Nerve growth factor (NGF), in addition to its well-known effects as a soluble neurite growth-promoting factor, also appears to promote the elongation of neurites when it is adsorbed to tissue culture ...substrates. Peripheral nerve Schwann cells appear to possess a receptor for NGF on their surfaces which is induced substantially after axotomy. We have found that the adsorption of NGF onto cryostat sections of the distal stump of previously severed sciatic nerve enhances neurite growth over this tissue. This finding, coupled with the two previous observations, suggests that Schwann cell surface NGF receptors serve to bind to NGF-like growth factors so as to provide favorable surfaces for regenerating peripheral nerve axons.
...distinguishing between lesions in the upper motor neurons and those in the lower motor neurons solely on the basis of physical signs is perilous, since acute injury to the upper motor neurons can ...be manifested by transient flaccid weakness and hyporeflexia. ...imaging studies may be necessary to rule out upper motor neuron disease. ...the repetitive-stimulation studies, performed in the distribution of the left median nerve at stimulation frequencies ranging from 3 to 50 Hz, showed no pathologic decremental or incremental response.\n
Rat pineal hydroxyindole-O-methyltransferase is controlled similarly to adrenal medullary phenylethanolamine N-methyltransferase. S-adenosylmethionine (SAM), the in vivo cofactor utilized by the ...enzyme to convert N-acetylserotonin to melatonin, protects this methyltransferase against tryptic proteolysis in vitro. Furthermore, in vivo studies suggest that the nucleoside itself is controlled by glucocorticoids. Hypophysectomy decreases hydroxyindole-O-methyltransferase levels as compared with control animals, while dexamethasone and SAM administration restore enzyme levels toward control values. In vitro proteolytic studies further demonstrate that, although N-acetylserotonin does not stabilize the enzyme against trypsinization, this substrate acts synergistically with SAM to confer greater stabilization than observed with SAM alone.
PDF
