头低位卧床期间四肢加压套带预防大脑中动脉血流下降

目的　观察头低位卧床 2 1d期间套带对大脑中动脉血流变化的影响 .方法　健康男性志愿者 12名随机分为对照组和套带组 ,每组 6人 ,进行 - 6°卧床试验 2 1d.套带组卧床每日 0 8:30～ 2 0 :30四肢加压套带 ,压力维持在 5 .3k Pa,对照组不做任何对抗措施 .卧床前、卧床 10 d及卧床结束时进行 3次立位耐力试验 .卧床前、卧床 1,3,10和 2 1d用经颅超声多普勒 (TCD)测量大脑中动脉血流动力学指标 .结果　对照组 2 1d卧床期间大脑中动脉血流速度下降 ,血流量减少 ,其中卧床 3 d和 2 1d较卧床前血流速 (vs,vm)明显降低 ,血流量减少 (P<0 .0 5或 P<0 .0 1) .套带组卧床期间及卧床结束时血流速度及血流量较卧床前无显著降低或减少 (P>0 .0 5 ) .卧床 10 d和卧床结束时立位耐力试验对照组 6人均未通过立位耐力试验 .套带组 4人顺利通过立位耐力试验 ,2人未通过立位耐力试验 .结论　头低位卧床期间使用套带能有效减缓大脑中动脉血流速度下降 ,对改善失重引起的脑缺血和立位耐力不良有明显的作用 .     

头高位倾斜时心血管反应的仿真

仿真头高位倾斜时心血管系统的反应,进一步研究有关立位应激的生理机制。方法以仿真下体负压时心血管反应的模型为基础,在血液重新分配子模中引入了重力致血液重新转移的环节,在压力反射控制子模型中考虑了心水平与颈动脉压力感受器间的流体静压差。     

Locating human quantitative trait loci: Guidelines for the selection of sibling pairs for genotyping

Simulation studies were conducted to assess the relative merits of different nonrandom sampling strategies for the selection of sibling pairs for genotyping in the attempt to locate individual loci (QTLs) contributing to variation in human quantitative traits. For a constant amount of variation contributed by a QTL (25% of the total) the frequencies and dominance relationships of a trait increasing allele were varied. Three strategies for selection of pairs for genotyping were based on the phenotypic values of the siblings: Concordant sib pairs (CSP) are pairs in which both individuals exceed a given threshold value; discordant sib pairs (DSP) are pairs in which one member exceeds a given upper threshold and the other is below a specified lower threshold; and most similar pairs (MSP) are pairs selected for falling below a specified percentile ranking of the within-pair mean square for the quantitative trait. Tests for linkage with markers at 1, 2, 5, 10, and 20 cM from each of the QTLs were conducted for each of the selected samples and compared with tests based on the regression, in the entire sample, of within pair variation on the proportion of alleles identical by descent (IBD) at each marker locus. Tests for the effect of the increasing allele at the QTL (candidate gene) were also conducted for the DSP pairs. No single nonrandom selection procedure yields as much as half the information realized in the total sample. However, a combined strategy which involves genotyping the 5% of MSP and DSP for the upper and lower quintiles of values of the quantitative trait (a further 3% of the sample approximately) yields lod scores which are usually more than 65% of the values realized for the entire sample. Tests comparing the proportion of increasing alleles in high- and low-scoring siblings from DSP samples are uniformly very powerful for detecting candidate loci. Even when it is not possible to measure the entire range of the phenotype with uniform precision, some attempt to differentiate among individuals in a common unaffected class of individuals can lead to considerable increase in power.     

尾部悬吊及恢复过程中大鼠动脉血管收缩反应的变化

目的 探讨模拟失重下动脉收缩反应变化的时程特征及其可逆性。方法 采用尾部悬吊大鼠模型模拟失重,利用离休动脉环测定血管收缩反应的变化。结果 尾部悬吊２ｗｋ后,大鼠的腹主动脉、肠系膜动脉和股动脉收缩反应明显降低,而颈总动脉无明显改变;悬吊４ｗｋ后,肠系膜动脉和股动脉的收缩反应与悬吊２ｗｋ相比有进一步的降低;悬吊８ｗｋ大鼠的动脉血管收缩反应性与悬吊４ｗｋ相比无明显差异;４ｗｋ尾部悬吊大鼠解除悬吊后５ｗｋ     

模拟飞行缺氧与吸氧对小鼠脏器自由基代谢的影响

目的 观察了两种模拟飞行条件（１５００ｍ轻度低压缺氧和５５００ｍ中度低压吸氧重复暴露下小鼠多脏器自由基代谢变化的特点。方法 昆明种小鼠６０只,随机分为６组（ｎ＝１０）进行缺氧与吸氧实验,实验完毕后,取小鼠尾血做血常规检查。次日,将小鼠断头处死,取脑、心、肺、肝、肾制备匀浆,测定丙二醛（ＭＤＡ）含量和超氧化物歧化酶（ＳＯＤ）活性。结果 １５００ｍ轻度低压缺氧重复暴露８ｗｋ使肺ＭＤＡ含量显著增高,提示     

Sodium channel blockade enhances dispersion of the cardiac action potential duration

Summary The goal of this study was to elucidate the causes why the proarrhythmic activity of sodium channel blocking drugs is enhanced during the post-infarction period. Therefore, we studied the effects of a reduction in sodium conductance on the action potential duration and its dispersion in a simulated array of 1600 ventricular myocytes. Cardiac tissue is known to possess anisotropic properties with regard to the intercellular electrical resistance (R). Infarction as well as aging causes deposition of collagen in the cardiac tissue, thereby inducing zones of high electrical resistance leading to a non-uniform anisotropy (Spach et al., Circ Res 62811, 1988). For our study an array of 40*40 ventricular myocytes was simulated using Beeler-Reuter-algorithms. Physical tissue properties were assumed to be either a) uniform anisotropic (i.e., all longitudinal R=5000 cm, all transversal R=20000 cm; UA) or b) non-uniform anisotropic (i.e., transversal R for the inner 10*10 cells was set to 10¹⁰ cm; NUA). Mean action potential duration (APD) was increased under UA (287 ms, dispersion: 0,8 ms) when compared to NUA (285 ms, disp.: 3,2 ms). Assuming a 25% decrease in sodium conductance, we found the total activation time (TAT) to be increased (from 99 to 139 ms), indicating slowing of conduction, APD to be shortened (from 287 to 259 ms), and the APD-dispersion to be increased (from 0.8 to 29 ms) in UA. These changes were more pronounced in the case of NUA: increase in TAT from 103 to 150 ms, APD-shortening from 285 to 214 ms and a marked increase in APD-Dispersion from 3.2 to 53 ms). From these results it is concluded that a) the effects of a reduced sodium conductance are more pronounced in NUA tissue, and b) that the resulting increase in dispersion may provoke arrhythmia by local differences in APD.This may be one of the mechanisms underlying the increased proarrhythmic risk of class I antiarrhythmic drugs in the postinfarction period.     

How do normal subjects learn a simple adaptative task: How and why do paranoid schizophrenic patients fail?

Summary The authors studied the behavior of normal subjects and paranoid schizophrenic patients in a simple problem-solving situation. The schizophrenics were divided into two sample groups, one of individuals under treatment and the other of individuals not under treatment.The learning process involved in this problem-solving situation is very similar to an instrumental conditioning, and can be understood by means of the following assumptions: (1) the subjects use decision functions in reacting to the stimuli, although they may be not fully aware of this; (2) learning is the result of successive transformations of these decisions in the course of time; (3) the changes have specific probabilities and are related to (a) those responses which are made to the latest stimuli, and (b) a differential probability for decision functions which were effective, or only interrupted painful reinforcement, or were completely ineffective.In schizophrenics further factors of importance were (1) an inertia factor and (2) the rigidly continued use of unsuccessful or only partially successful decision criteria.The authors used a systems theory based on Galois field theory and a calculus of operators specifying three groups of subjects. A computer program based on these hypotheses was tested in a simulation experiment.The statistical evaluation of the results showed a congruence between the theoretical approach and the experimental data.This work was carried out with financial support from the Institute de Alta Cultura, Lisbon, between 1970 and 1974     

Can virtual simulation of breast tangential portals accurately predict lung and heart volumes?

A treatment portal or simulator image has traditionally been used to demonstrate the lung and heart coverage of the breast tangential portal. In many cases, these images were acquired as a planning session on the linear accelerator. The patients were also CT scanned to assess the lung/heart volume and to determine the surgical site depth for the electron‐boost energy. A study using 50 consecutive patients was performed comparing the digitally reconstructed radiograph (DRR) from the virtual simulation with treatment portal images. Modification to the patient's arm position is required when performing the planning CT scans due to the aperture size of the CT scanner. Virtual simulation was used to assess the potential variation of lung and heart measurements. The average difference in lung volume between the DRR and portal image was less than 2 mm, with a range of 0?5 mm. Arm position did not have a sig­nificant impact on field deviation; however, great care was taken to minimize any changes in arm position. The modification of the arm position for CT scanning did not lead to significant variations between the DRRs and portal images. The Advantage Sim software has proven capable of producing good quality DRR images, providing a realistic representation of the lung and heart volume included in the treatment portal.     

不同定位法应用于鼻咽癌放疗临床分析

[目的]探讨鼻咽癌放射治疗时CT模拟定位的远期疗效及后遗症.[方法]随机将103例经病理证实的鼻咽癌病例分成CT模拟定位组53例和常规模拟定位组50例.CT模拟定位组先设面颈联合野和下颈切线野,常规分割照射,DT36～40Gy后面颈联合野后界前移避开脊髓,后上颈部采用9～12MeV电子线照射,最后阶段采用6MV X线多野适形缩野照射放疗前的肿瘤区,总量68～74Gy.常规模拟定位按骨性标记,先设面颈联合野和下颈切线野,DT36～40Gy后改成耳颞部侧野和耳后电子线野以及全颈切线野.[结果]两组随访5年以上.CT模拟定位组5年生存率、无复发生存率及复发率分别为69.8%、67.9%和7.5%,而常规组分别为50.0%、48.0%和24.0%,两组比较,差异具显著性(P＜0.05).放疗后遗症CT模拟定位组1例耳聋,常规组外展神经麻痹1例,耳聋2例,放射性脑病2例.两组均无放射性脊髓炎.[结论]鼻咽癌放射治疗时用CT定位适形放疗较常规模拟定位放疗能提高疗效,减少复发和放疗后遗症.     

由苍蝇传播引起E．coli O157：H7感染爆发的评估模型的建立

目的 建立苍蝇对E．coli O157：H7传播作用的定量危险性评估模型。方法 在Excel工作表中模拟E．coli O157：H7的粪口传播过程，利用@RISK软件对模型进行Monte Carlo模拟。结果 由此交叉污染途径引起人群感染的概率为10^-5～10^-3／餐。模型预测的结果与爆发调查数据基本吻合。通过模型分析可知，苍蝇排泄物中的含菌量及苍蝇的数量是影响人群感染危险性的重要因素。结论 以苍蝇污染途径模拟E．coli O157：H7感染危险性的定量评估模型，该模型是一个非常有用的评估危害与危险性关系的评估工具。