[Sonographic evaluation of the levator ani muscle in women with stress urinary incontinence]

Three-dimensional sonography has been used for about 15 years, not only to examine the female genital organs, but also the lower urinary tract and pelvic floor. Three-dimensional sonography offers more information than traditional two-dimensional sonography allowing for a dynamic representation of the examined structures and observation at any angle necessary. Translabial sonography is the best way of a sonographic examination of the lower urinary tract, because it does not affect the mutual relationship of any parts in the lower pelvic area, contrary to the transrectal or transvaginal probes. In order to establish proper treatment of the urinary incontinence symptoms, not only a functional examination of the lower urinary tract, but also a very accurate assessment of the statics of the female genital organs and pelvic floor need to be performed.

BACKGROUND

The aim of the study was to rate the area and diameters of the limbs of the levator ani muscle using a three-dimensional (3D) translabial sonography in women with stress urinary incontinence without the female genital tract prolapse.

MATERIAL AND METHODS

The study group included 100 patients who were examined with the GE Kretz Voluson 730 (GE, Austria), equipped with 6-9 MHz translabial probe. The first group with stress urinary incontinence consisted of 50 women (mean age 56.22 (+/- 10.43) years) and the second group included 50 women without symptoms (mean age 49.40 (+/- 13.22) years). All cases of urinary stress incontinence in the first group were confirm by means of a urodynamic examination. Women in both groups had similar body weight (kilograms), mean (+/- SD): 26.88 (+/- 2.02) and 26.20 (+/- 4,14), respectively. Menopausal status in both groups was not statistically significant and amounted to 7.21 (+/- 8.71) in the group of women with stress urinary incontinence and 4.70 (+/- 6.32) in the group without symptoms. Mean (+/- SD) number of deliveries was significantly higher in the group of women with stress urinary incontinence than in the control group (2.40 (+/- 1.03) and 1.56 (+/- 1.34), respectively). In all cases 3D coronal view of the pelvic diaphragm was obtained and the area and thickness of limbs of the levator ani muscle were measured. All women had about 200 ml urine in the bladder.

RESULTS

The results are presented as means +/- SD. Mean measurements of this area in both groups were 8.54 +/- 1.62 cm2 and 10.57 +/- 1.29 cm2, respectively. Mean thickness of the limbs in the groups were: 8.72 +/- 0.64mm and 10.85 +/- 0.89mm on the left side and 8.85 +/- 0.67mm and 10.89 +/- 0.87mm on right side, respectively. The differences between both groups in all measurements were statistically significant (p < 0.001).

CONCLUSIONS

There are some differences involving measurements of the thickness and the area of the limbs of the levator ani muscle in women with and without stress urinary incontinence and without the genital tract prolapse in both groups. The observed differences could have implications in physiotherapy of the pelvic floor muscles in women without statics abnormalities.

Subject-specific tendon-aponeurosis definition in Hill-type model predicts higher muscle forces in dynamic tasks

Neuromusculoskeletal models are a common method to estimate muscle forces. Developing accurate neuromusculoskeletal models is a challenging task due to the complexity of the system and large inter-subject variability. The estimation of muscles force is based on the mechanical properties of tendon-aponeurosis complex. Most neuromusculoskeletal models use a generic definition of the tendon-aponeurosis complex based on in vitro test, perhaps limiting their validity. Ultrasonography allows subject-specific estimates of the tendon-aponeurosis complex’s mechanical properties. The aim of this study was to investigate the influence of subject-specific mechanical properties of the tendon-aponeurosis complex on a neuromusculoskeletal model of the ankle joint. Seven subjects performed isometric contractions from which the tendon-aponeurosis force-strain relationship was estimated. Hopping and running tasks were performed and muscle forces were estimated using subject-specific tendon-aponeurosis and generic tendon properties. Two ultrasound probes positioned over the muscle-tendon junction and the mid-belly were combined with motion capture to estimate the in vivo tendon and aponeurosis strain of the medial head of gastrocnemius muscle. The tendon-aponeurosis force-strain relationship was scaled for the other ankle muscles based on tendon and aponeurosis length of each muscle measured by ultrasonography. The EMG-driven model was calibrated twice - using the generic tendon definition and a subject-specific tendon-aponeurosis force-strain definition. The use of subject-specific tendon-aponeurosis definition leads to a higher muscle force estimate for the soleus muscle and the plantar-flexor group, and to a better model prediction of the ankle joint moment compared to the model estimate which used a generic definition. Furthermore, the subject-specific tendon-aponeurosis definition leads to a decoupling behaviour between the muscle fibre and muscle-tendon unit in agreement with previous experiments using ultrasonography. These results indicate the use of subject-specific tendon-aponeurosis definitions in a neuromusculoskeletal model produce better agreement with measured external loads and more physiological model behaviour.

Longitudinal enhancement of the hyperechoic regions in ultrasonography of muscles using a Gabor filter bank approach: a preparation for semi-automatic muscle fiber orientation estimation

In this study, to complement our previously proposed method for estimating muscle fiber orientation, the Gabor filter bank (GF) technique was applied to sonograms of the biceps and forearm muscles to longitudinally enhance the coherently oriented and hyperechoic perimysiums regions. The method involved three steps: orientation field estimation, frequency map computation and Gabor filtering. The method was evaluated using a simulated image distorted with multiplicative speckle noises where the "muscles" were arranged in a bipennate fashion with an "aponeurosis" located in the middle. After enhancement using the GF approach, most of the original hyperechoic bands in the simulated image could be recovered. The proposed method was also tested using a group of biceps and forearm muscle sonograms collected from healthy adult subjects. Compared with the sonograms without enhancement, the enhanced images led to the detection of more linear patterns including muscle fascicles and smaller angle differences compared with the mean of manual results from two operators, therefore, were better prepared for the automatic estimation of muscle fiber orientation. The proposed method has the potential of assisting in the visualization of strongly oriented patterns in skeletal muscle sonograms as well as in the semi-automatic estimation of muscle fiber orientations.

Denervation dynamically regulates integrin alpha7 signaling pathways and microscopic structures in rats

BACKGROUND

Peripheral nerve injury causes serious problems in orthopedic and plastic surgeries. Cell adhesion molecules such as integrin alpha7 provoke cell binding and signaling pathways within myofibers. Expression profiles of integrin alpha7 signaling pathways and the molecule's microscopic structure were assessed to investigate the long-term dynamic changes in denervated rat skeletal muscle.

METHODS

A denervated rat skeletal muscle model was established by severing the sciatic nerve for 1 week, 2 weeks, 4 weeks, 8 weeks, 12 weeks, 20 weeks, and 26 weeks. Molecular expressions were investigated by mRNA and Western blot. The structural alterations were detected by immunohistochemistry, scanning electron microscopy, and transmission electron microscopy.

RESULTS

The denervated muscle atrophy presented the following dynamic molecular alterations: an initial increase around postdenervation in week (PIW) 8 and then a subsequent decay of integrin alpha7, integrin downstream signaling pathway (Ras or Raf or, ERK1/2), Akt, cleaved caspase-3, fast myosin heavy chain (MHC), beta actin, and RhoA. We demonstrated that the expressions of multiple signaling molecules were highly upregulated at PIW 8 (p<0.01). Scanning electron microscopy findings of the surface textures of myofibers showed more severe damage at PIW 8 and subsequently became smoother. Inner structures of myofibers separated with discontinuity on transmission electron microscopy examinations.

CONCLUSION

Our novel finding showed that time-series alterations of integrin alpha7 signaling molecules and surface microstructures in the long-term denervated rat skeletal muscle are biphasic and coherently dynamic. Persisted p-Akt elevation suggested that denervated muscle may regenerate if reinnervation or other treatment was performed.

Relationship of intramyocellular lipid to insulin sensitivity may differ with ethnicity in healthy girls and women

The prevalence of type 2 diabetes is greater among African Americans (AA) vs. European Americans (EA), independent of obesity and lifestyle. We tested the hypothesis that intramyocellular lipid (IMCL) or extramycellular lipid (EMCL) would be associated with insulin sensitivity among healthy young women, and that the associations would differ with ethnic background. We also explored the hypothesis that adipokines and estradiol would be associated with muscle lipid content. Participants were 57 healthy, normoglycemic, women and girls mean age 26 (±10) years; mean BMI 27.3 (±4.8) kg/m²; 32 AA, 25 EA. Soleus IMCL and EMCL were assessed with ¹H magnetic resonance spectroscopy (MRS); insulin sensitivity with an insulin-modified frequently sampled intravenous glucose tolerance test and minimal modeling; body composition with dual-energy X-ray absorptiometry; and intra-abdominal adipose tissue (IAAT) with computed tomography. Adiponectin, leptin, and estradiol were assessed in fasting sera. Analyses indicated that EMCL, but not IMCL, was greater in AA vs. EA (2.55 ± 0.16 vs. 1.98 ± 0.18 arbitrary units, respectively, P < 0.05; adjusted for total body fat). IMCL was associated with insulin sensitivity in EA (r = -0.54, P < 0.05, adjusted for total fat, IAAT, and age), but not AA (r = 0.16, P = 0.424). IMCL was inversely associated with adiponectin (r = -0.31, P < 0.05, adjusted for ethnicity, age, total fat, and IAAT). In conclusion, IMCL was a significant determinant of insulin sensitivity among healthy, young, EA but not AA women. Further research is needed to determine whether the component lipids of IMCL (e.g., diacylglycerol (DAG) or ceramide) are associated with insulin sensitivity in an ethnicity specific manner.

Investigations into pulsed high-intensity focused ultrasound-enhanced delivery: preliminary evidence for a novel mechanism

Pulsed high-intensity focused ultrasound (HIFU) exposures without ultrasound contrast agents have been used for noninvasively enhancing the delivery of various agents to improve their therapeutic efficacy in a variety of tissue models in a nondestructive manner. Despite the versatility of these exposures, little is known about the mechanisms by which their effects are produced. In this study, pulsed-HIFU exposures were given in the calf muscle of mice, followed by the administration of a variety of fluorophores, both soluble and particulate, by local or systemic injection. In vivo imaging (whole animal and microscopic) was used to quantify observations of increased extravasation and interstitial transport of the fluorophores as a result of the exposures. Histological analysis indicated that the exposures caused some structural alterations such as enlarged gaps between muscle fiber bundles. These effects were consistent with increasing the permeability of the tissues; however, they were found to be transient and reversed themselves gradually within 72 h. Simulations of radiation force-induced displacements and the resulting local shear strain they produced were carried out to potentially explain the manner by which these effects occurred. A better understanding of the mechanisms involved with pulsed HIFU exposures for noninvasively enhancing delivery will facilitate the process for optimizing their use.

Effects of therapeutic ultrasound on joint mobility and collagen fibril arrangement in the endomysium of immobilized rat soleus muscle

This study examined effects of therapeutic ultrasound on joint mobility and collagen fibril arrangement in the endomysium of immobilized rat soleus muscle. Twenty-two male Wistar rats were divided randomly into control (n = 5) and experimental groups (n = 17). In the experimental group, bilateral ankle joints of each rat were fixed in full plantar flexion with a plaster cast over a 4-wk period. Five animals in the experimental group were immobilized throughout the 4-wk (immobilization group) period, whereas the remaining rats in the experimental group were randomly divided into the ultrasound (US, n = 6) and sham (n = 6) treatment groups. Under anesthesia, continuous ultrasonic energy (frequency, 1 MHz; intensity, 1.0 W/cm(2)) was delivered to the triceps surae muscle of the US group for 15 min per d, 6 d per wk over the 4-wk immobilization period. Ultrasonic energy was not delivered to the triceps surae muscle in sham animals; only the transducer head was moved. Ankle joint mobility on dorsiflexion in the immobilization, sham and US groups was significantly smaller than that of the control group, whereas in the US group, this parameter was significantly greater than in the immobilization and sham groups. Collagen fibril arrangement in the endomysium of the control and US groups was longitudinal to the axis of the muscle fibers; in contrast, it was circumferential in the immobilization and sham groups. Our findings revealed that joint immobilization induces decreased joint mobility and collagen fibril movement in the endomysium; furthermore, ultrasound treatment can prevent these changes. We hypothesized that therapeutic ultrasound during the immobilization process may inhibit deterioration of muscle contracture.

[Ultrastructural analysis of mouse levator auris longus muscle intoxicated in vivo by botulinum neurotoxin type A]

We studied the short and long term ultrastructural changes produced by botulinum neurotoxin type A injected in vivo, at a sublethal dose, in mouse levator auris longus muscle. The neurotoxin had a temporary effect on nerve terminals which consisted in a generalized paralysis, that affected the following features of the neuromuscular sample's morphology: size of the nerve terminals, vesicle population, mitochondrial appearance, Schwann cell's morphology, development and distribution of post-synaptic membrane folds, and nuclear morphology of the different elements of the motor end plate. Besides, the amount of endomysial connective tissue was significantly greater compared to non-intoxicated cases, and these changes were more notorious during the first couple of weeks. 20 to 25 days after the injection, during the recovery phase, we observed nerve terminals with a variable appearance: some completely degenerated, enveloped by Schwann cell processes, and new contacts characterized ultrastructurally for their small size, scarce vesicles, partially enveloped by Schwann cells, early myelinized axons and barely developed synaptic folds. Sixty days after the injection, the axon terminal recovered its normal appearance: synaptic vesicles filled the axon's cytoplasm, and the mitochondria showed normal appearing cristae and electronic densities. We conclude that botulinum neurotoxin type A produces changes related to denervation of the nerve terminals and affects the motor end plate components. Schwann cells play an important role both in the morphofuntional recovery of nerve terminals and in their degradation.

Estimation of muscle fiber orientation in ultrasound images using revoting hough transform (RVHT)

Ultrasound imaging has been used frequently for the study of muscle contraction, including measurements of pennation angles and fascicle orientations. However, these measurements were traditionally conducted by manually drawing lines on the ultrasound images. In this study, we proposed a modified Hough transform (HT), aiming at automatically estimating orientations of straight line-shaped patterns, such as muscle fibers and muscle-bone interface in ultrasound images. The new method first located the global maximum in the HT accumulator matrix, which corresponded to the most dominant collinear feature points globally, using the standard HT; then the pixels close to the detected line were removed from the edge map, the HT accumulator matrix was calculated again, i.e., revoting, and a new line was detected. The iteration was repeated until the predefined termination conditions were satisfied. The performance of the algorithm was tested using computer-generated images with different levels of noises, as well as clinical ultrasound images, and compared with that of the conventional method. It was found that the orientation estimation results obtained by the new algorithm were well correlated (R2 = 0.965), with those obtained using the traditional method, i.e., drawing lines manually and reading the angles with the assistance of software. Further mean-difference plots revealed a difference of 0.18 +/- 2.41 degrees between the two methods at the 95% confidence level. Compared with the traditional method, the new algorithm was more capable of handling with highly noisy data and could avoid the aliasing problem, i.e., reporting multiple lines instead of single expected line. The results of this study suggested that the proposed revoting HT can be potentially used for the reliable and nonsubjective automatic estimation of the orientations of muscle fibers in musculoskeletal ultrasound images.

Regional variation in the measured apparent ultrasonic backscatter of mid-gestational fetal pig hearts

The goal of this study was to characterize and compare regional backscatter properties of fetal hearts through measurements of the apparent integrated backscatter. Sixteen excised, formalin-fixed fetal pig hearts, representing an estimated 53 to 63 days of gestation, were investigated. Spatially localized measurements of integrated backscatter from these specimens were acquired using a 50 MHz single-element transducer. The apparent integrated backscatter measurements demonstrate different patterns of backscatter from the myocardium of the right ventricle compared with that of the left ventricle. These backscatter measurements appear to be consistent with the anisotropy of the fiber orientation observed in histologic assessment of the same specimens. For each of the 16 hearts, the apparent integrated backscatter from the right ventricular myocardium was larger than that from the left ventricular myocardium, exhibiting mean apparent backscatter values of -35.9 +/- 2.0 dB and -40.1 +/- 1.9 dB (mean +/- standard deviation; n = 16; p < 0.001), respectively. This study suggests that the intrinsic ultrasonic properties of the left and right ventricular myocardium are distinct in fetal pig hearts at mid-gestation.

The acute effect of stretching on the passive stiffness of the human gastrocnemius muscle tendon unit

Passive stretching is commonly used to increase limb range of movement prior to athletic performance but it is unclear which component of the muscle-tendon unit (MTU) is affected by this procedure. Movement of the myotendinous junction (MTJ) of the gastrocnemius medialis muscle was measured by ultrasonography in eight male participants (20.5 +/- 0.9 years) during a standard stretch in which the ankle was passively dorsiflexed at 1 deg s(-1) from 0 deg (the foot at right angles to the tibia) to the participants' volitional end range of motion (ROM). Passive torque, muscle fascicle length and pennation angle were also measured. Standard stretch measurements were made before (pre-) and after (post-) five passive conditioning stretches. During each conditioning stretch the MTU was taken to the end ROM and held for 1 min. Pre-conditioning the extension of the MTU during stretch was taken up almost equally by muscle and tendon. Following conditioning, ROM increased by 4.6 +/- 1.5 deg (17%) and the passive stiffness of the MTU was reduced (between 20 and 25 deg) by 47% from 16.0 +/- 3.6 to 10.2 +/- 2.0 Nm deg(-1). Distal MTJ displacement (between 0 and 25 deg) increased from 0.92 +/- 0.06 to 1.16 +/- 0.05 cm, accounting for all the additional MTU elongation and indicating that there was no change in tendon properties. Muscle extension pre-conditioning was explicable by change in length and pennation angle of the fascicles but post-conditioning this was not the case suggesting that at least part of the change in muscle with conditioning stretches was due to altered properties of connective tissue.

Influence of concentric and eccentric resistance training on architectural adaptation in human quadriceps muscles

Studies using animal models have been unable to determine the mechanical stimuli that most influence muscle architectural adaptation. We examined the influence of contraction mode on muscle architectural change in humans, while also describing the time course of its adaptation through training and detraining. Twenty-one men and women performed slow-speed (30 degrees /s) concentric-only (Con) or eccentric-only (Ecc) isokinetic knee extensor training for 10 wk before completing a 3-mo detraining period. Fascicle length of the vastus lateralis (VL), measured by ultrasonography, increased similarly in both groups after 5 wk (Delta(Con) = +6.3 +/- 3.0%, Delta(Ecc) = +3.1 +/- 1.6%, mean = +4.7 +/- 1.7%; P < 0.05). No further increase was found at 10 wk, although a small increase (mean approximately 2.5%; not significant) was evident after detraining. Fascicle angle increased in both groups at 5 wk (Delta(Con) = +11.1 +/- 4.0%, Delta(Ecc) = +11.9 +/- 5.4%, mean = 11.5 +/- 3.2%; P < 0.05) and 10 wk (Delta(Con) = +13.3 +/- 3.0%, Delta(Ecc) = +21.4 +/- 6.9%, mean = 17.9 +/- 3.7%; P < 0.01) in VL only and remained above baseline after detraining (mean = 13.2%); smaller changes in vastus medialis did not reach significance. The similar increase in fascicle length observed between the training groups mitigates against contraction mode being the predominant stimulus. Our data are also strongly indicative of 1) a close association between VL fascicle length and shifts in the torque-angle relationship through training and detraining and 2) changes in fascicle angle being driven by space constraints in the hypertrophying muscle. Thus muscle architectural adaptations occur rapidly in response to resistance training but are strongly influenced by factors other than contraction mode.

Computed tomographic measurement of gluteal subcutaneous fat thickness in reference to failure of gluteal intramuscular injections

OBJECTIVE

Casual observation of gluteal region fat thickness on computed tomography (CT) of the pelvis leads to the hypothesis that, in some individuals, intended intramuscular injections are not properly deposited in the gluteal muscle. We gathered and analyzed data to determine whether this hypothesis was true.

METHODS

CT scans of the pelvis were analyzed over an 18-day period in the fall of 2005. The thickness of gluteal region subcutaneous fat was measured in a standardized manner.

RESULTS

Measurement of gluteal region subcutaneous fat thickness was performed for 298 pelvic CT scans. There were 150 male subjects and 148 female subjects. The average gluteal fat thickness for female subjects was 33.2 mm, whereas the average for male subjects was 23.1 mm. Analysis revealed a significant difference in gluteal region fat thickness between male and female subjects. A 37-mm needle, allowing for 6-mm penetration of the gluteal muscle, would not have entered the gluteal muscle fibres in 81 of 148 female subjects (54.7%), in 21 of 150 male subjects (14%), and in 102 of the 298 total sample (34.2%). Analysis revealed a significant difference between male and female subjects with regard to gluteal muscle needle penetration.

CONCLUSION AND RECOMMENDATION

An overall predicted failure rate of 34% was identified for intended gluteal intramuscular injections when the standard technique was used. This is important information for care providers who inject medications in the gluteal region. In a significant number of patients, the medications will be injected subcutaneously and not into the gluteal musculature, possibly altering the pharmacokinetics of the administered medication. An alternative injection site should probably be chosen to increase the success rate of intramuscular deposition of medications and vaccines in unselected adults.

Intra- and intermuscular variation in human quadriceps femoris architecture assessed in vivo

Despite the functional importance of the human quadriceps femoris in movements such as running, jumping, lifting and climbing, and the known effects of muscle architecture on muscle function, no research has fully described the complex architecture of this muscle group. We used ultrasound imaging techniques to measure muscle thickness, fascicle angle and fascicle length at multiple regions of the four quadriceps muscles in vivo in 31 recreationally active, but non-strength-trained adult men and women. Our analyses revealed a reasonable similarity in the superficial quadriceps muscles, which is suggestive of functional similarity (at least during the uni-joint knee extension task) given that they act via a common tendon. The deep vastus intermedius (VI) is architecturally dissimilar and therefore probably serves a different function(s). Architecture varies significantly along the length of the superficial muscles, which has implications for the accuracy of models that assume a constant intramuscular architecture. It might also have consequences for the efficiency of intra- and intermuscular force transmission. Our results provide some evidence that subjects with a given architecture of one superficial muscle, relative to the rest of the subject sample, also have a similar architecture in other superficial muscles. However, this is not necessarily true for vastus lateralis (VL), and was not the case for VI. Therefore, the relative architecture of one muscle cannot confidently be used to estimate the relative architecture of another. To confirm this, we calculated a value of whole quadriceps architecture by four different methods. Regardless of the method used, we found that the absolute or relative architecture of one muscle could not be used as an indicator of whole quadriceps architecture, although vastus medialis, possibly in concert with VL and the anterior portion of VI, could be used to provide a useful snapshot. Importantly, our estimates of whole quadriceps architecture show a gender difference in whole quadriceps muscle thickness, and that muscle thickness is positively correlated with fascicle angle whereas fascicle length is negatively, although weakly, correlated with fascicle angle. These results are supportive of the validity of estimates of whole quadriceps architecture. These data are interpreted with respect to their implications for neural control strategies, region-specific adaptations in muscle size in response to training, and gender-dependent differences in the response to exercise training.

Regional variations in intramyocellular lipid concentration correlate with muscle fiber type distribution in rat tibialis anterior muscle

1H MR spectroscopy (MRS) has proved to be a valuable noninvasive tool to measure intramyocellular lipids (IMCL) in research focused on insulin resistance and type II diabetes in both humans and rodents. An important determinant of IMCL is the muscle fiber type, since oxidative type I fibers can contain up to three times more IMCL than glycolytic type II muscle fibers. Because these different muscle fiber types are inhomogeneously distributed in rodent muscle, in the present study we investigated the distribution of IMCL within the rat tibialis anterior muscle (TA) in vivo using single-voxel 1H MRS along with the muscle fiber distribution in the TA ex vivo determined from immunohistological assays. IMCL levels in the TA differed by up to a factor of 3 depending on the position of the voxel. The distribution of IMCL over the TA cross section was not random, but emerged in a pattern similar to the distribution of the predominantly oxidative muscle fiber types. Dietary interventions, such as high-fat feeding and 15 hr of fasting, did not significantly change this typical fiber type-dependent pattern of IMCL content. These results stress the importance of voxel positioning when single-voxel 1H MRS is used to study IMCL in rodent muscle.

Intensity- and muscle-specific fascicle behavior during human drop jumps

The present study was designed to examine fascicle-tendon interaction in the synergistic medial gastrocnemius (MG) and soleus (Sol) muscles during drop jumps (DJ) performed from different drop heights (DH). Eight subjects performed unilateral DJ with maximal rebounds on a sledge apparatus from different DH. During the exercises, fascicle lengths (using ultrasonography) and electromyographic activities were recorded. The results showed that the fascicles of the MG and Sol muscles behaved differently during the contact phase, but the whole muscle-tendon unit and its tendinous tissue lengthened before shortening in both muscles. The Sol fascicles also lengthened before shortening during the ground contact in all conditions. During the braking phase, the Sol activation increased with increasing DH. However, the amplitude of Sol fascicle lengthening was not dependent on DH during the same phase. In the MG muscle, the fascicles primarily shortened during the braking phase in the lower DH condition. However, in the higher DH conditions, the MG fascicles either behaved isometrically or were lengthened during the braking phase. These results suggest that the fascicles of synergistic muscles (MG and Sol) can behave differently during DJ and that, with increasing DH, there may be specific length change patterns of the fascicles of MG but not of Sol.

Structural changes in the myosin filament and cross-bridges during active force development in single intact frog muscle fibres: stiffness and X-ray diffraction measurements

Structural and mechanical changes occurring in the myosin filament and myosin head domains during the development of the isometric tetanus have been investigated in intact frog muscle fibres at 4 degrees C and 2.15 microm sarcomere length, using sarcomere level mechanics and X-ray diffraction at beamline ID2 of the European Synchrotron Radiation Facility (Grenoble, France). The time courses of changes in both the M3 and M6 myosin-based reflections were recorded with 5 ms frames using the gas-filled RAPID detector (MicroGap Technology). Following the end of the latent period (11 ms after the start of stimulation), force increases to the tetanus plateau value (T(0)) with a half-time of 40 ms, and the spacings of the M3 and M6 reflections (S(M3) and S(M6)) increase by 1.5% from their resting values, with time courses that lead that of force by approximately 10 and approximately 20 ms, respectively. These temporal relations are maintained when the increase of force is delayed by approximately 10 ms by imposing, from 5 ms after the first stimulus, 50 nm (half-sarcomere)(-1) shortening at the velocity (V(0)) that maintains zero force. Shortening at V(0) transiently reduces S(M3) following the latent period and delays the subsequent increase in S(M3), but only delays the S(M6) increase without a transient decrease. Shortening at V(0) imposed at the tetanus plateau causes an abrupt reduction of the intensity of the M3 reflection (I(M3)), whereas the intensity of the M6 reflection (I(M6)) is only slightly reduced. The changes in half-sarcomere stiffness indicate that the isometric force at each time point is proportional to the number of myosin heads bound to actin. The different sensitivities of the intensity and spacing of the M3 and M6 reflections to the mechanical responses support the view that the M3 reflection in active muscle originates mainly from the myosin heads attached to the actin filament and the M6 reflection originates mainly from a fixed structure in the myosin filament signalling myosin filament length changes during the tetanus rise.

Assessment of muscle fatigue using sonomyography: muscle thickness change detected from ultrasound images

Muscle fatigue is an exercise-induced reduction in maximal voluntary muscle force. As the surface electromyography (SEMG) can be used to estimate the features of neuromuscular activations associated with muscle contractions, it has been widely employed as an objective tool to evaluate muscle fatigue. On the other hand, ultrasound imaging can inherently provide the morphological information of individual muscle, thus the architectural changes of muscles during fatigue can be obtained. In this study, we demonstrated the feasibility of using the dimensional change of muscles detected by ultrasound images, named as sonomyography (SMG), to characterize the behavior of muscles when they were in fatigue. The SEMG signals of the muscles were also recorded simultaneously and used for comparison. The right biceps brachii muscles of 8 normal young male adult subjects were tested for 30s under 80% of the maximal voluntary isometric contraction. The muscle fatigue was indicated by the change of the root-mean-square (RMS) and median frequency (MDF) of the SEMG signals. The results showed that the SEMG RMS had a linear increase with time with a rate of 2.9+/-1.9%/s (mean+/-S.D.), while the MDF decreased linearly with a rate of -0.60+/-0.26Hz/s. The muscle thickness, detected from the ultrasound images, continuously increased during the muscle fatigue but with a nonlinear increase with time, which was rapid during the initial 8.1+/-2.1s with a mean deformation rate of 0.30+/-0.19%/s and then became slower with a rate of 0.067+/-0.024%/s up to 20s after the contraction. The muscle deformation at 20s was 3.5+/-1.6%. The results demonstrated that the architectural change of muscles detected using SMG could potentially provide complementary information for SEMG for the muscle fatigue assessment.

Muscle fibre recruitment can respond to the mechanics of the muscle contraction

This study investigates the motor unit recruitment patterns between and within muscles of the triceps surae during cycling on a stationary ergometer at a range of pedal speeds and resistances. Muscle activity was measured from the soleus (SOL), medial gastrocnemius (MG) and lateral gastrocnemius (LG) using surface electromyography (EMG) and quantified using wavelet and principal component analysis. Muscle fascicle strain rates were quantified using ultrasonography, and the muscle-tendon unit lengths were calculated from the segmental kinematics. The EMG intensities showed that the body uses the SOL relatively more for the higher-force, lower-velocity contractions than the MG and LG. The EMG spectra showed a shift to higher frequencies at faster muscle fascicle strain rates for MG: these shifts were independent of the level of muscle activity, the locomotor load and the muscle fascicle strain. These results indicated that a selective recruitment of the faster motor units occurred within the MG muscle in response to the increasing muscle fascicle strain rates. This preferential recruitment of the faster fibres for the faster tasks indicates that in some circumstances motor unit recruitment during locomotion can match the contractile properties of the muscle fibres to the mechanical demands of the contraction.

MRI myocardial motion and fiber tracking: a confirmation of knowledge from different imaging modalities

OBJECTIVE

A helical configuration underlies the anatomy of cardiac structure, and a structure/function relationship is needed to determine if the ventricular myocardial band model defines this spatial relationship. This report explores how studies of velocity-encoded phase contrast magnetic resonance imaging (MRI) for myocardial motion and fiber tracking algorithms that imply fiber orientations can (a) quantify regional myocardial wall motion of the entire heart, (b) determine if these motion of implied fiber orientation link with the helical heart model, and (c) reveal if this new knowledge correlates with imaging information from other different imaging modalities.

METHODS

Accumulated left ventricular motion patterns that accurately differentiate radial (i.e. contraction and expansion), rotational (i.e. twisting and untwisting), and longitudinal (i.e. lengthening and shortening) motion components are correlated with structure/function data achieved by sonomicrometer crystals, echocardiography, corrosion casts, and MUGA recordings.

RESULTS

Acceleration fiber tracking to determine fiber orientation and cardiac motion during the ejection and rapid filling phases of the cardiac cycle corresponded to maximal force displayed by ultrasonic crystals placed into the angulation of the presumed functional units of the descending and ascending segments of the apical loop of the helical ventricular myocardial band, and motion by echocardiographic recordings. These integrated findings imply a favourable interaction of MRI with the myocyte orientation of the helical ventricular myocardial band.

CONCLUSIONS

These composite findings indicate that phase contrast MRI techniques for high temporal resolution velocity mapping during cardiac motion and myocardial fiber tracking confirm other technologies, and centralize the capacity of MRI to link other imaging methods together relative to a single helical structural model. The close agreement amongst a spectrum of imaging studies provide a very powerful integration that transcends a single look; the same thing is observed by each component of global technology, thereby implying that the helical ventricular band is the structural basis for these functional changes.

Resonance in the human medial gastrocnemius muscle during cyclic ankle bending exercise

We investigated the behavior of the muscle tendon unit (MTU) of the medial gastrocnemius muscle during cyclic ankle bending exercise at eight different frequencies (ranging from 1.33 to 3.67 Hz). The changes in the length of fascicle in the muscle during the exercises were determined by real-time ultrasound imaging. The coordinates of anatomical references and the ground reaction force were determined from video recording and a force plate, respectively. The length change of the MTU (the distance from the origin to insertion of the muscle) was calculated from changes in the knee and ankle joint angles. It was found that the amplitude ratio and phase difference between the fascicle and MTU lengths were both dependent on the movement frequency. At lower frequencies, the fascicle lengths varied almost in phase with the MTU length, whereas they varied out of phase at the higher frequencies. At intermediate frequency, the amplitude of the fascicle became very small compared with that of the MTU, which is considered resonance. We constructed a mechanical model of the MTU based on a notion of forced oscillation in a mass-spring system. The obtained data were well explained by the model. It was concluded that the behavior of the MTU highly depends on the movement frequency due to the viscoelasticity of the MTU.

Congenital myopathy with abundant nemaline rods in a cat

Nemaline myopathy is associated with rod-shaped structures in muscle fibers. At least seven distinct clinical forms have been described in humans and mutations have been identified in five different thin-filament genes. Only a few cases of spontaneously occurring nemaline myopathy have been reported in animals and include an adult-onset form in a family of cats and an early-onset form in a dog. Here, we describe a 2-year-old male, neutered, domestic shorthaired cat that was referred to the Veterinary Medical Teaching Hospital, University of California-Davis, for evaluation of chronic, progressive weakness, and fine tremors. Neurologic deficits were restricted to the neuromuscular system. Electromyography showed mild to moderate diffuse spontaneous activity. Although rod bodies were prominent on light and electron microscopic evaluation of biopsies from several muscles, sarcoplasmic accumulations of dystrophin, desmin, and spectrin also were identified by immunohistochemistry. These findings may represent the occurrence of rod bodies in conjunction with a protein-aggregate myopathy.

Myonuclei and satellite cells in denervated rat muscles: An electron microscopy study

The study and description of a separated cell type have been dependent on the evolution of the electron microscope. There have been few experiments designed to induce changes in myonucleus and satellite-cell populations in vivo without physically injuring muscle. In this regard, the most practical method to experimentally alter myonucleus and satellite-cell populations is denervation. The sciatic nerve was sectioned in order to observe myonuleus and satellite-cell behavior. After 7, 16, and 38 weeks postdenervation, the soleus and extensor digitorum longus muscles were observed under electron microscopy. In each studied period, the pattern, distribution, and possible cellular alterations were observed in the studied muscles. Myonuclei exhibited alterations such as shrinkage, nuclear membrane separation, condensed chromatin, ghost nuclei as well as normal ones, and disorganized myofibrils. The maximum and minimum myonucleus diameters were measured in each studied period. In both muscles, the maximum diameters decreased. On the other hand, the minimum myonucleus diameters did not show any differences. Regarding satellite cells, activation characteristics were observed. In both muscles, the satellite cells were located distant of capillary after denervation. Characterization of the different types of nuclei abnormalities, especially in chromatin condensation, should provide useful information for future morphological studies.

X-ray diffraction studies of the contractile mechanism in single muscle fibres

The molecular mechanism of muscle contraction was investigated in intact muscle fibres by X-ray diffraction. Changes in the intensities of the axial X-ray reflections produced by imposing rapid changes in fibre length establish the average conformation of the myosin heads during active isometric contraction, and show that the heads tilt during the elastic response to a change in fibre length and during the elementary force generating process: the working stroke. X-ray interference between the two arrays of myosin heads in each filament allows the axial motions of the heads following a sudden drop in force from the isometric level to be measured in situ with unprecedented precision. At low load, the average working stroke is 12 nm, which is consistent with crystallographic studies. The working stroke is smaller and slower at a higher load. The compliance of the actin and myosin filaments was also determined from the change in the axial spacings of the X-ray reflections following a force step, and shown to be responsible for most of the sarcomere compliance. The mechanical properties of the sarcomere depend on both the motor actions of the myosin heads and the compliance of the myosin and actin filaments.

Interaction between fascicle and tendinous tissues in short-contact stretch-shortening cycle exercise with varying eccentric intensities

The interaction between fascicle and tendinous tissues (TT) in short-contact drop jumps (DJ) with three different drop heights [low (Low), optimal (OP), and high (High)] was examined with 11 subjects. The ground reaction force (F(z)) and ankle and knee joint angles were measured together with real-time ultrasonography (fascicle length) and electromyographic activities of the medial gastrocnemius (MG) and vastus lateralis (VL) muscles during the movement. With increasing drop height, the braking force and flight time increased from Low to OP (P < 0.05). In High, the braking force increased but the flight time decreased compared with OP (P < 0.05). During contact of Low and OP conditions, the length of muscle-tendon unit and TT underwent lengthening before shortening in both MG and VL muscles. However, the two muscles differed in the fascicle behaviors. The MG fascicles behaved isometrically or shortened, and the VL fascicles underwent lengthening before shortening during contact. In High, the TT lengthening in both muscles decreased compared with OP (P < 0.05). The rapid stretch occurred in the MG fascicles but not in VL fascicles during the braking phase. The elastic recoil ratio decreased in both muscles with increasing the intensity during DJ. These findings demonstrated that TT underwent lengthening before shortening during DJ. However, the efficacy of elastic recoil decreased with increasing the drop intensity. The effective catapult action in TT can be limited by the drop intensity. In addition, the measured muscles behaved differently during DJ, providing evidence that each muscle may have a specific means of fascicle-TT interaction.

Intramuscular Bone Induction by the Simultaneous Administration of Recombinant Human Bone Morphogenetic Protein 2 and Bisphosphonate for Autobone Graft

An ideal substitute for bone graft is autobone tissue, of which there is an ample supply of the required form and with vascularity. Our strategy is to generate intramuscular autogenous bone by administering recombinant human bone morphogenetic protein 2 (rhBMP-2) with beta-tricalcium phosphate (beta-TCP) as a carrier, and to transplant this bone as a muscle-pedicled autograft. However, in a previous study (Jingushi et al., J. Orthop. Sci. 7, 490, 2002), bone resorption occurred early after bone induction. This study was conducted to determine whether rhBMP-2-induced bone tissue could be maintained by simultaneous administration of bisphosphonate, and to investigate whether the induced bone could be used for bone grafting. In this study, we first applied rhBMP-2 alone to a beta-TCP disk and inoculated it into rat quadriceps muscle. Bone area and the number of tartrate-resistant acid phosphatase (TRAP)-positive cells in the induced bone disk peaked at 2 weeks, and induced bone resorption occurred later. Bisphosphonate and rhBMP-2 were then simultaneously applied to a beta-TCP disk and inoculated as in the first experiment. The addition of bisphosphonate decreased the number of TRAP-positive cells and increased the bone area and compression strength at 4 weeks. In the last experiment, a rhBMP-2 applied beta-TCP disk treated with or without bisphosphonate was free-grafted to parietal bone 4 weeks after inoculation. Both bone disks united similarly. We concluded that the concurrent use of bisphosphonate prevented bone absorption attributed to osteoclast activity after bone induction by rhBMP-2. The bisphosphonate application did not disturb the union of induced bone to host bone.

Relationship between muscle architectural features and oxygenation status determined by near infrared device

This study tested whether regional differences in oxygenation status could result from differences in muscle fiber architecture. Architectural properties, oxygen supply, and consumption in the medial head of the gastrocnemius muscle (GM) were determined in vivo in six men using B-mode ultrasound and functional near infrared (NIR) imaging devices. Fascicle length, fascicle angle, NIR-O(2) saturation (deoxygenated Hb or oxygenated Hb), and NIR-blood volume (sum of deoxygenated and oxygenated Hb) were obtained in the distal and proximal portions of the GM at rest and during contraction. Exercise consisted of 2 min of standing plantar flexion at 1 Hz with an additional load of 50% of each subject's weight. Plantar flexion produced larger decreases (Delta: difference between rest and exercise values) in NIR-O(2) saturation [mean saturation (SD) of 0.14 (0.05) vs 0.07 (0.04) optical density units] and NIR-blood volume [mean saturation (SD) of -0.23 (0.08) vs -0.13 (0.04) optical density units] in the distal compared with the proximal portion ( P<0.05 for all comparisons). It also produced larger changes (Delta) in fascicle length [mean length (SD) of -16.5 (4.7) vs -8.2 (4.2) mm] and fascicle angle (mean angle (SD) of 10.8 (1.4) degrees vs 3.9 (2.1) degrees ] in the distal compared with the proximal portion ( P<0.05 for all comparisons). There were significant correlations between DeltaNIR-O(2 )saturation and Deltafascicle length ( r=-0.84, P<0.05), and between DeltaNIR-O(2) saturation and Deltafascicle angle ( r=-0.90, P<0.05), between DeltaNIR-blood volume and Deltafascicle length ( r=0.91, P<0.05), between DeltaNIR-blood volume and Deltafascicle angle ( r=-0.85, P<0.05). In conclusion, the plantar flexion exercise produced regional differences in oxygenation status consistent with regional differences in muscle architecture.

Interaction between fascicles and tendinous structures during counter movement jumping investigated in vivo

Behavior of fascicles and tendinous structures of the m. gastrocnemius medialis (MG) was quantitatively examined during human jumping in vivo. Eight male subjects performed maximal-effort counter movement jumping (CMJ) motions. Kinematic and kinetic data were obtained using a high-speed camera and a force platform. Behavior of fascicles and tendinous structures was determined using ultrasonography and electromyography. Although the muscle-tendon complex (MTC) shortened by only 1.6% during the downward phase of the counter movement, fascicles shortened as much as 10.4%. This shortening of fascicles caused elongation of tendinous structures by 2.2%. Although the MTC remained at almost constant length during the upward-I phase (-250 to -100 ms before toe-off), fascicles shortened by 19.2% of the initial length with an elongation of tendinous structures by 4.4%. The MTC shortened rapidly by 5.3% of the initial length during the upward-II phase (-100 to 0 ms), whereas fascicles shortened slightly during the first half of this phase and contracted in a quasi-isometric manner during the latter half of this phase. These findings implied that elastic energy was stored in tendinous structures throughout the latter half of the downward phase (1.0 J) and upward-I phase (5.6 J), which was thereafter rapidly released during the upward-II phase (3.8 J). It was found that muscle fibers of the MG were not stretched during counter movement; therefore, stretch reflex and potentiation of the contractile component of the MG might not contribute to the work enhancement in CMJ. It was suggested that the interaction between fascicles and tendinous structures was essential in a generation of higher joint power during the late push-off phase. This behavior of the MTC of the MG in CMJ was quite similar to what was observed in squat jumping performed without counter movement.

Measurement of muscle contraction with ultrasound imaging

To investigate the ability of ultrasonography to estimate muscle activity, we measured architectural parameters (pennation angles, fascicle lengths, and muscle thickness) of several human muscles (tibialis anterior, biceps brachii, brachialis, transversus abdominis, obliquus internus abdominis, and obliquus externus abdominis) during isometric contractions of from 0 to 100% maximal voluntary contraction (MVC). Concurrently, electromyographic (EMG) activity was measured with surface (tibialis anterior only) or fine-wire electrodes. Most architectural parameters changed markedly with contractions up to 30% MVC but changed little at higher levels of contraction. Thus, ultrasound imaging can be used to detect low levels of muscle activity but cannot discriminate between moderate and strong contractions. Ultrasound measures could reliably detect changes in EMG of as little as 4% MVC (biceps muscle thickness), 5% MVC (brachialis muscle thickness), or 9% MVC (tibialis anterior pennation angle). They were generally less sensitive to changes in abdominal muscle activity, but it was possible to reliably detect contractions of 12% MVC in transversus abdominis (muscle length) and 22% MVC in obliquus internus (muscle thickness). Obliquus externus abdominis thickness did not change consistently with muscle contraction, so ultrasound measures of thickness cannot be used to detect activity of this muscle. Ultrasound imaging can thus provide a noninvasive method of detecting isometric muscle contractions of certain individual muscles.

Heterogeneous activity of the human genioglossus muscle assessed by multiple bipolar fine-wire electrodes

Genioglossus (GG) electrical activity [measured by electromyogram (EMGgg)] is best measured by intramuscular electrodes; however, the homogeneity of EMGgg is undefined. We investigated the relationships between EMGgg and the site from which activity was measured to determine whether and to what extent inhomogeneity in activity occurred. Eight healthy human volunteers underwent ultrasound to determine GG depth and width. Four pairs of electrodes were then inserted percutaneously into the left and right GG muscle, anteriorly and posteriorly. Additional configurations were obtained by connecting electrodes across the midline and along each muscle belly. EMGgg activity was simultaneously recorded from these 10 configurations at rest and during various respiratory maneuvers. Heterogeneous behavior of the GG was evidenced by 1) the variable presence of phasic EMGgg at rest, which was undetectable in two subjects but evident in 65% of configurations in six subjects and present in all configurations in all subjects during voluntary hyperventilation; 2) a greater amplitude of EMGgg response to pharyngeal square-wave negative pressure in anterior than posterior configurations (14.1 +/- 7.1 vs. 8.5 +/- 5.1% of maximum, P < 0.05); and 3) variable (linear and alinear) relationships between EMGgg and lingual force within and between subjects. We hypothesize that regional differences in density and type of muscle fiber are the most likely sources of heterogeneity in these responses.

Length change of human gastrocnemius aponeurosis and tendon during passive joint motion

The extent of elongation and slackness of aponeurosis and tendon, and muscle fiber length of human medial gastrocnemius muscle are determined in vivo using ultrasonography. The ankle joint is passively moved at 5 degrees /s within the joint range of -36 to 7 degrees (0 degrees = neutral anatomic position; positive values for dorsiflexion) by a dynamometer while the length change of the aponeurosis and tendon is determined using ultrasonography (n = 8 men). Strain is calculated as the length change relative to the reference length of aponeurosis and tendon when the passive joint moment is 0. Elongation (positive strain values) of aponeurosis and tendon at 7 degrees are 2.1 +/- 1.1 and 2.4 +/- 1.0%, respectively. The extent of slackness (negative strain values) of aponeurosis and tendon at -36 degrees are -1.8 +/- 1.1 and -3.5 +/- 1.6%, respectively, and there is a significant difference between them (p < 0.05). This may be related to the existence of muscle fibers that attach to the aponeurosis over its whole length and do not allow it to fold. The results indicate that the length change of aponeurosis and tendon of medial gastrocnemius muscle occurs over the range of ankle joint positions even during passive joint motions.

Functional heterogeneity in the superior head of the human lateral pterygoid

The activity of the superior head of the human lateral pterygoid muscle (SHLP) is controversial. Given the non-parallel alignment of some SHLP fibers, the SHLP may be capable of differential activation. The aims were to clarify SHLP activity patterns in relation to location within SHLP. In 18 subjects, SHLP single motor units were intramuscularly recorded at computer-tomography-verified sites during horizontal (e.g., protrusion) and vertical (e.g., opening) jaw tasks (recorded by a jaw-tracking device) and at resting postural jaw position. None of 92 units was active at the resting postural position. Medially located units (21) showed activity during contralateral movement, protrusion, and opening; 5 were also active on jaw closing. There was a significant association between unit location and the number of units active during vertical tasks (i.e., jaw closing and clenching). Analysis of the data suggests differential activation within SHLP and raises the possibility of functional heterogeneity within SHLP.

An evaluation of leukaemia inhibitory factor as a potential therapeutic agent in the treatment of muscle disease

The exogenous delivery of growth factors and cytokines is a potential therapeutic strategy to alleviate the degenerative effects of primary inherited myopathies such as Duchenne muscular dystrophy. The mdx mouse diaphragm is a model for examining the progressive degeneration of dystrophic muscle. We have delivered leukaemia inhibitory factor to the mdx diaphragm using slow release alginate gels. Previous studies have reported an improvement in the histology of mdx diaphragms after delivery of leukaemia inhibitory factor in a similar manner, but little attention has been paid to the mechanism by which leukaemia inhibitory factor acts. We have used autoradiography to examine cell proliferation, Evans Blue Dye to examine myofibre damage, and morphometric analysis to examine histology in leukaemia-inhibitory-factor-treated diaphragms and compared them with untreated mdx and normal C57Bl10/ScSn diaphragms. Autoradiography showed that although myoblast proliferation was significantly increased in leukaemia inhibitory factor-treated mdx diaphragms, leukaemia inhibitory factor did not reduce myofibre damage and no histological improvement was observed. The data presented here, while demonstrating a role for leukaemia inhibitory factor in myoblast proliferation, do not support a strong and consistent benefit of leukaemia inhibitory factor on dystrophic muscle in vivo as a means of alleviating the effects of chronic dystrophic muscle degeneration.

Connections of the bladder plate and bladder neck with the bony pelvis in a fetus with classic bladder exstrophy

OBJECTIVES

To demonstrate that the bladder plate and bladder neck in classic bladder exstrophy are laying on smooth muscle fibers that extend laterally to the pubic bones.

METHODS

We compared a male fetus of 28 weeks' gestational age with classic bladder exstrophy with a normal fetus of the same age. The specimens were divided into two parts by a midsagittal section, from the bladder neck to the membranous urethra. Thin transverse slices were also obtained on one part, and longitudinal slices on the other part.

RESULTS

The smooth musculature of the bladder is normally differentiated cytologically and extends laterally to the bony structures of the pelvis. The musculature of the bladder neck and urethra are normally present compared with the control.

CONCLUSIONS

The results of this study demonstrate the musculoskeletal organization of the urogenital system in classic bladder exstrophy. They also indicate that these structures should be clearly individualized and repaired in the reconstruction of classic bladder exstrophy.

[Effect of trigeminus nerve on facialis-denervated facial muscle atrophy]

In the present study we made out an animal model on rabbit whose trigeminus and facialis nerves were simultaneously or only the latter one was severed. The pathological changes in facial muscle atrophy under different nerve injuries were investigated. The degeneration of contractile proteins of upper lip muscle -- myosin and actin was observed. In addition, we also examined the ultrastructural changes in the muscle atrophy in the two above-mentioned nerve injury cases. We observed that the intact trigeminus nerve could delay and lighten the atrophy of facialis-denervated facial muscle and attenuate the degeneration of myosin and actin, as well as decrease the increment of collagen and maintain the ultrastructure of the thick and thin muscle filaments. These results may provide the possibility of improvement of clinical treatment for facial muscle palsy.

In vivo muscle fibre behaviour during counter-movement exercise in humans reveals a significant role for tendon elasticity

Six men performed a single ankle plantar flexion exercise in the supine position with the maximal effort with counter movement (CM, plantar flexion preceded by dorsiflexion) and without counter movement (NoCM, plantar flexion only) produced by a sliding table that controlled applied load to the ankle (40 % of the maximal voluntary force). The reaction force at the foot and ankle joint angle were measured using a force plate and a goniometer, respectively. From real-time ultrasonography of the gastrocnemius medialis muscle during the movement, the fascicle length was determined. The estimated peak force, average power, and work at the Achilles' tendon during the plantar flexion phase in CM were significantly greater than those in NoCM. In CM, in the dorsiflexion phase, fascicle length initially increased with little electromyographic activity, then remained constant while the whole muscle-tendon unit lengthened, before decreasing in the final plantar flexion phase. In NoCM, fascicle length decreased throughout the movement and the fascicle length at the onset of movement was longer than that of the corresponding phase in CM. It was concluded that during CM muscle fibres optimally work almost isometrically, by leaving the task of storing and releasing elastic energy for enhancing exercise performance to the tendon.

The temperature dependence of ultrasound-stimulated acoustic emission

Given the high variability of tissue properties during sonication, temperature monitoring is one of the most crucial components for accurate thermal treatment of tissues with focused ultrasound and other thermotherapy devices. Recently, the method of ultrasound-stimulated acoustic emission (USAE) has been introduced as a potential method for measurements of mechanical properties of tissues. In this paper, the dependence of USAE on tissue temperature is determined. Because USAE depends on the acoustic and mechanical properties, both of which vary with temperature, it is hypothesized that the USAE signal is also temperature-dependent and in such a way that it can be used to guide thermal therapy. In a series of experiments, ex vivo porcine muscle and fat samples were exposed to ultrasound at power levels that induce temperature elevation. In both tissue types, below the coagulation threshold, the USAE amplitude was found to vary linearly with temperature. However, at higher powers, the correlation with temperature was lost due mainly to the irreversible nature of the changes in the tissue properties. Theoretical simulations were used to interpret the USAE response change with temperature involving both reversible and irreversible changes and during both heating and cooling. These results indicate that USAE may have important promise as a potential method for localizing temperature elevation and, thus, thermal surgery monitoring, as well as detection of irreversible changes in tissues.

Functional properties of single motor units in inferior head of human lateral pterygoid muscle: task relations and thresholds

The aim of this study was to clarify the normal function of the inferior head of the human lateral pterygoid muscle (IHLP). The hypothesis was that an important function of the IHLP is in the fine control of horizontal jaw movements. The activities of 99 single motor units (SMUs) were recorded from IHLP (22 recordings from 16 subjects). Most recording sites were identified by computer tomography (CT). All 99 SMUs were active during contralateral jaw movements with the teeth apart, and protrusive jaw movements with the teeth apart, and 81% (48 of 59 units studied during all 3 tasks) were active during submaximal jaw-opening movements. None were active on maximal ipsilateral or retrusive jaw movements with the teeth apart nor on jaw closing/clenching in intercuspal position; nor were they spontaneously active when the jaw was at the clinically determined postural jaw position. Thresholds of SMUs ranged from <0.2 mm of contralateral or protrusive horizontal displacements to 61-89% of the maximum contralateral or protrusive displacement, respectively. For the 35 units continuously active during the contralateral task, 23 (66%) were recruited within 2 mm of contralateral displacement [25 (63% of 40 units) for protrusion]. Recruitment thresholds (mm) of some of the units were rate dependent with thresholds significantly decreasing with increasing rate of horizontal jaw movement in protrusion and contralateral movements. At eight recording sites where up to six SMUs were able to be discriminated, the average thresholds of successively recruited SMUs were within a 1-mm increment of horizontal jaw displacement. After dividing IHLP into four regions, the SMUs recorded in the superior-medial zone exhibited significantly lower mean threshold values than for the SMUs recorded in the other zones (no units were recorded in the inferior-lateral zone). This provides suggestive evidence supporting previously proposed notions of functional heterogeneity within IHLP. Taken together, the data suggest that specific regions of the IHLP are capable of selective activation in a finely controlled manner to allow the application of the appropriate force vector (magnitude and direction) to effect the required condylar movement needed for the generation and control of horizontal jaw movements.

Comparing human skeletal muscle architectural parameters of cadavers with in vivo ultrasonographic measurements

The purpose of this study was to document and compare the architectural parameters (fibre bundle length, angle of pennation) of human skeletal muscle in cadaveric specimens and live subjects. The medial (MG) and lateral (LG) gastrocnemius, and posterior (PS) and anterior (AS) soleus were examined bilaterally in 5 cadavers (mean age 72.6, range 65-83 y) and 9 live subjects (mean age 76.3, range 70-92 y). Data were obtained from direct measurement of cadaveric specimens and from ultrasonographic scans of the live subjects. In cadaveric muscle, fibre bundles were isolated; their length was measured in millimetres and pennation angles were recorded in degrees. In live muscle, similar measurements were taken from ultrasonographic scans of relaxed and contracted muscle. For the scans of relaxed muscle, subjects were positioned prone with the foot at a 90 degrees angle to the leg, and for scans of contracted muscle, subjects were asked to sustain full plantarflexion during the scanning process. Fibre bundle length and angle of pennation were compared at matched locations in both groups. It was found that the relationship between cadaveric and in vivo values for fibre length and angle of pennation varied between muscle parts. The cadaveric architectural parameters did not tend to lie consistently towards either extreme of relaxation or contraction. Rather, within MG, PS and AS, cadaveric fibre bundle lengths lay between those for relaxed and contracted in vivo muscle. Similarly both the anterior and posterior cadaveric fibre angles of pennation lay between the in vivo values within LG and PS. In summary, architectural characteristics of cadaveric muscle differ from both relaxed and contracted in vivo muscle. Therefore, when developing models of skeletal muscle based on cadaveric studies, the architectural differences between live and cadaveric tissue should be taken into consideration.

Quadriceps muscle wasting persists 5 months after total hip arthroplasty for osteoarthritis of the hip: a pilot study

AIMS

To determine whether additional muscle fibre wasting of the ipsilateral vastus lateralis muscle occurs in the early postoperative period after total hip arthroplasty for osteoarthritis of the hip and whether there is an improvement in preoperative measures of quadriceps muscle thickness, strength, pain and function over a 5-month postoperative period.

METHODS

Twelve patients had ipsilateral needle quadriceps biopsy for muscle morphology and bilateral quadriceps muscle thickness ultrasound preoperatively, 5 days and 4 weeks postoperatively and a further muscle thickness measurement at 5 months. Seven additional patients and five age-matched control subjects had bilateral quadriceps muscle ultrasound thickness preoperatively, 6 weeks and 5 months postoperatively, with assessment of quadriceps muscle dynamometry, pain scores and Timed Up and Go (TUG) test.

RESULTS

Preoperatively, all 19 patients demonstrated significant atrophy of the ipsilateral compared with the contralateral quadriceps muscle (P = 1.8 x 10(-7)) on muscle ultrasound, which persisted at 5 months follow up (P = 0.009). Muscle morphology preoperatively showed type 2A and 2B muscle fibre atrophy on needle muscle biopsy, with further atrophy of all three fibre types (P = 0.029) at 5 days postoperatively associated with a fibre type shift from type 1 to 2A fibres (P = 0.0011) at 1 month. There was improvement in hip pain postoperatively and a significant improvement in the TUG test (P = 0.007). However, there was no improvement in muscle strength on dynamometry.

CONCLUSIONS

There is significant ipsilateral quadriceps atrophy and weakness with 2A and 2B fibre atrophy preoperatively in patients with osteoarthritis of the hip with exacerbation and further atrophy of all three fibre types 5 days postoperatively. Postoperative follow up showed that the reduction in ipsilateral quadriceps muscle thickness persisted at 5 months despite physical rehabilitation. Patients did note significant improvement in pain postoperatively and improvement on functional assessment with the TUG test. Other therapeutic strategies may have to be developed to reverse disuse muscle atrophy.

Changes in lumbar lordosis modify the role of the extensor muscles

STUDY DESIGN

Fiber angles of longissimus thoracis and iliocostalis lumborum at L3 were documented in vivo, using high resolution ultrasound, with the lumbar spine in neutral curve and when fully flexed.

OBJECTIVES

To evaluate the effect of changes in lumbar curvature on the mechanics of these muscles.

BACKGROUND

Full flexion modifies the failure tolerance of the lumbar spine, determines the load distribution among muscle and passive tissues, and modulates the types of tissue damage that occur. Related to this issue are the possible changes in muscle line of action with full flexion which changes the ability of the spine to support shear loads.

METHODS

Nine normal men and 5 normal women were scanned in three positions: (1) an upright standing posture; (2) with the hips flexed to approximately 30 degrees and the spine fully flexed; (3) hips flexed but the spine returned to a neutral curvature.

RESULTS

Mean longissimus/iliocostalis fiber angles for upright standing, hips flexed-spine flexed, and hips flexed-spine neutral lordosis were 25. 7 degrees, 10.7 degrees and 28.3 degrees, respectively.

CONCLUSIONS

Anterior shear load on the lumbar spine has been recently shown to be highly related to the risk of reporting a back injury. Bending forward allowing the spine to fully flex changes the line of action of the largest lumbar extensor muscles compromising their role to support anterior shear forces. Relevance Fiber angles of longissimus thoracis and iliocostalis lumborum were documented with high resolution ultrasound at L3, with the spine in neutral curvature and fully flexed. Full lumbar flexion changes the line of action of these muscle compromising their role to support anterior shear forces on the spine - anterior shear forces have been recently documented to be highly related to the risk of reporting a back injury.

Sonographic studies of human soleus and gastrocnemius muscle architecture: gender variability

The purpose of this study was to establish if there are gender differences in muscle architecture in relaxed human soleus and gastrocnemius muscles of normal, live subjects. Ultrasonography was used to measure fiber bundle length, muscle thickness, and angles of pennation in a total of ten predetermined sites in the medial and lateral heads of gastrocnemius and the anterior and posterior soleus in 19 males and 16 females. Percentage differences between males and females for each parameter were recorded. Gender differences were statistically analyzed using multivariate analysis of variance. In the gastrocnemius and soleus muscles of males and females the differences between the overall fiber bundle length, angle of pennation and muscle thickness were statistically significant (P < 0.05). Overall, females were found to have longer average muscle fiber bundle length and males thicker muscles and larger angles of pennation. The greatest percentage differences of the architectural parameters between males and females were in the posterior soleus: 13% difference in fiber length and 26% difference in angle of pennation in the midline of posterior soleus and 26% difference in muscle thickness of the lateral part of posterior soleus. No correlation was found between leg length and fiber length, angle of pennation or muscle thickness. Fiber length (decreased), angle of pennation (greater) and muscle thickness (greater) of most parts of the gastrocnemius and soleus muscles were significantly different in males and females. Leg length of males and females did not correlate to these architectural parameters.

Standardisation of muscular biopsy of gluteus medius in French trotters

Morphometric measurements were taken from 41 French trotters of various ages and both sexes. Biopsy location was determined for the dorsal compartment as being one-third of the distance from the tuber sacrale to the tuber coxae and for the ventral compartment as being one-third of the distance from the tuber coxae to the caudal Cd1-Cd2 intervertebral joint. Ten horses were biopsied at these 2 sites at a sampling depth equal to half the total depth of the compartment as measured by ultrasonography. The percentage of slow and fast myosin heavy chain fibres was measured by using an immunoenzymatic method. The depth of the dorsal and ventral compartments of the gluteus medius was significantly greater in males than in females. The depth of the ventral compartment was greater in the case of a straight hip than of a wide hip and was greater in young horses than in older horses. The ventral and the dorsal compartments were composed in the mid-portion of 81.3 and 75.6% of fast myosin heavy chains, respectively. It was concluded that the locations and sampling depths in the gluteus medius could be standardised in French trotters by taking into account anatomical references, sex, age and width of the hip.

Clinical, echocardiographic, and angiographic profile of patients with double-chambered right ventricle: experience with 48 cases

Forty-eight patients with double-chambered right ventricle (DCRV) were prospectively studied over a 3-year period. Clinical, echocardiographic, hemodynamic, and angiographic studies were done in all. Three patients were studied postoperatively also. Fifteen patients underwent surgery confirming the diagnosis. Echocardiography detected anomalous muscle bundles (AMBs) in 39/41 patients in whom this study was carried out. Angiographically AMBs were best demonstrated in anteroposterior views in a systolic frame. Common associated anomalies found with DCRV were ventricular septal defects (69%), pulmonary valve stenosis (38%), and double-outlet right ventricle (10%).

Relationship between muscle fiber pennation and force generation capability in Olympic athletes

The thickness (TBmt) and fiber pennation angle (TBpen) of triceps brachii as well as isokinetic force developed during elbow extension were measured in Olympic athletes to investigate the relationship between muscle fiber pennation and force generation capability. The subjects were male members of the 1996 Japanese Olympic team who competed in seven different events; 9 wrestlers, 16 soccer players, 11 sprinters, 5 judo athletes, 7 gymnasts, 9 rowers and 18 baseball players. The TBmt and TBpen, measured by a B-mode ultrasound, ranged between 29 mm and 50 mm and between 11 degrees and 30 degrees, respectively, and on average were larger in the judo athletes, wrestlers and gymnasts compared to the other groups. A significant correlation (r=0.580, p < 0.05) was found between TPpen and TBmt per unit of the upper arm length, and so the observed event-related differences in TBpen tended to reflect the differences in TBmt. The isokinetic forces relative to the cross-sectional area (CSA) estimated from TBmt, measured at two constant velocities of 1.05 rad/s (F1.05/CSA) and 3.14 rad/s (F3.14/ CSA), were negatively correlated to the CSA; r=-0.617 (p < 0.05) for F1.05/CSA and r=-0.635 (p < 0.05) for F3.14/CSA. In addition, low but significant negative correlations existed between TBpen and both F1.05/CSA (r=-0.365, p < 0.05) and F3.14/ CSA (r=-0.336, p <0.05). Even when the effect of TBpen was statistically normalized, the F1.05/CSA and F3.14/CSA were still negatively correlated to the CSA, r=-0.530 (p < 0.05) for F1.05/ CSA and r=-0.561 (p < 0.05) for F3.14/CSA. Therefore, at least in the Olympic athletes tested in this study, the magnitude of the pennation angles reflects muscle size, but it does not seem to be a factor that explains extensively the lower F/CSA in athletes with large muscle size.

Morphological and functional differences in the elbow extensor muscle between highly trained male and female athletes

The purpose of this study was to investigate the difference in the morphological and functional aspects of the triceps brachii muscle between highly trained male and female athletes who were members of the 1996 Japanese Olympic teams in each of three different events: soccer, gymnastics and judo. The thickness (TBmt) and fibre pennation angle (TBpen) of the triceps brachii muscle and force output during elbow extensions were determined using a B-mode ultrasound apparatus and an isokinetic dynamometer, respectively. The TBmt and its value relative to upper arm length (TBmt/l(ua)) were significantly larger in the men than in the women in all the events except judo. In all the subjects, a significant correlation was found between TBmt/l(ua)) and TBpen (r = 0.721, P < 0.05). The existence of the sex difference in TBpen within the same event was in agreement with that observed in TBmt/l(ua) except for the soccer players. The TBpen of the soccer players were similar in both sexes although a significant sex differences was found in TBmt/l(ua). The isokinetic forces measured using the two velocities 60 degrees x s(-1) (F60) and 180 degrees x s(-1) (F180) were significantly correlated to the cross-sectional area (CSA) of the triceps brachii muscle estimated from TBmt (r = 0.702, P < 0.05 for F60, and r = 0.776, P < 0.05 for F180). No significant sex differences were found in either F60/CSA or F180/CSA in any of the events. From these results, it could be assumed, at least in the Olympic athletes tested in this study, that the fibre angulation of the triceps brachii muscle was almost the same in the two sexes if allowance was made for the difference in the muscle size, and the sex difference in force generation capability of the triceps brachii muscle could in the main be attributed to the difference in CSA rather than in the architectural characteristics.