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At least 757 records · Page 42Linked to original sources
PubMed1994

[Effects of age on filtration coefficient in isolated zone 3 rat perfused lungs].

To investigate the effect of age on the filtration coefficient (Kf) in isolated rat perfused lungs, we divided 18 Sprague-Dawley rats randomly into 3 groups; 1) 5 wk of age, 150 +/- 1.5g, n = 6; 2) 10 wk of age, 320 +/- 18.8g, n = 6; and 3) 14 wk of age, 460 +/- 10.0g, n = 6. We used Krebs-Henseleit solution with 5% bovine serum albumin as the perfusate and maintained perfusion using constant pressure circuit system. We calculated the filtration coefficient in isolated rat perfused lungs in zone 3 conditions (pulmonary arterial pressure > pulmonary venous pressure > alveolar pressure) using gravimetric method. The filtration coefficients in rats of 14 wk of age were 3-fold higher than those in other two groups (Kf = 5.31 +/- 0.29 mg.min-1.cmH2O-1.g-1 in 5 wk of age, 5.38 +/- 0.49 mg.min-1.cmH2O-1.g-1 in 10 wk of age and 16.17 +/- 0.46 mg.min-1.cmH2O-1.g-1 in 14 wk of ages). Also, there were a large population of leukocytes in lung of 14 wk of age, but not in 5 wk and 10 wk of age. In addition, the filtration coefficients in 5 wk and 10 wk of age were of the same magnitude as in other investigators' reports. We conclude that rat in 10 wk of age is suitable for the evaluation of the pulmonary vascular permeability.

Aging↗
PubMed1993

The use of 5-fluorouracil in glaucoma filtration surgery.

Failure of glaucoma filtration surgery usually results from scarring at the surgical site. Studies have shown that fibroblast proliferation plays an important role in scar formation which results in a mechanical barrier to filtration (Gressel, Parris, & Folberg, 1984). Fibroblasts are immature collagen-producing cells which proliferate at the site of chronic inflammation. The antimetabolite 5-fluorouracil (5-FU) can inhibit fibroblast activity. Over the past ten years, the adjunctive use of 5-FU in filtration surgery has met with increased success and is particularly indicated in those patients at greatest risk of filtration failure.

Aged↗
PubMed1993

Hypotony maculopathy following the use of topical mitomycin C in glaucoma filtration surgery.

Intraoperative mitomycin C has been shown to be highly effective in increasing the success rate of glaucoma filtration surgery. Between October 1991 and June 1992, 169 eyes of 156 patients underwent filtration procedures with intraoperative mitomycin C. In the postoperative period, five eyes (2.9%) developed hypotony maculopathy, characterized by disc edema, vascular tortuosity, and chorioretinal folds in the macular area. Cryotherapy was applied to three eyes, and was effective in reversing the hypotony in two of them. However, the visual prognosis was poor: after a mean follow up of 5.3 months (range, 3.5 to 8 months), visual acuity returned to preoperative levels in one case. Hypotony maculopathy may develop after glaucoma filtration surgery with intraoperative mitomycin C. We suggest restricting the indication of its adjunctive use to eyes with poor surgical prognosis or those in which a very low intraocular pressure is desired. The use of extra sutures (which can be sectioned by laser) or releasable sutures to prevent excessive filtration in the postoperative period also is advisable.

Administration, Topical↗
PubMed1977

ST segment distortions by high-side frequency filtration in direct-writing ECG recorders.

ST segment depression in 12-lead resting and single-lead or multi-lead exercise ECGs is a useful screening criterion for detection of coronary heart disease (CHD). The recommended minimum frequency specification for direct-writing ECG recorders is 0.05-100 Hz (-3 dB). ST segment distortion by unintention low- and high-side frequency filtration could possibly weaken this screening capability. Consequently, one low- and two high-side potential filtration causes of such distortions were investigated in resting and exercise recordings of normal and both J-junction and ST-depressed ECGs. Of 4,914 filtered ST segments, 365 ST category changes were observed. Of these changes, approximately 15% was produced by filtration of the 0.05-0.1 Hz (amplifier function) and 45-100 Hz (60-Hz "noise" filtering) frequency bands. The remaining 85% was attributable to filtration of the 23-45 Hz (stylus overpressure) band. An optional remedy is discussed.

Adult↗
PubMed1996

Ultrastructural features of filtration blebs with different clinical appearances.

The authors studied two functioning filtration blebs to evaluate a possible transconjunctival route of aqueous humor flow and describe potential differences between thin cystic and thick opaque functioning filtration blebs. The specimens were prepared for light and electron microscopy immediately after surgical excision because of filtration bleb discomfort. Both blebs had normal collagen in the substantia propria. The collagen, however, was widely spaced and subepithelial connective tissue loosely arranged. Clear spaces were seen in the superficial substantia propria. Epithelial cells were focally acantholytic, separated by clear spaces. Consequently, clinically distinct blebs demonstrated similar histologic and ultrastructural features. The epithelial intercellular spaces observed in this study provide anatomic evidence that aqueous could move transconjunctivally as a mechanism for filtration bleb function.

Aged↗
PubMed1997

[Leukocyte filtration in elective colorectal surgery. Reduced transfusion associated immunosuppression after bedside procedures].

The objective of the study was to investigate certain immune parameters in patients undergoing elective colorectal surgery and receiving either whole blood transfusion or leucocyte-filtrated blood. Sixty consecutive patients were randomly allocated to receive either whole blood transfusion or leucocyte-filtrated blood leucocyte when transfusion was indicated. The immune parameters were investigated on the day of surgery and on day 3, 7 and 30 postoperatively. Transfusion with whole blood was followed by a significant decrease in lymphocyte proliferation and CD4+/CD8+ ratio (p < 0.01) as well as a significant increase in soluble interleukin-2 receptor and interleukin-6 (p < 0.01). Furthermore transfusion with whole blood was accompanied by a significant increase in postoperative infectious complications (p < 0.01). Patients transfused with leucocyte-filtrated blood had only minor and passing changes in the immune parameters and developed no infectious complications, indicating that effective leucocyte filtration abolishes transfusion-associated immunosuppression.

Adult↗
PubMed1997

Transconjunctival mitomycin C as an adjunct to conventional glaucoma filtration surgery in rabbits.

PURPOSE: Subconjunctival mitomycin C has been used in glaucoma filtration surgery with success. A prospective, randomized, masked, placebo-controlled study was performed to evaluate whether single transconjunctival mitomycin C applied either preoperatively or postoperatively would enhance the success of filtration surgery in rabbits. METHODS: Two groups of 5 rabbits were studied. In Group I, a Weck-Cel sponge soaked in 0.5 mg/ml mitomycin C was applied transconjunctively for 7 minutes immediately before a full thickness filtering procedure. The other eye was treated similarly with a sponge soaked in balanced salt solution. Group II first underwent filtration surgery followed by treatment with either mitomycin-c or balanced salt solution 3 days later. Postoperative intraocular pressure, bleb status, and complications were evaluated. Treatment failure was defined as postoperative pressure within 4 mmHg of that determined preoperatively or the absence of bleb formation. RESULTS: In Group I, mean time to failure (+/- SD) was significantly longer (p = 0.03) in experimental eyes (30 +/- 15.1 days) than control eyes (8.6 +/- 0.8 days). In Group II, the time to failure was 12.4 (+/- 2.6) days versus 9.6 (+/- 2.5) days in the experimental and control eyes respectively, but this was not statistically significant (p = 0.10). Transient limbal vascularization and corneal haze were seen in all experimental eyes. Serious complications included late bleb rupture in eyes pretreated with mitomycin C (all eyes in Group I) and corneal decompensation (one mitomycin-c eye). CONCLUSIONS: This study demonstrates that a single preoperative tranconjunctival application of mitomycin-c is more effective at the time of surgery than an application applied in the intermediate postoperative period. Additional studies are needed, however, to further refine both the dose and timing of mitomycin-c application during filtration surgery.

Animals↗
PubMed1982

Internephron heterogeneity of filtration fraction and disparity between protein- and hematocrit-derived values.

The variability of single nephron filtration fraction (SNFF) and the relationship between filtration fractions determined simultaneously from 125I albumin (SNFFALB) and hematocrit (SNFFHCT) values were assessed by multiple samplings, 5 to 8 per kidney, in normal, hydropenic, Munich-Wistar rats. Single nephron filtration rate (SNGFR) measurements served as an independent marker of internephron heterogeneity. Whether derived as SNFFALB or SNFFHCT, a wide degree of internephron variability in SNFF, comparable to that found for SNGFR (P greater than 0.2) was observed in all kidneys. Hematocrit-derived SNFF values, however, were some 80% higher than those obtained with 125I albumin (SNFFHCT 0.447 +/- SEM 0.016 versus SNFFALB 0.258 +/- 0.009, P less than 0.001). The disparity in results obtained by the two methods disappears if the efferent arteriolar hematocrit (Hctg) is assigned a value 17 +/- SEM 1.4% higher than the corresponding femoral arterial hematocrit and might well be a reflection of the perfusion of superficial glomeruli with erythrocyte rich blood produced by the "plasma-skimming" phenomenon. The data suggest that multiple estimates of SNGFR and SNFF in a given rat kidney are needed to provide representative mean values for glomerular dynamic studies.

Animals↗
PubMed1975

The role of membrane parameters and of filtration pressure in the determination of the shape of the polyvinylpyrrolidone sieving curve. An in vitro and in vivo study.

The theoretical equations describing the transport of a solute across a porous membrane predict that the shape of the sieving curve (ratio of solute concentrations in filtrate and filtrand versus molecular size) depends not only on the porosity of the membrane but also on the filtration pressure. This has been verified experimentally on an artificial membrane (Amicon XM-50). This model has been used to interpret the effects of angiotensin II on the shape of the glomerular 125I PVP sieving curve. The mean effective filtration pressure is increased by the intrarenal perfusion of angiotensin II.

Angiotensin II↗
PubMed1998

Yeast suspension filtration: flux enhancement using an upward gas/liquid slug flow-application to continuous alcoholic fermentation with cell recycle.

This study deals with the use of an upward gas/liquid slug flow to reduce tubular mineral membrane fouling. The injection of air into the feedstream is designed to create hydrodynamic conditions that destabilize the cake layer over the membrane surface inside the filtration module complex. Experimental study was carried out by filtering a biological suspension (yeast) through different tubular mineral membranes. The effects of operating parameters, including the nature of the membrane, liquid and gas flowrates, and transmembrane pressure, were examined. When external fouling was the main limiting phenomenon, flux enhancements of a factor of three could be achieved with gas sparging compared with single liquid phase crossflow filtration. The economic benefits of this unsteady technique have also been examined. To investigate the possibility of long-term operation of the two-phase flow principle, dense cell perfusion cultures of Saccharomyces cerevisiae were carried out in a fermentor coupled with an ultrafiltration module. The air injection allowed a high and stable flux to be maintained over 100 h of fermentation, with a final cell concentration of 150 g dry weight/L. At equal biomass level, a twofold gain in flux could be attained compared with classical steady crossflow filtration at half the cost.

Alcohols↗
PubMed1998

Flux enhancement for membrane filtration of bacterial suspensions using high-frequency backpulsing.

A promising method for reducing membrane fouling during crossflow microfiltration of biological suspensions is backpulsing. Very short backpulses (0.1-1.0 s) have been used to increase the net flux for washed bacterial suspensions and whole bacterial fermentation broths. The net fluxes under optimum backpulsing conditions for the washed bacteria are approximately 10-fold higher than those obtained during normal crossflow microfiltration operation, whereas only a 2-fold improvement in the net flux is achieved for the fermentation broths. A theory is presented that is based on external fouling during forward filtration and nonuniform cleaning of the membrane during reverse filtration. The model contains an adjustable parameter which is a measure of the cleaning efficiency during backpulsing; the cleaning efficiency found by fitting the model to the experiments increases with increasing frequency and duration of the backpulses. The theory predicts an optimum backpulsing frequency, as was observed experimentally. An economic analysis shows that crossflow microfiltration with backpulsing has lower costs than centrifugation, rotary vacuum filtration, and crossflow microfiltration without backpulsing.

Biotechnology↗
PubMed1998

Quality evaluation by capillary electrophoresis of amphotericin B injection after filtration through various membrane filters.

The determination of amphotericin B, an antifungal agent, was developed using micellar electrokinetic capillary chromatography (MEKC) with a diode array detector. Repeatability and intermediate precision of MEKC analysis were acceptable. A high correlation was found between amphotericin B levels in pharmaceutical solutions obtained by MEKC and those by high-performance liquid chromatography (HPLC) (r = 0.994). This MEKC method is therefore useful for the determination of amphotericin B. The concentration of amphotericin B did not significantly change after filtration through polyethersulfone (PES, 0.2 microm) and polyvinylidene difluoride (PVDF, 0.45 microm) membrane filters. When the Fungizone injection was filtered through PES (0.2 microm) and added to 5% dextrose for injection (500 mL), particulate matters larger than 10 microm decreased by 64% to a level under the standard defined by United States Pharmacopoeia (USP XXIII). PVDF filtration (0.45 microm) did not have this effect. Our results suggest that filtration of Fungizone injection through PES (0.2 microm) membrane filters is recommended for the preparation of intravenous amphotericin B fluid.

Amphotericin B↗
PubMed2001

Dynamic changes in cytokine levels in serum and synovial fluid following filtration leukocytapheresis therapy in patients with rheumatoid arthritis.

We attempted to determine whether various cytokine levels in the serum and synovial fluid (SF) of rheumatoid arthritis (RA) patients are influenced by the performance of filtration leukocytapheresis (LCP). The filtration LCP procedure that used a Cellsorba column (LCP group: n=22; responder subgroup: n=17, non-responder subgroup: n=5) or sham apheresis (control group; n=7) was repeated three times at 1-week intervals. Serum (LCP group, n=22; control group, n=7) and SF (LCP group, n=6; control group, n=3) samples were collected before and after LCP. Levels of tumor necrosis factor alpha (TNFalpha), interleukins (IL-1 beta, IL-2, IL-6, IL-8, IL-10, and IL-15), granulocyte-macrophage colony-stimulating factor (GM-CSF), monocyte chemoattractant protein-1 (MCP-1), RANTES were measured by an enzyme-linked immunosorbent assay. Serum TNF alpha, IL-15, and RANTES were significantly reduced only in the LCP group. Serum IL-10 significantly increased only in the LCP group. In the LCP subgroup, serum IL-15, GM-CSF, and RANTES levels were reduced significantly, while serum IL-10 levels increased significantly only in the responder group after treatment. Serum TNF alpha levels were reduced significantly in both subgroups. Changes in serum IL-10 correlated positively with the improvement of patient's assessment of pain and global severity, and physician's assessment of global severity. These results indicate that the removal of leukocytes from the peripheral blood of RA patients provokes dynamic changes in some cytokine levels in the serum and/or synovial fluid. These changes may explain some of the mechanisms by which the articular symptoms are improved by filtration LCP.

Adult↗
PubMed1989

Preparation of leukocyte-poor platelets by filtration.

There is evidence that leukocyte contaminating red blood cells and platelet concentrates are responsible for refractoriness to platelet transfusions. The efficacy of a cotton-wool filter to remove leukocytes from red blood cells has been documented previously. The present study was designed to evaluate whether the cotton-wool filters can effectively remove leukocytes from platelet concentrates. Sixty pools of random-donor platelets and single-donor plateletpheresis products were filtered through a cotton-wool filter. The efficacy of filtration was determined by measuring the absolute numbers of leukocytes and platelets and subpopulations of mononuclear cells. The average platelet loss was 8% per pool of random platelets and 10% per plateletpheresis product. The average leukocyte removal was 99% from a pool of random platelets and plateletpheresis concentrates collected by CS-3000 and 90% from plateletpheresis concentrates harvested by single-stage COBE/IBM-2997. The filtration removed 100% of granulocytes, 95% of monocytes, 90% of B-lymphocytes, and 85% of T-lymphocytes. We conclude that filtration through a cotton-wool filter is an efficient and cost-effective method for preparation of leukocyte-poor platelets.

Blood Component Removal↗
PubMed1993

Constant flowrate filtration of hybridoma cells suspensions.

The fouling mechanism of rotating sieves (also called spinfilters) in suspended mammalian cells reactors is still poorly understood, and their design is consequently largely empirical. A laboratory set-up enabling constant flowrate filtration experiments is reported and its use described in order to study the fouling kinetics of 10 microns opening sieves by suspended hybridomas. Significant differences were obtained depending upon cell type and cell viability, under similar operating conditions. A roughly linear pressure drop increase, as predicted by constant flowrate incompressible cake filtration models, was obtained for most experiments. However, the influences of pumping flowrate and cell concentration on pressure drop evolution do not obey incompressible cake constant flowrate filtration laws; a surface colonization approach could possibly lead to a better description in that case.

Animals↗
PubMed1976

Filtration rates of pharmaceutical suspension systems.

This study was undertaken to find it a correlation exists between the filtration rate and the Hu/Ho ratio. For this purpose, flocculated and coagulated structures of sulfamerazine were used. Suspension settling profiles and filtration rates, using additives and additive-free sulfamerazine suspensions, were studied. A straight-line correlation was found. Effects of filter bed parameters on refiltration rates were studied, and a relationship was found by the use of the Kozeny-Carman equation. A straight-line relationship existed between the H1/Ho ratio and the filtration rate exhibited by the different suspension aggregates.

Aluminum↗
PubMed2002

Early amniocentesis with the filtration technique: neonatal outcome in 123 singleton pregnancies.

OBJECTIVE: To evaluate results of a prospective study of pregnancies in which early amniocentesis with the filtration technique was performed at 10-13 weeks' gestation (mean 12.3 weeks' gestation). METHODS: 123 singleton pregnancies in which early amniocentesis with the modified filtration technique was performed at 10-13 weeks' gestation (mean 12.3 weeks' gestation). The amniotic fluid was aspirated into the syringe and reinjected through the filter. RESULTS: All the procedures were performed successfully by a single needle insertion. Neither dry taps nor filtration failures occurred. The mean time of amniocentesis was 4.02 min (95% confidence interval, 3 min and 36 s to 4 min and 18 s). The karyotyping success rate was 99.2%. Temporary amniotic fluid leakage occurred in three women (2.4%). There were 110 (89.4%) live births. Two cases of stillbirth occurred at week 38 and week 40. Two unintended losses occurred within three weeks after sampling (1.62%). Another additional unintended fetal death was notified at the 20-week screening ultrasonography. The total fetal-loss rate was 10.6%. In one case, talipes equinovarus was detected at the 20-week screening ultrasound study. CONCLUSIONS: Further studies are needed to determine the risk of amniotic leakage and its relation to duration of the procedure in patients undergoing early amnifiltration.

Amniocentesis↗
PubMed1994

Quantification of 35S-labeled proteoglycans complexed to alcian blue by rapid filtration in multiwell plates.

This paper describes a rapid filtration assay for the quantification of 35S-labeled proteoglycans and/or 35S-labeled glycosaminoglycans in a large number of samples. Separation of 35S-labeled proteoglycans and 35S-labeled glycosaminoglycans from unincorporated [35S]sulfate is effected by forming insoluble complexes between alcian blue and the glycosaminoglycan moieties of the proteoglycans and then filtering the solutions through "Durapore membrane" discs (0.45 microns pore size) fitted in a 96-well plate. Following brief rinsing steps, the discs are punched out and 35S-labeled macromolecules retained on the membrane are then quantified by scintillation counting. In this rapid filtration assay, the relationship between the amount of [35S]-aggrecan applied and radioactivity measured was linear over a broad range of concentrations (2-800 micrograms aggrecan/ml). The amount of 35S-labeled proteoglycans measured in media and 4 M guanidine HCl extracts of articular cartilage and three different chondrocyte culture systems (monolayer, agarose gel, and alginate bead) ranged between 90 and 101% of the value obtained by sieve chromatography on Sephadex G-25. The presence in samples of unlabeled proteoglycans (up to 1 mg/ml), bovine serum albumin (up to 4 mg/ml), DNA (up to 20 micrograms/ml), serum (up to 30%), or guanidine hydrochloride at 4 M did not affect recovery of 35S-labeled proteoglycans measurably. CPM values obtained for 35S-labeled proteoglycans or 35S-labeled glycosaminoglycans quantified by chromatography on Sephadex G-25 and the filtration assay showed a strong linear relationship (r > 0.99) irrespective of the type of culture medium, extract, or digest used.

Alcian Blue↗