Comparative electrochemical study on monolignols and dimers relevant for the comprehension of the lignification process

The objective of the present study is to complete previous electrochemical studies on coniferyl alcohol analogs by focusing on its dimers to further elucidate the lignification process, in order to distinguish between steric and electronic factors that inhibit oxidation. The results demonstrated that monolignols exhibit lower oxidation potential values than dimers and the β-O-4 dimer exhibited a quite peculiar behavior allowing two-electron oxidation. Moreover, we noticed that the pH turned out to affect the redox potential values. Phenol/phenol cation radical couples had a significantly higher potential than the corresponding phenate/phenoxy radical couple. These results emphasize the importance of understanding the specificities of in planta lignin growth and structure.

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Reduced cellulose synthesis invokes lignification and defense responses in Arabidopsis thaliana

The cell wall determines the shape of plant cells and is also the primary interface for pathogen interactions. The structure of the cell wall can be modified in response to developmental and environmental cues, for example to strengthen the wall and to create barriers to pathogen ingress. The ectopic lignin 1-1 and 1-2 (eli1-1 and eli1-2) mutations lead to an aberrant deposition of lignin, a complex phenylpropanoid polymer. We show that the eli1 mutants occur in the cellulose synthase gene CESA3 in Arabidopsis thaliana and cause reduced cellulose synthesis, providing further evidence for the function of multiple CESA subunits in cellulose synthesis. We show that reduced levels of cellulose synthesis, caused by mutations in cellulose synthase genes and in genes affecting cell expansion, activate lignin synthesis and defense responses through jasmonate and ethylene and other signaling pathways. These observations suggest that mechanisms monitoring cell wall integrity can activate lignification and defense responses.     

An approach to lignification in plants

A lignin-like substance was synthesized in vitro from coniferyl alcohol in the presence of peroxidase with coenzymes NADH and flavin. Eugenol was also polymerized in the same way.     

Metabolomics and its application to studying metal toxicity

Here we explain the omics approach of metabolomics and how it can be applied to study a physiological response to toxic metal exposure. This review aims to educate the metallomics field to the tool of metabolomics. Metabolomics is becoming an increasingly used tool to compare natural and challenged states of various organisms, from disease states in humans to toxin exposure to environmental systems. This approach is key to understanding and identifying the cellular or biochemical targets of metals and the underlying physiological response. Metabolomics steps are described and overviews of its application to metal toxicity to organisms are given. As this approach is very new there are yet only a small number of total studies and therefore only a brief overview of some metal metabolomics studies is described. A frank critical evaluation of the approach is given to provide newcomers to the method a clear idea of the challenges and the rewards of applying metabolomics to their research.     

Lignins and lignification: Selected issues

Lignin deposition in plant cell walls is one of the mechanisms which allowed the development of upright plants adapted to a terrestrial habitat. At the present time, lignins and lignification are the subject of very active research which has recently moved from chemical and biochemical aspects to more biological and developmental problems. In this review, three different topics will be addressed. (a) A first section will deal with recent advances related to the biosynthesis of lignins. It will be shown that a complex array of O-methyltransferases may control the production of differentially methylated monolignols, the precursors of lignins, but that the downstream enzymes in the synthesis of monolignols are probably not encoded by multigene families which would provide additional possibilities for fine-tuning the monomeric composition of lignins. In addition, recent results obtained on laccases will illustrate the difficulty in identifying the true nature of oxidases involved in the production of phenoxy radicals, the oxidation products of monolignols. (b) A second set of data will highlight the potential interest of Arabidopsis mutants for understanding lignin synthesis, deposition and function. Indeed, different classes of lignification mutants with modifications in lignin content or composition and alterations of vascular differentiation or global vascular pattern have already been characterized. The identification of the corresponding genes will undoubtedly give rise to new insights on key steps and regulation mechanisms in the lignification process. (c) The last section is dedicated to the future of lignin genetic engineering. It will be emphasized that, after a first period which has demonstrated the potential of the approach, it is necessary to consider in greater detail the unexpected side effects and compensation mechanisms associated with induced lignin modifications. New targets for future lignin genetic engineering experiments will be identified and the extension of the technology to new woody species, the advantages for the pulp industry and the problems associated with public perception of these new products will be envisaged. Lignification is a tightly regulated and dynamic process subject to modulation at different levels during normal development and in response to different stresses. Understanding these subtle mechanisms which also involve the other polymers of the cell wall is an important challenge facing plant biology as we enter the next century.     

Electrophoretic determination of sulfhydryl groups and its application to complex protein samples, in vitro protein synthesis mixtures, and cross-linked proteins

Without prior fractionation, the number of sulfhydryl groups of individual polypeptides in a protein mixture can be determined, provided their molecular weights and approximate isoelectric points are known. Urea-denatured protein samples are reacted with iodoacetamide and iodoacetate in a modified version of Creighton's procedure. After separation by sodium dodecyl sulfate - polyacrylamide gel electrophoresis and isoelectric focusing, the number of sulfhydryl groups is determined by counting the protein bands which have additional negative charges. This method requires little material and provides an additional parameter, besides the molecular weight and isoelectric point, for the identification and characterization of a protein. The sensitivity may be enhanced for nonradioactive proteins by using 14C-labeled iodoacetamide and iodoacetate. The procedure has been applied to prokaryotic in vitro protein synthesis mixtures, bacterial membrane protein, and trypsin-cleaved or chemically cross-linked subunits of the F1 ATPase from Escherichia coli.     

Prostaglandin production by human epidermal cells in vitro: a model for studying pharmacologic inhibition of prostaglandin synthesis

Blood prostaglandin A levels were measured in 10 healthy subjects under different conditions of collection and storage. Plasma levels ranged from 1.20 to 1.81 ng/ml (M + or - SE=1.50 + or - 0.10) in 5 females, to 1.23 to 1.68 ng/ml (1.45 + or - 0.09) in 5 males, when centrifuged and frozen immediately after collection. Storage at 4 degrees Centigrade (C) for varying times up to 24 hours and at 22 degrees C (room temperature) up to 4 hours did not affect mean plasma concentrations significantly, but increased the range obtained to 1.00 to 2.47 ng/ml for both male and female groups. Serum concentrations differed in males and females and were lower than corresponding mean plasma values for males and higher for females. Mean serum concentrations were 1.77 + or - 0.08 ng/ml in females and 1.18 + or - 0.05 ng/ml in males and did not change significantly up to 24 hours of storage at 4 decrees C. These results suggest that prostaglandin A assayed in both plasma and serum under the conditions described is stable and should allow for greater flexibility in sampling under different experimental conditions.     

Prostaglandin production by human epidermal cells in vitro: A model for studying pharmacologic inhibition of prostaglandin synthesis

An inv itro model for studying the biosynthesis of prostaglandins by isolated human epidermal cells is described. Production of prostaglandin E₂-equivalent activity over an 18-hour incubation period was measured using a radioimmunoassay. Prostaglandin production was significantly inhibited by indomethacin and aspirin in a concentration-dependent manner.     

Methods in comparative phylogeography, and their application to studying evolution in the north american aridlands

Historical biogeography and comparative phylogeography havemuch in common. Both seek to discover common historical patternsin the elements of biotas, although typically at different tiersof evolutionary history. Comparative phylogeography is basedon phylogeographic analyses of multiple taxa, usually widespreadspecies. By comparing the phylogeographic structures of numerouswidespread sympatric species, one can infer whether the currentfauna has been historically stable, as evidenced by the relativefrequency of geographically congruent reciprocally monophyleticgroups. Alternatively, if species distributions are ephemeralover evolutionary time, a mixture of phylogeographic structuresis expected. Coalescence analyses contribute information abouthistory irrespective of whether haplotype phylogenies are structuredor not. In the aridlands of North America, several isolatingevents are evident in the phylogeographic patterns of birds,mammals and herps. A mid-peninsular seaway in Baja California,dated at ca. one million years before present, had a pervasiveeffect, with 13 of 16 assayed species showing a concordant split.Hence, this community appears to have been a stable assemblageof species over the past one million years. In contrast, theavifauna of the Sonoran-Chihuahuan deserts consists of two specieswith a concordant split and three other species that are undifferentiatedacross both deserts. Hence, the species in this area have haddifferent histories. The Baja biota appears to resemble itsancestral configuration to a greater degree than the Sonoran-Chihuahuanone. A deeper evolutionary event separated taxa in Baja Californiafrom the eastern deserts, showing that the aridlands fauna wasaffected by events at different times resulting in overlaintiers of history.     

Pyridazinone derivatives: design, synthesis, and in vitro vasorelaxant activity

In an attempt to identify potential vasodilator-cardiotonic lead compounds, three series of pyridazinones were designed using three-dimensional pharmacophore developed with CATALYST software from a set of potent cyclic nucleotide phosphodiesterase III, cAMP PDEIII inhibitors. The features of the target compounds were based on the structures of many biologically active lead compounds with cAMP phosphodiesterase III inhibiting activity such as Milrinone and others. Compounds with higher fit scores to the developed pharmacophore were synthesized namely; 6-(3-ethoxycarbonyl-4-oxo-1,4-dihydroquinolin-6-yl)-4,5-dihydro-3(2H)-pyridazinones (3a and 3b), 6-[4-(2,6-disubstituted-quinolin-4-ylamino)phenyl]-4,5-dihydropyridazin-3(2H)-ones (5a-f), and 6-[3-(5-cyano-6-oxo-4-aryl-1,6-dihydro-2-pyridyl)phenylamino]-3(2H)pyridazinone (8a and 8b). The vasodilator activity of the newly synthesized compounds was examined on the isolated main pulmonary artery of the rabbit. Some of the tested compounds showed moderate vasorelaxant activity compared with standard drug, Milrinone.     

Fluorescence-tagged transgenic lines reveal genetic defects in pollen growth--application to the eIF3 complex

Background

Mutations in several subunits of eukaryotic translation initiation factor 3 (eIF3) cause male transmission defects in Arabidopsis thaliana. To identify the stage of pollen development at which eIF3 becomes essential it is desirable to examine viable pollen and distinguish mutant from wild type. To accomplish this we have developed a broadly applicable method to track mutant alleles that are not already tagged by a visible marker gene through the male lineage of Arabidopsis.

Methodology/Principal Findings

Fluorescence tagged lines (FTLs) harbor a transgenic fluorescent protein gene (XFP) expressed by the pollen-specific LAT52 promoter at a defined chromosomal position. In the existing collection of FTLs there are enough XFP marker genes to track nearly every nuclear gene by virtue of its genetic linkage to a transgenic marker gene. Using FTLs in a quartet mutant, which yields mature pollen tetrads, we determined that the pollen transmission defect of the eif3h-1 allele is due to a combination of reduced pollen germination and reduced pollen tube elongation. We also detected reduced pollen germination for eif3e. However, neither eif3h nor eif3e, unlike other known gametophytic mutations, measurably disrupted the early stages of pollen maturation.

Conclusion/Significance

eIF3h and eIF3e both become essential during pollen germination, a stage of vigorous translation of newly transcribed mRNAs. These data delimit the end of the developmental window during which paternal rescue is still possible. Moreover, the FTL collection of mapped fluorescent protein transgenes represents an attractive resource for elucidating the pollen development phenotypes of any fine-mapped mutation in Arabidopsis.     

Fungal silver nanoparticles: synthesis,application and challenges

Purpose: This paper aims to summarize recent developments regarding the synthesis, application and challenges of fungal AgNPs. Possible methods to overcome the challenge of synthesis and reduce the toxicity of AgNPs have been discussed.

Materials and methods: This review consults and summary a large number of papers.

Results: Silver nanoparticles (AgNPs) have great potential in many areas, as they possess multiple novel characteristics. Conventional methods for AgNPs biosynthesis involve chemical agents, causing environmental toxicity and high energy consumption. Fungal bioconversion is a simple, low-cost and energy-efficient biological method, which could successfully be used for AgNPs synthesis. Fungi can produce enzymes that act as both reducing and capping agents, to form stable and shape-controlled AgNPs.

Conclusions: AgNPs have great potential in the medical and food industries, due to their antimicrobial, anticancer, anti-HIV, and catalytic activities. However, the observed in vitro and in vivo toxicity poses considerable challenges in the synthesis and application of AgNPs.     

New methodologies for studying lipid synthesis and turnover: Looking backwards to enable moving forwards

Our ability to understand the pathogenesis of problems surrounding lipid accretion requires attention towards quantifying lipid kinetics. In addition, studies of metabolic flux should also help unravel mechanisms that lead to imbalances in inter-organ lipid trafficking which contribute to dyslipidemia and/or peripheral lipid accumulation (e.g. hepatic fat deposits). This review aims to outline the development and use of novel methods for studying lipid kinetics in vivo. Although our focus is directed towards some of the approaches that are currently reported in the literature, we include a discussion of the older literature in order to put “new” methods in better perspective and inform readers of valuable historical research. Presumably, future advances in understanding lipid dynamics will benefit from a careful consideration of the past efforts, where possible we have tried to identify seminal papers or those that provide clear data to emphasize essential points. This article is part of a Special Issue entitled: Modulation of Adipose Tissue in Health and Disease.     

N-Hydroxythiosemicarbazones: synthesis and in vitro antitubercular activity

N-Hydroxythiosemicarbazide was prepared by two methods starting from 2,4-dimethoxy benzyl amine and hydroxylamine hydrochloride, which in turn was reacted with various aldehydes and ketones to obtain the titled compounds. Eighteen compounds were tested for their in vitro activity against Mycobacterium tuberculosis H37Rv using the agar dilution method. Compound 10p was found to be the most potent compound (MIC: 0.28 microM) and was 2.5 times more active than standard isoniazid.     

Chlorin-PEI-labeled cellulose nanocrystals: synthesis, characterization and potential application in PDT

This Letter reports the synthesis and characterization of a new series of water-stable and soluble photosensitizers (PS-CNCs) composed of cellulose nanocrystals (CNCs) bearing polyaminated chlorin p6. With a view to improve cancer cell targeting, these photosensitizers were assayed for their antitumor activity against HaCat cell line. IC(50) values fell within the nanomolar-range, making these photosensitizers promising for further in vitro and in vivo investigations.     

A graftable LDV peptidomimetic: design, synthesis and application to a blood filtration membrane

A graftable LDV (Leu-Asp-Val) peptidomimetic molecule (B-c) has been prepared from 3-(5-amino-2-hydroxy)phenyl-propionic acid, as alpha(4)beta(1) (VLA-4) integrin ligand. For that purpose, the mechanism of 3-(4-azidophenyl)propionic acid rearrangement has been revisited. Activation of Durapore DVPP-hydrophilic membrane, by surface wet chemistry using triazine trifluoride, followed by covalent coupling of B-c produced a modified filter (0.8% of derivatisation from XPS analysis) with improved capacity of leukocyte retention.