La dieta en el tratamiento de la litiasis renal. Bases fisiopatológicas / [Diet in the treatment of renal lithiasis. Pathophysiological basis].

The composition of urine is influenced by diet and changes in dietary factors have been proposed to modify the risk of recurrent nephrolithiasis. Nutrients that have been implicated include calcium, oxalate, sodium, animal protein, magnesium and potassium. There is significant evidence showing that a high calcium diet is associated with a reduction of lithogenic risk. One of the possible mechanisms to explain this apparent paradox is that the higher intake of calcium in the intestine binds with dietary oxalate, reducing its absorption and urinary excretion. Oxalate from the diet seems to provide only a small contribution to excretion and dietary restriction is appropriate only in those with hyperoxaluria and hyperabsorption. Observational studies have shown a positive and independent association between sodium intake and the formation of new kidney stones. Consumption of animal protein creates an acid load that increases urinary excretion of calcium and uric acid and reduced citrate, all factors that could participate in the genesis of stones. Potassium-rich foods increase urinary citrate because of its alkali content. In prospective observational studies, diets rich in magnesium were associated with a lower risk of kidney stone formation in men. In conclusion, diet is a key element in the management of the patient with kidney stones but always subordinated to present metabolic risk factors.

Effects of calcium supplements on the risk of renal stone formation in a population with low oxalate intake.

It has been speculated that calcium supplement in subjects with low oxalate intake might increase the risk of calcium stone formation due to an increase in calcium absorption without a significant reduction in oxalate absorption. There have been no human studies addressing specifically the effects of taking calcium supplements in populations whose dietary oxalate is low. This study was conducted to determine the effects of calcium supplements on the risk of calcium stone formation in a population with low oxalate intake. Thirty-two healthy male navy privates, 22.7 +/- 1.9 (mean +/- SD) years old, who had oxalate intake of less than 1 mmol/day, a serum creatinine of less than 150 micromol/l, and no history of renal stones, participated in the study. Dietary oxalate was controlled to be under 1 mmol/day throughout the study. Twenty-four hour urine collections for the determination of urinary constituents were obtained at baseline and after taking calcium supplements. Detection of calcium oxalate was performed to assess the risk of calcium oxalate stone formation. The urinary excretion of calcium was significantly elevated above baseline values while taking the calcium supplements (3.48 +/- 2.13 vs 5.17 +/- 2.61 mmol/d, p < 0.05) and urinary oxalate was significantly decreased when the subjects took calcium supplements compared to the corresponding baseline value (0.13 +/- 0.05 vs 0.17 +/- 0.07 mmol/d, p = 0.01). Urinary citrate was significantly elevated when the subjects took calcium supplements compared to the baseline (0.83 +/- 0.57 vs 0.64 +/- 0.39 mmol/d, p = 0.03). There was no significant alteration in the activity products of calcium oxalate while taking the calcium supplements (0.54 +/- 0.25 vs 0.57 +/- 0.22, p = 0.54). The effect of calcium supplements with meals, for the reduction of the risk of calcium stone formation, was unchanged, even in a population whose oxalate intake is rather low. Taking calcium supplements resulted in a reduction in urinary oxalates and an elevation in urinary citrates. Both alterations in urinary constituents counterbalanced the elevation in urinary calcium which resulted from the calcium supplements.

Efectos de la hipnosis con tiopental sódico sobre los mecanismos de regulación glucémica en los perros / Effects of thiopentone hypnosis on blood glucose regulatory mechanisms in the dogs

Si bien se conoce que la hipnosis con tiopental sódico (TPS) no modifica los niveles de glucemia (G) en el hombre, en situaciones basales, se ha demostrado en diversos estudios experimentales que altera la capacidad del organismo para regular los niveles de G cuando se administran cantidades importantes de glucosa. Sin embargo no se conocen completamente los mecanismos que intervienen en la intolerancia hidrocarbonada referida. En el presente trabajo se ha estudiado el efecto de la hipnosis con TPS sobre la respuesta glucémica, insulinémica (IRI) y de los ácidos grasos no esterificados séricos (AGNE) de perros normales en condiciones basales y durante la realización de una prueba de tolerancia endovenosa a la glucosa (PTEG). Comparando los resultados obtenidos con los hallados en animales no anestesiados. Durante la PTEG, los perros anestesiados presentaron intolerancia a la glucosa, caracterizada por una menor respuesta insulínica a la hiperglucemia (menor pico de IRI) y un menor descenso de los niveles de AGNE que fue seguido por un escaso rebote de sus concentraciones séricas comparado al hallado en los perros no anestesiados. Esta alteración se debería a un efecto del agente hipnótico sobre los factores hormonales y nerviosos que regulan los mecanismos pancreáticos y extrapancreáticos de control de la G.