bluuebunny/crossref_metadata_2025 huggingface dataset:
Ecological and site historical aspects of N dynamics and current N status in temperate forests
Authors: BRUMME RAINER , KHANNA PARTAP K.
Published: September 2007

Ecological developments during Holocene age and high atmospheric depositions since industrialization have changed the N dynamics of temperate forest ecosystems. A number of different parameters are used to indicate whether the forests are N‐saturated or not, most common among them is the occurrence of nitrates in the seepage water below the rooting zone. The use of different definitions to describe N saturation implies that the N status of ecosystems is not always appropriately assessed. Data on N dynamics from 53 different German forests were used to classify various development states of forest ecosystems according to the forest ecosystem theory proposed by Ulrich for which N balances of input – (output plus plant N increment) were used. Those systems where N output equals N input minus plant N increment are described as (quasi‐) Steady State Type. Those forests where N output does not equal N input minus plant N increment as in a ‘transient state.’ Forests of the transient state may lose nitrogen from the soil (Degradation Type) or gain nitrogen [e.g., from atmospheric depositions (Accumulation Type)]. Forest ecosystems may occur in four different N states: (a) (quasi‐) Steady State Type with mull type humus, (b) Degradation Type with mull type humus, (c) Accumulation Type with moder type humus, and (d) (quasi‐) Steady State Type with moder type humus. Forests with the (quasi‐) steady state with mull type humus in the forest floor (n= 8) have high‐soil pH values, high N retention by plant increment, high N contents in the mineral soils, and have not undergone large changes in the N status. Forests of the Degradation Type lose nitrogen from the mineral soil (currently degradation is occurring on one site). Most forests that have moder or mor type humus and low‐soil pH values, and low N contents in the mineral soil have gone through the transient state of organic matter loss in the mineral soils. They accumulate organic matter in the forest floor (accumulation phase, currently 21 sites are accumulating 6–21 kg N ha−1 yr−1) or have reached a new (quasi‐) steady state with moder/mor type humus (n= 15). N retention in the accumulation phase has significantly increased in soil with N deposition (r2= 0.38), soil acidity (considering thickness of the forest floor as indices of soil acidity,r2= 0.43) and acid deposition (sulfate deposition,r2= 0.39). Retention of N (4–20 kg N ha−1 yr−1) by trees decreased and of soils increased with a decrease in the availability of base cations indicating the important role of trees for N retention in less acid soils and those of soils in more acid soils. Ecosystem theory could be successfully applied on the current data to understand the dynamics of N in temperate forest ecosystems.
Biomass and carbon accumulation in a fire chronosequence of a seasonally dry tropical forest
Authors: VARGAS RODRIGO , ALLEN MICHAEL F. , ALLEN EDITH B.
Published: September 2007

Seasonally dry tropical forests (SDTF) are a widely distributed vegetation type in the tropics, characterized by seasonal rainfall with several months of drought when they are subject to fire. This study is one of the first attempts to quantify above‐ and belowground biomass (AGB and BGB) and above‐ and belowground carbon (AGC and BGC) pools to calculate their recovery after fire, using a chronosequence approach (six forests that ranged form 1 to 29 years after fire and mature forest). We quantified AGB and AGC pools of trees, lianas, palms, and seedlings, and BGB and BGC pools (Oi, Oe, Oa soil horizons, and fine roots). Total AGC ranged from 0.05 to nearly 72 Mg C ha−1, BGC from 21.6 to nearly 85 Mg C ha−1, and total ecosystem carbon from 21.7 to 153.5 Mg C ha−1; all these pools increased with forest age. Nearly 50% of the total ecosystem carbon was stored in the Oa horizon of mature forests, and up to 90% was stored in the Oa‐horizon of early successional SDTF stands. The soils were shallow with a depth of <20 cm at the study site. To recover values similar to mature forests, BGC and BGB required <19 years with accumulation rates greater than 20 Mg C ha−1 yr−1, while AGB required 80 years with accumulation rates nearly 2.5 Mg C ha−1 yr−1. Total ecosystem biomass and carbon required 70 and 50 years, respectively, to recover values similar to mature forests. When belowground pools are not included in the calculation of total ecosystem biomass or carbon recovery, we estimated an overestimation of 10 and 30 years, respectively.
Simulated chronic nitrogen deposition increases carbon storage in Northern Temperate forests
Authors: PREGITZER KURT S. , BURTON ANDREW J. , ZAK DONALD R. , TALHELM ALAN F.
Published: September 2007

High levels of atmospheric nitrogen (N) deposition in Europe and North America were maintained throughout the 1990s, and global N deposition is expected to increase by a factor of 2.5 over the next century. Available soil N limits primary production in many terrestrial ecosystems, and some computer simulation models have predicted that increasing atmospheric N deposition may result in greater terrestrial carbon (C) storage in woody biomass. However, empirical evidence demonstrating widespread increases in woody biomass C storage due to atmospheric N deposition is uncommon. Increased C storage in soil organic matter due to chronic N inputs has rarely been reported and is often not considered in computer simulation models of N deposition effects. Since 1994, we have experimentally simulated chronic N deposition by adding 3 g N m−2 yr−1to four different northern hardwood forests, which span a 500 km geographic gradient in Michigan. Each year we measured tree growth. In 2004, we also examined soil C content to a depth of 70 cm. When we compared the control treatment with the NO3−deposition treatment after a decade of experimentation, ecosystem C storage had significantly increased in both woody biomass (500 g C m−2) and surface soil (0–10 cm) organic matter (690 g C m−2). The increase in surface soil C storage was apparently driven by altered rates of organic matter decomposition, rather than an increase in detrital inputs to soil. Our results, for study locations stretching across hundreds of kilometers, support the hypothesis that chronic N deposition may increase C storage in northern forests, potentially contributing to a sink for anthropogenic CO2in the northern Hemisphere.
Climatic variation and the distribution of an amphibian polyploid complex
Authors: OTTO CLINT R. V. , SNODGRASS JOEL W. , FORESTER DON C. , MITCHELL JOSEPH C. , MILLER ROBERT W.
Published: September 2007

The establishment of polyploid populations involves the persistence and growth of the polyploid in the presence of the progenitor species. Although there have been a number of animal polyploid species documented, relatively few inquiries have been made into the large‐scale mechanisms of polyploid establishment in animal groups. Herein we investigate the influence of regional climatic conditions on the distributional patterns of a diploid–tetraploid species pair of gray treefrogs, Hyla chrysoscelis and H. versicolor (Anura: Hylidae) in the mid‐Atlantic region of eastern North America.

Calling surveys at breeding sites were used to document the distribution of each species. Twelve climatic models and one elevation model were generated to predict climatic and elevation values for gray treefrog breeding sites. A canonical analysis of discriminants was used to describe relationships between climatic variables, elevation and the distribution of H. chrysoscelis and H. versicolor.

There was a strong correlation between several climatic variables, elevation and the distribution of the gray treefrog complex. Specifically, the tetraploid species almost exclusively occupied areas of higher elevation, where climatic conditions were relatively severe (colder, drier, greater annual variation). In contrast, the diploid species was restricted to lower elevations, where climatic conditions were warmer, wetter and exhibited less annual variation.

Clusters of syntopic sites were associated with areas of high variation in annual temperature and precipitation during the breeding season.

Our data suggest that large‐scale climatic conditions have played a role in the establishment of the polyploid H. versicolor in at least some portions of its range. The occurrence of the polyploid and absence of the progenitor in colder, drier and more varied environments suggests the polyploid may posses a tolerance of severe environmental conditions that is not possessed by the diploid progenitor.

Our findings support the hypothesis that increased tolerance to severe environmental conditions is a plausible mechanism of polyploid establishment.
Thermal tolerance and geographical range size in theAgabus brunneusgroup of European diving beetles (Coleoptera: Dytiscidae)
Authors: Calosi P. , Bilton D. T. , Spicer J. I. , Atfield A.
Published: September 2007

Aim Within clades, most taxa are rare, whilst few are common, a general pattern for which the causes remain poorly understood. Here we investigate the relationship between thermal performance (tolerance and acclimation ability) and the size of a species’ geographical range for an assemblage of four ecologically similar European diving beetles (theAgabus brunneusgroup) to examine whether thermal physiology relates to latitudinal range extent, and whether Brown’s hypothesis and the environmental variability hypothesis apply to these taxa.

Location Europe.

Methods In order to determine the species tolerances to either low or high temperatures we measured the lethal thermal limits of adults, previously acclimated at one of two temperatures, by means of thermal ramping experiments (± 1°C min−1). These measures of upper and lower thermal tolerances (UTT and LTT respectively) were then used to estimate each species’ thermal tolerance range, as total thermal tolerance polygons and marginal UTT and LTT thermal polygons.

Results Overall, widespread species have higher UTTs and lower LTTs than restricted ones. Mean upper lethal limits of theAgabus brunneusgroup (43 to 46°C), are similar to those of insects living at similar latitudes, whilst mean lower lethal limits (−6 to −9°C) are relatively high, suggesting that this group is not particularly cold‐hardy compared with other mid‐temperate‐latitude insects. Widespread species possess the largest thermal tolerance ranges and have a relatively symmetrical tolerance to both high and low temperatures, when compared with range‐restricted relatives. Over the temperature range employed, adults did not acclimate to either high or low temperatures, contrasting with many insect groups, and suggesting that physiological plasticity has a limited role in shaping distribution.

Main conclusions Absolute thermal niche appears to be a good predictor of latitudinal range, supporting both Brown’s hypothesis and the environmental variability hypothesis. Restricted‐range species may be more susceptible to the direct effect of climate change than widespread species, notwithstanding the possibility that even ‘thermally‐hardy’, widespread species may be influenced by the indirect effects of climate change such as reduction in habitat availability in Mediterranean areas.
How few whales were there after whaling? Inference from contemporary mtDNA diversity
Authors: JACKSON J. A. , PATENAUDE N. J. , CARROLL E. L. , BAKER C. SCOTT
Published: September 2007

Reconstructing the history of exploited populations of whales requires fitting a trajectory through at least three points in time: (i) prior to exploitation, when abundance is assumed to be at the maximum allowed by environmental carrying capacity; (ii) the point of minimum abundance or ‘bottleneck’, usually near the time of protection or the abandonment of the hunt; and (iii) near the present, when protected populations are assumed to have undergone some recovery. As historical abundance is usually unknown, this trajectory must be extrapolated according to a population dynamic model using catch records, an assumed rate of increase and an estimate of current abundance, all of which have received considerable attention by the International Whaling Commission (IWC). Relatively little attention has been given to estimating minimum abundance (Nmin), although it is clear that genetic and demographic forces at this point are critical to the potential for recovery or extinction of a local population. We present a general analytical framework to improve estimates ofNminusing the number of mtDNA haplotypes (maternal lineages) surviving in a contemporary population of whales or other exploited species. We demonstrate the informative potential of this parameter as anaposterioriconstraint on Bayesian logistic population dynamic models based on the IWC Comprehensive Assessment of the intensively exploited southern right whales (Eubalaena australis) and published surveys of mtDNA diversity for this species. Estimated historical trajectories from all demographic scenarios suggested a substantial loss of mtDNA haplotype richness as a result of 19th century commercial whaling and 20th century illegal whaling by the Soviet Union. However, the relatively high rates of population increase used by the IWC assessment predicted a bottleneck that was implausibly narrow (median, 67 mature females), given our corrected estimates ofNmin. Further, high levels of remnant sequence diversity (theta) suggested that pre‐exploitation abundance was larger than predicted by the logistic model given the catch record, which is known to be incomplete. Our results point to a need to better integrate evolutionary processes into population dynamic models to account for uncertainty in catch records, the influence of maternal fidelity on metapopulation dynamics, and the potential for inverse density dependence (an ‘Allee effect’) in severely depleted populations.
The origin of Phoxinus eos‐neogaeus unisexual hybrids
Authors: ANGERS BERNARD , SCHLOSSER ISAAC J.
Published: September 2007

Phoxinus eos‐neogaeus unisexual hybrids (Cyprinidae, Pisces) are among the few vertebrate taxa known to reproduce clonally by gynogenesis. These taxa have a broad distribution in North America, mostly located in regions previously covered by the last Pleistocene ice sheet. To assess whether asexual hybrids dispersed from glacial refuges at the end of the Pleistocene or they originated from current hybridization events, genetic diversity of mitochondrial DNA (mtDNA) sequences and microsatellite loci was determined in populations from 16 different sites in the Mississippi–Missouri River (Nebraska and Montana), Rainy River–Hudson Bay (Minnesota), and St Lawrence River (Quebec) drainages. The maternal species (P. neogaeus) occurred in Minnesota and Nebraska but was absent from Montana sites and was restricted to only two of 11 lakes sampled in Quebec, although hybrids were present at all sites. The genetic survey revealed a total of 49 clones, originating from 14 hybridization events. Several of the lineages were characterized by mtDNA haplotypes not detected in the maternal ancestor. Lineages as well as clones frequently displayed a large geographical distribution at a regional scale. Dating of hybridization events suggested a relatively recent origin (< 50 000 years ago) from the Mississippi glacial refuge, even in regions not covered by the last Pleistocene glacier. Altogether, these results indicate P. eos‐neogaeus hybrids are not the result of current hybridization events, but display a pattern predicted by postglacial dispersal. Our findings have considerable implications for the nature of selection processes affecting the diversity of these asexual taxa and their coexistence with sexual ancestors.
A role for oxidative stress in the Citrus limon/Phoma tracheiphila interaction
Authors: Reverberi M. , Betti C. , Fabbri A. A. , Zjalic S. , Spadoni S. , Mattei B. , Fanelli C.
Published: September 2007

Phoma tracheiphila, the agent of citrus ‘mal secco’, releases a toxic complex called malseccin into the plant. Oxidative stress was studied, both regarding the reaction of lemon (Citrus limon) leaves to the infiltration of fungal extracellular proteins, and the analysis of the pathogen's ability to cause symptoms in leaves of lemon cultivars with different degrees of susceptibility. Studies were perfomed in planta on three lemon cultivars: cv. Interdonato, partially tolerant to ‘mal secco’; cv. Monachello, tolerant; and cv. Femminello, susceptible. When inoculated with P. tracheiphila extracellular proteins, cv. Interdonato leaves showed chlorosis and necrosis symptoms and an increase in lipoxygenase and glutathione peroxidase of up to 100 and 76·5 fold, respectively. Furthermore, extracellular proteins of P. tracheiphila infiltrated into leaves induced lipoperoxide formation 10 fold in cvs Interdonato and Femminello and 3 fold in cv. Monachello compared to the control, with Monachello reacting earlier. In vitro analyses indicate that the presence of lyophilized twigs and leaves (LTV) of cv. Monachello in the fungal growth medium, stimulated concentrations of superoxide dismutases (~20–60 fold), glutathione peroxidase (~115 fold) and catalase (~15 fold) in fungal mycelia. When LTV of cv. Femminello was added, the pathogen produced a higher quantity of hydrolytic enzymes in vitro, polygalacturonase (~40 fold) and laccase (~110 fold). The MALDI‐TOF and TOF/TOF MS analyses performed on 60–70 KDa extracellular proteins of P. tracheiphila after inoculation in malseccin conducive media showed the presence of a monoamine oxidase enzyme able to release and H2O2 in the cell. Overall the results suggest oxidative stress occurs in this interaction.
Genetic variation in populations of the cacao wilt pathogen, Ceratocystis cacaofunesta
Authors: Engelbrecht C. J. B. , Harrington T. C. , Alfenas A. C. , Suarez C.
Published: September 2007

Ceratocystis cacaofunesta (= Ceratocystis fimbriata) causes a lethal wilt disease of cacao (Theobroma cacao) in Latin America. Polymorphic microsatellite markers, (CAT)5 nuclear DNA fingerprints and Hae III mitochondrial DNA fingerprints were used to compare genetic diversity among isolates of C. cacaofunesta collected from populations in western Ecuador, Costa Rica, Colombia, and Rondônia and Bahia in Brazil. Microsatellite markers and nuclear DNA fingerprints separated Ecuadorian isolates from isolates of the other four populations, and these two major groups correspond to genetic lineages already identified from ITS‐rDNA sequences and intersterility groupings. Mitochondrial DNA fingerprints also demonstrated substantial diversity and split the Ecuadorian isolates into two groups. All marker types showed limited variation in the Colombian, Costa Rican and Bahian populations, as might be expected for introduced populations that have gone through recent genetic bottlenecks. In contrast, the Rondonian and western Ecuadorian populations showed gene diversity values similar to natural populations of other Ceratocystis species. The Rondonian population was the only sampled population in the native range of T. cacao (the Upper Amazon), and the putatively introduced populations were more closely related to the Rondonian population than to the western Ecuadorian population. The Ecuadorian population is in an area with other native Theobroma species, which may serve as natural hosts.
Late Quaternary contourites and glaciomarine sedimentation in the Fram Strait
Authors: HOWE JOHN A. , SHIMMIELD TRACY M. , HARLAND REX , Eyles Nick
Published: September 2007

Two sites in the eastern Fram Strait, the Vestnesa Ridge and the Yermak Plateau, have been surveyed and sampled providing a depositional record over the last glacial‐interglacial cycle. The Fram Strait is the only deep‐water connection from the Arctic Ocean to the North Atlantic and contains a marine sediment record of both high latitude thermohaline flow and ice sheet interaction. On the Vestnesa Ridge, the western Svalbard margin, a sediment drift was identified in 1226 m of water. Gravity and multicores from the crest of the drift recovered turbidites and contourites. 14C dating indicates an age range of 8287 to 26 900 years BP (Early Holocene to Late Weichselian). The Yermak Plateau is characterized by slope sediments in 961 m of water. Gravity and multicores recovered contourites and hemipelagites. 14C ages were between 8615 and 46 437 years BP (Early Holocene to mid‐Weichselian). Downcore dinoflagellate cyst analyses from both sites provide a record of changing surface water conditions since the mid‐Weichselian, suggesting variable sea ice extent, productivity and polynyas present even during the Last Glacial Maximum. Four layers of ice‐rafted debris were also identified and correlated within the cores. These events occurred ca at 9, 24 to 25, 26 to 27 and 43 ka, asynchronous with Heinrich layers in the wider north‐east Atlantic and here interpreted as reflecting instability in the Svalbard/Barents Ice sheet and the northward advection of warm Atlantic water during the Late Weichselian. The activity of the ancestral West Spitsbergen Current is interpreted using mean sortable silt records from the cores. On the Vestnesa Ridge drift the modern mass accumulation rate, calculated using excess 210Pb, is 0·076 g cm−2 year−1. On the Yermak Plateau slope the modern mass accumulation rate is 0·053 g cm−2 year−1.
Petrography and textural development of inorganic and biogenic lithotypes in a relict barite tufa deposit at Flybye Springs, NT, Canada
Authors: BONNY SANDY M. , JONES BRIAN , Rankey Gene
Published: September 2007

A relict mound of Holocene barite (BaSO4) tufa underlies the Flybye Springs, a small, barium‐rich, cold sulphur spring system in the Northwest Territories of Canada. The tufa is composed of relatively pure barite with ≤0·34 wt% Ca2+ and ≤0·77 wt% Sr2+. The mound is made up of coated bubble, raft, undulatory sheet, stromatolitic, coated grain and detrital conglomerate barite tufa. Although previously unreported in barite, these lithotypes are akin to facies found in many carbonate spring deposits. Raft and ooid‐coated grain tufa was formed via ‘inorganic’ barite precipitation in spring water ponds and tributaries where rapid oxidation of sulphide to sulphate established barite supersaturation. Undulatory sheet tufa may have formed by the reaction of dissolved barium with sulphate derived from the oxidation of extracellular polysaccharide‐rich colloidal sulphur films floating in oxygenated, barite‐saturated spring water ponds. Coated bubble, oncoid‐coated grain and stromatolitic tufa with filamentous microfossils was formed in close association with sulphur‐tolerant microbes inhabiting dysoxic and oxygenated spring water tributaries and ponds. Adsorption of dissolved barium to microbial extracellular polysaccharide probably facilitated the development of these ‘biogenic’ lithotypes. Detrital conglomerate tufa was formed by barite cementation of microdetrital tufa, allochthonous lithoclasts and organic detritus, including caribou hair. Biogenic textures, organic artefacts and microfossils in the Flybye barite tufa have survived diagenetic aggradational recrystallization and precipitation of secondary cements, indicating the potential for palaeoecological information to be preserved in barite in the geological record. Similarities between the Flybye barite tufa and carbonate spring deposits demonstrate that analogous textures can develop in chemical sedimentary systems with distinct mineralogy, biology and physiochemistry.
Function of plastidial pyruvate kinases in seeds of Arabidopsis thaliana†
Authors: Baud Sébastien , Wuillème Sylvie , Dubreucq Bertrand , De Almeida Aurélie , Vuagnat Cindy , Lepiniec Loïc , Miquel Martine , Rochat Christine
Published: September 2007

Pyruvate kinase (PK) catalyses the irreversible synthesis of pyruvate and ATP, which are both used in multiple biochemical pathways. These compounds are essential for sustained fatty acid production in the plastids of maturing Arabidopsis embryos. Using a real‐time quantitative reverse transcriptase (RT)‐PCR approach, the three genes encoding putative plastidial PKs (PKps) in Arabidopsis, namely PKp1 (At3g22960), PKp2 (At5g52920) and PKp3 (At1g32440), were shown to be ubiquitously expressed. However, only PKp1 and PKp2 exhibited significant expression in maturing seeds. The activity of PKp1 and PKp2 promoters was consistent with this pattern, and the study of the PKp1:GFP and PKp2:GFP fusion proteins confirmed the plastidial localization of these enzymes. To further investigate the function of these two PKp isoforms in seeds comprehensive functional analyses were carried out, including the cytological, biochemical and molecular characterization of two pkp1 and two pkp2 alleles, together with a pkp1pkp2 double mutant. The results obtained outlined the importance of these PKps for fatty acid synthesis and embryo development. Mutant seeds were depleted of oil, their fatty acid content was drastically modified, embryo elongation was retarded and, finally, seed germination was also affected. Together, these results provide interesting insights concerning the carbon fluxes leading to oil synthesis in maturing Arabidopsis seeds. The regulation of this metabolic network by the WRINKLED1 transcription factor is discussed, and emphasizes the role of plastidial metabolism and the importance of its tight regulation.
Redox‐sensitive GFP in Arabidopsis thaliana is a quantitative biosensor for the redox potential of the cellular glutathione redox buffer
Authors: Meyer Andreas J. , Brach Thorsten , Marty Laurent , Kreye Susanne , Rouhier Nicolas , Jacquot Jean‐Pierre , Hell Rüdiger
Published: September 2007

The cellular glutathione redox buffer is assumed to be part of signal transduction pathways transmitting environmental signals during biotic and abiotic stress, and thus is essential for regulation of metabolism and development. Ratiometric redox‐sensitive GFP (roGFP) expressed in Arabidopsis thaliana reversibly responds to redox changes induced by incubation with H2O2 or DTT. Kinetic analysis of these redox changes, combined with detailed characterization of roGFP2 in vitro, shows that roGFP2 expressed in the cytosol senses the redox potential of the cellular glutathione buffer via glutaredoxin (GRX) as a mediator of reversible electron flow between glutathione and roGFP2. The sensitivity of roGFP2 toward the glutathione redox potential was tested in vivo through manipulating the glutathione (GSH) content of wild‐type plants, through expression of roGFP2 in the cytosol of low‐GSH mutants and the endoplasmic reticulum (ER) of wild‐type plants, as well as through wounding as an example for stress‐induced redox changes. Provided the GSH concentration is known, roGFP2 facilitates the determination of the degree of oxidation of the GSH solution. Assuming sufficient glutathione reductase activity and non‐limiting NADPH supply, the observed almost full reduction of roGFP2 in vivo suggests that a 2.5 mm cytosolic glutathione buffer would contain only 25 nm oxidized glutathione disulfide (GSSG). The high sensitivity of roGFP2 toward GSSG via GRX enables the use of roGFP2 for monitoring stress‐induced redox changes in vivo in real time. The results with roGFP2 as an artificial GRX target further suggest that redox‐triggered changes of biologic processes might be linked directly to the glutathione redox potential via GRX as the mediator.
Disruption of ATCSLD5 results in reduced growth, reduced xylan and homogalacturonan synthase activity and altered xylan occurrence in Arabidopsis
Authors: Bernal Adriana Jimena , Jensen Jakob Krüger , Harholt Jesper , Sørensen Susanne , Moller Isabel , Blaukopf Claudia , Johansen Bo , De Lotto Robert , Pauly Markus , Scheller Henrik Vibe , Willats William G.T.
Published: September 2007

Members of a large family of cellulose synthase‐like genes (CSLs) are predicted to encode glycosyl transferases (GTs) involved in the biosynthesis of plant cell walls. The CSLA and CSLF families are known to contain mannan and glucan synthases, respectively, but the products of other CSLs are unknown. Here we report the effects of disrupting ATCSLD5 expression in Arabidopsis. Both stem and root growth were significantly reduced in ATCSLD5 knock‐out plants, and these plants also had increased susceptibility to the cellulose synthase inhibitor isoxaben. Antibody and carbohydrate‐binding module labelling indicated a reduction in the level of xylan in stems, and in vitro GT assays using microsomes from stems revealed that ATCSLD5 knock‐out plants also had reduced xylan and homogalacturonan synthase activity. Expression in Nicotiana benthamiana of ATCSLD5 and ATCSLD3, fluorescently tagged at either the C‐ or the N‐terminal, indicated that these GTs are likely to be localized in the Golgi apparatus. However, the position of the fluorescent tag affected the subcellular localization of both proteins. The work presented provides a comprehensive analysis of the effects of disrupting ATCSLD5 in planta, and the possible role(s) of this gene and other ATCSLDs in cell wall biosynthesis are discussed.
The role of chromatin‐remodeling factor PKL in balancing osmotic stress responses during Arabidopsis seed germination
Authors: Perruc Elian , Kinoshita Natsuko , Lopez‐Molina Luis
Published: September 2007

Embryogenesis in Arabidopsis results in mature, osmotolerant embryos within dry seeds. Late‐embryogenesis programs involve the transcription factors ABI3 and ABI5, which are necessary for osmotolerance. ABI3 and ABI5 are degraded in seeds initiating germination, abolishing their protected state. However, during an early stage of germination, strong osmotic stresses, or ABA exposure maintain ABI3 and ABI5 expression, leading to growth arrest, and osmotolerance. Mild stress stimuli delay ABI3 and ABI5 disappearance, retarding germination but not preventing eventual closure of embryogenesis programs. PICKLE (PKL), a putative chromatin modifier, is necessary to repress ABI3 and ABI5 expression during germination in response to ABA. We show that pkl mutants display persistent high expression of ABI3 and ABI5 upon ABA stimulation. In turn, maintenance of ABI5 expression leads to hypersensitive germination responses to ABA in pkl seeds. We provide evidence that ABI3 and ABI5 are less associated with repressed chromatin in pkl mutants. Our results provide evidence that PKL‐dependent repression of embryonic gene expression extends to late‐embryogenesis genes and is associated with changes in chromatin. We suggest that effective closure of embryogenesis omostolerance programs during germination prevents excessive plant reactions to stress.
Standardization of nucleic acid amplification technique (NAT)‐based assays for different genotypes of parvovirus B19: a meeting summary
Authors: Baylis S. A.
Published: September 2007

An extraordinary meeting of the International Working Group on the Standardization of Genome Amplification Techniques for the safety testing of blood, tissues and organs for blood borne pathogens was held on 2 March 2007, at the National Institute for Biological Standards and Control. The aim of the meeting was to investigate ways to harmonize results obtained for the detection and quantification of different genotypes of parvovirus B19 (B19V) DNA by control laboratories and manufacturers of plasma derivatives. The meeting explored issues of B19V such as the classification of B19V strains, the prevalence and distribution of different genotypes, the clinical and biological significance of different genotypes, the detection of different genotypes in plasma‐derived products, and their susceptibility to virus‐inactivation procedures. At this meeting and through subsequent studies, high titre, high volume samples have been identified representing different genotypes of B19V, which will be evaluated by collaborative study to prepare reference panels for the purposes of assay validation.
A Link between PVYN CP Gene‐mediated Virus Resistance and Transgene Arrangement
Authors: Liu H. M. , Zhu C. X. , Zhu X. P. , Guo X. Q. , Song Y. Z. , Wen F. J.
Published: September 2007

RNA‐mediated virus resistance is one kind of post‐transcriptional gene silencing (PTGS). PTGS can be induced by transgenes or by viral infection that triggers the degradation of RNAs with homology or complementarity to the foreign genes’ transcript or viral RNA. In this study, tobacco plants transformed with untranslatable Potato virus YN (PVYN)‐coated protein (CP) gene were used to examine the correlation between transgene integration patterns and RNA‐mediated resistance more directly. HindIII and EcoRI were used to digest genomic DNAs from progeny T1 transgenic plants with a range of responses to PVYN infection. Southern blot analysis indicated that nearly all of the highly resistant plants contained repeat foreign sequences, including direct repeat (DR) and inverted repeat (IR). Specifically, the highly resistant plants always contained both or one of these constructs, with the majority containing both constructs. Conversely, almost all of the susceptible transgenic plants contained neither construct, though some contained multiply copies. Our results show that transgene integration rather than copy number is the key factor for RNA‐mediated virus resistance. Many researchers identified double‐stranded RNA (dsRNA) as the common link for PTGS triggered by various events. Therefore, we suggest that only transgenes can make dsRNA, by transcription or other pathways, and either repeated constructs (IR or DR) or single copy will induce RNA‐mediated PVYN resistance.
Uveitis associated with immunoglobulin E‐mediated allergic diseases
Authors: Amer Radgonde , Bamonte Giulio , Forrester John V
Published: September 2007

Abstract

Atopic dermatitis and food allergy are typically associated with elevated IgE levels. Ocular involvement in atopic dermatitis is usually limited to the ocular surface and ocular adnexae. We herein report on the unusual association of these two conditions with uveitis in two patients and describe the ocular and systemic outcome following the institution of systemic immunosuppression.
Etanercept associated optic neuropathy
Authors: Chang Vicky , McCurdy Deborah , Gordon Lynn K
Published: September 2007

Abstract

We report the case of a 14‐year‐old boy who developed optic neuropathy subsequent to the use of etanercept. There have been 15 reported cases of anti‐TNF‐α‐associated optic neuropathy to date and their characteristics are reviewed in this report, as well as possible pathophysiologic mechanisms behind such phenomenon. Such cases demonstrate the importance of prompt ophthalmologic evaluation of visual changes in patients being treated with anti‐TNF‐α antagonists.
Langerhans cell histiocytosis of the caruncle
Authors: Kiratli Hayyam , Kocabeyoğlu Sibel , Sağlam Arzu , Söylemezoğlu Figen
Published: September 2007

Abstract

A 37‐year‐old man presented with the complaint of a small non‐tender mass growing steadily on the left caruncle for 3 months. This was a soft, reddish‐yellow tumour, occupying the whole left caruncular area without impinging on the conjunctiva. Histopathological evaluation of the excisional biopsy specimen showed that the tumour was largely composed of Langerhans cells mixed with eosinophils and mature lymphocytes. There were strong CD1a and S‐100 positivity on immunohistochemical studies. Langerhans cell histiocytosis is an exceedingly rare tumour of the caruncle in the adult and this lesion cannot be distinguished from other amelanotic lesions on clinical grounds alone. Simple excision of the lesion provided a 4‐year disease‐free period.
Peripapillary haemorrhagic retinal pigment epithelium detachment following radial optic neurotomy
Authors: Maia Mauricio , Farah Michel E , Aggio Fabio B , Rodrigues Eduardo B , De Souza Eduardo C , Magalhães Octaviano
Published: September 2007

Abstract

Central retinal vein occlusion is a common vascular cause of blidness. In this paper, we first report focal haemorrhagic pigment epithelium detachment and chorioretinal anastomosis in the peripapillary area as an intraoperative complication of radial optic neurotomy (RON). A 65‐year‐old white man presented with ischaemic central vein occlusion OS. He underwent vitrectomy with RON, panretinal photocoagulation and intravitreal injection of triamcinolone acetonide. A circumscribed subretinal haemorrhage was noted intraoperatively at the nasal site of the RON. The haemorrhage size decreased at the seventh postoperative day when an optical coherence tomography scan disclosed a haemorrhagic pigment epithelium detachment. Fluorescein angiography and fundus photograph revealed a chorioretinal anastomosis formation nasal to the optic nerve confirmed by indocyanine green angiography. Best‐correlated visual acuity improved from hand movements to 6/18 at the fourth week and it was stable until last examination. This case illustrates the role of chorioretinal anastomosis formation in the vision improvement following RON.
Anterior clinoid mucocele causing acute monocular blindness
Authors: Thurtell Matthew J , Besser Michael , Halmagyi G Michael
Published: September 2007

Abstract

We report a patient who presented with acute painful monocular visual loss reminiscent of idiopathic optic neuritis. After treatment with corticosteroids was commenced, an anterior clinoid mucocele causing compressive optic neuropathy was demonstrated on imaging studies. The diagnosis was proven histopathologically following excision of the lesion via craniotomy. Although very rare as a cause of optic neuropathy, anterior clinoid mucocele should be excluded by adequately imaging the optic canal, as visual prognosis is poor if surgical decompression is not performed in a timely fashion.
A case of Oguchi's disease with diabetic retinopathy
Authors: Entezari Morteza , Ramezani Alireza , Ghamari Hamid Reza
Published: September 2007

Abstract

A 50‐year‐old Iranian diabetic woman with night blindness was referred to our clinic. Complete ophthalmic examination including ophthalmoscopy after dark adaptation and paraclinic evaluations such as fluorescein angiography and electroretinography were performed. Retinal neovascularization and preretinal haemorrhages compatible with high‐risk characteristic proliferative diabetic retinopathy were observed bilaterally. In addition, a golden‐yellowish discoloration of posterior pole was noted in her both eyes. The diagnosis of Oguchi's disease was made when this discoloration disappeared after dark adaptation for 3 h. Electroretinograms also confirmed the diagnosis by showing a slow negative wave followed by a slow positive wave in the photopic condition and absent a‐ and b‐waves in the scotopic state. We concluded that proliferative diabetic retinopathy might occur in a patient with Oguchi's disease. This report represents this association in an Iranian patient for the first time.
Relationship between the corticostriatal terminals from areas 9 and 46, and those from area 8A, dorsal and rostral premotor cortex and area 24c: an anatomical substrate for cognition to action
Authors: Calzavara Roberta , Mailly Philippe , Haber Suzanne N.
Published: September 2007

Our previous data indicate that there are specific features of the corticostriatal pathways from the prefrontal cortex. First, corticostriatal pathways are composed of focal, circumscribed projections and of diffuse, widespread projections. Second, there is some convergence between terminal fields from different functional regions of the prefrontal cortex. Third, anterior cingulate projections from area 24b occupy a large region of the rostral striatum. The goal of this study was to determine whether these features are also common to the corticostriatal projections from area 8A (including the frontal eye field; FEF), the supplementary eye field (SEF), dorsal and rostral premotor cortex (PMdr) and area 24c. Using a new approach of three‐dimensional reconstruction of the corticostriatal pathways, along with dual cortical tracer injections, we mapped the corticostriatal terminal fields from areas 9 and 46, 8A‐FEF, SEF, PMdr and 24b and c. In addition, we placed injections of retrogradely transported tracers into key striatal regions. The results demonstrated that: (i) a diffuse projection system is a common feature of the corticostriatal projections from different frontal regions; (ii) key striatal regions receive convergent projections from areas 9 and 46 and from areas 8A‐FEF, SEF, PMdr and 24c, suggesting a potential pivotal role of these striatal regions in integrating cortical information; (iii) projections from area 24c, like those from area 24b, terminate widely throughout the striatum, interfacing with terminals from several frontal areas. These features of the corticostriatal frontal pathways suggest a potential integrative striatal network for learning.
Altered kynurenine metabolism correlates with infarct volume in stroke
Authors: Darlington L. G. , Mackay G. M. , Forrest C. M. , Stoy N. , George C. , Stone T. W.
Published: September 2007

Inflammation and oxidative stress are involved in brain damage following stroke, and tryptophan oxidation along the kynurenine pathway contributes to the modulation of oxidative stress partly via the glutamate receptor agonist quinolinic acid and antagonist kynurenic acid, and via redox‐active compounds such as 3‐hydroxyanthranilic acid. We have confirmed that following a stroke, patients show early elevations of plasma neopterin, S100B and peroxidation markers, the latter two correlating with infarct volume assessed from computed tomography (CT) scans, and being consistent with a rapid inflammatory response. We now report that the kynurenine pathway of tryptophan metabolism was also activated, with an increased kynurenine : tryptophan ratio, but with a highly significant decrease in the ratio of 3‐hydroxyanthranilic acid : anthranilic acid, which was strongly correlated with infarct volume. Levels of kynurenic acid were significantly raised in patients who died within 21 days compared with those who survived. The results suggest that increased tryptophan catabolism is initiated before or immediately after a stroke, and is related to the inflammatory response and oxidative stress, with a major change in 3‐hydroxyanthranilic acid levels. Together with previous evidence that inhibiting the kynurenine pathway reduces brain damage in animal models of stroke and cerebral inflammation, and that increased kynurenine metabolism directly promotes oxidative stress, it is proposed that oxidative tryptophan metabolism may contribute to the oxidative stress and brain damage following stroke. Some form of anti‐inflammatory intervention between the rise of S100B and the activation of microglia, including inhibition of the kynurenine pathway, may be valuable in modifying patient morbidity and mortality.
GABAergic synaptogenesis marks the onset of differentiation of basket and stellate cells in mouse cerebellum
Authors: Simat Marija , Ambrosetti Lisa , Lardi‐Studler Barbara , Fritschy Jean‐Marc
Published: September 2007

Type 2 glycine transporter (GlyT2) mediates intracellular glycine transport and is expressed selectively in glycinergic neurons. Expression of GlyT2 gene promoter‐driven enhanced green fluorescent protein (eGFP) in BAC transgenic mice allows selective visualization of glycinergic neurons by fluorescence microscopy. Here, we show that cerebellar interneuron precursors identified by the transcription factor Pax2, including γ‐aminobutyric acid (GABA)ergic interneurons of the molecular layer (ML; basket and stellate cells), transiently express GlyT2‐eGFP during development. In contrast, expression of endogenous GlyT2 is restricted to glycinergic Golgi cells. Comparison with knock‐in mice expressing eGFP in GABAergic neurons [glutamic acid decarboxylase (GAD)67‐eGFP] revealed that GlyT2‐eGFP expression often precedes GAD67‐eGFP and is therefore a marker of immature GABAergic interneurons. In the internal granule cell layer, GABAergic Golgi cells differentiated shortly after birth, prior to glycinergic Golgi cells. In the ML, GlyT2‐eGFP‐positive precursor cells migrated until the boundary with the external granule cell layer, forming an inside‐out maturation gradient that determined the final position of interneurons in the ML. After migration, GlyT2‐eGFP gradually disappeared, while interneurons differentiated morphologically and became immunoreactive for parvalbumin, the GABAA receptor α1 subunit, and the K+Cl– exchanger KCC2 (K+Cl– cotransporter type 2). Numerous presumptive GABAergic synaptic terminals were seen on immature ML interneurons as early as P4, preceding the expression of these neurochemical markers. These results suggest that GABAergic synaptogenesis marks the onset of differentiation of basket and stellate cells in the mouse cerebellum, and that GABAergic synaptic function might contribute to the differentiation of interneurons in the cerebellar cortex.
Relationships between bacterial diversity and environmental variables in a tropical marine environment, Rio de Janeiro
Authors: Vieira Ricardo P. , Gonzalez Alessandra M. , Cardoso Alexander M. , Oliveira Denise N. , Albano Rodolpho M. , Clementino Maysa M. , Martins Orlando B. , Paranhos Rodolfo
Published: September 2007

This study is the first to apply a comparative analysis of environmental chemistry, microbiological parameters and bacterioplankton 16S rRNA clone libraries from different areas of a 50 km transect along a trophic gradient in the tropical Guanabara Bay ecosystem. Higher bacterial diversity was found in the coastal area, whereas lower richness was observed in the more polluted inner bay water. The significance of differences between clone libraries was examined with libshuff statistics. Paired reciprocal comparisons indicated that each of the libraries differs significantly from the others, and this is in agreement with direct interpretation of the phylogenetic tree. Furthermore, correspondence analyses showed that some taxa are related to specific abiotic, trophic and microbiological parameters in Guanabara Bay estuarine system.
Fear of visual loss in patients with diabetes: results of the Prevalence of Diabetic Eye Disease in Tayside, Scotland (P‐DETS) study
Authors: Luckie R. , Leese G. , McAlpine R. , MacEwen C. J. , Baines P. S. , Morris A. D. , Ellis J. D. ,   for the DARTS/MEMO Collaboration
Published: September 2007

Aims  To describe the relationship between fear of visual loss and dependent variables (visual acuity, retinopathy treatment, severity of retinopathy) in community‐based diabetic patients.

Methods  Subjects were identified from the Diabetes Audit and Research in Tayside, Scotland (DARTS) diabetes register. From a total of 4825 individuals known to have diabetes and who were resident in Dundee and Perth (population 216 204; diabetes prevalence 2.23%), 586 persons with diabetes were randomly selected. Participants completed a self‐administered questionnaire in Likert grade format which incorporated two items addressing presence and intensity of fear of visual loss.

Results  Questionnaires were returned by 61.4% of the cohort. Fear of visual loss was ‘often in mind’ for 37% of respondents, and that fear was intense for 47.4%. Analysis by diabetes type revealed differences in reported fear of Type 1 and Type 2 patients in relation to disease and treatment variables. Linear regression highlighted the complexity of the issue with retinal status, acuity and treatment only partly explaining reported patient concern (r2 range: 0.051–0.125 for presence of fear; 0.026–0.04 for intensity of fear, depending on diabetes type).

Conclusions  Fear of visual loss is preoccupying and intense for a substantial proportion of the diabetic population. Reasons for this are multiple and complex. Objective measures of visual impairment and retinal status are inadequate predictors of fear. Carers and researchers need to be mindful of this when approaching patients with diabetes.