[
J Am Soc Nephrol,
1994]
Apoptosis is a programmed form of cell death mediating the precisely controlled deletion of "unwanted" cells. This review discusses the key features of this cell death program, emphasizing that apoptosis is regulated by factors extrinsic and intrinsic to the dying cell. Furthermore, because apoptosis leads to the swift phagocytic clearance of intact cells, tissues are protected against the noxious effect of cell contents. Apoptosis occurs in the developing and adult kidney, and nephrologists now need to consider whether abnormalities of this program may contribute to renal disease. Evidence suggests that such defects could contribute to developmental abnormalities including polycystic disease, induce autoimmunity to renal tissue, and exacerbate renal inflammation and scarring. Finally, apoptosis may offer new avenues for therapy.
[
J Neurophysiol,
2007]
The work of Clark et al. in this issue of J. Neurophysiology extends the analysis of thermotaxis in C. elegans by providing a detailed analysis of the adaptation of thermotactic behavior. Previous work indicates that thermotaxis in C. elegans involves a biased random walk in which changes in temperature alter the duration of the runs that an animal makes between turns. Interestingly, the authors find that although behavioral responses to increases and decreases in temperature have opposite effects on run length, the two responses are of similar magnitude and adapt with similar kinetics. These properties are predicted to allow the system act as a band-pass filter that would be less sensitive to temperature fluctuations occurring on a time-scale significantly faster or slower than the time needed for an average run. This analysis of C. elegans thermotaxis raises potential parallels to bacterial chemotaxis, with the kinetics of adaptation playing an important role in determining the ability of the organism to sense a stimulus gradient. This raises the possibility that diverse organisms may exploit similar system properties to solve similar problems, such as the problem of responding robustly to subtle gradations in an external stimulus.