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201.
202.
Shrihari Bhavaraju SR Modak JM Kumar R Gandhi KS 《Biotechnology and bioengineering》1993,41(6):612-616
The growth of Thiobacillus ferrooxidans on sulphur is known to proceed through the attachment of cells to the sulphur particles. Experiments, However, show that the cells in the liquid phase, which are not attached to the sulphur particles, also grow. It has been shown through the use of a two-compartment membrane reactor that this increase is partially due to the release of ions, corresponding to partially oxidized of sulphur, into the solution by the attached cells. The main soluble ion has been found to the thiosulphate, but traces of sulphite have also been detected. (c) 1993 John Wiley & Sons, Inc. 相似文献
203.
The effects of terminal heterologies on gene targeting by insertion vectors in embryonic stem cells. 总被引:3,自引:0,他引:3 下载免费PDF全文
We have examined the effects of placing nonhomologous DNA on the ends of an insertion-type gene targeting vector. The presence of terminal heterologies was found to be compatible with insertion targeting, and the terminal heterologies were efficiently removed. Terminal heterologies reduced the frequency of gene targeting to variable extents. The degree of inhibition of targeting was dependent on the length and the position of the heterology: 2.1kb heterologous sequences were more inhibitory than shorter regions of heterology, and heterology placed on the end of the long (4.8kb) arm of homology was more inhibitory than heterology positioned on the end of the short (0.8kb) arm. When heterology was placed on both arms of the targeting vector the targeting efficiencies were similar to or higher than when heterology was present on the long arm only. These results suggest that terminal sequences are removed simultaneously from both ends of targeting vectors. The removal of terminal sequences probably occurs by exonucleolytic degradation of both strands at each end, and removal of at least one of the strands is intimately coupled with the process of homologous recombination. These findings have implications for the design of gene targeting vectors. 相似文献
204.
Self-cleavage activity of the genomic HDV ribozyme in the presence of various divalent metal ions. 总被引:3,自引:2,他引:1 下载免费PDF全文
To identify the divalent metal ions that can support the self-cleavage activity of the genomic ribozyme of human hepatitis delta virus (HDV), we tested the activity of various divalent metal ions in the ribozyme reactions catalyzed by HDV88 (683-770 nt) and 88DI3 (HDV88 with the sequence from 740-752 nt deleted). Among various metal ions tested, Mg2+, Mn2+, Ca2+ and Sr2+ efficiently supported the self-cleavage reactions of the HDV88 and 88DI3 ribozymes. In the case of the 88DI3 ribozyme, other divalent metal ions, such as Cd2+, Ba2+, Co2+, Pb2+ and Zn2+, were also able to support the self-cleavage reaction to some extent (< 10%). In the presence of spermidine (0.5 mM), the cleavage reaction was promoted at lower concentrations of effective divalent metal ions. The HDV ribozyme represents the only example of ribozyme to date of a ribozyme that catalyzes the self-cleavage reaction in the presence of Ca2+ ions as efficiently as it does in the presence of Mg2+ ions. 相似文献
205.
Carlos Rafael Borges Mendes Raul Rodrigo Costa Afonso Ferreira Bruno Jesus Virginia Maria Tavano Tiago Segabinazzi Dotto Miguel Costa Leal Rodrigo Kerr Carolina Antuarte Islabão Andréa de Oliveira da Rocha Franco Mauricio M. Mata Carlos Alberto Eiras Garcia Eduardo Resende Secchi 《Global Change Biology》2023,29(7):1791-1808
The western Antarctic Peninsula (WAP) is a climatically sensitive region where foundational changes at the basis of the food web have been recorded; cryptophytes are gradually outgrowing diatoms together with a decreased size spectrum of the phytoplankton community. Based on a 11-year (2008–2018) in-situ dataset, we demonstrate a strong coupling between biomass accumulation of cryptophytes, summer upper ocean stability, and the mixed layer depth. Our results shed light on the environmental conditions favoring the cryptophyte success in coastal regions of the WAP, especially during situations of shallower mixed layers associated with lower diatom biomass, which evidences a clear competition or niche segregation between diatoms and cryptophytes. We also unravel the cryptophyte photo-physiological niche by exploring its capacity to thrive under high light stress normally found in confined stratified upper layers. Such conditions are becoming more frequent in the Antarctic coastal waters and will likely have significant future implications at various levels of the marine food web. The competitive advantage of cryptophytes in environments with significant light level fluctuations was supported by laboratory experiments that revealed a high flexibility of cryptophytes to grow in different light conditions driven by a fast photo-regulating response. All tested physiological parameters support the hypothesis that cryptophytes are highly flexible regarding their growing light conditions and extremely efficient in rapidly photo-regulating changes to environmental light levels. This plasticity would give them a competitive advantage in exploiting an ecological niche where light levels fluctuate quickly. These findings provide new insights on niche separation between diatoms and cryptophytes, which is vital for a thorough understanding of the WAP marine ecosystem. 相似文献
206.
Rizky Pasthika Kirana Kumar Gaurav Sanu Arora Gerlinde Wiesenberger Maria Doppler Sebastian Michel Simone Zimmerl Magdalena Matic Chinedu E. Eze Mukesh Kumar Ajla Topuz Marc Lemmens Rainer Schuhmacher Gerhard Adam Brande B. H. Wulff Hermann Buerstmayr Barbara Steiner 《Plant biotechnology journal》2023,21(1):109-121
Aegilops tauschii is the diploid progenitor of the wheat D subgenome and a valuable resource for wheat breeding, yet, genetic analysis of resistance against Fusarium head blight (FHB) and the major Fusarium mycotoxin deoxynivalenol (DON) is lacking. We treated a panel of 147 Ae. tauschii accessions with either Fusarium graminearum spores or DON solution and recorded the associated disease spread or toxin-induced bleaching. A k-mer-based association mapping pipeline dissected the genetic basis of resistance and identified candidate genes. After DON infiltration nine accessions revealed severe bleaching symptoms concomitant with lower conversion rates of DON into the non-toxic DON-3-O-glucoside. We identified the gene AET5Gv20385300 on chromosome 5D encoding a uridine diphosphate (UDP)-glucosyltransferase (UGT) as the causal variant and the mutant allele resulting in a truncated protein was only found in the nine susceptible accessions. This UGT is also polymorphic in hexaploid wheat and when expressed in Saccharomyces cerevisiae only the full-length gene conferred resistance against DON. Analysing the D subgenome helped to elucidate the genetic control of FHB resistance and identified a UGT involved in DON detoxification in Ae. tauschii and hexaploid wheat. This resistance mechanism is highly conserved since the UGT is orthologous to the barley UGT HvUGT13248 indicating descent from a common ancestor of wheat and barley. 相似文献
207.
Chathurika Henpita Rajesh Vyas Chastity L. Healy Tra L. Kieu Aditi U. Gurkar Matthew J. Yousefzadeh Yuxiang Cui Aiping Lu Luise A. Angelini Ryan D. O'Kelly Sara J. McGowan Sanjay Chandrasekhar Rebecca R. Vanderpool Danielle Hennessy-Wack Mark A. Ross Timothy N. Bachman Charles McTiernan Smitha P. S. Pillai Warren Ladiges Mitra Lavasani Johnny Huard Donna Beer-Stolz Claudette M. St. Croix Simon C. Watkins Paul D. Robbins Ana L. Mora Eric E. Kelley Yinsheng Wang Timothy D. O'Connell Laura J. Niedernhofer 《Aging cell》2023,22(4):e13782
Cardiomyopathy is a progressive disease of the myocardium leading to impaired contractility. Genotoxic cancer therapies are known to be potent drivers of cardiomyopathy, whereas causes of spontaneous disease remain unclear. To test the hypothesis that endogenous genotoxic stress contributes to cardiomyopathy, we deleted the DNA repair gene Ercc1 specifically in striated muscle using a floxed allele of Ercc1 and mice expressing Cre under control of the muscle-specific creatinine kinase (Ckmm) promoter or depleted systemically (Ercc1−/D mice). Ckmm-Cre+/−;Ercc1−/fl mice expired suddenly of heart disease by 7 months of age. As young adults, the hearts of Ckmm-Cre+/−;Ercc1−/fl mice were structurally and functionally normal, but by 6-months-of-age, there was significant ventricular dilation, wall thinning, interstitial fibrosis, and systolic dysfunction indicative of dilated cardiomyopathy. Cardiac tissue from the tissue-specific or systemic model showed increased apoptosis and cardiac myocytes from Ckmm-Cre+/-;Ercc1−/fl mice were hypersensitive to genotoxins, resulting in apoptosis. p53 levels and target gene expression, including several antioxidants, were increased in cardiac tissue from Ckmm-Cre+/−;Ercc1−/fl and Ercc1−/D mice. Despite this, cardiac tissue from older mutant mice showed evidence of increased oxidative stress. Genetic or pharmacologic inhibition of p53 attenuated apoptosis and improved disease markers. Similarly, overexpression of mitochondrial-targeted catalase improved disease markers. Together, these data support the conclusion that DNA damage produced endogenously can drive cardiac disease and does so mechanistically via chronic activation of p53 and increased oxidative stress, driving cardiac myocyte apoptosis, dilated cardiomyopathy, and sudden death. 相似文献
208.
Isha Gupta Devender Singh Sitender Singh Pawan Kumar Shri Bhagwan Vinod Kumar Harish Kumar Sunil Kumar Chhikara 《Luminescence》2023,38(5):585-599
Terbium(III)-doped yttrium aluminate perovskite (YAP:xTb3+) (x = 0.01–0.08 mol) was synthesized using a simple gel-combustion method. Structural elucidations were performed using X-ray diffraction (XRD) and Rietveld analysis. Fourier-transform infrared spectral studies validated the efficient synthesis of designed doped samples. Transmission electron microscopic images showed the agglomerated irregular dimensions of the synthesized nanocrystalline materials. When excited at 251 nm, a strong emissive line attributed to 5D4 → 7F5 electronic transition was observed at 545 nm (green emission). The maximum luminescence was found at the optimized concentration (0.05 mol) of Tb3+ ions; this emission was quenched by dipolar–dipolar (d–d) interactions. Chromaticity (x and y) and correlated colour temperature parameters were obtained by analysing the emission profiles. Finally, the colour coordinates of nanophosphors were closer to the National Television Standards Committee green coordinates, which replicates their potency in the design and architecture of R-G-B-based white LEDs. 相似文献
209.
L. Vijayalakshmi K. Naveen Kumar Kishor Palle Jong Dae Baek Abdallah A. A. Mohammed 《Luminescence》2023,38(9):1624-1631
Using the melt quenching technique, a lithium zinc borate glass (LZB) system with trivalent dysprosium ions (Dy3+) was synthesized, and the luminescence and lasing properties of these materials were examined for the generation of white light. Structural investigation through X-ray diffraction revealed that the prepared glass had an amorphous nature. The optimized glass containing 0.5 Dy3+ had a direct optical band gap of 2.782 eV and an indirect optical band gap of 3.110 eV. A strong excitation band at 386 nm (6H15/2→4I13/2) was recognized in the ultraviolet (UV) light region of its excitation spectrum. Emission bands could be seen in the photoluminescence spectrum at 659, 573, and 480 nm under the 386 nm excitation. These transitions of emission resembled electronic transitions such as (4F9/2→6H11/2), (4F9/2→6H13/2), and (4F9/2→6H15/2). In a pristine glass matrix, the higher intensity ratio of yellow to blue can result in the production of white light. The optimized Dy3+ ion concentration was observed to be 0.5 mol%. In addition, an analysis of lifetime decay was conducted for all synthesized glasses, and their decay trends were systematically investigated. Noticeably, we assessed the photometric parameters and found that they were close to the white light standard. Furthermore, a cytotoxicity study was carried out using lung fibroblast (WI-38) cell lines for the optimized 0.5Dy3+-doped LZB glass and it appeared to be noncytotoxic. It is clear from the results that the noncytotoxic LZB glass doped with 0.5 Dy3+ ions could be a suggestive choice for the manufacture of white light-emitting diodes and lasers using near-UVs. 相似文献
210.
A series of ZnB2O4 phosphors doped with different concentrations of Eu and Dy (0.05 0.1, 0.2, 0.5, 1.0 mol%) and co-doped with Ce (1, 2, 5, 7, 10 mol%) respectively was prepared via the solid-state reaction technique and the thermoluminescence (TL) behaviour of gamma ray-irradiated samples was studied. The synthesized samples were irradiated with γ-rays for the dose range 0.03–1.20 kGy. The TL intensity variations with dose, dopant concentration, and the effect of co-doping were studied. The TL response curves for ZnB2O4:Eu3+ and ZnB2O4:Dy3+, ZnB2O4:Eu3,Ce3+ and ZnB2O4:Dy3+,Ce3+ phosphor were observed. It was revealed that ZnB2O4:Eu3+ showed a linear TL behaviour for the dose 0.03–1.20 kGy and ZnB2O4:Dy3+ showed linearity for the gamma dose range 0.03–0.10 kGy. Furthermore, fading for all the samples was observed to be less than 10% for a storage period of 30 days. In addition to this, the trapping parameters, especially activation energies were evaluated using the Ilich method and the initial rise method. The activation energy values obtained from both methods were in complete agreement with each other. 相似文献