The effects of postural threat on cognitive strategies used to maintain upright stance

It is well established that postural threat modifies postural control, although little is known regarding the underlying mechanism(s) responsible. It is possible that changes in postural control under conditions of elevated postural threat result from alterations in cognitive strategies. The purpose of this study was to determine the influence of elevated postural threat on cognitive strategies and to determine the relationship between postural control, psychological, and cognitive measures. It was hypothesized that elevated postural threat would cause a shift to more conscious control of posture. It was also expected that a relationship between fear of falling and postural control would exist that could be explained by changes in conscious control of posture. Forty-eight healthy young adults stood on a force plate at two different surface heights: ground level (LOW) and 3.2m above ground level (HIGH). Center of pressure (COP) summary measures calculated to quantify postural control were the mean position (AP-COP MP), root mean square (AP-COP RMS) and mean power frequency (AP-COP MPF) in the anteriorposterior direction. Trunk sway measures calculated in the pitch direction were trunk angle and trunk velocity. Psychological measures including perceived balance confidence, perceived fear of falling, perceived anxiety, and perceived stability were self reported. As a physiological indicator of anxiety, electrodermal activity was collected. The cognitive strategies assessed were movement reinvestment and attention focus. A modified state-sp-ecific version of the Movement Specific Reinvestment Scale was used to measure conscious motor processing (CMP) and movement self-consciousness (MSC). An attention focus questionnaire was developed to assess the amount of attention directed to internal and external sources. An effect of postural threat on cognitive strategies was observed as participants reported more conscious control and a greater concern or worry about their posture at the HIGH postural threat condition as well as an increased internal and external focus of attention. In addition changes in postural control, psychological, and physiological measures were found. The participants leaned away from the edge of the platform, the frequency of their postural adjustments increased, and the velocity of their trunk movements increased. Participants felt less confident, more fearful, more anxious, and less stable with an accompanying increase in physiological anxiety. Significant correlations between perceived anxiety, AP-COP MP, and cognitive measures revealed a possible relationship that could be mediated by cognitive measures. It was found that with greater conscious motor processing, more movement self-consciousness, and a greater amount of attention focused externally there was a larger shift of the mean position away from the edge of the platform. This thesis provides evidence that postural threat can influence cognitive strategies causing a shift to more conscious control of movement which is associated with leaning away from the edge of the platform. Shifting the position of the body away from the direction of the postural threat may reflect a cognitive strategy to ensure safety in this situation due to the inability to employ a stepping strategy when standing on an elevated platform.

The surface electromyography-force relationship during isometric dorsiflexion in males and females

This study evaluated sex-related differences in the tibialis anterior (TA) surface electromyography (EMG) to force relationship. One-hundred participants (50 males and 50 females) performed three isometric contractions at 20, 40, 60, 80, and 100% of maximal voluntary contraction (MVC) in an apparatus designed to isolate the action of the dorsiflexors. The surface EMG signal was amplified (lOOOx), band-pass filtered (10-500Hz), and sampled at 2048 Hz. The load cell signal was low-passed filtered at 100 Hz and sampled at the same rate. Males were stronger than females {P <0.05). However, there was no significant difference in root-mean-square (RMS) values between sexes {P <0.05). Both sexes exhibited a quadratic increase in RMS across force levels (P <0.05). The mean power frequency (MNF) for males was greater than for females {P <0.05). Males and females exhibited a linear increase in both frequency measures up to 80% of MVC (P <0.05). Between 80 and 100% MVC, the frequency values for the females plateaued while males showed a decrease {P <0.05). The magnitude of the difference in MNF between males and females was consistent with sex-specific TA physiology. In general, the pattern of means for RMS and MNF between males and females revealed no sex-related differences in the surface EMG/force relationship. We therefore conclude that there are no sex-related differences in the gradation of muscle force.

Force potentiation in the MDX mouse

Large forces are the primary mechanism of injury in muscular dystrophy, and muscular dystrophy is especially damaging to type IIB muscle fibers. It was hypothesized that post-tetanic potentiation (PTP) would be down-regulated to prevent damage in Xlinked muscular dystrophy (mdx) mice since PTP increases force and PTP effects are greatest in IIB fibers. PTP experiments were performed on the extensor digitorum longus (EDL) of 50 day old mdx (YM) and C57BL/10 (YC) mice and 10 month old mdx (OM) and C57B1710 (OC) mice. Twitch and tetanic forces were lower in mdx than controls and lower in younger than older mice. Contrary to the hypothesis, PTP was higher in both mdx groups compared to controls. OM potentiated more than any other condition (OM: 29.8%, OC: 23.2%, YM: 21.9%, YC: 17.2%). In accordance with literature PTP increased in the older groups. To explain PTP changes, fiber typing and Western blots for myosin light chain kinase (MLCK) were performed. YM and YC had similar fiber type profiles (2% I, 58% IIX/D and 40% IIB). In accordance with literature but contrary to expected conditions for elevated PTP, OM had a slower fiber type profile (1.7% I, 69% IIX/D and 29% IIB) than OC (0.4% I, 61% IIX/D and 38% IIB). No differences were found in MLCK expression. It seems that PTP is up-regulated to maintain muscle function rather than being down-regulated to prevent muscle damage. Ca""^ transient and myosin phosphorylation measurements would be beneficial in explaining increased PTP seen in this study.

Sediment genotoxicity and its relationship to the frequency of chironomid labial plate deformities

Sediment samples were taken from seven locations in the WeIland River in December 1986 and April 1987. The DMSO extracts of these sediment samples showed a significant (pplate deformities (over 1000 individual specimens were observed) . The samples from station D-l showed the highest frequency of chironomid labial plate deformities (10 . 9% ± 3.2%), while samples from the upstream control (station A) displayed t,he lowest frequency of deformities (3.8% ± 1.3%). All samples were coded to avoid unconscious biases . The results of the genotoxicity study indicated that station D-l in the WeIland River was contaminated with genotoxic materials. The genotoxic materials may have induced the observed increased frequency in chironomid labial plate deformities . Samples from stations C and D-l, located in a downstream portion of the river bounded by an industrialized area were slightly toxic according to -the alkaline phosphatase inhib_ii~ion component of the 50S chromotest analyses. The toxicity of these samples was only evident once they had been activated by the 59 (liver extract) mixture.

Plant rhizosphere specificity and variability in the insect and plant adhesins, Madl and Mad2, within the genus Metarhizium suggest plant adaptation as an evolutionary force

Metarhizium is a soil-inhabiting fungus currently used as a biological control agent against various insect species, and research efforts are typically focused on its ability to kill insects. In section 1, we tested the hypothesis that species of Metarhizium are not randomly distributed in soils but show plant rhizosphere-specific associations. Results indicated an association of three Metarhizium species (Metarhizium robertsii, M. brunneum and M. guizhouense) with the rhizosphere of certain types of plant species. M. robertsii was the only species that was found associated with grass roots, suggesting a possible exclusion of M. brunneum and M. guizhouense, which was supported by in vitro experiments with grass root exudate. M. guizhouense and M. brunneum only associated with wildflower rhizosphere when co-occurring with M. robertsii. With the exception of these co-occurrences, M. guizhouense was found to associate exclusively with the rhizosphere of tree species, while M. brunneum was found to associate exclusively with the rhizosphere of shrubs and trees. These associations demonstrate that different species of Metarhizium associate with specific plant types. In section 2, we explored the variation in the insect adhesin, Madl, and the plant adhesin, Mad2, in fourteen isolates of Metarhizium representing seven different species. Analysis of the transcriptional elements within the Mad2 promoter region revealed variable STRE, PDS, degenerative TATA box, and TATA box-like regions. Phylogenetic analysis of 5' EF-Ia, which is used for species identification, as well as Madl and Mad2 sequences demonstrated that the Mad2 phylogeny is more congruent with 5' EF-1a than Madl. This suggests Mad2 has diverged among Metarhizium lineages, contributing to clade- and species-specific variation. While other abiotic and biotic factors cannot be excluded in contributing to divergence, it appears that plant associations have been the driving factor causing divergence among Metarhizium species.

Variability in the Insect and Plant Adhesins, Mad1 and Mad2, within the Fungal Genus Metarhizium Suggest Plant Adaptation as an Evolutionary Force

Several species of the insect pathogenic fungus Metarhizium are associated with certain plant types and genome analyses suggested a bifunctional lifestyle; as an insect pathogen and as a plant symbiont. Here we wanted to explore whether there was more variation in genes devoted to plant association (Mad2) or to insect association (Mad1) overall in the genus Metarhizium. Greater divergence within the genus Metarhizium in one of these genes may provide evidence for whether host insect or plant is a driving force in adaptation and evolution in the genus Metarhizium. We compared differences in variation in the insect adhesin gene, Mad1, which enables attachment to insect cuticle, and the plant adhesin gene, Mad2, which enables attachment to plants. Overall variation for the Mad1 promoter region (7.1%), Mad1 open reading frame (6.7%), and Mad2 open reading frame (7.4%) were similar, while it was higher in the Mad2 promoter region (9.9%). Analysis of the transcriptional elements within the Mad2 promoter region revealed variable STRE, PDS, degenerative TATA box, and TATA box-like regions, while this level of variation was not found for Mad1. Sequences were also phylogenetically compared to EF-1a, which is used for species identification, in 14 isolates representing 7 different species in the genus Metarhizium. Phylogenetic analysis demonstrated that the Mad2 phylogeny is more congruent with 59 EF-1a than Mad1. This would suggest that Mad2 has diverged among Metarhizium lineages, contributing to clade- and species-specific variation, while it appears that Mad1 has been largely conserved. While other abiotic and biotic factors cannot be excluded in contributing to divergence, these results suggest that plant relationships, rather than insect host, have been a major driving factor in the divergence of the genus Metarhizium.

Variability in the Insect and Plant Adhesins, Mad1 and Mad2, within the Fungal Genus Metarhizium Suggest Plant Adaptation as an Evolutionary Force

Several species of the insect pathogenic fungus Metarhizium are associated with certain plant types and genome analyses suggested a bifunctional lifestyle; as an insect pathogen and as a plant symbiont. Here we wanted to explore whether there was more variation in genes devoted to plant association (Mad2) or to insect association (Mad1) overall in the genus Metarhizium. Greater divergence within the genus Metarhizium in one of these genes may provide evidence for whether host insect or plant is a driving force in adaptation and evolution in the genus Metarhizium. We compared differences in variation in the insect adhesin gene, Mad1, which enables attachment to insect cuticle, and the plant adhesin gene, Mad2, which enables attachment to plants. Overall variation for the Mad1 promoter region (7.1%), Mad1 open reading frame (6.7%), and Mad2 open reading frame (7.4%) were similar, while it was higher in the Mad2 promoter region (9.9%). Analysis of the transcriptional elements within the Mad2 promoter region revealed variable STRE, PDS, degenerative TATA box, and TATA box-like regions, while this level of variation was not found for Mad1. Sequences were also phylogenetically compared to EF-1a, which is used for species identification, in 14 isolates representing 7 different species in the genus Metarhizium. Phylogenetic analysis demonstrated that the Mad2 phylogeny is more congruent with 59 EF-1a than Mad1. This would suggest that Mad2 has diverged among Metarhizium lineages, contributing to clade- and species-specific variation, while it appears that Mad1 has been largely conserved. While other abiotic and biotic factors cannot be excluded in contributing to divergence, these results suggest that plant relationships, rather than insect host, have been a major driving factor in the divergence of the genus Metarhizium.

Canadian Expeditionary Force Death Certificate - Samuel DeVeaux Woodruff

Canadian Expeditionary Force Death Certificate stating that Samuel DeVeaux Woodruff was killed in action on the 13th of July, 1918, dated Sept. 20, 1919.

Force potentiation as a modulator of contractile performance: Implications for control of skeletal muscle force and energetics of work

This thesis investigated the modulation of dynamic contractile function and energetics of work by posttetanic potentiation (PTP). Mechanical experiments were conducted in vitro using software-controlled protocols to stimulate/determine contractile function during ramp shortening, and muscles were frozen during parallel incubations for biochemical analysis. The central feature of this research was the comparison of fast hindlimb muscles from wildtype and skeletal myosin light chain kinase knockout (skMLCK-/-) mice that does not express the primary mechanism for PTP: myosin regulatory light chain (RLC) phosphorylation. In contrast to smooth/cardiac muscles where RLC phosphorylation is indispensable, its precise physiological role in skeletal muscle is unclear. It was initially determined that tetanic potentiation was shortening speed dependent, and this sensitivity of the PTP mechanism to muscle shortening extended the stimulation frequency domain over which PTP was manifest. Thus, the physiological utility of RLC phosphorylation to augment contractile function in vivo may be more extensive than previously considered. Subsequent experiments studied the contraction-type dependence for PTP and demonstrated that the enhancement of contractile function was dependent on force level. Surprisingly, in the absence of RLC phosphorylation, skMLCK-/- muscles exhibited significant concentric PTP; consequently, up to ~50% of the dynamic PTP response in wildtype muscle may be attributed to an alternate mechanism. When the interaction of PTP and the catchlike property (CLP) was examined, we determined that unlike the acute augmentation of peak force by the CLP, RLC phosphorylation produced a longer-lasting enhancement of force and work in the potentiated state. Nevertheless, despite the apparent interference between these mechanisms, both offer physiological utility and may be complementary in achieving optimal contractile function in vivo. Finally, when the energetic implications of PTP were explored, we determined that during a brief period of repetitive concentric activation, total work performed was ~60% greater in wildtype vs. skMLCK-/- muscles but there was no genotype difference in High-Energy Phosphate Consumption or Economy (i.e. HEPC: work). In summary, this thesis provides novel insight into the modulatory effects of PTP and RLC phosphorylation, and through the observation of alternative mechanisms for PTP we further develop our understanding of the history-dependence of fast skeletal muscle function.

Engineer force employed in the surveying ditch in marsh lands to the 23rd of February inclusive

Engineer force employed in the surveying ditch in marsh lands to the 23rd of February inclusive. This is signed by S.D. Woodruff, March 8, 1855.