SEARCH · PubMed Health

Results for “Dextrans”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 901 records · Page 50Linked to original sources

PubMed2005

[Application research on dextran-based hydrogel and its drug controlled release].

OBJECTIVE: To introduce the development of dextran-based hydrogel and its drug delivery system in drug sustained and/or controlled release, and to investigate their application in tissue engineering. METHODS: Related literature was extensively reviewed and comprehensively analyzed. RESULTS: In recent years, great progress was made in the studies of dextran-based hydrogels and study on dextran-based intelligent materials became an investigative hotspot especially in tissue engineering. CONCLUSION: Dextran-based hydrogel is considered to be a good potential material in field of drug delivery and tissue engineering. Endowed with new characteristics, a series of intelligent biomaterials can be derived from dextran-based hydrogels, which can be widely used in biomedicine. Further study should be done on the industrialization of its interrelated production.

Absorbable Implants↗

PubMed1990

Reduction of immunogenicity by covalent modification of murine and rabbit immunoglobulins with oxidized dextrans of low molecular weight.

This communication describes the covalent modification of monoclonal and polyclonal antibodies with oxidized dextrans of low molecular weight to generate conjugates having low immunogenicity in vivo. Conjugation conditions were optimized to generate monomeric, dextran-modified antibodies, free of both high-molecular-weight polymeric aggregates and unmodified antibodies. Conjugates could be prepared with varying levels of dextran substitution. These conjugates retained optimal immunoreactivity as well as in vivo pharmacokinetics and tumor-localization properties. In addition, multiple i.v. administrations of dextran-modified antibodies in animals did not elicit a measurable immune response to either the antibody or the dextran portion of these conjugates.

Animals↗

PubMed1990

Antitumor characteristics of the conjugate of N4-(4-carboxybutyryl)-ara-C with ethylenediamine-introduced dextran and its resistance to cytidine deaminase.

By oxidation of dextran, and reduction of the Schiff bases formed by reaction of the oxidised dextran with diaminoalkanes, several diaminoalkane-introduced dextrans were prepared and evaluated as drug carriers. Conjugates between N4-(4-carboxyburyryl)-1-beta-D-arabinofuranosylcytosine (glu-ara-C) and such drug carriers were prepared, and selected conjugates were tested in vivo, and investigated for inhibitory effects on cytidine deaminase. Ethylenediamine-introduced dextran prepared under 10% oxidation conditions was found to be most useful as a drug carrier from its chemical characteristics and toxicity evaluation in BDF1 mice. The conjugate obtained from glu-ara-C and ethylenediamine-introduced dextran 2000 showed high antitumor activity, significant at the relatively low dose of 100 mg equivalent ara-C/kg, in BDF1 mice bearing L1210 leukemia cells. Glu-ara-C and the conjugate were unaffected by cytidine deaminase under conditions in which 1-beta-D-arabinofuranosylcytosine was degraded rapidly to 1-beta-D-arabinofuranosyluracil.

Animals↗

PubMed1991

Thromboprophylaxis in patients with hip fractures: a prospective, randomized, comparative study between Org 10172 and dextran 70.

A prospective, randomized, assessor-blind trial has been undertaken to compare the thromboprophylactic effect and safety of the heparinoid Org 10172 (a mixture of low molecular-weight sulfated glycosaminoglycuronides) and dextran 70 in patients operated on for hip fracture. Prestudy biostatistical calculations led to the need for 260 patients. Three hundred eight patients were randomized and 19 were excluded after randomization, the majority because of postponed surgery. Analyses were made on the 289 patients on an intention-to-treat basis, as well as on the 247 patients given correct prophylaxis. Diagnosis of deep vein thrombosis was based on bilateral ascending phlebography on postoperative days 10 through 12. The frequency of deep vein thrombosis on an intention-to-treat basis was 10% in the Org 10172 group and 30% in the dextran 70 group and, on the basis of correct prophylaxis, 12% and 31%, respectively, both differences being significant (p less than 0.001). Two-month mortality rates were equal in the groups. Three fatal pulmonary emboli were seen in the dextran group. Significantly more patients in the dextran group received postoperative transfusions; no other differences in various hemorrhagic parameters were seen. Thus it can be concluded that Org 10172 has a significantly better thromboprophylactic effect than does dextran in patients with hip fractures without significant side effects.

Aged↗

PubMed1990

T cells regulate the IgM antibody response of BALB/c mice to dextran B1355.

The IgM antibody response of BALB/c mice to bacterial (Leuconostoc) dextran B1355 is influenced in a positive and negative manner by regulatory CD4+ and CD8+ T cells, respectively. Treatment with concanavalin A (ConA) at the time of immunization or 2 days later caused suppression and enhancement of the antibody response, respectively. Priming of mice with a sub-immunogenic dose of dextran resulted in profound suppression upon subsequent immunization 3 days later. None of these effects were demonstrable in athymic mice. Transfer of T cells from mice primed 18 h previously with a subimmunogenic dose of dextran suppressed the antibody response in immunized recipients; such suppression was abolished by the treatment of transferred cells with anti Thy 1.2 or anti Lyt 2.2 (CD8) antibody in the presence of complement. By contrast, the transfer of T cells from mice, which had been given an immunogenic dose of dextran 4 days previously, increased the antibody response in immunized recipients; such enhancement was abolished by treating transferred cells with anti Thy 1.2 or anti L3T4 (CD4) antibody in the presence of complement. These findings indicate that the immune response to dextran B1355 is regulated by CD4+ T-amplifier cells (Ta cells) and by CD8+ T-suppressor cells (Ts cells) which are activated during the course of a normal antibody response.

Animals↗

PubMed1991

Bioavailability of ketoprofen from orally administered ketoprofen-dextran ester prodrugs in the pig.

The bioavailability of ketoprofen after oral administration of aqueous solutions of various ketoprofen-dextran ester prodrugs in pigs was assessed. Conjugates derived from dextran fractions in the molecular weight range 10,000-500,000 were employed. Compared to the administration of an oral solution of an equivalent dose of parent ketoprofen, the average absorption fractions for the different prodrugs ranged from 100 to 67%. Relatively small inter-individual variation of ketoprofen bioavailability was observed. Apparently, the molecular size of the employed dextran transport group only has a minor influence on the pharmacokinetic parameters. The ketoprofen plasma profiles for all the administered prodrugs exhibited a characteristic lag time of ketoprofen appearance in the blood (2-3 h). Quite similar results were obtained from identical experiments carried out in the pig, employing naproxen-dextran esters. Thus, the present study adds support to a more versatile application of the dextran ester prodrug approach to providing selective colon delivery of drugs possessing a carboxylic acid functional group.

Administration, Oral↗

PubMed1991

Macromolecular prodrugs. IXX. Kinetics of hydrolysis of benzyl dextran carbonate ester conjugates in aqueous buffer solutions and human plasma.

Benzyl carbonate esters of dextran with varying degrees of substitution have been synthesized. The kinetics of the hydrolytic cleavage of the carbonate ester bond in aqueous solution within the pH range 0.44-10.46 (37 degrees C) has been investigated. The degradation reactions followed pseudo-first-order kinetics and a rate expression encompassing hydrogen ion-, hydroxide ion- and water-catalyzed hydrolysis of the dextran conjugates was derived. No influence of the degree of substitution on the reaction rates was observed. In alkaline solution a slightly enhanced lability of trifluorethyl benzyl carbonate ester compared to the benzyl dextran carbonate esters was observed, indicating a lack of any significant intramolecular catalytic effect in the hydrolysis of the dextran esters. Almost identical rates of liberation of benzyl alcohol were found in 80% human plasma and aqueous buffer of pH 7.4, indicating the lack of enzyme-mediated cleavage of the dextran carbonate ester bond.

Buffers↗

PubMed1976

[Comparison of a bivalent anti-foot-and-mouth disease vaccine with oil adjuvant to a vaccine with DEAE-dextran adjuvant in swine].

The report compares the compatibility, efficacity and serology response of two bivalent anti-foot-and-mouth disease vaccines (OC). One is oil-adjuvanted and the other based on diethyl-amino-ethyl-dextran (DEAE-Dextran). After vaccination no general clinical or local reactions are normally observed. Tissular reactions at the inoculation site are more severe with the oil-adjuvanted vaccine than with the DEAE-Dextran vaccine. Meat inspection, about three months after injection of the vaccine, showed the lesions to be in regression and negligible. The control of activity has been performed by the virulence test. For the oil-adjuvanted vaccine, protection against O1-Lausanne, 5, 21 and 90 days after vaccination is 90%, 80-100% and 55% respectively. For the DEAE-Dextran vaccine, these levels of protection are 80% after 5 days and 20-70% after 21 days. The percentage of swine protected against C-Noville 35 days after vaccination is 100% for the oil-adjuvanted vaccine and 70% for the DEAE-Dextran vaccine. The evolution of the amount of serum antibodies was followed for three months by the method of seroneutralization on cell cultures.

Adjuvants, Immunologic↗

PubMed1991

Evidence from endothelium of gastric absorption of heparin and of dextran sulfates 8000.

Heparin, hydrogenated dextran sulfate 8000 (Usherdex 8), and dextran sulfate 8000 were administered to rats, and the total drug was separated and determined in endothelium and plasma. A large amount of each drug was recovered from endothelium 2.4 and 6 minutes after intravenous injection. This accounted for the drug missing from plasma. The drugs in water were placed in the stomach by catheter. All three drugs were recovered from the endothelium and identified unchanged by electrophoresis and specific staining. The amounts that were recovered at 2.4 and 6 minutes were equivalent to most of the drug administered. Thus heparin, Usherdex 8, and dextran sulfate 8000 enter the body immediately on oral administration. At longer time intervals after intravenous and oral administration, much of each drug was not demonstrable in endothelium by the method used. Some drug could be detected in endothelium after 4 hours. After oral administration, plasma levels of each drug were rarely more than 0.5% of the dose. Formalin-alcohol was applied to the jugular veins of anesthetized rats to produce a thrombus, (see Blake et al. J Clin Path 1959;12:118-22) and the drugs were immediately introduced into the stomach. Four hours later the injured veins were inspected for thrombi. Incidence of thrombotic plug was 80% in rats that received saline solution, 4% with Usherdex 8, 0% with dextran sulfate 8000, and 0% with heparin. Usherdex 8, dextran sulfate 8000, and heparin demonstrate low, moderate, and high in vitro anticoagulant activity, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗

PubMed1985

Intestinal hemodynamic effects of dextran-induced hyperviscosity in the cat.

A hyperviscous state with red cell aggregation and increased plasma viscosity was induced in cats by intravenous infusion of high molecular weight dextran. A segment of the small intestine was isolated with intact vascular and nervous supply and placed in a plethysmograph for determination of the intestinal tissue volume and capillary filtration coefficient. The intestinal blood flow was measured by a drop recorder unit. Measurements of intestinal blood flow, flow resistance and capillary filtration coefficient were performed during normotension and regional hypotension before and after infusion of high molecular weight dextran. After infusion of high molecular weight dextran, there was a twofold increase of blood viscosity and a threefold increase of plasma viscosity. Erythrocyte sedimentation rate exceeded 100 mm/h. Intestinal blood flow decreased by 35% during normotension and by 45% during regional hypotension. Intestinal flow resistance increased by 45% during normotension and by 65% during hypotension. The capillary filtration coefficient was not affected by the dextran infusion. It is concluded that the intestinal hemodynamic effects of high molecular weight dextran are mainly dependent of the increased plasma viscosity and that the number of perfused capillaries is not reduced by obstructing red cell aggregates.

Animals↗

PubMed1985

Prevention of thrombosis after hip fracture surgery. Comparison of dextran 70 with and without dihydroergotamine.

The efficacy of dextran 70 with or without dihydroergotamine as prophylaxis against deep venous thrombosis (DVT) was tested prospectively in a randomized series of 65 patients with fracture of the hip. Diagnostic evaluation was made with bilateral ascending phlebography on postoperative day 7. In the dextran 70 group, 5 of the 27 phlebographically studied patients had DVT, an incidence not significantly different from the 10 DVT among 28 patients given dextran 70 + dihydroergotamine. Bleeding complications showed no intergroup difference. The study did not confirm a beneficial effect of dextran 70 in combination with dihydroergotamine as compared with dextran alone in regard to thrombotic complications after surgery for hip fracture.

Aged↗

PubMed1986

The use of a new dextran gradient medium for rapid isolation of functionally intact neonatal rat pancreatic islets.

The use of a new density gradient medium, Dextran M 70, is described for isolation of islets of Langerhans from collagenase digested pancreases of neonatal Wistar rats. Centrifugation in continuous as well as in discontinuous gradients of a less expensive dextran with a mol. wt. of 70,000 was performed and the results were compared with those obtained with Ficoll gradients. About 100 islets free from exocrine acinar parenchyma were obtained from each neonatal rat pancreas. There were no differences in glucose-stimulated insulin release and in potentiation of glucose-stimulated insulin release by the phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine (IBMX) between the islets isolated by centrifugation in Dextran M 70 or Ficoll 400 and those directly harvested from the pancreatic digest without density media. These data demonstrate that high numbers of pancreatic islets can be rapidly isolated in dextran gradients without any impairment of their functional integrity. Dextran M 70 gradients can be readily formed as continuous or 4-step discontinuous gradients without special osmotic compensators and its maximum density of 1.097 g/ml at a concentration of 23% (w/w) seems to be sufficient for the purification of other cell types too.

Animals↗

PubMed1987

Different VL and VH germ-line genes are used to produce similar combining sites with specificity for alpha(1----6)dextrans.

Monoclonal antibodies to alpha(1----6)dextrans produced in mice immunized with the T-independent antigens alpha(1----6)dextran or the stearylisomaltosyl oligosaccharides have been characterized immunochemically. To correlate the immunochemical properties of these monoclonal antibodies with their primary structure, we have sequenced the variable (V) regions of the light (L) and heavy (H) chains. Three V kappa germ-line genes belonging to two major gene families were used; differential J usages also contribute to diversity. Five different VH germ-line genes belonging to three major VH families were used. The VH genes were further modified by junctional diversity and differential J usage and possibly by somatic mutations. The effects of these modifications on the fine specificities of anti-alpha(1----6)dextrans are discussed. Thus far, six different combinations of VLJL-VH(D)JH chains that form groove-type combining sites specific for alpha(1----6)dextran have been found. We conclude that entirely different VL and VH can form combining sites specific for the internal linear sequence of alpha(1----6)dextran.

Amino Acid Sequence↗

PubMed1987

[Anaphylactogenicity of dextran-conjugated serum globulins].

Active anaphylaxis in 238 guinea-pigs has revealed a decrease in the anaphylactogenic activity of horse blood serum IgG conjugates with dextran and of serum treated with dextran according to Diaferm method. The conjugates were used for a challenge injection. The sensitizing activity of dextran-conjugated proteins was higher than that of native proteins. The effect was most pronounced with 150,000 D dextran used as a matrix. A lower increase in sensitizing protein activity and a decrease in anaphylactogenic activity were achieved with dextran matrix of the molecular weight of 35-50 D and protein/dextran ratio from 1:6 to 1:9.

Anaphylaxis↗

PubMed1988

A new strain-specific cross-reactive idiotope with possible regulatory function expressed on BALB/c anti-alpha (1-3) dextran antibodies.

We obtained a mAb, B5, defining a major crossreactive Id, the B5 Id, having an in vivo regulatory function. BALB/c mice immunized against the bacterial dextran Ag B1355S produce lambda 1-bearing anti-alpha (1-3) glucosidic linkage of dextran B1355S (DEX) antibodies. Of these antibodies 30% expressed the B5 Id determinant. As was observed for the IdX-Id, B5 idiotope expression was also linked to the BALB/c H chain allotype. The antibody family expressing the B5 Id included IdX+ as well as IdX- defined monoclonal anti-alpha (1-3) DEX antibodies. Injection into BALB/c mice of mAb B5 conjugated to keyhole limpet hemocyanin led to enhancement of serum anti-alpha (1-3) DEX antibody synthesis, and to a strong increase in B5+ Ig lacking dextran-binding activity. IdX+ serum Ig were also increased in these mice. Injection of this mAb into allotype congenic nonresponder C.B20 mice induced a significant serum lambda 1-bearing anti-alpha (1-3) dextran antibody response (5 to 50 micrograms/ml). However, in A/J nonresponder mice, a similar treatment induced only the dextran-nonbinding component, which reached high levels (approximately 7 mg/ml) in the sera of these mice. In the majority of these A/J mice, we detected a specific anti-(4-hydroxy-5-iodo-3-nitrophenyl)acetyl antibody response characterized by B5 Id-positive antibodies. This observation can be explained by an in vivo regulatory idiotope-mediated cross-regulation.

Adjuvants, Immunologic↗

PubMed1985

Effects of low molecular weight dextran in intraocular irrigating solutions on ERG B-wave.

We examined effects of low molecular weight dextran in intraocular irrigating solutions on in vitro ERGs of the rabbit. A significant difference in ERG b-wave amplitude was observed between dextran-free and 3-4% dextran-added solutions. The b-wave amplitudes were well maintained and even enhanced to 120% of the presubstitution level after 90 minutes incubation with 4% dextran-added solution (15 mM/L bicarbonate, 290 M0sm/kg). It is suggested that low molecular weight dextran might be a useful or, at least, non-toxic agent in intraocular irrigating solutions for maintaining the retinal function with respect to ERG b-wave.

Animals↗

PubMedDate not supplied

The effect of low molecular weight dextran on early platelet deposition onto vascular grafts.

Synthetic vascular grafts have a thrombogenic surface which probably is an important factor when small caliber arterial grafts occlude. We have in the present investigation studied the effect of low molecular weight dextran (Dextran-40, LMWD) in vivo in a sheep model in order to evaluate the graft-surface interaction, using Indium-III-oxine labelled platelets. It was found that the platelet deposition onto polytetrafluoroethylene, PTFE, grafts (4 mm inner diameter), was significantly lower in the dextran treated group than in the control group (p less than 0.001). These differences were also confirmed by histopathological examination where the dextran treated grafts showed a significantly larger thrombus free surface area than corresponding non-treated control grafts. We therefore conclude that low molecular weight dextran has a direct beneficial platelet effect and that the LMWD therefore can be recommended as a justified treatment in connection with small diameter vascular graft reconstructions.

Animals↗

PubMed1988

The uptake of fluorescein-conjugated dextran 70,000 by the small intestinal epithelium of the young rat and pig in relation to macromolecular transmission into the blood.

The macromolecular transmission from the intestinal lumen into the circulation, and its cessation (intestinal closure), were investigated in young rats and pigs in relation to the enterocytes ability to internalize macromolecules. After gavage feeding of FITC-labelled dextran 70,000 (FITC-dextran) and bovine serum albumin (BSA), the uptake of FITC-dextran into the enterocytes was examined by fluorescence microscopy, and the intestinal transmission of both markers was estimated from their blood serum concentrations. In both preclosure rats (14-days old) and piglets (newborn, unsuckled), high serum concentrations of the markers were correlated with the presence of highly fluorescent enterocytes. Although the transmission of the markers to the blood had ceased in postclosure suckling pigs (24-h old), the enterocytes showed a high fluorescence, indicating that the cellular uptake of FITC-dextran was still high. In the 6-days old piglets, only the distal part of the intestine showed uptake of FITC-dextran. In postclosure rats (21- and 30-days old) and in pigs 4-8 weeks old, no fluorescence in the enterocytes and only trace amounts of markers in the serum could be detected. These results reflect differences in the closure process between the species. In the rat, closure is likely to be due to a decrease in the endocytotic activity of the enterocytes, whereas closure in the pig is related to a cessation of the passage of internalized material into the blood (transcytosis).

Animals↗