Showing papers by "Katholieke Universiteit Leuven published in 1995"

Predictors of 30-Day Mortality in the Era of Reperfusion for Acute Myocardial Infarction Results From an International Trial of 41 021 Patients

Abstract: Background Despite remarkable advances in the treatment of acute myocardial infarction, substantial early patient mortality remains. Appropriate choices among alternative therapies and the use of clinical resources depend on an estimate of the patient's risk. Individual patients reflect a combination of clinical features that influence prognosis, and these factors must be appropriately weighted to produce an accurate assessment of risk. Prior studies to define prognosis either were performed before widespread use of thrombolysis or were limited in sample size or spectrum of data. Using the large population of the GUSTO-I trial, we performed a comprehensive analysis of relations between baseline clinical data and 30-day mortality and developed a multivariable statistical model for risk assessment in candidates for thrombolytic therapy. Methods and Results For the 41 021 patients enrolled in GUSTO-I, a randomized trial of four thrombolytic strategies, relations between clinical descriptors routinely collected at initial presentation, and death within 30 days (which occurred in 7% of the population) were examined with both univariable and multivariable analyses. Variables studied included demographics, history and risk factors, presenting characteristics, and treatment assignment. Risk modeling was performed with logistic multiple regression and validated with bootstrapping techniques. Multivariable analysis identified age as the most significant factor influencing 30-day mortality, with rates of 1.1% in the youngest decile ( 75 (adjusted chi(2)=717, P<.0001). Other factors most significantly associated with increased mortality were lower systolic blood pressure (chi(2)=550, P<.0001), higher Killip class (chi(2)=350, P<.0001), elevated heart rate (chi(2)=275, P<.0001), and anterior infarction (chi(2)=143, P<.0001). Together, these five characteristics contained 90% of the prognostic information in the baseline clinical data. Other significant though less important factors included previous myocardial infarction, height, time to treatment, diabetes, weight, smoking status, type of thrombolytic, previous bypass surgery, hypertension, and prior cerebrovascular disease. Combining prognostic variables through logistic regression, we produced a validated model that stratified patient risk and accurately estimated the likelihood of death. Conclusions The clinical determinants of mortality in patients treated with thrombolytic therapy within 6 hours of symptom onset are multifactorial and the relations complex. Although a few variables contain most of the prognostic information, many others contribute additional independent prognostic information. Through consideration of multiple characteristics, including age, medical history, physiological significance of the infarction, and medical treatment, the prognosis of an individual patient can be accurately estimated.

Lectins as Plant Defense Proteins

Abstract: Many plant species contain carbohydrate-binding proteins, which are commonly referred to as either lectins or agglutinins. Generally speaking, lectins are proteins that bind reversibly to specific monoor oligosaccharides. Since the initial discovery of a hemagglutinating factor in castor bean extracts by Stillmark in 1888, several hundred of these proteins have been isolated and characterized in some detail with respect to their carbohydrate-binding specificity, molecular structure, and biochemical properties. Lectins from different plant species often differ with respect to their molecular structure and specificity. It is important, therefore, to realize that all plant lectins are artificially classified together solely on the basis of their ability to recognize and bind carbohydrates. Moreover, the question arises whether proteins with a completely different structure and sugar-binding specificity fulfill the same physiological role. No conclusive answer can be given to this question as yet, for the simple reason that the role of most plant lectins is not known with certainty. There is, however, growing evidence that most lectins play a role in the plant's defense against different kinds of plant-eating organisms. The idea that lectins may be involved in plant defense is not new. In an earlier review, Chrispeels and Raikhel (1991) critically assessed the defensive role of the phytohemagglutinin family and a number of chitin-binding proteins. During the last few years important progress has been made in the study of plant lectins in general and in the understanding of their effects on other organisms in particular. In this Update we summarize the recent developments that support the defensive role of plant lectins and, in addition, discuss earlier work in this field against the background of our present knowledge of this group of plant proteins.

Spherical wavelets: efficiently representing functions on the sphere

Abstract: Wavelets have proven to be powerful bases for use in numerical analysis and signal processing. Their power lies in the fact that they only require a small number of coefficients to represent general functions and large data sets accurately. This allows compression and efficient computations. Classical constructions have been limited to simple domains such as intervals and rectangles. In this paper we present a wavelet construction for scalar functions defined on the sphere. We show how biorthogonal wavelets with custom properties can be constructed with the lifting scheme. The bases are extremely easy to implement and allow fully adaptive subdivisions. We give examples of functions defined on the sphere, such as topographic data, bidirectional reflection distribution functions, and illumination, and show how they can be efficiently represented with spherical wavelets. CR

Plant defensins: novel antimicrobial peptides as components of the host defense system.

Abstract: Various mechanisms to fend off microbial invaders have been devised by all living organisms, including microorganisms themselves. The most sophisticated of these mechanisms relies on the synthesis of immunoglobulins directed against specific microbial targets. However, immunoglobulin-based immunity operates only in a relatively minor subset of living species, namely the higher vertebrates. A much more ancient and widespread defense strategy involves the production of small peptides that exert antimicrobial properties. As products of single genes, antimicrobial peptides can be synthesized in a swift and flexible way, and because of their small size they can be produced by the host with a minimal input of energy and biomass. Wellknown examples of antimicrobial peptides are the cecropins that accumulate in the hemolymph of many invertebrates in response to injury or infection (reviewed by Boman and Hultmark, 1987) and the magainins that are secreted by glands in the skin of amphibians (reviewed by Bevins and Zasloff, 1990). Cecropins and magainins are small (20-40 residues) basic peptides displaying an amphipathic a-helical structure that can integrate in microbial membranes to form ion channels (Duclohier, 1994). Another class of antimicrobial peptides is formed by the Cys-rich peptides, which in contrast to cecropins and magainins, have a complex cystine-stabilized three-dimensional folding pattern often involving antiparallel ,3-sheets. Defensins are one class among the numerous types of Cys-rich antimicrobial peptides, which differ in length, number of cystine, bonds, or folding pattern (reviewed by Boman, 1995). Insect defensins (34-43 residues, three disulfide bridges) are, like cecropins, produced in a pathogeninducible manner by the insect fat body and secreted in the hemolymph (reviewed by Hoffmann and Hetru, 1992). Mammalian defensins (29-34 amino acids, three disulfide bridges) are produced by various specialized cells in the mammalian body (reviewed by Lehrer et al., 1993; Ganz and Lehrer, 1994). For example, they are very abundant in granules of phagocytic blood cells. These granules fuse with phagocytosis vesicles containing microorganisms, where the defensins are thought to contribute, together with other antimicrobial proteins and active oxygen species, to killing of the engulfed microorganisms. Defensins are also secreted by epithelial cells of the intestines and airways, where they may help maintain the normal microbial flora in a steady state. In addition, the expression of defensins in the airway epithelium has been shown to be up-regulated after exposure to bacterial lipopolysaccharides (Diamond et al., 1993). The importance of defensins in innate immunity of humans is underscored by the observation that certain disorders characterized by recurrent infections are associated with a lack of defensins in blood phagocytes (Ganz et al., 1988). Moreover, transposon mutants of a pathogenic Salmonella strain known to infect and grow inside phagocytes simultaneously lost their resistance to defensins (and other antimicrobial peptides) and their virulence (Groisman et al., 1992). Recently, we characterized a novel class of plant peptides whose structural and functional properties resemble those of insect and mammalian defensins. Hence, we termed this family of peptides "plant defensins" (Terras et al., 1995).

Lifting scheme: a new philosophy in biorthogonal wavelet constructions

Abstract: In this paper we present the basic idea behind the lifting scheme, a new construction of biorthogonal wavelets which does not use the Fourier transform. In contrast with earlier papers we introduce lifting purely from a wavelet transform point of view and only consider the wavelet basis functions in a later stage. We show how lifting leads to a faster, fully in- plane implementation of the wavelet transform. Moreover, it can be used in the construction of second generation wavelets, wavelets that are not necessarily translates and dilates of one function. A typical example of the latter are wavelets on the sphere.

Small cysteine-rich antifungal proteins from radish: their role in host defense.

Abstract: Radish seeds have previously been shown to contain two homologous, 5-kD cysteine-rich proteins designated Raphanus sativus-antifungal protein 1 (Rs-AFP1) and Rs-AFP2, both of which exhibit potent antifungal activity in vitro. We now demonstrate that these proteins are located in the cell wall and occur predominantly in the outer cell layers lining different seed organs. Moreover, Rs-AFPs are preferentially released during seed germination after disruption of the seed coat. The amount of released proteins is sufficient to create a microenvironment around the seed in which fungal growth is suppressed. Both the cDNAs and the intron-containing genomic regions encoding the Rs-AFP preproteins were cloned. Transcripts (0.55 kb) hybridizing with an Rs-AFP1 cDNA-derived probe were present in near-mature and mature seeds. Such transcripts as well as the corresponding proteins were barely detectable in healthy uninfected leaves but accumulated systemically at high levels after localized fungal infection. The induced leaf proteins (designated Rs-AFP3 and Rs-AFP4) were purified and shown to be homologous to seed Rs-AFPs and to exert similar antifungal activity in vitro. A chimeric Rs-AFP2 gene under the control of the constitutive cauliflower mosaic virus 35S promoter conferred enhanced resistance to the foliar pathogen Alternaria longipes in transgenic tobacco. The term "plant defensins" is proposed to denote these defense-related proteins.

Synthesis of phytohormones by plant-associated bacteria

Abstract: The plant hormones, auxins and cytokinins, are involved in several stages of plant growth and development such as cell elongation, cell division, tissue differentiation, and apical dominance. The biosynthesis and the underlying mechanism of auxins and cytokinins action are subjects of intense investigation. Not only plants but also microorganisms can synthesize auxins and cytokinins. The role of phytohormone biosynthesis by microorganisms is not fully elucidated: in several cases of pathogenic fungi and bacteria these compounds are involved in pathogenesis on plants; auxin and cytokinin production may also be involved in root growth stimulation by beneficial bacteria and associative symbiosis. The genetic mechanism of auxin biosynthesis and regulation by Pseudomonas, Agrobacterium, Rhizobium, Bradyrhizobium, and Azospirillum, are well studied; in these bacteria several physiological effects have been correlated to the bacterial phytohormones biosynthesis. The pathogenic bacteria Pseudomonas and Agrobacterium produce indole-3-acetic acid via the indole-3-acetamide pathway, for which the genes are plasmid borne. However, they do possess also the indole-3-pyruvic acid pathway, which is chromosomally encoded. In addition, they have genes that can conjugate free auxins or hydrolyze conjugated forms of auxins and cytokinins. In Agrobacterium there are also several genes, located near the auxin and cytokinin biosynthetic genes, that are involved in the regulation of auxins and cytokinins sensibility of the transformed plant tissue. Symbiotic bacteria Rhizobium and Bradyrhizobium synthesize indole-3-acetic acid via indole-3-pyruvic acid; also the genetic determinants for the indole-3-acetamide pathway have been detected, but their activity has not been demonstrated. In the plant growth-promoting bacterium Azospirillum, as in Agrobacterium and Pseudomonas, both the indole-3-pyruvic acid and the indole-3-acetamide pathways are present, although in Azospirillum the indole-3-pyruvic acid pathway is of major significance. In addition, biochemical evidence for a tryptophan-independent indole-3-acetic acid pathway in Azospirillum has been presented.

A single-chip 900 MHz CMOS receiver front-end with a high performance low-IF topology

Abstract: An analog receiver front end chip realized in a 0.7 /spl mu/m CMOS technology is presented. It uses a new, high performance, downconverter topology, called double quadrature downconverter, that achieves a phase accuracy of less than 0.3/spl deg/ in a large passband around 900 MHz, without requiring any external component or any tuning or trimming. A high performance low-IF receiver topology is developed with this double quadrature downconverter. The proposed low-IF receiver combines the advantages of both the classical IF receiver and the zero IF receiver: an excellent performance and a very high degree of integration. In this way, it becomes possible to realize a true fully integrated receiver front-end that does not require a single external component and which is, different from the zero-IF receiver, nonetheless totally insensitive to parasitic baseband signals and self-mixing products.

Composite flux-line lattices stabilized in superconducting films by a regular array of artificial defects.

Abstract: Flux creep rate and critical current have been measured in superconducting Pb $/$Ge multilayers with a square lattice of submicron holes. The new composite flux-line lattices consisting of single or multiquanta vortices at holes and single cortices at interstitial positions have been identified. The ``metallic'' behavior of the flux lines at the interstices at temperatures close to the critical temperature leads to a first-order phase transition analogous to the Mott insulator-metal transition for flux lines, introduced by Nelson and Vinokur.

Fps1, a yeast member of the MIP family of channel proteins, is a facilitator for glycerol uptake and efflux and is inactive under osmotic stress.

Abstract: The Saccharomyces cerevisiae FPS1 gene, which encodes a channel protein belonging to the MIP family, has been isolated previously as a multicopy suppressor of the growth defect of the fdp1 mutant (allelic to GGS1/TPS1) on fermentable sugars. Here we show that overexpression of FPS1 enhances glycerol production. Enhanced glycerol production caused by overexpression of GPD1 encoding glycerol-3-phosphate dehydrogenase also suppressed the growth defect of ggs1/tps1 delta mutants, suggesting a novel role for glycerol production in the control of glycolysis. The suppression of ggs1/tps1 delta mutants by GPD1 depends on the presence of Fps1. Mutants lacking Fps1 accumulate a greater part of the glycerol intracellularly, indicating that Fps1 is involved in glycerol efflux. Glycerol-uptake experiments showed that the permeability of the yeast plasma membrane for glycerol consists of an Fps1-independent component probably due to simple diffusion and of an Fps1-dependent component representing facilitated diffusion. The Escherichia coli glycerol facilitator expressed in a yeast fps1 delta mutant can restore the characteristics of glycerol uptake, production and distribution fully, but restores only partially growth of a ggs1/tps1 delta fps1 delta double mutant on glucose. Fps1 appears to be closed under hyperosmotic stress when survival depends on intracellular accumulation of glycerol and apparently opens rapidly when osmostress is lifted. The osmostress-induced High Osmolarity Glycerol (HOG) response pathway is not required for inactivation of Fps1. We conclude that Fps1 is a regulated yeast glycerol facilitator controlling glycerol production and cytosolic concentration, and might have additional functions.

Parameterization of randomly measured points for least squares fitting of B-spline curves and surfaces

Abstract: The paper presents a simple technique to assign parameter values to randomly measured points for the least squares fitting of B-spline surfaces. The parameterization is realized by projecting the measured points to a base surface. The parameters of the projected points are then used as the parameters of the measured points. The base surface is in fact a first approximation of the final fitted surface, and it can usually be created from some approximate boundary information in the form of either points or curves. A similar technique can also be used for B-spline curve fitting.

Effects of Disruption of The Plasminogen Gene on Thrombosis, Growth, and Health in Mice

Abstract: Background Circumstantial evidence suggests that the plasminogen/plasmin system plays a role in many biological processes, including hemostasis, cell migration, and development. Methods and Results The in vivo function of the plasminogen/plasmin system was studied by generation of plasminogen-deficient (Plg−/−) mice. Inactivation of the murine plasminogen gene (Plg) was achieved by replacing, via homologous recombination in embryonic stem cells, genomic sequences encoding the exons containing the catalytic site amino acids His605 and Asp648 with a neomycin phosphotransferase expression cassette. Germline transmission of the mutated allele, as determined by Southern blot hybridization and polymerase chain reaction, was obtained via blastocyst injection. Mendelian inheritance of the inactivated plasminogen allele was observed, and homozygous-deficient mice (Plg−/−) displayed normal viability but retarded growth up to at least 12 weeks of age. At 8 weeks of age, body weight was 21.8±1.2 g (n=10) for wild-typ...

Human perceptual learning in identifying the oblique orientation: retinotopy, orientation specificity and monocularity.

Abstract: 1. Human perceptual learning in discrimination of the oblique orientation was studied using psychophysical methods. Subjects were trained daily to improve their ability to identify the orientation of a circular 2.5 deg diameter unidimensional noise field. Dramatic improvements in sensitivity to contour orientation occurred over a period of 15-20 days. The improved performance persisted for several months. Improvement was more evident between daily sessions than within sessions. This was partly due to fatigue interfering with the learning effect. Moreover, a consolidation period seemed to be required. 2. Improvement was restricted to the position of the stimulus being trained. This position dependency of the learning effect proved very precise. After training at a specific stimulus position, merely displacing the stimulus to an adjacent position caused a marked increase in thresholds. 3. No transfer of the training effect was observed between orientations. Following a shift of 90 deg away from the trained orientation, performance fell, even below the initial level. 4. We observed complete to almost complete transfer between the two eyes. 5. Our results suggest plastic changes at a level of the visual processing stream where input from both eyes has come together, but where generalization for spatial localization and orientation has not yet occurred.

Incidence, determinants, and consequences of subclinical noncompliance with immunosuppressive therapy in renal transplant recipients.

Abstract: In this descriptive cross-sectional study, we investigated the incidence, determinants, and consequences of subclinical noncompliance with immunosuppressive therapy in 150 adult renal transplant recipients with more than one year posttransplant status. Symptom frequency and symptom distress, and self-care agency were measured by the Transplant Symptom Frequency and Symptom Distress Scale, and the Appraisal for Self-Care Agency Scale, respectively. The Long-Term Medication Behavior Self-Efficacy Scale and a renal transplant knowledge questionnaire were developed as part of this study to measure perceived self-efficacy and knowledge of the therapeutic regimen. Demographic variables were also measured. The incidence of subclinical noncompliance with immunosuppressive therapy as assessed by interview was 22.3%. Compliers and noncompliers differed significantly on the variables of marital status (P = 0.03), situational-operational knowledge (P = 0.02), self-care agency (P = 0.03), and perceived self-efficacy related to long-term medication intake (P = 0.048). A logistic regression model using gender, marital status, perceived self-efficacy, self-care agency, knowledge about medication administration and signs of infection, and situational operational knowledge as predictor variables, revealed a 78.6% correct classification of compliers versus noncompliers and a sensitivity ratio of 95.9%. There were significantly more acute late rejection episodes (P = 0.003) in the noncompliant group. Graft survival at 5 years in this group was also significantly lower (P = 0.03) than the compliant patients. No significant difference was found in terms of the occurrence of chronic rejection episodes or in terms of patient survival at 5 years. Because noncompliance is a risk factor for negative clinical outcome in renal transplant recipients, it is of utmost importance to develop intervention strategies to enhance compliance in this population by using determinants identified in exploratory studies.

Full- vs. Partial-mouth Disinfection in the Treatment of Periodontal Infections: Short-term Clinical and Microbiological Observations

Abstract: In a standard periodontal treatment strategy with consecutive root planings (per quadrant at a one- to two-week interval), re-infection of a disinfected area might occur before completion of the treatment. This study examines, both clinically and microbiologically, whether a full-mouth disinfection within 24 hours significantly improves the outcome of periodontal treatment. Ten patients with advanced chronic periodontitis were randomly allocated to a test and a control group. The patients from the control group received scalings and root planings as well as oral hygiene instructions per quadrant at two-week intervals. Full-mouth disinfection in the test group was sought by the removal of all plaque and calculus (in two visits within 24 hours). In addition, at each of these visits, the tongue was brushed with a 1 % chlorhexidine gel for one min and the mouth rinsed with a 0.2% chlorhexidine solution for two min. Furthermore, subgingival chlorhexidine (1%) irrigation was performed in all pockets. The recolo...

A Potent Antimicrobial Protein from Onion Seeds Showing Sequence Homology to Plant Lipid Transfer Proteins

Abstract: An antimicrobial protein of about 10 kD, called Ace-AMP1, was isolated from onion (Allium cepa L.) seeds. Based on the near-complete amino acid sequence of this protein, oligonucleotides were designed for polymerase chain reaction-based cloning of the corresponding cDNA. The mature protein is homologous to plant nonspecific lipid transfer proteins (nsLTPs), but it shares only 76% of the residues that are conserved among all known plant nsLTPs and is unusually rich in arginine. Ace-AMP1 inhibits all 12 tested plant pathogenic fungi at concentrations below 10 [mu]g mL-1. Its antifungal activity is either not at all or is weakly affected by the presence of different cations at concentrations approximating physiological ionic strength conditions. Ace-AMP1 is also active on two Gram-positive bacteria but is apparently not toxic for Gram-negative bacteria and cultured human cells. In contrast to nsLTPs such as those isolated from radish or maize seeds, Ace-AMP1 was unable to transfer phospholipids from liposomes to mitochondria. On the other hand, lipid transfer proteins from wheat and maize seeds showed little or no antimicrobial activity, whereas the radish lipid transfer protein displayed antifungal activity only in media with low cation concentrations. The relevance of these findings with regard to the function of nsLTPs is discussed.

Detection of visual symmetries

Abstract: This paper reviews empirical evidence for the detection of visual symmetries and explanatory theories and models of symmetry detection. First, mirror symmetry is compared to other types of symmetry. The idea that symmetry detection is preattentive is then discussed and other roles that attention might play in symmetry detection are considered. The major part of the article consists of a critical examination of the extensive literature about the effects on symmetry detection of several major factors such as the orientation of the symmetry axis, the location of the stimulus in the visual field, grouping, and perturbations. Constraints on plausible models of symmetry detection are derived from this rich database and several proposals are evaluated against it. As a result of bringing this research together, open questions and remaining gaps to be filled by future research are identified.

A consistent model for the thickness dependence of intrinsic breakdown in ultra-thin oxides

Abstract: A consistent model for the intrinsic time dependent dielectric breakdown (TDDB) of thin oxides is introduced. This model links the existing anode hole injection and the electron trap generation models together and describes wearout as a hole induced generation of electron traps. Breakdown is defined as conduction via these traps from one interface to the other. Implementing the model in a simulator, the oxide thickness dependence of the Weibull slope of the Q/sub BD/-distribution is predicted, and, using the unique relationship between hole fluence and generated electron trap density, the decrease of the critical hole fluence with oxide thickness is explained.

Describing instruction set processors using nML

Abstract: Programmable processors offer a high degree of flexibility and are therefore increasingly being used in embedded systems. We introduce the formalism nML which is especially suited to describe such processors in terms of their instruction set, an nML description is directly related to the standard description as found in the usual programmer's manuals. The nML formalism is based on a mixed structural and behavioural model facilitating exact yet concise descriptions. The philosophy of nML is already applied in two approaches to retargetable code generation and instruction set simulation. >

Influence of high-resistance and high-velocity training on sprint performance

Abstract: The purpose of this study is to analyze the effect of high-resistance (HR) and high-velocity (HV) training on the different phases of 100-m sprint performance Two training groups (HR and HV) were compared with two control groups (RUN and PAS) The HR (N = 22) and HV group (N = 21) trained 3 dwk-1 for 9 wk: two strength training sessions (HR or HV) and one running session There was a run control group (RUN, N = 12) that also participated in the running sessions (1 dwk-1) and a passive control group (PAS, N = 11) Running speed over a 100-m sprint was recorded every 2 m By means of a principal component analysis on all speed variables, three phases were distinguished: initial acceleration (0-10 m), building-up running speed to a maximum (10-36 m), and maintaining maximum speed in the second part of the run (36-100 m) HV training resulted in improved initial acceleration (P < 005 compared with RUN, PAS, and HR), a higher maximum speed (P < 005 compared with PAS), and a decreased speed endurance (P < 005 compared to RUN and PAS) The HV group improved significantly in total 100 m time (P < 005 compared with the RUN and PAS groups) The HR program resulted in an improved initial acceleration phase (P < 005 compared with PAS)