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A theory for ultrafiltration is presented which makes possible the characterization of a membrane at a given temperature and solute concentration by a single experiment at that temperature and concentration. The theory is applied to data in the literature and is shown to be consistent with those data.
A simple method for the detoxification of ultrafiltration concentrates of wastewaters for rotavirus assay by the indirect immunofluorescence technique has been developed. Polyacrylamide (Bio-Gel) or dextran (Sephadex G50) beads were mixed with concentrates (0.5 g/10 ml, wt/vol) of wastewaters seeded with simian rotavirus SA11 and allowed to stand for 2 h. The supernatant was decontaminated with antibiotics and then assayed for rotaviruses. Concentrates from raw sewage and treated effluents seeded with SA11 were used to infect MA104 or LLC MK2 cell lines. The concentrates, particularly those from raw sewage and anaerobic waste stabilization ponds, were very toxic to the tissue culture cells. These toxic effects were determined by the detachment and subsequent loss of cells after incubation with concentrates and assay medium for 24 h. They were either completely eliminated or were reduced by greater than 80% after treatment with beads.
We evaluated a commercially available radioimmunoassay technique for detecting the soluble antigen of Legionella pneumophila serogroup 1 using concentrated and nonconcentrated urine. Concentration was achieved by selective ultrafiltration. The sensitivity of the technique was 60.9% for nonconcentrated urine and 80.4% for concentrated samples, with 100% specificity in both cases.
A simple apparatus is described for the anaerobic ultrafiltration of a few millilitres of bile or other biological fluids. The principle employed enables viscous liquids which would normally block the membrane to be ultrafiltered successfully.
Large volumes of rubella virus were produced in Vero cell monolayers which were grown in the Corbeil-Bellco TM system. Infectious tissue culture fluids were concentrated at least 600 times in less than 4h by ultrafiltration on hollow fibers with a molecular weight cutoff of 100 000. Recovery of the hemagglutinating activity was 75%. Rubella virus was purified by three successive sucrose density gradient centrifugations using a combination and discontinuous and linear gradients. Specific activity was increased 1000-fold.
The sporocidal properties of peracetic acid, hydrogen peroxide, chlorine, and formaldehyde were compared in vitro using a dilution-neutralization micromethod. A combination of peracetic acid and hydrogen peroxide was also tested to assess their interactions. The activities of these agents, which are widely used as disinfectants, were evaluated against Bacillus spore isolates found on stored membranes and collection cultures. Peracetic acid and chlorine exhibited an excellent antimicrobial activity, with a destruction of 10(5) spores/mL after 5 min of contact. Generally the effects of the biocides tested were time dependent. The sporocidal activities of hydrogen peroxide and formaldehyde were the lowest. The combination of peracetic acid and hydrogen peroxide, tested by a checkerboard micromethod, was found to be synergistic. The minimal sporocidal concentration (MSC) was established in terms of time for each biocide. The lowest MSC values for peracetic acid, hydrogen peroxide, chlorine, and formaldehyde were 168-336 ppm (1-2 h of contact), 5625-11250 ppm (5-7 h), 168-336 ppm (2-3 h), and 1875-3750 ppm (5-30 min), respectively. The MSC of a biocide combination of peracetic acid and hydrogen peroxide showed that synergy was maintained with increasing contact time and that the MSC could be reduced by two to eight times when compared with those of the biocides alone. Optimal concentrations and contact times of those chemicals that were promising in vitro were then tested for their ability to disinfect ultrafiltration membranes. The sporocidal activities of peroxide compounds and chlorine were confirmed and the synergism between peracetic acid and hydrogen peroxide was also maintained.(ABSTRACT TRUNCATED AT 250 WORDS)
Five yeast extracts (YE) were fractionated by ultrafiltration (UF) with 1, 3, and 10 kDa molecular weight cutoff membranes, concentrated by freeze-drying, and the resulting powders of yeast extract filtrates (YEF) were evaluated for their growth-promoting properties on nine cultures of lactic acid bacteria (LAB). There was an increase in alpha-amino nitrogen content of the YEF powders as the pore size of the UF membranes used to filter the YE solutions decreased. The source of YE had a much greater effect than UF on the growth of LAB. This was also the case for the YEF contents in total and alpha-amino nitrogen. Growth curves of the LAB showed that maximum growth rate (mumax) data were on average 30% higher with bakers' YE than with brewers' YE, while maximum optical density (ODmax) values were on average 16% higher with bakers' YE. This could be related to the higher nitrogen content of the bakers' YE used in this study. Modification by UF of the YE had no significant influence on the growth of 4 of the 9 LAB strains. The three strains of Lactobacillus casei were negatively influenced by UF, as they did not grow as well in the media containing the YEF obtained after filtering with 1 and 3 kDa membranes. On a total solids basis, the 2.5 x retentates from the 10 kDa membrane gave, on average, 4% lower mumax and 5% lower ODmax values as compared to cultures where the corresponding YEF was used as medium supplement. This could also be partially related to the different nitrogen contents of the filtrates and retentates.
Ultrafiltration failure (UFF) is a common complication of long-term peritoneal dialysis (PD). Functionally UFF is in most cases characterized by an enhanced peritoneal mass transfer area coefficient for glucose (PS(g)) combined with a largely unchanged peritoneal glucose osmotic conductance (L(p)Ssigma(g)). Morphologically, marked UFF occurs with fibrosis of the submesothelial zone in the peritoneum, combined with vasculopathy and vascular proliferation in deeper tissues. To computer simulate UFF, changes both in the vasculature and in the interstitium have to be taken into account. For that purpose, we used a three-pore membrane/fiber matrix serial barrier model, applying the three-pore model to the capillaries and the fiber-matrix model to the interstitium. The parameters of the three-pore model have been published previously. The interstitial fiber density was set at 0.5% (vol/vol) and the fiber radius (r(f)) at 6 A during control. If the interstitial fiber density was increased from 0.5 to 3%, and r(f) to 7.5 A (cf. collagen) while the capillary surface area was increased by 40% from control, then PS(g) increased from 9.3 to 11.5 ml/min, while the UF coefficient (L(p)S) was largely unchanged. Further increases in vascular surface area combined with further increases in fiber density caused further increments in PS(g), whereas L(p)S remained unchanged. It is concluded that a matrix of fibers coupled in series with a three-pore membrane may be used for simulating the pathophysiological alterations occurring in the peritoneum in UFF, explaining the commonly observed "uncoupling" of small solute transport (PS) from the peritoneal UF coefficient (L(p)S) in this condition.
Various experimental maneuvers, hormones, and pharmacological agents are reported to exert their effects on glomerular filtration largely or exclusively by changing the ultrafiltration coefficient (Kf) of the filtration barrier. In light of a number of uncertainties discussed in this review, however, it is by no means certain that the Kf actually does play this central role in the physiological regulation of glomerular function.
BACKGROUND/AIMS: To compare dialysance and ultrafiltration (UF) of peritoneum in diabetes mellitus (DM) and non-DM patients on continuous ambulatory peritoneal dialysis. METHODS: A total of 162 adult patients on continuous ambulatory peritoneal dialysis (40 DM and 122 non-DM patients) were studied with the peritoneal equilibration test (PET) using 2.5% glucose dialysis solution retained for 4 h. Patients using 2,000 or 1,500 ml of infusion volume were classified into groups A (23 DM and 63 non-DM patients) and B (16 DM and 41 non-DM patients), respectively. PET results were compared between DM and non-DM patients by unpaired t test. Using Pearson's correlation and least-square multiple regression, the most powerful predictors of UF rate were also evaluated in DM and non-DM patients. RESULTS: There were no differences between PET parameters and UF rate between DM and non-DM patients in the whole group (WG) and group A. The only significant difference (p < 0.05) was an increased D4/D0 value in DM patients in group B. The most simple but powerful method to predict UF rate was (100 - GAP)/(D4/D0), where GAP corresponds to the glucose absorption percentage and D4/D0 is the PET 4-hour dialysate glucose level/PET 0-hour dialysate glucose level. GAP and D4/D0 were two major determinants of UF rate in the DM group, non-DM group and WG. CONCLUSIONS: Peritoneal permeability did not differ between DM and non-DM patients, and GAP and D4/D0 were two major factors predicting UF rate.
To determine the effect of dialysate osmolarity on peritoneal dialysis drug transfer, peritoneal dialysis clearances of theophylline, phenobarbital, and tobramycin were determined in 10 rabbits using dialysate containing 1.5 and 4.25% glucose. Urea and creatinine clearances were also obtained for comparison. Under similar dialysis conditions, the peritoneal clearances of the three drugs remained unchanged for the two types of dialysate. In contrast, the peritoneal clearances of urea and creatinine were significantly higher with the use of 4.25% glucose dialysate (p less than 0.001). Thus, peritoneal dialysis clearances of theophylline, phenobarbital and tobramycin are not significantly affected by hypertonicity-induced ultrafiltration during acute peritoneal dialysis.
During continuous ambulatory peritoneal dialysis (CAPD) treatment, loss of ultrafiltration capacity (UFC) is a common complication that can be associated with increased peritoneal fluid absorption rate. The aim of the present study was to investigate the relative importance of lymphatic absorption for total peritoneal fluid absorption in patients with permanent loss of UFC associated with a high peritoneal absorption rate (KE, ml/min; high-KE group, n = 4). Clinically stable CAPD patients (n = 23) as well as patients with loss of UFC associated with increased diffusive mass transport coefficients (KBD, ml/min; high-KBD group, n = 8) served as control groups. The patients were investigated with a 6-hour dwell study with 3.86% glucose solution. The total fluid absorption rate was estimated by the disappearance rate (KE) of 131I-radioiodinated human serum albumin (RISA) from the peritoneal cavity, and the lymphatic absorption rate was estimated by the rate of RISA appearance in plasma (KPP, ml/min). The values of KE and KPP in the high-KE group (4.65 +/- 0.93 and 0.42 +/- 0.31 ml/min, respectively) were markedly higher than in the clinically stable CAPD patients (1.77 +/- 0.60 and 0.15 +/- 0.06 ml/min, respectively; both p < 0.001 vs. the high-KE group). In the high-KBD group, KE was lower (2.19 +/- 0.38 ml/min, p < 0.001) compared to the high-KE group, whereas KPP was similar (0.26 +/- 0.09 ml/min, NS). The fraction of KE which could be accounted for by KPP was on average only 9 +/- 5% in the high-KE group and did not differ from the fractions in the clinically stable patients or in the high-KBD group (9 +/- 5 and 12 +/- 4%, respectively). In 5 patients in whom plasma RISA activity was measured for 24 h from the beginning of the 6-hour dwell study, a continuous increase of the RISA level in plasma was observed during this time period. We conclude that although KPP was increased in patients with UFC loss associated with high KE, it accounted for only a minor part of KE. Furthermore, the relatively slow but prolonged appearance of RISA in plasma indicates that the interstitial compartment may serve as a reservoir of macromolecules which are slowly absorbed by local lymphatics. The present study supports previous findings that direct lymphatic absorption is only of relatively minor importance for the fluid absorption in peritoneal dialysis.
Undetected excessive ultrafiltration (UF) occurred in 2 patients on maintenance haemodialysis (HD) using a Gambro AK-10 monitor and Ergo 120 A-G blood lines. In spite of alarms present on the monitor, the dialysis staff was not alerted to the faulty condition. Through investigation of the HD 'set-up' at the time of the incidents it was found that a partial obstruction (kinking) had occurred in the extracorporeal blood circuit where the flexible tubing joined the venous chamber. This created a very high positive pressure within the dialyzer compartment and excessive UF, which the blood circuit pressure monitoring transducer was unable to detect. To prevent kinking of the blood lines, dialysis staff and patients should be instructed to ensure that blood lines lie in smooth curves.
Removal of excessive fluid with a negative-pressure hydrostatic ultrafiltration technique using a partial vacuum was performed successfully in eight patients. The technique appears to be a satisfactory means of fluid removal.
Although genetically engineered human growth hormone (hGH) is now commercially available, native pituitary-derived hGH is still used by physicians in many countries for the treatment of hormone deficiency states. We describe a method using ultrafiltration and 6 M urea that reduced infectivity in human pituitary tissue that had been deliberately contaminated with scrapie virus (an animal analogue of human Creutzfeldt-Jakob disease virus) from an initial level of 10(9.7) infectious units to just 5 infectious units. Based on estimates of the frequency of contamination and infectivity levels in batches of human pituitaries, the use of this protocol to prepare GH from cadaveric human glands yields a calculated probability of exposure to a contaminated vial of not greater than 1 in 3.2 million recipients; therefore, native hormone prepared by this method may be considered to be essentially risk-free. The same methodology may be useful in the preparation of other hormones, such as prolactin, for which no synthetic substitutes are currently available, as well as biological products derived from sheep or cattle, that may be infected with scrapie or bovine spongiform encephalopathy.
We studied the role of blood-dialyzer-membrane interactions in hemodialysis-induced hypoxemia by measuring PaO2 and white blood cell counts during isolated ultrafiltration (UF). These values were compared to those obtained from the same patients during subsequent hemodialysis (HD; utilizing the same dialyzer and membrane). Patients in the UF period displayed no hypoxemia, rather a slight increase in PaO2 (from 82.5 +/- 3.0 to 88.5 +/- 2.0 mm Hg, mean +/- SE, p greater than 0.05). In contrast, these patients displayed significant hypoxemia when HD was imposed (88.5 +/- 2.0-78.0 +/- 1.5 mm Hg, mean +/- SE, p less than 0.02). We suggest that the hypoxemia characteristic of HD initiation is not solely dependent on blood-dialyzer-membrane interactions, but also requires blood-dialysate interactions.
Ultrafiltration experiments, using Amicon membranes with molecular weight exclusions of 1,000, 10,000 and 30,000 daltons, have revealed that Desferal, both in vitro and in vivo, markedly increases aluminum ultrafilterability in plasma from patients with dialysis dementia. Ultrafilterability was greater with the 10,000-dalton membrane (60%) as compared with the 1,000-dalton membrane (40%); the difference could be related to the presence of an 8,000-dalton aluminum-binding protein in the 10,000-dalton filtrate. These observations are pertinent to in vivo dialysis studies which have demonstrated enhanced aluminum clearance with high-permeability polyacrylonitrile dialysis membranes.
In September 1996, perfusionists from 50 paediatric open-heart surgery programmes were contacted to identify centres that are currently using the technique of modified ultrafiltration (MUF). Of the 50 centres contacted, 22 (44%) were utilizing the technique. These centres were surveyed on the following: neonatal circuit description, patient entry criteria, MUF circuit description, conduct of MUF, use of extracorporeal safety devices and/or modifications, and technical complications. All 22 centres used roller pumps and membrane oxygenators. In 19 centres, MUF was utilized exclusively in the arteriovenous mode (86%), while two centres (9%) used the venovenous mode and one centre (5%) used both methods. Most (82%) of the 22 MUF centres used a blood cardioplegia system for myocardial preservation. After cardiopulmonary bypass (CPB), these blood cardioplegia systems were often converted for use as MUF circuits in a variety of ways. Other methods of accessing the CPB circuit for MUF included utilizing either a recirculation line or a dedicated port added to the circuit specifically for MUF. Blood flow rates during MUF, pump strategies, haemoconcentrator vacuum levels and endpoints were variable from centre to centre. Technical complications related to MUF were reported by 82% of the surveyed MUF centres. The most common complication, air cavitating into the circuit, was reported by 15 centres. From these data, we propose recommendations on the integration of MUF into CPB circuits, the conduct of perfusion during MUF, and appropriate safety considerations to minimize technical complications.