In vivo studies on the metabolism of [15,16-3H]tetracosanoic acid (lignoceric acid) in adult rat brain

Lipids of nervous tissue: composition and metabolism

As indicated in the Introduction, the many significant developments in the recent past in our knowledge of the lipids of the nervous system have been collated in this article. That there is a sustained interest in this field is evident from the rather long bibliography which is itself selective. Obviously, it is not possible to summarize a review in which the chemistry, distribution and metabolism of a great variety of lipids have been discussed. However, from the progress of research, some general conclusions may be drawn. The period of discovery of new lipids in the nervous system appears to be over. All the major lipid components have been discovered and a great deal is now known about their structure and metabolism. Analytical data on the lipid composition of the CNS are available for a number of species and such data on the major areas of the brain are also at hand but information on the various subregions is meagre. Such investigations may yet provide clues to the role of lipids in brain function. Compared to CNS, information on PNS is less adequate. Further research on PNS would be worthwhile as it is amenable for experimental manipulation and complex mechanisms such as myelination can be investigated in this tissue. There are reports correlating lipid constituents with the increased complexity in the organization of the nervous system during evolution. This line of investigation may prove useful. The basic aim of research on the lipids of the nervous tissue is to unravel their functional significance. Most of the hydrophobic moieties of the nervous tissue lipids are comprised of very long chain, highly unsaturated and in some cases hydroxylated residues, and recent studies have shown that each lipid class contains characteristic molecular species. Their contribution to the properties of neural membranes such as excitability remains to be elucidated. Similarly, a large proportion of the phospholipid molecules in the myelin membrane are ethanolamine plasmalogens and their importance in this membrane is not known. It is firmly established that phosphatidylinositol and possibly polyphosphoinositides are involved with events at the synapse during impulse propagation, but their precise role in molecular terms is not clear. Gangliosides, with their structural complexity and amphipathic nature, have been implicated in a number of biological events which include cellular recognition and acting as adjuncts at receptor sites. More recently, growth promoting and neuritogenic functions have been ascribed to gangliosides. These interesting properties of gangliosides wIll undoubtedly attract greater attention in the future.(ABSTRACT TRUNCATED AT 400 WORDS)

Change of galactolipids and metabolism of fatty acids in the organotypic culture of myelinating mouse brain

The concentrations of cerebrosides and sulfatides, myelin-characteristic galactolipids, can be determined in organotypic culture of newborn mouse cerebellum by high-performance liquid chromatography. These galactolipids can be detected at 9-days in vitro explants and increased steadily until the explants were more tan 3 weeks old. The levels of nonhydroxycerebroside, hydroxycerebroside, nonhydroxysulfatide, hydroxysulfatide, and monogalactosyl diacylglycerol were 0.3, 0.6, 0.3, 0.2, and 0.3 nmol/mg protein at 9 days in vitro, respectively, and 1.0, 2.7, 0.9, 0.4, and 0.6 at 21 days in vitro, respectively. When serum was removed from the feeding medium after 9 days, the levels of these lipids did not increase and myelination failed to occur. When a 17 day explant was kept in medium containing [1-14C]lignoceric acid for 4 days, considerable radioactivity was taken up by the explant and incorporated into nonhydroxy- and hydroxycerebrosides, sulfatides and sphingomyelin. Most of the radioactivity in the alpha-hydroxy fatty acids was found in cerebronic acid, the product of lignoceric acid alpha-hydroxylation. Similar explants also took up [1-14C]palmitic acid when it was added to the medium. The radioactivity was, however, mostly incorporated into neutral lipids and glycerophospholipids. These observations indicate that the cultured mouse cerebellum explants synthesize and accumulate myelin-characteristic lipids as does brain in vivo.

Cerebrospinal fluid lipids in demyelinating disease. I. Sphingolipids

The lipid composition of CSF, serum and lymphocytes from patients without demyelinating disease (controls) as well as from patients with acute and chronic MS is analyzed. Individual lipid fractions are isolated by TLC and their fatty acid composition determined. Lipid and fatty acid composition of normal CSF resembles the results found in lymphocytes and it is deduced that CSF lipids are derived mainly from lymphocytes rather than white matter (myelin) or serum. There is an increase of CSF sphingomyelin in patients with acute MS (showing pleocytosis) which is apparently derived from disintegrated lymphocytes; there is also an increase of linoleic acid concentration which could come from serum because of dysfunction of the blood-brain barrier. The role of the CNS in contributing to CSF lipids is considered negligible both in controls and in patients with demyelination.

Activity of acid: Co A ligase (AMP) in the course of experimental allergic encephalomyelitis

In studies concerned with the activation of fatty acids, a metabolic step initiating the biosynthesis of fatty acids rendering them suitable for elongation, desaturation, esterification or degradation, we have demonstrated that the activity of acid: Co A ligase (AMP) -- E.C.6.2.1.3. is declined throughout the whole investigated period of experimental allergic encephalomyelitis (EAE). This observation clearly indicates that in this experimental disease it is not only the increased catabolism of lipid constituents furnishing the various membraneous structures, including myelin sheats, but also an overall impaired capacity of synthesing new lipids by the diseased cells of the nervous system which must be taken into consideration.