Huntington's disease (HD) is a late-onset neurodegenerative disorder that is characterized neuropathologically by the presence of neuropil aggregates and nuclear inclusions. However, the profile of aggregate structures that are present in the brains of HD patients or of HD mouse models and the relative contribution of specific aggregate structures to disease pathogenesis is unknown. We have used the Seprion ligand to develop a highly sensitive enzyme-linked immunosorbent assay (ELISA)-based method for quantifying aggregated polyglutamine in tissues from HD mouse models. We used a combination of electron microscopy, atomic force microscopy (AFM) and sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) to investigate the aggregate structures isolated by the ligand. We found that the oligomeric, proto-fibrillar and fibrillar aggregates extracted from the brains of R6/2 and HdhQ150 knock-in mice were remarkably similar. Using AFM, we determined that the nanometre globular oligomers isolated from the brains of both mouse models have dimensions identical to those generated from recombinant huntingtin exon 1 proteins. Finally, antibodies that detect exon 1 Htt epitopes differentially recognize the ligand-captured material on SDS–PAGE gels. The Seprion-ligand ELISA provides an assay with good statistical power for use in preclinical pharmacodynamic therapeutic trials or to assess the effects of the genetic manipulation of potential therapeutic targets on aggregate load. This, together with the ability to identify a spectrum of aggregate species in HD mouse tissues, will contribute to our understanding of how these structures relate to the pathogenesis of HD and whether their formation can be manipulated for therapeutic benefit.

The developing distal lung epithelium displays an evolving liquid transport phenotype, reflecting a changing and dynamic balance between Cl- ion secretion and Na+ ion absorption, which in turn reflects changing functional requirements. Thus in the fetus, Cl--driven liquid secretion predominates throughout gestation and generates a distending pressure to stretch the lung and stimulate growth. Increasing Na+ absorptive capacity develops toward term, anticipating the switch to an absorptive phenotype at birth and beyond. There is some empirical evidence of ligand-gated regulation of Cl- transport and of regulation via changes in the driving force for Cl- secretion. Epinephrine, O2, glucocorticoid, and thyroid hormones interact to stimulate Na+ absorption by increasing Na+ pump activity and apical Na+ conductance (GNa+) to bring about the switch from net secretion to net absorption as lung liquid is cleared from the lung at birth. Postnatally, the lung lumen contains a small Cl--based liquid secretion that generates a surface liquid layer, but the lung retains a large absorptive capacity to prevent alveolar flooding and clear edema fluid. This review explores the mechanisms underlying the functional development of the lung epithelium and draws upon evidence from classic integrative physiological studies combined with molecular physiology approaches.

SummaryTree species growing along the forest-grassland ecotone are near the moisture limit of their range. Small increases in temperature can increase vapor pressure deficit (VPD) which may increase tree water use and potentially hasten mortality during severe drought.We tested a 40% increase in VPD due to an increase in growing temperature from 30 to 33°C (constant dewpoint 21°C) on seedlings of 10 tree species common to the forest-grassland ecotone in the southern Great Plains, USA.Measurement at 33 vs 30°C during reciprocal leaf gas exchange measurements, that is, measurement of all seedlings at both growing temperatures, increased transpiration for seedlings grown at 30°C by 40% and 20% for seedlings grown at 33°C. Higher initial transpiration of seedlings in the 33°C growing temperature treatment resulted in more negative xylem water potentials and fewer days until transpiration decreased after watering was withheld. The seedlings grown at 33°C died 13% (average 2 d) sooner than seedlings grown at 30°C during terminal drought.If temperature and severity of droughts increase in the future, the forest-grassland ecotone could shift because low seedling survival rate may not sufficiently support forest regeneration and migration.

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STUDY QUESTIONAre significant abnormalities of CatSper function present in IVF patients with normal sperm concentration and motility and if so what is their functional significance for fertilization success?SUMMARY ANSWERSperm with a near absence of CatSper current failed to respond to activation of CatSper by progesterone and there was fertilization failure at IVF.WHAT IS KNOWN ALREADYIn human spermatozoa, Ca2+ influx induced by progesterone is mediated by CatSper, a sperm-specific Ca2+ channel. A suboptimal Ca2+ influx is significantly associated with, and more prevalent in, men with abnormal semen parameters, and is associated with reduced fertilizing capacity. However, abnormalities in CatSper current can only be assessed directly using electrophysiology. There is only one report of a CatSper-deficient man who showed no progesterone potentiated CatSper current. A CatSper 2 genetic abnormality was present but there was no information on the [Ca2+]i response to CatSper activation by progesterone. Additionally, the semen samples had indicating significant abnormalities (oligoasthenoteratozoospermia) multiple suboptimal functional responses in the spermatozoon. As such it cannot be concluded that impaired CatSper function alone causes infertility or that CatSper blockade is a potential safe target for contraception.STUDY DESIGN, SIZE, DURATIONSpermatozoa were obtained from donors and subfertile IVF patients attending a hospital assisted reproductive techniques clinic between January 2013 and December 2014. In total 134 IVF patients, 28 normozoospermic donors and 10 patients recalled due to a history of failed/low fertilization at IVF took part in the study.PARTICIPANTS/MATERIALS, SETTING, METHODSSamples were primarily screened using the Ca2+ influx induced by progesterone and, if cell number was sufficient, samples were also assessed by hyperactivation and penetration into viscous media. A defective Ca2+ response to progesterone was defined using the 99% confidence interval from the distribution of response amplitudes in normozoospermic donors. Samples showing a defective Ca2+ response were further examined in order to characterize the potential CatSper abnormalities. In men where there was a consistent and robust failure of calcium signalling, a direct assessment of CatSper function was performed using electrophysiology (patch clamping), and a blood sample was obtained for genetic analysis.MAIN RESULTS AND THE ROLE OF CHANCEA total of 101/102 (99%) IVF patients and 22/23 (96%) donors exhibited a normal Ca2+ response. The mean (±SD) normalized peak response did not differ between donors and IVF patients (2.57 ± 0.68 [n = 34 ejaculates from 23 different donors] versus 2.66 ± 0.68 [n = 102 IVF patients], P = 0.63). In recall patients, 9/10 (90%) showed a normal Ca2+ response. Three men were initially identified with a defective Ca2+ influx. However, only one (Patient 1) had a defective response in repeat semen samples. Electrophysiology experiments on sperm from Patient 1 showed a near absence of CatSper current an...

Studies of HeLa cells and serum-and glucocorticoid-regulated kinase 1 (SGK1) knockout mice identified threonine residues in the n-myc downstream-regulated gene 1 protein (NDRG1-Thr 346/356/366 ) that are phosphorylated by SGK1 but not by related kinases (Murray et al., Biochem J 385:1-12, 2005). We have, therefore, monitored the phosphorylation of NDRG1-Thr 346/356/366 in order to explore the changes in SGK1 activity associated with the induction and regulation of the glucocorticoid-dependent Na + conductance (G Na ) in human airway epithelial cells.Transient expression of active (SGK1-S422D) and inactive (SGK1-K127A) SGK1 mutants confirmed that activating SGK1 stimulates NDRG1-Thr 346/356/366 phosphorylation. Although G Na is negligible in hormone-deprived cells, these cells displayed basal SGK1 activity that was sensitive to LY294002, an inhibitor of 3-phosphatidylinositol phosphate kinase (PI3K). Dexamethasone (0.2 μM) acutely activated SGK1 and the peak of this response (2-3 h) coincided with the induction of G Na , and both responses were PI3K-dependent. While these data suggest that SGK1 might mediate the rise in G Na , transient expression of the inactive SGK1-K127A mutant did not affect the hormonal induction of G Na but did suppress the activation of SGK1. Dexamethasone-treated cells grown on permeable supports formed confluent epithelial sheets that generated short circuit current due to electrogenic Na + absorption. Forskolin and insulin both stimulated this current and the response to insulin, but not forskolin, was LY294002-sensitive and associated with the activation of SGK1. While these data suggest that SGK1 is involved in the control of G Na , its role may be minor, which could explain why sgk1 knockout has different effects upon different tissues.

A regulated apical Na ϩ conductance in dexamethasone-treated H441 airway epithelial cells. with dexamethasone raised the abundance of mRNA encoding the epithelial Na ϩ channel ␣-and ␤-subunits and increased transepithelial ion transport (measured as short-circuit current, I sc) from Ͻ4 A ⅐ cm Ϫ2 to 10 -20 A ⅐ cm Ϫ2 . This dexamethasone-stimulated ion transport was blocked by amiloride analogs with a rank order of potency of benzamil Ն amiloride Ͼ EIPA and can thus be attributed to active Na ϩ absorption. Studies of apically permeabilized cells showed that this increased transport activity did not reflect a rise in Na ϩ pump capacity, whereas studies of basolateral permeabilized cells demonstrated that dexamethasone increased apical Na ϩ conductance (GNa) from a negligible value to 100 -200 S ⅐ cm Ϫ2 . Experiments that explored the ionic selectivity of this dexamethasone-induced conductance showed that it was equally permeable to Na ϩ and Li ϩ and that the permeability to these cations was approximately fourfold greater than to K ϩ . There was also a small permeability to N-methyl-Dglucammonium, a nominally impermeant cation. Forskolin, an agent that increases cellular cAMP content, caused an ϳ60% increase in I sc, and measurements made after these cells had been basolaterally permeabilized demonstrated that this response was associated with a rise in G Na. This cAMP-dependent control over GNa was disrupted by brefeldin A, an inhibitor of vesicular trafficking. Dexamethasone thus stimulates Na ϩ transport in H441 cells by evoking expression of an amiloride-sensitive apical conductance that displays moderate ionic selectivity and is subject to acute control via a cAMP-dependent pathway. airway epithelium; epithelial sodium channel; Ussing chambers; glucocorticoids; apical membrane GLUCOCORTICOID HORMONES CONTRIBUTE to the development and maintenance of the distal airway epithelia's capacity to absorb Na ϩ from the overlying film of surface liquid (see Refs. 37,41,50,52), a process that is vital to the integrated functioning of the respiratory tract (see Ref. 6). In most tissues, the absorption of Na ϩ is clearly dependent on epithelial Na ϩ channels (ENaC), transport proteins composed of three subunits (␣-, ␤-, and ␥-ENaC) that form a highly selective, amiloride-sensitive Na ϩ conductance if coexpressed in Xenopus oocytes or mammalian systems (8,9,16,17). Because glucocorticoids can regulate the expression of at least some members of this gene family (37,41,52), it is tempting to attribute glucocorticoidevoked pulmonary Na ϩ transport to increased expression of such selective Na ϩ channels, but, despite this, many authors have been unable to identify selective Na ϩ channels in distal airway epithelia. Indeed, the majority of studies suggests that regulated Na ϩ influx in these cells occurs via nonselective cation channels that discriminate very poorly between Na ϩ and K ϩ (24, 29 -32, 36, 49). Moreover, there is evidence that these channels may be formed when ␣-ENaC is expressed independently of the ␤-and ␥-subunit...

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