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Priyesh gupta

· started a discussion

· 1 Months ago

Answer should be option a (Question:117906.2)

Blood vessels are made by human embryonic cells

Question:
DIRECTIONS: In the following question you have brief passages with questions following each passage. Read the passage carefully and choose best answer to each question out of the four alternatives.


Scientists seeking new ways to repair damaged arteries and ailing hearts have coaxed stem cells from a human embryo into forming tiny blood vessels. It's the first time human embryonic stem cells have been nurtured to the point where they will organie into blood vessels that could nourish the body, according to Robert Langer, leader of a laboratory team at the Massachusetts Institute of Technology. But it isn't likely to be the last, as scientists pursue research into uses for stem cells despite debate over the ethics of using the cells. The new development was reported in. the online issue of the proceedings of the National Academy of Sciences. Dr. John Gearhart of the Johns Hopkins School of Medicine said the research was a "nice illustration" of how stem cells can serve as a source of various types of cells, in this case for blood vessels. "I think this is terrific", said Gearhart, who was not part of the research team. "It's another good example of the isolation of an important cell type from -human embryonic stem cells. These are the kinds of papers we are going to see a lot of', Gearhart added. Langer said the work showed that endothelial cells could be made from human embryonic stem cells. Endothelial cells line veins, arteries and lymph tissues. They are key to the structures that carry blood throughout the body. He said that if the technique was refilled, scientists could eventually be able to make in the laboratory blood vessels that could be used to replace diseased arteries in the body. "There are thousands of operations a year now where doctors take vessels from one part of the body and transplant them to another", said Langer. Eventually, he said, such vessels might be made outside the body from embryonic stem cells. Langer said endothelial cells also might be used to restore circulation to the cells damaged by the heart attacks. He said the processed stem cells may be able to re-establish blood flow to heart's failing due to blocked arteries. The research was conducted under a private grant, but Langer said that the cell culture used is one of 61 worldwide that have been approved by the National Institute of Health for federally funded research. The use of embryonic stem cells is controversial because extracting the cells kills a living human embryo. President Bush last summer decided that federal funding would be permitted only for stem cell cultures that already existed and were made from embryos that were to be discarded by fertility clinics. The aim was to prevent further killing for research purposes of other human embryos. Langer said his lab will seek federal money to continue research using the same stem cell cultures, which were obtained from the Rambam Medical Center in Haifa, Israel. Embryonic stem cells are the ancestral cells of every cell in the body. In a developing embryo, they transform into cells that make up the organs, bone, skin and other tissues. Researchers hope to direct the transformation of such cells to treat ailing hearts, livers, brains and other organs. Langer said his team cultured the cells in such a way that they were allowed to develop into the various types of cells that are precursors to mature tissue. From this colony, the researchers extracted cells that were following a linage that would lead to mature endothelial cells. These were further cultured and some eventually formed primitive vascular structures.

Endothelial cells are said to have all of the following qualities expect that:

Options:
A) They are used to make blood vessels
B) They carry blood throughout the body
C) They line veins, arteries and lymph tissues
D) They are useful in restoring circulation to the damaged cell
Solution:
Ans: (d)

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