Biomedical subjects

I Lundström

Publications and source records attributed to I Lundström.

At least 37 records · Page 2Linked to original sources

PubMed2000

Melatonin-induced organelle movement in melanophores is coupled to tyrosine phosphorylation of a high molecular weight protein.

Melanophores, brown to black pigment cells from, for example, Xenopus laevis, contain mobile melanin filled organelles, and are well suited for studies on organelle movement. The intracellular regulation of the movement seems to be controlled by serine and threonine phosphorylations and dephosphorylations. Melatonin induces aggregation of the melanosomes to the cell centre through a G(i/o)-protein-coupled receptor, Mel1c, which leads to an inhibition of PKA and a stimulation of PP2A. However, this study shows that the melatonin-induced aggregation of melanosomes is also accompanied by tyrosine phosphorylation of a protein with a molecular weight of approximately 280 kDa. Cells pre-incubated with genistein, an inhibitor of tyrosine phosphorylations, showed inhibited melanosome movement after melatonin stimulation, and a lower degree of tyrosine phosphorylation of the approximately 280 kDa protein. The adenylyl cyclase activator forskolin, and the G(i/o) protein inhibitor pertussis toxin, also inhibited tyrosine phosphorylation of the approximately 280 kDa protein. The results indicate that melatonin stimulation generates tyrosine phosphorylation of a high molecular weight protein, an event that seems to be essential for melanosome aggregation.

Adenylate Cyclase Toxin↗

PubMed2000

Sensitivity deviation: instrumental linearity errors that influence concentration analyses and kinetic evaluation of biomolecular interactions.

Many scientific instruments utilise multiple element detectors, e.g. CCD's or photodiode arrays, to monitor the change in a position of an optical pattern. For example. instruments for affinity biosensing based on surface plasmon resonance (SPR) or resonant mirror are equipped with such detectors. An important and desired property of these bioanalytical instruments is that the calculation of the movement or change in shape follows the true change. This is often not the case and it may lead to linearity errors, and to sensitivity errors. The sensitivity is normally defined as the slope of the calibration curve. A new parameter is introduced to account for the linearity errors, the sensitivity deviation, defined as the deviation from the undistorted slope of the calibration curve. The linearity error and the sensitivity deviation are intimately related and the sensitivity deviation may lead to misinterpretation of kinetic data, mass transport limitations and concentration analyses. Because the linearity errors are small (e.g. 10 pg/mm2 of biomolecules on the sensor surface) with regard to the dynamic range (e.g. 30,000 pg/mm2), they can be difficult to discover. However, the linearity errors are often not negligible with regard to a typical response (e.g. 0-100 pg/mm2). and may therefore cause serious problems. A method for detecting linearity errors is outlined. Further on, this paper demonstrates how integral linearity errors of less than 1% can result in a sensitivity deviation of 10%, a value that in our opinion cannot be ignored in biospecific interaction analysis (BIA). It should also be stressed out that this phenomenon also occurs in other instruments using array detectors.

Kinetics↗

PubMed2000

Comparison of surface plasmon resonance and quartz crystal microbalance in the study of whole blood and plasma coagulation.

The coagulation of blood plasma and whole blood was studied with a surface plasmon resonance (SPR) based device and a quartz crystal microbalance instrument with energy dissipation detection (QCM-D). The SPR and QCM-D response signals were similar in shape but differing in time scales, reflecting differences in detection mechanisms. The QCM-D response time was longer than SPR, as a physical coupling of the sample to the substrate is required for molecules to be detected by the QCM-method. Change of sample properties within the evanescent field is sufficient for detection with SPR. Both the SPR signals and the QCM-D frequency and dissipation shifts showed dependency on concentrations of coagulation activator and sensitivity to heparin additions. The ratio of dissipation to frequency shifts, commonly considered to reflect viscoelastic properties of the sample, varied with the concentration of activator in blood plasma but not in whole blood. Additions of heparin to the thromboplastin activated whole blood sample, however, made the ratio variation reoccur. Implications of these observations for the understanding of the blood coagulation processes as well as the potential of the two methods in the clinic and in research are discussed.

Animals↗

PubMed2000

Suramin blocks nucleotide triphosphate binding to ribosomal protein L3 from Trypanoplasma borreli.

Ribosomal protein L3 (L3) has been demonstrated to participate in formation of the peptidyltransferase center and is essential for its catalytic activity. In the present study we show that L3 is able to bind nucleotide triphosphates with high and specific affinity in vitro. L3 was serendipitously identified by screening of a genomic phage library from a primitive kinetoplastid flagellate Trypanoplasma borreli with the ATPase domain of the topoisomerase II gene as a probe. The cloned gene was overexpressed and purified as a his-tag fusion protein in E. coli. Radioligand binding experiments, using [gamma-35S]ATP, showed that L3 is able to bind ATP but also GTP and UTP with similar high affinity (IC50 50-100 nM), while it has no ATPase activity. Furthermore, we showed that L3 has more than 500-fold higher affinity for nucleotide triphosphates compared to the corresponding nucleotide monophosphates and diphosphates. Molecular genetic and biochemical analyses allowed us to localize the NTP binding domain of L3 to the N-terminal 296 residues. Suramin, a polysulfonated naphthylamine derivative of urea, known for its chemotherapeutic effects completely inhibited the binding of [gamma-35S]ATP at subclinical levels. Results obtained with surface plasmon resonance technology showed that suramin both forms weak multimolecular complexes with L3 and binds strongly to L3 in nearly stoichiometric amounts.

Adenosine Triphosphatases↗

PubMed1999

Characterization of cellular response to thiol-modified gold surfaces implanted in mouse peritoneal cavity.

The early inflammatory reaction in vivo to three well defined surfaces-gold, gold coated with glutathione (GSH), and 3-mercapto-1, 2-propanediol (MG)-was assessed as manifested by the adherence and activation of inflammatory cells during implantation intraperitoneally in mice. Evaluation of cell adhesion and activation was done by immunohistochemistry using specific monoclonal antibodies directed against cell differentiation antigens CD11b/CD18, CD74, and CD25 or by measurement by chemoluminescence of reactive oxygen radical species produced by adhering cells. Cell recruitment and activation was slow on the GSH-coated gold surfaces. These surfaces also had the highest percentage of adhering cells with an intact cell membrane. The MG-coated surfaces, on the other hand, rapidly recruited and activated cells and also caused cell membrane leakage to propidium iodide, suggesting cell membrane damage or cell death. The respiratory burst of adhering cells was stimulated by phorbol-myristate acetate on the GSH-coated surface but not on the MG-coated surface and by opsonized zymosan on the Mg-coated surface but only to a small degree on the GSH-coated surface. The respiratory burst following zymosan activation of cells adhering to the MG-coated surface was inhibited by treatment with 2. 3-diphosphoglycerate, a phospholipase D inhibitor. The presented data suggest that peritoneal leukocytes adhering to foreign materials may raise a respiratory burst response via a phospholipase D-dependent and protein kinase C-independent pathway.

Animals↗

PubMed1999

Surface plasmon resonance (SPR) analysis of coagulation in whole blood with application in prothrombin time assay.

It is previously shown that surface plasmon resonance (SPR) can be used to study blood plasma coagulation. This work explores the use of this technique for the analysis of tissue factor induced coagulation, i.e. prothrombin time (PT) analysis, of whole blood and plasma. The reference method was nephelometry. The prothrombin time analysis by SPR was performed by mixing two volumes of blood/plasma, one volume of thromboplastin, and one volume of CaCl2 solution directly on a sensor surface. The measurements show good agreement between nephelometry and SPR plasma analysis and also between SPR plasma and whole blood analysis. The effect of anticoagulant treatment on the clotting times was significant both quantitatively and qualitatively. The impact on the SPR signal of different physiological events in the coagulation process is discussed, and tentative interpretations of the sensorgram features are given. The major advantage of the SPR method compared to nephelometry is the possibility to perform analysis on whole blood instead of plasma. In conclusion, SPR is a promising method for whole blood coagulation analysis.

Anticoagulants↗

PubMed1999

TMD in patients with primary Sjögren syndrome: a comparison with temporomandibular clinic cases and controls.

AIMS: The aim of this study was to investigate the prevalence of temporomandibular disorders (TMD) in patients with primary Sjögren syndrome (1 degree SS), analyze the impact of the disease on mandibular function, and assess psychosocial distress. METHODS: Sixty-three subjects, 60 women and 3 men, participated in the study; 21 1 degree SS patients were compared with age-matched and gender-matched groups of TMD subjects and controls. Patients were examined according to the Research Diagnostic Criteria for Temporomandibular Disorders. RESULTS: Results showed that the subjective, clinical, and radiographic signs of TMD are not more common in patients with 1 degree SS than in controls. The impact of the autoimmune disease on mandibular function, e.g., speech and chewing ability, revealed limitations in oral functioning similar to those in patients with TMD pain. CONCLUSION: Both 1 degree SS and chronic TMD may be associated with appreciable physical discomfort and psychosocial dysfunction. However, the underlying mechanisms of the oral dysfunction of 1 degree SS and TMD are quite different and essentially unrelated.

Adult↗

PubMed1998

Aggregation of HSA, IgG, and Fibrinogen on Methylated Silicon Surfaces.

Ellipsometry was used to quantify adsorption and tapping mode atomic force microscopy to study surface aggregation of human serum albumin (HSA), immunoglobulin G (IgG), and fibrinogen (Fib) adsorbed from aqueous solutions onto methylated silicon surfaces. After exposure to air the protein monolayers were spontaneously restructured, exposing disorganized areas with heterogeneity depending on the degree of surface methylation. The aggregation patterns also depended on some properties of the adsorbed protein (such as the number of contact points with the surface), but seemed to be almost independent of the adsorption time. The results indicate that aggregates were formed due to lateral reorganization on the adsorbed layer at the air-liquid interface during the drying process. The interpretation is that the heterogeneous structures result from a thermodynamically driven interaction between the hydrophobic surface and the similarly hydrophobic air. The main conclusion that can be extracted from this work is that fibrinogen (hydrophobic and large protein) interacts more irreversibly with the silicon surfaces than IgG, and much more so than HSA, which is less hydrophobic and smaller than fibrinogen. Copyright 1998 Academic Press.

Journal Article↗

PubMed1998

Biosensing with G-protein coupled receptor systems.

Many cell membrane bound receptors communicate with the inside of the cell through guanine nucleotide binding proteins (G-proteins). This holds also for olfactory receptor neurons, which respond to odorants with G-protein mediated increases in the concentration of cyclic adenosine 3', 5'-monophosphate (cAMP) and/or inositol 1,4,5-triphosphate (InsP3). These substances regulate the ionic conductivity of the wall of the cilia. We have studied a similar system, namely G-protein coupled alpha 2-adrenoceptors, present for example in the cells of certain fish scales. These receptors react on, catecholamines and the G-protein mediates a decrease in cAMP, which causes an aggregation of pigment containing granulas to the middle of the cells. The light transmission of the cell increases due to this aggregation. This simple physiological response has been used in a sensitive biosensor for noradrenaline and for pertussis toxin that is based on isolated fish scales from cuckoo wrasse (Labrus ossifagus). The results were obtained with a simple photometer. Measurements can be performed also on single isolated melanophores. The main purpose of this contribution is, however, to point out that G-protein coupled receptors together with a simple physiological response form a principle for biosensing, which could also be an interesting alternative for odour sensing.

Animals↗

PubMed1998

Monitoring specific interaction of low molecular weight biomolecules on oxidized porous silicon using ellipsometry.

Porous silicon dioxide surfaces have been used for monitoring the specific affinity binding of low molecular weight molecules to streptavidin. Streptavidin was immobilized to the porous silicon dioxide surface by spontaneous adsorption at pH 7.4. Binding of biotin and an oligopeptide synthesized by means of combinatorial chemistry were monitored with an in situ null ellipsometer. Measurements were also done with hydroxy-azobenzene-2-carboxylic acid and DL-6-8-thioctic acid amide. The performance of porous silicon dioxide as a potential surface in biosensor applications was compared with a planar silicon dioxide surface. Porous silicon dioxide showed a 10-fold amplification of the response compared to planar silicon dioxide. It was possible to monitor the binding of biotin and the oligopeptide in the concentration range 2-40 microM. A response time as low as 30 s was obtained for the oligopeptide at 40 microM.

Adsorption↗

PubMed1998

A multisensor array for visualizing continuous state transitions in biopharmaceutical processes using principal component analysis.

An array of sensors with varying sensitivities, a so-called multisensor array, has been used for monitoring the growth and production states of biopharmaceutical processes. The sensor array produced continuous and characteristic response patterns from the processes due to the differences of the sensors. By analysing these patterns with the multivariate method principal component analysis, the state as well as the change of state of the bioprocesses could be visualized. The sensors used in the array were well-known semiconductor and optical gas sensors and the array was connected in an on-line set-up to the bioreactor's headspace effluent. The sensor array was applied to the monitoring of two recombinant bioprocesses, the production of human growth hormone in Escherichia coli and human factor VIII in Chinese ovary hamster cells. The sensor array could clearly visualize the characteristic transitions during the main growth or production phases of these two bioprocesses.

Animals↗

PubMed1998

Protein adsorption studies on model organic surfaces: an ellipsometric and infrared spectroscopic approach.

The development of accurate analytical tools to control the interfacial properties of solid substrates is of importance for the design of new biomaterials, as well as for the understanding of biomolecular interactions on surfaces. Considerable research efforts are presently devoted to this area on different levels of molecular complexity, i.e. both in the presence and in the absence of the biomolecules. In this contribution we review briefly applications of infrared reflection-absorption spectroscopy (IRAS) and ellipsometry as tools for analysis of the chemical properties of model surfaces, and their biological response in vitro when in contact with blood plasma or serum, respectively. The strength of the combination of the techniques is demonstrated by determination of protein adsorption patterns on a series of chemically well-defined so-called self-assembled alkanethiolate monolayers (SAMs) of 16-thiohexadecanol (HS-(CH2)16-OH) and n-hexadecanethiol (HS-(CH2)15-CH3) on gold. The protein adsorption patterns after incubations in plasma were determined by the specific binding of antibodies to the surfaces.

Adsorption↗

PubMed1998

Studies on protein adsorption and activation of complement on hydrated aluminium surfaces in vitro.

Adsorption of human plasma and serum proteins onto hydrated aluminium was studied by ellipsometry/antibody techniques, and soluble complement components iC3b, Bb, and C4d with commercial ELISA plates. Aluminium that was incubated in plasma for 1 min bound significant amounts of anti-lipoproteins (anti-LP), no antibodies against contact activation of coagulation proteins, and no anti-fibrinogen (anti-Fib). Time course studies with serum revealed increasing deposition of anti-C3c with time. Complement factor 1q (C1q) was antibody detectable only after short-time serum incubations, but no anti-IgG and anti-properdin bound to the protein film at any time. Anti-C3c was not deposited after exposure of the surfaces to Clq-depleted serum. Intriguingly, and in spite of increasing deposition of C3 to the surface with time, the combined ellipsometry and ELISA results gave no unequivocal proof of activation of complement by hydrated aluminium.

Adsorption↗

PubMed1998

The effect of acupuncture in the treatment of patients with primary Sjögren's syndrome. A controlled study.

Twenty-one patients, 20 women and 1 man, participated in a controlled study. All patients were diagnosed with primary Sjögren's syndrome (primary SS) according to the Copenhagen and San Diego criteria. The patients were randomly assigned to either a group receiving acupuncture treatment or a control group with no active treatment. The patients in the control group received acupuncture after 10 weeks when the acupuncture treatment was completed in the first group. A majority of the patients subjectively reported some improvement after treatment, and a significant increase in paraffin-stimulated saliva secretion was found after treatment. No statistically significant differences between the acupuncture group and the control group were seen in unstimulated salivary secretion or most of the subjective variables. The study showed that acupuncture is of limited value for patients with primary SS.

Acupuncture Points↗

PubMed1997

Electronic nose for microbial quality classification of grains.

The odour of grains is in many countries the primary criterion of fitness for consumption. However, smelling of grain for quality grading should be avoided since inhalation of mould spores or toxins may be hazardous to the health and determinations of the off-odours are subjective. An electronic nose, i.e. a gas sensor array combined with a pattern recognition routine might serve as an alternative. We have used an electronic nose consisting of a sensor array with different types of sensors. The signal pattern from the sensors is collected by a computer and further processed by an artificial neural network (ANN) providing the pattern recognition system. Samples of oats, rye and barley with different odours and wheat with different levels of ergosterol, fungal and bacterial colony forming units (cfu) were heated in a chamber and the gas in the chamber was led over the sensory array. The ANN could predict the odour classes of good, mouldy, weakly and strongly musty oats with a high degree of accuracy. The ANN also indicated the percentage of mouldy barley or rye grains in mixtures with fresh grains. In wheat a high degree of correlation between ANN predictions and measured ergosterol as well as with fungal and bacterial cfu was observed. The electronic nose can be developed to provide a simple and fast method for quality classification of grain and is likely to find applications also in other areas of food mycology.

Avena↗

PubMed1997

The initial reactions of TiO2 with blood.

The natural titanium oxide (TiO2) layer of commercial sheet titanium was dissolved in hydrofluoric acid. A new oxide layer was grown by oxidation in nitric acid or by annealing at 700 degrees C in air. At this temperature, reaction with nitrogen is unlikely. The purity of the oxidized sheet-titanium surfaces was investigated by Auger spectroscopy. The composition of both surfaces was TiO2 with carbon impurities. The carbon content of the acid-oxidized titanium was 20 +/- 2%, and the carbon content of the heat-oxidized titanium was 14 +/- 2% The initial reactions of the TiO2 surfaces with blood were investigated by short-time exposure to capillary blood and by detection of surface-adsorbed plasma proteins and cells with immunofluorescence. Antibodies specific to fibrinogen, complement factor C1q, prothrombin/thrombin, and platelet membrane antigen were used, and the fluorescence was quantitated by computer-aided image analysis. The results show that serine proteases are the dominating proteins adsorbed onto annealed titanium (C1q = 67 +/- 4.6; pt/t = 97 +/- 0.2; fib = 47 +/- 0.2). The adsorption of serine proteases was lower and the amount of fibrinogen was higher on the acid-oxidized surface (C1q = 46.3 +/- 2.6; pt/t = 25 +/- 2.9; fib = 64 +/- 0.7). Platelets adhered and spread on the annealed titanium surface within 5 sec of blood-material contact. The number of adhering platelets was higher on the acid-oxidized surface.

Biocompatible Materials↗

PubMed1997

Temporal studies on the deposition of complement on human colostrum IgA and serum IgG immobilized on methylated silicon.

The temporal deposition of selected complement proteins from human serum onto immobilized human colostrum immunoglobulin (Ig)A and human IgG on hydrophobic silicon was studied by ellipsometry-antibody techniques after incubations at 37 degrees C for up to 1 h. In parallel experiments the serum soluble iC3b, C4d, and Bb were detected by enzyme-linked immunosorbent assay techniques. The IgA-coated surfaces showed activation via the alternative pathway, and displayed a lag phase in the deposition of increased amounts of serum proteins, and anti-C3c and antiproperdin. Anti-IgG, -C1q, -C4, -factor H and -factor B were not deposited at any time to IgA surfaces. Upon coating of the surface with IgG, the classical pathway was rapidly activated and bound, then anti-C3c, antiproperdin, and after short serum incubation times, also anti-C1q and anti-IgG. When factor B-depleted or heat-treated sera were used, the observation was that properdin deposited onto IgG-coated surfaces from both. Ellipsometry and antibody techniques offer a convenient and rapid way to indicate the activation of the complement system on solid surfaces and facilitates a time-resolved determination of the activation pathway(s).

Biocompatible Materials↗

PubMed1997

Autoantibodies and primary Sjögren's syndrome in a hypocitraturic stone population.

Primary Sjögren's syndrome may be complicated by distal renal tubular acidosis (dRTA) and hypocitraturia, which are risk factors for calcium stone formation. Approached from a different perspective, in patients with urolithiasis and dRTA, autoantibodies and various autoimmune diseases are not uncommon. In search for signs of autoimmune disease, we analysed antinuclear antibodies and total levels of serum IgG in 197 hypocitraturic stone formers (67 women and 130 men). Antinuclear antibodies were present in 1.5% of the men and in 18% of the women. An isolated increase in serum IgG was found in 9% of the men and in 3% of the women. Anti-SS-A antibodies were analysed in a subgroup of 46 women and were estimated to occur in 16% of all hypocitraturic stone forming women. Four of 4 examined women, but no men, fulfilled the criteria of definite or possible primary Sjögren's syndrome. We recommend the analysis of anti-SS-A antibodies in female hypocitraturic stone formers.

Adult↗