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Biomedical subjects

U Jönsson

Publications and source records attributed to U Jönsson.

16 recordsLinked to original sources
PubMed2006

A conceptual model for the development of Phytophthora disease in Quercus robur.

Here, a conceptual model is presented for the development of Phytophthora disease in pedunculate oak. The model is presented using the causal loop diagram tool and gives an overview of how various abiotic and biotic factors, such as soil moisture, nutrient availability and mycorrhizal colonization, may affect the reproduction and the infective capacity of soil-borne Phytophthora species, the susceptibility of the host and subsequent disease development. It is suggested that the link between the root damage caused by Phytophthora species and overall tree vitality is in the assimilation and allocation of carbon within the plants. The potential impact of environmental factors on these processes is discussed. The model is presented with reference to scenarios related to variation in soil moisture and nutrient availability. The need for species-specific validation of the model and the implications of the model are discussed.

Carbon↗
PubMed2002

A slow form of alpha-2-macroglobulin in diseased and healthy dogs.

Alpha-macroglobulins (AMs) function as non-specific protease inhibitors by using a so-called trapping mechanism, which is a compaction of the molecule that can be seen as a "fast" form in native polyacrylamide gel electrophoresis (PAGE). AMs also play a role in the transport and clearance of cytokines and growth factors from the circulation. In the dog, two AMs are known, alpha-1-macroglobulin (A1M) and alpha-2-macroglobulin (A2M). Using agarose and polyacrylamide gel electrophoresis of canine serum or plasma, we detected a cathodal, slow form of A2M. Upon activation with elastase, slow A2M resembled normal A2M in agarose gel electrophoresis, showing decreased negative charge at semi-saturation but not at full saturation with enzyme. In PAGE, however, slow A2M, unlike normal A2M, did not exhibit a "fast" form after short-term incubation with elastase. After incubation overnight, the "fast" form was seen, indicating a retarded reaction. Incubation of slow A2M with ammonium sulphate, a known activator of AMs, resulted in decreased negative charge in agarose gel electrophoresis and no reaction or partial reaction in PAGE. Slow A2M is present in fresh blood samples or may develop from partial alterations within a few days of storage. Moreover, it is sometimes reversible. Our findings may indicate that slow A2M is a result of an instability of the molecule, leading to a conformational change, which affects electrical charge and impairs the ability to develop into the "fast" form upon activation. This may lead to a delayed clearance of protease and inflammatory mediators from the circulation. Slow A2M was predominantly found in diseased dogs, especially in the Labrador retriever.

Animals↗
PubMed1998

Differences in co-variation of inorganic elements in the bulk and surface of human deciduous enamel: an induction analysis study.

This paper demonstrates a method for determination of co-variation between some inorganic elements in the bulk and surface areas of human tooth enamel. The technique is based on a computerised induction analysis of data obtained by secondary ion mass spectrometry (SIMS). When comparing the present data with an earlier study from our laboratory, it became evident that with only a moderate increase in the amount of data for the induction analysis, the results increased very considerably in reliability and precision. The patterns of co-variation between different elements differed between the bulk- and surface enamel. Only Mg expressed a similar pattern. In the bulk enamel the elements Na and P expressed a high degree of co-variation. Similarly, Mg and C expressed a high degree of co-variation. Mg was an element often found to co-vary with bulk enamel elements. In the enamel surface, F and Cl co-varied. In addition, Cl was an element often found to co-vary with other enamel surface elements.

Carbon↗
PubMed1993

Isolation, partial characterization, and molecular cloning of a human colon adenocarcinoma cell-surface glycoprotein recognized by the C215 mouse monoclonal antibody.

The monoclonal antibody C215 (IgG2a) was obtained by the immunization of BALB/c mice with the human colon adenocarcinoma cell line COLO 205 and used in the targeting of colorectal carcinomas. The partial characterization and purification of the C215 target molecule from solubilized COLO 205 membranes indicated that it is an integral membrane glycoprotein of the non-mucin type. The denatured antigen appeared as a major 40-kDa form in Western blots after SDS-polyacrylamide gel electrophoresis and migrated as a monomeric 36-kDa species after the reductive cleavage of intramolecular disulfide bridges. Using a five-step procedure, the antigen was purified 4,300-fold from COLO 205 tumors raised in nude mice to a homogeneity of 95% when assessed by capillary electrophoresis. Removal of N-linked carbohydrate by peptide:N-glycosidase treatment did not affect the visualization of the purified antigen in immunoblots but resulted in a faster migration in the SDS gels. The amino acid sequence was partially determined. Seventeen contiguous NH2-terminal amino acids were identified and coincided exactly with residues 82-98 of the GA733-2 protein cloned by Szala et al. (Szala, S., Froehlich, M., Scollon, M., Kasai, Y., Steplewske, Z., Koprowski, H., and Linnenback, A. J. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 3542-3546). Therefore, the predicted amino acid sequence of this protein was used to prepare overlapping synthetic peptides that cover the entire extracellular domain in order to identify the C215 epitope. A likely epitope, close to the NH2 terminus and corresponding to the first distinct hydrophilic stretch after the putative signal sequence, was identified in a peptide enzyme-linked immunosorbent assay. Moreover, GA733-2 cDNA was used for the cloning of the C215 protein from COLO 205 cells and the subsequent transfection to K36.16 mouse T cell leukemia cells. The transfected cells were C215 reactive in fluorescence-activated cell sorter analysis, and a 42 kDa band was visualized in Western blots under both non-reducing and reducing conditions. Our findings indicate a close relationship between the C215 antigen and other members of the GA-733 family, some of which are currently being used as targets in clinical trials with monoclonal antibodies. The mammalian expression system described here will enable further studies into the biological role of this protein and the construction of animal models in order to develop optimal therapeutic strategies.

Adenocarcinoma↗
PubMed1993

Introducing a biosensor based technology for real-time biospecific interaction analysis.

This report describes a system for real-time biospecific interaction analysis, using biosensor technology based on the optical phenomenon surface plasmon resonance. The biospecific interface is a sensor chip consisting of a thin gold film deposited on a glass support and covered with a hydrogel matrix. One component of the interaction being studied is attached covalently to the hydrogel, and other interactants are passed over the chip in solution. The interaction is followed in real time in terms of changes in the mass concentration of biomolecules at the sensor surface. Surface concentrations down to 10 pg/mm2 can be measured. The technique does not require molecular labels such as isotopes or spectroscopic markers, and purification of interacting components can often be avoided. Repeated analyses can be performed on the same sensor chip. With this system, the same general procedure can be used for a wide range of different applications, including concentration determination, kinetic measurements and multi-site binding studies. The sensitivity of the technique can be adjusted by choice of reagents and experimental procedure: determination of specific proteins in serum down to 20 ng/ml and macromolecular association constants from 10(7) M-1 up to 4 x 10(11) M-1 are documentated examples. No other single analytical system has the same versatility and general applicability to biospecific interaction analysis. The system is developed and marketed by Pharmacia Biosensor AB, Sweden.

Biosensing Techniques↗
PubMed1991

Binding sites for the cytotoxic metabolites of estramustine phosphate (Estracyt) in rat and human pancreas that are distinct from pancreatic estrogen-binding protein.

The interaction of estramustine and estromustine, cytotoxic metabolites of estramustine phosphate (Estracyt), with protein-binding sites in rat pancreatic tissue was examined. These compounds were bound with relatively high affinity (Kd 10 nmol/L) to binding sites constituting 0.02-0.03% of total protein. Further characterization of these binding sites revealed a native molecular weight of 24-30,000 a sedimentation coefficient of 3.4 S, and a heterogenous surface-charge distribution by ion-exchange chromatography. Removal of endogenously bound ligand(s) by acetone precipitation or charcoal treatment increased binding significantly. Similar binding sites were present in two of two human pancreatic tumors, but was low or absent in the only histopathologically normal pancreas examined as well as in serum and pancreatic juice. These binding sites were distinct from the "estrogen-binding protein" reported in normal pancreas from various species, but were similar to the "estramustine-binding protein" (EMBP) in rat ventral prostate with respect to ligand specificity and the positive effect of endogenous ligand removal on binding. Furthermore, specimens demonstrating presence of these binding sites also indicated cross-reactivity with antibodies raised against the latter protein, suggesting an immunochemical relation between estra-/estromustine-binding sites in the pancreas and rat prostate EMBP. The presence of high-affinity sites for estramustine and estromustine in human pancreatic carcinomas make this type of tumor a possible target tissue for compounds that exert antiproliferative as well as antimitotic activity in vitro.

Aged↗
PubMed1991

Real-time biospecific interaction analysis using surface plasmon resonance and a sensor chip technology.

We report here the development and application of a biosensor-based technology that employs surface plasmon resonance for label-free studies of molecular interactions in real time. The sensor chip interface, comprising a thin layer of gold deposited on a glass support, is derivatized with a flexible hydrophilic polymer to facilitate the attachment of specific ligands to the surface and to increase the dynamic range for surface concentration measurements. The sensor can be used to measure surface concentrations down to 10 pg/mm2. Typical coefficients of variation are from two to five percent. We anticipate that the ability to monitor multi-molecular complexes as they form will greatly contribute to the understanding of biorecognition and the structural basis of molecular function.

Antibodies, Monoclonal↗
PubMed1986

Calcium-independent release of gamma-aminobutyrate from nerve processes in the developing rabbit retina.

Retinas from 3- and 10-day-old rabbits, and from young (29 days), or adult animals were used to study in parallel the development of synaptic vesicles in amacrine cells and the Ca2+ dependence of the K+-stimulated [3H]gamma-aminobutyrate release from them. Few synaptic vesicles were observed in the amacrine cell processes in retinas from the 3-day-old rabbits. The number of vesicles significantly increased between 3 and 10 days and increased further between day 10 and the adult animal. The Ca2+ dependence of the K+-stimulated release decreased with increasing age. There is thus a poor correlation between the Ca2+ dependent transmitter release and the number of synaptic vesicles in the nerve terminal, favouring the existence of a Ca2+ dependent nonvesicular process for the [3H]gamma-aminobutyrate release in the rabbit retina.

Aging↗
PubMed1985

Immobilization of immunoglobulins on silica surfaces. Stability.

The development of new immunosensors based on surface-concentration-measuring devices requires a stable and reproducible immobilization of antibodies on well-characterized solid surfaces. We here report on the immobilization of immunoglobulin G (IgG) on chemically modified silica surfaces. Such surfaces may be used in various surface-oriented analytical methods. Reactive groups were introduced to the silica surfaces by chemical-vapour deposition of silane. The surfaces were characterized by ellipsometry, contact-angle measurements and scanning electron microscopy. IgG covalently bound by the use of thiol-disulphide exchange reactions, thereby controlling the maximum number of covalent bonds to the surface, was compared with IgG adsorbed on various silica surfaces. This comparison showed that the covalently bound IgG has a superior stability when the pH was lowered or incubation with detergents, urea or ethylene glycol was carried out. The result was evaluated by ellipsometry, an optical technique that renders possible the quantification of amounts of immobilized IgG. The results outline the possibilities of obtaining a controlled covalent binding of biomolecules to solid surfaces with an optimal stability and biological activity of the immobilized molecules.

Cross-Linking Reagents↗
PubMed1985

Immobilization of immunoglobulins on silica surfaces. Kinetics of immobilization and influence of ionic strength.

The kinetics of, and the influence of ionic strength on, the immobilization of rabbit immunoglobulin G (IgG) on different types of well-characterized silica surfaces were investigated. Adsorptive immobilization was compared with covalent attachment via thiol-disulphide exchange reactions. The amount of immobilized IgG on five different types of silica surfaces as a function of IgG concentration, at two different ionic strengths, was determined. The IgG-solid-surface interaction involved different types of interaction forces, depending on the surface chemistry of the solid surface. The solid-surface chemistry is an important parameter determining the immobilized amount of IgG. When conditions for covalent attachment of IgG to the surfaces were fulfilled, the IgG showed high affinity and the immobilized amount of IgG showed a fast saturation. Changes in ionic strength showed no significant influence on the kinetics of immobilization on these surfaces. The amount of covalently attached IgG was partially ionic-strength-dependent, indicating that adsorptive interactions were involved. The results are of fundamental interest for the development of new immunosensors based on surface-concentration-measuring devices.

Adsorption↗
PubMed1983

Electron microscopic analysis of the bone-titanium interface.

Ten cylindrical implants, made of polycarbonate and covered with a 120-250-nm-thick layer of pure titanium, were implanted into each tibial metaphysis of five rabbits. Observation time was 12 weeks. The implants were surrounded by mature, living bone. No soft tissue intervened between bone and implant at any point. With TEM microscopy the titanium was shown to be bordered by a 20-nm-thick layer of proteoglycans, showing the characteristics of ground substance, and separating the collagen from the implant surface. Cells at the interface were likewise separated from the titanium by such a layer. Hydroxyapatite crystals were observed within the ground substance layer, occasionally seemingly in direct contact with the titanium. Normal mineralization was present 100-500 nm from the implant surface. While this study aims at defining interface anatomy, it also shows that macroscopically smooth-surfaced titanium can readily heal into bone without a soft tissue envelope. This could be of help for materials' choice and design of permanently fixed implants.

Animals↗