Travelling wave patterns in a model of the spinal pattern generator using spiking neurons.

The aim of this study is to produce travelling waves in a planar net of artificial spiking neurons. Provided that the parameters of the waves--frequency, wavelength and orientation--can be sufficiently controlled, such a network can serve as a model of the spinal pattern generator for swimming and terrestrial quadruped locomotion. A previous implementation using non-spiking, sigmoid neurons lacked the physiological plausibility that can only be attained using more realistic spiking neurons.

Synthesis of a hafnocene disilene complex.

Reaction of the magnesium transmetalation product of a 1,2-dipotassiodisilane with hafnocene dichloride gives a disilene hafnocene complex. X-ray crystallography of the respective trimethylphosphane adduct provides structural proof for this assignment.

Phase correlation of laser waves with arbitrary frequency spacing.

The theoretically predicted correlation of laser phase fluctuations in Lambda-type interaction schemes is experimentally demonstrated. We show that the mechanism of correlation in a Lambda scheme is restricted to high-frequency noise components, whereas in a double-Lambda scheme, due to the laser phase locking in a closed-loop interaction, it extends to all noise frequencies. In this case the correlation is weakly sensitive to coherence losses.

Regulation of activity in vitro and in vivo of three phospholipases B from Saccharomyces cerevisiae.

The genome of the yeast, Saccharomyces cerevisiae, contains three highly similar genes coding for phospholipases B/lysophospholipases. These enzymes behave differently with respect to substrate preferences in vitro and relative contributions to phospholipid catabolism in vivo [Merkel, Fido, Mayr, Pruger, Raab, Zandonella, Kohlwein and Paltauf (1999) J. Biol.

Contribution of different pathways to the supply of phosphatidylethanolamine and phosphatidylcholine to mitochondrial membranes of the yeast Saccharomyces cerevisiae.

In the yeast, three biosynthetic pathways lead to the formation of phosphatidylethanolamine (PtdEtn): (i) decarboxylation of phosphatidylserine (PtdSer) by phosphatidylserine decarboxylase 1 (Psd1p) in mitochondria; (ii) decarboxylation of PtdSer by Psd2p in a Golgi/vacuolar compartment; and (iii) the CDP-ethanolamine (CDP-Etn) branch of the Kennedy pathway. The major phospholipid of the yeast, phosphatidylcholine (PtdCho), is formed either by methylation of PtdEtn or via the CDP-choline branch of the Kennedy pathway. To study the contribution of these pathways to the supply of PtdEtn and PtdCho to mitochondrial membranes, labeling experiments in vivo with [(3)H]serine and [(14)C]ethanolamine, or with [(3)H]serine and [(14)C]choline, respectively, and subsequent cell fractionation were performed with psd1Delta and psd2Delta mutants.

Contribution of different biosynthetic pathways to species selectivity of aminoglycerophospholipids assembled into mitochondrial membranes of the yeast Saccharomyces cerevisiae.

In the yeast Saccharomyces cerevisiae, three pathways lead to the formation of cellular phosphatidylethanolamine (PtdEtn), namely the mitochondrial conversion of phosphatidylserine (PtdSer) to PtdEtn catalyzed by phosphatidylserine decarboxylase 1 (Psd1p), the equivalent reaction catalyzed by phosphatidylserine decarboxylase 2 (Psd2p) in the Golgi, and the CDP-ethanolamine branch of the so-called Kennedy pathway which is located to the microsomal fraction. To investigate the contributions of these three pathways to the cellular pattern of PtdEtn species (fatty acid composition) we subjected lipids of wild-type and yeast mutant strains with distinct defects in the respective pathways to mass spectrometric analysis. We also analyzed species of PtdSer and phosphatidylcholine (PtdCho) of these strains because formation of the three aminoglycerophospholipids is linked through their biosynthetic route.

[Investigation of sleep disorders in the vicinity of high frequency transmitters].

To investigate the potential impact of RF electromagnetic fields of transmitters on the sleep quality of nearby residents, a new study design is presented. In a double-blind crossover field study the effect of on-site shielding, rather than of additional exposure, is investigated. For improved sleep quality differentiation the polysomnographic parameters are expanded by additional parameters.

Preparation and structural characterisation of methoxybis(trimethylsilyl)silyl potassium and its condensation product.

Depending on the conditions the reaction of tris(trimethylsilyl)methoxysilane (1) with potassium tert-butoxide either in benzene and in the presence of 18-crown-6 or in THF gives either the crown ether adduct of potassium-methoxybis(trimethylsilyl)silane (2), or 2-methoxytetrakis(trimethylsilyl)disilanyl potassium (3).

Open, cyclic, and bicyclic compounds of double silylated phosphorus and boron.

Salt elimination reactions of tris(trimethylsilyl)silyl potassium (1), and two 1,4-dipotassiooligosilanes (3, 5) with 2,2,6,6-tetramethylpiperidinodichloroborane and diethylaminodichlorophosphane have generated open (2), cyclic (4) and bicyclic (6) bora- and phosphaoligosilanes. A monosilylated phosphane and the two five-membered cyclosilanes have been subjected to single crystal X-ray diffraction analysis.

Dynamics of neutral lipid storage in yeast.

Since energy storage is a basic metabolic process, the synthesis of neutral lipids occurs in all kingdoms of life. The yeast, Saccharomyces cerevisiae, widely accepted as a model eukaryotic cell, contains two classes of neutral lipids, namely steryl esters and triacylglycerols. Triacylglycerols are synthesized through two pathways governed by the acyl-CoA diacylglycerol acyltransferase Dga1p and the phospholipid diacylglycerol acyltransferase Lro1p, respectively.

Probing the aglycon binding site of a beta-glucosidase: a collection of C-1-modified 2,5-dideoxy-2,5-imino-D-mannitol derivatives and their structure-activity relationships as competitive inhibitors.

A range of new C-1 modified derivatives of the powerful glucosidase inhibitor 2,5-dideoxy-2,5-imino-D-mannitol has been synthesised and their biological activities probed with the beta-glucosidase from Agrobacterium sp. Ki values are compared with those of previously prepared close relatives. Findings suggest dramatic effects exerted by the aglycon binding site on substrate/inhibitor binding.

Targeting of proteins involved in sterol biosynthesis to lipid particles of the yeast Saccharomyces cerevisiae.

In the yeast Saccharomyces cerevisiae, three enzymes of the sterol biosynthetic pathway, namely Erg1p, Erg6p and Erg7p, are located in lipid particles. Whereas Erg1p (squalene epoxidase) is also present in the endoplasmic reticulum (ER) to a significant amount, only traces of Erg6p (sterol C-24 methyltransferase) and Erg7p (lanosterol synthase) are found in the ER. We have chosen these three Erg-proteins as typical representatives of lipid particle proteins to study targeting to their destination.

A yeast strain lacking lipid particles bears a defect in ergosterol formation.

Lipid particles of the yeast Saccharomyces cerevisiae are storage compartments for triacylglycerols (TAG) and steryl esters (STE). Four gene products, namely the TAG synthases Dga1p and Lro1p, and the STE synthases Are1p and Are2p contribute to storage lipid synthesis. A yeast strain lacking the four respective genes is devoid of lipid particles thus providing a valuable tool to study the physiological role of storage lipids and lipid particles.

Bioactive carbohydrates and recently discovered analogues as chemotherapeutics.

Infectious diseases such as tuberculosis, malaria, the "simple flu" or HIV and HBV, are killing more than 50,000 people a day according to estimations by the World Health Organisation (WHO). Consequently, the development of biologically active agents in general, such as antibiotics and chemotherapeutics, is of great importance. Hand in hand with the understanding of the mechanisms of biological agents, structures carrying sugar moieties have become increasingly important during the last decades.

Counterion-directed regioselective acetylation of octyl beta-D-glucopyranoside.

[reaction: see text] The DMAP-catalyzed acetylation of octyl beta-D-glucopyranoside with a series of acetylating agents has been investigated. The nature of the counterion of the catalytic DMAP-acetyl complex dramatically influences the outcome of the reaction, indicating that the deprotonation of the transition state is controlling the reaction. Noncovalent interactions of the acetate ion with the substrate seem to direct the acetylation toward secondary hydroxyl groups.

Identification of various lipolytic enzymes in crude porcine pancreatic lipase preparations using covalent fluorescent inhibitors.

We developed a specific method for determination and discrimination of lipo-/estero-lytic enzymes in crude lipase preparations. Here we study the composition of commercial porcine pancreatic lipase (PPL), since it is widely used for bioconversions of synthetic and natural substrates. Our method is based on incubation of enzyme samples with fluorescently labeled alkyl- or dialkylglyceryl-phosphonates in an appropriate solvent followed by protein separation by electrophoresis and fluorescence detection with a CCD camera.

[EEG-based communication--a new concept for rehabilitative support in patients with severe motor impairment].

This paper describes a paralyzed patient diagnosed with severe infantile cerebral palsy, trained over a period of several months to use an EEG-based brain-computer interface (BCI) for verbal communication. The patient learned to "produce" two distinct EEG patterns by mental imagery and to use this skill for BCI-controlled spelling. The EEG feedback training was conducted at a clinic for Assisted Communications, supervised from a distant laboratory with the help of a telemonitoring system.

[Influence of body size on the electric current perception threshold].

Although the threshold for electric current perception is of great importance for safety considerations and safety regulations, important aspects remain unsolved, e.g. the role of age or body size.

Activity levels of 137Cs and 40K in the skin and the cutaneous organs of a cow.

We have performed an extensive study to determine the activity distributions of radiocesium (137Cs) and of the radioisotope 40K of potassium in the whole body of a cow. ICRP assumes that cesium and potassium are distributed homogeneously throughout the whole body of an organism. The current investigation measured concentrations of 137Cs and 40K in components of the skin, horns, and hooves of a cow.

The solution structure of (Me3Si)3CSiBr--an ab initio/NMR study.

The first halosilylene stable in solution was investigated by ab initio/NMR calculations (IGLO SOS-DFPT PW91/B2//B3LYP/6-31+G(d)). The delta (29)Si(calc) of (Me(3)Si)(3)CSiBr (446 ppm) does not agree with the measured NMR signal at 106 ppm assigned to the free halosilylene. From the possible silylene complexes in the reaction solution, two structures agree with the observed NMR signal: the (Me(3)Si)(3)CSiBr(2) anion (delta (29)Si(calc)=124 ppm) and the unsolvated and solvated complex of the anion with two Li(+) (delta (29)Si(calc)=117 and estimated 134 ppm).

Oxidized phospholipids in minimally modified low density lipoprotein induce apoptotic signaling via activation of acid sphingomyelinase in arterial smooth muscle cells.

Oxidized phospholipids, including 1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphocholine (PGPC) and 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine (POVPC), typically present in minimally modified low density lipoprotein, have been found in atherosclerotic lesions. These compounds are gaining increasing importance as inducers of different cellular responses (inflammation, proliferation, or cell death). It was the aim of this study to understand their impact on intracellular signal transduction pathways that are responsible for these biological effects.

Triacylglycerol biosynthesis in yeast.

Triacylglycerol (TAG) is the major storage component for fatty acids, and thus for energy, in eukaryotic cells. In this mini-review, we describe recent progress that has been made with the yeast Saccharomyces cerevisiae in understanding formation of TAG and its cell biological role. Formation of TAG involves the synthesis of phosphatidic acid (PA) and diacylglycerol (DAG), two key intermediates of lipid metabolism.

YMR313c/TGL3 encodes a novel triacylglycerol lipase located in lipid particles of Saccharomyces cerevisiae.

Previous work from our laboratory (Athenstaedt, K., Zweytick, D., Jandrositz, A.

Biogenesis and cellular dynamics of aminoglycerophospholipids.

Aminoglycerophospholipids phosphatidylserine (PtdSer), phosphatidylethanolamine (PtdEtn), and phosphatidylcholine (PtdCho) comprise about 80% of total cellular phospholipids in most cell types. While the major function of PtdCho in eukaryotes and PtdEtn in prokaryotes is that of bulk membrane lipids, PtdSer is a minor component and appears to play a more specialized role in the plasma membrane of eukaryotes, e.g.