Reduced numbers and intense anti-ubiquitin immunostaining of bovine motor neurons affected with spinal muscular atrophy.

Motor neurons in the spinal cord affected with bovine spinal muscular atrophy (SMA) were investigated immunohistochemically using antibodies against bovine ubiquitin. Anti-ubiquitin immunostained many chromatolytic and swollen degenerating motor neurons in the ventral horn of the SMA-affected spinal cord. The most severely swollen cells showed a lightly-stained center and a strongly-stained periphery after immunostaining. However, there were many dark, shrunken neurons in a more advanced stage that showed a completely negative reaction when immunostained. Motor neuron counts differed significantly between SMA-affected and normal animals at the lumbar intumescence and at the fourth lumbar neuromere, but not at the brachial intumescence or the second cervical level.