Showing papers by "Hungarian Academy of Sciences published in 1976"
TL;DR: Summary Procedures for the isolation and culture of mesophyll protoplasts of Nicotiana sylvestris, and for the induction of plants from the resultant callus, are described.
363 citations
TL;DR: In this article, a simple method has been developed to transform experimental data, even at high conversions, to be used in the differential form of copolymerization equation, and an average monomer composition is assigned to the corresponding experimental average copolymers composition.
Abstract: If copolymerizations are carried to high conversions, the determination of copolymerization parameters involves significant computational difficulties because the exact integrated form of the copolymerization equation has to be applied. A simple method has been developed to transform experimental data, even at high conversions, to be used in the differential form of copolymerization equation. In this method an average monomer composition is assigned to the corresponding experimental average copolymer composition. The proposed approximation extends the use of our linearization technique previously developed for low conversions. It was established that this method yields highly reliable results for practically.
229 citations
178 citations
166 citations
TL;DR: A 3×106-dalton sequence which includes the TEM β-lactamase gene found on some plasmids of the P-incompatibility class can integrate into the Escherichia coli chromosome3 and into plasmid of other compatibility groups1,4,5.
Abstract: THE wide host range of plasmids of the P-incompatibility class1,2 has attracted interest in this group of R factors. A 3×106-dalton sequence which includes the TEM β-lactamase gene found on some plasmids of this group can integrate into the Escherichia coli chromosome3 and into plasmids of other compatibility groups1,4,5. This translocatable sequence has been termed transposon A (TnA)4,6 and resembles the insertion sequences (IS) of E. coli, in that TnA insertions can result in gene inactivation, giving rise to strong polar mutations7.
148 citations
TL;DR: It is concluded that (EtOCO) 2 O is not a unique compound, and not a specific enzyme inhibitor in a strict sense, and exemplifies the general mechanisms and problems of concern in the confrontation of cell constituents with acylating agents and other electrophiles.
Abstract: Publisher Summary Interest in the biological and biochemical effects of diethyl pyrocarbonate, (EtOCO) 2 O, was initiated through the introduction of the compound as a cold sterilizer for beverages. The compound emerged in nucleic acid biochemistry through the demonstration of its nuclease-inhibiting property and through the suggestion of exploiting this property in the extraction of undegraded nucleic acids. Since the experimental verification of this suggestion and the elaboration of a method for the extraction of undegraded nucleic acids, based on its use as a nuclease inhibitor, the reagent was found to be useful in a number of laboratories for securing nuclease-free conditions. This chapter describes that (EtOCO) 2 O reacts with single-stranded nucleic acids and nucleic acid constituents. Such reactions were found to lead to a loss of the biological activity of RNA. This reactivity toward RNA has made some authors conclude that the use of this reagent in nucleic acid extraction might be impracticable. Since the reactions of diethyl pyrocarbonate with nucleophiles are not instantaneous, it is found practical with the purpose of systematizing data, to introduce the concept of “dose” of the electrophile ((EtOCO) 2 O. Fianlly, it concludes that (EtOCO) 2 O is not a unique compound, and not a specific enzyme inhibitor in a strict sense. The study of its interactions with biological materials is, therefore, of interest not only to the immediate, practical use of this compound in nucleic acid research, but it also exemplifies the general mechanisms and problems of concern in the confrontation of cell constituents with acylating agents and other electrophiles.
108 citations
TL;DR: A new method for the reconstruction of cell membrane structure and function in bimolecular lipid membranes (BLM) with functionally active PM was described, which were very stable and exhibited both large-amplitude photovoltaic and photo-
102 citations
TL;DR: In this article, the authors found that fish are able to adjust the pattern of the biosynthesis of fatty acids very rapidly to the prevailing temperature and to assure by this way the proper physicochemical properties of their membranes.
Abstract: Incorporation in vivo of sodium 1-14C-acetate into different lipid classes and fatty acids of total lipids and phospholipids of warm adapted and cold adapted carp livers was studied at 5 C and 22 C, respectively. The fatty acid composition of total lipids and phospholipids was also determined. The level of long chain polyunsaturated fatty acids in both total lipid and phospholipid fractions was higher in cold adapted fish than in warm adapted ones. The distribution of radioactivity among different lipid classes depended only on the actual incorporation temperature and was independent of the temperature history of the animals. Livers of fish incorporated a higher percentage of radioactivity into long chain polyunsaturated fatty acids of total lipids and phospholipids in 5 C than in 22 C. The distribution of radioactivity among different fatty acids was dependent on the experimental temperature rather than on the temperature to which the fish were adapted. The results suggest that fish are able to adjust the pattern of the biosynthesis of fatty acids very rapidly to the prevailing temperature and to assure by this way the proper physicochemical properties of their membranes. The possible mechanisms involved in this rapid response are discussed.
97 citations
TL;DR: It is proposed that T cells activated in MLR carry stimulator alloantigens on their surface, and that this is due to specific antigen binding, not requiring the presence of B-cell-derived antibody, and these histocompatibility antigen-binding T blasts can be detected by appropriate antistimulator alliators.
Abstract: Immunoglobulin (Ig) is present on a large fraction of T cells from unfractionated lymphocytes activated by in vitro stimulation with H-2-incompatible cells (mixed lymphocyte reaction [MLR]). Removal of bursa equivalent-derived (B) cells from the responder cell population before mixed culture, by filtration through nylon wool columns, reduces the percentage of Ig-bearing responder T blasts to background levels. Thus, Ig on the T blast is probably of B cell origin. A large fraction of T blasts activated against the stimulator cells. This staining occurs with "early" and hyperimmune alloantisera, including the 7S fraction of the latter. B-depleted responder cells were activated against a mixture of two different stimulator cells and the resulting T blasts stained with different concentrations of sera directed either against one or both stimulator cells. We obtained results which strongly suggest that most or all responder T blasts stain with only one antistimulator serum. When antisera directed against different segments of the H-2 complex of the stimulator cells were used, it seemed that most responder T cells only bound antibody directed against a single segment. We propose that T cells activated in MLR carry stimulator alloantigens on their surface, and that this is due to specific antigen binding, not requiring the presence of B-cell-derived antibody. These histocompatibility antigen-binding T blasts can be detected by appropriate antistimulator alloantibodies.
91 citations
TL;DR: In this paper, it was shown that for every k there is a constant c k such that if n > ck then there exists a Hamiltonian cycle with adjacent edges having different colours.
Abstract: Coloar the edges of a complete graph with n vertices in such a way that no vertex is on more than k edges of the same colour . We prove that for every k there is a constant c ksuch that if n > ck then there is a Hamiltonian cycle with adjacent edges having different colours . We prove a number of other results in the same vein and mention some unsolved problems .
88 citations
TL;DR: In this paper the connection between the self-information of a source letter from a finite alphabet and its code-word length in a Huffman code is investigated.
Abstract: In this paper the connection between the self-information of a source letter from a finite alphabet and its code-word length in a Huffman code is investigated. Consider the set of all independent finite alphabet sources which contain a source letter a of probability p . The maximum over this set of the length of a Huffman codeword for a is determined. This maximum remains constant as p varies between the reciprocal values of two consecutive Fibonacci numbers. For the small p this maximum is approximately equal to \left[ \log_{2} \frac{1+ \sqrt{5}}{2} \right]^{-1} \approx 1.44 times the self-information.
TL;DR: The principles discussed in the chapter concerning the reaction of the amino acid residues on protein molecules with an active group on some support material, are also applicable to the other methods involving covalent coupling of the protein.
Abstract: Publisher Summary Proteins can be immobilized (active but not soluble) in a number of different ways. When a protein is covalently coupled to an insoluble support, two techniques may be employed. One technique is to activate the support material for reaction with groups on the protein. Second, one can use a coupling reagent to link protein to matrix. A third possibility would be to activate the protein molecule for coupling to the support material. This chapter discusses the groups on the protein that is available for covalent coupling to various matrices and some of the most commonly used procedures. The reactivity of a certain group in the protein depends on the location and environment in which the amino acid residues are placed. Because the proteins are large molecules, many of the site changes are partially “buried” and may be relatively inert, while some residues that are exposed to the solvent may be highly reactive. The principles discussed in the chapter concerning the reaction of the amino acid residues on protein molecules with an active group on some support material, are also applicable to the other methods involving covalent coupling of the protein.
TL;DR: In this article, the infrared spectra of lowland peats and purified humic, hymatomelanic and fulvic acids, as well as their acetylated derivatives and metal complexes were studied.
TL;DR: Given the viability of the pollen is not significantly reduced during drying, the pollen remains viable and fertile when kept at −196°C, so a certain degree of drying must be carried out before storage.
Abstract: The water content of pollen has a decisive influence on its storability in liquid nitrogen. Pollen with an initial high water content cannot be stored successfully at extremely low temperatures, so a certain degree of drying must be carried out before storage. Provided the viability of the pollen is not significantly reduced during drying, the pollen remains viable and fertile when kept at −196°C.
TL;DR: The results indicated that ATP citrate lyase has a subunit structure of four polypeptides of similar size, and that the trypsin-treated enzyme did not differ significantly from the untreated enzyme with respect to sedimentation behavior, phosphorylation by ATP, Km for citrate, and immunoreactivity.
TL;DR: The results indicate that in most npr lethals the tissue cannot respond to the hormone, and it is estimated that there are 100–200 such lethals in the genome of D. melanogaster.
Abstract: THE metamorphosis of insects provides a model system for the study of hormone action. In Drosophila, metamorphosis is initiated by the formation of a puparium with a rigid cuticle that becomes tanned early in the prepupal period. Subsequently many larval tissues degenerate and the imaginal tissues develop to produce the adult insect. These processes are initiated in Drosophila by the steroid moulting hormone, β-ecdysone1. We are interested in the mechanisms by which β-ecdysone elicits adult development. The recovery of mutants which cannot respond to the hormone would facilitate investigation into the nature of the action of β-ecdysone. We have isolated systematically a series of late larval and prepupal X-linked lethals (ref. 2 and unpublished results of I.K. et al.), about 15% of which are non-pupariating (npr) lethals in which metamorphosis is not initiated. We have investigated whether the npr condition is a result of the autonomous inability of the mutant target tissues to respond normally to β-ecdysone or rather is a stage-specific failure in the production of the hormone. Our results indicate that in most npr lethals the tissue cannot respond to the hormone. Futhermore, we estimate that there are 100–200 such lethals in the genome of D. melanogaster.
TL;DR: The derivation of theoretical curves for the prediction of crosslinking patterns of tetramers produced by reaction with a bifunctional reagent and subsequent sodium-dodecylsulphage-gel electrophoretic analysis is presented.
Abstract: A method based upon the principle that unlike domains of bonding are reflected in different re-activities and distribution of residues that can be crosslinked, has been elaborated for the determination of symmetry of oligomeric proteins.
The derivation of theoretical curves for the prediction of crosslinking patterns of tetramers produced by reaction with a bifunctional reagent and subsequent sodium-dodecylsulphate-gel electrophoretic analysis is presented. Based upon the theory the symmetry properties of a tetramer, to the extent whether it is an isologous or heterologous associationn, can be deduced by a simple calculation.
Crosslinking patterns obtained with rabbit muscle aldolase and pig muscle lactate dehydrogenase after treatment with a series of diimidoesters of increasing chain length are evaluated and shown to be consistent with the expectations for isologous tetramers. From the patterns obtained with the various reagents the distances between lysyl residues located nearest to each other in different subunits in the two proteins could also be determined.
TL;DR: The transient nature of the resistance and its association with differentiated cells indicate that the new phenotype is not due to a mutation, but rather to an alteration in gene expression.
Abstract: Cylcoheximide-resistant cell lines have been recovered from tissue cultures of haploid Nicotiana tabacum at the usual mutant frequency (10(-6)) One such line, CR 4/6 was studied in detail Resistance is based on the potential of the callus to inactive cycloheximide The transient nature of the resistance and its association with differentiated cells indicate that the new phenotype is not due to a mutation, but rather to an alteration in gene expression
TL;DR: An electron diffraction determination of the molecular geometry of hexamethyldisiloxane has removed much of the uncertainty concerning this structure as discussed by the authors, and the length of the Si-O bond and the SiO-Si bond angle were determined to be 1.631 ± 0.003 A and 148 ± 3°, respectively.
TL;DR: The formation of the adsorbed layer, however, is preceded by bulk deposition as discussed by the authors, and with the ionization of the bulk metal the formation of a strongly adorbed species is begun.
TL;DR: In this article, the Pn[Co(CO)3]4−n (n = 1, 2, 3) tetrahedral clusters have been prepared and characterized, and the very unstable PCo3[Co]9 can be stabilized in the form of (CO)4FePCo3(Co)9.
TL;DR: In this article, it was proved that the partial adsorbed quantities can be calculated from the individual adsorption isotherms, which can be carried out by equations which take into' account the energetical heterogeneity of the surface of adsorbent as well.
Abstract: It was proved that the partial adsorbed quantities can be calculated from the individual adsorption isotherms. This calculation can be carried out by equations which take into' account the energetical heterogeneity of the surface of adsorbent as well. Thus, the partial isotherms equations which can be applied are as followsV A (p A ,p B ) =p A /[b a + (p A +b AB p B ) m ] 1/m andV B (p A ,p B ) =p B /[b B + (p B +b BA p A ) m ] 1/m wherep A andp B are the partial equilibrium pressures, whileb A ,b B andm are constants which can be determined on the basis of the individual isotherms.
TL;DR: In this paper, the authors consider a graph with n vertices and m edges and define a minimal integer with the property that every G(n, m), where m = md(ri), contains a Kd.
Abstract: This note is a sequel to [1]. First let us recall some of the notations. Denote by G{n, m) a graph with n vertices and m edges. Let Kd(ru ..., rd) be the complete dpartite graph with r{ vertices in its i-th class and put Kd(t) = Kd(t, ..., t), Kd = Kd(\\). Given integers n ̂ d(^ 2), let md(n) be the minimal integer with the property that every G(n, m), where m ^ md(ri), contains a Kd. The function md(n) was determined by Turan [5]. It is easily seen that
Journal Article•
TL;DR: The results suggest that certain cholinergic pathways participate in the mediation of analgesia, and it is inferred that opiate receptors are not exclusively involved in the regulation of TRACh.
Abstract: In rats, an ED50 for analgesia of morphine, meperidine, viminol R2 or azidomorphine decreases the turnover rate of acetylcholine (TRACh) in cortex and hippocampus. These four analgetics fail to change to TRACh in striatum when given in a dose range from ED30 for analgesia up to a cataleptic dose. Viminol S2, a nonanalgesic stereoisomer of vimonol R2, fails to decrease the TRACh in cortex and hippocampus. Naltrexone, an opiate antagonist, also fails to change the cortical and hippocampal TRACh but it antagonizes the decrease in cortical and hippocampal TRACh elicited by the four analgetics. Since the ED50 of these four analgetics fails to change the TRACh in striatum which contains a high density of opiate receptors and intrinsic cholinergic neurons, but decreases the TRACh in hippocampus and cortex which contain a low density of opiate receptors, it can be inferred that opiate receptors are not exclusively involved in the regulation of TRACh. However, the results suggest that certain cholinergic pathways participate in the mediation of analgesia.
TL;DR: In this article, the AsCo3(CO)9 trigonal pyramidal cluster, its cyclic trimer, and the phosphorus-containing analog of the latter, P3Co9 (CO)24 have been characterized.
TL;DR: In this article, the infrared spectra of the PR 3 or P(OR) 3 substituent were obtained in all cases in the axial position and the expected C s or C 1 symmetry was established.
TL;DR: The prosthetic group of citrate (pro-3S)-lyase from Klebsiella aerogenes was obtained by mild alkaline hydrolysis of the enzyme and purified by DEAE-cellulose chromatography, and is the first shown to substitute for coenzyme A in the latter reaction.
Abstract: The prosthetic group of citrate (pro-3S)-lyase [citrate oxaloacetate-lyase (pro-3S-CH2COO- leads to acetate); EC 4.1.3.6] from Klebsiella aerogenes was obtained by mild alkaline hydrolysis of the enzyme and purified by DEAE-cellulose chromatography. Several chemical and enzymatic degradation products of the compound have been isolated, and analyses of these have shown the structure of the prosthetic group to be 3'(or 2') leads to 1 inch-(5 inches-phosphoribosyl) dephosphocoenzyme A. Proof as to the exact linkage between the two ribose moieties and the anomeric configuration of the glycosidic bonds has not yet been obtained. A similar analysis was obtained for a product isolated after Pronase digestion of the enzyme (without alkaline hydrolysis). The isolated prosthetic group also can serve as a substrate for a crude preparation of acetate:-SH-(acyl carrier protein) enzyme ligase (AMP) from K. aerogenes, pure pig heart citrate (si)-synthase (EC 4.1.3.7), and pure rat liver ATP citrate (pro-3S)-lyase (EC4.1.3.8). This compound is the first shown to substitute for coenzyme A in the latter reaction.
TL;DR: The proposed mechanisms of citrate synthase, obtained from steady state kinetics, were examined in light of the elution pattern of the enzyme obtained using combinations of substrates and substrate analogs.