Responses of the mussel Mytilusedulis L. to simulated subarctic tide pool conditions

Mussels in subarctic Norway commonly occur in shallow intertidal pools. By living in pools (a habitat rarely inhabited in lower latitudes) they are insulated against low air temperatures but exposed to high salinities (<70°/oo) beneath overlying ice. Mussels avoid exposing their tissues to such high salinities because a shell valve closure response to low temperature operates at about ?1.5°C before ice sheets form and bottom water salinities rise. Shell valve closure coincides with very low cardiac and ciliary activity.     

Hemodynamic monitoring by intracardiac impedance measured by cardiac resynchronization defibrillators: Evaluation in a controlled clinical setting (BIO.Detect HF II study)

BackgroundIn patients with cardiac resynchronization therapy defibrillators (CRT-Ds), intracardiac impedance measured by dedicated CRT-D software may be used to monitor hemodynamic changes. We investigated the relationship of hemodynamic parameters assessed by intracardiac impedance and by echocardiography in a controlled clinical setting.MethodsThe study enrolled 68 patients (mean age, 66 ± 9 years; 74% males) at 12 investigational sites. The patients had an indication for CRT-D implantation, New York Heart Association class II/III symptoms, left ventricular ejection fraction 15%–35%, and a QRS duration ≥150 ms. Two months after a CRT-D implantation, hemodynamic changes were provoked by overdrive pacing. Intracardiac impedance was recorded at rest and at four pacing rates ranging from 10 to 40 beats/min above the resting rate. In parallel, echocardiography measurements were performed. We hypothesized that a mean intra-individual correlation coefficient (r_mean) between stroke impedance (difference between end-systolic and end-diastolic intracardiac impedance) measured by CRT-D and the aortic velocity time integral (i.e., stroke volume) determined by echocardiography would be significantly larger than 0.65.ResultsThe hypothesis was evaluated in 40 patients with complete data sets. The r_mean was 0.797, with a lower confidence interval bound of 0.709. The study hypothesis was met (p = 0.007). A stepwise reduction of stroke impedance and stroke volume was observed with increasing heart rate.ConclusionsIntracardiac impedance measured by implanted CRT-Ds correlated well with the aortic velocity time integral (stroke volume) determined by echocardiography. The impedance measurements bear potential and are readily available technically, not requiring implantation of additional material beyond standard CRT-D system.     

经皮心脏瓣膜置换术研究进展

经皮心脏瓣膜置换术是心血管疾病治疗领域中起步不久的新技术。随着生物工程学的发展,人体经皮肺动脉瓣膜、主动脉瓣膜置换取得了初步成功,它为微创治疗瓣膜疾病提供了一个崭新的思路。本文主要介绍这一技术的发展现状与未来的前景。     

Subcutaneous Angiotensin II Infusion using Osmotic Pumps Induces Aortic Aneurysms in Mice

Osmotic pumps continuously deliver compounds at a constant rate into small animals. This article introduces a standard protocol used to induce aortic aneurysms via subcutaneous infusion of angiotensin II (AngII) from implanted osmotic pumps. This protocol includes calculation of AngII amount and dissolution, osmotic pump filling, implantation of osmotic pumps subcutaneously, observation after pump implantation, and harvest of aortas to visualize aortic aneurysms in mice. Subcutaneous infusion of AngII through osmotic pumps following this protocol is a reliable and reproducible technique to induce both abdominal and thoracic aortic aneurysms in mice. Infusion durations range from a few days to several months based on the purpose of the study. AngII 1,000 ng/kg/min is sufficient to provide maximal effects on abdominal aortic aneurysmal formation in male hypercholesterolemic mouse models such as apolipoprotein E deficient or low-density lipoprotein receptor deficient mice. Incidence of abdominal aortic aneurysms induced by AngII infusion via osmotic pumps is 5 - 10 times lower in female hypercholesterolemic mice and also lower in both genders of normocholesterolemic mice. In contrast, AngII-induced thoracic aortic aneurysms in mice are not hypercholesterolemia or gender-dependent. Importantly, multiple features of this mouse model recapitulate those of human aortic aneurysms.     

Structure and orientation of collagen fibres in human mitral valve

The structure and distribution of collagen fibres in chordae tendineae, anterior leaflet and annulus fibrous of human mitral valve has been investigated using high and small angle X-ray diffraction. The molecular packing of collagen in native mitral valve components is very similar to that in native rat tail tendon. The distribution and orientation of collagen fibres in unstretched and stretched specimens has been deduced by the arcing of the high and small angle meridional reflections. Collagen fibres, which are aligned along the chordae tendineae, are preferentially distributed along the branchings of the chordae into the anterior leaflet and then course towards the annulus fibrous. However, in the anterior leaflet a considerable amount of collagen fibres are organized in a tridimensional isotropic network even after high deformation of the tissue.     

Pulsatile spiral blood flow through arterial stenosis

Pulsatile spiral blood flow in a modelled three-dimensional arterial stenosis, with a 75% cross-sectional area reduction, is investigated by using numerical fluid dynamics. Two-equation k-ω model is used for the simulation of the transitional flow with Reynolds numbers 500 and 1000. It is found that the spiral component increases the static pressure in the vessel during the deceleration phase of the flow pulse. In addition, the spiral component reduces the turbulence intensity and wall shear stress found in the post-stenosis region of the vessel in the early stages of the flow pulse. Hence, the findings agree with the results of Stonebridge et al. (2004). In addition, the results of the effects of a spiral component on time-varying flow are presented and discussed along with the relevant pathological issues.     

Absence of Cardiac Valve Dysfunction in Obese Patients Treated with Sibutramine

BACH, DAVID S., AILA M. RISSANEN, CARL M. MENDEL, GILLIAN SHEPHERD, STEVEN R. WEINSTEIN, FINIAN KELLY, TIMOTHY B. SEATON, BABABHAI PATEL, TUULA A. PEKKARINEN, AND WILLIAM F. ARMSTRONG. Absence of cardiac valve dysfunction in obese patients treated with sibutramine. Obes Res. Objective: Serotonin-releasing agents prescribed as weight-loss medications have been implicated as a cause of acquired aortic and mitral valve abnormalities. Sibutramine hydrochloride (MERIDIA®) is a serotonin and norepi-nephrine reuptake inhibitor with proven efficacy of weight reduction. The purpose of this study was to determine the incidence of cardiac valve disease in sibutramine-treated patients. Research Methods and Procedures: Obese patients with type 2 diabetes mellitus enrolled in an ongoing double-blind, placebo-controlled, parallel-arm, 12-month study of sibutramine (followed by a 12-month open label extension) underwent transthoracic echocardiographic imaging and color Doppler interrogation for assessment of cardiac valve anatomy and function. Results: A total of 210 patients were evaluated. Of these, 133 were receiving sibutramine (72 in the double-blind period), and 77 were receiving placebo. The mean ± Standard Deviation age was 54±9 years, and the mean duration of treatment was 229±117 days (approximately 7. 6 months). The prevalence of left-sided cardiac valve dysfunction was low and similar for the two treatment groups (sibutramine 31133, or 2. 3%; placebo 2/77, or 2. 6%). All five cases were cases of aortic insufficiency; four were mild, one was severe (in a placebo patient). All three sibutramine cases were patients over age 50; two had a history of systemic hypertension. Conclusion: The prevalence of left-sided cardiac valve dysfunction was not higher than background in obese patients treated with sibutramine for an average of 7. 6 months.     

Photobiomodulation and estrogen stabilize mitochondrial membrane potential in angiotensin–II challenged porcine aortic smooth muscle cells

Rupture of Abdominal aortic aneurysm (AAA) is among the 15 leading causes of death after age 65. Using high frequency ultrasound, we showed that photobiomodulation (PBM) prevents formation and progression of AAA in the angiotensin-II (Ang-II)-infused, apolipoprotein-e-deficient mouse model. In the current study we report that while challenge of porcine aortic Smooth Muscle Cells (SMCs) with Ang-II (1 μM) resulted in a marked decay in mitochondrial membrane potential (MitMP) vs non-challenged cells, treatment with PBM (continuous diode laser, 780 nm, 6.7 mW/cm², 5 minutes, 2 J/cm²) or pre-incubation with estrogen (50 nM, 1 hour) significantly attenuated this deterioration in MitMP. We also report that PBM and estrogen markedly affected porcine aortic SMC contraction and modified mitochondrial dispersion reflecting important influence on SMC function. These studies provide strong evidence of the important underlying role of mitochondria in the preventive effect of PBM on formation and progression of AAA and its reduced incidence and delayed onset in women.     

A surgeon’s quest

This last part of surgery, namely, operations, is a reflection on the healing art; it is a tacit acknowledgement of the insufficiency of surgery. It is like an armed savage who attempts to get that by force which a civilised man would get by stratagem. John Hunter [Palmer John (ed.) 1835 The works of John Hunter, Vol. 1 (London: Longman)]