For cell transplantation studies, 16-month-old male C57BL/6 mice were obtained from the National Institute on Aging (NIA). Mice were housed 4-5 per cage. Mice were sorted using body weight from low to high. Next, either SEN or CON transplant treatments were assigned to every other mouse using a random number generator, with the intervening mice being assigned to the other treatment, so that pairs of SEN- and CON-transplanted mice were matched by weight. After 1 month of acclimation, cells were transplanted at age 17 months. Physical function tests were performed 1 month after transplantation, at age 18 months. After that, no further tests were performed on these mice except for checking their cages. The earliest death occurred approximately 2 months after the last physical function test. For D+Q studies, 19-21-month-old C57BL/6 mice were obtained from the NIA. Mice were housed 3-5 per cage. As with the transplanted mice, animals were sorted based body weight and randomly assigned to D+Q or V treatment by a person unaware of the study design. Starting at age 24-27 months, mice were treated every 2 weeks with D+Q or V by oral gavage for 3 consecutive days. Some of the mice were moved from their original cages during the course of the study to minimize single cage-housing stress. RotaRod and hanging tests were conducted monthly because these tests are sensitive and non-invasive. We euthanized mice and scored them as having died if they exhibited more than one of the following signs59 : 1) unable to drink or eat; 2) reluctant to move even with stimulus; 3) rapid weight loss; 4) severe balance disorder; or 5) bleeding or ulcerated tumor. No mouse was lost due to fighting, accidental death, or dermatitis. The Cox proportional hazard model was used for survival analyses.