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Trauma, dextran 40 and metastasis formation after intravenous tumour cell injection in rats.

Dextran 40 did not influence the formation of pulmonary metastases after intravenous tumour cell injection in untraumatized dextran non-sensitive Wistar rats. Trauma significantly increased the formation of metastases and treatment with dextran 40 enhanced this effect of trauma markedly. No definite explanation of the effect of dextran 40 on pulmonary metastasis formation when combined when trauma can be offered, but possible mechanisms are discussed.

Animals↗

Preparation and characterization of a dextran-trypsin conjugate.

Bovine pancreatic trypsin was coupled to dextran after activation of the polysaccharide by cyanogen bromide. The soluble dextran-trypsin conjugated was purified by molecular sieve chromatography. After coupling, 53% of the esterase activity of trypsin remained, but the conjugate had only 7% of the caseinolytic activity of the native enzyme. The modified trypsin showed greater resistance than the native enzyme to inactivation by heat treatment, autodigestion, or denaturing agents, and was also more resistant to inhibition by trypsin inhibitors, particularly ovomucoid. Treatment with dextranase partly removed the improved stability properties and resistance to inhibition of the trypsin-dextran conjugate. The conjugated enzyme preparation consists of a heterogenous mixture of macromolecular aggregates, each containing many trypsin and many dextran molecules linked together. Intramolecular cross-linking of enzyme molecules by polysaccharide chains is considered to be responsible for stabilization of the tertiary structure of the enzyme molecules in the conjugate.

Animals↗

The use of dextran after keratoplasty for visualizing the vitreous cavity.

BACKGROUND AND OBJECTIVE: Corneal edema during penetrating keratoplasty (PK) precludes the visualization of the fundus required to perform vitreoretinal surgery. In this study, the clearing of the cornea and fundus visualization with dextran 40 following PK was evaluated. PATIENTS AND METHODS: Topical dextran 40 was used in 12 eyes that underwent uncomplicated PK (phase 1) and in 5 eyes that underwent combined PK with vitreoretinal surgery (phase 2). RESULTS: Clearing of the cornea and visualization of the fundus were observed in all eyes after dextran had been instilled for a mean of 4 and 5 minutes in eyes for phase 1 and 2, respectively. Vitreoretinal surgery could successfully be performed after PK in all eyes of phase 2. CONCLUSION: Topical use of dextran 40 following PK produces enough clearing of the cornea to enable visualization of the fundus for further vitreoretinal procedures after the graft has been sutured.

Administration, Topical↗

[The influence of cumulative dexamethasone, promethazine and dextran 70 used as protection against intraperitoneal adhesions on selected parameters of humoral immunity in women operated on for infertility].

One of the most frequent reasons of the intraperitoneal adhesions formation in young women is pelvic inflammatory disease and surgical operations of pelvic organs. The element of more complex activities against adhesion creation is to limit an inflammatory reaction in the area of operation by intraperitoneal and systemic pharmacotherapy. The system of activities put into practice in the Clinic of Gynaecology includes in the field of pharmacological prophylaxis a systemic and intraperitoneal use of dexamethasone and promethazine before, during and after the operation, in total doses respectively: 250 mg and 300 mg, as well as intraperitoneal dosing of 500 ml of dextran 70, just before closing the peritoneal cavity. Verification of the results of these activities during laparoscopy or laparotomy shows its high effectiveness. For many years we did not observe any complications of any wound healing after the operations. Due to existing reports about possible complications in the postoperation period, which are probably caused by the use of the above-mentioned pharmaceutics, I decided to investigate how dexamethasone, promethazine and dextran 70 influence the selected parameters of humoral resistance in women who were operated on due to mechanical infertility. The investigated group consisted of 30 women, while the control group comprised 10 women who had gynaecological operations of similar extent. The venal blood samples were collected before the operation and on the third, fifth and twenty first day after the operation. The levels of selected acute phase proteins were checked and the character as well as the dynamics of value changes were monitored in both groups. Because of great variability between the proteins the fractions were picked out focusing on the differences in dynamics of metabolism, half-life time and biological functions. Following proteins were investigated: C-reactive protein, alfa1-acid glycoprotein, haptoglobin, alfa1-antitripsin, ceruloplazmin, alpha2-macroglobin, hemopexin, immunoglobulins A, G, M, albumins, transferrin, alpha2-HS-glycoprotein. The analysis of the study results has indicated that the application of dexamethasone, promethazine and dextran 70 only exerts modulating influence on the course of acute phase reaction induced by the operations. In the group having been studied earlier (in 3rd postoperative 24-hours) significant changes were revealed concerning the level of particular proteins in accordance with their physiological character (increase or decrease of level) in the control group such changes appeared later (about 5th 24-hours) and were characterized by markedly smaller amplitude and dynamics (Tab. 1-2, Fig. 1-15). The levels of proteins defined prior to operation were reached faster by patients of the study group (up to 21st 24-hours after operation). It has been disclosed that the use of composed antiadhesion therapy with dexamethasone, promethazine and dextran 70 accelerates, intensifies and simultaneously restricts the duration of transformations defined as acute phase reaction, which result in reducing the number of intraperitoneal adhesions. This therapy does not impair the mechanisms of humoral immunity in patients operated on.

Acute-Phase Reaction↗

A protocol for coadministration of i.v. iron dextran and heparin in chronic hemodialysis patients.

The coadministration of intravenous iron dextran and heparin as a continuous infusion during hemodialysis (HD) is a safe and effective method used in maintaining and/or increasing iron stores and hematocrit levels in patients with end stage renal disease (ESRD). The technique of mixing iron dextran in low doses with heparin and infusing this mixture via the heparin syringe pump on the dialysis machine has shown to be cost effective, as well as instrumental in reducing the risk of adverse reactions due to rapid infusion or large dose infusion of iron dextran. At the Cleveland Clinic Foundation, we developed a protocol based on this methodology. A total of more than 1,000 doses of intravenous iron dextran and heparin have been administered to our HD patients using this technique, and no adverse reactions have been reported or observed.

Algorithms↗

THE UPTAKE OF IRON IN RABBIT SYNOVIAL TISSUE FOLLOWING INTRA-ARTICULAR INJECTION OF IRON DEXTRAN. A LIGHT AND ELECTRON MICROSCOPE STUDY.

Iron dextran (molecular weight 7,000) diffuses rapidly from the joint cavity through the synovium, along lymphatics and extracellular tissue spaces; articular cartilage is impermeable to iron dextran. There is also rapid cellular uptake by synovial lining cells, particularly of the vacuolar type; endoplasmic reticulum-containing lining cells rarely take up iron dextran. Cellular uptake is probably effected by pseudopodial folds projecting from the cell surface and enclosing extracellular material. Cells containing iron may degenerate and be ingested by phagocytes, and this may account for the concentration of iron in a smaller proportion of cells on or below the synovial surface in the later stages. At 6 to 18 hours after injection there is a mild inflammatory reaction and some synovial proliferation; from this stage onwards intracellular iron occurs in the form of haemosiderin. Granules of haemosiderin are present in the synovium 3 months after injection and possibly longer.

Animals↗

An enzyme from Streptococcus mutans forms branches on dextran in the absence of sucrose.

An enzyme in glucosyltransferase preparations from Streptococcus mutans catalyzed the transfer of [14C]glucopyranoside from purified isomaltosaccharides, each containing [14C]glucopyranoside at its non-reducing terminus, to acceptor dextran, in the absence of sucrose. Half of the radioactivity present in the resulting [14C]dextrans was resistant to hydrolysis by amylo-1,6-glucosidase. Treatment of the [14C]dextrans with endodextranase resulted in extensive hydrolysis and produced [14C]-labeled limit oligosaccharides containing branch sites. Acetolysis of the [14C]-labeled limit oligosaccharides yielded [14C]nigerose, thus indicating the formation of branch sites on dextran in the absence of sucrose. The enzyme catalyzing this reaction has not been identified but appears to be independent of the major extracellular glucosyltransferases of S. mutans.

Amino Acids, Branched-Chain↗

The effect of beta 2-glycoprotein I on the dextran sulfate and sulfatide activation of the contact system (Hageman factor system) in the blood coagulation.

1. beta 2-Glycoprotein I, inhibits the initiation of the contact system in plasma accomplished by dextran sulfate. 2. The dextran sulfate induced activation could be inhibited both when dextran sulfate was preincubated with beta 2-glycoprotein I and when the amount of beta 2-glycoprotein I in plasma was increased. 3. The concentration of beta 2-glycoprotein I at which an inhibitory effect could be registered was dependent upon the concentration of negatively charged groups on the surface. Calculation of the molar ratios between beta 2-glycoprotein I and sulfate residues in dextran sulfate showed that beta 2-glycoprotein I had to be present in excess of a 1:1 stoichiometric ratio of the sulfate group in order to inhibit the activation. 4. beta 2-Glycoprotein I does not inhibit the initiation of the contact system in plasma accomplished by sulfatide, unless the sulfatide has been preincubated with beta 2-glycoprotein I.

Apolipoproteins↗

Permeability of the Peritrophic Envelopes of Herbivorous Insects to Dextran Sulfate: a Test of the Polyanion Exclusion Hypothesis.

We tested the hypothesis that the permeability of the peritrophic envelope in herbivorous insects is greatly reduced for polyanions as a result of an extensive network of anionic sites in the proteoglycans of the matrix. 14C-Dextran sulfate (polyanionic, 8000 M(w)) and fluorescein isothiocyanate-labeled (FITC) dextran (monoanionic, 9400 M(w)) were introduced together into the endoperitrophic space of the midguts of Orgyia leucostigma (Lepidoptera) larvae and Melanoplus sanguinipes (Orthoptera) adults. In all cases more of the 14C-dextran sulfate permeated the peritrophic envelope than the FITC-dextran, the opposite of the result predicted by the polyanion exclusion hypothesis. We conclude that polyanion exclusion is not a mechanism that contributes significantly to the permeability properties of the peritrophic envelopes of these two species, or that explains the failure of tannic acid to cross the peritrophic envelopes of lepidopteran larvae. Copyright 1997 Elsevier Science Ltd. All rights reserved

Journal Article↗

Dextran-magnetite complex: temperature dependence of its NMR relaxivity.

The NMR relaxivity of proton by dextran-magnetite (DM) complex was examined at temperatures from 20 to 80 degrees C. The decrease in T1 relaxivity with increasing temperature is due to the thermal activation of motion of water molecules in and/or surrounding DM particle. The decrease in magnetization of magnetite core is the secondary effect. The temperature dependence of T1 relaxivity was found to depend on molecular weight of dextran. The motion of dextran chains binding to core may affect the thermal activation of "heavy water" interacted with dextran. The Arrhenius plots of T1 relaxivity showed different slopes at 20-40 degrees C and 50-80 degrees C, while, no change in slope was observed for Fe(NO3)3, CuSO4 and Gd-DTPA solutions.

Journal Article↗

Macromolecular prodrugs. XVI. Colon-targeted delivery--comparison of the rate of release of naproxen from dextran ester prodrugs in homogenates of various segments of the pig gastrointestinal (GI) tract.

We have determined initial rates of naproxen formation from dextran-naproxen ester prodrugs incubated in homogenates of various segments of the pig GI tract. Drug liberation proceeded 15-17 times faster in cecum and colon homogenates than in aqueous pH 7.4 buffer or homogenates of the small intestine. The degree of conjugate substitution did not affect the liberation rates, whereas enhanced drug activation was observed with decreasing molecular size of the carrier dextran. During incubation in colon homogenates the average molecular weight of the dextran prodrugs decreased. The mechanism of drug activation from the prodrugs may therefore involve an initial depolymerization step of the dextran chains by dextranases secreted from bacteria in the pig colon. The generated small fragments then serve as substrates for esterases and other hydrolases.

Animals↗

Blue dextran Sepharose chromatography of the tryptophanyl-tRNA synthetase of E. coli: a potential application for the purification of the enzyme.

E. coli tryptophanyl-tRNA synthetase can form a complex with Blue-dextran Sepharose, in the presence or in the absence of Mg++. In its absence, the complex is dissociated by either ATP or cognate tRNATrp. However, in the presence of Mg++, only tRNATrp can dissociate the complex whereas ATP has no effect. E. coli total tRNA or tRNAMet, at the same concentration, cannot displace the synthetase from the complex. It is suggested that the Blue-dextran binds to the synthetase through its tRNA binding domain. This hypothesis is supported by previous findings with polynucleotide phosphorylase showing that Blue-dextran Sepharose can be used in affinity chromatography to recognize a polynucleotide binding site of the protein. The selective elution by its cognate tRNA of Trp-tRNA synthetase bound to Blue-dextran Sepharose provides a rapid and efficient purification of the enzyme. Examples of other synthetases and nucleotidyl transferases are also discussed.

Amino Acyl-tRNA Synthetases↗

Blue-dextran--Sepharose affinity chromatography: recognition of a polynucleotide binding site of a protein.

Native Escherichia coli polynucleotide phosphorylase can be retained on blue-dextran--Sepharose. The bound enzyme cannot be displaced by its mononucleotide substrates such as ADP, UDP, CDP, GDP and IDP, but it is easily eluted by its polymeric substrates. Under identical conditions, lactate dehydrogenase, bound on blue-dextran--Sepharose, is not eluted by poly(I) but can be specifically displaced by NADH. On the other hand, the trypsinized polynucleotide phosphorylase, known to be an active enzyme which has lost its polynucleotide site, does not bind to the affinity column. The native polynucleotide phosphorylase can also be tightly bound to poly(U)--agarose and displaced from it only by high salt concentration. The trypsinized enzyme is not bound at all on poly(I)--AGAROSe. Moreover, the native enzyme linked on blue-dextran--Sepharose, remains active indicating a free access of nucleoside diphosphates to the active center. These results taken together show that the dye ligand is not inserted onto the mononucleotide binding site and suggest rather that it binds to the polynucleotide binding region. The implications of this study and the application of blue-dextran--Sepharose affinity chromatography to other proteins having affinity for nucleic acids are discussed.

Chromatography, Affinity↗

Effect of iron-dextran on lethality of Nigerian isolates of Campylobacter jejuni in mice.

Mice were orally and intragastically challenged with standard suspensions containing 1 x 10(9-10) Colony Forming Units (C.F.Us) per ml of strains "2" and "5" of Campylobacter jejuni isolated in Lagos. Another group of mice received the same amount of C. jejuni and 1pc iron-dextran which was incorporated into the bacterial suspension ad Mueller-Hinton broth. Two sets of control mice were included in the study. One set received only 0.2 ml of phosphate buffered saline while the second set received a mixture of killed C. jejuni and 1pc iron-dextran. A standard control organism (C. jejuni) NCTC strain 11168 was included in the study. Results presented show that infection of mice with only C. jejuni did not result in clinical diarrhoea or death of the animals as was also observed in the two sets of control. However, when the mixture of 1pc iron-dextran and C. jejuni was given, 15 (75pc) and 13 (65pc) of twenty mice each given by infant mouse infection and intragastic challenge respectively died. All the surviving animals developed diarrhoea. The difference in this result when compared with controls and those that received only C. jejuni was statistically significant (P less than 0.05). Incorporation of iron-dextran into C. jejuni suspension in the Mueller-Hinton broth enhanced virulence of the organism.

Animals↗

Reduction of low-density lipoproteins with dextran sulfate in patients with familial hypercholesterolemia.

A novel on-line system for the selective precipitation of low-density lipoprotein (LDL) using dextran sulfate has been devised and tested in four patients with heterozygous familial hypercholesterolemia (type II). The mean pretreatment serum cholesterol was 410 mg/dl. Plasma was generated by membrane filtration and LDL and VLDL (very-low-density lipoprotein) were completely precipitated with 10-35 mg% dextran sulfate (Mr 5,000) in the presence of 55 mM Ca2+. The precipitate was removed by filtration and the excess Ca2+ by dialysis. For 41 procedures the mean reduction of plasma solutes was LDL + VLDL 65%, HDL 23%, fibrinogen 19%, albumin 15%, IgG 20%, IgA 19%, IgM 24%. We conclude that dextran sulfate precipitation is an effective method for selective on-line removal of LDL from plasma.

Adult↗

Iron-dextran as a magnetic susceptibility contrast agent: flow-related contrast effects in the T2-weighted spin-echo MRI of normal rat and cat brain.

Iron-dextran (1 mmol Fe/kg) was used as an intravascular, paramagnetic contrast agent in rat and cat brain in conventional spin-echo T2-weighted (TR 2800/TE 100) 1H magnetic resonance imaging. The resulting images displayed differential decreases (30-50%) in intensity whose pattern was similar to that obtained with the superparamagnetic particulate iron oxide AMI-25 (0.18 mmol Fe/kg). Postcontrast images displayed improved anatomic detail, and contrast effects were observed to be greater in cortical and subcortical gray matter than in adjacent white matter. Intravenous injection of acetazolamide after administration of iron-dextran caused a small additional decrease in image intensity. Measurement of whole blood and plasma at 5 min postinjection of either contrast agent revealed significant increases in their volume magnetic susceptibilities. The contrast effect appears to be related to magnetic susceptibility changes brought about by the iron-dextran; it has both blood volume and blood flow components. The static model of magnetic susceptibility effects in brain capillaries is modified to include bolus flow of erythrocytes, providing a mechanism for the observed flow effects.

Acetazolamide↗

Suppression of liver uptake of orally fed liposomes by injection (i.p.) of dextran sulfate 500.

125Iodine labelled human immunoglobulin-G encapsulated liposomes were administered orally to rats. Distribution of radioactivity was checked in various tissues and in portal blood. The effect of dextran sulfate (DS 500,000 m. wt., liver blockade agent) injection (i.p.) on the liver uptake of liposomes and on the amount of liposomes appearing in the portal blood from the gastrointestinal tract have been studied. An increased amount of radioactivity was observed in the portal blood and the amount of radioactivity in the liver decreased appreciably after injection of dextran sulfate. In both the cases the action of dextran sulfate started 2 hours after injection and reached maximum at 12 hour, falling slightly at 24 hour.

Administration, Oral↗

Preparation and enzymatic properties of subtilisin Novo chemically attached to soluble DEAE-dextran and insoluble DEAE-sephadex.

Analogous soluble and insoluble derivatives of subtilisin Novo (EC 3.4.21.14) were prepared by coupling the enzyme to CNBr-activated DEAE-dextran and DEAE-Sephadex, respectively. The DEAE-dextran-subtilisin displayed pH optima and Km values for ester hydrolysis similar to subtilisin, whereas the pH versus activity profiles obtained with DEAE-Sephadex-subtilisin were shifter towards the alkaline pH region and the Km values were increased. Compared with subtilisin, DEAE-dextran-subtilisin showed a 40-65% reduction of kcat for hydrolysis of N-acetyl-L-tyrosine ethyl ester, p-tosyl-L-arginine methyl ester and benzyloxycarbonyl-glycyl-L-tyrosinamide and its maximum velocities for digestion of casein and clupein also amounted to 40-60% of the subtilisin values. With Deae-sephadex-subtilisin, in contrast, the maximum velocity of hydrolysis decreased to a greater extent for polypeptide substrates compared to ester substrates. The present results indicate that the chemical nature of a support can effect intrinsic properties of a matrix-bound enzyme in addition to the steric and diffusional effects usually observed with polymer-attached enzymes.

Caseins↗