Showing papers by "Hungarian Academy of Sciences published in 1996"

Adenosine receptor agonists differentially regulate IL-10, TNF-alpha, and nitric oxide production in RAW 264.7 macrophages and in endotoxemic mice.

Abstract: Adenosine released into the extracellular space by immunologic and nonimmunologic stimuli has been shown to regulate various immune functions In this study we report that ip pretreatment of mice with CGS-21680 HCl (CGS), a selective agonist of A2 adenosine receptors, at 02 to 2 mg/kg caused an augmentation of plasma IL-10 levels induced by ip injection of LPS, but decreased plasma levels of LPS-induced TNF-alpha 2-Chloro-N6-cyclopentyladenosine (CCPA), an agonist of A1 adenosine receptors, at 05 mg/kg diminished LPS-induced plasma TNF-alpha concentrations, but enhanced LPS-induced IL-10 levels only at the highest dose used (2 mg/kg) The specific A3 adenosine receptor agonist 1-deoxy-1-[6-[[(3-iodophenyl)methyl]amino]-9H-purin-9-yl]-N-methyl-beta- D-ribofuranuronamide, at 02 and 05 mg/kg potentiated LPS-stimulated IL-10 production and inhibited LPS-induced TNF-alpha production LPS-induced plasma nitrite and nitrate levels (the breakdown products of nitric oxide (NO)) were suppressed by CGS and CCPA In the RAW 2647 macrophage cell line, pretreatment of the cells with both CGS and CCPA inhibited LPS-induced IL-10, TNF-alpha, and NO production, each in a concentration-dependent manner The inhibitory effect of these drugs on cytokine and NO production was associated with improved mitochondrial respiration Neither CGS nor CCPA affected the LPS-induced nuclear translocation of transcription factor nuclear factor-kappaB in these cells These results demonstrate that adenosine receptor stimulation differentially modulates the LPS-induced production of IL-10, TNF-alpha, and NO in vitro and in vivo The increase in LPS-induced IL-10 production and suppression of LPS-induced TNF-alpha and NO production caused by adenosine receptor activation may explain some of the immunomodulatory actions of adenosine released in excess during inflammatory and/or ischemic insult

Interneurons Containing Calretinin Are Specialized to Control Other Interneurons in the Rat Hippocampus

Abstract: Spine-free calretinin-immunoreactive (CR-IR) interneurons form a subpopulation of GABAergic cells in the rat hippocampus. A characteristic feature of these cells--located in all areas and layers--is the frequent dendro-dendritic and axo-dendritic contacts they form with each other. In this study we examined in detail the connectivity of these neurons by reconstructing their dendritic and axonal arbor and by identifying their postsynaptic targets. Radially running dendrites of CR-IR cells, located in different layers, intermingled into long braids. An average cell was in contact with dendrites of three to seven other CR-IR cells. Reconstruction of the dendritic trees from six consecutive sections demonstrated that at least 15 cells may participate in a dendro-dendritically connected cluster. Electron microscopical examination revealed that regularly spaced zonula adherentia connect the touching dendrites. The postsynaptic targets of CR-IR neurons have been examined using postembedding immunogold staining for GABA. CR-containing GABA-immunoreactive axons of local origin formed multiple symmetrical synaptic contacts (two to five) exclusively on GABAergic dendrites (CR-negative as well as CR-positive). Two to 10 CR-IR axons may converge onto a single CR-IR neuron, often from cells belonging to the same dendro-dendritically connected cluster. Using double immunocytochemistry, CR-IR cells were shown to heavily innervate calbindin D28k-containing interneurons and VIP-containing basket cells but avoided the parvalbumin-containing basket and axo-axonic cells. The unique connectivity of CR-IR cells may enable them to play a crucial role in the generation of synchronous, rhythmic hippocampal activity by controlling other interneurons terminating on different dendritic and somatic compartments of principal cells.

Automatic computer simulations of ESR spectra

Abstract: A versatility of automatic ESR simulation procedures has been developed to obtain high quality of fitting and produce additional information. The following examples are treated: derivation of long-range proton hyperfine coupling constants from unresolved lines; determination of13C hf couplings from the naturally abundant isotope satellites; analyzing chemical exchange phenomena with two-sites model; decomposition of superimposed spectra consisting of poorly resolved components. In order to achieve best agreement between calculated and experimental spectra within a reasonable number of iteration cycles, we combined various approaches, like consecutive independent parameter optimization, least-square approach, optimization on “serpentines” and optimization of compound parameters. The spectra can be computed both for liquid and solid state samples, for non-oriented, partially oriented and single crystal samples. Second order perturbation formulas are used for the spin Hamiltonian includingg- and hyperfine tensors that have isotropic, axial and rhombic symmetry. For chemical exchange the modified Bloch equation for two-site model is used. Various lineshapes, including Lorentzian, Gaussian, mixed, modulation and dispersion distorted forms are applied. Third order parabolic interpolations are used for building up spectra from individual lines. In order to correct sweep non-linearity a third order interpolation converts the spectrum to become equidistant. This procedure can occasionally improve square deviation by an order of magnitudes for well resolved spectra. In the analysis of strongly overlapping superimposed spectra, simultaneous adjustment of two independent experimental spectra can give an exact decomposition. The inclusion of long-range couplings offers highly perfect fitting and allows one to resolve contributions of naturally abundant13C isotopes.

Genetic evidence for an essential role of brassinosteroids in plant development

Abstract: Annette Kauschmann 1, Alison Jessop 1,t, Csaba Koncz 2,3, Miklos Szekeres 3, Lothar Willmitzer 1.t and Thomas Altmann 1,t.* llnstitut fQr Genbiologische Forschung Berlin GmbH, Ihnestra~e 63, D-14195 Berlin, Germany, 2Max-Planck-lnstitut fQr Z0chtungsforschung, Carl-yon Linn6-Weg 10, D-50829 K61n, Germany, and 3Institute of Plant Biology, Biological Research Center of Hungarian Academy of Sciences, H-6701 Szeged, P.O. Box 521, Temesv ri krt. 62, Hungary

A measure concentration inequality for contracting markov chains

Abstract: The concentration of measure phenomenon in product spaces means the following: if a subsetA of then'th power of a probability space Χ does not have too small a probability then very large probability is concentrated in a small neighborhood ofA. The neighborhood is in many cases understood in the sense of Hamming distance, and then measure concentration is known to occur for product probability measures, and also for the distribution of some processes with very fast and uniform decay of memory. Recently Talagrand introduced another notion of neighborhood of sets for which he proved a similar measure concentration inequality which in many cases allows more efficient applications than the one for a Hamming neighborhood. So far this inequality has only been proved for product distributions. The aim of this paper is to give a new proof of Talagrand's inequality, which admits an extension to contracting Markov chains. The proof is based on a new asymmetric notion of distance between probability measures, and bounding this distance by informational divergence. As an application, we analyze the bin packing problem for Markov chains.

Identification and grouping of Newcastle disease virus strains by restriction site analysis of a region from the F gene

Abstract: A 75% region of the F gene (between nucleotides 334 and 1682) of Newcastle disease virus (NDV) RNA was amplified by reverse transcription polymerase chain reaction (RT-PCR). PCR products were cleaved by three restriction endonucleases and the positions of thirty cleavage sites were mapped in more than 200 NDV strains. Restrictions site analysis established six major groups of NDV isolates and unique fingerprints of vaccine strains. Group I comprised lentogenic strains isolated mainly from waterfowl with some from chickens. "Old" (prior to 1960s) North American isolates of varying virulence including lentogenic and mesogenic vaccine strains belonged to group II. Group III included two early isolates from the Far East. Early European strains (Herts 33 and Italien) of the first panzootic (starting in the late 1920s) and their descendants with some modifications were placed into group IV. NDV strains isolated during the second panzootic of chickens (starting in the early 1960s) were classified into two groups. Group V included strains originating in imported psittacines and in epizootics of chickens in the early 1970s. Group V1 comprised strains from the Middle East in the late 1960s and later isolates from Asia and Europe. Pigeon paramyxovirus-1 strains that were responsible for the third panzootic formed a distinct subgroup in group V1. Our grouping of NDV strains has confirmed group differences established by monoclonal antibodies. It is concluded that restriction site analysis of F gene PCR amplicons is a relatively fast, simple and reliable method for the differentiation and identification of NDV strains.

Membrane lipid perturbation modifies the set point of the temperature of heat shock response in yeast

Abstract: Addition of a saturated fatty acid (SFA) induced a strong increase in heat shock (HS) mRNA transcription when cells were heat-shocked at 37 degrees C, whereas treatment with an unsaturated fatty acid (UFA) reduced or eliminated the level of HS gene transcription at 37 degrees C. Transcription of the delta 9-desaturase gene (Ole1) of Histoplasma capsulatum, whose gene product is responsible for the synthesis of UFA, is up-regulated in a temperature-sensitive strain. We show that when the L8-14C mutant of Saccharomyces cerevisiae, which has a disrupted Ole1 gene, is complemented with its own Ole1 coding region under control of its own promoter or Ole1 promoters of H. capsulatum, the level of HS gene transcription depends on the activity of the promoters. Fluorescence anisotropy of mitochondrial membranes of completed strains corresponded to the different activity of the Ole1 promoter used. We propose that the SFA/UFA ratio and perturbation of membrane lipoprotein complexes are involved in the perception of rapid temperature changes and under HS conditions disturbance of the preexisting membrane physical state causes transduction of a signal that induces transcription of HS genes.

Conversion of methane to benzene over Mo2C and Mo2C/ZSM-5 catalysts

Abstract: The activation and dehydrogenation of CH2 on Mo2C and MO2C/ZSM-5 have been investigated under non-oxidizing conditions. Unsupported Mo2C exhibited very little activity towards methane decomposition at 973 K. The main reaction pathway was the decomposition of methane to give hydrogen and carbon with a trace amount of ethane. Mixing Mo2C with ZSM-5 support somewhat enhanced its catalytic activity, but did not change the products of the reaction. A dramatic change in the product formation occurred on partially oxidized Mo2C/ZSM-5 catalyst; besides some hydrocarbons benzene was produced with a selectivity of 70–80% at a conversion of 5–7%. Carburization of highly dispersed MoO3 on ZSM-5 also led to a very active catalyst: the conversion of methane at the steady state was 5–6% and the selectivity of benzene formation was 85%.

Thermally activated carrier transfer and luminescence line shape in self‐organized InAs quantum dots

Abstract: We investigated the temperature dependence (10–180 K) of the photoluminescence (PL) emission spectrum of self‐organized InAs/GaAs quantum dots grown under different conditions. The temperature dependence of the PL intensity is determined by two thermally activated processes: (i) quenching due to the escape of carriers from the quantum dots and (ii) carrier transfer between dots via wetting layer states. The existence of different dot families is confirmed by the deconvolution of the spectra in gaussian components with full width half maxima of 20–30 meV. The transfer of excitation is responsible for the sigmoidal temperature dependence of the peak energies of undeconvoluted PL bands.

Identification of functional domains and evolution of Tc1-like transposable elements

Abstract: Tc1-like transposable elements from teleost fish have been phylogenetically examined to determine the mechanisms involved in their evolution and conserved domains of function. We identified two new functional domains in these elements. The first is a bipartite nuclear localization signal, indicating that transposons can take advantage of the transport machinery of host cells for nuclear uptake of their transposases. The second is a novel combination of a paired domain-related protein motif juxtaposed to a leucine zipper-like domain located in the putative DNA-binding regions of the transposases. This domain coexists with a special inverted repeat structure in certain transposons in such phylogenetically distant hosts as fish and insects. Our data indicate that reassortment of functional domains and horizontal transmission between species are involved in the formation and spread of new types of transposable elements.

Bose-Einstein Correlations for Three-Dimensionally Expanding, Cylindrically Symmetric, Finite Systems

Abstract: There are two types of scales present simultaneously in the spacelike as well as in the timelike directions in a model class describing a cylindrically symmetric, finite, three-dimensionally expanding boson source. One type of scale is related to the finite lifetime or geometrical size of the system, and the other type is governed by the rate of change of the local momentum distribution in the considered temporal or spatial direction. The parameters of the Bose-Einstein correlation function may obey an ${\mathit{M}}_{\mathit{t}}$ scaling, as observed in S+Pb and Pb+Pb reactions at CERN SPS. This ${\mathit{M}}_{\mathit{t}}$ scaling may imply that the Bose-Einstein correlation functions view only a small part of a large and expanding system. The full sizes of the expanding system at the last interaction are shown to be measurable with the help of the invariant momentum distribution of the emitted particles. A vanishing duration parameter can also be generated, with a specific ${\mathit{M}}_{\mathit{t}}$ dependence, in the considered model class. \textcopyright{} 1996 The American Physical Society.

Molecular cloning of a high-affinity receptor for the growth factor-like lipid mediator lysophosphatidic acid from Xenopus oocytes

Abstract: Lysophosphatidic acid (1-acyl-2-lyso-sn-glycero-3-phosphate, LPA) is a multifunctional lipid mediator found in a variety of organisms that span the phylogenetic tree from humans to plants. Although its physiological function is not clearly understood, LPA is a potent regulator of mammalian cell proliferation; it is one of the major mitogens found in blood serum. In Xenopus laevis oocytes, LPA elicits oscillatory Cl− currents. This current, like other effects of LPA, is consistent with a plasma membrane receptor-mediated activation of G protein-linked signal transduction pathways. Herein we report the identification of a complementary DNA from Xenopus that encodes a functional high-affinity LPA receptor. The predicted structure of this protein of 372 amino acids contains features common to members of the seven transmembrane receptor superfamily with a predicted extracellular amino and intracellular carboxyl terminus. An antisense oligonucleotide derived from the first 5–11 predicted amino acids, selectively inhibited the expression of the endogenous high-affinity LPA receptors in Xenopus oocytes, whereas the same oligonucleotide did not affect the low-affinity LPA receptor. Expression of the full-length cRNA in oocytes led to an increase in maximal Cl− current due to increased expression of the high-affinity LPA receptor, but activation of the low-affinity receptor was, again, unaffected. Oocytes expressing cRNA prepared from this clone showed no response to other lipid mediators including prostaglandins, leukotrienes, sphingosine 1-phosphate, sphingosylphosphorylcholine, and platelet-activating factor, suggesting that the receptor is highly selective for LPA.

The GAGA factor is required in the early Drosophila embryo not only for transcriptional regulation but also for nuclear division

Abstract: The GAGA protein of Drosophila was first identified as a stimulatory factor in in vitro transcription assays using the engrailed and Ultrabithorax promoters. Subsequent studies have suggested that the GAGA factor promotes transcription by blocking the repressive effects of histones; moreover, it has been shown to function in chromatin remodeling, acting together with other factors in the formation of nuclease hypersensitive sites in vitro. The GAGA factor is encoded by the Trithorax-like locus and in the studies reported here we have used the maternal effect allele Trl13C to examine the functions of the protein during embryogenesis. We find that GAGA is required for the proper expression of a variety of developmental loci that contain GAGA binding sites in their upstream regulatory regions. The observed disruptions in gene expression are consistent with those expected for a factor involved in chromatin remodeling. In addition to facilitating gene expression, the GAGA factor appears to have a more global role in chromosome structure and function. This is suggested by the spectrum of nuclear cleavage cycle defects observed in Trl13C embryos. These defects include asynchrony in the cleavage cycles, failure in chromosome condensation, abnormal chromosome segregation and chromosome fragmentation. These defects are likely to be related to the association of the GAGA protein with heterochromatic satellite sequences which is observed throughout the cell cycle.

Cross-field normalization of scientometric indicators

Abstract: Comparative assessment of scientometric indicators is greatly hindered by the different standards valid in different science fields and subfields. Indicators concerning to different fields can be compared only after first gauging them against a properly chosen reference standard, and their relative standing can then be compared. Methods of selecting reference standards and scaling procedures are surveyed in this study, and examples are given to their practical application.

Mycoplasmoses in poultry

Abstract: The most important mycoplasmas isolated from domestic avian species include Mycoplasma gallisepticum (MG), M. synoviae (MS), M. meleagridis (MM) and M. iowae (MI). MG causes chronic respiratory disease of chickens and infectious sinusitis in turkeys, resulting in economic losses. MS causes infectious synovitis or mild upper respiratory disease. MM infects only turkeys, causing airsacculitis and sub-optimal production and hatchability. MI is associated with reduced hatchability in turkey flocks. Transmission is either direct, from bird to bird or through the egg, or indirect. Diagnosis is based on isolation and identification of mycoplasmas, according to biochemical, serological or molecular biology tests, or serological examination of host sera by slide agglutination, haemagglutination inhibition or enzyme-linked immunosorbent assay (ELISA) tests. Antibiotics (i.e. tetracyclines, macrolides, quinolones and tiamulin) may be used for therapeutic treatment or prophylactic medication. The eradication of mycoplasma infection can be achieved through improvements in hygiene and management practices, therapeutic treatment of breeder layers and/or of hatching eggs and better monitoring procedures.

UV-B-induced inhibition of photosystem II electron transport studied by EPR and chlorophyll fluorescence. Impairment of donor and acceptor side components.

Abstract: Inhibition of photosystem II electron transport by UV-B radiation has been studied in isolated spinach photosystem II membrane particles using low-temperature EPR spectroscopy and chlorophyll fluorescence measurements. UV-B irradiation results in the rapid inhibition of oxygen evolution and the decline of variable chlorophyll fluorescence. These effects are accompanied by the loss of the multiline EPR signal arising from the S2 state of the water-oxidizing complex and the induction of Signal IIfast originating from stabilized Try-Z+. The EPR signals from the QA-Fe2+ acceptor complex, Tyr-D+, and the oxidized non-heme iron (Fe3+) are also decreased during the course of UV-B irradiation, but at a significantly slower rate than oxygen evolution and the multiline signal. The decrease of the Fe3+ signal at high g values (g = 8.06, g = 5.6) is accompanied by the induction of another EPR signal at g = 4.26 that arises most likely from the same Fe3+ ion in a modified ligand environment. UV-B irradiation also affects cytochrome b-559. The g = 2.94 EPR signal that arises from the dark- oxidized form is enhanced, whereas the light inducible g = 3.04 signal that arises from the photo-oxidizable population of cytochrome b-559 is diminished. UV-B irradiation also induces the degradation of the D1 reaction center protein. The rate of the D1 protein loss is slower than the inhibition of oxygen evolution and of the multiline signal but follows closely the loss of Signal IIslow, the QA-Fe2+ and the Fe3+ EPR signals, as well as the release of protein-bound manganese. It is concluded from the results that UV-B radiation affects photosystem II redox components at both the donor and acceptor side. The primary damage occurs at the water-oxidizing complex. Modification and/or inactivation of tyrosine-D, cytochrome b-559, and the QAFe2+ acceptor complex are subsequent events that coincide more closely with the UV-B-induced damage to the protein structure of the photosystem II reaction center.