Showing papers by "Université libre de Bruxelles published in 1990"
TL;DR: A minimal model shows how the exploratory pattern may be generated by the individual workers' simple trail-laying and -following behavior, illustrating how complex collective structures in insect colonies may be based on self-organization.
Abstract: Workers of the Argentine ant, Iridomyrmex humilis,start to explore a chemically unmarked territory randomly. As the exploratory front advances, other explorers are recruited and a trail extends from it to the nest. Whereas recruitment trails are generally constructed between two points, these exploratory trails have no fixed destination, and strongly resemble the foraging patterns of army ants. A minimal model shows how the exploratory pattern may be generated by the individual workers' simple trail-laying and -following behavior, illustrating how complex collective structures in insect colonies may be based on self-organization.
957 citations
TL;DR: The alterations in maternal thyroid function during gestation are intricate and far from fully understood, and regulation of the maternal thyroid is complex, resulting from both elevated hCG and increasing TSH.
Abstract: A prospective study was undertaken in 606 healthy women during pregnancy to evaluate the changes occurring in maternal thyroid economy as a result of 1) the increased thyroid hormone-binding capacity of serum, 2) the effects of increased levels of hCG on TSH and on the thyroid, and 3) a marginally low iodine intake in the population (50-75 micrograms/day). Four main features were observed. First, thyroidal activity adjusted to the marked increase in serum T4-binding globulin: pregnancy was accompanied by an overall reduction in the T4/T4-binding globulin ratio, with lower free T4 and T3 levels, although in most cases free hormone levels remained within the normal range. The adjustment of thyroidal output of T4 and T3 did not occur similarly in all subjects. In approximately one third of the women, there was relative hypothyroxinemia, higher T3/T4 ratios (presumably indicating preferential T3 secretion), and higher, although normal, serum TSH concentrations. Second, high hCG levels were associated with thyroid stimulation, both functionally (lower serum TSH) and anatomically (increased thyroid size). The data are consistent with a TSH-like effect of hCG on the thyroid. Hence, regulation of the maternal thyroid is complex, resulting from both elevated hCG (mainly in the first half of gestation) and increasing TSH (mainly in the second half of gestation). Third, a significant increase in serum thyroglobulin levels was observed throughout gestation, especially during the last trimester. Fourth, increased thyroid volume was common, and goiter formation not uncommon (goiter was found in 9% of women at delivery). In conclusion, the alterations in maternal thyroid function during gestation are intricate and far from fully understood. In areas of marginally low iodine intake, gestation is associated in a significant number of women with relative hypothyroxinemia, increased thyroglobulin, and enlarged thyroid.
676 citations
TL;DR: Results indicate that repetitive Ca2+ spikes evoked by external stimuli do not necessarily require the concomitant, periodic variation of InsP3, and might be effectively encoded in terms of their frequency through the phosphorylation of a cellular substrate by a protein kinase activated by cytosolic Ca2+.
Abstract: In a variety of cells, hormonal or neurotransmitter signals elicit a train of intracellular Ca2+ spikes. The analysis of a minimal model based on Ca2(+)-induced Ca2+ release from intracellular stores shows how sustained oscillations of cytosolic Ca2+ may develop as a result of a rise in inositol 1,4,5-trisphosphate (InsP3) triggered by external stimulation. This rise elicits the release of a certain amount of Ca2+ from an InsP3-sensitive intracellular store. The subsequent rise in cytosolic Ca2+ in turn triggers the release of Ca2+ from a second store insensitive to InsP3. In contrast to the model proposed by Meyer and Stryer [Meyer, T. & Stryer, L. (1988) Proc. Natl. Acad. Sci. USA 85, 5051-5055], the present model, which contains only two variables, predicts the occurrence of periodic Ca2+ spikes in the absence of InsP3 oscillations. Such results indicate that repetitive Ca2+ spikes evoked by external stimuli do not necessarily require the concomitant, periodic variation of InsP3. The model is closely related to that proposed by Kuba and Takeshita [Kuba, K. & Takeshita, S. (1981) J. Theor. Biol. 93, 1009-1031] for Ca2+ oscillations in sympathetic neurones, based on Ca2(+)-induced Ca2+ release. We extend their results by showing the minimal conditions in which the latter process gives rise to periodic behavior and take into account the role of the rise in InsP3 caused by external stimulation. The analysis further shows how signal-induced Ca2+ oscillations might be effectively encoded in terms of their frequency through the phosphorylation of a cellular substrate by a protein kinase activated by cytosolic Ca2+.
630 citations
TL;DR: HADS appears in this study to be a simple, sensitive and specific tool for screening for psychiatric disorders in an oncology in-patient population.
Abstract: The Hospital Anxiety and Depression Scale (HADS), a four-point, 14-item questionnaire, was tested as a screening method for adjustment disorders and major depressive disorders in a sample of 210 cancer in-patients. A receiver operating characteristic (ROC) analysis was performed, giving the relationship between the true positive rate (sensitivity) and the false positive rate (1-specificity). This makes it possible to choose an optimal cut-off point that takes into account the costs and benefits of treatment of psychological distress. For screening for major depressive disorders only, a cut-off score of 19 gave 70% sensitivity and 75% specificity. For screening for adjustment disorders and major depressive disorders taken together, a cut-off score of 13 gave 75% sensitivity and 75% specificity. HADS appears in this study to be a simple, sensitive and specific tool for screening for psychiatric disorders in an oncology in-patient population.
512 citations
01 Jan 1990
TL;DR: The probability function is derived axiomatically the probability function that should be used to make decisions given any form of underlying uncertainty.
Abstract: Summary We derive axiomatically the probability function that should be used to make decisions given any form of underlying uncertainty.
511 citations
TL;DR: Attenuated total reflection Fourier-transform infrared spectroscopy of thin hydrated films of soluble and membrane protein included in a phospholipid bilayer is shown to provide useful information as to the secondary structure of the protein.
Abstract: Attenuated total reflection Fourier-transform infrared spectroscopy of thin hydrated films of soluble and membrane protein included in a phospholipid bilayer is shown to provide useful information as to the secondary structure of the protein. The analysis of the amide I band of deuterated samples by Fourier self-deconvolution followed by a curve fitting was performed by a new procedure in which all the input parameters are generated by the computer rather than by the investigator. The results of this analysis provide a correct estimation of the alpha-helix and beta-sheet structure content with a standard deviation of 8.6% when X-ray structures are taken as a reference. We also show that the orientation of the different secondary structures resolved by the Fourier self-deconvolution/curve-fitting procedure and of the phospholipid acyl chains can be simultaneously evaluated for membrane proteins reconstituted in a lipid bilayer. Of special interest for reconstitution of membrane proteins, the lipid/protein ratio can be accurately and quickly determined from the infrared spectrum.
500 citations
TL;DR: A series of experiments shows how the andLasius niger uses its trail recruitment system to select between two food sources, simultaneously presented with to 1M sucrose solution and when offered a 1M solution together with a 0.1M solution.
Abstract: A series of experiments shows how the andLasius niger uses its trail recruitment system to select between two food sources Simultaneously presented with to 1M sucrose solution it concentrates on one of them When offered a 1M solution together with a 01M solution it selects the richer source, unless the trait to the 01M source had become well-developed before the 1M source was introduced In the same situation, however, the group/mass recruiting antTetramorium caespitum uses its more individual transmission of information to switch to the 1M source A mathematical model describes these processes and its dynamics reflect the experimental results
332 citations
TL;DR: The deduced amino acid sequence of GAP1 protein presents strong similarities to those of the yeast arginine, histidine and proline permeases, suggesting a common evolutionary origin for these amino acid permeases.
Abstract: In Saccharomyces cerevisiae, mutations at the GAP1 locus selectively abolish the activity of the general amino acid transport system. This permease catalyses active transport of apparently all biological amino acids across the plasma membrane. We have determined the nucleotide sequence of the GAP1 gene. The sequence contains an open reading frame of 601 codons corresponding to a polypeptide of Mr 65578. This polypeptide is strongly hydrophobic; it exhibits three potential glycosylation sites. Hydropathy analysis suggests 12 membrane-spanning regions. The N-terminal domain is charged, it does not resemble hydrophobic signal sequences found in secreted proteins. Hence the GAP1 gene encodes a protein with characteristics typical of integral membrane proteins translocating ligants across cellular membranes. The deduced amino acid sequence of GAP1 protein presents strong similarities to those of the yeast arginine, histidine and proline permeases, suggesting a common evolutionary origin for these amino acid permeases. Nitrogen-source regulation of the GAP1 permease is believed to occur at two distinct levels, i.e. permease synthesis and permease activity [Grenson (1983) Eur. J. Biochem. 133, 135-139]. Northern analysis of GAP1-specific transcripts in wild-type and in mutant strains is in agreement with these views and indicates that nitrogen catabolite repression of GAP1 synthesis occurs at the RNA level.
292 citations
TL;DR: The cDNA of an unidentified recently cloned G protein-coupled receptor, RDC8, has been expressed in Y1 adrenal cells, in dog thyrocytes in primary culture and in Xenopus oocytes, and this physiologically constitutive activator was inhibited by adenosine deaminase and by inhibitors of the adenosines A2 receptor.
283 citations
TL;DR: Compared by immunohistochemistry the localization of both calcium-binding proteins in the retina of monkey, pig, sheep, rat, cat, pigeon, and salamander, there are many differences between species and not within species, but some aspects of the distribution are conserved.
Abstract: Calbindin-D28K and calretinin are homologous calcium-binding proteins localized in many neurons of the central nervous systems. We have compared polyclonal antibodies against calbindin and calretinin and have shown by western blots using purified calbindin and calretinin from rat that (1) anti-calretinin does not recognize calbindin and (2) anti-calbindin presents some cross-reactivity with calretinin. In this report, we have compared by immunohistochemistry the localization of both calcium-binding proteins in the retina of monkey, pig, sheep, rat, cat, pigeon, and salamander. These results are compared with previous data for chick. There are many differences between species and not within species, but some aspects of the distribution are conserved. All species, except rat and monkey, have some cones which contain calbindin only. Most species also have some bipolar cells containing calbindin only. Calretinin is rarely seen in photoreceptors or bipolar cells. All species have horizontal cells which contain calretinin or calbindin or both. All species have amacrine cells and ganglion cells containing one or other protein. In the cat ganglion cell layer, the calretinin antisera define a new, asymmetric, type of cell.
258 citations
TL;DR: Analysis of time series of satellite images is a promising way to assess in a quantitative and synoptic way the patchy distribution of phytoplankton over large regions, as the balance between primary production and consumption of organic matter appears to vary both geographically and seasonally.
Journal Article•
TL;DR: Himbacine and methoctramine were shown to discriminate two muscarinic receptor subtypes having a high affinity for 4-diphenylacetoxy-N-methylpiperidine methiodide and hexahydrosiladifenidol, intermediate affinity for pirenzepine, and low affinity for AF-DX 116.
Abstract: To compare the proportions of four muscarinic receptors in different rat brain regions, we used competition curves with four selective antagonists, at 1-[N-methyl-3H]scopolamine methyl chloride [( 3H]NMS) binding equilibrium and after allowing [3H]NMS dissociation for 35 min. Himbacine and methoctramine were shown to discriminate two muscarinic receptor subtypes having a high affinity for 4-diphenylacetoxy-N-methylpiperidine methiodide and hexahydrosiladifenidol, intermediate affinity for pirenzepine, and low affinity for AF-DX 116. One M4 subtype had a high affinity for himbacine and methoctramine; it was found predominantly in homogenates from rat striatum (46% of total [3H]NMS receptors) and in lower proportion in cortex (33% of [3H]NMS receptors) and hippocampus (16% of [3H]NMS receptors). Its binding properties were identical to those of muscarinic receptors in the neuroblastoma x glioma NG 108-15 hybrid, suggesting that it was encoded by m4 mRNA. The M3 subtype (typically found in rat pancreas, a tissue expressing the m3 mRNA) had a low affinity for himbacine and methoctramine and represented about 10% of all [3H]NMS receptors in rat brain cortex, hippocampus, striatum, and cerebellum. M1 and M2 receptors were identified in rat brain by their high affinity for pirenzepine and AF-DX 116, respectively.
01 Dec 1990
TL;DR: The Lagrangian approach to the BRST symmetry based on the antifield formalism is reviewed in this article, where the concept of open algebra is clarified, and the problem of spacetime locality of the gauge fixed action is also briefly addressed.
Abstract: The Lagrangian approach to the BRST symmetry based on the antifield formalism is reviewed. First, the concept of “open algebra” is clarified. It is then explicitly indicated how gauge invariance is incorporated in the theory through the BRST cohomology at ghost number zero. This result holds for both the non-gauge fixed and gauge fixed versions of the BRST symmetry in Lagrangian form. The properties of the Lagrangian integration measure are discussed and the role of the Schwinger-Dyson equation is stressed. The problem of spacetime locality of the gauge fixed action is also briefly addressed. The discussion is illustrated in the cases of electromagnetism and of free p-form gauge fields.
TL;DR: In this article, the precise relation between the gauge transformations in lagrangian and hamiltonian form is derived for any gauge theory, and the analysis yields as by-products: (i) a systematic way to derive all the gauge symmetries of a given Lagrangian; (ii) a precise criterion for counting the physical degrees of freedom of a gauge theory directly from the form of gauge transformations.
TL;DR: In both muscles, motor units of different force thresholds showed a proportionally identical twitch tension decrease and slowing of their time course after immobilization, document motoneuronal plasticity in human muscles of different fibre type composition.
Abstract: 1. The contractile properties, recruitment and firing rates of motor units from the human adductor pollicis and the first dorsal interosseous were studied during voluntary isometric contractions after 6-8 weeks' immobilization of the corresponding limbs. 2. In both muscles, motor units of different force thresholds showed a proportionally identical twitch tension decrease and slowing of their time course after immobilization. 3. When expressed as a percentage of the maximal voluntary contraction, more high-threshold motor units were recorded in disused muscles than in control muscles, but the order of recruitment was maintained. 4. The motor unit firing rate at recruitment was identical in control and disused muscles, but the maximal firing rate decreased in all motor units after immobilization. This decrease of the maximal firing rate was greater in motor units of lower threshold than in those of higher threshold. 5. The results further document motoneuronal plasticity in human muscles of different fibre type composition.
TL;DR: It is proved that the field alone cannot create a low-frequency coherence exceeding this threshold and it is analyzed the double-\ensuremath{\Lambda} configuration involving a four-level medium in which the upper and lower pairs of atomic levels have a high-frequency separation while optical transitions take place between the two pairs of states.
Abstract: We study the propagation of a bichromatic field in three-level and four-level media. In the case of a three-level medium, we consider the \ensuremath{\Lambda} configuration and demonstrate that if the upper level is not empty there is a critical value for the low-frequency coherence such that below this threshold and for intense fields, coherent bleaching occurs. This implies a sharp reduction of the field absorption and the fluorescence emission whereas above this threshold a parametric instability takes place. It corresponds to an amplification of the field that does not need a population inversion between the optical transitions. Finally we prove that the field alone cannot create a low-frequency coherence exceeding this threshold. Therefore we analyze the double-\ensuremath{\Lambda} configuration involving a four-level medium in which the upper and lower pairs of atomic levels have a low-frequency separation while optical transitions take place between the two pairs of states. An intense bichromatic field that is resonant with one upper state and the lower levels and a weak bichromatic field resonant with the other upper state and the same two lower states are sent into the medium. We analyze the limit in which the low-frequency coherence created between the lower pair of states has a relaxation time which is large. Then there will be population trapping in the lower states leading to coherent bleaching if there is no inversion between the upper levels but there will be amplification if there is inversion between the upper levels. In this way amplification at the optical transitions without population inversion between these states is realized.
TL;DR: For dynamical systems of large spatial extension giving rise to transport phenomena, like the Lorentz gas, a relationship between the transport coefficient and the difference between the positive Lyapunov exponent and the Kolmogorov-Sinai entropy per unit time is established.
Abstract: For dynamical systems of large spatial extension giving rise to transport phenomena, like the Lorentz gas, we establish a relationship between the transport coefficient and the difference between the positive Lyapunov exponent and the Kolmogorov-Sinai entropy per unit time, characterizing the fractal and chaotic repeller of trapped trajectories. Consequences for nonequilibrium statistical mechanics are discussed.
TL;DR: The data strongly suggest that the intracellular accumulation of parvoviral NS products jeopardizes the survival of the cells, which cannot be detected unless a threshold protein concentration is reached, and confirms the essential role played by the NS proteins in the parVoviral cytotoxicity.
Abstract: Although its dependence on the target cell type is well established, the cytopathogenicity of parvoviruses has remained elusive to date as far as its mechanism is concerned However, indirect evidence suggested that parvoviral non-structural (NS) proteins may be the cytotoxic effectors In order to test this hypothesis, a molecular clone of parvovirus MVMp was modified, by replacing the P4 promoter of the NS transcription unit by the glucocorticoid-inducible promoter of the mouse mammary tumour virus Clones of neoplastic human cells that had incorporated this construct and that were induced to produce NS proteins by dexamethasone, showed a cytopathic effect and eventually died Our data strongly suggest that the intracellular accumulation of parvoviral NS products jeopardizes the survival of the cells, which cannot be detected unless a threshold protein concentration is reached Interestingly, a cell variant could be isolated which resisted dexamethasone-induced killing, although it was fully inducible for the production of NS proteins This variant was also unusually resistant to infection with MVMp virions, thus confirming the essential role played by the NS proteins in the parvoviral cytotoxicity and indicating that the cytocidal activity of the parvoviral NS products is modulated by cellular factors that may vary from one cell to another
TL;DR: The results demonstrate unequivocally that a single transcription unit has the potential to encode receptor molecules coupled to both cascades in intracellular cascades.
TL;DR: In this paper, the structure of the adriamycin-cardiolipin complex has been investigated by using physico-chemical techniques and via conformational analysis, and the results open a rational way to design new structures that are less cardiotoxic.
TL;DR: Five life-threatening anaphylactoid reactions occurring within the very first minutes of hemodialysis on polyacrylonitrile (AN69) capillary dialyzers in three patients receiving ACE inhibitors are reported.
01 Oct 1990
TL;DR: This paper adopted a largely pragmatic attitude attempting to find the best hybridizing between the biological lessons and the engineering needs to satisfy internal "viability" constraints.
Abstract: Biology gives us numerous examples of self-assertional systems whose essence does not precede their existence but is rather revealed through it. Immune system is one of them. The fact of behaving in order not only to satisfy external constraints as a pre-fixed set of possible environments and objectives, but also to satisfy internal "viability" constraints justifies a sharper focus. Adaptability, creativity and memory are certainly interesting "side-effects" of such a tendency for self-consistency. However in this paper, we adopted a largely pragmatic attitude attempting to find the best hybridizing between the biological lessons and the engineering needs. The great difficulty, also shared by neural net and GA users, remains the precise localisation of the frontier where the biological reality must give way to a directed design.
TL;DR: The time-dependent solution of the periodically forced Fokker-Planck equation is determined, following an iteration procedure, and the mixing property of the system is verified.
Abstract: The time-dependent solution of the periodically forced Fokker-Planck equation is determined, following an iteration procedure. The mixing property of the system is verified. The enhancements of the autocorrelation and the signal-to-noise ratio are distinguished and localized, in different noise strength regions. The conditions for the validity of the adiabatic approximation and the way to systematically improve the adiabatic result are clarified.
TL;DR: The human thyrotropin receptor cDNA was transfected in CHO cells and individual clones were isolated for their response to thyrotopin, forskolin and antibodies from a patient with high levels of thyroid stimulating antibodies.
TL;DR: In this paper, the algebraic structure of the antifield-antibracket formalism for both reducible and irreducible gauge theories is clarified by using the methods of Homological Perturbation Theory.
Abstract: The algebraic structure of the antifield-antibracket formalism for both reducible and irreducible gauge theories is clarified. This is done by using the methods of Homological Perturbation Theory (HPT). A crucial ingredient of the construction is the Koszul-Tate complex associated with the stationary surface of the classical extremals. The Koszul-Tate differential acts on the antifields and is graded by the antighost number. It provides a resolution of the algebraA of functions defined on the stationary surface, namely, it is acyclic except at degree zero where its homology group reduces toA. Acyclicity only holds because of the introduction of the ghosts of ghosts and provides an alternative criterion for what is meant by a proper solution of the master equation. The existence of the BRST symmetry follows from the techniques of HPT. The classical Lagrangian BRST cohomology is completely worked out and shown to be isomorphic with the cohomology of the exterior derivative along the gauge orbits on the stationary surface. The algebraic structure of the formalism is identical with the structure of the Hamiltonian BRST construction. The role played there by the constraint surface is played here by the stationary surface. Only elementary quantum questions (general properties of the measure) are addressed.
TL;DR: It is suggested that extensive reading can provide learners with a set of linguistic models which may then, by a process of over-learning, be assimilated and incorporated into learners' active L2 repertoire.
TL;DR: A one-dimensional theory of dynamical hysteresis in periodically switched bistable systems is formulated and a law for the increase in input power necessary to maintain repetitive switching of the bistables system as the driving frequency is increased is deduced.
Abstract: A one-dimensional theory of dynamical hysteresis in periodically switched bistable systems is formulated. The predictions of the theory are tested and verified by experiments on a bistable semiconductor laser. We find that the increase of the area of the hysteresis loop scales as the two-thirds power of the switching frequency. From this, we deduce a law for the increase in input power necessary to maintain repetitive switching of the bistable system as the driving frequency is increased.
TL;DR: This cloning of putative G protein-coupled receptor by selective amplification using the polymerase chain reaction and degenerate primers corresponding to conserved regions of known receptors led to the cloning of the TSH receptor, where HGMP08 appeared as preferentially expressed in the brain.
Abstract: We described previously the cloning of putative G protein-coupled receptor by selective amplification using the polymerase chain reaction and degenerate primers corresponding to conserved regions of known receptors (1). This approach led to the cloning of the TSH receptor (2). Amongst the other characterized clones, HGMP08 appeared as preferentially expressed in the brain. The full coding region was isolated by screening a human brain stem library constructed in lambda gt l l . Sequencing on both strands was performed after subcloning in M13mp derivatives. This clone was identified as a human cannabinoid receptor clone, based on its high similarity with the rat cannabinoid receptor cDNA published recently (3). Human and rat sequences are 90% identical in terms of nucleotides and 98% in terms of amino acids. Complete functional characterization is now under investigation.
TL;DR: In this paper, the authors present different examples of floating-force kinetics obtained from polymeric matrix floating forms, amongst which several are marketed products and others have undergone in vivo experiments conducted on human volunteers.