In this task, you are given a sentence. You are expected to write the name of the organism substances in the body mentioned in the input. Although there might be several correct answers, you need to write one of them.

[EX Q]:  Abrupt hypertension increased blood flow to all brain regions .
[EX A]: blood

[EX Q]:  A 20 - mul aliquot of the supernatant was added to 12 . 5 mul of assay buffer ( 20 mm ATP , 40 mm MgCl2 , 0 . 4 m Tris - Cl , pH 7 . 8 ) .
[EX A]: supernatant

[EX Q]:  We plan to systematically investigate the effects of thawing and refreezing on RNA integrity , by deliberately thawing and freezing small samples of brain tissue over varying time intervals and temperatures .
[EX A]:
samples