Showing papers by "University of Cologne published in 1984"
1,176 citations
TL;DR: The efficiency of methyl-directed DNA mismatch-repair of E. coli acting in vivo on heteroduplex genomes of phage M13 was found to be strongly dependent on the nature of the base/base mismatch to be corrected.
516 citations
TL;DR: In this article, an analytic approach based on a connection between the quasinormal modes and the bound states of the inverted black-hole effective potentials has been proposed for the problem of black hole oscillations, which has been investigated numerically thus far.
Abstract: We describe a new analytic approach to the problem of black-hole oscillations, which has been investigated numerically thus far. Our treatment is based on a connection between the quasinormal modes and the bound states of the inverted black-hole effective potentials. Approximate analytic formulas for the quasinormal frequencies of Schwarzschild, Reissner-Nordstr\"om, and slowly rotating Kerr black holes are provided. We find that a real quasinormal frequency for an extreme Kerr black hole has vanishing amplitude in the ordinary (i.e., nonsuperradiant) regime; therefore, extreme Kerr black holes are not marginally unstable in this case. These results are significant for the question of the stability of a black hole as well as for the late-time behavior of radiation from gravitationally collapsing configurations.
430 citations
TL;DR: The results indicate that gene 2 of the T region, which participates in tumorous growth of plant cells, codes both in bacteria and in plants for an amidohydrolase involved in the biosynthesis of the plant hormone indole-3-acetic acid.
Abstract: Gene 2 from the T region of Ti plasmids appears to be expressed both in eucaryotic and in procaryotic systems. In transformed plant cells it participates in auxin-controlled growth and differentiation, and in bacteria it is expressed into a defined protein of Mr 49000. We investigated the possibility that it codes for an enzyme involved in auxin biosynthesis.
Only extracts from Escherichia coli cells expressing gene 2 hydrolyzed indole-3-acetamide into a substance which was unambiguously identified as indole-3-acetic acid. The same reaction was found in Agrobacteria containing gene 2, but not in strains lacking the gene. Extracts from tobacco crown gall cells, but not from non-transformed cells, showed the same enzyme activity, and the reaction product was also identified as indole-3-acetic acid. The results indicate that gene 2 of the T region, which participates in tumorous growth of plant cells, codes both in bacteria and in plants for an amidohydrolase involved in the biosynthesis of the plant hormone indole-3-acetic acid.
358 citations
01 Sep 1984
TL;DR: The morphological aspects of early neurogenesis in Drosophila, in particular with the segregation of neuroblasts from the neurogenic region of the ectoderm and the pattern formed by those wells within both the germ band and the procephalic lobe, were discussed in this article.
Abstract: This paper deals with morphological aspects of early neurogenesis inDrosophila, in particular with the segregation of neuroblasts from the neurogenic region of the ectoderm and the pattern formed by those wells within both the germ band and the procephalic lobe. The neurogenic ectoderm was found to contain neural precursors intermingled with epidermal precursors, extending from the midline up to the primordia of the tracheal tree along the germ band and laterodorsally in the procephalic lobe. Germ band neuroblasts segregate from the neurogenic ectoderm during a period of several hours according to characteristic spatial and temporal patterns. During the first half of the segregation process the pattern of germ band neuroblasts was found to be the same in different animals in both spatial arrangement and number of cells; this permitted the identification of individual neuroblasts from different embryos. Later in development several difficulties were encountered which precluded an exact description of the neuroblast pattern. The constitution of the neurogenic region is discussed in relation to the phenotype of mutants affecting neurogenesis.
336 citations
TL;DR: In this article, a critical analysis of the classical papers of H. Thirring and J. Lense on rotating masses in the relativistic theory of gravitation is presented.
Abstract: The purpose of this work is to provide a critical analysis of the classical papers of H. Thirring [Phys. Z.,19, 33 (1918);Phys. Z.,22, 29 (1921)] and J. Lense and H. Thirring [Phys. Z.,19, 156 (1918)] on rotating masses in the relativistic theory of gravitation and to render them accessible to a wider circle of scholars. An English translation of these papers is presented which follows the original German text as closely as possible. This is followed by a concise account of the significance of the results of these papers as well as the possibility of measuring the gravitational effects of rotating masses.
318 citations
TL;DR: In vivo dMM inhibits the equivalent of the mannosidase IA/B activities and blocks conversion of high-mannose to complex oligosaccharides, which could prove to be a powerful way to manipulate carbohydrate structure in vivo.
Abstract: Many secretory and membrane proteins are glycoproteins carrying asparagine-linked (N-linked) oligosaccharides. There are two types of N-linked glycans, referred to as high-mannose and complex type, respectively. Biosynthesis of N-linked glycans of the complex type proceeds via a high-mannose intermediate. After the initial transfer of a high-mannose oligosaccharide with the composition (Glc)3(Man)9(GlcNAc)2 from a lipid carrier to the nascent polypeptide chain, trimming reactions take place. Trimming glucosidases remove the glucose residues quantitatively and mannosidases IA/B and II can remove all but three mannose residues. After trimming, terminal sugars such as N-acetylglucosamine, galactose, sialic acid and fucose may be added and result in the conversion to a glycan of the complex type. Because suitable inhibitors were lacking, it was difficult to assess the importance of the trimming reactions for proper intracellular traffic, modification reactions other than the addition of terminal sugars, or as regulatory steps in glycoprotein processing. Here we describe the action of 1-deoxymannojirimycin (1,5-dideoxy-1,5-imino-D-mannitol, dMM; Fig. 1) on the biosynthesis of IgM and IgD. dMM is the mannose analogue of 1-deoxynojirimycin (dNM; Fig. 1), itself a glucosidase inhibitor. We present evidence that dMM is a mannosidase inhibitor. In vivo dMM inhibits the equivalent of the mannosidase IA/B activities and blocks conversion of high-mannose to complex oligosaccharides. It is the first such inhibitor to be reported. Interference with the biosynthetic pathway of N-linked glycans could prove to be a powerful way to manipulate carbohydrate structure in vivo.
292 citations
TL;DR: In this paper, it was shown that the relationship between regime type and war involvement is not significantly related to each other until Rummel recently challenged this consensus, concluding that democratic states are less intensively involved in foreign conflict and tend to participate in wars less often than do other states.
Abstract: Most quantitative researchers had agreed that regime type and war involvement are not significantly related to each other until Rummel recently challenged this consensus. According to Rummel, libertarian or democratic states are less intensively involved in foreign conflict and tend to participate in wars less often than do other states. Rummel's assertion is disputed in this article. Relying on various definitions of war and compilations of data for the 1960s and 1970s, it is demonstrated that democracy and war involvement are not consistently and significantly correlated with each other. Only in the late seventies did democracies succeed in avoiding involvement in wars. Unfortunately, this period seems rather exceptional.
233 citations
TL;DR: In this article, photoelectron spectroscopy and high-resolution electron energy loss spectrograms were used to identify a surface complex in which both nitrogen atoms interact with the metal and formed the immediate precursor to dissociation.
Abstract: ${\mathrm{N}}_{2}$ chemisorbed on Fe(111) is identified by photoelectron spectroscopy and high-resolution electron energy-loss spectroscopy as a $\ensuremath{\pi}$-bonded surface complex in which both nitrogen atoms interact with the metal. This species forms the immediate precursor to dissociation.
189 citations
TL;DR: The longest continuous tree-ring chronology is based on the bristlecone pine (Pinus aristata and Pinus longaeva) growing in the White Mountains of California as discussed by the authors.
Abstract: Long tree-ring chronologies provide a unique calendrical record that is of value for archaeological dating, climatic and post-glacial studies. They also form a standard for the calibration of the radiocarbon time scale. The world's longest continuous tree-ring chronology is based on the bristlecone pine (Pinus aristata and Pinus longaeva) growing in the White Mountains of California1–3. The great age of living and sub-fossil trees of this species enabled a continuous tree-ring sequence of 8,681 years to be established, providing absolutely dated wood samples for the first radiocarbon calibration4,5. We have now established an unbroken west European tree-ring sequence spanning the past 7,272 years.
186 citations
TL;DR: The conservation of the 5' flanking region of the WAP genes may be related to regulation of expression of WAP by peptide and/or steroid hormones.
Abstract: Whey acidic protein (WAP), a hormonally-regulated 14,000 dalton cysteine-rich protein, is the principal whey protein found in rodent milk. Genomic clones encompassing both the 2.8 Kb rat and 3.3 Kb mouse WAP genes have been characterized. The genes consist of four exons and three introns. The middle two exons encode the two cysteine-rich regions which probably form separate protein domains. Homology in the 5' flanking DNA of the mouse and rat extends at least 325 bp upstream of the putative CAP site, including a precisely conserved stretch of 50 bp around the unusual TATA and CAAT sites. The homology previously observed between the 3' noncoding sequences of the rat and mouse mRNAs extends at least 20 bp into the 3' flanking region. Several potential glucocorticoid receptor binding sites have been found in the 5' flanking region of the WAP gene. The conservation of the 5' flanking region of the WAP genes may be related to regulation of expression of WAP by peptide and/or steroid hormones.
TL;DR: Analyse de ⊇ 2 φ(r) for plusieurs molecules as mentioned in this paper provoque une diminution d'energetic locale, entrainant une "liaison chimique sans densite d'electrons de liaison".
Abstract: Analyse de ⊇ 2 φ(r) pour plusieurs molecules. Cas ou la densite electronique φ(r) entre deux atomes provoque une diminution d'energie locale, entrainant une «liaison chimique sans densite d'electrons de liaison»
TL;DR: The potential of endonuclease VII as a probe of cruciform structure and the utility of short cruciform structures as Holliday junction models are demonstrated.
TL;DR: Trimming glucosidase I and II have been solubilized from crude calf liver microsomes and partially enriched by a fractionated extraction procedure applying different concentrations of nonionic detergent and salt, which discriminates them from hydrolases of lysosomal origin acting on p-nitrophenyl glycosides with the highest rate at more acidic pH.
Abstract: Trimming glucosidase I and II have been solubilized from crude calf liver microsomes and partially enriched by a fractionated extraction procedure applying different concentrations of nonionic detergent and salt. The pH optimum of both enzymes was found to be close to 6.2, which discriminates them from hydrolases of lysosomal origin acting on p-nitrophenyl glycosides with the highest rate at more acidic pH. Glucosidase I and II and the nonspecific alpha-glucosidase(s) were inhibited by 1-deoxynojirimycin with median inhibitory concentration of 3 microM, 20 microM, 12 microM, respectively. Discrimination between these enzymes was strongly enhanced by N-alkylation of 1-deoxynojirimycin and formed the basis for the design of the affinity ligand. Glucosidase I has been purified to homogeneity by affinity chromatography on AH-Sepharose 4B with N-carboxypentyl-1-deoxynojirimycin as ligand. Sodium dodecyl sulfate gel electrophoresis of the purified enzyme revealed a subunit molecular mass of about 85 kDa. The molecular mass of the native enzyme, determined by gel chromatography, was approximately equal to 320-350 kDa, pointing to the association of subunits to a tetramer. Glucosidase I is rather stable when stored at 4 degrees C in the presence of detergent (t 1/2 approximately equal to 20 days) and showed high specificity for the hydrolysis of the terminal (alpha 1,2)-linked glucose residue in the natural substrate Glc3-Man9-(GlcNAc)2.
TL;DR: It is concluded that the phenotypic differences between the two waxy alleles are not caused by structural differences in the Ac elements but rather may be attributable to the differences in their insertion sites.
Abstract: The sequence of the Ac element isolated from the wx-m7 allele has been determined. The Ac element is 4563 bp long. A central portion of roughly 3.1 kb is occupied by three open reading frames, two of which point in one direction and the third in the opposite direction. One of the reading frames potentially encodes a protein with a ten-fold repeat of pro gluN and pro glu dipeptides near its N-terminus. The sequences outside the open reading frames are characterized by the presence of a number of direct and inverted repeats. The Ac element may thus have evolved from a simpler progenitor structure. The sequence we have determined for the Ac from the wx-m7 allele differs in a few key positions from that reported for the Ac element from the wx-m9 allele (Pohlman et al. 1984). We have resequenced these positions in both Ac elements and find them to be identical. We conclude that the phenotypic differences between the two waxy alleles are not caused by structural differences in the Ac elements but rather may be attributable to the differences in their insertion sites.
TL;DR: The differences found in the expression of the neurogenic genes are discussed with respect to a hypothesis on the genetic control of neurogenesis.
Abstract: Six zygotically expressed genomic loci of Drosophila melanogaster, N, bib, mam, neu, Dl and E (spl), have previously been found to be involved in the commitment of ectodermal cells as neuroblasts. We have studied phenotypes induced by various mutant alleles at these 6 loci in imaginal epidermal cells, in order to assess possible implications of the genes in functions other than early neurogenesis. When homozygous, any of these mutations except bib affected the development of bristles and compound eye in various ways. These range from cell death to the production of additional bristles and several defects in ommatidial patterning, depending on the allele used. In contrast clones of bib homozygous cells exhibited wild-type phenotypes. The differences found in the expression of the neurogenic genes are discussed with respect to a hypothesis on the genetic control of neurogenesis.
TL;DR: The results indicate the existence of either heterogeneous glycoprotein components or mucus molecules with variations in the degree of glycosylation of their oligosaccharide chains in the different cells.
Abstract: Labeled lectins with binding specificity to the hexose components of mucus glycoproteins (HPA, RCA I, PNA, Con A, WGA, and UEA I) were used to demonstrate structural differences in the glycoprotein composition of various cell types of the normal, benign and malignant gastrointestinal mucosa. While in the RCA I, UEA I, and WGA binding of normal mucus secreting cell types only quantitative differences were observed, the mucus in the surface epithelial cells of gastric mucosa and in the colonic goblet cells was characterized by the absence of PNA, Con A, and PNA, HPA binding sites, respectively. These lectins, however, showed a strong binding to the supranuclear, Golgi-region in the undifferentiated or activated forms of these cells. Even the staining intensity of the luminal membrane surfaces of the non mucinous parietal and chief cells was often stronger by PNA, HPA, and RCA I lectins than that of the mucus secretions in the highly differentiated mucus cells. These results indicate the existence of either heterogeneous glycoprotein components or mucus molecules with variations in the degree of glycosylation of their oligosaccharide chains in the different cells. The latter seems more likely since in benign and malignant alterations lectin binding sites appear in great density, which were found to be characteristic of the undifferentiated mucus cells or for the non mucinous cells of the normal gastric mucosa. Similarly in some gastric cancers which do not stain with the periodic acid-Schiff reaction at all, large amount of free or neuraminic acid substituted PNA binding sites can be detected.
TL;DR: Renate Dildrop has compared heavy chain variable-region sequences of mouse immunoglobulins at the amino acid level and determined the homology within the coding region of the entire VHgene segment.
TL;DR: In this paper, a new analytic method for the determination of quasinormal oscillations of a black hole is presented, based on a connection between the quasinorm modes and the bound states of the inverted black-hole potentials.
Abstract: A new analytic method for the determination of quasinormal oscillations of a black hole is presented. It is based on a connection between the quasinormal modes and the bound states of the inverted black-hole potentials. With use of this method, the quasinormal frequencies of a Schwarzschild, a Reissner-Nordstr\"om, and a slowly rotating Kerr black hole are determined in the eikonal approximation, Moreover, we provide evidence for the stability of an extreme Kerr black hole.
01 Apr 1984-Zentralblatt für Bakteriologie, Mikrobiologie und Hygiene. 1. Abt. Originale. A, Medizinische Mikrobiologie, Infektionskrankheiten und Parasitologie
TL;DR: The attachment of bacteria to solid surfaces like biomaterials is an important phenomenon because of its possible role as the very first step in the development of an infection.
TL;DR: The results obtained with different methods agree with one another in describing the position and extent of the entire primary visual cortex as well as its monocular (medial) and binocular (lateral) subareas.
Abstract: Primary visual cortex in the rat was studied by a variety of methods: transsynaptic transport of labelled amino acids, 2-deoxyglucose, and staining for perikarya, myelin, and acetylcholinesterase. The analysis was aided by a computer-controlled television image analyzer. The results obtained with different methods agree with one another in describing the position and extent of the entire primary visual cortex as well as its monocular (medial) and binocular (lateral) subareas.
TL;DR: In this article, the zero temperature limit of the self-consistent perturbation theory of a degenerate Anderson impurityin a metal is partially solved with analytical methods, and the energy scales relevant to the system are made explicit and closed expressions are derived for the local level propagator around the Fermi energy and for the dynamical susceptibility.
Abstract: The zero temperature limit of the self-consistent perturbation theory of a degenerate Anderson impurityin a metal is partially solved with analytical methods. In particular, the energy scales relevant to the system are made explicit and closed expressions are derived for the local level propagator around the Fermi energy and for the dynamical susceptibility. Results are compared with what is known from Fermi liquid theory. The argument that the theory is valid for large degeneracy is disturbed by certain pathologies.
TL;DR: McClintock et al. as mentioned in this paper showed that unstable mutations can be caused by the insertion and excision of transposable elements into and from a gene, which can be detected as somatic reversions.
TL;DR: High concentrations of dMM showed some inhibition of mannose incorporation into lipid-linked oligosaccharides with the NWS strain in a 3-h incubation, but no inhibition was observed after 48 h of incubation.
TL;DR: In this paper, the modes of oscillation of a Schwarzschild black hole were determined within an analytic framework, and the quasi-normal modes were related to the bound states of the inverted black hole potential which was approximated by the inverted Eckart potential.
TL;DR: In this paper, a detailed Monte Carlo study is presented for classical diffusion (random walks) on random L * L triangular lattices, with L up to 4096 and 256, respectively, and the speed of a Cyber 205 vector computer is found to be about one order of magnitude larger than that of a usual CDC Cyber 76 computer.
Abstract: A detailed Monte Carlo study is presented for classical diffusion (random walks) on randomL * L triangular andL * L* L simple cubic lattices, withL up to 4096 and 256, respectively. The speed of a Cyber 205 vector computer is found to be about one order of magnitude larger than that of a usual CDC Cyber 76 computer. To reach the asymptotic scaling regime, walks with up to 10 million steps were simulated, with about 1011 steps in total forL=256 at the percolation threshold. We review and extend the dynamical scaling description for the distance traveled as function of time, the diffusivity above the threshold, and the cluster radius below. Earlier discrepancies between scaling theory and computer experiment are shown to be due to insufficient Monte Carlo data. The conductivity exponent μ is found to be 2.0 ± 0.2 in three and 1.28 ± 0.02 in two dimensions. Our data in three dimensions follow well the finite-size scaling theory. Below the threshold, the approach of the distance traveled to its asymptotic value is consistent with theoretical speculations and an exponent 2/5 independent of dimensionality. The correction-to-scaling exponent atp
c seems to be larger in two than in three dimensions.
TL;DR: In this article, it was shown that at temperatures below 160 K, crystalline NaN is transformed into an extremely long-living metastable state, and the new state decays exponentially with red light.
Abstract: Below 160 K, crystalline ${\mathrm{Na}}_{2}$[Fe${(\mathrm{CN})}_{5}$NO] \ifmmode\cdot\else\textperiodcentered\fi{} 2${\mathrm{H}}_{2}$O is transformed into an extremely longliving metastable state ($\ensuremath{\tau}g{10}^{7}$ sec) by irradiation with 400-540-nm light. At $Tg160$ K and by irradiation with red light the new state decays exponentially. During population the transmission of the crystal shows characteristic time behavior with wavelength-dependent saturation. Raman spectra show the coexistence of the ground and metastable states. New infrared and visible absorption bands are interpreted in terms of an energy scheme of the metastable state.
TL;DR: In this article, the conductivity of a random network of resistors and insulators in two dimensions is calculated for strips of size $N\ifmmode\times\else\texttimes\fi{}L$ with $L$ of the order of several ${10}^{6}$ and $N$ up to 350.
Abstract: The conductivity of a random network of resistors and insulators in two dimensions is calculated for strips of size $N\ifmmode\times\else\texttimes\fi{}L$ with $L$ of the order of several ${10}^{6}$ and $N$ up to 350. At the percolation threshold I find the finite-size conductivity exponent $\frac{t}{\ensuremath{
u}}$ to be 0.973\ifmmode\pm\else\textpm\fi{}0.005 in contradiction to the Alexander-Orbach conjecture $\frac{t}{\ensuremath{
u}}\ensuremath{\approx}0.948$ and also incompatible with $\frac{t}{\ensuremath{
u}}=1.0$.
TL;DR: The construction of an expression bank made directly from randomly generated fragments of P. falciparum genomic DNA is described, detects several clones which react strongly with human African immune sera and expresses an antigenic determinant composed of occasionally degenerated repeats of a peptide nonamer.
Abstract: Plasmodium falciparum causes malaria infections in its human host. Its wide distribution in tropical countries is a major world health problem. Before a vaccine can be produced, the identification and characterization of parasite antigens is necessary. This can be achieved by the cloning and subsequent analysis of genes coding for parasite antigens1–4. Recently established cDNA banks allow the expression of cDNA derived from the simian parasite Plasmodium knowlesi5 and P. falciparum6,7 in Escherichia coli. Recombinants encoding parasite antigens have been identified by immunodetection in both banks. Two of them contain repetitive units of 11 (ref. 7) or 12 (ref. 5) amino acids. We describe here the construction of an expression bank made directly from randomly generated fragments of P. falciparum genomic DNA. We detect several clones which react strongly with human African immune sera. One clone expresses an antigenic determinant composed of occasionally degenerated repeats of a peptide nonamer.
TL;DR: [3H] Conduritol C cis-epoxide (1,2-anhydro-epi-inositol, I) was synthesized as an active-site-directed inhibitor for lacZ beta-galactosidase from Escherichia coli and the participation of the carboxylate of Glu-461 in catalysis is discussed.
Abstract: [3H] Conduritol C cis-epoxide (1,2-anhydro-epi-inositol, I) was synthesized as an active-site-directed inhibitor for lacZ beta-galactosidase from Escherichia coli. A considerable kinetic isotope effect was noted in the reduction by [3H]NaBH4 of the p-benzoquinone-derived precursor for I. Complete loss of beta-galactosidase activity occurred on incorporation of 4 mol I/mol beta-galactosidase tetramer. The inhibitor was very labile in the denatured enzyme at pH greater than 8, implying the formation of an ester bond between I and a carboxylate at the active site. The radioactive material released from the labeled enzyme was identified as allo-inositol. The stereochemistry of the expoxide reaction (trans-diaxial ring opening) is thus the same as for beta-glucosidases with the corresponding epoxides. The binding site for I was identified as Glu-461 by the isolation and partial sequence analysis of a radioactive octapeptide from the cyanogen bromide and pepsin fragments of the labeled enzyme. A failure to determine the N-terminal amino acid of the labeled peptide is ascribed to the great reactivity of the esterified gamma-carboxyl group of its N-terminal Glu-461 which causes rapid cyclisation of this residue to pyroglutamate, even under weakly basic conditions. The participation of the carboxylate of Glu-461 in catalysis is discussed.