Thiamine deprived mice are a classic model of systemic oxidative stress, used in research of Alzheimer's disease.

S&P said the downgrades were "primarily driven by our assessment that the policy initiatives that have been taken by European policy-makers in recent weeks may be insufficient to fully address ongoing systemic stresses in the eurozone".

Today's rating actions are primarily driven by our assessment that the policy initiatives that have been taken by European policymakers in recent weeks may be insufficient to fully address ongoing systemic stresses in the eurozone.

In our view, systemic stress in the eurozone has risen in recent weeks and reached such a level that a review of all eurozone sovereign ratings is warranted.

We believe that this systemic stress emanates from five interrelated factors.

The rating agency had explained its move by warning that recent European policies "may be insufficient to fully address systemic stresses in the eurozone".

There are some management teams, such as at Wells Fargo, J. P. Morgan, and Goldman Sachs, that seem to have done a decent job overall, considering the systemic stresses they endured.

The agency said that its actions on eurozone ratings were "primarily driven by insufficient policy measures by EU leaders to fully address systemic stresses".

Such systemic stresses are beyond doubt: the European Central Bank itself has enacted a series of "non-standard" measures to help the eurozone banking system and try to prevent a credit crunch.

There must be debt pooling and a lender of last resort to stop "systemic stress".