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Eldorado Desperadoes I: Of Mice and Men
About a week ago, the Internet went wild with the announcement that a “fountain of youth” drug had been found that extends life by about 10%. I picked a site at random and read the report, knowing full well what I would find buried somewhere in the story. Sure enough, there it was, tucked at the end of a paragraph halfway down: the study was done on mice.
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COMMENTS
Posted by Ben Scarlato on 07/18 at 01:04 PM
Than you, Athena, for countering the undeserved hype this story has been getting.
I first heard about this study on the Nature podcast, and while it was a fascinating result, even then it was made clear that its crippling effect on the human immune system alone meant that we were, at best, a long way off from getting any practical benefit. It never hurts to be reminded of the weaknesses of animal models.
Posted by James on 07/18 at 02:52 PM
It's interesting that you say "mouse sexual arousal and mothering behavior depend on smell pheromones.". There have been numerous, recognized studies at institutions such as Monell Chemical Senses Center, University of Penn, Lafayette, etc that have shown the effects of male axillary pheromones on female ovulation and mating patterns, etc. And the current studies on oxytocin show the effect of cuddling in both male and female parents and their children. Some good links:
http://www.livescience.com/health/060213_attraction_rules.html
http://www.scientificblogging.com/news_releases/pheromones_some_females_can_smell_reproductive_fitness_and_even_ancestry_males
http://www.pheromonefacts.com/science/pheromone-related-links.aspx
http://www.athenainstitute.com/science.html?tab=0
http://blogs.wsj.com/juggle/2009/06/19/fathers-day-why-men-are-hard-wired-to-cuddle-their-babies/
Posted by Athena Andreadis on 07/18 at 07:54 PM
I'm glad you enjoyed the essay, Ben! Indeed, animal models are enormously informative and helpful -- but their applications and conclusions are finite.
James, humans are primarily visual and this is true for sexual attraction as well. Two areas of the human brain are disproportionately large: the prefrontal cortical lobe and the regions associated with receiving and processing visual cues.
Anosmic mice do not go into heat and hence cannot mate. Anosmic humans have no such problem (Kallmann syndrome sufferers are anosmic and sterile, but that is due to lack of pituitary hormones, not because the lack of smell abolishes interest in sex). Smell is our weakest sense.
Oxytocin may be the hormone de jour in TH circles for its (largely scifi) potential for happifying drugs. It does turn male voles monogamous. Voles, not humans. In humans, its primary action is to induce smooth muscle contraction, hence its use during labor.
In most of these links (none of which are primary research), the talk starts in humans and soon afterwards veers into other animals, particularly... could it be?... mice!
Posted by Dick Hogan on 07/19 at 09:36 AM
I agree with Ben that this story has gotten wway more publicity than it deserves. Anthony Serafini in his classic work THE EPIC HISTORY OF BIOLOGY also suggested caution it relying on animal models.
Posted by Michael on 07/19 at 07:50 PM
Wickipedia tells us it all about the rodents:
* Sexual arousal. Oxytocin injected into the cerebrospinal fluid causes spontaneous erections in rats,[9] reflecting actions in the hypothalamus and spinal cord.
* Bonding. In the Prairie Vole, oxytocin released into the brain of the female during sexual activity is important for forming a monogamous pair bond with her sexual partner. Vasopressin appears to have a similar effect in males.[10] Oxytocin has a role in social behaviors in many species, and so it seems likely that it has similar roles in humans.
* Maternal behavior. Rat females given oxytocin antagonists after giving birth do not exhibit typical maternal behavior.[13] By contrast, virgin female sheep show maternal behavior towards foreign lambs upon cerebrospinal fluid infusion of oxytocin, which they would not do otherwise.[14]
So, with oxytocin being the sexual hormone de jour, there is some validity to the effects it has on maternal behaviors, sexual arousal and smooth muscle contraction in humans. Just out of curiosity, what are your thoughts on the VNO in humans? Thank you.
Posted by Athena Andreadis on 07/20 at 02:04 AM
Michael, humans have a vomeronasal organ (VNO) during development, but then it shrinks and remains (if at all) vestigial. There seem to be no active neurons in humans that correspond to that of the VNO in other mammals. Furthermore, most genes that correspond to the VNO receptors have become pseudogenes in humans, which means they don't express functional proteins. So the overall evidence so far indicates that olfactory cues from the VNO are either absent or minimal in our species.
As for oxytocin being the sexual hormone du jour, you know Tina Turner's immortal words: Today cock of the walk, tomorrow a feather duster (*laughs*).
Posted by veronica on 07/20 at 10:06 AM
Usually, Creationists are considered science stoppers, but in the case of VNO, we must not let scientists be the science stoppers by definitively calling the VNO a vestigial organ, and hence stop looking for a function. We've been burned before. Fortunately we have scientists like Witt and Shirokova looking into VNO very carefully.
Posted by Susan Kuchinskas on 07/20 at 12:12 PM
Having written a book on oxytocin's neurochemical effects on bonding, as well as its pivotal role as a hormone in sexual arousal, I agree with James, Michael and Veronica.
There is strong scientific evidence that the human vomeronasal organ functions, from studies at Monell and others. I think it made scientists queasy to think that we huffed each other just like animals, but soon the evidence that we do will be incontrovertible.
For more refs, see: http://www.hugthemonkey.com/2007/10/smells-like-tee.html#_edn2
Athena, I don't think we know enough about genes and their expression to use a genetic argument that the VNO is not active.
Michael, I'd say there's a lot more than "some validity" to the effects of oxytocin on sexuality and behavior. I'd say it's a done deal.
Posted by Athena Andreadis on 07/20 at 01:02 PM
People, pay attention: I said "the overall evidence so far". Additionally, the vestigial status of the VNO is true not only for humans, but also for most primates. It seems to be an evolutionary event, that's all. Nothing to do with queasiness about huffing.
Veronica, there may well be other functions for the VNO and nobody is stopping the research just because it's not "sexy" (literally and metaphorically).
Susan, we know a fair amount about genes and their expression. Not everything by far, but enough to know if a gene we examine is being expressed or not. I know you wrote a book about oxytocin, which is great. But primary research has the disconcerting effect of constantly discovering nuances and exceptions. It would be wonderful if everything fell neatly into place, but that rarely happens in biology. And if something sounds too good to be true, it invariably is.
Posted by Davie Springer on 07/20 at 03:13 PM
All this may sound esoteric, but the conclusion is simple: mouse models, especially those based on highly inbred strains, recapitulate only limited aspects of many human functions and diseases. first and last question of non-biologists should be: what were (or when will we know) the results of the human tests
Yes very good! This point was made by Anthony Serafini is his work THE EPIC HISTORY OF BIOLOGY
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