Freethought & Rationalism Archive

Oolon Colluphid · 12-18-2002, 01:28 AM

Hi folks, getting back to relative normality after my op. Apologies to those of you I need to reply to by email etc – getting there gradually

.

Now, the point. I’m wondering if I’ve done the right thing in cancelling my New Scientist subscription; I rarely got to read it propoerly, and it was often too ‘popular’, so I saved the money. However, browsing through the 9 November edition, I found out something I’d never have realised could be turned to anti-creationist advantage, from the unpromising PNAS title alone. The title is:

“Developmental regulation of intestinal angiogenesis by indigenous microbes via Paneth cells”

(by Stappenbeck, Hooper and Gordon, in Proc. Natl. Acad. Sci. USA, Vol. 99, Issue 24, 15451-15455, November 26, 2002, DOI: 10.1073/pnas.202604299)

Eh? What? How’s that?

Ah, but wait. What it amounts to is that mice guts don’t form properly unless they have certain micro-organisms in there too.

Abstract:

Quote:

The adult mouse intestine contains an intricate vascular network. The factors that control development of this network are poorly understood. Quantitative three-dimensional imaging studies revealed that a plexus of branched interconnected vessels developedin small intestinal villi during the period of postnatal development that coincides with assembly of a complex society of indigenous gut microorganisms (microbiota). To investigate the impact of this environmental transition on vascular development, we compared the capillary networks of germ-free mice with those of ex-germ-free animals colonized during or after completion of postnatal gut development. Adult germ-free mice had arrested capillary network formation. The developmental program can be restarted and completed within 10 days after colonization with a complete microbiota harvested from conventionally raised mice, or with Bacteroides thetaiotaomicron, a prominent inhabitant of the normal mouse/human gut. Paneth cells in the intestinal epithelium secrete antibacterial peptides that affect luminal microbial ecology. Comparisons of germ-free and B. thetaiotaomicron-colonized transgenic mice lacking Paneth cells established that microbial regulation of angiogenesis depends on this lineage. These findings reveal a previously unappreciated mechanism of postnatal animal development, where microbes colonizing a mucosal surface are assigned responsibility for regulating elaboration of the underlying microvasculature by signaling through a bacteria-sensing epithelial cell.

(My emphases.)

Now, I’d not push this as evidence of poor design, in itself. It is however more than a bit odd that mouse guts can’t form properly unless B thetaiotaomicron is in them. Why on earth not? Especially since a job of paneth cells is to secrete stuff that normally kills bacteria. A rather convoluted design... and so not a ‘good’ one, for good designs tend to show simplicity and economy.

But we can go a bit further, and make some testible predictions (since I doubt this has been much investigated in other animals). I predict that this may be the case in other mammals: maybe just the Muridae, maybe in rodents, maybe in Eutheria, or all mammals... I predict that this will not however be the case in all animals with relevantly homologous guts.

In which case, the question arises: how come -- if they were designed by a high intelligence -- this group (however large it is) requires the micro-organisms to grow correctly, whereas other creatures manage just fine without them...?

Cheers, DT

scigirl · 12-18-2002, 08:11 AM

DT - that's a fascinating study.

I wonder how many more instances like these exist in biology. I read an article once about how scientists think the placenta evolved because of a syncytial virus.

I also wonder what the creationist response to this is.

scigirl

Nickle · 12-18-2002, 10:24 AM

*raises hand*

Um, Goddidit?

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12-18-2002, 08:11 AM	#2
scigirl Veteran Member Join Date: Jul 2001 Location: Seattle Posts: 4,261	DT - that's a fascinating study. I wonder how many more instances like these exist in biology. I read an article once about how scientists think the placenta evolved because of a syncytial virus. I also wonder what the creationist response to this is. scigirl

12-18-2002, 10:24 AM	#3
Nickle Regular Member Join Date: Oct 2001 Location: Texas Posts: 385	raises hand Um, Goddidit?

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