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PubMed1984

Estimation of isogravimetric capillary pressure by a filtration method in skeletal muscle and lung.

Pre- to postcapillary resistance ratios (Ra/Rv) and isogravimetric capillary pressures (Pc,i) were estimated using a modified filtration method and compared with estimates obtained by application of traditional isogravimetric techniques in isolated rat hindquarters and canine lungs. Pc,i's and Ra/Rv's were estimated using both methods in rat hindquarters perfused with whole blood or an artificial plasma and in blood-perfused canine lung. In each of the three experimental conditions studied, the modified filtration method yielded the same Pc,i and Ra/Rv as the isogravimetric technique. Maximal vasodilation of the rat hindquarter with papaverine reduced Ra/Rv approximately fourfold to a level which was not different from that obtained in hindquarters perfused with artificial plasma, although Pc,i was unchanged. These results indicate that the more easily applied modified filtration method provides an excellent measurement of Ra/Rv and Pc,i in whole organ studies.

Animals↗
PubMed1998

Blood flow vs. venous pressure effects on filtration coefficient in oleic acid-injured lung.

On the basis of changes in capillary filtration coefficient (Kfc) in 24 rabbit lungs, we determined whether elevations in pulmonary venous pressure (Ppv) or blood flow (BF) produced differences in filtration surface area in oleic acid-injured (OA) or control (Con) lungs. Lungs were cyclically ventilated and perfused under zone 3 conditions by using blood and 5% albumin with no pharmacological modulation of vascular tone. Pulmonary arterial, venous, and capillary pressures were measured by using arterial, venous, and double occlusion. Before and during each Kfc-measurement maneuver, microvascular/total vascular compliance was measured by using venous occlusion. Kfc was measured before and 30 min after injury, by using a Ppv elevation of 7 cmH2O or a BF elevation from 1 to 2 l . min-1 . 100 g-1 to obtain a similar double occlusion pressure. Pulmonary arterial pressure increased more with BF than with Ppv in both Con and OA lungs [29 +/- 2 vs. 19 +/- 0.7 (means +/- SE) cmH2O; P < 0. 001]. In OA lungs compared with Con lungs, values of Kfc (200 +/- 40 vs. 83 +/- 14%, respectively; P < 0.01) and microvascular/total vascular compliance ratio (86 +/- 4 vs. 68 +/- 5%, respectively; P < 0.01) increased more with BF than with Ppv. In conclusion, for a given OA-induced increase in hydraulic conductivity, BF elevation increased filtration surface area more than did Ppv elevation. The steep pulmonary pressure profile induced by increased BF could result in the recruitment of injured capillaries and could also shift downstream the compression point of blind (zone 1) and open injured vessels (zone 2).

Animals↗
PubMed2003

Positive effects of a fresh air filtration system on hay fever symptoms.

BACKGROUND: Avoidance of allergen exposure is the basic preventive measure in reducing symptoms of immediate-type allergies. As room air cleaners were found to have no benefic effect on general health, their use has not been recommended. The purpose of this study was to evaluate the effect of a fresh air filtration system installed in the bedrooms of non-air-conditioned homes on hay fever symptoms. METHODS: In a placebo-controlled, double-blind, two-period, crossover study, we investigated the effectiveness of a fresh air filtration system installed in the bedrooms of volunteers suffering from hay fever. RESULTS: Volunteers only suffering from pollinosis reported an improvement of their allergy symptoms. We observed a significant decrease in nighttime hay fever symptoms and an increase in morning peak expiratory flow rates (PEFR). No effects were recognized in volunteers who additionally had perennial allergy. CONCLUSION: Based upon these results, the installation of fresh air filtration systems in bedrooms should be recommended for patients suffering from hay fever.

Adult↗
PubMed1982

Reversible uremia and its effect on the glomerular filtration rate.

As the nephron population diminishes and azotemia develops, each remaining nephron adapts and increases its function by as much as 80%. To determine whether this adaption is permanent or transient, a rat model utilizing one remnant kidney and one normal control kidney was used. In stage one, immediately after ligation of the ureter to the control kidney, the glomerular filtration rate in the remnant kidney was 0.185 cm3/min. 1 week after ligation of the ureter to the control kidney, the glomerular filtration rate in the remnant kidney had increased to 0.336 cm3/min (stage two), and 2 weeks later, after removal of the obstruction to the control kidney, the glomerular filtration rate in the remnant kidney was 0.155 cm3/min (stage three), p less than 0.01.

Adaptation, Physiological↗
PubMed1996

Nitric oxide modulates glomerular filtration and renal blood flow of the newborn rabbit.

The current study was performed in 17 anesthetized and mechanically ventilated newborn rabbits to investigate the role of nitric oxide (NO) in the regulation of basal renal function of the immature kidney. Renal blood flow and glomerular filtration rate were determined by the clearance of p-aminohippuric acid and inulin, respectively. In 9 newborn rabbits (group 1), L-NAME, a NO synthesis inhibitor, significantly increased the renal vascular resistance by 31 +/- 9% and decreased the renal blood flow by 20 +/- 6%. The fraction of filtration significantly increased by 8 +/- 5% despite a delayed decline in glomerular filtration rate by 13 +/- 5%. Mean arterial pressure and heart rate were not altered. In 8 additional newborn rabbits (group 2), L-arginine, the physiological precursor of NO synthesis, partially reversed the renal hemodynamic changes induced by L-NAME. The present results demonstrate that the decrease in NO production induced by L-NAME (1) significantly affects the renal microcirculation of the immature newborn rabbit kidney and (2) predominantly increases the postglomerular renal vascular resistance. Endogenous NO thus appears to play a major role in maintaining the basal perfusion of the immature kidney.

Animals↗
PubMed1975

Glomerular filtration response to elevated ureteral pressure in both the hydropenic and the plasma-expanded rat.

The factors affecting glomerular ultrafiltration with elevated ureteral pressure were examined in both plasma-expanded (2.5% body weight) and hydropenic Munich-Wistar rats. Elevated ureteral pressure (20 mm Hg) alternated as the initial condition in both groups. Glomerular capillary hydrostatic pressure (PG) and Bowman's space pressure (Pt) were measured directly in surface glomeruli with a servonulling device (deltaP = PG - PT), systemic (piA) and efferent (piE) peritubular capillary oncotic pressures were estimated by microprotein methods, and single-nephron glomerular filtration rates (sngfr) were determined by micropuncture techniques under control ureteral pressure and after increased ureteral pressure in both experimental groups. All data were then applied to equations describing the process of glomerular ultrafiltration to define the profile of effective filtration pressure (EFP = deltaP - pi) and the glomerular permeability coefficient (LpA), where sngfr = LpA-EFP. In plasma-expanded rats, sngfr fell from 44.8 +/- 2.2 to 38.5 +/- 1.5 nilters/min g-1 kidney weight (P less than 0.025) with elevated ureteral pressure entirely as a result of a decrease in the hydrostatic pressure gradient (deltaP), since PG did not rise and nephron plasma flow remained constant. In hydropenic rats, sngfr fell from 34.7 +/- 1.6 to 27.3 +/- 1.6 nliters/min g-1 kidney weight with increased ureteral pressure. PG rose 8.7 mm Hg (P less than 0.001) due to an increase in vascular resistance between the peritubular capillaries and the renal vein which prevented the reduction in deltaP. The reduction in sngfr appeared to result from a reduction in LpA resulting in disequilibration of EFP. Nephron plasma flow was not changed. The filtration response to elevated ureteral pressure was modified by the prior state of volume expansion and was not associated with changes in either nephron blood flow or afferent arteriolar resistance.

Animals↗
PubMed1977

Availability of active amphotericin B after filtration through membrane filters.

The availability of active amphotericin B after filtration of the intravenous form of the drug through in-line filters was examined. Filtration through circular filters of 25-mm diameter and 0.45-micronm pore size resulted in little loss of active drug, although a marked decrease in flow occurred with time. Filtration through either circular or cylindrical filters with 0.22-micronm pores resulted both in significant losses of active drug and in marked decreases in flow. Thus, membrane filters of 0.22-micronm pore size are not suitable for use in intravenous administration of amphotericin B. The use of filters of 0.45-micronm pore size is appropriate only in situations in which decreased flow is acceptable.

Amphotericin B↗
PubMed1976

Acute effects of antiglomerular basement membrane antibody on the process of glomerular filtration in the rat.

Nehron filtration rate (sngfr) and the factors controlling filtration were examined before and with 60 min of the intravenous infusion of 225-450 mug of antiglomerular basement membrane antibody (AGBM Ab) (greater than 50% antigenic saturation) in plasma-expanded (2.5% body wt) Munich-Wistar rats. Pressures in glomerular capillaries (PG) and bowman's space (Pt) were measured with a servo-nulling device, systemic (piA) and efferent arteriolar oncotic pressures (piE) were measured by microprotein methods, and nephron plasma flow (rpf) and sngfr were measured by micropuncture techniques in both control and post-AGBM Ab conditions in each rat. The sngfr fell from 52.7+/-2.9 to 24.1+/-1.9 nl/min per g kidney wt (n = 7, P less than 0.001). Both afferent and efferent arteriolar resistances increased and rpf fell from 221+/-25 to 90+/-9 nl/min per g kidney wt (P less than 0.001) but the hydrostatic pressure gradient across the glomerular membrane deltaP = PG - Pt) increased from 37+/- 1 to 50+/-2 mm Hg (P less than 0.001). The increase in deltaP and a numerical decrease in piA both acted to maintain sngfr after AGBM Ab and effectively nullified the influence of decreased rpf upon sngfr. The mean effective filtration pressure (EFP = deltaP - pi) increased from 14+/-2 to 30+/-3 mm Hg (P less than 0.001) while sngfr decreased. The major and critical reason for this reduction in sngfr was a decrease in the glomerular permeability coefficient from 0.077+/-0.017 to 0.014+/-0.001 nl/s per g kidney wt per mm Hg P less than 0.001) where sngfr=EFP-LpA.

Animals↗
PubMed1978

Studies on the tubulo-glomerular feedback system in the rat. The mechanism of reduction in filtration rate with benzolamide.

The specific mechanism whereby superficial nephron glomerular filtration rate (sngfr) is reduced after the administration of benzolamide, a carbonic anhydrase inhibitor with a primary inhibitory effect in the proximal tubule, have been examined by measuring pertinent pressures, flows, and glomerular permeabilities in the hydropenic Munich-Wistar rat, a strain with surface glomeruli. Because benzolamide decreases absolute proximal reabsorptive rate, the rate of delivery of tubular fluid to the distal nephron should be at least transiently increased and may reduce sngfr by activating the tubulo-glomerular feedback system. Sngfr fell from 29.2+/2.0 to 2.1+/3.1 nl/min (P less than 0.01) after benzolamide (group 1), a percentage reduction equal to kidney glomerular filtration rate and similar to sngfr obtained in collections from distal tubules. Separate studies (group 2) revealed that if transient increases in distal nephron delivery were prevented by insertion of a long oil block in proximal tubules before control, the decrease in sngfr was prevented (30.3+/1.0 vs. 30.3+/1.8 nl/min, P greater than 0.9). In paired "unblocked" nephrons in the same rats, sngfr fell in group 2 (33.0+/1.0 vs. 25.2+/2.3 nl/min, P less than 0.01). In "blocked" nephrons in which sngfr reduction was prevented, the rate of fluid leaving the proximal tubule increased from 16.9+/ to 23.1+/1.0 nl/min (P less than 0.01). In group 1 studies in which sngfr fell and transient increases in flow out of the last segment of the proximal tubule (distal delivery) (approximately equal to 8 nl/min) were not prevented, steady-state distal delivery was unchanged by benzolamide (13.9+/1.1 vs. 14.2+/2.2 nl/min). Also, sngfr returned toward control, pre-benzolamide values, when a proximal oil block was placed for 15 min and the rate of distal delivery reduced after benzolamide administration, which suggests that this activation was reversible. These data suggest that activation of tubulo-glomerular feedback by transient increases in distal delivery was responsible for decreases in sngfr. Analysis of all determinants of glomerular ultra-filtration revealed that the efferent mechanism leading to reduced sngfr after benzolamide was decreased nephron plasma flow (101+/13 vs. 66+/13 nl/min, P less than 0.01). Hydrostatic pressure and the glomerular permeability coefficient did not contribute to reductions in sngfr with benzolamide. Because the rate of distal delivery remained constant in spite of large changes in both sngfr and absolute proximal reabsorptive rate, it is suggested that the rate of distal delivery may be the physiologic entity that is regulated by the tubulo-glomerular feedback system via alterations in sngfr.

Animals↗
PubMed1993

Glomerular filtration and tubular reabsorption of albumin in preproteinuric and proteinuric diabetic rats.

Microalbuminuria (26-250 mg/d) is considered to be an indicator of incipient diabetic nephropathy in humans in insulin-dependent diabetes (IDD). However, before microalbuminuria is observed, glomerular alterations, such as glycosylation of the glomerular basement membrane and glomerular hyperfiltration, in IDD may result in increased filtration of albumin before any observed increase in albumin excretion. Glomerular and tubular albumin kinetics were examined in streptozotocin (65 mg/kg body wt, i.v.) diabetic, Munich-Wistar rats at 7-10 (untreated) and 50-70 d (poorly controlled with small doses of insulin) after the onset of diabetes and compared with nondiabetic controls. Additional rats in each condition received acute lysine treatment to prevent tubular protein reabsorption. Urinary albumin excretion and nonvascular albumin distribution volumes were measured in the renal cortex and compared with morphometric measurements of interstitial space and the proximal tubule to assess intracellular uptake of albumin in the proximal tubule. Urinary albumin excretion under anesthesia was not different in 7-10-d IDD versus controls (19 +/- 3 vs. 20 +/- 3 micrograms/min) but increased in the 50-70-d IDD (118 +/- 13 micrograms/min, P < 0.05). Lysine treatment resulted in increased albumin excretion compared with respective nontreatment in 7-10-d IDD (67 +/- 10 micrograms/min, P < 0.05) but not in controls (30 +/- 6 micrograms/min) or in 50-70-d IDD (126 +/- 11 micrograms/min). Glomerular filtration rate was increased both in 7-10-d IDD (2.7 +/- 0.1 ml/min, P < 0.05) and in 50-70-d IDD (2.6 +/- 0.1 ml/min, P < 0.05) compared with control (2.2 +/- 0.1 ml/min). Calculated urinary space albumin concentrations increased early in IDD with 2.5 +/- 0.4 mg% in 7-10-d IDD and 4.9 +/- 0.6 mg% in 50-70-d IDD compared with control (1.4 +/- 0.3 mg%). The increase in filtration of albumin is in excess of that attributable to hyperfiltration before increased albumin excretion early in diabetes. In 50-70-d IDD, absolute tubular reabsorption of albumin is decreased, correlating to the decrease in brush border height of the proximal tubule.

Animals↗
PubMedDate not supplied

Effects of in-line filtration on lipid particle size distribution in total nutrient admixtures.

BACKGROUND: The recent Food and Drug Administration Safety Alert recommends in-line filtration for all total parenteral nutrition admixtures. Although rigid crystalline particulates can be effectively removed by in-line filters, the fate of flexible lipid droplets (LDs) enlarged through electromechanical destabilization is less clear. Lipid globules > 5 microns could lodge in the pulmonary microvasculature and produce an embolic syndrome. Recent evidence suggests that TNAs (Total Nutrient Admixtures) with LDs of 5 microns or more constituting > 0.4% of the final fat concentration are unstable. METHODS: Six pairs of 1.5-L TNA dispersions of varying degrees of stability were prepared in duplicate (n = 12) and studied over 30 hours. The number of enlarged fat globules was assessed by laser light extinction for all LDs > or = 1.75 microns at 0, 6, 24, and 30 hours after preparation. After LD assessments at time 0, admixtures were placed in a temperature-controlled chamber at 25 degrees C +/- 0.1 degree C. At 6 hours, a simulated patient infusion was begun using a 1.2-microns filter at a continuous flow rate of 55 mL/h. Pre- and postfiltration samples were taken at 6, 24, and 30 hours, equal to times 0, 18, and 24 hours of the simulated infusion. A repeated measure two-way analysis of variance assessing treatment and time was performed. Dependent variable analyses included number-weighting of fat globules as > 5 microns (LD1), total number > or = 1.75 microns (LD2), LD1-LD2 ratio (as %), and volume-weighted percent of fat (PFAT) > 5 microns. RESULTS: In all cases, time was a significant factor and was an expected finding as the stability of all extemporaneously prepared admixtures deteriorates with time. Of the number-weighted variables, a significant postfiltrate reduction was observed in LD1 (p = .041), LD2 (p < .001), and LD1-LD2 ratio (p < .0001). Of greatest clinical importance, the volume-weighted PFAT > 5 microns was significantly reduced by the in-line filter (p = .029). CONCLUSIONS: The TNA1 1.2-microns filter significantly reduced the total number and concentration of enlarged fat globules. The higher LD1-LD2 ratio may reflect the effects of filtration on electrically destabilized fat globules. However, total exposure to unstable and very large LDs was significantly reduced, suggesting that in-line TNA filtration should be a standard part of nutrition therapy.

Drug Stability↗
PubMed2001

Leukocyte filtration in the early reperfusion phase on cardiopulmonary bypass reduces myocardial injury.

Improved myocardial protection and cardiopulmonary bypass (CPB) have limited, but not abolished, intraoperative myocardial damage due to surgical reperfusion injury after release of the aortic crossclamp. In this double-blind, randomized study, we evaluated whether short-term leukocyte filtration during reperfusion may further reduce myocardial damage. Thirty-eight patients with coronary artery disease were randomly assigned to CPB with (group I; n = 19) or without leukocyte filtration (group II; n = 19). There was no difference in bypass time or crossclamp time between the groups. No patient in group I required catecholamines, whereas three patients in group II were supported with adrenaline or dobutamine on the first and second postoperative day. In addition, troponin T plasma levels were lower in group I (p < 0.05), whereas other markers for tissue injury (CK, CK-MB, LDH, S-GOT and S100B) did not differ. In conclusion, leukocyte filtration during reperfusion may further improve CPB by reducing myocardial damage.

Aged↗
PubMed2001

Leukocyte filtration in cardiac surgery: a review.

Leukocyte filtration has evolved as an important technique in cardiac surgery with cardiopulmonary bypass to prevent pathogenic effector functions mediated by activated leukocytes. The underlying mechanisms that result in an improvement of laboratory variables as well as clinical outcome are not resolved yet. Moreover, the optimum strategy for the use of current filtration technology has not been systematically evaluated. This paper, therefore, reviews how activated leukocytes may lead to tissue damage, summarizes the known effects of leukocyte filtration on clinical outcome and laboratory parameters, and deals with current experimental and clinical efforts to further limit the pathogenic effects of leukocytes in cardiac surgery.

Adult↗
PubMed2001

Filtration of malignant cells: tumour cell depletion in an ex vivo model using a leukocyte adhesion filter.

The clinical use of leukocyte adhesion filters is based on differentiated depletion of blood cells, although most of the mechanisms of filtration are still unclear. There is also evidence that leukocyte adhesion filters can remove disseminated tumour cells from patients' blood. The following proves this observation and consists of three parts: in the first part we analysed the depletion capacity of the LeucotrapWB filter medium (Pall) in an employed small-scale model for the cell line HT29 (colorectal origin) in phosphate-buffered saline (PBS) solution. A depletion rate of more than 99.6% for HT29 cells was seen. In the second part of the study, samples of whole blood were spiked with HT29 cells in a similar setting, showing comparable results. In the last part, defined cell suspensions of various human primary tumours were admixed to whole blood samples and afterwards filtrated in a scale-up model. Again, a nearly complete tumour cell reduction was seen after filtration. Results show a significant tumour cell reduction and, for most cases, a complete depletion of tumour cells independently from quality and origin of the tumour tissue. These experiments and further investigation are supposed to help to reduce the risk of dissemination of tumour cells in patients undergoing oncological surgery.

Cell Adhesion↗
PubMed2002

Carbide sludge management in acetylene producing plants by using vacuum filtration.

Carbide sludge (10.4-11.5 tonnes day(-1)) is generated from the reaction of calcium carbide (900 kg) and water (6,000 L) in the production of acetylene (2,400 m3), in three selected acetylene manufacturing plants. The sludge (of pH 12.2 and containing Cu, Pb, Fe, Mn, Ni and Zn ions whose concentrations exceed the Department of Environment limits for industrial wastewater) was treated by vacuum filtration as a substitute for the ponding system, which is environmentally less acceptable. A similar system by flocculation was also developed. The filtration system represents an improvement over the ponding method, as shown by a pH of 7 for the clear filtrate; the solid cake, which contains 98% of the metals, can be conveniently disposed at an integrated scheduled waste treatment centre.

Acetylene↗
PubMed1988

Cell cycle synchronization of Gonyaulax polyedra by filtration: quantized generation times.

A size filtration method to synchronize cultures of the dinoflagellate Gonyaulax polyedra to the beginning of the G1 phase has been developed. This technique selects newly born cells by two sequential filtrations, based on the fact that cell division is restricted to the beginning of the day, so that a decrease in cell volume occurs at this time. The fraction of synchronized cells immediately after the second filtration is about 90%; the procedures do not alter the free-running period or phase of glow rhythm, and the selected cells divide again in a few days. Applying this method, we have found that the generation times of this species in a light-dark cycle (LD 12:12) are indeed quantized to multiples of 24 hr, but are variable from generation to generation.

Animals↗
PubMed2005

Comparison of 3 AT1 receptor binding assays: filtration assay, ScreenReady Target, and WGA Flashplate.

In this article, the study of 3 different angiotensin II type 1 (AT(1)) receptor binding assays in terms of reproducibility, robustness, and feasibility for high-throughput screening (HTS) is described. The following methods were used: a nonhomogeneous filtration assay in a 96-well format using CHO-AT(1) cell membranes and 2 homogeneous assays, which include the commercially available ScreenReady Target for the AT(1) receptor and the wheat germ agglutinin (WGA) Flashplate, which was coated "in-house" with the CHO-AT(1) cell membranes. Receptors were labeled with [(125)I]-Sar(1)-Ile(8)-angiotensin II, and radioligand binding was displaced using the antagonist losartan and the natural agonist angiotensin II. Reproducible K(d), B(max), and K(i) values and good total binding/nonspecific binding (TB/NSB) ratios were obtained with both the ScreenReady Targets and the filtration assay, whereas the WGA Flashplates showed unacceptably high nonspecific binding and high variation when applied as a homogeneous assay. However, when applied as a heterogeneous assay (i.e., when a wash step at the end of the assay is included), the results were significantly better. Interestingly, ligand affinities were consistently lower in Flashplate-based assays than in the filtration assay. This may be due to the immobilization of the receptors onto the solid surface of the plate, affecting their conformation. In terms of reproducibility, robustness, and feasibility for HTS, the authors conclude that the ScreenReady Target plates are most suitable for AT(1) receptor binding screening.

Angiotensin II↗
PubMed1980

Ontogeny of single nephron filtration distribution in canine puppies.

The ontogeny of single nephron filtration distribution was studied in 29 canine puppies two hr to 42 days old using the [14C] ferrocyanide method as modified by Coehlo (9). The ratio of 14C counts in outer cortical nephrons (OC) to counts in juxtamedullary nephrons (JM) were plotted against age for each puppy. This ratio (OC:JM) provided an index for comparing the single nephron glomerular filtration between regions. A four-fold increase in OC:JM occurred from two days to four wk. The youngest puppy, two hr old, showed a ratio of zero because no counts were detected in OC at that age. The most rapid increase occurred in the first 8 days of life. By the fourth wk, the mean OC:JM ratio was 0.72 +/- 0.06, approaching values reported by other laboratories for adult dogs. In contrast to age-related changes in OC:JM ratio, the ratio of middle cortical to JM counts showed no age-related increase. Cortical blood flow distribution was determined by the microsphere method. The ratio of blood flow to outer and inner cortex increased from 0.43 at one-half a day to a mean of 2.93 after one wk. The ratio of OC:JM single nephron filtration of OC/inner cortical nephron renal blood flow was 0.36 from 3 days to 26 days (n = 12) and did not change significantly with age, indicating that changes in zonal filtraion matched the alterations in cortical blood flow distribution.

Age Factors↗