Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.

Precursor cells have been shown to be affected by oxidative stress, in vivo and vitro, but little is known about the expression of antioxidant mechanisms in neuronal/glial differentiation. We have characterized the expression of Cu/Zn superoxide dismutase (Cu/Zn SOD), one of the main antioxidant proteins involved in the breakdown of superoxide, in the immature rat dorsolateral subventricular zone (SVZ), rostral migratory stream (RMS) and hippocampal subgranular zone (SGZ). Progenitor cells were identified immunohistochemically on cryostat sections by 5'Bromodeoxyuridine (BrdU) incorporation and expressing cells were further characterized using double labeling for progenitor markers. In the SVZ, only a subpopulation of BrdU+ cells, mostly found in the medial SVZ, expressed Cu/Zn SOD. These cells were mostly nestin+ and some were also vimentin+. In contrast, in the lateral SVZ few Cu/Zn SOD+/BrdU+ cells were found. These were primarily nestin+, vimentin-, showed some PSA-NCAM expression, but only a few were NG2+. In the RMS and SGZ virtually all BrdU+ progenitors were Cu/Zn SOD+ and expressed nestin and vimentin. Some RMS cells were also PSA-NCAM+. These findings show a heterogeneous expression of Cu/Zn SOD in restricted cell types in the germinative zones and suggest a role for antioxidant Cu/Zn SOD in progenitor cells of the immature rat brain.
Which intermediate filament (IF) protein can be used as a non-specific marker of the neuronal precursor cells of the subventricular zone?

In the 1950s, a family that owned a farm near Beulah, Michigan kept a bull chained to an elm . The bull paced around the tree, dragging the heavy iron chain, which led to a groove in the bark . The groove deepened over the years. Though for whatever reason, it did not kill the tree. After some years, the family took their bull away. They cut the chain, leaving the loop around the tree and one link hanging down. Then one year, agricultural disaster struck Michigan in the form of Dutch Elm Disease. All of the elms lining the road leading to the farm became infected and died. Everyone thought that the old elm would be the next. The farm owners considered doing the safe thing: pulling it out and cutting it up into firewood before it died. But they simply could not bring themselves to do it. It was as if the old tree had become a family friend. So they decided to let nature take its course. Amazingly, the tree did not die. Nobody could understand why it was the only elm still standing in the county! Plant experts from Michigan State University came out to observe the tree. They observed the scar left by the iron chain, now almost completely covered by bark. The experts decided that it was the chain that saved the elm's life. They reasoned that the tree must have absorbed so much iron from the chain that it became immune to the virus. It's said that what doesn't kill you will make you stronger. Or, as Earnest Hemingway put it, "Life breaks us all, but afterwards, many of us are strongest at the broken places."
What actually saved the elm?

TVN24 Biznes i Swiat (TVN24 BiS; Polish: TVN24 Business and World) is a Polish 24-hour hybrid business and world news channel, sister station to TVN24.

Which industry is TVN24 Biznes i Świat associated with?