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  • 1
    Electronic Resource
    Electronic Resource
    The anatomy and fine structure of the echidnaTachyglossus aculeatus snout with respect to its different trigeminal sensory receptors including the electroreceptors (1991)
    Springer
    Anatomy and embryology 184 (1991), S. 371-393 
    Details
    ISSN: 1432-0568
    Keywords: Tachyglossus aculeatus (echidna) ; Echidna bill ; Sensory receptors ; Electroreceptor ; Mechanoreceptor ; Trigeminal nerve ; Monotreme ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The gross anatomy and nerve supply of the bill of echidna (Tachyglossus aculeatus) is described in relation to its function as an outstanding sensory organ. The sensory innervation of the skin of the echidna snout was investigated by means of frontal serial sections, after decalcification of the specimens. A comprehensive light and electron microscopic description of the location and fine structure of cutaneous sensory receptors of the trigeminal system was made by this means. The encapsulated and non-encapsulated Ruffini receptors, the types of other free receptors in the connective tissue and the Merkel cell receptor do not differ morphologically from those of higher mammals, whereas the pacinian-like corpuscle shows a unique organization of its outer core. This is composed of large perineural cells containing a unique reticulum of parallel-orientated endoplasmic membranes. Lamellated corpuscles, seen in isolation or in association with push rods, are numerous in the snout and in the tip of the tongue of echidna. Push rod receptor organs occur in the hairless skin of the bill with a very dense array at its rostral end and in the pseudopalatal ridges. Gland duct receptors are restricted to the skin adjacent to the nostrils and the mouth opening, including the pseudopalatal plates. Only about one quarter of the total number of 400 seromucous glands receive a sensory innervation of their intraepidermal duct segment. Within each innervated gland two types of receptor terminals are identified. The distributions of the different receptor types are mapped for different regions of the skin, the mucous membrane of the nasal and oral vestibule and the tip of the tongue. The fine structure of nerve terminals is discussed from a comparative anatomical point of view, and some speculations are made about possible transduction processes that underlie the known electrophysiological properties. The sensory organs such as the “push rod” and “gland duct receptor”, and most of their sensory terminals, are less differentiated in echidna snout than in the platypus (Ornithorhynchus anatinus) bill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00957899
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  • 2
    Electronic Resource
    Electronic Resource
    Sprouting of fusimotor neurones after partial denervation of the cat soleus muscle (1992)
    Springer
    Experimental brain research 90 (1992), S. 369-374 
    Details
    ISSN: 1432-1106
    Keywords: Muscle spindle ; Fusimotor ; Extrafusal ; Motor unit ; Contraction ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Normally, γ motoneurones innervate only the intrafusal fibres of muscle spindles. This is a report of sprouting of γ motoneurones to innervate extrafusal muscle fibres following partial denervation of the soleus muscle of kittens. In eight newborn animals, the L7 ventral root was cut on one side under anaesthesia and the animals were then allowed to recover. At approximately 100 days of age animals were reanaesthetised and a study made of mechanical properties of motor units whose axons ran in the S1 ventral root and supplied the partially denervated soleus muscle. Evidence was obtained for sprouting of all surviving α motoneurones. In addition, in four experiments axons conducting within the γ range, on stimulation, produced measurable tension. In one experiment, stimulation of one such γ axon also produced specific fusimotor effects on four afferents identified as coming from primary endings of muscle spindles. The γ axon was therefore a fusimotor axon. The effect observed on stimulation of the γ axon suggested a largely dynamic action. Other examples of γ axons were encountered that on stimulation produced tension, but which could not be specifically associated with spindles. In addition, a number of γ axons that did not develop tension were shown, on stimulation, to have fusimotor effects that were static in action. It is concluded that in extensively denervated muscles γ motoneurones may sometimes sprout to innervate extrafusal fibres. The mechanical properties of the extrafusal fibres innervated by such γ axons were similar to those of ordinary α motor units.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227250
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  • 3
    Electronic Resource
    Electronic Resource
    The responses of secondary endings of cat soleus muscle spindles to succinyl choline (1994)
    Springer
    Experimental brain research 100 (1994), S. 58-66 
    Details
    ISSN: 1432-1106
    Keywords: Muscle spindle ; Fusimotor Succinyl choline ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This report describes the effects of succinylcholine (SCh) on the secondary endings of cat soleus muscle spindles and attempts to explain them in terms of the action of the drug on intrafusal fibres. All but 2 of 41 secondary endings studied in detail showed a significant response to a single intravenous injection of 200 μg kg-1 SCh. This consisted of a rise in the resting rate or development of a resting discharge if the spindle had previously been silent and an increase in the response to stretch. The increases in the responses to stretch were weaker than those observed for primary endings of spindles, but were much larger than those of tendon organs, which showed very little effect with this concentration of drug. The response to SCh showed two features consistent with its action being mediated via an intrafusal muscle fibre contraction rather than a direct depolarising action on the afferent nerve ending. In the presence of SCh, secondary endings were able to maintain a discharge during muscle shortening at rates, on average, more than 5 times greater than under control conditions. Secondly, the increase in spindle discharge produced by SCh showed a length dependence similar to that for fusimotor stimulation. Further support for the action of SCh being principally via an intrafusal fibre contraction was provided by the observation that its effects were abolished by the neuromuscular blocker gallamine triethiodide. The time course of recovery of SCh responses, following their blockade by gallamine, was much slower than recovery of extrafusal tension and closely paralleled that for the recovery of fusimotor responses. In three separate experiments on the medial gastrocnemius muscle the possibility that SCh may exert an excitatory action on spindle sensory endings through the liberation of potassium ions from the muscle was tested by tetanic stimulation of the muscle. This had no detectable excitatory effect. Several observations were made on the effect of SCh on responses of cutaneous receptors. SCh did not change levels of spontaneous activity or responses to mechanical stimulation of either slowly or rapidly adapting mechanoreceptors. It was argued for both tendon organs and cutaneous receptors that if SCh had a direct action on the nerve ending at the concentrations used here, some responses of these receptors to the drug might have been expected. All of the above supports the view that secondary endings of spindles are able to respond to SCh by the development of an intrafusal fibre contracture. The question of the intrafusal fibre types involved is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227279
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  • 4
    Electronic Resource
    Electronic Resource
    The responses of frog muscle spindles during stimulation of slow motor axons (1982)
    Springer
    Experimental brain research 45 (1982), S. 364-370 
    Details
    ISSN: 1432-1106
    Keywords: Muscle spindles ; Slow axons ; Dynamic effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Responses of muscle spindles of the iliofibularis muscle of the frogLitoria aurea have been recorded during single shock and repetitive stimulation of single functional motor axons. Repetitive stimulation of axons which innervated slow muscle, and on four occasions, axons which innervated twitch muscle, produced a large increase in the dynamic response of the spindle to a ramp-and-hold stretch. While extrafusal slow muscle did not respond to a single motor volley, some spindles did, especially if at the same time the muscle was being stretched. In an explanation of the effect of muscle stretch on responses of spindles to slow motor volleys it was proposed that stretch acted to reduce the internal motion in muscle fibres produced by a non-uniform distribution of sarcomere lengths. It was proposed that this kind of effect may account for dynamic fusimotor actions in all vertebrate spindles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01208596
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  • 5
    Electronic Resource
    Electronic Resource
    The transformation of cross-reinnervated slow-twitch muscle after deafferentation in the cat (1984)
    Springer
    Experimental brain research 55 (1984), S. 152-157 
    Details
    ISSN: 1432-1106
    Keywords: Deafferentation ; Cross reinnervation ; Contractile properties ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cross-reinnervations were effected between the extensor digitorum longus and soleus muscles in the cat hind limb. At the same time dorsal root section or ganglionectomy was performed over segments L6-S1. Completeness of the deafferentation was subsequently confirmed either by dissection or by dorsal root recording. The isometric and forcevelocity properties of the muscles were measured. In animals with a unilateral cross plus deafferentation the conversion of the contractile properties of the normally slow-twitch soleus to those resembling a fast-twitch muscle was typical of that seen with an intact afferent supply. In cats with a bilateral cross-reinnervation and unilateral deafferentation there was no significant difference in the degree of transformation between the two sides. It is concluded that at least for the conversion of a slow-twitch to a fast-twitch muscle afferent feedback does not play a major role.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00240509
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  • 6
    Electronic Resource
    Electronic Resource
    Vibration-evoked responses from lamellated corpuscles in the legs of kangaroos (1986)
    Springer
    Experimental brain research 62 (1986), S. 648-653 
    Details
    ISSN: 1432-1106
    Keywords: Receptors ; Afferent ; Pacinian ; Marsupials ; Sensory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A group of lamellated corpuscles are present in the interosseous region of the legs of macropod marsupials. Structurally, they are similar to, but simpler than the Pacinian corpuscles of eutherian mammals, in having fewer lamellae. Responses of mechanoreceptors with axons coursing in the interosseous nerve were recorded from filaments, containing single functional units, dissected from the sciatic nerve of the wallaby Thylogale billardierii. The receptors were all maximally sensitive to stimuli applied in the interosseous region, where the cluster of lamellated corpuscles is located. Most units had low mechanical thresholds and were sensitive to sinusoidal vibration over a wide range of frequencies. Functional properties generally resembled those of eutherian Pacinian corpuscles, but the marsupial receptors were less rapidly adapting. The afferent nerve fibres conducted at 45 to 60 ms−1, while the diameter of axons in the osmium-stained interosseous nerve ranged between 7.5 and 12 μm. It is suggested that one important function of the receptors might be the detection of ground-borne vibration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236045
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  • 7
    Electronic Resource
    Electronic Resource
    The discharge of cat tendon organs during unloading contractions (1985)
    Springer
    Experimental brain research 61 (1985), S. 222-226 
    Details
    ISSN: 1432-1106
    Keywords: Tendon organ ; Motor unit ; Contraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Tendon organs respond preferentially to contractions of a select set of motor units. If a tendon organ is given a resting discharge by raising the passive tension in the muscle, other motor units can be identified which on contraction interrupt the discharge, presumably by unloading the passive tension. These experiments investigate the possibility that stimulation of motor units with unloading effects can reduce the response of a tendon organ to a loading contraction. We find that over most of the range of muscle lengths the unloading contraction produces only a transient lowering of the firing rate. Only at short muscle lengths where further shortening is accompanied by a steep fall in tension is the unloading contraction able to induce a sustained reduction of afferent discharge.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235640
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  • 8
    Electronic Resource
    Electronic Resource
    Mechanical sensitivity of muscle afferents in a nerve treated with colchicine (1998)
    Springer
    Experimental brain research 119 (1998), S. 391-398 
    Details
    ISSN: 1432-1106
    Keywords: Key words Mechanoreceptor ; Axoplasm ; Muscle spindle ; Colchicine ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The experiments reported here demonstrate that the mechanical sensitivity of peripheral nerve fibres typically seen after injury can be induced without overtly injuring the nerve, but by simply applying colchicine topically to the nerve. In cats anaesthetised with pentobarbitone sodium, the medial gastrocnemius nerve was exposed and 10 mM colchicine applied topically for 15 min. The animals recovered from the operation normally and showed no subsequent motor deficit. Six days later animals were re-anaesthetised, a laminectomy carried out and responses recorded in single afferents at the level of the dorsal root. It was found that many afferents, particularly those with conduction velocities in the group II–III range, had become sensitive to local mechanical stimulation of the nerve in the region treated with colchicine and showed slowly adapting responses to stretch of the nerve. Many of the smaller fibres exhibited spontaneous activity. Mechanically sensitive afferents exhibited impulse conduction blocks at the colchicine-treated site. Some afferents, which appeared to conduct impulses normally through the treated region, were associated with muscle receptors having normal response properties. However, other muscle receptors were clearly abnormal and were insensitive to muscle stretch or contraction or exhibited only phasic responses. When the nerve was cut proximal to the colchicine-treated site, some, but not all, spontaneous activity was abolished. It was subsequently shown using a collision technique that the activity in some axons had its origin in the cell body in the dorsal root ganglion. In one experiment, it was shown that after nerve section proximal to the colchicine-treated region three of five axons switched their activity from a peripheral to a central origin. It is postulated that colchicine disrupts fast axonal transport of mechanically sensitive or voltage-sensitive ion channels, from the cell body to the peripheral terminals of the axons, leading to an accumulation of these channels at the treated site. This induces mechanical sensitivity and spontaneous activity. It is postulated that interruption of a retrogradely transported signal induces the spontaneous activity in the cell body. These experiments suggest that an important influence is exerted by the cell body on the peripheral terminals of mechanoreceptors to confer on them their normal response properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050354
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  • 9
    Electronic Resource
    Electronic Resource
    Vibration sensitivity of cat muscle spindles at short muscle lengths (1999)
    Springer
    Experimental brain research 124 (1999), S. 166-172 
    Details
    ISSN: 1432-1106
    Keywords: Key words Muscle spindle ; Vibration ; Capsule ; Connective tissue ; Resting discharge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Experiments are described in which the vibration sensitivity was tested for primary and secondary endings of soleus muscle spindles of the anaesthetised cat. The vibratory stimulus was applied longitudinally to the muscle tendon and, after locating the site of the spindle in the muscle, applied transversely to muscle fibres directly overlying the spindle. All measurements were made with the muscle slack, at 20 mm shorter than its maximum physiological length (L m–20 mm). Spindles were separated into two groups: spontaneous spindles, which maintained background activity at this length, and silent spindles, which did not. Two forms of muscle conditioning were used: hold-long, in which the muscle was stretched by 5 mm, contracted and then returned to the test length, and hold-test, in which a conditioning contraction was given at the test length. After hold-test, most spindles responded to longitudinal vibration; after hold-long, most did not. This difference in responsiveness was attributed to the presence or absence of slack in intrafusal and extrafusal fibres, due to the muscle’s thixotropic property. When the vibration was applied transversely, at a site directly overlying the spindle, responses of silent spindles continued to show thixotropic behaviour, whereas responses of spontaneous spindles were almost independent of the form of muscle conditioning. It is proposed that the ability of spontaneous spindles to maintain background activity at short muscle lengths is due to connective tissue or elastic fibre links between the sensory ending and the spindle capsule. The vibratory stimulus, applied transversely, reaches the sensory ending via these strands which, as non-muscle tissue, do not alter their mechanical state as a result of muscle conditioning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002210050611
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  • 10
    Electronic Resource
    Electronic Resource
    The relation between tension and axonal conduction velocity for motor units in the medial gastrocnemius muscle of the cat (1976)
    Springer
    Experimental brain research 26 (1976), S. 325-328 
    Details
    ISSN: 1432-1106
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234936
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