X-Message-Number: 15998
Date: Wed, 4 Apr 2001 05:18:34 -0400 (EDT)
From: Ben Best <>
Subject: Cryopreservation of Sperm, Embryos and Hippocampal Slices

On Tue, 27 Mar 2001, Rick Potvin wrote:

> I don't understand why hippocampal slices are more difficult to freeze and 
> thaw than sperm and embryos. Presumably if you take a slice of tissue you 
> CAN freeze and thaw it successful -- witness sperm and embryos. The problem 
> arises with larger organs. 

    Sperm are not tissues, they are single cells. Cryoprotectant diffuses
much more easily into single cells than into tissues, although diffusion
probably isn't the only issue. Embryos are not much more than single-cells
-- less than 8 cells. (The best survival rates are for embryos consisting
of 2-4 cells.) Thus they are barely what can be called a tissue. A 
hippocampal slice is a true tissue, probably millions of cells, although
I am just guessing at a number. 

> So a hippocampal slice, presumably, would be LIKE sperm and embryos in 
> many ways because the "slice" is thin and the cells are easier to deal 
> with-- no ice crushing going on, presumably. Yet this hippocampal slice 
> is seen as a much bigger deal than sperm. Why? 

    Just because a hippocampal slice is called a "slice" doesn't mean 
that it is razor-thin such as to be only a few cells thick. These slices
are many cells thick. Again, I am just making a wild guess, but I would 
guess that the thickness of the slice is at least many thousands of cells
thick. 

    Hippocampal slices are important for another reason: they are a
part of your brain. And not just any part, one of the most ischemic
sensitive parts and a part that plays a crucial role in the formation
of memories. If we want cryonics to work -- to preserve our identity --
we would do well to find the cryoprotectants and protocols that best 
preserve our brains. However, commercial incentives for development
of cryoprotectants and protocols for preserving brains are far less
than for other tissues. It is primarily cryonicists who are interested
in this technology. So if someone is to pay for the research, it must
be cryonicists. 

> When was sperm first successfully frozen and thawed? An embryo that was 
> frozen was successful thawed and brought to term in a pregancy in 1984. 
> Where is THAT guy today? Where are ALL the "frozen embryo" kids and adults 
> today? The oldest is 16. Is he a potential candidate for cryonics sign-up? 
> You'd THINK he WOULD be wouldn't you? 

    Sperm was first successfully cryopreserved with glycerol in 1949. Today,
most cattle come from bull sperm that was once at liquid nitrogen temperature.
However, even sperm is not so easy to cryopreserve as you might imagine. The
process is successful with bulls because bull sperm can be produced (so to
speak) in great quantities. Cool enough bull sperm and some of them will
be viable. For humans, it is not so easy. Only about 10% of human donors 
have sperm that can be cryopreserved (or such was the case 2 years ago when
I last heard anything about the matter). 

    The number of human embryos now in storage at the liquid nitrogen 
temperature worldwide is currently in excess of a million. There are 
tens of thousands of children who were once cryopreserved embryos 
(vitrified, not frozen). We don't get many cryonics sign-ups from 
the 17 and under age group. 

> But this thread deals just with the technical issue of why hippocampus 
> slices are more difficult to deal with than sperm and embryos. If I knew 
> that, and if I had extra money, I'd be more likely to know whether I ought 
> to contribute to Best's HCSP or not. 

    I think I have answered your question, but if it was not to your 
satisfaction, you are welcome to ask more questions. I have more 
information on vitrification on my website at:

     http://www.benbest.com/cryonics/vitrify.html

    I'm not sure what you mean by "extra money". If you felt that this 
research was really important to your survival -- and if you were convinced 
that you could not survive by counting on others to make sufficient 
contributions to save you -- I think you could find the money if you 
looked closely at how much you fritter-away on nonessentials. But this
is a "public goods" problem, and it is easy to rely on the belief that
others will contribute sufficient money. 

    It is not for me to moralize about this matter. I think this 
research is vitally important, which is why I have contributed to it more
than anyone else. I only wish I were in a position now to contribute more. 
If you don't think contributing to this research will affect your
survival, then you will find more important uses for your money. Again, that 
is your choice, and it is not business what you do with your money. 

    For those who do wish to contribute, please send money to:

             The Institute for Neural Cryobiology
             238 Davenport Road #240
             Toronto, Ontario
             M5R 1J6  CANADA

------------------------------------------------------
              -- Ben Best, President
              The Institute for Neural Cryobiology
              http://www.neurocryo.org/

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