Pancreatic islets by scarce alpha, delta and PP cells in the periphery, human islets display alpha and beta cells in close relationship with each other throughout the cluster. Islets can influence each other through paracrine and autocrine communication, and beta cells are coupled electrically to six to seven other beta cells (but not to other cell types). The paracrine feedback system of the pancreatic islets has the following structure: A large number of G protein-coupled receptors (GPCRs) regulate the secretion of insulin, glucagon and somatostatin from pancreatic islets, and some of these GPCRs are the targets of drugs used to treat type-2
Effect of spaceflight on the human body responses of the human body in space. At the moment only rigorously tested humans have experienced the conditions of space. If off-world colonization someday begins, many types of people will be exposed to these dangers, and the effects on the very young are completely unknown. On October 29, 1998, John Glenn, one of the original Mercury 7, returned to space at the age of 77. His space flight, which lasted 9 days, provided NASA with important information about the effects of space flight in older people. Factors such as nutritional requirements and physical environments which have so far not been