Showing papers by "Université catholique de Louvain published in 1991"

Beyond the emotional event: Six studies on the social sharing of emotion

Abstract: We argue that emotion cannot only be conceived of as a short-lived and intrapersonal phenomenon. Rather, based on five theoretical arguments, we propose that the social sharing of an emotional experience forms an integral part of the emotional processes. A series of six studies investigated different aspects of this hypothesis. Study 1 showed that an overwhelming majority of people reported sharing their emotional experiences and that the memories of these experiences tended to come back spontaneously to their consciousness. No difference was found among emotions. Using a different procedure, Studies 2 and 3 replicated these findings in two different populations. In addition, these studies provided indications that women share their experiences with a wider array of individuals than do men. The first three studies did not find any differences among emotions, but they did not include shame. It could be argued that people are less inclined to socially share shame experiences which are typically eli...

Islet Function in Offspring of Mothers on Low-Protein Diet During Gestation

Abstract: A low-protein diet (8 vs. 20%) administered during pregnancy affects the structure and function of the endocrine pancreas of the offspring. At 21.5 days of gestation, we reported a reduction of cell proliferation, islet size, islet vascularization, and pancreatic insulin content. In this study, we demonstrated an impairment of insulin secretion of these fetal islets when stimulated in vitro with amino acids such as arginine and leucine. If the offspring is kept on the same low-protein diet during suckling, weaning, and adulthood, fasting insulin levels remain low in the presence of normal blood glucose levels. Glucose tolerance at 70 days is impaired, with lower insulin response. In addition, permanent functional damage seems to be induced in utero by a low-protein diet, because a normal diet given from birth to adulthood does not restore normal insulin response after a glucose challenge. Our experimental results stress the impact of a balanced diet with qualitative and quantitative amino acid composition for the fetal endocrine pancreas to develop normally, without lasting functional and structural consequences in adulthood.

Analysis of virC, an operon involved in the secretion of Yop proteins by Yersinia enterocolitica.

Abstract: Upon incubation at 37 degrees C in the absence of Ca2+ ions, pathogenic yersiniae release large amounts of pYV plasmid-encoded proteins called Yops that are involved in pathogenesis. Yersinia enterocolitica also expresses an outer membrane protein that is considered an adhesin and called YadA (previously called P1 or YopA). The production of Yops is coordinately regulated by a 20-kb region of the plasmid referred to as the Ca2+ dependence region and containing at least four loci called virA, virB, virC, and virF. The virF gene encodes a key transcriptional activator of yop genes. We have shown here that virF is also required for transcription of yadA and that virB is necessary for full transcription of the yop and yadA genes. In contrast, mutations in genes virA and virC had only a weak influence on the transcription of yop and yadA genes. These mutations did not affect the production of YadA but they completely inhibited the translocation of Yops from the intracellular compartment to the extracellular milieu. We inferred from these data that virA and virC are involved in the specific transport of Yops. We analyzed the 8.5-kb virC region and showed that it is most probably a single operon containing 13 open reading frames called yscA to yscM (for Yop secretion). Protein YscC has a putative signal sequence and shares significant homology with outer membrane proteins involved in the secretion of pullulanase by Klebsiella pneumoniae (PulD) or in the assembly of filamentous bacteriophages (gene IV product). At least the putative products of yscD, yscJ, and yscL were shown to be required for the export of Yops. YscJ turned out to be YlpB, a lipoprotein that we had detected previously. The yscM gene shares homology with yopH, the adjacent gene on the pYV plasmid. Its product does not appear to be necessary for the production of Yops. Transcription of the virC operon was subjected to the same regulation as the yop genes.

First-principles study of the electronic properties of graphite

Abstract: The electronic properties of hexagonal graphite have been studied in the framework of the density-functional technique, using nonlocal ionic pseudopotentials and a large number of plane waves. The valence charge density and the density of states are presented, as well as the band structure and the charge-density contributions of some typical wave functions. The electronic energies, at the Fermi level, are parametrized by the Slonczewski-Weiss-McClure model, and compared with the parametrization of experimental data. The numerical accuracy of the calculation has been controlled, in order to provide a reliable comparison between theory and experiment. In particular, the agreement obtained in the framework of the density-functional theory for electronic energies at the Fermi level is surprisingly good.

Secretion of hybrid proteins by the Yersinia Yop export system.

Abstract: After incubation at 37 degrees C in the absence of Ca2+ ions, pathogenic strains of Yersinia spp. release large amounts of a set of plasmid-encoded proteins called Yops. The secretion of these proteins, involved in pathogenicity, occurs via a mechanism that involves neither the removal of a signal sequence nor the recognition of a C-terminal domain. Analysis of deletion mutants allowed the secretion recognition domain to be localized within the 48 N-terminal amino acids of protein YopH, within the 98 N-terminal residues of protein YopE, and within the 76 N-terminal residues of YopQ. Comparison of these regions failed to reveal any sequence similarity, suggesting that the secretion signal of Yop proteins is conformational rather than sequential. Hybrid proteins containing the amino-terminal part of YopH fused to either the alpha-peptide of beta-galactosidase or to alkaline phosphatase deprived of its signal sequence were efficiently secreted to the Yersinia culture medium. This observation opens new prospects in using Yersinia spp. as chimeric-protein producers and as potential live carriers for foreign antigens.

PIF1: a DNA helicase in yeast mitochondria.

Abstract: The PIF1 gene is involved in repair and recombination of mitochondrial DNA (mtDNA). In this study, the PIF1 gene product, which cannot be identified in normal yeast cells, has been overproduced from the GALI promoter to detectable protein levels. Location of PIF1 in mitochondria has been shown by immunoelectron microscopy and in vivo import experiments using ts mas1 mutants deficient in the mitochondrial matrix-localized processing protease. Overproduction of PIF1 protein in pif1 mutants restores mtDNA recombination proficiency but is toxic to yeast cells as observed by slower growth. The overproduced PIF1 protein, which is firmly associated with insoluble mitochondrial structures, has been partially purified in a mitochondrial nuclease deficient nuc1 strain by a procedure including solubilization by urea and renaturation by dialysis at alkaline pH. PIF1 is a single-stranded (ss) DNA-dependent ATPase and a DNA helicase which unwinds partially DNA duplexes in a 5' to 3' direction with respect to the ss DNA on which it binds first.

Controllability and state feedback stabilizability of non holonomic mechanical systems

Abstract: The dynamics of non holonomic mechanical system are described by the classical Euler-Lagrange equations subjected to a set of non-integrable constraints. Non holonomic systems are strongly accessible whatever the structure of the constraints. They cannot be asymptotically stabilized by a smooth pure state feedback. However smooth state feedback control laws can be designed which guarantee the global marginal stability of non holonomic systems.

Solving Multi-Item Lot-Sizing Problems Using Strong Cutting Planes

Abstract: We consider two classes of multi-item lot-sizing problems. The first is a class of single stage problems involving joint machine capacity constraints and/or start up costs, and the second is a class of multistage problems with general product structure. The problems are solved as mixed integer programs based on i an appropriate choice of the initial problem formulation and ii the addition of cuts which are generated automatically by a mathematical programming system MPSARX. Our results extend and complement those of Karmarkar and Schrage 1985, Afentakis and Gavish 1986, Eppen and Martin 1987 and Van Roy and Wolsey 1987. A major advantage of this approach is its robustness or flexibility. By using just a matrix generator and a mathematical programming system with automatic cut generation routines we can formulate and solve model variants without incurring the costs of adapting an algorithm.

Postnatal maturation of excitation-contraction coupling in rat ventricle in relation to the subcellular localization and surface density of 1,4-dihydropyridine and ryanodine receptors.

Abstract: To better understand excitation-contraction coupling in cardiac muscle, we investigated the main Ca2+ channels involved in that process in adult and neonatal rat ventricle. Voltage-dependent (L-type) Ca2+ channels and sarcoplasmic reticulum Ca2+ release channels were labeled by means of [3H] (+)-PN200-110 and [3H]ryanodine, respectively. The number of [3H]ryanodine binding sites (per gram tissue) increased more than that of [3H] (+)-PN200-110 binding sites over the postnatal period (2.1-fold versus 1.35-fold, respectively). After equilibration of microsomal fractions in density gradient, ryanodine receptors were characterized by a heavy distribution pattern that did not change appreciably between days 1 and 30 after birth. In neonatal tissue, 1,4-dihydropyridine receptors were found mainly in low-density subfractions, together with other sarcolemmal constituents, whereas in adult tissue, they were recovered predominantly in high-density subfractions, together with ryanodine receptors. Thus, after birth, and in parallel with the development of T tubules, there was a progressive concentration of L-type Ca2+ channels in junctional structures of high equilibrium density, where they were situated close to the Ca2+ release channels of the sarcoplasmic reticulum. In adult ventricle, L-type channels were, on an average, threefold more abundant in T tubules than in external sarcolemma. In parallel mechanical studies, we found that the inhibitory action of ryanodine on systolic contraction was much more pronounced in adult than in neonatal right ventricle, and that, conversely, neonatal tissue was more sensitive that adult tissue to inhibitors of L-type channels. We conclude that, in view of the presumed mechanism of Ca2+ release from the sarcoplasmic reticulum, that is, Ca(2+)-induced Ca2+ release, the predominant localization in adult rat ventricle of the major Ca2+ entry pathway in the vicinity of the Ca2+ release pathway is of great functional significance. Furthermore, owing to the relative stoichiometry of Ca2+ entry and Ca2+ release channels in junctional structures (about 1:9), a physical link between these channels is not likely to be involved in the modulation of Ca2+ release from the sarcoplasmic reticulum in cardiac muscle.

Gestures and Speech: Psychological Investigations

Abstract: Achnowledgements Introduction 1. Body language 2. Language as gesture: an ethnological approach 3. Autonomy of gestures and speech: the notion of nonverbal communication 4. Cognitive approaches 5. Developmental perspectives 6. Gestures and speech in neuropsychology and psychopathology References Subject index.

Modelling and control of non-holonomic wheeled mobile robots

Abstract: A general dynamical model is derived for three-wheel mobile robots with nonholonomic constraints by using a Lagrange formulation and differential geometry. It is shown that a static state feedback allows one to reduce the dynamics of the system to a form in which stabilizing input-output linearizing control is possible. >

Random-walks in Asymmetric Random-environments

Abstract: We consider random walks on Z d with transition ratesp(x, y) given by a random matrix. Ifp is a small random perturbation of the simple random walk, we show that the walk remains diffusive for almost all environmentsp ifd>2. The result also holds for a continuous time Markov process with a random drift. The corresponding path space measures converge weakly, in the scaling limit, to the Wiener process, for almost everyp.

Adaptive Stabilization of Nonlinear-systems

Abstract: An overview of the various parametric approaches which can be adopted to solve the problem of adaptive stabilization of nonlinear systems is presented. The Lyapunov design and two estimation designs —equation error filtering and regressor filtering— are revisited. This allows us to unify and generalize most of the available results on the topic and to propose a classification depending on the required extra assumptions — matching conditions or growth conditions.

Failure of insulin-like growth factor-I (IGF-I) infusion to promote growth in protein-restricted rats despite normalization of serum IGF-I concentrations.

Abstract: Dietary protein restriction in young rats induces GH resistance characterized by growth arrest and low serum insulin-like growth factor-I (IGF-I) concentrations. To determine whether the low serum IGF-I concentrations are responsible for the stunted growth, we infused 4-week-old protein-restricted rats with recombinant human IGF-I (300 micrograms/day) or rat GH (200 micrograms/100 g body wt/day) by osmotic minipump for 1 week. Despite the normalization of serum IGF-I concentrations by IGF-I infusion, carcass growth was not stimulated. In contrast, growth of the spleen and kidney was enhanced (+45% and +28%, respectively). Serum IGF-binding protein 3 (IGFBP-3), the principal carrier of IGF-I in the serum at this age, is decreased by 34% in protein-restricted animals and restored to normal by IGF-I infusion. Contrary to the selective effects of IGF-I on growth of protein-restricted rats, well nourished hypophysectomized rats infused with 150 micrograms/day recombinant human IGF-I showed a significant growth response, including carcass and organ growth and normalization of IGFBP-3 values. These responses indicate that our IGF-I preparation and mode of delivery were effective. We conclude that: 1) dietary protein restriction causes organ-specific resistance to the growth-promoting properties of exogenous IGF-I; 2) IGF-I mediates the stimulatory effects of growth hormone on IGFBP-3 synthesis; and 3) the absence of carcass growth in the presence of normal serum IGF-I concentrations during infusion of IGF-I suggests that the growth arrest that accompanies protein restriction is mediated in part by resistance to IGF-I.

Tight-binding model for the electronic properties of simple hexagonal graphite.

Abstract: The band structure of graphite with the hypothetical simple hexagonal structure has been investigated near the Fermi energy, using a tight-binding approximation. Some general features of the structure of the π bands in the neighborhood of the zone edge are obtained and are expressed in terms of appropriate parameters. The Fermi surface is analyzed. The density of states and the resulting behavior near the Fermi level are compared to the results obtained for the Bernal structure (Slonczewski-Weiss-McClure model) and for the rhombohedral structure (Haering-McClure model). Possible application to disordered graphite (turbostratic) is also discussed.

Viability and stability of yeast cells and filamentous fungus spores during freeze-drying: effects of protectants and cooling rates

Abstract: Two parameters of a one step freeze-drying process, cooling rate and protecting media, are studied in an effort to improve the viability and the stability of the preserved fungal strains. Cooling rates of 1.6 C, 3 C and 40 C/min are applied on cells of Saccharomyces cerevisiae and Brettanomyces bruxellensis and on spores of Trichoderma viride and Arthrobotrys arthrobotryoides preserved in 93 suspending media containing polymers, sugars, albumin, milk, honey, polyols, amino acids alone or in combination. The viability rate of Saccharomyces cerevisiae cells is increased from 30% to 96-98% by using an appropriate protecting medium containing 10% skim milk with 2 compounds among honey, sodium glutamate, trehalose or raffinose in the freeze-drying process carried out at a 3 C/min cooling rate. In the same conditions Arthrobotrys arthrobotryoides spores, the most sensitive strain among the four tested, provides 60-65% viability, while this strain does not survive a classical freeze-drying in 10% skim milk. Moreover, with the improved method the stability of properties of Penicillium expansum is demonstrated.

Traffic modeling and state feedback control for metro lines

Abstract: A complete traffic analysis for sequential metro lines with or without reference to a nominal time schedule is developed. The intrinsic instability of metro lines is pointed out. It is shown how well-chosen state-space formulations allow design of state-feedback control algorithms ensuring the stability of the system. The proposed traffic control algorithms have simple forms and are easy to implement in real-life systems. Simulations show the robustness of the proposed traffic control algorithms against disturbances occurring randomly on a loop line and their efficiency when compared to a classical time margin strategy. >

Popliteal sciatic nerve block aided by a nerve stimulator: a reliable technique for foot and ankle surgery.

Abstract: The reliability of popliteal sciatic nerve blocks was prospectively assessed in 625 blocks performed in 507 patients. The sciatic nerve was approached at the apex of the popliteal fossa, in the midline, with an insulated needle connected to a peripheral nerve stimulator partially designed by one of the authors. When needed, an inguinal paravascular femoral nerve block was also performed. The drugs used were 1% mepivacaine or 0.5% bupivacaine with or without 1:200,000 epinephrine. The sciatic and femoral nerves were blocked with 30 ml and 10 ml of local anesthetic, respectively. The block was sufficient to provide surgical anesthesia in 92%; supplemental analgesia was necessary in 5% and general anesthesia was required in 3% of the cases. Discomfort associated with the block procedure was found to be minimal by 89% of the patients, moderate by 9% and severe by 2%. Overall satisfaction with perioperative analgesia was evaluated by 466 patients: 444 (95%) were completely satisfied, 20 (4%) expressed moderate reservations and two (1%) expressed major reservations. The authors conclude that the technique is a safe and reliable alternative to more common forms of anesthesia for surgery below the knee. They attribute the great success rate to a high popliteal approach, the use of insulated needles, a discriminating mode of nerve stimulation and the systematic search for optimal response to needle stimulation.

Secure implementation of identification systems

Abstract: In this paper we demonstrate that widely known identification systems, such as the public-file-based Feige-Fiat-Shamir scheme, can be insecure if proper care is not taken with their implementation. We suggest possible solutions. On the other hand, identity-based versions of the Feige-Fiat-Shamir scheme are conceptually more complicated than necessary.

A new model for the regulation of ester synthesis by alcohol acetyltransferase in saccharomyces cerevisiae during fermentation

Abstract: The factors that influence ester synthesis were evaluated by measuring and comparing specific activities of in vivo and in vitro alcohol acetyltransferase (AAT) (EC 2.3.1.84) during different condi...

Evidence that pretranslational and translational defects decrease serum insulin-like growth factor-I concentrations during dietary protein restriction.

Abstract: Dietary protein restriction causes GH resistance and decreases serum insulin-like growth factor-I (IGF-I) concentrations. To determine whether pretranslational or translational defects are involved in the decline of serum IGF-I concentrations during protein restriction, we measured hepatic IGF-I mRNA abundance together with the serum IGF-I peptide response to exogenous GH after 1 week of protein restriction (5% casein in diet; P5) in hypophysectomized rats. We compared these responses with those of hypophysectomized rats fed a protein-sufficient diet (15% casein in diet; P15) and given exogenous GH. A single injection of rat GH (200 micrograms/100 g BW) produced a comparable IGF-I mRNA increment in both groups (at 6 h, 7.8 +/- 1.1 arbitrary units in P5 vs. 8.2 +/- 1.1 in P15), but failed to raise serum IGF-I normally in the P5 group (at 6 h, 90 +/- 15 ng/ml in P5 vs. 216 +/- 63 in P15; P less than 0.01). The post-GH decline of the 7.5-kilobase (kb) IGF-I mRNA abundance was faster in P5 than in P15 animals. In another experiment in intact rats subjected to protein restriction, injections of pharmacological doses of rat GH (400 micrograms/100 g BW.day) for 1 week restored liver IGF-I mRNA abundance to normal without normalization of serum IGF-I (403 +/- 91 vs. 713 +/- 53 ng/ml; P less than 0.01). Our data suggest that 1) the machinery involved in the transcription of the liver IGF-I gene is intact in protein-restricted rats, because these animals retain the ability to muster normal IGF-I mRNA responses to high doses of exogenous GH; 2) the stability of the 7.5-kb IGF-I mRNA is probably decreased by the protein restriction, as suggested by the faster decline of the 7.5-kb transcript in P5 than in P15 hypophysectomized rats; and 3) the discrepancy between normal liver IGF-I mRNA abundance and low serum and liver IGF-I peptide concentrations suggests that translational stalling of the IGF-I mRNAs or increased serum IGF-I clearance is involved in the low serum IGF-I concentrations during dietary protein restriction.

Determination of the N-13 (p, gamma) O-14 reaction cross section using a N-13 radioactive ion beam

Abstract: The cross section for the astrophysically important $^{13}\mathrm{N}$(p,\ensuremath{\gamma}${)}^{14}$O reaction has been measured directly with an intense (3\ifmmode\times\else\texttimes\fi{}${10}^{8}$ particles/s) and pure (g99%) 8.2-MeV $^{13}\mathrm{N}$ radioactive ion beam. The average value, for the 5.8--8.2-MeV $^{13}\mathrm{N}$ energy range, is 106(30) \ensuremath{\mu}b. The partial \ensuremath{\gamma} width of the resonance which occurs in this reaction at a center-of-mass energy of 0.545 MeV has been deduced to be 3.8(1.2) eV. It is compared with theoretical predictions and indirect determinations.