Biochemical evidence on the role of gangliosides in nerve-endings

Fetal alcohol effects: mechanisms and treatment

This article represents the proceedings of a symposium at the 2000 ISBRA Meeting in Yokohama, Japan. The chair was Edward P. Riley. The presentations were (1) Does alcohol withdrawal contribute to fetal alcohol effects? by Jennifer D. Thomas and Edward P. Riley; (2) Brain damage and neuroplasticity in an animal model of binge alcohol exposure during the "third trimester equivalent," by Charles R. Goodlett, Anna Y. Klintsova, and William T. Greenough; (3) Ganglioside GM1 reduces fetal alcohol effects, by Basalingappa L. Hungund; and (4) Fetal alcohol exposure alters the wiring of serotonin system at mid-gestation, by F. Zhou, Y. Sari, Charles Goodlett, T. Powrozek, and Ting-Kai Li.

Effects of chronic ethanol exposure on cultured cerebellar granule cells

The aim of this study was to investigate the lipid content and composition of rat cerebellar granule cells grown in the presence of ethanol (40, 55, or 80 mM) during in vitro differentiation. Quantitative analyses showed no effects of 40 mM ethanol, whereas a significant increase of total cholesterol was observed at 55 mM. Cells exposed to the highest ethanol dose (80 mM) were characterized by a higher sialidase activity, and by the modification of the ganglioside pattern and phospholipid fatty acid composition. The observed modifications were accompanied by changes of membrane anisotropy fluorescence assessed by the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene.

Ganglioside GM1 reduces fetal alcohol effects in rat pups exposed to ethanol in utero

We have investigated the effect of in utero ethanol exposure and ganglioside GM1 pretreatment on the endogenous ganglioside profile of the rat fetal brain. Prenatal ethanol exposure on gestation day (GD) 7 and GD8 and/or GD13 and GD14 leads to a very significant increase in the ganglioside GM1 content in at least 50% of the pup brains when assayed on GD20. This treatment protocol also results in significant decrease in the content of polysialogangliosides GD1a, GT1b, and GQ1b. GM1 treatment of pregnant dams before ethanol administration prevented this alteration in pup brain ganglioside profile. Ganglioside GM1 pretreatment appears to block the cellular membrane changes associated with fetal alcohol effects and thereby minimizes alterations in brain maturation and associated behavioral dysfunction.

Developmental change in ganglioside expression in primary culture of rat neurons

Developmental changes in ganglioside levels and patterns were investigated in neuronal cells dissociated from 17-day-old fetal rat hemispheres for up to 7 days of culture. Increases in ganglioside contents and the onset of GM3 synthesis, which is associated with proliferation of glial cells, were observed as the neuronal network was established in cell cultures. The distribution of gangliosides in developing neurons was monitored by the indirect immunofluorescent technique using three anti-ganglioside antibodies. Anti-GM1 antibody showed immunofluorescence only on the cell soma 1 and 3 days after plating and additional binding between cell aggregates by 7 days in culture. GD3 ganglioside, the predominant species in embryonic neurons, was not detected on the neuronal cell surface, whereas the number of positively stained non-neuronal cells was increased at 7 days. Monoclonal A2B5 antibody suggested that polysialogangliosides play a role in neuronal network formation. In 1-day-old culture, however, all antibodies bound poorly to cell surface antigens and strongly to cells, the membranes of which were permeabilized with acetone. These results suggest that a substantial amount of gangliosides are retained, transformed within the cell to more complex gangliosides, and translocated to the cell surface following neurite outgrowth and morphological changes.

Developing rat cerebellum--III. Effects of abnormal thyroid states and undernutrition on gangliosides

Alteration of rat postnatal cerebellar development produced by undernutrition, thyroxine treatment and thyroid deficiency also involves ganglioside deposition. The distribution of the different ganglioside types is apparently unaffected but quantitative alterations are present that reflect the reduction of cell number and cell process surface in the adult, and either acceleration or slowing down or reduction of cell formation and maturation occurring during cerebellar development in the three experimental situations.

Management of peripheral neuropathy in diabetes mellitus. Recent research findings and their therapeutic implications

Peripheral neuropathy in diabetes begins as a physiologic aberration related to hyperglycemia and its subsequent effects of endoneurial hypoxia, elevated sorbitol levels, and decreased myoinositol levels. Resultant decreases in sodium-potassium-adenosine triphosphatase levels ultimately lead to structural alterations at the nodes of Ranvier. Aldose reductase inhibitors and dietary myoinositol supplementation are being used in long-term clinical studies to monitor the possibility that they may prevent or reverse these abnormalities. In the meantime, symptomatic treatment remains the mainstay of management.

Glycolipid sialosyltransferase activity in synaptosomes exhibits a product specificity for (2-8)disialosyl lactosyl ceramide (ganglioside GD3)

Intact synaptosomes prepared from 28-day-old rat brains were incubated with CMP-N-acetyl-(14C) neuraminic acid in Krebs-Henseleit buffer in an atmosphere of 95% O2: 5% CO2, at 37 degrees C. The activity of CMP-NANA:ganglioside sialosyltransferase using endogenous acceptors was 0.84 pmoles NANA transferred/mg synaptosomal protein/hr. Analysis of the distribution of labeled sialic acid revealed that GD3 ganglioside (alpha 2----8 disialosyl, alpha 2----3 galactosyl, beta 1----4 glucosyl, beta 1----1-ceramide) was the major product in the membrane carrying 32% of the total lipid bound label. Treatment of the reaction products with Clostridium neuraminidase liberated labeled sialic acid from GD3 and yielded labeled GM3, then unlabeled lactosyl ceramide. Lac-cer and GM3 are present in small amounts in synaptosomes, and GD3 represents less than 2% of the total ganglioside. Our findings indicate that the sialosyltransferase activity of synaptosomes exhibits a preferential product specificity for the small pool of synaptosomal membrane GD3 ganglioside that may be formed in situ, via sialosylation of its precursor (GM3 or lactosyl ceramide) which pre-exists in the synaptosomal plasma membrane. The second major labeled product quantitatively was GD1a whose precursor substrate, GM1, is quite abundant in the membrane, so that the conversion rate of GM1 to GD1a was low in comparison with GD3 formation. Sialosylation of other synaptosomal membrane gangliosides was negligible.

Affinity-purified tetanus neurotoxin interaction with synaptic membranes: properties of a protease-sensitive receptor component

The pharmacokinetic interaction of an affinity-purified 125I-labeled tetanotoxin fraction with guinea pig brain synaptosomal preparations was investigated. Binding of tetanotoxin was time- and temperature-dependent, was proportional to protein concentration, and was saturable at about 8 X 10(-9) M as estimated by a solid-surface binding assay. Binding was optimal at pH 6.5 under low ionic strength buffer and was almost entirely blocked by gangliosides or antitoxin. In analogy to intact nerve cells, binding of toxin to membranes resulted in a tight association operationally defined as sequestration. Binding and sequestration were abolished after membrane pretreatment with sialidase. The enzyme could not dissociate the membrane-bound toxin formed at 4 or 37 degrees C under low ionic strength conditions, which is in part compatible with internalization as defined in nerve cell cultures. In the latter system the toxin could be removed at 4 degrees C but not at 37 degrees C. Binding was significantly reduced upon pretreatment of guinea pig brain membranes by a variety of hydrolytic enzymes. Trypsin and chymotrypsin inhibited binding between 55% and 68% while bacterial protease abolished it by 91-95%. The effect was species-specific as it was not seen in rat or bovine synaptosomes. Collagenase and hyaluronidase had little or no inhibitory effect when applied to synaptosomes (27% and 9%) but inhibited binding to synaptic vesicles by 56% and 49%, respectively. Phospholipases A2 and C caused 42-43% inhibition of binding in vesicles and less than 22% in synaptosomes.(ABSTRACT TRUNCATED AT 250 WORDS)

Association of endogenous substrate with solubilized bovine brain sialidase

Nonidet P40 solubilized up to 90% of the sialidase, active towards added ganglioside substrate, that was associated with the total membrane fraction prepared from gray matter of bovine brains. Solubilized sialidase acted upon endogenous substrate (sialic acid containing compounds solubilized with the enzyme), hydrolyzing approximately 50% of the readily available sialosyl residues within 20 min. During a 2-hr reaction time 80% of the polysialylated gangliosides solubilized with the enzyme were acted upon. A 20-min lag was observed before sialidase acted upon added ganglioside substrate. The lag could be reduced to less than 2 min when the enzyme was allowed to act on endogenous substrate prior to exposure to exogenous substrate, suggesting that the solubilized enzyme acted preferentially on endogenous substrate. A protease inhibitor prevented much of the 86% loss of activity towards added substrate that was seen when the enzyme was stored at 4 degrees C for 6 days; activity towards endogenous substrate decreased only 34%.

Treatment of peripheral neuropathies

There are three general approaches to treatment of peripheral neuropathy. First, an attempt should be made to reverse the pathophysiological process if its nature can be elucidated. Second, nerve metabolism can be stimulated and regeneration encouraged. Third, even if the neuropathy itself cannot be improved, symptomatic therapy can be employed. This review outlines the options available for each approach.

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)

Modulatory effects of different temperatures and Ca2+ concentrations on gangliosides and phospholipids in monolayers at air/water interfaces and their possible functional role

Gangliosides are neuraminic acid-containing glycolipids preferently localized in nervous membranes and showing physicochemical peculiarities, e.g., drastically changing amphiphilic properties by Ca2+ binding. On account of this they are favorite compounds to act as modulators of membraneous organization and functions during synaptic transmission. Lipid monolayers are suitable experimental systems for the study of the surface behavior of amphipatic molecules and therefore are useful to interpret membraneous organization. The surface pressure/area isotherms of monolayers of different individual gangliosides (GM1, GD1a, GD1b, GT1b) of an artificial reconstituted and a natural ganglioside mixture from bovine brain and of ganglioside mixtures from different brain parts of summer- and winter-adapted dsungarian hamsters were compared at three temperatures (11, 20, and 37 degrees C) with egg phosphatidylcholine (PC) and phosphatidylserine (PS) monolayers. The monolayers were formed in a Teflon trough on a triethanolamine/HCl-buffered (pH 7.4) subphase, in some cases containing different amounts of CaCl2. The surface pressure/area isotherms of ganglioside monolayers, in contrast to phospholipids, generally showed slowly rising slopes, with transitions from the liquid-expanded to the liquid-condensed state at a surface pressure of 20-30 mN/m. Ganglioside monolayers, in particular from GD1a or GT1b versus GD1b or from mixtures from summer- versus winter-adapted hamster brain, were differently affected by temperature and/or by Ca2+. PS monolayers were slightly condensed only by Ca2+. PC monolayers, however, were influenced neither by temperature nor by Ca2+. In mixed monolayers of the unpolar natural lipid cholesterol (Ch) and the disialoganglioside GD1a, intermolecular interactions were indicated. Ganglioside monolayers, in contrast to phospholipids, were shown to be easily modulated by temperature and/or Ca2+ ions, thus enabling gangliosides to act as possible membrane modulators, e.g., during synaptic transmission. In particular, the differences concerning the influences of temperature and/or Ca2+ on the surface behavior of ganglioside mixtures from the brain of summer- compared with winter-adapted hamsters are correlated with other physiologically relevant data.

Gangliosides in rabbit and human skeletal muscle with denervation atrophy

In experimental denervation of rabbit skeletal muscle, an increase of gangliosides has been reported. Ganglioside, DNA, total lipid and protein levels were studied in experimental denervation of rabbit gastrocnemius muscle and in human skeletal muscle with denervation atrophy. In severe human denervation atrophy total ganglioside, DNA and total lipid levels were increased, and protein levels decreased as compared with controls. The ganglioside pattern was changed in severe human denervation atrophy and showed a significant increase of a GT1b-like and moderate decrease of a GM1-like compound. Findings in experimentally denervated rabbit muscle resembled results obtained in human denervation atrophy, showing a significant increase of total ganglioside levels as well as a moderate increase of GT1b-like and decrease of GM1-like compounds.

Neurotransmitter chemistry in feline GM1 gangliosidosis: a model for human ganglioside storage disease

Assays for synaptosomal high-affinity uptake activity (glutamate, gamma-aminobutyric acid, norepinephrine), neurotransmitter synthesizing enzymes (choline acetyltransferase, glutamate decarboxylase, tyrosine hydroxylase), and endogenous neurotransmitters were performed in cats with advanced inherited GM1 gangliosidosis. A significant reduction in uptake activity, ranging from 24 to 77% of control, was demonstrated in motor, occipital, and cerebellar brain regions. This reduction was unassociated with comparable alterations in neurotransmitter levels or synthesizing enzyme activity. We hypothesize that the defect of neurotransmitter inactivation is part of an overall abnormality of synaptic membrane function that could contribute to the neurological symptoms seen in the hereditary gangliosidoses.

Gangliosides and sialoglycoproteins in normal and denervated rat diaphragm muscle

Ganglioside-and glycoprotein-bound sialic acid in endplate and non-endplate regions of rat diaphragm muscles were assessed 1-16 days after phrenic nerve transection. Sialic acid in glycoproteins (90% of total) and gangliosides (10% of total) from intact hemidiaphragms was distributed uniformly throughout endplate and nonendplate regions. Afer denervation, the total sialic acid per hemidiaphragm increased (days 1-4) and reached a maximum level (days 8-12) which remained constant (days 12-16). These sialic acid changes reflected increments in gangliosides (40% over control), which occurred simultaneously in endplate and non-endplate regions (days 1-8), and increments in sialoglycoproteins (70%-80% over control), which took place much earlier in endplate (days 1-8) than in nonendplate (days 8-14) regions. The results of this study, together with previous data, favor the hypothesis that maintenance of both sialoglycoproteins and gangliosides depends upon an intact innervation, probably through separate mechanisms involving different neurogenic factors.

[Histochemical demonstration of sialic acid-containing compounds in the CNS of mice and goldfish by means of the mPAT ("mild" periodic acid-thionine)-method (author's transl)]

The "mild" periodic acid-thionine (mPAT)-method was examined for the quantitative research of histochemical localization of sialic acid (NeuAc)-containing compounds in brain samples of goldfish and albino mice in comparison to salivary gland (Glandula submandibularis) of the mouse. Biochemical determinations of NeuAc contents of the tissues showed that during histological treatment a significant decrease in the amount of lipid-bound NeuAc, especially in the brain had occurred, because of its high content of lipid-bound NeuAc. A previous KOH-treatment caused in an increase of the colour reaction, which indicated mainly the amount of O-acylated NeuAc just as possibly lactone containing NeuAc-compounds. The intensity of staining, especially in the optic tectum of goldfish, decreased to 45% after neuraminidase-treatment. The low concentration of NeuAc-compounds in the brain in comparison to the salivary glands, results in only a faint staining. Therefore, the use of the mPAT-method seems to be not very suitable for a specific and quantitative staining of all NeuAc-compounds in the CNS.

Treatment of denervated muscle by gangliosides

Short-duration cooling of the nerve to the extensor digitorum longus muscle of the rat in vivo induced partially reversible denervation of the muscle and atrophy in the type 2 muscle fibers. Increases in cyclic adenosine monophosphate, cyclic guanosine monophosphate phosphodiesterase, adenylate cyclase, and guanylate cyclase were observed in the denervated muscle. Treatment with gangliosides of the bovine brain cortex seemed to improve the excitability of the surviving motor units and to encourage recovery of neuromuscular trophic control, but it did not affect the nerve conduction velocity or the contractile properties of the denervated muscle.

Genetic variability for regional brain gangliosides in five strains of young mice

The quantitative and qualitative distributions of gangliosides were determined in the cerebrum, cerebellum, and brain stem of five inbred strains (C57BL/6J, DBA/2J, LG/J, C3H/HeJ, BALB/cJ) of mice at 21 days of age. Genetic differences were found among the strains for wet weight, absolute amount of gangliosides per region, and concentration of ganglioside (expressed on bolth a wet and a dry weight basis) in all three regions of the brain. The water content of the various brain regions showed the least amount of genetic variability. Coefficients of genetic determination were used to estimate the magnitude of genetic influence on these traits in each brain region. Significant differences were also found among the five strains for the distribution of certain gangliosides. The DBA strain, which is susceptible to audiogenic seizure at this age, had the highest level of the myelin-enriched ganglioside GM1 in all brain regions. Most of the genetic variation that influences the content and distribution of gangliosides among neurologically normal mice can be considered polygenic. Several possible sources of this genetic variation that may contribute to the differences observed among the strains are discussed.

Effects of brain gangliosides on functional recovery in experimental regeneration and reinnervation

The effect of brain cortex gangliosides has been tested in two different experimental models of peripheral sympathetic regeneration and reinnervation: a) the preganglionic trunks of the cervical sympathetic nerve were joined in an end-to-end anastomosis after severing the preganglionic trunk, caudally to the superior cervical ganglion; this reinnervation is mainly of cholinergic type. b) the postganglionic trunks of the superior cervical ganglion were joined in an end-to-end anastomosis after severing the postganglionic trunk; this reinnervation is mainly of adrenergic type. Functional recovery following the regeneration and reinnervation has been evaluated by measuring tha contraction of the nictitating membrane, evoked by electrical stimulation of the sympathetic trunk caudally to the point of anastomosis. Some of the operated animals were daily treated with 50mg/kg i.p. of brain cortex gangliosides during the entire post-operative period. Forty-five, sixty days after the operation we observed in the treated animals of both experimental sets a relevant increase in the functional recovery (between 30 and 100%) compared to the operated but untreated controls. In the case of postganglionic anastomosis the physio-pharmacological studies were substantiated by the histochemical fluorescence observations of the distributions of catecholamines in the smooth muscle of the nictitating membranes. These results strongly suggest that the treatment with gangliosides greatly influences the regeneration and reinnervation process of both cholinergic and adrenergic nerve fibers.