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Biomedical subjects

H van Dijk

Publications and source records attributed to H van Dijk.

At least 91 records · Page 5Linked to original sources
PubMed1985

Opsonic defense to Staphylococcus epidermidis in the premature neonate.

The determinants of opsonic defense to Staphylococcus epidermidis were studied in 47 premature newborns. Opsonic activity for S. epidermidis in serum from premature newborns proved to be proportional to gestational age (r = .664, P less than .001). The level of IgG antibodies to staphylococcal peptidoglycan in neonatal sera was similarly proportional to gestational age (r = .604, P less than .001). However, all opsonic activity of premature neonatal serum proved to be heat labile, i.e., dependent on activation of complement. Thus, no heat-stable, IgG-dependent opsonic activity to S. epidermidis was detected in any of the preterm sera, despite the presence of IgG antibodies to peptidoglycan. Further studies with purified IgG isolated from paired sera from term neonates and their mothers revealed that at similar concentrations the opsonic activity to S. epidermidis of neonatal, transplacentally derived IgG was only 26% of the activity of maternal IgG, a finding that may explain the absence of heat-stable opsonic activity in preterm newborns.

Antibodies, Bacterial↗
PubMed1985

Increased local complement levels upon intraperitoneal injection of mice with Listeria monocytogenes and regulation by polyanions.

Alternative complement pathway activity in mouse peritoneal fluid was determined by a sensitive microtiter assay with rabbit erythrocytes as target cells and cobra venom factor as the inducer of bystander hemolysis. The intra- and interstrain variations in five mouse strains were 30% and, maximally, 64%, respectively. No activity was detected in genetically C5-deficient mice. In C5-sufficient mice, intraperitoneal injection of heat-inactivated Listeria monocytogenes resulted in a 250% increase in local complement activity within 30 min. This effect was reversed by simultaneous injection of dextran sulfate but not heparin. These results are discussed in relation to the ability of listeriae to activate the mouse alternative complement pathway in vitro and the effectiveness of dextran sulfate and the failure of heparin in functioning as an adjuvant in the induction of a protective response in mice by a heat-inactivated listeria vaccine.

Animals↗
PubMed1984

Complement inhibitory and anticoagulant activities of fractionated heparins.

Almost monodisperse heparin fractions (Mw/Mn less than 1.1) were obtained by gel filtration of a commercial heparin. These fractions were assayed for anticoagulant activity (thrombin times and APTT), chromogenic anti-factor Xa activity, inhibitory activity for the human classical complement pathway, carboxyl group content and total sulfate content. Linear relationships were observed between the molecular weight of the heparin fractions and the anti-coagulant activities as determined by thrombin time- and APTT-assay and the classical complement pathway inhibitory activity. On the other hand a hyperbolic-like relationship was observed between the molecular weight of the heparin fractions and the chromogenic anti-factor Xa activity. The heparin fractions did not show significant differences with respect to the carboxyl group and total sulfate content. Low- and high affinity heparin fractions were obtained by affinity chromatography using immobilized AT III. High- and low-affinity fractions greatly differed not only with respect to their APTT activity, but also where their complement-inhibitory activities were concerned. The latter in contrast to literature data available. These differences could not be explained by the observed differences in molecular weight of high and low affinity heparin respectively.

Animals↗
PubMed1982

An esterase duplication in Drosophila: differences in expression of duplicate loci within and among related species.

An esterase duplication is described in the sibling species pair Drosophila mojavensis and Drosophila arizonensis. We present evidence for two separate structural loci mapping at a distance of less than 0.16 recombination units from each other. Alleles at the two loci have the same substrate specificities and form small amounts of interlocus heterodimers. One locus (Est-5) is functioning throughout the insect's life cycle and appears at high concentrations in the hemolymph and the fat body. Its duplicate (Est-4) functions only during the late larval stage and is concentrated mainly in the carcass. No null alleles at either locus were observed in population surveys. An examination of 12 other species from the repleta group, to which D. mojavensis and D. arizonesis belong, suggests that Est-5 is universally present, but the activity levels of Est-4 vary among species and may be totally absent in some species. Variation in the level of Est-4 activity does not closely follow the phylogenetic relationship.

Age Factors↗
PubMed1982

Role of C4-binding protein in the defective lysis of sensitized sheep erythrocytes by mouse complement.

Passage of mouse EDTA-plasma over an anti-C4-binding protein (anti-C4-bp) affinity column reduced the C4-bp level by an average of 34% and increased the classical C pathway activity as measured with sensitized normal and desialylated sheep erythrocytes, but not versus sensitized rabbit erythrocytes. This suggests that C-regulation by C4-bp is independent of membrane sialic acid and provides evidence for the presence of a hitherto unknown preferential site for mouse C4-bp on sheep erythrocytes. The absence of both this site and sialic acid on their membranes makes sensitized rabbit erythrocytes useful target cells for assay of mouse classical C pathway activity.

Animals↗
PubMed1981

Development of a simple passive haemagglutination-inhibition assay for Listeria monocytogenes lipoteichoic acid.

A simple assay for listeria lipoteichoic acid was devised. It is based on the property of this substance to attach spontaneously to erythrocytes. Thus coated rabbit erythrocytes were agglutinated by a rabbit antiserum raised towards dead listeria. Inhibition of this passive agglutination was used as a measure of listeria lipoteichoic acid. Cross-reactivity of lipoteichoic acid from Lactobacillus fermenti in the assay and inhibition by simple sugars suggest that the assay is specific for terminal galactose.

Animals↗
PubMed1981

Involvement of membrane-associated sialic acid in the resistance of sheep erythrocytes to lysis by mouse complement.

The sensitivity of the murine complement system to regulation by membrane-associated sialic acid was investigated. Therefore the C-mediated lysis of sialic acid-rich sheep erythrocytes, sialic acid-poor rabbit erythrocytes and enzymatically desialylated sheep erythrocytes was studied. Mouse complement differed from human and guinea pig complement in that besides the alternative, also the classical pathway appeared sensitive to regulation by surface sialic acid. The possible reaction mechanisms behind the selective sensitivity of the murine classical pathway to membrane-linked sialic acid are discussed and will be subject of further study.

Animals↗
PubMed1981

Interactions of killed Listeria monocytogenes with the mouse complement system.

Incubation of mouse serum with Listeria monocytogenes involved activation of the alternative complement pathway, resulting in depletion of both classical and alternative pathway activity. The activation process gave rise to reactive (calcium- and magnesium-independent) lysis of, specifically, rabbit erythrocytes, which become resistant to this form of hemolysis by sensitization with antibodies. The possible implications of these findings for L. monocytogenes as an intracellular parasite and for rabbit erythrocytes as target cells for mouse alternative complement pathway activity are discussed.

Animals↗
PubMed1980

Estimation of classical pathway of mouse complement activity by use of sensitized rabbit erythrocytes.

A simple photometric assay was devised for determining classical complement pathway activity in mouse serum using sensitized rabbit erythrocytes as target cells. These cells appeared more sensitive to lysis by mouse complement than sensitized mouse and sheep erythrocytes, most probably by their ability to escape the C3b inactivator system. Advantages of the assay over other techniques are the high sensitivity and the avoidance of the use of radioisotopes. With this test it is possible to get more insight in the complement system of an animal species that has been most widely in use in immunological research.

Animals↗
PubMed1980

Histamine 2-receptor-mediated immunomodulation in the mouse. II. Immunomodulation by the H2 antagonist metiamide.

Modulation of delayed hypersensitivity and antibody formation to sheep red cells by metiamide were studied in the mouse system. Depending on the time and dose of antigen and metiamide administration suppression or enhancement of the delayed hypersensitivity response was observed. The effects in this system did not differ from those reported for the H2 agonist tolazoline, which were most probably mediated by suppressor cells. As far as the humoral response was concerned metiamide tended to stimulate the IgM response. Optimal stimulation was reached if 50 mg metiamide/kg was administered 3 days before immunization with 2 x 10(8) SRBC. Under all conditions tested the IgG response was unaffected. These results suggest antagonistic effects of metiamide for tolazoline and adduce further evidence for the presence of H2 receptors on B cells. The IgM production per plasmacell was enhanced suggesting different H2 receptors to be involved in differentiative and proliferative B cell responses. The possible consequences of H2 antagonist application in human therapy are discussed.

Animals↗
PubMed1979

Regulation of the immune response by macrophages.

Regulation of the immune response by macrophages was studied with cellular resistance to Listeria monocytogenes as parameter. The use of agents which suppress macrophage activity during the induction-phase of immunity enabled the induction of protective immunity with killed listeria. Fractionation of the cell content of listeria yielded an RNA'se sensitive fraction which in a dose of 300 ng and in combination with the cationic surfactant dimethyl dioctadecyl ammonium bromide induced protective immunity against listeria.

Adjuvants, Immunologic↗
PubMed1979

Adjuvanticity of lactobacilli. I. Differential effects of viable and killed bacteria.

The adjuvanticity of Lactobacillus brevis and Lactobacillus plantarum was the subject of this study. The latter was the better adjuvant in both delayed hypersensivity and antibody formation to sheep red blood cells. Viable L. plantarum stimulated exclusively the delayed hypersensivity, where heat-killed bacteria had an adjuvant effect on antibody formation. For optimal adjuvant effects lactobacilli had to be injected in a dose of 10(8) into the same site as the antigen. Viable lactobacilli and to a lesser degree heat-killed bacteria induce hepato-splenomegaly, suggesting mediation of the adjuvant activity by the reticuloendothelial system. Granuloma formation with mainly mononuclear cell infiltrates could be observed after subcutaneous administration of viable lactobacilli whereas heat-killed lactobacilli induced granulomata containing about equal numbers of granulocytes and mononuclear cells. The possible clinical application of L. plantarium in the immunotherapy of tumours is suggested.

Adjuvants, Immunologic↗