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. Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=9954