Evaluate the grain size effect on geochemical composition and proxies of Miocene loess in China

The Quaternary loess-soil sequence, the red clay sediments, and the Miocene eolian deposits combine a unique and near continuous terrestrial archive containing information about the onsets of the Asian inland desertification andAsianandglobalclimatechanges.GeochemicalindicessuchasCIA,CIW,Na2O+MgO+K2O/TiO2 andsoon have been widely used in paleoclimate research of loess. There are three main factors in common to control the chemical composition of loess: geochemistry of parent material in provenance, grain size sorting during the transportation, and post-depositional pedogenesis weathering. Early studies on major, trace and Rare Earth Elements composition of Chinese loess showed that the parent material are homogeneous, thus the geochemial composition are mainly affected by eolian processes and chemical weathering. Grain size effects on Quaternary loess and Red clay sediments have already been conducted, and found that some chemical weathering indices seem useful in Quaternary loess-soil sequences, but go invalid in red clay. In this study, we systematically analyzed the chemical composition of eolian sediments in different grain sizes of Miocene samples, aim to discover the grain size effects onMioceneloessandsoilchemicalcompositionatthefirsttimeandcomparewiththoseoftheQuaternaryandred clay counterparts and to evaluate the grain size effect on geochemical indices of loess-paleosol studies in China since Miocene and extract an appropriate one which is more sensible to chemical weathering and eliminated the grain size sorting. The results show that: the contents of Si, Na, Zr and Sr are higher in the coarser fractions while Ti and Nb have the highest contents in the 2-8 µm fractions. Al, Fe, Mg, K, Mn, Rb, Cu, Ga, Zn, V, Cr, Ni, LOI have clear relationships with grain-size, more abundant in the fine fraction while non significant relationship is observed for Y. Based on these features, we suggest that K2O/Al2O3 ratio can be used to address the dust provenance, and that VR (Vogt ratio = (Al2O3+K2O)/(MgO+CaO+Na2O)) can be used as a chemical weathering proxy for the Miocene eolian deposits because of their relative independence on the grain size. SiO2/Al2O3 molar ratio is a best geochemical indicator of original eolian grain size, as suggested in earlier studie

Astrocytic and neuronal accumulation of elevated extracellular K+ with a 2/3 K+/Na+ flux ratio - consequences for energy metabolism, osmolarity and higher brain function

Brain excitation increases neuronal Na+ concentration by 2 major mechanisms: i) Na+influx caused by glutamatergic synaptic activity; and ii) action-potential-mediateddepolarization by Na+ influx followed by repolarizating K+ efflux, increasingextracellular K+ concentration. This review deals mainly with the latter and it concludesthat clearance of extracellular K+ is initially mainly effectuated by Na+,K+-ATPasemediatedK+ uptake into astrocytes, at K+ concentrations above ~10 mM aided by uptakeof Na+, K+ and 2 Cl- by the cotransporter NKCC1. Since operation of the astrocytic Na+,K+-ATPase requires K+-dependent glycogenolysis for stimulation of the intracellularATPase site, it ceases after normalization of extracellular K+ concentration. This allowsK+ release via the inward rectifying K+ channel Kir1.4, perhaps after trans-astrocyticconnexin- and/or pannexin-mediated K+ transfer, which would be a key candidate fordetermination by synchronization-based computational analysis and may have signalingeffects. Spatially dispersed K+ release would have little effect on extracellular K+concentration and allow K+ accumulation by the less powerful neuronal Na+,K+-ATPase,which is not stimulated by increases in extracellular K+. Since the Na+,K+-ATPaseexchanges 3 Na+ with 2 K+, it creates extracellular hypertonicity and cell shrinkage.Hypertonicity also stimulates NKCC1, which, aided by -adrenergic stimulation of theNa+,K+-ATPase, causes regulatory volume increase, furosemide-inhibited undershoot in[K+]e and perhaps facilitation of the termination of slow neuronal hyperpolarization(sAHP), with behavioral consequences. The ion transport processes involved minimizeionic disequilibria caused by the asymmetric Na+,K+-ATPase fluxes

Dissociation between conceptual and perceptual implicit memory：Evidence from patients with frontal and occipital lobe lesions

The latest neuroimaging studies about implicit memory have revealed that different implicit memory types may be processed by different parts of the brain. However, studies have rarely examined what subtypes of implicit memory processes are affected in patients with various brain-injuries. Twenty patients with frontal lobe injury, 25 patients with occipital lobe injury, and 29 healthy controls were recruited for the study. Two subtypes of implicit memory were investigated by using structurally parallel perceptual (picture identification task) and conceptual (category exemplar generation task) implicit memory tests in the three groups, as well as explicit memory tests. The results indicated that the priming of conceptual implicit memory and explicit memory tasks in patients with frontal lobe injury was poorer than that observed in healthy controls, while perceptual implicit memory was identical between the two groups. In contrast, the priming of perceptual implicit memory in patients with occipital lobe injury was poorer than that in healthy controls, while the priming of conceptual implicit memory and explicit memory was similar to that in healthy controls. This double dissociation between perceptual and conceptual implicit memory across the brain areas implies that occipital lobes may participate in perceptual implicit memory, while frontal lobes may be involved in processing conceptual memory

Decrease of gene expression of astrocytic 5-HT2B receptor parallels development of anhedonia in a mouse model of Parkinson’s disease

Astrocytes contribute to pathogenesis of neuropsychiatric disorders, including major depression. Stimulation of astroglial 5-HT2B receptors transactivates epidermal growth factor receptors and regulates gene expression. Previously we reported that expression of 5-HT2B receptors in cortical astrocytes is down-regulated in animals, which developed anhedonia in response to chronic stress; moreover this down-regulation as well as anhedonia, are reversed by chronic treatment with fluoxetine. In this study we have investigated whether astrocytic 5-HT2B receptor is involved in anhedonia in C57BL/6 mice model of Parkinson’ disease (PD) induced by intraperitoneal injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) for 7 days. The MPTP treatment induced anhendonia in 66.7% of animals. The appearance of depressive behaviour was accompanied with motor deficiency and decrease of tyrosine hydroxylase (TH) expression. Expression of mRNA and protein of 5-HT2B receptor in animals that became anhedonic decreased to 77.3% and 79.3% of control groups, respectively; in animals that received MPTP but did not develop anhedonia the expression of 5-HT2B receptor did not change. Experiments with FACS-sorted isolated cells demonstrated that decrease in 5-HT2B receptor expression was confined to astrocytes, and did not occur in neurons. Fluoxetine corrected MPTP-induced decrease of 5-HT2B receptor expression and depressive behaviour. Our findings indicate that regulation of gene expression of 5-HT2B receptors in astroglia may be associated with pathophysiological evolution of PD-induced depression

Toxic effects of decabromodiphenyl ether (BDE-209) on human embryonic kidney cells

Polybrominated diphenyl ethers (PBDEs) are widely used as flame-retardant additives in consumer and household products and can escape into the environment over time. PBDEs have become a global environmental organic pollutant due to the properties of persistence, toxicity, and bioaccumulation. The well-studied toxic effects of PBDEs mainly include thyroid hormone disruption and neurotoxicity. There is no consistent conclusions on the carcinogenic potential of PBDEs to date. Here, we explored the toxic effects of BDE-209 on human embryonic kidney cells (HEK293T). The comparison of the gene expression profiles of HEK293T cells with BDE-209 treatment and the negative control found that BDE-209 exposure may alter nucleosome organization through significantly changing the expression of histone gene clusters. The remodeled chromatin structure could further disturb systemic lupus erythematosus as one of the toxic effects of BDE-209. Additionally, gene sets of different cancer modules are positively correlated with BDE-209 exposure. This suggests that BDE-209 has carcinogenic potential for a variety of tumors. Collectively, BDE-209 has a broader toxicity not limited to disruption of thyroid hormone-related biological processes. Notably, the toxic effects of BDE-209 dissolved in dimethyl sulfoxide (DMSO) is not the simply additive effects of BDE-209 and DMSO alone