Showing papers by "University of Amsterdam published in 1982"

Factoring Polynomials with Rational Coefficients

Abstract: In this paper we present a polynomial-time algorithm to solve the following problem: given a non-zero polynomial fe Q(X) in one variable with rational coefficients, find the decomposition of f into irreducible factors in Q(X). It is well known that this is equivalent to factoring primitive polynomials feZ(X) into irreducible factors in Z(X). Here we call f~ Z(X) primitive if the greatest common divisor of its coefficients (the content of f) is 1. Our algorithm performs well in practice, cf. (8). Its running time, measured in bit operations, is O(nl2+n9(log(fD3).

Dose fractionation, dose rate and iso-effect relationships for normal tissue responses

Abstract: An analysis is,,presented of responses of a variety of normal tissues in animals to fractionated irradiations. It is shown that the influence of fractionation can be described on the basis of a simple formula relating the effectiveness for induction of cellular effects to the dose per fraction: F(D) = 1D + a2D2. The ratio a 1 a 2 is derived as an essential parameter for, the description of fractionation effects. It is concluded that the values of a 1 a 2 for responses of various tissues range widely from 2 to 10 Gy. On the basis of the review of radiobiological data, a formalism is developed for the analysis and prediction of iso-effect relations for tissue tolerance, which can be used as an alternative to the nominal standard dose (NSD) formula of Ellis and its derived equations. An essential characteristic of the formalism is that three groups of tissue responses are distinguished which can be described with respect to fractionation effects by average values of a l a 2 = 10 ; 5 and 2.5 Gy, respectively. These groups comprise a l: a.o. skin and intestine; 2: connective tissue; 3:a.o. lung and vascular system. Dose rate effects can be described by a similar formalism. For the calculation of equivalent total doses to be applied in clinical treatments, a concept denoted Extrapolated Tolerance Dose (ETD) of Extrapolated Response Dose (ERD) is introduced. ETD is the tolerance dose for an infinite number of very small fractions. This concept is shown to be useful for the summation of different fractionated schedules and of low dose rate treatments. A number of examples is presented illustrating similarities and differences in comparison with calculations based on the NSD formula. An important feature of the described formalism is that it is directly based on radiobiological insights and it provides a more logical concept to account for the diversity of tissue responses than the assumption of different exponents of N and T in the NSD formula.

True and Spurious Duration Dependence: The Identifiability of the Proportional Hazard Model

Abstract: Lancaster and Nickell (1980) have argued that in the proportional hazard model the effects of time dependence (true duration dependence) and unobserved sample heterogeneity (spurious duration dependence) cannot be distinguished. We show that both effects can be distinguished if the model allows for observed explanatory variables in the hazard. We also discuss the application of our result to practical situations.

Factors promoting the tissue dissolving capability of sodium hypochlorite.

Abstract: The authors thank Mr A. J. Lammens for his technical assistance and Dr S. R. Fox for his assistance in preparing the manuscript.

The thyroglossal cyst

Abstract: The thyroglossal cyst is the most common nonodontogenic cyst in the neck. This cyst may also occur in the lingual or submental areas, though more rarely. Malignant changes have been described. Clinically, no differentiation between a benign cyst and a malignancy can be made. The literature is reviewed regarding the embryology, epidemiology, etiology, symptomatology, radiology, histology, and treatment of this cyst and its malignant counterpart.

1,4-Diaza-1,3-butadiene (a-diimine) ligands: their coordination modes and the reactivity of their metal complexes

Abstract: Publisher Summary Molecules containing the 1,4-diaza-1,3-butadiene skeleton have attracted much interest because of both their versatile coordination behavior and the interesting properties of their metal complexes. 1,4-diaza-1,3-butadienes (R-DAB) may be prepared by condensation reactions involving glyoxals, α-ketoaldehydes or α, β-–diketones with primary amines RNH2. It was concluded from nuclear magnetic resonance (NMR) spectra, dipole moments, and infrared (IR) spectra that the R-DAB molecule exists in solution in the E configuration at both C=N double bonds while the conformation of the central C–C bond is predominantly s-trans. So far stable complexes containing monodentate R–DAB have only been reported for the square planar d8–metals Pd11, Pt11, and Rh1. The reports of metal complexes with R–DAB ligands date back to 1953 when Krumholz described the synthesis of some ferrous complexes. The unusual stability and characteristic color being ascribed to the presence of π bonding between the metal and the nitrogen atoms. Factors, such as the substituents R and R, the metal atom, and the other ligands bonded to the metal atom, will influence the type of coordination of the R–DAB( R’,R) ligands. Just as 2, 2’-bipyridine, the R–DAB ligands can be readily converted to stable paramagnetic radical anions by potassium in 1,2-dirnethoxyethane or tetrahydrofuran (THF).

A systemic lupus erythematosus (SLE)-like disease in mice induced by abnormal T-B cell cooperation. Preferential formation of autoantibodies characteristic of SLE.

Abstract: This is the first report describing the experimental induction of a full-blown clinical syndrome strongly resembling systemic lupus erythematosus (SLE) The method used was the induction of a chronic graft-vs-host reaction (GVHR) employing genetically nonautoimmune strains of mice Many of the F1 mice undergoing a GVHR (GVH F1 mice) revealed the following pathological alterations: splenomegaly, periarteritis, immunecomplex glomerulonephritis accompanied by elevated proteinuria and ascites, dysgammaglobulinemia, persistently increased production of IgG in the spleen, and formation of autoantibodies to thymocytes, erythrocytes, nuclear antigens, double-stranded DNA, and antibodies deposited along the basement membrane of skin In spite of the excessive T cell help, the GVH F1 animals failed to produce spontaneous serum antibodies to dextran and the bacteriophage fd They also had no increased numbers of spontaneous indirect plaque-forming cells to sheep red blood cells and trinitrophenyl These negative findings indicate that antigen has to be present during the GVHR to trigger antibody formation This in turn suggests that the persistent presence of self-antigens was essential for the formation of IgG autoantibodies in GVH F1 mice However, whereas autoantibodies typical of SLE were readily produced, none of the GVH F1 mice had autoantibodies to thyroglobulin, or other autoantibodies not typical of SLE Conceivably, not only the presence of self-antigens, but also their antigenic configuration, may determine whether or not autoreactive B cells are successfully triggered during abnormal T-B cell cooperation Given the lack of carrier-specific T helper cells in abnormal T-B cell cooperation, protein self-antigens, such as thyroglobulin, may be intrinsically less apt than the self-antigens involved in SLE to bind to the corresponding autoreactive B cells The self-antigens involved in SLE, such as DNA and cell-surface epitopes, are assumed to be capable of multipoint high-avidity binding to and cross-linking of the Ig receptors of these B cells, thus providing an effective signal 1

Clinical significance of polymerization shrinkage of composite resins.

Abstract: The volumetric polymerization shrinkage of some composite resin restorative materials was measured with a modified dilatometer. It is emphasized that only the shrinkage from the start of the gelation, the rigid contraction of the material, is of clinical relevance. The amount of gelation was determined with an instrument that indicates the first moment at which the setting material is rigid enough to exert tensile forces. In addition, the influences of storage, testing conditions, and mixing ratio on the rigid contraction were studied for one light-cured as well as some chemically cured composite resins.

Reflex control of heart rate in normal subjects in relation to age: a data base for cardiac vagal neuropathy.

Abstract: We examined the heart rate changes induced by forced breathing and by standing up in 133 healthy subjects in the age range 10–65 years in order to establish a data base for studies on parasympathetic heart rate control in autonomic neuropathy. Test results declined with age. Log-transformation was used to define the lower limit of normal (P0.10) and an uncertainty range (values between P0.10 and P0.025). The lower limit of normal decreased from 22 to 11 beats/ min for forced breathing and from 26 to 16 beats/min for standing up, with age increasing from 10 to 65 years. No subject scored below and only two subjects scored in or below the uncertainty range for both tests. Lack of correlation between both tests (r=0.17) documents the different afferent mechanisms of the reflex heart rate changes. In combination these two tests form a simple and reliable bedside method to establish cardiac vagal neuropathy.

The Role of BK Virus in Acute Respiratory Tract Disease and the Presence of BKV DNA in Tonsils

Abstract: The significance of BKV infections relative to infections by generally tested respiratory agents was investigated in children with acute respiratory disease. Paired sera from 177 children admitted to a hospital for acute respiratory disease were tested for significant rises in antibodies. Sera from seven patients showed a seroconversion to BKV and clinical signs of acute upper respiratory tract infection were exhibited by each of these patients. BKV infections were present in 8% of the patients with upper respiratory tract disease while seroconversions to adenovirus (2%), influenza A virus (1%), parainfluenza virus (5%), RS virus (6%) and mycoplasma pneumoniae (1%) were observed in 15% of the patients with upper respiratory tract disease. BKV was isolated from the urine of one child with tonsillitis with a concomitant seroconversion to BKV. Tonsils from children with recurrent attacks of acute respiratory disease were tested for the presence of BKV DNA by hybridization with a cloned genomic 32P-labeled DNA of prototype BKV. Five of twelve tonsil DNAs showed hybridization with BKV DNA. Each tonsil showing hybridization with BKV DNA contained multiple nonintegrated copies of the BKV genome per diploid amount of host cell DNA. Attempts to recover infective BKV by transfection of primary human embryonic cells with tonsil DNAs or by co-cultivation of tonsillar cells with primary human embryonic cells were unsuccessful.

The distribution and origin of serotonin‐containing fibers in the septal area: A combined immunohistochemical and fluorescent retrograde tracing study in the rat

Abstract: The distribution of 5-hydroxytryptamine (serotonin, 5-HT)-containing nerve fibers and terminals in the septal area of the rat was studied by using immunohistochemistry with specific antibodies to 5-HT in combination with fluorescent retrograde tracing methods. The 5-HT innervation of the septum is heterogeneous with regard to both the morphology of individual processes and the density of distribution in different parts of the septum. Three major classes of 5-HT like immunoreactive processes can be distinguished: (1) thin, convoluted fibers with small, round or elongated varicosities; (2) thick and relatively straight fibers with few varicosities; and (3) pericellular plexuses with large varicosities in close association with perikarya in the lateral septum. Three areas of the septum receive a prominent innervation by 5-HT processes: the diagonal band of Broca, the ventral part of the lateral septum, and and area bordering the medial edge fo the islands of Calleja (insula magna). Whereas the two latter areas contain dense terminal networks, the diagonal band of Broca is occupied primarily by 5-HT fibers en route to other parts of the septum. Intraseptal injections of HRP or fluorescent dyes (granular blue, propidium iodide) resulted in retrograde labeling of neuronal cell bodies in several nuclei of the brainstem which are known to contain 5-HT neurons: the dorsal raphe, the median raphe, the nucleus reticularis tegmenti pontis, the raphe pontis, and the raphe magnus. Where fluorescent retrograde tracing was performed with 5-HT immunohistochemistry on the same tissue section, a prominent 5-HT containing pathway and a non-5-HT-containing pathway from the raphe nuclei to the septum were revealed. Finally, double retrograde fluorescent labeling after injections of granular blue or propidium iodide into the septum and entorhinal area respectively of the same rat revealed extensive branching of the raphe efferents. Thus, individual raphe neurons may simultaneously connect with septum and the entorhinal area, two structures essential for normal hippocampal function.

Unreacted Methacrylate Groups on the Surfaces of Composite Resins

Abstract: The unreacted methacrylate groups on the surface of conventional composites and microfilled composites were studied by means of multiple internal reflection infrared spectroscopy. The influences of polymerization time, temperature, and the effect of polishing were studied. We also attempted to relate the results of some mechanical tests to the degree of chemical unsaturation measured in the different resins. All surface treatment and manipulative variables caused a decrease in double bond content and interfacial bond strength.

Time course and properties of late adaptation in spinal motoneurones of the cat.

Abstract: In the spinal cord of anaesthetized cats, motoneurones of m.gastrocnemius medialis were stimulated to repetitive firing by very long-lasting steady currents injected through an intracellular microelectrode (maximum duration 4 min). In such discharges, a gradual decline of impulse frequency was found to occur during several tens of seconds. Most of this “late adaptation” occurred during the first 30 s of firing. Comparisons between the responses of different cells showed that the frequency-drop during late adaptation was strongly correlated to the impulse rate at the beginning of the discharge. For one and the same cell, late adaptation was more prominent at strong than at weaker intensities of stimulation (i.e., at high than at lower initial firing rates). In cells capable of discharging continuously for several minutes, a semi-stationary discharge rate tended to be reached after about 1 min or less.

Virulence of black-pigmented Bacteroides strains from periodontal pockets and other sites in experimentally induced skin lesions in mice.

Abstract: The virulence of different black-pigmented Bacteroides strains (BPB) was studied using monoinfections in an experimental animal model. Bacterial suspensions were injected subcutaneously in the back of mice. After four days the mice were killed and the induced inflammations were examined histologically. Bacteroides gingivalis strains, which are mostly isolated from subgingival plaque associated with adult destructive periodontitis. were characterized by inducing a spreading type of inflammation, mostly resulting in a gravity abscess or a phlegmonous abscess. Strains of Bacteroides melaranogenicus subspecies intermedius, isolated from gingivitis or periodontitis, always induced a localized abscess at the site of injection. Most Bacteroides asaccharolyticus strains, which are isolated from nonoral sites, caused a localized inflammation, and Bacteroides melaninogenicus subspecies melaninogenicus strains caused only minimal inflammation.

Food selection by Dreissena polymorpha Pallas (Mollusca: Bivalvia)

Abstract: SUMMARY. The role of the selection systems in the mantle cavity and the stomach of Dreissena polymorpha was investigated by comparing the composition of particles in the plankton, the stomach and the mid-gut. Both systems selected particles of 15–40 μm for food. The selection mechanism functioned more efficiently in the presence of simple algal mixtures than in the presence of lake plankton, but did not function at all in animals fed after 16 h starvation. The composition of successive pseudo-faecal pellets differed. It is concluded that selection of different kinds of particle occurs in specific places in the mantle cavity. Cryptomonas spp. were highly preferred as food. Indications were found that not only does size-selection occur, but also selection of a chemical nature.

Intracellular Compartment ation and Control of Alanine Metabolism in Rat Liver Parenchymal Cells

Abstract: The catabolism of alanine in isolated rat liver cells was studied using a perifusion system in order to titrate the cells with different concentrations of alanine. The Concentrations of the components of the alanine aminotransferase reaction in the cytosolic and mitochondrial compartments were measured after digitonin fractionation of samples of the cell suspension taken during each steady state. Comparison of the mass-action ratios with the equilibrium constant indicated that the cytosolic enzyme is poised towards pyruvate formation at all concentrations of alanine used, whereas the mitochondrial enzyme is always poised towards alanine formation. The calculated flux through cytosolic alanine aminotransferase, using literature data for the kinetic parameters of the enzyme and experimental data for the concentration of metabolites, was in close agreement with the measured carbon flux. It is concluded that the transamination step in alanine catabolism occurs in the cytosol. The concentration of the components of the glutamate dehydrogenase and 3-hydroxybutyrate dehydrogenase reactions in the mitochondrial compartment during each steady state were also measured. The ΔG of the combined reactions did not change appreciably on increasing the extracellular alanine concentration to 0.6 mM. At higher alanine concentrations ΔG became slightly more negative. As the extracellular Concentration of alanine was increased, the concentration of glutamate in both the cytosolic and the mitochondrial compartments increased. However, the cytosolic alanine concentration was always lower than that in the extracellular compartment even at the highest concentration of alanine (6 mM) infused. When increasing concentrations of pyruvate were infused together with a fixed concentration of alanine (0.6 mM), the cytosolic concentration of alanine increased to levels even higher than that in the perifusate. However, there was no significant effect in the rate of formation of nitrogenous products. It is concluded that the transport of alanine across the plasma membrane is the only rate-controlling step in alanine catabolism under the conditions used.