for fixed values of the control parameters several distinct stable regimes can coexist, each corresponding to different initial conditions. We show that this multistability has clear, experimentally-observable, signatures in the electron transport characteristics.Comment: 14 pages 11 figure

An introduction to Elinor Glyn : her life and legacy

This special issue of Women: A Cultural Review re-evaluates an author who was once a household name, beloved by readers of romance, and whose films were distributed widely in Europe and the Americas. Elinor Glyn (1864–1943) was a British author of romantic fiction who went to Hollywood and became famous for her movies. She was a celebrity figure of the 1920s, and wrote constantly in Hearst's press. She wrote racy stories which were turned into films—most famously, Three Weeks (1924) and It (1927). These were viewed by the judiciary as scandalous, but by others—Hollywood and the Spanish Catholic Church—as acceptably conservative. Glyn has become a peripheral figure in histories of this period, marginalized in accounts of the youth-centred ‘flapper era’. Decades on, the idea of the ‘It Girl’ continues to have great pertinence in the post-feminist discourses of the twenty-first century. The 1910s and 1920s saw the development of intermodal networks between print, sound and screen cultures. This introduction to Glyn's life and legacy reviews the cross-disciplinary debate sparked by renewed interest in Glyn by film scholars and literary and feminist historians, and offers a range of views of Glyn's cultural and historical significance and areas for future research

Specific requirements for MRE foundation analysis

PublishedMarine Renewable Energy (MRE) systems involve single or arrays of devices that are secured to the seafloor via foundations and/or anchors. These MRE devices will transmit long-term cyclic loads to the seafloor sediment or rock, which may affect seafloor material properties and hence the overall physical performance of the MRE system. The response of seafloor sediments or rock formations is uncertain for the novel MRE systems and especially large arrays of 10s to >1000s of devices. This report summarizes critical inputs and tools for the design and analysis of foundations, anchors, and the response of the seafloor materials. Followed by an introduction in Section 1, Section 2 reviews the offshore structure and MRE literature to highlight current approaches and needed inputs for assessing interactions between foundations or anchors and seafloor materials, including potential environmental impacts. Section 3 addresses relevant marine geological settings that control key geotechnical engineering properties. Data collection activities are described, including in-situ site surveys and laboratory testing. Section 4 considers the unique interactions between MRE systems and seafloor materials, particularly cyclic loading and sediment response. Section 5 describes analytical and numerical tools and associated inputs for the design process of MRE foundations and anchors. Constitutive models are key to simulating sediment response and thus are discussed in detail. Important summary tables relate key variables of geology, geotechnical parameters, foundation or anchor type, and quantitative assessment tools including numerical analysis. Section 5 also addresses the incorporation of the geotechnical analysis into system-level tools to support decision making for MRE arrays. Section 6 presents conclusions and recommendations for future work.European Commission’s 7th Framework; Grant agreement number: 60859

The stochastic spectator

We study the stochastic distribution of spectator fields predicted in different slow-roll inflation backgrounds. Spectator fields have a negligible energy density during inflation but may play an important dynamical role later, even giving rise to primordial density perturbations within our observational horizon today. During de-Sitter expansion there is an equilibrium solution for the spectator field which is often used to estimate the stochastic distribution during slow-roll inflation. However slow roll only requires that the Hubble rate varies slowly compared to the Hubble time, while the time taken for the stochastic distribution to evolve to the de-Sitter equilibrium solution can be much longer than a Hubble time. We study both chaotic (monomial) and plateau inflaton potentials, with quadratic, quartic and axionic spectator fields. We give an adiabaticity condition for the spectator field distribution to relax to the de-Sitter equilibrium, and find that the de-Sitter approximation is never a reliable estimate for the typical distribution at the end of inflation for a quadratic spectator during monomial inflation. The existence of an adiabatic regime at early times can erase the dependence on initial conditions of the final distribution of field values. In these cases, spectator fields acquire sub-Planckian expectation values. Otherwise spectator fields may acquire much larger field displacements than suggested by the de-Sitter equilibrium solution. We quantify the information about initial conditions that can be obtained from the final field distribution. Our results may have important consequences for the viability of spectator models for the origin of structure, such as the simplest curvaton models