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In the freezing procedure a womans eggs are frozen and saved for pregnancy at a later dateabout half of a 30-year-old womans eggs are chromosomally normal but by age 44 this figure drops to 2 percent, according to Grifo. Thats why he advises women interested in egg freezing to do so before age 38

The procedure was developed in the 1980s for women with cancer, so they could preserve their eggs before losing fertility fromchemotherapy.Egg extraction costs $10,000, storing them is about $1,000 per year and using them adds another $5,000,FreezingOnethree hoursMedical professionals evaluate the health of harvested eggs in the lab. To prepare the healthy ones for freezing, they remove the liquid using chemical solvents in a process called vitrification. Ice crystals can damage the cytoskeleton of the egg, so removing water is key to their preservation. Eggs are then loaded for storage intocryo-vialsand plunged into liquid nitrogen to flash freeze them within seconds.7. FertilizationMonths to years laterAll of the eggs are thawed, evaluated for their viability and injected with sperm. The best embryo candidate (the one dividing most successfully) is injected into the uterus with a catheter. Grifo says about 90 percent of eggs survive freezing, about 70 percent are successfully fertilized and about half become babies. Any leftover unused eggs can be refrozen for another pregnancy.Possible side effects: psychological distress if the procedure is unsuccessful

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C. J. GUERIN, MRC TOXICOLOGY UNIT/SCIENCE SOURCEA tightly packed assembly of cells including astrocytes (green) forms the barrier between blood vessels (black) and neurons (red).

A sound way to clean up the brainMicrobubbles injected into the blood vibrate under ultrasound, temporarily forcing cellslining the blood-brain barrier apart. This may allow amyloid-fighting antibodies to slip intobrain tissue (shown) or rouse cells that clean up the protein.

T cells attacking a tumor cell.16