Trends of summertime extreme temperatures in the Arctic

Extreme temperature events can influence the natural environment and societal activities more so than mean temperature events. This study used daily data from 238 stations north of 60°N, obtained from the Global Summary of the Day dataset for the period 1979–2015, to investigate the trends of summertime extreme temperature. The results revealed most stations north of 60°N with trends of decrease in the number of cold days (nights) and increase in the number of warm days (nights). The regional average results showed trends of consistent decline (rise) of cold days and nights (warm days and nights) in Eurasia and Greenland. Similarly, the trends of the seasonal maximum and minimum values were most significant in these regions. In summer, of three indices considered (i.e., Arctic Oscillation, Arctic dipole, and El Niño–Southern Oscillation), the largest contributor to the trends of extreme temperature events was the Arctic dipole. Prevailing southerly winds in summer brought warm moist air across northern Eurasia and Greenland, conducive to increased numbers of warm days (nights) and decreased numbers of cold day (nights). Moreover, we defined extreme events using different thresholds and found the spatial distributions of the trends were similar

Hyperglycemia Alters the Schwann Cell Mitochondrial Proteome and Decreases Coupled Respiration in the Absence of Superoxide Production

Hyperglycemia-induced mitochondrial dysfunction contributes to sensory neuron pathology in diabetic neuropathy. Although Schwann cells (SCs) also undergo substantial degeneration in diabetic neuropathy, the effect of hyperglycemia on SC mitochondrial proteome and mitochondrial function has not been examined. Stable isotope labeling with amino acids in cell culture (SILAC) was used to quantify the temporal effect of hyperglycemia on the mitochondrial proteome of primary SCs isolated from neonatal rats. Of 317 mitochondrial proteins identified, about 78% were quantified and detected at multiple time points. Pathway analysis indicated that proteins associated with mitochondrial dysfunction, oxidative phosphorylation, the TCA cycle and detoxification were significantly increased in expression and over-represented. Assessing mitochondrial respiration in intact SCs indicated that hyperglycemia increased the overall rate of oxygen consumption but decreased the efficiency of coupled respiration. Although a glucose-dependent increase in superoxide production occurs in embryonic sensory neurons, hyperglycemia did not induce a substantial change in superoxide levels in SCs. This correlated with a 1.9 fold increase in Mn superoxide dismutase expression which was confirmed by immunoblot and enzymatic activity assays. These data support that hyperglycemia alters mitochondrial respiration and can cause remodeling of the SC mitochondrial proteome independent of significant contributions from glucose-induced superoxide production

Inhibiting heat-shock protein 90 reverses sensory hypoalgesia in diabetic mice

Increasing the expression of Hsp70 (heat-shock protein 70) can inhibit sensory neuron degeneration after axotomy. Since the onset of DPN (diabetic peripheral neuropathy) is associated with the gradual decline of sensory neuron function, we evaluated whether increasing Hsp70 was sufficient to improve several indices of neuronal function. Hsp90 is the master regulator of the heat-shock response and its inhibition can up-regulate Hsp70. KU-32 (N-{7-[(2R,3R,4S,5R)-3,4-dihydroxy-5-methoxy-6,6-dimethyl-tetrahydro-2H-pyran-2-yloxy]-8-methyl-2-oxo-2H-chromen-3-yl}acetamide) was developed as a novel, novobiocin-based, C-terminal inhibitor of Hsp90 whose ability to increase Hsp70 expression is linked to the presence of an acetamide substitution of the prenylated benzamide moiety of novobiocin. KU-32 protected against glucose-induced death of embryonic DRG (dorsal root ganglia) neurons cultured for 3 days in vitro. Similarly, KU-32 significantly decreased neuregulin 1-induced degeneration of myelinated Schwann cell DRG neuron co-cultures prepared from WT (wild-type) mice. This protection was lost if the co-cultures were prepared from Hsp70.1 and Hsp70.3 KO (knockout) mice. KU-32 is readily bioavailable and was administered once a week for 6 weeks at a dose of 20 mg/kg to WT and Hsp70 KO mice that had been rendered diabetic with streptozotocin for 12 weeks. After 12 weeks of diabetes, both WT and Hsp70 KO mice developed deficits in NCV (nerve conduction velocity) and a sensory hypoalgesia. Although KU-32 did not improve glucose levels, HbA1c (glycated haemoglobin) or insulin levels, it reversed the NCV and sensory deficits in WT but not Hsp70 KO mice. These studies provide the first evidence that targeting molecular chaperones reverses the sensory hypoalgesia associated with DPN.This work was supported by grants from the Juvenile Diabetes Research Foundation and the National Institutes of Health [NS054847 and DK073594] (to R.T.D.) and [CA120458 and CA109265] (to B.S.J.B.)

Inhibiting heat-shock protein 90 reverses sensory hypoalgesia in diabetic mice

Increasing the expression of Hsp70 (heat-shock protein 70) can inhibit sensory neuron degeneration after axotomy. Since the onset of DPN (diabetic peripheral neuropathy) is associated with the gradual decline of sensory neuron function, we evaluated whether increasing Hsp70 was sufficient to improve several indices of neuronal function. Hsp90 is the master regulator of the heat-shock response and its inhibition can up-regulate Hsp70. KU-32 (N-{7-[(2R,3R,4S,5R)-3,4-dihydroxy-5-methoxy-6,6-dimethyl-tetrahydro-2H-pyran-2-yloxy]-8-methyl-2-oxo-2H-chromen-3-yl}acetamide) was developed as a novel, novobiocin-based, C-terminal inhibitor of Hsp90 whose ability to increase Hsp70 expression is linked to the presence of an acetamide substitution of the prenylated benzamide moiety of novobiocin. KU-32 protected against glucose-induced death of embryonic DRG (dorsal root ganglia) neurons cultured for 3 days in vitro. Similarly, KU-32 significantly decreased neuregulin 1-induced degeneration of myelinated Schwann cell DRG neuron co-cultures prepared from WT (wild-type) mice. This protection was lost if the co-cultures were prepared from Hsp70.1 and Hsp70.3 KO (knockout) mice. KU-32 is readily bioavailable and was administered once a week for 6 weeks at a dose of 20 mg/kg to WT and Hsp70 KO mice that had been rendered diabetic with streptozotocin for 12 weeks. After 12 weeks of diabetes, both WT and Hsp70 KO mice developed deficits in NCV (nerve conduction velocity) and a sensory hypoalgesia. Although KU-32 did not improve glucose levels, HbA1c (glycated haemoglobin) or insulin levels, it reversed the NCV and sensory deficits in WT but not Hsp70 KO mice. These studies provide the first evidence that targeting molecular chaperones reverses the sensory hypoalgesia associated with DPN

The seasonal Antarctic sea ice concentration anomalies related to the Atlantic Niño index

Antarctic sea ice concentration anomalies (ASICA) have been found to be linked to sea surface temperature anomalies in tropical oceans. However, it is not clear whether and how ASICA is linked to the Atlantic Niño mode (ANM). This study demonstrates a significant relationship between ASICA and ANM. The relationships vary by season, with a peak in austral winter and a secondary one in spring. Significant sea ice anomalies associated with a positive phase of ANM are mostly negative in austral winter and spring, and mostly positive in austral summer and autumn. This teleconnection is established by atmospheric wavetrains that are excited over the tropical southwestern Pacific and Indian Oceans and the southern Atlantic Oceans and propagate over the Southern Ocean. These wavetrains induce anomalous near-surface circulations, which generate dynamic and thermodynamic forcing on sea ice, resulting in the observed ASICA patterns. The absence of El Niño Southern Oscillation weakens the connection

Determination of Organochlorine Pesticides in Green Leafy Vegetable Samples via Fe3O4 Magnetic Nanoparticles Modified QuEChERS Integrated to Dispersive Liquid-Liquid Microextraction Coupled with Gas Chromatography-Mass Spectrometry

A fast method based on Fe3O4 magnetic nanoparticles (Fe3O4 MNPs) modified QuEChERS integrated to dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry was established for the determination of 8 organochlorine pesticides (OCPs) in green leafy vegetables. The factors involved in the purification by QuEChERS and concentration by DLLME were optimized. In the QuEChERS process, Fe3O4 MNPs were used as a new impurity adsorbent after the sample extraction procedure by acetonitrile, which achieved phase separation rapidly. Carbon black was used as an alternative to costly graphitized carbon black without affecting the recovery. In the process of DLLME, 1 mL of the extract obtained by QuEChERS was used as the dispersive solvent, 40 μL of chloroform was used as the extractive solvent, and 4 mL of water was added. Making them mix well, then the dispersed liquid-liquid microextraction concentration was subsequently carried out. The enrichment factors of 8 OCPs ranged from 22.8 to 36.6. The recoveries of the proposed method ranged from 78.6% to 107.7%, and the relative standard deviations were not more than 7.5%. The limits of detection and limits of quantification were 0.15–0.32 μg/kg and 0.45–0.96 μg/kg, respectively. The method has been successfully applied to the determination of OCPs in green leafy vegetable samples

In-situ growth of CoFeS2 on metal-organic frameworks-derived Co-NC polyhedron enables high-performance oxygen electrocatalysis for rechargeable zinc-air batteries

The development of efficient and cost-effective bi-functional electrocatalysts toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is promising for high-performance rechargeable metal-air batteries. In this article, a bi-functional catalyst (Co-NC@CoFeS2) towards ORR and OER is synthesized via the simple in-situ growing of cobalt-iron sulfide on cobalt and nitrogen co-doped polyhedral carbon (Co-NC). The combination of cobalt-iron sulfide and Co-NC substrate not only enlarges accessible channels for the reaction but also promotes electron transfer in the catalytic process. Benefiting from the synergy of the Co-NC substrate and the supported cobalt-iron sulfide in regulating the electrochemical interfaces, the electrical conductivity and the electronic structure, a narrow voltage gap of 0.646 V between the OER potential at 10 mA cm−2 and the half-wave potential of the ORR is observed for Co-NC@CoFeS2, showing an enhanced catalytic capability than that of the standard Pt/C + RuO2 composite. Moreover, a rechargeable Zn-air battery with Co-NC@CoFeS2 as an air electrode exhibits a large open-circuit voltage (1.44 V), high peak power density (174.4 mW cm−2), and long cycle life (over 400 cycles). Therefore, this work provides a new vision for the design and preparation of promising functional electrocatalysts for Zn-air batteries