Benjamin Ziman, Peter Karabinis, Paul Barghouth, and Nestor J. Oviedo

Nutrient availability upon feeding leads to an increase in body size in the planarian Schmidtea mediterranea. However, it remains unclear how food consumption integrates with cell division at the organismal level. Here we show that Sirtuins is evolutionarily conserved in planarians and specifically demonstrate that Sirtuin-1 (Smed-Sirt-1) regulates organismal growth by impairing both feeding behavior and intestinal morphology. Disruption of Smed-Sirt-1 with either RNAi or pharmacological treatment leads to reduced animal growth. Conversely, enhancement of Smed-Sirt-1 with resveratrol accelerates growth. Differences in growth rates were associated with changes in the amount of time to locate food and overall consumption. Furthermore, Smed-Sirt-1(RNAi) animals displayed reduced cell death and increased stem cell proliferation accompanied by impaired expression of intestinal lineage progenitors and reduced branching of the gut. Altogether, our findings indicate Sirtuin-1 is a crucial metabolic hub capable of controlling animal behavior, tissue renewal and morphogenesis of the adult intestine.

Björn Eismann, Teresa G. Krieger, Jürgen Beneke, Ruben Bulkescher, Lukas Adam, Holger Erfle, Carl Herrmann, Roland Eils, and Christian Conrad

3D cell cultures enable the in vitro study of dynamic biological processes such as the cell cycle, but their use in high-throughput screens remains impractical with conventional fluorescent microscopy. Here, we present a screening workflow for the automated evaluation of mitotic phenotypes in 3D cell cultures by light-sheet microscopy. After sample preparation by a liquid handling robot, cell spheroids are imaged for 24 hours in toto with a dual-view inverted selective plane illumination microscope (diSPIM) with a much improved signal-to-noise ratio, higher imaging speed, isotropic resolution and reduced light exposure compared to a spinning disc confocal microscope. A dedicated high-content image processing pipeline implements convolutional neural network based phenotype classification. We illustrate the potential of our approach by siRNA knock-down and epigenetic modification of 28 mitotic target genes for assessing their phenotypic role in mitosis. By rendering light-sheet microscopy operational for high-throughput screening applications, this workflow enables target gene characterization or drug candidate evaluation in tissue-like 3D cell culture models.

Julian Chollet, Alexander Dünkler, Anne Bäuerle, Laura Vivero-Pol, Medhanie A. Mulaw, Thomas Gronemeyer, and Nils Johnsson

Yeast cells select the position of their new bud at the beginning of each cell cycle. The recruitment of the septins to this prospective bud site is one of the critical events in a complex assembly pathway that culminates in the outgrowth of a new daughter cell. Hereby, the septin-rods follow the high concentration of Cdc42_GTP that is generated by the focused localization of its GEF Cdc24. We show that shortly before budding Cdc24 not only activates Cdc42 but also transiently interacts with Cdc11, the septin subunit that caps both ends of the septin rods. Mutations in Cdc24 reducing the affinity to Cdc11 impair septin recruitment and decrease the stability of the polarity patch. The interaction between septins and Cdc24 thus reinforces bud assembly at sites where septin structures are formed. Once the septins polymerize into the ring, Cdc24 is found at the cortex of the bud and directs its further outgrowth from this position.

Isabella Guardamagna, Elisabetta Bassi, Monica Savio, Paola Perucca, Ornella Cazzalini, Ennio Prosperi, and Lucia A. Stivala

Assessing DNA repair is an important endpoint to study the DNA damage response for investigating the biochemical mechanisms of this process and the efficacy of chemotherapy, which often uses DNA damaging compounds. Numerous in vitro methods to biochemically characterize DNA repair mechanisms have been developed so far. However, they show some limitations mainly due to the lack of chromatin organization. Here we describe a functional cell-free system to study DNA repair synthesis in vitro, using G1-phase nuclei isolated from human cells treated with different genotoxic agents. Upon incubation in the correspondent damage-activated cytosolic extracts, containing biotin-16-dUTP, nuclei are able to initiate DNA repair synthesis. The use of specific DNA synthesis inhibitors markedly decreased biotinylated dUTP incorporation, indicating the specificity of the repair response. Exogenously added human recombinant PCNA protein, but not the sensors of UV-DNA damage DDB2 or DDB1, stimulated UVC induced dUTP incorporation. In contrast, a DDB2^PCNA- mutant protein, unable to associate with PCNA, interfered with DNA repair synthesis. Given its responsiveness to different type of DNA lesions, this system offers an additional tool to study DNA repair mechanisms.

Smithsonian Institution Libraries has recently acquired a rare first edition of Darwin's Geological Observations on the Volcanic Islands, Visited During the Voyage of the H.M.S. Beagle.

The post With 1844 first edition, Smithsonian Libraries completes its collection of Charles Darwin’s three-volume geology series appeared first on Smithsonian Insider.

The humble salamander may provide evidence to support a controversial claim that North and South America were joined together much earlier than previously thought. The […]

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Scientists from the Smithsonian and the University of Rhode Island have found unsuspected linkages between the oxidation state of iron in volcanic rocks and variations […]

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Even tiny crustaceans scuttling across the deepest, darkest depths of the ocean floor will feel the effects of climate change, according to a new study […]

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Antarctica is home to fewer insect species than anywhere else on earth. But it wasn’t always that way. A geologist digging in bluffs on Antarctica’s […]

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Several weeks before it went on display in mid-November at the Smithsonian’s National Museum of Natural History, minerals curator Jeff Post stood in the museum’s […]

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As average annual temperatures increase, mosquitoes have also been on the move—up the mountains of the Hawaiian islands. Once a refuge for native birds susceptible […]

The post Scientists race to find genetic clues as malaria decimates rare Hawaiian honeycreepers appeared first on Smithsonian Insider.

The use of strongly bent crystals in spectrometers for pulses of a hard X-ray free-electron laser is explored theoretically. Diffraction is calculated in both dynamical and kinematical theories. It is shown that diffraction can be treated kinematically when the bending radius is small compared with the critical radius given by the ratio of the Bragg-case extinction length for the actual reflection to the Darwin width of this reflection. As a result, the spectral resolution is limited by the crystal thickness, rather than the extinction length, and can become better than the resolution of a planar dynamically diffracting crystal. As an example, it is demonstrated that spectra of the 12 keV pulses can be resolved in the 440 reflection from a 20 µm-thick diamond crystal bent to a radius of 10 cm.

The transformations from the primitive cells of the centered Bravais lattices to the corresponding centered cells have conventionally been listed as three-by-three matrices that transform three-space lattice vectors. Using those three-by-three matrices when working in the six-dimensional space of lattices represented as Selling scalars as used in Delone (Delaunay) reduction, one could transform to the three-space representation, apply the three-by-three matrices and then back-transform to the six-space representation, but it is much simpler to have the equivalent six-by-six matrices and apply them directly. The general form of the transformation from the three-space matrix to the corresponding matrix operating on Selling scalars (expressed in space S6) is derived, and the particular S6matrices for the centered Delone types are listed. (Note: in his later publications, Boris Delaunay used the Russian version of his surname, Delone.)

A new approach is presented to obtain candidate structures from atomic pair distribution function (PDF) data in a highly automated way. It fetches, from web-based structural databases, all the structures meeting the experimenter's search criteria and performs structure refinements on them without human intervention. It supports both X-ray and neutron PDFs. Tests on various material systems show the effectiveness and robustness of the algorithm in finding the correct atomic crystal structure. It works on crystalline and nanocrystalline materials including complex oxide nanoparticles and nanowires, low-symmetry and locally distorted structures, and complicated doped and magnetic materials. This approach could greatly reduce the traditional structure searching work and enable the possibility of high-throughput real-time auto-analysis PDF experiments in the future.

Black holes sound wildly complicated. After all, there are all sorts of bizarre things going on: intense gravity, the warping of the fabric of space, the distortion of time itself. But when it comes to describing black holes, it comes down to just two numbers: the mass of the black hole and its spin. That’s right. Everything you physically need to describe a black hole is found in just these two numbers.

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John Ososky, preparator in the Osteology Laboratory at the Smithsonian's National Museum of Natural History in Washington, D.C., explains how skeletons of animal specimens are prepared for exhibtion and for study—with the assistance of nearly 1 million flesh-eating beetles.

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The post Meet Our Scientist: National Zoo veterinarian Katharine Hope appeared first on Smithsonian Insider.

Keeper Tracey Barnes talks about Billie Jean, an Andean bear, and her two new cubs at the Smithsonian's National Zoo.

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Dr. JoGayle Howard of the Smithsonian's National Zoo discusses her work to breed and study one of the world's most endangered cats, the clouded leopard. More about the National Zoo's work to save clouded leopards: http://nationalzoo.si.edu/SCBI/ReproductiveScience/ConsEn...
http://nationalzoo.si.edu/support/annualappeal/cloudedleo... ... (more info)

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Dr. Thomas R. Watters of the Center for Earth and Planetary Studies at the Smithsonian's National Air and Space Museum talks about his research in astronomy, particularly our moon. More about space science at http://www.nasm.si.edu

The post Meet Our Scientist: Tom Watters – Moon Science appeared first on Smithsonian Insider.

Dr. Mary Hagedorn, a marine biologist at the Smithsonian Institution, talks about her research to understand and conserve our oceans' corals.

The post Meet Our Scientist: Mary Hagedorn – Coral Science appeared first on Smithsonian Insider.

Smithsonian Tropical Research Center Botanist Stefan Schnitzer talks about his work studying lianas (woody vines) in the jungles of Panama. These hardy vines compete with trees for water and nutrients and also act as highways for jungle animals moving through the forest canopy.

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What determines the variety of trees in a tropical forest? Is it the seed size? Perhaps seed-hungry animals? And what happens to forests that are being drastically changed by humans? Smithsonian Tropical Research Center Botanist, Helene Muller Landau, talks about her attempt to find answers to these questions.

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Invasive plant species are threatening native species across the globe. Learn how scientists at the Smithsonian Tropical Research Center in Panama are trying to fight one species of grass in Panama that is wreaking havoc on the country's tropical biodiversity.

The post Meet Our Scientist: Jefferson Hall – Invasive Plant Science appeared first on Smithsonian Insider.

Smithsonian Scientist Helen James dives into dormant Hawaiian volcanoes to find bird fossils. Her work to identify these species (some new species, some extinct) helps us learn about the past--specifically, how humans might have caused the extinction of certain bird species.

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The post Smithsonian ecologist John Parker discusses his work with white-tailed deer and invasive plant species appeared first on Smithsonian Insider.

When birds and planes collide: Carla Dove, a forensic ornithologist at the Smithsonian's National Museum of Natural History, talks about the work of the Smithsonian's Feather Identification Lab and its role in improving aviation safety.

The post Meet Our Scientist: Forensic ornithologist Carla Dove explains bird-strike science appeared first on Smithsonian Insider.

Join National Zoo Conservation Biologist Brian Gratwicke in his work to save Panama's amphibians from extinction. You can also catch up on his dispatches from the field on the Panamanian Amphibian Rescue and Conservation Project's blog: http://amphibianrescue.org/

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The post Learn about the National Zoo’s flamingo flock with keeper Sara Hallager appeared first on Smithsonian Insider.

The three male cheetahs that left the Zoo's D.C. campus in 2009 returned in November and are now on exhibit. The five-and-a-half-year-old brothers―Draco, Granger, and Zabini, named after characters in the Harry Potter stories―have been living at the Zoo's Smithsonian Conservation Biology Institute's Cheetah Science Facility in Front Royal, Virginia.

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The post Many years of research are celebrated in the December 2010 birth of two cheetah cubs at the Smithsonian Conservation Biology Institute appeared first on Smithsonian Insider.

As enjoyable as scientific work can be, says entomologist Dave Roubik, its greatest satisfactions are often long delayed. He gives the best example from his career: a seventeen-year study that finally helped to change our understanding of the notorious "killer bees."

The post Long-term killer bee study in tropics yields unexpected discovery: invasive killer bees are good for the native bees appeared first on Smithsonian Insider.

Mark Torchin, a marine ecologist at the Smithsonian Tropical Research Institute (STRI) in Panama, talks about how he studies the parasites of invasive marine animals such as snails. Much of his research focuses on biological invasions and the dynamics between the host, the parasites and the surrounding ecosystem.

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On June 7 the Sun unleashed an spectacular solar flare with a substantial coronal mass ejection. A large cloud of plasma mushroomed up, and while some parts fell back into the Sun, most rushed off into space. The first two segments of this video are seen through the Atmospheric Imaging Assembly aboard NASA's Solar Dynamics Observatory. The AIA was developed by Smithsonian scientists.

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Digging up early human and animal remains from the field in Africa, performing examination and publishing research about her findings, then enticing and educating the public about the implications are all in a week's work for Briana Pobiner.

The post Meet Our Scientist–Briana Pobiner, human origins researcher at the National Museum of Natural History appeared first on Smithsonian Insider.

Keepers at the Smithsonian's National Zoo perform an artificial insemination procedure on a pair of Stanley Cranes. A Stanley Crane chick was successfully hatched on May 23, 2011.

The post Bird keepers at the National Zoo demonstrate the art of artificially inseminating Stanley cranes appeared first on Smithsonian Insider.

What's possibly the most calming yet nerve-racking job in the world? Come behind the scenes of the Smithsonian's Freer Gallery of Art to find out!

The post Zen and the art of fine art conservation: Behind the scenes in the Freer Gallery’s art conservation lab appeared first on Smithsonian Insider.

Meet the Smithsonian's Matthew Carrano, curator of Dinosauria at the Smithsonian's National Museum of Natural History in Washington, D.C. Matthew studies all things dinosaur, but focuses on the evolutionary history of predatory (meat eating) dinosaurs.

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Meet Rachel Collin, a staff scientist and director of the Bocas Research Station at the Smithsonian Tropical Research Institute in Panama. Rachel studies the evolution of marine gastropods (snails) and oversees multiple disciplines of marine biology at the Collin Lab in Bocas del Toro.

The post Meet Our Scientist: Rachel Collin, an expert in the evolution and development of snails who is working in Panama appeared first on Smithsonian Insider.

Meet Smithsonian scientist Justin Touchon, a National Science Foundation (NSF) postdoctoral researcher at the Smithsonian Tropical Research Institute in Panama.

Justin's work focuses on developmental ecology and reproductive plasticity of the hourglass treefrog (Dendropsophus ebraccatus) and red-eyed treefrog (Agalychnis callidryas). Justin and his advisor, Karen Warkentin, were the first to have witnessed the frogs laying eggs in water, in addition to doing so on land -- something with major implications for the evolutionary biology of similar creatures.

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