Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “FILTERS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 19 recordsLinked to original sources
PubMed1998

In vitro function of an adjustable temporary venous spring filter: comparison with the temporary RF02 filter and the permanent Greenfield vena cava filter.

RATIONALE AND OBJECTIVES: The authors compared in vitro function of a temporary venous spring filter with that of a temporary RF02 filter and a permanent Greenfield filter. MATERIALS AND METHODS: All three types of filters were placed in thin polyethylene tubes (diameters, 10.0-18.0 mm). Physiologic saline was substituted for flowing blood, and blood clots of three sizes (6 x 10 mm, 6 x 20 mm, 9 x 20 mm) were funneled to the filters. Clot-trapping ability of each filter and elevation of intraluminal pressure after clot trapping were assessed for each tube size. RESULTS: No statistically significant elevation in intraluminal pressure was detected immediately after placement of any filter. The clot-trapping ability of the spring filter and of Greenfield filter were slightly lower than that of the RF02 filter, but the differences were not statistically significant. After filters had trapped large clots, a high pressure gradient was detected in the 10.0-mm tube for all filters. The spring filter was associated with a higher pressure than the other filters in the 12.0-mm tube (P < .05). CONCLUSION: In vitro function of the spring filter was satisfactory in comparison with that of the RF02 filter and the Greenfield filter. For efficient filtering in the inferior vena cava, development of a larger version of the filter may be necessary.

Equipment Design↗
PubMed2001

Gas/solid partitioning of semivolatile organic compounds (SOCs) to air filters. 3. An analysis of gas adsorption artifacts in measurements of atmospheric SOCs and organic carbon (OC). WHen using teflon membrane filters and quartz fiber filters.

Adsorption of gaseous semivolatile organic compounds (SOCs) onto the filter(s) of a filter/sorbent sampler is a potential source of measurement error when determining specific SOCs as well as organic carbon (OC) levels in the atmosphere. This work examines partitioning to both Teflon membrane filters (TMFs) and quartz fiber filters (QFFs) for purposes of predicting the magnitude of the compound-dependent gas adsorption artifact as a function of various sampling parameters. The examination is based on values of Kp,face (m3 cm(-2)), the gas/filter partition coefficient expressed as [ng sorbed per cm2 of filter face]/[ng per m3 in the gas phase]. Values of Kp,face were calculated based on literature values of the gas/solid partition coefficient Kp,s [ng sorbed per m2 of filter]/[ng per m3 in gas phase] for the adsorption of various polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzodioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) to TMFs, and for the adsorption of PAHs to QFFs. At relative humidity (RH) values below approximately 50%, the Kp,face values for PAHs are lower on TMFs than on ambient-backup QFFs. The gas adsorption artifact will therefore be lower for PAHs with TMFs than with QFFs under these conditions. In the past, corrections for the gas/filter adsorption artifact have been made by using a backup filter, and subtracting the mass amount of each compound found on the backup filter from the total (particle phase + sorbed on filter) amount found on the front filter. This procedure assumes that the ng cm(-2) amounts of each SOC sorbed on the front and backup filters are equal. That assumption will only be valid after both filters have reached equilibrium with each of the gaseous SOCs in the incoming sample air. The front filter will reach equilibrium first. The minimum air sample volume Vmin,f+b required to reach gas/filter sorption equilibrium with a pair of filters is 2Kp,face Afilter where Afilter (cm2) is the per-filter face area. Kp,face values, and therefore Vmin,f+b values, depend on the compound, relative humidity (RH), temperature, and filter type. Compound-dependent Vmin,f+b values are presented for PAHs and PCDD/Fs on both TMFs and QFFs. Compound-dependent equations which give the magnitude of the filter adsorption artifact are presented for a range of different sampling arrangements and circumstances. The equations are not intended for use in actually correcting field data because of uncertainties in actual field values of relevant parameters such as the compound-dependent Kp,face and gas/particle Kp values, and because of the fact that the equations assume ideal step-function chromatographic movement of gas-phase compounds through the adsorbing filter. Rather, the main utility of the equations is as guidance tools in designing field sampling efforts that utilize filter/sorbent samplers and in evaluating prior work. The results indicate that some backup-filter-based corrections described in the literature were carried out using sample volumes that were too small to allow proper correction for the gas adsorption artifactfor some specific SOCs of interest. Similar conclusions are reached regarding artifacts associated with the measurement of gaseous and particulate OC.

Adsorption↗
PubMed1992

Comparison of filters in an oversized vena caval phantom: intracaval placement of a bird's nest filter versus biiliac placement of Greenfield, Vena Tech-LGM, and Simon nitinol filters.

For patients with an oversized inferior vena cava (IVC) (diameter greater than 28 mm, corrected for magnification) who require vena caval filtration for prophylaxis against pulmonary emboli, the accepted treatment has been the biiliac venous placement of Greenfield filters. Because of its wide strut span, the Bird's Nest filter (BNF) has been successfully placed in patients having an oversized IVC. However, the effects of the BNF on caval blood flow and its clot-capturing ability in an oversized IVC are not clearly understood. The authors created a flow phantom simulating an oversized IVC with "iliac" tributaries of normal inner diameter to analyze flow turbulence, pressure gradients, and the clot-capturing ability of the BNF, tested within the "caval" segment of the phantom, and the Greenfield, Vena Tech-LGM, and Simon nitinol filters, tested in the "iliac" segments. All filters were tested for flow disturbances before and after clot capture. The authors' results demonstrate that within an oversized IVC, the BNF creates less flow disturbance and is less occlusive with clot capture than biiliac filters. The BNF displayed a clot-capturing ability equal to that of biiliac filters. Thus, for patients with an oversized IVC, these results suggest that placement of a single intracaval BNF is preferable to biiliac placement of filters.

Humans↗
PubMed2000

Electrostatic respirator filter media: filter efficiency and most penetrating particle size effects.

New electrostatic filter media has been developed for use in 42 CFR 84 negative pressure particulate respirator filters. This respirator filter media was not available for evaluation prior to the change from 30 CFR 11 to 42 CFR 84. Thus, characterization of this filter media is warranted. In this study, the new 42 CFR 84 electrostatic respirator filters were investigated with respect to filter penetration and most penetrating particle size. Three different models of N95 filters, along with one model each of the N99, R95, and P100 class filters were used in this study. First, three of each filter were loaded with a sodium chloride (NaCl) aerosol, and three of each filter were loaded with a dioctyl phthalate (DOP) aerosol to obtain normal background penetration results for each filter. Then, two new filters of each type were dipped in isopropanol for 15 seconds and allowed to dry. This isopropanol dip should reduce or eliminate any electrostatic charge on the fibers of each filter, as reported in the technical literature. These dipped filters, along with controls of each filter type, were tested on a TSI 8160 filter tester to determine the most penetrating particle size. These same filters were then tested against a NaCl aerosol to get final penetration values. Electret filters rely heavily on their electrostatic charge to provide adequate filter efficiencies, and correlations between penetration and a filter's electrostatic characteristics are found in the technical literature. In all six of the filter models tested, filter penetration values increased considerably and the most penetrating particle size noticeably shifted toward larger particles. These results are important in better understanding how these new filter materials perform under various conditions, and they indicate the need for additional research to define environmental conditions that may affect electrostatic filter efficiency.

Equipment Design↗
PubMed1999

In vivo evaluation of the adjustable temporary venous spring filter and the RF02 temporary filter: comparative study.

RATIONALE AND OBJECTIVES: The authors performed this study to compare the in vivo efficacies of the temporary venous spring filter and the RF02 filter in an animal model. MATERIALS AND METHODS: Either the spring filter or the RF02 filter was placed in the inferior vena cava of 10 pigs each, and two clots (5 x 20 mm) were funneled into the filters at 1-hour intervals. The second clots were funneled without removing the first clots captured by the filters. Clot-trapping ability, caval occlusion associated with the clot-trapping procedure, arterial blood gas concentrations, and changes in arterial and iliac venous pressures were evaluated. RESULTS: Placement of the RF02 filter caused elevation of iliac venous pressure with a maximum of 2.2 mm Hg (median) (n = 13, P = .003). Placement of the spring filter parallel to venous flow enabled capture of 90% (nine of 10) and 100% (six of six) of the first and second clots, respectively. The RF02 filter captured clots consistently. The difference between filters was not statistically significant. Both filters equally contributed to elevation of iliac venous pressure (median, 9.3 and 7.2 mm Hg [n = 9] with the spring filter and RF02 filter, respectively). Caval occlusion occurred in 17% (one of six) and 67% (six of nine) of animals after two clots were trapped in the spring filter and RF02 filter, respectively (P = .06). Other parameters were not influenced by the clot-trapping procedure. CONCLUSION: Although a larger version should be developed and better stability of the filter is needed, the spring filter proved to be an efficient filtering device and had a lower rate of caval occlusion compared with the RF02 filter.

Animals↗
PubMed1995

Preparation of white cell-reduced red cells by filtration: comparison of a bedside filter and two blood bank filter systems.

BACKGROUND: Concern has been raised about the quality of white cell (WBC)-reduced red cells (RBCs) obtained by bedside filtration. The bedside performance and workload of a routine bedside filter have been compared to the laboratory performance and workload of two blood bank filter systems. STUDY DESIGN AND METHODS: Buffy coat-depleted saline-adenine-glucose-mannitol (SAGM) RBCs (90 units) were prepared. Thirty units were filtered with each of the two blood bank filter systems, and 30 units were filtered (but not transfused) with the bedside filter in a clinical department after 8 to 24 days of storage. The RBCs lost and the postfiltration WBC content (Nageotte chamber) were determined for all filtered units, and the workload associated with filtration by each of the filter systems/filter was assessed. Units with a postfiltration content of > or = 2 x 10(6) WBCs were regarded as filtration failures. RESULTS: Four (13%) of the 30 units filtered at the bedside were filtration failures, compared to no failures with either of the blood bank filter systems. In addition, the median WBC content (0.14 x 10(6)) of the units filtered at the bedside (2 units/filter) was significantly higher than that of the units filtered in the blood bank (0.05 x 10(6)). The RBC loss was significantly higher with the filter systems than with the bedside filter, provided 2 units per filter were processed with the latter. The timed workload of the filter systems was 45 to 75 minutes per 12 units, which was similar to the time required for bedside filtration. CONCLUSION: Bedside filtration of 2 units of stored buffy coat-depleted SAGM RBCs per filter resulted in a higher incidence of filtration failure and higher postfiltration WBC content than did laboratory filtration of 1 unit of fresh buffy coat-depleted SAGM RBCs per filter with either of two blood bank filter systems.

Blood Component Removal↗
PubMed2004

Retrieving "nonretrievable" inferior vena caval Greenfield filters: a therapeutic option for filter malpositioning.

Filter malpositioning is a possible complication of inferior vena caval (IVC) filter insertion that may result in inadequate protection from pulmonary embolism. For nonretrievable filters, this is traditionally managed with either observation or additional filter placement. The purpose of this study is determine the incidence of filter malpositioning after bedside insertion under duplex ultrasound (DUS) or intravascular ultrasound (IVUS) guidance, and to report techniques for retrieving and repositioning IVC filters previously considered nonretrievable. All IVC filter insertions performed under DUS or IVUS guidance over an 8-year period were identified. Data regarding insertion technique, device used, and technical success were retrospectively collected. Cases of IVC filter malpositioning were determined and form the basis of this study. Technical details for IVC filter retrieval and repositioning are described. Of 486 patients undergoing DUS (n = 435) or IVUS (n = 51) guided IVC filter insertion, 12 patients (2.4%) had inadequate positioning as determined by postoperative radiography. Two of these patients had no further filter manipulation, three had a second filter placed under fluoroscopic guidance, and the most recent five had filters retrieved and repositioned under fluoroscopic guidance. Of those patients undergoing retrieval and repositioning, all five had Greenfield filters, which are not traditionally regarded as retrievable. All attempted retrievals or replacements were technically successful without additional filter-related complications. Bedside IVC filter insertion under DUS or IVUS guidance has a low incidence of filter misplacement. Although not traditionally regarded as retrievable, Greenfield filters can be safely retrieved and repositioned using advanced endovascular techniques in the event of malpositioning.

Adolescent↗
PubMedDate not supplied

Temporary inferior vena cava filters: in vitro comparison with permanent IVC filters.

PURPOSE: An in vitro comparison of clot-trapping abilities of permanent and temporary inferior vena cava (IVC) filters. MATERIALS AND METHODS: A flow model was used to simulate the IVC. Two permanent IVC filters, the titanium Greenfield and LG-Medical (LGM), were compared with two temporary filters, the Filcard International and Gunther. Clot sizes used were 2.5 x 2.5 mm, 2.5 x 5 mm, 5 x 5 mm, 5 x 10 mm, and 5 x 20 mm. Individual clots were presented to the filters with the simulated IVC in a horizontal or vertical orientation. Clot-trapping dynamics and pressure gradient changes during the injection of multiple, sequential clots were also examined. RESULTS: As clot size diminished, all filters trapped fewer clots; however, the temporary filters trapped more small clots than the permanent filters. Very little difference was observed in clot-trapping abilities among the filters for clots of 5 x 10 mm or greater. In the horizontal orientation, the permanent filters trapped 38% of all clots delivered, while the temporary filters trapped 73%, chi 2 = 24.8 (P < .001). In the vertical orientation, the overall clot-trapping abilities of the filters improved, with the permanent filters trapping 73% of all clots delivered, while the temporary filters trapped 95%, chi 2 = 18 (P < .001). During trapping of multiple clots, the temporary filters allowed fewer clots to pass. CONCLUSION: The temporary filters performed better than the permanent filters in both individual clot-trapping orientations. During multiple clot-trapping experiments, fewer clots were allowed to pass by the temporary filters. The temporary filters demonstrated the ability to capture clots both inside and outside the wire struts.

Animals↗
PubMed2005

Experience with the recovery filter as a retrievable inferior vena cava filter.

PURPOSE: This study evaluates clinical experience with the Recovery filter as a retrievable inferior vena cava (IVC) filter. MATERIALS AND METHODS: One hundred seven Recovery filters were placed in 106 patients with an initial clinical indication for temporary caval filtration. Patients were followed up to assess filter efficacy, complications, eventual need for filter removal, time to retrieval, and ability to remove the filter. RESULTS: The patient cohort consisted of 62 men and 44 women with a mean age of 48 years (range, 18-90 y). Mean implantation time was 165 days. Indications for filter placement in patients with deep vein thrombosis (DVT) and/or pulmonary embolism (PE) included contraindication to anticoagulation (n = 33), complications of anticoagulation (n = 8), poor cardiopulmonary reserve (n = 6), large clot burden (n = 3), and PE while receiving anticoagulation (n = 1). Indications for filter placement in patients without proven PE or DVT included immobility after trauma (n = 35); recent intracranial hemorrhage, neurosurgery, or brain tumor (n = 18); and other surgical or invasive procedure (n = 3). Three patients (2.8%) had symptomatic PE after placement of the Recovery filter. No caval thromboses were detected. No symptomatic filter migrations occurred. Recovery filter removal was attempted in 15 of 106 patients (14%) at a mean of 150 days after placement. The Recovery filter was successfully retrieved in 14 of 15 patients (93%); one removal was unsuccessful at 210 days after placement. Ninety-two filters (87%) currently remain in place. CONCLUSIONS: Although all the filters were placed with the intention of being removed, a large percentage of filters were not retrieved. The Recovery filter was safe and effective in preventing PE when used as a retrievable IVC filter.

Adolescent↗
PubMedDate not supplied

Method for qualifying microbial removal performance of 0.1 micron rated filters. Part III: bacterial challenge tests on 0.2/0.22 and 0.1 micron rated filter cartridges with Hydrogenophaga (formerly Pseudomonas) pseudoflava.

We have previously reported on the preliminary characterization of Hydrogenophaga (formerly Pseudomonas) pseudoflava for potential use as a standard challenge organism to qualify 0.1 microm rated filters. This article reports on the retention efficiencies of a large panel of 0.2/0.22 microm and 0.1 microm rated filter cartridges for H. pseudoflava (ATCC 700892) versus the retention capabilities of the same filters for Brevundimonas diminuta (ATCC 19146). A total of thirty-two 0.2/0.22 microm rated filter cartridges, spanning nine different "sterilizing grade" filter types from four different filter manufacturers, were challenged with H. pseudoflava at challenge levels exceeding 10(7) cfu/cm2. H. pseudoflava was shown to penetrate every 0.2/0.22 microm rated filter tested, with log titer reduction (LTR) values ranging from 3.5 to 7.7 logs. H. pseudoflava was shown to be more penetrative than B. diminuta under the same challenge conditions. B. diminuta was fully retained by nineteen of the twenty 0.2/0.22 microm rated filters that were challenged with both organisms. In the case of 0.1 microm rated filters, eighteen filter cartridges, spanning five different filter types from three manufacturers were tested. H. pseudoflava was consistently retained by four out of the five filter types tested, with LTR values in excess of 11.5 to 12.2 logs. The 0.1 microm rated filter type that was penetrated by H. pseudoflava has been previously demonstrated to be not fully retentive for naturally occurring bacteria. The data show that H. pseudoflava penetrates 0.2/0.22 microm rated filters just as readily as B. diminuta penetrates 0.45 microm rated filters. In addition, titer reductions provided by 0.2/0.22 microm rated filters for H. pseudoflava are comparable to those reported for A. laidlawii mycoplasma, albeit under different conditions. This study demonstrates that H. pseudoflava meets all criteria for use as a standard organism for qualifying the microbial removal performance of 0.1 microm rated filters for enhanced sterility assurance.

Acholeplasma↗
PubMedDate not supplied

Optional vena cava filters: preliminary experience with a new vena cava filter.

PURPOSE: To prevent pulmonary embolism, some clinical situations only need a vena cava filter for several days, without the inconveniences of temporary vena cava filters in the short-medium term and without the drawbacks of permanent ones in the long term. We report our initial experience with a new definitive vena cava filter, easy to retrieve when it becomes unnecessary. MATERIAL AND METHODS: From the beginning of January 1999 to December 2001, 18 ALN vena cava filters were deployed. The approach used was transbrachial in ten patients, transjugular in seven, and transfemoral in the others. The indications were pelvic trauma in eleven patients, hip replacement in three; four filters were "prophylactically" placed before surgery in patients at high risk of thromboembolic disease (three with ileal or femoral or ileo-femoral thrombosis, and one without clinically manifest thromboembolic disease). Optional vena cava filters were evaluated for malpositioning, caval perforation, filter migration, acute caval thrombosis or access site thrombosis. Seven optional vena cava filters were retrieved. CT was performed before retrieving the vena cava filters to document the absence of thrombi inside the filters. The transjugular ap-proach was used to retrieve the filters. RESULTS: Technical success was achieved in all patients. No complications were encountered during the procedure; no migration or rupture of the filters was detected during the follow-up. No thrombosis of the vena cava or at the insertion site was encountered. The median retrieval time for the filters was 12': only the transfemoral filters required 15' of fluoroscopy. The median permanence was 63 days. No thrombi were found inside the filters. DISCUSSION: A definitive vena cava filter, easy to retrieve when it becomes unnecessary, is the ideal device in many clinical conditions: young subjects with pelvic fractures orthopaedic and gynaecologic interventions.

Adult↗
PubMed1993

Leukodepletion blood filters: filter design and mechanisms of leukocyte removal.

Modern leukocyte removal filters have been developed after years of refinement in design. Current filters are composite filters in which synthetic microfiber material is prepared as a nonwoven web. The filter material may be surface modified to alter surface tension or charge to improve performance. The housing design promotes effective contact of blood with the filter material and decreases shear forces. The exact mechanisms by which these filters remove leukocytes from blood components are uncertain, but likely represent a combination of both physical and biological processes whose contributions to leukocyte removal are interdependent. Small-pore microfiber webs result in barrier phenomena that permit retention of individual cells and increase the total adsorptive area of the filter. Modifications in surface charge can increase or decrease cell attraction to the fibers. Optimum interfacial surface tensions between blood cells, plasma, and filter fibers not only permit effective blood flow through small fiber pores, but also facilitate cell contact with the material. Barrier retention is a common mechanism for all modern leukocyte-removal filters and applies to all leukocyte subtypes. Because barrier retention does not depend on cell viability, it is operative for cells of any age and will retain any nondeformable cell, including whole nuclei from lymphocytes or monocytes. Barrier retention is supplemented by retention by adhesion. RBCs, lymphocytes, monocytes, granulocytes, and platelets differ in their relative adhesiveness to filter fibers. Different adhesive mechanisms are used in filters designed for RBCs compared with filters designed for platelets. Although lymphocytes, monocytes, and granulocytes can adhere directly to filter fibers, the biological mechanisms underlying cell adhesion may differ for these cell types. These differences may depend on expression of cell adhesion molecules. In the case of filtration of fresh RBCs, platelet-leukocyte interaction seems to supplement other mechanisms of leukocyte retention. The interactions of cells with biomaterials is an area of important research for implantable medical devices, artificial organs, and orthopedic, vascular, and dental prosthetics. Research in these areas is likely to contribute to improved biomaterials for blood filters. Improved techniques for the preparation of hybrid polymers and new techniques for surface modification of existing polymers will increase the technical opportunities for the development of synthetic surfaces ideally designed for leukocyte removal. It is therefore likely that the performance of leukocyte-removal filters will continue to improve. The development of cost-effective leukocyte removal filters specifically designed for use during component preparation would permit leukocyte depletion of all cellular blood components.

Biomechanical Phenomena↗
PubMed2006

Comparison of the roex and gammachirp filters as representations of the auditory filter.

Although the rounded-exponential (roex) filter has been successfully used to represent the magnitude response of the auditory filter, recent studies with the roex(p, w, t) filter reveal two serious problems: the fits to notched-noise masking data are somewhat unstable unless the filter is reduced to a physically unrealizable form, and there is no time-domain version of the roex(p, w, t) filter to support modeling of the perception of complex sounds. This paper describes a compressive gammachirp (cGC) filter with the same architecture as the roex(p, w, t) which can be implemented in the time domain. The gain and asymmetry of this parallel cGC filter are shown to be comparable to those of the roex(p, w, t) filter, but the fits to masking data are still somewhat unstable. The roex(p, w, t) and parallel cGC filters were also compared with the cascade cGC filter [Patterson et al., J. Acoust. Soc. Am. 114, 1529-1542 (2003)], which was found to provide an equivalent fit with 25% fewer coefficients. Moreover, the fits were stable. The advantage of the cascade cGC filter appears to derive from its parsimonious representation of the high-frequency side of the filter. It is concluded that cGC filters offer better prospects than roex filters for the representation of the auditory filter.

Acoustics↗
PubMed1995

In vitro testing of six inferior vena cava filters: filtering efficiency and pressure measurements.

UNLABELLED: The purpose of this study is to compare in standarddised ex vivo conditions the performances of six percutaneous vena cava filters available on the European Market. METHODS: We use a mock circulation with polyethylene beads simulating clots to objectively determine the filtering efficiency of the different devices. We measured pressure at contact points with the wall of the tube simulating vena cava, and also gradient of pressure induced by the empty and full filter. Statistical analysis of the data obtained (at least 100 measurements for each filter) showed great consistency in the response of a given filter to the different conditions of mock circulation. RESULTS: The Greenfield Filter, which served as the reference, was compared to the other models. Its filtering efficiency was acceptable as was that of the L.G. Filter. The Cardial Filter and Vascor Filter were the most efficient. The Antheor Filter and the Filcard Filter performed poorly. CONCLUSION: The mock circulation give reliable and reproducible data on the filtering efficiency for a device but ease of placement and clinical studies must be taken into account for the choice of the filter.

Blood Pressure↗
PubMed2005

Filter Buffy Coats (FBC): a source of peripheral blood leukocytes recovered from leukocyte depletion filters.

In compliance with federal regulations, blood banks routinely use leukocyte depletion filters to eliminate contaminating leukocytes from blood products such as red blood cell and platelet concentrates. We developed and optimized conditions to elute leukocytes adsorbed to these filters; resulting in leukocyte suspensions which we termed Filter Buffy Coats (FBCs). These Filter Buffy Coats can replace standard buffy coats for various research applications. After optimizing both the filter elution medium as well as elution protocols, we compared commonly used leukocyte depletion filters from four different manufacturers. Relative fractions as well as total recoveries of leukocyte subsets, such as lymphocytes, monocytes and granulocytes, found in Filter Buffy Coats were identified and compared among the filters as well as to standard buffy coats and whole blood. Flow cytometric analysis of Filter Buffy Coats confirmed the presence of T- and B-lymphocytes, NK cells and monocytes. Furthermore, a significant quantity of CD34(+) hematopoietic stem or progenitor cells (HSC/HPC) was detected in Filter Buffy Coats prepared from different filters, thus making FBCs a valuable source for research on HSC/HPC. Colony assays revealed that most of these CD34(+) cells are functional. Using immunomagnetic cell sorting (MACS), we isolated a variety of leukocyte populations from FBC mononuclear cells (Filter-PBMCs) including T lymphocytes (CD4(+), CD8(+), CD3(+)), B lymphocytes (CD19(+)), NK cells (CD56(+)), HSC/HPC (CD34(+), CD133(+)) or dendritic cells (BDCA-4(+)). Functional properties of Filter-PBMCs, as well as of some of these isolated leukocyte populations, were confirmed using standard assays. In summary, Filter Buffy Coats are a valuable and convenient source of different peripheral leukocyte populations and can replace standard buffy coat preparations for research applications.

Antigens, CD↗
PubMed1992

Filter elution assays for DNA damage: practical and mechanistic significance of the DNA in the filter support wash.

The alkaline and neutral (or nondenaturing) filter elution assays are popular methods for the measurement of DNA strand breakage and its repair in eukaryotic cells. In both alkaline and neutral elution, it is recommended practice to wash the filter support after removal of the filter and to analyze the DNA recovered by this procedure together with that remaining on the filter as uneluted DNA, although it is not obvious why the DNA in the filter support wash should be so interpreted. We have observed that the sum of the DNA on the filter and that recovered in the filter support wash is approximately constant when the pH of the alkaline filter elution assay for total strand breaks is increased from 12.1 to 12.6, whereas the fraction on the filter itself is markedly smaller at the higher pH. This behavior characterized DNA elution from undamaged cells, as well as from cells treated with various DNA-damaging agents. These findings are consistent with the "tug-of-war" mechanism that has been proposed for alkaline elution, but are inconsistent with the simplest mechanism of the "sieve" class. In the neutral filter elution assay for double-strand breaks, by contrast, the distribution of DNA between the filter and the filter support wash is pH-independent. This suggests that single- and double-stranded DNA segments traverse a filter by different physical mechanisms. Our observations underscore the importance of carrying out the filter support wash and the analysis of the DNA it contains as uneluted DNA in alkaline elution, while indicating that a different analysis of this DNA might be appropriate for neutral elution.

DNA Damage↗
PubMedDate not supplied

Suprarenal vena caval filter placement: follow-up of four filter types in 22 patients.

PURPOSE: To determine if suprarenal placement of inferior vena cava (IVC) filters is associated with renal dysfunction or other complications. MATERIALS AND METHODS: Case files of all patients with suprarenal vena caval filter placement since 1985 were reviewed for clinical and biochemical evidence of renal dysfunction and renal vein thrombosis. The occurrence of associated complications, including IVC occlusion, filter fracture, device migration, and recurrence of pulmonary embolism was also recorded. RESULTS: Twenty-two (2.9%) of 764 IVC filters were implanted above the renal veins: titanium Greenfield filter modified hook (TGF-MH) (n = 16), LGM type I (n = 2), LGM type II (n = 2), and Bird's Nest (BN) type I (n = 2). Reasons for suprarenal filter placement included thrombus to the level of the renal veins (n = 9), failure or poor position of the infrarenal filter (n = 6), pregnancy or intent of pregnancy (n = 4), and the malpositioning of BN filters above the renal veins (n = 2). A single patient demonstrated evidence of transient renal dysfunction. Pulmonary embolus was found at autopsy in one patient. Abdominal radiographs were obtained at follow-up of 18 patients and demonstrated a 2 cm or more migration of the filter in five patients (27.7%). This rate of migration was significantly different from the 3% migration rate reported by the authors' institution in the follow-up of 320 infrarenal IVC filters. There was one filter fracture (5.5%.) and penetration of the IVC occurred in one patient (5.5%). CONCLUSION: Follow-up indicates suprarenal IVC filter placement is safe, and no evidence of permanent renal dysfunction after placement was found. Filter migration was the most frequent complication, but no clinical sequelae were noted with these patients.

Adult↗
PubMedDate not supplied

Method for qualifying microbial removal performance of 0.1 micron rated filters. Part I: characterization of water isolates for potential use as standard challenge organisms to qualify 0.1 micron rated filters.

Although 0.1 microm rated filters intended for pharmaceutical sterilization applications have been commercially available for at least 15 years, there is no industry-wide standard for qualifying the microbial removal performance of these filters. In this article, we report on the bacterial challenge methodology used to screen four bacterial species for potential utility as a standard challenge organism to qualify 0.1 microm rated filters. These isolates were, in their natural state, demonstrated to penetrate 0.2/0.22 microm rated filters in prior studies. In the screening challenges described in this study, three out of these four candidates tested demonstrated consistent penetration of one 0.22 microm rated filter type tested (when cultured in a low nutrient medium under standard laboratory conditions). These included 6204-22 (FAME ID Acidovorax avenae citrulli), 6266-15 (FAME ID Comamonas acidovorans), and 6266-34 (FAME ID Hydrogenophaga pseudoflava). Of these, H. pseudoflava (6266-34) was chosen for additional experiments with other 0.2 microm rated filter membranes. In total, seventeen 0.2 and 0.22 microm rated filter discs, spanning five different "sterilizing grade" filter types from three different filter manufacturers were tested. H. pseudoflava penetration was observed for every filter tested. Under the same challenge conditions, H. pseudoflava was consistently retained by a 0.1 microm rated hydrophilic PVDF (polyvinylidenefluoride) filter with a specified high titer reduction claim for Acholeplasma laidlawii. In order to ensure selection of the most stable penetrative phenotype (i.e., select for nonrevertants), H. pseudoflava was subjected to three rounds of "filter cloning," and these results are described herein. The advantages of using H. pseudoflava for qualifying the microbial removal performance of 0.1 microm rated filters are also discussed.

Acholeplasma↗