X-Message-Number: 9954
Date: Mon, 29 Jun 1998 20:47:44 -0400
From: Jan Coetzee <>
Subject: Interesting

Freeze-dried mouse sperm fertilizes eggs

NEW YORK, Jun 29 (Reuters) -- Though technically dead, reconstituted
freeze-dried mouse
sperm can still be used to fertilize eggs -- and the process results in
normal offspring, according
to a groundbreaking study in the July issue of Nature Biotechnology.

The study is the first confirmed and replicated research showing that
freeze-dried sperm can
produce normal offspring, write the authors, Dr. Teruhiko Wakayama of
the University of Hawaii
School of Medicine in Honolulu, and Dr. Ryuzo Yanagimachi of the
University of Tokyo in
Japan.

Sperm from many species -- including humans and cows -- can be frozen
and stored in liquid
nitrogen and remain viable. But this technique, called cryopreservation,
is expensive and does
not work well for other species, including mice. Since many scientists
use genetically engineered
mice and other animals in their research, they need a reliable way to
store, and ship, sperm from
these animals.

Freeze-drying could prove a reliable, less costly, and more convenient
alternative to
cryopreservation, Dr. Robin Lovell-Badge of MRC National Institute for
Medical Research in
London, UK, writes in an editorial accompanying the study. In addition
to facilitating research,
the technique might also prove useful in wildlife conservation,
Lovell-Badge writes.

In a series of trials, Wakayama and Yanagimachi freeze-dried mouse sperm
and stored it at room
temperature for up to 3 months. The researchers then tested the sperm,
and found they were dead
"in the conventional sense."

After rehydrating the sperm with distilled water, the researchers used a
technique -- called
intracytoplasmic sperm injection -- to inject the sperm into eggs
removed from female mice. The
technique involves separating the tails from the sperm and injecting the
heads -- the parts that
contain the genetic material -- into the eggs.

"The majority of fertilized eggs developed... in vitro and many
developed into normal offspring
when transferred to foster mothers," Wakayama and Yanagimachi report.
"All offspring grew
normally."

Later, when the researchers mated a number of the male and female
offspring, they found all were
fertile, and had normal-sized litters.

The freeze-drying method will assist research by making the shipping of
strains of mice (or other
species) around the world "much easier," writes Lovell-Badge. Rather
than deal with the
problems shipping live animals, "it should be possible to simply put the
freeze-dried sperm in an
envelope and mail them." SOURCE: Nature Biotechnology 1998;16: 618-619,
639-641.

J.C.

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