Archive for the 'Science-y stuff' category

A simple bump on the head can kill you

Mar 18 2009 Published by under Medicine, Science-y stuff

How can a seemingly trivial head injury kill you?
To answer this, you need a little anatomy.
Your brain is a pretty important organ, and is well protected. It sits inside a thick armor (the skull) and floats cushioned in a bath of cerebral-spinal fluid. It's surrounded by several layers of tissue, and its blood supply is kept relatively separate from the rest of the body (the "blood-brain barrier"). This separation helps keep out toxins and micro-organisms (but is imperfect). Just beneath the skull is a tough, leathery layer called the dura mater. This picture shows the skull cut away, and the dura peeled back by a forceps.

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85 responses so far

Experiment--woo woo journal club

Jan 22 2009 Published by under Absurd medical claims, Medicine, Science-y stuff

This is just for kicks, and requires a little work. I recently became aware of a dreadful article that I'd love to share with you, but then I thought, "my readers are pretty damned smart; let's see what they have to say first."
The article in question, "External Qi of Yan Xin Qigong differentially regulates the Akt and extracellular signal-regulated kinase pathways and is cytotoxic to cancer cells but not to normal cells" just seems ripe for feeding into the dewooificator. Now, the full text is behind a paywall, and it wouldn't do for me to share my full text copy with you. I certainly can't prevent readers from participating in academic discourse and sharing the article with each other. Anyway, here's the rest of the citation:
Xin Yana, Hua Shenb, Hongjian Jiangc, Chengsheng Zhangd, Dan Hud, Jun Wangb and Xinqi Wue. The International Journal of Biochemistry & Cell Biology. Volume 38, Issue 12, 2006, Pages 2102-2113. doi:10.1016/j.biocel.2006.06.002.
Thank you in advance for posting your well-thought out comments on this, er, groundbreaking paper.

20 responses so far

Salmonella--a little background

Jan 19 2009 Published by under Medicine, Science-y stuff

You've probably read about the current Salmonella outbreak. It's a fine example of what can happen when food is produced and distributed on an industrial scale---even one small contamination event can spread widely in the food supply, and there isn't much of a system in place to follow the trail of contaminants. Others have covered the public health implications of this outbreak, so I'd like to examine some other facts that make this outbreak disturbing.
Salmonella likes non-human animals
Some species of Salmonella cause typhoid fever. Typhoid fever, a nasty epidemic disease of humans, is easily spread, but easily controlled. Humans are the only significant reservoir for the species of Salmonella that cause typhoid fever, so once you control humans and their water and waste, you can control and prevent outbreaks. The species that cause gastroenteritis (or "stomach flu") are not so picky about hosts. They can infect many different animals, so even if you can control humans and their waste, you still haven't controlled a large reservoir of potential trouble. Eggs are commonly contaminated with Salmonella, and outbreaks do to other foods are common. Meticulous food preparation can often prevent infection---thorough cooking of eggs, proper handling of meats. But the current outbreak is a bit more tricky.
Salmonella is easily killed with cooking
That's great, if it contaminates food that you cook. In this case, peanut butter for industrial-scale use was contaminated. In all probability the peanuts for the product are from many different places, and many batches of butter may have been combined. But even more troubling is that peanut butter is not a product that people normally wash or cook. You simply open it and eat it. Lucky for Salmonella, unlucky for you. When meat or eggs are contaminated at the source of production, we still have a fighting chance through cooking. If it's peanut butter, all is lost.
You don't have to be sick to spread it
Not unique to this outbreak is the fact that a person can carry Salmonella and excrete it in their stool without becoming ill. Not only that, but compared to the dose necessary to become ill, it doesn't take as many organisms ingested to turn someone into a carrier.
Natural defenses---some gaps
The treatment of gastro-esophageal reflux disease has been revolutionized by the introduction of H2-blockers such as famotidine ("Pepcid") and PPIs such as omeprazole ("Prilosec"). These medications are very effective, and very safe. But (and you knew there had to be a "but"), these medicine work by raising gastric pH, which weakens one of our defenses against Salmonella. The bacterium doesn't like dropping into a cauldron of acid, but it's just fine at the relatively higher pH of a stomach treated with omeprazole. This stuff is over the counter, so millions of people take it, rendering them more susceptible to infection, should they be unlucky enough to encounter contaminated food.
Antibiotics---stop asking for them, please
Antibiotics can reduce the normal flora of the GI tract. Some studies have shown that the disruption of normal intestinal flora with antibiotics renders people more susceptible to infection.
What do I do now?
The usual precautions are always a good bet, among them:

  • Wash fruits and veggies thoroughly
  • Salmonella often contaminates the surface of meat (via intestinal contents/poo), so make sure any surface that touches the meat's surface is thoroughly decontaminated. Also, ground meats are basically "all surface" so they must be cooked well.
  • If the CDC or FDA or other agency recommends avoiding a particular food, take them seriously.

Many cases of food-borne illness can be prevented at the consumer level---the current outbreak makes that a bit harder. Eat carefully.

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