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871.
Summary Large quantities of dihydrofolate reductase are synthesized in bacteriophage T5 infected E. coli cells. Some evidence that this enzyme is the product of a viral gene was published by Mathews (1967). Further evidence is presented now by showing that the newly synthesized enzyme differs from the preexisting E. coli reductase in molecular weight and salt solubility.The expression of the T5 dihydrofolate reductase gene was not affected by deletions in the del region of the phage genome. The map position of the reductase gene was determined by marker rescue experiments designed as helped transfection procedure: When E. coli B cells were preinfected with T5 dihydrofolate reductase amber mutants, made competent, and transfected with T5 wild type DNA, viable phages were obtained. Wild type recombinant phages were observed, when the transfecting DNA had been digested with the restriction endonucleases EcoRI, HpaI, PstI, and SalI. No rescue occurred when the DNA had been digested with AluI, EcoRII, HindII, HindIII, MboII, Sau3A, and XbaI. Single EcoRI, HpaI, and SalI restriction fragments were isolated and found to rescue the dihydrofolate reductase gene. Their common overlapping sequence corresponds to 8.6% of the phage DNA, a segment of about 10,000 base pairs length, which extends from position 0.37 to position 0.46 of the physical map. After cleaving this segment at its single HindIII recognition site marker rescue no longer occurred. From these results it was concluded that the dihydrofolate reductase gene either lies at or very close to this site at position 0.4.The helped transfection method was also used to rescue T5 mutants with defects in the genes C2 and D9. Gene C2 was localized on an EcoRI fragment that covers the DNA from map position 0.08 to map position 0.25. By localizing the two genes B3 and C2 on the restriction map of the T5 DNA a correlation of the genetic and the physical maps of the T5 genome has been established.
Abbreviations. The symbols for T5 phages follow those of McCorquodale (1975) and the nomenclature for restriction nucleases that of Smith and Nathans (1973). kb=kilo base pairs 相似文献
872.
Rehr M Cahenzli J Haas A Price DA Gostick E Huber M Karrer U Oxenius A 《Journal of virology》2008,82(7):3391-3404
Progressive human immunodeficiency virus type 1 (HIV-1) infection is often associated with high plasma virus load (pVL) and impaired CD8(+) T-cell function; in contrast, CD8(+) T cells remain polyfunctional in long-term nonprogressors. However, it is still unclear whether CD8(+) T-cell dysfunction is the cause or the consequence of high pVLs. Here, we conducted a longitudinal functional and phenotypic analysis of virus-specific CD8(+) T cells in a cohort of patients with chronic HIV-1 infection. During the initiation and maintenance of successful antiretroviral therapy (ART), we assessed whether the level of pVL was associated with the degree of CD8(+) T-cell dysfunction. Under viremic conditions, HIV-specific CD8(+) T cells were dysfunctional with respect to cytokine secretion (gamma interferon, interleukin-2 [IL-2], and tumor necrosis factor alpha), and their phenotype suggested limited potential for proliferation. During ART, cytokine secretion by HIV-specific CD8(+) T cells was gradually restored, IL-7Ralpha and CD28 expression increased dramatically, and PD-1 levels declined. Thus, prolonged ART-induced reduction of viral replication and, hence, presumably antigen exposure in vivo, allows a significant functional restoration of CD8(+) T cells with the appearance of polyfunctional cells. These findings indicate that the level of pVL as a surrogate for antigen load has a dominant influence on the phenotypic and functional profile of virus-specific CD8(+) T cells. 相似文献
873.
Chironomus riparius (Diptera) genome sequencing reveals the impact of minisatellite transposable elements on population divergence 下载免费PDF全文
Ann‐Marie Oppold Hanno Schmidt Marcel Rose Sören Lukas Hellmann Florian Dolze Fabian Ripp Bettina Weich Urs Schmidt‐Ott Erwin Schmidt Robert Kofler Thomas Hankeln Markus Pfenninger 《Molecular ecology》2017,26(12):3256-3275
Active transposable elements (TEs) may result in divergent genomic insertion and abundance patterns among conspecific populations. Upon secondary contact, such divergent genetic backgrounds can theoretically give rise to classical Dobzhansky–Muller incompatibilities (DMI), thus contributing to the evolution of endogenous genetic barriers and eventually causing population divergence. We investigated differential TE abundance among conspecific populations of the nonbiting midge Chironomus riparius and evaluated their potential role in causing endogenous genetic incompatibilities between these populations. We focussed on a Chironomus‐specific TE, the minisatellite‐like Cla‐element, whose activity is associated with speciation in the genus. Using a newly generated and annotated draft genome for a genomic study with five natural C. riparius populations, we found highly population‐specific TE insertion patterns with many private insertions. A significant correlation of the pairwise FST estimated from genomewide single‐nucleotide polymorphisms (SNPs) and the FST estimated from TEs is consistent with drift as the major force driving TE population differentiation. However, the significantly higher Cla‐element FST level due to a high proportion of differentially fixed Cla‐element insertions also indicates selection against segregating (i.e. heterozygous) insertions. With reciprocal crossing experiments and fluorescent in situ hybridization of Cla‐elements to polytene chromosomes, we documented phenotypic effects on female fertility and chromosomal mispairings. We propose that the inferred negative selection on heterozygous Cla‐element insertions may cause endogenous genetic barriers and therefore acts as DMI among C. riparius populations. The intrinsic genomic turnover exerted by TEs may thus have a direct impact on population divergence that is operationally different from drift and local adaptation. 相似文献
874.
Kornmann H Rhiel M Cannizzaro C Marison I von Stockar U 《Biotechnology and bioengineering》2003,82(6):702-709
An in-situ, mid-infrared sensor was used to monitor the major analyte concentrations involved in the cultivation of Gluconacetobacter xylinus and the production of gluconacetan, a food-grade exopolysaccharide. To predict the analyte concentrations, three different sets of standard spectra were used to develop calibration models, applying partial least-squares regression. It was possible to build a valid calibration model to predict the 700 spectra collected during the complete time course of the cultivation, using only 12 spectra collected every 10 h as standards. This model was used to reprocess the concentration profiles from 0 to 15 g/L of nine different analytes with a mean standard error of validation of 0.23 g/L. However, this calibration model was not suitable for real-time monitoring as it was probably based on non-specific spectral features, which were correlated only with the measured analyte concentrations. Valid calibration models capable of real-time monitoring could be established by supplementing the set of 12 fermentation spectra with 42 standards of measured analytes. A pulse of 5 g/L ethanol showed the robustness of the model to sudden disturbances. The prediction of the models drifted, however, toward the end of the fermentation. The most robust calibration model was finally obtained by the addition of 34 standard spectra of non-measured analytes. Although the spectra did not contain analyte-specific information, it was believed that this addition would increase the variability space of the calibration model. Therefore, an expanded calibration model containing 88 spectra was used to monitor, in real time, the concentration profiles of fructose, acetic acid, ethanol and gluconacetan and allowed standard errors of prediction of 1.11, 0.37, 0.22, and 0.79 g/L, respectively. 相似文献
875.
Kraushaar U Blanckenhorn WU 《Evolution; international journal of organic evolution》2002,56(2):307-321
Body size is one of the most important quantitative traits under evolutionary scrutiny. Sexual size dimorphism (SSD) in a given species is expected to result if opposing selection forces equilibrate differently in both sexes. We document variation in the intensity of sexual and fecundity selection, male and female body size, and thus SSD among 31 and 27 populations of the two dung fly species, Scathophaga stercoraria and Sepsis cynipsea, across Switzerland. Whereas in S. cynipsea females are larger, the SSD is reversed in S. stercoraria. We comprehensively evaluated Fairbairn and Preziosi's (1994) general, three-tiered scenario, hypothesizing that sexual selection for large male size is the major driving force of SSD allometry within these two species. Sexual selection intensity on male size in the yellow dung fly, S. stercoraria, was overall positive, greater, and more variable among populations than fecundity selection on females. Also, sexual selection intensity in a given population correlated positively with mean male body size of that population for both the field-caught fathers and their laboratory-reared sons, indicating a response to selection. In S. cvnipsea, sexual selection intensity on males was lower overall and significantly positive, about equal in magnitude, but more variable than fecundity selection on females. However, there was no correlation between the intensity of sexual selection and mean male body size among populations. In both species, the laboratory-reared offspring indicate genetic differentiation among populations in body size. Despite fulfillment of all key prerequisites, at least in S. stercoraria, we did not find hypoallometry for SSD (Rensch's rule, i.e., greater evolutionary divergence in male size than female size) for the field-caught parents or the laboratory-reared offspring: Female size was isometric to male size in both species. We conclude that S. cynipsea does not fit some major requirements of Fairbairn and Preziosi's (1994) scenario, whereas for S. stercoraria we found partial support for it. Failure to support Rensch's rule within the latter species may be due to phylogenetic or other constraints, power limitations, erroneous estimates of sexual selection, insufficient genetic isolation of populations, or sex differences in viability selection against large size. 相似文献
876.
Krishnegowda Jayachandra M. D. Milan Gowda Gotravalli V. Rudresha Vaddarahally N. Manjuprasanna Amog P. Urs Manuganahally Basavarajappa Nandana Madeva Bharatha Noor Mohamed Jameel Bannikuppe S. Vishwanath 《Journal of cellular biochemistry》2023,124(2):294-307
The arachidonic acid (AA) metabolic pathway, plays a vital role in the production of eicosanoids by the action of pro-inflammatory secretory phospholipase A2 (PLA2). Release of eicosanoids is known to be involved in many inflammatory diseases. Identification of the inhibitory molecules of this AA pathway enzyme along with the regulation of intracellular signaling cascades may be a finer choice to develop as a powerful anti-inflammatory drug. In this regard, we have screened few cell-permeable antioxidant molecules Tempo, Mito-TEMPO, N,N'-Bis(salicylideneamino)ethane-manganese(II) (EUK)-134, and EUK-8 against pro-inflammatory sPLA2s. Among these, we found EUK-8 is a potent inhibitor with its IC50 value ranges 0.7–2.0 µM for sPLA2s isolated from different sources. Furthermore, docking studies confirm the strong binding of EUK-8 towards sPLA2. In vivo effect of EUK-8 was studied in HSF-sPLA2-induced edema in mouse paw model. In addition to neutralizing the edema, EUK-8 significantly reduces the phosphorylation level of inflammatory proteins such as p38 member of MAPK pathway, Akt, and p65 along with the suppression of pro-inflammatory cytokine (interleukin-6) and chemokine (CXCL1) in edematous tissue. This shows that EUK-8 not only inhibits the sPLA2 activity, it also plays an important role in the regulation of sPLA2-induced cell signaling cascades. Apart from the sPLA2 inhibition, we also examine the regulatory actions of EUK-8 with other downstream enzymes of AA pathway such as 5-LOX assay in human polymorphonuclear leukocytes (PMNs) and COX-2 expression in carrageenan-λ induced paw edema. Here EUK-8 significantly inhibits 5-LOX enzyme activity and downregulates COX-2 expression. These data indicate that EUK-8 found to be a promising multitargeted inhibitory molecule toward inflammatory pathway. In conclusion, mitochondrial targeted antioxidant EUK-8 is not only the powerful antioxidant, also a potent anti-inflammatory molecule and may be a choice of molecule for pharmacological applications. 相似文献
877.
Mélanie-Louise Leblanc Mary I. O'Connor Zou Zou A. Kuzyk Fanny Noisette Kaleigh E. Davis Ernie Rabbitskin Laura-Lee Sam Urs Neumeier Rémi Costanzo Jens K. Ehn David Babb C. Julián Idrobo Jean-Philippe Gilbert Brigitte Leblon Murray M. Humphries 《Global Change Biology》2023,29(2):432-450
Over the last few decades, there has been an increasing recognition for seagrasses' contribution to the functioning of nearshore ecosystems and climate change mitigation. Nevertheless, seagrass ecosystems have been deteriorating globally at an accelerating rate during recent decades. In 2017, research into the condition of eelgrass (Zostera marina) along the eastern coast of James Bay, Canada, was initiated in response to reports of eelgrass decline by the Cree First Nations of Eeyou Istchee. As part of this research, we compiled and analyzed two decades of eelgrass cover data and three decades of eelgrass monitoring data (biomass and density) to detect changes and assess possible environmental drivers. We detected a major decline in eelgrass condition between 1995 and 1999, which encompassed the entire east coast of James Bay. Surveys conducted in 2019 and 2020 indicated limited changes post-decline, for example, low eelgrass cover (<25%), low aboveground biomass, smaller shoots than before 1995, and marginally low densities persisted at most sites. Overall, the synthesized datasets show a 40% loss of eelgrass meadows with >50% cover in eastern James Bay since 1995, representing the largest scale eelgrass decline documented in eastern Canada since the massive die-off event that occurred in the 1930s along the North Atlantic coast. Using biomass data collected since 1982, but geographically limited to the sector of the coast near the regulated La Grande River, generalized additive modeling revealed eelgrass meadows are affected by local sea surface temperature, early ice breakup, and higher summer freshwater discharge. Our results caution against assuming subarctic seagrass ecosystems have avoided recent global declines or will benefit from ongoing climate warming. 相似文献
878.
Amanda D. Melin Jeremy D. Hogan Fernando A. Campos Eva Wikberg Gillian King-Bailey Shasta Webb Urs Kalbitzer Norberto Asensio Evin Murillo-Chacon Saul Cheves Hernandez Adrian Guadamuz Chavarria Colleen M. Schaffner Shoji Kawamura Filippo Aureli Linda Fedigan Katharine M. Jack 《Biotropica》2020,52(6):1041-1064
Research on non-human primates in the endangered tropical dry forest of Sector Santa Rosa (SSR), Área de Conservación Guanacaste (ACG), was launched in 1983 and is now one of the longest running studies of primates globally. Such continuous study provides a rare opportunity to ask questions that are only answerable through decades-long monitoring of these long-lived monkeys. In turn, the mounting data generated by long-term study, including knowledge of lifetime reproductive success, familial relatedness, comprehensive behavioral and dietary repertoires, and patterns of inter- and intra-annual variation in forest productivity, provide diverse opportunities to researchers, and facilitate studies that are of shorter duration. Here, we review some of the contributions of our longitudinal research on white-faced capuchins and Geoffroy's spider monkeys, together with newer studies on mantled howler monkeys. We begin by synthesizing findings from our research on demography, dispersal, social relationships, and reproduction. These life history and social traits interact with their foraging and sensory ecology, which we review next. We end by highlighting how the longitudinal study of primates in Sector Santa Rosa has made direct and indirect contributions to the conservation of the critically endangered dry forest biome and its inhabitants, as well as to education, community, and forest restoration initiatives. In particular, we focus our review on how long-term research is uniquely positioned to make key contributions spanning different topical areas. 相似文献
879.
880.
Jinghua Piao Susan Zabierowski Brittany N. Dubose Ellen J. Hill Monalisa Navare Nidia Claros Siera Rosen Kiran Ramnarine Callie Horn Craig Fredrickson Karen Wong Brent Safford Sonja Kriks Abderrahman El Maarouf Urs Rutishauser Claire Henchcliffe Yongzeng Wang Isabelle Riviere Viviane Tabar 《Cell Stem Cell》2021,28(2):217-229.e7