千频交流电刺激在外周神经传导阻断中的作用

感觉、运动或自主神经系统的异常病理活动与疼痛和痉挛等多种神经机能障碍有关。千频交流电（kilohertz frequency alternating current，KHFAC）刺激是一种阻断异常病理活动在外周神经内传导的有效方法，它在缓解相关神经机能障碍方面具有临床应用潜力。KHFAC产生的神经传导阻断受千频信号波形和参数、阻断电极设置和位置以及神经纤维类型和直径等因素影响，具有快速性、可控性、可逆性、局部作用和副作用小的特点。但是，在产生完全传导阻断前，KHFAC首先在靶向神经上激活一簇高频初始放电，这种初始响应可能导致肌肉抽搐或疼痛感。同时，在撤去KHFAC后处于阻断状态的靶向神经需要经历一段时间才能恢复正常传导能力，这是该技术导致的后续效应。目前，关于KHFAC阻断神经传导的生物物理机制假说包括千频信号诱发K⁺通道激活和Na⁺通道失活。本文首先介绍了KHFAC技术的电生理实验研究方法和计算模型仿真方法，然后综述目前关于KHFAC作用下神经传导阻断的研究进展，重点论述初始响应特性及消除方法、传导阻断的后续效应、刺激波形和参数的影响、电极设置与位置的影响以及该技术潜在的临床应用，同时归纳KHFAC阻断神经传导的生物物理机制，最后对该技术未来的相关研究进行展望。     

Neuromodulatory Control of Neocortical Microcircuits with Activity-Dependent Short-Term Synaptic Depression

A biophysical model of a neocortical microcircuit system is formulated and employed in studies of neuromodulatory control of dynamics and function. The model is based on recent observations of reciprocal connections between pyramidal cells and inhibitory interneurons and incorporates a new type of activity-dependent short-term depression of synaptic couplings recently observed. The model neurons are of a low-dimensional type also accounting for neuronal adaptation, i.e. the coupling between neuronal activity and excitability, which can be regulated by various neuromodulators in the brain. The results obtained demonstrate a capacity for neuromodulatory control of dynamical mode linked to functional mode. The functional aspects considered refer to the observed resolution of multiple objects in working memory as well as the binding of different features for the perception of an object. The effects of neuromodulators displayed by the model are in accordance with many observations on neuromodulatory influence on cognitive functions and brain disorders.     

Quantifying structural changes and stoichiometry of protein interactions using size and density profiling

Summary The use of Dual Polarisation Interferometry, and emerging analytical biophysical technique, is described for the determination of the optogeometrical properties (thickness and density) at high resolution of adsorbed protein layers at the solid-liquid interface. The technique has been used to quantify, in real time and at subatomic resolution, the structural changes occurring in two well-characterised protein interaction systems, an antibody-antigen interaction and the biotin-streptavidin interaction. The realtime data obtained on structural changes during the interactions is in excellent agreement with previously reported X-ray crystallography and neutron reflection data. The precision of the measurements taken was of the order of 0.01 nm with respect to protein size. The dual-parameter approach also allowed the stoichiometry of both of these interactions to be calculated, giving values that confirm the current understanding of the interactions. This approach provides detailed insights into the inherent and subtle link between structural change and function in proteins, to a degree not previously possible through mass change measurements alone. The technique is expected to find utility in the increasingly important study of protein structure and function.     

Estimating clear-day solar radiation: An evaluation of three models

Three models for estimating clear-day solar radiation were compared to one another and to values of solar radiation measured at Ft Collins, Colo. The models of Campbell (1977), Gates (1962) and McCullough and Porter (1971) all correlate closely with measurements of clear-day solar radiation. The Campbell and the Gates models require less technical expertise and less expensive computations to produce estimates of the direct component of solar radiation. All of the models appear to require calibration in order to correct estimates of the input variables to measured values of irradiance so that accurate calculations of direct solar radiation can subsequently be made. The best estimates of the diffuse component of solar radiation are obtained from the model of McCullough and Porter. The easiest and most accurate predictions of total solar radiation can be obtained from the direct-radiation models of Campbell (1977) and Gates (1962) and a modification of the diffuse-component model of McCullough and Porter (1971).     

The Analysis of Synaptically Generated Traveling Waves

Mathematical and computational models for the propagation of activity in excitatorily coupled neurons are simulated and analyzed. The basic measurable quantity—velocity—is found for a wide class of models. Numerical bifurcation techniques, asymptotic analysis, and numerical simulations are used to show that there are distinct scaling laws for the velocity as a function of a variety of parameters. In particular, the obvious linear relationships between speed and spatial spread or synaptic decay rate are shown. More surprisingly, it is shown that the velocity scales as a power law with synaptic coupling strength and that the exponent is dependent only on the rising phase of the synapse.