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PubMed1992

Stabilization of basic fibroblast growth factor with dextran sulfate.

Dextran sulfate protected bFGF from heat and acid inactivation and from proteolytic degradation. The protective effect was stronger than that of heparin which is known as a stabilizer of bFGF. Dextran sulfate and bFGF formed a high molecular weight complex via ionic interaction when mixed together in aqueous solution. The complex was dissociated when the ionic strength was increased and the protective effect was completely abolished. Successive digestion of bFGF with Staphylococcus aureus V8 protease and pepsin followed by affinity chromatography on an immobilized dextran sulfate column and reversed-phase high performance liquid chromatography yielded three positively charged fragment peptides, Tyr24-Phe30, Tyr106-Trp114 and Tyr124-Leu138. These results suggest that dextran sulfate stabilizes bFGF by binding close to the putative heparin binding sites of the bFGF molecule.

Amino Acid Sequence↗
PubMed1978

Sheep erythrocyte rosettes in pigs, sheep, cattle and goats demonstrated in the presence of dextran.

Formation of rosettes with sheep RBC by blood lymphocytes from young pigs was increased from 24.4% +/- 2.2 (mean +/- S.E.) in PBS to 54.1% +/- 1.9 in the presence of dextran. This increase was achieved without inducing appreciable rosette formation with other RBC which do not form rosettes in PBS. Lymphocytes which rosette only in dextran are predominant in pigs between 20 and 160 days old, when the peripheral lymphocyte pool is increasing very rapidly. The use of dextran revealed major populations of blood lymphocytes rosetting with SRBC in adult sheep (30.7% +/- 2.0), adult cattle (37.3% +/- 4.2) and adult goats (13.3% +/- 1.2). Proportions of rosette-forming lymphocytes tended to increase with age. In calf lymphoid tissues the distribution of rosette-forming lymphocytes suggested that these were T cells. In the improvement of rosette formation with SRBC, dextran was more effective than foetal calf serum, papain treatment of the SRBC or combinations of these treatments.

Age Factors↗
PubMed1980

Separation of granulocytes from peripheral blood in a single step using discontinuous density gradients of Ficoll-Urografin. A comparative study with separation by dextran.

A single-step method for separating granulocytes from peripheral blood using two different gradients of Ficoll-Urografin (F-U) density 1.075 and 1.097 g/ml) is described. The morphological, cytochemical and ultrastructural properties of neutrophils isolated by this method were compared to those isolated by dextran-enhanced sedimentation and neutrophils from the peripheral blood. These studies indicated fewer alterations in neutrophils separated by F-U centrifugation than in neutrophils concentrated by dextran. Finally, the granulocyte layer recovered by F-U fractionation was 98% pure (dextran 71%) and yielded 64% (dextran 79%) of total granulocytes.

Adult↗
PubMed1993

Serum antibody production by oral immunization with dextran B512.

Serum antibodies to dextran were detected when dextran B512 was orally administered to C3H/He mice. The amounts of serum antibodies were increased along with the dose of orally administered dextran B512. For serum antibody production, differences were observed among the strains of mice. C3H/He, C57BL/6 and CBA mice produced high levels of serum antibodies to dextran, while BALB/c and DBA/2 mice produced low levels of serum antibodies. The serum antibodies had groove-type combining sites, as determined by ELISA inhibitory assay.

Administration, Oral↗
PubMed1982

Effect of dextran-coated charcoal on radioimmunoassays of unconjugated estriol in serum.

Lipid interference in the radioimmunoassay of steroids can cause an apparent variation in post-prandial serum concentrations of unconjugated estriol. The effects of increased concentrations of dextran-coated charcoal (15--60 g/l) in the radioimmunoassay of estriol standards with and without triglycerides were studied. All concentrations of dextran-coated charcoal used in this study eliminated the previously observed effects of estriol-lipid partitioning. When we used similar concentrations of dextran-coated charcoal, we found that serum cortisol levels in pregnant women declined significantly during the day (P less than 0.001), but no significant variation in estriol concentrations was observed. These results indicate that the previously reported diurnal variation in serum unconjugated estriol concentrations attributed to steroid-lipid partitioning can be eliminated by increasing the concentration of dextran-coated charcoal in assays using this method of separation.

Charcoal↗
PubMed1986

Segmental differences of microvascular permeability for FITC-dextrans measured in the hamster cheek pouch.

An intravital microscopic method for quantitative measurement of interstitial concentrations of fluorescent tracers has been applied to the investigation of microvascular permeability in the hamster cheek pouch. Some nanoliters of FITC-dextran mean mol wt (Mw) 20,000, 3000, or sodium fluorescein (Mw 376) were injected into an arteriole of the exposed cheek pouch via micropipet. The extravasation of fluorochromes was measured by a photodensitometric method including two sets of calibration procedures (in vitro and in vivo). Postcapillary and collecting venules exhibited the highest absolute increase of fluorochrome concentration in the tissue for all tracer molecules tested when compared to arterioles or capillaries. The permeability of the vascular wall was quantified, assuming that diffusion processes play the main role for the transport of the investigated molecules under the experimental conditions of a high concentration gradient across the membrane. Permeability coefficients P (cm/sec) and apparent diffusion coefficients D' (cm2/sec) of the microvascular wall were calculated using a mathematical model for one-dimensional diffusion in composite media. The analysis is based on measured data of interstitial diffusion coefficients of the tracers used. For all tracer molecules tested, the wall of the capillaries and postcapillary venules was significantly more permeable than the arteriolar wall. For the largest test molecule (FITC-dextran Mw 20,000), the permeability coefficient of the vessel wall showed a maximum in the postcapillary venules. These findings support the concept of a "gradient of permeability" with a nonuniform distribution of exchange capacity only for the precapillary microvessels. A marked preponderance of venular over capillary permeability could, if at all, only be detected for FITC-dextran Mw 20,000. The present study characterizes the vessel wall by apparent diffusion coefficients which are, for FITC-dextran Mw 3000, and free fluorescein, roughly three orders of magnitude lower than the apparent diffusion coefficients in connective tissue.

Animals↗
PubMed1987

Quantitation of bradykinin-induced microvascular leakage of FITC-dextran in rat cremaster muscle.

We studied the in vivo effects of bradykinin (BK) on transvascular movement of macromolecules in the rat cremaster muscle. The muscle was fashioned as a single layer, placed in a transparent chamber, and superfused with a bicarbonate buffer solution (pH 7.4, 35 degrees). FITC-Dextran 150 (MW 150,000) was injected iv as a macromolecular tracer. The fluorescent tracer remained in the vascular compartment during control observations. BK (8 X 10(-8) to 8 X 10(-7) M) was topically applied for periods of 5 min. Depending on the dose, leakage of FITC-Dextran 150 started 2-3 min after the application of BK. Discrete leakage sites were detected for a short period at the beginning of the response only. Subsequently, the entire interstitial space became fluorescent as the leakage lasted for several minutes. The preparation returned to control appearance after 40-60 min of continuous superfusion with bicarbonate buffer. Macromolecular leakage was observed in postcapillary venules ranging from 15 to 50 microns in diameter. Neither arterioles nor true capillaries showed leakage of the tracer. To better quantitate the effect of BK on macromolecular transport, the superfusate output was collected at 5-min intervals and analyzed by fluorometry to determine FITC-Dextran 150 concentration. After BK, fluorochrome concentration in the superfusate rose, peaked by 15-20 min, and returned to control levels following 60 min of washout. A direct dose-response relationship was found between BK concentration and clearance of FITC-Dextran 150. These data demonstrate the feasibility of quantitatively studying blood-tissue transport of macromolecules in vivo in skeletal muscle.

Animals↗
PubMed1991

Endothelial surface charge of intestinal mucosal capillaries and its modulation by dextran.

Capillary endothelial surface charge was investigated by perfusing the intestinal circulation of anesthetized rats in situ with 0.1 or 10 mg/ml native ferritin (NF, pI = 3.8-4.2) or with 0.1 mg/ml cationized ferritin (CF, pI greater than 10.0) for 5 min, with or without 5% Dextran 40. Ferritin binding was quantified by electron microscopy. All electron micrographs of capillaries perfused with NF showed some NF binding. Mean NF particle densities (particles/microns) were significantly greater at vesicle necks (PDv) than elsewhere on the endothelial surface (PD). Capillaries perfused with CF showed binding in only 60% of the transverse sections examined. The binding was very marked in a large proportion of these vessels. Mean CF particle densities were significantly greater at fenestrae (PDf) than elsewhere. These results demonstrate that mucosal capillaries have a variable negative electrostatic charge on the endothelial surface and support the hypothesis that some vesicle diaphragms act as preferential attractors for anionic macromolecules. Such structures could promote transendothelial vesicular transport of albumin. Dextran significantly decreased PD for NF from 25.4 +/- 2.4 (SEM) to 13.1 +/- 0.9 and PD, PDv, and PDf for CF from 45.9 +/- 4.6 to 31.0 +/- 2.7, from 62.1 +/- 6.2 to 43.6 +/- 5.4, and from 152.9 +/- 15.5 to 114.5 +/- 8.6, respectively. The above responses result from dextran's weak interaction with the endothelial surface. Dextran reduces access of ferritin molecules to the cell surface by steric hindrance and/or electrostatic shielding of the glycocalyx.

Animals↗
PubMed1991

Effects of desmopressin and dextran on coagulation and fibrinolysis in healthy volunteers.

The effects of desmopressin and dextran on haemostasis and fibrinolysis were studied in four healthy volunteers. Both drugs were compared to placebo, each volunteer being subject to four experiments. Dextran 70 (30 g i.v.) moderately decreased VIII:C and vWF:Ag and slightly increased antithrombin III, also when haemodilution and diurnal variation were considered. Desmopressin (0.3 micrograms/kg BW i.v.), alone as well as in combination with dextran, increased VIII: C, vWF:Ag, protein C and tPA and decreased PAI-1. The combination of desmopressin and dextran stimulated coagulation and fibrinolysis and might be of relevance to surgical blood loss as well as to postoperative thromboembolism.

Adult↗
PubMed1986

Comparison of the effect of fluosol DA and dextran 40 on regional cerebral blood flow, infarction size, and mortality in cats with temporary occlusion of the middle cerebral artery.

Twenty-four cats were divided into two groups and treated with an intravenous infusion of either fluosol DA or dextran. One-half of the animals in each group were ventilated with room air and one-half with 100% oxygen. The right middle cerebral artery was occluded for a period of 4 hours through a transorbital approach. Regional blood flow by the hydrogen clearance method was measured before and after the infusion of fluosol DA or dextran, after oxygenation in the animals on 100% oxygen, three times during the period of ischemia, and after reperfusion. Regional cerebral blood flow increased slightly with the infusion of fluosol or dextran, decreased slightly with hyperoxygenation in the animals so treated, and decreased markedly in the right hemisphere during temporary occlusion of the right middle cerebral artery in all groups. With reperfusion regional flows in the right hemisphere varied considerably, with some animals showing hyperperfusion and others essentially no flow. There was no significant difference in average regional cerebral blood flow between any of the groups. The severity of infarction in all groups was directly related to the decrease in regional cerebral blood flow in the right hemisphere during temporary occlusion. There was also a strong correlation between the regional cerebral blood flow in the right hemisphere after reperfusion and the severity of infarction. In general, the animals showing normal or increased flow after reperfusion had small infarcts and those showing no reflow had large infarcts. Mortality was high in all groups, was not significantly different between any of the groups, and was highly correlated to the size of infarction. In brief, in this study fluosol offered no advantage over dextran, and probably neither agent, in the dose used, offered any protection against cerebral ischemia.

Animals↗
PubMed1994

A new process for the production of clinical dextran by mixed-culture fermentation of Lipomyces starkeyi and Leuconostoc mesenteroides.

A mixed-culture fermentation system was designed for the production of size-limited dextrans. This process was simpler and more economical than traditional methods. It required the establishment of microbial consortia of Lipomyces starkeyi ATCC 74054 and Leuconostoc mesenteroides ATCC 10830. Controlling initial conditions, growth, and enzyme production by both organisms controlled the product size. In this process, both strains were grown separately and then mixed. Dextran fermentation was then allowed to proceed. At the desired time (and molecular size), the fermentation was harvested. The optimum pH and temperature for production of clinical dextran (75,000 MW) were 5.2 (+/- 0.1) and 28 (+/- 0.5) degrees C, respectively. Varying the ratio of L. mesenteroides to L. starkeyi in the inoculum did not significantly affect either the final cell ratios or dextran production.

Biotechnology↗
PubMed1994

Functional changes of dextran-modified alkaline proteinase from alkalophilic Bacillus sp.

A serine alkaline proteinase (EC 3.4.21.62) from Bacillus sp. (ALPase I) was modified with the 2,4-dialdehyde derivative of clinical dextran (dialdehyde dextran). The modified preparation was purified using an ion-exchange column and gel filtration. The modified enzyme contained 75% carbohydrate by weight. The isoelectric point (pI) of ALPase I was converted from 8.2 to approximately 5.0 by this modification. The specific activity of the dextran-modified ALPase I was 56% of that of the native enzyme when milk casein was used as a substrate. It also had some superior characteristics: the thermostability of the modified enzyme at pH 10.0 was about 10-15 degrees C higher than that of control. In organic solvents such as n-hexane, benzene, and toluene, the hydrolysis reaction of the modified ALPase I for the fluorogenic substrate, succinyl-L-alanyl-L-alanyl-L-prolyl-L-phenylalanyl-4-methylcoumaryl-7-am ide (Suc-Ala-Ala-Pro-Phe-MCA), was several times higher than that of the native. This modification greatly improved the stability of ALPase I against nonionic and anionic surfactants. After exposure to lauryl benzene sulfonate and sodium lauryl sulfonate the modified enzyme retained over 95 and 90% of its activity, respectively, but the native enzyme lost its activity. We conclude that modification of serine proteinases with dialdehyde-dextran might be a useful method for improving enzyme character for enzyme technology.

Amino Acid Sequence↗
PubMed1991

Enzymatic degradation and immunogenic properties of derivatized dextrans.

Dextran T40 was modified with carboxylic, benzylamide and benzylamine-sulphonated groups (samples 1-10). The polymers were incubated with dextranase and the decrease of molecular weight was determined by high performance size exclusion chromatography. It was shown that the higher the substitution of dextrans, the lower their degradability. Modification of dextran with benzylamine and benzylamine-sulphonated groups appeared to hinder the formation of the enzyme-substrate complex more than the same quantity of carboxylic groups. The immunogenicity of one of the modified dextrans, containing 54% of carboxylic groups and 19.5% of benzylamine-sulphonated groups, was determined after subcutaneous and intravenous administration into Balb/c mice. The antibody titre was very low even if administered in complete Freund's adjuvant and did not depend on the injected dose. On the average, the titres of antibodies were lower by five orders of magnitude compared to bovine gamma globulin.

Animals↗
PubMed1986

Immunochemical studies of mouse monoclonal antibodies to dextran B1355S--II. Combining site specificity, sequence, idiotype and affinity.

The specificities of the combining sites of 19 mouse monoclonal antibodies to dextran B1355S have been characterized immunochemically by quantitative precipitin and precipitin inhibition assays; association constants for B1355S were determined by affinity gel electrophoresis. Cross-reactive and individual idiotypes related to the BALB/c B1355S-binding myeloma proteins MOPC104E [IdI(MOPC104E)] and J558 [IdI(J558)], determined by a radioimmunoassay, and heavy-chain variable-region sequences, are presented. Antibodies to B1355S are "alpha (1----3) alpha (1----6)-specific" as determined by precipitin and precipitin inhibition assays with dextrans and oligosaccharides, respectively, containing alternating alpha (1----3) alpha (1----6) linkages compared with oligosaccharides composed solely of alpha (1----3) or alpha (1----6) linkages; all antibodies have low association constants (less than or equal to 10(5) ml/g). However, there is also considerable diversity among the proteins as seen in the five groups of different patterns of reactivity with numerous dextrans having different structures, and the variability in affinity even among antibodies showing the same fine specificity by precipitin assay. There is little observable correlation of heavy-chain variable-region amino-acid sequence with specificity or affinity; however, all proteins having D-region amino acids Tyr,Asp at positions 96,97 express the MOPC104E individual idiotype and belong to precipitin specificity group 5, the group most cross-reactive with numerous dextrans, whereas those proteins having the J558 individual idiotype, Arg,Tyr or Asn,Tyr at 96,97 are found in all five precipitin groups.

Amino Acid Sequence↗
PubMedDate not supplied

Specificity and variable region cDNA sequence of an isogeneic monoclonal antiidiotype to an anti-alpha(1----6)dextran.

We have characterized a monoclonal isogeneic antiidiotype, IdB5.7, from a BALB/c mouse immunized with the anti-alpha(1----6)dextran C57BL/6 45.21.1. It defined a hapten-inhibitable idiotope expressed on four of the 2 myeloma and 37 hybridoma anti-alpha(1----6)dextrans tested. Sequence comparison of Id+ and Id- anti-alpha(1----6)dextrans suggested that two extra amino acids at VH 100A and 100B and different residues at VH 101 abolish the expression of the idiotope in the Id- anti-alpha(1----6)dextrans. Sequence analysis of the VH of IdB5.7 showed a CDR1 longer than usual and a D segment in CDR3 formed by the fusion of two D minigenes. The IdB5.7 V kappa uses the V kappa 1 germline gene K5.1 with a few substitutions. The D-D fusion in VH CDR3 is a feature which has been reported in several other antiidiotypic antibodies.

Amino Acid Sequence↗
PubMed1986

Structural variations in soluble iron complexes of models for ferritin: an x-ray absorption and Mössbauer spectroscopy comparison of horse spleen ferritin to Blutal (iron-chondroitin sulfate) and Imferon (iron-dextran).

Variations in the turnover of storage iron have been attributed to differences in apoferritin and in the cytoplasm but rarely to differences in the structure of the iron core (except size). To explore the idea that the iron environment in soluble iron complexes could vary, we compared horse spleen ferritin to pharmaceutically important model complexes of hydrous ferric oxide formed from FeCl3 and dextran (Imferon) or chondroitin sulfate (Blutal), using x-ray absorption (EXAFS) and Mössbauer spectroscopy. The results show that the iron in the chondroitin sulfate complex was more ordered than in either horse spleen ferritin or the dextran complex (EXAFS), with two magnetic environments (Mössbauer), one (80%-85%) like Fe2O3 X nH2O (ferritinlike) and one (15%-20%) like Fe2O3 (hematite); since sulfate promotes the formation of inorganic hematite, the sulfate in the chondroitin sulfate most likely nucleated Fe2O3 and hydroxyl/carboxyls, which are ligands common to chondroitin sulfate, ferritin and dextran most likely nucleated Fe2O3 X nH2O. Differences in the structure of the iron complexed with chondroitin sulfate or dextran coincide with altered rates of iron release in vivo and in vitro and provide the first example relating function to local iron structure. Differences might also occur among ferritins in vivo, depending on the apoferritin (variations in anion-binding sites) or the cytoplasm (anion concentration).

Animals↗
PubMed1983

Replacement of sodium chloride with dextran or polyethylene glycol for immunoprecipitation of lipopolysaccharide with antibodies in chicken or turkey sera.

Dextran or polyethylene glycol could replace sodium chloride in agarose gels for inducing immunoprecipitation of Pasteurella multocida lipopolysaccharides with antibodies in chicken or turkey sera. Resolution of immunoprecipitates was best when 3% concentrations of either dextran or polyethylene glycol were used. Higher concentrations increased opacity of the gels. Nonspecific precipitation of serum or gamma-globulin fractions in gels was caused by the electrophoresis buffer, dextran, and polyethylene glycol. Dialysis of serum or gamma-globulin fractions against the electrophoresis buffer and soaking gels in buffers of pH greater than 7.0 that contained 3% polyethylene glycol reduced nonspecific precipitation. Incorporation of dextran or polyethylene glycol into gels enhanced immunoprecipitation in rocket immunoelectrophoresis but resulted in slower mobility of antigen.

Animals↗
PubMed1992

Molecular weight determination and compositional analysis of dextran-protein conjugates using low-angle laser light scattering technique combined with high-performance gel chromatography.

The low-angle laser light scattering technique combined with high-performance gel chromatography was applied for characterization of the dextran-ovalbumin and dextran-lysozyme conjugates obtained from the mild heating in dry state, which is attracting interest as a way leading to stabilization of proteins and to production of proteins with excellent emulsifying or antimicrobial ability (Nakamura, S., Kato, A. and Kobayashi, K. (1991) J. Agric. Food Chem. 39, 647-650). According to the above technique, providing the information about the molecular weight distribution and the composition of the conjugates, one or two dextran molecules were found to be linked to one molecule of the proteins. In addition, each of the conjugates was shown to exist as an oligomeric assembly of which formation is promoted by an increase in the salt concentration of buffer. The observations suggest that the increase in the hydrophobicity of the protein moiety as a result of partial denaturation and the introduction of the hydrophilic dextran chain affords the conjugate an amphiphilic property.

Chromatography, Gel↗