Showing papers by "Université catholique de Louvain published in 1989"
TL;DR: The unprocessed Gag precursor from HIV-1, when expressed in recombinant baculovirus-infected insect cells, is targeted to the plasma membrane and assembles in 100-120 nm particles budding from the cell surface, mimics HIV immature particle formation.
777 citations
TL;DR: The central ingredient in this scheme is an efficient use of the ``2n+1'' theorem of the perturbation theory, which allows us to obtain the third-order derivatives of the total energy by using only byproducts of a first-order perturbations calculation.
Abstract: We propose a general scheme, within the density-functional theory, for an accurate computation of a large class of nonlinear-response coefficients of solids The scheme is applicable to all kinds of adiabatic perturbations of the crystal ground state, such as the application of mechanical strains, static electric fields of any wavelength, or individual atomic displacements, and allows the study of coefficients which describe anharmonicities or coupling of simultaneously applied disturbances Total-energy changes as a function of the perturbation wavelength, as needed to obtain phonon group velocities, can also be considered The formalism, which avoids the use of supercells and large-matrix inversions, contains as a special case the treatment of linear-response coefficients recently suggested by Baroni, Giannozi, and Testa The central ingredient in our scheme is an efficient use of the ``2n+1'' theorem of the perturbation theory, which allows us to obtain the third-order derivatives of the total energy by using only byproducts of a first-order perturbation calculation
313 citations
TL;DR: Results show that setting occurs after dissolution of MCPM, as a result of the precipitation of dicalcium phosphate dihydrate (DCPD) in the paste, and the ultimate tensile strength of the hardened cement is proportional to the amount of DCPD formed.
274 citations
01 Jan 1989
251 citations
TL;DR: It is shown in this paper that transcription of virF is thermodependent and presumably autoregulated, and that virF activates transcription of the yop genes independently of the presence of calcium ions.
Abstract: Virulent yersiniae (Yersinia pestis, Y. pseudotuberculosis, and Y. enterocolitica) restrict their growth at 37 degrees C in rich medium deprived of calcium. This property, called calcium dependency, correlates with the secretion of Yersinia outer membrane proteins (Yops) and with pathogenicity. It is mediated by a 70-kilobase plasmid called pYV. The structural genes of the Yops (yop genes), as well as genes involved in the control of their expression (vir genes), have been localized on pYV. In this communication we show that virF encodes a transcriptional activator controlling the yop regulon. This activator is a 30,879-dalton protein related to AraC, the regulator of the Escherichia coli and Salmonella typhimurium arabinose operons. We also show in this paper that transcription of virF is thermodependent and presumably autoregulated. virF is thus responsible for the effect of temperature on the production of the Yops. Finally, we show that virF activates transcription of the yop genes independently of the presence of calcium ions. The role of calcium therefore remains unaccounted for.
249 citations
TL;DR: In this paper, a model with two firms competing in location and sales is analyzed for the case of spatial discrimination, where consumers are uniformly distributed along a line segment and have identical downward sloping demands.
214 citations
TL;DR: The gene, encoding the A4 peptide found in the amyloid core of senile plaques isolated from the cerebral cortex of patients with Alzheimer's disease, produces at least three precursors that resemble cell surface receptors.
Abstract: The gene, encoding the A4 peptide found in the amyloid core of senile plaques isolated from the cerebral cortex of patients with Alzheimer's disease, produces at least three precursors that resemble cell surface receptors. A clone isolated from a human brain complementary DNA library contained the structural sequence for an A4 amyloid peptide precursor with a serine protease inhibitor domain in which 208 amino acids at the carboxyl terminal are replaced by 20 amino acids derived from nucleotide sequences with homology to the Alu repeat family. This protein devoid of the transmembrane domain most likely represents a secreted form of the A4 amyloid peptide precursor.
212 citations
TL;DR: The MIP1 gene encodes the catalytic subunit of the replicative mitochondrial DNA polymerase, which exhibits sequence similarities with both eukaryotic nuclear DNA polymerases and reverse transcriptases.
196 citations
TL;DR: In this paper, the authors discuss the principal theoretical and practical problems of the economics of collusion, collusion, and horizontal merger, and empirical tests of factors that facilitate or hinder collusion are of two sorts.
Abstract: Publisher Summary This chapter discusses the principal theoretical and practical problems of the economics of cartels, collusion, and horizontal merger. Because the new theoretical approaches are not easily modified to encompass welfare considerations, except in a very partial-equilibrium setting, the positive side of the analysis has received more weight than the normative. The principal factors that facilitate or hinder collusion are considered. The chapter discusses the types and extent of horizontal collusion. The principal forms of explicit agreement are cartels, joint ventures, and horizontal mergers. Empirical tests of factors that facilitate or hinder collusion are of two sorts: econometric and experimental. In a series of experiments described in the chapter, the pricing performance of an industry with and without certain types of contractual clauses, advance notice of price changes, and public price posting are compared. The combination of these practices is sufficient to raise price significantly above the level observed when the practices are removed.
183 citations
TL;DR: The transcription activator VirF is a member of a new family of regulators including those of the arabinose and rhamnose operons as well as a regulator of enteric colonization pili.
Abstract: Growth of yersiniae is restricted at 37 degrees C in the absence of calcium ions. This phenomenon correlates with the massive release of a set of proteins called Yops. Growth restriction and Yops production are governed by a 70 kb plasmid called pYV. yop genes are distributed throughout pYV and constitute a thermoactivated regulon controlled by the gene virF. The transcription activator VirF is a member of a new family of regulators including those of the arabinose and rhamnose operons as well as a regulator of enteric colonization pili. The role of calcium ions on the release of Yops remains largely unknown.
177 citations
TL;DR: In this paper, a specific characteristics framework is proposed to construct linkages between alternative conceptual approaches to model product differentiation, which is illustrated for the logit, probit and linear probability models of discrete choice theory.
Abstract: We propose a specific characteristics framework in order to construct linkages between alternative conceptual approaches to modelling product differentiation. First, it is shown that a demand system which satisfies the gross substitutes property imposes specific requirements on the locations of products. In particular, the dimension of the characteristics space must be larger than or equal to the number of products minus one. We then identify a method for casting a given demand system (subject to certain restrictions) into our characteristics framework. This is illustrated for the logit, probit and linear probability models of discrete choice theory. Finally, we find a characteristics representation of the CES representative consumer.
TL;DR: It is concluded that the regulator plays a role in the physiological control of the activity of glucokinase, particularly with respect to the stimulatory effect of fructose in isolated hepatocytes.
Abstract: At a concentration of 1 mM, fructose 1-phosphate stimulated about twofold, and glucose 6-phosphate inhibited by about 30%, the phosphorylation of 5 mM glucose in high-speed supernatants prepared from rat liver or from isolated hepatocytes, but did not affect, or barely so, the activity of a partially purified preparation of glucokinase. Anion-exchange chromatography of liver extracts separated glucokinase from a fructose-6-phosphate-sensitive and fructose-1-phosphate-sensitive inhibitor of that enzyme. This inhibitor could be further purified by chromatography on phospho-Ultrogel. It was destroyed by trypsin and was heat-labile. It inhibited glucokinase competitively with respect to glucose and its inhibitory effect was greatly reinforced by fructose 6-phosphate although not by glucose 6-phosphate. Fructose 1-phosphate relieved the enzyme of the inhibitory effect of the regulator and antagonised the effect of fructose 6-phosphate in a competitive manner. It is concluded that the regulator plays a role in the physiological control of the activity of glucokinase, particularly with respect to the stimulatory effect of fructose in isolated hepatocytes (see preceding paper in this journal).
TL;DR: The diametral strength of the specimen was found to level off at about 60% of its initial value, for ageing times beyond 1 d, and this behaviour has been ascribed to the progressive dissolution of the CSD fraction of the hardened cement, compensated by the crystallization of further amounts of DCPD.
TL;DR: In this paper, the changes of the catalytic properties in 1-butanol dehydration of γ-alumina modified by introduction of small amounts (02-20 wt %) of ions: SO 4 2−, PO 4 3−, Cl −, F −, Mg 2+ and Na +.
TL;DR: These findings suggest that the secretion of IGF-I and at least one IGF-BP may be linked, providing a mechanism by which their extracellular fluid concentrations are coordinated.
Abstract: The insulin-like growth factors (IGFs) are small peptides that are present in serum and extracellular fluids and stimulate the growth of many cell types. In extracellular fluids the IGFs are bound to carrier proteins that are believed to modify the biological actions of the IGFs. At least three structurally distinct IGF-binding proteins (IGF-BPs) have been identified, and the serum concentrations of one of these has been shown to be regulated by pituitary GH. We report here that this GH responsive protein [39,000-45,000 mol wt (Mr)] can be induced (7-fold) by infusion of IGF-I in hypophysectomized rats or (3.5-fold) in protein-deprived rats, whereas two other forms of IGF-BP (e.g. 31,000-34,000 and 24,000 Mr) showed no change in the hypophysectomized animals and minimal increases in the protein-deprived animals. Likewise, GH injections in hypophysectomized animals resulted in a 7-fold increase in the 39,000-45,000 Mr form and no change in the 31,000-34,000 and 24,000 Mr forms. The protein-deprived animals showed a 3.2-fold increase in the 39,000-45,000 Mr and 2.4- to 1.8-fold increases in the 31,000-34,000 and 24,000 Mr forms, respectively. Changes in the larger Mr IGF-BP in these experimental models are paralleled by changes in serum IGF-I, suggesting that the GH dependence of the former protein is mediated at least partially via IGF-I. Our findings also suggest that the secretion of IGF-I and at least one IGF-BP may be linked, providing a mechanism by which their extracellular fluid concentrations are coordinated. Because IGF-BPs are present in extracellular fluids and can modulate IGF-I-receptor interaction, induction of this protein may be an important mediator of IGF action.
TL;DR: In this patient, a lesion of this pathway related to the cerebellar infarct probably explains the homolateral cessation of essential tremor.
Abstract: The case of a patient with essential tremor in whom tremor disappeared on the right side after a homolateral cerebellar infarct is reported. The pathophysiology of essential tremor remains unknown. Vascular and surgical lesions of dentorubrothalamic pathway have been reported to improve various kinds of tremor including essential tremor. In this patient, a lesion of this pathway related to the cerebellar infarct probably explains the homolateral cessation of essential tremor.
TL;DR: This tumor cell growth inhibitory effect was completely suppressed by the addition of catalase to the culture medium containing vitamins C and K3, suggesting an excessive production of hydrogen peroxide as being implied in mechanisms responsible for the above‐mentioned effects.
Abstract: The effects of sodium ascorbate (vitamin C) and 2-methyl-1,4-naphthoquinone (vitamin K3) administered separately or in combination on the in vitro cultured human neoplastic cell lines MCF-7 (breast carcinoma), KB (oral epidermoid carcinoma), and AN3-CA (endometrial adenocarcinoma) have been examined. When given separately, vitamin C or K3 had a growth inhibiting action only at high concentrations (5.10(3) mumol/1 and 10(5) nmol/l, respectively). Combined administration of both vitamins demonstrated a synergistic inhibition of cell growth at 10 to 50 times lower concentrations. At this level separately given vitamins are not toxic. The sensitivity to this treatment was somewhat different in the three cell lines, being slightly higher for KB line. This tumor cell growth inhibitory effect was completely suppressed by the addition of catalase to the culture medium containing vitamins C and K3, suggesting an excessive production of hydrogen peroxide as being implied in mechanisms responsible for the above-mentioned effects.
TL;DR: It appears from this study that semi-continuous cultivation in spinner flasks of hybridoma cells, after cloning and progressive adaptation, in a chemically defined, serum- and protein-free medium, permitted MAb secretion to be increased to a mean of 144 micrograms/ml.
TL;DR: Recognition of depth insufficiency in the proximal portion of the trochlea should prompt a search for patellar instability.
Abstract: The depth of the trochlear groove was frequently noted to be insufficient in knees with patellar instability, particularly in the proximal portion of the trochlea. To confirm this observation, the depth of the trochlear groove of the femur was measured on lateral radiographs of 218 knees: 40 knees in 20 asymptomatic subjects, 116 knees in 69 patients undergoing radiography for various symptoms (96 without and 20 with patellar subluxation, determined on axial radiographs), and 62 knees in 34 patients who underwent surgery for recurrent dislocation or subluxation of one or both patellae (40 treated and 22 contralateral knees). In the 40 knees that had been operated on, the proximal trochlear depth (measured 1 cm below the upper limit of the trochlear groove) was 2.74 mm +/- 1.35, in contrast to 5.94 mm +/- 1.74 in the asymptomatic subjects and 5.84 mm +/- 1.53 in the patients with symptoms but no patellar instability. Recognition of depth insufficiency in the proximal portion of the trochlea should prompt a search for patellar instability. Axial views made with 30 degrees of knee flexion and lateral rotation of the leg are particularly helpful.
TL;DR: In this study, progressive deletions of the PMA1 promoter fused to the beta-galactosidase gene have identified two upstream activating sequences that have high homologies with the consensus sequence known to control the expression of the ribosomal protein genes (RPG).
TL;DR: Because the uptake of aminoglycosides by the kidney is saturable, administration of daily doses of these drugs as one or two injections, rather than as multiple injections or by continuous infusion, may also decrease the risk for toxicity.
TL;DR: Results suggest that positron emission tomography with [18F] fluorodeoxyglucose may provide an index of cell and processes degeneration in the striatum in striatonigral degeneration and is able to detect functional deficits in frontal cortex.
Abstract: Nine positron emission tomography studies of regional cerebral glucose metabolism were performed in 7 patients with probable striatonigral degeneration, a disorder characterized by parkinsonian features and absent or poor response to L-dopa. When compared with values obtained in normal volunteers, mean cerebral glucose metabolism was slightly reduced in subjects with striatonigral degeneration who, in addition, had a marked (20.5%, +/- 3 SD) relative hypometabolism in putaminal and caudate nuclei. Significant hypometabolism was also found in motor/premotor as well as in prefrontal cortex. In 2 subjects who were studied twice a deterioration of relative striatal metabolism paralleled clinical evolution. Magnetic resonance imaging disclosed the presence of abnormal iron deposits in the putamen in all cases but showed no cortical anomalies. These results suggest that positron emission tomography with [18F]fluorodeoxyglucose may provide an index of cell and processes degeneration in the striatum in striatonigral degeneration and is able to detect functional deficits in frontal cortex. The presence of striatal hypometabolism might be a predictor of a poor response to L-dopa.
TL;DR: The properties of yeast trehalose-6-phosphate synthase were reinvestigated in relation with the recent claim made by Panek et al. that the enzyme would be stimulated by ATP and partially inactivated by cAMP-dependent protein kinase, suggesting that they are part of a single bifunctional protein.
Abstract: The properties of yeast trehalose-6-phosphate synthase were reinvestigated in relation with the recent claim made by Panek et al. [Panek, A. C., de Araujo, P. S., Moura-Neto, V. and Panek, A. D. (1987) Curr. Genet. II, 459-465] that the enzyme would be stimulated by ATP and partially inactivated by cAMP-dependent protein kinase. Trehalose-6-phosphate synthase activity was measured by the sum of [14C]trehalose 6-phosphate and [14C]trehalose formed from UDP-[14C]glucose and glucose 6-phosphate. The activity measured in an extract of Saccharomyces cerevisiae was not affected by any treatment of the cells, such as incubation in the presence of glucose or of dinitrophenol, which are known to greatly increase the intracellular concentration of cAMP, nor by preincubation of the extract in the presence of ATP-Mg, cAMP and bovine heart cAMP-dependent protein kinase. The activity was also not significantly different in several mutants affected in the cAMP system. The kinetic properties of the partially purified enzyme were investigated; no effect of ATP could be detected but Pi acted as a potent noncompetitive inhibitor (Ki = 2 mM). The activity of trehalose-6-phosphate phosphatase was measured by the amount of [14C]trehalose formed from [14C]trehalose 6-phosphate. The enzyme could be separated from other phosphatases and appeared to be highly specific for trehalose 6-phosphate. It was Mg dependent and its kinetics for trehalose 6-phosphate was hyperbolic. Studies performed with intact cells, crude extracts or the purified enzyme did not reveal any cAMP-dependent change in its activity. Remarkably, trehalose-6-phosphate synthase and trehalose-6-phosphate phosphatase copurified in the course of different chromatographic procedures, suggesting that they are part of a single bifunctional protein. A 50-fold purification of the two enzymes could be achieved with a yield of only 2% by chromatography on Mono S followed by gel filtration on Superose 6B.
TL;DR: This paper describes the mutagenesis of the pYV plasmid from Yersinia enterocolitica W22703 (serotype O:9) with Tn2507, a new element generating operon fusions, and identifies an additional Yop protein called Yop20 and the mapping of yop20, yop44, Yop48, and lcrV, the gene encoding the V antigen.
Abstract: This paper describes the mutagenesis of the pYV plasmid from Yersinia enterocolitica W22703 (serotype O:9) with Tn2507, a new element generating operon fusions. Analysis of the mutants allowed the identification of an additional Yop protein called Yop20 and the mapping of yop20, yop44, yop48, and lcrV, the gene encoding the V antigen. The last gene appeared to be part of an operon that also may contain yop37 and yop44. At 37 degrees C, mutants affected in this operon grew poorly, irrespective of the presence of Ca2+, or they even died in the presence of Ca2+. This operon is thus involved in the regulation by Ca2+, and we called it car, for Ca2+ regulation. It is presumably the Y. enterocolitica counterpart of the lcrGVH operon of Yersinia pestis. Transcription of yop20 and of the car operon was strongly regulated by temperature and only slightly by calcium. Hence, these genes behaved like the other genes of the yop regulon. Mutants affected in yop20 or in yop48 were markedly less virulent for the desferrioxamine-treated mouse than was the parental strain. Yop20 and Yop48 thus probably are Yersinia virulence factors.
TL;DR: The characteristics of eight pedons developed in Quaternary basaltic pyroclasts in Western Cameroon under humid tropical conditions are reported in this paper, where the soil weathering sequence consists of an Andept-Tropept-Udalf-Uddult association.
TL;DR: Three cases of spontaneous healing of aneurysmal bone cysts suggest that when the diagnosis can be made with confidence, and the lesion is in a location and at a stage that does not entail any risk of fracture or compression, expectant management should be considered.
Abstract: We report three cases of spontaneous healing of aneurysmal bone cysts (ABC). In one case histological material was obtained after resection of the already ossified expansile mass discovered as a lytic lesion seven months previously. In the two other patients, spontaneous ossification of a radiologically presumed ABC in the lytic and expansile phase was observed after nine and seven months respectively. The healed lesions have remained stable at 12, 32, and 36 months respectively. These findings suggest that when the diagnosis can be made with confidence, and the lesion is in a location and at a stage that does not entail any risk of fracture or compression, expectant management should be considered. Our three patients were aged 22, 19 and 18 years, older than usual for developing ABC. This is also true for many of the few other reported cases of spontaneous or almost spontaneous healing and suggests that ABC has a greater tendency to stabilise in older patients.
01 Sep 1989
TL;DR: A carry-free division algorithm is described based on the properties of redundant signed digit (RSD) arithmetic to avoid carry propagation and uses the minimum hardware per bit, i.e. one full adder.
Abstract: A carry-free division algorithm is described. It is based on the properties of redundant signed digit (RSD) arithmetic to avoid carry propagation and uses the minimum hardware per bit, i.e. one full adder. Its application to a 1024-b RSA (Rivest, Shamir, and Adelman) cryptographic chip is presented. The features of this new algorithm allowed high performance (8 kb/s for 1024-b words) to be obtained for relatively small area and power consumption (80 mm/sup 2/ in a 2- mu m CMOS process and 500 mW at 25 MHz). >
TL;DR: Arthroscopic drainage is a method that has proved effective, with minimal morbidity, in attempts to cure septic arthritis of the knee, particularly in cases of hematogenous arthritis, and could also be effective in total arthroplasties of septic knees.
Abstract: The results are presented of a multicenter study, conducted by questionnaire, of 46 cases of septic arthritis of the knee treated by arthroscopic drainage. This series consisted of 28 male and 16 female patients. Two patients had bilateral arthritides. The average follow-up period was 7.1 months. There were 11 cases of hematogenous arthritides, 15 arthritides secondary to puncture and infiltration, and 20 postoperative arthritides. There were 29 positive cultures (63%). After thorough articular lavage (average, 7 L) and prolonged antibiotic therapy (average 2 months) there were 36 bacteriological cures (78.3%), five failures (10.9%) due to persistent articular sepsis, and five recurrences of the infection (10.9%) after an initial remission. Five infectious flare-ups recovered secondarily, four recovered after repeated arthroscopy and one recovered after synovial centesis. The rate of cure after this second therapeutic attempt was 89.2%. Different parameters were used in evaluating the quality of the results: the etiology of the arthritis, the causal germ, and the delay prior to arthroscopy. Arthroscopic drainage is a method that has proved effective, with minimal morbidity, in attempts to cure septic arthritis of the knee, particularly in cases of hematogenous arthritis. This method could also be effective in total arthroplasties of septic knees.
TL;DR: The sensitivity of the Earth's orbital frequencies, involved in the astronomical theory of palaeoclimates, to the Earth-Moon distance and consequently to the length of the day and to the dynamical ellipticity, has been investigated for the last billion years.
Abstract: The sensitivity of the Earth's orbital frequencies, involved in the astronomical theory of palaeoclimates, to the Earth-Moon distance and consequently to the length of the day and to the dynamical ellipticity of the Earth has been investigated for the last billion years. The shortening of the Earth-Moon distance and of the length of the day back in time induces a shortening of the fundamental astronomical periods for the obliquity and the precession, a shortening which is larger for the longer periods. These periods of precession and obliquity influenced by the changing Earth-Moon distance, length of the day and dynamical ellipticity of the Earth, have been recomputed for the last 440 million years.