Hydrodynamic aspects of pyelocalyceal peristalsis

This study was undertaken to determine the nature of pressure changes in manometric studies of renal pelvis and calyces. In previous studies in pigs it has been assumed that pressure increases occur in the contracting segments of the renal pelvis and calyces, but our observations suggested that these increases were actually due to distension of noncontracted segments. Pressures were recorded with two catheters introduced percutaneously into the pyelocalyceal system with simultaneous video recording of the fluoroscopic image. There was no pressure rise in the calyces or the renal pelvis when these segments contracted; however, pressure rose when the noncontracted calyces were distended by a remote contraction ring. These findings confirmed the observations at kinetic urography. They agreed with the hydrodynamic experience that the pressure in a ring-shaped contracted segment is lower than upstream and downstream of that segment. It was concluded that if the porcine pyelocalyceal system is a valid model of the human, the pressure increases, assumed to be contractions, were actually caused by the injection and distension of the noncontracted segments.     

Advection and Diffusion of Substances in Biological Tissues With Complex Vascular Networks

For highly diffusive solutes the kinetics of blood–tissue exchange is only poorly represented by a model consisting of sets of independent parallel capillary–tissue units. We constructed a more realistic multicapillary network model conforming statistically to morphometric data. Flows through the tortuous paths in the network were calculated based on constant resistance per unit length throughout the network and the resulting advective intracapillary velocity field was used as a framework for describing the extravascular diffusion of a substance for which there is no barrier or permeability limitation. Simulated impulse responses from the system, analogous to tracer water outflow dilution curves, showed flow-limited behavior over a range of flows from about 2 to 5 ml min^–1 g^–1, as is observed for water in the heart in vivo. The present model serves as a reference standard against which to evaluate computationally simpler, less physically realistic models. The simulated outflow curves from the network model, like experimental water curves, were matched to outflow curves from the commonly used axially distributed models only by setting the capillary wall permeability–surface area (PS) to a value so artifactually low that it is incompatible with the experimental observations that transport is flow limited. However, simple axially distributed models with appropriately high PSs will fit water outflow dilution curves if axial diffusion coefficients are set at high enough values to account for enhanced dispersion due to the complex geometry of the capillary network. Without incorporating this enhanced dispersion, when applied to experimental curves over a range of flows, the simpler models give a false inference that there is recruitment of capillary surface area with increasing flow. Thus distributed models must account for diffusional as well as permeation processes to provide physiologically appropriate parameter estimates. © 2000 Biomedical Engineering Society. PAC00: 8719-j, 8710+e     

Preponderance for either α or β-adrenoceptor mediated sensitization in the rat submaxillary gland

The sensitivity of the rat submaxillary gland was examined 3–4 weeks after either parasympathetic decentralization or sympathetic decentralization or denervation. The threshold doses for secretion of saliva of parasympathomimetic (methacholine) and sympathomimetic (noradrenaline, adrenaline, phenylephrine and isoprenaline) drugs were estimated and the amount of saliva secreted in response to supraliminal doses of these drugs was measured. Each type of operation caused the development of a supersensitivity that involved all three types of receptors, i.e. muscarinic cholinoceptors, alpha;-adrenoceptors and β-adrenoceptors. Following parasympathetic decentralization the sensitization was predominantly mediated via α-adrenoceptors, and also via cholinoceptors. Following sympathetic decentralization or denervation the postjunctional sensitization was predominantly mediated via β-adrenoceptors; most of the supersensitivity to noradrenaline, adrenaline and phenylephrine found after sympathetic denervation was of the prejunctional type. An increase in receptor density and an intracellular arrangement where the response of cholinoceptors and α-adrenoceptors is mediated via one pathway and the response of β-adrenoceptors via another are suggested as factors that may be of importance for the development of the postjunctional supersensitivity. The present study shows that the traffic of secretory impulses in the sympathetic nerve is of importance for the level of sensitivity of the secretory cells. Since postjunctional supersensitivity following sympathetic denervation did not exceed that following sympathetic decentralization it is suggested that under normal conditions a continuous release of noradrenaline from the nerve endings is of little importance for the level of sensitivity.     

Removal of cardiac beat artifact in oesophageal pressure measurement by frequency analysis

Oesophageal pressure (Pes) measurements are important in medical research and useful in clinical diagnosis. Measurements, however, are contaminated heavily by cardiac artifacts. The spectrum and waveform of the Pes signal is obtained from the oesophageal balloon. Adaptive finite impulse response (AFIR) filter and modified adaptive noise cancellation (MANC) methods are adopted to filter out cardiac beat interference. These results are compared. In the frequency domain, frequency variations and spectral overlap between the Pes components and cardiac beat signal components impact on the performance of the filter. From our experimental results on power strength, the fourth or higher harmonics did not have any significant effect on the filter performance. However, the second harmonics of these signals had a significant effect on the filtering result. Thus, in the design of AFIR filters, attention is needed to minimise these effects. In frequency analysis, these harmonics or overlapping frequencies do not affect MANC. MANC was the better method for eliminating cardiac beat artifact in Pes measurement. The dynamic compliance (Cdyn) was also used to evaluate the performance of MANC and AFIR. The standard deviation of Cdyn was less than 0.15 using MANC, compared with standard deviations as high as 0.57 for AFIR. We conclude that MANC performs better than AFIR.     

Reference equations of the impulse oscillatory in healthy Thai adults

BackgroundThe ethnicity is significantly under-reported and this may limit the applicability of current impulse oscillometry (IOS) equations to heterogeneous patient populations. Establishing predictive equations for the IOS in the Thai adult population is still required. Therefore, this study aimed to establish reference equations for the IOS in the Thai adult population.MethodsThis retrospective cross-sectional study of IOS parameters in healthy adults aged greater than 20 years old with normal spirometry and who had no chronic respiratory diseases. Pre-bronchodilator (BD) IOS was performed in all subjects. Reference equations were calculated separately for men and women using multivariable linear regression analysis.ResultsA total of 127 subjects (87 men and 40 women) with a mean age of 48.7±17.2 (range, 22–92) years were included. The resistance at 5 Hz (R5), resistance at 20 Hz (R20), and area under reactance curve between 5 Hz and resonant frequency (AX) were significantly higher in women compared to men. The reference equations of the IOS parameters were established for men and women. Age, height, and bodyweight were shown to be the influential predictor as they contributed to the most of IOS indices except for the R5–R20 in men equations. Bodyweight was shown to be the influential predictor as it contributed to the most IOS indices except for the X5 in women’s equations.ConclusionsWe provided the reference equations for the IOS indices in Thai adults. IOS indices including R5, R20, and AX were significantly higher in women compared to men.     

泌乳素瘤多巴胺受体激动剂治疗相关冲动控制障碍的诊疗进展

泌乳素瘤是最常见的功能性垂体腺瘤,首选多巴胺受体激动剂作为一线治疗方案。在接受多巴胺受体激动剂治疗的泌乳素瘤患者中可能出现各种类型的冲动控制障碍(impulse control disorders,ICDs),如病理性赌博、强迫性购物、性欲亢进、强迫性进食等。这些不良反应会对患者的工作和生活造成严重的影响。然而目前国内缺少相关研究报道,内分泌学界对冲动控制障碍的临床表现、诊断及治疗缺乏全面的认识。本文就泌乳素瘤中ICDs的发生比例、发生机制、危险因素、诊断及治疗等方面展开综述,以深入了解泌乳素瘤多巴胺受体激动剂治疗相关ICDs,为今后在临床诊治中筛查识别及诊治提供帮助。     

声辐射力脉冲成像技术在评价肝纤维化程度的临床价值

目的分析声辐射力脉冲成像技术(acoustic radiation force impulse,ARFI)在评价慢性肝病患者肝纤维化程度中的临床价值。方法利用声辐射力脉冲成像技术对61例慢性肝病患者和56例正常人肝脏右叶进行检查,测得感兴趣区肝脏组织弹性量化值,即声触诊组织量化值(virtual touch quantification,VTQ),并与肝脏穿刺病理结果相对照。结果①61例慢性肝病患者病理活检结果:S0期8例,S1期12例,S2期10例,S3期13例,S4期18例;②VTQ值与肝纤维化程度有很好的相关性(Spearman r=0.737,P<0.01),不同阶段肝纤维化VTQ平均值是,正常对照组=1.03±0.26,S0=1.05±0.20,S1=1.14±0.28,S2=1.36±0.45,S3=2.01±0.76,S4=2.43±0.39;③正常对照组与S0组与S1组之间、S0组与S1组之间的VTQ值差异无统计学意义(P>0.05),其他各组之间的VTQ值差异均有统计学意义(P=0.000或P=0.016)。结论声脉冲辐射力成像技术能够反映肝组织弹性硬度的定量性息,对评估肝纤维化程度有重要价值。     

脉冲振荡法在慢性咳嗽临床应用中的探讨

目的 观察本院门诊就诊的慢性咳嗽患者的肺通气功能及气道阻力变化情况.方法 设立实验组和健康对照组,采用普通肺功能及脉冲振荡法检查,比较两组75%最大呼气流量(MEF75)、50%最大呼气流量(MEF50)、25%最大呼气流量(MEF25)以及脉冲振荡法之呼吸总阻抗(Z5)、总气道阻力(R5)、中心气道阻力(R20)及周边弹性阻力(X5)各项指标的数值变化.实验组行支气管扩张剂治疗14 d,再观察上述指标.结果 治疗前实验组同健康组比较,各项指标差异有统计学意义.实验组治疗前后比较,各项指标差异有统计学意义.治疗后实验组与对照组比较,各项指标差异无统计学意义.结论 总气道阻力、小气道阻力及周边弹性阻力增加,大气道阻力未增加.支气管扩张剂治疗慢性咳嗽有效.     

Accurate Measurement of Magnetic Resonance Imaging Gradient Characteristics

Recently, gradient performance and fidelity has become of increasing interest, as the fidelity of the magnetic resonance (MR) image is somewhat dependent on the fidelity of the gradient system. In particular, for high fidelity non-Cartesian imaging, due to non-fidelity of the gradient system, it becomes necessary to know the actual k-space trajectory as opposed to the requested trajectory. In this work we show that, by considering the gradient system as a linear time-invariant system, the gradient impulse response function (GIRF) can be reliably measured to a relatively high degree of accuracy with a simple setup, using a small phantom and a series of simple experiments. It is shown experimentally that the resulting GIRF is able to predict actual gradient performance with a high degree of accuracy. The method captures not only the frequency response but also gradient timing errors and artifacts due to mechanical vibrations of the gradient system. Some discussion is provided comparing the method presented here with other analogous methods, along with limitations of these methods.