Metabolic variation among alpha-motoneurons innervating different muscle-fiber types. I. Oxidative enzyme activity

1984 ◽  
Vol 51 (3) ◽  
pp. 529-537 ◽  
Author(s):  
D. W. Sickles ◽  
T. G. Oblak
Keyword(s):  
Optical Density ◽  
Muscle Fiber ◽  
Enzyme Activities ◽  
Tibialis Anterior ◽  
Fiber Type ◽  
Ventral Horn ◽  
Oxidative Enzyme ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Fast Twitch

We have examined the oxidative metabolism of rat alpha-motoneurons innervating muscles composed predominantly of one muscle-fiber type. Intramuscular injections of horseradish peroxidase (HRP) into the tensor fasciae latae (TFL) (approximately 94% fast-twitch glycolytic fibers, FG), tibialis anterior (TA) (approximately 66% fast-twitch oxidative-glycolytic, FOG; 32% FG), and soleus (SOL) (approximately 84% slow-twitch oxidative, SO) muscles permitted identification of motoneurons innervating these muscles. gamma-Motoneurons (less than 25-micron average soma diameter) were eliminated from the sampling. The alpha-motoneurons innervating the TFL were considered as FG, those innervating the tibialis anterior as FOG, and those of the soleus as SO. Alternate 5-micron serial cryostat sections were processed for HRP and nicotinamide adenine dinucleotide-diapharase (NADH-D) (oxidative enzyme) activities. Controls were included to assure reliability of reaction product quantitation. Motoneuron pools of each muscle were characterized by their shape and location within the ventral horn. Cells identified on HRP sections as innervating each of the muscles were located on sections processed for NADH-D activity. The optical density of motoneurons in sections processed for NADH-D activity was measured with a Zeiss Zonax MPM 03 microdensitometer. The mean relative NADH-D activities (optical density) of alpha-motoneurons innervating the TFL (FG), TA (FOG), and SOL(SO) muscles were 0.261, 0.305, and 0.447, respectively. Although some overlap in distribution of enzyme activities was observed, statistical analysis indicated significant differences between the NADH-D activities of each type of alpha-motoneuron. This is the first report of any metabolic difference in alpha-motoneurons belonging to different motor-unit types.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood flow to different skeletal muscle fiber types during contraction

1983 ◽  
Vol 245 (2) ◽  
pp. H265-H275 ◽  
Author(s):  
B. G. Mackie ◽  
R. L. Terjung
Keyword(s):  
Skeletal Muscle ◽  
Blood Flow ◽  
Muscle Fiber ◽  
Fiber Type ◽  
Oxidative Capacity ◽  
Skeletal Muscle Fiber ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Blood Flows ◽  
Fast Twitch

Blood flow to fast-twitch red (FTR), fast-twitch white (FTW), and slow-twitch red (STR) muscle fiber sections of the gastrocnemius-plantaris-soleus muscle group was determined using 15 +/- 3-microns microspheres during in situ stimulation in pentobarbital-anesthetized rats. Steady-state blood flows were assessed during the 10th min of contraction using twitch (0.1, 0.5, 1, 3, and 5 Hz) and tetanic (7.5, 15, 30, 60, and 120/min) stimulation conditions. In addition, an earlier blood flow determination was begun at 3 min (twitch series) or at 30 s (tetanic series) of stimulation. Blood flow was highest in the FTR (220-240 ml X min-1 X 100 g-1), intermediate in the STR (140), and lowest in the FTW (70-80) section during tetanic contraction conditions estimated to coincide with the peak aerobic function of each fiber type. These blood flows are fairly proportional to the differences in oxidative capacity among fiber types. Further, their absolute values are similar to those predicted from the relationship between blood flow and oxidative capacity found by others for dog and cat muscles. During low-frequency contraction conditions, initial blood flow to the FTR and STR sections were excessively high and not dependent on contraction frequency. However, blood flows subsequently decreased to values in keeping with the relative energy demands. In contrast, FTW muscle did not exhibit this time-dependent relative hyperemia. Thus, besides the obvious quantitative differences between skeletal muscle fiber types, there are qualitative differences in blood flow response during contractions. Our findings establish that, based on fiber type composition, a heterogeneity in blood flow distribution can occur within a whole muscle during contraction.

scholarly journals Skeletal muscle and fiber type-specific intramyocellular lipid accumulation in obese mice

2021 ◽  
Author(s):  
Nejc Umek ◽  
Simon Horvat ◽  
Erika Cvetko
Keyword(s):  
Muscle Fiber ◽  
Lipid Accumulation ◽  
High Fat Diet ◽  
Fiber Type ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Intramyocellular Lipid ◽  
Obese Mice ◽  
Slow Twitch ◽  
Fast Twitch

In obesity, accumulation of lipid droplets in skeletal muscle fibers and a shift towards fast muscle fiber types can both contribute to insulin resistance. However, it is not yet clear how intramyocellular lipid accumulation and fiber type changes are associated. Therefore, we investigated to what extent the lipids accumulated in a fiber type-specific manner in the functionally similar fast-, intermediate- and slow‑twitch gastrocnemius, plantaris, and soleus muscles, respectively, in high-fat diet-induced obese 54-week-old female C57BL/6JOlaHsd mice (n=9) compared to control standard-diet-treated lean mice (n=9). A high-fat diet was administered for 26 weeks. Fiber-type specific intramyocellular lipid content analysis and muscle fiber typing were performed using histochemical analysis of lipids with Sudan Black and immunohistochemical analysis of myosin heavy chains on serial sections of skeletal muscles. Compared to the lean mice, the lipid accumulation was most prominent in types 2a and 2x/d fibers (p<0.05) of fast-twitch gastrocnemius and intermediate plantaris muscles in the obese mice, while in slow-twitch soleus muscle, there was no significant lipid accumulation in the obese animals. Furthermore, the slow-twitch soleus muscle of the obese mice with no significant change in muscle fiber diameters exhibited the most pronounced shift towards fast-type myosin heavy chain isoform expression (p<0.05). In contrast, the fast-twitch and intermediate-twitch gastrocnemius and plantaris muscles, respectively, in which the muscle fiber diameters increased (p<0.05), were more resistant toward myosin heavy chain expression changes. In conclusion, we demonstrated both muscle- and fiber-type specificity in intramyocellular lipid accumulation in obese mice, suggesting that in obesity, similar muscle fiber types in different muscles accumulate lipids differentially.

Slow- and fast-twitch hindlimb skeletal muscle phenotypes 12 wk after ⅚ nephrectomy in Wistar rats of both sexes

2015 ◽  
Vol 309 (7) ◽  
pp. F638-F647 ◽  
Author(s):  
Luz M. Acevedo ◽  
Alan Peralta-Ramírez ◽  
Ignacio López ◽  
Verónica E. Chamizo ◽  
Carmen Pineda ◽  
...  
Keyword(s):  
Muscle Fiber ◽  
Soleus Muscle ◽  
Fiber Type ◽  
Serum Testosterone ◽  
Oxidative Capacity ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Nuclear Density ◽  
Type Transformation ◽  
Fast Twitch

This study describes fiber-type adaptations in hindlimb muscles, the interaction of sex, and the role of hypoxia on this response in 12-wk ⅚ nephrectomized rats (Nx). Contractile, metabolic, and morphological features of muscle fiber types were assessed in the slow-twitch soleus and the fast-twitch tibialis cranialis muscles of Nx rats, and compared with sham-operated controls. Rats of both sexes were considered in both groups. A slow-to-fast fiber-type transformation occurred in the tibialis cranialis of Nx rats, particularly in males. This adaptation was accomplished by impaired oxidative capacity and capillarity, increased glycolytic capacity, and no changes in size and nuclear density of muscle fiber types. An oxidative-to-glycolytic metabolic transformation was also found in the soleus muscle of Nx rats. However, a modest fast-to-slow fiber-type transformation, fiber hypertrophy, and nuclear proliferation were observed in soleus muscle fibers of male, but not of female, Nx rats. Serum testosterone levels decreased by 50% in male but not in female Nx rats. Hypoxia-inducible factor-1α protein level decreased by 42% in the tibialis cranialis muscle of male Nx rats. These data demonstrate that 12 wk of Nx induces a muscle-specific adaptive response in which myofibers do not change (or enlarge minimally) in size and nuclear density, but acquire markedly different contractile and metabolic characteristics, which are accompanied by capillary rarefaction. Muscle function and sex play relevant roles in these adaptations.

Physiological, morphological, and histochemical properties of cat external anal sphincter

1988 ◽  
Vol 255 (6) ◽  
pp. G772-G778 ◽  
Author(s):  
J. Krier ◽  
T. Adams ◽  
R. A. Meyer
Keyword(s):  
Muscle Fiber ◽  
Fiber Type ◽  
Muscle Fibers ◽  
Succinic Dehydrogenase ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Motor Axons ◽  
Fast Twitch Muscle ◽  
Fast Twitch ◽  
Stimulation Of

The contractile properties, morphology, and the distribution of striated muscle fiber types of the external and sphincter (EAS) were determined using axial force measurements, fiber size cross-sectional area measurements, and histochemistry. Electrical stimulation of motor axons in pudendal nerve at supramaximal intensities (10 V, 0.05 ms duration) elicited twitch contractions of EAS. The time to peak force after a single pulse ranged from 37 to 42 ms. The time for relaxation to half-maximal twitch force ranged from 20 to 29 ms. Repetitive stimulation of motor axons (0.1-3.0 Hz) produced potentiation and fatigue of single twitch contractile force, suggesting that the EAS of the cat is comprised predominantly of fast-twitch muscle fibers. Confirmation of skeletal muscle fiber types was determined by histochemistry. Frozen serial cross sections of EAS were incubated to demonstrate succinic dehydrogenase (SDH) and myosin adenosine triphosphatase after alkaline preincubation (pH 10.4). Based on these reactions, muscle fibers were classified as fast glycolytic (FG) (high ATPase, low SDH), fast oxidative-glycolytic (FOG) (high ATPase, high SDH), and slow oxidative (SO) (low ATPase, high SDH). The mean percentage +/- SE of each histochemical type was the following: FG, 73.5 +/- 3.9; FOG, 22.8 +/- 3.7; and SO, 3.7 +/- 0.6. These results indicate that the predominant fiber type for the EAS is FG. The EAS of the cat is considered a nominally fast-twitch muscle.

scholarly journals lncRNA-Six1 Is a Target of miR-1611 that Functions as a ceRNA to Regulate Six1 Protein Expression and Fiber Type Switching in Chicken Myogenesis

Cells ◽  
2018 ◽  
Vol 7 (12) ◽  
pp. 243 ◽  
Author(s):  
Manting Ma ◽  
Bolin Cai ◽  
Liang Jiang ◽  
Bahareldin Ali Abdalla ◽  
Zhenhui Li ◽  
...  
Keyword(s):  
Fiber Type ◽  
Muscle Fibers ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Proliferation And Differentiation ◽  
Slow Twitch Muscle ◽  
Fast Twitch Muscle ◽  
Slow Twitch ◽  
Slow Twitch Fibers ◽  
Fast Twitch

Emerging studies indicate important roles for non-coding RNAs (ncRNAs) as essential regulators in myogenesis, but relatively less is known about their function. In our previous study, we found that lncRNA-Six1 can regulate Six1 in cis to participate in myogenesis. Here, we studied a microRNA (miRNA) that is specifically expressed in chickens (miR-1611). Interestingly, miR-1611 was found to contain potential binding sites for both lncRNA-Six1 and Six1, and it can interact with lncRNA-Six1 to regulate Six1 expression. Overexpression of miR-1611 represses the proliferation and differentiation of myoblasts. Moreover, miR-1611 is highly expressed in slow-twitch fibers, and it drives the transformation of fast-twitch muscle fibers to slow-twitch muscle fibers. Together, these data demonstrate that miR-1611 can mediate the regulation of Six1 by lncRNA-Six1, thereby affecting proliferation and differentiation of myoblasts and transformation of muscle fiber types.

Human Skeletal Muscle Fiber Types: Delineation, Development, and Distribution

1997 ◽  
Vol 22 (4) ◽  
pp. 307-327 ◽  
Author(s):  
Robert S. Staron
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fiber ◽  
Human Skeletal Muscle ◽  
Fiber Type ◽  
Skeletal Muscle Fiber ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Key Words Aging ◽  
Fiber Number ◽  
Human Limb

This brief review attempts to summarize a number of studies on the delineation, development, and distribution of human skeletal muscle fiber types. A total of seven fiber types can be identified in human limb and trunk musculature based on the pH stability/ability of myofibrillar adenosine triphosphatase (mATPase). For most human muscles, mATPase-based fiber types correlate with the myosin heavy chain (MHC) content. Thus, each histochemically identified fiber has a specific MHC profile. Although this categorization is useful, it must be realized that muscle fibers are highly adaptable and that innumerable fiber type transients exist. Also, some muscles contain specific MHC isoforms and/or combinations that do not permit routine mATPase-based fiber typing. Although the major populations of fast and slow are, for the most part, established shortly after birth, subtle alterations take place throughout life. These changes appear to relate to alterations in activity and/or hormonal levels, and perhaps later in life, total fiber number. Because large variations in fiber type distribution can be found within a muscle and between individuals, interpretation of data gathered from human muscle is often difficult. Key words: aging, myosin heavy chains, myogenesis, myofibrillar adenosine triphosphate

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.

On the mechanism of the mediolateral gradient of parasternal activation

1996 ◽  
Vol 80 (5) ◽  
pp. 1490-1494 ◽  
Author(s):  
A. De Troyer ◽  
A. Legrand ◽  
G. Gayan-Ramirez ◽  
M. Cappello ◽  
M. Decramer
Keyword(s):  
Fiber Type ◽  
Maximal Activity ◽  
Intercostal Nerve ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Unequal Distribution ◽  
Dorsal Rhizotomy ◽  
Fiber Type Distribution ◽  
Fast Twitch ◽  
Spontaneously Breathing

Recent studies have shown that in spontaneously breathing dogs the parasternal intercostals are activated according to a mediolateral gradient. To assess the mechanism of this regionalization of activity, we assessed the pattern of activation of these muscles after section of the dorsal roots and examined the topographic distribution of the muscle fiber types from the sternum to the chondrocostal junctions. The pattern of parasternal activity after dorsal rhizotomy was similar in all respects to that previously observed in intact animals. Thus activity in the medial parasternal bundles at the onset of inspiration frequently preceded activity in the middle bundles, and no activity was recorded from the lateral bundles. The amount of medial activity, when expressed as a percentage of the activity recorded during supramaximal tetanic stimulation of the internal intercostal nerve (maximal activity), was also consistently greater than the amount of middle activity (52.6 +/- 4.6 vs. 23.1 +/- 2.6% maximal activity; P < 0.001). Furthermore, the medial, middle, and lateral parasternal bundles had a higher proportion of slow-twitch oxidative fibers than of fast-twitch oxidative-glycolytic fibers; no topographic difference in fiber type distribution was observed. We conclude, therefore, that the mediolateral gradient of parasternal activity is probably due to the unequal distribution of central inputs throughout the pool of alpha-motoneurons.

Muscle fiber types and size in trained and untrained muscles of elite athletes

1985 ◽  
Vol 59 (6) ◽  
pp. 1716-1720 ◽  
Author(s):  
P. A. Tesch ◽  
J. Karlsson
Keyword(s):  
Muscle Fiber ◽  
Fiber Type ◽  
Vastus Lateralis ◽  
Deltoid Muscle ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Relative Distribution ◽  
Long Distance ◽  
Tissue Samples ◽  
Greco Roman

Tissue samples were obtained from vastus lateralis and deltoid muscles of physical education students (n = 12), Greco-Roman wrestlers (n = 8), flat-water kayakers (n = 9), middle- and long-distance runners (n = 9), and olympic weight and power lifters (n = 7). Histochemical stainings for myofibrillar adenosinetriphosphatase and NADH-tetrazolium reductase were applied to assess the relative distribution of fast-twitch and slow-twitch (ST) muscle fiber types and fiber size. The %ST was not different in the vastus (mean SD 48 +/- 14) and deltoid (56 +/- 13) muscles. The %ST was higher (P less than 0.001), however, in the deltoid compared with vastus muscle of kayakers. This pattern was reversed in runners (P less than 0.001). The %ST of the vastus was higher (P less than 0.001) in runners than in any of the other groups. The %ST of the deltoid muscle was higher in kayakers than in students, runners (P less than 0.001), and lifters (P less than 0.05). The mean fiber area and the area of ST fibers were greater (P less than 0.01) in the vastus than the deltoid muscle. Our data show a difference in fiber type distribution between the trained and nontrained muscles of endurance athletes. This pattern may reflect the adaptive response to long-term endurance training.

scholarly journals Calcineurin Is Necessary for the Maintenance but Not Embryonic Development of Slow Muscle Fibers

2005 ◽  
Vol 25 (15) ◽  
pp. 6629-6638 ◽  
Author(s):  
Misook Oh ◽  
Igor I. Rybkin ◽  
Victoria Copeland ◽  
Michael P. Czubryt ◽  
John M. Shelton ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Fiber Type ◽  
Oxidative Capacity ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Specific Expression ◽  
Interacting Protein ◽  
Type Composition ◽  
Slow Fiber ◽  
Fast Twitch

ABSTRACT Skeletal muscles are a mosaic of slow and fast twitch myofibers. During embryogenesis, patterns of fiber type composition are initiated that change postnatally to meet physiological demand. To examine the role of the protein phosphatase calcineurin in the initiation and maintenance of muscle fiber types, we used a “Flox-ON” approach to obtain muscle-specific overexpression of the modulatory calcineurin-interacting protein 1 (MCIP1/DSCR1), an inhibitor of calcineurin. Myo-Cre transgenic mice with early skeletal muscle-specific expression of Cre recombinase were used to activate the Flox-MCIP1 transgene. Contractile components unique to type 1 slow fibers were absent from skeletal muscle of adult Myo-Cre/Flox-MCIP1 mice, whereas oxidative capacity, myoglobin content, and mitochondrial abundance were unaltered. The soleus muscles of Myo-Cre/Flox-MCIP1 mice fatigued more rapidly than the wild type as a consequence of the replacement of the slow myosin heavy chain MyHC-1 with a fast isoform, MyHC-2A. MyHC-1 expression in Myo-Cre/Flox-MCIP1 embryos and early neonates was normal. These results demonstrate that developmental patterning of slow fibers is independent of calcineurin, while the maintenance of the slow-fiber phenotype in the adult requires calcineurin activity.

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