X-Message-Number: 26093
Date: Tue, 26 Apr 2005 21:07:19 -0700 (PDT)
From: Doug Skrecky <>
Subject: (-152 degree C) ultra-freezers

Theriogenology. 2005 Jan 1;63(1):72-82.
Cryopreservation of semen in the dog: use of ultra-freezers of -152
degrees C as a viable alternative to liquid nitrogen.
  This experimental work was carried out to validate the use of a -152
degrees C ultra-low temperature freezer to freeze and store canine
semen. The semen of three dogs was pooled and processed to obtain a final
dilution with a concentration of 100 x 10(6) spermatozoa/mL, glycerol at
5% and Equex at 0.5%. Then, four freezing protocols were tested to
evaluate the cryosurvival of sperm at 1, 7, 30, 60 and 120 days after
freezing: (I) semen was frozen and stored in liquid nitrogen; (II) semen
was frozen in liquid nitrogen and stored in the ultra-low freezer at
-152 degrees C; (III) semen was frozen in the vapour of liquid nitrogen
and stored in the ultra-low freezer at -152 degrees C; (IV) semen was
frozen and stored in the ultra-low freezer at -152 degrees C. Data were
statistically analyzed by repeated measures analysis of variance to
determine the effect of the freezing protocol and time on the sperm
characteristics assessed. The percentages of sperm motility and of
dead/live spermatozoa were similar throughout the experimental period,
with no significant differences (P < 0.05) to be observed between four
different freezing techniques tested. At 120 days after freezing, the
percentage of abnormal cells and the percentage of sperm cells with
abnormal acrosome were not significantly different between the freezing
techniques. Although the number of dogs used was slightly low, in vitro
results of this preliminary study showed that the use of ultra-freezers
at -152 degrees C to freeze and store canine semen could be a viable
alternative to liquid nitrogen.

Cryo Letters. 2002 May-Jun;23(3):167-72
Is sperm cryopreservation at -150 degree C a feasible alternative?
  A series of experiments was carried out to validate a -150 degree C
ultra-low temperature freezer for its possible use to properly freeze and
store semen. In the first part, crude sample handling was simulated to
see whether temperature of stored samples was maintained within a safe
range; also, the freezing point and latent heat of fusion plateau of a
semen extender were monitored. In the second part, buck semen was (i)
frozen in liquid nitrogen and stored in the ultra-low freezer, (ii)
frozen and stored in the ultra-low freezer, and (iii) frozen and stored
in liquid nitrogen, to compare sperm cryosurvival between freezing
methods. Both, frequent removal of samples and long opening of the
freezer door did not negatively affect stored sample temperature; latent
heat of fusion plateau was 5 minutes long. Semen stored either at -150
degree C or at -196 degree C cryosurvived similarly after 2 days and after
2 months of cryopreservation.

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