Showing papers by "Hungarian Academy of Sciences published in 1987"
958 citations
TL;DR: Exon insertions and exon duplications, two major mechanisms of exon shuffling, are shown to involve modules that have introns of the same phase class at both their 5′‐ and 3′‐ends.
285 citations
TL;DR: Observations are made on the complexity of cutting planes proofs in general and when restricted to proving the unsatisfiability of formulae in the propositional calculus.
258 citations
TL;DR: Auditory evoked potentials elicited by standard (STs) and deviant tones (DTs) of different probabilities were studied in freely moving cats during wakefulness and sleep and a large double peaked negativity, so-called mismatch negativity, was evoked by the unattended low probability DTs.
254 citations
01 Jan 1987
TL;DR: In this article, a new representation theorem for distributions of real-valued random variables is presented, which is based on a relationship between different truncated moments of the same random variable.
Abstract: A new representation theorem for distributions of real-valued random variables is presented. The theorem is based on a relationship between different truncated moments of the same random variable. As an example of its application, characterization theorems for some families of both continuous and discrete distributions are derived. Further applications can be obtained after certain transformations. These characterizations may also serve as a basis for parameter estimation.
208 citations
TL;DR: The role of silver ions as an inhibitor of ethylene action was supported by a reversal of the inhibitory effects of 2,4-D and ethylene on morphogenesis in wheat callus cultures.
Abstract: Silver nitrate effectively promoted shoot regeneration in wheat (Triticum aestivum L.) callus cultures derived from immature embryos. This effect could be observed in both weakly and strongly regenerating cultivars, and in using material from both field and greenhouse grown plants. The role of silver ions as an inhibitor of ethylene action was supported by a reversal of the inhibitory effects of 2,4-D and ethylene on morphogenesis in wheat callus cultures.
203 citations
TL;DR: Experiments with nodA–lacZ gene fusions demonstrate that the MPIK3030 nodD1 regulates expression of the nodABC genes and indicates that the carboxy‐terminal region is responsible for the interaction with plant factor(s) and may have evolved in different rhizobia specifically to interact with plant–host factors.
Abstract: We have identified a nodD gene from the wide host-range Rhizobium strain MPIK3030 (termed nodD1) which is essential for nodulation on Macroptilium atropurpureum (siratro). Experiments with nodA–lacZ gene fusions demonstrate that the MPIK3030 nodD1 regulates expression of the nodABC genes. Additionally, we used nodC–lacZ fusions of Rhizobium meliloti to show that the MPIK3030 nodD1 gene induces expression of these fusions by interacting with plant factors from siratro and from the non-host Medicago sativa (alfalfa). The R. meliloti nodD genes, however, only interact with alfalfa exudate. In line with these results, no complementation of MPIK3030 nodD1 mutants could be obtained on siratro with the R. meliloti nodD genes, while the MPIK3030 nodD1 can complement nodD mutants of R. meliloti on alfalfa. Furthermore, R. meliloti transconjugants harbouring the MPIK3030 nodD1 efficiently nodulate the illegitimate host siratro. When compared with other nodD sequences, the amino acid sequence of the MPIK3030 nodD1 shows a conserved aminoterminus, whereas the carboxy-terminus of the putative gene product diverges considerably. Studies on a chimeric MPIK3030/R. meliloti nodD gene indicates that the carboxy-terminal region is responsible for the interaction with plant factor(s) and may have evolved in different rhizobia specifically to interact with plant–host factors.
193 citations
TL;DR: The effect of glucocorticoids on corticotropin-releasing factor (CRF) gene expression was studied by combination of in situ hybridization histochemistry and steroid implantation.
Abstract: The effect of glucocorticoids on corticotropin-releasing factor (CRF) gene expression was studied by combination of in situ hybridization histochemistry and steroid implantation. Dexamethasone micropellets, implanted around the hypothalamic paraventricular nucleus (PVN), caused total inhibition of the hybridizable CRF mRNA signal above the parvocellular neurons of the PVN. Unilateral implantation of dexamethasone around the PVN resulted in a decrease of hybridizable CRF mRNA at the dexamethasone-implanted side. Dexamethasone implants into the cerebral cortex, dorsal hippocampus, ventral subiculum, lateral septum or amygdala were without any effect on the CRF expression in the PVN. Corticosterone did not result in any significant change in CRF mRNA, when implanted into the paraventricular region, dorsal hippocampus or ventral subiculum. When it was placed into the amygdala however, in a few cases it slightly inhibited the CRF mRNA levels in the ipsilateral PVN.
165 citations
TL;DR: In this paper, a new potential is presented which describes the methanol-methanol interactions on the basis of a flexible three-site model, and the intramolecular part of the potential has been derived from spectroscopic data.
Abstract: A new potential is presented which describes the methanol-methanol interactions on the basis of a flexible three-site model. The intramolecular part of the potential has been derived from spectroscopic data. A molecular dynamics study has been performed with this potential at 286 K. The structural properties of liquid methanol calculated from the simulations are in good agreement with X-ray measurements. The average geometrical arrangement of nearest neighbors and their hydrogen bonding are discussed. The potential describes correctly the gas-liquid frequency shifts of the intramolecular vibrations. Several thermodynamic properties calculated from the simulation compare favorably with experimental results.
156 citations
TL;DR: Structural and kinetic data may be assembled to provide a plausible picture of the C1 activation mechanism; moreover, this raises new questions and poses interesting problems for future studies.
Abstract: Recent physical and chemical studies have contributed substantially to our knowledge of the structures of subcomponents Clq, Clr, and CIs and their assembly into Cl. Kinetic studies have provided new insight into the activation process, particularly the central role played by C1-inhibitor: This protein appears to be loosely associated with the Cl complex and functions in preventing spontaneous activation and in regulating activation by immune complexes. New probes of C1 activation-monoclonal anti bodies directed against C1q and their (Fab)2 and Fab fragments-have been used to show that activation requires multivalent binding to C1q, but not the presence of the antibody Fc piece. These structural and kinetic data may be assembled to provide a plausible picture of the C1 activation mechanism; moreover, this raises new questions and poses interesting problems for future studies. Models for the activation of C1 have been suggested (1-4). For a comprehensive review of C1, see (5). Other recent reviews include (6-10).
156 citations
TL;DR: The consensus sequence method succeeded in finding some new members of these protein families that could not be detected by earlier methods of sequence comparison.
TL;DR: The genomic construct of these somatic hybrids made the transmission of the resistance character into the next sexual generation possible and resulted in aneuploid somatics hybrids with significantly lower chromosome number than predicted by simple addition of parental chromosome number.
Abstract: Transfer of methotrexate and 5-methyltryptophan resistance from carrot (Daucus carota) to tobacco (Nicotiana tabacum) was achieved by fusion between leaf mesophyll protoplasts of tobacco and irradiated cell culture protoplasts of carrot. Some of the regenerated somatic hybrids exhibited normal tobacco morphology with coexpression and independent segregation of the transferred resistance markers. Chromosomal instability resulted in aneuploid somatic hybrids with significantly lower chromosome number than predicted by simple addition of parental chromosome number. The methotrexate resistance phenotype was correlated with the expression of carrot-specific dihydrofolate reductase as judged by isozyme and immunological characteristics of the enzyme. The genomic construct of these somatic hybrids made the transmission of the resistance character into the next sexual generation possible.
TL;DR: The results indicate that the Krebs tricarboxylic acid cycle exists as a sequential complex of enzymes, a metabolon, in situ, as well as an in vivo organization of this pathway.
01 Jan 1987
TL;DR: There is strong observational and experimental evidence that in phytophagous insects host plant recognition and utilization on the one hand, and avoidance or rejection of nonhost plants, are largely determined genetically, thus, they cannot be changed basically by experience.
Abstract: There is strong observational and experimental evidence that in phytophagous insects host plant recognition and utilization on the one hand, and avoidance or rejection of nonhost plants, on the other hand, are largely determined genetically, thus, they cannot be changed basically by experience. Nevertheless, it has been shown, mostly during the last two decades, that experience may play a considerable role in shaping subtle details of host plant finding, acceptance, preference, etc., from which important general conclusions can be drawn.
TL;DR: The adaptive pathway, catalyzed by PPi-PFK, varies in maximum activity with a variety of phenomena such as plant development or changing biological and physical environments, which enable plants to cope with the environmental and developmental changes that occur during their lifetimes.
Abstract: Plant cells have two cytoplasmic pathways of glycolysis and gluconeogenesis for the reversible interconversion of fructose 6-phosphate (F-6-P) and fructose 1,6-bisphosphate (F-1,6-P2). One pathway is described as a maintenance pathway that is catalyzed by a nucleotide triphosphate-dependent phosphofructokinase (EC 2.7.1.11; ATP-PFK) glycolytically and a F-1,6 bisphosphatase (EC 3.1.3.11) gluconeogenically. These are non-equilibrium reactions that are energy consuming. The second pathway, described as an adaptive pathway, is catalyzed by a readily reversible pyrophosphate-dependent phosphofructokinase (EC 2.7.1.90; PP-PFK) in an equilibrium reaction that conserves energy through the utilization and the synthesis of pyrophosphate. A constitutive regulator cycle is also present for the synthesis and hydrolysis of fructose 2,6-bisphosphate (F-2,6-P2) via a 2-kinase and a 2-phosphatase, respectively. The pathway catalyzed by the ATP-PFK and F-1,6-bisphosphatase, the maintenance pathway, is fairly constant in maximum activity in various plant tissues and shows less regulation by F-2,6-P2. Plants use F-2,6-P2 initially to regulate the adaptive pathway at the reversible PPi-PFK step. The adaptive pathway, catalyzed by PPi-PFK, varies in maximum activity with a variety of phenomena such as plant development or changing biological and physical environments. Plants can change F-2,6-P2 levels rapidly, in less than 1 min when subjected to rapid environmental change, or change levels slowly over periods of hours and days as tissues develop. Both types of change enable plants to cope with the environmental and developmental changes that occur during their lifetimes. The two pathways of sugar metabolism can be efficiently linked by the cycling of uridylates and pyrophosphate required for sucrose breakdown via a proposed sucrose synthase pathway. The breakdown of sucrose via the sucrose synthase pathway requires half the net energy of breakdown via the invertase pathway. Pyrophosphate occurs in plant tissues as a substrate pool for biosynthetic reactions such as the PPi-PFK or uridine diphosphate glucose pyrophosphorylase (EC 2.7.7.9; UDPG pyrophosphorylase) that function in the breakdown of imported sucrose. Also, pyrophosphate links the two glycolytic/gluco-neogenic pathways; and in a reciprocal manner pyrophosphate is produced as an energy source during gluconeogenic carbon flow from F-1,6-P2 toward sucrose synthesis.
01 Jan 1987
TL;DR: It is shown that the basic problems of permutation group manipulation admit efficient parallel solutions and that isomorphism of graphs with bounded multiplicity of eigenvalues is in NC.
Abstract: We show that the basic problems of permutation group manipulation admit efficient parallel solutions. Given a permutation group G by a list of generators, we find a set of NC-efficient strong generators in NC. Using this, we show, that the following problems are in NC: membership in G; determining the order of G; finding the center of G; finding a composition series of G along with permutation representations of each composition factor. Moreover, given G, we are able to find the pointwise stabilizer of a set in NC. One consequence is that isomorphism of graphs with bounded multiplicity of eigenvalues is in NC. The analysis of the algorithms depends, in several ways, on consequences of the classification of finite simple groups.
TL;DR: It is proved that the isomorphism classes of all n -element relational structures (not only graphs) with cyclic automorphism have the anticipated simple form if and only if n = 1 or n = 4, where ϕ( n ) is Euler's ϕ function.
Abstract: The problem we discuss here is the conjecture of Adam [1] concerning the isomorphism problem of cyclic (or, in other words, circulant) graphs and its generalization by Babai [4]. We attempt to give a fairly complete survey of results related to Adam's conjecture. We prove that the isomorphism classes of all n -element relational structures (not only graphs) with cyclic automorphism have the anticipated simple form if and only if ( n , ϕ( n )) = 1 or n = 4, where ϕ( n ) is Euler's ϕ function. The same result holds if only quaternary relational structures are considered.
TL;DR: The paper introduces the citation strategy indicator which relates impact factors of cited periodicals with the mean impact factor of periodicals in the corresponding research subfield and introduces theitation threshold concept which tries to characterize the effect of citing motivations quantitatively.
Abstract: On the basis of investigating author's opinion on citing motivations of chemistry papers aquasi-quantitative model for citing is suggested. The model selects professional and nonprofessional motivations of citing and introduces thecitation threshold concept which tries to characterize the effect of citing motivations quantitatively. Possible reasons for missing citations are also treated. Mean ages of real and of self-citations were calculated by subtracting the average of the publication years of cited papers from the publication year of the citing publication. The difference between the mean ages may characterize thesynchronity of the author's research in comparison with those working on similar topics. The paper introduces thecitation strategy indicator which relates impact factors of cited periodicals with the mean impact factor of periodicals in the corresponding research subfield.
TL;DR: In this article, the uniqueness of nonnegative solutions of the Cauchy problem and of the first and mixed boundary value problems for a class of degenerate parabolic equations was proved.
TL;DR: It is suggested that the maximal velocity and theCa2+ affinity on the erythrocyte Ca2+ pump may be regulated independently and that independent polypeptide regions of the enzyme are involved in the regulations.
12 Oct 1987
TL;DR: The Generalized Riemann Hypothesis is assumed to be correct, and the factorization of any polynomial with a bounded number of irreducible factors with polynomials over finite fields is obtained inPolynomial time.
Abstract: We propose a new deterministic method of factoring polynomials over finite fields. Assuming the Generalized Riemann Hypothesis (GRH), we obtain, in polynomial time, the factorization of any polynomial with a bounded number of irreducible factors. Other consequences include a polynomial time algorithm to find a nontrivial factor of any completely splitting even degree polynomial when a quadratic nonresidue in the field is given.
TL;DR: In this article, the L X-ray spectra of Au and Th have been measured in collisions with C, F, Mg, Si, S and Cu ions in the energy range 0.5-2.5 MeV amu-1.
Abstract: The L X-ray spectra of Au and Th have been measured in collisions with C, F, Mg, Si, S and Cu ions in the energy range 0.5-2.5 MeV amu-1. From the shifts of the yield ratios and energies of the L/sub // , Lalpha , Leta and Ly1 lines relative to those for 2.5 MeV proton bombardment, the average numbers of M4.5 (and N4) vacancies present during the L-vacancy decay have been determined. The corresponding outer-shell ionisation probabilities show remarkable agreement with the geometrical model of Sulik et al. (1985) except for the Cu projectile.
TL;DR: It is shown here that virulence can be restored by marker rescue of the Bartha strain to which an intact Us has been restored (but not to the parental Bartha strains) by sequences derived from approximate map units 0.460 and 0.505 of the wild-type virus genome.
Abstract: We have shown previously (Lomniczi et al., J. Virol. 52:198-205, 1984) that the Bartha vaccine strain of pseudorabies virus has a deletion in the short unique (Us) region of its genome--a deletion that is related to the absence of virus virulence. This strain is, however, also defective in other genes involved in virulence. We show here that virulence can be restored by marker rescue of the Bartha strain to which an intact Us has been restored (but not to the parental Bartha strain) by sequences derived from approximate map units 0.460 and 0.505 of the wild-type virus genome. No difference in the ability to grow in cell culture was observed between parental Bartha, Bartha 43/25a (Bartha to which an intact Us has been restored), or the doubly rescued Bartha strains. However, only the doubly rescued Bartha strain was virulent for both chickens and pigs and replicated to high titers when inoculated directly into the brains of chickens. The sequences that could restore virulence to the Bartha 43/25a strain encode four genes, all of which are involved in processes leading to the assembly of nucleocapsids. Since these sequences rescue virulence, it appears that a function that plays a role in nucleocapsid assembly is defective in the Bartha strain and that this defect contributes to the lack of virulence of this virus.
TL;DR: In this article, the role of d-orbitals in the bonds of hypervalent sulphur atoms is discussed in some detail, and it is shown that the d-orbals are true valence orbitals and cannot be substituted by using a more flexible s-p basis.
Abstract: The bond order and valence indices proposed recently for use with ab initio wave functions are utilized to discuss the role of d-orbitals in some sulphur compounds. It is concluded that, for sulphur atoms with formal valences of 4 and 6, the chemically reasonable bond order and valence values can be recovered only if the basis contains atomic orbitals of d-symmetry on the sulphur. This indicates that for such hypervalent sulphur atoms, the d-orbitals are true valence orbitals (and not merely polarization functions as for the first-row atoms or two-valent sulphur) and cannot, therefore, be substituted by using a more flexible s-p basis. Different aspects of d-orbital participation in the bonds of hypervalent sulphur atoms are discussed in some detail.
TL;DR: A theorem of Moon and Moser is generalized to determine the maximum number of maximal independent sets in a connected graph on n vertices for n sufficiently large, e.g., n > 50.
Abstract: Generalizing a theorem of Moon and Moser, we determine the maximum number of maximal independent sets in a connected graph on n vertices for n sufficiently large, eg, n > 50
TL;DR: Reflectance data for the high-temperature superconductor YBa/sub 2/Cu/sub 3/O/sub 7/, and the Kramers-Kronig transformed conductivity are presented and changes to the low-lying phonons are associated with superconductivity.
Abstract: We present reflectance data for the high-temperature superconductor YBa/sub 2/Cu/sub 3/O/sub 7/, and the Kramers-Kronig transformed conductivity from 50 to 900 cm/sup -1/. There is a rich phonon structure with peaks at 151, 191, 279, 310, 548, and 609 cm/sup -1/. The continuous background is Drude type at high temperature but below the superconducting transition there is a region of suppressed conductivity consistent with a superconducting gap with the weak-coupling BCS value. Also associated with superconductivity are changes to the low-lying phonons and a plasma-type edge at 60 cm/sup -1/.
TL;DR: In this article, the Na form of a commercial, pelleted X-type zeolite by ion exchange with alkali cations was used for side-chain alkylation of toluene with methanol.
TL;DR: This paper investigates several problems concerning the existence and enumeration of highly irregular graphs as well as their independence numbers, with particular focus on the corresponding problems for highly irregular trees.
Abstract: A connected graph is highly irregular if each of its vertices is adjacent only to vertices with distinct degrees. In this paper we investigate several problems concerning the existence and enumeration of highly irregular graphs as well as their independence numbers, with particular focus on the corresponding problems for highly irregular trees.
TL;DR: It is suggested that astrocytes are an important source of brain prostanoids because of the close similarities between the characteristic features of prostanoid synthesis in both brain and astroglial homogenates.