Anterior Latissimus Dorsi Research Articles

Increased latissimus dorsi and teres major muscle volume after anterior transfer for irreparable anterior superior rotator cuff tear: correlation with improved internal rotation strength.

While the well-established correlation between increased muscle volume and enhanced muscle strength is widely recognized, there have been no studies assessing volumetric muscle changes in transfer surgery in the shoulder. This study aimed to evaluate changes in transferred muscle volume and their clinical implications in anterior latissimus dorsi and teres major (aLDTM) tendon transfer in patients with anterior superior irreparable rotator cuff tears (ASIRCTs). The study retrospectively examined 40 patients who underwent aLDTM tendon transfers for ASIRCTs between August 2018 and January 2022. Using ImageJ software, the LDTM muscle was segmented in T2-weighted oblique axial images, and total muscle volume (tLDTMV) of both immediate and postoperative 1-year were calculated. Pearson correlation analysis was used to determine the correlation between ΔtLDTMV and ΔASES scores, Δactive-ROM, and Δstrength. The current study revealed an 11.4% increase in tLDTMV at 1-year postoperative. Patients were grouped based on postoperative ASES score: Group 1 (Optimal, n = 17) and Group 2 (Suboptimal, n = 23). Although tLDTMVimmediate postoperative values were similar between groups (P = 0.954), tLDTMV1-year postoperative value was significantly higher in Group 1 compared to Group 2 (P = 0.021). In correlation analysis, ΔtLDTMV showed significant correlations with ΔASES score (r = 0.525, P < 0.001), ΔaROM of forward elevation (FE) (r = 0.476, P = 0.002), ΔaROM of internal rotation (IR) at back (r = 0.398, P = 0.011), Δstrength of FE (r = 0.328, P = 0.039), Δ strength of IR at 90° abduction (r = 0.331, P = 0.037), and IR at side (r = 0.346, P = 0.029). Significant increase in tLDTMV was observed at 1-year postoperative for ASIRCT patients. Notably, greater ΔtLDTMV exhibited a correlation with better ASES scores, increased aROM and strength in both FE and IR. Nevertheless, further research is required by employing more robust standardized measurement tools and a larger sample size.

Anterior Latissimus Dorsi Transfer for Irreparable Subscapularis Tears Improves Shoulder Kinematics in a Dynamic Biomechanical Cadaveric Shoulder Model

Background: In young patients with irreparable subscapularis deficiency (SSC-D) and absence of severe osteoarthritis, anterior latissimus dorsi transfer (aLDT) has been proposed as a treatment option to restore the anteroposterior muscular force couple to regain sufficient shoulder function. However, evidence regarding the biomechanical effect of an aLDT on glenohumeral kinematics remains sparse. Purpose/Hypothesis: The purpose of this study was to investigate the effects of an aLDT on range of glenohumeral abduction motion, superior migration of the humeral head (SM), and cumulative deltoid force (cDF) in a simulated SSC-D model using a dynamic shoulder model. It was hypothesized that an aLDT would restore native shoulder kinematics by reestablishing the insufficient anteroposterior force couple. Study Design: Controlled laboratory study. Methods: Eight fresh-frozen cadaveric shoulders were tested using a validated shoulder simulator. Glenohumeral abduction angle (gAA), SM, and cDF were compared across 3 conditions: (1) native, (2) SSC-D, and (3) aLDT. gAA and SM were measured using 3-dimensional motion tracking, while cDF was recorded in real time during dynamic abduction motion by load cells connected to actuators. Results: The SSC-D significantly decreased gAA (Δ–9.8°; 95% CI, –14.1° to −5.5°; P < .001) and showed a significant increase in SM (Δ2.0 mm; 95% CI, 0.9 to 3.1 mm; P = .003), while cDF was similar (Δ7.8 N; 95% CI, –9.2 to 24.7 N; P = .586) when compared with the native state. Performing an aLDT resulted in a significantly increased gAA (Δ3.8°; 95% CI, 1.8° to 5.7°; P < .001), while cDF (Δ–36.1 N; 95% CI, –48.7 to −23.7 N; P < .001) was significantly reduced compared with the SSC-D. For the aLDT, no anterior subluxation was observed. However, the aLDT was not able to restore native gAA (Δ–6.1°; 95% CI, –8.9° to −3.2°; P < .001). Conclusion: In this cadaveric study, performing an aLDT for an irreparable subscapularis insufficiency restored the anteroposterior force couple and prevented superior and anterior humeral head migration, thus improving glenohumeral kinematics. Furthermore, compensatory deltoid forces were reduced by performing an aLDT. Clinical Relevance: Given the favorable effect of the aLDT on shoulder kinematics in this dynamic shoulder model, performing an aLDT may be considered as a treatment option in patients with irreparable SSC-D.

Restoration of active internal rotation following reverse shoulder arthroplasty: anterior latissimus dorsi and teres major combined transfer.

Reverse shoulder arthroplasty (RSA) for irreparable massive rotator cuff tear (mRCT) and cuff tear arthropathy (CTA) demonstrates satisfactory clinical outcomes. However, many studies have reported no significant improvements in internal and external rotation. To our knowledge, there have been no studies on new attempts to restore active internal rotation following RSA. The purpose of this study was to compare RSA alone and RSA with anterior latissimus dorsi and teres major (aLDTM) tendon transfer in patients with CTA and mRCT with combined loss of active elevation and internal rotation (CLEIR). This retrospective cohort study included patients who underwent RSA with a lateralized design and had CLEIR between October 2014 and January 2019. Two groups were classified: patients who underwent RSA alone (group R, n=36) and patients who underwent RSA with aLDTM tendon transfer (group T, n=24). Clinical outcomes, including the visual analog scale score, Constant score, American Shoulder and Elbow Surgeons score, active range of motion, score for activities of daily living requiring active internal rotation (ADLIR), and ability to perform toileting activity, were compared. Moreover, radiologic outcomes and complications were compared. The mean follow-up period was 36.8±11.6 months (range, 24-67 months). Both group R and group T showed significant improvements in clinical scores and active range of motion preoperatively and postoperatively. In group T, the Constant score (65.2±7.5 vs. 58.1±12.3, P=.008), ADLIR score (26.1±3.1 vs. 20.3±5.0, P<.001), internal rotation level with the arm behind the back (P<.001), and subscapularis-specific physical examination findings (P<.001) were significantly better than in group R. However, no significant difference in the American Shoulder and Elbow Surgeons score, forward flexion, and external rotation at 0° and 90° of abduction were found at final follow-up. Transient axillary nerve palsy was found in 2 patients in group T. However, there were no significant differences in complication rates between 2 groups. Lateralized RSA with aLDTM tendon transfer for patients with CTA and mRCT with CLEIR restored shoulder function and improved clinical outcomes, especially the ability to perform ADLIR and toileting activity.

Distinct Effects of Mesterolone on Oxidative and Glycolytic Fibers of Avian Skeletal Muscle

AimOxidative and glycolytic muscle fibers differ in their responses to physiological stimuli and pathological insults. We examined whether these fibers respond differentially to exogenous anabolic androgenic steroids (AASs) by comparing morphological and histological changes between the oxidative anterior latissimus dorsi (ALD) and glycolytic pectoralis major (PM) fibers in adult avian muscles.MethodsThe AAS mesterolone was selected for this study. Mesterolone is a synthetic steroid that has no estrogenic side effects, low hepatotoxicity, and confers oral activity that allows its oral route of administration. Adult female White Leghorn chickens (Gallus gallus) were randomly divided into five groups: a vehicle control and four mesterolone treatment groups (4, 8, 12, and 16 mg/kg). Mesterolone was administered orally every three days for 4 weeks. Immunocytochemical techniques and morphometric analyses were employed to measure the changes in muscle weight, fiber size, satellite cell (SC) composition, and number of myonuclei.ResultsMesterolone increased both body and muscle weights and induced hypertrophy in glycolytic PM fibers but not in oxidative ALD fibers. Mesterolone induced SC proliferation in both muscles; however, the myonuclear accretion was noticeable only in the PM muscle. In both muscles, the collective changes maintained a constant myonuclear domain size and the changes were dose independent.ConclusionMesterolone induced distinct dose‐independent effects in avian oxidative and glycolytic skeletal muscle fibers; these findings might be clinically valuable in the treatment of age‐related sarcopenia.

Differential response of oxidative and glycolytic skeletal muscle fibers to mesterolone

Oxidative and glycolytic muscle fibers differ in their ultrastructure, metabolism, and responses to physiological stimuli and pathological insults. We examined whether these fibers respond differentially to exogenous anabolic androgenic steroids (AASs) by comparing morphological and histological changes between the oxidative anterior latissimus dorsi (ALD) and glycolytic pectoralis major (PM) fibers in adult avian muscles. Adult female White Leghorn chickens (Gallus gallus) were randomly divided into five groups: a vehicle control and four mesterolone treatment groups (4, 8, 12, and 16 mg/kg). Mesterolone was administered orally every three days for four weeks. Immunocytochemical techniques and morphometric analyses were employed to measure the changes in muscle weight, fiber size, satellite cell (SC) composition, and number of myonuclei. Mesterolone increased both body and muscle weights and induced hypertrophy in glycolytic PM fibers but not in oxidative ALD fibers. Mesterolone induced SC proliferation in both muscles; however, the myonuclear accretion was noticeable only in the PM muscle. In both muscles, the collective changes maintained a constant myonuclear domain size and the changes were dose independent. In conclusion, mesterolone induced distinct dose-independent effects in avian oxidative and glycolytic skeletal muscle fibers; these findings might be clinically valuable in the treatment of age-related sarcopenia.

Arthroscopic-Assisted Anterior Latissimus Dorsi Transfer for Irreparable Anterior Rotator Cuff Tear: A Technical Note

Several reconstruction techniques for irreparable tears of the subscapularis tendon have been described with variable results regarding pain relief, functional recovery, and dynamic stabilization of the glenohumeral joint. Because of a more advantageous direction of movement compared with previously described transfer techniques such as transfer of the pectoralis major and pectoralis minor tendons, the anterior latissimus dorsi (LD) transfer has been proposed as a potentially beneficial treatment method. This Technical Note aims to introduce an alternative technique for the anterior LD transfer that combines the advantages of a proper muscle release and tendon reinforcement through an axillary incision with the arthroscopic intra-articular and periarticular work, including detachment of the LD tendon from its humeral insertion and reattachment at the lesser tuberosity.

Endoscopic Assisted Transaxially Approach for First Rib Resection in Thoracic Outlet Syndromes

Thoracic outlet syndrome (TOS) is a complex of signs and symptoms resulting from compression of the nerves and vessels supplying the upper limb. Previous articles described that physicians who do not regularly treat patients with TOS may not have an accurate view of this disorder, its treatment, or the possible success rate of treatment. Roos reported that TOS is underdiagnosed. Difficulty in diagnosis of TOS correctly may cause unexplained various symptoms and less objective diagnostic criteria. Moreover, surgical management for TOS remains more challenging. Transaxillary first rib resection is a well-established surgical treatment for patients with symptomatic TOS. However, it does not allow an adequate exposure of the insertion of the scalene muscle to the first rib. Because surgery for TOS involves many complex and intimately related structures, theoretical complications are numerous and may be severe. There were reported complications including brachial plexus dysfunction and fatal subclavian artery or vein injury. Recent articles showed that with the help of the endoscope, more safety and less invasive surgery has been achieved. The purpose of this study is to access the feasibility of endoscopic assisted transaxially approach for first rib resection in TOS. Forty-eight cases of TOS (21 women and 27 men; mean age, 28.1 years; range, 13-57 years) who underwent endoscopic assisted first rib partial resection were reviewed retrospectively. Conventional transaxially approach described by Roos was underwent before identification of the first rib. A 4.0 mm 30°arthroscope was introduced with an additional small port placed anterior latissimus dorsi. The scope allowed for visual identification and confirmation of the first rib and the contents of the thoracic outlet. Endoscopic classification of neurovascular bundle patterns (NVB), that is, alignment of the nerve, artery, and vein were evaluated intraoperatively. In addition, distance between anterior and middle scalene muscle at the edge of the first clavicle was measured. The first rib was transected anteriorly near the costochondral junction and posteriorly as close to the transverse process as possible in a piece by piece fashion under good visualization with great care to avoid injury to the subclavian vein immediately anterior to the anterior scalene muscles. Roos and Wood score and DASH score was obtained postoperatively. Intraoperative endoscopic findings revealed 3 classifications of NVB patterns based on alignment of scalene muscles, nerve, and artery: parallel type (9 cases) in which the artery and nerve travel parallelly; oblique type (24 cases), in which the nerve was behind the artery; vertical type (15 cases), in which the nerve were totally behind the middle scalene muscle or abnormal band. Abnormal NVB patterns (24 oblique and 15 vertical type) were found in 39 cases (81.3%). In many patients, the interscalene distance was narrow (4.9 mm, range 0-13 mm). Of the congenital abnormal fibrous bands that were identified, 26 of 31 selectively were compressing the lower trunk of the brachial plexus. The insertion of the anterior or middle scalene exceeded the scalene tubercle and extended onto the superior surface of the rib in 13 cases and this was through to narrow the interscalene interval. Postoperative clinical findings showed that excellent or good results by Roos score were obtained in 38 cases (79.2%) and fair to poor results were recorded in 10 cases (20.8%). Pre- and postoperative mean DASH scores were, 35.1 (range 2-77) and 19 (0-72), respectively. No major complication was reported except one pneumothorax. Although transaxillary first rib resection is a well-established surgical treatment for patients with symptomatic TOS, this procedure requires meticulous technique with special attention to fine details to achieve the best results with the least complications. Therefore, many physicians may hesitate to diagnose and treatment TOS.

Intermuscular S-ICD Implantation in Pediatric Patients

The use of conventional implantable cardioverter-defibrillators (ICDs) in children presents important technical challenges. We present the surgical technique necessary to adapt the subcutaneous ICD (S-ICD) implantation designed for adults, to children, including patients weighing less than 20 kg. The implant procedure implies a two-incision technique and interfascial serratus anterior-latissimus dorsi dissection to accommodate the device. S-ICD implantation was successfully performed in three patients of 19, 28, and 24 kg, respectively, two of them suffered cardiorespiratory arrest. Intermuscular thoracic implantation of S-ICD might represent an effective strategy for primary or secondary prevention of sudden cardiac death in pediatric patients.

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&lt;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&lt;0.05) by 32% compared to the number of myonuclei in the control birds. In addition, no significant (P&gt;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

Video assistant thoracoscopic (VATS) lobectomy: right lower lobe.

The 60-year-old female had a nodule in the right lower lobe of the lung, which was identified as a tumor by CT and PET-CT. Then the right lower lobectomy was performed. The posterior trocar placement, different from other surgery, is in the 5th intercostals space in the anterior latissimus dorsi, which can be built by a small incision when operation is needed. There is a vessel heteromorphosis that the inferior pulmonary vein and the mid pulmonary vein share the same stem. Also, this patient has many intumescentia lymph nodes. We can see, the lymph nodes can be ablated completely by VATS.

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.

Mitochondrial KATP channels in skeletal muscle: are protein kinases C and G, and nitric oxide synthase involved in the fatigue process?

Correspondence: Rocio Montoya-Perez Coordinacion General de Estudios de Posgrado, Universidad Michoacana de San Nicolas de Hidalgo, Francisco J Mujica s/n Ciudad Universitaria, Edif C5, Col Felicitas del Rio 58030, Morelia, Michoacan, Mexico Tel +52 44 3322 3500 ext 4157 Email biochio@yahoo.com.mx Background: Fatigue in skeletal muscle is defined as a reduction in the physical power needed to execute a function or as an inability to maintain mitochondrial ATP production. The mitochondrial potassium channel (mitoK ATP ) participates in combating fatigue in skeletal muscle. In this work, we evaluated the role of the mitoK ATP channel activator (diazoxide) and inhibitors of the signaling routes (protein kinase C, staurosporine; protein kinase G, KT5823; and nitric oxide synthase, metil N-Nitro-L-arginine ester, L-NAME), on muscle fatigue tension. In addition, we evaluated the main signaling routes used by the nitric oxide synthase protein and protein kinase C and G, in the presence of their specific activators. Methods: We used the anterior latissimus dorsi skeletal muscle of 2–3-week-old chicks. This muscle consists of slow muscle fibers. Tension was achieved by applying repetitive electrical stimulation that induced fatigue in an in vitro model. Results: Diazoxide significantly reduced muscle fatigue (P = 0.0002 in peak tension, P = 0.000002 in maximum tension) by increasing post-fatigue tension, in spite of the fact that 5-hydroxydecanoate, a selective inhibitor of mitoK ATP , did not suppress post-fatigue tension. Conclusion: Our results suggest a lack of direct interaction in inhibition of the signaling routes during fatigue-induced mitoK ATP activation. This effect is possibly due to the type of skeletal muscle fibers (slow), the stimulation protocols (twitch), and the animal (avian) model used in the study.

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.