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Hypoxia refers to any condition in which the water is less than fully saturated with oxygen. Although it is generally accepted that adults are more tolerant of hypoxic conditions than larval stages, there is little information to support this assumption. To determine whether reduced concentrations of dissolved oxygen (DO) affect fishes differently during various early life stages, I examined the responses of two species of fish (fathead minnows (Pimephales promelas) and rainbow trout (Oncorhynchus mykiss)) exposed to low dissolved oxygen concentrations at different ages during the first 100 days post-hatch. The changes in oxygen requirements and respiratory patterns that occur during ontogeny and exposure to hypoxia were observed. The results of this study suggest that the early larval stages appear to be at least as tolerant of short-term exposure to low dissolved oxygen concentrations as the older, more developed stages. Fathead minnows underwent a gradual transition from being metabolic conformers to regulators during development. Hemoglobin appeared to be playing a larger role in oxygen supply in the early post-hatch trout than in the minnows. Fathead minnow larvae produced relatively low concentrations of lactate upon exposure to hypoxia. Conversely, rainbow trout larvae exhibited significant increases in lactate concentration under similar conditions. This implies that there is a threshold oxygen concentration below which trout larvae utilize anaerobic metabolism to provide additional energy. Lactate dehydrogenase activity increased as the rainbow trout larvae aged, suggesting that they develop an anaerobic capacity which could be used to provide additional energy during hypoxia. The minnows did not exhibit this increase in activity. The ability of larval fishes to detect and avoid hypoxic conditions was also examined. The overall trends suggest that throughout this period of development, both fish species gradually leave an area as the dissolved oxygen concentration decline. Both species appeared to leave the hypoxic areas with deliberate motions, indicating that a directed sensor system allowed them to detect oxygen gradients. The results suggest that a combination of physiological, biochemical, and behavioral mechanisms may allow fishes to cope with hypoxia. / Ph. D.

The aim of this thesis was to investigate the extent of peripheral and central components in the development of fatigue during maximal exercise. Fatigue during maximal and supramaximal exercise has traditionally been modelled from the peripheral context of an inadequate capacity to supply metabolic substrate to the contracting muscles to meet the increased energy demand. However, there are a number of observations that are not compatible with the peripheral fatigue model but which support a reduced central drive during exercise acting to prevent organ failure that might occur should the work be continued at the same intensity. Candidates for the role of “exercise stopper” have been identified as mechanical forces, teleoanticipation, cardiovascular capacity and dyspnoea. We explored these various possibilities in order to determine the most likely cause of exercise cessation during high intensity exercise.The development of a plateau in oxygen consumption during maximal incremental exercise has traditionally been used as evidence that an oxygen deficiency in the exercising muscles causes the termination of exercise. However, the incidence of this “plateau phenomenon” depends largely on mode of exercise, testing protocol and sampling frequency. The aim of this study was to examine whether the development of the “plateau phenomenon” is an artefact of pedalling cadence. In the first study nine healthy individuals performed in random order a maximal incremental ramp test (0.5 W.s-1) on four occasions at a fixed cadence of 60, 80 or 100 rpm and at a self-selected cadence. Oxygen consumption (VO2), CO2 production (VCO2), minute ventilation (VE) and heart rate were measured throughout each trial and averaged over 30 s. Cadence was recorded every second. Neither VO2max nor peak power output were different between trials. Submaximum VO2, VCO2 and VE were not influenced by cadence. A plateau in oxygen consumption was observed in 14% of the trials. Cadence declined significantly towards the end of the self-selected cadence trial (p < 0.05). This ramp protocol produces a low incidence of the “plateau phenomenon” and the measured physiological variables are unaffected by cadence. Furthermore, only one subject displayed this phenomenon on more than one occasion. This confirms that the “plateau phenomenon” is an artefact of the testing protocol. The significant fall in cadence in anticipation of exercise termination during the self-selected cadence trial indicates the presence of a neural regulation, which would lead to a “plateau phenomenon” in those cycle tests in which the work rate is cadence-dependent.The purpose of the second study was to assess whether pacing strategies are adopted during supramaximal exercise bouts lasting longer than 30 s. Eight healthy males performed six Wingate Anaerobic Tests (WAnT). Subjects were informed that they were performing four 30 s WAnT and a 33 s and 36 s WAnT. However, they actually completed two trials of 30, 33 and 36 s each. Temporal feedback in the deception trials was manipulated so that subjects were unaware of the time discrepancy. Power output (PO) was determined from the angular displacement of the flywheel and averaged over 3 s. The peak power (PPI), mean power (MPI) and fatigue (FI) indices were calculated for each trial. Power output was similar for all trials up to 30 s. However, at 36 s the PO was significantly lower in the 36 s deception trial compared to the 36 s informed trial (392 ± 32 W vs 470 ± 88 W) (p < 0.001). The MPI was significantly lower in the 36 s trials (714 ± 76 W and 713 ± 78 W) compared to the 30 s trials (745 ± 65 W and 764 ± 82 W) although they were not different at 30 s (764 ± 83 W and 755 ± 79 W). The significant reduction in FI was greatest in the 36 s deception trial. In conclusion, the significant reduction in PO in the last six seconds of the 36 second deception trial, but not in the 36 second informed trial, indicates the presence of a pre-programmed 30 second “end point” based on the anticipated exercise duration from previous experience. Furthermore the similarity in pacing strategy in all informed trials suggests that the pacing strategy is centrally regulated and is independent of the total work to be performed.Athletes adopt a pacing strategy to delay fatigue and optimise athletic performance. However, many current theories of the regulation of muscle function during exercise do not adequately explain all observed features of such pacing strategies. We studied power output, oxygen consumption and muscle recruitment strategies during successive 4km cycling time trials to determine whether alterations in muscle recruitment by the central nervous system could explain the observed pacing strategies. Seven, highly trained cyclists performed three consecutive 4 km time trial intervals, each separated by 17 minutes. Subjects were instructed to perform each trial in the fastest time possible, but were given no feedback other than distance covered. Integrated electromyographic (iEMG) readings were measured at peak power output and for 90 s before the end of each trial. Subjects reach a VO2max in each interval. Time taken to complete the first and third intervals was similar. Peak power output was highest in the first interval but average power output, oxygen consumption, heart rate and postexercise plasma lactate concentrations were not different between intervals. Power output and iEMG activity rose similarly during the final 60 s in all intervals but were not different between trials. The similar pacing strategies in successive intervals and the parallel increase in iEMG and power output towards the end of each interval suggests that these pacing strategies could not have been controlled by peripheral mechanisms. Rather, these findings are compatible with the action of a centrally regulated that are recruited and de-recruited during exercise. The extent to which peripheral feedback influences recruitment patterns could not be determined from these experiments.The fourth study examined whether the supplementation of inspired air with a hyperoxic mixture results in a dose-dependent increase in peak work rate and maximal oxygen consumption (VO2max) during a ramp test to volitional exhaustion. To avoid the methodological disadvantages associated with breathing the gas mixtures from mixing bags, the trials were performed in a sealed chamber in which the oxygen fraction (FIO2) in the ambient air was altered and subjects were able to inhale directly from the environment. The three oxygen fractions in which the subjects exercised were 21% (room air), 35 or 60%. Arterial blood sampling occurred at rest and every 3 min during the trial. The blood was analysed for the partial pressure of oxygen (pO2), and carbon dioxide (pCO2); pH; oxygen saturation (sO2); haemoglobin saturation (O2Hb); and lactate concentrations. Expired gas and heart rate were measured continuously. Arterial sO2 and O2Hb were elevated in both hyperoxic conditions and did not fall throughout either trial. However in the normoxic trial sO2 and O2Hb declined over the duration of the trial. Lactate concentrations and pH were similar between all trials. VO2max was significantly higher with an FIO2 of 35 and 60% but was not different between hyperoxic conditions. Maximal ventilation (VEmax), carbon dioxide production (VCO2max) and heart rate were similar for all trials. Peak power output was increased in the trained athletes in the 60% FIO2 trial. Since the plateau phenomenon occurred infrequently in all trial (~9%) and the effect of hyperoxia on performance was less than the changes in blood oxygen carrying capacity, we conclude that hyperoxia improved exercise performance not solely by increasing oxygen delivery to the exercising muscles.In order to be able to directly compare the results from studies using different equipment it is important to know the interchangeability of the results from the machines. The fifth study tested the reliability and interchangeability of the two automated metabolic gas analyser systems that would be used in this series of studies at a range of submaximal workloads. Eight highly trained cyclists performed two incremental submaximal cycle ergometer tests. For each session either a Schiller CS-200 or a Vmax Series 229 automated gas analyser was used for expired gas analysis. Data for oxygen consumption (VO2), CO2 production (VCO2), minute ventilation (VE) and respiratory exchange ration (RER) were averaged for each of the five stages (200, 250, 275, 300 and 325 W). The VO2, VE and RER were similar between trials at all workloads. However, VCO2 was significantly lower in the Schiller trial at workloads above 200 W (p < 0.05). Although there was a significant correlation between the two automated systems for the measured parameters (VO2 = 0.78; VCO2 = 0.80; VE = 0.82; RER = 0.72) (p < 0.05), a Bland-Altman plot revealed that the limits of agreement between the two systems were unacceptably large (VO2 = 0.53 to 1.30 L.min-1; VCO2 = 0.55 to 0.64 L.min-1; VE = -22.3 to 30.3 L.min-1; RER = - 0.03 to 0.13). The co-efficient of variation within the analysers was insignificant for both systems. Both the systems provide reliable measures of expired gas parameters. However, care should be taken in directly comparing studies that have used the two different systems due to the poor agreement between the systems.The factors causing the termination of maximal exercise at sea level are unknown. A widely held view is that skeletal muscle anaerobiosis consequent to an inadequate oxygen delivery to the exercising muscles limits exercise. However, there is also evidence that respiratory muscle fatigue at the high ventilatory volumes achieved during maximal exercise delivery and respiratory muscle work on maximal exercise performance, we exercised 8 highly trained cyclists in a pressure-sealed chamber in which O2 concentrations were manipulated and helium (He) was substituted for nitrogen in the ambient air in order to reduce the work of breathing during exercise. This system ensured that external inspiratory and expiratory resistance was minimised and identical in all experimental conditions and approximated conditions present during usual exercise. During trials with O2 enriched ambient air the peak work rate increased (451 ± 58 W vs. 429 ± 59 W). Neither maximum nor submaximal oxygen consumption was altered in FIO2 of 35% (5.0 ± 0.6 l.min-1) compared to 21% (4.9 ± 0.7 l.min- 1). Substituting helium for nitrogen had no additional effect on work (453 ± 56 W) or VO2max (4.9 ± 0.7 l.min-1) beyond those observed for the hyperoxic conditions. Although submaximum VE was reduced with helium, VEmax was unchanged. Since exercise was terminated at the same peak work rate (± 5 W) in the two hyperoxic conditions we postulate that the actual work rate may be the sensed variable that determines maximal exercise performance. The findings from these studies suggest that the maintenance of physiological homeostasis and the avoidance of organ and cellular damage are of fundamental importance during maximal exercise. This is achieved through central regulation of work output based, possibly, on afferent information from the mechanoreceptors in the exercising skeletal muscles or alternatively, the extent of motor unit recruitment during maximal exercise may be hardwired in the central nervous system in a system of feed-forward control.

Sphingosine 1-phosphate (S1P) is a cellular signaling molecule that has been implicated in a variety of diseases including cancer, fibrosis, Alzheimer's, and sickle cell disease. It is formed from the phosphorylation of sphingosine (Sph) by sphingosine kinase (SphK) and SphK exists as two isoforms-"SphK1 and SphK2, which differ with respect to their cellular activity and localization. As the key mediators in the synthesis of S1P, SphKs have attracted attention as viable targets for pharmaceutical inhibition. To validate their potential as therapeutic targets, we aimed to develop potent, selective, and in vivo active inhibitors of SphK. Herein, we describe the design, synthesis and biological evaluation of SphK2 inhibitors. We first describe the development of six SphK2 inhibitors that assess the utility of replacing lipophilic tail groups with heterocyclic rings. These six compounds demonstrate that the lipid binding pocket for SphK2 cannot accommodate compounds with tail groups that are conformationally restricted or positively charged. We then describe the development of aminothiazole-based analogues of an SphK1-selective inhibitor. A library of 37 aryl-substituted aminothiazole tail groups were synthesized, revealing a structure-activity relationship study that examines electronic effects on the aryl-substituted aminothiazoles and the effect of modifying the amino portion of the aminothiazole. These molecules show surprisingly good potency and selectivity for SphK2. In particular, we highlight 3.20dd (SLC4101431), a biphenyl aminothiazole that is the post potent and selective SphK2 inhibitor to date, with an SphK2 Ki of 90 nM and 100-fold selectivity for SphK2. This molecule's in vivo activity will also be discussed. Mitochondrial uncouplers are small molecules that shuttle protons from the inter membrane space to the mitochondrial matrix independent of ATP synthase, which disrupts oxidative phosphorylation and promotes increased nutrient metabolism for homeostasis to be maintained. Consequently, small molecule mitochondrial uncouplers have been pursued as probes for mitochondrial function and as potential therapeutics for the treatment of obesity and type 2 diabetes. Herein, we describe the design, synthesis, and biological evaluation of small molecule mitochondrial uncouplers. We report a library of 52 compounds that have good mitochondrial uncoupling activity over a wide therapeutic range, including 5.16t (SHC4111522) and 5.17i (SHC4091665), which have EC50 values of 0.63 uM and 1.53 uM, respectively, and achieve at least 2-fold increase in oxygen consumption rates relative to basal levels. With these molecules, we demonstrate that pKa and cLogP significantly contribute to uncoupling activity and must be accounted for when developing new generation small molecule mitochondrial uncouplers. / Ph. D. / Sphingosine kinase 1 and 2 (SphK1 and SphK2) are enzymes that facilitate the production of the biomolecule sphingosine 1-phosphate (S1P), which plays an essential role in cell growth and survival. However, overproduction of S1P has been linked to a number of diseases including cancer, Alzheimer’s, and sickle cell disease. Therefore, because S1P is involved in these diseases, the amount of available S1P must be controlled. This work describes the design, development, and biological study of over 40 compounds that could be used as potential inhibitors of SphK2 to help control S1P levels and, therefore, hopefully alleviate the effects of disease. In particular, this work describes molecules that probe the SphK2 binding pocket and demonstrates that the molecules cannot be rigid or positively charged when binding to the hydrophobic portion of the SphK2 binding pocket. Additionally, this work describes the most potent and selective reported SphK2 inhibitor to date, 3.20dd (SLC4101431). Mitochondrial uncouplers are compounds that target our body's mitochondria and aim to make ATP production challenging, causing the mitochondria to burn extra energy in the form of glucose and fatty acids to allow normal levels of ATP to be produced. By making the mitochondria burn extra energy, mitochondrial uncouplers have the potential to be treatments for diseases such as obesity and diabetes. This works describes the design, development, and biological study of over 50 mitochondrial uncouplers that are capable of increasing mitochondrial activity over a wide concentration range, including 5.16t (SHC4111522) and 5.17i (SHC4091665), which are very potent and effective uncouplers.

Five indicators of water quality, namely biochemical oxygen consumption in five days, chemical oxygen consumption by dichromate method, nitrate nitrogen, ammonium nitrogen and total phosphorus, were determined in the river Stropnice. The samples were monitored at four offtake places along the river monthly during the year 2013. Twice a year water samples were analyzed also fromthe dischargeof the wastewater treatment plants. The results show that some changes of the individual parameters can be traced during the year, such as increase of oxygen consumption and total phosphorus in the summer months. However, no significant fluctuation was indicated for the measured parameters at any of the offtake places. Based on the values of the individual parameters water in Stropnice can be ranked to quality classes II. - IV. In the long-term frame of water quality examination from the year 2008 average indicators' values and characteristic values were determined. The results revealed that neither in this case substantial changes of water quality regarding the measured indicators can be observed.

One of the most meaningful technical innovations in cycling over the past two decades was the development of mobile power meters. With the ability to measure the physical strain under “real world” outdoor conditions, the knowledge of the demand during cycling has improved enormously. Power output has been described as the most direct measure of intensity during cycling and consequently power meters becomes a popular tool to monitor the training and racing of cyclists. However, only limited research data are available on the utilisation of power meters for performance assessment in the field or the analysis of training data. Therefore, the aims of the thesis were to evaluate the ecological validity of a field test, to provide an extensive insight into the longitudinal training strategies of world-class cyclists and to investigate the effects of interval training in the field at difference cadences. The first study aimed to assess the reproducibility of power output during a 4-min (TT4) and a 20-min (TT20) time-trial and the relationship with performance markers obtained during a laboratory graded exercise test (GXT). Ventilatory and lactate thresholds during a GXT were measured in competitive male cyclists (n = 15; VO2max 67 ± 5 mL . min−1 . kg−1; Pmax 440 ± 38 W ). Two 4- min and 20-min time-trials were performed on flat roads. Strong intraclass-correlations for TT4 (r = 0.98; 95 % CL: 0.92-0.99) and TT20 (r = 0.98; 95 % CL: 0.95-0.99) were observed. TT4 showed a bias ± random error of −0.8 ± 23W or −0.2 ± 5.5%. During TT20 the bias ± random error was −1.8 ± 14 W or 0.6 ± 4.4 %. Both time-trials were strongly correlated with performance measures from the GXT (p < 0.001). Significant differences were observed between power output during TT4 and GXT measures (p < 0.001). No significant differences were found between TT20 and power output at the second lactate-turn-point (LTP 2) (p = 0.98) and respiratory compensation point (RCP) (p = 0.97). In conclusion, TT4 and TT20 mean power outputs are reliable predictors of endurance performance. TT20 was in agreement with power output at RCP and LTP 2. Study two aimed to quantify power output (PO) and heart rate (HR) distributions across a whole season in elite cyclists. Power output and heart rate were monitored for 11 months in ten male (age: 29.1 ± 6.7 y; VO2max: 66.5 ± 7.1 mL . min−1 . kg−1) and one female (age: 23.1y; VO2max: 71.5 mL . min−1 . kg−1) cyclist. In total, 1802 data sets were sampled and divided into workout categories according to training goals. The PO at the RCP was used to determine seven intensity zones (Z1-Z7). PO and HR distributions into Z1-Z7 were calculated for all data and workout categories. The ratio of mean PO to RCP (intensity factor, IF) was assessed for each training session and for each interval during the training sessions (IFINT). Variability of PO was calculated as coefficient of variation (CV ). There was no significant difference in the distribution of PO and HR for the total season (p = 0.15), although significant differences between workout categories were observed (p < 0.001). Compared with PO, HR distributions showed a shift from low to high intensities. IF was significantly different between categories (p < 0.001). The IFINT was related to performance (p < 0.01), although the overall IF for the session was not. Also, total training time was related to performance (p < 0.05). The variability in PO was inversely associated with performance (p < 0.01). In conclusion, HR accurately reflects exercise intensity over a total season or low intensity workouts but is limited when applied to high intensity workouts. Better performance by cyclists was characterised by lower variability in PO, greater training volume and the production of higher exercise intensities during intervals. The third study tested the effects of low-cadence (60 rev . min−1) uphill (Int60) or high-cadence (100 rev . min−1) flat (Int100) interval training on PO during 20 min uphill (TTup) and flat (TTflat) time-trials. Eighteen male cyclists (VO2max: 58.6 ± 5.4 mL . min−1 . kg−1) were randomly assigned to Int60, Int100 or a control group (Con). The interval training comprised of two training sessions per week over four weeks, which consisted of 6 bouts of 5 min at the PO at RCP. For the control group, no interval training was conducted. A two-factor ANOVA revealed significant increases on performance measures obtained from GXT (Pmax: 2.8 ± 3.0 %; p < 0.01; PO and VO2 at RCP: 3.6 ± 6.3 % and 4.7 ± 8.2 %, respectively; p < 0.05; and VO2 at ventilatory threshold: 4.9 ± 5.6 %; p < 0.01), with no significant group effects. Significant interactions between group and the uphill and flat time-trials, pre vs. post-training on time-trial PO were observed (p < 0.05). Int60 increased PO during both, TTup (4.4 ± 5.3 %) and TTflat (1.5 ± 4.5 %), whereas the changes were − 1.3 ± 3.6 %; 2.6 ± 6.0 % for Int100 and 4.0 ± 4.6 %; − 3.5 ± 5.4 % for Con, during TTup and TTflat, respectively. PO was significantly higher during TTup than TTflat (4.4 ± 6.0 %; 6.3 ± 5.6 %; pre and post-training, respectively; p < 0.001). These findings suggest that higher forces during the low-cadence intervals are potentially beneficial to improve performance. In contrast to the GXT, the time-trials are ecologically valid to detect specific performance adaptations.

Skeletal muscle dysfunction in chronic obstructive pulmonary disease (COPD) is a condition in which peripheral skeletal muscle undergoes myopathic changes which impair muscle function, limit physical performance, and can lead to significant disability. While the etiology of the dysfunction is unknown, this study was conducted to test the hypothesis that chronic hypoxemia leads to alterations in oxygen transport and muscle function. A primary objective was to validate elastase-induced emphysema in rats as an animal model of skeletal muscle dysfunction in COPD.Arterial blood gases were used to determine the severity of hypoxemia and sodium dodecyl sulfate- polyacrylamide gel electrophoresis was used to determine the proportions of myosin heavy chain isoforms I, IIa, IIx, and IIb. Measures of microvascular oxygenation and blood flow in the spinotrapezius muscle allowed for determination of both convective and diffusive oxygen supply to the muscle, as well as calculation of muscle oxygen consumption at rest and during electrically stimulated three-minute muscle contractions. Muscle performance measures included peak force, force-time integral, and fatigue index. Due to a presumed rat respiratory virus, which likely resulted in the control group being nearly as hypoxemic as the elastase-induced emphysema group, this study was not able to definitively test the hypothesis that chronic hypoxemia leads to both a diminished supply and demand of oxygen in skeletal muscle. Although many of the results of the present study were not statistically significant, they exhibited consistent trends over time and are likely of physiological significance. All measures of muscle performance were lower in the emphysema group. In addition, spinotrapezius muscle oxygen consumption and blood flow were lower in the emphysema group. The addition of supplemental oxygen during isolated, small-muscle mass exercise did increase the force-time integral by ~18% in both groups, suggesting that muscle work in these hypoxemic animals may be limited by oxygen supply. Thus, the data on muscle fiber type, oxygen consumption and muscle performance suggest that elastase-induced emphysema in rats leads to a similar skeletal muscle dysfunction that is observed in humans with COPD, and indicates that it is a valid animal model of skeletal muscle dysfunction in COPD.

Title: The relationship between rest and the maximum spirometric indicators in the triathlon Made by: Bc. Zdeněk Kučera Supervisor: Mgr. Lenka Kovářová, Ph.D., MBA Objectives: The aim of thesis is to analyze the relationship between rest and the maximum spirometric indicators for triathletes, who are members of the SCM. It will be also determined whether the analyzed indicators show statistically significantly better performance of triathletes in the representation compared to other triathletes in the SCM. Methods: Data were collected on basis of standard test, which was attended by triathletes in term of SCM. Data were statistically analyzed based on correlation analysis and unpaired non-parametric test. Statistical significance was assessed at the level of 0.05 or 0.01. Results: In the group of men can be confirmed that between rest and maximum indicators is statistically significant correlation relationship (except for respiratory rate and the economy). Another output is achieved for women, a statistically significant relationship exists mainly between rest spirometric indicators and tidal volume and respiratory rate. Higher values of VO2max is achieved in groups with better performance, this is valid for both group of men and women. Keywords: diagnostics, maximum oxygen consumption, vital...

Title The energy performance at the growth rate in ski-mountaineering Objectives Measure group skialpinists of different ages and performance of the ski-mountaineering simulator with a gradient 21ř and speed 1,4 km/h to 5,4 km/h with increasing 0,4 km/h in every minute. Determine their energy expenditure in different speeds as the speed increases and with constant slope. Methods Seven ski-mountaineerers of different levels were testing in laboratory of ski-mountaineering simulator. We calculate of maximum oxygen consumption and anaerobic threshold. Results The probands attained average energy expenditure 8,18 kJ per minute at the end of the first minutes and they attained average energy expenditure 29,32 kJ per minute at the end of the 10th minutes. The average energy expenditure of probands increased by 2,35 kJ per minute an average with a standard deviation 0,69 kJ per minute. Keywords ski-mountaineering, heart rate, oxygen consumption, ski-mountaineer trainer.