I have some frozen semen which was collected & frozen in 1996. The straws were taken to a new location for storage in 2000. I recently wanted to collect a straw for evaluation and it took the facility a week to find it, after numerous phone calls which weren't returned and a general lack of concern on their part. When they did, a straw was missing.
When I asked where it was I was told "it probably exploded and pieces of it were probably sitting at the bottom of the storage container" and that this "is not uncommon for frozen semen where the air bubble has a pressure buffering role" and that I must "accept this explanation of pros and cons of storing genetic material".
Is this fact and can I expect my straws to explode one by one? Can semen that has been frozen for nearly 10 yrs suddenly 'explode'?
This is irreplaceable semen so I am pretty concerned.
If the semen was frozen by knowledgeable personnel, with an air bubble in the middle, then the chances of it exploding are minimal. HOWEVER... if the air bubble (in a 5-ml straw) is at the top end, that is suggestive that (a) the semen was not frozen by knowledgeable personnel; or (b) that it has thawed out at some point and been refrozen - typically because of a tank being allowed to go dry and then being refilled with liquid nitrogen. This air bubble floating to the top is one of the benefits that we see with the 5-ml straw over the half-ml straw, wherein the air bubble will not float to the top in the case of inadvertent thawing and refreezing (so with the half-ml straw you don't know it's happened).
The reason the straw explodes in the above cases is that nitrogen seeps past the sealant at the end, and mixes with the air in the bubble, but when thawed, nitrogen expands 700 times faster than air, hence the "explosion". If the bubble is in the middle however, the nitrogen cannot get to the bubble, and therefore does not enter the straw, so no "explosion".
What I would suggest as a starting point for you would be - if the straws are the larger 5-ml "macro" straws - to see where the air bubble is located, and if it is at the top end to consider that you may have an issue related to one of the two causes I mention above.
If you have half-ml straws, you don't have that option, but I would suggest confirming motility post-thaw in case they have been thawed and refrozen.
If the air bubble is still happily resident in the center of the straw, then the chances of an "explosion" are minimal.
What may be an issue, is the possibility that the straws have been banged around, causing micro-fractures, which can separate when being thawed, causing breakage, or possibly even prior to thawing - when stored in the nitrogen and frozen, the straws can become brittle, so rough manipulation can break them.
FWIW - I have never had a straw break by itself in the storage tank...
Thank you very much, Jos, for the great info. It was frozen by one of the top facilities in North America and they are the 5ml straws.
I have a suspicion that they have been manhandled somewhat as the place where they are stored now does not seem very professional. However, I have no proof and they are telling me it's my problem - like it or lump it.
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