Showing papers in "The Journal of Physiology in 1960"

Interactions between motoneurones and muscles in respect of the characteristic speeds of their responses.

Abstract: In the preceding paper (Buller, Eccles & Eccles, 1960) evidence was presented which suggested that the differentiation of slow muscles of the cat hind limb to a large extent failed to occur after certain operative procedures on the spinal cord. This finding indicates that in some way the central nervous system controls muscle differentiation. A more analytic investigation into this postulated influence of nerve on muscle has been accomplished by dividing and cross-uniting nerves to fast and slow muscles, so that motoneurones formerly innervating the fast muscle come to innervate the slow muscle by virtue of the regenerative outgrowth of their fibres, and vice versa for the motoneurones of the slow muscle. The effect of this crossed innervation on the speed of muscle contraction has been tested at varying times after the cross-union. These investigations have also been carried out on animals subjected to the operative procedures on the spinal cord, as previously described (Buller et al. 1960). Cross-union experiments allow in addition an investigation into the possible effects in the reverse direction, i.e. of speed of muscle contraction on the conduction velocity of the axons and the after-hyperpolarization of the motoneurones which innervate it. A preliminary account of part of this investigation has already been published (Bulier, Eccles & Eccles, 1958).

The release of histamine and formation of a slow-reacting substance (SRS-A) during anaphylactic shock.

Abstract: The release of histamine during anaphylaxis has been demonstrated in several species and various tissues, but it is well known that histamine alone cannot satisfactorily account for all the effects on smooth muscle observed during the anaphylactic reaction. The experiments presented in the present paper show that in addition to the release of histamine, the antigen-antibody reaction results in the formation of another smoothmuscle-stimulating substance which causes a slow and long-lasting contraction of the guinea-pig ileum, and which is resistant to anti-histamine drugs. This substance will be referred to as SRS-A. The existence ofa slow-reacting substance in the effluent collected during shock from the perfused lungs ofthe guinea-pig was recognized by Kellaway & Trethewie (1940). They were, however, unable to separate its effect upon the guinea-pig gut from that of histamine in the effluent, and their evidence for its presence was based on the observation that the active effluent caused a more prolonged contraction of the gut than did histamine alone. The use of anti-histamine drugs now makes it possible to study SRS-A separately.

Differentiation of fast and slow muscles in the cat hind limb.

Abstract: Ranvier (1874) described the first systematic investigation of the contractions of the slow and fast limb muscles, and a further systematic investigation was made by Fischer (1908). Banu (1922), Denny-Brown (1929b) and Koschtojanz & Rjabinowskaja (1935) showed that all limb muscles were slow at birth and differentiation into the fast and slow types occurred in mammals during the first few weeks after birth. Recently it has been found that motoneurones innervating slow muscles have as a rule much longer after-hyperpolarizations following the discharge of an impulse than do the motoneurones supplying fast muscles (Eccles, Eccles & Lundberg, 1958). Thus the characteristic frequencies of discharge of these two types of motoneurones (Denny-Brown, 1929a; Granit, Henatsch & Steg, 1956; Granit, Phillips, Skoglund & Steg, 1957) are explicable by their intrinsic properties. The shorter after-hyperpolarization of motoneurones supplying fast muscles allows their fast frequency of firing, which is appropriately related to the contraction time of their muscles; and complementarily those motoneurones with longer after-hyperpolarizations have as a consequence frequencies of discharge appropriate to the slow muscles they innervate. It was, therefore, of interest to re-investigate the process of differentiation into fast and slow muscles, in an attempt to determine whether this appropriate matching ofmotoneurones to muscles was brought about by motoneurones influencing muscle differentiation, or, vice versa, by muscle influencing motoneurones. The present paper describes a detailed study of muscle differentiation as defined by various measurements of the speed of muscle contraction. It also describes the effects of various nerve lesions on this differentiation. A more analytical investigation is described in the following paper (Buller, Eccles & Eccles, 1960).

The acetylcholine sensitivity of frog muscle fibres after complete or partial denervation

Abstract: Structures deprived of their innervation become supersensitive to their normal chemical transmitter as well as to other substances (see Cannon & Rosenblueth, 1949). Nerve cells usually have a great number of fibres converging upon them and are 'innervated' at numerous points oftheir surface (Wyckoff & Young 1956). Skeletal muscle fibres may also be innervated at more than one point (Katz & Kuffler, 1941; Hunt & Kuffler, 1954), and slow muscle fibres may have many synapses distributed along their length (Couteaux, 1955). This morphological feature immediately prompts the question as to the effects of partial denervation of these tissues and how they compare with those which follow complete denervation.

Potassium contractures in single muscle fibres.

Abstract: It has been known for a long time that muscles can be made to contract by raising the potassium concentration in the external medium. In skeletal muscles these contractions are difficult to study, because potassium ions take some time to diffuse through the interspaces and the contractions which they set up are usually transient. The difficulties of interpretation become les acute if single fibres are employed; in that case, as was first shown by Kuffler (1946), a rise in external potassium concentration causes a rapid depolarization and a prompt contraction. The quantitative effects of sudden changes of potassium concentration on membrane potential have been described previously (Hodgkin & Horowicz, 1959, 1960); the present article deals with the effect of similar changes on the tension developed by single muscle fibres. For relevant work on whole muscles the excellent review of Sandow (1955) should be consulted.

The chemical excitation of spinal neurones by certain acidic amino acids.

Abstract: The presence of comparatively large quantities of glutamic acid in nervous tissue has led to speculation concerning its function therein (Waelsch, 1955). Hitherto metabolic aspects have been stressed, but the recent demonstrations of the action of y-amino-n-butyric acid (GABA) upon neurones (Curtis, Phillis & Watkins, 1959b) together with the metabolic relationship of this substance to glutamic acid (Waelsch, 1955) suggested that the actions of glutamic acid and related acidic amino acids upon neurones should be investigated. A preliminary report has been published (Curtis, Phillis & Watkins 1959a). The close similarity which has been observed between the action of cysteic acid and those of aspartic and glutamic acids has led to tha inclusion of the sulphonic acid also in this report.

On the permeability of end-plate membrane during the action of transmitter

Abstract: Movements of specific ions in excitable tissues have been emphasized by a number of recent experiments. In particular, there have been many quantitative experiments which show that the rising phase of the nerve impulse in invertebrate giant axons is associated with an inflow of sodium and the falling phase with an outflow of potassium (Hodgkin, Huxley & Katz, 1952; Hodgkin & Huxley, 1952) and similar selective permeability changes have been observed accompanying the propagated action potential in muscle fibres and in myelinated nerve fibres (Dodge & Frankenhaeuser, 1959; Hodgkin & Horowicz, 1959a). In addition, the inhibitory potentials observed in some nerve cells (Coombs, Eccles & Fatt, 1955; Edwards & Hagiwara, 1959), heart muscle fibres (Burgen & Terroux, 1953; Hutter & Trautwein, 1956; Trautwein & Dudel, 1958), and crustacean muscle (Fatt & Katz, 1953; Boistel & Fatt, 1958) have been shown to be produced by changes in permeability of the post-synaptic membrane to potassium and/or chloride ions. On the other hand, it has been considered that at the end-plate the transmitter produces a rapid simultaneous transfer of sodium and potassium, and possibly also of all other free ions on either side of the membrane (Fatt & Katz, 1951; del Castillo & Katz, 1954, 1955, 1956). An approximately linear relationship has been observed between the amplitude of the end-plate potential (e.p.p.) and the membrane potential, the equilibrium potential being about -15 mV (Fatt & Katz, 1951). A similar relationship has also been observed in the amplitude of end-plate current (e.p.c.) obtained when the membrane was clamped at a constant potential during neuromuscular transmission (Takeuchi & Takeuchi, 1959). The membrane potential at which e.p.c. becomes zero may be called provisionally 'e.p.c. equilibrium potential'. In the present experiment, the e.p.c. equilibrium potential was measured in solutions of various ionic composition and the ions which contributed to the e.p.c. were determined. It will be shown

Single unit activity in lateral geniculate body and optic tract of unrestrained cats.

Abstract: In two recent studies of the cat's striate cortex (Hubel, 1959; Hubel & Wiesel, 1959) single units were shown to react to light stimuli in a highly specific manner. Most units responded either feebly or not at all to stimulation of the retina with diffuse light, but gave brisk responses to stationary or moving restricted spots of light. Responses to moving spots often varied with the direction of movement. It was clear that such responses must be the result of complex integrative mechanisms. The present study was undertaken to find out whether similar responses occur in retinal ganglion cells or cells of the dorsal lateral geniculate body. Lateral geniculate units have not previously been studied with restricted light stimulation, and although the cat's retinal ganglion cell has been extensively investigated by Kuffler and his co-workers (Kuffler, 1953; iKuffler, FitzHugh & Barlow, 1957), responses to moving spots were not examined. Thus it has not been possible to say whether the complex activity of cortical units originates in the cortex itself, or at lower levels. Methods for stereotaxic depth recordings in the unanaesthetized unrestrained animal were developed in order to make cortical and depth studies under similar conditions. These techniques make it possible to record from single units from virtually any part of the brain of the freely moving animal.

The fine structure of the neuromuscular junction of the frog.

Abstract: In recent years fairly detailed information has been obtained on the physiological events which occur at the vertebrate neuromuscular junction. Experiments on frog and mammalian muscle have shown that the transmitter, acetylcholine, is released from the axon terminals in discrete multi-molecular packets, and attention has been directed to the presence of submicroscopic 'vesicles' inside the nerve endings and their possible significance in the quantal distribution of the transmitter agent (de Robertis & Bennett, 1954, 1955; del Castillo & Katz, 1956; Robertson, 1956b; Palay, 1956; de Robertis, 1958; Reger, 1958; Katz, 1958). The purpose of the present work was to examine in more detail the submicroscopic structure of the myoneural junction in the frog from which the greater part of the physiological evidence had been derived. The basic information on the structure of this synapse is already available, as a result of the remarkable microscopic and histochemical studies of Couteaux (1947, 1955, 1958).

Receptive fields of optic nerve fibres in the spider monkey.

Abstract: Our present knowledge ofhow mammalian retinal ganglion-cell receptive fields are organized is based mainly on findings in the cat by Kuffler (1953). These results have since been confirmed and extended (Barlow, FitzHugh & Kuffler, 1957; Hubel, 1960; Wiesel, 1960), but up to now similar studies have not been made in primates. The retina of the monkey is of interest, since in most species, including Ateles (spider monkey) and Macaca mulatta, it is deeply pigmented and has a well defined fovea. It appears to be much closer to the human retina than to that of the cat, which has a highly reflectile tapetum and lacks a fovea. The purpose of this report is to describe the receptive fields of single optic nerve fibres in the spider monkey. In view of the monkey's ability to discriminate colours, some observations were also made on ganglion cell responses to monochromatic stimuli.

Functional analysis of group III afferent fibres of mammalian muscles.

Abstract: It is generally accepted that the myelinated afferent fibres of some muscle nerves fall into three groups according to the diameter of their nerve fibres (Lloyd, 1943; Lloyd & Chang, 1948; Rexed & Therman, 1948; Hagbarth & Wohlfart, 1952), a grouping also borne out by electrophysiological studies (Hunt, 1954). The fibres of Group I (12-20 p) arise from muscle spindles and Golgi tendon organs (Hunt & Kuffler, 1951; Hunt, 1954). Those of Group II (4-12,u) also arise from muscle spindles (Merton, 1953; Hunt, 1954) but not from tendon organs (Hunt, 1954). Further, recent evidence indicates that the Group II fibres probably arise from the secondary endings of the muscle spindle (Cooper, 1959). So far nothing is known about the endings of Group III afferent fibres (1-4,u), although there is considerable information about the distribution of fibre diameters within this group in different muscle nerves (Lloyd & Chang, 1948; Rexed & Therman, 1948; Hagbarth & Wohlfart, 1952). As will become clear from the present paper, this gap in our knowledge of the sensory innervation of muscles was apparently due to the difficulty in stimulating some of the Group III endings and also to certain experimental procedures followed by previous workers. The experiments to be described in this paper were therefore, at first, specifically designed to elucidate the behaviour of these Group III endings, the basic procedure being to isolate a Group III afferent fibre, i.e. one with a conduction velocity below 24 m/ sec, and then to determine how its ending could be stimulated. The results of this procedure have revealed that most Group III afferent fibres end in pressure receptors, i.e. receptors that are stimulated by local pressure but not by stretching the muscle or by asphyxia. Hitherto little attention has been paid to these receptors owing to the general belief that there are few of them in muscles (Hagbarth & Wohlfart, 1952). However, the recent

The mechanical properties of relaxing muscle

Abstract: The response of a muscle to stimulation is classically divided into two phases: contraction and relaxation. The mechanical properties of the muscle in the first phase have been extensively studied (for references, see Jewell & Wilkie, 1958) and much is known about the way in which tension is developed and work is done, but the second phase is much less clearly understood. A. V. Hill (1949b) defined relaxation simply in terms of the external mechanical changes in the muscle, as 'the process by which the muscle returns, after contraction, to its initial length or tension'. Originally our interest in relaxation was aroused by the marked difference between the time courses of isotonic and of isometric twitches. For instance, in Fig. 1, one is confronted by the apparently paradoxical situation that after having lifted a load of 3 g wt. the muscle has completely relaxed at a time when it could have borne tension of 5 g wt. under isometric conditions. Admittedly, with small loads like this, the situation is complicated by an additional factor, for in the isotonic case the muscle has shortened appreciably. However, even with large loads, where the isotonic shortening is much less, mechanical activity has apparently ended at a time when the isometrically contracting muscle is still capable of bearing a considerable tension.

Supersensitivity of skeletal muscle produced by botulinum toxin.

Abstract: In a chronically denervated mammalian skeletal muscle the entire membrane becomes sensitive to applied acetylcholine (ACh). About 4 days after denervation, the size of the ACh-sensitive area at the end-plate starts to increase and a few days later covers the larger part or all of the muscle membrane (Axelsson & Thesleff, 1959). The conversion of the membrane, following denervation, into an AChsensitive surface might be due to the absence of some chemical influence exerted when the motor innervation is intact. The purpose of the present investigation was to see whether or not the release of the chemical transmitter agent might provide such an influence. Use was made of botulinum toxin, which is considered to prevent release of ACh from cholinergic nerve terminals (Burgen, Dickens & Zatman, 1949; Brooks, 1956). This mode of action of the toxin was confirmed, and it will be shown that when the transmitter output was reduced or abolished the size of the receptor area in muscle started to increase in a manner which was identical with that observed after denervation.

The antagonism between tubocurarine and substances which depolarize the motor end‐plate

Abstract: It is well known that acetylcholine (ACh) depolarizes the end-plate region of skeletal muscle, and that this action can be blocked by tubocurarine (Cowan, 1936; Kuffler, 1943). By using the contracture response of the frog's rectus as a measure of drug action, several workers (van Maanen, 1950; Kirschner & Stone, 1951; Ariens, van Rossum & Simonis, 1956) have studied this antagonism quantitatively, concluding that these and several related substances compete for receptors at the end-plate, as originally proposed by Langley (1905). In the present work the action of tubocurarine has been examined by the more direct method of determining the effect ofknown concentrations on the end-plate depolarizations evoked by bath-applied ACh or carbachol. Extracellular recording was used for the most part, but in some experiments micro-electrodes were employed to measure the responses of single fibres. In this way it was found that individual end-plates have similar affinities for tubocurarine.

Actions of pure bradykinin.

Abstract: Bradykinin, first described by Rocha e Silva, Beraldo & Rosenfeld (1949), is one of a group of polypeptides called plasma kinins. Plasma kinins are known to stimulate certain types ofsmooth muscle, to cause vasodilatation, to increase capillary permeability and to produce pain when brought into contact with pain fibres. It has not been clear hitherto whether bradykinin is responsible for all these actions or whether several peptides are involved, as in all experiments crude extracts have been employed. However, recently bradykinin has been isolated (Elliott, Lewis & Horton, 1960a) and its structure determined (Elliott, Lewis & Horton, 1960b,c). It is therefore now possible to examine the actions of the pure peptide. The present investigation was carried out to answer the question, does the crude preparation of bradykinin contain one peptide having all the actions reported for the crude mixture, or does it contain a group of related peptides each of which is responsible for one or more of the biological actions? The results show that pure bradykinin possesses all the actions of the crude mixture, that is, smooth-muscle stimulation, vasodilatation, increased capillary permeability and pain production.

Dynamics of accommodation responses of the human eye.

Abstract: It is not till recently that an optometer has become available (Campbell, 1956; Campbell & Robson, 1959) that enables one to obtain continuous, high-resolution records of changes in the refractive power of the human eye. Using this optometer we have investigated the nature of the accommodation responses when young emmetropic subjects were presented monocularly with a variety of focus-stimulating conditions.

A quantitative study of sensitive cutaneous thermoreceptors with C afferent fibres.

Abstract: It has been demonstrated that heating or cooling the cat's skin can elicit a discharge of impulses in slowly-conducting (C) afferent fibres (Iggo, 1958b, 1959a, b; Douglas, Ritchie & Straub, 1959; Douglas & Ritchie, 1959). However, it was not clear whether the C group contained fibres from 'specific' thermoreceptors comparable in sensitivity with those in the cat's tongue (Hensel & Zotterman, 1951 a; Dodt & Zotterman, 1952). Most of the C fibre thermoreceptors hitherto found responded only to rather extreme heating or cooling (Iggo, 1959 a, b) and therefore were possibly concerned with pain. They were relatively insensitive to mechanical stimulation. There are also numerous C fibres which respond both to mild mechanical stimulation and to sudden cooling of the skin (Douglas et al. 1959; Iggo, 1959a). They have been classified as mechanoreceptors by Iggo (1960). In the present investigation sensitive specific cold and warm receptors with afferent C fibres have been found and their behaviour has been studied quantitatively. The opportunity has also been taken to examine quantitatively the responses of C heat receptors (Iggo, 1959b) and of a few C mechanoreceptors to thermal stimulation. A preliminary account of these results has been published (Hensel, Iggo & Witt, 1959).

The effect of sudden changes in ionic concentrations on the membrane potential of single muscle fibres

Abstract: In an earlier paper on single muscle fibres (Hodgkin & Horowicz, 1959), we showed that the displacements of membrane potential produced by changes in the external ionic concentration were quantitatively consistent with the idea that the membrane potential is determined by the concentration ratios of the potassium and chloride ions. Without making further measurements it might be supposed that the rate of change of membrane potential in response to a sudden alteration of [K]o or [Cl]o would also be of a relatively simple kind. If ions in the extemal solution could reach the membrane without appreciable delay, the rate of change of membrane potential should be determined by the membrane time constant, which is normally about 30 msec (Fatt & Katz, 1951). If there were a straightforward diffusion delay it should be possible to measure the delay in one record and to predict the shape of all other records. The results described here show that the actual situation is more complicated, the main findings being that [Cl]o affects the membrane potential more rapidly than [K]o and that the depolarization associated with a rise of [K]0 is quicker than the repolarization associated with a fall. A partial explanation is that the sites which are sensitive to potassium ions are less accessible than those which are sensitive to chloride and that appreciable quantities of potassium can be retained in a special region of the fibre. This suggestion accounts for a number of puzzling observations, but something further is needed to explain why the effect of a rise in [K]0 is so much more rapid than that of a fall. In the present paper the words rapid and slow have a different meaning from those used in our previous article (Hodgkin & Horowicz, 1959). In describing the earlier results, any change taking place in less than a minute was regarded as 'rapid' and the word 'slow' was reserved for the drifts in membrane potential, lasting minutes or hours, that are associated

The chloride conductance of frog skeletal muscle.

Abstract: It has long been established that the cell membrane of skeletal muscle is permeable to chloride ions (Boyle & Conway, 1941), but the magnitude of the chloride conductance did not immediately attract attention. Recently Hodgkin & Horowicz (1957b, 1959b) have shown that under some conditions changes in the chloride concentration ratio may have a greater effect on the membrane potential than equivalent changes in the distribution of potassium; and Hutter & Padsha (1959) have found a decrease in the membrane conductance by more than one half on replacement of chloride by less permeant anions. The indication is that chloride contributes the major share to the membrane conductance. The aim of the present experiments was to determine the proportion of the resting membrane conductance attributable to chloride by measuring the conductance change on replacement of chloride by an impermeant anion. Sulphate is know to be impermeant (Conway & Moore, 1945), but has the disadvantage of reducing the concentration of ionized calcium. The monovalent anions methylsulphate and pyroglutamate (Boistel & Fatt, 1958) have therefore been used as substitutes for chloride. The results show that in the resting state chloride ions account for 68% of the total membrane conductance. The opportunity has also been taken to study the influence of chloride on the electrical and mechanical response of skeletal muscle.

The absence of position sense in the human eye.

Abstract: It has been widely held (e.g. Sherrington, 1918; Hoffmann, 1934, p. 28) that we have a sense of position of the eyeball which depends on afferent nerve fibres from the extraocular muscles. However, the experiments of Helmholtz (1867) indicate that such a position sense, if it exists, is not used to correct visual impressions when the eye is passively displaced. The following experiments, done on four subjects, show that the eye has no position sense.

Properties of regenerating neuromuscular synapses in the frog

Abstract: Regeneration of nerve fibres into frog (R. temporaria) sartorius muscles was examined after either complete or partial denervation. The former was achieved by section of the sciatic nerve in the pelvis: the nerve is very easily exposed at a point just rostral to the pyriformis and vastus externus muscles. A stretch of nerve 4-5 mm long was usually removed, but when a longer delay in regeneration was desired, the 7th, 8th and 9th spinal nerves were resected together with the sciatic. In some instances complete denervation was obtained by dividing the sartorius nerve in the muscle itself. Partial denervation consisted in section and removal of one or more of the intramuscular nerve branches (see Miledi, 1960a). At different times after denervation, both sartorii and their nerves were dissected and mounted side-by-side for examination with intracellular micro-electrodes. Acetylcholine (ACh) was applied either diffusely to the two muscles by perfusion of the chamber, or locally to a muscle fibre by iontophoresis through a micropipette. Neostigmine 10-6 (w/v) was generally added to the solutions, except when iontophoretic microapplication of ACh was made. The experiments were made from August 1958 to June 1959. For a more detailed account of the experimental procedures see Miledi (1960a).

The osmotic effects of some simple molecules and ions on gastric emptying.

Abstract: The idea that the rate of emptying of the stomach is strongly influenced by the osmotic pressure of the gastric contents stems from the experiments of Carnot & Chassevant (1905). They found that in dogs with duodenal fistulae saline nearly isosmotic with plasma left the stomach more rapidly than saline solutions which were more concentrated or more dilute. The influence of the concentration of salt on gastric emptying appears to be much the same in man as it is in dogs. Shay & Gershon-Cohen (1934) in their radiographic studies noted that tap water left the stomach more slowly than isotonic saline. They also concluded that in order to slow emptying-presumably relative to the emptying oftap water-' hypertonic' solutions of salts and glucose were necessary, whereas hydrochloric acid slowed emptying in solutions less concentrated than plasma in terms of milli-osmoles per litre. The present experiments, extending those described by Hunt in 1956, are a study of the working of the receptors concerned in the slowing of gastric emptying that appear to be sensitive to the osmotic properties of the luminal contents of the duodenum and small intestine (Shay & Gershon-Cohen, 1934). The results of some experiments with acids which probably work differently (Sircus, 1958) are also described for comparison.

Junctional and extra-junctional acetylcholine receptors in skeletal muscle fibres.

Abstract: While examining the sensitivity of frog muscle fibres to acetylcholine (ACh) applied from a micro-electrode it was noticed that the reactive portion of the fibre appeared to be greater than the neuromuscular junction itself (Miledi, 1959). On account of the length and variability of the junctional nerve branches in the frog (Kuhne, 1887; Couteaux, 1947; Cole, 1955), it is difficult to make there a proper comparison between the extent ofthe muscle fibre sensitive to ACh and that ofthe synaptic contact. It was therefore decided to repeat these experiments on neuromuscular junctions of the rat diaphragm, where the synaptic region occupies a circular surface area of only 19-28,u diameter (Cole, 1957).