bluuebunny/crossref_metadata_2025 huggingface dataset:
Holocene vegetation change in the northern Peten and its implications for Maya Prehistory
Authors: Wahl David , Byrne Roger , Schreiner Thomas , Hansen Richard
Published: February 2006

An ∼8400 cal yr record of vegetation change from the northern Peten, Guatemala, provides new insights into the environmental history of the archaeological area known as the Mirador Basin. Pollen, loss on ignition, and magnetic susceptibility analyses indicate warm and humid conditions in the early to mid-Holocene. Evidence for a decrease in forest cover around 4600 cal yr B.P. coincides with the first appearance ofZea mayspollen, suggesting that human activity was responsible. The period between 3450 cal yr B.P. and 1000 cal yr B.P. is characterized by a further decline in forest pollen types, includes an abrupt increase in weedy taxa, and exhibits the highest magnetic susceptibility values since the early Holocene, all of which suggest further agricultural disturbance in the watershed. A brief drop in disturbance indicators around 1800 cal yr B.P. may represent the Preclassic abandonment of the area. Changing pollen frequencies around 1000 cal yr B.P. indicate a cessation of human disturbance, which represents the Late Classic collapse of the southern Maya lowlands.
Should Quaternary sea-level changes be used to correct glacier ELAS, vegetation belt altitudes and sea level temperatures for inferring climate changes?
Authors: Osmaston Henry A.
Published: February 2006

Changes in the altitudes of glacier snowlines (ELAs) and the altitudes of montane vegetation belts (VBAs) measure Quaternary climatic change. An accepted ‘correction’ to such changes by deducting the amount of contemporary sea level fall is wrong, since the air displaced by the ice sheets approximately fills the space left by the falling sea level and so there is no overall downward movement of the troposphere. This also causes a reduced cooling at the lowered sea level relative to that at the former inter-glacial sea level, about 1°C at the Las Glacial Maximum, which reduces the discrepancies previously noted by others between terrestrial and marine estimates of sea-level cooling. The change in temperature is indicated by the product of the ELA or VBA lowering and the environmental lapse rate (ELR). Prior estimates of ΔELA (−900 ± 135 m) and ELR (−6° ± 0.1°C km−1) would indicate a cooling of −5.4°C at interglacial sea level and −4.4°C at glacial sea level, although glacial-period ELRs are not known reliably. Established ELA corrections for local epeirogenic uplift or subsidence are appropriate.
Work-related stressors, depression and quality of life in Danish managers
Authors: Bech P. , Andersen M.B. , Bech-Andersen G. , Tønnesen S. , Agnarsdottir E. , Borg V.
Published: February 2006

Background

By use of valid questionnaires to investigate work-related stress and distress in Danish managers.

Methods

The survey focused on members of the Danish Association of Managers and Executives who no longer were active (formermanagers' group). Acting managers (active managers' group) served as controls. Questionnaires measuring stressors at work and general life events were used. For the measurement of distress, scales for depression and quality of life were used.

Results

The Mokken analysis proved the validity of the questionnaires, i.e. their summed-up total scores were sufficient statistics. No differences were found between former (n= 1256) and active managers (n= 942) as to life events. Approximately 20% of former managers were at risk of depression and 12% had developed major depression. Among the specific work-related stressors were role overload, lack of team spirit and lack of social support. The percentage of active managers at risk of or suffering from major depression did not differ significantly from the Danish general population. Approximately 37% of the former managers had a decreased well-being. Alcohol use was found to be significantly associated with depression.

Conclusions

The study identified specific work-related stressors in managers, 12% of whom developed a major depression.
What a psychiatrist needs to know about diabetes
Authors: Charbonnel B.
Published: February 2006

Diabetes mellitus is a complex metabolic disorder, caused by defects in insulin action and/or insulin production and is defined as afasting hyperglycaemia of >126 mg/dl, with normoglycaemia being ≥70 and ≤ 110 mg/dl. There are two main types of diabetes. Type 1 diabetes (around 10% of cases) is an autoimmune disease, usually of early onset, in which pancreatic islet beta cells that secrete insulin are destroyed. Type 2 diabetes (around 85% of cases) is characterised principally by insulin resistance and impaired insulin secretion. Heredity and obesity are major risk factors for Type 2 diabetes. Diabetes is associated with potentially life-threatening microvascular and macrovascular complications caused by elevated serum glucose levels. Treatment of diabetes aims at restoring glycaemic control. In Type 1 diabetes, this can be achieved by injecting insulin. Oral hypoglycaemic medications that stimulate insulin secretion and/or modify glucose metabolism can be used as a first-line treatment in Type 2 diabetes mellitus. However, insulin is usually necessary in later phases of the disease. Lifestyle changes, such as diet and exercise, are also important. Glycaemic control can be measured by fasting blood glucose levels and also by glycosylated haemoglobin levels. The latter measure gives an indication of glycaemic control over a period of three months, and a reduction in glycosylated haemoglobin is the most appropriate treatment goal in the management of diabetes.
Data on diabetes from the French cohort study in schizophrenia
Authors: Philippe A. , Vaiva G. , Casadebaig F.
Published: February 2006

To establish the impact of antipsychotic medication on the incidence of diabetes, we have analysed data from the prospective French Cohort study of mortality in schizophrenia. This generated a large database of 3470 patients with schizophrenia initially enrolled in 1993 for which data collection on comorbidity has been collected systematically every three years since. The primary objective of the study was to evaluate the mortality rate in the study cohort. From this database, the prevalence and incidence of diabetes can be studied. In 1993, nine patients in 10 were prescribed conventional antipsychotics and the remainder amisulpride and clozapine. Since the introduction of risperidone and olanzapine, atypical antipsychotics are now used in one-third of patients. Multiple antipsychotic medications are used in many patients, with the exception of those receiving clozapine. At inclusion, 2.2% of patients in the study cohort had a diagnosis of diabetes. Morbidity rates were higher in females than in males (3.4% and 1.6%, respectively) and it was only in females that the standard morbidity ratio with respect to the general population was significantly elevated (2.2; 95% confidence intervals: 1.6 and 2.9). The prevalence of diabetes in the study cohort rose over the course of the study. Multivariate regression analysis was performed in order to identify potential determinants of diabetes. For pre-existing diabetes, four factors were identified: age at first hospitalisation, age, obesity and duration of schizophrenia. The same factors with the exception of length of illness were identified for the incident cases. There was no evidence for an interaction between the class and type of antipsychotic medication and risk of treatment emergent diabetes. However, the use of multiple antipsychotic treatments makes the individualisation of specific risks associated with any other antipsychotic drug impossible.
Context-dependence of long-term responses of terrestrial gastropod populations to large-scale disturbance
Authors: Bloch Christopher P. , Willig Michael R.
Published: February 2006

Large-scale natural disturbances, such as hurricanes, can have profound effects on animal populations. Nonetheless, generalizations about the effects of disturbance are elusive, and few studies consider long-term responses of a single population or community to multiple large-scale disturbance events. In the last 20 y, two major hurricanes (Hugo and Georges) have struck the island of Puerto Rico. Long-term population trends of 17 species of terrestrial gastropod were evaluated to determine whether gastropods respond to hurricane disturbances in a consistent fashion. Some species increased, some decreased, and some exhibited no simple trend in density or spatial variability following disturbance. In addition, some species responded differently to the two hurricanes with respect to population density, absolute spatial variability, or relative spatial variability. Population responses probably hinge on trade-offs between sensitivity to microclimatic changes and resource availability resulting from the relocation of biomass from the canopy to the forest floor. The historical context within which a hurricane occurs may be as important, or more so, than the intensity of the storm, per se.
Nutrient use efficiency at ecosystem and species level in savanna areas of Central Brazil and impacts of fire
Authors: Nardoto Gabriela Bielefeld , da Cunha Bustamante Mercedes Maria , Pinto Alexandre Siqueira , Klink Carlos Augusto
Published: February 2006

Nutrient resorption efficiency of woody plants, litterfall and nutrient fluxes were investigated in a burned and an unburned cerrado plot between October 1997 and September 1999. A large experiment (Fire Project, Brasília, Brazil) on the effects of prescribed burnings was initiated in 1992. Cerrado plots were delimited and subjected to different fire regimes. Seasonal trend of litterfall was similar in both plots but the production in the burned plot was 42.2 g m−2 y−1 before the fourth prescribed fire (September 1998) and decreased by 22% 1 y after burning while in the unburned plot it was around 230 gm−2 y−1. Although nutrient concentrations in leaf litter were higher in the burned plot, the nutrient fluxes were 60–80% lower than in the unburned plot. Nutrient use efficiency (ecosystem level) was 4373 for P and 137 for N. Measured resorption efficiency for 10 cerrado species ranged from 14.5 to 37.2% for N and from 40 to 70.4% for P and in general, there were no differences between plots. N is in short supply, partly because of fire history, but the results, both at ecosystem and species levels (mean N/P in fresh leaves was 18), indicated a stronger limitation by P than by N.
Dispersal of Canarium euphyllum (Burseraceae), a large-seeded tree species, in a moist evergreen forest in Thailand
Authors: Kitamura Shumpei , Suzuki Shunsuke , Yumoto Takakazu , Poonswad Pilai , Chuailua Phitaya , Plongmai Kamol , Maruhashi Tamaki , Noma Naohiko , Suckasam Chumphon
Published: February 2006

We investigated the dispersal of a large-seeded tree species, Canarium euphyllum (Burseraceae), in the moist evergreen forests of the Khao Yai National Park in Thailand. By combining direct observations of fruit consumption in tree canopies (543 h) and the camera-trapping observations of fallen fruit consumption on the forest floor (175 camera-days), we identified the frugivore assemblage that foraged on the fruits of C. euphyllum and assessed their role in seed dispersal and seed predation. In the canopy, our results showed that seeds were dispersed by a limited set of frugivores, one pigeon and four hornbill species, and predated by two species of squirrel. On the forest floor, seven mammal species consumed fallen fruits. A combination of high rates of fruit removal and short visiting times of mountain imperial pigeons (Ducula badia) and hornbills (Buceros bicornis, Aceros undulatus, Anorrhinus austeni and Anthracoceros albirostris) led us to conclude that these large frugivorous birds provide effective seed dispersal for this tree species, in terms of quantity. These frugivorous species often have low tolerance to negative human impacts and loss of these dispersers would have severe deleterious consequences for the successful regeneration of C. euphyllum.
Post-fire resprouting of Colophospermum mopane saplings in a southern African savanna
Authors: Mlambo Donald , Mapaure Isaac
Published: February 2006

Fire is a common feature of tropical savannas and it has an important role in the ecology and evolution of the flora. Many woody species in tropical savannas are well adapted to fire and have a vigorous resprouting ability that enables them to survive recurring fire (Frost & Robertson 1987, Hoffmann & Solbrig 2003, Meyer et al. 2005). Studies on the interaction between fire and woody plants in Mediterranean-climate regions have considerably increased our understanding of the subject but relationships between plant attributes (stem diameter and height) and post-fire resprouting ability of southern African savanna woody species are poorly understood. Resprouting is a widespread mechanism by which many plants regenerate after partial or total defoliation (Bellingham & Sparrow 2000, Bond & Midgley 2001).
Constraints on Indian plate motion since 20 Ma from dense Russian magnetic data: Implications for Indian plate dynamics
Authors: Merkouriev S. , DeMets C.
Published: February 2006

We use more than 230,000 km of Russian marine magnetic and bathymetric data from the Carlsberg and northern Central Indian ridges, comprising one of the most geographically extensive, dense shipboard surveys anywhere in the ocean basins, to describe in detail seafloor spreading since 20 Ma along the trailing edge of the Indian plate. India‐Somalia plate rotations for ∼1 Myr intervals over the past 20 Myr are derived from inversions of more than 6600 crossings of 20 magnetic reversals and ∼1400 crossings of fracture zones that offset these two ridges. Statistical analysis of the numerous data indicates that outward displacement of reversal boundaries due to finite seafloor emplacement widths and correlated noise for anomaly crossings from individual spreading segments constitute two distinct sources of systematic bias in the locations of magnetic anomaly crossings, contrary to the often‐made assumption that random, Gaussian‐distributed noise dominates the error budget. Seafloor spreading rates slowed gradually by 30% from 20 Ma to 10 ± 1 Ma about a relatively stationary pole of rotation. From 11 Ma to 9 Ma the rotation axis migrated several angular degrees toward the plate boundary, modestly increasing the spreading gradient along the plate boundary. India‐Somalia kinematic data for times since ∼9 Ma are consistent with remarkably steady motion, with no evidence for a change in either the rotation pole or rate of angular opening within the few percent precision of our data. The timing and nature of changes in India‐Somalia motion since 20 Ma closely resemble those for the Capricorn‐Somalia plate pair, indicating that India and Capricorn plate motions are strongly coupled. We speculate that the slowdown in seafloor spreading at the trailing edges of the Indo‐Capricorn composite plate from 20 Ma to 10 ± 1 Ma resulted from the increasing amount of work that was needed to build topography in the Himalayan collisional zone. The transition to stable India‐Somalia and Capricorn‐Somalia seafloor spreading at ∼10–9 Ma corresponds well with the onset at 8 Ma of folding and faulting across an equatorial plate boundary separating the Indian and Capricorn plates, suggesting that the latter may have played a fundamental role in restoring equilibrium between the torques that were driving and resisting the northward motions of the Indian and Capricorn plates.
Variability of the Lower Circumpolar Deep Water in Drake Passage 1926–2004
Authors: Williams Adam , Bacon Sheldon , Cunningham Stuart
Published: February 2006

Lower Circumpolar Deep Water (LCDW) is an important component of the global overturning circulation as it upwells south of the Antarctic Circumpolar Current (ACC) renewing the ocean interior. The LCDW also aids the transport of water properties between the major ocean basins. The property variability of the LCDW Salinity Maximum layer was examined using 37 meridional sections across Drake Passage between 1926–2004. Within the limits of experimental error and high frequency variability, the core properties of this layer have remained constant between 1926–2004. A comparison of modern sections and the 1932 Discovery II cruise indicates that this observation may be true for LCDW throughout the Southern Ocean. The significance of this result in terms of the observations of decadal changes in the Southern Ocean Intermediate and Mode waters is that these changes are most likely due to contemporary atmospheric forcing and not due to variations in the source water properties.
Impact of plant water uptake strategy on soil moisture and evapotranspiration dynamics during drydown
Authors: Teuling Adriaan J. , Uijlenhoet Remko , Hupet François , Troch Peter A.
Published: February 2006

Experiments have shown that plants can compensate for water stress in the upper, more densely rooted, soil layers by increasing the water uptake from deeper layers. By adapting root water uptake to water availability, plants are able to extend the period of unstressed transpiration. This strategy conflicts with the approach in many land surface schemes, where plant water uptake is treated as a static process. Here we derive expressions for the typical drydown trajectories of evapotranspiration and soil moisture for both strategies. We show that the maximum difference in evapotranspiration between the two strategies during drydown can exceed 50%. This in turn leads to a difference in root zone soil moisture of up to 25%. The results stress the importance of incorporating realistic root water uptake concepts in land surface schemes.
Mechanisms of genetic robustness in RNA viruses
Authors: Elena Santiago F , Carrasco Purificación , Daròs José‐Antonio , Sanjuán Rafael
Published: February 2006

Two key features of RNA viruses are their compacted genomes and their high mutation rate. Accordingly, deleterious mutations are common and have an enormous impact on viral fitness. In their multicellular hosts, robustness can be achieved by genomic redundancy, including gene duplication, diploidy, alternative metabolic pathways and biochemical buffering mechanisms. However, here we review evidence suggesting that during RNA virus evolution, alternative robustness mechanisms may have been selected. After briefly describing how genetic robustness can be quantified, we discuss mechanisms of intrinsic robustness arising as consequences of RNA‐genome architecture, replication peculiarities and quasi‐species population dynamics. These intrinsic robustness mechanisms operate efficiently at the population level, despite the mutational sensitivity shown by individual genomes. Finally, we discuss the possibility that viruses might exploit cellular buffering mechanisms for their own benefit, producing a sort of extrinsic robustness.
Microphase separation in multiblock copolymer melts: Nonconventional morphologies and two-length-scale switching
Authors: Smirnova Yuliya G , ten Brinke Gerrit , Erukhimovich Igor Ya.
Published: February 2006

The phase behavior of AfmN(BN∕2AN∕2)B(1−f)mN multiblock copolymer melts is studied within the weak segregation theory. The interplay between ordering on different length scales is shown to cause dramatic changes both in the ordered phase symmetry and periodicity upon small variation of the architectural parameters of the macromolecules. Phase diagrams are presented in the (f,χN) plane (χ is the Flory-Huggins parameter) for various values of the architecture parameters n and m. Near the critical surface, i.e., for (f−0.5)2⪡1, such nonconventional cubic phases as the face-centered cubic (FCC), simple cubic (SC), (double) gyroid, and the so-called BCC2 (single gyroid) are found to be stable. The lamellar morphology is shown to be replaced by BCC2, FCC, or SC (depending on the structural parameters) as the most stable low-temperature phase.
Diffusion and velocity relaxation of a Brownian particle immersed in a viscous compressible fluid confined between two parallel plane walls
Authors: Felderhof B. U.
Published: February 2006

The diffusion tensor and velocity correlation function of a Brownian particle immersed in a viscous compressible fluid confined between two parallel plane walls are calculated in point approximation. The fluid is assumed to satisfy stick boundary conditions at the walls. It is found that the velocity correlation function decays asymptotically with a negative t−2 long-time tail due to coupling to overdamped sound waves. The coefficient of the long-time tail is calculated and shown to be independent of fluid viscosity.
High-efficiency blue light-emitting electrophosphorescent device with conjugated polymers as the host
Authors: Zhang Xiuju , Jiang Changyun , Mo Yueqi , Xu Yunhua , Shi Huahong , Cao Yong
Published: February 2006

Highly efficient blue polymer phosphorescent organic light-emitting diode (PPHOLED)-containing iridium(III) bis (2,4-difluorophenyl-2-pyridine) (2-(4H-1, 2, 4-triazol-3-yl)pyridine) [Ir(PPF)2(PZ)] complex embedded into wide-gap poly (9,9′-alkyl-3, 6-silafluorene) (PSiFC6C6) has been fabricated. Despite the significant quenching of photophosphorescence emission of the iridium complexes by a PSiFC6C6 host polymer, organic light-emitting diodes containing Ir(PPF)2(PZ) doped into the polymer host PSiFC6C6 emit high-efficiency blue light peaked at 462nm. The maximal external quantum and luminance efficiencies were, respectively, 4.8% photons/electrons and 7.2cd∕A at 644cd∕m2 and with Commission Internationale de l’Eclairage coordinates of (0.15,0.26).
Fe implanted ferromagnetic ZnO
Authors: Potzger K. , Zhou Shengqiang , Reuther H. , Mücklich A. , Eichhorn F. , Schell N. , Skorupa W. , Helm M. , Fassbender J. , Herrmannsdörfer T. , Papageorgiou T. P.
Published: February 2006

Room-temperature ferromagnetism has been induced within ZnO single crystals by implant doping with Fe ions. For an implantation temperature of 623 K and an ion fluence of 4×1016cm−2, very tiny Fe particles, formed inside the host matrix, are responsible for the ferromagnetic properties. They were identified using synchrotron x-ray diffraction and Mössbauer spectroscopy. On the other hand, Fe ions implanted at a temperature of 253 K and an ion fluence of 4×1015cm−2 are incorporated into the host matrix and develop a room temperature diluted magnetic semiconductor.
Control of polarized single quantum dot emission in high-quality-factor microcavity pillars
Authors: Daraei A. , Tahraoui A. , Sanvitto D. , Timpson J. A. , Fry P. W. , Hopkinson M. , Guimarães P. S. S. , Vinck H. , Whittaker D. M. , Skolnick M. S. , Fox A. M.
Published: February 2006

Small size microcavity pillars with elliptical cross section and high quality factors Q are reported and are shown to provide nearly 100% linearly polarized single photon sources. It is shown that the polarization of the emission of quantum dots embedded within the pillars can be controlled by using the coupling of the dot emission with the photonic modes. A notable dependence of the Q value is found on the polarization of the mode even though calculations of the mode profiles show that the electric field distribution is very similar.
An RNA interference-based screen identifies MAP4K4/NIK as a negative regulator of PPARγ, adipogenesis, and insulin-responsive hexose transport
Authors: Tang Xiaoqing , Guilherme Adilson , Chakladar Abhijit , Powelka Aimee M. , Konda Silvana , Virbasius Joseph V. , Nicoloro Sarah M. C. , Straubhaar Juerg , Czech Michael P.
Published: February 2006

The insulin-regulated glucose transporter GLUT4 is a key modulator of whole body glucose homeostasis, and its selective loss in adipose tissue or skeletal muscle causes insulin resistance and diabetes. Here we report an RNA interference-based screen of protein kinases expressed in adipocytes and identify four negative regulators of insulin-responsive glucose transport: the protein kinases PCTAIRE-1 (PCTK1), PFTAIRE-1 (PFTK1), IκB kinase α, and MAP4K4/NIK. Integrin-linked protein kinase was identified as a positive regulator of this process. We characterized one of these hits, MAP4K4/NIK, and found that it is unique among mitogen-activated protein (MAP) kinases expressed in cultured adipocytes in attenuating hexose transport. Remarkably, MAP4K4/NIK suppresses expression of the adipogenic transcription factors C/EBPα, C/EBPβ, and PPARγ and of GLUT4 itself in these cells. RNA interference-mediated depletion of MAP4K4/NIK early in differentiation enhances adipogenesis and triglyceride deposition, and even in fully differentiated adipocytes its loss up-regulates GLUT4. Conversely, conditions that inhibit adipogenesis such as TNF-α treatment or depletion of PPARγ markedly up-regulate MAP4K4/NIK expression in cultured adipocytes. Furthermore, TNF-α signaling to down-regulate GLUT4 is impaired in the absence of MAP4K4/NIK, indicating that MAP4K4 expression is required for optimal TNF-α action. These results reveal a MAP4K4/NIK-dependent signaling pathway that potently inhibits PPARγ-responsive gene expression, adipogenesis, and insulin-stimulated glucose transport.
FRET imaging reveals that functional neurokinin-1 receptors are monomeric and reside in membrane microdomains of live cells
Authors: Meyer Bruno H. , Segura Jean-Manuel , Martinez Karen L. , Hovius Ruud , George Nathalie , Johnsson Kai , Vogel Horst
Published: February 2006

The lateral organization of a prototypical G protein-coupled receptor, the neurokinin-1 receptor (NK1R), was investigated in living cells by fluorescence resonance energy transfer (FRET) microscopy, taking advantage of the recently developed acyl carrier protein (ACP) labeling technique. The NK1R was expressed as fusion protein with ACP to which small fluorophores were then covalently bound. Our approach allowed the recording of FRET images of receptors on living cells with unprecedented high signal-to-noise ratios and a subsequent unequivocal quantification of the FRET data owing to (
i
) the free choice of optimal fluorophores, (
ii
) the labeling of NK1Rs exclusively on the cell surface, and (
iii
) the precise control of the donor–acceptor molar ratio. Our single-cell FRET measurements exclude the presence of constitutive or ligand-induced homodimers or oligomers of NK1Rs. The strong dependence of FRET on the receptor concentration further reveals that NK1Rs tend to concentrate in microdomains, which are found to constitute ≈1% of the cell membrane and to be sensitive to cholesterol depletion.
Multiple rare variants in
NPC1L1
associated with reduced sterol absorption and plasma low-density lipoprotein levels
Authors: Cohen Jonathan C. , Pertsemlidis Alexander , Fahmi Saleemah , Esmail Sophie , Vega Gloria L. , Grundy Scott M. , Hobbs Helen H.
Published: February 2006

An approach to understand quantitative traits was recently proposed based on the finding that nonsynonymous (NS) sequence variants in certain genes are preferentially enriched at one extreme of the population distribution. The NS variants, although individually rare, are cumulatively frequent and influence quantitative traits, such as plasma lipoprotein levels. Here, we use the NS variant technique to demonstrate that genetic variation in
NPC1L1
contributes to variability in cholesterol absorption and plasma levels of low-density lipoproteins (LDLs). The ratio of plasma campesterol (a plant sterol) to lathosterol (a cholesterol precursor) was used to estimate relative cholesterol absorption in a population-based study. Nonsynonymous sequence variations in
NPC1L1
were five times more common in low absorbers (
n
= 26 of 256) than in high absorbers (
n
= 5 of 256) (
P
< 0.001). The rare variants identified in low absorbers were found in 6% of 1,832 African-Americans and were associated with lower plasma levels of LDL cholesterol (LDL-C) (96 ± 36 mg/dl vs. 105 ± 36 mg/dl;
P
= 0.005). These data, together with prior findings, reveal a genetic architecture for LDL-C levels that does not conform to current models for quantitative traits and indicate that a significant fraction of genetic variance in LDL-C is due to multiple alleles with modest effects that are present at low frequencies in the population.
Dictyostelium
myosin II mechanochemistry promotes active behavior of the cortex on long time scales
Authors: Girard Kristine D. , Kuo Scot C. , Robinson Douglas N.
Published: February 2006

Cell cortices rearrange dynamically to complete cytokinesis, crawlin response to chemoattractant, build tissues, and make neuronal connections. Highly enriched in the cell cortex, actin, myosin II, and actin crosslinkers facilitate cortical movements. Because cortical behavior is the consequence of nanoscale biochemical events, it is essential to probe the cortex at this level. Here, we use high-resolution laser-based particle tracking to examine how myosin II mechanochemistry and dynacortin-mediated actin crosslinking control cortex dynamics in
Dictyostelium
. Consistent with its low duty ratio, myosin II does not directly drive active bead motility. Instead, myosin II and dynacortin antagonistically regulate other active processes in the living cortex.
The role of the airline transportation network in the prediction and predictability of global epidemics
Authors: Colizza Vittoria , Barrat Alain , Barthélemy Marc , Vespignani Alessandro
Published: February 2006

The systematic study of large-scale networks has unveiled the ubiquitous presence of connectivity patterns characterized by large-scale heterogeneities and unbounded statistical fluctuations. These features affect dramatically the behavior of the diffusion processes occurring on networks, determining the ensuing statistical properties of their evolution pattern and dynamics. In this article, we present a stochastic computational framework for the forecast of global epidemics that considers the complete worldwide air travel infrastructure complemented with census population data. We address two basic issues in global epidemic modeling: (
i
) we study the role of the large scale properties of the airline transportation network in determining the global diffusion pattern of emerging diseases; and (
ii
) we evaluate the reliability of forecasts and outbreak scenarios with respect to the intrinsic stochasticity of disease transmission and traffic flows. To address these issues we define a set of quantitative measures able to characterize the level of heterogeneity and predictability of the epidemic pattern. These measures may be used for the analysis of containment policies and epidemic risk assessment.
siRecords: an extensive database of mammalian siRNAs with efficacy ratings
Authors: Ren Yongliang , Gong Wuming , Xu Qiqi , Zheng Xin , Lin Dong , Wang Yejun , Li Tongbin
Published: January 2006

Summary: Short interfering RNAs (siRNAs) have been gaining popularity as the gene knock-down tool of choice by many researchers because of the clean nature of their workings as well as the technical simplicity and cost efficiency in their applications. We have constructed siRecords, a database of siRNAs experimentally tested by researchers with consistent efficacy ratings. This database will help siRNA researchers develop more reliable siRNA design rules; in the mean time, siRecords will benefit experimental researchers directly by providing them with information about the siRNAs that have been experimentally tested against the genes of their interest. Currently, more than 4100 carefully annotated siRNA sequences obtained from more than 1200 published siRNA studies are hosted in siRecords. This database will continue to expand as more experimentally tested siRNAs are published.

Availability: The siRecords database can be accessed at

Contact:  toli@biocompute.umn.edu
Transition from ectothermy to endothermy: the development of metabolic capacity in a bird (Gallus gallus)
Authors: Seebacher Frank , Schwartz Tonia S , Thompson Michael B
Published: February 2006

The evolution of endothermy is one of the most significant events in vertebrate evolution. Adult mammals and birds are delineated from their early ontogenetic stages, as well as from other vertebrates, by high resting metabolic rates and consequent internal heat production. We used the embryonic development of a bird (Gallus gallus) as a model to investigate the metabolic transition between ectothermy and endothermy. Increases in aerobic capacity occur at two functional levels that are regulated independently from each other: (i) upregulation of gene expression; and (ii) significant increases in the catalytic activity of the main oxidative control enzymes. Anaerobic capacity, measured as lactate dehydrogenase activity, is extremely high during early development, but diminishes at the same time as aerobic capacity increases. Changes in lactate dehydrogenase activity are independent from its gene expression. The regulatory mechanisms that lead to endothermic metabolic capacity are similar to those of ectotherms in their response to environmental change. We suggest that the phylogenetic occurrence of endothermy is restricted by its limited selective advantages rather than by evolutionary innovation.
Decoding the fine-scale structure of a breast cancer genome and transcriptome
Authors: Volik Stanislav , Raphael Benjamin J. , Huang Guiqing , Stratton Michael R. , Bignel Graham , Murnane John , Brebner John H. , Bajsarowicz Krystyna , Paris Pamela L. , Tao Quanzhou , Kowbel David , Lapuk Anna , Shagin Dmitri A. , Shagina Irina A. , Gray Joe W. , Cheng Jan-Fang , de Jong Pieter J. , Pevzner Pavel , Collins Colin
Published: February 2006

A comprehensive understanding of cancer is predicated upon knowledge of the structure of malignant genomes underlying its many variant forms and the molecular mechanisms giving rise to them. It is well established that solid tumor genomes accumulate a large number of genome rearrangements during tumorigenesis. End Sequence Profiling (ESP) maps and clones genome breakpoints associated with all types of genome rearrangements elucidating the structural organization of tumor genomes. Here we extend the ESP methodology in several directions using the breast cancer cell line MCF-7. First, targeted ESP is applied to multiple amplified loci, revealing a complex process of rearrangement and coamplification in these regions reminiscent of breakage/fusion/bridge cycles. Second, genome breakpoints identified by ESP are confirmed using a combination of DNA sequencing and PCR. Third, in vitro functional studies assign biological function to a rearranged tumor BAC clone, demonstrating that it encodes antiapoptotic activity. Finally, ESP is extended to the transcriptome identifying four novel fusion transcripts and providing evidence that expression of fusion genes may be common in tumors. These results demonstrate the distinct advantages of ESP including: (1) the ability to detect all types of rearrangements and copy number changes; (2) straightforward integration of ESP data with the annotated genome sequence; (3) immortalization of the genome; (4) ability to generate tumor-specific reagents for in vitro and in vivo functional studies. Given these properties, ESP could play an important role in a tumor genome project.
NMDA and muscarinic receptors of the nucleus accumbens have differential effects on taste memory formation
Authors: Ramírez-Lugo Leticia , Zavala-Vega Sergio , Bermúdez-Rattoni Federico
Published: February 2006

Animals recognize a taste cue as aversive when it has been associated with
post-ingestive malaise; this associative learning is known as conditioned
taste aversion (CTA). When an animal consumes a new taste and no negative
consequences follow, it becomes recognized as a safe signal, leading to an
increase in its consumption in subsequent presentations (attenuation of
neophobia, AN). It has been shown that the nucleus accumbens (NAcc) has an
important role in taste learning. To elucidate the involvement of
N-methyl-d-aspartate (NMDA) and muscarinic receptors in
the NAcc during safe and aversive taste memory formation, we administrated
bilateral infusions of DL-2-amino-5-phosphonopentanoic acid (APV) or
scopolamine in the NAcc shell or core respectively. Our results showed that
pre-training injections of APV in the NAcc core and shell disrupted aversive
but not safe taste memory formation, whereas pre-training injections of
scopolamine in the NAcc shell, but not core, disrupted both CTA and AN. These
results suggest that muscarinic receptors seem to be necessary for processing
taste stimuli for either safe or aversive taste memory, whereas NMDA receptors
are only involved in the aversive taste memory trace formation.
Dimethylallyl Diphosphate and Geranyl Diphosphate Pools of Plant Species Characterized by Different Isoprenoid Emissions
Authors: Nogués Isabel , Brilli Federico , Loreto Francesco
Published: February 2006

Dimethylallyl diphosphate (DMADP) and geranyl diphosphate (GDP) are the last precursors of isoprene and monoterpenes emitted by leaves, respectively. DMADP and GDP pools were measured in leaves of plants emitting isoprene (Populus alba), monoterpenes (Quercus ilex and Mentha piperita), or nonemitting isoprenoids (Prunus persica). Detectable pools were found in all plant species, but P. persica showed the lowest pool size, which indicates a limitation of the whole pathway leading to isoprenoid biosynthesis in nonemitting species. The pools of DMADP and GDP of nonemitting, isoprene-emitting, and monoterpene-emitting species were partially labeled (generally 40%–60% of total carbon-incorporated 13C) within the same time by which volatile isoprenoids are fully labeled (15 min). This indicates the coexistence of two pools for both precursors, the rapidly labeled pool presumably occurring in chloroplasts and thereby synthesized by the methylerythritol phosphate pathway and the nonlabeled pool presumably located in the cytosol and synthesized by the mevalonic pathway. In M. piperita storing monoterpenes in specialized leaf structures, the GDP pool remained totally unlabeled, indicating either that monoterpenes are totally formed by the mevalonic pathway or that labeling occurs slowly in comparison to the large pool of stored monoterpenes in this plant. The pools of DMADP and GDP increased during the season (from May to July) but decreased when the leaf was darkened or exposed to very high temperature. In the dark, the pool of DMADP of the isoprene-emitting species decreased faster than the pool of GDP. However, after 6 h of darkness, both pools were depleted to about 10% of the pool size in illuminated leaves. This indicates that both the chloroplastic and the cytosolic pools of precursors are depleted in the dark. When comparing measurements over the season and at different temperatures, an inverse correlation was observed between isoprene emission by P. alba and the DMADP pool size and between monoterpene emission by Q. ilex and the GDP pool size. This suggests that the pool size does not limit the emission of isoprenoids. Rather, it indicates that the flux of volatile isoprenoids effectively controls the size of their pools of precursors.
Comparative Analysis of the Heat Stable Proteome of Radicles of Medicago truncatula Seeds during Germination Identifies Late Embryogenesis Abundant Proteins Associated with Desiccation Tolerance
Authors: Boudet Julie , Buitink Julia , Hoekstra Folkert A. , Rogniaux Hélène , Larré Colette , Satour Pascale , Leprince Olivier
Published: February 2006

A proteomic analysis was performed on the heat stable protein fraction of imbibed radicles of Medicago truncatula seeds to investigate whether proteins can be identified that are specifically linked to desiccation tolerance (DT). Radicles were compared before and after emergence (2.8 mm long) in association with the loss of DT, and after reinduction of DT by an osmotic treatment. To separate proteins induced by the osmotic treatment from those linked with DT, the comparison was extended to 5 mm long emerged radicles for which DT could no longer be reinduced, albeit that drought tolerance was increased. The abundance of 15 polypeptides was linked with DT, out of which 11 were identified as late embryogenesis abundant proteins from different groups: MtEm6 (group 1), one isoform of DHN3 (dehydrins), MtPM25 (group 5), and three members of group 3 (MP2, an isoform of PM18, and all the isoforms of SBP65). In silico analysis revealed that their expression is likely seed specific, except for DHN3. Other isoforms of DNH3 and PM18 as well as three isoforms of the dehydrin Budcar5 were associated with drought tolerance. Changes in the abundance of MtEm6 and MtPM25 in imbibed cotyledons during the loss of DT and in developing embryos during the acquisition of DT confirmed the link of these two proteins with DT. Fourier transform infrared spectroscopy revealed that the recombinant MtPM25 and MtEm6 exhibited a certain degree of order in the hydrated state, but that they became more structured by adopting α helices and β sheets during drying. A model is presented in which DT-linked late embryogenesis abundant proteins might exert different protective functions at high and low hydration levels.
AtATM3 Is Involved in Heavy Metal Resistance in Arabidopsis
Authors: Kim Do-Young , Bovet Lucien , Kushnir Sergei , Noh Eun Woon , Martinoia Enrico , Lee Youngsook
Published: February 2006

AtATM3, an ATP-binding cassette transporter of Arabidopsis (Arabidopsis thaliana), is a mitochondrial protein involved in the biogenesis of iron-sulfur clusters and iron homeostasis in plants. Our gene expression analysis showed that AtATM3 is up-regulated in roots of plants treated with cadmium [Cd(II)] or lead (II); hence, we investigated whether this gene is involved in heavy metal tolerance. We found that AtATM3-overexpressing plants were enhanced in resistance to Cd, whereas atatm3 mutant plants were more sensitive to Cd than their wild-type controls. Moreover, atatm3 mutant plants expressing 35S promoter-driven AtATM3 were more resistant to Cd than wild-type plants. Since previous reports often showed that the cytosolic glutathione level is positively correlated with heavy metal resistance, we measured nonprotein thiols (NPSH) in these mutant plants. Surprisingly, we found that atatm3 contained more NPSH than the wild type under normal conditions. AtATM3-overexpressing plants did not differ under normal conditions, but contained less NPSH than wild-type plants when exposed to Cd(II). These results suggest a role for AtATM3 in regulating cellular NPSH level, a hypothesis that was further supported by our gene expression study. Genetic or pharmacological inhibition of glutathione biosynthesis led to the elevated expression of AtATM3, whereas expression of the glutathione synthase gene GSH1 was increased under Cd(II) stress and in the atatm3 mutant. Because the closest homolog of AtATM3 in fission yeast (Schizosaccharomyces pombe), HMT1, is a vacuolar membrane-localized phytochelatin-Cd transporter, it is tempting to speculate that glutathione-Cd(II) complexes formed in the mitochondria are exported by AtATM3. In conclusion, our data show that AtATM3 contributes to Cd resistance and suggest that it may mediate transport of glutamine synthetase-conjugated Cd(II) across the mitochondrial membrane.
High-Resolution Single-Copy Gene Fluorescence in Situ Hybridization and Its Use in the Construction of a Cytogenetic Map of Maize Chromosome 9
Authors: Wang Chung-Ju Rachel , Harper Lisa , Cande W. Zacheus
Published: February 2006

High-resolution cytogenetic maps provide important biological information on genome organization and function, as they correlate genetic distance with cytological structures, and are an invaluable complement to physical sequence data. The most direct way to generate a cytogenetic map is to localize genetically mapped genes onto chromosomes by fluorescence in situ hybridization (FISH). Detection of single-copy genes on plant chromosomes has been difficult. In this study, we developed a squash FISH procedure allowing successful detection of single-copy genes on maize (Zea mays) pachytene chromosomes. Using this method, the shortest probe that can be detected is 3.1 kb, and two sequences separated by ∼100 kb can be resolved. To show the robust nature of this protocol, we localized nine genetically mapped single-copy genes on chromosome 9 in one FISH experiment. Integration of existing information from genetic maps and the BAC contig-based physical map with the cytological structure of chromosome 9 provides a comprehensive cross-referenced cytogenetic map and shows the dramatic reduction of recombination in the pericentromeric heterochromatic region. To establish a feasible mapping system for maize, we also developed a probe cocktail for unambiguous identification of the 10 maize pachytene chromosomes. These results provide a starting point toward constructing a high-resolution integrated cytogenetic map of maize.
The Chimeric Arabidopsis CYCLIC NUCLEOTIDE-GATED ION CHANNEL11/12 Activates Multiple Pathogen Resistance Responses
Authors: Yoshioka Keiko , Moeder Wolfgang , Kang Hong-Gu , Kachroo Pradeep , Masmoudi Khaled , Berkowitz Gerald , Klessig Daniel F.
Published: February 2006

To investigate the resistance signaling pathways activated by pathogen infection, we previously identified the Arabidopsis thaliana mutant constitutive expresser of PR genes22 (cpr22), which displays constitutive activation of multiple defense responses. Here, we identify the cpr22 mutation as a 3-kb deletion that fuses two cyclic nucleotide-gated ion channel (ATCNGC)–encoding genes, ATCNGC11 and ATCNGC12, to generate a novel chimeric gene, ATCNGC11/12. Genetic, molecular, and complementation analyses suggest that ATCNGC11/12, as well as ATCNGC11 and ATCNGC12, form functional cAMP-activated ATCNGCs and that the phenotype conferred by cpr22 is attributable to the expression of ATCNGC11/12. However, because overexpression of ATCNGC12, but not ATCNGC11, suppressed the phenotype conferred by cpr22, the development of this phenotype appears to be regulated by the ratio between ATCNGC11/12 and ATCNGC12. Analysis of knockout lines revealed that both ATCNGC11 and ATCNGC12 are positive mediators of resistance against an avirulent biotype of Hyaloperonospora parasitica. Through epistatic analyses, cpr22-mediated enhanced resistance to pathogens was found to require NDR1-dependent and EDS1/PAD4-dependent pathways. In striking contrast, none of these pathways was required for cpr22-induced salicylic acid accumulation or PR-1 gene expression. These results demonstrate that NDR1, EDS1, and PAD4 mediate other resistance signaling function(s) in addition to salicylic acid and pathogenesis-related protein accumulation. Moreover, the requirement for both NDR1-dependent and EDS1/PAD4-dependent pathways for cpr22-mediated resistance suggests that these pathways are cross-regulated.
Inadvertent sclerostomy with encysted bleb following trans‐scleral contact diode laser cyclophotocoagulation
Authors: Gupta Viney , Sony Parul , Sihota Ramanjit
Published: February 2006

Abstract

A 22‐year‐old woman underwent 360° trans‐scleral contact diode laser cyclophotocoagulation for refractory glaucoma. Conjunctival burns and scleral thinning were noticed inferonasally at the last laser application. Intraocular pressure in the first week was normal. Six months later the patient presented with encysted filtering bleb and high intraocular pressure. Ultrasound biomicroscopy revealed a full thickness sclerostomy. This report suggests that inadvertent sclerostomy may present with encysted bleb months after trans‐scleral contact diode laser cyclophotocoagulation.
Changing from Snellen to LogMAR: debate or delay?
Authors: Hussain Badrul , Saleh George M , Sivaprasad Sobha , Hammond Christopher J
Published: February 2006

Abstract

Visual acuity is the most commonly used test to assess visual function. The Snellen chart is the universally accepted tool for testing visual acuity despite its poor reliability and reproducibility. Newer logMAR charts are now available that have negated the disadvantages of the Snellen chart. However, these charts are not being used regularly in daily practice. This article discusses the reasons for the delayed acceptance of the logMAR chart.