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Biomedical subjects

H Rahmann

Publications and source records attributed to H Rahmann.

At least 127 records · Page 7Linked to original sources
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↗
PubMed1979

Effects of exogenous neuraminidase on unit activity in frog spinal cord and fish optic tectum.

The effect of exogenous neuraminidase on spontaneous and evoked synaptic activity was investigated following injection of the enzyme into frog spinal cord and into cord and into the carp optic tectum. 1. Injection of enzyme into spinal cord segments caused a significant increase of motoneuron activity in the corresponding spinal nerve, which lasted for 7--31 min. 2. The amplitude of postsynaptic evoked potentials in the optic tectum was increased after neuraminidase injection up to 200% of control level for 20--40 min, whereas the amplitude of summed action potentials of retino-tectal afferents remained unchanged. 3. Similar effects were observed in single cell responses of the optic tectum with some differences in the degree of increase in activity, as well as latency and final depression of the stimulus response. 4. The extent of neuraminic acid liberation following neuraminidase treatment was determined biochemically. In both tissues investigated the amount of free neuraminic acid was increased significantly (4--5.5 fold) after enzyme treatment. Whereas after enzyme injection into spinal cord and optic tectum the percentage release of total glycoprotein- and glycolipidbound neuraminic acid was 12% and 15%, respectively, liberation from enzyme incubated tissue homogenates was somewhat higher (20.5% and 24%).

Animals↗
PubMed1979

Changes in brain ganglioside composition of normothermic and hibernating golden hamsters (Mesocricetus auratus).

1. Brain ganglioside patterns of normothermic and hibernating golden hamsters (Mesocricetus auratus) and laboratory mice had been investigated. 2. The ganglioside pattern of normothermic golden hamsters in comparison to that of mice is characterized by an unusual high amount of the polar trisialoganglioside GT1. 3. In the hibernating golden hamster in contrast to normothermic counterparts the brain gangliosides are more polar (polysialization-effect). 4. The results are discussed with regard to the hypothesis that neuronal membranes provided with more polar gangliosides at lower environmental temperatures might be more efficient with respect to the high complexation ability of gangliosides with Ca2+-ions.

Animals↗
PubMed1979

Binding of d-tubocurarine by gangliosides.

The binding of d-tubocurarine by ganglioside mixtures from chicken and bovine brain as well as by the single gangliosides GGtet1-NeuAc, GGtet2aNeuAc and GGtet3aNeuAc was demonstrated by means of equilibrium gel filtration. The sialyl-oligosaccharide derivatives of GGtet1NeuAc and GGtet2aNeuAc, however, did not bind any d-tubocurarine. A lack of binding was also found for the gangliotetraosyl-ceramide GgOse4Cer, free NeuAc, mucin and sphingomyelin. Under saturation conditions, GGtet1NeuAc bound 0.58, GGtet2aNeuAc 0.92 and GGtet3a-NeuAc 1.23 mol d-tubocurarine per mol ganglioside. Half-maximal binding was achieved between 1 and 1.5 x 10(-5)M d-tubocurarine. Ca2 was found to inhibit the binding of d-tubocurarine to gangliosides (50% at 4 x 10(-4)M Ca2). Mg2 was about 4 times less effective. Acetylcholine caused a 40% inhibition at 4 x 10(-3)M, whereas K and Na had only slight effects even at 5 x 10(-2)M.

Animals↗
PubMed1979

[The complexing ability of gangliosides for Ca2, I. Influence of mono- and divalent cations and of acetylcholin (author's transl)].

The binding of Ca2 to single ganglioside species (GGtet1NeuAc, GGtet2aNeuAc, GGtet 3aNeuAc), to their free, reducing sialyl-oligosaccharides and to ganglioside mixtures from chicken brain was investigated by means of ion-sensitive electrodes (potentiometry). Unlike the sialyl-oligosaccharides and free N-acetylneuraminic acid, gangliosides were found to possess two different modes of binding for Ca2, depending on the total concentration of Ca2. This was mainly indicated by a release of up to 75% of previously bound Ca2 after raising the total Ca2-concentration above a critical level of about 5--9 X 10(-5)M. Addition of acetylcholin (9mM), Li, K, and Na, respectively, caused a release of Ca2 from ganglioside-Ca2-complexes (0.1mM Ca2, 0.1mM ganglioside-NeuAc) in the sequence: acetylcholin : Li : K : Na = 4 : 3 : 1 : 1 composed on molar basis (9mM).

Acetylcholine↗