Advances in preparation and application of monodisperse colloidal silica particles

The applications of monodisperse colloidal silica particles are constantly extended because of their uniformity in morphology and size as well as their easily-modified surface properties. This review summarizes the research progress made by the author and co-workers on the formation conditions and mechanism of monodisperse system and the applications in various fields such as particle analysis, chromatography, catalysis, optical physics, and intelligent materials.     

Topography and synaptic shaping of direction selectivity in primary auditory cortex

The direction of frequency-modulated (FM) sweeps is an important temporal cue in animal and human communication. FM direction-selective neurons are found in the primary auditory cortex (A1), but their topography and the mechanisms underlying their selectivity remain largely unknown. Here we report that in the rat A1, direction selectivity is topographically ordered in parallel with characteristic frequency (CF): low CF neurons preferred upward sweeps, whereas high CF neurons preferred downward sweeps. The asymmetry of 'inhibitory sidebands', suppressive regions flanking the tonal receptive field (TRF) of the spike response, also co-varied with CF. In vivo whole-cell recordings showed that the direction selectivity already present in the synaptic inputs was enhanced by cortical synaptic inhibition, which suppressed the synaptic excitation of the non-preferred direction more than that of the preferred. The excitatory and inhibitory synaptic TRFs had identical spectral tuning, but with inhibition delayed relative to excitation. The spectral asymmetry of the synaptic TRFs co-varied with CF, as had direction selectivity and sideband asymmetry, and thus suggested a synaptic mechanism for the shaping of FM direction selectivity and its topographic ordering.     

水中胶体微粒在管道中的对流传质分析

对常物性条件下，水中含有的金属腐蚀产物微小颗粒在管道中的层流与紊流对流传质，在壁面上杂质的质量分数或质流密度为常数的条件下进行了理论分析和数值计算，给出了对流传质问题的理论解及计算关联式。结果表明：Ｌｅ越大，扩散边界层越薄。质量分数的剧烈变化发生在紧靠壁面的一薄层内。对于紊流对流传质，当离管壁的量纲为一的距离小于６时的质量分数分布对传质的影响甚大，因此，对紊流传质必须采用修正的紊流模型，而不能简单地假设紊流施密特数等于１。     

Occurrence and extracellular actions of inositol pentakis- and hexakisphosphate in mammalian brain

Although inositol 1,3,4,5,6-pentakisphosphate (InsP5) and hexakisphosphate (InsP6) have been recognized for some time as naturally-occurring metabolites of inositol, their occurrence in mammalian cell types, including one of neural origin, has only recently been documented. This is of interest because of the recognized second messenger role of inositol 1,4,5-trisphosphate (InsP3) in intracellular signalling; coupling surface stimuli to cytoplasmic calcium discharge. The metabolism, existence in normal mature tissues, and possible functional roles of these inositol polyphosphates are unknown. Here we report evidence that InsP5 and InsP6 are synthesized in intact brain after labelling with [3H]inositol in vivo. We also show that local infusion of InsP5 and InsP6 into a discrete brain stem nucleus implicated in cardiovascular regulation, results in dose-dependent changes in heart rate and blood pressure.     

Long-term in vivo imaging of experience-dependent synaptic plasticity in adult cortex

Do new synapses form in the adult cortex to support experience-dependent plasticity? To address this question, we repeatedly imaged individual pyramidal neurons in the mouse barrel cortex over periods of weeks. We found that, although dendritic structure is stable, some spines appear and disappear. Spine lifetimes vary greatly: stable spines, about 50% of the population, persist for at least a month, whereas the remainder are present for a few days or less. Serial-section electron microscopy of imaged dendritic segments revealed retrospectively that spine sprouting and retraction are associated with synapse formation and elimination. Experience-dependent plasticity of cortical receptive fields was accompanied by increased synapse turnover. Our measurements suggest that sensory experience drives the formation and elimination of synapses and that these changes might underlie adaptive remodelling of neural circuits.     

A laminin-like adhesive protein concentrated in the synaptic cleft of the neuromuscular junction

A striking example of topographic specificity in synapse formation is the preferential reinnervation of original synaptic sites on denervated muscle fibres by regenerating motor axons. This specificity is mediated by the basal lamina of the synaptic cleft. A glycoprotein, s-laminin, has now been identified that is selectively associated with synaptic basal lamina and is recognized by motoneurons. Molecular cloning reveals that s-laminin is a novel homologue of laminin, a potent promoter of neurite outgrowth.     

αCaMKII过量表达增强小鼠岛叶皮层兴奋性突触传递

为了研究αCaMKII在小鼠前脑过量表达对岛叶皮层兴奋性锥体细胞基本电生理特性和突触传递的影响,利用脑片膜片钳技术研究αCaMKII-F89G转基因小鼠岛叶皮层锥体细胞的基本电生理性质及突触传递.结果显示:野生型和αCaMKII-F89G转基因型小鼠岛叶皮层锥体细胞在静息膜电位,动作电位及电流—电压曲线方面没有显著性差...     

The colour centre in the cerebral cortex of man

Anatomical and physiological studies have shown that there is an area specialized for the processing of colour (area V4) in the prestriate cortex of macaque monkey brain. Earlier this century, suggestive clinical evidence for a colour centre in the brain of man was dismissed because of the association of other visual defects with the defects in colour vision. However, since the demonstration of functional specialization in the macaque cortex, the question of a colour centre in man has been reinvestigated, based on patients with similar lesions in the visual cortex. In order to study the colour centre in normal human subjects, we used the technique of positron emission tomography (PET), which measures increases in blood flow resulting from increased activity in the cerebral cortex. A comparison of the results of PET scans of subjects viewing multi-coloured and black-and-white displays has identified a region of normal human cerebral cortex specialized for colour vision.     

Single-cell atlas of domestic pig cerebral cortex and hypothalamus

The brain of the domestic pig(Sus scrofa domesticus)has drawn considerable attention due to its high similarities to that of humans.However,the cellular composi...     

Coding of smooth eye movements in three-dimensional space by frontal cortex

Through the development of a high-acuity fovea, primates with frontal eyes have acquired the ability to use binocular eye movements to track small objects moving in space. The smooth-pursuit system moves both eyes in the same direction to track movement in the frontal plane (frontal pursuit), whereas the vergence system moves left and right eyes in opposite directions to track targets moving towards or away from the observer (vergence tracking). In the cerebral cortex and brainstem, signals related to vergence eye movements--and the retinal disparity and blur signals that elicit them--are coded independently of signals related to frontal pursuit. Here we show that these types of signal are represented in a completely different way in the smooth-pursuit region of the frontal eye fields. Neurons of the frontal eye field modulate strongly during both frontal pursuit and vergence tracking, which results in three-dimensional cartesian representations of eye movements. We propose that the brain creates this distinctly different intermediate representation to allow these neurons to function as part of a system that enables primates to track and manipulate objects moving in three-dimensional space.