Dextran Mw Research Articles

Influence of serum level, cell line, flow type and viscosity on flow-induced lysis of suspended mammalian cells

An investigation was conducted of the parametric dependence of cell lysis observed when mammalian cells growing in suspension are subjected intermittently to intense hydrodynamic forces. Two flow devices were tested: one consisting of a sudden contraction into a short length of capillary tubing, in which turbulent flow is obtained, and another consisting of a smoothly converging and diverging tube, in which laminar flow is obtained. Changes in the cell line and the serum level in which the cells were grown and subjected to flow trauma both affected the specific lysis rate (fraction of cells lysed per pass through the flow device) in the turbulent flow device. The threshold value of the average wall shear stress level was approximately the same in the turbulent and laminar flow devices (1500–1800 dyn/cm2). Increasing the viscosity of the medium with 70,000 MW dextran had no effect on the specific lysis rate in either flow device.

Leukocyte phagocytosis and alterations in microvascular integrity elicited by FITC-dextran 150 and epi-illumination in the microcirculation of the hamster cheek pouch

Fluorescein-labeled dextran MW 150K (FITC-Dx 150) is commonly utilized as a macromolecular fluorochrome in inflammatory studies. We examined the influence of FITC-Dx 150 on leukocyte activity as assessed by adherence to cheek pouch microvessels. Transcapillary exchange was evaluated as fluorochrome clearance (Cl). Few leukocytes adhered to the microvascular wall in venous segments prior to and immediately following administration of the dextran fluorochrome. Spontaneous leukocyte adhesion to venous endothelium ensued within 30 min in epi-illuminated, FITC-Dx 150-loaded vessels. However, the Cl of FITC-Dx 150 (1.75 ± 0.68 nl/min) remained unaltered (2.21 ± 1.83 nl/min). Hamsters pretreated with FITC-Dx 150 (a minimum of 7 hr prior to experimentation) and subsequently exposed to epi-illumination showed marked leukocyte adhesion in small venules and an impressive pool of marginating leukocytes in large venules. Leukocyte aggregation, thrombus formation, lymphatic distension, and leukocyte adherence to arteriolar endothelium also ensued as a consequence of epi-illumination. Uptake of FITC-Dx 150 by extravascular phagocytes was evident. Some hamsters pretreated with FITC-Dx 150 developed spontaneous leaky sites upon epifluorescent stimulation. Focal accumulation of interstitial phagocytes was suggestive of fluorochrome uptake and elicitation by FITC-Dx 150. These effects were not observed in control animals treated with FITC-albumin. The results of this study suggest caution in employing FITC-Dx 150 as a permeability probe for studies involving inflammatory processes, especially those dependent on neutrophil/endothelial interactions and prolonged circulation time of fluorochrome.

多糖類による赤血球集合現象 代用血しょうの問題点

The effect of plasma substitutes composed of polysaccharides on the velocity of erythrocyte aggregation was examined with a rheoscope combined with a video camera, an image analyser and a computer, and the mechanism of polysaccharide-induced erythrocyte aggregation was studied.1) Dextran (Mw 40, 000 and Mw 70, 000) and hydroxyethyl starch (Mw 200, 000) in plasma substitutes increased the velocity of erythrocyte aggregation in 60% diluted plasma. The accelerating effect was marked in the high molecular weight dextran. The accelerating effect by dextran was less in glucose than in saline or lactate Ringer's solution.2) The velocity of erythrocyte aggregation became maximum at an optimal concentration of dextran. The optimal concentration was lower in higher molecular weight dextran, but was not affected by shear rate.3) The aggregation induced by high molecular weight dextran (Mw 70, 400) was inhibited by low molecular weight dextrans (Mw 43, 900 and Mw 10, 300), disaccharides (sucrose, maltose and isomaltose) and glucose. The aggregation induced by fibrinogen, IgG and plasma was affected by low molecular weight dextrans.4) The aggregation induced by pullulan (Mw 70, 000; linear polysaccharide) was more marked than that induced by dextran (Mw 70, 400; branched polysaccharide).5) The mechanism of polysaccharide-induced erythrocyte aggregation was discussed, and the suitable prescription for plasma substitutes was proposed from the rheological point of view.

Assessment of ischemia reperfusion injury in skeletal muscle by macromolecular clearance

Qualitative changes in skeletal muscle injury after ischemia are well known; however, quantitative assessments have not been well documented. We have determined microvascular permeability changes by measuring the clearance of fluorescein-labeled dextran of MW 150,000 (FITC-Dextran-150). The cremaster muscle of anesthetized rats was fashioned as a single layer, splayed on a lucite chamber and suffused with bicarbonate buffer solution at 35°C. Clearance is the product of suffusion rate times the ratio of suffusate to plasma concentrations of FITC-Dx 150. After a 1-hr period of baseline data collection, ischemia was produced by cross-clamping the cremasteric vascular pedicle for periods of 30 min and 2 hr in separate experiments. Clearance of FITC-Dx 150 increased from a control value (mean ± SE) of 8.3 ± 2.7 to 29.9 ± 8.1 μl/min/g after reperfusion following a 30-min period of ischemia, and from a control value of 36.2 ± 13.6 to 274 ± 94.5 after 2 hr of ischemia. The differences were statistically significant ( P < 0.05). Our results show a significant increase in microvascular permeability occurring after only 30 min of ischemia. They also demonstrate a direct relationship between the extent of the permeability change and the duration of the ischemic period.

Haemodilution therapy in ischaemic stroke: Plasma concentrations and plasma viscosity during long-term infusion of dextran 40 or hydroxyethyl starch 200/0.5

In 21 patients with ischaemic strokes we have monitored plasma viscosity, total plasma concentration, numeric average molecular weight (Mn), and weight average molecular weight (Mw) of Dextran 40 (dextran) and hydroxyethylstarch 200/0.5 (HES) during 10 days of treatment (days 1-4, 2 X 500 ml; days 5-10, 1 X 500 ml). Plasma concentrations of dextran increased during the first 4 days (8.3 mg X ml-1 on the first day to 18.0 mg X ml-1 on the fifth day), reached an apparent steady state of 17.2 mg X ml-1 during the next 6 days, and declined subsequently with a half-time (t1/2) of 4.03 days. After ten days treatment Mn and Mw were shifted towards higher values. Plasma viscosity increased from 1.26 mPas to 1.69 mPas on Day 10 (p less than 0.01) and was linearly correlated with the total plasma concentration of dextran (p less than 0.001; r = 0.88). Total plasma concentrations of HES averaged 11.7 mg X ml-1 on Day 1 and 12.4 mg X ml-1 on Day 5. The molecular weight distribution did not change during the infusions but decreased in comparison with the administered solution. Plasma viscosity fell from 1.40 mPas to 1.30 mPas at Day 10 (p less than 0.05) and was not related to the concentration of HES. The haemodiluting effect, as indicated by a decrease of the haematocrit, was 22% and 16.8% for dextran and HES respectively. These data suggest several advantages of HES compared with dextran in haemodilution therapy of ischaemic stroke.

Effects of Adjuvants to Local Anaesthetics on Their Duration

Local anaesthetics of the amide type were studied in a modified rat infraorbital nerve block model, with which it was possible to determine varying degrees of sensory block. Of the agents investigated, 0.5% bupivacaine tended to give a longer duration of block than 2% prilocaine or 2% lidocaine, while 0.5% etidocaine had the shortest duration. The duration of prilocaine was prolonged by addition of adrenaline, 5 micrograms/ml, more than that of the other agents. Addition of dextrans of Mw 40-110 X 10(3) did not cause any prolongation of block induced by bupivacaine. When mixed with dextrans over a wide range of Mw (40-4900 X 10(3), prilocaine exhibited significant prolongations of its action by up to 200%. The extent of prolongation was dependent on the degree of block, the concentration of dextrans in the local anaesthetic solution, and the Mw of the dextran although in a less uniform way. An increase in the relative viscosity of the solutions might be a factor of importance for the prolonging effect of addition of dextran to local anaesthetics. Since a formulation providing analgesia of a long duration would be of clinical value, further studies on combinations of the comparatively low-toxicity agent prilocaine and macromolecular substances are of interest.

Effect of dextran on the release of gonadotropin-releasing hormone (GnRH) injected into rats: plasma GnRH and gonadotropin response.

Prolonged release of the peptide gonadotropin-releasing hormone (GnRH) from its aqueous solution was achieved by addition of the polymer dextran (Mw ∼ 500,000). This effect observed in an in vitro system was caused by a decrease of the diffusion coefficient of the peptide. When GnRH was intramuscularly injected into male rats, the addition of dextran to the injected peptide solution led to a prolongation of the GnRH plasma level at the expense of its peak value. This change can be explained by a decrease of the absorption rate of GnRH into blood, which parallels the in vitro observation. As a result, the gonadotropin response to GnRH was stronly increased.

A survey of surface hemorheological experiments on the inhibition of fibrinogenin formation employing surface layers of fibrinogen systems with heparins and other substances. A contribution on antithrombogenic action

In earlier studies using a modified Weissenberg Rheogoniometer, we found decreased rigidity or torque values (⊥) in surface layers of heparin plasma, when compared to ⊥ of oxalate plasma from the same blood withdrawal (Thrombosis Res. 1, 1–17, 1972). In subsequent studies of the viscoelasticity of surface layers of highly purified fibrinogen (97–100% clottability) of human and bovine origin, we found, with some heparins, marked lowering of surface viscous moduli ( η′ s) and of surface elastic moduli (G s). With some heparins no changes in ⊥, η′ s and G s occurred. Certain low molecular weight (LMW) preparations of heparins showed decreases, but some did not. This is also the case with heparins of low and high affinity for antithrombin. Calcium heparin and Ca 2+ alone always increased η′ s and G s, when added to the fibrinogen system. N-de-sulfated heparin both decreased or did not change η′ s and G s. Preparations of fibrinogen in dog plasma, to which sodium heparin was added, resulted in a decrease of ⊥ values. These results appear to emphasize that plasma proteins other than fibrinogen, and other plasma constituents, may affect surface hemorheological values. These findings suggest needed interface studies of fibrinogen systems to which plasma or plasma constituents are added. We found also that other substances, i.e., dextran MW 20,000; dextran sulfate MW 17,000; sodium hyaluronate and depolymerized hyaluronate decreased ⊥, η′ s and G s markedly. Recent findings in the literature are discussed in relation to thrombogenesis in which fibrinogenin gelation is considered as the initial phase of blood clotting. Fibrinogenin is the new term for initial fibrinogen aggregation and subsequent fibrinogen gelation without thrombin participation. The inhibition of fibrinogenin formation extra vivum is considered to be a valid indicator of antithrombogenic activity of substances which play a significant role in investigations on the therapy and prevention of thrombotic conditions.

CO2 CAUSES EXOCYTOSIS OF VESICLES CONTAINING H* PUMPS IN ISOLATED SEGMENTS OF COLLECTING DUCT (CD) AND PROXIMAL STRAIGHT TUBULE (PST)

CO2 directly stimulates H+ secretion, possibly by causing an increase in the number of H+ pumps in the luminal membrane. In order to test this hypothesis we perfused CD and PST on the stage of an inverted epifluorescence microscope with fluorescein isothiocyanate dextran (mw 70,000) in CO2-free medium. Uptake of this substance can only occur by endocytosis. After wash out we noted punctate fluorescence in endocytic vesicles in some CD and in all PST cells. More cells took up fluorescent dextran in medullary than in cortical CD, consistent with the greater rate of H+ secretion in medullary CD. Using the pH dependence of the excitation spectrum of the fluorescence we found the pH of the vesicles to be acid (c. pH 6). Addition of NH3 or nigericin increased vesicular pH by 0.6 ± 0.2 units, suggesting that the acidity of the vesicles was due to H+ pumps. CO2 added isohydrically to the medium reduced fluorescence intensity by 25±7% in CD and 29 ± 5% in PST. Since this effect was prevented by colchicine added to the bath, we believe that CO2 causes a decrease in cytoplasmic fluorescence by stimulating exocytic fusion of the vesicles. We conclude that some cells in CD and all cells in PST incorporate fluorescent dextran into the apical cytoplasmic vesicles and acidify them with H+ pumps. CO2 causes fusion of these vesicles with the luminal membrane and thus stimulates H+ secretion, at least in part, by increasing the number of functioning H+ pumps.

The physiological significance of the endoendothelial fibrin lining (EEFL) as the critical interface in the ‘vessel-blood organ’ and the importance of in vivo ‘fibrinogenin formation’ in health and disease

The author's theory of the endoendothelial fibrin lining (EEFL), first advanced in 1953 and developed by him ever since, localizes the homeostasis between steady fibrin formation and deposition, or ‘fibrination’, and continuous fibrinolysis in the more or less immobile portion of the plasmatic zone next to the vessel wall. In 1971, the author advanced, in relation to the EEFL, the theory of fibrinogen gel clotting without thrombin action or ‘fibrinogenin’ formation in vivo. Considerable direct and indirect experimental evidence, secured by the author and by several other investigators, advanced markedly the knowledge of the normal physiology and the pathophysiology of various disease processes involving the vessel wall and blood circulation. The information presented is an extension to that given in the author's recent overview (Clin. Hemorheology 1 , 9–72, 1981). It deals both with new data by several investigators including those by the author, as well as with older data from the literature. The author maintained already in 1960 that the blood together with the blood vessels, in which it circulates, constitute ‘an entity’. In 1981 he postulated this entity to be a very special organ, named conveniently ‘vessel-blood organ’, which is ubiquitous and penetrates all other organs and adjacent tissues. The EEFL of the vessel-blood organ is considered by the author as the crucial critical interface between the blood and the vessel wall. It is the primary barrier, followed by the endothelium (comprising the endothelial cells and the interendothelial cement substance which contains or is identical with ‘cement fibrin’) and the basement membrane for the exchanges between the blood, the vessel wall and its surrounding tissues and spaces. The EEFL acts as anticoagulant, is antithrombogenic, maintains vascular patency and aids cardiac action by decreasing significantly the apparent viscosity of blood, referred to in the literature as the ‘Copley-Scott Blair phenomenon’. A new concept of leukocyte emigration traversing the capillary wall is presented, affecting focal fibrinolysis of the EEFL and of fibrin contained in the interendothelial cement substance and in the basement membrane. The physical property of capillary (or vascular) permeability is related to the existence of the EEFL, since, as found by Copley et al, both fibrinopeptides, liberated in the transition of fibrinogen to fibrin, and plasminopeptides, freed in the conversion of plasminogen to plasmin, enhance capillary permeability. Capillary fragility, which is antagonistic to capillary permeability, is in great part due to fibrinolytic action on fibrin as a constituent of the basement membrane. Pseudohemorrhages occur as minute microaneurysms in augmented capillary permeability, when the basement membrane remains intact and blood escapes through the interendothelial junctions into the exoendothelial space between the endothelium and the basement membrane. The occurrence of petechiae can be either due to focal lesions in the basement membrane leading to extravasation of blood or due to these pseudohemorrhages. Thus, petechiae are not necessarily identical with capillary hemorrhages. New surface hemorheological findings, obtained by Chien, King and Copley with a modified Weissenberg rheogoniometer, are presented. We found Ca 2+ to increase markedly the viscous and elastic moduli of fibrinogen surface layers. Other studies concern marked decreases of these surface rheological moduli by the addition to fibrinogen solution of the following substances: heparins of low molecular weights of 4400, 5300, and 5900; chondroitin A, B and C; dextran MW 20,000; dextran sulfate MW 17,000; and sodium hyaluronate. The author considers these findings of inhibition of fibrinogenin formation to mirror antithrombogenic actions of these different agents, which are expected to prevent thrombogenesis. The pathogenesis of different disease processes, such as thrombosis, hyperthermia therapy of cancer, (non-thrombocytopenic) vascular purpura, and atherogenesis is briefly discussed. The author relates these disease processes to the theories of the EEFL and of in vivo fibrinogenin formation. In this conclusions he suggests a number of studies to be made towards the advancement of knowledge pertaining to these theories involving health and disease.

Affinity sensor: a new technique for developing implantable sensors for glucose and other metabolites.

We describe affinity sensors for monitoring various metabolites in blood plasma by optical means. The principle of detection is similar to that used in radioimmunoassays and is based on the competitive binding of a particular metabolite and a fluorescein-labeled analogue with receptor sites specific for the metabolite and the labeled ligand. This concept has been directed toward the development of an affinity sensor for glucose. Concanavalin A, a protein with specific binding character for glucose, was immobilized on the inside surface of a hollow dialysis fiber. Fluorescein-labeled dextran was selected as the competitive labeled ligand. The molecular weight cutoff of the dialysis fiber is low enough to completely retain the 70,000 MW dextran within the fiber lumen while glucose can freely pass through the dialysis membrane. The sensor is completed by inserting a single optical fiber in the lumen of the dialysis fiber, thus allowing measurement of the unbound FITC-dextran. Preliminary tests of the sensor indicated the feasibility of the approach. Sensitivity to glucose in the physiologic range was obtained, but further work will be required to optimize the sensitivity and response time of the sensor.

Water‐soluble copolymers. III. Dextran‐g‐poly(acrylamides) control of grafting sites and molecular weight by Ce(IV)‐induced initiation in homogeneous solutions

AbstractModel graft copolymers were synthesized by grafting acrylamide onto dextran (Mw = 500,000) utilizing an initiation method in which a Ce(IV)/HNO3 solution was added to the dextran solution in order to allow coplexation prior to monomer addition. Three synthetic reaction parameters were optimized on the basis of conversion and solution viscosity: monomer concentration, dextran concentration, and nitric acid concentration. Molar ratios of [Ce(IV)]/[dextran] were changed systematically to affect the number and length of the acrylamide grafts. The number of grafting sites and graft chain lengths, determined by selective hydrolysis of the carbohydrate backbone, were in good agreement with those theortically predicted from knowledge of initiation efficiency and monomer conversion. Rheological studies of the model graft copolymers were conducted in aqueous solutions as a function of temperature, added salt, and copolymer concentration.

Activities of cell fusion and lysis of the hybrid type of chemical fusogens (I) structure and function of the promotor of cell fusion

Summary Monomeric lipids, for example, oleic acid, stearic acid, lauric acid, oleyl alcohol and p-isooctyl phenol, were introduced through ester or ether bonds to oligoethylene glycol with various molecular weights. The activities of hemolysis and fusion of these oligomeric lipids were examined using human erythrocytes in the presence or absence of high molecular weight of water-soluble polymers such as polyethylene glycol (Mw=6,000) or dextran (Mw=70,000). When the chain length of polyoxyethylene of the oligomeric lipids was less than 20, the activities of hemolysis and fusion were both enhanced. On the other hand, when the chain length was more than 20, the two activities were reduced to a different degree for each other.

Pulmonary Microvascular and Alveolar Epithelial Permeability Characteristics in N-Nitroso-N-Methylurethane-Injected Dogs

The subcutaneous injection of 5 to 6 mg/kg of body weight of N-nitroso-N-methylurethane (NNNMU) has been reported to cause acute alveolar injury in animals. To determine the permeability characteristics of the alveolar epithelium, we employed the in vivo saline-filled dog lung model and determined the time to 50 percent equilibration in minutes of a specific tracer in the blood and the lung model and determined the time to 50 percent equilibration in minutes of a specific tracer in the blood and the lung liquid (T 1/2) for endogenous serum albumin (MW 69,000 daltons, molecular radius 35 A) and exogenously administered 500,000 MW polydispersed dextrans (molecular radius 200 A). Compared to control animals, T1/2 decreased (permeability increased) in NNNMU-injected dogs from 3,500 +/- 100 to 682 +/- 160 minutes for albumin and from 20,000 +/- 250 to 2,790 +/- 750 minutes for 500,000 MW dextran (P less than 0.001). To determine the permeability characteristics of the pulmonary microvasculature, we employed the right lymph duct cannulation dog model and measured lymph flow/30 minutes, lymph albumin and dextran concentration, and lymph/plasma albumin and dextran ratios in control and NNNMU-injected dogs. Compared to control animals, lymph flow was significantly greater in NNNMU dogs, 2.07 +/- 1.1 vs .71 +/- .50 ml/30 minutes (P less than 0.01), respectively. We conclude that NNNMU injection increases permeability in both the alveolar epithelium and the pulmonary microvasculature.

Permeability of blood vessels after thermal injury

Summary The permeability of the microcirculation in the canine mesentery, following heat stresses and topical application of histamine, was studied by introducing directly into the mesentric circulation albumin or dextran conjugated with fluorescein isothiocyanate, and then photographing while using an image intensifier (× 50 000). The experimental procedures were: ( a ) raising the temperature of an area of mesentery (0·33 × 0·21 inch) to 56 °C for 45 s; ( b ) infusing 10 ml of 0·9 per cent NaCl at a temperature of 55 °C into a mesenteric artery supplying the region being observed and then allowing the dog's own blood to perfuse this area; and ( c ) applying 2 ml of a 0·9 mg/ml solution of histamine in Ringer's solution topically to the mesentery; the histamine was washed off the mesentery 2 min later. The infusion of fluorescein-tagged materials was performed at about 10 min after completing an experimental procedure and still or cine film was exposed at 5, 10 and 60 s after infusion of the tagged materials. The principal findings were that albumin and both the 70 000 and 150 000 MW dextrans passed from the circulating blood into the interstitial spaces primarily at bifurcations of venules when the tissue had not been exposed to heat or histamine. Following exposure to radiant heat, heated saline or histamine, venules and venous capillaries appeared to become more permeable to albumin and the two dextrans throughout their entire lengths. Venules and venous capillaries were less permeable to the 150 000 MW dextran than to albumin and the 70 000 MW dextran. No exit of tagged materials was observed from true capillaries. Based upon these and other observations in this laboratory, the cause of increased permeability appears to be a swelling of endothelial cells which we believe results from imbibition of water when the cells are subjected to heat injury or to an abnormal concentration of histamine. Since cell membranes are relatively non-distensible, a swollen endothelial cell becomes more spherical (less hexahedron-shaped) and consequently its contacting surfaces tend to pull away from adjacent surfaces of other endothelial cells. This causes spaces to open between the cells permitting leakage of relatively large molecules through walls of venules and venous capillaries.

The Lysis of Artificial Thrombi

The susceptibility to lysis of artificial thrombi formed from native rabbit blood in the presence or absence of dextran was determined using the Chandler loop technique. Thrombi of identical weight were formed in the presence of saline or dextran and when spontaneous thrombolysis was allowed to take place, thrombi formed in the presence of dextran 70 were lysed to a greater extent than those formed under control conditions. The possible factors influencing this observation were studied. Increasing concentrations of streptokinase increased the extent of thrombolysis in both control and dextran treated thrombi. Maximal streptokinase induced thrombolysis occured in the presence of a 2 per cent final concentration of dextran Mw 40,000 and 500,000 and dextran 70 at a final concentration of 1.2 per cent. Increased thrombolysis was not observed when albumin was substituted for dextran. Finally, similar observations were recorded for streptokinase induced thrombolysis using human blood.

The effect of dextran on the incidence of thrombosis in microvenous Nakayama ring pin anastomoses. Including further studies on the histopathology of Nakayama anastomoses.

Anastomoses of the posterior facial veins in the rabbits neck (diameter appr. 1.5-2.0 mm) were performed under the operating microscope, using the Nakayama ring pin stapler. Immediately before the operation the animals received clinical dextran (mw 70000) or physiological saline intravenously in a double-blind randomized pattern. The total incidence of partial or complete thrombosis in this experiment was low (around 10%). No difference between the two groups were detected. All anastomoses were examined in vivo, under the microscope and histologically. The histological findings are penetrated.

Dextran/glucan binding by Streptococcus mutans: the role of molecular size and binding site in agglutination.

1) S. mutans strains of serotypes a, d and g were strongly agglutinated with soluble glucans and dextran T2000. Homologous glucan did not in all cases produce agglutination. 2) The quantity of low molecular weight dextrans bound (T20 and T70) does not correspond to the agglutination induced by glucan or T2000. 3) The agglutination and binding of high molecular weight glucan by B13 cells was sensitive to heat, trypsin, dextranase, EDTA, SDS and urea, whereas no inhibition of binding of T20 and T70 was seen. 4) Pretreatment of B13 cells with anti-d, or anti-glucan sera, or Con A, RCA I, or RCA II completely inhibited agglutination by T2000 and caused a significant reduction of the binding of glucan. No reduction in the binding of T20 and T70 occurred. 5) An agglutination-negative mutant was agglutinated by sucrose but not by T2000 or high molecular weight glucan. It bound normal levels of T20 and T70. 6) The results indicate that B13 cells possess multiple glucan binding sites and that the site responsible for agglutination consists of both polysaccharide and protein. 7) Inhibition studies on agglutination and adherence using B13 cells indicate that the two processes involve different mechanisms.

The water and cation content of nonmetabolizing perfused rabbit kidneys.

Rabbit kidneys treated with cyanide and iodoacetate have been perfused with solutions containing various compounds that were intended to control the passage of fluid across the capillaries or the cell membranes. Following perfusion the albumin and EDTA space of each kidney and its water and cation content was measured. Total water content increased significantly unless 7–8% (wv) polyethylene glycol or dextran of mean MW 6000 was present in the perfusate. The EDTA space always increased, but this may have been due, at least in part, to penetration of the intracellular space by the marker. The albumin space was increased only in the presence of hydroxyethyl starch or sucrose. All the kidneys gained sodium and lost potassium, but this effect was least with the perfusate containing dextran of MW 6000 which also gave the lowest EDTA space, a normal total water content, and a normal vascular resistance. It is suggested that the addition of low molecular weight polymers to perfusates used for organ preservation will help to control edema, which may result in improved function after transplantation.

Macromolecular transport in the cat mesentery

Movement of macromolecules from the bloodstream across microvascular walls, into and through the surrounding tissue was studied in the cat mesentery with intravital fluorescence microscopy. Rapid passage of small molecules, such as unconjugated fluoroscein isothiocyanate (FITC), MW 389, and FITC-Dextran, MW = 3400, was found along the entire length of most microvessels, although more prominently on venous capillaries and venules. For species with MW 19,000 or higher, a distinctly spotty pattern of movement out of the microvessels was seen, mostly in localized areas on venous capillaries or venules. These localized regions may represent the “large pore” regions frequently postulated. Diffusion coefficients for movement within the interstitial space were calculated for dextrans as well as for bovine serum albumin (BSA), using a one-dimensional diffusion equation with a time dependent boundary condition at the origin. The calculated diffusion coefficients for dextrans of MW 41,200 and below, and for BSA (MW 69,000) are, within experimental error, the same as the free diffusion coefficients for dextrans of the same molecular weight in water. Dextrans with MW = 152,700 and MW = 393,900 showed smaller diffusion coefficients in the tissue than in water, consistent with increased volume exclusion for larger molecules. The calculated diffusion coefficient for BSA is only two-thirds of that in water. This may possibly be explained by the negative charge on the BSA.