Muscle fibres are multinuclear cells, and the cytoplasmic territory where a single myonucleus controls transcriptional activity is called the myonuclear domain (MND). MND size shows flexibility during muscle hypertrophy. The MND ceiling hypothesis states that hypertrophy results in the expansion of MND size to an upper limit or MND ceiling, beyond which additional myonuclei via activation of satellite cells are required to support further growth. However, the debate about the MND ceiling hypothesis is far from settled, and various studies show conflicting results about the existence or otherwise of MND ceiling in hypertrophy. The aim of this review is to summarise the literature about the MND ceiling in various settings of hypertrophy and discuss the possible factors contributing to a discrepancy in the literature. We conclude by describing the physiological and clinical significance of the MND ceiling limit in the muscle adaptation process in various physiological and pathological conditions.
Humans ; Muscle Fibers, Skeletal/physiology* ; Hypertrophy/pathology* ; Muscle, Skeletal

Calpains are intracellular nonlysosomal Ca(2+-) regulated cysteine proteases, widely located in the tissues of most mammals. Skeletal muscle tissue mainly expresses m-calpain, µ-caplain, n-calpain, and their endogenous inhibitor calpastatin. They are closely related to the cell apoptosis, cytoskeleton formation, cell cycles, etc. Calpains are also considered to be participating in the protein degradation process. Severe burns are typically followed by hypermetabolic responses that are characterized by hyperdynamic circulatory responses with increased proteolysis and cell apoptosis. Recently, overloading of Ca(2+) in skeletal muscle cells, which activates the calpains is observed after a serious burn. This paper aims to review the current research of the relationship between calpains and post-burn skeletal muscle wasting from the perspectives of structure, function, and physiological activities.
Animals ; Burns ; metabolism ; pathology ; Calpain ; metabolism ; Muscle, Skeletal ; metabolism ; pathology

Animals ; Hindlimb ; Male ; Mice ; Mice, Inbred C57BL ; Muscle Fibers, Skeletal ; Muscle, Skeletal/pathology* ; Muscular Atrophy

Most of the major advances in burn treatment were made within the last five decades. However, hypermetabolic response after severe burn remains a problem in the treatment of patients with massive burn. As skeletal muscle accounts for over 50% of body cell dry weight, its catabolism exerts profound effect on body metabolism as a whole. Main mechanisms underlying skeletal muscle wasting induced by severe burn include activation of ubiquitin-proteasome pathway, bringing about breakdown of muscle protein, and myonuclear apoptosis. Therapeutic strategies for skeletal muscle wasting after burn mainly include maintenance of room temperature at (31.5 +/- 0.7) degrees C, early active and passive exercise of skeletal muscles, administration of beta adrenergic receptor blocker such as Propranolol, recombinant growth hormone, androgen, and insulin, which has lately been proven to possess the effect of suppressing myonuclear apoptosis after burn. Combination of multiple therapeutic strategies is beneficial in reducing complications of burn patients, particularly wide ranged skeletal muscle atrophy, to achieve a better clinical outcome.
Apoptosis ; Burns ; drug therapy ; metabolism ; pathology ; Humans ; Muscle, Skeletal ; metabolism

A variation of the trapezius muscle was observed in a Korean female adult cadaver during routine student dissection. The lateral, upper three-fourths of the descending portion of the trapezius muscle were separated from the remainder of the muscle. This single, isolated bundle fused above the insertion of the midpoint of the clavicle, and attached to the clavicle as a separate tendon. The remaining descending portion inserted into the clavicle and scapula as usual. This abnormal muscle bundle is considered as a variant of the cleido-occipitalis cervicalis, and formation of this variation is discussed based on the embryological development of the relative muscular structures.
Female ; Human ; Korea ; Middle Aged ; Muscle, Skeletal/*abnormalities/pathology ; *Shoulder

An unusual variation creates interest among anatomists, but is a cause of concern among clinicians when it mimics a pathology. The sternalis muscle is one such variant of the anterior chest wall located subcutaneously over the pectoralis major, ranging from a few short fibers to a well-formed muscle. We observed a bilateral case, which was accompanied by an atypical presentation on the left side where a huge, bulky sternalis muscle was associated with the absence of the sternal fibers of the pectoralis major. The fibers arose as a lateral strip from the upper two-thirds of the body of the sternum and costal cartilages 2 through 6 with the intervening fascia and aponeurosis of the external oblique. The right sternalis was strap-like and was placed vertically over the sternal fibers of the pectoralis major, arising from the underlying fascia and aponeurosis of the external oblique. The sternalis muscles, on each side, converged into an aponeurosis over the manubrium that was continuous with the sternal heads of the right and left sternocleidomastoid muscle, respectively. This rare anomaly has puzzled radiologists and surgeons in confirming diagnosis, missing it all together or mistaking it for a tumor on mammography or CT scan. These findings prompted us to review its topography, development, and application in relation to the anterior chest wall.
Adult ; Human ; Male ; Muscle Fibers/pathology ; Muscle, Skeletal/*abnormalities/pathology ; *Thorax

Buttocks ; pathology ; Humans ; Muscle Neoplasms ; diagnosis ; Muscle, Skeletal ; pathology ; Synovitis, Pigmented Villonodular ; diagnosis

Histopathological findings of eosinophilic myositis in the carcass of a slaughtered Korean native cow are presented. Lesions contained massive fibrous septae with vacuolar changes in some lesions, and the hypercontraction and rupturing of muscle bundles, with replacement by eosinophils. Necrosis and severe eosinophil infiltration were observed. Sarcoplasmic fragmentation and atrophy developed. Typical of granuloma, calcified myofibers were focally surrounded by macrophages and numerous inflammatory cells, and multinucleated giant cell formation was evident.
Animals ; Cattle ; Cattle Diseases/*pathology ; Eosinophilia/pathology/*veterinary ; Female ; Muscle, Skeletal/*pathology ; Muscular Diseases/pathology/*veterinary

OBJECTIVETo study the histochemical changes of muscle fibers and motor end-plates of paravertebral muscles, and analyze their relationship with the etiology of scoliosis associated with syringomyelia as compared with adolescent idiopathic scoliosis (AIS) and non-scoliotic patients.

METHODSAll the enrolled patients were divided into three groups: Group I consisted of 20 patients with scoliosis associated with syringomyelia, Group II included 16 patients with AIS, and Group III included 10 patients without scoliosis. Bilateral biopsy of paravertebral muscles was performed during scheduled spinal surgery. HE staining, nicotin-lateral biopsy of paravertebral muscles was performed during scheduled spinal surgery. HE staining, nicotinamide adenine dinucleotide hydrogen-tetrazolium reductase ( NADH-TR), and alpha-naphthyl acetate esterase staining techniques were used for histological evaluation. Neurogenic and myogenic pathological changes and changes of motor end-plates of paravertebral muscles were compared among these three groups.

RESULTSNeurogenic pathological changes of muscle fibers were found in 12 (60% ) patients in Group I but was not found in Group II and III. The numbers of both T0 type motor end-plates and pathological end-plates on the convex side were significantly larger than those on the concave side in Group I ( P < O. 05 ). In Group II , however, the numbers of both T0 type motor end-plates and pathological end-plates on the concave side were significantly larger than those on the convex side (P < 0.05). No significant difference was found between two sides in Group III.

CONCLUSIONThe histochemical changes of paravertebral muscles in patients with scoliosis and syringomyelia are different from those in AIS patients. It is suggested that a primary denervation of paravertebral muscles exist in scoliosis associated with syringomyelia, which may play a role in the pathogenesis of scoliosis.

Adolescent ; Adult ; Case-Control Studies ; Child ; Female ; Humans ; Male ; Motor Endplate ; pathology ; Muscle Fibers, Skeletal ; pathology ; Muscle, Skeletal ; pathology ; Scoliosis ; complications ; pathology ; Staining and Labeling ; Syringomyelia ; complications ; pathology

Congenital neuromuscular disease with uniform type 1 fiber (CNMDU1) is a rare but distinct form of nonprogressive, congenital myopathy. CMNDU1 is characterized by a type 1 muscle fiber content of more than 99%. This condition has only been previously described in a few reports. The authors report an 11-year-old girl who exhibited delayed developmental milestones, proximal muscle weakness, and bilateral ptosis. Her serum creatine kinase level was normal but an electromyographic study showed myopathic changes. A biopsy specimen from the left deltoid muscle revealed a uniformity of type 1 fibers (greater than 99%) with a moderate variation in fiber size. This is the first case of CNMDU1 reported in Korea.
Biopsy ; Child ; Developmental Disabilities/*pathology ; Female ; Human ; Muscle Fibers, Slow-Twitch/*pathology ; Muscle, Skeletal/*pathology ; Neuromuscular Diseases/congenital/*pathology