Pain perception and physiological responses to thermal and mechanical experimental pain : foundation for pain studies in dancers and non-dancers

Pain perception is a complex phenomenon comprised of the transmission of nociceptive signals and central neural processing to initiate responses to noxious stimuli. Great strides have been made in our understanding of the neurophysiological processes behind nociception, the role of psychosocial factors in modulating pain perception and how individuals respond physiologically to painful stimuli. However, there are still gaps in the literature regarding how individuals may respond to different types of experimental pain stimuli. This is particularly critical when looking at pain responses in populations who may experience a particular type of pain regularly. One such group is dancers. The primary gaps in the literature centre around the inconsistencies in reported physiological responses to thermal and chemical experimental pain and the appropriateness of methods used to test dancers and non-dancers pain experience in a laboratory setting. It is hypothesised that both the cold pressor test and hypertonic saline infusion pain protocols are associated with significant physiological responses, including increased heart rate, blood pressure and MSNA. However, it is hypothesised that the cold pressor test is associated with greater increases in these variables, and greater perceived pain compared with the hypertonic saline infusion. Dancers are hypothesised to demonstrate greater autonomic responses and lower perceived pain during the two pain protocols compared to non-dancers. The primary aim for this project was therefore to measure pain perception and physiological responses to two distinct types of experimental pain, a cold pressor task and a 5% hypertonic saline infusion into the tibialis anterior muscle. The secondary aim of this study was to pilot these protocols with groups of dancers and non-dancers to gain preliminary insights into the differences in pain perception and physiological responses between the two groups. The primary findings of this study indicate that there is a significant difference in how female populations respond to noxious cold compared to noxious chemical stimuli with reference to both physiological responses and perceived pain intensity. The disparity in these responses emphasises the highly nuanced nature of pain perception which needs to be considered by researchers when designing experimental protocols. If pain models that don’t accurately reflect the pain type that regularly afflicts a sample population are chosen, then the reported physiological responses or pain perception ratings cannot be seen as immediately transferrable to clinical understanding

Developmental Changes in Gene Expression in the Visual Cortex of Mice with Retinal Degeneration

Retinal degeneration can be caused by many genetic mutations. The Pde6b-mutation affects rod photoreceptors, which are list in mice by post-natal day (PND) 21 (Marc et al., 2003: Chang et al., 2002). Mice that are homozygous for the Pde6b-mutation are born with vision and go blind over time. Behavioural studies suggest that Pde6b- mice lose their visual activity by age PND 42 and subsequently lose their ability to detect differences in light illumination by PND 100. Behavioral changes have been correlated with changes in gene expression in specific cells in earlier studies. In this study, gene expression changes were examined for astrocytes in the visual cortex using real-time PCR for astrocyte-specific genes GFAP, Vimentin adn S100. GFAP and vimentin have been found to be useful for identifying the link between behavioral changes and their corresponding gene expression pattern changes (Kafitz et al., 1999). S100 MRNA expression is also useful because it can influence GFAP and Vimentin at teh protein level (Muller Et al., 1993). It was hypothesized that astrocyte-specific gene expression changes will be found at relevant ages (PND 21, 42, and 100) in astrocytes of the visual cortex in our Pde6b- mice compared to Pde6b+ mice, due to remodeling after a loss of visual function idicated by behavioral changes at these ages. We hypothesize that GFAP expression will decrease, vimentin expression will icrease and we are not sure what will happen to the expression of S100 at these relevant ages. Results suggest that changes in gene expression are takingplace at PND 7, 21, and 49. Our hypothesis may not be fully supported at the ages where behaviors were changing, but our data do suggest changes in gene expression at other possibly relevant ages. PND 21 was the age that showed a change in gene expression for vimentin coinciding with the age that rod photoreceptors are lost. This age could be examined further at the protein level for the glial genes.Master'sCollege of Arts and Sciences: BiologyUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/117690/1/Cornett.pd

The effect of Merger Anticipation on Bidder and Target Firm Announcement Period Returns

Cataloged from PDF version of article.This paper examines investors' anticipation of bidder and target merger candidacy and if investor anticipations about candidacy affect the distribution of value between bidder and target firm shareholders. We find that bidder firms can be predicted more accurately than target firms. To investigate how merger announcement period returns are distributed among bidder and target shareholders, we control for different degrees of predictability in bidder and target selection and find that the difference between bidder and target firm three-day cumulative abnormal returns around a merger announcement decreases significantly. Thus, the evidence supports the hypothesis that the asymmetry in investor anticipations about merger candidacy causes disparity in bidder and target firm announcement period abnormal returns

Competitive swimmers modify racing start depth upon request

To expand upon recent findings showing that competitive swimmers complete significantly shallower racing starts in shallower pools, 12 more experienced and 13 less experienced swimmers were filmed underwater during completion of competitive starts. Two starts (1 routine and 1 “requested shallow”) were executed from a 0.76 m block height into water 3.66 m deep. Dependent measures were maximum head depth, head speed at maximum head depth, and distance from the starting wall at maximum head depth. Statistical analyses yielded significant main effects (p < 0.05) for both start type and swimmer experience. Starts executed by the more experienced swimmers were deeper and faster than those executed by the less experienced swimmers. When asked to dive shallowly, maximum head depth decreased (0.19 m) and head speed increased (0.33 ms-1) regardless of experience. The ability of all swimmers to modify start depth implies that spinal cord injuries during competitive swimming starts are not necessarily due to an inherent inability to control the depth of the start

Block height influences the head depth of competitive racing starts

The purpose of this study was to determine whether or not starting block height has an effect on the head depth and head speed of competitive racing starts. Eleven experienced, collegiate swimmers executed competitive racing starts from three different starting heights: 0.21 m (pool deck), 0.46 m (intermediate block), and 0.76 m (standard block). One-way repeated measures ANOVA indicated that starting height had a significant effect on the maximum depth of the center of the head, head speed at maximum head depth, and distance from starting wall at maximum head depth. Racing starts from the standard block and pool deck were significantly deeper, faster, and farther at maximum head depth than starts from the intermediate block. There were no differences between depth, speed, or distance between the standard block and pool deck. We conclude that there is not a positive linear relationship between starting depth and starting height, which means that starts do not necessarily get deeper as the starting height increases

Water depth influences the head depth of competitive racing starts

Recent research suggests that swimmers perform deeper starts in deeper water (Blitvich, McElroy, Blanksby, Clothier, & Pearson, 2000; Cornett, White, Wright, Willmott, & Stager, 2011). To provide additional information relevant to the depth adjustments swimmers make as a function of water depth and the validity of values reported in prior literature, 11 collegiate swimmers were asked to execute racing starts in three water depths (1.53 m, 2.14 m, and 3.66 m). One-way repeated measures ANOVA revealed that the maximum depth of the center of the head was significantly deeper in 3.66 m as compared to the shallower water depths. No differences due to water depth were detected in head speed at maximum head depth or in the distance from the wall at which maximum head depth occurred. We concluded that swimmers can and do make head depth adjustments as a function of water depth. Earlier research performed in deep water may provide overestimates of maximum head depth following the execution of a racing start in water depth typical of competitive venues

Start depth modification by adolescent competitive swimmers

To expand upon previous studies showing inexperienced high school swimmers can complete significantly shallower racing starts when asked to start “shallow,” 42 age group swimmers (6-14 years old) were filmed underwater during completion of competitive starts. Two starts (one normal and one “requested shallow”) were executed from a 0.76 m block into 1.83 m of water. Dependent measures were maximum depth of the center of the head, head speed at maximum head depth, and distance from the starting wall at maximum head depth. Statistical analyses yielded significant main effects (p < 0.05) for start type and age. The oldest swimmers’ starts were deeper and faster than the youngest swimmers’ starts. When asked to start shallowly, maximum head depth decreased (0.10 m) and head speed increased (0.32 ms-1) regardless of age group. The ability of all age groups to modify start depth implies that spinal cord injuries during competitive swimming starts are not necessarily due to age-related deficits in basic motor skills

Racing start safety: head depth and head speed during competitive backstroke starts

Research on competitive swim start safety has focused on starts involving a dive from above the water surface. The purpose of this study was to determine the depths, speeds, and distances attained when executing backstroke starts, which begin in the water, and to investigate whether or not these variables are a function of age. Backstroke starts (n = 122) performed in 1.22 m of water during competition were stratified according to age group (8&U, 9-10, 11-12, 13-14, and 15&O). Dependent measures were maximum depth of the center of the head (MHD), head speed at maximum head depth (SPD), and distance from the wall at maximum head depth (DIST). Main effects were shown for age group for MHD (F = 8.86, p < 0.05), SPD (F = 4.64, p < 0.05), and DIST (F = 17.21, p < 0.05). Because they performed starts that were deeper and faster than the younger swimmers, the older swimmers seem to be at a greater risk for injury when performing backstroke starts in shallow water