Scientists in Britain have shown that stem cells extracted from human embryos can develop in the laboratory into the early forms of cells that become eggs or sperm, raising the possibility that one day eggs and sperm needed for infertility treatment could be grown in a dish.
Preliminary experiments also suggest that scientists may eventually be able to use the technique to create a supply of eggs for cloning.
But the more immediate benefit of the work could be a better understanding why some men and women do not create their own sperm or eggs and whether toxic chemicals in the environment may play a role, one of the researchers said before the start of the annual conference of the European Society of Human Reproduction and Embryology. The findings were scheduled to be presented yesterday.
"It may allow us to investigate the very earliest processes of how a human [ovary and testis] develops," said Harry Moore, a professor of reproductive and developmental medicine at Sheffield University in England.
Many scientists believe that chemical pollutants, such as pesticides, that mimic the action of hormones, might interfere with human development at the stage where eggs and sperm -- called germ cells -- are forming and that this disruption may cause birth abnormalities, infertility and possibly cancer.
"By developing suitable tests with embryonic stem cells as they differentiate into germ cells we can investigate the action of these chemicals in the laboratory," Moore said.
Stem cells are the master cells of the body, appearing when embryos are just a few days old and developing into every type of cell and tissue in the body, including sperm and eggs.
Scientists can study the stem cells by extracting them from the embryo. If the researchers create the embryo by cloning a cell from a patient, any resulting cells would be a genetic match to the patient.
The cloning technique, called cell nuclear replacement, involves emptying out the genetic material in an egg and replacing it with the genetic material of another cell, say a skin cell taken from an adult. Instead of being fertilized by sperm, the new reconstituted egg is then bathed in chemical nutrients and electrocuted to shock it into dividing. It then evolves into an embryo, from which stem cells can be extracted.
"We would need to prove that sperm or eggs produced in this way were safe before we could contemplate using them to treat patients," Moore said.
Other experts said the advance from the University of Sheffield could also raise some ethical issues.
"It opens new and challenging possibilities because the technique can be used to generate eggs from a man's [adult] cells, gay couples could have children genetically related to both,'' said Anna Smajdor, a medical ethicist at Imperial College in London.
The military is to begin conscripting civilians next year, Cambodian Prime Minister Hun Manet said yesterday, citing rising tensions with Thailand as the reason for activating a long-dormant mandatory enlistment law. The Cambodian parliament in 2006 approved a law that would require all Cambodians aged 18 to 30 to serve in the military for 18 months, although it has never been enforced. Relations with Thailand have been tense since May, when a long-standing territorial dispute boiled over into cross-border clashes, killing one Cambodian soldier. “This episode of confrontation is a lesson for us and is an opportunity for us to review, assess and
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