HTEA对全脑缺血/再灌注大鼠脑血流及海马细胞凋亡的影响

目的:研究上胸段硬膜外阻滞(high thoracic epidural anesthesia,HTEA)对大鼠全脑缺血再灌注损伤(global cerebral ischemia,GCI)再灌注期间脑血流及凋亡相关蛋白Bcl-2和Bax的影响。方法:本研究选用成年雄性Wistar大鼠成功进行T4-5间隙硬膜外置管,并建立四血管阻断的全脑缺血模型进行15 min的全脑缺血。根据通过硬膜外导管输注药物不同,随机分为四组:假手术组(Sham,0.9%生理盐水)、假手术-硬膜外组(Sham-HTEA,0.25%布比卡因)、全脑缺血组(GCI,0.9%生理盐水)和硬膜外组(HTEA,0.25%布比卡因)。给药时间从缺血前15 min开始以20μL/h的速度持续输注至再灌注24 h。缺血前至再灌注2 h观察平均动脉压(MAP)和心率(HR),激光多普勒血流仪监测脑血流(cerebral blood flow,CBF),Western-blot检测再灌注24 h海马凋亡蛋白Bcl-2和Bax含量。结果:HTEA组与GCI组相比,缺血期间及再灌注2 h内的MAP和HR无统计学差异,而与Sham组相比,GCI组的MAP缺血时升高,而再灌注时降低(P0.05);再灌注10 min的高灌注期HTEA组CBF明显低于GCI组(123.1%±35.2%vs 177.5%±32.4%,P0.01),再灌注60 min至120 min的低灌注期的大部分时间点HTEA组CBF均高于GCI组(P0.05);再灌注24 h海马组织Bax/Bcl-2比例明显降低(P0.01)。结论:0.25%的布比卡因20μL·h-1连续上胸段硬膜外阻滞可以维持血流动力学稳定,且可改善大鼠全脑缺血再灌注后低灌注期的脑血流量,并减少再灌注24 h海马Bax/Bcl-2比例。     

Regulation of fibronectin matrix assembly and capillary morphogenesis in endothelial cells by Rho family GTPases

Fibronectin (FN) fibrillogenesis is an essential biological process mediated by α5β1 integrin and cellular contractile forces. Assembly of a FN matrix by activated endothelial cells occurs during angiogenic blood vessel remodeling and signaling components that control this event represent attractive therapeutic targets. Here we examined the role of individual Rho GTPases in FN matrix remodeling by selectively attenuating their expression in cultured endothelial cells. Whereas pharmacological ablation of myosin-regulated contractility abrogated matrix assembly, no significant decrease was detected in the amount of FN deposited by RhoA, RhoB-, RhoC-, Rac1-, or Cdc42-depleted cells. Rather, distinct differences in fiber arrangement were observed. Most strikingly, RhoA silenced cells assembled a fine FN meshwork beneath α5β1 integrin-based fibrillar adhesions, in the absence of classical focal adhesions and actin stress fibers, indicating that α5β1 integrin translocation and FN fibril elongation can occur in low tension states such as those encountered by newly-forming vessels in tissue. In contrast, highly contractile Cdc42-deficient cells deposited FN globules and Rac-deficient cells assembled long arrays, reflecting their increased motility. We propose that regulation of FN scaffolds by Rho GTPase signaling impacts bidirectional communications and mechanical interactions between endothelial cells and their extracellular matrix during vascular morphogenesis.     

叉头框-c2基因在主动脉弓发育过程中的作用

为了研究叉头框-c2（Forkhead Box c2, Fox c2）基因在心血管发生和发育中的作用, 通过制作小鼠的Fox c2 基因无效突变,解析该基因缺失鼠主动脉弓的异常发育状况.纯合子胎鼠从12.5天胚胎(embryo, E)开始有宫内死亡;即使完成宫内发育过程,新生鼠出生24 h后也全部死亡.这些鼠全部表现出与人的先天性心血管发育缺陷相似的B型或C型主动脉弓离断.杂合子鼠发育正常.E10.5胚胎的原位杂交分析显示,Fox c2 mRNA在第三、第四和第六弓型动脉强烈表达,而第四弓型动脉在E10.5胚胎后逐渐消失.这些结果表明,在主动脉弓形成过程中,Fox c2基因产物是左第四弓形动脉广泛改建所必需.     

Aquaporin-facilitated transmembrane diffusion of hydrogen peroxide

Background

Hydrogen peroxide (H₂O₂) is an important signaling compound that has recently been identified as a new substrate for several members of the aquaporin superfamily in various organisms. Evidence is emerging about the physiological significance of aquaporin-facilitated H₂O₂ diffusion.

Scope of review

This review summarizes current knowledge about aquaporin-facilitated H₂O₂ diffusion across cellular membranes. It focuses on physicochemical and experimental evidence demonstrating the involvement of aquaporins in the transport of this redox signaling compound and discusses the regulation and structural prerequisites of these channels to transmit this signal. It also provides perspectives about the potential importance of aquaporin-facilitated H₂O₂ diffusion processes and places this knowledge in the context of the current understanding of transmembrane redox signaling processes.

Major conclusions

Specific aquaporin isoforms facilitate the passive diffusion of H₂O₂ across biological membranes and control H₂O₂ membrane permeability and signaling in living organisms.

General significance

Redox signaling is a very important process regulating the physiology of cells and organisms in a similar way to the well-characterized hormonal and calcium signaling pathways. Efficient transmembrane diffusion of H₂O₂, a key molecule in the redox signaling network, requires aquaporins and makes these channels important players in this signaling process. Channel-mediated membrane transport allows the fine adjustment of H₂O₂ levels in the cytoplasm, intracellular organelles, the apoplast, and the extracellular space, which are essential for it to function as a signal molecule. This article is part of a Special Issue entitled Aquaporins.     

Osteopathic Manipulative Treatment as a Useful Adjunctive Tool for Pneumonia

Pneumonia, the inflammatory state of lung tissue primarily due to microbial infection, claimed 52,306 lives in the United States in 2007¹ and resulted in the hospitalization of 1.1 million patients². With an average length of in-patient hospital stay of five days², pneumonia and influenza comprise significant financial burden costing the United States $40.2 billion in 2005³. Under the current Infectious Disease Society of America/American Thoracic Society guidelines, standard-of-care recommendations include the rapid administration of an appropriate antibiotic regiment, fluid replacement, and ventilation (if necessary). Non-standard therapies include the use of corticosteroids and statins; however, these therapies lack conclusive supporting evidence⁴. (Figure 1)Osteopathic Manipulative Treatment (OMT) is a cost-effective adjunctive treatment of pneumonia that has been shown to reduce patients’ length of hospital stay, duration of intravenous antibiotics, and incidence of respiratory failure or death when compared to subjects who received conventional care alone⁵. The use of manual manipulation techniques for pneumonia was first recorded as early as the Spanish influenza pandemic of 1918, when patients treated with standard medical care had an estimated mortality rate of 33%, compared to a 10% mortality rate in patients treated by osteopathic physicians⁶. When applied to the management of pneumonia, manual manipulation techniques bolster lymphatic flow, respiratory function, and immunological defense by targeting anatomical structures involved in the these systems^{7,8, 9, 10}.The objective of this review video-article is three-fold: a) summarize the findings of randomized controlled studies on the efficacy of OMT in adult patients with diagnosed pneumonia, b) demonstrate established protocols utilized by osteopathic physicians treating pneumonia, c) elucidate the physiological mechanisms behind manual manipulation of the respiratory and lymphatic systems. Specifically, we will discuss and demonstrate four routine techniques that address autonomics, lymph drainage, and rib cage mobility: 1) Rib Raising, 2) Thoracic Pump, 3) Doming of the Thoracic Diaphragm, and 4) Muscle Energy for Rib 1.^5,11     

Numerical simulation of blood flow in the left ventricle and aortic sinus using magnetic resonance imaging and computational fluid dynamics

Understanding cardiac blood flow patterns has many applications in analysing haemodynamics and for the clinical assessment of heart function. In this study, numerical simulations of blood flow in a patient-specific anatomical model of the left ventricle (LV) and the aortic sinus are presented. The realistic 3D geometry of both LV and aortic sinus is extracted from the processing of magnetic resonance imaging (MRI). Furthermore, motion of inner walls of LV and aortic sinus is obtained from cine-MR image analysis and is used as a constraint to a numerical computational fluid dynamics (CFD) model based on the moving boundary approach. Arbitrary Lagrangian–Eulerian finite element method formulation is used for the numerical solution of the transient dynamic equations of the fluid domain. Simulation results include detailed flow characteristics such as velocity, pressure and wall shear stress for the whole domain. The aortic outflow is compared with data obtained by phase-contrast MRI. Good agreement was found between simulation results and these measurements.     

Computer modelling of maximal displacement forces in endoluminal thoracic aortic stent graft

The objective of this study was to determine the orientation and magnitude of maximal displacement forces (DFs) in the thoracic aortic aneurysm endograft (TAA endograft) in three-dimensional (3D) space. Theoretical computer model representing the anatomically worst-case scenario with respect to DF magnitude was used to calculate the magnitude and orientation of maximal DF. A patient-specific anatomical computer model of typically seen, average size anatomy was used to analyse the progression of DF throughout the cardiac cycle. Maximal DFs were 35.01 and 37.32 N in standing and supine position, respectively, in 46-mm diameter TAA graft with 90° bend. A patient-specific model shows that a maximal DF magnitude is achieved at the peak systolic flow. In both models, the orientation of the DF vector was perpendicular to the greater curvature of the aorta, with upward (cranial) and sideways components. The effect of shearing force on the total DF that acts on the TAA endograft was found negligible due to the several orders of magnitude stronger contribution of pressure forces to the total DF relative to the wall shear stress contribution, resulting in aortic diameters and angulation being the main drivers of DF. It was discovered that the TAA endografts can be subjected to much stronger DF than previously suspected. The magnitude of maximal DF in thoracic aorta in the worst-case scenario could be as high as 35.01 N (standing) and 37.32 N (supine). This new information should be used in the process of designing new generations of TAA endografts with better migration resistance properties.     

Superoxide signaling in perivascular adipose tissue promotes age‐related artery stiffness

We tested the hypothesis that superoxide signaling within aortic perivascular adipose tissue (PVAT) contributes to large elastic artery stiffening in old mice. Young (4–6 months), old (26–28 months), and old treated with 4‐Hydroxy‐2,2,6,6‐tetramethylpiperidine 1‐oxyl (TEMPOL), a superoxide scavenger (1 mm in drinking water for 3 weeks), male C57BL6/N mice were studied. Compared with young, old had greater large artery stiffness assessed by aortic pulse wave velocity (aPWV, 436 ± 9 vs. 344 ± 5 cm s^‐1) and intrinsic mechanical testing (3821 ± 427 vs. 1925 ± 271 kPa) (both P < 0.05). TEMPOL treatment in old reversed both measures of arterial stiffness. Aortic PVAT superoxide production was greater in old (P < 0.05 vs. Y), which was normalized with TEMPOL. Compared with young, old controls had greater pro‐inflammatory proteins in PVAT‐conditioned media (P < 0.05). Young recipient mice transplanted with PVAT from old compared with young donors for 8 weeks had greater aPWV (409 ± 7 vs. 342 ± 8 cm s^‐1) and intrinsic mechanical properties (3197 ± 647 vs. 1889 ± 520 kPa) (both P < 0.05), which was abolished with TEMPOL supplementation in old donors. Tissue‐cultured aortic segments from old in the presence of PVAT had greater mechanical stiffening compared with old cultured in the absence of PVAT and old with PVAT and TEMPOL (both, P < 0.05). In addition, PVAT‐derived superoxide was associated with arterial wall hypertrophy and greater adventitial collagen I expression with aging that was attenuated by TEMPOL. Aging or TEMPOL treatment did not affect blood pressure. Our findings provide evidence for greater age‐related superoxide production and pro‐inflammatory proteins in PVAT, and directly link superoxide signaling in PVAT to large elastic artery stiffness.