Elucidating a normal function of huntingtin by functional and microarray analysis of huntingtin-null mouse embryonic fibroblasts

Background

Multi-sensory integration is necessary for organisms to discriminate different environmental stimuli and thus determine behavior. Caenorhabditis elegans has 12 pairs of amphid sensory neurons, which are involved in generating behaviors such as thermotaxis toward cultivation temperature, and chemotaxis toward chemical stimuli. This arrangement of known sensory neurons and measurable behavioral output makes C. elegans suitable for addressing questions of multi-sensory integration in the nervous system. Previous studies have suggested that C. elegans can process different chemoattractants simultaneously. However, little is known about how these organisms can integrate information from stimuli of different modality, such as thermal and chemical stimuli.

Results

We studied the behavior of a population of C. elegans during simultaneous presentation of thermal and chemical stimuli. First, we examined thermotaxis within the radial temperature gradient produced by a feedback-controlled thermoregulator. Separately, we examined chemotaxis toward sodium chloride or isoamyl alcohol. Then, assays for simultaneous presentations of 15°C (colder temperature than 20°C room temperature) and chemoattractant were performed with 15°C-cultivated wild-type worms. Unlike the sum of behavioral indices for each separate behavior, simultaneous presentation resulted in a biased migration to cold regions in the first 10 min of the assay, and sodium chloride-regions in the last 40 min. However, when sodium chloride was replaced with isoamyl alcohol in the simultaneous presentation, the behavioral index was very similar to the sum of separate single presentation indices. We then recorded tracks of single worms and analyzed their behavior. For behavior toward sodium chloride, frequencies of forward and backward movements in simultaneous presentation were significantly different from those in single presentation. Also, migration toward 15°C in simultaneous presentation was faster than that in 15°C-single presentation.

Conclusion

We conclude that worms preferred temperature to chemoattractant at first, but preferred the chemoattractant sodium chloride thereafter. This preference was not seen for isoamyl alcohol presentation. We attribute this phase-dependent preference to the result of integration of thermosensory and chemosensory signals received by distinct sensory neurons.     

To turn the tide in the Soviet scientific instrumentation: in memoriam Erlen I. Fedin (1926–2009)

Structural Chemistry - A brief account of Soviet magnetic resonance (MR) scientific instrumentation in the 1970s–1980s is given. The impact of Erlen Ilyich Fedin (1926–2009), the head...     

Fredholmness and invertibility of Toeplitz operators with matrix almost periodic symbols

We consider Toeplitz operators with symbols that are almost periodic matrix functions of several variables. It is shown that under certain conditions on the group generated by the Fourier support of the symbol, a Toeplitz operator is Fredholm if and only if it is invertible.

     

The system Na2CO3–CaCO3–MgCO3 at 6 GPa and 900–1250°C and its relation to the partial melting of carbonated mantle

In order to constrain the Na₂CO₃–CaCO₃–MgCO₃ T–X diagram at 6?GPa in addition to the binary and pseudo-binary systems we conducted experiments along the Na₂CO₃–Ca_0.5Mg_0.5CO₃ join. At 900–1000°C, melting does not occur and isothermal sections are presented by one-, two- and three-phase regions containing Ca-bearing magnesite, aragonite, Na₂CO₃ (Na₂) and Na₂(Ca_1–0.9Mg_0-0.1)_3-4(CO₃)_4-5 (Na₂Ca_3-4), Na₄(Ca_1–0.6Mg_0–0.4)(CO₃)₃ (Na₄Ca), Na₂(Ca_0-0.08Mg_1–0.92)(CO₃)₂ (Na₂Mg) phases with intermediate compositions. The minimum melting point locates between 1000°C and 1100°C. This point would resemble that of three eutectics: Mgs–Na₂Ca₃–Na₂Mg, Na₂Mg–Na₂Ca₃–Na₄Ca or Na₂Mg–Na₄Ca–Na₂, in the compositional interval of [45Na₂CO₃·55(Ca_0.6Mg_0.4)CO₃]–[60Na₂CO₃·40Ca_0.6Mg_0.4CO₃]. The liquidus projection has seven primary solidification phase regions for Mgs, Dol, Arg, Na₂Ca₃, Na₄Ca, Na₂ and Na₂Mg. The results suggest that extraction of Na and Ca from silicate to carbonate components has to decrease minimum melting temperature of carbonated mantle rocks to 1000–1100°C at 6?GPa and yields Na-rich dolomitic melt with a Na# (Na₂O/(Na₂O?+?CaO?+?MgO))?≥?28?mol%.     

RGDS‐ and SIKVAVS‐Modified Superporous Poly(2‐hydroxyethyl methacrylate) Scaffolds for Tissue Engineering Applications

Three‐dimensional hydrogel supports for mesenchymal and neural stem cells (NSCs) are promising materials for tissue engineering applications such as spinal cord repair. This study involves the preparation and characterization of superporous scaffolds based on a copolymer of 2‐hydroxyethyl and 2‐aminoethyl methacrylate (HEMA and AEMA) crosslinked with ethylene dimethacrylate. Ammonium oxalate is chosen as a suitable porogen because it consists of needle‐like crystals, allowing their parallel arrangement in the polymerization mold. The amino group of AEMA is used to immobilize RGDS and SIKVAVS peptide sequences with an N‐γ‐maleimidobutyryloxy succinimide ester linker. The amount of the peptide on the scaffold is determined using ¹²⁵I radiolabeled SIKVAVS. Both RGDS‐ and SIKVAVS‐modified poly(2‐hydroxyethyl methacrylate) scaffolds serve as supports for culturing human mesenchymal stem cells (MSCs) and human fetal NSCs. The RGDS sequence is found to be better for MSC and NSC proliferation and growth than SIKVAVS.

     

19F NMR studies of the native and denatured states of green fluorescent protein

Biosynthetic preparation and (19)F NMR experiments on uniformly 3-fluorotyrosine-labeled green fluorescent protein (GFP) are described. The (19)F NMR signals of all 10 fluorotyrosines are resolved in the protein spectrum with signals spread over 10 ppm. Each tyrosine in GFP was mutated in turn to phenylalanine. The spectra of the Tyr --> Phe mutants, in conjunction with relaxation data and results from (19)F photo-CIDNP (chemically induced dynamic nuclear polarization) experiments, yielded a full (19)F NMR assignment. Two (19)F-Tyr residues (Y92 and Y143) were found to yield pairs of signals originating from ring-flip conformers; these two residues must therefore be immobilized in the native structure and have (19)F nuclei in two magnetically distinct positions depending on the orientation of the aromatic ring. Photo-CIDNP experiments were undertaken to probe further the structure of the native and denatured states. The observed NMR signal enhancements were found to be consistent with calculations of the HOMO (highest occupied molecular orbital) accessibilities of the tyrosine residues. The photo-CIDNP spectrum of native GFP shows four peaks corresponding to the four tyrosine residues that have solvent-exposed HOMOs. In contrast, the photo-CIDNP spectra of various denatured states of GFP show only two peaks corresponding to the (19)F-labeled tyrosine side chains and the (19)F-labeled Y66 of the chromophore. These data suggest that the pH-denatured and GdnDCl-denatured states are similar in terms of the chemical environments of the tyrosine residues. Further analysis of the sign and amplitude of the photo-CIDNP effect, however, provided strong evidence that the denatured state at pH 2.9 has significantly different properties and appears to be heterogeneous, containing subensembles with significantly different rotational correlation times.     

Tricarboranyl pentaerythritol-based building block

A new tricarborane building block based on pentaerythritol was prepared for applications in boron neutron capture therapy (BNCT). Its X-ray single-crystal structure revealed a high degree of steric congestion. To enable the attachment of the building block to other moieties, a succinimidyl linker has been introduced at the focal point, and a generation-2 hexacarborane-containing dendron carrying 60 boron atoms has been prepared using a 2,2-bis(hydroxymethyl)propionic acid core.