You will be given a definition of a task first, then some input of the task.
Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.

Abstract: Light and electron microscopy were used to demonstrate extensive matrix degradation in a failed chymopapain-treated disc as compared with an untreated degenerative control disc. Both specimens contained viable cells with patches of degenerative cells. There was a loss of disc height in the chymopapain-treated disc, but no improvement of symptoms. These results illustrated that even in well-circumscribed cases with documented disc protrusion into the spinal canal, the disc space narrowing following injection may aggravate the symptoms of nerve root entrapment, especially if a low-grade lateral recess stenosis is associated with the disc protrusion. The persistence or aggravation of symptoms probably is related to these anatomic considerations. The low level of enzyme activity in the injected area may or may not be correlated with the clinical response to treatment.
Output:
Aged