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- A major difference in these studies to those previously reported in Science (4) was the substitution of Methocel (Dow Chemical Co., Midland, Michigan) for Ficoll in the density—gradient medium. This was prompted by receiving several shipments of Ficoll CPharmacia Limited, New York, N. Y.) containing contaminating salts which seemed to break down cellular membranes of tissue preparations and interfered with successful fractionation (low cellular yields). Methocel products are water-soluble polymers which form aqueous dispersions by swelling and successive hydration of their structural layers. Because of this swelling mechanism they act as fluid thickeners and there can be no sharp solubility limit such as occurs in dissolution of ionizing salts. Accordingly, Methocel solutions can be controlled very accurately by concentration for degree of viscosity desired. The full utility of Methocel solutions for fractionation studies in the zonal system was not investigated, rather a 50 CPS viscosity buffered solution was used duplicating the viscosity of 30 percent (w/v) Ficoll density gradient used in the previous successful fractionations reported
- The mammalian central nervous system is a network of axon and dendrite processes (neuropil) and soma of neurons and glia which vary in their shape, in mass, and in morphological relation to each other in situ. Thus, it is difficult to mechanically separate intact brain tissue in preparation of the brain cellular filtrates without inflicting considerable breakage of the neuronal processes. Nevertheless, morphological identification of the various neuronal and glial cell types is possible after zonal centrifugation shown in these studies (Fig. 3)
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- Dill , R. E. and Martin , J. H. 1966 . Texas Rep. Biol. Med. , 24 : 720 were able to differentially stain neurons and gliain situ using Paragon polychromatic stain. Neuronal cytoplasmic RNA constituents (Nissl bodies) and nuclei of the cells were stained respectively light blue and pale blue with a prominently stained single nucleolus, while the olig-odendroglia nuclear chromatin and perikaryal cytoplasm (periplasm) were stained uniformly dark magenta color
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