11.   The study was designed to measure the safety and benefits of surgically transplanting neural cells from a fetal pig into the brain to replace cells lost to the disease.

12.   These cells can turn into fat, bone and cartilage and possibly into neural cells, the company says.

13.   They can turn into different types of neural cells but probably not into others, like kidney or liver cells.

14.   To achieve that, researchers need neural cells that can multiply in a laboratory.

15.   Scientists do not know what causes the sticky brain deposits that inevitably kill off neural cells until memory disintegrates and ultimately the patient dies.

16.   Scientists do not know what causes the sticky brain deposits that inevitably kill off neural cells until memory disintegrates and, ultimately, the patient dies.