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H Rahmann

Publications and source records attributed to H Rahmann.

At least 127 records · Page 7Linked to original sources
PubMed1984

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↗
PubMed1984

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↗
PubMed1984

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↗
PubMed1984

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↗
PubMed1984

[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↗
PubMed1984

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↗
PubMed1984

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↗
PubMed1983

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↗
PubMed1983

Histochemical localization of neuraminidase in the CNS of mice and fish by means of 5-brom-3-indolyl-alpha-ketoside of 5-N-acetyl-D-neuraminic acid (BI-NeuAc).

The applicability of the 5-brom-3-indolyl-alpha-ketoside of N-acetyl-D-neuraminic acid (BI-NeuAc) as substrate for the histochemical indication of neuraminidase (GOSSRAU et al. 1977) was examined in frozen sections of brain, small intestine and kidney from suckling and adult mice and respectively from a cichlid fish (Sarotherodon mosambicus) with and without formaldehyde fixation. Following biochemical investigations using tritiated gangliosides as substrate a decrease in the activity of neuraminidase took place from about 50 to 80% after tissue fixation with formaldehyde. Nevertheless significant histochemical reactions were found only in fixed tissue sections. The specificity of this reaction was shown by means of inhibitions tests using 2,3-dehydro-2-desoxy-N-acetyl-neuraminic acid according to KUMAR et al. (1981). In contrast to distinct staining of neuraminidase activity in the small intestine and kidney, only faint reactions occurred in brain sections. From this it is concluded that the application of the new synthetic substrate for quantitative staining of neuraminidase seems to be not very suitable for the CNS.

Animals↗
PubMed1983

Calcium binding to liposomes composed of negatively charged lipid moieties.

Ca2+-binding to liposomes was investigated by means of equilibrium dialysis using 45Ca as tracer. Liposomes composed of various lipids (phospholipids: phosphatidylcholine, -serine, -inositol, -inositol-3, 4-bisphosphate; glycosphingolipids: ganglioside mixture from bovine brain; isolated ganglioside species GM1, GD1a, GT1b; cholesterol) in ratios resembling those of natural cell surface membranes were prepared by the detergent dialysis method. Ca2+ was applied in concentrations ranging from 5 microM to 0.15 mM. Pure phosphatidylcholine liposomes showed only poor Ca2+-binding affinities; however, negatively charged liposomes bound Ca2+ in a rather distinct and specific manner. Ca2+-binding to liposomes containing phosphatidylinositol-3,4-bisphosphate in their bilayers was highest. All the liposomes (except those containing phosphatidylinositol-3,4-bisphosphate) showed no simple Ca2+-binding characteristics, that is, continuous Ca2+-binding was interrupted at a concentration of about 50 microM of total Ca2+ in each Ca2+-binding plot, implying that a certain amount (10%-45%) of previously bound Ca2+ was released. These results are discussed with regard to the different possibilities on the molecular basis of physico-chemical processes as well as in relation to their possible functional role at the process of neuronal synaptic transmission.

Calcium↗
PubMed1982

Effects of neonatal 6-hydroxydopamine treatment on cortical development in mice and rats as monitored by developmental changes of gangliosides.

In a comparative study newborn rats and mice received subcutaneous (s.c.) injections of 6-hydroxydopamine (6-OHDA: 100 mg/kg) on postnatal days (p.d.) 1-3. In rats the treatment permanently reduced synaptosomal 3H-noradrenaline (3H-NA) uptake in the cortex to about 50-60% of control values. Conversely, cortical 3H-NA uptake was only temporarily reduced in treated mice during the first week and central noradrenergic neurons completely recovered during the second and third week. The different response of mice and rats to 6-OHDA is suggested to be due to earlier maturation of the noradrenergic system in mice, making it less vulnerable to neonatal injections of the neurotoxin. To determine whether the development of the cortex would be altered after degeneration of its noradrenergic innervation, developmental changes of cortical ganglioside content and composition of 6-OHDA-treated animals were compared to that of littermate controls. In 18-day-old rats, where reduction of 3H-NA uptake had persisted, ganglioside content was reduced by 16.5%, indicating growth impairment of neuronal membrane structures. Cortical gangliosides of younger rats and all the stages studied in mice were not affected by 6-OHDA treatment.

Animals↗
PubMed1982

Gangliosides and synaptic transmission.

Several physiologically relevant findings are reported indicating a functional involvement of gangliosides (sialoglycolipids) in the process of neuronal transmission: a) changes of gangliosides in both concentration and composition during developmental maturation of the CNS and with the level of phylogenetic organization; b) metabolic variations of gangliosides in relation to sensory stimulations; c) involvement of gangliosides in the process of thermal adaptations; d) correlations between long-lasting compensatory changes in the composition of brain gangliosides and long-term changes in the bio-electrical activity of the CNS and the learning ability; e) pronounced ability of gangliosides to complex with Ca2+-ions. On the basis of these experimental data an actualized hypothesis on the molecular interaction of brain gangliosides in the process of synaptic transmission is presented. The main feature of this hypothesis is the assumption that when the negatively charged sialic acids of gangliosides form complexes with Ca2+-ions (cluster-formation) these parts of the synaptic membrane become rigid. Dissociation of the Ca2+-ganglioside-complexes induces an "opening" of the presynaptic zone of interactions by means of an increase of membraneous fluidity, together with Ca2+-influx thus enabling fusion of vesicles and release of transmitter.

Acclimatization↗
PubMed1981

[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.

Animals↗
PubMed1981

[Ultrastructural differences in the morphology of the optic tectum of the carp (Cyprinus carpio) and rainbow trout (Salmo gairdneri) with special reference to the synapses].

The optic tectum of two years old rainbow trout (Salmo gairdneri) and carp (Cyprinus carpio) had been compared morphologically, especially concerning the ultrastructural appearance of synapses. Differences between these two species were most pronounced in the stratum fibrosum marginale (SM). In addition to differences in the relative thickness of this lamina as compared with the dimension of the whole tectum (carp: 12%; trout: 23%) significant variations concerning the ultrastructural differentiation were conspicuous: for the carp numerous marginal fibers form convergent synapses together with dendritic spines of pyramide cells, whereas the SM of the trout appears to be less differentiated in so far as convergent synaptic contacts in this species are almost absent. The quantitative analysis of synapses in the SM brought highly significant differences between the two species: number of synapses (carp 45, trout 62 per 1000 micrometer 2); length of synaptic contact (carp 0,31, trout 0,24 micrometer); density of synaptic vesicles (carp 122, trout 61 per micrometer 2). The occurrence of highly effective convergent synapses in carp obviously seems to be compensated in trout by means of an increase in the number of synapses and the intensity of the interlacement of fibers.

Animals↗
PubMed1980

Quantitative ultrastructural investigations on synaptogenesis in the cerebellum and the optic tectum of light-reared and dark-reared rainbow trout (Salmo gairdneri Rich.).

The morphogenetic differentiation of synapses in the cerebellum and the optic tectum of dark-and light- reared rainbow trout was investigated at critical stages of development. During normal differentiation the cerebellum is characterized by the appearance of 'indented', spinelike synapses. This type of synapses increases with age and prevails from day 60 on. At the same time the number of 'flat' synapses decreases. In the cerebellum the highest synaptic density (123 +/- 12 synapses/1,000 micrometer2) is reached 30 days after hatching when the larvae begin to swim. The optic tectum is characterized by a preponderance of flat synapses in early postnatal and adult life; maximal synaptic density (66 +/- 5 synapses/1,000 micrometer2) is reached 60 days after hatching when the larvae have reached optimal visual acuity. Light deprivation causes a considerable and significant reduction in the number of synapses per unit area in the cerebellum and the optic tectum. The length of synaptic contacts do not change. If light-deprived, the density of synaptic vesicles decreases significantly in the optic tectum of a 25-day-old trout (74 +/- 3 instead of 132 +/- 7 vesicles/micrometer2). In the cerebellum this effect is absent.

Animals↗