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Biomedical subjects

L C Rome

Publications and source records attributed to L C Rome.

At least 37 records · Page 2Linked to original sources
PubMed1996

Contraction dynamics and power production of pink muscle of the scup (Stenotomus chrysops).

Although the contribution of red muscle to sustained swimming in fish has been studied in detail in recent years, the role of pink myotomal muscle has not received attention. Pink myotomal muscle in the scup (Stenotomus chrysops) lies just medial to red muscle, has the same longitudinal fibre orientation and is recruited along with the red muscle during steady sustainable swimming. However, pink muscle has significantly faster rates of relaxation, and the maximum velocity of shortening of pink muscle (7.26 +/- 0.18 muscle lengths s-1, N = 9, at 20 degrees C, and 4.46 +/- 0.15 muscle lengths s-1, N = 6, at 10 degrees C; mean +/- S.E.M.) is significantly faster than that of red muscle. These properties facilitate higher mass-specific maximum oscillatory power production relative to that of red muscle at frequencies similar to the tailbeat frequency at maximum sustained swimming speeds in scup. Additionally, pink muscle is found in anatomical positions in which red muscle is produces very little power during swimming: the anterior region of the fish, which undergoes the lowest strain during swimming. Pink muscle produces more oscillatory power than red muscle under low-strain conditions (+/- 2-3%) and this may allow pink muscle to supplement the relatively low power generated by red muscle in the anterior regions of swimming scup.

Animals↗
PubMed1996

Muscle length changes during swimming in scup: sonomicrometry verifies the anatomical high-speed cine technique.

Recent attempts to determine how fish muscles are used to power swimming have employed the work loop technique (driving isolated muscles using their in vivo strain and stimulation pattern). These muscle strains have in turn been determined from the anatomical high-speed cine technique. In this study, we used an independent technique, sonomicrometry, to attempt to verify these strain measurements and the conclusions based on them. We found that the strain records measured from sonomicrometry and the anatomical-cine techniques were very similar. The ratio of the strain measured from sonomicrometry to that from the anatomical-cine technique was remarkably close to unity (1.046 +/- 0.013, mean +/- S.E.M., N = 15, for transducers placed on the muscle surface and corrected for muscle depth, and 0.921 +/- 0.028, N = 8, in cases where the transducers were inserted to the average depth of the red muscle). These measurements also showed that red muscle shortening occurs simultaneously with local backbone curvature, unlike previous results which suggested that white muscle shortening during the escape response occurs prior to the change in local backbone curvature.

Animals↗
PubMed1995

A device for synchronizing biomechanical data with cine film.

Biomechanists are faced with two problems in synchronizing continuous physiological data to discrete, frame-based kinematic data from films. First, the accuracy of most synchronization techniques is good only to one frame and hence depends on framing rate. Second, even if perfectly correlated at the beginning of a 'take', the film and physiological data may become progressively desynchronized as the 'take' proceeds. A system is described, which provides synchronization between cine film and continuous physiological data with an accuracy of +/- 0.2 ms, independent of framing rate and the duration of the film 'take'. Shutter pulses from the camera were output to a computer recording system where they were recorded and counted, and to a digital device which counted the pulses and illuminated the count on the bank of LEDs which was filmed with the subject. Synchronization was performed by using the rising edge of the shutter pulse and by comparing the frame number imprinted on the film to the frame number recorded by the computer system. In addition to providing highly accurate synchronization over long film 'takes', this system provides several other advantages. First, having frame numbers imprinted both on the film and computer record greatly facilitates analysis. Second, the LEDs were designed to show the 'take number' while the camera is coming up to speed, thereby avoiding the use of cue cards which disturb the animal. Finally, use of this device results in considerable savings in film.

Analog-Digital Conversion↗
PubMed1994

Built for jumping: the design of the frog muscular system.

Frogs must generate a high level of mechanical power when they jump. The muscular system of frogs that jump is presumably designed to deliver these high powers. The length changes and activation pattern that muscles undergo during jumping were measured, and isolated muscle bundles were driven through this in vivo pattern. During jumping, muscles generated maximum power. Specifically, the muscle fibers (i) operated at optimal sarcomere lengths, (ii) operated at optimal shortening velocities, and (iii) were maximally activated during power generation. Thus, many different parameters must have evolved in concert to produce a system capable of this explosive jumping movement.

Animals↗
PubMed1993

How fish power swimming.

It is thought that fish generate the power needed for steady swimming with their anterior musculature, whereas the posterior musculature only transmits forces to the tail and does negative work. Isolated red muscle bundles driven through the length changes and stimulation pattern that muscles normally undergo during steady swimming showed the opposite pattern. Most of the power for swimming came from muscle in the posterior region of the fish, and relatively little came from the anterior musculature. In addition, the contractile properties of the muscle along the length of the fish are significantly adapted to enhance power generation.

Animals↗
PubMed1992

The influence of temperature on muscle function in the fast swimming scup. I. Shortening velocity and muscle recruitment during swimming.

In this study, electromyography showed that scup can swim to a maximum speed of 80 cm s-1 with their red muscle whereas previous results showed that carp can swim to only 45 cm s-1. Our aim was to evaluate the adaptations that enable scup to swim nearly twice as fast as carp. Although we anticipated that, at their respective maximum speeds, the red muscle of scup would be shortening at twice the velocity (V) of carp muscle, we found that the values of V were the same (2.04 muscle lengths s-1). At any given swimming speed, V was higher in carp than in scup because carp had a larger sarcomere length excursion and higher tail-beat frequency. The smaller sarcomere excursion in scup is primarily associated with using a less undulatory style of swimming (i.e. with a smaller backbone curvature). This less undulatory style of swimming may be an important adaptation that not only reduces V but may also reduce drag. At their respective maximum speeds, however, the 28% lower sarcomere length excursion in scup is balanced by a 26% higher tail-beat frequency, giving an equal V to that of carp. Although the scup in this study were somewhat longer than the carp in the previous one (19.7 vs 13.4 cm), we believe that many of the observed differences are species-related rather than size-related. We also found that scup swam in a kinematically similar fashion at 10 degrees C and 20 degrees C. However, at 10 degrees C, the scup could swim to only 54 cm s-1 before recruiting their white muscle whereas, at 20 degrees C, they could swim to 80 cm s-1. The difference in speed of initial white muscle recruitment, as well as information on muscle mechanics, suggests that the scup compress their recruitment order into a narrow speed range at low temperatures, thereby recruiting more muscle fibres. Quantitative analysis of red muscle electromyograms in this paper supports this hypothesis.

Animals↗
PubMed1992

The influence of temperature on muscle function in the fast swimming scup. II. The mechanics of red muscle.

To understand better how scup can swim twice as fast as carp with its red muscle, we measured the mechanical properties of red muscle bundles in scup. The values of the mean maximum velocity of shortening (Vmax) at 10 degrees C (3.32 muscle lengths s-1) and at 20 degrees C (5.55 muscle lengths s-1; Q10 = 1.69) were nearly the same as those in carp. Isometric force, however, was approximately 50% greater (183 kN m-2; Q10 = 1.08). The maximal power generation was correspondingly about 50% greater in scup than in carp (71 W kg-1 at 10 degrees C and 134 W kg-1 at 20 degrees C; Q10 = 1.88). The larger power output of its muscle may be important in the faster swimming of the scup. In addition, the fact that scup use a less undulatory style of swimming means that, when they are swimming twice as fast, their red muscle shortens at the same velocity (V) and with the same V/Vmax (0.37, i.e. where maximum power is generated) as that of carp. The importance of V/Vmax is further shown by the comparison of scup swimming at different temperatures. The 1.69-fold higher Vmax at 20 degrees C than at 10 degrees C enables scup to swim with a 1.67-fold faster V at 20 degrees C. Thus, at both 10 degrees C and 20 degrees C, red muscle is used only over the same narrow range of V/Vmax (0.17-0.37), where experiments on isolated muscle suggest that power and efficiency are maximal. Therefore, V/Vmax appears to be an important design constraint that limits the range of velocities over which muscle is used in vivo, both at different temperatures and in fast- and slow-locomoting species.

Animals↗
PubMed1992

Scaling of muscle fibres and locomotion.

To reconcile the scaling of the mechanics and energetics of locomotion to recent data on the scaling of the mechanics of muscle fibres, I have extended the theory of Taylor and colleagues that the energetic cost of locomotion is determined by the cost of generating force by the fibres. By assuming (1) that the cost of generating force in a fibre is proportional to V(max) (maximum velocity of shortening) and (2) that, at physiologically equivalent speeds, animals of different body sizes recruit the same fibre types, this extension quantitatively predicts the scaling of the energetics of locomotion, as well as other observations, from the scaling of V(max) of the muscle fibres. First, the energetic cost of locomotion at physiologically equivalent speeds scales with Mb-0.16, where Mb is body mass, as does V(max) of a given fibre type. However, the energetic cost at absolute speeds (cost of transport) scales with Mb-0.30, because small animals must compress their recruitment order into a narrower speed range and, hence, recruit faster muscle fibre types at a given running speed. Thus, it costs more for small animals to move 1 kg of their body mass 1 km not only because a given muscle fibre type from a small animal costs more to generate force than from a large one, but also because small animals recruit faster fibre types at a given absolute running speed. In addition, this analysis provides evidence that V(max) scales similarly to 1/tc (where tc is foot contact time) and muscle shortening velocity (V), in agreement with recent models. Finally, this extension predicts that, at physiologically equivalent speeds, the weight-specific energetic cost per step is independent of body size, as has been found empirically.

Animals↗
PubMed1992

The influence of temperature on power output of scup red muscle during cyclical length changes.

To gain insight into how temperature affects locomotory performance, we measured power output of scup red muscle during oscillatory length changes at 10 degrees C and 20 degrees C. When we optimized work loop parameters, we found that maximum power was 27.9 W kg-1 at 20 degrees C and 12.8 W kg-1 at 10 degrees C, giving a Q10 of 2.29. Maximum power was generated at a higher oscillation frequency at 20 degrees C (5 Hz) than at 10 degrees C (2.5 Hz), and the Q10 for power output at a given oscillation frequency ranged from about 1 at 1 Hz to about 5 at 7.5 Hz. An analysis of the results in terms of crossbridge kinetics suggests that the higher power output at 20 degrees C is associated with both a higher Vmax (i.e. more power per cycling crossbridge) and faster activation and relaxation (i.e. a greater number of cycling crossbridges). To obtain a more realistic understanding of the functional importance of temperature effects on muscle, we imposed on isolated muscle in vivo length changes and oscillation frequencies (measured during previous experiments on swimming scup) and the in vivo stimulus duty cycle (measured from electromyograms in this study). At 20 degrees C, muscle bundles tested under these in vivo conditions produced nearly maximal power, suggesting that the muscle works optimally during locomotion and, thus, important contractile parameters have been adjusted to produce maximum mechanical power at the oscillation frequencies and length changes needed during swimming. At 10 degrees C, muscle bundles tested under in vivo conditions produced much less power than was obtained during the 'optimized' work loop experiments discussed above. Furthermore, although 'optimized' work loop experiments showed that maximum power output occurs at 2.5 Hz, scup do not appear to swim with such a low tailbeat frequency. Although the reason for these apparent discrepancies at 10 degrees C are not known, it shows that simple extrapolation from isolated muscle to the whole animal, without knowledge of how the muscle is actually used in vivo, can be misleading.

Animals↗
PubMed1991

Myofilament overlap in swimming carp. I. Myofilament lengths of red and white muscle.

To assess myofilament overlap during locomotion, we estimated the length of myosin and actin filaments in axial red and white muscle of carp. Myosin filament lengths were 1.52 +/- 0.009 and 1.50 +/- 0.037 micron (means +/- SD) in the red and white muscle, respectively, as measured from thin sections. After correction for shrinkage (using the troponin-based 385-A axial periodicity), thin filaments were 0.96 +/- 0.009 and 0.97 +/- 0.023 micron in the red and white muscles, respectively. Filaments were also isolated from the white muscle and negatively stained. Myosin filaments were 1.56 +/- 0.025 microns, and actin filaments were 0.99 +/- 0.024 micron in length. The data from thin sections and isolated filaments agreed within 2% for actin and 4% for myosin filaments. The number of actin filament periods (24 for the red and white muscle) and the length of the filaments are the same as in frog. This suggests that the classic sarcomere length-tension curve of frog muscle may be used to estimate the functional properties of carp red and white muscle.

Actin Cytoskeleton↗
PubMed1991

Myofilament overlap in swimming carp. II. Sarcomere length changes during swimming.

This study was performed to determine myofilament overlap during swimming in carp. By using frozen sections, we found that sarcomere lengths of the red and white muscle could be related to the curvature of the backbone. Sarcomere length (SL) during swimming was calculated from an analysis of backbone curvature in high-speed motion pictures. Because carp have the same myofilament lengths as frogs, we related force generation to SL using the frog SL-tension curve. At slow swimming speeds, the red fibers are used at a SL of 1.91-2.22 microns, where force generation is calculated to be no less than 96% maximal. If the red fibers powered the escape response they would have to shorten to 1.45-1.55 microns, where force generation would be reduced to approximately 50% maximal and the fibers damaged. Instead, the white muscle fibers are recruited and because of their helical orientation (resulting in a higher gear ratio), they shorten to only 1.75 microns, where they generate no less than 85% maximal tension. Thus, by recruitment of fiber types with different orientations, the full range of movements is powered by fibers operating at nearly maximal overlap. This suggests that myofilament overlap is an important design constraint of muscular systems.

Actin Cytoskeleton↗
PubMed1990

Functional morphology of dewlap extension in the lizard Anolis equestris (Iguanidae).

The dewlap is an extendible flap of skin ordinarily folded under the throat. Lizards, particularly those in the genus Anolis, extend their dewlaps during interactions with conspecifics, other lizards, and potential predators. Dewlap extension is effected by movements of elements of the hyoid apparatus. This paper describes the anatomy of the hyoid and associated musculature in Anolis equestris, a large arboreal lizard with a prominent dewlap. A mechanism for dewlap extension is proposed based on results of morphological and experimental techniques. Specializations of the hyoid skeleton for dewlap extension include elongated second ceratobranchials and highly movable joints between the ceratohyals and the hypohyals and between the first ceratobranchials and the body of the hyoid. A well developed M. ceratohyoideus extends between the ceratohyals and the first ceratobranchials of the hyoid apparatus. During dewlap extension, the hyoid apparatus acts as a first order lever. Contraction of M. ceratohyoideus pulls the ceratohyals posteriorly causing the hypohyals and the body of the hyoid to rotate dorsally around the first ceratobranchial/body joints. This movement results in the second ceratobranchials swinging forward and down, unfolding the dewlap. The relative immobility of the first ceratobranchials provides stability to the hyoid apparatus during dewlap extension. A comparison is made of dewlap extension and other hyoid displays.

Animals↗
PubMed1990

The influence of temperature on mechanics of red muscle in carp.

1. We measured the influence of temperature on maximum velocity of shortening (Vmax) of red muscle in carp in order to better understand the influence of temperature on locomotory performance. 2. A stable red muscle bundle preparation containing about 100 muscle fibres was developed. The bundles could not be activated directly by electrical stimulation, but rather contained sufficient nervous tissue so that acetylcholine released from the nerve terminals caused activation of the muscle. A high level of activation was achieved (116 kN/m2) by adding a combination of a 1 mM-caffeine and 10(-5) g/ml eserine to physiological Ringer solution and electrically stimulating the preparation. 3. Force-velocity characteristics were determined at 10 and 20 degrees C by the force clamp method. The data were well fitted by a hyperbola not constrained to pass through P0 = 1 (where P0 is the isometric force). The mean Vmax at 10 degrees C was 3.55 +/- 0.26 muscle lengths/s (ML/s) (n = 6) and at 20 degrees C, 5.71 +/- 0.29 ML/s (n = 6). The mean Q10 for Vmax was 1.63 +/- 0.07 (n = 6). The a/P0* (Hill constant) and Po* (where P0* is the extrapolated load at zero velocity) were 0.49 +/- 0.06 (n = 6) and 1.19 +/- 0.04 (n = 6) respectively at 10 degrees C and 0.29 +/- 0.06 (n = 6) and 1.51 +/- 0.20 (n = 6) respectively at 20 degrees C. 4. The mean Q10 for maximum isometric tension was 1.13 +/- 0.02 (n = 6). The maximal power generation was 59.7 +/- 2.3 W/kg (n = 6) at 10 degrees C and 94.3 +/- 3.2 W/kg (n = 6) at 20 degrees C representing a Q10 of 1.58. The Q10 is less than the product of Q10s for P0 and Vmax because of the greater curvature of the force-velocity curve at 20 degrees C. 5. The 1.63-fold higher Vmax at 20 degrees C than at 10 degrees C enables fish to swim with a 1.6-fold faster muscle shortening velocity, V, at the higher temperature. Thus at both 10 and 20 degrees C, red muscle is used only over the same narrow range of V/Vmax (0.18-0.36), where isolated muscle experiments suggest that power and efficiency are maximal. Thus V/Vmax appears to be an effective design constraint which limits the range of velocities over which muscle is used in vivo at different temperatures.

Animals↗
PubMed1990

Maximum velocity of shortening of three fibre types from horse soleus muscle: implications for scaling with body size.

1. To explore how maximum velocity of shortening (Vmax) of fibres varies within one muscle and how Vmax varies with body size, we measured Vmax of muscle fibres from soleus muscle of a large animal, the horse. 2. Vmax was determined by the slack test on skinned single muscle fibres at 15 degrees C during maximal activation (pCa = 5.2). The fibre type was subsequently determined by a combination of single-cell histochemistry and gel electrophoresis of the myosin light chains. 3. Vmax values for the type I, IIA and IIB muscle fibres were 0.33 +/- 0.04 muscle lengths/s (ML/s) (+/- S.E.M., n = 6), 1.33 +/- 0.08 ML/s (n = 7) and 3.20 +/- 0.26 ML/s (n = 6), respectively. It is likely that the large range in Vmax is due to differences observed in the myosin heavy chains and light chains associated with the three fibre types. 4. Comparison of Vmax over a 1200-fold range (450 kg horse vs. 0.38 kg rat) of body mass (Mb) suggests that slow fibres scale more dramatically (Mb-0.18) than do fast glycolytic fibres (Mb-0.07). This difference may enable the slow fibres to work at high efficiencies in the large animal while the fast fibres can still generate a large mechanical power when necessary.

Animals↗
PubMed1990

Influence of temperature on muscle recruitment and muscle function in vivo.

Temperature has a large influence on the maximum velocity of shortening (Vmax) and maximum power output of muscle (Q10 = 1.5-3). In some animals, maximum performance and maximum sustainable performance show large temperature sensitivities, because these parameters are dependent solely on mechanical power output of the muscles. The mechanics of locomotion (sarcomere length excursions and muscle-shortening velocities, V) at a given speed, however, are precisely the same at all temperatures. Animals compensate for the diminished power output of their muscles at low temperatures by compressing their recruitment order into a narrower range of locomotor speeds, that is, recruiting more muscle fibers and faster fiber types at a given speed. By examining V/Vmax, I calculate that fish at 10 degrees C must recruit 1.53-fold greater fiber cross section than at 20 degrees C. V/Vmax also appears to be an important design constraint in muscle. It sets the lowest V and the highest V over which a muscle can be used effectively. Because the Vmax of carp slow red muscle has a Q10 of 1.6 between 10 and 20 degrees C, the slow aerobic fibers can be used over a 1.6-fold greater range of swim speeds at the warmer temperature. In some species of fish, Vmax can be increased during thermal acclimation, enabling animals to swim at higher speeds.

Acclimatization↗
PubMed1990

The influence of temperature on muscle velocity and sustained performance in swimming carp.

The aim of this study was to evaluate how fish locomote at different muscle temperatures. Sarcomere length excursion and muscle shortening velocity, V, were determined from high-speed motion pictures of carp, Cyprinus carpio (11-14 cm), swimming steadily at various sustained speeds at 10, 15 and 20 degrees C. In the middle and posterior regions of the carp, sarcomeres of the lateral red muscle underwent cyclical excursions of 0.31 microns, centered around the resting length of 2.06 microns (i.e. from 1.91 to 2.22 microns). The amplitudes of the sarcomere length excursions were essentially independent of swimming speed and temperature. As tail-beat frequency increased linearly with swimming speed regardless of temperature, the sarcomeres underwent the same length changes in a shorter time. Thus, V increased in a linear and temperature-independent manner with swimming speed. Neither temperature nor swimming speed had an influence on tail-beat amplitude or tail height. Our findings indicate that muscle fibres are used only over a narrow, temperature-independent range of V/Vmax (0.17-0.36) where power and efficiency are maximal. Carp start to recruit their white muscles at swimming speeds where the red muscle V/Vmax becomes too high (and thus power output declines). When the V/Vmax of the active muscle falls too low during steady swimming, carp switch to 'burst-and-coast' swimming, apparently to keep V/Vmax high. Because Vmax (maximum velocity of shortening) of carp red muscle has a Q10 of 1.63, the transition speeds between swimming styles are lower at lower temperatures. Thus, carp recruit their white anaerobic muscle at a lower swimming speed at lower temperatures (verified by electromyography), resulting in a lower maximum sustainable swimming speed. The present findings also indicate that, to generate the same total force and power to swim at a given speed, carp at 10 degrees C must recruit about 50% greater fibre cross-sectional area than they do at 20 degrees C.

Animals↗