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PubMed1975

Destruction of dextran-coated target cells by normal human lymphocytes and monocytes. Induction by a human anti-dextran serum with IgG antibodies restricted to the IgG2 subclass.

A human anti-dextran serum, EAK, with IgG antibodies restricted to subclass IgG2, was tested for its capacity to induce lysis of dextran-coated chicken erythrocytes by normal human lymphocytes or monocytes. Another human anti-dextran serum, RGM, with most antibodies belonging to sublass IgG1, and a hyperimmune rabbit anti-dextran serum were used for reference. In lymphocyte-mediated erythrolysis, serum EAK gave rise to 51-Cr release varying from 20% to 80% in different experiments. The hyperimmune rabbit serum was 100 to 1000 times more active, whereas serum RGM was consistently negative. These results correlated well with the concentration of anti-dextran antibodies in these sera. In monocyte-mediated erythrolysis serum EAK had a somewhat higher titer than in lymphocyte-mediated lysis, and serum RGM had a weak but significant activity at low dilutions. Serum EAK also induced erythrophagocytosis by monocytes. Ultracentrifugation did not significantly decrease the inductive capacity of this serum. The results show that antibodies of human sublass IgG2 are efficient inducers of effector functions in both lymphocytic and monocytic cells. Myeloma proteins of the four IgG subclasses were tested for inhibitory capacity in lymphocyte- or monocyte-mediated erythrolysis. Either serum EAK or the rabbit reference serum was used for induction of erythrolysis. Individual myeloma proteins within and between the subclasses varied considerably in inhibitory power. However, whereas IgG1, IgG2, and IgG3 proteins inhibited lymphocyte-mediated erythrolysis induced by either type of antiserum, the two IgG4 proteins tested were essentially negative. These results suggest a lack of specificity of the Fc receptor for subclasses IgG1, IgG2, and IgG3 in both heterologous and homologous inhibition. In monocyte-mediated erythrolysis, IgG1 and IgG3 were strong inhibitors, whereas inhibition by IgG2 and IgG4 was weak and inconsistent. This pattern was seen regardless of whether and inducing antiserum was of rabbit or human origin. Similar results were obtained in monocyte-induced erythrophagocytosis induced by serum EAK. These and previous results suggest that effector cells of the lymphocytic (K cell) variety have Fc receptors different from those of monocytic cells. However, the basis for the differences observed in the inhibition tests remains to be elucidated.

Animals↗

PubMed1976

Dextran-mediated interbacterial aggregation between dextran-synthesizing streptococci and Actinomyces viscosus.

Streptococcus sanguis and Streptococcus mutans bind to the surface of Actinomyces viscosus, producing large microbial aggregates. Aggregates form rapidly and are not easily dissociated by vigorous mixing. The binding is mediated by dextran. Glucose-grown streptococci will not aggregate unless they are first mixed with high-molecular-weight dextran. Aggregation is induced with dextrans isolated from Leuconostoc, S. sanguis, or S. mutans. Sucrose-grown streptococci will adhere to A. viscosus without the addition of an exogenous source of dextran. A. viscosus will bind dextran and then bind glucose-grown streptococci. Aggregation occurs over a wide pH range and is dependent on cations. The aggregating activity of A. viscosus is both protease and heat sensitive. The aggregating activity of S. sanguis is heat stable but sensitive to dextranase.

Actinomyces↗

PubMed1999

Combined administration of dextran 70 and dalteparin does not increase perioperative blood loss compared to dextran 70 alone in major orthopedic surgery.

A prospective open-labeled clinical study was carried out to compare the safety of dextran 70 and low molecular weight heparin (dalteparin; DD group) versus dextran 70 alone (D group) in patients subjected to elective hip replacement surgery. Dalteparin, 5,000 IU/day and dextran 70, 500 ml during surgery and on the first postoperative day were administered to 214 patients. Dextran 70 alone was infused in 44 patients, 500 ml during surgery and on the 1st, 3rd and 5th postoperative day. Mean total blood loss during the operation and until the 2nd postoperative day was 1,708 ml in the DD group and 1,712 ml in the D group (p = 0.79). During the 1st postoperative week, no group differences were found in the relative number of patients that received packed red blood cells (p = 0.95), the amount of transfused packed red blood cells (p = 1.0) and changes in hemoglobin concentrations (p = 0.69). The present results suggest that dextran 70 and dalteparin can be combined in recommended doses without significantly increasing perioperative bleeding in patients undergoing hip replacement surgery. Bone traumatization and insufficient plugging of surgical traumatized bone surfaces with bone cement favor bleeding. Further well-designed studies are needed to evaluate the safety and efficacy of this regimen.

Aged↗

PubMed1975

Dextrans and the formation of pulmonary metastases after intravenous tumour cell injection in rats non-sensitive to dextran.

This study showed, that in a syngeneic tumour-host system in rats non-sensitive to dextran, dextran 40 and dextran 100 did not stimulate metastasis formation after intravenous tumour cell injection, neither when given as intravenous pretreatment nor when given in the tumour cell suspension. Dextran 1000 stimulated the formation of metastases in both these situations. Disturbed microcirculation, intravascular coagulation and effects upon the tumour cell membrane appear to be the main resons, why dextran 1000 stimulated metastasis formation under the experimental conditions used.

Animals↗

PubMed1993

Antiproliferative capacity of synthetic dextrans on smooth muscle cell growth: the model of derivatized dextrans as heparin-like polymers.

Proliferation of vascular smooth muscle cells (SMC) is postulated to be a key step in the pathogenesis of atherosclerosis or restenosis after vascular interventions such as angioplasty. Natural glycosaminoglycans, such as heparin and heparan sulfate, are known for their ability to inhibit SMC proliferation in vivo and in vitro. The antiproliferative activity of synthetic derivatized dextrans exhibiting heparin-like anticoagulant and anticomplement capacities have been investigated with rat aorta smooth muscle cells in culture. We report here that some derivatized dextrans grafted with benzylamide sulfonate moieties are potent antiproliferative agents for rat smooth muscle cell (SMC) in vitro. These synthetic polymers inhibit the SMC proliferation as well as heparin. The SMC growth inhibition is dose dependent, reversible and non-toxic. Highly anionic carboxylic dextrans are not capable of inhibiting the SMC growth, excluding a simple charge effect mechanism. Using fluorescent (DTAF) probes, we demonstrated that the synthetic antiproliferative polymers and heparin are internalized into the SMC. No binding or internalization was observed with native dextran devoid of antiproliferative capacity. We conclude that a suitable distribution of functional groups on the dextran backbone can simulate heparin activity in terms of antiproliferative capacity on SMC growth.

Animals↗

PubMed1994

Is sodium acetate dextran superior to sodium chloride dextran for small volume resuscitation from traumatic hemorrhagic shock?

Small volumes (4 mL/kg body weight (bw)) of hypertonic sodium chloride dextran effectively restore cardiac output and nutritional blood flow and increase arterial pressure in severe hemorrhagic shock. It has been suggested that the chloride anion be replaced with acetate to provide a solution that avoids the risk of hyperchloremia and has the advantage of supplying a buffering base to optimize hypertonic resuscitation. This study compares the effects of hypertonic sodium chloride dextran solution (7.2% NaCl/10% dextran 60 [NaCl-Dx]; n = 7) with sodium acetate dextran (10.4% Na-Ac/10% dextran 60 [NaAc-Dx]; n = 6) on hemodynamic, oxygen transport, and metabolic variables. Both solutions had the identical osmolality (2400 mOsmol/kg). Dogs (16.9 +/- 1.9 kg) were anesthetized and mechanically ventilated. Shock was induced by exteriorization of intestine and blood withdrawal (50% of blood volume) to maintain mean arterial blood pressure (MAP) at 40 mm Hg for 75 min. Thereafter, resuscitation was performed either with NaCl-Dx (4 mL/kg over 2 min) or NaAc-Dx (4 mL/kg over 4 min). During hypertonic resuscitation, there was a short-lasting decrease in MAP, which was more pronounced in the NaAc-Dx group (delta MAP -7.3 +/- 2.5 mm Hg). Cardiac index and oxygen consumption were normalized within 5 min after resuscitation with both solutions. In NaAc-Dx-treated animals, MAP remained at lower values as compared to NaCl-Dx-treated dogs at 5 and 30 min after resuscitation (52 +/- 3 vs 74 +/- 6, and 61 +/- 7 vs 79 +/- 12 mm Hg; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗

PubMed1997

Dextran syndrome. Acute hypotension, noncardiogenic pulmonary edema, anemia, and coagulopathy following hysteroscopic surgery using 32% dextran 70.

Dextran solutions are favored distending media for many hysteroscopic procedures because they are easy to administer, distribute uniformly within the uterine cavity, and are relatively nontoxic. We present the case of a 26-year-old woman who developed hypotension, noncardiogenic pulmonary edema, and hemorrhagic diathesis following hysteroscopic surgery with 32% dextran 70. A medical literature review indicates that following hysteroscopic surgery in which dextran solution has been used, "dextran syndrome" has been diagnosed in some patients. This syndrome is characterized by acute hypotension, hypoxia, coagulopathy, and anemia. We speculate on the pathogenesis of this condition and offer recommendations on how to evaluate and treat this rare dextran-related complication.

Acute Disease↗

PubMed1989

Dextran concentrations in plasma and urine following administration of 6% dextran-70/7.5% NaCl to hemorrhaged and euvolemic conscious swine.

Dextran metabolism was investigated in ten hemorrhaged and seven euvolemic conscious swine. Chronically instrumented, splenectomized swine were subjected to a progressive fixed-volume hemorrhage (27 ml/kg over 45 min). Resuscitation with 4 ml/kg of a 7.5% NaCl/6% dextran 70 (HSD) solution was begun 5 min later. Blood and urine samples were drawn before and during hemorrhage, and at 15, 60, and 120 min following intravenous HSD infusion. Hemorrhage significantly reduced cardiac output (CO) and mean arterial pressure (MAP) and eliminated urinary flow. HSD administration to hemorrhaged pigs returned CO and MAP to control values and improved urinary flow. Creatinine clearance returned to prehemorrhage values. These parameters were not affected by HSD in nonhemorrhaged animals. Plasma dextran concentrations were 20-30% higher in hemorrhaged pigs compared with euvolemic swine. In additional studies, plasma t1/2 for dextran was 9.4 hr in hemorrhaged pigs (n = 3) compared to 10.8 hr in euvolemic animals (n = 2). These data show that HSD ameliorates the effects of hemorrhage on cardiovascular and renal function and suggest that plasma clearance of dextran may be affected by hemorrhage.

Animals↗

PubMed1977

Peroperative infusion of dextran 70 and dextran 40 in the prevention of postoperative deep venous thrombosis as confirmed by the I-125-labelled fibrinogen uptake method.

The antithrombotic effect of dextran 70 and dextran 40 was studied by a double blind trial in 235 patients with major or medium sized elective procedures. 6% dextran 70 (Macrodex) or 10% dextran 40 (Rhemacrodex) or 5% dextrose in 0.9% saline were given in a double blind manner in 500 ml quantities over 30 minutes starting with the induction of anaesthesia. The diagnosis of deep venous thrombosis was confirmed objectively by the I-125-labelled fibrinogen uptake method. Statistically significant differences in the incidence of deep venous thrombosis between the controls and the dextran groups were not found.

Clinical Trials as Topic↗

PubMedDate not supplied

Adjuvant properties of polysaccharides: effect of iota-carrageenan, pectic acid, pectin, dextran and dextran sulphate on the humoral immune response in the rat.

Iota-carrageenan can both enhance agglutinating antibody responses and trigger reaginic antibody production against a protein associated antigen in rats. The present study investigates the strain specificity of this phenomenon and compares the adjuvanticity of high and low molecular weight iota-carrageenan with a series of structurally distinct polysaccharides (pectin, pectic acid, dextran and dextran sulphate). Using ovalbumin as the test antigen, high molecular weight iota-carrageenan induced a potent ovalbumin specific reaginic antibody response in PVG and Hooded Lister strain rats, an intermediate response in Sprague Dawley rats and a weak response in DA, AO and F344 strain rats. Further studies in PVG rats revealed that the nature and magnitude of the antibody response induced was influenced by the type of polysaccharide carrier used. Thus, whereas, high molecular weight carrageenan enhanced the agglutinating antibody (agglutinin) response and simultaneously elicited de novo reaginic antibody production to co-administered ovalbumin, low molecular weight carrageenan facilitated reaginic antibody production but had no effect on the agglutinin response. Pectin and dextran had no effect on the agglutinin response and failed to elicit reaginic antibody production. Conversely, pectic acid and dextran sulphate enhanced the agglutinin response and elicited a transient reaginic anti-ovalbumin response.

Adjuvants, Immunologic↗

PubMed2004

The role of dextran conjugation in transfection mediated by dextran-grafted polyethylenimine.

BACKGROUND: Conjugation through primary amines is one of the most commonly used methods to modify polycationic vectors for gene delivery. A better understanding of the effect of the conjugation on the mechanisms of transgene expression can help design efficient polycationic vectors. METHODS: Dextran with a molecular weight of 1500 was grafted onto polyethylenimine (PEI) to produce various degrees of grafting in an effort to investigate how the conjugation affected the mechanisms of transgene expression. Flow cytometry was employed to quantitate the cellular entry of plasmid and the level of transgene expression, which were measured using ethidium monoazide labeled plasmid and green fluorescent protein (GFP), respectively. The buffering capacity of the grafted PEI was determined by titration, and the integrity of the DNA-polymer complexes were examined by exposure to heparin. RESULTS: Grafting of dextran onto PEI was found to significantly diminish the cytotoxicity, buffering capacity, cellular entry, and the integrity of the DNA-polymer complexes. The reductions enlarged as the degree of grafting increased from 0 to 1.84%; however, at an optimal degree of grafting, the dextran-grafted PEI enhanced the percentages of GFP-positive cells to a level 3 times and 1.3 times of those mediated by unmodified PEI for CHO and MDA-MB-231 cells, respectively. CONCLUSIONS: These results demonstrated that the conjugation of dextran onto the primary amines of PEI inhibited the entry of plasmid across the cell membrane, but the change in the structures of the DNA-polymer complexes was able to promote transgene expression when the degrees of conjugation fell below 0.64%.

Animals↗

PubMed1992

Analysis of the interaction between an alpha (1----6)dextran-specific mouse hybridoma antibody and dextran B512 by affinity electrophoresis.

Carbohydrates are common environmental antigens. As dextran B512 is composed of a repeating structure of simple antigenic determinants, it is widely used to study the immunochemical properties of immunoglobulins. Two-dimensional affinity electrophoresis patterns of a mouse monoclonal antidextran antibody (35.8.2H; IgG1, BALB/c) were produced to obtain insights into the microheterogeneity of the monoclonal antibody. The monoclonal antibody was separated into about six spots which had an identical affinity to dextran B512, but differed in their isoelectric points (pI). In addition, the pH dependence of the binding affinity of this antidextran to dextran B512 was examined. By comparing affinities obtained by affinity electrophoresis between weakly basic (pH 9.5) and weakly acidic (pH 3.8) discontinuous buffer systems, the latter showed an affinity about 500 times lower than the former. The change in the affinity was investigated with a continuous pH gradient by an affinity titration curve and was seen to change markedly at about pH 6. This suggests that the histidine at residue 34 in the light-chain CDR1 is largely responsible for the dextran binding.

Amino Acid Sequence↗

PubMed1985

Plasma dextran levels after abdominal instillation of 32% dextran 70: evidence for prolonged intraperitoneal retention.

Postoperative ascites in patients receiving intraperitoneal dextran 70 may result from slow absorption. We tested this by instilling 250 ml of dextran 70 into the peritoneal cavity of patients undergoing tuboplasty. Serum dextran levels were undetectable until 24 hours after operation and rose during the next 4 days. Ascites in patients with intraperitoneal dextran 70 results from third spacing in response to the persistent osmotic load.

Absorption↗

PubMedDate not supplied

Synthesis of dextran derivatives with thiol-specific reactive groups for the preparation of dextran-protein conjugates.

A novel strategy is described for the preparation of dextran-protein conjugates containing disulfide linkages. "Dormant" protected thiol groups are introduced as side chains on dextran. These can, in a later stage, be converted into thiol-specific reactive disulfides by reaction with (alkoxycarbonyl)sulfenyl chloride. A dextran-protein conjugate is then easily formed by reaction with a thiol group of a cysteine side chain. The disulfide linkage between dextran and the model tripeptides reduced glutathione and N-Ac-L-Cys-L-Ala-L-Lys remains intact, even after 24 h of incubation at 37 degrees C in blood.

Amino Acid Sequence↗

PubMed1988

Hemodynamic effects of colloid concentration in experimental hemorrhage: a comparison of Ringer's acetate, 3% dextran-60, and 6% dextran-70.

Hemodynamic effects of iso-oncotic 3% dextran-60, 6% dextran-70, and Ringer's acetate were compared in 28 male pigs (25 to 30 kg) subjected to experimental trauma and hemorrhage. The animals were kept anesthetized with 75% N2O/25% O2, 0.8% halothane. Hemodynamic and respiratory conditions were allowed to stabilize for one hour preoperatively (baseline data). After surgical trauma (arthroplasty), three 0.5 L of arterial blood samples were withdrawn and replaced with autologous red cells mixed with one liter of 3% dextran-60 in one group 1 (n = 9), one liter of 6% dextran-70 in group 2 (n = 10), and 3 L of Ringer's acetate in group 3 (n = 9). Pulmonary capillary wedge pressure (WP) was kept at baseline level for a further 10 h with infusion of the respective fluid; for this purpose, groups 1 through 3 needed additional infusions of 0.8 +/- 0.3, 0.5 +/- 0.4, and 5.3 +/- 3 (SD) L, respectively. Group 1 showed the highest jejunal capillary blood flow at 10 h and the lowest intragroup variations in hemodynamic and respiratory data. Group 2 had the highest pulmonary arterial pressures and group 3 had the lowest colloid oncotic and arterial BP and left ventricular volume indices. In group 3, the Hct and serum albumin indicated insufficient plasma volume replacement. This group had a significantly larger (p less than .05) amount of tissue water in skin, skeletal muscle, and jejunum than the other groups; no significant difference in lung or heart muscle water was found between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1978

Immunological tolerance to the thymus-independent antigen dextran can be abrogated by thymus-dependent dextran conjugates: evidence against clonal deletion as the mechanism of tolerance induction.

Tolerance to the alpha1--6 epitope of native dextran B512 was found to be very stable and could not be broken by the injection of dextran conjugated to several substances, such as protein A, keyhole limpet haemocyanin, edistin, concanvalin A or Staphylococcus bacteria, strain Cowan. However, when tolerant mice were injected with dextranase, all the above conjugates induced a strong anti-alpha1--6 immune response. In contrast, native dextran itself never induced a response in tolerant, dextranase-treated mice. It was concluded that tolerance only affects the specific B-cell subpopulation that can respond to the polyclonal B-cell-activating (PBA) property of dextran, whereas other specific B cells having PBA receptors for, e.g., signals delivered by collaborating T cells remain in a resting state. These B cells can respond in a specific immune response against the tolerogen after removal of the antigen, which blocks the Ig receptors and therefore prevents them from passively focusing the antigen. Thus, immunological tolerance is not caused by clonal elimination of the antigen-specific clone, but only affects a small subfraction of cells with Ig receptors against the tolerogen.

Animals↗

PubMed1990

Biliary excretion of mitomycin C dextran conjugates in relation to physicochemical characteristics of carrier dextran.

Biliary excretion characteristics of polymeric prodrugs of mitomycin C (MMC), mitomycin C-dextran conjugates with cationic or anionic charge (MMC-Dcat, MMC-Dan) and with different molecular weights of dextran (10,000, 70,000, and 500,000) were studied in rat. Following intravenous injection, bile was periodically collected and concentrations of free and dextran-conjugated MMC in it were determined by bioassay. MMC administered as a free form was excreted rapidly into bile and 1.8% of the dose was recovered within 2 h. A small amount of MMC was gradually excreted into bile after administration of all MMC-Ds and total recovery at 8 h was less than 1% of dose. In this case, a major part of excreted MMC was recovered as a conjugated form. MMC-Dcat gave a larger total excretion of MMC than MMC-Dan and excretion was also affected by the molecular weight of carrier dextran. The biliary recovery of MMC-Dcat labeled with 14C at a spacer moiety was significantly higher than that of conjugated MMC determined by bioassay suggesting release and/or inactivation of MMC in MMC-D during the circulation in the body. These results were compared with biliary excretion of model macromolecules with the same molecular weight but different electric charge in order to clarify the effect of electric charge on the biliary excretion of macromolecules. Cationic macromolecules exhibited higher biliary excretion in relation to greater hepatic uptake.

Animals↗

PubMed1985

Igh restriction of the anti-alpha (1-3) dextran response: polyclonal B cell activators induce the synthesis of anti-alpha (1-3) dextran antibodies in lymphocytes from Igha mice only.

The only strains of mice which are able to synthesize lambda 1-bearing antibodies in response to alpha (1-3) Dextran are those expressing the Igha allotypic haplotype or those having an Igh V region identical to Igha mice. The experiments reported here were designed to investigate whether the nonresponsiveness of mice which do not express the Igha haplotype is a consequence of an absence of a polyclonal B cell receptor for the alpha (1-3) Dextran TI-antigen. B cells of several mouse strains were stimulated with polyclonal B cell activators (PBA) known to either stimulate non-overlapping B cell subsets or to stimulate B cells at different stages of maturation, i.e., lipopolysaccharide, Nocardia delipidated cell mitogens and alloreactive T helper cells. Whereas all three PBA induced B cells from Igha mice to secrete lambda 1-bearing anti-alpha (1-3) antibodies, the PBA were incapable of inducing B cells from non-Igha mice to mount an anti-alpha (1-3) Dextran response. The data suggest that non-Igha mice lack a functional VH Dex gene for the lambda 1-bearing anti-alpha (1-3) Dextran response.

Animals↗