The effect of the armored scale,Rhizaspidiotus donacis (Hemiptera: Diaspididae), on shoot growth of the invasive plant Arundo donax (Poaceae: Arundinoideae)

The effect of feeding by the armored scale, Rhizaspidiotus donacis (Leonardi, 1920) (Hemiptera: Diaspididae) on the growth of the plant Arundo donax L. (Poaceae) was evaluated under field conditions in its native range. The study was designed to evaluate the impact of R. donacis, a candidate agent for biological control of A. donax which is invasive in arid riparian ecosystems of the Southwestern USA and Mexico. The study was carried out at five A. donax sites in the Province of Alicante, Spain, differing in altitude and climate. At each site, 30 infested lateral shoots were selected and 15 were randomly treated monthly with imidacloprid insecticide. Shoot lengths were measured monthly over a 1-year period in a comparative growth analysis. Shoots infested with R. donacis had an over 2-fold reduced growth rate as compared to treated shoots. Growth of shoots varied by site, and the effect of R. donacis on growth was most pronounced in the late spring, when mature females produced first instar scale crawlers. The impact of R. donacis on A. donax growth under field conditions in the native range, combined with its narrow host specificity, indicate that R. donacis is a promising candidate for biological control of A. donax in North America and other areas invaded by this weed.     

High-level expression of murine terminal deoxynucleotidyl transferase inEscherichia coli grown at low temperature and overexpressingargU tRNA

Terminal deoxynucleotidyl transferase (TdT) is a highly conserved vertebrate enzyme that possesses the unique ability to catalyze the random addition of deoxynucleoside 5′-triphosphates onto the 3′-hydroxyl group of a single-stranded DNA. It plays an important role in the generation of immunoglobin and T-cell receptor diversity. TdT is usually obtained from animal thymus gland or produced in a baculovirus system, but both procedures are rather tedious, and proteolysis occurs during purification. Attempts to overexpress TdT in bacteria have been unsuccessful or have yielded an enzyme with a lower specific activity. A dearth of TdT has thus hampered detailed structural and functional studies. In the present study, we report that by lowering growth temperature and overexpressing a rare arginyl tRNA, it is possible to boost the production inEscherichia coli of murine TdT with minimal proteolysis and high specific activity.     

Bile acids,FGF15/19 and liver regeneration: From mechanisms to clinical applications

The liver has an extraordinary regenerative capacity rapidly triggered upon injury or resection. This response is intrinsically adjusted in its initiation and termination, a property termed the “hepatostat”. Several molecules have been involved in liver regeneration, and among them bile acids may play a central role. Intrahepatic levels of bile acids rapidly increase after resection. Through the activation of farnesoid X receptor (FXR), bile acids regulate their hepatic metabolism and also promote hepatocellular proliferation. FXR is also expressed in enterocytes, where bile acids stimulate the expression of fibroblast growth factor 15/19 (FGF15/19), which is released to the portal blood. Through the activation of FGFR4 on hepatocytes FGF15/19 regulates bile acids synthesis and finely tunes liver regeneration as part of the “hepatostat”. Here we review the experimental evidences supporting the relevance of the FXR-FGF15/19-FGFR4 axis in liver regeneration and discuss potential therapeutic applications of FGF15/19 in the prevention of liver failure. This article is part of a Special Issue entitled: Cholangiocytes in Health and Disease edited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.     

表皮生长因子受体与他莫西芬耐药机制

雌激素受体及其信号通路在乳腺癌的发生发展中发挥着关键作用。到目前为止,抑制或阻断雌激素信号通路的内分泌治疗尤其是他莫西芬,仍是对雌激素受体阳性乳腺癌患者最有效的治疗手段之一。然而,他莫西芬的耐药问题直接影响了乳腺癌患者的治疗及预后。最近多项研究表明雌激素受体与表皮生长因子受体家族尤其是HER2介导的信号传导通路在多个点上相互交叉,彼此影响,与他莫西芬的耐药密切相关     

外源基因表达造成的群体感应细菌生存压力的建模分析

外源基因的表达及其对细菌种群的影响对于群体感应系统和合成生物学产业的研究具有重要意义。然而,人们对于表达外源蛋白的细菌本身的行为模式仍然知之甚少。为了研究菌落生长和外源基因表达的过程究竟受到哪些因素的影响,文中测量了受Lux类受体调控的外源基因在N-酰基高丝氨酸内酯 (N-acyl homoserine lactone,N-AHL) 信号分子诱导下的表达,并模拟了其对细菌种群动态的影响。文中建立了一个假设性的数学模型,对信号分子诱导表达下细菌种群生长受影响的现象进行了分析。先前的研究通常将细菌种群生长受群体感应系统影响的现象归咎于合成群体感应信号分子的消耗与N-AHL信号分子的毒性,文中提供了对于这种生存压力的另一种可能的解释。     

Correlation of changes in transglutaminase activity and polyamine content of neoplastic tissue during the metastatic process

Transglutaminase activity and the levels of the polyamines putrescine, spermidine and spermine were measured in two transplantable rat sarcomata: P₈ which metastasises consistently to the lung, and P₇ which metastasises infrequently. With the P₇ sarcoma no metastases were detected following implantation; similarly, no significant changes occurred in the levels of transglutaminase activity, putrescine, spermidine or spermine during tumour growth. However, with the P₈ sarcoma at approx. 30 days after implantation there was a marked decrease in transglutaminase activity, mirrored exactly by a 20-fold increase in the levels of acid-soluble putrescine. Measurement of covalently-bound polyamines in the P₈ sarcoma indicated a significant and corresponding decrease in the levels of bound putrescine. The timing of these changes coincided with the time at which the P₈ sarcoma was shown to have metastasised, and suggests that the changes observed may be related to this phenomenon.     

Response of physiological integration in Trifolium repens to heterogeneity of UV-B radiation

Physiological integration has been documented in many clonal plants growing under resource heterogeneity. Little is still known about the response of physiological integration to heterogeneous ultraviolet-B radiation. In this paper, the changes in intensity of physiological integration and of physiological parameters under homogeneous and heterogeneous ultraviolet-B radiation (280-315 nm) were measured in order to test the hypothesis that in addition to resource integration a defensive integration in Trifolium repens might exist as well. For this purpose, homogeneous and heterogeneous ultraviolet-B radiation was applied to pairs of connected and severed ramets of the stoloniferous herb Trifolium repens. Changes in intensity of water and nutrient integration were followed with acid fuchsin dye and ¹⁵N-isotope labeling of the xylem water transport. In order to assess the patterns of physiological integration contents of chlorophyll, ultraviolet-B absorbing compounds, soluble sugar and protein were determined and activities of superoxide dismutase (SOD) and peroxidase (POD) measured. When ramets were connected and exposed to heterogeneous UV-B radiation, the velocity of water transportation from the UV-B treated ramet to its connected sister ramet was markedly lower and the percentage of ¹⁵N left in labelled ramets that suffered from enhanced UV-B radiation was higher and their transfer to unlabelled ramets lower. In comparison with clones under homogeneous ultraviolet-B radiation, the content of chlorophyll, ultraviolet-B absorbing compounds, soluble sugar and activities of SOD and POD increased notably if ultraviolet-B stressed ramets were connected to untreated ramets. Chlorophyll and UV-B absorbing compounds were shared between connected ramets under heterogeneous UV-B radiation. This indicated that physiological connection improved the performance of whole clonal plants under heterogeneous ultraviolet-B radiation. The intensity of physiological integration of T. repens for resources decreased under heterogeneous ultraviolet-B radiation in favor of the stressed ramets. Ultraviolet-B stressed ramets benefited from unstressed ramets by physiological integration, supporting the hypothesis that clonal plants are able to optimize the efficiency of their resistance maintaining their presence also in less favorable sites. The results could be helpful for further understanding of the function of heterogeneous UV-B radiation on growth regulation and microevolution in clonal plants.