Reflections on Pandemic (H1N1) 2009 and the International Response

Gabriel Leung and Angus Nicoll provide their reflections on the international response to the 2009 H1N1 influenza pandemic, including what went well and what changes need to be made in anticipation of future flu pandemics

Do advanced mathematics skills predict success in biology and chemistry degrees?

The mathematical preparedness of science undergraduates has been a subject of debate for some time. This paper investigates the relationship between school mathematics attainment and degree outcomes in biology and chemistry across England, a much larger scale of analysis than has hitherto been reported in the literature. A unique dataset which links the National Pupil Database for England (NPD) and Higher Education Statistics Agency (HESA) data is used to track the educational trajectories of a national cohort of 16-year-olds through their school and degree programmes. Multilevel regression models indicate that students who completed advanced mathematics qualifications prior to their university study of biology and chemistry were no more likely to attain the best degree outcomes than those without advanced mathematics. The models do, however, suggest that success in advanced chemistry at school predicts outcomes in undergraduate biology and vice versa. There are important social background differences and the impact of the university attended is considerable. We discuss a range of possible explanations of these findings

Effects of Antiepileptic Drugs on GABA Responses and on Reduction of GABA Responses by PTZ and DMCM on Mouse Neurons in Cell Culture

The mechanisms of action of antiepileptic drugs effective against generalized absence seizures (antiabsence AEDs) remain uncertain. Antiabsence AEDs are generally effective against seizures induced in experimental animals by pentylenÉtÉtrazol (PTZ) and methyl-6,7-dimethoxy-4-ethyl-Β-carboline-3-carboxylate (DMCM), drugs which reduce GABAergic inhibition. Thus, antiabsence AEDs have been suggested to enhance GABAergic inhibition. We studied the effects of several AEDs on GABA responses recorded from mouse spinal cord neurons grown in primary dissociated cell culture. Four antiabsence AEDs were included: ethosuximide (ESM), dimethadione (DMO), sodium valproate (VPA), and diazepam (DZP). Two experimental AEDs, CGS 9896 and ZK 91296, with anticonvulsant action against PTZ- or DMCM-induced seizures were also included. Possible effects of the antiabsence and experimental AEDS on PTZ- and DMCM-induced inhibition of GABA responses were also evaluated. PTZ and DMCM revers-ibly reduced GABA responses in a concentration-dependent manner. PTZ complÉtÉly inhibited GABA responses at 10 mM (IC 50 of 1.1 mM), whereas DMCM-induced inhibition of GABA responses reached a plateau level of 39% of control values at 1 p.M (IC 50 of 33 nM). ESM (1,200 ΜM), DMO (6 mM), VPA (200 u.M), CGS 9896 (2 ΜM), and ZK 98% (2 Μ M ) did not alter GABA responses. DZP enhanced GABA responses in a concentration-dependent manner. The inhibition of GABA responses produced by PTZ 1 mM was unaltered by ESM (600 Μ M ), DMO (6 mM), CGS 9896 (1 Μ M), or ZK 9896 (1 ΜM)- Coapplication of VPA (200 ΜM) and PTZ (1 mM) slightly enhanced the PTZ effect. DZP (> 10 nM), however, reversed the PTZ-induced reduction of GABA responses. The DMCM (250 nM) inhibition of GABA-responses was unaltered by ESM (600 Μ.M), DMO (2 mM), or VPA (200 ΜM). CGS 9896 (2 Μ M ) and ZK 91296 (2 ΜM), however, antagonized the DMCM effect. DZP (> 10 nM) significantly reversed the DMCM-induced inhibition of GABA responses. The lack of effect of VPA, ESM, and DMO on postsynaptic GABA responses suggests that direct enhancement of postsynaptic GABA action is not a common mechanism of action of antiabsence AEDs. The AEDs DZP, CGS 98%, and ZK 912% all reversed DMCM, but not PTZ, reduction of GABA responses, suggesting that these AEDs blocked DMCM seizures by acting at benzodiazepine receptors. However, since only DZP enhanced GABA responses, it is unclear how CGS 98% and ZK 912% blocked PTZ seizures. Key Words: Anticonvulsants–GABA–Neuron culture–Cell culture–Spinal cord neurons–Convulsants. RESUMEN Los mecanismos de accidn de las medicaciones antiepilÉpticas eficaces contra los ataques generalizados de ausencia (AEDs antiausencia) permanecen inciertos. Los AEDs antiausencia son, generalmente, eficaces contra ataques experimentales inducidos por el pentilentetrazol (PTZ) y el metil-6,7-dimetoxy-4-etil-Pcarbolina-3-carboxilato (DMCM) en animates, medicaciones que reducen la inhibiciÓn GABAÉrgica. Hemos estudiado los efectos de varios AEDs sobre respuestas-GABA registradas en las neuronas de la mÉdula espinal de ratones que habian crecido en cultivos de cÉlulas primarieas disociadas. Cuatro AEDs antiausencia fueron incluidos: etoxusimida (ESM), dimetadiona (DMO), valproato sÓdico (VPA) y diazepan (DZP). TambtÉn se incluyeron dos AEDs experimentales, CGS 9896 y ZK 912%, con acciÓn anticonvulsiva contra los ataques inducidos por PTZ o DMCM. TambiÓn se valoraron los posibles efectos de los AEDs antiausencia y experimentales sobre el PTZ y la inhibiciÓn de las respuestas-GABA inducidas por el DMCM. El PTZ y el DMCM redujeron las respuestas-GABA de modo reversible y dependiendo de sus concentraciones. El PTZ inhibiÓ cmpleta-mente las respuestas-GABA a 10 mM (IC 50 de 1.1 mM) mientras que la inhibitiÓn de las respuestas GABA inducida por el DMCM alcanzÓ un nivel estable del 39% de los valores control con 1 Μ. M (IC 50 de 33 mM). La ESM (1200 Μ.M), la DMO (6 mM), el VPA (200 Μ M ), el CGS 98% (2 Μ M) y el ZK 98% (2 Μ M) no alteraron las respuestas-GABA. El DZP aumentÓ las respuestas GABA de una manera concentraciÓn-dependiente. La inhibition de las respuestas-GABA producidas por el PTZ (1 mM), no se altero con las ESM (600 Μ M), la DMO (6 mM), el CGS 98% (1 Μ M) o el ZK 98% (1 Μ .M). La co-aplicacion de VPA (200 Μ M) y el PTZ (1 mM) aument6 ligeramente los efectos del PTZ. Sin embargo el DZP (10 nM) revirtiÓ significativamente la inhibition de las respuestas GABA inducidas por el DMCM. La falta de efectos de CPA, ESM y DMO sobre las respuestas GABA post-sinÁpticas sugiere que el incremento de la acciÓn GABA post-sinÁptica no es un mecanismo comÚn de actuatiÓn de las AEDs antiausencia. Todas las AEDs DZP, CGS 98% y ZK 912% revirtieron la reduction de las respuestas GABA producidas por el DMCM pero no las inducidas por el PTZ lo que sugiere que estos AEDs bloquean los ataques DMCM actuando sobre los receptores de la benzodiazepina. Sin embargo, puesto que el incremento de las respuestas GABA sÓlÓ se produce por el DZP, permanece todavia sin aclarar el por quÉ el CGS 98% y el ZK 912% bloquean los ataques producidos por el PTZ. ZUSAMMENFASSUNG Der Wirkmechansimus von Antiepileptika gegen generalisierte Absencen ist unklar. Antiabsencemittel sind generell wirkungs-voll gegen PTZ- und Methyl-6,7-Dimethoxy-4-Äthyl-P-Carbolin-Β-Carboxylat (DMCM) induzierte tierexperimentelle AnfÄlle, also von Medikamenten, die die GABA-erge Inhibition reduzieren. Es wurde vermutet, daß Antiabsencemittel die GABA-erge Inhibition verstÄrken. Wir untersuchten die Wirkung von verschiedenen Antiepileptika auf GABA-Antworten in spinalen MÄuseneuronen, die in Zellkulturen gew-achsen waren. Es wurden 4 Absencemittel untersucht: Ethosux-imid (ESM), Dimethadion (DMD), Sodium Valproat (VPA) und Diazepam (DZP). ZusÄtzlich wurden 2 experimentelle Antiepileptika, CGS 98% und ZK 912%, die gegen PTZ0 oder DMCM-induzierte AnfÄlle wirkungsvoll sind, eingeschlossen. Mogliche Wirkungen der Antiabsence- und experimentellen Antiepileptika auf PTZ- und DMCM-induzierte Hemmung der GABA-Antworten wurden ebenfalls ausgewertet. PTZ und DMCM zeigten eine konzentrationsabhÄngige reversible Reduktion der GABA-Antworten. PTZ zeigte eine komplette Hemmung der GABA-Antworten bei 10 mM (IC 50 1,1 mM), DMCM-Hemmung der GABA-Antworten zeigte ein Plateau von 39% der Kontroll-werte bei 1 uJtf (ICJO von 33 mAfl. ESM (1200 uJtf), DMD (6 mM), VPA (200 Μ M), CGS 98% (2 Μ M) und ZK 98% (2 Μ M) anderten nicht die GABA-Antworten. DZP verstarkte die GABA-Antworten konzentrationsabhangig. Die durch PTZ (1 mM) hervorgerufene Hemmung der GABA-Antworten war bei ESM (600 Μ M), DMD (6 mM), CGS 98% (1 mAO und ZK 3836 (1 mM) unverÄndert. ZusÄtliche Anwendung von VPA (200 mM) und PTZ (1 mM) verstÄrkten geringfÜgig den PTZ-Effekt. DZP (10 nM) kehrte die durch PTZ hervorgerufene Reduktion der GABA-Antworten um. Die durch DMCM (250 nM) hervorgerufene Hemmung der GABA-Antworten war durch ESM (600 Μ .M), DMD (2 mM) und VPA (200 Μ M ) unbeeinflusst. CGS 98% (2 Μ M) und ZK 912% (2 Μ M ) antagonisierten die DMCM-Wirkung. DZP (>10 nM) kehrte die durch DMCM-induzierte Hemmung der GABA-Antworten um. Das Fehlen einer Wirkung von VPA. ESM und DMD auf die postsynaptischen GABA-Antworten legen nahe, daß eine direkte VerstÄrkung der postsynaptischen GABA-Aktion kein gemeinsamer Mechanis-mus der Antiabsencemittel darstellt. Die Antiepileptika DZP, CGS 98% und ZK 912% kehrten die DMCM-Wirkung auf die GABA-Antworten um, jedoch nicht die von PTZ, was vermuten lapt, daß diese Antiepileptika die DMCM-AnfÄlle Über die Wirkung an den Benzodiazipin-Rezeptoren verhinderte. Da jedoch nur DZP GABA-Antworten verstarkte, ist unklar, in welcher Weise CGS 98% und ZK 912% die PTZ-AnfaUe ver-hinderten.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65188/1/j.1528-1157.1989.tb05275.x.pd

Fatigue strength of common tibial intramedullary nail distal locking screws

Premature failure of either the nail and/or locking screws with unstable fracture patterns may lead to angulation, shortening, malunion, and IM nail migration. Up to thirty percent of all unreamed nail locking screws can break after initial weight bearing is allowed at 8–10 weeks if union has not occurred. The primary problem this presents is hardware removal during revision surgery. The purposes of our study was to evaluate the relative fatigue resistance of distal locking screws and bolts from representative manufacturers of tibial IM nail systems, and develop a relative risk assessment of screws and materials used. Evaluations included quantitative and qualitative measures of the relative performance of these screws

Hippocampal LTP and contextual learning require surface diffusion of AMPA receptors

Long-term potentiation (LTP) of excitatory synaptic transmission has long been considered a cellular correlate for learning and memory. Early LTP (eLTP, <1 hour) had initially been explained either by presynaptic increases in glutamate release or by direct modification of post-synaptic α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) function. Compelling models have more recently proposed that synaptic potentiation can occur by the recruitment of additional post-synaptic AMPARs, sourced either from an intracellular reserve pool by exocytosis or from nearby extra synaptic receptors pre-existing on the neuronal surface. However, the exact mechanism through which synapses can rapidly recruit new AMPARs during eLTP is still unknown. In particular, direct evidence for a pivotal role of AMPAR surface diffusion as a trafficking mechanism in synaptic plasticity is still lacking. Using AMPAR immobilization approaches, we show that interfering with AMPAR surface diffusion dramatically impaired synaptic potentiation of Schaffer collateral/commissural inputs to cornu ammonis area 1 (CA1) in cultured slices, acute slices and in vivo. Our data also identifies distinct contributions of various AMPAR trafficking routes to the temporal profile of synaptic potentiation. In addition, AMPAR immobilization in vivo in the dorsal hippocampus (DH) before fear conditioning, indicated that AMPAR diffusion is important for the early phase of contextual learning. Therefore, our results provide a direct demonstration that the recruitment of new receptors to synapses by surface diffusion is a critical mechanism for the expression of LTP and hippocampal learning. Since AMPAR surface diffusion is dictated by weak Brownian forces that are readily perturbed by protein-protein interactions, we anticipate that this fundamental trafficking mechanism will be a key target for modulating synaptic potentiation and learning

Efficacy of the New Neuraminidase Inhibitor CS-8958 against H5N1 Influenza Viruses

Currently, two neuraminidase (NA) inhibitors, oseltamivir and zanamivir, which must be administrated twice daily for 5 days for maximum therapeutic effect, are licensed for the treatment of influenza. However, oseltamivir-resistant mutants of seasonal H1N1 and highly pathogenic H5N1 avian influenza A viruses have emerged. Therefore, alternative antiviral agents are needed. Recently, a new neuraminidase inhibitor, R-125489, and its prodrug, CS-8958, have been developed. CS-8958 functions as a long-acting NA inhibitor in vivo (mice) and is efficacious against seasonal influenza strains following a single intranasal dose. Here, we tested the efficacy of this compound against H5N1 influenza viruses, which have spread across several continents and caused epidemics with high morbidity and mortality. We demonstrated that R-125489 interferes with the NA activity of H5N1 viruses, including oseltamivir-resistant and different clade strains. A single dose of CS-8958 (1,500 µg/kg) given to mice 2 h post-infection with H5N1 influenza viruses produced a higher survival rate than did continuous five-day administration of oseltamivir (50 mg/kg twice daily). Virus titers in lungs and brain were substantially lower in infected mice treated with a single dose of CS-8958 than in those treated with the five-day course of oseltamivir. CS-8958 was also highly efficacious against highly pathogenic H5N1 influenza virus and oseltamivir-resistant variants. A single dose of CS-8958 given seven days prior to virus infection also protected mice against H5N1 virus lethal infection. To evaluate the improved efficacy of CS-8958 over oseltamivir, the binding stability of R-125489 to various subtypes of influenza virus was assessed and compared with that of other NA inhibitors. We found that R-125489 bound to NA more tightly than did any other NA inhibitor tested. Our results indicate that CS-8958 is highly effective for the treatment and prophylaxis of infection with H5N1 influenza viruses, including oseltamivir-resistant mutants

At What Stage of Neural Processing Does Cocaine Act to Boost Pursuit of Rewards?

Dopamine-containing neurons have been implicated in reward and decision making. One element of the supporting evidence is that cocaine, like other drugs that increase dopaminergic neurotransmission, powerfully potentiates reward seeking. We analyze this phenomenon from a novel perspective, introducing a new conceptual framework and new methodology for determining the stage(s) of neural processing at which drugs, lesions and physiological manipulations act to influence reward-seeking behavior. Cocaine strongly boosts the proclivity of rats to work for rewarding electrical brain stimulation. We show that the conventional conceptual framework and methods do not distinguish between three conflicting accounts of how the drug produces this effect: increased sensitivity of brain reward circuitry, increased gain, or decreased subjective reward costs. Sensitivity determines the stimulation strength required to produce a reward of a given intensity (a measure analogous to the KM of an enzyme) whereas gain determines the maximum intensity attainable (a measure analogous to the vmax of an enzyme-catalyzed reaction). To distinguish sensitivity changes from the other determinants, we measured and modeled reward seeking as a function of both stimulation strength and opportunity cost. The principal effect of cocaine was a two-fourfold increase in willingness to pay for the electrical reward, an effect consistent with increased gain or decreased subjective cost. This finding challenges the long-standing view that cocaine increases the sensitivity of brain reward circuitry. We discuss the implications of the results and the analytic approach for theories of how dopaminergic neurons and other diffuse modulatory brain systems contribute to reward pursuit, and we explore the implications of the conceptual framework for the study of natural rewards, drug reward, and mood

Spatiotemporal Properties of the Action Potential Propagation in the Mouse Visual Cortical Slice Analyzed by Calcium Imaging

The calcium ion (Ca2+) is an important messenger for signal transduction, and the intracellular Ca2+ concentration ([Ca2+]i) changes in response to an excitation of the cell. To reveal the spatiotemporal properties of the propagation of an excitatory signal with action potentials in the primary visual cortical circuit, we conducted a Ca2+ imaging study on slices of the mouse visual cortex. Electrical stimulation of layer 4 evoked [Ca2+]i transients around the stimulus electrode. Subsequently, the high [Ca2+]i region mainly propagated perpendicular to the cortical layer (vertical propagation), with horizontal propagation being restricted. When the excitatory synaptic transmission was blocked, only weak and concentric [Ca2+]i transients were observed. When the action potential was blocked, the [Ca2+]i transients disappeared almost completely. These results suggested that the action potential contributed to the induction of the [Ca2+]i transients, and that excitatory synaptic connections were involved in the propagation of the high [Ca2+]i region in the primary visual cortical circuit. To elucidate the involvement of inhibitory synaptic connections in signal propagation in the primary visual cortex, the GABAA receptor inhibitor bicuculline was applied. In this case, the evoked signal propagated from layer 4 to the entire field of view, and the prolonged [Ca2+]i transients were observed compared with the control condition. Our results suggest that excitatory neurons are widely connected to each other over the entire primary visual cortex with recurrent synapses, and inhibitory neurons play a fundamental role in the organization of functional sub-networks by restricting the propagation of excitation signals

Cellular Bases of Barbiturate and Phenytoin Anticonvulsant Drug Action

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65509/1/j.1528-1157.1982.tb06093.x.pd

Sex-specific effects of the local social environment on juvenile post-fledging dispersal in great tits

An individual’s decision to disperse from the natal habitat can affect its future fitness prospects. Especially in species with sex-biased dispersal, we expect the cost–benefit balance for dispersal to vary according to the social environment (e.g., local sex ratio and density). However, little is known about the social factors affecting dispersal decisions and about the temporal and spatial patterns of the dispersal process. In our study, we investigated experimentally the effects of the social environment on post-fledging dispersal of juvenile great tits by simultaneously manipulating the density and sex ratio of fledglings within forest plots. We expected young females in the post-fledging period mainly to compete for resources related to food and, as they are subordinate to males, we predicted higher female dispersal from male-biased plots. Juvenile males compete for vacant territories already in late summer and autumn; thus, we predicted increased male dispersal from high density and male-biased plots. We found that juvenile females had a higher probability to leave male-biased plots and had dispersed further from male-biased plots in the later post-fledging phase when juvenile males start to become territorial and more aggressive. Juvenile males were least likely to leave male-biased plots and had smallest dispersal distances from female-biased plots early after fledging. The results suggest that the social environment differentially affected the costs and benefits of philopatry for male and female juveniles. The local sex ratio of individuals is thus an important social trait to be considered for understanding sex-specific dispersal processes