Engineering education under stress     

Walsh J 《Science (New York, N.Y.)》1981,213(4515):1479-1480

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Clusters of hyperactive neurons near amyloid plaques in a mouse model of Alzheimer's disease     

Busche MA  Eichhoff G  Adelsberger H  Abramowski D  Wiederhold KH  Haass C  Staufenbiel M  Konnerth A  Garaschuk O 《Science (New York, N.Y.)》2008,321(5896):1686-1689

The neurodegeneration observed in Alzheimer's disease has been associated with synaptic dismantling and progressive decrease in neuronal activity. We tested this hypothesis in vivo by using two-photon Ca2+ imaging in a mouse model of Alzheimer's disease. Although a decrease in neuronal activity was seen in 29% of layer 2/3 cortical neurons, 21% of neurons displayed an unexpected increase in the frequency of spontaneous Ca2+ transients. These "hyperactive" neurons were found exclusively near the plaques of amyloid beta-depositing mice. The hyperactivity appeared to be due to a relative decrease in synaptic inhibition. Thus, we suggest that a redistribution of synaptic drive between silent and hyperactive neurons, rather than an overall decrease in synaptic activity, provides a mechanism for the disturbed cortical function in Alzheimer's disease.  相似文献   

Arms Control and Disarmament: SALT, CCD, CTB, MBFR, Etc     

Walsh J 《Science (New York, N.Y.)》1972,175(4019):281-282

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Looking at the debits on r&d tax credits     

Walsh J 《Science (New York, N.Y.)》1984,225(4663):700-701

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Structure of DNMT1-DNA complex reveals a role for autoinhibition in maintenance DNA methylation     

Song J  Rechkoblit O  Bestor TH  Patel DJ 《Science (New York, N.Y.)》2011,331(6020):1036-1040

Maintenance of genomic methylation patterns is mediated primarily by DNA methyltransferase-1 (DNMT1). We have solved structures of mouse and human DNMT1 composed of CXXC, tandem bromo-adjacent homology (BAH1/2), and methyltransferase domains bound to DNA-containing unmethylated CpG sites. The CXXC specifically binds to unmethylated CpG dinucleotide and positions the CXXC-BAH1 linker between the DNA and the active site of DNMT1, preventing de novo methylation. In addition, a loop projecting from BAH2 interacts with the target recognition domain (TRD) of the methyltransferase, stabilizing the TRD in a retracted position and preventing it from inserting into the DNA major groove. Our studies identify an autoinhibitory mechanism, in which unmethylated CpG dinucleotides are occluded from the active site to ensure that only hemimethylated CpG dinucleotides undergo methylation.  相似文献   

Quantum dot superlattice thermoelectric materials and devices     

Harman TC  Taylor PJ  Walsh MP  LaForge BE 《Science (New York, N.Y.)》2002,297(5590):2229-2232

PbSeTe-based quantum dot superlattice structures grown by molecular beam epitaxy have been investigated for applications in thermoelectrics. We demonstrate improved cooling values relative to the conventional bulk (Bi,Sb)2(Se,Te)3 thermoelectric materials using a n-type film in a one-leg thermoelectric device test setup, which cooled the cold junction 43.7 K below the room temperature hot junction temperature of 299.7 K. The typical device consists of a substrate-free, bulk-like (typically 0.1 millimeter in thickness, 10 millimeters in width, and 5 millimeters in length) slab of nanostructured PbSeTe/PbTe as the n-type leg and a metal wire as the p-type leg.  相似文献   

Synaptic transmission at single glomeruli in the turtle cerebellum   总被引：1，自引：0，他引：1  

J V Walsh  J C Houk  R L Atluri  E Mugnaini 《Science (New York, N.Y.)》1972,178(63):881-883

We have recorded from the granular layer of the turtle cerebellum extracellular unitary potentials that appear to reflect pre- and postsynaptic events at the synapse between a single swelling of a mossy fiber and the dendritic tips of several granule cells. The presynaptic component is an all-or-none potential. It can be directly activated by spinal stimulation and is unaltered by repetitive activity or by high concentrations of magnesium. The postsynaptic component is a graded potential. It follows the presynaptic component by approximately 1 millisecond and is depressed by repetitive activity and by high concentrations of magnesium. The recording of large potentials produced by the flow of postsynaptic current within a single glomerulus suggests powerful transmission. Electron micrographs demonstrate large cerebellar glomeruli in the turtle and a substantial accumulation of mitochondria in the dendritic tips of granule cells.  相似文献   

Total doctorates edge up in science, engineering     

Walsh J 《Science (New York, N.Y.)》1984,226(4676):815

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Ethylene modulates stem cell division in the Arabidopsis thaliana root     

Ortega-Martínez O  Pernas M  Carol RJ  Dolan L 《Science (New York, N.Y.)》2007,317(5837):507-510

The construction of multicellular organisms depends on stem cells-cells that can both regenerate and produce daughter cells that undergo differentiation. Here, we show that the gaseous messenger ethylene modulates cell division in the cells of the quiescent center, which act as a source of stem cells in the seedling root. The cells formed through these ethylene-induced divisions express quiescent center-specific genes and can repress differentiation of surrounding initial cells, showing that quiescence is not required for these cells to signal to adjacent stem cells. We propose that ethylene is part of a signaling pathway that modulates cell division in the quiescent center in the stem cell niche during the postembryonic development of the root system.  相似文献   

Journals: photocopying is not the only problem     

Walsh J 《Science (New York, N.Y.)》1974,183(4131):1274-1277

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