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PubMed1995

Characterization of the swelling-induced alkalinization of endocytotic vesicles in fluorescein isothiocyanate-dextran-loaded rat hepatocytes.

Short-term cultivated rat hepatocytes were allowed to endocytose fluorescein isothiocyanate (FITC)-coupled dextran and the apparent vesicular pH (pHves) was measured by single-cell fluorescence. After 2 h of exposure to FITC-dextran, the apparent pH in the vesicular compartments accessible to endocytosed FITC-dextran was 6.01 +/- 0.05 (n = 39) in normo-osmotic media. Hypo-osmotic exposure increased, whereas hyper-osmotic exposure decreased apparent pHves. by 0.18 +/- 0.02 (n = 26) and 0.12 +/- 0.01 (n = 23) respectively. Incubation of the cells with unlabelled dextran for 2h before a 2-h FITC-dextran exposure had no effect on apparent pHves and its osmosensitivity. When, however, hepatocytes were exposed to unlabelled dextran for 5 h after a 2 h exposure to FITC-dextran, in order to allow transport of endocytosed FITC-dextran to late endocytotic/lysosomal compartments, apparent pHves. decreased to 5.38 +/- 0.04 (n = 12) and the apparent pH in the vesicular compartment containing the dye was no longer sensitive to aniso-osmotic exposure. These findings indicate that the osomosensitivity of pHves. is apparently restricted to early endocytotic compartments. Aniso-osmotic regulation of apparent pHves. in freshly FITC-loaded hepatocytes was not accompanied by aniso-osmolarity-induced changes of the cytosolic free calcium concentration, and neither vasopressin nor extracellular ATP, which provoked a marked Ca2+ signal, affected apparent pHves. Dibutyryl-cyclic AMP (cAMP) or vanadate (0.5 mmol/l) were without effect on apparent pHves. and its osmosensitivity. However, pertussis toxin-treatment or genistein (but not daidzein) or the erbstatin analogue methyl 2,5-dihydroxycinnamate fully abolished the osmo-sensitivity of apparent pHves., but did not affect apparent pHves. It is concluded that regulation of pHves. by cell volume occurs in early endocytotic compartments, but probably not in lysosomes, and is mediated by a G-protein and tyrosine kinase-dependent, but Ca2+- and cAMP-independent mechanism.

Animals↗

PubMed1998

The low molecular weight Dextran 40 inhibits the adhesion of T lymphocytes to endothelial cells.

Dextrans are complex colloidal macromolecules widely used as haemorrheologic substances and anti-thrombotic agents. Here we describe a novel function of Dextran 40 by demonstrating an inhibition of T lymphocyte adhesion to endothelial cells (EC). We applied an established microassay in which constitutive and tumour necrosis factor-alpha (TNF-alpha)-induced binding of mouse T lymphoma cells (TK-1) to mouse endothelioma (eEND.2) cells is mediated by the interaction of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) on EC with their counter-receptors the LFA-1 heterodimer (CD11a/CD18) and VLA-4 on T cells. Dextran 40 in therapeutically achievable levels (2-32 mg/ml) reduced both constitutive and TNF-alpha-stimulated TK-1 adhesion to eEND.2. Selective preincubation of eEND.2 or TK-1 revealed that Dextran 40 acted exclusively on the T cells. To explore further the mechanisms by which Dextran 40 interfered with TK-1 adhesion, their LFA-1 and VLA-4 expression was analysed by FACS. The surface expression levels of neither receptor were affected by Dextran 40. However, confocal microscopy revealed that Dextran 40 interfered with the activation-dependent capping and clustering of LFA-1 and VLA-4 on the surface of TK-1. We conclude that Dextran 40 inhibits the capacity of TK-1 T cells to adhere to eEND.2 endothelial cells and thus may be useful for therapeutic intervention in diseases associated with enhanced T lymphocyte binding to microvascular endothelium.

Animals↗

PubMed2000

Effects of hypertonic saline-dextran solution on regional blood flow and thrombogenicity in PTFE grafts in the vena cava of the rabbit.

OBJECTIVES: to study the effects of hypervolaemic haemodilution with hypertonic saline-dextran solution (HSD) on regional blood flow and thrombogenicity of small diameter polytetrafluoroethylene (PTFE) grafts. DESIGN: blood flow in rabbit aorta, vena cava and femoral, renal and ear arteries was determined in five groups: controls, isovolaemic haemodilution with dextran-70 (10 ml/kg body weight (b.w. )), hypervolaemic haemodilution (10 ml/kg b.w.) with either dextran-70, 7.5% NaCl or a combination of dextran and NaCl (HSD). In a second series PTFE grafts were inserted into the vena cava of rabbits treated with hypervolaemic haemodilution with dextran, hypertonic saline or HSD and examined after two days. RESULTS: blood flow increased in aorta, vena cava and femoral artery after haemodilution. The increase was transient in animals treated with hypertonic NaCl alone but sustained in the dextran-70 groups. The grafts from animals treated with hypertonic saline alone had a lower thrombus mass and higher blood flow compared to those from rabbits haemodiluted with dextran-70 only, indicating that both dextran and NaCl have antithrombotic effects. Superior results were obtained with HSD solution. CONCLUSIONS: HSD solution has a strong flow-promoting action in several vascular beds and beneficial effects on the patency of small diameter vessel grafts.

Animals↗

PubMed2002

[Epithelial damage of corneal grafts after prolonged storage in dextran-containing organ culture medium - a prospective study].

BACKGROUND: High-molecular dextran added to organ culture medium is used for deswelling of corneal grafts before surgery. As we had the impression to have more often epithelial desquamation if storage time in dextran-containing medium was longer than 1 day, we investigated this problem in a pilot study. METHODS: We examined prospectively the effect of the storage period on the graft epithelium one day after penetrating keratoplasty in 137 corneal grafts which were stored in dextran-containing storage medium (dextran T500 6 %). 88 corneal grafts were stored for 1 - 2 days (12 - 48 hours) and 49 corneal grafts were stored for 3 - 4 days (60 - 96 hours). Before deswelling, all 137 grafts had been stored 10 - 14 days in dextran-free organ culture medium. Postoperative epithelial defects observed 1 day after surgery were classified as margin and central erosions of the graft. RESULTS: With a storage period in dextran-containing organ culture medium of 1 - 2 days statistically significantly less epithelial defects were observed in comparison to a longer storage period of 3 - 4 days (33 % vs. 57 %, p = 0,005). We found a statistically high significant correlation between storage time in dextran-containing organ culture medium and central erosions (p = 0,001), whereas margin erosions were observed after 1 - 2 days as well as after 3-4 days (p = 0,2). CONCLUSION: Our data show that early postoperative epithelial stability of corneal grafts depends on the storage period in dextran-containing organ culture medium.

Corneal Diseases↗

PubMed1999

Polymer structure and solubility of deoxyhemoglobin S in the presence of high concentrations of volume-excluding 70-kDa dextran. Effects of non-s hemoglobins and inhibitors.

Earlier observations indicated that volume exclusion by admixed non-hemoglobin macromolecules lowered the polymer solubility ("Csat") of deoxyhemoglobin (Hb) S, presumably by increasing its activity. In view of the potential usefulness of these observations for in vitro studies of sickling-related polymerization, we examined the ultrastructure, solubility behavior, and phase distributions of deoxygenated mixtures of Hb S with 70-kDa dextran, a relatively inert, low ionic strength space-filling macromolecule. Increasing admixture of dextran progressively lowered the Csat of deoxyHb S. With 12 g/dl dextran, a 5-fold decrease in apparent Csat ("dextran-Csat") was obtained together with acceptable sensitivity and proportionality with the standard Csat when assessing the effects of non-S Hb admixtures (A, C, and F) or polymerization inhibitors (alkylureas or phenylalanine). The volume fraction of dextran excluding Hb was 70-75% of total deoxyHb-dextran (12 g/dl) volumes. Electron microscopy showed polymer fibers and fiber-to-crystal transitions indistinguishable from those formed without dextran. Thus when Hb quantities are limited, as with genetically engineered recombinant Hbs or transgenic sickle mice, the dextran-Csat provides convenient and reliable screening of effects of Hb S modifications on polymerization under near-physiological conditions, avoiding problems of high ionic strength.

Anemia, Sickle Cell↗

PubMed1983

Mechanism of unresponsiveness to the alpha 1-6 epitope of dextran B512 in a C57BL substrain.

C57BL/10ScCr mice are low responders to the alpha 1-6 epitope of dextran B512, although other C57BL mice are high responders. Both thymus-independent and thymus-dependent forms of dextran failed to induce an immune response in C57BL/10ScCr mice, but dextran functioned as a good carrier for antihapten responses in this strain. Dextran is a potent polyclonal B cell activator for cells from C57BL/10ScCr mice, although such cells are not activated by LPS. The C57BL/10ScCr mice possess the Igh-V gene coding for antibodies against dextran and the antidextran antibodies induced in (A X C57BL/10ScCr)F1 hybrids share an idiotype with antidextran antibodies produced in C57BL/10 mice. Bone marrow cells from C57BL/10ScCr mice do not respond to dextran when transferred into lethally irradiated C57BL/10 mice and C57BL/10 cells transferred into C57BL/10ScCr mice give a strong antidextran response. Thus, B cells having both the Igh-V gene coding for antibodies against dextran and activation receptors for dextran cannot be activated into antibody synthesis against any form of this immunogen. This determinant specific immunodeficiency suggests the existence of as yet unknown regulatory influences on Igh-V gene expression or B cell activation.

Animals↗

PubMed2003

Effect of dextran-induced changes in refractive index and aggregation on optical properties of whole blood.

The purpose of the present study is to investigate systematically the mechanisms of alterations in the optical properties of whole blood immersed in the biocompatible agent dextran, and to define the optimal concentration of dextrans required for blood optical clearing in order to enhance the capability of light penetration depth for optical imaging applications. In the experiments, dextrans with different molecular weights and various concentrations were employed and investigated by the use of the optical coherence tomography technique. Changes in light attenuation, refractive index and aggregation properties of blood immersed in dextrans were studied. It was concluded from the results that the mechanisms for blood optical clearing are characteristic of the types of dextrans employed, their concentrations and the application stages. Among the substances applied, Dx500 at a concentration at 0.5 g dl(-1) gives the best result in improving light penetration depth through the blood. The increase of light transmission at the beginning of the addition of dextrans is mainly attributed to refractive index matching between the scattering centres and the ground matter. Thereafter, the transmission change is probably due to a dextran-induced aggregation-disaggregation effect. Overall, light scattering in the blood could be effectively reduced by the application of dextrans. It represents a promising approach to increasing the imaging depth for in vivo optical imaging of biological tissue, for example optical coherence tomography.

Adult↗

PubMed2024

Mannose receptor (MRC1) mediates uptake of dextran by bone marrow-derived macrophages.

Macrophages survey their environment using receptor-mediated endocytosis and pinocytosis. Receptor-mediated endocytosis allows internalization of specific ligands, whereas pinocytosis nonselectively internalizes extracellular fluids and solutes. CRISPR/Cas9 whole-genome screens were used to identify genes regulating constitutive and growth factor-stimulated dextran uptake in murine bone marrow-derived macrophages (BMDM). The mannose receptor c-type 1 (MRC1/CD206) was a top hit in the screen. Targeted gene disruptions of Mrc1 reduced dextran uptake but had little effect on fluid-phase uptake of Lucifer yellow. Other screen hits also differentially affected the uptake of dextran and Lucifer yellow, indicating internalization by separate mechanisms. Visualization of dextran and Lucifer yellow uptake by microscopy showed enrichment of dextran in small puncta, which was inhibitable by mannan, a ligand of MRC1. In contrast, Lucifer yellow predominantly was internalized in larger macropinosomes. In addition, IL4-treated BMDMs internalized more dextran than untreated BMDM correlating with increased MRC1 expression. Therefore, dextran is not an effective marker for pinocytosis in BMDMs since it is internalized by receptor-mediated process. Numerous genes that regulate dextran internalization in primary murine macrophages were identified in the whole-genome screens, which can inform understanding of the regulation of MRC1 expression and MRC1-mediated uptake in macrophages.

Animals↗

PubMed2000

The effect of In vitro hemodilution with gelatin, dextran, hydroxyethyl starch, or Ringer's solution on Thrombelastograph.

UNLABELLED: To determine the effects of progressive in vitro hemodilution with various plasma substitutes on whole blood coagulation, blood was obtained from six healthy volunteers. The Thrombelastograph((R)) (TEG; Haemoscope Corp., Morton Grove, IL) variables of reaction time, coagulation time, maximum amplitude, and growth angle were determined. The following plasma substitutes were tested: two gelatin solutions (4% gelatin polysuccinate and 5.5% oxypolygelatin); two dextrans (10% dextran 40 and 6% dextran 60); and five hydroxyethyl starch (HES) preparations (6% HES 70/0.5-0.55, 3% HES 200/0.5, 6% HES 200/0.5, 10% HES 200/0.5, and 6% HES 450/0.7). Ringer's solution was also tested to assist analyzing the intrinsic effect of colloid molecules on blood coagulation. The dilution ratios of citrated blood volume to plasma substitute volume were 10:2, 10:4, and 10:10. Blood coagulation was affected by plasma substitutes when the dilution ratios of citrated blood volume to colloid solution volume were 10:4 and 10:10. TEG variables did not change significantly after in vitro hemodilution with lactated Ringer's solution. The tested gelatin solutions showed less intrinsic effect on blood coagulation than other plasma substitutes. All HES preparations showed similar intrinsic effects as 6% dextran 60. The plasma substitute of 10% dextran 40 had the strongest effect on coagulation. Coagulation time was the most markedly affected TEG variable. Blood coagulation may be compromised when the dilution ratio of blood volume to colloid solution volume is >10:4. Whereas gelatin solutions have less intrinsic effect on blood coagulation, 10% dextran 40 has the strongest effect on coagulation. IMPLICATIONS: Blood coagulation may be compromised when the dilution ratio of blood volume to colloid solution volume is >10:4. Whereas gelatin solutions have less intrinsic effect on blood coagulation than hydroxyethyl starch or dextran, 10% dextran 40 has the strongest effect on coagulation.

Blood Coagulation↗

PubMed1990

Ringer's acetate and dextran-70 with or without hypertonic saline in endotoxin-induced shock in pigs.

The effects of Ringer's acetate, 6% dextran-70, 7.5% NaCl, and the combination of 7.5% NaCl and dextran-70 were tested in resuscitation from endotoxin shock induced by continuous iv infusion of Escherichia coli endotoxin in pigs. After about 3 h, a reproducible shock state was achieved and treatment was started, governed by the left atrial pressure. The hypertonic solutions (7.5% NaCl and 7.5% NaCl in dextran-70) did not show any overall advantages over the isotonic solutions (Ringer's acetate and dextran-70). Only transient beneficial hemodynamic effects lasting less than 30 min after infusion were seen. When dextran-70 was administered, cardiovascular function was markedly improved and oxygen delivery (DO2) and survival were significantly higher compared with the crystalloid groups (Ringer's acetate and 7.5% NaCl). Administration of large amounts of Ringer's acetate resulted in an immediate deterioration of pulmonary function. It was difficult to elevate left atrial pressure or even to keep it at baseline level, and cardiac index was only transiently increased. The overall result was a deterioration of DO2 and poor survival compared with the dextran-70 treated pigs. We conclude that dextran-70 is superior to Ringer's acetate in resuscitation from endotoxin-induced shock in pigs. Furthermore, we found no role for the use of hypertonic saline, alone or in combination with dextran, in the treatment of this type of prolonged endotoxin shock.

Animals↗

PubMed1991

Dose response characteristics of hypertonic saline dextran solutions.

In an effort to find the best hypertonic saline-dextran solution (HSD) for prehospital use, 33 chronically catheterized sheep were bled using a fixed pressure shock model (50 mm Hg x 2 hours) and resuscitated with 4 ml/kg of HSD solution (2-minute bolus). In the first set of experiments colloid was varied and sodium chloride was held constant, as 7.5% NaCl was paired with either 0%, 6%, or 12% dextran 70. A dose-response relationship existed, with cardiac output increasing 20% with each sequential dextran 70 concentration. Mean arterial blood pressure was higher in animals that were resuscitated with either the 7.5% NaCl/6% dextran 70 or 7.5% NaCl/12% dextran 70 solution (p less than 0.05). Using the optimal dextran 70 concentration from the first set of experiments (i.e., 12%), solute was varied in a second set of experiments comparing 0.9%, 3.8%, 7.5%, or 10% NaCl/12% dextran 70. Again, dose-response features were demonstrated, as cardiac output increased as a function of NaCl concentration. However, this response plateaued with the 7.5% NaCl concentration and no advantage was obtained by increasing the NaCl concentration to 10%. We conclude that a 4-ml/kg bolus of 7.5% NaCl/12% dextran 70 solution may be a more effective form of therapy than those previously evaluated. This new solution is now being included in our ongoing clinical trials.

Animals↗

PubMed1980

Effects of molecular weight of dextran on the adherence of Streptococcus sanguis to damaged heart valves.

Dextran-producing streptococci such as Streptococcus sanguis are the organisms most frequently associated with infective endocarditis in humans. A series of experiments was designed to study how the molecular weight of dextrans affects the adherence of an endocarditis strain of S. sanguis to canine heart valves covered with platelets and fibrin. The data indicated that this adherence was dependent on dextrans of high molecular weight, such as dextran T-2000 or glucans isolated from S. sanguis or S. mutans. The adherence properties of the strain studied were not modified by prior exposure of the bacterial cells of valve leaflets to high-molecular-weight dextrans. Preexposure of bacterial cells or valve leaflets to low-molecular-weight dextrans decreased their adherence. Low-molecular-weight dextrans interfered with adherence of dextran-positive strains to damaged heart valves.

Animals↗

PubMed1978

Blood replacement in dogs by dextran-hemoglobin.

Exchange transfusions in dogs were performed with a solution of either dextran or a covalent complex between dextran and human hemoglobin. Dogs transfused with dextran alone died when their hematocrit was lowered to 6-10%. Dogs transfused with dextran-hemoglobin complex, however, survived a reduction of their hematocrit to 2% or below. In the latter animals, the dextran-hemoglobin complex disappeared from the circulation with an average half-life of 2.4 days. Correcting for oxidation of the hemoglobin moiety to methemoglobin, the half-life of functional unoxidized dextran-hemoglobin in the circulation was 1.9 days. In compensation for the loss of dextran-hemoglobin, vigorous erythropoiesis was observed at a rate of close to 5% hematocrit per day over the first 2 days following the exchange transfusion. As a result, the total hemoglobin concentration in blood was maintained at 5-6% during this period, and the animals went on to complete recovery in room air without the need for further transfusion with dextran-hemoglobin.

Animals↗

PubMed1985

Dextran and capillary filtration coefficient in cat hindlimb.

To investigate the possible mechanisms through which dextran modifies capillary filtration coefficient (CFC), the effects of perfusion with a protein-free dextran solution were compared with those of perfusion with a Ringerlike solution. With the use of the isolated cat hindlimb, CFC was measured during perfusion at constant flow with three solutions, a control blood-albumin mixture, a Ringerlike solution called dialysate, and 3.7 g/dl dextran dissolved in dialysate. The solutions were warmed to 37-38 degrees C, bubbled with 95% O2-5% CO2, and contained 0.015 g/dl or more papaverine. CFC was calculated from the rate of limb weight gain following a step increase in venous pressure. Dextran perfusion increased CFC to 2.0 +/- 0.2 (SD, n = 8) times control, which was significantly less (P less than 0.001) than 3.1 +/- 0.6 (n = 8) times control previously reported for dialysate perfusion. The difference between the measured viscosity of dextran (1.35 cP) and dialysate (0.72) could account for this reduction. However, when a dialysate perfusion followed a dextran perfusion, CFC only increased to 2.3 +/- 0.4 (n = 8) times control. This value is also significantly less (P less than 0.01) than 3.1. This observation suggests 1) that dextran is retained within the transcapillary channel and 2) that dextran reduces CFC mainly by partially blocking the transcapillary channel rather than by increasing viscosity.

Animals↗

PubMed1983

Canine renal vascular response to hyperoncotic dextran in kidneys with or without glomerular filtration.

The effect of intrarenal arterial infusion of hyperoncotic dextran on renal hemodynamics and excretion was studied in anesthetized dogs. To examine the role of glomerular filtration and tubular flow in the hemodynamic response, several kidney models were employed. Nonfiltering kidneys (NFK) were produced by combined ischemia and ureteral obstruction (UO). Additionally, kidneys with only UO and a lack of filtration as well as kidneys with only ischemia and glomerular filtration were studied. Renal blood flow in normal kidneys was increased by hyperoncotic dextran from 357 +/- 47 to 486 +/- 65 ml X min-1 X 100 g-1, with a corresponding decrease in renal vascular resistance. Ischemic kidneys responded likewise to the dextran infusion, increasing renal blood flow from 261 +/- 31 to 339 +/- 29 ml X min-1 X 100 g-1. Glomerular filtration rate was reduced by the dextran infusion from 80.1 +/- 7.9 to 60.7 +/- 6.6 in normal kidneys and from 31.8 +/- 9.6 to 20.2 +/- 5.8 ml X min-1 X 100 g-1 in ischemic kidneys. Urine flow and sodium excretion were also reduced in these kidneys. In contrast, both NFK and UO, which lacked filtration and tubular flow, did not vasodilate in response to dextran. Renal blood flow remained unchanged from control values (NFK: 146 +/- 6, UO: 111 +/- 22 ml X min-1 X 100 g-1) in these kidneys. These experiments show that the renal vascular response to hyperoncotic dextran is not due to a change in blood volume or viscosity nor to a direct pharmacologic action of dextran. The most likely explanation is that hyperoncotic dextran alters tubuloglomerular feedback control of renal vascular resistance by decreasing filtration and altering tubular flow and/or composition. However, the involvement of another intrarenal vasodilatory system cannot be discounted.

Animals↗

PubMed2003

Effect of adsorbent of Riposorber, a cellulose microparticle with immobilized dextran sulfate, on the serum complement system.

Abstract-Apheresis. using columns of cellulose microparticles with immobilized dextran sulfate, Riposorber, has been applied to treatment of patients with various diseases, such as hypercholesterolemia and systemic lupus erythematosus. Unfortunately, it has been reported that the apheresis activates the complement system. It might exert unpleasant side effects on patients during lifelong treatment. In this study, the interaction of the serum complement system with cellulose microparticles with immobilized dextran sulfate and its components, nontreated cellulose microparticles and dextran sulfate, were examined in vitro to get some ideas for development of an extracorporeal apparatus which does not give any serious damage to patient blood. The cellulose microparticles with immobilized dextran sulfate reduces both the CH50 and the ACH50. Decrease in CH50 is not due to the classical pathway activation, but to adsorption of C2 or Cl components including Clq. The alternative pathway was not activated by the addition of the dextran sulfate alone to serum, but the addition of non-treated cellulose microparticles to serum activated complement. Form these, decrease in ACH50 is not caused by dextran sulfate on the microparticles, but by the hydroxyl groups of the cellulose microparticles that is the core of the column. For prevention of complement activation, hydroxyl groups remaining after dextran sulfate immobilization should be blocked by further treatment with a reagent that reacts with them, or else dextran sulfate might be immobilized on particles without nucleophiles such as hydroxyl or amino groups.

Cellulose↗

PubMed1978

Bacterial adherence in the pathogenesis of endocarditis. Interaction of bacterial dextran, platelets, and fibrin.

The role of dextran in the pathogenesis of bacterial endocarditis was investigated by studying the adherence of dextran producing oral streptococci to the constituents of nonbacterial thrombotic endocarditis (NBTE) in vitro and in vivo. The adherence of Streptococcus sanguis to fibrin and platelets was determined in an in vitro assay system simulating nonbacterial thrombotic endocarditis. Adherence was increased when the organisms were grown in sucrose-supplemented media (adherence ratio X 10(4), 177 +/- 6 in 5% sucrose vs. 140 +/- 7 in 0.5% sucrose, P less than 0.001), and decreased by incubating the organisms in dextranase (adherence ratio X 10(4), 117 +/- 16, P less than 0.001), an effect which was nullified by heat inactivating this enzyme (adherence ratio X 10(4), 192 +/- 7, P less than 0.001). The amount of dextran produced in broth by three different oral streptococci correlated directly with the adherence observed to fibrin and a fibrin-platelet matrix in vitro (P less than 0.001). These organisms adhered more readily to a fibrin-platelet matrix than to fibrin alone (adherence ratio X 10(4), 455 +/- 30 vs. 177 +/- 6, respectively, P less than 0.001). The role of dextran formation was also examined in vivo in rabbits with preexisting NBTE. After injection of 10(7) S. sanguis, 12 of 17 animals developed endocarditis. In contrast, when the organisms were pretreated with dextranase (an enzyme that removes dextran from the bacterial cell surface), the same inoculum resulted in endocarditis in only 5 of 19 animals (P less than 0.05). In addition, a fresh strain of S. sanguis that produced high levels of dextran (1,220 +/- 50 microgram/ml) and adhered avidly to fibrin (adherence ratio X 10(4), 220 +/- 11) produced endocarditis in 12 of 18 rabbits after injection of 10(7) organisms. Another isolate of the same strain that had been passed repeatedly in the laboratory produced less dextran (400 +/- 30 microgram/ml), adhered poorly to fibrin (adherence ratio X 10(4), 140 +/- 7), and produced endocarditis in only 3 of 14 rabbits under identical conditions (P less than 0.05). This study demonstrates that dextran production is important in the adherence of oral streptococci to the constituents of NBTE and may play a role in the pathogenesis of bacterial endocarditis by oral streptococci.

Animals↗

PubMed2002

The effect of hypertonic saline dextran solutions on hypoxic pulmonary vasoconstriction in anaesthetised piglets.

Hypoxic pulmonary vasoconstriction (HPV) is a regulatory mechanism by which blood is diverted from poorly ventilated to better ventilated areas of the lung. The aim of the present study was to assess the extent to which hypertonic saline dextran and dextran solutions modify the magnitude of HPV during isovolumic haemodilution in intact acutely instrumented piglets. Eighteen large white piglets were anesthetised and assigned to two groups. Mean pulmonary arterial pressure (PAP) and cardiac output (Q), systemic arterial pressure and left arterial pressure (LAP) were measured. A decrease in Q was obtained by reducing venous return. This enabled measurement of transpulmonary pressures (mean PAP minus LAP) at four levels of Q in hyperoxia (inspiratory oxygen fraction (FiO2)=0.4) then in hypoxia (Fi,O2=0.1) in the two groups before blood soustraction (10 mL x kg(-1)) and after loading with sodium chloride (NaCl) 7.5% and dextran 6% or with dextran 6% alone. Dextran alone led to a decrease in mean PAP-LAP/Q values, and NaCl with dextran was associated with a significant shift of mean PAP-LAP/Q plots to higher pressures in hypoxia. Hypertonic saline dextran solution, as replacement fluid in isovolaemic haemodilution increased the magnitude of hypoxic pulmonary vasoconstriction, whereas dextran solution reduced it.

Anesthesia, Inhalation↗