Modelled temperature-dependent excitability behaviour of a single ranvier node for a human peripheral sensory nerve fibre

The objective of this study was to determine whether the Hodgkin–Huxley model for unmyelinated nerve fibres could be modified to predict excitability behaviour at Ranvier nodes. Only the model parameters were modified to those of human, with the equations left unaltered. A model of a single Ranvier node has been developed as part of a larger model to describe excitation behaviour in a generalised human peripheral sensory nerve fibre. Parameter values describing the ionic and leakage conductances, corresponding equilibrium potentials, resting membrane potential and membrane capacitance of the original Hodgkin–Huxley model were modified to reflect the corresponding parameter values for human. Parameter temperature dependence was included. The fast activating potassium current kinetics were slowed down to represent those of a slow activating and deactivating potassium current, which do not inactivate. All calculations were performed in MATLAB^TM. Action potential shape and amplitude were satisfactorily predicted at 20, 25 and 37°C, and were not influenced by activation or deactivation of the slow potassium current. The calculated chronaxie time constant was 65.5 μs at 37°C. However, chronaxie times were overestimated at temperatures lower than body temperature.     

Protein phosphorylation in human peripheral nerve: Altered phosphorylation of a 25-kDa glycoprotein in leprosy

Protein phosphorylation in a low speed supernatant of human peripheral nerve (tibial and sural) homogenate was investigated. The major phosphorylated proteins had molecular mass in the range of 70, 55, 45, and 25 kDa. Mg²⁺ or Mn²⁺ was essential for maximum phosphorylation although Zn²⁺, Co²⁺, and Ca²⁺, could partially support phosphorylation. External protein substrates casein and histone were also phosphorylated. The protein phosphatase inhibitor orthovanadate enhanced the phosphorylation of the 45 and 25 kDa proteins significantly. Concanavalin A-Sepharose chromatography of the phosphorylated peripheral nerve proteins showed that the 25 kDa protein was a glycoprotein. Protein phosphorylation of peripheral nerves from leprosy affected individuals was compared with normals. The phosphorylation of 25 kDa protein was decreased in most of the patients with leprosy.     

人脑对不同频率穴位电刺激反应的功能性磁共振成像

利用功能性磁共振方法研究人脑对不同频率穴位体表电刺激（transcutaneous electric nerve stimulation,TENS)的反应。实验对11名志愿得进行了22次脑部功能性磁共振成像。成像过程中,每名志愿者分别接受了2和100HzTENS刺激,刺激部位为左腿足三里和三阴交穴,结果为不同频率TENS都激活了初级和次级躯体感觉区,频率特异性的激活信号出现在与运动相关的区域、丘脑、边缘系统和联络皮层。结果显示,在相同穴位给予不同频率的TENS要以在大脑引起不同的反应,提示2和100HzTENS可能激活了不同的神经通路,这些神经通路分别在中枢神经系统起着不同的作用。