1.   And because embryonic cells are so primitive and so easily manipulated, he said, they might be made more compatible with my cells.

2.   Another occurs when embryonic cells are so committed to their eventual body parts that splitting into identical-twin embryos is no longer possible.

3.   Because of congressional and federal restrictions, what progress there is with the embryonic cells is taking place outside the country or in small, privately funded studies.

4.   Biologists at the National Institutes of Health have learned how to make the embryonic cells of a mouse generate structures very similar to the islets of the pancreas gland.

5.   Biologists at Geron, of Menlo Park, Calif. have succeeded in making human embryonic cells develop into heart muscle cells.

6.   A disadvantage is that such cells are hard to isolate and cannot be grown as easily in test tubes as embryonic cells.

7.   A patient could then be treated with tissues made from his or her own embryonic cells.

8.   A stem cell can also divide into two stem cells, as embryonic cells do when kept in lab culture.

9.   After two or more clusters of the embryonic cells are returned to the womb and the woman becomes pregnant, the remaining surplus cells are destroyed.

10.   But embryonic cells seem less antagonistic to the immune system than are ordinary cells.