Hand use predicts the structure of representations in sensorimotor cortex.

Fine finger movements are controlled by the population activity of neurons in the hand area of primary motor cortex. Experiments using microstimulation and single-neuron electrophysiology suggest that this area represents coordinated multi-joint, rather than single-finger movements. However, the principle by which these representations are organized remains unclear. We analyzed activity patterns during individuated finger movements using functional magnetic resonance imaging (fMRI). Although the spatial layout of finger-specific activity patterns was variable across participants, the relative similarity between any pair of activity patterns was well preserved. This invariant organization was better explained by the correlation structure of everyday hand movements than by correlated muscle activity. This also generalized to an experiment using complex multi-finger movements. Finally, the organizational structure correlated with patterns of involuntary co-contracted finger movements for high-force presses. Together, our results suggest that hand use shapes the relative arrangement of finger-specific activity patterns in sensory-motor cortex

Genomic survey of the non-cultivatable opportunistic human pathogen, Enterocytozoon bieneusi

© 2009 The Authors. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS Pathogens 5 (2009): e1000261, doi:10.1371/journal.ppat.1000261.Enterocytozoon bieneusi is the most common microsporidian associated with human disease, particularly in the immunocompromised population. In the setting of HIV infection, it is associated with diarrhea and wasting syndrome. Like all microsporidia, E. bieneusi is an obligate, intracellular parasite, but unlike others, it is in direct contact with the host cell cytoplasm. Studies of E. bieneusi have been greatly limited due to the absence of genomic data and lack of a robust cultivation system. Here, we present the first large-scale genomic dataset for E. bieneusi. Approximately 3.86 Mb of unique sequence was generated by paired end Sanger sequencing, representing about 64% of the estimated 6 Mb genome. A total of 3,804 genes were identified in E. bieneusi, of which 1,702 encode proteins with assigned functions. Of these, 653 are homologs of Encephalitozoon cuniculi proteins. Only one E. bieneusi protein with assigned function had no E. cuniculi homolog. The shared proteins were, in general, evenly distributed among the functional categories, with the exception of a dearth of genes encoding proteins associated with pathways for fatty acid and core carbon metabolism. Short intergenic regions, high gene density, and shortened protein-coding sequences were observed in the E. bieneusi genome, all traits consistent with genomic compaction. Our findings suggest that E. bieneusi is a likely model for extreme genome reduction and host dependence.This research was supported by National Institutes of Health (NIH) grants R21 AI064118 (DEA) and R21 AI52792 (ST). HGM was supported in part by NIH contracts HHSN266200400041C and HHSN2662004037C (Bioinformatics Resource Centers) and by the G. Unger Vetlesen Foundation

Microsporidia amitochondrial protists possess a 70-kDa heat shock protein gene of mitochondrial evolutionary origin

An intronless gene encoding a protein of 592 amino acid residues with similarity to 70-kDa heat shock proteins (HSP70s) has been cloned and sequenced from the amitochondrial protist Encephalitozoon cuniculi (phylum Microsporidia). Southern blot analyses show the presence of a single gene copy located on chromosome XI. The encoded protein exhibits an N-terminal hydrophobic leader sequence and two motifs shared by proteobacterial and mitochondrially expressed HSP70 homologs. Phylogenetic analysis using maximum likelihood and evolutionary distances place the E. cuniculi sequence in the cluster of mitochondrially expressed HSP70s, with a higher evolutionary rate than those of homologous sequences. Similar results were obtained after cloning a fragment of the homologous gene in the closely related species E. hellem. The presence of a nuclear targeting signal-like sequence supports a role of the Encephalitozoon HSP70 as a molecular chaperone of nuclear proteins. No evidence for cytosolic or endoplasmic reticulum forms of HSP70 was obtained through PCR amplification. These data suggest that Encephalitozoon species have evolved from an ancestor bearing mitochondria, which is in disagreement with the postulated presymbiotic origin of Microsporidia. The specific role and intracellular localization of the mitochondrial HSP70-like protein remain to be elucidated

The use of foil metallurgy processing to achieve ultrafine grained Mg-9 Li laminates and Mg-9Li-5B4C particulate composites

A foil metallurgy processing technique has been developed to prepare fine-grained laminates based on a two-phase Mg-9Li alloy and fine-grained particulate composites based on hard B4C powders embedded in the two-phase Mg-9Li alloy. The processing steps involve principally cold-rolling and low-temperature recovery processing for preparation of foils, and low-temperature press-bonding for preparation of laminates and composites. In this manner, contamination of the highly reactive alloy is minimized. Good tensile strength and ductility were achieved at room temperature with specific stiffness values of about 3.1 × 106 m3. Both the fine-grained laminates and the particulate composite are superplastic at 200 ° C, exhibiting a strain-rate-sensitivity exponent,m, of 0.5.Peer reviewe

Superplastic behavior of a fine-grained two-phase Mg-9wt.%Li alloy

A two-phase Mg-9Li alloy (where the composition is in weight per cent) was made fine grained (d≈6–35 μm) by extensive cold rolling into foils and press bonding the foils at low homologous temperatures. The material exhibited superplastic properties in the temperature range 423–523 K ((0.49–0.61)T/Tm) with elongations to failure as high as 460%. The creep rate was determined to be inversely proportional to approximately the square of grain size and to the second power of stress. The activation energy for superplastic flow was equal to that for lattice diffusion in the major b.c.c. β phase. The Mg-9Li laminate alloy was found to be similar in its flow characteristics to MA-21, a multicomponent Mg-8.1Li fine-grained commercial Soviet alloy.Peer reviewe

C-13 NMR evidence for dynamics of nanotubes in ropes

We report on C-13 nuclear magnetic resonance from 10 up to 350 K on single wall carbon nanotubes. The magic angle spinning NMR spectrum shows one isotropic line at 126 ppm and the static spectrum a powder pattern typical for a curved graphene sheet. The T dependence of the spin-lattice relaxation rate T-1(-1) reveals an unusual phenomenon which could be explained by thermally activated small amplitude motion (SAM) of the nanotubes. If above 170 K, diffusion of twistons might be responsible for the local SAM of the C-13 sites, below this transition temperature frozen in twistons could appear with an orientational order of the nanotubes in the ropes