Fibrotic myopathy of the iliopsoas muscle in a dog

Fibrotic myopathy of the iliopsoas muscle developed in a dog, following extensive migration of a grass awn within the muscle and adjacent subcutaneous tissue. The dog was initially presented for evaluation of a fluctuant swelling over the right flank region. The clinical and imaging findings were suggestive of iliopsoas fibrotic myopathy and the diagnosis was confirmed by histopathology. This is the third report of iliopsoas fibrotic myopathy in a dog, the first report to describe the postmortem pathologic changes and the first report of iliopsoas fibrotic myopathy subsequent to foreign body migration.     

Applications of a semitendinosus muscle flap in two dogs

The proximal half of the semitendinosus muscle can be used as a versatile vascularized local transposition flap to reconstruct anatomic faults in the adjacent perineum in dogs. The flap is easy to dissect, and the arc of rotation is considerably beyond the midline. The location, size, and direction of the major vascular pedicle from the caudal gluteal artery is conducive to dependable flap perfusion.     

Cinematographic analysis of the gait of lame horses V: Fibrotic myopathy

A horse with fibrotic myopathy of the semitendinosus muscle of the right hind limb was studied. Observation of the horse in movement showed that protraction of the affected limb terminated abruptly and the hoof was slapped down on the ground. High speed cinematography with computer-aided analysis of the film was used to analyze the gait in greater detail. The results showed that the right hind limb approached the ground almost vertically making impact toe-first, whereas the left hind limb was moving forward relative to the ground when it made heel-first impact. Significant differences were recorded in the sequence and placement of the limbs on the 2 diagonals. The hind limb preceded the forelimb at impact on both diagonals, but at lift-off the lame right hind limb preceded the left forelimb, whereas the sound left hind limb lifted off later than the right forelimb. The distance between the diagonal limb pair during the stance phase was shorter for the left diagonal (left fore-right hind limb pair) than for the right diagonal (right fore-left hind limb pair) (P<0.01). The suspension following the left diagonal was longer than that following the right diagonal (P<0.01).     

Hypodipsic hypernatremia and associated myopathy in a hydrocephalic cat with transient hypopituitarism

Hypodipsic hypernatremia developed in association with hypopituitarism and hydrocephalus in a 7-month-old cat. Initial clinical signs (generalized weakness, cervical ventroflexion) were related to a hypernatremia-induced polymyopathy. Forced water intake and dietary sodium restriction corrected the hypernatremia and signs of muscle dysfunction. After restoration of eunatremia, secretion of pituitary hormones normalized. It was speculated that hypothalamic dysfunction, possibly related to hydrocephalus, induced both hypodipsia and transient hypopituitarism.     

Avulsion of the lateral head of the gastrocnemius muscle in a cat

A 7-year-old male, castrated, domestic shorthair cat was presented with a plantigrade stance of the left pelvic limb. An avulsion of the lateral head of the gastrocnemius muscle was diagnosed based on clinical examination and radiographic assessment. Surgical reduction and fixation were achieved with modified locking loop sutures through bone tunnels in the supracondylar tuberosity of the distal femur. Additionally, a temporary calcaneotibial positional screw was placed in order to neutralise forces on the gastrocnemius muscle. No postoperative complications were encountered and the cat made a full recovery.     

Sarcomere length influences postmortem proteolysis of excised bovine semitendinosus muscle

The interaction between sarcomere length and postmortem proteolysis as related to meat tenderness is not clear. The extent of thick and thin filament overlap alters actomyosin binding and may alter substrate availability during aging-induced tenderization. The objective of this study was to determine the influence of sarcomere length on proteolytic degradation in beef. Strips from bovine semitendinosus were either stretched 40% and restrained or allowed to shorten unrestrained in an ice bath. After rigor completion, 0.6-cm cross sections were fabricated and were randomly assigned to 2, 4, 7, or 10 d of aging treatments. Myofibrils were isolated for sarcomere length determination. Samples were collected and frozen for shear force analysis, and muscle proteins were extracted for SDS-PAGE and Western blotting analyses to determine troponin T (TnT) proteolysis. Sarcomere length was greater (P < 0.01) in stretched muscle samples compared with shortened samples (2.57 vs. 1.43 microm, respectively). Correspondingly, shear force values were greater (P < 0.05) in shortened samples than stretched samples. Western blots revealed the presence of 3 major intact TnT bands that diminished with time postmortem and 4 bands (TnT degradation products) that accumulated during postmortem storage. Quantification of intact TnT showed increased (P < 0.05) proteolysis at 4 and 7 d postmortem in samples with long sarcomeres. By 10 d, only traces of the greatest molecular weight intact TnT band were evident in both shortened and stretched samples, suggesting this TnT band may be more susceptible to proteolysis than other intact TnT bands. Degradation products of TnT appeared earlier postmortem in samples with long sarcomeres. The 30-kDa TnT fragment appeared after 7 d of postmortem storage in samples with long sarcomeres but not until 10 d in muscle containing short sarcomeres. Collectively, these data show that postmortem TnT proteolysis is sarcomere length-dependent and suggest that thick and thin filament overlap may influence the postmortem aging process in beef.     

Plasma indicators of muscle damage in a model of nutritional myopathy in weaner sheep

SUMMARY Subclinical nutritional myopathy was induced in 5-month-old sheep by feeding them a diet low in vitamin E and selenium. Subsequently clinical myopathy was induced by dosing with protected polyunsaturated fatty acids. Plasma activities of creatine kinase (CK), pyruvate kinase, aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase and aldolase, enzymes of muscle origin, all remained above their reference ranges in clinically affected sheep, but fluctuated widely. Similar fluctuations occurred in subclinically affected animals, resulting in some activities being within the reference ranges and some above, at different times. Plasma malondialdehyde, an indicator of lipid peroxidation, proved of no diagnostic value. Terminal plasma CK activities were significantly correlated with microscopic damage in the vastus lateralis (VL), but not the vastus intermedius (VI) or the tensor fascia lata (TFL) muscles. AST was the most highly correlated with damage in VI and VL. In two clinically affected sheep successfully treated with an oral dose of α-tocopherol actetate all enzymes decreased steadily to within their reference ranges, at rates probably related to their plasma half-lives. These results suggest that measurement of plasma CK activity would be useful in monitoring recovery of treated sheep.     

Linear arrector pili muscle hamartoma on the tail of a sphynx cat

Arrector pili muscle (APM) hamartoma is reported in humans and dogs. We describe a linear APM hamartoma in a sphynx cat. The lesion was characterized by multiple nodules distributed linearly along the tail, made of randomly arranged hypertrophic smooth muscles, the size of which tended to wax-and-wane during a one year follow-up.     

Cutaneous smooth muscle tumors in the dog and cat

Cutaneous smooth muscle tumors may arise from arrector pili muscles and from smooth muscles of the dermal vasculature. This report describes histologic and immunohistochemical features of eight arrector pili hamartomas in 8 dogs, 15 piloleiomyomas in 10 dogs and 3 cats, 10 piloleiomyosarcomas in 9 dogs and 1 cat, 1 angioleiomyoma in 1 cat, and 9 angioleiomyosarcomas in 6 dogs and 3 cats. Hamartomas and tumors arising from arrector pili muscles preferentially originated from the dorsal trunk. 5/5 (100%) arrector pili hamartomas, 10/12 (83%) piloleiomyomas, 4/5 (80%) piloleiomyosarcomas, 1/1 (100%) angioleiomyoma, and 6/7 (86%) angioleiomyosarcomas were positive for smooth muscle actin. 5/5 (100%) arrector pili hamartomas, 10/12 (83%) piloleiomyomas, 4/5 (80%) piloleiomyosarcomas, 1/1 (100%) angioleiomyoma, and 1/7 (14%) angioleiomyosarcomas were positive for desmin. Two incompletely excised canine angioleiomyosarcomas recurred locally. Metastases were not reported.