16 research outputs found

    Characterizing the comfort limits of forces applied to the shoulders, thigh and shank to inform exosuit design.

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    Recent literature emphasizes the importance of comfort in the design of exosuits and other assistive devices that physically augment humans; however, there is little quantitative data to aid designers in determining what level of force makes users uncomfortable. To help close this knowledge gap, we characterized human comfort limits when applying forces to the shoulders, thigh and shank. Our objectives were: (i) characterize the comfort limits for multiple healthy participants, (ii) characterize comfort limits across days, and (iii) determine if comfort limits change when forces are applied at higher vs. lower rates. We performed an experiment (N = 10) to quantify maximum tolerable force pulling down on the shoulders, and axially along the thigh and shank; we termed this force the comfort limit. We applied a series of forces of increasing magnitude, using a robotic actuator, to soft sleeves around their thigh and shank, and to a harness on their shoulders. Participants were instructed to press an off-switch, immediately removing the force, when they felt uncomfortable such that they did not want to feel a higher level of force. On average, participants exhibited comfort limits of ~0.9-1.3 times body weight on each segment: 621±245 N (shoulders), 867±296 N (thigh), 702±220 N (shank), which were above force levels applied by exosuits in prior literature. However, individual participant comfort limits varied greatly (~250-1200 N). Average comfort limits increased over multiple days (p<3e-5), as users habituated, from ~550-700 N on the first day to ~650-950 N on the fourth. Specifically, comfort limits increased 20%, 35% and 22% for the shoulders, thigh and shank, respectively. Finally, participants generally tolerated higher force when it was applied more rapidly. These results provide initial benchmarks for exosuit designers and end-users, and pave the way for exploring comfort limits over larger time scales, within larger samples and in different populations

    Combined expression trait correlations and expression quantitative trait locus mapping.

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    Coordinated regulation of gene expression levels across a series of experimental conditions provides valuable information about the functions of correlated transcripts. The consideration of gene expression correlation over a time or tissue dimension has proved valuable in predicting gene function. Here, we consider correlations over a genetic dimension. In addition to identifying coregulated genes, the genetic dimension also supplies us with information about the genomic locations of putative regulatory loci. We calculated correlations among approximately 45,000 expression traits derived from 60 individuals in an F2 sample segregating for obesity and diabetes. By combining the correlation results with linkage mapping information, we were able to identify regulatory networks, make functional predictions for uncharacterized genes, and characterize novel members of known pathways. We found evidence of coordinate regulation of 174 G protein-coupled receptor protein signaling pathway expression traits. Of the 174 traits, 50 had their major LOD peak within 10 cM of a locus on Chromosome 2, and 81 others had a secondary peak in this region. We also characterized a Riken cDNA clone that showed strong correlation with stearoyl-CoA desaturase 1 expression. Experimental validation confirmed that this clone is involved in the regulation of lipid metabolism. We conclude that trait correlation combined with linkage mapping can reveal regulatory networks that would otherwise be missed if we studied only mRNA traits with statistically significant linkages in this small cross. The combined analysis is more sensitive compared with linkage mapping alone

    Regulation of <i>Riken32G18</i> Inversely Parallels the Regulation of Lipogenic Genes

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    <div><p>(A) Metabolic regulation of <i>Riken32G18</i>. Expression of lipogenic genes and <i>Riken32G18</i> in adipose tissues of lean versus obese mice.</p><p>(B) Expression of lipogenic genes and <i>Riken32G18</i> in livers of lean versus obese mice.</p><p>(C) Expression of LXRα target genes and <i>Riken32G18</i> in mouse livers treated with LXRα agonist T0901317.</p></div

    Expression QTL in the (B6 × BTBR) F<sub>2</sub>-<i>ob/ob</i> Cross

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    <div><p>(A) Expression QTL that regulate gene expression in the (B6 × BTBR) F<sub>2</sub>-<i>ob/ob</i> cross. The physical locations of the transcripts are organized on the y-axis. The chromosome regions (x-axis) to which those transcripts are mapped were obtained using the <i>scanone</i> function in the R/qtl package with 5-cM intervals. The gray scale reflects the strength of the linkage signals (LOD scores greater than 8 are scaled to 8). Transcripts appearing on the diagonal are inferred to be <i>cis</i>-regulated. The chromosomes were concatenated to form a 2,300-Mb genome, starting from Chromosome 1 and ending with Chromosome 19.</p><p>(B) Global display of mapping patterns of linkage clusters. The y-axis shows the 6,016 mapping transcripts. The x-axis shows the physical locations to which these transcripts map. The transcripts are grouped based on the hierarchical clustering of linkage mapping patterns across the genome. Darker areas indicate the regions to which traits are comapped or coregulated. The boxes correspond to the hot spots on Chromosomes 2, 10, and 13. The gray scale reflects the strength of the linkage signals (LOD scores greater than 8 are scaled to 8).</p></div

    Coordinate Regulation of Genes for GPCR Protein Signaling Pathways

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    <div><p>(A) GPCR protein signaling pathway genes show coordinated changes across the 60 F<sub>2</sub> mice. The rescaled expression levels of 174 distinct transcripts (y-axis) that belong to the GPCR pathway. The x-axis displays the 60 F<sub>2</sub> mice. The plot shows that the subset of GPCR traits identified by our trait correlation-GO analysis has vertical patterns that indicate coordinate expression across the 60 F<sub>2</sub> mice (<i>P</i> = 1e10<sup>−4</sup> by permutation test).</p><p>(B) Histogram of pairwise correlation coefficients of GPCR traits identified with different seeds.</p><p>(C) Scaled expression levels of traits from one realization of the permuted lists. Thirty-eight lists of correlated traits were randomly sampled from a total of 1,341 correlated trait lists. The list sizes were adjusted to match those of the GPCR lists. The expression values were scaled to have mean intensity = 0 and variance = 1, as in the GPCR list in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.0020006#pgen-0020006-g002" target="_blank">Figure 2</a>A.</p></div

    An Expression Quantitative Trait Locus on Chromosome 2 Regulates Many GPCR Protein Pathway Genes

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    <div><p>(A) Comapping of GPCR pathway traits to loci on Chromosome 2. The figure shows the peaks on Chromosome 2 versus LOD score for 174 GPCR protein signaling pathway traits. The closed circles correspond to 38 seed traits.</p><p>(B) Comapping of GPCR pathway traits. The figure shows the magnitude (y-axis) versus location of LOD peaks (x-axis is scaled by cM) for 174 GPCR protein signaling pathway traits. The closed circles correspond to the 38 seed traits. The interval mapping LOD profiles for all 38 seeds are included in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.0020006#pgen-0020006-sg002" target="_blank">Figure S2</a>.</p></div

    Lipid Metabolism Pathway Genes Show Coordinated Expression across the F<sub>2</sub> Mice

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    <p>The rescaled expression levels of 184 distinct transcripts (y-axis) that belong to the lipid metabolism pathway are shown for each of the 60 F<sub>2</sub> mice (x-axis). Plot shows that the subset of lipid metabolism traits identified by our trait correlation-GO analysis has preserved vertical patterns (<i>P</i> = 4e10<sup>−4</sup> by permutation test).</p
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