Incorporation of glycoproteins into peripheral nerve myelin

Anisotropic properties of the myelin sheath

Form birefringence curves were determined for fixed (and unfixed rat axons before and after lipid extraction. The total detected birefringence was assumed to be due to the macromolecular array of myelin sheath components (phospholipids, cholesterol, and proteins). Unfixed nerves displayed negative form birefringence. Their form birefringence curve exhibited a = refractive index match point positioned at n = 1.46 (intrinsic birefringence). Formalin fixation induced decrease in the optical retardation values but did not affect the profile of the form birefringence curves. After lipid removal, however, the anisotropic patterns of the fixed and unfixed nerves changed. A positive form birefringence was then exhibited, which is attributed to the macromolecular orientation of the protein framework of the myelin sheath. Changes in the shape of the form birefringence curve and in the localization (and number) of the refractive index match point were found. They varied as lipids had been removed from nerves subjected or not to fixation. Therefore, the form birefringence of the myelin sheath proteins plays a part in the total phenomen observed in the whole nerves interfering with that displayed by phospholipids and cholesterol of the mentioned structure.

Developmental-related changes in the lectin binding to cells of the central nervous system

Developmental related changes in Concanavalin A binding to nerve tissue are reported in this paper. ConA binding sites were studied in brains of rats and chicks at different embryological stages using the ConA-Peroxidase-DAB sequence. Developmental related changes in the extent, and pattern of ConA binding sites were observed in the neuronal perikaryon. An increment in the uptake of ConA is parallel to neuronal maturation, and to the development of Golgi apparatus and endoplasmic reticulum. A great density of ConA binding sites is found in radial glial processes in rat brain at day 15 following insemination. The density of ConA binding sites in radial glial processes decreases in the following days. At day 18 ConA binding sites in these glial processes are not found. ConA binding sites in oligodendroglia and myelin coat are not found before birth.