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J Sadowski

Publications and source records attributed to J Sadowski.

At least 73 records · Page 4Linked to original sources
PubMed1990

Renal tissue impedance: responses of the real and imaginary component to experimental variations in medullary electrolytes.

In order to assess the renal corticomedullary electrolyte gradient, electrical impedance (zeta) and phase angle (phi) were measured in the in-situ kidney of anaesthetized rats. A set of platinum/iridium needle electrodes was used, and the frequency (f) of the measuring current was varied between 0.5 and 50 kHz. zeta and its imaginary component (chi c) fell sharply as f increased from 0.5 to 3.5 kHz, and then decreased slowly or stabilized, whereas the real component (R) decreased progressively over the entire f range. Ion concentration in the renal medulla was experimentally lowered by administration of furosemide or hypertonic mannitol or by inducing a haemorrhage, and raised by infusing hypertonic NaCl solution. Both R and chi c varied inversely with tissue electrolyte concentration. Raising f from 3.5 to 10 and further to 20 kHz did not significantly amplify the changes in zeta. Within this frequency range R was not a more sensitive index of tissue electrolyte changes compared with overall zeta-value. The results verify previous empirical data indicating that changes in medullary tissue electrolytes can be dynamically estimated by monitoring tissue impedance.

Animals↗
PubMed1990

Atrial peptide natriuresis in the rat without genuine rise in filtration rate or wash-out of medullary electrolytes.

1. Effects of synthetic atrial natriuretic peptide (ANP) on renal excretion, total renal blood flow (RBF), glomerular filtration rate (GFR) and tissue electrical admittance (reciprocal impedance, an estimate of tissue electrolytes) were determined in pentobarbitone-anaesthetized rats. GFR was measured both as inulin clearance (Cin) and as a product of renal plasma flow (RPF) and inulin extraction ratio (Ein). 2. With the lowest dose of ANP (0.35 micrograms/(kg min) I.V.) a 5-fold increase in sodium excretion occurred without measurable change in Cin, RPF x Ein nor medullary electrolyte concentration estimated from tissue electrical admittance. 3. With medium and high dosage (2 and 6 micrograms/(kg min), respectively), major and rapid increases in sodium excretion and urine flow were associated with an acute increase in Cin but not RPF x Ein. 4. The RBF increase observed in all groups of rats was not dose-related and did not parallel the natriuresis. Electrolyte concentration in the medullary tissue showed a modest transient decrease in rats given medium and high ANP doses. 5. We conclude that pronounced ANP natriuresis can develop in the absence of a measurable increase of GFR, estimated by a method not subject to urinary dead space error (RPF x Ein). The small transient decrease in medullary tissue electrolytes observed with higher peptide doses does not support solute wash-out as an important mechanism of increased sodium excretion.

Animals↗
PubMed1990

Cysteine enhances in vivo natriuretic potency of ethacrynic acid in the rat.

Total renal blood flow, glomerular filtration rate, and renal excretory function were determined in anesthetized rats treated with intravenous infusion of ethacrynic acid, 0.36 mg.min-1.kg-1, alone or in combination with cysteine. Simultaneously, the corticomedullary electrolyte gradient was evaluated in vivo from measurement of tissue electrical admittance (reciprocal impedance). Renal hemodynamics was not altered by drug infusion. Sodium excretion increased 1.7-fold with ethacrynic acid alone and 5-fold after the addition of cysteine. Tissue electrolytes of inner medulla decreased much more in rats given ethacrynic acid plus cysteine. We conclude that the addition of cysteine to intravenous infusion of ethacrynic acid greatly enhances its in vivo natriuretic potency in the rat.

Animals↗
PubMed1990

Tissue electrical admittance (electrolyte concentration) in rat renal medulla: effects of furosemide and acetazolamide.

Fluctuations of total electrolyte concentration in the renal medulla were estimated from continuous measurement of tissue electrical admittance (reciprocal impedance) by means of needle electrodes placed in the kidney of anaesthetized rats. To compare effects of two diuretic agents with different sites of action, rats received either furosemide, 0.3 mg/kg i.v. followed by an infusion at 0.3 mg/kg.h, or acetazolamide, a single injection of 10 mg/kg. At this dosage similar increases in renal excretion were obtained with either drug. After furosemide (a loop diuretic) admittance fell sharp within first 10 min, then partly recovered and reached a plateau 35 min after injection. Acetazolamide (inhibitor of proximal reabsorption) caused no changes in admittance compared to the pattern observed in untreated control animals. We conclude that dissipation of tissue electrolytes from the renal medulla is not simply a consequence of diuresis and natriuresis but depends critically on the site of transport inhibition in the nephron.

Acetazolamide↗
PubMed1988

Reduced and total ascorbate in guinea pig eye tissues in response to dietary intake.

Guinea pigs were fed 5 different levels of dietary ascorbate representing a 65-fold range (0.8-52 mg animal-1 day-1). After two months on the diets, levels of reduced and total ascorbate were determined in aqueous humor, vitreous humor, lens and plasma. At low-dietary levels, proportionally higher levels of ascorbate are found in the lens than in other eye tissues. Tissue ascorbate levels began to plateau at dietary intake of approximately 11 mg animal-1 day-1. This is the amount suggested for optimal health, but it is ten times the level needed to prevent scurvy. Over 75% of the eye tissue ascorbate is in the reduced form in animals fed diets which provided 11 mg ascorbate. However, there was less than 50% reduced ascorbate in the eye tissues of the animals fed about 1mg ascorbate per day.

Animals↗
PubMed1988

Studies of tissue electrical admittance: relation to tissue sodium for different zones of rabbit kidney.

Tissue electrical admittance (reciprocal impedance) and Na+ concentration were determined in slices of rabbit renal cortex, outer medulla, inner medulla and the papilla. In each zone admittance was highly and significantly correlated to tissue Na+ (r = 0.71 to 0.91, p less than 0.001). The cortex admittance proved a relatively insensitive index of tissue electrolyte concentration. The highest sensitivity was observed for the outer medulla: values for the inner medulla and papilla were slightly lower. The data confirm the usefulness of admittance measurement for dynamic assessment of the cortico-papillary electrolyte gradient but show that the values measured in the outer medulla cannot be directly compared with those for the inner medulla and the papilla.

Animals↗
PubMed1988

Renal vein outflow recording in rats and rabbits: alternative method of R.B.F. measurement.

A method is described for continuous measurement of total renal blood flow in anesthetized rats and rabbits. It consists of recording time intervals in which a fixed volume of renal vein outflow enters into an extracorporeal renin vein - jugular vein shunt and is pumped back to animals' circulation. This technique yields absolute flow values of unequalled accuracy and requires virtually no calibration; however, it is not suitable for recording rapid flow transients. The RBF measured averaged 5.5 +/- (SE) 0.1 ml/min.g kidney weight in rats and 2.5 +/- 1.1 ml/min.g in rabbits; the flow was stable over at least 1.5-2 hrs. The rat kidneys tested showed usual capacity to autoregulate blood flow during graded reduction in renal perfusion pressure.

Animals↗
PubMed1984

A method for in situ measurement of ionic concentration in picoliter samples of renal tubular fluid.

A method permitting rapid and frequent determination of the total ionic concentration in renal tubular fluid samples, by measuring sample electrical impedance, is described. No special electrodes or sophisticated equipment are required. Since picoliter volumes are sufficient for measurement, tubular fluid dynamics are not significantly disturbed by the sampling procedure. The sample is aspirated into the tip of the standard glass micropipette and its ionic concentration, in the range of 100-1000 mmol/l, can be determined by any sensitive impedance-measuring device. In the present studies the Wheatstone bridge of the Wiederhielm apparatus for pressure measurement in micropuncture studies was used for the purpose. The obvious limitation of the method is that the measurements do not include non-electrolytes and cannot differentiate between individual ion species.

Animals↗