A calibration of cellulose isotopes in modern prostrate Nothofagus and its application to fossil material from Antarctica.

Carbon and oxygen isotopes (δ13C and δ18O) in tree rings are widely used to reconstruct palaeoclimate variables such as temperature during the Holocene (12 thousand years ago - present), and are used increasingly in deeper time. However, their use is largely restricted to arboreal trees, which excludes potentially important data from prostrate trees and shrubs, which grow in high latitude and altitude end-member environments. Here, we calibrate the use of δ13C and δ18O as climatic archives in two modern species of southern beech (Nothofagus) from Tierra del Fuego, Chile, at the southern limit of their current range. We show that prostrate trees are potentially suitable archives for recording climatological means over longer periods (on the order of decades), which opens up these important environments for tree ring isotope analysis. We then apply our new understanding to a remarkable late Neogene (17-2.5 Ma) fossil Nothofagus assemblage from the Transantarctic Mountains, Antarctica, representative of a prostrate tundra shrub growing during a period of significant ice sheet retreat. The δ13C of the fossil cellulose was found to be ~4‰ enriched relative to that of the modern tress. This is likely to be due to a combination of a more positive δ13C of contemporaneous atmospheric CO2 and enhanced water use efficiency at the fossil site. Using the cellulose-δ18O in the fossil wood, we are able to reconstruct precipitation oxygen isotopes over the Antarctic interior for the first time for this time period. The results show that δ18Oprecip over Antarctica was -16.0 ± 4.2‰, around 12‰ enriched relative to today, suggesting changes in the hydrological cycle linked to warmer temperatures and a smaller ice sheet.

Temperate rainforests near the South Pole during peak Cretaceous warmth.

The mid-Cretaceous period was one of the warmest intervals of the past 140 million years1-5, driven by atmospheric carbon dioxide levels of around 1,000 parts per million by volume6. In the near absence of proximal geological records from south of the Antarctic Circle, it is disputed whether polar ice could exist under such environmental conditions. Here we use a sedimentary sequence recovered from the West Antarctic shelf-the southernmost Cretaceous record reported so far-and show that a temperate lowland rainforest environment existed at a palaeolatitude of about 82° S during the Turonian-Santonian age (92 to 83 million years ago). This record contains an intact 3-metre-long network of in situ fossil roots embedded in a mudstone matrix containing diverse pollen and spores. A climate model simulation shows that the reconstructed temperate climate at this high latitude requires a combination of both atmospheric carbon dioxide concentrations of 1,120-1,680 parts per million by volume and a vegetated land surface without major Antarctic glaciation, highlighting the important cooling effect exerted by ice albedo under high levels of atmospheric carbon dioxide.

Macrofossil evidence for a rapid and severe Cretaceous-Paleogene mass extinction in Antarctica.

Debate continues about the nature of the Cretaceous-Paleogene (K-Pg) mass extinction event. An abrupt crisis triggered by a bolide impact contrasts with ideas of a more gradual extinction involving flood volcanism or climatic changes. Evidence from high latitudes has also been used to suggest that the severity of the extinction decreased from low latitudes towards the poles. Here we present a record of the K-Pg extinction based on extensive assemblages of marine macrofossils (primarily new data from benthic molluscs) from a highly expanded Cretaceous-Paleogene succession: the López de Bertodano Formation of Seymour Island, Antarctica. We show that the extinction was rapid and severe in Antarctica, with no significant biotic decline during the latest Cretaceous, contrary to previous studies. These data are consistent with a catastrophic driver for the extinction, such as bolide impact, rather than a significant contribution from Deccan Traps volcanism during the late Maastrichtian.

The Early Origin of the Antarctic Marine Fauna and Its Evolutionary Implications.

The extensive Late Cretaceous - Early Paleogene sedimentary succession of Seymour Island, N.E. Antarctic Peninsula offers an unparalleled opportunity to examine the evolutionary origins of a modern polar marine fauna. Some 38 modern Southern Ocean molluscan genera (26 gastropods and 12 bivalves), representing approximately 18% of the total modern benthic molluscan fauna, can now be traced back through at least part of this sequence. As noted elsewhere in the world, the balance of the molluscan fauna changes sharply across the Cretaceous - Paleogene (K/Pg) boundary, with gastropods subsequently becoming more diverse than bivalves. A major reason for this is a significant radiation of the Neogastropoda, which today forms one of the most diverse clades in the sea. Buccinoidea is the dominant neogastropod superfamily in both the Paleocene Sobral Formation (SF) (56% of neogastropod genera) and Early - Middle Eocene La Meseta Formation (LMF) (47%), with the Conoidea (25%) being prominent for the first time in the latter. This radiation of Neogastropoda is linked to a significant pulse of global warming that reached at least 65°S, and terminates abruptly in the upper LMF in an extinction event that most likely heralds the onset of global cooling. It is also possible that the marked Early Paleogene expansion of neogastropods in Antarctica is in part due to a global increase in rates of origination following the K/Pg mass extinction event. The radiation of this and other clades at ∼65°S indicates that Antarctica was not necessarily an evolutionary refugium, or sink, in the Early - Middle Eocene. Evolutionary source - sink dynamics may have been significantly different between the Paleogene greenhouse and Neogene icehouse worlds.

Medication to prevent breast cancer--too much to swallow?

Selective oestrogen receptor modulators effectively reduce breast cancer in women at moderate to high risk, so why aren't they being discussed routinely?

Reducing time to diagnosis does not improve outcomes for women with symptomatic ovarian cancer: a report from the Australian Ovarian Cancer Study Group.

PURPOSE: To determine if time to diagnosis is associated with stage of disease at diagnosis or survival among women with symptomatic ovarian cancer. METHODS: A representative sample of Australian women (n = 1,463) with ovarian cancer diagnosed between 2002 and 2005 who participated in a population-based case-control study were interviewed regarding the events leading to their diagnosis and were observed for mortality for 5 years. RESULTS: Of the 1,318 women (90%) who presented to a medical practitioner with symptoms, 55% presented within 1 month, 70% in less than 2 months, and 92% within 6 months of symptom onset. There were no significant differences in the time from symptom onset to first medical practitioner consultation (P = .19) or symptom onset to diagnosis (P = .64) among women with borderline, early (International Federation of Gynecology and Obstetrics [FIGO] stages I to II) or late (FIGO stages III to IV) disease. There was also no association between time to diagnosis and survival; adjusted hazard ratio for long delay (> 12 months from symptom onset to diagnosis) versus short delay (≤ 1 month) was 0.94 (95% CI, 0.68 to 1.30). Women who had asymptomatic cancers diagnosed incidentally (n = 145) were younger and were more likely to have borderline or stage I disease compared with women who had symptomatic ovarian cancer. CONCLUSION: The results of this study suggest that, once ovarian cancer is symptomatic, reducing the time to diagnosis would not greatly alter stage of disease at diagnosis or survival.

Are there pre-Quaternary geological analogues for a future greenhouse warming?

Given the inherent uncertainties in predicting how climate and environments will respond to anthropogenic emissions of greenhouse gases, it would be beneficial to society if science could identify geological analogues to the human race's current grand climate experiment. This has been a focus of the geological and palaeoclimate communities over the last 30 years, with many scientific papers claiming that intervals in Earth history can be used as an analogue for future climate change. Using a coupled ocean-atmosphere modelling approach, we test this assertion for the most probable pre-Quaternary candidates of the last 100 million years: the Mid- and Late Cretaceous, the Palaeocene-Eocene Thermal Maximum (PETM), the Early Eocene, as well as warm intervals within the Miocene and Pliocene epochs. These intervals fail as true direct analogues since they either represent equilibrium climate states to a long-term CO(2) forcing--whereas anthropogenic emissions of greenhouse gases provide a progressive (transient) forcing on climate--or the sensitivity of the climate system itself to CO(2) was different. While no close geological analogue exists, past warm intervals in Earth history provide a unique opportunity to investigate processes that operated during warm (high CO(2)) climate states. Palaeoclimate and environmental reconstruction/modelling are facilitating the assessment and calculation of the response of global temperatures to increasing CO(2) concentrations in the longer term (multiple centuries); this is now referred to as the Earth System Sensitivity, which is critical in identifying CO(2) thresholds in the atmosphere that must not be crossed to avoid dangerous levels of climate change in the long term. Palaeoclimatology also provides a unique and independent way to evaluate the qualities of climate and Earth system models used to predict future climate.

Pathways to the diagnosis of epithelial ovarian cancer in Australia.

OBJECTIVE: To describe the diagnostic pathways experienced by a large, representative group of Australian women with ovarian cancer, and to document the time between first presentation to a medical professional and clinical diagnosis. DESIGN, SETTING AND PARTICIPANTS: 1463 women with epithelial ovarian cancer from an Australia-wide population-based study (2002-2005) completed a telephone interview in which they described the events that led to the diagnosis of their cancer. MAIN OUTCOME MEASURES: Number and type of doctors consulted, investigations performed, referral patterns and the time from first presentation to diagnosis. RESULTS: Of the 1463 women, 145 had their cancer diagnosed incidentally and were excluded from analysis. Most of the remaining 1318 women (1222, 93%) presented first to their general practitioner. As a result of their first medical consultation, 75 women (6%) were given a diagnosis, and 484 (37%) were referred to a gynaecologist, gynaecological oncologist or oncologist for further assessment. Overall, 85% of women visited three or fewer doctors before their cancer was diagnosed; 66% of cancers were diagnosed within 1 month of the initial presentation, and 80% were diagnosed within 3 months. For 12% of women, the diagnostic process took longer than 6 months; this was more likely for women residing in remote Australia, those with lower incomes, and those presenting with abdominal pain or bowel symptoms, or with more than one symptom. CONCLUSIONS: Despite anecdotal suggestions to the contrary, most women with ovarian cancer in Australia are investigated and diagnosed promptly. The diagnostic process is more protracted for a minority of women, and the factors we found to be associated with diagnostic delay warrant further investigation.

Population screening and early detection of ovarian cancer in asymptomatic women.

The National Breast and Ovarian Cancer Centre position statement: 'Population screening and early detection of ovarian cancer in asymptomatic women', was developed and agreed following a Forum in February 2009 attended by key Australian stakeholders. The final position statement and supporting background information have been endorsed by key Australian colleges and agencies. Position statement on population screening and early detection of ovarian cancer in asymptomatic women: 1) There is currently no evidence that any test, including pelvic examination, CA125 or other biomarkers, ultrasound (including transvaginal ultrasound), or combination of tests, results in reduced mortality from ovarian cancer. 2) There is no evidence to support the use of any test, including pelvic examination, CA125 or other biomarkers, ultrasound (including transvaginal ultrasound), or combination of tests, for routine population-based screening for ovarian cancer. 3) Further validation in large clinical trials is required before current or new biomarkers could be recommended for routine use in a population screening setting.

Introduction. Pliocene climate, processes and problems.

Climate predictions produced by numerical climate models, often referred to as general circulation models (GCMs), suggest that by the end of the twenty-first century global mean annual surface air temperatures will increase by 1.1-6.4 degrees C. Trace gas records from ice cores indicate that atmospheric concentrations of CO2 are already higher than at any time during the last 650000 years. In the next 50 years, atmospheric CO2 concentrations are expected to reach a level not encountered since an epoch of time known as the Pliocene. Uniformitarianism is a key principle of geological science, but can the past also be a guide to the future? To what extent does an examination of the Pliocene geological record enable us to successfully understand and interpret this guide? How reliable are the 'retrodictions' of Pliocene climates produced by GCMs and what does this tell us about the accuracy of model predictions for the future? These questions provide the scientific rationale for this Theme Issue.