头颈部肿瘤射野摆位误差的差异性研究

目的：研究采用电子射野系统评价头颈部肿瘤患者摆位误差时的观察者间变异和观察者自身变异。方法：两队研究小组，分别由四名医师和四名技师组成，两组分别对6名头颈部肿瘤的患者，采用电子射野影像仪（electronic portal imaging device，EPID）拍摄验证片（electronic portal images，EPIs），在EPIs上勾画骨性标志，以放疗计划生成的数字重建图像（digitally reconstructed radiographs，DRRs）做为参考图像，定量分析不同观察研究人员之间和研究人员自身采用EPID确定头颈部肿瘤患者的射野摆位误差（field placement errors，FPEs）的差异性。结果：在前／后位射野图像上．不同医师之间、医师自身及技师自身对摆位误差的判断无明显差异，但在技师之间出现了明显的自身差异性．医师组和技师组在前／后射野图像上的均方根（root-mean—square，RMS）分别为2．52±0．46和3．43±0．43，两者具有明显差异；在侧位野图像上，医师自身对摆位误差的判断有较好的稳定性，但部分不同医师之间在腹背、头足方向上部分患者中出现差异，而不同的技师之间存在明显差异性，医师组和技师组在侧位射野图像上的RMS分别为2．72±0．16和2．62±0．22．两者无明显差异。结论：医师和技师组在采用电子射野系统对头颈部摆位误差进行判断时存在人员之间的误差，应对所有人员进行统一训练才能减少射野摆位误差，从而提高IMRT治疗效果。     

全脑全脊髓照射仰卧位CT模拟定位技术

目的：探讨全脑全脊髓照射仰卧位CT模拟定位技术。方法：7名患者分别躺在真空负压袋固定器上，进行CT模拟定位，打印正侧位数字重建射线彩像（DRR）图，放射治疗前拍摄正侧位定位验证片，测量解剖参考点和射野边界之间的距离。结果：患者左右方向及背腹方向误差在2mm以内。人体上下方向误差在4mm以内；放疗后，患者受照射的皮肤部位均出现色素沉着。结论：仰卧位全脑全脊髓照射CT模拟定位技术可用于俯卧位不合作的患者。     

腹主动脉与其主支夹角的空间定位

甲醛固定的成人尸体32具(男19,女13),造影拍片和实地解剖对照观察,测量腹主动脉主支的发出高度、起点方位、与主动脉的夹角,以及与矢状面的交角。综合以上四项指标,即能构想腹主动脉与其主支夹角的空间位置和变动范围。     

Representation of heading direction in far and near head space

Manipulation of objects around the head requires an accurate and stable internal representation of their locations in space, also during movements such as that of the eye or head. For far space, the representation of visual stimuli for goal-directed arm movements relies on retinal updating, if eye movements are involved. Recent neurophysiological studies led us to infer that a transformation of visual space from retinocentric to a head-centric representation may be involved for visual objects in close proximity to the head. The first aim of this study was to investigate if there is indeed such a representation for remembered visual targets of goal-directed arm movements. Participants had to point toward an initially foveated central target after an intervening saccade. Participants made errors that reflect a bias in the visuomotor transformation that depends on eye displacement rather than any head-centred variable. The second issue addressed was if pointing toward the centre of a wide-field expanding motion pattern involves a retinal updating mechanism or a transformation to a head-centric map and if that process is distance dependent. The same pattern of pointing errors in relation to gaze displacement was found independent of depth. We conclude that for goal-directed arm movements, representation of the remembered visual targets is updated in a retinal frame, a mechanism that is actively used regardless of target distance, stimulus characteristics or the requirements of the task.     

Changing patterns of binocular visual connections in the intertectal system during development of the frog,Xenopus laevis

Summary In the frog, Xenopus laevis, a system of intertectal connections underlies the visual projection from an eye to its ipsilateral tectal lobe and is involved in the topographic representation of binocular visual space. Rotation of one eye in early life may be followed by a radical rearrangement of the connections in this system. The modified pattern which later emerges is that which keeps the visual projection through the ipsilateral eye in topographic registration with the direct visual projection from the contralateral eye to the same tectal lobe. This plasticity requires visual experience.In this paper we describe the time-course and sequence of events by which this plasticity is effected. Following rotation of one eye in larval animals or in animals undergoing metamorphic climax, the earliest evidence of intertectal modification was found 3–4 weeks after metamorphosis. With increasing intervals after metamorphosis an increasing proportion of animals displayed modified intertectal systems. At intermediate intervals many animals showed partial modifications, which were interpreted as transitional stages in the modification process. Analysis of these transitional stages indicated that the sequence of events involved in the elaboration of a modified intertectal system following the experimental alteration of eye alignment exhibits features in common with rearrangements of the system that occur during normal development in response to growth-related alterations in eye alignment.     

Recommendations for the standardization of lead positions in surface electromyography

Summary Standardized lead positions for recording myoelectric signals are given for various muscles. The positions are given in terms of (1) the lead line connecting two anatomical landmarks and (2) the central lead point about which the electrodes are placed symmetrically on the lead line.This research was financially supported by the Sonderforschungsbereich 152 of the Deutsche Forschungsgemeinschaft     

Electrode Positioning for Reliable Telemetry ECG Recordings During Social Stress in Unrestrained Rats

We describe a surgical procedure for optimizing the location of telemetry ECG leads in rats. The new location was aimed at obtaining an accurate representation of ECG features throughout the cardiac cycle by limiting the voltage instability usually observed during intense somatomotor activity and improving the signal-to-noise ratio. The two electrodes (wire loops) were fixed on the dorsal surface of the xiphoid process and in the anterior mediastinum close to the right atrium. The implantation procedure was fast, little invasive, and allowed animals to completely recover from intervention. The performance of the “improved” location (IL, n = 10) with respect to two subcutaneous (SC) positionings (“conventional positioning,” CSP, n = 5; “updated location,” USL, n = 5) was evaluated by comparing ECGs obtained in baseline, stress and recovery conditions and during different behavioral activities (immobility and grooming). The resident-intruder test (emotional/physical challenge) was chosen as experimental stress paradigm. The noise level of ECGs obtained from IL rats was lower than in CSP and USL animals, in all recording conditions. Percentages of correctly recognized beats (CRBs) over the total number of beats (TBs) were significantly higher in IL rats than in CSP and USL animals, both in baseline conditions (99% vs. 11% and 40%) and situations involving high somatomotor activity (stress: 97%, 5% and 16%; recovery: 97%, 7%, and 15%) (p < 0.01). The performance of IL as compared to CSP and USL was also better when percentages during grooming and immobility were considered (grooming: 93% vs. 4% and 23%; immobility: 97%, 6%, and 33%; p < 0.01).     

大鼠肝再生过程中碱性磷酸酶活性变化及其超微细胞化学研究

目的 研究2／3肝切除后大鼠肝再生过程中碱性磷酸酶(AKP)活性的变化及其细胞定位。方法 利用比色法对AKP活性进行定量分析；用酶的原位复性电泳技术分析再生肝中AKP的种类和活性变化；用电镜细胞化学方法研究酶定位。结果 在肝部分切除后的肝再生期间，AKP出现两个活性高峰(16h和19h)，在每个活性高峰后，AKP均有显著下降；获得3种肝型AKP同工酶(140、160和180kD)，其中180kD的AKP只在肝再生过程中出现；随着肝再生的进展，AKP活性出现在细胞的不同部位。结论 AKP在肝再生过程中起重要作用，可能参与细胞代谢、物质转运、DNA合成和细胞分化。     

The relationship between the electromyogram-amplitude and isometric extension torques of neck muscles at different positions of the cervical spine

A group of 12 healthy men volunteered for the experiment. Electromyograms (EMG) were obtained from semispinalis capitis, splenius capitis, levator scapulae, and trapezius muscles. The flexion angle of the cervical spine was precisely adjusted to 0°, 10°, 20°, and 30° relative to the horizontal, with a constant angle of the atlanto-occipital joint. The subjects made eight short (about 2 s) vertical extension forces (6%, 12%,18%, 24%, 30%, 36%, 42%, and 48% of maximal voluntary peak contraction force). For each position, the centre of pressure under the head was determine as the basis for the calculation of the external lever arm. The presence of motor endplate regions was ascertained by multiple surface electrodes. The slopes of individual linear regression lines for the root mean square (rms)-values were dependent on the existence of endplates in the area of the electrodes — endplates caused smaller rms values per Newton metres of external torque. Significant intersubject differences between regression equations could not be eliminated by the normalization of EMG-parameters and/or torques. The elimination of gravity, the continuous monitoring of positions, and the consideration of localization of motor endplate regions were essential prerequisites for the acquisition of reliable relationships between EMG of different neck muscles and external torques. Two important conclusions were derived for the prediction of torques from EMG measurements: firstly, individual regression equations which take into account the position of the head and neck should be used; secondly, normalization procedures do not justify the application of average regressions to a group of subjects.     

Control of single-joint movements in deafferented patients: evidence for amplitude coding rather than position control

Two deafferented patients and several control subjects participated in a series of experiments to investigate how accurate single-joint movements are programed, spatially calibrated, and updated in the absence of proprioceptive information. The deafferented patients suffered from a permanent and severe loss of large sensory myelinated fibers below the neck. Subjects performed, with and without vision, sequences of forearm supinations and pronations with two temporal delays between each movement (0 s and 8 s). Overall, the lack of proprioception did not yield any significant decrease in movement accuracy when vision was available. Without vision, the absence of proprioceptive afferents yielded (1) significantly larger spatial errors, (2) amplitude errors similar to those of control subjects, and (3) a significant drift when an 8-s delay was introduced between two successive movements. Subjects also performed, without vision, a 20 supination followed by a 20 pronation that brought back the wrist to the starting position. On some trials, the supination was blocked unexpectedly by way of a magnetic brake. When the supination was blocked, subjects were already on the second target and no pronation was required when the brake was released. The defferented patients, unaware of the procedure, always produced a 20 pronation. These data confirm that deafferented patients were not coding a final position. It rather suggests that they coded an amplitude and translated the spatial distance between the two targets in a corresponding force pulse. Overall, the results highlight the powerful and key role of proprioceptive afferents for calibrating the spatial motor frame of reference.