Electrophysiological Properties of Embryonic Stem Cell-Derived Neurons

In vitro generation of functional neurons from embryonic stem (ES) cells and induced pluripotent stem cells offers exciting opportunities for dissecting gene function, disease modelling, and therapeutic drug screening. To realize the potential of stem cells in these biomedical applications, a complete understanding of the cell models of interest is required. While rapid advances have been made in developing the technologies for directed induction of defined neuronal subtypes, most published works focus on the molecular characterization of the derived neural cultures. To characterize the functional properties of these neural cultures, we utilized an ES cell model that gave rise to neurons expressing the green fluorescent protein (GFP) and conducted targeted whole-cell electrophysiological recordings from ES cell-derived neurons. Current-clamp recordings revealed that most neurons could fire single overshooting action potentials; in some cases multiple action potentials could be evoked by depolarization, or occurred spontaneously. Voltage-clamp recordings revealed that neurons exhibited neuronal-like currents, including an outward current typical of a delayed rectifier potassium conductance and a fast-activating, fast-inactivating inward current, typical of a sodium conductance. Taken together, these results indicate that ES cell-derived GFP+ neurons in culture display functional neuronal properties even at early stages of differentiation

Development of X-43A Mach 10 Leading Edges

The nose leading edge of the Hyper-X Mach 10 vehicle was orginally anticipated to reach temperatures near 4000 F at the leading-edge stagnation line. A SiC coated carbon/carbon (C/C) leading-edge material will not survive that extreme temperature for even a short duration single flight. To identify a suitable leading edge for the Mach 10 vehicle, arc-jet testing was performed on thirteen leading-edge segments fabricated from different material systems to evaluate their performance in a simulated flight environment. Hf, Zr, Si, and Ir based materials, in most cases as a coating on C/C, were included in the evaluation. Afterwards, MER, Tucson, AZ was selected as the supplier of the flight vehicle leading edges. The nose and the vertical and horizontal tail leading edges were fabricated out of a 3:1 biased high thermal conductivity C/C. The leading edges were coated with a three layer coating comprised of a SiC conversion of the top surface of the C/C, followed by a chemical vapor deposited layer of SiC, followed by a thin chemical vapor deposited layer of HfC. This paper will describe the fabrication of the Mach 10 C/C leading edges and the testing performed to validate performance

Endocannabinoid Regulation of Acute and Protracted Nicotine Withdrawal: Effect of FAAH Inhibition

Evidence shows that the endocannabinoid system modulates the addictive properties of nicotine. In the present study, we hypothesized that spontaneous withdrawal resulting from removal of chronically implanted transdermal nicotine patches is regulated by the endocannabinoid system. A 7-day nicotine dependence procedure (5.2 mg/rat/day) elicited occurrence of reliable nicotine abstinence symptoms in Wistar rats. Somatic and affective withdrawal signs were observed at 16 and 34 hours following removal of nicotine patches, respectively. Further behavioral manifestations including decrease in locomotor activity and increased weight gain also occurred during withdrawal. Expression of spontaneous nicotine withdrawal was accompanied by fluctuation in levels of the endocannabinoid anandamide (AEA) in several brain structures including the amygdala, the hippocampus, the hypothalamus and the prefrontal cortex. Conversely, levels of 2-arachidonoyl-sn-glycerol were not significantly altered. Pharmacological inhibition of fatty acid amide hydrolase (FAAH), the enzyme responsible for the intracellular degradation of AEA, by URB597 (0.1 and 0.3 mg/kg, i.p.), reduced withdrawal-induced anxiety as assessed by the elevated plus maze test and the shock-probe defensive burying paradigm, but did not prevent the occurrence of somatic signs. Together, the results indicate that pharmacological strategies aimed at enhancing endocannabinoid signaling may offer therapeutic advantages to treat the negative affective state produced by nicotine withdrawal, which is critical for the maintenance of tobacco use

Maternal Education and Perinatal Outcomes Among Spanish Women Residing in Southern Spain (2001-2011).

Evidence suggests that educational differences in perinatal outcomes have increased in some countries (Eastern Europe) while remained stable in others (Scandinavian countries). However, less is known about the experience of Southern Europe. This study aims to evaluate the association between maternal education and perinatal outcomes derived from birthweight (low birthweight and macrosomia) and gestational age (pre-term and post-term births) among Spaniards living in the Autonomous Community of Andalusia during the period 2001-2011 (around 19 % of births in Spain); and to evaluate whether the educational differences narrowed or widened during that period, which includes both an economic boom (2001-2008) and the global economic crisis (2009-2011). This study uses the Andalusian Population Longitudinal Database and the Vital Statistics Data provided by the Spanish National Statistics Institute. We study live and singleton births of Spanish mothers who lived in Andalusia at the time of delivery (n = 404,951). ORs with 95 % confidence intervals (crude and adjusted) were estimated using multinomial regression models. A negative educational gradient is observed in all perinatal outcomes studied (i.e., the higher the educational status, the lower the risk of negative perinatal outcomes). However, when disaggregating the sample in two periods, the gradient is only statistically significant for pre-term birth during 2001-2008, while a full gradient is observed in all perinatal indicators in the period 2009-2011 with an increase in the educational inequalities in macrosomia and post-term. Further studies are needed in order to confirm whether there is a causal association between the widening of the educational differences in perinatal outcomes and the onset of the economic crisis in Spain, or the widening can be explained by other factors, such as changes in childbearing patterns and the composition of women accessing motherhood

K+ Currents in Isolated Vestibular Afferent Calyx Terminals

Vestibular hair cells transduce mechanical displacements of their hair bundles into an electrical receptor potential which modulates transmitter release and subsequent action potential firing in afferent neurons. To probe ionic mechanisms underlying sensory coding in vestibular calyces, we used the whole-cell patch-clamp technique to record action potentials and K+ currents from afferent calyx terminals isolated from the semicircular canals of Mongolian gerbils. Calyx terminals showed minimal current at the mean zero-current potential (−60 mV), but two types of outward K+ currents were identified at potentials above −50 mV. The first current was a rapidly activating and inactivating K+ current that was blocked by 4-aminopyridine (4-AP, 2.5 mM) and BDS-I (up to 250 nM). The time constant for activation of this current decreased with membrane depolarization to a minimum value of ∼1 ms. The 4-AP-sensitive current showed steady-state inactivation with a half-inactivation of approximately −70 mV. A second, more slowly activating current (activation time constant was 8.5 ± 0.7 ms at −8 mV) was sensitive to TEA (30 mM). The TEA-sensitive current also showed steady-state inactivation with a half-inactivation of −95.4 ± 1.4 mV, following 500-ms duration conditioning pulses. A combination of 4-AP and TEA blocked ∼90% of the total outward current. In current clamp, single Na+-dependent action potentials were evoked following hyperpolarization to potentials more negative than the resting potential. 4-AP application increased action potential width, whereas TEA both increased the width and greatly reduced repolarization of the action potential

A general procedure for the enantioselective synthesis of the minor tobacco alkaloids nornicotine, anabasine, and anatabine

The minor tobacco alkaloids nornicotine, anabasine, and anatabine fromNicotiana tobacum are known to possess nicotinic receptor agonist activity, although they are relatively less potent than S-(−)-nicotine, the principal tobacco alkaloid. Previous pharmacological investigations and structure-activity studies have been limited owing to the lack of availability of the optically pure forms of these minor alkaloids. We now report a 2-step synthetic procedure for the enantioselective synthesis of the optical isomers of nornicotine and anabasine, and a modified procedure for the synthesis of anatabine enantiomers. These procedures involve initial formation of the chiral ketimine resulting from the condensation of either 1R, 2R, 5R-(+)- or 1S, 2S, 5S-(−)-2-hydroxy-3-pinanonewith3-(aminomethyl)pyridine followed by enantioselective C-alkylation with an appropriate halogenoalkane or halogenoalkene species, N-deprotection, and base-catalyzed intramolecular ring closure, to form the appropriate, chirally pure minor tobacco alkaloid. Using this approach, theR-(+)-andS-(−)-enantiomers of the above minor tobacco alkaloids were obtained in good overall chemical yield and excellent enantomeric excess