线栓法制备大鼠局灶性脑缺血模型的研究

人类脑血管病的发病率随着社会环境因素和饮食结构的改变正在日益增加,其中缺血性脑血管病占80%以上,大脑中动脉闭塞(Middle cerebral artery occlusion,MCAO)占血管闭塞的43%,针对这一情况对MCAO的研究显得尤为重要.对缺血性脑血管的研究,首先需要建立简便有效的动物模型,而制备模型的方法很多.目前,线栓法制备的大鼠局灶性脑缺血模型被公认的较为理想的局灶性脑缺血模型.它具有不开颅,损伤小,重复性好的优点,并可准确控制缺血和再灌注的时间,因此应用范围广泛.但目前仍有很多因素制约着模型的成功复制,现就模型的制备、影响因素及其现状进行研究.     

星形胶质细胞与缺血性脑水肿

随着对神经系统疾病机制研究的不断深入,人们认识到,它在生理和病理下均发挥极其重要的作用.脑水肿及后继的颅内压升高和脑疝形成是脑缺血主要的并发症.星形胶质细胞可通过多种途径影响脑水肿的发生.发展以及消退.明确星形胶质细胞在缺血性脑水肿中的作用及其机制,可能将为脑缺血的治疗提供新的靶点.     

Anatomical and functional MR imaging in the macaque monkey using a vertical large-bore 7 Tesla setup

Functional magnetic resonance imaging (MRI) in the nonhuman primate promises to provide a much desired link between brain research in humans and the large body of systems neuroscience work in animals. We present here a novel high field, large-bore, vertical MR system (7 T/60 cm, 300 MHz), which was optimized for neuroscientific research in macaque monkeys. A strong magnetic field was applied to increase sensitivity and spatial resolution for both MRI and spectroscopy. Anatomical imaging with voxel sizes as small as 75×150×300 μm³ and with high contrast-to-noise ratios permitted the visualization of the characteristic lamination of some neocortical areas, e.g., Baillarger lines. Relaxation times were determined for different structures: at 7 T, T1 was 2.01/1.84/1.54 s in GM/GM-V1/WM, T2 was 59.1/54.4 ms in GM/WM and T2* was 29 ms. At 4.7 T, T1 was 25% shorter, T2 and T2* 18% longer compared to 7T. Spatiotemporally resolved blood-oxygen-level-dependent (BOLD) signal changes yielded robust activations and deactivations (negative BOLD), with average amplitudes of 4.1% and −2.4%, respectively. Finally, the first high-resolution (500 μm in-plane) images of cerebral blood flow in the anesthetized monkey are presented. On functional activation we observed flow increases of up to 38% (59 to 81 ml/100 g/min) in the primary visual cortex, V1. Compared to BOLD maps, functional CBF maps were found to be localized entirely within the gray matter, providing unequivocal evidence for high spatial specificity. The exquisite sensitivity of the system and the increased specificity of the hemodynamic signals promise further insights into the relationship of the latter to the underlying physiological activity.     

Effect of high dose isoflurane on cerebral blood flow in macaque monkeys

The effect of high dose isoflurane on cerebral blood flow (CBF) was investigated in adult macaque monkeys receiving 1% to 2% isoflurane with the pseudo continuous arterial-spin-labeling (pCASL) MRI technique. High concentration (2%) of isoflurane resulted in significant increase in the mean CBF of the global, cortical, subcortical regions and the regional CBF in all subcortical structures and most cortical structures (such as motor cortex, anterior cingulate cortex, but not media prefrontal cortex). In addition, the changes of regional CBF in the affected regions correlated linearly with increasing isoflurane concentrations. The study demonstrates region-specific CBF abnormal increase in adult macaque monkeys under high dose (2%) isoflurane and suggests that the brain functionality in the corresponding structures may be affected and need to be taken consideration in either human or non-human primate neuroimaging studies.     

Intravoxel incoherent motion (IVIM) imaging at different magnetic field strengths: What is feasible?

Background

Due to limited SNR the cerebral applications of the intravoxel incoherent motion (IVIM) concept have been sparse. MRI hardware developments have resulted in improved SNR and this may justify a reassessment of IVIM imaging for non-invasive quantification of the cerebral blood volume (CBV) as a first step toward determining the optimal field strength.

Purpose

To investigate intravoxel incoherent motion imaging for its potential to assess cerebral blood volume (CBV) at three different MRI field strengths.

Materials and methods

Four volunteers were scanned twice at 1.5 T, 3 T as well as 7 T. By correcting for field-strength-dependent effects of relaxation, estimates of corrected CBV (cCBV) were obtained in deep gray matter (DGM), frontal gray matter (FGM) and frontal white matter (FWM), using Bayesian analysis. In addition, simulations were performed to facilitate the interpretation of experimental data.

Results

In DGM, FGM and FWM we obtained cCBV estimates of 2.2 ml/100 ml, 2.7 ml/100 ml, 1.4 ml/100 ml at 1.5 T; 3.7 ml/100 ml, 5.0 ml/100 ml, 3.2 ml/100 ml at 3 T and 15.5 ml/100 ml, 20.3 ml/100 ml, 7.0 ml/100 ml at 7 T.

Conclusion

Quantitative cCBV values obtained at 1.5 T and 3 T corresponded better to physiological reference values, while 7 T showed the largest deviation from expected values. Simulations of synthetic tissue voxels indicated that the discrepancy at 7 T can partly be explained by SNR issues. Results were generally more repeatable at 7 T (intraclass correlation coefficient, ICC = 0.84) than at 1.5 T (ICC = 0.68) and 3 T (ICC = 0.46).     

Abnormalities of cerebral blood flow in multiple sclerosis: A pseudocontinuous arterial spin labeling MRI study

Arterial spin labeling (ASL) is a noninvasive technique that can measure cerebral blood flow (CBF). To our knowledge, there is no study that examined regional CBF of multiple sclerosis (MS) patients by using this technique. The present study assessed the relationship between clinical presentations and functional imaging data in MS using pseudocontinuous arterial spin labeling (pCASL). Twenty-seven patients with MS and 24 healthy volunteers underwent magnetic resonance imaging and pCASL to assess CBF. Differences in CBF between the two groups and the relationships of CBF values with the T2-hyperintense volume were evaluated. Compared to the healthy volunteers, reduced CBF was found in the bilateral thalami and right frontal region of the MS patients. The volume of the T2-hyperintense lesion was negatively correlated with regional CBF in some areas, such as both thalami. Our results suggest that demyelinated lesions in MS mainly have a remote effect on the thalamus and that the measurement of CBF using ASL could be an objective marker for monitoring disease activity in MS.     

辽宁大学职工病死调查及分析

本校教职工九年共死亡１０８人，在职工人数２５１２人没有大幅度增加的情况下、死亡率逐年增加，甚至成倍增加。从年龄段分析６１￣７１岁死亡率是高，其次是５１￣６０岁，男比女高，疾病种类占首位的是恶性肿瘤，以下顺序是脑溢血，心肌梗死，肺心病。上述情况与生活环境、不良饮食习惯、烟酒嗜好、环境污染等因素危害身体健康有关。它提醒人们认清损害身体的诸因素，提高防病意识，加强自身保健能力。     

年轻人脑梗死临床研究

目的：研究年轻人脑梗死的病因及危险因素，方法：对31例年轻人脑梗死的病因及危险因素进行分析总结，结果：年轻人脑梗死主要病因为早发性脑动脉硬化，心源性脑栓塞是常见病因，脑动脉炎、酒精中毒等较常见，女性患者与偏头痛、吸烟、口服避孕药密切相关，结论年轻人脑梗死病因复杂，危险因素多样，加强多学科深入合作，加强对高危人群的筛查，早发现、早预防。     

Reduced cell death by inosine pretreatment after photochemically-induced cerebral ischemia in adult rats

Protective effect of inosine against cell death after photochemically induced focal cerebral ischemia was investigated in adult rats. Intraperitoneal injection of inosine was started 24 h before operation and continued till the animals were sacrificed. The TUNEL method and Nissl staining were used to identify apoptosis and necrosis, respectively. TUNEL-positive cells were located in the transitional zone between the necrotic core and normal cortex. The mean maximum area of the necrotic cores and mean number of TUNEL-positive cells 24 h after operation were reduced significantly in the inosine-treated rats when compared with those in the saline-treated control animals. We suggest that inosine can significantly reduce both necrosis and apoptosis following cerebral ischemia induced by photothrombosis in adult rats.     

Validation study of a pulsed arterial spin labeling technique by comparison to perfusion computed tomography

Abnormalities in cerebral blood flow (CBF) are believed to play a significant role in the development of major neonatal neuropathologies. One approach that would appear ideal for measuring CBF in this fragile age group is arterial spin labeling (ASL) since ASL techniques are noninvasive and quantitative. The purpose of this study was to assess the accuracy of a pulsed ASL method implemented on a 3-T scanner dedicated to neonatal imaging. Cerebral blood flow was measured in nine neonatal piglets, the ASL–CBF measurements were acquired at two inversion times (TI) (1200 and 1700 ms), and CBF was measured by perfusion computed tomography (pCT) for validation. Perfusion CT also provided images of cerebral blood volume, which were used to identify large blood vessels, and contrast arrival time, which were used to assess differences in arterial transit times between gray and white matter. Good agreement was found between gray matter CBF values from pCT (76±1 ml/min per 100 g) and ASL at TI=1700 ms (73±1 ml/min per 100 g). At TI=1200 ms, ASL overestimated CBF (91±2 ml/min per 100 g), which was attributed to substantial intravascular signal. No significant differences in white matter CBF from pCT and ASL were observed (average CBF=60±1 ml/min per 100 g), nor was there any difference in contrast arrival times for gray and white matter (0.95±0.04 and 0.99±0.03 s, respectively), which suggests that the arterial transit times for ASL were the same in this animal model. This study verified the accuracy of the implemented ASL technique and showed the value of using pCT to study other factors that can affect ASL–CBF measurements.