Posts Tagged ‘medicine’

Arsenic is unlikely warrior against cancer [Medical Breakthroughs]

Tuesday, July 13th, 2010

(reprinted from: io9)

Arsenic is unlikely warrior against cancerThe deadly poison made famous in countless Agatha Christie mysteries isn't known for its health benefits. But an arsenic compound has helped treat leukemia sufferers for over a decade, and we've just discovered it can fight other cancers as well.

The specific compound is arsenic trioxide, and it's already been approved by the FDA for the treatment of humans. The arsenic is combined with other therapies to fight cancers brought on by an error in a cellular signaling pathway known as the Hedgehog pathway. This signaling cascade regulates embryonic development and remains crucial to properly functioning cells in adults. Malfunctions in the Hedgehog pathway have been shown to cause tumors in the skin, brain, blood, and muscle.

Arsenic trioxide works in relatively low quantities by blocking one of the final steps in the Hedgehog pathway, preventing a few of the cell's genes being expressed that would otherwise cause runaway, cancerous growth. Other treatments currently on the market also target the Hedgehog pathway, but they do so at much earlier points in the signaling cascade. That gives the malfunctioning pathway many more opportunities to mutate around the drug and relay its self-destructive messages to the cells. The arsenic treatment takes effect so late in the pathway that's there is nearly no chance for the cancer to mutate around it.

Researchers Philip Beachy and Jynho Kim at the Stanford medical school first became interested in arsenic as a treatment for cancer when they noticed that birth defects brought on by arsenic exposure are very similar to the physical effects of not having an active Hedgehog pathway. They found that the same small amounts of arsenic trioxide that treated leukemia patients could also shut off the Hedgehog pathway, providing a potential treatment for sufferers of many other kinds of cancer.

Arsenic trioxide works by inhibiting a protein called Gli2 from causing gene transcription in the cell nucleus. Without Gli2, the Hedgehog pathway comes to a sudden, ineffectual end. Early tests of this treatment on mice found that most tumors either slowed down or stopped growing completely. Best of all, this works even in cells that have already proven resistant to other drugs that target the Hedgehog pathway.

[Proceedings of the National Academy of Sciences]

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A new facility is being built to harvest rare atoms [Mad Science]

Wednesday, July 7th, 2010

(reprinted from: io9)

A new facility is being built to harvest rare atomsFind out how a particle accelerator will be used to make rare isotopes used for nuclear medicine.

Technetium 99m sounds like something in a bad fifties science fiction film that would be injected into someone to give them psychic powers, or twelve hours, or both. This goes double when it's combined with the ominous phrase ‘nuclear medicine.' Together they call to mind a hapless tourist being held down by a hulking orderly named Nurse Mugsy while a guy with salt and pepper hair and a lab coat brandishes a glowing syringe and talks about how the only way humans will survive the coming nuclear winter is by spiking the water supply with technetium 99m. It may or may not be raining, depending on the sensibilities of the director.

A new facility is being built to harvest rare atoms

The realities of nuclear medicine aren't that much brighter. Technetium 99m and nuclear medicine are not fun things to experience. The isotope is radioactive, and throws off x-rays from inside a person's body. X-rays go through flesh like it's not even there, so the technetium 99m inside a person is measurable from outside of the person's body. In medicine it is often added to a chemical that will attach itself to tumors or growths inside a person. That chemical attaches itself to the tumor, and technetium 99m's x-rays allow doctors to see how big a tumor is without having to cut that person open. Being a human x-ray projector is much, much better.

Seriously, though, technetium is both massively useful and massively used. The problem is, x-rays are not thrown off because an element is planning to stick around. They are tossed out as an unstable atom becomes more stable, and the isotope technetium 99m doesn't have a long shelf life. This means that the has to be a way of getting it. Nuclear reactors are able to produce it, but they are not the safest things around.

A new facility is being built to harvest rare atoms

Canada, perhaps encouraged by the fact that the Large Hadron Collider did not turn out to be a doomsday device, has come up with a plan to build a particle accelerator in order to make and harvest technetium 99m. The accelerator will hurl a stream of electrons at a metal target. Once at the target, the electrons will either swerve off course, or stop dead in their tracks in the comical fashion of Wyle E Coyote, after he has been fired at a wall in a Warner Brothers cartoon.

A new facility is being built to harvest rare atoms

Either way, the electrons will produce high-energy photons through bremsstrahlung.

‘Bremsstrahlung' comes to us courtesy of the Germans, who are fresh off their win with schadenfreude and looking for other compound words to popularize. It means ‘braking energy.' When the electrons swerve off course or stop at the target, they lose momentum, thus losing energy. Any hippie will tell us that, like, energy goes on forever, man, and can never really be lost, and of course hippies are never wrong. To conserve energy, some photons are produced to make up for the energy lost by the electrons. The electrons whizzing by also mess with the electromagnetic fields at the target, producing even more photons.

These photons form another beam which hits another target, this one made of heavy elements. These elements break down, producing rare isotopes. Those isotopes, including technetium 99m are harvested and used in nuclear medicine. Possibly also by a nurse named Mugsy. People will call their kids anything these days.

Sources: About.com, NDT, Physics World, and TRIUMF.

Top image of facility for rare isotope beams at at Michigan State.

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Cancer caused by DNA repair gone haywire [Medical Science]

Thursday, July 1st, 2010

(reprinted from: io9)

Cancer caused by DNA repair gone haywireWe don't know how to cure it, but now we've got a better idea what causes cancer. The disease starts when cells mess up their attempts to repair damage to their DNA.

There's a certain tragic irony to this, as these terrible diseases seem to begin with cells trying to fix the far more minor problem of damage to DNA strands. According to James Haber, Wade Hicks, and Minlee Kim of Brandeis University, cells that are showing the very earliest signs of cancer start to have errors in the DNA replication process. To fix this, the cells use a number or methods to repair the damage, one of which is known as gene conversion.

Gene conversion repairs the break in the DNA strand by using an almost identical sequence from elsewhere in the cell's DNA, providing a template from which the original strand can be reconstructed. Although this was once thought to be a mostly error-free process, the new study actually suggests it leads to a far greater number - about 1,400 times the usual amount - of DNA mutations than would otherwise be expected. Once these mutations affect the various genes that provide the cell's ability to control its own growth, the cell quickly becomes cancerous.

Coauthor James Haber says this theory explains why cells turn cancerous so quickly:

"It has been hard to imagine how cells could accumulate so many mutations in the few generations that they undergo cell division on the way to becoming cancerous. We think that the elevated rate of mutation at sites where DNA has been broken may be an important source of these gene changes."

Wade Hicks builds on this by noting that the mutations are themselves unique, and this could help test the validity of their ideas:

"During repair, mutation rates increase, and the types of mutation during repair are different from normal mutagenesis. It would be interesting to do an in depth analysis of the types of mutations in cancer cells and compare to those we observed in a repair event to see if they match up."

Their examination of gene conversion revealed that the copying of DNA during repair was often interrupted, which presented major complications. Most strikingly, the copying mechanisms would often choose the wrong template when they restarted, choosing an unhelpful sequence that provided little useful information for the strand in need of repair, which naturally created errors and mutations in the repair process. Gene conversion also fails to use another cellular repair system known as "mismatch repair", which is the only way the cell can notice and fix mutations that crop up. As such, gene conversion leaves all mutations in place, hastening their takeover of the cell's DNA.

The researchers say they will next focus on how often these template switches occur and what proteins are involved in the process. The hope is that this will better explain the runaway mutagenesis that leads to cancer and perhaps offer some clue as to how to prevent it from happening in the first place.

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The man who grew a finger

Wednesday, April 30th, 2008

Quite an incredible story about a powder being developed that can regrow body parts.

“I put my finger in,” Mr Spievak says, pointing towards the propeller of a model airplane, “and that’s when I sliced my finger off.”

It took the end right off, down to the bone, about half an inch.

“We don’t know where the piece went.”

The photos of his severed finger tip are pretty graphic. You can understand why doctors said he’d lost it for good.

Today though, you wouldn’t know it. Mr Spievak, who is 69 years old, shows off his finger, and it’s all there, tissue, nerves, nail, skin, even his finger print.

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