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Biomedical subjects

I Lundström

Publications and source records attributed to I Lundström.

At least 19 recordsLinked to original sources
PubMed1992

Antisera binding onto metals immersed in human plasma in vitro.

Titanium (Ti), silicon (Si), silver (Ag), vanadium (V), gold (Au), and chromium (Cr) surfaces were made hydrophilic by radiofrequency plasma treatment. The binding of antifibrinogen (a-fib) and anti-high-molecular-weight kininogen (a-HMWK) after incubation of surfaces in 10% human blood plasma was investigated with ellipsometry. Ti and Si surfaces bound a-HMWK but no detectable amounts of a-fib, whereas the other metals bound both types of antisera. Protein adsorption in a fluid gradient produced under a convex lens indicated that the small deposition of a-fib on Ti and Si surfaces is probably a result of protein displacement. This displacement was not evident at lens positions simulating low plasma concentrations where large amounts of a-fib adsorbed. Surfaces washed sequentially in trichloroethane, acetone, and ethanol produced more hydrophobic surfaces and resulted in slower rates of a-fib displacement. These studies would indicate that some metals form complexes with specific plasma proteins or, alternatively, that different metals may bind equal amounts of plasma proteins which express differing antigenicities toward their surroundings.

Adsorption↗
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↗
PubMed1992

Measurements of light transmission through single melanophores.

A photometrical method has been developed that allows assessment of subcellular pigment migration in melanophores of the fish cockoo wrasse (Labrus ossifagus L.) The pigment migration was studied with local light spot transmission measurements. Depending on where the light beam is placed on the melanophores it is possible to study events within an area of approximately 75 microns 2. Measuring pigment translocation in different parts of a melanophore gives new possibilities to study how cell membrane receptor-mediated signals are spread within a single cell, which will increase our understanding of how receptor activating drugs exert their cellular effect. The technique can be used in pharmacological and biophysical studies and in biosensors, pharmaceutical screens, environmental detectors, etc. The method clearly has the ability to study local and small changes in light transmission due to displacement of melanophore pigment granules. Since one melanophore on the tip of an optical fibre would be enough to obtain a measurable effect, the presented technique provides the basis for future development of biosensors small enough for in vivo applications, e.g., to monitor the catecholamine levels of circulating blood.

Animals↗
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↗
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↗