Tag: Human Physiology

Biomechanical Changes in Obstacle Crossing During Walking Following Concussion in High School Athletes

Presenter : Michael Kado

Mentor : Li-Shan Chou

Major : Human Physiology

Poster 20

Approximately 136,000 sports related concussions are diagnosed within the high school athletic population annually with little known about the longitudinal impairments that follow. The objective of this study was to investigate the longitudinal effects of concussion on gait during an obstacle-crossing task. Concussed subjects (n=20) were diagnosed by a physician or certified athletic trainer. Control subjects (n=20) were matched by height, weight, age, and sport participation and examined in similar time increments. Gait variables examined were average walking speed, step length, step width, cadence, and obstacle clearance height during an obstacle-crossing task. Subjects were tested at 72 hours, 1 week, 2 weeks, 1 month, and 2 months post-concussion. We hypothesized that concussed subjects would have decreased average walking speed, step length, cadence, obstacle clearance height, and increased step width compared to control subjects. Motion data was collected using 29 reflective markers and a 10-camera motion analysis setup. Subjects were instructed to walk over an obstacle set at approximately 10% of their height. Of the five variables investigated, step length and width showed the greatest differences between groups. Step length of concussed subjects was less than control subjects over the two months. Additionally, step width of concussed subjects was greater over the two months following injury. These results suggest altered walking performance while crossing obstacles in concussed individuals while recovering.

Tracing the Endocardial Cell Lineage of Developing Heart Valves Using MADMMatter Pools?

Presenter : Amy Jones

Mentor : Kryn Stankunas

Major : Biology, Human Physiology

Poster 15

Heart valve development is a complex, multi-step process. During development, endocardial cushions form at specific locations in
the early heart tube. These cushions are populated by endocardial cells that delaminate in a process known as epithelial-mesenchymal transformation (EMT). In the mouse, EMT takes place between embryonic day 9.5-10.5. It is a vital process to understand since the heart valves are derived from this cardiac cushion tissue. Current models of cushion EMT suggest that a large number of endocardial cells undergo EMT. An alternative hypothesis is that only a few individual cells initially populate the cushions that then proliferate to expand cushion mesenchyme.To better understand how endocardial-derived cells contribute to heart valves, I am using a novel mouse genetic system termed MADM (mosaic analysis with double markers). MADM uses the Cre-lox system to permanently label specified cells by fluorescent protein expression. For my studies, I use the Tie2 promoter to direct Cre expression and instruct the MADM system to specifically trace the endocardial cell lineage. The low frequency by which labeled cells are generated allows me to exquisitely moni- tor contributions of clonally-related endocardial cells to developing valves. By gaining a complete understanding of the contribution of endothelial-lineage cells to developing valves, we can identify when embryonic heart malformations originate, supporting the development of therapeutics to prevent defective valves from progressing to a diseased state.

AICAR Administration Promotes a Cytoprotective and Pro-Angiogenic Stimulation in an Ex Vivo Model of Placental Ischemia

Presenter : Sarah Johnson

Mentor : Jeffrey Gilbert

Major : Biology/Human Physiology

Poster 28

The pregnancy-specific hypertension known as preeclampsia (PE) is widely observed worldwide and is recognized as a leading contributor to sickness and death of a mother and her baby. This pervasive condition is yet to be fully characterized, as is an effective therapy of symptom relief outside of inducing early delivery. We have recently reported treatment with an adenosine-mimetic, AICA-riboside (AICAR), in an experimental model of PE reduces the onset of PE-like characteristics; however, the underlying mechanisms are poorly understood. Therefore, our hypothesis was AICAR would initiate cytoprotective and pro-angiogenic stimulation in cultured placental tissue explants, and this effect would be mediated by the adenosine (ENT1/2) transporter. Tissues were cultured at 37°C for 12 hours in physiologic normoxic (8% O2) or hypoxic (1.5% O2) conditions, and treated with AICAR (2mM) and an adenosine transporter blocker (dipyridamole, DPM) (100μM). Explants treated with AICAR exhibited a decreased (P<0.05) secreted sFlt-1 in both O2 conditions, and DPM blocked this effect. The energy regulatory protein AMPKα phosphorylation was elevated in the tissues treated with AICAR, but was not statistically significant (0.1>P>0.05). Through modeling placental ischemia ex vivo, we have demonstrated AICAR decreas- es placental secretion of sFlt-1, mediated by adenosine transport activity. In concert with our previous in vivo studies with AICAR, this study further supports a placental specific mechanism of AICAR’s actions in vivo.

A Comparison of Hip Joint Extension, Thigh Segment Extension, and Pelvic Tilt Between Individu- als Who Exhibit Poor Hip Extension and Individuals With Good Hip Extension

Presenter : Richard Howey

Mentor : Li-Shan Chou

Major : Human Physiology

Poster 11

Full 3D kinematic analysis is often used for biomechanical assessment of running mechanics and corresponding injury risk. However, conclusions drawn from these analyses are highly dependent on data analysis methods. For example, poor hip joint extension (HJE) at toe-off is often interpreted clinically as resulting from weakness in extensor muscles. However, because joint angles are often calculated as movement of the distal segment relative to the proximal, two absolute orientations may result in the same calculated joint angle. Therefore, poor HJE could result in movements of the thigh or the pelvis. The purpose of this study is to compare hip joint, thigh seg- ment and pelvic tilt angles in runners with good and poor HJE. Data from this study were drawn from a database of 100 runners who had been analyzed in the motion analysis laboratory. Ten individuals with HJE 1.5 standard deviations above and below the database mean comprised the good and poor groups, respectively. While the two groups were different in HJE (good: M = -15.28° ± 1.34°; poor: M = 3.51° ± 4.94°; p < .001) the angle of the thigh segment relative to vertical was not different between groups (good: M = 3.52° ± 8.38°; poor: M = 3.41° ± 4.94°; p = .991). The pelvis angles also were significantly different between groups (good: M = -4.88° ± 8.76°; poor: 7.17° ± 8.03°; p = .005). These findings suggest that pelvic instability should be considered in addition to weakness in hip exten- sors when reduced HJE is observed.

Determining the Effects of Essential Amino Acid Supplementation for Total Knee Arthroplasty Patients

Presenter : Caitlin Gibson

Mentor : Hans Dreyer

Major : Human Physiology

Poster 18

Osteoarthritis affects 60% of the US population over 65 years of age. Total Knee Arthroscopy (TKA), used to mitigate osteoarthritis knee pain, is the leading cause of hospitalization for adults, ages 45-84 years old. The most significant clinical barrier following TKA surgery is persistent muscle atrophy and weakness. Previous research has shown that essential amino acid (EAA) ingestion is a potent means to stimulate muscle protein synthesis in older adults. PURPOSE: To determine the effects of twice-daily ingestion of 20g of EAA for 1 week prior to, and for 2 weeks post-TKA, on muscle mass, strength, and functional mobility. METHODS: Magnetic resonance imaging (MRI), isometric quadriceps strength and functional mobility were obtained at baseline, 2 and 6 weeks post-TKA from older adults supplemented with EAA or placebo. RESULTS: Quadriceps muscle atrophy was greater in the placebo group at 2 and 6 weeks post-surgery. The intervention group had significantly less loss in quadriceps strength and performed significantly better at 2 and 6 weeks post-surgery on functional mobility tests. CONCLUSIONS: Our results show that TKA surgery is associated with significant muscle atrophy, declines in muscle strength and reductions in functional mobility. Our findings will help us to better understand the potential for EAA supplementation in order to attenuate muscle loss and boost recovery of muscle mass, strength and function follow- ing TKA in older adults.

Testing Different Models for Cutaneous Thermal Hyperemia

Presenter : Patricia Choi

Mentor : Christopher Minson

Major : Human Physiology

Poster 2

Currently, the assessment of cutaneous thermal hyperemia is done by locally heating the forearm skin from a baseline of 33 to 42 oC at a rate of 0.1oC/1s. The purpose of this study was to test two different heating protocols from the standard heating protocol. The first heating protocol decreased the target temperature to 39oC compared to the standard heating protocol. The second heating protocol used gradual heating rate of 0.1oC/60s compared to the standard heating proto- col. Four microdialysis fibers were placed in the forearm skin of 16 young healthy subjects. In protocol 1 and 2 (female = 8, male = 8): (1) Control, (2) NO inhibitor, L-NAME (3) KCa channel inhibitor, tetraethylammonium (TEA), and (4) L-NAME +TEA . For both studies, skin sites were locally heated on the forearm from a baseline of 33oC to target temperatures. After maintaining the target temperature for about 40 minutes, the four skin sites were heated to 43.5oC to attain maximal skin blood flow (SkBF). SkBF was measured with Laser Doppler flowmetry. Data are presented as % maximal cutaneous vascular conductance (CVC), which equals blood flow divided by mean arterial pressure. In protocol 1, all drug sites attenuated plateau CVC from the control sites. Compared to the control plateau CVC, there was 80.1 % decrease with L-NAME, close to 77.6% decrease in the L-NAME +TEA site, and 35.2% decrease with TEA. In protocol 2, L-NAME and L-NAME + TEA sites showed attenuated plateau CVC, 29.1% and 32.2% decrease, respectively, compared to the control site.

The Neurocognitive Development of HIV Positive Children and Adolescents

Presenter: Sophia Tarzaban

Mentor: Janis Weeks

Oral Presentation

Major: Human Physiology 

Research has displayed that children living with HIV diagnoses have showed signs of progressive encephalopathy; and these children exhibited higher rates of residual neurologic, cognitive, and scholastic impairment compared
with the average school age child. My research highlights the fact that antiretroviral drug treatments (ARVs) are developmentally unsafe to be administered to infants, children, and adolescents, due to the decreased neurocognitive development that is displayed as they progress into adulthood. In addition, my research exposes the physiological mechanism that causes HIV to damage the developing brain of infants. My goal is to draw awareness to this issue by arguing that these children require special attention and are too often overlooked, in order to help prevent them from losing their right to an education.The data I collected is from a review of over 30 research papers and will be presented as a meta-analysis of relevant cognition testing performed on children born with HIV. These cognitive assessments provide statistical comparisons that are used to compare and contrast scholastic performance in various disciplines.

My research is important as it displays strong evidence that ARVs are not a safe treatment method for combating HIV in youth and adolescents. While ARVs are the current, most effective treatment in increasing child mortality, they are also increasing the rates of encephalopathy amongst school children. Discovering a new, safer method of treatment for HIV+ children could produce a generation of adolescents and adults who are not only immunologically stable, but also cognitively sound.

Variation of Self-sorting Behavior and Jaw Bone Morphology in Early Development within Chinook Salmon (Oncorhynchus tshawytscha)

Presenter: Natasha Mckibben

Mentor: Charles Kimmel

Poster: 22

Major: Human Physiology

Research at Oregon State University has shown that two types of juvenile fish are present in a hatchery stock of spring run Chinook salmon derived from locations along the Upper Willamette River Basin in Oregon. The two groups differ in body morphology, agonistic behavior, growth, and whether they live at the surface or the bottom of the water column. However, they maintain the same diet and identical rearing conditions under captivity. The juveniles appear to resemble wild fish rearing in downstream and upstream sites in the Willamette River Basin respectively, and leave their home streams for the main stem of the river during the same time of year each wild group does. Based on understanding in another species, stickleback, I hypothesize that the fish growing at different depths also differ in their feeding strategies and, therefore, might exhibit changed jaw morphologies and mechanics, even though the genetic basis is unknown. To test this prediction, I quantitatively compared lower jaw bone morphologies in the two types of juveniles at the 50 mm stage. Supporting my hypothesis, I found significant differences between the groups in the shapes of both lower jaw bones, the angular-articular and the dentary. No difference was present in the bone sizes relative to body size. These results provide further evidence that early differences in behavior may be predictive of juvenile life history tactics.

Examination of Foot Strike Patterns and Ankle Muscle Strength

Presenter: Chris Gronseth

Mentor: Li-Shan Chou

Poster: 38

Major: Human Physiology 

Recent research on foot and ankle injuries has initiated debates about the ideal foot strike position in running. This study chose to investigate whether ankle plantarflexion strength (PFS) or dorsiflexion strength (DFS) was related to a runner’s foot strike position at initial contact. Twenty-five subjects, who ran at least 20 miles per week, participated in the study and ran continuous laps of ~40 meters in the UO Motion Analysis Laboratory. Foot strike indices (FSI) were calculated for each limb (n=50) using center of pressure data obtained from three force plates located in series. Isometric PFS and DFS were collected using a Biodex System 3 dynamometer. A one-way ANOVA was used to test for differences between strength among forefoot, rearfoot, and midfoot strikers while a Pearson correlation analysis was used to test the strength of the relationship between FSI and both PFS and DFS. No differences in PFS (p = .44) or DFS (p = .64), were seen among groups. No significant correlations were found between FSI and PFS or between FSI and DFS, which indicates that there was no relationship between ankle muscle strength and foot strike indices. This study was limited by a relatively small sample size and subject self-selection of shoe type. To better understand the relationship between FSI and muscle strength, future studies should consider more subjects and the influence of knee and hip strength on foot strike patterns.

Exposure to perchlorate affects differentiating germ cells in teleost fish

Presenter: Nathaniel Earp

Mentor: William Cresko

Poster: 37

Major: Human Physiology 

Perchlorate is a widespread contaminant in the environment. We have found that perchlorate has masculinizing effects on threespine stickleback, Gasterosteus aculeatus. The mechanism of this masculinization is unknown. Our previous studies found that during development female stickleback show increased proliferation of undifferentiated primordial germ cells (PGC) followed by a larger wave of apoptosis compared to male stickleback. We hypothesize that perchlorate treated stickleback will show a decrease in total number of PGCs compared to control fish. To test our hypothesis, stickleback of 15 and 20 days post fertilization (dpf) – a critical time for primary sexual differentiation– were grown from fertilization to the end of the experiment in 10 or 100 ppm perchlorate treated medium or control medium with no perchlorate. Stickleback were sectioned and stained with hematoxylin and eosin, and visualized by light microscope. Total number of PGCs were counted and characterized as either pre-meiotic or meiotic based on morphology of the PGC and nucleus. Perchlorate treated fish show a significant decrease (27.6%) in total number of PGCs compared to controls. Furthermore, control stickleback showed a decrease in total number of PGCs from 15 dpf to 20 dpf, presumably due to female germ cell apoptosis, while perchlorate treated stickleback did not show this decrease. These findings are consistent with perchlorate’s masculinizing effect. We are further investigating the effects of perchlorate on total PGC count in zebrafish, Danio rerio, as perchlorate has been shown to have a feminizing effect on zebrafish, giving us an opportunity to explore the basic mechanisms underlying the reproductive abnormalities caused by perchlorate. Our findings contribute to understanding mechanisms of perchlorate induced reproductive abnormalities in vertebrates, and to better understand the underlying process of sex determination in two divergent teleosts.