226 research outputs found
Radiocarbon dating of methane and carbon dioxide evaded from a temperate peatland stream
Streams draining peatlands export large quantities of carbon in different chemical forms and
are an important part of the carbon cycle. Radiocarbon (14C) analysis/dating provides unique
information on the source and rate that carbon is cycled through ecosystems, as has recently
been demonstrated at the air-water interface through analysis of carbon dioxide (CO2) lost
from peatland streams by evasion (degassing). Peatland streams also have the potential to
release large amounts of methane (CH4) and, though 14C analysis of CH4 emitted by ebullition
(bubbling) has been previously reported, diffusive emissions have not. We describe methods
that enable the 14C analysis of CH4 evaded from peatland streams. Using these methods, we
investigated the 14C age and stable carbon isotope composition of both CH4 and CO2 evaded
from a small peatland stream draining a temperate raised mire. Methane was aged between
1617-1987 years BP, and was much older than CO2 which had an age range of 303-521 years
BP. Isotope mass balance modelling of the results indicated that the CO2 and CH4 evaded
from the stream were derived from different source areas, with most evaded CO2 originating
from younger layers located nearer the peat surface compared to CH4. The study demonstrates
the insight that can be gained into peatland carbon cycling from a methodological
development which enables dual isotope (14C and 13C) analysis of both CH4 and CO2 collected
at the same time and in the same way
Identification of β-Secretase (BACE1) Substrates Using Quantitative Proteomics
β-site APP cleaving enzyme 1 (BACE1) is a transmembrane aspartyl protease with a lumenal active site that sheds the ectodomains of membrane proteins through juxtamembrane proteolysis. BACE1 has been studied principally for its role in Alzheimer's disease as the β-secretase responsible for generating the amyloid-β protein. Emerging evidence from mouse models has identified the importance of BACE1 in myelination and cognitive performance. However, the substrates that BACE1 processes to regulate these functions are unknown, and to date only a few β-secretase substrates have been identified through candidate-based studies. Using an unbiased approach to substrate identification, we performed quantitative proteomic analysis of two human epithelial cell lines stably expressing BACE1 and identified 68 putative β-secretase substrates, a number of which we validated in a cell culture system. The vast majority were of type I transmembrane topology, although one was type II and three were GPI-linked proteins. Intriguingly, a preponderance of these proteins are involved in contact-dependent intercellular communication or serve as receptors and have recognized roles in the nervous system and other organs. No consistent sequence motif predicting BACE1 cleavage was identified in substrates versus non-substrates. These findings expand our understanding of the proteins and cellular processes that BACE1 may regulate, and suggest possible mechanisms of toxicity arising from chronic BACE1 inhibition
Quantum corrections and black hole spectroscopy
In the work \cite{BRM,RBE}, black hole spectroscopy has been successfully
reproduced in the tunneling picture. As a result, the derived entropy spectrum
of black hole in different gravity (including Einstein's gravity,
Einstein-Gauss-Bonnet gravity and Ho\v{r}ava-Lifshitz gravity) are all evenly
spaced, sharing the same forms as , where physical process is only
confined in the semiclassical framework. However, the real physical picture
should go beyond the semiclassical approximation. In this case, the physical
quantities would undergo higher-order quantum corrections, whose effect on
different gravity shares in different forms. Motivated by these facts, in this
paper we aim to observe how quantum corrections affect black hole spectroscopy
in different gravity. The result shows that, in the presence of higher-order
quantum corrections, black hole spectroscopy in different gravity still shares
the same form as , further confirming the entropy quantum is universal
in the sense that it is not only independent of black hole parameters, but also
independent of higher-order quantum corrections. This is a desiring result for
the forthcoming quantum gravity theory.Comment: 14 pages, no figure, use JHEP3.cls. to be published in JHE
Back reaction, emission spectrum and entropy spectroscopy
Recently, an interesting work, which reformulates the tunneling framework to
directly produce the Hawking emission spectrum and entropy spectroscopy in the
tunneling picture, has been received a broad attention. However, during the
emission process, most related observations have not incorporated the effects
of back reaction on the background spacetime, whose derivations are therefore
not the desiring results for the real physical process. With this point as a
central motivation, in this paper we suitably adapt the \emph{reformulated}
tunneling framework so that it can well accommodate the effects of back
reaction to produce the Hawking emission spectrum and entropy spectroscopy.
Consequently, we interestingly find that, when back reaction is considered, the
Parikh-Wilczek's outstanding observations that, an isolated radiating black
hole has an unitary-evolving emission spectrum that is \emph{not} precisely
thermal, but is related to the change of the Bekenstein-Hawking entropy, can
also be reproduced in the reformulated tunneling framework, meanwhile the
entropy spectrum has the same form as that without inclusion of back reaction,
which demonstrates the entropy quantum is \emph{independent} of the effects of
back reaction. As our final analysis, we concentrate on the issues of the black
hole information, but \emph{unfortunately} find that, even including the
effects of back reaction and higher-order quantum corrections, such tunneling
formalism can still not provide a mechanism for preserving the black hole
information.Comment: 16 pages, no figure, use JHEP3.cls. to be published in JHE
Transcriptome Analysis of the Vernalization Response in Barley (Hordeum vulgare) Seedlings
Temperate cereals, such as wheat (Triticum spp.) and barley (Hordeum vulgare), respond to prolonged cold by becoming more tolerant of freezing (cold acclimation) and by becoming competent to flower (vernalization). These responses occur concomitantly during winter, but vernalization continues to influence development during spring. Previous studies identified VERNALIZATION1 (VRN1) as a master regulator of the vernalization response in cereals. The extent to which other genes contribute to this process is unclear. In this study the Barley1 Affymetrix chip was used to assay gene expression in barley seedlings during short or prolonged cold treatment. Gene expression was also assayed in the leaves of plants after prolonged cold treatment, in order to identify genes that show lasting responses to prolonged cold, which might contribute to vernalization-induced flowering. Many genes showed altered expression in response to short or prolonged cold treatment, but these responses differed markedly. A limited number of genes showed lasting responses to prolonged cold treatment. These include genes known to be regulated by vernalization, such as VRN1 and ODDSOC2, and also contigs encoding a calcium binding protein, 23-KD jasmonate induced proteins, an RNase S-like protein, a PR17d secretory protein and a serine acetyltransferase. Some contigs that were up-regulated by short term cold also showed lasting changes in expression after prolonged cold treatment. These include COLD REGULATED 14B (COR14B) and the barley homologue of WHEAT COLD SPECIFIC 19 (WSC19), which were expressed at elevated levels after prolonged cold. Conversely, two C-REPEAT BINDING FACTOR (CBF) genes showed reduced expression after prolonged cold. Overall, these data show that a limited number of barley genes exhibit lasting changes in expression after prolonged cold treatment, highlighting the central role of VRN1 in the vernalization response in cereals
Evidence and perceptions of rainfall change in Malawi: Do maize cultivar choices enhance climate change adaptation in sub-Saharan Africa?
Getting farmers to adopt new cultivars with greater tolerance for coping with climatic extremes and variability is considered as one way of adapting agricultural production to climate change. However, for successful adaptation to occur, an accurate recognition and understanding of the climate signal by key stakeholders (farmers, seed suppliers and agricultural extension services) is an essential precursor. This paper presents evidence based on fieldwork with smallholder maize producers and national seed network stakeholders in Malawi from 2010 to 2011, assessing understandings of rainfall changes and decision-making about maize cultivar choices. Our findings show that preferences for short-season maize cultivars are increasing based on perceptions that season lengths are growing shorter due to climate change and the assumption that growing shorter-season crops represents a good strategy for adapting to drought. However, meteorological records for the two study areas present no evidence for shortening seasons (or any significant change to rainfall characteristics), suggesting that short-season cultivars may not be the most suitable adaptation option for these areas. This demonstrates the dangers of oversimplified climate information in guiding changes in farmer decision-making about cultivar choice
A Preclinical Assessment of Neural Stem Cells as Delivery Vehicles for Anti-Amyloid Therapeutics
Transplantation of neural stems cells (NSCs) could be a useful means to deliver biologic therapeutics for late-stage Alzheimer's disease (AD). In this study, we conducted a small preclinical investigation of whether NSCs could be modified to express metalloproteinase 9 (MMP9), a secreted protease reported to degrade aggregated Aβ peptides that are the major constituents of the senile plaques. Our findings illuminated three issues with using NSCs as delivery vehicles for this particular application. First, transplanted NSCs generally failed to migrate to amyloid plaques, instead tending to colonize white matter tracts. Second, the final destination of these cells was highly influenced by how they were delivered. We found that our injection methods led to cells largely distributing to white matter tracts, which are anisotropic conduits for fluids that facilitate rapid distribution within the CNS. Third, with regard to MMP9 as a therapeutic to remove senile plaques, we observed high concentrations of endogenous metalloproteinases around amyloid plaques in the mouse models used for these preclinical tests with no evidence that the NSC-delivered enzymes elevated these activities or had any impact. Interestingly, MMP9-expressing NSCs formed substantially larger grafts. Overall, we observed long-term survival of NSCs in the brains of mice with high amyloid burden. Therefore, we conclude that such cells may have potential in therapeutic applications in AD but improved targeting of these cells to disease-specific lesions may be required to enhance efficacy
Budd-Chiari Syndrome: Long term success via hepatic decompression using transjugular intrahepatic porto-systemic shunt
<p>Abstract</p> <p>Background</p> <p>Budd-Chiari syndrome (BCS) generally implies thrombosis of the hepatic veins and/or the intrahepatic or suprahepatic inferior vena cava. Treatment depends on the underlying cause, the anatomic location, the extent of the thrombotic process and the functional capacity of the liver. It can be divided into medical treatment including anticoagulation and thrombolysis, radiological procedures such as angioplasty and transjugular intrahepatic porto-systemic shunt (TIPS) and surgical interventions including orthotopic liver transplantation (OLT). Controlled trials or reports on larger cohorts are limited due to rare disease frequency. The aim of this study was to report our single centre long term results of patients with BCS receiving one of three treatment options i.e. medication only, TIPS or OLT on an individually based decision of our local expert group.</p> <p>Methods</p> <p>20 patients with acute, subacute or chronic BCS were treated between 1988 and 2008. Clinical records were analysed with respect to underlying disease, therapeutic interventions, complications and overall outcome.</p> <p>Results</p> <p>16 women and 4 men with a mean age of 34 ± 12 years (range: 14-60 years) at time of diagnosis were included. Myeloproliferative disorders or a plasmatic coagulopathy were identified as underlying disease in 13 patients, in the other patients the cause of BCS remained unclear. 12 patients presented with an acute BCS, 8 with a subacute or chronic disease. 13 patients underwent TIPS, 4 patients OLT as initial therapy, 2 patients required only symptomatic therapy, and one patient died from liver failure before any specific treatment could be initiated. Eleven of 13 TIPS patients required 2.5 ± 2.4 revisions (range: 0-8). One patient died from his underlying hematologic disease. The residual 12 patients still have stable liver function not requiring OLT. All 4 patients who underwent OLT as initial treatment, required re-OLT due to thrombembolic complications of the graft. Survival in the TIPS group was 92.3% and in the OLT group 75% during a median follow-up of 4 and 11.5 years, respectively.</p> <p>Conclusion</p> <p>Our results confirm the role of TIPS in the management of patients with acute, subacute and chronic BCS. The limited number of patients with OLT does not allow to draw a meaningful conclusion. However, the underlying disease may generate major complications, a reason why OLT should be limited to patients who cannot be managed by TIPS.</p
A Genome-Wide SNP Scan Reveals Novel Loci for Egg Production and Quality Traits in White Leghorn and Brown-Egg Dwarf Layers
Availability of the complete genome sequence as well as high-density SNP genotyping platforms allows genome-wide association studies (GWAS) in chickens. A high-density SNP array containing 57,636 markers was employed herein to identify associated variants underlying egg production and quality traits within two lines of chickens, i.e., White Leghorn and brown-egg dwarf layers. For each individual, age at first egg (AFE), first egg weight (FEW), and number of eggs (EN) from 21 to 56 weeks of age were recorded, and egg quality traits including egg weight (EW), eggshell weight (ESW), yolk weight (YW), eggshell thickness (EST), eggshell strength (ESS), albumen height(AH) and Haugh unit(HU) were measured at 40 and 60 weeks of age. A total of 385 White Leghorn females and 361 brown-egg dwarf dams were selected to be genotyped. The genome-wide scan revealed 8 SNPs showing genome-wise significant (P<1.51E-06, Bonferroni correction) association with egg production and quality traits under the Fisher's combined probability method. Some significant SNPs are located in known genes including GRB14 and GALNT1 that can impact development and function of ovary, but more are located in genes with unclear functions in layers, and need to be studied further. Many chromosome-wise significant SNPs were also detected in this study and some of them are located in previously reported QTL regions. Most of loci detected in this study are novel and the follow-up replication studies may be needed to further confirm the functional significance for these newly identified SNPs
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