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 current understanding of lactate metabolism in fish is based almost entirely on interpretation of concentration measurements that cannot be used to infer changes in flux. Moreover, the transporters regulating these fluxes have never been characterized in rainbow trout. My goals were: (1) to quantify lactate fluxes in rainbow trout under normoxic resting conditions, during acute hypoxia, and exercise by continuous infusion of [U-14C] lactate; (2) to determine lactate uptake capacity of trout tissues by infusing exogenous lactate in fish rest and during graded exercise, and (3) to clone monocarboxylate transporters (MCTs) and determine the effects of exhausting exercise on their expression. Such information could prove important to understand the mechanisms underlying the classic “lactate retention” seen in trout white muscle after intense exercise. In normoxic resting fish, the rates of appearance (Ra) and disappearance (Rd) of lactate were always matched (~18 to 13 µmol kg-1 min-1), thereby maintaining a low baseline blood lactate concentration (~0.8 mM). In hypoxic fish, Ra lactate increased from baseline to 36.5 µmol kg-1 min-1, and was accompanied by an unexpected 52% increase in Rd reaching 30.3 µmol kg-1 min-1, accounting for a rise in blood lactate to 8.9 mM. In exercising fish, lactate flux was stimulated > 2.4 body lengths per second (BL s-1). As the fish reached critical swimming speed (Ucrit), Ra lactate was more stimulated (+67% to 40.4 μmol kg-1 min-1) than Rd (+41% to 34.7 μmol kg-1 min-1), causing an increase in blood lactate to 5.1mM. Fish infused with exogenous lactate stimulated Rd lactate by 300% (14 to 56 μmol kg-1 min-1) during graded exercise, whereas the Rd in resting fish increased by only 90% (21 to 40 µmol kg-1 min-1). Four MCT isoforms were partially cloned and characterized in rainbow trout: MCT1b was the most abundant in heart, and red muscle, but poorly expressed in gill and brain where MCT1a and MCT2 were prevalent. MCT4 was more expressed in the heart. Transcript levels of MCT2 (+260%; brain), MCT1a (+90%; heart) and MCT1b (+50%; heart) were stimulated by exhausting exercise. This study shows that: (i) the increase in Rd lactate plays a strategic role in reducing the lactate load imposed on the circulation. Without this response, blood lactate accumulation would double; (ii) a high capacity for lactate disposal in rainbow trout tissues is elicited by the increased blood-to-tissue lactate gradient when extra lactate is administered; and (iii) rainbow trout may be unable to release large lactate loads rapidly from white muscle after exhausting exercise (lactate retention) because they poorly express MCT4 in white muscle and fail to upregulate its expression during exercise.

The current understanding of lactate metabolism in fish is based almost entirely on interpretation of concentration measurements that cannot be used to infer changes in flux. Moreover, the transporters regulating these fluxes have never been characterized in rainbow trout. My goals were: (1) to quantify lactate fluxes in rainbow trout under normoxic resting conditions, during acute hypoxia, and exercise by continuous infusion of [U-14C] lactate; (2) to determine lactate uptake capacity of trout tissues by infusing exogenous lactate in fish rest and during graded exercise, and (3) to clone monocarboxylate transporters (MCTs) and determine the effects of exhausting exercise on their expression. Such information could prove important to understand the mechanisms underlying the classic “lactate retention” seen in trout white muscle after intense exercise. In normoxic resting fish, the rates of appearance (Ra) and disappearance (Rd) of lactate were always matched (~18 to 13 µmol kg-1 min-1), thereby maintaining a low baseline blood lactate concentration (~0.8 mM). In hypoxic fish, Ra lactate increased from baseline to 36.5 µmol kg-1 min-1, and was accompanied by an unexpected 52% increase in Rd reaching 30.3 µmol kg-1 min-1, accounting for a rise in blood lactate to 8.9 mM. In exercising fish, lactate flux was stimulated > 2.4 body lengths per second (BL s-1). As the fish reached critical swimming speed (Ucrit), Ra lactate was more stimulated (+67% to 40.4 μmol kg-1 min-1) than Rd (+41% to 34.7 μmol kg-1 min-1), causing an increase in blood lactate to 5.1mM. Fish infused with exogenous lactate stimulated Rd lactate by 300% (14 to 56 μmol kg-1 min-1) during graded exercise, whereas the Rd in resting fish increased by only 90% (21 to 40 µmol kg-1 min-1). Four MCT isoforms were partially cloned and characterized in rainbow trout: MCT1b was the most abundant in heart, and red muscle, but poorly expressed in gill and brain where MCT1a and MCT2 were prevalent. MCT4 was more expressed in the heart. Transcript levels of MCT2 (+260%; brain), MCT1a (+90%; heart) and MCT1b (+50%; heart) were stimulated by exhausting exercise. This study shows that: (i) the increase in Rd lactate plays a strategic role in reducing the lactate load imposed on the circulation. Without this response, blood lactate accumulation would double; (ii) a high capacity for lactate disposal in rainbow trout tissues is elicited by the increased blood-to-tissue lactate gradient when extra lactate is administered; and (iii) rainbow trout may be unable to release large lactate loads rapidly from white muscle after exhausting exercise (lactate retention) because they poorly express MCT4 in white muscle and fail to upregulate its expression during exercise.

Abstract provided by Publisher Complex performance diagnostics in sports medicine should contain maximal aerobic and maximal anaerobic performance. The requirements on appropriate stress protocols are high. To validate a test protocol quality criteria like objectivity and reliability are necessary. Therefore, the present study was performed in intention to analyze the reliability of maximal lactate production rate (VLamax) by using a sprint test, maximum oxygen consumption (VO2max) by using a ramp test and, based on these data, resulting power in calculated maximum lactate-steady-state (PMLSS) especially for amateur cyclists. All subjects (n=23, age 26 ± 4 years) were leisure cyclists. At three different days they completed first a sprint test to approximate VLamax. After 60 min of recreation time a ramp test to assess VO2max was performed. The results of VLamax-test and VO2max-test and the body weight were used to calculate PMLSS for all subjects. The intra class correlation (ICC) for VLamax and VO2max was 0.904 and 0.987, respectively, coefficient of variation (CV) was 6.3 % and 2.1 %, respectively. Between the measurements the reliable change index of 0.11 mmol∙l-1∙s-1 for VLamax and 3.3 ml∙kg-1∙min-1 for VO2max achieved significance. The mean of the calculated PMLSS was 237 ± 72 W with an RCI of 9 W and reached with ICC = 0.985 a very high reliability. Both metabolic performance tests and the calculated PMLSS are reliable for leisure cyclists.

Adaptation to hypoxia is a well-known phenomenon increasing myocardial resistance to ischemia-reperfusion (I/R) injury as an appropriate physical exercise which improves the contractile function of the heart. Lactate is a major energy substrate for the heart muscle during physical activity and hypoxia. The metabolism of lactate was and still is associated with muscle fatigue, but in the last decades it has been considered its significant modulating function of metabolism during exercise at cellular level and whole organism level. It has been shown that its effects might be similar to the effects of hypoxia and its oxidized form, pyruvate, has the cardioprotective effects. The aim of this study was to compare the expression of LDHA and LDHB isoforms between left and right ventricle in the cardioprotective scheme of adaptation to hypoxia. Another objective/goal was to determine the left ventricular response to I/R insult in the perfused heart model adapted to hypoxia compared with the normoxic controls on/at the expression level of both LDH isoforms. Our results showed differences in the LDHA expression in the left and right ventricle and an increased response of the left ventricle to I/R insult in rats adapted to hypoxia which is reflected at the expression level of both isoforms. Key words: heart,...

Made available in DSpace on 2014-06-11T19:23:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-05-16Bitstream added on 2014-06-13T19:50:57Z : No. of bitstreams: 1 soares_oab_me_jabo_prot.pdf: 1519067 bytes, checksum: 98437b3bc201f8ee82ba7715b0f41aed (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O esporte eqüestre vem exigindo um grau crescente de profissionalismo no mundo todo. Testes de desempenho, como a aferição do Limiar anaeróbio (LA), inserem-se neste contexto. Este trabalho comparou sete protocolos de mensuração do LA, cinco lactacidêmicos (V2, V4, LAI, LAI0,5, Lacmin) e dois glicêmicos (LGI e Glicmin). Todos foram comparados a Máxima fase estável do lactato (MFEL), protocolo padrão de aferição do LA. Catorze eqüinos Puro Sangue Árabe foram utilizados, entre machos e fêmeas. As médias e desvios-padrão das velocidades associadas aos testes foram: V2 = 9,49 ± 0,83 m/s, V4 = 10,83 ± 0,71 m/s, VLAI = 9,62 ± 0,91 m/s, VLAI0,5 = 10,21 ± 0,80 m/s, VLacmin = 7,49 ± 0,55 m/s, VLGI = 7,69 ± 1,68 m/s, VGlicmin = 8,31 ± 1,64 m/s e VMFEL = 6,06 ± 0,51 m/s. Somente a VLacmin não diferiu da VMFEL, além de obter correlação significativa com a mesma de ρ = 0,76 (Correlação de Spearman). A Tendência e os Limites de Concordância entre a VLacmin e a VMFEL foram de 1,43; 0,79 e 2,05. Além de predizer velocidades diferentes da VMFEL, os limiares LAI, LGI e Glicmin apresentaram dificuldades operacionais. As diferenças entre as velocidades preditas pelos protocolos V2, V4, LAI e LAI0,5, LGI e Glicmin a VMFEL podem ser parcialmente explicadas por variações de composição de protocolo e dificuldades operacionais. Apesar de não diferirem estatisticamente, as VLacmin e as VMFEL apresentaram baixa concordância, o que provavelmente pode ser melhorado com ajustes finos no protocolo do Lacmin. / Equestrian sports are demanding a growing degree of professionalism all over the world. Performance tests, as Anaerobic threshold (AT) assessment, are inserted in that context. The present study compared seven protocols for anaerobic threshold assessment: five of them using the lactacidemia (V2, V4, IAT, IAT0.5 and Lacmin) and two glicemia (IGT and Glicmin). All of them were compared to the Maximal Lactate Steady State (MLSS), the gold standard for AT assessment. Fourteen Arabian horses, males and females were submitted to the protocols. Velocity means and standard deviation associated to each protocol were: V2 = 9.49 ± 0.83; V4 = 10.83 ± 0.71; VIAT = 9.62 ± 0.91; VIAT0,5 = 10.21 ± 0.80; VLacmin = 7.49 ± 0.55; VIGT = 7.69 ± 1.68; VGlicmin = 8.31 ± 1.64 e VMLSS = 6.06 ±0.51. Only VLacmin did not differ from VMLSS, moreover, they correlate significantly with ρ = 0.76 (Spearman correlation). Bias ant Limits of Agreement of the two methods were 1.43; 0.79 and 2.05. Besides they predicted different velocities when compared to VMLSS, IAT, IGT and Glicmin showed operational difficulties. The differences between the velocities associated with the several protocols and the VMLSS could be partially attributed to protocol components variations and some operational difficulties. Regardless the statistical equality, VLacmin and VMLSS revealed poor agreement, what could probably be improved with adjustments in the Lacmin protocol.

Orientador: Antonio de Queiroz Neto / Banca: José Corrêa de Lacerda Neto / Banca: Benedito Sérgio Denadai / Resumo: O esporte eqüestre vem exigindo um grau crescente de profissionalismo no mundo todo. Testes de desempenho, como a aferição do Limiar anaeróbio (LA), inserem-se neste contexto. Este trabalho comparou sete protocolos de mensuração do LA, cinco lactacidêmicos (V2, V4, LAI, LAI0,5, Lacmin) e dois glicêmicos (LGI e Glicmin). Todos foram comparados a Máxima fase estável do lactato (MFEL), protocolo padrão de aferição do LA. Catorze eqüinos Puro Sangue Árabe foram utilizados, entre machos e fêmeas. As médias e desvios-padrão das velocidades associadas aos testes foram: V2 = 9,49 ± 0,83 m/s, V4 = 10,83 ± 0,71 m/s, VLAI = 9,62 ± 0,91 m/s, VLAI0,5 = 10,21 ± 0,80 m/s, VLacmin = 7,49 ± 0,55 m/s, VLGI = 7,69 ± 1,68 m/s, VGlicmin = 8,31 ± 1,64 m/s e VMFEL = 6,06 ± 0,51 m/s. Somente a VLacmin não diferiu da VMFEL, além de obter correlação significativa com a mesma de ρ = 0,76 (Correlação de Spearman). A Tendência e os Limites de Concordância entre a VLacmin e a VMFEL foram de 1,43; 0,79 e 2,05. Além de predizer velocidades diferentes da VMFEL, os limiares LAI, LGI e Glicmin apresentaram dificuldades operacionais. As diferenças entre as velocidades preditas pelos protocolos V2, V4, LAI e LAI0,5, LGI e Glicmin a VMFEL podem ser parcialmente explicadas por variações de composição de protocolo e dificuldades operacionais. Apesar de não diferirem estatisticamente, as VLacmin e as VMFEL apresentaram baixa concordância, o que provavelmente pode ser melhorado com ajustes finos no protocolo do Lacmin. / Abstract: Equestrian sports are demanding a growing degree of professionalism all over the world. Performance tests, as Anaerobic threshold (AT) assessment, are inserted in that context. The present study compared seven protocols for anaerobic threshold assessment: five of them using the lactacidemia (V2, V4, IAT, IAT0.5 and Lacmin) and two glicemia (IGT and Glicmin). All of them were compared to the Maximal Lactate Steady State (MLSS), the gold standard for AT assessment. Fourteen Arabian horses, males and females were submitted to the protocols. Velocity means and standard deviation associated to each protocol were: V2 = 9.49 ± 0.83; V4 = 10.83 ± 0.71; VIAT = 9.62 ± 0.91; VIAT0,5 = 10.21 ± 0.80; VLacmin = 7.49 ± 0.55; VIGT = 7.69 ± 1.68; VGlicmin = 8.31 ± 1.64 e VMLSS = 6.06 ±0.51. Only VLacmin did not differ from VMLSS, moreover, they correlate significantly with ρ = 0.76 (Spearman correlation). Bias ant Limits of Agreement of the two methods were 1.43; 0.79 and 2.05. Besides they predicted different velocities when compared to VMLSS, IAT, IGT and Glicmin showed operational difficulties. The differences between the velocities associated with the several protocols and the VMLSS could be partially attributed to protocol components variations and some operational difficulties. Regardless the statistical equality, VLacmin and VMLSS revealed poor agreement, what could probably be improved with adjustments in the Lacmin protocol. / Mestre

Several studies have reported that rating of perceived exertion (RPE) covaries more with blood lactate concentration (BLC) than other measures of relative exercise intensity. If BLC is used as the intensity criterion, then RPE could be used as a valid tool for exercise prescription. However, few have shown the relationship between RPE and BLC across a variety of graded exercise tests (GXTs) and exercise training settings. The purpose of this study was to determine if differences exist in RPEs at matched BLC between two GXTs and steady state exercise in the field setting. Thirteen healthy males (25 ± 5.3 yrs) completed two maximal treadmill protocols (Bruce and Balke) and one steady state exercise trial on a treadmill at two intensities which lasted approximately 7 minutes each. The intensities (40% & 70% max heart rate reserve) were below and above their ventilatory threshold. RPEs were recorded during the last minute of each workload of the field trial (FT). Immediately following the end of each workload, blood samples were collected for BLC analysis. RPEs from the FT were compared with RPEs from the GXTs at matched BI-Cs using a repeated measures ANOVA across exercise trials. The results show that there were no significant differences in RPEs at a matched BLC of 1.5 mM between the FTand and the Bruce and Balke GXT at the lower intensity, with the RPEs being 9.6 ± 1.7, 9.8 ± 2.6, and 10.2 ± 2.4, respectively. However, at the higher intensity, RPEs at a matched BLC of 3.0 mM were significantly different, with the FT < Bruce < Balke (11.9 ± 1.9, 13.5 ± 2.2 and 15.2 ± 2.0, p < 0.05). These results suggest that the relationship between RPE and BLC established during a GXT may not be transferable to the exercise training setting at exercise intensities in the typical prescription range of 50-85%. Therefore, using RPE for exercise prescription may not be an effective method for regulating exercise intensity according to BLC. / School of Physical Education

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

The optimization of powder x-ray diffraction (PXRD) for the study of cheese crystals was the focus of this study. A survey was conducted of various manifestations of calcium lactate crystals on the rindless surface and within mechanical openings of Cheddar cheese using PXRD. The diffraction reference card database contained a card that was entitled calcium lactate pentahydrate and corresponded to some of the crystalline material found on the cheeses. Diffractions patterns generated from other samples of crystalline material revealed the existence of an unknown crystal that resembled and behaved similarly to calcium lactate pentahydrate, but did not match the reference card. The existence of two enantiomeric variants of calcium lactate pentahydrate had been firmly established; an experiment was thus designed to determine if the unknown diffraction pattern represented one enantiomeric form, and if the ambiguously named reference card represented the other. This experiment demonstrated that the existing reference card corresponded to calcium DL-lactate pentahydrate and that the unknown diffraction pattern was generated from calcium L-lactate pentahydrate. This study resulted in the proposal of a new reference card for calcium L-lactate pentahydrate and the proposed renaming of the existing card to calcium DL-lactate pentahydrate. This discovery allows the rapid identification of both forms of calcium lactate that form in and on cheese. In order to conduct the survey and experiment that are described above, the PXRD method needed to be adjusted for use with cheese crystals. Samples of cheese crystals pose a particular challenge because they are often composed of high proportions of moisture, fat, protein, and other amorphous material; these all disrupt the efficient diffraction of crystals and thus needed to be removed or minimized. The removal of water from samples is a particular challenge because some cheese crystals contain water of hydration that may be driven off in the process, thereby destroying the crystals. A protocol for the preparation of cheese samples for PXRD was consequently developed.