阈值前病变１型和阈值期早产儿视网膜病变的激光和冷冻治疗

目的评价激光和（或）冷冻治疗阈值前病变１型和阈值期早产儿视网膜病变(ROP)的疗效。方法回顾分析2003年 1 月30日至2005年1月13日期间通过ROP筛查发现并施行视网膜激光和（或）冷冻治疗的阈值前病变１型和阈值期ROP共15例（29只眼），随访比较治疗前后的ROP病变情况，记录任何有关的局部和全身并发症。结果激光和（或）冷冻治疗的29只眼中，19只眼（65.5%）病变完全退化，7只眼（24.1%）残存牵引状视网膜，3只眼（10.3%）进展为视网膜脱离。初次治疗病变即完全退化者12只眼（41.4%），再次治疗后完全退化者7只眼（24.1%）。治疗中2只眼出现一过性角膜混浊，1只眼发生玻璃体积血，1只眼黄斑区误光凝1处。所有病例均未出现全身并发症。结论对阈值前病变１型和阈值期ROP进行及时的激光和（或）冷冻治疗具有比较满意的疗效。（中华眼底病杂志，2005，21：278-281）     

一种基于小波变换消除图像噪声方法

提出了一种基于小波变换消除图像噪声方法。该方法包括水平、垂直和对角线多个方向一维（1D）与二维（2D）两个小波变换消噪处理过程,汲取了1D方向数组小波变换消噪能较好保持方向性边沿的优点,消除了2D图像小波变换阈值法消噪造成的边沿模糊。与常规方法相比,此方法在有效抑制噪声的同时,能较大程度保留图像边沿。经实际噪声图像测试,具有误差小、信噪比高的特点。     

正常人手部神经感觉定量的测定

目的：研究正常人手部定量感觉测试（QSD的阈值及意义。方法：检测230例正常人左手大小鱼际肌的冷觉、温觉、冷痛觉、热痛觉，对其中28例右手做相同测试，对其中21例2周后做重复测试。结果：本组正常人QST测试的重复性较好，左右手QST阈值左右侧之间差异无显著性。各年龄段温度觉阈值存在显著性差异。结论：年龄对定量感觉检查影响显著，应该按年龄段制定正常参考值。定量感觉检查具有可重复性。身体两侧同一部位定量感觉检查具有对称性。     

Classes of feedforward neural networks and their circuit complexity

This paper aims to place neural networks in the context of boolean circuit complexity. We define appropriate classes of feedforward neural networks with specified fan-in, accuracy of computation and depth and using techniques of communication complexity proceed to show that the classes fit into a well-studied hierarchy of boolean circuits. Results cover both classes of sigmoid activation function networks and linear threshold networks. This provides a much needed theoretical basis for the study of the computational power of feedforward neural networks.     

The effects of chronic administration of ethanol on startle thresholds in rats

The thresholds for startle responses to electric shock were measured in adult male Wistar strain rats given ethanol daily in doses rising from 3 to 7 g/kg over a 30-day period, and in controls receiving equicaloric doses of sucrose. Tests made 23, 36, or 47 h after ethanol (i.e., during partial or complete ethanol withdrawal) gave threshold values significantly lower than those obtained with sucrose-treated controls. The difference became greater after longer ethanol treatment and larger doses. However, when threshold measurements were made under the acute influence of ethanol in the experimental group, the mean values were virtually equal to those of the sucrose controls. This normalization, by ethanol, of a disturbance produced by absence of ethanol in a chronically treated animal is indicative of physical dependence. Following termination of ethanol treatment there was a gradual return of startle thresholds almost to control values over a relatively short period, indicating that the changes underlying the hyperexcitability are readily reversible.     

Pain perception in man after long term spinal cord stimulation

Summary Thresholds of non-painful and painful perception for electrical stimuli are not altered significantly during dorsal column stimulation either in the area of induced paresthesia or outside it.After long term stimulation of the dorsal column the thresholds for stimuli are significantly higher within the area of induced paresthesia but not outside it.Median nerve evoked somatosensory cortical potentials are not altered by conditioning or simultaneous DC stimulation.During DCS in three of eight patients only the vibration evoked cortical potentials were attenuated in the early three components of the potential.Supported by Sonderforschungsbereich Hirnforschung und Sinnesphysiologie (SFB 70) der Deutschen Forschungsgemeinschaft (DFG) and Bundesminister für Arbeit und Sozialordnung     

Utility of a dynamic termination criterion in the ZEST adaptive threshold method

Bayesian adaptive threshold procedures may be run for a fixed number of trials, or may be stopped when the calculated confidence interval for the threshold reaches a selected limit (a dynamic termination criterion). This study used Monte-Carlo simulations to determine whether the confidence interval is a useful predictor of errors in the estimated threshold. No difference was found between the distribution of errors in a fixed trial procedure versus a dynamically terminated procedure of the same average number of trials. In addition, the width of the confidence interval failed to usefully predict observer variability arising from a shallow psychometric function slope or increased false positive response probabilities. This study suggests that dynamic termination criteria are of little use in Bayesian adaptive threshold procedures.     

Evaluation of nonthreshold leukemogenic response to methyl nitrosourea in p53-deficient C3H/He mice

The classic controversy of whether genotoxic chemicals induce cancers with or without a certain low-dose limit, i.e., the threshold, is revisited because of a number of current publications available addressing the plausibility of "practical" thresholds even for genotoxic carcinogens, the mechanism of which may be hypothesized to be due, in part, to a repair system composed of ordinarily available various defense mechanisms under the steady-state DNA damage. The question of whether an absolute nonthreshold or a relative nonthreshold, i.e., a "practical" threshold specifically in the low-dose level, is present may not be answered even with the use of a prohibitively large number of wild-type mice. Could the excessive incidence of tumorigenesis in p53-deficient mice contribute to our understanding of the threshold vs nonthreshold issue in genotoxic carcinogenesis? This is considered because an exaggeration of tumorigenesis in p53-deficient mice is hypothesized to reduce or eliminate the range of threshold due to the p53-deficiency-mediated reduction of DNA repair and apoptosis. The present study of chemical leukemogenesis in p53-deficient mice by transplantation assay was designed to answer this question. Briefly, 218 C3H/He mice were lethally irradiated and repopulated with bone marrow cells from wild-type, heterozygous p53-deficient, and homozygous p53-deficient C3H/He mice. This was followed by treatment with a single and graded dose of methyl nitrosourea at 6.6, 14.8, 33.3, 50.0, and 75.0 mg/kg body wt, with the vehicle-treated control groups treated with zero dose for each genotype. Whereas mice repopulated with p53-deficient bone marrow cells showed a marked reduction of the threshold for leukemogenicity, mice repopulated with wild-type bone marrow cells did not exhibit leukemia at a dose of 33.3 mg/kg body wt and showed a curve with a high probability for the linear regression model with a positive dose intercept, predicting a threshold by the likelihood ratio test. Thus, the failure of wild-type mice to show an increase in incidence of leukemogenesis at low doses of genotoxic carcinogens may be due not to a statistical rarity, but to various p53-related pharmacophysiological functions, possibly including DNA repair and apoptosis that may account for a threshold.     

缝隙连接蛋白Cx43基因在针刺镇痛中的作用

目的:探讨缝隙连接蛋白Cx43与针刺镇痛作用的相关性。方法:选用缝隙连接蛋白Cx43基因敲除小鼠,随机分为4组:野生型(widetype,WT)对照组、野生型针刺组、杂合子(heterozy-gous,HT)对照组、杂合子针刺组。分别通过热板、扭体法致痛,观察针刺对杂合子和野生型小鼠镇痛作用的不同效应。结果:杂合子和野生型小鼠的基础痛阈值差异无显著性意义(P>0.05)。针刺能明显提高野生型和杂合子小鼠热板致痛的痛阈值;延长首次扭体潜伏期,减少扭体反应次数,与针刺前相比,差异分别有非常显著(P<0.01)和显著性意义(P<0.05)。针刺后,杂合子小鼠的痛阈值、首次扭体潜伏期和扭体反应次数与野生型相比,差异有显著性意义(P<0.05)。结论:敲除缝隙连接蛋白Cx43基因可部分抑制针刺镇痛效应,提示Cx43与经络及针刺镇痛效应具有一定的相关性。     

Influence of Forward Head Posture on Myotonometric Measurements of Superficial Neck Muscle Tone,Elasticity, and Stiffness in Asymptomatic Individuals With Sedentary Jobs

ObjectiveThe objective of the study was to assess the influence of forward head posture on the mechanical parameters and pressure pain threshold of superficial neck muscles in clinically nonsymptomatic individuals with sedentary jobs.MethodsTwenty-five office workers with forward head posture and 25 office workers with normal head posture were matched for sex, age, body mass index, and the nature and duration of their work and were compared at a single point. The study participants were divided into study groups on the basis of photometric craniovertebral angle measurements. The upper trapezius, sternocleidomastoid, and splenius capitis mechanical properties were assessed in the sitting position. Primary outcome measures were muscle stiffness (N/m), muscle tone (Hz), and muscle elasticity. The secondary variable was perceived pain threshold.ResultsNo significant differences between the groups were found for biomechanical properties and perceived pain threshold in the studied muscles.ConclusionForward head posture has no impact on muscle stiffness, tone, and elasticity, nor does it increase the pressure sensitivity of superficial neck muscles in healthy, mildly symptomatic office workers. It is most likely that not incorrect posture of the cervical spine, but probably other factors combined with forward head posture, like comorbid acute and chronic cervical pain and musculoskeletal disorders or prolonged sitting, contribute to changes in active myofascial tone and tensegrity as well as increased pressure sensitivity of neck muscles.