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| Vol. 20, No. 18 |
| October 1, 1998 |
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A Conversation with Dr. Fuller Bazer...
Fuller W. Bazer, Ph.D., is director of the Institute of Biosciences and Technology of Texas A&M University and professor and O. D. Butler Chair of Animal Science at Texas A&M University and director of A&M's Center for Animal Biotechnology. Dr. Bazer came to Texas A&M in 1992 from the University of Florida, Gainesville, where he was professor of animal science and pediatrics. His major area of expertise is the bioscience and technology of animal reproduction. Dr. Bazer recently spoke with the Texas Medical Center News about his work.
TMCN: Pregnancy is a little more complicated than most people think, isn't it? FB: You'd think an event like getting a pregnancy started would have a common theme, but in fact each species has a little different way of going about it. It's very interesting to study these different kinds of pregnancies when they occur, and to see how the embryos interact with the maternal systems. Take the salmon swimming upstream. The female uses a lot of resources to produce her eggs, and there is no guarantee that any of them will be fertilized and produce offspring. For mammals, this kind of reproductive effort would be a waste of energy, so they have another sort of system for reproduction. In women - and nearly all mammals - there is a time to ovulate. In most primate species, there is more frequent mating during this period, and in the sub-primates this is the only time mating occurs. The chances of the egg being fertilized are maximized. TMCN: I know you've written about the interaction between the embryo and the mother. Am I phrasing that correctly? FB: Well the embryo actually has to "signal" the mother that she is indeed pregnant, and if the embryo doesn't send this signal then there is a mechanism to act on the ovarian structure producing progesterone to cause it to regress, and so the cycle starts all over again for another chance to become pregnant. In most mammals, pregnancy is the norm; not being pregnant is abnormal. This is true in some women, especially with women who are constantly with their babies, allowing the baby to suckle during the night because mother and infant sleep together. The constant lactation "shuts off" the hormone which would tell the brain to allow the cycle - end of lactating, ovulating, becoming pregnant - to begin again. This has been studied in detail in some small sects in this country - notably, the Hatterites in the northwest U.S. - and in certain nomadic African tribes. TMCN: What is the mechanism of the "signal" you mentioned? FB: In most primates, including the human, the ovarian cycle is independent of the uterus. So even after a hysterectomy, the ovarian cycle continues making estrogen and progesterone. But in the sub-primates, without a uterus the cycles cease. The hormone prostaglandyn F-2 alpha comes from the ovaries in primates and uterus in sub-primates and involves the ovaries and uterus so the embryo must produce a signal to protect the ova. You can see this hormonal signal pretty dramatically at the corner drug store. We can buy pregnancy test kits, and with a urine sample see that mom is indeed pregnant. The embryo has sent the signal through the blood stream to the ovary to tell mom that she is pregnant. This hormonal change begins to occur within seven days after the egg is fertilized. After this, the placenta forms and takes on a life of its own. TMCN: Your studies of animal reproduction have some pretty profound impacts on human health. FB: Let me just start a little more at the beginning. Assisted reproduction is now done pretty routinely in order to accelerate genetic improvement in livestock used for food and fiber as well as companion animals. We can now genetically modify animals for improved rates of survival, for desired production rates, increased resistance to parasites and disease and increased beauty and performance. We have gained a great deal of information through this work which will be of great benefit, I think - not just for greater efficiency in livestock production but for better reproductive health for humans. For example, we see in the ruminants - sheep, cows, goats - that the embryos produce an interferon, and you remember how dramatically this was used in cancer treatment. Now we see that this sheep interferon may be very useful in multiple sclerosis, a viral disease. It appears to block the virus from replicating itself in the nerve cells. We will begin clinical trials in California in the fall. In another example, sheep have a disease similar to pediatric AIDS, and in lambs we can totally block that disease, but treatment has to be done very early in development. If we begin therapy later in a lamb's infancy, the anti-viral strategies just can't make headway. Of course there has been news about zenotransplants, where organs from primates and ruminants are transplanted into humans, usually as a life-saving measure. The transgenic pigs developed at Texas A&M by Dr. Jorge Piedrahita are very promising in the area of pharmaceuticals, and if the work continues going well in modifying some genes in the pig, there may well be advances in heart, liver and kidney transplantation. TMCN: It's an area of excitement and controversy, isn't it? FB: It's a very exciting time. We can read the genome, and we are beginning to "cut and paste." The next step will be the ability to turn certain genes on and off. Certainly we are entering an area where there are moral questions. The cloning of Dolly the sheep by Dr. Ian Wilmut in Scotland last year brought a sudden - and to some people, a troubling - reality to the situation. Interestingly, two months ago 50 lab mice were cloned at a laboratory in Hawaii, and it was not nearly the news story of Dolly. Perhaps we quickly become desensitized. Because the "tools" that we use in cellular and molecular biotechnologies allow us to understand and alter the very blueprint of life, there are hopes and fears. Clearly, if you can alter an enzyme in a fruit or vegetable so that decay is slowed, that's good for the farmer and consumer. These and other tools in biotechnology have helped us predict, treat and even eliminate diseases as well as work towards an improved food supply. The first embryo transfers were done in 1894, so we're not in all that new an area really. Certainly, during the last 20 years there has been much serious thought given to these issues we're talking about. I spoke at a conference recently, and in the audience there were several religious leaders. It was a very interesting discussion, and what we all agreed on was that these questions need the involvement of everyone. - ROGER WIDMEYER
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