FEATURED IMAGE: Saturn and its rings. I know that this huge planet is a favorite of many of our members. Hat tip to Phil Plait: what a fantastic grayscale photo! Look at those rings. I cannot get enough of them. This shot was taken by Cassini, which has been circling Saturn since 2004. The rings are composed of many bits of pure water ice. Some things to look for in this picture; that dark circular spot with the bright rim is a storm which is approximately 4,000 kilometers (2,400 miles) across; and the small spot of light in the upper left is Saturn’s moon Tethys, which is ~1,100 kilometers (660 miles) wide. And for more discussions, photographs, etc., don’t forget to visit and join our Group The Daily Cosmos.
FEATURED VIDEO: Cheetahs in slow motion
I can’t get enough of this video. Some of you may find it boring or repetitive, but I’ve watched it several times (watch it full screen if you can, and in HD); every time I see it again, I focus on different muscles and different part of the magnificent feline bodies. Look at the spine and the explosive power it produces by bending. The video, "Cheetahs on the Edge", was made by Nat Geo and the Cincinnati Zoo. They used a Phantom camera filming at 1200 frames per second while zooming beside a sprinting cheetah, as up to the point where the animal was running at > 60 miles/hour. Stick till the end so you can see the set-up that was used to capture the movement in this unique way.
Who knew that parasites could be eye candy? They are, when talented cell biologists and microscopists with a knack for art create beautiful images. Check out the entire slide show here. This photo was taken by a team of scientists from the Université Libre de Bruxelles. In blue, you can see 2 Trypanosoma bruceiparasites (this protozoan parasite is the causative agent of African sleeping sickness), interacting with immune cells from the liver of an infected mouse. The end result of that interaction is the parasites being phagocytized (eaten) by the immune cells. The technique used was scanning electron microscopy of a liver slice.
ODDITIES OF NATURE
Tick bites and allergy to meat. I have to confess that I did not even know that people could be allergic to meat. And the allergy is caused by the bite of a tick; that makes it even more unusual in my mind. So, meat lovers out there, especially those living in the southeastern US, the region with the highest prevalence of the meat allergy, called alpha-gal, beware of tick bites. The offending meats are beef, lamb and pork, and the name alpha-gal derives from alpha-galactose, a sugar present only in mammalian meat. The symptoms are a rash (hives), and in some unfortunate people, an anaphylactic reaction that can be life-threatening, that occurs about 4 hours after eating meat. The alpha-gal allergy has been found in people who have been bitten by the lone-star tick
(Amblyomma americanum). People who have ben bitten by the tick can develop antibodies against alpha-galactose, which trigger the allergic reaction to the meat sugar. Many people do not correlate the allergy to meat consumption because it takes a few hours to develop. Interestingly, the alpha-gal allergy was initially studied in correlation to allergic reactions against the cancer drug cetuximab, which contains the same alpha-galactose as meat. Doctors noticed that the allergic reaction to the drug occurred almost exclusively in cancer patients in the southeastern US; patients who develop the allergy had antibodies against alpha-gal. And some of the cetuximab treated patients, along with some noncancer patients in the same region, reported having severe allergic reactions after eating meat. Thomas Platts-Mills, an allergy researcher working in Virginia, who had studied the cetuximab allergy, made the connection with the tick bite when he was bitten by ticks on a hiking trip. He subsequently developed the meat allergy as well as high levels of alpha-gal antibodies. What is no clear so far is what substance in the tick saliva triggers the development of alpha-gal antibodies. Tick saliva is very complex but scientists are working now on isolating the guilty party. The meat allergy has also been reported in areas as far from the southeastern US as Hawaii, and either the tick’s range is expanding or people have been bitten while vacationing in areas where the tick lives. This type of tick is very aggressive and bites humans even in its larval forms. Perhaps a tick will be more powerful than all the health warnings or ethical considerations in the world, and succeed in achieving a reduction in the meat consumption, at least in the US. Of note, ticks love the warm weather and the milder winters and early spring we have been having are a boon for tick populations in the eastern United States.
Odd olfaction: “white” smells. I’m sure you have heard of “white” noise and white light. They are produced when combining different sound frequencies or different wavelengths. The end result is a non-descript noise and a neutral color, white. A team of Israeli neuroscients has now discovered “white” smell. The team studied mixtures of different aromas and found that when you mix around 30 different aroma molecules across the odor spectrum, the mix ended up smelling the same to a team of volunteers, even if the mixtures contained totally different components. During gradual mixing, as more components were added to each of two mixtures, the more alike they smelled to people. By 30 compounds, the smell became the equivalent of “olfactory white”. Volunteers consistently began to find the mixtures similar at 20 or more components, and by 30 components the mixtures were “highly similar” — a trend that implies there is an end point of perceptual convergence, olfactory white. The findings enhance the idea that the olfactory system detects scents as a whole, and not individual odorant molecules. The practical application is that the “white smell” effectively masked distinct smells. The neuroscientists mixed the 4 compounds responsible from the smell of roses and added an olfactory white mixture to them: people could no longer smell the roses! It’s possible then to prepare these scent combinations to mask unpleasants smells. The physiological mechanism that causes different mixtures to smell alike is still unknown. It’s possible that activating many olfactory receptors at once confuses the brain.
Animal vision evolved 700 million years ago. Do not miss this lengthy but excellent piece on opsin, the protein at the basis of visual perception. Opsin is a member of a large family of proteins, called "G-protein coupled receptors" (GPCRs). Most GPCRs detect the presence of specific molecules, sending a signal to the cell where the receptors are located. But opsin does not bind molecules
directly; it senses light by sensing the presence of a photon. This causes a conformational change in the protein, and down the road, a neuron fires and sends a signal to the brain, which then gets the luminous message. Because all animals have some form of opsin or another, it is clear that this is an ancient molecule. Since Cnidaria (jellyfish, anemonies, corals, etc.) have opsins but sponges do not, these proteins must have arisen after the split of sponges from the rest of the animal world, but before the cnidarian split from the bilateral animals (Bilateria). But since our world is filled with endless forms most beautiful, there is a convenient group of animals, the placozoans, which are a very small, flat, pancake like animal that lives on the sea floor, scavenging detritus. The placozoans are between sponges and Cnidaria/Bilateria. There is only one recognized species Trichoplax (in the photo). And they have 2 opsins. But these opsins do not detect light! Because they lack a crucial aminoacid called lysine-296. So now we have two events to consider: one is when the first opsin arose, and the other is when it acquired the mutationthat rendered it light-sensitive. The opsin lineage itself arose between 755 and 711 million years ago, and since the last common ancestor of Bilateria and Cnidaria lived between 711 and 700 million years ago, the ability of animals to detect light is at least 700 million years old. Of course, a light sensing protein does not an eye make. But there is no eye or vision without opsins.
DNA AND MORE DNA
What DNA looks like. Of course, DNA was visualized decades ago using X-ray crystallography that reveled its double helix structure. But for the first time, we can actually see that iconic helical structure and photographic under an electron microscope, using a trick: researchers at the Istituto Italiano di Tecnologia in Genoa, Italy, strung a molecule between two nano-towers and subjected it to transmission electron microscopy at extreme magnification. They used super hydrophobic self-aggregating DNA molecules that produced robust and highly ordered paired DNA nanofibers. The molecule looks exactly like we expected it to look from the models. The original publication can be seen here.
Making nano-sculptures from DNA bricks. The magnificent Ed Yong (Not Exactly Rocket Science) writes a great piece on very recent research by researchers at the Dana-Farber Cancer Institute. First a solid block of DNA is built out of individual “Lego” bricks, which are the product of a single strand of DNA folding into a U-shape and interlocking with identical neighboring molecules. Different shapes can then be created by leaving out specific bricks, similar to the way a sculptor removes chips of a marble block to produce a statue. This is the latest development in the field of “DNA origami.” Although this field is still in its infancy, and it is more a question of creating tools than having real-life applications, the DNA sculptures could one day be used to deliver drugs or to measure nano-scale distances, or as a guide to organize other molecules into sheets or grids.
Bigfoot DNA sequenced? Come join our lively discussion of the presumed sequencing of Sasquatch’s DNA. Big red flag: the scientist in question, Dr. Melba S. Ketchum of Nacogdoches, Texas, is making these big press release before the study is peer-reviewed or the sequenced released to the scientific community. The claim is that Bigfoot is the result of a hybrid mating between a Homo sapiens female and a previously unknown "male non-human", that occurred supposedly 15,000 years ago. The story apparently involved a Michigan property teaming with Bigfoot (should the plural be simple “Bigfoot” or “Bigfeet? I was hoping Don Bredes would weigh in) with a taste for blueberry bagels and a hint of angel DNA as well (non-human, non-ape, never-seen DNA). Don Bredes also posted a discussion on the psychology of Bigfoot chasers: are they true believers, playing a game, or a combination of both? Tell us what you think, at this link: Bigfoot and the psychology of conviction.
A universal blood test to detect cancer? One of the meccas of cancer biology is to be able to detect cancer in very early forms, at stages at which the disease can be cured, not simply treated. And if the test was cheap and non-invasive, it would be ideal. We are not at the cheap part, but researchers at the Johns Hopkins University School of Medicine in Baltimore have now made a big step towards possible early detection out of a simple blood test. Tumors shed abnormal DNA into the bloodstream, and that DNA can be extracted from plasma and sequenced.
Basically all tumor cells have substantially abnormal chromosomes, with extra copies of certain genes or strange rearrangements and swaps of DNA pieces. These chromosomal abnormalities can be potentially detected in the plasma DNA, by sequencing it. To test their hypothesis, they used DNA extracted from the blood of people with cancer and from healthy people. They used deep sequencing methods (reading every bit of DNA numerous times) to determine the entire genome of the DNA in the blood. The cancer patients all had altered DNA of the type you find in chromosomal abnormalities, while none of the healthy people did. Right now the test costs thousands of dollars and it takes at least a month to get the results. But DNA sequencing keeps getting cheaper thanks to technology innovations and improvements. They would have to sequence very deep in order to detect early cancers, since their current models involved a portion of abnormal DNA in the blood ranging from >40% to ~2%, and to detect small, curable tumors, probably 0.1% or lower of the circulating DNA in the blood would be abnormal. At the rate DNA sequencing is advancing, this approach could be ready to use for diagnostics in the next 5-10 years. One would hope that if this pans out, there would be screening for everyone and not just the very rich. Besides saving human lives, money would be saved if cancers were detected at the curable, early stage.