Monalisa Research Articles

Randomized controlled phase III trial to investigate superiority of robot-assisted gastrectomy over laparoscopic gastrectomy for clinical stage T1-4aN0-3 gastric cancer patients (JCOG1907, MONA LISA study): a study protocol

BackgroundLaparoscopic gastrectomy (LG) is considered a standard treatment for clinical stage I gastric cancer. Nevertheless, LG has some drawbacks, such as motion restriction and difficulties in spatial perception. Robot-assisted gastrectomy (RG) overcomes these drawbacks by using articulated forceps, tremor-filtering capability, and high-resolution three-dimensional imaging, and it is expected to enable more precise and safer procedures than LG for gastric cancer. However, robust evidence based on a large-scale randomized study is lacking.MethodsWe are performing a randomized controlled phase III study to investigate the superiority of RG over LG for clinical T1-2N0-2 gastric cancer in terms of safety. In total, 1,040 patients are planned to be enrolled from 46 Japanese institutions over 5 years. The primary endpoint is the incidence of postoperative intra-abdominal infectious complications, including anastomotic leakage, pancreatic fistula, and intra-abdominal abscess of Clavien–Dindo (CD) grade ≥ II. The secondary endpoints are the incidence of all CD grade ≥ II and ≥ IIIA postoperative complications, the incidence of CD grade ≥ IIIA postoperative intra-abdominal infectious complications, relapse-free survival, overall survival, the proportion of RG completion, the proportion of LG completion, the proportion of conversion to open surgery, the proportion of operation-related death, and short-term surgical outcomes. The Japan Clinical Oncology Group Protocol Review Committee approved this study protocol in January 2020. Approval from the institutional review board was obtained before starting patient enrollment in each institution. Patient enrollment began in March 2020. We revised the protocol to expand the eligibility criteria to T1-4aN0-3 in July 2022 based on the results of randomized trials of LG demonstrating non-inferiority of LG to open surgery for survival outcomes in advanced gastric cancer.DiscussionThis is the first multicenter randomized controlled trial to confirm the superiority of RG over LG in terms of safety. This study will demonstrate whether RG is superior for gastric cancer.Trial registrationThe protocol of JCOG1907 was registered in the UMIN Clinical Trials Registry as UMIN000039825 (http://www.umin.ac.jp/ctr/index.htm). Date of Registration: March 16, 2020. Date of First Participant Enrollment: April 1, 2020.

A new 165-SNP low-density lipoprotein cholesterol polygenic risk score based on next generation sequencing outperforms previously published scores in routine diagnostics of familial hypercholesterolemia

Genetic diagnosis of familial hypercholesterolemia (FH) remains unexplained in 30 to 70% of patients after exclusion of monogenic disease. There is now a growing evidence that a polygenic burden significantly modulates LDL-cholesterol (LDL-c) concentrations. Several LDL-c polygenic risk scores (PRS) have been set up. However, the balance between their diagnosis performance and their practical use in routine practice is not clearly established. Consequently, we set up new PRS based on our routine panel for sequencing and compared their diagnostic performance with previously-published PRS. After a meta-analysis, four new PRS including 165 to 1633 SNP were setup using different softwares. They were established using two French control cohorts (MONA LISA n=1082 and FranceGenRef n=856). Then the explained LDL-c variance and the ability of each PRS to discriminate monogenic negative FH patients (M-) versus healthy controls were compared with 4 previously-described PRS in 785 unrelated FH patients. Between all PRS, the 165-SNP PRS developed with PLINK showed the best LDL-c explained variance (adjusted R²=0.19) and the best diagnosis abilities (AUROC=0.77, 95%CI=0.74-0.79): it significantly outperformed all the previously-published PRS (p<1 × 10−4). By using a cut-off at the 75th percentile, 61% of M- patients exhibited a polygenic hypercholesterolemia with the 165-SNP PRS versus 48% with the previously published 12-SNP PRS (p =3.3 × 10−6). These results were replicated using the UK biobank. This new 165-SNP PRS, usable in routine diagnosis, exhibits better diagnosis abilities for a polygenic hypercholesterolemia diagnosis. It would be a valuable tool to optimize referral for whole genome sequencing.

Randomized controlled phase III trial to investigate superiority of robot-assisted gastrectomy over laparoscopic gastrectomy for clinical stage T1-2N0-2 gastric cancer patients: Japan Clinical Oncology Group study JCOG1907 (MONA LISA study).

TPS254 Background: Postoperative complications reportedly affect oncological outcomes in various cancers according to the timing of adjuvant chemotherapy and by influencing the immune function. Particularly, postoperative intra-abdominal infectious complications, including intra-abdominal abscess, pancreatic fistula, and anastomotic leakage, have been identified as prognostic factors for gastric cancer. Given the negative impact of such complications on patient survival, considering the short- and long-term outcomes, it is important to develop surgical procedures with fewer complications. In Japan, laparoscopic gastrectomy is a standard treatment modality for early gastric cancer. Randomized controlled trials have shown that laparoscopic gastrectomy is relatively less invasive and has similar postoperative complications and non-inferior patient survival rates when compared with open gastrectomy. However, several challenges associated with the procedure need to be overcome, such as the limited movement of the forceps. Robot-assisted gastrectomy allows surgeons to perform more meticulous surgical interventions with articulated devices; therefore, reducing the possibility of postoperative complications, as demonstrated by a few prospective studies performed in Japan. However, a non-randomized controlled trial conducted in Korea reported that there were no benefits of robot-assisted gastrectomy in terms of postoperative complications. Furthermore, no randomized controlled trials have directly compared robot-assisted and laparoscopic gastrectomy to provide solid evidence regarding the merits of the former. Methods: To confirm the superiority of robot-assisted gastrectomy over laparoscopic gastrectomy for patients with cT1-2N0-2M0 gastric cancer, we designed JCOG1907 (UMIN000039825) as a multicenter randomized phase III trial. In the standard arm, we performed laparoscopic gastrectomy with lymphadenectomy, while in the experimental arm, we performed robot-assisted gastrectomy with lymphadenectomy. The primary endpoint is the incidence of postoperative intra-abdominal infectious complications of Clavien–Dindo classification grade ≥II. Major secondary endpoints are relapse-free survival, overall survival, overall postoperative complications, and short-term clinical outcomes after gastrectomy. The planned sample size is 1040 participants, with a one-sided alpha of 5% and a power of 70%, with an expected 3% decrease in postoperative intra-abdominal infectious complications (6% vs. 3%). Over the period of 5 years, patients will be enrolled from 35 Japanese institutions. Enrollment has started in March 2020, and as of August 2020, 30 patients have already been enrolled. Clinical trial information: UMIN000039825.

MONA LISA 2020 - SUSPENSE BEHIND THE PORTRAIT- A specific study on motherhood and its existential approach

MONA LISA 2020 - SUSPENSE BEHIND THE PORTRAIT- A specific study on motherhood and its existential approach

Metabolomics reveals plausible interactive effects between dairy product consumption and metabolic syndrome in humans

Metabolic syndrome (MetS) induces major disturbances in plasma metabolome, reflecting abnormalities of several metabolic pathways. Recent evidences have demonstrated that the consumption of dairy products may protect from MetS, but the mechanisms remains unknown. The present study aimed at identify how the consumption of different types of dairy products could modify the changes in plasma metabolome during MetS. In this observational study, we analyzed how the consumption of dairy products could modify the perturbations in the plasma metabolome induced by MetS in a sample of 298 participants (61 with MetS) from the French MONA LISA survey. Metabolomic profiling was analyzed with UPLC-MS/MS. Subjects with MetS exhibited major changes in plasma metabolome. Significant differences in plasma levels of branched chain amino acids, gamma-glutamyl amino acids, and metabolites from arginine and proline metabolism were observed between healthy control and Mets subjects. Plasma levels of many lipid species were increased with MetS (mono- and diacylglycerols, eicosanoids, lysophospholipids and lysoplasmalogens), with corresponding decreases in short chain fatty acids and plasmalogens. The consumption of dairy products, notably with a low fat content (milk and fresh dairy products), altered metabolite profiles in plasma from MetS subjects. Specifically, increasing consumption of dairy products promoted accumulation of plasma C15:0 fatty acid and was inversely associated to some circulating lysophospholipids, sphingolipids, gamma-glutamyl amino acids, leukotriene B4 and lysoplasmalogens. the consumption of low fat dairy products could mitigate some of the variations induced by MetS.

Effect of Exericse and Nutrition upon Lifestyle-Related Disease and Cognitive Function.

Bray has proposed the "MONA LISA" hypothesis, an acronym for Most Obesities kNown Are Low In Sympathetic Activity indicating that obesity is associated with a relative or absolute reduction in the activity of the thermogenic component of the sympathetic nervous system. Our series of studies have suggested a potential reversibility in ANS activity regulating fat metabolism and appetite control by regular exercise training in middle aged individuals and obese children with depressed ANS activity. In other words habitual exercise plays a vital role in enhancing not only fat and glucose metabolism, but also ANS activities in the prevention of obesity and appetite control. There are growing expectations that too much sitting is a real and substantial risk to health. One of the intriguing findings from these accelerometer measurement studies is that breaks in sedentary time were shown to have beneficial associations with metabolic biomarkers, due possibly to challenging and enhancing autonomic nervous system that regulates body weight and appetite. Recent findings of brain-derived neurotrophic factors (BDNF) seem to have shed some light upon age-related neurodegenerative diseases and appear to influence energy metabolism, appetite and aspects of neuro-cognitive function. These data strongly suggest that a lack of exercise as characterized by a sedentary lifestyle and an unhealthy diet may lead to accelerated ageing, diseases of the body and brain, and an overall decline in the quality of life.

Effects of established BMI-associated loci on obesity-related traits in a French representative population sample.

BackgroundGenome-wide association studies have identified variants associated with obesity-related traits, such as the body mass index (BMI). We sought to determine how the combination of 31 validated, BMI-associated loci contributes to obesity- and diabetes-related traits in a French population sample. The MONA LISA Lille study (1578 participants, aged 35–74) constitutes a representative sample of the population living in Lille (northern France). Genetic variants were considered both individually and combined into a genetic predisposition score (GPS).ResultsIndividually, 25 of 31 SNPs showed directionally consistent effects on BMI. Four loci (FTO, FANCL, MTIF3 and NUDT3) reached nominal significance (p ≤ 0.05) for their association with anthropometric traits. When considering the combined effect of the 31 SNPs, each additional risk allele of the GPS was significantly associated with an increment in the mean [95% CI] BMI of 0.13 [0.07-0.20] kg/m2 (p = 6.3x10-5) and a 3% increase in the risk of obesity (p = 0.047). The GPS explained 1% of the variance in the BMI. Furthermore, the GPS was associated with higher fasting glycaemia (p = 0.04), insulinaemia (p = 0.008), HbA1c levels (p = 0.01) and HOMA-IR scores (p = 0.0003) and a greater risk of type 2 diabetes (OR [95% CI] = 1.06 [1.00-1.11], p = 0.03). However, these associations were no longer statistically significant after adjustment for BMI.ConclusionOur results show that the GPS was associated with a higher BMI and an insulin-resistant state (mediated by BMI) in a population in northern France.

Relationship Between Markers of Insulin Resistance, Markers of Adiposity, HbA1c, and Cognitive Functions in a Middle-Aged Population–Based Sample: the MONA LISA Study

OBJECTIVE To determine the relationship between markers of insulin resistance (fasting insulin and homeostasis model assessment of insulin resistance), markers of adiposity (BMI, waist circumference, and body fat), HbA1c, and cognitive performances in a middle-aged population–based sample free of diabetes.RESEARCH DESIGN AND METHODS Our study sample consisted of 1,172 people aged 35–64 years (49% women), free of diabetes, and recruited between 2005 and 2007 in the MONA LISA survey. Cognitive functions (memory, attention, and processing speed) were evaluated by neuropsychological tests: word-list learning test, digit symbol substitution test (DSST), word fluency test, and Stroop Test. Multiple logistic regressions were used to estimate the relationship between cognitive performance and metabolic markers. We serially adjusted for age, sex, education, and occupational status (model A), additionally for income, smoking, alcohol consumption, sedentarity, and psychotropic substance use (model B), and finally, included variables linked to the metabolic syndrome (hypertension, dyslipidemia, vascular disease, and C-reactive protein) and depression (model C).RESULTS Elevated markers of adiposity were associated with poor cognitive performance in tests evaluating processing speed. The probability of being in the lowest quartile of each test was nearly doubled for participants in the upper quartile of BMI, compared with those in the lowest one [BMI, adjusted odds ratio (OR) 2.18, P = 0.003 (DSST), and OR 2.09, P = 0.005 (Stroop Test)]. High HbA1c was associated with poor cognitive performance in DSST (adjusted OR 1.75, P = 0.037). Waist circumference was linked to poor cognitive performance in men but not in women.CONCLUSIONS Poor cognitive performance is associated with adiposity and hyperglycemia in healthy middle-aged people.

Arcuate NPY Controls Sympathetic Output and BAT Function via a Relay of Tyrosine Hydroxylase Neurons in the PVN

Neuropepetide Y (NPY) is best known for its powerful stimulation of food intake and its effects on reducing energy expenditure. However, the pathways involved and the regulatory mechanisms behind this are not well understood. Here we demonstrate that NPY derived from the arcuate nucleus (Arc) is critical forthe control of sympathetic outflow and brown adipose tissue (BAT) function. Mechanistically,a key change induced by Arc NPY signaling is a marked Y1 receptor-mediated reduction in tyrosine hydroxylase (TH) expression in the hypothalamic paraventricular nucleus (PVN), which is also associated with a reduction in TH expression in the locus coeruleus (LC) and other regions in the brainstem. Consistent with this, Arc NPY signaling decreased sympathetically innervated BAT thermogenesis, involving the downregulation of uncoupling protein 1 (UCP1) expression in BAT. Taken together, these data reveal a powerful Arc-NPY-regulated neuronal circuit that controls BAT thermogenesis and sympathetic output via TH neurons.

Attainment of low-density lipoprotein cholesterol target in the French general population according to levels of cardiovascular risk: Insights from the MONA LISA study

Controlling low-density lipoprotein (LDL)-cholesterol concentration is of tremendous importance to reduce cardiovascular risk. To investigate the attainment of LDL-cholesterol targets recommended in French and European guidelines on cardiovascular prevention, according to levels of cardiovascular risk. Participants aged 35 to 74 years (n=4609) were randomly selected from the general population of three French regions. A standardized data collection was performed to assess cardiovascular risk as described in the French and European guidelines. Overall, 17.5% of participants were considered to be at high risk and 25.4% at high or very high risk, according to the French and European guidelines, respectively. Only 1.2% of participants with no cardiovascular risk factors according to the French guidelines had an LDL-cholesterol concentration above the recommended target, whereas 82.5% of high-risk subjects did not attain their goal (70.8% among high-risk subjects receiving lipid-lowering therapy). Among untreated people, the median reduction in LDL-cholesterol needed to reach target ranged from 6.6% (lowest-risk groups) to 36.0% (highest-risk subjects). When risk was classified according to the European guidelines, the majority of participants did not reach the recommended LDL-cholesterol targets, irrespective of their level of risk or lipid-lowering therapy. In a majority of primary prevention candidates with multiple risk factors and in most high-risk subjects, LDL-cholesterol targets recommended by French guidelines are not being achieved, either because of insufficient treatment or because subjects are not recognized as being at risk. More stringent targets proposed by the European guidelines are not being achieved in most cases.

Impact of REV-ERB alpha gene polymorphisms on obesity phenotypes in adult and adolescent samples

REV-ERBα has been shown to regulate adipogenesis and lipid metabolism as well as to link the circadian timing system to whole body metabolic homeostasis. We thus tested whether polymorphisms in REV-ERBα could be associated with metabolic phenotypes in human population samples. We analyzed the associations between 5 REV-ERBα polymorphisms and anthropometric (body weight, body mass index (BMI), waist and hip circumferences), biochemical (plasma lipid, glucose and insulin levels) and clinical (systolic and diastolic blood pressure) variables in three population-based studies (MONICA Lille n=1155 adults, MONA LISA Lille n=1170 adults and HELENA n=1155 adolescents). We assessed in vitro, the potential influence of one REV-ERBα polymorphism in transient transfection assays using two different cell lines. We observed significant and consistent associations between the T minor allele of the REV-ERBα rs2071427 polymorphism (located in intron 1) and higher BMI (mean allele effect=+0.33 kg m(-2)) in the MONICA Lille (P=0.02), MONA LISA (P=0.02) and HELENA (P=0.03) studies. The odds ratios for obesity associated with this allele were 1.67 (1.00-2.79) (P=0.05) in MONICA Lille, 1.29 (1.01-1.65) (P=0.04) in MONA LISA Lille and the odds ratio for overweight was 1.48 (1.08-2.03) (P=0.01) in HELENA. In transfection experiments in human hepatocyte-derived cell lines, the REV-ERBα intron 1 directed the transcription of a luciferase reporter gene independently of the rs2071427 polymorphism. Our results suggest that the REV-ERBα rs2071427 polymorphism modulates body fat mass in both adult and young people.

Estimation et caractérisation de l’insuffisance rénale chronique en France

Chronic kidney disease (CKD) is a major public health issue. In France, few studies have evaluated CKD prevalence. The objective of the MONA LISA study was to estimate and to characterize CKD in three representative cross-sectional surveys in subjects aged 35–74.9years. CKD was defined as subjects having MDRD glomerular filtration rate lower than 60mL/min/1.73m2. Prevalence of CKD in MONA LISA was standardized according to the French population. A multiple logistic regression analysis was performed in order to find independent factors associated to CKD. The French estimate of CKD prevalence was 8.2% (95% confidence interval: 7.4–8.9%), that is 2,454,548 (95% confidence interval: 2,215,080–2,664,082) subjects aged 35–74.9years. Factors significantly and independently associated to CKD were older age, hypertension and dyslipidemias. In conclusion, the MONA LISA study evaluated for the first time in France CKD prevalence in subjects aged 35–74.9years. This prevalence probably underestimates the real CKD size due to selection bias present in every representative cross-sectional survey.

High blood pressure prevalence and control in a middle-aged French population and their associated factors: the MONA LISA study

This work aims to assess high blood pressure (BP) prevalence and control and their associated factors in a population-based study conducted in three French areas: the Urban Community of Lille and the districts of Bas-Rhin and Haute-Garonne, between 2005 and 2007. Participants were randomly recruited from electoral rolls after stratification on sex, 10-year age group (35-74 years) and town size. BP was measured by trained medical staff following standardized procedures. High BP was defined as BP at least 140/90 mmHg and/or taking antihypertensive drugs or following a specific diet. BP below 140/90 mmHg among treated individuals was considered adequately controlled (<130/80 mmHg among diabetics). Four thousand eight hundred and twenty-five participants were recruited (mean age 55.5 ± 11.3 years). The prevalence of high BP was greater in men (47%) than in women (35%). Antihypertensive treatment concerned 80% of the hypertensive individuals with most often a combination therapy. Control rates concerned only 38% of women and 22% of men and decreased with age. Metabolic risk factors and aging were independently associated with high BP prevalence as were low educational level and alcohol consumption. Diabetes and high cardiovascular risk were strong independent predictors of uncontrolled BP. The use of multiple drug treatment did not predict a better control. Hypertension is frequent in France, particularly in the age group 55-74 years. Control rates remain low, particularly in high-risk, older and diabetic individuals. Intensified efforts are required to improve lifestyle, awareness of the condition, and use of appropriate and well tolerated combination therapy.

ONE ‘MONA LISA’ MYSTERY SOLVED

RETURN TO ISSUEPREVNewsNEXTONE ‘MONA LISA’ MYSTERY SOLVEDScientists show how da Vinci achieved amazing shadowing with many strokes of PIGMENTED GLAZESARAH EVERTSCite this: Chem. Eng. News 2010, 88, 30, 42Publication Date (Print):July 26, 2010Publication History Published online27 March 2011Published inissue 26 July 2010https://doi.org/10.1021/cen-v088n030.p042Copyright © 2010 AMERICAN CHEMICAL SOCIETYArticle Views27Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (666 KB) SUBJECTS:Anatomy,Particulate matter,Thickness,X-rays Get e-Alerts

285 Prevalence and trends of the metabolic syndrome in French adults: the MONA LISA Study

To assess ten-year change in the prevalence of the metabolic syndrome among French subjects using the National Cholesterol Education Program (NCEPATP III) criteria with the American Diabetes Association's updated definition of elevated fasting glucose (≥ 1g/l). Two definitions were assessed, one taking into account a treatment for hypertension and for elevated triglycerides or reduced high-density lipoprotein (HDL) cholesterol (Met2) and the other not (Met). Two cross-sectional representative surveys of the general population were carried out in 1996 and 2006 in three French areas: the Urban Community of Lille in the North, the districts of Bas-Rhin in the East and of Haute-Garonne in the South. Inhabitants aged 35-64 years were randomly recruited from electoral rolls after stratification on gender, 10 year-age group and town size. Standardized sociodemographic, medical and anthropometric data were collected and a fasted blood sample was analysed centrally. Prevalences in the age group 35-64 years were adjusted for the French population of year 2000. A total of 3405 subjects in 1996 and 3554 subjects in 2006 were included in the analyses. In both years the metabolic syndrome was more common among men than among women and increased with age. The age-adjusted prevalences [95% confidence interval] of Met were 26.3% [23.9-28.7] and 18.1% [16.1-20.1] in 1996 and 23.1% [20.9-25.3] and 15.1% [13.3-16.9] in 2006, in men and women respectively. The equivalent results for Met2 were 30.5%, 21.5%, 24.8% and 16.4%. The age-adjusted prevalence of Met (Met2) decreased significantly by 12.1% (18.7%) in men and 16.6% (23.7%) in women. Of the five Met criteria, decreasing trends were observed in the prevalence of high blood pressure, elevated fasting glucose, low HDL cholesterol. By contrast, prevalence of abdominal obesity appeared unchanged whereas prevalence of hypertriglyceridemia increased significantly. In France, the prevalence of the metabolic syndrome tended to decline in the last decade in both genders, particularly in women.

Without Animals Life is Not Worth Living

POOKIE: A TALE Let’s imagine spending a moment or two in the Middle Ages. What are the images that come to mind? Turreted castles, ladies in rose-coloured gowns and pointy hats, peasants gathering sheaves of wheat, monks in black cassocks.........and pigs! Flick through the pages of any Book of Hours or look at any medieval tapestry and there they are, wandering in alleyways or grubbing for acorns in oak-leafy woods, always in tilted profile, like the animals in bestiaries, and always with that mona lisa smile and those knowing human eyes. The jolly pig, rotund and self-satisfied.

A new tectonic model for the Laurentia−Avalonia−Baltica sutures in the North Sea: A case study along MONA LISA profile 3

We present a new model for the lithospheric structure of the transitions between Laurentia, Avalonia and Baltica in the North Sea, northwestern Europe based on 2¾D potential field modelling of MONA LISA profile 3 across the Central Graben, with constraints from seismic P-wave velocity models and the crustal normal incidence reflection section along the profile. The model shows evidence for the presence of upper-and lower Palaeozoic sedimentary rocks as well as differences in crustal structure between the palaeo-continents Laurentia, Avalonia and Baltica. Our new model, together with previous results from transformations of the gravity and magnetic fields, demonstrates correlation between crustal magnetic domains along the profile and the terrane affinity of the crust. This integrated interpretation indicates that a 150 km wide zone, characterized by low-grade metamorphosis and oblique thrusting of Avalonia crust over Baltica lower crust, is characteristic for the central North Sea area. The magnetic susceptibility and the density across the Coffee Soil Fault range from almost zero and 2715 kg/m 3 in Avalonia crust to 0.05 SI and 2775 kg/m 3 in Baltica crust. The model of MONA LISA profile 3 indicates that the transition between Avalonia and Baltica is located beneath the Central Graben with a ramp–flat–ramp geometry. Our results indicate that the initial rifting of the Central Graben and the Viking Graben was controlled by the location of the Caledonian collisional suture, located at the Coffee Soil Fault, and that the deep crustal part of Baltica extends further to the west than hitherto believed.

Seismic tomographic interpretation of Paleozoic sedimentary sequences in the southeastern North Sea

Seismic wide-angle data were recorded to more than 300-km offset from powerful airgun sources during the MONA LISA experiments in 1993 and 1995 to determine the seismic-velocity structure of the crust and uppermost mantle along three lines in the southeastern North Sea with a total length of 850 km. We use the first arrivals observed out to an offset of 90 km to obtain high-resolution models of the velocity structure of the sedimentary layers and the upper part of the crystalline crust. Seismic tomographic traveltime inversion reveals 2–8-km-thick Paleozoic sedimentary sequences with P-wave velocities of 4.5–5.2 km/s. These sedimentary rocks are situated below a Mesozoic-Cenozoic sequence with variable thickness: ∼2–3 km on the basement highs, ∼2–4 km in the Horn Graben and the North German Basin, and ∼6–7 km in the Central Graben. The thicknesses of the Paleozoic sedimentary sequences are ∼3–5 km in the Central Graben, more than 4 km in the Horn Graben, up to ∼4 km on the basement highs, and up to 8 km in the North German Basin. The Paleozoic strata are clearly separated from the shallower and younger sequences with velocities of ∼1.8–3.8 km/s and the deeper crystalline crust with velocities of more than 5.8–6.0 km/s in the tomographic P-wave velocity model. Resolution tests show that the existence of the Paleozoic sediments is well constrained by the data. Hence, our wide-angle seismic models document the presence of Paleozoic sediments throughout the southeastern North Sea, both in the graben structures and in deep basins on the basement highs.

Upper-mantle reflectors: modelling of seismic wavefield characteristics and tectonic implications

SUMMARY Deep seismic experiments on continental lithosphere generally reveal marked reflectivity from structures in the crust and a significant decrease in reflectivity from the upper mantle. However, reflected and refracted energy from mantle lithosphere are observed in both near-normal incidence and wide-angle data. The origin of the reflective structures is a matter of debate. Hypotheses include remnant subduction zones, shear zones, fluids and seismic anisotropy. Through analytical and numerical modelling studies, including full wavefield modelling, we investigate seismic characteristic signatures generated from a variety of geologically plausible models. We have found that both upper-mantle shear zones of reduced velocity and density and remnant subduction slabs containing high-density eclogites may contain sufficient seismic impedance contrasts to normal mantle peridotites to generate near-normal incidence reflectivity. Wide-angle energy originates from subduction slabs containing either high- or lowvelocity eclogites, whereas intermediate-velocity eclogites are unlikely to produce significant wide-angle phases. In general, energy of seismic phases originating from upper-mantle zones of anomalous seismic velocities and densities is significantly increased if homogeneous zones are replaced by zones of inhomogeneous petrophysical properties resulting from constructive interference. Maximum wavefield anomalies are generated from sub Moho dipping slabs of incomplete transformation of low-velocity/low-density crustal material to high-velocity/highdensity eclogites. Localized shear zones generated in mantle peridotite generally do not produce significant wide-angle energy. Only if highly inhomogeneous structures containing material of marked (ca 10 per cent) velocity and density reduction are present, may shear zones be observed in wide-angle data. Analyses of two specific deep-seismic data sets (MONA LISA data) from the North Sea and (BABEL data) from the Baltic Sea, show good agreement between observations and modelling results for dipping remnant subduction slabs containing small-scale inhomogeneities associated with incomplete transformation. Our modelling results improve our possibilities of distinguishing between two often contrasting tectonic interpretations for dipping upper-mantle seismic reflectors, the remnant subduction and shear zone models.

The southern margin of the East European Craton: new results from seismic sounding and potential fields between the North Sea and Poland

The extension of eastern Avalonia from Britain through the NE German Basin into Poland is, in some sense, a virtual structure. It is covered almost everywhere by late Paleozoic and younger sediments. Evidence for this terrane is only gathered from geophysical data and age information derived from magmatic rocks. During the last two decades, much geophysical and geological information has been gathered since the European Geotraverse (EGT), which was followed by the BABEL, LT-7, MONA LISA, DEKORP-Basin'96, and POLONAISE'97 deep seismic experiments. Based on seismic lines, a remarkable feature has been observed between the North Sea and Poland: north of the Elbe Line (EL), the lower crust is characterised by high velocities (6.8–7.0 km/s), a feature which seems to be characteristic for at least a major part of eastern Avalonia (far eastern Avalonia). In addition, the seismic lines indicate that a wedge of the East European Craton (EEC) (or Baltica) continues to the south below the southern Permian Basin (SPB)—a structure which resembles a passive continental margin. The observed pattern may either indicate an extension of the Baltic crust much farther south than earlier expected or oceanic crust of the Tornquist Sea trapped during the Caledonian collision. In either case, the data require a reinterpretation of the docking mechanism of eastern Avalonia, and the Elbe–Odra Line (EOL), as well as the Elbe Fault system, together with the Intra-Sudedic Faults, appear to be related to major changes in the deeper crustal structures separating the East European crust from the Paleozoic agglomeration of Middle European terranes.