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PubMed1977

Inhibitory effect of methylxanthines on feedback control of glomerular filtration rate in the rat kidney.

Microperfusion experiments were performed in rats to assess the effect of luminal application of theophylline and the more lipophilic 3-isobutyl-1-methylxanthine (IBMX) on feedback regulation of glomerular filtration rate. Elevation of loop of Henle flow from 0 to 40 nl/min caused a 20.3 +/- 4.5% reduction of stop flow pressure (SFP) and a 32.2 +/- 3.7% reduction of early proximal flow rate (EPFR) when the perfusate was a 140 mM NaCl solution. When theophylline was added in a concentration of 5mM SFP fell by only 5.3 +/- 1.8% and EPFR by 7.9 +/- 33%, changes which were significantly smaller than in the control perfusions (P less than 0.01). An identical change of loop of Henle flow in the presence of IBMX in concentration of 1 and 5 mM was associated with a 4.5 +/- 3.9% decrease and a 12.1 +/- 2.7% increase of EPFR. In orthograde perfusion experiments full inhibition of the feedback response was noted at an IBMX concentration of about 1 mM while during retrograde perfusion a concentration of 0.4 mM was sufficient to produce the same effect. This indicates that methylxanthines diffuse out of the loop of Henle to a considerable extent. Methylxanthines reduced absolute and fractional water absorption along the loop of Henle to some extent while Cl absorption rates and early distal Cl concentrations were not significantly altered. Cyclic AMP applied from the luminal side in a concentration of 10 mM did not affect the feedback response of EPFR to flow elevation from 0 to 40 nl/min. Luminal application of dibutyryl cyclic AMP at 10 mM induced a small, but significant reduction of the feedback response when tested by paired t-test (P less than 0.05). Our results show that luminal application of methylxanthines strongly interfere with feedback regulation of glomerular filtration rate. It is unclear at present whether this effect is related to inhibition of cyclic nucleotide phosphodiesterase and a rise in tissue cyclic AMP levels or to interference with a mechanism involving the local action of adenosine or 5'-AMP.

Animals↗
PubMed1976

Single nephron glomerular filtration rate ratios of superficial, intercortical and juxtamedullary nephrons in rats during development.

In 20, 40 and 60-day-old rats the filtration rate was studied using Baines modification of Hanssen's Na4Fe (14CN)6 method enabeling the determination of single nephron glomerular filtration rate (SNGFR) ratio between superficial (S), intercortical (I) and juxtamedullary (J) nephrons. The proximal tubule lengths were determined as well. A close correlation was obtained between age and S/I, I/J and S/J of proximal tubule lengths and between age and I/J, S/J 14C-activities of ferro-cyanide. Presented findings confirm the data on the increasing role of superficial nephrons in the course of postnatal development of rat.

Age Factors↗
PubMed1983

Estimation of glomerular filtration rate in conscious dogs following a bolus of creatinine. Comparison with simultaneously determined inulin clearance.

The renal clearance of creatinine was measured following orogastric administration in conscious dogs. Values of creatinine clearance were compared with simultaneously determined values of inulin clearance, when urine volume, glomerular filtration rate and volume status were acutely altered by a variety of experimental manoeuvres. At urine volumes greater than 20 microliters X min-1 X kg-1, creatinine clearance was not significantly different from inulin clearance. At low urine volumes there was some evidence of creatinine reabsorption. It is concluded that the bolus creatinine technique provides reliable estimates of glomerular filtration rate and is particularly applicable to long-term studies in conscious dogs.

Animals↗
PubMed1985

Maleate induced fall of glomerular filtration rate. A micropuncture study in the rat.

Maleate causes an enhanced excretion of amino acids, glucose, phosphate and bicarbonate. In addition to this inhibition of fluid and electrolyte reabsorption malate decreases glomerular filtration rate (GFR). The present investigation was designed to study the mechanisms of this fall in GFR. In group I (Sprague-Dawley rats; N = 8) maleate (2 mmol/kg body weight i.v.) increased the hydrostatic pressure in proximal tubule from 12.6 +/- 0.5 to 16.3 +/- 0.8 mm Hg (mean + SEM) and stop flow pressure in the first accessible loop of the proximal tubule was unchanged (33.6 +/- 0.4 vs 33.1 +/- 1.3 mm Hg; n.s.). Directly measured hydrostatic pressure in the glomerular capillaries in Munich-Wistar rats (N = 7), however, was reduced by maleate from 47.6 +/- 1.6 to 42.4 +/- 1.9 mm Hg. In group II (N = 8) we determined single nephron filtration rate (SNGFR) from distal and proximal collection sites in the same nephron in a paired fashion under control conditions and after maleate administration to assess the activity of the tubuloglomerular feedback. In the control periods SNGFR (16 nephrons) from distal collection sites was 26.3 +/- 1.6 nl/min whereas SNGFR from proximal collection sites was 31.8 +/- 2.4 nl/min. Following maleate distal SNGFR (17 nephrons) was 15.2 +/- 1.7 nl/min and proximal SNGFR was 24.3 +/- 2.2 nl/min. The ratio distal/proximal SNGFR was 1.23 +/- 0.07 under control conditions and increased to 1.76 +/- 0.1 following maleate indicating enhanced activity of tubuloglomerular feedback.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Effect of hyperfiltration on long-term follow-up of glomerular filtration rate in male Wistar rats.

It has been suggested that a prolonged course of hyperfiltration could lead to progressive deterioration of renal function. In order to test this hypothesis, the following protocol was applied to 60 male Wistar rats. At 12 weeks of life, the rats were submitted to a surgical procedure: sham operation (25 rats), unilateral nephrectomy (25 rats) or 3/4 nephrectomy (10 rats). The three groups were again divided into two subgroups: one with high-protein intake (36%) and one with a low-protein intake (12%). In order to avoid any additional traumatic procedure which could shorten the animal's life, the glomerular filtration rate (GFR) was measured without blood sampling, using a previously validated technique based on an image recorded by a gamma camera between the 9th and the 10th min after intravenous injection of 99m technetium diethylenetriaminepentaacetate (DPTA). The sum of both kidneys and bladder activity was expressed as a percentage of the injected dose. The test was performed before surgery and every month thereafter. Six weeks after surgery, the highest filtration rate was found in the rats with "two kidneys/high-protein diet", followed by the "two kidneys/low-protein diet", the "one kidney/high-protein diet", the "one kidney/low-protein diet" and the "1/2 kidney". The overall GFR in the one kidney/high-protein diet rat and in the 1/2 kidney rat was respectively 80% and 55% of the pre-operative values. Until 109 weeks of age, the survival rate was comparable in the five groups of rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Fractionation of Pneumocystis carinii developmental stages by counterflow centrifugal elutriation and sequential filtrations.

Immunomagnetic sorting, sequential filtrations, and counterflow centrifugal elutriation were compared for their ability to obtain enriched populations of Pneumocystis carinii developmental stages from infected rat-lung homogenates. Elutriation combined with sequential filtrations resulted in highly (> 95%) enriched populations of P. carinii cysts and trophozoites with excellent viability. This approach offers advantages over previously described methods of obtaining enriched P. carinii cell populations and should have important applications to research on this organism.

Animals↗
PubMed1987

Characterization of quisqualate recognition sites in rat brain tissue using DL-[3H]alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) and a filtration assay.

The binding of [3H]AMPA (DL-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid), a ligand for the putative quisqualate excitatory amino acid receptor subtype, was evaluated using centrifugation and filtration receptor binding techniques in rat brain crude synaptosomal membrane preparations. Maximal specific binding of [3H]AMPA occurred in Triton X-100 treated membranes in the presence of the chaotropic agent potassium thiocyanate (KSCN). The effects of KSCN on binding were reversible and optimal at 100 mM. Supernatant obtained from detergent-treated membranes inhibited specific [3H]AMPA and [3H]kainic acid binding, suggesting the presence of an inhibitory agent which was tentatively identified as glutamate. Using centrifugation, saturation analysis revealed two distinct binding sites in both the absence and presence of KSCN. The chaotrope was most effective in increasing binding at the low affinity binding site, enhancing the affinity (Kd) without a concommitant change in the total number of binding sites. Using filtration, a single binding site was detected in Triton-treated membranes. Like the data obtained by centrifugation, KSCN enhanced the affinity of the receptor (Kd value = 10 nM) without altering the number of binding sites (Bmax = 1.2 pmol/mg protein). The rank order of potency of various glutamate analogs in the [3H]AMPA binding assay was quisqualate greater than AMPA greater than L-glutamate greater than kainate greater than D-glutamate, consistent with the labeling of a quisqualate-type excitatory amino acid receptor subtype. L-glutamic acid diethylester, and 2-amino-7-phosphonoheptanoic acid (AP7) were inactive. The present technique provides a rapid, reliable assay for the evaluation of quisqualate-type excitatory amino acid agonists and/or antagonists that may be used to discover more potent and selective agents.

Animals↗
PubMed1979

Red cell filtration by paper filters.

A method for the assessment of red cell filterability with paper filters is described. Two milliliters of a washed red cell suspension with a hematocrit of 50% was filtered through a filter paper cone in a glass funnel and the filtration half-time (FT1/2) was measured. The filter papers were calibrated by previous measurement of the filtration time for the suspending solution, the calibration time (CT). A linear correlation between CT and FT1/2 was found for individual red cell suspensions (p less than 0.001) as well as for a normal population (p less than 0.001). Consequently, the index FT1/2/CT should represent a more reproducible parameter than FT1/2 and experimentally this appears to be the case. In fact, elimination of erratic values in a normal population was realized. Furthermore, discrimination between normal and abnormal values was improved and the coefficient of variation of single measurements passed from 28.4 to 9.4%. The reproducibility and reliability of this extremely simple method are therefore decisively enhanced without complication of the procedure.

Erythrocytes↗
PubMed1978

High granulocyte yield with a simple method of filtration leukapheresis.

A simple continuous filtration leukapheresis has been devised whereby two Leuko-Pak filters can be charged and eluted within 5 h with approximately 121 of blood in a closed system of tubes. Blood flows by means of gravity without the use of pumps. Without premedication with prednisolone the average yield from 10 donors was 3.66 x 10(10) granulocytes per leukapheresis and after premedication with 150 mg prednisolone orally it was 6.44 x 10(10) granulocytes per leukapheresis. The in vitro function of filter granulocytes was not reduced even after premedication with prednisolone. In comparison with leukapheresis by blood cell separators this modified method of filtration leukapheresis offers the following advantages: 1) the granulocyte yield per litre of whole blood processes is higher, 2) technical assistants in a blood-bank can carry out the method on several donors simultaneously, 3) the method is more economical than leukapheresis by blood cell separators.

Cell Survival↗
PubMed1977

Hyperparathyoidism: influence of glomerular filtration rate on urinary excretion of cyclic AMP.

Urinary cyclic AMP excretion per 24 h or per g creatinine in primary hyperparathyroidism (1 degrees HPT) has been evaluated by several authors with conflicting results. In 50 patients with 1 degrees HPT, 25 patients with secondary (2 degrees) HPT and 35 healthy control persons we determined urinary cyclic AMP per 24 h or per g creatinine. These parameters did not satisfactorily discriminate patients from controls, especially when glomerular filtration rate (GFR) as determined by creatinine clearance was reduced. Since urinary cyclic AMP is derived from plasma by glomerular filtration and from kidney by tubular production-the amount of tubules is reflected by GFR-the cyclic nucleotide was related to GFR. In controls urinary cyclic AMP correlated better with GFR than with creatinine excretion. Additionally, in 45 of 50 patients with 1 degrees HPT and in all with 2 degrees HPT, urinary cyclic AMP/GFR was raised. In 1 degrees HPT serum levels of parathyroid hormone correlated closer with urinary cyclic AMP/GFR than with urinary cyclic AMP/g creatinine. The ratio cyclic AMP/GFR decreased to normal or subnormal values after removal of adenomatous or hyperplastic glands in 1 degrees HPT and during infusion of calcium in 2 degrees HPT. In 50 patients with renal lithiasis caused by diseases other than 1 degrees HPT (anatomical variations, pyelonephritis, immobilization after tetraplegia) the ratio cyclic AMP/GFR was not raised. Urinary cyclic AMP/GFR, therefore, reflects parathyroid hormone excess more reliably than cyclic AMP/g creatinine.

Adolescent↗
PubMed1979

Tangential flow filtration of Bordetella pertussis submerse cultures.

A procedure is reported for the large scale separation of Bordetella pertussis microorganisms from liquid culture media by tangential flow filtration (cross flow filtration) using anisotropic membranes with a cut-off limit of 1 x 10(6) daltons, and microporous membranes with a pore size of 0.22 micrometer.

Bordetella pertussis↗
PubMed1988

Reassessment of selective agars and filtration techniques for isolation of Campylobacter species from faeces.

Four different studies were conducted in order to re-evaluate conventional methods and assess the efficacy of new selective agars and a filtration method for the isolation of campylobacters. Skirrow's medium, Preston agar, modified CCD agar and Fennell's medium, incubated microaerobically at 37 degrees C for 48 h, gave similar Campylobacter isolation rates from 225 faecal samples, but the latter two media were more selective. Evaluation of modified CCD agar demonstrated that campylobacters could be isolated from that medium more successfully after incubation at 37 degrees C (173/177 positive samples) than at 42 degrees C (152/177 positive samples). In a larger study 1286 faecal specimens were cultured using modified CCD agar, Fennell's medium and a 0.45 micron membrane filtration technique, all incubated at 37 degrees C. Campylobacters were isolated from 89% (178), 86% (171) and 60% (130) of 199 positive samples respectively. Modified CCD agar was most successful in isolation of the majority of campylobacters, but Fennell's medium was essential for recovery of "Campylobacter cinaedi" and "Campylobacter fennelliae", whereas the 0.45 micron membrane technique was the only method to isolate all of the catalase-negative campylobacter strains. Further evaluation of the 0.45 micron and 0.65 micron pore size membranes showed that more strains of Campylobacter jejuni and Campylobacter coli were isolated using the larger pore size membranes.

Agar↗
PubMed1987

Value of isotypic characterization of antibodies to Echinococcus granulosus by enzyme-linked immuno-filtration assay.

In order to establish prognostic criteria for patients with hydatid cysts and to identify functional antigenic components of Echinococcus granulosus 87 sera from 36 patients were studied by enzyme-linked immuno-filtration assay (ELIFA) to characterize the four main classes of specific immunoglobulins and to determine compared immunological profiles (CIP) between samples or subjects. This method uses filtration with labelled antibodies to reveal precipitating systems preformed by immuno-electro-diffusion on cellulose acetate strips. IgG antibodies were demonstrated in the arc 5 and in 11 others bands. Specific IgA, IgE and IgM to Echinococcus granulosus was found in 19%, 53% and 69% respectively of patients with hydatids. The presence of IgM and/or IgE antibodies one year after treatment always correlated with disease. Specific IgA was detected more often in patients with pulmonary cysts. Pre- and post-operative monitoring by CIP-ELIFA proved simple and rapid to perform and of decided prognostic value. Two antigens, corresponding to arc 5 and arc X, were frequently associated with the poly-isotypic immune response.

Animals↗
PubMed1977

[Methodical investigations concerning the measurement of red cell deformability dependent on plasma viscosity, plasma proteins, hematokrit, filtration pressure as well as osmolarity (author's transl)].

The measurement of red cell deformability (flexibility or fluidity) according to the method of filtration strongly depends on the suspension medium, the hematokrit, filtration pressure as well as osmolarity and is hard to differentiate over the influence of red cell aggregation. Therefore, data concerning the flexibility of red cells have to be established under standardized conditions, e.g. suspension medium, such as albumin, stabilized hematokrit, constant osmolarity and pressure.

Blood↗
PubMed1979

Elucidation of an A and L system for amino acid transport in the human lymphoblast using a membrane filtration technique.

Optimum conditions have been established for the measurement of amino acid transport by human lymphoblastoid cell lines using a membrane-filtration technique. The parameters we found to be important for the reproducibility of the method are: the types and combination of filters, the strength of the vacuum applied to the filters and the density of the cultures at the time of harvesting and during uptake and filtration. We found that bovine serum albumin added to phosphate buffered saline (PBS) glucose in which the cells are washed, resuspended and assayed is essential for the maintenance of viability, the prevention of clumping and the retention of the accumulated amino acid. Using this procedure we have characterized two transport systems for the neutral amino acids; an A and an L system, which are similar but not identical to the A and L systems characterized in rodent cell lines. These A and L systems have characteristically lower Km's and Vm's for alanine and phenylalanine, when compared to rodent cell lines. In addition, we find alpha-AIB to be a poor competitor of alanine and phenylalanine uptake.

Alanine↗
PubMed1993

Modified simplified method for isolation of lysostaphin from the culture filtrate of Staphylococcus staphylolyticus.

The present paper reports a modified method for isolation of lysostaphin--a bacteriolytic agent with specific affinity for staphylococcal cell wall. The proposed purification scheme includes three steps. The first procedure is ultrafiltration through a membrane filter giving a yield of 75.6%. The result of ultrafiltration is a concentrated, 10-times purified preparation of lysostaphin with specific activity 0.62 U/mg which can be used for digestion of S. aureus cells. Further step, performed by ion-exchange chromatography on DEAE-cellulose, yields a 60-times purified preparation containing a mixture of enzyme components of lysostaphin. The yield of this step is 47.2%, the preparation contains 3.54 U/mg protein. Using gel filtration on Sephadex G-50 a component with hexosaminidase activity was separated from the endopeptidase component on the basis of molar mass difference. A 270-times purified preparation of lysostaphin-endopeptidase with minimum of contaminating substances was obtained in this step. The yield of gel filtration was 22.1%, specific activity increased up to 16.3 U/mg protein.

Amino Acid Sequence↗
PubMed1998

The effect of reducing proximal tubular fluid delivery on the rate of filtration of single nephrons.

The rate of delivery of tubular fluid from the proximal tubule (PT) is thought to reset nephron filtration rate (SNGFR). In micropuncture experiments in rats we tested this hypothesis by reducing the efflux from the PT by simultaneously "double collecting" (DC) tubular fluid from the early distal tubule (DT) and from the last convolution of the PT of the same nephrons. SNGFR measured by total collection of tubular fluid was 34 +/- 3 nl/min at the DT and 34 +/- 3 nl/min at the PT (p > 0.97, n = 42). The simultaneous collection from proximal and distal sampling site was performed between these two paired measurements. It yielded an average SNGFR of 40 +/- 3 nl/min (p < 0.02). This may be due to the collection, at the distal site, of the extra amount of inulin stored between distal and proximal pipette, prior to starting the aspiration of tubular fluid. Since this error would decrease in longer collections, the difference in SNGFR between single and double collections was plotted against the duration of collections. In fact it was negatively correlated with the sampling time (p < 0.01), indicating no difference in SNGFRs for collections > 4 minutes. Reduction and complete interruption of the delivery of native proximal tubular fluid to the Macula Densa does not seem to influence the measurement of SNGFR. Filtration rate is not significantly different when measured within few minutes at the DT and PT of the same nephrons.

Animals↗
PubMed2004

Bedside estimation of absolute renal blood flow and glomerular filtration rate in the intensive care unit. A validation of two independent methods.

OBJECTIVE: To evaluate various treatment strategies in critically ill patients with ischaemic acute renal failure, there is a need for reliable bedside measurements of total renal blood flow (RBF), glomerular filtration rate (GFR) and renal oxygen consumption without the need for urine collection. DESIGN: The continuous renal vein thermodilution method and the infusion clearance techniques were validated against the gold standard technique, the urinary clearance of paraaminohippurate (PAH) and chromium ethylenediaminetetraacetic acid, respectively. SETTING: University hospital cardiothoracic ICU. PATIENTS: Seventeen uncomplicated mechanically ventilated post-cardiac surgical patients. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Renal blood flow, GFR and the renal filtration fraction (FF) were measured for two consecutive 30-min periods by urinary clearance and compared with simultaneous measurements made by the thermodilution and infusion clearance techniques. Urinary clearance for PAH was corrected for by renal extraction of PAH. The within-group error, repeatability coefficient and the coefficient of variation were highest for the thermodilution technique and lowest for the infusion clearance technique with regard to RBF, GFR and FF. The infusion clearance technique had a higher agreement with the urinary clearance method than the thermodilution method. For estimations of RBF and GFR, the between-group errors were 33% and 43% comparing infusion clearance with urinary clearance and 65% and 67% comparing thermodilution with urinary clearance. CONCLUSIONS: The infusion clearance method had the highest reproducibility and the highest agreement with the urinary clearance reference method. The renal vein thermodilution technique is less reliable in the ICU setting due to poor repeatability and poor agreement with the reference method.

Aged↗