May 1, 2006, 0:13 AM CT

botanist and the vintner - Book Review

A phids have never enjoyed a especially good press. Their huddled masses rain excrement on our parked cars and bring disease and destruction to the crops and gardens of almost all temperate regions. But in the aphid rogues' gallery, one species has pride of place, the arch villain of them all-the grape phylloxera, which practically destroyed the French wine industry in the 19th century. Christy Campbell's book tells the epic story of how this insect was eventually defeated. It is a tale worth telling because this was an immensely important episode in ecological history, indeed a classic of invasion biology, with lessons that resonate for us today as we face mounting threats from the ravages of non-native species.

The bare bones of the story will be familiar to most wine drinkers. Phylloxera was introduced into a French vineyard in the Rhone Valley on the roots of living American vines in the 1860s. French vines, in contrast to most American vines, were very susceptible to the insect, which had evolved with the native American vine species and did not cause them appreciable damage. Phylloxera spread slowly but inexorably across the wine-growing regions of France, reaching the Champagne in 1890, and it eventually conquered all the major wine-growing regions of the world, with the exception of Chile. America provided the cure as well as the cause. American vines, the insects' Trojan horse, were not harmed by the insect, and could be used as rootstocks on which the susceptible European vine species Vitis vinifera could be grafted. This method was amazingly successful and continues to be used to keep the insect at bay. In hindsight the solution may seem obvious, but this book makes clear what an immense struggle was involved. Indeed, Campbell's book illustrates what a difficult, messy, and unpredictable business science can be, and what sheer hard work it is to translate scientific results into action.........

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April 29, 2006, 8:42 AM CT

High-Throughput Sea Urchins

Transgenic techniques like those used with fish and frogs are not confined to vertebrate models. One especially useful invertebrate for transgenic research is the sea urchin. Humans and sea urchins both belong to a very ancient lineage of animals whose members share certain features of early embryonic development.

With NCRR funding, Eric Davidson, Norman Chandler Professor of Cell Biology at the California Institute of Technology, studies a regulatory network of about 50 genes involved in embryonic development in the purple sea urchin (Strongylocentrotus purpuratus). Davidson's research group uses transgenic sea urchins to determine when and where specific regulatory elements exert their control on gene expression and to reveal the identities and functions of the a number of transcription factors involved in this process. Studying these complex regulatory interactions requires a lot of genetic material, and sea urchins have no trouble supplying it. A single female can release millions of eggs at a time, and individual eggs are easy to inject with transgenes.

A single female purple sea urchin is able to release millions of eggs at a time, yielding an abundant supply of genetic material for studies of embryonic development. (Photo by Laura Francis, National Oceanic and Atmospheric Administration).........

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April 29, 2006, 8:30 AM CT

Driving Force for Sexual Segregation

Sexual segregation is widespread throughout the animal kingdom. Eventhough many hypotheses have been proposed to account for observed patterns, the generality of the mechanisms remains debated. One possible reason for this is the focus on segregation patterns in large mammals such as ungulates, where the majority of studies are descriptions of a single population. Here, we present the results of a cross-population comparison of patterns of sexual segregation in the Trinidadian guppy, Poecilia reticulata.

We relate observed patterns to experimental quantification of predation risk and sexual harassment of females by males in eight populations. We find that the degree of segregation increases with predation risk, with deeper waters becoming increasingly female biased. Furthermore, we observed that levels of male harassment are lower in deeper water but only in those rivers that contain major guppy predators. We conclude that sexual segregation in guppies is consistent with the predation risk hypothesis: sexual segregation results from a combination of predation risk driving males (the more vulnerable sex) into less risky habitats and females gaining benefits of reduced sexual harassment by remaining in high-predation environments.........

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April 26, 2006, 7:56 PM CT

Chemist Discovers Secret Behind Nature's Medicines

After years of wondering how organisms managed to create self-medications, such as anti-fungal agents, chemists have discovered the simple secret.

Researchers already knew that a particular enzyme was able to coax a reaction out of stubborn chemical concoctions to generate a large family of medically valuable compounds called halogenated natural products. The question was, how do they do it?.

Chemists would love to have that enzyme's capability so they could efficiently reproduce, or slightly re-engineer, those products, which include antibiotics, anti-tumor agents, and fungicides.

Thanks to MIT chemistry Associate Professor Catherine L. Drennan's recent crystallography sleuthing, the secret to the enzyme's enviable prowess has come to light and it appears almost anti-climactic. It's simply a matter of the size of one of its parts.

"If an enzyme is a gun that fires to cause a reaction, then we wanted to know the mechanism that pulls the trigger," Drennan said. "In chemistry, we often have to look at 'molecules in, molecules out.' With halogenated natural products, though, we couldn't figure out how it happened, because the chemicals are so nonreactive. Now that we have the enzyme's structure and figured out how it works, it makes sense. But it's not what we would have predicted."........

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April 26, 2006, 6:54 PM CT

Virtual 'forest' used to measure navigation skills

A new study recently published in Journal of Vision, an online, free access publication of the Association for Research in Vision and Ophthalmology (ARVO), shows that an individual's navigation skills can be measured by using an immersive virtual "forest" in which peripheral visual field losses are simulated.

The study, conducted by scientists from the Lions Vision Center, Wilmer Eye Institute, Johns Hopkins University in Baltimore, Md., involved varying the study participants' visual field of view and recording several performance measures such as walking time and path efficiency. Participants were then identified as either "good navigators" or "poor navigators." The results suggest that poor navigators rely on visual information to solve the task while good navigators are able to use visual information in conjunction with an internal representation of the environment. As a result of these differences, the performance of the poor navigators improved more than the performance of the good navigators as the amount of available visual information increased.

"By simulating peripheral visual field losses during navigation, we were able to create a paradigm that systematically controls the amount of external visual information available to participants. This allows us to directly test the extent to which participants rely on this type of information, and identify those individuals who are able to rely on alternative sources of information to learn about their environments," said lead researcher Francesca Fortenbaugh, BS. "Knowing what types of information individuals use when navigating and how performance deteriorates when that information is removed is important not only for understanding human navigation in general, but also for the development of rehabilitation protocols for individuals with visual impairments".........

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April 24, 2006, 6:44 PM CT

Studying Ivory-billed Woodpecker

In late April 2005, the sighting of an Ivory-billed Woodpecker (Campephilus principalis) in the Big Woods of Arkansas was one of the most widely reported events in the history of conservation. There had been no confirmed sightings of this species since 1944. Ornithologists have spent the past three field seasons in the Big Woods trying to obtain data. Due to the elusiveness of this species, there have only been a handful of sightings, a brief video, and some audio recordings of calls and double raps.

In February 2000, Michael Collins, a Naval Research Laboratory scientist and bird watcher, heard the unmistakable calls of an ivorybill at NRL's Stennis Space Center site, located next to the Pearl River Basin, which runs north of Interstate 10 along the Mississippi-Louisiana border. After hearing the news of the discovery in Arkansas, Collins was inspired to conduct a serious search in the Pearl.

Collins has located ivorybills in an area where there had been a history of unconfirmed sightings. A sighting by David Kulivan, a Louisiana State University (LSU) graduate student, in 1999 generated a renewed interest in searching for the ivorybill. Researchers from LSU and Cornell University and a number of bird watchers visited the area in the following years, but they were unable to confirm the sightings or obtain data.........

Posted by: Ashley      Permalink         Source

April 23, 2006, 11:36 PM CT

Automated System Predicts Grape Yields

Estimating grape yields is a time-consuming, laborious affair. But that could change, thanks to a high-tech helping hand from Agricultural Research Service (ARS) researchers in Prosser, Wash.

There, ARS horticulturist Julie Tarara and his colleagues have developed an automated system for estimating grape yields based on tension changes in the trellis wire used to support the vine crop. Her team is still field-testing the system. The hope is that the yield estimates it produces will allow growers and processors to better synchronize their pruning, watering, picking and juice-making operations.

As per Tarara, who works in ARS' Horticultural Crops Research Unit at Prosser, the current method of estimating grape yields involves counting berry clusters on sample vines, followed by counting and weighing of individual berries. The averages are then compared to records from past seasons to predict the current crop's likely yield.

Imprecise estimates can sometimes be costly. For example, an inflated yield estimate might lead a winery to order more barrels than it actually needs. The "pain" is in the price tag: New American oak barrels start at around $300, while new French oak barrels cost from $600 to around $800 each.

The scientists' automated system employs a device called a load cell to detect increases in the tension of trellis wire as grape clusters form and berries enlarge. A data logger records signals generated by the tension changes every 10 seconds, formulating an average every 15 minutes. Now, Tarara's team must download, inspect and "clean" data logger information for processing and eventual use in predicting grape yield. Once validated with field tests, though, the process will be completely automated, providing users with real-time information on their crop's progress, as per Tarara.........

Posted by: Jessica      Permalink         Source

April 19, 2006, 10:08 PM CT

Simple Developmental Changes Gave Bats Flight

A change in a single gene may be in large part responsible for the evolution of flight in bats, as per new studies by Howard Hughes Medical Institute researchers. The findings not only help explain the emergence of flight in these animals, but also illustrate how alterations in genes that govern development can lead to the abrupt, dramatic changes in body shape frequently seen throughout evolution.

The fossil record indicates that bats, the only mammals with powered flight, date back to the Eocene, an era that began approximately 55 million years ago. Notably, bat wing anatomy has not changed substantially over the past 50 million years - an observation that served as a starting point for the new work, which was published April 17, 2006, in an advanced online publication of the Proceedings of the National Academy of Sciences.

"We saw that the evolution of flight was quite sudden," said Lee A. Niswander, a Howard Hughes Medical Institute investigator at the University of Colorado Health Sciences Center who led the study. "That means there could be just a few key changes in limb development that resulted in more dramatic downstream consequences."

To find those key changes, Niswander and his colleagues focused on the third, fourth, and fifth digits of the bat forelimb. These digits - equivalent to a human's middle, ring, and pinky fingers - are highly elongated and provide the support necessary for the wing membrane to be used for flight.........

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April 17, 2006, 11:36 AM CT

Red Tide CausesTurtle Death

The culprit is microscopic in size, but its effects are monstrous. Deadly algal blooms- known as "red tide" for the reddish pigments contained in these single-celled organisms at the base of the ocean's food web-have caused the deaths of some 200 sea turtles.

The event occurred in November 2005 off the southern coast of El Salvador. Soon after the first appearance of the red-tinged water, some of the region's people fell ill. The government responded by closing shellfish beds in the area, warning against eating seafood from affected areas. The first reports of dead and dying sea turtles washing up on shore occurred in the second week of December. Most of the victims were olive ridley turtles, and a few green and hawksbill turtles were among those stranded.

Working quickly, the Salvadoran government and the US Agency for International Development (USAID) called for assistance. WCS veterinary pathologist Dr. Julie White traveled to the site of the crisis in January, where she performed post-mortem examinations on one of the turtles. While there, she also trained Salvadorian colleagues in tissue collection techniques. Samples were then sent to Florida's Fish and Wildlife Research Institute, operated by the National Marine Fisheries Service and the University of Florida. There, researchers diagnosed the problem: high densities of saxitoxin, which is produced by species of algae and sea plankton. The toxin affects the nervous systems of humans and animals alike.........

Posted by: Ashley      Permalink         Source

April 13, 2006, 0:11 AM CT

Higher Carbon Dioxide, Lack Of Nitrogen Limit Plant Growth

Earth's plant life will not be able to "store" excess carbon from rising atmospheric carbon dioxide levels as well as scientists once thought because plants likely cannot get enough nutrients, such as nitrogen, when there are higher levels of carbon dioxide, according to scientists publishing in this week's issue of the journal Nature.

That, in turn, is likely to dampen the ability of plants to offset increases in atmospheric carbon dioxide.

"We found that atmospheric carbon dioxide levels may rise even faster than anticipated, because ecosystems likely will not store as much carbon as had been predicted," said Peter Reich of the University of Minnesota, lead author of the study, which was conducted at the National Science Foundation (NSF)'s Cedar Creek Long-Term Ecological Research (LTER) site in Minn.

"As a result, soils will be unable to sustain plant growth over time [as atmospheric carbon dioxide continues to increase]," said plant ecologist David Ellsworth of the University of Michigan.

Estimating the role of terrestrial ecosystems as current and future sinks--or storage places--for excess carbon dioxide hinges on an ability to understand the complex interaction between atmospheric carbon dioxide and nitrogen in soils, the scientists believe.........

Posted by: Jessica      Permalink         Source

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