What are muscles made of? Describe.
Long, multinucleated cells
Little to no regenerative capacity
Describe: Type 1 muscle
Rich in mitochondria
High oxidative metabolism
Describe: Type 2A
Mixed oxidative/glycolytic metabolism
Quick, short contractions
Describe: Type 2B
Describe: Type 2c
Describe: Stellate cells
Run along length of myofibers
Full capacity of division + fusion
Restore - mature myofibers
What are the two classifications of changes in myofibers?
What are neuropathic changes to myofibers?
Effect or absence of nerve supply
What are myopathic changes in myofibers?
Primary changes within muscle cells/fibers
What is involved in nueromusclar disease?
Lower motor neurons
Neuromusclar junctions and muscles
What are clinicopathologic findings to suggest that there is damage to the muscle?
Creatine kinase elevation
AST + LDH elevation
Carbonic anhydrase III + FABP
Possible cause for pallor
Possible cause for pale streaking
Possible cause for dark red mottling
Possible cause for green color to muscles
Possible cause for lipofuscin
Possible cause for black
Possible cause for thickened/firm muscle texture
Possible cause for soft texture to muscles
Fat infiltration or necrosis
How do you collect muscle samples?
Collect strip not larger than 1 cm
Myofibers running length wise
Place sample on rigid surface to avoid contraction band artifact
What are degenerative muscle disease?
Myopathies resulting in segmental or global necrosis in which inflammatory cells are not the cause of damage
What are the possible causes of degenerative muscle disease?
What can cause ischemia that leads to degerneation of the muscle?
Occulusion of a major blood vessel
External pressure on a muscle
Swelling of a muscle in a nonexpendable compartment
What is an example of ischemic necrosis in cattle?
Downer cow syndrome
What animal most commonly sees muscle degeneration due to nutritional defiecencies?
What nutritional deficiencies cause muscle degeneration?
What is the function of selenium?
trace mineral vital of glutathione peroxidase system
Protects from oxidative injurt
What disease does selenium deficiency cause?
White muscle disease
What are the three major toxins that cause muscle degeneration?
Who is affected by pasture-associated myopathy?
What are the ionophores that can cause muscle degeneration?
What are examples of plants that cause muscle degeneration?
What predisposes an animal to exertional myopathies?
Vit E/Selenium deficency
Glycogen storage disease
Severe electrolyte depletion
What are examples of extertional rhabdomyolysis?
Monday morning sickness
What are the three classes of congenital defects that lead to musclar degeneration?
Describe: Muscular dystrophy
Inherited, progressive, degenerative primary disease of myofibers
Ongoing necrosis + regeneration
What is a disease of muscular dystrophy in cats and dogs? What is affected?
Duchennes's muscular dystrophy
Inability of myofibers to relax
= spasmodic contractions
Most due to abnormal ion channel formation
What are the three types of anatomical defects that lead to musclar degeneration?
Failure of normal development
What is an example of genetic defect in cattle and dogs that cuase muscular degeneration?
aka congenital muscular hyperplasia
How does malignant hyperthermia occur?
Unregulated release of calcium from sarcoplasmic reticulum
Leads to excessive contraction = heat
Increased body temperature is the result
What animals are affected by malignant hyperthermia?
Dogs + Horses + Pigs
What is the defect in exactly that causes malignant hyperthermia?
What can trigger a maligant hyperthermia episode?
Stress - porcine stress syndrome
What characterizes a metabolic myopathy?
Reduced muscle cell energy production
Describe: Type II Glycogenoses
Acid maltase deficiency
Describe: Type IV glycogenoses
Glycogen branching enzyme deficiency
Describe: Type V glycogenoses
Describe: Type VII glycogenoses
What occurs with most endocrine myopathies?
Result in muscle atrophy
Mostly in type 2 fibers
What happens in dogs with hypercortisolism?
What electrolyte imbalances can cause muscle weakness?
Describe: Neuromuscular junction disorders
Impair the ability nerves impulses across the neuromuscular juncton
What are the three most common neuromuscular junction disorders?
What is the tick responsible for tick paralysis?
How does tick paralysis occur?
Toxin from tick block the release of acetylcholine from axon terminal
What animal is most commonly infected by tick paralysis?
how is recovery initiated in regards to tick paralysis?
Removal of the tick
24 to 48 hours
What bacteria is responsible for botulism?
Where is clostridium found?
What is botulism characterized by?
Profound flaccid paralysis
What is the mechanism by which the botulism toxin causes paralysis?
Cleavage of proteins in charge of release of acetylcholine from presynaptic vesciles
What type of botulism toxin are dogs most sensitive to?
What type of botulism toxin are cattle most sensitive to?
Type C + D
What type of botulism toxins are horses most sensitive to?
Type B + C
What animal is most sensitive to botulism overall?
How does the acquired form of myasthenia gravis occur?
Immune-mediated disorder caused via circulated autoantibodies against skeletal muscle acetylcholine receptor
What is the acquired form of myasthenia gravis associated with?
Secondary loss of self-tolerance to acetylcholine receptors
How is the acquired form of myasthenia gravis diagnosed?
Detection of autoantibodies to acetylcholine receptors in the blood
How does the congenital form of myasthenia gravis occur?
Dogs and Cats
Born with defective NMJ that decrease membrane surface area as a result of reduced actylcholine receptor density
What are the signs of myasthenia gravis?
Profound, sustained and progressive muscle weakness
What are the primary neoplasms of the muscle?
Peripheral nerve sheath tumors
What does rhabdomyoma/sarcoma arise from?
Intramuscular pluripotential cells
Dogs + horses + Cats
Smooth, nodular, pink, unencapsulated
Where are rhabdomyomas most commonly occur?
Larynx of adult dogs
Where are rhabdomyosarcomas most commonly found?
Oral Cavity - Tongue
What do rhabdomyosarcomas look like grossly?
Grossly pink and fleshy, often have prominent local invasion
Where do hemangiosarcomas most commonly metastasize to?
What animals are hemangiosarcomas most commonly found in?
What is seen with clostridial myositis in horses?
What are the clostridium species that infect horses causing clostridial myositis?
How does clostridium infect the muscles of a horse?
What does clostridium do in anaerobic condition?
What are the clinical signs of clostridial myositis?
Acute onset of heat, swelling and pain
Fever, depression, anorexia, and dehydration
Mild to Moderate increase in CK + AST
What does the muscle look like grossly when infected with clostridial myositis?
Swollen, edematous, and hemorrhagic
Dark red to pale areas
What are the clinical signs of botulism?
Tongue + Eyelid weakness
CK and AST are WNL
What is seen either grossly or histologically with botulism?
Aspiration pneumonia can occur
What is used to diagnose animal with botulism?
Detection of toxin in stomach contents
What bateria is responsible for piegon fever?
What are the clinical signs of piegon fever?
Multifocal intramusclar abscesses
Pectoral muscle most commonly infected
What is seen grossly with pigeon fever?
Swelling + Edema
Localized areas of suppurative exudate accumulation
What is the pathogenesis of pigeon fever?
Enter the body through wounds
Bacterial exotoxin (phospholipase D)
Leads to vascular damage + Inhibits neutrophil function
What are the two degenerative myopathies associated with streptococcus equi equi infections?
Rhabdomyloysis + muscle atrophy
What is seen histologically with purpura hemorrhagica?
Fibrinoid necrosis of blood vessels
What is the gross appearance of purpura hemorrhagica?
Disscecting hemorrhage + edema
No gas bubbles
What are the clinical signs of purpura hemorrhagica?
Petechial +/- ecchymoses
Very High CK + AST
What is the pathogenesis of purpura hemorrhagica?
Immune response to bacteria
Immune complexes form (IgA + Antigen)
Deposit in small blood vessels
Vasculitis --> vascular necrosis > hemorrhage > ischemia
What is the gross appearance of streptococcal-associated rhabdomyosis?
Decrease in muscle mass
What are the clinical signs of streptococcal-associated rhabdomyolysis + muscle atrophy?
Atrophy along paraspinal + gluteal muscles
High elevations of CK + AST
No purpura hemorrhagica seen
What is the pathogenesis of streptococcal-associated rhabdomyolysis?
Predisposed to immune-mediated damage caused by cross-reaction of streptococcal antibodies with muscle proteins
What animals are most likely to get streptococcal-associated rhabdomyolysis?
What is the cause of protozoal myopathy?
Most commonly Fayeri
What is seen histologically with protozoal myopahty?
Cysts within myofibers
No inflammatory reaction generated
What is the pathogenesis of nutritional myopathy?
Lack of elements enhance oxidative injury of actively contracting muscle fibers
What is the gross appearance of nutritional myopathy?
Depends on stage of necrosis
What are the clinical signs of nutritional myopathy?
Weak suckling or impaired mastication
Bilateral symmetrical atrophy of masseter musccles
Mild to moderate increase in CK + AST
What is the pathogenesis behind ionophore toxicity?
Results in calicum overload
Leads to necrosis of skeletal + cardiac muscle cells
Describe: Hyperkalemic periodic paralysis
Point mutation in gene encoding for alpha unit of skeletal muscle sodium channel
What are the gross findings in HYPP?
What is seen histologically in HYPP cases?
Vacular degeneration of type 2 myofibers
What are the clinical signs of HYPP?
Transient muscle spasms
Protrustion of third eyelid
Gerenalized flaccid paralysis
CK + AST normal
What is the pathogenesis of HYPP?
Delayed inactivation of sodium channel acitivity
Leads to membrane instability + continous electrical activity
Describe: Equine polysaccharide storage myopathy
Autosomal dominant trait
Point mutation in skeletal muscle glycogen synthase 1 gene
What horses are most affected by EPSSm?
Pony of Americas
What are the clinical signs of EPSSM?
Symmetric muscle atrophy
CK + AST normal
What is seen histologically with EPSSM?
Aggregates of intracytoplasmic material
Stains postive with PAS reaction for glycogen
What is seen grossly with EPSSM?
Affected muscles are pale pink or diffusely red tinged
What is the pathogensis of EPSSM?
Accumulation of glycogen within myofibers
Leads to insuffiecent energy prodcution + abnormal myofiber function
Describe: Glycogen brancher enzyme deficiency
Accumulation of unbranched chains of glycose occur wtihin the cell
Leads to abnormal glycogen formation + intramyofiber deposits
What are the gross findings with GBE def?
What are the clinical signs of GBE def?
Foals may be aborted, stillborn, or weak
Rhabdomyosis or cardiac failure early in life
What is seen histologically with GBE def?
Hyaline inclusions within skeletal and cardiac muscle
RESISTANT TO AMYLASE DIGESTION
Positive stain with PAS
What is the cause of monday morning sicknees?
What is seen grossly with monday morning sickness?
Similar to EPSSM
What is seen histologically with monday morning sickness?
Localized widespread type 2 myofiber necrosis
What are the clinical signs of monday morning sickness?
Sudden onset of stiff gait
Reluctance to move
Swelling of muscle grousp
CK + AST markedly elevated
What does ischemic myopathy affect?
Describe: Postanesthetic myopathy
Occurs in horses
Prolonged recumbency during general anesthesia
What are the four peripheral neuropathies in horses?
Unilateral scapular muscle atrophy
Due to traunma or damage to suprascapular nerve
Poorly fitted harness
Sporadic pelvic limb neuropathy
Exaggerated flexion of one or both limbs
Possible: Hypochoeris plant
Describe: Fibrotic myopathy
Hamstring muscle trauma
restriction of forward swing of affected limb
What nerve is affected in laryngeal hemiplagia?
Left recurrent laryngeal
What are possible causes of laryngeal hemiplagia?
Extension of guttural pouch infection and/or tumors
What is a characteristic of laryngeal hemiplagia?
What are the two kinds of motor neuronopathies seen in horses?
Equine protozoal myeloencephalitis
Equine motor neuron disease
What organism is responsible for EPM?
How does EPM occur?
Denervation atrophy of fasical + gluteal muscles
What causes equine motor neuron disease?
Prolonged vit E deficiency
What are the clinical signs of equine motor neuron disease?
Rapid muscle wasting
What is seen grossly in a horse with equine motor neuron disesae?
Muscles turn yello-tan
What bacteria is responsible for black leg in cattle?
What is the pathogenesis of blackleg?
Spores remain dormate in muscle
Hypoxia/anoia leads to spore activation
Bacterial production of toxins
Capillary wall damage
Hemorrhage + Edema + Necrosis
What are the pyogenic bacteria that affect cattle?
What does actinomyces bovis cause in cattle?
What is the pathogenesis of lumpy jaw?
Bacteria infects bone of jaw
Chronic granulomatous to pyogranulomatous/fibrosing osteomyelitis
What does actinobacillus lignieresii cause in cattle?
What are the clinical signs of wooden tongue in cattle?
Excessive salivation due to difficulty swallowing
What are the gross findings with wooden tongue?
Rigid and swollen tongue
What is seen histologically with wooden tongue?
Multiple areas of pyo/granulomatous inflammation
Contains eosinophilci material
What is the pathogenesis of wooden tongue?
Severe granulomatous to pyogranulomatous
Fibrosis myositisi glossitis
What are the gross findings in cattle infected with trueperella pyogenes?
Single or multiple
Abscesses and/or cellulitis
Thick, yellow-green, foul smelling pus
What are the protozoal myopathies in cattle?
What occurs with neospora caninum infections in cattle?
No clinical disease in cattle
Can infect fetus leading to abortion
Describe: Eosinophilic myositis
Involved in hypersensitivity
Green discoloration of muscle due to massive infiltration of EOS
Necrosis and fibrosis occur
What muscles are most affected by nutritional myopathy in cattle?
Postural + Locomotion
How is nutritional myopathy diagnosed in cattle?
Blood levels of vit e. and selenium
What plant most commonly causes degenerative myopathy in cattle?
aka coffee weed
What does coffee weed cause in cattle?
Minimal to no mineralization
What are the clinical signs of ionophore toxicity?
CK + AST exteremely high
What is the cause of steatosis in cattle?
Defective in-utero muscle development
Replacement of adiopocytes
What is seen histologically in cattle with steatosis?
Replacement of myofibers by adiopocytes
Sudan black stain
Describe: Congenital muscular hyperplasia
Defect in myostatin gene
Animal affected: Multisystemic necrotizing vasculopathy
young Gelbvieh cattle
Animal affected: Motor neuron degenerative disease
Brown Swiss cattle
What are the causes of hypokalemic myopathy in cattle?
Glucocorticoids iwth high mineralcorticoid activity
Activation of glucose transport w/ IV administration
What are the clinical signs of hypokalemic myopath?
CK + AST moderatly elevated
What are the gross findings in hypokalemic myopathy?
Necrosis of strenal muscles
What are the bacterial/protozoal myopathies in small ruminants and camelids?
What plant causes toxic myopathy in goats?
Porsopis glandulosa - honey mesquite
What does honey mesquite do to goats?
Degeneration of motor nucleus of the trigeminal nerve
Denervation of masticatory muscles
Progressive emaciation due to inability to eat
What are the clinical signs of myotonia in goats?
Severe muscle spasms characterized by stiffness
Adoption of sawhorse stance
CK + AST normal
What is since histologically in goats with myotonia?
Moderate myofiber hypertrophy
What is the cause of myotonia in goats?
Genetic defect of skeletal muscle chloride channel
Decreased chloride conductance
Ionic instability of sarcolemma
Describe: Megaesophagus in camelids
Tunica muscularis contains skeletal muscle
Abnormal motility + dilation occur in adults
What are the causes of bacterial myopathies in pigs?
What does T. pyogenes cause in pigs?
Muscular abscesses + cellulitis
What is the cause of trichinosis in pigs?
What are the gross findings in pigs with a trichinosis infection?
Small white nodules in muscle
What is seen histologically in pigs with a trichinosis infection?
Mixed inflammatory infiltrate inducing EOS
What is the pathogensis of trichinosis of pigs?
Adult nematode lives in SI
Larvae penetrate mucosa + reach bloodstream
Larvae encyst in myofibers
Active muscle preferentially affected
What is plant affects pigs? How?
How does ionophore toxicity affect pigs?
Atria of the heart
What does gossypol cause in pigs?
Skeletal + Cardiac muscle necrosis
Liver + Lungs lesions
Describe: Myofibrillar hypoplasia
aka Splay leg
Abduction of limbs laterally
Progressive flattension of the sternum
What pigs are most commonly affected by Porcine stress syndrome?
Pigs with unpigmented hair coats
What is the cause of porcine stress syndrome?
Genetic defect in ryanodine receptor
What are the clinical signs of porcine stress syndrome?
Dramatically increased body temperature
Severe muscle rigidity
CK + AST markedly elevated
What gross findings are seen with porcine stress syndrome?
Muscles are pale, moist, swollen, and appear cooked
Shoulder, back, and thigh most affected
What is seen histologically with porcine stress syndrome?
What is the pathogenesis of porcine stress syndrome?
Ryanodine receptor = Calcium release channel in SR
Uncontrolled intracytoplasimic Ca Release
What causes protozoal myopathy in dogs?
What are clinical signs of neospora infection in a dog?
Marked muscle atrophy
CK + AST slightly increased
What is seen grossly in dogs infected with neospora?
Atrophied, pale and firm muscles
What is seen histologically in dogs with a neospora infection?
Lymphoplasmacyctic inflammatory infiltrate
Intracytoplasmic protozoal cysts
What is the pathogenesis of neospora infection in dogs?
Transmitted in utero
Invade peripheral nervous system + skeletal muscle
Affects ventral spinal roots = denervation of muscles
What are the clinical signs of Duchenne's type?
Less severe: stiff short strife gait and excercise
What is the cause of Duchenne's type in dogs?
Dystropin gene affected
Codes for membrane associated cytoskeletal protein
Repeated bouts of myofiber necrosis + regeneration
What causes death in Duchenne's type?
Respiratory failure related to severe diaphragmatic necrosis
What is seen histologically with Duchenne's type?
Progressive dissecting fibrosis
What are the clinical signs of Lab. retriever centronuclear myopathy?
Neuromuscular weakness first 6 months
Loss of patellar + triceps reflex
CK + AST normal
What are the gross findings seen with centronuclear myopathy?
What is seen histologically with centronuclear myopathy?
Clusters of atrophic myofibers
What breeds of dogs are affected by congenital myotonia?
What are the gross and histological findings of congenital myotonia in dogs?
Marked musclar hypertrophy
What are the clincal signs of congenital myotonia in dogs?
Movement with splayed, stiff thoracic limbs
Bunny hop gait in pelvic limbs
What is the cause of congenital myotonia?
Decreased chloride conduction
What are the endocrine myopathies seen in dogs?
What are the clinical signs of hypothyroidism?
What are the gross findings in a dog with hypothyroidism?
Overall muscle atrophy
Thyroid gland bilateral atrophy
What is seen histologically in a dog with hypothyroid ism?
Atrophy of type 2 myofibers
What causes hypercortisolism in dogs?
Increased adrenocortical cortisol production
What are the clinical signs of hypercortisolism in dogs?
CK + AST normal
Define: Cushingoid pseudomyotonia
Remarkabley stiff, stilted pelvic gait
Increased muscle tone of proximal thigh muscles
What are the gross + histological findings in a dog with hypercortisolism?
Sysmmetric muscle atrophy
Bilateral cortical atrophy
What causes polymyositis in dogs?
Antibodies directed to skeletal muscles only
What are the gross findings in dogs with polymysitis?
Muscle throughout body can be affected
Atrophy of temporal + masseter muscles
Esophageal muscle involvement = megaesophagus
What is seen histologically in acute cases of polymuositisi?
Variable degree myofiber necrosis
What is seen histologically in chronic cases of polymyositis?
What causes masticatory myositis?
Antibodies against myosin isoform present in type 2 myofibers in dogs
What are the clincal/gross findings in a dog with masticatory myositisis?
Bilateral symmetric swelling of temporalis and masseter muscles
Inability of full opening of the jaw
What is histological appearance of masticatory myosistis in dogs?
Lymphocytic myosistis (B-lymphocytes)
Regeneration of myfibers
What dogs seem to get extraocular muscle myositis?
< 2 years old
How does extraocular muscle myositis present?
Actue onset of bilateral exopthalmos
What are the gross findings seen with extraocular muscle myosistis?
Extraocular muscles are swollen + pale yellow
What is seen histologically with extraocular muscle myosistis?
Regeneration + Lymphocytic inflammation of muscles
What are the three disorders seen in dogs of the NMJ?
What dogs are predisposed to myasthenia gravis?
Smooth fox terriers
What breeds of dogs are predisposed to exertional rhabdomyolysis?
What muscles are most affected in dogs with exterional rhabdomyolysis?
Back + Thigh muscles
What breeds of dogs are predisposed to Motor neuron disease?
What is elevated in a cat with duchenne's type?
CK + AST + ALT
How does x-linked musclar dystrophy present in a cat?
Progressive, presistent stiff gait
Associated with marked muscular atrophy
What does FeLV cause in cats muscularly?
Immune mediated myositis