The Role of GLUK5-Containing Kainate Receptors in Entorhinal Cortex Gamma Frequency Oscillations

Using in vitro brain slices of hippocampus and cortex, neuronal oscillations in the frequency range of 30–80 Hz (gamma frequency oscillations) can be induced by a number of pharmacological manipulations. The most routinely used is the bath application of the broad-spectrum glutamate receptor agonist, kainic acid. In the hippocampus, work using transgenic kainate receptor knockout mice have revealed information about the specific subunit composition of the kainate receptor implicated in the generation and maintenance of the gamma frequency oscillation. However, there is a paucity of such detail regarding gamma frequency oscillation in the cortex. Using specific pharmacological agonists and antagonists for the kainate receptor, we have set out to examine the contribution of kainate receptor subtypes to gamma frequency oscillation in the entorhinal cortex. The findings presented demonstrate that in contrast to the hippocampus, kainate receptors containing the GLUK5 subunit are critically important for the generation and maintenance of gamma frequency oscillation in the entorhinal cortex. Future work will concentrate on determining the exact nature of the cellular expression of kainate receptors in the entorhinal cortex

The Role of GLUK5-Containing Kainate Receptors in Entorhinal Cortex Gamma Frequency Oscillations

Using in vitro brain slices of hippocampus and cortex, neuronal oscillations in the frequency range of 30–80 Hz (gamma frequency oscillations) can be induced by a number of pharmacological manipulations. The most routinely used is the bath application of the broad-spectrum glutamate receptor agonist, kainic acid. In the hippocampus, work using transgenic kainate receptor knockout mice have revealed information about the specific subunit composition of the kainate receptor implicated in the generation and maintenance of the gamma frequency oscillation. However, there is a paucity of such detail regarding gamma frequency oscillation in the cortex. Using specific pharmacological agonists and antagonists for the kainate receptor, we have set out to examine the contribution of kainate receptor subtypes to gamma frequency oscillation in the entorhinal cortex. The findings presented demonstrate that in contrast to the hippocampus, kainate receptors containing the GLUK5 subunit are critically important for the generation and maintenance of gamma frequency oscillation in the entorhinal cortex. Future work will concentrate on determining the exact nature of the cellular expression of kainate receptors in the entorhinal cortex

Mid-infrared colour gradients and the colour-magnitude relation in Virgo early-type galaxies

We make use of Spitzer imaging between 4 and 16 micron and near-infrared data at 2.2 micron to investigate the nature and distribution of the mid-infrared emission in a sample of early-type galaxies in the Virgo cluster. These data allow us to conclude, with some confidence, that the emission at 16 micron in passive ETGs is stellar in origin, consistent with previous work concluding that the excess mid-infrared emission comes from the dusty envelopes around evolved AGB stars. There is little evidence for the mid-infrared emission of an unresolved central component, as might arise in the presence of a dusty torus associated with a low-luminosity AGN. We nonetheless find that the 16 micron emission is more centrally peaked than the near-infrared emission, implying a radial stellar population gradient. By comparing with independent evidence from studies at optical wavelengths, we conclude that a metallicity that falls with increasing radius is the principal driver of the observed gradient. We also plot the mid-infrared colour-magnitude diagram and combine with similar work on the Coma cluster to define the colour-magnitude relation for absolute K-band magnitudes from -26 to -19. Because a correlation between mass and age would produce a relation with a gradient in the opposite sense to that observed, we conclude that the relation reflects the fact that passive ETGs of lower mass also have a lower average metallicity. The colour-magnitude relation is thus driven by metallicity effects. In contrast to what is found in Coma, we do not find any objects with anomalously bright 16 micron emission relative to the colour-magnitude relation. Although there is little overlap in the mass ranges probed in the two clusters, this may suggest that observable ``rejuvenation'' episodes are limited to intermediate mass objects.Comment: 8 pages, 4 figure

Radio Sources in Low-Luminosity Active Galactic Nuclei. I. VLA Detections of Compact, Flat-Spectrum Cores

We report a 0.2" resolution, 15 GHz survey of a sample of 48 low-luminosity active galactic nuclei with the Very Large Array. Compact radio emission has been detected in 57% (17 of 30) of LINERs and low-luminosity Seyferts, at least 15 of which have a flat to inverted radio spectrum (alpha > -0.3). The compact radio cores are found in both type 1 (i.e. with broad Halpha) and type 2 (without broad Halpha) nuclei. The 2 cm radio power is significantly correlated with the emission-line ([OI] lambda6300) luminosity. While the present observations are consistent with the radio emission originating in star-forming regions, higher resolution radio observations of 10 of the detected sources, reported in a companion paper (Falcke et al. 2000), show that the cores are very compact (= 10^8K) and probably synchrotron self-absorbed, ruling out a starburst origin. Thus, our results suggest that at least 50% of low-luminosity Seyferts and LINERs in the sample are accretion powered, with the radio emission presumably coming from jets or advection-dominated accretion flows. We have detected only 1 of 18 `transition' (i.e. LINER + HII) nuclei observed, indicating their radio cores are significantly weaker than those of `pure' LINERs.Comment: To appear in the Astrophysical Journal, October 20, 200

The response of Monalisa apples to high CO2 storage conditions, harvest maturity and 1-MCP treatment.

This study aimed to determine the effects of harvest maturity, 1-MCP treatment and storage conditions with high CO2 partial pressures on ?Monalisa? apples physicochemical quality and susceptibility to physiological disorders and decay during long-term storage, plus 7 d of shelf life at 22 ◦C. The study was composed by two experiments. In Experiment 1, fruit were harvested in one growing season (2011) at the same maturity stage and were treated or not treated with 1-MCP (1 μL L-1). In Experiment 2, fruit were harvested in two growing seasons (2019 and 2020), at two maturity stages. In both experiments, all fruit were stored under CA with four CO2 partial pressure (0.5, 1.5, 3.0 and 4.5 kPa) and regular air (RA, standard of comparison) for 6 or 7 months at 0.8 ◦C, plus 7 d shelf life at 22 ◦C. CA was very effective on delaying fruit ripening, senescent disorders and decay incidences, regardless of the CO2 partial pressure. However, under CA, ?Monalisa? apples were very susceptible to CO2 injury, expressed as dark flesh browning and cavities that were exacerbated with increasing CO2 partial pressures. Therefore, ?Monalisa? apples should be stored under CA with CO2 no higher than 0.5 kPa. The response of ?Monalisa? apples to high CO2 is more pronounced in late harvested fruit, which were also more prone to develop senescent flesh browning, cracking and rough skin. 1-MCP application had no effect on ?Monalisa? apple susceptibility to CO2 damages, while it reduced fruit softening and acidity loss in both RA and CA storages

The polymer phase of the TDAE-C60_{60} organic ferromagnet

The high-pressure Electron Spin Resonance (ESR) measurements were preformed on TDAE-C$_{60}$ single crystals and stability of the polymeric phase was established in the $P - T$ parameter space. At 7 kbar the system undergoes a ferromagnetic to paramagnetic phase transition due to the pressure-induced polymerization. The polymeric phase remains stable after the pressure release. The depolymerization of the pressure-induced phase was observed at the temperature of 520 K. Below room temperature, the polymeric phase behaves as a simple Curie-type insulator with one unpaired electron spin per chemical formula. The TDAE$^+$ donor-related unpaired electron spins, formerly ESR-silent, become active above the temperature of 320 K and the Curie-Weiss behavior is re-established.Comment: Submitted to Phys. Rev.

Two-Dimensional Infrared Spectroscopy of Antiparallel β-Sheet Secondary Structure

We investigate the sensitivity of femtosecond Fourier transform two-dimensional infrared spectroscopy to protein secondary structure with a study of antiparallel β-sheets. The results show that 2D IR spectroscopy is more sensitive to structural differences between proteins than traditional infrared spectroscopy, providing an observable that allows comparison to quantitative models of protein vibrational spectroscopy. 2D IR correlation spectra of the amide I region of poly-L-lysine, concanavalin A, ribonuclease A, and lysozyme show cross-peaks between the IR-active transitions that are characteristic of amide I couplings for polypeptides in antiparallel hydrogen-bonding registry. For poly-L-lysine, the 2D IR spectrum contains the eight-peak structure expected for two dominant vibrations of an extended, ordered antiparallel β-sheet. In the proteins with antiparallel β-sheets, interference effects between the diagonal and cross-peaks arising from the sheets, combined with diagonally elongated resonances from additional amide transitions, lead to a characteristic “Z”-shaped pattern for the amide I region in the 2D IR spectrum. We discuss in detail how the number of strands in the sheet, the local configurational disorder in the sheet, the delocalization of the vibrational excitation, and the angle between transition dipole moments affect the position, splitting, amplitude, and line shape of the cross-peaks and diagonal peaks.

A Non-Invasive method of quantifying pancreatic volume in mice using micro-MRI

In experimental models of pancreatic growth and recovery, changes in pancreatic size are assessed by euthanizing a large cohort of animals at varying time points and measuring organ mass. However, to ascertain this information in clinical practice, patients with pancreatic disorders routinely undergo non-invasive cross-sectional imaging of the pancreas using magnetic resonance imaging (MRI) or computed tomography (CT). The aim of the current study was to develop a thinsliced, optimized sequence protocol using a high field MRI to accurately calculate pancreatic volumes in the most common experimental animal, the mouse. Using a 7 Telsa Bruker micro-MRI system, we performed abdominal imaging in whole-fixed mice in three standard planes: axial, sagittal, and coronal. The contour of the pancreas was traced using Vitrea software and then transformed into a 3-dimensional (3D) reconstruction, from which volumetric measurements were calculated. Images were optimized using heart perfusion-fixation, T1 sequence analysis, and 0.2 to 0.4 mm thick slices. As proof of principle, increases in pancreatic volume among mice of different ages correlated tightly with increasing body weight. In summary, this is the first study to measure pancreatic volumes in mice, using a high field 7 Tesla micro-MRI and a thin-sliced, optimized sequence protocol. We anticipate that micro-MRI will improve the ability to non-invasively quantify changes in pancreatic size and will dramatically reduce the number of animals required to serially assess pancreatic growth and recovery.© 2014 Paredes et al

The Effects of Cocaine on Different Redox Forms of Cysteine and Homocysteine, and on Labile, Reduced Sulfur in the Rat Plasma Following Active versus Passive Drug Injections

Received: 28 November 2012 / Revised: 19 April 2013 / Accepted: 6 May 2013 / Published online: 16 May 2013 The Author(s) 2013. This article is published with open access at Springerlink.comThe aim of the present studies was to evaluate cocaine-induced changes in the concentrations of different redox forms of cysteine (Cys) and homocysteine (Hcy), and products of anaerobic Cys metabolism, i.e., labile, reduced sulfur (LS) in the rat plasma. The above-mentioned parameters were determined after i.p. acute and subchronic cocaine treatment as well as following i.v. cocaine self-administration using the yoked procedure. Additionally, Cys, Hcy, and LS levels were measured during the 10-day extinction training in rats that underwent i.v. cocaine administration. Acute i.p. cocaine treatment increased the total and protein-bound Hcy contents, decreased LS, and did not change the concentrations of Cys fractions in the rat plasma. In turn, subchronic i.p. cocaine administration significantly increased free Hcy and lowered the total and protein-bound Cys concentrations while LS level was unchanged. Cocaine self-administration enhanced the total and protein-bound Hcy levels, decreased LS content, and did not affect the Cys fractions. On the other hand, yoked cocaine infusions did not alter the concentration of Hcy fractions while decreased the total and protein-bound Cys and LS content. This extinction training resulted in the lack of changes in the examined parameters in rats with a history of cocaine self-administration while in the yoked cocaine group an increase in the plasma free Cys fraction and LS was seen. Our results demonstrate for the first time that cocaine does evoke significant changes in homeostasis of thiol amino acids Cys and Hcy, and in some products of anaerobic Cys metabolism, which are dependent on the way of cocaine administration