scholarly journals Comprehensive Simulation of Ca2+ Transients in the Continuum of Mouse Skeletal Muscle Fiber Types

2021 ◽  
Vol 22 (22) ◽  
pp. 12378
Author(s):  
Oscar A. Rincón ◽  
Andrés F. Milán ◽  
Juan C. Calderón ◽  
Marco A. Giraldo
Keyword(s):  
Binding Sites ◽  
Muscle Fiber Types ◽  
Type I ◽  
Fiber Types ◽  
Tetanic Stimulation ◽  
Contraction Coupling ◽  
Single Twitch ◽  
Store Operated Calcium Entry ◽  
Kinetics Of ◽  
The Continuum

Mag-Fluo-4 has revealed differences in the kinetics of the Ca2+ transients of mammalian fiber types (I, IIA, IIX, and IIB). We simulated the changes in [Ca2+] through the sarcomere of these four fiber types, considering classical (troponin –Tn–, parvalbumin –Pv–, adenosine triphosphate –ATP–, sarcoplasmic reticulum Ca2+ pump –SERCA–, and dye) and new (mitochondria –MITO–, Na+/Ca2+ exchanger –NCX–, and store-operated calcium entry –SOCE–) Ca2+ binding sites, during single and tetanic stimulation. We found that during a single twitch, the sarcoplasmic peak [Ca2+] for fibers type IIB and IIX was around 16 µM, and for fibers type I and IIA reached 10–13 µM. The release rate in fibers type I, IIA, IIX, and IIB was 64.8, 153.6, 238.8, and 244.5 µM ms−1, respectively. Both the pattern of change and the peak concentrations of the Ca2+-bound species in the sarcoplasm (Tn, PV, ATP, and dye), the sarcolemma (NCX, SOCE), and the SR (SERCA) showed the order IIB ≥ IIX > IIA > I. The capacity of the NCX was 2.5, 1.3, 0.9, and 0.8% of the capacity of SERCA, for fibers type I, IIA, IIX, and IIB, respectively. MITO peak [Ca2+] ranged from 0.93 to 0.23 µM, in fibers type I and IIB, respectively, while intermediate values were obtained in fibers IIA and IIX. The latter numbers doubled during tetanic stimulation. In conclusion, we presented a comprehensive mathematical model of the excitation–contraction coupling that integrated most classical and novel Ca2+ handling mechanisms, overcoming the limitations of the fast- vs. slow-fibers dichotomy and the use of slow dyes.

scholarly journals Lifetime of autofluorescence: A novel method to determine murine skeletal muscle fiber types

2021 ◽  
Vol 154 (9) ◽  
Author(s):  
C. Manno ◽  
E. Tammineni ◽  
Y. Oropeza ◽  
L. Figueroa ◽  
E. Rios
Keyword(s):  
Fiber Type ◽  
Myosin Heavy Chain Isoforms ◽  
Muscle Fiber Types ◽  
Fluorescence Lifetime Imaging ◽  
Type I ◽  
Fiber Types ◽  
Mean Values ◽  
Lifetime Imaging ◽  
Oxidation Reduction ◽  
Murine Skeletal Muscle

This work describes a simple way to identify fiber types in living muscles by fluorescence lifetime imaging microscopy (FLIM). We quantified the mean values of lifetimes derived from a two-exponential fit (τ1 and τ2) in freshly dissected mouse FDB and soleus muscles. While τ1 values did not change between muscles, the distribution of τ2 shifted to higher values in FDB. To understand the origin of this difference, we obtained maps of autofluorescence lifetimes in cryosections of both muscles and paired them with immunofluorescence images of myosin heavy chain isoforms (MHC), which allow identification of fiber types. In soleus, τ2 was 3.1 ns for type I (SEM = 0.009, n = 49), 3.4 ns for type IIA (SEM = 0.01, n = 30), and 3.3 ns for type IIX (SEM = 0.01, n = 21). In FDB muscle, τ2 was 3.17 ns for type I (SEM = 0.04, n = 18), 3.5 ns for type IIA (SEM = 0.03, n = 27), and 3.62 ns for type IIX (SEM = 0.03, n = 22). From the distribution of measures, it follows that an FDB fiber with τ2 >3.3 ns is expected to be of type II, and of type I otherwise. This simple classification method has first- and second-class errors estimated at 0.06 and 0.27, respectively. Studies in progress aim at further elucidating the reasons for the different lifetimes, not just among fiber types but between fibers of the same type in the two muscles. Preliminary results point at differences in both the oxidation-reduction and protein-bound versus free states of flavins as causes for the observed divergence of fluorescence lifetimes. Lifetime maps of autofluorescence therefore constitute a tool to identify fiber type that, being practical, fast, and noninvasive, can be applied in living tissue without compromising other experimental interventions.

Carnitine metabolism in human muscle fiber types during submaximal dynamic exercise

1996 ◽  
Vol 80 (3) ◽  
pp. 1061-1064 ◽  
Author(s):  
D. Constantin-Teodosiu ◽  
S. Howell ◽  
P. L. Greenhaff
Keyword(s):  
Muscle Fiber ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Group Formation ◽  
Free Carnitine ◽  
Muscle Fiber Types ◽  
Type I ◽  
Fiber Types ◽  
Carnitine Metabolism ◽  
Type I Fibers

The effect of prolonged exhaustive exercise on free carnitine and acetylcarnitine concentrations in mixed-fiber skeletal muscle and in type I and II muscle fibers was investigated in humans. Needle biopsy samples were obtained from the vastus lateralis of six subjects immediately after exhaustive one-legged cycling at approximately 75% of maximal O2 uptake from both the exercised and nonexercised (control) legs. In the resting (control) leg, there was no difference in the free carnitine concentration between type I and II fibers (20.36 +/- 1.25 and 20.51 +/- 1.16 mmol/kg dry muscle, respectively) despite the greater potential for fat oxidation in type I fibers. However, the acetylcarnitine concentration was slightly greater in type I fibers (P < 0.01). During exercise, acetylcarnitine accumulation occurred in both muscle fiber types, but accumulation was greatest in type I fibers (P < 0.005). Correspondingly, the concentration of free carnitine was significantly lower in type I fibers at the end of exercise (P < 0.001). The sum of free carnitine and acetylcarnitine concentrations in type I and II fibers at rest was similar and was unchanged by exercise. In conclusion, the findings of the present study support the suggestion that carnitine buffers excess acetyl group formation during exercise and that this occurs in both type I and II fibers. However, the greater accumulation of acetylcarnitine in type I fibers during prolonged exercise probably reflects the greater mitochondrial content of this fiber type.

scholarly journals Identification of Differentially Expressed Genes in Different Types of Broiler Skeletal Muscle Fibers Using the RNA-seq Technique

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Han Wang ◽  
Zhonghao Shen ◽  
Xiaolong Zhou ◽  
Songbai Yang ◽  
Feifei Yan ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Differentially Expressed Genes ◽  
Muscle Fiber ◽  
Muscle Development ◽  
Skeletal Muscle Fiber ◽  
Differentially Expressed ◽  
Muscle Fiber Types ◽  
Type I ◽  
Fiber Types ◽  
Rna Seq

The difference in muscle fiber types is very important to the muscle development and meat quality of broilers. At present, the molecular regulation mechanisms of skeletal muscle fiber-type transformation in broilers are still unclear. In this study, differentially expressed genes between breast and leg muscles in broilers were analyzed using RNA-seq. A total of 767 DEGs were identified. Compared with leg muscle, there were 429 upregulated genes and 338 downregulated genes in breast muscle. Gene Ontology (GO) enrichment indicated that these DEGs were mainly involved in cellular processes, single organism processes, cells, and cellular components, as well as binding and catalytic activity. KEGG analysis shows that a total of 230 DEGs were mapped to 126 KEGG pathways and significantly enriched in the four pathways of glycolysis/gluconeogenesis, starch and sucrose metabolism, insulin signalling pathways, and the biosynthesis of amino acids. Quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) was used to verify the differential expression of 7 selected DEGs, and the results were consistent with RNA-seq data. In addition, the expression profile of MyHC isoforms in chicken skeletal muscle cells showed that with the extension of differentiation time, the expression of fast fiber subunits (types IIA and IIB) gradually increased, while slow muscle fiber subunits (type I) showed a downward trend after 4 days of differentiation. The differential genes screened in this study will provide some new ideas for further understanding the molecular mechanism of skeletal muscle fiber transformation in broilers.

Cross-reinnervated motor units in cat muscle. I. Flexor digitorum longus muscle units reinnervated by soleus motoneurons

1985 ◽  
Vol 54 (4) ◽  
pp. 818-836 ◽  
Author(s):  
R. P. Dum ◽  
M. J. O'Donovan ◽  
J. Toop ◽  
R. E. Burke
Keyword(s):  
Muscle Fibers ◽  
Motor Units ◽  
Muscle Fiber Types ◽  
Type I ◽  
Fiber Types ◽  
Glycogen Depletion ◽  
Flexor Digitorum Longus ◽  
Wet Weight ◽  
Flexor Digitorum ◽  
Individual Motor

The properties of flexor digitorum longus (FDL) muscles and of individual motor units were studied in cats 30-50 wk after self-reinnervation by FDL motoneurons (FDL----FDL) or cross-reinnervation by soleus (SOL) motoneurons (SOL----FDL). Individual motor units were functionally isolated by intracellular recording and stimulation of identified SOL alpha-motoneurons. Glycogen-depletion methods permitted histochemical study of muscle fibers belonging to physiologically characterized muscle units. The observations were compared with data from normal cat FDL muscles and motor units (27). Intentionally self-reinnervated FDL muscles (FDL----FDL; n = 5) were normal in size and wet weight. FDL----FDL motor units could be classified into the same physiological categories found in normal FDL [types: fast contracting, fatigable (FF), fast contracting, fatigue resistant (FR), and slow (S); n = 24], with approximately the same proportions as normal. The histochemical muscle fiber types associated with these categories were also qualitatively normal although there was evidence of marked distortion of the normal histochemical mosaic. These data confirm other studies of self-reinnervation and suggest that self-reinnervation can produce complete interconversion of muscle fiber types. Cross-reinnervation of FDL muscle by SOL motoneurons (SOL----FDL; n = 12) produced muscles that were smaller (about half the normal wet weight) and more red than normal. SOL----FDL muscle contracted more slowly than normal or FDL----FDL muscles and had much higher proportions of histochemical type I muscle fibers. In those SOL----FDL muscles, in which little or no unwanted self-reinnervation could be demonstrated, greater than 95% of the muscle fibers were type I. Forty-one individual motor units in SOL----FDL muscles were isolated by intracellular penetration in functionally identified SOL alpha-motoneurons. Their muscle units were all type S by physiological criteria (absence of "sag" in unfused tetani and marked resistance to fatigue). SOL----FDL muscle units had contraction times and fatigue properties that were essentially identical to those of type S units in the normal FDL. All of the seven units, successfully studied by glycogen depletion, exhibited histochemical type I fibers. SOL motoneurons that innervated FDL muscle units had slightly shorter afterhyperpolarization durations than normal SOL cells, but axonal conduction velocities were normal.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of ACE inhibition and beta-blockade on skeletal muscle fiber types in dogs with moderate heart failure

1996 ◽  
Vol 270 (1) ◽  
pp. H115-H120 ◽  
Author(s):  
H. N. Sabbah ◽  
H. Shimoyama ◽  
V. G. Sharov ◽  
T. Kono ◽  
R. C. Gupta ◽  
...  
Keyword(s):  
Heart Failure ◽  
Skeletal Muscle ◽  
Exercise Intolerance ◽  
Beta Blockade ◽  
Muscle Fiber Types ◽  
Type I ◽  
Fiber Types ◽  
Type Ii ◽  
Early Therapy ◽  
Type I Fibers

The proportion of slow-twitch, fatigue-resistant type 1 skeletal muscle (SM) fibers is often reduced in heart failure (HF), while the proportion of fatigue-sensitive type-II fibers increases. This maladaptation may be partially responsible for the exercise intolerance that characterize HF. In this study, we examined the effects of early monotherapy with the angiotensin-converting enzyme inhibor, enalapril, and the beta-blocker, metoprolol, on SM fiber type composition in 18 dogs with moderate HF produced by intracoronary microembolizations. HF dogs were randomized to 3 mo therapy with enalapril (10 mg twice daily), metoprolol (25 mg twice daily), or no treatment. Triceps muscle biopsies were obtained at baseline, before randomization, and at the end of 30 mo of therapy. Type I and type II SM fibers were differentiated by myofibrillar adenosinetriphosphatase (pH 9.4). In untreated dogs, the proportion of type I fibers was 27 +/- 1% before randomization and decreased to 23 +/- 1% (P < 0.05) at the end of 3 mo of follow up. In dogs treated with enalapril or metoprolol, the proportion of type I fibers was 30 +/- 4 and 28 +/- 2% before randomization and 33 +/- 4 and 33 +/- 1%, respectively, after 3 mo of therapy. In conclusion, in dogs with moderate HF, early therapy with enalapril or metoprolol prevents the progressive decline in the proportion of type I SM fibers.

Relationship between muscle fiber characteristics and meat quality parameters in Turkish native goat breeds

2018 ◽  
Author(s):  
Emre Sirin
Keyword(s):  
Meat Quality ◽  
Muscle Fiber ◽  
Quality Parameters ◽  
Muscle Fiber Types ◽  
Type I ◽  
Fiber Types ◽  
Fiber Number ◽  
Weaning Age ◽  
Positive Correlations

This study was conducted to determine muscle fiber characteristics and their effect on some meat quality parameters in Longissimus dorsi (LD) and Semitendinosus (ST) muscles from kids of some Turkish native goat breeds. Male kids of Hair (n=6), Angora (n=6), Kilis (n=6) and Honamli (n=6) (pure breeds) were used as experimental animals. All kids were slaughtered at 3 months of weaning age and muscles samples were collected for determination of type I, IIA and IIB muscle fibers and some meat quality parameters. It was found that type IIA fiber number of Hair and Honamli kids were higher than those of other breeds in LD muscle. Similarly, Hair kids had higher number of (P less than 0.05) type IIA in ST muscle compared to other breeds. Generally, there were negative correlations between tenderness, pH and number of muscle fiber types in LD and ST muscles of all breeds (P less than0.05). Also, there were positive correlations between intra muscular fat and number of muscle fiber types in LD muscles of all breeds (P less than 0.05). Conclusively, kids of Turkish native goat breeds had different muscle fiber characteristics which can affect meat quality.

scholarly journals Immunocytochemical localization of carbonic anhydrase isozymes I, II, and III in rat skeletal muscle.

1986 ◽  
Vol 34 (4) ◽  
pp. 513-516 ◽  
Author(s):  
S Jeffery ◽  
N D Carter ◽  
A Smith
Keyword(s):  
Skeletal Muscle ◽  
Carbonic Anhydrase ◽  
Skeletal Muscle Fiber ◽  
Muscle Fiber Types ◽  
Type I ◽  
Fiber Types ◽  
Rat Skeletal Muscle ◽  
Specific Antisera ◽  
Type I Fibers ◽  
Atpase Staining

Specific antisera were raised against the three carbonic anhydrase (CA) isozymes, CAI, CAII, and CAIII, and were used to determine the fiber distribution of these isozymes in skeletal muscle. Fiber types were determined by ATPase staining, and the CA isozymes were detected using a peroxidase-anti-peroxidase (PAP) technique. All three isozymes were present in type I fibers; CAII and CAIII were exclusive to these fibers, and CAI were also present in some small type 2A fibers.

scholarly journals Metabolic and morphometric profile of muscle fibers in chronic hemodialysis patients

2012 ◽  
Vol 112 (1) ◽  
pp. 72-78 ◽  
Author(s):  
Michael I. Lewis ◽  
Mario Fournier ◽  
Huiyuan Wang ◽  
Thomas W. Storer ◽  
Richard Casaburi ◽  
...  
Keyword(s):  
Muscle Fiber ◽  
Muscle Fibers ◽  
Exercise Intolerance ◽  
Maintenance Hemodialysis ◽  
Muscle Fiber Types ◽  
Vastus Lateralis Muscle ◽  
Type I ◽  
Fiber Types ◽  
Dense Matrix ◽  
Individual Fiber

Muscle weakness and effort intolerance are common in maintenance hemodialysis (MHD) patients. This study characterized morphometric, histochemical, and biochemical properties of limb muscle in MHD patients compared with controls (CTL) with similar age, gender, and ethnicity. Vastus lateralis muscle biopsies were obtained from 60 MHD patients, 1 day after dialysis, and from 21 CTL. Muscle fiber types and capillaries were identified immunohistochemically. Individual muscle fiber cross-sectional areas (CSA) were quantified. Individual fiber oxidative capacities were determined (microdensitometric assay) to measure succinate dehydrogenase (SDH) activity. Mean CSAs of type I, IIA, and IIX fibers were 33, 26, and 28% larger in MHD patients compared with CTL. SDH activities for type I, IIA, and IIX fibers were reduced by 29, 40, and 47%, respectively, in MHD. Capillary to fiber ratio was increased by 11% in MHD. The number of capillaries surrounding individual fiber types were also increased (type I: 9%; IIA: 10%; IIX: 23%) in MHD patients. However, capillary density (capillaries per unit muscle fiber area) was reduced by 34% in MHD patients, compared with CTL. Ultrastuctural analysis revealed swollen mitochondria with dense matrix in MHD patients. These results highlight impaired oxidative capacity and capillarity in MHD patients. This would be expected to impair energy production as well as substrate and oxygen delivery and exchange and contribute to exercise intolerance. The enlarged CSA of muscle fibers may, in part, be accounted for by edema. We speculate that these changes contribute to reduce limb strength in MHD patients by reducing specific force.

Inducible isoform of HSP70 is constitutively expressed in a muscle fiber type specific pattern

1991 ◽  
Vol 261 (5) ◽  
pp. C774-C779 ◽  
Author(s):  
M. Locke ◽  
E. G. Noble ◽  
B. G. Atkinson
Keyword(s):  
Muscle Fiber ◽  
Fiber Type ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Constitutive Expression ◽  
Muscle Fiber Types ◽  
Type I ◽  
Fiber Types ◽  
Nylon Membrane ◽  
White Gastrocnemius

The most prominent group of stress or heat-shock proteins (HSPs) has an Mr of approximately 70,000 and is collectively referred to as the HSP70 family. The extent of stress inducibility and subcellular location of the various HSP70 isoforms differ, but all appear to be involved with ATP-dependent stabilization or solubilization of proteins. One isoform, termed the inducible isoform of HSP70 (HSP72i), is normally absent in unstressed cells. In a previous study, we detected a protein corresponding in Mr and pI to HSP72i in unstressed rat muscle. Therefore, it was of interest to determine if this expression in unstressed muscle cells is general or confined to specific muscle fiber types. To answer this question we have employed various rat hindlimb muscles that differ in fiber type proportion from predominantly type I (soleus) to predominantly type IIB (white gastrocnemius). Proteins from muscle homogenates were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, blotted to a nylon membrane, probed with a monoclonal antibody for HSP72i, and visualized using an alkaline phosphatase-conjugated secondary antibody. Immunoblot analyses demonstrate the constitutive expression of HSP72i in rat muscles comprised primarily of type I muscle fibers (soleus), but not in muscles comprised primarily of type IIB fibers (white gastrocnemius). In muscles of mixed fiber type, HSP72i content is roughly proportional to the percentage of type I fibers. These results substantiate that unstressed rat muscles express the inducible HSP72 isoform and demonstrate that its constitutive expression is proportional to the type I muscle fiber composition.

Comparison of diaphragmatic fatigue in newborn and older rabbits

1988 ◽  
Vol 65 (3) ◽  
pp. 1040-1044 ◽  
Author(s):  
P. N. Le Souef ◽  
S. J. England ◽  
H. A. Stogryn ◽  
A. C. Bryan
Keyword(s):  
Histological Analysis ◽  
Muscle Fiber Types ◽  
Type I ◽  
Fiber Types ◽  
Occlusion Pressure ◽  
Phrenic Nerve Stimulation ◽  
Newborn Rabbit ◽  
Diaphragmatic Fatigue ◽  
Lower Maximum ◽  
Type I Fibers

The ability to maintain occlusion pressure (i.e., fatigability) during activation of the diaphragm via phrenic nerve stimulation was compared in newborn (less than 14 days old) and older (greater than 30 days old) rabbits. The younger animals had lower maximum inspiratory pressures (MIP) and markedly greater falls in pressure during sustained diaphragmatic contractions at greater than 40% MIP than did the older animals. Histological analysis showed a paucity of high-oxidative type I fibers in the diaphragms of the young animals. We therefore conclude that the newborn rabbit diaphragm is extremely susceptible to fatigue and that this susceptibility correlates with the distribution of muscle fiber types.

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