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41.
Implication of nifA in regulation of genes located on a Rhizobium meliloti cryptic plasmid that affect nodulation efficiency. 总被引:5,自引:1,他引:5 下载免费PDF全文
We examined the contribution of a cryptic plasmid, pRmeGR4b, to the nodulation of Medicago sativa by strain GR4 of Rhizobium meliloti. A 905-base-pair PstI DNA fragment in pRmeGR4b was found to hybridize DNA of the R. meliloti fixA promoter region as a probe. Sequence analysis of the PstI fragment showed a 206-base-pair region displaying high homology with the DNA upstream of the RNA start points of the P1 and P2 symbiotic promoters. Putative nif promoter consensus sequences were conserved in this DNA segment. Expression of DNA downstream of the nif promoterlike sequence, monitored by beta-galactosidase activity of different lacZ fusions, was demonstrated to depend on a functional nifA gene, both in microaerobically free-living cells and in nodules. Individual transposon Tn3-HoHo1 insertions in this DNA region caused a reduced nodulation competitiveness. This new symbiotic region, occupying approximately 5 kilobases of pRmeGR4b DNA, was called nfe (nodule formation efficiency). 相似文献
42.
Eiichi Hasegawa Harry Sweigard Deeba Husain Ana M. Olivares Bo Chang Kaylee E. Smith Amy E. Birsner Robert J. D’Amato Norman A. Michaud Yinan Han Demetrios G. Vavvas Joan W. Miller Neena B. Haider Kip M. Connor 《PloS one》2014,9(9)
Background
Vision loss due to vascular disease of the retina is a leading cause of blindness in the world. Retinal angiomatous proliferation (RAP) is a subgroup of neovascular age-related macular degeneration (AMD), whereby abnormal blood vessels develop in the retina leading to debilitating vision loss and eventual blindness. The novel mouse strain, neoretinal vascularization 2 (NRV2), shows spontaneous fundus changes associated with abnormal neovascularization. The purpose of this study is to characterize the induction of pathologic angiogenesis in this mouse model.Methods
The NRV2 mice were examined from postnatal day 12 (p12) to 3 months. The phenotypic changes within the retina were evaluated by fundus photography, fluorescein angiography, optical coherence tomography, and immunohistochemical and electron microscopic analysis. The pathological neovascularization was imaged by confocal microscopy and reconstructed using three-dimensional image analysis software.Results
We found that NRV2 mice develop multifocal retinal depigmentation in the posterior fundus. Depigmented lesions developed vascular leakage observed by fluorescein angiography. The spontaneous angiogenesis arose from the retinal vascular plexus at postnatal day (p)15 and extended toward retinal pigment epithelium (RPE). By three months of age, histological analysis revealed encapsulation of the neovascular lesion by the RPE in the photoreceptor cell layer and subretinal space.Conclusions
The NRV2 mouse strain develops early neovascular lesions within the retina, which grow downward towards the RPE beginning at p15. This retinal neovascularization model mimics early stages of human retinal angiomatous proliferation (RAP) and will likely be a useful in elucidating targeted therapeutics for patients with ocular neovascular disease. 相似文献43.
G Sanchez A Wallace M Olivares N Diaz X Aguilera W Apt A Solari 《Experimental parasitology》1990,71(1):125-133
Thirty-one Trypanosoma cruzi isolates from Chile, Peru, and Bolivia were studied in their capacity to differentiate in vitro from epimastigotes to metacyclic trypomastigotes on TAU-3AAG medium. Zymodeme 1 parasites displayed the best level of differentiation, which ranges from 60 to 90% depending on the isolate. Zymodeme 2 parasites exhibited highly heterogenous differentiation rates. This differentiation method permits the obtention of large amounts of metacyclic trypomastigotes from zymodeme 1 parasites. Metacyclic trypomastigotes obtained in vitro were infective to nude Balb/c hybrid mice. Zymodeme 1 parasites produced high parasitemias in this murine model; in contrast, zymodeme 2 parasites displayed lower parasitemias. Of a total of 27 T. cruzi isolates, 20 proved to be infective to mice, 12 gave enough parasites for further studies, and 8 of these were used for biological characterization. Results are compared with the infective clone Dm28 and Tulahuén strains maintained since 1954 in mice. 相似文献
44.
Introduction and Purpose
The policy of school organisation for grouping students in the same academic year is based on date of birth. The differences in the experiences and maturation of older students involve a relatively better performance in academic settings, which is known as the relative age effect (RAE). This effect is more important the younger the student is. The goal of this study is to identify the connections of influence that RAE, socioeconomic status (SES), and type of institution have on academic performance in a school population of eighth graders.Methods
The study is based on a population-based, representative sample of 15,234 8th graders (50.4% female; average age = 13.61 years) in the 2011 National System of Quality Assessment in Education Survey (SIMCE) from Chile. The SIMCE for global academic performance consists of 4 tests: reading, mathematics, social studies, and science. All tests consist of multiple-choice and closed questions. In addition, in order to have the information of general academic performance, an extra variable expressing the average score of each student was created. Also, the SIMCE includes additional variables for the evaluation process such as SES or type of school. Students were assigned to one of five age groups in terms of date of birth (G1, G2, G3, G4, and G5), in which students belonging to G1 are the oldest and students belonging to G5 are the youngest.Results
The results achieved in the structural equation modelling indicate a good global fit. Individual relationships show significant effects of the three variables observed on academic performance, although SES received the highest values. The influence of RAE took place both in the full sample and sub-samples composed according to the SES and academic performance, showing higher values for students with lower scores. Although the influence of RAE decreases when SES is controlled, its effect is still significant and contributes to additionally explain the performance.Conclusions
The RAE remains, even with residual values, an explanatory factor in academic performance even in eighth graders. Since the RAE decreases as the influence of schooling increases, the potential adverse effects for some students would be placed in previous and initial moments of formal schooling. These findings may be useful into taking steps towards flexibilisation on age of entry in compulsory schooling. Moreover, the need to implement early, comprehensive evaluation systems which include aspects related to neurodevelopment in order to provide maximum information to parents and educators is also drawn. 相似文献45.
A new species of Ctenomyidae from the late Pliocene of Uquía Formation (northwestern Argentina) is described. The new remains consist of a fragmentary rostrum, and a left mandible with partial lower dentition. Its phylogenetic affinity and morphological specializations for tooth-digging support its assignation to the South American rodent genus Ctenomys. In this context, we highlight the importance of unique morphological specializations for the delimitation of genera within an intrafamilial clade in which similar adaptive strategies could have evolved more than once. The new materials are the oldest fossils for the genus (ca. 3.5 Ma), and their finding in the central Andes agrees with previous hypotheses about the possible area of origin of Ctenomys. They precede by about one million years the presence of Ctenomys chapalmalensis in the Pliocene of the Pampean region of central Argentina, the oldest record previously known for the genus. Nevertheless, the new species does not contribute key information about ancestral character states for the genus beyond those already known through C. chapalmalensis. The phylogenetic, adaptive and even chronological information supplied by these new materials would be linked to the differentiation of the genus rather than to its origin. 相似文献
46.
Liliana I. Cichón Jimena Soleño Silvina A. Garrido Natalia Guiñazú Cristina M. Montagna Pierre Franck Jerome Olivares Selim Musleh Marcela A. Rodríguez Eduardo Fuentes-Contreras 《Journal of Applied Entomology》2021,145(9):911-921
The codling moth (Cydia pomonella (L.)) is an invasive pest of pome fruits introduced to the Americas in the 19–20th centuries. This pest is widespread on both sides of the Andes range separating Argentina and Chile. We performed an analysis of the population genetic variability and structure of C. pomonella in Argentina and Chile using 13 microsatellite markers and sampled C. pomonella from apple as the main host plant along its distribution area (approx. 1,800 km). A total of 22 locations (11 from Chile and 11 from Argentina) were sampled. Significant genetic differentiation was observed among samples from Argentina and Chile (FSC = 0.045) and between all localities (FST = 0.085). Significant isolation by distance (IBD) was found for each country and when samples from both sides of the Andes range were pooled, although a lower correlation coefficient was observed. The Mantel test showed that the geographic distance and highest altitude of the mountains between locations were significantly associated with the pairwise FST when samples from both sides of the Andes range were pooled. According to a Bayesian assignment test (STRUCTURE), samples from Argentina and Chile conformed to two distinct genetic clusters. Our results also suggest that the recent invasion of C. pomonella in the southernmost localities (Aysén Region in Chile and Santa Cruz Province in Argentina) originated in populations from the respective sides of the Andes range. Our results indicate a genetic exchange of C. pomonella within each country and significant genetic differentiation between countries, which could be explained by dispersal mediated by human activities related to fruit production within each country with little exchange between them. A possible explanation is that the Andes range could be a significant barrier for dispersal by flight, and quarantine barriers could prevent the movement of plant material or infested fruit between countries. 相似文献
47.
Xavier Solé Marta Crous-Bou David Cordero David Olivares Elisabet Guinó Rebeca Sanz-Pamplona Francisco Rodriguez-Moranta Xavier Sanjuan Javier de Oca Ramon Salazar Victor Moreno 《PloS one》2014,9(9)
Background
Accurate detection of characteristic proteins secreted by colon cancer tumor cells in biological fluids could serve as a biomarker for the disease. The aim of the present study was to identify and validate new serum biomarkers and demonstrate their potential usefulness for early diagnosis of colon cancer.Methods
The study was organized in three sequential phases: 1) biomarker discovery, 2) technical and biological validation, and 3) proof of concept to test the potential clinical use of selected biomarkers. A prioritized subset of the differentially-expressed genes between tissue types (50 colon mucosa from cancer-free individuals and 100 normal-tumor pairs from colon cancer patients) was validated and further tested in a series of serum samples from 80 colon cancer cases, 23 patients with adenoma and 77 cancer-free controls.Results
In the discovery phase, 505 unique candidate biomarkers were identified, with highly significant results and high capacity to discriminate between the different tissue types. After a subsequent prioritization, all tested genes (N = 23) were successfully validated in tissue, and one of them, COL10A1, showed relevant differences in serum protein levels between controls, patients with adenoma (p = 0.0083) and colon cancer cases (p = 3.2e-6).Conclusion
We present a sequential process for the identification and further validation of biomarkers for early detection of colon cancer that identifies COL10A1 protein levels in serum as a potential diagnostic candidate to detect both adenoma lesions and tumor.Impact
The use of a cheap serum test for colon cancer screening should improve its participation rates and contribute to decrease the burden of this disease. 相似文献48.
Guillermo Ruiz-Irastorza Nerea Olivares Ioana Ruiz-Arruza Agustin Martinez-Berriotxoa Maria-Victoria Egurbide Ciriaco Aguirre 《Arthritis research & therapy》2009,11(4):R109-8
Introduction
Infections commonly complicate the course of systemic lupus erythematosus (SLE). Our aim is to investigate the clinical predictors of major infections in patients with SLE. 相似文献49.
Endoplasmic reticulum (ER) stress activates the unfolded protein response (UPR), a highly conserved signaling cascade that functions to alleviate stress and promote cell survival. If, however, the cell is unable to adapt and restore homeostasis, then the UPR activates pathways that promote apoptotic cell death. The molecular mechanisms governing the critical transition from adaptation and survival to initiation of apoptosis remain poorly understood. We aim to determine the role of hepatic Xbp1, a key mediator of the UPR, in controlling the adaptive response to ER stress in the liver. Liver-specific Xbp1 knockout mice (Xbp1LKO) and Xbp1fl/fl control mice were subjected to varying levels and durations of pharmacologic ER stress. Xbp1LKO and Xbp1fl/fl mice showed robust and equal activation of the UPR acutely after induction of ER stress. By 24 h, Xbp1fl/fl controls showed complete resolution of UPR activation and no liver injury, indicating successful adaptation to the stress. Conversely, Xbp1LKO mice showed ongoing UPR activation associated with progressive liver injury, apoptosis, and, ultimately, fibrosis by day 7 after induction of ER stress. These data indicate that hepatic XBP1 controls the adaptive response of the UPR and is critical to restoring homeostasis in the liver in response to ER stress. 相似文献
50.
Sara G Becker-Catania Julie K Nelson Shantel Olivares Shu-Jen Chen George H DeVries 《ASN neuro》2011,3(1)
The ability of an AEF (axolemma-enriched fraction) to influence the proliferation, survival and differentiation of OPC (oligodendrocyte progenitor cells) was evaluated. Following addition of AEF to cultured OPC, the AEF associated with the outer surface of OPC so that subsequent metabolic events were likely mediated by direct AEF-OPC contact. Addition of AEF to the cultured OPC resulted in a dose- and time-dependent increase in proliferation that was partially dependent on Akt (protein kinase B) and MAPK (mitogen-activated protein kinase) activation. The major mitogen in an AEF-SE (soluble 2.0 M NaCl extract of the AEF) was identified as aFGF (acidic fibroblast growth factor) and accounted for 50% of the mitogenicity. The remaining 50% of the mitogenicity had properties consistent with bFGF (basic fibroblast growth factor) but was not unequivocally identified. Under conditions that limit the survival of OPC in culture, AEF treatment prolonged the survival of the OPC. Antigenic and morphological examination of the AEF-treated OPC indicated that the AEF treatment helped the OPC survive in a more immature state. The potential downstream metabolic pathways potentially activated in OPC by AEF and the consequences of these activated pathways are discussed. The results of these studies are consistent with the view that direct contact of axons with OPC stimulates their proliferation and survival while preventing their differentiation. 相似文献