2010年03月05日

Targeting KRAS cancers

Mutations in genes of the RAS family are preset on about 20% of human cancers, making RAS proteins prime potential targets for cancer therapy.

Direct targeting of RAS proteins has not so far been productive, but two papers published in this issue offer the prospect of alternative targets in a signalling pathway downstream of RAS.

Using a synthetic lethality RNAi screen, Barbie et al.
identify TBK1 as a kinase in the NF-KB signalling pathway that is essential for the survial of KRAS-transformed cells.

TBK1 induces anti-apoptotic signals and may be a therapeutic cancer target.

And in an elegant mouse model for lung cancer driven by Kras mutation and loss of p53, Meylan et al.
show that NF-KB signalling is a activated by the concerted actions of these two alterations and required for tumour initiation and tumour maintenance.


### database ###
nature 462,1-126 5 November 2009 Issue no.7269
Letter pp.104 / Requirement for NF-KB signalling in a mouse model of lung adenocarcinoma / E meylan et al. (Massachusetts Institute Technology)
Letter pp.108 / Systematic RNA interference reveals that oncogennic KRAS-driven cancers require TBK1 / D A Barbie et al.
news and views p.44 / Cancer : A tumour gene's fatal flaws / Julian Downward


posted by 0≠素子 at 12:10| Comment(0) | cancers | このブログの読者になる | 更新情報をチェックする

2009年12月09日

Electronic movies

Strong laser fields can tear an electron away from a molecule, leaving a fole in the electronic wavefunction that races through the molecule.

The ultrafast motion ofsuch a hole has been traced at last.



The first event in a light-induced reaction is that the electrons in the irradiated molecule respond to the incident light.

This response occurs on attosecond tinescales ( 1 attosecond is 10^-18 seconds), and even the fastest time-resolved measurements have been unable to probe the dynamics of the prosess.

But on page 972 of this isse, Smirnova et al. provide a glimpse into the fascinating world of attosecond electron dynamics, in effect revealing the opening frames of a movie that records the rearrangement of electrons when a molecuke is ionized by a laser.


(… to be continue…)

### database ###
nature 460,925-1050 20 August 2009 Issue no.7258
Article p.972 / High harmonic interferometry of multi-electron dynamics in molecules / O Smirnova et al. (カナダ国家研究会議およびマックス・ボルン研究所)
news and views p.960 / Chemical Physics : Electronic movies / Marc Vrakking
物理:アト秒の世界を見る

see page
posted by 0≠素子 at 23:31| Comment(0) | chamical physics | このブログの読者になる | 更新情報をチェックする

2009年11月19日

An upper limit on the stochastic gravitational-wave background of cosmological origin

A stochastic background of gravitational waves is expected to arise from a superposition of a large number of unresolved gravitational-wave sources of astrophysical and cosmological origin.

It should carry unique signatures from the earliest epochs in the evolution of the Universe, inaccessible to standerd astrophysical observations.

Direct measurements of the amplitude of this background are therefore of fun damenral importance for understanding the evolution of the Universe when it was yonger than one minute.

Here we report limits on the amplitude of the stochastic gravitational-wave background using the data from a tow-year scibatory (LIGO).

Our result constrains the energy density of the stochastic gravitationa-wave background normalized by the critical energy dendity of the Universe, in the frequency band around 100 Hz, to be < 6.9*10^-6 at 95% confidence.

The data rule out models of early Universe evolution with relatively large equation-of-state parameter, as well as well as cosmic (super) string models with relatively small string tension that are favoured in some string theory models.

This search for the stochastic background improves on the indirect limits from Big Bang nucleosynthesis and cosmic microwave background at 100 Hz.


### see dada / data bace ###
nature 460,925-1050 20 August 2009 Isse no 7258
Letter p.990 / An upper limit on the stochastic gravitational-wave background of cosmological origin / LIGO & Virgo
News and Views p.964 / Astrophysixs : Garavity ripples chased / Marc Kamionkowski
LIGO in the background

posted by 0≠素子 at 19:10| Comment(0) | cosmos | このブログの読者になる | 更新情報をチェックする

2009年11月14日

Gravity ripples chased

Discovering gravitational waves would not only validate Einstein's theory of gravitation but also reveal aspects of the Universe's earliest moments.

The hunt for these elusive ripples is now well under way.


For several decads, physicists have been racing to detect gravitational waves ― tiny disturbances in space-time that propagate at the seed of light.

But the experiments are challenging.

They require detection of minute changes ― a mere fraction of the size of an atomic nucleus ― in kiloletre-scale separations between free-floating masses.

Although gravitational waves have yet to be detected, on page 990 of this issue the LIGO Scientific Collaboration and the Virgo Collaboration report a milestone in this quest.

The authors imorove on a long-standing upper limit to the number of gravitational waves generated in the early Univerce.



### see dada / data bace ###
nature 460,925-1050 20 August 2009 Isse no 7258
Letter p.990 / An upper limit on the stochastic gravitational-wave background of cosmological origin / LIGO & Virgo
News and Views p.964 / Astrophysixs : Garavity ripples chased / Marc Kamionkowski
LIGO in the background

posted by 0≠素子 at 23:44| Comment(0) | astrophysics | このブログの読者になる | 更新情報をチェックする

2009年11月05日

Quantum theory in context

Quantum mechanics has had notable success in the almost 90 years since it was introduced, and its predictions have been confrmed in many experimebts.

Nevertheless, many physicists not content with the axioms of the theory have been searching for an explanation of quantum physical predictions in terms of a classical theory.

An intuitive feature of classical models in non-contextuality : the property that any measurement has a value independent of other compatible measurements being carried out at the same time.

Theory suggests that non-contextuality is in conflict with quantum mechanics, and experiments undertaken with photons and neutrons seem to support this.

However, these tests required the generation of special quantum states and left some loopholes open.

Now Kirchmair et al. have oerformed an exoeriment with trapped ions that overcomes these problems and cannot be explained in non-contextual terms.

Contextuality is therefore a property of nature that does not require the generation of special quantum states or quantum entanglement.

### DataBace ###
nature Vol.460 429-544 Issue no.7254 23 July 2009
Letter p.494
News & Views p.434
posted by 0≠素子 at 18:49| Comment(0) | quantum mechanics | このブログの読者になる | 更新情報をチェックする

2009年10月31日

Evolution has no reverse

Whether evolution can go back to an ancestral structure just by reversing the selection pressure on function has been a long-standing issue but one hard to address based on just the history of forms.

Bridgham et al. have nowphysically reconstituted ancient versions of a regulatory protein (the glucocoricoid receptor) and dissected the structural constraints imposed on the evolution of their function (which hormone they bind) at atmic resolution.

They find that amino acids that were essential in an ancestral protein become newtral in a more recent from, where they are then subject to erosion by genetic drift.

This loss deprives natural selection of the necessary raw material with which to reverse the historical substitutions ― they are no longer 'adaptive' as they were in the other direction.

Evolutionarily spealing, there is no turning back.


### DataBace ###
nature Vol.461 837-1018 Issue no.7266 15 Octiber 2009
Letter p.515
Abstractions p.446
posted by 0≠素子 at 18:21| Comment(0) | evolution | このブログの読者になる | 更新情報をチェックする

2009年10月30日

The seat of literacy

Studing the changes that take place in the brain when we learn to read and write is very difficult as literacy is usually achieved during childhood, when many other developmental changes occur.

An opportunity to use brain imaging to study the process arose when a group of former guerrillas in Colombia, including some who had not been taught to read as children, were reintegrated
into Colombian society.

Comparing brain architecture of 'late literates' to their illiterate compatriots highlighted a number of brain areas potentially involved in the acquisition of literacy.

Interconnections between the left and right anglular gyri in the parietal lobe emerge as important for reading irrespective of age of reading acquisition and ability.


### DataBace ###
nature Vol.461 837-1018 Issue no.7266 15 Octiber 2009
Letter p.983 / An anatomical signature for literacy / M Carreiras te al.
Abstractions p.846 / First Author

posted by 0≠素子 at 19:56| Comment(1) | brain | このブログの読者になる | 更新情報をチェックする

2009年10月29日

The inside story on place cells

Neurons known as place cells encode spatial information that is needed to guide an animal's movement.

Nearly 40 years after these cells were discovered, neuroscience gets a look at their internal dynamics.


On page 941 (see page of this issue, Haevey et al.(Harvey,c.d.,Collman,F.,Do,bec,D.A.&Tank,D.W. Nature 461,941-946/2009) deecribe a novel combination of techniques that they have used to address unresolved questions about brain function.

The experiments involve mice navigating within a virtual-reality setting while intracellular electrophysiological recordingsare made of particular neurons ― pyramidal neurons ― in the hippocampus.

The ability to gather such data adds greatly to the information thatcan be glened from the accompanying extracellular recordings.


### DataBace ###
nature Vol.461 837-1018 Issue no.7266 15 Octiber 2009
Article p.941 / Intracellular dynamics of hippocampal place cells during virtual navigation / C D Harvey et al. (Princeton University)
News and Views p.889 / Neuro Science : The insade story on place cells / Douglas Niz


posted by 0≠素子 at 22:25| Comment(0) | neuron | このブログの読者になる | 更新情報をチェックする

2009年10月26日

Place cells know their place

As we move around, spatial information is encoded and processed by 'place' cells in the hippocampus.

Each of these neurons increases its firing rate when situated in its 'place', thus equating rate coding with location.

The firing patterns of hippocampal place cells have been studied extensively over the past 40 years and theoretical models have been proposed to explain the mechanisms responsible for encoding place and time in newral circuits.

Now the development of techniques allowing intracellular recording from place cells in awake, behaving mice navigating a virtual reality maze makes it possible to test these models.

Initial results point to the existence of two subthreshold signatures of place fields : an incrase in the amplitude of membrane potential oscillations at theta frequencies and a ramp - like depolarization of baseline membrane potential.


### DataBace ###
nature Vol.461 439-558 Issue no.7263 24 September 2009
Article p.941 / Intracellular dynamics of hippocampal place cells during virtual navigation / C D Harvey et al. (Princeton University)
News and Views p.889 / Neuro Science : The insaide story on place cells / Douglas Nitz


see
posted by 0≠素子 at 18:39| Comment(0) | brain | このブログの読者になる | 更新情報をチェックする

2009年10月24日

Prion disease transmission

Chonic wasting disease (CWD) is a highly contagious prion disease that causes neurodegeneration in several species in the deer family, including the elk and moose.

The precise mechanisms of natureal CWD transmission are unresolved.

IT is known that once an animal shows signs of the disease, its excretions can contain contagious prions.

Stanley Prusiner and colleagues show that mule deer in infected with CWD begin to excrete in fectious prions in faeces long before they develop visible signs of the disease.

This suggests a plausible, natural mechanism that could explain the high incidence and efficient horizontal transmission of CWD among deer - and may also be relevant for the similarly contagious scrapie in sheep.


### DataBace ###
nature Vol.461 439-558 Issue no.7263 24 September 2009
Letter p.529 / Asymptomatic deer excrete infectious prions / G. Tamguney et al. (University of California, San Francisco)

posted by 0≠素子 at 15:21| Comment(0) | medical science | このブログの読者になる | 更新情報をチェックする
×

この広告は1年以上新しい記事の投稿がないブログに表示されております。