FM sonography in diffuse liver disease: prospective assessment and blinded analysis

FM sonography - a signal-processing technique that uses frequency and phase information as well as amplitude data - shows promise in evaluation of patients with diffuse liver disease. In a prospective blinded review of 37 patients with biopsy-proved liver disease and 42 healthy volunteers, FM sonography was clearly superior to traditional amplitude-based (AM) sonography in distinguishing healthy from diseased subjects. Statistically significant differences were seen in accuracy (FM, 98.7%; AM, 84.8%), sensitivity (FM, 97.3%; AM, 70.3%), and negative predictive value (FM, 97.7%; AM, 78.8%). Our data also suggest that current FM sonographic techniques cannot differentiate among histologic findings associated with different hepatic parenchymal abnormalities. It is unclear, therefore, whether FM imaging can reduce the numbers of patients who require biopsy for diagnosis or the frequency of biopsy procedures in patients with known disease.     

Asbestos-related focal lung masses: manifestations on conventional and high-resolution CT scans

In 260 asbestos-exposed individuals evaluated by means of computed tomography (CT), 43 unsuspected pulmonary masses were found in 27 individuals. The masses included fissural pleural plaques (n = 10), dense fibrotic bands (n = 3), round atelectasis (n = 11), carcinomas (n = 3), and other presumed benign masses (n = 16). The most helpful features in the diagnosis of rounded atelectasis with CT were (a) contiguity to areas of diffuse pleural thickening, (b) a lentiform or wedge-shaped outline, (c) evidence of volume loss in the adjacent lung, and (d) a characteristic "comet tail" of vessels and bronchi sweeping into the margins of the mass. Less advanced areas of focal atelectasis had fewer classic features. Intrafissural pleural plaques were readily identified with high-resolution CT. In asbestos-related masses, the demonstration of stability over time is necessary. Careful interpretation of CT and high-resolution CT features and close surveillance can obviate the need for biopsy in the majority of instances.     

肝细胞生长因子诱导实验性视网膜脱离的病理机制研究

目的 观察肝细胞生长因子（HGF）对视网膜色素上皮（RPE）细胞屏障功能的影响以及RPE内过度表达HGF导致视网膜脱离（RD）的病理机制。 方法 编码HGF（AdCMV.HGF）、绿色荧光蛋白（Ad CMV.GFP）的E1/E3缺失的腺病毒载体，以5×10⁴ 噬斑形成单位（pfu）/眼注射到成年有色兔的视网膜下。检查注射后3、7、14、28 d时的眼底及组织病理变化,利用免疫组织化学和酶联免疫吸附试验（ELISA）方法检测HGF在视网膜和玻璃体的表达水平。 结果 对照组注射Ad CMV.GFP眼显示GFP几乎仅表达于PRE单核细胞层，AdCMV.HGF注射眼在注射点处的PRE细胞出现强的HGF免疫阳性反应。玻璃体内HGF的表达水平在注射7 d后达到最高峰、28 d后降低到基础水平。在HGF的表达期内AdCMV.HGF注射眼出现慢性RD和脉络膜慢性炎症。在RD区域，视网膜下的空间内可见增生性的RPE细胞，部分实验兔眼还产生多层的细胞膜结构。 结论 RPE内过度表达的HGF能引发慢性浆液性RD，同时伴有视网膜下RPE增生。提示HGF可能作为治疗RD的作用靶点。(中华眼底病杂志，2007，23：193-197)     

听性稳态反应应用于婴幼儿听力评估的现状

刺激速率为70～110 Hz的听性稳态反应(auditory steady-state response, ASSR)(亦称为80 Hz)最近倍受听力学工作者特别是小儿听力学工作者的关注,设备制造商也正在推销其产品.本文回顾了ASSR的技术、应用基础,并总结了其应用于婴幼儿听力评估的现状.文中斜体字为基本原则.详细的ASSR方法学、正常值以及一些ASSR研究结果请参阅Picton(2003)的综述.ASSR并不是一个新发现的听觉反应,1960年Geisler就从人类头颅上记录到了该反应;以后研究者又记录到了短声、正弦调制波以及方波调制波所诱发的反应.Galambos等在1981年发表的有关40 Hz事件相关电位将ASSR引入听力领域.不同刺激速率的ASSR的产生部位是不同的,40 Hz的ASSR产生于皮层和脑干,而80 Hz的ASSR主要来源于脑干,而且很有可能它就是ABR的波Ⅴ,只是与ABR的刺激和记录方法不同而已.ASSR的重要特征之一就是在频域内分析的方法,通过计算位相相关性或刺激速率值处的信噪比,再根据统计学分析来判定反应的引出与否,这种客观性使ASSR显著优于ABR.ASSR的刺激信号最早是象ABR一样的短纯音信号,以后主要用调幅调制声,有时也加入10%～20%的调频调制,目前大多数设备都采用这一信号,最近一种新ASSR设备的缺省设置是5～8 ms的短音.ASSR的另一个重要特征是能够同时记录多个刺激声信号所产生的反应,这种多频刺激的方法能够同时记录双耳八个频率(每耳四个频率)的反应.研究证明只要各个信号的频率相距一个倍频程以上,强度在75 dB SPL以下,多个刺激声之间的干扰就很小或没有.不对称型的听力图、不同频率所产生的反应幅度的不同以及多频刺激方式所导致的各个频率反应幅度整体的下降延长了这种方法的测试时间,使其不如理想中的那么省时,但仍比单一刺激方式快2～3倍.80 Hz ASSR通常采用的是正弦调幅调制纯音,因为其特有的频率特异性而被认为是优于短纯音ABR的一个方面,但是声信号的频率特异性只是其中的一方面,还应考虑到耳蜗基底膜的部位特异性以及神经反应的特异性.研究证明ASSR的频率特异性与短纯音ABR是非常接近的.ASSR技术以飞快的速度发展,十年前还没有商用的设备,五年前只有两家,而目前至少有六种不同的设备.随着设备的增加,各个设备之间标准化的问题突显出来.有些设备有很浑厚的研究背景,而有些则没有,使用者应该根据设备的性能及临床资料而加以选择.关于80 Hz ASSR与行为听力测试相关性的研究很多,多为感音神经性聋成人或较大儿童,结果表明至少在该人群中ASSR的阈值能够很好地预测行为听力阈值.许多ABR与ASSR的比较研究声称ASSR比ABR能够更好地评估残余听力,也就是当受试者听力损失很重、ABR不能引出时,仍能够引出ASSR.尽管这一现象客观存在,但是还有一些其他需要考虑的影响因素,如:①所比较的信号在某一特定频率上的能量是不相等的,众所周知短声的能量分布频率范围很宽,其最大输出强度较ASSR信号小;②ASSR在高强度会有伪迹或非听性反应;③ASSR的长时强声刺激会导致耳蜗损害.因此需慎重对待这一问题.目前还没有关于传导性聋或混合性聋气导ASSR的研究,模拟传导性聋的研究表明气导ASSR阈值远高于行为听阈,而且ASSR骨气导差过大.骨导ASSR的研究显示听力正常婴幼儿各个频率的ASSR的阈值与成人显著不同.正常听力婴幼儿的短纯音ABR阈值以及诊断标准已经确立,而ASSR在这一方面的研究则显得不足,而且不同研究所采用的刺激(单频与多频)及记录(不同信噪比、噪声标准以及记录时间)方法不同,使这一形势更加恶化.综合不同调幅调制纯音ASSR的研究结果,正常听力婴幼儿在500、1 000、2 000及4 000 Hz的平均阈值分别为41、43、35和32 dB HL,如果转换为dB SPL则与短纯音ABR非常相似.如果以均值的90%～95%为可信区间,取二倍标准差,则诊断标准在500 Hz为60 dB HL,1 000、2 000及4 000 Hz为50 dB HL.关于感音神经性聋儿童ASSR的研究有很多,这种研究比较理想的方法应该将婴幼儿的ASSR阈值与行为听阈或短纯音ABR阈值相比较.遗憾的是多数研究都是短声ABR与ASSR的比较.总结以上工作发现,首先样本数量还很少,其次多数有方法学的缺陷,加之不同研究所采用的刺激和记录方法不同,临床资料就更加减少.最后还没有不同类型听力损失的婴幼儿ASSR的研究.总而言之,尽管ASSR在婴幼儿听力评估方面很有前途,但目前单独以此作为听力诊断的电生理方法还为时过早,还必须结合短纯音ABR,因为只有短纯音ABR才具有充足的基础、临床研究和明确的诊断标准,因而也是目前婴幼儿听力诊断电生理方法的金标准.根据上述回顾,ASSR在婴幼儿听力诊断的现状总结如下:①新的刺激及记录方法通常都没有经过同行审阅的临床科研为依据,特别是缺乏听力障碍婴幼儿的数据;②不同设备采用不同的刺激和记录方法,且缺少专业人员的评估;③不同的方法或设备层出不穷,缺乏标准化;④刺激声信号的校准问题以及ASSR与行为听力之间的关系问题还没有解决,各种设备采用不同的刺激和记录方法更加恶化了这一状况;⑤极重度聋者的ABR和ASSR的关系还有待于进一步研究;⑥听力损失儿童的ASSR与行为听力测试的关系的研究还很少,而且现有的大多数研究没有能够将ASSR与听力诊断的金标准--行为听力和/或短纯音ABR进行比较;⑦六个月以下婴幼儿的ASSR 研究还很少;⑧传导性聋或混合性聋成人和婴幼儿的研究还很少;⑨成人的骨导ASSR研究很少,还没有婴幼儿骨导ASSR的研究报道,也没有病理状态下成人或婴幼儿的骨导ASSR研究(极重度聋除外).如果上述问题得不到解决,ASSR技术就不能称为成熟.因为对于一个结果,无法准确地判定该阈值是正常还是升高.短纯音ABR的研究虽然尚需完善,但它已有非常多的研究背景和临床数据,能够提供气导和骨导听阈,是当前婴幼儿(特别是6个月以下儿童)听阈确定的首选方法.因此目前ASSR还需与短纯音ABR或行为听力测试结合使用. 80 Hz ASSR除了用于阈值的评估外,也可以用于阈上功能的评估,如单词识别或助听器效果的预估.结果 表明在正常或异常听力成人以言语调制声为信号,其识别阈与ASSR有显著相关性,它反映了较低水平的听觉处理能力.     

Timing of supplementation of selenium and isoflavones determines prostate cancer risk factor reduction in rats

Drug-drug interactions have become an important issue in health care. It is now realized that many drug-drug interactions can be explained by alterations in the metabolic enzymes that are present in the liver and other extra-hepatic tissues. Many of the major pharmacokinetic interactions between drugs are due to hepatic cytochrome P450 (P450 or CYP) enzymes being affected by previous administration of other drugs. After coadministration, some drugs act as potent enzyme inducers, whereas others are inhibitors. However, reports of enzyme inhibition are very much more common. Understanding these mechanisms of enzyme inhibition or induction is extremely important in order to give appropriate multiple-drug therapies. In future, it may help to identify individuals at greatest risk of drug interactions and adverse events.     

Ventricular rate stabilization for the prevention of pause dependent ventricular tachyarrhythmias: results from a prospective study in 309 ICD recipients

Reviews of stored electrograms from ICDs revealed a 5-30% incidence of short-long-short intervals preceding the onset of recurrent ventricular tachyarrhythmias. Rate stabilization by dedicated antibradycardia pacing algorithms has, therefore, been suggested to prevent onset of pause dependent tachyarrhythmias. However, the clinical efficacy of this approach has not been studied systematically. In a prospective multicenter crossover study, patients were randomized to activation or deactivation of an implemented ventricular rate stabilization algorithm (VRS) after first implant of a dual chamber ICD. After 3 months, all patients were crossed over to the alternate programming. The rate of appropriate spontaneous VA episodes was compared between VRS On and VRS Off. Stored electrograms were reviewed for evaluation of the mode of onset of tachyarrhythmias. Overall efficacy analysis was based on 309 patients enrolled in the study. Forty percent (124/309) of the patients experienced 4,973 VA episodes. Based on an intention-to-treat analysis, VRS Off and On arrhythmia incidence was 10.2 and 6.6 normalized to 3 months, respectively (risk reduction 35%; P = 0.18) On an on-treatment basis, a reduction from 9.0 episodes to 8.1 episodes (10% risk reduction, P = 0.24) was seen. In an extended Cox model adjusting for confounding variables, the relative risk for recurrent episodes was 0.92 during VRS On compared to Off (95% CI: 0.58-1.48; P = 0.74). During VRS Off, pause dependent onset was documented in only 36 (8%) of 427 visually analyzed episodes. There was no significant reduction in the incidence of recurrent ventricular tachyarrhythmias with VRS On compared to the Off programming in this prospective study.