QUESTION 21 A toxicologist studies the toxic effects of three substances (A-C) on cultured nerve cells at different concentrations over different...

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QUESTION 21A toxicologist studies the toxic effects of three substances (A-C) on cultured nerve cells at differentconcentrations over different times. He measures cell death by the exclusion of trypan blue, which canonly enter and stain cells that have disrupted membranes. He measures the leakage of lactatedehydrogenase (LDH), a cytosolic enzyme that leaves cells when the membrane is disrupted. Hemeasures cell blebbing with a fluorescent dye that permeates the intact membrane. Finally, he measuresDNA fragmentation with a fluorescent assay that stains for histone-associated DNA in the cytoplasm. Theresults are shown in the table.Sub-CellLDHBlebbed |DNAstancedeathleakagecellsfragmentation(%)(%)(%)(rel. A405 mm)3h 18h 3h 18h 3h 18h 3h18 hControl2300.29.30A3784405503361300 UM2 MM73936172123041b4870196030784510 UM.73100 UM841004555133331 mM20801060540.320.7Which statement best describes the actions of Substance C?A. Substance C causes apoptosis and necrosis at early times.B. Substance C causes necrosis at early times and apoptosis atlater times.C. Substance C causes apoptosis and necrosis at later timesD. Substance C causes apoptosis at early times and necrosis at