Different types of potassium transport linked to carbachol and γ-aminobutyric acid actions in rat sympathetic neurons

Carbachol and γ-aminobutyric acid depolarize mammalian sympathetic neurons and increase the free extracellular K+-concentration. We have used double-barrelled ion-sensitive microelectrodes to determine changes of the membrane potential and of the free intracellular Na+-, K+- and Cl−-concentrations ([Na+]i, [K+]iand [Cl−]i) during neurotransmitter application. Experiments were performed on isolated, desheathed superior cervical ganglia of the rat, maintained in Krebs solution at 30°C. Application of carbachol resulted in a membrane depolarization accompanied by an increase of [Na+]i, a decrease of [K+]i and no change in [Cl−]i. Application of γ-aminobutyric acid also induced a membrane depolarization which, however, was accompanied by a decrease of [K+]i and [Cl−]i, whereas [Na+]i remained constant. Blockade of the Na+/K+-pump by ouabain completely inhibited both the reuptake of K+ and the extrusion of Na+ after the action of carbachol, and also the post-carbachol undershoot of the free extracellular K+-concentration. On the other hand, in the presence of ouabain, no changes in the kinetics of the reuptake of K+ released during the action of γ-aminobutyric acid could be observed. Furosemide, a blocker of K+/Cl−-cotransport, inhibited the reuptake of Cl− and K+ after the action of γ-aminobutyric acid. In summary, the data reveal that rat sympathetic neurons possess, in addition to the Na+/K+-pump, another transport system to regulate free intracellular K+-concentration. This system is possibly a K+/Cl−-cotransport

Glucose availability and sensitivity to anoxia of isolated rat peripheral nerve

The contrast between resistance to ischemia and ischemic lesions in peripheral nerves of diabetic patients was explored by in vitro experiments. Isolated and desheathed rat peroneal nerves were incubated in the following solutions with different glucose availability: 1) 25 mM glucose, 2) 2.5 mM glucose, and 3) 2.5 mM glucose plus 10 mM 2-deoxy-D-glucose. Additionally, the buffering power of all of these solutions was modified. Compound nerve action potential (CNAP), extracellular pH, and extracellular potassium activity (aKe) were measured simultaneously before, during, and after a period of 30 min of anoxia. An increase in glucose availability led to a slower decline in CNAP and to a smaller rise in aKe during anoxia. This resistance to anoxia was accompanied by an enhanced extracellular acidosis. Postanoxic recovery of CNAP was always complete in 25 mM HCO3(-)-buffered solutions. In 5 mM HCO3- and in HCO3(-)-free solutions, however, nerves incubated in 25 mM glucose did not recover functionally after anoxia, whereas nerves bathed in solutions 2 or 3 showed a complete restitution of CNAP. We conclude that high glucose availability and low PO2 in the combination with decreased buffering power and/or inhibition of HCO3(-)-dependent pH regulation mechanisms may damage peripheral mammalian nerves due to a pronounced intracellular acidosis

Differential effects of mineralocorticoid and angiotensin II on incentive and mesolimbic activity

The controls of thirst and sodium appetite are mediated in part by the hormones aldosterone and angiotensin II (AngII). The present study examined the behavioral and neural mechanisms of altered effort-value in animals treated with systemic mineralocorticoids, intracerebroventricular AngII, or both. First,rats treated with mineralocorticoid and AngII were tested in the progressive ratio operant task. The willingness to work for sodium versus waterdepended on hormonal treatment. In particular, rats treated with both mineralocorticoid and AngII preferentially worked for access to sodium versus water compared with rats given only one of these hormones. Second, components of the mesolimbic dopamine pathway were examined for modulation by mineralocorticoids and AngII. Based on cFos immunohistochemistry, AngII treatment activated neurons in the ventral tegmental area and nucleus accumbens, with no enhancement by mineralocorticoid pretreatment. In contrast, western blot analysis revealed that combined hormone treatmentincreased levels of phospho-tyrosine hydroxylase in the ventral tegmental area. Thus, mineralocorticoid and AngII treatments differentially engaged the mesolimbic pathway based on tyrosine hydroxylase levelsversus cFos activation

NMR Evidence for Charge Inhomogeneity in Stripe Ordered La_{1.8-x}Eu_{0.2}Sr_{x}CuO_4

We report ^{17}O Nuclear Magnetic Resonance (NMR) results in the stripe ordered La_{1.8-x}Eu_{0.2}Sr_{x}CuO_4 system. Below a temperature T_q ~ 80K, the local electric field gradient (EFG) and the absolute intensity of the NMR signal of the planar O site exhibit a dramatic decrease. We interpret these results as microscopic evidence for a spatially inhomogeneous charge distribution, where the NMR signal from O sites in the domain walls of the spin density modulation are wiped out due to large hyperfine fields, and the remaining signal arises from the intervening Mott insulating regions.Comment: 4 pages, to appear in Phys. Rev. Let

Stress, coping, resilience, and sleep during the COVID-19 pandemic: A representative survey study of US adults

Introduction: The COVID-19 pandemic is a global health emergency resulting in widespread death and substantial disruption to daily life. Previous research has shown that novel disease outbreaks are associated with high stress levels and sleep impairments that lead to neuropsychiatric consequences. Therefore, it is vital to study both stress and protective factors such as coping and resilience that may hinder or help sleep quality during the COVID-19 pandemic. Further, as gender disparities exist in sleep quality, it is important to understand the relationship between pandemic-related stress, coping strategies, resilience, and sleep in bothgenders during the COVID-19 pandemic. Methods: Our study examined how gender, stress, coping, and resilience were associated with sleep cross-sectionally during the COVID-19 pandemic in a representative sample of US adults (N = 393). Results: Consistent with many recent studies, we found that worsened sleep quality in women compared to men persisted during the COVID-19 pandemic. Interestingly, pandemic-related stress was not significantly associated with sleep quality, but pandemic-related coping was associated with sleep independent of robust controls and trait resilience. Conclusions: Greater primary control engagement coping was associated with better sleep quality, while involuntary engagement coping was associated with poor sleep quality. Future research should extend the findings with actigraphy and explore ways to enhance beneficial coping and sleep health during pandemics

Long-term impact of different fertilization management on microbial P mobilization and community structure in the bulk soil and rhizosphere of maize

The efficiency of the arable P use can be fundamentally increased by improving the management. We aim to disclose soil microbial fundamentals to optimize P storage, P mobilization and P turnover in agricultural systems for plant growth promotion. We investigated treatments from a long-term fertilization experiment in Rostock (Mecklenburg-Western Pomerania). Soil sampling was conducted in spring and autumn of 2015 and 2016. Microbial P storage, enzymatic P mobilization and the community structure of bacteria and arbuscular mycorrhizal fungi (AMF) as key players of the P mobilization and transfer were analysed at four fertilization treatments with no additional P (control), mineral P-fertilizer (TSP), organic P-fertilizer (compost) and a combination of mineral and organic P-fertilizers. Microbial P (Pmic) was significantly affected by the type of P-fertilization and increased by factor two to three in fertilized treatments compared to the control. The microbial P storage did not differ significantly between mineral and organic fertilization treatments. Organic P fertilization leads to a short term increase of the Pmic pool in the soil. Enzyme activities were significantly higher in treatments with organic fertilization compared to those with no or mineral fertilisation, independent on season. This pattern was found for enzymes of the P-cycle (acid and alkaline phosphomonoesterases, phosphodiesterase) and of the C-cycle (ß-glucosidases) indicating a strong correlation between C and P cycling. Further, enzymatic P mobilization is rather controlled by availability of substrates than by the current P demand of the vegetation. Community structure of AMF and bacteria show similar results. A pool of species was site-specific common in each treatment, whereas a small fraction was treatment-specific. The findings contribute to one of the overarching objective of the BonaRes-project (BMBF) InnoSoilPhos to improving the P use efficiency of arable crops by selection of suitable management strategies in the agricultural practice

A chloride channel in rat and human axons

Current recordings from single chloride channels were obtained from excised and cell-attached patches of rat and human axons. In rat axons the channels showed an outwardly rectifying current-voltage relationship with a slope conductance of 33 pS at negative membrane potentials and 65 pS at positive potentials (symmetrical 150 mM CsCl). They were measurably for cations (PNa/PCs/PCl=0.1/0.2/1). Channel currents were independent of cytoplasmatic calcium concentration. Inactivation was not observed and gating was weakly voltage dependent. Cl− channels in human axons showed similar gating behavior but had a lower conductance