127 research outputs found
Mouse precision-cut liver slices as an ex vivo model to study drug-induced cholestasis
Drugs are often withdrawn from the market due to the manifestation of drug-induced liver injury (DILI) in patients. Drug-induced cholestasis (DIC), defined as obstruction of hepatic bile flow due to medication, is one form of DILI. Because DILI is idiosyncratic, and the resulting cholestasis complex, there is no suitable in vitro model for early DIC detection during drug development. Our goal was to develop a mouse precision-cut liver slice (mPCLS) model to study DIC and to assess cholestasis development using conventional molecular biology and analytical chemistry methods. Cholestasis was induced in mPCLS through a 48-h-incubation with three drugs known to induce cholestasis in humans, namely chlorpromazine (15, 20, and 30 µM), cyclosporin A (1, 3, and 6 µM) or glibenclamide (25, 50, and 65 µM). A bile-acid mixture (16 µM) that is physiologically representative of the human bile-acid pool was added to the incubation medium with drug, and results were compared to incubations with no added bile acids. Treatment of PCLS with cholestatic drugs increased the intracellular bile-acid concentration of deoxycholic acid and modulated bile-transporter genes. Chlorpromazine led to the most pronounced cholestasis in 48 h, observed as increased toxicity; decreased protein and gene expression of the bile salt export pump; increased gene expression of multidrug resistance-associated protein 4; and accumulation of intracellular bile acids. Moreover, chlorpromazine-induced cholestasis exhibited some transition into fibrosis, evidenced by increased gene expression of collagen 1A1 and heatshock protein 47. In conclusion, we demonstrate that mPCLS can be used to study human DIC onset and progression in a 48 h period. We thus propose this model is suited for other similar studies of human DIC
Historical Distribution and Molecular Diversity of Bacillus anthracis, Kazakhstan
This study provides useful baseline data for guiding future disease control programs
Evolution and Global Transmission of a Multidrug-Resistant, Community-Associated Methicillin-Resistant Staphylococcus aureus Lineage from the Indian Subcontinent.
The evolution and global transmission of antimicrobial resistance have been well documented for Gram-negative bacteria and health care-associated epidemic pathogens, often emerging from regions with heavy antimicrobial use. However, the degree to which similar processes occur with Gram-positive bacteria in the community setting is less well understood. In this study, we traced the recent origins and global spread of a multidrug-resistant, community-associated Staphylococcus aureus lineage from the Indian subcontinent, the Bengal Bay clone (ST772). We generated whole-genome sequence data of 340 isolates from 14 countries, including the first isolates from Bangladesh and India, to reconstruct the evolutionary history and genomic epidemiology of the lineage. Our data show that the clone emerged on the Indian subcontinent in the early 1960s and disseminated rapidly in the 1990s. Short-term outbreaks in community and health care settings occurred following intercontinental transmission, typically associated with travel and family contacts on the subcontinent, but ongoing endemic transmission was uncommon. Acquisition of a multidrug resistance integrated plasmid was instrumental in the emergence of a single dominant and globally disseminated clade in the early 1990s. Phenotypic data on biofilm, growth, and toxicity point to antimicrobial resistance as the driving force in the evolution of ST772. The Bengal Bay clone therefore combines the multidrug resistance of traditional health care-associated clones with the epidemiological transmission of community-associated methicillin-resistant S. aureus (MRSA). Our study demonstrates the importance of whole-genome sequencing for tracking the evolution of emerging and resistant pathogens. It provides a critical framework for ongoing surveillance of the clone on the Indian subcontinent and elsewhere.IMPORTANCE The Bengal Bay clone (ST772) is a community-associated and multidrug-resistant Staphylococcus aureus lineage first isolated from Bangladesh and India in 2004. In this study, we showed that the Bengal Bay clone emerged from a virulent progenitor circulating on the Indian subcontinent. Its subsequent global transmission was associated with travel or family contact in the region. ST772 progressively acquired specific resistance elements at limited cost to its fitness and continues to be exported globally, resulting in small-scale community and health care outbreaks. The Bengal Bay clone therefore combines the virulence potential and epidemiology of community-associated clones with the multidrug resistance of health care-associated S. aureus lineages. This study demonstrates the importance of whole-genome sequencing for the surveillance of highly antibiotic-resistant pathogens, which may emerge in the community setting of regions with poor antibiotic stewardship and rapidly spread into hospitals and communities across the world
Arabidopsis HDA6 Regulates Locus-Directed Heterochromatin Silencing in Cooperation with MET1
Heterochromatin silencing is pivotal for genome stability in eukaryotes. In
Arabidopsis, a plant-specific mechanism called
RNA–directed DNA methylation (RdDM) is involved in heterochromatin
silencing. Histone deacetylase HDA6 has been identified as a component of such
machineries; however, its endogenous targets and the silencing mechanisms have
not been analyzed globally. In this study, we investigated the silencing
mechanism mediated by HDA6. Genome-wide transcript profiling revealed that the
loci silenced by HDA6 carried sequences corresponding to the RDR2-dependent
24-nt siRNAs, however their transcript levels were mostly unaffected in the
rdr2 mutant. Strikingly, we observed significant overlap of
genes silenced by HDA6 to those by the CG DNA methyltransferase MET1.
Furthermore, regardless of dependence on RdDM pathway, HDA6 deficiency resulted
in loss of heterochromatic epigenetic marks and aberrant enrichment for
euchromatic marks at HDA6 direct targets, along with ectopic expression of these
loci. Acetylation levels increased significantly in the hda6
mutant at all of the lysine residues in the H3 and H4 N-tails, except H4K16.
Interestingly, we observed two different CG methylation statuses in the
hda6 mutant. CG methylation was sustained in the
hda6 mutant at some HDA6 target loci that were surrounded
by flanking DNA–methylated regions. In contrast, complete loss of CG
methylation occurred in the hda6 mutant at the HDA6 target loci
that were isolated from flanking DNA methylation. Regardless of CG methylation
status, CHG and CHH methylation were lost and transcriptional derepression
occurred in the hda6 mutant. Furthermore, we show that HDA6
binds only to its target loci, not the flanking methylated DNA, indicating the
profound target specificity of HDA6. We propose that HDA6 regulates
locus-directed heterochromatin silencing in cooperation with MET1, possibly
recruiting MET1 to specific loci, thus forming the foundation of silent
chromatin structure for subsequent non-CG methylation
Simvastatin attenuates trinitrobenzene sulfonic acid-induced colitis, but not oxazalone-induced colitis.
PURPOSE: To determine whether simvastatin is able to inhibit inflammation in trinitrobenzene sulfonic acid (TNBS)-induced or oxazalone (OXA)-induced colitis. RESULTS: In the prophylactic protocol, simvastatin dose-dependently suppressed the decrease in body weight and inflammatory grade of TNBS-treated mice. In contrast, in the therapeutic protocol, no significant difference in body weight reduction was observed between simvastatin-treated and control mice. IFN-gamma release from LP cells was significantly suppressed in mice receiving high-dose simvastatin in the prophylactic protocol. In contrast to TNBS colitis, even high-dose prophylactic simvastatin had no suppressive effects on either weight reduction or the inflammatory grade in OXA colitis. CONCLUSION: Our results indicate that simvastatin negatively regulates inflammation in TNBS-induced colitis, but not in OXA-induced colitis. In TNBS-induced colitis, simvastatin suppressed the Th1-polarized immune response. Our findings suggest that simvastatin has potential effects as a therapeutic agent in human inflammatory bowel disease, particularly Crohn\u27s disease
Finishing the euchromatic sequence of the human genome
The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead
Separation and recovery of critical metal ions using ionic liquids
Separation and purification of critical metal ions such as rare-earth elements (REEs), scandium and niobium from their minerals is difficult and often determines if extraction is economically and environmentally feasible. Solvent extraction is a commonly used metal-ion separation process, usually favored because of its simplicity, speed and wide scope, which is why it is often employed for separating trace metals from their minerals. However, the types of solvents widely used for the recovery of metal ions have adverse environmental impact. Alternatives to solvent extraction have been explored and advances in separation technologies have seen commercial establishment of liquid membranes as an alternative to conventional solvent extraction for the recovery of metals and other valuable materials. Liquid membrane transport incorporates solvent extraction and membrane separation in one continuously operating system. Both methods conventionally use solvents that are harmful to the environment, however, the introduction of ionic liquids (ILs) over the last decade is set to minimize the environmental impact of both solvent extraction and liquid membrane separation processes. ILs are a family of organic molten salts with low or negligible vapour pressure which may be formed below 100 oC. Such liquids are also highly thermally stable and less toxic. Their ionic structure makes them thermodynamically favorable solvents for the extraction of metallic ions. The main aim of this article is to review the current achievements in the separation of REE, scandium, niobium and vanadium from their minerals, using ILs in either solvent extraction or liquid membrane processes. The mechanism of separation using ILs is discussed and the engineering constraints to their application are identified
A roadmap for Antarctic and Southern Ocean science for the next two decades and beyond
Antarctic and Southern Ocean science is vital to understanding natural variability, the processes
that govern global change and the role of humans in the Earth and climate system. The potential for new
knowledge to be gained from future Antarctic science is substantial. Therefore, the international Antarctic
community came together to ‘scan the horizon’ to identify the highest priority scientific questions that
researchers should aspire to answer in the next two decades and beyond. Wide consultation was a
fundamental principle for the development of a collective, international view of the most important future
directions in Antarctic science. From the many possibilities, the horizon scan identified 80 key scientific
questions through structured debate, discussion, revision and voting. Questions were clustered into seven
topics: i)Antarctic atmosphere and global connections, ii) Southern Ocean and sea ice in a warming world,
iii) ice sheet and sea level, iv) the dynamic Earth, v) life on the precipice, vi) near-Earth space and beyond,
and vii) human presence in Antarctica. Answering the questions identified by the horizon scan will require
innovative experimental designs, novel applications of technology, invention of next-generation field and
laboratory approaches, and expanded observing systems and networks. Unbiased, non-contaminating
procedures will be required to retrieve the requisite air, biota, sediment, rock, ice and water samples.
Sustained year-round access toAntarctica and the Southern Ocean will be essential to increase winter-time
measurements. Improved models are needed that represent Antarctica and the Southern Ocean in the
Earth System, and provide predictions at spatial and temporal resolutions useful for decision making.
A co-ordinated portfolio of cross-disciplinary science, based on new models of international collaboration,
will be essential as no scientist, programme or nation can realize these aspirations alone.Tinker Foundation, Antarctica New Zealand, The New Zealand
Antarctic Research Institute, the Scientific Committee on
Antarctic Research (SCAR), the Council of Managers of
National Antarctic Programs (COMNAP), the Alfred
Wegner Institut, Helmholtz Zentrum für Polar und
Meeresforschung (Germany), and the British Antarctic
Survey (UK).http://journals.cambridge.org/action/displayJournal?jid=ANShb201
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