Showing papers by "Vrije Universiteit Brussel published in 1987"
TL;DR: It is confirmed by DNA hybridization that tumor lines obtained after infection of this plant by Agrobacterium strains harboring wild-type nopaline and octopine tumor-inducing plasmids are stably transformed and contain transferred DNA (T-DNA) segments identical to the T-DNA found in dicotyledonous plants.
Abstract: Asparagus officinalis was the first monocotyledonous plant from which hormone-independent and opine-producing crown gall tissue could be isolated. We confirm by DNA hybridization that tumor lines obtained after infection of this plant by Agrobacterium strains harboring wild-type nopaline and octopine tumor-inducing (Ti) plasmids are stably transformed and contain transferred DNA (T-DNA) segments identical to the T-DNA found in dicotyledonous plants. We have also infected Asparagus with a nononcogenic T-DNA vector that carries a chimeric aminoglycoside phosphotransferase [NOS-APH(3')II] gene and selected transformed tissues on kanamycin-containing medium. The transformed status of these tissues was then confirmed by DNA hybridization. From these calli we regenerated kanamycin-resistant shoots that were subsequently rooted. Thus we report the isolation of transgenic monocotyledonous plants engineered via the Agrobacterium vector system.
187 citations
TL;DR: The authors argued that family formation is conditioned not only by economic factors (more particularly, opportunity structures), but also by ideational changes: the economic factors produce period fluctuations that are superimposed on long-term (and often cohort-driven) ideational effects.
Abstract: It is argued in this article that family formation is conditioned not only by economic factors (more particularly, opportunity structures), but also by ideational changes: the economic factors produce period fluctuations that are superimposed on long-term (and often cohort-driven) ideational effects. Value orientations are explored and compared across countries and across age groups using the internationally-comparable data sets provided by the European Values Studies. The analysis indicates the existence of two latent dimensions with respect to familism: tolerance of non-conformism in family formation, and the meaning attached to parenthood. These two dimensions are not completely distinct from each other though, and both are related to religious and political variables (religiosity, ‘post-materialism’, nationalism, leftism, etc.). Theoretical links are made both with Easterlin's hypothesis which implies fluctuating fertility levels and with Simon's thesis concerning the importance of ‘civil religion’ in supporting fertility. The results are, however, largely in line with Aries' thesis of two successive and quite distinct fertility transitions in the West, and suggest that fertility is very likely to remain at below-replacement levels.
166 citations
TL;DR: Methods for the purification of islet cells and for their in vitro analysis were developed to examine the functional characteristics of B cells which had been isolated from their natural environment, and to reconstitute, step by step, their in situ configuration and functional activities.
Abstract: For almost a century, diabetes research has focused on the endocrine pancreas and its secretory products. This particular orientation started in 1889, after yon Meting and Minkowski had noted the development of diabetes in pancreatectomized dogs [1]. Four years later, Minkowski demonstrated that the antidiabetic activity of the pancreatic organ was not the result of its exocrine secretion [2]. Within the same year, the islets of Langerhans were held responsible for an internal secretion which regulated glucose homeostasis [3, 4]. It then took seven decades before the islet tissue was submitted to functional analysis. The development of techniques for the isolation of pancreatic islets [5-7] finally created opportunities to study the insulin releasing B cells in vitro. Reviews by previous Minkowski lecturers have outlined how this in vitro work has elucidated major events in the process of insulin biosynthesis and release [8-141. The recognition of a cellular heterogeneity in mammalian islets raised, however, the question to which extent the functions of the pancreatic B cells depend on a particular organisation of these cells within their own society or within other (neuro)endocrine systems (Fig. 1). In order to investigate this issue, we developed methods for the purification of islet cells and for their in vitro analysis. It was the purpose to first examine the functional characteristics of B cells which had been isolated from their natural environment, and then to reconstitute, step by step, their in situ configuration and functional activities.
151 citations
TL;DR: In this paper, the Madelung potential was used to calculate the effective electronegativity χα of an atom α in a molecule or crystal, i.e., the charge-dependent "effective" electric conductivity of the atom.
Abstract: The charge‐dependent ‘‘effective’’ electronegativity χα of an atom α in a molecule or crystal, i.e., χα=(χ0α+Δχα)+2(η0α +Δηα)qα +∑β≠α qβ/Rαβ differs from the expression for the isolated atom (χ0α+2η0αqα) because of corrections to the electronegativity (Δχα) and hardness (Δηα), respectively, and due to the external potential generated by the surrounding charges qβ at distances Rαβ (new quantum‐mechanical proof given). After calibration of Δχα and Δηα for all atom types, ab initio charges can be reproduced to within a few hundredths of an electron by the electronegativity equilization method (using χav=χα=χβ⋅⋅⋅ and ∑β qβ=constant). Application of this algorithm to the solid state (i.e., charges and external potential being generated in a self‐consistent way and using Ewald’s method for determining the Madelung potential) leads to a novel method for determining ‘‘ab initio quality’’ charges and the value of the average electronegativity. If applied to SiO2 polymorphs, a relation between the refractive index ...
124 citations
TL;DR: The presence of high affinity receptors for IGF-I on adult islet A and B cells provides a molecular basis for this growth factor to influence growth, survival, and/or function of these endocrine cell types.
Abstract: Purified rat pancreatic islet cells express somatomedin receptors which are identified by their affinity for insulin-like growth factor (IGF)-I, IGF-II, and insulin. Binding of [125I]IGF-I to islet A cells was half-maximally inhibited by 7.10-10 M IGF-I, while IGF-II, insulin, and proinsulin were respectively 10-, 500-, and 10,000-fold less potent displacers of IGF-I binding. Unrelated hormones such as glucagon or GH did not compete with [125I] IGF-I binding to A cells. The concentration of IGF-I receptors on A cells was estimated at 5000 IGF-I binding sites per cell with affinity constant (Ka) of 2 × 109 M-1. Islet B cells were found to exhibit a reversible time- and temperature-dependent binding with [125I]IGF-I. Specificity and affinity of IGF-I binding sites were identical for islet A and B cells. Linear Scatchard plots of competitive binding data on B cells suggest 1 single class of IGF-I receptors in a concentration of 12,000 sites per cell. The presence of high affinity receptors for IGF-I on adult...
116 citations
TL;DR: In this paper, the problem of small HP construction in a wide area covering many regions is formulated, the criteria are estimated and quantified, and location planning is obtained by using the Promethee methodology.
111 citations
TL;DR: In this paper, the influence of macroeconomic factors such as interest and inflation on the classical risk and surplus process is studied, and the authors propose a model to study the effect of macro-economic factors on the risk-and-surplus process.
Abstract: In the present paper the influence of macro-economic factors such as interest and inflation on the classical risk and surplus process is studied.
106 citations
TL;DR: It is suggested that a duration of 10 s static stretching is sufficient for improving coxo-femoral flexibility.
Abstract: The purpose of this study was to determine the effect of different durations of static stretching exercises on coxo‐femoral (hip) flexibility. The experimental group, consisting of 20 sedentary women (20–30 years of age), participated in an exercise programme of static stretching exercises with emphasis on the hamstring muscles. The programme lasted for 10 weeks and consisted of two 50‐min sessions per week. A control group of 15 sedentary women did not participate in the programme. Hip flexibility was determined before, during and at the end of the programme by means of a goniometric measuring technique developed by us and described elsewhere. Three sub‐groups were formed, each following the same programme except that the duration of the static stretch differed (group 1,10 s; group 2, 20 s; group 3, 30 s). The ANOVA tests showed that for all groups ‐ the control group excepted ‐ the hip flexibility had improved significantly after 10 weeks (P <0.05). No significant differences in hip flexibility...
82 citations
TL;DR: It appears that the best adipose tissue predictors are different from those used in general, and the problem of estimating body fat content by skinfold is compounded by the fact that two identical thicknesses of adipOSE tissue may contain significantly different concentrations of fat.
Abstract: The interest in skinfolds, given the easy accessibility of the subcutaneous layer and its non‐invasive nature, has led to a proliferation of ‘skinfold’ applications and formulae. To obtain data to investigate body composition methods, particularly the use of skinfolds, two separate cadaver dissection studies were undertaken, allowing for the analysis of data from 32 cadavers with more than 2500 data per cadaver. In addition, 40 elderly ‘living’ subjects of the same age range were compared with the cadaver population and no significant macro‐morphological differences were found. The available data have clearly demonstrated that skinfold compressibility is by no means constant. Adipose tissue patterning by assessment of skinfold thickness using calipers and incision confirms significant sex differences but emphasizes the neglected importance of skin thickness. It appears that the best adipose tissue predictors are different from those used in general. Also the problem of estimating body fat content...
80 citations
TL;DR: A national one-day prevalence survey of nosocomial infections was carried out in March 1984 in 106 Belgian acute-care hospitals involving 8723 patients of whom 6130 had undergone surgery and found no association between perioperative antibiotic prophylaxis and the prevalence of the infections studied.
69 citations
TL;DR: Haploid plantlets from male fertile and male sterile sugarbeet plants could be induced at frequencies up to 2.2% using ovule culture using ovary culture, and all plants were haploid and originated from the haploid cells of the embryo sac.
Abstract: Haploid plantlets from male fertile and male sterile sugarbeet plants could be induced at frequencies up to 2.2% using ovule culture. Ovary culture on media without charcoal resulted in a similar induction frequency. Plant development was inhibited by callus development originating from the mother tissue. When the callus parts were removed and the ovule transferred to a new medium without 2,4 D, callus formation could be inhibited by adding 0.5% charcoal to the medium. Up to 6.1% haploids were induced. Chromosome counts in leaf tips, chloroplast counts and isozyme patterns revealed that all plants were haploid and originated from the haploid cells of the embryo sac. Root tips showed spontaneous polyploidisation.
TL;DR: It is concluded that carvedilol possesses definite antihypertensive and renal vasodilating properties, both acutely and after chronic treatment.
Abstract: A randomized, double-blind, placebo-controlled study was set up to study the effects of acute and chronic administration of carvedilol, a vasodilatory beta-blocker in essential hypertension. Acute administration of a single dose of 50 mg of carvedilol reduced systolic and diastolic blood pressure, without inducing reflex tachycardia. Renal blood flow was preserved; accordingly renal vascular resistance was significantly reduced. A significant reduction of glomerular filtration rate and filtration fraction was observed. Plasma renin activity (PRA) and plasma aldosterone were not changed. Chronic carvedilol treatment produced a significant fall in systolic and diastolic office and ambulatory blood pressure, heart rate, cardiac output, PRA and plasma aldosterone. Blood pressure variability was not changed. Renal blood flow, glomerular filtration rate and filtration fraction also remained unchanged; renal vascular resistance decreased significantly. It is concluded that carvedilol possesses definite antihypertensive and renal vasodilating properties, both acutely and after chronic treatment.
TL;DR: It is concluded that although U. urealyticum is a common inhabitant of the lower genital tract, it may play a role in the etiology of spontaneous abortion and uncontrollable preterm labor.
Abstract: The role of U. urealyticum in spontaneous and recurrent spontaneous abortion was studied in 633 women. Cervical colonization with U. urealyticum was found in 42.6% of 310 normal pregnant women, in 41.6% of 84 patients who underwent induced abortion, in 41.5% of 41 normal fertile patients, in 53.3% of 122 patients with spontaneous abortion and in 64.5% of 76 patients with recurrent spontaneous abortion. The cervical isolation rate was significantly higher in patients with spontaneous abortion (p less than 0.05) and recurrent spontaneous abortion (p less than 0.005) than in normal pregnant women. Endometrial colonization was more frequent in patients with recurrent spontaneous abortion (27.6%) than in normal fertile women (9.7%) (p less than 0.05). Moreover, in 6 patients with intact membranes and uncontrollable preterm labor resulting in fetal loss (all between the 20th and 28th week of gestation) U. urealyticum was isolated in 5 of them from the cervix, in 4 patients from the placenta and in 2 out of 4 from the amniotic fluid. Histological examination of the placenta showed signs of chorioamnionitis in 5 patients. From this study we conclude that although U. urealyticum is a common inhabitant of the lower genital tract, it may play a role in the etiology of spontaneous abortion and uncontrollable preterm labor.
TL;DR: The complete nucleotide sequence of the ARG3 structural gene encoding the monomer of the trimeric ornithine carbamoyltransferase (OTCase) has been determined and points to residues probably involved in catalysis and structural folding in OTCases.
Abstract: The complete nucleotide sequence of the ARG3 structural gene encoding the monomer of the trimeric ornithine carbamoyltransferase (OTCase) (EC 2.1.3.3) has been determined. It consists of 338 codons with a corresponding molecular mass of 37842 Da. Comparing OTCases from Escherichia coli, yeast, Aspergillus, rat and man emphasizes peculiarities of the yeast enzyme but also brings to light an important degree of conservation between these proteins. Comparing the various OTCases with E. coli aspartate carbamoyltransferase (ATCase) (EC 2.1.3.2) confirms the evolutionary relationship previously noted between the two types of carbamoyltransferases and points to residues probably involved in catalysis and structural folding in OTCases.
TL;DR: In poliovirus-infected cells, the viral protein and RNA synthesis were severely reduced, provided 3-methylquercetin was present between 1 and 2 h post-infection, and the virally induced host shut-off remained in effect.
TL;DR: The serotonin deficiency sheds light on possible mechanisms of myoclonus in Alzheimer's disease and appears to be relatively unaffected by the disease process.
TL;DR: A new fast kit preparation of 123I labelled radio-pharmaceuticals such as IMP, HIPDM, MIBG and Hippuran is proposed, based on the nucleophilic exchange in presence of Cu(I) and an excess of reducing agents.
Abstract: A new fast kit preparation of 123I labelled radiopharmaceuticals such as IMP, HIPDM, MIBG and Hippuran is proposed. A radiochemical yield greater than 99% is obtained at 100 degrees C within 10-30 min. The new labelling procedure is based on the nucleophilic exchange in presence of Cu(I) and an excess of reducing agents. The four kit prepared 123I-radiopharmaceuticals have been used with success in clinical studies involving 400 patients. The proposed method is also compared with earlier described methods which, yielding labelled side products and 123I2, do not fulfill the requirements for kit labelling.
TL;DR: Petrological, geochemical and K/Ar radiometrical whole rock age data of volcanic rocks from SW Egypt and N Sudan in the area of Gebel Kamil-Lake Nasser-Laqia Arbain-Nile are presented in this paper.
TL;DR: Although it is perhaps a little premature to consider cystatin C as a marker for multiple sclerosis, this protein is nevertheless associated to demyelination; consequently its biochemical assay in cerebrospinal fluid is recommended as a complementary diagnostic tool.
Abstract: Cystatin C, alias post-gamma-globulin or gamma-trace protein, has been shown to be a potent inhibitor of cysteine proteinases; this protein is normally present in different biological fluids, but particularly so in cerebrospinal fluid. The concentration of cystatin C was determined by radial immunodiffusion in cerebrospinal fluid from patients affected with multiple sclerosis, patients affected with various neurological diseases and in controls; it was also determined in brain tissue from 2 patients affected with multiple sclerosis and 3 control brains. Cystatin C cerebrospinal fluid levels were undetectable or depressed in many multiple sclerosis cases and the median value differed significantly from the control one. Its low concentration in multiple sclerosis suggests that the regulation of cysteine proteinases is impaired in this disease; hence enhanced activity of cysteine proteinases could initiate, or increase the breakdown of myelin. Although it is perhaps a little premature to consider cystatin C as a marker for multiple sclerosis, this protein is nevertheless associated to demyelination; consequently its biochemical assay in cerebrospinal fluid is recommended as a complementary diagnostic tool.
TL;DR: The results demonstrate the presence of osteocalcin in odontoblasts and dentin and its immunocytochemical localization may be compatible with a distinct role in early dentinogenesis.
Abstract: Osteocalcin was purified by gel chromatography from a crude extract obtained after decalcification of rat incisors The apparent molecular weight, as determined by 5-15% SDS-polyacrylamide gel electrophoresis, was 18,000, and amino acid analysis revealed 60 γ-carboxyglutamic acid residues per 1000 Antisera against osteocalcin, raised in rabbits, reacted specifically with osteocalcin when investigated by immuno-electroblotting of dentin crude extract 4-μm cryosections of formaldehyde-fixed tooth germs showed positive immunocytochemical staining for osteocalcin in dentin and odontoblasts The staining of the mantle dentin at the coronal sides of the tooth germs was more intense than that of the adjacent circumpulpal dentin, while the odontoblasts involved in the formation of mantle dentin showed stronger immunoreactivity than did odontoblasts involved in circumpulpal dentin formation This marked difference was not observed on the root sides of the tooth germs In 1-μm cryosections, osteocalcin immunoreac
TL;DR: Experimental infections with Trypanosoma brucei AnTat 1.1.
Abstract: Experimental infections with Trypanosoma brucei AnTat 1.1.E not only account for a suppression of interleukin 2 (IL 2) production, but also induce an impairment of IL 2 receptor expression. Indeed, lymph node cells derived from infected mice failed to express IL 2 receptors following mitogenic stimulation as compared to normal controls. This impairment was not attributed to a modulation of the number of T cells and was not caused by the presence of living parasites. Furthermore, the basal level of IL 2 receptor expression could not be re-established through the exogenous supply of recombinant IL 2. This impairment of receptor expression was found to be mediated by suppressive cells that affect the relative number of receptor-positive cells as well as the mean receptor density. On the other hand, the mitogen-induced secretion of other T cell-derived lymphokines was not inhibited during infection, indicating that the severe suppression of IL 2 regulation was not attributed to a total paralysis of the T cell responsiveness.
TL;DR: An analytical method is described which allows a fast, reliable and precise determination of levodopa and its metabolises 3-O-methyldopa and dopamine, as well as the peripheral aromatic amino acid decarboxylase inhibitor carbidopa, in a single 1 ml plasma sample of Parkinsonian patients.
TL;DR: Peroxisomes and their metabolites the plasmalogens were visualized in chorionic villi by quick and simple procedures and may contribute to early prenatal diagnosis of peroxisomal disorders.
Abstract: Peroxisomes and their metabolites the plasmalogens were visualized in chorionic villi by quick and simple procedures. Villi were stained and mounted in toto, and can also be embedded. These methods may contribute to early prenatal diagnosis of peroxisomal disorders (Zellweger syndrome, neonatal adrenoleukodystrophy, infantile Refsum's disease a.o.).
TL;DR: It is suggested that at least part of the rat islet cells with class II antigen expression can exhibit phagocytotic properties leading to the uptake of fragments from damaged endocrine cells, which may implicate this particular islet cell type in the pathology of the endocrine pancreas in type I diabetes.
Abstract: In the normal rat pancreas, only few islet cells express MHC-class II antigens. Their nature and function has not yet been elucidated. We report a method for the purification of la-positive islet cells by fluorescenceactivated cell sorting. The isolated mononuclear cells appear of nonendocrine origin but contain vacuoles with partially digested secretory vesicles. Both insulinand glucagon-immunoreactive granules were identified in these vacuoles of varying size and composition. It is suggested that at least part of the rat islet cells with class II antigen expression can exhibit phagocytotic properties leading to the uptake of fragments from damaged endocrine cells. This functional characteristic may implicate this particular islet cell type in the pathology of the endocrine pancreas in type I diabetes.
TL;DR: The European School of Brussels as mentioned in this paper showed that both curricular and extra-curricular factors combine to account for high levels of proficiency in three or four languages, and that self-initiated meaningful two-way negotiation is used as a supplement to formal instruction.
Abstract: Analysis of multilingual acquisition processes in the European School of Brussels reveals how both curricular and extra-curricular factors combine to account for high levels of proficiency in three or four languages. The school operates in seven languages, and all pupils must learn at least three, though the combination is open to choice. Curricular design ties in with the prerequisites for success as posited in Cummins' (1981, 1984) Interaction Hypothesis, Krashen's (1982) Input Hypothesis, and Swain's (1983) Output Hypothesis. These alone do not account for the high levels of achievement attested, because they do not include the extra-curricular factors which provide the essential supplementary conditions for active, productive use of a given language in meaningful two-way negotiation among peers. Schumann's (1979) Acculturation Model allows one to tap this primordial extra-curricular factor, even though it was not designed for an educational context. Four soft techniques were used to test the hypotheses: participant observation, written questionnaires, informal interviews, and open-ended formal interviews based on a 26-item questionnaire (N = 8). Results indicate that only Schumann's model can bring to the fore whether self-initiated meaningful two-way negotiation is used as a supplement to formal instruction in a multilingual environment; they also show how social and psychological distance tie in with curricular structure to enhance the acquisition process.
TL;DR: In this article, the crystal and molecular structure of Me 2 Sn(S 2 PEt 2 ) 2 has been determined by X-ray diffraction, and the compound is monoclinic space group C 2/c, with a 20.814(11), b 6.243(3), c 16.092(8) A, 105.42 (8)°, Z = 4, D x 1.500 g cm −3.
TL;DR: The demonstration of DOPac and HVA in the spinal cord is another argument against the hypothesis that CSF levels of HVA and DOPAC reflect closely the activity of the dopaminergic systems in the brain.
Abstract: The concentrations of the acidic dopamine (DA) catabolites homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) measured in human CSF are supposed to reflect the "turnover" of DA in the brain. The notion of "turnover" is, however, not synonymous with impulse nerve activity in the dopaminergic systems. Significant amounts of DOPAC and HVA could, indeed, be demonstrated in brain structures wherein dopaminergic innervation has not been documented. It must also be noted that DA is not only a neurotransmitter itself, but also a precursor of norepinephrine and epinephrine. Furthermore, in lumbar CSF, levels of biogenic amine catabolites partially reflect metabolism in the spinal cord and may have limited relevance to neurotransmission in the brain. To elucidate these points further, we determined the concentrations of DOPAC and HVA in 22 areas of six human brains and eight levels of six human spinal cords. The data were correlated with the concentration of DA. Quantitative determinations were done using HPLC with electrochemical detection, after solvent and ion-pair extraction. In this study, significant amounts of both DOPAC and HVA were demonstrated in brain structures not previously associated with dopaminergic innervation. The relatively lower DA concentration in these structures suggests that in these regions, the DOPAC and HVA concentrations are unrelated to dopaminergic neurotransmission. The possible role of capillary walls and glial cells in the catabolism of DA must be further evaluated. The demonstration of DOPAC and HVA in the spinal cord is another argument against the hypothesis that CSF levels of HVA and DOPAC reflect closely the activity of the dopaminergic systems in the brain.
TL;DR: In this article, the authors explored the use of various hierarchical and non-hierarchical cluster analysis methods to define the number of distinct particle classes within an auto emission source sample, each class was then separately modeled using a disjoint principal component procedure and membership of each particle in defined classes was tested.
TL;DR: The observed diploidisation may provide a functional advantage for the expansion of putative preneoplastic cells and seem to point towards an increase of nucleolar activity in the early steps of PB promotion.
Abstract: Two complementary genetic parameters were followed in liver parenchymal cells during the first steps of rat hepatocarcinogenesis: the expression of nucleolar genes estimated from their silver stainability and the nuclear DNA content determined after Feulgen staining. Putative preneoplastic lesions as foci and nodules were induced by the triphasic 'Gerlans protocol'. Initiation with a single dose of diethylnitrosamine (DEN) was followed by a selection of initiated cells with 2-acetylaminofluorene (2-AAF) in combination with a single necrogenic dose of CCl4 as a proliferative stimulus. Finally after 1 week of normal diet, the animals were treated or not with phenobarbital (PB) for periods up to 2 months. Serial sections were analysed after silver staining (AgNO3), methyl-green--pyronin staining (Unna-Brachet) and Feulgen staining with densitometric and morphometric methods. Silver staining, which is known to stain an acidic protein associated with rRNA synthesis, increased gradually with the duration of the PB treatment. Morphometry revealed an increase in both nucleolar and nuclear volume; the fraction of nuclei with one nucleolus also increased. These results seem to point towards an increase of nucleolar activity in the early steps of PB promotion. Moreover, this shift cannot be ascribed to an increase of DNA content. Indeed, a parallel study on neighbouring sections stained with Feulgen revealed a shift towards a population of diploid nuclei, in contrast to normal liver cells, which are mostly tetraploid. The observed diploidisation may therefore provide a functional advantage for the expansion of putative preneoplastic cells.
01 Jan 1987
TL;DR: The paper outlines the components of second generation expert systems and gives an example of a heuristic reasoning system that can learn new rules by examining the results of deep reasoning.
Abstract: Second generation expert systems are able to combine heuristic reasoning based on rules, with deep reasoning based on a model of the problem domain This solves a number of major problems of current expert systems, most importantly the problem of knowledge acquisition: second generation expert systems can learn new rules by examining the results of deep reasoning The paper outlines the components of second generation expert systems and gives an example