Variability of the pattern electroretinogram

Conflicting results have been obtained concerning the parametric properties of the pattern electroretinogram. These discrepancies may be due to the large amount of variability inherent in recording amplitudes. We have found the variability within a single stimulus condition to be so large (ranging from 30% to 67% of the mean value) that it could mask any underlying spatial frequency tuning. Changing the stimulus conditions failed to significantly reduce the observed variability, although changing recording conditions produced some reduction. The use of a narrower rejection band, a greater number of sweeps, and placement of the reference electrode on the ipsilateral ear (as opposed to the ipsilateral temple) combined to decrease variability of the pattern electroretinogram within a single recording session; however, intersession variability remained high. Therefore one must be careful in evaluating data from this technique, and caution is advised in its clinical use.     

Influence of individually estimated portion size on the assessment of nutritional risk in colorectal cancer in Portugal

We evaluated the influence of individually estimated portion sizes on the estimate of nutrient related risk of colorectal cancer, using data from a Portuguese hospital based case-control study on diet and colorectal cancer. A total of 100 patients with colorectal adenocarcinoma (aged 15-92 years) and 211 controls (aged 36-89 years) were included. Two data sets were created for nutrient analysis, the first one allowed estimates of food intake using data on portion size as collected with visual aids during the interview. The second estimate substituted respondents' estimate with a standard portion size, as used in the semi-quantitative (SQ) food frequency approach. The two analytic approaches yielded similar energy and nutrient intakes in cases and controls. The percent range of concordance is acceptable, in the same quartile varying from 44 to 82% (mean: 56%) and very good in the same or adjacent (+/-1) quartile (mean: 91%, range: 85-97%). The two estimates lead to a similar pattern of multivariate odd's ratio, however the SQ estimates resulted in more significant findings. We conclude that little extra information is gained by including individual portion size information when assessing diet-related risk of colorectal cancer.     

Alpha and gamma motoneurons in the peroneal nuclei of the cat spinal cord: an ultrastructural study.

The aim of the present study was to investigate whether ultrastructural features can be used as a guide to identify alpha- and gamma-motoneurons among the intermediate-size neurons of the peroneal motor nuclei. The peroneus brevis and peroneus tertius muscles of adult cats were injected with horseradish peroxidase, and motoneurons labeled by retrograde axonal transport were examined by electron microscopy. In both nuclei, the distributions of cell-body diameters, measured in the light microscope, were bimodal covering the range of 28-84 microns, with a trough around 50 microns. The sample of 25 motoneurons selected for the ultrastructural study included not only large (presumed alpha) and small (presumed gamma) neurons but also intermediate-size cell bodies with diameters in the 40-60 microns range. For each motoneuron, 2-5 profiles were reconstructed from ultrathin sections taken at 6-8 microns intervals. Synaptic boutons were counted and their lengths of apposition were measured. On the basis of three criteria, namely: (1) bouton types present on the membrane, (2) percentage of membrane length covered by synapses, and (3) the aspect of the nucleolus, all the examined motoneurons, including those with intermediate sizes, fell into one of two categories. Fourteen motoneurons, with cell-body diameters in a range of 55-84 microns, were contacted by all types of boutons (mainly S-type with spherical vesicles, F-type with flattened vesicles, and C-type with subsynaptic cistern); the synaptic covering of the somatic membrane was over 40% and the nucleus contained a vacuolated nucleolus. These were considered alpha-motoneurons. Eleven motoneurons, with only S and F boutons, a synaptic covering under 30%, a compact nucleolus and a cell-body diameter ranging between 28 and 50 microns, were considered gamma-motoneurons. No other combination of the three criteria was observed. These results show that unequivocal distinction of alpha- and gamma-motoneurons is possible in the peroneal nuclei, on the basis of morphological differences independent of cell-body size.     

乳头溢液性疾病的高频超声与乳腺导管声学造影的对比研究

目的:探讨乳腺导管声学造影对乳头溢液性病变的诊断价值。方法:34例乳头溢液患者术前均行高频超声及声学造影检查,所有检查结果均与手术病理结果比较。结果:乳头溢液疾病高频超声及声学造影检查结果与手术病理结果比较诊断符合率分别为61.7%及79.4%,二者比较差异无统计学意义(P>0.05)。导管内乳头状瘤高频超声与声学造影诊断符合率分别为40%及73.3%,二者比较差异有统计学意义(P<0.05)。结论:乳腺导管声学造影可提高导管内小病变的检出率,显示详细的病变部位及扩张的导管,为手术提供重要的参考依据。尤其是导管内乳头状瘤声学造影检查明显优于高频超声检查。此种检查简单、方便、准确性较高,可作为乳头溢液性疾病的首选检查方法。     

Optimization of self-reference thermometry using complex field estimation.

Referenceless, or self-reference, thermometry is a technique for mapping temperature differences in the region of interest (ROI) using the baseline phase estimated by extrapolating the field in the surrounding region for estimation (RFE) and subtracting the estimated baseline from the measured field. In the present work a self-reference technique based on complex field estimation using 2D polynomials comprising complex-valued coefficients was proposed and optimized. Numerical simulations with a Gaussian-profiled phase distribution demonstrated that the ROI radius had to be 2.3-2.5 times the standard deviation (SD) of the Gaussian function in order to keep the error below 8% of the peak phase change. The area ratio between the ROI and the RFE had to be larger than 2.0 to maintain the error level. Based on the simulations, and phantom and volunteer experiments, the complex-based method with independently optimized polynomial orders for the two spatial dimensions was compared with the phase-based method using the similar-order optimization strategy. The complex-based method appeared to be useful when phase unwrapping was not removed. Otherwise, the phase-based method yielded equivalent results with less polynomial orders.     

Separation discrimination with embedded targets

Previous research has shown that separation discrimination thresholds are independent of the internal spatial scale (local spatial frequency) of the targets whose separation is being judged. The experiments reported here tested the generality of this conclusion for separation discrimination of targets that were embedded in an array of identical objects, where crowding could enhance the importance of the scale at which the individual target locations are encoded. No effect of the local spatial scale of the targets was found under these conditions.     

高频喷射通气结合胸壁挤压对组胺致肺损伤犬呼吸循环功能的影响

以高频喷射通气结合胸壁挤压（ＨＦＪＶ＋ＣＷＣ）为通气模式，观察其对组胺致肺损伤犬呼吸循环功能的影响，并与单纯高频喷射通气（ＨＦＪＶ）进行比较。结果表明：与ＨＦＪＶ相比，ＨＦＪＶ＋ＣＷＣ时的功能残气量（ＦＲＣ）、ＰａＣＯ＿２和ＰＣＯ＿２均显著降低（Ｐ＜０．０１），肺泡通气量（Ｖ＿Ａ）和二氧化碳排出量（ＣＯ＿２）均显著增高（Ｐ＜０．０１），每分呼出气量（Ｖ＿Ｅ）、ＰａＯ＿２、ＰＣＯ＿２、吸气峰压（ＰＩＰ）、平均气道压（Ｐａｗ）、呼气末压（ＥＥＰ）、ＨＲ、平均动脉压（ＭＡＰ）、肺动脉压（ＰＡＰ）和肺毛细血管楔压（ＰＣＷＰ）均无显著变化（Ｐ＞０．０５）。提示：ＨＦＪＶ＋ＣＷＣ除保留单纯ＨＦＪＶ时气道开放、气道低压、良好的血液氧合、不影响循环功能等特点外，还具有增加呼气动力，改善肺泡通气，显著促进ＣＯ＿２排除等优点。     

高频喷射通气时麻醉犬动脉血二氧化碳分压的估计

作用测定５－８次常频呼吸后呼气末二氧化碳分压的方法，探讨了高频喷射通气时麻醉犬动脉脉血二氧化碳分压与Ｐｅｔｃｏ２的关系，结果表明，在通气频率分别为６０，１００及２００次／ｍｉｎ时，Ｐｅｔｃｏ２和Ｐａｃｏ２均无显性差异，Ｐｅｔｃｏ２呈显相关（ｒ＝０．８３，Ｐ＜０．０１）。结果提示，测定５－８次常频呼吸后的Ｐｅｔｃｏ２可较准确地评估ＨＦＪＶ时麻醉犬的Ｐａｃｏ２。     

神经网络分析方法用于心脏病诊断的研究

神经网络可以很好的拟合任意的非线性函数。我们从 QRS波群的高频三维频谱中提取出一些定量的特征参数 ,用神经网络的方法对这些参数进行有监督的学习训练 ,最终能在由这些特征参数张成的 m维空间中构建出一个 m维的曲面来区分病人和健康人的 QRS波群高频三维频谱 ,从而使得训练后的网络能基于 QRS波群的高频三维频谱自行诊断出病人和健康人     

丘脑底核高频电刺激对大鼠纹状体多巴胺代谢影响的研究

目的研究丘脑底核(STN)高频电刺激(HFS)对大鼠纹状体多巴胺(DA)代谢的影响。方法给予正常大鼠一侧STN-HFS,应用微透析观察其对纹状体DA及其代谢产物的影响,应用免疫组化观察其对黑质DA能神经元的影响。结果微透析检测发现刺激侧纹状体DA代谢产物明显增高(P<0.05),DA水平无变化(P>0.05);免疫组化检测发现刺激组和对照组酪氨酸羟化酶(TH)阳性神经元数量无差异(损毁侧分别为24.00±6.81、23.43±5.49,P>0.05)。结论STN-HFS可能通过影响黑质-纹状体DA代谢发挥作用,STN-HFS对黑质DA能神经元可能无保护作用。