Gallstone Ileus: An Unlikely Cause of Mechanical Small Bowel Obstruction.

Gallstone ileus is a rare disease that accounts for 1-4% of intestinal obstructions. Almost exclusively a condition in the older female population, it is a difficult diagnosis to make. We report the case of gallstone ileus in a 94-year-old Caucasian female, who presented to the emergency department with acute-onset nausea, coffee-ground emesis, lack of bowel movement, and abdominal distension. On CT scan, the diagnosis of gallstone ileus was made by the presence of a cholecystoduodenal fistula, pneumobilia, and small bowel obstruction. Emergent laparotomy with a one-stage procedure of enterolithotomy and stone removal by milking the bowel distal to the stone were performed. The postoperative course was uneventful until postoperative day 4 when the patient was found tachycardic, lethargic, and unresponsive. We reviewed the literature on the diagnosis and treatment of gallstone ileus.

A tunable artificial circadian clock in clock-defective mice.

Self-sustaining oscillations are essential for diverse physiological functions such as the cell cycle, insulin secretion and circadian rhythms. Synthetic oscillators using biochemical feedback circuits have been generated in cell culture. These synthetic systems provide important insight into design principles for biological oscillators, but have limited similarity to physiological pathways. Here we report the generation of an artificial, mammalian circadian clock in vivo, capable of generating robust, tunable circadian rhythms. In mice deficient in Per1 and Per2 genes (thus lacking circadian rhythms), we artificially generate PER2 rhythms and restore circadian sleep/wake cycles with an inducible Per2 transgene. Our artificial clock is tunable as the period and phase of the rhythms can be modulated predictably. This feature, and other design principles of our work, might enhance the study and treatment of circadian dysfunction and broader aspects of physiology involving biological oscillators.