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PubMed1992

Macromolecular prodrugs. XX. Factors influencing model dextranase-mediated depolymerization of dextran derivatives in vitro.

Endo-dextranase-mediated depolymerization of dextran and dextran derivatives under various experimental conditions in vitro was determined. By a simultaneous determination of Mn and MW of dextrans treated with the enzyme in aqueous buffer, an initial increase of the polydispersity of the polysaccharide sample was observed, indicating that dextranase cleaved the dextran molecules into chains which differed significantly in length. A pH optimum of 5 for the enzyme action was found. However, in the pH range 5-8, which prevails in the colon, the initial depolymerization rates differed by a factor of less than 2. Dextranase treatment of a dextran sample resulted in a constant increase of the concentration of terminal reducing glucose residues per time unit suggesting, that the initial depolymerization reaction followed zero-order kinetics. For degrees of substitution below 12 the efficacy of dextranase fragmentation of dextran conjugates decreased almost linearly with increasing DS. The chemical nature of the attached drug did not significantly affect the depolymerization rates. Maximally depolymerized dextran derivatives were obtained by the combined action of dextranase and various alpha-glucosidases. Treatment of such solutions with: a) model esterases b) 80% plasma and c) 20% liver homogenate did not give rise to an acceleration of the initial drug regeneration, as compared to identical experiments carried out in pure buffer solution (pH 7.4 and 37 degrees C).

Animals↗

PubMed1991

Effect of dextran sulfate on fusion of Sendai virus with human erythrocyte ghosts.

The effect of dextran sulfate on the fusion of Sendai virus and erythrocyte ghosts was studied as a function of dextran sulfate concentration and pH of cell suspension solutions. In order to examine the interaction of dextran sulfate with Sendai virion and erythrocyte ghost surfaces, the turbidity of cell suspensions was also measured with respect to the same parameters as above. It was found that dextran sulfate inhibited the fusion of Sendai virus with erythrocyte ghosts. The lower the pH of the suspension solution was, the more effective was dextran sulfate in suppressing virion erythrocyte ghost fusion. Dextran sulfate of a higher molecular weight was slightly more effective in suppressing fusion than that of a lower molecular weight. From turbidity measurements of Sendai virus and erythrocyte ghost suspensions, it is likely that dextran sulfate interacts preferentially with Sendai virion surfaces and inhibits interaction between Sendai virions and erythrocyte ghosts.

Depression, Chemical↗

PubMed1990

Effects of desmopressin acetate (DDAVP) and dextran on hemostatic and thromboprophylactic mechanisms.

The effects on hemostatic and thromboprophylactic mechanisms of intravenous desmopressin (DDAVP, 0.3 micrograms/kg) and dextran 40 and 70 given both separately and in various combinations were evaluated in five male volunteers. Dextran did not inhibit the DDAVP-induced hemostatic changes. The dextran-induced decrease in platelet adhesiveness and the prolonged bleeding time were totally reversed by DDAVP. Hematocrit decrease was seen after both drugs, lasting longer when they were combined. We conclude that DDAVP and dextran may be used concomitantly, each with maintained beneficial properties. DDAVP will still act hemostatically by increasing platelet adhesiveness, factor VIII and von Willebrand factor and by shortening the dextran-induced prolongation of bleeding time. Dextran and DDAVP may even have additive antithrombotic effects due to the DDAVP-induced stimulation of the fibrinolytic activity, which is not inhibited by dextran, and to rheologic changes such as hematocrit decrease induced by both drugs.

Adult↗

PubMed1991

Induction of IL-5 receptors on normal B cells by cross-linking surface Ig with anti-Ig-dextran.

Regulation of IL-5R expression in normal, non-Ly-1 (CD5) B cells was evaluated. Freshly isolated unfractionated spleen B cells express little or no detectable IL-5R. In contrast, B cells stimulated with anti-Ig-dextran conjugates express substantial numbers of IL-5R. Phenotypic analysis of the B cells responding to anti-Ig-dextran, and expressing IL-5R, demonstrates that these cells do not express Ly-1 or Mac-1. Scatchard analysis of B cells stimulated with anti-IgD-dextran reveals two classes of IL-5R: a high affinity receptor with a Kd of 17 pM and approximately 300 receptors/cell, and a low affinity receptor with a Kd of 0.6 nM and approximately 1000 receptors/cell. Peak receptor expression in response to anti-IgD-dextran is seen 72 h after stimulation and with a dose of 10 ng/ml. The induced receptors are functional, because both proliferation and Ig secretion by B cells treated with anti-IgD-dextran are enhanced by IL-5. Other B cell mitogens such as LPS, soluble anti-Ig/IL-4, or phorbol esters/ionomycin are poor inducers of the IL-5R. Finally, not only does LPS fail to induce significant IL-5R expression on spleen B cells, it suppresses both high and low affinity IL-5R expression induced by anti-IgD-dextran. These data indicate that normal, non-Ly-1 B cells are capable of expressing both high and low affinity IL-5R but that receptor expression is critically dependent on the type of stimulus provided to the B cell. A stimulus that produces extensive cross-linking of surface Ig on B cells, i.e., anti-Ig-dextran, is very effective in inducing IL-5R whereas a variety of other B cell mitogens are ineffective.

Animals↗

PubMed1986

Complications of intraperitoneal dextran application for prevention of adhesions.

In 47 patients (dextran group: 32 patients, control group: 15 patients) undergoing laparotomy for microsurgical detachment of adhesions and tuboplasty, the complications of a repeated postoperative intraperitoneal instillation of 6% dextran 60 (5 days) were monitored. In the dextran treated group, abdominal pain and dyspnea occurred significantly more frequently than in the control group. In 6 cases, we observed an edema of the vulva and in two cases an edema of the thigh. During the intraperitoneal irrigation with dextran, a significant increase of body weight and central venous pressure occurred. Bradycardia was observed between the 3rd and 6th postoperative days. Blood pressure remained unchanged. 75% of the patients in the dextran group had pleural effusions containing dextran on the 5th postoperative day. We think that the uncertain desired effects of dextran in the prevention of adhesions do not outweigh the certain and substantial undesired side effects.

Adult↗

PubMed1987

A dextran-bound amiloride derivative is a selective inhibitor of Na+/H+ antiport. Application for studying the role of the antiporter in cellular proliferation in human fibroblasts.

Inhibitors of Na+/H+ exchange from the amiloride series are known to accumulate within the cell and cause an inhibition of a variety of cellular functions. In order to render the amiloride molecule impermeable to cells, we have synthesized a potent amiloride analog, 5-N-(3-aminophenyl)amiloride (compound A35, Ki = 60 nM). The isothiocyanate derivative of A35 (A35-NCS) was coupled to soluble dextrans of 15-20 kDa that have been derivatized with diaminoalkane spacer groups. Dextran-bound amiloride derivatives showed good inhibition of Na+/H+ exchange in human foreskin fibroblasts and A431 cells. Among several spacer groups tested, dextran derivatized with ethylenediamine showed the highest inhibitory activity. The intrinsic inhibitory potency of this polymer increased with increasing degree of substitution with A35, approaching that of free A35 with substitution of approximately 3 mol of A35 per mole of dextran. Coupling to dextran largely diminished side effects of the amiloride derivative on cells such as the inhibition of protein synthesis. A35-dextran was an effective inhibitor of serum-induced reinitiation of DNA synthesis in human foreskin fibroblasts in a bicarbonate-free medium, pH 7.1, but had little effect when either the pH of the medium was more alkaline or when the medium contained a bicarbonate buffer. These findings suggest that the selective inhibition of Na+/H+ antiport by A35-dextran prevents the reinitiation of DNA synthesis when the external conditions are such that the antiporter activity is required for the establishment of a permissive intracellular pH. Polymer-bound amiloride analogs should be useful as selective inhibitors in studies of the physiological role of the Na+/H+ antiporter, as well as for affinity purification of the antiporter.

Amiloride↗

PubMed1989

The effect of isotype and the J kappa region on antigen binding and idiotype expression by antibodies binding alpha (1----6) dextran.

Gene transfection and expression techniques have been used to produce three antibodies specific for alpha (1----6) linked dextran B512 with altered isotypes and J kappa regions. Expression of the L chain V region joined to J kappa 4 or J kappa 5 instead of to J kappa 2 reduced or abolished dextran binding. One antidextran with a reduced binding constant for dextran had the same combining site size as the parental mAb. Transfectoma Ig unreactive with dextran B512 did not bind to other class I or class II dextrans. Antibodies with J kappa 4-containing L chains expressed the 10.16.1 (anti-alpha(1----6) dextran) idiotype. In contrast variants expressing L chains with J kappa 5 lost idiotype expression, except when oligosaccharide is present on VH; all antibodies with J kappa 5 L chains continued to bind dextran but with reduced affinity. The presence of carbohydrate in VH may alter the conformation of both paratope and idiotope. Alteration of H chain isotype did not appear to significantly alter the ability of the antidextran to bind Ag; an exception may be that switching V regions to the IgM C region may decrease the apparent affinity for Ag.

Animals↗

PubMed1985

Regulation of clones responding to dextran B1355S. III. The thymic-independent and thymic-dependent antibody responses.

The primary antibody response of different mouse strains challenged with two antigenic forms of alpha (1-3) dextran, dextran B1355S and dextran-hemocyanin, was examined. Only BALB/c mice responded with both kappa and lambda antibodies. The kappa to lambda ratio was affected by factors such as the antigenic form of dextran, the time at which the serum was analyzed, and the priming regimen. Surprisingly, priming with hemocyanin in adjuvant increased the kappa portion of the response not only to dextran-hemocyanin but also to dextran B1355S. Other strains of mice responded with only lambda antibodies. These results extend our previous results on the analysis of dextran-specific B cell precursors.

Animals↗

PubMed1979

Human granulocyte function during dextran infusion.

The granulocyte function was determined in healthy persons before and immediately after the infusion of 500 ml of dextran for 4 hours. The nitroblue tetrazolium (NBT) reduction reflecting the metabolic activity of these cells was measured both in cells at rest and after stimulation with E. coli, as well as with and without the addition of plasma. In 13 persons, the NBT-reduction was slightly but significantly increased in all four types of experiments after the dextran infusion. When dextran was added in vitro to granulocytes from normal volunteers, the NBT reduction of these cells was increased and the effect was dose-dependent. A surface effect of dextran together with phagocytosis of dextran molecules are the most probable reasons for the elevated NBT-reduction. - In 9 persons tested, the bactericidal capacity was not significantly influenced by dextran infusion. - When dextran was added in vitro to granulocytes neither the bactericidal capacity nor the chemotactic and random migration of the cells were changed. -

Adult↗

PubMed1977

[Coagulation-physiological studies on the prevention of thromboembolism with dextran 60. I. The effect on platelet function].

Platelet aggregation, spreading capacity, adhesiveness (methods according to BREDDIN) have been investigated in 3 groups of 20 patients each after gynecological surgery. Group A (control group) got only 4-hydroxycumarin (Sintrom), group B--in addition to that--intraoperative 500 ml Dextran 60 (Macrodex 6%), group C 500 ml Dextran 60 as well intraoperative as on the 1., 2., 4., 7. and 10. day after surgery. The present data show that depending on the duration of Dextran application, platelet spreading capacity and adhesiveness are inhibited differently as to duration and extent. There was, above all, a reduction and with that a normalisation of the postoperatively increased spontaneous platelet aggregation. It is possible to influence the phase of early postoperative embolism in a favorable way by applicating Dextran already intraoperatively. After that one can use further infusions of Dextran, a prophylaxis by Cumarins or other anticoagulants. Giving dextran only once during surgery one can prove this normalisation of the increased platelet aggregation up to 24 hours postoperatively. By further infusions of Dextran 60 on the 1., 2., 4., 7. and 10. postoperative day it is possible to keep the extent of aggregation on a significantly reduced level till the complete mobilisation of the patient and consequently attain a protective effect on a possible development of deep venous thrombosis of the legs.

Cell Count↗

PubMedDate not supplied

The effects of high molecular weight dextran on the preservation of human corneas.

Paired human corneas (48) were preserved at 31 degrees C for different periods of time up to 122 days in a modified MEM tissue culture medium free of or supplemented with 8% dextran T500. Cell density and vitality of the endothelial cells were analysed using morphometry, light microscopy after trypan blue staining, followed by sucrose provoked swelling and fine structural observations. Culturing for periods up to 7 weeks resulted in an endothelial cell loss of 11% of dextran-blue and of 15% in dextran-supplemented medium. For preservation periods between 9-13 weeks, these values were 43% and 36% respectively. The differences between dextran-free and dextran-supplemented preservation media were not significant. As deduced from trypan blue staining, sucrose provoked swelling and fine structural observations; the remaining cells were vital. Dextran was taken up by the endothelial cells. The practical consequences of endothelial cell loss and the toxic effects of dextran are discussed in relation to penetrating keratoplasty.

Aged↗

PubMed1981

[Prevention of antibody mediated dextran side effects by hapten inhibition in dogs (author's transl)].

The effectiveness of low molecular dextran (dextran 1) in preventing antibody mediated dextran side effects (hapten inhibition) was investigated in immunized dogs. After injection of clinical dextran (dextran 60) a rapid fall of systolic blood pressure and a decrease of leucocytes, thrombocytes and haemolytic complement activity was noted. The protective effect of a dextran 1 preinjection was clearly demonstrated; in contrast the built-in hapten injection (dextran + hapten together) was ineffective.

Animals↗

PubMed1980

Incidence, pathomechanism and prevention of dextran-induced anaphylactoid / anaphylactic reactions in man.

The symptoms of dextran-induced anaphylactoid/anaphylactic reactions (DIAR) range from skin reactions to severe circulatory shock (severity grades I-IV). The reported incidence of DIAR varies between 0.03% and 4.7%, severe reactions comprising 0.008% and 0.6% resp. Studies to elucidate the pathomechanism of DIAR and to possibly prevent them were made during the last decade: No evidence for a pathogenic role of contaminating macromolecules was found, but the dextran molecule itself could be incriminated as elicitor agent. High titres of dextran reactive antibodies (DRA) of predominantly IgG class are regularly found in sera of patients with grade III+IV reactions. Such DRA reflect immunization with dextran cross-reactive bacterial polysaccharides or native dextran. No DRA of IgE class were found. Presence of high IgG-DRA levels, reduction of complement factor Clq and histopathological findings in lungs, all indicate that DIAR should be classified as aggregate (immune complex) anaphylaxis. Hapten inhibition was therefore proposed to prevent DIAR. Based on positive results in animal models, clinical trials were started 1978. Hitherto, 60 485 patients have been studied. It is concluded that the combined use of preinjection of 20 ml Dextran 1 (Pharmacia AB, Uppsala, Sweden) and infusion of Macrodex or Rheomacrodex improves the safety of dextran administration.

Anaphylaxis↗

PubMed1982

[1st direct comparison of allergic side effects of dextran with and without hapten].

In a Swiss multicentre study for evaluation of heparindihydroergotamine in the prevention of postoperative thromboembolic complications, 3887 patients received dextran 70 for comparison. During this trial monovalent hapten-dextran was introduced in two of the participating centres for clinical evaluation. 701 patients in the trial therefore received either 10 or 20 ml hapten before the first dextran infusion was started. Thus, direct evaluation of the incidence of dextran-induced anaphylactoid reactions in two groups of patients, on receiving hapten prevention and the other not, was possible for the first time. 32 dextran-induced anaphylactoid reactions occurred in the 3186 patients not receiving hapten. The incidence of these reactions is therefore 1%. Four of the reactions were severe and 1 was fatal. In the group of patients receiving hapten there was no reaction either to the dextran infusion or to the hapten injection. According to the zero hypothesis, 7 dextran-induced anaphylactoid reactions were expected.

Adult↗

PubMed1978

Binding of dextran sulfate by virus-transformed cells, with reference to altered growth behavior by its treatment.

Binding of 3H-labeled dextran sulfate on transformed and untransformed cells was studied in relation to the altered growth of transformed cells by this treatment. 3T3 and SV3T3 cells, and the isolated cells (SV3T3-R5) insensitive to dextran sulfate treatment were used. The rate of binding of 3H-dextran sulfate on SV3T3 cells was dose-dependent when examined by the liquid scintillation method. It was revealed in autoradiographic analysis that there was no difference in the binding capacity of 3H-dextran sulfate among 3T3, SV3T3, and SV3T3-R5 cells. The rate of binding proceeded linearly during the first 10 hr and then tended to decline. Thin sections (0.3 approximately 0.5 micron) of SV3T3 cells were autoradiographed to examine the site of localization of 3H-dextran sulfate. Depending on the incubation time with the cells, 3H-dextran sulfate was located first on the cell surface and then in the cytoplasm when incubated further. Finally, silver grains were detected even in the nucleus of SV3T3 cells. This process of localization was similar in 3T3 cells. Binding of 3H-dextran sulfate on SV3T3 cells was independent of the presence of calf serum in the medium.

Binding Sites↗

PubMed1978

Comparison of the homogeneous, primary anti-dextran B1355 antibody raised in BALB/c mice with protein 104E.

The primary antibody response to dextran B1355 in BALB/c mice is largely a homogenous IgM antibody. This antibody appears to be similar if not identical to the myeloma protein, protein 104E, for the following reasons: a) isoelectric focusing of the 7S monomers, separately and together in co-isoelectric focusing, give the same pattern, both in the presence and absence of 4M urea; b) the inhibition of lysis of the dextran-coated SRBC by specifically purified anti-dextran antibody and by protein 104E required essentially the same concentration of dextran B1355. This similarity was further demonstrated by plaque assays with dextran-coated SRBC, in which the formation of plaques was inhibited by free dextran. Inhibition of plaques produced by both types of cells required essentially the same concentration of dextran B1355. On these bases, there appears to be no difference in properties (or in structure) between the myeloma protein and the induced antibody.

Animals↗

PubMed1978

Ultrastructural studies on the surface coat of human platelet aggregated by polylysine and dextran.

Positively charged macromolecule, polylysine (mol. wt. 15,000; 23,000; 180,000) could induce the platelet aggregation in low concentration but high concentration was required in the case of neutral macromolecule, dextran (mol. wt. 40,000; 250,000; 2,000,000). The larger molecules of polylysine and dextran were more effective in inducing platelet aggregation. In the dextran-induced aggregation, positively charged Thorotrast particles on the cell surface did not decrease significantly. On the other hand, the surface membranes of platelets aggregated by polylysine were essentially devoid of bound particles. Heparin inhibited the polylysine-induced platelet aggregation but not the dextran-induced aggregation. These findings suggested that polylysine induced aggregation more effectively than dextran by reducing the negative surface charge and giving stronger adsorption force on cell surface. In platelet-rich plasma, polylysine elicited the release reaction of 14C-serotonin but dextran did not. Possible mechanism by which polylysine could elicit the release reaction is the formation of more tightly packed platelet aggregate than that by dextran in the presence of the low calcium ion concentration in citrated platelet-rich plasma. Average distance between plasma membranes of aggregated platelets, however, did not vary with the degrees of polymerization of these macromolecules.

Adenosine↗

PubMed1994

An evaluation of the ability of dextrans to reduce acute tubular necrosis during cold storage preservation.

In this study, the ability of low molecular dextrans to prevent morphologically detectable acute tubular necrosis during cold storage was evaluated. Rat kidneys were flushed with a sodium phosphate buffer (pH 7.2) containing different concentrations of dextran 10 (m.w. of 10,000 or less) and stored at 0-2 degrees C for up to 5 days (samples taken at 24-hr intervals). It was found that solutions containing 20% or more of dextran 10 provided significantly improved morphological preservation of kidney nephrons when compared with currently popular kidney cold storage preservation solutions (i.e. University of Wisconsin and Euro-Collins solutions). Adding smaller amounts (i.e., 15%) of dextran 10 to a cold storage solution already containing another effective osmotic agent (i.e., sucrose) also resulted in superior morphological preservation, indicating a beneficial additive effect of using more than one osmotic agent. Dextran 40 (m.w. 40,000) did not provide as good morphological preservation as did a similar concentration of dextran 10. It is concluded that the use of the proper kind and proper amount of low molecular weight dextrans in preservation solutions can significantly reduce the morphologically detectable acute tubular necrosis during cold storage.

Adenosine↗