A specific antibody to myelin basic protein has been used to localize the protein in developing rat oligodendroglia and myelin. Basic protein is found in the oligodendroglial cytoplasm of anterior commissures of 5-and 7-day old rats before the beginning of myelination. Staining of basic protein in oligodendroglia increases, becoming most intense during early myelination; it decreases during rapid myelination. Staining intensity of oligodendroglia is dependent upon age, brain region, and nervous tract studied. In myelin, reaction of basic protein with antibody decreases when large compact sheaths are present, unless tissue sections are first treated with alcohol.Myelin basic protein (MBP) comprises about 30% of the myelin proteins of the central nervous system (CNS) and is unique to the myelin membrane. Morphological evidence indicates that the myelin membrane is a spirally wrapped extension of the oligodendroglial surface membrane (1). During development of rat CNS myelin, radioimmunoassay measurements of initial MBP appearance in CNS tissue homogenates correlate with the morphological detection of compact myelin in spinal cords of 5-day-old rats. The rate of MBP accumulation can be related to the rate of myelin synthesis (2). Polyacrylamide gel electrophoresis of myelin proteins has also been used to correlate amounts of MBP with the rate of myelin synthesis (3). MBP has been found in isolated oligodendroglia of myelinated fetal bovine brain (4). However, interpretation of these results is uncertain because of probable absorption of soluble MBP present in the tissue suspension (5). Thus, the relationships among MBP synthesis, oligodendroglia, and myelin formation are not well defined.Recently, we used a light-microscopic immunocytochemical method to show that MBP is present in myelin-forming oligodendroglia of spinal cords and brains of newborn and immature rats (6). Here, we present immunocytochemical and electron microscopic evidence demonstrating that oligodendroglia in the developing CNS contain MBP before myelin sheaths are formed. As development proceeds, the amount of MBP in oligodendroglia increases as myelination begins and subsequently decreases during rapid myelin formation.
MATERIALS AND METHODSNewborn to 25-day-old Osborne-Mendel rats were anesthetized with chloral hydrate and fixed by intracardiac perfusion for 10 min with a solution containing 76 ml of HgCl2 (saturated at 00) and 20 ml of 37% (vol/vol) formaldehyde. Brain and body weights of littermates were measured. Cervical spinal cord, medulla oblongata, pons, midbrain, diencephalon, and anteriorThe costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked 'advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact. commissure were dissected and fixed for an additional 2-3 hr at 4°. Saggital midline sections of the anterior commissure, 20 uAm thick, were cut on a Vibratome. All other regions were sectioned coronally.Sections were stain...
An immunocytochemical method for detecting myelin basic protein in oligodendrocytes and myelin of newborn rat C.N.S. is described. C.N.S. tissue is perfused and fixes in HgCl2--formaldehyde and 20 micron Vibratome sections are treated with antibodies to myelin basic protein using the peroxidase--antiperoxidase method. Oligodendrocytes in the newborn rat are intensely stained by antiserum to basic protein and multiple stained processes extend from the perikaryon to myelin sheaths. With this procedure it is possible to demonstrate the geometric relationships between a single oligodendrocyte and multiple myelin sheaths. Stained oligodendrocytes and myelin are present in newborn cervical spinal cord, medulla oblongata, pons and midbrain. By 25 days of age, staining in oligodendrocytes is less intense than in newborn rats and differences in amount of staining can be detected in areas that are myelinating at different rates. With anticerebroside serum, cerebroside, of newborn and developing rat C.N.S. tissue is localized only in myelin. In the developing P.N.S., myelin basic protein is localized in Schwann cell cytoplasm and myelin sheaths of the trigeminal ganglion. Cerebroside is found only in myelin.
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