Sunday, July 29, 2007

Mosquitos and cat(nip)...

Earlier this month I was quite confused. Although we are in the prime of summer--hot and humid Illinois weather--I hadn't gotten a single mosquito bite. Unfortunately I had that thought a little too soon. Last weekend when I awoke on Saturday morning I was covered in tiny red welts, evidence that my screen windows just aren't doing their job and that the little vampires had attacked me in the night. So what chemicals can help to keep away these pesky insects?

DEET, or meta-N,N-diethyl toluamide, is one of the most common mosquito repellents that I have seen used in the United States. While I haven't read any complete studies describing exactly how DEET works, it is believed that this molecule somehow binds to female mosquito sensory receptors (on a sidenote, generally it is only the female mosquitos that practice hematophagy, as they require extra protein in order to reproduce) and prevents them from recognizing some of the chemicals excreted by the human body, especially lactic acid and carbon dioxide. Inhibition of these receptors leaves the mosquito circling in confusion and allows us to enjoy itch-free summer evenings by the lake. DEET does have some unpleasant side effects; it can damage many synthetic fibers (though leaves cotton and many natural fibers untouched) and has long been known to have negative-side effects in aquatic life. Additionally, studies published in the Journal of Toxicology and Environmental Health and Experimental Neurology by Mohamed Abou-Donia and coworkers have shown that prolonged use of DEET in rats can cause neurodegeneration, particularly in the cerebral cortex, the cerebellum, and the hippocampus [1], [2].

In Europe Icaridin / Picaridin is a common insect repellent, and some studies have shown that its activity is similar to that of DEET, but without any of the toxic side effects. Of course we all have heard of "natural" alternatives to these compounds, including citronella, beautyberry, geranium, lemon and eucalyptus oils, but did you know that catnip* (nepetalactone) has also been promoted as a "chemical free" means of eliminating mosquito bites [3], [4]? Interesting how the word chemical is generally considered taboo when promoting a new product; nepetalactone sure looks like an organic chemical to me!

If you are interested, the University of Florida has complied a list of several commonly available insect repellents with their effectiveness here.

*At the risk of sounding like carbon based curiosities, I just had to include some kind of reference to cats in this post. Last week I adopted a wonderful tabby! Isn't he cute?


Friday, July 20, 2007

Wednesday, July 18, 2007

Maiglöckchen

Well, I seem to be having some sort of internet connection problems at home, thus the lack of posts of late. It is very frustrating to pay for something and then not have it work, don't you agree?

Yesterday I was once again allowed to "play" with the confocal microscope; actually this was the second of my training sessions (for a total of 4 hours), so now I'm kind of an expert (not really) and allowed to use it on my own. Certainly I'm not close to being a know-it-all with the confocal scope, but it is nice to be able to make the judgment between just a pretty image and an accurate representation of what is on the microscope slide. I was quite surprised to learn that sometimes the two things don't go hand in hand. Today the first sample that I worked with came from Zeiss, and thus all of the names on the microscope slides were in German. While my instructor had never heard of a Maiglöckchen, if you have ever been to Germany in the spring, then you certainly have seen lily of the valley flowers. Though I have to admit that I don't know much about plant biology, the images are of the rhizome, which is the underground stem of the plant. The dyes used were a rhodamine derivative and fluorescein isothiocyanate (FITC) .

Monday, July 9, 2007

Fullerenes and the allergic response

Last year I was quite intrigued when I learned that cosmetics containing fullerenes are actually already on the market, so when I noticed this paper, I decided to look it over. Everyone has heard of "bucky balls," an allotropic form of carbon named after the architect famous for building geodesic dome structures. Incorporation of C60 into skin creams has been the subject of much debate; while known to be quite stable, only a handful of biological studies exist and some of them hint at the possible toxicity of fullerenes.

Interestingly, this recent study from Ryan and coworkers in the Journal of Immunology indicates that polyhydroxy C60 and N-ethylpolyamine C60 (water soluble "bucky balls") are capable of inhibiting the allergic response of human mast cells and peripheral blood basophils. Even though the electrons of C60 are not fully delocalized throughout the entire molecule, fullerenes have long been known to be radical sponges, and it is believed that this contributes to their negative regulation of the allergic response. Mice injected with up to 250ng of fullerene showed no adverse affects, and the authors demonstrate that the concentration needed to inhibit anaphylaxis in mice is 400,000-fold lower than the dose that has been shown to be toxic in vivo. As C60 is believed to reduce cellular ROS levels, it has been proposed that its antioxidant effects might be useful in the treatment of neuordegenerative diseases such as Parkinson's, Alzheimer's and Lou Gehrig's disease.

Me?? I'm just waiting for B80.