Universe bound by cosmic thread

The Australian National University

"The filament of star clusters and small galaxies around the Milky Way is like the umbilical cord that fed our Galaxy during its youth.” Image: inhauscreative/iStockphoto Astronomers at The Australian National University have found evidence for the textile that forms the fabric of the Universe. In findings published in the October Astrophysical Journal, the researchers discovered proof of a vast filament of material that connects our Milky Way galaxy to nearby clusters of galaxies, which are similarly interconnected to the rest of the Universe. The team included Dr Stefan Keller, Dr Dougal Mackey and Professor Gary Da Costa from the Research School of Astronomy and Astrophysics at ANU. “By examining the positions of ancient groupings of stars, called globular clusters, we found that the clusters form a narrow plane around the Milky Way rather than being scattered across the sky,” Dr Keller said. “Furthermore, the Milky Way’s entourage of small satellites are seen to inhabit the same plane. “What we have discovered is evidence for the cosmic thread that connects us to the vast expanse of the Universe. “The filament of star clusters and small galaxies around the Milky Way is like the umbilical cord that fed our Galaxy during its youth.” Dr Keller said there were two types of matter that made up the Universe – the dominant, enigmatic dark matter and ordinary matter in the form of galaxies, stars and planets. “A consequence of the Big Bang and the dominance of dark matter is that ordinary matter is driven, like foam on the crest of a wave, into vast interconnected sheets and filaments stretched over enormous cosmic voids – much like the structure of a kitchen sponge,” he said. “Unlike a sponge, however, gravity draws the material over these interconnecting filaments towards the largest lumps of matter, and our findings show that the globular clusters and satellite galaxies of the Milky Way trace this cosmic filament. “Globular clusters are systems of hundreds of thousands of ancient stars tightly packed in a ball. In our picture, most of these star clusters are the central cores of small galaxies that have been drawn along the filament by gravity. “Once these small galaxies got too close the Milky Way the majority of stars were stripped away and added to our galaxy, leaving only their cores. “It is thought that the Milky Way has grown to its current size by the consumption of hundreds of such smaller galaxies over cosmic time.” Editor's Note: Original news release can be found here.

Photosynthesis ‘faster than thought’

CSIRO

A new insight into global photosynthesis, the chemical process governing how ocean and land plants absorb and release carbon dioxide, has been revealed in research that will assist scientists to more accurately assess future climate change. In a paper published in Nature, a team of US, Dutch and Australian scientists have estimated that the global rate of photosynthesis, the chemical process governing how ocean and land plants absorb and release CO2, occurs 25 per cent faster than previously thought. From analysing more than 30 years of data collected by Scripps Institution of Oceanography, UC San Diego, including air samples collected and analysed by CSIRO and the Bureau of Meteorology from the Cape Grim Air Pollution Monitoring Station, scientists have deduced the mean rate of photosynthesis over several decades and identified the El Nino-Southern Oscillation phenomenon as a regulator of the type of oxygen atoms found in CO2 from the far north to the south pole. "Our analysis suggests that current estimates of global primary production are too low and the refinements we propose represent a new benchmark for models to simulate carbon cycling through plants," says co-author Dr Colin Allison, an atmospheric chemist at CSIRO's Aspendale laboratories. The study, led by Dr Lisa Welp from the Scripps Institution of Oceanography, California, traced the path of oxygen atoms in CO2 molecules, which tells researchers how long the CO2 has been in the atmosphere and how fast it had passed through plants. From this, they estimated that the global rate of photosynthesis is about 25 percent faster than previously thought. "It's difficult to measure the rate of photosynthesis for forests, let alone the entire globe. For a single leaf it’s straightforward, you just put it in an instrument chamber and measure the CO2 decreasing in the chamber air," said Dr Welp. "But you cannot do that for an entire forest. What we have done is to use a naturally occurring marker, an oxygen isotope, in atmospheric CO2 that allows us to track how often it ended up inside a plant leaf, and from oxygen isotopic CO2 data collected around the world we can estimate the mean global rate of photosynthesis over the last few decades." In other studies, analysis of water and oxygen components found in ocean sediments and ice cores have provided scientists with a 'big picture' insight into carbon cycling over millions of years, but the search for the finer details of exchanges or uptake through ocean algae and terrestrial plant leaves has been out of reach. The authors said that their new estimate of the rate of global photosynthesis will help guide other estimates of plant activity, such as the capacity of forests and crops to grow and fix carbon, and help re-define how scientists measure and model the cycling of CO2 between the atmosphere and plants on land and in the ocean. Dr Allison said understanding the exchange of gases, including CO2 and water vapour, in the biosphere – oceans, land and atmosphere – is especially significant to climate science, and to policymakers, because of its relevance to global management of carbon emissions. "Quantifying this global production, centred on the exchange of growth-promoting CO2 and water vapour, has been historically difficult because there are no direct measurements at scales greater than leaf levels. "Inferences drawn from atmospheric measurements provide an estimate of ecosystem exchanges and satellite-based observations can be used to estimate overall primary production, but as a result of this new research, we have re-defined the rate of biospheric carbon exchange between atmosphere, land and ocean. "These results can be used to validate the biospheric components included in carbon cycle models and, although still tentative, may be useful in predicting future climate change," Dr Allison said. CSIRO's Dr Roger Francey was a co-author on the project, led by Scripps' Drs Welp and Ralph Keeling. Other study co-authors are Harro Meijer from the University of Groningen in the Netherlands; Alane Bollenbacher, Stephen Piper; Martin Wahlen from Scripps; and Kei Yoshimura from the University of Tokyo, Japan. Dr Allison said a critical element of the research was access to long data sets at multiple locations, such as Cape Grim, Mauna Loa and South Pole, extending back to 1977 when Cape Grim was established in Tasmania’s north-west, together with more recent samples from facilities such as Christmas Island, Samoa, California and Alaska. The Cape Grim Baseline Air Pollution Station provides vital information about changes to the atmospheric composition of the Southern Hemisphere. The Cape Grim Baseline Air Pollution Station, funded and managed by the Australian Bureau of Meteorology, detects atmospheric changes as part of a scientific research program jointly supervised by CSIRO's Marine and Atmospheric Research Division and the Bureau. Editor's Note: Original news release can be found here.

Study reveals world of fat cell

Garvan Institute

The dysfunction of fat cells is one factor that leads to Type 2 diabetes. For the first time, Australian scientists have detailed the proteins, or functional molecules, inside and around the ‘plasma membrane’ of a fat cell, the permeable barrier between the cell’s inner workings and the rest of the body. Mapping a healthy fat cell at a basal level, or in a ‘pure’ state unaffected by its environment, allows us to understand exactly how it responds when exposed to hormones and other substances that blood carries around the body. Why a fat cell? Because it plays a central role in metabolism, and its dysfunction is one of the factors that leads to the complex lifestyle-related illness we call Type 2 diabetes. Professor David James, Leader of the Diabetes Program at Sydney’s Garvan Institute of Medical Research, along with Drs Matthew Prior and Mark Larance from his lab, focused particularly on how fat cells respond to insulin, the hormone that facilitates movement of fats and sugars from the blood to the cell interior, where they can be burned for energy. When a fat cell is exposed to insulin, armies of proteins spring into action. Receptor proteins on the cell surface send signals into the cell, forcing a chain of events. Glucose transport proteins speed along intracellular tramways towards the cell surface where they can pump glucose into the cell; motor proteins help push them so that they glide easily to the surface. Pore-opening proteins allow entry of nutrients, as well as ‘ions’, charged molecules that bring about important biochemical changes in the cell, such as a rise in pH levels. All this activity takes place within seconds – thousands of identical reactions within millions of fat cells. The complexity is almost unimaginable. For that reason, James, Prior and Larance used a sophisticated mass spectrometer, along with mathematical analysis, to allow them to glimpse what the eye cannot see – even with the most powerful electron microscopes. Their findings, which took around two years to compile and analyse, are now published online in the Journal of Proteome Research. In addition to the descriptive analysis, the research team has uploaded its data to an online repository, available to all scientists in the field. “This is very novel - a detailed study of the plasma membrane has not been done on any cell, let alone a fat cell,” said Dr Matthew Prior. “Proteins carry out the work of the cell, and their precise location tells us a lot about what they do. This study highlights the proteins that are either embedded within, or have a strong association with, the plasma membrane. It reveals aspects of function, which in some cases was a mystery until now.” “We isolated cells and brought them to basal level – so we could work out the proteome of the cell surface in the absence of stimulation.” “By then looking at the cell surface in the presence of insulin, we could see which proteins changed. Some proteins moved away from the cell surface, while other proteins moved towards it. A good example is the glucose transporter GLUT 4 – which in response to insulin moves to the cell surface to facilitate the entry of glucose into the cell.” “GLUT 4 was our positive control – as we already know that it’s regulated by insulin. As well as seeing a rise in GLUT 4 levels, we also saw a number of other proteins, not previously known to be insulin-responsive, move to the cell surface.” “It’s already known that when you put insulin into a cell, the pH goes up. One of the abundant proteins we identified is involved with intracellular pH.” “Metabolism of food – facilitated by insulin – generates lactic acid and other acidic metabolites. Because of this, we surmise that insulin increases the cell’s pH as a way of buffering it against acidity.” “In all, there were around 10 proteins that robustly changed with insulin exposure.” Most importantly, the study gives the science community the fat cell fingerprint, the receptors on the surface of a fat cell being very different from those found on a muscle cell or a bone cell. This kind of cellular specificity is important in the development of new drug targets, the best of which are cell surface proteins. Editor's Note: Original news release can be found here.