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.     

Spatial use and interaction of the invasive raccoon dog and the native red fox in Central Europe: competition or coexistence?

The main objective was to discover extent of interference and/or exploitative competition between the native red fox (Vulpes vulpes) and the introduced, invasive raccoon dog (Nyctereues proconoides) in the intensively used, agricultural landscape of northeast Germany (Mecklenburg-Western Pomerania) using very high frequency (VHF) radio telemetry. We recorded location data for 12 foxes and 16 raccoon dogs between July 2004 and December 2006. Species had similar average home range sizes estimated in each season (K95). Home ranges of adjacent raccoon dogs and foxes overlapped from 0.5 to 74.5 % with a mean of 26.4 %. We found a significantly different home range overlap index between the species showing that raccoon dog ranges shifted between seasons to a greater extent than red fox ranges. The raccoon dog differed significantly from the red fox in its use of habitat types, preferring dense vegetation cover and avoiding open areas. The red fox displayed less preference for or avoidance of specific habitat types. Moreover, an almost neutral inter-specific interaction index ranging from ?0.12 to 0.12 indicates that raccoon dogs and red foxes ignored each other. It is concluded that widespread and available resources and differences in spatial use patterns prevent competition between red foxes and raccoon dogs in the agricultural landscape of northeast Germany.     

Sialic acid incorporation into gangliosides and glycoproteins of the fish brain

—The concentration of lipid- and non-lipid-bound sialic acid in the optic nerve tract and tectum and in whole brain of fish was estimated. The incorporation of sialic acid into gangliosides and non-lipid components was studied in fish by intracranial or intraocular application of N-[³H]acetylmannosamine or N-[³H]acetylglucosamine. After intracranial injection of N-[³H]acetylmannosamine autoradiography showed lipid- and non-lipid-bound radioactivity in the tectum opticum evenly distributed over regions of nerve fibres or perikarya indicating an ubiquitous incorporation of label. Sialic acid incorporation into glycoproteins after intracranial injection of N-acetylmannosamine always exceeded that into gangliosides. TCA-precipitable non-lipid material is labelled from intracranially applied N-acetylmannosamine in the sialic acid portion and also in nonsialic acid components, whereby the percentage of label in sialic acid increases reaching 90 per cent of the total radioactivity after 90 min. After intraocular application of N-[³H]acetylmannosamine, sialic acid in gangliosides was generally found to be more highly labelled than in glycoproteins. The ratio of radioactivity in gangliosides and glycoproteins increased with time of incubation and the distance from the eye. TCA-soluble radioactivity was translocated by fast axonal transport. Cycloheximide inhibited incorporation of N-acetylmannosamine-derived radioactivity into gangliosides and proteins but not the transport of TCA-soluble material, which accumulates in the tectum. After intraocular application of N-[³H]acetylglucosamine, TCA-soluble label arrives later in the optic tectum than radioactivity of high molecular weight components. The ratio of lipid to non-lipid-bound radioactivity does not change considerably with the time after injection or the distance from the eye. There was no accumulation of TCA-soluble radioactivity after the inhibition of incorporation into high molecular weight components.     

Evolutionary history of Caenorhabditis elegans inferred from microsatellites: evidence for spatial and temporal genetic differentiation and the occurrence of outbreeding

Although diverse biological disciplines employ the nematode Caenorhabditis elegans as a highly efficient laboratory model system, little is known about its natural history. We investigated its evolutionary past using 10 polymorphic trinucleotide and tetranucleotide microsatellites, derived from across the whole genome. These microsatellites were analyzed from the 35 previously available natural isolates from different parts of the world and also 23 new strains isolated from northwest Germany. Our results highlight that C. elegans lineages differentiate genetically with respect to geographic distance and, to a lesser extent, differences in the time of strain isolation. The latter indicates some turnover of strain genotypes at specific locations. Our data also demonstrate the coexistence of highly diverse genotypes in the population from northwest Germany, which is best explained by recent migration events. Furthermore, selfing is confirmed as the primary mode of reproduction for this hermaphroditic nematode in nature. Importantly, we also find evidence for the occurrence of occasional outbreeding. Taken together, these results support the previous notion that C. elegans is a colonizer, whereby selfing may permit rapid dispersal within new habitats even in the absence of potential mates, whereas occasional outcrossing may serve to compensate for the disadvantages of inbreeding. Such information about the natural history of C. elegans should be of great value for an in-depth understanding of the complexity of this organism, including its multifaceted developmental, neurological, or molecular genetic pathways.     

Autoradiographische Untersuchungen zum Einbau von N-Acetyl-3H-Mannosamin im optischen System von Teleosteern

Zusammenfassung Der Einbau von intracranial sowie intraocular-appliziertem N-acetyl-3H-Mannosamin (N-Ac-3H-Man) in das optische System (Tectum opticum bzw. Tractus opticus) von Scardinius erythrophthalmus und Carassius carassius (cyprinidae, Telosteer) wurde autoradiographisch untersucht und mit dem Einbau von 3H-Histidin verglichen.1. Intracranial appliziertes N-Ac-3H-Man wird im Tectum opticum in Glykoproteine und Ganglioside im Verhältnis von 2:1 eingebaut.2. Die Synthese von Gangliosiden und Sialo-Glycoproteinen erfolgt im Nervengewebe im Gegensatz zu der von Proteinen ubiquitär, d. h. sowohl in den Perikaryen als auch in den Fasern.3. Nach einseitiger intraocularer Applikation von N-Ac-3H-Man werden bereits nach 24 stündiger Inkorporationszeit ausschließlich die mit dem injizierten Auge zusammenhängenden Sehschichten (Stratum opticum) des kontralateralen Tectum opticum radioaktiv markiert. Im Zusammenhang mit ergänzenden biochemischen Analysen ergibt sich, daß die Radioaktivität niedermolekularer Aminozucker mit dem schnellen axonalen Transport (>40 mm/d) zum Zwecke einer peripheren Gangliosid-Synthese im Tractus opticus proximo-distal verlagert wird.

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Autoradiographic investigations on the incorporation of N-Acetyl-3H-Mannosamine into the optic system of teleosts

Summary The incorporation of intra-cranially and intra-ocularly injected (N-Ac-3H-Man) and 3H-histidine into the optic systems (optic tectum and optic tract) of Scardinius erythrophthalmus and Carassius carassius was investigated by means of autoradiography.1. N-Ac-3H-Man injected intra-cranially, is incorporated into gangliosides and glycorproteins in a ratio of 1:2 in the optic tectum.2. In nervous tissue gangliosides and sialo-glycoproteins are labeled ubiquitously, i.e. in the perikarya as well as in the fibers.3. Following an intra-ocular injection of N-Ac-3H-Man and after an incorporation period of 24 hrs, only the optic layers in the contralateral optic tectum are labelled (gangliosides). Together with corresponding biochemical data, this shows, that in the optic tract radioactivity of low molecular amino sugars is transported proximo-distally by means of rapid axonal flow (>40 mm/d), before the incorporation into high molecular compounds.

Mit dankenswerter Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Opsonin-dependent phagocytosis of bacteria by murine macrophage-like cells

We have investigated the phagocytic properties of the macrophage-like cell line DCH-7, derived from fusion of mouse macrophages with a mouse T-lymphoma cell line. These cells phagocytosed opsonized bacteria. IgG appeared to be the major opsonin forStaphylococcus aureus Wood 46 as well as for threeEscherichia coli strains; complement components were not required as opsonins. Intracellular bacteria survived to a large extent. This model system should be a useful tool for studying the process of phagocytosis and phagocytic killing of bacteria.     

HDAC inhibitors induce apoptosis in glucocorticoid-resistant acute lymphatic leukemia cells despite a switch from the extrinsic to the intrinsic death pathway

Inhibitors of histone deacetylases (HDACi's) are promising novel tools for cancer therapy. We have compared the growth inhibitory and apoptogenic potential of the pan-HDACi SAHA and the sub-class I selective HDAC inhibitor MS275, as well as valproic acid (VPA) on glucocorticoid sensitive and resistant B (B-ALL) and T (T-ALL) cell acute lymphoblastic leukemia cells and patients blasts. In contrast, to our previous results with U937 acute myeloid leukemia (AML) cells which showed a similar activity of MS275 and SAHA in growth inhibition and apoptosis induction, both B and T-ALL cells were much more efficiently killed by SAHA and VPA than by MS275. The same relative potency was observed with some patient ALL blasts treated ex vivo. SAHA displayed similar efficacy on glucocorticoid-sensitive and insensitive ALL cells but did not synergize with dexamethasone. In studying mediators of apoptosis we found that the TRAIL receptor DR5 is constitutively expressed in glucocorticoid-sensitive CEM-C7 cells which are also TRAIL sensitive. In contrast, glucocorticoid-insensitive CEM-C1 cells do not express DR5 and are insensitive to TRAIL. However, SAHA induces, in addition to p21(WAF1/CIP1) also re-expression of DR5. Importantly, SAHA-induced apoptosis of CEM-C7 cells operates through initiator caspase 10, while it induces apoptosis of CEM-C1 cells through the intrinsic, as well as through caspase-independent death pathways. Our data suggest that the generation of resistance to glucocorticoids has dramatically altered death signaling in these cells and that SAHA overcomes these restrictions by inducing alternative death pathways.     

The high-level similarity of some disparate gene expression measures

Probe-level data from Affymetrix GeneChips can be summarized in many ways to produce probe-set level gene expression measures (GEMs). Disturbingly, the different approaches not only generate quite different measures but they could also yield very different analysis results. Here, we explore the question of how much the analysis results really do differ, first at the gene level, then at the biological process level. We demonstrate that, even though the gene level results may not necessarily match each other particularly well, as long as there is reasonably strong differentiation between the groups in the data, the various GEMs do in fact produce results that are similar to one another at the biological process level. Not only that the results are biologically relevant. As the extent of differentiation drops, the degree of concurrence weakens, although the biological relevance of findings at the biological process level may yet remain.