Reaching out: Cortical Mechanisms of Directed Action

Recordings from monkey cortex have demonstrated a sophisticated neural mechanism for the complex transformational mapping demanded by visually guided reaching.     

Chromosome Organization: Reaching out to Embrace New Models

New information on the architecture of protein complexes involved in the dynamic organization of chromosomes challenges existing models of their structures and provides fresh insight into their mechanisms of action.     

Reaching out for signals: filopodia sense EGF and respond by directed retrograde transport of activated receptors

ErbB1 receptors situated on cellular filopodia undergo systematic retrograde transport after binding of the epidermal growth factor (EGF) and activation of the receptor tyrosine kinase. Specific inhibitors of the erbB1 receptor tyrosine kinase as well as cytochalasin D, a disruptor of the actin cytoskeleton, abolish transport but not free diffusion of the receptor-ligand complex. Diffusion constants and transport rates were determined with single molecule sensitivity by tracking receptors labeled with EGF conjugated to fluorescent quantum dots. Retrograde transport precedes receptor endocytosis, which occurs at the base of the filopodia. Initiation of transport requires the interaction and concerted activation of at least two liganded receptors and proceeds at a constant rate mediated by association with actin. These findings suggest a mechanism by which filopodia detect the presence and concentration of effector molecules far from the cell body and mediate cellular responses via directed transport of activated receptors.     

Reaching for answers

The exact function of motor cortex continues to be an enigma. In this issue of Neuron, present provocative data showing that microstimulation of the precentral cortex evokes complex movements, and conclude that the motor and premotor cortex together may form a single map of complex postures.     

Out of the shade and into the light

Plants reach for the sun by avoiding the shade and by directly growing towards the light. Two studies now suggest that the polar relocation of PIN3, a transporter directing the flow of the plant hormone auxin, drives both growth processes. PIN3 repolarization occurs downstream of shade perception through phytochrome photoreceptors, whereas blue light perceived by phototropin initiates polar recycling of PIN3 and growth towards the light.     

心跳蓝天门

一直没有想过,一张漂亮的照片里面包含了摄影师怎样的辛劳和汗水,甚至是血泪。而今天,在周海翔的身上,我想我看到了比他照片更可贵也更美的东西,就是他那种舍命拍片的精神。在一般人的眼中,他甚至是带着一种病念的狂热和执著,追寻自然婀娜美丽的身影。那,应该是对大自然最高的赞美吧?     

Reaching maturity - 25 years of the TDR

In its first 25 years of existence, TDR has become a key player in the development of new tools for the control of tropical diseases and the training of researchers from disease-endemic countries. In order to maintain its leading position, cope with new health challenges and profit from new avenues opened by science and technology breakthroughs, a new strategic vision is now being implemented. It aims at a closer interaction with health systems and disease control programmes, capacity strengthening based on selected research initiatives and full exploitation of scientific and technological advances in the biomedical, social and information sciences, as discussed here by Carlos Morel.     

Inter- and intraspecific relationships between shade tolerance and shade avoidance in temperate trees

Patterns of physiological and architectural adaptation and acclimation to decreasing light availability were investigated along a light gradient for saplings of 12 common species of temperate deciduous trees in southeastern Ontario, Canada. Physiological adaptation and acclimation (shade tolerance physiology) were quantified at the leaf level by measuring leaf mass per unit area (LMA), dark respiration per unit leaf nitrogen, chlorophyll per unit leaf nitrogen and the chlorophyll a:b ratio for the newest fully expanded leaf on the leader. Architectural adaptation and acclimation (shade avoidance) were quantified by measuring branching intensity and side shoot:main shoot length ratios for the most recent three years of growth on the leader and selected side branches. Within species, increases in LMA, chlorophyll a:b ratio and respiration per unit nitrogen and decreases in chlorophyll per unit nitrogen indicated that shade tolerance physiology generally increased with decreasing canopy openness. Increases in the branching intensity and side shoot:main shoot ratios of the leader and side branches indicated that shade avoidance also increased with decreasing canopy openness for the majority of species; however, in some species, stem bending under deep shade resulted in lateral growth. Interspecific variation in shade tolerance physiology was minimal when species were compared under equal amounts of canopy openness. In contrast, interspecific variation in shade avoidance variables was relatively high under equal canopy openness, with saplings of shade tolerant canopy species exhibiting higher shade avoidance than saplings of shade tolerant understory species.