On a relaxation-labelling algorithm for quantitative assessment of tumour vasculature in tissue section images

Although tumour vasculature constitutes a biological factor playing a crucial role in the radiation response of tumours, the current procedures of assessment are semiquantitative, typically employing visual examination of stained histological material. Such techniques are also time consuming, and inefficient of extracting essential information on the vascular network. Image analysis has yet to contribute significantly in this direction, and most studies to date focus on blood vessel segmentation through empirical, user-selected thresholds. The present paper proposes an alternative segmentation approach, based on a probabilistic relaxation algorithm, applied in microscopic images of stained tissues. After image partitioning various information is obtained, such as vascular domains and geometrical characteristics of vessels.     

Relaxation times of choline, creatine and N-acetyl aspartate in human cerebral white matter at 1.5 T

Several studies have investigated the T1 and T2 relaxation time of choline, creatine and N-acetyl aspartate in cerebral white matter in normal human subjects. However, these studies demonstrate a large variation in T1 and T2 values. In the present study, relaxation times of choline, creatine and N-acetyl aspartate were determined in cerebral white matter in 15 control subjects (age 21 +/- 2 y, mean +/- SD) at 1.5 T. Using PRESS, seven or eight data points were obtained to fit the T1 and T2 relaxation curves to, respectively. The mean voxel size was 14 cm3. The T1 relaxation times of choline, creatine and N-acetyl aspartate were 1091 +/- 132 (mean +/- SD), 1363 +/- 137 and 1276 +/- 132 ms. The T2 relaxation times were 352 +/- 52, 219 +/- 29 and 336 +/- 46 ms, respectively.     

Ensemble noise and current relaxation analysis of K+ current in single isolated salivary acinar cells from rat

The K⁺ channel in rat parotid gland acinar cells were investigated by ensemble current noise analysis in single isolated cells employing the giga-seal whole cell current recording mode. Sets of 20–40 identical de- and hyperpolarization voltage steps were applied and the resultant current records were processed by computer to obtain the mean and the variance of the current. The time-course of the mean current could be fitted by the sum of two exponentials, suggesting a 3-state model. The simplest plausible hypothesis is a model with one open and two closed states. Assuming this model, the relationship between the variance (₂) and the mean current (I) could be fitted by the function ₂/I=i–I/N. The estimated single channeli/V-relations were similar to those taken from single channel current recordings, and the size of the population of channels per cell (N) was 76±26 (n=12). The validity of the model was tested by a successful simulation of the time-course of the variance.     

正常国人腰间盘纤维软骨粘弹性实验研究

研究了正常国人急性外伤致死的成人新鲜尸体10个腰间盘L3-4、14-5纤维软骨的力学性质。以一维拉伸的方法得出了L3-4、L4-5腰间盘纤维软骨的破坏载荷、伸长比、Lagrange张应力、Lagrange张应变等数据。以多项式，用回归分析方法得出椎间盘L3-4、L4-5纤维软骨的应力-应变关系表达式及应力-应变曲线。还对椎间盘L3-4、L4-5纤维软骨进行拉伸应力松弛、蠕变实验。得出了椎间盘L3-4、L4-5纤维软骨的归一化应力松弛函数、蠕变函数G(t)、J(t)表达式。以冯元桢教授的软组织大变形准线性理论，构建了L3-4、L4-5椎间盘纤维软骨的松弛函数K(λ，t)=G(t)T^(e)(λ)的表达式，对实验结果进行分析讨论。     

模拟腰椎前路、后路间盘摘除术T12-L5腰段脊柱应力松弛蠕变实验研究

研究了18例新鲜尸体T12－L5腰段脊柱应力松弛，蠕变特性。测定了完整脊柱（正常组）及模拟前路（对照1组），后路手术（对照2组）腰段脊柱的应力松弛和蠕变效应，得出了在恒应变，应力条件下应力－时间曲线及数据，用回归分析的方法处理实验数据，得出了归一化应务松弛，蠕变函数及曲线，对前路间盘摘除术与后路间盘摘除术对脊柱粘弹性的影响进行分析讨论。     

Sarcomeric determinants of striated muscle relaxation kinetics

Ca²⁺ is the primary regulator of force generation by cross-bridges in striated muscle activation and relaxation. Relaxation is as necessary as contraction and, while the kinetics of Ca²⁺-induced force development have been investigated extensively, those of force relaxation have been both studied and understood less well. Knowledge of the molecular mechanisms underlying relaxation kinetics is of special importance for understanding diastolic function and dysfunction of the heart. A number of experimental models, from whole muscle organs and intact muscle fibres down to single myofibrils, have been used to explore the cascade of kinetic events leading to mechanical relaxation. By using isolated myofibrils and fast solution switching techniques we can distinguish the sarcomeric mechanisms of relaxation from those of myoplasmic Ca²⁺ removal. There is strong evidence that cross-bridge mechanics and kinetics are major determinants of the time course of striated muscle relaxation whilst thin filament inactivation kinetics and cooperative activation of thin filament by cycling, force-generating cross-bridges do not significantly limit the relaxation rate. Results in myofibrils can be explained well by a simple two-state model of the cross-bridge cycle in which the apparent rate of the force generating transition is modulated by fast, Ca²⁺-dependent equilibration between off- and on-states of actin. Inter-sarcomere dynamics during the final rapid phase of full force relaxation are responsible for deviations from this simple model.     

Continuous Biofeedback and Discrete Posttrial Verbal Feedback in Frontalis Muscle Relaxation Training

During training to relax the frontalis muscle, continuous biofeedback (BF) was compared to discrete verbal feedback (VF) delivered immediately after each trial. Both feedback modalities were based on frontalis electromyographic (EMG) activity. Training consisted of 3 consecutive daily session-each comprised of 3 baseline (nonfeedback) trials followed by 10 training trials of 128 see. The presence or absence of the two informationally positive feedback modalities were combined factorially to define four training conditions: BF + VF, NO BF + VF, BF + NO VF, and NO BF + NO VF. Results indicated that while VF alone facilitated muscle relaxation, BF was clearly prepotent ill effecting consistent decreases in EMG activity both across trials and days of training. Additionally, the facilitating effect of BF transferred to nonfeedback trials while VF did not affect performance on nonfeedback trials. Finally, accuracy of self-evaluations of performance on a trial by trial basis was markedly improved by BF, while VF improved accuracy only for trials having a very large absolute difference between levels of EMG activity. Ss receiving no feedback neither reduced muscle tension during training not were able to evaluate their performance accurately even when large absolute differences occurred between trials in frontalis EMG activity.     

骨质疏松对骨的粘弹性性质影响的实验研究

目的研究正常大鼠股骨和维甲酸所致大鼠骨质疏松股骨的压缩粘弹性性质,为临床提供生物粘弹性力学参数。方法选用175～245g,6月龄Wistar大鼠30只,随机分为正常对照组15只,模型组15只。对模型组大鼠每日灌服维甲酸(70mg·kg-1·d-1),实验动物于第12周末处死。取股骨进行压缩应力松弛、蠕变实验。结果得出了正常对照组和模型组股骨应力松弛,蠕变数据和曲线。对应力松弛蠕变实验数据进行归一化处理,得出归一化应力松弛函数、蠕变函数及曲线。结论模型组的7200s应力松弛、蠕变量指标显著低于正常对照组(P<0.05)。     

Effect of EMG Biofeedback and Progressive Muscle Relaxation Training on Awareness of Frontalis Muscle Tension

Awareness of muscle tension, as estimated by a modification of the Kinsman et al. (1975) procedure for determining probability of correct estimation (P(c)) of absolute differences in muscle tension between adjacent trials, was examined before and after volunteer subjects underwent 4 sessions of either: 1) EMG biofeedback (BF) training, 2) progressive muscle relaxation (PMR) training, or 3) a placebo-control (MC) procedure which involved listening to music as an alleged guide for relaxation. The subjects were 30 females (mean age = 28.3 yrs) responding to an offering of experimental treatment for anxiety and tension. Measurements of frontalis muscle tension (EMG) and P(c) were made before and after training. The results showed that EMG was significantly reduced by BF and PMR training but not by the MC procedure. Increases in P(c) after training were significantly greater for BF than for PMR or MC training. There were no group differences for subjective report of tension. Correlations between pre- to post-training EMG and P(c) change scores were significant only for the BF group and the combined group of BF and PMR subjects. These results suggest that: 1) both BF and PMR training were effective in producing frontalis EMG reductions, 2) the following relationship may exist among training groups in terms of relative influence upon awareness of tension—BF training > PMR training > MC training, and 3) awareness of tension appears to be related to the ability to reduce EMG although the exact nature of this relationship remains unclear.     

牦牛主动脉瓣叶的流变学性质

作者研究了牦牛主动脉瓣叶的单向拉伸和应力松弛行为。发现在生理应变范围内,试件的应力应变曲线斜率在纤维方向比其垂直方向约大20倍,瓣叶对应变速率不很敏感。在分析瓣叶的松弛行为时应用了冯元桢[9](1972)提出的松弛模型,根据实验结果,得到了牦牛主动脉瓣叶的归一化松弛函数。