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PubMed1982

Isoelectric focusing of oestradiol receptor protein from human mammary carcinoma--a comparison with dextran coated charcoal assay.

Two simple methods for the detection of specific oestradiol--17 beta protein in breast tumour tissue were investigated. Isoelectric focusing of receptor protein in polyacrylamide gel was examined as an alternative micromethod to dextran-coated charcoal receptor assay. In a series of 32 cytosols prepared from unselected breast tumour tissue, assay results agreed on the presence or absence of receptors in 97% of cases. Quantitative analysis of the positive results showed a correlation coefficient, r = 0.88. Isoelectric focusing gave significantly lower receptor concentrations than the dextran-coated charcoal method. Twenty-six Tru-Cut biopsy tumour specimens were analyzed for receptor by isoelectric focusing and the results were compared with those obtained by the dextran-coated charcoal method on the same tumour. In 88% of the specimens examined, both methods agreed as to the presence or absence of receptor protein. A correlation coefficient, r = 0.62, was calculated from the 15 positive results. There was no significant difference between the results from the two methods. Quantitative results were related to total protein concentration in the cytosol. Negative receptor status was defined as less than 5 fmol/mg cytosol protein for both methods.

Breast Neoplasms↗
PubMed1985

Pitfalls in the Dextran-coated charcoal assay of estrogen receptors in breast cancer tissue.

This study investigated the influence of the degree of concentration of breast tumor cytosols on the apparent estrogen receptor content as measured by the Dextran-charcoal assay. It was found that the dilution of cytosols to 1-2 mg protein/ml frequently but not always causes highly underestimated receptor concentrations. This could not be explained by the protein loss through adsorption to the charcoal. The effect was also studied in the presence of gelatin, sodium molybdate or with limited trypsinization of the incubation mixture. Addition of 1 mg/ml gelatin in the Dextran-charcoal suspension was very useful in most cases in preventing dilution induced losses in receptor sites. Both trypsinization and addition of sodium molybdate produced increases in receptor concentrations that were not as susceptible to inactivation through dilution of the cytosol. These data suggest that the observed high variability in the dilution induced receptor losses can be explained by receptor heterogeneity: some receptor form(s) are either readily absorbed to or "stripped" by the charcoal particles. As a conclusion we recommend that in order to optimize the estrogen receptor assay as regards both binding sites and affinities the cytosol concentrations should be maintained as high as possible and a protein expander be included in the Dextran-charcoal suspension. Though sodium molybdate frequently gives considerable increases in estrogen binding sites it occasionally has an opposite effect. For this reason we hesitate to recommend its use in routine assays of estrogen receptors.

Adsorption↗
PubMed1983

Platelet aggregation induced in the hamster cheek pouch by a photochemical process with excited fluorescein isothiocyanate-dextran.

Excitation of intravascular fluorescein isothiocyanate (FITC)-dextran by light induces platelet aggregation in arterioles of the hamster cheek pouch. Time to aggregate appearance (TAA) was found to be 45 +/- 5.6 sec in vessels of 10-14 micron diameter. The interindividual differences of TAA are low (coefficient of variance = 12.5%) and the TAA in individual animals can be reproduced for several hours with a coefficient of variance of 14.5%. TAA decreased at higher concentrations of intravascular FITC-dextran (r = 0.98) and with increased energy of the exciting beam. Scavengers of singlet oxygen, sodium azide, and trans-beta-carotene, delayed TAA. A scavenger of hydroxyl radicals, dimethyl sulfoxide, did not influence TAA. Acetylsalicylic acid showed a dose-dependent inhibitory effect from 1 (P less than 0.01) to 100 mg/kg body weight ia. The time-dependent increase of TAA after administration of 100 mg/kg acetylsalicylic acid is demonstrated; the dosage finally delayed TAA to longer than 360 seconds. The findings suggest that platelet formation, initiated by exciting FITC-dextran may involve local production of singlet oxygen. The consequently observed damaging process and the primary role of the endothelial cell damage are described. It is postulated that the described procedure provides a new model of intravascular platelet aggregation, characterized by a good reproducibility. A new damaging mechanism is proposed to study platelet aggregation in vivo.

Animals↗
PubMed1978

Prophylactic activity in rodents of trypanocides complexed with dextran.

The prophylactic activity of prepared complexes of each of several trypanocidal drugs with dextran sulphate (M.W. 5 X 10(5)) was determined in rodents at the same time as that of the corresponding uncomplexed drug, and also the suramin complex in some cases. All the dextran complexes tested showed some degree of enhanced prophylaxis over the uncomplexed drug but in most cases a significant extension of prophylaxis was demonstrated only at dose levels well in excess of those used in the field. The dextran complex of isometamidium, however, showed very considerable enhancement effects over a range of dose levels. An amount of this complex containing an equivalent of the therapeutic dose of uncomplexed drug extended the period of effective prophylaxis by several months in both rats and mice. The suramin complex of isometamidium, on the other hand, was almost invariably less effective than the uncomplexed drug.

Animals↗
PubMed1994

Prevention of experimental venous thrombosis in rabbits with low molecular weight heparin, dextran and their combinations, administered before or during induction of venous endothelial trauma.

An in vivo experimental venous thrombosis model based on endothelial damage and flow reduction was used to investigate the effect of low molecular weight heparin (LMWH) alone and in combination with dextran and the effect of surgical and endothelial trauma on thrombus formation, formation of occlusive thrombi and thrombus weights. Five groups with 15 rabbits in each were studied. Two groups received dalteparin (50 anti-Xa IU/kg i.v.) before surgical trauma or after, during the endothelial trauma and two groups received dalteparin (50 anti-Xa IU/kg i.v.) with dextran 70 (1 g/kg i.v.) before surgical trauma or after, during the endothelial trauma. Compared to a control group (saline) all treatment regimes reduced significantly the frequency of thrombosis and occlusive thrombi as well as thrombus weights. No significant difference was observed between the identical treatment groups when the substances were introduced before respective after surgical trauma. It is concluded, from the present study that thromboprophylaxis with LMWH in this particular in vivo model, given before or after surgical trauma is equally effective. Dextran has a certain augmenting thromboprophylactic effect when added to LMWH in this model.

Animals↗
PubMed1991

Molecular motions of polysaccharides in the solid state: dextran, pullulan and amylose.

Dextran, pullulan and amylose have been investigated by differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical and dielectric spectroscopy over a wide range of temperatures and frequencies. No melting or glass transition is seen below the range of thermal degradation (about 300 degrees C) for either amylose or pullulan; only dextran shows a Tg at 223 degrees C (delta cp = 0.40 J/g deg). The viscoelastic spectrum of the 'dry' polysaccharides is characterized by a low temperature relaxation that occurs at -94, -73 and -59 degrees C, at 1 kHz, (activation energy 32, 39 and 52 kJ/mol) in dextran, pullulan and amylose respectively and is assigned to small entity local motions of the polysaccharide backbone. Absorbed water strongly modifies the relaxation spectrum, inducing a new relaxation below room temperature and dissipation regions associated with water loss above room temperature. The former appears at temperatures higher than the relaxation characteristic of the dry polymer and moves to lower temperature with increasing water content. In normal 'room humidity' conditions (about 10% absorbed water) the water-induced relaxation, attributed to the motion of complex polymer-water relaxing units, is the only observable feature in the dynamic mechanical and dielectric spectrum below room temperature.

Amylose↗
PubMed1985

Anticomplementary activity of dextran derivatives.

Substitution with carboxylic and benzylamine sulphonated groups conferred on dextran both antithrombic activity and the capacity to inhibit formation of the amplification C3 convertase of complement. In dextrans substituted with carboxylic groups (greater than 40%), a high content of sulphonate (greater than 10%) resulted in both anticomplementary and antithrombic properties whereas a lower content of sulphonate resulted in high anticomplementary but weak antithrombic activity. The anticomplementary activity of highly substituted dextrans was similar to that of heparin, although anticoagulant activity was much lower than in heparin, confirming independent structural requirements for both activities in the heparin molecule.

Complement C3-C5 Convertases↗
PubMed1988

The immune response of carp against dextran. An analysis of the idiotype heterogeneity.

The expression of a "species-specific" idiotype with specificity for alpha(1-6) dextran in carp is described. All tested carp anti-dextran antisera react with a rabbit anti-Id (carp anti-dex) serum. The rabbit anti-Id serum can be partially inhibited by the specific ligand, dextran T70 or isomaltodecaose but not or only weak with other, unrelated carbohydrates. These data confirm our statement, that a limited germline V-gene repertoire may code for antibodies in fish.

Animals↗
PubMed1988

The specificities of polyclonal and monoclonal anti-idiotypes to anti-alpha(1----6)dextrans; possible correlations of idiotype with amino acid sequence.

The specificities of polyclonal and monoclonal anti-idiotypes to three anti-alpha(1----6)dextrans-10.16.1, QUPC52, and W3129--were examined by competition ELISA. A major idiotype was defined by two polyclonal and two monoclonal anti-idiotypes to 10.16.1, and a polyclonal anti-idiotype to QUPC52. Another monoclonal anti-idiotype to 10.16.1 defines a non-overlapping determinant. One monoclonal anti-idiotype to 10.16.1 and one to W3129 were hapten inhibitable. By comparing amino acid sequences of Id+ and Id- anti-alpha(1----6)dextrans, the major idiotype was assigned to residues in VH CDR3, with a possible contribution from VH CDR2, a conclusion supported by the hapten inhibition results. Both a monoclonal and a previously described polyclonal anti-idiotype to W3129 define a determinant found on only W3129, among the anti-alpha(1----6)dextrans tested.

Amino Acid Sequence↗
PubMedDate not supplied

Sulfonated dextran inhibits complement activation and complement-dependent cytotoxicity in an in vitro model of hyperacute xenograft rejection.

In the present study, we demonstrate that a substituted soluble dextran derivative bearing 73% carboxylic groups and 15% benzylamide sulfonate groups, termed CMDBS25, inhibits complement activation and complement-mediated damage in an in vitro model of xenogeneic rejection. Incubation of porcine aortic endothelial cells with normal human serum resulted in time-dependent complement consumption as assessed by C3a generation in the fluid phase and deposition of activated complement fragments C3, C5 and of C5b-9 on target cells. The presence of C5b-9 membrane attack complex was associated with 51Cr release from prelabelled endothelial cells. The addition of 5-25 mg of CMDBS25/ml under the experimental conditions used, inhibited complement activation and C3a generation in a dose-dependent fashion. CMDBS25 (25 mg/ml) totally suppressed iC3b, C5 and C5b-9 cytolytic complex deposition on cells and inhibits by 42% lysis of target endothelial cells. Native dextran had no effect. Our observations document the anti-complementary properties of sulfonated dextran derivatives and their potential as therapeutic agents for the prevention of complement-dependent hyperacute xenograft rejection.

Animals↗
PubMed1991

Sequential double labelling with different fluorescent dyes coupled to dextran amines as a tool to estimate the accuracy of tracer application and of regeneration.

We present a technique to estimate the accuracy of a given application procedure for neuronal tracers. In a second series of animals we used this technique for the estimation of successful regeneration of peripheral nerves. Dextran amine coupled to rhodamine was applied to the cut trochlar nerve in Xenopus tadpoles. To assess the accuracy of tracer application, experiments were done in which a second dye, dextran amine coupled to fluorescein, was applied after 1 day proximal to the first dye. More then 90% of all trochlear motoneurons were doubly labelled after this procedure. Their total numbers were not significantly different from numbers obtained after single labelling with HRP in a comparable age group. To assess success of regeneration after 5 and 8 days, the second application of fluorescein dextran amine was distal to the first application side. Statistically significant differences suggest incomplete regeneration of many neurons. After 42 days the numbers of singly and doubly labelled motoneurons was in the same proportion as before regeneration. This suggests that about 90% of the surviving motoneurons had successfully regenerated back to the periphery.

Amines↗
PubMed1994

Combined anterograde tracing with biotinylated dextran-amine, retrograde tracing with fast blue and intracellular filling of neurons with lucifer yellow: an electron microscopic method.

In order to determine the presence of synaptic connectivity between fibres originating from a specific source and neurones with a known morphology and known fibre projection, we have introduced a method for electron microscopy that combines three techniques: retrograde fluorescent tracing, anterograde tracing using biotinylated dextran-amine and intracellular injection of Lucifer Yellow (LY) in lightly fixed brain slices. Neurones in the rat entorhinal cortex that project to the infralimbic cortex and that might be in synaptic contact with fibres originating in the dorsal subiculum served as a model. After surgical application of the tracers and a survival period enabling transport, the brain was fixed and vibratome slices 300 microns thick were prepared in which retrogradely labelled cells were intracellularly injected with LY. This substance and the transported biotinylated dextran-amine were converted into different electron-dense labels. First, LY immunocytochemistry was conducted, then followed by silver-gold enhancement of the immunoprecipitate. Subsequently, the tissue sections were treated with an avidin-biotin-horseradish peroxidase complex and subjected to a diaminobenzidine-peroxide reaction. This protocol resulted in labelling of biotinylated dextran-amine-positive fibres and terminals that could easily be differentiated from the LY-positive neuronal elements and also showed well preserved ultrastructural detail.

Amidines↗
PubMed1982

The isolation and characterization of a mouse myeloma protein with anti-dextran activity.

A myeloma protein in ascitic fluid from BALB/c mice bearing W3129 plasma cell tumors was isolated by affinity chromatography. This protein exhibits anti-dextran activity and has been obtained in highly purified form by selective adsorption on isomaltosyl-Sepharose and elution with isomaltose solution. The isomaltosyl-Sepharose was synthesized from maltose, p-aminophenyl glucoside and cyanogen bromide-activated Sepharose by a new procedure utilizing glucosyltransferase and chemical coupling reactions. Results of gel electrophoresis, isoelectrofocusing and agar diffusion experiments showed that the purified myeloma protein consisted of 6 isomeric proteins with each isomer possessing anti-dextran activity. Data from hapten inhibition studies were interpreted to show that the W3129 myeloma protein combines with terminal isomaltosyl units of branched dextrans and oligosaccharides.

Animals↗
PubMed1983

Modification of human hemoglobin by covalent association with soluble dextran.

Stroma-free Hb solutions present some drawbacks when used as erythrocyte substitutes, mainly because the protein has a short in vivo half-life, due to its small hydrodynamic volume. Covalent coupling of oxyHb with dialdehyde-dextran (Mw congruent to 40 000; Mn congruent to 25 000) leads to adducts whose properties depend upon the pH of the condensations. At pH less than 9.6, many labile imine linkages are formed and the conjugates have a high molecular weight at the end of the reaction. In contrast, the final products obtained as pH increases from 9.6 to 10 contain a low-molecular-weight adduct in an increasing ratio; in this case the bond between dextran and Hb is stable and this stability is assumed to result from the rearrangement of a specific imine linkage formed at an NH2 site of Hb, into a ketoamine group (Amadori rearrangement). Dextran-Hb conjugates have oxygen-binding properties characterized by increased oxygen affinity, and decreased subunit cooperativity and alkaline Bohr effect, relative to unconjugated Hb. These differences become less as the time of condensation reaction decreases and seem to be due to modification of amine groups involved in the salt bridges that stabilize the deoxy form of the protein. Taking into account their oxygen-binding characteristics, the low-molecular-weight conjugates can be regarded as potential erythrocyte substitutes.

Chromatography, Gel↗
PubMed1984

Stabilization of dextransucrase from Leuconostoc mesenteroides NRRL B-512F by nonionic detergents, poly(ethylene glycol) and high-molecular-weight dextran.

Dextransucrase (sucrose: 1,6-alpha-D-glucan 6-alpha-D-glucosyltransferase, EC 2.4.1.5) (3 IU/ml culture supernatant) was obtained by a modification of the method of Robyt and Walseth (Robyt, J.F. and Walseth, T.F. (1979) Carbohydr. Res. 68, 95-111) from a nitrosoguanidine mutant of Leuconostoc mesenteroides NRRL B-512F selected for high dextransucrase production. Dialyzed, concentrated culture supernatant (crude enzyme) was treated with immobilized dextranase (EC 3.2.1.11) and chromatographed on a column of Bio-Gel A-5m. The resulting, purified enzyme lost activity rapidly at 25 degrees C or on manipulation, as did the crude enzyme when diluted below 1 U/ml. Both enzyme preparations could be stabilized by low levels of high-molecular-weight dextran (2 micrograms/ml), poly(ethylene glycol) (e.g., 10 micrograms/ml PEG 20 000), or nonionic detergents (e.g., 10 micrograms/ml Tween 80). The stabilizing capacity of poly(ethylene glycol) and of dextran increased with molecular weight. Calcium had no stabilizing action in the absence of other additions, but reduced the inactivation that occurred in the presence of 0.5% bovine serum albumin or high concentrations (greater than 0.1%) of Triton X-100. In summary, dextransucrase could be stabilized against activity losses caused by heating or by dilution through the addition of low concentrations of nonionic polymers (dextran, PEG 20000, methyl cellulose) or of nonionic detergents at or slightly below their critical micelle concentrations.

Calcium↗
PubMed1990

Covalent fixation of hemoglobin to dextran phosphates decreases its oxygen affinity.

The interactions between various dextran phosphates and Hb (hemoglobin) were studied by measuring the oxygen-binding parameters of the mixtures. The effector properties of polymers were found to depend on the concentration of monoalkylmonophosphate groups on the polymers and also on their molecular weights. The covalent fixation of dextran phosphates bearing aldehydic groups to oxyHb and deoxyHb was carried out. The oxygen-binding properties of the conjugates thus obtained depended upon the initial form of the protein. Thus, only the conjugates synthesized from deoxyHb exhibited a low oxygen affinity, which means that, in this case, the linkages between the dextran phosphate and the protein allow a permanent interaction of the phosphate groups with amines of the 2,3-diphosphoglycerate binding site. The Hill coefficient values of these conjugates were smaller than that of free Hb, corresponding to a loss of the cooperativity of the protein upon fixation of polymers. However, as these new conjugates are capable of unloading more O2 than blood when subjected to oxygen pressures corresponding to physiological conditions, they can be regarded as potential erythrocyte substitutes.

Dextrans↗
PubMed1995

Inhibition by dextran derivatives of FGF-2 plasmin-mediated degradation.

In previous work we have shown that some new regenerating agents (RGTAs), molecules which correspond to some dextran derivatives (DxD) containing defined amounts of carboxymethyl (CM), benzylamide (B) and benzylamide sulfonate (BS) groups, were able to stimulate tissue repair when applied at the site of injury. Based on in vitro studies showing that these DxD could interact and protect heparin binding growth factors (HBGFs), we postulated that DxD could also act in vivo by protecting endogenously released HBGFs against protease degradation. We now present data demonstrating that human plasmin (HP1), one of the known proteases involved in extracellular matrix remodelling and in the local activation of some growth factors is specifically inhibited by some specific DxD. The most efficient compounds for inhibiting the amidolytic activity were substituted by all functions with IC50 at 0.26 microM for RGTA11 (a DxD obtained from a 40,000 Da dextran containing 110% of CM, 2.5% of B and 36.5% of BS units and with IC50 at 1.1 microM for RGTA10 (derived from 10,000 Da dextran and containing 110% of CM, 0% of B and 27.3% of BS). Compounds which were substituted with only one or two functions were less effective. The degradation of FGF-2 by HP1 was analyzed by SDS-PAGE and by measuring its residual growth promoting activity using a bioassay on human skin fibroblasts. In this assay, RGTA11 at a concentration of 1 microM could inhibit by 80-100% FGF-2 degradation induced by HP1 treatment. In conclusion, the inhibitory activity of some DxD towards HP1 as well as the ability of these DxD to protect FGF-2 against this proteinase could partially explain its beneficial influence on extracellular matrix remodelling following tissue injury.

Adult↗
PubMed1978

Effects of phloretin and dextran-linked phloretin on pancreatic islet metabolism and insulin release.

The effects of phloretin on islet metabolism and insulin release have been studied in isolated pancreatic islets of the rat. At a concentration of 0.18 mM phloretin inhibited insulin release stimulated by glucose or leucine but did not affect the oxidation rates of glucose or leucine, the rate of glucose utilization and the islet content of ATP. Higher concentrations of phloretin caused inhibition of the rate of glucose metabolism, but stimulation of insulin release. Insulin release stimulated by phloretin was inhibited by mannoheptulose but was independent on extracellular Ca2+ and was not potentiated by caffeine. Both inhibitory and stimulatory effects of dextran-linked phloretin on insulin release were also seen; a concentration of dextran-linked phloretin that did not inhibit islet metabolism inhibited glucose-stimulated insulin release, but not release stimulated by leucine or glyceraldehyde. Higher concentrations of dextran-linked phloretin inhibited glucose oxidation but stimulated insulin release. These data are discussed in terms of current models of the beta-cell glucose-sensor mechanism.

Animals↗