Address of the President Sir Alan Hodgkin, O. M. at the Anniversary Meeting, 30 November 1973

1974 ◽  
Vol 185 (1078) ◽  
Keyword(s):  
Surface Membrane ◽  
Muscular Activity ◽  
Nerve Impulse ◽  
Muscular Contraction ◽  
Single Fibre ◽  
Muscle Fibres ◽  
Constant Length ◽  
Axon Membrane ◽  
Ultrastructural Studies ◽  
Mathematical Skill

The Copley Medal is awarded to Professor A. F. Huxley, F. R. S. A. F. Huxley has made outstanding contributions to our knowledge of the nerve impulse and of the mechanism by which muscle fibres are caused to contract. Jointly with Hodgkin, he introduced the powerful method of intracellular recording from nerve cells and showed that during the propagation of an impulse the mem­brane potential reverses its sign, and does not simply fall towards zero as had been widely believed. This work - interrupted by the 1939-45 war, but later resumed - led to the proposal that the impulse arises from a transient influx of sodium ions through the axon membrane. The ‘ionic theory’ of nervous conduction was then established by a series of convincing experiments and calculations for which Huxley later shared the Nobel Prize. Huxley next turned his attention to the mechanism of muscular contraction. He equipped himself for this purpose by inventing a new type of interference microscope. In experiments on living isolated muscle fibres, Huxley showed that contraction is accompanied by a shortening of the isotropic band of each sarco­mere, while the remaining portion (the anisotropic band) retains approximately constant length. His findings complemented the important ultrastructural studies of H. E. Huxley and led them both to propose a ‘sliding filament’ mechanism as the basis of muscular motion. During further microscopic observations on the living muscle fibre, A. F. Huxley produced most striking evidence on the way in which an excitatory potential change of the surface membrane is communicated, through local tubular channels, to the interior of the fibre where it activates the contractile elements. In his most recent work, A. F. Huxley has continued to develop his single-fibre technique to resolve even finer details of the dynamic changes which occur during muscular activity. His work is characterized by a rare combination of profound theoretical insight, mathematical skill and superb technical mastery, all of which has enabled him to select problems of first-rate importance and to pursue them with outstanding success.

Address of the President Sir Alan Hodgkin, O. M. at the Anniversary Meeting, 30 November 1973

1974 ◽  
Vol 336 (1604) ◽  
Keyword(s):  
Surface Membrane ◽  
Muscular Activity ◽  
Nerve Impulse ◽  
Muscular Contraction ◽  
Single Fibre ◽  
Muscle Fibres ◽  
Constant Length ◽  
Axon Membrane ◽  
Ultrastructural Studies ◽  
Mathematical Skill

The Copley Medal is awarded to Professor A. F. Huxley, F. R. S. A. F. Huxley has made outstanding contributions to our knowledge of the nerve impulse and of the mechanism by which muscle fibres are caused to contract. Jointly with Hodgkin, he introduced the powerful method of intracellular recording from nerve cells and showed that during the propagation of an impulse the membrane potential reverses its sign, and does not simply fall towards zero as had been widely believed. This work – interrupted by the 1939–45 war, but later resumed – led to the proposal that the impulse arises from a transient influx of sodium ions through the axon membrane. The ‘ionic theory’ of nervous conduction was then established by a series of convincing experiments and calculations for which Huxley later shared the Nobel Prize. Huxley next turned his attention to the mechanism of muscular contraction. He equipped himself for this purpose by inventing a new type of interference microscope. In experiments on living isolated muscle fibres, Huxley showed that contraction is accompanied by a shortening of the isotropic band of each sarcomere, while the remaining portion (the anisotropic band) retains approximately constant length. His findings complemented the important ultrastructural studies of H. E. Huxley and led them both to propose a ‘sliding filament’ mechanism as the basis of muscular motion. During further microscopic observations on the living muscle fibre, A. F. Huxley produced most striking evidence on the way in which an excitatory potential change of the surface membrane is communicated, through local tubular channels, to the interior of the fibre where it activates the contractile elements. In his most recent work, A. F. Huxley has continued to develop his single-fibre technique to resolve even finer details of the dynamic changes which occur during muscular activity. His work is characterized by a rare combination of profound theoretical insight, mathematical skill and superb technical mastery, all of which has enabled him to select problems of first-rate importance and to pursue them with outstanding success.

Linear electrical properties of striated muscle fibres observed with intracellular electrodes

1964 ◽  
Vol 160 (978) ◽  
pp. 69-123 ◽  
Keyword(s):  
Electrical Properties ◽  
Striated Muscle ◽  
Surface Membrane ◽  
Fibre Surface ◽  
Step Function ◽  
Muscle Fibres ◽  
Appreciable Effect ◽  
Current Application ◽  
Current Path ◽  
Wide Range

The linear electrical properties of muscle fibres have been examined using intracellular electrodes for a. c. measurements and analyzing observations on the basis of cable theory. The measurements have covered the frequency range 1 c/s to 10 kc/s. Comparison of the theory for the circular cylindrical fibre with that for the ideal, one-dimensional cable indicates that, under the conditions of the experiments, no serious error would be introduced in the analysis by the geometrical idealization. The impedance locus for frog sartorius and crayfish limb muscle fibres deviates over a wide range of frequencies from that expected for a simple model in which the current path between the inside and the outside of the fibre consists only of a resistance and a capacitance in parallel. A good fit of the experimental results on frog fibres is obtained if the inside-outside admittance is considered to contain, in addition to the parallel elements R m = 3100 Ωcm 2 and C m = 2.6 μF/cm 2 , another path composed of a resistance R e = 330 Ωcm 2 in series with a capacitance C e = 4.1 μF/cm 2 , all referred to unit area of fibre surface. The impedance behaviour of crayfish fibres can be described by a similar model, the corresponding values being R m = 680 Ωcm 2 , C m = 3.9 μF/cm 2 , R e = 35 Ωcm 2 , C e = 17 μF/cm 2 . The response of frog fibres to a step-function current (with the points of voltage recording and current application close together) has been analyzed in terms of the above two-time constant model, and it is shown that neglecting the series resistance would have an appreciable effect on the agreement between theory and experiment only at times less than the halftime of rise of the response. The elements R m and C m are presumed to represent properties of the surface membrane of the fibre. R e and C e are thought to arise not at the surface, but to be indicative of a separate current path from the myoplasm through an intracellular system of channels to the exterior. In the case of crayfish fibres, it is possible that R e (when referred to unit volume) would be a measure of the resistivity of the interior of the channels, and C e the capacitance across the walls of the channels. In the case of frog fibres, it is suggested that the elements R e , C e arise from the properties of adjacent membranes of the triads in the sarcoplasmic reticulum . The possibility is considered that the potential difference across the capacitance C e may control the initiation of contraction.

Memoirs: The Muscles of the Adult Honey-bee (Apis mellifera L.)

1928 ◽  
Vol s2-71 (284) ◽  
pp. 563-651
Author(s):  
GUY D. MORISON
Keyword(s):  
Apis Mellifera ◽  
Alimentary Canal ◽  
Muscular Activity ◽  
Reproductive Organs ◽  
Muscle Fibres ◽  
Muscle Attachment ◽  
Apparent Lack ◽  
Histological Appearance ◽  
The Individual ◽  
Alary Muscles

1. The entire musculature of the alimentary canal is described in gross and in histological detail. The development of the muscle is considered. The innervation is described, likewise the tracheation and its relation to muscular activity and the bloodstream. 2. The heart is described with a detailed histological account of its muscle-fibres. Its tracheation is described and its apparent lack of innervation is discussed. 3. The ‘alary’ muscles of the dorsal diaphragm are described with a detailed account of their histology, innervation, and tracheation. 4. The ventral diaphragm is described as well as the histology, innervation, and tracheation of its muscle-fibres. The course of blood and physiological questions connected with it receive discussion. 5. The muscles of the reproductive organs of drone, queen, and worker are described with particular reference to the histology, innervation, tracheation, and physiology of their fibres. 6. The indirect muscles of the wings (fibrous muscle) have their histology, innervation, and tracheation described in detail. The method of contraction of the entire muscles and of the individual fibres and fibrils is discussed. The sarcosomes are described with their physiological significance to contraction. 7. The attachment of all the types of muscle found in the bee is described in histological detail. Different opinions of muscle attachment to chitin are summarized. 8. Throughout the paper, histological measurements are given for the various types of muscle-fibres and their nuclei in the three castes of bee. Since in the three castes the histological appearance is so similar for each type of muscle, the illustrations have been limited to portions of the muscles of worker bees.

Acetylcholine Receptors of Cultured Muscle Cells Demonstrated with Ferritin-α-Bungarotoxin Conjugates

1974 ◽  
Vol 16 (2) ◽  
pp. 473-479
Author(s):  
B. T. HOURANI ◽  
B. F. TORAIN ◽  
M. P. HENKART ◽  
R. L. CARTER ◽  
V. T. MARCHESI ◽  
...  
Keyword(s):  
Binding Sites ◽  
Acetylcholine Receptors ◽  
Surface Membrane ◽  
Freeze Fracture ◽  
Muscle Cells ◽  
Muscle Fibres ◽  
Toxin Binding ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Small Clusters

α-Bungarotoxin-ferritin conjugates were used to visualize by freeze-fracture and thin-section electron microscopy toxin-binding sites, presumably acetylcholine (ACh) receptors, in membranes of muscle cells grown in tissue culture. Toxin conjugated to ferritin by a glutaraldehyde reaction and purified by column chromatography in a buffer of high ionic strength remains active in blocking the effect of iontophoretically applied ACh. The potency of the conjugates was decreased 5-10 times compared to native α-bungarotoxin. Toxin-ferritin conjugates were identified in small clusters which were not uniformly distributed over the surface membrane. Binding was inhibited by preincubation in D-tubocurare or unconjugated toxin. The relation of the clusters to the non-uniform distribution of ACh sensitivity and α-bungarotoxin binding on cultured muscle fibres is discussed.

Detubulation experiments localise delayed rectifier currents to the surface membrane of amphibian skeletal muscle fibres

2004 ◽  
Vol 25 (4-5) ◽  
pp. 389-395 ◽  
Author(s):  
Jann Yee chin ◽  
Hugh R Matthews ◽  
James A Fraser ◽  
Jeremy N Skepper ◽  
Sangeeta Chawla ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Surface Membrane ◽  
Delayed Rectifier ◽  
Muscle Fibres ◽  
Skeletal Muscle Fibres

scholarly journals Cortical Oscillations during Gait: Wouldn’t Walking Be So Automatic?

2020 ◽  
Vol 10 (2) ◽  
pp. 90 ◽  
Author(s):  
Arnaud Delval ◽  
Madli Bayot ◽  
Luc Defebvre ◽  
Kathy Dujardin
Keyword(s):  
Posterior Parietal Cortex ◽  
Brain Activity ◽  
Muscular Activity ◽  
Cortical Activity ◽  
Muscular Contraction ◽  
Gait Pattern ◽  
Cortical Control ◽  
Time Frequency ◽  
Cortical Oscillations ◽  
Induced Changes

Gait is often considered as an automatic movement but cortical control seems necessary to adapt gait pattern with environmental constraints. In order to study cortical activity during real locomotion, electroencephalography (EEG) appears to be particularly appropriate. It is now possible to record changes in cortical neural synchronization/desynchronization during gait. Studying gait initiation is also of particular interest because it implies motor and cognitive cortical control to adequately perform a step. Time-frequency analysis enables to study induced changes in EEG activity in different frequency bands. Such analysis reflects cortical activity implied in stabilized gait control but also in more challenging tasks (obstacle crossing, changes in speed, dual tasks…). These spectral patterns are directly influenced by the walking context but, when analyzing gait with a more demanding attentional task, cortical areas other than the sensorimotor cortex (prefrontal, posterior parietal cortex, etc.) seem specifically implied. While the muscular activity of legs and cortical activity are coupled, the precise role of the motor cortex to control the level of muscular contraction according to the gait task remains debated. The decoding of this brain activity is a necessary step to build valid brain–computer interfaces able to generate gait artificially.

Visual identification of synaptic boutons on living ganglion cells and of varicosities in postganglionic axons in the heart of the frog

1971 ◽  
Vol 177 (1049) ◽  
pp. 485-508 ◽  
Keyword(s):  
Electron Microscopy ◽  
Cell Body ◽  
Ganglion Cells ◽  
Surface Membrane ◽  
Time Lapse ◽  
Interatrial Septum ◽  
Optical Systems ◽  
Muscle Fibres ◽  
Electron Microscopic ◽  
Synaptic Boutons

1. Parasympathetic neurons were studied in the transparent interatrial septum of the frog ( Rana pipiens ) with light- and electron-microscopic techniques. The aim was to identify visually cellular and subcellular details in a living preparation, especially synaptic boutons on ganglion cells and the varicosities in postganglionic axons supplying the muscles of the heart. 2. The interatrial septum contains the following nervous elements: unipolar parasympathetic ganglion cells, their preganglionic vagal innervation, postganglionic sympathetic axons and sensory fibres. These structures and the nuclei of their related Schwann cells can be viewed with various optical systems, especially differential interference contrast optics. The same neural elements identified in the live preparation can be sectioned for electron microscopy. 3. Most ganglion cells are innervated by a single presynaptic axon, terminating in up to 27 synaptic boutons which on the average cover about 3.0 % of the surface of nerve cell bodies. A few scattered boutons also occur on the initial axonal portion of the ganglion cells. 4. Synaptic boutons on ganglion cells were recognized in the living unstained preparation. Their identity was confirmed by electron microscopy and by light microscopy combined with methylene blue, zinc iodide and osmium, and cholinesterase staining methods. 5. The terminal branches of postganglionic axons have numerous varicosities along their course. Some are as close as a few hundred angstroms (10 Å = 1 nm) to muscle fibres, others are many pm away. There are two types of varicosities: (i) those which contain predominantly granular vesicles characteristic of neurons releasing catecholamines, and (ii) those with predominantly agranular vesicles which belong to the cholinergic axons of septal ganglion cells. Regardless of their distance from muscle fibres, the cholinergic varicosities have the same fine structural features, including membrane thickenings, as synaptic boutons on the ganglion cells. These findings support earlier suggestions that the varicosities along postganglionic axons are a series of transmitter release sites. 6. Varicosities were observed in the live septum; their identity was confirmed by subsequent electron microscopy. Many live varicose axons were traced back to the vicinity of individual septal ganglion cells. Additional evidence that they belonged to a particular ganglion cell, and were therefore cholinergic, was obtained by injecting Procion yellow into the cell body and observing the neuron with a fluorescence microscope after the dye had spread into the axonal processes. Time lapse photography of up to 24 h showed no ‘ peristaltic ’ movement of varicosities. 7. Granular or agranular vesicles also occur along cylindrical axons within nerve bundles many pm away from muscle fibres. Like the vesicles in varicosities, they are clustered close to ‘thickenings’ in the surface membrane and belong to postganglionic nerve fibres. 8. Ganglion cells in isolated septa survive for 2 weeks or longer, still giving membrane potentials and impulses. Time lapse cinematography for up to 2 weeks after removing the septum showed that the organelles within the neurons were in motion and that a two-way traffic takes place between the cell body and axon, as commonly found in cultured neurons.

The Florey Lecture, 1982 Discovery: accident or design?

1982 ◽  
Vol 216 (1204) ◽  
pp. 253-265 ◽  
Keyword(s):  
Electron Microscope ◽  
Muscle Fibre ◽  
19Th Century ◽  
Surface Membrane ◽  
Frog Muscle ◽  
Muscle Fibres ◽  
Personal Factors ◽  
Local Activation ◽  
Microscope Technique ◽  
The 19Th Century

The lecturer reviews the extent to which his own experiments on muscle have followed the course intended when they were planned. His observations on changes in the striation pattern were designed to reinvestigate the formation of ‘contraction bands’, repeatedly observed in the 19th century but neglected more recently. This phenomenon was indeed seen during active shortening,. but the most important outcome consisted of two quite unexpected observations which suggested the existence of a sliding-filament system. Experiments on local activation were planned on the hypothesis that activation was conducted inward from the surface membrane along the Z line. This was apparently confirmed in the first experiments, on fibres from frog muscle, but experiments on muscle fibres from other animals, together with improvements in electron microscope technique, showed that this was a coincidence and that the Z line as such is not involved. Investigation of the transient changes of tension when a stimulated muscle fibre is suddenly shortened required a series of exploratory measurements before a useful hypothesis could be formulated. Some personal factors that have motivated scientists, including Lord Florey himself, are discussed.

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