470 research outputs found
Adaptation and acclimatization to ocean acidification in marine ectotherms: an in situ transplant experiment with polychaetes at a shallow COâ vent system
Metabolic rate determines the physiological and life-history performances of ectotherms. Thus, the extent to which such rates are sensitive and plastic to environmental perturbation is central to an organism's ability to function in a changing environment. Little is known of long-term metabolic plasticity and potential for metabolic adaptation in marine ectotherms exposed to elevated pCOâ. Consequently, we carried out a series of in situ transplant experiments using a number of tolerant and sensitive polychaete species living around a natural COâ vent system. Here, we show that a marine metazoan (i.e. Platynereis dumerilii) was able to adapt to chronic and elevated levels of pCOâ. The vent population of P. dumerilii was physiologically and genetically different from nearby populations that experience low pCOâ, as well as smaller in body size. By contrast, different populations of Amphiglena mediterranea showed marked physiological plasticity indicating that adaptation or acclimatization are both viable strategies for the successful colonization of elevated pCOâ environments. In addition, sensitive species showed either a reduced or increased metabolism when exposed acutely to elevated pCOâ. Our findings may help explain, from a metabolic perspective, the occurrence of past mass extinction, as well as shed light on alternative pathways of resilience in species facing ongoing ocean acidification
Detection of potentially toxic metals by SERS using salen complexes
Surfaced enhanced Raman scattering (SERS) can discriminate between metal complexes due to the characteristic âspectral fingerprintsâ obtained. As a result, SERS has the potential to develop relatively simple and sensitive methods of detecting and quantifying a range of metal ions in solution. This could be beneficial for the environmental monitoring of potentially toxic metals (PTMs). Here, salen (C16H16N2O2) was used as a ligand to form complexes of Ni(II), Cu(II), Mn(II) and Co(II) in solution. The SERS spectra showed characteristic spectral differences specific to each metal complex, thus allowing the identification of each of these metal ions. This method allows a number of metal ions to be detected using the same ligand and an identical preparation procedure. The limit of detection (LOD) was determined for each metal ion, and it was found that Ni(II), Cu(II) and Mn(II) could be detected below the WHOâs recommended limits in drinking water at 1, 2 and 2 ”g L-1, respectively. Co(II) was found to have an LOD of 20 ”g L-1, however no limit has been set for this ion by the WHO as the concentration of Co(II) in drinking water is generally <1-2 ÎŒg L-1. A contaminated water sample was also analysed where Mn(II) was detected at a level of 800 ”g L-1
Inhibition of chylomicron assembly leads to dissociation of hepatic steatosis from inflammation and fibrosis
Regulating dietary fat absorption may impact progression of nonalcoholic fatty liver disease (NAFLD). Here we asked if inducible inhibition of chylomicron assembly, as observed in intestine-specific microsomal triglyceride transfer protein knockout mice (Mttp-IKO), could retard NAFLD progression and/or reverse established fibrosis in two dietary models. Mttp-IKO mice fed a methionine/choline deficient (MCD) diet exhibited reduced hepatic triglycerides (TG), inflammation and fibrosis, associated with reduced oxidative stress and downstream activation of JNK and NFÎșB signaling pathways. However, when Mtt
Binge-Like Alcohol Exposure During Adolescence Disrupts Dopaminergic Neurotransmission in the Adult Prelimbic Cortex
Repeated binge-like exposure to alcohol during adolescence has been reported to perturb prefrontal cortical development, yet the mechanisms underlying these effects are unknown. Here we report that adolescent intermittent ethanol exposure induces cellular and dopaminergic abnormalities in the adult prelimbic cortex (PrL-C). Exposing rats to alcohol during early-mid adolescence (PD28â42) increased the density of long/thin dendritic spines of layer 5 pyramidal neurons in the adult PrL-C. Interestingly, although AIE exposure did not alter the expression of glutamatergic proteins in the adult PrL-C, there was a pronounced reduction in dopamine (DA) D1 receptor modulation of both intrinsic firing and evoked NMDA currents in pyramidal cells, whereas D2 receptor function was unaltered. Recordings from fast-spiking interneurons also revealed that AIE reduced intrinsic excitability, glutamatergic signaling, and D1 receptor modulation of these cells. Analysis of PrL-C tissue of AIE-exposed rats further revealed persistent changes in the expression of DA-related proteins, including reductions in the expression of tyrosine hydroxylase and catechol-O-methyltransferase (COMT). AIE exposure was associated with hypermethylation of the COMT promoter at a conserved CpG site in exon II. Taken together, these findings demonstrate that AIE exposure disrupts DA and GABAergic transmission in the adult medial prefrontal cortex (mPFC). As DA and GABA work in concert to shape and synchronize neuronal ensembles in the PFC, these alterations could contribute to deficits in behavioral control and decision-making in adults who abused alcohol during adolescence
Dysregulation of mannose-6-phosphateâdependent cholesterol homeostasis in acinar cells mediates pancreatitis
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Mitigation of Moral Hazard and Adverse Selection in Venture Capital Financing: The Influence of the Countryâs Institutional Setting
A venture capitalist (VC) needs to trade off benefits and costs when attempting to mitigate agency problems in their investor-investee relationship. We argue that signals of ventures complement the VCâs capacity to screen and conduct a due diligence during the pre-investment phase, but its attractiveness may diminish in institutional settings supporting greater transparency. Similarly, whereas a VC may opt for contractual covenants to curb potential opportunism by ventures in the post-investment phase, this may only be effective in settings supportive of shareholder rights enforcement. Using an international sample of VC contracts, our study finds broad support for these conjectures. It delineates theoretical and practical implications for how investors can best deploy their capital in different institutional settings whilst nurturing their relationships with entrepreneurs
Down-regulation of the caffeic acid \u3cem\u3eO\u3c/em\u3e-methyltransferase gene in switchgrass reveals a novel monolignol analog
Background
Down-regulation of the caffeic acid 3-O-methyltransferase EC 2.1.1.68 (COMT) gene in the lignin biosynthetic pathway of switchgrass (Panicum virgatum) resulted in cell walls of transgenic plants releasing more constituent sugars after pretreatment by dilute acid and treatment with glycosyl hydrolases from an added enzyme preparation and from Clostridium thermocellum. Fermentation of both wild-type and transgenic switchgrass after milder hot water pretreatment with no water washing showed that only the transgenic switchgrass inhibited C. thermocellum. Gas chromatographyâmass spectrometry (GCMS)-based metabolomics were undertaken on cell wall aqueous extracts to determine the nature of the microbial inhibitors. Results
GCMS confirmed the increased concentration of a number of phenolic acids and aldehydes that are known inhibitors of microbial fermentation. Metabolomic analyses of the transgenic biomass additionally revealed the presence of a novel monolignol-like metabolite, identified as trans-3, 4-dimethoxy-5-hydroxycinnamyl alcohol (iso-sinapyl alcohol) in both non-pretreated, as well as hot water pretreated samples. iso-Sinapyl alcohol and its glucoside were subsequently generated by organic synthesis and the identity of natural and synthetic materials were confirmed by mass spectrometric and NMR analyses. The additional novel presence of iso-sinapic acid, iso-sinapyl aldehyde, and iso-syringin suggest the increased activity of a para-methyltransferase, concomitant with the reduced COMT activity, a strict meta-methyltransferase. Quantum chemical calculations were used to predict the most likely homodimeric lignans generated from dehydration reactions, but these products were not evident in plant samples. Conclusions
Down-regulation of COMT activity in switchgrass resulted in the accumulation of previously undetected metabolites resembling sinapyl alcohol and its related metabolites, but that are derived from para-methylation of 5-hydroxyconiferyl alcohol, and related precursors and products; the accumulation of which suggests altered metabolism of 5-hydroxyconiferyl alcohol in switchgrass. Given that there was no indication that iso-sinapyl alcohol was integrated in cell walls, it is considered a monolignol analog. Diversion of substrates from sinapyl alcohol to free iso-sinapyl alcohol, its glucoside, and associated upstream lignin pathway changes, including increased phenolic aldehydes and acids, are together associated with more facile cell wall deconstruction, and to the observed inhibitory effect on microbial growth. However, iso-sinapyl alcohol and iso-sinapic acid, added separately to media, were not inhibitory to C. thermocellum cultures
Modular Synthesis and Biological Investigation of 5-Hydroxymethyl Dibenzyl Butyrolactones and Related Lignans
Dibenzyl butyrolactone lignans are well known for their excellent biological properties, particularly for their notable anti-proliferative activities. Herein we report a novel, efficient, convergent synthesis of dibenzyl butyrolactone lignans utilizing the acyl-Claisen rearrangement to stereoselectively prepare a key intermediate. The reported synthetic route enables the modification of these lignans to give rise to 5-hydroxymethyl derivatives of these lignans. The biological activities of these analogues were assessed, with derivatives showing an excellent cytotoxic profile which resulted in programmed cell death of Jurkat T-leukemia cells with less than 2% of the incubated cells entering a necrotic cell death pathway
Observations of Binary Stars with the Differential Speckle Survey Instrument. IX. Observations of Known and Suspected Binaries, and a Partial Survey of Be Stars
We report 370 measures of 170 components of binary and multiple star systems,
obtained from speckle imaging observations made with the Differential Speckle
Survey Instrument at Lowell Observatory's Discovery Channel Telescope in 2015
through 2017. Of the systems studied, 147 are binary stars, 10 are seen as
triple systems, and 1 quadruple system is measured. Seventy-six high-quality
non-detections and fifteen newly resolved components are presented in our
observations. The uncertainty in relative astrometry appears to be similar to
our previous work at Lowell, namely linear measurement uncertainties of
approximately 2 mas, and the relative photometry appears to be uncertain at the
0.1 to 0.15 magnitude level. Using these measures and those in the literature,
we calculate six new visual orbits, including one for the Be star 66 Oph, and
two combined spectroscopic-visual orbits. The latter two orbits, which are for
HD 22451 (YSC 127) and HD 185501 (YSC 135), yield individual masses of the
components at the level of 2 percent or better, and independent distance
measures that in one case agrees with the value found in the Gaia DR2, and in
the other disagrees at the 2- level. We find that HD 22451 consists of
an F6V+F7V pair with orbital period of days and masses of
and . For HD 185501, both stars
are G5 dwarfs that orbit one another with a period of days,
and the masses are and . We
discuss the details of both the new discoveries and the orbit objects
Myeloid-specific Asxl2 deletion limits diet-induced obesity by regulating energy expenditure
We previously established that global deletion of the enhancer of trithorax and polycomb (ETP) gene, Asxl2, prevents weight gain. Because proinflammatory macrophages recruited to adipose tissue are central to the metabolic complications of obesity, we explored the role of ASXL2 in myeloid lineage cells. Unexpectedly, mice without Asxl2 only in myeloid cells (Asxl2ÎLysM) were completely resistant to diet-induced weight gain and metabolically normal despite increased food intake, comparable activity, and equivalent fecal fat. Asxl2ÎLysM mice resisted HFD-induced adipose tissue macrophage infiltration and inflammatory cytokine gene expression. Energy expenditure and brown adipose tissue metabolism in Asxl2ÎLysM mice were protected from the suppressive effects of HFD, a phenomenon associated with relatively increased catecholamines likely due to their suppressed degradation by macrophages. White adipose tissue of HFD-fed Asxl2ÎLysM mice also exhibited none of the pathological remodeling extant in their control counterparts. Suppression of macrophage Asxl2 expression, via nanoparticle-based siRNA delivery, prevented HFD-induced obesity. Thus, ASXL2 controlled the response of macrophages to dietary factors to regulate metabolic homeostasis, suggesting modulation of the cells\u27 inflammatory phenotype may impact obesity and its complications
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