Anterior Latissimus Dorsi Muscle Research Articles

Mesterolone Increases Satellite Cell Number without Inducing Hypertrophy in Type I Oxidative Muscle Fibers

Mesterolone is a synthetic oral anabolic androgenic steroid used to treat hypogonadism. Limited information is available about how this drug exerts its effects on skeletal muscle. Satellite cells (SCs) are mononuclear myogenic stem cells that contribute to postnatal skeletal muscle growth and maintenance. As SCs' activation and subsequent differentiation to new myonuclei is a major event during skeletal muscle hypertrophy, this study investigated the influence of Mesterolone on SC distribution within type I oxidative fibers of the adult avian skeletal muscle. Immunocytochemical techniques and morphometric analyses were used to calculate the fiber size, and numbers of SCs and myonuclei within the anterior latissimus dorsi (ALD) muscle of the chicken. The ALD is a slow (tonic) contracting muscle that is made up exclusively of slow‐twitch type I oxidative red fibers. The number of SCs was significantly (P<0.01) increased by very high doses (12 and 16 mg/kg) of Mesterolone administration. Similarly, the number of myonuclei was increased by administering the high doses of Mesterolone. However, this increase did not reach significant levels except at the Mesterolone dose of 12 mg/kg as the number of myonuclei increased significantly (P<0.05) by 32% compared to the number of myonuclei in the control birds. In addition, no significant (P>0.05) differences were detected in the fiber area and the myonuclear domain size between control and Mesterolone‐treated birds. This study indicates that Mesterolone treatment can increase the numbers of SCs and myonuclei without inducing hypertrophy in type I fibers of the adult avian skeletal muscle. This is because SCs in type I fibers are, most probably, required for fiber maintenance rather than hypertrophy since these fibers have a higher rate of protein breakdown because they are the ones that mostly used in daily routine activities.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Histomorphometric study of the anterior latissimus dorsi muscle and evaluation of enzymatic markers of broilers affected with dorsal cranial myopathy

Dorsal cranial myopathy (DCM), which affects the anterior latissimus dorsi (ALD) muscles of commercial broilers, is of unknown etiology, and it represents up to 6% of the partial condemnations in Brazilian slaughterhouses. This study was performed to achieve histomorphometric characterizations of the ALD muscles from male Cobb 500 broilers slaughtered at either 35 d or 42 d and to evaluate the effects of DCM on the enzymatic markers aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatine kinase (CK), and lactate dehydrogenase (LDH) and on uric acid and creatinine metabolites. Blood samples (1.5 to 3mL) and ALD muscle fragments were collected from each carcass, all of which were processed in a commercial inline processing system. For each age, twelve macroscopically normal animals and twelve animals found to exhibit DCM were randomly selected for histomorphometric evaluation and analysis of serologic profiles. Microscopic evaluations demonstrated that the muscle fibers of those with DCM exhibited a strong presence of multifocal regenerative myodegeneration as well as a substitution of muscle tissue with connective tissue (P <0.001) through fibrosis, thus characterizing the chronicity and hardness of the affected muscle. It is suggested that DCM is a localized muscle lesion because the detected serum levels of CK (P < 0.001), AST (P <0.001), ALT (P = 0.01), and LDH (P <0.001) enzymes were strongly associated with the group affected by DCM. Additional studies are needed to gain an understanding of this myopathy because it is an emerging problem in the poultry industry. In addition, it is related to DCM lesions in fast-growing broilers with the greatest slaughter weights.

Evaluation of Physiological Parameters of Broilers with Dorsal Cranial Myopathy

ABSTRACT There are several causes of carcass condemnation in poultry processing plants, including dorsal cranial myopathy (DCM), in which the anterior latissimus dorsi (ALD) muscle is affected. DCM etiology has not been elucidated yet, but this lesion impairs the visual quality of carcasses and causes economic losses due to downgrading and condemnation. The effects of this lesion on the systemic health of broilers are still unknown. In this context, the objective of this study was to evaluate muscle injury and systemic health indicators in broilers presenting or not DCM. The following parameters were evaluated: complete blood count (CBC), total protein, albumin, globulin, cholesterol, lactate, and glucose serum levels, aspartate aminotransferase (AST) and creatine kinase (CK) serum activities, and breast muscle pH. Blood samples were collected from 800 42-day-old broilers before feed withdrawal and transportation. In the processing plant, 28 carcasses presented DCM during inspection, and 28 carcasses with no DCM were used as controls. Blood biochemical parameters were not significantly different between broilers with DCM and the controls, except for AST and CK, which activities were higher in the DCM group than in the control group, suggesting that the DCM does not affect the systemic health of the broilers.

Effect of N‐2‐mercaptopropionyl glycine in postfatigue tension in avian skeletal muscle

Use of antioxidants can reduce the development of fatigue and reverse the decline of force induced by ROS. It have been reported that N‐2‐mercaptopropionyl glycine (MPG), a potent cell permeable ROS scavenger, prevents ischemic damage in heart during exercise; a process analogous in skeletal muscle fatigue, which also involves triggering of several signaling pathways, among those found the production of ROS. Thus, the purpose of this study was to determine the effect of MPG during fatigue. Anterior Latissimus Dorsi muscle of chicks was dissected and mounted on an experimental recording chamber by placing the distal end of the muscle to the hook of a mechanic‐electric transducer (Grass FT03), which through an amplifier and a analog‐digital interface (Digidata 1322A) allowed to acquire the muscle tension generated in a computer and a software of data acquisition (AXOTAPE, pCLAMP 9.2). We performed a fatigue protocol by twitches (100 V, 300 ms , 0.5 Hz). Once force decreased by 60 %, MPG was applied for 6 min (500 uM, 1 mM and 1.5 mM). The mayor effect observed by administration of MPG was at 1 mM on single twitch post‐fatigue tension. The post‐fatigue tension increased to 20.18 ± 5.92 % in peak tension (p=0.034), while in total tension was 39.95 ± 14.56 % (p= 0.046) compared to fatigued condition. Results suggest that the removal of certain amount of ROS can improve force, but it is also necessary a quantity of ROS for its normal function.

Myocytes changes and satellite cells proliferation following denervation of ALD (Anterior Latissimus Dorsi) and PLD (Posterior Latissimus Dorsi) muscles in two strains of turkey (Meleagris gallopavo)

Morphological features and chronology of myocytes changes after denervation were studied over 35 days period in 2 heavy (HW) and light-­weight (LW) strains of 5-­week-­old male turkeys. Denervation caused progressive atrophy in posterior latissimus dorsi (PLD). By day 28, the weight of the PLD muscle had reached about 62% of the non-­denervated contralateral muscle weight in both strains. On the contrary, ALD muscle mass increase progressively after denervation. Thus the maximum hypertrophy of the ALD, expressed as a percentage of contralateral muscle, was respectively about 67% and 37%,day 21 in the HW strain and day 28 in LW strain after denervation. ALD hypertrophy ceased apparently after day 21 (HW strain) and day 28 (LW strain). Morphometric analysis revealed that fast twitch (type II) fibers were atrophied after denervation, whereas slow tonic (type III) fibers were hypertrophied from day 7.Coagulative necrosis with fragmentation and lysis associated with moderate infiltration of inflammatory cells, were similar in both strains. Irregularities in mitochondrial distribution occurred mainly in type III fibers of ALD muscle at day 7. Seven and 14 days after denervation, immunolabelling of proliferating cell nuclear antigen (PCNA) revealed satellite cell activation in denervated muscles. The number of activated satellite cells was greater in the LW than HW mainly in ALD muscles

Effects of capsaicin on tension in the slow skeletal muscle fibers of the chicken (LB823)

Skeletal muscle possesses two types of muscle fibers: 1) fast and 2) slow or tonic. In skeletal muscle fibers exists evidence of vanilloid receptors presence. It is known that vanilloid receptor TRPV1 is activated by capsaicin. On the other hand, primary sensitive neurons from chicks the vanilloid receptors are capsaicin‐insensitive.By using isometric recording in bundles of the slow skeletal muscle fibers of one or two‐week age chicken dissected from the anterior latissimus dorsi muscle, the effect of capsaicin (10 μM) on caffeine (6 mM) evoked contractures was measured in the presence and absence of the antagonist capsazepine (1 μM). Capsaicin diminished maximum tension in the slow skeletal muscle fibers until 83.25±11.5%, (n=7, p=0.002) respecting to control, an effect that was partially reverted in the presence of the TRPV1 antagonist capsazepine. However, this reduction of maximum tension was not statistically significative (mean was 91.30±5.04%, n=5, p&gt;0.05). These results suggest capsaicin is capable to activate the vanilloid receptor in avian skeletal muscle fibers.Grant Funding Source: CIC2014‐RMP

The vitamin C transporter SVCT2 is down-regulated during postnatal development of slow skeletal muscles

Vitamin C plays key roles in cell homeostasis, acting as a potent antioxidant as well as a positive modulator of cell differentiation. In skeletal muscle, the vitamin C/sodium co-transporter SVCT2 is preferentially expressed in oxidative slow fibers. Besides, SVCT2 is up-regulated upon the early fusion of primary myoblasts. However, our knowledge of the postnatal expression profile of SVCT2 remains scarce. Here we have analyzed the expression of SVCT2 during postnatal development of the chicken slow anterior and fast posterior latissimus dorsi muscles, ranging from day 7 to adulthood. SVCT2 expression is consistently higher in the slow than in the fast muscle at all stages. After hatching, SVCT2 expression is significantly down-regulated in the anterior latissimus dorsi, which nevertheless maintains a robust slow phenotype. Taking advantage of the C2C12 cell line to recapitulate myogenesis, we confirmed that SVCT2 is expressed in a biphasic fashion, reaching maximal levels upon early myoblasts fusion and decreasing during myotube growth. Together, these findings suggest that the dynamic expression levels of SVCT2 could be relevant for different features of skeletal muscle physiology, such as muscle cell formation, growth and activity.

Downgrading of Heavy Broiler Chicken Carcasses Due to Myodegeneration of the Anterior Latissimus Dorsi: Pathologic and Epidemiologic Studies

Recently, in some Brazilian poultry companies, a dorsal cranial muscular lesion has been increasingly detected in broilers, causing heavy economic losses due to carcass downgrading. The observed gross lesions located in the anterior latissimus dorsi (ALD) muscle are characterized by yellowish discoloration of the skin and swelling on the dorsal cranial region of that muscle. When the ALD muscle is cut, subcutaneous edema, muscular superficial hemorrhage, pallor, adherence, and increased thickness and density are observed. Microscopically, findings indicate degenerative and polyphasic features, variation in fiber size and splitting, presence of hyaline, necrotic and regenerative myofibers, extensive fibrosis, and adipose tissue with lymphohistiocytic infiltration in all ALD muscles affected. The etiology of the lesion is unknown, and no detailed report was found in literature. The highest frequency of carcass downgrading due to this lesion was found in the heaviest and the oldest males of high-yield broiler strains (P < 0.01). This study is the first to describe the pathologic and some epidemiologic aspects of this new myopathy.

REDUCTION OF FATIGUE IN SKELETAL MUSCLE BY DIAZOXIDE: POSSIBLE PARTICIPATION OF MITOKATP.

The decrease in the ATP has an important role in the development of muscle fatigue and any event related to alteration of production of energy, this determine the tendency of muscle fatigue (Allen et al. 2008). KATP channels have been described in the inner mitochondrial membrane (mitoKATP) (Inoue et al. 1991). Garcia et al. (2009) showed that mitoKATP plays an important role in protecting the muscle during fatigue. The intention of this study was to determine the possible participation of mitoKATP channels during fatigue exploring the effect of Diazoxide (a selective activator) and selective inhibitor 5‐HD, in tension of slow skeletal muscle of chicken in a in vitro model of fatigue.Anterior Latissimus Dorsi (ALD) muscle of Arbor acres variety chicken was used. The muscle was mounted on an experimental recording chamber by mecanoelectric transducer (Grass FT03), which through an amplifier and a analog‐digital interface (Digidata 1322A) allowed to acquire the muscle tension generated by a computer (Pentium 4) and a “software” of data acquisition (pCLAMP 9.2). The muscle was stimulated until the force decreased by 70‰ repetitive electrical stimulation, then applied Diazoxide for 6 min to observe its effect (10, 30 and 100 μM, and 500 μM of 5‐HD.In a Diazoxide dose‐response curve, effect of 30 μM increased postfatige tension (40.67±8‰), combination 5‐HD with Diazoxide had no significant effect in fatigue. The results shows a protective effect of muscle by Diazoxide, however the lack of effect of 5‐HD may be due an unspecific interaction with channels of skeletal muscle.

Differential expression of genes characterizing myofibre phenotype

Skeletal muscle is composed of metabolically heterogeneous myofibres that exhibit high plasticity at both the morphological and transcriptional levels. The objective of this study was to employ microarray analysis to elucidate the differential gene expression between the tonic-'red' anterior latissimus dorsi (ALD) muscle, the phasic-'white' posterior latissimus dorsi (PLD) and 'mixed'-phenotype biceps femoris (BF) in 1-week-and 19-week-old male turkeys. A total of 170 differentially expressed genes were identified in the muscle samples analysed (P < 0.05). Gene GO analysis software was utilized to identify top gene networks and metabolic pathways involving differentially expressed genes. Quantitative real-time PCR for selected genes (BAT2D, CLU, EGFR and LEPROT) was utilized to validate the microarray data. The largest differences were observed between ALD and PLD muscles, in which 32 genes were over-expressed and 82 genes were under-expressed in ALD1-PLD1 comparison, and 70 genes were over-expressed and 70 under-expressed in ALD19-PLD19 comparison. The largest number of genes over-expressed in ALD muscles, as compared to other muscles, code for extracellular matrix proteins such as dystroglycan and collagen. The gene analysis revealed that phenotypically 'red' BF muscle has high expression of glycolytic genes usually associated with the 'white' muscle phenotype. Muscle-specific differences were observed in expression levels of genes coding for proteins involved in mRNA processing and translation regulation, proteosomal degradation, apoptosis and insulin resistance. The current findings may have large implications in muscle-type-related disorders and improvement of muscle quality in agricultural species.

MitoQ10 induces adipogenesis and oxidative metabolism in myotube cultures

Coenzyme Q(10) (CoQ(10)) plays an essential role in determination of mitochondrial membrane potential and substrate utilization in all metabolically important tissues. The objective of the present study was to investigate the effect of Coenzyme Q analog (MitoQ(10)) on oxidative phenotype and adipogenesis in myotubes derived from fast-glycolytic Pectoralis major (PM) and slow-oxidative Anterior latissimus dorsi (ALD) muscles of the turkey (Meleagris gallopavo). The myotubes were subjected to the following treatments: fusion media alone, fusion media+125 nM MitoQ(10), and 500 nM MitoQ(10). Lipid accumulation was visualized by Oil Red O staining and quantified by measuring optical density of extracted lipid at 500 nm. Quantitative Real-Time PCR was utilized to quantify the expression levels of peroxisome proliferator-activated receptor (PPARγ) and PPARγ co-activator-1α (PGC-1α). MitoQ(10) treatment resulted in the highest (P<0.05) lipid accumulation in PM myotubes. MitoQ(10) up-regulated genes controlling oxidative mitochondrial biogenesis and adipogenesis in PM myotube cultures. In contrast, MitoQ(10) had a limited effect on adipogenesis and down-regulated oxidative metabolism in ALD myotube cultures. Differential response to MitoQ(10) treatment may be dependent on the cellular redox state. MitoQ(10) likely controls a range of metabolic pathways through its differential regulation of gene expression levels in myotubes derived from fast-glycolytic and slow-oxidative muscles.

Changes in satellite cell proliferation and differentiation during turkey muscle development

Posthatch muscle growth is determined by the activation, differentiation, and fusion of satellite cells. Satellite cells composing an individual muscle are heterogeneous, which will differentially affect muscle growth. The proliferation and differentiation of turkey primary pectoralis major muscle cells were investigated in vitro at 1 d of age and at 4, 8, 16, 26, 35, 45, and 54 wk of age. The turkey was selected for these studies because turkey skeletal muscle fibroblasts do not grow in primary muscle cell cultures. Results from the proliferation analysis showed a decrease in proliferation by 8 wk of age. Differentiation into myotubes was significantly decreased by 4 wk of age and myotube diameter was decreased. The changes in muscle weight relative to total BW were measured for the anterior latissimus dorsi, biceps brachii, pectoralis major, sartorius, biceps femoris, and gastrocnemius muscles to compare the relative growth of different muscles. The age at which the muscles reached their maximum relative weight was muscle-dependent, with the biceps brachii plateauing the earliest at 4 wk and the sartorius the latest at 45 wk of age. These data suggested that changes in myogenic cells begin to occur early in muscle development and the activity of the satellite cells during these initial stages of posthatch growth is critical in overall muscle mass accumulation.

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Retention of Pax3 Expression in Satellite Cells of Muscle Spindles

Intrafusal fibers within muscle spindles retain features characteristic of immaturity, unlike the larger and more numerous extrafusal fibers constituting the bulk of skeletal muscle. Satellite cells (SCs), myogenic progenitors, are detected on the surfaces of both intrafusal and extrafusal fibers, but little is known of spindle SCs. We have recently demonstrated that, like their extrafusal counterparts, SCs in muscle spindles of posthatch chickens express paired box transcription factor 7 (Pax7) protein. During vertebrate embryogenesis, myogenic progenitors express both Pax7 and Pax3 proteins. In postnatal mice, Pax3 appears in rare SC subsets, whereas Pax7 is expressed by all SCs within extrafusal fibers. Here we test the hypothesis that Pax3 protein maintains localized expression within SCs of muscle spindles. Immunohistochemical techniques were used to identify SCs by their Pax7 expression within anterior latissimus dorsi muscle excised from posthatch chickens of various ages. A greater percentage of SCs express Pax3 within intrafusal than extrafusal fibers at each age, and the proportion of SCs expressing Pax3 declines with aging. This is the first study to localize Pax3 expression in posthatch avian muscle and within SCs of muscle spindles. We suggest that Pax3-positive SCs are involved in fiber maintenance.

Pax3 expression by satellite cells of avian skeletal muscle spindles

Pax3 protein is usually co‐expressed with Pax7 by embryonic dermomyotome cells which give rise to skeletal muscle fibers. Following myogenesis, it is held that Pax3 expression becomes restricted to a few satellite cells (SCs) of select mature muscles. Intrafusal fibers of muscle spindles are thought to persist in an immature state as, unlike extrafusal fibers, they maintain small diameters, developmental myosins, Myf5 expression and high concentrations of SCs. Thus, we hypothesize that Pax3 expression is maintained in intrafusal fibers. Immunohistochemical methods were used to quantify nuclear numbers in chicken anterior latissimus dorsi muscles excised at 9, 30, 62, and 138 days post‐hatch. SCs were identified by their Pax7 expression. In intrafusal fibers, the percentage of SCs expressing Pax3 decreased from 76% at 9 days to 16% at 138 days post‐hatch and, at each age studied, was higher in intrafusal than extrafusal fibers. In extrafusal fibers, after 14% at 9 days, only 0‐2% of SCs expressed Pax3. Muscle spindles offer a novel model for the study of Pax3 expression in SCs. Funded by the Natural Sciences and Engineering Research Council of Canada.Grant Funding SourceNSERC

Pax7 Shows Higher Satellite Cell Frequencies and Concentrations within Intrafusal Fibers of Muscle Spindles

Intrafusal fibers within muscle spindles make up a small subpopulation of muscle fibers. These proprioceptive fibers differ from most extrafusal fibers because, even in maturity, their diameters remain small, and they retain expression of developmental myosins. Although both extrafusal and intrafusal fibers contain satellite cells (SCs), comparatively little is known about intrafusal SCs. Analyzing chicken fast-phasic posterior (PLD) and slow-tonic anterior (ALD) latissimus dorsi muscles, we show that SCs of both intrafusal and extrafusal fibers express Pax7. We further test the hypotheses that intrafusal fibers display parameters reflective of extrafusal immaturity. These hypotheses are that intrafusal fibers contain (a) higher SC frequencies (number of SC nuclei/all nuclei within basal lamina) and concentrations (closer together) and (b) smaller myonuclear domains than do adjacent extrafusal fibers. IHC techniques were applied to PLD and ALD muscles excised at 30 and 138 days posthatch. The hypotheses were validated, suggesting that intrafusal fibers have greater capacities for growth, regeneration, and repair than do adjacent extrafusal fibers. During maturation, extrafusal and intrafusal fibers show similar trends of decreasing SC frequencies and concentrations and increases in myonuclear domains. Thus, extrafusal and intrafusal fibers alike should exhibit reduced capacities for growth, regeneration, and repair during maturation.

Physiological factors influencing the growth of skeletal muscle.

The growth of muscle can be regulated by developmental changes or by alterations in hormone levels or in the rate or amount of work demanded. The mechanisms and structures involved in growth processes can be studied by controlling these factors. The models used are chicken anterior latissimus dorsi (ALD) muscle under the influence of overloading and rabbit tibialis anterior (TA) muscle under the influence of chronic nerve stimulation. Both models involve changes in the isoform of myosin that is expressed. Methods of study include quantitative ultrastructural analysis, immunofluorescence and in situ mRNA hybridization. In overloaded chick ALD fibres polysomes are nonuniformly distributed between the myofibrils and in a peripheral annulus even though subcellular concentrations of the new isoform are not found. In normal rabbit muscle the highest concentration of myosin mRNA detected by in situ hybridization is found in the subsarcolemmal zone. In stimulated TA polysomes are found between myofibrils. It appears that the myosin mRNA accumulates at specific cell locations before translation; then diffusion of isomyosin and rapid exchange into myofibrils follows. Therefore, regulation of growth may be possible at the transcriptional, translational and assembly stages.

Point:Counterpoint: Satellite cell addition is/is not obligatory for skeletal muscle hypertrophy

Myofiber size is dynamically regulated, increasing and decreasing depending on muscle use. Hypertrophy is defined by increases in myofiber cross-sectional area and mass as well as myofibrillar protein content. Myofibers contain many hundreds of nuclei, each of which has a nuclear domain. A nuclear

Subcellular responses of p53 and Id2 in fast and slow skeletal muscle in response to stretch-induced overload

Tumor suppressor p53 and inhibitor of DNA-binding/differentiation Id2 were examined after 7 or 21 days of wing weighting in fast patagialis (PAT) and slow anterior latissimus dorsi (ALD) wing muscles of young adult and old Japanese quails. The contralateral wing served as the intra-animal control. Seven days of loading increased PAT and ALD muscle weight by 28 and 96%, respectively, in young birds. PAT and ALD muscle weight was 49 and 179% greater, respectively, than control muscles after 21 days of loading in young birds. In aged birds, no PAT or ALD hypertrophy was found after 7 days of loading; however, PAT and ALD muscle weight increased by 29 and 102%, respectively, after 21 days of loading. Id2 protein in the nuclear muscle fraction increased in both PAT and ALD muscles from young adult and old birds that were loaded for 7 days and in ALD muscles after 21 days of loading relative to contralateral control muscles. Nuclear p53 protein was greater in 7- or 21-day loaded PAT and ALD muscles relative to control muscles in both age groups. Cytosolic Id2 and p53 protein contents were not changed in loaded PAT or ALD muscles relative to control muscles at any time point. These data suggest that nuclear, but not cytosolic, Id2 and p53 are responsive to stretch-induced muscle overload. Moreover, the attenuated ability of the aged skeletal muscle to achieve hypertrophy does not appear to be explained by the subcellular changes in Id2 and p53 content with overload.

Effect of dimethyl sulfoxide on excitation-contraction coupling in chicken slow skeletal muscle.

To evaluate the suitability of dimethyl sulfoxide (DMSO) as a solvent for muscle-contraction studies in the chicken, its effect on the slow muscle contracture induced by high-K(+) solution was explored using the anterior latissimus dorsi (ALD) muscle from one-week-old chicks. Measurements were made of isometric tension and various characteristics of the contractures [peak tension, total tension (area under the curve), duration of contraction, drop in tension from peak to plateau, and resting tension], in the presence and absence of DMSO (20 mM). Exposure to DMSO led to a concentration-dependent reduction in resting tension of up to 9 +/- 1.8% (n = 4) with respect to the control. The threshold concentration was 10 mM, and the maximum effect was reached between 20 and 30 mM. The drop in tension from peak to plateau was three times larger in the presence of DMSO (20 mM) than in its absence. At the same concentration, there was a 10 +/- 2.3% increase in the time constant of activation. No significant changes were observed in peak tension or in total tension in the presence of 20 mM DMSO. As a consequence, this type of biological preparation is not suitable for research on muscle contractures involving drugs that must be dissolved in DMSO (at the DMSO concentrations tested here).