Differenciálgeometriai kutatások = Research in Differential Geometry

Csikós Balázs eredményei közt szerepel a Schläfli-formula egy messzemenő általánosítása, a Kneser-Poulsen-sejtés és azzal rokon sejtések speciális eseteinek bizonyítása. Vizsgálta a sejtés kiterjeszthetőségének határait Riemann-sokaságokra. Moussong Gábor a Kneser-Poulsen-sejtés korlátainak (ellenpéldák és pozitív eredmény) felderítésével foglalkozott elliptikus terekben (Csikós Balázzsal közösen). Ezen kívül az euklideszi tér rácsnégyzeteivel és rácskockáival kapcsolatos osztályozási, kiterjesztési és leszámlálási tételeket bizonyított. Szenthe János a gömbszimmetrikus téridő globális elméletének a felépítésével és kidolgozásával foglalkozott. Szőke Róbert általánosította a komplex koronatér fogalmát affin szimmetrikus terekre és jellemezte azokat a tereket, melyekre a koronatér egyenlő az érintőnyalábbal. Bebizonyította, hogy két lokálisan nem hiperkähler, lokálisan irreducibilis Kähler-sokaság közötti izometria vagy holomorf, vagy antiholomorf Verhóczki és Csikós bebizonyították, hogy az F_4 kivételes Lie-csoporthoz tartozó kompakt szimmetrikus Riemann-terek jól-definiált csőszerű struktúrával rendelkeznek. Egy explicit formulát adtak meg kompakt szimmetrikus terekben az izotrópia-csoportok principális orbitjainak térfogatára vonatkozóan. Verhóczki 1-kohomogenitású izometrikus csoporthatásokat vizsgált E_6/K típusú szimmetrikus tereken, és ennek során meghatározta az orbitok és a befoglaló terek térfogatait. | Among the results of B. Csikós are a far-reaching generalization of the Schläfli formula, proofs of special cases of the Kneser-Poulsen conjecture and its relatives. He studied extendability of the conjecture to Riemannian manifolds. G. Moussong explored the limitations of the Kneser-Poulsen conjecture (counterexamples and positive results) in elliptic spaces (joint work with B. Csikós). He also proved classification, extension, and enumeration theorems on lattice squares and lattice cubes in Euclidean space. J. Szenthe worked on laying the foundations of the global theory of spherically symmetric space-time. R. Szőke generalized the notion of complex crown to affine symmetric spaces and characterized with the help of the curvature tensor those spaces for which the complex crown equals the tangent bundle. He proved that an isometry between two locally irreducible Kähler, locally not hyperkähler manifolds is either holomorphic or antiholomorphic. L. Verhóczki and B. Csikós proved that the compact Riemannian symmetric spaces associated to the exceptional Lie group F_4 have got well-defined tubular structures. They gave an explicit formula for volumes of principal orbits of isotropy subgroups in compact symmetric spaces. L. Verhóczki studied cohomogeneity one isometric actions on compact symmetric spaces of type E_6/K, and among others he determined the volumes of the orbits and the ambient spaces

The Catalytic Aspartate Is Protonated in the Michaelis Complex Formed between Trypsin and an in Vitro Evolved Substrate-like Inhibitor: A REFINED MECHANISM OF SERINE PROTEASE ACTION.

The mechanism of serine proteases prominently illustrates how charged amino acid residues and proton transfer events facilitate enzyme catalysis. Here we present an ultrahigh resolution (0.93 A) x-ray structure of a complex formed between trypsin and a canonical inhibitor acting through a substrate-like mechanism. The electron density indicates the protonation state of all catalytic residues where the catalytic histidine is, as expected, in its neutral state prior to the acylation step by the catalytic serine. The carboxyl group of the catalytic aspartate displays an asymmetric electron density so that the O(delta2)-C(gamma) bond appears to be a double bond, with O(delta2) involved in a hydrogen bond to His-57 and Ser-214. Only when Asp-102 is protonated on O(delta1) atom could a density functional theory simulation reproduce the observed electron density. The presence of a putative hydrogen atom is also confirmed by a residual mF(obs) - DF(calc) density above 2.5 sigma next to O(delta1). As a possible functional role for the neutral aspartate in the active site, we propose that in the substrate-bound form, the neutral aspartate residue helps to keep the pK(a) of the histidine sufficiently low, in the active neutral form. When the histidine receives a proton during the catalytic cycle, the aspartate becomes simultaneously negatively charged, providing additional stabilization for the protonated histidine and indirectly to the tetrahedral intermediate. This novel proposal unifies the seemingly conflicting experimental observations, which were previously seen as either supporting the charge relay mechanism or the neutral pK(a) histidine theory

Astaxanthin Exerts Anabolic Effects via Pleiotropic Modulation of the Excitable Tissue

Astaxanthin is a lipid-soluble carotenoid influencing lipid metabolism, body weight, and insulin sensitivity. We provide a systematic analysis of acute and chronic effects of astaxanthin on different organs. Changes by chronic astaxanthin feeding were analyzed on general metabolism, expression of regulatory proteins in the skeletal muscle, as well as changes of excitation and synaptic activity in the hypothalamic arcuate nucleus of mice. Acute responses were also tested on canine cardiac muscle and different neuronal populations of the hypothalamic arcuate nucleus in mice. Dietary astaxanthin significantly increased food intake. It also increased protein levels affecting glucose metabolism and fatty acid biosynthesis in skeletal muscle. Inhibitory inputs innervating neurons of the arcuate nucleus regulating metabolism and food intake were strengthened by both acute and chronic astaxanthin treatment. Astaxanthin moderately shortened cardiac action potentials, depressed their plateau potential, and reduced the maximal rate of depolarization. Based on its complex actions on metabolism and food intake, our data support the previous findings that astaxanthin is suitable for supplementing the diet of patients with disturbances in energy homeostasis

Gyula László: Das awarenzeitliche Gräberfeld in Csákberény–Orondpuszta. Red.: József Szentpéteri.

Ez a monográfia – melyet az iskolateremtő professzor pályatársaiból, tanítványaiból és tisztelőiből álló szakemberek egy az 1936 és 1939 közötti csákberény–orondpusztai feltárások publikálására vállalkozó csoportja készített el – tisztelgés mindnyájunk Mestere, László Gyula (1910–1998) emléke előtt. A szerzőtársakkal és a kötetet befogadó Monumenta Avarorum Archaeologica sorozat szerkesztőivel együtt biztosak vagyunk abban, hogy pontosan 80 esztendővel a lelőhely felfedezése után nem csak egy régi adósságunkat törlesztjük a könyv publikálásával, s nem csupán a lelőhellyel kapcsolatos tudományos eredményeket foglaljuk össze a hazai és a nemzetközi szakirodalom számára, de megteremtjük a hiteles hátterét a további kutatómunka – így mindenekelőtt az egykor kényszerűen félbeszakadt ásatások – folytatásának is

Astaxanthin Exerts Anabolic Effects via Pleiotropic Modulation of the Excitable Tissue

Astaxanthin is a lipid-soluble carotenoid influencing lipid metabolism, body weight, and insulin sensitivity. We provide a systematic analysis of acute and chronic effects of astaxanthin on different organs. Changes by chronic astaxanthin feeding were analyzed on general metabolism, expression of regulatory proteins in the skeletal muscle, as well as changes of excitation and synaptic activity in the hypothalamic arcuate nucleus of mice. Acute responses were also tested on canine cardiac muscle and different neuronal populations of the hypothalamic arcuate nucleus in mice. Dietary astaxanthin significantly increased food intake. It also increased protein levels affecting glucose metabolism and fatty acid biosynthesis in skeletal muscle. Inhibitory inputs innervating neurons of the arcuate nucleus regulating metabolism and food intake were strengthened by both acute and chronic astaxanthin treatment. Astaxanthin moderately shortened cardiac action potentials, depressed their plateau potential, and reduced the maximal rate of depolarization. Based on its complex actions on metabolism and food intake, our data support the previous findings that astaxanthin is suitable for supplementing the diet of patients with disturbances in energy homeostasis

Astrocytes convert network excitation to tonic inhibition of neurons

<p>Abstract</p> <p>Background</p> <p>Glutamate and γ-aminobutyric acid (GABA) transporters play important roles in balancing excitatory and inhibitory signals in the brain. Increasing evidence suggest that they may act concertedly to regulate extracellular levels of the neurotransmitters.</p> <p>Results</p> <p>Here we present evidence that glutamate uptake-induced release of GABA from astrocytes has a direct impact on the excitability of pyramidal neurons in the hippocampus. We demonstrate that GABA, synthesized from the polyamine putrescine, is released from astrocytes by the reverse action of glial GABA transporter (GAT) subtypes GAT-2 or GAT-3. GABA release can be prevented by blocking glutamate uptake with the non-transportable inhibitor DHK, confirming that it is the glutamate transporter activity that triggers the reversal of GABA transporters, conceivably by elevating the intracellular Na⁺concentration in astrocytes. The released GABA significantly contributes to the tonic inhibition of neurons in a network activity-dependent manner. Blockade of the Glu/GABA exchange mechanism increases the duration of seizure-like events in the low-[Mg²⁺] <it>in vitro </it>model of epilepsy. Under <it>in vivo </it>conditions the increased GABA release modulates the power of gamma range oscillation in the CA1 region, suggesting that the Glu/GABA exchange mechanism is also functioning in the intact hippocampus under physiological conditions.</p> <p>Conclusions</p> <p>The results suggest the existence of a novel molecular mechanism by which astrocytes transform glutamat<it>ergic </it>excitation into GABA<it>ergic </it>inhibition providing an adjustable, <it>in situ </it>negative feedback on the excitability of neurons.</p

INVARIANTS OF KINETIC DIFFERENTIAL EQUATIONS ∗

Polynomial differential equations showing chaotic behavior are investigated using polynomial invariants of the equations. This tool is more effective than the direct method for proving statements like the one: the Lorenz equation cannot be transformed into an equation which would be a mass action type kinetic model of a chemical reaction