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Pathomechanisms of dextran-induced anaphylactoid/anaphylactic reactions in man.

Immune complex-mediated (type III) anaphylaxis is shown to be the pathomechanism of severe dextran-induced anaphylactic reactions in man. Mild reactions may be either antibody-dependent or not. Patients with severe reactions have regularly high titers of preformed, circulating dextran-reactive antibodies and represent a small subpopulation of high responders to dextran. Upon infusion of clinical dextran, noxious immune complexes are formed, leading to mediator release and symptoms of anaphylaxis. Consequently, application of the hapten inhibition principle is recommended for prevention of such reactions.

Anaphylaxis↗

Distribution of 3H-dextran in two colonies of Wistar rats after intravenous injection.

The rate of elimination of 3H-dextran from the blood after intravenous administration was found to be considerably faster in rats which react to dextran with an anaphylactoid reaction than in rats which do not. Correspondingly, the rate of appearance of 3H-dextran in the anaphylactoid target organs such as the footpad was faster in reactive rats, approximately three times as much radioactivity being located in their footpads, 30 min after injection. This difference in distribution may reflect differences in the sensitivity of mast cells of the two rat colonies to dextran.

Anaphylaxis↗

Comparison of the anaphylactoid response induced in rats by castanospermine and dextran.

The plant alkaloid castanospermine (10 mg/kg or higher, i.p.; 400 mg/kg, p.o.) induced in some rat strains an anaphylactoid reaction similar to that induced by dextran, i.e. erythema and edema of the snout, ears and paws, for several hours after administration. 86% of the rats from a responsive strain responded to castanospermine while 79% responded to dextran. Rats which responded to castanospermine showed marked, but transient, tachyphylaxis to a second dose of castanospermine or dextran. Rats maintained on a complex-carbohydrate-free diet also responded to castanospermine, excluding the possibility that the effect was due to absorption of dextran-like, dietary, complex carbohydrates. These data raise the possibility that some apparent food allergies in man could be due to the presence in the diet of plant alkaloids with properties similar to those of castanospermine.

Anaphylaxis↗

Permeability studies with exogenous macromolecules: problems arising from the use of iodinated PVP and dextrans.

The permeability of the glomerular filtration barrier with respect to molecular size could best be studied by substances which are neither secreted nor reabsorbed and have a mean molecular weight of about 40,000--80,000 daltons. Uncharged molecules are preferred because the charge definitely influences the glomerular filtration. Several such substances are available; however, in most permeability studies labelled PVP, mainly 125I- or 131I-PVP, and dextrans have been applied. Gel filtration and binding studies with 125I-PVP have demonstrated that this substance should not be used because of unspecific binding of radioactive material. The application of dextran gives more reliable results. Disadvantages, however, include the large amounts which must be administered and some cases of intolerance, particularly in rats. Therefore, experiments with dextran seem feasible in some species but not in others. Ficoll, a synthetic polysucrose, is better tolerated than dextran but still causes allergic reactions in susceptible animals.

Animals↗

Synthesis and biological properties of antitumor-active conjugates of ADR with dextran.

Three kinds of polymeric adriamycin (ADR) conjugates of dextran were synthesized, namely a dextran-Gly-Leu-Gly-ADR (DGLGA) conjugate with a lysosomally degradable tripeptide spacer group, a dextran-Gly-Leu-Gly-ADR-galactosamine (DGLGA-Ga) conjugate with a targeting moiety of galactosamine on DGLGA, and a dextran-C6H10-ADR (DC6A) conjugate with a hexamethylen spacer group. The content of the ADR moiety in the polymeric-drug conjugate was about 3 mol%. Enzyme hydrolysis of DGLGA and DC6A was carried out by incubation with papain. The total amount of ADR released after 48 h was 43 mol% for DGLGA and less than 1 mol% for DC6A. In an in vitro cytotoxicity experiment, the DGLGA-Ga conjugate has higher cytotoxic efficacy than the other conjugates for incubation with Hep-3B cells and consequently, the capability of targeting hepatoma cells of the galactosamine residue was determined. In contrast, for the incubation with SiHa cells of these conjugates, there was no significant cytotoxicity effect. The in vivo cytotoxic efficacy of each conjugate (20 mg ADR equiv./kg) against CT-26 mice colon cells implanted subcutaneously in Balb-C mice was studied. The DGLGA conjugate generated the best therapeutic effect with the presence of long-term survival (LTS) at day 50 (2/6).

Animals↗

Dextran sulfate as a material for the preparation of a membrane for immunoisolation.

Bioartificial pancreas, in which the islets of Langerhans (islets) are enclosed in an artificial membrane to be protected from the host immune system, is expected to be a promising medical device to treat patients who suffer from insulin-dependent diabetes. Our strategy for preparation of a bioartificial pancreas involves utilizing a membrane including polymeric materials that can inhibit the complement. In our series of studies, we have examined interactions of various polyanions with the complement system to search for potential complement inhibitors. In this study, we concentrated our efforts to clarify the effects of dextran sulfate on the complement system. All of the dextran sulfates examined inhibited the complement activation through both classical and alternative pathways as previously reported. In addition to their inhibitory effects, a certain species of dextran sulfate (molecular mass 10 kDa, degree of sulfonation in a pyranose ring 1.99) specifically degraded C3 without complement activation and, thus, anaphylatoxins that trigger inflammatory reactions were not generated. These facts suggest that a membrane including dextran sulfate effectively protects the islet cells from humoral immunity in addition to not triggering inflammatory reactions. These properties of the membrane make it suitable for a bioratificial pancreas.

Bioartificial Organs↗

Permselectivity of the glomerular capillary wall. Studies of experimental glomerulonephritis in the rat using dextran sulfate.

To determine whether the increased filtration of serum proteins after glomerular injury is the consequence of altered electrostatic properties of the glomerular capillary wall, we measured fractional clearances of the anionic polymer, dextran sulfate, in nine Munich-Wistar rats in the early autologous phase of nephrotoxic serum nephritis (NSN). In agreement with previous studied from this laboratory, whole kidney and single nephron glomerular filtration rates were normal in NSN rats despite histological evidence of glomerular injury, and despite a marked reduction in the glomerular capillary ultrafiltration coefficient to approximately one-third of normal. In the companion study (9), it was shown that in NSN rats the mean fractional clearances of neutral dextrans over the range of effective molecular radii from 18 to 42 A were reduced, compared to normla. In contrast, in the present study the mean fractional clearances for dextran sulfate over the same range of molecular radii were significantly greater than those found previously for normal Munich-Wistar rats. The fractional clearance of dextran sulfate molecules of the same molecular radius as serum albumin (approximately 36 A) was increased markedly, from 0.015 +/- 0.005 (SEM) in nonnephritic controls to 0.24 +/- 0.03 in NSN (P less than 0.001). The sialoprotein content of glomeruli, estimated by the colloidal iron reaction, was reduced in NSN rats as compared to normal controls. It is concluded that the abnormal filtration of anionic serum proteins, such as albumin, seen in glomerulopathies is, at least in part, the consequence of loss of fixed negative charges from the glomerular capillary wall.

Animals↗

A prospective study of dextran-induced anaphylactoid reactions in 5745 patients.

A prospective study of dextran-induced anaphylactoid reactions (DIAR) in 5745 gynaecological and obstetric patients who received dextran 70 solution intravenously while undergoing major surgery revealed 8 patients who had Grade I or II reactions and 7 patients who had Grade III or IV reactions. The incidence of severe reactions was 1:821 patients treated. The overall incidence of reactions per patient treated was 1:383. One neonatal death followed a dextran-induced cardiac arrest in a woman about to undergo caesarean section. The risks of dextran 70 treatment exceeded the risks of thromboembolism in these patients.

Adult↗

A protective effect of glutathione-dextran macromolecular conjugates on acetaminophen-induced hepatotoxicity dependent on molecular size.

Glutathion (GSH) was covalently attached to dextrans with various molecular weights of 2, 5, 10, 40, and 70 kDa by the cyanogen bromide activation method. The conjugates obtained synthetically were white or pale yellowish powders containing 6-10% (w/w) of GSH. The average molecular weights of the conjugates were estimated to be larger and the molecular weight distribution was a little broader than that of each original dextran. The conjugates significantly stabilized GSH and liberated it gradually under physiological conditions (t1/2 = 0.99-1.6h). Mice depleted of GSH by treatment with buthionine sulfoximine, a potent inhibitor of gamma-glutamylcysteine synthetase, exhibited a significant increase in hepatic GSH level after intravenous injection of the conjugates. In mice given a hepatotoxic dose of acetaminophen, the survival rate increased progressively with coadministration of the conjugates, whereas a small improvement was found when free GSH was given. The conjugate of GSH attached to dextran with the molecular weight of 40 kDa exhibited the highest prophylactic effect on acetaminophen-induced hepatotoxicity in mice. The prolonged retention of the conjugates of larger molecular weight in the circulation would cause a higher hepatic accumulation. These results suggested that molecular size would be the most critical factor in the delivery of GSH, as a dextran conjugate, into the liver.

Acetaminophen↗

Tissue distribution of 111In-labeled uricase conjugated with charged dextrans and polyethylene glycol.

Uricase (UC) was conjugated with dextran, cationic diethylaminoethyl-dextran (DEAED), and anionic carboxymethyl-dextran (CMD) giving a molecular weight of 10000 by the periodate oxidation method. Their disposition characteristics were studied after intravenous injection (i.v.) in mice. Disposition of the conjugate with activated polyethylene glycol (PEG2) with a similar molecular weight was also studied for comparison. Tissue distribution of the 111In-labeled UC in these conjugates was evaluated by a tissue uptake clearance index calculated in terms of clearance. After i.v. injection, 111In-UC was slowly eliminated from the circulation and gradually accumulated in the liver, spleen, and kidney. Conjugation with neutral dextran slightly enhanced the uptake of 111In-UC by the liver and spleen, while PEG2 conjugation decreased the tissue uptake and resulted in extremely long plasma retention. On the other hand, DEAED and CMD conjugation resulted in significant enhancement and reduction of hepatic uptake, respectively. These results demonstrated that the pharmacokinetic behaviour of UC can be widely controlled by chemical modification with macromolecules having adequate physiochemical properties.

Animals↗

Biochemical and biopharmaceutical properties of macromolecular conjugates of uricase with dextran and polyethylene glycol.

Uricase (UC) was conjugated with dextran and polyethylene glycol and their biochemical and biopharmaceutical properties were studied. UC-dextran conjugates (UC-D) synthesized by four methods, periodate oxidation, cyanogen bromide, carbodiimide and cyanuric chloride largely retained the UC enzymatic activity depending on the extent to which they modified amino groups. The periodate oxidation method seemed best because it gave a conjugate with high yield and satisfactory activity retention. The conjugate of UC with activated polyethylene glycol (UC-PEG2) was also obtained with high yield but the remaining activity was somewhat lower than those of dextran conjugates at the same modification extent. UC-D and UC-PEG2 showed sustained enzymatic activity in plasma after intravenous injection to rats. The advantage of chemical modification of proteins, especially with dextran, by the periodate oxidation method for preparation of a protein-delivery system was thus suggested.

Animals↗

Comparison of hypertonic saline solutions and dextran in dialysis-induced hypotension.

The efficacy of three hypertonic saline solutions for treating dialysis-induced hypotension in a randomized, blinded, crossover clinical trial of 10 patients (a minimum of three cycles per solution) was compared. Dialysis-induced hypotension, defined as a decrease in systolic blood pressure of at least 10 mm Hg or systolic blood pressure less than 100 mm Hg, was treated with an iv bolus of either 10 mL of 23% saturated hypertonic saline, 30 mL of 7.5% hypertonic saline, or 30 mL of 7.5% saline with 6% dextran 70, each containing similar osmolar loads of 80, 80, and 100 mosM, respectively. All three solutions raised systolic blood pressure within 5 min (mean pretreatment systolic blood pressure, 87 mm Hg; mean posttreatment systolic blood pressure, 101 mm Hg; P < 0.05). The magnitude of the increase was greater with saturated hypertonic saline (15 mm Hg) and dextran 70 (17 mm Hg) compared with that with hypertonic saline (9 mm Hg; P < 0.05). At 10 min, dialysis-induced hypotension was less frequent with saturated hypertonic saline (incidence, 9%) compared with hypertonic saline (45%). Beyond 10 min, however, there was a trend toward a lower incidence of further dialysis-induced hypotension with dextran 70. There were no side effects. Given equal osmole loads, the more concentrated solution produced a greater increase in systolic blood pressure. The addition of an oncotic agent such as dextran may prolong the blood pressure response beyond 10 min. It was concluded that hypertonic saline solutions safely and effectively treat dialysis-induced hypotension.

Aged↗

Dextran penetration through nonkeratinized and keratinized epithelia in monkeys.

The purpose of this study was to determine if polysaccharide dextrans would pass through intact-nonkeratinized and induced-keratinized sulcular epithelia in monkeys. Dextran penetration through normally keratinized oral gingival epithelium also was evaluated in the same gingival specimens. Each of three Rhesus monkeys received a thorough prophylaxis 1 week prior to the experiment. During this week, the monkeys also received daily IV injections of Achromycin. After the antibiotic treatment, the teeth were polished and cleaned with a rubber cup using prophylactic paste for 2 consecutive months, as follows: (1) the right maxillary and mandibular teeth received daily prophylaxes on weekdays and (2) the left maxillary and mandibular teeth received one prophylaxis weekly. These frequencies of plaque removal on one-half of the mouth maintained clinically healthy gingiva and produced keratinization of the sulcular epithelium. At the end of the 2-month prophylaxes, a 5% solution of dextrans derived from Leuconostoc mesenteroides was applied topically to the gingiva once daily for 3 consecutive weeks. During this time, the monkeys continued having dental prophylaxes following the previous time schedule. The study showed that induced-keratinized sulcular epithelium as well as normally keratinized oral gingival epithelium resisted penetration of dextrans, whereas intact-nonkeratinized sulcular epithelium apparently lacked a surface layer resistant to penetration.

Administration, Topical↗

Prevention of intraperitoneal adhesions by dextran. Hydrocortisone and chymotrypsin. An experimental study.

The purpose of an experimental study in guineapigs was to prevent adhesion formation in the intra-abdominal space by simultaneous intraperitoneal infusion of hydrocortisone, dextran and chymotrypsin. An examination made three weeks after the operation revealed a highly significant (p less than 0.001) difference in favour of the dextran, dextran-chymotrypsin and dextran-chymotrypsin-hydrocortisone groups when compared with the NaC1 and control groups.

Animals↗

Safety of enoxaparin and dextran-70 in the prevention of venous thromboembolism in digestive surgery. A play-the-winner-designed study.

A total of 327 patients were included in a play-the-winner (PTW)-designed study comparing the safety of prophylaxis with enoxaparin and dextran-70 in patients undergoing digestive surgery. In a PTW-designed study the treatment of any next patient will depend on the outcome of the previous one. If successful, the next patient will receive the same treatment. Excessive bleeding, on the basis of specified criteria, severe adverse effects, or occurrence of clinically detected venous thromboembolism was classified as failure. The PTW design allocates most patients to the superior treatment. In this study 200 patients were given enoxaparin and 127 dextran-70. The success rate was 83% in the enoxaparin group and 74.8% in the dextran-70 group (p = 0.05). The survival analysis of 'Number of patients before change in treatment' shows a significant difference in favour of enoxaparin (p = 0.05). Enoxaparin seems to be superior to dextran-70 as a prophylaxis in digestive surgery. The PTW model is a suitable design in such studies.

Adolescent↗

Hyperoncotic dextran and systemic aprotinin in necrotizing rodent pancreatitis.

BACKGROUND: Dextrans improve pancreatic microcirculation in acute experimental pancreatitis. They could therefore facilitate the transport of a protease inhibitor to ischemic areas of tissue injury and be of additional benefit. METHODS: To compare the effects of dextrans with and without aprotinin, necrotizing pancreatitis was induced in 33 male dextran-resistant Wistar rats by intraductal infusion of low-dose glycodeoxycholic acid (10 mmol/l) followed by intravenous cerulein (5 micrograms/kg/h) for 6 h. Three and four hours after the start of the cerulein infusion the animals received infusions of either Ringer's lactate (RL) (12 ml/kg), 70,000 Da dextran (10%) (DEX-70) (4 ml/kg) alone, or DEX-70 (4 ml/kg) with aprotinin (5000 IU/kg) (DEX-70/A). RESULTS: The death rate was 60% within 9 h in the RL group (6 of 10) but only 10% in the DEX-70 group (1 of 10) (p < 0.03; Fisher's exact test) and 23% in the DEX-70/A group (3 of 13). Histomorphometry demonstrated a significant reduction of acinar necrosis in both treatment groups compared with control animals (p < 0.014; t test). Total amounts of trypsinogen activation peptides (TAP) in ascites were also significantly lower in these groups (p < 0.05; t test). CONCLUSIONS: DEX-70 given 3 h and 4 h after induction of pancreatitis significantly reduced the levels of TAP, limited acinar necrosis, and improved survival rate in acute necrotizing rodent pancreatitis. There was no additional benefit from the combination with aprotinin.

Acute Disease↗

99mTc-dextran-antibody conjugates. Labelling procedures.

Dextran forms stable chelates with 99mTc, a radionuclide with ideal properties for planar scintigraphic and tomographic imaging. This study investigates some of the factors of importance to the formation of 99mTc-dextran. The complex was used for the technetium labelling of a monoclonal antibody. Two radiolabelling methods were studied: direct dextran labelling with the reductant dissolved in HCI and labelling via a weak 'transfer' chelator (tartaric acid) with the reductant dissolved in ethanol. Different conditions during the labelling reaction were studied. Finally, dextran was coupled to a monoclonal anticytokeratin antibody and the conjugate was subsequently radiolabelled with 99mTc. Gel filtration (GFR) and thin layer chromatography (TLC) were compared as methods for estimation of the labelling efficiency. When using 10-500 microM of ligand, 5-100 microM SnCl2 with 10-500 MBq of technetium at pH 7 incubated for 10-15 min, the radiolabelling seemed optimal (70-75% labelling efficiency). It was found that 100 microM tartaric acid used as a weak intermediate chelator with SnCl2 dissolved in ethanol improved the reproducibility of the labelling. The labelling efficiency was not affected by either the presence of oxygen or the addition of an oxygen scavenger during the labelling incubation. In general, TLC showed higher labelling efficiencies than GFR, indicating inadequate separation of the different moieties.

Antibodies, Monoclonal↗

Production of antibodies to dextran using liposome as adjuvant.

The kinetics and nature of the immune response to dextran-BSA entrapped into liposomes was studied in rabbit. The antibody titer in the secondary immunization was found to be higher as compared to that in the primary response. In the primary response antibodies were of both IgG and IgM type but following secondary immunization the IgG level was increased. The conjugate entrapped into liposomes could establish an immunological memory for dextran. In order to eliminate the carrier effect of BSA, dextran was either entrapped or coupled to liposome and the immune response was studied in mice. The results revealed that dextran entrapped into liposomes or coupled to liposome surface induced IgM type immune response and antibody titer did not increase on secondary immunization.

Adjuvants, Immunologic↗