Rabu, 19 Desember 2007

The Concept of Sustainability in Agriculture

An article in the New York Times free online edition this week discusses two possible examples of what might turn out to be unsustainable modern agricultural practices (“Our Decrepit Food Factories”, by Michael Pollan. nytimes.com, Dec. 16). Mr. Pollan suggests that MRSA (methicillin-resistant Staphylococcus aureas) infections in humans may become more common due to the widespread use of antibiotics in pig feed. He also presents some good arguments for why the worldwide collapse of honeybee populations may be due in part to unsustainable modern farming practices that stress the bees.

It makes for easy reading at the student level. The article could be used to spark a discussion about how best to actually achieve agricultural sustainability in the face of pressures to produce more food for a growing world population.

Kamis, 13 Desember 2007

Cancer Therapy

The January issue of Scientific American, now available in electronic form, will have an interesting article about how antiangiogenic drugs (drugs that inhibit blood vessel growth) such as Avastin actually work in cancer therapy. It turns out that it’s not just that they reduce the overall blood supply to a tumor, although that is one of their actions. In fact, they also normalize the remaining vessels, pruning them and improving their permeability properties. As a result, antiangiogenic drugs improve the effectiveness of other cancer treatments such as chemotherapy, because now the chemotherapeutic drugs are better able to reach the tumor cells.

But there is only a window of opportunity in which the combination of antioangiogenic drugs and other therapies is particularly effective, because the antiangiogenic drugs are hard on blood vessels throughout the body and because tumors may eventually lose their responsiveness to the drugs. Nevertheless, our improved understanding of how antiangiogenic drugs actually work is opening new avenues for developing more specific cancer treatment regimens. To learn more, read the original article (“Taming Vessels to Treat Cancer”, by Rakesh K. Jain. Scientific American Jan. 2008, pp. 56-63).

Kamis, 06 Desember 2007

Stem Cell Breakthrough

In late November Dr. Shimya Yamanaka reported in Cell that he had produced human stem cells from adult human cells taken from the cheek of a middle-aged woman. On the same day, Dr. James Thomson reported in the online version of Science that he had achieved similar success with foreskin cells from newborns.

Scientists are hailing these two reports as a technical breakthrough in stem cell research. The key is that these two researchers derived their stem cells from older cells, NOT from embryonic cells. Stem cell research has always been highly controversial because most of the stem cells used in research come from human embryos (see the Current Issue in Human Biology 5th ed., pp. 72-73). But if human stem cells can be created from older cells without sacrificing human embryos, then the whole “sanctity-of-life” issue is off the table. An added benefit is that if a simple cheek cell can be used, then stem cells could be grown specifically for any patient, using cells taken from that patient.

It’s way too early to think of growing a new heart for a patient in heart failure from his/her own cells, though. Although these new findings show that we have reached a basic level of understanding of how to create stem cells, we don’t yet understand how to direct them into becoming the specific human organs or tissues we might need to treat disease. Many scientists, including Dr. Yamanaka and his colleagues, argue that it would be “a serious mistake” to move too quickly to end all embryonic stem cell research, based on these very first successes at creating stem cells from adult cells. They believe that embryonic stem cells are still likely to be necessary for decades to come.

Still, it’s encouraging to think that in our lifetimes, the controversy over stem cell research may just slowly disappear.
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