Shell structure and distribution of Cloudina, a potential index fossil for the terminal Proterozoic.
Botanical Museum, Harvard University, Cambridge, Massachusetts 02138, USA.
Cloudina-bearing biosparites and biomicrites in the lower part of the Nama Group, Namibia, contain a wide morphological diversity of shell fragments that can all be attributed to the two named species C. hartmannae and C. riemkeae. The curved to sinuous tubular shells of Cloudina were multi-layered. Each shell layer was 8 to 50 micrometers thick and in the form of a slightly flaring tube with one end open and the other closed. Growth appears to have been periodic with successive shell layers forming within older layers. Each added layer was slightly elevated from the previous layer at the proximal end and was asymmetrically placed within the older layer so that only a portion of the new shell layer was fused to the previous layer. This type of growth left a relatively large unminerialized area between the shell layers which was often partially or fully occluded by early marine cements. The thin shell layers exhibit both plastic and brittle deformation and were likely formed of a rigid CaCO3-impregnated organic-rich material. Often the shell layers are preferentially dolomitized suggesting an original mineralogy of high-magnesian calcite. Both species in the Nama Group formed thickets, or perhaps bioherms, and this sedentary and gregarious habit suggests that Cloudina was probably a filter-feeding metazoan of at least a cnidarian grade of organization. The unusual shell structure of Cloudina gives rise to a characteristic suite of taphonomic and diagenetic features that can be used to identify Cloudina-bearing deposits within the Nama Group and in other terminal Proterozoic deposits around the world. Species of Cloudina occur in limestones from Brazil, Spain, China, and Oman in sequences consistent with a latest Proterozoic age assignment. In addition, supposed lower Cambrian, pre-trilobitic, shelly fossils from northwest Mexico and the White-Inyo Mountains in California and Nevada, including Sinotubulites, Nevadatubulus, and Wyattia, are all either closely related to or con-generic with Cloudina. Hence, it is probable that these outcrops are latest Proterozoic in age, and that Cloudina or Cloudina-like organisms were widely distributed at that time. It is possible, moreover, to suggest that metazoan biomineralization occurred on a global scale by the latest Proterozoic, at the same time that evidence for complex multicellularity and locomotion in animals appears in siliciclastic "Ediacaran" rocks in the form of body and trace fossils.
Geobiology. 2010 Sep ;8 (4):256-77 20550583
Department of Earth Science, University of California at Santa Barbara, Santa Barbara, California, USA. firstname.lastname@example.org
A longstanding question in paleontology has been the influence of calcite and aragonite seas on the evolution of carbonate skeletons. An earlier study based on 21 taxa that evolved skeletons during the Ediacaran through Ordovician suggested that carbonate skeletal mineralogy is determined by seawater chemistry at the time skeletons first evolve in a clade. Here I test this hypothesis using an expanded dataset comprising 40 well-defined animal taxa that evolved skeletons de novo in the last 600 Myr. Of the 37 taxa whose mineralogy is known with some confidence, 25 acquired mineralogies that matched seawater chemistry of the time, whereas only two taxa acquired non-matching mineralogies.(Ten appeared during times when seawater chemistry is not well constrained.) The results suggest that calcite and aragonite seas do have a strong influence on carbonate skeletal mineralogy, however, this appears to be true only at the time mineralized skeletons first evolve. Few taxa switch mineralogies (from calcite to aragonite or vice versa) despite subsequent changes in seawater chemistry, and those that do switch do not appear to do so in response to changing aragonite-calcite seas. This suggests that there may be evolutionary constraints on skeletal mineralogy, and that although there may be increased costs associated with producing a mineralogy not favored by seawater, the costs of switching mineralogies are even greater.
Carbon and oxygen isotope geochemistry of Ediacaran outer platform carbonates, Paraguay Belt, central Brazil.
After the late Cryogenian glaciation the central region of Brazil was the site of extensive deposition of platformal carbonates of the Araras Group. This group includes a basal cap carbonate sequence succeeded by transgressive, deep platform deposits of bituminous lime mudstone and shale. Facies and stratigraphic data combined with carbon and oxygen isotopic analyses of the most complete section of the transgressive deposits, exposed in the Guia syncline, were used to evaluate the depositional paleoenvironment and to test the correlation of these deposits along the belt and with other units worldwide. The studied succession consists of 150 m thick tabular beds of black to grey lime mudstone and shale with predominantly negative delta13C PDB values around -2.5 to -1 . The delta13C PDB profile of Guia syncline shows a clear correlation with the upper portion of Guia Formation in the Cáceres region, about 200 km to the southwest. The delta13C PDB profile of the Araras Group is comparable with delta13C PDB profiles of Ediacaran units of the southern Paraguay Belt, western Canada, and the Congo and Kalahari cratons. Moreover, facies distribution, stratigraphy and the carbon isotopic profile of the Araras Group match the middle Tsumeb Subgroup in Namibia, which reinforces the Ediacaran age assigned to the Araras Group.
Biomineralization of unicellular organisms: an unusual membrane biochemistry for the production of inorganic nano- and microstructures.
Abteilung Membranbiochemie, Max-Planck-Institut für Biochemie, Am Klopferspitz 18 A, 82152 Martinsried, Germany. email@example.com
With evolution, Nature has ingeniously succeeded in giving rise to an impressive variety of inorganic structures. Every organism that synthesizes biogenic minerals does so in a form that is unique to that species. This biomineralization is apparently biologically controlled. It is thus expected that both the synthesis and the form of every specific biogenic mineral is genetically determined and controlled. An investigation of the mechanism of biomineralization has only become possible with the development of modern methods in molecular biology. Unicellular organisms such as magnetic bacteria, calcareous algae, and diatoms, all of which are amongst the simplest forms of life, are particularly suited to be investigated by these methods. Crystals and composites of proteins and amorphous inorganic polymers are formed as complex structures within these organisms; these structures are not known in conventional inorganic chemistry.
Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Integrated sequence stratigraphic and chemostratigraphic data yield a framework for correlations of stratigraphic units in the terminal Proterozoic to Cambrian Witvlei and Nama Groups of Namibia. Coupled with precise U-Pb zircon age constraints, these correlations make it possible to construct a composite reference section for use in calibrating terminal Proterozoic chronostratigraphy. The Namibian reference section starts with two distinct glacial horizons and extends up to within 1 million years of the Proterozoic-Cambrian boundary. The two glacial horizons may represent each of two distinct Varanger-age glaciations better known from the North Atlantic region. From the higher of the two glacial horizons up, the composite stratigraphy preserves one of the thickest and most complete available records of carbon-isotope variability in post-Varanger terminal Proterozoic seawater. Four carbon-isotope chemostratigraphic intervals are recognized:(1) a postglacial negative delta 13C excursion (Npg interval);(2) a rising interval (Pr interval) of increasing positive delta 13C values;(3) a falling interval (Pf interval) characterized by decreasing positive delta 13C and culminating in near zero or negative values; and (4) an interval of moderately positive, relatively invariant delta 13C values (I interval) that extends up to the unconformity that contains the Proterozoic-Cambrian boundary. Each of these chemostratigraphic intervals can be recognized in widely separated correlative sections around the world. By comparing sediment accumulation rate in the radiometrically calibrated Namibian stratigraphy with sediment accumulation rates in correlative sections in Arctic Canada and Oman, a maximum age of 564 Ma is estimated for the end of the younger Varanger glaciation, 25 m.y. younger than previous estimates.
Department of Geography and Geology, Mount Holyoke College, South Hadley, MA 01075, USA.
The Ediacaran biota is the earliest diverse community of macroscopic animals and protoctists. Body and trace fossils in the Clemente Formation of northwestern Sonora extend downward the geologic range of Ediacaran forms. Taxa present in the Clemente Formation include cf. Cyclomedusa plana, Sekwia sp., an erniettid (bearing an air mattress-like "pneu" body construction), and the trace fossils Lockeia ichnosp. and Palaeophycus tubularis. The trace fossils confirm the presence of sediment-dwelling animals in this shallow marine community. The body fossils are headless, tailless, and appendageless. Some may be body fossils of animals but others may be fossils of large protoctists. These body and trace fossils, recovered from thinly bedded sandstones and siltstones, occur 75 meters lower in the Sonoran stratigraphic section than a distinctive Clemente Formation oolite. The stratigraphic position of the fossils below this oolite permits long-distance correlation between fossiliferous Proterozoic strata of Mexico and the United States. Correlations utilizing both the Clemente Formation oolite and a trace fossil (Vermiforma antiqua) confirm the antiquity (600 million years or more) of this body fossil-rich community of macroscopic eukaryotes. The recently discovered body fossils are the oldest known remains of the Ediacaran biota.
Botanical Museum, Harvard University, Cambridge, MA 02138, USA.
In 1989, the International Commission on Stratigraphy established a Working Group on the Terminal Proterozoic Period. Nine years of intensive, multidisciplinary research by scientists from some two dozen countries have markedly improved the framework for the correlation and calibration of latest Proterozoic events. Three principal phenomena--the Marinoan ice age, Ediacaran animal diversification, and the beginning of the Cambrian Period--specify the limits and character of this interval, but chemostratigraphy and biostratigraphy based on single-celled microfossils (acritarchs), integrated with high-resolution radiometric dates, provide the temporal framework necessary to order and evaluate terminal Proterozoic tectonic, biogeochemical, climatic, and biological events. These data also provide a rational basis for choosing the Global Stratotype Section and Point (GSSP) that will define the beginning of this period. A comparable level of stratigraphic resolution may be achievable for the preceding Cryogenian Period, providing an opportunity to define this interval, as well, in chronostratigraphic terms--perhaps bounded at beginning and end by the onset of Sturtian glaciation and the decay of Marinoan ice sheets, respectively. Limited paleontological, isotopic, and radiometric data additionally suggest a real but more distant prospect of lower Neoproterozoic correlation and stratigraphic subdivision.
Neoproterozoic variations in the C-isotopic composition of seawater: stratigraphic and biogeochemical implications.
Botanical Museum, Harvard University, Cambridge, MA 02138, USA.
The recent proliferation of stratigraphic studies of delta 13C variation in carbonates and organic C in later Neoproterozoic and basal Cambrian successions (approximately 850-530 Ma) indicates a strong oscillating trend in the C-isotopic composition of surface seawater. Alone, this trend does not adequately characterize discrete intervals in Neoproterozoic time. However, integrated with the vectorial signals provided by fossils and Sr-isotopic variations, C isotope chemostratigraphy facilitates the interbasinal correlation of later Neoproterozoic successions. Results of these studies are evaluated in terms of four stratigraphic intervals:(1) the Precambrian/Cambrian boundary,(2) the post-Varanger terminal Proterozoic,(3) the late Cryogenian, and (4) the early Cryogenian. Where biostratigraphic or radiometric data constrain the age of Neoproterozoic sedimentary sequences, secular variations in C and Sr isotopes can provide a level of stratigraphic resolution exceeding that provided by fossils alone. Isotopic data place strong constraints on the chemical evolution of seawater, linking it to major tectonic and paleoclimatic events. They also provide a biogeochemical framework for the understanding of the initial radiation of macroscopic metazoans, which is associated stratigraphically, and perhaps causally, with a global increase in the burial of organic C and a concomitant rise of atmospheric O2.
Paleobiology. 1996 ;22 (1):1-7 11539205
Botanical Museum, Harvard University, Cambridge, Massachusetts 02138, USA.
Isotopic compositions of carbonates and organic carbon from upper Proterozoic successions in Namibia: stratigraphic variation and the effects of diagenesis and metamorphism.
Department of Geology, Indiana University, Bloomington 47405-5101, USA.
The carbon isotope geochemistry of carbonates and organic carbon in the late Proterozoic Damara Supergroup of Namibia, including the Nama, Witvlei, and Gariep groups on the Kalahari Craton and the Mulden and Otavi groups on the Congo Craton, has been investigated as an extension of previous studies of secular variations in the isotopic composition of late Proterozoic seawater. Subsamples of microspar and dolomicrospar were determined, through petrographic and cathodoluminescence examination, to represent the "least-altered" portions of the rock. Carbon-isotopic abundances in these phases are nearly equal to those in total carbonate, suggesting that 13C abundances of late Proterozoic fine-grained carbonates have not been significantly altered by meteoric diagenesis, although 18O abundances often differ significantly. Reduced and variable carbon-isotopic differences between carbonates and organic carbon in these sediments indicate that isotopic compositions of organic carbon have been altered significantly by thermal and deformational processes, likely associated with the Pan-African Orogeny. Distinctive stratigraphic patterns of secular variation, similar to those noted in other, widely separated late Proterozoic basins, are found in carbon-isotopic compositions of carbonates from the Nama and Otavi groups. For example, in Nama Group carbonates delta 13C values rise dramatically from -4 to +5% within a short stratigraphic interval. This excursion suggests correlation with similar excursions noted in Ediacaran-aged successions of Siberia, India, and China. Enrichment of 13C (delta 13C>+5%) in Otavi Group carbonates reflects those in Upper Riphean successions of the Akademikerbreen Group, Svalbard, its correlatives in East Greenland, and the Shaler Group, northwest Canada. The widespread distribution of successions with comparable isotopic signatures supports hypotheses that variations in delta 13C reflect global changes in the isotopic composition of late Proterozoic seawater. Within the Damara basin, carbon-isotopic compositions of carbonates provide a potentially useful tool for the correlation of units between the Kalahari and Congo cratons. Carbonates depleted in 13C were deposited during and immediately following three separate glacial episodes in Namibia. The correspondence between ice ages and negative delta 13C excursions may reflect the effects of lowered sea levels; enhanced circulation of deep, cold, O2-rich seawater; and/or the upwelling of 13C-depleted deep water. Iron-formation is additionally associated with one of the glacial horizons, the Chuos tillite. Carbon-13 enriched isotopic abundances in immediately pre-glacial carbonates suggest that oceanographic conditions favored high rates of organic burial. It is likely that marine waters were stratified, with deep waters anoxic. A prolonged period of ocean stratification would permit the build-up of ferrous iron, probably from hydrothermal sources. At the onset of glaciation, upwelling would have brought 13C-depleted and iron-rich deep water onto shallow shelves where contact with cold, oxygenated surface waters led to the precipitation of ferric iron.
Botanical Museum, Harvard University, Cambridge, Massachusetts 02138.
The end of the Proterozoic Eon was a time of pronounced biological, biogeochemical, climatic and tectonic change. New bio- and chemostratigraphic data provide an improved framework for stratigraphic correlation, making possible a deeper understanding of latest Proterozoic Earth history and providing tools for a chronostratigraphic division of late Proterozoic time.
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Br J Surg. 2012 Sep 21;: 23001820
Preoperative cardiopulmonary exercise testing and risk of early mortality following abdominal aortic aneurysm repair.
Department of Anaesthesia, Manchester Royal Infirmary, Central Manchester University Hospitals, Manchester, UK.
BACKGROUND: Cardiopulmonary exercise testing (CPET) provides an objective assessment of functional capacity. The aim of this study was to assess whether preoperative CPET identifies patients at risk of early death following elective open and endovascular abdominal aortic aneurysm (AAA) repair. METHODS: Prospective data were collected from a pilot study between September 2005 and February 2007, and from all patients who underwent CPET before elective AAA repair at two vascular centres between February 2007 and November 2011. Symptom-limited, maximal CPET was performed on each patient. Univariable and multivariable analyses were used to identify risk factors for 30- and 90-day mortality. RESULTS: Some 415 patients underwent CPET before elective AAA repair. Anaerobic threshold (AT), peak oxygen consumption (peak V̇O(2)) and ventilatory equivalents for carbon dioxide were associated with 30- and 90-day mortality on univariable analysis. On multivariable analysis, open repair (odds ratio (OR) 4·92, 95 per cent confidence interval 1·55 to 17·00; P = 0·008), AT below 10·2 ml per kg per min (OR 6·35, 1·84 to 29·80; P = 0·007), anaemia (OR 3·27, 1·04 to 10·50; P = 0·041) and inducible cardiac ischaemia (OR 6·16, 1·48 to 23·07; P = 0·008) were associated with 30-day mortality. Anaemia, inducible cardiac ischaemia and peak V̇O(2) less than 15 ml per kg per min (OR 8·59, 2·33 to 55·75; P = 0·005) were associated with 90-day mortality on multivariable analysis. Patients with two or more subthreshold CPET values were at increased risk of both 30- and 90-day mortality. CONCLUSION: An AT below 10·2 ml per kg per min, peak V̇O(2) less than 15 ml per kg per min and at least two subthreshold CPET values identify patients at increased risk of early death following AAA repair. Copyright © 2012 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd.
Vascular Governance North West, 1st Floor Education and Research Centre, University Hospital of South Manchester, Southmoor Road, Manchester, England, United Kingdom.
INTRODUCTION Carotid endarterectomy (CEA) should be performed within two weeks of symptoms for patients with carotid stenosis >50%. Whether these standards are being achieved and causes of delay between symptoms and CEA were investigated. DESIGN An analysis of prospectively collected multi-centre data. MATERIALS Consecutive data for patients undergoing CEA between January-2006 and September-2010 were collected. Asymptomatic patients and those with no details on the timing of cerebral symptoms were excluded. METHODS 'Delay' from symptom to CEA was defined as more than two weeks and 'prolonged-delay' more than eight weeks. Univariable and multivariable analyses were used to identify factors associated with these delays. RESULTS Of 2147 patients with symptoms of cerebral ischaemia, 1522(70.9%) experienced 'delay' and 920(42.9%) experienced 'prolonged delay'. Patients with ischaemic heart disease were more likely to experience 'delay'(OR = 1.56; 95% CI 1.11-2.19, p = 0.011), whereas patients with stroke (OR = 0.77; 95%CI 0.63-0.94, p = 0.011) and those treated at hospitals with a stroke-prevention clinic (OR = 0.57; 95%CI 0.46-0.71, p < 0.001) were less likely to experience 'delay'. Patients treated after the publication of National Institute for Health and Clinical Excellence (NICE) guidelines were less likely to experience 'prolonged delay'(OR = 0.77; 95%CI 0.65-0.91, p = 0.003) but not 'delay'. CONCLUSION Few patients achieved CEA within two weeks of symptoms. Introducing stroke-prevention clinics with one-stop carotid imaging appears important.
Response to Letter to the Editor Re "What are the Risk Factors for Renal Failure Following Open Elective Abdominal Aortic Aneurysm Repair?"
The University of Manchester, Manchester Academic Health Science Centre, UHSM, Academic Surgery Unit, Education and Research Centre, Southmoor Road, Manchester, England M23 9LT, UK.
Br J Surg. 2012 May ;99 (5):673-9 22415901
Evaluation of five risk prediction models for elective abdominal aortic aneurysm repair using the UK National Vascular Database.
University of Manchester, Manchester Academic Health Science Centre, University Hospital of South Manchester, Academic Surgery Unit, Education and Research Centre, Manchester, UK.
BACKGROUND There is no consensus on the best risk prediction model for mortality following elective abdominal aortic aneurysm (AAA) repair. The objective was to evaluate the performance of five risk prediction models using the UK National Vascular Database (NVD). METHODS Data on elective AAA repairs from the NVD between January 2008 and December 2010 were analysed. The models assessed were: Glasgow Aneurysm Score (GAS), Vascular Biochemical and Haematological Outcome Model (VBHOM), physiological component of the Vascular Physiological and Operative Severity Score for enUmeration of Mortality (V-POSSUM), Medicare and Vascular Governance North West (VGNW). Overall model discrimination and calibration in equally sized risk-group quintiles were assessed. RESULTS The study cohort included 10,891 patients undergoing elective AAA repair (median age 74 years, 87.3 per cent men). The in-hospital mortality rates following endovascular and open repair were 1.3 and 4.7 per cent respectively (2.9 per cent overall). The Medicare and VGNW models both showed good discrimination (area under receiver operating characteristic (ROC) curve 0.71), whereas the GAS, VBHOM and V-POSSUM models showed poor discrimination (area under ROC curve 0.60, 0.61 and 0.62 respectively). The VGNW model was the only one to predict the overall mortality rate in the cohort (3.3 per cent predicted versus 2.9 per cent observed; P = 0.066). The VGNW model demonstrated good calibration, predicting risk accurately in four risk-group quintiles. The Medicare, V-POSSUM and VBHOM models accurately predicted risk in three, two and no risk-group quintiles respectively. CONCLUSION The Medicare and VGNW models contain similar risk factors and showed good discrimination when applied to the NVD. Both models would be suitable for risk prediction after elective AAA repair in the UK.
What are the risk factors for renal failure following open elective abdominal aortic aneurysm repair?
The University of Manchester, Manchester Academic Health Science Centre, UHSM, Academic Surgery Unit, Education and Research Centre, Southmoor Road, Manchester M23 9LT, UK.
OBJECTIVES Renal failure following abdominal aortic aneurysm (AAA) repair is a common and significant complication. The objective of this study was to identify risk factors for renal failure following open elective AAA repair. DESIGN A retrospective analysis of prospectively collected multi-centre data. MATERIALS Consecutive data on patients undergoing open elective AAA repair were collected between January 2000 and December 2010. Patients with pre-operative serum creatinine >200 μmol/L were excluded. METHODS Renal failure was reported by clinicians and included all patients requiring post-operative renal-replacement therapy. Univariate and multivariate analyses were used to identify renal failure risk factors. A simplified clinical risk score was developed. RESULTS Post-operative renal failure occurred in 140 (6.0%) of 2347 patients and was associated with age >75 (OR = 1.58, 95%CI 1.11-2.26), symptomatic AAA (OR = 1.77, 95%CI 1.24-2.52), supra/juxta renal AAA (OR = 2.17, 95%CI 1.32-3.57) pre-operative serum creatinine >150 (OR = 2.75, 95%CI 1.69-4.50), treated hypertension (OR = 1.87, 95%CI 1.28-2.74), and respiratory disease (OR = 2.08, 95%CI 1.45-2.97). Patients with post-operative renal failure had significantly higher 30-day mortality (35.0% vs. 4.3%, p < 0.001). CONCLUSIONS Renal failure following open elective AAA repair was associated with an increased risk of mortality. Risk factors for post-operative renal failure were identified and a simple clinical risk score developed to facilitate focussed care strategies for high-risk patients.
Heart. 2012 Jan ;98 (1):60-4 21990387
What is the impact of endoscopic vein harvesting on clinical outcomes following coronary artery bypass graft surgery?
University of Manchester, Manchester Academic Health Science Centre, University Hospital of South Manchester, Southmoor Road, Manchester M23 9LT, UK.
Objective Endoscopic vein harvesting (EVH) is increasingly used as an alternative to open vein harvesting (OVH) for coronary artery bypass graft (CABG) surgery. Concerns about the safety of EVH with regard to midterm clinical outcomes following CABG have been raised. The objective of this study was to assess the impact of EVH on short-term and midterm clinical outcomes following CABG. Design This was a retrospective analysis of prospectively collected multi-centre data. A propensity score was developed for EVH and used to match patients who underwent EVH to those who underwent OVH. Setting Blackpool Victoria Hospital, Plymouth Derriford Hospital and the University Hospital of South Manchester were the main study settings. Patients There were 4709 consecutive patients who underwent isolated CABG using EVH or OVH between January 2008 and July 2010. Main outcome measures The main outcome measure was a combined end point of death, repeat revascularisation or myocardial infarction. Secondary outcome measures included in-hospital morbidity, in-hospital mortality and midterm mortality. Results Compared to OVH, EVH was not associated with an increased risk of the main outcome measure at a median follow-up of 22 months (HR 1.15; 95% CI 0.76 to 1.74). EVH was also not associated with an increased risk of in-hospital morbidity, in-hospital mortality (0.9% vs 1.1%, p=0.71) or midterm mortality (HR 1.04; 95% CI 0.65 to 1.66). Conclusions This multi-centre study demonstrates that at a median follow-up of 22 months, EVH was not associated with adverse short-term or midterm clinical outcomes. However, before the safety of EVH can be clearly determined, further analyses of long-term clinical outcomes are required.
Br J Surg. 2011 Sep ;98 (9):1337 21792859
Authors' reply: Logistic risk model for mortality following elective abdominal aortic aneurysm repair (Br J Surg 2011; 98: 652-658).
University of Manchester, Manchester Academic Health Science Centre, University Hospital of South Manchester, Academic Surgery Unit, Education and Research Centre, Southmoor Road, Manchester M23 9LT, UK. firstname.lastname@example.org.
Br J Surg. 2011 May ;98 (5):652-8 21412997
University of Manchester, Manchester Academic Health Science Centre, University Hospital of South Manchester, Academic Surgery Unit, Education and Research Centre, Manchester, UK.
BACKGROUND The aim was to develop a multivariable risk prediction model for 30-day mortality following elective abdominal aortic aneurysm (AAA) repair. METHODS Data collected prospectively on 2765 consecutive patients undergoing elective open and endovascular AAA repair from September 1999 to October 2009 in the North West of England were split randomly into development (1936 patients) and validation (829) data sets. Logistic regression analysis was undertaken to identify risk factors for 30-day mortality. RESULTS Ninety-eight deaths (5·1 per cent) were recorded in the development data set. Variables associated with 30-day mortality included: increasing age (P = 0·005), female sex (P = 0·002), diabetes (P = 0·029), raised serum creatinine level (P = 0·006), respiratory disease (P = 0·031), antiplatelet medication (P < 0·001) and open surgery (P = 0·002). The area under the receiver operating characteristic (ROC) curve for predicted probability of 30-day mortality in the development and validation data sets was 0·73 and 0·70 respectively. Observed versus expected 30-day mortality was 3·2 versus 2·0 per cent (P = 0·272) in low-risk, 6·1 versus 5·1 per cent (P = 0·671) in medium-risk and 11·1 versus 10·7 per cent (P = 0·879) in high-risk patients. CONCLUSION This multivariable model for predicting 30-day mortality following elective AAA repair can be used clinically to calculate patient-specific risk and is useful for case-mix adjustment. The model predicted well across all risk groups in the validation data set.
Does the choice of risk-adjustment model influence the outcome of surgeon-specific mortality analysis? A retrospective analysis of 14,637 patients under 31 surgeons.
University Hospital of South Manchester NHS Foundation Trust, Southmoor Road, Manchester M23 9LT, UK.
OBJECTIVES To compare implications of using the logistic EuroSCORE and a locally derived model when analysing individual surgeon mortality outcomes. DESIGN Retrospective analysis of prospectively collected data. SETTING All NHS hospitals undertaking adult cardiac surgery in northwest England. PATIENTS 14,637 consecutive patients, April 2002 to March 2005. MAIN OUTCOME MEASURES We have compared the predictive ability of the logistic EuroSCORE (uncalibrated), the logistic EuroSCORE calibrated for contemporary performance and a locally derived logistic regression model. We have used each to create risk-adjusted individual surgeon mortality funnel plots to demonstrate high mortality outcomes. RESULTS There were 458 (3.1%) deaths. The expected mortality and receiver operating characteristic (ROC) curve values were: uncalibrated EuroSCORE -5.8% and 0.80, calibrated EuroSCORE -3.1% and 0.80, locally derived model -3.1% and 0.82. The uncalibrated EuroSCORE plot showed one surgeon to have mortality above the northwest average, and no surgeon above the 95% control limit (CL). The calibrated EuroSCORE plot and the local model showed little change in surgeon ranking, but significant differences in identifying high mortality outcomes. Two of three surgeons above the 95% CL using the calibrated EuroSCORE revert to acceptable outcomes when the local model is applied but the finding is critically dependent on the calibration coefficient. CONCLUSIONS The uncalibrated EuroSCORE significantly overpredicted mortality and is not recommended. Instead, the EuroSCORE should be calibrated for contemporary performance. The differences demonstrated in defining high mortality outcomes when using a model built for purpose suggests that the choice of risk model is important when analysing surgeon mortality outcomes.
W E Lawson, S W Grant, V Ambrosini, K E Womble, E P Dawson, K B Lane, C Markin, E Renzoni, P Lympany, A Q Thomas, J Roldan, T A Scott, T S Blackwell, J A Phillips 3rd, J E Loyd, R M du Bois
Department of Medicine, Division of Allergy, Pulmonary and Critical Care Medicine, Vanderbilt University School of Medicine, Nashville, TN 37232-2650, USA.
BACKGROUND While idiopathic pulmonary fibrosis (IPF) is one of the most common forms of interstitial lung disease, the aetiology of IPF is poorly understood. Familial cases of pulmonary fibrosis suggest a genetic basis for some forms of the disease. Recent reports have linked genetic mutations in surfactant protein C (SFTPC) with familial forms of pulmonary fibrosis, including one large family in which a number of family members were diagnosed with usual interstitial pneumonitis (UIP), the pathological correlate to IPF. Because of this finding in familial cases of pulmonary fibrosis, we searched for SFTPC mutations in a cohort of sporadic cases of UIP and non-specific interstitial pneumonitis (NSIP). METHODS The gene for SFTPC was sequenced in 89 patients diagnosed with UIP, 46 patients with NSIP, and 104 normal controls. RESULTS Ten single nucleotide polymorphisms in the SFTPC sequence were found in IPF patients and not in controls. Only one of these created an exonic change resulting in a change in amino acid sequence. In this case, a T to C substitution resulted in a change in amino acid 73 of the precursor protein from isoleucine to threonine. Of the remaining polymorphisms, one was in the 5' UTR, two were exonic without predicted amino acid sequence changes, and six were intronic. One intronic mutation suggested a potential enhancement of a splicing site. CONCLUSIONS Mutations in SFTPC are identified infrequently in this patient population. These findings indicate that SFTPC mutations do not contribute to the pathogenesis of IPF in the majority of sporadic cases.
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In situ observation of Ni-Mo-S phase formed on NiMo/Al(2)O(3) catalyst sulfided at high pressure by means of Ni and Mo K-edge EXAFS spectroscopy.
Department of Applied Chemistry, Graduate School of Engineering, Tohoku University, Aoba-ku, Sendai, Japan. email@example.com
To obtain direct evidence of the formation of the Ni-Mo-S phase on NiMo/Al(2)O(3) catalysts under high-pressure hydrodesulfurization conditions, a high-pressure EXAFS chamber has been constructed and used to investigate the coordination structure of Ni and Mo species on the catalysts sulfided at high pressure. The high-pressure chamber was designed to have a low dead volume and was equipped with polybenzimidazole X-ray windows. Ni K-edge k(3)chi(k) spectra with high signal-to-noise ratio were obtained using this high-pressure chamber for the NiMo/Al(2)O(3) catalyst sulfided at 613 K and 1.1 MPa over a wide k range (39.5-146 nm(-1)). The formation of Ni-Mo and Mo-Ni coordination shells was successfully proved by Ni and Mo K-edge EXAFS measurement using this chamber. Interatomic distances of these coordination shells were almost identical to those calculated from Ni K-edge EXAFS of NiMo/C catalysts sulfided at atmospheric pressure. These results support the hypothesis that the Ni-Mo-S phase is formed on the Al(2)O(3)-supported NiMo catalyst sulfided under high-pressure hydrodesulfurization conditions.
Development of lower Triassic wrinkle structures: implications for the search for life on other planets.
Department of Earth Sciences, University of Southern California, Los Angeles, California 90089-0740, USA. firstname.lastname@example.org
Wrinkle structures are microbially mediated sedimentary structures that are a common feature of Proterozoic and earliest Phanerozoic siliciclastic seafloors on Earth and occur only rarely in post-Cambrian strata. These macroscopic microbially induced sedimentary structures are readily identifiable at the outcrop scale, and their recognition on other planetary bodies by landed missions may suggest the presence of past microbial life. Wrinkle structures of the Lower Triassic (Spathian) Virgin Limestone Member of the Moenkopi Formation in the western United States record an occurrence of widespread microbialite formation in the wake of the end-Permian mass extinction, the largest biotic crisis of the Phanerozoic. Wrinkle structures occur on proximal sandy tempestites deposited within the offshore transition. Storm layers appear to have been rapidly colonized by microbial mats and were subsequently buried by mud during fair-weather conditions. Wrinkle structures exhibit flat-topped crests and sinuous troughs, with associated mica grains oriented parallel to bedding, suggestive of trapping and binding activity. Although Lower Triassic wrinkle structures postdate the widespread occurrence of these features during the Proterozoic and Cambrian, they exhibit many of the same characteristics and environmental trends, which suggests a conservation of microbial formational and preservational processes in subtidal siliciclastic settings on Earth from the Precambrian into the Phanerozoic. In the search for extraterrestrial life, it may be these conservative characteristics that prove to be the most useful and robust for recognizing microbial features on other planetary bodies, and may add to an ever-growing foundation of knowledge for directing future explorations aimed at seeking out macroscopic microbial signatures.
Institute of Paleobiology, Polish Academy of Sciences, Twarda 51/55, PL-00-818 Warsaw, Poland. email@example.com
It has been generally thought that scleractinian corals form purely aragonitic skeletons. We show that a well-preserved fossil coral, Coelosmilia sp. from the Upper Cretaceous (about 70 million years ago), has preserved skeletal structural features identical to those observed in present-day scleractinians. However, the skeleton of Coelosmilia sp. is entirely calcitic. Its fine-scale structure and chemistry indicate that the calcite is primary and did not form from the diagenetic alteration of aragonite. This result implies that corals, like other groups of marine, calcium carbonate-producing organisms, can form skeletons of different carbonate polymorphs.
Carbonaceous shales of the Middle Proterozoic Newland Limestone, Belt Supergroup, Little Belt Mountains, Montana, contain abundant and well-preserved filamentous and spheroidal microfossils. The filamentous forms, ranging from less than 1 to 12 micrometers in width, are interpreted as representing the preserved sheaths of at least four species of nostocalean cyanophytes. The spheroidal forms, ranging from 15 to 108 micrometers in size, are evidently planktonic forms and are tentatively interpreted as representing the encystment stage of eukaryotic algae. The Newland microbiota is adaptable to petrographic thin-section work, and useful for evaluating the potential of such microfossils for intercontinental biostratigraphic correlation. It is the oldest shale-facies microbiota presently known from North America.
Synthesis and structure of new water-soluble and stable tantalum compound: ammonium tetralactatodiperoxo-mu-oxo-ditantalate(V).
Valery Petrykin, Masato Kakihana, Kohtaro Yoshioka, Satoshi Sasaki, Yoshihiro Ueda, Koji Tomita, Yoshiyuki Nakamura, Motoo Shiro, Akihiko Kudo
IMRAM, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai 980-8577, Miyagi, Japan.
The stable water-soluble tantalum complex with lactic acid (ammonium tetralactatodiperoxo-mu-oxo-ditantalate(V)),(NH4)4[Ta2(C3H4O3)4(O2)2O].3H2O, was prepared in the crystalline form. According to the single-crystal X-ray diffraction data, this compound forms a monoclinic cell with a = 13.85(2) A, b = 9.06(1) A, c = 12.32(2) A, and beta = 116.30 degrees , space group C2 (No. 2), and has Z = 2 molecules per unit cell. The solid-state 13C NMR data and low flack parameter are consistent with the determined structure. Appearance of the same vibration modes in Raman and IR spectra supports the choice of the space group without inversion symmetry. The solution of the tantalum complex was successfully applied for the synthesis of two photocatalytic materials, NaTaO3 and Sr2Ta2O7.
K E Herkenhoff, S W Squyres, R Arvidson, D S Bass, J F Bell 3rd, P Bertelsen, B L Ehlmann, W Farrand, L Gaddis, R Greeley, J Grotzinger, A G Hayes, S F Hviid, J R Johnson, B Jolliff, K M Kinch, A H Knoll, M B Madsen, J N Maki, S M McLennan, H Y McSween, D W Ming, J W Rice Jr, L Richter, M Sims, P H Smith, L A Soderblom, N Spanovich, R Sullivan, S Thompson, T Wdowiak, C Weitz, P Whelley
U.S. Geological Survey Astrogeology Team, Flagstaff, AZ 86001, USA. firstname.lastname@example.org
The Microscopic Imager on the Opportunity rover analyzed textures of soils and rocks at Meridiani Planum at a scale of 31 micrometers per pixel. The uppermost millimeter of some soils is weakly cemented, whereas other soils show little evidence of cohesion. Rock outcrops are laminated on a millimeter scale; image mosaics of cross-stratification suggest that some sediments were deposited by flowing water. Vugs in some outcrop faces are probably molds formed by dissolution of relatively soluble minerals during diagenesis. Microscopic images support the hypothesis that hematite-rich spherules observed in outcrops and soils also formed diagenetically as concretions.
Instituto de Geología y Minería, Universidad Nacional de Jujuy, Avenida Bolivia 1661, San Salvador de Jujuy (4600), Argentina. email@example.com
Euthycarcinoids are one of the most enigmatic arthropod groups, having been assigned to nearly all major clades of Arthropoda. Recent work has endorsed closest relationships with crustaceans or a myriapod-hexapod assemblage, a basal position in the Euarthropoda, or a placement in the Hexapoda or hexapod stem group. Euthycarcinoids are known from 13 species ranging in age from Late Ordovician or Early Silurian to Middle Triassic, all in freshwater or brackish water environments. Here we describe a euthycarcinoid from marine strata in Argentina dating from the latest Cambrian period, extending the group's record back as much as 50 million years. Despite its antiquity and marine occurrence, the Cambrian species demonstrates that morphological details were conserved in the transition to fresh water. Trackways in the same unit as the euthycarcinoid strengthen arguments that similar traces of subaerial origin from Cambro-Ordovician rocks were made by euthycarcinoids. Large mandibles in euthycarcinoids are confirmed by the Cambrian species. A morphology-based phylogeny resolves euthycarcinoids as stem-group Mandibulata, sister to the Myriapoda and Crustacea plus Hexapoda.
Crystal structure of ovocleidin-17, a major protein of the calcified Gallus gallus eggshell: implications in the calcite mineral growth pattern.
Instituto de Química, Universidad Nacional Autónoma de México (UNAM) Circuito Exterior, C.U. México, D.F. 04510, Mexico.
Ovocleidin-17 (OC17) from Gallus gallus is one of the best candidates to control and regulate the deposition of calcium carbonate in the calcified eggshell layer. Here, the crystal structure of monomeric OC17, determined at a resolution of 1.5 A, was refined to a crystallographic R-factor of 20.1%. This is the first protein directly involved in a non-pathological biomineralization process resolved by x-ray diffraction to date. The protein has a mixed alpha/beta structure containing a single C-type lectin-like domain. However, although OC17 shares the conserved scaffold of the C-type lectins, it does not bind carbohydrates. Nevertheless, in vitro OC17 modifies the crystalline habit of calcium carbonate (CaCO3) and the pattern of crystal growth at intervals of 5-200 microg/ml. Determining the three-dimensional structure of OC17 contributes to a better understanding of the biological behavior of structurally related biomolecules and of the mechanisms involved in eggshell and other mineralization processes.
The thio-Mitsunobu reaction: a useful tool for the preparation of 2,5-anhydro-2-thio- and 3,5-anhydro-3-thiopentofuranosides.
Institut für Organische Chemie der Universität Hamburg, Martin-Luther-King-Platz 6, D-20146 Hamburg, Germany.
The unprotected methyl l-arabinofuranosides, d-ribofuranosides and d-xylofuranosides are transformed into the corresponding S-acetyl-5-thio derivatives by the thio-Mitsunobu reaction. Mesylation and subsequent reaction with sodium hydrogen carbonate led, depending on the configuration of the intermediate, to 2,5-anhydro-2-thio- or 3,5-anhydro-3-thiopentofuranosides. Due to inversion at C-3 or C-2 during the intramolecular nucleophilic displacement the products exhibit l-lyxo-, d-arabino- or d-lyxo-configuration. Analogously, the methyl 2,3-anhydro-d-ribofuranosides yielded 5-thio-S-acetates with intact 2,3-oxirane groups, which were cyclised with sodium hydrogen carbonate by epoxide ring opening and concomitant ring closure to form exclusively 3,5-anhydro-3-thio-d-xylofuranosides. A related 3,5-anhydro-3-seleno-d-lyxofuranoside was obtained by reaction of a 3,5-di-O-mesyl-d-arabinofuranoside with sodium hydrogen selenide. Several X-ray diffraction analyses proved the structures of the products.
Laboratory of Human Bacterial Pathogenesis, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 903 S. 4th St., Hamilton, MT 59840, USA.
Important pathogens in the genus Yersinia include the plague bacillus Yersinia pestis and two enteropathogenic species, Yersinia pseudotuberculosis and Yersinia enterocolitica. A shift in growth temperature induced changes in the number and type of acyl groups on the lipid A of all three species. After growth at 37 degrees C, Y. pestis lipopolysaccharide (LPS) contained the tetra-acylated lipid IV(A) and smaller amounts of lipid IV(A) modified with C10 or C12 acyl groups, Y. pseudotuberculosis contained the same forms as part of a more heterogeneous population in which lipid IV(A) modified with C16:0 predominated, and Y. enterocolitica produced a unique tetra-acylated lipid A. When grown at 21 degrees C, however, the three yersiniae synthesized LPS containing predominantly hexa-acylated lipid A. This more complex lipid A stimulated human monocytes to secrete tumour necrosis factor-alpha, whereas the lipid A synthesized by the three species at 37 degrees C did not. The Y. pestis phoP gene was required for aminoarabinose modification of lipid A, but not for the temperature-dependent acylation changes. The results suggest that the production of a less immunostimulatory form of LPS upon entry into the mammalian host is a conserved pathogenesis mechanism in the genus Yersinia, and that species-specific lipid A forms may be important for life cycle and pathogenicity differences.