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See detailSite-directed mutagenesis of dicarboxylic acid residues of the penicillin-binding module of the Escherichia coli penicillin-binding protein 3
Goffin, Colette ULg; Ayala, J. A.; Nguyen-Distèche, Martine ULg et al

in FEMS Microbiology Letters (1993), 113(3), 247-251

The glutamic acid E396, aspartic acid D409 and glutamic acid E411 residues of the Escherichia coli penicillin-binding protein 3 were each converted into an alanine residue. As deduced from penicillin ... [more ▼]

The glutamic acid E396, aspartic acid D409 and glutamic acid E411 residues of the Escherichia coli penicillin-binding protein 3 were each converted into an alanine residue. As deduced from penicillin-binding and complementation experiments, none of these dicarboxylic acid residues is involved in the mechanism of acylation by penicillin and none of them is essential for the in vivo functioning of the PBP. The mutation E396, however, causes an increased thermolability of the protein. [less ▲]

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See detailLongterm Photometry of Variables at ESO - Part Two - the Second Data Catalogue 1986-1990
Sterken, C.; Manfroid, Jean ULg; Anton, K. et al

in Astronomy and Astrophysics. Supplement Series (1993), 102

In this paper we present the second catalogue of photometric data in the Strömgren system obtained during the period October 1986- September 1990 in the framework of the Long-Term Photometry of Variables ... [more ▼]

In this paper we present the second catalogue of photometric data in the Strömgren system obtained during the period October 1986- September 1990 in the framework of the Long-Term Photometry of Variables (LTPV) program at the European Southern Observatory. The catalogue is available in computer readable form at the Centre de Données de Strasbourg. [less ▲]

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See detailInteractions between Active-Site-Serine Beta-Lactamases and Mechanism-Based Inactivators: A Kinetic Study and an Overview
Matagne, André ULg; Ghuysen, M. F.; Frère, Jean-Marie ULg

in Biochemical Journal (1993), 295((Pt 3)), 705-711

The interactions between three class A beta-lactamases and three beta-lactamase inactivators (clavulanic acid, sulbactam and olivanic acid MM13902) were studied. Interestingly, the interaction between the ... [more ▼]

The interactions between three class A beta-lactamases and three beta-lactamase inactivators (clavulanic acid, sulbactam and olivanic acid MM13902) were studied. Interestingly, the interaction between the Streptomyces cacaoi beta-lactamase and clavulanate indicated little irreversible inactivation. With sulbactam, irreversible inactivation was found to occur with the three studied enzymes, but no evidence for transiently inactivated adducts was found. Irreversible inactivation of the S. albus G and S. cacaoi enzymes was particularly slow. With olivanate, irreversible inactivation was also observed with the three enzymes, but with the S. cacaoi enzyme, no hydrolysis could be detected. A tentative summary of the results found in the literature is also presented (including 6 beta-halogenopenicillanates), and the general conclusions underline the diversity of the mechanisms and the wide variations of the rate constants observed when class A beta-lactamases interact with beta-lactamase inactivators, in agreement with the behaviours of the same enzymes towards their good and poor substrates. [less ▲]

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See detailFormation of P Cygni Line Profiles in Relativistically Expanding Atmospheres. II. The Effect of the Continuum Frequency Shape and Limb Darkening of the Core
Hutsemekers, Damien ULg

in Astrophysical Journal (1993), 417

Abstract image available at: http://adsabs.harvard.edu/abs/1993ApJ...417...97H

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See detailMixmaster universe in fourth-order gravity theories
Cotsakis, S.; Demaret, Jacques; De Rop, Yves ULg et al

in Physical Review. D : Particles and Fields (1993), 48

We analyze the behavior of the Bianchi type-IX cosmological model in the full fourth-order theory of gravity in four space-time dimensions on approach to the singularity both analytically and numerically ... [more ▼]

We analyze the behavior of the Bianchi type-IX cosmological model in the full fourth-order theory of gravity in four space-time dimensions on approach to the singularity both analytically and numerically. By directly analyzing the full fourth-order field equations we prove explicitly that the Belinski-Khalatnikov-Lifshitz (BKL) analytic solution (and the accompanying bounce law) is also a solution to the more general case that we consider. But it appears to be nongeneric, because a perturbation analysis shows that power-law Kasner asymptotes are unstable on approach to the singularity. On the other hand, we find that the model possesses a stable isotropic monotonic power-law asymptotic solution and accordingly we show that there is a general solution which is nonchaotic near the space-time singularity. Numerical experiments confirm the existence of such a behavior. The inclusion of matter fields does not alter the evolution in the neighborhood of the singularity. The role of space-time dimensionality on the chaotic evolution of the mixmaster universe in these theories is also spelled out. In particular, we show that it is impossible to build a mixmaster universe in space-time dimensions higher than four in the full fourth-order gravity theory based on the BKL approximation scheme. [less ▲]

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See detailUse of G.I.S. and remote sensing in hydrological model for impact study of land cover change in a malagasy rural basin
Randriamaherisoa, Alain; Binard, Marc ULg; Persoons, Etienne

in International Journal "Advances in Remote Sensing" (1993), 2(3), 154-164

A conceptual distributed-based model has been developed for flood simulation and forecasting. The model structure consists of a square grid network, in analogy with the raster form of numerical maps. The ... [more ▼]

A conceptual distributed-based model has been developed for flood simulation and forecasting. The model structure consists of a square grid network, in analogy with the raster form of numerical maps. The square-pixel is the analysis unit for hydrologie balance in relation with physi-cal characteristics. Punctual and cartographical data sources are used to characterize each mesh. Aerial photo-graphy and satellite imagery give information about land use. Topographical characteristics are obtained from Digi-tal Terrain Model (DTM). Soil type can be numerized to help in estimating the drainage condition. Hydrological data are distributed in accordance with the Thiessen's polygons or the associated sub-basin. All the data are handled by the GIS part in order to classify the surface runoff potential of all meshes. This procedure allow to consider the physical characteristics and the spatial vari-ability of the parameters at small scale, to manage special devices like storm basins, pumping stations and spillways and to do a quick study of the spatio-temporal evolution of the characteristics. Impact analysis of land cover modi-fications on the river flow regime is therefore possible. In one large rural Malagasy watershed, rince the 1960's, several waterworks were achieved in order to struggle against the flooding of the upstream fertile plain (subject of various developments). Meanwhile, the forest of the basin hillslopes was and still strongly claimed for pluvial rice crop, which is necessary for the subsistence of a fast growing population. The main object of this work is to study the hydrological impacts of these changes of land use on the watershed behaviour and to forecast the basin water regime evolution. [less ▲]

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See detailTowards a rational utilization of satellite imagery for Lisbon's metropolitan planning
Binard, Marc ULg; Nadasdi, Istvan

in EARSeL International Journal "ADVANCES IN REMOTE SENSING" (1993), 2(3), 130-137

The knowledge of the actual structure and 'intensity of land cover is a fundamental information for the urban planning. Some aspects of the seeked information can be extracted from satellite imagery. This ... [more ▼]

The knowledge of the actual structure and 'intensity of land cover is a fundamental information for the urban planning. Some aspects of the seeked information can be extracted from satellite imagery. This presentation gives some exemples over the Metropolitan area of Lisbon. First, an image segmentation is accomplished over an XS3 band. This process leads to a rather valid subdivision of the region in morphological units. Secondly, the urban and vegetal categories, issued from a land cover classification, are modeled in the form of statistical surfaces. The statistical surfaces take advantage of the analytical power of a raster solving approach. Fi-nally, the urban and vegetal intensity surfaces are merged. The result can be considered as an attempt of ecozoning the considered region. The paper discuss also the possibilities of using remotly sensed data for urban planning. [less ▲]

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See detailPhysiologie de la femme enceinte et facteurs de risques
Foidart, Jean-Michel ULg

in Contraception, Fertilite, Sexualité (1992) (1993), 21(11), 811-5

Physiological adaptations of the pregnant woman involve the circulatory, respiratory, digestive, renal, endocrine and metabolic systems. Their precise knowledge allows the clinician to verify the quality ... [more ▼]

Physiological adaptations of the pregnant woman involve the circulatory, respiratory, digestive, renal, endocrine and metabolic systems. Their precise knowledge allows the clinician to verify the quality of the adaptation of the pregnant woman and to avoid unnecessary treatment of physiological changes misconsidered as pathological changes in reference to prepregnancy standards. [less ▲]

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See detailBenign Prostatic Hyperplasia and Normal Prostate Aging: Differences in Types I and Ii 5 Alpha-Reductase and Steroid Hormone Receptor Messenger Ribonucleic Acid (Mrna) Levels, but Not in Insulin-Like Growth Factor Mrna Levels
Bonnet, Pierre ULg; Reiter, E.; Bruyninx, M. et al

in Journal of Clinical Endocrinology and Metabolism (The) (1993), 77(5), 1203-8

Benign prostatic hyperplasia (BPH) is so common in elderly men that the development of adenomatous nodules in this organ can be seen as a normal age-dependent process. In this work, we used Northern ... [more ▼]

Benign prostatic hyperplasia (BPH) is so common in elderly men that the development of adenomatous nodules in this organ can be seen as a normal age-dependent process. In this work, we used Northern blotting to compare the levels of androgen, estrogen, and insulin-like growth factor-I (IGF-I) receptor in young (age range, 23-33; n = 3), old normal (age range, 52-80; n = 3), and BPH-affected subjects (age range, 66-87; n = 15). We have also investigated in these groups the expression of genes coding for the two 5 alpha-reductases (types I and II), aromatase, IGF-I, and IGF-II. Our results show significantly increased levels of IGF mRNA in old healthy and BPH-affected subjects; the respective rises for IGF-I, IGF-II, and IGF-I receptor mRNAs were 3.0-, 2.9-, and 1.5-fold (BPH) and 2.7-, 2.4-, and 1.8-fold (old normal controls). For estrogen receptor, androgen receptor, and type I and II 5 alpha-reductase mRNAs, a marked but opposite effect was observed in adenomatous tissues only; the respective levels were 2.2-, 1.8-, 3.9-, and 1.7-fold lower than those in young adult subjects, whereas no significant differences were recorded between the two normal groups. Morphometric analysis of each tissue specimen confirmed the significantly lower epithelium/stroma ratio in adenomas compared to young or old healthy tissues. Together, these observations suggest that prostatic adenomas may result from at least two conjugate processes: one characterized by a drop in the mRNA levels of steroid hormone receptors, which might be associated with a lower epithelium/stroma ratio, and another characterized by normal aging phenomena, of which the increased production of IGFs and IGF-I receptor transcripts could be biochemical markers. [less ▲]

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See detailHigh-field magnetization of U2T2X compounds (T = Co, Ni, Rh, Pd, Ir, Pt and X = In, Sn)
Nakotte, Heinz; Prokes, Karel; Brück, E. et al

Poster (1993, November)

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See detailEnhancement of Tumorigenicity of Human Breast Adenocarcinoma Cells in Nude Mice by Matrigel and Fibroblasts
Noël, Agnès ULg; Gillet, Marie-Claire ULg; Purnell, G. et al

in British Journal of Cancer (1993), 68(5), 909-15

The failure of MCF7 cells to induce the formation of tumours after sub-cutaneous inoculation into athymic nude mice can be obviated by the simultaneous injection of an extract of basement membrane ... [more ▼]

The failure of MCF7 cells to induce the formation of tumours after sub-cutaneous inoculation into athymic nude mice can be obviated by the simultaneous injection of an extract of basement membrane proteins (matrigel). Tumour growth is promoted and the latency period is low (2 to 4 weeks). In the absence of matrigel, the simultaneous inoculation of fibroblasts and MCF7 cells also resulted in the development of tumours, but with a longer latency period (about 2 months). The tumorigenic synergy between matrigel and fibroblasts was evidenced by co-inoculating MCF7 cells MDA-MB 231 cells with fibroblasts and matrigel. This co-inoculation decreased the delay of appearance of the tumours and/or accelerated the tumour growth, depending upon the number of fibroblasts injected. Repeated injections of fibroblasts conditioned medium, at the site of inoculum of tumour cells also enhanced tumour growth, suggesting the involvement of soluble factors secreted by fibroblasts. Histologically, tumours induced by co-inoculation of tumour cells and fibroblasts contained more stromal structures including vimentin-positive cells, fibronectin and interstitial collagens. These data suggest that human tumours may be reconstituted and grown in athymic nude mice using basement membrane components and fibroblasts as inductors. [less ▲]

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See detailAcute Suppression of Gonadotropin-Releasing Hormone Secretion by Insulin-Like Growth Factor I and Subproducts: An Age-Dependent Endocrine Effect
Bourguignon, Jean-Pierre ULg; Gerard, Arlette ULg; Alvarez Gonzalez, Maria-Luz ULg et al

in Neuroendocrinology (1993), 58(5), 525-30

Using rat hypothalamic explants, we showed previously that activation of N-methyl-D-aspartate (NMDA) receptors was involved in the mechanism of gonadotropin-releasing hormone (GnRH) secretion. (1-3 ... [more ▼]

Using rat hypothalamic explants, we showed previously that activation of N-methyl-D-aspartate (NMDA) receptors was involved in the mechanism of gonadotropin-releasing hormone (GnRH) secretion. (1-3)Insulin-like growth factor I (IGF-I), the N-terminal tripeptide of IGF-I, was suggested to be a possible antagonist at NMDA receptors. Here, we study the effects of IGF-I and its subproducts, (1-3)IGF-I and (4-70)IGF-I, either given in vivo as a single subcutaneous injection or used in vitro, on the secretion of GnRH by hypothalamic explants. At the three ages studied (15, 25 and 50 days), (4-70)IGF-I does not show any effect. At 50 days, the in vivo administration or the in vitro use of IGF-I results in a dose-related inhibition of the GnRH secretion induced by veratridine, a depolarizing agent. In addition, the spontaneous pulsatile secretion of GnRH in vitro is transiently suppressed after the in vivo administration of IGF-I. (1-3)IGF-I results in an inhibitory effect similar to that of IGF-I. At 25 days, IGF-I and (1-3)IGF-I show the same effects as at 50 days though higher concentrations are required. At 15 days, IGF-I does not show any effect whereas a potent inhibition of GnRH secretion is observed using (1-3)IGF-I either in vivo or in vitro. At all ages, the effects of (1-3)IGF-I parallel those of AP-5, a competitive antagonist at NMDA receptors.(ABSTRACT TRUNCATED AT 250 WORDS) [less ▲]

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See detailControl of Pulsatile Secretion of Gonadotrophin Releasing Hormone from Hypothalamic Explants
Bourguignon, Jean-Pierre ULg; Gerard, Arlette ULg; Alvarez Gonzalez, Maria-Luz ULg et al

in Human Reproduction (1993), 8 Suppl 2(NULL), 18-22

We have studied the secretion of gonadotrophin releasing hormone (GnRH) from hypothalamic explants of male rats at different ages in an attempt to delineate the neuroendocrine mechanism of the onset of ... [more ▼]

We have studied the secretion of gonadotrophin releasing hormone (GnRH) from hypothalamic explants of male rats at different ages in an attempt to delineate the neuroendocrine mechanism of the onset of puberty. In this paper, we review some of our recent studies and we provide evidence of a dual control played by receptors to neuroexcitatory amino acids. We showed previously that isolated explants of rat hypothalamus could secrete GnRH in a pulsatile manner. The onset of puberty was characterized by a 2-fold increase in frequency of GnRH secretory pulses. This reduction of the interval between GnRH pulses involved an inhibitory autofeedback effect of GnRH on the pulse generator which was shut off following a secretory episode. This period of refractoriness was longer before puberty than after the onset of puberty. Activation of receptors to neuroexcitatory amino acids (N-methyl-D-aspartate; NMDA-type) was involved in the mechanism of pulsatile GnRH secretion. Striking developmental changes in NMDA-receptor-mediated GnRH secretion were demonstrated with a maximal activity around the time of the onset of puberty. Similar changes occurred in orchidectomized animals, indicating that this maturational process was gonad-independent. While evidence accumulated that NMDA receptors were involved in a stimulatory control of GnRH secretion, we found that NMDA receptors mediated an inhibitory effect on GnRH secretion. This inhibitory effect was very potent in the immature hypothalamus and it showed a marked reduction in potency before onset of puberty.(ABSTRACT TRUNCATED AT 250 WORDS) [less ▲]

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See detailModèles de croissance et gestion des forêts : une étroite complémentarité
Rondeux, Jacques ULg

in Les modèles de croissance forestière et leurs utilisations (1993, November)

The aim of this paper is to propose some examples of use for growth and yield models in forest management at different levels of resolution (stand, forest, region)especially by projecting the stand under ... [more ▼]

The aim of this paper is to propose some examples of use for growth and yield models in forest management at different levels of resolution (stand, forest, region)especially by projecting the stand under planned management or silvicultural practices to evaluate their impact. The first example deals with a flexible yield and managment model "a whole stand model) for evenaged stands, it uses the principle of numerical thinnings. The second example is based upon an individual tree distance independent model useful to manage and control natural unevenaged stands. The third is above all an application of a forest growth projection system linked to a regional forest inventory. [less ▲]

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See detailJean-Pierre Verheggen, Les Folies-Belgères
Durand, Pascal ULg

in Textyles : Revue des Lettres Belges de Langue Française (1993), 9

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See detailPrendre l'humour au sérieux: prolégomènes à une étude du discours comique
Defays, Jean-Marc ULg

Conference (1993, November)

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See detailJean-Pierre Verheggen, Pubères, putains
Durand, Pascal ULg

in Textyles : Revue des Lettres Belges de Langue Française (1993), 9

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