Regulation of Human Adenovirus Replication by RNA Interference

Adenoviruses cause a wide variety of human infectious diseases. Adenoviral conjunctivitis and epidemic keratoconjunctivitis are commonly associated with human species D adenoviruses. Currently, there is no sufficient or appropriate treatment to counteract these adenovirus infections. Thus, there is an urgent need for new etiology-directed therapies with selective activity against human adenoviruses. To address this problem, the adenoviral early genes E1A and E2B (viral DNA polymerase) seem to be promising targets. Here, we propose an effective approach to downregulate the replication of human species D adenoviruses by means of RNA interference. We generated E1A expressing model cell lines enabling fast evaluation of the RNA interference potential. Small interfering RNAs complementary to the E1A mRNA sequences of human species D adenoviruses mediate significant suppression of the E1A expression in model cells. Furthermore, we observed a strong downregulation of replication of human adenoviruses type D8 and D37 by small hairpin RNAs complementary to the E1A or E2B mRNA sequences in primary human limbal cells. We believe that our results will contribute to the development of efficient anti-adenoviral therapy.

Assessment, validation and deployment strategy of a two-barcode protocol for facile genotyping of duckweed species

Lemnaceae, commonly called duckweeds, comprise a diverse group of floating aquatic plants that have previously been classified into 37 species based on morphological and physiological criteria. In addition to their unique evolutionary position among angiosperms and their applications in biomonitoring, the potential of duckweeds as a novel sustainable crop for fuel and feed has recently increased interest in the study of their biodiversity and systematics. However, due to their small size and abbreviated structure, accurate typing of duckweeds based on morphology can be challenging. In the past decade, attempts to employ molecular barcoding techniques for species assignment have produced promising results; however, they have yet to be codified into a simple and quantitative protocol. A study that compiles and compares the barcode sequences within all known species of this family would help to establish the fidelity and limits of this DNA-based approach. In this work, we compared the level of conservation between over 100 strains of duckweed for two intergenic barcode sequences derived from the plastid genome. By using over 300 sequences publicly available in the NCBI database, we determined the utility of each of these two barcodes for duckweed species identification. Through sequencing of these barcodes from additional accessions, 30 of the 37 known species of duckweed could be identified with varying levels of confidence using this approach. From our analyses using this reference dataset, we also confirmed two instances where mis-assignment of species has likely occurred. Potential strategies for further improving the scope of this technology are discussed.

A rare WNT1 missense variant overrepresented in ASD leads to increased Wnt signal pathway activation

Wnt signaling, which encompasses multiple biochemical pathways that regulate neural development downstream of extracellular Wnt glycoprotein ligands, has been suggested to contribute to major psychiatric disorders including autism spectrum disorders (ASD). We used next-generation sequencing and Sequenom genotyping technologies to resequence 10 Wnt signaling pathway genes in 198 ASD patients and 240 matched controls. Results for single-nucleotide polymorphisms (SNPs) of interest were confirmed in a second set of 91 ASD and 144 control samples. We found a significantly increased burden of extremely rare missense variants predicted to be deleterious by PolyPhen-2, distributed across seven genes in the ASD sample (3.5% in ASD vs 0.8% in controls; Fisher's exact test, odds ratio (OR)=4.37, P=0.04). We also found a missense variant in WNT1 (S88R) that was overrepresented in the ASD sample (8 A/T in 267 ASD (minor allele frequency (MAF)=1.69%) vs 1 A/T in 377 controls (MAF=0.13%), OR=13.0, Fisher's exact test, P=0.0048; OR=8.2 and P=0.053 after correction for population stratification). Functional analysis revealed that WNT1-S88R is more active than wild-type WNT1 in assays for the Wnt/β-catenin signaling pathway. Our findings of a higher burden in ASD of rare missense variants distributed across 7 of 10 Wnt signaling pathway genes tested, and of a functional variant at the WNT1 locus associated with ASD, support that dysfunction of this pathway contributes to ASD susceptibility. Given recent findings of common molecular mechanisms in ASD, schizophrenia and affective disorders, these loci merit scrutiny in other psychiatric conditions as well.

Preparation of well-dispersed gold/magnetite nanoparticles embedded on cellulose nanocrystals for efficient immobilization of papain enzyme

A nanocomposite consisting of magnetite nanoparticles (Fe3O4NPs) and Au nanoparticles (AuNPs) embedded on cellulose nanocrystals (CNCs) was used as a magnetic support for the covalent conjugation of papain and facilitated recovery of this immobilized enzyme. Fe3O4NPs (10-20 nm in diameter) and AuNPs (3-7 nm in diameter) were stable and well-dispersed on the CNC surface. Energy-dispersive spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy were used to evaluate the surface composition and structure of CNC/Fe3O4NPs/AuNPs. The nanocomposite was successfully used for the immobilization and separation of papain from the reaction mixture. The optimal enzyme loading was 186 mg protein/g CNC/Fe3O4NPs/AuNPs, significantly higher than the value reported in the literature. The activity of immobilized papain was studied by electrochemical detection of its specific binding to the Thc-Fca-Gly-Gly-Tyr-Arg inhibitory sequence bound to an Au electrode. The immobilized enzyme retained 95% of its initial activity after 35 days of storage at 4 °C, compared to 41% for its free form counterpart.

Graphene versus Multi-Walled Carbon Nanotubes for Electrochemical Glucose Biosensing

: A simple procedure was developed for the fabrication of electrochemical glucose biosensors using glucose oxidase (GOx), with graphene or multi-walled carbon nanotubes (MWCNTs). Graphene and MWCNTs were dispersed in 0.25% 3-aminopropyltriethoxysilane (APTES) and drop cast on 1% KOH-pre-treated glassy carbon electrodes (GCEs). The EDC (1-ethyl-(3-dimethylaminopropyl) carbodiimide)-activated GOx was then bound covalently on the graphene- or MWCNT-modified GCE. Both the graphene- and MWCNT-based biosensors detected the entire pathophysiological range of blood glucose in humans, 1.4-27.9 mM. However, the direct electron transfer (DET) between GOx and the modified GCE's surface was only observed for the MWCNT-based biosensor. The MWCNT-based glucose biosensor also provided over a four-fold higher current signal than its graphene counterpart. Several interfering substances, including drug metabolites, provoked negligible interference at pathological levels for both the MWCNT- and graphene-based biosensors. However, the former was more prone to interfering substances and drug metabolites at extremely pathological concentrations than its graphene counterpart.

Why is Design-Build Commonly Used in the Public Sector? An Illustration from Hong Kong

The Design and Build (D&B) procurement method is one of the systems advocated to overcome inadequacies with the traditional procurement method. In recent years, this innovative procurement method has been put to practice in Hong Kong where a vast amount of infrastructure works is taking place. This paper aims to illustrate the applicability of design-build in the Hong Kong setting.As most D&B projects are undertaken by the public sector of Hong Kong, the main features of a public sector project and reasons for its wider use on D&B are fully examined in the paper. To further explore the benefits of D&B in actual practice, structured interviews have been conducted with clients, contractors and consultants running D&B projects in Hong Kong. Summary of major problems of running D&B projects from the previous study by the authors is also outlined. With the increasing use of D&B in the public sector of Hong Kong and worldwide, more research can be undertaken on the quantitative comparison of the traditional mode of procurement and how to carry out a D&B project successfully so as to develop a knowledge base for the D&B procurement method.

Noninvasive cell-based impedance spectroscopy for real-time probing inhibitory effects of graphene derivatives

Three water-dispersible graphene derivatives, graphene oxide (GO), sulfonated graphene oxide (SGO), and sulfonated graphene (SG), were prepared and probed for their plausible cytotoxicity by non-invasive electric cell-substrate impedance sensing (ECIS). With Spodoptera frugiperda Sf9 insect cells adhered on gold microelectrodes as an active interface, it is feasible to monitor changes in impedance upon exposure to different graphene derivatives. Sf9 insect cells were then exposed to different concentrations of graphene derivatives and their spreading and viability were monitored and quantified by ECIS in real-time. On the basis of the 50% inhibition concentration (ECIS50), none of the graphene derivatives were judged to have any significant cytotoxicity with respect to the chosen cell line as the ECIS50 values were all above 100 μg/mL. However, all graphene derivatives exhibited inhibitory effects on the Sf9 response at the cell spreading level with the following order: SG (ECIS50 = 121 ± 8 μg/mL), SGO (ECIS50 = 151 ± 9 μg/mL), and GO (ECIS50 = 232 ± 27 μg/mL), reflecting differences observed in their ζ-potential and surface area. The presence of phenyl sulfonyl groups in SGO and SG improves their aqueous dispersity which enables these materials to have a greater inhibitory effect on Sf9 insect cells in comparison to GO. Such results were corroborated well with the cell count and viability by the Trypan Blue exclusion assay.

Catalysis using gold nanoparticles decorated on nanocrystalline cellulose

A novel nanocomposite was prepared by deposition of carbonate-stabilized Au nanoparticles (AuNPs) onto the surface of poly(diallyldimethyl ammonium chloride) (PDDA)-coated carboxylated nanocrystalline cellulose (NCC). The hybrid material possessed AuNPs (1.45% by weight) with an average diameter of 2.95 ± 0.06 nm. The catalytic activity of AuNP/PDDA/NCC for reducing 4-nitrophenol to 4-aminophenol was compared to other Au-supported composites. An activation energy of 69.2 kJ mol(-1) was obtained for the reaction. Indeed, the reaction rate constant k of (5.1 ± 0.2) × 10(-3) s(-1) was comparable to the benchmark literature value obtained using AuNPs (<5 nm in diameter) decorated on a network of crystalline cellulose fibers. Our strategy promotes the use of natural resources to prepare reusable hybrid inorganic-organic materials for important reactions with facilitated product isolation/purification.

A differentiated porcine bronchial epithelial cell culture model for studying human adenovirus tropism and virulence

The species specificity of human adenoviruses (HAdV) almost precludes studying virulence and tropism in animal models, e.g. rodent models, or derived tissue and cell culture models. However, replication of HAdV type 5 (HAdV-C5) has been shown after intravenous injection in swine. In order to study adenovirus replication in airway tissue propagation of bronchial epithelial cells from porcine lungs was established. These primary cells proved to be fully permissive for HAdV-C5 infection in submerged culture, demonstrating efficient HAdV genome replication, infectious viral particle release (1.07×10(8) TCID(50)/ml±6.63×10(7)) and development of cytopathic effect (CPE). Differentiation of porcine bronchial epithelial cells was achieved at the air-liquid interface on collagen I coated 0.4μm polyester membranes. Morphology, expression of tubulin and occludin, the development of tight-junctions and cilia were similar to human bronchial epithelial cells. Infection with HAdV-C5 from the basolateral side resulted in release of infectious virus progeny (2.05×10(7) TCID(50)/ml±2.39×10(7)) to the apical surface as described recently in human bronchial epithelial cells, although complete CPE was not observed. Differentiated porcine bronchial epithelial cells hold promise as a novel method for studying the virulence and pathophysiology of pneumonia associated HAdV types.

Bax inhibitor-1: a highly conserved endoplasmic reticulum-resident cell death suppressor

In spite of fundamental differences between plant and animal cells, it is remarkable that some cell death regulators that were identified to control cell death in metazoans can also function in plants. The fact that most of these proteins do not have structural homologs in plant genomes suggests that they may be targeting a highly conserved 'core' mechanism with conserved functions that is present in all eukaryotes. The ubiquitous Bax inhibitor-1 (BI-1) is a common cell death suppressor in eukaryotes that has provided a potential portal to this cell death core. In this review, we will update the current status of our understanding on the function and activities of this intriguing protein. Genetic, molecular and biochemical studies have so far suggested a consistent view that BI-1 is an endoplasmic reticulum (ER)-resident transmembrane protein that can interact with multiple partners to alter intracellular Ca(2+) flux control and lipid dynamics. Functionally, the level of BI-1 protein has been hypothesized to have the role of a rheostat to regulate the threshold of ER-stress inducible cell death. Further, delineation of the cell death suppression mechanism by BI-1 should shed light on an ancient cell death core-control pathway in eukaryotes, as well as novel ways to improve stress tolerance.

Synthesis of furfural from xylose by heterogeneous and reusable nafion catalysts

Nafion 117 has been proven as a robust and reusable heterogeneous catalyst for the dehydration of 9.1 % (w/w) xylose in dimethyl sulfoxide (DMSO) to yield 60 % furfural in 2 h at 150 °C. The catalytic high activity promoted shorter reaction times to limit the formation of side-products which otherwise would lead to decreased yields. Within the allowable operating temperature range of Nafion (125 to 175 °C), the reaction was kinetically controlled. In corroboration with AFM and SEM imaging, ATR-FTIR confirmed that the Nafion catalytic activity remained unchanged after 15 repeated uses. With excellent chemical and thermal stability under the conditions for xylose dehydration compared to existing solid acid catalysts, this reusable Nafion system could be a step towards the more economical production of furfural from renewable biomass, an intermediate chemical for the preparation of value-added chemicals.

Reconstruction of the chloroplast noncyclic electron transport pathway from water to NADP with three integral protein complexes

RECONSTRUCTION OF PHOTOSYNTHETIC NONCYCLIC ELECTRON TRANSPORT FROM WATER TO NADP HAS BEEN ACCOMPLISHED BY USING THREE INTEGRAL PROTEIN COMPLEXES ISOLATED FROM CHLOROPLAST THYLAKOID MEMBRANES: photosystems I and II and the cytochrome b(6)-f complex. This system shows an absolute dependence on the presence of all three protein complexes for NADP reduction, in addition to plastocyanin, ferredoxin, and ferredoxin-NADP reductase. The reconstructed system was found to be sensitive to low concentrations of known inhibitors of noncyclic electron transport. Depletion of the Rieske iron-sulfur center and bound plastoquinone from the cytochrome b(6)-f complex resulted in an inhibition of the photoreduction of NADP.

Function of HES6 an Inhibitor of HES1, in the Breast Cancer Cell Lines T47D and MCF-7 Is to Up-Regulate E2F-1 and Increased Proliferation

Hormone resistance remains as a major obstacle in breast cancer treatment. The majority of breast tumors are dependent on estrogens to grow, therefore anti-estrogens such as Tamoxifen is an effective treatment option. We have found that a transcription factor Hes6, earlier described in the nervous tissue, is up-regulated in hormone-independent breast cancer cells compared to normal estrogen sensitive breast cancer cells. By using a lenti-virus system, we have over-expressed Hes6 in T47D cells which are estrogen sensitive. This resulted in increased proliferation. We also found that estrogen treatment of MCF-7 breast cancer cells induced expression of endogenous Hes6 in the G1-phase. We could not find any binding of estrogen receptor α to the HES6 gene but instead found a binding site up-steam of the promoter in the ASCL1 gene. ASCL1 is a known inducer of HES6 and we are showing that ASCL1 is up-regulated by 17β-estradiol in MCF-7 cells. To find the mechanism behind the tumorogenic effects of Hes6, we analysed important factors of the cell-cycle. We found that the G1-phase factor E2F-1 was up-regulated in response to increased Hes6 expression. Since HES6 have been shown to be an inhibitor of HES1, this is in agreement with a previous study where we found that HES1 inhibited proliferation by binding to the promoter of and down-regulating E2F-1 expression. E2F-1 is an important limiting factor in late G1-phase of the cell cycle and can drive cell proliferation.We believe that the HES1-HES6 interplay is important in antiestrogen-resistant breast cancer. Studies are now ongoing to investigate if Hes6 is up-regulated in estrogen-independent human breast cancer samples.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2153.

The glass transition in twinned ((phenyl)4As)2C60Cl crystals

We have studied the crystal structure of ((phenyl)4As)2C60Cl at room temperature and below the phase transition at Tc = 125 K by single-crystal x-ray diffraction. At room temperature tetragonal lattice parameters were found as a = b = 12.588(1)Å and c = 20.345(1)Å. At T = 120 K the lattice parameters were determined as a = b = 12.5060(1)Å and c = 20.4420(1)Å. The room temperature and low-temperature structures were found to be isostructural, with space group I4/m. Structure refinements were performed with restrictions on the C60 molecules according to the noncrystallographic isohedral point symmetry Ih . Derivations from this symmetry could not be found, suggesting that any possible Jahn-Teller distortion of the C60 radical anions will be smaller than 0.01Å. The phase transition observed in ESR at Tc = 125 K is proposed to be a glass transition. At room temperature there is dynamic disorder between two orientations of the C60 molecules as they are related by the 4-fold rotation. Below Tc the disorder becomes static. Two types of twinning have been observed in different crystals. The first type is represented by a rotation over 180 about [1,1,1] axis. It results in different orientations of the 4-fold unique axes with angles of 82.4 degrees between them. Secondly, merohedral twinning was observed corresponding to the two orientations of the structure with 4/m symmetry on the tetragonal lattice. Both twinnings result in extra orientations of the C60 molecules, and they should be taken into account, when analysing the anisotropy of the physical properties of crystals of this compound.

Critical role of FoxO3a transcription factor in response to therapy with EGFR inhibitors, gefitinib and lapatinib, in breast cancer

21018

Background: Inhibition of the EGF-receptor is a potential therapeutic strategy for breast cancer. The PI3-K/PKB signalling pathway plays an important role in cell proliferation, survival and malignant transformation. The Forkhead box group O transcriptional factor, FoxO3a, is a direct downstream target of PKB. Here we studied the role of the FoxO3a in response to the EGFR inhibitors Gefitinib and Lapatinib. Methods: Response of breast cancer cell lines to treatment with Gefitinib and Lapatinib was evaluated by proliferation assay and FACS analysis. Expression of FoxO3a and its downstream targets was analysed using Western blotting. Sub-cellular localisation of FoxO3a was analysed by confocal microscopy. FoxO3a mRNA level was measured by RTq-PCR. siRNA transfections were performed using Oligofectamine reagent. Immunohistological staining was performed on patient samples to validate our findings. Results: Treatment of a panel of breast cancer cell lines with both inhibitors resulted in decreased proliferation due to G1-arrest and apoptosis in two sensitive cell-lines, BT474 and SKBR3. Western blot analysis revealed that response to the treatment was associated with a decrease in PKB and FoxO3a phosphorylation and thus the nuclear relocalisation of FoxO3a. Confocal microscopy confirmed that treatment induced nuclear translocation of FoxO3a only in sensitive but not resistant cells. This relocation of FoxO3a was accompanied by an induction of FoxO3a mRNA and its principal targets, p27kip1 and Bim. Transfection of the sensitive BT474 cells with FoxO3a specific siRNA resulted in a significant reduction in FoxO3a protein expression and Gefitinib-induced cell death. Comparison of immunohistochemical staining of biopsies from breast cancer patients before and after Gefitinib treatment revealed that therapy resulted in a significant increase in nuclear FoxO3a staining. Conclusion: Our results demonstrate for the first time that the EGFR-family inhibitors, Gefitinib and Lapatinib, specifically target FoxO3a to induce cell cycle arrest and apoptosis. This finding helps to define the mechanism of action of Gefitinib and Lapatinib and may provide novel insights into the molecular basis for resistance to these inhibitors.

No significant financial relationships to disclose.

Cryptococcosis in apparently immunocompetent patients

BACKGROUND

Few reports have described the clinical and microbiological features of cryptococcosis in immunocompetent patients.

AIM

To compare clinical presentations and outcomes of cryptococcosis in immunocompetent vs. immunocompromised patients.

DESIGN

Retrospective case series.

METHODS

All culture- or histology-confirmed cases (n = 46) of cryptococcosis in two acute hospitals in Hong Kong (1995-2005) were included. Clinical presentations, rates of fungaemia, cerebrospinal fluid (CSF) parameters and clinical outcomes were recorded.

RESULTS

Twenty patients (43.5%) were apparently immunocompetent, 17 (37.0%) had predisposing factors other than HIV infection, and 9 (19.6%) were HIV-positive. Thirty-one (67.4%) presented with meningitis, four (8.7%) with pulmonary cryptococcosis, and 11 (23.9%) with extraneural, extrapulmonary cryptococcosis. Of the immunocompetent patients with retrievable isolates (n = 8), three (37.5%) were Cryptococcus gattii; all isolates (n = 6) from immunocompromised patients were Cryptococcus neoformans var. grubii. Immunocompetent patients more commonly presented with meningitis (80.0% vs. 47.1%, p = 0.03), and tended toward lower rates of fungaemia (10.0% vs. 35.3%, p = 0.06) and mortality (25.0% vs. 52.9%, p = 0.06). Death was associated with fungaemia (p = 0.01) and underlying malignancy (p < 0.01). In cryptococcal meningitis, immunocompetent patients had longer mean time from illness onset to presentation (34.4 vs. 12.6 days, p = 0.02), more intense inflammatory responses (CSF: white blood cells 108 vs. 35 x 10(9)/l, p = 0.03; protein 1.61 g/l vs. 0.79 g/l, p = 0.07), less fungaemia (0% vs. 26.7%, p = 0.04) and more satisfactory clinical outcomes (81.3% vs. 46.7%, p = 0.04).

DISCUSSION

A substantial proportion of patients with cryptococcosis are apparently immunocompetent. C. neoformans var. grubii and C. gattii are the common causes. Immunocompetent patients tend to present with localized, indolent neurological disease, with more intense inflammatory responses but better clinical outcomes.

New insights into the interactions of serum proteins with bis(maltolato)oxovanadium(IV): transport and biotransformation of insulin-enhancing vanadium pharmaceuticals

Significant new insights into the interactions of the potent insulin-enhancing compound bis(maltolato)oxovanadium(IV) (BMOV) with the serum proteins, apo-transferrin and albumin, are presented. Identical reaction products are observed by electron paramagnetic resonance (EPR) with either BMOV or vanadyl sulfate (VOSO4) in solutions of human serum apo-transferrin. Further detailed study rules out the presence of a ternary ligand-vanadyl-transferrin complex proposed previously. By contrast, differences in reaction products are observed for the interactions of BMOV and VOSO4 with human serum albumin (HSA), wherein adduct formation between albumin and BMOV is detected. In BMOV-albumin solutions, vanadyl ions are bound in a unique manner not observed in comparable solutions of VOSO4 and albumin. Presentation of chelated vanadyl ions precludes binding at the numerous nonspecific sites and produces a unique EPR spectrum which is assigned to a BMOV-HSA adduct. The adduct species cannot be produced, however, from a solution of VOSO4 and HSA titrated with maltol. Addition of maltol to a VOSO4-HSA solution instead results in formation of a different end product which has been assigned as a ternary complex, VO(ma)(HSA). Furthermore, analysis of solution equilibria using a model system of BMOV with 1-methylimidazole (formation constant log K1 = 4.5(1), by difference electronic absorption spectroscopy) lends support to an adduct binding mode (VO(ma)2-HSA) proposed herein for BMOV and HSA. This detailed report of an in vitro reactivity difference between VOSO4 and BMOV may have bearing on the form of active vanadium metabolites delivered to target tissues. Albumin binding of vanadium chelates is seen to have a potentially dramatic effect on pharmacokinetics, transport, and efficacy of these antidiabetic chelates.

Reactions of 2-indolylphosphines with Ru3(CO)12: cluster capping with μ3,η2-indolylphosphine as an anionic six-electron P,N-donor ligand

Stepwise bidentate coordination of the novel indolylphosphine ligands HL (1, HL = P(C(6)H(5))(2)(C(9)H(8)N)(diphenyl-2-(3-methylindolyl)phosphine); 2, HL = P(C(6)H(5))(C(9)H(8)N)(2)(phenyldi-2-(3-methylindolyl)phosphine); and 3, HL = P(C(6)H(5))(C(17)H(12)N(2))(di(1H-3-indolyl)methane-(2,12)-phenylphosphine)) to the ruthenium cluster Ru(3)(CO)(12) is demonstrated. Reactions of 1-3 with Ru(3)(CO)(12) led to the formation of Ru(3)(CO)(11)(HL) (4-6), in which HL is mono-coordinated through the phosphorus atom. The X-ray structures of 4-6 show that the phosphorus atom is equatorially coordinated to the triruthenium core. In all cases, gentle heating of Ru(3)(CO)(11)(HL) resulted in the formation of Ru(3)(CO)(9)(mu-H)(mu(3),eta(2)-L)(7-9) in which the NH proton of the indolyl substituent had migrated to the ruthenium core to form a bridging hydride ligand. The X-ray structure of Ru(3)(CO)(9)(mu-H)[mu(3),eta(2)-P(C(6)H(5))(2)(C(9)H(7)N)] (7) shows the deprotonated nitrogen atom of the indolyl moiety bridging over the face of the triruthenium core, bonding to the two ruthenium metal centers to which the phosphorus atom is not bound. The phosphorus atom is forced to adopt an axial bonding mode due to the geometry of the indolylphosphine ligand. Cluster electron counting and X-ray data suggest that the indolylphosphine behaves as a six-electron ligand in this mode of coordination. Compounds 4-9 have been characterized by IR, (1)H, (13)C and (31)P NMR spectroscopy.

Trans-dominant suppression of plant TGA factors reveals their negative and positive roles in plant defense responses

Salicylic acid (SA) is a key regulator for the induction of systemic acquired resistance (SAR), and NPR1 is a critical mediator for the biological effects of SA. Physical interactions between NPR1 and TGA factors, a conserved family of basic-leucine-zipper (bZip) proteins in plants, have suggested a role for these transcription factors in mediating SAR induction via the regulation of defense genes. To elucidate this function, we constructed a trans-dominant mutant that specifically eliminates DNA-binding activities of this class of bZip proteins in transgenic tobacco plants. Our results demonstrate that the loss of TGA DNA-binding activities is correlated with suppression of two xenobiotic-responsive genes, GNT35 and STR246, and enhanced induction of pathogenesis-related (PR) genes by SA. In addition, these TGA-suppressed plants exhibited higher levels of PR gene induction by pathogen challenge and an enhanced SAR. These results suggest that TGA transcription factors serve both negative and positive regulatory roles in mediating plant defense responses.

Enzyme biosensor for studying therapeutics of Alzheimer's disease

An electrochemical method for the investigation and comparison of anti-Alzheimer medications that is based on the inhibition of the acetylcholinesterase is presented. The developed amperometric biosensor determines the in-vitro inhibition of the acetylcholinesterase that is co-immobilized with choline oxidase on the working electrode surface of a three-electrode system using gel entrapment. The sensor has been applied to determine the IC50 values of two known and one newly developed Alzheimer remedy. A simultaneous measurement with the photometric standard method shows the applicability of our method for fast drug screening.

Programmed cell death, mitochondria and the plant hypersensitive response

The plant response to attempted infection by microbial pathogens is often accompanied by rapid cell death in and around the initial infection site, a reaction known as the hypersensitive response. This response is associated with restricted pathogen growth and represents a form of programmed cell death (PCD). Recent pharmacological and molecular studies have provided functional evidence for the conservation of some of the basic regulatory mechanisms underlying the response to pathogens and the activation of PCD in animal and plant systems. In animals, the mitochondrion integrates diverse cellular stress signals and initiates the death execution pathway, and studies indicate a similar involvement for mitochondria in regulating PCD in plants. But many of the cell-death regulators that have been characterized in humans, worms and flies are absent from the Arabidopsis genome, indicating that plants probably use other regulators to control this process.

Detection of chromosomes tagged with green fluorescent protein in live Arabidopsis thaliana plants

BACKGROUND

Structural and dynamic studies of chromosomes tagged with green fluorescent protein (GFP) in yeast and cultured animal cells have revealed some surprises. Although this technology can be very powerful, only a few studies using this approach with developed multicellular systems have been reported for the study of chromatin behavior in situ.

RESULTS

We established vectors and conditions to visualize tagged loci stably inserted in the Arabidopsis genome via GFP fused to a bacterial DNA-binding protein. Using this system, three-dimensional coordinates for tagged loci within nuclei from cells of a live plant can be directly determined with concomitant visualization of the position of the nucleolus. Chromosome polyploidization in epidermal cells at the elongation zone of the root in transgenic plants can be visualized in situ using this technique.

CONCLUSION

We have established that GFP fusion with DNA-binding proteins can be used in conjunction with concatameric binding-site arrays to track genomic loci in living Arabidopsis plants. It should now be feasible to study the mechanisms of organization and dynamics of chromatin in specific cell types during various times of plant development, taking advantage of the well developed genetic systems and resources available for Arabidopsis.

Clinical study of lamotrigine and valproic acid in patients with epilepsy: using a drug interaction to advantage?

Lamotrigine (LTG) is one of the newer antiepileptic drugs which has been shown to have a spectrum of drug interactions (including with other epilepsy drugs) that can have a pronounced effect on LTG kinetics. The present study examined the LTG metabolic inhibition dose-response relationship with valproic acid (VPA) in eight patients with epilepsy with a view to using this to benefit the patient. This could benefit the patient not only by attaining higher plasma LTG concentrations with "standard" dosages of LTG, but also possibly by achieving better seizure control through providing a less variable peak-to-trough fluctuation in LTG concentrations as a result of extending the half-life of LTG. The dosages of VPA trialed were 0, 200, 500, and 1,000 mg/d which resulted in a mean increase in LTG area under the curve of 83.7 +/- 14.7% at 200 mg VPA/d, to and 160 +/- 37.9% at 1,000 mg VPA/d. The presence of concomitant enzyme inducers in some patients did not influence the percentage increase from baseline in half-life observed, although clearly those on inducers started from a lower absolute half-life as a result of the induction. The effect was shown to be quite variable, particularly at the highest dosage of VPA tested (1,000 mg/d), suggesting that this effect could be best applied with the support of the therapeutic drug monitoring laboratory determining plasma LTG concentrations to allow individualization of the LTG dosage.

Caspase-like protease involvement in the control of plant cell death

Cell death as a highly regulated process has now been recognized to be an important, if not essential, pathway that is ubiquitous in all multicellular eukaryotes. In addition to playing key roles in the morphogenesis and sculpting of the organs to give rise to highly specialized forms and shapes, cell death also participates in the programmed creation of specialized cell types for essential functions such as the selection of B cells in the immune system of mammals and the formation of tracheids in the xylem of vascular plants. Studies of apoptosis, the most well-characterized form of animal programmed cell death, have culminated in the identification of a central tripartite death switch the enzymatic component of which is a conserved family of cysteine proteases called caspases. Studies in invertebrates and other animal models suggest that caspases are conserved regulators of apoptotic cell death in all metazoans. In plant systems, the identities of the main executioners that orchestrate cell death remain elusive. Recent evidence from inhibitor studies and biochemical approaches suggests that caspase-like proteases may also be involved in cell death control in higher plants. Furthermore, the mitochondrion and reactive oxygen species may well constitute a common pathway for cell death activation in both animal and plant cells. Cloning of plant caspase-like proteases and elucidation of the mechanisms through which mitochondria may regulate cell death in both systems should shed light on the evolution of cell death control in eukaryotes and may help to identify essential components that are highly conserved in eukaryotes.

Caspase-like protease involvement in the control of plant cell death

Cell death as a highly regulated process has now been recognized to be an important, if not essential, pathway that is ubiquitous in all multicellular eukaryotes. In addition to playing key roles in the morphogenesis and sculpting of the organs to give rise to highly specialized forms and shapes, cell death also participates in the programmed creation of specialized cell types for essential functions such as the selection of B cells in the immune system of mammals and the formation of tracheids in the xylem of vascular plants. Studies of apoptosis, the most well-characterized form of animal programmed cell death, have culminated in the identification of a central tripartite death switch the enzymatic component of which is a conserved family of cysteine proteases called caspases. Studies in invertebrates and other animal models suggest that caspases are conserved regulators of apoptotic cell death in all metazoans. In plant systems, the identities of the main executioners that orchestrate cell death remain elusive. Recent evidence from inhibitor studies and biochemical approaches suggests that caspase-like proteases may also be involved in cell death control in higher plants. Furthermore, the mitochondrion and reactive oxygen species may well constitute a common pathway for cell death activation in both animal and plant cells. Cloning of plant caspase-like proteases and elucidation of the mechanisms through which mitochondria may regulate cell death in both systems should shed light on the evolution of cell death control in eukaryotes and may help to identify essential components that are highly conserved in eukaryotes.

Nitric oxide and salicylic acid signaling in plant defense

Salicylic acid (SA) plays a critical signaling role in the activation of plant defense responses after pathogen attack. We have identified several potential components of the SA signaling pathway, including (i) the H(2)O(2)-scavenging enzymes catalase and ascorbate peroxidase, (ii) a high affinity SA-binding protein (SABP2), (iii) a SA-inducible protein kinase (SIPK), (iv) NPR1, an ankyrin repeat-containing protein that exhibits limited homology to IkappaBalpha and is required for SA signaling, and (v) members of the TGA/OBF family of bZIP transcription factors. These bZIP factors physically interact with NPR1 and bind the SA-responsive element in promoters of several defense genes, such as the pathogenesis-related 1 gene (PR-1). Recent studies have demonstrated that nitric oxide (NO) is another signal that activates defense responses after pathogen attack. NO has been shown to play a critical role in the activation of innate immune and inflammatory responses in animals. Increases in NO synthase (NOS)-like activity occurred in resistant but not susceptible tobacco after infection with tobacco mosaic virus. Here we demonstrate that this increase in activity participates in PR-1 gene induction. Two signaling molecules, cGMP and cyclic ADP ribose (cADPR), which function downstream of NO in animals, also appear to mediate plant defense gene activation (e.g., PR-1). Additionally, NO may activate PR-1 expression via an NO-dependent, cADPR-independent pathway. Several targets of NO in animals, including guanylate cyclase, aconitase, and mitogen-activated protein kinases (e.g., SIPK), are also modulated by NO in plants. Thus, at least portions of NO signaling pathways appear to be shared between plants and animals.

Pathogen-induced programmed cell death in plants, a possible defense mechanism

As much as the definition of life may be controversial, the definition of death also may prove problematic. In recent years it became apparent that the death of a living cell may follow more than one possible scenario: it may result from an externally applied physical injury (an accidental death), or it may be the outcome of activating an internal pathway for cell suicide (a programmed death). That cells can participate in their own execution may indicate that certain types of cell deaths that were previously considered to be caused by foreign agents such as pathogens or drugs may actually result from the activation of a programmed cell death pathway that is normally latent in cells. Here, we describe the activation of such a cell suicide pathway in plant cells upon the recognition of an invading pathogen. We discuss the possible use of this pathway as a defense mechanism against infection and the possibility that in many ways the use of this type of cell death in plants is functionally analogous to that used by mammalian cells in response to infection by pathogens.

NPR1 differentially interacts with members of the TGA/OBF family of transcription factors that bind an element of the PR-1 gene required for induction by salicylic acid

NPR1 is a critical component of the salicylic acid (SA)-mediated signal transduction pathway leading to the induction of defense genes, such as the pathogenesis-related (PR)-1 gene, and enhanced disease resistance. Using a yeast two-hybrid screen, we identified several NPR1-interacting proteins (NIPs). Two of these NIPs are members of the TGA/OBF family of basic leucine zipper (bZIP) transcription factors; this family has been implicated in the activation of SA-responsive genes, including PR-1. Six TGA family members were tested and shown to differentially interact with NPR1: TGA2 and TGA3 showed strong affinity for NPR1; TGA5 and TGA6 exhibited weaker affinity; and TGA1 and TGA4 displayed little or no detectable interaction with NPR1, respectively. Interestingly, the amino-termini of these factors were found to decrease their stability in yeast and differentially affect their apparent affinity toward NPR1. The interacting regions on NPR1 and the TGA factors were also defined. Each of four point mutations in NPR1 that disrupt SA signaling in Arabidopsis completely blocked interaction of NPR1 with TGA2 and TGA3. TGA2 and TGA3 were also found to bind the SA-responsive element of the Arabidopsis PR-1 promoter. These results directly link NPR1 to SA-induced PR-1 expression through members of the TGA family of transcription factors.

Die and let live - programmed cell death in plants

Cysteine and serine proteases are prominent players in the control of developmental and pathogen-activated cell deaths in plants. Ethylene, salicylic acid, the small G-protein Rac, calcium and reactive oxygen species are recurring mediators of death signaling. Lastly, the mitochondrion has emerged in both plant and animal systems as a 'central depot' that interprets multiple signals and in some instances determines the fate of the cell.

Nonspecific inhibition of myogenic tone by PD98059, a MEK1 inhibitor, in rat middle cerebral arteries

Activation of MAP kinase kinase, also called ERK kinase (MEK), may lead to desinhibition of thin filament regulatory proteins and we therefore investigated the acute effects of the potent MEK inhibitor, PD98059 on the contractile properties of pressurized rat middle cerebral arteries. Cerebral arteries (diameter 100-150 microm) were mounted on a pressure myograph and PD98059 (10 microM, 40 microM) significantly inhibited (15% and 64%) myogenic tone (P < 0.001). At these concentrations, PD98059 also significantly reduced the vasopressin (0.1 microM)- and KCl (60 mM)-induced tone. Cumulative addition of exogenous Ca2+ (0.4-1.6 mM) increased myogenic tone to approximately 50% of constriction at 80 mmHg. This effect was inhibited by PD98059 (P < 0.001). These results demonstrate that pressure-induced myogenic tone is inhibited by PD98059 at the concentrations that have been reported to be selective for inhibition of MEK and the MAP kinase cascade. However, our results also demonstrate that PD98059 may have nonspecific effects on voltage-sensitive Ca2+ entry in vascular smooth muscle.

Markers for hypersensitive response and senescence show distinct patterns of expression

Controlled cellular suicide is an important process that can be observed in various organs during plant development. From the generation of proper sexual organs in monoecious plants to the hypersensitive response (HR) that occurs during incompatible pathogen interactions, programmed cell death (PCD) can be readily observed. Although several biochemical and morphological parameters have been described for various types of cell death in plants, the relationships existing between those different types of PCD events remain unclear. In this work, we set out to examine if two early molecular markers of HR cell death (HIN1 and HSR203J) as well as a senescence marker (SAG12) are coordinately induced during these processes. Our result indicates that although there is evidence of some cross-talk between both cell death pathways, spatial and temporal characteristics of activation for these markers during hypersensitive response and senescence are distinct. These observations indicate that these markers are relatively specific for different cell death programs. Interestingly, they also revealed that a senescence-like process seems to be triggered at the periphery of the HR necrotic lesion. This suggests that cells committed to die during the HR might release a signal able to induce senescence in the neighboring cells. This phenomenon could correspond to the establishment of a second barrier against pathogens. Lastly, we used those cell death markers to better characterize cell death induced by copper and we showed that this abiotic induced cell death presents similarities with HR cell death.

Signals controlling the expression of cytosolic ascorbate peroxidase during pathogen-induced programmed cell death in tobacco

In plants ascorbate peroxidase (APX) is an important H2O2-detoxifying enzyme. The expression of APX is rapidly induced in response to stresses that result in the accumulation of reactive oxygen species (ROS). We have recently reported that the steady-state level of transcripts encoding cytosolic APX (cAPX) is dramatically induced during the hypersensitive response (HR) of tobacco plants infected with tobacco mosaic virus (TMV). Because cAPX expression is closely linked to the production of ROS in plant cells, studying the regulation cAPX mRNA can reveal some of the signal transduction events associated with ROS metabolism during the HR. Analysis of cAPX mRNA induction during the HR suggested that the expression of cAPX is under the control of the HR signal transduction pathway. The activation of cAPX expression followed signaling events such as changes in protein phosphorylation and induction of ion fluxes. Expression of cAPX was suppressed under conditions of low oxygen pressure, and could only be mimicked by enhancing the intracellular generation of ROS. Interestingly, salicylic acid (SA), which is thought to be involved in ROS metabolism during the HR, did not affect the induction of cAPX mRNA during TMV-induced HR. Using cAPX expression as a marker for the production of ROS, it is suggested that SA may not be involved in the formation of ROS during the HR of tobacco to TMV, and that ROS may not be involved in the induction of the pathogenesis-related protein, PR-1, during this process.

Caspases and programmed cell death in the hypersensitive response of plants to pathogens

The hypersensitive response (HR) is induced by certain plant pathogens and involves programmed cell death (PCD) to restrict the spread of pathogens from the infection site [1]. Concurrent with the induction of cell death, the host activates a defense response [2]. The cell death associated with the HR in several plant-pathogen systems has morphological similarities to animal apoptosis [3,4], which suggests that cell death mechanisms in plants and animals may share common components that lead to similar cellular events. Caspases are conserved cysteine proteases that regulate animal PCD [5]; caspase activity or an involvement of caspases in cell death has yet to be reported in plants. In this work, we investigated the participation of caspases in HR cell death. Caspase-specific peptide inhibitors, Ac-YVAD-CMK [6] and Ac-DEVD-CHO [7], could abolish bacteria-induced plant PCD but did not significantly affect the induction of other aspects of HR, such as the expression of defense genes. This result confirmed our previous model that cell death can be uncoupled from defense gene activation during HR [8]. Caspase-like proteolytic activity was detected in tobacco tissues that were developing HR following infection with tobacco mosaic virus (TMV). Our results provide evidence for the presence of caspase-like plant protease(s) that participate in HR cell death.

Inhibition of myogenic tone by mibefradil in rat cerebral arteries

The inhibitory effects of mibefradil (1.0 nM-1.0 microM), a putative selective inhibitor of T-type Ca2+ channels that has peripheral and coronary vasodilating properties with few negative inotropic effects, on pressure-induced vasoconstrictions were compared to depolarization- and [Arg8] vasopressin-induced tone in isolated middle cerebral arteries of the rat. The concentration-response relationships (IC50) for myogenic tone (70 +/- 20 nM), depolarization- (53 +/- 9 nM) and vasopressin-induced tone (70 +/- 10 nM) were equally inhibited by mibefradil. Pressure-induced responses were consistently inhibited by mibefradil throughout the myogenically active pressure range (20-100 mmHg). These results demonstrate that mibefradil is nonselective in inhibiting Ca2+ dependent cerebral artery tone due to myogenic activation, depolarization or receptor activation.

Activation of hsr203, a plant gene expressed during incompatible plant-pathogen interactions, is correlated with programmed cell death

hsr203J is a tobacco gene whose activation is rapid, highly localized, and specific for incompatible interactions between tobacco and the bacterial pathogen Ralstonia solanacearum. The effect of other hypersensitive response (HR)-inducing pathogens and elicitors has been tested with transgenic plants containing the hsr203J promoter-GUS reporter gene fusion, and confirms the generality of the preferential inducibility of the hsr203J gene promoter during incompatible interactions: bacterial and viral pathogens inducing an HR in tobacco were able to induce the promoter fusion, as were inducers of HR-like responses such as harpin, elicitins, and PopA1 proteins. A tomato hsr203 homologous cDNA was isolated (Lehsr203) and used to examine the effect of avr gene products on the expression of such genes. Lehsr203 was shown to be rapidly and transiently induced in leaves of the tomato Cf-9 line, following Avr9 product infiltration, but not in those of the Cf-0 line. Among potential effectors of HR or resistance such as H2O2, salicylic acid, methyl jasmonate, and 2,6-dichloro-isonicotinic acid (INA), none is able to induce a significant increase in promoter activation. In contrast, heavy metals that cause leaf necrosis can trigger such an activation. In addition, hsr203-GUS fusion expression is detected in transgenic tobacco lines expressing the bO gene and exhibiting spontaneous HR-like lesions. Taken together, these results demonstrate a strong correlation between hsr203 and genetically controlled cell death in tobacco and tomato. The expression of this gene should be a useful marker for programmed cell death occurring in response not only to diverse pathogens, but also to diverse death-triggering extracellular agents.