Alternative splicing, muscle contraction and intraspecific variation: associations between troponin T transcripts, Ca2+ sensitivity and the force and power output of dragonfly flight muscles during oscillatory contraction

2001 ◽  
Vol 204 (20) ◽  
pp. 3457-3470 ◽  
Author(s):  
James H. Marden ◽  
Gail H. Fitzhugh ◽  
Mahasweta Girgenrath ◽  
Melisande R. Wolf ◽  
Stefan Girgenrath
Keyword(s):  
Intraspecific Variation ◽  
Relative Abundance ◽  
Power Output ◽  
Troponin T ◽  
Specific Power ◽  
Published Data ◽  
Specific Work ◽  
Wingbeat Frequency ◽  
Flight Muscles ◽  
Contractile Performance

SUMMARYThe flight muscles of Libellula pulchella dragonflies contain a mixture of six alternatively spliced transcripts of a single troponin T (TnT) gene. Here, we examine how intraspecific variation in the relative abundance of different TnT transcripts affects the Ca2+ sensitivity of skinned muscle fibers and the performance of intact muscles during work-loop contraction regimes that approximate in vivo conditions during flight. The relative abundance of one TnT transcript, or the pooled relative abundance of two TnT transcripts, showed a positive correlation with a 10-fold range of variation in Ca2+ sensitivity of skinned fibers (r2=0.77, P<0.0001) and a threefold range in peak specific force (r2=0.74, P<0.0001), specific work per cycle (r2=0.54; P<0.0001) and maximum specific power output (r2=0.48, P=0.0005) of intact muscle. Using these results to reanalyze previously published data for wing kinematics during free flight, we show that the relative abundances of these particular transcripts are also positively correlated with wingbeat frequency and amplitude. TnT variation alone may be responsible for these effects, or TnT variation may be a marker for changes in a suite of co-regulated molecules. Dragonflies from two ponds separated by 16 km differed significantly in both TnT transcript composition and muscle contractile performance, and within each population there are two distinct morphs that showed different maturational trajectories of TnT transcript composition and muscle contractility. Thus, there is broad intraspecific variability and a high degree of population structure for contractile performance phenotypes, TnT ribotypes and ontogenetic patterns involving these traits that affect locomotor performance.

scholarly journals Flightin maintains myofilament lattice organization required for optimal flight power and courtship song quality in Drosophila

2017 ◽  
Vol 284 (1854) ◽  
pp. 20170431 ◽  
Author(s):  
Samya Chakravorty ◽  
Bertrand C. W. Tanner ◽  
Veronica Lee Foelber ◽  
Hien Vu ◽  
Matthew Rosenthal ◽  
...  
Keyword(s):  
Power Output ◽  
Lattice Structure ◽  
Courtship Song ◽  
Fine Tuning ◽  
Male Reproductive Success ◽  
Supporting Evidence ◽  
Force Transmission ◽  
Wingbeat Frequency ◽  
Terminal Domain ◽  
Flight Muscles

The indirect flight muscles (IFMs) of Drosophila and other insects with asynchronous flight muscles are characterized by a crystalline myofilament lattice structure. The high-order lattice regularity is considered an adaptation for enhanced power output, but supporting evidence for this claim is lacking. We show that IFMs from transgenic flies expressing flightin with a deletion of its poorly conserved N-terminal domain ( fln ΔN62 ) have reduced inter-thick filament spacing and a less regular lattice. This resulted in a decrease in flight ability by 33% and in skinned fibre oscillatory power output by 57%, but had no effect on wingbeat frequency or frequency of maximum power output, suggesting that the underlying actomyosin kinetics is not affected and that the flight impairment arises from deficits in force transmission. Moreover, we show that fln ΔN62 males produced an abnormal courtship song characterized by a higher sine song frequency and a pulse song with longer pulses and longer inter-pulse intervals (IPIs), the latter implicated in male reproductive success. When presented with a choice, wild-type females chose control males over mutant males in 92% of the competition events. These results demonstrate that flightin N-terminal domain is required for optimal myofilament lattice regularity and IFM activity, enabling powered flight and courtship song production. As the courtship song is subject to female choice, we propose that the low amino acid sequence conservation of the N-terminal domain reflects its role in fine-tuning species-specific courtship songs.

scholarly journals GENETIC VARIABILITY OF FLIGHT METABOLISM IN DROSOPHILA MELANOGASTER. II. RELATIONSHIP BETWEEN POWER OUTPUT AND ENZYME ACTIVITY LEVELS

Genetics ◽  
1985 ◽  
Vol 111 (4) ◽  
pp. 845-868
Author(s):  
C C Laurie-Ahlberg ◽  
P T Barnes ◽  
J W Curtsinger ◽  
T H Emigh ◽  
B Karlin ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Power Output ◽  
Mechanical Power ◽  
Activity Levels ◽  
Substitution Lines ◽  
Wingbeat Frequency ◽  
Metabolism Enzymes ◽  
Mechanical Power Output ◽  
Flight Metabolism ◽  
Flight Muscles

ABSTRACT The major goal of the studies reported here was to determine the extent to which genetic variation in the activities of the enzymes participating in flight metabolism contributes to variation in the mechanical power output of the flight muscles in Drosophila melanogaster. Isogenic chromosome substitution lines were used to partition the variance of both types of quantitative trait into genetic and environmental components. The mechanical power output was estimated from the wingbeat frequency, wing amplitude and wing morphology of tethered flies by applying the aerodynamic models of Weis-Fogh and Ellington. There were three major results. (1) Chromosomes sampled from natural populations provide a large and repeatable genetic component to the variation in the activities of most of the 15 flight metabolism enzymes investigated and to the variation in the mechanical power output of the flight muscles. (2) The mechanical power output is a sensitive indicator of the rate of flight metabolism (i.e., rate of oxygen consumption during tethered flight). (3) In spite of (1) and (2), no convincing cases of individual enzyme effects on power output were detected, although the number and sign of the significant enzyme-power correlations suggests that such effects are not totally lacking.

The Specific Power Output of Aerobic Muscle, Related to the Power Density of Mitochondria

1984 ◽  
Vol 108 (1) ◽  
pp. 377-392 ◽  
Author(s):  
C. J. PENNYCUICK ◽  
MARCIO A. REZENDE
Keyword(s):  
Power Density ◽  
Power Output ◽  
Beat Frequency ◽  
Volume Ratio ◽  
Operating Frequency ◽  
Specific Power ◽  
Specific Power Output ◽  
Mechanical Power Output ◽  
Flight Muscles ◽  
High Level

A simple theory is proposed to account for the quantity of mitochondria present in aerobic muscles. Attention is restricted to muscles adapted to operate aerobically at a well-defined ‘operating frequency’. For this special case, it is shown that the volume ratio of mitochondria to myofibrils should depend on the power density of mitochondria, and the operating frequency, but not on the mechanical properties of the myofibrils. If the underlying assumptions are valid, this would mean that the specific power output of such muscles could be determined by examination of electron micrographs. We provisionally estimate that the inverse power density of mitochondria, in flight muscles running at a high temperature, is in the range 1.010−6 to 1.310−6m3W−1, that is, that a little over 1 ml of mitochondria is required to sustain 1 W of mechanical power output. On this basis, a muscle with equal volumes of mitochondria and myofibrils should be able to deliver a specific power of about 430 W kg−1, at an operating frequency around 40 Hz for nonfibrillar, or 230 Hz for fibrillar muscle. The limiting specific power should be twice this level in either case, i.e. about 860Wkg−1. It is predicted that a survey of flight muscles should yield a straight-line relationship between wing-beat frequency and the volume ratio of mitochondria to myofibrils, in a set of muscles of the same general type. It is not known whether lack of exercise, either on a long-term or short-term basis is likely to affect this. As a preliminary to such a survey, we have examined the pectoralis muscles of domesticated quail, and a wild house sparrow. Both showed a high level of variability in the mitochondria: myofibril ratio, but this may be due, at least in part, to sampling artifacts caused by the shape of mitochondrial arrays. The quail showed distinct populations of aerobic and non-aerobic fibres, apparently identical to those described in wild birds with similar flight requirements by George & Berger (1966), but the quantity of mitochondria in the aerobic fibres was less than half that expected, by comparison with other species.

Structural Limitations on the Power Output of the Pigeon'S Flight Muscles

1966 ◽  
Vol 45 (3) ◽  
pp. 489-498
Author(s):  
C. J. PENNYCUICK ◽  
G. A. PARKER
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Flight Muscle ◽  
Compressive Load ◽  
Bending Moment ◽  
Specific Power ◽  
Wingbeat Frequency ◽  
Flight Muscles ◽  
Centre Of Rotation

1. The tensile strength of the flight-muscle tendons, the distances through which they move and the wingbeat frequency set a maximum of 48 W on the power which could conceivably be transmitted to the pigeon's wings. 2. A minimum of 9·1 W is required to account for observed climbing performance. 3. The safety factor on tension of the muscle insertions cannot exceed 5·2 and is probably substantially less than this. 4. The maximum possible average specific power over one complete cycle is 0·58 W/g.wt. for the pectoralis and 0·28 W/g.wt. for the supracoracoideus. The maximum possible peak specific power during shortening is 0·86 W/g.wt. for both muscles. The minimum average specific power for the flight muscles as a whole is 0·10 W/g.wt. (from rate of climb measurements). 5. These figures do not imply any unusual mechanical properties in the muscles, as compared to other vertebrate muscles. 6. The coracoid can bear a compressive load of over 40 kg. wt., which appears to be about 3·7 times as much as could ever be applied to it in life. 7. The greatest bending moment (about the centre of rotation of the head of the humerus) which the pectoralis could apply to the humerus is 10·2 kg. wt. cm. The supracoracoideus could apply a maximum of 0·88 kg. wt. cm. 8. The tensile strength of supracoracoideus tendon is about 250 kg. wt./cm.2. The compressive strength of coracoid bone is about 1140 kg. wt./cm.2.

The mechanical power output of the flight muscles of blue-breasted quail (Coturnix chinensis) during take-off

2001 ◽  
Vol 204 (21) ◽  
pp. 3601-3619 ◽  
Author(s):  
Graham N. Askew ◽  
Richard L. Marsh ◽  
Charles P. Ellington
Keyword(s):  
Body Mass ◽  
Power Output ◽  
High Speed ◽  
The Body ◽  
Three Dimensions ◽  
Total Power ◽  
Muscle Fibres ◽  
Wingbeat Frequency ◽  
Mechanical Power Output ◽  
Flight Muscles

SUMMARYBlue-breasted quail (Coturnix chinensis) were filmed during take-off flights. By tracking the position of the centre of mass of the bird in three dimensions, we were able to calculate the power required to increase the potential and kinetic energy. In addition, high-speed video recordings of the position of the wings over the course of the wing stroke, and morphological measurements, allowed us to calculate the aerodynamic and inertial power requirements. The total power output required from the pectoralis muscle was, on average, 390 W kg–1, which was similar to the highest measurements made on bundles of muscle fibres in vitro (433 W kg–1), although for one individual a power output of 530 W kg–1 was calculated. The majority of the power was required to increase the potential energy of the body. The power output of these muscles is the highest yet found for any muscle in repetitive contractions.We also calculated the power requirements during take-off flights in four other species in the family Phasianidae. Power output was found to be independent of body mass in this family. However, the precise scaling of burst power output within this group must await a better assessment of whether similar levels of performance were measured across the group. We extended our analysis to one species of hawk, several species of hummingbird and two species of bee. Remarkably, we concluded that, over a broad range of body size (0.0002–5 kg) and contractile frequency (5–186 Hz), the myofibrillar power output of flight muscles during short maximal bursts is very high (360–460 W kg–1) and shows very little scaling with body mass. The approximate constancy of power output means that the work output varies inversely with wingbeat frequency and reaches values of approximately 30–60 J kg–1 in the largest species.

scholarly journals TEG Design for Waste Heat Recovery at an Aviation Jet Engine Nozzle

2018 ◽  
Vol 8 (12) ◽  
pp. 2637 ◽  
Author(s):  
Pawel Ziolkowski ◽  
Knud Zabrocki ◽  
Eckhard Müller
Keyword(s):  
Fuel Consumption ◽  
Power Output ◽  
Waste Heat ◽  
Positive Impact ◽  
Element Model ◽  
System Level ◽  
Specific Power ◽  
Transfer Coefficients ◽  
Te Modules ◽  
Te Material

Finite element model (FEM)-based simulations are conducted for the application of a thermoelectric generator (TEG) between the hot core stream and the cool bypass flow at the nozzle of an aviation turbofan engine. This work reports the resulting requirements on the TEG design with respect to applied thermoelectric (TE) element lengths and filling factors (F) of the TE modules in order to achieve a positive effect on the specific fuel consumption. Assuming a virtual optimized TE material and varying the convective heat transfer coefficients (HTC) between the nozzle surfaces and the gas flows, this work reports the achievable power output. System-level requirement on the gravimetric power density (>100 Wkg−1) can only be met for F ≤ 21%. When extrapolating TEG coverage to the full nozzle surface, the power output reaches 1.65 kW per engine. The assessment of further potential for power generation is demonstrated by a parametric study on F, convective HTC, and materials performance. This study confirms a feasible design range for TEG installation on the aircraft nozzle with a positive impact on the fuel consumption. This application translates into a reduction of operational costs, allowing for an economically efficient TEG-installation with respect to the cost-specific power output of modern thermoelectric materials.

Shortening deactivation: quantifying a critical component of cyclical muscle contraction

2021 ◽  
Author(s):  
Amy K. Loya ◽  
Sarah K. Van Houten ◽  
Bernadette M. Glasheen ◽  
Douglas M. Swank
Keyword(s):  
Power Output ◽  
Muscle Activation ◽  
Muscle Relaxation ◽  
Length Change ◽  
Isometric Tension ◽  
Energetic Cost ◽  
Muscle Shortening ◽  
Shortening Deactivation ◽  
Muscle Types ◽  
Flight Muscles

A muscle undergoing cyclical contractions requires fast and efficient muscle activation and relaxation to generate high power with relatively low energetic cost. To enhance activation and increase force levels during shortening, some muscle types have evolved stretch activation (SA), a delayed increased in force following rapid muscle lengthening. SA's complementary phenomenon is shortening deactivation (SD), a delayed decrease in force following muscle shortening. SD increases muscle relaxation, which decreases resistance to subsequent muscle lengthening. While it might be just as important to cyclical power output, SD has received less investigation than SA. To enable mechanistic investigations into SD and quantitatively compare it to SA, we developed a protocol to elicit SA and SD from Drosophila and Lethocerus indirect flight muscles (IFM) and Drosophila jump muscle. When normalized to isometric tension, Drosophila IFM exhibited a 118% SD tension decrease, Lethocerus IFM dropped by 97%, and Drosophila jump muscle decreased by 37%. The same order was found for normalized SA tension: Drosophila IFM increased by 233%, Lethocerus IFM by 76%, and Drosophila jump muscle by only 11%. SD occurred slightly earlier than SA, relative to the respective length change, for both IFMs; but SD was exceedingly earlier than SA for jump muscle. Our results suggest SA and SD evolved to enable highly efficient IFM cyclical power generation and may be caused by the same mechanism. However, jump muscle SA and SD mechanisms are likely different, and may have evolved for a role other than to increase the power output of cyclical contractions.

Performance Comparison and Parametric Analysis of sCO2 Power Cycles Configurations

2018 ◽  
Author(s):  
Ali S. Alsagri ◽  
Andrew Chiasson ◽  
Ahmad Aljabr
Keyword(s):  
Power Output ◽  
Thermal Efficiency ◽  
Performance Comparison ◽  
Specific Power ◽  
Brayton Cycle ◽  
Computationally Efficient ◽  
Power Cycles ◽  
Optimization Study ◽  
Specific Power Output ◽  
Improve Calculation

A thermodynamic analysis and optimization of four supercritical CO2 Brayton cycles were conducted in this study in order to improve calculation accuracy; the feasibility of the cycles; and compare the cycles’ design points. In particular, the overall thermal efficiency and the power output are the main targets in the optimization study. With respect to improving the accuracy of the analytical model, a computationally efficient technique using constant conductance (UA) to represent heat exchanger performances is executed. Four Brayton cycles involved in this compression analysis, simple recaptured, recompression, pre-compression, and split expansion. The four cycle configurations were thermodynamically modeled and optimized based on a genetic algorithm (GA) using an Engineering Equation Solver (EES) software. Results show that at any operating condition under 600 °C inlet turbine temperature, the recompression sCO2 Brayton cycle achieves the highest thermal efficiency. Also, the findings show that the simple recuperated cycle has the highest specific power output in spite of its simplicity.

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