Spatial summation of perceived pressure,sharpness and mechanically evoked cutaneous pain

Psychophysically, spatial summation can be demonstrated as a decrease in threshold accompanying an increased field of stimulation. The present study examined to what extent different mechanically evoked percepts (pressure, sharpness, and pain) show spatial summation. Various probes were used to apply prescribed forces to the dorsal surface of the digits of 19 healthy subjects. The threshold for three perceptual qualities showed differing degrees of spatial summation: sharpness showed no statistically significant spatial summation; pain demonstrated some significant summation (46% on average); pressure showed the greatest degree of spatial summation (76% on average). The lack of significant spatial summation for sharpness threshold is consistent with the theory that perceived sharpness can be evoked by near threshold activity of a single nociceptor. The modest amount of spatial summation for pain implies that distinctly suprathreshold activation of nociceptors is required for mechanically evoked pain perception, and such input summates centrally, but not completely. The greater spatial summation observed for pressure vs. pain thresholds implies a greater degree of central summation for slowly adapting mechanoreceptors vs. nociceptors.     

显微摄像条件对细胞形态测试结果的影响

目的:研究显微摄像条件对细胞形态测试结果的影响情况。方法:以苏木精-伊红(HE)染色的胃壁细胞为研究对象,分别在不同光亮度、对比度、饱和度和锐度的成像条件下进行显微摄像,采用图像分析软件(Image-Pro Plus 6.0)测试胃壁细胞的色度学和几何形态学参数,并对测试结果进行分析比较。结果:不同光亮度、对比度、饱和度组的胃壁细胞红、绿、蓝三基色差异均有统计学意义(P<0.05),其中红、绿、蓝基色值在高光亮度和高对比度组最高,同时红基色值在高饱和组最高,而绿、蓝基色值在高饱和组最低(P<0.05);不同锐度的胃壁细胞红、绿、蓝三基色差异没有统计学意义(P>0.05)。不同光亮度、对比度、饱和度和锐度的胃壁细胞的面积、周长、平均直径差异均没有统计学意义(P>0.05)。结论:光亮度、对比度和饱和度对细胞色度学参数影响明显,而对几何形态学参数无明显影响。