September 11, 2006, 8:18 PM CT
Electric Jolt Triggers Release Of Biomolecules
Peter Searson, professor of materials science and engineering, The Johns Hopkins University
Johns Hopkins scientists have devised a way to use a brief burst of electricity to release biomolecules and nanoparticles from a tiny gold launch pad. The technique could someday be used to dispense small amounts of medicine on command from a chip implanted in the body. The method also may be useful in chemical reactions that require the controlled release of extremely small quantities of a material.
The technique was described Sept. 10 in a presentation by Peter C. Searson, a Johns Hopkins professor of materials science and engineering, during the 232nd national meeting of the American Chemical Society in San Francisco. "You can think of the useful biomolecule or nanoparticle as a balloon tethered to a surface," he said. "We use an electrical pulse to cut the tether, and it floats away".
This method could be used to control the release of drug molecules; nanoparticles; biopolymers such as peptides, proteins and DNA; and protein assemblies such as viruses, said Searson, who also is director of the Institute for NanoBioTechnology at Johns Hopkins.
"The technique is relatively simple, but nothing like this has been done before," he said. "Researchers have known that molecules could be removed from a surface in this way, but it's never been considered useful. They've been more interested in preventing this from happening".........
Posted by: Ashley Permalink Source
September 9, 2006, 10:28 AM CT
Rice Domestiction Confiirmed
Photo courtesy USDA
Biologists from Washington University in St. Louis and their collaborators from Taiwan have examined the DNA sequence family tree of rice varieties and have determined that the crop was domesticated independently at least twice in various Asian locales.
Jason Londo, Washington University in Arts & Sciences biology doctoral candidate, and his adviser, Barbara A. Schaal, Ph.D., Washington University Spencer T. Olin Professor of Biology in Arts & Sciences, ran genetic tests of more than 300 types of rice, including both wild and domesticated, and found genetic markers that reveal the two major rice types grown today were first grown by humans in India and Myanmar and Thailand (Oryza sativa indica) and in areas in southern China (Oryza sativa japonica).
Schaal said that she was surprised and "delighted" by their results.
"People have moved rice around so much and the crop crosses with its wild ancestors pretty readily, so I was fully prepared to see no domestication signal whatsoever,," Schaal said.
"I would have expected to see clustering of the cultivated rice, but I was delighted to see geographical clustering of the wild rice. I was thrilled that there was even genetic structure in the wild rice."
In contrast to rice, other staple crops such as wheat, barley and corn appears to have been domesticated just once in history.........
Posted by: Jessica Permalink Source
September 6, 2006, 5:01 AM CT
World fruit flies on three continents
Old World fruit fly, Drosophila subobscura superimposed over chromosomes from the species.
Fast-warming climate appears to be triggering genetic changes in a species of fruit fly that is native to Europe and was introduced into North and South America about 25 years ago.
"This is a clear signal on three different continents that climate change is occurring, and that genetic change is going along with it," said Raymond Huey, a University of Washington biology professor who is co-author of a paper describing the findings, published Aug. 31 in Science Express, the online edition of the journal Science.
The research deals with an Old World fruit fly species called Drosophila subobscura, which originally ranged from the Mediterranean Sea to Scandinavia. European biologists who studied the insect's genetic makeup more than 40 years ago noted that sections of chromosomes were inverted, something like taking part of a bar code from a consumer product and flipping it backwards. The biologists found that the frequency of particular inversions was correlated with the latitude where a given insect was found. Inversions that were common in the north were uncommon in the south, and vice versa.
The fruit flies were accidentally introduced to the Pacific Coast of Chile in the late 1970s and to the North American West Coast in the early 1980s, probably on cargo ships. They spread rapidly, and in North America they are now found from near Santa Barbara, Calif., to northern Vancouver Island in British Columbia.........
Posted by: Ashley Permalink Source
September 5, 2006, 10:12 PM CT
Biological Switch from Plant Molecule
Nanoscientists have transformed a molecule of chlorophyll-a from spinach into a complex biological switch that has possible future applications for green energy, technology and medicine.
The study offers the first detailed image of chloropyhll-a - the main ingredient in the photosynthesis process - and shows how scientists can use new technology to manipulate the configuration of the spinach molecule in four different arrangements, report Ohio University physicists Saw-Wai Hla and Violeta Iancu in today's early edition of the journal Proceedings of the National Academy of Sciences.
The scientists used a scanning tunneling microscope to image chlorophyll-a and then injected it with a single electron to manipulate the molecule into four positions, ranging from straight to curved, at varying speeds. (View a movie here) Though the Ohio University team and others have created two-step molecule switches using scanning tunneling microscope manipulation in the past, the new experiment yields a more complex multi-step switch on the largest organic molecule to date.
The work has immediate implications for basic science research, as the configuration of molecules and proteins impacts biological functions. The study also suggests a novel route for creating nanoscale logic circuits or mechanical switches for future medical, computer technology or green energy applications, said Hla, an associate professor of physics.........
Posted by: Jessica Permalink Source
September 2, 2006, 9:59 PM CT
Weeds In The Garden
A 15-year study of flixweed, a member of the mustard family, helps explain plant population oscillations and may be useful in crop protection.
Credit: Courtesy J.L. Gonzalez-Andujar
Some years, no matter how diligently you pull, your backyard garden is always covered with weeds. Other years, with the minimum of effort, your garden remains weed-free. What is the cause of these oscillations? A group of weed scientists based at the Spanish National Research Council (CSIC) spent fifteen years studying flixweed a member of the mustard family commonly found in areas where the ground has been cultivated or disturbed in an attempt to identify the processes underlying these fluctuations.
"The failure to recognize the intrinsic nature of many weed population changes may result in over-application of control inputs, with subsequent negative economic and environmental effects," says Jose Gonzalez-Andujar, who co-authored the study, forthcoming in The American Naturalist, with Cesar Fernandez-Quintanilla and Luis Navarrete.
Many populations exhibit cyclic oscillations. Everybody can recall a summer where mosquitoes hindered attempts at al fresco dining. These cycles can be produced by climatic conditions or by internal feedback mechanisms. However, in contrast with studies of insect and animal populations, little attention has been directed at the study of cycles in plants. What happens with your garden weeds?
The researchers demonstrate that there are some intrinsic mechanisms that explain observed plant oscillations more specifically, evidence of cycles produced by delayed density dependence in a plant population growing under field conditions. This study can have a capital importance in crop protection.........
Posted by: Jessica Permalink Source
September 2, 2006, 9:54 PM CT
Equations That Model Interplanetary Gravity
Scientists from Penn State University and the University of Virginia show that the spread of diseases by insects can be described by equations similar to those that describe the force of gravity between planetary objects. Their findings are detailed in the recent issue of The American Naturalist.
Insects tend to transmit diseases in the course of feeding on plants, and their movement between plants is influenced by plant quality (how good of a meal they'll get) and the distance between plants, or, how far they'll have to travel to get to the next meal, explain Matthew Ferrari, Jessica Partain, Janis Antonovics, and Ottar Bjornstad.
"It turns out insects are more likely to move shorter distances between better plants," write the authors. "Interestingly, then, the probability of disease being passed between two plants goes up if they are closer and/or better, which parallels the stronger gravity between closer and larger planets".
The scientists tracked a fungal disease spread by bees and moths in the course of pollinating and feeding on nectar from white campion flowers at the University of Virginia's Mountain Lake Biological Station. As predicted by the behaviour of insects, the disease was more likely to spread shorter distances between plants that had a number of flowers.........
Posted by: Ashley Permalink Source
September 2, 2006, 9:45 PM CT
Power Structures Arising From Status Communication
Research on communication typically focuses on how individuals use signals to influence the behavior of receivers, thus primarily focusing on pairs of individuals. However, the role communication plays in the emergence of social structures is rarely studied. In a new paper from The American Naturalist, Santa Fe Institute researchers Jessica Flack and David Krakauer study how power structures arise from a status communication network in a monkey society. Power structure is important because it can influence the complexity of interactions among group members.
"When building a society, it is of utemost importance that signals be informative and any sources of ambiguity minimized," says Krakauer. "This requirement is reflected in the structure and function of communication networks. A goal of this research has been to study communication at a group level rather than the more traditional communication we associate with pairs".
Using information theory, the researchers show that power emerges through consensus. There is a high degree of consensus among group members that an individual is powerful if that individual has received multiple subordination signals from many individuals in the case of pigtailed macaque monkeys, a silent bared-teeth display. On the other hand, there is little consensus if signals come from just a few individuals.........
Posted by: Ashley Permalink Source
September 2, 2006, 9:17 PM CT
Fighting Weeds With Plant Pathogens
Eventhough plant pathogens are typically viewed as detrimental, plant pathologists with the American Phytopathological Society (APS) say plant pathogens may be a successful, eco-friendly tool for managing weeds.
"The use of plant pathogens to suppress weeds is considered as one of the alternative weed control options for areas or production systems where the use of chemical herbicides is not permitted or feasible," said Erin Rosskopf, USDA, Agricultural Research Service, Fort Pierce, FL. "Plant pathogens may also be used when the herbicide selection or usage must be rotated with other control methods in order to prevent the development of resistant weeds or lessen the impact of herbicides on the environment," she said.
Weed management is important due to the amount of damage weeds can cause to agricultural productivity. Weeds can reduce crop yields by as much as 12 percent (causing up to $32 billion in losses), based on the potential value of all U.S. crops of approximately $267 billion/year. Weeds also pose serious ecological problems. Invasive weeds are capable of altering ecosystem processes and displacing native plant and animal species. In addition, weeds serve as reservoirs for plant pathogens that impact crops.
As per Rosskopf, there are two approaches used for managing weeds with plant pathogens-the classical biological control approach and the bioherbicides approach. The classical biocontrol approach uses a pathogen imported from a foreign location to control a native or naturalized weed with minimal technological manipulations.........
Posted by: Jessica Permalink Source
August 31, 2006, 5:16 AM CT
Lead Poisoning In Condors
A study led by environmental toxicologists at the University of California, Santa Cruz, has confirmed what wildlife biologists have long suspected: Bullet fragments and shotgun pellets in the carcasses of animals killed by hunters are the principal sources of lead poisoning in California condors that have been reintroduced to the wild.
Lead poisoning is a major factor limiting the success of efforts to rebuild populations of the endangered California condor. Since the mid-1980s, condors have been bred in captivity and released back into the wild in California, Arizona, and Baja California. The birds, which feed on carrion, can ingest lead from ammunition in animal carcasses or gut piles left behind by hunters.
The UCSC researchers used a "fingerprinting" technique based on the unique isotope ratios found in different sources of lead. The technique enabled them to match the lead in blood samples from condors to the lead in ammunition. Their findings were published online today by the journal Environmental Science & Technology.
"There had been anecdotal reports for years about condors being exposed to lead from ammunition, but there was never enough clear evidence to document the extent of the problem. We knew that we could probably identify the sources of the lead using isotopic signatures," said Donald Smith, professor and chair of environmental toxicology at UCSC and a coauthor of the paper.........
Posted by: Ashley Permalink Source
August 29, 2006, 5:54 PM CT
Cylindropuntia Bigelovii
This isn't my best photograph of Cylindropuntia bigelovii or teddybear cholla, but it is one of the better ones I have from this particular location: the Cholla Cactus Garden in Joshua Tree National Park. This small area has the densest concentration of teddybear chollas within this massive park. While enjoying this tiny natural wonder, a thought did creep into my head: "Why build a road (and then highway) right through it?" I'm sure the decision was made before I was born, but I wonder if any thought has been given to rerouting the highway around this small patch, and then reclaiming the decommissioned road for the cholla.
Despite the common name of teddybear cholla, you do not want to hug this plant. Its needles have barbed ends that pierce and lodge. Tweezers or a comb are recommended to pick the needles out if they become embedded in your skin; attempting to pluck them out with your fingers will merely sink them into your fingertips (as I experienced).
The Living Desert has a good resource page on teddybear cholla, while Brad Biringer has photographs of the Cholla Cactus Garden taken in superior light conditions in this photo essay.
Photography resource link: Photoshop Tips and Tricks from the tips section of the Pacific Northwest Nature Photographers group.........
Posted by: Jessica Permalink Source
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