Developmental changes in myelin-induced proliferation of cultured Schwann cells.
Schwann cell proliferation induced by a myelin-enriched fraction was examined in vitro. Although nearly all the Schwann cells contained material that was recognized by antisera to myelin basic protein after 24 h, only 1% of the cells were synthesizing DNA. 72 h after the addition of the mitogen a maximum of 10% of the cells incorporated [3H]thymidine. If the cultures were treated with the myelin-enriched fraction for 24 h and then washed, the number of proliferating Schwann cells decreased by 75% when compared with those cells that were incubated with the mitogen continuously. When Schwann cells were labeled with [14C]thymidine followed by a pulse of [3H]thymidine 24 h later, every Schwann cell labeled with [3H]thymidine was also labeled with [14C]thymidine. Although almost every Schwann cell can metabolize the myelin membranes within 24 h of exposure, a small population of cell initially utilizes the myelin as a mitogen, and this population continues to divide only if myelin is present in the extracellular media. The percentage of the Schwann cells that initially recognize the myelin-enriched fraction as a mitogen is dependent upon the age of the animal from which the cells were prepared.
D000818:Animals; D002250:Carbon Radioisotopes; D002455:Cell Division; D002478:Cells, Cultured; D004261:DNA Replication; D007124:Immunoenzyme Techniques; D007700:Kinetics; D004676:Myelin Basic Protein / Q000032:analysis; D009186:Myelin Sheath / Q000502:physiology*; D051381:Rats; D012583:Schwann Cells / Q000166:cytology*; D013936:Thymidine / Q000378:metabolism; D014316:Tritium
D002250:Carbon Radioisotopes; D004676:Myelin Basic Protein; D014316:Tritium; D013936:Thymidine