天然放射性气溶胶的粒径分布及其测量方法

天然放射性气溶胶粒径分布的变化会引起氡及其子体所致肺剂量的较大涨落。由于我国对其报道甚少，在肺剂量估算中均引用ＵＮＳＣＥＡＲ的推荐值。为验证这种引用的合理性和建立气溶胶粒径分布的测量方法，开展本项研究。方法采用金属丝网筛（１６５目）扩散法测量天然空气经不同数目网筛扩散前后的放射性浓度比（衰减比）来绘制衰减曲线，然后用池边模式计算出粒径分布曲线。衰减比、粒径分布的计算和曲线的绘制均采用计算机。结果室内外天然放射性气溶胶粒径呈几何正态分布，分布的峰值的平均值分别为（０．２０±０．０９）μｍ和（０．２７±０．１１）μｍ。粒径分布和氡浓度、气压、气温、湿度等未发现相关关系。结论本研究结果与ＵＮＳＣＥＡＲ报告书（１９８８）的推荐值相比，室内值相同，室外值略高，与Ｊａｃｏｂｉ的研究相近。由此可得出结论，福州地区引用ＵＮＳＣＥＡＲ报告书的推荐值来估算氡及其子体所致肺剂量是合适的。此结论能否推广到其他地区，还需作进一步的研究。     

医用氧舱检验与安全

本文介绍了医用氧舱的检验，医用氧舱的检验包括舱体、供排气、氧系统、电气系统等“硬件”设备的检验和设计、安装与使用管理的“软件”方面的检验。同时，针对检验过程中发现的影响医用氧舱安全使用的常见问题，本文进行了详细的讨论。     

Axial tissue diffusion can account for the disparity between current models of hepatic elimination for lipophilic drugs

An assumption of previous models of hepatic elimination is that there is negligible axial diffusion in the liver. We show, by construction of a stochastic model and analysis of published data, that compounds which are readily diffusible and partitioned into hepatocytes may undergo axial tissue diffusion. The compounds most likely to be affected by axial tissue diffusion are the lipophilic drugs for which the cell membranes provide little resistance and which are highly extracted, thereby creating steep concentration gradients along the sinusoid at steady state. This phenomenon greatly modifies the availability of the compound under conditions of altered hepatic blood flow and protein binding. For moderately diffusible compounds, these relationships are similar to those predicted by the simplistic venous-equilibrium model. Hence, the paradoxical ability of the venous-equilibrium model to describe the steady-state kinetics of lipophilic drugs such as lidocaine, meperidine, and propranolol may be finally resolved. The effects of axial tissue diffusion and vascular dispersion on hepatic availability of drugs are compared. Vascular dispersion is of major importance to the availability of poorly diffusible compounds, whereas axial tissue diffusion becomes increasingly dominant for highly diffusive and partitioned substances.This study was supported by the National Health and Medical Research Council of Australia.     

Reversible and irreversible effects of chemical fixation on the NMR properties of single cells.

The effects of chemical fixation are known to alter MR parameters, such as relaxation times and the apparent diffusion coefficient (ADC) of water. It is often assumed that such changes are reversible after samples have been reimmersed in a buffer solution for a sufficient period of time. In this study we characterize the changes associated with fixation of single Xenopus laevis oocytes and their subsequent reimmersion in buffer. Substantial reductions in both T(1) and T(2) values were measured for all compartments of the cell after fixation, with the cytoplasm showing larger changes than the nucleus. After reimmersion in buffer, there were small but statistically significant differences in MR parameters between fresh and reimmersed cells. Experiments with a gadolinium (Gd) contrast agent showed evidence of irreversible changes in the permeability of cellular membranes to small molecules.     

阶跃切应力对内皮细胞释放前列环素的影响

采用流室定量研究阶跃切应力对内皮细胞释放前列环素（ｐＧＩ＿２）的影响。对流室中的内皮细胞连续１００分钟施加１、１０、２０ｄｙｎｅ／ｃｍ￣２的阶跃剪切应力，用放免法测流室的８个时间段流出液的６－ｋｅｔｏ－ＰＧＦｉ＿（１ａ）。绘出切应力刺激内皮细胞释放ＰＧＩ＿２的曲线。结果表明：未施加切应力时，内皮细胞释放ＰＧＩ＿２的量在检测限以下，施加切应力后，ＰＧＩ＿２释放速率很快达极大值，且又在数分钟内减小．施加阶跃切应力越大，ＰＧＩ＿２释放速率曲线峰值越高，但衰减也越快，在８０～１００分钟时间内的前列环素释放速率平均值也越大。由此提示，在活体中血液流变学因素一血流切应力对血管内皮细胞释放前列环素有促进作用。     

青光眼小梁切除术后浅前房临床分析

目的 探讨青光眼小梁切除术后浅前房的原因及发生情况。方法 回顾总结我院1997年1月至2001年12月连续92例104只眼小梁切除术后发生浅前房的程度及原因。结果 本组发生术后浅前房16眼；占15.4％，其中结膜漏1眼(6．25％)，滤过过强11眼(68．75％)，脉络膜睫状体脱离4眼(25％)。结论 青光眼小梁切除术后浅前房原因复杂，与术前眼压关系密切，与患者年龄及青光眼类型无关，最常见的原因是房水滤过过强。     

Rapid monitoring of changes in water diffusion coefficients during reversible ischemia in cat and rat brain

Changes in the diffusion constant of water during reversible brain ischemia and cardiac arrest were monitored with a 10-s time resolution. Results (five cats, three rats) indicate that these changes are reversible and that the bulk of the changes are not caused by temperature or motion related to brain pulsations and blood flow. The rapid time course of the changes corresponds to the known time course for changes in energy state, signal transduction, and ionic homeostasis.     

磁共振扩散加权成像在肝癌介入治疗前后应用的初步研究

目的探讨肝癌经导管动脉化疗栓塞术(TACE)前后不同b值下瘤区组织的平均表观扩散系数(ADC)的变化及其意义。方法对17例临床及影像学诊断为肝癌并行介入治疗的患者,术前及术后7天行常规平扫和磁共振扩散加权成像,比较不同b值下瘤区组织的平均ADC值的变化。结果在b值为50和100s/mm2时术前术后比较无统计学意义。在b值为300、500和700s/mm2时,术前术后的平均ADC值变化有显著性差异。当b值大于300s/mm2时,随着b值的升高平均ADC值逐渐升高,术后瘤区组织的平均ADC值较术前升高,在b值为1000和1300s/mm2时图像质量太差无法测量。结论对肝癌TACE术后疗效进行评价时,b值最好选择300～700s/mm2之间。DWI通过瘤区DWI图像、eADC图像、ADC图像信号的变化和平均ADC值可以反映TACE术后瘤组织内的微观及超微结构的变化,平均ADC值可以为其早期疗效的判断提供量化标准。     

高血压脑病的MRI表现

目的 分析高血压脑病的MRI表现。资料与方法 搜集8例经临床诊断高血压脑病患者，行MR T1WI和T2WI检查，其中4例加行扩散加权成像（DWI），分析血压变化、MRI表现及ADC值变化。结果 发病时平均血压199．63／123．5mmHg（1mmHg=0．133kPa），平均升高25．73％／28．71％。MRI上病变主要呈TI稍低、T2稍高信号，以顶枕叶、小脑半球多见。DWI病变呈等及稍高信号，ADC值较正常平均升高58％。仅1个病灶DWI出现明显高信号，ADC值减低。结论 MRI有助于高血压脑病的诊断及鉴别诊断、预后及疗效观察，DWI是将其与急性脑梗死区分开的最佳影像学检查方法。     

Diffusion‐Weighted MRI in Creutzfeldt‐Jakob Disease: A Better Diagnostic Marker Than CSF Protein 14‐3‐3?

Two middle-aged patients presented with rapidly progressive dementia and ataxia, nonspecific electroencephalography findings, and negative cerebrospinal fluid (CSF) protein 14-3-3. Both patients underwent brain magnetic resonance imaging (MRI) scans that demonstrated abnormalities on diffusion-weighted imaging (DWI) sequences, and both were later confirmed to have Creutzfeldt-Jakob disease. (CJD) by tissue examination. Because a recent position paper from the American Academy of Neurology characterized CSF protein 14-3-3 as a gold standard for clinically diagnosing CJD, the authors reviewed studies of CJD in which DWI-MRI imaging and CSF protein 14-3-3 studies were both performed. Among 19 reported cases of CJD with DWI-MRI lesions, CSF protein 14-3-3 was negative in 6 cases and positive in 2 others. The authors' findings suggest that multifocal cortical and subcortical hyperintensities confined to gray matter regions in DWI-MRI may be a more useful noninvasive diagnostic marker for CJD than CSF protein 14-3-3. These observations provide a compelling rationale for a prospective comparative study.