Seasonal variation in muscle fatigue in the sartorius muscle of the frog Rana pipiens

1991 ◽  
Vol 69 (6) ◽  
pp. 1712-1715
Author(s):  
Jean Marc Renaud
Keyword(s):  
Seasonal Variation ◽  
Rana Pipiens ◽  
Recovery Period ◽  
Sartorius Muscle ◽  
Tetanic Force ◽  
Fatigue Development ◽  
Significant Seasonal Variation ◽  
Significant Difference ◽  
Force Recovery ◽  
Frog Sartorius

The goal of this study was to determine whether seasonal variation occurs in the rates of fatigue development and force recovery in the frog sartorius muscle. The data were gathered from different experiments performed during a 6-year period (1983–1989). All frog sartorius muscles were stimulated to fatigue with tetanic contractions at the rate of 1/s for 3 min. The decrease in tetanic force after 1.5 and 3 min of stimulation was relatively consistent throughout the year. The only significant difference occurred in the muscles tested in September and October, which were less fatigue resistant than those tested in December. Following fatigue, muscles were stimulated at the rate of one contraction every 100 s, so that the recovery of tetanic force could be followed. A large and significant seasonal variation was observed in the recovery period. Frog sartorius muscles tested between March and July recovered their tetanic force at a faster rate than those tested between August and October. It was shown that the highest capacity to recover force coincides with the time of the year when frogs are the most active.

The effects of isotonic contractions on the rate of fatigue development and the resting membrane potential in the sartorius muscle of the frog, Rana pipiens

1991 ◽  
Vol 69 (11) ◽  
pp. 1754-1759 ◽  
Author(s):  
Jean Marc Renaud ◽  
Melvin Kong
Keyword(s):  
Relaxation Time ◽  
Resting Potential ◽  
Resting Membrane Potential ◽  
Sartorius Muscle ◽  
Tetanic Force ◽  
Fatigue Development ◽  
The Difference ◽  
Initial Difference ◽  
Isotonic Contractions ◽  
Frog Sartorius

The goal of this study was to characterize how isotonic contractions affect the rate of fatigue development. Muscle bundles dissected from frog sartorius muscles were stimulated with 100-ms long train of pulses (0.5 ms, 6 V, 140 Hz). To measure the effect of the isotonic contractions, isometric tetanus were elicited at regular time intervals during the stimulation to fatigue. In general, isotonic contractions caused a faster decrease in tetanic force than isometric contractions. The difference in tetanic force between an isotonic and isometric fatigue increased gradually over a 20-min period to 7.9 and 13.5% at 0.04 and 0.1 trains/s (TPS), respectively. At 0.2, 0.5, and 1.0 TPS, the decrease in tetanic force was also faster during an isotonic fatigue, which resulted in an initial difference in tetanic force between the two types of fatigue. The difference did not exceed 18.5% and did not persist throughout the stimulation period; i.e., the difference disappeared before the end of the fatigue stimulation. The half-relaxation time was prolonged during fatigue development, and the prolongation was greater during an isotonic fatigue, except at 0.04 TPS. The increases in the half-relaxation time at 0.2, 0.5, and 1.0 TPS were followed by a decrease, and the decreases were especially pronounced during an isotonic fatigue at 0.5 and 1.0 TPS. The results showed for the first time that isotonic contractions cause a faster rate of fatigue development in frog sartorius muscles, and this effect depends on the frequency of stimulation.Key words: muscle, fatigue, force, shortening, resting potential.

The effects of pH on the kinetics of fatigue and recovery in frog sartorius muscle

1985 ◽  
Vol 63 (11) ◽  
pp. 1435-1443 ◽  
Author(s):  
J. M. Renaud ◽  
G. W. Mainwood
Keyword(s):  
Extracellular Ph ◽  
Sartorius Muscle ◽  
Frog Sartorius Muscle ◽  
Fatigue Development ◽  
Effects Of Ph ◽  
Force Recovery ◽  
Ph Dependent ◽  
Contraction Cycle ◽  
Kinetics Of ◽  
Frog Sartorius

The effects of pH on the kinetics of fatigue and recovery in frog sartorius muscle were studied to establish whether the pH to which muscles are exposed (extracellular pH) has an effect on both the rate of fatigue development and recovery from fatigue. When frog sartorius muscles were stimulated with short tetanic stimuli at rates varying from 0.2 to 2.0 trains/s, a time- and frequency-dependent decrease in force development was observed, but extracellular pH had comparatively little effect. The recovery of tetanic force was dependent on the extracellular pH. This effect was characterized by a rapid recovery in force at pH 8.0 and an inhibition of recovery at pH 6.4 even when force decreased by only 25% during stimulation. Even when muscles were fatigued at pH 8.0 the rate of force recovery was still very small at pH 6.4. A model is proposed in which a step of the contraction cycle changes from a normal to a fatigued state. The rate of this transition is a function of the stimulation frequency and not pH. The reverse transition, from a fatigued to normal state is pH dependent; i.e., it is inhibited by H+. Measurements of resting and action potentials show that extracellular pH influences these parameters in the fatigue state, but there is no evidence that these changes are directly responsible for the pH-dependent step in the reversal of fatigue.

scholarly journals Clearance of Extracellular K+ during Muscle Contraction—Roles of Membrane Transport and Diffusion

2008 ◽  
Vol 131 (5) ◽  
pp. 473-481 ◽  
Author(s):  
Torben Clausen
Keyword(s):  
Extracellular Space ◽  
Time Course ◽  
Inhibitory Effects ◽  
Tension Development ◽  
Tetanic Force ◽  
New Information ◽  
Significant Difference ◽  
Force Recovery ◽  
Transport And Diffusion ◽  
Contractile Performance

Excitation of muscle often leads to a net loss of cellular K+ and a rise in extracellular K+ ([ K+ ]o), which in turn inhibits excitability and contractility. It is important, therefore, to determine how this K+ is cleared by diffusion into the surroundings or by reaccumulation into the muscle cells. The inhibitory effects of the rise in [K+ ]o may be assessed from the time course of changes in tetanic force in isolated muscles where diffusional clearance of K+ is eliminated by removing the incubation medium and allowing the muscles to contract in air. Measurements of tetanic force, endurance, and force recovery showed that in rat soleus and extensor digitorum longus (EDL) muscles there was no significant difference between the performance of muscles contracting in buffer or in air for up to 8 min. Ouabain-induced inhibition of K+ clearance via the Na+,K+ pumps markedly reduced contractile endurance and force recovery in air. Incubation in buffer containing 10 mM K+ clearly inhibited force development and endurance, and these effects were considerably reduced by stimulating Na+,K+ pumps with the β2-agonist salbutamol. Following 30–60 s of continuous stimulation at 60 Hz, the amount of K+ released into the extracellular space was assessed from washout experiments. The release of intracellular K+ per pulse was fourfold larger in EDL than in soleus, and in the two muscles, the average [K+ ]o reached 52.4 and 26.0 mM, respectively, appreciably higher than previously detected. In conclusion, prevention of diffusion of K+ from the extracellular space of isolated working muscles causes only modest interference with contractile performance. The Na+,K+ pumps play a major role in the clearance of K+ and the maintenance of force. This new information is important for the evaluation of K+-induced inhibition in muscles, where diffusional clearance of K+ is reduced by tension development sufficient to suppress circulation.

scholarly journals Physical and biochemical energy balance during an isometric tetanus and steady state recovery in frog sartorius at 0 degree C.

1983 ◽  
Vol 81 (3) ◽  
pp. 337-354 ◽  
Author(s):  
R J Paul
Keyword(s):  
Steady State ◽  
Heat Production ◽  
Isometric Force ◽  
Recovery Period ◽  
Lactate Production ◽  
High Energy ◽  
Sartorius Muscle ◽  
State Recovery ◽  
Frog Sartorius ◽  
Initial Heat

Frog sartorius muscle stimulated isometrically for 3 s every 256 s to attain a steady state in which initial heat (QI), recovery heat (QR), rate of O2 consumption (JO2), and isometric force (PO) generated are constant for each cycle. For a 3-s tetanus given every 256 s, JO2 was 0.106 mumol/(min . g blotted weight), approximately 71% of the maximum rate observed, whereas lactate production was negligible under these conditions. QI, QT(= QI + QR), and QT/QI were 88.2, 181.5, 2.06 mJ/g blotted weight, respectively. The high-energy phosphate breakdown (delta approximately P) breakdown during the first 3-s tetanus was not different from that during a contraction in the steady state and averaged 1.1 mumol/g blotted weight. Less than half of the initial heat could be accounted for in terms of the extent of the known chemical reactions occurring during contraction. From the stoichiometry of the theoretical biochemical pathways, the amount of ATP synthesized in the steady state exceeds delta approximately P during contraction by more than twofold, corresponding to an apparent ADP:O ratio of 1.5. If it is assumed that carbohydrate oxidation is the only net chemical reaction in the steady state, the total heat production can be explained on the basis of the measured JO2. Under this assumption, heat production during recovery was less than that expected on the basis of the oxygen consumption and delta approximately P during contraction. These observations support the hypothesis that the unexplained enthalpy production and low apparent ADP:O ratio are causally related, i.e., that the reaction(s) producing the unexplained heat during contraction is reversed during the recovery period.

Seasonality in Suicide: A Study of Farming Suicides in England and Wales

Crisis ◽  
2003 ◽  
Vol 24 (3) ◽  
pp. 93-97 ◽  
Author(s):  
Sue Simkin ◽  
Keith Hawton ◽  
Paul S.F. Yip ◽  
Carrie H.K. Yam
Keyword(s):  
Seasonal Variation ◽  
Harmonic Analysis ◽  
Nonparametric Tests ◽  
Occupational Group ◽  
Seasonal Patterns ◽  
Chi Square ◽  
England And Wales ◽  
Significant Seasonal Variation ◽  
Significant Difference ◽  
Chi Square Test

Summary: Seasonality in suicide rates has long been reported. Spring peaks in suicide deaths have been positively correlated with the proportion of the workforce engaged in agriculture. Some studies have indicated that suicides using violent methods are more likely to show seasonality. Recent research has suggested that seasonal patterns have diminished. This study examined deaths in male farmers, an occupational group which might be expected to be more vulnerable to seasonal influences because of the nature of their work and the relatively high proportion of farmers using violent methods for suicide. Data on suicides between 1982 and 1999 by males in England and Wales aged 15 years and over were provided by the Office for National Statistics. Seasonal patterns of suicide in farmers and nonfarmers were examined by nonparametric tests and harmonic analysis. No significant seasonal variation was found for farmers. For nonfarmers, although a chi-square test showed significant variation in monthly distribution, this was not found when a harmonic analysis was applied. There was no significant difference in the variation of violent suicides throughout the year. This study reinforces recent findings that seasonal variation in suicide appears to be diminishing, even in an occupational group where this might be expected.

Is the change in intracellular pH during fatigue large enough to be the main cause of fatigue?

1986 ◽  
Vol 64 (6) ◽  
pp. 764-767 ◽  
Author(s):  
J. M. Renaud ◽  
Y. Allard ◽  
G. W. Mainwood
Keyword(s):  
Intracellular Ph ◽  
Extracellular Ph ◽  
Sartorius Muscle ◽  
Bathing Solution ◽  
Tetanic Contraction ◽  
Tetanic Force ◽  
Fatigue Effect ◽  
Frog Sartorius Muscle ◽  
Stimulation Period ◽  
Frog Sartorius

The intracellular pH of frog sartorius muscles exposed to an extracellular pH 8.0 (25 mM HCO3−, 1% CO2) was 6.9–7.1. Following a fatiguing stimulation period (one tetanic contraction per second for 3 min), the intracellular pH was 6.5–6.7. When similar experiments were repeated with frog sartorius muscles exposed to pH 6.4 (2 mM HCO3−, 1% CO2), the intracellular pH was 6.8–6.9 at rest and 6.3–6.4 following fatigue. So, in both experiments the intracellular pH decreased by 0.4–0.5 pH unit during fatigue. When the CO2 concentration of the bathing solution was increased from 1 to 30%, the intracellular pH of resting muscles decreased from 7.0 to 6.2–6.3. Although the effect of CO2 on the intracellular pH was greater than the fatigue effect, the decrease in tetanic force with CO2 was less than 40%, while during fatigue the tetanic force decreased by at least 70%. Therefore in frog sartorius muscle the decrease in tetanic force during fatigue exceeds the decrease that is expected from just a change in intracellular pH.

Na+ and K+ effect on contractility of frog sartorius muscle: implication for the mechanism of fatigue

1995 ◽  
Vol 268 (6) ◽  
pp. C1528-C1536 ◽  
Author(s):  
R. Bouclin ◽  
E. Charbonneau ◽  
J. M. Renaud
Keyword(s):  
Sartorius Muscle ◽  
Combined Effects ◽  
Large Decrease ◽  
Tetanic Contraction ◽  
Muscle Contractility ◽  
Tetanic Force ◽  
Twitch Force ◽  
Individual Effects ◽  
K Concentration ◽  
Frog Sartorius

Although a decrease in extracellular Na+ and an increase in K+ concentration are believed to contribute to the decrease in force during fatigue, the force of unfatigued muscle decreases only with quite large changes in Na+ and K+ concentration. The objective of this study was to determine whether concomitant and smaller changes in Na+ and K+ concentration have greater effects on muscle contractility than individual changes. At 3 mM K+, a large decrease in Na+ from 120 to 60 mM had no effect on the twitch force, while the tetanic force decreased by 31.2%. At 120 mM Na+, an increase in K+ from 3 to 9 mM potentiated the twitch force by 41.1%, had no effect on the tetanic force at 7 mM, and decreased the tetanic force by 40.4% at 9 mM; both the twitch force and tetanic force were completely abolished at 11 mM K+. The potentiation of the twitch force between 3 and 9 mM K+ was less at 60, 80, and 100 mM than at 120 mM Na+. A reduction in Na+ concentration also reduced the K+ concentration at which the twitch force and tetanic force decreased and were completely abolished. It is shown that the combined effects of Na+ and K+ on the twitch and tetanic contractions were greater than the sum of their individual effects. Furthermore, it is proposed that neither Na+ nor K+ alone can be considered as an important factor in the decrease in force during fatigue, whereas together they are important for the tetanic contraction, but not for the twitch contraction.

scholarly journals Variations in Organic Carbon Content and Dehydrogenases Activity in Post-Agriculture Forest Soils: A Case Study in South-Western Pomerania

Forests ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 459
Author(s):  
Katarzyna Wiatrowska ◽  
Jolanta Komisarek ◽  
Janusz Olejnik
Keyword(s):  
Seasonal Variation ◽  
Organic Carbon ◽  
Forest Soils ◽  
Stand Age ◽  
Organic Carbon Content ◽  
Sharp Drop ◽  
The North ◽  
Significant Seasonal Variation ◽  
Significant Difference ◽  
Dehydrogenases Activity

Temperate forest soils of Europe are regarded as an important sink of carbon and thought to have potential to sequester CO2 from atmosphere. However, there are insufficient data not only on organic carbon (OC) content in forest soils and its temporal changes but also on microbiological activity and especially their relationship to carbon turnover. In this study seven research plots were located on afforested land in the north-western part of Poland in Tuczno Forest District (Western Pomerania) in order to examine seasonal variation in OC content and dehydrogenases activity (DHA) during 2012–2016. Based on the studies conducted, statistically significant seasonal variation of the OC content was observed. Higher amounts of OC in the A horizon were observed during spring and autumn seasons and lower in summer. However, no seasonal variation on OC content was observed in the organic horizon (O horizon). Although DHA is thought to exhibit strong seasonal variability, no seasonal variation on DHA was observed. However, a statistically significant difference was observed among studied years (2012–2016), a sharp drop of DHA was noted from spring 2014. Statistical analyses revealed that OC content in soils was a function of forest stand age and progressing acidification of soil. Moreover, OC content in O horizon was negatively correlated with soil moisture and DHA, suggesting that periods with higher microbial activity lead to lower accumulation of carbon in the O horizon. During 2012–2016 only for the O horizon was an increase in OC content was observed.

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