PubMed Health⌕ Search

Biomedical subjects

W Probst

Publications and source records attributed to W Probst.

At least 37 records · Page 2Linked to original sources
PubMed1987

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↗
PubMed1987

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↗
PubMed1986

Ultrastructural localization of calcium in the CNS of vertebrates.

The ultrastructural localization of calcium in synaptic areas of the CNS of fish was investigated. Prefixation with phosphate-buffered glutaraldehyde followed by post-fixation with osmium/potassium-bichromate was used to precipitate and visualize endogenous calcium without the addition of external calcium. The presence of calcium in the electron-dense precipitates produced using this method was demonstrated by electron spectroscopic imaging using a Zeiss EM-902 transmission electron microscope, and in various control experiments using the calcium chelator EGTA. In the optic tectum of fish, electron dense precipitates containing calcium were found not only in intracellular compartments, e.g. the smooth endoplasmic reticulum, mitochondria and synaptic vesicles, but also at extracellular locations, particularly in synaptic clefts. In the extracellular sites, only chelate complexes of ionic calcium were found. This would seem to be in agreement with electrophysiological and biochemical data reported in earlier studies. Thus, using the present method, it should be possible to obtain further ultrastructural information concerning the mechanisms of synaptic transmission.

Animals↗
PubMed1984

[Adenocarcinoma of the kidney (hypernephroma)].

Adenocarcinomas of the kidney are rare tumors. This malignancy has been called the "internist's tumor" because of its often unusual presentation and systemic symptoms. The diagnosis is largely based on urography, sonography and CT-scan. Radical tumornephrectomy is the only treatment with curative potential. Interventional angiography with tumor embolization has become an important tool for palliation. On the other hand, the results of systemic treatment, such as hormone therapy, chemotherapy or immunotherapy, remain disappointing.

Androgens↗
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

[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): 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

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

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

[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↗
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↗