bluuebunny/crossref_metadata_2025 huggingface dataset:
Natural Product Hybrids
Authors: Gademann Karl
Published: December 2006

This review highlights several classes of natural product hybrids First, structural hybrids emanating from different biosynthetic pathways exemplified by the polyketide peptide alkaloid anachelin are discussed. Another class is the so-called functional hybrids, where different functions
of natural products are hybridized. The conjugate between nostocarboline and the well-known antibacterial agent ciprofloxacin displays a very broad spectrum of activity combining photosynthesis and gyrase-inhibiting activity. Last, higher order hybrids are discussed. We present the ternary
hybrid of titanium dioxide, the anachelin chromophore and poly-ethyleneglycol (PEG). This chimera allows for the functionalization of Tio2 surfaces to render those protein resistant. This article thus shows how natural products can be hybridized to generate compounds with unprecedented
bioactivity thus enabling the development of novel drugs and advanced materials.
Headspace Solid-Phase Microextraction of Pesticide Residues in Cannabis Samples
Authors: Ilias Yara , Rudaz Serge , Christen Philippe , Veuthey Jean-Luc
Published: December 2006

A headspace solid-phase microextraction method combined with gas chromatography–mass spectrometry was evaluated for the extraction and analysis of selected pesticides, namely alachlor, ?-hexachlorocyclohexane, bromopropylate, carbaryl, diazinon, linuron, polychlorobipheny
l209, permethrine and simazinein cannabis samples. Usinga 100 ?m PDMS fibre, compounds were directly extracted in the headspace mode at 150 °C for 5 min and desorption was performed in the GC injector in the splitless mode at 280 °C for 3 min. Pesticide analysis was achieved
and method repeatability, given as the coefficient of variation, ranged between 2.4% for bromopropylate and 12.6% for linuron. The limits of detection obtained using single ion monitoring (SIM) were between 0.014 and 0.83 mg/kg, depending on the pesticide.
Automated Auto-Ignition Temperature Measurement with Optical Flame Detection
Authors: Schulz Pierre , Dimitrov Anne , Mermillon Béatrice , Smitha Alexander , Ferregutti Franco , De Mestral Federico , Rodriguez Domingo
Published: December 2006

An automated auto-ignition installation in accordance with the safety standards described in DIN 51 794 and CENELEC EN 50014 CLC detecting the appearance of a flame and the controlling testing program using LabVIEW software package were developed and tested. The results obtained are
reproducible. Its main advantage is time-saving.
Geoarchaeology and late glacial landscapes in the western lake superior region, Central North America
Authors: Hill Christopher L.
Published: December 2006

The transition from full glacial to interglacial conditions along the southern margin of the Laurentide ice sheet resulted in dramatic changes in landscapes and biotic habitats. Strata and landforms resulting from the Wisconsin Episode of glaciation in the area directly west of Lake Superior indicate a context for late Pleistocene biota (including human populations) connected to ice margins, proglacial lakes, and postglacial drainage systems. Late Glacial landscape features that have the potential for revealing the presence of Paleoindian artifacts include abandoned shorelines of proglacial lakes in the Superior and Agassiz basins and interior drainages on deglaciated terrains. The linkage between Late Pleistocene human populations and Rancholabrean fauna has yet to be demonstrated in the western Lake Superior region, although isolated remains of mammoth ( Mammuthus) have been documented, as well as fluted points assigned to Clovis, Folsom, and Holcombe‐like artifact forms. Agate Basin and Hell Gap (Plano‐type) artifacts also imply the presence of human groups in Late Glacial landscapes associated with the Agassiz and Superior basins.© 2007 Wiley Periodicals, Inc.
A primer on fiscal sponsorship
Authors: Wyland Michael L.
Published: December 2006

Fiscal Sponsorship: Six Ways to Do It Right, 2nd ed., by Gregory L. Colvin. San Francisco: Study Center Press, 2006. 120 pp., $29.95 cloth, $19.95 paper.
Severe endothelial dysfunction in the aorta of a mouse model of Fabry disease; partial prevention by N‐butyldeoxynojirimycin treatment
Authors: Heare T. , Alp N. J. , Priestman D. A. , Kulkarni A. B. , Qasba P. , Butters T. D. , Dwek R. A. , Clarke K. , Channon K. M. , Platt F. M.
Published: December 2006

Objective: Fabry disease results from α‐gala‐ ctosidase A deficiency and is characterized by the lysosomal accumulation of globotriaosylceramide. Globotriaosylceramide storage predominantly affects endothelial cells, altering vascular wall morphology and vasomotor function. Our objective was to investigate aortic globotriaosylceramide levels, morphology and function in a mouse model of Fabry disease, and the effect of substrate reduction therapy, using the glycosphingolipid biosynthesis inhibitor N‐butyldeoxynojirimycin. Methods and results: Mice used were C57BL/6J and α‐galactosidase A knockout (Fabry). We show progressive accumulation of aortic globotriaosylceramide throughout the lifespan of untreated Fabry mice (55‐fold elevation at 2 months increasing to 187‐fold by 19 months), localized to endothelial and vascular smooth‐muscle cells; there was no effect on vascular wall morphology in young Fabry mice. In old mice, storage resulted in intimal thickening. Endothelial function declined with age in Fabry mouse aorta. Aortae from N‐butyldeoxynojirimycin‐treated Fabry mice at 19 months of age had reduced endothelial globotriaosylceramide storage, fewer morphological abnormalities and less severe vasomotor dysfunction compared with untreated littermates. Conclusion: We provide evidence of a novel vascular phenotype in the Fabry mouse that has relevance to vascular disease in Fabry patients. N‐Butyldeoxynojirimycin treatment partially prevented the phenotype in the Fabry mouse by reducing endothelial globotriaosylceramide storage.
Angiopoietin‐1 for myocardial angiogenesis: A comparison between delivery strategies
Authors: Ye Lei , Haider Husnain Kh , Jiang Shujia , Tan Ru San , Toh Wee Chi , Ge RuoWen , Sim Eugene K.W.
Published: December 2006

We compare the effectiveness of direct adenoviral angiopoietin‐1 (Ad‐Ang‐1) injection with transplantation of skeletal myoblasts (SkMs) over‐expressing angiopoietin‐1 (Ang‐1) for angiogenic response and improvement of heart function in an experimental porcine model of myocardial infarction (MI).

Methods

Ad‐Ang‐1 was used for intramyocardial injection or transduction of SkMs. Three weeks after coronary artery ligation in 32 female pigs, animals were grouped to receive multiple intramyocardial injections of DMEM without cells (group‐1; n=7), or containing 3∑108 Lac‐z labelled SkMs transduced with Ad‐Null vector carrying no gene (group‐2; n=7), or 1∑1010 PFU Ad‐Ang‐1 (group‐3; n=9), or 3∑108 Lac‐z labelled SkMs transduced with Ad‐Ang‐1 (group‐4; n=9). The animals were immunosuppressed for 6‐weeks. After euthanasia, their heart tissue was processed for histological studies.

Results

Extensive survival of Lac‐z positive SkMs was observed in and around the infarct 6 and 12‐weeks after transplantation. Fluorescent immunostaining for vWF‐VIII at 6‐weeks revealed increased blood vessel density (∑100) in group‐4 (p<0.05) as compared with other groups. Regional blood flow (ml/g/min) in the peri‐infarct area was improved in group‐4 (2.7; p<0.05) as compared with group‐1 (1.2±0.1), group‐2 (1.1±0.4) and group‐3 (1.7±0.1) at 6‐weeks. Similarly, ejection fraction was significantly higher in group‐4 (49.2±5.9%, p=0.03) as compared with group‐1 (36.8±3%) at 6 weeks.

Conclusion

SkMs mediated Ang‐1 delivery is associated with improved angiogenic response, regional myocardial perfusion and heart function as compared with direct Ad‐Ang‐1 administration.
Using the Schedules for Clinical Assessment in Neuropsychiatry (SCAN 2.1) as a diagnostic interview providing dimensional measures: Cross-national findings on the psychometric properties of psychopathology scales
Authors: Schützwohl Matthias , Kallert Thomas , Jurjanz Luisa
Published: December 2006

Background

The Schedules for Clinical Assessment in Neuropsychiatry (SCAN) is a set of clinical assessment instruments developed under the auspices of WHO. In contrast to other structured diagnostic interviews, SCAN also provides possibilities for dimensional assessment of psychopathology. This paper reports cross-national findings on the psychometric properties of psychopathology scales derived from SCAN 2.1.

Methods

Within a randomized controlled trial, SCAN 2.1 was used in Dresden (Germany), Michalovce (Slovak Republic), Prague (Czech Republic), and Wrocław (Poland). Forty-seven items from Part I of SCAN 2.1, identified as qualifying for constructing dimensional measures, were, on the one hand, grouped according to their allocation to five specific SCAN 2.1 sections. On the other hand, principal component analyses were used to group the items according to their statistical relationship. To estimate the reliability of the scales, Cronbach's α was computed. To assess factor similarity across sites, Tucker's congruence coefficients were calculated. To appraise concurrent validity, mean scale scores were compared across different diagnostic groups.

Results

Reliability was qualified as moderate to substantial for all generated scales. Factor-solutions differed across sites. Differences in mean scores supported the assumption that the scales might possess, in addition to face validity, concurrent validity.

Conclusions

This is the first cross-national study on the psychometric properties of psychopathology scales derived from SCAN 2.1, and findings are very encouraging concerning its use as a dimensional measure. However, further studies are needed to substantiate implementation of the scales established.
Clusters of eclampsia in a Nigerian teaching hospital
Authors: Ekele B.A. , Bello S.O. , Adamu A.N.
Published: December 2006

Objective: To describe the pattern of eclampsia between 1995 and 2004 at the Usmanu Danfodiyo University Teaching Hospital, Sokoto, northwestern Nigeria. Study design: A retrospective cohort of all deliveries and eclamptics seen from 1st January 1995 to 31st December 2004. Clusters of eclampsia were identified using purely temporal scan statistics. Results: Of 15,318 deliveries during the period, 657(4.29%) had eclampsia. The yearly incidence of eclampsia at the beginning of the study period (1995) was 0.39% but this had increased to 7.0% in 2004 at a background exponential rate best described by quadratic curve fitting prediction model and a forecast curve that predicts an incidence of eclampsia of at least 32.4% of total deliveries by 2009. Temporal clusters occurred in 1996, 2001 and 2003–2004. Conclusion: The incidence of eclampsia is unusually high and is increasing. It has shown 3 clusters in the last 10 years.
A Window into Biocatalysis and Biotransformations
Authors: Coward‐Kelly Guillermo , Chen Rachel Ruizhen
Published: December 2006

Eight papers were presented in this yearapos;s symposium “Advances in Biocatalysis” at the 232nd ACS National Meeting, accentuating the most recent development in biocatalysis. Researchers from both industry and academia are addressing several fundamental problems in biocatalysis, including the limited number of commercially available enzymes that can be provided in bulk quantities, the limited enzyme stability and activity in nonaqueous environments, and the permeability issue and cell localization problems in whole‐cell systems. A trend that can be discerned from these eight talks is the infusion of new tools and technologies in addressing various challenges facing biocatalysis. Nanotechnology, bioinformatics, cellular membrane engineering and metabolic engineering (for engineering whole‐cell catalysts), and protein engineering (to improve enzymes and create novel enzymes) are becoming more routinely used in research laboratories and are providing satisfactory solutions to the problems in biocatalysis. Significant progress in various aspects of biocatalysis from discovery to industrial applications was highlighted in this symposium.
Coupling characteristics of surface modes in truncated two-dimensional photonic crystals
Authors: Choi Hyoung-Gyu , Oh Sang Soon , Lee Sun-Gu , Kim Myeong-Woo , Kim Jae-Eun , Park Hae Yong , Kee Chul-Sik
Published: December 2006

We investigate the coupling properties of localized modes between two identical truncated triangular photonic crystals composed of air holes in a dielectric background. The frequency of even parity modes varies more sensitively to the distance between the truncated faces of the crystals; i.e., the coupling distance. This behavior is explained in terms of photonic bands and spatial distribution of fields. This localized mode with even parity is shown to be a good guided mode from the finite-difference time-domain simulation. The guided range can be tuned by varying the coupling distance and the degree of truncation.
Dependences of Young’s modulus of porous silica low dielectric constant films on skeletal structure and porosity
Authors: Takada Syozo , Hata Nobuhiro , Seino Yutaka , Fujii Nobutoshi , Kikkawa Takamaro
Published: December 2006

Porous silica films were prepared by spin coating the mixtures of acidic silica sol and nonionic surfactant template. The (a) porosity and (b) skeletal structure of the films were varied by adjusting the (a) template concentration and the (b) annealing temperature, respectively. Fourier transform infrared spectroscopic ellipsometry was employed to evaluate the skeletal silica structure of the films. The analysis was focused on the midinfrared (1000–1300cm−1) spectral structure which is assigned as the asymmetric stretching vibration mode of Si–O–Si bonds [Kamitsos et al., Phys. Rev. B 48, 12499 (1993)]. The spectral structure depended on both porosity and chemical bonding structure. Bruggemann’s effective medium theory was employed to obtain the spectrum of “skeletal” silica from that of “porous” silica. The skeletal silica structure was then discussed in terms of the peak positions of the transverse optical (ωTO) and longitudinal optical (ωLO) vibration modes of Si–O–Si network. It was shown that the Young’s elastic modulus of skeletal silica correlates well with ωLO2∕ωTO2. We have obtained good correlations between ωLO2∕ωTO2 of skeletal silica and elastic modulus E for two series of porous silica films with around 55% and 40% porosity. The experimental results show that the structural change in silica skeleton strongly affects the mechanical properties of porous silica low-k films.
Quantal cumulant dynamics: General theory
Authors: Shigeta Yasuteru , Miyachi Hideaki , Hirao Kimihiko
Published: December 2006

The authors have derived coupled equations of motion of cumulants that consist of a symmetric-ordered product of the position and momentum fluctuation operators in one dimension. The key point is the utilization of a position shift operator acting on a potential operator, where the expectation value of the shift operator is evaluated using the cumulant expansion technique. In particular, the equations of motion of the second-order cumulant and the expectation values of the position and momentum operators are given. The resultant equations are expressed by those variables and a quantal potential that consists of an exponential function of the differential operators and the original potential. This procedure enables us to perform quantal (semiclassical) dynamics in one dimension. In contrast to a second-order quantized Hamilton dynamics by Prezhdo and Pereverzev which conserves the total energy only with an odd-order Taylor expansion of the potential [J. Chem. Phys. 116, 4450 (2002); 117, 2995 (2002)], the present quantal cumulant dynamics method exactly conserves the energy, even if a second-order approximation of the cumulants is adopted, because the present scheme does not truncate the given potential. The authors propose three schemes, (i) a truncation, (ii) a summation of derivatives, and (iii) a convolution method, for evaluating the quantal potentials for several types of potentials. The numerical results show that although the truncation method preserves the energy to some degree, the trajectory obtained gradually deviates from that of the summation scheme after 2000 steps. The phase space structure obtained by the truncation scheme is also different from that of the summation scheme in a strongly anharmonic region.
The discovery of transcriptional modules by a two-stage matrix decomposition approach
Authors: Li Huai , Sun Yu , Zhan Ming
Published: December 2006

Motivation: We address the problem of identifying gene transcriptional modules from gene expression data by proposing a new approach. Genes mostly interact with each other to form transcriptional modules for context-specific cellular activities or functions. Unraveling such transcriptional modules is important for understanding biological network, deciphering regulatory mechanisms and identifying biomarkers.

Method: The proposed algorithm is based on two-stage matrix decomposition. We first model microarray data as non-linear mixtures and adopt the non-linear independent component analysis to reduce the non-linear distortion and separate the data into independent latent components. We then apply the probabilistic sparse matrix decomposition approach to model the ‘hidden’ expression profiles of genes across the independent latent components as linear weighted combinations of a small number of transcriptional regulator profiles. Finally, we propose a general scheme for identifying gene modules from the outcomes of the matrix decomposition.

Results: The proposed algorithm partitions genes into non-mutually exclusive transcriptional modules, independent from expression profile similarity measurement. The modules contain genes with not only similar but different expression patterns, and show the highest enrichment of biological functions in comparison with those by other methods. The usefulness of the algorithm was validated by a yeast microarray data analysis.

Availability: The software is available upon request to the authors.

Contact:  zhanmi@mail.nih.gov
Learning influences host choice in tsetse
Authors: Bouyer Jérémy , Pruvot Mathieu , Bengaly Zacharia , Guerin Patrick M , Lancelot Renaud
Published: December 2006

A learning capacity for feeding is described in many insect species including vectors of diseases, but has never been reported in tsetse flies (Diptera, Glossinidae), the cyclic vectors of human (sleeping sickness) and animal trypanosomoses in Africa. Repeated feeding on the same host species by a disease vector is likely to increase the within-species disease-transmission risk, but to decrease it between species.

An experiment with cattle and reptiles in a stable provides evidence that the species of host selected for the second blood meal in tsetse flies depends on the host encountered for the first blood meal when the between-meal interval is 2 days. This preference disappears when the between-meal interval is extended to 3 days. The energetic advantages of this acquired preference and its importance in trypanosomoses epidemiology are discussed.
Mycobacterium bovisshedding patterns from experimentally infected calves and the effect of concurrent infection with bovine viral diarrhoea virus
Authors: Kao R.R , Gravenor M.B , Charleston B , Hope J.C , Martin M , Howard C.J
Published: December 2006

Concurrent infection of cattle with bovine viral diarrhoea virus (BVDV) andMycobacterium bovisis considered to be a possible risk factor for onward transmission of bovine tuberculosis (BTB) in infected cattle and is known to compromise diagnostic tests. A comparison is made here ofM. bovisshedding (i.e. release) characteristics from 12 calves, six experimentally co-infected with BVDV and six infected withM. bovisalone, using simple models of bacterial replication. These statistical and mathematical models account for the intermittent or episodic nature of shedding, the dynamics of within-host bacterial proliferation and the sampling distribution from a given shedding episode. We show that while there are distinct differences among the shedding patterns of calves given the same infecting dose, there is no statistically significant difference between the two groups of calves. Such differences as there are, can be explained solely in terms of the shedding frequency, but with all calves potentially excreting the same amount of bacteria in a given shedding episode post-infection. The model can be thought of as a process of the bacteria becoming established in a number of discrete foci of colonization, rather than as a more generalized infection of the respiratory tract. In this case, the variability in the shedding patterns of the infected calves can be explained solely by differences in the number of foci established and shedding being from individual foci over time. Should maximum exposure on a particular occasion be a critical consideration for cattle-to-cattle transmission of BTB, cattle that shed only intermittently may still make an important contribution to the spread and persistence of the disease.
Stochastic amplification in epidemics
Authors: Alonso David , McKane Alan J , Pascual Mercedes
Published: December 2006

The role of stochasticity and its interplay with nonlinearity are central current issues in studies of the complex population patterns observed in nature, including the pronounced oscillations of wildlife and infectious diseases. The dynamics of childhood diseases have provided influential case studies to develop and test mathematical models with practical application to epidemiology, but are also of general relevance to the central question of whether simple nonlinear systems can explain and predict the complex temporal and spatial patterns observed in nature outside laboratory conditions. Here, we present a stochastic theory for the major dynamical transitions in epidemics from regular to irregular cycles, which relies on the discrete nature of disease transmission and low spatial coupling. The full spectrum of stochastic fluctuations is derived analytically to show how the amplification of noise varies across these transitions. The changes in noise amplification and coherence appear robust to seasonal forcing, questioning the role of seasonality and its interplay with deterministic components of epidemiological models. Childhood diseases are shown to fall into regions of parameter space of high noise amplification. This type of ‘endogenous’ stochastic resonance may be relevant to population oscillations in nonlinear ecological systems in general.
Warm water occupancy by North Sea cod
Authors: Neat Francis , Righton David
Published: December 2006

The North Sea has warmed in recent years and there is an ongoing debate into how this is affecting the distribution of fishes and other marine organisms. Of particular interest is the commercially important Atlantic cod (
Gadus morhua
L.), which has declined sharply in abundance in the North Sea over the past 20 years. Observations of the temperature experienced by 129 individual cod throughout the North Sea were made during a large-scale electronic tagging programme conducted between 1999 and 2005. We asked whether individual cod fully occupied the thermal habitat available to them. To this end, we compared the temperature experience of cod with independently measured contemporaneous sea-bottom temperature data. The majority of cod experienced a warmer fraction of the sea than was potentially available to them. By summer, most of the individuals in the south experienced temperatures considered superoptimal for growth. Cooler waters were within the reach of the cod and a small number of individuals migrated to areas that allowed them to experience lower temperatures, indicating that the cod had the capacity to find cooler water. Most did not, however, suggesting that the changing thermal regime of the North Sea is not yet causing adult cod to move to cooler waters.
Individuals from different-looking animal species may group together to confuse shared predators: simulations with artificial neural networks
Authors: Tosh Colin R , Jackson Andrew L , Ruxton Graeme D
Published: December 2006

Individuals of many quite distantly related animal species find each other attractive and stay together for long periods in groups. We present a mechanism for mixed-species grouping in which individuals from different-looking prey species come together because the appearance of the mixed-species group is visually confusing to shared predators. Using an artificial neural network model of retinotopic mapping in predators, we train networks on random projections of single- and mixed-species prey groups and then test the ability of networks to reconstruct individual prey items from mixed-species groups in a retinotopic map. Over the majority of parameter space, cryptic prey items benefit from association with conspicuous prey because this particular visual combination worsens predator targeting of cryptic individuals. However, this benefit is not mutual as conspicuous prey tends to be targeted most poorly when in same-species groups. Many real mixed-species groups show the asymmetry in willingness to initiate and maintain the relationship predicted by our study. The agreement of model predictions with published empirical work, the efficacy of our modelling approach in previous studies, and the taxonomic ubiquity of retinotopic maps indicate that we may have uncovered an important, generic selective agent in the evolution of mixed-species grouping.
Response of pollen diversity to the climate-driven altitudinal shift of vegetation in the Colombian Andes
Authors: Weng Chengyu , Hooghiemstra Henry , Duivenvoorden Joost F
Published: December 2006

Change in diversity of fossil pollen through time is used as a surrogate for biodiversity history. However, there have been few studies to explore the sensitivity of the measured pollen diversity to vegetation changes and the relationship between pollen diversity and plant diversity. This paper presents results of a study to assess the relationship between pollen diversity and relative abundance of pollen from different altitudinal vegetation belts (subandean forest, Andean forest, subparamo and grassparamo) in three records from the tropical Andes in Colombia. The results indicated that plant diversity in the vegetation declined with altitude and pollen diversity is positively correlated to the abundance of pollen from lower altitude vegetation belts and negatively correlated to that from the grassparamo. These results, therefore, suggest that pollen diversity coarsely reflects the diversity of the surrounding vegetation. Using this interpretation, we were able to predict changes in plant diversity over the past 430 000 years in the Colombian Andes. Results indicated that under warmer climatic conditions, more species-diverse vegetation of low elevation moved upslope to contribute more pollen diversity to the study sites, and under colder conditions, species-poor grassparamo moved downslope and observed pollen diversity was lower. This study concludes that fossil pollen diversity may provide an important proxy to reconstruct the temporal changes in plant diversity.
Xylella fastidiosa Infection and Ethylene Exposure Result in Xylem and Water Movement Disruption in Grapevine Shoots
Authors: Pérez-Donoso Alonso G. , Greve L. Carl , Walton Jeffrey H. , Shackel Ken A. , Labavitch John M.
Published: December 2006

It is conventionally thought that multiplication of the xylem-limited bacterium Xylella fastidiosa (Xf) within xylem vessels is the sole factor responsible for the blockage of water movement in grapevines (Vitis vinifera) affected by Pierce's disease. However, results from our studies have provided substantial support for the idea that vessel obstructions, and likely other aspects of the Pierce's disease syndrome, result from the grapevine's active responses to the presence of Xf, rather than to the direct action of the bacterium. The use of magnetic resonance imaging (MRI) to observe the distribution of water within the xylem has allowed us to follow nondestructively the development of vascular system obstructions subsequent to inoculation of grapevines with Xf. Because we have hypothesized a role for ethylene produced in vines following infection, the impact of vine ethylene exposure on obstruction development was also followed using MRI. In both infected and ethylene-exposed plants, MRI shows that an important proportion of the xylem vessels become progressively air embolized after the treatments. The loss of xylem water-transporting function, assessed by MRI, has been also correlated with a decrease in stem-specific hydraulic conductivity (K  S) and the presence of tyloses in the lumens of obstructed water conduits. We have observed that the ethylene production of leaves from infected grapevines is greater than that from healthy vines and, therefore, propose that ethylene may be involved in a series of cellular events that coordinates the vine's response to the pathogen.
Arabidopsis Transcriptome Changes in Response to Phloem-Feeding Silverleaf Whitefly Nymphs. Similarities and Distinctions in Responses to Aphids
Authors: Kempema Louisa A. , Cui Xinping , Holzer Frances M. , Walling Linda L.
Published: December 2006

Phloem-feeding pests cause extensive crop damage throughout the world, yet little is understood about how plants perceive and defend themselves from these threats. The silverleaf whitefly (SLWF; Bemisia tabaci type B) is a good model for studying phloem-feeding insect-plant interactions, as SLWF nymphs cause little wounding and have a long, continuous interaction with the plant. Using the Affymetrix ATH1 GeneChip to monitor the Arabidopsis (Arabidopsis thaliana) transcriptome, 700 transcripts were found to be up-regulated and 556 down-regulated by SLWF nymphs. Closer examination of the regulation of secondary metabolite (glucosinolate) and defense pathway genes after SLWF-instar feeding shows that responses were qualitatively and quantitatively different from chewing insects and aphids. In addition to the RNA profile distinctions, analysis of SLWF performance on wild-type and phytoalexin-deficient4 (pad4) mutants suggests aphid and SLWF interactions with Arabidopsis were distinct. While pad4-1 mutants were more susceptible to aphids, SLWF development on pad4-1 and wild-type plants was similar. Furthermore, although jasmonic acid genes were repressed and salicylic acid-regulated genes were induced after SLWF feeding, cytological staining of SLWF-infested tissue showed that pathogen defenses, such as localized cell death and hydrogen peroxide accumulation, were not observed. Like aphid and fungal pathogens, callose synthase gene RNAs accumulated and callose deposition was observed in SLWF-infested tissue. These results provide a more comprehensive understanding of phloem-feeding insect-plant interactions and distinguish SLWF global responses.
MPB2C, a Microtubule-Associated Plant Factor, Is Required for Microtubular Accumulation of Tobacco Mosaic Virus Movement Protein in Plants
Authors: Curin Mirela , Ojangu Eve-Ly , Trutnyeva Kateryna , Ilau Birger , Truve Erkki , Waigmann Elisabeth
Published: December 2006

Movement protein binding 2C (MPB2C) is a plant endogenous microtubule-associated protein previously identified as an interaction partner of tobacco (Nicotiana tabacum) mosaic virus movement protein (TMV-MP). In this work, the role of MPB2C in cell-to-cell transport of TMV-MP, viral spread of TMV, and subcellular localization of TMV-MP was examined. To this end, plants with reduced MPB2C levels were generated by a gene-silencing strategy. Local and systemic spread of TMV and cell-to-cell movement of TMV-MP were unimpaired in MPB2C-silenced plants as compared to nonsilenced plants, indicating that MPB2C is not required for intercellular transport of TMV-MP itself or spread of TMV. However, a clear change in subcellular distribution of TMV-MP characterized by a nearly complete loss of microtubular localization was observed in MPB2C-silenced plants. This result shows that the MPB2C is a central player in determining the complex subcellular localization of TMV-MP, in particular its microtubular accumulation, a phenomenon that has been frequently observed and whose role is still under discussion. Clearly, MPB2C mediated accumulation of TMV-MP at microtubules is not required for intercellular spread but may be a means to withdraw the TMV-MP from the cell-to-cell transport pathway.
Desiccation and Zinc Binding Induce Transition of Tomato Abscisic Acid Stress Ripening 1, a Water Stress- and Salt Stress-Regulated Plant-Specific Protein, from Unfolded to Folded State
Authors: Goldgur Yehuda , Rom Slava , Ghirlando Rodolfo , Shkolnik Doron , Shadrin Natalia , Konrad Zvia , Bar-Zvi Dudy
Published: December 2006

Abscisic acid stress ripening 1 (ASR1) is a low molecular weight plant-specific protein encoded by an abiotic stress-regulated gene. Overexpression of ASR1 in transgenic plants increases their salt tolerance. The ASR1 protein possesses a zinc-dependent DNA-binding activity. The DNA-binding site was mapped to the central part of the polypeptide using truncated forms of the protein. Two additional zinc-binding sites were shown to be localized at the amino terminus of the polypeptide. ASR1 protein is presumed to be an intrinsically unstructured protein using a number of prediction algorithms. The degree of order of ASR1 was determined experimentally using nontagged recombinant protein expressed in Escherichia coli and purified to homogeneity. Purified ASR1 was shown to be unfolded using dynamic light scattering, gel filtration, microcalorimetry, circular dichroism, and Fourier transform infrared spectrometry. The protein was shown to be monomeric by analytical ultracentrifugation. Addition of zinc ions resulted in a global change in ASR1 structure from monomer to homodimer. Upon binding of zinc ions, the protein becomes ordered as shown by Fourier transform infrared spectrometry and microcalorimetry, concomitant with dimerization. Tomato (Solanum lycopersicum) leaf soluble ASR1 is unstructured in the absence of added zinc and gains structure upon binding of the metal ion. The effect of zinc binding on ASR1 folding and dimerization is discussed.
A Multidrug Resistance Transporter in Magnaporthe Is Required for Host Penetration and for Survival during Oxidative Stress
Authors: Sun Chuan Bao , Suresh Angayarkanni , Deng Yi Zhen , Naqvi Naweed I.
Published: December 2006

In prokaryotes and eukaryotes, multidrug resistance (MDR) transporters use energy-dependent efflux action to regulate the intracellular levels of antibiotic or xenobiotic compounds. Using mutational analysis of ABC3, we define an important role for such MDR-based efflux during the host penetration step of Magnaporthe grisea pathogenesis. Mutants lacking ABC3 were completely nonpathogenic but were surprisingly capable of penetrating thin cellophane membranes to some extent. The inability of abc3Δ to penetrate the host surface was most likely a consequence of excessive buildup of peroxide and accumulation of an inhibitory metabolite(s) within the mutant appressoria. Treatment with antioxidants partially suppressed the host penetration defects in the abc3Δ mutant. abc3Δ was highly sensitive to oxidative stress and was unable to survive the host environment and invasive growth conditions. ABC3 transcript levels were redox-regulated, and on host surfaces, the activation of ABC3 occurred during initial stages of blast disease establishment. An Abc3-green fluorescent protein fusion localized to the plasma membrane in early appressoria (and in penetration hyphae) but became predominantly vacuolar during appressorial maturity. We propose that ABC3 function helps Magnaporthe to cope with cytotoxicity and oxidative stress within the appressoria during early stages of infection-related morphogenesis and likely imparts defense against certain antagonistic and xenobiotic conditions encountered during pathogenic development.
Defects in CTP:PHOSPHORYLETHANOLAMINE CYTIDYLYLTRANSFERASE Affect Embryonic and Postembryonic Development in Arabidopsis
Authors: Mizoi Junya , Nakamura Masanobu , Nishida Ikuo
Published: December 2006

A TILLING strategy (for targeting-induced local-scale lesions in genomes) was used in Arabidopsis thaliana to isolate mutants of a gene encoding CTP:PHOSPHORYLETHANOLAMINE CYTIDYLYLTRANSFERASE (PECT; EC 2.7.7.14), a rate-limiting enzyme in phosphatidylethanolamine biosynthesis. A null mutation, pect1-6, caused embryo abortion before the octant stage. However, reciprocal crosses revealed that pect1-6 caused no significant gametophytic defect. In pect1-4, PECT activity was decreased by 74%. Growth was generally normal in these mutants, despite delays in embryo maturation and reduced fertility. At low temperatures, however, homozygotic pect1-4 plants displayed dwarfism. PECT activity was decreased by 47% in heterozygotic pect1-6 plants and by 80% in pect1-4/pect1-6 F1 plants, which also displayed a small but significant decrease of phosphatidylethanolamine and a reciprocal increase in phosphatidylcholine. These lipid changes were fully reversed by wild-type PECT1 expression. pect1-4/pect1-6 F1 plants displayed severe dwarfism, tissue abnormalities, and low fertility, which was attributable in part to inhibition of anther, embryo, and ovule development, as was the reduced fertility of pect1-4 seedlings. PECT1 cDNA expression under the control of an inducible promoter partially rectified the mutant phenotypes observed in pect1-4/pect1-6 F1 seedlings, indicating that malfunctions in different tissues have a synergistic effect on the mutant phenotypes.
Dynamics of a Mobile RNA of Potato Involved in a Long-Distance Signaling Pathway
Authors: Banerjee Anjan K. , Chatterjee Mithu , Yu Yueyue , Suh Sang-Gon , Miller W. Allen , Hannapel David J.
Published: December 2006

BEL1-like transcription factors interact with Knotted1 types to regulate numerous developmental processes. In potato (Solanum tuberosum), the BEL1 transcription factor St BEL5 and its protein partner POTH1 regulate tuber formation by mediating hormone levels in the stolon tip. The accumulation of St BEL5 RNA increases in response to short-day photoperiods, inductive for tuber formation. RNA detection methods and heterografting experiments demonstrate that BEL5 transcripts are present in phloem cells and move across a graft union to localize in stolon tips, the site of tuber induction. This movement of RNA to stolon tips is correlated with enhanced tuber production. Overexpression of BEL5 transcripts that include the untranslated sequences of the BEL5 transcript endows transgenic lines with the capacity to overcome the inhibitory effects of long days on tuber formation. Addition of the untranslated regions leads to preferential accumulation of the BEL5 RNA in stolon tips under short-day conditions. Using a leaf-specific promoter, the movement of BEL5 RNA to stolon tips was facilitated by a short-day photoperiod, and this movement was correlated with enhanced tuber production. These results implicate the transcripts of St BEL5 in a long-distance signaling pathway that are delivered to the target organ via the phloem stream.
C‐terminal loop of Streptomyces phospholipase D has multiple functional roles
Authors: Uesugi Yoshiko , Arima Jiro , Iwabuchi Masaki , Hatanaka Tadashi
Published: December 2006

We have recently shown that two flexible loops of Streptomyces phospholipase D (PLD) affect the catalytic reaction of the enzyme by a comparative study of chimeric PLDs. Gly188 and Asp191 of PLD from Streptomyces septatus TH‐2 (TH‐2PLD) were identified as the key amino acid residues involved in the recognition of phospholipids. In the present study, we further investigated the relationship between a C‐terminal loop of TH‐2PLD and PLD activities to elucidate the reaction mechanism and the recognition of the substrate. By analyzing chimeras and mutants in terms of hydrolytic and transphosphatidylation activities, Ala426 and Lys438 of TH‐2PLD were identified as the residues associated with the activities. We found that Gly188 and Asp191 recognized substrate forms, whereas residues Ala426 and Lys438 enhanced transphosphatidylation and hydrolysis activities regardless of the substrate form. By substituting Ala426 and Lys438 with Phe and His, respectively, the mutant showed not only higher activities but also higher thermostability and tolerance against organic solvents. Furthermore, the mutant also improved the selectivity of the transphosphatidylation activity. The residues Ala426 and Lys438 were located in the C‐terminal flexible loop of Streptomyces PLD separate from the highly conserved catalytic HxKxxxxD motifs. We demonstrated that this C‐terminal loop, which formed the entrance of the active well, has multiple functional roles in Streptomyces PLD.
Crystal structure of the BTB domain from the LRF/ZBTB7 transcriptional regulator
Authors: Stogios Peter J. , Chen Lu , Privé Gilbert G.
Published: December 2006

BTB‐zinc finger (BTB‐ZF) proteins are transcription regulators with roles in development, differentiation, and oncogenesis. In these proteins, the BTB domain (also known as the POZ domain) is a protein–protein interaction motif that contains a dimerization interface, a possible oligomerization surface, and surfaces for interactions with other factors, including nuclear co‐repressors and histone deacetylases. The BTB‐ZF protein LRF (also known as ZBTB7, FBI‐1, OCZF, and Pokemon) is a master regulator of oncogenesis, and represses the transcription of a variety of important genes, including the ARF, c‐fos, and c‐myc oncogenes and extracellular matrix genes. We determined the crystal structure of the BTB domain from human LRF to 2.1 Å and observed the canonical BTB homodimer fold. However, novel features are apparent on the surface of the homodimer, including differences in the lateral groove and charged pocket regions. The residues that line the lateral groove have little similarity with the equivalent residues from the BCL6 BTB domain, and we show that the 17‐residue BCL6 Binding Domain (BBD) from the SMRT co‐repressor does not bind to the LRF BTB domain.
Physical State of Cellulose During Ripening of Peach
Authors: STERLING CLARENCE
Published: December 2006

Cell walls of ripening fruits of peach were purified of a large part of their non‐cellulosic components and examined with X‐ray techniques. Small, but distinct, increases in micellar size, and perhaps in percentages of crystallinity, are a function of the maturation process. These increases are interpreted as evidence of a limited degradation of cellulose (broadly defined).
The Xanthophylls of Tomatoes
Authors: CURL A. LAURENCE
Published: December 2006

The carotenoids of ripe tomatoes were found to contain about 6% xanthophylls; the composition of the latter was about 15% monols, 49% diols, 4% monoepoxide diols, 22% diepoxide diols, and 11% polyols. The diol and polyol xanthophylls were much like those of green leaves, with lutein the major pigment, somewhat smaller amounts of violaxanthin and neoxanthin, and much smaller amounts of zeaxanthin, lutein 5,6‐epoxide, and several others.

The monol fraction contained lycoxanthin and “monol 487” (which may be 3‐hydroxy‐delta‐carotene), together with substances tentatively identified as polycis isomers of lycoxanthin, rubixanthin, and “monol 487.”
Relative Efficiency of Paired Comparisons and Rank Order in Preference Discrimination among Coffees
Authors: GIRARDOT N. F. , PERYAM D. R. , LOCKHART E. E.
Published: December 2006

SUMMARY: Four samples of instant coffee, which varied only in str̀ength, were preference tested by 1152 coffee drinkers by three different methods. Half tested by paired comparisons with two pairs served, one‐third used 3‐sample rank order and one‐sixth used 4‐sample rank order. The direction of preference was the same with all methods. The weaker coffees were preferred over the stronger ones. Within the paired comparison method, discrimination was slightly better with the second than with the first pair. Paired comparisons and 3‐sample rank order discriminated equally well. Discrimination by 4‐sample rank order was slightly poorer than with the other two methods when the between‐sample differences were small.
Bisulfite Effect on the Chemistry and Activity of Horseradish Peroxidase
Authors: EMBS R. J. , MARKAKIS P.
Published: December 2006

SUMMARY: Bisulfite retarded the inactivaton of horseradish peroxidase by weak acids. Spectral analysis indicated that the retardation was accomplished by the stabilization of the linkage between the iron containing prosthetic group and the protein. Cyanide, azide and fluoride, which form reversible complexes with peroxidase iron, exerted a similar effect; thus, it is inferred that bisulfite also forms a complex with peroxidase iron. A kinetic method was used to calculate a dissociation constant of 0.2M for the bisulfite peroxidase complex.
Vapor Analysis of the Production by Banana Fruit of Certain Volatile Constituents
Authors: MYERS MARSHALL J. , ISSENBERG PHILLIP , WICK EMILY L.
Published: December 2006

SUMMARY: Direct gas chromatographic vapor analyses were utilized to determine whether banana slices at different stages of ripeness in an in vitro system produced iso‐amyl acetate and iso‐amyl alcohol, known banana aroma constituents; and whether a precursor‐product relationship could be observed between these compounds and L‐leucine. Production of iso‐amyl acetate by unripe slices was demonstrated based on experiments with metabolic inhibitors. The behavior of ripe and overripe slices was inconclusive since the vapor concentration of the acetate remained constant. The vapor concentration of iso‐amyl alcohol was essentially unchanged at all ripeness stages. Investigations with L‐leucine‐U‐14C showed conclusively that leucine was a precursor and that both compounds were continually produced at all ripeness stages. The interpretation of direct vapor analyses over respiring fruit is considered.
Pectin Changes in the Ripening of Irradiated and Stored Strawberries
Authors: BELLI‐DONINI M. L. , STORNAIUOLO M. R.
Published: December 2006

SUMMARY: Strawberries of the “Red Gauntlet” variety picked at two different stages of maturation were irradiated with a 60Co source at 200 krads. After irradiation the fruits were stored in a refrigerated cell at a temperature varying from 0 to 3°C and at a R.H. between 85‐90%. During the storage a part of the control berries was irradiated at different times to find out differences in irradiation response at successive stages of ripeness in storage conditions. The effects of irradiation on the pectic substances, pectinmethylesterase activity and anthocyanin content were investigated. In addition, changes in softening and extent of fungal growth were followed. A different response of strawberries irradiated at two different stages of ripeness was found. The different ripeness in storage conditions also influences the radiation response of the strawberries. The possible practical applications of these findings are discussed.