Author: Dark5

Examination of DNA from 21 primate species – from squirrel monkeys to humans – exposes an evolutionary war against infectious bacteria over iron that circulates in the bloodstream. Supported by experimental evidence, these findings, published in Science on Dec. 12, demonstrate the vital importance of an underappreciated defense mechanism, nutritional immunity.

“We’ve known about nutritional immunity for 40 years,” says Matthew Barber, Ph.D., first author and postdoctoral fellow in human genetics at the University of Utah. “What this study shows us is that over the last 40 million years of primate evolution, this battle for iron between bacteria and primates has been a determining factor in our survival as a species.” The study models an approach for uncovering reservoirs of genetic resistance to bacterial infections, knowledge that could be used to confront antibiotic resistance and emerging diseases.

Following infection, the familiar sneezing, runny nose, and inflammation are all part of the immune system’s attempts to rid the body of hostile invaders. Lesser known is a separate defense against invasive microbes, called nutritional immunity, that quietly takes place under our skin. This defense mechanism starves infectious bacteria by hiding circulating iron, an essential nutrient it needs for survival. The protein that transports iron in the blood, transferrin, tucks the trace metal safely out of reach.

Clever as it sounds, the ploy is not enough to keep invaders at bay. Several bacterial pathogens – including those that cause meningitis, gonorrhea, and sepsis – have developed a weapon, transferrin binding protein (TbpA), that latches onto transferrin and steal its iron. Though scientists have known of the offensive strategy, they failed to realize how pivotal the battle over iron has been in the conflict between host and pathogen.

“Interactions between host and pathogen are transient and temporary,” says senior author Nels Elde, Ph.D., assistant professor of human genetics at the University of Utah. “It took casting a wide net across all of primate genetic diversity to capture the significance.”

Just as details of a struggle can be gleaned from battle scars, Barber and Elde reconstructed this evolutionary conflict by documenting when and where changes in transferrin and TbpA have occurred over millennia. They examined the DNA of transferrin in 21 species from the primate family tree, and of TbpA from dozens of bacterial strains. The majority of accumulated changes in transferrin and TbpA cluster around a single region of contact between the two proteins, highlighting it as a site of evolutionary conflict between host and pathogen. The authors then used these genetic observations as a guide to perform experiments, which showed changes in TbpA enable the protein to grasp hold of transferrin, and that recent changes in transferrin allow it to evade TbpA.

Up to 25 percent of people in the world’s populations have a small alteration in the transferrin gene, which prevents recognition by several infectious bacteria, the most recent sign of this long battle. “Up until this study no one had come up with a functional explanation for why this variation occurs at an appreciable frequency in human populations,” says Elde. “We now know that it is a consequence of the pathogens we and our ancestors faced over millions of years.”

Understanding the strategies that underlie natural defense mechanisms, including nutritional immunity, could inform new approaches to combatting antibiotic-resistant bacteria and emerging diseases. “By examining the natural conflicts that have played out for millions of years, we can determine what has worked, and apply them in new situations,” says Elde.

Escape from iron piracy through rapid evolution of transferrin. MF Barber, NC Elde, Science Dec 12, 2014

The work was supported by awards from the Pew Charitable Trusts and the National Institutes of Health

Yuletide 24 from NATS on Vimeo.

Lovely analysis from from astronomer and astrophysicist Linda Harden.

1. No known species of reindeer can fly. BUT there are 300,000 species of living organisms yet to be classified, and while most of these are insects and germs, this does not COMPLETELY rule out flying reindeer which only Santa has ever seen.
2. There are 2 billion children (persons under 18) in the world. BUT since Santa doesn’t (appear to) handle the Muslim, Hindu, Jewish and Buddhist children, that reduces the workload to 15% of the total – 378 million according to Population Reference Bureau. At an average (census)rate of 3.5 children per household, that’s 91.8 million homes. One presumes there’s at least one good child in each.
3. Santa has 31 hours of Christmas to work with, thanks to the different time zones and the rotation of the earth, assuming he travels east to west(which seems logical). This works out to 822.6 visits per second. This is to say that for each Christian household with good children, Santa has 1/1000th of a second to park, hop out of the sleigh, jump down the chimney, fill the stockings, distribute the remaining presents under the tree, eat whatever snacks have been left, get back up the chimney, get back into the sleigh and move on to the next house. Assuming that each of these 91.8 million stops are evenly distributed around the earth (which, of course, we know to be false but for the purposes of our calculations we will accept), we are now talking about .78 miles per household, a total trip of 75-1/2 million miles, not counting stops to do what most of us must do at least once every 31 hours, plus feeding etc.
4. This means that Santa’s sleigh is moving at 650 miles per second, 3,000 times the speed of sound. For purposes of comparison, the fastest man- made vehicle on earth, the Ulysses space probe, moves at a poky 27.4 miles per second – a conventional reindeer can run, tops, 15 miles per hour.
5. The payload on the sleigh adds another interesting element. Assuming that each child gets nothing more than a medium-sized lego set (2 pounds), the sleigh is carrying 321,300 tons, not counting Santa, who is invariably described as overweight. On land, conventional reindeer can pull no more than 300 pounds. Even granting that “flying reindeer” (see point #1) could pull TEN TIMES the normal anoint, we cannot do the job with eight, or even nine. We need 214,200 reindeer. This increases the payload – not even counting the weight of the sleigh – to 353,430 tons. Again, for comparison – this is four times the weight of the Queen Elizabeth.
6. 353,000 tons traveling at 650 miles per second creates enormous air resistance – this will heat the reindeer up in the same fashion as spacecrafts re-entering the earth’s atmosphere. The lead pair of reindeer will absorb 14.3 QUINTILLION joules of energy. Per second. Each. In short, they will burst into flame almost instantaneously, exposing the reindeer behind them, and create deafening sonic booms in their wake.The entire reindeer team will be vaporized within 4.26 thousandths of a second. Santa, meanwhile, will be subjected to centrifugal forces 17,500.06 times greater than gravity. A 250-pound Santa (which seems ludicrously slim)would be pinned to the back of his sleigh by 4,315,015 pounds of force.

In conclusion — If Santa ever DID deliver presents on Christmas Eve, he’s dead now.

Condition 1 weather at the Scott Base in Antarctica means that no one is allowed outside.

Condition 3

Must meet all of the following criteria:

• Visibility is either greater than ¹⁄₄ mile (400 m), or it falls to ¹⁄₄ mile or less for less than one minute at a time
• Windspeed is either below 48 knots (89 km/h; 55 mph), or it reaches 48 knots or above for less than one minute at a time
• Air temperature and wind chill are either above −75 °F (−59 °C), or falls to −75 °F or below for less than one minute at a time

Condition 2

Must meet all of the following criteria:

• Visibility is either greater than or equal to 100 feet (30 m), or it falls below 100 feet for less than one minute at a time
• Windspeed is either less than or equal to 55 knots (102 km/h; 63 mph), or it exceeds 55 knots for less than one minute at a time
• Air temperature and wind chill are either −100 °F (−73 °C) or above, or falls below −100 °F for less than one minute at a time

And also must meet one or more of the following criteria:

• Visibility is less than or equal to ¹⁄₄ mile (400 m), sustained for one minute or longer
• Windspeed greater than 48 knots (89 km/h; 55 mph), sustained for one minute or longer
• Air temperature and/or wind chill of −75 °F (−59 °C) or below, sustained for one minute or longer

Condition 1

Must meet one or more of the following criteria:

• Visibility less than 100 feet (30 m), sustained for one minute or longer
• Windspeed over 55 knots (102 km/h; 63 mph), sustained for one minute or longer
• Air temperature and/or wind chill below −100 °F (−73 °C), sustained for one minute or longer

The ability of electric eels to shock their prey with a 600-volt blast is well known, but exactly how the fish orchestrate their attacks has remained a question as murky as the waters they hunt in.

Now it looks as if eels use a high-frequency barrage of shocks to disable fish by mimicking their prey’s nerve signals and making their muscles contract. In essence, they hijack the muscles and remote controlling the prey to near-certain death (see video above).

And if a fish is hiding behind a rock or algae, the eel has another shock pattern that makes the fish muscles twitch involuntarily, giving away their hiding place to the formidable predator.

The experiments that untangled these mechanisms were devised and run byKenneth Catania at Vanderbilt University in Nashville, Tennessee. In a natural environment, Catania watched an eel hunting and measured its electric discharges. As the eel was poised to strike, it emitted a barrage of high-voltage electric pulses. This stopped the fish in its tracks, allowing the eel to catch it easily.

To work out what was happening, Catania anaesthetised fish, removed their brains, and dangled them behind an electrically permeable agar barrier in an eel tank. Worms were then put into the tank for the eels to feed on, and the electric zaps sent out to catch the worms also reached the fish.

After about 3 milliseconds, the fish’s muscles completely contracted.

A chemical injected into another brainless fish to stop its motor neurons working, and another fish with its spine removed helped to complete the picture: the electric shock makes the motor neurons fire and contract the muscles, and it happens without the need for the central nervous system.

Catania also discovered that a different, high-voltage, two-pulse signal fired out by the eel makes a fish within range twitch uncontrollably, giving away its position and allowing the eel to go after it with its conventional attack of series of high-voltage pulses.

This two-pulse signal seems to tell the eel whether possible prey is living when information is limited, such as in murky or rocky environments, where the prey is hidden, the researchers say.

How and why the eel evolved this ability is still unknown, says Catania.

“It is possible that lower voltages had a similar effect in the course of evolution,” he says. “Smaller ‘blips’ induced in prey neurons by the ancestral eel discharge added together over a short time,” he suggests.

“This is an immensely interesting and important finding for electric fish biology,” says Jason Gallant at Michigan State University in East Lansing. “The discharge patterns have been described previously, but the mechanism by which the discharges act on their poor prey was only supposed.”

That eels evolved to not only disable prey, but to also flush them out is a surprise, Gallant says, and he wonders if this behaviour is eel-specific or is seen in other fish, even those that can’t produce such a forceful zap.