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1.
The biodegradability of petroleum hydrocarbons such as polycyclic aromatic hydrocarbons (PAHs) and n-branched alkanes etc. of 2T engine oil were studied in aqueous media using bacterial strain isolated from petroleum contaminated
soil of high altitude. Out of five petroleum degrading bacterial strain one of the most growing bacteria was identified as
Enterobacter strain by morphological, physiological, biochemical and partial sequencing of 16S rDNA. This strain was capable of degrading
75 ± 3% of n-alkanes, 32 ± 5% PAHs, and the abiotic loss was 24 ± 6% during 10 days incubation period. 85 ± 2% of n-alkanes and 51 ± 3% PAHs were biodegraded in 20 days. The abiotic loss during this period was 15 ± 3%. In 30 days of incubation
period 98% ± 1% n-alkanes and 75 ± 3% PAHs were degraded. As expected abiotic losses were smaller with increasing long chain alkanes and PAH’s
concentration. An increment in oil degradation was correlated to an increase in cell number indicating that the bacterial
isolate was responsible for the oil degradation. The hydrocarbon contents were measured by Shimadzu QP-2000 Gas chromatography/mass
spectrometry by ULBON HR-1 column. 相似文献
2.
Effects of meiotic stage and cumulus status on development of equine oocytes after vitrification was evaluated. Immature oocytes with corona radiata (IMM); in vitro-matured oocytes with corona radiata (MAT CR+); and in vitro-matured oocytes denuded of cumulus (MAT CR-) were vitrified using the Cryotech® method. Warming medium was equilibrated either in 5% CO 2 or Air. IMM oocytes underwent in vitro maturation after warming. Recovery, survival, and maturation rates, and cleavage and blastocyst rates after ICSI, were evaluated. Recovery was higher for oocytes warmed in CO 2- than Air-equilibrated medium (86 ± 3 vs. 76.9 ± 4%, respectively). Maturation for all vitrified-warmed oocyte treatments (37 ± 6.5 to 45.9 ± 5.8%) was not different from control (50 ± 4.1%), except for MAT CR- CO 2 (20.3 ± 4.6%). Cleavage for MAT CR- CO 2 and Air groups was similar to control (67.7 ± 12.1, 71.4 ± 8.1, and 78 ± 5.3%, respectively). One blastocyst was produced (MAT CR + CO 2), representing the first equine blastocyst reported after vitrification of an in vitro-matured oocyte. 相似文献
3.
The unceasing emerging of multidrug-resistant bacteria imposes a global foremost human health threat and discovery of new alternative remedies are necessity. The use of plant essential oil in the treatment of many pathogenic bacteria is promising. Acne vulgaris is the most common skin complaint that fears many people about their aesthetic appearance. In this work we investigated the antibacterial activity of some plant oils against acne-inducing bacteria. Three bacterial isolates were identified from Egypt, biochemically and by means of 16s rRNA gene typing, and were designated as Staphylococcus aureus EG-AE1, Staphylococcus epidermidis EG-AE2 and Cutibacterium acnes EG-AE1. Antibiotic susceptibility test showed resistance of the isolates to at least six antibiotics, yet they are still susceptible to the last resort Vancomycin. In vitro investigations of eleven Egyptian plant oils, identified tea tree and rosemary oils to exhibit antibacterial activity against the antibiotic-resistant acne isolates. Inhibition zones of 15 ± 0.5, 21.02 ± 0.73 and 20.85 ± 0.76 mm was detected when tea tree oil applied against the above-mentioned bacteria respectively, while inhibition zones of 12.5 ± 1.5, 15.18 ± 0.38 and 14.77 ± 0.35 mm were detected by rosemary oils. Tea tree and rosemary oils exhibited bacteriostatic and bactericidal activity against all the strains with MICs/MBCs ranging between 39-78 mg/L for tea tree oil and 39–156 mg/L for rosemary oil. All the isolates were killed after 4 and 6 h upon growing with 200 mg/L of tea tree and rosemary oils, respectively. Additionally, gas chromatography mass spectrometry (GC/MS) profiling identified and detected a variable number of antimicrobial compounds in both oils. 相似文献
4.
Using experimental mesocosms, we tested the strength of bottom–up controls by nutrients and top–down controls by an omnivorous
fish ( Hyphessobrycon bifasciatus; family Characidae), and the interaction between them on the CO 2 partial pressure ( pCO 2) in the surface waters of a tropical humic lake (Lake Cabiúnas, Brazil). The experiment included the addition of nutrients
and fish to the mesocosms in a factorial design. Overall, persistent CO 2 emissions to the atmosphere, supported by an intense net heterotrophy, were observed in all treatments and replicates over
the 6-week study period. The CO 2 efflux (average ± standard error) integrated over the experiment was similar among the control mesocosms and those receiving
only fish or only nutrients (309 ± 2, 303 ± 16, and 297 ± 17 mmol CO 2 m −2 day −1, respectively). However, the addition of nutrients in the presence of fish resulted in a high algal biomass and daytime net
autotrophy, reducing the CO 2 emissions by 35% (by 193 ± 7 mmol CO 2 m −2 day −1). These results indicate that high CO 2 emissions persist following the eutrophication of humic waters, but that the magnitude of these emissions might depend on
the structure of the food web. In conclusion, fish and nutrients may act in a synergistic manner to modulate persistent CO 2 emissions from tropical humic lakes. 相似文献
5.
The essential oil from the leaves of Peperomia borbonensis from Réunion Island was obtained by hydrodistillation and characterized using GC‐FID, GC/MS and NMR. The main components were myristicin (39.5%) and elemicin (26.6%). The essential oil (EO) of Peperomia borbonensis and its major compounds (myristicin and elemicin), pure or in a mixture, were evaluated for their insecticidal activity against Bactrocera cucurbitae (Diptera: Tephritidae) using a filter paper impregnated bioassay. The concentrations necessary to kill 50% ( LC50) and 90% ( LC90) of the flies in three hours were determined. The LC50 value was 0.23 ± 0.009 mg/cm 2 and the LC90 value was 0.34 ± 0.015 mg/cm 2 for the EO. The median lethal time ( LT50) was determined to compare the toxicity of EO and the major constituents. The EO was the most potent insecticide ( LT50 = 98 ± 2 min), followed by the mixture of myristicin and elemicin (1.4:1) ( LT50 = 127 ± 2 min) indicating that the efficiency of the EO is potentiated by minor compounds and emphasizing one of the major assets of EOs against pure molecules. 相似文献
6.
The first trees in New York were Middle Devonian (earliest Givetian) cladoxyls ( ?Duisbergia and Wattieza), with shallow-rooted manoxylic trunks. Cladoxyl trees in New York thus postdate their latest Emsian evolution in Spitzbergen. Progymnosperm trees ( ?Svalbardia and Callixylon–Archaeopteris) appeared in New York later (mid-Givetian) than progymnosperm trees from Spitzbergen (early Givetian). Associated paleosols are evidence that Wattieza formed intertidal to estuarine mangal and Callixylon formed dry riparian woodland. Also from paleosols comes evidence that Wattieza and Callixylon required about 350 mm more mean annual precipitation than plants of equivalent stature today, that Wattieza tolerated mean annual temperature 7 °C less than current limits of mangal (20 °C), and Callixylon could tolerate temperatures 14 °C less than modern mangal. Devonian mangal and riparian woodland spread into New York from wetter regions elsewhere during transient paleoclimatic spikes of very high CO 2 (3923 ± 238 ppmv), and subhumid (mean annual precipitation 730 ± 147 mm) conditions, which were more likely extrinsic atmospheric perturbations rather than consequences of tree evolution. For most of the Middle Devonian CO 2 was lower (2263 ± 238 ppmv), and paleoclimate in New York was semiarid (mean annual precipitation 484 ± 147 mm). Such transient perturbations and immigration events may explain the 40 million year gap between the late Emsian (400 Ma) evolution of trees and Famennian (360 Ma) CO 2 drawdown and expansion of ice caps. 相似文献
7.
This study investigated the potential functions of Pleurotus florida (an edible mushroom) in the biodegradation of gas oil at concentrations of 0 (control), 2.5, 5, and 10% (V: V) for 30 days. The gas oil increased dry weight and protein concentration in all treatments (by an average of 19.5 and 108%, respectively). Moreover, the pH, surface tension (ST), and interfacial tension (IFT) were reduced by the mushroom supplementation. The lowest surface tension (31.9 mN m −1) and the highest biosurfactant production belonged to the 10% gas oil treatment (0.845 ± 0.03 mg mL −1). The results demonstrated that the adsorption isotherm agreed well with the Langmuir isotherm. The maximum Langmuir adsorption capacity was calculated at 0.743 mg g −1 wet biomass of P. florida. The fungal supplementation efficiently remedied the total petroleum hydrocarbons (TPHs) by an average of 55% after 30 days. Gas chromatography (GC) analysis revealed that P. florida effectively detoxified C 13–C 28 hydrocarbons, Pristane, and Phytane, implying its high mycoremediation function. The toxicity test showed that mycoremediation increased the germination by an average of 35.82% ± 8.89 after 30 days. Laccase activity increased significantly with increasing gas oil concentration in the treatments. The maximum laccase activity was obtained in the 10% gas oil treatment (142.25 ± 0.72 U L −1). The presence of pollutants was also associated with induction in the tyrosinase activity when compared to the control. These results underline the high mycoremediation capacity of P. florida through the involvement of biosurfactants, laccase, and tyrosinase. 相似文献
8.
Poplar leaves, poplar bark and poplar wood were deoxy-liquefied directly in an air-proof stainless steel reactor at different temperatures. The oils from leaves at 350 °C, from bark at 400 °C and from wood at 450 °C, at which the liquid product yields were the maximum, were analyzed by GC–MS. The oils obtained from three parts of poplar tree were quite different from each other in the relative contents of their compositions. The oil from leaves was rich in hydrocarbons (alkanes: C 7–C 29; aromatics) and poor in phenolics, while oil from wood was rich in phenolics and poor in hydrocarbons. The oil from bark was moderate. Relative contents of hydrocarbons in the leaves oil were as high as 60.01% but decreased to 29.71% in bark oil and 11.43% in wood oil. GC analysis of gases and FT-IR, GC–MS and elemental analysis of oils were performed in this study. 相似文献
9.
The impact of in-situ CO2 nano-bubbles generation on the freezing properties of soft serve, milk, and apple juice was investigated. Carbonated (0, 1000, and 2000 ppm) liquid foods contained in a tube were submerged and cooled for 90 min in a pre-set ethylene glycol bath (−15 °C). Before the enclosed liquid reached 0 °C, the vibration was discharged through ultrasound in the bath to create nano-bubbles within the carbonated food samples, and the changes in temperature for 90 min of each food were recorded as a freezing curve. The time for onset of nucleation of control soft serve mix was halved in samples with 2000-ppm CO2 due to the presence of nano-bubbles. Likewise, the nucleation time for milk with and without nano-bubbles at the same CO2 concentration of 2000 ppm was 7.9 ± 0.1 and 2.8 ± 0.8 min, respectively. The generation of CO2 nano-bubbles from 2000-ppm CO2 level in 10 oBx apple juice displayed −9.3 ± 0.3 °C nucleation temperature while the control one had −11.7 ± 0.9 °C. 相似文献
10.
The chemical composition, antioxidant, cytotoxic, anticholinesterase and anti‐tyrosinase activities of the hydrodistilled essential oil of the aerial parts of Beta vulgaris subsp. maritime (L.) Arcang . from Tunisia have been evaluated. The chemical composition of the oil (yield 0.037% [ w/ w]), determined by GC‐FID and GC/MS is reported for the first time. Twenty five components, accounting for 98.1% of the total oil have been identified. The oil was characterized by a high proportion of oxygenated sesquiterpenes (39.2%), followed by sesquiterpene hydrocarbons (30.3%) and one apocarotenoids (26.3%). The main compounds were γ‐irone (26.3%), α‐cadinol (12.1%), T‐cadinol (10.6%), bicyclogermacrene (10.4%) and δ‐cadinene (6.0%). The isolated oil was tested for its antioxidant activity using the DPPH ·, ABTS +·, catalase, and paraoxonase assays and also for its cytotoxic, anticholinesterase, and anti‐tyrosinase activities. The essential oil exhibited high antioxidant activity ( IC50 = 0.055 ± 0.006 mg/ml) and important result oncatalase (524.447 ± 2.58 Units/mg protein). Furthermore, it exerted a significant cytotoxic effect against A549 cell line, with IC50 = 42.44 ± 1.40 μg/ml. The results indicate that the essential oil of B. vulgaris subsp. maritima (L.) Arcang . aerial parts may be used in future as an alternative to synthetic antioxidant agents, with potential application in the food and pharmaceutical industries. 相似文献
11.
Diatoms are responsible for a large proportion of global carbon fixation, with the possibility that they may fix more carbon under future levels of high CO 2. To determine how increased CO 2 concentrations impact the physiology of the diatom Thalassiosira pseudonana Hasle et Heimdal, nitrate‐limited chemostats were used to acclimate cells to a recent past (333 ± 6 μatm) and two projected future concentrations (476 ± 18 μatm, 816 ± 35 μatm) of CO 2. Samples were harvested under steady‐state growth conditions after either an abrupt (15–16 generations) or a longer acclimation process (33–57 generations) to increased CO 2 concentrations. The use of un‐bubbled chemostat cultures allowed us to calculate the uptake ratio of dissolved inorganic carbon relative to dissolved inorganic nitrogen (DIC:DIN), which was strongly correlated with fCO 2 in the shorter acclimations but not in the longer acclimations. Both CO 2 treatment and acclimation time significantly affected the DIC:DIN uptake ratio. Chlorophyll a per cell decreased under elevated CO 2 and the rates of photosynthesis and respiration decreased significantly under higher levels of CO 2. These results suggest that T. pseudonana shifts carbon and energy fluxes in response to high CO 2 and that acclimation time has a strong effect on the physiological response. 相似文献
12.
The ongoing work on global warming resulting from green house gases (GHGs) has led to explore the possibility of bacterial strains which can fix carbon dioxide (CO 2) and can generate value-added products. The present work is an effort in this direction and has carried out an exhaustive batch experiments for the fixation of CO 2 using B. Cereus SM1 isolated from sewage treatment plant (STP). The work has incorporated 5-day batch run for gaseous phase inlet CO 2 concentration of 13 ± 1 % (%v/v). 84.6 (±5.76) % of CO 2 removal was obtained in the gaseous phase at mentioned CO 2 concentration (%v/v). Energetic requirement for CO 2 fixation was assessed by varying Fe[II] ion concentration (0–200 ppm) on the per-day basis. The cell lysate obtained from CO 2 fixation studies (Fe[II] ion = 100 ppm) was analyzed using Fourier transformation infrared spectroscopy (FTIR) and gas chromatography-mass spectroscopy (GC–MS). This analysis confirmed the presence of fatty acids and hydrocarbon as valuable products. The hydrocarbons were found in the range of C 11–C 22 which is equivalent to light oil. The obtained fatty acids were found in the range of C 11–C 19. The possibility of fatty acid conversion to biodiesel was explored by carrying out the transesterification reaction. The yield of biodiesel was obtained as 86.5 (±0.048) % under the transesterification reaction conditions. Results of this research work can provide the valuable information in the implementation of biomitigation of CO 2 at real scenario. 相似文献
13.
The value of ecosystems functions performed by forests in the climate change era has prompted increasing attention towards assessment of carbon stocks and fluxes in tropical forests. The aim of this study was to understand how forest management approaches and environmental controls impacted on soil CO 2 efflux in a tropical Eastern Mau forest which is one of the blocks of the greater Mau complex in Kenya. Nested experimental design approach was employed where 32 plots were nested into four blocks (disturbed natural, undisturbed natural, plantation and glades). In 10 m 2 plots, data were collected on soil CO 2 efflux, soil temperature and soil moisture using soda lime methods, direct measurement and proxy techniques, respectively. There was significant forest management type effect ( F3,127 = 3.01, p = 0.033) and seasonality effect ( t test = 3.31, df = 1, p < 0.05) on mean soil CO 2 efflux. The recorded mean soil CO 2 efflux levels were as follows: plantation forest (9.219 ± 3.067 g C M ?2 day ?1), undisturbed natural forest (8.665 ± 4.818 g C M ?2 day ?1), glades (8.592 ± 3.253 g C M ?2 day ?1) and disturbed natural forest (7.198 ± 3.457 g C M ?2 day ?1). The study concludes that managing a forest in plantation form is primarily responsible for forest soil CO 2 efflux levels due to aspects such as increased microbial activity and root respiration. However, further studies are required to understand the role and impact of soil CO 2 efflux on the greater forest carbon budget. 相似文献
14.
The main objective of this study was to evaluate the effect of oily sludge concentration on its biodegradability in soil. Oily sludge was collected and applied to microcosms at full-, half-, or quarter-strength concentrations equivalent to 44.2, 22.2, and 11.1 g kg ?1 soil, respectively, of total petroleum hydrocarbons (TPH) contained in oily sludge. The biodegradability of oily sludge was evaluated by measuring CO 2 evolution and by measuring removal of TPH as well as its main composing fractions; namely; alkanes, aromatics, NSO-compounds, and asphaltenes. The collected soil contained 3.63 × 10 6 cfu g ?1 soil of hydrocarbon-degrading bacteria, which is satisfactory to drive successful biodegradation of hydrocarbons in soil. These numbers increased significantly with oily sludge addition at a rate proportional to the added TPH reaching 3.35 × 10 7 cfu g ?1 soil in the half-strength treatment. TPH mineralization rate followed the same pattern. However, TPH-mineralization efficiency was the greatest in quarter-strength treatment at 18.3%. TPH-removal efficiency was also highest in quarter-strength treatment at 30.9%. Nutrients addition caused mineralization inhibition. Since nutrients were added as a ratio of the added carbon, inhibition was the greatest with the highest TPH treatment. While alkanes were degraded, aromatics and asphaltenes were not, and NSO-compounds were enriched. Although SDS was completely biodegradable in soil, its addition promoted mineralization and removal of TPH from soil. 相似文献
15.
In 2017, the Birmingham Institute of Forest Research (BIFoR) began to conduct Free Air Carbon Dioxide Enrichment (FACE) within a mature broadleaf deciduous forest situated in the United Kingdom. BIFoR FACE employs large‐scale infrastructure, in the form of lattice towers, forming ‘arrays’ which encircle a forest plot of ~30 m diameter. BIFoR FACE consists of three treatment arrays to elevate local CO 2 concentrations (e[CO 2]) by +150 µmol/mol. In practice, acceptable operational enrichment (ambient [CO 2] + e[CO 2]) is ±20% of the set point 1‐min average target. There are a further three arrays that replicate the infrastructure and deliver ambient air as paired controls for the treatment arrays. For the first growing season with e[CO 2] (April to November 2017), [CO 2] measurements in treatment and control arrays show that the target concentration was successfully delivered, that is: +147 ± 21 µmol/mol (mean ± SD) or 98 ± 14% of set point enrichment target. e[CO 2] treatment was accomplished for 97.7% of the scheduled operation time, with the remaining time lost due to engineering faults (0.6% of the time), CO 2 supply issues (0.6%) or adverse weather conditions (1.1%). CO 2 demand in the facility was driven predominantly by wind speed and the formation of the deciduous canopy. Deviations greater than 10% from the ambient baseline CO 2 occurred <1% of the time in control arrays. Incidences of cross‐contamination >80 µmol/mol (i.e. >53% of the treatment increment) into control arrays accounted for <0.1% of the enrichment period. The median [CO 2] values in reconstructed three‐dimensional [CO 2] fields show enrichment somewhat lower than the target but still well above ambient. The data presented here provide confidence in the facility setup and can be used to guide future next‐generation forest FACE facilities built into tall and complex forest stands. 相似文献
16.
Present work deals with the bio-mitigation potential of gaseous phase CO 2 by chemolithotrophic bacterium Halomonas stevensii isolated from haloalkaliphilic habitat using thiosulfate ion (S 2O 32−) as an energy source. H. stevensii was tested for various abiotic stress tolerances such as salt [2–12% (w/v)], temperature (10–60 °C) and pH (2–12). Batch studies were conducted for 6 days at 15 (±1) % (v/v) inlet CO 2 concentration to find the CO 2 fixing capability of H. stevensii under varying concentration of energy substrate i.e. 0, 50 and 100 mM Na 2S 2O 3. Approximately 98% CO 2 removal from gaseous phase was achieved at 50 and 100 mM Na 2S 2O 3. Evaluation of CO 2 fixation by H. stevensii and carbon allocation into different cellular organic pool (carbohydrate, proteins and primary metabolite) was carried out by growing H. stevensii at 5%, 10% and 15% (v/v) inlet CO 2 concentration for the duration of 6 days. The obtained leachate was quantified using chemical technique, FT-IR and GC. Utilization of gaseous phase CO 2 by H. stevensii was also proven by conducting the approximate materials balance and energy assessment for the present CO 2 fixation process. The mechanism of CO 2 metabolism by H. stevensii was evaluated using GC–MS and carbon partitioning into cellular organic pool analysis. 相似文献
17.
We have investigated the chemical composition and the antibacterial activity of the essential oil of Dysphania ambrosioides (L.) Mosyakin & Clemants (Chenopodiaceae) (DA‐EO) against a representative panel of cariogenic bacteria. We have also assessed the in vitro schistosomicidal effects of DA‐EO on Schistosoma mansoni and its cytotoxicity to GM07492‐A cells in vitro. Gas chromatography (GC) and gas chromatography‐mass spectrometry (GC/MS) revealed that the monoterpenes cis‐piperitone oxide (35.2%), p‐cymene (14.5%), isoascaridole (14.1%), and α‐terpinene (11.6%) were identified by as the major constituents of DA‐EO. DA‐EO displayed weak activity against Streptococcus sobrinus and Enterococcus faecalis (minimum inhibitory concentration ( MIC) = 1000 μg/ml). On the other hand, DA‐EO at 25 and 12.5 μg/ml presented remarkable schistosomicidal action in vitro and killed 100% of adult worm pairs within 24 and 72 h, respectively. The LC50 values of DA‐EO were 6.50 ± 0.38, 3.66 ± 1.06, and 3.65 ± 0.76 μg/ml at 24, 48, and 72 h, respectively. However, DA‐EO at concentrations higher than 312.5 μg/ml significantly reduced the viability of GM07492‐A cells ( IC50 = 207.1 ± 4.4 μg/ml). The selectivity index showed that DA‐EO was 31.8 times more toxic to the adult S. mansoni worms than GM07492‐A cells. Taken together, these results demonstrate the promising schistosomicidal potential of the essential oil of Dysphania ambrosioides. 相似文献
18.
The essential oil of different parts of Senecio graciliflorus DC was obtained by hydrodistillation and analysed by GC-FID and GC–MS for the first time. A total of 17, 20, 19 and 17 constituents were identified comprising 99.90, 95.50, 98.93 and 95.96% of the essential oil of flower, leaf, stem and root parts of Senecio graciliflorus respectively. Monoterpene hydrocarbons predominated in the essential oil with 85.28% in flower, 57.53% in leaf, 67.74% in stem and 64.98% in root oil. α-pinene, cis-ocimene, 1,2,3-trimethylcyclohexane and β-pinene were the major constituents of the essential oil. The flower essential oil exhibited a strong antioxidant potential displaying IC 50 values of 21.6 ± 0.6 and 26.0 ± 1.0 μg/ml in DPPH and hydroxyl radical assays respectively. On the other hand the essential oil of flower and root displayed highest cytotoxicity against lung (A-549) cancer cell lines (IC 50 = 19.1 ± 0.9 and 21.3 ± 1.1 μg/ml respectively. This study which represents the first report of the essential oil composition and bioevaluation of Senecio graciliflorus, can serve as a new source of cytotoxic and antioxidant activity. 相似文献
19.
The aim of this study was to explore effects of hypoxia, glucose deprivation (HGD) and recovery on expression and activities
of equilibrative nucleoside transporters (rENT) and concentrative nucleoside transporters (rCNT) in rat astrocytes in primary
culture. Amounts of cellular ATP in the control group (CG, 5% CO 2 in air, medium containing 7 mM d-glucose, 1 mM Na +-pyruvate, 1 h), HGD group (2% O 2/5% CO 2 in N 2, pyruvate-free medium containing 1.5 mM d-glucose and 10 mM 2-deoxy- d-glucose, 1 h) and recovery group (RG, HGD for 1 h, followed by 1 h exposure to the same conditions as the CG) were (nmol/mg
protein, n = 4) 18 ± 1.6, 4.9 ± 0.6 and 10.1 ± 0.8, respectively. Extracellular adenosine concentrations increased from (nM, n = 3) 42 ± 4 in the CG, to 99 ± 8 in the HGD group and 86 ± 3 in the RG. Real-time PCR and immunoblotting revealed that in
the HGD group and RG, the amounts of rENT1 mRNA and protein were reduced to 40 and 50%, when compared to the CG, respectively.
Astrocyte cultures took up [ 3H]adenosine by concentrative and equilibrative transport processes; however, rENT1-mediated uptake was absent in the RG and
cultures from the RG took up significantly less [ 3H]adenosine by equilibrative mechanisms than cultures from the CG. 相似文献
20.
Permafrost peatlands are biogeochemical hot spots in the Arctic as they store vast amounts of carbon. Permafrost thaw could release part of these long‐term immobile carbon stocks as the greenhouse gases (GHGs) carbon dioxide (CO 2) and methane (CH 4) to the atmosphere, but how much, at which time‐span and as which gaseous carbon species is still highly uncertain. Here we assess the effect of permafrost thaw on GHG dynamics under different moisture and vegetation scenarios in a permafrost peatland. A novel experimental approach using intact plant–soil systems (mesocosms) allowed us to simulate permafrost thaw under near‐natural conditions. We monitored GHG flux dynamics via high‐resolution flow‐through gas measurements, combined with detailed monitoring of soil GHG concentration dynamics, yielding insights into GHG production and consumption potential of individual soil layers. Thawing the upper 10–15 cm of permafrost under dry conditions increased CO 2 emissions to the atmosphere (without vegetation: 0.74 ± 0.49 vs. 0.84 ± 0.60 g CO 2–C m ?2 day ?1; with vegetation: 1.20 ± 0.50 vs. 1.32 ± 0.60 g CO 2–C m ?2 day ?1, mean ± SD, pre‐ and post‐thaw, respectively). Radiocarbon dating ( 14C) of respired CO 2, supported by an independent curve‐fitting approach, showed a clear contribution (9%–27%) of old carbon to this enhanced post‐thaw CO 2 flux. Elevated concentrations of CO 2, CH 4, and dissolved organic carbon at depth indicated not just pulse emissions during the thawing process, but sustained decomposition and GHG production from thawed permafrost. Oxidation of CH 4 in the peat column, however, prevented CH 4 release to the atmosphere. Importantly, we show here that, under dry conditions, peatlands strengthen the permafrost–carbon feedback by adding to the atmospheric CO 2 burden post‐thaw. However, as long as the water table remains low, our results reveal a strong CH 4 sink capacity in these types of Arctic ecosystems pre‐ and post‐thaw, with the potential to compensate part of the permafrost CO 2 losses over longer timescales. 相似文献
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