Biomedical subjects

L Olsson

Publications and source records attributed to L Olsson.

At least 73 records · Page 4Linked to original sources

PubMed1991

A preformed, ordered structure of a 25-residue peptide derived from a major histocompatibility complex class I antigen is required to affect insulin receptor function.

It was recently shown that a 25-residue peptide, Dk-(61-85), derived from the alpha 1 domain of a murine major histocompatibility class I molecule (H-2Dk), affects insulin receptor functions (Hansen, T., Stagsted, J., Pedersen, L., Roth, R. A., Goldstein, A., and Olsson, L. (1989) Proc. Natl. Acad. Sci. U. S. A. 86, 3123-3126; Stagsted, J., Reaven, G. M., Hansen, T., Goldstein, A., and Olsson, L. (1990) Cell 62, 297-307). We now report that this peptide can reversibly assume a biologically active or inactive state as measured in the rat adipocyte glucose uptake assay, implying that the peptide has at least two interconvertible conformations. The peptide has an ordered conformation in 0.1 M HCl or 0.1 M NaCl stock solution as shown by circular dichroism, but has a disordered molecular structure and is inactive when dissolved in H2O. The biologically active peptide forms liquid crystals at the stock solution concentration (1 mM), so the CD spectra do not provide information on the secondary structure. Under all conditions tested, biological activity (measured after transfer to assay buffer) is associated with an ordered conformation in stock solution. Biological activity and an ordered conformation of the peptide in H2O stock solution can be induced by increasing ionic strength (greater than 100 mM NaCl for maximal effect) or increasing pH (greater than 5 for maximal effect). The induction rate of the ordered conformation is slow with a half-maximal value obtained after approximately 20 min. Both biological activity and the ordered structure are lost upon heating of stock solution to 90 degrees C or upon transfer to assay buffer. A similar correlation of ordered structure with biological activity was observed with two truncated peptides derived from Dk-(61-85). It is inferred from these results that the Dk-(61-85) peptide and related peptides only affect insulin-stimulated glucose uptake in rat adipocytes if they have assumed an ordered conformation in stock solution prior to transfer to assay buffer and exposure to cells.

Adipose Tissue↗

PubMed1991

Immobilization of pyranose oxidase (Phanerochaete chrysosporium): characterization of the enzymic properties.

Immobilization of pyranose oxidase (E.C.1.1.3.10) from Phanerochaete chrysosporium is described. The enzyme was bound to a glass-beaded support according to the glutardialdehyde, diazo, and carbodiimide methods with activity yields of 10%-23.3%. Characterization of the enzyme immobilized with the glutardialdehyde showed enhanced operational, storage, and temperature stability. The temperature optimum remained unchanged, but the pH optimum was slightly altered. Kinetic properties and the relative substrate specificities for glucose and xylose showed certain differences.

Agaricales↗

PubMed1991

Analysis and classification of secondary sounds from the disintegration of kidney stones with acoustic shock waves.

Secondary sound emission, partly in the audible frequency range, from shock wave disintegration of kidney stones has been recorded during the treatment of two patients. A skilled operator can determine by listening if the stone is hit by the shock-wave or not. Spectral analysis of these recordings show differences between the sounds which can be used to evaluate the fragmenting effect on the stone. Results are presented of a preliminary discriminating method based on parameters in an autoregressive signal model.

Humans↗

PubMed1991

Registration of surface structures using airborne focused ultrasound.

A low-cost measuring system, based on a personal computer combined with standard equipment for complex measurements and signal processing, has been assembled. Such a system increases the possibilities for small hospitals and clinics to finance advanced measuring equipment. A description of equipment developed for airborne ultrasound together with a personal computer-based system for fast data acquisition and processing is given. Two air-adapted ultrasound transducers with high lateral resolution have been developed. Furthermore, a few results for fast and accurate estimation of signal arrival time are presented. The theoretical estimation models developed are applied to skin surface profile registrations.

Humans↗

PubMed1991

Are regional variations in ischaemic heart disease related to differences in coronary risk factors? The project 'myocardial infarction in mid-Sweden'.

In a previous report, a large regional variation was reported in total mortality and mortality rate from ischaemic heart disease (IHD) in mid-Sweden. In this report, IHD prevalence and risk factor data are presented. A postal questionnaire was sent out to a random sample of men aged 45-64 years in each of 40 communities. 14,675 men (88%) responded. Based on a validity study, IHD cases were defined as those with a history of myocardial infarction and/or angina pectoris. Age, smoking habits, antihypertensive treatment, body mass index, food habits, stress and physical activity during leisure time were used as risk factors. IHD prevalence showed the same geographical variation as IHD mortality, with a low prevalence in the east and a high prevalence in the west. There was a moderate variation in risk factor levels over the 40 communities. When this variation was taken into account the geographical IHD variation was somewhat smaller but still substantial. Other factors may involve socio-economics, drinking water qualities, mineral soil content or other environmental factors. Which of these cause the largest IHD variation is at present unknown, but is subject to systematic examination in this project.

Angina Pectoris↗

PubMed1990

Regulation of insulin receptor functions by a peptide derived from a major histocompatibility complex class I antigen.

A 25 residue peptide, Dk-(61-85), derived from the alpha 1 domain of a murine MHC class I molecule (H-2Dk), enhances cellular glucose uptake, prolongs the effect of insulin, and inhibits insulin receptor internalization without affecting insulin binding or dissociation. Full effect of the peptide is obtained at 10-100 microM. The magnitude of the peptide-mediated enhancement of glucose uptake is insulin dependent and is at maximum approximately 50% above that of full insulin stimulation, excluding a merely insulinomimetic action of the peptide. Dk-(61-85) does not interact directly with the glucose transporter molecule. Furthermore, the peptide-mediated inhibition of insulin receptor internalization results in 2-3 times more receptors in the plasma membrane. The peptide also causes hypoglycemia in rats. The biological activity of Dk-(61-85) suggests that an important nonimmunological role of MHC class I molecules is to affect some of the key functions of ligand-activated receptors.

Amino Acid Sequence↗

PubMed1990

Beta 1 integrin-mediated collagen gel contraction is stimulated by PDGF.

The attachment of primary rat hepatocytes and fibroblasts to collagen type I is mediated by non-RGD-dependent beta 1 integrin matrix receptors. In this report we describe a novel 96-well microtiter plate assay for the quantification of fibroblast-mediated contraction of floating collagen type I gels. Fetal calf serum and platelet-derived growth factor (PDGF), but not transforming growth factor-beta 1, stimulated primary rat heart fibroblasts and normal human diploid fibroblasts (AG 1518) to contract collagen gels to less than 10% of the initial gel volume within a 24-h incubation period. Rabbit polyclonal antibodies directed to the rat hepatocyte integrin beta 1-chain inhibited the PDGF-stimulated collagen gel contraction. The inhibitory activity on contraction of the anti-beta 1 integrin IgG could be overcome by adding higher doses of PDGF. The contraction process was not blocked by anti-fibronectin IgG nor by synthetic peptides containing the tripeptide Arg-Gly-Asp (RGD), in concentrations that readily blocked fibroblast attachment to fibronectin-coated planar substrates. Autologous fibronectin or control peptides containing the tripeptide Arg-Gly-Glu were without effect. Immunofluorescence microscopy on fibroblasts grown within collagen gels revealed a punctate distribution of the beta 1 integrin and a lack of detectable levels of endogenously produced fibronectin. Collectively these data suggest a role for integrin collagen receptors with affinity for collagen fibers, distinct from the previously described RGD-dependent fibronectin receptors, in the fibronectin-independent PDGF-stimulated collagen gel contraction process.

Actins↗

PubMed1990

Transplacental passage and fetal kidney binding of 14C-dichlorovinyl cysteine (DCVC) in mice.

In order to assess the potential hazard of the nephrotoxic compound S-1,2-dichlorovinyl-L-cysteine (DCVC) during gestation, studies on its disposition and degenerative effects were performed in pregnant mice. In late gestation, binding of 14C-DCVC (spec. act. 1.01 microCi/mumol) equivalents was observed by autoradiography in the inner cortex of the kidney, in the liver and gastrointestinal tract of the fetuses. The uptake of radioactivity in the fetal kidney increased from day 13 to day 18 of gestation when measured by liquid scintillation. When fetuses were injected in utero, a distinct binding of 14C-DCVC was present in the kidney cortex. This fact suggests that bioactivation occurs in situ, as the reactive products are not likely to be transported far from their site of formation. The concentration of radioactivity in the fetal kidney at day 18 of gestation was about 10% of that found in the maternal kidney. Limiting factors for fetal kidney uptake may be both transplacental transfer, and renal bioactivation and transport activities. No distinct histopathological changes in the fetal kidney were observed when a nephrotoxic dose (25 mg/kg) of DCVC was given to the dam. These results suggest that the fetal kidney during late gestation is able to activate and bind DCVC. However, the degree of fetal binding seems too low to cause any visible histopathological effects.

Animals↗

PubMed1990

Portable closed loop feedback system for control of the blood glucose level in the pig.

To establish the difference in glucose consumption of healthy compared to diabetic pigs, a transportable system for the feedback control of insulin and glucose was used in conscious pigs. The system for controlling glucose levels, as well as glucose consumption, was easy to use and adjusted smoothly to rapid changes in insulin level. Five days prior to the first day of experiment, healthy animals were prepared with intravenous jugular catheters tunnelled subcutaneously to the neck. On the first day of experiment, measurements of glucose were continuously taken before and after food ingestion. The animals were rendered diabetic after 2 days using Alloxan and streptozotocin. The measurements were then repeated. To be able to obtain constant glucose levels of approximately 3 mmol during both fasting and postprandial periods requires only small glucose adjustment infusion in the diabetic pigs, as opposed to healthy ones. Using the described system, it would be possible to evaluate subclinical diabetes and control unstable diabetics with different therapeutic regimes.

Animals↗

PubMed1990

Discrepancy between transcriptional products and cell surface expression of MHC class I antigens in metastatic and non-metastatic Lewis lung tumor cells.

Major histocompatibility complex class I transcriptional products and cell surface expression of their corresponding proteins were measured in tumorigenic Lewis lung carcinoma cells with either high metastatic activity (G4 cells) or with no metastatic activity (G2 cells). The transcriptional products were measured by hybridization to gene-specific oligonucleotide probes for H-2Kb and H-2Db respectively. The cell surface density of the corresponding H-2 glycoproteins was determined by FACS cell sorter analysis and by radioimmunoassay using anti-H-2Kb and anti-H-2Db specific monoclonal antibodies. The analyses revealed that the cell surface density of both Kb and Db was reduced 4-9 fold in G4 cells compared to G2 cells. However, this reduction of G4 cell surface expression of MHC class I molecules was not reflected at the mRNA level since both subclones had similar low levels of detectable Kb and Db specific mRNA. beta 2-microglobulin was analysed at the mRNA and protein level and found not to be the rate-limiting factor in the MHC class I expression of the metastatic G4 cells. Thus, the cell surface expression of H-2Kb and H-2Db by the two Lewis lung carcinoma subclones did not correlate with the amount of specific mRNA. Other regulatory mechanisms of gene expression acting at the levels between transcription and the appearance of the gene product at the cell surface must therefore account for the observed difference in the cell surface expression of MHC class I molecules of the two Lewis lung carcinoma cells. The potential importance of MHC class I expression in the metastatic capacity of the tumor cells is discussed.

Animals↗

PubMed1990

Structural and compositional divergencies in the extracellular matrix encountered by neural crest cells in the white mutant axolotl embryo.

The skin of the white mutant axolotl larva is pigmented differently from that of the normal dark due to a local inability of the extracellular matrix (ECM) to support subepidermal migration of neural crest-derived pigment cell precursors. In the present study, we have compared the ECM of neural crest migratory pathways of normal dark and white mutant embryos ultrastructurally, immunohistochemically and biochemically to disclose differences in their structure/composition that could be responsible for the restriction of subepidermal neural crest cell migration in the white mutant axolotl. When examined by electron microscopy, in conjunction with computerized image analysis, the structural assembly of interstitial and basement membrane ECMs of the two embryos was found to be largely comparable. At stages of initial neural crest cell migration, however, fixation of the subepidermal ECM in situ with either Karnovsky-ruthenium red or with periodate-lysine-paraformaldehyde followed by ruthenium red-containing fixatives, revealed that fibrils of the dark matrix were significantly more abundant in associated electron-dense granules. This ultrastructural discrepancy of the white axolotl ECM was specific for the subepidermal region and suggested an abnormal proteoglycan distribution. Dark and white matrices of the medioventral migratory route of neural crest cells had a comparable appearance but differed from the corresponding subepidermal ECMs. Immunohistochemistry revealed only minor differences in the distribution of fibronectin, laminin, collagen types I, and IV, whereas collagen type III appeared differentially distributed in the two embryos. Chondroitin- and chondroitin-6-sulfate-rich proteoglycans were more prevalent in the white mutant embryo than in the dark, especially in the subepidermal space. Membrane microcarriers were utilized to explant site-specifically native ECM for biochemical analysis. Two-dimensional gel electrophoresis of these regional matrices revealed a number of differences in their protein content, principally in constituents of apparent molecular masses of 30-90,000. Taken together our observations suggest that local divergences in the concentration/assembly of low and high molecular mass proteins and proteoglycans of the ECM encountered by the moving neural crest cells account for their disparate migratory behavior in the white mutant axolotl.

Ambystoma↗

PubMed1989

Specific molecular interaction between the insulin receptor and a D product of MHC class I.

The density of MHC class I was determined on a murine thymoma cell line (R1), an H-2 negative variant (R1E), and R1E-derived cell lines in which H-2 expression was restored by transfection of various MHC class I genes (Db, Kb, and truncated Db) and/or a beta-2-microglobulin gene (beta 2-m; B2). Appreciable MHC class I expression was found on R1 cells and on the variants in which MHC class I expression was restored by transfection of Db/beta 2-m or Kb/beta 2-m genes. Only approximately 20% difference was observed between the number of Db molecules and Kb molecules on the R1E/B2/Db and on R1E/B2/Kb, respectively. However, specific insulin binding was significantly different between these lines. By using a computer assisted curve fitting program, the insulin binding data for R1 and R1E/B2/Db cell lines best fitted a two-site model (K approximately 6 x 10(-9) M for high-affinity sites and a 2 to 3 x 10(-7) M for low-affinity sites), whereas all other lines only expressed one type of insulin binding site. These sites were unrelated to IGF-I and IGF-II receptors. Cross-linking of 125I-labeled insulin demonstrated specific binding of the ligand to a Mr approximately 130,000 dalton band in all lines. In the R1E/B2/Db cells, insulin also cross-linked to cell membrane molecules with Mr approximately 48,000 and approximately 60,000 Da, which were identified by immunoprecipitation to be the H chain of MHC class I and the heavy chain of MHC class I plus beta 2-m, respectively. It is concluded that the insulin receptors in the cell membrane interact specifically with D-products of MHC class I and that class I molecules of MHC may have a crucial role in insulin receptor expression. This may reflect a more general nonimmunologic role of MHC class I.

Animals↗

PubMed1989

Inhibition of insulin receptor phosphorylation by peptides derived from major histocompatibility complex class I antigens.

Peptides from the alpha 1 region (residues 61-85) of the D and K molecules of the major histocompatibility complex class I antigens inhibit insulin-induced tyrosine kinase activity of the purified human insulin receptors (IRs) as measured both by autophosphorylation and IR-mediated substrate [poly(Glu,Tyr)] phosphorylation. Half-maximal effect of the Dk-(61-85) peptide on IR autophosphorylation is obtained at 1.2 microM, and almost complete inhibition of IR kinase activity is obtained at 10 microM peptide. The corresponding K kappa-(61-85) peptide has a significantly weaker effect on autophosphorylation. No such effects are observed with nine peptides of similar length, but unrelated to major histocompatibility complex class I antigens. Neither of the major histocompatibility complex class I-derived peptides has any effect on the constitutively active kinase of a genetically engineered cytoplasmic IR domain. Further, insulin binding to IR is unaltered in the presence of the major histocompatibility complex class I-derived peptides. The inhibitory activity of the peptides on insulin-induced IR phosphorylation facilitated the observation that IRs require insulin to become substrate for an independent tyrosine kinase. In the presence of an inhibitory peptide, the constitutively active cytoplasmic IR kinase domain only phosphorylates the intact IR in the presence of insulin. We conclude that the tyrosine kinase activity of IRs may be altered by peptide interaction at an allosteric site and, moreover, IRs require insulin to assume a conformation permitting phosphorylation by an independent kinase.

Allosteric Site↗

PubMed1989

Validity of a postal questionnaire with regard to the prevalence of myocardial infarction in a general population sample.

In order to evaluate the possibility of finding persons who have suffered a myocardial infarction (MI) by postal questionnaire, a self-administered questionnaire was sent to a random sample of 4400 men aged 45-64 years, drawn from the general population. The response rate was 95%. 176 men indicated that they had been hospitalized for MI, out of which 124 cases could be verified from medical records. Of the remaining men, 33 had evidence of cardiovascular disease (CVD) in their records but no MI, and 19 men had no evidence of CVD. The sensitivity (estimated from a subsample) was 100% and the specificity 98.7%. The predictive value was 100% for a negative response and 70.5% for a positive response. The 33 positive responders whose MI could not be verified but who had evidence of CVD had characteristics fairly similar to the responders with verified MIs. However, the 19 positive responders whose MI could not be verified and who had no evidence of CVD had characteristics that were dissimilar from the MI group as well as from the negative responders. The questionnaire thus identified all the MI cases. The need for validation can be limited to the relatively small group of positive responders.

Cardiovascular Diseases↗

PubMed1988

A carbohydrate epitope associated with human squamous lung cancer.

A monoclonal antibody, 43-9F, specifically recognizes a tumor-associated antigen expressed both on surface membrane glycoproteins and on secreted soluble mucins of human squamous lung carcinoma (SLC) cells, and the corresponding antigen can be detected as a circulating tumor marker in plasma of SLC patients. Thin-layer chromatography immunostaining of neutral glycolipids extracted from SLC cells reveals a 43-9F-reactive glycolipid whose carbohydrate structure, as determined by fast atom bombardment-mass spectrometry, is identical with that of an Lea-active pentaglycosylceramide described previously: Gal beta 1-3[Fuc alpha 1-4]-GlcNAc beta 1-3Gal beta 1-4Glc-Cer. However, the Lea-active oligosaccharide hapten, lacto-N-fucopentaose II, with the same carbohydrate structure, fails to inhibit binding of 43-9F, and a well-characterized anti-Lea monoclonal antibody blocks only 40% of 43-9F binding sites on SLC cells, suggesting that the major epitope recognized by 43-9F is more complex than the Lea epitope. To search for a higher affinity 43-9F epitope among more complex oligosaccharides, a mixture of tritiated neutral oligosaccharide alditols from pooled human milk was passed through a 43-9F affinity column. A major retarded oligosaccharide was purified by high-performance liquid chromatography and shown by fast atom bombardment-mass spectrometry to have the following structure: Gal beta 1-3[Fuc alpha 1-4]GlcNAc beta 1-3Gal beta 1-4[Fuc alpha 1-3] GlcNAc beta 1-3Gal beta 1-4Glc. Oligosaccharides containing this sugar sequence are at least 100-fold more active than lacto-N-fucopentaose II as competitive inhibitors of 43-9F. Thus, antibody 43-9F binds to the above difucosyl Lea-X determinant with high affinity and weakly cross-reacts with the Lea antigen under some conditions such as occurs in thin-layer chromatography and enzyme-linked immunosorbent assay where multiple weak interactions of the decavalent IgM antibody may occur.

Antibodies, Monoclonal↗

PubMed1988

Tumorigenic human squamous lung cancer cells have defined cell surface carbohydrates that are absent from nontumorigenic cells.

Cells of cloned lines derived from human squamous lung carcinomas spontaneously become heterogeneous with respect to several tumor-associated cell surface carbohydrates such as the sialosyl-Lea oligosaccharide antigen or the recently described oligosaccharide recognized by monoclonal antibody 43-9F. Subclones derived from these cultures are initially homogeneous with respect to the presence or absence of a specific cell surface carbohydrate but gradually revert back to a heterogeneous population. Cells of homogeneous subclones having both the sialosyl-LEa and 43-9F cell surface antigens and other subclones lacking them were injected subcutaneously in nude mice. All clones expressing these tumor-associated cell surface carbohydrates were found to be highly tumorigenic, whereas those lacking them were nontumorigenic or, at most, weakly tumorigenic. Clones having the tumor-associated cell surface carbohydrates were more resistant to cytotoxic attack by purified mouse natural killer cells than those clones lacking these carbohydrates, suggesting that the tumorigenicity of the former clones may be influenced by immunoprotective effects of these novel carbohydrates.

Animals↗

PubMed1988

Measurement of gingival swelling from dental casts by generation of a moiré pattern with laser light.

The aim of the study was to develop a sensitive measuring method enabling direct evaluation of gingival swelling to be made as registered on dental casts. On two separate occasions, when different degrees of severity of gingival inflammation were present in the same subject, reversible hydrocolloid impressions were taken of the mandible. The casts obtained were located successively in identical three-dimensional relationships in a field of interference fringes generated by two intersecting beams of collimated helium-neon laser light, and were photographed. The evaluation of the moiré pattern obtained directly by superimposition of the two images of the surface studied indicated that a decrease in gingival height of 0.38 mm in the direction of the camera had occurred between the two occasions. The use of a computer-based image-processing system considerably improved the visibility of the pattern. The reproducibility of the impression technique, as well as the relocation and superimposing techniques, proved satisfactory at the moiré resolution used (0.19 mm). The method has potential application in clinical experimental research, and therefore warrants further evaluation.

Adult↗

PubMed1987

Association between expression of a tumor-associated carbohydrate epitope and the proliferative and tumorigenic activity of a human squamous lung cancer cell line and epitope-positive and -negative sublines.

A previously described epitope (designated 43-9F) with high specificity for human squamous carcinoma and adenocarcinoma of the lung is here reported to be associated with the proliferative and tumorigenic activity of a cloned human squamous lung carcinoma (SLC) cell line (SLC-L11) and a number of cloned sublines. Lines with appreciable 43-9F epitope density (43-9F+) had a short population doubling time and were tumorigenic in athymic nude mice, whereas clones with low 43-9F epitope density (43-9F-) of the same line had longer population doubling times and did not result in 43-9F- tumors in athymic nude mice. Some of the 43-9F- clones reverted to the 43-9F+ phenotype and then became tumorigenic. Two other SLC lines (SLC-L12 and SLC-L13), positive and negative, respectively, for 43-9F also expressed tumorigenic and proliferative behavior concordant with the data for SLC-L11 and its sublines. Cell lines of human squamous cell carcinomas had a pronounced intratumoral heterogeneity in respect to 43-9F epitope expression. Fluorescence-activated cell sorting of cells with high and low 43-9F density and subsequent cloning demonstrated that the cloning capacity was confined almost exclusively to cells with high antigen density. Immunoaffinity chromatography and gel filtration showed that the epitope was expressed in glycoproteins with molecular weights in the range of 5 X 10(6)-5 X 10(4). Mild alkaline hydrolysis reduced the binding of 43-9F antibody to SLC-glycoproteins while neuraminidase treatment augmented the 43-9F antibody binding. It is concluded that expression of 43-9F+ glycoproteins seems linked to the proliferative and tumorigenic features of human squamous lung carcinoma cell lines.

Animals↗