A toxicologist studies the toxic effects of three substances (A-C) on cultured nerve cells at different
concentrations over different times. He measures cell death by the exclusion of trypan blue, which can only enter and stain cells that have disrupted membranes. He measures the leakage of lactate dehydrogenase (LDH), a cytosolic enzyme that leaves cells when the membrane is disrupted. He measures cell blebbing with a fluorescent dye that permeates the intact membrane. Finally, he measures DNA fragmentation with a fluorescent assay that stains for histone-associated DNA in the cytoplasm. The results are shown in the table.
Which statement best describes the actions of Substance B?
a. Low and high concentrations of Substance B cause only necrosis.
b. Low concentrations of Substance B cause apoptosis, while high concentrations produce necrosis.
c. Low and high concentrations of Substance B cause only apoptosis.
d. Low concentrations of Substance B cause necrosis, while high concentrations produce apoptosis.