Effects of 24-hour unilateral ureteral obstruction on glomerular hemodynamics in rat kidney

Glomerular hemodynamics were studied, by micropuncture, in Munich-Wistar rats submitted to 24-hour unilateral ureteral ligation (UUL). Glomerular capillary pressure (PG), intratubular pressure (PT) and pressure in the first-order peritubular capillaries (EAP) were measured with a servonulling device. Single nephron filtration fraction (SNIFF) was calculated fmom arterial and peritubular blood protein concentration. SNGFR was both measured by conventional micropuncture techniques and calculated from efferent arteriole blood flow (EABF) and SNFF. Afferent arteriole blood flow (AABF) and resistance of afferent (Ra) and efferent (Re) arterioles were calculated. Measurements were repeated 1 to 2 hours after the release of the ureter. Sham-operated rats were used as control. UUL caused a marked increase in Ra (from 4.9 +/- [SD] 2.4 to 12.7 +/- 5.1 dynes/sec/cm-5). The fall in SNGFR (from 111.9 +/- [SD] 23.9 to 34.4 +/- 23.1 nl/min/kg body wt) was secondary to a decrease in both PG and AABF. A further increase in Ra (16.0 +/- 6.7 dynes.sec.cm-5) occurred after releasing the ureter. SNGFR, however, was unaltered (33.7 +/- 16.6 nl/min/kg body wt) since PG decreased parallel to PT, but AABF did not significantly change. Conclusion. Ureteral obstruction determines, in 24 hours, a marked cortical ischemia that is not promptly reversed by ureteral release.

Critical appraisal of haemofiltration and ultra-filtration. The development of ultra-short dialysis: preliminary results

The clinical experience obtained with 2 hours every other day recirculation dialysis, using 20-40 liters of dialysate, without sorbents, and standard cuprophane dialyzers of 1.0-1.5 sq.mt. is reported. So far, over 350 treatments in 8 patients have been performed. After 2 hours of treatment the removal of urea, creatinine, phosphate and uric acid, is similar to that obtained by 4-6 hours of haemofiltration. The alkalinazation of the patient through direct venous infusion of bicarbonate, makes predialysis acid-base significantly better than in standard haemodialysis and haemofiltration. Asymptomatic correction of severe fluid overload is easily obtained like in isolated ultrafiltration. The role of osmolality and vasopressors are discussed. A dry weight below the value obtained by previous dialysis treatment is achieved, and volume dependent hypertensions as in haemofiltration are corrected after 2-8 weeks. As an additional advantage, this method offers a highly semplified technical approach and a further reduction of the dialysis time.

Effects of acute ureteral obstruction on glomerular hemodynamics in rat kidney

In order to study the effects of acute ureteral obstruction on glomerular hemodynamics, glomerular hydrostatic capillary pressure (PG), pressure in the first-order peritubular capillaries (EAP), and intratubular pressure (PT) were directly measured in superficial nephrons on Munich-Wistar rats by micropuncture with a servo-nulling device, in control conditions and one to two hours after ureteral ligation. Single nephron filtration fraction (SNFF) was calculated from arterial and peritubular blood protein concentration. SNGFR was measured by conventional micropuncture techniques in control conditions and was calculated from efferent arteriole blood flow (EABF) and SNFF during ureteral obstruction. EABF was obtained by timed complete collection of blood from superficial efferent arterioles. Afferent arteriole blood flow (AABF) and resistance of afferent (Ra) and efferent arterioles (Re) were calculated from conventional equations. Ureteral obstruction markedly increased PT from 12.9 +/- 1.4 to 36.8 +/- 6.1 (SD) mm Hg. The fall in SNGFR (from 23.3 +/- 6.4 to 17.9 +/- 5.2 [SD] nl/min) was blunted by the rise in PG (from 45.5 +/- 3.6 to 59.3 +/- 4.0 [SD] mm Hg) and AABF (from 130.0 +/- 59.1 to 144.2 +/- 69.0 [SD] nl/min), secondary to a fall in Ra. These results demonstrate that SNGFR is maintained early after complete ureteral obstruction because of afferent arteriole dilatation.

Role of the efferent arteriole in glomerular hemodynamics of superficial nephrons

Hemodynamic pressure in glomerular capillaries (GCP) and in first order peritubular capillaries (EAP) in superficial nephrons of mutant Wistar rats with surface glomeruli was measured by micropuncture with a servo-nulling device in the following conditions: 1) control;2) norepinephrine infusion (NE); 3) epinephrine infusion (E): 4) dopamine infusion (D); 5) hemorrhagic hypotension (HH); 6) HH + NE; 7) HH + E; 8) HH + D; 9) acute hypertension secondary to bilateral cervical vagotomy and occlusion of both common carotid arteries. BP was also recorded. Both GCP/BP and EAP/GCP ratios averaged 0.40 in control conditions, but only the EAP/GCP ratio remained constant in all conditions under study, indicating that approximately 60% of the hydrostatic pressure in glomerular capillaries is constantly dissipated by the efferent arteriole. When all values of EAP were plotted against the respective values of GCP, a liner relationship was detected (r=0.843). These results indicate that changes of pressure in the first order peritubular capillaries of superficial nephrons are merely secondary to changes in glomerular capillary pressure.

[Middle molecules separation from uraemic serum (author's transl)]

The following method is proposed to make the serum concentration of the middle molecules evident and to isolate them: 1) Fractioning of serum by gel filtration with sephadex G 75 columns in order to eliminate proteins and other substances with mol. weight less than 3,000-3,500. 2) Collection of fractions with mol. weight greater than 3,000-3,500 their lyophilisation and their successive gel filtration by sephadex G 15 columns. The concentration of substances in the single fractions is evaluated by ultraviolet light absorption (wave length 254 nm). The peaks of the patterns show a great difference between normals and uremics. The uremic peaks are always higher than normals. The mol. weight the substances in the peaks obtained by gel filtration with sephadex G 75 and G 15 was verified by radiolabelled substances of known mol. weight added before gel filtration. The substances isolated by sephadex G 75 from 10 and 20 cases of uremics and normal controls were diafiltered by Diaflo membrane UM 05 (nominal mol. weight cut - off 500). The diafiltered substances (mol. weight between 500 and 3,500) were investigated. A great difference between uremics and normal controls of dry mol. weight was observed, while the percentage concentration of C, H, N and of amino acids evaluated after acid hydrolysis showed no difference between the two groups. The liberation of amino acids after acid hydrolysis confirmed the presence of peptides among the middle molecules. Middle molecules in the urine of uremic and normal subjects have been investigated by the same method.

Preliminary results obtained with short dialysis schedules

The results regarding the treatment of 55 patients, 6 of them treated for, at least 10 months, with 1 sq. meter disposable dialyzers and a dialysis strategy of 3 hours every other day or 4 hours trice weekly have been presented. Clinical indexes especially regarding erythropoiesis and peripheral nerve status will be discussed. Th results show that this new method of treatment is feasible and may become in the future a routine strategy for chronic intermittent dialysis.

The kinetics of aminosidine in renal patients with different degrees of renal failure

The plasma concentration and urinary excretion after a single 500 mg dose of Aminosidine have been studied in 12 patients with different degrees of renal failure and 4 normal subjects. In normal subjects the plasma half-life is 2.47 hr; in patients with creatinine clearance (Ccr) of 30-60 ml/min, its 6.7 hrs.; in patients with Ccr of 10-30 ml/min, it is 16.7hrs.; in patients with Ccr less than 10 ml/min, it is 36.6 hrs. A dose of 0.5 g of Aminosidine should be given to normal subjects every 12 hr. When renal function is reduced, the interval (in hr) between doses should be the following: Ccr 60-40 ml/min: 19-28;Ccr 40-30 ml/min; 28-35; Ccr 30-20 ml/min: 35-47; Ccr 20-10 ml/min: 47; Ccr less than 10 ml/min: 76.