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PubMedDate not supplied

[Analysis of geometric parameters and mechanical properties of erythrocytes by filtration through nuclear membrane filters. II. Experimental verification of a mathematical model].

In the accompanying paper the process of erythrocyte passage through pores of membrane nuclear filters has been modelled. In order to test the model we have studied how the filtration rate of human erythrocyte suspension depends on osmoticity of the resuspending medium at various experimental conditions. We have tested and verified the model conclusion that the zero filtration rate is reached at the critical osmoticity value which depends only on geometrical parameters of the pore and the cell and not on other properties of the erythrocyte. It has been demonstrated that the relative filtration rate only weakly depends on the hydrostatic pressure, in agreement with the model predictions. There is a good correspondence between the model and the experimental data about how the filtration rate is influenced by the viscosity of the intracellular content and the mechanical characteristics of the erythrocyte membrane at various temperatures.

Biomechanical Phenomena↗
PubMed1994

Filtration of cerebrospinal fluid in acute inflammatory demyelinating polyneuropathy (Guillain-Barré syndrome).

INTRODUCTION: Acute Guillain-Barré syndrome (GBS) is a disease where cell-mediated and humoural immune reactions play a key role. Breakdown of the blood-nerve barrier, inflammation of the nerve roots and conduction block are leading symptoms. As it is likely that pathological humoural or cellular factors are concentrated in the subarachnoid space and since factors in the cerebrospinal fluid (CSF) of GBS patients were shown to block sodium channels, a direct therapeutic intervention in the intrathecal compartment seemed worthwhile. METHODS: For this purpose, we developed a technique to purify CSF from pathological factors. Filtration was achieved by withdrawal of CSF (through a lumbally inserted 18 G catheter) and reinfusion via specially developed filters. RESULTS: Twenty severely affected GBS patients were treated with 4 to 38 CSF filtrations. This eliminated cells (> 99%) and reduced the protein content. Clinical improvement was achieved probably by improvement of nerve conduction following a reduction of sodium channel blocking factors. The median time to one grade improvement was 19 days, to reach grade 2 (independent walking) was 42 days. Ventilated patients were weaned from the ventilator after 16 days (median). Patients for which CSF filtration was the first kind of treatment improved faster than patients that had not responded to other treatments, such as plasma exchange or intravenous immunoglobulins. DISCUSSION AND CONCLUSION: Severe side effects were not observed, except sometimes transient headache during the withdrawal phase. This therapy seams to shorten treatment time (in comparison to times reported in studies with and without GBS-specific treatment by plasma exchange or immunoglobulins) and to reduce the degree of remaining neurological deficits. An open randomized controlled study is currently being conducted to compare CSF filtration with plasma exchange.

Acute Disease↗
PubMed1993

Membrane filtration of pharmaceutical solutions.

The principles and uses of membrane filtration in the preparation of pharmaceutical solutions are discussed. The preparation of pharmaceutical solutions often requires their passage through a thin polymeric membrane containing many tiny pores. The purpose is to remove viable and nonviable particles in order to clarify or sterilize the solution. Particles may be retained by sieving, entrapment, or electrostatic attraction. The largest pore size that will yield a sterile filtrate is 0.2 microns. Membrane filters are either hydrophobic or hydrophilic. The rate of flow through a filter is affected by the resistance of the filter, the viscosity of the solution, and pressure. Filters are commonly composed of mixed esters of cellulose, polysulfone, polyvinylidene difluoride, nylon 66, polycarbonate, or polytetrafluoroethylene. In selecting a membrane filter, a pharmacist must consider pore size, compatibility, fluid volume, particulate load, and the filter holder. Various tests are available to evaluate the integrity of filters. Filters are useful in testing end products for sterility. The use of an in-line filter during the administration of large-volume injectable solutions can prevent the introduction of particles, air, and microorganisms into the patient. Therapies in which a 0.2-micron filter may be contraindicated include lipid emulsions, low-dose infusions, low-volume infusions, drugs for which the pharmacologic properties are altered by the membrane filter, and drugs that adhere to the membrane. Pharmacists need an in-depth understanding of the principles of filtration, the characteristics of filters, and their use in the filtration of pharmaceutical solutions.

Drug Compounding↗
PubMed1994

Bedside filtration of blood products in the prevention of HLA alloimmunization--a prospective randomized study. Alloimmunisation Study Group.

To test the efficacy of poststorage bedside leucodepletion of blood products in the prevention of primary HLA alloimmunization and its clinical sequelae, 172 patients with hematologic malignancy requiring intensive red blood cell and platelet support were randomized to receive either standard or filtered red blood cells and platelets. Quality control of bedside filtration was explored by sequential sampling downstream of the filter, but this did not predict the total number of leucocytes transfused. After exclusions, 123 evaluable patients were assessed every two weeks until the end of therapy. HLA antibodies developed in 21 of 56 (37.5%) nonfilter (NF) and 15 of 67 (22%) filter (F) patients (risk ratio estimate, 0.60 [95% confidence interval, 0.34 to 1.05]; P = .07). Patients with acute myeloid leukemia (AML; n = 53) had higher alloimmunization rates in both arms of the study, with a greater effect of filtration (62.5% NF and 31.0% F; P = .025). Bedside filtration did not affect the overall incidence of febrile transfusion reactions (FTRs; 37% NF and 34% F; P = .71) or of platelet refractoriness assessed in 50 patients (30% NF and 26% F), despite an association between broad HLA reactivity and both FTRs and refractoriness. However, FTRs were also seen in 28 patients without HLA antibodies. Five alloimmunized refractory patients (2 F and 3 NF) required HLA-selected platelets. This report, the first prospective study of bedside filtration, has failed to show clear clinical benefit. Methodological limitations may account in part for this failure, notably the difficulties in accurately assessing the number of leucocytes transfused.

Adolescent↗
PubMed1996

[Double filtration and immunoadsorption plasmapheresis in Guillain-Barré syndrome].

We studied the effect of double filtration and immunoadsorption plasmapheresis in Guillain-Barré syndrome retrospectively in 70 patients. Thirty three patients had plasmapheresis, of whom 23 had double filtration and 10 immunoadsorption. The rest of 37 patients consisted of a control group. Clinical disability was evaluated using the functional grading scale by Hughes. In patients having a maximum disability of grade 4 and 5, the double filtration plasmapheresis group showed statistically significant improvement at 3 months after the treatment. There was no significant difference in prognoses between the immunoadsorption plasmapheresis and control groups. In mildly-illed patients having grade 2 and 3, the prognoses were not different between the three groups. In Guillain-Barré syndrome, double filtration plasmapheresis, as well as well-established plasma exchange, had benefit for severely-illed patients.

Adult↗
PubMed1996

[Clinical experience of automated double filtration plasmapheresis].

Double filtration plasmapheresis, one kind of fractionation plasmapheresis, was developed from membrane type plasmapheresis to remove only the pathogen and return the normal protein back to the patient. We started our automated double filtration plasmapheresis since December 1993. There were 13 patients who received one hundred treatments totally during one year period. And they are myasthenia gravis (8 patients); acute inflammatory demyelinating polyneuropathy (1 patient), multiple myeloma (1 patient); acquired factor VIII inhibitor (1 patient); autoimmune hemolytic anemia (1 patient); systemic lupus erythematous (1 patient). Technically double filtration plasmapheresis is easy to perform and time-saving. It also makes necessity of replacement fluid less frequent. Incidence of complication is rare, and this includes hypotension 2%, palpitation 1%, headache 1%, hemolysis 4%, air emboli 1%, high secondary pressure 2%, and no motality during our treatment. Clinical response is documented in cases of myasthenia gravis; acute inflammatory demyelinating polyneuropathy and acquired factor VIII inhibitor in our study. In conclusion, double filtration plasmapheresis is a time-saving, convenient, and safe therapeutic modality with rare complication. Because its effectiveness on limited kinds of diseases and costs relatively high price, thus plasmapheresis should be used in selected cases and treat aggressively if indicated.

Adolescent↗
PubMed1977

Effect of inline filtration on the potency of drugs administered intravenously.

The binding of cephalothin sodium, phenobarbital sodium, dexamethasone sodium phosphate, isoproterenol hydrochloride, digoxin, dactinomycin and phenytoin sodium to three intravenous inline filters--a 5-micrometer stainless steel depth filter, a 0.2-micrometer cellulose ester membrane and a 0.2-micrometer polycarbonate membrane--was studied. The experiments were conducted simulating inline i.v. filtration of these drugs in three i.v. solutions--lactated Ringer's, 5% dextrose and normal saline. Cephalothin was assayed colorimetrically, phenobarbital and phenytoin spectrophotometrically, and the other drugs by radiotracer technique. Binding of the drugs to the filter was found to be insignificant from a therapeutic standpoint, except for dactinomycin which bound to the 0.2-uicrometer filters. The binding of dactinomycin was approximately 13% of the amount administered through cellulose ester and polycarbonate membranes, respectively. The binding occurred during the initial period of filtration of the drug solution. It was concluded that inline filtration of drugs administered in relatively high does should not present any problem concerning the reduction of the therapeutic potency because of filtration.

Cephalothin↗
PubMed1979

Combination of a viability test and a quantification method for Schistosoma haematobium eggs (filtration--trypan blue-staining-technique).

The efficiency of the polycarbamate membrane filtration technique for detecting Schistosoma haematobium eggs in urine has been increased by using a pore size of 14 micrometers diameter and the suction of a water jet pump. The technique permits filtration of several 1000 ml of urine in one test. Eggs concentrations of 1 egg in more than 1000 ml of urine were detected. Viability was assess after filtration by staining with trypan blue. Preliminary data of 118 Schistosoma haematobium-positive urine samples of 32 patients suggest that the filtration trypan blue-staining-technique is of high validity in light infection with scanty egg-output.

Filtration↗
PubMed1994

[In-line-filtration of erythrocyte concentrates using the Leukotrap-RC system].

'In-line filtration' was performed on whole blood (WB) of 12 healthy donors. The WB was drawn into the triple-bag Leukotrap-RC system. Six red cell concentrates (RCC) were filtrated 1 h after donation either with or without buffy-coat and stored 35 days in AS-3. We measured the loss of red cells, the residual white cell count (Nageotte chamber), platelet count in fresh frozen plasma (FFP); 2,3-DPG, K+, Hbe, pH, O2Hb and pO50. The system was easy to handle but needed circular centrifugation holders because the filter is placed and fixed just at the top of the bags during centrifugation. RCC without buffy coat led to a faster filtration (15 vs, 38 min) and to an improved FFP quality (platelet count 23 vs, 54 Gpt/l). The leucocyte removal rate of the integrated PALL-RC-350 was similar, residual white cell count less than 3 x 10(6), in both preparations. All storage parameters were found within the normal range except a significant increase of O2Hb in filtrated red cells compared with the unfiltered control.

Blood Donors↗
PubMedDate not supplied

Measurement of nephron filtration from distal and proximal tubules.

Nephron filtration rate (SNGFR), measured proximally by micropuncture using the technique of total collection of tubular fluid, may be spuriously high as the fall in intratubular pressure during collection may increase the net filtration pressure. Alternatively, the interrupted distal delivery of tubular fluid during proximal collection may up-regulate SNGFR by activating the tubulo-glomerular feedback. The accuracy of nephron filtration measurements was tested in 65 rats, by sampling from the distal and then from the proximal tubule of the same nephrons. Collections were also made in the presence of high concentrations of furosemide at the dose of 10 mg/kg i.v. In 290 nephrons, distal SNGFR was not significantly different from the paired measurements obtained from the proximal tubule (39+/-1 vs 39+/-1 nl/min, p > 0.83). During furosemide, the paired data were 42+/-2 vs 41+/-2 nl/min, p > 0.82, n=92. Different hydration conditions did not influence the results. The correlation between distally and proximally measured filtration rates held for the whole range of measurements (R=0.56; p < 0.0001). Under the present experimental conditions, SNGFR is not spuriously high when measured by total blockade of the proximal tubule. The accuracy of measurements and their reproducibility is not influenced by the site of sampling.

Animals↗
PubMed1998

Kinetics of bradykinin levels during and after leucocyte filtration of platelet concentrates.

OBJECTIVE: To measure bradykinin levels in platelet concentrates during and after leucocyte filtration. METHODS: Platelet concentrates were leukocyte depleted using three different leucocyte-depletion filters selected to represent filters with negative, positive or neutral charge, respectively. Bradykinin levels were analysed before, during and up to 90 min post-filtration. RESULTS: Significant levels of bradykinin were generated when negatively charged leucocyte depletion filters were used. However, we found a high variation between platelet concentrates prepared from different donors as well as within the same concentrate when this was divided into three aliquots. Generated bradykinin was rapidly degraded in the collection bag and no bradykinin was detectable 60 min post-filtration. CONCLUSION: Bradykinin generation is more pronounced when negatively charged leucocyte removal filters are used. Due to a rapid degradation of bradykinin in the storage bag, pre-storage filtration should minimise the risk of bradykinin related adverse reactions during transfusion with some filters.

Adolescent↗
PubMed1999

Mitotic effect of autologous blood injection and diode laser bleb revision on rabbit filtration blebs.

OBJECTIVE: To investigate the effect of intrableb autologous blood injection and diode laser bleb revision on cellular proliferation in filtration blebs of rabbits. METHODS: Bilateral filtration surgery with mitomycin was performed on 19 white 2.5- to 3-kg New Zealand rabbits. Autologous blood injection (n = 9) or diode laser bleb revision (n = 10) was performed on blebs of right eyes (intervention eyes) on day 14 after filtration surgery. The blebs of the left eyes served as controls. Cellular proliferation was assessed by in vivo incorporation of 5-bromo-2'-deoxyuridine (BrdU), after BrdU, 10 mg/kg, was injected via the ear vein on days 15, 16, and 18. The rabbits were euthanized on day 21. Conjunctival sections were stained with hematoxylin-eosin for total cell counts and with anti-BrdU antibody for counts of proliferating cells. The BrdU labeling index was calculated by dividing the mean proliferating cell count by the mean total cell count. RESULTS: The BrdU labeling index was significantly increased in the blood-injected eyes as compared with the control eyes (P = .03). The BrdU labeling index was increased in the diode laser-revised eyes as compared with the control eyes, approaching significance (P = .06). Intraocular pressure increased significantly in the eyes that underwent bleb interventions in both groups from baseline and compared with the control eyes. CONCLUSIONS: Intrableb autologous blood injection and diode laser bleb revision stimulate cellular proliferation in the rabbit filtration bleb, which may contribute to the rise in intraocular pressure observed clinically after these interventions.

Animals↗
PubMed1999

Filtration leukocytapheresis therapy in rheumatoid arthritis: a randomized, double-blind, placebo-controlled trial.

OBJECTIVE: To determine the efficacy and safety of filtration leukocytapheresis (LCP) for the treatment of rheumatoid arthritis (RA). METHODS: Twenty-five patients with drug-resistant RA were randomly assigned to undergo filtration LCP and 7 to undergo sham apheresis (control group) in a randomized, double-blind, placebo-controlled study. Three apheresis procedures were performed, with 1-week intervals between procedures. The efficacy of filtration LCP was evaluated according to the American College of Rheumatology definition of improvement in RA. Medications for each patient were unchanged for at least 6 months prior to enrollment and throughout the study. RESULTS: Tender joint counts, swollen joint counts, patient assessment of pain and global severity, physician assessment of global severity, and Health Assessment Questionnaire Disability Index were significantly improved in the LCP group compared with the control group (P < 0.05 for patient assessment of pain; P < 0.01 for all others). Seventy-nine percent of the patients in the LCP group exhibited significant overall improvement, while none of the patients in the control group were improved (P < 0.001). CONCLUSION: The results indicate that filtration LCP is an effective and well-tolerated treatment for patients with drug-resistant RA.

Adult↗
PubMed1995

A filtration-based assay to quantitate granulocyte-macrophage colony-stimulating factor binding.

Filtration-based binding assays have numerous advantages over centrifugation-based assays, yet they have not been established for many protein ligands due to the high nonspecific binding of the protein to the membrane filter. This paper describes a vacuum filtration method that permits quantitative evaluation of [125I]GM-CSF binding to its receptor on intact cells. The method includes the use of glass fiber filters presoaked in a solution of polyvinylpyrrolidone and Tween 20 to greatly reduce nonspecific binding of the protein ligand. The ratio of specific:nonspecific binding observed with this filtration assay was comparable to values reported for centrifugation assays. [125I] GM-CSF binding to HL-60 cells was shown to be time-dependent, saturable, and specific. The estimated Kd (70 pM) and Bmax (160 r/cell) were similar to values reported using centrifugation assays. This filtration method is much less labor-intensive, has greater sample throughput, and allows for a more rapid determination of GM-CSF binding compared to the centrifugation-based assay. Although developed to quantitate the binding of GM-CSF to its receptor on intact cells, this assay is also applicable to other cytokines and can be used with both intact cells and isolated plasma membrane preparations.

Cell Line↗
PubMed2000

The removal of viruses during the purification of equine antisera using filtration aids Hyflo Super-Cel and Fulmon Super A.

The manufacturing process in Australia for equine antisera against various venoms/toxins is based primarily on ammonium sulphate precipitation of pepsin-digested IgG, whereby Fc and F(ab')(2)fragments are separated. The capacity of the process to remove non-enveloped and enveloped model viruses was assessed using a scaled-down process. Each virus was added to mid-process samples from equine plasma before the material was applied to Hyflo Super-Celtrade mark filtration followed by Fulmonttrade mark Super A filtration. Samples were analysed pre- and post-filtration and the log clearance of the viruses calculated. The mean clearance factors for viral load of canine adenovirus type II (CAV(2)), poliovirus type 1 (PV1), infectious bovine rhinotracheitis virus (IBR) and canine distemper virus (CDV) were 5.3 logs, 4.2 logs, 5.7 logs and 4. 0 logs respectively. Clearance results as virus is adsorbed to the filtration aids which are removed from the process, thereby demonstrating improved viral safety of equine antisera produced by CSL.

Adenoviruses, Canine↗
PubMed1997

Particle Detachment in Deep Bed Filtration

The paper examines the behavior of particle detachment in deep bed filtration and the dependence of particle detachment on several filtration operating parameters. Theoretical analysis was carried out by considering the balance of various relevant interaction forces. Based on the results, experiments were conducted to study the effect of particle size, filter grain size, and headloss gradient on particle detachment in deep bed filtration. In one set of experiments, the filter was operated at constant filtration rate in order to build up the headloss across the filter bed continuously. In the other set of experiments, the filter in operation was allowed to experience a short period of flow shock (i.e., to be subject to a higher flow rate during this period). Both sets of experiments confirmed the dependence of particle detachment on particle size, collector gain size, and headloss gradient (degree of filter clogging) of the filter, as predicted by the analysis.

Journal Article↗
PubMedDate not supplied

Atrial natriuretic peptide alters neither capillary filtration nor vascular compliance of both skin and skeletal muscle of humans.

We studied the effects of hANP 99-126 on capillary filtration and venous compliance in both the calf (mainly skeletal muscle) and foot (mainly skin) of humans. Six healthy mean received ANP (intravenous injection of 25 micrograms followed by continuous infusion of 0.1 microgram.kg-1.min-1) for 30 min. Another six men served as time controls. Capillary filtration coefficient, venous compliance, and also volume and blood flow of both calf and foot were measured repeatedly by occlusion plethysmography before, during, and after ANP. Additionally, we determined hematocrit, central venous pressure, venous pressure in the foot, arterial pressure, and heart rate. Filtration coefficients, venous compliance, blood flow of both calf and foot as well as arterial blood pressure did not change systematically during the infusion of ANP, and yet leg volume and central venous pressure (3.1 +/- 0.8 cm H2O) decreased while both hematocrit (3.1 +/- 1.0%) and heart rate (17 +/- 11 min-1) increased. Thus, the ANP-evoked decrease in central venous pressure and increase in hematocrit are unrelated to blood pooling or increases in capillary filtration in skeletal muscle and skin of healthy humans.

Adult↗
PubMedDate not supplied

Assessing microvascular volume change and filtration from venous hematocrit variation of canine liver and lung.

The volume increase of canine liver after 1 min of a 10 mmHg elevation in hepatic venous pressure has been reported as 251 ml/kg tissue. An analysis of the transient hematocrit variation in hepatic venous blood indicated that 16% of the volume change results from transcapillary filtration, 72% from microvascular expansion, and 12% from macrovascular expansion. In the analysis, we first used the temporal change of the liver volume to determine the time course of the filtration and microvascular and macrovascular volume change. We next deduced, for a permeable microcirculation with a microvascular hematocrit lower than the feed hematocrit (the Fahraeus effect), how the filtration and microvascular volume change (MVC) produce a hematocrit variation in the blood leaving microcirculation. By accounting for the dispersion of the blood flow, the analysis predicted a hematocrit variation in the hepatic venous blood that matched well with the measured variation over the 1-min course of experiment. A reasonable fit with the hematocrit variation of pulmonary blood also was obtained for experiment with an 8 mm/Hg increase in the arterial and venous pressure perfusing the canine left lower lung lobe. The tissue and vascular volume increase at 1 min was 149 ml/kg tissue with 4% as a result of filtration, 41% as a result of microvascular expansion, and 55% as a result of macrovascular expansion. The large MVCs from the hepatic and pulmonary circulation indicate their microcirculations function as a reservoir in controlling blood volume redistribution.

Animals↗