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.

Bipasha Dey and Richa Rikhy

Cell shape morphogenesis from spherical to polygonal occurs in epithelial cell formation in metazoan embryogenesis. In syncytial Drosophila embryos, the plasma membrane incompletely surrounds each nucleus and is organized as a polygonal epithelial-like array. Each cortical syncytial division cycle shows circular to polygonal plasma membrane transition along with furrow extension between adjacent nuclei from interphase to metaphase. In this study, we assess the relative contribution of DE-cadherin and Myosin II at the furrow for polygonal shape transition. We show that polygonality initiates during each cortical syncytial division cycle when the furrow extends from 4.75 to 5.75 µm. Polygon plasma membrane organization correlates with increased junctional tension, increased DE-cadherin and decreased Myosin II mobility. DE-cadherin regulates furrow length and polygonality. Decreased Myosin II activity allows for polygonality to occur at a lower length than controls. Increased Myosin II activity leads to loss of lateral furrow formation and complete disruption of polygonal shape transition. Our studies show that DE-cadherin-Myosin II balance regulates an optimal lateral membrane length during each syncytial cycle for polygonal shape transition.

The Hope Diamond’s red glow has long been considered a unique property of that stone. Most blue diamonds produce a bluish-white phosphorescence if exposed to ultraviolet light. The few other diamonds known to emit red phosphorescence were commonly assumed to have been from the even larger original stone from which the Hope was cut.

The post Bombarded with ultraviolet light, the blue Hope diamond glows red appeared first on Smithsonian Insider.

Fluorite is well known and prized for its rich variety of colors, most commonly pale green, purple, yellow, orange, blue, pink and colorless. “We acquired this specimen because it is a very nice quality fluorite with an attractive color and it is large enough to be exhibited,” Curator Jeff Post says.

The post Smithsonian’s National Gem Collection acquires a yellow fluorite from Tanzania appeared first on Smithsonian Insider.

The Smithsonian Research Online program recently surpassed the mark of 10,000 publications in the Digital Repository. This collection of digital publications by Smithsonian staff represents a broad review of research done by researchers at the Institution.

The post Smithsonian Digital Repository Now Contains 10,000 Items appeared first on Smithsonian Insider.

Recent airborne geophysical surveys near Decorah, Iowa are providing an unprecedented look at a 470-million-year-old meteorite crater concealed beneath bedrock and sediments. The aerial surveys, […]

The post Iowa meteorite crater confirmed appeared first on Smithsonian Insider.

Many traits unique to humans were long thought to have originated in the genus Homo between 2.4 and 1.8 million years ago in Africa. A […]

The post Human Evolution Rewritten: We owe our existence to our ancestor’s flexible response to climate change appeared first on Smithsonian Insider.

We’ve seen a serious series of super moons this summer and the show’s not over yet. Mark your calendars: the next one will light up […]

The post Cutting through the dust: Radar shows moon’s true face for first time appeared first on Smithsonian Insider.

Nearly four billion years ago, life arose on Earth. Life appeared because our planet had a rocky surface, liquid water, and a blanketing atmosphere. But […]

The post Sun-like Star Shows Magnetic Field Critical for Life on the early Earth appeared first on Smithsonian Insider.

Have an upset stomach? Pop a chalky, chewable antacid. Maybe you’ve got a painful cut or burn. No problem; reach for a healing ointment or […]

The post Glittering, mesmerizing, lifesaving: Hospital exhibit showcases minerals used in medicine appeared first on Smithsonian Insider.

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 […]

The post Colossal diamond’s eerie glow earns it a fiery name appeared first on Smithsonian Insider.

Monday, Aug. 21 was an unusual day across North America. Early in the morning, families, colleagues and tourists were searching for special solar glasses with […]

The post Crowds gather at Air and Space Museum to view solar eclipse appeared first on Smithsonian Insider.

A hunter touches an infected animal’s blood, a farmer breathes the moist air exhaled by sick cows, contaminated meat is served at an outdoor market—these […]

The post What causes disease outbreaks and how can we stop them? appeared first on Smithsonian Insider.

Structural investigations of amorphous and nanocrystalline phases forming in solution are historically challenging. Few methods are capable of in situ atomic structural analysis and rigorous control of the system. A mixed-flow reactor (MFR) is used for total X-ray scattering experiments to examine the short- and long-range structure of phases in situ with pair distribution function (PDF) analysis. The adaptable experimental setup enables data collection for a range of different system chemistries, initial supersaturations and residence times. The age of the sample during analysis is controlled by adjusting the flow rate. Faster rates allow for younger samples to be examined, but if flow is too fast not enough data are acquired to average out excess signal noise. Slower flow rates form older samples, but at very slow speeds particles settle and block flow, clogging the system. Proper background collection and subtraction is critical for data optimization. Overall, this MFR method is an ideal scheme for analyzing the in situ structures of phases that form during crystal growth in solution. As a proof of concept, high-resolution total X-ray scattering data of amorphous and crystalline calcium phosphates and amorphous calcium carbonate were collected for PDF analysis.

Crystal structure identification of thin organic films entails a number of technical and methodological challenges. In particular, if molecular crystals are epitaxially grown on single-crystalline substrates a complex scenario of multiple preferred orientations of the adsorbate, several symmetry-related in-plane alignments and the occurrence of unknown polymorphs is frequently observed. In theory, the parameters of the reduced unit cell and its orientation can simply be obtained from the matrix of three linearly independent reciprocal-space vectors. However, if the sample exhibits unit cells in various orientations and/or with different lattice parameters, it is necessary to assign all experimentally obtained reflections to their associated individual origin. In the present work, an effective algorithm is described to accomplish this task in order to determine the unit-cell parameters of complex systems comprising different orientations and polymorphs. This method is applied to a polycrystalline thin film of the conjugated organic material 6,13-pentacene­quinone (PQ) epitaxially grown on an Ag(111) surface. All reciprocal vectors can be allocated to unit cells of the same lattice constants but grown in various orientations [sixfold rotational symmetry for the contact planes (102) and (102)]. The as-determined unit cell is identical to that reported in a previous study determined for a fibre-textured PQ film. Preliminary results further indicate that the algorithm is especially effective in analysing epitaxially grown crystallites not only for various orientations, but also if different polymorphs are present in the film.

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