Histomorphometry of masticatory muscles in the muscular dystrophic mouse

Cross sections of normal and dystrophic digastric, masseter and temporalis muscles from 7-week-old mice were studied by histomorphological and histomorphometrical methods in the light microscope. The histomorphological part of the study revealed marked differences in morphology between normal and dystrophic muscles. Mutual differences between the dystrophic muscles were also observed. Comparisons of the parameters chosen for the histomorphometrical part of the study, i.e., cell size and number of centrally positioned nuclei in a given number of fibers, revealed that the digastric muscle seems to be the least affected and the masseter muscle the most affected by the disease.     

Two-dimensional proton magnetic resonance of human muscle extracts

In continuation of our previous work on one-dimensional (1D) proton nuclear magnetic resonance (1H-NMR) of normal and diseased human muscle extracts we recorded the two-dimensional (2D) J-correlated proton magnetic resonance spectra of these extracts. Significant differences between normal and diseased muscle extracts, not observed in the 1D 1H-NMR spectra, were seen from their 2D connectivity contour patterns. Taurine was not present in cerebral palsy muscle extract while both normal and scoliosis muscles contained this metabolite. Only the normal muscle had carnitine. Carnosine was present in all muscles. alpha-Ketoglutarate was found only in the diseased muscle extracts. While the amino acids lysine, cysteine and glutamine were common to normal and diseased muscles, threonine was seen only in the diseased muscles. Additional small differences were detected in the 2D patterns of human muscle extracts.     

The properties of the extraocular muscles of the frog. II. Pharmacological properties of the isolated superior oblique and superior rectus muscles.

The pharmacological properties of the superior oblique and the superior rectus muscles of the frog's eye were investigated in comparison with those of a skeletal muscle (iliofibularis muscle) of the same animal. Acetylcholine causes sustained contractures of the extraocular muscles; this effect is increased by physostigmine and decreased or abolished by d-tubocurarine. Also the applications of succinylcholine, choline or caffeine are able to evoke contractures. There are no striking differences in pharmacological properties between extraocular and skeletal muscles of the frog. The time-course of the contractures and the sensitivity of the muscle preparations to the drugs which evoke contractures are identical in extraocular and iliofibularis muscles. In comparison with skeletal muscles there is no higher sensitivity of the extraocular muscles against curare-like drugs. The existence of adrenergic receptors could not be found neither in extraocular nor in skeletal muscles of the frog. It is concluded that in frogs no pharmacological differences exist between the muscle fibre types which compose the extraocular and the skeletal muscles.     

Muscle-specific enzyme activity patterns of the capillary bed of human oro-facial,masticatory and limb muscles

Enzyme-histochemical methods were used to analyse the activities of alkaline phosphatase (AP), dipeptidylpeptidase IV (DPP IV) and adenosine triphosphatase (ATPase) in capillaries of four different human oro-facial muscles, the major and minor zygomatic, the orbicularis oris and buccinator, one masticatory, the masseter and two limb muscles, the biceps brachii and first dorsal interosseus muscles. In all muscles, except for the orbicularis oris, the majority of the capillaries lacked enzyme activity. Therefore, none of these enzymes seems to be reliable as a general marker for human muscle capillaries. In general, the capillaries of the limb muscles and the major and minor zygomatic and the buccinator, were similar in their staining pattern for AP and ATPase, but differed in DPP IV staining. The orbicularis oris muscle differed from the other muscles by showing the largest proportion of capillaries with AP and ATPase activity. The masseter muscle had the largest proportion of capillaries stained for DPP IV. The muscle specific differences in enzyme activity of the capillaries are in agreement with our previous findings of specific differences between limb, oro-facial and masticatory muscles with respect to capillary supply and composition of fibre types and myosins. The results reflect functional specialization of the capillary bed of human muscles.     

Protein composition of cockroach muscles: Identification of candidate recognition macromolecules

The protein composition of each of the coxal depressor muscles from the leg of the cockroach, Periplaneta americana, was analyzed by SDS polyacrylamide gel electrophoresis. The proteins from each muscle were fractionated according to their extractability in Ringer's solution, 1% Triton X-100 and 1% SDS. The gel protein patterns of the fractionated muscles revealed some biochemical differences that could be correlated with mechanical and ultrastructural differences observed among the muscles. In addition, proteins were detected that were considered to be candidate recognition macromolecules that are responsible for the intercellular recognition process that enables regenerating motor neurons to specifically recognize and make stable, functional connections only with the muscles to which they were originally connected. The major evidence for this identification of candidate recognition macromolecules was that their presence in the muscle could best be correlated with innervation by an identified motor neuron. In addition, these proteins remain present in denervated muscles for at least as long as it takes for the original innervation pattern to be reformed by the regenerating motor neurons.     

Patterns of amino acid enzyme in domestic fowl breast and leg muscle during development

Activities of alanine and aspartate transaminases, glutamine synthetase, adenylate deaminase, glutamate and xanthine dehydrogenases and lactate dehydrogenase were measured in leg and breast muscles of developing chicks from day 10 in ovo to day 5 of free life, and compared with measurements for adult hens. Xanthine dehydrogenase activity was low in both muscles with adult levels attained on day 15 in ovo. Glutamine synthetase for chicks was maintained higher during development than for adults in both muscles. Minor differences were observed between both muscles in all enzymes tested up to day 18. With low embryonic values and important rises before hatching, the differences were initiated in the posthatching period. Important differences were observed between adult levels of activity. Leg muscle revealed higher enzyme values except for lactate dehydrogenase and indistinguishable levels for adenylate deaminase and xanthine dehydrogenase in both muscles. Alanine, instead of glutamine, is postulated as the main nitrogen transport between muscle and liver in the domestic fowl.     

The influence of denervation of the maturation of the flight muscle of Periplaneta americana.

The metathoracic musculature of the American cockroach Periplaneta americana was denervated by dissecting the nerves originating in the metathoracic ganglion on one side within 2 days after the last moult. The biochemical and morphological differences between normal and denervated musculature were followed two weeks later. Denervation completely prevents the gain in weight, protein content and cytochrome oxidase activity which occur in normal muscles during the two weeks after previous moulting. The content of phosphoarginine in the denervated muscle does not differ from the control muscle and is lower than in young muscles. The ability to resynthesize phosphoarginine postanaerobically is substantially lower in the denervated muscle than in control muscles, or in young muscles immediately after the last moult. The ultramicroscopic structure of the denervated muscle differs from that of the normal muscle: the mitochondria possess less cristae, the matrix between them appears less dense and the sarcoplasmatic reticulum is less developed. Thus the denervated muscle not only fails to mature, but also developes serious structural and biochemical disorders.     

The muscle line of action in current models of the human cervical spine: a comparison with in vivo MRI data

Cervical muscles are commonly represented by line-of-action models. This investigation evaluates the performance of three types of model implementations, based on their ability to mimic geometric in-vivo aspects of muscles. Five prominent pairs of neck muscles were reconstructed in three head positions using magnetic resonance imaging. Based on the reconstructions, muscle approximations were created that represent the muscles with piecewise straight lines. Measured and modelled muscle approximations were compared with respect to their pulling directions at the attachment sites and the overall distance between the muscle paths. Muscle lengths were evaluated in two ways. First, length discrepancies were determined between measured and modelled muscles depending on the head position. Second, the difference of muscle lengths in neutral and deflected head positions for measurement and models were calculated. The results indicate considerable differences between models and measurements. Pulling directions, for instance, differed by up to 40°, depending on the chosen muscle and the type of muscle implementation.     

Hindlimb muscle fiber types in two frogs (Rana catesbeiana and Litoria caerulea) with different locomotor behaviors: histochemical and enzymatic comparison

To test how differences in locomotor behaviors may be reflected in muscle fiber-type diversity within anurans, a comparison of hindlimb muscles between the powerful terrestrial hopper, Rana catesbeiana, and the tree frog, Litoria caerulea, was done. One postural muscle (tibialis posticus, TP) and one primary hopping muscle (plantaris longus, PL), were characterized to identify muscle fiber types using standard histochemical methods. In addition, spectophotometric analysis of activity levels of the oxidative enzyme citrate synthase (CS) and the glycolytic enzyme lactate dehydrogenase (LDH) were done in each muscle. In spite of presumed differences in behavior between the species, we found no significant differences in the proportions of the identified fiber types when the muscles were compared across species. In addition, there were no significant differences in the proportions of the different fiber types between the postural versus phasic muscles within species. Within Rana, the postural muscle (TP) had greater oxidative capacity (as measured by CS activity) than did the phasic muscle (PL). Both muscles had equivalent LDH activities. Within Litoria, PL and TP did not differ in either LDH or CS activities. Both PL and TP of Litoria had less LDH activity and greater CS activity than their homologs in Rana. Thus, in spite of the uniform populations of fiber types between muscles and species, the metabolic diversity based on enzyme activity is consistent with behavioral differences between the species. These results suggest that the range of functional diversity within fiber types may be very broad in anurans, and histochemical fiber typing alone is not a clear indicator of their metabolic or functional properties.     

Similarities in Form and Developmental Sequence for Three Larval Shell Muscles in Nudibranch Gastropods

Shell-anchored muscles that extend into the cephalopodium of five species of planktotrophic nudibranch larvae were studied by ultrastructural examination of sequential larval developmental stages. All species, regardless of larval shell type (inflated or non-inflated), showed a similar basic pattern of shell muscles. The larval retractor muscle (LRM) differentiates prior to hatching and its fibres insert on epithelia of the velum, apical plate, stomodeal region, or mantle fold. Many fibres also connect with subepithelial intrinsic muscles of the cephalopodium. Most but not all LRM fibres Project to left-sided targets and are innervated from the left cerebral ganglion. Two pedal muscles, which are innervated from the pedal ganglia, differentiate during the post-hatching larval stage and both insert primarily on pedal epithelium attached to the operculum. The left pedal muscle is anchored to the shell immediately adjacent to the attachment plaque of the LRM and consists of basal and distal tiers of muscle cells. The right pedal muscle arises on the ventral rim of the shell aperture and consists of a single tier of muscle cells. Ontogenic changes in larval retraction behaviour correlate with developmental change in the muscle effectors. Although some interspecific differences were noted, the presence of a common ground plan for larval shell muscles in these five species contrasts with previous indications of marked variability for nudibranch larval shell muscles.     

Architecture of the hind limb muscles of cats: Functional significance

Force, velocity, and displacement properties of a muscle are determined in large part by its architectural design. The relative effect of muscle architecture on these physiological variables was studied by determining muscle weight, fiber length, average sarcomere length, and approximate angle of pinnation for 24 cat hind limb muscles. Muscle lengths ranged from 28.3 to 144 mm, whereas fiber lengths ranged from 8.4 to 105.5 mm. Generally, fiber to muscle length ratios were similar throughout a muscle. Estimated angles of pinnation of muscle fibers varied from 0 to 21° with most having an angle of less than 10°. The cross-sectional area of the knee extensors was similar to the knee flexors (16.43 vs. 16.83 cm²) whereas the cross-sectional area of the ankle extensors was more than six times greater than the ankle flexors (18.59 vs. 2.83 cm²). There was a 6.7-fold difference in the maximal force between muscles, when normalized to a constant weight, that could be attributed to architectural features. Rations of wet weight to predicted maximal tetanic tension for each muscle and group were calculated to compare the relative priority of muscle force versus muscle length-velocity for a given mass of muscle. These ratios varied from 0.4 to 4.84. The ratios suggest that velocity and/or displacement is a priority for the hamstrings, whereas force is a priority for the quadriceps and lower leg muscles. As much as a 12.6-fold difference in maximal velocity between muscles can be attributed to differences in fiber lengths. This can be compared to approximately a 2.5-fold difference in maximal velocity reported to occur as a result of biochemical (intrinsic) differences.     

Determination of age- and exercise-dependent changes in myoglobin contents in murine skeletal and cardiac muscles

A new method was developed to determine myoglobin (Mb) contents in as least as 5 mg of murine skeletal muscles. The method was a modification of Reynafarje's spectroscopic technique and was based on the Soret absorptions at 416 and 422 nm of the muscle extract. Mb contents in the skeletal and cardiac muscles increased with age and were widely different from muscle to muscle. The contents in most of the 13 muscles examined at the 30th week of age were less than 1.5 mg/g wet muscle, but the cardiac, soleus and gracilis muscles showed exceptionally high values of 2.2-6.0 mg/g. The relative content of one muscle to the other was the same independent of differences in age, strain and sex. There was a positive correlation between the muscle Mb contents and citrate synthase activity (r = 0.930). Young male mice (5 wk-old) were endurance-trained by a gradual load-increment program on treadmill for 10 weeks (5 days/week), but the training had no effects on the Mb contents. No substantial alteration of the contents was also observed in the limbs immobilized by plaster-fixation for 4 weeks.     

The muscle line of action in current models of the human cervical spine: a comparison with in vivo MRI data

Cervical muscles are commonly represented by line-of-action models. This investigation evaluates the performance of three types of model implementations, based on their ability to mimic geometric in-vivo aspects of muscles. Five prominent pairs of neck muscles were reconstructed in three head positions using magnetic resonance imaging. Based on the reconstructions, muscle approximations were created that represent the muscles with piecewise straight lines. Measured and modelled muscle approximations were compared with respect to their pulling directions at the attachment sites and the overall distance between the muscle paths. Muscle lengths were evaluated in two ways. First, length discrepancies were determined between measured and modelled muscles depending on the head position. Second, the difference of muscle lengths in neutral and deflected head positions for measurement and models were calculated. The results indicate considerable differences between models and measurements. Pulling directions, for instance, differed by up to 40°, depending on the chosen muscle and the type of muscle implementation.     

Comparison Between the Effects of Botulinum Toxin-Induced Paralysis and Denervation on Molecular Forms of Acetylcholinesterase in Muscles

Abstract: Velocity sedimentation analysis of acetylcholinesterase (AChE) molecular forms in the fast extensor digitorum longus muscle and in the slow soleus muscle of the rat was carried out on days 4, 8, and 14 after induction of muscle paralysis by botulinum toxin type A (BoTx). The results were compared with those observed after muscle denervation. In addition, the ability of BoTx-paralyzed muscles to resynthesize AChE was studied after irreversible inhibition of the preexistent enzyme by diisopropyl phosphorofluoridate. Major differences were observed between the effects of BoTx treatment and nerve section on AChE in the junctional region of the muscles. A precipitous drop in content of the asymmetric A12 AChE form was observed after denervation, whereas its decrease was much slower and less extensive in the BoTx-paralyzed muscles. Recovery of junctional AChE and of its A12 form after irreversible inhibition of the preexistent AChE in BoTx-paralyzed muscles was nevertheless very slow. It seems that a greater part of the junctional A12 AChE form pertains to a fraction with a very slow turnover that is rapidly degraded after denervation but not after BoTx-produced muscle paralysis. The postdenervation decrease in content of junctional A12 AChE is therefore not primarily due to muscle inactivity. The extrajunctional molecular forms of AChE seem to be regulated mostly by muscle activity because they undergo virtually identical changes both after denervation and BoTx paralysis. The differences observed in this respect between the fast and slow muscles after their inactivation must be intrinsic to muscles.     

Reciprocal neural regulation of extrajunctional acetylcholinesterase and collagen Q in rat muscles--the role of calcineurin signaling

There are two main differences regarding acetylcholinesterase (AChE) expression in the extrajunctional regions of fast and slow rat muscles: (1) the activity of AChE catalytic subunits (G1 form) is much higher in fast than in slow muscles, and (2) the activity of the asymmetric forms of AChE (A(8) and A(12)) is quite high extrajunctionally in slow muscles but virtually absent in fast muscles. The latter is due to the absence of the expression of AChE-associated collagen Q (ColQ) in the extrajunctional regions of fast muscle fibers, in contrast to its ample expression in slow muscles. We showed that both differences are caused by different neural activation patterns of fast vs. slow muscle fibers, which determine the respective levels of mRNA of both proteins. Whereas the changes in AChE mRNA levels in fast and slow muscles, as well as the levels of ColQ mRNA levels in slow muscles, observed in response to exposing either slow or fast muscles to different muscle activation patterns, are completely reversible, the extrajunctional suppression of ColQ expression in fast muscle fibers seems to be irreversible. Calcineurin signaling pathway in muscles is activated by high-average sarcoplasmic calcium concentration resulting from tonic low-frequency muscle fiber activation pattern, typical for slow muscle fibers, but is inactive in fast muscle fibers, which are activated by infrequent high-frequency bursts of neural impulses. Application to rats of two inhibitors of calcineurin (tacrolimus-FK506 and cyclosporin A) demonstrated that the mRNA levels of both the AChE catalytic subunit and ColQ in the extrajunctional regions of the soleus muscle are regulated by the calcineurin signaling pathway, but in a reciprocal way. Under the conditions of low calcineurin activity, AChE expression is enhanced and that of ColQ is suppressed, and vice versa. Our results also indicated that different, calcineurin-independent regulatory pathways are responsible for the reduction of AChE expression during muscle denervation, and for maintaining high ColQ expression in the neuromuscular junctions of fast muscle fibers.     

Relationship between Superprecipitating Activity and Constituents of Myosin B Prepared from Normal and PSE Porcine Muscle

Myosin B from normal and PSE porcine muscles was studied by superprecipitation and SDS polyacrylamide gel electrophoresis. Similar studies were made on the fractions derived from the myosin B preparation after ultracentrifugation. Myosin B and its fractions from PSE muscle showed much less superprecipitation than normal. This difference between normal and PSE muscle seems to reflect differences in biological activity of their myofibrillar proteins, rather than differences in myofibrillar protein composition.     

Regional differences in serotonergic input to canine parasternal intercostal motoneurons.

There is a mediolateral gradient in activation of the parasternal intercostal (PI) muscle during inspiration. In the present study, we tested the hypotheses that serotonergic [5-hydroxytryptamine (5-HT)] input from descending central drive and/or intrinsic size-related properties of PI motoneurons leads to the differential activation of PI muscles. In dogs, PI motoneurons innervating the medial and lateral regions of the PI muscles at the T(3)-T(5) interspaces were retrogradely labeled by intramuscular injection of cholera toxin B subunit. After a 10-day survival period, PI motoneurons and 5-HT terminals were visualized by using immunohistochemistry and confocal imaging. There were no differences in motoneuron morphology among motoneurons innervating the medial and lateral regions of the PI muscle. However, the number of 5-HT terminals and the 5-HT terminal density (normalized for surface area) were greater in motoneurons innervating the medial region of the PI muscle compared with the lateral region. These results suggest that differences in distribution of 5-HT input may contribute to regional differences in PI muscle activation during inspiration and that differences in PI motoneuron recruitment do not relate to size.     

Sexual dimorphism and ontogenetic allometry of soft tissues in Rattus norvegicus.

Most studies of sexual dimorphism in mammals focus on overall body size. However, relatively little is known about the differences in growth trajectories that produce dimorphism in organ and muscle size. We weighed six organs and four muscles in Rattus norvegicus to determine what heterochronic and allometric scaling differences exist between the sexes. This cross-sectional growth study included 113 males and 109 females with ages ranging from birth to 200 days of age. All muscle and organ weights were ultimately greater in males than in females, because males grew for a longer period of time, had a greater maximum rate of growth, and spent more time near the maximum rate. No ontogenetic scaling differences existed between the sexes in organ weight except for lungs and gonads. During growth, organ weights were negatively allometric to body weight. No scaling differences relative to body weight existed between the sexes for muscles; however, there was variation in the allometric relations among muscles relative to body weight. Sexual dimorphism in muscles and organs appears to be a size difference resulting from differences in the duration and rates of growth.     

Muscle plasticity: comparison of a 30-Hz burst with 10-Hz continuous stimulation

The changes in the contractile properties induced by a 30-Hz phasic stimulation paradigm were measured and compared with the changes induced by a 10-Hz continuous stimulation paradigm. The study was performed on the tibialis anterior muscles of cats with one paradigm applied to one hindlimb muscle and the other to the contralateral limb. Both hindlimb muscles received the same number of stimuli in a day, making the average stimulation frequency 10 Hz. Two periods of daily stimulation were studied, 8 and 24 h/day. Muscles stimulated at 30 Hz produced greater overall tetanic tension and, during a prolonged stimulation test, exerted a greater mean tension than muscles stimulated at 10 Hz (50 and 32% increase for animals stimulated for 8 and 24 h/day, respectively). Muscle mass was least reduced and fewer pathological abnormalities were observed in the muscles stimulated at 30 Hz. There were no apparent differences in the histochemistry or biochemistry between muscles stimulated at 10 and 30 Hz, which could account for these differences in muscle properties. These results indicate the 30-Hz paradigm may be better suited than 10 Hz continuous stimulation for applications requiring sustained muscle tension such as correction of scoliosis or muscle conditioning for motor prostheses.