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Biomedical subjects

A Dal Canton

Publications and source records attributed to A Dal Canton.

At least 55 records · Page 3Linked to original sources
PubMed1989

Acute cyclosporine renal dysfunction reversed by dopamine infusion in healthy subjects.

Up to now, no studies have been performed in normal humans to investigate the role of renal hemodynamic abnormalities in relation to acute-cyclosporin A (CsA) renal dysfunction and to verify whether the specific renal vasodilator, dopamine, can counteract these abnormalities. Eight normal subjects were examined both (A) after oral CsA (12 mg/kg body wt) and (B) after oral CsA + dopamine infusion (2 mg/kg body wt/min), under water diuresis. Both in protocols A and in B, four basal renal clearances were performed before CsA and every twenty minutes for four hours after CsA administration. In protocol A, after CsA, inulin (GFR) and PAH clearance (RPF) fell by up to 27% and to 41%, respectively, so that filtration fraction (FF) increased (P less than 0.01). A slight (not significant) hypertension occurred while renal resistances were markedly raised (P less than 0.001). Fractional urine and Na+ excretion as well as CH2O decreased, while UOsm increased (P less than 0.01). In protocol B, dopamine was infused from 120 to 180 minutes after CsA (that is, when the maximal adverse effects of CsA on renal hemodynamics had been observed in A). Dopamine infusion could reverse completely the effects of CsA on RPF, GFR, fractional urine output and CH2O; only UOsm remained higher than normal in conclusion with an increased fractional excretion of sodium (P less than 0.01). No changes were observed in plasma renin activity, aldosterone and in urinary epinephrine and norepinephrine excretion both in protocols.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Reversibility of acute cyclosporin nephrotoxicity by dopamine. Micropuncture study in the rat.

The ability of dopamine to neutralise the effects acutely induced by cyclosporin (CsA) on glomerular dynamics was evaluated in four groups of female Munich-Wistar rats, prepared for micropuncture: group I (n = 9), normal rats receiving saline as placebo; group II (n = 10), rats treated with CsA (20 mg/kg b.w. in 1 h); group III (n = 8) rats treated with CsA, as in group II, and then with vasodilating doses of dopamine (1.2-2.0 micrograms/100 g b.w./min in continuous intravenous infusion); group IV (n = 7), rats administered Cremophore EL, the vehicle of CsA, in corresponding doses. Single nephron GFR (SNGFR), glomerular plasma flow (GPF), afferent and efferent arteriole resistances (Ra and Re, respectively), SN filtration fraction (SNFF), ultrafiltration coefficient (Kf) were measured. Body weight, blood pressure and haematocrit were similar in the four groups. GFR was significantly reduced in group II (0.83 +/- 0.08 ml/min vs 1.29 +/- 0.01 in group I, 1.46 +/- 0.25 in group III, and 1.40 +/- 0.09 in group IV, P less than 0.05 vs all the groups), while no statistical difference was detected in urinary volume. SNGFR was significantly reduced in group II vs group I (18.7 +/- 1.8 nl/min vs 30.6 +/- 1.3, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Glomerular dynamics and salt balance in pregnant rats with renal hypertension.

These studies were aimed at investigating whether chronic hypertension in pregnancy causes changes both in salt excretion (NaE) and in glomerular hemodynamics. Metabolic and renal micropuncture studies were performed in pregnant (P) and Virgin (V) Munich-Wistar rats with normal blood pressure (N) and two-kidney Goldblatt hypertension (H). Mean NaE was higher in PN than VN (2.7 vs. 1.7 meq/day, P less than 0.01). Hypertension raised NaE both in P and V rats: in P and V rats with "benign" hypertension (blood pressure less than 180 mmHg) NaE averaged 3.2 and 2.6 meq/day, respectively (P less than 0.05); mean NaE was 5.9 and 3.8 meq/day, respectively (P less than 0.01), in P and V rats with "malignant" hypertension (blood pressure greater than or equal to 180 mmHg). Afferent arteriole resistance (Ra) averaged 1.73 and 3.50 10 dyn.s-1.cm5 in PN and VN, respectively (P less than 0.01). Hypertension raised Ra in V, but not in P rats (4.47 vs. 2.14 10 dyn.s-1.cm5, P less than 0.01). Thus glomerular plasma flow, glomerular capillary hydrostatic pressure, and single-nephron glomerular filtration rate were markedly higher in PH than VH rats: in PH rats single-nephron filtration fraction was significantly lower than in VH. These results show that in PH rats a marked rise in NaE is associated with glomerular vasodilation.

Animals↗
PubMed1989

Effects of uremia, acetate and bicarbonate dialysis on beta-adrenergic responsiveness as assessed by epinephrine-stimulated adenylate cyclase.

This study was designed to evaluate beta-adrenergic responsiveness as assessed by the generation of cyclic AMP after the subcutaneous administration of epinephrine in 31 subjects: normal controls, patients with chronic renal insufficiency, hemodynamically stable patients on chronic acetate dialysis and hemodynamically unstable patients with acetate intolerance on chronic bicarbonate dialysis. As compared with controls, only unstable patients on bicarbonate dialysis presented impaired beta-responsiveness, which, in turn, was acutely reduced only after acetate but not bicarbonate dialysis. Our results show that acetate dialysis impairs the beta-adrenergic responsiveness and that the observed beta-hyporesponsiveness in unstable patients with acetate intolerance may represent part of a broader spectrum of autonomic dysfunction which may develop in some patients on chronic hemodialysis.

Acetates↗
PubMed1988

Effects of furosemide therapy on free-water excretion in uremic patients.

To assess the intrinsic effects of treatment with furosemide on free-water excretion in patients with chronic renal failure, two groups of patients with and without replacement of diuretic-induced salt losses have been studied. Furosemide therapy was administered for 1 week during constant sodium intake (100 mEq/day). In neither of the groups did furosemide cause hyponatremia, while it did decrease the urine to plasma osmolality ratio, an effect lasting even when the diuretic effect was exhausted. During water diuresis, furosemide decreased the fractional sodium reabsorption in diluting segments but not the absolute rate of the free-water generation (CH2O). Presumably the expected decrease of CH2O was masked by the increased distal delivery of tubular fluid mainly due to an additional effect of the diuretic on the proximal tubule. The hypotonicity of urine after furosemide treatment may be secondary to the dissipation of medullary hypertonicity, caused by furosemide, in the condition of decreased water permeability of the collecting duct due to uremic disease.

Furosemide↗
PubMed1987

Renal handling of urea in subjects with persistent azotemia and normal renal function.

Fourteen subjects with persistent azotemia and normal glomerular filtration rate were studied by renal clearances and hormonal determinations to establish the nephron site of altered urea transport and the mechanism(s) responsible for their azotemia. During constant alimentary protein, urea nitrogen appearance was normal and urea clearance was much lower than in 10 age-matched control subjects (23.3 +/- 2.1 ml/min and 49.6 +/- 2.6 ml/min per 1.73 m2, P less than 0.001). Inulin and para-aminohippurate clearances, blood volume and plasma concentration of antidiuretic hormone were within normal limits. During maximal antidiuresis, in spite of greater urea filtered load, the urinary excretion of urea was less, and both the maximum urinary osmolality and the free-water reabsorption relative to osmolar clearance per unit of GFR were greater than in control subjects. After sustained water diuresis, the plasma urea concentration markedly decreased to near normal levels in azotemic subjects. The basal urinary excretion of prostaglandins E2 was significantly reduced in azotemic subjects and was directly correlated with fractional urea clearance (r = 0.857, P less than 0.001). An additional group of control subjects (N = 8) showed a marked reduction of fractional clearance of urea after inhibition of prostaglandin synthesis (P less than 0.01). These data suggest that azotemia is due to increased tubular reabsorption of urea in the distal part of nephron, presumably because of increased back diffusion in the papillary collecting duct, accounting for the enhanced maximum urinary osmolality and free-water reabsorption. Renal prostaglandin E2 may participate in the pathogenesis of azotemia by altering recycling of urea in the medulla.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

The causal role of salt depletion in acute renal failure due to captopril in hypertensive patients with a single functioning kidney and renal artery stenosis.

Captopril (C) causes ARF in hypertensive patients with renal artery stenosis (RAS) with a single functioning kidney (SK). Retrospective studies in two patients showed that episodes of C-induced ARF were preceded by a rise in urinary Na+ excretion and a rapid decrease in body weight. These observations prompted us to investigate whether extracellular fluid volume depletion secondary to C-induced natriuresis can be responsible for ARF. Prospective studies were performed in four patients with RAS-SK treated with C. These studies have shown that: ARF is associated with negative Na+ balance and is corrected by salt replacement, even without interrupting C; ARF is preceded by a rise in urinary prostaglandin (PG) E2 and 6-keto-F1 alpha; ARF is prevented by either saline infusion or aspirin administration; ARF does not occur when the dose of C is not sufficient to raise PGs and urinary N + excretion. We conclude therefore that C-induced ARF in patients with RAS-SK can be secondary to salt depletion dependent on a raised secretion of PGs.

Acute Kidney Injury↗
PubMed1987

[Delta agent infection and immunoglobulin G in acute HBsAg-positive hepatitis with chronic course].

In 18 patients with clinical evidence of acute hepatitis, positive for HBsAg, and evolution to chronic infection, we detected the presence of antibodies to the delta agent (anti-HDV), in relation to the immunoglobulin serum level. The IgG were significantly higher during the beginning of the acute phase in the 6 positive cases for anti-HDV than in the patients who were anti-HDV negative. In the group positive for anti-HDV, the IgG remained high also during the following months, with a more severe clinical evolution. Among patients positive for anti-HDV there were no significant differences between the initial level of IgG and the presence or not of IgM anti-HBc during the acute phase of the disease (respectively patients with co-infection or super-infection). These results show that the presence of high levels of IgG during the acute phase of HBsAg positive hepatitis suggests the co-existence of delta infection.

Acute Disease↗
PubMed1986

Is 3000 S Hospal a suitable dialyzer to shorten dialysis time schedule? A cooperative study on biofiltration.

The Biofilter 3000 S Hospal may combine higher convective clearance rates (Cc) with usual diffusive clearance rates (Cd) (i.e. similar to Cuprophan dialyzers), giving a higher total clearance rate (Ct) of small and middle molecules. Use of the Biofilter has been suggested to shorten dialysis time schedules. This study was carried out in 8 patients on RDT 3 times weekly, by cuprophan filter and acetate dialysis. The patients were shifted to dialysis with 3000 S guided by two principles: to shorten dialysis time by 1 hour per session, and to reinfuse 6 liters of bicarbonate-saline solution (40 mEq/l) per single dialysis. Besides the usual clinical and laboratory controls, in three patients clearance studies were carried out during four different dialysis sessions: Ct, Cc and Cd of urea K+, creatinine, uric acid and phosphate were measured. No change was observed in the main clinical and laboratory parameters after 3-5 months (average 3.9) of treatment with Biofilter 3000 S; in addition, serum alkaline phosphatase concentration decreased progressively. Clearance results, however, indicate that the expected high values of Ct do not occur, because Cd decreases as Cc is increased. A primary goal of research in hemodialysis is to reduce the average time of treatment while ensuring simultaneously "physiological" dialysis. A possible approach to this problem is to use dialyzers with highly permeable and biocompatible membranes such as the "biofilter" 3000 S Hospal.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetates↗
PubMed1986

Polyuric prerenal failure after reduction from high to normal dietary intake of sodium.

In a patient with renal amyloidosis secondary to chronic urinary tract infection with nephrotic syndrome, polyuric acute renal failure developed after reduction from a high to a normal dietary intake of sodium and was reversed by salt replacement therapy. As documented by functional and morphological studies, the patient had a marked defect of tubular sodium reabsorption at the proximal site and along the ascending limb of Henle's loop, a distal tubular unresponsiveness to aldosterone, and severe tubulointerstitial damage in the medulla. We propose that the sodium dietary reduction in conjunction with severe tubular dysfunction and hypovolemia due to nephrotic syndrome is responsible for this unused form of polyuric acute prerenal failure.

Acute Kidney Injury↗