In 1939 beriberi patients in China were noted to have decreased zinc levels in skin and nails. In 1940 zinc levels in a series of autopsies found it to be present in all tissues examined. In 1942 a study showed most zinc excretion was via the feces. In 1950 a normal serum zinc level was first defined, and found to be 17.3–22.1 micromoles/liter. In 1956 cirrhotic patients were found to have low serum zinc levels. In 1963 zinc was determined to be essential to human growth, three enzymes requiring zinc as a cofactor were described, and a report was published of a 21-year-old Iranian man with stunted growth, infantile genitalia, and anemia which were all reversed by zinc supplementation. In 1972 fifteen Iranian rejected army inductees with symptoms of zinc deficiency were reported: all responded to zinc. In 1973 the first case of acrodermatitis enteropathica due to severe zinc deficiency was described. In 1974 the National Academy of Sciences declared zinc to be an essential element for humans and established a recommended daily allowance. In 1978 the Food and Drug Administration required zinc to be in total parenteral nutrition fluids. In the 1990s there was increasing attention on the role of zinc deficiency in childhood morbidity and mortality in developing countries. In 2002 the zinc transporter protein ZIP4 was first identified as the mechanism for absorption of zinc in the gut across the basolateral membrane of the enterocyte.
Osteochondritis is a painful type of osteochondrosis where the cartilage or bone in a joint is inflamed.It often refers to osteochondritis dissecans (OCD). The term dissecans refers to the "creation of a flap of cartilage that further dissects away from its underlying subchondral attachments (dissecans)".The other recognized types of osteochondritis are osteochondritis deformans juvenilis (osteochondritis of the capitular head of the epiphysis of the femur) and osteochondritis deformans juvenilis dorsi (osteochondrosis of the spinal vertebrae, also known as Scheuermanns disease).Osteochondritis, and especially osteochondritis dissecans, can manifest in animals as a primary cause of elbow dysplasia, a chronic condition in some dog breeds. References


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