Part of the inflammatory response in Alzheimer's disease (AD) is the upregulation of the inducible nitric oxide synthase (NOS2) resulting in increased NO production. NO contributes to cell signaling by inducing posttranslational protein modifications. Under pathological conditions there is a shift from the signal transducing actions to the formation of protein tyrosine nitration by secondary products like peroxynitrite and nitrogen dioxide. We identified amyloid β (Aβ) as an NO target, which is nitrated at tyrosine 10 (3NTyr(10)-Aβ). Nitration of Aβ accelerated its aggregation and was detected in the core of Aβ plaques of APP/PS1 mice and AD brains. NOS2 deficiency or oral treatment with the NOS2 inhibitor L-NIL strongly decreased 3NTyr(10)-Aβ, overall Aβ deposition and cognitive dysfunction in APP/PS1 mice. Further, injection of 3NTyr(10)-Aβ into the brain of young APP/PS1 mice induced β-amyloidosis. This suggests a disease modifying role for NOS2 in AD and therefore represents a potential therapeutic target.

1. Intracellular sharp electrode and whole-cell patch-clamp recording from characterized paraventricular nucleus (PVN) neurones in rat hypothalamic slices were used to study the synaptic mechanisms and associated neurotransmitters that mediate their response to suprachiasmatic nucleus (SCN) stimulation. 2. Electrical stimulation restricted to SCN evoked short-latency inhibitory postsynaptic potentials (IPSPs) or combinations of IPSPs and excitatory postsynaptic potentials (EPSPs) in all (n = 59) PVN neurones tested. Type I neurones (n = 18) were magnocellular and a majority (13/18) demonstrated monosynaptic IPSPs that reversed polarity at the chloride equilibrium potential and were sensitive to bicuculline. 3. Type II (n = 10) and III parvocellular (n = 13), and unclassifiable neurones (n = 18) displayed combinations of IPSPs and EPSPs following similar stimuli applied to SCN. IPSP blockade with bicuculline uncovered SCN-evoked monosynaptic dual-component EPSPs that were sensitive to N-methyl-D-aspartate (NMDA) and non-NMDA receptor antagonists. In addition, chemical microstimulation within SCN was associated with transient increases in spontaneous EPSPs recorded from these PVN neurones. 4. These data imply that the amino acids GABA and glutamate are important mediators of fast monosynaptic transmission from SCN to defined neurones in PVN, and are candidates for conveying circadian rhythmicity to PVN processes.

1. Whole cell patch clamp recordings of neurons in slices of the suprachiasmatic nucleus (SCN) were made in order to assess their electrophysiological and morphological heterogeneity. This assessment was accomplished by (i) quantification of intrinsic membrane properties recorded in current clamp mode, (ii) studying frequency distributions of these properties, (iii) grouping of cells based on visual inspection of data records, and (iv) use of cluster analysis methods. 2. Marked heterogeneity was found in the resting membrane potential, input resistance, time constant, rate of frequency adaptation, size of rebound depolarization (low-threshold Ca2+ potential) and regularity of firing. The frequency distribution of these membrane properties deviated significantly from a normal distribution. Other parameters, including spike amplitude and width, amplitude and rising slope of the spike after-hyperpolarization (AHP) and amplitude of the spike train AHP, showed considerable variability as well but generally obeyed a normal distribution. 3. Visual inspection of the data led to partitioning of cells into three clusters, viz. cluster I characterized by monophasic spike AHPs and irregular firing in the frequency range from 1.5 to 5.0 Hz; cluster II with biphasic spike AHPs and regular firing in the same range; and cluster III with large rebound depolarizations and biphasic spike AHPs. In a post hoc analysis, these clusters also appeared to differ in other membrane properties. This grouping was confirmed by hierarchical tree clustering and multidimensional scaling. 4. The light microscopic properties of recorded neurons were studied by biocytin labelling. Neurons had monopolar, bipolar or multipolar branching patterns and were often varicose. Axons sometimes originated from distal dendritic segments and usually branched into multiple collaterals. Many cells with extra-SCN projections also possessed intranuclear axon collaterals. We found no morphological differences between clusters except that cluster III neurons possessed more axon collaterals than cluster I or II cells. 5. These results suggest that SCN neurons are heterogeneous in some basic as well as active membrane properties and can be partitioned into at least three clusters. Cluster I and II cells fire spontaneously in a regular and irregular mode, respectively, and sustain prolonged spike trains. In contrast, cluster III cells have low firing rates but may adopt a burst-like firing mode when receiving appropriate input. While all clusters transmit output to target cells within and outside SCN, cluster III cells in particular are suggested to affect excitability of large numbers of SCN neurons by their extensive local network of axon collaterals.

To date, long-term consequences of septic encephalopathy on cerebral metabolism, cognition, learning, and memory capabilities and factors involved are poorly understood. In this study, we used a murine sepsis model to demonstrate that bacterial lipopolysaccharide (LPS) causes long-term cognitive deficits in mice. Two months after LPS treatment, wild-type mice committed more working and reference memory errors than controls. The behavioral impairment was independent of the cerebral glucose uptake as evidenced by 18 F-Fluordeoxyglucose small animal positron emission tomography. In contrast, mice deficient for the inducible nitric oxide synthase gene (NOS2Ϫ/Ϫ) did not show any cognitive changes when challenged with LPS. Immunohistochemical analysis demonstrated that LPS did not lead to neuronal cell death but caused sustained microglial activation in wild-type as compared to NOS2Ϫ/Ϫ mice. Expression analysis showed that LPS-treated NOS2Ϫ/Ϫ mice had lower brain mRNA levels for proinflammatory factors compared with wild-type mice. Expression analysis demonstrated distinct changes in the content of synaptic proteins in wild-type mice, which were not observed in the NOS2Ϫ/Ϫ mice. Together, this data set outlines the importance of the NOS2 activation for long-term cerebral changes after severe sepsis.

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This study demonstrates the suitability of CASL to consistently detect differences between groups, regions, and resting states even after seven weeks. This emphasizes its usefulness for longitudinal designs.

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In this work we demonstrate, to the best of our knowledge, a novel wide field-of-view upconversion system, supporting upconversion of monochromatic mid-infrared (mid-IR) images, e.g., for hyperspectral imaging (HSI). An optical parametric oscillator delivering 20 ps pulses tunable in the 2.3-4 μm range acts as a monochromatic mid-IR illumination source. A standard CCD camera, in synchronism with the crystal rotation of the upconversion system, acquires in only 2.5 ms the upconverted mid-IR images containing 64 kpixels, thereby eliminating the need for postprocessing. This approach is generic in nature and constitutes a major simplification in realizing video-frame-rate mid-IR monochromatic imaging. A second part of this paper includes a proof-of-principle study on esophageal tissues samples, from a tissue microarray, in the 3-4 μm wavelength range. The use of mid-IR HSI for investigation of esophageal cancers is particularly promising as it allows for a much faster and possibly more observer-independent workflow than state-ofthe-art histology. Comparing histologically stained sections evaluated by a pathologist to images obtained by either Fourier transform IR or upconversion HSI based on machine learning shows great promise for further work pointing towards clinical translation using the presented mid-IR HSI upconversion system.