October 29, 2006, 8:11 PM CT

New insight into cell division

When cells divide, control mechanisms ensure that the genetic material, in other words the chromosomes, is correctly distributed to the daughter cells. Scientists at the Max Planck Institute for Molecular Genetics in Berlin have now explained the molecular principles of these control processes. The so-called checkpoint kinases, i.e. the enzymes which perform this controlling, are not directly associated only with the chromosomes, as was previously assumed to be the case. On the contrary, they interact with a different category of proteins which are involved in the development of the cell division spindle. This finding is highly significant, since incorrect distribution of the chromosomes can lead to abnormalities and diseases such as cancer. The new understanding of this process will in turn promote a better understanding of the molecular principles of the development of cancer (Science, October 27, 2006).

The rod-shaped filaments of the microtubules are responsible for dividing the chromosomes in a cell. They form a correlation between the starting point in the chromosomes, the kinetochors, and the centrosome. The centrosome organizes the spindle-shaped arrangement of the microtubule filaments in the cell by means of gamma tubulin ring complexes. Until now it was assumed that control of even distribution of chromosomes was only monitored by the checkpoint kinases in the kinetochors. When microtubules are correctly attached to the kinetochors, these kinases then inform the cell that a precise distribution of chromosomes can be carried out.........

Posted by: Janet      Permalink         Source

October 29, 2006, 7:45 PM CT

Untold Stories Of Elk Skeleton

Seeing the well-preserved antlers, skull and partial skeleton of a very large elk that was found in northern Wisconsin was impressive enough. But what really intrigued Jean Hudson was what was found nearby - a Clovis point, a type of spearhead used by hunters from about 10,000 years ago.

Very few have been found this far north, and this spearhead may be the one that doomed the animal all those millennia ago, says Hudson, an associate professor of anthropology. Or the two specimens could be completely unrelated, she says.

If the two are linked, it would mean that the elk remains are especially rare. More physical evidence of animals such as mastodons, wooly mammoths and giant bison exists than that of elk, says Hudson.

But decoding the secrets of an animal skeleton requires asking the same questions you would at a crime scene investigation: What were the time, cause and circumstances of death? It also involves sometimes getting it wrong, leading to new questions.

A swimmer discovered the antlers of what appears to be a prehistoric elk at the bottom of Middle Eau Claire Lake in Barnes, Wis., last summer. Matt McKay of the Department of Natural Resources in Hayward, who is assigned to the maintenance of the Clam Lake elk herd, estimated the elk would have been between 1,000 and 1,100 pounds when it was alive.........

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October 29, 2006, 6:52 PM CT

Flight of the Bumblebee

Rebecca Flanagan has probably come as close as a human can to reading the mind of a bumblebee.

Flanagan, a graduate student in biological sciences, and Associate Professor Jeffrey Karron are studying the behaviors of bees as they gather pollen - which plant species the bees forage on, which flowers they probe and in what order, and how a number of blooms they visit before moving on to another plant. In doing so, the bees make plant reproduction possible by dispersing pollen.

To predict where each bee that she tracks will carry its pollen next, Flanagan has to literally think like one.

"Once they've learned a foraging style that's been successful, they are more likely to stick with it rather than invest time in learning something new," says Flanagan.

But why go to such lengths to map the flight of the bumblebee? It may seem random and inconsequential. But it is neither, says Karron.

The bees are pivotal players in determining which plant populations survive through successful reproduction. If researchers could better understand nature's decision-making process, then they could use the information to increase crop yields and to boost conservation of native plant communities.

Best bee practices

Because there are a number of bee behaviors, the task isn't simple, but with tedious scrutiny it is documentable.........

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October 27, 2006, 9:23 PM CT

How Female Pronghorns Choose Mate?

When a female animal compares males to choose a mate, she can't order a laboratory genetic screen for each suitor. Instead, she has to rely on external cues that may indicate genetic quality. Until now, biologists have focused on elaborate ornaments, such as the peacock's tail, as cues that females might use.

The thorny problem has been to explain how the connection between male genetic quality and ornament quality can be maintained. If an ornament gives a male a mating advantage, then evolution would rapidly move to the point where all males, regardless of genetic quality, have high-quality ornaments.

"Female mate choice is likely a very important evolutionary force that does much more than select for ornaments in a few species," said John Byers of the University of Idaho. "It may be universally important in maintaining population genetic quality".

In work supported by the National Science Foundation (NSF), Byers has shown that certain females can choose good genes in a species that does not have ornaments, such as the American pronghorn, an antelope-like mammal that evolved in North America. Byers has been studying pronghorn at the National Bison Range, a 30-square-mile National Wildlife Refuge in northwestern Montana, for 20 years, and recognizes all individual pronghorn in the population.........

Posted by: Kelly      Permalink         Source

October 27, 2006, 9:01 PM CT

Mate-attracting Chemicals

Silkworm moths are white-haired with two-inch wingspans
It's all about "the birds and the bees." And now, "the silkworm moths and the fruit flies".

A chemical ecologist and a genetics researcher at the University of California, Davis, have joined forces to trick fruit flies into thinking that silkworm moths are potential mates.

Groundbreaking research in the labs of chemical ecologist Walter Leal and genetics researcher Deborah Kimbrell shows that genetically engineered fruit flies responded to the silkworm moth scent of a female.

The practical implications of the findings could be widespread. Methods that can attract or repel insects have important applications for agricultural pests and medical entomology. The research could lead to designing better chemicals to attract insects and designing better chemicals to suppress insect communication. That is because insects communicate or smell through their antennae.

A number of insect species, including silkworm moths, release sex pheromones or chemical signals to attract a mate. "Silkworm moths utilize smell more strongly than any other senses," said Leal, professor and chair of the Department of Entomology. "Moths keep on the trail of a scent until they find a female".

"We got a very clear response," he said. "Our electrophysiological recordings and direct stimulation testing showed that the transgenic fruit flies definitely responded to the moth pheromone."........

Posted by: Kelly      Permalink         Source

October 27, 2006, 5:19 AM CT

What Killed Dinosaurs 65 Million Years Ago

Growing evidence shows that the dinosaurs and their contemporaries were not wiped out by the famed Chicxulub meteor impact alone, as per a paleontologist who says multiple meteor impacts, massive volcanism in India and climate changes culminated in the end of the Cretaceous Period.

The Chicxulub impact may have been the lesser and earlier of a series of meteor impacts and volcanic eruptions that pounded life on Earth for more than 500,000 years, say Princeton University paleontologist Gerta Keller and her collaborators Thierry Adatte from the University of Neuchatel, Switzerland, and Zsolt Berner and Doris Stueben from Karlsruhe University in Gera number of.

A final, much larger and still unidentified impact 65.5 million years ago appears to have been the last straw, said Keller, exterminating two-thirds of all species in one of the largest mass extinction events in the history of life. It's that impact - not Chicxulub - that left the famous extraterrestrial iridium layer found in rocks worldwide that marks the impact that finally ended the Age of Reptiles, Keller believes.

"The Chicxulub impact alone could not have caused the mass extinction," said Keller, "because this impact predates the mass extinction".

Keller is scheduled to present that evidence at the annual meeting of the Geological Society of America (GSA) in Philadelphia, on Tuesday, October 24, 2006.........

Posted by: Kelly      Permalink         Source

October 27, 2006, 4:39 AM CT

What Makes A Bee A He Or A She?

Three years ago, researchers pinpointed a gene called csd that determines gender in honey bees, and now a research team led by University of Michigan evolutionary biologist Jianzhi "George" Zhang has unraveled details of how the gene evolved. The new insights could prove useful in designing strategies for breeding honey bees, which are major pollinators of economically important crops-and notoriously tricky to breed.

The findings of Zhang and collaborators appear in a special issue of Genome Research devoted to the biology of the honey bee. The issue will be published online and in print Oct. 26, coinciding with the publication of the honey bee genome sequence in the journal Nature.

Researchers have long known that in bees-as well as wasps, ants, ticks, mites and some 20 percent of all animals-unfertilized eggs develop into males, while females typically result from fertilized eggs. But that's not the whole story, and the discovery in 2003 of csd (the complementary sex determination gene) helped fill in the blanks. The gene has a number of versions, or alleles. Males inherit a single copy of the gene; bees that inherit two copies, each a different version, become female. Bees that have the misfortune of inheriting two identical copies of csd develop into sterile males but are quickly eaten at the larval stage by female worker bees.........

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October 26, 2006, 4:56 AM CT

Pollinators Help One-third Of Crop Production

Pollinators such as bees, birds and bats affect 35 percent of the world's crop production, increasing the output of 87 of the leading food crops worldwide, finds a new study published recently (Wednesday, Oct. 25), in the Proceedings of the Royal Society B: Biological Sciences and co-authored by a conservation biologist at the University of California, Berkeley.

The study is the first global estimate of crop production that is reliant upon animal pollination. It comes one week after a National Research Council (NRC) report detailed the troubling decline in populations of key North American pollinators, which help spread the pollen needed for fertilization of such crops as fruits, vegetables, nuts,.

Of particular concern in the NRC report was the decline of the honey bee, a species introduced from Europe and a critical pollinator for California's almond industry. The report pointed out that it takes about 1.4 million colonies of honey bees to pollinate 550,000 acres of this state's almond trees.

In an effort to better understand how dependent crop production is upon pollinators worldwide, an international research team led by Alexandra-Maria Klein, an agroecologist from the University of Goettingen in Gera number of, conducted an extensive review of scientific studies from 200 countries and for 115 of the leading global crops.........

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October 26, 2006, 4:50 AM CT

Nuclear Receptors In Bee Genome

Susan Fahrbach, a Wake Forest University biologist, is among the more than 170 scientists who helped decode the honey bee genome. She contributed to the article on the bee genome sequence that appears in the Oct. 26 issue of Nature.

Her piece of the puzzle -- analyzing the nuclear hormone receptors found in the bee genome -- also appears in the current issue of Insect Molecular Biology.

The honey bee was chosen to have its genome sequenced because of its dual importance to agriculture and medicine. The well-known pollination activities of honey bees add billions of dollars of value to U.S. crops every year, but bees are also used in the laboratory to study issues correlation to human health such as immunity, longevity and diseases of the X chromosome. In addition, brain researchers are interested in the honey bee's complex social life and their ability to communicate the location of flowers to other members of the hive.

Fahrbach, Reynolds Professor of Developmental Neuroscience, and her co-scientists at Wake Forest and the University of Illinois, searched the genome sequence to find all of the nuclear receptors encoded in the bee genome. They observed that the same nuclear receptors that control the development of the nervous system during the early.........

Posted by: Kelly      Permalink         Source

October 24, 2006, 7:19 PM CT

New Theory For Mass Extinctions

A new theory on just what causes Earth's worst mass extinctions may help settle the endless scientific dust-up on the matter. Whether you favor meteor impacts, volcanic eruptions, cosmic rays, epidemics, or some other cause for the worst mass extinction events in Earth's history, no single cause has ever satisfied all scientists all the time for any extinction event. That may be because big extinctions aren't simple events.

The new Press/Pulse theory gets around the controversy by rejecting the all-or-nothing approach to mass extinction, calling instead on a combination of deadly sudden catastrophes - "pulses" - with longer, steadier pressures on species - "presses".

"What we wanted to do is move away from the idiosyncratic approach to extinction mechanisms and look for what these intervals had in common. If you have A and B you will get a mass extinction," said Ian West, a 2006 graduate of Hobart and William Smith Colleges in Geneva, NY.

West and Hobart and William Colleges paleontology professor Nan Crystal Arens are scheduled to present their work on the Press/Pulse theory on Wednesday, 25 October, at the Annual Meeting of the Geological Society of America in Philadelphia.

Using databases that chart genera of marine organisms and their extinctions through the fossil record, West and Arens divided the last 488 million years of geologic history into four groups: times of suspected impact events (Pulses), times of massive volcanic eruptions (Presses), times when neither Presses nor Pulses occurred, and times when Press and Pulse coincided. They compared average extinction rates in geologic stages in each of these groups.........

Posted by: Janet      Permalink         Source