Thursday, October 11, 2007

The Appendix: Not so useless?

Here's some recent news from the field of theoretical biology: Long described in high school biology classes as a vestigial structure - an evolutionary remnant with no functional use - the appendix may have a purpose after all (other than getting inflamed and keeping surgeons busy with appendectomies). The function, it turns out, may be to repopulate the gut with bacteria. Illnesses or antibiotic treatment can purge many of the "good" bacteria that aid in digestion and vitamin K production, and this new theory proposes that the appendix serves as a 'safe house' for commensal bacteria, and re-inoculates the intestinal tract after such a purge. The reason an appendix can be removed without ill effect may be due to our living conditions - in a highly populated, industrialized environment we're more likely to re-acquire these bacteria from our neighbours, but the appendix may still be important in less developed countries. Link to the full paper here [pdf, subscription may be required]


Keith Robison said...

Aaargh! If you don't have a subscription, you can't even read the abstract (well, it comes up blank)

kamel said...

Sorry Keith,
I know it sucks. We have an institutional subscription, but it's a preprint manuscript (accepted for publication August 30) with only a link to the pdf and not the abstract or even an HTML version. I'm sure it will be on pubmed soon enough.

The paper is entitled: 'Biofilms in the large bowel suggest an apparent function of the human vermiform appendix'

Authors: R. Randal Bollinger, Andrew S. Barbas, Errol L.
Bush, Shu S. Lin,William Parker

The abstract:
The human vermiform (“worm-like”) appendix is a 5 to 10 cm long and 0.5 to 1 cm wide pouch that extends from the cecum of the large bowel. The architecture of the human appendix is unique among mammals, and few mammals other than humans have an appendix at all. The function of the human appendix has long been a matter of debate, with the structure often considered to be a vestige of evolutionary development despite
evidence to the contrary based on comparative primate anatomy. The appendix is thought to have some immune function based on its association with substantial lymphatic tissue, although the specific nature of that putative function is unknown. Based (a) on a recently acquired understanding of immune-mediated biofilm formation by commensal bacteria in
the mammalian gut, (b) on biofilm distribution in the large bowel, (c) the association of lymphoid tissue with the appendix, (d) the potential for biofilms to protect and support colonization by commensal bacteria, and (e) on the architecture of the human bowel, we
propose that the human appendix is well suited as a “safe house” for commensal bacteria, providing support for bacterial growth and potentially facilitating re-inoculation of the colon in the event that the contents of the intestinal tract are purged following exposure to a pathogen."

runnings said...

hello, how are u?