ACTH stimulation of glucocorticoid production by the adrenal cortex involves an intrinsic adrenal circadian clock [8 -10] . These clocks are sustained by the stimulatory and inhibitory transcriptional-translational feed-back loops of a group of genes, named clock genes, and their proteins. Of these, PER1 is part of the inhibitory loop and BMAL1 is part of the stimulatory loop. BMAL1 [Brain-Muscle (ARNT)-like] protein also drives a number of genes containing E-boxes in their promoters like the steroidogenic acute regulatory protein (StAR) [11] , mediating cholesterol transport to the mitochondria; a limiting step in ACTH-stimulated adrenal cortisol production [12] . A possible relationship between melatonin, human adrenal cortisol response to ACTH and clock genes, is suggested by the direct inhibitory eff ect of melatonin on BMAL1 and PER2 mRNA expression demonstrated in the capuchin monkey adrenal gland [13] .Abstract ▼ * Both authors contributed equally to this work.

The classic approach to renal stone disease includes shockwave lithotripsy, ureteroscopy or percutaneous nephrolithotripsy, and, in some cases, a combination of both. The usefulness of laparoscopy in this regard remains debated. In this report and video, we present our technique of laparoscopic pyelolithotomy assisted by flexible instrumentation to achieve maximal stone clearance in a selected group of patients.

The three lithotripsy devices evaluated behaved similarly in terms of the ability to fragment stones, and were equally effective for distal ureteral stones. Adequate fragmentation and fragment removal are mainly dependant on stone size and surgical technique (use of auxiliary wire).

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(Rev Méd Chile 2008; 136: 1390-7).