Showing papers by "Radboud University Nijmegen published in 1992"

Myotonic dystrophy mutation: an unstable CTG repeat in the 3' untranslated region of the gene

Abstract: Myotonic dystrophy (DM) is the most common inherited neuromuscular disease in adults, with a global incidence of 1 in 8000 individuals. DM is an autosomal dominant, multisystemic disorder characterized primarily by myotonia and progressive muscle weakness. Genomic and complementary DNA probes that map to a 10-kilobase Eco RI genomic fragment from human chromosome 19q13.3 have been used to detect a variable length polymorphism in individuals with DM. Increases in the size of the allele in patients with DM are now shown to be due to an increased number of trinucleotide CTG repeats in the 3' untranslated region of a DM candidate gene. An increase in the severity of the disease in successive generations (genetic anticipation) is accompanied by an increase in the number of trinucleotide repeats. Nearly all cases of DM (98 percent or 253 of 258 individuals) displayed expansion of the CTG repeat region. These results suggest that DM is primarily caused by mutations that generate an amplification of a specific CTG repeat.

An unstable triplet repeat in a gene related to myotonic muscular dystrophy.

Abstract: Synthetic oligonucleotides containing GC-rich triplet sequences were used in a scanning strategy to identify unstable genetic sequences at the myotonic dystrophy (DM) locus. A highly polymorphic GCT repeat was identified and found to be unstable, with an increased number of repeats occurring in DM patients. In the case of severe congenital DM, the paternal triplet allele was inherited unaltered while the maternal, DM-associated allele was unstable. These studies suggest that the mutational mechanism leading to DM is triplet amplification, similar to that occurring in the fragile X syndrome. The triplet repeat sequence is within a gene (to be referred to as myotonin-protein kinase), which has a sequence similar to protein kinases.

The relationship between stress shielding and bone resorption around total hip stems and the effects of flexible materials

Abstract: Bone resorption around hip stems is a disturbing phenomenon, although its clinical significance and its eventual effects on replacement longevity are as yet uncertain. The relationship between implant flexibility and the extent of bone loss, frequently established in clinical patient series and animal experiments, does suggest that the changes in bone morphology are an effect of stress shielding and a subsequent adaptive remodeling process. This relationship was investigated using strain-adaptive bone-remodeling theory in combination with finite element models to simulate the bone remodeling process. The effects of stem material flexibility, bone flexibility, and bone reactivity on the process and its eventual outcome were studied. Stem flexibility was also related to proximal implant/bone interface stresses. The results sustain the hypothesis that the resorptive processes are an effect of bone adaptation to stress shielding. The effects of stem flexibility are confirmed by the simulation analysis. It was also established that individual differences in bone reactivity and mechanical bone quality (density and stiffness) may account for the individual variations found in patients and animal experiments. Flexible stems reduce stress shielding and bone resorption. However, they increase proximal interface stresses. Hence, the cure against bone resorption they represent may develop into increased loosening rates because of interface debonding and micromotion. The methods presented in this paper can be used to establish optimal stem-design characteristics or check the adequacy of designs in preclinical testing procedures.

Presupposition Projection as Anaphora Resolution

Abstract: The present paper presents an anaphoric account of presupposition. It is argued that presuppositional expressions should not be seen as referring expressions, nor is presupposition to be explicated in terms of some non-standard logic. The notion of presupposition should not be relegated to a pragmatic theory either. Instead presuppositional expressions are claimed to be anaphoric expressions which have internal structure and semantic content. In fact they only differ from pronouns and other semantically less loaded anaphors in that they have more descriptive content. It is this fact which enables them to create an antecedent in case discourse does not provide one. If their capacity to accommodate is taken into account they can be treated by basically the same mechanism which handles the resolution of pronouns. The theory is elaborated in the framework of discourse representation theory. It is shown that pragmatic factors interfere in the resolution of presuppositio nal anaphors. The resulting account can neither be classified as wholly semantic nor wholly pragmatic. Section 1 presents a survey of standing problems in the theory of presupposition projection and discusses the major competing approaches. An argumentation for a purely anaphoric account of presupposition is given in section 2. Section 3 presents a coding of presuppositional expressions in an extension of discourse representation theory. The final section is devoted to a discussion of the constraints which govern the resolution of presuppositional anaphors.

Detection of an unstable fragment of DNA specific to individuals with myotonic dystrophy.

Abstract: Myotonic dystrophy (DM) is the most common form of adult muscular dystrophy, with a prevalence of 2-14 per 100,000 individuals The disease is characterized by progressive muscle weakness and sustained muscle contraction, often with a wide range of accompanying symptoms The age at onset and severity of the disease show extreme variation, both within and between families Despite its clinical variability, this dominant condition segregates as a single locus at chromosome 19q133 in every population studied It is flanked by the tightly linked genetic markers ERCC1 proximally and D19S51 distally; these define the DM critical region We report the isolation of an expressed sequence from this region which detects a DNA fragment that is larger in affected individuals than in normal siblings or unaffected controls The size of this fragment varies between affected siblings, and increases in size through generations in parallel with increasing severity of the disease We postulate that this unstable DNA sequence is the molecular feature that underlies DM

Controlled-valence properties of La1-xSrxFeO3 and La1-xSrxMnO3 studied by soft-x-ray absorption spectroscopy.

Abstract: The controlled-valence properties of ${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{FeO}}_{3}$ and ${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{MnO}}_{3}$ are studied by means of soft-x-ray absorption spectroscopy. A comparison between the transition-metal 2p spectra and atomic-multiplet calculations is used to determine the 3d count. The O 1s spectrum is used to characterize changes in unoccupied states that contain oxygen p character. The results indicate that the holes induced by substitution for both series are located in states of mixed metal 3d--oxygen 2p character. The ground state of ${\mathrm{LaFeO}}_{3}$ is mainly 3${\mathit{d}}^{5}$ and becomes 3${\mathit{d}}^{5}$L (where L denotes a ligand hole) in the ${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{FeO}}_{3}$ series for low Sr concentration. The main component of the ground state of ${\mathrm{LaMnO}}_{3}$ is 3${\mathit{d}}^{4}$ and becomes a mixture of 3${\mathit{d}}^{3}$ and 3${\mathit{d}}^{4}$L in the ${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{MnO}}_{3}$ series. The trends in controlled- valence properties of similar oxides across the transition-metal series can be rationalized within the framework of the Zaanen-Sawatzky-Allen model.

Cloning of the essential myotonic dystrophy region and mapping of the putative defect

Abstract: Myotonic dystrophy is a common dominant disorder (global incidence of 1:8,000) with variable onset and a protean nature of symptoms mainly involving progressive muscle wasting, myotonia and cataracts. To define the molecular defect, we have cloned the essential region of chromosome 19q13.3, including proximal and distal markers in a 700-kilobase contig formed by overlapping cosmids and yeast artificial chromosomes (YACs). The central part of the contig bridges an area of about 350 kilobases between two new flanking crossover borders. This segment has been extensively characterized through the isolation of five YAC clones and the subsequent subcloning in cosmids from which a detailed EcoRI, HindIII, MluI and NotI restriction map has been derived. Two genomic probes and two homologous complementary DNA probes were isolated using the cosmids. These probes are all situated within approximately 10 kilobases of genomic DNA and detect an unstable genomic segment in myotonic dystrophy patients. The length variation in this segment shows similarities to the instability seen at the fragile X locus. The physical map location and the genetic characteristics of the length polymorphism is compatible with a direct role in the pathogenesis of myotonic dystrophy.

Genus and species- specific identification of mycoplasmas by 16s rrna amplification

Abstract: Systematic computer alignment of mycoplasmal 16S rRNA sequences allowed the identification of variable regions with both genus- and species-specific sequences. Species-specific sequences of Mycoplasma collis were elucidated by asymmetric amplification and dideoxynucleotide sequencing of variable regions, using primers complementary to conserved regions of 16S rRNA. Primers selected for Mycoplasma pneumoniae, M. hominis, M. fermentans, Ureaplasma urealyticum, M. pulmonis, M. arthritidis, M. neurolyticum, M. muris, and M. collis proved to be species specific in the polymerase chain reaction. The genus-specific primers reacted with all mycoplasmal species investigated as well as with members of the genera Ureaplasma, Spiroplasma, and Acholeplasma. No cross-reaction was observed with members of the closely related genera Streptococcus, Lactobacillus, Bacillus, and Clostridium or with any other microorganism tested. On the basis of the high copy number of rRNA, a highly sensitive polymerase chain reaction assay was developed in which the nucleic acid content equivalent to a single organism could be detected.

Biannual Radiographic Assessments of Hands and Feet in a Three-Year Prospective Followup of Patients with Early Rheumatoid Arthritis

Abstract: In a prospective followup study of 147 patients with rheumatoid arthritis of recent onset, we assessed the progression of radiographic evidence of joint damage on films of the patients' hands and feet obtained biannually. Patients were receiving first-line and second-line treatment. Ninety patients were followed up for 3 years, and 57 were followed up for only 2 years. Radiographic damage was determined by a modification of the method described by Sharp, and to ensure comparability of findings, we determined the percentage of damage per joint group (actual score divided by the maximum possible score). After 3 years, radiographic damage was present in 70% of the patients, all of whom could be identified after 1 year of study. Overall, 18-20% of the joints of the hands and feet were affected after 3 years, with relatively little abnormality per joint (approximately 8% of maximum possible score). During the entire followup, more foot joints than hand joints were affected. The rate of progression in the first year was significantly higher than in the second and third years of study, indicating a flattening of the curve of radiographic progression of joint damage.

CHELATOR: an improved method for computing metal ion concentrations in physiological solutions.

Abstract: An algorithm is presented for the calculation of metal ion concentrations from given total metal concentrations (and vice versa) in physiological media containing metal-chelating compounds. In such media, conditions differ from those used for stability constant determination of metal-chelator equilibria; therefore calculated metal ion concentrations are incorrect. We recompute stability constants to reflect the effects of ionic strength and temperature of physiological solutions. Twelve different equilibria can be considered per metal-chelator pair. The computer program also calculates the contribution of ionized species of metals, chelator, complexes and pH buffers to ionic strength. Measurements with a Ca-selective electrode and with fura-2 show that calculated ionic Ca2+ concentrations are correct from 10 nM up to the millimolar range. The importance of the correct calculation of metal ion concentrations in physiological experiments is demonstrated by data, and derived kinetic parameters, on Na+/Ca2+ exchange and the ATP-dependent Ca2+ pump of enterocyte plasma membrane vesicles. The program is written in Turbo Pascal and will run on IBM-compatible computers. It is menu-driven and supports the use of a Microsoft mouse.

General primer-mediated polymerase chain reaction for detection of enteroviruses: application for diagnostic routine and persistent infections.

Abstract: The aim of this study was to determine the applicability of the polymerase chain reaction (PCR) for routine diagnostic use and for the detection of persistent enteroviral infections. To this end, general primers were selected in the highly conserved part of the 5'-noncoding region of the enteroviral genome. They were tested on 66 different enterovirus serotypes. A specific fragment was amplified from 60 of 66 serotypes. An amplification product was not observed from coxsackievirus types A11, A17, and A24 and echovirus types 16, 22, and 23. Enteroviral RNA was detected by the PCR in routinely collected throat swabs and stool specimens that were found to be positive for enterovirus by isolation in tissue culture. Enteroviral RNA was detected in one of five myocardial biopsy specimens from patients with dilated cardiomyopathy, implicating virus persistence. No amplification product was obtained from eight control samples. Our results demonstrate the significance of the PCR for the detection of enteroviral RNA and, in particular, for the demonstration of persistent enteroviral infections.

Validity of single variables and composite indices for measuring disease activity in rheumatoid arthritis.

Abstract: There is no agreement as to which variable best mirrors disease activity in rheumatoid arthritis (RA) and no studies have been performed on the validity of disease activity variables. In this study the validity of 10 commonly used single variables and three composite indices was tested. All patients participated in a large follow up study in two clinics. The patients (n = 233) had classical or definite RA and a disease duration of less than one year at entry. The mean follow up time was 30 months; the follow up frequency was once every four weeks; 6011 records were used in the analysis. The validation criteria included correlations with the other variables (correlational validity), with the physical disability (criterion validity I), and with the radiographically determined damage of hands and feet (construct validity). The judgment of a group of rheumatologists in clinical practice was also used as a model of criterion validity (II). In this comparison the disease activity score and Mallya index showed the best validity. The best single variable was the number of swollen joints. The validity of most single variables was poor and these variables were not suitable as single endpoint measures in clinical trials.

Prognostic factors for radiographic damage and physical disability in early rheumatoid arthritis. a prospective follow-up study of 147 patients

Abstract: We studied the influence of demographic, clinical, laboratory and genetic features and radiographic damage at onset on the outcome after 2 years in a prospective study of 147 patients with classical or definite RA with disease duration shorter than 1 year at entry. Outcome was determined by physical disability and by radiographic damage of hands and feet. By means of multiple regression analysis and discriminant analysis outcome was explained from variables at the start and during the first 6 months. No clinically relevant conclusions could be made for physical disability due to the low explained variance and small number of patients with bad physical disability. Radiographic damage after 2 years was predicted by high disease activity at the start (measured as erythrocyte sedimentation rate, C-reactive protein or Disease Activity Score) combined with DR4 or DR2 (as a prognostically favourable factor) and rheumatoid factor positivity. Radiographic damage could be better predicted if disease activity during the first 6 months was included. Absence or presence of progression of radiographic damage could be correctly predicted in 83% of the patients.

On the Representation and Use of Language Information in Bilinguals

Abstract: The present chapter examines how the bilingual's knowledge of what language a particular word belongs to is represented in bilingual memory and how that knowledge could be used to facilitate bilingual language comprehension. Two basic hypotheses (the language tag and the language network hypotheses) are presented within the framework of bilingual versions of two different models of visual word recognition (serial search and interactive activation). It appears that the bilingual interactive activation model best accommodates some recent data on bilingual word recognition.

Occupational exposure to antineoplastic agents at several departments in a hospital. Environmental contamination and excretion of cyclophosphamide and ifosfamide in urine of exposed workers.

Abstract: The occupational exposure to cyclophosphamide (CP), ifosfamide (IF), 5-fluorouracil (5FU), and methotrexate (MTX) of 25 pharmacy technicians and nurses from four departments of a hospital was investigated. Previously developed methods for the detection of exposure to some antineoplastic agents were validated. Exposure to CP, IF, 5FU, and MTX was measured by the analysis of these compounds in the environment (air samples and wipe samples from possible contaminated surfaces and objects). Contamination of the work environment was found not only on the working trays of the hoods and on the floors of the different rooms but also on other objects like tables, the sink unit, cleaned urinals and chamber pots, and drug vials and ampules used for preparation and packing of drugs. The gloves used during preparation of the drugs and during cleaning of the hoods were always contaminated. The uptake of CP or IF was determined by the analysis of both compounds in urine. CP or IF was detected in the urine of eight pharmacy technicians and nurses. The amounts ranged from < 0.01 to 0.5 μg (median: 0.1 μg). CP and IF were found not only in the urine of pharmacy technicians and nurses actively handling these compounds (n = 2) but also in the urine of pharmacy technicians and nurses not directly involved in the preparation and administration of these two drugs (n = 6). CP and IF were excreted during different periods ranging from 1.40 to 24.15 h after the beginning of the working day, suggesting different times of exposure, different exposure routes, and/or interindividual differences in biotransformation and excretion rate for these compounds. The urinary CP and IF determination method seems to be sensitive and suitable for monitoring the exposure to and measuring the uptake of these toxic compounds by pharmacy technicians and nurses during occupational activities.

Isolation of a candidate gene for Norrie disease by positional cloning.

Abstract: The gene for Norrie disease, an X–linked disorder characterized by progressive atrophy of the eyes, mental disturbances and deafness, has been mapped to chromosome Xp11 close to DXS7 and the monoamine oxidase (MAO) genes. By subcloning a YAC with a 640 kilobases (kb) insert which spans the DXS7–MAOB interval we have generated a cosmid contig which extends 250 kb beyond the MAOB gene. With one of these cosmids, microdeletions were detected in several patients with Norrie disease. Screening of cDNA libraries has enabled us to isolate and sequence a likely candidate gene for Norrie disease which is expressed in retina, choroid and fetal brain. No homologous sequences were found in DNA and protein databases indicating that this cDNA is part of a gene encoding a ‘Pioneer’ protein.

Constraining psycholinguistic models of morphological processing and representation: The role of productivity

Abstract: Listeners can understand novel lexical forms without apparent difficulty. This ability to analyze and interpret an unfamiliar input string raises some important psycholinguistic questions. We are led to ask how this parsing is actually accomplished and what its role is in the recognition of familiar word forms. The Standard psycholinguistic answer to the latter question has been that the human parsing abilities at the lexical level are of only minor importance. Indeed, in modeling lexical processing, psycholinguists have not been particularly concerned with morphological productivity and its implications for lexical processing and storage. This neglect of productivity is clearly apparent in the default view of language comprehension which is assumed to be based upon two radically different processing mechanisms. The first is exploited during word recognition and involves retrieving information from a permanent memory store, the lexicon. The second mechanism allows the integration of the semantic and syntactic information associated with the individually recognized words and their order. These latter processes parse and construct novel sentential representations. Thus, the mechanisms that are capable of generating new linguistic structure are typically reserved for the post-lexical processes.

Heterogeneity among Peer-Rejected Boys: Subtypes and Stabilities.

Abstract: Cluster analysis was used to identify subtypes among 98 peer-rejected 5–7-year-old boys. Repeated sociometric nominations obtained over a 1-year interval permitted examination of the relation between rejection subtype and sociometric stability. Results revealed that 48% of these rejected boys were aggressive, impulsive, disruptive, and noncooperative as well as not involved in mutual liking. A smaller number (13%) were socially shy, perceived themselves to be negatively regarded by their peers, and were uninvolved in mutual liking. Two other subtypes, accounting for 39% of these boys, did not seem especially deviant. These behavioral characteristics generally typified the four rejection subtypes 1 year later. 66% of the nonaggressive subtypes changed sociometric classification (i.e., became average or popular) after a year, whereas only 42% of the aggressive-rejected children did so, suggesting that peer rejection that involves aggression is more stable than rejection that does not.

Particle morphology and chemical microstructure of colloidal silica spheres made from alkoxysilanes

Abstract: Monodisperse colloidal silica spheres with radii in the range 10–500 nm were prepared by hydrolysis and condensation of tetraethoxysilane (TES) in a mixture of water, ammonia and a lower alcohol at several temperatures. It was attempted to establish a relation between the morphology and the chemical microstructure of the particle. Particle morphologies were examined with transmission electron microscopy and static and dynamic light scattering. The microstructure of the spheres was studied with quantitative direct excitation 29Si nuclear magnetic resonance (NMR) spectroscopy and a combination of qualitative cross-polarization 13C NMR and elemental analysis. A comparison was made between these particles and particles prepared from TES in an ammonia/water in cyclohexane microemulsion and also with Ludox® silica particles. The siloxane microstructure was found to show almost no variation as a function of concentration of reagents, catalyst, co-solvent and temperature. Around 65% of the silicon nuclei was bonded through siloxane bonds with four other silicons, approximately 30% was bonded with three other silicons and a few percent with only two. It was shown that under most experimental conditions several percent of the ethoxy groups never leave the TES molecule and end up inside the silica. The Ludox particles were found to consist of a more condensed silicon structure as compared with particles synthesized in alcohol, ammonia, water mixtures, whereas the spheres prepared in the microemulsion were less condensed and contained more alkoxy groups. The differences in particle morphologies — ranging from irregularly shaped rough particles to perfect, smooth spheres — are not caused by differences in siloxane and ethoxy microstructure. It is proposed instead, that a smooth and spherical particle shape is the result of the growth by monomers or small oligomers, and that a rough, irregular shape is the result of growth by larger silicon structures.

Stress distribution around dental implants: influence of superstructure, length of implants, and height of mandible

Abstract: The stress distribution around dental implants was investigated by use of a two-dimensional model of the mandible with two implants. A vertical load of 100 N was imposed on abutments or the bar connection. The stress was calculated for a number of superstructures under different loading conditions with the help of the finite element method. The length of the implants and the height of the mandible were also varied. A model with solitary abutments showed a more uniform distribution of the stress when compared with a model with connected abutments. The largest compressive stress was also less in the model without the bar. Using shorter implants did not have a large influence on the stress around the implants. When the height of the mandible was reduced, a substantially larger stress was found in the bone around the implants because of a larger overall deformation of the lower jaw.

Decreased Expression of E-Cadherin in the Progression of Rat Prostatic Cancer

Abstract: Cadherins represent a family of Ca 2+ -dependent cell adhesion molecules involved in homotypic, homophilic cell-cell interactions. Recent studies have shown that the cadherins can play a role in invasive and metastatic behavior. Using the established Dunning R-3327 model system of serially transplantable rat prostate cancers, the expression of E- and P-cadherin in rat prostatic cancer was studied. Analysis within this system demonstrated that whereas E-cadherin was expressed in the normal rat prostate and the well- or moderately differentiated, noninvasive Dunning tumors, no expression, either at the mRNA or at the protein level, could be detected in the invasive sublines. Since not all invasive Dunning tumors studied have metastatic ability, these results suggest that a decreased expression of E-cadherin is correlated with invasive behavior rather than with metastatic ability. Recently, genetic instability occurred in an animal bearing the well differentiated, androgen-responsive, slow growing, nonmetastatic Dunning R-3327-H rat prostate cancer resulting in the progression to an anaplastic, androgen-independent, fast growing, highly metastatic state. This spontaneously arising tumor, termed the AT6 subline, in its original host was heterogeneously composed of both a well differentiated and an anaplastic population of cancer cells in which areas of squamous cell differentiation were occasionally observed. The original animal bearing this heterogeneous AT6 cancer developed multiple metastases, the lung metastases being heterogeneously composed of anaplastic and squamous cell populations. Cytogenetic analysis demonstrated that the lung metastases were derived from a specific subpopulation of cancer cells present in the original AT6 primary tumor. Immunohistochemical studies demonstrated that only the area of lung metastases displaying squamous morphology were positive for E-cadherin. In contrast, the anaplastic areas of the lung metastases and the metastases in other organs were E-cadherin negative. By the first passage of the AT6 tumor only the anaplastic cells were present and no detectable E-cadherin mRNA or protein was found in the primary tumor and metastatic deposits. These results suggest that a decreased expression of E-cadherin is associated with the progression of prostatic cancer.

Evolution of the spectral function in Mott-Hubbard systems with d1 configuration.

Abstract: We have studied the photoemission spectra of perovskite-type Ti 3+ and V 4+ oxides, which have formally the d 1 configuration ranging from a Mott insulator to a paramagnetic metal. The results indicate that as the Mott-Hubbard gap closes, spectral weight is transferred from the upper and lower Hubbard bands to the region near the Fermi level with decreasing U/W (U, d-d Coulomb repulsion energy; W, one-electron d-band width), i.e., from the incoherent to the coherent part of the single-particle spectral function