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Biomedical subjects

O Sonne

Publications and source records attributed to O Sonne.

At least 19 recordsLinked to original sources
PubMed2001

[Early clinical exposure--an instant success. The new medical curriculum at the University of Aarhus].

INTRODUCTION: In the new medical curriculum at the University of Aarhus, a third term, 20-week course focussing on early patient contact was launched. MATERIAL AND METHODS: Nine prototypical and clinically important disease entities each formed the basis of one-week courses covering an introductory clinical lecture, presentation of "paper" cases, and formalised training of pertinent clinical skills. This was integrated with plenaries and group work in physiology pertaining to the disease and the patient cases. In addition, seminars were held in patient-doctor relationships, and environmental and social medicine. Introductory lectures were given on topics, such as medical ethics, taxonomy of diseases, the organisation of hospital-based health care. At the end of the term, the students resided for eight weeks at county hospitals, which do not traditionally participate in pregraduate teaching. Each student followed one particular patient, which formed the basis of a written essay. RESULTS: Early clinical lectures (87 +/- 8%, mean +/- SD) and use of clinical cases (73 +/- 8%) were well received by third term students, and 87% found that the "paper" cases facilitated their understanding of physiology. The evaluation of the hospital training was very positive (rated excellent or good by > 95%). DISCUSSION: We conclude that early introduction to clinical practice is feasible and well received by the students.

Clinical Competence↗
PubMed2001

Identification of the haemoglobin scavenger receptor.

Intravascular haemolysis is a physiological phenomenon as well as a severe pathological complication when accelerated in various autoimmune, infectious (such as malaria) and inherited (such as sickle cell disease) disorders. Haemoglobin released into plasma is captured by the acute phase protein haptoglobin, which is depleted from plasma during elevated haemolysis. Here we report the identification of the acute phase-regulated and signal-inducing macrophage protein, CD163, as a receptor that scavenges haemoglobin by mediating endocytosis of haptoglobin-haemoglobin complexes. CD163 binds only haptoglobin and haemoglobin in complex, which indicates the exposure of a receptor-binding neoepitope. The receptor-ligand interaction is Ca2+-dependent and of high affinity. Complexes of haemoglobin and multimeric haptoglobin (the 2-2 phenotype) exhibit higher functional affinity for CD 163 than do complexes of haemoglobin and dimeric haptoglobin (the 1-1 phenotype). Specific CD163-mediated endocytosis of haptoglobin-haemoglobin complexes is measurable in cells transfected with CD163 complementary DNA and in CD163-expressing myelo-monocytic lymphoma cells.

Animals↗
PubMed1992

In vivo inflammatory stimulation induces a transient change in the binding of thrombin to rat peritoneal macrophages.

The binding of 125I-labeled thrombin to rat peritoneal macrophages isolated 20 h after the ip injection of thioglycollate broth or lipopolysaccharide decreased to 20% of the value found in resident macrophages due to a decrease in the number of receptors. The binding returned to normal values within a week after the injection. The decline parallelled more or less the Vmax for the 5'-nucleotidase activity. This decrease in the binding of thrombin could not be explained by an immigration of monocytes into the peritoneal cavity, since the binding of 125I-labeled alpha 2-macroglobulin-trypsin complex increased 4.5-fold in the same cell population due to an increase in the number of receptors, and blood monocytes do not bind alpha 2-macroglobulin-trypsin complex. The increase in the binding of alpha 2-macroglobulin-protease complex parallelled an increase in the incorporation of glucosamine, although the latter did not increase to the same extent. Engulfment of plasma membrane after phagocytosis did not result in a decreased binding of thrombin, but preincubation at 37 degrees C with concanavalin A caused a minor reduction in the binding. There was a positive correlation between the binding of alpha 2-macroglobulin-trypsin complex and the fraction of polymorphonuclear leukocytes in the peritoneal exudate and a negative correlation between the binding of thrombin and the fraction of polymorphonuclear leukocytes in the exudate, when the inflammation was induced by a milder stimulus, sterile NaCl, indicating a common signal for the polymorphonuclear leukocyte chemotaxis and the macrophage differentiation.

Animals↗
PubMed1991

A thrombin receptor in resident rat peritoneal macrophages.

Resident rat peritoneal macrophages possess 6 x 10(2) high-affinity binding sites per cell for bovine thrombin with a Kd of 11 pM, and 7.5 x 10(4) low-affinity sites with a Kd of 5.8 nM. These binding sites are highly specific for thrombin. Half-maximal binding of 125I-labeled bovine thrombin is achieved after 1 min at 37 degrees C, and after 12 min at 4 degrees C. The reversibly bound fraction of the ligand dissociates according to a biexponential time course with the rate constants 0.27 and 0.06 min-1 at 4 degrees C. Part of the tracer remains cell-associated even after prolonged incubation, but all cell-associated radio-activity migrates as intact thrombin upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The bound thrombin is minimally endocytosed as judged by the resistance to pH 3 treatment, and the receptor does not mediate a quantitatively important degradation of the ligand. The binding is not dependent on the catalytic site of thrombin, since irreversibly inactivated thrombin also binds to the receptor. 125I-labeled thrombin covalently cross-linked to its receptor migrates in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a Mr 160,000, corresponding to an approximate receptor size of Mr 120,000.

Amino Acid Sequence↗
PubMed1991

A rapid microtitration plate assay for non-specific esterase.

A simple and convenient colorimetric assay for the quantification of non-specific esterase is described. The assay takes advantage of the microtitration plate format, and the high capacity of repetitive dispensers and the microplate reader for this format. The assay is well suited for the quantification changes in the esterase activity in homogeneous cell populations like monocytes maturing into macrophages.

Animals↗
PubMed1990

Isolation of rat peritoneal mononuclear and polymorphonuclear leucocytes on discontinuous gradients of Nycodenz.

Centrifugation of rat leucocytes from thioglycollate-induced inflammatory peritoneal exudate on a discontinuous gradient of Nycodenz with a density of 1106 g/l and an osmolarity of 400 mosmol/l separated the polymorphonuclear from the mononuclear leucocytes. The cells on the interphase between the buffer and the gradient medium contained 96% mononuclear leucocytes with a recovery of greater than 60%, and the bottom fraction consisted of 98% polymorphonuclear leucocytes with a yield of 91%, when an exudate isolated 20 h after the injection of thioglycollate was fractionated. Leucocytes isolated from non-inflamed rat peritoneum could be enriched in the fraction of nonspecific esterase-positive cells from 86% to 96% with a recovery of 82% on a gradient with a density of 1091 g/l and an osmolarity of 325 mosmol/l. The viability of the isolated cells was greater than 95% (trypan blue exclusion test), and there was no measurable reduction in the fraction of phagocytosing cells (latex and opsonized zymosan) after exposure to the hypertonic gradient material.

Animals↗
PubMed1990

Cellular targets and receptors for interleukin-6. I. In vivo and in vitro uptake of IL-6 in liver and hepatocytes.

Interleukin-6 (IL-6) is a potent stimulator of the hepatic synthesis of acute-phase proteins. 125I-labelled IL-6 disappeared from the blood of rats with an overall half-time of about 1.5 min; 41% of the injected tracer dose was recovered in the liver by 15 min. The clearance was biphasic. The simultaneous injection of tracer and an excess of unlabelled IL-6 eliminated the initial rapid phase, and reduced the hepatic uptake to 14%. Light microscopic autoradiography showed 5% of the grains over non-hepatocytes, and 80% over hepatocytes, accumulating in areas around the bile canaliculi. Thereafter, degradation products accumulated in the bile. At 4 degrees C, isolated rat hepatocytes bound IL-6 with an apparent Kd of 39 pmol l-1 to a uniform class of 4500 receptors per cell with an apparent molar mass of 115-120 kg mol-1. The HepG2 human hepatocellular cell line bound IL-6 with an apparent Kd of 21 pmol l-1 to a uniform class of 1200 receptors per cell with an apparent molar mass of 155-160 kg mol-1. At 37 degrees C, both cell types endocytosed the bound ligand slowly, and degradation products appeared in the medium after a relatively long lag period (40 min in hepatocytes and 1 h in HepG2 cells).

Animals↗
PubMed1990

Cellular targets and receptors for interleukin-6. II. Characterization of IL-6 binding and receptors in peripheral blood cells and macrophages.

Within 15 min, approximately 2.5% of 125I-labelled interleukin-6 (IL-6) injected intravenously into rats was taken up by the spleen. As determined by light microscopic autoradiography, uptake was mainly (60%) accounted for by macrophages in the red pulp. 125I-IL-6 binding in rat peritoneal macrophages was quantitatively similar to that in cultured human monocytes and T-cells. By comparison, IL-6 binding to polymorphonuclear granulocytes and freshly isolated monocytes was low. Stimulation with antigen, but not with mitogen (PWM), induced receptor presentation in B-cells, whereas antigen and mitogen downregulated the binding in T-cells. At 4 degrees C, labelled IL-6 bound to cells with a half-time of about 1.5 h. Binding appeared reversible, but dissociation was slow and incomplete. The apparent Kd for IL-6 binding was about 30 pmol l-1 in most cell types, however, values of approximately 120 pmol l-1 were obtained in polymorphonuclear granulocytes. At 37 degrees C, 125I-IL-6 was rapidly internalized by T-cells and monocyte-macrophages, and after a lag time, TCA-soluble radioactivity was released from the cells following a sigmoidal curve. Polyacrylamide gel electrophoresis of radiolabelled IL-6 cross-linked to its binding sites in T-cells, yielded receptor-ligand complexes with molar masses of 70-80 and 120-140 kg mol-1. This would agree with a dimeric conformation of the IL-6 receptor.

Animals↗
PubMed1988

Characterization of the binding of bovine thrombin to isolated rat hepatocytes.

Isolated rat hepatocytes possess per cell 4,500 high-affinity binding sites for thrombin with a Kd of 30-40 pM, and 2.8 X 10(5) low-affinity sites with a Kd of 30 nM. These binding sites are highly specific for thrombin. Half-maximal binding of 125I-labelled thrombin is achieved after 3 min at 37 degrees C and 7 min at 4 degrees C. The reversibly bound fraction of the ligand dissociates according to a biexponential time course with the rate constants 1-2 X 10(-2) s-1 and 3-4 X 10(-4) s-1. Part of the tracer remains cell-associated even after prolonged incubation, but all cell-associated radioactivity migrates as intact thrombin upon sodium dodecyl sulphate polyacrylamide gel electrophoresis. The bound thrombin is minimally endocytosed as judged by the resistance to pH 3-treatment. Cell-associated radioactivity dissociated from the cells binds just as well in a receptor assay as tracer incubated in a conditioned medium under the same conditions, indicating the absence of a quantitatively important receptor-mediated degradation of the ligand.

Animals↗
PubMed1988

The cellular dynamics of hepatic receptors for alpha 2-macroglobulin.protease complex and for insulin are different.

Making freshly isolated rat hepatocytes permeable by 0.4 g/liter digitonin doubled the number of binding sites for alpha 2-macroglobulin.trypsin complex without changing the affinity. Thus, digitonin unmasked a receptor pool, probably of intracellular origin. The total cellular binding capacity was measured in the presence of digitonin, the surface-exposed in its absence. Upon preincubation of the cells at 37 degrees C, the total cellular binding capacity for alpha 2-macroglobulin.trypsin decreased over a 2-h period to 0.26 of the initial value. By contrast, the surface-exposed binding capacity initially increased in response to a preincubation at 37 degrees C, reached after 20 min a peak value 1.74 times that at 0 time, followed by a decrease. Neither the increase in nor the loss of surface-exposed binding capacity was influenced by inhibitors of lysosomal functions, protein synthesis and glycosylation. Colchicine abolished the increase in surface-exposed binding capacity but not the disappearance. By contrast, phenylarsine oxide (inhibitor of endocytosis), N-ethylmaleimide, and phenylmethanesulphonyl fluoride inhibited the receptor loss, suggesting that the loss occurred by proteolysis. The insulin receptor concentration, studied in parallel, remained practically constant in the investigated period in the presence and absence of digitonin. Thus, the hepatic receptor for alpha 2-macroglobulin.protease complexes is regulated independently of other specialized plasma membrane proteins.

Animals↗
PubMed1988

The specific binding of thrombin to human polymorphonuclear leucocytes.

Thrombin is a chemotaxin for polymorphonuclear leucocytes. In this paper the binding kinetics of 125I-labelled thrombin to purified polymorphonuclear leucocytes is characterized. At 4 degrees C, the 125I-labelled thrombin bound to the cells with a half-time of about 3 min. About 0.77 of the bound tracer dissociated upon addition of a surplus of unlabelled thrombin or hirudin. Each cell possessed about 50 receptors with a Kd of 18 pmol/l and about 6000 receptors with a Kd of 31 nmol/l. Although the binding affinity at 37 degrees C was 7-10-fold lower than that measured at 4 degrees C, it may be high enough to constitute the molecular basis for the reported thrombin-induced chemotaxis.

Chemotaxis, Leukocyte↗
PubMed1987

Receptor-mediated degradation of insulin in isolated rat adipocytes. Formation of a degradation product slightly smaller than insulin.

More than 90% of the radioactivity associated with isolated rat adipocytes incubated with [TyrA14-125I]monoiodoinsulin represented at steady state iodoinsulin possessing full binding affinity. In contrast, about half of the radioactivity dissociating from the cells was [125I]monoiodotyrosine. The other half was of a molecular size similar to that of iodoinsulin as judged from gel-filtration chromatography. However, the descending limb of the 'insulin' peak (i.e., the smaller molecules) possessed a reduced binding activity compared with native iodoinsulin, material from the ascending limb, or a similar fraction isolated from dissociation medium from IM-9 lymphocytes, a cell type devoid of receptor-mediated insulin degradation. The cells, thus, release an intermediary degradation product.

Adipose Tissue↗
PubMed1986

Preparative reversed-phase high-performance liquid chromatography of iodinated insulin retaining full biological activity.

Insulin monoiodinated in Tyr A14, A19, B16 and B26 can be separated from insulin and diiodoinsulins using reversed-phase high-performance liquid chromatography on LiChrosorb RP-18 columns. Monoiodoinsulins with high and low specific activities were isolated from a number of buffer systems without any reduction in binding affinity and biological activity in isolated rat fat cells. The reason for the previously observed reduction in the binding affinity was probably column bleeding, i.e., chemical degradation of the column support.

Adipose Tissue↗
PubMed1986

Evidence for binding of human pregnancy zone protein-proteinase complex to alpha 2-macroglobulin receptors.

125I-labelled human pregnancy zone protein complexed with chymotrypsin was removed from the circulation with a half-time of 2.3 min after intravenous injection in rats. After 6 min about 67% of the label was present in the liver and about 3% was in the spleen, both in male and in female pregnant rats. The half-time of removal was more than 30 min for native pregnancy zone protein. Uptake into other organs, including placentae and feti, was negligible. 30 pM labelled pregnancy zone protein X chymotrypsin was specifically bound to rat hepatocytes and adipocytes and to human fibroblasts and monocyte-derived macrophages at 4 degrees C. Binding was almost completely abolished by a saturating concentration of unlabelled alpha 2-macroglobulin X trypsin. Binding of 15 pM labelled macroglobulin complex was completely abolished by a saturating concentration of pregnancy zone protein X chymotrypsin. In rat hepatocytes, binding of pregnancy zone protein complex was lower than that of alpha 2-macroglobulin complex at low ligand concentrations. Half-maximal receptor occupancy was obtained with about 300 pM pregnancy zone protein complex. Unlabelled alpha 2-macroglobulin or pregnancy zone protein complex failed to accelerate dissociation of the labelled pregnancy zone protein complex under conditions where dissociation of alpha 2-macroglobulin was markedly enhanced. It is concluded that pregnancy zone protein and alpha 2-macroglobulin complexes bind to the same receptors. The quantitative differences may be related to the fact that alpha 2-macroglobulin is a tetramer whereas the functional unit of pregnancy zone protein is probably a dimer.

Animals↗
PubMed1986

The reversible receptor binding of insulin in isolated rat adipocytes measured at 37 degrees C. The binding is not rate limiting for cellular uptake.

The bimolecular binding reaction between mono[TyrA14-125I]iodoinsulin and the insulin receptor was investigated at 37 degrees C in intact isolated rat adipocytes in which membrane traffic was inhibited by 1 mM KCN. This treatment decreased the fraction of cell-associated radioactivity resistant to treatment at pH 3 (usually regarded as internalized ligand) from 70% to 17%. The total amount of tracer being cell-associated at steady state was reduced to about half of the control value partly because of a decreased apparent binding affinity. The t1/2 for the forward reaction was reduced from 414 s in the control cell to 26 s in the KCN treated cell. Likewise, the t1/2 for the dissociation was reduced from 461 s to 67 s. Both rate constants were pH sensitive, the association rate constant being 7-8-fold more than the dissociation rate constant. Since both rate constants for the bimolecular reaction were one order of magnitude greater than those for the uptake and the release of label in the untreated cell, other processes than binding constitute the rate-limiting step(s) in the cellular reaction with insulin.

Adipose Tissue↗
PubMed1986

Luminal uptake and intracellular transport of insulin in renal proximal tubules.

It is generally accepted that proteins taken up from the renal tubular fluid are transported into lysosomes in proximal tubule cells. Recently, however, it has been postulated that insulin in isolated perfused rat kidneys did not accumulate in lysosomes but to a certain degree in the Golgi region. The present study was undertaken to investigate the intracellular handling of biologically unaltered insulin in rat renal proximal tubule cells. Rats were prepared for in vivo micropuncture and either a colloidal gold insulin complex or insulin monoiodinated in the A-14 position (125I-insulin) was microinfused into proximal tubules. After 5, 10, 25 or 60 min the tubules were fixed by microinfusion of glutaraldehyde and processed for electron microscopy or electron microscope autoradiography. A qualitative analysis of tubules infused with colloidal gold insulin or 125I-insulin showed that insulin was taken up by endocytosis and transported to lysosomes, and a quantitative autoradiographic analysis of the 125I-insulin microinfused tubules showed that the grain density after five min was significantly increased for endocytic vacuoles and for lysosomes. After 60 min the grain density was still significant over lysosomes. The accumulation of grains was non-significant over all other areas analyzed at any time. This study shows that insulin is taken up from the luminal side of the proximal tubule by endocytosis and transported to the lysosomes. There was no significant transport to the Golgi region.

Animals↗
PubMed1985

Increased inhibitory potency of free fatty acid-poor albumin on the released and activity of insulin-degrading enzymes from isolated rat adipocytes and hepatocytes.

Isolated rat adipocytes and hepatocytes release protease(s) into the medium which degrade insulin and glucagon. This can be partially inhibited by high concentrations of bovine serum albumin. Free fatty acid-poor albumin prepared by charcoal treatment at pH 3 is a more potent inhibitor than untreated albumin. However, the increase in inhibitory potency depends on the exposure of the albumin to the low pH and not on the removal of the fatty acids. Optimum conditions for this treatment are overnight exposure to pH 3-4 at 37 degrees C. In hepatocytes, but not in adipocytes, the treated albumin also diminishes the release of enzymes into the medium.

Adipose Tissue↗