PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Ultrafiltration”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,009 records · Page 56Linked to original sources
PubMed2004

Structure and rheological behavior of casein micelle suspensions during ultrafiltration process.

The stability and mechanism underlying the formation of deposits of casein micelles during ultrafiltration process were investigated by small-angle and ultra small-angle x-ray scattering (SAXS and USAXS). The casein micelle dispersions consisted of phospho-caseinate model powders and the measurements probed length scales ranging from 1 to 2000 nm. Rheometric and frontal filtration measurements were combined with SAXS to establish the relationship between the rheological behavior of deposits (shear and/or compression) and the corresponding microstructure. The results revealed two characteristic length scales for the equilibrium structure with radius of gyrations R(g), about 100 and 5.6 nm pertaining to the globular micelles and their non-globular internal structure, respectively. The SAXS measurements further indicated that the increase of temperature from 20 to 70 degrees C or the decrease of pH from 6.6 to 6 lead to agglomeration of the globular micelles. In situ scattering measurements showed that the decrease of permeation flows is directly related to the deformation and compression of the micelles in the immediate vicinity of the membrane.

Caseins↗
PubMed2003

The effect of capillary ultrafiltration probes on skin flap edema.

OBJECTIVE: Edema clearly has deleterious effects on the microcirculation and, consequently, cell viability. Prior work from this laboratory demonstrated that hyperosmolar microdialysis can reduce tissue edema, but this method is technically challenging. A new, simpler technique of microdialysis using capillary ultrafiltration probes (CUPs) has been studied to determine if CUP microdialysis is as effective in reducing tissue edema in the same animal model. METHODS: Twenty-four Sprague-Dawley rats were studied using a modified McFarlane skin flap. Microdialysis was accomplished using a catheter constructed of four 4-cm hollow fibers that were connected to polyethylene tubing. Catheters on the experimental side of the flap were attached to a vacuum manifold for 8 hours. The control side was treated in 2 ways. In group 1, catheters were placed but not applied to suction. In group 2, no catheters are placed on the control side. Tissue water content was determined by a biopsy-drying technique. RESULTS: Tissue water content was significantly reduced (by paired t test) in both groups by a mean of 3.2 mL/100 g of wet tissue. CONCLUSION: CUP microdialysis reduced tissue water content as effectively as did hyperosmolar microdialysis, but in a simpler and therefore more cost-effective method. The technique could be easily adapted for clinical application.

Animals↗
PubMed2001

Affinity of human serum albumin for bilirubin varies with albumin concentration and buffer composition: results of a novel ultrafiltration method.

Albumin binding is a crucial determinant of bilirubin clearance in health and bilirubin toxicity in certain disease states. However, prior attempts to measure the affinity of albumin for bilirubin have yielded highly variable results, reflecting both differing conditions and the confounding influence of impurities. We therefore have devised a method based on serial ultrafiltration that successively removes impurities in [(14)C]bilirubin until a stable binding affinity is achieved, and then we used it to assess the effect of albumin concentration and buffer composition on binding. The apparent binding affinity of human serum albumin for [(14)C]bilirubin was strongly dependent on assay conditions, falling from (5.09 +/- 0.24) x 10(7) liters/mol at lower albumin concentrations (15 microm) to (0.54 +/- 0.05) x 10(7) liters/mol at higher albumin concentrations (300 microm). To determine whether radioactive impurities were responsible for this change, we estimated impurities in the stock bilirubin using a novel modeling approach and found them to be 0.11-0.13%. Formation of new impurities during the study and their affinity for albumin were also estimated. After correction for impurities, the binding affinity remained heavily dependent on the albumin concentration (range (5.37 +/- 0.26) x 10(7) liters/mol to (0.65 +/- 0.03) x 10(7) liters/mol). Affinities decreased by about half in the presence of chloride (50 mm). Thus, the affinity of human albumin for bilirubin is not constant, but varies with both albumin concentration and buffer composition. Binding may be considerably less avid at physiological albumin concentrations than previously believed.

Bilirubin↗
PubMed2005

Surfactant sodium lauryl sulfate enhances skin vaccination: molecular characterization via a novel technique using ultrafiltration capillaries and mass spectrometric proteomics.

The skin is a highly accessible organ and thus provides an attractive immune environment for cost-effective, simple, and needle-free delivery of vaccines and immunomodulators. In this study, we pretreated mouse skin with an anionic surfactant, sodium lauryl sulfate (SLS), for a short period of time (10 min) followed by epicutaneous vaccination with hen egg lysozyme antigen. We demonstrated for the first time that pretreatment of skin with surfactant SLS significantly enhances the production of antibody to hen egg lysozyme. Short term pretreatment with SLS disorganized the stratum corneum, extracted partial lamellar lipids, induced the maturation of Langerhans cells, and did not result in epidermis thickening. To reveal the mechanism underlying these changes, particularly at the molecular level, we used a novel proteomic technique using ultrafiltration capillaries and mass spectrometry to identify in vivo proteins/peptides secreted in the SLS-pretreated skin. Two secretory proteins, named as calcium-binding protein S100A9 and thymosin beta4, were identified by this novel technique. These two proteins thus may provide new insight into the enhancing effect of surfactants on skin vaccination.

Administration, Cutaneous↗
PubMed1999

Combined ultrafiltration-transduction in a hollow-fiber bioreactor facilitates retrovirus-mediated gene transfer into peripheral blood lymphocytes from patients with mucopolysaccharidosis type II.

The process of growing and transducing large quantities of human primary peripheral blood lymphocytes (PBLs) with high gene transfer efficiency continues to be one of the major challenges for clinical and experimental gene therapy. Toward developing a clinical trial of lymphocyte gene therapy for mucopolysaccharidosis type II (i.e., Hunter syndrome), we investigated a novel method that exploited the innate capability of a hollow-fiber bioreactor system to filter large quantities of vector supernatant and facilitate transduction. An aliquot (5 x 10(7)) of PBL apheresis product was precultured in a gas-permeable culture bag or a bioreactor, and then transduced with a retroviral vector L2SN containing the iduronate-2-sulfatase (IDS) and neomycin resistance genes. We observed that the total number of PBLs could be expanded up to 187-fold, yielding up to 10(10) cells at the end of a 7-day culture period. The multiplicity of infection could be increased (up to 20-fold) by ultrafiltrating a large volume of vector supernatant through the semipermeable membrane of this system. A high level of transduction efficiency (up to 57%) was achieved, resulting in IDS enzyme activity as high as 1250 U/mg/hr in transduced PBL(MPS) 15 days after transduction. This level was markedly increased from that of nontransduced cells (<3 U/mg/hr) and was even greater than that of normal PBLs (mean, 809; n = 10). After 12 days of G418 selection, PBL(MPS) transductants exhibited a proviral IDS enzyme level approximately threefold higher than that in normal PBLs. These results indicated that the hollow-fiber bioreactor could be used to culture and transduce human primary PBLs in clinically useful quantities with relatively high gene transfer efficiency and transgene expression.

Bioreactors↗
PubMed1981

Nuclease sensitivity of chromatin containing active genes: kinetic analyses utilizing continuous elution of digestion products from an ultrafiltration cell.

Methods have been developed to analyze the kinetics of digestion of chromatin by nucleases. Radioactively labeled nuclei were incubated with enzyme in an ultrafiltration apparatus and digestion rates of different chromatin samples were computed employing a least-squares curve fitting technique to fit the data to zero-order and/or first-order kinetic models. These methods allow detailed kinetic analyses on small amounts of chromatin. Two biological systems were studied. 1) Tetrahymena thermophila macronuclei and micronuclei were compared; these nuclei differ in their transcriptional activities. 2) Ribosomal DNA (rDNA) of Tetrahymena pyriformis, approximately 60% of which codes for rRNA, can be preferentially labeled during starvation-refeeding; its digestion kinetics relative to bulk chromatin were studied. DNase I digested 20-40% of the macromolecular DNA about 3 times faster than bulk macronuclear or micronuclear DNA, and 60-80% of ribosomal gene-containing chromatin about 5 times faster than bulk chromatin. Filter hybridization studies of the DNAase I sensitivity of tRNA, 5S RNA, and ribosomal genes yielded similar results. These data are consistent with the observation that transcribed genes are especially sensitive to attach by DNase I and suggest that activated chromatin structure as probed by extensive DNase I digestion is the same in higher and lower eucaryotes for genes transcribed by all three RNA polymerases. Digestion kinetics of micrococcal nuclease were found to depend on the digestion conditions employed. These two biological systems and the methods we have developed should facilitate analyses of the factors responsible for maintaining an active chromatin structure.

Animals↗
PubMed1997

Dioctyl sodium sulphosuccinate increases net ultrafiltration in peritoneal dialysis.

BACKGROUND: The surface-active substance dioctyl sodium sulphosuccinate (DSS) has been reported to increase the peritoneal clearances of urea and creatinine. This study investigated the effects of DSS on the fluid and solute transport characteristics of the peritoneum. DESIGN: A 4-h single-dwell experiment session of peritoneal dialysis using 25 ml of 3.86% glucose dialysis solution with an intraperitoneal volume maker was performed in 16 male Sprague-Dawley rats. In eight rats, 0.005% (50 p.p.m.) DSS was added to the dialysis fluid. No DSS was given to the other eight rats (control group). The transport of fluid, glucose, potassium, sodium, urea, phosphate and urate were analysed. RESULTS: There was a significant increase in the intraperitoneal volume in the DSS group. At 240 min, the drain volume in DSS group (33.0 +/- 2.9 ml) was significantly higher compared to the control group (28.8 +/- 2.1 ml, P < 0.01). This increase in the drain volume was mainly due to a decrease in peritoneal fluid absorption rate in the DSS group (0.040 +/- 0.013 ml/min) as compared to the control group (0.054 +/- 0.010 ml/min, P < 0.05). There was no significant difference in the diffusive permeability and sieving coefficient for the small solutes between these two groups. However, the clearances for urea and sodium were higher in the DSS group, mainly due to the increase in the dialysate volume. CONCLUSION: Our results suggest that DSS significantly increases the net ultrafiltration of peritoneal dialysis. This effect, which was mainly due to a decrease in the fluid absorption rate, contributed to the increased clearances for urea and sodium. DSS did not alter the diffusive permeability and sieving coefficient for the small solutes.

Animals↗
PubMed2001

Regulation of NO synthase isoforms in the peritoneum: implications for ultrafiltration failure in peritoneal dialysis.

BACKGROUND: Ultrafiltration (UF) failure often complicates peritoneal dialysis (PD). At least two molecules might be involved in UF failure: aquaporin-1 (AQP1), a water channel thought to be the ultra small pore of the peritoneal membrane (PM), and nitric oxide (NO), which might regulate effective peritoneal surface area and microvascular permeability. METHODS: The contributions of AQP1 and NO in UF failure were evaluated by combining different experimental approaches. Specific antibodies were used to investigate the expression (immunoblotting) and localization (immunostaining) of AQP1 and NO synthase (NOS) isoforms in the peritoneum, in correlation with: (i) morphometric analyses; (ii) the l-citrulline assay, which specifically measures NOS enzymatic activities; and (iii) permeability parameters across the PM. RESULTS: AQP1 is located in the endothelium lining peritoneal capillaries, and its expression is remarkably stable in samples ranging from normal to highly inflamed peritoneum and even when transcellular water permeability is absent (loss of sodium sieving). A significant NOS activity, mediated by specific NOS isoforms, can be assayed in the peritoneum. The NOS activity significantly increases in conditions such as peritonitis and long-term PD, and this increase is mirrored by up-regulation of NOS isoforms, as well as angiogenesis and increased endothelial area. CONCLUSIONS: These data suggest that the NO-mediated increase in effective peritoneal surface area, followed by a dissipation of the osmotic gradient, is a major mechanism accounting for the loss of UF in PD. Other biological consequences of increased NO levels in the peritoneum might include initiation of angiogenesis or modification of functionally important proteins such as AQP1.

Animals↗
PubMed2001

Effect of ultrafiltration on peripheral urea sequestration in haemodialysis patients.

BACKGROUND: Ultrafiltration (UF) is assumed to enhance urea removal during haemodialysis (HD) because of convective transport and because of contraction of urea distribution volume. However, UF-induced blood volume reduction has been hypothesized to enhance peripheral urea sequestration and post-dialysis urea rebound (PDUR), possibly reducing HD effectiveness. The effect of UF on PDUR was investigated in this study. METHODS: Nine HD patients were studied on two subsequent treatment days. The first HD was performed with UF (UF-rate=0.78+/-0.27 l/h), and the second treatment without UF. Serial measurements of serum water urea nitrogen concentration, arterial blood pressures (BP), and relative blood volume changes (BV%) were obtained over the duration of HD. RESULTS: BP and BV% decreased with UF (BP(sys)= -9%, BP(dia)=-8%, BP(mean)=-9%, BV%=-15%) but increased or remained unchanged without UF (BP(sys)= 9%, BP(dia)=12%, BP(mean)=11%, BV%=1%). PDUR was 28.6+/-9.6% without UF, and increased in every single patient with UF (40.7+/-13.2%, P<0.01). Modelled perfusion of the peripheral low-flow compartment decreased from 1.45+/-0.54 l/min without UF to 0.91+/-42 l/min with UF (P<0.05), thereby explaining an enhanced two-compartment effect and increasing PDUR. CONCLUSION: The significant increase in the two-compartment effect of urea kinetics observed in current HD accompanied by UF can be explained by compensatory, intradialytic blood flow redistribution induced by blood volume reduction. Because of the link between UF and blood flow, limited solute clearance treatment modes that optimize fluid removal such as variable UF will also have favourable effects on delivered dose of dialysis.

Blood Pressure↗
PubMed2006

Inherent high peritoneal transport and ultrafiltration deficiency: their mid-term clinical relevance.

BACKGROUND: High peritoneal transport has been associated with poorer outcome in peritoneal dialysis (PD) patients, but not necessarily because of PD-dependent conditions. Our primary objective was to analyse the influences of baseline peritoneal small solute transport and ultrafiltration (UF) capacity on patient and technique survival, after adjusting for comorbid conditions. A secondary objective was to determine whether high transport was associated with basal comorbidity. METHODS: In this prospective observational patient/technique survival study, we followed 410 patients who started PD. At the baseline, we collected data to define comorbidities, tally the Charlson index, determine the baseline mass transfer area coefficients (MTAC) of urea and creatinine, net UF, plasma albumin and residual renal function (RRF). No data other than the information on patient and technique survival were recorded after baseline. RESULTS: The mean follow-up was 33 +/- 28 months. Dropouts during the study were due to renal transplantation in 140 cases, death in 142 cases and transfer to haemodialysis (HD) in 77 cases. Patients with inherent UF deficiency, high transport rate or both were not significantly different in the survival analysis from the rest. In the Cox hazards analysis, only age, Charlson index and a lower RRF were the significant mortality risk factors. None of the baseline parameters studied was a predictor of technique failure. High transporter patients had lower plasma albumin and UF capacity, comorbidity and more frequent liver diseases than the rest. Moderate to severe liver disease (n = 14) was significantly associated with the inherent high transport status, but was never accompanied by UF failure (UFF). UFF patients showed higher RRF, creatinine-MTAC and age. CONCLUSIONS: Neither the high transport nor the inherent UFF status has any influence on patient and technique survival. The inherent high small solute transport status is associated with hypoalbuminaemia and a greater comorbidity index. The Charlson index, age and lower RRF are the only independent predictors of mortality. Technique dropout is not predicted by any of the variables studied at the baseline.

Aged↗
PubMed1992

Analysis of lectin properties with membrane ultrafiltration and high-pressure liquid chromatography.

A convenient method for the analysis of the binding properties of lectin with fluorogenic sugar chains is described. A lectin (concanavalin A or Datura stramonium agglutinin) was mixed with pyridylaminated sugar chains in buffer and the free chains obtained were isolated by membrane ultrafiltration. The amount of free sugar chains in the filtrate was measured by high-pressure liquid chromatography. The binding constants with the sugar chains, reaction kinetics, and other properties of these lectins were easily investigated. The method is simple and could be used to study the characteristics of any lectin in native form.

Binding Sites↗
PubMedDate not supplied

Ultrafiltration of dialysis fluid for hemodialysis.

Since the quality of water in dialysis fluid varies considerably, and, in view of the fact that endotoxin or active derivatives can cause acute side effects in patients, the dialysis fluid must be sterile. The predialyzer fluid in 20 hemodialysis patients was investigated. Bacterial loading was between 5/ml and 5,000/ml, and the endotoxin concentration was high and extremely variable. After ultrafiltration of the dialysis fluid by a polyamide hollow fiber membrane, all samples were free of bacteria, and the concentration of endotoxin was lower than the detectable limit. With this procedure we can obtain sterile dialysis fluid, which is endotoxin free.

Colony Count, Microbial↗
PubMedDate not supplied

The influence of dialysate sodium and variable ultrafiltration on fluid balance during hemodialysis.

An important factor in the development of hypotension during hemodialysis (HD) is a decrease in blood volume, due to ultrafiltration (UF) and an insufficient refill of the intravascular compartment. This insufficient refill might be caused by a transcellular fluid shift from the extracellular to the intracellular compartment. We studied the influence of dialysate sodium concentration and UF rate on the refill rate, blood volume, intracellular (ICV) and extracellular fluid volume (ECV). Three different HD strategies were studied in 15 patients: (A) conventional HD (dialysate sodium 140 mmol/L); (B) HD with a sodium profile (140-148 mmol/L); and (C) HD with a sodium profile and a variable UF rate (high-low UF rate). ICV and ECV were measured by non-invasive conductivity measurements, blood volume was calculated from erythrocyte counts before and after treatment. Blood volume decrease was most pronounced during conventional HD, due to insufficient refilling without a detectable transcellular fluid shift. The sum of the decrease in ICV and EVC was less than during (B) and (C). The insufficient refill led to a higher prevalence of hypotension and cramps. The strategies (B) and (C) led to an significant and comparable transcellular fluid shift to the extracellular compartment. Thus, the use of a sodium profile led to a better intravascular refill and clinical tolerance of HD. Addition of a UF profile did not improve this any further.

Blood Volume↗
PubMed1999

Individualized protein fortification of human milk for preterm infants: comparison of ultrafiltrated human milk protein and a bovine whey fortifier.

BACKGROUND: To improve the nutritional management of pre-term infants, a new individualized human milk fortification system based on presupplementation milk protein analyses was evaluated. METHODS: In an open, prospective, randomized multicenter study, 32 healthy preterm infants (birth weights, 920-1750 g) were enrolled at a mean of 21 days of age (range, 9-36 days) when tolerating exclusive enteral feedings of 150 ml/kg per day. All infants were fed human milk and were randomly allocated to fortification with a bovine whey protein fortifier (n = 16) or ultrafiltrated human milk protein (n = 16). All human milk was analyzed for protein content before fortification with the goal of a daily protein intake of 3.5 g/kg. During the study period (mean, 24 days) daily aliquots of the fortified milk were obtained for subsequent analyses of the protein content. RESULTS: Both fortifiers were well tolerated, and growth gain in weight, length, and head circumference, as well as final preprandial concentrations of serum urea, transthyretin, transferrin, and albumin were similar in both groups. The ultimate estimated protein intake was equivalent in both groups (mean 3.1+/-0.1 g/kg per day). Serum amino acid profiles were similar in both feeding groups, except for threonine (significantly higher in the bovine fortifier group) and proline and ornithine (significantly higher in the human milk protein group). CONCLUSIONS: Protein analyses of the milk before individual fortification provides a new tool for an individualized feeding system of the preterm infant. The bovine whey protein fortifier attained biochemical and growth results similar to those found in infants fed human milk protein exclusively with the corresponding protein intakes.

Amino Acids↗
PubMed1983

Serum and plasma for total and free anticonvulsant drug analyses: effects on EMIT assays and ultrafiltration devices.

The suitability of serum and plasma anticoagulated with heparin, EDTA, citrate, or oxalate was assessed for analysis of free and total phenytoin, carbamazepine, and valproic acid. The free fraction was isolated by ultrafiltration through FreeLevel devices (Syva, Palo Alto, CA). Serum, heparin, and EDTA plasma were satisfactory for both free and total phenytoin and carbamazepine. EDTA could not be used for EMIT (Syva) analysis of valproate. Citrate and, to a lesser degree, oxalate cause a significant negative interference in the concentration of these three drugs as measured both by EMIT and gas-liquid chromatography.

Anticonvulsants↗
PubMed1985

Ultrafiltration compared with equilibrium dialysis in the determination of unbound phenytoin in plasma.

Protein binding of phenytoin (PHT) was studied in 36 patients with normal kidney function and six uremic patients. We compared a newly introduced ultrafiltration (UF) technique (EMIT Free Level System I) for measuring unbound PHT in plasma with an equilibrium dialysis (ED) method. The precision of the UF method was satisfactory (the CV within samples was 4.2%, and between days, 3.4%). PHT concentrations were measured with both homogeneous enzyme immunoassay and high performance liquid chromatography using plasma samples from epileptic patients. The values obtained agreed well. Unbound concentrations of PHT determined by the UF technique and ED were identical in both normal and uremic plasma obtained from patients under treatment. Unbound concentrations of PHT correlated significantly to total concentrations in both groups of patients. The investigated UF technique thus appears to be accurate for measuring unbound concentrations of PHT in plasma. Controlled clinical studies are required to show that this is a cost-effective clinical service.

Blood Proteins↗
PubMed1986

Evaluation of a rapid ultrafiltration technique for determination of quinidine protein binding and comparison with equilibrium dialysis.

The free level ultrafiltration (UF) assay by the enzyme multiplied immunoassay technique (EMIT) for determination of unbound quinidine concentration in serum (Qf) was evaluated in 50 samples obtained from cardiac patients treated with quinidine for ventricular arrhythmias. Equilibrium dialysis (ED) at 37 degrees C and high performance liquid chromatography (HPLC) served as standard methods for comparison. A good agreement was found between EMIT and HPLC at the low range of free quinidine concentration (0.1-0.7 mg/L) observed in our patients (r = 0.959). Although the correlation between UF and ED was high (r = 0.972), Qf was systematically underestimated by UF. This bias was due to the fact that UF was performed according to the recommendations of the manufacturer at 25 degrees C. No systematic differences were found when 20 additional samples were assayed by the two methods at the same temperature (25 degrees C; r = 0.992). The quinidine binding ratio showed a correlation with the serum concentration of alpha 1-acid-glycoprotein (r = 0.61). The metabolites 3(S)-hydroxyquinidine and quinidine-N-oxide did not influence the protein binding of the parent drug. The importance of adjusting the serum pH to physiological values before measurement of Qf was confirmed in this study. Our results show that, if performed under the same conditions, ED and UF yield practically identical values. Because of easy handling, the EMIT Free Level System II should be applicable under clinical conditions.

Chromatography, High Pressure Liquid↗