NEURAMINIDASE INJECTED INTO THE CEREBROSPINAL-FLUID IMPAIRS THE ASSEMBLY OF THE GLYCOPROTEINS SECRETED BY THE SUBCOMMISSURAL ORGAN PREVENTING THE FORMATION OF REISSNERS FIBER

Neuraminidase was injected into the cerebrospinal fluid of normal rats to investigate the assembly and fate of the desialylated Reissner's f iber glycoproteins. It was established that a single injection of neur aminidase cleaved the sialic acid residues of the Reissner's fiber gly coproteins that had been assembled before the injection, and of the mo lecules that were released over a period of at least 4 h after the inj ection. These desialylated glycoproteins underwent an abnormal assembl y that led to the formation of spheres instead of a fiber. The number of these spheres increased during the 4-h period following the injecti on, indicating that neuraminidase did not prevent the secretion of the Reissner's fiber glycoproteins into the cerebrospinal fluid. The sphe res remained attached to the surface of the subcommissural organ and b ecame intermingled with infiltrating cells, many of which were immunoc ytochemically identified as macrophages. The latter were seen to conta in immunoreactive Reissner's fiber material. It is concluded that the desialylated Reissner's fiber glycoproteins forming the spheres underw ent an in situ degradation by macrophages, thus resembling the normal process undergone by the Reissner's fiber glycoproteins reaching the m assa caudalis.