• Salivary and Serum Concentrations of Cortisol and Testosterone at Rest and in Response to Intense Exercise in Boys and Men

      Adebero, Tony; Applied Health Sciences Program
      This study compared salivary and serum concentrations of testosterone and cortisol at rest and in response to high-intensity exercise, in boys and men. Early morning saliva and venous blood samples were obtained pre- and 15 min post-exercise from 31 competitive swimmers (15 boys, 14.3±1.8y; 16 men, 21.6±3.1y). Exercise included an all-out 200 m swim, followed by a high-intensity interval swimming protocol (5 x 100m, 5 x 50m, and 5 x 25m). Testosterone (but not cortisol) concentration was higher in men than boys in serum and saliva (p<0.05). Cortisol concentration was higher in serum compared with saliva (p<0.01). Salivary and serum cortisol increased post-exercise, with a greater increase in men compared with boys (group-by-time interaction, p<0.001). Serum testosterone declined post-exercise in serum but not in saliva (medium-by-time interaction, p<0.01). Serum and salivary cortisol (but not testosterone) were strongly correlated in both men and boys, as evidenced by the high intraclass correlation coefficients (ICC=0.86 and 0.90, respectively; p<0.001). In summary, early morning high-intensity exercise results in a decrease in testosterone in serum, but not saliva, and an increase in cortisol irrespective of the medium used, in both boys and men. The lack of correlation in testosterone between media suggests that saliva may not be an appropriate medium to examine changes in testosterone following intense exercise. The high ICC observed between serum and saliva cortisol indicates that, in both boys and men, saliva may be used to monitor the cortisol response to exercise.
    • Sarcolemmal lipid analysis from mechanically skinned rat muscle fibres.

      Fajardo, Val Andrew; Applied Health Sciences Program (Brock University, 2011-10-24)
      Membrane lipid composition, which includes phospholipid (PL) headgroup, and fatty acid (FA) saturation, has been shown to affect cellular function. The sarcolemma (SL) membrane is integral to skeletal muscle function and health. Previous studies assessing SL lipid composition are limited as they have 1) restricted analysis to a PL level and neglected FA composition and 2) relied on aggressive membrane isolation procedures resulting in t-tubule and sarcoplasmic reticulum contamination and unknown levels of nuclear and mitochondrial contamination. Thus, to overcome these limitations, this study assessed a method of individually skinned skeletal muscle fibres as an alternative to analyze complete sarcolemmal membrane lipid composition. The major findings of this study were 1) complete SL lipid composition can be obtained 2) the SL had higher sphingomyelin content than previous studies and 3) the SL membrane had minimal nuclear and mitochondrial contamination and was void of contamination from sarcoplasmic reticulum and t-tubules.
    • Secretory immunity in overweight and obese versus normal-weight early-and late-pubertal females

      Corbett, Lauren.; Applied Health Sciences Program (Brock University, 2008-06-15)
      Obesity is a condition associated with a wide variety of health problems including hypertension, dyslipidemia, diabetes mellitus, certain forms of cancer, cardiovascular disease, and gallstones (157). TTiere is growing evidence that obesity may also be related to compromised immune function due to altered metabolic, psychological, and physical attributes (93). The aim of this study was to compare: a) immunity-related variables such as frequency of upper respiratory tract infections (URTI) and salivary secretory immunoglobulin A (sIgA) levels between overweight/obese (OB) and normal weight (NW) early-pubertal and late-pubertal girls, and b) stress-related variables such as Cortisol, melatonin, the melatonin/cortisol ratio, testosterone and the testosterone/cortisol ratio. Physical activity levels, stress indicators, and fatigue were used to explain potential differences in the dependent variables. It was hypothesized that the OB females would have lower melatonin (M) and higher Cortisol (C) and testosterone (T) levels compared with NW girls, regardless of maturity status. The altered levels of melatonin, Cortisol, and testosterone, would result in decreased M/C and T/C ratios, despite the increase in testosterone in OB females. It was hypothesized that this altered hormonal status results in a compromised immunity marked by higher frequency of upper respiratory tract infections (URTI) and decreased levels of secretory immunoglobulin A (sIgA). It was also hypothesized that OB girls would participate in less hours of physical activity than their NW counterparts and that this would relate to their stress and immunity levels. Forty (16 early- and 24 late-pubertal) overweight and obese females were compared to fifty-three (27 eariy- and 26 late-pubertal) age-matched normal-weight control subjects. Participants were categorized as early-pubertal (EP) or late-pubertal (LP) using Tanner self-staging of secondary sex characteristics. Subjects were classified into the two adiposity groups according to relative body fat (%BF), where normal weight (NW) subjects had a %BF less than 25%, and overweight and obese (OB) subjects had a %BF greater than 27.5%. Participants completed a number of questionnaires and information was collected on menstrual history, smoking history, alcohol and caffeine consumption, and medical history. Following the determination of maturity status, a complete anthropometric assessment was made including height, body mass, and body composition. All questionnaires and measurements were completed during a one-hour visit between 1 500 and 1900 hours Relative body fat was assessed using bioelectrical impedance analysis. Resting saliva samples were obtained and assayed (ELISA) for testosterone, Cortisol, melatonin and secretory immunoglobulin A. Physical activity was self-reported using the Godin- Shephard Leisure time questionnaire, and quantified using Actigraph GTIM accelerometers, which participants wore for seven consecutive days from the time they woke up in the morning, until the time they went to bed. Late-pubertal girls also completed questionnaires on their perceived stress and fatigue. Finally, all participants also filled out a one-month health log to record frequency of symptoms of upper respiratory tract infections (URTI). Significant age effects were found for testosterone, Cortisol, incidence of sickness, and sIgA when controlling for physical activity, however there were no significant effects of adiposity on any of the variables. There was a trend which neared-significance for an effect of adiposity on sIgA (p=0.01). There were no significant differences between the groups on the total selfreported leisure-time physical activity in METs per week, however EP girls recorded significantly greater levels of moderate, hard, and very hard physical activity from accelerometers. Results of the perceived stress and fatigue questionnaires in late-pubertal girls demonstrated that contrary to what was hypothesized, NW girls reported more stress and more fatigue than OB girls. Results of the present study suggest that excess adiposity in early- and latepubescent girls may not have a negative impact on immunity as hypothesized.
    • Self-Esteem and Mastery in Maintenance Cardiac Rehabilitation

      Pretty, Chelsea; Applied Health Sciences Program (Brock University, 2012-06-15)
      Background: CVD is the second leading cause of death in Canada. Mastery and self-esteem are psychosocial factors, suggested to be emerging risk factors for CVD. Purpose: The purpose of the study was two-fold; first to establish whether mastery and self-esteem predicted adherence to maintenance CR; and second, whether mastery and self-esteem improved after a 6-month maintenance CR program. Methods: Data were collected at the Brock University Heart Institute. The study involved a sample of 98 participants. At intake to the program and 6-month follow-up, participants completed a questionnaire battery which included the Rosenberg Self-Esteem Scale and the Pearlin-Schooler Mastery Scale. Results: Mastery and self-esteem scores did not alter the likelihood of adherence to the CR program. Mastery and self-esteem did significantly improve after 6-months of CR amongst participants with the lowest exercise capacity. Conclusion: Maintenance CR does improve mastery and self-esteem amongst those with diminished exercise capacity.
    • Self-Esteem and Obesity: A Longitudinal Analysis among Children and Adolescents in Niagara, Canada

      Aggarwal, Harish; Applied Health Sciences Program
      As the prevalence of obesity has surged in the past decade, with a marked increase in the rates among North American youth, it is important to comprehensively understand its downstream effects and the burden these may have on society. Besides the countless physical comorbidities of overweight and obesity in youth, several psychosocial effects have been identified including self-esteem issues. The purpose of this study is to understand the longitudinal relationship between obesity and self-esteem in Canadian children and adolescents. By quantifying this association, it may not only provide evidence for prevention, but be useful for future resource planning. The research questions are as follows: Is there a correlation between body mass and self-esteem? Is obesity status and body mass over time associated with changes in self-esteem, and if so among which sub-domains? Is the temporal relationship bi-directional where self-esteem also predicts changes in body mass? Is the relative difference in body mass between those in the same cohort also associated with self-esteem change longitudinally? Which covariate factors are significant in these suggested relationships? Data was obtained from the PHAST cohort study conducted from 2004-2010 among 2,278 children at baseline from Niagara, Canada. Participants were excluded if missing all data related to body mass and self-esteem, and multiple imputation regression was utilized to impute missing observations. Cross-sectional analysis between variables was conducted using the Pearson correlation test. Linear mixed modelling regression was conducted to examine the proposed bi-directional relationships longitudinally, accounting for fixed and random variables as well as relevant covariates and interactions. There were weak to moderate significant negative linear correlations between BMI and all self-esteem sub-domains. Baseline obesity status and BMI increases were significant predictors of decreased physical, global, athletic, and social self-esteem longitudinally. With each kg/m2 increase in BMI, physical appearance self-esteem was reduced by 0.25 units (95% CI: -0.29, -0.21, p<0.0001) over a 5-year period. Compared to those of a normal weight, those obese at baseline had an average athletic self-esteem 1.51 units lower (95% CI: -2.15, -0.87, p<0.0001). With each standard deviation increase from the mean BMI of one’s sex and age, global self-esteem was reduced by 0.53 units (95% CI: -0.62, -0.43, p<0.0001). Also, low baseline self-esteem and decreases in physical, global, and athletic self-esteem levels significantly predicted increased BMI over time. Physical activity was a significant covariate, predicting both increased self-esteem levels and decreased BMI longitudinally. The results suggest that there is a bi-directional relationship present between body mass and self-esteem in school children. Having a greater body size impairs areas of self-esteem, and having stronger self-esteem helps mitigate obesity. Physical activity is a key factor in maintaining appropriate self-esteem and body mass levels. This study can be used to guide public health officials and resource planners given the escalation of the obesity epidemic in youth.
    • Self-presentational motives in eating disorders : a known groups difference approach

      Strong, Heather.; Applied Health Sciences Program (Brock University, 2005-07-14)
      Self-presentation reflects the processes by which individuals attempt to monitor and control the impressions others form of them (Schlenker & Leary, 1982). Concerns over impressions conveyed have been linked to numerous health behaviors (Crawford & Eklund, 1994; Martin, Leary, & O'Brien, 2001). The present study investigated the role of cognitive manifestations of dispositional and situational self presentational motivation (SPM) in 131 females with known groups differences on a measure of eating disorders. Participants were classified as in-treatment (IN = 39); at risk (AT = 46); and not at risk (NOT = 46) for eating disordered behaviour. Each participant completed The Brief Fear of Negative Evaluation Scale (FNE; Leary, 1983), the Public Self-Consciousness Scale (PSC; Fenigstein, Sheier, & Buss, 1975), and the Social Physique Anxiety Scale (SPA; Hart, Leary, & Rejeski, 1989), as measures of dispositional SPM. Situational SPM was assessed through Self-Presentational Efficacy (SPE; Gammage, Hall, & Martin, 2004), and the Exercise Motivation Inventory-2 (Markland & Ingeldew, 1997). Significant differences emerged on the measure of eating disorder behaviour between AT and NOT. To determine if group differences existed on measures of trait SPM an ANOVA was conducted. Results indicated that the NOT group experienced less FNE, PSC and SPA than the IN and AT groups, and the AT group experienced less FNE and PSC than the IN group. Pearson bivariate correlations were conducted on measures of trait SPM and EMI-2 subscales theoretically linked to SPM. It was found that FNE, PSC and SPA were all positively correlated with weight management for the NOT group. To determine if group differences existed on selfpresentational exercise motives independent samples I-tests were conducted. Results revealed that the AT group was more motivated to exercise for weight management, and appearance, and social recognition than the NOT group. To determine if group differences existed on the state measure of self-presentational efficacy a series of ANOVA's were conducted. Results revealed that the NOT group experienced significantly greater self-presentational efficacy expectancy and self-presentational outcome value than the AT group. Finally, a discriminant function analysis was conducted to determine if trait SPM would predict group membership. Results revealed that 63.4% of participants were correctly classified, with SPA, PSC, and FNE differentiating the NOT group from the AT and IN groups and FNE and PSC differentiating the AT group from the IN group. Thus self-presentation motivation appears to have an influence on females who have an eating disorder and those at risk for an eating disorder. Potential applications of the influence of self-presentational motives on eating disorders and future research directions are discussed.
    • 'Sent down? Called up?': Exploring the roller coaster of loans and re-assignments in professional hockey

      McLaughlin, Bryan; Applied Health Sciences Program
      Athletes constantly face transitions in their sporting careers, which can influence the quality of their performance and well-being. The purpose of the study is to explore professional hockey players’ lived experiences with being called up and sent down in organizations. For example, an athlete can play in the National Hockey League (NHL) and is then sent down to their affiliated team in the American Hockey League (AHL) for a variety of reasons. The study utilized a phenomenological approach to understand athletes lived experiences with being called up and sent down, this allowed the researcher to move beyond brief descriptions toward understanding this specific transition athletes face. Semi-structured interviews were audio-recorded and transcribed verbatim, which occurred with six current hockey players (five current professional athletes and one competitive athlete). Data-analysis followed a two-phase process analysis to determine themes and patterns within each interview and then compared patterns across interviews to see what is common across interviews. The results were presented in three clusters such as the performance and well-being of an athlete, external influences on career, and interpretations of experiences. Further research is needed to explore the impact that loaning can have on an athlete and their well-being.
    • Sex-related differences in the microvascular function of pre-pubertal children

      Massarotto, Raffaele Joseph; Applied Health Sciences Program
      There is little research examining the effect of sex on skin blood flow (SkBF) in adults, and less in children. Sex-related differences in SkBF may help explain known thermoregulatory differences between males and females. The purpose of this study is to determine whether there are sex-related differences in the SkBF response to exercise, local heating, and acetylcholine (ACh). Additionally, the role of nitric oxide (NO) was examined. Laser-Doppler fluxmetry was used to assess forearm SkBF. Responses to exercise (30 min cycling, 60%O2max), local heating (44˚C), and ACh iontophoresis were assessed in 12 pre-pubertal boys (age=10.9 ±1.1y, O2max =1665 ± 282 ml·min-1) and 12 girls (age=11.1±1.2y, O2max =1537± 296 ml·min-1), with and without NO synthase inhibition, using Nω-nitro-L-arginine methyl ester (L-NAME) iontophoresis. Exercise-induced increase in SkBF was greater in boys compared with girls (528±290 and 374±192% of baseline, respectively, p=0.03). L-NAME blunted the SkBF response to exercise in boys and in girls (group-by-treatment interaction, p=.82). Local heating-induced SkBF was not significantly different between boys and girls (1445±900% and 1432±582%, respectively, p=.57). The ACh-induced SkBF was not different between the boys and girls, with no difference in the increase in SkBF (673±434% and 558±405%, respectively, p=.18). L-NAME blunted the SkBF response to ACh in boys and girls (group-by-treatment interaction, p=.19). These findings demonstrate that there are no differences between boys and girls in the responses to ACh and to local heating (44˚C). Additionally, the role of NO in the SkBF response appears similar in boys and girls both during exercise and ACh-mediated vasodilation. The greater SkBF response in the boys during exercise may be workload-related. Absolute and relative (%O2max) exercise intensity were not different between the two groups. Therefore, it is possible that the greater SkBF response in boys may be related to their greater workload relative to body mass (p=0.01). Additionally, sex-related factors (e.g., hormones) may interact with the exercise response or other vasodilators may be involved, resulting in the observed sex-related difference in the SkBF response to exercise.
    • Six-month outcomes of a multi-campus smoking cessation contest

      Wilson, Julie Dawn.; Applied Health Sciences Program (Brock University, 2006-05-21)
      Background: Up to 40% of North American post-secondary students smoke at least occasionally, and most want to quit. Given students' preferences for free, easy-to-access, self-directed, convenient cessation methods, a motivational, incentive-based cessation contest may be an effective way to assist students to quit. The current study describes 3- and 6-month outcomes experienced by post-secondary student smokers who entered the 'Let's Make A Deal!' contest. Methodology: Contestants from five university campuses who chose to quit completely ('Quit For Good') or reduce their tobacco consumption by 50% ('Keep The Count') were invited to participate in a study of the contest. Three and six months after registration, participants were contacted by phone to assess their smoking and quitting behaviours. Qualitative and quantitative measures were collected, including weekly tobacco consumption, efficacy to resist temptations to smoke, use of quitting aids, and strategies to cope with withdrawal. Quitting was assessed using 7-day point prevalence and continuous abstinence. Results: Seventy-four (64.9%) of the 114 participants recruited for the study completed the follow-ups. Over 31 % of participants who entered Quit For Good and 23.5% of participants who entered Keep The Count were identified as quitters at the 6-month follow-up. Among the quitters, 45.5% experienced sustained abstinence from smoking for the 6-month duration of the study. Keep The Count contestants reduced their tobacco consumption by 57.2% at 3-month follow-up and sustained some of this reduction through to the 6-month follow-up. Qualitative data provides insights into how quitters coped with withdrawal and what hampered continuing smokers' efforts to quit. Significance: A motivational, incentive-based contest for post-secondary students can facilitate both smoking cessation and harm reduction. The contest environment, incentives, resources, and "buddies" provide positive structural and social supports to help smokers overcome potential barriers to quitting, successfully stop smoking, and manage potential triggers to relapse. The contest cessation rates are higher than the typical 5-7% associated with unassisted quitting.
    • Skeletal muscle fibre-type comparison of whole tissue and subcellular membrane phospholipids and fatty acids

      Stefanyk, Leslie Elizabeth.; Applied Health Sciences Program (Brock University, 2009-06-15)
      Membranes are dynamic structures that affect cell structure and function. Compositional changes ofmembranes have been shown with the application of a perturbation; however these are limited to whole tissue analysis. The purpose of this thesis was to compare the phospholipid (PL) fatty acid (FA) composition of rat whole muscle (Wm) to 1) purified and non-purified subsarcolemmal (SS) mitochondria in soleus, plantaris, and red gastrocnemius, and 2) sarcolemma, transverse-tubules, SS and intermyofibrillar (IMF) mitochondria fix)m whole hindlimb. The major findings were that 1) contamination significantly altered the PL FA composition of the SS mitochondrial membrane fraction, 2) Wm and SS mitochondria compositions differed between muscle types, and 3) Wm did not accurately reflect the PL FA composition of any isolated subcellular membranes, with each being unique from each other. As such, the relevancy of the trends reported in the literature of the effects of perturbations on Wm may be limited.
    • Skeletal muscle protein content of lipolytic inhibitor G(0)/G(1) switch gene-2 protein: the effect of endurance training

      Turnbull, Patrick Carson; Applied Health Sciences Program (Brock University, 2014-10-29)
      The first and rate-limiting step of lipolysis is the removal of the first fatty acid from a triglyceride molecule; it is catalyzed by adipose triglyceride lipase (ATGL). ATGL is co-activated by comparative gene identification-58 (CGI-58) and inhibited by the G(0)/G(1) switch gene-2 protein (G0S2). G0S2 has also recently been identified as a positive regulator of oxidative phosphorylation within the mitochondria. Previous research has demonstrated in cell culture, a dose dependent mechanism for inhibition by G0S2 on ATGL. However our data is not consistent with this hypothesis. There was no change in G0S2 protein content during an acute lipolytic inducing set of contractions in both whole muscle, and isolated mitochondria yet both ATGL and G0S2 increase following endurance training, in spite of the fact that there should be increased reliance on intramuscular lipolysis. Therefore, inhibition of ATGL by G0S2 appears to be regulated through more complicated intracellular or post-translation regulation.
    • Social physique anxiety across physical activity settings : a meta-analytical review

      Waddell, Lindsay.; Applied Health Sciences Program (Brock University, 2006-05-21)
      The purpose of this meta-analytic investigation was to review the empirical evidence specific to the effect of physical activity context on social physique anxiety (SP A). English language studies were located from computer and manual literature searches. A total of 146 initial studies were coded. Studies included in the meta-analysis presented at least one empirical effect for SPA between physical activity participants (i.e., athletes or exercisers) and non-physical activity participants. The final sample included thirteen studies, yielding 14 effect sizes, with a total sample size of 2846. Studies were coded for mean SPA between physical activity participants and non-physical activity participants. Moderator variables related to demographic and study characteristics were also coded. Using Hunter and Schmidt's (2004) protocol, statistical artifacts were corrected. Results indicate that, practically speaking, those who were physically active reported lower levels of SPA than the comparison group (dcorr = -.12; SDeorr.-=-;22). Consideration of the magnitude of the ES, the SDeorr, and confidence interval suggests that this effect is not statistically significant. While most moderator analyses reiterated this trend, some differences were worth noting. Previous research has identified SPA to be especially salient for females compared to males, however, in the current investigation, the magnitude of the ES' s comparing physical activity participants to the comparison group was similar (deorr = -.24 for females and deorr = -.23 for males). Also, the type of physical activity was investigated, and results showed that athletes reported lower levels of SP A than the comparison group (deorr = -.19, SDeorr = .08), whereas exercisers reported higher levels of SPA than the comparison group (deorr = .13, SDeorr = .22). Results demonstrate support for the dispositional nature of SP A. Consideration of practical significance suggests that those who are involved in physical activity may experience slightly lower levels of SPA than those not reporting physical activity participation. Results potentially offer support for the bi-directionality of the relationship between physical activity and SP A; however, a causality may not be inferred. More information about the type of physical activity (i.e., frequency/nature of exercise behaviour, sport classificationllevel of athletes) may help clarify the role of physical activity contexts on SPA.
    • Socio-demographic factors, smoking, symptoms, morbidities and pulmonary function and quality of life in individuals with a heavy smoking history

      Ventresca, Matthew; Applied Health Sciences Program
      Objective: To determine which socio-demographic, exposure, morbidity and symptom variables are associated with health-related quality of life among former and current heavy smokers. Methods: Cross sectional data from 2537 participants were studied. All participants were at ≥2% risk of developing lung cancer within 6 years. Linear and logistic regression models utilizing a multivariable fractional polynomial selection process identified variables associated with health-related quality of life, measured by the EQ-5D. Results: Upstream and downstream associations between smoking cessation and higher health-related quality of life were evident. Significant upstream associations, such as education level and current working status and were explained by the addition of morbidities and symptoms to regression models. Having arthritis, decreased forced expiratory volume in one second, fatigue, poor appetite or dyspnea were most highly and commonly associated with decreased HRQoL. Discussion: Upstream factors such as educational attainment, employment status and smoking cessation should be targeted to prevent decreased health-related quality of life. Practitioners should focus treatment on downstream factors, especially symptoms, to improve health-related quality of life.
    • Soil-Transmitted Helminth Infections, Nutrition and Growth in School-age Children from Rural Communities in Honduras

      Usuanlele, Mary-Theresa; Applied Health Sciences Program (Brock University, 2012-10-11)
      Background: Soil-transmitted helminth (STH) infections are endemic in Honduras but their impact on children’s health is not well studied. Objectives: To evaluate the prevalence and intensity of STH infections and their association with nutrition and growth in a sample of Honduran children. Methodology: A cross-sectional study was done among Honduran rural school-age children in 2011. Blood and stool samples and anthropometric measurements were obtained to determine nutritional status, STH infection and growth status, respectively. Results: The STH prevalence among 320 studied children was 72.5%. Prevalence by species was 30%, 67% and 16% for Ascaris, Trichuris and 16% hookworms, respectively. High intensity infections were associated with decreased growth scores but regardless of intensity, co-infections negatively affected growth indicators. Conclusions: The health burden of STH infections is related to high parasitic load but also to the presence of low-intensity concurrent infections. The synergistic effects of polyparasitism in underprivileged children warrants more attention.
    • The Structural and Functional Changes of Blood Vessels during Aging

      Ratsep, Matthew T; Applied Health Sciences Program (Brock University, 2011-02-28)
      The vascular adventitia is recognized as a dynamic mediator of vascular structure and function, yet its role in aging is not understood. The purpose of this thesis was to examine the age-related changes of the vascular adventitia and determine the underlying mediators responsible. Male Sprague-Dawley rats were aged to 15, 30, 50 and 80 weeks before being anesthetised and euthanized by exsanguination. Thoracic aortas, mesenteric and pudental arteries were isolated, formalin fixed, and embedded in paraffin then sectioned at 5μm. Vessels were examined by microscopy and protein expression was determined by indirect immunofluorescence. The thickness of the adventitia increased dramatically with age. Immunofluorescence revealed a robust expression of endothelin system proteins in the adventitia. Additionally, extracellular matrix proteins collagen and fibronectin, and the proliferation marker Ki67 showed strong adventitial origin. The changes observed in the vascular adventitia with aging clearly demonstrate an important role in the process of vascular aging.
    • The structural and functional changes of blood vessels during aging

      Rätsep, Matthew T.; Applied Health Sciences Program (2012-07-05)
      The vascular adventitia is recognized as a dynamic mediator of vascular structure and function, yet its role in aging is not understood. The purpose of this thesis was to examine the age-related changes of the vascular adventitia and determine the underlying mediators responsible. Male Sprague-Dawley rats were aged to 15,30,50 and 80 weeks before being anesthetised and euthanized by exsanguination. Thoracic aortas, mesenteric and pudental arteries were isolated, formalin fixed, and embedded in paraffin then sectioned at 51lm. Vessels were examined by microscopy and protein expression was determined by indirect immunofluorescence. The thickness of the adventitia increased dramatically with age. Immunofluorescence revealed a robust expression of endothelin system proteins in the adventitia. Additionally, extracellular matrix proteins collagen and fibronectin, and the proliferation marker Ki67 showed strong adventitial origin. The changes observed in the vascular adventitia with aging clearly demonstrate an important role in the process of vascular aging.
    • Structural Equation Model of Father Involvement in Infant Development in Vietnam using Identity Theory

      Salaeva, Dinara; Applied Health Sciences Program
      Child development is an important determinant of global health, and fathers’ involvement can enhance child behavioural, social, and cognitive development. However, fathers’ involvement varies between cultures, and research on fatherhood in Asia is limited, especially in developing countries such as Vietnam. The aim of this study was to examine fathers’ involvement using identity theory including the following constructs: fathers’ affective and interactional commitment, psychological centrality and role performance. In addition, socioeconomic status and marital relationship quality were examined in the context of the fathers’ involvement. Ultimately, the influence of the fathers’ involvement on infants’ developmental outcomes was analyzed. To achieve the objectives of the study, control group (N = 370) data from a longitudinal father involvement intervention study in Vietnam was used. Indicators of the fathers’ role performance and child development were examined using structural equation modeling. Psychological centrality was strongly positively associated with the role performance and infants’ development. Furthermore, marital relationship quality predicted the fathers’ psychological centrality and role performance. These findings suggest that fathers’ emotional relationship with their spouses and infants and the centrality of the father’s role identity to a man has a significant influence on the fathers’ involvement and infants’ development. The present study contributes to understanding of the factors that affect fathers’ involvement and infants’ development in the Asian context. In addition, the present study provides support to development and implementation of social programs aiming to increase fathers’ involvement in Vietnam and globally.
    • The surface electromyography-force relationship during isometric dorsiflexion in males and females

      Lenhardt, Sean Alexander.; Applied Health Sciences Program (Brock University, 2009-06-15)
      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.
    • A systematic observation of hostile aggression in Junior B hockey

      Gee, Chris J.; Applied Health Sciences Program (Brock University, 2004-07-14)
      Aggressive behaviours within the sport of hockey appear to be increasing in both prevalence and consequence (Biasca, Wirth, & Tegner, 2002). Accordingly, this area of inquiry is currently garnering a considerable amount of attention from society and academics alike. The problem however, is that our current understanding of these behaviours has been deemed both incomplete and unreliable. The inconsistencies inherent within this body of knowledge have been traced back to a variety of methodological shortcomings. The purpose of this investigation was to assess hostile aggression using a more ecologically valid and comprehensive research design. Ten Junior B hockey games were tapped and subsequently coded by three independent observers, using a validated operational list. Two hundred and fifty-nine behaviours were extrapolated and examined according to the score differential, period, position of the aggressor, status of the aggressor's team, and whether the aggressor was a member of the home or visiting team. It was concluded that the frequency of aggressive behaviours significantly differed according to the score differential, and status of the aggressor's team (p < .01). However, these hostile acts did not differ according the aggressor's position, period, and the home versus away status of the aggressor's team (p > .01). It was also determined that the majority of aggressive acts (69.1 1%) across these ten games went unsanctioned. This highlights the profound influence that "positive misses" have on penalty measures of aggression, while concurrently highlighting the ecological validity present with observational designs. Consequently, by assessing aggressive behaviour in a more inclusive and ecologically valid manner, a more accurate picture of the frequency and distribution of hostile aggression may be provided.
    • Taenia solium transmission in a rural community in Honduras : an examination of risk factors and knowledge

      Pang, Haiyan.; Applied Health Sciences Program (Brock University, 2004-11-04)
      Taenia soliurn taeniasis and cysticercosis are recognized as a major public health problem in Latin America. T. soliurn transmission not only affects the health of the individual, but also social and economic development, perpetuating the cycle of poverty. To determine prevalence rates, population knowledge and risk factors associated with transmission, an epidemiological study was undertaken in the rural community of Jalaca. Two standardized questionnaires were used to collect epidemiological and T. soli urn general knowledge data. Kato-Katz technique and an immunoblot assay (EITB) were used to determine taeniasis and seroprevalence, respectively. In total, 139 individuals belonging to 56 households participated in the study. Household characteristics were consistent with conditions of poverty of rural Honduras: 21.4% had no toilet or latrines, 19.6% had earthen floor, and 51.8% lacked indoor tap water. Pigs were raised in 46.4% of households, of which 70% allowed their pigs roaming freely. A human seroprevalence rate of 18.7% and a taeniasis prevalence rate of 2.4% were found. Only four persons answered correctly 2: 6 out of ten T. soliurn knowledge questions, for an average passing score of 2.9%. In general, a serious gap exists in knowledge regarding how humans acquire the infections, especially neurocysticercosis was identified. After regression analysis, the ability to recognize adult tapeworms and awareness of the clinical importance of taeniasis, were found to be significant risk factors for T. soliurn seropositivity. These results demonstrate a high level of transmission and a low level of kn~,wledge about Taenia soliurn in Jalaca. Consequently, intervention measures integrated with health education are necessary to decrease the burden caused by this parasite.