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Old 07-11-2017, 01:14 PM   #7
Carcharodon
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Location: Honolulu, HI

Join Date: Jul 2015
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Quote:
Originally Posted by danthescienceman View Post
great advice, it fits with what i was thinking



Did you notice if the size, or rather dimensions, affected things, i'd assume a larger specimen would freeze slower but is this noticeably different or did you chop them up first?

btw a few years ago i did some (admittedly basic) experiments on the affects of freeze thaw and found no noticeable degradation (but this was only checked on a gel as there was no long-read tech back then to worry about)
I actually hadn't noticed, but the fin-clips I collected were of different sizes (up to the size of a thumb-nail for adults, and maybe as small as half the area of a pinky-nail for neonates.

I goofed up and hadn't scored/diced the tissue, so when extracting DNA, I tend to cut and subsample from the margins of the tissue (following the logic of FlausFSU re: preservative soaking and efficiency).

Also, good to know (about the freezing experiment)!

In terms of freezing, it's hard to say. Often the samples went into a -80 C freezer directly. At that temperature, things freeze very quickly. But other times they had to sit in a cooler of water-ice, or were in a home freezer.

In short, I just don't know. But it is generally good practice to cut tissue into small chunks before placing them in any type of perservative.

I did have a colleague who put whole gobies into vials of RNA-Later. Usually when people take a whole animal, they make sure to open them up a bit so the preservative/fixative can soak through cell layers inside and out.

Another consideration (my apologies if you already know all of this, but it came to mind): when dealing with a dehydrating agent like ethanol (or even RNA-Later), if you have BIG tissue chunks, it's a good idea to let them sit in the preservative overnight, then replace the preservative with a fresh batch. This is because the water content of the sample can actually dilute the preservative somewhat significantly!

Last edited by Carcharodon; 07-11-2017 at 01:16 PM.
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