Golf & Grapes OR Grandkids (but not both!)

Pesticides may be bad for you, but they are devastating for your great grandchildren, because there will be no great great grandchildren. Photo Credit: JetsandZeppelins from Flickr under CC BY 2.0 license
Pesticides may be bad for you, but they are devastating for your great grandchildren, because there will be no great great grandchildren. Photo Credit: JetsandZeppelins from Flickr under CC BY 2.0 license

Transgenerational epigenetic inheritance (TGI) refers to the inheritance of a trait from one generation to another without altering the DNA code (normally, evolution is driven by changes in the DNA itself). Instead, it happens by modifying the proteins that wrap around the DNA, the histones; these histones, in turn, control what genes will be expressed and when. Until a decade ago, TGI was considered impossible, nay, a scientific heresy since it had too close of a resemblance to Lamarckian evolution. But, true to its guiding principles, the scientific endeavor had to bite the bullet in front of amassing evidence and accept the fact that it may have been a kernel of truth to the so called ‘soft inheritance’.

Anway et al.’s paper was one of the first to promote the concept, ten years ago. They exposed pregnant rats to the pesticides vinclozolin or methoxychlor (only vinclozolin is still used widely in U.S.A. and several EU countries, particularly in agriculture, wine production, and turf maintenance; methoxychlor was banned in the early noughts). The authors found out that more than 90% of the male offspring had “increased incidence of male infertility”. These effects were transferred through the male germ line to nearly all males of all subsequent generations examined” up to great great grandsons, inclusively (Anway et al., 2005). (I don’t want to speculate how they managed to breed the low fertility males…). That doesn’t mean that the F5 generation was OK (the great great great gransons); it means that they stopped investigating after the F4 generation (or they couldn’t breed the F4s). Moreover, the mechanism of inheritance seems to be altered methylation of the DNA histones of the male germline, and not alteration of the DNA itself. Females were affected too, but they didn’t have enough data on that experiment (the Ph.D. student that did the work had to graduate sometime…).

Although the authors used higher amounts of pesticides than they suspected back then, in 2005, to be found in the environment, the study still gives pause for thought. After all, it has been 10 years since this paper plus the previous 20 years of use of the stuff. And no, you cannot get rid of it by washing your grapes and vegetables really thoroughly.

Reference: Anway, M. D., Cupp, A. S., Uzumcu, M., & Skinner, M. K. (3 June 2005). Epigenetic transgenerational actions of endocrine disruptors and male fertility. Science, 308(5727): 1466-1469. DOI:10.1126/science.1108190. Article + Science Cover + FREE PDF

by Neuronicus, 25 September 2015

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Zap the brain to get more lenient judges

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Reference: Buckholtz et al. (2015). Credit: Neuronicus

Humans manage to live successfully in large societies mainly because we are able to cooperate. Cooperation rests on commonly agreed rules and, equally important, the punishment bestowed upon their violators. Researchers call this norm enforcement, while the rest of us call it simply justice, whether it is delivered in its formal way (through the courts of law) or in a more personal manner (shout at the litterer, claxon the person who cut in your lane etc.). It is a complicate process to investigate, but scientists managed to break it into simpler operations: moral permissibility (what is the rule), causal responsibility (did John break the rule), moral responsibility (did John intend to break the rule, also called blameworthiness or culpability), harm assessment (how much harm resulted from John breaking the rule) and sanction (give the appropriate punishment to John). Different brain parts deal with different aspects of norm enforcement.

The approximate area where the stimulation took place. Note that the picture depicts the left hemisphere, whereas the low punishment judgement occured when the stimulation was mostly on the right hemisphere.
The approximate area where the stimulation took place. Note that the picture depicts the left hemisphere, whereas the low punishment judgement occurred when the stimulation was mostly on the right hemisphere.

Using functional magnetic resonance imaging (fMRI), Buckholtz et al. found out that the dorsolateral prefrontal cortex (DLPFC) gets activated when 60 young subjects decided what punishment fits a crime. Then, they used repetitive transcranial magnetic stimulation (rTMS), which is a non-invasive way to disrupt the activity of the neurons, to see what happens if you inhibit the DLPFC. The subjects made the same judgments when it came to assigning blame or assessing the harm done, but delivered lower punishments.

Reference: Buckholtz, J. W., Martin, J. W., Treadway, M. T., Jan, K., Zald, D.H., Jones, O., & Marois, R. (23 September 2015). From Blame to Punishment: Disrupting Prefrontal Cortex Activity Reveals Norm Enforcement Mechanisms. Neuron, 87: 1–12, http://dx.doi.org/10.1016/j.neuron.2015.08.023. Article + FREE PDF

by Neuronicus, 22 September 2015