The Chemical Composition of Myelin in Organ Cultures of Rat Cerebellum

Abstract

Myelinating organ cultures of rat cerebellum were maintained in vitro for up to 130 days. Extensive myelination took place between 7 DIV (days in vitro) and 28 DIV. Centrifugation of a crude culture myelin fraction on a discontinuous gradient yielded three layers termed light myelin, heavy myelin and membrane fraction, which exhibited an ultrastructure virtually identical to that of comparable layers prepared from surviving littermates. However, culture myelin layers showed a gross deficiency of galactolipids with a relative increase in phospholipids. The 2,3′‐cyclic nucleoside‐monophosphate phosphodiesterase (CNP) activity was decreased in the culture myelin layers, but not to an extent comparable to the cerebroside deficiency. A form of “slow myelin maturation” takes place in vitro with both myelin cerebrosides and sulphatides increasing in cultures older than 60 DIV. The results indicate that CNS myelination comprises at least two phases, and that the second phase involving galactolipid enrichment of myelin can, under experimental conditions, be partly uncoupled from the first phase without affecting the morphology or ultrastructure of the sheaths.

Chemical Analysis of Organotypic Cultures of Mouse Spinal Cord in Normal, Demyelinative, and Nondemyelinative Conditions

“…On the contrary, it is able to induce an increase in the amount of total and major individual lipids although there was a 30% decrease in the CNPase activity. A dissociation between myelin lipid levels and CNPase activity was also found in cultured cerebellum (Bradbury and Lumsden, 1979) in in vivo (Drummond et al, 1971). These findings agree with the previous reports by Lehrer et al (1979), who noted a stimulation of myelin lipid synthesis by anti-white matter serum in the absence of complement.…”

“…The low content of galactolipids resembles the observation previously reported in organ cultures of rat cerebellum (Latovitzki and Silberberg, 1973;Bradbury and Lumsden, 1979;Satomi and Kishimoto, 1981). In those cultures the phase of relative galactolipid enrichment is delayed for at least 6 weeks, whereas during normal myelination in vivo, myelin galactolipids increase from 14 days postpartum (Bradbury and Lumsden, 1979).…”

“…Recent studies have focused on the incorporation of lipids and lipid precursors and on patterns of lipids and fatty acids during the normal development of nervous tissue in vitvo (Latovitzki and Silberberg, 1973;Pleasure and Kim, 1976;Giesing and Zilliken, 1976;Bradbury and Lumsden, 1979;Satomi and Kishimoto, 1981). Also, CNS tissue culture was used to study the effect of anti-white matter serum on myelin and lipid synthesis (Lehrer et al, 1978Lapin et al, 1979).…”

Myelin

“…Two groups of investigators have purified myelin fraClions from pooled explants and analyzed them far either lipids (Bradbury and Lumsden, 1979) or proteins (Fagg et al, 1979b). The cerebroside levels in myelin from rat cerebellar cultures were abnormally low (Bradbury and Lumsden, 1979), and the myelin proteins from rat spinal-cord cultures contained a greater proportion of high-molecular-weight proteins than found in spinal-cord myelin at the same developmental age (Fagg et al, 1979b). These findings are similar to those reparted in immature myelin (see Section IIl.A.4).…”

“…Myelin isolated. from explant eultures has a low eerebroside content (Bradbury and Lumsden, 1979), suggesting that its eomposition is more like that of immature myelin.…”