The thermodynamics of thinking: connections between neural activity,energy metabolism and blood flow

Several current functional neuroimaging methods are sensitive to cerebral metabolism and cerebral blood flow (CBF) rather than the underlying neural activity itself. Empirically, the connections between metabolism, flow and neural activity are complex and somewhat counterintuitive: CBF and glycolysis increase more than seems to be needed to provide oxygen and pyruvate for oxidative metabolism, and the oxygen extraction fraction is relatively low in the brain and decreases when oxygen metabolism increases. This work lays a foundation for the idea that this unexpected pattern of physiological changes is consistent with basic thermodynamic considerations related to metabolism. In the context of this thermodynamic framework, the apparent mismatches in metabolic rates and CBF are related to preserving the entropy change of oxidative metabolism, specifically the O₂/CO₂ ratio in the mitochondria. However, the mechanism supporting this CBF response is likely not owing to feedback from a hypothetical O₂ sensor in tissue, but rather is consistent with feed-forward control by signals from both excitatory and inhibitory neural activity. Quantitative predictions of the thermodynamic framework, based on models of O₂ and CO₂ transport and possible neural drivers of CBF control, are in good agreement with a wide range of experimental data, including responses to neural activation, hypercapnia, hypoxia and high-altitude acclimatization.This article is part of the theme issue ‘Key relationships between non-invasive functional neuroimaging and the underlying neuronal activity’.     

新生儿首次呼吸前后脐带动静脉血液氧和二氧化碳变化探索呼吸调控机制的初步报告II—同一个新生儿同一时间的脐带动静脉血液氧和二氧化碳分压差值个体化分析*

目的: 为探讨新生儿自主呼吸产生机制,前文已对新生儿出生后自主呼吸开始前脐带动静脉氧气和二氧化碳差值进行了人群组间分析;而本部分则对相关信息进行个体化分析。方法: 在产前经所有胎儿父母签署知情同意书,新生儿出生后还没有呼吸之前在脐带动脉和脐带静脉分别连续逐搏取血,仅有3例同时采集到Pua和Puv血液样本进行血气分析测定,计算分析脐带静脉和脐带动脉的异同和动态变化。结果: 虽然准备了数十产妇,但仅有3例同时采集到Pua和Puv血液样本,同一时间的PuvO₂显著高于PuaO₂（P均<0.01）,平均相差（24.17±7.09） mmHg;而PuvCO₂显著低于PuaCO₂（P均<0.01）,平均相差（-7.67±3.70） mmHg。在同一时间的Puv-uaO₂显著高于Puv-uaCO₂（P<0.05）。结论: 新生儿出生后自主呼吸前,全部氧气供应由脐带静脉运输,只要胎盘开始剥离则新生儿的PuaO₂随时间（心跳次数）逐渐降低,当PuaO₂达到触发呼吸阈值（最低值）诱发第一次吸气开始其自主呼吸。     

超声评分法及肾动脉阻力指数对胎儿肾积水预后的评价价值分析

目的:研究超声评分法及肾动脉阻力指数(RRI)对胎儿肾积水预后的评价价值。方法:将从2016年1月2019年1月经我院超声检查发现的孕晚期肾积水胎儿210例纳入研究,测定其肾实质厚度(RPT)、肾盂前后径(APD)以及肾盂肾盏形态,对上述各项超声检测指标进行评分,累计计算分值。此外,对所有胎儿的积水肾脏肾门部位的RRI值进行测定,并以受试者工作特征(ROC)曲线分析超声评分法与RRI值诊断胎儿肾积水预后类型的价值。结果:所有胎儿出生1年内分别行超声检查以及临床诊断,结果显示210例胎儿,共计420只肾脏,共发生285只肾积水,包括病理性肾积水84只(病理性组),非病理性肾积水201只(非病理性组)。病理性肾积水胎儿超声评分为13分的肾只数占比显著低于非病理性胎儿(P<0.05),而79分的肾只数占比显著高于非病理性胎儿(P<0.05)。病理性肾积水胎儿的平均RRI值为0.74±0.05,显著高于非病理性肾积水胎儿的0.63±0.02,差异有统计学意义(t=26.563,P=0.000)。超声评分法与RRI联合诊断病理性肾积水的曲线下面积(AUC)、敏感度、特异度、准确度均显著高于超声评分法或RRI单独诊断(P<0.05)。结论:超声评分法及RRI诊断对胎儿肾积水预后评价具有较重要的价值,值得临床推广应用。     

CT定量分析在冠心病介入治疗前后血流灌注改变的评估价值

摘要 目的：探讨CT定量分析在冠心病介入治疗前后血流灌注改变的评估价值。方法：2018年2月到2020年11月选择在本院诊治的冠心病患者95例作为研究对象,所有患者都给予经皮冠状动脉介入治疗,在介入前1 d与介入后1个月进行CT定量与超声检查,随访介入后6个月的冠状动脉再狭窄情况并进行相关性分析。结果：所有患者都顺利完成介入治疗,介入期无严重并发症发生。95例患者介入后1个月的左室射血分数(ejectionfraction,EF)、左室短轴缩短率(fractionalshortening,FS)高于介入前1 d(P<0.05),介入前后左室等容舒张时间(iso-volumicrelaxationtime,IVRT)对比差异无统计学意义(P>0.05)。95例患者介入后1个月的心肌血流量(Myocardialbloodflow,MBF)、心肌血容量(Myocardialbloodvolume,MBV)高于介入前1d(P<0.05),达峰时间(Timetopeak,TTP)低于介入前1 d(P<0.05)。介入后随访6个月,冠状动脉再狭窄14例,再狭窄率14.7 %,其中中度狭窄12例,重度狭窄2例;Pearson分析显示冠心病患者介入前1 d的MBF、MBV、TTP与FS、EF都存在相关性(P<0.05);Logistic回归分析显示MBF、MBV、TTP、FS、EF为影响冠心病患者介入后随访再狭窄率的重要因素(P<0.05)。结论：CT定量分析在冠心病介入前后的应用能有效反映血流灌注改变情况,且与患者的心功能存在相关性,也可有效预测患者介入随访冠状动脉再狭窄发生情况。     

醒脑静联合纳洛酮对急性脑出血伴意识障碍患者神经功能、炎性因子和氧化应激的影响

摘要 目的：探讨纳洛酮联合醒脑静对急性脑出血（ACH）伴意识障碍患者炎性因子、神经功能和氧化应激的影响。方法：选取2017年2月~2019年12月期间我院收治的95例ACH伴意识障碍患者,按照随机数字表法将上述患者分为对照组（n=47）和研究组（n=48）,对照组患者予以纳洛酮治疗,研究组则在对照组的基础上联合醒脑静治疗,比较两组患者疗效、神经功能、炎性因子和氧化应激指标,记录两组不良反应发生情况。结果：研究组治疗10 d后的临床总有效率为91.67%（44/48）,高于对照组的74.47%（35/47）（P<0.05）。两组治疗10 d后美国国立卫生研究院卒中量表（NIHSS）评分,白介素-6（IL-6）、C反应蛋白（CRP）以及肿瘤坏死因子-α（TNF-α）、丙二醛（MDA）水平均较治疗前下降,且研究组低于对照组（P<0.05）。两组治疗10 d后超氧歧化酶 (SOD)水平均较治疗前升高,且研究组高于对照组（P<0.05）。两组不良反应发生率对比未见统计学差异（P>0.05）。结论：醒脑静联合纳洛酮治疗ACH伴意识障碍患者,疗效显著,可有效改善患者神经功能、炎性因子和氧化应激,且安全性较好。     

冠状动脉磁共振血管成像和CT对可疑冠心病患者心脏事件的预测价值的比较研究

摘要 目的：探讨与比较冠状动脉核磁共振(MR)血管成像和CT对可疑冠心病患者心脏事件的预测价值。方法：2018年4月到2020年10月选择在本院诊治的103例可疑冠心病患者作为研究对象,所有患者都给予冠状动脉MRI血管成像与64层螺旋CT冠状动脉成像检查,记录影像学特征。随访患者的预后并进行预测价值分析。结果：103例可疑冠心病患者随访到2021年4月1日,发生心血管不良终点事件23例(不良事件组),发生率为22.3%。不良事件组的MRI血管成像显示右冠状动脉血管长度与内径都低于非不良事件组(P<0.05)。不良事件组的CT显示斑块率、斑块性质等与非不良事件组对比差异有统计学意义(P<0.05),两组斑块位置对比差异无统计学意义(P>0.05)。多因素Cox回归分析显示斑块性质、斑块率、右冠状动脉血管长度与内径都为导致心血管不良终点事件的重要因素(P<0.05)。结论：冠状动脉MRI血管成像和CT都可有效预测可疑冠心病患者心脏事件发生情况,能满足临床诊断可疑冠心病与预测预后的要求。     

IMPROV-ED trial: eHealth programme for faster recovery and reduced healthcare utilisation after CABG

Netherlands Heart Journal - After coronary artery bypass grafting (CABG), healthcare utilisation is high and is partly unplanned. eHealth applications have been proposed to reduce healthcare...     

Adaptive Finite Element Analysis of the Anisotropic Biphasic Theory of Tissue-Equivalent Mechanics

Abstract

The nonlinear partial differential equations of the anisotropic biphasic theory of tissue-equivalent mechanics are solved with axial symmetry by an adaptive finite element system. The adaptive procedure operates within a method-of-lines framework using finite elements in space and backward difference software in time. Spatial meshes are automatically refined, coarsened, and relocated in response to error indications and material deformation. Problems with arbitrarily complex two-dimensional regions may be addressed. With meshes graded in high-error regions, the adaptive solutions have fewer degrees of freedom than solutions with comparable accuracy obtained on fixed quasi-uniform meshes. The adaptive software is used to address problems involving an isometric cell traction assay, where a cylindrical tissue equivalent is adhered at its end to fixed circular platens; a prototypical bioartificial artery; and a novel configuration that is intended as an initial step in a study to determine bioartificial arteries having optimal collagen and cell concentrations.     

A gait index may underestimate changes of gait: a comparison of the Movement Deviation Profile and the Gait Deviation Index

The ability of the Movement Deviation Profile (MDP) and Gait Deviation Index (GDI) to detect gait changes was compared in a child with cerebral palsy who underwent game training. Conventional gait analysis showed that sagittal plane angles became mirrored about normality after training. Despite considerable gait changes, the GDI showed minimal change, while the MDP detected a difference equal to a shift between 10-9 on the Functional Assessment Questionnaire scale. Responses of the GDI and MDP were examined during a synthetic transition of the patient's curves from before intervention to a state mirrored about normality. The GDI showed a symmetric response on the two opposite sides of normality but the neural network based MDP gave an asymmetric response reflecting faithfully the unequal biomechanical consequences of joint angle changes. In conclusion, the MDP can detect altered gait even if the changes are missed by the GDI.     

Computational haemodynamics in two idealised cerebral wide-necked aneurysms after stent placement

Endovascular stents are being commonly used to treat cerebral wide-necked aneurysms recently. The effect of a stent placed in the parent artery is not only to protect the parent artery from occlusion, due to extension of coils and thrombosis, but also to act as flow diverter to vary the haemodynamics in the aneurysm. In this article, two idealised cerebral wide-necked aneurysms were created, one was sidewall aneurysm with curved parent vessel and the other was terminal aneurysm with the bifurcated parent vessel. The plexiglass models of the two aneurysms were ‘treated’ with commercial porous intravascular stents. The stented physical models were scanned by Micro-CT and the numerical models of the two idealised cerebral wide-necked aneurysms after stent placement were constructed from the scanned image files. The pulsatile flow of non-Newtonian fluid inside the models was simulated by using computational fluid dynamics package. From the simulated flow dynamics, various haemodynamic characteristics such as velocity contours, wall shear stress and oscillatory shear index (OSI) were computed. The velocity of the jet entering the sacs reduced after stent was deployed across the necks of both sidewall and terminal aneurysms; the wall shear stress on the distal neck of sidewall aneurysm reduced, the wall shear stress on the dome of the terminal aneurysm increased and the OSI on the dome of the terminal aneurysm reduced. Therefore, stent placement not only promotes thrombus formation in both aneurysm models but also reduces the regrowth risk of the sidewall aneurysm and the rupture risk of the terminal aneurysm.