Epsilon cell Epsilon cell Epsilon cells (ε-cells) are endocrine cells found in the Islets of Langerhans and produce the hormone ghrelin. They were discovered in mice. In human fetal pancreases, single epsilon cells scattered in primitive exocrine tissue were observed to start aggregating into clusters after gestational week 13. From gestational week 21, epsilon cells were observed around developing islets, forming an almost continuous layer at the rim of the islets. In adult pancreas samples, they remained localized on the mantle of the islets in different amounts. Production of ghrelin with insulin, glucagon, or somatostatin was not detected during development. Co-production with
Effect of spaceflight on the human body Effect of spaceflight on the human body Venturing into the environment of space can have negative effects on the human body. Significant adverse effects of long-term weightlessness include muscle atrophy and deterioration of the skeleton (spaceflight osteopenia). Other significant effects include a slowing of cardiovascular system functions, decreased production of red blood cells, balance disorders, eyesight disorders and a weakening of the immune system. Additional symptoms include fluid redistribution (causing the "moon-face" appearance typical in pictures of astronauts experiencing weightlessness), loss of body mass, nasal congestion, sleep disturbance, and excess flatulence. The engineering problems associated with leaving Earth and developing