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Resistant Clones (resistant + clone)
Selected AbstractsPost-gall induction performance of Adelges Abietis (L.) (Homoptera: Adelgidae) is influenced by clone, shoot length, and density of colonising gallicolaeECOLOGICAL ENTOMOLOGY, Issue 1 2010LEAH FLAHERTY 1. We evaluated the effect of clone (one susceptible and one resistant clone), shoot length, crown level, and gallicola density on post-gall induction performance of Adelges abietis. Galls that had been successfully induced by one fundatrix on a range of shoot sizes were selected, and the number of gallicolae that could colonise the gall was manipulated. 2. Post-induction gall development success was inversely related to shoot length and was higher on the susceptible clone than on the resistant clone. As gallicola density did not influence the proportion of galls that successfully completed development, reduced post-induction gall development on large shoots was not likely to be result of an insufficient stimulus from gallicolae. 3. Clone was the only factor that significantly influenced gall volume and galls were larger on the susceptible clone than on the resistant clone. As gall volume did not increase when more gallicolae attempted to colonise a gall, competition within a gall increased. Gallicola survival was inversely related to the number of colonising gallicolae. Our results suggest that gall size may be limiting at natural densities. 4. Previous studies report positive relationships between gall induction success and fundatrix density, and between gall size and fundatrix density. As each fundatrix produces one egg mass of gallicolae, this study suggests that there may be a trade-off between the successful induction of a large gall and subsequent survival of gallicolae. 5. In the present study, clone influenced all measures of post-gall induction performance. Performance was always higher on the susceptible than on the resistant clone. [source] First hybrid plane trees to show resistance against canker stain (Ceratocystis fimbriata f. sp. platani)FOREST PATHOLOGY, Issue 5 2004A. Vigouroux Summary Canker stain, caused by the ascomycete Ceratocystis fimbriata f. sp. platani, is a major threat to plane trees in Europe. The American plane tree (Platanus occidentalis) carries some genetic resistance, but this species is not adapted to the climatic conditions in Europe. Therefore, hybrids between susceptible oriental plane trees (Platanus orientalis) and resistant P. occidendalis were screened for disease resistance in France. Among 960 hybrids, we found 18 individuals which survived two successive inoculations. These putatively resistant trees were cut back and, after 18 months, on each tree 12 of the newly produced shoots as well as two roots, were inoculated again. From these trees, only one showed complete and another one partial resistance. This selection process resulting in the resistant clone ,Vallis clausa' is described in detail. Résumé La maladie du chancre coloré provoquée par l'ascomycète Ceratocystis fimbriata f. sp. platani, constitue une menace majeure pour le platane en Europe. Le platane américain (Platanus occidentalis) recèle une résistance génétique mais est très mal acclimaté aux conditions de milieu de l'Europe. Des hybrides entre le platane d'orient (Platanus orientalis) et des clones résistants de P. occidentalis ont donc été sélectionnés pour la résistance au chancre. Parmi les 960 hybrides, 18 individus ont survécu à deux inoculations successives sur le tronc. Rabattus, ces arbres, après 18 mois, ont été inoculés sur 12 des rejets produits par arbre, ainsi que sur deux de leurs racines. De ces arbres, seul un sujet a montré une résistance totale aux deux niveaux, un autre arbre montrant une résistance un peu moins complète. Zusammenfassung Der Platanenkrebs, verursacht durch den Ascomyceten Ceratocystis fimbriata f.sp. platani ist eine grosse Bedrohung für die Platanen in Europa. Die Amerikanische Platane (Platanus occidentalis) verfügt über eine gewisse Resistenz, aber diese Baumart ist nicht an die klimatischen Bedingungen in Europa angepasst. Deshalb wurden Hybriden zwischen anfälligen Platanen (Platanus orientalis) und resistenten P. occidentalis in Frankreich auf ihre Resistenz geprüft. Von 960 Hybriden überlebten 18 Individuen zwei aufeinander folgende Inokulationen. Diese möglicherweise resistenten Bäume wurden auf den Stock gesetzt und nach 18 Monaten wurden jeweils 12 der Neutriebe und zwei Wurzeln pro Pflanze erneut inokuliert. Hierbei zeigte ein Baum völlige, ein zweiter teilweise Resistenz. Dieser Selektionsprozess, welcher den resistenten Klon ,Vallis clausa' ergab, wird im Detail beschrieben. [source] Determinants of sensitivity and resistance to gemcitabine: The roles of human equilibrative nucleoside transporter 1 and deoxycytidine kinase in non-small cell lung cancerCANCER SCIENCE, Issue 9 2004Hiroyuki Achiwa Gemcitabine is one of the most commonly used agents for lung cancer chemotherapy, but the determinants of sensitivity and/or resistance to this agent are not yet fully understood. In this study we used quantitative RT-PCR to examine the expression levels of human equilibrative nucleoside transporter 1 (hENT1) and deoxycytidine kinase (dCK) genes in non-small cell lung cancer (NSCLC) cell lines in relation to sensitivity and resistance to gemcitabine. The basal expression levels of hENT1 were significantly correlated with the IC50 values for gemcitabine (r=-0.6769, P=0.0005), whereas dCK expression levels were not. In a highly gemcitabine-sensitive cell line, NCI-H23, the sensitivity to gemcitabine was inhibited by nitrobenzylmercaptopurine ribonucleoside (NBMPR), an inhibitor of hENT1, without significant modulation of hENT1 expression. These data suggest that hENT1 is associated with gemcitabine sensitivity in lung cancer. We also continuously exposed NCI-H23 cells to gemcitabine and subsequently established the drug-resistant clone H23/GEM-R, which showed a significant decrease of dCK expression; however, hENT1 expression was not altered in the continuously exposed sublines or in the resistant clone. We conclude that increased hENT1 expression is a determinant of gemcitabine sensitivity, while decreased dCK expression is associated with acquired resistance to gemcitabine in NSCLC cells. Thus, hENT1 and dCK might be useful as predictive markers for efficacy of gemcitabine therapy in NSCLC. [source] Reduced FAS transcription in clones of U937 cells that have acquired resistance to Fas-induced apoptosisFEBS JOURNAL, Issue 2 2009Jeanette Blomberg Susceptibility to cell death is a prerequisite for the elimination of tumour cells by cytotoxic immune cells, chemotherapy or irradiation. Activation of the death receptor Fas is critical for the regulation of immune cell homeostasis and efficient killing of tumour cells by apoptosis. To define the molecular changes that occur during selection for insensitivity to Fas-induced apoptosis, a resistant variant of the U937 cell line was established. Individual resistant clones were isolated and characterized. The most frequently observed defect in the resistant cells was reduced Fas expression, which correlated with decreased FAS transcription. Clones with such reduced Fas expression also displayed partial cross-resistance to tumour necrosis factor-, stimulation, but the mRNA expression of tumour necrosis factor receptors was not decreased. Reintroduction of Fas conferred susceptibility to Fas but not to tumour necrosis factor-, stimulation, suggesting that several alterations could be present in the clones. The reduced Fas expression could not be explained by mutations in the FAS coding sequence or promoter region, or by silencing through methylations. Protein kinase B and extracellular signal-regulated kinase, components of signalling pathways downstream of Ras, were shown to be activated in some of the resistant clones, but none of the three RAS genes was mutated, and experiments using chemical inhibitors could not establish that the activation of these proteins was the cause of Fas resistance as described in other systems. Taken together, the data illustrate that Fas resistance can be caused by reduced Fas expression, which is a result of an unidentified mode of regulation. [source] ABCG2 overexpression in colon cancer cells resistant to SN38 and in irinotecan-treated metastasesINTERNATIONAL JOURNAL OF CANCER, Issue 6 2004Laurent Candeil Abstract Overcoming drug resistance has become an important issue in cancer chemotherapy. Among all known mechanisms that confer resistance, active efflux of chemotherapeutic agents by proteins from the ATP-binding cassette family has been extensively reported. The aim of the present study was to determine the involvement of ABCG2 in resistance to SN38 (the active metabolite of irinotecan) in colorectal cancer. By progressive exposure to increasing concentrations of SN38, we isolated 2 resistant clones from the human colon carcinoma cell line HCT116. These clones were 6- and 53-fold more resistant to SN38 than the HCT116-derived sensitive clone. Topoisomerase I expression was unchanged in our resistant variants. The highest resistance level correlated with an ABCG2 amplification. This overexpression was associated with a marked decrease in the intracellular accumulation of SN38. The inhibition of ABCG2 function by Ko143 demonstrated that enhanced drug efflux from resistant cells was mediated by the activity of ABCG2 protein and confirmed that ABCG2 is directly involved in acquired resistance to SN38. Furthermore, we show, for the first time in clinical samples, that the ABCG2 mRNA content in hepatic metastases is higher after an irinotecan-based chemotherapy than in irinotecan-naive metastases. In conclusion, this study supports the potential involvement of ABCG2 in the development of irinotecan resistance in vivo. © 2004 Wiley-Liss, Inc. [source] XPC genetic polymorphisms correlate with the response to imatinib treatment in patients with chronic phase chronic myeloid leukemia,AMERICAN JOURNAL OF HEMATOLOGY, Issue 7 2010Vicent M. Guillem Chronic myeloid leukemia (CML) is driven by the BCR-ABL protein, which promotes the proliferation and viability of the leukemic cells. Moreover, BCR-ABL induces genomic instability that can contribute to the emergence of resistant clones to the ABL kinase inhibitors. It is currently unknown whether the inherited individual capability to repair DNA damage could affect the treatment results. To address this, a comprehensive analysis of single nucleotide polimorfisms (SNPs) on the nucleotide excision repair (NER) genes (ERCC2-ERCC8, RPA1-RPA3, LIG1, RAD23B, XPA, XPC) was performed in 92 chronic phase CML patients treated with imatinib upfront. ERCC5 and XPC SNPs correlated with the response to imatinib. Haplotype analysis of XPC showed that the wild-type haplotype (499C-939A) was associated with a better response to imatinib. Moreover, the 5-year failure free survival for CA carriers was significantly better than that of the non-CA carriers (98% vs. 73%; P = 0.02). In the multivariate logistic model with genetic data and clinical covariates, the hemoglobin (Hb) level and the XPC haplotype were independently associated with the treatment response, with patients having a Hb ,11 g/dl (Odds ratio [OR] = 5.0, 95% confidence interval [CI] = 1.5,16.1) or a non-CA XPC haplotype (OR = 4.1, 95% CI = 1.6,10.6) being at higher risk of suboptimal response/treatment failure. Our findings suggest that genetic polymorphisms in the NER pathway may influence the results to imatinib treatment in CML. Am. J. Hematol., 2010. © 2010 Wiley-Liss, Inc. [source] Selection for verticillium wilt resistance in potato breeding populations derived from four cross typesPLANT BREEDING, Issue 3 2009J. Bae Abstract Verticillium wilt (VW) is one of the important yield-limiting diseases for potato production. To develop resistant clones, the potential for early generation selection was studied using three basic selection methods, individual, family, and within family selection, for two clonal generations. A total of 152 clones were derived from four cross types (2x × 2x, 2x × 4x, 4x × 2x and 4x × 4x). Clones were evaluated for maturity, symptom expression, yield and stem colonization in replicated trials. Heritability and selection response for the traits were estimated for each selection method. Direct selection in the second clonal generation and individual selection showed more gain than that from other methods. Both 2x × 2x and 4x × 2x families were higher yielding and had lower stem colonization scores than 2x × 4x and 4x × 4x crosses. Therefore, 2x × 2x or 4x × 2x crosses between carefully chosen parents with high yield and VW resistance may produce offspring with superior performance. [source] | |||||||||||||