Endogenous ADP-ribosylation of Gs subunit and autonomous regulation of adenylate cyclase

Although cholera toxin induces a marked stimulation of adenylate cyclase activity in rat adipocyte plasma membranes, the holotoxin induces only a slight increase of cyclic AMP accumulation in intact cells. A similar apparent anomaly is seen with pertussis toxin, which has been shown to inhibit the Gi subunit of adenylate cyclase, and has a greater effect on cAMP accumulation and lipolysis than the activation by cholera toxin of the Gs subunit. To understand better the way in which these bacterial toxins are modifying the adipocyte cells, we prepared adipocyte plasma membranes and submitted them to ADP-ribosylation by cholera and pertussis toxins. During the incubation of control cells, we found endogenous ADP-ribosylation of Gs as a result of sustained stimulation of Gi by adenosine. Our results point to a possible homoeostatic system in which the autonomous adjustment of the basal activity of Gs as a function of that of Gi, under the control of feedback inhibitory ligands, ensures a steady production of cAMP within the cell.     

Biochemical evidence of cannibalism at a prehistoric Puebloan site in southwestern Colorado

The existence of cannibalism is one of the most controversial issues in the archaeology of the American Southwest. Disarticulated, cut-marked and heat-altered human remains from non-burial contexts at prehistoric Puebloan (Anasazi) archaeological sites in the Four Corners region of the American Southwest have been interpreted by some scholars as evidence of cannibalism. Osteological studies indicate that many of the disarticulated bodies found at these sites were processed in a manner consistent with food preparation. Opponents of this interpretation point out that non-cannibalistic practices such as secondary interment, corpse mutilation and ritualized witch executions might account for the assemblages. Osteological evidence alone does not document the actual ingestion of human flesh. Here we show consumption of human flesh did occur as demonstrated in preserved human waste containing identifiable human tissue remains from a site with osteological evidence of cannibalism.