Effect of intracellular pH on force development depends on temperature in intact skeletal muscle from mouse

1996 ◽  
Vol 271 (3) ◽  
pp. C878-C886 ◽  
Author(s):  
R. W. Wiseman ◽  
T. W. Beck ◽  
P. B. Chase
Keyword(s):  
Muscle Fatigue ◽  
Intracellular Ph ◽  
Force Production ◽  
Resonance Spectroscopy ◽  
Dependent Inhibition ◽  
Effects Of Ph ◽  
Different Temperatures ◽  
Lower Temperature ◽  
Glycerinated Fibers

The cellular mechanism of muscle fatigue is still in debate. Opposite conclusions regarding the role of intracellular pH (pHi) in fatigue have been drawn from skinned fiber vs. isolated perfused muscle studies. Because these experiments are typically performed at different temperatures, we tested the hypothesis that temperature alters the effects of pH on force. Tetanic force of isolated mouse extensor digitorum longus was measured at temperatures between 13 and 25 degrees C in either normocapnia (5% CO2) or hypercapnia (25% CO2). Hypercapnia decreased pHi (monitored by 31P nuclear magnetic resonance spectroscopy) by the same amount at both 15 and 25 degrees C. However, inhibition of force by hypercapnia was greater at the lower temperature. A similar pattern of temperature-dependent inhibition of force by pH was observed in glycerinated fibers from rabbit psoas at maximum Ca2+ activation. We conclude that temperature differences are responsible for disparate conclusions on the role of pHi in muscle fatigue. Based on our results, we suggest that changes in pHi may have little or no role in the loss in force production associated with muscular fatigue at physiological temperatures.

Comparative Analysis of Autoxidation of Haemoglobin

2001 ◽  
Vol 204 (11) ◽  
pp. 2029-2033
Author(s):  
Frank B. Jensen
Keyword(s):  
Temperature Sensitivity ◽  
Oxidation Rate ◽  
Protective Role ◽  
Yellowfin Tuna ◽  
Histidine Residue ◽  
River Lamprey ◽  
Different Temperatures ◽  
Lower Temperature ◽  
The Impact

SUMMARY Autoxidation of oxyhaemoglobin (oxyHb) to methaemoglobin was measured at different temperatures in haemoglobin solutions from Atlantic hagfish, river lamprey, common carp, yellowfin tuna and pig. The aims were to evaluate the impact of the absent distal histidine in hagfish haemoglobin, the importance of oxyHb being either monomeric (hagfish and lamprey) or tetrameric (carp, tuna and pig) and to gain information on the temperature-sensitivity of autoxidation. The rate of autoxidation was lower in hagfish than in carp, yellowfin tuna and lamprey haemoglobins at any given temperature. Substitution of the distal histidine residue (His E7) with glutamine in hagfish haemoglobin was therefore not associated with an accelerated autoxidation, as might be expected on the basis of the normal protective role of His E7. Glutamine may have similar qualities to histidine and be involved in the low susceptibility to autoxidation. The low oxidation rate of hagfish haemoglobin, together with an oxidation rate of lamprey haemoglobin that did not differ from that of carp and yellowfin tuna haemoglobins, also revealed that autoxidation was not accelerated in the monomeric oxyhaemoglobins. Pig haemoglobin was oxidised more slowly than fish haemoglobins, demonstrating that fish haemoglobins are more sensitive to autoxidation than mammalian haemoglobins. The rate of autoxidation of hagfish haemoglobin was, however, only significantly greater than that of pig haemoglobin at high temperatures. Autoxidation was accelerated by rising temperature in all haemoglobins. Arrhenius plots of carp and yellowfin tuna haemoglobin revealed a break at 25°C, reflecting a lower temperature-sensitivity between 5 and 25°C than between 25 and 40°C.

scholarly journals Contraction frequency modulates muscle fatigue and the rate of myoglobin desaturation during incremental contractions in humans

2008 ◽  
Vol 33 (5) ◽  
pp. 915-921 ◽  
Author(s):  
Danielle M. Wigmore ◽  
Douglas E. Befroy ◽  
Ian R. Lanza ◽  
Jane A. Kent-Braun
Keyword(s):  
Muscle Fatigue ◽  
Muscle Force ◽  
Force Production ◽  
Metabolic Cost ◽  
Resonance Spectroscopy ◽  
Isometric Contractions ◽  
Metabolic Demand ◽  
Contraction Frequency ◽  
Duty Cycles ◽  
Force Time

The metabolic cost of force production, and therefore the demand for oxygen, increases with intensity and frequency of contraction. This study investigated the interaction between fatigue and oxygenation, as reflected by deoxymyoglobin (dMb), during slow and rapid rhythmic isometric contractions having the same duty cycles and relative force–time integrals (FTIs). We used 1H magnetic resonance spectroscopy and measures of dorsiflexor muscle force to compare dMb and fatigue (fall of maximal voluntary force, MVC) in 11 healthy adults (29 ± 7 y) during 16 min of slow (4 s contraction, 6 s relaxation) and rapid (1.2 s, 1.8 s) incremental (10%–80% MVC) contractions. We tested the hypotheses that (i) the rate of Mb desaturation would be faster in rapid than in slow contractions and (ii) fatigue, Mb desaturation, and the fall in FTI would be greater, and PO2 (oxygen tension) lower, at the end of rapid contractions than at the end of slow contractions. Although dMb increased more quickly during rapid contractions (p = 0.05), it reached a plateau at a similar level in both protocols (~42% max, p = 0.49), likely due to an inability to further increase force production and thus metabolic demand. Despite the similar dMb at the end of both protocols, fatigue was greater in rapid (56.6% ± 2.7% baseline) than in slow (69.5% ± 4.0%, p = 0.01) contractions. These results indicate that human skeletal muscle fatigue during incremental isometric contractions is in part a function of contraction frequency, possibly due to metabolic inhibition of the contractile process.

Phase Transformation from Mg to MgH2 Studied by SEM Metallography

2009 ◽  
Vol 1216 ◽  
Author(s):  
Amelia Montone ◽  
Annalisa Aurora ◽  
Daniele Mirabile Gattia ◽  
Marco Vittori Antisari
Keyword(s):  
Phase Transformation ◽  
Kinetic Analysis ◽  
Hydrogenation Reaction ◽  
Hydrogen Gas ◽  
Thermodynamic Force ◽  
Different Temperatures ◽  
Lower Temperature ◽  
Experimental Findings ◽  
Kinetics Of

AbstractMetallographic information has been used to support the kinetic analysis and the relative experimental findings in the phase transformation from Mg to MgH2, by absorption of hydrogen gas. In particular the method provides detailed information on the role of localized features like catalyst particles and defects present in the sample, which is obtained from ball milled MgH2 enriched with 5wt% Fe. In this work we have compared the kinetics of the hydrogenation reaction carried out at two different temperatures while keeping constant the thermodynamic force driving the reaction. This last was achieved by carefully controlling the hydrogen gas pressure. Despite this fact, the sample microstructure shows a marked effect of the temperature on the nucleation mechanism. In particular we have noticed that the density of sites active for nucleation is higher at lower temperature.Instant nucleation deduced by the kinetic analysis was confirmed by comparing the microstructure of samples at different reaction stages.

Muscle Fatigue: The Role of Metabolism

2002 ◽  
Vol 27 (1) ◽  
pp. 70-82 ◽  
Author(s):  
Kevin K. Mccully ◽  
Bertrand Authier ◽  
Jennifer Olive ◽  
Bernard J. Clark
Keyword(s):  
Muscle Fatigue ◽  
Resonance Spectroscopy ◽  
High Group ◽  
Tension Development ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
Medium Intensity ◽  
End Products ◽  
Stimulation Period

This paper examined the role of metabolites in causing muscle fatigue. Previous studies have shown that Pi [Formula: see text] and H+ may be important factors in causing fatigue. A key question is the potential interaction between metabolic end-products and calcium related excitation-contraction coupling fatigue (ECC). An in vivo rat muscle model was used to measure tension development and metabolic end-products in response to electrical stimulation. Two stimulation protocols were used, high intensity stimulation followed by a medium intensity stimulation (High Group), and low intensity stimulation followed by a medium intensity stimulation (Low Group). Metabolic fatigue was based on concentrations of [Formula: see text] measured with phosphorus magnetic resonance spectroscopy. ECC fatigue was measured as the fatigue in excess of metabolic fatigue, and as the relative decline of force at low compared to high stimulation frequencies. During the initial stimulation period, the High Group had greater metabolic fatigue (p < 0.001) and greater ECC fatigue (p = 0.007). During the second stimulation period and recovery, the High Group had no difference in metabolic fatigue (p = 0.07) and greater ECC fatigue (p = 0.015). These results present a method for determining the relative amounts of metabolic and ECC fatigue, and suggest that metabolites can increase the amount of ECC fatigue. Key words: fatigue, skeletal muscle, excitation contraction coupling

Muscle fatigue in the frog semitendinosus: role of the high-energy phosphates and Pi

1992 ◽  
Vol 263 (4) ◽  
pp. C803-C809 ◽  
Author(s):  
L. V. Thompson ◽  
R. H. Fitts
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fatigue ◽  
Force Production ◽  
High Energy ◽  
High Energy Phosphates ◽  
Time Period ◽  
Freeze Dried ◽  
Force Recovery ◽  
Small Decline

The purpose of this study was to determine the concentration of ATP, phosphocreatine (PC), Pi, lactate, and glycogen in single frog skeletal muscle fibers and assess their role in the etiology of muscle fatigue. The frog semitendinosus (ST) muscle was fatigued, quick frozen at selected time points of recovery, and freeze-dried, and single fibers were dissected, weighed, and assayed for ATP, PC, lactate, Pi, and glycogen. The fatigue protocol reduced peak tetanic force (Po) to 8.5% of initial, while ATP and PC decreased from 45.18 to 33.16 and 128.90 to 28.76 mmol/kg dry wt, respectively. Lactate and Pi increased from 29.36 to 100.84 and 33.04 to 142.50 mmol/kg dry wt, respectively. It is doubtful that the small decline in ATP limited cross-bridge force production. Although a significant correlation between the recovery of PC and Po was demonstrated (r = 0.994), the time period showing the fastest rate of force recovery coincided with little change in PC. A significant correlation was demonstrated between the recovery of both total and the H2PO4- form of Pi and Po. In conclusion, the results of this study are incompatible with the hypothesis that the high-energy phosphates (ATP and PC) mediate muscle fatigue. The large increase in Pi with stimulation and the high correlation between the recovery of both total and the H2PO4- form of Pi and Po support a role for Pi in the production of skeletal muscle fatigue.

Dilution acidosis: evidence for a role of intracellular pH in the control of ventilation

1996 ◽  
Vol 80 (5) ◽  
pp. 1804-1810 ◽  
Author(s):  
C. E. Kasserra ◽  
D. R. Jones
Keyword(s):  
Ion Exchange ◽  
Intracellular Ph ◽  
Pekin Duck ◽  
Disulfonic Acid ◽  
Resonance Spectroscopy ◽  
Electrolyte Balance ◽  
Extracellular Acidosis ◽  
Arterial Ph ◽  
Water And Electrolyte Balance

Acute hyperosmolality results in an extracellular dilution acidosis and hypercarbia that does not stimulate ventilatory compensation. The osmotic stress is also associated with shifts in water and electrolyte balance and an increase in intracellular pH. The alkaline intracellular pH was hypothesized to have a role in preventing a normal respiratory response to the extracellular acidosis and hypercarbia. Therefore, this study examined the effect of ion-exchange blockade on intra- and extracellular pH and ventilation during acute hyperosmolality in the Pekin duck (Anas platyrhynchos) by using 31P-nuclear magnetic resonance spectroscopy. Both 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and amiloride inhibited the development of the intracellular alkalosis that normally develops in muscle during acute hyperosmolality. Instead, exposure to hyperosmotic stress during ion-exchange blockade resulted in a significant acidosis both intracellularly and extracellularly. Arterial pH decreased 0.10 +/- 0.04 pH unit with a sucrose infusion after either blocker, and intracellular pH decreased 0.11 +/- 0.06 and 0.16 +/- 0.04 pH units with a sucrose infusion after DIDS and amiloride, respectively. Ventilation increased 79 +/- 28 and 122 +/- 100%, respectively, during acute hyperosmolality after ion-exchange blockade with either DIDS or amiloride. The results suggest that intracellular pH may play a role in the ventilatory response to acid-base perturbations. The data also indicate that both Cl-/HCO3- and Na+/H+ exchanges are involved in the development of the intracellular alkalosis during hyperosmotically induced extracellular acidosis.

Investigation on the antibacterial activity of electronic cigarette liquids (ECLs): a proof of concept study

2020 ◽  
Vol 21 ◽  
Author(s):  
Virginia Fuochi ◽  
Massimo Caruso ◽  
Rosalia Emma ◽  
Aldo Stivala ◽  
Riccardo Polosa ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Bacterial Species ◽  
A549 Cells ◽  
Bactericidal Effect ◽  
Minimal Bactericidal Concentration ◽  
Viability Assay ◽  
Dependent Inhibition ◽  
Dose Dependent Inhibition ◽  
Dose Dependent

Background: The key ingredients of e-cigarettes liquid are commonly propane-1,2-diol (also called propylene glycol) and propane-1,2,3-triol (vegetal glycerol) and their antimicrobial effects are already established. The nicotine and flavors which are often present in e-liquids can interfere with the growth of some microorganisms. Objective: The effect of the combining these elements in e-liquids is unknown. The aim of the study was to investigate the possible effects of these liquids on bacterial growth in the presence or absence of nicotine and flavors. Methods: Susceptibilities of pathogenic strains (Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa, Acinetobacter baumannii, Escherichia coli, Enterococcus faecalis and Sarcina lutea) were studied by means of a multidisciplinary approach. Cell viability and antioxidant assays were also evaluated. Results: All e-liquids investigated showed antibacterial activity against at least one pathogenic strain. A higher activity was correlated to the presence of flavors and nicotine. Discussion: In most cases the value of minimal bactericidal concentration is equal to the value of minimal inhibitory concentration showing that these substances have a bactericidal effect. This effect was observed in concentrations up to 6.25% v/v. Antioxidant activity was also correlated to presence of flavors. Over time, the viability assay in human epithelial lung A549 cells showed a dose-dependent inhibition of cell growth. Conclusion: Our results have shown that flavors considerably enhance the antibacterial activity of propane-1,2-diol and propane-1,2,3-triol. This study provides important evidence that should be taken into consideration in further investigative approaches, to clarify the different sensitivity of the various bacterial species to e-liquids, including the respiratory microbiota, to highlight the possible role of flavors and nicotine.

Neurometabolic alterations in the nucleus accumbens of smokers assessed with 1 H magnetic resonance spectroscopy: The role of glutamate and neuroinflammation

2021 ◽  
Author(s):  
Colette A. Steinegger ◽  
Niklaus Zoelch ◽  
Andreas Hock ◽  
Anke Henning ◽  
Etna J.E. Engeli ◽  
...  
Keyword(s):  
Nucleus Accumbens ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy

scholarly journals DNA methylation and lipid metabolism: an EWAS of 226 metabolic measures

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Monica del C. Gomez-Alonso ◽  
Anja Kretschmer ◽  
Rory Wilson ◽  
Liliane Pfeiffer ◽  
Ville Karhunen ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Lipid Metabolism ◽  
Population Based ◽  
Total Serum ◽  
Resonance Spectroscopy ◽  
Metabolic Disturbances ◽  
Cpg Sites ◽  
Gene Transcripts

Abstract Background The discovery of robust and trans-ethnically replicated DNA methylation markers of metabolic phenotypes, has hinted at a potential role of epigenetic mechanisms in lipid metabolism. However, DNA methylation and the lipid compositions and lipid concentrations of lipoprotein sizes have been scarcely studied. Here, we present an epigenome-wide association study (EWAS) (N = 5414 total) of mostly lipid-related metabolic measures, including a fine profiling of lipoproteins. As lipoproteins are the main players in the different stages of lipid metabolism, examination of epigenetic markers of detailed lipoprotein features might improve the diagnosis, prognosis, and treatment of metabolic disturbances. Results We conducted an EWAS of leukocyte DNA methylation and 226 metabolic measurements determined by nuclear magnetic resonance spectroscopy in the population-based KORA F4 study (N = 1662) and replicated the results in the LOLIPOP, NFBC1966, and YFS cohorts (N = 3752). Follow-up analyses in the discovery cohort included investigations into gene transcripts, metabolic-measure ratios for pathway analysis, and disease endpoints. We identified 161 associations (p value < 4.7 × 10−10), covering 16 CpG sites at 11 loci and 57 metabolic measures. Identified metabolic measures were primarily medium and small lipoproteins, and fatty acids. For apolipoprotein B-containing lipoproteins, the associations mainly involved triglyceride composition and concentrations of cholesterol esters, triglycerides, free cholesterol, and phospholipids. All associations for HDL lipoproteins involved triglyceride measures only. Associated metabolic measure ratios, proxies of enzymatic activity, highlight amino acid, glucose, and lipid pathways as being potentially epigenetically implicated. Five CpG sites in four genes were associated with differential expression of transcripts in blood or adipose tissue. CpG sites in ABCG1 and PHGDH showed associations with metabolic measures, gene transcription, and metabolic measure ratios and were additionally linked to obesity or previous myocardial infarction, extending previously reported observations. Conclusion Our study provides evidence of a link between DNA methylation and the lipid compositions and lipid concentrations of different lipoprotein size subclasses, thus offering in-depth insights into well-known associations of DNA methylation with total serum lipids. The results support detailed profiling of lipid metabolism to improve the molecular understanding of dyslipidemia and related disease mechanisms.

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