Category Archives: Life Science

Scientists Witness the Birth of a Brain Cell

The Birth of a Brain Cell: Scientists Witness Neurogenesis

For the first time, researchers have developed a way to view stem cells in the brains of living animals, including humans—a finding that allows scientists to follow the process neurogenesis (the birth of neurons). The discovery comes just months after scientists confirmed that such cells are generated in adult as well as developing brains.
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The key ingredient in this process is a substance unique to immature cells that is neither found in mature neurons nor in glia, the brain’s nonneuronal support cells. Maletic-Savatic and her colleagues collected samples of each of the three cell types from rat brains (stem cells from embryonic animals, the others from adults) and cultured the varieties separately in the lab. They were able to determine the chemical makeup of each variety – and isolate the compound unique to stem cells – with nuclear magnetic resonance (NMR) spectroscopy. (NMR helps to determine a molecule’s structure by measuring the magnetic properties of its subatomic particles.) Although the NMR could identify the biomarker, but not its makeup, Maletic-Savatic speculates it is a blend of fatty acids in a lipid (fat) or lipid protein.

Bacteria Survive On All Antibiotic Diet

Bacteria Survive on All-Antibiotic Diet

The scientists wanted to make sure they had a good control—a group of bacteria that didn’t grow at all—so they bathed some of the bacteria in antibiotics. But there was a problem: The bacteria didn’t just survive in the antibiotics, they consumed them. The researchers then gathered soil from 11 sites with varying degrees of exposure to human-made antibiotics (from manure-filled cornfields to an immaculate forest) and found that every site contained bacteria, including relatives of Shigella and the notorious E. coli that could survive solely on antibiotics. And these weren’t just piddling doses—the bacteria could tolerate levels of antibiotics that were up to 100 times higher than would be given to a patient, and 50 times higher than what would qualify a bacterium as resistant.

Royal Ant Genes

Royal corruption is rife in the ant world

“The accepted theory was that queens were produced solely by nurture: certain larvae were fed certain foods to prompt their development into queens and all larvae could have that opportunity,” explains Dr Hughes. “But we carried out DNA fingerprinting on five colonies of leaf-cutting ants and discovered that the offspring of some fathers are more likely to become queens than others. These ants have a ‘royal’ gene or genes, giving them an unfair advantage and enabling them to cheat many of their altruistic sisters out of their chance to become a queen themselves.”
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“When studying social insects like ants and bees, it’s often the cooperative aspect of their society that first stands out,” says Dr Hughes. “However, when you look more deeply, you can see there is conflict and cheating – and obviously human society is also a prime example of this. It was thought that ants were an exception, but our genetic analysis has shown that their society is also rife with corruption – and royal corruption at that!”

Interesting. I am not convinced of the “corruption” but maybe the research itself provides more evidence of this trait not just being interesting but equivalent to corruption.

Androgenesis

All Dad by Carl Zimmer

This week’s revelation is androgenesis. Androgenesis is what happens when kids get all their genes from their father.
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Androgenesis, it turns out, transforms fatherhood into a parasitic invasion. It begins like normal fertilization, with a sperm fusing to an egg. But then the egg’s DNA gets hurled out of its nucleus, so that the sperm’s genes are the only ones left in the egg. The egg begins to develop into an embryo, but only after it has lost the mother’s DNA.

Don’t Eat What Doesn’t Rot

Here is a nice interview of Michael Pollan by Amy Goodman – Don’t Eat Anything That Doesn’t Rot:

Another assumption of nutritionism is that you can measure these nutrients and you know what they’re doing, that we know what cholesterol is and what it does in our body or what an antioxidant is. And that’s a dubious proposition.
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if you look at the layout of the average supermarket, the fresh whole foods are always on the edge. So you get produce and meat and fish and dairy products. And those are the foods that, you know, your grandmother would recognize as foods. They haven’t changed that much. All the processed foods, the really bad stuff that is going to get you in trouble with all the refined grain and the additives and the high-fructose corn syrup, those are all in the middle. And so, if you stay out of the middle and get most of your food on the edges, you’re going to do a lot better.

Appetite for Destruction

photo of Mountain Pine Beetle

Appetite for Destruction (link broken, so I removed it) by Eric R. Olson:

“Once the beetles are at the level they’re at in British Columbia, there’s nothing you can do – it’s like a rapidly spreading fire,” says Barbara Bentz, research entomologist with the U.S. Department of Agriculture Forest Service. If the beetle continues to devour trees at the current rate, 80 percent of British Columbia’s mature pines will be killed off by 2013, according to Natural Resources Canada, an arm of the Canadian government.

Global climate change, which is pushing temperatures higher, has altered the beetle’s natural life cycle. Now the insect threatens one of the world’s largest forest systems: Canada’s boreal forest, a 600-mile-wide band of pine woodlands that stretches from the Yukon in Alaska all the way to Newfoundland on the East Coast.
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The source of all this destruction is an insect not much bigger than a grain of rice. A native of North America, the pine beetle does its damage by burrowing beneath the bark and feeding on the living tissue of the tree called the phloem. This tissue is composed of long tubes that transport nutrients from root to limb, and once it is destroyed, the tree can no longer survive.

In the past, cold snaps — quick drops in temperature in the spring and fall — have kept beetle populations in check. Although the insects can survive temperatures as low as minus 35 degrees Fahrenheit in the winter, it takes time for their bodies to accumulate enough glycol, the same ingredient found in antifreeze, to survive such frigid temperatures.

Photo: Mountain Pine Beetle (Dendroctonus Ponderosae) under a scanning electron microscope. [Credit: Leslie Manning/Canadian Forest Service]

Secrets of Spider Silk’s Strength

The strength of a biological material like spider silk lies in the specific geometric configuration of structural proteins, which have small clusters of weak hydrogen bonds that work cooperatively to resist force and dissipate energy, researchers in Civil and Environmental Engineering have revealed.

This structure makes the lightweight natural material as strong as steel, even though the “glue” of hydrogen bonds that hold spider silk together at the molecular level is 100 to 1,000 times weaker than the powerful glue of steel’s metallic bonds or even Kevlar’s covalent bonds.
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“Using only one or two hydrogen bonds in building a protein provides no or very little mechanical resistance, because the bonds are very weak and break almost without provocation,” said Buehler, the Esther and Harold E. Edgerton Assistant Professor in the Department of Civil and Environmental Engineering. “But using three or four bonds leads to a resistance that actually exceeds that of many metals. Using more than four bonds leads to a much-reduced resistance. The strength is maximized at three or four bonds.”

Ballast-free Ships

ballast-free ship’ could cut costs while blocking aquatic invaders

University of Michigan researchers are investigating a radical new design for cargo ships that would eliminate ballast tanks, the water-filled compartments that enable non-native creatures to sneak into the Great Lakes from overseas. At least 185 non-native aquatic species have been identified in the Great Lakes, and ballast water is blamed for the introduction of most—including the notorious zebra and quagga mussels and two species of gobies.

This week, the U.S. Saint Lawrence Seaway Development Corp. will implement new rules designed to reduce Great Lakes invaders. Ships will be required to flush ballast tanks with salt water before entering the Seaway, a practice corporation officials describe as an interim measure, not a final solution.
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Instead of hauling potentially contaminated water across the ocean, then dumping it in a Great Lakes port, a ballast-free ship would create a constant flow of local seawater through a network of large pipes, called trunks, that runs from the bow to the stern, below the waterline.

“In some ways, it’s more like a submarine than a surface ship,” Parsons said. “We’re opening part of the hull to the sea, creating a very slow flow through the trunks from bow to stern.

Giant Star Fish and More in Antarctica

photo of giant starfish

Photo by John Mitchell, New Zealand’s National Institute of Water and Atmospheric Research. Read a great deal about the New Zealand Census of Antarctic Marine Life project: 26 scientists and 18 crew took a 50-day voyage aboard RV Tangaroa in February-March 2008.

Benthic invertebrates in Antarctica are well known for their large size. This feature, known as “gigantism” is common amongst certain groups including sea spiders, sponges, isopods, starfish, and amphipods. The phenomenon is a subject of intense scientific investigation, but there are many contributing factors.

Slow growth rates, late reproductive maturation, prolonged periods of embryonic development, and low predation rates that are typical of Antarctic waters contribute to long life-spans for many species and can also result in large size animals. Animal physiology is thought to play a role as well, as those groups that require large amounts of calcium should not, in theory, grow well in Antarctic waters. This is because the calcium carbonate (needed for growth of shells, or starfish ‘tests’) has low solubility in very cold seawater. Yet starfish, which have a calcareous exoskeleton or ‘test’ which needs lots of calcium, can reach much larger sizes than found in New Zealand waters, as seen in [photo].

Another crucial part of the story is that the low sea temperatures allow more oxygen to be dissolved in the sea water than in warmer latitudes. Sea spiders for example are not only larger, but reach more than 1000 times the weight of most temperate species. Amphipod crustaceans in the Southern Ocean are also large; more than five times as long as the largest temperate species.

Baby Sand Dollars Clone Themselves When They Sense Danger

Baby sand dollars clone themselves when they sense danger

The odds of growing up aren’t good for baby sand dollars. Smaller than the head of a pin, the larvae drift in the ocean — easy prey for anything with a mouth.

But a University of Washington graduate student has discovered the tiny animal has a surprising survival strategy: Faced with the threat of being gobbled up, it makes like Dr. Evil from the Austin Powers movies and clones itself. The resulting “mini-me” may escape hungry fish because it is even teenier than the original — and harder to see.

“If you are eaten, but the smaller version of you survives, you’re still a winner from an evolutionary standpoint,” said Dawn Vaughn.
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Familiar inhabitants of Washington’s subtidal zone, sand dollars start life though the chance encounter of sperm and egg, simultaneously released into the water by mature adults. The larvae free-float for about six weeks before metamorphosing into miniature sand dollars that settle in colonies and eventually grow to full size.
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The white shells that wash up on the beach are the creatures’ external skeletons. Living sand dollars are covered with velvety, purple spines used to grab food particles. Vaughn knew many other marine invertebrates shift their shape to avoid being eaten. Colonial animals called bryozoans grow spikes when voracious sea slugs crawl across them. Barnacles take on a bent posture to repel snails. Vaughn’s own previous research showed periwinkle larvae narrow their shell openings to keep out marauding crab larvae.