Wednesday, January 19, 2011

WATER PURIFICATION MADE SIMPLER

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Inside a growing number of homes in the developing world, sand and biological organisms are collaborating to decontaminate drinking water.

Arranged in barrels of concrete or plastic, these biosand water filtration systems (BSFs) remove 95 to 99 percent of the bacteria, viruses, worms and particles contained in rain or surface water. A layer of microorganisms at the top of the sand bed consumes biological and other organic contaminants, while the sand below removes contaminants that cause cloudiness and odor.

A BSF can produce several dozen liters of clean water in an hour. But it can weigh several hundred pounds and cost up to $30, an expense some families in developing countries cannot afford.

Kristen Jellison and her students are trying to build a BSF that is smaller than the standard system, but just as effective.

“Smaller, lighter BSFs,” says Jellison, an associate professor of civil and environmental engineering, “would be cheaper, easier to transport and available to a broader global market. Preliminary research has shown the potential for smaller systems to remove most disease-causing organisms, except possibly viruses.”

Jellison, who is affiliated with the university’s STEPS (Science, Technology, Environment, Policy and Society) initiative, has devoted most of her career to improving drinking water. As a co-adviser to Lehigh’s chapter of Engineers Without Borders, she helped lead efforts to design and build a 20,000-gallon water-storage tank and chlorination system in Pueblo Nuevo, Honduras.

With support from NSF and the Philadelphia Water Department, she has spent five years studying the parasite Cryptosporidium parvum and its transport and fate in water bodies. The parasite is found in multiple hosts, is difficult to eradicate, and can be deadly to people with compromised immune systems.

In an effort to identify possible sources of Cryptosporidium contamination in the Philadelphia watershed, Jellison studies the DNA of various species using a technique called polymerase chain reaction (PCR). She also studies the impact on Cryptosporidium of biofilms, the slimy layers of microorganisms that form on rocks, pipes and other surfaces in water.

Jellison’s group is conducting experiments on BSFs of various sizes, including systems that fit inside two- and five-gallon plastic pails. (The typical BSF is 3 feet high.) The group will change the depth of the sand column, add rusty nails to several pails (in an effort to increase virus removal), and alter other parameters.

“BSFs were developed in the 1980s,” says Jellison. “This is the most comprehensive study to date to characterize the efficiency of different filter types.”

(Photo: Lehigh U.)

Lehigh University

IF MANY WANT TO FEED: HOW SEABIRDS SHARE THEIR HABITAT

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When different species of seabirds share a habitat with limited sources of food, they must differ in their feeding habits. This specialisation is known by biologists as an "ecological niche". Researchers at the Max Planck Institute for Ornithology in Radolfzell have investigated how flexible these ecological niches really are.

They discovered that the preying habits of diving seabirds are very different, both in location and timing, within species as well as between different species. Ecological niches are not inflexible; they are affected by different habitats and the need to avoid competition with neighbours or evade predators, and also lead to different forms of behaviour within a single species.

Seabirds are an excellent species for studying the question of how animals share the limited supply of food in their habitat. Seabirds must live on land during the breeding season, and over this period they have to share space and food with many other animals. The birds breed in nesting colonies, often in confined spaces that provide protection from predators—the food supply, however, is widely distributed throughout the sea off the coast. The birds must leave the colony to find food and then return to the islands to feed their chicks.

The scientists wanted to know how several species, similar in their demands, are able to breed together on an island and what exactly the differences in their ecological niches are. Using GPS-depth loggers that allow scientists to track birds detailed in three dimensions, researchers in the past have discovered the hunting areas and depths of several diving seabirds, such as penguins and cormorants, but always only for sample colonies. Until now it has been unknown whether these data can be transferred to entire species.

On New Island, part of the Faulkland Islands in the southern Atlantic Ocean, scientists at the Max Planck Institute for Ornithology used GPS-depth loggers to comprehensively study complete a comprehensive study of the hunting habits of four diving seabirds: three species of penguins—Gentoo penguins, Rock Hopper penguins and Magellan penguins—and Imperial shags. In addition, the researchers compared two colonies of each of the three penguin species.

"The results were very surprising," says biologist Dr. Juan Masello. "Based on the ecological niche theory, we had expected especially strong differences between species. However, the data show that the spatial and temporal distribution of birds within the species can also differ greatly."

Magellan penguins, for example, used hunting areas about 40 kilometres apart from each other, whereas the two colonies on land were only two kilometres apart. In contrast, one of the Gentoo penguin colonies often hunted at night, while the other neighboured colony hunted only in the daytime. In this way, the colonies avoid an overlap in feeding areas and small-scale differences are used effectively." adds Dr. Petra Quillfeldt. In the colony of Imperial shags, the females and males hunt both at different times and places: in the mornings, the females go hunting near the coast, and in the afternoons, the males hunt in the open sea. Thus the different species of seabirds found different solutions to avoid competing with their own species for food.

"Of course, food is not the only factor that determines the distribution of birds around the island," Dr. Quillfeldt explains. "In two of the penguin species, it was very clear that the animals avoided swimming near a seal colony where they could themselves become the prey. This dangerous zone also contributed to the spatial separation of the birds in the sea."

This is the first comprehensive study showing the ecological niches within a species, as well as between species, over the same period of time. It shows that seabirds of different species, as well as colonies of the same species, differ in their temporal and spatial distribution and that they search for food in different areas of the ocean, often far apart, and at different depths and temperatures. The ecological niches of the species studied are far less rigid than previously thought. Even small differences in habitat or in behaviour, or the need to avoid competition or predators, contribute to this specialisation.

Max Planck Institute

DIFFERENT SOURCES, SAME RESULT

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Numerous patients suffering from chronic liver diseases are currently receiving inadequate treatment due to the lack of organs donated for transplantation. However, hepatocytes derived from induced pluripotent stem cells (iPSCs) could offer an alternative for the future.

Scientists from the Max Planck Institute for Molecular Genetics in Berlin compared hepatocytes from embryonic stem cells with hepatocytes from iPS cells and found that their gene expression is very similar. Nevertheless, in comparison to "real" hepatocytes, just under half of the genes exhibited a different gene expression. Therefore, the gene expression of hepatocytes derived from iPS cells still requires adaptation before the cells could be used in the treatment of liver diseases.

Induced pluripotent stem cells can be derived from different cell types and have the same genetic background as their progenitors. Hepatocytes derived from iPSCs therefore constitute an ideal point of departure for future regenerative therapy, as immune rejection between donor and host cells can be avoided.

In their study, the Max Planck scientists compared hepatocyte-like cells derived from iPS cells and embryonic stem cells with "real" hepatocytes in early and later stages of development. Justyna Jozefczuk from the Max Planck Institute for Molecular Genetics explains: "It is the only way to determine actual differences between the cell types, and any flaws still present in the ‘synthetic’ hepatocytes". The scientists were able to show that the gene expression of hepatocytes based on embryonic stem cells and iPSCs is about 80 per cent similar. However, compared to isolated cells from the foetal human liver, the gene expression match is only 53 per cent.

Hepatocyte-like cells from iPSCs and embryonic stem cells activate many of the typical liver proteins, e.g., albumin, alpha-fetoprotein and cytokeratin 18. Moreover, the "synthetic" hepatocytes can store glycogen and produce urea, just like the "real" hepatocytes. In addition, they are able to absorb and break down foreign molecules. In contrast, the genes around the enzyme group cytochrome P450 in the iPSCs and in real hepatocytes display different expression levels. These enzymes metabolise, among other things, drugs and foreign substances. "This knowledge not only helps us better understand the causes of liver diseases; it also allows us to develop more efficient, patient-specific drugs", says James Adjaye from the Max Planck Institute for Molecular Genetics.

Max Planck Institute

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