Glycogen In Muscle Fibers Research Articles

Functional correlates of lemur masticatory muscle fiber architecture visualized in 3D using DiceCT

The functional morphology of primate masticatory musculature has been the subject of many studies. However, with the exception of analyses of four taxa, these have always described this anatomy using traditional, destructive, gross anatomical dissections. In the current study, we use diffusible iodine‐based contrast‐enhanced computed tomography (DiceCT), in which specimens are stained with Lugol’s iodine that binds to the glycogen in muscle fibers to increase their radio‐opacity to the point of being able to discriminate between fascicles using x‐ray‐based imagery, to examine the masticatory muscle fiber architecture of nine strepsirrhine species across four genera of lemurid and Propithecus, Daubentonia and Otolemur. Not only do we report data on the traditional architectural variables of muscle volume, fascicle length (FL), physiological cross‐sectional area (PCSA), but also on variables unattainable except through three‐dimensional visualization: fascicular curvature and 3D orientation. The breadth of this sample more than triples the number of primates for which DiceCT has been applied to questions of fascicular architecture, allowing, for the first time, functional interpretation using this non‐destructive visualization technique. We have confirmed that this approach yields similar FL and PCSA measurements compared to those collected using destructive dissection. Further, this approach allows findings unavailable without this three‐dimensional visualization. Namely, fascicle angularity seems to relate to gouging – Daubentonia fascicles clearly align with its anteroposterior jaw motions. Further, fascicular compression seems relate to diet, with the most folivorous taxon in our sample, Propithecus, having 7% lower fascicular compression at near occlusion than that of Varecia, our most frugivorous taxon which has the highest arc:chord ratio (1.16) in the sample. While the scanning and subsequent “digital dissection” of the fascicles costs more time and money than does architectural data collection using traditional gross dissection, these expenses are coming down as scanners are becoming better and cheaper and digital tools (including improved selection algorithms) will allow faster fascicular analysis. Most importantly, these techniques not only yield data non‐destructively (allowing the study of specimens too precious to physically dissect), but they also preserve important three‐dimensional spatial relationships previously unavailable. This allows for the first analyses of true in situ fascicular orientation which is important for understanding naturalistic force vectors – a feature that may have important benefits for more accurate computer modeling of this complicated system – and fascicular compression – a feature with implications for understanding variable muscle activation during the chewing cycle – something previously only ever attainable with invasive live animal experimentation.

Clinical heterogeneity and phenotype/genotype findings in 5 families with GYG1 deficiency.

Objective:To describe the variability of muscle symptoms in patients carrying mutations in the GYG1 gene, encoding glycogenin-1, an enzyme involved in the biosynthesis of glycogen, and to discuss genotype-phenotype relations.Methods:We describe 9 patients from 5 families in whom muscle biopsies showed vacuoles with an abnormal accumulation of glycogen in muscle fibers, partially α-amylase resistant suggesting polyglucosan bodies. The patients had either progressive early-onset limb-girdle weakness or late-onset distal or scapuloperoneal muscle affection as shown by muscle imaging. No clear definite cardiac disease was found. Histologic and protein analysis investigations were performed on muscle.Results:Genetic analyses by direct or exome sequencing of the GYG1 gene revealed 6 different GYG1 mutations. Four of the mutations were novel. They were compound heterozygous in 3 families and homozygous in 2. Protein analysis revealed either the absence of glycogenin-1 or reduced glycogenin-1 expression with impaired glucosylation.Conclusions:Our report extends the genetic and clinical spectrum of glycogenin-1–related myopathies to include scapuloperoneal and distal affection with glycogen accumulation.

Neuromuscular, cognitive and metabolic implications of McArdle Syndrome: a global overview

Carbohydrates are the main source of body energy and they can be stored in the organism in form of glycogen and degraded when there is a need for energy. However, McArdle Syndrome patients exhibit problems to degrade glycogen due to a deficiency in myophosphorylase enzyme, making these patients intolerant to high intensity exercises because a lack of ATP available in muscle cells. It has been found muscular weakness and subsarcolemmal accumulation of glycogen in muscle fibers and in neuronal cells in McArdle Syndrome patients. In its later-onset form, it is associated to muscular dysmorphia, myoglobinuria and rhabdomyolisis. Analyzing the biochemical aspects, it is possible to notice that these patients have a low rate of ATP production due to a reduction in the availability of glucose, reducing oxidative phosphorylation. However, the metabolic “second wind” effect allows the use of other energy sources. Excessively decreased exercise-induced lactate is also characteristic of patients with McArdle Syndrome. Electromyography studies describe alterations in nerve conduction and the necessity of recruiting more motor units to contract muscle in these patients. McArdle Syndrome produces several metabolic changes in patients due to absence of myophophorylase activity. The practice of aerobic exercise acts positively in these patients probably by increasing mitochondrial metabolism.

Impact of Caffeine and Protein on Postexercise Muscle Glycogen Synthesis

Both protein and caffeine coingestion with CHO have been suggested to represent effective dietary strategies to further accelerate postexercise muscle glycogen synthesis in athletes. This study aimed to assess the effect of protein or caffeine coingestion on postexercise muscle glycogen synthesis rates when optimal amounts of CHO are ingested. Fourteen male cyclists were studied on three different test days. Each test day started with a glycogen-depleting exercise session. This was followed by a 6-h recovery period, during which subjects received 1.2 g·kg⁻¹·h⁻¹ CHO, the same amount of CHO with 0.3 g·kg⁻¹·h⁻¹ of a protein plus leucine mixture (CHO + PRO), or 1.7 mg·kg⁻¹·h⁻¹ caffeine (CHO + CAF). All drinks were enriched with [U-¹³C₆]-labeled glucose to assess potential differences in the appearance rate of ingested glucose from the gut. Muscle biopsies were collected immediately after cessation of exercise and after 6 h of postexercise recovery. The plasma insulin response was higher in CHO + PRO compared with CHO and CHO + CAF (P < 0.01). Plasma glucose responses and glucose appearance rates did not differ between experiments. Muscle glycogen synthesis rates averaged 31 ± 4, 34 ± 4, and 31 ± 4 mmol·kg⁻¹ dry weight·h⁻¹ in CHO, CHO + PRO, and CHO + CAF, respectively (P = NS). In accordance, histochemical analyses did not show any differences between net changes in Type I and Type II muscle fiber glycogen content between experiments. Coingestion of protein or caffeine does not further accelerate postexercise muscle glycogen synthesis when ample amounts of CHO (1.2 g·kg⁻¹·h⁻¹) are ingested.

Ball-Sport Endurance and Sprint Test (BEAST90): Validity and Reliability of a 90-Minute Soccer Performance Test

The aim of this study was to determine the validity and reliability of a 90-minute soccer performance test: Ball-sport Endurance and Sprint Test (BEAST90). Fifteen healthy male amateur soccer players participated and attended 5 testing sessions over a 10-day period to perform physiologic and soccer-specific assessments. This included familiarization sessions and 2 full trials of the BEAST90, separated by 7 days. The total 90-minute distance, mean percent peak heart rate (HRpeak), and estimated percent peak oxygen uptake of the BEAST90 were 8,097 ± 458 m, 85 ± 5% and 82 ± 14%, respectively. Measures obtained from trial 1 and trial 2 were not significantly different (p > 0.05). Reliability of measures over 90 minutes ranged from 0.9-25.5% (% typical error). The BEAST90 protocol replicated soccer match play in terms of time, movement patterns, physical demands (volume and intensity), distances, and mean and HRpeak values, as well as having an aerobic load similar to that observed during a soccer match. Reproducibility of key physical measures during the BEAST90 were mostly high, suggesting good reliability. The BEAST90 could be used in studies that wish to determine the effects of training or nutritional interventions on prolonged intermittent physical performance.

Differential susceptibility of diaphragm muscle fibers to neuromuscular transmission failure.

The pattern of glycogen utilization was used to determine whether various muscle fiber types in the rat diaphragm are differentially susceptible to neuromuscular transmission failure. Muscle segments from the midcostal region were repetitively stimulated directly or via the phrenic nerve at 10 or 75 Hz. Muscle fiber types were classified histochemically as type I, IIa, or IIb. The amount of muscle fiber glycogen depletion with direct stimulation depended on stimulation rate (75 Hz > 10 Hz) and fiber type (IIb > IIa > I). However, with nerve stimulation, muscle fiber glycogen depletion did not display the same dependency on stimulation rate (10 Hz > 75 Hz), although with stimulation at 10 Hz, the same rank order of fiber depletion was observed (IIb > IIa > I). This rank order of depletion was reversed (I > IIa > IIb) during repetitive stimulation of the nerve at 75 Hz. By intermittently stimulating the muscle directly during continuous nerve stimulation, we determined that neuromuscular transmission failure contributed significantly to the force decline after 2 min of stimulation at 75 Hz but relatively little to the force decline after 2 min of stimulation at 10 Hz. A significantly greater fraction of the force decline could be attributed to neuromuscular transmission failure with repetitive bouts of stimulation at 10 Hz. We conclude that neuromuscular transmission failure causes a significant portion of the force decline after 8 min of stimulation at 10 and 75 Hz, that all diaphragm fiber types are susceptible to neuromuscular transmission failure, but that type IIb fibers are particularly susceptible at higher frequencies of stimulation.

Innervation ratio is an important determinant of force in normal and reinnervated rat tibialis anterior muscles.

1. The technique of glycogen depletion and periodic acid-Schiff (PAS) staining, which identifies glycogen-free muscle fibers, was used to directly count the number (N) and measure the cross-sectional area (CSA) of muscle fibers in single motor units (MUs) from normal and reinnervated tibialis anterior (TA) muscles. Indirect estimates, derived from the proportions of muscle fiber types to MU types, were also made, and force per unit area (or specific force, SF) was calculated. Previous results using direct and indirect approaches have been contradictory. To shed more light on this issue, the relative contributions of N, mean fiber area (A), and SF to muscle-unit force were determined by the use of both methods. 2. TA muscles were examined in experimental rats 3.5-10 mo after cutting and resuturing the common peroneal nerve in one hindlimb and in muscles in age-matched control rats. Ventral roots were dissected to isolate and characterize single MUs according to contraction speed, sag, and fatigability. One unit per muscle was selected for repetitive tetanic stimulation designed to deplete muscle fiber glycogen stores. Muscles were removed for identification of the unit with the PAS reaction and histochemical fiber typing by the use of modified standard techniques. 3. In the total population of MUs sampled, isometric tetanic force ranged from 5 to 441 mN in normal muscles and from 5 to 498 mN in reinnervated muscles, and the mean values were not significantly different. In the smaller sample of glycogen-depleted units from normal muscle, for a force range of 14-217 mN, N varied from 57 to 202, and A varied from 1,135 +/- 45 to 6,706 +/- 172 (SE) microns2. Within each unit the variation in fiber area is broad. After reinnervation, for a force range of 30-278 mN, N varied from 70 to 374, and A varied from 1,694 +/- 81 to 5,425 +/- 93 microns2. Mean fiber number was 153 +/- 18 in reinnervated muscle, which is significantly higher (P less than 0.01) than the normal value of 121 +/- 9. 4. The contribution of N and A to MU tetanic force was assessed by plotting each factor as a function of force on a log-log scale. N accounts for 39% and A for 49% of the variation in force in normal muscle. The contributions are changed after reinnervation where N, accounting for 65% of force, appears to compensate for the reduced range in A, which accounts for only 19% of the variation in force.(ABSTRACT TRUNCATED AT 400 WORDS)

Neuromuscular organization of the pectoralis (pars thoracicus) of the pigeon (Columba livia): implications for motor control.

The pectoralis (pars thoracicus) of the domestic pigeon (Columba livia) is divisible into two anatomical parts, the pars sternobrachialis (SB) and the pars thoracobrachialis (TB). Innervation to this complex is from rostral and caudal branches of the brachial ventral cord. In four anesthetized pigeons, the distribution of muscle units associated with each nerve branch was mapped after prolonged stimulation of each nerve and subsequent analysis for muscle fiber glycogen. An additional three animals were used to analyze the morphology, distribution, and histochemical profiles of the muscle fibers in the SB and TB subregions. Fibers were characterized on the basis of their reactions for myofibrillar adenosine triphosphates (alkaline and acid preincubation) and reduced nicotinamide adenine dinucleotide diaphorase (NADH-D). The SB is primarily innervated by the rostral nerve branch and the TB by the caudal nerve branch. For two-thirds of the muscle's length, the SB is separated from the TB by an aponeurosis, the membrana intermuscularis (MI). SB and TB fibers located posteroventral to the caudal margin of the MI are innervated variously by both nerves. Two populations of fibers were recognized, distinguishable primarily by 1) fiber diameter and 2) density of the NADH-D reaction product. Compared to the TB, the SB possesses a higher average percentage of large fibers. Within the SB but not the TB the percentage of large fibers increases from deep to superficial. These data support our previous findings that the pars thoracicus of the pigeon is partitioned into at least two functional subunits, each with a potential for independent action on the wing during flight.

Infantile acid maltase deficiency

In infantile acid maltase deficiency (AMD), masses of glycogen accumulate in muscle fibers and are then gradually digested. The metachromatic material found in some glycogen-filled fibers, not previously studied with the electron microscope, has two different fine structural appearances. Some is similar in shape and size to glycogen beta granules, but is more intensely stained, and some is in larger granules, irregular in shape, and has even higher stain affinity. Since acid maltase deficiency was identified by Hers, others have proposed that more than one genetic defect or additional extralysosomal factors are required to account for massive glycogen accumulation and metachromasia. There is no direct evidence of additional rare genetic defects. Presented herein are two simple proposals consistent with the primary deficiency. The first is that some partly digested glycogen is condensed and that this concentrates the sites that bind dye, producing metachromasia and other differences from normal glycogen. The second is that the massive accumulation of glycogen in muscle fibers involves, in addition to previously recognized lysosomal storage and lysosomal rupture, inactivation of sarcoplasmic phosphorylase caused by disruption of excitation-contraction linkages. These two proposals are physiologically plausible and potentially testable and do not invoke the coincidence of two or more rare genetic mutations.

The alpha-glucan-uridine diphosphate glucosyltransferase reation for the identification of glycogen-depleted muscle fibers.

This paper decribes the use of the alpha-glucan uridine di-phosphate glucosyl transferase reaction for enhancing the contrast between glycogen depleted and non-depleted muscle fibers in the periodic acid schiff (PAS) reaction. Muscle fiber glycogen was depleted by prolonged repetitive stimulation of single motor units of the extensor digitorum longus muscle from the rat.

Motor unit recruitment as reflected by muscle fibre glycogen loss in a prosimian (bushbaby) after running and jumping.

A qualitative histochemical assessment of glycogen loss in biopsies was made in bush-babies after running and jumping. Glycogen loss was related to the specific type of exercise. After running, glycogen loss was greatest in the slow-twitch oxidative fibre and depletion in the fast-twitch oxidative glycolytic fibres was similarly greater than in the fast-twitch glycolytic fibres. After jumping, the opposite pattern of glycogen utilization occurred (FG>FOG>SO).

Histochemical fiber composition of some facial muscles in the cat in relation to their contraction properties.

AbstractA histochemical analysis has been performed of the activity of myofibrillar ATPase, succinic dehydrogenase. NADH2 tetrazolium reductase and phosphorylase and of the content of glycogen and fat in the orbicularis oculi, orbicularis oris and the depressor conchae muscles in the cat. All three muscles contain fibers with a low activity (type I) and such with a high activity (type II) of myofibrillar ATPase. The type II fibers predominate. In general, the type II fibers of the orbicularis oris have a higher activity of oxidative enzymes than those of the other two muscles. Differences in contraction times in relation to fiber composition are discussed. Stimulation of the orbicularis oculi at 5 Hz causes a contractile fatigue of 22–48 % in a 10 min period, which is related to a depletion of glycogen in muscle fibers with a low activity of succinic dehydrogenase. The orbicularis oris fatigues very little (2–21 %) during such a period and no significant glycogen depletion is seen. This is explained by a higher activity of oxidative enzymes in this muscle.