The goal of making silage is to produce a stable feed with a high recovery of dry matter, energy, and highly digestible nutrients compared with the fresh crop. Microbial fermentation in the silo ...produces an array of end products and can change many nutritive aspects of a forage. High-quality silage should be void of undesirable compounds that could negatively affect animal performance, the environment, or net farm income. This review discusses the interpretation of the common fermentation end products, microbial populations, organoleptic properties, and changes in nutritive aspects of silages during storage of silages with emphasis on a North American perspective.
The Twentieth Century Reanalysis Project Compo, G. P.; Whitaker, J. S.; Sardeshmukh, P. D. ...
Quarterly journal of the Royal Meteorological Society,
January 2011 Part A, 2011, 2011-01-00, 20110101, 2011-01-01, Letnik:
137, Številka:
654
Journal Article
Dam removal: Listening in Foley, M. M.; Bellmore, J. R.; O'Connor, J. E. ...
Water resources research,
July 2017, 2017-07-00, 20170701, Letnik:
53, Številka:
7
Journal Article
Recenzirano
Dam removal is widely used as an approach for river restoration in the United States. The increase in dam removals—particularly large dams—and associated dam‐removal studies over the last few decades ...motivated a working group at the USGS John Wesley Powell Center for Analysis and Synthesis to review and synthesize available studies of dam removals and their findings. Based on dam removals thus far, some general conclusions have emerged: (1) physical responses are typically fast, with the rate of sediment erosion largely dependent on sediment characteristics and dam‐removal strategy; (2) ecological responses to dam removal differ among the affected upstream, downstream, and reservoir reaches; (3) dam removal tends to quickly reestablish connectivity, restoring the movement of material and organisms between upstream and downstream river reaches; (4) geographic context, river history, and land use significantly influence river restoration trajectories and recovery potential because they control broader physical and ecological processes and conditions; and (5) quantitative modeling capability is improving, particularly for physical and broad‐scale ecological effects, and gives managers information needed to understand and predict long‐term effects of dam removal on riverine ecosystems. Although these studies collectively enhance our understanding of how riverine ecosystems respond to dam removal, knowledge gaps remain because most studies have been short (< 5 years) and do not adequately represent the diversity of dam types, watershed conditions, and dam‐removal methods in the U.S.
Key Points
Dam removal is an increasingly common approach to river restoration in the United States
Dam‐removal studies provide insights on key controls influencing the physical and ecological responses to dam removal
Although many aspects of physical and ecological systems react quickly to dam removal, overall response trajectories depend on how and where dams are removed and overall watershed conditions
Calcium signalling in astrocytes couples changes in neural activity to alterations in cerebral blood flow by eliciting vasoconstriction or vasodilation of arterioles. However, the mechanism for how ...these opposite astrocyte influences provide appropriate changes in vessel tone within an environment that has dynamic metabolic requirements remains unclear. Here we show that the ability of astrocytes to induce vasodilations over vasoconstrictions relies on the metabolic state of the rat brain tissue. When oxygen availability is lowered and astrocyte calcium concentration is elevated, astrocyte glycolysis and lactate release are maximized. External lactate attenuates transporter-mediated uptake from the extracellular space of prostaglandin E(2), leading to accumulation and subsequent vasodilation. In conditions of low oxygen concentration extracellular adenosine also increases, which blocks astrocyte-mediated constriction, facilitating dilation. These data reveal the role of metabolic substrates in regulating brain blood flow and provide a mechanism for differential astrocyte control over cerebrovascular diameter during different states of brain activation.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Riboswitches are structural RNA elements that are generally located in the 5' untranslated region of messenger RNA. During regulation of gene expression, ligand binding to the aptamer domain of a ...riboswitch triggers a signal to the downstream expression platform. A complete understanding of the structural basis of this mechanism requires the ability to study structural changes over time. Here we use femtosecond X-ray free electron laser (XFEL) pulses to obtain structural measurements from crystals so small that diffusion of a ligand can be timed to initiate a reaction before diffraction. We demonstrate this approach by determining four structures of the adenine riboswitch aptamer domain during the course of a reaction, involving two unbound apo structures, one ligand-bound intermediate, and the final ligand-bound conformation. These structures support a reaction mechanism model with at least four states and illustrate the structural basis of signal transmission. The three-way junction and the P1 switch helix of the two apo conformers are notably different from those in the ligand-bound conformation. Our time-resolved crystallographic measurements with a 10-second delay captured the structure of an intermediate with changes in the binding pocket that accommodate the ligand. With at least a 10-minute delay, the RNA molecules were fully converted to the ligand-bound state, in which the substantial conformational changes resulted in conversion of the space group. Such notable changes in crystallo highlight the important opportunities that micro- and nanocrystals may offer in these and similar time-resolved diffraction studies. Together, these results demonstrate the potential of 'mix-and-inject' time-resolved serial crystallography to study biochemically important interactions between biomacromolecules and ligands, including those that involve large conformational changes.
Summary
Libraries of 16S rRNA genes cloned from methanogenic oil degrading microcosms amended with North Sea crude oil and inoculated with estuarine sediment indicated that bacteria from the genera ...Smithella (Deltaproteobacteria, Syntrophaceace) and Marinobacter sp. (Gammaproteobacteria) were enriched during degradation. Growth yields and doubling times (36 days for both Smithella and Marinobacter) were determined using qPCR and quantitative data on alkanes, which were the predominant hydrocarbons degraded. The growth yield of the Smithella sp. 0.020 g(cell‐C)/g(alkane‐C), assuming it utilized all alkanes removed was consistent with yields of bacteria that degrade hydrocarbons and other organic compounds in methanogenic consortia. Over 450 days of incubation predominance and exponential growth of Smithella was coincident with alkane removal and exponential accumulation of methane. This growth is consistent with Smithella's occurrence in near surface anoxic hydrocarbon degrading systems and their complete oxidation of crude oil alkanes to acetate and/or hydrogen in syntrophic partnership with methanogens in such systems. The calculated growth yield of the Marinobacter sp., assuming it grew on alkanes, was 0.0005 g(cell‐C)/g(alkane‐C) suggesting that it played a minor role in alkane degradation. The dominant methanogens were hydrogenotrophs (Methanocalculus spp. from the Methanomicrobiales). Enrichment of hydrogen‐oxidizing methanogens relative to acetoclastic methanogens was consistent with syntrophic acetate oxidation measured in methanogenic crude oil degrading enrichment cultures. qPCR of the Methanomicrobiales indicated growth characteristics consistent with measured rates of methane production and growth in partnership with Smithella.
Historical research had shown that forage particle size influences chewing activity, ruminal pH, volatile fatty acid profiles, and milk fat percentage. With this in mind, Mertens in 1997 published ...one of the most frequently cited papers in the Journal of Dairy Science that laid out a comprehensive system for integrating neutral detergent fiber (NDF) and particle size of feeds into one measure: physically effective NDF (peNDF). Based on total chewing time (i.e., eating plus ruminating), peNDF enabled ration formulation to meet the minimum fiber requirements of ruminants to maintain ruminal pH and milk fat. Total chewing time is related to feed NDF content and particle size, so Mertens proposed that peNDF could be determined simply from a chemical measure of NDF and particle size measured as the fraction of dry matter retained on a 1.18-mm sieve with vertical shaking of a dried sample. In the past 2 decades, the peNDF system has been incorporated into nutrition models and is routinely used in ration formulation. Early on, Mertens recognized that starch would affect the minimum peNDF requirements, and his work was the first to demonstrate that starch and fermentation pH affect ruminal fiber degradation kinetics. Subsequently, Mertens's insight into particle size analysis was extended from fibrous feeds to corn silage processing with the development of the commonly used corn silage fragmentation index for assessing starch availability. Participants at the 33rd Discover Conference on fiber in 2017 ranked improved physical description of feeds as a top priority for future research, undoubtedly recognizing the need to carry forward Mertens's pioneering work. Future research will likely focus on improving the physicochemical and biological evaluation of rumen fiber degradation and passage, thereby improving the prediction of animal response. The comprehensive system that David Mertens built for meeting the fiber requirements of ruminants has transformed ration formulation.
This is a cross-sectional, observational study to determine the frequency and associated features of HIV-associated neurocognitive disorders (HAND) in a large, diverse sample of infected individuals ...in the era of combination antiretroviral therapy (CART).
A total of 1,555 HIV-infected adults were recruited from 6 university clinics across the United States, with minimal exclusions. We used standardized neuromedical, psychiatric, and neuropsychological (NP) examinations, and recently published criteria for diagnosing HAND and classifying 3 levels of comorbidity (minimal to severe non-HIV risks for NP impairment).
Fifty-two percent of the total sample had NP impairment, with higher rates in groups with greater comorbidity burden (40%, 59%, and 83%). Prevalence estimates for specific HAND diagnoses (excluding severely confounded cases) were 33% for asymptomatic neurocognitive impairment, 12% for mild neurocognitive disorder, and only 2% for HIV-associated dementia (HAD). Among participants with minimal comorbidities (n = 843), history of low nadir CD4 was a strong predictor of impairment, and the lowest impairment rate on CART occurred in the subset with suppressed plasma viral loads and nadir CD4 ≥200 cells/mm(3) (30% vs 47% in remaining subgroups).
The most severe HAND diagnosis (HAD) was rare, but milder forms of impairment remained common, even among those receiving CART who had minimal comorbidities. Future studies should clarify whether early disease events (e.g., profound CD4 decline) may trigger chronic CNS changes, and whether early CART prevents or reverses these changes.
Iterative liver injury results in progressive fibrosis disrupting hepatic architecture, regeneration potential, and liver function. Hepatic stellate cells (HSCs) are a major source of pathological ...matrix during fibrosis and are thought to be a functionally homogeneous population. Here, we use single-cell RNA sequencing to deconvolve the hepatic mesenchyme in healthy and fibrotic mouse liver, revealing spatial zonation of HSCs across the hepatic lobule. Furthermore, we show that HSCs partition into topographically diametric lobule regions, designated portal vein-associated HSCs (PaHSCs) and central vein-associated HSCs (CaHSCs). Importantly we uncover functional zonation, identifying CaHSCs as the dominant pathogenic collagen-producing cells in a mouse model of centrilobular fibrosis. Finally, we identify LPAR1 as a therapeutic target on collagen-producing CaHSCs, demonstrating that blockade of LPAR1 inhibits liver fibrosis in a rodent NASH model. Taken together, our work illustrates the power of single-cell transcriptomics to resolve the key collagen-producing cells driving liver fibrosis with high precision.
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•scRNA-seq reveals spatial zonation of hepatic stellate cells (HSCs)•HSCs partition into topographically diametric lobule regions•Functional zonation of HSCs during centrilobular injury-induced fibrosis is uncovered•LPAR1 is a therapeutic target on pathological central vein-associated HSC
Dobie et al. use scRNA-seq to reveal spatial and functional zonation of hepatic stellate cells (HSCs) across the hepatic lobule, identifying central vein-associated HSCs as the dominant pathogenic collagen-producing cells during centrilobular injury-induced fibrosis. This illustrates the power of scRNA-seq to resolve the key collagen-producing cells driving liver fibrosis.
This paper summarizes Spirit Rover operations in the Columbia Hills, Gusev crater, from sol 1410 (start of the third winter campaign) to sol 2169 (when extrication attempts from Troy stopped to ...winterize the vehicle) and provides an overview of key scientific results. The third winter campaign took advantage of parking on the northern slope of Home Plate to tilt the vehicle to track the sun and thus survive the winter season. With the onset of the spring season, Spirit began circumnavigating Home Plate on the way to volcanic constructs located to the south. Silica‐rich nodular rocks were discovered in the valley to the north of Home Plate. The inoperative right front wheel drive actuator made climbing soil‐covered slopes problematical and led to high slip conditions and extensive excavation of subsurface soils. This situation led to embedding of Spirit on the side of a shallow, 8 m wide crater in Troy, located in the valley to the west of Home Plate. Examination of the materials exposed during embedding showed that Spirit broke through a thin sulfate‐rich soil crust and became embedded in an underlying mix of sulfate and basaltic sands. The nature of the crust is consistent with dissolution and precipitation in the presence of soil water within a few centimeters of the surface. The observation that sulfate‐rich deposits in Troy and elsewhere in the Columbia Hills are just beneath the surface implies that these processes have operated on a continuing basis on Mars as landforms have been shaped by erosion and deposition.
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