If your heart stops beating for five or more minutes, you're dead. Right? Wrong! (Newsweek report.) Oxygen-deprived cells in cardiac muscle don't die after five minutes, or even an hour. But if they're deprived of oxygen for more than about five minutes, then when reperfusion begins, the presence of oxygen triggers apoptosis, a cell death mechanism (that usually defends us against cancer by causing cancer cells to self-destruct). More on reperfusion injury here (educated layperson level); if you really want to know more, start with the references on this page.
Is Alzheimers a type of diabetes? Insulin isn't just a hormone that modulates cellular uptake of glucose and uptake and conversion of blood lipids into cell-bound triglycerides — it's found in the brain, where it serves to stimulate choline acetyltransferase, a key enzyme in the synthesis of acetylcholine, a neurotransmitter without which you're stuffed. And levels of insulin in the brains of Alzheimer's patients drop in step with the degree of dementia. There's nothing conclusive here yet, but if this is the root cause of Alzheimer's, then it suggests where researchers ought to be looking for new treatments.
(Anyone want to add anything to this list?)