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Lindinger MI. Total Carbon Dioxide in Adult Standardbred and Thoroughbred Horses. J Equine Vet Sci 2021; 106:103730. [PMID: 34670689 DOI: 10.1016/j.jevs.2021.103730] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Revised: 08/02/2021] [Accepted: 08/08/2021] [Indexed: 10/20/2022]
Abstract
The TCO2 (total carbon dioxide) test is performed on the blood of racehorses as a means of combatting the practice of administering alkalizing agents for the purpose of enhancing performance. The purposes of this review are to present an overview of the factors contributing to TCO2 and to review the literature regarding TCO2 in adult Standardbred and Thoroughbred horses to demonstrate the range of variability of TCO2 in horses. Most of the research published on the topic of TCO2 or bicarbonate measurement in racehorses was accessed and reviewed. PubMed and Google Scholar were the primary search engines used to source the relevant literature. The main physicochemical factors that contribute to changes in TCO2 in horses at rest are changes in strong ions concentration, followed by changes in weak acid (i.e. plasma albumin) concentrations. There is a wide normal distribution of TCO2 in horses ranging from 23 mmol/L to 38 mmol/L. Independent of administration of alkalizing agents, blood TCO2 is affected mainly by feeding, time of day (diurnal variation), season and exercise. There are few studies that have reported hour-by-hour changes in TCO2. Racehorse population studies suffer from lack of validation regarding whether or not a horse was administered an alkalizing agent. It is concluded that the normal range of TCO2 in non-alkalized Standardbred and Thoroughbred horses is significantly wider than has been appreciated, that periods of elevated TCO2 appear to be normal for many horses at rest, and that a TCO2 test alone is not definitive for the purposes of determining of an alkalizing agent has been administered to a horse.
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Vasileiadis I, Alevrakis E, Gialelis N. Stewart's approach: Just a heresy or another lens into acid-base physiology? Acta Physiol (Oxf) 2021; 232:e13622. [PMID: 33555125 DOI: 10.1111/apha.13622] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ioannis Vasileiadis
- Intensive Care Unit 1st Department of Respiratory Medicine National and Kapodistrian University of AthensSotiria Hospital Athens Greece
| | | | - Nikolaos Gialelis
- Department of Mathematics National and Kapodistrian University of Athens Athens Greece
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Magder S, Magder A, Samoukovic G. Intracellular pH regulation and the acid delusion. Can J Physiol Pharmacol 2020; 99:561-576. [PMID: 33356898 DOI: 10.1139/cjpp-2020-0631] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The hydrogen ion concentration ([H+]) in intracellular cytoplasmic fluid (ICF) must be maintained in a narrow range in all species for normal protein functions. Thus, mechanisms regulating ICF are of fundamental biological importance. Studies on the regulation of ICF [H+] have been hampered by use of pH notation, failure to consider the roles played by differences in the concentration of strong ions (strong ion difference, SID), the conservation of mass, the principle of electrical neutrality, and that [H+] and bicarbonate ions [HCO3-] are dependent variables. This argument is based on the late Peter Stewart's physical-chemical analysis of [H+] regulation reported in this journal nearly forty years ago (Stewart. 1983. Can. J. Physiol. Pharmacol. 61: 1444-1461. Doi:10.1139/y83-207). We start by outlining the principles of Stewart's analysis and then provide a general understanding of its significance for regulation of ICF [H+]. The system may initially appear complex, but it becomes evident that changes in SID dominate regulation of [H+]. The primary strong ions are Na+, K+, and Cl-, and a few organic strong anions. The second independent variable, partial pressure of carbon dioxide (PCO2), can easily be assessed. The third independent variable, the activity of intracellular weak acids ([Atot]), is much more complex but largely plays a modifying role. Attention to these principles will potentially provide new insights into ICF pH regulation.
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Affiliation(s)
- Sheldon Magder
- Department of Critical Care, McGill University Health Centre, 1001 Decarie Blvd, Montreal, QC H4A 3J1, Canada.,Department of Critical Care, McGill University Health Centre, 1001 Decarie Blvd, Montreal, QC H4A 3J1, Canada
| | - Alexandr Magder
- Department of Critical Care, McGill University Health Centre, 1001 Decarie Blvd, Montreal, QC H4A 3J1, Canada.,Department of Critical Care, McGill University Health Centre, 1001 Decarie Blvd, Montreal, QC H4A 3J1, Canada
| | - Gordan Samoukovic
- Department of Critical Care, McGill University Health Centre, 1001 Decarie Blvd, Montreal, QC H4A 3J1, Canada.,Department of Critical Care, McGill University Health Centre, 1001 Decarie Blvd, Montreal, QC H4A 3J1, Canada
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4
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Alevrakis E, Gialelis N, Vasileiadis I. Strong ion difference in urine: A measure of proton excretion or of the net plasma charge alteration? Acta Physiol (Oxf) 2020; 230:e13559. [PMID: 32930472 DOI: 10.1111/apha.13559] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2020] [Revised: 09/08/2020] [Accepted: 09/08/2020] [Indexed: 11/27/2022]
Affiliation(s)
| | - Nikolaos Gialelis
- Department of Mathematics National and Kapodistrian University of Athens Athens Greece
| | - Ioannis Vasileiadis
- Intensive Care Unit 1 Department of Respiratory Medicine National and Kapodistrian University of AthensSotiria Hospital Athens Greece
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Baumann L, Studhalter M. [Lactic Acidosis and Other Misunderstandings]. PRAXIS 2020; 109:979-983. [PMID: 32933388 DOI: 10.1024/1661-8157/a003508] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Lactic Acidosis and Other Misunderstandings Abstract. Lactic acidosis is a frequently encountered clinical problem in intensive care medicine. Nevertheless, many of the underlying biochemical processes are insufficiently understood, which leads to various misconceptions. Physiologically, lactate is an important, continuously produced carrier of energy and by no means a metabolic 'waste product'. Lactate is the corresponding base to lactic acid and is produced directly from pyruvate. In this reaction H+ is consumed and therefore lactate production itself cannot be directly responsible for the simultaneously arising acidosis. An elevated lactate level allows no conclusions about the underlying pathophysiological process, and, more importantly, it is not an appropriate marker for tissue oxygenation.
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Messonnier LA, Gellen B, Lacroix R, Peyrot S, Rupp T, Mira J, Peyrard A, Berkenou J, Galactéros F, Bartolucci P, Féasson L. Physiological Evaluation for Endurance Exercise Prescription in Sickle Cell Disease. Med Sci Sports Exerc 2020; 51:1795-1801. [PMID: 30920486 DOI: 10.1249/mss.0000000000001993] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
PURPOSE Although strenuous exercise may expose sickle cell disease (SCD) patients to risks of vaso-occlusive crisis, evidence suggests that regular endurance exercise may be beneficial. This study aimed to test (i) the safety and usefulness of a submaximal incremental exercise in evaluating physical ability of SCD patients and identify a marker for the management of endurance exercise and (ii) the feasibility of endurance exercise sessions in SCD patients. METHODS Twenty adults with SCD (12 men and 8 women) performed a submaximal incremental exercise used to determine the first lactate threshold (LT1) and stopped as soon as blood lactate concentration ([lactate]b) reached ≥4 mmol·L. Fifteen of those patients (8 men and 7 women) also performed three 30-min endurance exercise sessions at ~2.5 mmol·L of [lactate]b on separate occasions. RESULTS LT1 occurred at 47 ± 3 and 33 ± 3 W for men and women, respectively, demonstrating the extreme deconditioning and, thus, low physical ability of adult SCD patients. During endurance exercise, peripheral oxygen saturation and [lactate]b most often remained stable and within acceptable ranges. CONCLUSIONS The proposed strategy of submaximal incremental exercise allowed safe determination of LT1, an important parameter of patients' physical ability. The study also demonstrated the feasibility and safety of individually tailored endurance exercises at ~2.5 mmol·L of [lactate]b. These latter results suggest that endurance training programs may be considered for adult SCD patients and that the method proposed here may be helpful in that regard.
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Affiliation(s)
- Laurent A Messonnier
- University Savoie Mont Blanc, Inter-university Laboratory of Human Movement Sciences, Chambéry EA7424, FRANCE
| | - Barnabas Gellen
- Department of Cardiac Rehabilitation, Henri-Mondor University Hospital, AP-HP, Creteil, FRANCE.,ELSAN, Polyclinique de Poitiers, Poitiers, FRANCE
| | - Roxane Lacroix
- University Savoie Mont Blanc, Inter-university Laboratory of Human Movement Sciences, Chambéry EA7424, FRANCE
| | - Sandrine Peyrot
- Department of Cardiac Rehabilitation, Henri-Mondor University Hospital, AP-HP, Creteil, FRANCE
| | - Thomas Rupp
- University Savoie Mont Blanc, Inter-university Laboratory of Human Movement Sciences, Chambéry EA7424, FRANCE
| | - José Mira
- University Savoie Mont Blanc, Inter-university Laboratory of Human Movement Sciences, Chambéry EA7424, FRANCE
| | - Arthur Peyrard
- University Savoie Mont Blanc, Inter-university Laboratory of Human Movement Sciences, Chambéry EA7424, FRANCE
| | - Jugurtha Berkenou
- Sickle Cell Referral Center, Department of Internal Medicine, Henri-Mondor University Hospital-UPEC, AP-HP, Créteil, FRANCE
| | - Frédéric Galactéros
- Sickle Cell Referral Center, Department of Internal Medicine, Henri-Mondor University Hospital-UPEC, AP-HP, Créteil, FRANCE.,IMRB, Henri-Mondor Hospital-UPEC, GRex, Créteil, FRANCE
| | - Pablo Bartolucci
- Sickle Cell Referral Center, Department of Internal Medicine, Henri-Mondor University Hospital-UPEC, AP-HP, Créteil, FRANCE.,IMRB, Henri-Mondor Hospital-UPEC, GRex, Créteil, FRANCE
| | - Léonard Féasson
- Inter-university Laboratory of Human Movement Sciences, University of Lyon, UJM-Saint-Etienne, EA7424, Saint-Etienne, FRANCE.,Myology Unit, Referent Center of Rare Neuromuscular Diseases, Euro-NmD, University Hospital of Saint-Etienne, Saint-Etienne, FRANCE
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Reduced expression of carbonic anhydrase III in skeletal muscles could be linked to muscle fatigue: A rat muscle fatigue model. J Orthop Translat 2019; 22:116-123. [PMID: 32440507 PMCID: PMC7231961 DOI: 10.1016/j.jot.2019.08.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2019] [Revised: 08/12/2019] [Accepted: 08/28/2019] [Indexed: 11/21/2022] Open
Abstract
Background Carbonic anhydrase III (CAIII) is expressed abundantly in slow skeletal muscles, adipocytes, and the liver. It plays a critical role in maintaining intracellular pH, antioxidation, and energy metabolism, which are further involved in fatigue. However, its function and mechanism in maintaining the physiological function of muscles or antifatigue are still ambiguous. We hypothesized that changes of CAIII in skeletal muscles might be related to the occurrence of muscle fatigue. Method After establishing a rat soleus muscle fatigue model, we measured the protein expression of the CAIII in muscles. And the muscle intracellular biochemical indices [malondialdehyde (MDA), adenosine triphosphate (ATP), and lactic acid] were also measured using assay kits. After transfected by CAIII-overexpressing and knockdown lentiviral vectors, the rat soleus muscles were induced to fatigue to investigate the effects and possible molecular mechanisms of CAIII in antifatigue. Results The expression of CAIII in fatigued soleus muscles was significantly decreased compared with that of the control group (P < 0.001). Moreover, the ATP level in the fatigued muscle also significantly decreased, whereas lactic acid and MDA levels were significantly increased (P < 0.001). After posttransfection for 21 days, CAIII levels in muscles were significantly reduced in the CAIII-interfering lentivirus group, but increased in the CAIII-overexpressed lentivirus group (P < 0.001). In addition, CAIII knockdown muscles showed more reduction of the maximal muscle force and ATP levels and more increase of MDA and lactic acid levels during the fatigue test than the control group, (P < 0.05). On the other hand, CAIII-overexpressed muscles showed less reduction of the maximal muscle force and ATP levels and less increase of MDA and lactic acid levels during muscle fatigue than the control group (P < 0.05). Conclusions Our study showed that soleus muscle fatigue induced by electrical stimulation could result in downregulation of CAIII and ATP levels and accumulation of lactic acid and MDA. Further study showed that CAIII knockdown led to more reduction of the maximal muscle force, whereas CAIII overexpression showed less reduction of the maximal muscle force, which suggested that CAIII levels in muscles might be related to the occurrence of muscle fatigue. Translational potential CAIII plays an important role in muscle fatigue. Up-regulating the expression of CAIII might contribute to dissipating fatigue, which would provide a new method to solve the difficulties in eliminating muscular fatigue.
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Key Words
- ATP, adenosine triphosphate
- CAIII, carbonic anhydrase III
- CAs, carbonic anhydrases
- Carbonic anhydrase III
- Ct, threshold cycle
- MDA, malondialdehyde
- Muscle fatigue
- NS, saline injection group
- PBS, phosphate-buffered saline
- PBST, PBS with Tween 20
- PVDF, polyvinylidene difluoride
- RIPA, radioimmunoprecipitation assay
- ROS, reactive oxygen species
- SD, Sprague Dawley
- SDS–PAGE gel, sodium dodecyl sulphate–polyacrylamide gel electrophoresis
- Soleus muscle
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8
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Chen F, Zhu K, Chen L, Ouyang L, Chen C, Gu L, Jiang Y, Wang Z, Lin Z, Zhang Q, Shao X, Dai J, Zhao Y. Protein target identification of ginsenosides in skeletal muscle tissues: discovery of natural small-molecule activators of muscle-type creatine kinase. J Ginseng Res 2019; 44:461-474. [PMID: 32372868 PMCID: PMC7195589 DOI: 10.1016/j.jgr.2019.02.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Revised: 02/19/2019] [Accepted: 02/27/2019] [Indexed: 12/15/2022] Open
Abstract
Background Ginseng effectively reduces fatigue in both animal models and clinical trials. However, the mechanism of action is not completely understood, and its molecular targets remain largely unknown. Methods By screening for proteins that interact with the primary components of ginseng (ginsenosides) in an affinity chromatography assay, we have identified muscle-type creatine kinase (CK-MM) as a potential target in skeletal muscle tissues. Results Biolayer interferometry analysis showed that ginsenoside metabolites, instead of parent ginsenosides, had direct interaction with recombinant human CK-MM. Subsequently, 20(S)-protopanaxadiol (PPD), which is a ginsenoside metabolite and displayed the strongest interaction with CK-MM in the study, was selected as a representative to confirm direct binding and its biological importance. Biolayer interferometry kinetics analysis and isothermal titration calorimetry assay demonstrated that PPD specifically bound to human CK-MM. Moreover, the mutation of key amino acids predicted by molecular docking decreased the affinity between PPD and CK-MM. The direct binding activated CK-MM activity in vitro and in vivo, which increased the levels of tissue phosphocreatine and strengthened the function of the creatine kinase/phosphocreatine system in skeletal muscle, thus buffering cellular ATP, delaying exercise-induced lactate accumulation, and improving exercise performance in mice. Conclusion Our results suggest a cellular target and an initiating molecular event by which ginseng reduces fatigue. All these findings indicate PPD as a small molecular activator of CK-MM, which can help in further developing better CK-MM activators based on the dammarane-type triterpenoid structure.
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Affiliation(s)
- Feiyan Chen
- Department of Pathology and Pathophysiology, School of Medicine and Life Science, Nanjing University of Chinese Medicine, Nanjing, China
- Research Center, Basic Medical College, Nanjing University of Chinese Medicine, Nanjing, China
| | - Kexuan Zhu
- Department of Pathology and Pathophysiology, School of Medicine and Life Science, Nanjing University of Chinese Medicine, Nanjing, China
- Hanlin College, Nanjing University of Chinese Medicine, Taizhou, China
| | - Lin Chen
- Department of Physiology, School of Medicine and Life Science, Nanjing University of Chinese Medicine, Nanjing, China
| | - Liufeng Ouyang
- Department of Pathology and Pathophysiology, School of Medicine and Life Science, Nanjing University of Chinese Medicine, Nanjing, China
- Laboratory of Pathological Sciences, College of Medicine, Yan'an University, Yan'an, China
| | - Cuihua Chen
- Research Center, Basic Medical College, Nanjing University of Chinese Medicine, Nanjing, China
| | - Ling Gu
- Research Center, Basic Medical College, Nanjing University of Chinese Medicine, Nanjing, China
| | - Yucui Jiang
- Research Center, Basic Medical College, Nanjing University of Chinese Medicine, Nanjing, China
| | - Zhongli Wang
- School of Nursing, Jiujiang University, Jiujiang, China
| | - Zixuan Lin
- Department of Pathology and Pathophysiology, School of Medicine and Life Science, Nanjing University of Chinese Medicine, Nanjing, China
| | - Qiang Zhang
- Department of Pathology and Pathophysiology, School of Medicine and Life Science, Nanjing University of Chinese Medicine, Nanjing, China
| | - Xiao Shao
- Department of Pathology and Pathophysiology, School of Medicine and Life Science, Nanjing University of Chinese Medicine, Nanjing, China
| | - Jianguo Dai
- Department of Pathology and Pathophysiology, School of Medicine and Life Science, Nanjing University of Chinese Medicine, Nanjing, China
| | - Yunan Zhao
- Department of Pathology and Pathophysiology, School of Medicine and Life Science, Nanjing University of Chinese Medicine, Nanjing, China
- Research Center, Basic Medical College, Nanjing University of Chinese Medicine, Nanjing, China
- Corresponding author. Department of Pathology and Pathophysiology, School of Medicine and Life Science, Nanjing University of Chinese Medicine, Nanjing, 210046, China.
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The Effect of Physical and Mental Stress on the Heart Rate, Cortisol and Lactate Concentrations in Rock Climbers. J Hum Kinet 2019; 65:111-123. [PMID: 30687424 PMCID: PMC6341950 DOI: 10.2478/hukin-2018-0024] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rock climbing is a physical activity that not only causes an increase in muscle tension, heart rate and blood pressure, but also results in the elevation of stress hormones including cortisol. It has not been established which of the above mentioned variables serve as the most accurate indicator of rock climbing-induced physical and mental stress. The aim of this study was to evaluate the effect of physical activity, short-term fatigue and mental demand on heart rate (HR), salivary cortisol (C) and blood plasma lactate (LA) concentrations in rock climbers under laboratory conditions. Twelve male and female rock climbers of comparable climbing performance (5a – 6b OS) were recruited. The participants completed two routes of different climbing difficulty (effect of physical demand), repeated a difficult route with a short 5-min recovery period three times (effect of fatigue), and repeated a difficult lead climb (effect of mental demand). Heart rate as well as C and LA concentrations were determined. The results indicated that more difficult climbing routes elicited increases in HR (especially relative values) and LA concentrations, whereas fatigue accumulation had an effect on climbing HR and relative C concentration values. Lead climbing only caused an increase in climbing HR. Based on the results it was concluded that HR was a good indicator of physical and mental stress intensity. Performing the same difficult route three times with a short recovery period in-between turned out to be the most demanding task and resulted in the highest increase of the cortisol concentration. Dynamics of changes in lactate concentrations depend on muscle loading (local muscular effort), lactate clearance and technical/tactical skills of the climber.
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Gellen B, Messonnier LA, Galactéros F, Audureau E, Merlet AN, Rupp T, Peyrot S, Martin C, Féasson L, Bartolucci P, Habibi A, Guillet E, Gellen-Dautremer J, Ribeil JA, Arlet JB, Mattioni S, Berkenou J, Delrieux N, Lionnet F, Grenot JF, Mira J, Peyrard A, Lacroix R, Garcin A, Di Liberto G, Hourdé C. Moderate-intensity endurance-exercise training in patients with sickle-cell disease without severe chronic complications (EXDRE): an open-label randomised controlled trial. LANCET HAEMATOLOGY 2018; 5:e554-e562. [PMID: 30389037 DOI: 10.1016/s2352-3026(18)30163-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2018] [Revised: 09/20/2018] [Accepted: 09/21/2018] [Indexed: 01/17/2023]
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Exacerbated metabolic changes in skeletal muscle of sickle cell mice submitted to an acute ischemia-reperfusion paradigm. Clin Sci (Lond) 2018; 132:2103-2115. [PMID: 30185507 DOI: 10.1042/cs20180268] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 08/27/2018] [Accepted: 09/05/2018] [Indexed: 11/17/2022]
Abstract
Sickle cell disease (SCD) is characterized by painful vaso-occlusive crisis. While there are several metabolic abnormalities potentially associated with muscular ischemia-reperfusion cycles that could be harmful in the context of SCD, the metabolic consequences of such events are still unknown. Ten controls (HbAA), thirteen heterozygous (HbAS), and ten homozygous (HbSS) SCD mice were submitted to a standardized protocol of rest-ischemia-reperfusion of the left leg during which adenosine triphosphate, phosphocreatine, and inorganic phosphate concentrations as well as intramuscular pH were measured using phosphorous magnetic resonance spectroscopy (MRS). Forty-eight hours later, skeletal muscles were harvested. Oxidative stress markers were then measured on the tibialis anterior. At the end of the ischemic period, HbSS mice had a lower pH value as compared with the HbAA and HbAS groups (P<0.01). During the reperfusion period, the initial rate of phosphocreatine resynthesis was lower in HbSS mice as compared with HbAA (P<0.05) and HbAS (P<0.01) animals. No significant difference among groups was observed regarding oxidative stress markers. HbSS mice displayed a higher intramuscular acidosis during the ischemic period while their mitochondrial function was impaired as compared with their HbAA and HbAS counterparts. These metabolic abnormalities could worsen the complications related to the pathology of SCD.
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12
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Rosenstein PG, Tennent-Brown BS, Hughes D. Clinical use of plasma lactate concentration. Part 1: Physiology, pathophysiology, and measurement. J Vet Emerg Crit Care (San Antonio) 2018. [PMID: 29533512 DOI: 10.1111/vec.12708] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
OBJECTIVE To review the current literature with respect to the physiology, pathophysiology, and measurement of lactate. DATA SOURCES Data were sourced from veterinary and human clinical trials, retrospective studies, experimental studies, and review articles. Articles were retrieved without date restrictions and were sourced primarily via PubMed, Scopus, and CAB Abstracts as well as by manual selection. HUMAN AND VETERINARY DATA SYNTHESIS Lactate is an important energy storage molecule, the production of which preserves cellular energy production and mitigates the acidosis from ATP hydrolysis. Although the most common cause of hyperlactatemia is inadequate tissue oxygen delivery, hyperlactatemia can, and does occur in the face of apparently adequate oxygen supply. At a cellular level, the pathogenesis of hyperlactatemia varies widely depending on the underlying cause. Microcirculatory dysfunction, mitochondrial dysfunction, and epinephrine-mediated stimulation of Na+ -K+ -ATPase pumps are likely important contributors to hyperlactatemia in critically ill patients. Ultimately, hyperlactatemia is a marker of altered cellular bioenergetics. CONCLUSION The etiology of hyperlactatemia is complex and multifactorial. Understanding the relevant pathophysiology is helpful when characterizing hyperlactatemia in clinical patients.
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Affiliation(s)
- Patricia G Rosenstein
- Department of Veterinary Clinical Sciences, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, Victoria, Australia
| | - Brett S Tennent-Brown
- Department of Veterinary Clinical Sciences, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, Victoria, Australia
| | - Dez Hughes
- Department of Veterinary Clinical Sciences, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Werribee, Victoria, Australia
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Nezakati T, Seifalian A, Tan A, Seifalian AM. Conductive Polymers: Opportunities and Challenges in Biomedical Applications. Chem Rev 2018; 118:6766-6843. [DOI: 10.1021/acs.chemrev.6b00275] [Citation(s) in RCA: 354] [Impact Index Per Article: 59.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Toktam Nezakati
- Google Inc.., Mountain View, California 94043, United States
- Centre for Nanotechnology and Regenerative Medicine, Division of Surgery and Interventional Science, University College London, London NW3 2QG, United Kingdom
| | - Amelia Seifalian
- UCL Medical School, University College London, London WC1E 6BT, United Kingdom
| | - Aaron Tan
- UCL Medical School, University College London, London WC1E 6BT, United Kingdom
| | - Alexander M. Seifalian
- NanoRegMed Ltd. (Nanotechnology and Regenerative Medicine Commercialization Centre), The London Innovation BioScience Centre, London NW1 0NH, United Kingdom
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Prohaska BK, Bethea DM, Poulakis GR, Scharer RM, Knotek R, Carlson JK, Grubbs RD. Physiological stress in the smalltooth sawfish: effects of ontogeny, capture method, and habitat quality. ENDANGER SPECIES RES 2018. [DOI: 10.3354/esr00892] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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15
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Frizzell KM, Jendral MJ, Maclean IM, Dixon WT, Putman CT. Physicochemical determinants of pH in pectoralis major of three strains of laying hens housed in conventional and furnished cages. Br Poult Sci 2018; 59:286-300. [PMID: 29480030 DOI: 10.1080/00071668.2018.1445198] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
1. Post-mortem decline in muscle pH has traditionally been attributed to glycogenolysis-induced lactate accumulation. However, muscle pH ([H+]) is controlled by complex physicochemical relationships encapsulated in the Stewart model of acid-base chemistry and is determined by three system-independent variables - strong ion difference ([SID]), total concentration of weak acids ([Atot]) and partial pressure of CO2 (PCO2). 2. This study investigated these system-independent variables in post-mortem pectoralis major muscles of Shaver White, Lohmann Lite and Lohmann Brown laying hens housed in conventional cages (CC) or furnished cages (FC) and evaluated the model by comparing calculated [H+] with previously measured [H+] values. 3. The model accounted for 99.7% of the variation in muscle [H+]. Differences in [SID] accounted for most or all of the variations in [H+] between strains. Greater PCO2 in FC was counteracted by greater sequestration of strong base cations. The results demonstrate the accuracy and utility of the Stewart model for investigating determinants of meat [H+]. 4. The housing differences identified in this study suggested that hens housed in FC have improved muscle function and overall health due to the increased opportunity for movement. These findings support past studies showing improved animal welfare for hens housed in FC compared to CC. Therefore, the Stewart model has been identified as an accurate method to assess changes in the muscle at a cellular level that affect meat quality that also detect differences in the welfare status of the research subjects.
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Affiliation(s)
- K M Frizzell
- a Faculty of Physical Education and Recreation, University of Alberta , Exercise Biochemistry Laboratory , Edmonton , Canada
| | - M J Jendral
- a Faculty of Physical Education and Recreation, University of Alberta , Exercise Biochemistry Laboratory , Edmonton , Canada.,b Department of Plant and Animal Sciences , Dalhousie University Agricultural Campus , Truro , Canada
| | - I M Maclean
- a Faculty of Physical Education and Recreation, University of Alberta , Exercise Biochemistry Laboratory , Edmonton , Canada
| | - W T Dixon
- c Department of Agriculture, Food and Nutritional Science, Faculty of Agriculture, Life and Environmental Sciences , University of Alberta , Edmonton , Canada
| | - C T Putman
- a Faculty of Physical Education and Recreation, University of Alberta , Exercise Biochemistry Laboratory , Edmonton , Canada.,d Faculty of Medicine & Dentistry , Neuroscience and Mental Health Institute, University of Alberta , Edmonton , Canada
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16
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Qian Q. Reply to Robergs et al. Physiology (Bethesda) 2018; 33:13. [PMID: 29212887 DOI: 10.1152/physiol.00034.2017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 10/30/2017] [Indexed: 11/22/2022] Open
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Thomsen MT, Wang T, Milsom WK, Bayley M. Lactate provides a strong pH-independent ventilatory signal in the facultative air-breathing teleost Pangasianodon hypophthalmus. Sci Rep 2017; 7:6378. [PMID: 28743938 PMCID: PMC5527003 DOI: 10.1038/s41598-017-06745-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Accepted: 06/16/2017] [Indexed: 01/15/2023] Open
Abstract
Fish regulate ventilation primarily by sensing O2-levels in the water and arterial blood. It is well established that this sensory process involves several steps, but the underlying mechanisms remain frustratingly elusive. Here we examine the effect of increasing lactate ions at constant pH on ventilation in a teleost; specifically the facultative air-breathing catfish Pangasianodon hypophthalmus. At lactate levels within the physiological range obtained by Na-Lactate injections (3.5 ± 0.8 to 10.9 ± 0.7 mmol L−1), gill ventilation increased in a dose-dependent manner to levels comparable to those elicited by NaCN injections (2.0 µmol kg−1), which induces a hypoxic response and higher than those observed in any level of ambient hypoxia (lowest PO2 = 20 mmHg). High lactate concentrations also stimulated air-breathing. Denervation of the first gill arch reduced the ventilatory response to lactate suggesting that part of the sensory mechanism for lactate is located at the first gill arch. However, since a residual response remained after this denervation, the other gill arches or extrabranchial locations must also be important for lactate sensing. We propose that lactate plays a role as a signalling molecule in the hypoxic ventilatory response in fish.
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Affiliation(s)
- Mikkel T Thomsen
- Department of Bioscience, Zoophysiology, Aarhus University, Aarhus, Denmark.
| | - Tobias Wang
- Department of Bioscience, Zoophysiology, Aarhus University, Aarhus, Denmark
| | - William K Milsom
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | - Mark Bayley
- Department of Bioscience, Zoophysiology, Aarhus University, Aarhus, Denmark
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Barclay CJ. Energy demand and supply in human skeletal muscle. J Muscle Res Cell Motil 2017; 38:143-155. [PMID: 28286928 DOI: 10.1007/s10974-017-9467-7] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2016] [Accepted: 02/14/2017] [Indexed: 12/18/2022]
Abstract
The energy required for muscle contraction is provided by the breakdown of ATP but the amount of ATP in muscles cells is sufficient to power only a short duration of contraction. Buffering of ATP by phosphocreatine, a reaction catalysed by creatine kinase, extends the duration of activity possible but sustained activity depends on continual regeneration of PCr. This is achieved using ATP generated by oxidative processes and, during intense activity, by anaerobic glycolysis. The rate of ATP breakdown ranges from 70 to 140 mM min-1 during isometric contractions of various intensity to as much as 400 mM min-1 during intense, dynamic activity. The maximum rate of oxidative energy supply in untrained people is ~50 mM min-1 which, if the contraction duty cycle is 0.5 as is often the case in cyclic activity, is sufficient to match an ATP breakdown rate during contraction of 100 mM min-1. During brief, intense activity the rate of ATP turnover can exceed the rates of PCr regeneration by combined oxidative and glycolytic energy supply, resulting in a net decrease in PCr concentration. Glycolysis has the capacity to produce between 30 and 50 mM of ATP so that, for example, anaerobic glycolysis could provide ATP at an average of 100 mM min-1 over 30 s of exhausting activity. The creatine kinase reaction plays an important role not only in buffering ATP but also in communicating energy demand from sites of ATP breakdown to the mitochondria. In that role, creatine kinases acts to slow and attenuate the response of mitochondria to changes in energy demand.
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Affiliation(s)
- C J Barclay
- School of Allied Health Sciences, Griffith University, Gold Coast, QLD, 4222, Australia.
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Hall MM, Rajasekaran S, Thomsen TW, Peterson AR. Lactate: Friend or Foe. PM R 2017; 8:S8-S15. [PMID: 26972271 DOI: 10.1016/j.pmrj.2015.10.018] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Revised: 09/22/2015] [Accepted: 10/04/2015] [Indexed: 12/01/2022]
Abstract
Lactic acid has played an important role in the traditional theory of muscle fatigue and limitation of endurance exercise performance. It has been called a waste product of anaerobic metabolism and has been believed to be responsible for the uncomfortable "burn" of intense exercise and directly responsible for the metabolic acidosis of exercise, leading to decreased muscle contractility and ultimately cessation of exercise. Although this premise has been commonly taught, it is not supported by the scientific literature and has led to a great deal of confusion among the sports medicine and exercise science communities. This review will provide the sports medicine clinician with an understanding of contemporary lactate theories, including lactate's role in energy production, its contributions to metabolic acidosis, and its function as an energy substrate for a variety of tissues. Lactate threshold concepts will also be discussed, including a practical approach to understanding prediction of performance and monitoring of training progress based on these parameters.
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Affiliation(s)
- Mederic M Hall
- Department of Orthopaedics and Rehabilitation, University of Iowa Sports Medicine, 2701 Prairie Meadow Dr, Iowa City, IA 52242(∗).
| | - Sathish Rajasekaran
- Department of Orthopaedics and Rehabilitation, University of Iowa Sports Medicine, 2701 Prairie Meadow Dr, Iowa City, IA 52242(†)
| | - Timothy W Thomsen
- Department of Orthopaedics and Rehabilitation, University of Iowa Sports Medicine, 2701 Prairie Meadow Dr, Iowa City, IA 52242(‡)
| | - Andrew R Peterson
- Stead Family Department of Pediatrics, University of Iowa Sports Medicine, Iowa City, IA(¶)
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20
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White GE, Wells GD. The effect of on-hill active recovery performed between runs on blood lactate concentration and fatigue in alpine ski racers. J Strength Cond Res 2016; 29:800-6. [PMID: 25546445 DOI: 10.1519/jsc.0000000000000677] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Alpine skiing is a high-intensity intermittent sport that results in lactate accumulation and muscle acidosis, which has been shown to contribute to peripheral neuromuscular fatigue. Active recovery influences the removal of lactate from the muscle and blood by maintaining blood flow to fatigued muscles and enhancing aerobic utilization of lactate by nonfatigued tissues. The purpose of this study was to investigate the effect of on-hill active recovery on blood lactate concentration in alpine skiers. Fourteen highly trained alpine skiers (7 women, 7 men) completed 8 training runs in a 45-gate slalom or a 25-gate giant slalom corridor at 2,600 m above sea level. Skiers were randomized to active (ACT) or static recovery (CON) performed at the top of each run. Blood lactate concentration and perceived fatigue were recorded at the top and bottom of each run. Performance was measured by time to complete each training run and rate of incomplete runs. A significant time (p < 0.01) and interaction (p = 0.001) effect was observed for blood lactate concentration measured at the top, with ACT being associated with significantly lower values. A significant time effect (p < 0.001) was observed for blood lactate concentration measured at the bottom. Training run completion time was longer (p ≤ 0.05), and higher rate of incomplete runs were observed in the CON group, despite no between-group differences in rating of perceived fatigue. On-hill active recovery performed between runs promotes blood lactate clearance in alpine skiers and is associated with delayed fatigue as indicated by faster training runs and fewer incomplete runs.
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Affiliation(s)
- Gillian E White
- 1Department of Exercise Sciences, University of Toronto, Toronto, Ontario, Canada; 2Faculty of Kinesiology and Physical Education, University of Toronto, Toronto, Ontario, Canada; and 3Physiology and Experimental Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada
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21
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Percival ME, Martin BJ, Gillen JB, Skelly LE, MacInnis MJ, Green AE, Tarnopolsky MA, Gibala MJ. Sodium bicarbonate ingestion augments the increase in PGC-1α mRNA expression during recovery from intense interval exercise in human skeletal muscle. J Appl Physiol (1985) 2015; 119:1303-12. [PMID: 26384407 PMCID: PMC4669344 DOI: 10.1152/japplphysiol.00048.2015] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 09/11/2015] [Indexed: 11/22/2022] Open
Abstract
We tested the hypothesis that ingestion of sodium bicarbonate (NaHCO3) prior to an acute session of high-intensity interval training (HIIT) would augment signaling cascades and gene expression linked to mitochondrial biogenesis in human skeletal muscle. On two occasions separated by ∼1 wk, nine men (mean ± SD: age 22 ± 2 yr, weight 78 ± 13 kg, V̇O(2 peak) 48 ± 8 ml·kg(-1)·min(-1)) performed 10 × 60-s cycling efforts at an intensity eliciting ∼90% of maximal heart rate (263 ± 40 W), interspersed with 60 s of recovery. In a double-blind, crossover manner, subjects ingested a total of 0.4 g/kg body weight NaHCO3 before exercise (BICARB) or an equimolar amount of a placebo, sodium chloride (PLAC). Venous blood bicarbonate and pH were elevated at all time points after ingestion (P < 0.05) in BICARB vs. PLAC. During exercise, muscle glycogen utilization (126 ± 47 vs. 53 ± 38 mmol/kg dry weight, P < 0.05) and blood lactate accumulation (12.8 ± 2.6 vs. 10.5 ± 2.8 mmol/liter, P < 0.05) were greater in BICARB vs. PLAC. The acute exercise-induced increase in the phosphorylation of acetyl-CoA carboxylase, a downstream marker of AMP-activated protein kinase activity, and p38 mitogen-activated protein kinase were similar between treatments (P > 0.05). However, the increase in PGC-1α mRNA expression after 3 h of recovery was higher in BICARB vs. PLAC (approximately sevenfold vs. fivefold compared with rest, P < 0.05). We conclude that NaHCO3 before HIIT alters the mRNA expression of this key regulatory protein associated with mitochondrial biogenesis. The elevated PGC-1α mRNA response provides a putative mechanism to explain the enhanced mitochondrial adaptation observed after chronic HIIT supplemented with NaHCO3 in rats.
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Affiliation(s)
- Michael E Percival
- Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada; and
| | - Brian J Martin
- Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada; and
| | - Jenna B Gillen
- Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada; and
| | - Lauren E Skelly
- Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada; and
| | - Martin J MacInnis
- Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada; and
| | - Alex E Green
- Department of Pediatrics and Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Mark A Tarnopolsky
- Department of Pediatrics and Medicine, McMaster University, Hamilton, Ontario, Canada
| | - Martin J Gibala
- Department of Kinesiology, McMaster University, Hamilton, Ontario, Canada; and
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Abstract
Therapeutic hypothermia is the only treatment currently recommended for moderate or severe encephalopathy of hypoxic‒ischaemic origin in term neonates. Though the effects of hypothermia on human physiology have been explored for many decades, much of the data comes from animal or adult studies; the latter originally after accidental hypothermia, followed by application of controlled hypothermia after cardiac arrest or trauma, or during cardiopulmonary bypass. Though this work is informative, the effects of hypothermia on neonatal physiology after perinatal asphyxia must be considered in the context of a prolonged hypoxic insult that has already induced a number of significant physiological sequelae. This article reviews the effects of therapeutic hypothermia on respiratory, cardiovascular, and metabolic parameters, including glycaemic control and feeding requirements. The potential pitfalls of blood‒gas analysis and overtreatment of physiological changes in cardiovascular parameters are also discussed. Finally, the effects of hypothermia on drug metabolism are covered, focusing on how the pharmacokinetics, pharmacodynamics, and dosing requirements of drugs frequently used in neonatal intensive care may change during therapeutic hypothermia.
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Putman CT, Gallo M, Martins KJB, MacLean IM, Jendral MJ, Gordon T, Syrotuik DG, Dixon WT. Creatine loading elevates the intracellular phosphorylation potential and alters adaptive responses of rat fast-twitch muscle to chronic low-frequency stimulation. Appl Physiol Nutr Metab 2015; 40:671-82. [PMID: 26039543 DOI: 10.1139/apnm-2014-0300] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
This study tested the hypothesis that elevating the intracellular phosphorylation potential (IPP = [ATP]/[ADP]free) within rat fast-twitch tibialis anterior muscles by creatine (Cr) loading would prevent fast-to-slow fibre transitions induced by chronic low-frequency electrical stimulation (CLFS, 10 Hz, 12 h/day). Creatine-control and creatine-CLFS groups drank a solution of 1% Cr + 5% dextrose, ad libitum, for 10 days before and during 10 days of CLFS; dextrose-control and dextrose-CLFS groups drank 5% dextrose. Cr loading increased total Cr (P < 0.025), phosphocreatine (PCr) (P < 0.003), and the IPP (P < 0.0008) by 34%, 45%, and 64%, respectively. PCr and IPP were 46% (P < 0.002) and 76% (P < 0.02) greater in creatine-CLFS than in dextrose-CLFS. Higher IPP was confirmed by a 58% reduction in phospho-AMP-activated protein kinase α (Thr172) (P < 0.006). In dextrose-CLFS, myosin heavy chain (MyHC) I and IIa transcripts increased 32- and 38-fold (P < 0.006), respectively, whereas MyHC-IIb mRNA decreased by 75% (P < 0.03); the corresponding MyHC-I and MyHC-IIa protein contents increased by 2.0- (P < 0.03) and 2.7-fold (P < 0.05), respectively, and MyHC-IIb decreased by 30% (P < 0.03). In contrast, within creatine-CLFS, MyHC-I and MyHC-IIa mRNA were unchanged and MyHC-IIb mRNA decreased by 75% (P < 0.003); the corresponding MyHC isoform contents were not altered. Oxidative reference enzymes were similarly elevated (P < 0.01) in dextrose-CLFS and creatine-CLFS, but reciprocal reductions in glycolytic reference enzymes occurred only in dextrose-CLFS (P < 0.02). Preservation of the glycolytic potential and greater SERCA2 and parvalbumin contents in creatine-CLFS coincided with prolonged time to peak tension and half-rise time (P < 0.01). These results highlight the IPP as an important physiological regulator of muscle fibre plasticity and demonstrate that training-induced changes typically associated with improvements in muscular endurance or increased power output are not mutually exclusive in Cr-loaded muscles.
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Affiliation(s)
- Charles T Putman
- a Exercise Biochemistry Laboratory, Faculty of Physical Education and Recreation, University of Alberta, Edmonton, AB T6G 2H9, Canada.,b The Centre for Neuroscience, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2E1, Canada
| | - Maria Gallo
- a Exercise Biochemistry Laboratory, Faculty of Physical Education and Recreation, University of Alberta, Edmonton, AB T6G 2H9, Canada
| | - Karen J B Martins
- a Exercise Biochemistry Laboratory, Faculty of Physical Education and Recreation, University of Alberta, Edmonton, AB T6G 2H9, Canada
| | - Ian M MacLean
- a Exercise Biochemistry Laboratory, Faculty of Physical Education and Recreation, University of Alberta, Edmonton, AB T6G 2H9, Canada
| | - Michelle J Jendral
- a Exercise Biochemistry Laboratory, Faculty of Physical Education and Recreation, University of Alberta, Edmonton, AB T6G 2H9, Canada
| | - Tessa Gordon
- b The Centre for Neuroscience, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T6G 2E1, Canada.,d Division of Physical Medicine and Rehabilitation, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB T5G 0B7, Canada
| | - Daniel G Syrotuik
- a Exercise Biochemistry Laboratory, Faculty of Physical Education and Recreation, University of Alberta, Edmonton, AB T6G 2H9, Canada
| | - Walter T Dixon
- c Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB T6G 2P5, Canada
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Hackney KJ, English KL. Protein and Essential Amino Acids to Protect Musculoskeletal Health during Spaceflight: Evidence of a Paradox? Life (Basel) 2014; 4:295-317. [PMID: 25370374 PMCID: PMC4206848 DOI: 10.3390/life4030295] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Revised: 06/19/2014] [Accepted: 06/23/2014] [Indexed: 11/17/2022] Open
Abstract
Long-duration spaceflight results in muscle atrophy and a loss of bone mineral density. In skeletal muscle tissue, acute exercise and protein (e.g., essential amino acids) stimulate anabolic pathways (e.g., muscle protein synthesis) both independently and synergistically to maintain neutral or positive net muscle protein balance. Protein intake in space is recommended to be 12%-15% of total energy intake (≤1.4 g∙kg-1∙day-1) and spaceflight is associated with reduced energy intake (~20%), which enhances muscle catabolism. Increasing protein intake to 1.5-2.0 g∙kg-1∙day-1 may be beneficial for skeletal muscle tissue and could be accomplished with essential amino acid supplementation. However, increased consumption of sulfur-containing amino acids is associated with increased bone resorption, which creates a dilemma for musculoskeletal countermeasures, whereby optimizing skeletal muscle parameters via essential amino acid supplementation may worsen bone outcomes. To protect both muscle and bone health, future unloading studies should evaluate increased protein intake via non-sulfur containing essential amino acids or leucine in combination with exercise countermeasures and the concomitant influence of reduced energy intake.
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Affiliation(s)
- Kyle J Hackney
- Department of Health, Nutrition, and Exercise Sciences, North Dakota State University, Fargo, ND 58102, USA.
| | - Kirk L English
- Exercise Physiology and Countermeasures Laboratory, JES Tech, Houston, TX 77058, USA.
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25
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Lindinger M. Determining dehydration and its compartmentation in horses at rest and with exercise: a concise review and focus on multi-frequency bioelectrical impedance analysis. COMPARATIVE EXERCISE PHYSIOLOGY 2014. [DOI: 10.3920/cep13034] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Multi-frequency bioelectrical impedance analysis (MFBIA) has been, and likely will increasingly be, used to rapidly and non-invasively assess the time course of volume losses and recovery in horses. Dehydration in performance horses is frequently the cause of health and performance problems, and presently used techniques for objectively quantifying optimum hydration are time consuming and challenging to perform accurately. Dehydration can take a number of different forms, with a balanced loss of water and electrolytes from both extra- and intracellular fluid compartments, or a primarily extracellular or intracellular dehydration. This review summarises the current state of knowledge regarding the quantification of dehydration, losses of water and electrolytes from extra- and intracellular fluid compartments. The effects of dehydration on exercise performance, muscle function, cardiovascular function, thermoregulation and feeding are briefly summarised. The review provides a quantitative description of the magnitude and time course of compartmental fluid losses and recovery in horses in response to feeding and due to exercise at different intensities and durations representing the endurance horse to the track race horse. Effective rehydration requires knowledge of the losses from the main body fluid compartments, which is now possible using MFBIA technology. The present review outlines the key approaches that have been used to assess dehydration in horses, including the new technique of MFBIA.
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Affiliation(s)
- M.I. Lindinger
- The Nutraceutical Alliance, 10526 4th Line Nassagaweya, Campbellville, ON L0P 1B0, Canada
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26
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Abstract
This paper describes the interactions between ventilation and acid-base balance under a variety of conditions including rest, exercise, altitude, pregnancy, and various muscle, respiratory, cardiac, and renal pathologies. We introduce the physicochemical approach to assessing acid-base status and demonstrate how this approach can be used to quantify the origins of acid-base disorders using examples from the literature. The relationships between chemoreceptor and metaboreceptor control of ventilation and acid-base balance summarized here for adults, youth, and in various pathological conditions. There is a dynamic interplay between disturbances in acid-base balance, that is, exercise, that affect ventilation as well as imposed or pathological disturbances of ventilation that affect acid-base balance. Interactions between ventilation and acid-base balance are highlighted for moderate- to high-intensity exercise, altitude, induced acidosis and alkalosis, pregnancy, obesity, and some pathological conditions. In many situations, complete acid-base data are lacking, indicating a need for further research aimed at elucidating mechanistic bases for relationships between alterations in acid-base state and the ventilatory responses.
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Affiliation(s)
- Michael I Lindinger
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada.
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Stickland MK, Lindinger MI, Olfert IM, Heigenhauser GJF, Hopkins SR. Pulmonary gas exchange and acid-base balance during exercise. Compr Physiol 2013; 3:693-739. [PMID: 23720327 PMCID: PMC8315793 DOI: 10.1002/cphy.c110048] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
As the first step in the oxygen-transport chain, the lung has a critical task: optimizing the exchange of respiratory gases to maintain delivery of oxygen and the elimination of carbon dioxide. In healthy subjects, gas exchange, as evaluated by the alveolar-to-arterial PO2 difference (A-aDO2), worsens with incremental exercise, and typically reaches an A-aDO2 of approximately 25 mmHg at peak exercise. While there is great individual variability, A-aDO2 is generally largest at peak exercise in subjects with the highest peak oxygen consumption. Inert gas data has shown that the increase in A-aDO2 is explained by decreased ventilation-perfusion matching, and the development of a diffusion limitation for oxygen. Gas exchange data does not indicate the presence of right-to-left intrapulmonary shunt developing with exercise, despite recent data suggesting that large-diameter arteriovenous shunt vessels may be recruited with exercise. At the same time, multisystem mechanisms regulate systemic acid-base balance in integrative processes that involve gas exchange between tissues and the environment and simultaneous net changes in the concentrations of strong and weak ions within, and transfer between, extracellular and intracellular fluids. The physicochemical approach to acid-base balance is used to understand the contributions from independent acid-base variables to measured acid-base disturbances within contracting skeletal muscle, erythrocytes and noncontracting tissues. In muscle, the magnitude of the disturbance is proportional to the concentrations of dissociated weak acids, the rate at which acid equivalents (strong acid) accumulate and the rate at which strong base cations are added to or removed from muscle.
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Affiliation(s)
- Michael K. Stickland
- Division of Pulmonary Medicine, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
| | - Michael I. Lindinger
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - I. Mark Olfert
- Robert C. Byrd Health Sciences Center, Center for Cardiovascular and Respiratory Sciences, Division of Exercise Physiology, West Virginia University School of Medicine, Morgantown, West Virginia
| | | | - Susan R. Hopkins
- Departments of Medicine and Radiology, University of California, San Diego, San Diego, California
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Shang X, Bao Y, Chen S, Ren H, Huang H, Li Y. Expression and purification of TAT-fused carbonic anhydrase III and its effect on C2C12 cell apoptosis induced by hypoxia/reoxygenation. Arch Med Sci 2012; 8:711-8. [PMID: 23056085 PMCID: PMC3460508 DOI: 10.5114/aoms.2012.30295] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2011] [Revised: 12/11/2011] [Accepted: 01/24/2012] [Indexed: 02/07/2023] Open
Abstract
INTRODUCTION Carbonic anhydrase III (CAIII) is remarkably abundant in slow skeletal muscles. It has multiple biological activities which could dissipate or resist some fatigue-related substances. In this study, we purified trans-activating transcriptional activator (TAT) fused CAIII protein and investigated its effect on C2C12 cell apoptosis induced by hypoxia/reoxygenation. MATERIAL AND METHODS The CAIII and TAT-CAIII genes were constructed, cloned into plasmid pET28a and expressed in Escherichia coli BL21 (DE3). The fusion proteins were purified with a nickel-nitrilotriacetic acid affinity chromatography column and then verified by Western blot and phosphatase activity staining subsequently. The C2C12 cells were treated respectively with serum-free medium containing 1 μM TAT-CAIII or 1 μM CAIII for 1 h and the intracellular distributions of fusion proteins were observed by indirect immunofluorescence. The effect of TAT-CAIII on C2C12 cell apoptosis induced by hypoxia/reoxygenation was detected by flow cytometry. RESULTS The CAIII and TAT-CAIII fusion proteins were expressed and purified successfully. After being cultured for 1 h, green fluorescence was visible in TAT-CAIII group cells under the fluorescence microscope, while no fluorescence was found in the CAIII group. Compared with the oxygen-glucose deprivation group, the apoptosis rate of C2C12 cells induced by hypoxia/reoxygenation in the TAT-CAIII group decreased significantly (p < 0.001). CONCLUSIONS The purified TAT-CAIII could be transferred into cells efficiently and clearly decreased the apoptosis rate of C2C12 cells induced by hypoxia/reoxygenation, which indicated that it had antioxidative activity. This study lays an experimental basis for future research on the relationship between CAIII and muscle fatigue.
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Affiliation(s)
- Xiliang Shang
- Department of Sports Medicine, Huashan Hospital, Fudan University, China
| | - Yuanyuan Bao
- Department of Endocrinology and Metabolism, Huashan Hospital, Fudan University, China
| | - Shiyi Chen
- Department of Sports Medicine, Huashan Hospital, Fudan University, China
| | - Huimin Ren
- Institute of Neurology, Fudan University, Shanghai, China
| | - He Huang
- Institute of Neurology, Fudan University, Shanghai, China
| | - Yunxia Li
- Department of Sports Medicine, Huashan Hospital, Fudan University, China
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Belfry GR, Raymer GH, Marsh GD, Paterson DH, Thompson RT, Thomas SG. Muscle metabolic status and acid-base balance during 10-s work:5-s recovery intermittent and continuous exercise. J Appl Physiol (1985) 2012; 113:410-7. [PMID: 22604889 DOI: 10.1152/japplphysiol.01059.2011] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Gastrocnemius muscle phosphocreatine ([PCr]) and hydrogen ion ([H(+)]) were measured using (31)P-magnetic resonance spectroscopy during repeated bouts of 10-s heavy-intensity (HI) exercise and 5-s rest compared with continuous (CONT) HI exercise. Recreationally active male subjects (n = 7; 28 yr ± 9 yr) performed on separate occasions 12 min of isotonic plantar flexion (0.75 Hz) CONT and intermittent (INT; 10-s exercise, 5-s rest) exercise. The HI power output in both CONT and INT was set at 50% of the difference between the power output associated with the onset of intracellular acidosis and peak exercise determined from a prior incremental plantar flexion protocol. Intracellular concentrations of [PCr] and [H(+)] were calculated at 4 s and 9 s of the work period and at 4 s of the rest period in INT and during CONT exercise. [PCr] and [H(+)] (mean ± SE) were greater at 4 s of the rest periods vs. 9 s of exercise over the course of the INT exercise bout: [PCr] (20.7 mM ± 0.6 vs. 18.7 mM ± 0.5; P < 0.01); [H(+)] (370 nM ± 13.50 vs. 284 nM ± 13.6; P < 0.05). Average [H(+)] was similar for CONT vs. INT. We therefore suggest that there is a glycolytic contribution to ATP recovery during the very short rest period (<5 s) of INT and that the greater average power output of CONT did not manifest in greater [H(+)] and greater glycolytic contribution compared with INT exercise.
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Affiliation(s)
- Glen R Belfry
- University of Western Ontario, London, Ontario, Canada.
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30
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JOHNSON MICHAELA, MILLS DEANE, BROWN DAVIDM, BAYFIELD KATIEJ, GONZALEZ JAVIERT, SHARPE GRAHAMR. Inspiratory Loading Intensity Does Not Influence Lactate Clearance during Recovery. Med Sci Sports Exerc 2012; 44:863-71. [DOI: 10.1249/mss.0b013e31824079d0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Rees SE. The Intelligent Ventilator (INVENT) project: the role of mathematical models in translating physiological knowledge into clinical practice. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2011; 104 Suppl 1:S1-S29. [PMID: 22152752 DOI: 10.1016/s0169-2607(11)00307-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
This dissertation has addressed the broad hypothesis as to whether building mathematical models is useful as a tool for translating physiological knowledge into clinical practice. In doing so it describes work on the INtelligent VENTilator project (INVENT), the goal of which is to build, evaluate and integrate into clinical practice, a model-based decision support system for control of mechanical ventilation. The dissertation describes the mathematical models included in INVENT, i.e. a model of pulmonary gas exchange focusing on oxygen transport, and a model of the acid-base status of blood, interstitial fluid and tissues. These models have been validated, and applied in two other systems: ALPE, a system for measuring pulmonary gas exchange and ARTY, a system for arterialisation of the acid-base and oxygen status of peripheral venous blood. The major contributions of this work are as follows. A mathematical model has been developed which can describe pulmonary gas exchange more accurately that current clinical techniques. This model is parsimonious in that it can describe pulmonary gas exchange from measurements easily available in the clinic, along with a readily automatable variation in F(I)O(2). This technique and model have been developed into a research and commercial tool (ALPE), and evaluated both in the clinical setting and when compared to the reference multiple inert gas elimination technique (MIGET). Mathematical models have been developed of the acid- base chemistry of blood, interstitial fluid and tissues, with these models formulated using a mass-action mass-balance approach. The model of blood has been validated against literature data describing the addition and removal of CO(2), strong acid or base, and haemoglobin; and the effects of oxygenation or deoxygenation. The model has also been validated in new studies, and shown to simulate accurately and precisely the mixing of blood samples at different PCO(2) and PO(2) levels. This model of acid-base chemistry of blood has been applied in the ARTY system. ARTY has been shown to accurately and precisely calculate arterial values of acid-base and oxygen status in patients residing in the ICU, and in those with chronic lung disease. The INtelligent VENTilator (INVENT) system has been developed for optimization of mechanical ventilator settings using physiological models and utility/penalty functions, separating physiological knowledge from clinical preference. The models can be tuned to the individual patient via parameter estimation, providing patient specific advice. The INVENT team has shown prospectively that the system provides advice on F(I)O(2) which is as good as clinical practice, and retrospectively that the system provides reasonable suggestions of tidal volume, respiratory frequency and F(I)O(2). In general, this dissertation has illustrated a further example of the role of modeling in describing and understanding complex systems. The dissertation has shown that when dealing with complexity the goal of the model must be in focus if a correct balance is to be maintained between system complexity and model parameterization. The original goal of the INVENT team, i.e. to build, evaluate and integrate a DSS for control of mechanical ventilation has not as yet been completed. However, the broader hypothesis that building models generates new and interesting questions has been successfully demonstrated. The ALPE model and system has been applied in intensive care, post operative care and cardiology and is currently being evaluated in new clinical domains. ARTY has been shown to have potential benefit in eliminating the need for painful arterial punctures, and may also be useful as a screening tool. These systems illustrate the benefits of investing in models as a mechanism for translating physiological knowledge to clinical practice.
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Affiliation(s)
- Stephen E Rees
- Center for Model-based Medical Decision Support, Department of Health Science and Technology, Aalborg University, Denmark
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32
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Lindinger MI. Lactate: metabolic fuel or poison. Exp Physiol 2011. [DOI: 10.1113/expphysiol.2011.059634] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Vinnakota KC, Kushmerick MJ. Point: Muscle lactate and H+ production do have a 1:1 association in skeletal muscle. J Appl Physiol (1985) 2011; 110:1487-9; discussion 1497. [DOI: 10.1152/japplphysiol.01506.2010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Kalyan C. Vinnakota
- Biotechnology and Bioengineering Center
- Department of Physiology Medical College of Wisconsin Milwaukee, Wisconsin
| | - Martin J. Kushmerick
- Departments of Radiology and
- Bioengineering and
- Physiology and Biophysics University of Washington Seattle, Washington
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Beard DA. Comments on Point:Counterpoint: Muscle lactate and H⁺ production do/do not have a 1:1 association in skeletal muscle. Calculations of Robergs support the view of Vinnakota and Kushmerick. J Appl Physiol (1985) 2011; 110:1493. [PMID: 21372102 PMCID: PMC5395467 DOI: 10.1152/japplphysiol.00242.2011] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Increase in serum growth hormone induced by electrical stimulation of muscle combined with blood flow restriction. Eur J Appl Physiol 2011; 111:2715-21. [DOI: 10.1007/s00421-011-1899-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Accepted: 03/01/2011] [Indexed: 10/18/2022]
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Affiliation(s)
- George A. Brooks
- Department of Integrative Biology, University of California, Berkeley, California
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Vinnakota KC, Rusk J, Palmer L, Shankland E, Kushmerick MJ. Common phenotype of resting mouse extensor digitorum longus and soleus muscles: equal ATPase and glycolytic flux during transient anoxia. J Physiol 2010; 588:1961-83. [PMID: 20308252 DOI: 10.1113/jphysiol.2009.185934] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Rates of ATPase and glycolysis are several times faster in actively contracting mouse extensor digitorum longus muscle (EDL) than soleus (SOL), but we find these rates are not distinguishable at rest. We used a transient anoxic perturbation of steady state energy balance to decrease phosphocreatine (PCr) reversibly and to measure the rates of ATPase and of lactate production without muscle activation or contraction. The rate of glycolytic ATP synthesis is less than the ATPase rate, accounting for the continual PCr decrease during anoxia in both muscles. We fitted a mathematical model validated with properties of enzymes and solutes measured in vitro and appropriate for the transient perturbation of these muscles to experimental data to test whether the model accounts for the results. Simulations showed equal rates of ATPase and lactate production in both muscles. ATPase controls glycolytic flux by feedback from its products. Adenylate kinase function is critical because a rise in [AMP] is necessary to activate glycogen phosphorylase. ATPase is the primary source of H+ production. The sum of contributions of the 13 reactions of the glycogenolytic and glycolytic network to total proton load is negligible. The stoichiometry of lactate and H+ production is near unity. These results identify a default state of energy metabolism for resting muscle in which there is no difference in the metabolic phenotype of EDL and SOL. Therefore, additional control mechanisms, involving higher ATPase flux and [Ca2+], must exist to explain the well-known difference in glycolytic rates in fast-twitch and slow-twitch muscles in actively contracting muscle.
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Affiliation(s)
- Kalyan C Vinnakota
- University of Washington, Mail Box 357115, Department of Radiology, 1959 NE Pacific Avenue, HSC AA010, Seattle, WA 09105-7115, USA
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Jacobs CB, Peairs MJ, Venton BJ. Review: Carbon nanotube based electrochemical sensors for biomolecules. Anal Chim Acta 2010; 662:105-27. [PMID: 20171310 DOI: 10.1016/j.aca.2010.01.009] [Citation(s) in RCA: 781] [Impact Index Per Article: 55.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2009] [Revised: 12/22/2009] [Accepted: 01/05/2010] [Indexed: 11/30/2022]
Abstract
Carbon nanotubes (CNTs) have been incorporated in electrochemical sensors to decrease overpotential and improve sensitivity. In this review, we focus on recent literature that describes how CNT-based electrochemical sensors are being developed to detect neurotransmitters, proteins, small molecules such as glucose, and DNA. Different types of electrochemical methods are used in these sensors including direct electrochemical detection with amperometry or voltammetry, indirect detection of an oxidation product using enzyme sensors, and detection of conductivity changes using CNT-field effect transistors (FETs). Future challenges for the field include miniaturizing sensors, developing methods to use only a specific nanotube allotrope, and simplifying manufacturing.
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Affiliation(s)
- Christopher B Jacobs
- Dept. of Chemistry, University of Virginia, PO Box 400319, Charlottesville, VA 22904, United States
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40
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Macedo DV, Lazarim FL, Catanho da Silva FO, Tessuti LS, Hohl R. Is lactate production related to muscular fatigue? A pedagogical proposition using empirical facts. ADVANCES IN PHYSIOLOGY EDUCATION 2009; 33:302-307. [PMID: 19948679 DOI: 10.1152/advan.00039.2009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The cause-effect relationship between lactic acid, acidosis, and muscle fatigue has been established in the literature. However, current experiments contradict this premise. Here, we describe an experiment developed by first-year university students planned to answer the following questions: 1) Which metabolic pathways of energy metabolism are responsible for meeting the high ATP demand during high-intensity intermittent exercise? 2) Which metabolic pathways are active during the pause, and how do they influence phosphocreatine synthesis? and 3) Is lactate production related to muscular fatigue? Along with these questions, students received a list of materials available for the experiment. In the classroom, they proposed two protocols of eight 30-m sprints at maximum speed, one protocol with pauses of 120 s and the other protocol with pauses of 20 s between sprints. Their performances were analyzed through the velocity registered by photocells. Blood lactate was analyzed before the first sprint and after the eighth sprint. Blood uric acid was analyzed before exercise and 15 and 60 min after exercises. When discussing the data, students concluded that phosphocreatine restoration is time dependent, and this fact influenced the steady level of performance in the protocol with pauses of 120 s compared with the performance decrease noted in the protocol with pauses of 20 s. As the blood lactate levels showed similar absolute increases after both exercises, the students concluded that lactate production is not related to the performance decrement. This activity allows students to integrate the understanding of muscular energy pathways and to reconsider a controversial concept with facts that challenge the universality of the hypothesis relating lactate production to muscular fatigue.
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Affiliation(s)
- Denise Vaz Macedo
- Exercise Biochemistry Laboratory, Biochemistry Department, Biology Institute, State University of Campinas, Campinas, São Paulo, Brazil.
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41
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Mathematical modelling of the acid-base chemistry and oxygenation of blood: a mass balance, mass action approach including plasma and red blood cells. Eur J Appl Physiol 2009; 108:483-94. [PMID: 19841930 DOI: 10.1007/s00421-009-1244-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/30/2009] [Indexed: 10/20/2022]
Abstract
Mathematical models of the acid-base chemistry of blood based upon mass action and mass balance equations have become popular as diagnostic tools in intensive care. The reference models using this approach are those based on the strong ion approach, but these models do not currently take into account the effects of oxygen on the buffering characteristics of haemoglobin. As such these models are limited in their ability to simulate physiological situations involving simultaneous changes of O(2) and CO(2) levels in the blood. This paper describes a model of acid-base chemistry of blood based on mass action and mass balance equations and including the effects of oxygen. The model is used to simulate the mixing of venous blood with the same blood at elevated O(2) and reduced CO(2) levels, and the results compared with the mixing of blood sampled from 21 healthy subjects. Simulated values of pH, PCO(2), PO(2) and SO(2) in the mixed blood compare well with measured values with small bias (i.e. 0.000 pH, -0.06 kPa PCO(2), -0.1% SO(2), -0.02 kPa PO(2)), and values of standard deviations (i.e. 0.006 pH, 0.11 kPa PCO(2), 0.8% SO(2), 0.13 kPa PO(2)) comparable to the precision seen in direct measurement of these variables in clinical practice. These results indicate that the model can reliably simulate the mixing of blood and has potential for application in describing physiological situations involving the mixing of blood at different O(2) and CO(2) levels such as occurs in the mixing of lung capillary and shunted pulmonary blood.
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Shang X, Chen S, Ren H, Li Y, Huang H. Carbonic anhydrase III: the new hope for the elimination of exercise-induced muscle fatigue. Med Hypotheses 2009; 72:427-9. [PMID: 19135807 DOI: 10.1016/j.mehy.2008.10.027] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2008] [Revised: 10/03/2008] [Accepted: 10/10/2008] [Indexed: 10/21/2022]
Abstract
Fatigue, defined as the failure to maintain the required or expected power output, is a complex problem. Its occurrence mechanism is extremely complicated. The obvious reasons are that it is a multifactorial situation and that the limiting factors may vary with force intensity, exercise duration and muscle type. In recent years, it has been found that carbonic anhydrase III(CAIII) which is present in high concentrations in muscles has multiple biological activities that can dissipate or resist some fatigue related substances. Therefore, we hypothesize that the CAIII supplementation may contribute to dissipate fatigue. Confirmation of this hypothesis will further add to our understanding of the physiological functions of CAIII and will be hopeful to solve the difficulties in eliminating muscular fatigue.
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Affiliation(s)
- Xiliang Shang
- Department of Sports Medicine, Huashan Hospital, Fudan University, Shanghai 200040, PR China
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43
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Rebuttal from Drs. Lindinger and Heigenhauser. J Appl Physiol (1985) 2008. [DOI: 10.1152/japplphysiol.00162.2008c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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44
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Böning D, Maassen N. Point:Counterpoint: Lactic acid is/is not the only physicochemical contributor to the acidosis of exercise. J Appl Physiol (1985) 2008; 105:358-9. [DOI: 10.1152/japplphysiol.00162.2008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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45
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Walsh B, Stary CM, Howlett RA, Kelley KM, Hogan MC. Glycolytic activation at the onset of contractions in isolated Xenopus laevis single myofibres. Exp Physiol 2008; 93:1076-84. [PMID: 18515473 DOI: 10.1113/expphysiol.2008.042440] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Intracellular pH (pHi) was measured in isolated Xenopus laevis single myofibres at the onset of contractions, with and without glycolytic blockade, to investigate the time course of glycolytic activation. Single myofibres (n=8; CON) were incubated in 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein acetoyxmethyl ester (10 microM; for fluorescence measurement of pHi) and stimulated for 15 s at 0.67 Hz in anoxia in the absence (control condition; CON) and presence of a glycolytic inhibitor (1 mM iodoacetic acid; IAA). Intracellular pHi and tension were continuously recorded, and the differences in pHi between conditions were used to estimate the activation time of glycolysis. An immediate and steady increase in pHi (initial alkalosis) at the onset of contractions was similar between CON and IAA trials for the first 9 s of the contractile bout. However, from six contractions (approximately 10 s) throughout the remainder of the bout, IAA demonstrated a continued rise in pHi, in contrast to a progressive decrease in pHi in CON (P<0.05). These results demonstrate, with high temporal resolution, that glycolysis is activated within six contractions (10 s at 0.67 Hz) in single Xenopus skeletal muscle fibres.
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Affiliation(s)
- Brandon Walsh
- University of California at San Diego, Department of Medicine, Physiology Division, 9500 Gilman Drive, MC0623A, La Jolla, CA 92093-0623, USA
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Abstract
The cell-to-cell lactate shuttle was introduced in 1984 and has been repeatedly supported by studies using a variety of experimental approaches. Because of its large mass and metabolic capacity, skeletal muscle is probably the major component of the lactate shuttle in terms of both production and consumption. Muscles exercising in a steady state are avid consumers of lactate, using most of the lactate as an oxidative fuel. Cardiac muscle is highly oxidative and readily uses lactate as a fuel. Lactate is a major gluconeogenic substrate for the liver; the use of lactate to form glucose increases when blood lactate concentration is elevated. Illustrative of the widespread shuttling of lactate, even the brain takes up lactate when the blood level is increased. Recently, an intracellular lactate shuttle has also been proposed. Although disagreements abound, current evidence suggests that lactate is the primary end-product of glycolysis at cellular sites remote from mitochondria. This lactate could subsequently diffuse to areas adjacent to mitochondria. Evidence is against lactate oxidation within the mitochondrial matrix, but a viable hypothesis is that lactate could be converted to pyruvate by a lactate oxidation complex with lactate dehydrogenase located on the outer surface of the inner mitochondrial membrane. In another controversial area, the role of lactic acid in acid-base balance has been hotly debated in recent times. Careful analysis reveals that lactate, not lactic acid, is the substrate/product of metabolic reactions. One view is that lactate formation alleviates acidosis, whereas another is that lactate is a causative factor in acidosis. Surprisingly, there is little direct mechanistic evidence regarding cause and effect in acid-base balance. However, there is insufficient evidence to discard the term "lactic acidosis."
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Affiliation(s)
- L Bruce Gladden
- Department of Kinesiology, Auburn University, Auburn, AL 36849-5323, USA.
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47
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Abstract
Regulation of pH in skeletal muscle is the sum of mechanisms involved in maintaining intracellular pH within the normal range. Aspects of pH regulation in human skeletal muscle have been studied with various techniques from analysis of membrane proteins, microdialysis, and the nuclear magnetic resonance technique to exercise experiments including blood sampling and muscle biopsies. The present review characterizes the cellular buffering system as well as the most important membrane transport systems involved (Na(+)/H(+) exchange, Na-bicarbonate co-transport and lactate/H(+) co-transport) and describes the contribution of each transport system in pH regulation at rest and during muscle activity. It is reported that the mechanisms involved in pH regulation can undergo adaptational changes in association with physical activity and that these changes are of functional importance.
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Affiliation(s)
- C Juel
- Copenhagen Muscle Research Centre, Department of Molecular Biology, University of Copenhagen, Copenhagen, Denmark.
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48
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de Paoli FV, Overgaard K, Pedersen TH, Nielsen OB. Additive protective effects of the addition of lactic acid and adrenaline on excitability and force in isolated rat skeletal muscle depressed by elevated extracellular K+. J Physiol 2007; 581:829-39. [PMID: 17347268 PMCID: PMC2075200 DOI: 10.1113/jphysiol.2007.129049] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 01/24/2007] [Accepted: 02/21/2007] [Indexed: 11/08/2022] Open
Abstract
During strenuous exercise, extracellular K(+) ([K(+)](o)) is increased, which potentially can reduce muscle excitability and force production. In addition, exercise leads to accumulation of lactate and H(+) and increased levels of circulating catecholamines. Individually, reduced pH and increased catecholamines have been shown to counteract the depressing effect of elevated K(+). This study examines (i) whether the effects of addition of lactic acid and adrenaline on the excitability of isolated muscles are caused by separate mechanisms and are additive and (ii) whether the effect of adding lactic acid or increasing CO(2) is related to a reduction of intra- or extracellular pH. Rat soleus muscles were incubated at a [K(+)](o) of 15 mM, which reduced tetanic force by 85%. Subsequent addition of 20 mM lactic acid or 10(-5) M adrenaline led to a small recovery of force, but when added together induced an almost complete force recovery. Compound action potentials showed that the force recovery was associated with recovery of muscle excitability. The improved excitability after addition of adrenaline was associated with increased Na(+)-K(+) pump activity resulting in hyperpolarization and an increase in the chemical Na(+) gradient. In contrast, addition of lactic acid had no effect on the membrane potential or the Na(+)-K(+) pump activity, but most likely increased excitability via a reduction in intracellular pH. It is concluded that the protective effects of acidosis and adrenaline on muscle excitability and force took place via different mechanisms and were additive. The results suggest that circulating catecholamines and development of acidosis during exercise may improve the tolerance of muscles to elevated [K(+)](o).
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Kemp G. Muscle cell volume and pH changes due to glycolytic ATP synthesis. J Physiol 2007; 582:461-5; author reply 467-70. [PMID: 17446216 PMCID: PMC2075294 DOI: 10.1113/jphysiol.2007.134643] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
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50
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Affiliation(s)
- M I Lindinger
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON, Canada N1G 2W1.
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