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1.
Activity of aspartate aminotransferase, an enzyme which catalyzes the interconversion of the excitatory transmitter candidates, glutamate and aspartate, has been measured in fiber tracts of rat, with an emphasis on sensory and motor systems of the brain. Most tracts had significantly higher activities than the cholinergic facial nerve root, consistent with the possibility that a component of aspartate aminotransferase activity might serve as a marker for neurons using glutamate and/or aspartate as neurotransmitter. Highest activity was in the auditory nerve root. On the other hand, a close correlation was found between aspartate aminotransferase and malate dehydrogenase activities in the fiber tracts, raising the question whether aspartate aminotransferase activity may be more closely related to energy metabolism than to transmitter metabolism.  相似文献   

2.
目的:探讨双环己酮草酰二腙(cuprizone)诱导大鼠脑白质脱髓鞘及其病因,证实双环己酮草酰二腙引起脑白质脱髓鞘与细胞凋亡有关。方法:用环己酮草酰二腙制备大鼠脑白质脱髓鞘模型(酮腙组),与安定(安定组)、苯巴比妥(苯巴比妥组)、生理盐水对照组(对照组)比较,应用电镜技术及caspase3免疫组化染色,观察各组第14天、28天、42天时脑组织结构变化及细胞凋亡的信号传导通路。结果:电镜显示,安定组、苯巴比妥组、酮腙14天组和对照组白质结构完整致密,无脱髓鞘现象;酮腙28天组可见髓鞘排列较紊乱,部分结构松解变性,但无典型脱髓鞘改变;酮腙42天组胼胝体压部可见髓鞘肿胀,多部位髓鞘被涡轮状空泡所裂解。caspase3染色:酮腙28天、42天组可见皮层下白质、胼胝体、脑干及小脑白质caspase3阳性染色,与安定组、苯巴比妥组、对照组和酮腙14天组比较差异具有统计学意义(P<0.05);酮腙42天组caspase3阳性染色明显多于28天组,差异具有统计学意义(P<0.05)。结论:环己酮草酰二腙可诱导大鼠脑白质脱髓鞘、空泡样变;病变白质区存在大量caspase3阳性染色,且早于脱髓鞘。提示:caspase蛋白酶级联反应参与了环己酮草酰二腙诱导脑白质脱髓鞘的过程,进一步说明细胞凋亡可能是脑白质脱髓鞘原因之一。  相似文献   

3.
Neurochemical Research - White matter degeneration in the central nervous system (CNS) has been correlated with a decline in cognitive function during aging. Ultrastructural examination of the...  相似文献   

4.
Abstract: Separate analyses were made of gray matter and white matter from rat brain after neonatal undernutrition. Newborn rats were redistributed into control, large-litter, and protein-deficient groups. Large litters had 16 rather than 8 pups with a dam. Protein-deficient dams were fed a 4%, instead of a 24%, casein diet. For controls at 21 days of age, the 2',3'-cyclic nucleotide-3'-phosphohydrolase activity was more than fivefold greater in white matter than in gray matter. Severe undernutrition (protein-deficient) gave 2',3'-cyclic nucleotide-3'-phosphohydrolase activities that were 36% lower in gray matter and 56% lower in white matter. Lipid galactose concentrations were 17% less than control in both gray matter and white matter. In protein-deficient white matter, phospholipid concentrations were 15% lower than control. Ethanolamine plasmalogens and phosphatidyl serine were affected most. Moderate undernutrition (large litter) had no effect on 2',3'-cyclic nucleotide-3'-phosphohydrolase activity. A 14% deficit of galactolipids was the only difference from controls in large-litter white matter. In large-litter gray matter, phospholipid concentrations were 16% higher than controls. Nearly all glycerophos-pholipids, including plasmalogens, were affected. With the exception of the myelination markers, 2',3'-cyclic nucleotide-3'-phosphohydrolase and lipid galactose, the development of lipids in gray matter is almost completely spared from the effects of undernutrition. The primary effect of undernutrition is on myelination, especially in white matter.  相似文献   

5.
Abstract: Purified myelin from rat brainstem was found to have an appreciable level of guanylyl cyclase activity, as seen in the formation of 3',5'-cyclic GMP from [3H]GTP at a rate ∼45% that of whole brainstem. Freshly isolated myelin from pooled rat brain-stems was incubated with GTP in an appropriate mixture. This gave rise to 29.9 ± 3.6 pmol of 3',5'-cyclic GMP/mg of protein/min measured by HPLC and a similar result (26.7 ± 2.6 pmol/mg/min) with 125l-3',5'-cyclic GMP radioimmunoassay. The latter method applied to the reaction product from whole brainstem gave a value of 56.6 ± 3.4 pmol/mg/min. In analyzing brainstem products by HPLC we observed in most trials concurrent formation of a second radiolabeled product that comigrated with 2',3'-cyclic GMP but that, on further examination, proved not to be that product. Its identity remains unknown.  相似文献   

6.
DTI is a technique that identifies white matter tracts (WMT) non-invasively in healthy and non-healthy patients using diffusion measurements. Similar to visual pathways (VP), WMT are not visible with classical MRI or intra-operatively with microscope. DTI will help neurosurgeons to prevent destruction of the VP while removing lesions adjacent to this WMT. We have performed DTI on fifty patients before and after surgery between March 2012 to January 2014. To navigate we used a 3DT1-weighted sequence. Additionally, we performed a T2-weighted and DTI-sequences. The parameters used were, FOV: 200 x 200 mm, slice thickness: 2 mm, and acquisition matrix: 96 x 96 yielding nearly isotropic voxels of 2 x 2 x 2 mm. Axial MRI was carried out using a 32 gradient direction and one b0-image. We used Echo-Planar-Imaging (EPI) and ASSET parallel imaging with an acceleration factor of 2 and b-value of 800 s/mm². The scanning time was less than 9 min.The DTI-data obtained were processed using a FDA approved surgical navigation system program which uses a straightforward fiber-tracking approach known as fiber assignment by continuous tracking (FACT). This is based on the propagation of lines between regions of interest (ROI) which is defined by a physician. A maximum angle of 50, FA start value of 0.10 and ADC stop value of 0.20 mm²/s were the parameters used for tractography.There are some limitations to this technique. The limited acquisition time frame enforces trade-offs in the image quality. Another important point not to be neglected is the brain shift during surgery. As for the latter intra-operative MRI might be helpful. Furthermore the risk of false positive or false negative tracts needs to be taken into account which might compromise the final results.  相似文献   

7.
Diffusion tensor imaging (DTI) studies of human brain development have consistently shown widespread, but nonlinear increases in white matter anisotropy through childhood, adolescence, and into adulthood. However, despite its sensitivity to changes in tissue microstructure, DTI lacks the specificity to disentangle distinct microstructural features of white and gray matter. Neurite orientation dispersion and density imaging (NODDI) is a recently proposed multi-compartment biophysical model of brain microstructure that can estimate non-collinear properties of white matter, such as neurite orientation dispersion index (ODI) and neurite density index (NDI). In this study, we apply NODDI to 66 healthy controls aged 7–63 years to investigate changes of ODI and NDI with brain maturation, with comparison to standard DTI metrics. Using both region-of-interest and voxel-wise analyses, we find that NDI exhibits striking increases over the studied age range following a logarithmic growth pattern, while ODI rises following an exponential growth pattern. This novel finding is consistent with well-established age-related changes of FA over the lifespan that show growth during childhood and adolescence, plateau during early adulthood, and accelerating decay after the fourth decade of life. Our results suggest that the rise of FA during the first two decades of life is dominated by increasing NDI, while the fall in FA after the fourth decade is driven by the exponential rise of ODI that overcomes the slower increases of NDI. Using partial least squares regression, we further demonstrate that NODDI better predicts chronological age than DTI. Finally, we show excellent test—retest reliability of NODDI metrics, with coefficients of variation below 5% in all measured regions of interest. Our results support the conclusion that NODDI reveals biologically specific characteristics of brain development that are more closely linked to the microstructural features of white matter than are the empirical metrics provided by DTI.  相似文献   

8.
为探讨血清硫氧还蛋白1 (thioredoxin 1, Trx1)含量与脑外伤后白质恢复的相关性关系,本研究选取60例脑外伤患者,根据格拉斯哥昏迷指数(Glasgow coma scale, GCS)将患者分为3组(轻度,中度和重度脑外伤患者),每组20例,采用核磁共振成像(magnetic resonance imaging, MRI)检测各组患者头颅白质情况,并通过ELISA方法检测各组患者血清Trx1水平,最后利用SPSS软件Pearson方法检测血清硫氧还蛋白1含量与脑外伤后白质恢复的相关性。结果显示,轻度脑损伤患者的GCS分值明显高于中度和重度脑外伤患者;轻度脑外伤患者的Trx1含量明显高于中度和重度患者;轻度和中度脑外伤患者的白质恢复情况明显优于重度患者;脑损伤患者的血清Trx1含量和白质恢复程度呈正相关。本研究初步结论表明脑外伤患者的白质恢复情况与血清Trx1存在正相关性关系,这将为脑外伤的治疗提供新思路。  相似文献   

9.
A significant number of patients suffering from traumatic brain injury (TBI) have a high blood alcohol level at the time of injury. Furthermore, drinking alcohol in a binge-like pattern is now recognized as a national problem, leading to a greater likelihood of being injured. Our objective was to determine the consequences of a binge paradigm of alcohol intoxication at the time of TBI on long-term functional outcome using a sensitive test of sensorimotor function. We trained adult, male, Sprague Dawley rats on the skilled forelimb reaching task and then administered a single binge dose of ethanol (2g/kg, i.p.) or saline for three consecutive days (for a total of 3 doses). One hour after the final ethanol dose, rats underwent a TBI to the sensorimotor cortex corresponding to the preferred reaching forelimb. Animals were then tested for seven weeks on the skilled forelimb reaching task to assess the profile of recovery. We found that the group given ethanol prior to TBI displayed a slower recovery curve with a lower recovery plateau as compared to the control group. Therefore, even a relatively short (3 day) episode of binge alcohol exposure can negatively impact long-term recovery from a TBI, underscoring this significant public health problem.  相似文献   

10.

Background

White matter disruption has been suggested as one of anatomical features associated with Alzheimer''s disease (AD). Diffusion tensor imaging (DTI), which has been widely used in AD studies, obtains new insights into the white matter structure.

Methods

We introduced surface-based geometric models of the deep white matter tracts extracted from DTI, allowing the characterization of their shape variations relative to an atlas as well as fractional anisotropy (FA) variations on the atlas surface through large deformation diffeomorphic metric mapping (LDDMM). We applied it to assess local shapes and FA variations of twenty-three deep white matter tracts in 13 patients with AD and 19 healthy control subjects.

Results

Our results showed regionally-specific shape abnormalities and FA reduction in the cingulum tract and the sagittal stratum tract in AD, suggesting that disruption in the white matter tracts near the temporal lobe may represent the secondary consequence of the medial temporal lobe pathology in AD. Moreover, the regionally-specific patterns of FA and shape of the white matter tracts were shown to be of sufficient sensitivity to robustly differentiate patients with AD from healthy comparison controls when compared with the mean FA and volumes within the regions of the white matter tracts. Finally, greater FA or deformation abnormalities of the white matter tracts were associated with lower MMSE scores.

Conclusion

The regionally-specific shape and FA patterns could be potential imaging markers for differentiating AD from normal aging.  相似文献   

11.
Prefrontal cortex mediates cognitive control by means of circuitry organized along dorso-ventral and rostro-caudal axes. Along the dorso-ventral axis, ventrolateral PFC controls semantic information, whereas dorsolateral PFC encodes task rules. Along the rostro-caudal axis, anterior prefrontal cortex encodes complex rules and relationships between stimuli, whereas posterior prefrontal cortex encodes simple relationships between stimuli and behavior. Evidence of these gradients of prefrontal cortex organization has been well documented in fMRI studies, but their functional correlates have not been examined with regard to integrity of underlying white matter tracts. We hypothesized that (a) the integrity of specific white matter tracts is related to cognitive functioning in a manner consistent with the dorso-ventral and rostro-caudal organization of the prefrontal cortex, and (b) this would be particularly evident in healthy older adults. We assessed three cognitive processes that recruit the prefrontal cortex and can distinguish white matter tracts along the dorso-ventral and rostro-caudal dimensions –episodic memory, working memory, and reasoning. Correlations between cognition and fractional anisotropy as well as fiber tractography revealed: (a) Episodic memory was related to ventral prefrontal cortex-thalamo-hippocampal fiber integrity; (b) Working memory was related to integrity of corpus callosum body fibers subserving dorsolateral prefrontal cortex; and (c) Reasoning was related to integrity of corpus callosum body fibers subserving rostral and caudal dorsolateral prefrontal cortex. These findings confirm the ventrolateral prefrontal cortex''s role in semantic control and the dorsolateral prefrontal cortex''s role in rule-based processing, in accordance with the dorso-ventral prefrontal cortex gradient. Reasoning-related rostral and caudal superior frontal white matter may facilitate different levels of task rule complexity. This study is the first to demonstrate dorso-ventral and rostro-caudal prefrontal cortex processing gradients in white matter integrity.  相似文献   

12.
Premature birth is highly prevalent and associated with neurodevelopmental delays and disorders. Adverse outcomes, particularly in children born before 32 weeks of gestation, have been attributed in large part to white matter injuries, often found in periventricular regions using conventional imaging. To date, tractography studies of white matter pathways in children and adolescents born preterm have evaluated only a limited number of tracts simultaneously. The current study compares diffusion properties along 18 major cerebral white matter pathways in children and adolescents born preterm (n = 27) and full term (n = 19), using diffusion magnetic resonance imaging and tractography. We found that compared to the full term group, the preterm group had significantly decreased FA in segments of the bilateral uncinate fasciculus and anterior segments of the right inferior fronto-occipital fasciculus. Additionally, the preterm group had significantly increased FA in segments of the right and left anterior thalamic radiations, posterior segments of the right inferior fronto-occipital fasciculus, and the right and left inferior longitudinal fasciculus. Increased FA in the preterm group was generally associated with decreased radial diffusivity. These findings indicate that prematurity-related white matter differences in later childhood and adolescence do not affect all tracts in the periventricular zone and can involve both decreased and increased FA. Differences in the patterns of radial diffusivity and axial diffusivity suggest that the tissue properties underlying group FA differences may vary within and across white matter tracts. Distinctive diffusion properties may relate to variations in the timing of injury in the neonatal period, extent of white matter dysmaturity and/or compensatory processes in childhood.  相似文献   

13.
14.
ALTHOUGH the presence of alcohol dehydrogenase (ADH) in cerebral tissue has been established1, a physiological role for such a brain ethanol-oxidizing system has been unclear. The brain may be more biochemically adaptive than was once thought2; thus, it seemed possible that brain ADH may be substrate-induced. We now report that significant elevations of brain ADH activity occur in alcohol-imbibing rats; no changes from control values were found in liver ADH, liver aldehyde dehydrogenase (AldDH), or brain AldDH activities.  相似文献   

15.
16.

Purpose

The aim of the study was to determine the usefulness of diffusion tensor tractography (DTT) in parkinsonian disorders using a recently developed method for normalization of diffusion data and tract size along white matter tracts. Furthermore, the use of DTT in selected white matter tracts for differential diagnosis was assessed.

Methods

We quantified global and regional diffusion parameters in major white matter tracts in patients with multiple system atrophy (MSA), progressive nuclear palsy (PSP), idiopathic Parkinson’s disease (IPD) and healthy controls). Diffusion tensor imaging data sets with whole brain coverage were acquired at 3 T using 48 diffusion encoding directions and a voxel size of 2×2×2 mm3. DTT of the corpus callosum (CC), cingulum (CG), corticospinal tract (CST) and middle cerebellar peduncles (MCP) was performed using multiple regions of interest. Regional evaluation comprised projection of fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD) and the apparent area coefficient (AAC) onto a calculated mean tract and extraction of their values along each structure.

Results

There were significant changes of global DTT parameters in the CST (MSA and PSP), CC (PSP) and CG (PSP). Consistent tract-specific variations in DTT parameters could be seen along each tract in the different patient groups and controls. Regional analysis demonstrated significant changes in the anterior CC (MD, RD and FA), CST (MD) and CG (AAC) of patients with PSP compared to controls. Increased MD in CC and CST, as well as decreased AAC in CG, was correlated with a diagnosis of PSP compared to IPD.

Conclusions

DTT can be used for demonstrating disease-specific regional white matter changes in parkinsonian disorders. The anterior portion of the CC was identified as a promising region for detection of neurodegenerative changes in patients with PSP, as well as for differential diagnosis between PSP and IPD.  相似文献   

17.
18.
After stroke, the brain has shown to be able to achieve spontaneous functional recovery despite severe cerebral damage. This phenomenon is poorly understood. To address this issue, focal transient ischemia was induced by 60 min middle cerebral artery occlusion in Wistar rats. The evolution of stroke was followed using two magnetic resonance imaging modalities: diffusion spectrum imaging (acquired before, one and four weeks after stroke) and functional magnetic resonance imaging (acquired before and five weeks after stroke). To confirm the imaging observations, immunohistochemical staining for myelin, astrocytes and macrophages/microglia was added. At four weeks after stroke, a focal alteration of the diffusion anisotropy was observed between the ipsilesional ventricle and the lesion area. Using tractography this perturbation was identified as reorganization of the ipsilesional internal capsule. Functional imaging at five weeks after ischemia demonstrated activation of the primary sensorimotor cortex in both hemispheres in all rats except one animal lacking a functional response in the ipsilesional cortex. Furthermore, fiber tracking showed a transhemispheric fiber connection through the corpus callosum, which-in the rat without functional recovery-was lost. Our study shows the influence of the internal capsule reorganization, combined with inter-hemispheric connections though the corpus callosum, on the functional activation of the brain from stroke. In conclusion, tractography opens a new door to non-invasively investigate the structural correlates of lack of functional recovery after stroke.  相似文献   

19.
Glycogen Metabolism in Neonatal Rat Brain During Anoxia and Recovery   总被引:1,自引:1,他引:1  
Abstract: Metabolic alterations in glycogen and in glycogen-related metabo lites were studied in neonatal rat brain during controlled anoxia and recovery. One-day postnatal rats were exposed to 100% N, at 37°C for up to 20 min; some rats were allowed to recover in air. Animals were frozen in liquid N, and the brains were prepared for fluorometric analysis of compounds involved in glycogen turnover. During anoxia, glycogen decreased by 29% and 42% at 10 and 20 min, respectively; the free (soluble) and bound (insoluble) components of glycogen decreased in nearly equal proportions. Brain glucose decreased by 72% at 10 min with little further change there after; G-6-P, G-1-P, and UDPG also declined. During recovery from anoxia, glucose and G-6-P increased above control levels for up to 60 min. G-1-P paralleled G-6-P levels, but UDPG remained low. Glycogen returned to control values by 4 h. The findings suggest that although glycogen is mobilized slowly in newborn rat brain, the metabolite contributes at least one-third of the cerebral energy supply during anoxia. Presumably, readily available stores of glycogen combined with low cerebral metabolic requirements underscore the known tolerence of immature animals to hypoxic stress. Glycogen accumulation during recovery appears to be facilitated at the synthetase step, since equilibrium measurements of the phosphoglucomutase and pyrophosphorylase systems indicate that these reactions are not rate-limiting for glycogen synthesis.  相似文献   

20.
The brain is the major dose-limiting organ in patients undergoing radiotherapy for assorted conditions. Radiation-induced brain injury is common and mainly occurs in patients receiving radiotherapy for malignant head and neck tumors, arteriovenous malformations, or lung cancer-derived brain metastases. Nevertheless, the underlying mechanisms of radiation-induced brain injury are largely unknown. Although many treatment strategies are employed for affected individuals, the effects remain suboptimal. Accordingly, animal models are extremely important for elucidating pathogenic radiation-associated mechanisms and for developing more efficacious therapies. So far, models employing various animal species with different radiation dosages and fractions have been introduced to investigate the prevention, mechanisms, early detection, and management of radiation-induced brain injury. However, these models all have limitations, and none are widely accepted. This review summarizes the animal models currently set forth for studies of radiation-induced brain injury, especially rat and mouse, as well as radiation dosages, dose fractionation, and secondary pathophysiological responses.  相似文献   

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