scholarly journals Efficiency of energy conversion during shortening of muscle fibres from the dogfish Scyliorhinus canicula

1991 ◽  
Vol 158 (1) ◽  
pp. 343-353 ◽  
Author(s):  
N. A. Curtin ◽  
R. C. Woledge
Keyword(s):  
Total Energy ◽  
Energy Conversion ◽  
Heat Production ◽  
Mechanical Power ◽  
Energy Output ◽  
Muscle Fibres ◽  
Fibre Bundles ◽  
Velocity Of Shortening ◽  
Myotomal Muscle ◽  
Fibre Preparation

Force and heat production were measured during isovelocity shortening of tetanized white myotomal muscle fibres from the dogfish at 12 degrees C. For each fibre preparation a range of velocities was used. Mechanical power was calculated from force X velocity of shortening. The rate of total energy output during shortening was evaluated as the sum of mechanical power and the rate of heat production. The ratio of mechanical power to total energy rate was taken as a measure of efficiency of energy conversion to mechanical power during shortening. Efficiency was maximal and varied little in the range of shortening velocities 0.42-0.89 fibres lengths s-1 (0.11-0.23 Vmax); maximal efficiency was 0.33 +/− 0.01 (+/− S.E.M., N = 23 measurements on seven fibre bundles). The efficiency of the white fibres from dogfish was less than that measured in the same way in earlier experiments on frog muscle and tortoise muscle.

EFFICIENCY OF ENERGY CONVERSION DURING SINUSOIDAL MOVEMENT OF WHITE MUSCLE FIBRES FROM THE DOGFISH SCYLIORHINUS CANICULA

1993 ◽  
Vol 183 (1) ◽  
pp. 137-147 ◽  
Author(s):  
N. A. Curtin ◽  
R. C. Woledge
Keyword(s):  
Power Output ◽  
High Efficiency ◽  
Fibre Length ◽  
Dry Mass ◽  
Energy Output ◽  
Maximum Efficiency ◽  
Muscle Fibres ◽  
Work Output ◽  
Sinusoidal Movement ◽  
Myotomal Muscle

Net work output and heat production of white myotomal muscle fibres from the dogfish were measured during complete cycles of sinusoidal movement at 12°C. The peak-to-peak movement was about 9 % of the muscle fibre length; three stimuli at 32 ms intervals were given in each mechanical cycle. The frequency of movement and the timing of the stimulation were varied for each preparation to find the optimal conditions for power output and those optimal for efficiency (the ratio of net work output to total energy output as heat+work). To achieve either maximum power or maximum efficiency, the tetanus must start while the muscle fibres are being stretched, before the beginning of the shortening part of the mechanical cycle. The highest power output, averaged over one cycle, was 0.23+/−0.014 W g-1 dry mass (+/−s.e.m., N=9, 46.9+/−2.8 mW g-1 wet mass) and was produced during movement at 3.5 Hz. The highest efficiency, 0.41+/−0.02 (+/−s.e.m., N=13), occurred during movements at 2.0-2.5 Hz. This value is higher than the efficiency previously measured during isovelocity shortening of these fibres. The implications of the high efficiency for crossbridge models of muscle contraction are discussed.

scholarly journals Power Output and Force-Velocity Relationship of Live Fibres from White Myotomal Muscle of the Dogfish, Scyliorhinus Canicula

1988 ◽  
Vol 140 (1) ◽  
pp. 187-197 ◽  
Author(s):  
N. A. CURTIN ◽  
R. C. WOLEDGE
Keyword(s):  
Power Output ◽  
Maximum Velocity ◽  
Muscle Fibres ◽  
Fish Length ◽  
Skinned Fibres ◽  
Step Method ◽  
Velocity Relationship ◽  
Velocity Of Shortening ◽  
Force Velocity ◽  
Myotomal Muscle

The relationship between force and velocity of shortening and between power and velocity were examined for myotomal muscle fibre bundles from the dogfish. The maximum velocity of shortening, mean value 4.8 ± 0.2 μms−1 half sarcomere−1 (±S.E.M., N = 13), was determined by the ‘slack step’ method (Edman, 1979) and was found to be independent of fish length. The force-velocity relationship was hyperbolic, except at the high-force end where the observations were below the hyperbola fitted to the rest of the data. The maximum power output was 91 ± 14 W kg−1 wet mass (±S.E.M., N = 7) at a velocity of shortening of 1.3 ± 0.13μms−1 halfsarcomere−1 (±S.E.M., N = 7). This power output is considerably higher than that previously reported for skinned fibres (Bone et al. 1986). Correspondingly the force-velocity relationship is less curved for intact fibres than for skinned fibres. The maximum swimming speed (normalized for fish length) predicted from the observed power output of the muscle fibres decreased with increasing fish size; it ranged from 12.9 to 7.8 fish lengths s−1 for fish 0155–0.645m in length.

Power at the expense of efficiency in contraction of white muscle fibres from dogfish Scyliorhinus canicula

1996 ◽  
Vol 199 (3) ◽  
pp. 593-601 ◽  
Author(s):  
N Curtin ◽  
R Woledge
Keyword(s):  
Duty Cycle ◽  
White Muscle ◽  
Fibre Length ◽  
Energy Output ◽  
Muscle Fibres ◽  
Cycle Duration ◽  
Scyliorhinus Canicula ◽  
Stimulus Timing ◽  
High Level ◽  
Myotomal Muscle

Work and heat production of white myotomal muscle fibres from dogfish were measured during sinusoidal movement (0.71-5.0 Hz) at 12 C. Stimulus phase (stimulus timing relative to movement) and duty cycle (stimulus duration as a fraction of movement cycle duration) were varied to determine the parameters optimal for power output and for efficiency (work/total energy output). Movements of 0.067 and 0.120L0 were used, where L0 is the muscle fibre length giving maximum force in an isometric tetanus. At each frequency of movement and duty cycle, the stimulus phase giving the highest power was the same as that giving the highest efficiency. In contrast, at each frequency and optimal stimulus phase, the dependence of power on duty cycle was very different from the dependence of efficiency on duty cycle. Power generally increased with increasing duty cycle, whereas efficiency decreased. Thus, high power can be achieved at the expense of efficiency by adjusting stimulus duty cycle. When stimulus phase and duty cycle were optimized, efficiency was always higher for the larger distance of movement. The efficiency of energy conversion can be maintained at a high level as the frequency of movement increases from 1.25 to 5.0 Hz.

The variation of total heat production in a twitch with velocity of shortening

1964 ◽  
Vol 159 (977) ◽  
pp. 596-605 ◽  
Keyword(s):  
Total Energy ◽  
Heat Production ◽  
Total Heat ◽  
Constant Speed ◽  
Complete Cycle ◽  
Velocity Of Shortening ◽  
Speed Of Shortening

In single twitches of toad sartorii at 0 °C, released at constant speed by an ergometer, the relation has been studied experimentally between total heat production and velocity of shortening. The curve is complex, first falling and then rising with increasing speed. The reasons for the form of the curve are discussed. Carlson, Hardy & Wilkie (1963 a , b ) reported recently that in after-loaded isotonic twitches the heat production remained about constant when the load was varied. They concluded that in the complete cycle of a twitch there is no evidence for heat of shortening. In the present experiments, in which the speed of shortening was varied instead of the load, the results were quite different. The heat altered considerably and the heat of shortening was obvious. An explanation of the contradiction is offered. Mean curves are given for the heat H , the total energy ( H + W ) and the efficiency W /( H + W ) as functions of the velocity of shortening in a twitch. An Appendix refers to Fenns original experiments (1923).

EFFICIENCY OF ENERGY CONVERSION DURING SINUSOIDAL MOVEMENT OF RED MUSCLE FIBRES FROM THE DOGFISH SCYLIORHINUS CANICULA

1993 ◽  
Vol 185 (1) ◽  
pp. 195-206 ◽  
Author(s):  
N. A. Curtin ◽  
R. C. Woledge
Keyword(s):  
Power Output ◽  
Fibre Length ◽  
Stimulus Frequency ◽  
Energy Output ◽  
Maximum Efficiency ◽  
Muscle Fibres ◽  
Work Output ◽  
Sinusoidal Movement ◽  
The Difference ◽  
Myotomal Muscle

Bundles of red myotomal muscle fibres isolated from dogfish were electrically stimulated at 12 sC. Peak twitch force was 54 % of that produced by a brief isometric tetanus. Relaxation was slower than in white fibres, but much faster than would be expected for the tonic fibres found in amphibian muscle. These two results indicate that the red fibres in dogfish are slow, but not tonic, in their behaviour. Net work output and heat production were measured during complete cycles of sinusoidal movement. The following variables were kept constant: peak-to-peak movement, about 7 % of the muscle fibre length; tetanus duration, 33 % of the mechanical cycle time; stimulus frequency, 40 Hz. The frequency of movement and the timing of the stimulation were varied for each preparation to find the conditions optimal for power output and those optimal for efficiency (the ratio of net work output to total energy output as heat+work). To achieve either maximum power or maximum efficiency, the tetanus must start while the muscle fibres are being stretched, before the beginning of the shortening part of the mechanical cycle. The highest power output was produced during movement at 1.02 Hz. The highest efficiency, 0.507+/−0.045 (+/−s.e.m., N=9), was at 0.61-0.95 Hz. The efficiency is higher than that previously measured during sinusoidal movement of white fibres; the difference, 0.095+/− 0.045 (+/−s.e.m. of the difference, d.f. 20), is statistically significant at the 5 % level.

scholarly journals Comparison of energy inputs and energy efficiency for maize in a long-term tillage experiment under Pannonian climate conditions

2021 ◽  
Vol 67 (No. 5) ◽  
pp. 45-52
Author(s):  
Gerhard Moitzi ◽  
Reinhard W. Neugschwandtner ◽  
Hans-Peter Kaul ◽  
Helmut Wagentristl
Keyword(s):  
Energy Efficiency ◽  
Total Energy ◽  
Fuel Consumption ◽  
Crop Production ◽  
Energy Input ◽  
Conservation Tillage ◽  
Energy Output ◽  
No Tillage ◽  
Tillage Systems ◽  
Total Energy Input

Sustainable crop production requires an efficient usage of fossil energy. This six-year study on a silt loam soil (chernozem) analysed the energy efficiency of four tillage systems (mouldboard plough 25–30 cm, deep conservation tillage 35 cm, shallow conservation tillage 8–10 cm, no-tillage). Fuel consumption, total energy input (made up of both direct and indirect input), grain of maize yield, energy output, net-energy output, energy intensity and energy use efficiency were considered. The input rates of fertiliser, herbicides and seeds were set constant; measured values of fuel consumption were used for all tillage operations. Total fuel consumption for maize (Zea mays L.) production was 81.6, 81.5, 69.5 and 53.2 L/ha for the four tillage systems. Between 60% and 64% of the total energy input (17.0–17.4 GJ/ha) was indirect energy (seeds, fertiliser, herbicides, machinery). The share of fertiliser energy of the total energy input was 36% on average across all tillage treatments. Grain drying was the second highest energy consumer with about 22%. Grain yield and energy output were mainly determined by the year. The tillage effect on yield and energy efficiency was smaller than the growing year effect. Over all six years, maize produced in the no-tillage system reached the highest energy efficiency.  

scholarly journals Energy and Greenhouse Gases Balances of Cotton Farming in Iran: A Case Study

2018 ◽  
Vol 66 (1) ◽  
pp. 101-109 ◽  
Author(s):  
Moslem Sami ◽  
Habib Reyhani
Keyword(s):  
Total Energy ◽  
Ghg Emissions ◽  
Energy Output ◽  
Consumption Pattern ◽  
Cotton Production ◽  
Energy Productivity ◽  
Energy Inputs ◽  
Golestan Province ◽  
Ratio Energy

This study evaluated the impacts of cotton farming on the climate changes in terms of energy and greenhouse gas (GHG) emission indices. Energy consumption pattern and sensitivity of energy inputs were evaluated and share of each input in GHG emissions was determined in the form of direct and indirect emissions for cotton farms in Golestan province of Iran. The total energy input and energy output were calculated to be 34,424.19 and 41,496.67 MJ/ha respectively. The share of fertilizers by 45.0 % of total energy inputs was the highest. This was followed by energies of fuel (18.4 %) and irrigation (17.9 %) respectively. Fertilizers and fuels were also the biggest producers of GHGs in the farms with shares of 61.95 and 24.32 % of total GHGs emission. Energy ratio, energy balance, energy intensity and energy productivity were found as 1.21, 7,072.48 MJ/ha, 9.79 MJ/kg and 0.10 kg/MJ, respectively. Results of sensitivity analysis indicated that the cotton production was more sensitive to energies of seed and human labour than other inputs and an additional use of 1 MJ of each of these inputs would lead to a change in the yield by −0.75 and 0.73 kg/ha, respectively. The results also showed, in the process of cotton farming 897.80 and 1177.67 kg CO2 – equivalent of direct and indirect GHG were emitted per hectare respectively.

scholarly journals Integrated Process for Ethanol, Biogas, and Edible Filamentous Fungi-Based Animal Feed Production from Dilute Phosphoric Acid-Pretreated Wheat Straw

2017 ◽  
Vol 184 (1) ◽  
pp. 48-62 ◽  
Author(s):  
Ramkumar B. Nair ◽  
Maryam M. Kabir ◽  
Patrik R. Lennartsson ◽  
Mohammad J. Taherzadeh ◽  
Ilona Sárvári Horváth
Keyword(s):  
Phosphoric Acid ◽  
Total Energy ◽  
Wheat Straw ◽  
Ethanol Fermentation ◽  
Biogas Production ◽  
Waste Stream ◽  
Energy Output ◽  
Yield Potential ◽  
Generation Process ◽  
Pretreated Wheat Straw

AbstractIntegration of wheat straw for a biorefinery-based energy generation process by producing ethanol and biogas together with the production of high-protein fungal biomass (suitable for feed application) was the main focus of the present study. An edible ascomycete fungal strain Neurospora intermedia was used for the ethanol fermentation and subsequent biomass production from dilute phosphoric acid (0.7 to 1.2% w/v) pretreated wheat straw. At optimum pretreatment conditions, an ethanol yield of 84 to 90% of the theoretical maximum, based on glucan content of substrate straw, was observed from fungal fermentation post the enzymatic hydrolysis process. The biogas production from the pretreated straw slurry showed an improved methane yield potential up to 162% increase, as compared to that of the untreated straw. Additional biogas production, using the syrup, a waste stream obtained post the ethanol fermentation, resulted in a combined total energy output of 15.8 MJ/kg wheat straw. Moreover, using thin stillage (a waste stream from the first-generation wheat-based ethanol process) as a co-substrate to the biogas process resulted in an additional increase by about 14 to 27% in the total energy output as compared to using only wheat straw-based substrates.

The energetic cost of activation of white muscle fibres from the dogfish Scyliorhinus canicula

1997 ◽  
Vol 200 (3) ◽  
pp. 495-501 ◽  
Author(s):  
F Lou ◽  
N Curtin ◽  
R Woledge
Keyword(s):  
Heat Production ◽  
White Muscle ◽  
Isometric Force ◽  
Force Production ◽  
Total Heat ◽  
Energetic Cost ◽  
Maximum Efficiency ◽  
Muscle Fibres ◽  
Scyliorhinus Canicula ◽  
A Value

The energetic cost of activation was measured during an isometric tetanus of white muscle fibres from the dogfish Scyliorhinus canicula. The total heat production by the fibres was taken as a measure of the total energetic cost. This energy consists of two parts. One is due to crossbridge interaction which produces isometric force, and this part varies linearly with the degree of filament overlap in the fibres. The other part of the energy is that associated with activation of the crossbridges by Ca2+, mainly with uptake of Ca2+ into the sarcoplasmic reticulum by the ATP-driven Ca2+ pump. Total heat production was measured at various degrees of filament overlap beyond the optimum for force development. Extrapolation of heat versus force production data to evaluate the heat remaining at zero force gave a value of 34±5 % (mean ± s.e.m., N=24) for activation heat as a percentage of total heat production in a 2.0 s isometric tetanus. Values for 0.4 and 1.0 s of stimulation were similar. Comparison with values in the literature shows that the energetic cost of activation in dogfish muscle is very similar to that of frog skeletal muscle and it cannot explain the lower maximum efficiency of dogfish muscle compared with frog muscle. The proportion of energy for activation (Ca2+ turnover) is similar to that expected from a simple model in which Ca2+ turnover was varied to minimize the total energy cost for a contraction plus relaxation cycle.

Sign in / Sign up

Export Citation Format

Share Document