An Unusual Type of Muscle-Fibre

1948 ◽  
Vol s3-89 (6) ◽  
pp. 139-141
Keyword(s):  
Connective Tissue ◽  
Muscle Fibre ◽  
Hollow Cylinder ◽  
Lumbricus Terrestris ◽  
Muscle Fibres ◽  
Single Nucleus ◽  
Unusual Type

The protractor muscles of the bristle-like chaetae of serpulids and sabellids consist of discrete fibres. Each fibre consists of a hollow cylinder of unstriped fibrils surrounded by a sheath of cytoplasm which is expanded into two or more frilled membranes extending along the fibre. The single nucleus lies in one of these membranes. The fibre is apparently ensheathed by a sarcolemma of fine connective tissue-fibres. Similar frilled membranes are present on the muscle-fibres in the walls of the ‘hearts’ of Lumbricus terrestris.

Distribution of acetylcholine receptors in the vicinity of nerve terminals on skeletal muscle of the frog

1972 ◽  
Vol 181 (1065) ◽  
pp. 431-440 ◽  
Keyword(s):  
Skeletal Muscle ◽  
Connective Tissue ◽  
Neuromuscular Junction ◽  
Muscle Fibre ◽  
Nerve Terminal ◽  
Acetylcholine Receptors ◽  
Postsynaptic Membrane ◽  
Muscle Membrane ◽  
Muscle Fibres ◽  
Nerve Terminals

1. The acetylcholine (ACh) sensitivity of muscle fibres at the neuromuscular junction of the frog was investigated in preparations in which the nerve terminals could be clearly seen. 2. ACh released iontophoretically from a micropipette that was precisely positioned at various points along the muscle fibre in the vicinity of the synapse showed that the peak chemosensitivity (up to 1900 mV/nC) is confined to an area of postsynaptic membrane within a few micra of the nerve terminal; a tenfold decline in sensitivity was obtained when the ACh was released only 5 to 10 μm from the terminal’s edge. It is estimated that most of the response obtained when ACh is released within 40 μm from the terminal (the area covered in this study) is due to diffusion to the immediate postsynaptic area. The extrasynaptic chemosensitivity of the muscle membrane was too low to be measured with the present methods. 3. The accuracy with which micropipettes could be positioned in synaptic areas and the clarity of viewing nerve terminals were improved by bathing the tissue in collagenase, which reduced the amount of connective tissue. The distribution of chemosensitivity remained unchanged by such treatment. The ACh response was not detectably altered when nerve terminals were lifted off the muscle, exposing the subsynaptic muscle surface.

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.

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.

scholarly journals Post-synaptic morphology of mouse neuromuscular junctions is linked to muscle fibre type

2020 ◽  
Author(s):  
Aleksandra M. Mech ◽  
Anna-Leigh Brown ◽  
Giampietro Schiavo ◽  
James N. Sleigh
Keyword(s):  
Motor Neuron ◽  
Muscle Fibre ◽  
Fibre Type ◽  
Neuromuscular Junctions ◽  
Fibre Diameter ◽  
Neuromuscular Diseases ◽  
Neuronal Morphology ◽  
Muscle Fibre Type ◽  
Muscle Membrane ◽  
Muscle Fibres

AbstractThe neuromuscular junction (NMJ) is the highly specialised peripheral synapse formed between lower motor neuron terminals and muscle fibres. Post-synaptic acetylcholine receptors (AChRs), which are found in high density in the muscle membrane, bind to acetylcholine released into the synaptic cleft of the NMJ, ultimately facilitating the conversion of motor action potentials to muscle contractions. NMJs have been studied for many years as a general model for synapse formation, development and function, and are known to be early sites of pathological changes in many neuromuscular diseases. However, information is limited on the diversity of NMJs in different muscles, whether muscle fibre type impacts NMJ morphology and growth, and the relevance of these parameters to neuropathology. Here, this crucial gap was addressed using a robust and standardised semi-automated workflow called NMJ-morph to quantify features of pre- and post-synaptic NMJ architecture in an unbiased manner. Five wholemount muscles from wild-type mice were dissected and compared at immature (post-natal day, P7) and early adult (P31-32) timepoints. Post-synaptic AChR morphology was found to be more variable between muscles than that of the motor neuron terminal and there were greater differences in the developing NMJ than at the mature synapse. Post-synaptic architecture, but not neuronal morphology or post-natal synapse growth, correlates with fibre type and is largely independent of muscle fibre diameter. Counter to previous observations, this study indicates that smaller NMJs tend to innervate muscles with higher proportions of fast twitch fibres and that NMJ growth rate is not conserved across all muscles. Furthermore, healthy pre- and post-synaptic NMJ morphological parameters were collected for five anatomically and functionally distinct mouse muscles, generating reference data that will be useful for the future assessment of neuromuscular disease models.Graphical Abstract

scholarly journals Memoirs: On the Nephridiostome of Lumbricus

1932 ◽  
Vol s2-75 (297) ◽  
pp. 165-179
Author(s):  
EDWIN S. GOODRICH
Keyword(s):  
Connective Tissue ◽  
Lumbricus Terrestris ◽  
Coelomic Epithelium ◽  
Lower Lip ◽  
Excretory Organ ◽  
Marginal Cells ◽  
Straightforward Interpretation

The structure of the nephridiostome of Lumbricus terrestris L. is described, including the anatomical relations of canal, gutter, central, and marginal cells and their cytological characters. The extent and relation of the lower lip to other parts are also described. An account of the development of the nephridium is given from the stage when the rudiment still bears a single large ‘funnel-cell’ bulging forwards through the septum into the coelom. The whole nephridiostome (excluding the covering of coelomic epithelium and the connective tissue) is shown to arise from the nephridial rudiment, wholely or partly from that part of the funnel-rudiment which is derived from the ‘funnel-cell’. Upper, lateral, and lower lips are all developed from the funnel rudiment in which the lumen becomes pierced. There is no evidence that the coelomic epithelium contributes any part of the true nephridiostome. The view sometimes put forward that the excretory organ of Lumbricus is a nephromixium is not founded on sound evidence, and is opposed to the simple straightforward interpretation of its morphology which follows most naturally from the facts and a comparison with lower forms.

The spindle and extrafusal innervation of a frog muscle

1957 ◽  
Vol 146 (924) ◽  
pp. 416-430 ◽  
Keyword(s):  
Muscle Fibre ◽  
Short Distance ◽  
Frog Muscle ◽  
Muscle Fibres ◽  
Intrafusal Muscle ◽  
Intrafusal Fibre ◽  
Unmyelinated Axons ◽  
Intrafusal Fibres ◽  
Break Up ◽  
Tonic System

In the frog muscle, ext. long. dig. IV, there are two or three spindle systems. Each consists of a bundle of intrafusal muscle fibres with two, three or four discrete encapsulated sensory regions distributed in mechanical series along it. A sensory region is usually comprised of the coiled branches of one afferent axon. These embrace the intrafusal fibres and ultimately form long fine varicose endings on or near them. The intrafusal striations appear to be lost for a short distance within the sensory region, and in this region the intrafusal fibre nuclei crowd together. The ‘small’ extrafusal efferents break up into trusses of fine unmyelinated axons and terminate as ‘grape’ end-plates, several of which can occur on the same muscle fibre. This is the ‘tonic’ system. The ‘large’ extrafusal efferents terminate as ‘Endbiischel’ end-plates on muscle fibres not supplied by grape endings. This is the ‘twitch’ system. Both ‘grape' and ‘twitch’ end-plates occur on the intrafusal bundle (probably on separate fibres) between the sensory regions. They are supplied by branches of ‘small’ or ‘large’ axons respectively, which also innervate extrafusal fibres. Thus like the extrafusals the intrafusal bundle is composed of ‘tonic’ and ‘twitch’ muscle fibres. This situation contrasts with that of the mammal, where extrafusals are exclusively ‘twitch’ fibres and intrafusals ‘tonic’.

Neuromuscular Physiology of the Longitudinal Muscle of the Earthworm, Lumbricus Terrestris

1974 ◽  
Vol 60 (2) ◽  
pp. 453-467
Author(s):  
C. D. DREWES ◽  
R. A. PAX
Keyword(s):  
Time Course ◽  
Longitudinal Muscle ◽  
Lumbricus Terrestris ◽  
Single Pulse ◽  
Repetitive Stimulation ◽  
Muscle Fibres ◽  
Mechanical Responses ◽  
Segmental Nerve ◽  
Earthworm Lumbricus ◽  
Stimulation Of

1. Patterns of innervation of the longitudinal muscle of the earthworm, Lumbricus terrestris, were examined electrophysiologically. 2. The longitudinal musculature of a segment is innervated by relatively few axons, a fast and slow axon being present in segmental nerve I and in the double nerve, segmental nerve II-III. 3. Single-pulse stimulation of the fast axon produces large external muscle potentials and small twitch-like contractions, which with repetitive stimulation are antifacilitating. 4. Repetitive stimulation of the slow axon produces large, slowly developing and sustained mechanical responses, with electrical and mechanical responses showing summation and facilitation. 5. The amplitude and time course of slow mechanical responses are related to the frequency of stimulation. 6. Individual longitudinal muscle fibres are innervated by either the fast or slow axon in a segmental nerve, or by both fast and slow axons. 7. No evidence was found for peripheral inhibitory innervation of the longitudinal muscle.

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