Three-dimensional visualization of stationary flow behind artificial heart valves]

The visualization and quantitative analysis of flow offers a possibility for the hydrodynamic characterization of artificial heart valves. Different types of valves can be compared if velocity profile and the turbulent shear stress caused by the prosthesis are known. The tracer technique was selected, since it permits visualization also of turbulent flow through the valve. With the aid of a simple optical device the three-dimensional flow pattern behind the valve is determinable. The main features of the method are: The regions of interest can easily be identified. Velocity profiles can be determined and shear stress and turbulence intensities estimated. The experimental setup is simple, calibration is not necessary, and it can be used for turbulent flows. The method can be used only with transparent fluids and vessels; measurements in blood are not possible. Because of the large number of measuring points required the method is very time-consuming. The use of an automatic picture analyzing system would make it possible to increase the number of pictures processed, and thus increase resolution. The velocity profile of a three-finger-valve, the TAD 29, was established at a distance of 20 mm from the ring, and compared with known profiles from the literature. The valve has an opening angle of 70 degrees. All typical regions for the flow of an artificial heart valve, such as jet, stagnation gone, backflow and turbulence were demonstrated.     

Synoptic-scale nonlinear stationary magnetized Rossby waves in the ionospheric E-layer

Magnetized Rossby waves are produced by a dynamo electric field and represent the ionospheric generalization of tropospheric Rossby waves in a rotating atmosphere with a spatially inhomogeneous geomagnetic field. They are described by the modified Charney-Obukhov equation with a Poisson-bracket convective nonlinearity. This type of equation has solutions in the form of synoptic-scale nonlinear solitary dipole vortex structures of 1000–3000 km in diameter. With the use of equivalence conditions, various stationary nonlinear solutions are obtained and investigated analytically. The basic characteristics of stationary vortex structures for magnetized Rossby waves are investigated. Published in Russian in Fizika Plazmy, 2006, Vol. 32, No. 12, pp. 1079–1091. The text was submitted by the authors in English.     

Interactions between prostaglandins E2 and F2alpha and isoprenalin in the dog heart in situ]

The effects of PGE2 and PGF2alpha on the isoprenaline induced elevation of myocardial contractility were studied on hearts of anesthetized dogs. The steady state effects were determined after single or simultaneous infusion of the substances. Two indices of contractility were used for the quantification of inotropic effects. PGE2 but not PGF2alpha showed positivinotropic effects. PGE2 significantly inhibited the inotropic responses induced by isoprenaline (p less than 0,01); whereas PGF2alpha was without any effect in this direction. The results are discussed with respect of a postjunctional action of PGE2.     

对犬心丝虫病的一点认识

2000年我们购家犬50只供实验用。饲养中部分犬出现食欲不佳、胃肠功能紊乱、精神烦躁、呼吸异常等临床症状,并伴有心电图异常,甚至死亡。经解剖观察,在右心室内发现有犬恶丝虫。我们重点观察了犬心丝虫病的症状,结合系统尸体解剖,获得一些体会,供同行参考。1 动物来源农村家犬50只,收购于四川省简阳市农村。这些犬为村民散养,伺养环境一般,外观健康,年龄1～3岁以上,体重7～13kg,雌雄各半。2 临床症状及解剖观察     

Plasticity of death rates in stationary phase in Saccharomyces cerevisiae

For the species that have been most carefully studied, mortality rises with age and then plateaus or declines at advanced ages, except for yeast. Remarkably, mortality for yeast can rise, fall and rise again. In the present study we investigated (i) if this complicated shape could be modulated by environmental conditions by measuring mortality with different food media and temperature; (ii) if it is triggered by biological heterogeneity by measuring mortality in stationary phase in populations fractionated into subpopulations of young, virgin cells, and replicatively older, non-virgin cells. We also discussed the results of a staining method to measure viability instead of measuring the number of cells able to exit stationary phase and form a colony. We showed that different shapes of age-specific death rates were observed and that their appearance depended on the environmental conditions. Furthermore, biological heterogeneity explained the shapes of mortality with homogeneous populations of young, virgin cells exhibiting a simple shape of mortality in conditions under which more heterogeneous populations of older cells or unfractionated populations displayed complicated death rates. Finally, the staining method suggested that cells lost the capacity to exit stationary phase and to divide long before they died in stationary phase. These results explain a phenomenon that was puzzling because it appeared to reflect a radical departure from mortality patterns observed for other species.     

Urinary clearance of noradrenaline in the dog]

Glomerular filtration rate (GFR) and noradrenaline clearance are highly correlated in anesthetized dogs (ratio CNA-3H/GFR approximately 1).     

Urinary clearance of dl-isopropylnoradrenaline in the dog]

In dogs, the urinary clearance of IPNA-3H is very near GFR (ratio CIPNA-3H/GFR = 0,92). This ratio is not modified by cocaine. In our experimental conditions, we observe no tubulary secretion of IPNA-3H.     

Computer analysis of ventricular pressure recordings: evaluation of myocardial contractility on the dog heart in situ]

The contractile indices Vmax (maximum shortening velocity of the contractile element) and ARPD (power averaged rate of power density generation) which have been shown to be unaffected by alterations in preload and afterload were computed from isovolumic left ventricular pressure data of dogs. The two indices were tested for their ability to detect changes in contractility induced by a positive inotropic drug (Isoprenalin). Whereas a good correlation was found between ARPD and Vmax (coefficient of correlation 0,895) the index ARPD was more sensitive to augmentation of myocardial contractility; also because it is simpler to obtain computationally and more appropriate for the intact heart from a theoretical point of view. ARPD should be useful especially for quantification of acute changes in myocardial contractility.     

Protection of the ischaemic dog heart by oxfenicine

Myocardial ischaemia was produced in closed-chest anaesthetised dogs by coronary embolisation with Sephadex microspheres. Myocardial enzyme release and lactate production were used to quantitate the severity of ischaemia. In dogs pretreated with oxfenicine (S-4-hydroxyphenylglycine; 0.1mmol.kg^?1) 1h prior to embolisation, peak lactate production (extraction ratio ?25±13%) was significantly less than in control dogs (?72±5%; p < 0.01), and the time post-embolisation at which nett lactate uptake became re-established was reduced from 1.4h to 0.4h. Myocardial release of lactate dehydrogenase isoenzyme 1 (HBDH) up to 5h post-embolisation was reduced by 40% in oxfenicine pretreated dogs and there was a similar reduction in the HBDH arterio-coronary sinus difference. Since oxfenicine pretreatment did not modify the major haemodynamic determinants of myocardial oxygen consumption, we conclude that these beneficial effects result from the ability of oxfenicine to divert myocardial metabolism from fatty acid to carbohydrate oxidation, with a consequent reduction in oxygen demand.