Center-surround vs. distance-independent lateral connectivity in the olfactory bulb

Lateral neuronal interactions are known to play important roles in sensory information processing. A center-on surround-off local circuit arrangement has been shown to play a role in mediating contrast enhancement in the visual, auditory, and somatosensory systems. The lateral connectivity and the influence of those connections have been less clear for the olfactory system. A critical question is whether the synaptic connections between the primary projection neurons, mitral and tufted (M/T) cells, and their main inhibitory interneurons, the granule cells (GCs), can support a center-surround motif. Here, we study this question by injecting a “center” in the glomerular layer of the olfactory bulb (OB) with a marker of synaptic connectivity, the pseudorabies virus (PRV), then examines the distribution of labeling in the “surround” of GCs. We use a novel method to score the degree to which the data fits a center-surround model vs. distance-independent connectivity. Data from 22 injections show that M/T cells generally form lateral connections with GCs in patterns that lie between the two extremes

Lateral Connectivity in the Olfactory Bulb is Sparse and Segregated

Lateral connections in the olfactory bulb were previously thought to be organized for center–surround inhibition. However, recent anatomical and physiological studies showed sparse and distributed interactions of inhibitory granule cells (GCs) which tended to be organized in columnar clusters. Little is known about how these distributed clusters are interconnected. In this study, we use transsynaptic tracing viruses bearing green or red fluorescent proteins to further elucidate mitral- and tufted-to-GC connectivity. Separate sites in the glomerular layer were injected with each virus. Columns with labeling from both viruses after transsynaptic spread show sparse red or green GCs which tended to be segregated. However, there was a higher incidence of co-labeled cells than chance would predict. Similar segregation of labeling is observed from dual injections into olfactory cortex. Collectively, these results suggest that neighboring mitral and tufted cells receive inhibitory inputs from segregated subsets of GCs, enabling inhibition of a center by specific and discontinuous lateral elements

A REVIEW ON A FLASH CHROMATOGRAPHY

ABSTRACT Flash chromatography is rapid form of preparative column chromatography-preparative liquid chromatography based upon an air pressure driven hybrid of medium and short column chromatography optimized for rapid separation of organic compounds. As technology has evolved available guidelines for normal-phase flash chromatography have become less relevant. Years of experience performing chromatography with disposable columns have been condensed into simple guidelines useful for translating TLC results into either isocratic-or gradient-flash chromatography. The described studies should provide researchers with a means of selecting adequate columns and guidelines to reduce the waste of solvents, silica, time, and money. Modern flash chromatography systems are sold as pre-packed plastic cartridges and the solvent is pumped through the cartridge. These systems may also be linked with detectors and fraction collectors providing automation. The introduction of gradient pumps has resulted in quicker separations and less solvent usage

Sphingomyelin Functions as a Novel Receptor for Helicobacter pylori VacA

The vacuolating cytotoxin (VacA) of the gastric pathogen Helicobacter pylori binds and enters epithelial cells, ultimately resulting in cellular vacuolation. Several host factors have been reported to be important for VacA function, but none of these have been demonstrated to be essential for toxin binding to the plasma membrane. Thus, the identity of cell surface receptors critical for both toxin binding and function has remained elusive. Here, we identify VacA as the first bacterial virulence factor that exploits the important plasma membrane sphingolipid, sphingomyelin (SM), as a cellular receptor. Depletion of plasma membrane SM with sphingomyelinase inhibited VacA-mediated vacuolation and significantly reduced the sensitivity of HeLa cells, as well as several other cell lines, to VacA. Further analysis revealed that SM is critical for VacA interactions with the plasma membrane. Restoring plasma membrane SM in cells previously depleted of SM was sufficient to rescue both toxin vacuolation activity and plasma membrane binding. VacA association with detergent-resistant membranes was inhibited in cells pretreated with SMase C, indicating the importance of SM for VacA association with lipid raft microdomains. Finally, VacA bound to SM in an in vitro ELISA assay in a manner competitively inhibited by lysenin, a known SM-binding protein. Our results suggest a model where VacA may exploit the capacity of SM to preferentially partition into lipid rafts in order to access the raft-associated cellular machinery previously shown to be required for toxin entry into host cells

Anisotropic study of ReSe

Transition metal dichalcogenides (TMDCs) are extensively in demand as photodetectors due to their extraordinary electrical and optical properties. In this work, we have reported the synthesis of high-quality bulk single crystals of rhenium diselenide (ReSe2) by the DVT technique. X-ray diffraction, Raman spectroscopy, and elemental mapping confirmed the crystal structure, crystallinity, and phase singularity of the material. TEM and SEM confirm the crystallinity and layered structure of the grown material. Owing to these unique properties, we have utilized the ReSe2 crystal to construct a high-performance anisotropic photodetector. The crystals’ photodetection capacity was confirmed in terms of typical detector parameters such as responsivity, detectivity, and rise time for white light under different intensities, biasing voltages, and wavelengths. The anisotropy in the properties due to its unique layered structure is also explored here. Observing the encouraging results, ReSe2 is a potential choice in 2D TMDCs for electrical and optoelectronic applications

Assessment of Suitability of Saxagliptin Hydrochloride for Development of Controlled Release Parenteral Formulation by Preformulation Studies

The main objective of pre-formulation study is to develop the stable, elegant, safe and effective drug delivery system by establishing drug kinetic profile, formulation compatibility with different excipients and physico-chemical parameters of new drug molecules. This could provide key evidence for implementing formulation design or requirement of the molecular alteration. So, in the present study preformulation studies were performed on Saxagliptin Hydrochloride (SXG) to assess its suitability for parenteral formulation. SXG is a potent and selective reversible inhibitor of dipeptidyl peptidase-4 used to treat type –II diabetes mellitus. The authenticity of SXG was established by differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy(FTIR) spectra. An ultraviolet–visible (UV) spectrophotometric and high performance liquid chromatography (HPLC) methods were employed for determination of SXG in bulk API (active pharmaceutical ingredient). The UV method was linear within the range of 1-40 μg/ml. The proposed methodology is robust which can be concluded from the lower percentage standard deviation percentage co efficient of variance (% CV) values of intraday and inter day variability. The retention time was observed 1.3 min of SXG in HPLC method. The higher regression coefficient value (0.999) indicates the methodology is robust.&nbsp

Performance evaluation of the Asante Rapid Recency Assay for verification of HIV diagnosis and detection of recent HIV-1 infections: Implications for epidemic control.

We previously described development of a rapid test for recent infection (RTRI) that can diagnose HIV infection and detect HIV-1 recent infections in a single device. This technology was transferred to a commercial partner as Asante Rapid Recency Assay (ARRA). We evaluated performance of the ARRA kits in the laboratory using a well-characterized panel of specimens. The plasma specimen panel (N = 1500) included HIV-1 (N = 570), HIV-2 (N = 10), and HIV-negatives (N = 920) representing multiple subtypes and geographic locations. Reference diagnostic data were generated using the Bio-Rad HIV-1-2-O EIA/Western blot algorithm with further serotyping performed using the Multispot HIV-1/2 assay. The LAg-Avidity EIA was used to generate reference data on recent and long-term infection for HIV-1 positive specimens at a normalized optical density (ODn) cutoff of 2.0 corresponding to a mean duration of about 6 months. All specimens were tested with ARRA according to the manufacturer's recommendations. Test strips were also read for line intensities using a reader and results were correlated with visual interpretation. ARRA's positive verification line (PVL) correctly classified 575 of 580 HIV-positive and 910 of 920 negative specimens resulting in a sensitivity of 99.1% (95% CI: 98.0-99.6) and specificity of 98.9% (95% CI: 98.1-99.4), respectively. The reader-based classification was similar for PVL with sensitivity of 99.3% (576/580) and specificity of 98.8% (909/920). ARRA's long-term line (LTL) classified 109 of 565 HIV-1 specimens as recent and 456 as long-term compared to 98 as recent and 467 as long-term (LT) by LAg-Avidity EIA (cutoff ODn = 2.0), suggesting a mean duration of recent infection (MDRI) close to 6 months. Agreement of ARRA with LAg recent cases was 81.6% (80/98) and LT cases was 93.8% (438/467), with an overall agreement of 91.7% (kappa = 0.72). The reader (cutoff 2.9) classified 109/566 specimens as recent infections compared to 99 by the LAg-Avidity EIA for recency agreement of 81.8% (81/99), LT agreement of 9% (439/467) with overall agreement of 91.9% (kappa = 0.72). The agreement between visual interpretation and strip reader was 99.9% (95% CI: 99.6-99.9) for the PVL and 98.1% (95% CI: 96.6-98.9) for the LTL. ARRA performed well with HIV diagnostic sensitivity >99% and specificity >98%. Its ability to identify recent infections is comparable to the LA-Avidity EIA corresponding to an MDRI of about 6 months. This point-of-care assay has implications for real-time surveillance of new infections among newly diagnosed individuals for targeted prevention and interrupting ongoing transmission thus accelerating epidemic control