Previous research has shown an inverse relationship between age and the relative intensity at which ventilatory threshold (VT) occurs in adolescent boys. However, no study has examined the effect of maturity status on VT in the differences in boys from the onset of puberty, adolescents. The purpose of this study was to compare VT among adolescent boys of different maturational groups. Methods: For this study, moderately active adolescent male participants (14 ± 3 y) completed this study. Maturational status of the participants was determined via years from peak height velocity (PHV), which is an estimation of somatic maturity status derived from age, standing height, seated height, body mass, and leg length. Participants were categorized into PRE- (lesser than 1 year till PHV), PERI- (within 1 year of PHV), and POST-PHV (greater than 1 year past PHV). All participants completed a ramp graded exercise test on a cycle ergometer. During the test, participants were given a three-minute warm-up with no resistance before starting at a workload of 30 watts which increased at a rate of 1 watt every 3 seconds until volitional fatigue. Throughout the test, oxygen consumption (VO2) and ventilation were measured. VT was determined, as a percentage of VO2max, from the ventilation versus VO2 graph using the maximal deviation method. Differences in VT between maturational groups were examined using one-way ANOVA. Results: A significant (F=5.36; p=0.014) difference in VT among maturational groups was found (Appendix A, Figure 2). Post hoc analysis revealed that PRE (p=0.029) and PERI (p=0.009) had VT occur at a significantly greater relative percentage of VO2max than POST. However, no significant (p=0.970) differences were found between PRE and PERI (Appendix A, Figure 3). Conclusion: Adolescent males in PRE and PERI demonstrated higher VT as a percentage of their VO2max compared to POST. This finding suggests the differences in the delayed switch from aerobic to anaerobic metabolism during incremental exercise in adolescent boys who are PRE and PERI.

No description available.

No description available.

All forms of exercise equipment require a period of habituation in which individuals adapt to the novel movement required in operating the device and reach a point of physiological stability. During this adaptation period, physiological variables which indicate cardiopulmonary demand typically will change. In general, such changes are expected with devices that require complex movements. The influence of this habituation on physical performance is vital for establishing research methodology in which precise control of power output is necessary. The StairMaster® corporation has recently introduced the CrossRobics™ 2650UE (2650UE), an ergometer which simulates the kayak stroke pattern. In contrast to bicycle and arm crank ergometers, with which the user follows a set motion, the 2650UE allows the user to adopt a variety of movement patterns. To determine responses during habituation to the 2650UE, 14 female and 12 male subjects (18-32 years of age) were monitored during their first four exercise trials. Each session was 10 min long at a constant load of 0.36 watts/kg ± 0.02SD and 0.55 watt/kg ±0.02SD for female and male subjects, respectively. Significant differences (p<O.OOI) were found for V02, -.vO₂, -.vE, HR and RPE across the four trials, with decreases of 6.3% to 9.5% from the mean values in trial 1 to trial 2. Post hoc analysis indicates that a minimum of two 10 min practice trials are required for measures of oxygen consumption to stabilize, whereas one 10 min practice trial is required for measures of-.v E, HP and RPE to stabilize. / Master of Science

Mitochondrial uncouplers have the capacity of passively shuttling protons from the mitochondrial intermembrane space to the mitochondrial matrix, independent of ATP synthase. This results in the disruption of oxidative phosphorylation and increased rate of metabolism as a counter action from the mitochondria. Therefore, small molecule mitochondrial uncouplers have potential for the treatment of obesity, diabetes, non-alcoholic fatty liver disease (NAFLD), neurodegenerative disorders, amongst others. A one-pot method for the synthesis of 1H-imidazo[4,5-b]pyrazines from [1,2,5]oxadiazolo[3,4-b]pyrazines is herein disclosed. In the presence of Fe, Yb(OTf)3, and the desired electrophile partner, in situ reduction of the oxadiazole fragment followed by cyclization afforded imidazolopyrazines in moderate to good yields. The selection of different orthoesters as electrophiles also allowed functionalization on the 2-position of the imidazole ring. This new method was used to synthesize 1H-imidazo[4,5-b]pyrazines to perform structure-activity relationship studies. Thus, a library of 75 compounds was synthesized and characterized for mitochondrial uncoupling activity. The biological activity of the compounds was demonstrated in oxygen consumption rate assays affording potent mitochondrial uncouplers. The method was further applied to the synthesis of 5-alkoxy-2-(trifluoromethyl)-1H-imidazo[4,5-b]pyrazin-6-amines, with over 50 derivatives synthesized. A structure-activity relationship study was performed using a variety of substituents to fine-tune the scaffold's potency. The installation of a methoxy group at the 5-position of the scaffold resulted in the discovery of compound 4.3.20, which exhibited the best activity with an EC50 of 3.6 ± 0.4 μM in rat L6 myoblasts and a half-life of 4.4 h in mice. Compound 4.3.20 displayed potential as an anti-obesity agent in a mouse model with an effective dose of 50 mg kg-1 without changes in food intake or lean mass. Tissue distribution studies revealed predominance in the liver and both white and brown adipose tissue. In addition, 4.3.20 improved serum markers of insulin sensitivity and hyperlipidemia such as insulin, glucose, triglycerides, cholesterol, and HOMA-IR. Taken together, compound 4.3.20 and related mitochondrial uncouplers show promise for further development in the treatment of obesity and other diseases. / Doctor of Philosophy / The mitochondria, which is an organelle within our cells, is where all the nutrients ingested in the form of food are metabolized, and either used for energy or stored as fat if they are not used. The latter is the main cause of obesity, carrying with it a myriad other comorbidities, such as high blood pressure, heart disease, diabetes, certain types of cancer. Obesity has become a great concern with an incidence of 42% in the US. Mitochondrial uncouplers are molecules that target the mitochondria with a mechanism of action of converting some of the energy ingested in the form of nutrients to be lost as heat instead of being stored as fat. The potential result is a regulated form of weight-loss. Herein, we developed a method for the synthesis of a novel mitochondrial uncoupler scaffold and disclose the mitochondrial uncoupler activity of over 150 molecules. In particular, compound 4.3.20 was tested in an obesity mouse model and was shown to induce fat loss with mice fed a high fat diet. Our investigations support potential use of mitochondrial uncouplers as a mechanism for the treatment and prevention of obesity and other metabolic diseases.

Understanding the respiratory physiology and energy metabolism is important for establishing the dissolved oxygen (DO) requirements of freshwater mussels, determining the metabolite(s) indicative of environmental stress, and interpreting environmental conditions based on physiological indicators of mussels. Three studies were undertaken to address these questions. The first study was conducted with seven mussel species collected from reservoir and riverine habitats. The two objectives were to determine the diurnal patterns of valve gaping of freshwater mussels from different habitats, and to monitor heart rate changes of a mussel species that exhibited the diurnal gaping. The results showed that night gaping is evident for the mussels collected from lentic areas, but not for those collected from lotic areas. The heart rate of Pyganodon grandis increased when they gaped. The second study was conducted with nine species of freshwater mussels from different habitats. The three objectives were to determine the patterns (i.e., regulator and conformer) of oxygen consumption (OC) rate under declining DO, evaluate the effects of temperature on ability to regulate OC under declining DO, and finally to use this information to predict DO criteria for maintaining freshwater mussels in captivity. The results showed that mussels living in the habitats subjected to low DO have a better ability to regulate the OC and were more tolerant to hypoxia. The third study assessed three mussel species from different habitats with different abilities to regulate OC under low DO. The two objectives in this study were to identify the energetic metabolite changes under different DO levels and air exposure for the three species, and to determine the appropriate tissue(s) and metabolite(s) to use for estimating the stress in mussels. The results showed that different biochemical strategies were used by Villosa iris, Elliptio complanata, and Pyganodon grandis. Villosa iris had the lowest anaerobic capacity. Elliptio complanata had a more efficient anaerobic metabolism, and P. grandis reduced energy metabolism under low DO and air exposure. posterior adductor muscle, gill and mantle were good tissues for evaluating hypoxic stress. The mantle tissue had the highest glycogen store and was the best tissue for non-lethal study of physiological condition. / Ph. D.

Background: The maximum rate of oxygen consumption (V̇O2max) can be measured through numerous tests, either directly or indirectly, where direct methods are considered more accurate, whereas indirect methods are more of an estimation with various degrees of reliability. Cooper's Test is one example of an indirect method considered reliable in estimating V̇O2max, with reliability coefficients ranging between 0.897-0.960. Cooper's Test is thus a test that is often used when estimating V̇O2max. However, there is a lack of test-retest research done utilising Cooper's Test on a younger population, which is the reasoning behind this study focusing on adolescents. Aim: The aim of the study was to study the test-retest reliability of Cooper's Test, in adolescents aged 16-19 years. Methods: Twelve healthy adolescents, aged 16-19 years, attending a sports high school participated in a test-retest study (test 1 and test 2) of Cooper's Test. The tests were performed on the short sides of a synthetic grass field, with 66 metres between the two sides, were the participants were instructed to cover as much distance as possible, with high motivation and intensity, for the whole 12 minutes of the Cooper's Test. Each individual participant's data was measured, recorded and later analysed. The total distance covered was then translated into miles and compared to Cooper's original estimated maximal oxygen consumption table for an estimation of each participant's V̇O2max value in ml*kg-1*min-1 from test 1 and test 2. The data from the test-retest and its variance was then analysed by a two-way mixed model of intraclass correlation coefficient (ICC) with an absolute agreement type. Results: The analysed data from test 1 and test 2 of Cooper's Test showed the results of an ICC (95% CI) of 0.06 (-0.353 to 0.544), indicating a substantial error variance between the two separate Cooper's Tests. Conclusion: The data and analysis from this study implied that Cooper's Test was not reliable in the study population, consisting of adolescents. Possible factors influencing the result however were lack of participant motivation and the level of intensity variance during the test-retest of Cooper's Test. Further researchers and amateur and professional users should keep these factors in mind when utilising Cooper's Test to predict V̇O2max. More research is needed within this study's age population to draw any definite conclusions on the reliability of Cooper's test on adolescents.

Antarctic fish from the suborder Notothenioidei inhabit what is perhaps the most thermally stable ocean environment on Earth. Evolutionary theory suggests that by specialising for this environment, Antarctic fish have traded-off their ability to respond to variations in temperature, and like their environment, have become extremely stenothermal. However, previous research has revealed that the Antarctic notothenioid fish Pagothenia borchgrevinki is not as thermally limited as evolutionary theory might predict, and is capable of acclimation to 4 ℃ during a one month period. The purpose of the current research was to investigate the physiological mechanisms that underpin this remarkable acclimatory ability. P. borchgrevinki were acclimated for one month to 4 ℃ and changes in oxygen consumption, prolonged swimming ability, cardiovascular function, enzyme activity and haematology were measured. Significant changes in resting oxygen consumption rate and prolonged swimming ability occurred during the acclimation period, and these changes were mediated by adjustments of enzyme activity and specific aspects of the haematology. By monitoring resting oxygen consumption and prolonged swimming ability over a much longer, six month, acclimation period it was confirmed that the adjustments evident during one month at 4 ℃ were sustainable in the long-term, and were not short-term compensatory mechanisms. Interestingly, fish infected with x-cell gill disease did not possess the same ability to acclimate as was demonstrated by healthy P. borchgrevinki. P. borchgrevinki are unusual among the notothenioids, possessing an active, pelagic lifestyle which differs from the sedentary, benthic lifestyle of most other species within the suborder. Therefore, it was hypothesised that the acclimatory ability demonstrated by this species may also be unusual among the notothenioids. To test this hypothesis, the acclimation ability of three sedentary, benthic notothenioids (Trematomus bernacchii, T. hansoni and T. pennellii) was investigated. Results confirmed the hypothesis, with all three species demonstrating very poor survival at 4 ℃ and absolutely no capacity for acclimation. Such results present a disturbing scenario for the future of Antarctic notothenioid fish in Earth?s rapidly warming climate, and highlights the need for continued research combined with immediate action to combat the warming which currently threatens Antarctic marine biodiversity.

Superior swimming stamina in adult fish is presumably passed on to their offspring, but the ontogeny of the appearance of superior stamina and the requisite enhanced cardio-respiratory support for locomotion in larval fishes has not been determined. Is the expression of the suite of parental traits enabling superior swimming stamina in their offspring dependent upon their achieving juvenile/adult morphology, or does it appear earlier in their larvae? To answer this, adults were classified into three groups based on swimming stamina, followed by measurement of length, mass, and width. Larval offspring from the two parental groups -high stamina larvae (HSL) and low stamina larvae (LSL)- were reared at 27°C in aerated water (21% O2). Routine and active heart rate, routine and active mass specific oxygen consumption were recorded through 21dpf, and cost of transport (COT) and factorial aerobic scope were derived from oxygen consumption measurements. Routine heart rate at 2dpf of LSL was 164 ± 1 b·min-1, compared to only 125 ± 2 b·min-1 for HSL. Routine heart rate subsequently peaked at 203 ± 1 b·min-1 at 5dpf in the HSL group, compared to 207 ± 1 b·min-1, at 4dpf in the LSP larvae. Active heart rate at 5 dpf of LSL was 218 ± 2 b·min-1 compared to 216 ± 2 b·min-1 for HSL. Active heart rate increased slightly to 227 ± 2 b·min-1 for LSL before decreasing again, while active heart rate remained relatively constant for HSL. Routine O2 consumption at 2dpf of HSL was 0.09 μmol·mg-1·hr-1, compared to 0.03 μmol·mg-1·hr-1 in LSL. Routine O2 consumption subsequently peaked at 0.70 μmol·mg-1·hr-1 at 9dpf in the HSL, compared to 0.71 μmol·mg-1·hr-1, at 9dpf in the LSL. These values dramatically decreased before leveling off at around 0.20 μmol·mg-1·hr-1 and 0.15 μmol·mg-1·h-1, respectively. Active O2 consumption at 5dpf for HSL was 0.38 μmol·mg-1·hr-1, compared to 0.57 μmol·mg-1·hr-1 for LSL. Active O2 consumption subsequently peaked at 0.97 μmol·mg-1·hr-1 at 10dpf in HSL, compared to 1.19 μmol·mg-1·hr-1 at 7dpf in LSL. These values also dramatically decreased and leveled off. Significant differences (p < 0.05) in heart rate and oxygen consumption persisted through 21dpf. The onset of differences observed in routine and active heart rate in early larvae, correlated with parent stamina, show that juvenile or adult features are not required as a precondition for the emergence of phenotypic physiological differences.

Established interspecific metabolic allometric relationships do not adequately describe the complexity and variable physiological states of developing animals. Consequently, intraspecific allometric relationships of oxygen consumption and carbon dioxide production as a function of body mass; the respiratory quotient; the function of the silk cocoon; and body composition were investigated for each distinct developmental stage of the silkworm, Bombyx mori. Whole animal O2 consumption in Bombyx ranged from 0.00064 + 0.000047 ml O2 .hr-1 at larval instar I to 0.77 + 0.06 ml O2 .hr-1 in pre-pupal, falling to 0.21+ 0.01 ml O2 .hr-1 in the pupae. Those instars having a significant relationship between O2 consumption as a function of body mass, the slope of the line relating O2 consumption to body mass varied between 0.99 and 1.02, while across all instars the slope was 0.82. Developmental allometry should be presented for individual developmental stages because the individual allometric exponents of the stages can be significantly different from the overall allometric exponent throughout development and in some cases, the overall allometric exponent can be a statistical artifact. The first larval instar of Bombyx mori has the lowest cross sectional area of high metabolic tissue of the midgut (27%) and had one of the highest percentages of some metabolically inert tissues (i.e. lipid, 7.5%). Body composition of the first instar does not support the idea that smaller mass animals having the highest O2 consumption are composed of a greater percentage of metabolically active organs when compared to larger animals. However, this developmental stage has the highest percentage of the mitochondrial marker cytochrome oxidase, which correlates well with the high O2 consumption rate of the smaller mass. Therefore, established interspecific principles should not be assumed to function as valid models for intraspecific developmental relationships of metabolism as a function of body mass. Developmental allometry should include an analysis of individual stages of development as well as an analysis of development as a whole to gain a comprehensive understanding of the complexity of allometry of the developing animal such as the silkworm.