Skip to main content

View Diary: Radioactive Isotopes from French Commercial Nuclear Fuel Found In Mississippi River. (77 comments)

Comment Preferences

  •  Don't forget another benefit of atmospheric (0+ / 0-)

    testing of nuclear weapons - it allows you to figure out how old your cells are!

    Defining the life span of specific human cell populations is limited by our inability to mark the exact time when cells are born in a way that can be detected over many years. this issue of Cell, Spalding et al. (2005) describe a clever strategy for retrospectively birth dating human cells in vivo, based on their incorporation of 14C during a peak in atmospheric levels of this isotope resulting from above-ground nuclear arms testing in the 1950s.

    Results . . .

    We next birth dated cells in different adult organs. We selected intestine, skeletal muscle, and two brain regions, based on the assumption that these tissues have different rates of cell turnover. Intestinal epithelial cells have an average life span of about 5 days (Marshman et al., 2002), whereas many nonepithelial cells in the gut are likely to be long lived. There is thought to be very little cell replacement in the cerebral cortex and cerebellum. All tissues contain blood, but nucleated cells only account for about 1/1000 of cells in peripheral blood, and their effect on the average age of cells in an organ will be negligible. 14C birth dating revealed that the average age of cells in the intestine (jejunum) is 10.7 ± 3.6 years (mean ± SD from three individuals of average age 34.8 years; Figure 3). We quantified the proportion of epithelial cells to other cells in histological sections of jejunum and found that in average 42% ± 3% (n = 5 individuals) of all cells in the specimen were epithelial. Assuming that all epithelial cells are contemporary, the average age of the nonepithelial cells is 15.9 years. Measurement of the level of 14C in DNA from intercostal skeletal muscle from two individuals (37 and 38 years old) indicated an average age of 15.1 years.

    The average age of cells in the gray matter of the cerebellum was almost as old as the individual (born at the age of 2.9 ± 1.2 years, Table 1), whereas cells from the occipital-cortex gray matter were substantially younger (Figure 3), indicating more cell turnover in the cerebral cortex than in the cerebellum. Analysis of multiple samples from the same individuals revealed a precision of ±2 years (1 SD) for the dating procedure and a high degree of reproducibility between individuals (Table 1).

Subscribe or Donate to support Daily Kos.

Click here for the mobile view of the site