bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tumour‐associated macrophages and melanoma tumourigenesis: integrating the complexity
Authors: Hussein Mahmoud R. 
Published: May 2006

SummaryWhen the body discovers a tumour cell (foreign antigen), several kinds of mechanisms and cells operate in what is called an immune response. The latter has evolved into two mechanisms: non‐specific immunity and specific immunity, which are closely linked to and influence each other. The former represents the first line of defence against neoplastic cells. The adaptive (specific) immunity is orchestrated by antigen‐specific T and B lymphocytes. The effector cells of innate immunity include granulocytes, macrophages and natural killer cells. Among these cells, macrophages represent the most important part of innate immunity against tumours. Tumour‐associated macrophages (TAMs) are important antigen‐presenting cells and as such an understanding of their interactions with tumour cells gives insights into novel therapeutic strategies. In tumours, the effect of TAMs is the outcome of their two concomitantly competing interactions: tumour growth reduction and tumour growth promotion. The macrophage (TAMs) content of melanoma ranges from 0 to 30% and their density increases with increasing tumour thickness. The melanoma cells and TAMs seem to interact with each other through the release of soluble factors that either prevent or enhance tumour growth. For instance, syngeneic macrophages from tumour‐bearing mice can inhibit melanoma growth in the nude mice more than the control macrophages. Alternatively, metastatic B16 melanoma cells can produce some macrophage cytotoxic substances that help tumour cells not only escape the host immunosurveillance system but also prevent distant metastasis. Together, these observations suggest opposing effects for these soluble factors in melanoma. To date, little is available in the literature about the interactions between TAMs and melanoma cells. This viewpoint not only tries to examine these interactions but also provides relevant speculations.
TGFβ1 induces epithelial–mesenchymal transition, but not myofibroblast transdifferentiation of human kidney tubular epithelial cells in primary culture
Authors: Forino Monica , Torregrossa Rossella , Ceol Monica , Murer Luisa , Vella Manuela Della , Prete Dorella Del , D'Angelo Angela , Anglani Franca 
Published: May 2006

SummaryThe origin and fate of renal interstitial myofibroblasts (MFs), the effector cells of renal fibrosis, are still debated. Experimental evidence suggests that renal MFs derive from tubular epithelial cells throughout the epithelial–mesenchymal transition (EMT) process. Primary human tubular epithelial cells (HUTECs) were cultured for 4 and 6 days on plastic or type I collagen‐coated plates with 1, 5, 10 and 50 ng/ml of transforming growth factor β1 (TGFβ1). The EMT process was monitored by morphology and immunophenotyping for αSMA, cytokeratin 8–18, E‐cadherin, vimentin and collagen III. Quantitative comparative RT/PCR and real‐time PCR were used to evaluate the expression of collagen III and IV, fibronectin, tenascin, MMP‐2, CTGF, E‐cadherin and cadherin 11 genes, as well as those of the Smad signalling pathway. TGFβ1 was found capable of reactivating the mesenchymal programme switched off during tubulogenesis, but it induced no de novo expression of αSMA gene or myofibroblast phenotype. We demonstrate that the EMT process is conditioned by the extracellular matrix and characterized by TGFβ1‐driven Smad3 downregulation. Our study results suggest that TGFβ1 could function as a classic embryonal inducer, initiating a cascade of de‐differentiating events that might be further controlled by other factors in the cellular environment.
Morphological evaluation of the radioprotective effects of melatonin against X‐ray‐induced early and acute testis damage in Albino rats: an animal model
Authors: Hussein Mahmoud R. , Abu‐Dief Eman E. , Abou El‐Ghait Amal T. , Adly Mohamed A. , Abdelraheem Mohamad H. 
Published: May 2006

SummaryIrradiation has profound effects on the reproductive function. Our knowledge about radioprotective effects of melatonin against X‐ray‐induced testis damage is rudimentary. In this investigation, we hypothesized that melatonin can minimize germ‐cell depletion and morphological features of cell damage in testis following X‐ray irradiation (XRI). To examine these effects, and to test our hypothesis, an animal model comprised of 60 Albino rats was established. The animals were divided into five groups: Group 1, non‐irradiated; Group 2, X‐ray irradiated (XRI, 8 Grays); Group 3, XRI pretreated with solvent (ethanol and phosphate‐buffered saline); Group 4, non‐irradiated group treated with melatonin and Group 5, XRI pretreated with melatonin. The testes were evaluated for both histological (light microscopy) and ultrastructural changes (transmission electron microscopy). Histologically, there were marked depletions (66%) of the germinal epithelial cells, in XRI group (Groups 2 and 3), whereas these changes were almost absent in XRI testis of animals pretreated with melatonin (Group 5). The number of spermatogenic cells in XRI testis of animals pretreated with melatonin (Group 5) was comparable (95%) to that of non‐irradiated group (Groups 1 and 4) but significantly (P < 0.05) higher than those in XRI testis (34%, Groups 2 and 3). Ultrastructurally, XRI testis (Groups 2 and 3) showed features of apoptosis (condensation of the nuclei, vacuolization of the cytoplasm, increased cytoplasmic density and apoptotic bodies). These features were absent in XRI testis of animals pretreated with melatonin (Group 5). Also, this Group showed features of an increased metabolic activity (large acrosomal vesicle, prominent Golgi, increased mitotic activity, increased complement of cytoplasmic organelles and appearance of nucleoli‐like bodies). There was a minimal depletion of the Sertoli and Leydig cells following XRI. Also, morphological features of apoptosis were infrequent in these cells. Administration of melatonin (MEL) prior to irradiation can protect testis against its destructive effects. The protective effects include amelioration of germ‐cell depletion and apoptotic changes. The clinical ramifications of these observations mandate further studies.
Regulation ofEscherichia coli hchA, a stress‐inducible gene encoding molecular chaperone Hsp31
Authors: Mujacic Mirna , Baneyx François 
Published: May 2006

SummaryEscherichia coliHsp31 is a homodimeric member of the ThiI/DJ‐1/PfpI superfamily that combines molecular chaperone and aminopeptidase activities. Although it was originally identified on the basis of its induction by heat shock, little is known about the regulation ofhchA, the structural gene encoding Hsp31. Here, we show thathchAis transcribed from dual promoters recognized by the σD(σ70) and σS(σ38) subunits of RNA polymerase (E). In exponentially growing cells, the nucleoid‐binding protein H‐NS downregulates Hsp31 synthesis, andhchAthermal induction primarily relies on the relief of H‐NS‐mediated silencing of EσD‐dependent transcription. This uncommon alternative to the use of a heat‐shock sigma factor guarantees that Hsp31 concentration remains high throughout the length of the high temperature exposure phase. Entry into stationary phase leads to enhancedhchAtranscription from its EσS‐dependent promoter. Consistent with a role of Hsp31 in the management of starvation,hchAnull mutants exhibit a decrease ability to survive in deep stationary phase relative tohchA+cells. Based onhchAheat‐inducibility and membership in the σSgeneral stress regulon, we propose that Hsp31 performs a protective function under a wide range of stress conditions.
A mechanical role for the chemotaxis system in swarming motility
Authors: Mariconda Susana , Wang Qingfeng , Harshey Rasika M. 
Published: May 2006

SummaryThe chemotaxis system, but not chemotaxis, is essential for swarming motility in Salmonella enterica serovar Typhimurium. Mutants in the chemotaxis pathway exhibit fewer and shorter flagella, downregulate class 3 or ‘late’ motility genes, and appear to be less hydrated when propagated on a surface. We show here that the output of the chemotaxis system, CheY∼P, modulates motor bias during swarming as it does during chemotaxis, but for a distinctly different end. A constitutively active form of CheY was found to promote swarming in the absence of several upstream chemotaxis components. Two point mutations that suppressed the swarming defect of a cheY null mutation mapped to FliM, a protein in the motor switch complex with which CheY∼P interacts. A common property of these suppressors was their increased frequency of motor reversal. These and other data suggest that the ability to switch motor direction is important for promoting optimal surface wetness. If the surface is sufficiently wet, exclusively clockwise or counterclockwise directions of motor rotation will support swarming, suggesting also that the bacteria can move on a surface with flagellar bundles of either handedness.
Cooperation of two distinct ExpR regulators controls quorum sensing specificity and virulence in the plant pathogen Erwinia carotovora
Authors: Sjöblom Solveig , Brader Günter , Koch Gudrun , Palva E. Tapio 
Published: May 2006

SummaryQuorum sensing, the population density‐dependent regulation mediated by N‐acylhomoserine lactones (AHSL), is essential for the control of virulence in the plant pathogen Erwinia carotovora ssp. carotovora (Ecc). In Erwinia carotovora ssp. the AHSL signal with an acyl chain of either 6 or 8 carbons is generated by an AHSL synthase, the expI gene product. This work demonstrates that the AHSL receptor, ExpR1, of Ecc strain SCC3193 has strict specificity for the cognate AHSL 3‐oxo‐C8‐HSL. We have also identified a second AHSL receptor (ExpR2) and demonstrate a novel quorum sensing mechanism, where ExpR2 acts synergistically with the previously described ExpR1 to repress virulence gene expression in Ecc. We show that this repression is released by addition of AHSLs and appears to be largely mediated via the negative regulator RsmA. Additionally we show that ExpR2 has the novel property to sense AHSLs with different acyl chain lengths. The expI expR1 double mutant is able to act in response to a number of different AHSLs, while the expI expR2 double mutant can only respond to the cognate signal of Ecc strain SCC3193. These results suggest that Ecc is able to react both to the cognate AHSL signal and the signals produced by other bacterial species.
Establishment of a patterned GAL4‐VP16 transactivation system for discovering gene function in rice
Authors: Liang Dacheng , Wu Changyin , Li Caishun , Xu Caiguo , Zhang Jianwei , Kilian Andrzej , Li Xianghua , Zhang Qifa , Xiong Lizhong 
Published: May 2006

SummaryA binary GAL4‐VP16–UAS transactivation system has been established in rice (Oryza sativaL.) in this study for the discovery of gene functions. This binary system consists of two types of transgenic lines, pattern lines and target lines. The pattern lines were produced by transformation of Zhonghua 11, a japonica cultivar, with a construct consisting of the transactivator geneGAL4‐VP16controlled by a minimal promoter and the GUSplus reporter controlled by the upstream activation sequence (UAS;cis‐element to GAL4). Target lines were generated by transformation of Zhonghua 11 with constructs carrying the EGFP reporter and target genes of interest, both controlled by the UAS but in opposite directions. Hybrid plants were obtained by crossing target lines of 10 putative transcription factor genes from rice with six pattern lines showing expression in anther, stigma, palea, lemma and leaves. The EGFP and target genes perfectly co‐expressed in hybrid plants with the same expression patterns as in the pattern lines. Various phenotypic changes, such as delayed flowering, multiple pistils, dwarfism, narrow and droopy leaves, reduced tillers, growth retardation and sterility, were induced as a result of the expression of the target genes. It is concluded that this transactivation system can provide a useful tool in rice to unveil latent functions of unknown or known genes.
Association of Arabidopsis type‐II ROPs with the plasma membrane requires a conserved C‐terminal sequence motif and a proximal polybasic domain
Authors: Lavy Meirav , Yalovsky Shaul 
Published: May 2006

SummaryPlant ROPs (or RACs) are soluble Ras‐related small GTPases that are attached to cell membranes by virtue of the post‐translational lipid modifications of prenylation and S‐acylation. ROPs (RACs) are subdivided into two major subgroups called type‐I and type‐II. Whereas type‐I ROPs terminate with a conserved CaaL box and undergo prenylation, type‐II ROPs undergo S‐acylation on two or three C‐terminal cysteines. In the present work we determined the sequence requirement for association of Arabidopsis type‐II ROPs with the plasma membrane. We identified a conserved sequence motif, designated the GC‐CG box, in which the modified cysteines are flanked by glycines. The GC‐CG box cysteines are separated by five to six mostly non‐polar residues. Deletion of this sequence or the introduction of mutations that change its nature disrupted the association of ROPs with the membrane. Mutations that changed the GC‐CG box glycines to alanines also interfered with membrane association. Deletion of a polybasic domain proximal to the GC‐CG box disrupted the plasma membrane association of AtROP10. A green fluorescent protein fusion protein containing the C‐terminal 25 residues of AtROP10, including its polybasic domain and GC‐CG box, was primarily associated with the plasma membrane but a similar fusion protein lacking the polybasic domain was exclusively localized in the soluble fraction. These data provide evidence for the minimal sequence required for plasma membrane association of type‐II ROPs in Arabidopsis and other plant species.
Crosstalk between jasmonic acid, ethylene and Nod factor signaling allows integration of diverse inputs for regulation of nodulation
Authors: Sun Jongho , Cardoza Vinitha , Mitchell David M. , Bright Lydia , Oldroyd Giles , Harris Jeanne M. 
Published: May 2006

SummaryPlant hormones interact at many different levels to form a network of signaling pathways connected by antagonistic and synergistic interactions. Ethylene and jasmonic acid both act to regulate the plant's responsiveness to a common set of biotic stimuli. In addition ethylene has been shown to negatively regulate the plant's response to the rhizobial bacterial signal, Nod factor. This regulation occurs at an early step in the Nod factor signal transduction pathway, at or above Nod factor‐induced calcium spiking. Here we show that jasmonic acid also inhibits the plant's responses to rhizobial bacteria, with direct effects on Nod factor‐induced calcium spiking. However, unlike ethylene, jasmonic acid not only inhibits spiking but also suppresses the frequency of calcium oscillations when applied at lower concentrations. This effect of jasmonic acid is amplified in the ethylene‐insensitive mutant skl, indicating an antagonistic interaction between these two hormones for regulation of Nod factor signaling. The rapidity of the effects of ethylene and jasmonic acid on Nod factor signaling suggests direct crosstalk between these three signal transduction pathways. This work provides a model by which crosstalk between signaling pathways can rapidly integrate environmental, developmental and biotic stimuli to coordinate diverse plant responses.
Caterpillar‐elicited methanol emission: a new signal in plant–herbivore interactions?
Authors: Von Dahl Caroline C. , Hävecker Michael , Schlögl Robert , Baldwin Ian T. 
Published: May 2006

SummaryPlants release into the atmosphere large quantities of volatile organic compounds (VOCs), of which methanol (MeOH), a putative waste product, is the second most abundant. Using online proton‐transfer‐reaction mass spectrometry (PTR‐MS), we demonstrate that when Manduca sexta larvae attack Nicotiana attenuata plants, the wound‐induced release of MeOH dramatically increases. The sustained MeOH emission 24 h after herbivore feeding is already substantially greater than the release of the well‐characterized green‐leaf VOC E‐2‐hexenal. Herbivore attack and treatment of puncture wounds with larval oral secretions (OS) increased the transcript accumulation and activity of leaf pectin methylesterases (PMEs), and decreased the degree of pectin methylation, as determined by 1H‐NMR; therefore, we propose that the released MeOH originates from the activation of PMEs by herbivore attack. The herbivore‐ and OS‐elicited MeOH results not from the activity of previously characterized elicitors in OS but from a pH shift at the wound site when larval OS (pH 8.5–9.5) are introduced into the wounds during feeding. Applying MeOH to plants in quantities that mimic the herbivory‐elicited release decreases the activity of the potent plant defense proteins trypsin proteinase inhibitors (TPI), and increases the performance of the attacking larvae. The pH of lepidopteran larvae regurgitants is commonly very high, and the MeOH released during feeding that is elicited by the pH change at the wound site functions as a quantitative signal that influences the outcome of the plant–herbivore interaction.
Katanin's severing activity favors bundling of cortical microtubules in plants
Authors: Stoppin‐Mellet Virginie , Gaillard Jérémie , Vantard Marylin 
Published: May 2006

SummaryHigher plant cells exhibit interphase microtubule arrays specific to plants, which are essential for their developmental program. These cortical microtubules (CMT) consist of a population of highly dynamic microtubules that are usually organized into bundles in the cortex of the cells. The organization of CMT is intimately linked to the acquisition of specialized functions, and subsequentchanges in their distribution affect their properties. The mechanisms underlying the formation and the distribution of CMT are still unclear, and little is known about the proteins that are involved in this phenomenon. Here we investigated the putative role of katanin, the only known plant microtubule‐severing protein, in the organization of CMT. We generated transgenic Arabidopsis lines that overexpress katanin under the control of an ethanol‐inducible promoter. In response to an induced overexpression of katanin, CMT organized into numerous and thick bundles, which ultimately depolymerized. From the analyses of CMT patterns together with recent data on CMT dynamics, we propose that, in interphase cells, katanin's main activity is to free CMT, generating motile microtubules that incorporate into bundles.
Characterization and functional analysis of ABSCISIC ACID INSENSITIVE3‐like genes from Physcomitrella patens
Authors: Marella Heather H. , Sakata Yoichi , Quatrano Ralph S. 
Published: May 2006

SummaryAlthough the moss Physcomitrella patens is known to respond to abscisic acid (ABA) by activating gene expression, the transcriptional components involved have not been characterized. Initially, we used the ABA‐responsive Em promoter from wheat linked to β‐glucuronidase (GUS) to determine whether ABI3/VP1, transcriptional regulators in the ABA‐signaling pathway in angiosperms, were similarly active in the ABA response of P. patens. We show by particle bombardment that ABI3 and VP1 affect Em–GUS expression in P. patens in a manner similar to angiosperms. We also show the involvement of ABI1 in the pathway, utilizing the abi1‐1 mutant allele. We isolated three ABI3‐like genes from P. patens. Using an Em‐like ABA‐responsive promoter from P. patens (PpLea1), we demonstrate that PpABI3A, only in the presence of ABA, strongly enhances PpLea1–GUS expression in P. patens. PpABI3A also enhances ABA‐induced Em–GUS expression in P. patens. In barley aleurone, PpABI3A transactivates Em–GUS but to a lesser extent than VP1 and ABI3. PpABI3A:GFP is localized to the nucleus of both protonemal cells and barley aleurone, indicating that the nuclear localization signals are conserved. We show that at least a part of the inability of PpABI3A to fully complement the phenotypes of the Arabidopsis abi3‐6 mutant is due to a weak interaction between PpABI3A and the bZIP transcription factor ABI5, as assayed functionally in barley aleurone and physically in the yeast‐two‐hybrid assay. Our data clearly demonstrate that P. patens will be useful for comparative structural and functional studies of components in the ABA‐response pathway such as ABI3.
Impaired sucrose induction1 encodes a conserved plant‐specific protein that couples carbohydrate availability to gene expression and plant growth
Authors: Rook Fred , Corke Fiona , Baier Margarete , Holman Rachel , May Alexander G. , Bevan Michael W. 
Published: May 2006

SummaryTo identify the molecular mechanisms underlying carbohydrate allocation to storage processes, we have isolated mutants in which the sugar induction of starch biosynthetic gene expression was impaired. Here we describe the IMPAIRED SUCROSE INDUCTION1 (ISI1) gene, which encodes a highly conserved plant‐specific protein with structural similarities to Arm repeat proteins. ISI1 is predominantly expressed in the phloem of leaves following the sink‐to‐source transition during leaf development, but is also sugar‐inducible in mesophyll cells. Soil‐grown isi1 mutants show reduced plant growth and seed set compared to wild‐type Arabidopsis. This growth reduction is not due to reduced carbohydrate availability or a defect in sucrose export from mature leaves, suggesting that isi1 mutant plants do not utilize available carbohydrate resources efficiently. ISI1 interacts synergistically with, but is genetically distinct from, the abscisic acid (ABA) signalling pathway controlling sugar responses via ABI4. Our data show that ISI1 couples the availability of carbohydrates to the control of sugar‐responsive gene expression and plant growth.
Long‐term lamivudine monotherapy prevents development of hepatitis B virus infection in hepatitis B surface‐antigen negative liver transplant recipients from hepatitis B core‐antibody‐positive donors
Authors: Prakoso Emilia , Strasser Simone I. , Koorey David J. , Verran Deborah , McCaughan Geoffrey W. 
Published: May 2006

Abstract:  Background:  Liver transplantation from hepatitis B core‐antibody (HBcAb)‐positive donors to hepatitis B surface‐antigen (HBsAg)‐negative recipients has been associated with a risk of hepatitis B virus (HBV) infection in the absence of antiviral prophylaxis. The aim of this study is to assess the efficacy of long‐term lamivudine monotherapy to prevent development of HBV infection in HBsAg‐negative recipients of liver allografts from HBcAb‐positive donors.Methods:  From 315 cadaveric adult liver transplantations performed at our unit between July 1999 and March 2005, 18 recipients (5.7%) received liver allografts from HBcAb‐positive donors, 13 of whom were HBsAg‐negative pre‐transplantation. The recipients consisted of four females and 14 males, age range 28–65 yr (median 49.5 yr). Post‐transplantation, HBsAg‐negative recipients were administered lamivudine 100 mg daily long term. HBsAg‐positive recipients were administered low‐dose hepatitis B immunoglobulin (HBIg) and lamivudine according to our usual protocol. Standard post‐transplantation immunosuppression was given. Recipients were followed up regularly (range 2–69 months, median 21 months) for development of de novo HBV infection.Results:  Ten HBsAg‐negative recipients received long‐term lamivudine. One patient (HBcAb and HBsAb positive pre‐transplant) did not receive lamivudine and, in two patients, lamivudine was discontinued following urgent re‐transplantation for primary graft non‐function. All 13 of the HBsAg‐negative recipients were still alive, with no evidence of HBV infection at the end of follow‐up.Conclusion:  Long‐term lamivudine monotherapy was effective in preventing development of HBV infection in HBsAg‐negative liver transplant recipients from HBcAb‐positive donors.