Quick-release Method Research Articles

Visual Psychophysics in Head-Fixed Mice.

We describe a set of protocols for doing visual psychophysical experiments in head-fixed mice. The goal of this approach was to conduct in mice the same type of precise and well-controlled tests of visual perception and decision making as is commonly done in primates. For example, these experimental protocols were the basis for our demonstration that mice are capable of visual selective attention in paradigms adapted from classic attention cueing paradigms in primates. Basic Protocol 1 describes how to construct the experimental apparatus, including the removable wheel assembly on which the mice run during the visual tasks, the lick spout used to deliver rewards and detect licks, and the behavioral box that places these components together with the visual displays. We also describe the functions of the computerized control system and the design of the customized head fixture. Basic Protocol 2 describes the preparation of mice for the experiments, including the detailed surgical steps. Basic Protocol 3 describes the transition to a food schedule for the mice and how to operate the experimental apparatus. Basic Protocol 4 outlines the logic of the task design and the steps necessary for training the mice. Finally, Basic Protocol 5 describes how to obtain and analyze the psychometric data. Our methods include several distinctive features, including a custom quick-release method for holding the head and specific strategies for training mice over multiple weeks. Published 2020. U.S. Government. Basic Protocol 1: Experimental apparatus Basic Protocol 2: Head fixture surgery Basic Protocol 3: General operation of the experimental apparatus Basic Protocol 4: Behavioral task design and training Basic Protocol 5: Psychometric data collection and analysis.

Influence of Cervical Muscle Fatigue on Musculo-Tendinous Stiffness of the Head-Neck Segment during Cervical Flexion.

AimThe aim of this study is to determine if the fatigue of cervical muscles has a significant influence on the head-neck segment musculo-tendinous stiffness.MethodsTen men (aged 21.2 ± 1.9 years) performed four quick-release trials of flexion at 30 and 50% MVC before and after the induction of muscular fatigue on cervical flexors. Electromyographic activity was recorded on the sternocleidomastoids (SCM) and spinal erectors (SE), bilaterally. Musculo-tendinous stiffness was calculated through the quick-release method adapted to the head-neck segment.ResultsWe noticed a significant linear increase of the head-neck segment musculo-tendinous stiffness with the increase of exertion level both before (P < 0.0001) and after the fatigue procedure (P < 0.0001). However, this linear relationship was not different before and after the fatigue procedure. EMG analysis revealed a significant increase of the root mean square for the right SCM (P = 0.0002), the left SCM (P < 0.0001), the right SE (P < 0.0001), and the left SE (P < 0.0001) and a significant decrease of the median power frequency only for the right (P = 0.0006) and the left (P = 0.0003) SCM with muscular fatigue.DiscussionWe did not find significant changes in the head-neck segment musculo-tendinous stiffness with fatigue of cervical muscles. We found a significant increase in EMG activity in the SCM and the SE after the induction of fatigue of the SCM. Our findings suggest that with fatigue of cervical flexors, neck muscle activity is modulated in order to maintain the musculo-tendinous stiffness at a steady state.

Optimization in measurement of MVC and active stiffness in wrist using the quick release method

The quick release method was used for measurement of Biomechanical parameters in the wrist joints. Wrist joint was previously studied in many researches for its biomechanical characteristics. However, more automation in measurement process has been discussed. In this research, a new test rig with a specified control unit was fabricated. Measurement of parameters in few seconds after the release was considered in the design of the new test rig. Based on reliability tests performed, the fabricated test rig showed firmly reliable measurements for maximum voluntary contraction, and active stiffness. These were true for both cases of left and right wrists during flexion and extension.

Interaction between gastrocnemius medialis fascicle and Achilles tendon compliance: a new insight on the quick-release method

The insufficient temporal resolution of imaging devices has made the analysis of very fast movements, such as those required to measure active muscle-tendon unit stiffness, difficult. Thus the relative contributions of tendon, aponeurosis, and fascicle to muscle-tendon unit compliance remain to be determined. The present study analyzed the dynamic interactions of fascicle, tendon, and aponeurosis in human gastrocnemius medialis during the first milliseconds of an ankle quick-release movement, using high-frame-rate ultrasonography (2,000 frames/s). Nine subjects performed the tests in random order at six levels of maximal voluntary contraction (MVC) (30% to 80% of MVC). These tests were carried out with the ultrasound probe placed on the muscle belly and on the myotendinous junction. Tendon, muscle fascicle, and aponeurosis length changes were quantified in relation to shortening of the muscle-tendon unit during the first few milliseconds following the release. The tendon was the main contributor (around 72%) to the shortening of the muscle-tendon unit, whereas the muscle fascicle and aponeurosis contributions were 18% and 10%, respectively. Because these structures can be considered in series, the quantified contributions can be regarded as relative contributions to muscle-tendon compliance. These contributions were not modified with the level of MVC or the time range used for the analysis between 10 and 25 ms. The constant contribution of tendon, muscle fascicle, and aponeurosis to muscle-tendon unit compliance may help to simplify the mechanism of compliance regulation and to maintain the important role of tendons in enhancing work output and movement efficiency.

Musculo-tendinous stiffness of head–neck segment in the sagittal plane: An optimization approach for modeling the cervical spine as a single-joint system

Despite the multi-linked architecture of the cervical spine, all previous studies that have made estimations of mechanical properties of the neck have considered the head–neck segment as a rigid link, with a fixed center of rotation at C7. The aim of this study was to consider the head–neck segment as a changeable geometry system for locating the resultant center of rotation and for calculating the musculo-tendinous stiffness by the quick-release method. Head kinematics during quick-releases was analyzed by recording the trajectory of surface markers. With an optimization procedure, the position of the resultant center of rotation of the head–neck segment was estimated. Thereafter, the angular displacement and acceleration of the head, together with the isometric torque developed by the cervical muscles were used to calculate the segment's stiffness. The results showed a consistent center of rotation and a significant increase of the musculo-tendinous stiffness with increasing torque.

Effects of pretension on work and power output of the muscle-tendon complex in dynamic elbow flexion

The purpose of the present study was to investigate the effects of pretension on work and power output of the muscle-tendon complex during dynamic elbow flexion under several submaximal and maximal conditions. The subjects were 10 healthy female students. Randomized trials from 0% to 100% maximal voluntary contraction (MVC) pretension (PT) at 60 degrees elbow flexion were conducted. After about 3 s of static PT, subjects maximally flexed the elbow joint to 90 degrees using a quick release method. The weight was individually selected for each subject to provide an optimal load for the development of maximal power. A Hill-type model was utilized to analyze the performance of the elbow muscle-tendon complex (MTC). PT 0, 30, 60 and 90% MVC data were used for comparison, and all data were expressed as the mean and standard deviation. Multiple paired comparisons between the value of PT 0% MVC and that of the other PT levels were performed post-hoc using Dunnett's method. The work of the series elastic component (SEC) increased gradually with the PT level because elastic energy was stored in the PT phase. However, the work of the contractile component (CC) decreased gradually with an increase in PT level. Moreover, the work of the MTC also decreased, closely related to the CC work decrement. The phenomenon of CC work decrement was caused by force depression and was not related to either the force-length or force-velocity relationships of the CC. EMG activity (agonist and antagonist) showed no significant differences. Muscle geometry changes or intracellular chemical shifts may have occurred in the PT phase.

Studies on Kinetic Viscoelasticity of Slow Muscle Fibers: 2. Dynamic Stiffness Changes Studied by Quick Release Method and Frequency Response Method

To evaluate the mechanical properties of slow fibers and fast fibers which make up the extraocular muscles in rabbits. I studied the contractile properties and viscoelastic properties of the superior rectus muscle(SR) and the retractor bulbi muscle (RB) of rabbits using the quick release method and the frequency response method. In the quick release method, isometric tension transients were slower in the SR than in the RB. In the frequency response method, the muscle length is perturbed sinusoidally to measure kinetic viscoelasticity. In resting muscle, dynamic stiffness was not changed with increasing frequency. In contracted muscle, dynamic stiffness was increased with increasing frequency, and the rate of increase was greater in the SR than in the RB. It was concluded that the viscoelasticity of the activated cross bridge is greater in slow fibers than in fast fibers.

Moment dependency of the series elastic stiffness in the human plantar flexors measured in vivo

The moment dependency of the series elastic stiffness (SES) in the human plantar flexors was investigated in vivo with the quick release method. At an ankle moment of 100 N m produced with either voluntary or electrical stimulation we found non-significantly different SES of 506±72 and 529±125 N m rad −1, respectively. It has recently been proposed that the amount of series elastic tissue involved in plantar flexion changes with the moment level produced by the plantar flexors (Hof, J. Biomech 31 (1998) 793). However, our results indicate that the amount of series elastic tissue involved in plantar flexions remained constant with changing moment levels. We therefore propose that the series elastic component (SEC) in human plantar flexors act as one structure or rather one combination of anatomical structures which is engaged at all muscle activation levels, and that the mechanical properties (i.e. the stress–strain function) are determined by the combined tissue mechanical properties. Additionally, our results demonstrated that the SES in the human plantar flexors at moments levels up to about isometric maximum did not reach an asymptote where the stiffness is independent of moment, i.e. SEC of the plantar flexors is, during many daily activities, loaded for the greatest part in the non-linear part of the stress–strain function.

Effectiveness of Seismic Isolation of Highly Skewed P/C I-Girder Bridge

Experimental and analytical investigations were conducted to evaluate the effectiveness of isolating the superstructure from the substructure of a highly skewed prestressed concrete slab on a girder bridge. Dynamic testing of the bridge was performed using the pullback, quick-release method. A 3D finite elemental model of the bridge was calibrated and refined to match experimentally determined natural frequencies and mode shapes. Time-history analyses, using site-specific acceleration records, were conducted for the seismically isolated bridge model and an identical nonisolated bridge model. Seismic isolation was found to appreciably reduce forces that the bridge substructure and foundation must resist. When compared to the nonisolated bridge for the design earthquake (or 50-year event), the maximum pier moments were reduced between 32% and 62%, and the maximum shears were reduced between 30% and 66%.

Shortening velocity is different in longitudinal and circular muscle layers of the rabbit urethra.

The aim of the study was to investigate whether the functional difference between circular and longitudinal muscles in the female rabbit urethra is reflected in their shortening properties and lactate dehydrogenase (LDH) activity. For mechanical experiments the preparations were chemically skinned to avoid influence of membrane-related mechanisms and to enable maximal activation. Force velocity relations and the maximal shortening velocity (v(max)) were determined using the isotonic quick-release method. The v(max) was three times higher in longitudinal muscle. LDH isoform pattern was determined on agarose gels. The M-subunit, favourable for lactate formation, constituted 70% of the total in both types of muscle. There was no difference in the LDH isoform pattern despite the marked difference in v(max). We conclude that the difference in v(max) reflects differences in the contractile machinery itself. These mechanical characteristics are advantageous for the role of the circular as a tonic muscle contracting during bladder filling, and the longitudinal as a phasic muscle active in opening up the urethra during micturition.

Pullback Testing of Seismically Isolated P/C I-Girder Bridge

Dynamic testing was performed on a highly skewed, three-span, seismically isolated, prestressed concrete, slab-on-girder bridge. The pullback, quick-release method of testing was used, a first for this bridge type. Several new developments facilitated the quick-release testing. A simple new quick-release mechanism was employed with relatively low lateral test force. Also, a new method of attaching the pullback cable to the bridge was implemented. After testing, a three-dimensional finite element model of the bridge was created. An optimization program was used to refine, or calibrate, the model to match experimentally determined natural frequencies and mode shapes. This automated, systematic optimization of model parameters produced an accurate analytical representation of the bridge. Mode shapes and frequencies from the experimental and analytical investigations are presented.

Oxytocin-mediated recruitment of slowly cycling cross bridges and isometric force in rat myometrium.

The relationship between cross-bridge cycling rate and isometric stress was investigated in rat myometrium. Stress production by myometrial strips was measured under resting, K+ depolarization, and oxytocin-stimulated conditions. Cross-bridge cycling rates were determined from measurements of maximal unloaded shortening velocity, using the quick-release method. Force redevelopment after the quick release was used as an index of cross-bridge attachment. With maximal K+ stimulation, stress increased with increased cross-bridge cycling (+76%; P < 0.05) and attached cross bridges (+112%; P < 0.05). Addition of oxytocin during K+ stimulation further increased stress (+30%; P < 0.05). With this force component, the cross-bridge cycling rate decreased (-60%; P < 0.05) similar to that under resting conditions. Attached cross-bridges did not increase with this additional stress. The results suggest two distinct mechanisms mediating myometrial contractions. One requires elevated intracellular calcium and rapidly cycling cross bridges. The other mechanism may be independent of calcium and appears to be mediated by slowly cycling cross bridges, supporting greater unit stress.

Isometric および eccentric な予備緊張が肘屈曲速度に及ぼす影響 : Concentric な収縮中の負荷重量および動作範囲に着目して

This study investigated the effects of isometric and eccentric preliminary muscle contractions on elbow flexion velocity with special reference to load and range of motion during concentric contraction. Subjects were fifteen healthy males. They performed elbow flexion with maximum concentric contraction, just followed by three types of preliminary muscle contraction, i.e., resting condition (After-load method: AL), maximum isometric contraction (Isometric quick release method: IQR), and maximum eccentric contraction (Eccentric quick release method: EQR). Loads during concentric contraction were nine kinds of equivalent mass ranging from 11.4 to 556.7 kg. Comparisons of force, velocity and EMG during concentric contraction were made among three methods. Although the effect of the preliminary contraction on the elbow flexion velocity was observed, the effect of EQR was larger than that of IQR. Furthermore,the effects of both EQR and IQR were remarkable in the only early phase during concentric contraction with the lighter loads. We discussed physiological and mechanical background producing forces at the starting point and from initial to final phases during concentric contraction, since the above effects of the preliminary muscle contractions would be caused by magnitude of their forces. Consequently, it was suggested that the effects of isometric and eccentric preliminary muscle contractions were caused by the complex of positive and negative effects based on some physiologidal and mechanical factors, i.e., activntion level of muscle at the starting point, reuse of elastic energy and decrease of loss energy in early phase, and excitation and inhibition of contractile energy from initial to middle phases during concentric contraction.

Static Deformations of Bridges From Quick‐Release Dynamic Experiments

This paper illustrates the application of a new method for performing baseline corrections on accelerograms generated by the quick-release method. These accelerograms are produced when highway bridges are subjected to dynamic excitations by initially deforming the structure and subsequently quick-releasing the loads causing the deformations. In the past, the displacements caused by the quick-release loads have not been recovered because an adequate correction procedure was not available. A baseline-correction method was developed such that the step-function character of the quick-release baseline is preserved. This feature allows the complete static deformation state to be recovered by integrating the accelerograms. The power of the method is demonstrated by applying it to a suite of quick-release data obtained during full-scale field tests of the Meloland Road Overcrossing located near El Centro, California. As a result, complete static deformations of this bridge are obtained as a by-product of the dynamic experiments.

Phosphorylation and thiophosphorylation by myosin light chain kinase: Different effects on mechanical properties of chemically skinned ventricular fibers from the pig

The influence of myosin light chain phosphorylation (treatment with myosin light chain kinase = MLCK, calmodulin and ATP) and thiophosphorylation (incubation with MLCK, calmodulin and ATPγS) on the maximal shortening velocity ( V max) and Ca 2+ sensitivity of chemically-skinned ventricular fibers from the pig has been studied. V max was determined by the slack-test method and by extrapolation of the force-velocity relation by the isotonic quick release method. V max was 1.53 muscle length/s (L/s) and 1.94 L/s using the force-velocity relation and the slack-test, respectively. Phosphorylation increased the Ca 2+ sensitivity for isometric force development of skinned fibers but had no influence on V max. Thiophosphorylation decreased V max but had no influence on Ca 2+ sensitivity. Phosphorylation pattern of the myosin light chains of the skinned fibers was studied using [γ- 32P]ATP or [γ-P 35S]ATP (250 μCi each) and autoradiography. Incubation of skinned fibers with labeled ATP led to a phosphate incorporation into the 18-kDa myosin light chain (MPLC or regulatory light chain) while incubation with labeled ATPγS led to an incorporation of thiophosphate into the 28-kDa myosin light chain (alkali light chain) and tropomyosin. We suggest that the difference in mechanical behavior between phosphorylated and thiophosphorylated skinned fibers are due to differences in the phosphorylation profiles of myofibrillar regulatory proteins.

Normally cycling and latch bridges in venous smooth muscle.

We have studied the mechanical properties of the crossbridges of canine saphenous venous smooth muscle during activation by electrical stimulation. A length-tension relationship study showed that at optimal length (1o) the maximum isometric tension (Po) developed was 87.9 mN/mm2. Resting tension at 1o was only 6% Po, which indicates a very compliant muscle. Active tension was observed at muscle lengths greater than 0.3 1o. The maximum shortening capacity was 0.65 1o. Force-velocity and series elastic characteristics were determined by the method of quick release to a set of load clamps applied during the course of an isometric contraction. The data were fitted by the hyperbolic Hill equation. Estimated maximum shortening velocity at zero load (Vo) an index of the crossbridge cycling rate) was 0.26 1o/s which was attained early in the contraction (5 s after the stimulation). A 11.9% decline in Vo was observed at the plateau of the contraction which occurred at 15 s. The stress (sigma)-strain (epsilon) curve for the series elastic component could be approximated by the equation sigma = B[exp(A epsilon)-1], where A = 76.51 (1/1o), B = 2.89 mN/mm2 at 5 s and A = 61.49 (1/1o), B = 1.85 mN/mm2 at 15 s. Like other smooth muscles, in general, saphenous vein develops considerable isometric tension and has a high shortening capacity but a low shortening velocity. The reduction in shortening velocity that occurs after 5 s in an isometric contraction is probably due to the development of so-called latch bridges.

Cross-bridge behaviour in skinned smooth muscle of the guinea-pig taenia coli at altered ionic strength.

1. The effects of varied levels (25-300 mM) of ionic strength on mechanical properties and ATP hydrolysis rate of chemically skinned guinea-pig taenia coli fibres were investigated. 2. The tension development following activation by calcium (pCa 4.8), and relaxation following removal of calcium (pCa 9), were slower in 25 mM compared to 150 mM ionic strength. In fibres activated by thiophosphorylation of myosin light chains, by exposure to ATP-gamma-S, the tension development was rapid and independent of ionic strength. 3. The maximal shortening velocity (Vmax) was obtained from force-velocity relations determined by the quick-release method. The rate of ATP hydrolysis (JATP) was determined by measurement of pyruvate released from phosphoenolpyruvate (PEP). In order to obtain maximal Vmax and JATP at a Mg-ATP concentration of 1 mM, an ATP regenerating system was required. In thiophosphorylated fibres 2 mM-phosphocreatine (PCr) or 3.2 mM-PEP were adequate for maximal Vmax and JATP respectively. In calcium-activated fibres 5 mM-PCr was required for maximal Vmax. 4. The isometric force of thiophosphorylated fibres showed a biphasic dependence on ionic strength with a maximum at 90 mM. Vmax was essentially unchanged between 50 and 200 mM ionic strength. At 25 mM ionic strength, isometric force and Vmax were decreased by, respectively, about 15 and 25%. At 250 mM ionic strength, isometric force and Vmax were decreased by, respectively, 47 and 33%. 5. Vmax decreased with decreasing [Mg-ATP]. At [Mg-ATP] less than 0.1 mM there was no difference in Vmax between 35 and 150 mM ionic strength. At 250 mM ionic strength Vmax was lower than that at 150 mM at all [Mg-ATP]. 6. JATP during contraction in thiophosphorylated fibres at 35, 150 and 250 mM ionic strength was respectively, 0.62, 0.98 and 0.93 mumol g-1 min-1. The energetic tension cost (JATP/force) increased with ionic strength. 7. The force response to a quick stretch was investigated in the relaxed, contracted and rigor states at 25, 150 and 250 mM ionic strength. Stiffness in the relaxed state increased with speed of stretch and was higher the lower the ionic strength. In the contracted and rigor states, stiffness was also affected by ionic strength, but the relative effect in the contracted state was small.(ABSTRACT TRUNCATED AT 400 WORDS)

Force-velocity constants in smooth muscle: afterloaded isotonic and quick-release methods.

In using pharmacologic stimuli, force-velocity (FV) curves are usually obtained by the method of quick release (QR) and redevelopment of shortening at peak tetanic tension; the advantage of the method being that the active state is at maximum. However, the QR may itself reduce the intensity of the active state and result in reduced values of FV constants. We tested this by delineating FV curves in canine tracheal smooth muscle using both conventional afterloaded isotonic contractions (ALI), and redevelopment of shortening after QR methods. For both these studies a supramaximal tetanizing electrical stimulus was used. The analysis of 11 experiments revealed that the latter method resulted in statistically significant reductions of all FV constants except for Po (maximum isometric tetanic tension). The means and standard errors for the sets of constants for the ALI and QR, respectively, are as follows: Vmax (maximum velocity of shortening) = 0.275 lo (optimal muscle length)/s +/- 0.024 (SE), and 0.216 lo/s + 0.023; a (hyperbolic constant with units of force) = 294 g/cm2 +/- 35 and 236 g/cm2 +/- 32; b (hyperbolic constant with units of velocity) = 0.059 lo +/- 0.004 and 0.039 lo/s +/- 0.005; a/Po = 0.214 +/- 0.028 and 0.182 +/- 0.026; and Po = 1.362 kg/cm2 +/- 0.106 and 1.294 kg/cm2 +/- 0.097. These data clearly show that the quick-release method for measuring force-velocity relationships in canine smooth muscle results in significant underestimates of muscle shortening properties.

Bridge Dynamic Tests: Implications for Seismic Design

A five span, 400 ft (120m) long, reinforced concrete box girder bridge supported on single column piers, which are pile founded, was subjected to extensive dynamic tests. The pullback and quick release method of excitation was used. Two D-8 crawler tractors were used to apply total release loads which had a magnitude of about one-quarter of the earthquake design loads. System identification techniques were used to extract the experimental in situ dynamic stiffness of the pier pile group foundations from the suite of field data. An independent geotechnical analysis of the bridge's pile foundations yielded pile group stiffness which were in acceptable to good agreement with the experimentally determined values. Moreover, this analysis indicated that for design level seismic loadings the pile group stiffnesses are quite deflection dependent. It was further shown that it is essential to include the soil-structure interaction effect in the analytical model if correct distributions of seismic loads are to be obtained.

Dynamic Tests and System Identification of Bridges

A five-span, four-hundred-foot long, reinforced concrete box girder birdge supported on single column piers that are pile-founded was subjected to extensive dynamic tests. The pullback and quick-release method of excitation was used. Two D-8 crawler tractors were used to apply total release loads that had a magnitude of about one-quarter of the earthquke design loads. The transverse mode shapes and natural frequencies obtained from these tests were used in conjunction with the system identification procedure outlined herein. By using these techniques, it is possible to identify the in situ dynamic stiffnesses of the pier foundations as well as the abutment structures. In addition, the dynamic bending and shear stiffness factors for the superstructure deck were also obtained. Thus, carefully conducted dynamic tests of full-scale highway bridges provide detailed information about the structure. At the same time, they shed much experimental light on the soil-structure interaction aspects of the problem, which in many cases greatly affects the distribution of seismic loads in bridges.