Polysialic acid on the neural cell adhesion molecule correlates with expression of polysialyltransferases and promotes neuroblastoma cell growth.

Neuroblastomas and cell lines derived from these tumors bear the oncodevelopmental antigen polysialic acid (PSA) bound to the neural cell adhesion molecule. Polysialyation of neural cell adhesion molecule can be achieved by two different polysialyltransferases, ST8SiaII and ST8SiaIV. This study was undertaken to investigate the pattern of polysialyltransferases expressed in the human neuroblastoma cell line SH-SY5Y. Reverse transcription-PCR showed simultaneous expression of the two enzymes, and in situ hybridization demonstrated that the polysialyltransferase mRNA expression parallels immunoreactivity with the PSA-specific monoclonal antibody 735. After retinoic acid-induced differentiation, only the PSA-positive, neuron-like cell type gave clear signals for ST8SiaII and ST8SiaIV in in situ hybridization, whereas both signals were drastically reduced in the weakly PSA-positive substrate adherent phenotype. Like the SH-SY5Y cells, a primary, PSA-positive neuroblastoma specimen revealed expression of the two polysialyltransferases. To investigate the role of PSA for cell growth and differentiation, SH-SY5Y cells were treated with the PSA-specific endo-N-acetylneuraminidase E. Although loss of PSA was accompanied with a marked reduction of cell growth, it did not interfere with retinoic acid-induced differentiation. Together, our results suggest that PSA surface expression is regulated on the level of polysialyltransferase transcription. Moreover, the similarity to the primary neuroblastoma tissue makes SH-SY5Y cells a suitable model system to examine further the role of polysialylation in tumor cell growth and the orchestration of PSA synthesis in neuroblastoma.

Characteristic and differential calcium signals from cell structures of the root cap detected by energy-filtering electron microscopy (EELS/ESI).

Characteristic calcium signals were analyzed in structures of three cell types of the root cap of cress: statocytes, meristematic cells and secretion cells. Twenty-four hour-old roots were fixed with glutaraldehyde (postfixed with osmiate/potassium bichromate) or with potassium permanganate. No visible precipitates were formed, but calcium signals typical for different cell structures could be detected by means of energy-filtering transmission electron microscopy (EELS/ESI). In statocytes, calcium signals were recorded from the plasma membrane, the membranes of the endoplasmic reticulum, the amyloplast envelope and the mitochondrial membranes. In contrast to the excitable statocytes, the two other, non-excitable cell types, meristematic and secretion cells, exhibited much lower intensities of the calcium signals recorded from the same membrane systems. The revealed characteristic calcium-related properties of the different membrane systems may be related to the special function of statocytes, namely transduction of the gravity stimulus. In all three cell types, additional calcium signals were recorded from cell structures with well known calcium contents, i.e., mitochondrial granules, starch grains and cell walls. For the first time, clear calcium signals were detected from the lipid bodies which are mobilized during the developmental stage of the examined roots. It is supposed that free fatty acids and lipases are the binding sites for calcium. The reliability of the applied method is especially proven by comparison of the electron microscopic images from lipid bodies according to the two different fixation methods. After glutaraldehyde fixation followed by osmiate/potassium bichromate postfixation, the lipid bodies were well fixed and appeared homogeneously grey with homogeneous calcium signals. However, due to potassium permanganate fixation the lipid bodies were only partly fixed; they had an electron-lucid core, from which the lipids are lost during the dehydration procedure, without calcium signals and an electron-dense border zone, which is a reaction product of potassium permanganate with triacylglycerols, with calcium signals.

Effect of calcium and temperature on mixed lipid-valinomycin monolayers. A comparison of glycosphingolipids (ganglioside GT1b, sulphatides) and phosphatidylcholine.

The influence of calcium and temperature on pure lipid (bovine brain PC, sulphatides, ganglioside GT1b), valinomycin and mixed lipid-valinomycin monolayers at the air/water interface was studied. In mixed films, evidence was found that the two components were miscible. On the other hand, at higher surface pressures, phase separation occurs in the cases of PC and sulphatides. Measuring the area requirement and the collapse pressure the stability of both lipid and the peptide was increased in particular due to ganglioside-valinomycin interaction. The addition of 10(-5) M calcium into the subphase at 20 and 37 degrees C and surface pressures of 10 and 20 mN/m led to a condensing effect in ganglioside mixtures, with formation of aggregates as indicated also by the nearly ideal behaviour of two component monolayers.

Effect of light stimulation on the cytochemical localization of cytochrome C oxidase in photoreceptor cells of cichlid fish.

Cytochrome oxidase activity was evaluated cytochemically in rod photoreceptor cells in the retina of the cichlid fish Oreochromis mossambicus after different stimulation protocols. The enzyme activity was assessed semiquantitatively by estimating the volume ratio of mitochondria classified according to the intensity of enzyme reactivity. Dark adaptation for 5 hr induced an increase of cytochrome oxidase activity both in vivo and in vitro, i.e., in isolated retinas. Short-term illumination (1 hr) of isolated retinas adapted previously in vivo to darkness caused a significant decrease of enzyme activity, whereas short-term darkening after in vivo light adaptation had no effect. Chemical stimulation for 15 min with increased K+ concentration (20 mM) reduced the enzyme activity, i.e., chemical depolarization did not have the same effect as depolarization induced by darkening. Significant changes in cytochrome oxidase activity were apparent within 1 hr of stimulation, so that this method for analysis of neuronal activity can be applied even in short-term experiments.

Cytochemical localization of high-affinity Ca2(+)-ATPase activity in synaptic terminals.

High-affinity Ca2(+)-ATPase activity in the optic tectum of the brain of cichlid fish was cytochemically localized using cerium ions to precipitate phosphate. Activation of the enzyme with micromolar instead of millimolar calcium concentrations (i.e., physiological cytoplasmic instead of extracellular concentrations) resulted in intracellular localization of reaction product attached to the cytoplasmic side of plasma membranes and to synaptic vesicles. The plasmalemmal enzyme activity was concentrated in synaptic regions. Synaptic vesicles in some terminals exhibited high amounts of ATPase activity, whereas others were free of reaction product. By use of electron energy-loss spectroscopy (EELS) and electron spectroscopic imaging (ESI) techniques, even small amounts of cerium-containing precipitates could be analyzed and precisely localized. The cytochemical observations are in good agreement with biochemical findings and therefore indicate that the calcium pump of neuronal plasma membranes can be successfully localized.

Influence of Ca2+ and temperature on the interaction of gangliosides with valinomycin in mixed monolayers at the air/water interface.

The effects of Ca2+ and temperature on mixed ganglioside-valinomycin-monolayers at the air/water interface were studied. Surface pressure-area isotherms of the pure gangliosides (GM1, GD1a) exhibited the typical monolayer characteristics. Pressure-area isotherms of the cyclodepsipeptide, valinomycin, were determined. In mixed monolayers, positive and negative deviation from the mean molecular area indicated the two components were miscible. Especially in GD1a mixtures, the addition of 0.01 mM calcium exhibited, with low molar fractions of valinomycin, a demixing effect in the direction of the phase separation of the components.

Evidence for the presence of a specific ganglioside GM1/valinomycin complex in mixed monolayers.

The effect of a negatively charged mono-sialoglyco-sphingolipid (GM1-ganglioside) on the molecular organization and on physiochemical properties of lipid/peptide (valinomycin) systems was investigated in monolayers at the air/water interface. At a high molar fraction of GM1, the surface pressure/area isotherms of the two-component films of the system GM1/valinomycin and the isotherm of the pure ganglioside monolayer are identical concerning the space requirement of the molecules and thereby the packing of the monolayer. Using space-filling molecular models, a simple calculation gives the theoretical amount of 4.5 ganglioside molecules associated with one molecule of the depsipeptide valinomycin. The average surface potential indicates, that valinomycin, interacting with the polar head group of GM1, becomes partly embedded within the lipid interface. For GM1/eicosanol and valinomycin/eicosanol mixtures, the agreement between theory and experimental data strongly supports the model of ideal mixing without any molecular interactions between the different components. The results suggest the formation of a ganglioside/valinomycin complex with simultaneous alteration of the surface potential and molecular structure of the single components.

Comparative monolayer investigations of surface properties of negatively charged glycosphingolipids from vertebrates (gangliosides) and invertebrates (SGL-II, lipid IV).

The surface properties of four negatively charged glycosphingolipids from vertebrates, the sialo-glycosphingolipids (= gangliosides) GM1, GD1a, GT1b and a sulfo-glycosphingolipid (= sulfatide), and of the two negatively charged glycosphingolipids from lower invertebrates, the glucurono-glycosphingolipid Lipid IV and the aminophosphono-glycosphingolipid SGL-II were investigated in monolayers at the air/water interface. The molecular peculiarities under investigation were surface pressure (pi) and surface potential (delta V) which are described for Lipid IV and SGL-II for the first time. The surface pressure/area isotherms of all glycosphingolipids were typical of a liquid-expanded monolayer and, with the exception of SGL-II, exhibited a phase transition to a liquid-condensed state at surface pressures above 20 mN/m. The surface potential/molecular area data found for gangliosides in the closely packed state at pi = 30 mN/m (GM1: delta V = -17 mV; GD1a: delta V = -35 mV; GT1b: delta V = -39 mV) showed only a slight influence of the additional number of negatively charged residues. For Lipid IV, the surface behavior was very similar to GM1 both possessing one negative group per molecule, whereas in SGL-II also the surface potential data (delta V = +173 mV) were different compared with GD1a both possessing two negative groups per molecule. The addition of Ca2+ condensed the monolayers of all glycolipids and increased the potential in the direction to more positive values, but these findings were less effective in SGL-II films. On the basis of monolayer results presented here, in biological membranes of invertebrates especially Lipid IV might play a similar role as the ganglioside GM1 in vertebrate cells.

Retinal synthesis and axonal transport of gangliosides during regeneration of the goldfish optic nerve.

In the present study, the left optic nerve of the goldfish was transected between eye bulb and optic chiasm. One to 39 days after lesion, the fish received an intraperitoneal injection of [3H]proline or [3H]NAc-glucosaraine. After one or two days of incorporation, both retinae and optic nerves were analyzed for protein- and ganglioside-bound radioactivity. A transient enhancement of label incorporation into proteins (up to 2-fold) and gangliosides (up to 1.5-fold) of the regenerating retina was found. Simultaneously, a transiently enhanced accumulation (up to 4.5-fold) of protein- and ganglioside-bound radioactivity in the regenerating optic nerve took place. These regeneration-related 'metabolic' changes came to a maximum at 6-8 days after nerve transection and were still measurable after 40 days. In the regenerating retina, there were no changes either of the ganglioside pattern or of the relative distribution of radioactivity of individual gangliosides. In the regenerating optic nerve, however, ganglioside GPlc, identified by immuno-TLC, and a fraction migrating like GD3/GM1 were enhanced with respect to their relative proportion of total ganglioside sialic acid and radioactivity. The radioactivity proportion of a ganglioside migrating like GDlb was decreased.

Brain creatine kinase activity during ontogeny of the cichlid fish oreochromis mossambicus and the clawed toad Xenopus laevis, influence of gravity?

The development of creatine kinase (CK) activity was studied in the brain of cichlid fish and clawed toads. The activity of CK in the whole brain of the fish decreases immediately after hatching (stage 6) from values of about 135 nmol substrate cleaved/mg protein/min to a value of about 105 at stage 8 (5 days post hatch at 20 degrees C). With the exception of a significant peak (125 nmol) between stages 9 and 10 (7 and 9 days respectively, post hatch at 20 degrees C) and a small intermediate peak at stages 12 and 13 (about 10 days post hatch at 20 degrees C) a constant level of about 100 nmol cleaved substrate is maintained until maturity. In contrast, CK activity was determined to be 3-fold higher in the whole brain of the clawed toad. With the exception of two significant peaks at stages 47 and 49 (5 and 12 days respectively, post fertilization at 23 degrees C) a value of about 360 nmol was found during larval development and metamorphosis, as well as in the adult brain. In investigating the possible influence of gravity on CK activity during early ontogeny of the brain both animal species were exposed to hyper-gravity (3 +/- 1 g) for 7 days. A significant decrease of total CK activity of 20% was found in the fish brain and of about 5% in the toad.(ABSTRACT TRUNCATED AT 250 WORDS)

Development and altered gravity dependent changes in glucose-6-phosphate dehydrogenase activity in the brain of the cichlid fish Oreochromis mossambicus.

Glucose-6-phosphate dehydrogenase activity was studied in the brain of the cichlid fish Oreochromis mossambicus during early ontogenetic development. In general a slight but continuous decrease in enzyme activity was found (9.5 +/- 0.5 nmol substrate cleaved per mg protein and per min at developmental stage 13 [= 1 day post hatch at 28 degrees C] to a value of 7.9 +/- 0.6 in adult brain). In order to investigate the possible influence of altered gravity during early ontogenetic brain development, fish larvae were exposed to an increased acceleration of three times earth gravity (3 g) or to functional weightlessness in a fast-rotating clinostat for 7 days. A significant increase of brain G6PDH activity of approx. 15% was found after exposure to hyper gravity, whereas a significant decrease of the enzyme activity, approximately 10%, was detected following functional weightlessness in respect to the corresponding 1 g controls. Analyses concerning the regain of normal control enzyme activity of the larvae revealed dramatic fluctuations within the first 5 h after exposure to an increased acceleration of 3 g. Thereafter, between day 1 and day 3 after exposure, brain glucose-6-phosphate dehydrogenase decreased slowly. At day 3 after exposure no further differences of the hyper-g larvae compared to the controls were found. Only slight changes in total brain glucose-6-phosphate dehydrogenase activity occur during ontogenetic development of cichlid fish. This suggests that a more or less constant enzyme activity is important during brain development, but is reacting very sensitively to changes in the environmental factor gravity.

Variability in brain ganglioside content and composition of endothermic mammals, heterothermic hibernators and ectothermic fishes.

Content and composition of brain gangliosides were compared among endothermic mammals, heterothermic hibernators and ectothermic fishes from habitats with extreme ambient temperatures (tropic vs. antarctic waters). In general the content of brain gangliosides in fishes is significantly lower and exhibits a greater variability than in mammals. The composition of brain gangliosides was investigated using both one- and two-dimensional High Performance Thin Layer Chromatography (HPTLC). Both techniques showed a remarkable increase in the number of individual ganglioside fractions and an additional increase of higher polar fractions in fishes as compared with mammals. The 2D-HPTLC revealed a significant decrease in the relative proportion of alkali-labile gangliosides in the course of evolution from fish to mammals. Moreover this decrease in alkali-lability is correlated with the state of thermal adaptation (antarctic fishes, 53-66%; tropical cichlid fish, 35%). These results provide additional evidence for the notion that the extremely high polarity of brain gangliosides, especially of cold-blooded vertebrates, reflects a very efficient mechanism on the molecular level to keep the neuronal membrane functional under low temperature conditions.

Calcium-ganglioside interactions and synaptic plasticity: effect of calcium on specific ganglioside/peptide (valinomycin, gramicidin A)-complexes in mixed mono- and bilayers.

A controlled exchange of calcium between the extracellular space (mM Ca2+) and the neuroplasm (microM Ca2+) is considered to be an essential prerequisite for almost every stage of neuronal activity. Our research interest is focused on those compounds, which due to their physico-chemical properties and localization within the synaptic membrane might fulfill the task as neuromodulators for functional synaptic proteins. Because of this specific binding properties towards calcium and their peculiar interactions with calcium in model systems gangliosides (amphiphilic sialic acid containing glycosphingolipids) are favorite candidates for a functional involvement in synaptic transmission of information. In this study we used monolayers to investigate the molecular packing and surface potential at the air/water interface, the interaction of gangliosides with the depsipeptide valinomycin (= monovalent ion carrier), and its influenceability by calcium. Furthermore we looked at calcium effects on the single channel conductance and mean channel life-time of the monovalent ion channel gramicidin A in mixed PC/ganglioside bilayers. In pure ganglioside monolayers the addition of 0.01 mM Ca2+ induces monolayer condensation, a rise in collapse pressure (= higher film stability), a shift of phase transition (= change of conformation), and a more negative head group potential (change of electric properties). In mixed ganglioside-valinomycin monolayers the addition of Ca2+ causes phase separation and/or aggregate formation between the ganglioside and the peptide. Single channel conductance fluctuations as well as mean channel life-time were analyzed for gramicidin A incorporated into binary mixed black lipid membranes of negatively charged gangliosides (GM1, GD1a, GT1b, GMix) and neutral lecithin (DOPC) in different molar ratios. At monovalent electrolyte concentrations up to < 250 mM CsCl the single channel conductance was significantly larger in the negatively charged mixed DOPC/ganglioside membranes than in the neutral DOPC membrane. Additionally, in the presence of gangliosides the mean channel life-time is increased. The addition of calcium (0.05 mM) induced a reduction of single channel conductance of gramicidin A in DOPC- and mixed DOPC/ganglioside membranes. These physico-chemical data in connection with new electromicroscopical evidences for a precise localization of calcium, a calcium pump (Ca(2+)-ATPase), a clustered arrangement of gangliosides in synaptic terminals, and biochemical results with regard to activatory nature of exogenous gangliosides for neuronal protein phosphorylation and ATPases, support the hypothesis of a modulatory function of gangliosides in synaptic transmission.

Influence of exogenous gangliosides (G(M1), G(D1a), G(Mix)) on a Ca(2+)-activated Mg(2+)-dependent ATPase in cellular and subcellular brain fractions of the djungarian dwarf hamster (Phodopus sungorus).

The influence of 150 nM exogenously-added gangliosides (G(M1), G(D1a), G(Mix)) on a Ca(2+)-activated, Mg(2+)-dependent ATPase was investigated in cellular and subcellular fractions (P1-fraction, synaptosomal fraction, synaptic membranes) from whole brain, cortex, cerebellum and brain stem of the djungarian dwarf hamster (Phodopus sungorus). Gangliosides are effective at this concentration in stimulating the enzyme activity in all fractions from whole brain. Inhomogenous results (stimulation, inhibition and no effects), however, were obtained in the different individual brain regions.

Implication of membrane bound neuraminidase in developmental and adaptational processes of different vertebrate species.

Determination of brain membrane-bound sialidases by means of 4-methylumbelliferyl-neuraminic acid as exogenous, artificial substrate provides a good measure for functional implications of this enzyme in brain ontogeny and adaptation to changes in different environmental parameters. In rainbow trout and Cichlid fish a striking increase in brain sialidase-activity occurs during ontogenetical development, especially in post-hatching-larvae up to free swimming, reaching adult values of 75 and 50 nmol of sialic acid released per h and mg protein, respectively. Dark adapted Cichlid fish show a considerably lower turnover in brain (28 nmol per h and mg protein). Principally sialidase activity is in mammals about 5-fold lower than in fish and seems to be highest in cortex (compared with cerebellum and basal brain). Hibernating dwarf- and golden hamsters show a significant lower sialidase activity in summer, though these differences also occur in non-hibernating animals kept at constant ambient temperatures, thus indicating a temperature-independent, possibly genetically fixed enzyme regulation.

Gangliosides and neuronal differentiation.

Using the GD3-specific mAb R24 we demonstrate by immunohistochemistry that the first embryonic cells of chicken expressing GD3 represent heavily proliferating cells of mesodermal origin (mesenchymal stem and endothelial cells). At this developmental stage (E1-1.5) neuroectodermal cells of the forming neural tube are not stained by R24 or any other available anti-ganglioside antibodies. These cells of the neural tube start to express GD3 at around E1.5 in parallel with increasing proliferative activity. Likewise proliferating and migrating neuronal crest derivates as well as undifferentiated retinal cells, the forming lens and otic placodes increasingly express GD3 in an organ-specific pattern following the spatiotemporal increase in mitotic activity. Immunostaining of GD1b (mAb D21b) or c-pathway polysialogangliosides (mAb Q211) is not obtained before E2.5, is nervous tissue specific and restricted to "new-born" neurons, which start to migrate and form first neurites. This striking change in ganglioside synthesis and expression also occurs in primary cell cultures (after or without previous Q211-mediated complement kill of neurons) during differentiation of mitotic progenitor cells to neurons (neurogenesis). In cell culture, the fluorescence staining is evenly distributed over the whole neuronal surface including filopodia at the growth cones. Monensin (10(-8) M) prevents expression of GD1b and c-polysialogangliosides and simultaneously differentiation of neuronal morphology (neurogenesis). The presence of exogenous gangliosides from bovine brain leads to a decrease of the monensin effect or even abolishes it.

Gangliosides and regeneration of the goldfish optic nerve in vivo and in vitro.

One to forty days after optic nerve transection, goldfish received an i.p. injection of [3H]proline (proteins), 3HNAcGluc (gangliosides) or [3H]thymidine (DNA). After 1 or 2 days of incorporation, both optic systems were analyzed by biochemical and autoradiographical procedures. In the regenerating retina an enhanced retinal mitotic activity, protein synthesis (up to 2-fold) and ganglioside synthesis (up to 1.5-fold) was found. Simultaneously, a transiently enhanced accumulation (up to 4.5-fold) of axonally transported protein- and ganglioside-bound radioactivity in the regenerating optic nerve stump occurred. These regeneration-related proliferative and metabolic changes were found to be maximal at 6-8 days post lesion, but still measurable after 40 days. Concerning the endogenous ganglioside metabolism, in the regenerating retina no obvious change in ganglioside synthesis and composition could be observed, while in the regenerating optic nerve there was an enhanced accumulation of the ganglioside GP1c. Daily i.p. application of a ganglioside mixture from bovine brain (GMix) or of the monosialoganglioside GM1, did not alter significantly the degree and time course of the above regeneration induced metabolic changes or the regain of visual acuity. Sprouting activity of goldfish retinal explants was found to strongly depend upon a conditioning lesion of the optic nerve, reaching a maximum 8 days after nerve transection. This result strictly coincided with the profile of metabolic changes observed in vivo. Again, daily i.p. or i.o. injection of exogenous gangliosides did not influence the lesion induced increase of retinal sprouting activity. However, in normal, not regenerating animals, a local i.o. injection of GMix or GM1 led to a significant enhancement of the "basal" sprouting activity, normally occurring after lesion of the retina after injection of 0.9% NaCl. This ganglioside related stimulation was maximal at low concentrations (3 micrograms/eye) and did not occur at high concentrations (> 30 micrograms/eye). Injection of the phospholipid phosphatidylcholine or phosphatidylserine had no or a slightly inhibitory effect, when compared to NaCl controls. These data suggest an involvement of gangliosides in the complex process of induction of axonal sprouting.

Cell surface distribution of endogenous and effects of exogenous gangliosides on neuronal survival, cell shape and growth in vitro.

In vitro immunostaining of neurons from spinal cord or brain of embryonic chicken by means of monoclonal anti-ganglioside antibodies (Q211, D21b) revealed a fluorescence-labeling of c-polysialogangliosides and GD1b evenly distributed over the entire neuronal surface including filopodia at the growth cones. On electronmicroscopical level the gold-stained ganglioside-antigens were found more or less densely packed in small adjacent areas suggesting a concentration in local "domains". Survival in serum-free or serum-containing medium of embryonic spinal cord motoneurons, which normally died if not cultivated in muscle conditioned medium or in contact to myotubes, was remarkably improved in the presence of a ganglioside mixture (10 microM) from bovine brain. If embryonic neurons from optic lobes were cultivated at low Ca(2+)-concentration (< 20 microM) they developed flat, broad cell bodies with many filopodia and only a few flat-shaped short processes. A very weak cytoskeleton-staining by means of rhodamine-linked phalloidine indicated that polymerization of actin was impaired in these neurons. At the same low Ca(2+)-concentration of < 20 microM but in the presence of ganglioside GM1 (up to 100 microM) most of the neurons developed a "normal" cell shape with rounded perikarya and thin neurites with "normal" shaped growth cones. In this case rhodamine-linked phalloidine revealed a much more intense staining mainly concentrated within the growing tips. The morphology and growth of the ganglioside-treated neurons resembled that of neurons cultivated at a higher Ca(2+)-concentration of at least 600 microM.

Nervous system ganglioside composition of normothermic and hibernating dormice (Glis glis).

The ganglioside pattern of seven different regions, olfactory bulb, forebrain cortex, midbrain (corpora quadrigemina), cerebellum, brain stem, pons and spinal cord, of nervous system of normothermic and hibernating dormice (Glis glis) were investigated by two dimensional thin layer chromatography and densitometric quantification. Up to thirty different ganglioside spots were resolved, fifteen of which belonging to alkali labile species. Alkali labile gangliosides were present in all the regions obtained from normothermic animals, and their content, expressed as percentage of total ganglioside-bound sialic acid, ranged from a minimum of 10.2% in olfactory bulb, to a maximum of 30.1% in spinal cord. The most abundant alkali labile gangliosides were O-Ac-GT1b, O-Ac-GQ1b and an unidentified one, we coded I3. Alkali labile gangliosides were practically undetectable in hibernating dormice. They could be recognized only in brain stem, 3.3% and olfactory bulb, 0.6%.

Differential involvement of gangliosides versus phospholipids in the process of temperature adaptation in vertebrates. A comparative phenomenological and physicochemical study.

The data presented support the idea that gangliosides are involved in thermal adaptation of neuronal membranes. Brain ganglioside patterns from cold-blooded vertebrate species living in different climates and from mammals during ontogenetical or seasonal changes in their body temperature were compared. The general rule "the lower the environmental temperature the more polar is the composition of brain gangliosides" as derived from these data was confirmed by the changes in ganglioside patterns evoked by experimentally induced cold acclimation of fish. To assess whether gangliosides are able to modulate the temperature-dependent properties of membranes, artificial mono- and bilayer membrane model systems were used. Incorporation of gangliosides in the model bilayer membranes evoked drastic changes in the dynamics of a peptide channel, suggesting that gangliosides are able to modulate basic membrane properties. In addition, data on thermosensitivity of ganglioside-calcium interactions and on surface behavior of gangliosides in monolayers are reviewed.