scholarly journals The surface membranes of muscle fibres

1937 ◽  
Vol 122 (827) ◽  
pp. 140-154 ◽  
Keyword(s):  
Action Potential ◽  
Muscle Fibre ◽  
Algal Cell ◽  
Surface Membrane ◽  
Sartorius Muscle ◽  
Muscle Fibres ◽  
Plant Vacuole ◽  
Injured Part ◽  
A Cell ◽  
Aqueous Layer

The electrical properties of muscle are best explained in terms of the state of polarization of the surface of the muscle fibre. The uninjured surface of an isolated frog sartorius muscle is equipotential. Localized injury causes the injured part to be electrically negative to the uninjured surface. This indicates that normally the outside of the surface is positive to the inside. The same condition appears to exist in nerve fibres. Stimulation of muscle or nerve causes an impulse to move along the fibre. This impulse is a phase of depolarization which passes longitudinally along the surface of the fibre. The action potential which is a consequence of the depolarization has been much studied, but little is yet known of the nature and properties of the surface membrane at which the depolarization occurs. A consideration of the results of studies on the electrical behaviour of large single plant cells promises to throw some light on this problem (Osterhout 1929, 1931, 1934, 1935). The protoplasm of a cell of Valonia or Nitella forms a layer about 10 μ thick surrounding an aqueous vacuole. This protoplasm consists probably of an outer and inner layer of non-aqueous material and an intermediate aqueous layer. The evidence for this derives from (1) the shape of the action potential curve, and (2) the fact that a circuit consisting of cell sap—protoplasmic layer—cell sap has a considerable e. m. f., which would not be so if the protoplasm were homogeneous. It is the purpose of this paper to apply the method of the second criterion to muscle fibre, and to study this “asymmetry” potential. It is difficult to apply the same criteria to a muscle as to a large single algal cell for the following reasons. (1) A muscle comprises many fibres and the response of the inner fibres to a solute in he external medium is governed by the time of diffusion of the solute into the muscle. (2) An algal cell and a muscle fibre are histologically dissimilar. (3) It is impossible to extract the semi-liquid contents of a muscle fibre in the way that sap can be taken from a large plant vacuole. And an aqueous solution cannot be prepared of the same inorganic salt composition as muscle fibre because the phosphate content is too high and causes precipitation of Ca and Mg.

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.

scholarly journals Histology of Muscle Development in Pigs, Epigenetics from Myotubes to Tapered Fibres

2021 ◽  
Vol 9 (6) ◽  
Author(s):  
Howard J. Swatland
Keyword(s):  
Connective Tissue ◽  
Muscle Fibre ◽  
Radial Growth ◽  
Muscle Development ◽  
Transverse Section ◽  
Longitudinal Growth ◽  
Sartorius Muscle ◽  
Muscle Fibres ◽  
Peroneus Longus ◽  
Peripheral Position

Pre-natal muscle development in pigs starts with myotubes (axial nuclei in a tube of myofibrils) and secondary fibres (peripheral nuclei on an axial strand of myofibrils). By the time of birth, the nuclei of myotubes move to a peripheral position like secondary fibres. As pre-natal secondary fibres grow in length, the number of fibres in a transverse section may appear to increase. This stereology may also occur in post-natal muscles that have tapered fibres anchored in endomysial connective tissue around adjacent fibres and with one or both ends not reaching the end of their fasciculus. Up to 100 days gestation, Peroneus longus (no tapered fibres) had larger (P < 0.001) diameter secondary fibres than Longissimus thoracis (with tapered fibres). Up to 100 days gestation, no radial growth of secondary fibres was detected, but myotubes decreased in diameter (P < 0.001).  From a curve showing the relative numbers of myotubes and secondary fibres, it was deduced that approximately 80% of muscle fibres in pigs are derived from secondary fibres. In post-natal Sartorius muscle there was an increase (P < 0.005) in the apparent number of muscle fibres attributed to longitudinal growth of tapered fibres. Myotubes located centrally within their fasciculi had the same position as slow-contracting fibres with a high myoglobin content in adult muscle. Post-natal changes in muscle fibre histochemistry were achieved through transitional types, probably neurally regulated rather than by differential longitudinal growth of tapered endings. Secondary fibres are important – they give rise to both the majority of muscle fibres in adult pigs and affect subsurface optical pathways and pork colourimetry.

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.

scholarly journals MICRURGICAL STUDIES IN CELL PHYSIOLOGY

1926 ◽  
Vol 10 (1) ◽  
pp. 9-21 ◽  
Author(s):  
Paul Reznikoff
Keyword(s):  
Heavy Metals ◽  
Metal Cation ◽  
Surface Membrane ◽  
The Other ◽  
Contractile Vacuole ◽  
Toxic Action ◽  
Cell Physiology ◽  
Relative Toxicity ◽  
A Cell

I. Plasmalemma. 1. The order of toxicity of the salts used in these experiments on the surface membrane of a cell, taking as a criterion viability of amebæ immersed in solutions for 1 day, is HgCl2, FeCl3&gt; AlCl3&gt; CuCl2&gt; PbCl2&gt; FeCl2. Using viability for 5 days as a criterion, the order of toxicity is PbCl2&gt; CuCl2&gt; HgCl2&gt; AlCl3&gt; FeCl3&gt; FeCl2. 2. The rate of toxicity is in the order FeCl3&gt; HgCl2&gt; AlCl3&gt; FeCl2&gt; CuCl2&gt; PbCl2. 3. The ability of amebæ to recover from a marked tear of the plasmalemma in the solutions of the salts occurred in the following order: AlCl3&gt; PbCl2&gt; FeCl2&gt; CuCl2&gt; FeCl3&gt; HgCl2. II. Internal Protoplasm. 4. The relative toxicity of the salts on the internal protoplasm, judged by the recovery of the amebæ from large injections and the range over which these salts can cause coagulation of the internal protoplasm, is in the following order: PbCl2&gt; CuCl2&gt; FeCl3&gt; HgCl2&gt; FeCl2&gt; AlCl3. 5. AlCl3 in concentrations between M/32 and M/250 causes a marked temporary enlargement of the contractile vacuole. FeCl2, FeCl3, and CuCl3 produce a slight enlargement of the vacuole. 6. PbCl2, in concentrations used in these experiments, appears to form a different type of combination with the internal protoplasm than do the other salts. III. Permeability. 7. Using the similarity in appearance of the internal protoplasm after injection and after immersion to indicate that the surface is permeable to a substance in which the ameba is immersed, it is concluded that AlCl3 can easily penetrate the intact plasmalemma. CuCl2 also seems to have some penetrating power. None of the other salts studied give visible internal evidence of penetrability into the ameba. IV. Toxicity. 8. The toxic action of the chlorides of the heavy metals used in these experiments, and of aluminum, is exerted principally upon the surface of the cell and is due not only to the action of the metal cation but also to acid which is produced by hydrolysis.

scholarly journals THE CAPILLARY PATTERN IN HUMAN MASSETER MUSCLE DURING AGEING

2013 ◽  
Vol 32 (3) ◽  
pp. 135 ◽  
Author(s):  
Erika Cvetko ◽  
Jiří Janáček ◽  
Lucie Kubínová ◽  
Ida Eržen
Keyword(s):  
Muscle Fibre ◽  
Masseter Muscle ◽  
3D Visualization ◽  
Fibre Length ◽  
Fibre Surface ◽  
Fibre Volume ◽  
Immunohistochemical Method ◽  
Muscle Fibres ◽  
Age Related ◽  
Novel Approach

The effect of ageing on the capillary network in skeletal muscles has produced conflicting results in both, human and animals studies. Some of the inconsistencies are due to non-comparable and biased methods that were applied on thin transversal sections, especially in muscles with complicated morphological structures, such as in human masseter muscle. We present a new immunohistochemical method for staining capillaries and muscle fibres in 100 µm thick sections as well as novel approach to 3D visualization of capillaries and muscle fibres. Applying confocal microscopy and virtual 3D stereological grids, or tracing capillaries in virtual reality, length of capillaries within a muscle volume or length of capillaries adjacent to muscle fibre per fibre length, fibre surface or fibre volume were evaluated in masseter muscle of young and old subjects by an unbiased approach. Our findings show that anatomic capillarity is well maintained in masseter muscle in old subjects; however, vascular remodelling occurs with age, which could be a response to changed muscle function and age-related muscle fibre type transformations.

The fate of foreign endplates in cross-innervated rat soleus muscle

1980 ◽  
Vol 208 (1171) ◽  
pp. 189-222 ◽  
Keyword(s):  
Muscle Fibre ◽  
Proximal Region ◽  
Presynaptic Terminal ◽  
Motor Axon ◽  
Muscle Fibres ◽  
Nerve Terminals ◽  
Axon Terminals ◽  
Adult Rat ◽  
Rat Soleus Muscle ◽  
Postsynaptic Site

After transplantation of the superficial fibular and the medial plantar nerve to neighbouring sites in the proximal region of adult rat soleus muscles many muscle fibres were initially innervated by axons in both foreign nerves after resection of the original soleus nerve. The foreign endplates were formed at ectopic sites and were often separately locatedon individual muscle fibres. After 3-4 weeks many endplates had been eliminated and most muscle fibres were innervated by only a single foreign axon. Many muscle fibres still had multiple esterase-staining endplate sites in the region innervated by the foreign nerve. On exami­nation by electronmicroscopy, some of these sites were seen to have lost their presynaptic terminal while the postsynaptic structure of the endplate remained intact. Other sites were only partially occupied by motor axon terminals. On each muscle fibre there was always at least one fully occupied endplate region. In some instances separate endplate sites on the same muscle fibre were innervated by branches of the same motor axon. We conclude that the elimination of endplates is due to a competitive interaction between motor axons innervating the same muscle fibre. Morphologically, the elimination of functional endplates is caused by a retraction of nerve terminals from the postsynaptic site.

scholarly journals SLCV–a supervised learning—computer vision combined strategy for automated muscle fibre detection in cross-sectional images

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7053
Author(s):  
Anika Rettig ◽  
Tobias Haase ◽  
Alexandr Pletnyov ◽  
Benjamin Kohl ◽  
Wolfgang Ertel ◽  
...  
Keyword(s):  
Computer Vision ◽  
Supervised Learning ◽  
Muscle Fibre ◽  
Cross Sections ◽  
Reconstruction Error ◽  
Muscle Fibres ◽  
Dice Similarity Coefficient ◽  
Cross Sectional ◽  
Staining Methods ◽  
Combined Strategy

Muscle fibre cross-sectional area (CSA) is an important biomedical measure used to determine the structural composition of skeletal muscle, and it is relevant for tackling research questions in many different fields of research. To date, time consuming and tedious manual delineation of muscle fibres is often used to determine the CSA. Few methods are able to automatically detect muscle fibres in muscle fibre cross-sections to quantify CSA due to challenges posed by variation of brightness and noise in the staining images. In this paper, we introduce the supervised learning-computer vision combined pipeline (SLCV), a robust semi-automatic pipeline for muscle fibre detection, which combines supervised learning (SL) with computer vision (CV). SLCV is adaptable to different staining methods and is quickly and intuitively tunable by the user. We are the first to perform an error analysis with respect to cell count and area, based on which we compare SLCV to the best purely CV-based pipeline in order to identify the contribution of SL and CV steps to muscle fibre detection. Our results obtained on 27 fluorescence-stained cross-sectional images of varying staining quality suggest that combining SL and CV performs significantly better than both SL-based and CV-based methods with regards to both the cell separation- and the area reconstruction error. Furthermore, applying SLCV to our test set images yielded fibre detection results of very high quality, with average sensitivity values of 0.93 or higher on different cluster sizes and an average Dice similarity coefficient of 0.9778.

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