Showing papers by "University of Copenhagen published in 1998"

On Cox Processes and Credit Risky Securities

Abstract: A framework is presented for modeling defaultable securities and credit derivatives which allows for dependence between market risk factors and credit risk. The framework reduces the technical issues of modeling credit risk to the same issues faced when modeling the ordinary term structure of interest rates. It is shown how to generalize a model of Jarrow, Lando and Turnbull (1997) to allow for stochastic transition intensities between rating categories and into default. This generalization can handle contracts with payments explicitly linked to ratings. It is also shown how to obtain a term structure model for all different rating categories simultaneously and how to obtain an affine-like structure. An implementation is given in a simple one factor model in which the affine structure gives closed form solutions.

Hypothalamic CART is a new anorectic peptide regulated by leptin

Abstract: The mammalian hypothalamus strongly influences ingestive behaviour through several different signalling molecules and receptor systems Here we show that CART (cocaine- and amphetamine-regulated transcript), a brain-located peptide, is a satiety factor and is closely associated with the actions of two important regulators of food intake, leptin and neuropeptide Y Food-deprived animals show a pronounced decrease in expression of CART messenger RNA in the arcuate nucleus In animal models of obesity with disrupted leptin signalling, CART mRNA is almost absent from the arcuate nucleus Peripheral administration of leptin to obese mice stimulates CART mRNA expression When injected intracerebroventricularly into rats, recombinant CART peptide inhibits both normal and starvation-induced feeding, and completely blocks the feeding response induced by neuropeptide Y An antiserum against CART increases feeding in normal rats, indicating that CART may be an endogenous inhibitor of food intake in normal animals

Alendronate for the Prevention and Treatment of Glucocorticoid-Induced Osteoporosis

Abstract: Background Osteoporosis is a common complication of long-term glucocorticoid therapy for which there is no well-proved preventive or restorative treatment. Methods We carried out two 48-week, randomized, placebo-controlled studies of two doses of alendronate in 477 men and women, 17 to 83 years of age, who were receiving glucocorticoid therapy. The primary end point was the difference in the mean percent change in lumbar-spine bone density from base line to week 48 between the groups. Secondary outcomes included changes in bone density of the hip, biochemical markers of bone turnover, and the incidence of new vertebral fractures. Results The mean (±SE) bone density of the lumbar spine increased by 2.1±0.3 percent and 2.9±0.3 percent, respectively, in the groups that received 5 and 10 mg of alendronate per day (P<0.001) and decreased by 0.4±0.3 percent in the placebo group. The femoral-neck bone density increased by 1.2±0.4 percent and 1.0±0.4 percent in the respective alendronate groups (P<0.01) and decre...

Tissue transglutaminase selectively modifies gliadin peptides that are recognized by gut-derived T cells in celiac disease

Abstract: The action of tissue Transglutaminase (TGase) on specific protein-bound glutamine residues plays a critical role in numerous biological processes. Here we provide evidence for a new role of this enzyme in the common, HLA-DQ2 (and DQ8) associated enteropathy, celiac disease (CD). The intestinal inflammation in CD is precipitated by exposure to wheat gliadin in the diet and is associated with increased mucosal activity of TGase. This enzyme has also been identified as the main target for CD-associated anti-endomysium autoantibodies, and is known to accept gliadin as one of its few substrates. We have examined the possibility that TGase could be involved in modulating the reactivity of gliadin specific T cells. This could establish a link between previous reports of the role of TGase in CD and the prevailing view of CD as a T-cell mediated disorder. We found a specific effect of TGase on T-cell recognition of gliadin. This effect was limited to gliadin-specific T cells isolated from intestinal CD lesions. We demonstrate that TGase mediates its effect through an ordered and specific deamidation of gliadins. This deamidation creates an epitope that binds efficiently to DQ2 and is recognized by gut-derived T cells. Generation of epitopes by enzymatic modification is a new mechanism that may be relevant for breaking of tolerance and initiation of autoimmune disease.

GPCRDB: an information system for G protein-coupled receptors.

Abstract: Recent developments in G protein-coupled receptor (GPCR) structural biology and pharmacology have greatly enhanced our knowledge of receptor structure-function relations, and have helped improve the scientific foundation for drug design studies. The GPCR database, GPCRdb, serves a dual role in disseminating and enabling new scientific developments by providing reference data, analysis tools and interactive diagrams. This paper highlights new features in the fifth major GPCRdb release: (i) GPCR crystal structure browsing, superposition and display of ligand interactions; (ii) direct deposition by users of point mutations and their effects on ligand binding; (iii) refined snake and helix box residue diagram looks; and (iii) phylogenetic trees with receptor classification colour schemes. Under the hood, the entire GPCRdb front- and back-ends have been re-coded within one infrastructure, ensuring a smooth browsing experience and development. GPCRdb is available at http://www.gpcrdb.org/ and it's open source code at https://bitbucket.org/gpcr/protwis.

Evolution of Substrate Specificities in the P-Type ATPase Superfamily

Abstract: P-type ATPases make up a large superfamily of ATP-driven pumps involved in the transmembrane transport of charged substrates. We have performed an analysis of conserved core sequences in 159 P-type ATPases. The various ATPases group together in five major branches according to substrate specificity, and not according to the evolutionary relationship of the parental species, indicating that invention of new substrate specificities is accompanied by abrupt changes in the rate of sequence evolution. A hitherto-unrecognized family of P-type ATPases has been identified that is expected to be represented in all the major phyla of eukarya.

An event stratigraphy for the Last Termination in the North Atlantic region based on the Greenland ice-core record: a proposal by the INTIMATE group

Abstract: It is suggested that the GRIP Greenland ice-core should constitute the stratotype for the Last Termination. Based on the oxygen isotope signal in that core, a new event stratigraphy spanning the time interval from ca. 22.0 to 11.5 k GRIP yr BP (ca. 19.0-10.0 k 14 C yr BP) is proposed for the North Atlantic region. This covers the period from the Last Glacial Maximum, through Termination 1 of the deep-ocean record, to the Pleistocene-Holocene boundary, and encompasses the Last Glacial Late-glacial of the traditional northwest European stratigraphy. The isotopic record for this period is divided into two stadial episodes, Greenland Stadials 1 (GS-1) and 2 (GS-2), and two interstadial events, Greenland Interstadials 1 (GI-1) and 2 (GI-2). In addition, GI-1 and GS-2 are further subdivided into shorter episodes. The event stratigraphy is equally applicable to ice-core, marine and terrestrial records and is considered to be a more appropriate classificatory scheme than the terrestrially based radiocarbon-dated chronostratigraphy that has been used hitherto. © 1998 John Wiley & Sons, Ltd.

Asynchrony of Antarctic and Greenland climate change during the last glacial period

Abstract: A central issue in climate dynamics is to understand how the Northern and Southern hemispheres are coupled during climate events. The strongest of the fast temperature changes observed in Greenland (so-called Dansgaard–Oeschger events) during the last glaciation have an analogue in the temperature record from Antarctica. A comparison of the global atmospheric concentration of methane as recorded in ice cores from Antarctica and Greenland permits a determination of the phase relationship (in leads or lags) of these temperature variations. Greenland warming events around 36 and 45 kyr before present lag their Antarctic counterpart by more than 1 kyr. On average, Antarctic climate change leads that of Greenland by 1–2.5 kyr over the period 47–23 kyr before present.

Absence of host plasminogen activator inhibitor 1 prevents cancer invasion and vascularization

Abstract: Acquisition of invasive/metastatic potential through protease expression is an essential event in tumor progression. High levels of components of the plasminogen activation system, including urokinase, but paradoxically also its inhibitor, plasminogen activator inhibitor 1 (PAI1), have been correlated with a poor prognosis for some cancers. We report here that deficient PAI1 expression in host mice prevented local invasion and tumor vascularization of transplanted malignant keratinocytes. When this PAI1 deficiency was circumvented by intravenous injection of a replication-defective adenoviral vector expressing human PAI1, invasion and associated angiogenesis were restored. This experimental evidence demonstrates that host-produced PAI is essential for cancer cell invasion and angiogenesis.

Reciprocal interactions between β1-integrin and epidermal growth factor receptor in three-dimensional basement membrane breast cultures: A different perspective in epithelial biology

Abstract: Anchorage and growth factor independence are cardinal features of the transformed phenotype. Although it is logical that the two pathways must be coregulated in normal tissues to maintain homeostasis, this has not been demonstrated directly. We showed previously that down-modulation of β1-integrin signaling reverted the malignant behavior of a human breast tumor cell line (T4–2) derived from phenotypically normal cells (HMT-3522) and led to growth arrest in a three-dimensional (3D) basement membrane assay in which the cells formed tissue-like acini (14). Here, we show that there is a bidirectional cross-modulation of β1-integrin and epidermal growth factor receptor (EGFR) signaling via the mitogen-activated protein kinase (MAPK) pathway. The reciprocal modulation does not occur in monolayer (2D) cultures. Antibody-mediated inhibition of either of these receptors in the tumor cells, or inhibition of MAPK kinase, induced a concomitant down-regulation of both receptors, followed by growth-arrest and restoration of normal breast tissue morphogenesis. Cross-modulation and tissue morphogenesis were associated with attenuation of EGF-induced transient MAPK activation. To specifically test EGFR and β1-integrin interdependency, EGFR was overexpressed in nonmalignant cells, leading to disruption of morphogenesis and a compensatory up-regulation of β1-integrin expression, again only in 3D. Our results indicate that when breast cells are spatially organized as a result of contact with basement membrane, the signaling pathways become coupled and bidirectional. They further explain why breast cells fail to differentiate in monolayer cultures in which these events are mostly uncoupled. Moreover, in a subset of tumor cells in which these pathways are misregulated but functional, the cells could be “normalized” by manipulating either pathway.

BAP1: a novel ubiquitin hydrolase which binds to the BRCA1 RING finger and enhances BRCA1-mediated cell growth suppression

Abstract: We have identified a novel protein, BAP1, which binds to the RING finger domain of the Breast/Ovarian Cancer Susceptibility Gene product, BRCA1. BAP1 is a nuclear-localized, ubiquitin carboxy-terminal hydrolase, suggesting that deubiquitinating enzymes may play a role in BRCA1 function. BAP1 binds to the wild-type BRCA1-RING finger, but not to germline mutants of the BRCA1-RING finger found in breast cancer kindreds. BAP1 and BRCA1 are temporally and spatially co-expressed during murine breast development and remodeling, and show overlapping patterns of subnuclear distribution. BAP1 resides on human chromosome 3p21.3; intragenic homozygous rearrangements and deletions of BAP1 have been found in lung carcinoma cell lines. BAP1 enhances BRCA1-mediated inhibition of breast cancer cell growth and is the first nuclear-localized ubiquitin carboxy-terminal hydrolase to be identified. BAP1 may be a new tumor suppressor gene which functions in the BRCA1 growth control pathway.

Understanding gender and organizations

Abstract: The Many Faces of Gender and Organization Different Perspectives on Gender Division of Labour and Sex Typing Masculinities, Femininities and Work Gender and Identity Gender, Organizational Culture and Sexuality Women in Management Women in Management II Four Positions Broadening the Agenda Reconstructing Gender and Organization Studies

Smoking and risk of myocardial infarction in women and men: longitudinal population study

Abstract: Objective: To compare risk of myocardial infarction associated with smoking in men and women, taking into consideration differences in smoking behaviour and a number of potential confounding variables. Design: Prospective cohort study with follow up of myocardial infarction. Setting: Pooled data from three population studies conducted in Copenhagen. Subjects: 11 472 women and 13 191 men followed for a mean of 12.3 years. Main outcome measures: First admission to hospital or death caused by myocardial infarction. Results: 1251 men and 512 women had a myocardial infarction during follow up. Compared with non-smokers, female current smokers had a relative risk of myocardial infarction of 2.24 (range 1.85-2.71) and male smokers 1.43 (1.26-1.62); ratio 1.57 (1.25-1.97). Relative risk of myocardial infarction increased with tobacco consumption in both men and women and was higher in inhalers than in non-inhalers. The risks associated with smoking, measured by both current and accumulated tobacco exposure, were consistently higher in women than in men and did not depend on age. This sex difference was not affected by adjustment for arterial blood pressure, total and high density lipoprotein cholesterol concentrations, triglyceride concentrations, diabetes, body mass index, height, alcohol intake, physical activity, and level of education. Conclusion: Women may be more sensitive than men to some of the harmful effects of smoking. Interactions between components of smoke and hormonal factors that may be involved in development of ischaemic heart disease should be examined further.

Dynamical Systems Approach to Turbulence

Abstract: Introduction 1. Turbulence and dynamical systems 2. Phenomenology of turbulence 3. Reduced models for hydrodynamic turbulence 4. Turbulence and coupled map lattices 5. Turbulence in the complex Ginzburg-Landau equation 6. Predictability in high-dimensional systems 7. Dynamics of interfaces 8. Lagrangian chaos 9. Chaotic diffusion Appendix A. Hopf bifurcation Appendix B. Hamiltonian systems Appendix C. Characteristic and generalised Lyapunov exponents Appendix D. Convective instabilities Appendix E. Generalised fractal dimensions and multifractals Appendix F. Multiaffine fields Appendix G. Reduction to a finite-dimensional dynamical system Appendix H. Directed percolation.

Inhibition of the activity of dipeptidyl-peptidase IV as a treatment for type 2 diabetes.

Abstract: The insulinotropic hormone, glucagon-like peptide 1 (GLP-1), which has been proposed as a new treatment for type 2 diabetes, is metabolized extremely rapidly by the ubiquitous enzyme, dipeptidyl peptidase IV (DPP-IV), resulting in the formation of a metabolite, which may act as an antagonist at the GLP-1 receptor. Because of this, the effects of single injections of GLP-1 are short-lasting, and for full demonstration of its antidiabetogenic effects, continuous intravenous infusion is required. To exploit the therapeutic potential of GLP-1 clinically, we here propose the use of specific inhibitors of DPP-IV. We have demonstrated that the administration of such inhibitors may completely protect exogenous GLP-1 from DPP-IV-mediated degradation, thereby greatly enhancing its insulinotropic effect, and provided evidence that endogenous GLP-1 may be equally protected. Preliminary studies by others in glucose-intolerant experimental animals have shown that DPP-IV inhibition greatly ameliorates the condition. GLP-1 has multifaceted actions, which include stimulation of insulin gene expression, trophic effects on the beta-cells, inhibition of glucagon secretion, promotion of satiety, inhibition of food intake, and slowing of gastric emptying, all of which contribute to normalizing elevated glucose levels. Because of this, we predict that inhibition of DPP-IV, which will elevate the levels of active GLP-1 and reduce the levels of the antagonistic metabolite, may be useful to treat impaired glucose tolerance and perhaps prevent transition to type 2 diabetes. The actions of DPP-IV, other than degradation of GLP-1, particularly in the immune system are discussed, but it is concluded that side effects of inhibition therapy are likely to be mild. Thus, DPP-IV inhibition may be an effective supplement to diet and exercise treatment in attempts to prevent the deterioration of glucose metabolism associated with the Western lifestyle.

Predicting dyslexia from kindergarten : The importance of distinctness of phonological representations of lexical items

Abstract: This article presents results from a longitudinal study of children of dyslexic and of normally reading parents. The children were followed from the beginning of kindergarten (at the age of 6, 1 year before reading instruction in Denmark) until the beginning of the second grade. Children of dyslexic parents were found to have an increased risk of dyslexia (a 4.3 odds ratio) when dyslexia was defined as poor phonological recoding (poor reading of nonwords and pseudohomophones of real words). All language measures in kindergarten were statistically significant predictors of dyslexia. Logistic regression analyses with backwards stepwise selection indicated that three measures contributed independently to the prediction of dyslexia: letter naming, phoneme identification, and distinctness of phonological representations. The measure of distinctness of phonological representations also contributed significantly to the prediction of poor phoneme awareness in Grade 2—even when differences in early syllable and phoneme awareness, articulation, and productive and receptive vocabulary were accounted for. The results suggest that the quality of phonological representations in the mental lexicon is a determinant of the development of both segmental (e.g., phoneme) awareness and of the acquisition of phonological recoding skills in reading. ESTE TRABAJO presenta los resultados de un estudio longitudinal de ninos hijos de padres dislexicos y normales. El seguimiento de los ninos se produjo desde el comienzo del preescolar (a la edad de seis anos, un ano antes de comenzar la ensenanza de la lectura en Dinamarca), hasta el comienzo de segundo grado. Se hallo que entre los hijos de padres dislexicos aumentaba el riesgo de dislexia (a razon del 4.3) cuando se definia la dislexia como problemas de recodificacion fonologica (problemas para leer pseudo-palabras y pseudo-homofonos de palabras reales). Todas las medidas de lenguaje tomadas en preescolar fueron predictoras de dislexia estadisticamente significativas. Los analisis de regresion logistica con seleccion por pasos indicaron que las tres medidas contribuian independientemente a la prediccion de la dislexia: nombrar letras, identificar fonemas y la precision de las representaciones fonologicas. La medida de precision de las representaciones fonologicas tambien contribuyo significativamente a predecir problemas de conciencia fonologica en segundo grado - aun cuando se tomaron en cuenta las diferencias en conciencia silabica y fonologica tempranas. Los resultados sugieren que la calidad de las representaciones fonologicas en el lexico mental es determinante tanto del desarrollo de la conciencia segmental (por ej., fonologica) como de la adquisicion de habilidades fonologicas en la lectura. DIESER ARTIKEL stellt die Ergebnisse einer Langzeitstudie mit Kindern von dyslexischen und normal-lesenden Eltern vor. Die Kinder wurden mit Beginn des Kindergartens (im Alter von sechs, ein Jahr vor Beginn des Leseunterrichts in Danemark) bis zum Eintritt in das zweite Schuljahr betreut. Es wurde festgestellt, das Kinder von dyslexischen Eltern einem erhohten Risiko der Dyslexie unterliegen (im Wahrscheinlichkeitsverhaltnis von 4.3), wobei Dyslexie als unzureichende phonologische Wiedergabe definiert wurde (Leseschwache mit nicht-bestimmbaren Worten und scheinbaren Gleichlauten bzw. Pseudo-Homophonie bei realen Worten). Alle im Kindergarten ermittelten sprachlichen Masnahmen erwiesen sich als statistisch bedeutende Hinweise auf Dyslexie. Logistische Regressionsanalysen mit schrittweisen, ruckwirkenden Betrachtungsablaufen indizierten drei wesentliche Masnahmen, die unabhangig voneinander zur Bestimmung von Dyslexie beitragen: Buchstabieren, phonemische Unterscheidung und Deutlichkeit der phonologischen Ausdrucksweisen. Die systematische Bemessung der Deutlichkeit der phonologischen Reprasentation trug ebenfalls wesentlich zur Bestimmung eines voraussichtlich auftretenden geschwachten phonemischen Bewustseins bei Schulern in der zweiten Klasse bei, sogar wenn Unterschiede in der fruhen Erkenntnis von Silbenbildung und phonemischer Wahrnehmung, Artikulation bzw. Wortgliederung, sowie in produktiver und rezeptiver Wortbildung ermittelt wurden. Die Ergebnisse weisen daraufhin, das die Qualitat der phonologischen Vorstellungen im mentalen Lexikon ein Bestimmungsfaktor in der Entwicklung beider segmentaler (z.B. phonemischer) Aufnahmefahigkeiten und der Aneignung von phonologischen Wiedergabefahigkeiten beim Lesen ist. CE PAPIER presente des resultats provenant d'une etude longitudinale d'enfants de parents dyslexiques ou lisant normalement. Les enfants ont ete suivis du debut du jardin d'enfants (a six ans, un an avant l'enseignement de la lecture au Danemark) jusqu'au commencement de la seconde annee. On a trouve que les enfants de parents dyslexiques presentent un plus grand risque de dyslexie (4.3 fois plus) quand la dyslexie est definie comme un faible recodage phonologique (faible lecture de non-mots et de pseudo-homophones de mots reels). Tous les indicateurs langagiers au jardin d'enfants sont des predicteurs statistiquement significatifs de dyslexie. Des analyses de regression avec selection retroactive variable par variable ont montre que trois mesures contribuent independam ment a predire la dyslexie: la denomination de lettres, l'identification de phonemes, et la precision dans les representations phonologiques. La mesure de la precision dans les representations phonologiques contribue aussi de maniere significative a predire une faible conscience phonemique en deuxieme annee, meme si les differences initiales de conscience de la syllabe et du phoneme, de l'articulation, et du vocabulaire emis ou produit sont prises en consideration. Les resultats suggerent que la qualite des representations phonologiques dans le lexique interne est un determinant du developpement tant de la conscience segmentale (par exemple du phoneme) que de l'acquisition des habiletes de recodage phonologique en lecture.

Effects of Sodium Restriction on Blood Pressure, Renin, Aldosterone, Catecholamines, Cholesterols, and Triglyceride: A Meta-analysis

Abstract: Context.—One of the controversies in preventive medicine is whether a general reduction in sodium intake can decrease the blood pressure of a population and thereby reduce the number of strokes and myocardial infarctions. In recent years the debate has been extended by studies indicating that reduced sodium intake has adverse effects.Objective.—To estimate the effects of reduced sodium intake on systolic and diastolic blood pressure (SBP and DBP), body weight, and plasma or serum levels of renin, aldosterone, catecholamines, cholesterols, and triglyceride, and to evaluate the stability of the blood pressure effect in relation to additional trials.Data Sources.—MEDLINE search from 1966 through December 1997 and reference lists of relevant articles.Study Selection.—Studies randomizing persons to high-sodium and low-sodium diets were included if they evaluated at least one of the effect parameters.Data Extraction.—Two authors independently recorded data.Data Synthesis.—In 58 trials of hypertensive persons, the effect of reduced sodium intake as measured by urinary sodium excretion (mean, 118 mmol/24 h) on SBP was 3.9 mm Hg (95% confidence interval [CI], 3.0-4.8 mm Hg) (P<.001) and on DBP was 1.9 mm Hg (95% CI, 1.3-2.5 mm Hg) (P<.001). In 56 trials of normotensive persons, the effect of reduced sodium intake (mean, 160 mmol/24 h) on SBP was 1.2 mm Hg (95% CI, 0.6-1.8 mm Hg) (P<.001) and on DBP was 0.26 mm Hg (95% CI, −0.3-0.9 mm Hg) (P=.12). The cumulative analysis showed that this effect size has been stable since 1985. In plasma, the renin level increased 3.6-fold (P<.001), and the aldosterone level increased 3.2-fold (P<.001); the increases were proportional to the degree of sodium reduction for both renin (r=0.66; P<.001) and aldosterone (r=0.64; P<.001). Body weight decreased significantly, and noradrenaline, cholesterol, and low-density lipoprotein cholesterol levels increased. There was no effect on adrenaline, triglyceride, and high-density lipoprotein cholesterol.Conclusion.—These results do not support a general recommendation to reduce sodium intake. Reduced sodium intake may be used as a supplementary treatment in hypertension. Further long-term studies of the effects of high reduction of sodium intake on blood pressure and metabolic variables may clarify the disagreements as to the role of reduced sodium intake, but ideally trials with hard end points such as morbidity and survival should end the controversy.

A New Concept For Isokinetic Hamstring: Quadriceps Muscle Strength Ratio

Abstract: Conventionally, the hamstring:quadriceps strength ratio is calculated by dividing the maximal knee flexor (hamstring) moment by the maximal knee extensor (quadriceps) moment measured at identical angular velocity and contraction mode. The agonist-antagonist strength relationship for knee extension and flexion may, however, be better described by the more functional ratios of eccentric hamstring to concentric quadriceps moments (extension), and concentric hamstring to eccentric quadriceps moments (flexion). We compared functional and conventional isokinetic hamstring: quadriceps strength ratios and examined their relation to knee joint angle and joint angular velocity. Peak and angle-specific (50 degrees, 40 degrees, and 30 degrees of knee flexion) moments were determined during maximal concentric and eccentric muscle contractions (10 degrees to 90 degrees of motion; 30 and 240 deg/sec). Across movement speeds and contraction modes the functional ratios for different moments varied between 0.3 and 1.0 (peak and 50 degrees), 0.4 and 1.1 (40 degrees), and 0.4 and 1.4 (30 degrees). In contrast, conventional hamstring:quadriceps ratios were 0.5 to 0.6 based on peak and 50 degrees moments, 0.6 to 0.7 based on 40 degrees moment, and 0.6 to 0.8 based on 30 degrees moment. The functional hamstring:quadriceps ratio for fast knee extension yielded a 1:1 relationship, which increased with extended knee joint position, indicating a significant capacity of the hamstring muscles to provide dynamic knee joint stability in these conditions. The evaluation of knee joint function by use of isokinetic dynamometry should comprise data on functional and conventional hamstring:quadriceps ratios as well as data on absolute muscle strength.

The cold event 8200 years ago documented in oxygen isotope records of precipitation in Europe and Greenland

Abstract: Stable oxygen isotope ratios of ostracod valves in Late Glacial and Holocene sediments of core AS 92-5 from deep lake Ammersee (southern Germany) reflect variations of mean oxygen isotope ratios in past atmospheric precipitation. The record reconfirms the strong similarity of climate evolution in Europe and Greenland during the last deglaciation. For the first time in Europe, we find a 200-year-long negative δ18O-excursion, which is contemporaneous with the strongest negative δ18O-excursion in the Greenland ice around 8.2 ky before present. The 8.2 ky isotopic event on both sides of the North Atlantic ocean is interpreted as a cold period, most probably induced by a perturbation of the North Atlantic thermohaline circulation. We discuss two possible triggering mechanisms: (1) weak forcing (as proposed by Alley et al.), and (2) forcing by a strong and sudden freshwater pulse from the collapse of the Hudson Ice Dome.

Clinical findings with implications for genetic testing in families with clustering of colorectal cancer.

Abstract: Background Germ-line mutations in DNA mismatch-repair genes (MSH2, MLH1, PMS1, PMS2, and MSH6 ) cause susceptibility to hereditary nonpolyposis colorectal cancer. We assessed the prevalence of MSH2...

Bacterial Biogeochemistry: The Ecophysiology of Mineral Cycling

Abstract: Preface. Introduction. General Considerations: Bacterial Metabolism. Bioenergetics of Microbial Metabolism. Transport Mechanisms and Structure of Microbial Communities. Mineral Cycles: Hydrolysis of Organic Polymers. Comparison of Element Cycles. The Water Column: Prokaryotic Primary Producers. Water Column Bacteria and Mineralisation. Biogeochemical Cycling in Soils: Soil Water as a Master Variable. Responses to Plant Organic Matter. Responses of Soil Biogeochemistry to Disturbance and Change. Aquatic Sediments: Comparison of Freshwater and Marine Sediments. The Carbon Cycle. The Nitrogen Cycle. The Phosphorus Cycle. Manganese and Iron. Microbial Mats and Stratified Water Columns: Mats Based on Colourless Sulfur Bacteria. Cyanobacterial Mats. Other Types of Mats. Stratified Water Columns. Symbiotic Systems: The Role of Symbiosis in the Biosphere. Symbiotic Polymer Degradation. Symbiotic Nitrogen Fixation. Autotrophic Bacteria as Symbionts. Biogeochemistry and Extreme Environments. Microbial Biogeochemical Cycling and the Atmosphere: The Atmosphere as an Elemental Reservoir. Atmospheric Structure and Evolution. Synopsis of Trace Gas Biogeochemistry and Linkages to Climate Change. Trace Gas Dynamics and Climate Change: An Analysis of Methane Production and Consumption. Summary and Conclusion. Origins and Evolution of Biogeochemical Cycles: Biogeochemical Cycles and Thermodynamics. Pre-Biotic Earth and Mineral Cycles. Theoretical Perspectives on the Origin of Life. Evolution of Biogeochemical Cycles. Appendix: Thermodynamics and Calculation of Energy Yields of Metabolic Processes.

Influence of submerged macrophytes on sediment composition and near-bed flow in lowland streams

Abstract: 1. Submerged macrophytes have important physical and structural effects on lowland streams. This study investigated the ability of submerged macrophytes to modify the near-bed flow and to retain mineral and organic particles in patches of four common macrophytes in shallow Danish streams during mid-summer. 2. In dense patches of Callitriche cophocarpa and Elodea canadensis, where near-bed velocity was reduced, the sediment surface was markedly raised and enriched with fine particles. In dense patches of Ranunculus peltatus, fine sediments were deposited among rooted shoots in the upstream part of the patches, while erosion and coarse sediments prevailed in the downstream part of the patches because of the strong vortices that formed at the rear and moved up under the trailing canopy. The open canopy of Sparganium emersum, with its streamlined leaves, had little effect on flow and sediment. 3. Patterns of sediment deposition and composition were closely related to the morphology and canopy structure of plant species and the presence of low velocity above the sediment among the rooted shoots. The mineral particles retained probably originate from bed-load, and the enrichment with finer particles within the patches probably results mainly from size-selective processes during erosion and transport of particles rather than during deposition. The mixed sediment composition within patches suggests that the flow-resistant shoots generate an environment conducive to deposition of all transported particles. 4. Fine sediments within macrophyte beds contained high concentrations of organic matter, carbon, nitrogen and phosphorus. The wide scatter in the relationships between mineral grain size and the content of organic matter and nutrients reflects the spatial and temporal complexity of erosion, transport and sedimentation of mineral and organic particles. 5. Enrichment of sediment within macrophyte beds relative to the surrounding substratum ranged from 780 g organic matter m–2, 30 g N m–2 and 25 g P m–2 for the flow-resistant dense canopies af Callitriche cophocarpa to 150 g organic matter m–2, 6.6 g N m–2 and 3.4 g P m–2 for the open canopies of Sparganium emersum. Retention of nutrient-rich particles within the macrophyte beds is probably of limited importance for plant growth in most lowland European streams, because macrophyte growth is rarely nutrient limited.