Showing papers by "Max Planck Society published in 1989"

High-precision sampling for Brillouin-zone integration in metals

Abstract: We present a sampling method for Brillouin-zone integration in metals which converges exponentially with the number of sampling points, without the loss of precision of normal broadening techniques. The scheme is based on smooth approximants to the \ensuremath{\delta} and step functions which are constructed to give the exact result when integrating polynomials of a prescribed degree. In applications to the simple-cubic tight-binding band as well as to band structures of simple and transition metals, we demonstrate significant improvement over existing methods. The method promises general applicability in the fields of total-energy calculations and many-body physics.

Speaking: From Intention to Articulation

Abstract: In Speaking, Willem "Pim" Levelt, Director of the Max-Planck-Institut fur Psycholinguistik, accomplishes the formidable task of covering the entire process of speech production, from constraints on conversational appropriateness to articulation and self-monitoring of speech. Speaking is unique in its balanced coverage of all major aspects of the production of speech, in the completeness of its treatment of the entire speech process, and in its strategy of exemplifying rather than formalizing theoretical issues.

Dynamics of mitochondrial dna evolution in animals: amplification and sequencing with conserved primers

Abstract: With a standard set of primers directed toward conserved regions, we have used the polymerase chain reaction to amplify homologous segments of mtDNA from more than 100 animal species, including mammals, birds, amphibians, fishes, and some invertebrates. Amplification and direct sequencing were possible using unpurified mtDNA from nanogram samples of fresh specimens and microgram amounts of tissues preserved for months in alcohol or decades in the dry state. The bird and fish sequences evolve with the same strong bias toward transitions that holds for mammals. However, because the light strand of birds is deficient in thymine, thymine to cytosine transitions are less common than in other taxa. Amino acid replacement in a segment of the cytochrome b gene is faster in mammals and birds than in fishes and the pattern of replacements fits the structural hypothesis for cytochrome b. The unexpectedly wide taxonomic utility of these primers offers opportunities for phylogenetic and population research.

Oscillatory responses in cat visual cortex exhibit inter-columnar synchronization which reflects global stimulus properties.

Abstract: A FUNDAMENTAL step in visual pattern recognition is the establishment of relations between spatially separate features. Recently, we have shown that neurons in the cat visual cortex have oscillatory responses in the range 40–60 Hz (refs 1,2) which occur in synchrony for cells in a functional column and are tightly correlated with a local oscillatory field potential. This led us to hypothesize that the synchronization of oscillatory responses of spatially distributed, feature selective cells might be a way to establish relations between features in different parts of the visual field2,3. In support of this hypothesis, we demonstrate here that neurons in spatially separate columns can synchronize their oscillatory responses. The synchronization has, on average, no phase difference, depends on the spatial separation and the orientation preference of the cells and is influenced by global stimulus properties.

The density functional formalism, its applications and prospects

Abstract: A scheme that reduces the calculations of ground-state properties of systems of interacting particles exactly to the solution of single-particle Hartree-type equations has obvious advantages. It is not surprising, then, that the density functional formalism, which provides a way of doing this, has received much attention in the past two decades. The quality of the energy surfaces calculated using a simple local-density approximation for exchange and correlation exceeds by far the original expectations. In this work, the authors survey the formalism and some of its applications (in particular to atoms and small molecules) and discuss the reasons for the successes and failures of the local-density approximation and some of its modifications.

Hypervariability of simple sequences as a general source for polymorphic DNA markers

Abstract: Short simple sequence stretches occur as highly repetitive elements in all eukaryotic genomes and partially also in prokaryotes and eubacteria. They are thought to arise by slippage like events working on randomly occurring internally repetitive sequence stretches. This predicts that they should be generally hypervariable in length. I have used the polymerase chain reaction (PCR) process to show that several randomly chosen simple sequence loci with different nucleotide composition and from different species show extensive length polymorphisms. These simple sequence length polymorphisms (SSLP) may be usefully exploited for identity testing, population studies, linkage analysis and genome mapping.

Stimulus-specific neuronal oscillations in orientation columns of cat visual cortex

Abstract: In areas 17 and 18 of the cat visual cortex the firing probability of neurons, in response to the presentation of optimally aligned light bars within their receptive field, oscillates with a peak frequency near 40 Hz. The neuronal firing pattern is tightly correlated with the phase and amplitude of an oscillatory local field potential recorded through the same electrode. The amplitude of the local field-potential oscillations are maximal in response to stimuli that match the orientation and direction preference of the local cluster of neurons. Single and multiunit recordings from the dorsal lateral geniculate nucleus of the thalamus showed no evidence of oscillations of the neuronal firing probability in the range of 20-70 Hz. The results demonstrate that local neuronal populations in the visual cortex engage in stimulus-specific synchronous oscillations resulting from an intracortical mechanism. The oscillatory responses may provide a general mechanism by which activity patterns in spatially separate regions of the cortex are temporally coordinated.

Molecular cloning and expression of brain-derived neurotrophic factor.

Abstract: During the development of the vertebrate nervous system, many neurons depend for survival on interactions with their target cells. Specific proteins are thought to be released by the target cells and to play an essential role in these interactions. So far, only one such protein, nerve growth factor, has been fully characterized. This has been possible because of the extraordinarily (and unexplained) large quantities of this protein in some adult tissues that are of no relevance to the developing nervous system. Whereas the dependency of many neurons on their target cells for normal development, and the restricted neuronal specificity of nerve growth factor have long suggested the existence of other such proteins, their low abundance has rendered their characterization difficult. Here we report the full primary structure of brain-derived neurotrophic factor. This very rare protein is known to promote the survival of neuronal populations that are all located either in the central nervous system or directly connected with it. The messenger RNA for brain-derived neurotrophic factor was found predominantly in the central nervous system, and the sequence of the protein indicates that it is structurally related to nerve growth factor. These results establish that these two neurotrophic factors are related both functionally and structurally.

A multiubiquitin chain is confined to specific lysine in a targeted short-lived protein.

Abstract: The ubiquitin-dependent degradation of a test protein beta-galactosidase (beta gal) is preceded by ubiquitination of beta gal. The many (from 1 to more than 20) ubiquitin moieties attached to a molecule of beta gal occur as an ordered chain of branched ubiquitin-ubiquitin conjugates in which the carboxyl-terminal Gly76 of one ubiquitin is jointed to the internal Lys48 of an adjacent ubiquitin. This multiubiquitin chain is linked to one of two specific Lys residues in beta gal. These same Lys residues have been identified by molecular genetic analysis as components of the aminoterminal degradation signal in beta gal. The experiments with ubiquitin mutated at its Lys48 residue indicate that the multiubiquitin chain in a targeted protein is essential for the degradation of the protein.

The Cytoplasmic Domain of the Cell Adhesion Molecule Uvomorulin Associates With Three Independent Proteins Structurally Related in Different Species

Abstract: Uvomorulin belongs to the group of Ca2+-dependent cell adhesion molecules, which are integral membrane proteins with several structural features in common In particular, the cytoplasmic part of these proteins is highly conserved in different species, suggesting a common biological function To test this assumption we transfected a uvomorulin full-length cDNA into uvomorulin-negative mouse NIH 3T3 and L cells Immunoprecipitations with anti-uvomorulin antibodies detected, in addition to uvomorulin, three independent proteins of 102, 88 and 80 kd which are of host origin and which form complexes with uvomorulin Using cDNA constructs coding for uvomorulin with cytoplasmic or extracellular deletions it is shown that the 102, 88 and 80 kd proteins complex with the cytoplasmic domain of uvomorulin Peptide pattern analysis revealed that these three proteins are identical in different mouse cells When uvomorulin cDNA was introduced into cell lines from other species, such as human HeLa and avian fibroblasts, the expressed uvomorulin was also associated with endogenous 102, 88 and 80 kd proteins and, moreover, each of these proteins showed structural similarities to the respective mouse molecule A panel of antibodies specific for known cytoplasmic proteins of mol wts similar to those of the three proteins did not react with any of the described components This suggests that the 102, 88 and 80 kd proteins constitute a new group of proteins for which we propose the nomenclature of catenin alpha, beta and gamma respectively The characterization of these proteins provides a first molecular basis for a possible cytoplasmic anchorage of uvomorulin to the cytoskeleton

Importance of a novel GABAA receptor subunit for benzodiazepine pharmacology.

Abstract: NEUROTRANSMISSION effected by GABA (γ-aminobutyric acid) is predominantly mediated by a gated chloride channel intrinsic to the GABAA receptor. This heterooligomeric receptor1 exists in most inhibitory synapses in the vertebrate central nervous system (CNS) and can be regulated by clinically important compounds such as benzodiazepines and barbiturates2. The primary structures of GABAA receptor α- and β-subunits have been deduced from cloned complementary DNAs3,4. Co-expression of these subunits in heterologous systems generates receptors which display much of the pharmacology of their neural counterparts, including potentiation by barbiturates3–5. Conspicuously, however, they lack binding sites for, and consistent electrophysiological responses to, benzodiazepines4,5. We now report the isolation of a cloned cDNA encoding a new GABAA receptor subunit, termed γ2, which shares approximately 40% sequence identity with α-and β-subunits and whose messenger RNA is prominently localized in neuronal subpopulations throughout the CNS. Importantly, coexpression of the γ2 subunit with α1 and β1 subunits produces GABAA receptors displaying high-affinity binding for central benzodiazepine receptor ligands.

Cyclophilin and peptidyl-prolyl cis-trans isomerase are probably identical proteins.

Abstract: The enzyme peptidyl-prolyl cis-trans isomerase (PPIase) was recently discovered in mammalian tissues and purified from porcine kidney. It catalyses the slow cis-trans isomerization of proline peptide (Xaa-Pro) bonds in oligopeptides and accelerates slow, rate-limiting steps in the folding of several proteins. Here, we report the N-terminal sequence of PPIase together with further chemical and enzymatic properties. The results indicate that this enzyme is probably identical to cyclophilin, a recently discovered mammalian protein which binds tightly to cyclosporin A (CsA). Cyclophilin is thought to be linked to the immunosuppressive action of CsA. The first 38 amino-acid residues of porcine PPIase and of bovine cyclophilin are identical and the two proteins both have a relative molecular mass of about 17,000 (ref. 7). The catalysis of prolyl isomerization in oligopeptides and of protein folding by PPIase are strongly inhibited in the presence of low levels of CsA. The activities of both PPIase and cyclophilin depend on a single sulphydryl group. At present it is unknown whether the inhibition of prolyl isomerase activity is related with the immunosuppressive action of CsA.

A thin slice preparation for patch clamp recordings from neurones of the mammalian central nervous system.

Abstract: (1) A preparation is described which allows patch clamp recordings to be made on mammalian central nervous system (CNS) neurones in situ. (2) A vibrating tissue slicer was used to cut thin slices in which individual neurones could be identified visually. Localized cleaning of cell somata with physiological saline freed the cell membrane, allowing the formation of a high resistance seal between the membrane and the patch pipette. (3) The various configurations of the patch clamp technique were used to demonstrate recording of membrane potential, whole cell currents and single channel currents from neurones and isolated patches. (4) The patch clamp technique was used to record from neurones filled with fluorescent dyes. Staining was achieved by filling cells during recording or by previous retrograde labelling. (5) Thin slice cleaning and patch clamp techniques were shown to be applicable to the spinal cord and almost any brain region and to various species. These techniques are also applicable to animals of a wide variety of postnatal ages, from newborn to adult.

Structural parts involved in activation and inactivation of the sodium channel.

Abstract: Structure-function relationships of the sodium channel expressed in Xenopus oocytes have been investigated by the combined use of site-directed mutagenesis and patch-clamp recording. This study provides evidence that the positive charges in segment S4 are involved in the voltage-sensing mechanism for activation of the channel and that the region between repeats III and IV is important for its inactivation.

Dynamics of neuronal firing correlation: modulation of "effective connectivity"

Abstract: 1. We reexamine the possibilities for analyzing and interpreting the time course of correlation in spike trains simultaneously and separably recorded from two neurons. 2. We develop procedures to quantify and properly normalize the classical joint peristimulus time scatter diagram. These allow separation of the "raw" correlation into components caused by direct stimulus modulations of the single-neuron firing rates and those caused by various types of interaction between the two neurons. 3. A newly developed significance test ("surprise") is applied to evaluate such inferences. 4. Application of the new procedures to simulated spike trains allowed the recovery of the known circuitry. In particular, it proved possible to recover fast stimulus-locked modulations of "effective connectivity," even if they were masked by strong direct stimulus modulations of individual firing rates. These procedures thus present a clearly superior alternative to the commonly used "shift predictor." 5. Adopting a model-based approach, we generalize the classical measures for quantifying a direct interneuronal connection ("efficacy" and "contribution") to include possible stimulus-locked time variations. 6. Application of the new procedures to real spike trains from several different preparations showed that fast stimulus-locked modulations of "effective connectivity" also occur for real neurons.

Structure and biological activity of basement membrane proteins

Abstract: Collagen type IV, laminin, heparan sulfate proteoglycans, nidogen (entactin) and BM-40 (osteonectin, SPARC) represent major structural proteins of basement membranes. They are well-characterized in their domain structures, amino acid sequences and potentials for molecular interactions. Such interactions include self-assembly processes and heterotypic binding between individual constituents, as well as binding of calcium (laminin, BM-40) and are likely to be used for basement membrane assembly. Laminin, collagen IV and nidogen also possess several cell-binding sites which interact with distinct cellular receptors. Some evidence exists that those interactions are involved in the control of cell behaviour. These observations have provided a more defined understanding of basement membrane function and the definition of new research goals in the future.

Lutropin-choriogonadotropin receptor: an unusual member of the G protein-coupled receptor family.

Abstract: A complementary DNA (cDNA) for the rat luteal lutropin-choriogonadotropin receptor (LH-CG-R) was isolated with the use of a DNA probe generated in a polymerase chain reaction with oligonucleotide primers based on peptide sequences of purified receptor protein. As would be predicted from the cDNA sequence, the LH-CG-R consists of a 26-residue signal peptide, a 341-residue extracellular domain displaying an internal repeat structure characteristic of members of the leucine-rich glycoprotein (LRG) family, and a 333-residue region containing seven transmembrane segments. This membrane-spanning region displays sequence similarity with all members of the G protein-coupled receptor family. Hence, the LH-CG-R gene may have evolved by recombination of LRG and G protein-coupled receptor genes. Cells engineered to express LH-CG-R cDNA bind human choriogonadotropin with high affinity and show an increase in cyclic adenosine monophosphate when exposed to hormone. As revealed by RNA blot analysis and in situ hybridization, the 4.4-kilobase cognate messenger RNA is prominently localized in the rat ovary.

Perceiving the Causes of Success and Failure A Cross-Cultural Examination of Attributional Concepts

Abstract: The present study examines cross-cultural perceptions of causal attributions pertinent to success and failure in achievement-related contexts. Two groups of participants(taxi drivers and civil servants) from five nations (Belgium, West Germany, India, South Korea, and England) rated 22 causal ascriptions (including ability, effort, task difficulty, and luck) on four causal properties (locus, stability, controllability, and globality). There was high agreement among the two social class groups as well as among four of the nations regarding the ratings of specific causes on the causal dimensions. However, Indian respondents rated all causes as more external, variable, and uncontrollable than did participants from the other cultures. With the exception of the Indian data, the results suggest that a priori classifications of causal attributions have cross-cultural validity and that causal dimensions suggested by attribution theorists capture basic aspects of the meanings of causes that are shared in different...

Implications of the three-dimensional structure of alpha 1-antitrypsin for structure and function of serpins.

Abstract: Article synthese sur l'α1-antitrypsine: caracteristiques structurales et fonctionnelles (capacite de liaison a des modulateurs); utilisation de l'α1-antitrypsine en tant que modele pour toutes les serpines

Structure of the guanine-nucleotide-binding domain of the ha-ras oncogene product p21 in the triphosphate conformation

Abstract: The crystal structure of the guanine-nucleotide-binding domain of p21 (amino acids 1-166) complexed to the guanosine triphosphate analogue guanosine-5'-(beta, gamma-imido)triphosphate (GppNp) has been determined at a resolution of 2.6 A. The topological order of secondary structure elements is the same as that of the guanine-nucleotide-binding domain of bacterial elongation factor EF-Tu. Many interactions between nucleotide and protein have been identified. The effects of point mutations and the conservation of amino-acid sequence in the guanine-nucleotide-binding proteins are discussed.

The refined 1.9 A crystal structure of human alpha-thrombin: interaction with D-Phe-Pro-Arg chloromethylketone and significance of the Tyr-Pro-Pro-Trp insertion segment.

Abstract: A stoichiometric complex formed between human alpha-thrombin and D-Phe-Pro-Arg chloromethylketone was crystallized in an orthorhombic crystal form. Orientation and position of a starting model derived from homologous modelling were determined by Patterson search methods. The thrombin model was completed in a cyclic modelling-crystallographic refinement procedure to a final R-value of 0.171 for X-ray data to 1.92 A. The structure is in full agreement with published cDNA sequence data. The A-chain, ordered only in its central part, is positioned along the molecular surface opposite to the active site. The B-chain exhibits the characteristic polypeptide fold of trypsin-like proteinases. Several extended insertions form, however, large protuberances; most important for interaction with macromolecular substrates is the characteristic thrombin loop around Tyr60A-Pro60B-Pro60C-Trp60D (chymotrypsinogen numbering) and the enlarged loop around the unique Trp148. The former considerably restricts the active site cleft and seems likely to be responsible for poor binding of most natural proteinase inhibitors to thrombin. The exceptional specificity of D-Phe-Pro-Arg chloromethylketone can be explained by a hydrophobic cage formed by Ile174, Trp215, Leu99, His57, Tyr60A and Trp60D. The narrow active site cleft, with a more polar base and hydrophobic rims, extends towards the arginine-rich surface of loop Lys70-Glu80 that probably represents part of the anionic binding region for hirudin and fibrinogen.

Quantitative evaluation of Escherichia coli host strains for tolerance to cytosine methylation in plasmid and phage recombinants

Abstract: Many strains of E. coli K12 restrict DNA containing cytosine methylation such as that present in plant and animal genomes. Such restriction can severely inhibit the efficiency of cloning genomic DNAs. We have quantitatively evaluated a total of 39 E. coli strains for their tolerance to cytosine methylation in phage and plasmid cloning systems. Quantitative estimations of relative tolerance to methylation for these strains are presented, together with the evaluation of the most promising strains in practical recombinant cloning situations. Host strains are recommended for different recombinant cloning requirements. These data also provide a rational basis for future construction of 'ideal' hosts combining optimal methylation tolerance with additional advantageous mutations.

A cross-language study of prosodic modifications in mothers' and fathers' speech to preverbal infants.

Abstract: This study compares the prosodic modifications in mothers' and fathers' speech to preverbal infants in French, Italian, German, Japanese, British English, and American English. At every stage of data collection and analysis, standardized procedures were used to enhance the comparability across data sets that is essential for valid cross-language comparison of the prosodic features of parental speech. In each of the six language groups, five mothers and five fathers were recorded in semi-structured home observations while speaking to their infant aged 0;10-1;2 and to an adult. Speech samples were instrumentally analysed to measure seven prosodic parameters: mean fundamental frequency (f0), f0-minimum, f0-maximum, f0-range, f0-variability, utterance duration, and pause duration. Results showed cross-language consistency in the patterns of prosodic modification used in parental speech to infants. Across languages, both mothers and fathers used higher mean-f0, f0-minimum, and f0-maximum, greater f0-variability, shorter utterances, and longer pauses in infant-directed speech than in adult-directed speech. Mothers, but not fathers, used a wider f0-range in speech to infants. American English parents showed the most extreme prosodic modifications, differing from the other language groups in the extent of intonational exaggeration in speech to infants. These results reveal common patterns in caretaker's use of intonation across languages, which may function developmentally to regulate infant arousal and attention, to communicate affect, and to facilitate speech perception and language comprehension. In addition to providing evidence for possibly universal prosodic features of speech to infants, these results suggest that language-specific variations are also important, and that the findings of the numerous studies of early language input based on American English are not necessarily generalisable to other cultures.

Charged magnetic domain lines and the magnetism of high-tc oxides

Abstract: The breakdown of the antiferromagnetism in the high-{ital T}{sub {ital c}} oxides is studied taking into account the 3{ital d} charge fluctuations. We point out a tendency towards the formation of charged magnetic domain lines if holes are introduced in such a state, which can be viewed as a generalization of soliton of the Su, Schrieffer, and Heeger to two dimensions. In the ground state these domain lines line up, explaining the incommensurate spin phase observed in the high-{ital T}{sub {ital c}}'s superconductors.

The large-scale structure of the universe: Turbulence, intermittency, structures in a self-gravitating medium

Abstract: The density distribution arising at the nonlinear stage of gravitational instability is similar to intermittency phenomena in acoustic turbulence. Initially small-amplitude density fluctuations of Gaussian type transform into thin dense pancakes, filaments, and compact clumps of matter. It is perhaps surprising that the motion of self-gravitating matter in the expanding universe is like that of noninteracting matter moving by inertia. A similar process is the distribution of light reflected or refracted from rippled water. The similarity of gravitational instability to acoustic turbulence is highlighted by the fact that late nonlinear stages of density perturbation growth can be described by the Burgers equation, which is well known in the theory of turbulence. The phenomena discussed in this article are closely related to the problem of the formation of large-scale structure of the universe, which is also discussed.