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Biomedical subjects

P Ott

Publications and source records attributed to P Ott.

At least 127 records · Page 7Linked to original sources
PubMed1987

Segmental mean temperature differences in the diagnosis of acute venous thrombosis in the legs.

In 92 consecutive patients admitted with suspected acute deep venous thrombosis, (DVT), the screening value of a new thermographic equipment, DeVeTherm, was evaluated with phlebography as a reference. The predictive value was 0.29 (0.19-0.41) of a positive thermography, and 0.68 (0.43-0.87) of a negative thermography. These results do not justify application of DeVeTherm as a screening method for DVT.

Acute Disease↗
PubMed1986

Effect of sickling on dimyristoylphosphatidylcholine-induced vesiculation in sickle red blood cells.

To study the effect of sickling on dimyristoylphosphatidylcholine (DMPC)-induced vesiculation, sickle (SS) red blood cells were incubated with sonicated suspensions of DMPC under either room air or nitrogen. Like normal red cells, when sickle cells were incubated with DMPC under oxygenated conditions, incorporation of DMPC into the erythrocyte membrane occurred, followed by echinocytic shape transformation and subsequent release of membrane vesicles. On the other hand, when SS cells were induced to sickle by deoxygenation, DMPC-induced vesiculation of these cells was dramatically reduced. However, upon reoxygenation, release of vesicles from these sickle erythrocytes occurred immediately. When SS cells were incubated under hypertonic (500 mosM) and deoxygenated conditions (where hemoglobin polymerization occurs but red cells do not show the typical sickle morphology), a similar decrease in the extent of vesiculation was observed. Experiments with radiolabelled lipid vesicles indicated that incorporation of DMPC into erythrocyte membranes occurred in all cases and therefore was not the limiting factor in the reduction of vesiculation in deoxygenated SS cells. Taken together, these results indicate that cellular viscosity and membrane rigidity, both of which are influenced by hemoglobin polymerization, are two important factors in process of vesicle release from sickle erythrocytes.

Anemia, Sickle Cell↗
PubMed1986

Effect of membrane cholesterol on dimyristoylphosphatidylcholine-induced vesiculation of human red blood cells.

During incubation of intact human erythrocytes with sonicated dimyristoylphosphatidylcholine (DMPC) vesicles, the cells change their discoid morphology to form echinocytes and finally give rise to the release of membrane vesicles. In this process, the red cell membrane accumulates DMPC and loses up to 15% of its cholesterol. On the other hand, replacement of 25% of the endogenous phosphatidylcholine species by DMPC without affecting the cholesterol level of the erythrocytes can be achieved by incubation with DMPC/cholesterol (1:1, mol/mol) sonicated vesicles in the presence of the phosphatidylcholine-specific phospholipid-transfer protein from bovine liver. This replacement also gives rise to an echinocytic cell morphology, but no membrane vesiculation can be observed. However, the vesiculation process can as yet be initiated upon a subsequent decrease of the cholesterol level, by incubation of those modified cells in the presence of sonicated vesicles of pure egg phosphatidylcholine. Incubation of native erythrocytes with pure egg phosphatidylcholine vesicles, on the other hand, results in cholesterol depletion, but does neither induce the formation of echinocytes nor the release of membrane vesicles. Cellular ATP levels are not affected during these incubations. From these results, it can be concluded that a decrease in cholesterol content of the erythrocyte membrane is essential for the DMPC-induced vesiculation of those cells.

Acetylcholinesterase↗
PubMed1986

Streptokinase therapy in the routine management of deep venous thrombosis in the lower extremities. A retrospective study of phlebographic results and therapeutic complications.

One hundred and eight patients with phlebographically verified deep venous thrombosis were treated with streptokinase. Total or partial thrombolysis was phlebographically demonstrated in 60 patients (55.6%). Three patients died during treatment, all from pulmonary embolism. Six patients developed clinical signs suggestive of pulmonary embolism. In 16 patients (14.8%), major bleeding complicated the treatment. One patient had anaphylactic shock, while various allergic reactions were recorded in 22. Streptokinase therapy in the routine management of deep venous thrombosis carries an acceptable efficacy and safety similar to what has been achieved under research conditions.

Adolescent↗
PubMed1985

'Crossed immunoblotting': identification of proteins after crossed immunoelectrophoresis and electrotransfer to nitrocellulose membranes.

Human serum proteins or membrane proteins from human erythrocytes were separated by crossed immunoelectrophoresis in agarose gels under non-denaturating and non-reducing conditions and precipitated by polyspecific antibodies against the respective protein mixtures. The separated proteins were subsequently transferred electrophoretically to nitrocellulose sheets and incubated with mouse monoclonal antibodies against individual protein species. Visualization of the complexes of antigen and monoclonal antibody on the nitrocellulose sheets was performed with peroxidase-conjugated second antibodies. The additional electroblotting step clearly improved the analytical resolution possibilities of crossed immunoelectrophoresis: crossed immunoblotting allows a straightforward identification of individual proteins in complex crossed immunoelectrophoresis patterns. At the same time separation and characterization of proteins is performed under non-denaturing conditions, which is not possible with blotting techniques based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Adult↗
PubMed1985

The influence of cellular ATP levels on dimyristoylphosphatidylcholine-induced release of vesicles from human erythrocytes.

Release of membrane vesicles from human erythrocytes was induced by modulation of red cell ATP levels, by incubation of erythrocytes with sonicated dimyristoylphosphatidylcholine (DMPC) suspensions, or by a sequential combination of both procedures. When red blood cell ATP levels were decreased prior to incubation with DMPC, the lag-time between addition of the lipid and beginning of vesiculation was reduced. Furthermore, the rate of vesicle release itself was accelerated. Experiments carried out with a rapid ATP depletion technique showed that the onset of vesiculation and the release were most evidently accelerated in those cases where echinocytes had been formed prior to the addition of DMPC. The results suggest that red blood cells with reduced cellular ATP levels or an altered cell shape are more susceptible to a further perturbation of the membrane by addition of exogenous DMPC.

Adenosine Triphosphate↗
PubMed1985

Erythrocyte adenosine triphosphate depletion during voluntary hyperventilation.

Chronic hypophosphatemia in humans is associated with a slow depletion of adenosine triphosphate (ATP) and 2,3-diphosphoglycerate (2,3-DPG) in erythrocytes, combined with shape alteration, impaired deformability, and viability of the cells. Likewise, incubation of erythrocytes in alkaline solution is associated with ATP depletion. Since in hyperventilation both hypophosphatemia and alkalosis are present, we have investigated red cell organic phosphates, shape, deformability, and osmotic fragility before, during, and after 20 min of voluntary hyperventilation. On the average, red cell ATP decreased by 42%, the blood pH increased by 0.2 units, and plasma inorganic phosphorus decreased by 46% compared with the initial values. Red cell 2,3-DPG, shape, deformability, and osmotic fragility remained unchanged. After the end of hyperventilation ATP increased rapidly to control values in parallel with the normalization of the blood pH, whereas inorganic plasma phosphorus remained at the low level observed during hyperventilation. It is concluded that the combined effects of hypophosphatemia and alkalosis in acute hyperventilation lead to an isolated fall of red cell ATP, which occurs as rapid as after total inhibition of red cell glycolysis in vitro.

2,3-Diphosphoglycerate↗
PubMed1984

Amphiphile dependency of the monomeric and dimeric forms of acetylcholinesterase from human erythrocyte membrane.

Human erythrocyte membrane-bound acetylcholinesterase was converted to a monomeric species by treatment of ghosts with 2-mercaptoethanol and iodoacetic acid. After solubilization with Triton X-100, the reduced and alkylated enzyme was partially purified by affinity chromatography and separated from residual dimeric enzyme by sucrose density gradient centrifugation in a zonal rotor. Monomeric and dimeric acetylcholinesterase showed full enzymatic activity in presence of Triton X-100 whereas in the absence of detergent, activity was decreased to approx. 20% and 15%, respectively. Preformed egg phosphatidylcholine vesicles fully sustained activity of the monomeric species whereas the dimer was only 80% active. The results suggest that a dimeric structure is not required for manifestation of amphiphile dependency of membrane-bound acetylcholinesterase from human erythrocytes. Furthermore, monomeric enzyme appears to be more easily inserted into phospholipid bilayers than the dimeric species.

Acetylcholinesterase↗
PubMed1984

Detection of protein A gold 15 nm marked surface antigens by backscattered electrons.

Colloidal gold has become an important marker in electron microscopy. Due to its scattering properties colloidal gold is easily detected in TEM. Because of the material dependent signal, preferentially backscattered electrons are used in the SEM. In the present study, we used a YAG (cerium dotted yttrium aluminum garnet) single crystal annular scintillator mounted directly below the objective pole piece. The secondary (SE) and backscattered (BSE) images of protein A gold marked cell surface proteins on two test specimens were compared: Red blood cells with a smooth and yeasts with a highly structured surface. After freeze-drying, the specimens were coated with a layer of carbon (5-10 nm) to enhance conductivity. The specimens were observed in a field emission SEM. In the SE mode a distinction between the gold particles and organic structures was hardly possible; this mode, however, gave good surface information. In the BSE mode, individual gold particles of 10 to 15 nm were easily detected. Thus the combination of the high resolution surface image and the material dependent BSE image provides an accurate localization of the surface antigens.

Acetylcholinesterase↗
PubMed1983

A monomeric form of human erythrocyte membrane acetylcholinesterase.

Purified detergent solubilized dimeric human erythrocyte acetylcholinesterase (6.3 S form) was converted to a stable monomeric 3.9 S species when treated with 2-mercaptoethanol and iodoacetic acid. More than 60% of the enzymatic activity were recovered after this treatment. A decreased susceptibility to reduction and alkylation was observed with purified, detergent depleted acetylcholinesterase aggregates. When erythrocyte membranes (ghosts) were subjected to the same treatment, acetylcholinesterase could subsequently be solubilized as monomeric 3.9 S form and and more than 90% of the activity were recovered. Monomeric acetylcholinesterase was less reactive towards antibodies raised against (dimeric) human erythrocyte membrane acetylcholinesterase and towards antibodies against human erythrocyte membranes. The results suggest that acetylcholinesterase is present as dimeric species in human erythrocyte membranes despite the fact that fully active monomers can be obtained.

Acetylcholinesterase↗
PubMed1983

Reconstitution of pure acetylcholine receptor in phospholipid vesicles and comparison with receptor-rich membranes by the use of a potentiometric dye.

Acetylcholine receptor, isolated in Triton X-100 on a cobra alpha-neurotoxin affinity column was incorporated into unilamellar phospholipid vesicles by a detergent depletion method using Amberlite XAD-2. Vesicles of an average diameter of 25 nm were formed, as verified by freeze-fracture electron microscopy and gel filtration. 85 to 95% of the alpha-bungarotoxin binding sites of the reconstituted acetylcholine receptor were oriented towards the outside of the vesicles. In the reconstituted receptor one molecule of residual Triton X-100 per 2.5 alpha-bungarotoxin binding sites on the receptor molecule could be assessed. The reconstituted protein was not accessible to papain digestion, whereas the pure acetylcholine receptor, solubilized by Triton X-100 was split into smaller polypeptides under the same condition. Reconstituted acetylcholine receptor and receptor-rich membranes did not exhibit the same behavior as measured by use of a potentiometric dye. This is interpreted as an irreversible alteration of at least 95% of the receptors purified in the presence of Triton X-100. Furthermore, it could be shown that the fluorescence intensity changes induced by carbamylcholine in receptor-rich membranes did not reflect ion fluxes, but conformational changes of the protein or a displacement of the dye from the protein.

Animals↗