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Radiocarbon dating of the human eye lens crystallines reveal proteins without carbon turnover throughout life.

Lynnerup N, Kjeldsen H, Heegaard S, Jacobsen C, Heinemeier J - PLoS ONE (2008)

Bottom Line: Since the change in concentration is significant even on a yearly basis this allows very accurate dating.Our results allow us to conclude that the crystalline formation in the lens nucleus almost entirely takes place around the time of birth, with a very small, and decreasing, continuous formation throughout life.The precision with which the year of birth may be calculated points to forensic uses of this technique.

View Article: PubMed Central - PubMed

Affiliation: Department of Forensic Medicine, University of Copenhagen, Copenhagen, Denmark. n.lynnerup@antrolab.ku.dk

ABSTRACT

Background: Lens crystallines are special proteins in the eye lens. Because the epithelial basement membrane (lens capsule) completely encloses the lens, desquamation of aging cells is impossible, and due to the complete absence of blood vessels or transport of metabolites in this area, there is no subsequent remodelling of these fibers, nor removal of degraded lens fibers. Human tissue ultimately derives its (14)C content from the atmospheric carbon dioxide. The (14)C content of the lens proteins thus reflects the atmospheric content of (14)C when the lens crystallines were formed. Precise radiocarbon dating is made possible by comparing the (14)C content of the lens crystallines to the so-called bomb pulse, i.e. a plot of the atmospheric (14)C content since the Second World War, when there was a significant increase due to nuclear-bomb testing. Since the change in concentration is significant even on a yearly basis this allows very accurate dating.

Methodology/principal findings: Our results allow us to conclude that the crystalline formation in the lens nucleus almost entirely takes place around the time of birth, with a very small, and decreasing, continuous formation throughout life. The close relationship may be further expressed as a mathematical model, which takes into account the timing of the crystalline formation.

Conclusions/significance: Such a life-long permanence of human tissue has hitherto only been described for dental enamel. In confront to dental enamel it must be held in mind that the eye lens is a soft structure, subjected to almost continuous deformation, due to lens accommodation, yet its most important constituent, the lens crystalline, is never subject to turnover or remodelling once formed. The determination of the (14)C content of various tissues may be used to assess turnover rates and degree of substitution (for example for brain cell DNA). Potential targets may be nervous tissues in terms of senile or pre-senile degradation, as well as other highly specialised structures of the eyes. The precision with which the year of birth may be calculated points to forensic uses of this technique.

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Related in: MedlinePlus

The formation of eye lens crystallines determined by 14C.Nuclear bomb tests during 1955–63 produced large amounts of 14C, which after this period has declined exponentially (thin, grey line). Comparing the amount of 14C in eye-lens crystallines (red circles, plotted as a function of the year of birth) with the atmospheric concentration in units of pmC (percent modern Carbon) has made it possible to investigate the timing of the formation process. The red curve shows the output from our resulting lens-formation model, which provides the basis for predicting the year of birth accurately (Fig. 2).
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pone-0001529-g001: The formation of eye lens crystallines determined by 14C.Nuclear bomb tests during 1955–63 produced large amounts of 14C, which after this period has declined exponentially (thin, grey line). Comparing the amount of 14C in eye-lens crystallines (red circles, plotted as a function of the year of birth) with the atmospheric concentration in units of pmC (percent modern Carbon) has made it possible to investigate the timing of the formation process. The red curve shows the output from our resulting lens-formation model, which provides the basis for predicting the year of birth accurately (Fig. 2).

Mentions: We have exploited the radical variations of the atmospheric 14C content during the last 50 years to date the formation of the lens crystallines. The concentration of 14C in living tissues reflects the atmospheric 14C content at the time of growth. This is because cosmogenic 14C in the atmosphere reacts with oxygen to form carbon dioxide (CO2), which is incorporated by plants, and then ingested by animals. The plants and animals are ultimately ingested by humans. If there is only minimal turnover in the eye lens, the content of 14C in the lens crystallines should thus reflect the atmospheric concentration at the time the lens crystallines were formed. The amount of 14C in the atmosphere (see Fig 1) was almost constant until about 1955, when nuclear-bomb tests caused it to rise dramatically [5]. Subsequent to the Test Ban Treaty in 1963 the concentration has decreased rapidly, mainly because the atmospheric 14C has diffused into the oceans, while radioactive decay (the half-life of 14C is 5730 years) is of minor importance [6]. Since the change in concentration is significant even on a yearly basis this allows very accurate dating [7].


Radiocarbon dating of the human eye lens crystallines reveal proteins without carbon turnover throughout life.

Lynnerup N, Kjeldsen H, Heegaard S, Jacobsen C, Heinemeier J - PLoS ONE (2008)

The formation of eye lens crystallines determined by 14C.Nuclear bomb tests during 1955–63 produced large amounts of 14C, which after this period has declined exponentially (thin, grey line). Comparing the amount of 14C in eye-lens crystallines (red circles, plotted as a function of the year of birth) with the atmospheric concentration in units of pmC (percent modern Carbon) has made it possible to investigate the timing of the formation process. The red curve shows the output from our resulting lens-formation model, which provides the basis for predicting the year of birth accurately (Fig. 2).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2211393&req=5

pone-0001529-g001: The formation of eye lens crystallines determined by 14C.Nuclear bomb tests during 1955–63 produced large amounts of 14C, which after this period has declined exponentially (thin, grey line). Comparing the amount of 14C in eye-lens crystallines (red circles, plotted as a function of the year of birth) with the atmospheric concentration in units of pmC (percent modern Carbon) has made it possible to investigate the timing of the formation process. The red curve shows the output from our resulting lens-formation model, which provides the basis for predicting the year of birth accurately (Fig. 2).
Mentions: We have exploited the radical variations of the atmospheric 14C content during the last 50 years to date the formation of the lens crystallines. The concentration of 14C in living tissues reflects the atmospheric 14C content at the time of growth. This is because cosmogenic 14C in the atmosphere reacts with oxygen to form carbon dioxide (CO2), which is incorporated by plants, and then ingested by animals. The plants and animals are ultimately ingested by humans. If there is only minimal turnover in the eye lens, the content of 14C in the lens crystallines should thus reflect the atmospheric concentration at the time the lens crystallines were formed. The amount of 14C in the atmosphere (see Fig 1) was almost constant until about 1955, when nuclear-bomb tests caused it to rise dramatically [5]. Subsequent to the Test Ban Treaty in 1963 the concentration has decreased rapidly, mainly because the atmospheric 14C has diffused into the oceans, while radioactive decay (the half-life of 14C is 5730 years) is of minor importance [6]. Since the change in concentration is significant even on a yearly basis this allows very accurate dating [7].

Bottom Line: Since the change in concentration is significant even on a yearly basis this allows very accurate dating.Our results allow us to conclude that the crystalline formation in the lens nucleus almost entirely takes place around the time of birth, with a very small, and decreasing, continuous formation throughout life.The precision with which the year of birth may be calculated points to forensic uses of this technique.

View Article: PubMed Central - PubMed

Affiliation: Department of Forensic Medicine, University of Copenhagen, Copenhagen, Denmark. n.lynnerup@antrolab.ku.dk

ABSTRACT

Background: Lens crystallines are special proteins in the eye lens. Because the epithelial basement membrane (lens capsule) completely encloses the lens, desquamation of aging cells is impossible, and due to the complete absence of blood vessels or transport of metabolites in this area, there is no subsequent remodelling of these fibers, nor removal of degraded lens fibers. Human tissue ultimately derives its (14)C content from the atmospheric carbon dioxide. The (14)C content of the lens proteins thus reflects the atmospheric content of (14)C when the lens crystallines were formed. Precise radiocarbon dating is made possible by comparing the (14)C content of the lens crystallines to the so-called bomb pulse, i.e. a plot of the atmospheric (14)C content since the Second World War, when there was a significant increase due to nuclear-bomb testing. Since the change in concentration is significant even on a yearly basis this allows very accurate dating.

Methodology/principal findings: Our results allow us to conclude that the crystalline formation in the lens nucleus almost entirely takes place around the time of birth, with a very small, and decreasing, continuous formation throughout life. The close relationship may be further expressed as a mathematical model, which takes into account the timing of the crystalline formation.

Conclusions/significance: Such a life-long permanence of human tissue has hitherto only been described for dental enamel. In confront to dental enamel it must be held in mind that the eye lens is a soft structure, subjected to almost continuous deformation, due to lens accommodation, yet its most important constituent, the lens crystalline, is never subject to turnover or remodelling once formed. The determination of the (14)C content of various tissues may be used to assess turnover rates and degree of substitution (for example for brain cell DNA). Potential targets may be nervous tissues in terms of senile or pre-senile degradation, as well as other highly specialised structures of the eyes. The precision with which the year of birth may be calculated points to forensic uses of this technique.

Show MeSH
Related in: MedlinePlus