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PubMed1999

Increasing muscle mass in spinal cord injured persons with a functional electrical stimulation exercise program.

OBJECTIVE: To determine the magnitude of changes in muscle mass and lower extremity body composition that could be induced with a regular regimen of functional electrical stimulation (FES)-induced lower-extremity cycling, as well as the distribution of changes in muscle mass among the thigh muscles in persons with spinal cord injury (SCI). STUDY DESIGN: Thirteen men with neurologically complete motor sensory SCI underwent a 3-phase, FES-induced, ergometry exercise program: phase 1, quadriceps strengthening: phase 2, progressive sequential stimulation to achieve a rhythmic pedaling motion (surface electrodes placed over the quadriceps, hamstrings, and gluteal muscles); phase 3, FES-induced cycling for 30 minutes. Participants moved from one phase to the next when they met the objectives for the current phase. MEASURES: Computed tomography of legs to assess muscle cross-sectional area and proportion of muscle and adipose tissue. Scans were done at baseline (before subjects started the program), at first follow-up, typically after 65.4+/-5.6 (SD) weekly sessions, and at second follow-up, typically after 98.1+/-9.1 sessions. RESULTS: Increases in cross-sectional areas were found in the following muscles: rectus femoris (31%, p<.001). sartorius (22%, p<.025), adductor magnus-hamstrings (26%, p<.001), vastus lateralis (39%, p = .001), vastus medialis-intermedius (31%, p = .025). Cross-sectional area of adductor longus and gracilis muscles did not change. The ratio of muscle to adipose tissue increased significantly in thighs and calves. There was no correlation among the total number of exercise sessions and the magnitude of muscle hypertrophy. CONCLUSIONS: Muscle cross-sectional area and the muscle to adipose tissue ratio of the lower extremities increased during a regular regimen of 2.3 FES-induced lower extremity cycling sessions weekly. The distribution of changes was related to the proximity of muscles to the stimulating electrodes.

Adipose Tissue↗
PubMed1989

Motor activity in the isolated spinal cord of the chick embryo: synaptic drive and firing pattern of single motoneurons.

The cellular mechanisms underlying embryonic motility were investigated using intracellular recording from motoneurons and electrotonic recording from muscle nerves during motor activity generated by an isolated spinal cord preparation of 12- to 15-d-old chick embryos. DC-coupled recordings from sartorius (a flexor) and femorotibialis (an extensor) muscle nerves revealed that both sets of motoneurons were depolarized at the same time in each cycle even when the motoneurons fired out of phase. Sartorius motoneurons fired briefly on the rising phase of the depolarization and then stopped firing before discharging a second burst of spikes as the depolarization decayed. By contrast, femorotibialis motoneurons fired at the peak of their depolarization, which was coincident with the interruption in sartorius activity. Intracellular recordings from antidromically identified motoneurons confirmed that flexor and extensor motoneurons were depolarized at the same time during each cycle of activity. The discharge of femorotibialis motoneurons, and others presumed to be extensors, followed changes in membrane potential so that maximal firing occurred during peak depolarization. The relationship between discharge and membrane potential was different in sartorius motoneurons (and in others presumed to be flexors) because they fired briefly on the rising phase of the depolarization and then stopped firing during peak depolarization. In some of these cells firing resumed as the membrane potential decayed back to rest. Intracellular injection of depolarizing current into sartorius motoneurons during motor activity reversed the direction of the membrane potential change from depolarizing to hyperpolarizing during the pause in sartorius discharge. In addition, the discharge evoked by the depolarizing current was blocked during the reversed part of the synaptic potential revealing its inhibitory nature. The occurrence of the IPSP was accompanied by a large reduction in motoneuronal input impedance. Injection of depolarizing current steps into motoneurons produced steady firing with no evidence of a pause in discharge, indicating that the depolarization accompanying synaptic activity was not responsible for the pause in firing of flexor motoneurons. These results suggest that flexor and extensor motoneurons receive a similar depolarizing drive from a common set of excitatory premotor interneurons. The alternating pattern of flexor and extensor discharge is produced, in part, by the timing of a depolarizing IPSP coincident with extensor activity that silences flexor discharge.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1998

Implantation of a 16-channel functional electrical stimulation walking system.

A 16-channel electrical stimulation system was implanted in a 39-year-old patient with T10 paraplegia to restore sit to stand, walking, and exercise functions. System implantation required two surgical sessions. In the first session, the posterior muscle set consisting of bilateral semimembranosus, adductor magnus, and gluteus maximus muscles were exposed and epimysial electrodes sutured at the point of greatest muscle contraction. Closed double helix intramuscular electrodes were implanted in the erector spinae. Two weeks later, epimysial electrodes were attached to the eight anterior muscles consisting of the tibialis anterior, sartorius, tensor fasciae latae, and vastus lateralis with all 16 electrode leads passed to the anterior abdominal wall. The electrodes were connected to two eight-channel stimulators placed in the iliac fossae, and the system was checked by activating the individual muscles. The implanted stimulators received stimulation instructions and power via a radio frequency link to an external control. Stimulation patterns for standing, walking, sitting, and exercise functions were chosen from a preprogrammed menu via a finger key pad. After 3 weeks of restricted patient activity, all electrodes stimulated either the target muscle or had an acceptable spillover pattern. The patient is undergoing a 16-week rehabilitation course of stimulated exercises gradually increasing in intensity. At the conclusion, the goal is to discharge the patient with the system for spontaneous use. Although long term followup is required to determine system reliability, preliminary clinical results indicate that targeted, repeatable, functional muscle contractions in the lower extremity can be achieved with a system consisting of epimysial electrodes.

Adult↗
PubMed2002

Clinical and imaging findings in six cases of congenital muscular dystrophy with rigid spine syndrome linked to chromosome 1p (RSMD1).

We report clinical and imaging findings in six cases from five families affected by the form of congenital muscular dystrophy with rigid spine linked to the locus rigid spine muscular dystrophy 1 on chromosome 1p35-36. All cases showed rigidity of the spine, predominant neck and trunk weakness and frequent and severe thoracic scoliosis. Respiratory impairment was always observed in the first decade. Muscle imaging showed a marked involvement of adductors, sartorius and biceps femoris while rectus femoris and gracilis were relatively spared. This pattern of selective muscle involvement was consistent in all six cases and could be easily observed on either computerised tomography or magnetic resonance imaging. The results of this study suggest that muscle imaging, in combination with clinical assessment can help to identify the rigid spine muscular dystrophy 1 form of congenital muscular dystrophy and can help to target the appropriate genetic investigations.

Adolescent↗
PubMed1996

Adaptive control for backward quadrupedal walking V. Mutable activation of bifunctional thigh muscles.

1. In this, the fifth article in a series to assess changes in posture, hindlimb dynamics, and muscle synergies associated with backward (BWD) quadrupedal walking, we compared the recruitment of three biarticular muscles of the cat's anterior thigh (anterior sartorius, SAa; medial sartorius, SAm; rectus femoris, RF) for forward (FWD) and BWD treadmill walking. Electromyography (EMG) records from these muscles, along with those of two muscles (semitendinosus, ST; anterior biceps femoris, ABF) studied previously in this series, were synchronized with kinematic data digitized from high-speed ciné film for unperturbed steps and steps in which a stumbling corrective reaction was elicited during swing. 2. During swing, the relative timing of EMG activity for the unifunctional SAm (hip and knee flexor) was similar for unperturbed steps of FWD and BWD walking. The SAm was active before paw lift off and remained active during most of swing (75%) for both forms of walking, but there was a marked decrease in EMG amplitude after paw off during BWD and not FWD swing. In contrast, the relative timing of EMG activity for the SAa and RF, two bifunctional muscles (hip flexors, knee extensors), was different for FWD and BWD swing. During FWD swing, the SAa and the RF (to a lesser extent) were coactive with the SAm; however, during BWD swing, the SAa and RF were active just before paw lift off and then inactive for the rest of swing until just before paw contact (see 3). Thus the swing-phase activity of the SAa and RF was markedly shorter for BWD than FWD swing. 3. Activity in SAa and RF was also different during FWD and BWD stance. The RF was consistently active from mid-to-late stance of FWD walking, and the SAa was also active during this period in some FWD steps. During the stance phase of BWD walking, however, the onset of activity in both muscles consistently shifted to early stance as both muscles became active just before paw contact (the E1 phase). Activity in RF consistently persisted through most of BWD stance. The duration of SAa recruitment during BWD stance was more variable across cats with offsets ranging from mid- to late stance. 4. The activation patterns of the biarticular anterior thigh muscles during stumbling corrective reactions were, in general, similar to their different activations during FWD and BWD swing. The initial response to a mechanical stimulus applied to the dorsum of the paw that obstructed FWD swing was an augmentation of knee flexion and increased activity in ST and SAm. A mechanical stimulus applied to the ventral surface of the paw to obstruct BWD swing resulted in an initial conversion of hip extension to flexion and a slowing of knee flexion. There was a corresponding recruitment of SAa and RF and an enhancement of background activity in SAm. 5. The two forms of walking are differentiated by posture and limb dynamics, yet muscles participating in the basic flexor and extensor synergies are unchanged. Although central pattern generating (CPG) circuits determine the basic timing of these synergies, changes in the duration and waveform of muscle activity may depend on unique interactions among the CPG, supraspinal inputs that set posture and the animal's goal (to walk BWD or FWD) and motion-related feedback from the hindlimb. Output mutability to each muscle may depend on the balance of this tripartite input; muscles with immutable patterns may rely heavily on input from CPG circuits, whereas muscles with mutable patterns may rely more on form-specific proprioceptive and supraspinal inputs.

Adaptation, Physiological↗
PubMed1980

[Synaptoarchitectonic structure of muscles as a synchronizing apparatus for muscle contraction].

Synaptoarchitecture is a new notion, refering to the spatial distribution of motor and plates, to the shape of these synapses and to the last ramifications of motor were fibers. In muscles of the rats limbs, endplates are forming a small strip almost perpendicularly to the main direction of muscle fibers. But in sphincters and in orbicular muscles end plates are randomly distributed. The spatial distributions of end plates in muscles of the limbs build up a synchronizer for simultaneous contraction of all fibers in a given muscle. However in some few muscles of the rat, as are the m. sartorius, m. gracilis and mm. glutei, there are many strips, corresponding to the composite structure of these muscles. A composite structure is one which fibers are not only attached to a tendon, but also to other fibers in the midst of the muscle, without any tendon. It is possible to synchronize even a composite structure, if all synapses are properly located, the end plates being all at the same distance from the farthest insertion. In some rodents, lagomorphs and carnivores almost all muscles are composite. Consequently they are all of the disperse type. There is a bunivoque correspondence between the composite structure and the disperse type of innvervation. The shape of motor end plates is changeable under various pathological and physiological circumstances. Beside the common form, there are "myoid" synapses, as may be encountered in myasthenia gravis, in intensive corticotherapy and in the sphincter ani externus. Myoid synapses are of several sorts: elongated, multipartite and minute synapses. For explanation of these various shapes a hypothesis is put forward, concerning structural changes in the postsynaptic membrane. Finally nervous fibers are so located, as to permit the follow up of the pertinent motor endplate, dislocated by muscular contraction.

Animals↗
PubMed1984

The repeat distance of myosin in the thick filaments of various muscles.

The meridional spacing of the X-ray diffraction peak from the repeat of myosin along the thick filament of four muscles has been remeasured on the same apparatus. The frog sartorius gave a shorter repeat distance (143.7 A) than the three invertebrate muscles, which ranged from 144.9 to 145.4 A. These results confirm earlier measurements. Provided that the myosin molecules are staggered relative to one another by a constant 98 residues, it may be inferred that in vertebrate thick filaments part or all of the tail lies at a considerable angle to the filament axis, whereas in the invertebrates the angle is smaller.

Animals↗
PubMed1984

Myofilament diameters: an ultrastructural re-evaluation.

In situ, ultrastructural measurements of diameters of contractile filaments in skeletal and heart muscle differ considerably from those previously reported. Past measurements have been made in thin, transverse epoxy sections that were non-specifically stained with heavy metal salts to overcome background scattering of epoxy polymer. In our images from transverse de-embedded sections, the hexagonal lattice has some considerable differences from that seen in epoxy sections. Muscle samples from rat atrium and frog sartorius were fixed, dehydrated, embedded in polyethylene glycol, and sectioned. Sections were de-embedded in graded polyethylene glycol/ethanol, mounted on coated grids, critical point dried, and viewed in the electron microscope without staining. The backbone diameters of thick filaments were measured in the M band region and have an average value, after correction for shrinkage, of 25 nm. Thin filament diameters range from 6.5-9.5 nm. In regions of overlap of thin and thick filaments, the thick filament profiles varied from circular to asymmetric; diameters range up to 36 nm and yield eccentricity ratios varying from 1.5 to 1.0 (circular profiles). Portions of thick filaments touch or partially envelope neighboring thin filaments. The relative contributions of cytoskeletal components to these images of overlap regions remains to be determined, but the backbone diameters in glycerinated frog sartorius are not significantly different from control samples. The present results are consistent with those reported for rotary shadowed thick filaments; from recent experiments in muscles whose myofilament lattice is osmotically compressed; and with estimates of A band mass. This lattice geometry yields relatively low surface-to-surface distances between filaments. Steric considerations and their implications for cross bridge theory are discussed.

Animals↗
PubMed1993

Ratio of dihydropyridine to ryanodine receptors in mammalian and frog twitch muscles in relation to the mechanical hypothesis of excitation-contraction coupling.

An indirect argument in favour of the mechanical hypothesis of excitation-contraction (EC) coupling [Schneider & Chandler (1973) Nature 242, 244-246] is the fixed stoichiometry between the voltage-driven dihydropyridine receptor (DHP-R) on the transverse tubule (TT) and the ryanodine-sensitive Ca2+ channel (RyR) of sarcoplasmic reticulum (SR) terminal cisternae (TC), based mainly on the structural arrangement described by Block et al. at junctional triads of toadfish swimbladder muscle [Block, B., et al. (1988) J. Cell Biol. 107, 2587-2600]. We calculated the overall DHP-R/RyR ratios for a wide variety of rabbit twitch muscles, as compared to fast- and slow-twitch muscles of the rat, and to frog sartorius, following quantification of high-affinity binding sites for tritiated PN200-110 and ryanodine. To this purpose, we carried out our binding measurements on both skeletal muscle membranes detached from myofibrils by extensive extraction with low-ionic strength medium, and on the myofibrillar residue containing a proportion of binding sites. Our results expressed per gram of muscle allow the following main conclusions: i) The overall DHP-R/RyR ratio is approximately 2 in both fast-twitch and slow-twitch muscle of the rabbit, implying that most, if not all, Ca(2+)-channels at junctional triads are stoichiometrically associated with the voltage sensor; in agreement with Block's model; ii) There is a major inconsistency in these values, rather than in the absolute values of RyR sites, on side by side comparison of fast-twitch and of slow-twitch muscles of the rabbit and rat, in that the DHP-R/RyR ratio is invariably lower for the rat, i.e., only about 1.2. Since the absolute values of DHP-R sites, according to our calculations, agree well with those obtained for the same muscles by Lamb & Walsh [(1987) J. Physiol. 393, 595-617], it seems improbable that they were underestimated. On the assumption that there is a fixed stoichiometry between DHP-R and RyR at the junctional contact area between TT and TC, the relatively large excess of RyR sites in the rat, expressed per g. muscle, should be attributed to the presence of a proportion of Ca(2+)-channels that are located outside this area, i.e., are extrajunctional [Dulhunty, A., et al. (1992) Proc. R. Soc. Lond. (B) 247, 69-75].(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2000

Traumatic musculotendinous injuries of the knee: diagnosis with MR imaging.

Magnetic resonance (MR) imaging is the imaging modality of choice for evaluation of acute traumatic musculotendinous injuries of the knee. Three discrete categories of acute injuries to the musculotendinous unit can be defined: muscle contusion, myotendinous strain, and tendon avulsion. Among the quadriceps muscles, the rectus femoris is the most susceptible to injury at the myotendinous junction due to its superficial location, predominance of type II fibers, eccentric muscle action, and extension across two joints. Among the muscles of the pes anserinus, the sartorius is the most susceptible to strain injury due to its superficial location and biarticular course. The classic fusiform configuration of the semimembranosus along with a propensity for eccentric actions also make it prone to strain injury. MR imaging findings associated with rupture of the iliotibial tract include discontinuity and edema, which are best noted on coronal images. The same mechanism of injury that tears the arcuate ligament from its fibular insertion can also result in avulsion injury of the biceps femoris. The gastrocnemius muscle is prone to strain injury due to its action across two joints and its superficial location. Injuries of the muscle belly and myotendinous junction of the popliteus are far more common than tendinous injuries.

Contusions↗
PubMed1995

Distribution of parvalbumin in specific fibre types of chicken skeletal muscles.

1. The distribution of parvalbumin (PA), which functions as a relaxing factor in the skeletal muscles, was examined in slow anterior latissimus dorsi (ALD), fast posterior latissimus dorsi (PLD), mixed sartorius (SA), pectoralis superficialis (PS) and pectoralis profundus (PP) muscles from chickens. 2. The biochemical characteristics of these muscles were confirmed by the assay of total lactate dehydrogenase (LDH) activity as well as the LDH isozymes for anaerobic metabolism, and by the photometrical analysis of myoglobin for anaerobic metabolism, and by the photometrical analysis of myoglobin for aerobic metabolism. 3. PA in individual muscles was determined by a sandwich ELISA and was demonstrated by 2-dimensional polyacrylamide-gel electrophoresis. 4. Because of poor myoglobin and higher LDH activity or M-type isozyme pattern, the PLD was confirmed as containing primarily fast-twitch glycolytic and oxidative-glycolytic (FG/FOG) fibres, while the SA was shown to be composed mostly of FOG fibres because of the highest myoglobin content and the intermediate LDH activity or H and M-type isozyme pattern. PA content was high and variable in both PLD and SA. 5. PA was undetectable in the ALD which appears to contain exclusively slow-tonic (ST) fibres, being verified by its myoglobin-rich nature and lowest LDH activity or predominant H-type isozyme characteristics. PA was absent from the PS ad PP, which probably contain predominantly FG fibres because of negligible amounts of myoglobin and the highest LDH activities or M-type isozyme pattern.

Animals↗
PubMed2002

Differences of morphometrical parameters in hind limb muscle fibres between ovarectomized and sexually intact female dogs.

Slow and fast twitch fibres of the Mm. tibialis cranialis, semitendinosus and sartorius of seven sexually intact and seven ovarectomized female beagles were histochemically and morphometrically analysed. Along with type I and type IIA fibres, another main type II fibre (IIS), which seems to be peculiar to the dog, was found in the Mm. semitendinosus and tibialis cranialis. Type I fibers comprised 26% and type II fibres 74% of all recorded muscle fibres in the M. tibialis cranialis, 29% (type I) and 71% (type II) in the M. semitendinosus and 51% (type I) and 49% (type II) in the M. sartorius, respectively. The average single profile area and the corresponding mean diameter of fibre types I and II in the investigated hind limb muscles were generally larger in ovarectomized than in sexually intact animals. This was more evident in type II than in type I fibres. However only the type II fibres of the M. tibialis cranialis and sartorius exhibited a statistically significant increase in diameter (p < 0.01 and p < 0.05, respectively). Accordingly, the mean density (number of fibres/mm2) of both fibre types in the hind limb muscles of spayed dogs was generally reduced. Again, this reduction attained statistical relevance in the type I and II fibres of the tibialis cranialis. In addition, the fibre densities of type I in the semitendinosus and type II in the sartorius muscles were also significantly reduced in ovarectomized dogs. In conclusion, ovarectomized beagles showed a generally increased mean diameter of the investigated type I and II hind limb muscle fibres and a concomitant decreased average fibre density of the respective types when compared to sexually intact animals.

Adenosine Triphosphatases↗
PubMed2001

Tetranectin in slow intra- and extrafusal chicken muscle fibers.

Tetranectin is a C-type lectin that occurs in the mammalian musculoskeletal system. In the present report we describe the first studies on an avian tetranectin. A full-length chicken tetranectin cDNA was isolated. Comparison of the deduced amino acid sequence of chicken tetranectin with mouse and human tetranectin showed an identity of 67 and 68%, respectively. Northern blot analysis demonstrated broad expression of chicken tetranectin mRNA, which was first detected on embryonic day 4. Tetranectin protein was detected in chicken serum and egg yolk. Since muscle is one of few tissues in which tetranectin protein is retained, we examined the distribution of tetranectin in various muscle types in chicken. Myofibers strongly positive for tetranectin were observed in several muscles including m. tibialis ant. and m. sartorius (from embryonic day 10 to adult). Using antibodies to fast and slow myosin heavy chains (MHC) and double immunostaining techniques, we found that tetranectin was restricted to slow (type I) muscle fibers. Similarly only slow intrafusal fibers accumulated tetranectin. The pattern of immunostaining in chickens differs markedly from that seen in mouse muscles, indicating that tetranectin performs a role in muscle that is not associated with a hitherto recognized muscle type or function.

Adaptation, Physiological↗
PubMed1996

Relationships between range of motion, lo, and passive force in five strap-like muscles of the feline hind limb.

The relationships between range of motion, optimal length for force production (lo), and passive force provide useful insights into the structure and function of muscles but are unknown for most individual muscles. We measured these values and examined their relationships in five strap-like muscles of the cat hind limb: caudofemoralis, semitendinosus, sartorius anterior, tenuissimus, and biceps femoris anterior. The range of motion relative to lo was found to vary significantly between different muscles and even between different specimens of the same muscle. The passive force-length (FL) curve was found to be correlated with both lo and lmax (maximal in situ muscle length) but was correlated more strongly with lmax. The mean passive force produced by these muscles at lmax was less than 7% of estimated maximal isometric force, suggesting that passive force may not be important in these muscles during normal activation patterns. The variance in passive FL curves between specimens of the same muscle was found to be significantly lower when length was scaled by lmax as opposed to lo. These results suggest that lmax may provide a more useful scaling factor for generic models of muscle. However, the passive length-tension properties of mammalian muscle appear to reflect a complex mix of structures at both the myofilament and connective tissue levels that may differ depending on muscle-fiber architecture and perhaps on the history of trophic influences on a particular specimen.

Animals↗
PubMed1989

Effects of muscle and cutaneous hindlimb afferents on L4 neurons whose activity is modulated by neck rotation.

We recorded extracellularly, in decerebrate, labyrinthectomized cats, from spontaneously active L4 neurons whose activity was modulated by head rotation, and studied the effects of stimulation of ipsilateral hindlimb nerves. Rotation of the head about the longitudinal (roll) axis was more effective than rotation about the transverse (pitch) axis or vertical (yaw) axis for this group of neurons. Most units received convergent excitatory or inhibitory inputs from several nerves, with excitation being more prominent. The most effective muscle nerves were quadriceps (37/43 neurons), sartorius (19/21) and tibialis anterior (17/35); stimulation of biceps posterior-semitendinosus, biceps anterior-semimembranosus, or gastrocnemius rarely influenced the firing of the neurons. Group I effects were present in only a small fraction of neurons; however, short latency (central latency less than or equal to 5 ms) group II effects were observed in almost one-third. Longer latency group II as well as group III inputs were also common. All neurons received inputs from mixed and cutaneous nerves which usually had low thresholds and central latencies greater than 5 ms. Most recording sites were in medial lamina VII or lamina VIII; some of the units were identified by antidromic stimulation as propriospinal neurons which projected to the lumbar enlargement.

Action Potentials↗
PubMed1997

Structural and biochemical characteristics of locomotory muscles of emperor penguins, Aptenodytes forsteri.

Structural and biochemical characteristics of the primary muscles used for swimming (pectoralis, PEC and supracoracoideus, SC) were compared to those of leg muscles in emperor penguins (Aptenodytes forsteri). The mass of PEC-SC was four times that of the leg musculature, and mitochondrial volume density in PEC and SC (4%) was two-thirds that in sartorius (S) and gastrocnemius. The differences in muscle mass and mitochondrial density yielded a 2.2-fold greater total mitochondrial content in PEC-SC than leg muscles, which appears to account for the 1.8-fold greater whole-body highest oxygen consumption previously recorded in emperor penguins during swimming compared to walking. Calculation of maximal mitochondrial O2 consumption in PEC-SC and leg muscle yielded value of 5.8-6.9 ml O2 ml-1 min-1, which are similar to those in locomotory muscles of most mammals and birds. A distinct feature of emperor penguin muscle was its myoglobin content, with concentrations in PEC-SC (6.4 g 100 g-1 among the highest measured in any species. This resulted in a PEC-SC O2 store greater than that of the entire blood. In addition, ratios of myoglobin content to mitochondrial volume density and to citrate synthase activity were 4.4 and 2.5 times greater in PEC than in S, indicative of the significant role of myoglobin in the adaptation of muscle to cardiovascular adjustments during diving.

Animals↗
PubMedDate not supplied

Construction of a urinary sphincter by means of an electrically stimulated striated muscle: experimental procedure and urodynamic results on canine model.

A canine model of urinary neosphincter using electrically stimulated autologous striated muscle is described. The superior belly of canine sartorius was activated by a pacemaker with an intermittent low frequency stimulation (0.5-1 pulse per sec) during 7 weeks. Then, the muscle graft was passed around the urethra and sutured back on to itself to form a neosphincter. The surgical procedure was easy to perform and with no complication. Urethral pressure profile was performed initially (T0), and when the muscle was in peri-urethral position, before (T1) and during electrical stimulation (T2). The continence parameter readings (maximal urethral closure pressure MUP, functional length FL, continence zone CZ, and continence area CA) increased from T0 to T1, and from T1 to T2. We noted: 1) 28%, 38%, 52%, and 86% increases for the MUP, FL, CZ, and CA respectively from T0 to T1, 2) 10%, 41%, 30%, and 43% increases for MUP, FL, CZ, and CA respectively from T1 to T2. Chronic low frequency stimulation could transform a skeletal fast-twitch type 2 muscle into a slow-twitch fatigue-resistant type 1 muscle. In this study, morphological changes of the stimulated muscle were noted, whereas phenotype was unchanged. This dynamic autologous neosphincter may be a new alternative to the artificial urinary sphincter prosthesis with fewer complications. Further studies are ongoing to evaluate the efficacy of such a neosphincter as continent system for bladder substitution after pelvic exenteration for pelvic cancers.

Animals↗
PubMed2003

Muscle magnetic resonance imaging in patients with congenital muscular dystrophy and Ullrich phenotype.

The aim of this study was to evaluate muscle magnetic resonance imaging findings in patients with congenital muscular dystrophy and Ullrich phenotype. Fifteen children with congenital muscular dystrophy and Ullrich phenotype were included in the study. All patients had collagen VI studies in muscle and, when family structure was informative, linkage studies to the collagen 6 loci. Three of the 15 patients had reduced collagen in muscle. One of the three was from an informative family and linked to one of the collagen 6 loci. Another patient was linked to one of the collagen 6 loci but had normal expression of collagen in muscle. The remaining 11 all had normal collagen expression in muscle. Only two of these 11 were from informative families and linkage to collagen 6 loci was excluded in them. All patients had muscle magnetic resonance imaging of their leg muscles using transverse T1 sequences. With the exception of the two patients in whom linkage to the collagen 6 loci was excluded, the other 13 patients showed the same pattern of selective involvement on magnetic resonance imaging of thigh muscles. This consisted of relative sparing of sartorius, gracilis, adductor longus and rectus. This pattern was also found in the case linked COL6A1/A2 locus but with normal collagen. This finding, and the striking clinical and magnetic resonance imaging concordance between patients with normal and reduced collagen VI in muscle suggest that collagen VI could still be the culprit in several cases with normal collagen expression, or alternatively a primary defect in a protein that closely interacts with collagen VI. Mutation analysis of the collagen 6 genes in cases with normal collagen VI expression is needed to resolve this issue.

Adolescent↗