Replacement Rates for Human Tissue from Atmospheric Radiocarbon

Abstract

Carbon-14, derived from the testing of thermonuclear weapons in the atmosphere of the Northern Hemisphere during 1961-62, has been found in human tissues including the brain in amounts which reflect the atmospheric concentration of carbon-14 as of several months earlier. In collagen of cartilage, the rate of uptake of carbon-14 is much slower than in other tissues; essentially no radioactive carbon was found in the collagen of 70-year-old adults that had been exposed to the comparatively high concentrations of carbon-14 in the atmosphere during the years 1954 to 1964. Individuals from the Southern Hemisphere show little increase in the carbon-14 content of their tissues at present, and detailed tests with individuals traveling to the Northern Hemisphere from the Southern allow closer scrutiny of the tissue replacement rates.

Deposição de ácido linoléico conjugado (CLA) em tilápias-do-nilo

“…Segundo Tieszen et al (1983), os tecidos que apresentam rápido metabolismo refletem a alimentação recente, enquanto os de baixa taxa de substituição representam alimentações de um período mais prolongado. Segundo Libby et al (1964), tecidos metabolicamente mais ativos, como o fígado, o pâncreas e o tecido gorduroso têm taxa de substituição mais rápida que os menos ativos, como os ossos e o tecido conjuntivo. Carrijo et al (2000) observaram essas evidências quando avaliou o turnover de diferentes tecidos de poedeiras comerciais pela técnica dos isótopos estáveis ( 13 C/ 12 C).…”

Adult Neurogenesis in Humans

“…In the atmosphere, 14 C reacts with oxygen to form 14 CO 2 , which enters the food chain through plant photosynthesis. Being at the top of the food pyramid, 14 C concentration in the human body closely parallels that in the atmosphere at any given time (Libby et al 1964;Harkness 1972;Spalding et al 2005b). When cells undergo mitosis and duplicate their DNA, 14 C integrates into genomic DNA, and the 14 C concentration remains stable after the last cell division.…”

Marked longevity of human lung parenchymal elastic fibers deduced from prevalence of D-aspartate and nuclear weapons-related radiocarbon.

“…Excess 14C in the atmosphere, a result ofatomic weapons testing in the late 1950s and early 1960s, serves as a kinetic tracer for biogenic material (15). Weapons-related '4CO2 reaches the biosphere through photosynthesis, and reaches human tissues through the food chain, with a lag time of 1.0-1.5 yr (41)(42)(43). Thus, 14C prevalence in modern carbonaceous samples, including human tissues, provides a well-validated dating tool (15,43,44); '4C prevalence in human proteins can be assumed to reflect prevalence of '4C in the diet at the time of synthesis.…”