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Biomedical subjects

H Elwing

Publications and source records attributed to H Elwing.

At least 37 records · Page 2Linked to original sources
PubMed1992

Reflectance method for simple determination of proteinase activity in microliter samples of a complex serum-like fluid.

A technique using an optical instrument, a reflectometer, for quantitative determination of proteinase activity in microliter samples of complex serum-like fluids, e.g., crevicular exudate from single sites, was developed. The technique allowed the use of various proteins as enzyme substrate. The reflectometer measures the mass of a layer, such as protein, adsorbed to a reflecting surface. This is done by measuring the reflected light intensity of the p-polarized light beam on a surface. We used methylized silicon surfaces that were coated with fibrinogen, alpha 2-macroglobulin, or hemoglobin as enzyme substrates. The test solution was incubated overnight in a basin made in an agar gel applied on the top of the protein-coated surface. In 82 exudates from periodontitis sites, with pocket depths greater than or equal to 6 mm, fibrinogenolytic activity corresponding to 1 microgram ml-1 of trypsin and pronase P was found in 20% of the samples.

Endopeptidases↗
PubMed1992

Studies of surface activated coagulation: antisera binding onto methyl gradients on silicon incubated in human plasma in vitro.

Human plasma proteins factor XII, high molecular weight kininogen, prekallikrein, factor XI and fibrinogen, participate in surface-initiated coagulation. Antisera binding to methyl gradients made on hydrophilic silicon was studied after immersion in normal and deficient human blood plasma. Scanning ellipsometry was used to quantify the adsorbed organic material. The hydrophilic part of the gradient deposited anti-factor XII and anti-high molecular weight kininogen, but low amounts of anti-fibrinogen. Increased amounts of anti-fibrinogen bound onto the hydrophobic part, and the intermediate gradient region with mixed polar-nonpolar surface characteristics bound low amounts of anti-factor XII, anti-high molecular weight kininogen and anti-fibrinogen. Tentatively, in this gradient region, simultaneous polar and non-polar surface characteristics result in a low-level of surface-activated coagulation. Surfaces immersed in heparinized-and EDTA-plasma indicate different antisera depositions.

Adsorption↗
PubMed1991

The melanophore aggregating response of isolated fish scales: a very rapid and sensitive diagnosis of whooping cough.

Pertussis toxin (PT) has been found to block noradrenaline-induced pigment aggregation in fish melanophores, and, based on this, a rapid and highly sensitive assay for PT was developed. Some preliminary results have also indicated that it may be possible to detect PT-like activity in saliva samples from patients with clinically suspected pertussis. In the present study the diagnostic value of the fish melanophore method was evaluated in 70 patients suspected of having pertussis; culture, serology and physician diagnosis were used as reference methods. In 60 of the patients, pertussis was verified by at least one of the reference methods. The melanophore test showed PT-like activity in saliva samples from 58 of the patients. Three patients with reference-verified pertussis showed no PT-like activity in the test; among these, one patient had been immunized and had also been treated with erythromycin during 3 days immediately prior to visiting the hospital. The melanophore test has three major advantages: it allows detection of pertussis in the early and curable stage of the disease; it takes only 2 h to perform; and it requires no sophisticated equipment.

Adolescent↗
PubMed1991

Structure of adsorbed fibrinogen obtained by scanning force microscopy.

It is shown that scanning force microscopy (SFM), operated in the attractive mode, can be used to obtain high resolution pictures of adsorbed fibrinogen molecules on solid surfaces, without the need for staining or special microscope grids. SFM also reveals the three-dimensional structure of the adsorbed molecules. Two forms of adsorbed fibrinogen are demonstrated on hydrophobic silicone dioxide surfaces: a trinodular about 60 nm long and a globular with about a 40 nm diameter. Polymeric networks formed after storage of the surface with adsorbed fibrinogen in PBS for 11 days are also shown. The SFM-results for the trinodular structure suggest the existence of loops or peptide chains extending outside the basic structure of the fibrinogen molecule.

Fibrinogen↗
PubMed1991

'Lens-on-surface': a versatile method for the investigation of plasma protein exchange reactions on solid surfaces.

The exchange sequence of plasma proteins in narrow spaces on solid surfaces was studied by means of a modified 'lens-on-surface' method as originally described by Vroman and Adams. In our studies, lateral scanning ellipsometry was used as the detection method. With the use of antibodies it was demonstrated and confirmed that immunologically detectable plasma protein antigens appear and disappear in a time- and concentration-dependent sequence [IgG followed by fibrinogen followed by high-molecular weight kininogen (HMWK)] on silica surfaces. Plasma protein exchange reactions were also studied on hydrophilic titanium (Ti), vanadium (V), and silver (Ag) surfaces. Atypical exchange patterns were found on V and Ag surfaces as compared with hydrophilic silica (adsorbed fibrinogen was not removed).

Adsorption↗
PubMed1990

Bactericidal properties of a titanium-peroxy gel obtained from metallic titanium and hydrogen peroxide.

A stable titanium-peroxy-radical complex is formed when metallic titanium interacts with hydrogen peroxide. The radical appears as one component in an aqueous gel formed when excess peroxides have been (catalytically) decomposed. The interaction between titanium and hydrogen peroxide may be of importance also in vivo during an inflammatory response at the implant. We report in this paper on the bactericidal effects of the titanium gel in the lacto- and myeloperoxidase-halogen systems. Escherichia coli viable count was used to evaluate the bactericidal properties of the gel and of H2O2 for comparison. The gel had only small or no toxic properties at high dilutions. Higher concentrations of the gel had bactericidal properties similar to those of H2O2. The results indicate that at physiological pH, the decomposition products of the gel ae titanium hydroxide (Ti(IV)(OH-)4) and hydrogen peroxide (H2O2). It was found that the gel probably oxidizes glutathione directly in contrast to H2O2, which needs a peroxidase to do so. A model for the interaction between titanium and hydrogen peroxide is suggested. Its consequences for the properties of titanium in vivo are also discussed.

Chlorine↗
PubMed1990

Fish scales as biosensors for catecholamines.

Certain fish scales contain specialized cells (chromatophores) with pigment granulas, which can be dispersed or aggregated in the cells. The degree of aggregation is determined by a transmitter substance, noradrenaline, released by the sympathetic nerve endings in the skin. Isolated scales from, for example, cuckoo wrasse (Labrus ossifagus) retain a large sensitivity to externally applied noradrenaline (or more generally catecholamines) for several weeks. The degree of aggregation in isolated scales can be measured objectively by simple photometric techniques. We demonstrate in this paper how fish scales can be used to monitor catecholamine levels in human blood plasma. A discussion of other potential biosensor applications of this intact biological receptor-effector system is also given.

Animals↗
PubMed1989

Titanium-hydrogen peroxide interaction: model studies of the influence of the inflammatory response on titanium implants.

In vitro studies of titanium and TiO2 as well as other metals were carried out to investigate the role of these metals in the inflammatory response through the Fenton reaction. The TiOOH matrix formed traps the superoxide radical, so that no or very small amounts of free hydroxyl radicals are produced. Ellipsometry and spin trapping with spectrophotometry and electron spin resonance (ESR) were used to study the interaction between Ti and H2O2. Spectrophotometry results indicated that Ti, Zr, Au and Al are low free OH-radical producers. We propose a new model for the titanium-tissue interface where the oxidized titanium surface is covered with a hydrated TiOOH matrix after the inflammatory reaction. This matrix is suggested to possess good ion exchange properties, and extracellular components may interact with the Ti(IV)-H2O2 compound before matrix formation. The TiOOH matrix is formed when the H2O2 coordinated to the Ti(IV)-H2O2 complex is decomposed to water and oxygen. Superoxide (O2-) may be bound therein. The oxide layer initially present may be partly reformed to a TiOOH matrix due to the interaction with hydrogen peroxide.

Biocompatible Materials↗
PubMed1989

Interaction between hydrogen peroxide and titanium: a possible role in the biocompatibility of titanium.

Hydroxyl radicals formed from hydrogen peroxide during an inflammatory response are potent agents for cellular deterioration. The behaviour of implanted material in terms of its ability to sustain or stop free radical formation may be therefore very important. In vitro studies of titanium which is known to be biocompatible and osseointegrates into human bone were carried out. In our model studies, the production of free radicals from H2O2 at Ti and TiO2 surfaces was measured by spin trapping techniques. Our findings suggest that there is no sustained hydroxyl radical production at a titanium (oxide) surface. We propose that this is due to the quenching of the Fenton reaction through both trapping and oxidation of superoxide radicals in a TiOOH adduct.

Biocompatible Materials↗
PubMed1989

Determination of haemoglobin and prothrombin complex in whole blood using optothermal spectrometry.

Optothermal spectrometry measures the thermal energy produced as a result of absorption by molecules at a given modulation frequency and wavelength. Depending on the modulation frequency used, analysis can be performed in very thin layers (50-150 micrometers). A major advantage of optothermal spectrometry is that it is not very sensitive to light scattering. Haemoglobin in whole blood was measured without any reagent at 16 Hz and 2 Hz frequencies. The precisions (within-series, within-day and between-day) were acceptable, and comparisons with reference methods were excellent. As opposed to the reference methods, optothermal spectrometric determinations were not affected by lipaemia. When measured continuously, the signal for haemoglobin increased due to the packing of erythrocytes towards the light source. By converting soluble fibrinogen into insoluble fibrin, the erythrocyte packing could either be inhibited or stopped, and this process could be monitored by assessing the change in the rate of signal increase for haemoglobin. This principle was utilized to analyse the prothrombin complex; the method was found to have acceptable precision and to be comparable to a routine method.

Blood Coagulation Factors↗
PubMed1988

Pigment migration in fish erythrophores is controlled by alpha 2-adrenoceptors.

1. The aggregation of erythrosomes within erythrophores of the squirrel fish (Myripristis occidentalis; belonging to the family Holocentridae) was, on pharmacological grounds, shown to be mediated by alpha 2-adrenoceptors. 2. The erythrophores were shown to be controlled by adrenergic nerves activating the alpha 2-adrenoceptors. 3. The erythrophores themselves were found to possess a K+-sensitive mechanism of aggregation. 4. Some similarities and differences of the alpha 2-adrenoceptor-mediated chromatosome aggregation in melanophores and erythrophores are also discussed.

Animals↗
PubMed1988

Pronounced supersensitivity of postjunctional alpha adrenoceptors after denervation of fish melanophores.

The aggregation of melanosomes within melanophores (pigment cells) attached to isolated scales from the cuckoo wrasse (Labrus ossifagus L.) can be elicited either by stimulation of intrinsic nerves (electrical field stimulation of K+ depolarization) or by adrenoceptor agonists. The melanophores of isolated scales survived in a culture medium for up to 20 days. During this period a progressive increase in sensitivity to exogenously applied noradrenaline took place. After 8 days of isolation there was an about 300-fold increase in sensitivity to noradrenaline. The increased sensitivity was accompanied by a progressive loss of the nerve-elicited response during the first days of isolation. Before and during this early period cocaine was found to potentiate the effect of noradrenaline about 8-fold. On the 3rd day after isolation the effect of cocaine was lost, which coincided fairly well with the time when the nerve-mediated response was lost. The early developing increase in sensitivity to noradrenaline (8-fold) is therefore most likely caused by loss of presynaptic amine uptake, but the main part (50-fold) of the increase in sensitivity presumably has other explanations, like changes in the receptor population.

Adrenergic alpha-Agonists↗
PubMed1987

Competition between adsorbed fibrinogen and high-molecular-weight kininogen on solid surfaces incubated in human plasma (the Vroman effect): influence of solid surface wettability.

The influence of the surface energy on the competition between fibrinogen and high-molecular-weight kininogen has been studied with the use of a recently described wettability gradient method. One finding is that the decrease in the antifibrinogen binding on plasma incubated gradient surfaces was not associated with an increase in anti-HMWK binding at all parts of the gradient surfaces.

Adsorption↗
PubMed1987

Comparative studies on nerve- and noradrenaline-induced melanosome aggregation within different species of fish.

1. The aggregation of melanosomes within melanophores of the cuckoo wrasse (Labrus ossifagus; belonging to the family Labridae) has, on pharmacological grounds, been shown to be mediated by postsynaptic alpha 2-adrenoceptors which in turn act via an inhibitory control of adenylate cyclase. 2. In the present paper we have investigated some American species belonging to the Labridae, Haemulidae, Embiotocidae, Clinidae and Pleuronectidae. 3. In all instances, except in the case of sargo (Haemulidae), we could demonstrate that melanosome aggregation probably was mediated by postsynaptic alpha 2-adrenoceptors which mediate their effect by inhibiting the adenylate cyclase of the melanophores. 4. Although these receptors apparently, on pharmacological grounds, may be classified as alpha 2-adrenoceptors it was also concluded that there is a phylogenetic divergence among these receptors.

Adrenergic alpha-Antagonists↗
PubMed1986

Complement deposition from human sera on silicon surfaces studied in situ by ellipsometry. The influence of surface wettability.

Organic material deposition from human sera on silicon dioxide surfaces was studied in situ by means of ellipsometry, an optical method for quantification of thin organic films. The deposition of organic material from sera was followed continuously for 2 h on hydrophobic and hydrophilic silicon surfaces. Both types of surfaces adsorbed organic material and the additional incubation with anti-C3 resulted in further deposition of organic material indicating the presence of C3 in the organic layers. Addition of EDTA in serum or heat inactivation resulted in a decrease of the amount of organic material deposited on the hydrophobic surface as well as in a lack of subsequent anti-C3 deposition on both hydrophilic and hydrophobic surfaces. Preadsorption with immunoglobulin G on the surfaces caused a pronounced increase of the deposition of material from serum as well as of subsequent anti-C3 deposition. Both effects were absent if EDTA was present in the serum. Our results indicate that complement activation and deposition occur by incubation of human sera on hydrophobic and hydrophilic silicon dioxide surfaces, which are two surfaces with very simple and well-defined chemical composition. The degree of the reversibility of the deposition of immunoglobulin G was furthermore larger on hydrophilic silicon.

Complement Activation↗
PubMed1986

Action spectra of photoactivated cyclic GMP metabolism and relaxation in bovine mesenteric artery.

Strips of bovine mesenteric arteries, brought to sustained contraction by addition of 3.0 microM phenylephrine, relaxed during exposure to shortwave light. The action spectrum of the photorelaxation was characterized by most effectiveness of relaxation in the range of 360 to 400 nm; on the contrary, shortwave light of 280 to 300 nm increased the tension. The photo-induced relaxation was accompanied by an increase in the cGMP level, measured 30 sec after the onset of radiation, and the action spectrum of the increase in cGMP seemed to coincide fairly well with the action spectrum of relaxation. Both the increase in cGMP and relaxation in response to increasing light intensity at 400 nm fitted the rectangular hyperbolic equation. The K values (the intensity which gave half maximal response) for cGMP increase and relaxation, respectively, obtained by non-linear least square regression analysis, were found to assume very close values (1.3 mW/cm2 for cGMP increase and 1.5 mW/cm2 for relaxation). The action spectrum of the crude soluble guanylate cyclase (GC) activity displayed a peak around 400 nm. Our results suggest that there is a close association between photo-induced increase in cGMP and relaxation, probably as a result of interaction between shortwave light and the heme moiety of GC.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1985

Determination of molecular hydrogen in investigations of the susceptibility of Enterobacteriaceae to ampicillin.

One hundred and five enterobacterial isolates from urinary tract infections were examined for ampicillin-susceptibility by measurement of molecular hydrogen production with a palladium metal oxide semi-conductor (Pd-MOS sensor). Eighty-one per cent of hydrogen producing strains could be placed in the same susceptibility groups as recorded by disc-diffusion tests. However, it was harder to separate susceptible from intermediate types than to determine resistance. In all but five strains the hydrogen production allowed determination of viability within 5 h.

Ampicillin↗