Biomedical subjects

Mario G Bianchetti

Publications and source records attributed to Mario G Bianchetti.

41 records · Page 3Linked to original sources

PubMed2002

Modulation of renal calcium handling by 11 beta-hydroxysteroid dehydrogenase type 2.

Reduced concentration of serum ionized calcium and increased urinary calcium excretion have been reported in primary aldosteronism and glucocorticoid-treated patients. A reduced activity of the 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta HSD2) results in overstimulation of the mineralocorticoid receptor by cortisol. Whether inhibition of the 11 beta HSD2 by glycyrrhetinic acid (GA) may increase renal calcium excretion is unknown. Serum and urinary electrolyte and creatinine, serum ionized calcium, urinary calcium excretion, and the steroid metabolites (THF+5 alpha THF)/THE as a parameter of 11 beta HSD2 activity were repeatedly measured in 20 healthy subjects during baseline conditions and during 1 wk of 500 mg/d GA. One week of GA induced a maximal increment of 93% in (THF+5 alpha THF)/THE. Ambulatory BP was significantly higher at day 7 of GA than at baseline (126/77 +/- 10/7 versus 115/73 +/- 8/6 mmHg; P < 0.001 for systolic; P < 0.05 for diastolic). During GA administration, serum ionized calcium decreased from 1.26 +/- 0.05 to 1.18 +/- 0.04 mmol/L (P < 0.0001), and absolute urinary calcium excretion was enhanced from 29.2 +/- 3.6 to 31.9 +/- 3.1 micromol/L GFR (P < 0.01). Fractional calcium excretion increased from 2.4 +/- 0.3 to 2.7 +/- 0.3% (P < 0.01) and was negatively correlated to the fractional sodium excretion during GA (R = -0.35; P < 0.001). Moreover, serum potassium correlated positively with serum ionized calcium (R = 0.66; P < 0.0001). Inhibition of 11 beta HSD2 activity is sufficient to significantly increase the fractional excretion of calcium and decrease serum ionized calcium, suggesting decreased tubular reabsorption of this divalent cation under conditions of renal glucocorticoid/mineralocorticoid excess. The likely site of steroid-regulated renal calcium handling appears to be the distal tubule.

11-beta-Hydroxysteroid Dehydrogenase Type 2↗

PubMed2002

Maintenance hemodialysis and circulating ionized magnesium.

BACKGROUND: Circulating magnesium exists in the bound and in the free ionized form, that is biologically active. In kidney disease the relationship between ionized and total circulating magnesium is often altered. Little information is available on the influence of hemodialysis on the relationship between ionized and total circulating magnesium in end-stage kidney disease. METHODS: Plasma total and ionized magnesium and the plasma ionized magnesium fraction were assessed before and after hemodialysis (dialysate magnesium content 0.75 mmol/l) in 46 patients with end-stage kidney disease and in a control group of 25 healthy subjects. RESULTS: In patients plasma total (from 1.19 [1.05-1.33] to 1.10 [1.02-1.16] mmol/l; median and interquartile range) and ionized (from 0.71 [0.66-0.78] to 0.65 [0.63-0.69] mmol/l) magnesium significantly decreased during dialysis (control subjects: 0.82 [0.80-0.92], respectively, 0.57 [0.54-0.59] mmol/l). The plasma ionized magnesium fraction was significantly lower in patients both before (0.61 [0.58-0.64)] and after (0.60 [0.56-0.62]) hemodialysis than in controls (0.68 [0.65-0.70]). CONCLUSIONS: The study demonstrates a tendency towards a reduced circulating ionized magnesium fraction in end-stage kidney disease that is not corrected by hemodialysis.

Acid-Base Equilibrium↗

PubMed2002

Electrocardiographic QT prolongation and sudden death in renal hypokalemic alkalosis.

A 3-year-old boy was found to have a mixed tubulopathy with hypokalemia (1.9 mmol/l), alkalosis (blood pH 7.51, plasma carbon dioxide pressure 46 mm Hg, plasma bicarbonate 35.7 mmol/l) and hypophosphatemia (1.21 mmol/l). An electrocardiogram disclosed a prolonged heart rate corrected QT interval of 490 ms. The boy was put on potassium chloride, phosphate and nonsteroidal anti-inflammatory agents. With this treatment plasma phosphate normalized and plasma potassium increased up to 3.0-3.3 mmol/l. Three years later the child, who did not have history of gastroesophageal reflux or epileptic convulsions, suddenly died during sleep. The cause of death could not be determined through gross examination of the body. The history of hypokalemia, the QT-prolongation, the sudden death and the failure to assess the cause of death through gross examination of the body suggest that death was caused by an arrhythmia secondary to hypokalemia.

Alkalosis↗

PubMedDate not supplied

Behavioral and functional abnormalities linked with recurrent urinary tract infections in girls.

BACKGROUND: Most girls with recurrent urinary tract infections do not have major urinary tract abnormalities. Recent studies focus on predisposing behavioral and functional abnormalities: infrequent voiding, inadequate fluid intake, stool retention, poor genital hygiene and voiding dysfunction. METHODS: Complete history, bladder and bowel questionnaire, physical examination, voiding-drinking diary, sonography and uroflowmetry were used to assess infrequent voiding, functional stool retention, poor fluid intake, inadequate hygiene, or voiding dysfunction in girls referred for evaluation of three or more symptomatic urinary tract infections (with a first infection at the age of more than 36 months). RESULTS: A total of 141 girls aged 3.9 to 18 years were evaluated between 1996 and 1999; 212 abnormalities were noted in 120 patients: infrequent voiding (isolated, 16; combined with other abnormalities, 47), poor fluid intake (isolated, 10; combined, 50), functional stool retention (isolated, 5; combined, 25), inadequate hygiene or toilet habits (isolated, 3; combined, 24), dysfunctional voiding (isolated, 15; combined, 10), bladder overactivity (isolated, 5; combined, 2). CONCLUSIONS: Most girls referred for evaluation of three or more urinary tract infections have host-mediated predisposing abnormalities: infrequent voiding, poor fluid intake, functional stool retention or voiding dysfunction. Poor genital hygiene and toilet habits were almost always combined with other abnormalities, suggesting that infections are not necessarily related to poor genital hygiene or toilet habits. Two or more indications of predisposing behavior often concur in the same patient.

Adolescent↗

PubMedDate not supplied

False positive dipstick for urinary blood in childhood.

BACKGROUND: In view of the obvious practical advantages, the most common test for hematuria is currently a reagent strip. METHODS: A standardized microscopic examination of the sediment was performed in 20 asymptomatic children referred for evaluation of chronic isolated microhematuria detected by means of a reagent strip. RESULTS: In 6 of the 20 children the microscopic examination failed to confirm the result of the dipstick test. CONCLUSIONS: Confirmation for the presence of hematuria by microscopy is the most important step in children with a positive dipstick for urinary blood.

Adolescent↗