Impairment in Task-Specific Modulation of Muscle Coordination Correlates with the Severity of Hand Impairment following Stroke

Significant functional impairment of the hand is commonly observed in stroke survivors. Our previous studies suggested that the inability to modulate muscle coordination patterns according to task requirements may be substantial after stroke, but these limitations have not been examined directly. In this study, we aimed to characterize post-stroke impairment in the ability to modulate muscle coordination patterns across tasks and its correlation with hand impairment. Fourteen stroke survivors, divided into a group with severe hand impairment (8 subjects) and a group with moderate hand impairment (6 subjects) according to their clinical functionality score, participated in the experiment. Another four neurologically intact subjects participated in the experiment to serve as a point of comparison. Activation patterns of nine hand and wrist muscles were recorded using surface electromyography while the subjects performed six isometric tasks. Patterns of covariation in muscle activations across tasks, i.e., muscle modules, were extracted from the muscle activation data. Our results showed that the degree of reduction in the inter-task separation of the multi-muscle activation patterns was indicative of the clinical functionality score of the subjects (mean value = 26.2 for severely impaired subjects, 38.1 for moderately impaired subjects). The values for moderately impaired subjects were much closer to those of the impaired subjects (mean value = 46.1). The number of muscle modules extracted from the muscle activation patterns of a subject across six tasks, which represents the degree of motor complexity, was found to be correlated with the clinical functionality score (R = 0.68). Greater impairment was also associated with a change in the muscle module patterns themselves, with greater muscle coactivation. A substantial reduction in the degrees-of-freedom of the multi-muscle coordination post-stroke was apparent, and the extent of the reduction, assessed by the stated metrics, was strongly associated with the level of clinical impairment.     

Conserved intron positions in ancient protein modules

Background  

The timing of the origin of introns is of crucial importance for an understanding of early genome architecture. The Exon theory of genes proposed a role for introns in the formation of multi-exon proteins by exon shuffling and predicts the presence of conserved splice sites in ancient genes. In this study, large-scale analysis of potential conserved splice sites was performed using an intron-exon database (ExInt) derived from GenBank.     

Polymorphism and evolution in the constant region of the T-cell receptor beta chain in an advanced teleost fish

Sequence, PCR and Southern data are presented as evidence that, as in mammals, two gene loci encode C regions of the TCR beta chain in the bicolor damselfish, Stegastes partitus. The loci are distinguished by an insertion of ten amino acids in the c-d loop at one locus and by a high interlocus divergence of the third intron and fourth exon sequences. Unlike their mammalian counterparts, the damselfish TCRBC genes encode highly polymorphic regions. None of the eight complete cDNA or four partial genomic DNA sequences presented from a single animal are identical; and three of the four animals examined are heterozygous at both loci, suggesting high heterozygosity in the damselfish population. Coding regions of the eight cDNA clones differ by up to 12% at the DNA level and 23% at the amino acid level. Polymorphism is concentrated primarily in the less evolutionarily conserved regions, suggesting that this variation may be selectively neutral. However, a comparison of the variation between synonymous and non-synonymous sites suggests that at least a portion of the observed variation results from selection. As in mammals, a gradient of sequence homogenization between the two loci is observed. Data presented here suggest that both interlocus homogenization and the sharing of polymorphic segments are likely achieved by partial gene conversion.     

Simulation of the Seated Postural Stability of Healthy and Spinal Cord-Injured Subjects Using Optimal Feedback Control Methods

A two-dimensional, biomechanical computer model was developed, using the software package Working Model(TM), to simulate the postural control of seated individuals. Both able-bodied and spinal cord-injured subjects were represented. The model incorporated active control of the upper body through full-state feedback. Specifically, a linear quadratic regulator scheme was implemented in the model. Nonlinearities were included in the torque computations to mimic physiological constraints and disability. Interactions between the subject and the wheelchair were also included in the model. Simulation results were compared with those obtained from experiments in which the subjects had attempted to remain stable during the application of significant disturbance moments, similar to those experienced during braking in a vehicle. While subjects exhibited more complex control schemes, the model was able to simulate overall stability. Therefore, it is believed that the model could prove beneficial to future research examining the effects of various restraints on stability.     

Sepsis progression and outcome: a dynamical model

Background  

Sepsis (bloodstream infection) is the leading cause of death in non-surgical intensive care units. It is diagnosed in 750,000 US patients per annum, and has high mortality. Current understanding of sepsis is predominately observational and correlational, with only a partial and incomplete understanding of the physiological dynamics underlying the syndrome. There exists a need for dynamical models of sepsis progression, based upon basic physiologic principles, which could eventually guide hourly treatment decisions.     

A subset of Cowdria ruminantium genes important for immune recognition and protection

Cowdria ruminantium causes the tick-borne rickettsial disease of heartwater, which is devastating to livestock production in sub-Saharan Africa. Current diagnosis and control methods are inadequate. We have identified and sequenced a subset of genes encoding recombinant antigens recognized by antibody and peripheral blood mononuclear cells from immune ruminants. The identified genes include many with significant similarity to those of Rickettsia prowazekii, genes predicted to encode different outer membrane proteins and lipoproteins and a gene containing an unusual tandem repeat structure. Evidence is presented for immune protection by recombinant antigens in a mouse model of C. ruminantium infection. These data identify new recombinant antigens for evaluation in vaccines and diagnostic tests to control heartwater.     

Estimating the Risk of Chronic Pain: Development and Validation of a Prognostic Model (PICKUP) for Patients with Acute Low Back Pain

BackgroundLow back pain (LBP) is a major health problem. Globally it is responsible for the most years lived with disability. The most problematic type of LBP is chronic LBP (pain lasting longer than 3 mo); it has a poor prognosis and is costly, and interventions are only moderately effective. Targeting interventions according to risk profile is a promising approach to prevent the onset of chronic LBP. Developing accurate prognostic models is the first step. No validated prognostic models are available to accurately predict the onset of chronic LBP. The primary aim of this study was to develop and validate a prognostic model to estimate the risk of chronic LBP.ConclusionsBased on its performance in these cohorts, this five-item prognostic model for patients with acute LBP may be a useful tool for estimating risk of chronic LBP. Further validation is required to determine whether screening with this model leads to a net reduction in unnecessary interventions provided to low-risk patients.     

The Lipid Profile and Mortality Risk in Elderly Type 2 Diabetic Patients: A Ten-Year Follow-Up Study (ZODIAC-13)

Background

The precise relationship between the lipid profile and mortality in elderly patients with type 2 diabetes mellitus (T2DM) remains unclear. The aim of this study was to investigate the relationship between the lipid profile over time, and mortality in elderly patients with T2DM.

Methods and Findings

In 1998, 881 primary care patients with T2DM aged 60 years and older participated in the ZODIAC study, a prospective observational study. The cohort was divided into two age categories: 60–75 years and older than 75 years. Updated means of all lipid profile indices were calculated after a median follow-up time of 9.8 years. These values were used as time dependent covariates in a Cox proportional hazard model. The cholesterol-HDL ratio and LDL-cholesterol were positively related to both all-cause and cardiovascular mortality in the low age group. In contrast, except for the triglyceride level, none of the other lipid profile indices were related to all-cause mortality in patients aged over 75 years. The mortality risk decreased by 17% (95%CI: 5% to 27%) for each 1 mmol/L higher serum level of triglycerides. The relationships between the various lipid profile indices and cardiovascular mortality were not significant. However, the results were different after stratification for diabetes duration. In the subgroup of elderly patients with a diabetes duration of 8 years and longer, higher lipids were predictive of increased cardiovascular mortality. The main limitation of this study is its observational design, which prevents us drawing conclusions about causality.

Conclusion

Although the lipid profile was not predictive in the overall group of elderly patients, higher lipids were related to increased cardiovascular mortality in patients with diabetes of long duration. In order to make valid recommendations concerning lipid-lowering treatment, a randomized controlled trial or a meta-analysis concerning this specific population is mandatory.