Showing papers by "Vrije Universiteit Brussel published in 1975"
TL;DR: Evidence for the presence in the vertebrate nervous system of a hitherto undescribed brain gastrin immunoassayable peptide (BGP) is presented here.
Abstract: RELEASING factors1 and other brain peptides2 have been the subject of extensive studies and the high sensitivity of modern measurement techniques has led to the discovery, in various tissues3,4 and in the nervous system5–9, of new, unpredicted locations for otherwise well known peptides. Evidence for the presence in the vertebrate nervous system of a hitherto undescribed brain gastrin immunoassayable peptide (BGP) is presented here.
723 citations
TL;DR: Besides providing further evidence for the hypothesis that plasmid genes carry the genetic information for the tumour-inducing ability of Agrobacterium, the system offers the possibility of studying the genetics and functions of the plasmids.
Abstract: IT has been suggested that the tumour-inducing capacity of Agrobacterium is determined by plasmid genes1,2. The acquisition of virulence by non-pathogenic agrobacteria from pathogenic agrobacteria has been demonstrated by Kerr3,4. We investigated whether this phenomenon could be the result of transfer of a plasmid. Besides providing further evidence for the hypothesis that plasmid genes carry the genetic information for the tumour-inducing ability of Agrobacterium, the system offers the possibility of studying the genetics and functions of the plasmid.
256 citations
TL;DR: The fact that not all oncogenic, plasmid harbouring, Agrobacterium tumefaciens strains are sensitive to agrocin 84, points to the possibility that the genes determining agrocIn 84 sensitivity are not essential for tumour-inducing ability.
Abstract: It was shown for some oncogenic Agrobacterium tumefaciens strains that agrocin 84 sensitivity is determined by the presence of a large closed circular DNA plasmid, called the Ti-plasmid. Whereas wild-type strain C58 is agrocin 84 sensitive, all Ti-plasmid cured derivatives were found to be fully resistant. Moreover all independently isolated agrocin 84 resistant colonies were stably non-oncogenic and plasmid negative. In a growth experiment carried out at 37° C it was shown that the kinetics of appearance of non-oncogenic cells on the one hand and of agrocin 84 resistant cells on the other were identical. The fact that not all oncogenic, plasmid harbouring, Agrobacterium tumefaciens strains are sensitive to agrocin 84, points to the possibility that the genes determining agrocin 84 sensitivity are not essential for tumour-inducing ability.
105 citations
TL;DR: In this paper, the carbon-13 spectra of a series of cyclohexanone, cyclopentanone and 2-methylcyclohexenone enamines are reported.
Abstract: The carbon-13 spectra of a series of cyclohexanone, cyclopentanone and 2-methylcyclohexanone enamines are reported. The influence of the amino component was studied in a series of enamino ketones. The spectra reflect the amount of p-π overlap in the molecules and their conformation. Differences between 5-and 6-membered carbonyl components are evaluated.
37 citations
32 citations
TL;DR: In this article, the pattern of divergent transcription of the argECBH cluster of genes previously demonstrated by the hybridization of RNA to the separated strand of a ϕ80 drag transducing phage, is confirmed with the DNA of a set of different λdarg phages.
Abstract: The pattern of divergent transcription of the argECBH cluster of genes previously demonstrated by the hybridization of RNA to the separated strand of a ϕ80 drag transducing phage, is confirmed with the DNA of a set of different λdarg phages. The accurate determination of argE and argCBH m-RNA levels in different steady states of expression of the arg regulon supports the following conclusions:
30 citations
TL;DR: In this article, the Simplex technique is applied to the cation exchange separation of cadmium, zinc, copper, manganese and calcium ions in a mixed organic-aqueous solvent.
Abstract: This article discusses the optimisation of multicomponent chromatographic techniques with the Simplex technique. The most important difficulty is the choice of the criterion, which must be optimised. The informing power is proposed for this purpose. The technique is applied to the cation exchange separation of cadmium, zinc, copper, manganese and calcium ions in a mixed organic-aqueous solvent. The applicability of the method for chromatography in general is discussed and the limitations are given.
29 citations
TL;DR: Purified calf thymus DNA in solution was exposed to both therapeutic and obstetrical diagnostic doses of ultrasound, and intensities lower than those used in therapy have a drastic effect on purifiedDNA in solution.
Abstract: Because of the increasing medical use of ultrasound, especially in obstetrical diagnosis, it has become important to check its genetic harmlessness. Purified calf thymus DNA in solution was exposed to both therapeutic and obstetrical diagnostic doses of ultrasound. Intensities lower than those used in therapy have a drastic effect on purified DNA in solution, although intensities used in obstetrical diagnosis caused no visible effect.
29 citations
TL;DR: A series of simple mathematical techniques for the evaluation of solvents and solvent combinations in thin-layer chromatography conclude that they allow the selection of optimal systems or combination of systems.
28 citations
TL;DR: In this article, the maximum number of mutually disjoint S(λ;2,3,v) for all v ≡ 0 or 4 (mod 6) and v ≡ 2 (mod 2) was proved.
Abstract: Let D(λ;v) denote the maximum number of mutually disjoint S(λ;2,3,v). We prove that D(2;v)=v−2/2 for all v ≡ 0 or 4 (mod 6), v ≡ 0 and that D(6;v)=v−2/6 for all v ≡ 2 (mod 6).
26 citations
TL;DR: Three forms of NAD-dependent alcohol dehydrogenase have been characterized in yeast by their heat sensitivity, their specificity and their electrophoretic patterns, which shows a high affinity for alcohols with a double bond conjugated to the alcohol function.
TL;DR: The bacteria from 119 sediment samples collected off the Belgian and Dutch North Sea coast were enumerated on marine agar and a great number of species belonging to different taxonomic groups were revealed.
Abstract: The bacteria from 119 sediment samples collected off the Belgian and Dutch North Sea coast were enumerated on marine agar. Geographical and seasonal variations were observed. The colony formers were mainly obligate aerobes. Coliform organisms were relatively rare. An exhaustive analysis of a few samples revealed a great number of species belonging to different taxonomic groups. A survey of physiological and biochemical characteristics of 71 isolates is presented.
TL;DR: In this article, the pyrolyses of endo and exo-5-methylbicyclo (2.2) oct-2-ene (endo- and ex-o-MBO) have been studied between 608 and 679°K at pressures between 7 and 37 torr.
Abstract: The pyrolyses of endo- and exo-5-methylbicyclo (2.2.2) oct-2-ene (endo- and exo-MBO) have been studied between 608 and 679°K at pressures between 7 and 37 torr. These reactions correspond to parallel first-order eliminations of propene and ethylene:
The rate constants (in sec−1) for endo-MBO are given by
and those for exo-MBO by
Reaction mechanisms involving diradicals are shown to be compatible with the experimental results. The heats of formation and the entropies of endo and exo-MBO are estimated.
TL;DR: The accumulation or ornithine, citrulline, and possibly acetylornithine by Escherichia coli K-12 arginineless mutants provided with acetylarginine as source of arginine causes severe growth inhibition and allows the forward selection of several classes of archinine auxotrophs from strains deficient in carbamoylphosphate biosynthesis and thus capable of ornithines accumulation.
Abstract: The accumulation or ornithine, citrulline, and possibly acetylornithine by Escherichia coli K-12 arginineless mutants provided with acetylarginine as source of arginine causes severe growth inhibition. This occurs under conditions where comparable derivatives of E. coli W (Bollon and Vogel, 1973) show little or no growth inhibition. The same conditions, which have been reported to cause noncorrelative synthesis of acetylornithinase and argininosuccinase in E. coli W (Bollon and Vogel, 1973), do not alter the correlative pattern of enzyme synthesis observed in E. coli K-12. Moreover, previously reported effects of ornithine and citrulline on repression of the arginine regulon in E. coli W are not observed in the K-12 strains examined. The bearing of these observations on possible differences between the mechanism of enzyme repression operating in the two types of strains cannot yet be fully evaluated; it is, however, clear that considerable care should be exercised before extrapolating the results obtained with one type of strain to the other one. The particularly strong inhibition of acetylarginine utilization exerted by ornithine in E. coli K-12 allows the forward selection of several classes of arginine auxotrophs from strains deficient in carbamoylphosphate biosynthesis and thus capable of ornithine accumulation. Possible applications of this technique to the genetic analysis of the bipolar argECBH operon are discussed.
TL;DR: In this paper, the authors show how to apply the Gel'fand-Levitan equations with singular oscillating potentials and give the general procedure for solving these equations and illustrate the method by some examples.
TL;DR: In this article, the kinetic equation of an inhomogeneous relativistic plasma, consisting of an electron gas and a radiation field, is studied with particular regard to its eigenvalues in the hydrodynamical limit.
Abstract: The kinetic equation of an inhomogeneous relativistic plasma, consisting of an electron gas and a radiation field, is studied with particular regard to its eigenvalues in the hydrodynamical limit. The treatment is classical for the particles and quantum-mechanical for the field oscillators. After a suitable regularization, the eigenvalues are obtained by a perturbation theory through second order in the strength of the gradients. It is shown that these eigenvalues are in exact correspondence with the macroscopic relativistic plasma-dynamical modes. The important role played by the Vlassov operator in building up the peculiar structure of these modes is underlined. From a comparison of the macroscopic and microscopic eigenvalues we obtain general expressions for the thermal conductivity, the shear viscosity and the bulk viscosity of a relativistic plasma. The contribution of the radiation field to these quantities is a noteworthy feature of these expressions.
TL;DR: Cytochrome c-556 from Agrobacterium mefaciens B2a was isolated in a pure, homoneous state and substitution of the CM-cellulose step by isoelectric focusing was successful.
Abstract: Cytochrome c-556 from Agrobacterium mefaciens B2a was isolated in a pure, homoneous state. The best purification procedure volved ammonium sulphate fractionation, delting on Sephadex G-25, column chromatographic fractionation on DEAE- and CM-cellulose, and gel filtration on Sephadex G-75 superfine. Substitution of the CM-cellulose step by isoelectric focusing was successful. The purity of the final preparation is warranted by the purity index value, the electrophoretic patterns in the absence and presence of sodium dodecylsulphate, the sedimentation profile and the N-terminal amino acid analysis (alanine). The absorption spectrum of reduced cytochrome c-556 has maxima at 318, 419, 526 and 555.5 nm. The molar extinction coefficient for the alpha-band is 20 200M-1cm-1. The isoelectric point, determined both by preparative and analytical isoelectric focusing, is 5.55 +/- 0.10. The molecular weight of cytochrome c-556 was determined by gel filtration as 12000 and by dodecylsulphate gel electrophoresis as 11 500.
TL;DR: X-ray diffraction showed that the calcification in the brain of a child suffering from leukaemia consisted of amorphous calcium phosphate and acid calcium orthophosphate, most probably precursors of hydroxyapatite.
TL;DR: An extensive search for internal regularities in amino acid sequences has been made, using both the genetic code and the relative frequencies of amino acid alternatives in homologous proteins to suggest the occurrence of significant linear and inverted repetitions in several proteins.
Abstract: An extensive search for internal regularities in amino acid sequences has been made, using both the genetic code and the relative frequencies of amino acid alternatives in homologous proteins. The two methods give very similar results and strongly suggest the occurrence of significant linear and inverted repetitions (similar sequences of opposite polarity) in several proteins.
TL;DR: An extension of the classical Hamilton-Jacobi method for dynamical systems subject to nonholonomic constraints of Chetaev's type is established by applying a variational principle for the integral of action as mentioned in this paper.
Abstract: An extension of the classical Hamilton-Jacobi method for dynamical systems subject to nonholonomic constraints of Chetaev's type is established by applying a variational principle for the integral of action. The generalized method is illustrated by an example in which the constraint is nonlinear in the velocity components.
Eine Verallgemeinerung der klassischen Hamilton-Jacobi Methode fur dynamische Systeme, nichtholonomen Zwangsbedingungen des Chetaev-Typs unterworfen, wird durch Anwendung eines Variationsprinzipes fur das Wirkungsintegral eingefuhrt. Die verallgemeinerte Methode wird an einem Beispiel, in dem die Zwangsbedingung in den Geschwindigkeitskomponenten nichtlinear ist, illustriert.
TL;DR: In this article, the four possible diastereoisomers of this compound were obtained by reduction of the enamine 5,6,7,8,10,11-hexahydro-15bH-tribenzo[a,c,h]quinolizine.
TL;DR: Preliminary results, based on the differential action of cycloheximide and chloramphenicol on the isozyme pattern, indicate that mitochondrial isozymes could be under nuclear gene control.
TL;DR: The present report describes a system for the in vitro synthesis of arg m-RNA, with a ratio of leftwards (argE) over rightwards ( argCBH) transcription similar to that observed in vivo, which requires only the presence of RNA polymerase holoenzyme.
TL;DR: In rabbit, mouse, and man, the structural genes of the heavy chain of immunoglobulins are inherited as a closely linked complex but the situation in the rabbit is unique because a number of allotypic markers are found which are common to all classes of heavy chains and are presumably located in the variable region.
Abstract: In rabbit, mouse, and man, and probably in most animals, the structural genes of the heavy chain of immunoglobulins are inherited as a closely linked complex. The situation in the rabbit is unique because a number of allotypic markers are found which are common to all classes of heavy chains and are presumably located in the variable region. These so-called a locus markers al, a2, and a3 are found on most heavy chains of all classes and behave as alleles at the level of resolution of mammalian genetics. They are probably correlated with multiple amino acid interchanges. Other markers are only found on defined classes of heavy chains and these, when analyzed, are characterized by single amino acid differences in the constant region. In the 7 chain, the allelic dll
TL;DR: In this article, the frequencies and damping rates of both relativistic neutral-fluid modes and relativistically plasma modes are discussed in detail, and an anomalous, wavelength-independent damping coefficient of longitudinal and transverse plasma oscillations is exhibited.
Abstract: A plasma and a neutral fluid behave in very different ways in the so-called hydrodynamical limit, when submitted to a long-wavelength disturbance. Both cases can be treated however in the same way if the plasma-dynamical equations are properly regularized. The frequencies and damping rates of both relativistic neutral-fluid modes and relativistic plasma modes are discussed in detail. A new relativistic plasma effect is exhibited as an anomalous, wavelength-independent damping coefficient of longitudinal and transverse plasma oscillations. This effect originates from the contribution of the electric field to the heat flow in a relativistic plasma.
TL;DR: In this paper, the authors considered the effect of the enhanced hydrodynamic fluctuations in a fluid near the convective instability point on the motion of suspended brownian particles and found that the diffusion coefficient of the brownians increases when the instability point is approached.
Abstract: We consider the effect of the enhanced hydrodynamic fluctuations in a fluid near the convective instability point on the motion of suspended brownian particles. Using Faxen's theorem it is found that the diffusion coefficient of the brownian particles increases when the instability point is approached. The divergent part of the diffusion coefficient depends on the difference, between the Rayleigh number R and its critical value R c as | R c − R | −3/2 . The feasibility to observe this effect experimentally is considered.
TL;DR: In this paper, it was shown that the racemisation of methylneophyl-t-butyltin chloride or bromide in benzene is of second order in the nucleophile.
TL;DR: In this article, a non-uniform, non-rotating gravitational system with a restriction to short wavelengths is considered and a linearized form of the collisionless Boltzmann equation is considered.
Abstract: Dispersion relations are obtained and analysed for a non-uniform, non-rotating gravitational system. A restriction to short wavelengths makes it possible to consider a linearized form of the collisionless Boltzmann equation, differing from that for homogeneous systems by the appearance of a term expressing the effect of the mean self-gravitational field upon the motion. The mean field affects the radially directed wave perturbations, with a breaking of symmetry. Inwardly and outwardly directed modes have quite different propagation characteristics, inward modes being preferentially propagated. Locally, the stability of the system is found to be enhanced due to the effect of the mean field.
01 Jan 1975
TL;DR: The use of electrophoretic and activity mutants as well as biochemical data leads to the conclusion that the multiple molecular forms within a series are all products of a single gene and that the AP 1 isozymes are due to variation in charge rather than in size.
Abstract: . Following gel electrophoresis, three distinct groups of acid phosphatase enzymes (AP 1 , AP 2 , and AP 3 ) have been identified in leaf extracts of Arabidoipsis, thaliana . The AP 1 group includes three electrophoretic variants – a fast (F), an intermediate (I), and a slow (S) type. The genetic analysis shows that the AP^ variants are under the control of three codominant alleles at the AP 1 locus. Each allele specifies a series of four isozymes and isozymes belonging to the I series are found to correspond in migration rate with some bands of the F series and of the S series. The distribution of staining intensity between the bands in heterozygoses may indicate a dimeric structure of the AP 1 enzymes. The use of electrophoretic and activity mutants as well as biochemical data leads to the conclusion that the multiple molecular forms within a series are all products of a single gene and that the AP 1 isozymes are due to variation in charge rather than in size. The AP 2 group comprises two bands which migrate rapidly towards the anode. Three electrophoretic variants with a slow, an intermediate, and a fast migration rate have been identified to be under the control of the AP 2 locus with three codominant alleles, AP 2 , AP F 2 , AP I 2 , and AP S 2 There is no evidence for the formation of hybrid enzymes in heterozygotes. The AP 3 set is represented by the most anodal band. A slow variant has been discovered and in heterozygotes between a slow and a fast type a three band pattern is obtained which is consistent with the hypothesis that the AP 3 isozymes exist as dimers. The AP 3 locus comprises two allelic forms AP F 3 and AP S 3 . Organ specific differences in acid phosphatase pattern are mainly quantitative, except in seeds where other isozymes than those specified by the AP 1 gene seem to be operative during this stage of development.