Saturday, January 31, 2009
Implied by this definition is the fact that the device must not be continuously tethered to a stationary power supply, or other stationary resources, such as filters or chemical processing units. (Periodic rapid recharging of batteries, refilling of chemicals, and/or cleaning/replacing of filters, would exclude a device from being called an artificial organ.) Thus a dialysis machine, while a very successful and critically important life support device that completely replaces the duties of a kidney, is not an artificial organ. At this time a successful portable self-contained artificial kidney has not become available.
Reasons to construct and install an artificial organ, an extremely expensive process initially, which may entail many years of ongoing maintenance services not needed by a natural organ, might include:
Life support to prevent imminent death while awaiting a transplant (e.g. artificial heart)
Dramatic improvement of the patient's ability for self care (e.g. artificial limb)
Improvement of the patient's ability to interact socially (e.g. cochlear implant)
Cosmetic restoration after cancer surgery or accident
The use of any artificial organ by humans is almost always preceded by extensive experiments with animals. Initial testing in humans is frequently limited to those either already facing death, or who have exhausted every other treatment possibility. (Rarely testing may be done on healthy volunteers who are scheduled for execution pertaining to violent crimes.)
Although not typically thought of as organs, one might also consider replacement bone, and joints thereof, such as hip replacements, in this context.
Monday, January 26, 2009
A transgenic organism is a type of genetically modified organism (GMO) that has genetic material from another species that provides a useful trait.For instance, a plant may be given genetic material that increases its resistance to frost. Another example would be an animal that has been modified with genes that give it the ability to secrete a human protein.
Bioethics addresses the impact of technology on individuals and societies. Bioethical issues include an individual's right to privacy, equality of access to care, and doctor-patient confidentiality. In the case of transgenic organisms, a major bioethical issue is freedom of choice. Yet broader issues also arise, such as the ethics of interfering with nature, and effects of transgenic organisms on the environment.
The changes that are possible with transgenesis transcend what traditional gardening or agriculture can accomplish, although these too interfere with nature. A transgenic tobacco plant emits the glow of a firefly, and a transgenic rabbit given DNA from a human, a sheep, and a salmon secretes a protein hormone that is used to treat bone disorders. If mixing DNA in ways that would not occur in nature is deemed wrong, then transgenesis is unethical. Said a representative of a group opposed to GMOs in New Zealand at a government hearing, "To interfere with another life-form is disrespectful and another form of cultural arrogance."
A more practical objection to transgenic technology is the risk of altering ecosystems. Consider genetically modified Atlantic salmon, currently under review at the U.S. Food and Drug Administration (FDA). The fish have a growth hormone gene taken from Chinook salmon and a DNA sequence that controls the gene's expression taken from ocean pout, a fish that produces the hormone year-round. Because Atlantic salmon normally produce growth hormone only during the summer, the transgenic animal grows at more than twice the natural rate. Such genetically modified salmon could escape the farms where they are intended to be raised and invade natural ecosystems, where they may outcompete native fish for space, food, and mates.
Until recently, the fear that a transgenic organism might escape and infiltrate a natural ecosystem was based on theoretical scenarios. For example, a 1999 report of transgenic corn pollen harming Monarch butterfly larvae in a laboratory simulation was not confirmed by larger, more realistic studies. But in 2001 transgenic corn was discovered growing on remote mountain-tops in Mexico, ironically in the area where most natural corn variants originated. The corn was not supposed to have been able to spread beyond the fields where it was grown. At about the same time, 10,000 hectares (24,700 acres) of transgenic cotton were found in India. A farmer had crossed transgenic cotton he had obtained from the United States with a local variant and planted crops, not realizing that he had used a genetically modified product.
At the present time, American consumers cannot tell whether a food contains a genetically modified product or not because the two-thirds of processed foods that include GMOs and are sold in the United States have not been labeled. This lack of labeling is consistent with existing regulatory practice. While the FDA tests foods to determine their effect on the human digestive system, their biochemical makeup, and their similarity to existing foods (using a guiding principle called substantial equivalence), foods are not judged solely by their origin. For example, the FDA denied marketing of a potato derived from traditional selective breedingthat produces a toxin, while allowing marketing of a transgenic potato that has a high starch level and therefore absorbs less cooking oil, and is nontoxic. The FDA and U.S. Department of Agriculture approved transgenic crops in 1994, and deregulated the technology two years later, as did the U.S. Environmental Protection Agency. Ironically, as people in wealthier nations object to not having a choice in avoiding genetically modified foods, others complain that the technology is too expensive for farmers in developing nations to use.
Another ethical dimension to transgenic organisms is that the methods to create genetically modified seeds, and the seeds themselves, lie in the hands of a few multinational corporations. In the mid-1990s acompany sold transgenic plants resistant to the company's herbicides, but that could not produce their own seed, forcing the farmer to buy new seed each year. An international outcry led to the abandonment of this practice, but the use of crops that are resistant to certain herbicides, with a single company owning both seed and herbicide, continues. Some see this as a conflict of interest.
Groups that oppose genetically modified foods sometimes behave unethically. In 1999 environmental activists destroyed an experimental forest of poplars near London. The trees were indeed transgenic, but the experiments were designed to see if the trees would require fewer chemical herbicides, an activity the environmentalists had themselves suggested. More alarming were several incidents in the United States in 2000, when people who object to genetically modified foods vandalized laboratories and destroyed fields of crops, some of which were not even transgenic.
So far, foods containing GMOs appear to be safe. They may be easier to cultivate and may permit the development of new variants. However, it will take more time to determine whether or not they have longer term health and ecological effects.
Tuesday, January 20, 2009
Whenever GM plants are grown on open fields without containment, there are risks that their genetically altered seeds will escape into the general environment. This occurred on Canadian farmer Percy Schmeiser's farm in Bruno, Sakatchewan, Canada and led to a controversial court ruling regarding seed patents of the multinational corporation Monsanto. 75% of all farmers on earth depend on saved seeds to plant their farms each season and cross-pollination or any other natural process that may bring a GM organism to a farmer's land put's the farmer under infringement of patents. Most countries require biosafety studies prior to the approval of a new GM plant release, usually followed by a monitoring program to detect environmental impacts.
The coexistence of GM plants with conventional and organic crops has raised significant concern in many European countries. Since there is separate legislation for GM crops and a high demand from consumers for the freedom of choice between GM and non-GM foods, measures are required to separate foods and feed produced from GMO plants from conventional and organic foods. European research programmes such as Co-Extra, Transcontainer and SIGMEA are investigating appropriate tools and rules. At the field level, biological containment methods include isolation distances and pollen barriers.
In biological research, transgenic fruit flies (Drosophila melanogaster) are model organisms used to study the effects of genetic changes on development. Fruit flies are often preferred over other animals due to their fast generation time, cheap maintenance, and relatively simple genome compared to many vertebrates. Transgenic mice are often used to study cellular and tissue-specific responses to disease.
Transgenesis in fish with promotors driving an over-production of growth hormone (GH) has resulted in dramatic growth enhancement in several species, including salmonids, carps and tilapias. These fish have been created for use in the aquaculture industry to increase meat production and, potentially, reduce fishing pressure on wild stocks. None of these GM fish have yet appeared on the market, mainly due to the concern expressed among the public of the fishes potential negative effect on the ecosystem should they escape from rearing facilities
Genetically modified bacteria are used to produce the protein insulin to treat diabetes. Similar bacteria have been used to produce clotting factors to treat haemophilia, and human growth hormone to treat various forms of dwarfism. These recombinant proteins are much safer than the products they replaced, since the older products were purified from cadavers and could transmit diseases.Indeed the human-derived proteins caused many cases of AIDS and hepatitis C in haemophilliacs and Creutzfeldt-Jakob disease from human growth hormone.
In addition to bacteria being used for producing proteins, genetically modified viruses allow gene therapy. Gene therapy is a relatively new idea in medicine. A virus reproduces by injecting its own genetic material into an existing cell. That cell then follows the instructions in this genetic material and produces more viruses. In medicine, this process is engineered to deliver a gene that could cure disease into human cells. Although gene therapy is still relatively new, it has had some successes. It has been used to treat genetic disorders such as severe combined immunodeficiency, and treatments are being developed for a range of other currently incurable diseases, such as cystic fibrosis, sickle cell anemia, and muscular dystrophy.
For instance, the bacteria found that cause tooth decay are called Streptococcus mutans. These bacteria consume left over sugars in the mouth, producing acid that corrodes tooth enamel and ultimately causes cavities. Scientists have recently modified Streptococcus mutans to produce ethanol. These transgenic bacteria, if properly colonized in a person's mouth, could possibly reduce the formation cavities. Transgenic microbes have also been used in recent research to kill or hinder tumors, and fight Crohn's disease. Genetically modified bacteria are also used in some soils to facilitate crop growth, and can also produce chemicals which are toxic to crop pests.
Insulin is used medically to treat some forms of diabetes mellitus. Patients with Type 1 diabetes mellitus depend on external insulin (most commonly injected subcutaneously) for their survival because the hormone is no longer produced internally. Patients with Type 2 diabetes mellitus are insulin resistant, have relatively low insulin production, or both; some patients with Type 2 diabetes may eventually require insulin when other medications fail to control blood glucose levels adequately.
Insulin is a peptide hormone composed of 51 amino acid residues and has a molecular weight of 5808 Da. It is produced in the islets of Langerhans in the pancreas. The name comes from the Latin insula for "island".
Insulin's structure varies slightly between species of animal. Insulin from animal sources differs somewhat in 'strength' (i.e., in carbohydrate metabolism control effects) in humans because of those variations. Porcine (pig) insulin is especially close to the human version.