Oligodendrocytes, the myelin-forming cells of the central nervous system (CNS), and astrocytes constitute macroglia. This review deals with the recent progress related to the origin and differentiation of the oligodendrocytes, their relationships to other neural cells, and functional neuroglial interactions under physiological conditions and in demyelinating diseases. One of the problems in studies of the CNS is to find components, i.e., markers, for the identification of the different cells, in intact tissues or cultures. In recent years, specific biochemical, immunological, and molecular markers have been identified. Many components specific to differentiating oligodendrocytes and to myelin are now available to aid their study. Transgenic mice and spontaneous mutants have led to a better understanding of the targets of specific dys- or demyelinating diseases. The best examples are the studies concerning the effects of the mutations affecting the most abundant protein in the central nervous myelin, the p...

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Biology of Oligodendrocyte and Myelin in the Mammalian Central Nervous System

Chemistry and metabolism of lipids in the vertebrate retina

Lipids of nervous tissue: composition and metabolism.

Recent studies indicate that circulating peptides or plasma proteins, such as insulin or transferrin, or modified proteins, such as cationized albumin, undergo receptor-mediated or absorptive-mediated transport through the brain capillary wall, i.e., the blood-brain barrier (BBB). Although morphologic studies such as autoradiography or immunoperoxidase labeling can demonstrate transport of blood-borne protein into brain, there is a need for a rapid, sensitive, and quantifiable physiology-based technique for comparing the relative rates of transport of several different blood-borne peptides or proteins into brain. Therefore, the present investigations describe a carotid arterial infusion technique coupled with a capillary depletion method for quantifying transport of blood-borne cationized albumin, cationized IgG, and acetylated low-density lipoprotein (LDL). Because differentiation of true transcytosis into the postcapillary compartment of brain parenchyma from binding and/or endocytosis to the brain microvasculature is important, the present studies use a dextran density centrifugation step to deplete brain homogenate of the vasculature. In addition, 3H-labeled native albumin is used as a vascular space marker to account for release of capillary contents into the postcapillary supernatant following homogenization of brain. This study demonstrates rapid transport of cationized IgG or cationized albumin into brain, as these compounds achieve a volume of distribution of 20-30 microliters/g within 10 min of arterial perfusion. Conversely, acetylated LDL, although rapidly bound by cerebral microvasculature, is shown not to undergo transport into the post-capillary compartment of brain parenchyma. These studies provide the basis for a sensitive, quantifiable technique for studying transport of radiolabeled blood-borne peptides and proteins across the BBB of anesthetized animals.

Capillary Depletion Method for Quantification of Blood–Brain Barrier Transport of Circulating Peptides and Plasma Proteins

In the second edition of the book Neurochemistry, Rossiter (1962) stated, “Since pure ‘myelin’ is not available for direct chemical analysis, the neurochemist has been compelled to deduce the constituents of myelin from such analyses as are practicable.” The available analyses were extensive. Qualitative information had been accumulating from histological staining techniques since the latter half of the nineteenth century. Quantitative studies on brain constituents from which information on myelin could be deduced began shortly after the turn of the century. Thus in his chapter on “The Myelin Sheath, Metabolism of Myelin and Experimental Demyelination,” Rossiter was able to discuss myelin composition and metabolism with considerable assurance and accuracy. The direct analysis of myelin constituents was, however, not possible until techniques were developed for isolating myelin membranes essentially free of other subcellular structures. The first of such procedures were being developed and published in the same year Neurochemistry was published. In this chapter, I will discuss isolation procedures and the composition of purified myelin obtained by these procedures.

Isolation and Characterization of Myelin

The subcellular and submicrosomal distributions of four glycolipid-synthesizing transferases were studied in young rat brains.



(1) Two galactosyl transferases involved in the synthesis of cerebrosides, the cerebroside sulphotransferase which catalyses the synthesis of sulphatides, and the glucosyl transferase which plays an important role in the ganglioside biosynthesis were localized essentially in the microsomal fraction. Only low activities were detected in the crude mitochondrial and synaptosome-enriched fractions.



(2) A comparison of the activities of these enzymes in the crude myelin and two myelin subfractions showed that the galactosyl transferases and the cerebroside sulphotransferase had similar activities in the crude myelin and myelin-like fractions. A considerable galactosyl transferase activity was found in purified myelin. In this respect these two enzymes were different from cerebroside sulphotransferase, whose activity was much lower in purified myelin. On the other hand, glucosyl transferase had a relatively low specific activity in all three myelin fractions. Analysis of different markers showed that the activities were considerably higher than those expected from the maximum microsomal contamination calculated.



(3) Subfractionation of the microsomes demonstrated that the galactosyl transferases were more concentrated in the lower parts of the gradient, containing vesicles with attached ribosomes. Cerebroside sulphotransferase and glucosyl transferase were found predominantly in the upper and intermediate parts of the gradient, which were composed essentially of smooth-surfaced vesicles and membrane fragments. Chemical analysis of submicrosomal fractions confirmed the morphological observations.

Subcellular and submicrosomal distribution of glycolipid-synthesizing transferases in young rat brain

Quantitative thin-layer chromatography of glycolipids in animal tissues.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2871%2980486-6

N. M. Neskovic

Papers

Subcellular and submicrosomal distribution of glycolipid-synthesizing transferases in young rat brain

Quantitative thin-layer chromatography of glycolipids in animal tissues.

PAPS-cerebroside sulphotransferase activity in brain and kidney of neurological mutants.

Biosynthesis of glycolipids in myelin deficient mutants: brain glycosyl transferases in jimpy and quaking mice.

Enzymatic synthesis of lactosylceramide by a galactosyltransferase from developing chicken retina.