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Biomedical subjects

E Rump

Publications and source records attributed to E Rump.

8 recordsLinked to original sources
PubMed1999

Phosphorylcholine Coating of Iron Oxide Nanoparticles.

In order to develop thin-walled superparamagnetic nanoparticle suspensions as a contrast agent for magnetic resonance imaging, phosphorylcholine PC was used to coat iron oxide cores of 5 nm. Weak stable positively charged suspensions can be obtained at concentration greater than 3 mmol.l-1 (corresponding to about 3.2 molecules per nm2), while the addition of phosphorylglycerol PG decreases the electrophoretic mobility. Raising the pH over 6 leads to flocculation: the binding of PC on iron oxides as a function of pH appears to be reversible. By Langmuir analysis, two adsorption domains may be observed with a maximal density of 3.48 and 6.55 mol.nm-2, interpreted as a multilayer formation. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Introduction of the closed cranial window technique in gerbils and verification by observation of the effects of specific drugs.

The exact mechanisms of cerebral arterial hypoxia are not perfectly defined. Our purpose is to adapt and validate, with drugs well known in rats and rabbits, a closed cranial window technique in gerbils. The method was used with seventeen gerbils to measure diameter changes of the pial arterioles under normoxia (after the topical application of agonists and antagonists of ATP-sensitive and Ca2+-dependent potassium channels), as well as under hypoxia. In normoxia, aprikalim (10(-6) M), a direct activator of ATP-sensitive potassium channels, increases the diameter of pial arterioles by 10+/-2% (N = 17). This effect is inhibited by glibenclamide (10(-6) M), but not affected by iberiotoxin (10(-6) M), a specific inhibitor of Ca2+-dependent potassium channels. The adenosine-induced dilation by 19+/-5% (N = 17) is reduced by 59+/-16% with iberiotoxin, by 33+/-23% with glibenclamide and inhibited by theophylline (10(-5) M). In hypoxia (15% O2), pial arteriole diameters are increased by 24+/-5% (N = 17) and partially decreased by the application of glibenclamide and iberiotoxin to 59+/-11% and 54+/-5%, respectively. These data are similar to those obtained in other species and validate the closed cranial window technique on gerbils. They indicate that, as for rats and rabbits, both ATP-sensitive and Ca2+-dependent potassium channels are present in gerbil pial vessels and play a role in hypoxia.

Adenosine↗
PubMed1997

Supramolecular assembly using helical peptides.

We investigated supramolecular assemblies of various hydrophobic helical peptides. The assemblies were formed at the air/water interface or in aqueous medium. The hexadecapeptide, Boc-(Ala-Aib)s-OMe (BA16M), was reported to take alpha-helical structure by X-ray analysis. Several derivatives were prepared, which have the repeating sequence of Ala-Aib, Lys(Z)-Aib or Leu-Aib, or have the terminal chemically modified. CD spectra of the peptides indicated helical conformation in ethanol solution. The surface pressure-area isotherms of the peptide monolayers showed an inflection at the surface area corresponding to the cross section along the helix axis, and the monolayers were collapsed by further compression. All the helical peptides oriented their helix axis parallel to the air/water interface on the basis of the results of transmission IR spectra and RAS of the monolayers transferred onto substrates. A small mound was observed in the isotherm of BA16M and other derivatives, which was ascribed to the phase transition from the liquid state to the solid state. One mol% of FITC-labeled peptide was mixed into the monolayers to visualize the phase separation of the solid and liquid states at the surface pressure of the coexisting region. Various shapes of the dark domain were observed at the top of the mound in the isotherms by fluorescence microscopy. The helical peptides formed two-dimensional crystals at the air/water interface when they were compressed to the solid state. An amino-terminated helical peptide, HA16B, was suspended in an aqueous medium by a sonication method and transparent dispersion was obtained. The dynamic light scattering measurement of the dispersion revealed the particle size of 75 nm with a narrow size distribution. The molecular assembly of the helical peptide in water was called "Peptosome", because it takes a vesicular structure.

Air↗
PubMed1994

Formation of protein multilayers and their competitive replacement based on self-assembled biotinylated phospholipids.

Based on specific recognition processes the build-up of protein multilayers was achieved using streptavidin layers as a docking matrix. For this purpose, streptavidin was organized at biotin-containing monolayers, liposomes, and self-assembled layers on gold. Thus, mixed double and triple layers of streptavidin, Con A, Fab fragments, and hormones were prepared and characterized by fluorescence microscopy and plasmon spectroscopy. Using biotin analogues with lower binding constants several cycles of multilayer formation followed by competitive replacement could be achieved.

Bacterial Proteins↗
PubMed1993

Attempts to mimic docking processes of the immune system: recognition-induced formation of protein multilayers.

The assemblage of protein multilayers induced by molecular recognition, as seen, for example, in the immune cascade, has been mimicked by using streptavidin as a docking matrix. For these experiments, this protein matrix was organized on liposomes, monolayers at the air-water interface, and self-assembled layers on gold, all three containing biotin lipids. The docking of streptavidin to biotin at liposomal surfaces was confirmed by circular dichroism. Mixed double and triple layers of streptavidin, concanavalin A, antibody Fab fragments, and hormones are prepared at the air-water interface and on gold surfaces and were characterized by fluorescence microscopy and plasmon spectroscopy. With the use of biotin analogs that have lower binding constants it has been possible to achieve multiple formation and competitive replacement of the oriented protein assemblages.

Bacterial Proteins↗
PubMedDate not supplied

Nanoprecipitation technique for the encapsulation of agrochemical active ingredients.

In 1997, a research programme was initiated to assess the ability of nanospheres (NS) to improve the biodelivery of a new insecticide to plants. Stable polymeric NS, with a size near 135 nm and an encapsulation rate in the range of 3.5%, have been obtained using a nanoprecipitation method with Eudragit S100 polymer. Biological studies have been performed on cotton plants infested with aphid, to estimate the direct contact efficacy of NS formulations on the insects and the systemicity of the encapsulated active ingredient and its level of penetration through the plant, compared to a classical suspension used as a reference. Results indicate that NS formulations are not so good as the reference in terms of speed of action and sustained release. Nevertheless, NS formulation performed better than the reference to enhance the systemicity of the AI and improve its penetration through the plant. It is concluded that the NS do not provide a controlled release of AI but, due to their small size, they enhance the penetration in the plant compared to the classical suspension.

Animals↗