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PubMed1990

Filtration of platelet-poor plasma specimens yields platelet-free plasma. Application for batch analysis of beta-thromboglobulin and platelet factor 4.

The authors investigated filtration of platelet-poor plasma through a 0.2-micron filter for the analysis of beta-thromboglobulin (beta-TG) and platelet factor 4 (PF4) in frozen specimens. Platelets were detected by electron micrograph in the platelet-poor plasma preparation without filtration. No platelets or platelet fragments were seen after filtration. Freezing the unfiltered specimens resulted in a significant increase in the beta-TG and PF4 concentrations, presumably because of release of these proteins from the platelet alpha-granules during freezing and thawing. There was no change in the PF4 levels and only a slight decrease in beta-TG levels after freezing of the filtered specimens. The filtered samples could be frozen for later batch analysis, resulting in considerable cost savings to the laboratory.

Blood Platelets↗
PubMed1976

False-positive rabbit ileal loop reactions attributed to Vibrio parahaemolyticus broth filtrates.

Vibrio parahaemolyticus broth filtrates have previously been shown to produce positive reactions in rabbit ileal loops only if concentrated 10-fold by lyophilization. This method of concentration produces solutions that contain greater than 20% NaCl. In the present study, however, concentrations of NaCl of greater than or equal to 4% induced positive responses in ileal loops, and desalting rendered previously reactive, concentrated broth filtrates negative. Therefore, enterotoxin was not demonstrated in our broth filtrates of V. parahaemolyticus, a finding which suggests that previous studies require further evaluation. Since most culture media contain 0.5% NaCl, it is important to determine and to control the NaCl content and the osmolality of all lyophilized concentrates tested in the ligated rabbit ileum.

Animals↗
PubMed1996

Isolation of human uteroglobin from blood filtrate.

The purpose of this study was to assess the possibility of isolating biologically active peptides from human blood using large volumes of blood filtrate, which are available from patients undergoing extracorporeal ultrafiltration because of renal insufficiency. This filtrate was submitted to six chromatographic separation steps, yielding one purified peptide which was completely analysed in its primary structure. It was found to be strikingly similar to proteins, described initially as rabbit uteroglobin (or blastokinin) and, more recently, from human bronchial lavage as the '10 kDa Clare cell protein', as well as from human urine as 'protein-1'. The natural molecule contains two chains of identical amino acid sequences of 70 residues which are arranged as an antiparallel dimer due to the disulphide bonds between two cysteines at positions 3 and 69. Mass analysis of the molecular forms yielded molecular weights from 15827 Da (non-oxidized form) to 15859 Da (bi-oxidized form). We conclude that this peptide isolated from the filtrate represents the human uteroglobin, and we demonstrate for the first time that this peptide may be involved as a humoral factor in reproductive or other physiological functions.

Amino Acid Sequence↗
PubMed1989

A rapid filtration assay for cAMP.

The receptor-binding assay for cAMP was improved by using polyethylenimine-treated glass filters. A polyethylenimine-treated glass filter has high protein binding capacity. This high capacity allows an increase in the amount of protein per assay tube and the use of a crude preparation, such as a beef heart extract, as specific binding protein instead of a purified protein, which has been used in the classical filtration assays involving cellulose ester filters. Since the time required for the separation of the protein-cAMP complex and the free nucleotide can be shortened by the use of polyethylenimine-treated filters, the dissociation of the bound ligand during the separation procedure, which is a serious problem with other modified assay methods involving charcoal adsorption, is minimized. Filtration through polyethylenimine-treated glass filters also gives low blanks and prevents the loss of protein or ligand due to breakage of the filters, which is often observed with fragile cellulose ester membranes. In consequence, this simple and rapid filtration assay allows more accurate and reproducible determinations.

Animals↗
PubMed1976

Effects of Intersept micropore filtration of blood on microaggregates and other constituents.

Micropore filtration (Intersept) of whole, stored blood was examined in two studies. In Study A, 1 unit of 14-day-old blood flowed by gravity across the filter. In Study B, the filter was preloaded by passage of 2 units of blood, and the effects on a third, consisting of 21-day-old blood, flowing under 150 mm Hg pressure, were examined. Filtration did not significantly alter erythrocyte count, total hemoglobin, plasma hemoglobin, erythrocyte fragility, plasma sodium, potassium, albumin, or globulin in either study, although some platelets and leukocytes were removed. Microaggregates, assessed by Coulter counting, screen filtration pressure, total screen proteins, wet and dry weights of material retained, and scanning electron microscopy, were satisfactorily removed over the whole range of particle sizes. Comparison with the Bentley PFS-127, Fenwal 4C2417, Pall Ultipore, and Swank IL200 filters led to the conclusion that the Intersept is the most efficient filter available at the present time for removing microaggregates during massive blood transfusion.

Blood↗
PubMedDate not supplied

Dialysate contamination and back filtration may limit the use of high-flux dialysis membranes.

Endotoxins, or fragments thereof, can reach the blood stream of dialysis patients, transported by diffusion and connection across the intact high-flux membrane. This transfer depends upon the phenomenon of back filtration. Back filtration generally occurs under conventional high-flux dialysis conditions with membranes having an ultrafiltration coefficient in blood (UF-C) above 20 ml/hr/m2/mmHg. The clinical consequences of back filtration vary from center to center depending primarily on the quality of dialysate. We therefore surveyed the bacterial and endotoxin levels of purified water and effluent dialysate in a cross section of dialysis centers in the central United States. Using a high recovery medium, we found that 53% of the centers had bacterial counts above the Association for the Advancement of Medical Instruments standard in water (20% cfu/ml) and 35% above the standard in dialysate (2,100 cfu/ml). Endotoxin concentrations higher than 5.0 EU/ml in both water and dialysate were found in 4% and 11.8% of the centers, respectively. Since high-flux membranes are believed to be of benefit for long-term dialysis patients, manufacturers will have to offer dialysate preparation systems with additional safety features. The proper membrane design will be a key to the success of such systems.

Colony Count, Microbial↗
PubMed2001

Methylene blue reduces lung fluid filtration during the early phase of endotoxemia in awake sheep.

OBJECTIVE: To determine whether methylene blue (MB), an inhibitor of soluble guanylate cyclase and nitric oxide synthase, alters lung hemodynamics and fluid filtration after endotoxin in sheep. DESIGN: Prospective, randomized, controlled experimental study with repeated measurements. SETTING: University animal laboratory. SUBJECTS: Eight yearling, awake sheep. INTERVENTIONS: Sheep were instrumented for a chronic study with vascular and lung lymph catheters. In two experiments, separated by 1 wk of recovery, the animals received intravenously either an injection of MB 10 mg/kg or a corresponding volume of 0.9% sodium chloride as pretreatment. Thirty minutes later, sheep received a bolus injection of Escherichia coli endotoxin 1 microg/kg, followed by either an infusion of MB 2.5 mg/kg/hr or a corresponding volume of 0.9% sodium chloride for 5 hrs. MEASUREMENTS AND MAIN RESULTS: MB decreased the early phase endotoxin-induced rises in pulmonary capillary pressure and pulmonary vascular resistance. MB also reduced the increments in lung lymph flow (QL) and protein clearance (CL) as well as the rightward shift of the permeability-surface area product (PS). In addition, MB diminished the decrease in cardiac output, stabilized mean arterial pressure, and precluded the rise in plasma and lung lymph cyclic guanosine 3'-5' monophosphate. However, during the late phase, MB-treated sheep presented with a faster rise in QL with no difference in CL and PS from the endotoxemic controls. CONCLUSIONS: During the early phase of endotoxemia in sheep, MB attenuates lung injury by decreasing the enhanced lung fluid filtration as a result of reduced pulmonary capillary pressure and permeability. However, MB does not counteract the late phase increase in lung fluid filtration.

Animals↗
PubMed1987

The effect of rare earth filtration on patient exposure, dose reduction, and image quality in oral panoramic radiology.

Rare earth intensifying screen material (Gd2O2S:Tb) was added to the standard Al filtration of an oral panoramic x-ray unit, resulting in a beam capable of achieving reductions in patient dose without a loss of image quality. The added rare earth filtration technique resulted in patient dose reductions of 21-56%, depending on anatomic sites, when compared to the conventional Al filtration technique. Films generated from both techniques were measured densitometrically and evaluated by a panel of practicing clinicians. Diagnostically significant differences were minimal. The results indicate that use of rare earth filters in oral panoramic radiography is an effective means of reducing exposures of dental patients to ionizing radiation.

Film Dosimetry↗
PubMed1992

The interrelationships among filtration surface area, blood pressure, and chronic renal disease.

A primary role for the kidney in hypertension has long been recognized, but the pathogenetic interactions among renal hemodynamics, hormonal and hereditary factors, and dietary sodium intake remain ill defined. Reduction in the filtration surface area, whether acquired in the course of intrinsic renal disease or after surgical renal ablation, leads to systemic hypertension as well as to progressive renal insufficiency, sequellae made even more severe by dietary sodium excess. Moreover, hypertension and progressive renal disease occur in some individuals born with a solitary kidney, and occur almost invariably with more severe degrees of dysgenesis. Hypertension is also commonly observed in certain inbred rat strains in which the filtration surface area is congenitally deficient. Based on these and other lines of evidence reviewed herein, we postulate that a renal abnormality that contributes to essential hypertension in the general population is a reduced number of glomeruli and tubules, the consequences of which are limitations in the ability to excrete sodium and thus salt-sensitive hypertension. Furthermore, congenitally decreased filtration surface area may explain why only some, but not all, patients exposed to potentially injurious renal stimuli eventually manifest chronic nephropathy, and may also account for the susceptibility of subsets of type I and type II diabetics to develop overt glomerulopathy. Clinically, tests of renal reserve capacity may serve as a useful guide to identification of those patients at risk for the development of hypertension and progressive renal disease.

Aging↗
PubMed2000

Influence of membrane differential filtration on the natural course of age-related macular degeneration: a randomized trial.

PURPOSE: Membrane differential filtration is able to optimize rheologic parameters by eliminating high molecular weight proteins and lipoproteins from the blood. Following the hypothesis that these changes result in an improvement of the microcirculation, the authors tested the efficacy of membrane differential filtration in improving visual function in patients with age-related macular degeneration (ARMD). METHODS: Forty patients (40 eyes) were randomized into two groups. The treatment group was treated five times over a period of 21 weeks. In both groups, 9/20 of the eyes showed subfoveolar subretinal neovascularization. The main parameter of the study was visual acuity (VA). Electroretinogram (ERG), electrooculogram, and macular visual evoked potentials were also recorded. Plasma and whole blood viscosity and erythrocyte aggregation were measured. RESULTS: The 20 patients treated repeatedly over a period of 21 weeks showed a mean improvement of 0.63 lines (SD 1.8) of VA on Early Treatment Diabetic Retinopathy Study charts. The control group showed a deterioration of 0.94 lines (SD 1.7) compared to VA at baseline examination. The amplitude of the ERG photopic a-wave and the flicker ERG was significantly increased. The rheologic parameters were lowered in all treated patients. CONCLUSION: Repetitive treatment with membrane differential filtration is able to improve visual acuity of patients with ARMD and the natural course of this disease. Several questions arise from the results of this study. Further research will show if it is possible to optimize the selection of patients for subgroups with predictive responses through morphologic and functional tests and how to create an optimized and individual treatment strategy determined by the quality, intensity, and frequency of treatment sessions.

Aged↗
PubMed1982

Comparison of filtration leukapheresis and centrifugation leukapheresis in treatment of lymphosarcoma cell leukemia.

A patient with lymphosarcoma cell leukemia resistant to chemotherapy was treated with filtration leukapheresis and centrifugation leukapheresis. Filtration leukapheresis removed only 10(11) leukemia cells per 8.5 liters of blood processed, while centrifugation leukapheresis removed approximately six times as many leukemia cells from the same amount of blood. Lymph nodes and spleen diminished in size and the WBC count decreased after nine treatments. However, the patient remained markedly thrombocytopenic, and his bone marrow remained infiltrated with lymphosarcoma cells on repeat biopsy. This study shows that centrifugation leukapheresis is superior to filtration leukapheresis in removing significant numbers of circulating lymphosarcoma cells, though the clinical benefit of leukapheresis in this situation remains to be determined.

Blood↗
PubMed2003

Morphologic classification of filtering blebs after glaucoma filtration surgery: the Indiana Bleb Appearance Grading Scale.

PURPOSE: To establish a new classification system for filtering blebs according to clinical morphologic parameters. The purpose of this classification system is to provide a uniform and objective assessment of bleb appearance and establish a framework system through which outcomes of filtration surgery may be better correlated to clinical morphology. MATERIALS AND METHODS: The Indiana Bleb Appearance Grading Scale contains a set of photographic standards illustrating a range of filtering bleb morphology selected from the slide library of the Glaucoma Service at the Indiana University Department of Ophthalmology. These standards consist of slit lamp images for grading bleb height, extent, vascularity, and leakage with the Seidel test. For grading, the morphologic appearance of the filtration bleb is assessed relative to the standard images for the 4 parameters and scored accordingly. Fifty-one clinical bleb photographs were evaluated and scored by 3 glaucoma subspecialists in a masked fashion according to the scale. RESULTS: For all of the grading scales, high interobserver agreement was found using the scale to classify the appearance of filtering blebs (height +0.76; extent +0.78; vascularity +0.90, interclass correlation coefficient for consistency using a 2-way mixed effect model). CONCLUSION: The Indiana Bleb Appearance Grading Scale is a simple, reproducible, yet comprehensive system for classifying the morphologic slit lamp appearance of filtration blebs.

Filtering Surgery↗
PubMed2005

Cyclosporin as an adjunct to glaucoma filtration surgery.

PURPOSE: Current adjunctive therapies to glaucoma surgery have unreliable effects, are toxic, and have numerous late complications associated with their use. This study examined whether topical cyclosporin (CsA) prolongs bleb survival after glaucoma filtration surgery. METHODS: Anesthetized white New Zealand rabbits underwent glaucoma filtration surgery with a drainage tube. Cyclosporin (2%), applied intraoperatively or as topical treatment following glaucoma filtration surgery, was compared with intraoperative mitomycin C (MMC) and an untreated control group. RESULTS: The bleb remained elevated for 15.1 +/- 3.2 days in the untreated control group, 12.2 +/- 2.1 days after intraoperative cyclosporin, and 27.5 +/- 1.7 days after intraoperative mitomycin C (P < 0.001). When topical treatment with cyclosporin followed intraoperative mitomycin C, bleb survival significantly decreased to 19.2 +/- 4.6 days (P = 0.003). Intraocular pressure (IOP) remained significantly reduced in the mitomycin C-treated group longer than in either the control or cyclosporine-treated groups. CONCLUSIONS: In comparison with mitomycin C, neither intraoperative nor postoperative treatment with cyclosporin was associated with a decrease in intraocular pressure or prolonged bleb survival. Contrary to the initial hypothesis, topical treatment with cyclosporin actually mitigated the beneficial effects of mitomycin C on bleb survival. Clinical implications of these findings for patients with functioning blebs deserve further study.

Administration, Topical↗
PubMed2006

What can patients see during glaucoma filtration surgery under peribulbar anesthesia?

PURPOSE: To describe the visual sensations experienced by patients during glaucoma filtration surgery under peribulbar anesthesia and to determine possible risk factors that may affect the visual sensations experienced. SETTING: King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia. METHODS: In this prospective questionnaire study, 75 consecutive adult patients listed for glaucoma filtration surgery (trabeculectomy or Ahmed tube implantation) under peribulbar anesthesia were interviewed postoperatively about the visual sensations experienced in their operated eye during the surgery. RESULTS: The mean age of the 75 patients was 59.7 years (range, 27 to 83, SD +/-12.1). Sixty-five patients (86.7%) perceived light perception during the surgery and the overall light intensity fluctuated in 45 patients (60.0%). The mean age of the patients who retained light perception intraoperatively was significantly lower compared with those who lost light perception (58.3 y vs. 68.8 y; P=0.009). Forty-six patients (61.3%) were able to perceive colors, 32 patients (42.7%) perceived movement, 31 patients (41.3%) saw surgical instruments, and 33 patients (44.0%) reported seeing the surgeon's hands or fingers. The severity of glaucoma did not affect the proportion of patients who perceived the various visual sensations. One patient (1.3%) was frightened by his intraoperative visual experience. Of the remaining patients, 53 (70.7%) said the visual sensations did not affect them, whereas 21 (28.0%) found them unpleasant. CONCLUSIONS: The majority of patients undergoing glaucoma filtration surgery retained light perception intraoperatively and many also experienced various visual sensations. Only 1.3% of patients were frightened by their visual experience.

Adult↗
PubMed2003

The Günther Tulip retrievable filter: prolonged temporary filtration by repositioning within the inferior vena cava.

PURPOSE: To report experience with the retrievable Günther Tulip filter (GTF) as a means of temporary caval filtration for the prevention of pulmonary embolism (PE) with use of a technique that prolongs filter dwell time beyond 14 days. MATERIALS AND METHODS: Eighty-eight GTFs were implanted in 87 patients. The GTFs were placed with the intention of retrieval in all patients within 14 days after initial implantation. In 23 of the 87 patients (26%), there was a need to prolong temporary caval filtration beyond the recommended period of 14 days. This was successfully achieved with use of percutaneous techniques from the right internal jugular vein whereby the filter was repositioned to a different location within the inferior vena cava (IVC) before definitive device removal. RESULTS: Of 88 GTFs implanted in 87 patients, 70 were successfully retrieved and 18 were left in place permanently. Forty-seven filters in 46 patients were removed after initial implantation with no need for percutaneous repositioning within the IVC to prolong dwell time (mean dwell time, 13 days). In the 23 patients who required repositioning of 23 GTFs within the IVC to prolong temporary caval filtration, the mean dwell time was 34.8 days; the mean number of repositioning procedures was 1.5, the mean time between repositioning procedures was 13.8 days, and the mean fluoroscopy time was 4.4 minutes in patients in whom filter retrieval was attempted. One patient underwent placement and subsequent removal of the GTF twice for perioperative prophylaxis against PE on two separate occasions. No filters were misplaced in an unintended location or tilted (>15 degrees ) in relation to the main caval axis after deployment. In one patient, a GTF became permanently fixed in the IVC 16 days after initial implantation and could not be removed percutaneously. Nine patients had mild or moderate-sized cervical hematomas. One patient had recurrent asymptomatic PE 2 months after filter insertion. CONCLUSION: Dwell times of 14 days can be achieved in most patients before device removal. Prolongation of the dwell time beyond 14 days can be safely and easily achieved by performing percutaneous repositioning of the device within the IVC via a jugular approach.

Adolescent↗
PubMed1978

Purification and Properties of an Elicitor of Castor Bean Phytoalexin from Culture Filtrates of the Fungus Rhizopus stolonifer.

Evidence has been obtained for the presence in filtrates of 3-day-old cultures of the fungus Rhizopus stolonifer grown on potato-dextrose medium of both high molecular weight and low molecular weight elicitors of the production of the phytoalexin casbene in cell-free extracts of castor bean (Ricinus communis L.) seedlings. The high molecular weight elicitor activity was purified by means of gel filtration chromatography. Both protein and carbohydrate are associated with the most purified fraction containing elicitor activity. The elicitor is inactivated by treatments at 60 C or higher temperatures for 15 minutes. The molecular weight of the purified elicitor was estimated from gel filtration chromatography in 10 mm Na-phosphate (pH 7) to be 30,000 +/- 5,000. Treatments of the purified elicitor fraction with either sodium periodate or the nonspecific protease preparation, pronase, substantially reduced its activity as an elicitor of casbene production. On the basis of these properties it is concluded that the elicitor is most likely a protein and may be a glycoprotein. It is estimated that 2 x 10(-8)m elicitor gives about a 14-fold increase in casbene synthetase activity in extracts of treated split seedlings in comparison with controls. This corresponds to about 50% of the maximal activity obtainable in this assay system developed to measure elicitor activity.

Journal Article↗
PubMed1998

The influence of interface roughness on Mössbauer filtration of synchrotron radiation at an isotope interface.

The influence of interface irregularities on synchrotron radiation Mössbauer filtration at an isotope interface is examined theoretically. Calculations are performed for a random-roughness interface model for a (56)Fe/(57)Fe isotope interface. The analysis shows that, despite a drop in the efficiency in the real structures compared with the idealized structures, the efficiency of Mössbauer filtration of synchrotron radiation remains high enough to ensure a successful experiment. In particular it was found that, as well as a regular saw-like profile of the external interface, a randomly rough profile of the external interface may also be used in the Mössbauer filtration experiment if the roughness parameters satisfy certain demands.

Journal Article↗
PubMed1987

Response of ligated rabbit ileal loop to Clostridium perfringens type C strains and their toxic filtrates.

The vegetative cells and toxic filtrates of Clostridium perfringens type C strains were injected into ligated rabbit ileal loops and the responses were observed. Out of 12 strains examined, 2 strains showed positive reaction in this test, when the vegetative cells were injected. One of these 2 strains was an enterotoxigenic and beta-toxigenic and the other was beta- and delta-toxigenic but not enterotoxigenic. Culture filtrates containing beta or delta toxin also showed fluid accumulation in the rabbit ileal loop. Histological findings of loops injected with culture filtrates containing beta toxin showed separated and effaced villi, hemorrhage in the mucosa, engorged vessels, inflammatory cell infiltration, and hyperplasia of the lymphoid tissue.

Animals↗