[escepticos] Transgenicos for you (largo)

[Josep Catala <jcatala@...>]

Toda vez que hace muuuuucho tiempo que no hablo de transgénicos, me
vais a permitir que largue a la lista unos 19Kb sobre el tema. Viene a ser
algo así como un resumen de lo más importante acontecido en el 2000.
La fuente de información, inmejorable.... (aunque quizás un pelín -sólo
un pelín- excesivamente optimista).

Saludos.

Josep Català
________________Los 19 Kb anunciados____________

> U.S. Food and Drug Administration
> FDA Consumer magazine
> January-February 2001
> Table of Contents
>
> A New Kind of Fish Story: The Coming of Biotech Animals
> By Carol Lewis
>
> Potatoes with built-in insecticide. Rice with extra vitamin A. Decaf coffee
> beans fresh off the tree. Just when Americans have begun to digest the idea
> of custom-built crops, along comes another major advance in biotechnology
> that could make an even bigger splash onto the dinner plate: genetically
> engineered fish.
>
> Using the same type of gene transfer techniques that give plants new, more
> desirable traits, scientists have created a genetically engineered variety
> of
> Atlantic salmon that grows to market weight in about 18 months, compared to
> the 24 to 30 months that it normally takes for a fish to reach that size.
> For
> fish farmers, raising these so-called transgenic fish could be faster and
> cheaper because it takes less feed and about half the time to produce a crop
> they can send to market.
>
> Transgenic animals are just another class of products developed through
> biotechnology that, it is hoped, will give renewed energy to the decades-old
> Green Revolution. Transgenic technology promises more and better crops and
> food animals to feed a continuously growing world population. Genetically
> engineered plant crops, such as corn and soybeans, have been on the market
> for several years. Now, genetically engineered animals may soon begin to
> make
> their way through the regulatory net, and ultimately to the dinner
> table--possibly starting with fast-growing fish that the sponsor promises
> will begin a "Blue Revolution."
>
> The potential benefits of transgenic animals, however, do not stop at food
> production. Scientists created the first transgenic animals to advance basic
> biomedical research, genetically modifying lab rats, mice, rabbits, and
> monkeys to give them characteristics that mimic human diseases. These
> research resources, for example, rapidly advanced the understanding of
> oncogenes--genes that have gone awry and are responsible for causing
> cancers.
> Moreover, researchers now seek ways to genetically modify the organs of
> animals, such as pigs, for possible transplantation into humans.
>
> And finally, transgenics can turn animals, such as cows, sheep and goats,
> into pharmaceutical factories that produce in their milk protein-based drugs
> such as alpha antitrypsin, a protein that can be used to treat cystic
> fibrosis.
>
> Despite these benefits, genetic engineering of animals has met with some of
> the same resistance already aimed at designer crops. Critics cite ecological
> concerns, ethical objections and food-safety issues.
>
> But no matter how transgenics is applied, the Food and Drug Administration
> will play a key role in regulating the products resulting from this rapidly
> emerging genetic technology. This means that any drug or biologic created
> through transgenic techniques will need to undergo the same FDA scrutiny as
> any other treatment that a company wants to market, including clinical
> trials
> that demonstrate safety and effectiveness. And while it's still too soon to
> tell how quickly foods derived from transgenic animals will move to the
> market, FDA has already begun to focus on how it will ensure that they meet
> the same safety standards as traditional foods.
>
> Making a Transgenic Animal
> Making a transgenic animal is deceptively simple, especially when compared
> to
> traditional breeding approaches. In traditional breeding, when farmers or
> breeders want to introduce some new characteristic into a type of animal,
> they must find an individual animal that carries the desired trait. They
> then
> mate the individual to try to create a new line of animals sharing the genes
> that express the desired quality.
>
> With genetic engineering, scientists possess the tools to isolate and
> manipulate single genes in the laboratory. In recent years, researchers have
> learned to insert single genes into the fertilized eggs of animals in such a
> way that the new gene is turned on in the resulting adult. (See "Creating A
> New Variety Of Fish".)
>
> First the scientist isolates the gene that conveys a particular trait of
> interest-disease resistance or faster growth, for example. Then a molecular
> vehicle is created that will carry the gene into the nucleus of the cell and
> permanently integrate it into the chromosome. The entire construct--the
> transplanted gene, called a transgene, and its transport vehicle--might be
> physically injected into a fertilized egg using a glass needle viewed under
> a
> microscope. Other approaches use disabled viruses to inject the construct
> into the cell. If the egg survives and begins to grow and divide, then the
> potential embryo is implanted into a surrogate mother. Of the offspring that
> make it to birth, only a very small number will carry the new gene
> integrated
> in such a way that it actually functions.
>
> But when it works, the result is a new individual of a variety of animal
> with
> a characteristic never before seen. The individual animal can then be
> multiplied by conventional breeding. The resulting animal may be enormously
> valuable. Inserting a single gene into an animal, that then manufactures a
> rare protein in its milk, could produce a drug that is worth many millions
> of
> dollars an ounce. The Genzyme Transgenics Corporation of Cambridge, Mass.,
> for example, has created a goat that carries the gene for antithrombin III,
> a
> blood protein that can prevent blood clotting in people. The company
> purifies
> the protein out of the goat's milk.
>
> But even though the medical applications of transgenics remain intriguing,
> the animal health and food production applications seem to be generating
> most
> of the new excitement and considerable concern.
>
> Foods Derived from Transgenic Animals
> Taking their lead from the scientists who created new genetically engineered
> crops that, for example, resist insects without the need for pesticide
> spraying, researchers involved in the production of food animals began to
> think about how they could use genetic modifications to improve the
> production or quality of their products.
>
> Typically, says John Matheson, a senior review scientist in FDA's Center for
> Veterinary Medicine (CVM), "Researchers start with the protein they want to
> add and work backwards." It's the protein that the transplanted gene encodes
> that actually gives the animal a new trait.
>
> The best example so far of the transgenic strategy in food animals, and its
> success, is the faster-growing salmon. The science behind the so-called
> supersalmon was discovered by accident 20 years ago when Choy Hew, PhD, then
> a researcher at Memorial University of Newfoundland in Canada, accidentally
> froze a tank filled with a particular species of flounder. When the tank was
> thawed out, the flounder were still alive. Initially, no one knew how they
> survived. This species, it turns out, has a gene that produces a protein
> that
> works like the antifreeze in a car's radiator. This antifreeze protein is
> found in many types of polar fish that must survive extremely cold
> conditions.
>
> Researchers isolated and copied the part of the flounder DNA that works like
> a genetic switch to turn on the production of the antifreeze protein.
> Normally, this genetic switch is only turned on when the fish is exposed to
> cold.
>
> Hew and his colleagues then attached the flounder's genetic on-switch to a
> previously isolated gene from Chinook salmon that produces a
> growth-stimulating hormone. Using transgenic techniques, they inserted the
> new combination--the flounder on-switch with the salmon growth hormone
> gene--into fertilized salmon eggs. In the resulting salmon, the flounder's
> genetic switch appears to stay turned on, producing a continuous supply of
> salmon growth hormone that then accelerates the fish's development. While
> the
> resulting fish do not seem to reach a mature size that is larger than
> conventional salmon, they grow much faster.
>
> Breeding transgenic varieties is an effective way to create an animal with a
> new characteristic, but large mammals-cows, pigs and goats-don't multiply as
> plentifully or as rapidly as fish. Several research teams have turned to
> cloning--as in Dolly, the sheep--as a way to expand the herd of transgenic
> animals. This approach combines two cutting-edge techniques. First, a
> transgenic animal with the desired characteristics is created. Then, cloning
> techniques are used to create replicas of the transgenic animal. Using a
> transgenic approach just makes it easier to get the desired genetic
> characteristics in the animal, which is then cloned to produce a core
> breeding herd.
>
> Transgenic Critics
> Useful as it may be, animal biotechnology won't go forward without
> objections. For all the promise that industry sees in the dawning era of
> genetically engineered animals, others-including animal rights activists,
> environmentalists, and consumers-see problems.
>
> The concern about genetically engineered foods, says Carol Tucker Foreman,
> director of the Food Policy Institute at the Consumer Federation of America
> (CFA) in Washington, D.C., "is in marked contrast to the public acceptance
> of
> genetically engineered drugs. When faced with serious illness, most people
> are willing to take risks to combat a disease." Food is different, she says,
> since it is so basic, both physically and emotionally. "It's not surprising
> that consumers are extremely averse to any food-related risk, especially if
> the risk is perceived as imposed by someone else, beyond individual control
> and without any countervailing benefit." Consumers, she says, are concerned
> mostly about such potential health problems as allergic reactions and
> antibiotic resistance.
>
> But FDA Commissioner Jane E. Henney, MD, points out that foods produced
> using
> bioengineering processes are evaluated to make sure they are not more likely
> to cause allergies. "Under the law and FDA's biotech food policy," she says,
> "companies must tell consumers on the food label when a product includes a
> gene from one of the common allergy-causing foods, unless it can show that
> the protein produced by the added gene does not make the food cause
> allergies."
>
> But Art Jaeger believes, "It's not just about dangerous foods--it's also a
> matter of consumer choice." The assistant director for CFA and advocate for
> mandatory labeling says consumers need to know when a food is genetically
> altered because many have religious or cultural convictions that would
> preclude them from selecting foods produced through transgenic technology.
> Jaeger says that his organization wants tougher regulations and feels that
> all information on the safety of biotechnology applications should be made
> publicly available.
>
> And then there are environmental concerns. Purdue University animal
> scientist
> Bill Muir and biologist Rick Howard conducted a study funded by USDA on
> genetically engineered fish, which led them to warn of possible risks from
> transgenic fish escaping into nature. They worry that transgenic fish
> escaping from aquaculture facilities into the wild, for example, could
> damage
> native populations, even to the point of extinction. But Elliot Entis,
> president of A/F Protein, Inc., an international biotechnology firm based in
> Waltham, Mass., feels that environmental concerns can be addressed by
> producing transgenic fish in closed aquaculture systems (controlled,
> artificial environments) or by producing all female, sterile fish.
>
> FDA, in cooperation with other federal agencies, will evaluate these
> proposed
> environmental safety measures prior to any approval.
>
> Ethically Speaking
> At a time when genetically engineered plant crops have spurred protests in
> the United States, the use of biotechnology in food-animal production is
> likely to attract an even larger set of critics because both transgenics and
> cloning deal with animals.
>
> People for the Ethical Treatment of Animals (PETA), a large animal rights
> organization headquartered in Norfolk, Va., for example, feels that people
> shouldn't be tinkering with animals like Frankenstein and is very much
> opposed to intensive animal agriculture.
>
> In general, CVM's Matheson says that for animal safety, the goal of
> regulating products of animal biotechnology is to ensure healthful
> surroundings, proper medical treatment, discovery of any special management
> measures needed, and freedom from pain and suffering.
>
> Regulating Transgenic Animals
> FDA already has the legal authority to regulate most products derived from
> transgenic animals, whether they are used as drugs, as human food, or as
> animal feed. Therefore, only guidances or regulations that cover specific
> aspects of animal biotechnology may need to be added-not whole new statutory
> frameworks for regulating the products. These guidances will likely address
> such issues as safety of the target animal and protection of the
> environment.
>
> Most of the gene-based modifications of animals for food production fall
> under CVM regulation as new animal drugs. The genetically modified growth
> hormone for the fish, for example, will be regulated the same way the agency
> regulates bovine somatotropin, the genetically engineered bovine growth
> hormone that makes cows produce more milk. Transgenics simply provides
> another means to add growth hormone to an animal.
>
> "When I speak to folks about the regulation of animal genetic engineering,"
> says Matheson, "the first reaction is often surprise that genetically
> engineered animals could possibly be viewed as containing new animal drugs."
> People are surprised, he says, because their experience with animal drugs is
> limited to products they buy for their pets.
>
> With transgenic salmon, the inserted growth hormone trait is inherited by
> subsequent generations. With cows, the drug is periodically injected into
> each one. Either way, products regulated as new animal drugs in the United
> States are subject to rigorous premarket requirements to determine
> effectiveness and ensure food, animal and environmental safety.
>
> "One of the good things about regulating transgenics as animal drugs," says
> CVM director Stephen F. Sundlof, DVM, PhD, "is that we can make sure that
> the
> environmental controls and other safety measures are built right into the
> process." This process includes target animal safety, safety to the
> environment, and safety for consumers to eat foods derived from genetically
> engineered animals.
>
> CVM intends to use various approaches, including a contract with the
> National
> Academy of Sciences, to identify further environmental safety issues
> associated with investigation and commercial use of transgenic animals. To
> do
> this, the agency will cooperate closely with other federal and state
> agencies
> that have related authorities, such as the Fish and Wildlife Service and the
> National Marine Fisheries Service, in the case of transgenic Atlantic
> salmon.
>
> Looking to the Future
> The agency already is gearing up for the major debates it expects regarding
> transgenic animals--debates likely to mirror the discussions now underway
> for
> bioengineered crops. At this time, no transgenic animals have been approved
> to enter the human food supply, but a few individual transgenic animals have
> been allowed to be rendered and used in animal feed.
>
> While it's true that new compounds to combat specific diseases or to
> optimize
> the nutritional value of food products can also be created by conventional
> means, researchers believe that transgenics technology can help make it
> possible to produce them more quickly, in larger quantities, and ultimately,
> at lower cost to consumers.
>
> "After over 10 years of examining products on a case-by-case basis," says
> Matheson, "I can say that the guidance and regulatory structure for animal
> biotechnology is starting to evolve. I hope we can learn from our
> experiences
> with plant biotechnology to make the road a little smoother."
>
> Carol Lewis is a staff writer for FDA Consumer.
>
> ------------------------------------------------------------------------------
>
> --
>
> Creating A New Variety of Fish: The Technique to Make Transgenic Animals
> Breeders can now use the tools of biotechnology to introduce new
> characteristics into animals. For example, researchers have figured out how
> to give a type of salmon a gene that directs the production of a growth
> hormone, causing the fish to grow to full size in substantially less time.
> Here is an outline of the steps needed to introduce the new growth hormone
> gene into the salmon.
>
> Scientists duplicate the DNA carrying the genetic information for the growth
> hormone.
> The gene is inserted into a circular piece of DNA called a plasmid that can
> be reproduced inside bacteria.
> Next, the plasmids go inside the bacteria.
> When the bacteria grow in the laboratory, they produce billions of copies of
> the plasmid carrying the growth hormone gene.
> After the copies of the plasmid carrying the growth hormone gene have been
> produced, they are isolated from the bacteria. The plasmid is then
> genetically edited, changing its circular structure into a linear bit of
> DNA.
> The linear DNA is sometimes called a gene cassette because it contains
> several sets of genetic material in addition to the growth hormone gene.
> The gene cassette is either directly injected or mixed with fertilized fish
> eggs in such a way that the eggs absorb the DNA, making the cassette a
> permanent part of the fish's genetic makeup. Since scientists insert the
> growth hormone gene into the fish's egg, the gene will be present in every
> cell in the fish's body.
> The eggs are allowed to hatch, producing a school of fish in which some are
> genetically changed and others are not.
> Fish that now carry the growth hormone gene are identified. Fish with the
> properly integrated gene are used to create a breeding stock of the new,
> faster-growing variety.
> --C.L