Posts Tagged ‘Assisted Reproduction Techniques’

Embryogenesis 101 – Aging Ova

// September 9th, 2009 // 3 Comments » // Sex and Reproduction

About 15% of couples trying to conceive experience infertility.

Possible causes are faulty ovulation, blocked tubes, old ova, swimmers which don’t swim, and erectile dysfuntion, to name just a few. Possible solutions run the full gambit from old wives tales to scientific technologies, and in the spirit of the Schooner I will focus exclusively on the latter (although most tales have a touch of truth to them).

Given that this topic is bigger than the big blue sea and just as fascinating, I’m going to post in bite-sized chunks once a week on what for a while will become Reproduction Wednesday. Before we go any further, this topic is not about me, I’m not pregnant, nor have any plans to that effect, so rest easy! With that out of the way, here’s the first installment of Reproduction Wednesday, Schooner style.

Old Ova, New Dicks Tricks

When a female enters the world, she has already stashed away all the ova she will ever have. They don’t keep replicating, they don’t spring up from nowhere, they’re already there. So by the time you’re thirty, your ova are thirty, and that’s really old for a cell. Almost all your other cells keep replicating throughout life, so on average your rib muscles are 15 years old, and the lining of your gut a mere 5 days (reference). But your ova keep getting older.

Old eggs are bad for fertility. DNA damage builds up, the mitochondria start losing their edge, and proteins in the cytoplasm get dodgy. This is important not only for the egg itself, but also the embryo. For the first three days of it’s life, an embryo doubles in cells but doesn’t change in size, it lives solely off the stuff already in the egg – like a packed lunch. Until the 16 or 32 cell stage, it is still the same size as an unfertilsed egg (reference), although there ain’t no cell in the human body bigger than an egg (to my knowledge.) Here’s a fertilised egg, splitting into multiple cells.

morula

Aging ova is not the end of the world, there is a procedure that gives them a face-lift. They’ll look and feel years younger with a Cytoplasmic Transfer!

It’s easy! Just take the nucleus from an old egg, and put it into a young egg that has had it’s nucleus removed. Hey presto – genetic material from a reproductively challenged woman, proteins from a donor, put it back into the body for implantation! Here it is in a thousand words.

cytoplasmic transfer

It’s the fountain of youth… or is it? This article says that by the time the nucleus is harvested, it is already too late. New proteins are needed while the egg is ripening, once the egg has been sent out into the world that ship has sailed. The jury is still out on that.

Either way, it creates an interesting scenerio… the DNA of one person, the proteins and mitochondrial DNA of another. It sounds scary, almost Frankensteinean to me. There are so many weird and wonderful things in the world of reproduction and embryogenesis, a face-lift for an egg is just the tip of the iceberg.






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