Aggregation-induced emission of 1-methyl-1,2,3,4,5-pentaphenylsilole

Aggregation greatly boosts emission efficiency of the silole, turning it from a weak luminophor into a strong emitter.

Activation of Arp2/3 complex-mediated actin polymerization by cortactin

Cortactin, a filamentous actin (F-actin)-associated protein and prominent substrate of Src, is implicated in progression of breast tumours through gene amplification at chromosome 11q13. However, the function of cortactin remains obscure. Here we show that cortactin co-localizes with the Arp2/3 complex, a de novo actin nucleator, at dynamic particulate structures enriched with actin filaments. Cortactin binds directly to the Arp2/3 complex and activates it to promote nucleation of actin filaments. The interaction of cortactin with the Arp2/3 complex occurs at an amino-terminal domain that is rich in acidic amino acids. Mutations in a conserved amino-acid sequence of DDW abolish both the interaction with the Arp2/3 complex and complex activation. The N-terminal domain is not only essential but also sufficient to target cortactin to actin-enriched patches within cells. Interestingly, the ability of cortactin to activate the Arp2/3 complex depends on an activity for F-actin binding, which is almost 20-fold higher than that of the Arp2/3 complex. Our data indicate a new mechanism for activation of actin polymerization involving an enhanced interaction between the Arp2/3 complex and actin filaments.

Recovery of mitogenic activity of a growth factor mutant with a nuclear translocation sequence

Heparin-binding growth factor-1 (HBGF-1) is an angiogenic polypeptide mitogen for mesoderm- and neuroectoderm-derived cells in vitro and remains biologically active after truncation of the amino-terminal domain (HBGF-1 alpha) of the HBGF-1 beta precursor. Polymerase chain reaction mutagenesis and prokaryotic expression systems were used to prepare a mutant of HBGF-1 alpha lacking a putative nuclear translocation sequence (amino acid residues 21 to 27; HBGF-1U). Although HBGF-1U retains its ability to bind to heparin, HBGF-1U fails to induce DNA synthesis and cell proliferation at concentrations sufficient to induce intracellular receptor-mediated tyrosine phosphorylation and c-fos expression. Attachment of the nuclear translocation sequence from yeast histone 2B at the amino terminus of HBGF-1U yields a chimeric polypeptide (HBGF-1U2) with mitogenic activity in vitro and indicates that nuclear translocation is important for this biological response.

Recombinant fibroblast growth factor-1 promotes intimal hyperplasia and angiogenesis in arteries in vivo

The prototype members of the heparin-binding fibroblast growth factor (FGF) family, acidic FGF (FGF-1) and basic FGF (FGF-2), are among the growth factors that act directly on vascular cells to induce endothelial cell growth and angiogenesis. In vivo, the role of the FGF prototypes in vascular pathology has been difficult to determine. We report here the introduction, by direct gene transfer into porcine arteries, of a eukaryotic expression vector encoding a secreted form of FGF-1. This somatic transgenic model defines gene function in the arterial wall in vivo. FGF-1 expression induced intimal thickening in porcine arteries 21 days after gene transfer, in contrast to control arteries transduced with an Escherichia coli beta-galactosidase gene. Where there was substantial intimal hyperplasia, neocapillary formation was detected in the expanded intima. These findings suggest that FGF-1 induces intimal hyperplasia in the arterial wall in vivo and, through its ability to stimulate angiogenesis in the neointima, FGF-1 could stimulate neovascularization of atherosclerotic plaques. Potentially, gene transfer of FGF-1 could also be used as a genetic intervention to improve blood flow to ischaemic tissues in selected clinical settings.

The role of tyrosine phosphorylation of cortactin in the locomotion of endothelial cells

Cortactin, a filamentous actin cross-linking protein and a substrate of Src protein tyrosine kinase, is phosphorylated at tyrosine residues upon stimulation by extracellular signals. We have previously demonstrated that the filamentous actin cross-linking activity of cortactin is attenuated by Src (Huang, C., Ni, Y., Gao, Y., Haudenschild, C. C., and Zhan, X. (1997) J. Biol. Chem. 272, 13911-13915). In vitro, tyrosine phosphorylation of cortactin occurs specifically within the region between the proline-rich sequence and the Src homology 3 domain. Among the nine tyrosine residues in this region, mutations at Tyr421, Tyr466, and Tyr482 significantly reduced Src-meditated tyrosine phosphorylation both in vitro and in vivo. Ectopic expression of wild-type cortactin in ECV304, a spontaneously transformed human umbilical endothelial cell line, resulted in an enhanced cell migration. In contrast, overexpression of a cortactin mutant deficient in tyrosine phosphorylation impaired the migration of endothelial cells. These findings reveal an intracellular signaling mechanism whereby the motility of endothelial cells is regulated by a Src-mediated tyrosine phosphorylation of cortactin.

Heat shock induces the release of fibroblast growth factor 1 from NIH 3T3 cells

Fibroblast growth factor 1 (FGF-1) is a potent angiogenic and neurotrophic factor whose structure lacks a classical signal sequence for secretion. Although the initiation of these biological activities involves the interaction between FGF-1 and cell surface receptors, the mechanism responsible for the regulation of FGF-1 secretion is unknown. We report that murine NIH 3T3 cells transfected with a synthetic gene encoding FGF-1 secrete FGF-1 into their conditioned medium in response to heat shock. The form of FGF-1 released by NIH 3T3 cells in response to increased temperature (42 degrees C, 2 hr) in vitro is not biologically active and does not associate with either heparin or the extracellular NIH 3T3 monolayer matrix. However, it was possible to derive biologically active FGF-1 from the conditioned medium of heat-shocked NIH 3T3 cell transfectants by ammonium sulfate fractionation. The form of FGF-1 exposed by ammonium sulfate fractionation is similar in size to cytosolic FGF-1 and can bind and be eluted from immobilized heparin similarly to the recombinant human FGF-1 polypeptide. Further, the release of FGF-1 by NIH 3T3 cell transfectants in response to heat shock is reduced significantly by both actinomycin D and cycloheximide. These data indicate that increased temperature may upregulate the expression of a factor responsible for the secretion of FGF-1 as a biologically inactive complex that requires an activation step to exhibit the biological activity of the extracellular polypeptide mitogen.

Down-regulation of the filamentous actin cross-linking activity of cortactin by Src-mediated tyrosine phosphorylation

Cortactin, a prominent substrate for pp60(c-src), is a filamentous actin (F-actin) binding protein. We show here that cortactin can promote sedimentation of F-actin at centrifugation forces under which F-actin is otherwise not able to be precipitated. Electron microscopic analysis after negative staining further revealed that actin filaments in the presence of cortactin are cross-linked into bundles of various degrees of thickness. Hence, cortactin is also an F-actin cross-linking protein. We also demonstrate that the optimal F-actin cross-linking activity of cortactin requires a physiological pH in a range of 7.3-7.5. Furthermore, pp60(c-src) phosphorylates cortactin in vitro, resulting in a dramatic reduction of its F-actin cross-linking activity in a manner depending on levels of tyrosine phosphorylation. In addition, pp60(c-src) moderately inhibits the F-actin binding activity of cortactin. This study presents the first evidence that pp60(c-src) can directly regulate the activity of its substrate toward the cytoskeleton and implies a role of cortactin as an F-actin modulator in tyrosine kinase-regulated cytoskeleton reorganization.

Iron sulphides mediated autotrophic denitrification: An emerging bioprocess for nitrate pollution mitigation and sustainable wastewater treatment

Iron sulphides, mainly in the form of mackinawite (FeS), pyrrhotite (Fe_1-xS, x = 0-0.125) and pyrite (FeS₂), are the most abundant sulphide minerals and can be oxidized under anoxic and circumneutral pH conditions by chemoautotrophic denitrifying bacteria to reduce nitrate to N₂. Iron sulphides mediated autotrophic denitrification (ISAD) represents an important natural attenuation process of nitrate pollution and plays a pivotal role in linking nitrogen, sulphur and iron cycles in a variety of anoxic environments. Recently, it has emerged as a promising bioprocess for nutrient removal from various organic-deficient water and wastewater, due to its specific advantages including high denitrification capacity, simultaneous nitrogen and phosphorus removal, self-buffering properties, and fewer by-products generation (sulphate, waste sludge, N₂O, NH₄⁺, etc.). This paper provides a critical overview of fundamental and engineering aspects of ISAD, including the theoretical knowledge (biochemistry, and microbial diversity), its natural occurrence and engineering applications. Its potential and limitations are elucidated by summarizing the key influencing factors including availability of iron sulphides, low denitrification rates, sulphate emission and leaching heavy metals. This review also put forward two key questions in the mechanism of anoxic iron sulphides oxidation, i.e. dissolution of iron sulphides and direct substrates for denitrifiers. Finally, its prospects for future sustainable wastewater treatment are highlighted. An iron sulphides-based biotechnology towards next-generation wastewater treatment (NEO-GREEN) is proposed, which can potentially harness bioenergy in wastewater, incorporate resources (P and Fe) recovery, achieve simultaneous nutrient and emerging contaminants removal, and minimize waste sludge production.

Occurrence of phthalic acid esters in source waters: a nationwide survey in China during the period of 2009-2012

The first nationwide survey of six phthalic acid esters (PAEs) (diethyl phthalate (DEP); dimethyl phthalate (DMP); di-n-butyl phthalate (DBP); butyl benzyl phthalate (BBP); bis(2-ethylhexyl) phthalate (DEHP); di-n-octyl phthalate (DnOP)) in source waters was conducted in China. The results showed these PAEs were ubiquitous in source waters. DBP and DEHP were the most frequently detected with high concentrations ranging nd-1.52 μg/L and nd-6.35 μg/L, respectively. These PAEs concentrations (except DBP) in surface water (rivers, lakes and reservoirs) were generally higher than those in groundwater; DBP had high concentrations in groundwater in Northeast China (Liao River Basin) and North China (Hai River Basin). Their concentrations in the northern regions were generally higher than those in the southern and eastern regions; particularly, in North China. Three short-chain PAEs (DMP, DEP and DBP) were detected with high concentrations in Hai River Basin, Pearl River Basin and Yellow River Basin.

The human FGF-5 oncogene encodes a novel protein related to fibroblast growth factors

We previously described the isolation of a human oncogene which had acquired transforming potential by a DNA rearrangement accompanying transfection of NIH 3T3 cells with human tumor DNA (X. Zhan, A. Culpepper, M. Reddy, J. Loveless, and M. Goldfarb, Oncogene 1:369-376, 1987). We now term this oncogene the FGF-5 gene, since it specifies the fifth documented protein related to fibroblast growth factors (FGFs. Two regions of the FGF-5 sequence, containing 122 of its 267 amino acid residues, were 40 to 50% homologous to the sequences of acidic and basic FGFs as well as to the sequences of the FGF-related oncoproteins int-2 and hst/KS3. The FGF-5 gene bears the three exon structures typical for members of this family. FGF-5 was found to be expressed in the neonatal brain and in 3 of the 13 human tumor cell lines examined. Several experiments strongly suggested that FGF-5 is a growth factor with properties common to those of acidic and basic FGFs. The rearrangement which activated the FGF-5 gene during DNA transfection had juxtaposed a retrovirus transcriptional enhancer just upstream from the native promoter of the gene.

A review on control of harmful algal blooms by plant-derived allelochemicals

Harmful algal blooms (HABs) have several negative impacts on aquatic ecosystem, and even harm to humans. Utilization of allelochemicals to inhibit microalgal overgrowth is an environment-friendly approach for controlling HABs. This paper demonstrated the development of allelochemicals with algicidal effects, including the development history of allelopathy, the application methods, the reported allelopathic plants and their derived allelochemicals. Allelopathy is a promising strategy to control HABs as the effectiveness of allelochemicals on inhibiting microalgae cells has been discovered and confirmed for many years. The proposed allelopathic mechanisms and species-selective properties were expounded as well. Moreover, this paper further proposed suggestions for the further research and development of allelopathy strategy for HABs control.

Regulation of ciliary beat frequency by the nitric oxide-cyclic guanosine monophosphate signaling pathway in rat airway epithelial cells

Nitric oxide (NO) upregulates ciliary beat frequency (CBF). The present study evaluates mechanisms of the NO-cyclic guanosine monophosphate (cGMP) pathway regulation of CBF. Rat tracheal explants were loaded with 4,5-diaminofluorescein diacetate for the demonstration of NO production by ciliated epithelial cells after L-arginine (L-Arg) stimulation. CBF was measured using phase contrast microscopy and videotape analysis. The roles of NO, soluble guanylate cyclase (sGC), cGMP-dependent protein kinase (PK) G, and phosphodiesterase (PDE) V in regulation of CBF were evaluated. NO synthase (NOS) was activated with L-Arg or inhibited with N(G)-monomethyl-L-Arg. sGC was stimulated with NO donors 1-hydroxy-2-oxo-3- (N-ethyl-2-aminoethyl)-3-ethyl-1-triazene and S-nitroso-L-glutathione or mimicked by 8-bromo-guanosine 3', 5'-cyclic monophosphate (8-Br-cGMP) and inhibited with 1H-[1,2, 4]oxadiazole[4,3-a]quinoxalin-1-one. The effects of the PKG inhibition with KT5823 and PDE V inhibition with Zaprinast were also examined. The studies demonstrate that ciliated epithelial cells produce NO, which is correlated with CBF stimulation. L-Arg dose- and time-dependently increases CBF, and NO donors, 8-Br-cGMP, and Zaprinast also enhance CBF. Inhibitors of NOS, sGC, and PKG can block the stimulant effect of L-Arg on CBF. Thus, NO is a regulator of CBF acting via sGC and PKG. The NO-cGMP signaling pathway regulates CBF in an autocrine manner in cultured rat ciliated airway epithelium.

Simultaneous nitrate and phosphate removal from wastewater lacking organic matter through microbial oxidation of pyrrhotite coupled to nitrate reduction

This study investigated the efficiency of a pyrrhotite autotrophic denitrification biofilter (PADB) technology for simultaneous N and P removal from wastewater lacking organic matter. A PADB was constructed with natural pyrrhotite as the biofilter medium and inoculated with autotrophic denitrifies enriched from anaerobic sludge. Over an operating period of 247 days, PADB efficiently removed NO3(-) and PO4(3-) simultaneously from wastewater that lacked organic matter. The hydraulic retention time (HRT), and influent NO3(-) and PO4(3-) concentrations affected the removal of NO3(-) and PO4(3-). A longer HRT led to lower concentrations of NO3(-) and PO4(3-) in the effluent. The PO4(3-) removal was influenced by NO3(-) removed; the more NO3(-) removed, the more PO4(3-) removed. As the synthetic wastewater containing NO3(-)-N of 28 mg L(-1) and PO4(3-)-P of 6 mg L(-1) in the absence of organic matter was treated by PADB at HRT of 24 h, total oxidized nitrogen (TON; NO2(-)-N + NO3(-)-N) and PO4(3-)-P concentrations of effluent were as low as 1.13 and 0.28 mg L(-1), respectively. When treatment of municipal wastewater treatment plant (WWTP) secondary effluent with TON of 21.11 mg L(-1) and PO4(3-)-P of 2.62 mg L(-1) at HRT of 24 h, the effluent TON was 1.89 mg L(-1) and PO4(3-)-P was 0.34 mg L(-1). PO4(3-) was removed through the formation of secondary minerals with Fe and Ca. These secondary minerals contained elevated phosphorus, which presents a potential for P recovery from wastewater.

Analysis of endogenous and exogenous nuclear translocation of fibroblast growth factor-1 in NIH 3T3 cells

Nuclear localization of fibroblast growth factors (FGF) have been reported by many laboratories. We demonstrate here that FGF-1, the precursor for acidic FGF contains a putative nuclear translocation sequence (NTS) NYKKPKL, which is able to direct the expression of the bacterial beta galactosidase (beta gal) gene to the nucleus of transfected NIH 3T3 cells. However, this NTS is unable to target either FGF-1 itself or a FGF-1-beta gal fusion protein into the nucleus, suggesting that FGF-1 may contain an additional sequence which prevents endogenously expressed FGF-1 from being translocated into the nucleus. Indeed, when FGF-1 was fused to the NTS derived from the yeast histone 2B gene, the chimeric construct also failed to be transported into the nucleus either by itself or as a beta gal fusion protein. Interestingly, when 125I-FGF-1 was used to stimulate quiescent NIH 3T3 cells, a significant amount of internalized 125I-FGF-1 (approximately 10%) was found within the nucleus and the nuclear localization of FGF-1 through the exogenous pathway could be significantly reduced by suramin, an inhibitor of the interaction of FGF-1 with its receptor. These data suggest that while FGF-1 contains a NTS, nuclear translocation requires an exogenous and not an endogenous pathway.

Cell volume-dependent phosphorylation of proteins of the cortical cytoskeleton and cell-cell contact sites. The role of Fyn and FER kinases

Cell volume affects diverse functions including cytoskeletal organization, but the underlying signaling pathways remained undefined. We have shown previously that shrinkage induces Fyn-dependent tyrosine phosphorylation of the cortical actin-binding protein, cortactin. Because FER kinase was implicated in the direct phosphorylation of cortactin, we investigated the osmotic responsiveness of FER and its relationship to Fyn and cortactin. Shrinkage increased FER activity and tyrosine phosphorylation. These effects were abolished by the Src family inhibitor PP2 and strongly mitigated in Fyn-deficient but not in Src-deficient cells. FER overexpression caused cortactin phosphorylation that was further enhanced by hypertonicity. Exchange of tyrosine residues 421, 466, and 482 for phenylalanine prevented cortactin phosphorylation by hypertonicity and strongly decreased it upon FER overexpression, suggesting that FER targets primarily the same osmo-sensitive tyrosines. Because constituents of the cell-cell contacts are substrates of Fyn and FER, we investigated the effect of shrinkage on the adherens junctions. Hypertonicity provoked Fyn-dependent tyrosine phosphorylation in beta-catenin, alpha-catenin, and p120(Cas) and caused the dissociation of beta-catenin from the contacts. This process was delayed in Fyn-deficient or PP2-treated cells. Thus, FER is a volume-sensitive kinase downstream from Fyn, and the Fyn/FER pathway may contribute to the cell size-dependent reorganization of the cytoskeleton and the cell-cell contacts.

Src is required for cell migration and shape changes induced by fibroblast growth factor 1

Fibroblast growth factor 1 (FGF-1) is a potent chemotactic factor and induces tyrosine phosphorylation of a cortical actin-associated protein (cortactin). The tyrosine phosphorylation of cortactin induced by FGF-1 requires the tyrosine residues 421, 482 and 466, which are targeted by the protein tyrosine kinase Src in vitro. Furthermore, FGF-1 is unable to induce tyrosine phosphorylation of cortactin within the cells derived from Src knockout mice (Src-/-), indicating that Src is required for the tyrosine phosphorylation of cortactin induced by FGF-1. Although Src-/- cells are able to undergo rapid proliferation, they are impaired to respond to FGF-1 for the shape change and cell migration. Morphological analysis further reveals that FGF-1 fails to induce the formation of polarized lamellipodia and the translocation of cortactin into the leading edge of Src-/- cells. Consistent with the mitogenic response to FGF-1, the lack of Src does not affect the tyrosine phosphorylation of Snt (or Frs2), a FGF-1 early signaling protein that links to Ras. Therefore, our data support the notion that Src and cortactin participate in a FGF signal pathway for cell migration and shape change rather than mitogenesis.

Anaerobic co-digestion: A critical review of mathematical modelling for performance optimization

Anaerobic co-digestion (AcoD) is a pragmatic approach to simultaneously manage organic wastes and produce renewable energy. This review demonstrates the need for improving AcoD modelling capacities to simulate the complex physicochemical and biochemical processes. Compared to mono-digestion, AcoD is more susceptible to process instability, as it operates at a higher organic loading and significant variation in substrate composition. Data corroborated here reveal that it is essential to model the transient variation in pH and inhibitory intermediates (e.g. ammonia and organic acids) for AcoD optimization. Mechanistic models (based on the ADM1 framework) have become the norm for AcoD modelling. However, key features in current AcoD models, especially relationships between system performance and co-substrates' properties, organic loading, and inhibition mechanisms, remain underdeveloped. It is also necessary to predict biogas quantity and composition as well as biosolids quality by considering the conversion and distribution of sulfur, phosphorus, and nitrogen during AcoD.

Regulation of the activities of African cassava mosaic virus promoters by the AC1, AC2, and AC3 gene products

DNA fragments comprising each of the promoter regions from the geminivirus African cassava mosaic virus (ACMV) were cloned into the pUC18-based vector, pG1, producing transcriptional fusions with the beta-glucuronidase gene (GUS) and nopaline synthase terminator sequence. The relative activity of each promoter construct was analyzed by a GUS expression assay of extracts from Nicotiana clevelandii protoplasts coelectroporated with the GUS reporter constructs and constructs in which individual ACMV open reading frames (ORFs) were placed under control of a cauliflower mosaic virus 35 S promoter. Results suggest repression of the AC1 gene by its gene product, which is required for ACMV DNA synthesis. The promoter activity observed for the single promoter for the DNA A genes encoding functions of spread and the regulation of replication (AC2 and AC3 ORFs) was unaffected by coelectroporation with any of the ACMV ORF constructs. Promoters for the AV1 (coat protein) gene and the two DNA B genes (BV1 and BC1) were activated by electroporation of the AC2 ORF construct. To a lesser extent promoters for the AV1 and BV1 genes were activated with the AC3 ORF construct. The same pattern of promoter repression and activation was observed when transgenic N. benthamiana plants expressing the GUS reporter constructions were inoculated with ACMV DNA A.

Role of phosphatidylinositol 4,5-bisphosphate in Ras/Rac-induced disruption of the cortactin-actomyosin II complex and malignant transformation

Oncogenic Ras mutants such as v-Ha-Ras cause a rapid rearrangement of actin cytoskeleton during malignant transformation of fibroblasts or epithelial cells. Both PI-3 kinase and Rac are required for Ras-induced malignant transformation and membrane ruffling. However, the signal transduction pathway(s) downstream of Rac that leads to membrane ruffling and other cytoskeletal change(s) as well as the exact biochemical nature of the cytoskeletal change remain unknown. Cortactin/EMS1 is the first identified molecule that is dissociated in a Rac-phosphatidylinositol 4,5-biphosphate (PIP2)-dependent manner from the actin-myosin II complex during Ras-induced malignant transformation; either the PIP2 binder HS1 or the Rac blocker SCH51344 restores the ability of EMS1 to bind the complex and suppresses the oncogenicity of Ras. Furthermore, while PIP2 inhibits the actin-EMS1 interaction, HS1 reverses the PIP2 effect. Thus, we propose that PIP2, an end-product of the oncogenic Ras/PI-3 kinase/Rac pathway, serves as a second messenger in the Ras/Rac-induced disruption of the actin cytoskeleton and discuss the anticancer drug potential of PIP2-binding molecules.

Impact of total solids content on anaerobic co-digestion of pig manure and food waste: Insights into shifting of the methanogenic pathway

Dry anaerobic digestion (AD) has advantages over wet AD in treating high-solid organic wastes like livestock and food wastes, but an elevated total solids (TS) content would affect the AD performances. In this study, methane production of digesters co-digesting pig manure (PM) and food waste (FW) at different TS contents (R₁, TS 5%; R₂, TS 10%; R₃, TS 15%; and R₄, TS 20%) was assessed. The results showed the specific methane yield had no significant difference with the increase of TS contents from 5% to 15% (278.8-291.7 NmL/g VS_added), while it was reduced at a 20% TS content (259.8 NmL/g VS_added). Two peaks of total volatile fatty acids and daily methane production were observed in the high-solid digesters (R₂-R₄), while only one peak occurred in wet AD (R₁). A new kinetics model was developed to describe the two-peak methane production behavior at high TS contents. The analysis on the microbial community structure clearly showed the different evolutions of methanogenic pathways in low and high solids content systems. In dry AD (R₄), there was a general shifting from the acetoclastic pathway, to mixotrophic pathway and hydrogenotrophic pathway, with the dominance of mixotrophic and hydrogenotrophic methanogens.

Proteolysis of platelet cortactin by calpain

Cortactin, a substrate of pp60(c-)src and a potent filamentous actin binding and cross-linking protein, is abundant in circulating platelets. After stimulation of platelet aggregation with collagen, cortactin undergoes a dramatic increase in tyrosine phosphorylation followed by a rapid degradation. The cleavage of platelet cortactin was detected in lysates prepared using either Triton-containing buffer or SDS-sample buffer. However, the degradation of cortactin was not observed in platelets derived from a Glanzmann's patient, who lacked functional integrin alphaIIbbeta3 (GPIIb-IIIa). In addition, the proteolysis of cortactin was abolished by treating platelets before but not after collagen stimulation with EGTA or calpeptin. Furthermore, recombinant cortactin was digested by mu-calpain in vitro in a dose-dependent manner, indicating that cortactin is a substrate for calpain. We also observed that the calpain-mediated digestion in vitro is dependent on the presence of a sequence containing a proline-rich region and multiple tyrosine residues that are phosphorylated by pp60(c-)src. Tyrosine phosphorylation by pp60(c-)src up-regulates the activity of calpain toward cortactin. Our data suggest that the calpain-mediated proteolysis of tyrosine-phosphorylated cortactin may provide a mechanism to remodel irreversibly the cytoskeleton in response to platelet agonists.

The nucleotide sequence of the infectious cloned DNA component of tobacco yellow dwarf virus reveals features of geminiviruses infecting monocotyledonous plants

An infectious clone of the Australian geminivirus tobacco yellow dwarf virus (TobYDV) was constructed from virus-specific double-stranded DNA isolated from infected tobacco and used to demonstrate a single-component genome. The nucleotide sequence of TobYDV DNA comprises 2580 nucleotides. TobYDV DNA has three coding regions, two in the virion sense and one in the complementary sense, homologous to those identified for other geminiviruses, particularly those infecting monocotyledonous (monocot) plants. The complementary sense coding region is comprised of two overlapping reading frames, with an intron of 86 nucleotides. Efficient splicing of the mRNA for this coding region was observed in the infected dicotyledonous (dicot) hosts bean and tobacco despite the intron having an A + U content (57%) more typical of geminiviruses of monocot plants. TobYDV encapsidates a small oligonucleotide able to prime synthesis of the complementary DNA strand in vitro. The TobYDV genome organization, low A + U intron, and encapsidated oligonucleotide primer resemble those of the monocot-infecting geminiviruses. These results strongly suggest that TobYDV is a monocot geminivirus which has become adapted to dicot hosts.

Effects of thermo-chemical pre-treatment of grass silage on methane production by anaerobic digestion

Dried grass silage (GS) was pre-treated at different NaOH loading rates (1%, 2.5%, 5% and 7.5% by volatile solids (VS) mass in grass silage) and temperatures (20 °C, 60 °C, 100 °C and 150 °C) to determine effects on its bio-degradability in terms of the hydrolysis yield and degradation of ligno-cellulosic materials for biogas production. At 100 °C and the four NaOH loadings, up to 45% of the total COD was solubilised and up to 65.6%, 36.1% and 21.2% of lignin, hemicellulose and cellulose were removed, respectively; biological methane production potentials obtained were 359.5, 401.8, 449.5 and 452.5 ml CH₄/g VS added, respectively, being improved by 10-38.9% in comparison with untreated GS. VS removals following anaerobic digestion were 67.6%, 76.9%, 85.3%, 95.2% and 96.7% for untreated GS and GS treated at the four NaOH loadings, respectively. 100 °C and the NaOH loading rate of 5% is recommended as a proper GS pre-treatment condition.

Tyrosine phosphorylation of cortactin is required for H2O2-mediated injury of human endothelial cells

Injury of endothelial cells induced by reactive oxygen species plays an important role in the development of early stages of vascular diseases such as hypertension and atherosclerosis. Exposure of human umbilical vein endothelial cells to hydrogen peroxide (H(2)O(2)), a common form of reaction oxygen species, triggers a series of intracellular events, including actin cytoskeletal reorganization, cytoplasm shrinkage, membrane blebbing and protein-tyrosine phosphorylation. The effect of H(2)O(2) on endothelial cells is dramatically enhanced when a survival pathway involving extracellular signal-regulated kinase is blocked by PD098059. In contrast, the injury of endothelial cells mediated by H(2)O(2) is inhibited by PP2, a selective specific inhibitor for protein-tyrosine kinase Src. Cortactin, a filamentous actin (F-actin)-associated protein, becomes phosphorylated at tyrosine residues upon stimulation by H(2)O(2) in a manner dependent on the activity of Src. The level of tyrosine phosphorylation of cortactin is correlated with the formation of membrane blebs. Overexpression of wild-type cortactin tagged with green fluorescent protein in endothelial cells via a retroviral vector substantiates the H(2)O(2)-induced morphological changes, whereas overexpression of a green fluorescent protein-cortactin mutant deficient in tyrosine phosphorylation renders endothelial cells resistant to H(2)O(2). The functional role of cortactin in H(2)O(2)-mediated shape changes was also evaluated in NIH 3T3 cells. Stable 3T3 transfectants expressing wild-type cortactin in the presence of either H(2)O(2)/PD098059 or H(2)O(2) alone at 200 microm exhibited a dramatic shape change characterized by rounding up or aggregation. However, the similar changes were not detected with cells overexpressing a cortactin mutant deficient in tyrosine phosphorylation. These data demonstrate an important role of the Src/cortactin-dependent actin reorganization in the injury of endothelial cells mediated by reactive oxygen species.