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Biomedical subjects

B Ekman

Publications and source records attributed to B Ekman.

At least 19 recordsLinked to original sources
PubMed1992

Effects of desmopressin on blood loss in hip arthroplasty. Controlled study in 50 patients.

50 patients undergoing elective total hip replacement under epidural anesthesia and dextran infusion were given two doses of the vasopressin analogue desmopressin 0.3 micrograms/kg BW or placebo in a double-blinded randomized prospective study. Intraoperative blood loss and drainage loss did not differ significantly between groups, but desmopressin reduced the mean total blood loss (calculated from hemoglobin decrease and blood transfusions) by 310 mL (P less than 0.05).

Aged↗
PubMed1991

Effects on coagulation and fibrinolysis of desmopressin in patients undergoing total hip replacement.

Twelve patients undergoing total hip replacement, with regional anaesthesia and with dextran infusion for plasma expansion and thromboprophylaxis, were given the vasopressin analogue desmopressin (DDAVP) or placebo in a randomized, double-blind prospective study. In controls (n = 6) we found a prolongation of the bleeding time, low factor VIII (FVIII) and von Willebrand factor (vWF) and a decrease in antithrombin III to levels known to be at risk for venous thrombosis. Desmopressin shortened postoperative bleeding time, gave an early FVIII/vWF complex increase, prevented antithrombin III from falling to critically low values and appeared to activate the fibrinolytic system, both by tPA increase and PAI-1 decrease. Thus in the controls we found changes in both coagulation and fibrinolysis indicating a haemorrhagic diathesis as well as a risk for thromboembolism. Desmopressin induced factor changes that possibly reduce both risks.

Adult↗
PubMed1984

Denture marking.

Reluctance about the identification marking of dentures has been the result of high costs and technical marking problems. The ID band system described here is inexpensive, fast, and requires no expensive special equipment. Embedding the band in a suitable part of the denture provides fully legible, radiopaque, lasting evidence of the denture wearer's identity. Since 1981, all dentures made in Sweden have been legally required to be marked.

Adult↗
PubMed1983

Membrane-coated tablets: a system for the controlled release of drugs.

Membrane-coated tablets were developed to provide a dosage form which exhibits zero-order kinetics. The delivery system consisted of a soluble tablet core surrounded by a porous membrane which controls the diffusion rate. In the system studied, the diffusion rate of potassium chloride was found to be more constant than with other controlled-release products and independent of pH changes within the physiological range. The release profile of a drug can be varied by changing the composition of the membrane. Substantial amounts of the active substance can be loaded into membrane-coated tablets. The membrane protects the gastric mucosa from direct contact with the undissolved active substance. This delivery system has a potential for use with all water-soluble agents where a controlled release is desirable.

Delayed-Action Preparations↗
PubMed1980

Immobilization of proteins in microspheres of biodegradable polyacryldextran.

Macromolecules were immobilized by an emulsion polymerization technique in biodegradable microspheres of polyacryldextran, prepared by copolymerizing bisacrylamide with acryldextran. Such particles can be characterized by D-T-C expressions, where D denotes the concentration of derivatized dextran, T is the total concentration of acrylic compounds in the monomeric solution, and C denotes the fraction of cross-linker. In microparticles based on dextran T40 with a D-T-C of 11-1-75, the yield of immobilized protein was greater than in polyacrylamide particles. The properties of the immobilized proteins, e.g., Km and Vmax, were retained. The heat stability of the proteins was improved so that 5--10% of carbonic anhydrase still was active after 30 min at 100 degrees. However, the leakage of proteins from the polyacryldextran particles was greater than from polyacrylamide particles.

Acrylic Resins↗
PubMed1978

Detection and separation of lymphocytes with specific surface receptors, by using microparticles.

Horse anti-(human lymphocyte) globulin was immobilized together with fluorescein labelled dextran in spherical microparticles of polyacrylamide (AHLG-particles). The particles had a diameter of 1-5 micrometer and a density of 1.12g/cm3, with globulin exposed on the surface. Human lymphocytes bearing the antigen (thymus-derived lymphocytes) bound the particles, which were easily detected by fluorescence microscopy. In this way, about 58% of circulating human lymphocytes were able to bind AHLG-particles at 23 degrees C. Non-specific binding was low, only 3% when human serum albumin was present in the buffer, and only 4% when non-specific horse globulins were incorporated in the microparticles. The cell-particle complexes could be separated from cells that had not reacted by density-gradient centrifugation in Ficoll/metrizoate. The viability was not changed after the separation procedure. The number of cells binding AHLG-particles corresponded well the the relative amount of T-cells. When the cells binding AHLG-particles were separated from the lymphocytes, the number of T-cells decreased remarkably, indicating that the antibodies bind preferably to the T-cell population. Concanavalin A immobilized in microparticles was sufficiently exposed to initiate the agglutination of the lymphocytes. The agglutination was completely inhibited by preincubating the microparticles with alpha-methyl mannoside.

Antilymphocyte Serum↗
PubMed1978

Direct and indirect determination of binding constants of drug-protein complexes with microparticles.

Albumin can be immobilized in microparticles of poly-acrylamide in such a way that its ligand-binding properties are retained. With radiolabeled salicylic acid, warfarin, and tryptophan, the same characteristics are obtained for binding to albumin in the microparticles as in free solution. The particles can be used conveniently to determine association constants and the number of binding sites directly. The association constant of a competitive displacer can be determined indirectly as well, as shown with diazepam-salicylic acid and tryptophan-salicylic acid.

Acrylamides↗
PubMed1978

Improved stability of proteins immobilized in microparticles prepared by a modified emulsion polymerization technique.

Proteins can be immobilized in spherical microparticles of polyacrylamide gel (having a diameter of about 1 microgram) by an emulsion--polymerization technique. Higher cross-linked gels have a structure consisting of relatively large pores. This structure is advantageous when dealing with biologically active proteins acting on molecules dissolved in the surrounding medium. A rapid equilibrium is established between the interior of the particles and the medium, and rate-limiting diffusion is not observed. A suspension of carbonic anhydrase immobilized in microparticles will thus have kinetic properties very much like the free enzyme. In addition to the entrapment of the protein molecules in the three-dimensional network formed by the polyacrylamide threads, protein molecules are also fixed in the cross-linked threads of polyacrylamide. This fixation is probably responsible for the improved stability of the protein molecules against heat denaturation. Not even autoclaving at 110 degrees for 30 min denatured the immobilized enzyme completely (more than 25% of the enzyme activity was left). The higher resistance of molecules in microparticles against proteolytic degradation also is documented.

Acrylamides↗
PubMed1976

Incorporation of macromolecules in microparticles: preparation and characteristics.

Macromolecules can easily be incorporated in microparticles of polyacrylamide by copolymerization with acrylamide in a water-in-oil emulsion. The microparticles preferably arount 1-3 mum in diameter, will have a macroporous structure formed by the polymeric network. The amount of incorporation of the macromolecules will depend on the structure of the network, which, in turn, will depend on the total amount of monomer (T) and the relative amount of cross-linking agent (C) in the monomeric solution. Two mechanisms are responsible for the incorporation; all macromolecules are, independently of the size, fixed in the threads of polyacrylamide and large ones are entrapped within the network formed by the threads. The amount entrapped will depend on the size of the macromolecule and the mean pore radius of the gel. In microparticles with a total concentration of monomers of 8% and a cross-linking of 25% (T-C=8-25) the biological properties of incorporated macromolecules are retained, due to the macroporous structure, as found in binding studies with albumin. The density of the particles will also depend on C and T and, to some extent, on the protein concentration. Due to the fixation in the polyacrylamide threads, some of the incorporated macromolecules will be exposed on the surface, allowing them to react with, for instance, cells, which cannot penetrate the particles. The optimal conditions for the incorporation of macromolecules in the microparticles are investigated.

Acrylamides↗
PubMed1970

[Fiber optics].

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Dental Instruments↗