Evolutionary change in the insulin receptors of hystricomorph rodents

INSULIN receptors have been thought to have remained unaltered despite evolutionary changes in the hormone(1). Because insulins from hystricomorph rodents are known to be highly substituted compared with other mammalian insulins, we decided to investigate the insulin receptor of some hystricomorphs to determine whether evolutionary change had occurred within the receptor itself. Here we present the first evidence that hystricomorph rodent insulin receptors have undergone evolutionary change.     

Retinal light adaptation--evidence for a feedback mechanism

Light adaptation is the adjustment of retinal response properties to variations in ambient illumination. It enables the encoding of visual information over a millionfold intensity range, from moonlight to broad daylight, despite the relatively small dynamic range of response of visual neurones. We have studied the effects of light adaptation on the dynamics and sensitivity of visual responses of neurones in the turtle retina, by measuring the responses of horizontal cells in the retina to light which was modulated with a sinusoidal time course around various mean levels. As a quantitative measure of the transduction from light to neural signals, we calculated the gain of response at each frequency. Gain is defined as the amplitude of the modulated response component divided by the amplitude of light modulation. We report here that the gain (mV photon-1) at low temporal frequencies decreased as the mean light level increased. Over a 2 log-unit range of mean light levels, low-frequency gain was inversely proportional to the mean light level, as in Weber's law. However, at high temporal frequencies, the gain was almost independent of mean light level. Our results are reminiscent of Kelly's results on human temporal-frequency sensitivity in various states of light adaptation. We found that a family of horizontal-cell temporal frequency responses, measured at various mean light levels, could be accounted for by a negative feedback model in which the feedback strength is proportional to mean light level.     

含硫代吖啶酮的光敏体系反应动力学的研究

采用膨胀计法,在30℃的恒温条件下,研究了由N-正丁基硫代吖啶酮(NBTA)、二甲基二苯基碘钅翁盐(DMDPI)、硫代水杨酸(TS)和甲基丙烯酸甲酯(MMA)组成的光敏聚合体系在氙灯照射下的聚合反应动力学;研究了温度对光聚合反应速率的影响。结果表明,30℃下,该体系的光聚合速率与各组分的关系可用下述动力学方程式表示:Rp=K[NBTA]^0.78[DMDPI]^0.56[TS]^0.6[MMA]^0.94;随着温度的增加,光聚合速率增大。     

紫外光Fenton试剂法处理染料废水研究

采用紫外光辅以Fenton试剂对染料废水进行深度处理.通过试验,讨论了H2O2的量、FeSO4·7H2O的量、pH值、紫外光波长、光照时间对染料废水COD去除率的影响,选定了最佳条件,并进一步作了循环式流动态试验,为染料废水的深度处理提供了依据.     

灵敏的共振光散射测定核酸的新方法

在表面活性剂十六烷基三甲基溴化铵(CTAB)存在下，姜黄素能与核酸发生作用．研究表明，在pH=4．3的BR(Britton—Robinson)缓冲溶液中，核酸与阳离子表面活性剂CTAB可协同增强姜黄素的共振光散射(RLS)强度，其增强程度与核酸的浓度在一定范围内呈良好的线性关系．在最佳实验条件下，鱼精子脱氧核糖核酸(fsDNA)，小牛胸腺脱氧核糖核酸(ctDNA)和酵母核糖核酸(yRNA)的线性范围分别为1～1000mg／L，3～1000mg／L和1～1000mg／L，检测限分别为：0．10，0．30和0．25mg／L．该方法已成功用于合成样品的测定．     

一种基于光点位置敏感器件的风速风向测试系统设计

以二维位置敏感检测器(PSD)为核心器件设计了二维风速风向测试系统,系统采用激光作为光源,光源射在PSD上的位置反映了环境风速和风向的大小.简要介绍了PSD的原理和特点,分析了测试系统的工作原理,利用矢量计算给出了风速和风向的计算方法.制作了测试系统,并对PSD位置定位和风速风向的关系进行了测试.该系统的风速测量范围在0～30 m/s,未经放大处理时,分辨率可达0.15 mV/(m·s-1),风向测试的平均误差小于7°.该传感系统结构简单,测试方便,受环境温度影响小.选择合适的风敏竿,可以进一步增加测试灵敏度和拓宽测量量程.     

Ghrelin induces adiposity in rodents

The discovery of the peptide hormone ghrelin, an endogenous ligand for the growth hormone secretagogue (GHS) receptor, yielded the surprising result that the principal site of ghrelin synthesis is the stomach and not the hypothalamus. Although ghrelin is likely to regulate pituitary growth hormone (GH) secretion along with GH-releasing hormone and somatostatin, GHS receptors have also been identified on hypothalamic neurons and in the brainstem. Apart from potential paracrine effects, ghrelin may thus offer an endocrine link between stomach, hypothalamus and pituitary, suggesting an involvement in regulation of energy balance. Here we show that peripheral daily administration of ghrelin caused weight gain by reducing fat utilization in mice and rats. Intracerebroventricular administration of ghrelin generated a dose-dependent increase in food intake and body weight. Rat serum ghrelin concentrations were increased by fasting and were reduced by re-feeding or oral glucose administration, but not by water ingestion. We propose that ghrelin, in addition to its role in regulating GH secretion, signals the hypothalamus when an increase in metabolic efficiency is necessary.     

地下鼠对洞道环境适应机制的研究进展

从器官结构和生理功能、氧稳态有关功能蛋白的分子结构及其基因的表达方面综述了地下鼠对低氧、高二氧化碳洞道环境的适应机制。