Exogenous gangliosides induce direct voltage and conductance changes on isolated neurons.
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Animals↗
Biomedical subjects
H Rahmann
Publications and source records attributed to H Rahmann.
Axonal transport of intraocularly injected [3H-Sph]-GD1a in the chicken optic system and the fate of the exogenous ganglioside distributed by blood.
Twelve-day-old chicks (White Leghorn) received an injection of 481 kBq (8.1 nmol) of [3H-Sph]-GD1a, which was labeled in its sphingoid, into the right eye. Structures of the injected and the non-injected (control) optic system (retinae, optic nerves, chiasm, optic lobes), the cerebrum, blood liver, kidney, and fly-muscle were analyzed 1, 4, 8 and 14 days later, with respect to total non-volatile radioactivity and to that bound to lower-phase lipids and gangliosides. It was demonstrated that exogenous [3H-Sph]-GD1a was taken up by the retina and mainly catabolized. 3H-label, reincorporated into the lower-phase lipids and gangliosides as well as authentic exogenous [3H-Sph]-GD1a were transported rapidly anterogradely in the entire optic system. [3H-Sph]-GD1a, distributed via the blood stream, was taken up by liver, kidney and muscle and was metabolized faster in these organs than in the retina. The cerebrum and the brain structures of the control optic system incorporated 3H-radioactivity to a much lower extent than the non-neural organs.
Animals↗
Seasonal variability of sialo-glycoconjugates in the brain of the Djungarian hamster (Phodopus sungorus).
The influence of season, photoperiod and ambient temperature on the content of proteins, sialo-glycoproteins and gangliosides and on the composition of gangliosides of three different brain regions (cortex, cerebellum and basalbrain) of the Djungarian dwarf hamster (Phodopus sungorus) had been investigated. Concomittantly changes in body wt and fur colouration were recorded. Dwarf hamsters living under natural photoperiod and ambient temperature conditions ("outside") showed a distinct annual cycle in body wt (summer: about 45 g; winter: about 25 g) and fur colouration (summer: dark grey; winter: whitish). Among the three brain regions the mean concentration of proteins ranged between 120 and 155 mg protein/g wet wt. The sialo-glycoprotein content varied between 260 and 410 micrograms NeuAc/g wet wt, and that of gangliosides between 800 and 1650 micrograms NeuAc/g wet wt. Seasonal fluctuations were not found. The composition of brain gangliosides remained uninfluenced throughout the year in the cerebellum, whereas seasonal variations were observed in cortex and basalbrain. Consequently the concentration ratio of the two major mammalian ganglioside fractions GD1a vs GT1b remained almost stable in cerebellum (0.3). In contrast to this the seasonal values of cortex and basalbrain changed from 0.6 and 0.8 in winter to 0.7 and 1.1 in summer. This indicated a higher polarity of the gangliosides in these brain regions during cold adaptation. The results are discussed with regard to modulatory functions of neuronal gangliosides for the process of synaptic transmission during seasonal adaptation.
Animals↗
Method for the OsO4-free preservation of brain tissue suitable for immunocytochemistry in TEM.
Following conventional OsO4-fixation and embedding of brain tissue in Epoxide resins for ultrastructural investigations, on the one hand, the wellknown good depiction of structures is obtained, on the other hand, however, according to these procedures a considerable loss up to 80% of glycolipid-bound and up to 50% of glycoprotein-bound neuraminic acid of important native compounds has to be put up with. The fixation of brain tissue by 1% glutaraldehyde and 1% paraformaldehyde in 0.1 mol/l Na-K-phosphate-buffer, followed by dehydration in acetone or ethanol at--25 degrees C and embedding in Lowicryl K4M preserves for instance amphiphilic glycolipids (gangliosides) to a high degree (95%) and in addition provides a good depiction of neuronal structures. The incubation of ultrathin sections of carp brain, treated as described above, with the specific antibody Q211 against polar gangliosides gave first evidence for a specific labelling of these amphiphilic glycosphingolipids and their localization within the brain tissue.
Animals↗
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.
Calcium↗
Changes in brain gangliosides of the neotene and metamorphic (thyroxine-induced) newt axolotl (Ambystoma mexicanum).
Qualitative and quantitative changes in the concentration of proteins, sialoglycoproteins and gangliosides and in the composition of gangliosides in the brains of the neotene and the thyroxine-induced metamorphic newt axolotl (Ambystoma mexicanum) were investigated. During metamorphosis two polar gangliosides (GT1b and GQ1b) decreased by about 5% each. On the contrary GD1a increased to 10%. Another developmental trend was a slight increase of two other disialogangliosides (GD1b, GD2). Additionally, incorporation profiles (2-8 days) of 14C-N-Ac-mannosamine, the specific precursor for gangliosides, in the brain of neotene and metamorphic axolotls were followed giving evidence of significant changes in the sialoglycoconjugate metabolism of the central nervous system during metamorphosis of this newt.
Ambystoma↗
Autoradiographic investigations on sialoglycoconjugates in the CNS of normothermic and hibernating fat dormice (Glis glis).
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Animals↗
Brain gangliosides in monotremes, marsupials and placentals: phylogenetic and thermoregulatory aspects.
The concentration and composition of brain gangliosides of 17 mammalian species belonging to the subclasses of Prototheria (monotremes), Metatheria (marsupials), and Eutheria (placentals) were investigated. The mean concentration of brain gangliosides ranges from 525 to 610 micrograms NeuAc/g wet wt in monotremes, 445-900 micrograms in marsupials and from 630 to 1130 micrograms in the placentals. In the phylogenetic series of mammals, a decrease in the complexity of brain ganglioside composition becomes obvious: a drastic reduction in the number of individual ganglioside fractions particularly those of the c-pathway of biosynthesis, took place from the level of monotremes to that of the marsupials and placentals. In monotremes, marsupials and "lower" placentals (insectivores) the percentage of alkali-labile gangliosides is relatively low (between traces and 5%), whereas in the higher evolved mammals it amounts to about 20% of all gangliosides. The ratio of the contents of the two major mammalian ganglioside fractions GD1a and GT1b is generally in the range of 1.0 and even higher; in the heterothermic platypus from the monotremes and in hibernators among the placental mammals, however, it is much lower (about 0.8). These data support the hypothesis that the brain ganglioside composition not only depends on the phylogenetic level of nervous organization (cephalization) but is additionally correlated with the state of thermal adaptation.
Animals↗
Brain gangliosides in birds with different types of postnatal development (nidifugous and nidicolous type).
Developmental profiles of 14 different brain gangliosides were followed from the first day after hatching to the adult stage in two bird species representing different strategies of posthatch development: the nidifugous type (leaving the nest directly post-hatch, e.g. quail) and the nidicolous type (remaining for longer period in the nest, e.g. finch). In the zebra finch, parallel with a striking increase in ganglioside concentration, two main postnatal changes in the ganglioside composition occurred: after hatching, concomittantly to an increased outgrowth of nerve fibers and synaptogenesis, the polysialogangliosides GQ1b and GP decreased in favour of the less polar fractions GD1b, GD1a and GT1b. The second period of changes started with the onset of myelination and was characterized by an increase of GM1 and GM1'. The results obtained for quails were in close agreement with those of chicken, showing only slight postnatal changes due to the nearly completed morphological differentiation. These data show that gangliosides are useful biochemical markers for brain development, indicating successive periods of brain maturation by means of preferential biosynthesis of specific fractions regardless of the type of development.
Age Factors↗
Mass spectrometric identification of the pentasialoganglioside GP1c of embryonic chicken brain.
Gangliosides were extracted from 11-day-old chicken embryos and finally purified by chromatography on high performance thin-layer plates. Four fractions migrating more slowly than ganglioside GQ1b were obtained by preparative thin-layer chromatography. With the aid of negative ion fast atom bombardment mass spectrometry, one of these could be identified as GP1c.
Animals↗
Brain gangliosides and thermal adaptation in vertebrates.
Comparative studies on brain gangliosides of about 80 species belonging to all classes of vertebrates reveal: a: distinct increases in concentration with phylogenetical progress of nervous organization, b) decreases in number of single fractions, c) changes in the polarity (degree of sialylation, N- or O-acetylation of sialic acids), d) alterations in the preponderance of one of the three possible pathways of biosynthesis. In addition to these phylogenetical trends, clear correlations between the brain ganglioside composition and the state of thermal adaptation were shown: "The lower the environmental (- body) temperature, the higher the polarity of brain gangliosides". This principle was proved for ectotherms being adapted to habitats with extreme temperatures, during seasonal acclimatization and for homeotherms during early neonatal heterothermic development or during hibernation. Surface pressure-area isotherms of monolayers from single ganglioside fractions (GD1a, GD1b) or differently composed ganglioside mixtures from brains of warm- or cold-adapted hamsters as physico-chemical parameters show significant differences in their variability concerning temperature and/or Ca2+-influences. The results are taken as evidence that variations in the composition of synaptic-bound gangliosides may induce alterations in physico-chemical properties of the neuronal membrane, thus modulating synaptic transmission during temperature adaptation.
Acclimatization↗
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.
Air↗
Binding of Ca2+ to phosphoinositols, phosphatidylserines and gangliosides.
The effect of K+, Mg2+ and serotonin on the interaction between Ca2+ and different phospholipids as well as glycosphingolipids (gangliosides) was studied by equilibrium dialysis using 45Ca as tracer. The highly polar phosphatidylinositol-4,5-bisphosphate (TPI) was found to bind more Ca2+ per lipid molecule than all other lipids tested and Ca2+ could not be released as easily as in the other lipids by K+, Mg2+ and serotonin. Ca2+ is released from all lipid-Ca2+ complexes most effectively by Mg2+, serotonin is less effective but enhances K+ in its capacity to displace Ca2+ from the respective binding sites. A remarkable dissociating influence of serotonin on ganglioside-Ca2+ and phosphatidylserine-Ca2+ complexes is observed. This effect is less pronounced with phosphatidylinositol-Ca2+ complexes under comparable comparable conditions. The possible functional role of phospholipids and gangliosides in vivo is discussed with regard to the specific Ca2+-binding properties of these lipids.
Calcium↗
Brain gangliosides in hibernating dormice (Glis glis) and cold-exposed laboratory mice.
The concentration of proteins, sialo-glycoproteins and gangliosides and the ganglioside composition of 8 brain regions from normothermic and hibernating fat dormice (Glis glis) and from laboratory mice being acclimated to 6, 22 and 28 degrees C were investigated. During hibernation the concentration of sialo-glycoproteins and gangliosides decreased significantly in brain of dormice; the protein content remained uninfluenced. Cold-exposure of laboratory mice yielded generally a slightly decreased sialo-glycoprotein concentration in brain; the data on ganglioside concentration in the CNS were not uniform. The ganglioside composition of brain of laboratory mice being kept at different environmental temperatures did not show any alterations. The brain gangliosides of hibernating dormice in contrast to their normothermic counterparts are more polar (higher amount of GTlb and GQlb.). Most striking is the complete absence of a distinct ganglioside fraction (O-acetylated-GTlb) during hibernation. Brain gangliosides of normothermic dormice were found to be more sensitive against neuraminidase treatment than those of hibernating animals. The results are discussed with regard to modulatory functions of neuronal gangliosides for the process of synaptic transmission during seasonal adaptation.
Animals↗
[Effect of different acclimatization temperatures on the ultrastructure of neuronal synapses of perch (Tilapia mariae; Cichlidae, Teleostei)].
The ultrastructure of synapses in the stratum fibrosum marginale (SM) of the optic tectum of cichlid fishes (Tilapia mariae) was investigated following acclimation to extreme environmental temperatures (experimental temperatures 16 degrees C and 32 degrees C; preference temperature: 26 degrees C). Four different types of synapses can be differentiated, from which 90% of all synapses belong to axodendritic spine synapses. The general ultrastructural appearance is more distinct in case of cold -adapted fishes, which in particular is due to a more pronounced staining of the polysaccharide-surface coat of the membranes. Analyzing quantitatively the axo-dendritic spine synapses (600 of each collective) significant differences were found for the length of the synaptic contact zone (16 degrees C: 0,391 micron; 32 degrees C: 0,369 micron) and for the thickness of postsynaptic densities (16 degrees C 42,6 nm; 32 degrees C: 52,7 nm). The number of mitochondria per presynapse was rised for cold-adapted animals to a value of 0,29 as compared to 0,18 mitochondria/presynapse for warm-adapted animals. The vesicle density per micron 2 of synaptic area, however, remained unchanged (approximately equal to 89 vesicles/micron 2). The morphological synaptic plasticity thus demonstrated in the optic tectum of chichlid teleosts, is correlated with behavioural changes and with alterations in the biochemical composition of synaptic membranes.
Acclimatization↗
Influence of dark-rearing on the ontogenetic development of Sarotherodon mossambicus (Cichlidae, Teleostei): I. Effects on body weight, body growth pattern, swimming activity and visual acuity.
The ontogenesis of the cichlid fish, Sarotherodon mossambicus was investigated under normal- and dark-rearing conditions from hatching to 100 days. Light deprivation did not change normal increase in body weight. The increase in body length was slightly retarded in dark-reared animals (DR), whereas the increase in body height was more pronounced as compared to normal-reared animals (NR). DR failed to swim up after resorption of the yolk sack. Visual acuity was severely impaired. The first deficits in visual discrimination were observed after 20-30 days in the dark. After 50 days DR failed to show any optokinetic nystagmus.
Animals↗
Influence of dark-rearing on the ontogenetic development of Sarotherodon mossambicus (Cichlidae, Teleostei): II. Effects on allometrical growth relations and differentiation of the optic tectum.
The effect of dark-rearing (DR) on the allometrical growth relations of defined brain structures, on the lamination and the synaptogenesis of the optic tectum of the cichlid teleost Sarotherodon mossambicus was studied. Dark-rearing did not alter allometric growth relations of the optic tectum. Both in dark-reared (DR) and in normal-reared animals (NR) the predominant outgrowth of the nerve fibers in the optic tectum took place within the first 20 days after hatching. Dark-rearing changed the laminar structure of the optic tectum. In 100-day-old DR the optic layer was significantly reduced as compared to NR. The morphometric differentiation of synapses was affected by dark-rearing. In DR no significant reduction in the length of synaptic contact zones occurred between 30 and 100 after hatching, as it did in NR. Moreover, specific layers (stratum marginale, stratum griseum centrale) in 100-day-old DR showed significant increase in the number of synaptic vesicles per nerve terminal.
Animals↗
Influence of electrical stimulation and deprivation on the electric organ discharge behaviour and metabolism of neuronal gangliosides of the tapirfish (Gnathonemus petersi, Mormyridae, Teleostei).
The influence of electrical stimulation ("attack"-frequency of 40 Hz, 2 V, 2 days) and of social and electrical deprivation on the metabolism of gangliosides of various brain structures and the electric organ of the weakly electric tapirfish (Gnathonemus petersi, Mormyridae) was investigated. After stimulation the daily average discharges of the electric organ increased from 9.4 to 11.1 Hz, whereas after deprivation they decreased to 7.9 Hz as compared with controls. There were significant and structure specific differences in some ganglioside-fractions (GM1, GD3, GD1a, GD1b and GP1) in concentration and in specific radioactive NeuAc-labelling between stimulated and deprived animals respectively, compared with controls.
Animals↗