孕育铸铁中石墨分布与力学性能的定量关系

本文利用图象分析技术,定量分析灰铸铁孕育处理后石墨相的分布情况。发现石墨相体积分率与灰铸铁综合性能有较为一致的关系,确定了孕育处理时孕育剂应用的最佳方案。     

Antinociception produced by mu opioid receptor activation in the amygdala is partly dependent on activation of mu opioid and neurotensin receptors in the ventral periaqueductal gray

Exposure to stressful or fear-inducing environmental stimuli activates descending antinociceptive systems resulting in a decreased pain response to peripheral noxious stimuli. Stimulating mu opioid receptors in the basolateral nucleus of the amygdala (BLA) in anesthetized rats produces antinociception that is similar to environmentally induced antinociception in awake rats. Recent evidence suggests that both forms of antinociception are mediated via projections from the amygdala to the ventral periaqueductal gray (PAG). In the present study, we examined the types of neurochemicals released in the ventral PAG that may be important in the expression of antinociception produced by amygdala stimulation in anesthetized rats. Microinjection of a mu opioid receptor agonist into the BLA resulted in a time dependent increase in tail flick latency that was attenuated by preadministration of a mu opioid receptor or a neurotensin receptor antagonist into the ventral PAG. Microinjection of a delta(2) opioid receptor antagonist or an NMDA receptor antagonist into the ventral PAG was ineffective. These findings suggest that amygdala stimulation produces antinociception that is mediated in part by opioid and neurotensin release within the ventral PAG.     

Phenytoin administration reveals a differential role of pontine reticular formation and periaqueductal gray neurons in generation of the convulsive behaviors of audiogenic seizures

The ventrolateral periaqueductal gray (PAG) and pontine reticular formation (PRF) are implicated in the neuronal network for audiogenic seizures (AGS). The AGS of genetically epilepsy-prone rats (GEPR-9s) culminate in tonic hindlimb extension (TE), and elevated acoustically evoked neuronal firing and burst firing, immediately preceding TE, have been observed in PAG and PRF. This study examined changes in PAG and PRF neuronal firing and behavior in GEPR-9s, following phenytoin administration. Recordings involved 16 PAG and nine PRF neurons in GEPR-9s. Phenytoin in doses (mean, 6. 3 mg/kg) that suppressed TE selectively did not consistently alter PAG neuronal firing. However, these doses of phenytoin resulted in significant (51.6% of control) suppression of PRF neuronal firing. Doses of phenytoin (mean, 8.3 mg/kg), which completely blocked AGS, significantly reduced PAG neuronal firing (64.6% of control), and more greatly suppressed PRF firing (25.8% of control). These results are consistent with a critical role for PRF neurons in generation of TE not evident for PAG. The suppression of PAG and PRF neuronal firing induced by phenytoin with complete seizure blockade is consistent with vital roles for both structures in the seizure network. The differential effects of phenytoin on structures requisite to the seizure network indicate that this experimental approach may be able to identify the most sensitive therapeutic target for anticonvulsant drugs, which could be critical to pharmacological suppression of specific seizure behaviors manifest in various types of convulsions, potentially including human epilepsy.     

超声医学图像灰度校正方法的改进

介绍了超声医学图像灰度校正常用方法的基本原理,这些方法主要有灰度级校正、灰度变换及直方图修正。对广泛应用且效果较好的直方图均衡化法作了较详细阐述,并针对其对于局部细节增强不显著及不具交互特征等缺点提出了改进方法,并将几种灰度校正方法级联起来对超声图像进行处理,实现了有选择地增强某个灰度值范围对比度的功能,增强了超声诊断图像的实用性。     

我国人口的灰色预测模型研究及其应用

应用GM(1,1)模型,根据1982~1990年我国人口的实际统计数据建立了灰色预测模型,并对我国未来人口进行了预测。     

改良V-Y外眦开大成形术的临床应用

目的：探讨改良V-Y外眦开大成形新术式。方法：将Y形切口线设计在睑缘灰线，板层劈开上下睑，并在切口末端增加两条垂直于睑缘的辅助切口线，切开睑板及睑结膜；部分或完全切断外眦韧带，充分分离使外眦呈“游离状态”。在无张或微张力的情况下外移外眦。结果：102例外眦开大成形术99例达到预期效果，开大外眦达1．5～5mm。结论：改良V-Y外眦开大成形术相比传统手术，保留了外眦外形结构，术后外眦无变形，远期回缩轻微，是目前比较理想的合乎美学原理的外眦开大成形术式。     

Frontal and subcortical contribution to visual hallucinations in dementia with Lewy bodies and Parkinson’s disease

Objectives: Visual hallucinations (VH) are common in Lewy body disease (LBD), and have been associated with cognitive and structural brain alterations. Evidence so far concerns mainly Parkinson’s disease (PD), but little is known about symptom-specific pathophysiological mechanisms across the LBD spectrum, especially related to the presence of dementia. The aim of the present pilot study was to investigate the neuroanatomical, and neuropsychological characteristics related to VH in two forms of LBD, namely dementia with Lewy bodies (DLB) and PD without dementia.

Methods: Whole brain voxel-based morphometry (VBM) analyses on 3D MRI acquired structural brain scans, and neuropsychological testing were performed on 28 clinically diagnosed DLB (11 with VH, 17 NVH), and 24 PD (9 with VH, and 15 NVH) patients. In order to assess differences in gray matter (GM) regional volumes, and cognitive performance, hallucinating patients for each group were compared with corresponding non-hallucinating ones.

Results: DLB patients with VH presented significantly worse visual attention deficits compared to those without, which persisted even when controlling for visual perception. Whole brain VBM analysis revealed decreased GM volume in DLB with VH in the right superior and medial frontal gyri, putamen, caudate nucleus and insula. Subcortical regional volumes were also significantly associated with visual attention performance. Hallucinating PD patients, instead, presented more severe executive dysfunction, but VBM showed no volumetric differences between the two PD subgroups. Post hoc region of interest analyses revealed striatal GM loss in PD with VH.

Conclusion: Frontal and striatal GM atrophy may contribute to the emergence of VH in DLB, which may be fostered by the more severe attention deficits. Striatal GM loss and executive dysfunction, instead, appeared to underlie VH in PD without dementia.     

Inversion recovery ultrashort echo time imaging of ultrashort T2 tissue components in ovine brain at 3 T: a sequential D2O exchange study

Inversion recovery ultrashort echo time (IR‐UTE) imaging holds the potential to directly characterize MR signals from ultrashort T₂ tissue components (STCs), such as collagen in cartilage and myelin in brain. The application of IR‐UTE for myelin imaging has been challenging because of the high water content in brain and the possibility that the ultrashort T₂* signals are contaminated by water protons, including those associated with myelin sheaths. This study investigated such a possibility in an ovine brain D₂O exchange model and explored the potential of IR‐UTE imaging for the quantification of ultrashort T₂* signals in both white and gray matter at 3 T. Six specimens were examined before and after sequential immersion in 99.9% D₂O. Long T₂ MR signals were measured using a clinical proton density‐weighted fast spin echo (PD‐FSE) sequence. IR‐UTE images were first acquired with different inversion times to determine the optimal inversion time to null the long T₂ signals (TI_null). Then, at this TI_null, images with echo times (TEs) of 0.01–4 ms were acquired to measure the T₂* values of STCs. The PD‐FSE signal dropped to near zero after 24 h of immersion in D₂O. A wide range of TI_null values were used at different time points (240–330 ms for white matter and 320–350 ms for gray matter at TR = 1000 ms) because the T₁ values of the long T₂ tissue components changed significantly. The T₂* values of STCs were 200–300 μs in both white and gray matter (comparable with the values obtained from myelin powder and its mixture with D₂O or H₂O), and showed minimal changes after sequential immersion. The ultrashort T₂* signals seen on IR‐UTE images are unlikely to be from water protons as they are exchangeable with deuterons in D₂O. The source is more likely to be myelin itself in white matter, and might also be associated with other membranous structures in gray matter.     

PSA灰区值时MRI+MRS在早期诊断前列腺癌中临床意义

目的：探讨PSA 灰区值时，MRI+MRS 在早期诊断前列腺癌中临床意义。方法对92例PSA4-10ng/ml 患者行MRI+MRS检查，对MRI 异常和（或）MRS 检查(胆碱+肌酸)/枸橼酸盐(Cho+Cre/Cit)≥0.75患者进行前列腺穿刺活检，MRI+MRS无异常者，有手术指征行前列腺电切术，术后行病理检查，无手术指征定期随访。结果73例MRI异常和（或）Cho+Cre/Cit≥0.75穿刺后，12例前列腺癌，其中1例前列腺癌患者MRI示前列腺肿瘤已侵及前列腺包膜，19例MRI+MRS无异常者术后病理1例前列腺癌。阳性组(前列腺癌组）Cho+Cre/Cit值与阴性组（前列腺增生）相比差异显著（P＜0.05)。结论 PSA4-10ng/ml前列腺增生患者，常规行MRI+MRS，有助于前列腺癌早期诊断及临床分期，以Cho+Cre/Cit≥1.29为穿刺的最佳临界值，但有待大样本研究进一步证实及界定。