bluuebunny/crossref_metadata_2025 huggingface dataset:
Expanded uncertainty quantification in inverse problems: Hierarchical Bayes and empirical Bayes
Authors: Malinverno Alberto , Briggs Victoria A.
Published: July 2004

A common way to account for uncertainty in inverse problems is to apply Bayes' rule and obtain a posterior distribution of the quantities of interest given a set of measurements. A conventional Bayesian treatment, however, requires assuming specific values for parameters of the prior distribution and of the distribution of the measurement errors (e.g., the standard deviation of the errors). In practice, these parameters are often poorly known a priori, and choosing a particular value is often problematic. Moreover, the posterior uncertainty is computed assuming that these parameters are fixed; if they are not well known a priori, the posterior uncertainties have dubious value.

This paper describes extensions to the conventional Bayesian treatment that assign uncertainty to the parameters defining the prior distribution and the distribution of the measurement errors. These extensions are known in the statistical literature as “empirical Bayes” and “hierarchical Bayes.” We demonstrate the practical application of these approaches to a simple linear inverse problem: using seismic traveltimes measured by a receiver in a well to infer compressional wave slowness in a 1D earth model. These procedures do not require choosing fixed values for poorly known parameters and, at most, need a realistic range (e.g., a minimum and maximum value for the standard deviation of the measurement errors). Inversion is thus made easier for general users, who are not required to set parameters they know little about.
True‐amplitude weight functions in 3D limited‐aperture migration revisited
Authors: Sun Jianguo
Published: July 2004

The true‐amplitude weight function in 3D limited‐aperture migration is obtained by extending its formula at an actual reflection point to any arbitrary subsurface point. This implies that the recorded seismic signal is a delta impulse. When the weight function is used in depth migration, it results in an amplitude distortion depending on the vertical distance from the target reflector. This distortion exists even if the correct velocity model is used. If the image point lies at a depth shallower than the half‐offset, the distortion cannot be ignored, even for a spatial wavelet having a short length. Using paraxial ray theory, I find a formula for the true‐amplitude weight function causing no amplitude distortion, under the condition that the earth's surface is smoothly curved. However, the formula is reflector dependent. As a result, amplitude distortion, in parallel with pulse distortion, is an intrinsic effect in depth migration, and true‐amplitude migration without amplitude distortion is possible only when the position of the target reflector is known. If this is the case, true‐amplitude migration without amplitude distortion can be realized by filtering the output of a simple unweighted diffraction stack with the weight function presented here. Also, using Taylor expansions with respect to the vertical, I derive an alternative formula for the true‐amplitude weight function that causes no amplitude distortion. Starting from this formula, I show that the previously published reflector‐independent true‐amplitude weight function is a zero‐order approximation to the one given here.
The quality of the surface‐consistency assumption in short‐wavelength static correction
Authors: Perez Gabriel , Larner Ken
Published: July 2004

Founded on the assumption of surface consistency, reflection‐based residual‐statics correct for the time distortions in seismic data arising from rapid near‐surface variations. The assumption is founded on a vertical‐path, ray‐theoretical model of wave propagation in the near surface. Since ray theory does not hold for models with rapid spatial variation, we resort to finite‐difference modeling to study the influence of wave‐theoretical aspects on the character of time distortions and the validity of the surface‐consistency assumption. For near‐surface models that are admittedly simple and idealized, we find that the character of time distortions is highly influenced by a wavefront‐healing phenomenon whose strength depends on the ratio of the size of the frequency‐dependent Fresnel zone to the wavelength of lateral variation in the model. As experienced in practice, the quality of the surface‐consistency assumption degrades with increasing ratio of spreadlength to reflector depth. The validity of the assumption is best for longer‐wavelength anomalies in a weathering layer that is relatively thin. Wavefront healing, however, limits significantly the time‐distortion problem where the weathering layer is relatively thick. Interestingly, wavefront healing also helps to reduce the size of the time‐distortion problem when the velocity in the surface layer is large relative to that in the layers beneath, such as in areas of permafrost.
Alternative methods of proxy-based climate field reconstruction: application to summer drought over the conterminous United States back to AD 1700 from tree-ring data
Authors: Zhang Zhihua , Mann Michael E. , Cook Edward R.
Published: July 2004

We describe an alternative method of climate field reconstruction and test it against an existing set of dendroclimatic reconstructions of summer drought patterns over the conterminous US back to AD 1700. The new reconstructions are based on a set of 483 drought-sensitive tree-ring chronologies available across the continental US. In contrast with the‘point-by-point’ (PPR) local regression technique used previously, the tree-ring data were calibrated against the instrumental record of summer drought (June-August Palmer Drought Severity Index (PDSI)) based on application of the‘Regularized Expectation Maximization’ (‘RegEM’) algorithm to relate large-scale patterns of variation in proxy and instrumental data over a common (twentieth century) interval. A screening procedure was first used to select an optimal subset of candidate tree-ring drought predictors, and the predictors (tree-ring data) and predictand (instrumental PDSI) were prewhitened prior to calibration, with serial correlation added back into the reconstruction at the end of the procedure. The PDSl field was separated into eight relatively homogenous regions of summer drought through a cluster analysis, and three distinct calibration schemes were investigated: (i)‘global’ (i.e., entire conterminous US domain) proxy data calibrated against‘global’ PDSI; (ii) regional proxy data calibrated against regional PDSI; and (iii) global proxy data calibrated against regional PDSI. The greatest cross-validated skill was evident for case (iii), suggesting the existence of useful non-local information in the tree-ring predictor set. Cross-validation results based on withheld late nineteenth/early twentieth-century instrumental data, as well as a regionally limited extension of cross-validation results back to the mid-nineteenth century based on long available instrumental series, indicate a modest improvement in reconstructive skill over the PPR approach. At the continental scale, the 1930s‘Dust Bowl’ remains the most severe drought event since 1700 within the context of the estimated uncertainties, but more severe episodes may have occurred at regional scales in past centuries.
Stable isotopic record of hydrological changes in subtropical Laguna Mar Chiquita (Argentina) over the last 230 years
Authors: Piovano Eduardo L. , Ariztegui Daniel , Bernasconi Stefano M. , McKenzie Judith A.
Published: July 2004

Laguna Mar Chiquita, a highly variable closed saline lake located in the Pampean plains of cetral Argentina, is presently the largest saline lake in South America ("-6000km2). The availability of hitorical, instrumental lake-level and salinity data for the past 100 years allows for the calibration of the isotopic archive recorded in the lake sediments. Prolonged intervals with either negative or positive hydrlogical balances have severely modified lakewater levels, salinity and primary productivity, and have also controlled the isotopic composition of both the authigenic carbonate (&8Ooarb and f133Ccarb) and sedimetary organic matter (6"C0,,). Extensive evaporation during lowstand stages results in an enrichment of 180 and 13C in the lake waters, and is recorded in the sediments as the most positive &8O8arb and 613C carb compositions (0.0%o and-1.9Yoo, respectively). Conversely, more negative 6f'8Ocarb and 813Ccarb values (-1.8%o and-3.8Yoo, respectively) are the result of increasing freshwater input into the lake system. The fi3Com values are related to the isotopic composition of the dissolved inorganic carbon pool and the cabonate equilibrium of the lake water. Relatively low 613COm values correspond with high lake levels, low salinity, low alkalinity and high lake productivity. High salinity during lowstands diminishes the amount of primary production and the 613Com value is correspondingly high. The calibrated isotopic model was extrapolated to reconstruct precipitation-evaporation variability from the end of the‘Little Ice Age’ (c. AD 1770) to the present. Low water levels predominated until the last quarter of the twentieth century, when a positive hydrological balance without equivalent in the previous history of Laguna Mar Chiquita became dominant.
Annual textural banding in Holocene estuarine silts, Severn Estuary Levels (SW Britain): patterns, cause and implications
Authors: Allen J. R.L.
Published: July 2004

A high-resolution textural study has been made of laminated and banded estuarine silts exposed intertidally at representative localities and horizons in the Holocene deposits of the Severn Estuary Levels. The laminae, on a submillimetre to millimetre scale, are sharp-based, graded couplets formed of a lower silty part overlain by a finer-textured clayey element. The centimetre-to decimetre-scale banding is formed of laminae in alternating, gradually intergrading sets of relatively coarse and relative fine-grained examples. At outcrop in the field, the banding is recognizable because the coarse sets prove to be recessive to varying degrees under the influence of weathering and current action. Independent evidence at two localities points toward an annual origin for the banding; at a third it arose during part of what appears to have been a relatively short period. Quantified physical arguments suggest that the textural banding is a response of suspended fine sediment to marked seasonal changes in sea temperature and windiness. The banded silts occur in four distinct stratigraphical contexts and record high deposition rates (order 0.01-0.1 m/yr). Because physical factors determine their textures, the silts potentially afford insights in all contexts into aspects of changing Holocene climatic conditions. In one context, the thickness of the bands points to high (order 0.01-0.1 m/yr) but comparatively short-lived (order lOs-lOOs yrs) rates of relative water-level rise. In the others, however, the banding has no implications for sea-level behaviour, and simply records gross environmental disequilibrium, for example, the recovery of mudflats/marshes after an erosional episode. Similarly, because on account of their rapid accumulation the banded silts prserve animal and human tracks and trackways especially well, they provide an archive of animal and human behaviour in the area during the Holocene.
An association of benthic foraminifera and gypsum in Holocene sediments of estuarine Chesapeake Bay, USA
Authors: Cann John , Cronin Thomas
Published: July 2004

Two cores of Holocene sediments recovered from the Cape Charles Channel of Chesapeake Bay yielded radiocarbon ages of about 6.8 to 5.8 ka for the lower intervals. Fossil foraminifera preserved in these lower sediments are dominated by species of Elphidium, which make up about 90% of the assemblage throughout, and probably signify deposition in hypersaline waters. Buccella frigida and Ammonia beccarii are the only other species commonly present. Hypersalinity of bottom waters seems to have been maitained by water-density stratification in a basin-like section of the channel. In core PTXT-4-P-1 transition to modem Chesapeake conditions, in which numbers of Ammonia beccarii exceed those of Elphidium, comenced about 400 years ago. In core PTXT-3-P-2 hypersalinity is further signified by the presence of abundant euhedral crystals of gypsum in association with the fossil Elphidium. This occurrence of gypsum is not attributed to palaeoclimatic aridity, but rather to inflow of groundwater from adjacent gypsiferous Miocene strata. The study shows that in palaeoclimatic investigations the significance of the presence of gysum should be evaluated with caution - it does not necessarily signify an evaporative regime.
Holocene vegetation changes in the northwestern Mediterranean: new palaeoecological data from charcoal analysis and quantitative eco-anatomy
Authors: Heinz C. , Figueira I. , Terral j J.-F. , Claustre F.
Published: July 2004

The stratigraphic sequence of Montou (Eastern Pyrenees, France) covers a period from the middle Neolithic to the late Bronze Age. Environmental changes are noticed since the middle Neolithic, when the decline of the deciduous oak favours, in the long term, the evergreen oaks. The Chalcolithic period witnesses the arrival and spread of mesomediterranean and thermomediterranean plant formations. This evolution may result from increasing anthropogenic pressure as shown by the maintenance of a garrigue vegetation during the Bronze Age. The association charcoal analysis/quantitative anatomy offers new perspectives concerning vegetation changes. Both approaches record the existence of mesomediterranean bioclimatic conditions during the middle Neolithic; thermomediterranean affinities are recorded first, by charcoal analysis, during the early Bronze Age, and by eco-anatomy during the transition from the middle to the late Bronze Age. Quantitative anatomy also pinpoints (1) the existence of two humid phases, (2) an increase in mean annual temperature, and (3) the exploitation and management of the olive tree since the early Bronze Age.
A high-resolution, 800-year glaciomarine record from Russkaya Gavan', a Novaya Zemlya fjord, eastern Barents Sea
Authors: Polyak Leonid , Murdmaa Ivar , Ivanova Elena
Published: July 2004

Sediment core ASV-987 from Russkaya Gavan', a tidewater fjord on the northwestern coast of Novaya Zemlya, provides the first multicentury record of sedimentary and hydrographic glaciomarine environments in Russian Arctic with a century-scale resolution. Age is constrained by seven 14C ages securing an especially robust control for the period between c. AD 1370 and 1600. Based on sediment struture, grain size, depositional rates, foraminiferal assemblages and stable isotopes in foraminiferal tests, we reconstruct the changes in fjord sedimentation and circulation in relation to the history of a tidewater glacier connected to the main Novaya Zemlya ice complex. We conclude that a noticeable glacier advance occurred c. AD 1400, contemporaneous with a change in North Atlantic atmospheric circulation inferred from GISP-2 ion-contents data. A major glacier retreat from Russkaya Gavan' occurred by c. AD 1600, succeeded by low sedimentary inputs. Intervals with depleted stable isotopic values, including the core top, may indicate intensified glacier melting. Stronger melting in the 1900s is consistent with an increase in sedimentation rates.
Kwäday Dän Ts'ìnchì, the first ancient body of a man from a North American glacier: reconstructing his last days by intestinal and biomolecular analyses
Authors: Dickson James H. , Richards Michael P. , Hebda Richard J. , Mudie Petra J. , Beattie Owen , Ramsay Susan , Turner Nancy J. , Leighton Bruce J. , Webster John M. , Hobischak Niki R. , Anderson Gail S. , Troffe Peter M. , Wigen Rebecca J.
Published: July 2004

We report on scientific analyses of the only well-preserved ancient human body ever recovered from a North American glacier. The body was found high in the mountains of northwest British Columbia at about 80 km from the nearest point of the strongly indented coast of southern Alaska. The geographical location suggests that the young man, aged about 20 years, could have lived either on the mild coast or in the continental interior. Preliminary environmental scanning electron microscopy (ESEM) and light microscope studies of the contents of the digestive tract reveal pollen of an intertidal salt-marsh plant and pieces of a marine crustacean. Remains of coastal zone plants (a fruit of a flowering plant and a needle of a coniferous tree) had adhered to the deceased's robe. Stable isotope analyses of bone and muscle show that more than 90% of the dietary protein was from marine sources. We conclude that this individual had strong coastal connections during his life and had been on the coast shortly before he died about 550 to 600 years ago.
Antibodies to mannose binding lectin in patients with systemic lupus erythematosus
Authors: Mok M Y , Jack D L , Lau C S , Fong D YT , Turner M W , Isenberg D A , Lydyard P M
Published: July 2004

Deficiency of mannose binding lectin (MBL), a C-type lectin with structural similarities to C1q, has been shown to predispose to the development of systemic lupus erythematosus (SLE). Some patients have low serum MBL levels which cannot be explained by either structural gene mutations or promoter polymorphisms. The objective of this study was to detect the presence of autoantibodies against MBL and to evaluate their relationship to serum MBL levels. Anti-MBL antibodies of IgM and IgG classes from consecutive SLE patients (n 1/4 135) and healthy subjects (n 1/4 50) were measured by an in-house ELISA. Using the 90th percentile of controls as a cutoff, more SLE patients [23.7% (32/135)] were found to have IgG anti-MBL antibodies than normal controls [10.0% (5/50)] (P 1/4 0.04). The same trend was observed when ethnicity was taken into account by analysing Caucasians alone (n 1/4 90). IgM anti-MBL antibodies were only found in two SLE patients (2/22, 9.1%) who had no concomitant IgG anti-MBL antibodies. Serum levels of IgG anti-MBL antibodies were found to correlate with serum MBL levels (r 1/4 0.55, P 1/4 0.049). However, the levels of anti-MBL antibodies did not correlate with overall disease activity. Thus the production of anti-MBL antibodies is likely to be a specific antigen-driven process. Its role in lupus pathogenesis remains to be elucidated.
Relational Ethics and Genetic Counseling
Authors: Evans Marilyn , Bergum Vangie , Bamforth Stephen , MacPhail Sandra
Published: July 2004

Genetic counseling is viewed as a therapeutic interrelationship between genetic counselors and their clients. In a previous relational ethics research project, various themes were identified as key components of relational ethics practice grounded in everyday health situations. In this article the relational ethics approach is further explored in the context of genetic counseling to enhance our understanding of how the counselor-client relationship is contextually developed and maintained. Qualitative interviews were conducted with six adult clients undergoing genetic counseling for predictive testing. Engagement, dialogue and presence were revealed as relevant to genetic counselor-client relationships. A relational ethics approach in genetic counseling challenges the concept of nondirectiveness and may enhance the outcome of counseling for both counselor and client.
Service innovations
Authors: Hodgson Richard , Smith Susan E. , Strange Richard C. , Fryer Anthony A.
Published: July 2004

Aims and Method

There are few descriptions in the literature of pharmacogenetic applications in psychiatry. We describe the relevance of pharmacogenetics to clinical psychiatry using a case-note review of the first 55 patients to have their cytochrome P450 (CYP2D6) status assessed in a general psychiatry clinic.

Results

The distribution of genotypes for CYP2D6 was the same as in the general population. A smaller number of reported side-effects (P=0.01) and higher medication dosages (P=0.001) were significantly associated with the extensive metabolism genotype.

Clinical Implications

This preliminary study suggests that CYP2D6 status may have an influence on medication dosage and adverse drug events reported by patients. Recommendations for further development are suggested.
Long-Term Cardiac Follow-Up in Relapse-Free Patients After Six Courses of Fluorouracil, Epirubicin, and Cyclophosphamide, With Either 50 or 100 mg of Epirubicin, As Adjuvant Therapy for Node-Positive Breast Cancer: French Adjuvant Study Group
Authors: Bonneterre Jacques , Roché Henri , Kerbrat Pierre , Fumoleau Pierre , Goudier Marie-Josèphe , Fargeot Pierre , Montcuquet Philippe , Clavère Pierre , Barats Jean-Claude , Monnier Alain , Veyret Corinne , Datchary Jean , Van Praagh Isabelle , Chapelle-Marcillac Isabelle
Published: July 2004

Purpose

To evaluate long-term cardiac function in patients without disease who had received six cycles of fluorouracil 500 mg/m2, epirubicin 50 mg/m2, and cyclophosphamide 500 mg/m2 (FEC 50) or the same regimen with epirubicin 100 mg/m2 (FEC 100) as adjuvant chemotherapy for node-positive breast cancer in the French Adjuvant Study Group–05 trial.

Patients and Methods

One hundred fifty patients (FEC 50, n = 65; FEC 100, n = 85) who were without disease and who gave their informed consent were enrolled for long-term cardiac assessment. The assessment included cardiac events occurring after the end of chemotherapy, vital signs, concomitant disease, ECG, isotopic left ventricular ejection fraction (LVEF), and echographic parameters. Abnormal files were blindly reviewed by cardiologists and oncologists.

Results

The median follow-up time was 102 months. After FEC 100, LVEF was less than 50% in five patients (radioisotopic method), and two patients experienced congestive heart failure (CHF) that was possibly related to treatment. Asymptomatic left ventricular dysfunction (LVD) was experienced in 18 patients after FEC 100 and in one patient after FEC 50. In these patients, treatment causality was probable in eight patients. Two additional years after this assessment, all 18 patients were still asymptomatic.

Conclusion

After more than 8 years of follow-up, the cardiac toxicity observed after adjuvant treatment with FEC 100 comprised two cases of well-controlled CHF and 18 cases of asymptomatic LVD. In the majority of women with primary breast cancer, the benefits of treatment with FEC 100 in terms of disease-free and overall survival outweigh the risks, and cardiac risk factors should be carefully evaluated in patient selection.
Phase II Study of Neoadjuvant Carboplatin and Paclitaxel Followed by Radiotherapy and Concurrent Cisplatin in Patients With Locoregionally Advanced Nasopharyngeal Carcinoma: Therapeutic Monitoring With Plasma Epstein-Barr Virus DNA
Authors: Chan Anthony T.C. , Ma Brigette B.Y. , Lo Y.M. Dennis , Leung S.F. , Kwan W.H. , Hui Edwin P. , Mok Tony S.K. , Kam Michael , Chan Lisa S. , Chiu Samuel K.W. , Yu K.H. , Cheung K.Y. , Lai Karen , Lai Maria , Mo Frankie , Yeo Winnie , King Ann , Johnson Philip J. , Teo Peter M.L. , Zee Benny
Published: July 2004

Purpose

To assess the efficacy of neoadjuvant paclitaxel and carboplatin (TC) followed by concurrent cisplatin and radiotherapy (RT) in patients with locoregionally advanced nasopharyngeal carcinoma (NPC) and to monitor treatment response with plasma Epstein-Barr virus (EBV) DNA.

Patients and Methods

Thirty-one patients with International Union Against Cancer stages III and IV undifferentiated NPC had two cycles of paclitaxel (70 mg/m2 on days 1, 8, and 15) and carboplatin (area under the curve 6 mg/mL/min on day 1) on a 3-weekly cycle, followed by 6 to 8 weeks of cisplatin (40 mg/m2 weekly) and RT at 66 Gy in 2-Gy fractions. Plasma EBV DNA was measured serially using the real-time quantitative polymerase chain reaction method.

Results

All patients completed planned treatment. Response to neoadjuvant TC was as follows: 12 patients (39%) achieved partial response (PR) and 18 achieved (58%) complete response (CR) in regional nodes; five patients (16%) achieved PR and no patients achieved CR in nasopharynx. At 6 weeks after RT, one patient (3%) achieved PR and 30 patients (97%) achieved CR in regional nodes, and 31 patients (100%) achieved CR in nasopharynx; 29 patients (93%) had EBV DNA level of less than 500 copies/mL. Neoadjuvant TC was well tolerated, and the most common acute toxicity of cisplatin plus RT was grade 3 mucositis (55%). At median follow-up of 33.7 months (range, 7 to 39.3 months), six distant and three locoregional failures occurred. Plasma EBV DNA level increased significantly in eight of nine patients who experienced treatment failure but did not increase in those who did not. The 2-year overall and progression-free survival rates were 91.8% and 78.5%, respectively.

Conclusion

This strategy was feasible and resulted in excellent local tumor control. Serial plasma EBV DNA provides a noninvasive method of monitoring response in NPC.
Ongoing Monoclonal B-Cell Proliferation Is Not Common in Gastric B-Cell Lymphoma After Combined Radiochemotherapy
Authors: Alpen Birgit , Kuse Rolf , Parwaresch Radzak , Müller-Hermelink Hans Konrad , Stolte Manfred , Neubauer Andreas
Published: July 2004

Purpose

Gastric marginal-zone B-cell lymphoma (MZBCL) of the mucosa-associated lymphoid tissue (MALT) is associated with chronic Helicobacter pylori gastritis. Stable complete remission (CR) can be induced by H pylori eradication. Whether this is paralleled by cure of the lymphoma remains unclear. Persisting monoclonal bands for immunoglobulin heavy chain variable region (VH) representing the lymphoma clone have been described in up to 50% of patients in CR. This retrospective study investigated whether this phenomenon also occurs after radiochemotherapy.

Patients and Methods

Biopsy samples of 20 patients receiving chemotherapy with cyclophosphamide, doxorubicin, vincristine, and prednisone and irradiation were analyzed before and after therapy. Study patients had Ann Arbor stage I/II primary gastric cancer, including four cases of MZBCL of MALT type, 12 cases of diffuse large-cell lymphomas (DLCL), and four cases of mixed MALT type/DLCL. Polymerase chain reaction (PCR) for VH rearrangement was performed. Monoclonal PCR products were cloned and sequenced.

Results

Fourteen of 20 patients had a monoclonal or oligoclonal band distribution at diagnosis converted into polyclonal pattern after radiochemotherapy. Of the remaining six patients, two were lost to follow-up. One patient did not respond and died of progressive disease. PCR in this patient showed persistent B-cell clonality. In three patients, the initial PCR showed a polyclonal pattern and thus could not be evaluated during follow-up.

Conclusion

In contrast with H pylori eradication alone, radiochemotherapy results in clearing of monoclonal cells during follow-up. This may result in better elimination of residual lymphoma cells. Further study is needed to determine whether this translates into lower risk of relapse.
Cytotrophoblasts Up-Regulate Soluble Fms-Like Tyrosine Kinase-1 Expression under Reduced Oxygen: An Implication for the Placental Vascular Development and the Pathophysiology of Preeclampsia
Authors: Nagamatsu Takeshi , Fujii Tomoyuki , Kusumi Maki , Zou Li , Yamashita Takahiro , Osuga Yutaka , Momoeda Mikio , Kozuma Shirou , Taketani Yuji
Published: July 2004

Sufficient cytotrophoblast (CT) invasion into the uterine wall and subsequent remodeling of maternal uterine vasculature is critical to establish uteroplacental circulation. The production of vascular endothelial growth factor (VEGF) family molecules is confirmed in placental cells including CTs, but it is not elucidated how the VEGF system in CTs is controlled by oxygen tension and how it is involved in the development of placental circulation. To address this, we explored the effect of oxygen tension on the expression of VEGF, placenta growth factor (PlGF), and their antagonist, soluble fms-like tyrosine kinase-1 (sFlt-1) using ELISA and real-time PCR in a primary CT cell culture. For comparison, the same was conducted in parallel using other cells comprising placenta, such as human umbilical vein endothelial cells (HUVECs) and villous fibroblasts (VFs). Reduced oxygen resulted in a pronounced increase in sFlt-1 mRNA amount and sFlt-1 release into the culture media in CTs, whereas this was not the case with HUVECs and VFs. Free (not bound to sFlt-1) VEGF was not detected in CT culture media regardless of oxygen concentration, even though VEGF expression was stimulated by reduced oxygen in CTs, which was similar to the stimulation in HUVECs and VFs. Free PlGF was also diminished in CT culture media by reduced oxygen. These results implicate that CTs possess a unique property to enhance sFlt-1 production under reduced oxygen, which could consequently antagonize angiogenic activity of VEGF and PlGF. The presented findings might provide a framework with which to understand the mechanism of uterine vascular remodeling and its perturbations as exemplified in preeclampsia.
Ghrelin Inhibits the Proliferative Activity of Immature Leydig Cells in Vivo and Regulates Stem Cell Factor Messenger Ribonucleic Acid Expression in Rat Testis
Authors: Barreiro M. L. , Gaytan F. , Castellano J. M. , Suominen J. S. , Roa J. , Gaytan M. , Aguilar E. , Dieguez C. , Toppari J. , Tena-Sempere M.
Published: July 2004

Ghrelin has emerged as putative regulator of an array of endocrine and nonendocrine functions, including cell proliferation. Recently, we provided evidence for the expression of ghrelin in mature, but not in undifferentiated, Leydig cells of rat and human testis. Yet testicular actions of ghrelin, other than modulation of testosterone secretion, remain unexplored. In the present study we evaluated the effects of ghrelin on proliferation of Leydig cell precursors during puberty and after selective elimination of mature Leydig cells by treatment with ethylene dimethane sulfonate. In these settings, intratesticular injection of ghrelin significantly decreased the proliferative activity of differentiating immature Leydig cells, estimated by 5-bromodeoxyuridine labeling. This response was selective and associated, in ethylene dimethane sulfonate-treated animals, with a decrease in the mRNA levels of stem cell factor (SCF), i.e. a key signal in spermatogenesis and a putative regulator of Leydig cell development. Thus, the effects of ghrelin on SCF gene expression were evaluated. In adult rats, ghrelin induced a significant decrease in SCF mRNA levels in vivo. Such an inhibitory action was also detected in vitro using cultures of staged seminiferous tubules. The inhibitory effect of ghrelin in vivo was dependent on proper FSH input, because it was detected in hypophysectomized rats only after FSH replacement. Overall, it is proposed that acquisition of ghrelin expression by Leydig cell precursors during differentiation may operate as a self-regulatory signal for the inhibition of the proliferative activity of this cell type through direct or indirect (i.e. SCF-mediated) mechanisms. In addition, we present novel evidence for the ability of ghrelin to modulate the expression of the SCF gene, which may have implications for the mode of action of this molecule in the testis as well as in other physiological systems.
Leptin Enhances Oocyte Nuclear and Cytoplasmic Maturation via the Mitogen-Activated Protein Kinase Pathway
Authors: Craig Jesse , Zhu Hai , Dyce Paul W. , Petrik Jim , Li Julang
Published: July 2004

Recent studies have suggested that leptin has a central role in female reproduction, including ovarian function. The leptin receptor (Ob-R) has six isoforms and can signal through either the MAPK or the Janus-activated kinase/signal transducer and activator of transcription signal-transduction pathway, depending on the isoform. Expression of Ob-R has been reported in human and mouse oocytes; however, the physiological role of leptin during follicular development and oocyte maturation is largely unknown. In the current study, expression of Ob-R during oocyte growth and maturation was investigated in porcine oocytes from small, medium, and large follicles and in oocytes in the germinal vesicle (GV), GV breakdown, and metaphase II (MII) stages at both the mRNA and protein levels. The proportion of oocytes expressing Ob-R was maximal in oocytes from medium follicles and at the GV breakdown stage (P < 0.05), whereas the proportion of oocytes expressing the long isoform, Ob-Rb, was found to be consistently low throughout growth and maturation. When included in oocyte maturation medium, leptin significantly increased the proportion of oocytes reaching MII (P < 0.01), elevated cyclin B1 protein content in MII-stage oocytes (P < 0.05), and enhanced embryo developmental potential (P < 0.05), suggesting that leptin plays a role in both nuclear and cytoplasmic maturation. During oocyte maturation, leptin increased phosphorylated MAPK content by 2.8-fold (P < 0.05), and leptin-stimulated oocyte maturation was blocked when leptin-induced MAPK phosphorylation was suppressed by a specific MAPK activation inhibitor, U0126 (P < 0.01), demonstrating that leptin enhances nuclear maturation via activation of the MAPK pathway.
Real-time lineage analysis reveals oriented cell divisions associated with morphogenesis at the shoot apex ofArabidopsis thaliana
Authors: Reddy G. Venugopala , Heisler Marcus G. , Ehrhardt David W. , Meyerowitz Elliot M.
Published: July 2004

Precise knowledge of spatial and temporal patterns of cell division,including number and orientation of divisions, and knowledge of cell expansion, is central to understanding morphogenesis. Our current knowledge of cell division patterns during plant and animal morphogenesis is largely deduced from analysis of clonal shapes and sizes. But such an analysis can reveal only the number, not the orientation or exact rate, of cell divisions. In this study, we have analyzed growth in real time by monitoring individual cell divisions in the shoot apical meristems (SAMs) of Arabidopsis thaliana. The live imaging technique has led to the development of a spatial and temporal map of cell division patterns. We have integrated cell behavior over time to visualize growth. Our analysis reveals temporal variation in mitotic activity and the cell division is coordinated across clonally distinct layers of cells. Temporal variation in mitotic activity is not correlated to the estimated plastochron length and diurnal rhythms. Cell division rates vary across the SAM surface. Cells in the peripheral zone (PZ)divide at a faster rate than in the central zone (CZ). Cell division rates in the CZ are relatively heterogeneous when compared with PZ cells. We have analyzed the cell behavior associated with flower primordium development starting from a stage at which the future flower comprises four cells in the L1 epidermal layer. Primordium development is a sequential process linked to distinct cellular behavior. Oriented cell divisions, in primordial progenitors and in cells located proximal to them, are associated with initial primordial outgrowth. The oriented cell divisions are followed by a rapid burst of cell expansion and cell division, which transforms a flower primordium into a three-dimensional flower bud. Distinct lack of cell expansion is seen in a narrow band of cells, which forms the boundary region between developing flower bud and the SAM. We discuss these results in the context of SAM morphogenesis.
Cell interactions that affect axonogenesis in the leechTheromyzon rude
Authors: Shain Daniel H. , Stuart Duncan K. , Huang Françoise Z. , Weisblat David A.
Published: July 2004

The leech nervous system comprises a relatively simple network of longitudinal (connective) and transverse (segmental) nerves. We have followed the normal pattern of axon development in the glossiphoniid leech Theromyzon rude by immunostaining embryonic preparations with antibody to acetylated α-tubulin. The dependence of the normal pattern of axon growth on cells in the mesodermal (M) and ectodermal (N, O, P and Q)lineages was examined by selectively ablating subsets of these lineages in developing embryos. We found that ablating mesoderm severely disrupted overall axonogenesis, while various ectodermal ablations induced a range of more specific phenotypes. In particular, formation of the posterior segmental nerve(PP) was abnormal in embryos deficient in primary neuroectoderm (N lineage). More specific ablations demonstrated that a subset of N-derived cells were required for establishing the PP nerve root. Previous studies have shown that the PP nerve root is normally pioneered by an O lineage-derived neuron(PD). Our results suggest that the role of the N lineage-derived cells is to induce the migration of neuron PD to its normal position in the posterior compartment of the hemiganglion.
Interactions between ID and OLIG proteins mediate the inhibitory effects of BMP4 on oligodendroglial differentiation
Authors: Samanta Jayshree , Kessler John A.
Published: July 2004

Bone morphogenetic protein (BMP) signaling inhibits the generation of oligodendroglia and enhances generation of astrocytes by neural progenitor cells both in vitro and in vivo. This study examined the mechanisms underlying the effects of BMP signaling on glial lineage commitment. Treatment of cultured neural progenitor cells with BMP4 induced expression of all four members of the inhibitor of differentiation (ID) family of helix-loop-helix transcriptional inhibitors and blocked oligodendrocyte (OL) lineage commitment. Overexpression of Id4 or Id2 but not Id1 or Id3 in cultured progenitor cells reproduced both the inhibitory effects of BMP4 treatment on OL lineage commitment and the stimulatory effects on astrogliogenesis. Conversely, decreasing the levels of Id4 mRNA by RNA interference enhanced OL differentiation and inhibited the effects of BMP4 on glial lineage commitment. This suggests that induction of Id4 expression mediates effects of BMP signaling. Bacterial two-hybrid and co-immunoprecipitation studies demonstrated that ID4,and to a lesser extent ID2, complexed with the basic-helix-loop-helix transcription (bHLH) factors OLIG1 and OLIG2, which are required for the generation of OLs. By contrast, ID1 and ID3 did not complex with the OLIG proteins. In addition, the OLIG and ID proteins both interacted with the E2A proteins E12 and E47. Further, exposure of cultured progenitor cells to BMP4 changed the intracellular localization of OLIG1 and OLIG2 from a predominantly nuclear to a predominantly cytoplasmic localization. These observations suggest that the induction of ID4 and ID2, and their sequestration of both OLIG proteins and E2A proteins mediate the inhibitory effects of BMP signaling on OL lineage commitment and contribute to the generation of astrocytes.
Interaction with eIF5B is essential for Vasa function during development
Authors: Johnstone Oona , Lasko Paul
Published: July 2004

The DEAD-box RNA helicase Vasa (Vas) is required for germ cell development and function, as well as for embryonic somatic posterior patterning. Vas interacts with the general translation initiation factor eIF5B (cIF2, also known as dIF2), and thus may regulate translation of specific mRNAs. In order to investigate which functions of Vas are related to translational control, we have analyzed the effects of site-directed vas mutations that reduce or eliminate interaction with eIF5B. Reduction in Vas-eIF5B interaction during oogenesis leads to female sterility, with phenotypes similar to a vasnull mutation. Accumulation of Gurken (Grk) protein is greatly reduced when Vas-eIF5B interaction is reduced, suggesting that this interaction is crucial for translational regulation of grk. In addition, we show that reduction in Vas-eIF5B interaction virtually abolishes germ cell formation in embryos, while producing a less severe effect on somatic posterior patterning. We conclude that interaction with the general translation factor eIF5B is essential for Vas function during development.
Release of a membrane-bound death domain by γ-secretase processing of the p75NTR homolog NRADD
Authors: Gowrishankar Kavitha , Zeidler Michael G. , Vincenz Claudius
Published: July 2004

Neurotrophin receptor alike death domain protein (NRADD) is a death-receptor-like protein with a unique ectodomain and an intracellular domain homologous to p75NTR. Expression of NRADD results in apoptosis, but only in certain cell types. This paper characterizes the expression and proteolytic processing of the mature 55 kDa glycoprotein. N-terminally truncated NRADD is processed by a γ-secretase activity that requires presenilins and has the same susceptibility to γ-secretase inhibitors as the secretion of amyloid β (Aβ). The ectodomain of endogenous NRADD is shed by activation of metalloproteinases. Inhibitor studies provide evidence that NRADD is cleaved in two steps typical of regulated intramembrane proteolysis (RIP). Inhibition of γ-secretase abrogates both the production of the soluble intracellular domain of NRADD and the appearance of NRADD in subnuclear structures. Thus, solubilized death domains with close homology to p75NTR might have a nuclear function. Furthermore, presenilin deficiency leads to abnormally glycosylated NRADD and overexpression of presenilin 2 inhibits NRADD maturation, which is dependent on the putative active site residue D366 but not on γ-secretase activity. Our results demonstrate that NRADD is an additional γ-secretase substrate and suggest that drugs against Alzheimer's disease will need to target γ-secretase in a substrate-specific manner.
Cdk5 regulates activation and localization of Src during corneal epithelial wound closure
Authors: Gao Chun Y. , Stepp Mary Ann , Fariss Robert , Zelenka Peggy
Published: July 2004

Recent studies have shown that Cdk5, a member of the cyclin-dependent-kinase family, regulates adhesion and migration in a mouse corneal epithelial cell line. Here, we extend these findings to corneal wound healing in vivo and examine the mechanism linking Cdk5 to cytoskeletal reorganization and migration. Cdk5 was overexpressed in the corneal epithelium of transgenic mice under control of the ALDH3 promoter. Elevated Cdk5 expression retarded corneal debridement wound closure in these animals and suppressed remodeling of the actin cytoskeleton. Conversely, the Cdk5 inhibitor, olomoucine, accelerated debridement wound healing in organ cultured eyes of normal mice, caused migrating cells to separate from the epithelial cell sheet, and increased the level of activated Src(pY416) along the wound edge. To explore the relationship between Cdk5 and Src in greater detail, we examined scratch-wounded cultures of corneal epithelial cells. Src was activated in cells along the wound edge and blocking this activation with the Src kinase inhibitor, PP1, inhibited wound closure by 85%. Inhibiting Cdk5 activity with olomoucine or a dominant negative construct, Cdk5T33, increased the concentration of Src(pY416), shifted its subcellular localization to the cell periphery and enhanced wound closure. Cdk5(pY15), an activated form of Cdk5, also appeared along the wound edge. Inhibiting Src activity with PP1 blocked the appearance of Cdk5(pY15), suggesting that Cdk5 phosphorylation is Src dependent. Cdk5 and Src co-immunoprecipitated from scratch-wounded cultures, demonstrating that both kinases are part of an intracellular protein complex. These findings indicate that Cdk5 exerts its effects on cell migration during corneal epithelial wound healing by regulating the activation and localization of Src.
Ribosome-translocon complex mediates calcium leakage from endoplasmic reticulum stores
Authors: Van Coppenolle Fabien , Vanden Abeele Fabien , Slomianny Christian , Flourakis Matthieu , Hesketh John , Dewailly Etienne , Prevarskaya Natalia
Published: July 2004

Under resting conditions, the endoplasmic reticulum (ER) intraluminal free calcium concentration ([Ca2+]ER) reflects a balance between active uptake by Ca2+-ATPases and passive efflux via `leak channels'. Despite their physiological importance and ubiquitous leak pathway mechanism, very little is known about the molecular nature of these channels. As it has been suggested that the open translocon pore complex of the ER is permeable to ions and neutral molecules, we hypothesized that the ribosome-bound translocon would be permeable to calcium after treatment with puromycin, a translation inhibitor that specifically releases polypeptide chains. At this time, the translocon channel is left open. We measured the fluctuations in cytoplasmic and luminal calcium concentrations using fluorescent dyes (fura-2 and magfura-2, respectively). The calcium release induced by thapsigargin (a Ca2+-ATPase inhibitor) was lower after puromycin treatment. Puromycin also reduced the [Ca2+]ER level when perfused into the medium, but was ineffective after anisomycin pre-treatment (an inhibitor of the peptidyl transferase). Puromycin had a similar effect in the presence of heparin and ryanodine. This puromycin-evoked [Ca2+]ER decrease was specific to the translocon. We conclude that the translocon complex is a major calcium leak channel. This work reveals a new role for the translocon which is involved in the control of the [Ca2+]ER and could therefore supervise many physiological processes, including gene expression and apoptosis.
Small hepatocytes in culture develop polarized transporter expression and differentiation
Authors: Pfändler Marguerite-Anne Sidler , Höchli Mathias , Inderbitzin Daniel , Meier Peter J. , Stieger Bruno
Published: July 2004

Rat small hepatocytes have been shown to proliferate in culture and to form organoids with differentiated hepatocytes in vitro. To evaluate the degree of polarized transporter differentiation of rat small hepatocytes during 9 weeks of culturing, we studied the time-dependent expression and subcellular localization of the major bile salt and organic anion transport systems of hepatocytes [i.e. the basolateral sodium-taurocholate co-transporting protein (Ntcp), organic-anion-transporting polypeptide 1b2 (Oatp1b2), the canalicular bile-salt export pump (Bsep) and multidrug-resistance-associated protein 2 (Mrp2)]. Small hepatocytes proliferated and differentiated in culture and formed sharply demarcated colonies as assessed by morphology, α-fetoprotein, albumin and Mrp1 expression. Polarized surface transporter expression was evident after 5 weeks of culturing for Ntcp, Oatp1b2 and Mrp2, and after 7 weeks for Bsep. After 9 weeks in culture, the vast majority of matured hepatocytes expressed Ntcp/Oatp1b2 at the basolateral and Bsep/Mrp2 at the canalicular plasma-membrane domains. This polarized transporter expression was accompanied by canalicular secretion of fluorescein-diacetate and cholylglycyl-fluorescein. Furthermore, an anastomizing three-dimensional network of bile canaliculi developed within piling-up colonies. These data demonstrate that cultured rat small hepatocytes acquire a fully differentiated transporter expression phenotype during their development into hepatic `organoid-like' clusters of mature hepatocytes. Thereby, the time-dependent sequence of transporter expression mirrored the ontogenesis of transporter expression in developing rat liver, supporting the concept that small hepatocytes correspond to the hepatocyte lineage derived from embryonic hepatoblasts and/or from a different pool of `committed hepatocyte progenitor cells'.