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PubMed1986

Intravenous versus intraperitoneal administration of dextran in the rabbit: effects on fibrinolysis.

Adhesions are the leading cause of small bowel obstruction and a frequent cause of failure of infertility operations. Fibrinolysis is involved in the formation and resolution of adhesions. Although intravenous dextran (Macrodex) is known to augment intravascular fibrinolysis, the effects of intraperitoneal dextran (Hyskon) on fibrinolysis have not been extensively studied. A fibrin plate assay system was used to assess plasminogen activator activity of rabbit peritoneum and plasma after treatment with intraperitoneal or intravenous dextran 70. Hyskon significantly reduced the ability of severe trauma to depress plasminogen activator activity of visceral peritoneum and was capable of direct plasminogen activation. Untraumatized or minimally traumatized peritoneum was not affected, nor was plasminogen activator activity of plasma. Pulmonary effusions and perioperative deaths were significantly associated with the use of Hyskon.

Animals↗
PubMed1989

Hypertonic saline-dextran solutions for the prehospital management of traumatic hypotension.

We report the results of the first clinical study on the use of a hypertonic saline-dextran solution for the prehospital management of hypotensive victims of penetrating trauma. During a 4-month period, 48 trauma patients with penetrating injuries and a prehospital systolic blood pressure of 90 mm Hg or less were infused in-field with 250 ml of either a hypertonic saline-dextran solution or the crystalloid plasmalyte A. There were no complications associated with the infusion of the hypertonic saline-dextran solution, and execution of the protocol by paramedic personnel was both safe and uniformly successful. The potential impact of this solution on medical care and the results of this feasibility study justify the initiation of a larger prospective, randomized clinical trial on the efficacy of this solution in the prehospital setting.

Adolescent↗
PubMed1986

A binding assay for the solubilized receptors of type beta transforming growth factor: adsorption and removal of free ligand by dextran-coated charcoal.

A binding assay was developed for the measurement of solubilized receptors for transforming growth factor type beta (TGF-beta). Solubilized receptors were incubated with 125I-TGF-beta, then the unbound ligand was removed by adsorption to dextran-coated charcoal. The binding of TGF-beta to solubilized receptors was saturable and specific, and increased in a linear manner with respect to the amount of membrane protein present. Crosslinking of radioactive complexes after adsorptive removal of unbound TGF-beta yielded complexes similar to affinity-labeled TGF-beta receptors from whole cells. Treatment of a 20% charcoal suspension with 0.2-0.4% dextran was optimal for the protection of receptors from adsorption to charcoal while allowing free TGF-beta to be removed; Mr approximately 250,000 dextran was most effective. This method can assay receptors from purified membranes and crude extracts of cells and tissues, and was used to demonstrate that TGF-beta receptors are glycosylated and retain a high affinity (Kd approximately 530 pM) for ligand after solubilization.

Adsorption↗
PubMed1987

Magnetic aqueous two-phase separation: a new technique to increase rate of phase-separation, using dextran-ferrofluid or larger iron oxide particles.

A new technique to speed up the phase separation of aqueous two-phase systems is described. The technique is based on the addition of magnetically susceptible additives (ferrofluids or iron oxide particles). In a magnetic field such additives will induce a faster phase separation. In one approach, dextran-stabilized ferrofluid was added to an aqueous two-phase system containing polyethylene glycol and dextran. The ferrofluid was totally partitioned to the dextran phase. After mixing of the two-phase system, it was possible to reduce the separation time by a factor of 35 by applying a magnetic field to the system. Another approach involved the use of 1-micron iron oxide particles instead of ferrofluid. In this case also, the phase-separation time was reduced, by a factor of about 70, when the system was placed in a magnetic field. The addition of ferrofluid and/or iron oxide particles was shown to have no influence on enzyme partitioning or on enzyme activity. The partitioning of chloroplasts, on the other hand, was influenced unless the ferrofluid used had been treated with epoxysilane. A column system comprising 15 magnetic separation stages was constructed and was used for semicontinuous separation of enzyme mixtures.

Cell Fractionation↗
PubMed1975

DNA replication by a possible continuous-discontinuous mechanism in homogenates of Physarum polycephalum containing dextran.

Nuclear DNA synthesis in homogenates of Physarum is greatly stimulated by the presence of dextran in the homogenizing medium. In this cell-free system, the DNA precursor is incorporated approximately equally into two classes of DNA intermediates. On of these is similar in size to that observed previously in the intact organism, i.e. its sedimentation rate in alkaline sucrose density gradients increases, presumably by chain elongation, as the organism progresses through the S phase. The other class (approx. 10 S) is similar to 'Okazaki' fragments. Thus, nuclear DNA synthesis in homogenates of Physarum may occur by a continuous-discontinuous mechanism. Substantial DNA-synthetic activity is obtained by the addition of dextran to dextran-free homogenates. Maximal activity in this system requires the presence of both the nuclear and post-nuclear supernatant fractions. It is possible that a partial separation and recombination of a DNA polymerase and the endogenous template is effected by this procedure.

Cell Division↗
PubMed1976

Purification of human blood clotting factor X by Blue Dextran agarose affinity chromatography.

Blue Dextran 2000 coupled covalently to agarose has been used as an affinity column for the rapid separation of human blood clotting Factor X. Factor X has been isolated with approximately 2000-fold purification from human citrated plasma and shows single-component behavior by sodium dodecyl sulfate gel electrophoresis. Affinity columns prepared with Blue Dextran chromophore (Cibacron blue) derivatized to agarose or Sepharose gave negative results. These studies have shown that Blue Dextran agarose possesses unique biospecific and nonbiospecific properties, both of which are essential to achieve resolution of Factor X from other vitamin K-dependent blood clotting factors.

Blood Protein Electrophoresis↗
PubMed1987

Covalent linkage of carboxypeptidase G2 to soluble dextrans--I. Properties of conjugates and effects on plasma persistence in mice.

The covalent attachment of the therapeutic enzyme carboxypeptidase G2 to soluble dextrans of varying molecular weight resulted in a 5-15-fold increase in plasma persistence in normal and tumour-bearing mice. The molecular weight of the dextran used markedly affected the number of dextran molecules present in the conjugate, resulting in a molecular weight distribution between 6 and 12 X 10(5) daltons. The isoelectric point of the conjugates varied between 4.1 and 4.8 compared to native enzyme 7.8. Conjugates were resistant to proteolysis by trypsin and chymotrypsin, but showed little difference in their affinity for substrate.

Animals↗
PubMed1986

The effects of arginine, dextran and Haemaccel infusions on urinary albumin, beta 2-microglobulin and N-acetyl-beta-D-glucosaminidase.

Male volunteers were infused with L-arginine dextran and Haemaccel. Arginine (0.5 g/kg body weight infused over 30 min) resulted in transient highly significant increases in urinary albumin (p less than 0.001), beta 2-microglobulin (p less than 0.001) and N-acetyl-beta-D-glucosaminidase [NAG] (p less than 0.001). These effects lasted less than 120 min. Dextran 40 and 70 (500 ml infused over 2 h) did not affect urinary albumin, beta 2-microglobulin or NAG excretion. Haemaccel (8 ml/kg body weight infused over 2 h) resulted in significant increases in urinary albumin (p less than 0.05) and beta 2-microglobulin (p less than 0.01) during the second hour of the infusion. It also caused a biphasic increase in urinary NAG excretion, the initial peak (p less than 0.05) coinciding with the peak of albumin and beta 2-microglobulin excretion. The second peak which was more defined (p less than 0.01) occurred 21-24 h after the beginning of the infusion. Neither arginine or Haemaccel have been reported to be nephrotoxic whereas dextran infusions are a well recognised cause of acute tubular necrosis. These data indicate that increases in urinary beta 2-microglobulin and NAG are not always reliable indicators of nephrotoxicity or renal tubular cell damage.

Acetylglucosaminidase↗
PubMed1983

Direct measurements of the dextran-dependent calcium uptake by rat peritoneal mast cells.

The metallochromic indicator murexide has been used to monitor calcium concentration changes during the dextran-induced, phosphatidylserine-dependent degranulation of rat peritoneal mast cells. The dextran-induced Ca2+-uptake showed an absolute dependence on the presence of phosphatidylserine. The extent of Ca2+-uptake increased with phosphatidylserine in a concentration-dependent manner. At 25 degrees C the half-life of the uptake process equalled 35 +/- 5 s. Exposure of the mast cells to dextran in the presence of Ca2+, but in the absence of phosphatidylserine, desensitized the cells. The subsequent addition of phosphatidylserine failed to restore the Ca2+-uptake activity. However, the Ca2+-ionophore A23187 did promote Ca2+ uptake by the cells without PS.

Animals↗
PubMed1984

Separation of cells labeled with immunospecific iron dextran microspheres using high gradient magnetic chromatography.

Immunospecific magnetic microspheres, consisting of ferromagnetic iron dextran conjugated to Protein A, were used to specifically label red blood cells (RBC) for cell separation studies using high gradient magnetic chromatography ( HGMC ). When 10(7)-10(8) RBC labeled with Protein A-iron dextran microspheres were applied to a column containing 30 mg stainless steel wire placed in a 7.5 kilogauss magnetic field, 96 +/- 2% of the cells were retained in the column. These cells could be eluted by removing the magnetic field and mechanically agitating the column. The retention of labeled cells by HGMC was shown to be dependent on the applied magnetic field and the amount of wire packed into the column. HGMC in conjunction with cell labeling with immunospecific iron dextran microspheres have useful applications for the separation of specific cell types.

Cell Separation↗
PubMed1989

Peritonitis and empyema following the use of dextran in tubal operations.

Two patients developed severe bacterial sepsis with peritonitis and pleural empyema following tubal surgery. Intraperitoneal low-molecular dextran was used in both patients and hydrocortisone was administered perioperatively. The use of dextran in tubal surgery probably increases the risk of severe postoperative infection and should be avoided in susceptible patients. Prophylactic antibiotics may be indicated when dextran is administered.

Adult↗
PubMed1993

Analytical gel filtration of dextran for the study of the glomerular barrier function.

Analytical gel filtration was used for the study of molecular size distribution of clinical dextran in serum and urine for the purpose of evaluations of changes in the human glomerular barrier function. The column was calibrated in terms of solute size using a simple and accurate technique recently described. Only one sample of a dextran possessing a broad molecular mass distribution was necessary for the calibration procedure and the calculations were performed using an ordinary spreadsheet. The accuracy of the calibration, as evaluated by protein samples, is better than 95%. The simplicity makes the method suitable for use in laboratories not normally specializing in analytical gel filtration. Calibration in terms of size is preferably done with respect to viscosity radius to obtain relevant information about the permeability of dextran into porous membranes.

Chromatography, Gel↗
PubMed1995

Purification of monoclonal antibodies on dextran-coated silica support grafted by thiophilic ligand.

Coated silica beads are promising supports for high-performance liquid chromatography (HPLC) of proteins; they combine the excellent mechanical properties of silica with minimal non-specific interactions with proteins in solution due to the presence of hydrophilic dextran polymers adsorbed at the silica surface. So, dextran-coated porous silica beads can be grafted with beta-mercaptoethanol by using divinylsulfone as coupling reagent to obtain new thiophilic supports usable in HPLC. The affinity of monoclonal IgG subclasses from mouse ascitic fluids for the active phases can be analysed. These dextran-coated silica supports grafted with thiophilic ligands allow a one-step purification of these antibodies. Moreover, the chromatographic separation of two subclasses, immunoglobulin G1 (IgG1) and IgG3, is observed and can be correlated to the high resolution of these new HPLC thiophilic supports.

Animals↗
PubMed1996

Synthesis and chromatographic characterization of dextran-coated zirconia high-performance liquid chromatographic stationary phases.

Porous zirconia particles made by the oil emulsion (OE) method and the polymerization-induced colloid aggregation (PICA) method have been coated with a small, carboxymethylated (approximately 5%) dextran polymer and crosslinked in place. The parameters of the coating process (dextran concentration, adsorption time and crosslinker concentration) have all been examined and an optimum value for each determined. The coated and uncoated materials were characterized by nitrogen sorptometry and size-exclusion chromatography (SEC) using solutes (polystyrenes and dextrans) of well-defined molecular masses. Nitrogen sorptometry results show that the PICA material has a much lower pore volume and smaller pore diameter than do the OE materials. Despite this, the elution volumes of the SEC probes change very little upon polymer coating the PICA material while the OE material shows a very large change upon coating.

Adsorption↗
PubMed1981

A major subpopulation of Fc receptor-bearing lymphocytes revealed by rosette formation in dextran media: studies with pig, sheep and rat lymphocytes.

Blood lymphocytes from young pigs which formed 9.1 +/-0.7% Fc rosettes (mean +/- S.E., range 4.1-16.0), with rabbit and pig immunoglobulin-coated indicator cells used in optimum conditions in phosphate-buffered saline (PBS), formed 32.6 +/- 1.8% (16.9-44.3) in the presence of 4% dextran (DFc). The proportion of DFc+/Fc+ lymphocytes varied from 2.2 to 5.9 (3.8 +/- 0.3). Compared with the PBS test, in dextran rosettes are formed with more lymphocytes and with red cells coated with less immunoglobulin. Ficoll at 14% gave similar enhancement. Dextran enhancement of Fc rosettes was also observed with sheep PBL, but not with rat thoracic duct lymphocytes. The FC portion of IgG is responsible for both Fc and DFc rosettes. Thus most Fc and DFc rosettes, formed with serum antibody-coated bovine RBC, are revealed by IgG coated but not F(ab')2-coated BRBC, and show dose-dependent inhibition in the presence of free pig IgG (complete at 5-10 mg/nl) but not IgM (up to 2 mg/ml). Separation of lymphocytes on nylon wool suggests that DFc rosettes are formed by B cells and some T cells. Over half of the weak Fc rosette-forming lymphocytes (DFc-Fc) elute in the non-adherent fraction, which contains few B cells, and therefore are a subpopulation of T cells.

Animals↗
PubMed1982

Immunospecific ferromagnetic iron-dextran reagents for the labeling and magnetic separation of cells.

Ferromagnetic iron dextran particles were prepared by reacting a mixture of ferrous chloride and ferric chloride with dextran polymers under alkaline conditions. Particles purified by gel filtration chromatography were in the size range of 30-40 nm, had an electron dense core of about 15 nm, were stable against aggregation in physiological buffer, showed little non-specific binding to cells and had a magnetic moment. Protein A from Staphylococcus aureus was covalently coupled to periodate-oxidized ferromagnetic iron-dextran particles. These conjugates were used to indirectly label antigen sites on human red blood cells and thymocytes for visualization by scanning and transmission electron microscopy. Cells labeled with these immunospecific ferromagnetic particles are were quantitatively retained by a simple permanent magnet and could be separated from unlabeled cells. Applications of these novel reagents in the separation of cells, cell membranes and receptors in drug targeting studies are discussed.

Animals↗
PubMed1984

Crystallized dextran nanospheres with entrapped antigen and their use as adjuvants.

A novel and simple method is described of preparing a matrix with entrapped antigen, the matrix consisting of well characterized carbohydrates with low toxicity, i.e., dextran and starch, stabilized by crystallization. The crystallized carbohydrate spheres produced probably derive their adjuvant effect from slow antigen release and macrophage stimulation. Five months after a single injection of 80 micrograms ovalbumin entrapped in dextran spheres, mice produced antibodies against ovalbumin and this response could be enhanced further by co-entrapment of immunomodulators such as DEAE- or SO4-dextrans into the spheres. A single injection of 8 micrograms entrapped bee venom into mice gave the same IgG antibody response as 2 X 80 micrograms bee venom dissolved in water. By the same method it was possible to inject 4 times the LD50 dose of entrapped bee venom in mice without any significant side reactions.

Adjuvants, Immunologic↗
PubMed1989

Rapid method for the isolation of neutrophils in high yield without the use of dextran or density gradient polymers.

A simple, rapid and economical method for the isolation of polymorphonuclear leucocytes (PMNs) from whole blood is compared with dextran and dextran/Lymphoprep gradient techniques. The method eliminates the use of dextran and density gradient polymers such as Ficoll which have been shown to affect PMNs adversely. The technique is based on the lysis of red cells with isotonic ammonium chloride solution followed by differential centrifugation to separate the PMNs. This method gave a PMN yield of 73% (SD +/- 3.5) and a purity of 78% (SD +/- 2.5). Both morphology and functional activity were preserved, as assessed by bacterial phagocytosis and killing, chemotaxis, polarising response, superoxide production and adherence. In contrast, the dextran and dextran/Lymphoprep techniques gave yields of 50% and 15% with purities of 78% and 91% respectively. In a series of 14 PMN isolations, the differential centrifugation method gave an average yield of 63% with an average purity of 83%.

Ammonium Chloride↗