scholarly journals THE ULTRASTRUCTURE OF THE NEUROMUSCULAR JUNCTIONS OF MAMMALIAN RED, WHITE, AND INTERMEDIATE SKELETAL MUSCLE FIBERS

1970 ◽  
Vol 46 (1) ◽  
pp. 27-41 ◽  
Author(s):  
Helen A. Padykula ◽  
Geraldine F. Gauthier
Keyword(s):  
Skeletal Muscle ◽  
Endoplasmic Reticulum ◽  
Neuromuscular Junctions ◽  
Fiber Diameter ◽  
Fiber Types ◽  
Rat Diaphragm ◽  
Mitochondrial Content ◽  
Albino Rat ◽  
Contact Points ◽  
White Fiber

Distinct ultrastructural differences exist at the neuromuscular junctions of red, white, and intermediate fibers of a mammalian twitch skeletal muscle (albino rat diaphragm). The primary criteria for recognizing the three fiber types are differences in fiber diameter, mitochondrial content, and width of the Z line. In the red fiber the neuromuscular relationship presents the least sarcoplasmic and axoplasmic surface at each contact. Points of contact are relatively discrete and separate, and axonal terminals are small and elliptical. The junctional folds are relatively shallow, sparse, and irregular in arrangement. Axoplasmic vesicles are moderate in number, and sarcoplasmic vesicles are sparse. In the white fiber long, flat axonal terminals present considerable axoplasmic surface. Vast sarcoplasmic surface area is created by long, branching, closely spaced junctional folds that may merge with folds at adjacent contacts to occupy a more continuous and widespread area. Axoplasmic and sarcoplasmic vesicles are numerous. Both axoplasmic and sarcoplasmic mitochondria of the white fiber usually contain intramitochondrial granules. The intermediate fiber has large axonal terminals that are associated with the most widely spaced and deepest junctional folds. In all three fiber types, the junctional sarcoplasm is rich in free ribosomes, cisternae of granular endoplasmic reticulum, and randomly distributed microtubules.

scholarly journals Polymorphism of myosin among skeletal muscle fiber types

1977 ◽  
Vol 74 (3) ◽  
pp. 760-779 ◽  
Author(s):  
GF Gauthier ◽  
S Lowey
Keyword(s):  
Skeletal Muscle ◽  
Motor Units ◽  
Small Region ◽  
Antigenic Determinants ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Rat Diaphragm ◽  
Mitochondrial Content ◽  
Slow Twitch Muscle ◽  
Fast Twitch Muscle

An immunocytochemical approach was used to localize myosin with respect to individual fibers in rat skeletal muscle. Transverse cryostat sections of rat diaphragm, a fast-twitch muscle, were exposed to fluorescein-labeled immunoglobulin against purified chicken pectoralis myosin. Fluorescence microscopy revealed a differential response among fiber types, identified on the basis of mitochondrial content. All white and intermediate fiber but only about half of the red fiber reacted with his antimyosin. In addition, an alkali-stable ATPase had the same pattern of distribution among fibers, which is consistent with the existence of two categories of red fibers. The positive response of certain red fibers indicates either that their myosin has antigenic determinants in common with "white" myosin, or that the immunogen contained a "red" myosin. Myosin, extracted from a small region of the pectorlis which consists entirely of white fibers, was used to prepare an immunoadsorbent column to isolate antibodies specific for white myosin. This purified anti-white myosin reacted with the same fibers of the rat diaphragm that had reacted with the white, intermediate, and some red fibers are sufficiently homologous to share antigenic determinants. In a slow-twitch muscle, the soleus, only a minority of the fiber reacted with antipectoralis myosin. The majority failed to respond; hence, they are not equivalent to intermediate fibers of the diaphragm; despite their intermediate mitochondrial content. Immunocytochemical analysis of two different musles of the rat has demonstrated that more than one isoenzyme of myosin can exist in a single muscle, and that individual fiber types can be recognized by immunological differences in their myosin. We conclude that, in the rat diaphragm, there are at least two immunochemically distinct types of myosin and four types of muscle fibers: white, intermediate, and two red. We suggest that these fibers correspond to the four types of motor units described by Burke et al. (Burke, R. E., D. N. Levine, P. Tsairis, and F. E. Zajac, III 1973. J. Physiol. (Lond) 234:723-748.)in the cat gastrocnemius.`

Influence of acclimation temperature on mitochondrial DNA, RNA, and enzymes in skeletal muscle

1998 ◽  
Vol 275 (3) ◽  
pp. R905-R912 ◽  
Author(s):  
Brendan James Battersby ◽  
Christopher D. Moyes
Keyword(s):  
Skeletal Muscle ◽  
Mitochondrial Dna ◽  
Steady State ◽  
Muscle Fiber ◽  
Copy Number ◽  
White Muscle ◽  
Fiber Types ◽  
Mitochondrial Enzymes ◽  
Dna Copy Number ◽  
Mitochondrial Content

Skeletal muscle fibers typically undergo modifications in their mitochondrial content, concomitant with alterations in oxidative metabolism that occur during the development of muscle fiber and in response to physiological stimuli. We examined how cold acclimation affects the mitochondrial properties of two fish skeletal muscle fiber types and how the regulators of mitochondrial content differed between tissues. After 2 mo of acclimation to either 4 or 18°C, mitochondrial enzyme activities in both red and white muscle were higher in cold-acclimated fish. No significant differences were detected between acclimation temperatures in the abundance of steady-state mitochondrial mRNA (cytochrome- c oxidase 1, subunit 6 of F0F1-ATPase), rRNA (16S), or DNA copy number. Steady-state mRNA for nuclear-encoded respiratory (adenine nucleotide translocase 1) and glycolytic genes showed high interindividual variability, particularly in the cold-acclimated fish. Although mitochondrial enzymes were 10-fold different between the two muscle types, mitochondrial DNA copy number differed only 4-fold. The relative abundance of mitochondrial mRNA and nuclear mRNA in red and white muscle reflected the differences in copy number of their respective genes. These data suggest that the response to physiological stimuli and determination of tissue-specific mitochondrial properties likely result from the regulation of nuclear-encoded genes.

scholarly journals CYTOLOGICAL STUDIES OF FIBER TYPES IN SKELETAL MUSCLE

1966 ◽  
Vol 28 (2) ◽  
pp. 333-354 ◽  
Author(s):  
Geraldine F. Gauthier ◽  
Helen A. Padykula
Keyword(s):  
Skeletal Muscle ◽  
Body Size ◽  
Metabolic Activity ◽  
Functional Activity ◽  
Comparative Investigation ◽  
High Rate ◽  
Fiber Types ◽  
Mitochondrial Content ◽  
Quantitative Manner ◽  
High Degree

A comparative investigation of the mammalian diaphragm has revealed a correlation between certain cytological aspects of red and white muscle fibers and functional activity. This skeletal muscle presents the advantage of a similar and constant function among the mammals, but its functional activity varies in a quantitative manner. Both the rate of breathing (and hence the rate of contraction of the diaphragm) and metabolic activity are known to be inversely related to body size; and this study has demonstrated a relationship between cytological characteristics of the diaphragm and body size of the animal. Small fibers rich in mitochondria (red fibers) are characteristic of small mammals, which have high metabolic activity and fast breathing rates; and large fibers with relatively low mitochondrial content predominate in large mammals, which have lower metabolic activity and slower breathing rates. In mammals with body size intermediate between these two groups (including the laboratory rat), the diaphragm consists of varying mixtures of fiber types. In general, the mitochondrial content of diaphragm fibers is inversely related to body size. It appears, then, that the red fiber reflects a high degree of metabolic activity or a relatively high rate of contraction within the range exhibited by this muscle.

Characteristics of Skeletal Muscle Fiber Types in the Miniature Pig and the Effect of Training

1973 ◽  
Vol 51 (11) ◽  
pp. 825-831 ◽  
Author(s):  
R. H. Fitts ◽  
F. J. Nagle ◽  
R. G. Cassens
Keyword(s):  
Skeletal Muscle ◽  
Enzyme Histochemistry ◽  
Fiber Type ◽  
Skeletal Muscle Fiber ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Miniature Pig ◽  
Fast Red ◽  
Fiber Type Distribution ◽  
White Fiber

The fiber types present in miniature pig skeletal muscle were determined with enzyme histochemical techniques. Three distinct fiber types were found: a fast white fiber, a fast intermediate fiber, and a slow red fiber. The fiber types found in miniature pig (large mammal) skeletal muscle were different from those in rat (rodent) skeletal muscle where the fiber types are classified as fast white, slow intermediate, and fast red. The fiber type distribution in miniature pig skeletal muscle was not altered by either an endurance or sprint running program, despite physiologically measurable training effects. It is concluded that enzyme histochemistry is a good qualitative tool for assessing the fiber types present in a muscle but lacks the sensitivity to measure or quantitate changes due to training.

Ultrastructural and Cytochemical Manifestations of Protein Synthesis in the Peripheral Sarcoplasm of Denervated and Newborn Skeletal Muscle Fibres

1974 ◽  
Vol 14 (1) ◽  
pp. 113-137
Author(s):  
GERALDINE F. GAUTHIER ◽  
SUSAN F. SCHAEFFER
Keyword(s):  
Skeletal Muscle ◽  
Endoplasmic Reticulum ◽  
Protein Synthesis ◽  
Cell Surface ◽  
Phrenic Nerve ◽  
Muscle Fibres ◽  
Preliminary Treatment ◽  
Rat Diaphragm ◽  
Newborn Rat ◽  
Skeletal Muscle Fibres

In muscle fibres of the rat diaphragm, there is widespread accumulation of free ribosomes and rough-surfaced endoplasmic reticulum in the subsarcolemmal sarcoplasm at 28 days following section of the phrenic nerve. A corresponding accumulation of basophilic material is visible at the periphery of the fibres when examined with the light microscope. Both the ribosomes and the basophilic material are removed by preliminary treatment with ribonuclease. Fibres comprising the diaphragm of the newborn rat display similar aggregations of subsarcolemmal ribosomes and peripheral basophilia. These ultrastructural and cytochemical manifestations of protein synthesis correspond closely in time to the well documented ‘supersensitivity’ to acetylcholine, which occurs along the entire length of muscle fibres in the newborn and denervated rat diaphragm. It is suggested, therefore, that this protein-synthetic machinery, which is concentrated at the cell surface, is involved in the formation of new receptors.

scholarly journals Different Expression of Mitochondrial and Endoplasmic Reticulum Stress Genes in Epicardial Adipose Tissue Depends on Coronary Atherosclerosis

2021 ◽  
Vol 22 (9) ◽  
pp. 4538
Author(s):  
Helena Kratochvílová ◽  
Miloš Mráz ◽  
Barbora J. Kasperová ◽  
Daniel Hlaváček ◽  
Jakub Mahrík ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Endoplasmic Reticulum ◽  
Adipose Tissue ◽  
Cardiac Surgery ◽  
Endoplasmic Reticulum Stress ◽  
Er Stress ◽  
Mrna Expression ◽  
Coronary Atherosclerosis ◽  
Stress Genes ◽  
Valvular Surgery

The aim of our study was to analyze mitochondrial and endoplasmic reticulum (ER) gene expression profiles in subcutaneous (SAT) and epicardial (EAT) adipose tissue, skeletal muscle, and myocardium in patients with and without CAD undergoing elective cardiac surgery. Thirty-eight patients, 27 with (CAD group) and 11 without CAD (noCAD group), undergoing coronary artery bypass grafting and/or valvular surgery were included in the study. EAT, SAT, intercostal skeletal muscle, and right atrium tissue and blood samples were collected at the start and end of surgery; mRNA expression of selected mitochondrial and ER stress genes was assessed using qRT-PCR. The presence of CAD was associated with decreased mRNA expression of most of the investigated mitochondrial respiratory chain genes in EAT, while no such changes were seen in SAT or other tissues. In contrast, the expression of ER stress genes did not differ between the CAD and noCAD groups in almost any tissue. Cardiac surgery further augmented mitochondrial dysfunction in EAT. In our study, CAD was associated with decreased expression of mitochondrial, but not endoplasmic reticulum stress genes in EAT. These changes may contribute to the acceleration of coronary atherosclerosis.

scholarly journals Hexokinase 2 in Cancer: A Prima Donna Playing Multiple Characters

2021 ◽  
Vol 22 (9) ◽  
pp. 4716
Author(s):  
Francesco Ciscato ◽  
Lavinia Ferrone ◽  
Ionica Masgras ◽  
Claudio Laquatra ◽  
Andrea Rasola
Keyword(s):  
Endoplasmic Reticulum ◽  
Aerobic Glycolysis ◽  
Neoplastic Progression ◽  
Malignant Growth ◽  
Hexokinase 2 ◽  
Genetic Ablation ◽  
Contact Points ◽  
Survival Pathways ◽  
The Family ◽  
Definition Of

Hexokinases are a family of ubiquitous exose-phosphorylating enzymes that prime glucose for intracellular utilization. Hexokinase 2 (HK2) is the most active isozyme of the family, mainly expressed in insulin-sensitive tissues. HK2 induction in most neoplastic cells contributes to their metabolic rewiring towards aerobic glycolysis, and its genetic ablation inhibits malignant growth in mouse models. HK2 can dock to mitochondria, where it performs additional functions in autophagy regulation and cell death inhibition that are independent of its enzymatic activity. The recent definition of HK2 localization to contact points between mitochondria and endoplasmic reticulum called Mitochondria Associated Membranes (MAMs) has unveiled a novel HK2 role in regulating intracellular Ca2+ fluxes. Here, we propose that HK2 localization in MAMs of tumor cells is key in sustaining neoplastic progression, as it acts as an intersection node between metabolic and survival pathways. Disrupting these functions by targeting HK2 subcellular localization can constitute a promising anti-tumor strategy.

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