bluuebunny/crossref_metadata_2025_split huggingface dataset:
TERMINAL FLOWER1 Is a Mobile Signal ControllingArabidopsisArchitecture
Authors: Conti Lucio , Bradley Desmond 
Published: March 2007

AbstractShoot meristems harbor stem cells that provide key growing points in plants, maintaining themselves and generating all above-ground tissues. Cell-to-cell signaling networks maintain this population, but how are meristem and organ identities controlled? TERMINAL FLOWER1 (TFL1) controls shoot meristem identity throughout the plant life cycle, affecting the number and identity of all above-ground organs generated; tfl1 mutant shoot meristems make fewer leaves, shoots, and flowers and change identity to flowers. We find that TFL1 mRNA is broadly distributed in young axillary shoot meristems but later becomes limited to central regions, yet affects cell fates at a distance. How is this achieved? We reveal that the TFL1 protein is a mobile signal that becomes evenly distributed across the meristem. TFL1 does not enter cells arising from the flanks of the meristem, thus allowing primordia to establish their identity. Surprisingly, TFL1 movement does not appear to occur in mature shoots of leafy (lfy) mutants, which eventually stop proliferating and convert to carpel/floral-like structures. We propose that signals from LFY in floral meristems may feed back to promote TFL1 protein movement in the shoot meristem. This novel feedback signaling mechanism would ensure that shoot meristem identity is maintained and the appropriate inflorescence architecture develops.
Micromorphology of soils derived from volcanic ash in Europe: a review and synthesis
Authors: Stoops G. 
Published: March 2007

SummaryAn analysis of the available literature on European volcanic ash soils has been made. Most has been published in Congress proceedings and Journals of national societies, less than half in English. More than half of the papers deal with soils on the Canary Islands. Many papers focus only on one aspect, and complete descriptions are found only in recent publications. Often the use of vague micromorphological terminology and the absence of analytical data make interpretation and comparisons difficult or impossible. Nonetheless, some general features do emerge. In the least‐weathered soils, the micromass forms first coatings around the coarse constituents, later granules, finally giving rise to a loose granular microstructure in the topsoil, and a compacted granular one in the Bw horizons of typic andic materials. The b‐fabric of the micromass is undifferentiated. With increasing weathering, clay coatings appear, the microstructure becomes more blocky and the b‐fabric becomes speckled or even striated. In Vertisols and Aridisols, micromorphological characteristics are not much different from those in the comparable non‐volcanic soils, except generally for the tendency to granular (intrapedal) microstructures. In Icelandic soils, microstratification, lenticular microstructure and preservation of plant residues as a result of cryic conditions and permanent volcanic and aeolian activity are observed. Weathering of volcanic glass in well‐drained conditions yields allophane alteromorphs similar to palagonite, which are easily subject to fragmentation by pedoturbation. The possible influence of surface transport and burial on the formation of Bw‐horizons in andic materials is discussed.
Rehabilitation of saline soils by means of volcanic material coverings
Authors: Tejedor M. , Jiménez C. , Díaz F. 
Published: March 2007

SummaryThe scarcity of water in arid regions promotes natural soil salinization processes, which limit soil productivity, cause degradation and contribute to desertification. Human activity can speed up these processes although it can also help reduce their effects and even rehabilitate affected soils. A number of traditional soil water conservation systems used in farming are also techniques for reducing soil salinity. Examples include systems that involve the use of volcanic materials as mulch, a practice known as ‘arenados’ that has been common for decades in the Canary Islands. The present work examines short‐term changes in the salinity of two saline soils, one with clay texture and the other with loamy texture, both of which were covered artificially with a 12‐cm layer of basaltic pyroclasts. Monitoring over a period of 4 years, during which rainfall averaged 130 mm for the clay soil and 120 mm for the loam, revealed a decrease of approximately 76% and 86%, respectively, in the salinity of the top 40 cm of the profile in the two soils. The decreased salinity of the rooting zone, which is associated with an improved moisture regime in the covered soils has given rise to a form of dryland farming with acceptable yields in a soil environment which is otherwise poorly suited to agriculture.
Weathering and allophane neoformation in soils developed on volcanic ash in the Azores
Authors: Gérard M. , Caquineau S. , Pinheiro J. , Stoops G. 
Published: March 2007

SummaryOn Faial and Pico islands (Azores), we studied two profiles on basaltic pyroclasts that contain buried horizons, and we focussed on petrography, micropedology and mineralogy. Emphasis was given to weathering of the lapilli and ashes, and the neoformation of allophane. A combination of optical studies, in situ chemical analyses, X‐ray diffraction and infrared spectroscopy of clay fractions revealed that allophane is present both in the micromass of the groundmass, in alteromorphs after lapilli or pumice, and in clay coatings. Whereas most studies describe allophane as a colloidal fraction formed by the congruent and total dissolution of the ashes, this study shows evidence for the formation of allophane alteromorphs, due to leaching of Si and cations, with preservation of the original shapes of the tephra. The allophane alteromorphs often display optical characteristics that resemble those of palagonite. Increasing alteration is observed through three steps: (i) hydration of the glass associated with strong cation and Si leaching, (ii) allophane hypocoatings, and (iii) allophane alteromorphs with development of intragrain bridges. The chemical signature of the alteromorphs varies from a pure alumino‐silicate at one extreme to an Fe(Ti) enriched alumino‐silicate at the other. Between those two extremes, the colour grades from yellow to dark orange, with microzonations. An Al‐rich allophane composition is associated with gibbsite in the EUR6‐Pico profile, whereas at the base of the EUR5‐Faial profile, Si‐rich allophane is associated with halloysite. Some variations of the palaeo‐environment are also suggested by strong iron segregation observed with various secondary phases (ferrihydrite, haematite, iddingsite).
Recovery of three arctic stream reaches from experimental nutrient enrichment
Authors: BENSTEAD JONATHAN P. , GREEN ADRIAN C. , DEEGAN LINDA A. , PETERSON BRUCE J. , SLAVIK KARIE , BOWDEN WILLIAM B. , HERSHEY ANNE E. 
Published: March 2007

Summary1. Nutrient enrichment and resulting eutrophication is a widespread anthropogenic influence on freshwater ecosystems, but recovery from nutrient enrichment is poorly understood, especially in stream environments. We examined multi‐year patterns in community recovery from experimental low‐concentration nutrient enrichment (N + P or P only) in three reaches of two Arctic tundra streams (Kuparuk River and Oksrukuyik Creek) on the North Slope of Alaska (U.S.A.).2. Rates of recovery varied among community components and depended on duration of enrichment (2–13 consecutive growing seasons). Biomass of epilithic algae returned to reference levels rapidly (within 2 years), regardless of nutrients added or enrichment duration. Aquatic bryophyte cover, which increased greatly in the Kuparuk River only after long‐term enrichment (8 years), took 8 years of recovery to approach reference levels, after storms had scoured most remnant moss in the recovering reach.3. Multi‐year persistence of bryophytes in the Kuparuk River appeared to prevent recovery of insect populations that had either been positively (e.g. the mayfly Ephemerella, most chironomid midge taxa) or negatively (e.g. the tube‐building chironomid Orthocladius rivulorum) affected by this shift in dominant primary producer. These lags in recovery (of >3 years) were probably driven by the persistent effect of bryophytes on physical benthic habitat.4. Summer growth rates of Arctic grayling (both adults and young‐of‐year) in Oksrukuyik Creek (fertilised for 6 years with no bryophyte colonisation), which were consistently increased by nutrient addition, returned to reference rates within 1–2 years.5. Rates of recovery of these virtually pristine Arctic stream ecosystems from low‐level nutrient enrichment appeared to be controlled largely by duration of enrichment, mediated through physical habitat shifts caused by eventual bryophyte colonisation, and subsequent physical disturbance that removed bryophytes. Nutrient enrichment of oligotrophic Arctic stream ecosystems caused by climate change or local anthropogenic activity may have dramatic and persistent consequences if it results in the colonisation of long‐lived primary producers that alter physical habitat.
Intensive trapping and increased fish predation cause massive population decline of an invasive crayfish
Authors: HEIN CATHERINE L. , VANDER ZANDEN M. JAKE , MAGNUSON JOHN J. 
Published: March 2007

Summary1. Invasive species frequently have adverse impacts on native communities and ecosystems. Management options are often limited. Our goal is to evaluate the effect of intensive trapping and fish predation on the population dynamics of an invasive crayfish.2. From 2001 to 2005, we removed invasive rusty crayfish (Orconectes rusticus) by trapping in Sparkling Lake in northern WI. In addition, the Wisconsin Department of Natural Resources restricted harvest of fish species known to consume crayfish, thereby increasing predation on crayfish that are too small to trap.3. After an initial increase, catch rates of rusty crayfish declined by approximately 95%, from 11 crayfish per trap per day in 2002 to 0.65 in 2004. The catch rate in 2005 remained low at 0.5 crayfish per trap. Females comprised nearly 50% of the catch from 2002 to 2004. Unlike rusty crayfish in Sparkling Lake, catch rates of O. rusticus and Orconectes propinquus in three nearby lakes increased or remained relatively constant over the 5‐year removal period.4. We also examined the influence of habitat and temperature on crayfish catch rates. Catch rates were highest at water temperatures between 20 and 25 °C and on cobble, log or macrophyte habitats that may serve as refuge from fish predation.5. Five summers of intensive trapping and fisheries management practices reduced abundances, but did not extirpate rusty crayfish in Sparkling Lake. To determine the potential of trapping as a management option for invasive crayfishes, these methods must be tested in other systems.
Using biological assemblage composition to infer the values of covarying environmental factors
Authors: YUAN LESTER L. 
Published: March 2007

Summary1. Observations of different organisms can often be used to infer environmental conditions at a site. These inferences may be useful for diagnosing the causes of degradation in streams and rivers.2. When used for diagnosis, biological inferences must not only provide accurate, unbiased predictions of environmental conditions, but also pairs of inferred environmental variables must covary no more strongly than actual measurements of those same environmental variables.3. Mathematical analysis of the relationship between the measured and inferred values of different environmental variables provides an approach for comparing the covariance between measurements with the covariance between inferences. Then, simulated and field‐collected data are used to assess the performance of weighted average and maximum likelihood inference methods.4. Weighted average inferences became less accurate as covariance in the calibration data increased, whereas maximum likelihood inferences were unaffected by covariance in the calibration data. In contrast, the accuracy of weighted average inferences was unaffected by changes in measurement error, whilst the accuracy of maximum likelihood inferences decreased as measurement error increased. Weighted average inferences artificially increased the covariance of environmental variables beyond what was expected from measurements, whereas maximum likelihood inference methods more accurately reproduced the expected covariances.5. Multivariate maximum likelihood inference methods can potentially provide more useful diagnostic information than single variable inference models.
Emission of methane from chalk streams has potential implications for agricultural practices
Authors: SANDERS I. A. , HEPPELL C. M. , COTTON J. A. , WHARTON G. , HILDREW A. G. , FLOWERS E. J. , TRIMMER M. 
Published: March 2007

Summary1. The emission of biogenic gases, particularly methane, is usually associated with wetlands rather than clean streams. Here, we investigated methane production from a southern English chalk stream, where increased sedimentation, compounded by extensive macrophyte growth, may have altered ecosystem function.2. Cover of the channel by the dominant macrophyte, Ranunculus penicillatus, peaked in August, when plant beds were associated with low water velocity and the accumulation of sediment (<2000 μm) dominated by the sand‐sized fraction (63–1000 μm).3. Over spring and summer there was a marked increase in the silt/clay fraction of the sediment, a concomitant drop in mean particle size and, hence, inferred permeability. At the same time there was an increase in CH4 transport through Ranunculus stems and an increase in water column CH4 concentration, while the sediment CH4 concentration increased 100‐fold between February and April. A marked seasonal enrichment in the δ15N of N2 dissolved in the pore water correlated with CH4 flux and, coupled to the shift in particle size, suggested a transient input of organic matter, possibly of terrestrial origin.4. Potential areal methane production and measured efflux were similar to that from some U.K. peatlands and represent one of the first accounts of significant methanogenesis to be measured in a stream channel. Most (>90%) of the methane flux is transported to the atmosphere through the Ranunculus stems.5. Although the total flux of methane from U.K. chalk streams is probably relatively modest (estimated at 3.2 × 10−6 Tg CH4 year−1), this phenomenon changes our perception of the health of these ecosystems and indicates another deleterious side effect of agriculture.
Modelling the effects of changing retention time on abundance and composition of phytoplankton species in a small lake
Authors: JONES I. D. , ELLIOTT J. A. 
Published: March 2007

Summary1. The phytoplankton community model, PROTECH, was used to model the algal response to changing annual mean retention time in a small lake.2. Simulations of short retention time with a fixed nutrient load resulted in a reduced chlorophyll concentration. A similar relationship was observed when the simulations were repeated but with inflowing nutrients increased in proportion to river discharge.3. Longer retention time caused the spring bloom to start earlier and the autumn bloom to persist longer.4. Changes in discharge of the inflowing river also caused a change in the thermal structure of the lake. This change in thermal structure, in turn, influenced the magnitude and composition of the phytoplankton population, particularly those in the CS‐functional group, such as Aphanizomenon.
Experimental assessment of the fecundity of Eucypris virens (Ostracoda, Crustacea) under natural sex ratios
Authors: VANDEKERKHOVE JOCHEN , MATZKE‐KARASZ RENATE , MEZQUITA FRANCESC , ROSSETTI GIAMPAOLO 
Published: March 2007

Summary1. The adaptive significance of the observed variations in sex ratios in non‐marine ostracods is unclear. This study quantified the fecundity of females taken from a presumed fully sexual Eucypris virens population that were experimentally combined with different proportions of males (male : female sex ratios: 1 : 1, 1 : 2, 1 : 4, 1 : 8 and 0 : 1).2. The results yielded no indications that female fecundity is altered by short‐term variations in the proportion of males, at least not within the range of sex ratios that are common in natural ostracod populations. Complete removal of males, however, did strongly reduce hatching success of dried eggs. This suggests the need for multiple mating events during the reproductive lifetime of the female. It also emphasizes the need for a minimum number of males, although this minimum number evidently may be rather low, as we found a high number of spermatozoa in the seminal receptacles after a single mating event.3. The sex ratio in the source population was strongly female biased (1 : 3.4; n = 514), whereas in the hatchling assemblages reared in the laboratory, males and females were found in equal proportions (1 : 1.0; n = 1516), irrespective of the prevailing sex ratio. This clear discrepancy is intriguing, and points to the importance of epigenetic factors for the determination of field sex ratios.
Food preference, growth and maturation of Nemurella pictetii (Plecoptera: Nemouridae)
Authors: LIESKE R. , ZWICK P. 
Published: March 2007

Summary1. The stonefly Nemurella pictetii has a highly variable life cycle and is semi‐ and uni‐, but also plurivoltine in different geographical areas.2. The influence of the type of food on growth and maturation of larvae was studied in laboratory experiments. Food preference was also assessed.3. Larvae of N. pictetii are strongly opportunistic feeders utilising a broad range of food sources. However, biofilm was preferred over detritus (conditioned leaves), green algae and animal food. The highly mobile larvae quickly found the preferred food. Larvae fed on biofilm grew and developed significantly faster than larvae fed on conditioned leaves.4. Larval growth and maturation in experiments as well as in the field differed with available food qualities. Phases of faster growth and maturation corresponded well with maximum availability of biofilm in the field. This contributes to the interpretations of differences in life cycles in the field.
BCG stimulated dendritic cells induce an interleukin‐10 producing T‐cell population with no T helper 1 or T helper 2 bias in vitro
Authors: Madura Larsen Jeppe , Stabell Benn Christine , Fillie Yvonne , Van Der Kleij Desiree , Aaby Peter , Yazdanbakhsh Maria 
Published: March 2007

Summary Mycobacterium bovis bacillus Calmette–Guérin (BCG) vaccine has been associated with beneficial effects on overall childhood mortality in low‐income countries; this cannot be explained merely by the prevention of tuberculosis (TB) deaths. The beneficial effects of BCG vaccine could be the result of either strengthening of pro‐inflammatory mechanisms, helping neonates to fight infections, or the induction of an immune‐regulatory network restricting overt inflammation and intense pathology. We aimed to study the effect of live BCG on the ability of dendritic cells (DCs) to polarize T‐cell responses. Monocyte‐derived DCs were matured in the presence or absence of BCG. The DC phenotype was assessed by CD83 expression, interleukin‐12 (IL‐12) and IL‐10 production, as well as for the ability to polarize T‐cell responses. Following stimulation with CD40 ligand, DCs matured in the presence of BCG showed enhanced IL‐10 and diminished IL‐12 production. These DCs primed naive T cells to develop into IL‐10‐producing T cells, with no T helper 1 or T helper 2 bias. These results suggest that BCG vaccination might result in the development of IL‐10‐producing DCs as well as IL‐10‐producing T cells that could contribute to restricting overt inflammation in infants exposed to pathogens and thus lead to lower infant mortality.
Sphingosylphosphorylcholine activates dendritic cells, stimulating the production of interleukin‐12
Authors: Ceballos Ana , Sabatté Juan , Nahmod Karen , Martínez Diego , Salamone Gabriela , Vermeulen Mónica , Maggini Julián , Salomón Horacio , Geffner Jorge 
Published: March 2007

SummaryCompared with other lysophospholipid mediators such as sphingosine‐1‐phosphate and lysophosphatidic acid, little is known about the physiological significance of the related bioactive lysosphingolipid sphingosylphosphorylcholine (SPC), which is present in high‐density lipoprotein particles. The present study was undertaken to evaluate the effect of SPC on human immature dendritic cells (DCs). Reverse transcription–polymerase chain reaction and flow cytometry assays revealed that DCs express two putative receptors for SPC, ovarian cancer G‐protein‐coupled receptor 1 and G‐protein‐coupled receptor 4. Exposure to SPC induced a rapid and transient increase in intracellular free calcium concentrations but did not stimulate endocytosis or chemotaxis of DCs. SPC increased the expression of HLA‐DR, CD86 and CD83 and improved the T‐cell priming ability of DCs, as well as the ability of DCs to stimulate the production of interferon‐γ by allogeneic peripheral blood mononuclear cells during the mixed lymphocyte reaction. Consistent with these results, we also observed that SPC stimulated the production of interleukin (IL)‐12 and IL‐18 by DCs. Taken together, our results support the notion that the accumulation of SPC in peripheral tissues during the course of inflammatory processes may favour the development of T helper type 1 immunity.
Potential functional role of plasmacytoid dendritic cells in cancer immunity
Authors: Kim Ryungsa , Emi Manabu , Tanabe Kazuaki , Arihiro Koji 
Published: March 2007

SummaryPlasmacytoid dendritic cells (pDCs), as well as myeloid dendritic cells (mDCs), have a dual role not only in initiating immune responses but also in inducing tolerance to exogenous and endogenous antigens. Tumour antigens originate from endogenous self‐antigens, which are poorly immunogenic and also subject to change during tumour progression. In general, tumour antigens derived from apoptotic cells are captured by immature mDCs, antigen presentation by which is most likely to result in immune tolerance. In contrast, tumour antigens may be taken up by pDCs through Toll‐like receptor 9 (TLR9) via receptor‐mediated endocytosis. TLR9‐dependent activation of pDCs results in the secretion of pro‐inflammatory cytokines such as interleukin (IL)‐12 and type I interferons (IFNs) through a MyD88‐dependent pathway. Type I IFNs also activate mDCs for T‐cell priming. Although pDCs recruited to the tumour site are implicated in facilitating tumour growth via immune suppression, they can be released from the tumour as a result of cell death caused by primary systemic chemotherapy, and can then be activated through TLR9. Thus, synergistically with mDCs, pDCs may also play a crucial role in mediating cancer immunity. In this review, the potential functional duality and plasticity of pDCs mediated by TLR9 ligation in cancer immunity will be discussed.