Competitive dissociation of encephalitogenic complexes between antigen presenting cells and myelin basic protein

Splenic T cells from myelin basic protein (MBP)-immunised Lewis rats were activated to transfer experimental autoimmune encephalomyelitis (EAE) by co-culture with MBP-pulsed lymphoid dendritic cells (DC). MBP-pulsed DC could be kept for at least 24 h at 37 degrees C in antigen-free medium without affecting their ability subsequently to activate encephalitogenic T cells. However, MBP-pulsed DC were rendered much less stimulatory after a 6 h, but not 2 h, secondary incubation with ovalbumin. Thus, although encephalitogenic complexes between MBP and DC appear very stable in the absence of competing antigens, in their presence, antigen exchange can take place over a period of a few hours; this has positive implications for therapy of EAE by antigen competition.     

Phase-derivative analysis in MR angiography: Reduced Venc dependency and improved vessel wall detection in laminar and disturbed flow

A problem of current MRA techniques is the inability to accurately depict the vascular anatomy, particularly in areas of disturbed flow. Various reasons, such as intravoxel phase dispersion, saturation, temporal variations, and maximum intensity projection (MIP) nonlinearity, cause a wrong delineation of vessel boundaries. A phase contrast (PC)-based postprocessing operation, the phase derivative (PhD), is introduced to detect phase fluctuations indicating flow. Two-dimensional and three-dimensional angiographic reconstruction algorithms are presented. Mathematical formulas are derived to predict the effect of sampling to flow profiles and the effect on the PhD of these profiles. Numerical, phantom, and preliminary in vivo experiments demonstrate that PhD images do not suffer from phase wraps and allow a velocity dynamic range extension only limited by a differential phase change. It is also shown that PhD MIPs produce higher signal-to-noise ratios than conventional PC angiograms and give a better impression of the anatomy of (stenotic) vessels and of their diameters for both laminar and disturbed flow.     

CT仿真结肠内窥镜的临床应用研究

目的:研究CT仿真结肠内窥镜(CT Virtual Colonoscopy,CTVC)的使用价值,应用方法及镜下表现。方法:使用Hispeed FX/i扫描机,扫描层厚3～5mm,螺距1～2,重叠重建率50％～67％。利用Navigator Smooth软件对容积扫描数据进行三维重建,获得仿真结肠内窥镜的影像,并与纤维肠镜和/或手术所见对照分析,全部病例经病理证实。结果:通过选择不同的观察方位,角度和阈值,CTVC能清楚显示靶器官内正常解剖结构的立体影像和病变的部位、大小、形态及其侵犯范围。CTVC对结肠病变形态的显示与FC或/和标本显示具有良好的对应性,另外,CTVC能从闭塞和狭窄的远端观察病变。但CTVC不能显示组织的颜色变化,不能活检。结论:CTVC作为一种新的非侵袭性结肠检查方法,可以作为纤维结肠镜的有效补充手段,有较好的临床应用价值。     

Vessel enhancement filtering in three-dimensional MR angiograms using long-range signal correlation

Small vessels in three-dimensional MR angiograms have low visibility in maximum-intensity projection images because of their low contrast. In a previous study, we had two nonlinear filters that appeared to give significant improvement in small vessel detail. In this paper, we report on a generalization of this filter that allows a more general modeling of the vessels and a more complete suppression of background. One implementation of the general filter gave a vessel mean contrast-to-noise ratio that is 2.52 and 3.51 times higher than the vessel mean contrast-to-noise ratio obtained using our previously reported maximum-minimum (max-min) filter and cross- section filter, respectively.     

改进虎杖、鸡血藤炮制方法的研究

对虎杖、鸡血藤作了切制、干燥时间和成品、主要成分及水浸出物的比较。结果表明,趁鲜切片优于传统切块、再切片,既能提高饮片的规格质量和成分含量,亦能减少重复劳动,节约能源,避免药材的浪费。     

In vivo comparison of two through-plane MR velocity mapping methods: Fast fourier encoding and phase mapping

Magnetic resonance imaging maps of velocity were acquired with a 1.5-T system in 10 subjects in a plane perpendicular to the main pulmonary artery. Velocity images were successively acquired with a method developed from Fourier-encoding velocity imaging (FEVI) principles with eight gradient steps and one excitation, and with two-point phase-subtraction mapping. Reconstruction in FEVI was implemented by zero-filling interpolation around the eight gradient steps and then around the four central steps. The methods were compared by using estimates of noise in velocity measurements based on the difference between the experimental map and a smooth fitted map. For the same acquisition time, FEVI with four encoding steps was more precise in velocity measurements than phase mapping. Precision was further increased by the use of eight encoding steps, but acquisition time was doubled.     

腹部CTA检查的质量保证

目的:探讨螺旋CT血管造影(Spiral CT angiography,SCTA)技术,以期提高SCTA造影的质量。材料与方法:采用Somatom Plus 4螺旋CT扫描系统对10例病人行腹部SCTA检查。扫描技术和造影剂参数按病变范围和性质而定,三维重建采用最大强度投影法(MIP)或表面阴影显示法(SSD)或弯曲平面重建法(CPR)。结果:SCTA检查技术能可靠地显示血管形态和病变,评价腹部肿瘤与邻近血管关系。结论:SCTA是无创伤性的血管成像术,在很大范围可替代创伤性的血管造影。     

Dopamine receptor agonists alter gap prestimulus modulation

An innocuous sensory event (a prestimulus) that briefly precedes a startle-eliciting stimulus (SES) will reduce the amplitude of the subsequently elicited reflex. In three experiments brief silent periods in otherwise continuous noise (gaps) were used as prestimuli to investigate the effects of the D₁ dopamine receptor agonist (±)-SKF-38393 (SKF) and the dopamine D₂ receptor group agonist (−)-quinpirole hydrochloride on gap inhibition of the rat’s acoustic startle reflex. Gap durations of 4 and 50 ms were analyzed. Quinpirole (0–1.6 mg/kg) had a biphasic effect on gap inhibition. Lower doses increased gap inhibition, an effect that peaked at the 0.4 mg/kg dose. For higher doses, inhibition returned to control levels for the 4-ms long gap, but remained elevated for the 50-ms long gap. SKF had no effect on gap inhibition, and haloperidol (0.2 mg/kg) reversed the quinpirole-induced increase of gap inhibition. These data implicate the D₂ dopamine receptor group in gap inhibition of startle modulation. The results are discussed in terms of the effects of catecholamine agonists on attention. Received: 25 July 1995/Final version: 28 April 1997     

Phenytoin desensitization monitored by antigen specific T cell response using carboxyfluorescein succinimidyl ester dilution assay

We evaluated drug-specific T cell responses in a patient with refractory partial seizures and paroxysmal kinesigenic choreoathetosis successfully treated with clinical desensitization to phenytoin. Drug-induced lymphocyte transformation test before desensitization was negative with a stimulation index of 130%. The frequencies and cytokine-producing phenotypes of phenytoin-specific T cells were examined simultaneously by using a carboxyfluorescein succinimidyl ester (CFSE) dilution assay. Before desensitization, the proportion of CFSElow CD4+ cells in whole CD4+ was 3.09%; 13.6% of CFSElow CD4+ cells were stained with anti-interferon gamma antibody. After desensitization, phenytoin-specific CFSElow CD4+ cells decreased to background level. These results indicate that CFSE dilution assay will be useful for the diagnosis and monitoring of drug hypersensitivity.     

A Critical Period of Ventricular Fibrillation More Susceptible to Defibrillation: Real-Time Waveform Analysis Using a Single ECG Lead

Previous studies have suggested that variations in the underlying ventricular fibrillation (VF) waveform may be one of the factors responsible for the probabilistic nature of defibrillation. The heart appeared to be more susceptible to defibrillation at higher absolute VF voltages (AVFV). This study investigated in an open-chest canine model (n = 8), a newly developed system that analyzed the VF waveform in real-time, instantaneously determined the time to shock, and immediately delivered a fixed low energy DC shock. A two parameter tracking technique using a running long-term and short-term AVFV average was devised to automatically identify a high voltage peak area of the VF waveform, which has been hypothesized to represent a critical period susceptible to defibrillation. Using a DC shock estimated at the 50% success level, the performance using this technique in 58 defibrillation trials was compared to the performance of the conventional method of shocking at a fixed time (random shock method) in 62 trials. Patch size, electrode location, and discharge voltage were kept constant while VF duration, transmyocardial resistance (TMR), energy delivered, and AVFV at the point of shock were measured. Shock energy and current, TMR, and VF duration were similar with both shock methods. A significantly higher AVFV was observed for trials performed with the peak shock method (0.66 ± 0.02 mV) as compared to trials performed with the random shock method (0.25 ± 0.09 mV) (P < 0.003). Using lead II as the only sensing lead, the success rate was increased in 6 of 8 dogs (75%) with the new method. One animal showed identical performance, and one animal a worse performance. The overall increase in success rate was 24% using a single ECG lead (range 0%-100%; P < 0.04). Our data document that using this algorithm a period of high VF voltage can be detected in realtime. The improved success in the majority of animals supports the hypothesis that a critical period susceptible to defibrillation exists during VF. However, the high AVFV detected using a single ECG lead did not translate to an improved success rate in all animals. This suggests that other factors in addition to the VF voltage measured on a single lead of the ECG are important in characterizing this critical period.