Sodium and calcium action potential in pituitary cells

Several endocrine cells or their neoplastic derivatives generate action potentials similar to those seen in neurones, and in the adrenal chromaffin cell such regenerative potentials depend primarily on a sodium mechanism. Kidokoro has described action potentials in the GH3 rat pituitary cell line which seem to depend on a calcium mechanism. We have re-investigated the action potential in GH3 cells and found that it results from combined Na and Ca mechanisms in physiological conditions. In addition, we have recorded similar electrical excitability from two human pituitary tumours grown in vitro.     

温度对荒漠沙蜥在体心脏单相动作电位的影响

采用吸附式电极记录了荒漠沙蜥在不同体温条件下 ,在体心脏的单相动作电位 (MAP:Monophasic Action Potential) .实验温度为 :5℃ ,10℃ ,15℃ ,2 0℃ ,2 5℃ ,30℃和 35℃ 7个温度等级 .结果表明 :(1)在最适温度 (2 0～ 2 5℃ )时 ,荒漠沙蜥心脏单相动作电位的基本波形与高等动物及人类基本相似 ;但也有其特殊性 :动作电位 0期除极期最大幅值为 11.4 2± 2 .5 8m V;复极 2期电位幅值基本保持恒定 ,呈平台期 (PP2 :Plateau Phase2 ) ;在复极 3期末 ,电位基本恢复到 0电位(膜电位为 0 m V) .(2 )随着体温的升高 (5～ 35℃ ) ,荒漠沙蜥心脏单相动作电位时程呈温度依赖性减小 ;0期最大除极速度 (Vmax)呈温度依赖性增加 (5℃为 77.0 8± 4 7.11m V/ms;35℃为 614.63±10 5 . 0 2 m V/ms) ;低于最适温度时 (2 0～ 2 5℃ ) ,在 2相平台期末 ,又出现一次除极电位 (后隆起波 ) .其最大电位为 0 .5 8± 0 .18m V.(3)随着体温的升高 ,荒漠沙蜥心脏单相动作电位复极 1期电位呈温度依赖性降低 (5℃为 2 .2 4± 1.31m V/ms;35℃为 0 .82± 0 .4 9m V/ms) .(4 )心电图 (ECG)的同步记录表明 :心电图中的 QRS波与心脏单相动作电位 0期除极完全相对应 ;T波与动作电位的复极 3期相对应 .     

Reconciling the temperature dependence of respiration across timescales and ecosystem types

Ecosystem respiration is the biotic conversion of organic carbon to carbon dioxide by all of the organisms in an ecosystem, including both consumers and primary producers. Respiration exhibits an exponential temperature dependence at the subcellular and individual levels, but at the ecosystem level respiration can be modified by many variables including community abundance and biomass, which vary substantially among ecosystems. Despite its importance for predicting the responses of the biosphere to climate change, it is as yet unknown whether the temperature dependence of ecosystem respiration varies systematically between aquatic and terrestrial environments. Here we use the largest database of respiratory measurements yet compiled to show that the sensitivity of ecosystem respiration to seasonal changes in temperature is remarkably similar for diverse environments encompassing lakes, rivers, estuaries, the open ocean and forested and non-forested terrestrial ecosystems, with an average activation energy similar to that of the respiratory complex (approximately 0.65?electronvolts (eV)). By contrast, annual ecosystem respiration shows a substantially greater temperature dependence across aquatic (approximately 0.65?eV) versus terrestrial ecosystems (approximately 0.32?eV) that span broad geographic gradients in temperature. Using a model derived from metabolic theory, these findings can be reconciled by similarities in the biochemical kinetics of metabolism at the subcellular level, and fundamental differences in the importance of other variables besides temperature—such as primary productivity and allochthonous carbon inputs—on the structure of aquatic and terrestrial biota at the community level.     

Profile characterization and temperature dependence of droplet control on textured surfaces

Droplet control on textured surfaces has attracted much attention in the fields of drag reduction and high-efficiency microreactors. We investigated the profile characterization and temperature dependence of droplet control between wetting and non-wetting on a series of textured silicon surfaces. Surfaces were fabricated using photolithography, and the temperature-dependent wettability of the single phase regime droplets was characterized using dynamic contact angle measurements. The experiments demonstrated that the profile of textured surfaces characterizes the droplets Leidenfrost point. The Leidenfrost point is proportional to the micro-pillar size and rectangular wave-length of the textured surface and is inversely proportional to ambient temperature. The Leidenfrost droplets moved freely on the textured surface, almost without hysteresis. Droplets could be directed on the surface of microreactors with a low driving force.     

醋酸水溶液声速与温度浓度关系研究

研究了超声波在不同温度、不同浓度醋酸水溶液中的速度传播特性.应用脉冲回波法,检测了醋酸水溶液在16～70℃温度范围及体积分数为10%～75%范围的超声波传播速度,给出了不同浓度及不同温度下的速度与温度关系曲线,实验结果和理论推导基本一致.