MicroSort Results



By Garry Kranz

Small Times Correspondent

Aug. 21, 2001 – About 210 tots owe their existence and even their genders to small tech.

Since 1995, a fertility clinic has been using a machine that sorts sperm into separate boys’ and girls’ schools — mostly for parents who pine for daughters. The procedure nearly doubles the odds they will conceive a female offspring, the clinic says.

Researchers at the Fairfax, Va.-based Genetics and IVF Institute (GIVF) say the sex-sorting technique increases the percentage of female embryos produced through in vitro fertilization to about 90 percent, up from an average of about 50 percent. The clinic is thought to be the first to develop sex-sorting procedures for use in humans.

The process, which the clinic calls MicroSort, has resulted in more than 300 pregnancies and about 210 live births of healthy children. Scientists at the institute claim the technique could make it possible for parents to dictate the gender of their children prior to conception. By dramatically boosting the odds, researchers claim, parents can achieve a well-balanced family – the ability to add daughters to a household of boys, for instance.

The MicroSort technique uses a fluorescent dye that latches on to individual spermatozoa and identifies its gender as male or female, based on the fact that X chromosome sperm cells contain 2.8 percent more DNA than spermatozoa with a Y chromosome. A sorting device using flow cytometry then is used to segregate sperm cells that carry the Y chromosome, which produces males, from sperm cells that carry the female-producing X chromosome.

In the MicroSort system, sorting the sperm produces enriched samples in which about 90 percent of the cells have a female-bearing X chromosome, MicroSort researchers have reported. Parents wishing to spawn boys, however, do not immediately gain the same odds. When Y-bearing sperm were targeted for sorting, 73 percent of the sorted spermatozoa were found to contain a Y chromosome. (MicroSort is 91% successful in conceiving girl babies and 76% successful in conceiving boy babies.)

Once the sperm have been distinguished and sorted, doctors are able to perform artificial insemination.

[Some] medical experts are curious but wary. They cite concerns about [the] flow cytometry [used by MicroSort], which uses a high-energy laser beam that creates ionizing radiation. That radiation, along with the fluorescent dye that is attached to DNA, raises fears that the procedure could cause genetic damage.

The concept as devised by the GIVF involves allowing individually stained sperm to be subject to a high-powered microscopic laser, said Dr. E. Scott Sills, a reproductive physician familiar with the MicroSort technology.

"The laser is targeted to each individual sperm as it passes through a gated channel. These microscopic droplets are gated such that there’s only one sperm cell per droplet. It’s precisely regulated so one droplet is emitted per interval of time," said Sills, associate medical director with Georgia Reproductive Specialists, Sills said the laser emits a wavelength of 351 nanometers to 364 nanometers, which creates enough ionizing radiation to potentially damage DNA.

"These two aspects – the dye and subjecting sperm cell to laser energy – are problematic. Any cell-sorting technique using that method should be carefully studied to make sure there are no deleterious effects."






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