Saturday, April 26, 2014

Male Goats' Stench Activates Female Goats' Reproductive System

goatsMale goats reek. Yet somehow, their mere presence can turn female goats on. Now scientists think they have figured out how this “male effect” works: They’ve discovered a citrus-scented chemical that males emit that speaks directly to females, activating their reproductive brain region and ramping up their sex hormones.

The study is the first to uncover a single molecule that could be activating the entire female reproductive center, according to the researchers.

Pheromones are chemicals released by the body to trigger particular reactions in members of the same species—in the case of sex pheromones, members of the opposite sex. All mammals have sex pheromones, and they come in two kinds: releaser and primer.

Releaser pheromones trigger behavioral responses in the brains of potential mates. The include things like attraction, for example, but the effects are pretty fleeting. Primer pheromones, on the other hand, have been much harder to pin down. They elicit actual physiological changes in the body that are much longer lasting—things like the release of reproductive hormones responsible for ovulation and menstruation.

But scientists hadn’t been able to isolate or identify these primer hormones in mammals until a team in Japan figured out how.

The researchers determined that the pheromones of interest were secreted from the skin on male goats’ heads. To capture these chemicals, the scientists fashioned custom-made caps for the goats that could adsorb (not absorb) them. Two groups of goats—one castrated and one not—donned the special hats for a week, allowing the researchers to collect and identify the chemicals coming from the goat noggins via gas chromatography-mass spectrometry. The researchers found several chemical compounds coming from the uncastrated goats that were missing from the sterile males. Many of them had never been found in nature before.

Next up was determining if and how the females would react to these chemicals. The researchers used electrodes to monitor neural activity in conscious female goat brains. They looked specifically at the hypothalamus, the particular region of the brain controls hormones, among other things.

When the female goats whiffed some male goat hair in a plastic cup, the scent activated something called the gonadotrpin-releasing hormone pulse generator. That’s a fancy way of saying it activated the master switch for all reproductive hormones. But here’s the kicker: the females’ reproductive systems were also turned on by the chemical compounds isolated in the lab.

One particular compound called 4-ethyloctanal triggered a really strong response, enough so that the researchers are pretty convinced it is the elusive primer pheromone. As further proof, when the chemical is exposed to the atmosphere, it oxidizes to become 4-ethyloctanoic acid—the main ingredient in the stench for which male goats are famous. The researchers think their results, published in Current Biology, could explain the power of the “male effect” in goats and could help us better understand how pheromones regulate reproduction in other mammals, including humans.

Image credit: Dudarev Mikhail/Shutterstock

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Monday, April 21, 2014

Swirling Cyclone Bears Down on California

As I write this, California is being lashed by rain and wind from a storm bringing much needed moisture — but which also threatens to cause some havoc in the form of mudslides and flooding.

Here’s how the National Weather Service in Los Angeles described it in their forecast discussion this morning:

A VIGOROUS WINTER STORM WILL AFFECT THE AREA THROUGH SATURDAY. EXPECT RAIN...MOUNTAIN SNOW...GUSTY WINDS...POSSIBLE THUNDERSTORMS...WATERSPOUTS...URBAN FLOODING...AND MUD AND DEBRIS FLOWS NEAR RESENT BURN AREAS. RAINFALL WILL BE INTENSE AT TIMES. A CLEARING AND DRYING TREND WILL START SUNDAY AFTERNOON. CLEAR WITH A WARMING TREND FOR EARLY NEXT WEEK.

Waterspouts?!

In the gallery above, you won’t see any of those. These images are various satellite views of the swirling cyclone that is bringing both relief and risk to California today and through tomorrow.

The first is a visualization of the storm’s cyclonic winds, as forecast by supercomputers. I chose it to lead off the gallery because it really emphasizes the structure of this powerful storm.

The next three images come from the GOES-13 weather satellite. The first is a true-color image of the storm. Next is a picture that shows water vapor over the Pacific. And in the third, North American is seen in the infra-red portion of the electromagnetic spectrum. I included this one because it shows the broader geographic context — and just how huge the storm is.

After the GOES satellite imagery comes two images captured by NASA’s Aqua satellite on Thursday, February 27. The first is in natural color, and it too emphasizes the sheer size of the storm. But I’m also intrigued by the much smaller cyclone-like pattern of clouds to the east, closer to the West Coast.

The second Aqua image is in false-color. Based on light in the visible part of the electromagnetic spectrum and short-wave infrared, this color scheme is good for revealing snow and ice — including small ice crystals in high-level clouds, which appear reddish-orange or peach. (This is the 3-6-7 band combination of Aqua’s MODIS instrument. For more detailed information, go here.)

Lastly, an image showing total precipitable water over the Pacific. The colors give an indication of the amount of atmospheric water vapor from the top of the atmosphere to the surface. It really emphasizes the tropical source of the moisture now dumping on California.

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