zoology biology benno meyer rochow science blog young

Parabiosis Shows the Path

To a younger body perhaps?

People spend millions if not billions worldwide to look younger, to feel younger, to be rejuvenated. Maybe I was different, because I always wanted to look older and for that reason stopped shaving when I was 21. But fact is that the business based on people wanting be younger is huge. Yet, very few want to look like children again or possess child-like features and almost nobody wants to be a baby once more; it’s young but not too young.

Mexican axolotls (also often called “walking fish”, although they are not fish, but amphibians, a kind of salamander) retain their external gills and other larval traits throughout their lives. Lack of the thyroid hormone thyroxin is responsible and if fed cattle or sheep thyroid or, better still, injected with a dose of thyroxin, the axolotl will respond with metamorphosis, during which the gills disappear, the eyes enlarge, and the bilaterally compressed tail (useful for swimming in the water) will turn into the more cylindrical of the terrestrial salamander. It really works: I have carried out such experiments at high school.

Many insects undergo an even more dramatic metamorphosis: think of the caterpillar that after 5 moults turns into a chrysalis (= pupa) and then into a butterfly or moth. Someone who has spent a considerable time of his research career on unravelling the hormonal control of insect moulting was Sir Vincent B. Wigglesworth of Cambridge University in England. (Incidentally, he was one of my PhD examiners and in the oral asked wonderfully fair questions.) Using the blood-sucking bug Rhodnius, he could show that the ratio between the moulting hormone, ecdysone (a steroid) and the juvenile hormone (a carotenoid) determines whether the moulted insect should be an adult or another larva, so-called instar.

When Prof. Wigglesworth experimentally fused the bodies of a 4 th instar individual with one that was one moult more advanced and, thus, ready to turn into an adult, the level of juvenile hormone in these parabiotically conjoined “Siamese twins” caused both to moult into yet another nymph. This meant he could prolong the juvenile life, but it did not mean, of course, that rejuvenation had occurred. However, using this same method of fusing the circulations of individuals of different ages through connecting them with each other, Prof. Wigglesworth went a step further and did succeed in rejuvenating the fully differentiated body of an adult Rhodnius bug. How did he achieve that; how could he do that?

If the adult body of a Rhodnius bug was connected with two fourth instar larvae (so-called nymphs), the circulating juvenile hormone together with some moulting hormone present in the body of this “bug complex” (consisting of the three conjoined individuals) caused the adult to moult once more, something that under natural conditions would be impossible as adult bugs can no longer moult. In this case the adult did moult and then obtained a body cuticle that was characteristic of an earlier, more youthful developmental stage: it became younger again! No doubt, for insects, fusion with a younger individual was the path that could return them to an earlier stage! Obviously, this approach is not feasible for humans, but hormone injections and hormonal potions are available to youth-craving folk. But do they work? I do not know, but one thing I do know: some people get very, very rich producing, recommending, and administering such treatment.

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2018.
Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com with appropriate and specific direction to the original content.

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