Biomedical subjects

H Van Dijk

Publications and source records attributed to H Van Dijk.

At least 37 records · Page 2Linked to original sources

PubMed1991

In vivo anti-complementary activities of the cobra venom factors from Naja naja and Naja haje.

The kinetics of complement (C) depletion and recovery of C levels upon injection of BALB/c mice with cobra venom factors (CVF), from N. naja (C3- and C5-depleting) and N. haje (selectively C3-depleting) were studied. The animals received i.p. or i.v. injections of either of the two preparations. CH50 and hemolytic C3 and C5 levels were followed as parameters of residual complement activity. N. naja CVF turned out to be as efficient in depleting total complement activity as N. haje CVF. Decreased CH50 values could largely be ascribed to C3 depletion. Complement consumption after N. naja CVF, however, lasted longer than after N. haje CVF administration. Estimated functional half-lives of N. naja and N. haje CVF were 11.5 and 4.5 h, respectively. Inhibition ELISAs showed that, after in vivo administration of either of the two CVF preparations, antigenic C3 and C5 kept circulating for days.

Animals↗

PubMed1991

Activity-guided isolation and identification of Azadirachta indica bark extract constituents which specifically inhibit chemiluminescence production by activated human polymorphonuclear leukocytes.

The A. indica crude aqueous bark extract inhibits the generation of chemiluminescence by activated human polymorphonuclear leukocytes (PMN). Guided by this activity the responsible compounds were purified by extraction with different organic solvents and HPLC. Gallic acid, (+)-gallocatechin, (-)-epicatechin, and (as a 2:1 mixture) (+)-catechin and epigallocatechin were isolated and identified by means of HPLC, TLC, MS, 1H-NMR, UV, and CD data. Commercial samples of gallic acid, (+)-catechin and (-)-epicatechin showed the same effects. To our knowledge the identified catechins have never been described as constituents of A. indica.

Humans↗

PubMed1991

C3- and T-cell-dependent adjuvant activity of in vivo formed immune complexes.

The effects of polyclonal antibodies to mouse serum components on the primary humoral immune response of mice in vivo were studied. It was observed that rabbit IgG to complement component C3 and albumin and mouse IgG to C5, but also heat-aggregated non-immune rabbit IgG, enhanced the agglutinating antibody response to sheep erythrocytes (SRBC). Since the increase in response was only observed when antigen and antibodies were administered via the same route (i.p.), immunological adjuvant activity was implicated. Ineffectiveness of anti-C5 IgG in C5-deficient mice indicated that the antibody-induced adjuvant activity is mediated by in vivo formed immune complexes (IC). The adjuvant activity of IC was reduced by selective C3-depletion of animals, pointing to a requirement of C3. The effect of variations in other parameters was studied with anti-C3 and anti-C5 IgG as immunoadjuvant. The immunostimulatory effect was most pronounced when the antibodies were administered simultaneously with or shortly before antigen. Treatment of animals with antibodies one or two days before antigen, however, resulted in a suppression of the response. The response to thymus-independent antigens was not enhanced by anti-C3 nor by anti-C5 IgG. Optimal adjuvant activity of anti-C3 IgG was observed at low antigen doses. Nude mice were insensitive to the immunopotentiating effect of anti-C3 and so was the F1 progeny of BALB/c male and CBA/N female mice expressing a B-cell maturation defect. C5 deficiency and lipopolysaccharide (LPS) non-responsiveness did not affect the adjuvant activity of in vivo formed C3-anti-C3 IC.

Adjuvants, Immunologic↗

PubMed1990

Functional assay of C5-activating and nonactivating cobra venom factor preparations in the mouse system.

This paper deals with a new, functional assay of cobra venom factor (CVF) preparations with or without C5-activating property. Existing methods lack sensitivity and use diluted human complement as target of inactivation. An adapted assay using diluted mouse serum as complement source was hampered by underestimation of C3 depletion by bystander lysis and an overvaluation of C5 consumption resulting from C3 inactivation in the reagent used. These disadvantages prompted us to develop the new assay which is based on the incubation of CVF preparations with undiluted mouse serum. After incubation, residual total C activity, as well as functional C3 and C5 are estimated by titration. The procedure permits the assessment of CVF activities with minimal interference from undesired processes. The conditions in the new assay approach the in vivo situation in mice by the use of undiluted serum from the same animal species.

Animals↗

PubMed1990

How flavonoids inhibit the generation of luminol-dependent chemiluminescence by activated human neutrophils.

The mechanism by which (a panel of) flanonoids inhibit the production of luminol-dependent chemiluminescence (CLlum) by activated human neutrophils is subject to this study. CLlum is frequently used as a bio-assay to quantify the effect of xenobiotics on the production of reactive oxygen species (ROS). Most of the flavonoids decreased CLlum by inhibition of ROS production by the cells. Four selected flavonoids (Taxifolin, Eriodictyol, Hesperetin and Luteolin), inhibited myeloperoxidase (MPO) release, while two of these (Taxifolin and Eriodictyol) strongly inhibited MPO activity. Because CLlum is a MPO-dependent process these activities might mask effects of the flavonoids on ROS production. Finally, our results provide evidence that essential determinants for inhibition of O2(-)-release are the OH-groups located in the B-ring of the flavonoid molecule. Flavonoids methylated at a single OH-group in the B-ring are only inhibitory when they react with activated neutrophils in the presence of myeloperoxidase.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1990

Reaction products of 1-naphthol with reactive oxygen species prevent NADPH oxidase activation in activated human neutrophils, but leave phagocytosis intact.

Activation of human neutrophils with opsonized particles in the presence of a nontoxic dose of 1-naphthol resulted in inhibition of superoxide anion production but not of the phagocytotic activity of the cells. In this study we have investigated the mechanism of action of 1-naphthol. The inhibition is not at the level of cellular activation since the FMLP-induced rise of intracellular free calcium was unaffected. Our results show that the (metabolic) activation of 1-naphthol to 1,4-naphthoquinone by reaction with H2O2 from the oxidative burst is a necessary event for the inhibition to occur. The study provides evidence that by its reactivity with essential thiol groups 1,4-naphthoquinone (1,4-NQ) prevents the assembly of a functional NADPH-oxidase in the neutrophil membrane.

Electrochemistry↗

PubMed1990

Metabolic activation of natural phenols into selective oxidative burst agonists by activated human neutrophils.

Phenols isolated from the traditional medicinal plant Picrorhiza kurroa inhibit the release of superoxide anion (O2-) by activated human neutrophils, but leave the phagocytotic capacity intact. Resting neutrophils and resting or activated human lymphocytes are insensitive to these agents. The underlying mechanism of this highly selective activity is investigated. A critical event is the reaction of the phenols with secretory products from the activated neutrophils. The reaction products interfere with the assembly of a functional NADPH-oxidase in the membrane. Analysis of the mode of activation of the phenols reveals two possible pathways. Catechols react directly with reactive oxygen species (ROS) from the oxidative burst. For the activation of the orthomethoxy-substituted catechols the combined activity of ROS and myeloperoxidase (MPO) is obligatory. Catechols with a dimethoxy substitution cannot be activated metabolically by neutrophil-derived ROS.

Biotransformation↗

PubMed1990

Optical performance of multifocal intraocular lenses.

The optical performance of one monofocal and five multifocal lenses was evaluated in the laboratory and photographically. The laboratory testing included determination of the modulation transfer function (MTF), through focus response (TFR), resolution efficiency, and Strehl ratio of each lens. The photographic testing included photographs of the Regan high contrast acuity chart at ten feet with clearest focus and 18 additional photographs in which the image was defocused using minus trial lenses in 0.25 diopter increments. A color photograph of the Kodak color chart was also taken using each lens. All testing was conducted using a 3 mm artificial pupil under ideal implant conditions with no decentration or tilt. The laboratory and photographic results demonstrate that all the multifocal lenses had a two- to three-fold increase in the depth of field with at least a 50% lower contrast in the retinal image. The photographic testing revealed a one to two line better resolution limit with the monofocal lens, which corresponded to the 12% to 41% better MTF cut-off value with the monofocal lens by laboratory testing. The measured resolution efficiencies of all six lenses were comparable. The color photographs revealed color mixing of adjacent colors with the multifocal lenses, whereas the colors appeared unchanged from the original with the monofocal lens.

Equipment Design↗

PubMed1989

Rapid isolation and characterization of native mouse complement components C3 and C5.

A rapid, 1 day procedure for the purification of mouse complement factors C3 and C5 is described. The method is based on fractionated precipitation by polyethylene glycol 6000, followed by Mono Q anion exchange chromatography on a system for fast protein liquid chromatography (FPLC). For C3 isolation, an additional FPLC separation step using Superose 12 (gel filtration) was used. C3 was purified 71-fold with a yield of 32% as measured by biological activity; the preparation contained no detectable contaminants as judged by SDS-PAGE. A comparable procedure for the isolation of C5 resulted in a preparation with a considerable contamination which could be easily removed by affinity chromatography using antibodies directed against these contaminants. With this combined procedure C5 was purified 536-fold with a yield of 28% based on biological activity. SDS-polyacrylamide gel electrophoresis revealed that mouse C3 and C5 had apparent Mrs of 170,000 and 190,000, respectively. Under reducing conditions the alpha and beta chains showed Mrs of 107,000 and 62,000 for C3, and 104,000 and 85,000 for C5.

Animals↗

PubMed1987

A one-step isolation procedure for phospholipase A2-free cobra venom factor by fast protein liquid chromatography.

A very rapid and efficient procedure for isolation of cobra venom factor (CoF) from Naja naja venom is presented. The method is based on Mono Q anion exchange chromatography on a system for fast protein liquid chromatography (FPLC). CoF was eluted by a buffer of pH 7.4 at 280 mM salt. A purification of 33.7 X was reached with a yield of at least 27%. Contamination with phospholipase was under the detection limit of a sensitive radiometric assay (less than 25 ppm), while the starting material contained 5%. The preparation displays high C-depleting activity in vivo.

Animals↗

PubMed1986

Effects of immunological adjuvants on the mouse complement system--II. Anti-complementary effects of surface-active compounds.

The anti-complementary effects of the surface-active immunological adjuvants dimethyldioctadecylammonium bromide (DDA) and pluronic polyols L101 and L121 were investigated in the mouse system. All three adjuvants showed complement (C)-inactivating effects. DDA caused a time- and dose-dependent reduction of alternative pathway (AP) and overall C activity, which varied with the serum concentration. Polyols induced a preferential inactivation of the AP by a more direct mechanism. A rather general, causative relationship between anti-complementary and immunological adjuvant activities is suggested. This might involve interference with nonspecific elimination of antigen, counteraction of immunosuppression by terminal C components, and/or moderation of C3b-mediated reduction of Ia-expression, leading to a better antigen presentation.

Adjuvants, Immunologic↗

PubMed1986

Simple sugars with affinity for the macrophage asialoglycoprotein receptor are adjuvants for the humoral immune response to neuraminidase-treated sheep erythrocytes.

The influence of monosaccharides on the humoral immune response of mice to normal and neuraminidase-treated sheep red blood cells (SRBC) was investigated. In these studies, both the sugars and antigen were administered i.p. D-Galactose displayed adjuvant activity for neuraminidase-treated but not for normal SRBC. This activity was optimal at an antigen dose of 3 X 10(6) cells. Other monosaccharides with an axial hydroxyl group at position 4 and D-mannose-6-phosphate behaved like D-galactose, whereas structurally unrelated sugars did not. The adjuvant activity of the saccharides corresponded to the affinity of the substances for the asialo-glycoprotein receptor. The adjuvant effects were also expressed in cobra venom factor-treated and C5-deficient mice. This suggests that blockade of the asialo-receptor rather than complement is involved in this form of immunoadjuvant activity. The findings are also in support of our hypothesis that obstruction of nonimmune antigen elimination, in this case at the level of macrophages, would be one of the mechanisms underlying immunologic adjuvant activity.

Adjuvants, Immunologic↗

PubMed1985

Study of the optimal reaction conditions for assay of the mouse alternative complement pathway.

The optimal reaction conditions for hemolytic assay of alternative complement pathway activity in mouse serum were investigated. A microtiter system was used, in which a number of 7.5 X 10(6) rabbit erythrocytes per test well appeared to be optimal. Rabbit erythrocytes were superior as target cells over erythrocytes from a number of other animal species. The optimal conditions were as follows: an incubation temperature of 39 degrees C, an ionic strength of about 200 mM, and a magnesium concentration of 2.5 mM. Incubation during 60 min was not sufficient for an end-point titration. Addition of 1 mg of zymosan A per test well, however, enhanced and accelerated the hemolytic activity of mouse serum via the alternative pathway resulting in a maximum value after 45 min. This, most probably, proceeded by a mechanism involving the formation of a zymosan-C5-convertase and bystander lysis of the target cells. In contrast to the normal alternative pathway assay the zymosan-potentiated test did, most probably, not involve natural antibodies. Cobra venom factor was more efficient in enhancing the sensitivity of the assay for the mouse alternative complement pathway than zymosan. This makes this factor very useful for testing C-poor body fluids.

Animals↗

PubMed1985

The selective localization of B lymphocytes in the spleen and the role of complement receptors.

The role of complement receptors on the localization of T and B cells in the spleen of mice was studied using short-term homing experiments in cobra venom factor (CoF)-treated animals. The localization ratio of B and T cells in the spleen of CoF-treated mice decreased significantly compared to control recipients. No changes could be found in the relative distribution of resident T and B cells in the spleen or other lymphoid organs of CoF-treated animals and when their spleen or lymph node cells were transferred, the localization pattern was normal. When cells were incubated in serum prior to transfer a disturbed localization ratio in the spleen of untreated recipients was observed. This was due to a blockade of complement receptors as determined by the inability of the incubated cells to form EAC rosettes. No blockade of EAC rosettes and no changes in localization ratios upon transfer could be observed when the cells were incubated in functionally C3-depleted serum. The results suggest a role for the complement-receptor on B cells in the initial localization in the spleen, whereas no influence upon the selective localization in high endothelial venules-bearing organs was found.

Animals↗

PubMed1985

Analytic study of the differential anticomplementary effects of dextran sulphate and heparin in the assay for the mouse alternative pathway.

In a recent paper, a linkage between immunological adjuvant activity in mice and in vitro anticomplementary (alternative pathway assay) effects was described for different polyanions. This connection was found only if mouse serum was used as a complement (C) source. In order to investigate the possible role of C in adjuvant activity, the differential effects of polyanions on mouse C were studied in detail. For this study, substances with different activity were selected, namely dextran sulphate with strong C-regulatory and immunoadjuvant activities, and heparin, which was weakly anticomplementary and devoid of adjuvant effect. In general, studies of mouse C are complicated by the unavailability of isolation procedures for the C-components involved. This difficulty was circumvented by making use of C5-deficient serum and of the haemolytic activity of mouse membrane attack complexes formed in the fluid phase. With yeast cells as alternative pathway activators it was shown that the effect of heparin on this pathway was restricted to activation of the terminal route. In contrast, dextran sulphate also caused a functional decay of a yeast-bound alternative pathway C5-convertase and interfered with the haemolytic activity of fluid-phase membrane attack complexes as well. Further studies will be needed to decide whether these specific effects of dextran sulphate are related to the immunological adjuvant activity of the substance in mice.

Animals↗

PubMed1984

Differential precipitation of the Clq subcomponent of the first complement component (C1) by polyethylene glycol from normal human serum and sera of patients with collagen diseases.

Sera were, under strictly standardized conditions, centrifuged in the presence of 0-5% PEG and the Clq concentration in the precipitates was measured by radial immunodiffusion. The presence of circulating immune complexes and rheumatoid factor(s) resulted in a shift of Clq precipitation to lower PEG concentrations. Clq precipitation at 1.5% PEG was shown to be specific for sera containing immune complexes. Under similar conditions addition of aggregated IgG to normal human serum gave rise to Clq precipitation directly proportional to the amount of aggregated IgG. Precipitation of endogenous Clq at 1.5% PEG and assay by radial immunodiffusion may therefore be useful for the detection and quantitation of immune complexes in human serum.

Antigen-Antibody Complex↗

PubMed1983

Microassay for colorimetric estimation of complement activity in guinea pig, human and mouse serum.

A sensitive colorimetric microassay for determining haemolytic complement activity was devised. It is carried out in U-welled microtitre dishes covered with plastic tape, which are incubated in a waterbath and subsequently centrifuged. The supernatant is transferred to flat-bottomed microtitre dishes and haemolysis is estimated by automatic measuring of the absorption using an interference filter of 405 nm in a Titertek Multiskan. Advantages of the method described are saving time and materials, and avoiding the use of radioactive nuclides. This microassay may therefore be a useful substitute for macro and semi-micro tests for colorimetric determination of serum complement activity and for microassays based on the release of a radio-isotope.

Animals↗

PubMed1983

A study of the sensitivity of erythrocytes to lysis by heterologous sera via the alternative complement pathway.

In order to get insight in the distribution of alternative complement pathway activities as detected by lysis of xenogeneic erythrocytes in the presence of magnesium and ethyleneglycol-bis-(2-aminoethyl)-tetra-acetic acid (EGTA) over the species, the 156 heterologous combinations of erythrocytes and sera out of thirteen animal species were tested. An order could be noticed in the species with respect to serum complement activity tending to negative correlation with the sensitivity of the corresponding erythrocytes to lysis by heterologous sera. So far, the most sensitive erythrocyte for each individual serum must be considered to be the target cell of choice for developing assays for alternative complement pathway activity in the serum involved. In this series of animals only for rabbit serum no sensitive target cell was found. The order observed, in connection with the failing lysis of erythrocytes by homologous sera, suggests further that in restriction of heterologous hemolysis in general one erythrocyte-associated, species-nonspecific regulatory principle may be involved, whereas in homologous restriction, most probably, also species-specific factors play a role.

Animals↗