Adenosine is released during thalamic oscillations to provide negative feedback control.

Physiological oscillations in the cortico-thalamo-cortical loop occur during processes such as sleep, but these can become dysfunctional in pathological conditions such as absence epilepsy. The purine neuromodulator adenosine can act as an endogenous anticonvulsant: it is released into the extracellular space during convulsive seizures to activate A1 receptors suppressing on-going activity and delaying the occurrence of the next seizure. However, the role of adenosine in thalamic physiological and epileptiform oscillations is less clear. Here we have combined immunohistochemistry, electrophysiology, and fixed potential amperometry (FPA) biosensor measurements to characterise the release and actions of adenosine in thalamic oscillations measured in rodent slices. In the thalamus, A1 receptors are highly expressed particularly in the ventral basal (VB) thalamus and reticular thalamic nucleus (nRT) supporting a role for adenosine signalling in controlling oscillations. In agreement with previous studies, both adenosine and adenosine A1 receptor agonists inhibited thalamic oscillations in control (spindle-like) and in epileptic conditions. Here we have shown for the first time that both control and epileptiform oscillations are enhanced (i.e., increased number of oscillatory cycles) by blocking A1 receptors consistent with adenosine release occurring during oscillations. Although increases in extracellular adenosine could not be directly detected during control oscillations, clear increases in adenosine concentration could be detected with a biosensor during epileptiform oscillation activity. Thus, adenosine is released during thalamic oscillations and acts via A1 receptors to feedback and reduce thalamic oscillatory activity.

DNA double-strand breaks in relation to persistent organic pollutants in a fasting seabird.

Lipophilic persistent organic pollutants (POPs) are released from fat reserves during fasting, causing increased blood concentrations. Thus, POPs represent a potential anthropogenic stressor during fasting periods. We analysed the blood of female common eiders (Somateria mollissima) by using agarose gel electrophoresis and image data analysis to quantify the DNA-fraction, of total DNA, that migrated into the gel (DNA-FTM) as a relative measure of DNA double strand-breaks (DSBs) during the fasting incubation period in the high arctic. In 2008 and in 2009 blood samples were obtained for analysis of 9 POPs and DNA-FTM at day 5 of the incubation period, and then in the same individuals at day 20. This unique study design gave us the opportunity to analyse the same individuals throughout two points in time, with low and high stress burdens. During the incubation period the body mass (BM) decreased by 21-24%, whereas the POP levels increased by 148-639%. The DNA-FTM increased by 61-67% (being proportional to the increase in DSBs). At day 5, but not day 20, DNA-FTM was positively correlated with most analysed POPs. The increase in DNA-FTM was positively correlated with the decrease in BM (g) during incubation. Thus, we suggest that fasting stress (BM loss) decreases DNA integrity and that stress caused by fasting on BM loss appeared to override the additional stress caused by concurrent increase in levels of the analysed POPs in the eiders. Blood levels of POPs in the eiders in Svalbard were relatively low, and additive and/or synergistic genotoxic effects of fasting stress and POP exposure may occur in populations with higher POP levels.

High speed terahertz modulation from metamaterials with embedded high electron mobility transistors.

We present a computational and experimental study of a novel terahertz (THz) device resulting from hybridization of metamaterials with pseudomorphic high electron mobility transistors (HEMTs), fabricated in a commercial gallium arsenide (GaAs) process. Monolithic integration of transistors into each unit cell permits modulation at the metamaterial resonant frequency of 0.46 THz. Characterization is performed using a THz time-domain spectrometer (THz-TDS) and we demonstrate switching values over 30%, and THz modulation at frequencies up to 10 megahertz (MHz). Our results demonstrate the viability of incorporating metamaterials into mature semiconductor technologies and establish a new path toward achieving electrically tunable THz devices.

Two mechanisms for fluorescence intermittency of single violamine R molecules.

The environment and temperature-dependent photoluminescence (PL) intermittency or "blinking" demonstrated by single violamine R (VR) molecules is investigated in two environments: poly(vinyl alcohol) (PVOH) and single crystals of potassium acid phthalate (KAP). In addition, temperatures ranging from 23 °C to 85 °C are studied, spanning the glass-transition temperature of PVOH (T(g) = 72 °C). The PL intermittency exhibited by VR is analyzed using probability histograms of emissive and non-emissive periods. In both PVOH and KAP, these histograms are best fit by a power law, consistent with the kinetics for dark state production and decay being dispersed as observed in previous studies. However, these systems have different temperature dependences, signifying two different blinking mechanisms for VR. In PVOH, the on- and off-event probability histograms do not vary with temperature, consistent with electron transfer via tunneling between VR and the polymer. In KAP the same histograms are temperature dependent, and show that blinking slows down at higher temperatures. This result is inconsistent with an electron-transfer process being responsible for blinking. Instead, a non-adiabatic proton-transfer between VR and KAP is presented as a model consistent with this temperature dependence. In summary, the results presented here demonstrate that for a given luminophore, the photochemical processes responsible for PL intermittency can change with environment.

Chromosome aberrations and DNA strand breaks in glaucous gull (Larus hyperboreus) chicks fed environmentally contaminated gull eggs.

In this present laboratory study, our results suggest that a complex mixture of pollutants found in the marine environment exerts genotoxic effects on glaucous gull (Larus hyperboreus) chicks fed environmentally contaminated gull eggs. Chromosome aberrations, quantified by cytogenetic analysis of blood cells, and DNA strand breaks, quantified by agarose gel electrophoresis and image data analysis, were determined in glaucous gull chicks fed environmentally contaminated gull eggs (exposed group) and in chicks fed hen eggs (control group). For both female and male gulls, the fraction of damaged metaphases was quantitatively higher in exposed than in control groups. On the other hand, the differences between the control and the exposed groups were more relevant when the chromosomal aberration data were treated as group totals rather than at the individual level. Consistent results were obtained in the DNA strand break analyses. The control group appeared to display a greater median molecular length (MML) than the exposed group.

Multiple norovirus genotypes characterised from an oyster-associated outbreak of gastroenteritis.

The diversity of norovirus (NV) genotypes was investigated in persons who were ill with acute gastroenteritis associated with the consumption of oysters. Initial results from a commercial enzyme immunoassay (EIA) indicated a mixed NV genogroup I (GI) and II (GII) outbreak. A reverse-transcriptase (RT)-PCR for NVs was applied to nucleic acid extracted from faecal specimens collected from symptomatic cases. Using primers that amplified contiguous sequences in the ORF1/2 region of the NV genome and a hemi-nested PCR derived from this assay, three different GII and two GI NV genotypes were detected and the strains were characterised by DNA sequencing. Using this approach a recombinant NV genotype, rGII-3a (recombinant Harrow/Mexico) the predominant strain identified in several symptomatic cases from the outbreak, was detected and characterised. No other gastroenteric viruses, including rotavirus, astrovirus, sapovirus and adenovirus 40/41 were detected by RT-PCR and PCR.