Selectivity of alterations in skeletal fibers in chronic Chagas' disease of the mouse

In mice chronically infected with Trypanosoma cruzi, the masseter muscle (rich in type II fibers) was devoid of inflammatory infiltrates and parasites. In contrast, other muscles, composed of type I and II fibers, showed a decrease of type I fibers, parasites and lesions, suggesting that in T. cruzi infection type I muscle fibers are selectively damaged.     

Selectivity of alterations in skeletal fibers in chronic Chagas' disease of the mouse

Summary In mice chronically infected withTrypanosoma cruzi, the masseter muscle (rich in type II fibers) was devoid of inflammatory infiltrates and parasites. In contrast, other muscles, composed of type I and II fibers, showed a decrease of type I fibers, parasites and lesions, suggesting that inT. cruzi infection type I muscle fibers are selectively damaged.     

Expression of alpha-cardiac myosin heavy chain in mammalian skeletal muscle.

We have investigated the reactivity of different human, rat and cat muscles to a monoclonal antibody directed against human alpha-cardiac myosin heavy chain. We have found that special fiber subpopulations of human masseter and extraocular muscles, as well as the bag fibers of human, rat and cat muscle spindles, were reactive to this antibody, indicating that these fibers expressed alpha-cardiac myosin heavy chain or a closely related isoform. This isomyosin was present in the spindle bag fibers at early fetal stages, whereas its expression in masseter and extraocular muscle fibers was not detected during the first 22 weeks of gestation. Our results add to the list of muscle proteins which are expressed in locations or at developmental stages other than those initially described, suggesting that a revision of the present nomenclature of the subgroups of myosin heavy chains might be considered in the future.     

The size of motor units in laryngeal muscles of the rat

Summary The size of motor units in rat laryngeal muscles was determined by correlating the number of neurons labeled by i.m. injections of horseradish peroxidase with the number of motor end plates stained for acetylcholinesterase. The cricothyroid has a motor unit size of 8 muscle fibers per motor neuron and the posterior cricoarytenoid 4–5 muscle fibers per motor neuron.     

The generation of new ‘white’ muscle fibers by budding in the lateral musculature of elversAnguilla anguilla (L.) during normal development

Summary The elver is a developmental stage of the European eel Anguilla anguilla (L.). During its growth, relatively large numbers of new muscle fibers are formed in the lateral musculature. We investigated the origin of these fibers. They proved to originate from already existing fibers by budding.     

A light microscopic study of denervation atrophy in serial sections

Summary Type I and type II muscle fibers from rat extensor digitorum longus muscle were sequentially followed in serial sections after various time intervals following denervation. The type II fibers exhibited the greatest degree of atrophy as well as showing a systematic diameter variability along its length.This study has been supported in part by Research grant No. G008003038 from the National Institute of Handicapped Research, Department of Education, and by the Muscular Dystrophy Association of America.     

Characteristics of mosaic muscle growth in rainbow troutSalmo gairdneri

Summary There are 4 stages in the growth of mosaic (axial) muscle, which is the predominating tissue in trout; the stages are distinguishable by the modal values and range of their fibre diameters over the size range 2.3 to 50+cm fork length. Up to 50 cm, most of the increase in mosaic muscle is attributable to continuous recruitment of new fibers. Beyond 50 cm, further growth is a result of increase in diameter of existing fibers.     

Expression of alpha-cardiac myosin heavy chain in mammalian skeletal muscle

We have investigated the reactivity of different human, rat and cat muscles to a monoclonal antibody directed against human -cardiac myosin heavy chain. We have found that special fiber subpopulations of human massetr and extraocular muscles, as well as the bag fibers of human, rat and cat muscle spindles, were reactive to this antibody, indicating that these fibers expressed -cardiac myosin heavy chain or a closely related isoform. This isomyosin was present in the spindle bag fibers at early fetal stages, whereas its expression in masseter and extraocular muscle fibers was not detected during the first 22 weeks of gestation. Our results add to the list of muscle proteins which are expressed in locations or at developmental stages other than those initially described, suggesting that a revision of the present nomenclature of the subgroups of myosin heavy chains might be considered in the future.     

Different intrafusal fiber composition of spindles in sheep and pig extraocular muscles

Histochemical profiles of intrafusal fibers have been examined in muscle spindles of extraocular muscles of sheep and pig. Results show that in the sheep the intrafusal content presents, in addition to chain fibers, at least one bag1 and one bag2 fiber, whereas in the pig almost all the spindles are one-bag-fiber [corrected] spindles.     

Structural characteristics and distribution of satellite cells along crayfish muscle fibers.

The distribution of satellite cells (sc) in long-sarcomere muscle fibers from the carpopod extensor muscle of the crayfish (Astacus fluviatilis) has been studied electron-microscopically. The sc are spindle-shaped and are oriented parallel to the long axis of a fiber. The mean lengths of sc nuclei (17.00 microns) and that of myonuclei (18.35 microns) differ non-significantly. In older animals, the mean ratio of the number of sc nuclei to the total number of nuclei (sc nuclei + myonuclei) is 0.0716, 0.0848, and 0.034 for the tendon, central and shell segments, respectively. The corresponding values for younger animals are 0.158, 0.166, and 0.081. The mean numbers of sc nuclei per mm of a fiber are 94, 117, and 47 (older animals), and 164, 117, and 94 (younger animals) for the tendon, central and shell segments, respectively. The high incidence of sc per unit fiber length in crayfish may be related to the fact that crayfish muscle fibers have a much larger diameter than vertebrate muscle cells.     

Myosin isoenzymes during in vivo and in vitro differentiation of chick muscles

Muscle fibers differentiated, in vitro, from myoblasts of embryonic Pectoralis (presumptive fast) and embryonic Adductor magnus (presumptive slow) muscles synthesise the same type of myosin, which is identical to the type synthesised in day 10 embryonic muscles. This type of myosin comigrates with the third isozyme of the adult fast-twitch muscle. There is no change in the kind of myosin in cultures aged from 2 to 7 weeks, whereas during the in vivo differentiation of the same muscles, new isozymes appear which are different in the two muscles. With regard to myosin, the muscle fibers differentiated, in vitro, from myoblasts of fast or slow muscles expressed the same phenotype.     

Uptake and transport of exogenous peroxidase in the masticatory muscles of cats. Localization of ganglionic neurons]

Retrograde axonal transport of Horseradish peroxydase (HRP) has been used to trace the cells of origin of proprioceptive fibers in jaw-closing and jaw-opening muscles. After injection of HRP in young cats' masticatory muscles (masseteric, temporal, pterygoid, mylohyoid and digastric) labelled neurons were found in the ipsilateral semi-lunar ganglion and trigeminal mesencephalic nucleus. It is concluded that sensory endings are present in jaw-opening as in jaw-closing muscles; possibly the afferent fibers from muscle endings of the opener muscles have their somata in the mesencephalic nucleus, afferent fibers from tendinous receptors in the semi-lunar ganglion.     

Antiarrhythmic peptide has no direct cardiac actions

The electrophysiologic, inotropic, and muscarinic effects of antiarrhythmic peptide (AAP) were examined in canine cardiac Purkinje fibers, ferret papillary muscle, and canine cardiac membranes, respectively. Aside from a prolongation of time to peak force in papillary muscle, no biologically significant effects of AAP could be determined in any preparation, suggesting that its antiarrhythmic effects are not mediated by direct membrane actions.     

Microinjection of synthetic protein kinase inhibitor into single barnacle muscle fibers before and after cyclic AMP

Single muscle fibers from the barnacle Balanus nubilus have been used as a preparation to see if a synthetic 20-residue PKI (5-24)-peptide is able to block or reverse the stimulatory response of the ouabain-insensitive Na efflux to injected cAMP. The results obtained show that this peptide behaves as a powerful inhibitor of the cAMP-mediated response and is also able to partially reverse the sustained stimulation of the Na efflux observed in ouabain-poisoned fibers following the injection of subunit A of cholera toxin.     

Antiarrhythmic peptide has no direct cardiac actions

Summary The electrophysiologic, inotropic, and muscarinic effects of antiarrhythmic, peptide (AAP) were examined in canine cardiac Purkinje fibers, ferret papillary muscle, and canine cardiac membranes, respectively. Aside from a prolongation of time to peak force, in papillary muscle, no biologically significant effects of AAP could be determined in any, preparation, suggesting that its antiarrhythmic, effects are not mediated by direct membrane actions.     

Role played in man by myelinated fibers of different diameters for the evocation of a nociceptive flex reflex and the accompanying pain sensation]

Using simultaneous recordings we have made in Man a comparative study of: the sural nerve afferent volley, the nociceptive flexor reflex of a muscle of the lower limb and the associated painful sensation. Two types of stimulations were used, a single short duration electric stimulus, and a train of electric shocks (100/sec). With a single stimulus, the nociceptive flexor reflex and the painful sensation develop only when A delta fibers are recruited. On the other hand, when the stimulations are given by trains the nociceptive flexor reflex and the painful sensation can develop with a stimulus sub-liminar to the threshold of A delta fibers, when A alpha fibers are recruited. When the stimulus activate both A alpha and A delta fibers, the flexion reflex and the pain disappear when a selective blockade of the A delta group is exerted by means of Lidocain.     

Frequency-dependent effect of verapamil on rat soleus muscle

In the presence of verapamil (0.1 mM) rat soleus muscle fibers failed to generate action potentials with overshoots. In fibers with their Vm set to a local level of -90 mV, verapamil produces a gradual reduction in the amplitude of the repetitive action potentials; this effect is more pronounced at high rates of stimulation (100 Hz). Our results suggest a local anesthetic action of this drug that could contribute with its calcium channel blocking effect to the diminished mechanical tension observed in the presence of the drug.     

Different intrafusal fiber composition of spindles in sheep and pig extraocular muscles

Summary Histochemical profiles of intrafusal fibers have been examined in muscle spindles of extraocular muscles of sheep and pig. Results show that in the sheep the intrafusal content presents, in addition to chain fibers, at least one bag₁ and one bag₂ fiber, whereas in the pig almost all the spindles are bag₁-fiber spindles.Acknowledgment. This study was supported by grants from C.N.R. and M.P.I.     

Structural characteristics and distribution of satellite cells along crayfish muscle fibers

The distribution of satellite cells (sc) in long-sarcomere muscle fibers from the carpopod extensor muscle of the crayfish (Astacus fluviatilis) has been studied electron-microscopically. The sc are spindle-shaped and are oriented parallel to the long axis of a fiber. The mean lengths of sc nuclei (17.00 m) and that of myonuclei (18.35 m) differ non-significantly. In older animals, the mean ratio of the number of sc nuclei to the total number of nuclei (sc nuclei + myonrclei) is 0.0716, 0.0848, and 0.034 for the tendon, central and shell segments, respectively. The corresponding values for younger animals are 0.158, 0.166, and 0.081. The mean numbers of sc nuclei per mm of a fiber are 94, 117, and 47 (older animals), and 164, 117, and 94 (younger animals) for the tendon, central and shell segments, respectively. The high incidence of sc per unit fiber length in crayfish may be related to the fact that crayfish muscle fibers have a much larger diameter than vertebrate muscle cells.     

Comparative ultrastructural and cytochemical analysis of the cephalopod systemic heart and its innervation

Summary The present knowledge of the morphology of cephalopod central hearts is presented. The cytological characteristics of the epicardial, myocardial and endothelial tissue layers are reviewed. Myocardial cells are characterized as obliquely striated myocytes with a high level of oxidative metabolism. The voluminous myocardium is intensively penetrated by nerve fibers controlling the myogenic heart rhythm by different chemical transmitter systems. Catecholaminergic fluorophores and acetylcholinesterase activity could be localized by means of histochemical and cytochemical investigations. A glio-interstitial cell system is shown to be present in connection with nerve fibers and also uncombined between heart muscle cells. Its content of large different-sized inclusions is described and their function discussed.