X-Message-Number: 13333 From: "James J. Hughes" <> Subject: Glassy vitrification Date: Tue, 29 Feb 2000 18:35:34 -0500 http://helix.nature.com/nsu/000302/000302-6.html medicine : Bypass of glass HENRY GEE Transplantation surgery is all too often a matter of matching supply with demand. A key ingredient of the process is a reliable way of storing organs for transplant, so that organs not used immediately can be held 'on ice' for some later date. It is estimated that 30% of patients in need of arterial bypass surgery do not have suitable veins of their own that might be used. Frozen, donated blood vessels provide an alternative source. Between 1985 and 1992, approximately 3,000 frozen vein segments were used for arterial bypass. But conventional freezing has its problems. The formation of jagged ice crystals in an organ during the cooling process can damage organs or tissue. And thawed, damaged transplants do not last as long as fresh. So researchers are increasingly looking at ways to cool tissues and organs without ice forming. One option is 'vitrification': solidification in a kind of glassy state, in which ice crystals do not form. By perfusing a tissue with a cocktail of chemicals as it is carefully cooled, medical specimens can be kept unfrozen even at temperatures approaching minus 80 degrees Centigrade. In the latest Nature Biotechnology (March 2000) Michael J. Taylor and colleagues of Organ Recovery Systems Inc., Charleston, South Carolina, show how vitrified blood vessels perform much better in transplants than conventionally frozen vessels. The researchers tested their procedures on rabbit jugular veins. They looked at how these veins responded to various drugs and tests when fresh, vitrified or conventionally frozen. The headline figures are impressive: smooth-muscle contraction in the walls of vitrified vessels was more than 80% that of fresh, unfrozen vessels. Frozen vessels never reached 30%. Relaxation in response to natural and artificial muscle relaxants showed a similar pattern, with vitrified vessels outstripping frozen ones. The feasibility of ice-free cryopreservation by vitrification has been established for some biological systems, such as certain white blood cells, egg cells, the 'islet' cells of the pancreas that secrete insulin, and very early embryos. But in these cases, vitrification is probably no better than freezing because all these systems essentially consist of single cells, and most damage is done by ice forming in water in spaces outside cells. However, when applied to multicellular tissues -- such as a blood vessel -- in which viability depends on all component parts working together smoothly, vitrification offers dramatic improvements over freezing, as this new research demonstrates for the first time. Macmillan Magazines Ltd 2000 - NATURE NEWS SERVICE Send unsubscribe requests to: Archive located at: http://www.excelsior.org/transhuman_tech_list/ ----------------------- J. Hughes "On Saturday, my teachers, me, and all Changesurfer Radio my friends went to Never Never Land. www.changesurfer.com It was a short trip." Tristan Bock-Hughes, 3 Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=13333