X-Message-Number: 5674
From:  (DJ du Plessis)
Newsgroups: sci.cryonics
Subject: Rat hearts - Pretoria
Date: Thu, 25 Jan 1996 07:42:36 GMT
Message-ID: <4e7c0g$>

Some  information:

The experimentation on cryopreservation at Pretoria got out
prematurely, and was reported by the popular media with some truths,
some half-truths and some lies.

The heart was used as the model solely because it is an organ that the
people involved in the experimentation are knowledgeable about from a
medical point of view. The rat heart was used because it is easy and
cheap to use for experimentation.

In summary what was done:
(a) Beating rat heart excised and perfused on a Langendorff system
within 2 minutes after removal
(b) The beating heart (rate=180/min) was perfused and cooled to
approximately 4 degrees Centigrade over 15 minutes (when it was
obviously not beating anymore but still perfused)
(c) The heart was immersed directly into a liquid nitrogen bath for 2
to 5 minutes without any surrounding container
(d) Rewarming up to 37 degrees Centigrade took approximately 15
minutes and reperfusion was started at appproximately zero degrees
(e) The rat hearts beat at the same rate afterwards, as they did
initially on the Langendorff system
(f) The beating hearts were kept on the Langendorff system for
approximately 40 minutes, during which no decrease in the heart rate
was seen.
(g) The fact that the hearts recovered to the extent that they did, is
seen by us to be proof of cellular viability - otherwise the heart
muscle would not have functioned at all, or very poorly.

A short article was sent to Cryobiology in December 1995, and it was
rejected for publication in January 1996 after peer review on the
grounds that the information was incomplete, which I agree with. I do
however, regret the outright rejection, as we would have liked other
researchers to take on different aspects of the matter as we do not
have the capability or resources to investigate all the different
avenues. We do however intend to try again !!

Experimentation is still ongoing on the rat hearts, and we are busy
with pig hearts at this stage as well.

Some other relevant/irrelevant aspects:
1. The woman mentioned in the public media is Ms Olga Visser whom is a
clinical perfusionist in Cardiothoracic Surgery
2. Experimantation on other organ (excluding hearts) are still in
pilot study stages.
3. Financially speaking (in response to a comment made) we are indeed
not well of, but the system in South Africa does not function on
research grants in same way as in many western countries. Therefore we
are always glad about any financial assistance, but not dependant on
it.

Professor Dirk J du Plessis
Head - Cardiothoracic Surgery
University of Pretoria
South Africa


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