Neuroendocrine differentiation in carcinoma of the breast. Tyramide signal amplification discloses chromogranin A-positive tumour cells in more breast tumours than previously realized

The aim of the study was to determine if, by means of tyramide signal amplification (TSA), the presence of chromogranin A (CgA)-positive tumour cells could be demonstrated in breast cancer cases found to be negative by conventional immunohistochemical staining. Sections from 44 cases of breast cancer (28 infiltrating ductal carcinomas, 2 lobular carcinomas, 4 ductal carcinomas in situ (DCIS), 7 lobular carcinomas in situ (LCIS), and 3 mucinous carcinomas) were stained for CgA by conventional immunohistochemical methods and by immunohistochemistry with TSA. The sections were also histologically graded and their oestrogen receptor (ER), progesterone receptor (PgR) and HER-2 oncogene status was recorded. Five of the tumours showed CgA-positive staining with the polyclonal antibody 430 with conventional methods. Thirty cases showed CgA-immunoreactive tumour cells after immunohistochemical staining with the polyclonal antibody 430 with TSA. However, eight of these also showed faint staining with the negative control antibody X0936 with TSA. One case showed immunopositivity for CgA using a monoclonal antibody without tyramide amplification and only a further two cases were positive when TSA was applied. The presence of CgA appears to be associated with a lower histological grade and may be more often found in oestrogen receptor-positive tumours.     

Localization of class i histocompatibility molecule assembly by subfractionation of the early secretory pathway

Class I molecules of the major histocompatibility complex bind peptides derived from cytosolic proteins and display them on the cell surface. This function alerts cytotoxic T cells to the presence of intracellular pathogens. Class I molecule assembly requires the association of the heavy chain with β₂-microglobulin, accompanied by peptide loading via specific transporters. This study localizes where these assembly steps take place, using monoclonal antibodies recognizing class I molecules in different assembly states to analyze subcellular fractions of the early secretory pathway. The distribution of peptide-loaded class I molecules was more localized than the distribution of the total pool of class I molecules in the early secretory pathway. Loaded molecules colocalized with the peptide transporter, free heavy chains, and the chaperone calnexin in high density rough endoplasmic reticulum (RER) membranes. These data suggest that subunit assembly and peptide acquisition occur at the same intracellular site. Class I molecules also localized to less dense subfractions of the early secretory pathway, which contained comparatively less peptide-loaded molecules than the high density RER fractions, at steady state. Following a 15 °C temperature block, class I molecules accumulated in these less dense membrane fractions, indicating that these fractions represent the intermediate compartment where empty class I molecules are trapped in mutant cells. In the presence of cycloheximide, a pool of class I molecules recycling to the RER was detected, suggesting empty molecules recycle to acquire peptide.     

基于线性调频信号的高帧率超声成像系统

基于有限衍射波束的高帧率超声成像系统能实现快速成像，但由于仅通过一次发射事件成像，信噪比较低，本研究针对该问题提出一种改进方案。它采用合成孔径雷达中所使用的线性调频信号作为激励信号，在接收端则利用线性调频信号的脉冲压缩比等于信号的时间带宽积的特征，将接收信号通过匹配滤波器处理。结果表明该方案不仅能显著提高成像系统的信噪比，改善重构图像的质量，增加成像深度，而且不损失分辨率。     

长序列心电信号最佳复杂度的确定

研究了长序列心电信号的最佳复杂度。先将原始序列符号化 ,再采用 L empel- Ziv算法来计算复杂度 ,探讨影响复杂度的各种因素 ,然后对三组不同信号即正常心电、心绞痛和心肌梗塞信号进行分析。结果表明 ,采用最佳阈值比用平均值为阈值得到的复杂度更能明显地分辨出正常和异常信号 ,原始序列符号化的阈值以及信号长度直接影响序列复杂度 ,因此 ,在实际信号的复杂度测量上 ,应采用最佳阈值和最佳信号长度。     

A mixture of experts network structure for modelling Doppler ultrasound blood flow signals

Mixture of experts (ME) is a modular neural network architecture for supervised learning. This paper illustrates the use of ME network structure to guide modelling Doppler ultrasound blood flow signals. Expectation-Maximization (EM) algorithm was used for training the ME so that the learning process is decoupled in a manner that fits well with the modular structure. The ophthalmic and internal carotid arterial Doppler signals were decomposed into time-frequency representations using discrete wavelet transform and statistical features were calculated to depict their distribution. The ME network structures were implemented for diagnosis of ophthalmic and internal carotid arterial disorders using the statistical features as inputs. To improve diagnostic accuracy, the outputs of expert networks were combined by a gating network simultaneously trained in order to stochastically select the expert that is performing the best at solving the problem. The ME network structure achieved accuracy rates which were higher than that of the stand-alone neural network models.     

SH2A 基因对细胞信号转导的影响及其亚细胞定位

目的 研究Src同源域2(src homology 2，SH2)A基因在细胞信号转导中的作用并进行亚细胞定位。方法 通过RT—PCR方法扩增SH2A cDNA编码序列，构建真核重组表达载体pcDNA3．1-SH2A，利用脂质体转染肝癌Bel7402细胞、COS7细胞，检测蛋白酶C(protein kinaseC，PKC)、酪氨酸蛋白激酶(tyrosine protein kinase，TPK)、丝裂原激活蛋白激酶(mitogen activated protein kinase，MAPK)活性的改变；另构建pEGEP—SH2A，转染同前，荧光显微镜观察荧光定位。结果 测序结果显示真核重组表达载体pcDNA3．1-SH2A及pEGFP—SH2A中均含有SH2AcDNA编码序列；肝癌Bel7402细胞、COS7细胞转染pcDNA3．1-SH2A后，胞浆PKC的活性下降了40％左右，MAPK和TPK活性未见明显改变。荧光显微镜观察发现SH2A基因在细胞质中表达。结论 SH2A基因编码蛋白在PKC信号转导通路中起抑制作用；SH2A基因编码蛋白定位于细胞质。     

Electrophysiological study on the high K+ sensitivity of rat glomerulosa cells

 Elevation of extracellular potassium concentration by as little as some tenth of mM activates rat adrenal glomerulosa cells. In the present study some factors responsible for this high K⁺ sensitivity were examined. Using whole-cell voltage-clamp technique we found that both T-type and L-type voltage-dependent Ca²⁺ channels have very low threshold potential (–71 and –58 mV, resp.). By means of patch-clamp technique combined with single-cell fluorimetry we also provided evidence that the activation of I_gl, a K⁺-activated inward rectifying current is associated with Ca²⁺ influx. Both the low activation threshold of voltage-dependent Ca²⁺ channels and the function of I_gl contribute to the exceptional K⁺ sensitivity of the glomerulosa cells. Received: 30 September 1997 / Accepted: 4 November 1997     

Extensive monosynaptic inhibition of ventral respiratory group neurons by augmenting neurons in the Bötzinger complex in the cat

Summary Axonal projections and synaptic connectivity of expiratory B?tzinger neurons with an augmenting firing pattern (Bot-Aug neurons) to neurons in the ipsilateral ventral respiratory group (VRG) were studied in anaesthetized cats. Antidromic mapping revealed extensive axonal arborizations of Bot-Aug neurons (24 of 45) to the rostral or caudal VRG, with some having arbors in both regions. Of 234 pairs of neurons studied with intracellular recording and spike-triggered averaging, monosynaptic inhibitory postsynaptic potentials (IPSPs) were evoked in 49/221 VRG neurons by 38/98 Bot-Aug neurons. The highest incidence of monosynaptic inhibition was found in inspiratory bulbospinal neurons (10 of 23 tested). Evidence was also found for monosynaptic inhibition, by a separate group of Bot-Aug neurons, of expiratory bulbospinal neurons (12/58), while excitatory postsynaptic potentials (EPSPs) were identified in another two of these neurons. In addition, monosynaptic IPSPs were recorded from 13 of 53 identified laryngeal motoneurons, and from 14 of 100 respiratory propriobulbar neurons. Presumptive disynaptic IPSPs were recorded from 11 of the 221 VRG neurons. We conclude that Bot-Aug neurons exert widespread inhibition on all major neuron categories in the ipsilateral VRG, and should be regarded as an important element in shaping the spatiotemporal output pattern of both respiratory motoneurons and premotor neurons.