Identification of a set of genes showing regionally enriched expression in the mouse brain

Background

We have recorded responses from single neurons in murine visual cortex to determine the effectiveness of the input from the two murine cone photoreceptor mechanisms and whether there is any unique selectivity for cone inputs at this higher region of the visual system that would support the possibility of colour vision in mice. Each eye was stimulated by diffuse light, either 370 (strong stimulus for the ultra-violet (UV) cone opsin) or 505 nm (exclusively stimulating the middle wavelength sensitive (M) cone opsin), obtained from light emitting diodes (LEDs) in the presence of a strong adapting light that suppressed the responses of rods.

Results

Single cells responded to these diffuse stimuli in all areas of striate cortex. Two types of responsive cells were encountered. One type (135/323 – 42%) had little to no spontaneous activity and responded at either the on and/or the off phase of the light stimulus with a few impulses often of relatively large amplitude. A second type (166/323 – 51%) had spontaneous activity and responded tonically to light stimuli with impulses often of small amplitude. Most of the cells responded similarly to both spectral stimuli. A few (18/323 – 6%) responded strongly or exclusively to one or the other spectral stimulus and rarely in a spectrally opponent manner.

Conclusion

Most cells in murine striate cortex receive excitatory inputs from both UV- and M-cones. A small fraction shows either strong selectivity for one or the other cone mechanism and occasionally cone opponent responses. Cells that could underlie chromatic contrast detection are present but extremely rare in murine striate cortex.     

The prediction of sequences

The problem of predicting the short-term future behavior of a sequence, after observing it as long as we please, so as to achieve a specified reliability against all possible sequences is considered. For a particular problem, namely, predicting when in a sequence of 0's and 1's the pair (1, 0) in that order is not coming next, a reliability of 3/4 can be approximated as closely as we please, but not achieved. This article appeared as a Research Memorandum of the Rand Corporation, RM-1570, 12 October 1955.     

Expanding dialogues: from natural autoinducers to non-natural analogues that modulate quorum sensing in Gram-negative bacteria

Bacteria are capable of "communicating" their local population densities via a process termed quorum sensing (QS). Gram-negative bacteria use N-acylated l-homoserine lactones (AHLs), in conjunction with their cognate LuxR-type receptors, as their primary signalling circuit for QS. In this critical review, we examine AHL signalling in Gram-negative bacteria with a primary focus on the design of non-natural AHLs, their structure-activity relationships, and their application in chemical biological approaches to study QS (72 references).     

New azaphilones from Chaetomium globosum isolated from the built environment

A strain of Chaetomium globosum (DAOM 240359) was isolated from an indoor air sample in Ottawa, Ontario, Canada. When fermented in liquid culture, this strain produced a number of known metabolites including chaetoglobosins A (6), C, and F (7), chaetomugilin D (5), chaetoviridin A (4), and three new nitrogenous azaphilones; 4′-epi-N-2-hydroxyethyl-azachaetoviridin A (1), N-2-butyric-azochaetoviridin E (2), and isochromophilone XIII (3). The structures were elucidated by spectroscopic analysis including; HRMS, 1D and 2D NMR, UV, and ORD. Compounds 2–7 were antimicrobial when tested using quantitative growth inhibition assays.     

Measurement at the field scale of soil δ13C and δ15N under improved grassland

Variations in natural abundance of carbon (C) and nitrogen (N) stable isotopes are widely used as tools for many aspects of scientific research. By examining variations in the ratios of heavy to light stable isotopes, information can be obtained as to what physical, chemical and biological processes may be occurring. The spatial heterogeneity of soil δ¹⁵N‐ and δ¹³C‐values across a range of scales and under different land use have been described by a number of researchers and the natural abundances of the C and N stable isotopes in soils have been found to be correlated with many factors including hydrology, topography, land use, vegetation cover and climate. In this study the Latin square sampling +1 (LSS+1) sampling method was compared with a simple grid sampling approach for δ¹³C and δ¹⁵N measurement at the field scale. A set of 144 samples was collected and analysed for δ¹⁵N and δ¹³C from a 12 × 12 grid (in a 1 ha improved grassland field in south‐west England). The dimension of each cell of the grid was approximately 11 × 6 m. The 12 × 12 grid was divided into four 6 × 6 grids and the LSS+1 sampling technique was applied to these and the main 12 × 12 grid for a comparison of sample means and variation. The LSS+1 means from the 12 × 12 grid and the four 6 × 6 grids compared well with the overall grid mean because of the low variation within the field. The LSS+1 strategy (13 samples) generated representative samples from the 12 × 12 grid, and hence would be an acceptable method for sampling similar plots for the measurement of mean isotopic composition. Copyright © 2010 John Wiley & Sons, Ltd.     

Diversity-oriented synthesis of biaryl-containing medium rings using a one bead/one stock solution platform

Diversity-oriented synthesis of structurally complex and diverse small molecules can be used as the first step in a process to explore cellular and organismal pathways. The success of this process is likely going to be dependent on advances in the synthesis of small molecules having natural product-like structures in an efficient and stereoselective manner. The development, scope, and mechanism of the oxidation of organocuprates was investigated and exploited in the atropdiastereoselective synthesis of biaryl-containing medium rings (9-, 10-, and 11-membered rings). The methodology was performed on high-capacity, large polystyrene beads by metalating aryl bromides with i-PrBu(2)MgLi, followed by transmetalating with CuCN x 2LiBr and then oxidizing with 1,3-dinitrobenzene, and was used in a diversity-oriented synthesis of biaryl-containing medium rings (library total theoretical maximum 1412 members). The high capacity beads were arrayed into 384-well plates and, using a process optimized during the development of a one bead/one stock solution technology platform, converted into arrays of stock solutions, with each stock solution containing largely one compound. These stock solutions were used in numerous phenotypic and protein-binding assays. The process described outlines a pathway that we feel will contribute to a comprehensive and systematic chemical approach to exploring biology (chemical genetics).     

Out of the oil bath and into the oven--microwave-assisted combinatorial chemistry heats up

The application of microwave irradiation to expedite solid-phase organic reactions could be the tool that allows combinatorial chemistry to deliver on its promise--providing rapid access to large collections of diverse small molecules. Herein, several different approaches to microwave (MW)-assisted solid-phase reactions and library synthesis are introduced, including the use of solid-supported reagents, multicomponent coupling reactions, solvent-free parallel library synthesis, and spatially addressable library synthesis on planar solid supports. The future impact of MW-assisted organic reactions on solid-phase and combinatorial chemistry could prove to be immense, and methods for further improvement of this strategic combination of technologies are highlighted.     

Effects of Adsorbed Polyaniline on Redox Process on MoO3 Surface

The effects exhibited by adsorbed conducting polyaniline on the redox process on a molybdenum oxide surface were studied. Thermogravimetric results indicate a 4% polyaniline deposition. Cyclic voltammograms of the adsorbed polymer on MoO3 show that polyaniline exerts remarkable effects on the molybdenum blue oxidation-reduction process, with oxidation and reduction potentials of 0.33 and 0.18 V, respectively. This effect strongly enhances the electrode response, and can be used as an important tool in qualitative and/or quantitative determinations of molybdenum in solution as well as in any substrate. Copyright 1999 Academic Press.     

Ring-closing metathesis of olefinic peptides: design, synthesis, and structural characterization of macrocyclic helical peptides

Heptapeptides containing residues with terminal olefin-derivatized side chains (3 and 4) have been treated with ruthenium alkylidene 1 and undergone facile ring-closing olefin metathesis (RCM) to give 21- and 23-membered macrocyclic peptides (5 and 6). The primary structures of peptides 3 and 4 were based upon a previously studied heptapeptide (2), which was shown to adopt a predominantly 3(10)-helical conformation in CDCl(3) solution and an alpha-helical conformation in the solid state. Circular dichroism, IR, and solution-phase (1)H NMR studies strongly suggested that acyclic precursors 3 and 4 and the fully saturated macrocyclic products 7 and 8 also adopted helical conformations in apolar organic solvents. Single-crystal X-ray diffraction of cyclic peptide 8 showed it to exist as a right-handed 3(10)-helix up to the fifth residue. Solution-phase NMR structures of both acyclic peptide 4 and cyclic peptide 8 in CD(2)Cl(2) indicated that the acyclic diene assumes a loosely 3(10)-helical conformation, which is considerably rigidified upon macrocyclization. The relative ease of introducing carbon-carbon bonds into peptide secondary structures by RCM and the predicted metabolic stability of these bonds renders olefin metathesis an exceptional methodology for the synthesis of rigidified peptide architectures.