Showing papers by "University of Antwerp published in 1992"

Presenile dementia and cerebral haemorrhage linked to a mutation at codon 692 of the β–amyloid precursor protein gene

Abstract: Several families with an early-onset form of familial Alzheimer's disease have been found to harbour mutations at a specific codon (717) of the gene for the beta-amyloid precursor protein (APP) on chromosome 21. We now report, a novel base mutation in the same exon of the APP gene which co-segregates in one family with presenile dementia and cerebral haemorrhage due to cerebral amyloid angiopathy. The mutation results in the substitution of alanine into glycine at codon 692. These results suggest that the clinically distinct entities, presenile dementia and cerebral amyloid angiopathy, can be caused by the same mutation in the APP gene.

Extra-pair paternity results from female preference for high-quality males in the blue tit.

Abstract: EXTRA-PAIR copulations (EPCs) seem to be one of the most widespread alternative reproductive behaviours by which male birds can increase their fitness1,2. In many species females actively solicit or freely engage in EPCs3–5, which suggests that they benefit from them. Of the eight hypothetical benefits proposed2,6, the most likely are genetic2. Often females engage in EPCs with more dominant males3,7 or with males with more elaborate ornaments8,9. In species in which paternity was assigned, extra-pair young were divided asymmetrically between males10–12. Here, combining detailed behavioural work with DNA-fingerprinting of an entire population, we present evidence that such an asymmetry is indeed caused by female behaviour, and that 'attractive' males do not suffer lost paternity, survive better and recruit more young. Our results support the genetic quality hypothesis.

The peripheral myelin protein gene PMP-22 is contained within the Charcot-Marie-Tooth disease type 1A duplication.

Abstract: Charcot-Marie-Tooth disease (CMT1) is the most common form of inherited peripheral neuropathy. Although the disease is genetically heterogeneous, it has been demonstrated that the gene defect is the most frequent type (CMT1A) is the result of a partial duplication of band 17p11.2. Recent studies suggested that the peripheral hypomyelination syndrome in the trembler (Tr) mouse, a possible animal model for CMT1 disease, is associated with a point mutation in the peripheral myelin protein-22 gene (pmp-22). Expression of pmp-22 is particularly high in Schwann cells, and the protein is found in peripheral myelin. We now report that the human PMP-22 gene is contained within the CMT1A duplication. We therefore, suggest that increased dosage of the PMP-22 gene may be the cause of CMT1A neuropathy.

Phase retrieval through focus variation for ultra-resolution in field-emission transmission electron microscopy.

Abstract: The use of a coherent field-emission electron source in transmission electron microscopy is combined with phase retrieval by digital processing of a focal image series. For the first time, a dramatic improvement of the high-resolution performance of the electron microscope beyond the usual ``point-to-point'' resolution has been realized: Experiments on a 200-kV microscope with a point resolution of 0.24 nm reveal reconstructed information down to 0.14 nm. Examples are shown in the field of high-${\mathit{T}}_{\mathit{c}}$ superconductors and ferroelectric oxides. The oxygen sublattice in these structures is revealed.

Mapping of a gene predisposing to early-onset Alzheimer's disease to chromosome 14q24.3

Abstract: Genetic linkage studies with chromosome 21 DNA markers and mutation analysis of the beta-amyloid protein precursor gene located in 21q21.3 have indicated that early-onset Alzheimer's disease (EOAD) is a heterogeneous disorder for which at least one other chromosomal locus exists. We examined two extended histopathologically confirmed EOAD pedigrees, AD/A and AD/B, with highly informative short tandem repeat (STR) polymorphisms and found complete linkage of the disease to a (CA)n dinucleotide repeat polymorphism at locus D14S43 in 14q24.3 (Zmax = 13.25 at theta = 0.0). Using additional chromosome 14 STR polymorphisms we were able to delineate the region containing the EOAD gene to an area of, at most, 8.9 centiMorgans between D14S42 and D14S53, flanking D14S43 on both sides.

The 4P Classification of the Marketing Mix Revisited

Abstract: McCarthy's 4P classification of the marketing mix instruments has received wide acceptance in past decades. In recent years, however, increasing criticism has been voiced, among other reasons becau...

Monoclonal antibodies with selective specificity for Alzheimer Tau are directed against phosphatase-sensitive epitopes.

Abstract: A modified form of the microtubule-associated protein Tau is the major component of the paired helical filaments (PHF) found in Alzheimer's disease. The characterization of these posttranslational Tau modifications is hindered by the lack of sufficient PHF-Tau-specific markers. Here we describe several monoclonal antibodies, prepared by immunization with PHF, two of which showed a selective specificity for PHF-Tau without cross-reactivity with normal Tau. Epitope recognition by these two monoclonals was sensitive to alkaline phosphatase treatment. In Western blotting these monoclonal antibodies reacted specifically with the abnormally phosphorylated epitopes on Alzheimer's disease-associated PHF-Tau. One of the new antibodies can be used for the construction of a sandwich enzyme-linked immunosorbent assay for the specific detection of PHF-Tau without cross-reactivity to normal Tau proteins.

Mutational analysis of SRY: nonsense and missense mutations in XY sex reversal

Abstract: XY females (n=17) were analysed for mutations in SRY (sex-determining region Y gene), a gene that has recently been equated with the testis determining factor (TDF). SRY sequences were amplified by the polymerase chain reaction (PCR) and analysed by both the single strand conformational polymorphism assay (SSCP) and DNA sequencing. The DNA from two individuals gave altered SSCP patterns; only these two individuals showed any DNA sequence variation. In both cases, a single base change was found, one altering a tryptophan codon to a stop codon, the other causing a glycine to arginine amino acid substitution. These substitutions lie in the high mobility group (HMG)-related box of the SRY protein, a potential DNA-binding domain. The corresponding regions of DNA from the father of one individual and the paternal uncle of the other, were sequenced and found to be normal. Thus, in both cases, sex reversal is associated with de novo mutations in SRY. Combining this data with two previously published reports, a total of 40 XY females have now been analysed for mutations in SRY. The number of de novo mutations in SRY is now doubled to four, adding further strength to the argument that SRY is TDF.

Density-dependent clutch size caused by habitat heterogeneity

Abstract: In some studies but not in others the average clutch size decreases with density. We propose that density-dependent fecundity occurs because, as density increases, proportionally more poor-quality sites (with small clutches) are occupied, and not because the clutch size in all territories decreases. This mechanism will only cause density dependence if the habitat is heterogeneous at the scale of the home range or territory of an individual. Density-dependent fecundity will be found in some populations but not in others because of differences in the scale of habitat heterogeneity

Issues in the cross-national assessment of health technology.

Abstract: With the growing international literature in economic evaluation and the rapid spread of new health technologies, there is a need to undertake, or at least interpret, economic evaluations on the international level. However, the ways in which cross-national differences affect the cost-effectiveness of health technologies or their evaluations have never been studied. This paper explores these issues by taking advantage of a unique situation in which the same economic evaluation of a new indication for a health technology was conducted simultaneously in four countries using an identical methodology. The study showed that if prior agreement on methods can be reached and local data applied, economic evaluations can be undertaken in a way that facilitates the extrapolation of results from country to country.

The structure of different phases of pure c-70 crystals

Abstract: Single crystal of pure C70 are grown from the vapour phase and the structure and morphology of these crystals is studied. By means of X-ray diffraction and TEM measurements five different phases are observed. The observed phases are (from high to low temperatures) fcc, rhombohedral, ideal hcp (c/a=1.63), deformed hcp (c/a=1.82) and a monoclinic phase. The occurrence of these different phases and the phase transitions is accounted for in a simple model. For the monoclinic structure a model for the stacking of the orientationally ordered molecules in the lattice is proposed. For both the hcp and fcc phases a Lennard-Jones type interaction potential is used to calculate bond strengths, lattice energies and the theoretical morphology.

Estimation of the size of the chromosome 17p11.2 duplication in Charcot-Marie-Tooth neuropathy type 1a (CMT1a). HMSN Collaborative Research Group.

Abstract: We have previously shown a duplication in 17p112 with probe pVAW409R3 (D17S122) in 12 families with hereditary motor and sensory neuropathy type I (HMSN I) or Charcot-Marie-Tooth disease type 1 (CMT1) In this study we aimed to estimate the size of the duplication using additional polymorphic DNA markers located in 17p112-p12 Two other 17p112 markers, pVAW412R3 (D17S125) and pEW401 (D17S61), were found to be duplicated in all HMSN I patients tested Furthermore, all HMSN I patients showed the same duplication junction fragment with probe pVAW409R3 On the genetic map the duplicated markers span a minimal distance of 10 cM while on the physical map they are present in the same NotI restriction fragment of 1150 kb The discrepancy between the genetic and physical map distances suggests that the 17p112 region is extremely prone to recombinational events The high recombination rate may be a contributing factor to the genetic instability of this chromosomal region

Electrical and thermal properties of a two-dimensional electron gas in a one-dimensional periodic potential

Abstract: We investigate the influence of a periodic weak modulation along the x direction on the electrical and thermal properties of a two-dimensional electron gas in the presence of a perpendicular magnetic field. The modulation lifts the degeneracy of the Landau levels and leads to one-dimensional magnetic bands whose bandwidth oscillates as a function of the magnetic field. At weak magnetic fields this gives rise to the Weiss oscillations in the magnetoresistance, discovered recently, which have a very weakly temperature-dependent amplitude and a period proportional to \ensuremath{\surd}${\mathit{n}}_{\mathit{e}}$ , when ${\mathit{n}}_{\mathit{e}}$ is the electron density. Diffusion-current contributions, proportional to the square of the bandwidth, dominate ${\mathrm{\ensuremath{\rho}}}_{\mathit{x}\mathit{x}}$, and collisional contributions, varying approximately as the square of the density of states, dominate ${\mathrm{\ensuremath{\rho}}}_{\mathit{y}\mathit{y}}$. The result is that ${\mathrm{\ensuremath{\rho}}}_{\mathit{x}\mathit{x}}$ and ${\mathrm{\ensuremath{\rho}}}_{\mathit{y}\mathit{y}}$ oscillate out of phase as observed. Asymptotic analytical expressions are presented for the conductivity tensor. Similar oscillations, of much smaller amplitude, occur in the thermodynamic quantities, such as the magnetization, the susceptibility, and the specific heat. We also predict oscillations in the Hall resistance, the cyclotron resonance position, the linewidth, as well as in the thermal conductivity and thermopower. The components of the thermal-resistance tensor have a magnetic-field dependence similar to that of the electrical-resistivity tensor.

Guanidino compounds in serum, urine, liver, kidney, and brain of man and some ureotelic animals.

Abstract: Guanidino compound levels were quantitatively determined in serum, urine, liver, kidney, and brain of man and of some ureotelic animals. The guanidino compounds were separated over a cation exchange resin, using sodium citrate buffers, and detected with the fluorescence ninhydrin method. Species-specific differences in the levels of some guanidino compounds in the studied ureotelic animals are shown. α-Keto-δ-guanidinovaleric acid is a naturally occurring guanidino compound in ureotelic animals, and is not restricted to the pathobiochemistry to hyperargininemic patients. The fasting serum levels observed in beagles are the same as those found in hyperargininemic patients. In serum, liver, and kidney, the homoarginine, β-guanidinopropionic acid, and γ-guanidinobutyric acid levels are the highest in rats. The last two compounds have the highest levels of the studied guanidino compounds, with the exception of creatine, in kidney. Specific high levels of γ-guanidinobutyric acid and argininic acid are found in brain of rabbits.

Disturbances in acute phase plasma proteins during melancholia: additional evidence for the presence of an inflammatory process during that illness.

Abstract: MAES, MICHAEL, SIMON SCHARPE, EUGENE BOSMANS, MAURITS VANDEWOUDE, EDUARD SUY, WIM UYTTENBROECK, WALTER COOREMAN, CARINE VANDERVORST and JEF RAUS Disturbances in Acute Phase Plasma Proteins during Melancholia Additional Evidence for an Inflammatory Process during that Illness. Prog. Neuro-Psychopharmacol & Biol Psychiat 1992,16(4)501–515. 1. 1. Leukocyte enumeration through flow cytometry has revealed that severe depression may be accompanied by a systemic immune activation, indicative of an Inflammatory response The latter condition allegedly involves an important modification of acute phase plasma protein (APP) equilibrium 2. 2. In order to elucidate whether the state of severe depression is represented by alterations in APPs, the authors measured: α, antitrypsin (α1,AT), α2, macroglobulln (α2,M), haptoglobin (Hp), α, acid glycoprotein (α1,S), transferrin (Tf), complement component 4 (C4) and C-reactive protein (CRP). Interleukin-1-β (II-1B) and lnterleukin-6 (II-6) circulating levels were determined 3. 3. Hyperhaptoglobinemia and hypotransferinemia are hallmarks for major depression and depression per se, respectively, The disorders in Hp and Tf circulating levels are highly sensitive to (83%) and specific for (100%) melancholia as opposed to the healthy state. 4. 4. Disorders in both APPs are significantly related to the absolute number of blood monocytes. 5. 5. The authors observed a trend towards lower α2M and higher α,S values in severely depressed subjects. Severity of depression was significantly related to Hp and α1S (both positively) and to α2M and Tf (both negatively) values. 6. 6. No significant intercategory differences in C4 could be established, whilst only a few subjects exhibited measurable CRP, II-1β and II-6 circulating levels. 7. 7. Our findings may support the hypothesis that depression Is accompanied by an inflammatory response

The endocardial endothelium.

Abstract: The heart wall with its complex trabecular structures is covered with a very thin layer of endocardial endothelial (EE) cells. EE cells appear early during cardiac development; they are involved in myocardial trabeculation and the formation of primitive nutrient vessels. This process precedes the development of coronary vessels, Purkinje fibers, and nerve fibers. EE has a different cell shape and cytoskeletal organization than vascular endothelium. The differences in permeability between EE and the coronary vascular endothelium in the subendocardial myocardium might assign characteristic electrochemical properties to the endocardium. Modulation of EE function by substances in the blood constitutes an important intracavitary autoregulation of muscle-pump performance of the heart, i.e., by altering the duration of contraction without significantly altering early contraction dynamics. Such an autoregulation resets the timing of ventricular relaxation and rapid filling with little effect on early systolic contraction and ejection. Both the release by the EE of various substances with inotropic properties and a trans-EE physicochemical control are postulated as possible underlying mechanisms.

Activity budget and foraging behaviour of red squirrels ( Sciurus vulgaris ) in coniferous and deciduous habitats

Abstract: Activity pattern, activity budget and foraging behaviour are compared between radiotagged squirrels in a coniferous and a deciduous habitat. Differences between habitats are explained in terms of differences in food availability, food choice and feeding rate.

Reactions to platelet transfusion: the effect of the storage time of the concentrate.

Abstract: Random platelet concentrates were pooled and depleted of leucocytes by centrifugation immediately prior to transfusion. The incidence and severity of reactions to 570 leucocyte-poor platelet transfusions in 74 patients were studied. An overall transfusion reaction rate of 13.7% was observed. The reaction rate to platelets stored for less than 3 days (8.7%) was significantly different from the reaction rate to platelets stored for 3 days or more (17.6%). Minor reactions as well as moderate and severe reactions were more frequent in the latter group. As most of the white blood cells were removed prior to transfusion, it is suggested that the reactions result from the transfusion of pyrogenic and/or vasoactive substances accumulated in the plasma of the concentrate during storage.

Evidence for a differential release of nitric oxide and vasoactive intestinal polypeptide by nonadrenergic noncholinergic nerves in the rat gastric fundus.

Abstract: The roles of vasoactive intestinal polypeptide (VIP) and nitric oxide (NO) in nonadrenergic noncholinergic (NANC) nerve-mediated relaxations were investigated in longitudinal muscle strips of the rat gastric fundus. Transmural stimulation (1-16 Hz for 2 min), VIP and noradrenaline evoked a prolonged relaxation of the rat gastric fundus, whereas NO evoked a transient relaxation. Only the electrically induced responses were blocked by tetrodotoxin. The inhibitor of NO biosynthesis NG-nitro-L-arginine (L-NNA) preferentially inhibited the relaxations induced by low frequency stimulation. In contrast, trypsin mainly reduced the electrically induced relaxations to high frequency stimulation; the NANC relaxations resistant to trypsin were further inhibited by L-NNA. VIP-induced relaxations were abolished by trypsin, but remained unaffected by L-NNA. NO- or noradrenaline-induced relaxations were not inhibited by either L-NNA or trypsin alone, whereas the combination of L-NNA and trypsin slightly reduced the noradrenaline-induced responses. These results suggest that NANC responses in the rat gastric fundus at low frequency are mediated mainly by NO, whereas at higher frequency NO together with a peptide, probably VIP, are released.

Converting nested algebra expressions into flat algebra expressions

Abstract: Nested relations generalize ordinary flat relations by allowing tuple values to be either atomic or set valued. The nested algebra is a generalization of the flat relational algebra to manipulate nested relations. In this paper we study the expressive power of the nested algebra relative to its operation on flat relational databases. We show that the flat relational algebra is rich enough to extract the same “flat information” from a flat database as the nested algebra does. Theoretically, this result implies that recursive queries such as the transitive closure of a binary relation cannot be expressed in the nested algebra. Practically, this result is relevant to (flat) relational query optimization.