Changes in the sciatic nerve of the rabbit and its tissue constituents during development

Gangliosides and neutral glycolipids in ependymal, neuronal and primitive neuroectodermal tumors

Neutral glycolipid and ganglioside compositions were determined on 11 ependymal tumors, 12 medulloblastomas, 6 other neuronal tumors of the brain, 4 peripheral neuroblastomas, 1 cerebral primitive neuroectodermal tumor (PNET), and 1 PNET of the thoracic wall. Within the group of tumors that can demonstrate neuronal phenotypes, there was an association between the degree of neuronal differentiation usually demonstrated by these tumors and the proportions of both GD1a and 1b-pathway gangliosides. The amount of globoside also correlated with the amount of 1b pathway gangliosides. Patients with medulloblastomas whose 1b gangliosides made up over 15% of the total gangliosides survived longer that those with lower proportions of 1b gangliosides. The only gangliosides in the choroid plexus papilloma were GM3 and GD1a, but other ependymal tumors had significant amounts of GD1b and its metabolic precursors. Ependymoma and anaplastic ependymoma had similar neutral glycolipid compositions, which were different from subependymoma, which lacked ceramide monohexoside and ceramide dihexoside. These differences in glycolipid compositions suggest that there may be fundamental biological differences between these types of ependymal tumors.

The chemical constitution of gangliosides of the vertebrate nervous system

Glycosphingolipids are uniquely distinguished amongst the glycoconjugates by the apparently systematic structuring of their ceramide-linked carbohydrate moieties. These often highly complex oligosaccharides provide a structural repertoire that may vary considerably according to cell types and animal species. However, as a possible reflection of their specific functional role in the central nervous system, the brain glycosphingolipids of all vertebrates follow the same principles of carbohydrate structuring with only minor variations: the anabolically early addition of sialic acid to lactosylceramide (Gal beta 4Glc beta Cer-->NeuAc alpha 3Gal beta 4Glc beta Cer) in central nervous tissue results in the preferential formation of 'gangliosides', i.e., sialic acid-containing glycosphingolipids. Higher gangliosides result from extensions of sialo-lactosylceramide by addition of nucleotide-activated monosaccharides. In consequence, gangliosides of the vertebrate central nervous system consist of ceramide-linked sialo-oligosaccharides of varying chain length with a ganglio-series core carbohydrate, i.e., GalNAc beta 4Gal beta 3GalNAc beta 4Gal beta 4Glc beta < 0. Substitution by mono-, bis-, or tris-sialo-groups may variably be at the galactoside- and N-acetylgalactosaminide residues in 3- and 6-positions of the ganglio-series oligosaccharides, respectively. Ganglioside, which is derived by sialylation of galactosylceramide, NeuAc alpha 3Gal beta Cer, is a characteristic constituent of glial cells. In nerve tissue, gangliosides of the lacto-(Gal beta(3GlcNAc beta 3Gal beta)n4Glc beta <) and the neolacto-series (Gal beta(4GlcNAc beta 3Gal beta)n4Glc <) are more characteristic of vertebrate peripheral nerves and neuroectoderm-derived tumours. Recent studies using monoclonal antibodies have revealed that various single ganglioside components are specifically distributed in nervous tissues. This finding adds a new dimension to the earlier notion that gangliosides are involved in membrane related phenomena including cell to cell interactions, as well as, the modulation of signalling mechanisms.

Experimental autoimmune neuropathy with anti-GM1 antibodies and immunoglobulin deposits at the nodes of Ranvier

Antibodies to GM1 or Gal(beta 1-3)GalNAc are associated with motor or sensorimotor neuropathy and with motor neuron disease. To investigate the role of these antibodies in the neurological disorder, rabbits were immunized with GM1 or with Gal(beta 1-3)GalNAc-BSA, and studied serologically, electrophysiologically and pathologically. Development of antibodies to the immunizing antigens was associated with a fall in the ratio of the amplitudes of the compound muscle action potential evoked by proximal versus distal stimulation of the sciatic nerve. Pathological studies revealed mild axonal degeneration and immunoglobulin deposits at the nodes of Ranvier in peripheral nerve, resembling those reported in a patient with motor neuropathy, motor conduction block and anti-GM1 antibodies. These studies provide evidence that anti-GM1 or anti-Gal(beta 1-3)GalNAc antibodies cause conduction abnormalities and indicate that the antibodies may exert their effect, in part, by binding at the nodes of Ranvier in peripheral nerve.

Ganglioside synthesis and transport in regenerating sensory neurons of the rat sciatic nerve

The sciatic nerves of rats were crushed with fine forceps and allowed to survive for 3 or 7 days, at which time the 5th lumbar dorsal root ganglion was injected with [3H]glucosamine. Animals were killed 18 h later and the nerves proximal and distal to the crush site were cut into 3 mm segments. Gangliosides were purified from these segments, and radioactivity was separately measured in gangliosides, neutral glycolipids and glycoproteins. For all 3 fractions, radioactivity was distributed similarly between the crush site and point of maximum axonal elongation. A second smaller peak of ganglioside radioactivity was seen to span a few segments immediately distal to the point of maximum axonal elongation. We propose two possible explanations for this: (1) it represents ganglioside synthesis by Schwann cells (from blood-borne [3H]glucosamine) as part of the mitogenic response of these cells to the reappearance of axons; or (2) recently synthesized, transported gangliosides are released from the growth cone and taken up by adjacent mitogenic Schwann cells.

Localization of neural epitopes that bind to IgM monoclonal autoantibodies (M-proteins) from two patients with motor neuron disease

We investigated IgM monoclonal antibodies (M-proteins) specific for the carbohydrate epitopes Gal(beta 1-3)GalNAc and Gal(beta 1-3)GlcNAc from two patients with motor neuron disease. The M-proteins from these patients immunostain central nervous system (CNS) and peripheral nervous system (PNS) tissue from human, monkey, dog and cat at greater dilutions than tissue from rabbit, guinea pig, rat and mouse, and immunostain gray matter at greater dilutions than white matter and nerve trunks. They also bind selectively to presynaptic structures at the motor endplate region, as denervation of muscle eliminates binding. Following in vivo injection of serum into the extracellular space of the spinal cord, the M-proteins appear to bind at the surface of cells and cell processes. These studies suggest that the M-proteins might act at any one of several anatomical sites in the nervous system. This information may be helpful in selecting an animal species for further investigation of the role of M-proteins in motor neuron disease.

Gangliosides in the nervous system during development and regeneration

Gangliosides are present in nervous tissues of echinoderms and chordates, but the amounts and patterns differ widely. There are changes in the ganglioside contents of nervous tissues during development in most animals studied. To a large extent, regional differences and changes with development and degeneration in ganglioside composition reflect changing and different proportions of cellular types and subcellular organelles within the tissue. GM1 and GM4 are enriched in myelin; GD1a may be a marker for dendritic arborization. During regeneration of fish optic nerve and rat sciatic nerve there is an increased amount of ganglioside proximal to the regenerating axon tips, which may largely be a result of accumulation. This could provide a relatively large reservoir of ganglioside to become incorporated into the sprouting axolemma. Gangliosides added exogenously to growth medium can induce neuritogenesis of several types of neurons. The mechanisms of this action are unknown but may be related to nerve growth factor, microskeletal organization, membrane fluidity, and other factors. Gangliosides injected into young animals affect brain development, but further studies are required to determine these effects more specifically. Ganglioside administration increases the number of sprouts in regenerating peripheral nerves, but does not seem to accelerate axonal elongation. Parenterally administered gangliosides alter the recovery of brain tissue from a variety of types of lesions, and clinical trials are in progress to determine if they are of benefit in human neurological disorders. The biochemical mechanisms of these in vivo ganglioside effects are poorly understood, but may involve modulation of several enzyme systems as well as other properties of neural membranes, such as fluidity. It is possible that gangliosides may play similar roles and operate through some of the same mechanisms in developing and regenerating nervous tissues.

Subcellular fractionation of rat sciatic nerve and specific localization of ganglioside LM1 in rat nerve myelin

Subcellular fractionation of rat sciatic nerve was developed to determine the specific localization of gangliosides in the nerve membrane fractions. Myelin, microsomal, and a plasma membrane-like fraction were isolated and purified by sucrose density gradient centrifugation. These subfractions were characterized by electron microscopy, marker enzyme assays, and their protein and lipid profile. In rat sciatic nerve myelin, 90 mol% of the total gangliosides were monosialogangliosides. LM1 (sialosyl-lactoneotetraosylceramide) (61 mol%) and GM3 (21%) were the major gangliosides of the rat nerve myelin. Two other neolacto series of gangliosides, viz., sialosyl-lactoneonorhexaosylceramide and sialosyl-lactoneooctaosylceramide, were also localized mostly in the myelin fraction. GM1 was only a minor (less than 2%) ganglioside in myelin. The ganglioside patterns of the microsomal and plasma membrane-like fractions were similar with minor quantitative differences and were entirely different from that of myelin. Monosialogangliosides were approximately 70-75 mol% of the total in these fractions. The major gangliosides of the microsomal and plasma membrane-like fractions were GM3 (approximately 40%) and GM1 (approximately 20%). LM1 in these fractions was minimal (less than approximately 5%). Significant amounts of GM3 with N-glycolylneuraminic acid (approximately 10%) and GM1b (4-14%) were also identified in the microsomal and plasma membrane-like fractions but not in myelin. These and the higher lactoneo series of gangliosides have not been previously reported to be present in the rat nervous system. Almost exclusive localization of LM1 in myelin in rat peripheral nervous system is consistent with our previous observation that deposition of LM1 in the nerve with age was very similar to that of myelin marker lipids cerebrosides and sulfatides.

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)

Biosynthesis and transport of gangliosides in peripheral nerve

Radiolabelled glucosamine was injected into L-7 dorsal root ganglion (DRG) of rabbits. At several different times after injection DRG, lumbosacral trunks (LST) and sciatic nerves (SN) removed and gangliosides extracted. Two and 3 weeks after injection the amounts of radioactivity in the ganglioside fractions of LST SN were significantly higher than at days 1 and 2. The TCA soluble radioactivity decreased dramatically over the same time period. Colchicine prevented the appearance of radiolabelled lipid in LST and SN. From these experiments we conclude that some ganglioside is synthesized in the neuronal cell bodies of DRG and transported in the axons of the sciatic nerve. In another experiment the sciatic nerve was transected and ends separated to prevent regeneration. Ganglioside synthesis and transport were studied in these animals the same way as the previous experiment. There was no difference the amount of radiolabelled ganglioside that was isolated from DRG or LST of transected compared with control nerves. The behavior of several potential acid soluble contaminants was studied in several steps used to isolate gangliosides. Of those studied only CMP-NeuAc could cause significant contamination of the final ganglioside preparation.

Characteristic constituents of glycolipids from frog brain and sciatic nerve

Cerebroside, sulfatide, monoglycosyl glyceride, and ester cerebroside were isolated from frog brain and sciatic nerve, and their distribution and chemical constituents were determined. The long-chain base compositions of cerebroside, sulfatide, and ester cerebroside were unique in the presence of branched-base components (5-15% of the total bases) and in the abundance of saturated dihydroxy base components (15-45% of the total). The amount of branched long-chain bases was greater in sciatic nerve than in brain. The hexose composition of the glycolipids consisted entirely of galactose except for brain cerebroside, in which a small amount of glucose was detected. Monogalactosyl glyceride consisted of the diacyl and alkylacyl forms, in a molar ratio of 81:19 for brain and 62:38 for sciatic nerve. The fatty acid composition of glycosphingolipids was characterized by the predominance of hydroxy and nonhydroxy 24:1 acids, and the concentration of 24:0 was extremely low. The proportion of unsaturated fatty acids accounted for 80% of the total. Major fatty acids of monogalactosyl glyceride were palmitic, oleic, stearic, and palmitoleic acids; the highest concentration was that of palmitic acid. Ester cerebroside was separated into three subfractions mainly on the basis of the proportion of hydroxy and nonhydroxy components in the amide-linked fatty acids.

Myelination of regenerating sciatic nerve of the rat: lipid components and synthesis of myelin lipids

Changes of lipid, free fatty acid, protein, DNA, and RNA content in proximal and distal segments of regenerating sciatic nerve, from 14 to 120 days after crush, were determined. During the early stage of Wallerian degeneration, a marked decrease of phospholipid, cerebroside and sulfatide content and, in contrast, a marked increase of protein, DNA, RNA, and free fatty acid content, in the distal segment of crushed nerve compared to control, was observed. A gradual increase of phospholipid, cerebroside, and sulfatide levels, approaching normal values, and a gradual slope in the increase of protein, DNA, RNA, and free fatty acid levels over the ensuing time periods of regeneration was seen. Total cholesterol content was relatively constant during regeneration, slightly increasing at day 120. The activity of 2', 3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) of myelin fraction purified from distal segment of regenerating sciatic nerve showed a significant increase in the 30-120 day regenerating period. A marked increase of the incorporation of [2-3H]glycerol and of [Me-14C]choline into myelin lipids of distal segment of regenerating nerve, was found. Labeling of myelin lipids with [3H]oleic acid (injected intravenously seven days before crush) support the evidence that a similar pattern of degeneration exists between two different types of trauma, i.e. nerve crush or cut. The findings suggest that, in the distal segment of crushed nerve, the lipid content as well as the myelin lipid synthesis increase as the regeneration period proceeds.

Modifications of ganglioside composition in peripheral nerve of myelin deficient Trembler mutant mouse

Ganglioside distribution was studied in peripheral nerves of normal controls and those of Trembler mutant mouse with defect in Schwann cell differentiation and myelination. Neuraminic acid content was considerably decreased in the mutant. Ganglioside distribution as evaluated by densitometry of resorcinol positive spots on thin-layer chromatography revealed a major peak for GD1a in normal controls. In the mutant, the relative proportion was modified with qualitative modifications in the GD1a area and a tremendous increase in GM3 content. The relation with the intense Schwann cell proliferation observed in the mutant is discussed.

Peripheral nerve phospholipid composition: development in normal nerve and age-dependent changes in Wallerian degenerated nerve

The phospholipid composition of normal peripheral nerve as a function of developmental age as well as that of Wallerian-degenerated nerve as a function of age at nerve transection and duration of Wallerian degeneration have been quantitated in rabbit sciatic nerve. During development, increases in the proportions of ethanolamine plasmalogen, sphingomyelin, and combined phosphatidyl serine plus phosphatidyl inositol and decreases in the proportions of phosphatidyl choline and phosphatidyl ethanolamine correlated well with the concurrent myelin accretion. During Wallerian degeneration, age-dependent changes in phospholipid composition were observed. The large and statistically significant increase in the proportion of phosphatidyl choline and decrease in the proportion of ethanolamine plasmalogen were manifest promptly in nerves transected at 2 weeks of age but in a delayed manner in nerves transected at 8, 12, and 20 weeks of age. The rate of loss of individual phospholipids was greater in nerves transected at younger ages. The findings from normal developing peripheral nerve may well serve as baseline data for subsequent studies of phospholipid composition in pathological peripheral nerve. The findings from Wallerian-degenerated peripheral nerve provide additional evidence for age-dependent chemical changes occurring in Wallerian-degenerated peripheral nerve that may be of significance in explaining the superior functional recovery from peripheral nerve injury observed in younger compared with older subjects.

Chemical and morphological studies on garfish peripheral nerves

Gangliosides were extracted, separated by thin layer chromatography, and quantitated in three cranial nerves of the garfish (Lepisosteus osseus): the completely unmyelinated olfactory nerve (OLF), and two nerves composed of both myelinated and unmyelinated fibers, viz., the main trunk of the maxillary nerve (MAX) and a branch of the maxillary nerve (BR-MAX). Morphological studies on each of these nerves were done to verify that the OLF had been excised free of any contamination from the accompanying myelinated BR-MAX, to aid in the interpretation of the biochemical findings, and to clarify the nature of the OLF supporting cell. The chief chemical findings were (1) documentation of the presence of gangliosides in nerves previously thought not to contain them, (2) demonstration that gangliosides can be associated with unmyelinated nerves, (3) demonstration of a greater proportion of one simple ganglioside (G-6) in the OLF but greater proportions of two complex gangliosides (G-2 and G-0) in the MAX and BR-MAX, and (4) that either GM4 or a variant of the GM3 is present in OLF. The morphological findings with respect to the difficulty of ascribing only peripheral nervous system characteristics to the OLF supporting cell are discussed in relation to the ganglioside band chromatographing slightly ahead of GM4 in the OLF.

Wallerian degeneration of peripheral nerve. Age-dependent loss of nerve lipids

The age-dependent loss of the major peripheral nerve lipids (cholesterol, phospholipid, and total galactolipid) was quantitated over a period of 9 weeks of Wallerian degeneration induced by surgical transection of rabbit sciatic nerves in animals of several ages. Proportionate losses of these lipids were determined by calculating the content of each lipid on a per nerve and on a per gram fresh weight basis remaining after a given period of Wallerian degeneration as a percent of original normal values at several time following surgery. The proportionate loss of each lipid from the distal stump was the most prompt and the most complete in nerves transected at 2 weeks of age, and the least in nerves transected at 20 weeks of age. The prompter clearance of these lipids from younger than older degenerating nerve gives convincing evidence that the suggestion from light-microscopic studies of faster clearance of neural debris in younger than in older animals is correct. A possible relationship between these biochemical findings and the phenomenon of greater functional recovery from peripheral nerve injury in younger than in older subjects is discussed.

Relationship between gangliosides and doubling times in cultured human brain and brain tumor cells

Cells cultured in vitro from normal human white matter and 3 individual brain tumors exhibited the following population doubling times: cells from normal human white matter, 64 +/- 22 h, glioblastoma multiforme, 43 +/- 11 h; malignant astrocytoma, 98 +/- 19 h; and anaplastic oligodendroglioma, 81 +/- 24 h. Cells were seeded at subconfluent density, pulse-labelled for 24 h with the ganglioside precursor D-[1-14C]glucosamine and harvested. Radioactive patterns of extracted gangliosides showed that incorporation of label into disialoganglioside was significantly higher in the samples with longer population doubling times than in samples with shorter population doubling times. These findings suggest gangliosides may play a role in regulation of cell growth.

[Fatty acid distribution of the normal sciatic nerve lipids in the rat]

We isolated and purified the main lipids of the rat sciatic nerve. After methanolysis, fatty acids were isolated and purified by thin layer chromatography, and studied by gas chromatography. C 16 and C 18 fatty acids are the most abundant. Among the long-chain fatty acids, arachidonic acid (20:4) is present in some lipids; highly desaturated fatty acids in C 22 and C 24 are also present. In general, the fatty acids are highly saturated; cholesterol esters and ethanolamine phosphoglyceride fatty acids are highly unsaturated.

An X-ray diffraction comparison of myelins from the human nervous system

Earlier small-angle X-ray diffraction studies have indicated that central and peripheral nerve myelins may be significantly different structurally, although relatively few examples for each system and for individual species have been examined. In order to understand better the intra- and inter-system relationships, this study has developed more extensive information for a single species: six cases centrally and ten peripherally, featuring cranial nerves and a few others of the human nervous system. Peripheral myelin spacings (membrane pair thicknesses) are relatively similar, 184.4 +/- 1.40 A, and the ratios of diffraction peak height intensities of the second to fourth orders are also closely bunched: 1.85 +/- 0.216. Central myelin spacings and intensity ratios are distinctly different and more variable: spacings 160.3-165.8 A and intensity ratios 2.81-4.46. It appears that within a given species or between closely related (e.g., mammalian) species peripheral myelins possess relatively invariant structures, though significant spacing declines are encountered for both systems as phylogenetic relationships become more distant. The observed greater variability of CNS structures within a single species may correspond to known compositional differences between CNS regions or result from observational difficulties. In any case there is a marked discontinuity between the myelin structures of CNS and PNS nerves.

Lipid composition of rat sciatic nerve

In the course of our study on the lipids of the rat sciatic nerve, the analysis of the neutral lipids allowed us to detect and characterize cholesteryl esters present at a relatively high level (5%). Among the phospholipids, ethanolamine phosphoglyceride is the most abundant fraction and contains neraly all the plasmalogens (20% of total lipid phosphorus). The glycolipids consist of five different fractions; the cerebrosides with hydroxy fatty acids account for 38% of total glycolipids. Monogalactosyl diglyceride represents 7% of total glycolipids.

Relation of axon membrane to myelin membrane in sciatic nerve during development: comparison of morphological and chemical parameters

The relationship of axon circumference to myelin area on cross-section both for myelinated and total fibres has been estimated at a mid-point in the sciatic nerve of two rabbits, one newborn and the other 20 weeks old. The slopes of the regression lines relating myelin area to axon circumference for myelinated fibres were 0.72 (standard error 0.03) with a correlation coefficient of 0.81 in the newborn nerve and 2.96 (standard error 0.05) with correlation coefficient of 0.96 in the 20-week nerve. Using the above parameters, and assuming constant thickness of axolemma and constant packing density of myelin, a correlation was made of the change in relationship of axolemma volume of myelinated fibres to myelin volume in the nerve between the two ages with the changes in content of two membrane lipids, ganglioside and cerebroside. This revealed a constant relationship of morphological to chemical parameters at the two ages although the proportion of unmyelinated fibres was much greater in the newborn. If cerebroside is regarded as a marker for myelin membrane, this observation suggests an association of gangliosides with myelination in peripheral nerve.