Effects of perfluorooctane sulfonate on action potentials and currents in cultured rat cerebellar Purkinje cells

Recently, PFOS was reported to be ubiquitously detected in the environment, as well as in human serum, raising concerns regarding its health risks. We investigated the effects of PFOS on action potentials and currents in cultured rat cerebellar Purkinje cells using whole-cell patch-clamp recording. In current-clamp experiments, PFOS significantly decreased the action potential frequency during current injection, the maximum rate of fall and the threshold of action potential, and negatively shifted the resting membrane potential at doses over 30microM. In voltage-clamp experiments, PFOS shifted the half-activation and inactivation voltages of I(Ca), I(Na), and I(K) toward hyperpolarization at 30microM. I(HCN1) expressed in Xenopus oocytes was similarly affected. Incorporation of PFOS into the cell membrane probably increased the surface negative charge density, thereby reducing the transmembrane potential gradient and resulting in hyperpolarizing shifts of both the activation and inactivation of ionic channels. These findings indicate that PFOS may exhibit neurotoxicity.     

Morbidity in the marshes: using spatial epidemiology to investigate skeletal evidence for Malaria in Anglo-Saxon England (AD 410-1050)

Concerns over climate change and its potential impact on infectious disease prevalence have contributed to a resurging interest in malaria in the past. A wealth of historical evidence indicates that malaria, specifically Plasmodium vivax, was endemic in the wetlands of England from the 16th century onwards. While it is thought that malaria was introduced to Britain during the Roman occupation (AD first to fifth centuries), the lack of written mortality records prior to the post-medieval period makes it difficult to evaluate either the presence or impact of the disease. The analysis of human skeletal remains from archaeological contexts is the only potential means of examining P. vivax in the past. Malaria does not result in unequivocal pathological lesions in the human skeleton; however, it results in hemolytic anemia, which can contribute to the skeletal condition cribra orbitalia. Using geographical information systems (GIS), we conducted a spatial analysis of the prevalence of cribra orbitalia from 46 sites (5,802 individuals) in relation to geographical variables, historically recorded distribution patterns of indigenous malaria and the habitat of its mosquito vector Anopheles atroparvus. Overall, those individuals living in low-lying and Fenland regions exhibited higher levels of cribra orbitalia than those in nonmarshy locales. No corresponding relationship existed with enamel hypoplasia. We conclude that P. vivax malaria, in conjunction with other comorbidities, is likely to be responsible for the pattern observed. Studies of climate and infectious disease in the past are important for modeling future health in relation to climate change predictions.     

Contribution of serine racemase/d-serine pathway to neuronal apoptosis

Recent data indicate that age-related N-methyl-d-aspartate receptor (NMDAR) transmission impairment is correlated with the reduction in serine racemase (SR) expression and d-serine content. As apoptosis is associated with several diseases and conditions that generally occur with age, we investigated the modulation of SR/d-serine pathway during neuronal apoptosis and its impact on survival. We found that in cerebellar granule neurons (CGNs), undergoing apoptosis SR/d-serine pathway is crucially regulated. In the early phase of apoptosis, the expression of SR is reduced, both at the protein and RNA level through pathways, upstream of caspase activation, involving ubiquitin proteasome system (UPS) and c-Jun N-terminal kinases (JNKs). Forced expression of SR, together with treatment with NMDA and d-serine, blocks neuronal death, whereas pharmacological inhibition and Sh-RNA-mediated suppression of endogenous SR exacerbate neuronal death. In the late phase of apoptosis, the increased expression of SR contribute to the last, NMDAR-mediated, wave of cell death. These findings are relevant to our understanding of neuronal apoptosis and NMDAR activity regulation, raising further questions as to the role of SR/d-serine in those neuro-pathophysiological processes, such as aging and neurodegenerative diseases characterized by a convergence of apoptotic mechanisms and NMDAR dysfunction.     

AMPA and kainate receptors mediate mutually exclusive effects on GABA(A) receptor expression in cultured mouse cerebellar granule neurones

Studies on animal models of epilepsy and cerebellar ataxia, e.g., stargazer mice (stg) have identified changes in the GABAergic properties of neurones associated with the affected brain loci. Whether these changes contribute to or constitute homeostatic adaptations to a state of altered neuronal excitability is as yet unknown. Using cultured cerebellar granule neurones from control [+/+; alpha-amino-3-hydroxyl-5-methyl-4-isoxazolepropionate receptor (AMPAR)-competent, Kainate receptor (KAR)-competent] and stg (AMPAR-incompetent, KAR-competent), we investigated whether non-NMDA receptor (NMDAR) activity regulates GABA(A) receptor (GABAR) expression. Neurones were maintained in 5 mmol/L KCl-containing basal media or depolarizing media containing either 25 mmol/L KCl or the non-NMDAR agonist kainic acid (KA) (100 micromol/L). KCl- and KA-mediated depolarization down-regulated GABAR alpha1, alpha6 and beta2, but up-regulated alpha4, beta3 and delta subunits in +/+ neurones. The KCl-evoked but not KA-evoked effects were reciprocated in stg neurones compatible with AMPAR-regulation of GABAR expression. Conversely, GABAR gamma2 expression was insensitive to KCl-mediated depolarization, but was down-regulated by KA-treatment in a 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX)-reversible manner in +/+ and stg neurones compatible with a KAR-mediated response. KA-mediated up-regulation of GABAR alpha4, beta3 and delta was inhibited by L-type voltage-gated calcium channel (L-VGCC) blockers and the Ca2+/calmodulin-dependent protein kinase inhibitor, 4-[(2S)-2-[(5-isoquinolinylsulfonyl)methylamino]-3-oxo-3-(4-phenyl-1-piperazinyl)propyl] phenyl isoquinoline sulfonic acid ester (KN-62). Up-regulation of GABAR alpha4 and beta3 was also prevented by calcineurin (CaN) inhibitors, FK506 and cyclosporin A. Down-regulation of GABAR alpha1, alpha6 and beta2 was independent of L-VGCC activity, but was prevented by inhibitors of CaN. Thus, we provide evidence that a KAR-mediated and at least three mutually exclusive AMPAR-mediated signalling mechanisms regulate neuronal GABAR expression.     

Mitochondrial free radical production induced by glucose deprivation in cerebellar granule neurons

Using a fluorescent probe for superoxide, hydroethidine, we have demonstrated that glucose deprivation (GD) activates production of reactive oxygen species (ROS) in cultured cerebellar granule neurons. ROS production was insensitive to the blockade of ionotropic glutamate channels by MK-801 (10 microM) and NBQX (10 microM). Inhibitors of mitochondrial electron transport, i.e. rotenone (complex I), antimycin A (complex III), or sodium azide (complex IV), an inhibitor of mitochondrial ATP synthase--oligomycin, an uncoupler of oxidative phosphorylation--CCCP, a chelator of intracellular Ca2+--BAPTA, an inhibitor of electrogenic mitochondrial Ca2+ transport--ruthenium red, as well as pyruvate significantly decreased neuronal ROS production induced by GD. GD was accompanied by a progressive decrease in the mitochondrial membrane potential and an increase in free cytosolic calcium ions, [Ca2+](i). Pyruvate, BAPTA, and ruthenium red lowered the GD-induced calcium overload, while pyruvate and ruthenium red also prevented mitochondrial membrane potential changes induced by GD. We conclude that GD-induced ROS production in neurons is related to potential-dependent mitochondrial Ca2+ overload. GD-induced mitochondrial Ca2+ overload in neurons in combination with depletion of energy substrates may result in the decrease of the membrane potential in these organelles.     

Amelogenesis imperfecta in the dentition of a wild chimpanzee

This report describes a case of amelogenesis imperfecta in the dentition of a female chimpanzee. Amelogenesis imperfecta is a group of rare genetic conditions that create severe enamel defects, which, although well researched in humans, has not yet been investigated in wild non‐human primates.     

活性氧参与一氧化氮诱导的神经细胞凋亡

采用激光共聚焦成像技术，用氧化还原敏感的特异性荧光探针(DCFH-DA和DHR123)直接研究了一氧化氮供体S-亚硝基-N-乙酰基青霉胺(SNAP)诱导未成熟大鼠小脑颗粒神经元凋亡过程中的细胞胞浆、线粒体中活性氧水平的变化，发现神经细胞经0.5 mmol/L SNAP处理1 h后，细胞胞浆及线粒体中活性氧水平大大增加.一氧化氮清除剂血红蛋白能够有效抑制细胞胞浆、线粒体中活性氧的产生，防止细胞凋亡.外源性谷胱甘肽对细胞也具有良好的保护作用，而当细胞中谷胱甘肽的合成被抑制后，一氧化氮的神经毒性大大增强.实验结果表明一氧化氮通过促进神经细胞产生内源性活性氧而启动细胞凋亡程序，而谷胱甘肽可能是重要的防止一氧化氮引发神经损伤的内源性抗氧化剂.