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J Sadowski

Publications and source records attributed to J Sadowski.

At least 19 recordsLinked to original sources
PubMed1992

Conductance studies of rat renal medulla for rapid estimation of extracellular electrolyte concentration.

A method is described for estimation of tissue extracellular electrolytes in fresh excised rat renal medulla on the basis of its electrical conductance. The inner medulla was placed between two standard flat electrodes and the conductance was measured at a frequency of 3.5 kHz. The data were corrected for the surface area and thickness of the tissue fragment. The standard conductance so determined clearly correlated with total electrolyte concentration, and Na+ and 2(Na+ + K+) concentrations in the whole tissue (r = 0.84, 0.81 and 0.77, respectively; P < 0.001). The method enables a rapid and simple estimation of medullary extracellular electrolytes, a variable that is physiologically more meaningful than whole tissue electrolyte concentration.

Animals↗
PubMed1991

Tissue PH2 measurement for continuous estimation of blood flow changes in rat kidney cortex and medulla.

A method is described for estimation of local blood flow changes in the renal cortex and medulla, based on continuous polarographic measurement of tissue pressure of electrochemically generated hydrogen (PH2). The technique was used in anaesthetized female Wistar rats. The changes in cortical PH2 were negatively correlated with those in flow velocity in the renal artery (Doppler probe). To evaluate the method, PH2 responses to a reduction of renal perfusion pressure (RPP) and to angiotensin II were examined. RPP reduction from 130 mmHg to 104 mmHg increased the cortical PH2 by 3.5% and medullary PH2 by 6.9% (difference significant at P less than 0.02). With RPP reduction from 113 mmHg to 76 mmHg the values were 6.9% and 11% respectively (difference significant at P less than 0.001). Angiotensin II infusion increased cortical PH2 by 8.7% and medullary PH2 by 4.1% (difference significant at P less than 0.005). It is concluded that the method enables continuous estimation of blood flow changes in the renal cortex and medulla.

Angiotensin II↗
PubMed1991

[Constrictive pericarditis].

Etiology of constrictive pericarditis is diversified. In recent years the role of viral and iatrogenic factors (X-ray therapy, cardiac surgery) has increased. Clinical manifestations, including subjective complaints, resemble those in congestive heart failure although the mechanism of hemodynamic disorders is different--namely impairment of ventricular filling and diastolic performance. One encounters major difficulties while differentiating constrictive pericarditis from restrictive cardiomyopathy. In some patients conservative treatment is effective, in a majority of them surgical operation, pericardiectomy is the treatment of choice.

Adolescent↗
PubMed1990

Ion concentration and haematocrit as determinants of impedance in an erythrocyte suspension model of renal medullary tissue.

In order to analyse the respective roles of ion concentration and fractional volume of the interstitial compartment as determinants of the impedance, Z, of renal medullary tissue, a model was needed in which both these factors could be varied independently. An array of blood cell suspensions ions in saline (different haematocrit values and different NaCl concentrations) was used for this purpose. It was found that: (i) up to a measuring frequency of about 10 kHz, the complex consisting of needle electrodes and 'tissue' can be regarded as serially connected resistances, R, and capacitances; (ii) the frequency range 3-10 kHz can be regarded as optimal since it simultaneously assures low electrode polarization and a negligible role of tissue capacitance; (iii) increasing the haematocrit had two consequences--a reduced contribution of polarization impedance to the total impedance measured and a decreased sensitivity of ion concentration measurement from R-1 (conductance); (iv) passive electrical properties of renal medullary tissue were close to those of a 75% haematocrit cell suspension; (v) since in high haematocrit suspensions the resistive component of impedance predominates, within the frequency range 3-10 kHz either conductance or admittance, Z-1, can be used as an index of ion concentration; and (vi) impedance changes in kidney tissue are primarily determined by fluctuations of ion concentration with a less important contribution from interstitial volume changes.

Animals↗
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↗