Anionic Dextran Sulfate Research Articles

Abstract P1088: Biophysical Crowding Of In Vitro Culture Media Alters The Growth Rate And Collagen Production Of Cells Used For Seeding Tissue-Engineered Heart Valves

Introduction: Ideal tissue-engineered heart valves (TEHVs) for valve replacement in congenital heart disease patients would have durability and growth potential. Endothelial colony-forming cells (ECFCs) isolated from peripheral blood are an attractive source for pre-cellularizing TEHVs with a patient’s own cells, as they are isolated non-invasively and can transform into valve endothelial and interstitial phenotypes. ECFC limitations include slow proliferation and uncertain mechanisms to control extracellular matrix (ECM) production. In other cell types, culture media “crowded” with large macromolecules limits paracrine diffusion and augments both ECM production and cell growth. Hypothesis: As a novel study of biophysical crowding on ECFCs, we hypothesized that media crowded with macromolecules dextran sulfate or Ficoll-400 would enhance the growth rate and collagen production of ovine ECFCs. Methods: ECFC lines (CD31+, α-SMA+) from n=3 animals at passages 2, 3, or 7 were cultured in media with no crowder or either Ficoll-400 or dextran sulfate at four concentrations in three separate replicates (n=10, n=120, n=384). Deposited and suspended collagen was quantified. Immunocytochemical cell scoring was quantified for vWF, VEGFR-2, CD34, vimentin, and α-SMA markers. Results and Conclusions: Anionic dextran sulfate (DS) caused significant dose-dependent increases in media soluble collagen, despite significantly lowering cell counts. Crowding with DS significantly increased CD34 positivity, a marker for anti-angiogenic and quiescent ECFC populations. Conversely, neutral Ficoll-400 significantly increased cell counts but did not alter media collagen or CD34 positivity. Both crowder groups had altered cellular morphology but did not cause reproducible differences in positivity for endothelial markers vWF and VEGFR-2 or interstitial markers vimentin and α-SMA. In conclusion, biophysical crowding of ECFC media alters cell count and morphology, CD34 positivity, and collagen production, which may allow for fine-tuning of ECFC properties when seeding onto TEHVs. Future studies will address the different effects of neutral and negatively charged crowders and how crowders impact cellular phenotype and growth on valvular scaffolds.

Transdermal delivery of doxorubicin and methotrexate from polyelectrolyte three layer nanoparticle of graphene oxide/polyethyleneimine/dextran sulphate for chemotherapy: In vitro and in vivo studies

In the present work, novel dual drug loaded - anionic graphene oxide/cationic polyethyleneimine/poly anionic dextran sulfate (GO/PEI/DS) was synthesized by a layer-by-layer self-assembly technique for transdermal anti-cancer drug delivery. Doxorubicin (DOX) was loaded onto folic acid conjugated graphene oxide (GO) and methotrexate (MTX) was loaded onto dextran sulfate (DS). The drug carrier was characterized by fourier transform infrared spectroscopy, x-ray diffraction spectroscopy, dynamic light scattering analysis, scanning electron microscopy, atomic force microscopy, transmission electron microscopy, zeta-potential analysis, drug loading and encapsulation efficiency, equilibrium swelling studies, in vitro drug release studies, hemocompatibility assays, in vitro cytotoxicity assay, skin irritation studies, ex vivo skin permeation studies and in vivo pharmacokinetic studies.The cytotoxicity of synthesized materials was evaluated against MCF-7 breast cancer cells using an MTT assay and apoptosis assay. The synergistic effect of DOX and MTX to inhibit the growth of cancer cells was also confirmed. The final dual drug-loaded carrier showed a cell viability of 36.38 % towards MCF-7 cancer cells while it showed a cell viability of >87.65 % towards normal L929 cell lines. The in vivo pharmacokinetic studies in Wistar rats through oral and transdermal routes of administration, the transdermal route of administration of dual drug-loaded material provided a sustained and prolonged drug existence in the blood circulation system. The mean residence time of drugs in the bloodstream via oral administration was 83.98 ± 3.71 h, while that of the transdermal route of administration was 149.62 ± 6.11 h. The results revealed that the synthesized dual drug-loaded material showed a good pH-dependent controlled and sustained release profile for both DOX and MTX via the transdermal route of administration in comparison with oral delivery.

Sonication-assisted Layer-by-Layer self-assembly nanoparticles for resveratrol delivery.

This paper advances the development of a novel drug nanodelivery solution to the oral administration of resveratrol (RSV), a low soluble drug whose recognized therapeutic applications are circumscribed when administered in the free compound form. Layer-by-Layer (LbL) self-assembly is an emergent nanotechnology proposed to address this concern with means to afford control over key formulation parameters, which are able to ultimately promote an improved pharmacokinetics. LbL self-assembly consists in the sequential adsorption of oppositely charged polyelectrolytes upon a low soluble drug nanoparticle (NP) template, giving rise to onion-like multilayered nanoarchitectures. In this work, RSV nanoprecipitation followed by LbL self-assembly of polyelectrolytes, led by a washless approach, was carried out by using the cationic poly(allylamine hydrochloride) (PAH) and the anionic dextran sulfate (DS) as polyelectrolytes towards the nanoencapsulation of RSV. Each saturated polyelectrolyte layer deposition involved the rigorous polyelectrolyte concentration assessment which was accomplished by tracing titration curves. This way, aqueous RSV nanocores and RSV LbL nanoformulations with a distinct number of PAH/DS bilayers were developed, including 2.5 (RSV-(PAH/DS)2.5 NPs), 5.5 (RSV-(PAH/DS)5.5 NPs) and 7.5 (RSV-(PAH/DS)7.5 NPs) bilayered nanoformulations. Homogenous particle size distributions at the desired nanoscale interval (ca. 116-220 nm; polydispersity index below 0.15), good colloidal (zeta potential magnitudes ca. ± 20-30 mV) and chemical stabilizations, high encapsulation efficiency (above 90%) together with an excellent cytocompatibility with Caco-2 cells (cell viability above 90%) were observed for all the nanoformulations. Eventfully, LbL NPs promoted a controlled release of RSV pursuant to the number of polyelectrolyte bilayers under simulated gastrointestinal conditions, particularly in the intestine medium, emphasizing their biopharmaceutical advantage. Our findings manifestly pinpoint that LbL PAH/DS NPs constitute a promising nanodelivery system for the oral delivery of RSV, providing a rational strategy to enlarge the implementation range of this interesting polyphenol, which is possibly the most actively investigated phytochemical worldwide.

Origin of Proteinuria as Observed from Qualitative and Quantitative Analysis of Serum and Urinary Proteins

It is well known that proteins present in the primary urine are reabsorbed in the renal proximal tubules, and that this reabsorption is mediated via the megalin‐ cubilin complex and the neonatal Fcγ receptor. However, the reabsorption is also thought to be influenced by an electrostatic interaction between protein molecules and the microvilli of the renal proximal tubules. By analyzing the charge diversity of urinary IgG, we showed that this reabsorption process occurs in a cationic charge-preferential manner. The charge‐selective molecular sieving function of the glomerular capillary walls has long been a target of research since Brenner et al. demonstrated the existence of this function by a differential clearance study by using the anionic dextran sulfate polymer. However, conclusive evidence was not obtained when the study was performed using differential clearance of serum proteins. We noted that immunoglobulin (Ig) A and IgG have similar molecular sizes but distinct molecular isoelectric points. Therefore, we studied the differential clearance of these serum proteins (clearance IgA/ clearance IgG) in podocyte diseases and glomerulonephritis. In addition, we studied this differential clearance in patients with Dent disease rather than in normal subjects because the glomerular sieving function is considered to be normal in subjects with Dent disease. Our results clearly showed that the chargeselective barrier is operational in Dent disease, impaired in podocyte disease, and lacking in glomerulonephritis.

Electrospun polystyrene fibers for HIV entrapment

The high versatility and ease of electrospinning of polymer solutions have recently resulted in electrospun fibers, which are of interest for a wide variety of chemical and biomedical applications. This is partially due to the high surface area of the fibers, which is attractive for the detection and capture of (bio)chemicals. In the present work, polystyrene (PS) fibers were electrospun and coated with cationic poly(allylamine hydrochloride) (PAH) or anionic dextran sulfate sodium (DSS). The fibers were physicochemically characterized. Upon incubation in a dispersion of inactivated HIV-1, avid binding of HIV to all types of fibers occurred. By atomic force microscopy and spatial selective photobleaching, the binding of the inactivated HIV-1 particles to the fibers could be confirmed. Interestingly, all fibers, especially the DSS-coated and PAH-coated ones, resulted in a significant reduction of infection of CD4+ TZMbl cells by replication-competent HIV-1. On top, DSS-coated PS fibers were not toxic for vaginal epithelial cells, which may make these fibers of potential interest to inhibit HIV infection in the context of topical prevention. Copyright © 2014 John Wiley & Sons, Ltd.

Mucoadhesive Chitosan–Dextran Sulfate Nanoparticles for Sustained Drug Delivery to the Ocular Surface

To characterize nanoparticles produced by self-assembly of oppositely charged polymers, cationic chitosan (CS), and anionic dextran sulfate (DS), for drug delivery to the ocular surface. The goal is to overcome the short residence time of topical drugs through their sustained release from mucoadhesive nanoparticles. Chitosan-dextran sulfate nanoparticles (CDNs) were produced by mixing CS and DS; polyethylene glycol-400 was used as a surface stabilizing agent. Fourier transform infrared spectroscopy (FTIR) spectra of CS, DS, and CDNs were determined in the wavenumber range of 4,000-700 cm(-1) to assess the ionic interactions in the formation of CDNs. The physicochemical properties, entrapment efficacy, and dissolution profile of CDNs were investigated using Rhodamine B (RhB) and Nile Red (NR) as drug analogs. The mucoadhesiveness of the CDNs was assessed by imaging the retention of the fluorescein isothiocyanate-labeled CDNs on the cornea ex vivo, which was subjected to shear stress by a steady stream of saline solution. CDNs were obtained by the polyelectrolyte complexation technique. The FTIR spectra of CDNs showed spectral shifts in the amine and sulfate regions, confirming an involvement of electrostatic interactions between cationic CS and anionic DS. The CDNs were spherical in shape and segregated. They possessed a particle size of ~400 nm with a polydispersity index of 0.3 and exhibited a zeta potential of ~40 mV. A high entrapment efficacy of up to 80% was observed with both RhB and NR. In the dissolution experiments, NR was released from CDNs within 60 min, but RhB was not released. This indicates that the release of drugs could depend on their molecular interactions with the particle. Exposure of CDNs to lysozyme, which is found in tears, had no effect on the mean particle size or the surface charge. Instillation of NR, RhB, and FITC in the presence of saline irrigation resulted in their rapid disappearance (<5 min) from the corneal surface. In contrast, fluorescent CDNs showed retention on the cornea even after 60 min. Cationic and biocompatible mucoadhesive CDNs have been developed for sustained drug delivery to the ocular surface. The CDNs were stable to lysozyme and showed prolonged adherence to the corneal surface.

Tubular multi‐bilayer polysaccharide biofilms on ultra‐thin cellulose fibers

AbstractMultiple bilayered polysaccharide biofilms have been assembled by electrostatic layer‐by‐layer (LBL), alternating deposition of cationic chitosan (CS, Mv = 405 kDa) and anionic dextran sulfate (DXS, Mw = 500 kDa) onto ultra‐fine cellulose (CELL) and partially hydrolyzed cellulose acetate fibers with diameters ranging from 350 to 410 nm. While the surfaces of partially hydrolyzed (degrees of substitution of 1.14 or 0.2) and CELL fibers were equally hydrophilic, higher surface charges on the more hydrolyzed fibers afford thicker bilayers. The elestrostatic interactions between CS and DXS were enhanced by the presence of NaCl in the dipping and rinsing solutions to allow uniform deposition of sequential polysaccharide bilayers. At 0.25M NaCl, each CS/DXS bilayer averaged 6.4 to 9.0 nm thick with the total thickness of the five bilayer (CS/DXS)5 varied from 64 to 77 nm. The CS/DXS bilayers exhibited much reduced BET surface area and pore volume indicating that these polysaccharides were much more densely packed on the fully hydrolyzed CELL fibers. The findings proofed the concept that long chain polysaccharide electrolytes can be self‐assembled as nanometer scale tubular bilayers on ultra‐fine cellulose fibers to afford wholly polysaccharidic fibrous architecture. The electrolytic nature, chemical reactivity, and structural versatility of these ultra‐high specific surface polysaccharides are advantageous and can be further tuned to serve biological functions and for biomedical applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Synthesis of 64Cu-Labeled Magnetic Nanoparticles for Multimodal Imaging

Complementary imaging modalities provide more information than either method alone can yield and we have developed a dual-mode imaging probe for combined magnetic resonance (MR) and positron emission tomography (PET) imaging. We have developed dual-mode PET/MRI active probes targeted to vascular inflammation and present synthesis of (1) an aliphatic amine polystyrene bead and (2) a novel superparamagnetic iron oxide nanoparticle targeted to macrophages that were both coupled to positron-emitting copper-64 isotopes. The amine groups of the polystyrene beads were directly conjugated with an amine-reactive form (isothiocyanate) of aza-macrocycle 1,4,7,10-tetraazacyclo-dodecane-1,4,7,10-tetraacetic acid (DOTA). Iron oxide nanoparticles are dextran sulfate coated, and the surface was modified to contain aldehyde groups to conjugate to an amine-activated DOTA. Incorporation of chelated Cu-64 to nanoparticles under these conditions, which is routinely used to couple DOTA to macromolecules, was unexpectedly difficult and illustrates that traditional conjugation methods do not always work in a nanoparticle environment. Therefore, we developed new methods to couple Cu-64 to nanoparticles and demonstrate successful labeling to a range of nanoparticle types. We obtained labeling yields of 24% for the amine polystyrene beads and 21% radiolabeling yield for the anionic dextran sulfate iron oxide nanoparticles. The new coupling chemistry can be generalized for attaching chelated metals to other nanoparticle platforms.

Prolonged degradation of end-capped polyelectrolyte multilayer films

Cationic chitosan (CT) and anionic dextran sulfate (Dex) were layer-by-layer (LbL) assembled from aqueous solutions containing 1 M NaCl on a quartz crystal microbalance (QCM) substrate, and the original films ((CT-Dex)3-CT)) were end-capped with LbL assembly from CT solutions containing 1 M NaCl and Dex solutions without NaCl. The enzymatic degradation of films by chitosanase was quantitatively analyzed by QCM in terms of numbers of end-capping steps. The degradation of films end-capped with (Dex-CT)3 was considerably prolonged when compared to those end-capped with other end-capping steps. A mechanism for the prolonged degradation was proposed by quantitative QCM data and zeta potential results.

The Presence of Mucin Increases the Anti-HIV-1 Activity of the Candidate Microbicide Polyethylene Hexamethylene Biguanide (PEHMB)

Topical microbicides that reduce or eliminate the risk of human immunodeficiency virus type 1 (HIV-1) sexual transmission must function effectively within the cervicovaginal environment where multiple factors may impact the efficacy of the active agent. Factors relevant to potential changes in microbicide efficacy include the presence of mucins within the cervical mucus. We hypothesize that polycationic PEHMB molecules will interact with the anionic mucin molecules to form a lattice-like network that serves as a physical barrier to the movement of infectious virus and HIV-1-infected cells to the cervical and vaginal epithelia. In vitro experiments demonstrated that the anti-HIV-1 activity of PEHMB was increased almost two logs in the presence of mucin. In contrast, the activity of anionic dextran sulfate was unaffected. These results suggest that electrostatic interactions between PEHMB and mucin molecules may augment the inherent antiHIV-1 activity of PEHMB by facilitating the formation of a physical barrier between HIV-1 and susceptible cells. This property would be expected to increase the in vivo efficacy of PEHMB. from 2005 International Meeting of The Institute of Human Virology Baltimore, USA, 29 August – 2 September 2005

Dextran-Controlled Crystallization of Silver Microcrystals with Novel Morphologies

The controlled synthesis of silver microcrystals with novel morphologies, such as solid or multiholed single crystalline disks, flowerlike aggregates consisting of platelike petals, and dendritic crystals consisting of wide leaves, was realized by using the polysaccharide dextran as a crystal growth modifier. The effects of dextran nature, dextran concentration, temperature, and solvent on the morphology of the silver crystals were investigated, and the obtained products were characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. While the nonionic dextran showed little effect on the silver crystallization, the anionic dextran sulfate exhibited a significant influence on the morphology of the silver crystals. Silver microdisks with solid or multiholed structures were facilely obtained in water at a high dextran sulfate concentration (100 g L-1). With the aid of formamide, silver microdisks with thicknesses as thin as 50 nm can be easily obtained at a relati...

Alternating bioactivity of polymeric layer-by-layer assemblies: anticoagulation vs procoagulation of human blood.

The layer-by-layer assembly between cationic chitosan and anionic dextran sulfate was analyzed quantitatively by a quartz crystal microbalance technique in the absence and presence of 0.2, 0.5, and 1 M NaCl in the polymer solution. The apparent film thickness increased upon increasing the NaCl concentration. The anti- versus procoagulant activity of these films against whole human blood was studied by the immersion of a substrate into blood for 30 min incubation time at 37 degrees C. The substrate was coated with films of varying NaCl concentrations and assembly step numbers. There was a critical concentration for the alternating activity; above a concentration of 0.5 M NaCl, both anti- and procoagulation could be observed on the dextran sulfate and chitosan surfaces, respectively. The underlying layer of the assembly was necessary for this alternating activity; after a five-step assembly, the activity was realized. The adsorption of a cationic dye (methylene blue) onto the films revealed that the anionic-charge density derived from dextran sulfate on the film surface was linearly increased with increased NaCl concentration. There was a critical charge density of the dextran sulfate for the anticoagulant activity. An assembly was also constructed from a combination of chitosan and heparin, but the activity was different from that of the former system; strong anticoagulant activity was observed even on the chitosan surface. We suggest that the polymer species and/or the assembly conditions are key factors for realizing the alternating bioactivities of films prepared by the layer-by-layer assembly.

Separation of microsomal cytochrome b5 via phase separation in a mixed solution of Triton X-114 and charged dextran

The successful introduction of a charged dextran into the Triton X-114 phase separation system for the selective extraction of cytochrome b 5 (cyt. b 5) in liver microsomes is described. In the absence of charged dextran, 55% of total microsomal proteins and 84% of cyt. b 5 were extracted into the surfactant-rich phase. In the presence of anionic dextran sulfate, the extractability of total microsomal proteins was greatly reduced while that of cyt. b 5 was increased. After triplicate extraction, cyt. b 5 was purified more than 10-fold from microsomes with a recovery of 91% in the surfactant-rich phase. In view of its operational simplicity, this method provides a good means for the partial purification of cyt. b 5 prior to chromatographic separations.

Molecular charge influences transperitoneal macromolecule transport

The influence of molecular charge on macromolecule transport during peritoneal dialysis was assessed by determining transperitoneal transport rates for fluorescent-labeled macromolecules (molecular radii from 15 to 40 A) that differed only in molecular charge: neutral dextran, anionic dextran sulfate and cationic diethylaminoethyl (DEAE) dextran. The test macromolecules were infused into the bloodstream of unanesthetized New Zealand White rabbits at a constant rate, and isotonic dialysis solution (40 ml/kg) was instilled into the peritoneal cavity. Blood and dialysate samples were taken hourly over a four hour dwell. Transperitoneal transport rates were assessed by calculating both the dialysate to plasma concentration ratio at four hours and the permeability-area product for the peritoneum, the latter parameter determined from the increase in the dialysate concentration with time. Transport rates for DEAE dextran were less (P < 0.05) than those for both neutral dextran and dextran sulfate; transport rates for neutral dextran and dextran sulfate were not different. Moreover, transperitoneal transport rates for fluorescent-labeled DEAE dextran were not affected by adding unlabeled DEAE dextran to the intravenous infusion solution, an observation suggesting that low transport rates for DEAE dextran were not due to its binding to plasma protein. We conclude that molecular charge is a determinant of transperitoneal macromolecule transport.

Effects of angiotensin II receptor blockade on remnant glomerular permselectivity

This study examined the mechanisms by which angiotensin II (Ang II) receptor blockade improves glomerular barrier function in rats with reduced nephron number. Proteinuria was measured at four weeks after 5/6 renal ablation, and rats were then divided into a group which received the Ang II receptor blocker MK954 and a group which received no treatment. Studies performed one week later showed that Ang II receptor blockade reduced proteinuria without altering GFR in renal ablated rats. Micropuncture studies showed that Ang II blockade reduced both mean arterial pressure (142 +/- 7 mm Hg, ablation without treatment; 105 +/- 2 mm Hg, ablation with treatment) and glomerular transcapillary pressure (54 +/- 3 mm Hg, ablation without treatment; 43 +/- 1 mm Hg, ablation with treatment). Dextran sieving studies showed that untreated rats developed a size-selective defect characterized by increased transglomerular passage of neutral dextrans with radii 54 to 76 A and a charge-selective defect characterized by an increased transglomerular passage of anionic dextran sulfate with a radius of approximately 18 A. Ang II blockade reduced fractional clearance values for large neutral dextrans near to values observed in normal rats but had no effect on the fractional clearance of dextran sulfate (0.68 +/- 0.11, ablation without treatment; 0.66 +/- 0.08, ablation with treatment; 0.46 +/- 0.05, normal rats). These findings indicate that reducing Ang II activity improves size-selectivity without affecting charge-selectivity in injured remnant glomeruli.

Permeation behavior of dextrans by charged ultrafiltration membranes of polyacrylonitrile photografted with ionic monomers

AbstractCharged copolymers, polyacrylonitrile, having grafts of quaternized poly(N,N‐dimethylaminoethylmethacrylate) and poly(sodium p‐styrenesulfonate), were synthesized by photograft‐polymerization. The charged ultrafiltration membranes, which had heterogeneous porous structures, were prepared by casting graft polymer solution containing poly(vinyl alcohol) into water.The permeation of nonionic dextran and anionic dextransulfate through the charged membranes was studied by ultrafiltration in aqueous solution. The molecular weight cutoff characteristics of the charged membrances were obtained using dextrans of various molecular sizes. The permeation behavior was discussed in terms of the charge effect of the graft polymers and electrostatic interaction between the polymers and the solute molecules.

Clearance of charged and uncharged dextrans from normal and injured lungs

To examine how molecular charge affects the transfer of molecules across the alveolar-capillary barrier, we prepared the following dextrans of equivalent molecular size (mol wt 10,000) but varying molecular charge: neutral dextran, cationic DEAE dextran, and anionic dextran sulfate. These were labeled with 99mTc. The lungs of three groups of anesthetized rabbits were insufflated with dextran aerosols, with six rabbits receiving each type, and the half-time pulmonary clearance (t1/2) was measured. Control t1/2's (95% confidence limits) were 95 (74-120), 227 (192-268), and 291 (246-345) min for neutral, cationic, and anionic dextrans, respectively. One week later, when the same animals were restudied 4 h after 3 micrograms/kg iv endotoxin, t1/2's were 102 (75-139), 167 (149-187), and 126 (102-154) min, respectively. After 30 min during this repeat study, animals were ventilated with 20 breaths of cigarette smoke, which acutely increased the clearance rate to 34 (26-46), 25 (20-31), and 13 (7-24) min, respectively. Mean carboxyhemoglobin levels were not significantly different in the three groups: 13.6, 12.7, and 11.1%, respectively. These results demonstrated that neutral dextrans showed the same clearance rate before and after endotoxin, whereas the charged dextrans had a significantly faster clearance after endotoxin. After smoke exposure the anionic dextran left the lung more rapidly than the neutral dextran. Thus molecular charge affects solute transfer across the alveolar-capillary barrier in both normal and injured lungs, and an effect of endotoxin on the lung can be detected with charged dextrans but not with neutral dextran.

Role of molecular charge in disruption of the blood-brain barrier during acute hypertension.

Acute hypertension disrupts the blood-brain barrier and may neutralize the negative charge on cerebral endothelium. The goal of this study was to determine the effects of molecular charge on permeability of the blood-brain barrier during acute hypertension. Intravital fluorescent microscopy and fluorescein-labeled dextrans were used to evaluate disruption of the blood-brain barrier during acute hypertension in rats. Disruption of the blood-brain barrier was quantitated by calculating clearance of neutral dextran and of anionic dextran sulfate in two groups of rats. Pressure in pial venules, which are the primary site of disruption of the blood-brain barrier during acute hypertension, was measured using a servo-null device. When systemic arterial pressure was increased from 87 +/- 5 (mean +/- SEM) to 188 +/- 5 mm Hg, clearance of neutral dextran increased from 0.04 +/- 0.01 to 4.38 +/- 0.72 ml/sec x 10(-6). When systemic arterial pressure was increased from 91 +/- 4 to 181 +/- 3 mm Hg, clearance of anionic dextran sulfate increased from 0.02 +/- 0.01 to only 0.70 +/- 0.23 ml/sec x 10(-6). Increases in pial venular pressure were similar in the two groups. Thus, similar increases in systemic arterial pressure and pial venular pressure during acute hypertension produce less disruption of the blood-brain barrier to anionic dextran sulfate than neutral dextran. The findings suggest that 1) the net negative charge of cerebral vessels may be preserved during acute hypertension, and 2) molecular charge is an important determinant of the severity of disruption of the blood-brain barrier during acute hypertension.

The mechanisms of proteinuria in aging rats

Aging is associated with the appearance of a selective proteinuria which cannot be attributed to any specific underlying renal disease. The present studies were conducted in conscious, chronically catheterized young (3–4 months), non-proteinuric male rats and old (22–25 months), proteinuric males to determine the mechanism(s) of the proteinuria. Compared with young males, old proteinuric rats had increased blood pressure, reduced glomerular filtration rate (GFR) and renal plasma flow and heavy proteinuria. Fractional clearance of neutral dextran (D) and anionic dextran sulfate (DS) were both significantly increased at the 36 Å molecular radius in old rats; the increase in DS fractional clearance being greater than the increase in D fractional clearance. The proteinuria of aging is therefore due to moderate increases in glomerular permeability and, more importantly, to loss of fixed glomerular polyanion. Striking glomerular morphologic changes were also evident in the old rats including thickening of the glomerular basement membrane and extensive glomerular sclerosis.