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Results for “Dextrans”

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PubMed1979

A thymus-independent IgG response against dextran B512 can be induced in C57BL but not in CBA mice, even though both strains possess a VHdex gene.

CBA and C57BL mice both possess a VHdex gene coding for antibodies against the alpha 1-6 epitope of dextran B512. After immunization with dextran, CBA mice produce IgM plaque-forming cells (PFC) only, which show regular cyclical fluctuations. The second PFC peak disappeared after injection of dextranase, indicating that it is antigen-dependent. The anti-dextran response in C57BL mice is characterized by only one IgM peak, followed 1 day later by an IgG peak that may exceed the IgM response by a factor of 10. The IgG anti-dextran response in C57BL mice was thymus-independent. CBA mice gave an IgG response to the hapten fluorescein isothiocyanate (FITC) after immunization with FITC-dextran, indicating that dextran can function as a carrier for an IgG response in this strain. Attempts to induce IgG PFC against dextran by immunizing CBA mice with thymus-dependent dextran-protein conjugates consistently failed, althouth the conjugates induced IgG fc in C57BL mice. Spleen cells from CBA mice failed to produce IgG antibodies against dextran after transfer into lethally irradiated C57BL mice, whereas the C57BL spleen cells produced IgG PFC after transfer into CBA mice. The lack of IgG synthesis against the alpha 1-6 epitope of dextran in CBA mice appears to be regulated exclusively at the B cell level and is restricted specifically to the VHdex gene product.

Animals↗

PubMed1980

A primary immune response to dextran B512 is followed by a period of antigen-specific immunosuppression caused by autoanti-idiotypic antibodies.

After a primary immune response to the alpha 1-6 epitope of dextran B512, dextran high responder strains exhibit a specific inability to produce IgM and IgG antibodies against this epitope, although they gave an expected secondary response to horse erythrocytes. Spleen cells from dextran-primed and-suppressed mice responded well to dextran after transfer to lethally irradiated previously untreated mice, indicating that tolerance or exhaustive proliferation of dextran reactive B cells is not responsible. Thymus-dependent dextran-protein conjugates also induced specific suppression. Suppression to both dextran and horse erythrocytes could be passively transferred into untreated recipients with immune serum. However, after absorption with horse erythrocytes and dextran, passive serum transfer only suppressed the response to dextran. It is suggested that the specific immunosuppression was caused by the appearance of autoanti-idiotypic antibodies directed against the immunoglobulin receptors of dextran-reactive B cells.

Animals↗

PubMed1982

Ontogenic development of the suppressed secondary response to native dextran.

The ontogenic development of the plaque-forming cell (PFC) response to the thymus-independent (TI) antigen alpha 1-6 native dextran B512 was studied to determine when the first minimal amounts of anti-dextran antibodies are formed. Substantial antibody responses to certain other TI polysaccharide antigens arise during the first month of life, whereas the development of the response to native dextran has been found to be conspicuously delayed in high-responder mice. Results indicated that CBA mice began to produce minimal amounts of anti-dextran antibodies between 15 and 21 days of age, and the development continued progressively until peak levels were reached at 90 days of age. The alpha 1-6 native dextran system is also one of the few murine models in which endogenous anti-idiotypic antibodies are formed subsequent to anti-dextran production. It has been shown that the anti-idiotypic antibodies are responsible for specific inhibition of secondary PFC responses to dextran. Suppression of the secondary response was used here to ascertain whether the initial low level of anti-dextran antibodies elicited in 15-day-old animals was sufficient to lead to inhibition of the secondary response. The approach confirmed the initiation of anti-dextran production at 15-21 days of age and indicated that the small amount of anti-dextran antibodies produced at this age was sufficient to induce the mechanism leading to suppression of the secondary response.

Age Factors↗

PubMed2001

Evidence of amiloride-sensitive fluid absorption in rat descending colonic crypts from fluorescence recovery of FITC-labelled dextran after photobleaching.

1. Fluorescence recovery after photobleaching (FRAP) of fluorescein isothiocyanate (FITC)-labelled 10 and 250 kDa dextran (FITC dextran) in isolated rat descending colonic crypts was measured at 35 degrees C using laser scanning confocal microscopy. 2. FRAP of either 10 or 250 kDa FITC dextran in crypt lumens was almost complete within 2-3 min. 3. In the presence of amiloride (0.1 mM), or in the absence of Na+, the rate of FITC dextran uptake into the crypt lumens was reduced by 70-80 %. 4. The rate of fluid uptake into the crypt lumen, as estimated from the rate of total FITC dextran uptake into the crypt lumen and its adjacent pericryptal region after FRAP, was between 1.3 x 10(-3) and 1.7 x 10(-3) cm x s(-1). 5. Convective flow during FRAP was also determined from the initial rate of FITC dextran advance along the crypt lumen. This effect was almost completely blocked by amiloride (0.1 mM). 6. The permeability of 10 kDa FITC dextran across the descending colonic crypt wall was found to be higher than that of 250 kDa FITC dextran (3.7 (+/- 0.6) x 10(-5) and 1.8 (+/- 0.3) x 10(-6) cm x s(-1), respectively; n = 3 for both, P < 0.01). The permeability of the caecal crypt wall to 10 kDa dextran was higher than that of the descending crypt wall (2.03 (+/- 0.21) x 10(-5) cm x s(-1); n = 3, P < 0.025). 7. Simulation of the flow of Na+, water and FITC dextran into the crypt lumen and across the crypt wall and pericryptal sheath corroborates the observed parameters of water and Na+ flows.

Amiloride↗

PubMed1992

Demonstration of the receptor-mediated hepatic uptake of dextran in mice.

To establish a rationale of designing a drug targeting system using dextran conjugation, the disposition behaviour of dextran itself was investigated in mice. At a high dose (100 mg kg-1), [14C]dextran was retained in the blood circulation for a considerably long period. However, [14C]dextran rapidly disappeared from the plasma and accumulated in the liver (up to 60% of dose in 1 h) after a dose of 1 mg kg-1. Cellular localization of [14C]dextran in the liver following intravenous administration was examined and the contribution of parenchymal cells was demonstrated as well as the case of galactosylated bovine serum albumin (Gal-BSA). Pharmacokinetic analysis based on a physiological model including Michaelis-Menten type uptake mechanisms revealed that the Michaelis constant Km,l of [14C]dextran was 100 times greater than that of Gal-BSA. Coadministration of Gal-BSA delayed the hepatic uptake of [14C]dextran and the simulation based on the physiological model suggested that [14C]dextran was taken up by the same mechanism as Gal-BSA. These results suggested that dextran conjugation of a drug might lead to its undesirable accumulation in the liver at a low dose and an appropriate modification of dextran, such as carboxymethylation, would be required in such cases.

Animals↗

PubMed1990

Effects of dextran 70 on hemodynamics and lung liquid and protein exchange in awake sheep.

We studied the effect of intravenous dextran 70 infusion on lung liquid and protein exchange to determine whether its effects were due to altered hemodynamics or to altered microvascular permeability. In each of six instrumented awake sheep with chronic lung lymph fistulas, we performed three experiments: 1) control, 2) a 30-minute infusion of 1 l of 6% dextran 70, and 3) an infusion of 1 l of 0.9% NaCl. In addition to pulmonary hemodynamics and lymph dynamics, we measured the plasma-to-lung lymph equilibration rate of [125I] albumin. We followed all the sheep for 10 hours, including a 2-hour baseline period. Dextran was more effective in expanding plasma volume (63 +/- 15% [mean +/- SD]) than saline (11 +/- 6%) at the end of the 30-minute infusion. Pulmonary vascular pressures increased after dextran and remained elevated for 8 hours, whereas after saline the pressures returned to baseline within 1 hour. After dextran, lung lymph flow increased and remained elevated. It was only transiently increased after saline. We confirmed that dextran equilibrated rapidly with lung lymph (half-time, less than 0.6 hour), even though it maintained plasma volume expansion for the whole body (half-time, 11.1 +/- 2.7 hours). The dextran increased both plasma and lymph total macromolecular osmotic pressure but did not increase the plasma-interstitial (lymph) osmotic pressure difference in the lung, except transiently during the infusion. The lymph/plasma protein concentration ratio increased after dextran due mainly to plasma protein dilution. There were no differences in the half-time of tracer albumin equilibration between plasma and lung lymph (control, 2.2 +/- 0.6 hours; saline, 2.0 +/- 0.6 hours; dextran, 2.3 +/- 0.6 hours). Dextran 70 increased liquid filtration mainly by increasing microvascular pressure and possibly filtration surface area. There was no evidence for a change in the leakiness of the lung microvascular barrier to albumin.

Animals↗

PubMed1991

Comparison of dextran and hematocrit effects in the pulmonary microcirculation.

We have compared the effects of an increase in perfusate viscosity induced by dextran and by hematocrit (Hct) on segmental vascular resistance in the pulmonary circulation and the effect of flow on microvascular resistance in lungs perfused with dextran and red blood cells. We isolated and perfused lungs of 39 neonatal rabbits weighing 670 +/- 250 g. To determine the effect of dextran, group 1 (n = 8) lungs were perfused with both 5% and 20% dextran 70 solutions (Hct, approximately 25%); to determine the effect of Hct, group 2 (n = 5) lungs were perfused alternately with 5% and 40% Hct solutions (5% dextran 70). In group 1 and group 2 lungs, experiments were done at constant flow and pressure. Group 3 and group 4 (each n = 4) lungs were perfused with 5% and 20% dextran 70, respectively (0 Hct); group 5 (n = 5), with 10% dextran 70; group 6 (n = 7), with 5% dextran 500; and group 7 (n = 6), with 20% dextran 70 (Hct, approximately 5%). All lungs were perfused in zone 3; airway and left atrial pressures were 6 and 8 cm H2O, respectively. To partition the circulation, we measured pressures in the pulmonary artery and left atrium continuously and pressures in 20-50-microns arterioles and 20-50-microns venules by micropuncture. We found that an increase in both the concentration and molecular weight of dextran increased perfusate viscosity and the resistance in all three longitudinal vascular segments: arteries, microvessels, and veins.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2002

A new vascular polyester prosthesis impregnated with cross-linked dextran.

It is essential that a synthetic vascular graft is preclotting prior to implantation in order to prevent blood leaking through the graft wall. We have impregnated a knitted polyester prosthesis with cross-linked dextran. The aim of this study was to develop a process for obtaining an impervious prosthesis and to compare the characteristics of this dextran-impregnated graft with those of a commercially available collagen-impregnated graft. This new vascular prosthesis was coated with dextran; sodium trimetaphosphate was utilized as the cross-linking agent. In an attempt to determine the optimal conditions for impregnation, the dynamic viscosity of the dextran solution was measured during the cross-linking reaction. The results suggest that the dynamic viscosity is correlated with the concentrations of dextran, sodium hydroxide, and sodium trimetaphosphate. The effect of temperature on the dynamic viscosity was also investigated. The water permeability, the coating weight, and the structure of the dextran-impregnated graft were compared with those of a collagen-impregnated prosthesis. The water permeability of the vascular grafts was reduced by dextran impregnation, from 1010 ml/min per cm2 for the control to 0.04 ml/min per cm2 under standard testing conditions. The dextran coating is capable of rendering the graft impervious to water. The coating weight of the graft treated with dextran was approximately the same as the weight of the collagen-impregnated graft. Finally, the morphology of the prosthetic wall was analyzed using scanning electron microscopy. The promotion of endothelial cell recovery was only observed for the polyester grafts treated with dextran or collagen.

Blood Vessel Prosthesis↗

PubMedDate not supplied

Influence of dextran molecular weight on capture in and release from decylamine carboxymethylcellulose capsules.

A series of dextran molecular weight markers were encapsulated in decylamine carboxymethylcellulose microcapsules to serve as probes of capsule retentivity. The capsules were prepared by allowing microdrops of aqueous sodium carboxymethylcellulose to fall into aqueous decylamine acetate solution. Salt exchange reaction at the droplet pseudointerface resulted in self-assembling films which essentially instantaneously enclosed the droplets. Concentrations of anionic polymer were varied in the range from 1-3%. Chromophore-bearing dextrans were incorporated into these capsules by blending the dextrans with the carboxymethylcellulose prior to the encapsulation step. Four dextrans of differing (light scattering) molecular weights were used: 2 x 10(6), 6 x 10(5), 7 x 10(4), and 1.9 x 10(4) amu. The mass balance of dextran retained in the capsules, released on washing the capsules or which escaped encapsulation was determined spectrophotometrically. To measure total dextran in a population of washed capsules, the capsules were lysed in a 0.3 M solution of sodium chloride. To monitor dextran release, washed capsules were suspended in water and dextran concentration in the supernatant was measured. Encapsulation efficiency exceeded 80% for high molecular weight dextran but was lower with the smaller dextrans.

Adsorption↗

PubMed1990

Hypertonic saline and dextran: impact on cardiac function in the isolated rat heart.

Hypertonic saline with dextran (HSD) has been recently introduced for prehospital resuscitation of hemorrhagic shock, and is currently undergoing clinical investigation. To determine the effect of clinically relevant amounts of hypertonic saline (7.5% NaCl) and/or 6% dextran 70 on non-ischemic and post-ischemic hearts, we infused rat hearts (Langendorff, 20 minutes global ischemia, 37 degrees, 40 minutes' reperfusion) with: 1) 0.9% NaCl (control); 2) 7.5% NaCl/dextran; 3) 7.5% NaCl; or 4) dextran. We found that 7.5% NaCl alone or with dextran depressed ventricular function (developed pressure, DP; contractility, +dP/dt; and relaxation rate, -dP/dt) in non-ischemic hearts. In contrast, equimolar (2,400 mOsm) sucrose increased myocardial contractility (+dP/dt) of non-ischemic hearts. Coronary flow was unchanged by the addition of 7.5% NaCl, dextran, or sucrose. Treatment of ischemic hearts with 7.5% NaCl/dextran, dextran alone, or sucrose improved recovery of ventricular function compared to 0.9% or 7.5% NaCl. Furthermore, dextran (but not sucrose) with or without 7.5% NaCl reduced myocardial hydrogen peroxide (H2O2) levels during ischemia and reperfusion. We conclude that when given in clinically relevant amounts in the isolated rat heart: 1) 7.5% NaCl directly depresses myocardial function; 2) 7.5% NaCl alone does not improve post-ischemic ventricular function; 3) 7.5% NaCl with dextran or dextran alone improves post-ischemic ventricular function in part by reducing myocardial H2O2; and 4) sucrose equimolar to 7.5% HSD increases ventricular function in non-ischemic and post-ischemic hearts. This investigation suggests that the post-shock benefit of HSD is unrelated to direct myocardial effects of saline but is due in part to toxic oxygen metabolite scavenging by dextran.

Animals↗

PubMed1979

Characteristics of the dextran-coated charcoal assay for estradiol receptor in breast cancer preparations.

The measurement of E2 receptor (E2R) in human breast cancer cytosol is significantly influenced by conditions usually employed in the dextran-coated charcoal assay. The incubation time and temperature have an influence on the rate of binding and stability of the receptor. Since lower temperatures preserve the integrity of the receptor, a 2 hr incubation at 4 degrees was selected as the standard incubation procedure. These conditions allow for the detection of at least 80% of the E2R. With supernatants from high-speed centrifugation of HBT biopsies or the human breast cancer cell line MCF-7, reducing agents increased the apparent E2R binding in the order: DTT greater than G-SH greater than MTG. The maximum enhancement of specific E2R binding by a given thiol agent was dependent on its concentration in the incubation medium. The optimum DTT level (7.5 mM) for MCF-7 cell homogenization and cytosol equilibration with tritiated E2 increased E2R to two times control (no DTT). For the HBT 150,000 g supernatant, 1 mM DTT was required to optimize the E2R quantitation. The duration of the dextran-coated charcoal extraction of the cytosol-[3H]E2 incubation had no effect on the level of E2R up to 21 hr. Minimum levels of nonspecific binding of [3H]E2 could be obtained after 4 hr extraction. Maximum depletion of specific [3H]E2 binding could be obtained by adding between 200- and 1000-fold molar excess of unlabeled E2. Greater amounts of unlabeled steroid displaced the radioactive E2 from the dextran-coated charcoal, thereby artifactually increasing the apparent nonspecific binding. This phenomenon may be overcome by utilizing more dextran-coated charcoal in the extraction. However, there was a 9% loss of specifically bound [3H]E2 per milligram of dextran-coated charcoal (1:10 dextran to charcoal by weight) when the cytosol protein was below 90 microgram per incubation. Supplementation with 200 microgram or more albumin per incubation prevented this loss. The dextran:charcoal ratio also prevented E2R loss in the order: 1:1 greater than 1:10 greater than 1:100. One milligram of dextran-coated charcoal (1:10) has the capacity to adsorb 0.3 to 0.4 microgram of free E2. Other unlabeled competitors are capable of displacing [3H]E2 on the receptor. Although DES was as effective as E2, U11,100A and estrone were inefficient competitors. It appeared that the levels of these two estrogen analogues required to maximally displace [3H]E2 on receptor also eluted labeled E2 from the dextran-coated charcoal. DES, however, was unable to displace significant quantities of the [3H] E2 from dextran-coated charcoal even at a molar excess of 50,000:1.

Biopsy↗

PubMed1995

Noninvasive measures of radiolabeled dextran transport in in situ rabbit lung.

UNLABELLED: Dextrans are nontoxic and can be obtained in a wide variety of molecular weights. The purpose of this study was to label 6-kDa and 40-kDa dextrans with gamma- (99mTc) and positron- (18F) emitting radioisotopes and monitor their transport across the pulmonary microvascular barrier. METHODS: External scan measurements for radiolabeled uncharged dextrans, albumin and red blood cells were obtained in eight blood-perfused in situ rabbit lung preparations. After 3 hr of external scanning, the lungs were removed for postmortem and extravascular distribution volume calculations. Extravascular distribution volumes were obtained in six additional rabbits following 4 hr of dextran perfusion to compare the effect of time. The normalized slope index (NSI), a measure of transvascular transport rate, was calculated for each diffusible tracer. RESULTS: The mean NSI for albumin (0.001676 +/- 0.000537 min-1) was significantly lower than NSI for the 40-kDa dextran (0.002303 +/- 0.0005426 min-1) as well as the 6-kDa dextran (0.004312 +/- 0.001134 min-1). The difference between the 6-kDa and the 40-kDa dextrans was also significant. After 4 hr of equilibration, distribution volumes were not significantly different than those obtained at 3 hr. CONCLUSION: Dextrans can be radiolabeled with gamma and positron emitters and small dextrans traverse the lung microvascular barrier more rapidly than albumin. Our results suggest that the use of small dextrans rather than albumin can reduce scan times in clinical applications and minimize motion artifact associated with the noninvasive gamma detection method.

Animals↗

PubMed1993

Chimeric antibodies with anti-dextran-derived complementarity-determining regions and anti-p-azophenylarsonate-derived framework regions.

The framework regions of antibodies fold into a conserved beta-sheet structure that acts as scaffolding for the antigen-contacting complementarity-determining regions (CDR). To test the structural equivalence of the frameworks between two antibodies with widely different combining sites, we created chimeric H and L chains by grafting the CDR of an alpha(1-->6)dextran specific antibody onto the framework of a p-azophenylarsonate (Ars) specific antibody through oligonucleotide-directed mutagenesis of the anti-Ars variable region genes. Antibodies consisting of various chain combinations of the chimeric, anti-dextran, and anti-Ars derived H and L chains were generated in transfectomas and tested for binding to dextran and Ars. Of the newly created chimeric and/or hybrid antibodies, an antibody with the chimeric H chain and the anti-dextran L chain bound to dextran with the same association constant as the parental anti-dextran antibody, and like the anti-dextran antibody was shown by immunochemical mapping to have a site complementary to six glucose residues. None of the other new variable region combinations, including the all-chimeric combination, showed binding to either dextran or Ars. These results indicate that the H chain but not the L chain anti-dextran and anti-Ars frameworks are functionally equivalent. Attempts to confer dextran binding on the H and L chain chimeric antibody, by mutagenizing selected framework residues, were unsuccessful. This study demonstrates the important role of the frameworks in the precise alignment of the CDR for Ag binding.

Amino Acid Sequence↗

PubMed1997

Inhibition of mannose receptor-mediated clearance of tissue-type plasminogen activator (t-PA) by dextran: a new explanation for its antithrombotic effect.

Dextran is used during surgery as a prophylactic agent to prevent deep venous thrombosis. Recently it has been shown that dextran increases t-PA plasma concentrations in patients. As dextran is a potential ligand for the mannose receptor, we studied whether this glucose-polymer would be able to inhibit mannose receptor-mediated clearance of t-PA. In this report we show that dextran 40 and dextran 70 were able to inhibit t-PA binding to the isolated human mannose receptor (IC50 14 and 4 mg/ml, respectively). Both glucose-polymers inhibited mannose receptor-mediated t-PA degradation by human monocyte-derived macrophages in vitro (IC50 7 and 2 mg/ml, respectively). The alpha2-macroglobulin receptor/low density lipoprotein receptor-related protein (LRP)-mediated t-PA degradation by the macrophages was not affected by dextran. During and after a 45 min infusion of dextran 70 (Macrodex) in rats, in plasma endogenous t-PA concentrations increased to 162 +/- 33% and 122 +/- 35% respectively. The plasma clearance of a bolus injection of exogenous t-PA was decreased by 33 +/- 9% in the same rats. We conclude that dextran inhibits mannose receptor-mediated t-PA clearance. The inhibition of t-PA clearance during dextran infusion results in increased endogenous t-PA plasma concentrations. Increased t-PA concentrations present during thrombus formation are known to increase thrombus lysability. Thus the inhibition of t-PA clearance can contribute to the antithrombotic effect of dextran.

Acetylgalactosamine↗

PubMed2000

Angiography of fluoresceinated anti-vascular endothelial growth factor antibody and dextrans in experimental choroidal neovascularization.

OBJECTIVE: To determine if anti-vascular endothelial growth factor antibody and a range of dextrans with varying diffusion radii and molecular weights are permeable through experimental choroidal neovascularization (CNV). METHODS: Choroidal neovascularization was induced in 10 cynomolgus monkey retinas by means of argon laser injury. Digital fundus fluorescein angiograms were performed with fluorescein sodium, fluoresceinated IgG antibodies (anti-vascular endothelial growth factor and a control antibody), and fluoresceinated dextrans with molecular weights of 4, 20, 40, 70 and 150 kd. The 40- and 70-kd dextrans straddle the effective diffusion radius of IgG. For each reagent, early and late angiograms were performed in a standardized fashion, with follow-up images obtained to monitor residual fluorescence. RESULTS: Perfusion of retinal vessels and choroidal vasculature was seen with all reagents. Fluorescein and 4- and 20-kd dextran leaked rapidly from the CNV within the first minute. Angiography with the use of 40-kd dextran and fluoresceinated antibody, either anti-vascular endothelial growth factor or control IgG, showed fluorescence within the CNV that increased during the first 1 to 5 hours, with mild leakage from the CNV. By 24 hours, fluorescence in the CNV was minimal, although in some cases persistent fluorescence in the surrounding tissue was evident up to 2 weeks. The 70-kd dextran showed fluorescence within the CNV and leakage in 1 of 3 eyes. The 150-kd dextran showed fluorescence within the CNV but did not demonstrate leakage. CONCLUSIONS: Fluoresceinated antibodies and dextran with smaller effective diffusion radii showed CNV perfusion and leakage. Dextrans with larger effective diffusion radii (70 kd and 150 kd) perfused into CNV but did not show leakage consistently. CLINICAL RELEVANCE: Determining the permeablity of antibodies and molecules of similar size through CNV can help ascertain the feasibility of using intravenously administered antibodies against angiogenic growth factors as a future treatment for choroidal neovascularization.

Animals↗

PubMed2006

Effect of crowding by dextrans and Ficolls on the rate of alkaline phosphatase-catalyzed hydrolysis: a size-dependent investigation.

The cell cytosol is crowded with macromolecules such as proteins, nucleic acids, and membranes. The consequences of such crowding remain unclear. How is the rate of a typical enzymatic reaction, involving a freely diffusing enzyme and substrate, affected by the presence of macromolecules of different sizes, shapes, and concentrations? Here, we mimic the cytosolic crowding in vitro, using dextrans and Ficolls, for the first time in a variety of sizes ranging from 15 to 500 kDa, in a concentration range 0-30% w/w. Alkaline phosphatase-catalyzed hydrolysis of p-nitrophenyl phosphate (PNPP) was chosen as the model reaction. A pronounced decrease in the rate with increase in fractional volume occupancy of dextran is observed for larger dextrans (200 and 500 kDa) in contrast to smaller dextrans (15-70 kDa). Our results indicate that, at 20% w/w, smaller dextrans (15-70 kDa) reduce the initial rate moderately (1.4- to 2.4-fold slowing), while larger dextrans (>200 kDa) slow the reaction considerably (>5-fold). Ficolls (70 and 400 kDa) slow the reaction moderately (1.3- to 2.3-fold). The influence of smaller dextrans was accounted by a combination of increase in viscosity as sensed by PNPP and a minor offsetting increase in enzyme activity due to crowding. Larger dextrans apparently reduce the frequency of enzyme substrate encounter. The reduced influence of Ficolls is attributed to their compact and quasispherical shape, much unlike the dextrans.

Alkaline Phosphatase↗

PubMed2005

Identification and quantification of the plasma volume expander dextran in human urine by liquid chromatography-tandem mass spectrometry of enzymatically derived isomaltose.

Plasma volume expanders are used in sports in order to control haematological parameters and/or to mask erythropoietin (EPO) misuse. A reliable method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for doping control purposes, enabling the identification and quantification of the plasma volume expander dextran in human urine. The dextran polymer was enzymatically hydrolysed by alpha-1,6-glucosidase (dextranase) followed by acetylation of the generated isomaltose subunits, allowing the chromatographic separation of different disaccharides, such as lactose, saccharose and isomaltose, as well as the identification and quantification of the analyte in human urine. The method was used to determine the basal concentration of isomaltose resulting from the enzymatic hydrolysis of polymeric 1,6-linked glucose in 238 routine doping control samples. In addition the concentration of dextran measured as isomaltose was estimated in seven urine specimens obtained from patients treated with dextran. Calibration curves for dextran were linear and reproducible. The inter- and intra-assay coefficients of variation for dextran ranged from 4.9 to 7.3% at three concentration levels between 53 and 1186 microg/mL. Recovery ranged from 97 to 112% (mean 106.9%). The assay limit of detection was 3.8 microg/mL and the lower limit of quantification was 12.5 microg/mL. In 96% of the investigated doping control samples, the concentrations of isomaltose were below the LLOQ of 12.5 microg/mL. Even the highest concentrations were approximately 100-300-fold lower than concentrations found in urine samples of patients after intravenous application of dextran. The presented results demonstrate the capability and reliability of the developed LC-MS/MS method for the identification and quantification of dextran in human urine and can be regarded as a method revealing the misuse of dextran in sports.

Aged↗

PubMed1995

Modulation of adhesive properties of DEAE-dextran with laminin.

Human squamous epithelial cells produce lower amounts of laminin and fibronectin when cultured on DEAE-dextran than when cultured on gelatin-coated polystyrene (Biotechnol. Bioeng., 33:1235). The epithelial cells also spread much more slowly on DEAE-dextran than they do on gelatin-coated polystyrene. To determine if the low level of matrix production by cells grown on DEAE-dextran contributed to the slowness of cell spreading on this substrate, microcarriers made from DEAE-dextran were treated with exogenous laminin (10 micrograms/cm2 of surface area) and then examined for ability to support cell adhesion. Squamous epithelial cells spread as rapidly on the laminin-treated DEAE-dextran as they did on gelatin-coated polystyrene (much more rapidly than on untreated DEAE-dextran). This indicates 1) that laminin can bind to DEAE-dextran in a fashion that is biologically usable by anchorage-dependent cells, and 2) that when laminin is bound to DEAE-dextran, the failure of squamous epithelial cells to rapidly spread is overcome. These data support the hypothesis that failure of the cells to synthesize an intact extracellular matrix on DEAE-dextran is responsible, at least in part, for the slowness with which cells spread on this substrate.

Adhesives↗