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Biomedical subjects

J Buijs

Publications and source records attributed to J Buijs.

18 recordsLinked to original sources
PubMed1999

Conformational stability of adsorbed insulin studied with mass spectrometry and hydrogen exchange.

A new method is described for direct monitoring of the conformational stability of proteins that are physically adsorbed from solution onto a solid substrate. The adsorption-induced conformational changes of insulin are studied using a combination of hydrogen/deuterium (H/D) exchange and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. The effect of the surface hydrophobicity on the adsorption-induced conformational changes in the insulin structure is probed by adsorbing insulin on a hydrophilic silica and a hydrophobic methylated silica surface before subjecting the insulin molecules to the isotopic exchange process. The present study describes the experimental procedure of this new application of MALDI. Results show that insulin is more highly and more irreversibly adsorbed to a hydrophobic methylated silica surface than to a hydrophilic silica surface. Hydrogen-exchange experiments clearly demonstrate that the strong interaction of insulin with the hydrophobic surface is accompanied by a strong increase in the H/D-exchange rates and thus in a reduction in the insulin native structural stability. In contrast, H/D-exchange rates of insulin are somewhat reduced upon adsorption on silica from solution.

Adsorption↗
PubMed1997

Adsorption Kinetics, Conformation, and Mobility of the Growth Hormone and Lysozyme on Solid Surfaces, Studied with TIRF

Interactions of recombinant human growth hormone and lysozyme with solid surfaces are studied using total internal reflection fluorescence (TIRF) and monitoring the protein's intrinsic tryptophan fluorescence. The intensity, spectra, quenching, and polarization of the fluorescence emitted by the adsorbed proteins are monitored and related to adsorption kinetics, protein conformation, and fluorophore rotational mobility. To study the influence of electrostatic and hydrophobic interactions on the adsorption process, three sorbent surfaces are used which differ in charge and hydrophobicity. The chemical surface groups are silanol, methyl, and quaternary amine. Results indicate that adsorption of hGH is dominated by hydrophobic interactions. Lysozyme adsoption is strongly affected by the ionic strength. This effect is probably caused by an ionic strength dependent conformational state in solution which, in turn, influences the affinity for adsorption. Both proteins are more strongly bound to hydrophobic surfaces and this strong interaction is accompanied by a less compact conformation. Furthermore, it was seen that regardless of the characteristics of the sorbent surface, the rotational mobility of both proteins' tryptophans is largely reduced upon adsorption.

Journal Article↗
PubMed1997

Relationship between allergic manifestations and Toxocara seropositivity: a cross-sectional study among elementary school children.

Toxocara (the cause of visceral larva migrans in humans) and allergy have in common both elevated immunoglobulin E (IgE) levels and eosinophilia. In the present study, we investigated: 1) associations between Toxocara seropositivity and allergic manifestations; 2) risk factors for Toxocara infection; and 3) differences in Toxocara seroprevalence, allergic manifestations and the associations between these two, in children from urban and rural environments. Blood samples from 1,379 Dutch urban and rural elementary schoolchildren, were examined for Toxocara antibodies, eosinophil numbers, total IgE concentrations, and the occurrence of inhaled allergen-specific IgE. Questionnaires investigating respiratory health and putative risk factors for infection were completed. It was found that 8% of the children had Toxocara antibodies, occurring significantly less often in females than in males. The means of total serum IgE levels and blood eosinophils were significantly higher in the Toxocara-seropositive than in the seronegative group. Allergic asthma/recurrent bronchitis was found in 7% of the children, allergic reaction on animal contact in 4%, and IgE to at least one inhaled allergen in 16%. These variables were associated with Toxocara seroprevalence. Inhaled allergen-specific IgE and asthma/recurrent bronchitis occurred significantly less often in rural than in urban areas, and significantly less often among girls than among boys. Furthermore, occurrence of allergen-specific IgE increased significantly with age. No association existed between Toxocara seroprevalence and assumed risks, i.e. contact with pet animals and public playgrounds. In conclusion, our results indicate that allergic manifestations occur more often in Toxocara-seropositive children. A relationship with an already existing allergic condition is plausible.

Animals↗
PubMed1996

Protein adsorption on solid surfaces.

The research field of protein adsorption on surfaces appears to be as popular as ever. In the past year, several hundred published papers tackled problems ranging from fundamental aspects of protein surface interactions to applied problems of surface blood compatibility and protein surface immobilization. Although some parts of the protein adsorption process, such as kinetics and equilibrium interactions, can be accurately predicted, other aspects, such as the extent and the rate of protein conformational change, are still somewhat uncertain. The whole field is ripe for a comprehensive theory on protein adsorption.

Journal Article↗
PubMed1995

Toxocara canis-induced airway eosinophilia and tracheal hyporeactivity in guinea pigs and mice.

Guinea pigs and mice infected with the parasitic worms Toxocara canis developed airway inflammation and tracheal hyporesponsiveness. Preceding inflammatory cell infiltration a brief hyperreactive response occurred in guinea pigs to histaminergic receptor stimulation at 3 days post infection (p.i.) and in mice to acetylcholine receptor stimulation at 1 day p.i. Few but large eosinophilic inflammatory foci developed in guinea pigs at 14 days p.i. Mice demonstrated progressive multifocal inflammation from 7 days p.i. In addition to eosinophils mouse airways were infiltrated by lymphocytes, forming perivascular and (partial) peribronchial infiltrates in an oedematous submucosa. The inflammation persisted in mice for > or = 3 months and likewise persisted tracheal hyporeactivity. Incubation of tracheae of non-infected mice with pulmonary inflammatory cells caused a significant decrease in cholinergic receptor responsiveness. This downward shift was prevented by 60% when a cyclooxygenase inhibitor was added to the incubation medium but not when inhibitors of lipoxygenase and superoxide formation were added, suggesting the involvement of prostaglandin E2. This suggestion was supported by the finding of significantly increased prostaglandin E2 concentrations in the bronchoalveolar lavage fluid at 14 and 28 days p.i. It was concluded that tracheal hyporeactivity coincided with the presence of large numbers of eosinophils in the airways of both, guinea pigs and mice and that prostaglandin E2 involvement was conceivable.

Animals↗
PubMed1995

Toxocara-induced eosinophilic inflammation. Airway function and effect of anti-IL-5.

The immunoinflammatory response to parasitic nematode infections and allergic diseases have some similarities, the most profound being the increases in eosinophils and serum total IgE concentration. Whether parasitic infections stimulate or inhibit allergic asthma is a matter of debate. We investigated the effect of Toxocara canis (T. canis) infection on airway function in BALB/c mice at various days post-infection. Within 24 h after infection, the trachea responded hyperreactive to carbachol stimulation. Eosinophils, and to a lesser degree lymphocytes, infiltrated the airways causing interstitial and alveolar inflammation (7 d post-infection). Concurrently with cell infiltration, the trachea became hyporesponsive to carbachol whereas the pulmonary resistance was increased and the dynamic compliance decreased. The hyporeactive response could be simulated in vitro by incubating normal tracheae with eosinophil-enriched bronchoalveolar lavage cells obtained from infected mice. The response depended on the number of cells added to the medium, a lower number causing a hyper- and a higher number a hyporeactive response. Anti-interleukin-5 (anti-IL-5) producing hybridoma cells given simultaneously with T. canis infection inhibited eosinophil infiltration in the airways but not that of lymphocytes. Anti-IL-5 treatment prevented tracheal hyporeactivity but not perivascular and peribronchial edema, increased pulmonary resistance, or decreased dynamic compliance. Treatment with isotype control antibody did not affect eosinophil number nor the observed changes in airway functions. It was concluded that T. canis-induced airway inflammation coincided with increased pulmonary resistance, decreased dynamic compliance, and perivascular/peribronchial edema. These phenomena were independent on the presence of eosinophils, whereas tracheal hyporeactivity was clearly associated with airway eosinophilia.

Animals↗
PubMed1994

Toxocara seroprevalence in 5-year-old elementary schoolchildren: relation with allergic asthma.

Toxocara seroprevalence and the relation between Toxocara seroprevalence and allergic asthma were investigated in Dutch schoolchildren aged 4-6 years. Data on Toxocara antibodies, allergen-specific immunoglobulin E, allergic manifestations, and risk factors (pets and playgrounds) were obtained from 235 children from The Hague and 477 from Rotterdam, the Netherlands. The surveys were carried out from September 1987 to January 1988 in The Hague and in March and April 1989 in Rotterdam. Logistic regression was used to evaluate putative relations. Toxocara seroprevalence was higher in The Hague (11%) than in Rotterdam (6%), but this difference was not quite significant. Seroprevalences varied widely among schools. No differences between socioeconomic categories or between the sexes were found. Occurrences of asthma/recurrent bronchitis and hospitalization due to asthma/recurrent bronchitis were significantly associated with seroprevalence. Furthermore, a marginally significant relation with eczema was found. Immunoglobulin E specific for inhaled allergens occurred significantly more often in the Toxocara-seropositive group. The risk factors investigated were not related to seroprevalence. It is suggested that Toxocara, among other environmental factors, may stimulate polyclonally immunoglobulin E production, including allergen-specific immunoglobulin E, and thus may contribute to the manifestation of allergic asthma and possibly of eczema in children predisposed to allergy.

Animals↗
PubMed1994

Photoacoustic characterization of different food samples.

Photoacoustic spectroscopy in the 350-700 nm range proved a useful tool for discriminating between a variety of opaque, light-scattering samples. Spectral features originating from powdered food specimens of different colour and grain size were observed. These results suggest the feasibility of photoacoustics for quality control in the food-processing industry.

Acoustics↗
PubMed1994

Toxocara canis-induced murine pulmonary inflammation: analysis of cells and proteins in lung tissue and bronchoalveolar lavage fluid.

The pulmonary immuno-inflammatory reaction and its effect on microvascular integrity was studied in Toxocara canis infected BALB/c mice. The investigation aimed to compare changes in lung histology and composition of bronchoalveolar lavage fluid (BALF) caused by T. canis infection with those described to occur in allergic asthma. Groups of (non)-infected mice (1000 ova) were investigated until 90 days post infection (p.i.). Migration of the larvae through the lungs was followed by a rapidly progressing multifocal interstitial and alveolar inflammation. Eosinophils and lymphocytes formed perivascular and partially peribronchial mixed cellular infiltrates. Lymphocytes with plasma cell morphology staining intracellularly for either alpha, epsilon or gamma immunoglobulins were demonstrated. BALF, collected from mice infected with either 250, 500 or 1000 ova was analysed at 14 and 28 days p.i. A dose-related increase in cell numbers and in albumin and IgA concentration was observed. IgE increase was independent of the infective dose. Peak values were measured at 14 days p.i. Albumin increase in lung homogenate was highest at 28 days p.i. 30% of the lymphocytes consisted of T cells carrying Thy-1,2 and L3T4 surface antigens. It is concluded that T. canis-induced pulmonary inflammation affects the permeability of the microvasculature. This is expressed by interstitial oedema and plasma exudation in the airway lumen. Both phenomena occur also in allergic asthma. It is suggested that increased permeability of the microvasculature is mediated by T cells and eosinophils.

Albumins↗
PubMed1992

Cerebral blood flow pattern and autoregulation during open-heart surgery in infants and young children: a transcranial, Doppler ultrasound study.

OBJECTIVES: To elucidate the effect of cardiopulmonary bypass on cerebral perfusion and on the autoregulatory ability of the cerebral vascular bed of infants and young children. SETTING: Operating room. DESIGN: Prospective study. PATIENTS: Thirteen newborn infants and young children undergoing open-heart surgery. INTERVENTIONS: Cerebral blood flow velocity was monitored in the patients undergoing open-heart surgery from just before the induction of anesthesia until the discontinuation of anesthesia after completion of the surgery. MEASUREMENTS AND MAIN RESULTS: Cerebral blood flow velocity was assessed by semicontinuous measurement of temporal mean blood flow velocity in the middle cerebral artery using a range-gated, pulsed Doppler flowmeter with a transducer that was firmly attached to the left temporal region of the head. Mean arterial pressure (MAP) and nasopharyngeal temperature were continuously monitored. During hypothermic (18.4 degrees C to 31.9 degrees C) cardiopulmonary bypass, cerebral blood flow velocity decreased and showed a close relationship with nasopharyngeal temperature (p less than .0001). During steady-state cardiopulmonary bypass, cerebral blood flow velocity showed a correlation with MAP (p less than .01). The nasopharyngeal temperature influenced this relationship: at lower (absolute) nasopharyngeal temperatures, lack of cerebral autoregulation was more common. CONCLUSIONS: The finding suggests that cerebral blood flow decreases with decreasing nasopharyngeal temperature. During hypothermic cardiopulmonary bypass, cerebral autoregulation seems to be easily disturbed, especially at low nasopharyngeal temperatures.

Anesthesia↗
PubMed1990

Toxocara canis-induced airway hyporeactivity in mice.

Migrating larvae of the canine nematode Toxocara canis induce inflammatory responses in the lungs of infected mice. Histological examination of the lungs showed that mice, developed persistent multifocal inflammation in which eosinophils (eos), macrophages (M phi) and many lymphocytes were involved. Cuffing of blood vessels and bronchioles with mixed cell populations was also observed. Investigation into the response of isolated tracheae to cholinergic and beta-adrenergic receptor agonists demonstrated a significant decreased reactivity despite the pronounced involvement of eos and M phi. This hyporeactive state persisted for greater than or equal to 4 weeks p.i..

Animals↗
PubMed1990

Quantification of the relation between electrophysiologic and morphologic changes in experimental endolymphatic hydrops.

The degree of hydrops in guinea pig ears that had undergone unilateral endolymphatic sac and duct obliteration was quantified. For 15 guinea pigs from a prior study, the correlation between the degree of hydrops and several electrophysiologic measures of the functional state of the cochlea was determined. A significant correlation between the degree of hydrops and a reduction in the low-frequency cochlear microphonic evoked by a 29-Hz tone was found. No correlation was found between the degree of hydrops and the magnitude of the summating potential evoked by 8-kHz probes. A weak correlation was found between the degree of hydrops and a reduction in the compound action potential evoked by 2-kHz probes. Possible differences in the way the endolymphatic duct obliteration exerts its effect on the different cochlear potentials are discussed.

Animals↗
PubMed1989

[How innocent is Toxocara?].

We have investigated 234 children (3-6 years of age) in The Hague, The Netherlands, for the presence of antibodies against Toxocara. Of these children 26 (11.1%) were seropositive to Toxocara. Cross-reactions with antibodies against Ascaris could be excluded. Of the seropositive children 31% had asthma or bronchitis, while this percentage was only 12% for the seronegative children. This might indicate that toxocariasis causes asthma or bronchitis in some children. If further investigations corroborate this hypothesis, one has to conclude that preventing human toxocariasis contributed to prevent a number of cases of asthma and bronchitis.

Animals↗
PubMed1989

Corneal astigmatism after cataract surgery.

206 Consecutive cataract patients were at random divided into three groups according to the way the cataract incision was closed: virgin silk 8-0, interrupted nylon 9-0, and double running nylon 9-0. The nylon, whether interrupted or continuous, yielded in the majority of cases a postoperative astigmatism with the rule, whereas virgin silk caused in nearly all patients a postoperative astigmatism against the rule and therefore behaved like an absorbable suture. Silk is chemically non-absorbable, but in virgin silk a natural worm-produced polymer is still present, which provokes a tissue reaction. Softening of tissue diminishes the tensile strength of the suture. With respect to the postoperative astigmatism, the suture material (nylon or virgin silk) seems a more important factor than the way in which it is used (interrupted or continuous).

Aged↗