Cat Tibialis Anterior Muscle Research Articles

Three-dimensional structure of cat tibialis anterior motor units.

The motor unit is the basic unit for force production in a muscle. However, the position and shape of the territory of a motor unit within the muscle have not been defined precisely. The territories of five motor units in the cat tibialis anterior muscle were reconstructed three-dimensionally (3-D) from tracings of the glycogen-depleted fibers belonging to each unit. The motor unit territories did not span the entire length of the muscle and their cross-sectional areas tapered along the proximodistal axis producing a conical shape. In addition, the position of the territory of each unit shifted in an anterior-posterior plane along the longitudinal axis of the muscle, presumably as a consequence of the pinnation of the fibers. The area of the motor unit territory at any given level along the proximodistal axis was highly correlated with the number of fibers within the territory at that level. Connective tissue boundaries (outlining fascicles) appeared to have a strong influence on the shape of the territory, territories showed abrupt changes at connective tissue boundaries as groups of motor unit fibers within a fascicle often terminated together while motor unit fibers in neighboring fascicles did not terminate. It is likely that the mechanical impact of the recruitment of a motor unit is affected by the location and shape of motor units within the same muscle area.(ABSTRACT TRUNCATED AT 250 WORDS)

Subdivision of primary afferents from passive cat muscle spindles based on a single slow-adaptation parameter

38 primary afferents originating from de-efferented cat tibialis anterior muscle spindles were investigated. Ramp-and-hold stretches of the host muscle were performed with a varying amount of muscle pre-stretch while recording the primary afferent discharges. From the discharge responses an interspike interval function was estimated. This revealed a slow adaptation during the hold phase of stretch which could be approximated quite well by a power function. The slow-adaptation power function exponent (SAE) was found to be rather independent of the amount of pre-stretch applied to the host muscle and grouped around a value characteristic for each afferent. These ‘characteristic SAEs’ showed a clearly bimodal distribution within the population of primaries studied. Moreover, the distribution around both modes was narrow enough to justify the subdivision of the primary afferents according to their characteristic SAE as either high-SAE (10 afferents; 26%) or low-SAE (28 afferents; 74%) afferents. The most likely explanation for this bimodality of slow-adaptation behavior in primary afferents is given by the assumption that the afferent discharge of the passive spindle is mainly provided from a branch innervating either the bag 1 (for high-SAE units) or the bag 2 and chain (for low-SAE units) intrafusal fibers.

Myofilament lengths of cat skeletal muscle: Theoretical considerations and functional implications

The cat is the primary model for neuromuscular research. However, sarcomere geometry, in particular thin-myofilament lengths of cat skeletal muscles, is not known, thus preventing adequate muscle modeling on the sarcomere level. The purpose of this study was to determine thin-myofilament lengths in cat skeletal muscle. It was found that average thin-myofilament lengths of cat tibialis anterior muscles (1.12 μm) were larger than the average values reported for frog (∼0.95 μm), rat (1.09 μm), and rabbit muscles (1.09 μm) and were smaller than the values reported for monkey (1.16 μm) and human skeletal muscles (1.27 μm). According to the cross-bridge theory of muscular contraction, this result implies that the range of sarcomere length on the ascending limb of the force-length relation for cat muscle is between those of frog, rat, and rabbit on the one side and monkey and human on the other side. It is speculated that the differences in thin-myofilament lengths of different animals are related to the functional demands of these muscles in everyday movement tasks. Isolated experimental observations appear to support this speculation.

The effect of tendon viscoelastic stiffness on the dynamic performance of isometric muscle

The effect of tendons viscoelastic stiffness on the dynamic response of the cat's tibialis anterior muscle under isometric conditions was determined. It was shown that the dynamic response model of the muscle derived under sinusoidal contraction-relaxation in the range of 20–80% of its maximal isometric tension was not statistically different before and after the disection of the whole distal tendon. It was suggested that under isometric conditions in the force range of 20–80% of the maximal, the tendon acts as a very stiff force transmission linkage without significantly modifying the muscle's performance.

Adaptive control of electrically stimulated muscle.

A discrete time adaptive control system for electrically stimulated muscle has been designed and evaluated experimentally. The control system is based on a previously developed discrete time model of electrically stimulated muscle. Performance was evaluated on the basis of stability and responses to step, ramp, and sinusoidal inputs. Cat tibialis anterior muscles that had been previously electrically exercised were activated to control ankle joint torque via chronically implanted epimysial electrodes.

Systemic Effects of Water Extract ofTetrapleura tetraptera, a Nigerian Plant Molluscicide Used in Schistosomiasis Control

AbstractThe effects of an aqueous extract of Tetrapleura tetraptera have been investigated in cats, dogs, rabbits and rats. Pharmacological examination showed that it possesses little or no hypotensive effect in cats, dogs and rabbits, but significantly depressed the blood pressure of anaesthetized rats. It had little or no effect on the PQRST complex of rats and dogs, aortic/dP/dt, LVPmax and LV dP/dt, respiratory rate and tidal volume, but dose-dependently decreased the cardiac effort index of these experimental animals. In one cat however, a cumulative dose of 136 mg/kg inhibited the neuromuscular activity of the cat tibialis anterior muscle in vivo. The concentration which caused this blockade (IC50 = 136 mg/kg in 4 h) is many times higher than the concentration required for molluscicidal activity in the laboratory and the field.

Topographic studies relating distribution of Ia- and γ-fibres in spinal cord and position of muscle spindles in cat tibialis anterior muscle

The segmental distribution of 115 Ia- and 115 paired gamma-fibres of the tibialis anterior muscle was studied in anaesthetized cats. All Ia-fibres recorded were found in the lumbar segments L6 and L7, from caudal L6 to middle L7. The paired gamma-axons were also mainly found in these parts of the spinal cord, only 7 gamma-fibres were localized in caudal L7. A total of 70% of all fibres was found in L7. Of the fibres constituting 'muscle spindle units' of the tibialis anterior 92.2% enter the same segment (a 'muscle spindle unit' is here defined as a muscle spindle with its Ia-fibres and one gamma-fibre innervating it). More than that, 88% of the afferent and efferent fibres of muscle spindle units were found in the same part of the segment. For the first time, the position of the muscle spindles was related to the location of their Ia- and gamma-fibres in the spinal cord. In general, the muscle spindles located in the proximal muscle region project to the more cranial part of the spinal cord and the muscle spindles localized distally in the muscle project to the more caudal part of the spinal cord. The topographic pattern of the muscle spindle units is discussed with respect to the topographically arranged monosynaptic reflex loop.

Effects on muscle of a toxin from indian cobra ( Naja naja naja) venom

—The mode of action of a purified toxin from Naja naja naja (Indian cobra) venom was investigated in frog rectus abdominis muscle, chick biventer cervicis muscle, cat tibialis anterior muscle (close-arterial) and in both innervated and denervated rat diaphragm muscle preparations. The toxin inhibited the acetyl-choline responses of rectus abdominis muscle. The inhibition was antagonized by neostigmine and increasing concentrations of acetylcholine, suggesting a competitive binding of the toxin to cholinergic receptors. The toxin, even at high doses, did not produce depolarizing contractures in chronically denervated diaphragm, biventer cervicis muscle and rectus abdominis muscle preparations. In both cat tibialis anterior and denervated diaphragm muscles, the toxin abolished the acetylcholine sensitivity of the muscles at a faster rate than its effects on muscle contraction, suggesting a preferred action on the motor end-plate. A well-maintained tetanic contraction and very poor post-tetanic potentiation was observed in all preparations treated with toxin, indicating an atypical Wedensky inhibition. Anti-curare agents, such as K + and Ca 2+, were ineffective in antagonizing the curare-like neuromuscular block in phrenic nerve-diaphragm preparations. A frequency-independent neuromuscular block observed in these nerve-muscle preparations was suggestive of the absence of a possible presynaptic effect. These results demonstrate that although the neurotoxin in some cases can imitate d-tubocurarine, its neuromuscular blocking activity is different from that of curare in many respects.

Preliminary Review of the Interactions of ORG NC 45 with Anaesthetics and Antibiotics in Animals

In vitro (rat hemidiaphragm) and in vivo (rat and cat tibialis anterior muscle preparation) studies of the interactions between Org NC 45 and some i.v. anaesthetics and antibiotics were carried out. With the exception of ketamine 1 mg kg-1 none of the drugs tested in vivo significantly changed the time course of an Org NC 45 bolus injection. All of the drugs caused an enhancement of the neuromuscular block using infusions in vivo and also in the in vitro preparations. Org NC 45 seems to be potentiated in a manner similar to pancuronium.

Frequency sweep analysis of neuromuscular junction continuity

A new technique for measuring neuromuscular junction continuity is described. Junctional transmission is evaluated by integration of the electromyographic (EMG) response induced by intramuscular electrical stimulation. The unique characteristics of this monitoring technique are the use of intramuscular stimulation and a varying stimulation rate. The stimulus frequency is made to increase exponentially from 1 to 100 pulses per second over a period of 10 or 15 seconds. Thin coiled wire electrodes are used for stimulation and recording of the EMG response. The frequency sweep electromyogram (FS-EMB) response was measured in uncurarized and curarized tibialis anterior muscle of cat. In the uncurarized preparation, the FS-EMG response was only slightly decreased with an increasing stimulus frequency. During neuromuscular blockade with d-tubocurarine the FS-EMG response diminished with increasing frequency. The response failed at successively lower frequencies during deeper levels of neuromuscular block. Recovery proceeded in the reverse order. The frequency sweep technique provides quantitative assessment of neuromuscular junction continuity over a broad spectrum of driving frequencies without inducing fatigue. This method does not require force measurements nor voluntary effort. Intramuscular stimulation minimises painful stimuli thus making the frequency sweep technique suitable for evaluating neuromuscular transmission in either conscious or unconscious individuals.

MULTIPEAKING OF THE COMPOUND ELECTROMYOGRAPHIC RESPONSE TO SINGLE NERVE STIMULUS: ITS OCCURRENCE AND PREVENTION IN AN EXPERIMENTAL MODEL

The compound electromyographic response to a single nerve stimulus was examined in the cat tibialis anterior muscle preparation, to determine the cause of and to find a method of preventing multipeaking of the waveform. Bundles of the sciatic nerve were separated and stimulated while the response was detected by unipolar electrodes and analysed with an instrument specifically designed for this purpose. It was found that the most cephalad bundle of the sciatic nerve at the sciatic notch innervated the tibialis anterior muscle and that restriction of stimulation to this bundle most readily rendered the response single-peaked. It is concluded that nerve-branching is a common cause, and therefore a straightforward alternative to "repetitive response of the muscle" as the explanation, of multipeaking of the neurally-elicited compound electromyogram. A method of eliciting and recording the compound electromyogram in the cat tibialis anterior model is described.

Scorpion ( Buthus minax, L. Koch) venom fractions with anticholinesterase activity

M. F. El-Asmar, M. Ismail, Kh. Ghoneim and O. H. Osman. Scorpion ( Buthis minax, L. Koch) venom fractions with anticholinesterase activity. Toxicon 15, 63–69, 1977.—Anticholinesterase activity was demonstrated in crude scorpion ( Buthus minax) venom. Venom fractions with similar activities were separated by cellulose acetate electrophoresis at pH 8·4 and by Biogel P 100 fractionation. Anticholinesterase activity was demonstrated towards both acylcholine-acyl-hydrolase (EC 3.1.1.8) and acetycholine-acetyl-hydrolase (EC 3.1.1.7). Both the crude venom and the fractions containing anticholinesterase activity increased the height of twitches of the rat phrenic nerve-hemidiaphragm preparation. The crude venom but not the fractions produced contracture of the cat tibialis anterior muscle preparation, followed by complete blockade of twitch activity. The crude venom markedly potentiated the contraction of the frog rectus abdominis muscle induced by acetylcholine, while none of the fractions showed such activity. Neither the crude venom nor the various fractions showed any effect on the superior cervical ganglion preparation of the cat nictitating membrane.

Some actions of 4,17a-dimethyl-4,17a-diaza-D-homo-5alpha-androstane dimethiodide (HS-342), a new neuromuscular blocking drug.

Abstract The effects of the newly-synthesized bisquaternary steroid 4,17a-dimethyl-4,17a-diaza-D-homo-5α-androstane dimethiodide (HS-342) have been investigated on the rat isolated phrenic nerve-hemidiaphragm, chick biventer cervicis and intact cat tibialis anterior muscle preparations, on the guinea-pig isolated ileum and on the rat isolated vas deferens preparations. The anticholinesterase activity of HS-342 was also measured. In the skeletal muscle preparations HS-342 exhibited properties of a post-junctionally active neuromuscular blocking agent of the non-depolarizing class. In the anaesthetized cat HS-342 exhibited approximately equal activity to that of tubocurarine, but its duration of action was about one-third of that of tubocurarine. HS-342 exhibited low anticholinesterase activity, low muscarinic blocking activity and apparently had no effect on the adrenergic neuroeffector junction studied.

Some studies on peripheral actions of mephenesin, methocarbamol and diazepam.

1. Mephenesin, methocarbamol and diazepam abolished polysynaptic reflex contractions of the cat tibialis anterior muscle elicited by stimulation of the homolateral femoral nerve.2. Mephenesin and methocarbamol caused a prolongation of the mean refractory period of directly or indirectly stimulated skeletal muscle. These effects were due to a direct action on the muscle fibres. There was no effect on responses to single stimuli.3. The increase in refractory period produced by mephenesin was greater in indirectly than in directly stimulated rat diaphragms. Experiments using the isolated phrenic nerve suggest that this difference is due to the local anaesthetic action of mephenesin.4. In the indirectly stimulated cat tibialis anterior muscle high frequency stimulation resulted in a non-maintained tetanus in the presence of mephenesin and methocarbamol.5. Diazepam was without peripheral effects on the responses of skeletal muscle.6. The results with mephenesin and methocarbamol are discussed in relation to their mode of action in reducing muscle spasm.

The neuromuscular blocking action of a series of bicyclic bis-oniu esters.

1. Thirteen bicyclic dicholine esters have been tested on mammalian and avian skeletal muscle preparations.2. One of the compounds exhibited depolarizing activity in all the preparations.3. Three of the compounds exhibited depolarizing or dual-blocking activity in avian and denervated mammalian preparations, but exhibited non-depolarizing blocking activity in innervated mammalian preparations.4. The remaining compounds exhibited non-depolarizing blocking activity with evidence of an additional facilitatory action.5. The activity exhibited was dependent upon the onium substituents and the structure of the bicyclic ring.6. All the compounds exhibited a choline-reversible block in the rapidly stimulated rat diaphragm preparation and six of them exhibited a secondary choline-reversible block of the rapidly stimulated cat tibialis anterior muscle.

A comparison between the effects of edrophonium and choline in the skeletal muscles of the cat.

The effects of edrophonium and choline have been compared with those of the depolarizing substances acetylcholine, decamethonium, and suxamethonium, in both innervated and chronically denervated tibialis anterior muscles of cats under chloralose anaesthesia. Both edrophonium and choline were more potent antagonists to paralysis by tubocurarine than could be accounted for by their ability to stimulate the motor end-plates directly. It appeared likely that direct depolarization of the end-plate played no part in the anti-curare action of edrophonium and only some part in the anti-curare action of choline. A paralysis produced by the neuromuscular blocking agent, benzoquinonium, was more readily antagonized by a tetanus or by acetylcholine, suxamethonium, and decamethonium than a similar paralysis produced by tubocurarine. The tetraethyl ammonium ion was also slightly more effective against a paralysis by benzoquinonium. On the other hand, edrophonium was about 300 times and choline about five times less potent as an antagonist to benzoquinonium than to tubocurarine. Furthermore, the previous administration of benzoquinonium abolished the antagonistic action to tubocurarine of normally effective doses of edrophonium and reduced that of choline. These results were similar to those previously obtained with neostigmine, physostigmine and ethyl pyrophosphate and suggested that there was some similarity in the mechanism of action of all of these substances. Benzoquinonium, therefore, showed promise as a useful pharmacological tool for distinguishing compounds with this particular type of action. These anti-curare compounds did not appear to act by cholinesterase inhibition, not by an increase in the sensitivity of the motor end-plates. In common with other workers, we suggest that there is a pre-synaptic mechanism of action.