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PubMed2005

Purification of pulsed laser synthesized single wall carbon nanotubes by magnetic filtration.

Great effort has been expended in the development of methods to purify raw nanotubes by chemical treatment, washing, mechanical filtration, or heat treatment in a vacuum or oxidative environment. These techniques are limited by incomplete removal of catalyst nanoparticles and by the damage to the nanotubes that often results. We have applied a new purification method using filtration in a magnetic field and oxidation and investigated the efficacy using magnetic filtration alone, or combined with chemical-based or annealing-based oxidative treatments. By applying magnetic filtration only, we reduce catalyst content from 11.7 to 3.7 wt %, which is a superior result to oxidation and/or chemical treated samples. By combining chemical and magnetic purification, metal catalyst content is reduced to as much as 0.3 wt %, which is the best result ever for SWNTs synthesized by the laser method. In addition to the reduction of catalyst content, the new purification method increased sample quality, confirmed by Raman spectroscopy and near-infrared absorption. Magnetic filtration is found to be very effective in removing metal catalysts, producing material with high quality and yields.

Journal Article↗
PubMed2005

Batch cooling crystallization and pressure filtration of sulphathiazole: the influence of solvent composition.

Currently there is a great interest in new process analytical approaches to increase the process understanding of pharmaceutical unit operations. In the present study, the influence of the solvent composition on the material properties and, further, on the filtration characteristics, of different crystal suspensions obtained through an unseeded batch-cooling-crystallization process was studied. Sulphathiazole, which is an antibiotic agent with multiple polymorphic forms, was produced by performing laboratory-scale cooling crystallization experiments from five different mixtures of water and propan-1-ol (n-propanol). The size, shape and polymorphic composition of the crystals produced were characterized with a scanning electron microscope, with a novel automated image analyser and with an X-ray powder diffractometer. All of the monitored crystal properties were found to clearly differ between the samples obtained from different solvents. The crystals produced in the batch-cooling-crystallization experiments were separated from the crystallizing solvents using a batch-type pressure Nutsche filter, and the filtration characteristics of the suspensions were evaluated on the basis of average filter-cake porosities and average specific cake resistances, which were determined from the experimentally obtained filtration data. Comparison between the calculated filtration characteristics revealed that considerable differences existed between the different suspensions, and it could therefore be concluded that the pressure-filtration process was influenced by the composition of the crystallizing solvent. The filterability of all the studied sulphathiazole suspensions was considered to be rather good on the basis of the relatively low cake porosities (0.51-0.63), which were accompanied with low average specific cake resistances [(8.7 x 10(7))-(1.2 x 10(9)) m/kg].

1-Propanol↗
PubMed1965

The gel-filtration behaviour of proteins related to their molecular weights over a wide range.

1. Correlation between elution volume, V(e), and molecular weight was investigated for gel filtration of proteins of molecular weights ranging from 3500 (glucagon) to 820000 (alpha-crystallin) on Sephadex G-200 columns at pH7.5. 2. Allowing for uncertainties in the molecular weights, the results for most of the carbohydrate-free globular proteins fitted a smooth V(e)-log(mol.wt.) curve. In the lower part of the molecular-weight range the results were similar to those obtained with Sephadex G-75 and G-100 gels. 3. V(e)-log(mol.wt.) curves based on results with the three gels are taken to represent the behaviour of ;typical' globular proteins, and are proposed as standard data for the uniform interpretation of gel-filtration experiments. 4. Some glycoproteins, including gamma-globulins and fibrinogen, do not conform to the standard relationship. The effect of shape and carbohydrate content on the gel-filtration behaviour of proteins is discussed. 5. As predicted by the theoretical studies of other authors, correlation exists between the gel-filtration behaviour and diffusion coefficients of proteins. 6. The lower molecular-weight limit for complete exclusion of typical globular proteins from Sephadex G-200 varies with the swelling of the gel, but is usually >10(6). 7. The concentration-dependent dissociation of glutamate dehydrogenase was observed in experiments with Sephadex G-200, and the sub-unit molecular weight estimated as 250000. The free sub-units readily lose enzymic activity. 8. Recognition of the atypical gel-filtration behaviour of gamma-globulins necessitates an alteration to several molecular weights previously estimated with Sephadex G-100 (Andrews, 1964). New values are: yeast glucose 6-phosphate dehydrogenase, 128000; bovine intestinal alkaline phosphatase, 130000; Aerobacter aerogenes glycerol dehydrogenase, 140000; milk alkaline phosphatase, 180000.

Chemical Phenomena↗
PubMed2003

Intracellular vacuolation induced by culture filtrates of Plesiomonas shigelloides isolated from environmental sources.

AIMS: Potential virulence factors produced by culture filtrates of Plesiomonas shigelloides isolated from water were investigated. METHODS AND RESULTS: Culture filtrates of P. shigelloides strains were assayed for cytotoxic activity in CHO (Chinese hamster ovary), Vero (African green monkey kidney), HeLa (human cervix), HT29 (human epithelial intestinal) and SK6 (swine epithelial kidney) cells. Microscopic analyses revealed intensive cytoplasmic vacuolation including cell rounding and swelling, with gradual destruction of the monolayer in filtrate-treated cells. Neutral red assays showed that CHO, HeLa and Vero cells were the most sensitive to the vacuolating activity, which was evident within 30 min of culture filtrate exposure. This activity was inactived by heating at 56 degrees C for 15 min and partially neutralized by antiserum to the cytotoxin of Aeromonas hydrophila. All P. shigelloides strains had a cell-associated haemolysin in the agar plate assay. Three isolates were found to produce a cell-free haemolytic activity at 37 degrees C. In the suckling mouse test, two P. shigelloides culture supernatants were positive for enterotoxic activity. CONCLUSIONS: P. shigelloides culture filtrates isolated from aquatic environment cause intracellular vacuolation on mammalian cells, and produce haemolytic and enterotoxic activities. SIGNIFICANCE AND IMPACT OF THE STUDY: This work revealed the presence of putative virulence factors that could be associated with human infections involving Plesiomonas strains.

Animals↗
PubMed1996

Optimal conditions for white cell reduction in red cells by filtration at the patient's bedside.

BACKGROUND: A quality control program of white cell (WBC) reduction in red cells at the bedside was implemented, based on postfiltration counting in a Nageotte chamber of the residual WBCs from samples taken from a segment of the transfusion set, after 1-in-10 sample dilution with Türks's solution. During a 1-year quality control program, 5.1 percent of counted units had apparent filtration failures, that is, WBC counts exceeding 5 x 10(6) per unit. The cause(s) for these apparent failures were investigated. STUDY DESIGN AND METHODS: In Study 1, residual WBCs from 150 buffy coat-free red cells filtered through one type of filter at 4 degrees C, 20 to 24 degrees C, or 27 degrees C in 5 to 10 minutes, 50 to 100 minutes, or 100 to 200 minutes were counted as described above. In Study 2, residual WBCs in samples collected from segments of the transfusion set and from the postfiltration bags were counted in parallel by a new, more sensitive counting method. In this method, 5 mL of filtered red cells was diluted with 20 mL of 3-percent paraformaldehyde and centrifuged, the pellet was resuspended to 500 microL with a lysis solution, and the WBCs were counted in a Nageotte chamber. In Study 3, residual WBCs were counted by the 3-percent paraformaldehyde method in samples from postfiltration bags of 1- to 2-day-old buffy coat-rich red cell units filtered through a second type of filter. Filtration was started within 30 minutes of the removal of the unit from the refrigerator, ambient temperature was 20 to 24 degrees C, and the median filtration time was 90 minutes per unit. RESULTS: Study 1: Median WBC counts per unit increased progressively from 51,000 at 4 degrees C to 934,000 at 27 degrees C, with intermediate values at 20 to 24 degrees C. In no unit did the WBC count exceed 5 x 10(6) if filtration at 20 to 24 degrees C was completed within 100 minutes, while counts in excess of 50 x 10(6) were found at 20 to 24 degrees C and at 27 degrees C with filtration times of 100 to 200 minutes, and 50 to 100 minutes, respectively. Study 2: The relation between segment and postfiltration bag WBC counts obtained by the 3-percent paraformaldehyde method was poor, with the latter being almost always lower than the former. Study 3: None of the 120 units filtered through the second type of filter at 20 to 24 degrees C in 50 to 100 minutes contained more than 3.2 x 10(6) WBCs; the median value was 147,000 WBCs per unit. CONCLUSION: On the basis of the results with the 3-percent paraformaldehyde method, which showed the unreliability of segment counts, a new policy was adopted for quality control of bedside WBC reduction, based on controlling the time of and temperature at transfusion. Bedside WBC reduction in 1- to 2-day-old red cells performed with the second type of filter at 20 to 24 degrees C in less than 100 minutes per unit allowed the preparation of units that meet the standard of fewer than 5 x 10(6) WBCs in all tested cases. Bedside WBC reduction with the second type of filter and under the controlled conditions reported seems effective.

Erythrocyte Transfusion↗
PubMed2001

Filtration of methylene blue-photooxidized plasma: influence on coagulation and cellular contamination.

BACKGROUND: Virus inactivation of plasma can be achieved by photodynamic methods in the presence of phenothiazine dyes such as methylene blue (MB). Subsequent filtration may increase the efficacy of virus inactivation and reduce adverse effects of WBC contamination and MB. STUDY DESIGN AND METHODS: This study examined the effect of filtration with three different filters (MBF1, MBF2, and MBF3) on MB concentration, residual cells, coagulation factors, and activation measures of coagulation, fibrinolysis, and complement in MB-treated (1 microM/L) plasma units. RESULTS: Filtration reduced the concentration of MB by > or = 89 percent. WBCs were depleted by 92 percent (MBF1) and >99.9 percent (MBF2 and MBF3). Treatment with MB significantly decreased the coagulation potency from levels in untreated plasma, as measured by thromboplastin time ratio (112 +/- 18% vs. 95 +/- 11%), activated partial thromboplastin time (40 +/- 3 sec vs. 44 +/- 3 sec), thrombin time (16.9 +/- 1.1 sec vs. 18.6 +/- 1.5 sec), factor VIII (1.09 +/- 0.21 U/mL vs. 0.85 +/- 0.13 U/mL), and vWF (0.94 +/- 0.65 U/mL vs. 0.65 +/- 0.24 U/mL). Filtration did not further decrease these values, while factor XI (0.75 +/- 0.22 U/mL vs. 0.37 +/- 0.20 U/mL) and prekallikrein values decreased in MB plasma units filtered with the MBF3. In addition, activated factor XII (0.7 +/- 0.5 microg/L vs. 4.5 +/- 1.0 microg/L) increased. CONCLUSION: WBCs and MB can be eliminated from MB-treated plasma units by filtration. Differences in biocompatibility of the different filters, especially the influence on the contact phase of coagulation, must be taken into consideration.

Blood Coagulation↗
PubMed2001

Programmed filtration, a new method for removing large molecules and regulating albumin leakage during hemodiafiltration treatment.

During hemodiafiltration (HDF) treatment for chronic renal failure patients, replacing large volumes using high-flux membranes with relatively large pores is preferred from the standpoint of enhancing the elimination of large molecules (10 to 50 kd). Aggressive protein-permeable treatment often results in massive leakage of essential albumin, however, which may cause fatigue, hypotension, and a decrease in the plasma albumin concentration in some patients. During 5-hour conventional HDF treatment with the filtration rate or pressure set at constant values, fractional albumin loss in the dialysate was assayed, which revealed that the albumin concentration in the dialysate showed a maximum value in the beginning with a steep decline within 1 hour. Approximately 40% to 50% of the total amount of albumin leakage occurred during the first 30 minutes. Concomitantly the large molecules transferred into the pores by aggressive filtration during the beginning partially plugged the pores, resulting in a decrease in the permeability for beta(2)-microglobulin. From the standpoint of achieving the highest clearance for large molecules, while suppressing albumin leakage below the acceptable range, the optimal profiles for filtration conditions in HDF have been proposed, in which either the transmembrane pressure is regulated according to the sigmoid curve in the pressure control manner or the flow rate is set along the concave in the flow control manner. The profiles of pressure or flow as a function of time have been programmed and installed in a HDF machine to perform an optimal HDF treatment automatically. The new filtration methods gave significantly higher beta(2)-microglobulin removal and lower albumin leakage than conventional HDF methods with constant filtration.

Albumins↗
PubMed1971

Human sarcomas in culture. Foci of altered cells and a common antigen; induction of foci and antigen in human fibroblast cultures by filtrates.

In a study of human sarcomas maintained in culture for periods up to two years, the following observations were made. The most prominent cell type in serially cultured osteosarcomas was fibroblastic in appearance. After 16-20 wk in culture some lines spontaneously developed foci of altered cells resembling the foci produced in monolayer cultures by oncogenic viruses. The presence of these foci in the sarcoma cultures was transient, and usually they did not reappear; but in one instance they recurred with a characteristic periodicity of several weeks. From one of the sarcoma lines, in which foci appeared after 5 months in culture, two subcultures were established from stored frozen cells and these both exhibited foci after approximately the same lapse of time. The same phenomenon has been seen with another line, suggesting that the time of appearance of foci is characteristic for particular sarcomas. Foci of similar type could sometimes be induced in monolayer cultures of human fibroblasts by filtered medium from cultured sarcomas; this bore no relation to the presence or absence of foci in the sarcoma cultures at the time the filtrate was prepared. Electron microscopy of the spontaneous and induced foci, and of the sarcoma cultures, revealed no demonstrable virus. 12 out of 15 sarcoma cultures contained an antigen (S) demonstrable by indirect immunofluorescence with human sera. It was not present in any of the original sarcoma specimens, nor in any culture lines other than sarcomas. At least 3-4 wk in culture appear to be required for its demonstration. The antigen was cytoplasmic, occurred in only a small proportion of the cells, and was unpredictably variable in its expression, even in the same culture line. It could be induced in monolayer cultures of human fibroblasts by filtrates of medium from sarcoma cultures. As with the foci, the induction of S antigen in indicator cultures was not dependent upon the expression of antigen in the sarcoma line from which the filtrates were obtained. There was no association between the presence of foci and of antigen, nor was there any apparent relation between the ability of filtrates to induce foci and their ability to induce antigen. 80% or more of the general population have S antibody, and the titer of antibody in patients with sarcoma is no higher than in normal subjects. Thus, as in the case of Burkitt's lymphoma antigen, it appears that most individuals have been exposed to S antigen. But unlike Burkitt's lymphoma, no relation has so far been established between any particular disease and a corresponding high titer or frequency of occurrence of S antibody. The occurrence of foci of altered cells and of a common antigen, and the transmission of these two characters to indicator cells by filtrates, are all suggestive of a virus specifically associated with human sarcomas, one to which the general population is widely exposed, as indicated by the prevalence of antibody.

Adenocarcinoma↗
PubMedDate not supplied

Whole-body systemic transcapillary filtration rates, coefficients, and isogravimetric capillary pressures in Bufo marinus and Rana catesbeiana.

Whole-body and organ-level transcapillary filtration rates and coefficients are virtually unexamined in ectothermal vertebrates. These filtration rates appear to be greater than in mammals when plasma volume shifts and lymphatic function are analyzed. Gravimetric techniques monitoring whole-body mass changes were used to estimate net systemic filtration in Bufo marinus and Rana catesbeiana while perfusing with low-protein Ringer's and manipulating venous pressure. Capillary pressures were estimated from arterial and venous pressures after measuring the venous to arterial resistance ratio of 0.23. The capillary filtration coefficient (CFC) for the two species was 25.2+/-1.47 mL min-1 kg-1 kPa-1. Isogravimetric capillary pressure (Pci), the pressure at which net fluid is neither filtered nor reabsorbed, was 1.12+/-0.054 kPa and was confirmed by an independent method. None of these variables showed a significant interspecific difference. The anuran CFC and Pci are significantly higher than those found using the same method on rats (7.6+/-2.04 mL min-1 kg-1 kPa-1 and 0.3+/-0.37 kPa, respectively) and those commonly reported in mammals. Despite the high CFC, the high Pci predicts that little net filtration will occur at resting in vivo capillary pressures.

Animals↗
PubMed1992

Statistical distance between texts and filtration methods in sequence comparison.

Upon searching local similarities in long sequences, the necessity of a 'rapid' similarity search becomes acute. Quadratic complexity of dynamic programming algorithms forces the employment of filtration methods that allow elimination of the sequences with a low similarity level. The paper is devoted to the theoretical substantiations of the filtration method based on the statistical distance between texts. The notion of the filtration efficiency is introduced and the efficiency of several filters is estimated. It is shown that the efficiency of the statistical l-tuple filtration upon DNA database search is associated with a potential extension of the original four-letter alphabet and grows exponentially with increasing l. The formula that allows one to estimate the filtration parameters is presented.

Amino Acid Sequence↗
PubMed2006

Relation of haemofilter type to venous catheter resistance is crucial for filtration performance and haemocompatibility in CVVH--an in vitro study.

BACKGROUND: Main factors for the overall performance of haemofilters (HF) are membrane features and filter durability without clogging/clotting of capillaries. However, the venous line resistance (Pv) is a powerful force for net filtrate flux resulting in haemoconcentration and thus is enhancing the phenomenon of membrane clogging. Therefore, we hypothesized that catheter type, as it is associated with Pv-levels, contributes to the extent in which filter longevity and filtration performance are restricted due to blocked hollow fibres. METHODS: Heparinized porcine blood (5 IU/ml) was circulated in an in vitro system for haemofiltration (FH6S-filters were used, Ca. Gambro). Three different sizes of catheters for peripheral vein access (Vygonuele V, Ca. Vygon) were alternately inserted into the circuit for blood return from the filter to the reservoir. To produce Pv-levels lower than commonly induced by Shaldon catheters, a 14G-vygonuele was used. Pv-levels standard for 11-12 French catheters were provided by using a 16G-vygonuele. To produce Pv-levels common for low-French or tri-lumen catheters, a shortened 18G-vygonuele was used. The respective Pv-levels attained were compared with respect to the overall filtration performance (system pressures, haemocompatibility and sieving coefficients). RESULTS: Catheters of 14 and 16G enabled transiently maximal blood flow (Qb)/filtration rates (Qf) of 300/60 ml/min and continuous filtration with Qb/Qf of 200/40 ml/min. The shortened 18G catheter reduced maximal flow rates down to Qb/Qf of 200/40 ml/min, and continuous flow rates down to Qb/Qf of 125/25 ml/min. At the end, median values for blocked hollow fibres were, 35% in the 14G-group, 40% in the 18G-group and 70% in the 16G-group. Haemocompatibility appeared to be higher in the 14G-group with respect to various parameters when compared with the other groups. CONCLUSIONS: The flow resistance by the catheter chosen for haemofiltration clearly influenced the filtration performance. Thus, investigations focused on compatibility of catheter type as it related to Pv-levels with the particular method of renal replacement therapy that should be performed. This point could be crucial in reducing filter clogging and haemostasis during CVVH.

Animals↗
PubMedDate not supplied

Subcutaneous capillary filtrate collector for measurement of blood glucose.

The capillary filtrate collector (CFC) is a device that creates an ultrafiltrate at 50-100 microliters/h from subcutaneous capillaries, and carries this filtrate out of the body for chemical analysis. From inside out, components include three looped hollow fiber ultrafiltration membranes, a polytetrafluoroethylene (PTFE) cuff, polyurethane tubing, a "Y" connector leading to a sampling port, a hub, and a needle placed into a 5 ml vacutainer tube. Animal studies have demonstrated that the CFC filtrate glucose level is exactly that of blood at the time the filtrate is created. The authors have performed clinical trials to determine the correlation of blood glucose and CFC glucose levels, and the time delay between contemporary samples. Seven diabetic patients wore the CFC device, tubing, and vacutainer tube for 1 month. In home monitored diabetic patients, fingerstick glucose measurements were performed at the usual daily schedule. The vacutainer was then evacuated, and this average sample analyzed and compared with the average of prior blood glucose levels. An optical device then was applied to measure the linear velocity of CFC fluid through external tubing, and predict the time for fluid to pass from fibers to the sampling port (average, 25 min). Capillary filtrate collector samples drawn at this time had glucose concentrations that generally correlated with blood levels. In diabetic patients on hemodialysis, the vacutainer was evacuated at the start of each treatment, and CFC and blood samples were drawn every 20 min during the treatment. Comparison of glucose-versus-time curves indicated a reasonable correlation between blood and CFC samples, with a delay related to flow rate (which declined 50% during dialysis).(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Glucose↗
PubMed1992

Atrial natriuretic peptide increases human capillary filtration and venous distensibility.

OBJECTIVE: The main aim of this study was to examine whether atrial natriuretic peptide (ANP) alters capillary filtration and venous distensibility. DESIGN: The study was designed to examine the local effects of i.a. infusion of ANP upon capillary filtration and venous distensibility in human forearms of eight healthy volunteers. METHODS: Using a water plethysmograph, we measured venous distensibility and capillary filtration from changes in forearm volume when transmural venous pressure was increased in a stepwise manner and held constant during i.a. infusion of saline, ANP and sodium nitroprusside (SNP). The doses of ANP and SNP were chosen to double baseline forearm blood flow obtained during saline infusion. RESULTS: ANP and SNP infusion both increased venous distensibility to the same extent compared with saline infusion. Capillary filtration was greater during ANP than during saline or SNP infusion. Small vein pressure was comparable during infusion of the two drugs. CONCLUSION: Our results suggest that ANP increases venous distensibility and capillary filtration in human forearms.

Adult↗
PubMed1995

Pharmacologic atrial natriuretic peptide reduces human leg capillary filtration.

Atrial natriuretic peptide (ANP) is produced and secreted by atrial cells. We measured calf capillary filtration rate with prolonged venous-occlusion plethysmography of supine healthy male subjects during pharmacologic infusion of ANP (48 pmol/kg/min for 15 min; n = 6) and during placebo infusion (n = 7). Results during infusions were compared to prior control measurements. ANP infusion increased plasma [ANP] from 30 +/- 4 to 2,568 +/- 595 pmol/l. Systemic hemoconcentration occurred during ANP infusion: mean hematocrit and plasma colloid osmotic pressure increased 4.6 and 11.3%, respectively, relative to preinfusion baseline values (p < 0.05). Mean calf filtration, however, was significantly reduced from 0.15 to 0.08 ml/100 ml/min with ANP. Heart rate increased 20% with ANP infusion, whereas blood pressure was unchanged. Calf conductance (blood flow/arterial pressure) and venous compliance were unaffected by ANP infusion. Placebo infusion had no effect relative to prior baseline control measurements. Although ANP induced systemic capillary filtration, in the calf, filtration was reduced with ANP. Therefore, pharmacologic ANP infusion enhances capillary filtration from the systemic circulation, perhaps at upper body or splanchnic sites or both, while having the opposite effect in the leg.

Adult↗
PubMed2003

Effect of filtration volume of continuous venovenous hemofiltration in the treatment of patients with acute renal failure in intensive care units.

OBJECTIVE: We evaluated the variable Kt/V, which has become established in the therapy of end-stage renal disease in acute renal failure, to assess the influence of the filtration volume of continuous venovenous hemofiltration on Kt/V. We measured the variables of acid-base balance and uremia control. DESIGN: Prospective interventional pilot study. SETTING: Medical intensive care unit of a university hospital. PATIENTS: Fifty-six patients with acute renal failure and continuous venovenous hemofiltration treatment. INTERVENTIONS: The patients were consecutively treated with a filtration volume of either 1 L/hr (group 1) or 1.5 L/hr (group 2). MEASUREMENTS AND MAIN RESULTS: Patients with a filtration volume of 1.5 L/hr achieved a Kt/V of 0.8 per day, which was significantly higher than in the patient group treated with 1 L/hr (0.53, p <.05). The filtration volume of 1.5 L/hr led to a markedly better control of blood urea nitrogen concentrations, 69.3 +/- 6.6 mg/dL vs. 52.1 +/- 5.2 (p <.05), and to a much quicker and longer lasting compensation of acidosis. Both groups had acidotic pH at the beginning of therapy (group 1, 7.29 +/- 0.02; group 2, 7.29 +/- 0.02, nonsignificant). In group 2, a significantly higher pH value than in group 1 was measured after 24 hrs of continuous venovenous hemofiltration (p < .001; 7.39 +/- 0.02 vs. 7.31 +/- 0.02). The pH values in group 1 did not normalize until after 4 days. The filtration volume of 1.5 L/hr led to a quicker increase in bicarbonate concentrations after 24 hrs of therapy (group 1, 2.8 +/- 3.2 mmol/L; group 2, 6.5 +/- 3.1 mmol/L, p <.001). CONCLUSIONS: The standardized urea clearance Kt/V is a valuable tool in the treatment of acute renal failure. Higher Kt/V levels were associated with a better control of uremia and acid-base balance. However, there were no differences in the clinical course, patient survival, percentage of patients with or without renal failure who were transferred from the intensive care unit, or Acute Physiology and Chronic Health Evaluation III scores.

APACHE↗
PubMed1982

Rapid fractionation of wheat leaf protoplasts using membrane filtration : the determination of metabolite levels in the chloroplasts, cytosol, and mitochondria.

A technique is presented for measuring the in vivo metabolite levels in the chloroplast stroma, the cytosol, and the mitochondrial matrix of wheat (Triticum aestivum, var ;Timmo') leaf protoplasts, in which membrane filtration is used to prepare fractions enriched in the different subcellular fractions within 0.1 seconds after disruption of the protoplasts. By closing a syringe, protoplasts are forced through a net and disrupted, diluting the cytosol into the medium and also releasing intact chloroplasts and mitochondria which can then be immediately removed on membrane filters placed behind the nylon net. By varying the membrane filters, different filtrates are obtained corresponding to (a) mainly cytosol, or (b) cytosol and mitochondria with only low levels of chloroplasts; alternatively, (c) the entire protoplast contents are obtained by omitting the filters. The filtrates are immediately split, half flowing into HClO(4) where they are immediately quenched for subsequent metabolite analyses; the other half flows into detergent and is used to monitor the exact distribution of marker enzymes in each individual fractionation. Using the measured distributions of metabolite and of marker enzymes in the three filtrates, the subcellular distribution of the metabolite can be algebraically calculated. The method is presented using ATP as an example.The quench time (0.1 second) made possible by membrane filtration is considerably faster than has been possible in the previously developed techniques using silicone oil centrifugation for chloroplasts (1 second) or mitochondria (1 minute). This rapid quench makes it possible to investigate subcellular pools which have a rapid turnover, like the adenine nucleotides.

Journal Article↗
PubMed1990

The interaction between Helicobacter pylori culture filtrate and indomethacin: effects on the integrity of human gastric antral mucosa and its prostaglandin E2 production in vitro.

Histopathological methods and radioimmunoassay were used to assess the microstructure and prostaglandin E2 production by paired specimens of human gastric antral mucosa; the specimens were studied after 48 h of incubation in base-line tissue culture medium, Helicobacter pylori culture filtrate, H. pylori culture control fluid, indomethacin, and H. pylori culture filtrate plus indomethacin. When applied alone, the filtrate did not affect the structure of the mucosal tissue or its prostaglandin E2 synthesis. In the overall group (n = 21), specimens incubated with the mixture of H. pylori filtrate and indomethacin had a median histological grade of 1 and prostaglandin E2 of 29 pg/mg tissue, compared to 2 pg/mg (P = 0.04) and 60 pg/mg (P = 0.0007) respectively, in specimens incubated with indomethacin alone. These results indicate that an interaction may exist between indomethacin and a factor contained in H. pylori culture filtrate. Such interaction is damaging to the human gastric antral mucosa, and its understanding might have therapeutic implications.

Adult↗
PubMed2003

The impact of increased Al filtration on x-ray tube loading and image quality in diagnostic radiology.

Previous work has shown that for nine common radiographic projections (AP abdomen, AP cervical spine, LAT cervical spine, PA chest, LAT chest, AP hip, AP lumbar spine, LAT lumber spine, and AP pelvis) increasing the total x-ray tube filtration from 2.5 mm Al equivalent (the regulatory minimum for general diagnostic radiology) to 4.0 mm Al equivalent, reduces the average effective dose and average skin entrance dose by 9% and 16%, respectively, using a 400 speed screen-film system. In this study, the effects of this filtration increase on x-ray tube loading and image quality were assessed. For the above projections and filtration increase, mean absolute and percentage increases in tube loading were 2.9 mAs and 15%, respectively, for a constant film density and fixed kVp. Tube current (mA) increases of 25% (a worst case) resulted in no statistically significant loss in focal spot resolution due to blooming for both large (1.2 mm) and small (0.6 mm) focal spot sizes, except at high mA low kVp techniques. The latter losses were below 10%, and when the image receptor blur was incorporated, the total system spatial resolution losses were on the order of one-quarter to one-half these values for typical clinical geometries. Radiographs of a contrast phantom taken with 2.5 and 4.0 mm total Al equivalent x-ray tube filtration were compared at 60, 70, 81, 90, 102, and 121 kVp. No statistically significant changes were observed with regard to (1) test object conspicuity as reported by three observers, (2) image contrast, as measured using a densitometer with a 3 mm aperture (+/-0.0017 OD, 95% confidence level), and (3) pixel value image noise, image contrast-to-noise ratios, and image signal-to-noise ratios, as measured using a scanning densitometer with a 12-bit acquisition depth and 85 micron pixel size (+/-2.5%, +/-3.1%, and +/-2.5%, 95% confidence levels, respectively). These results, combined with the linear no-threshold model for radiation risk and the ALARA principle, suggest that general radiography should be carried out using a minimum of 4.0 mm total Al equivalent filtration.

Dose-Response Relationship, Radiation↗