Defense Date


Document Type


Degree Name

Doctor of Philosophy



First Advisor

George H. DeVries


The molecule(s) involved at the axon plasma membrane (axolemma) which causes Schwann cells to proliferate has been investigated by three biochemical techniques: 1) Alkaline extraction of axolemma resulted in recovery of 95% of the mitogenic activity and 50% of the protein in the membrane-bound portion of the axolemma. 2) The axonal mitogen for Schwann cells may be associated with heparan sulfate proteoglycans at the axonal surface. Treatment of axolemma with heparitinase, which cleaves the glycosidic bonds of sulfated glycosaminoglycans, allowed mitogenic activity to be solubilized. 3) Treatment of axolemma with heparin, a highly sulfated glycosaminoglycan analogous to heparan sulfate, resulted in a soluble mitogenic extract which had a higher specific mitogenic activity than the starting material. The results of these biochemical treatments support the model of an axonal mitogen for Schwann cells which is positively charged and bound to the negatively charged portion of heparan sulfate proteoglycans.

A monoclonal antibody (1A5-2G3) was raised against the soluble mitogenic heparin extract of axolemma. The monoclonal antibody inhibited the mitogenicity of heparin extract as well as the mitogenicity of the starting axolemmal membrane. Non-specific monoclonal antibodies did not inhibit mitogenicity to as great an extent as 1A5-2G3. Mitogenic heparin extract was incubated with 1A5-2G3-coupled or non-specific antibody-coupled Sepharose. Sepharose coupled with 1A5-2G3 removed significantly more mitogenic activity from the heparin extract than did nonspecific antibodies. Using immunoaffinity techniques with the monoclonal antibody and the soluble heparin extract should permit separation of the axolemmal mitogen from other components of the axon plasma membrane.


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