The effect of placing an aortic wallstent across the renal artery origins in an animal model

Objectives:To assess the effect on renal blood flow and renal function of placing a Wallstent (Schneider (Europe) AG) across the renal artery origins in an animal model.Design:Laboratory animal study.Materials and methods:Six Large White pigs had Wallstents placed across the origins of one or both renal arteries. Preoperative jugular venous blood samples were submitted for blood count and urea and electrolyte estimation. The pigs were recovered for 6 weeks. At sacrifice the renal arteries and their origins were examined by aortography and direct pressure measurements were recorded from the renal arteries and both the stented and unstented portions of the aorta. Renal venous blood samples were submitted for blood count, urea and electrolyte and renin estimation while renal arterial blood samples were submitted to examination for red blood cell fragmentation. The aorta with contained stent, renal arteries and kidneys were submitted for histological examination.Results:At sacrifice no renal arteries had occluded and the stent-covered origins appeared normal with no evidence of stenosis. This was confirmed histologically. There was no statistically significant difference between the arterial pressures measured in the stented and unstented portions of aorta and the renal arteries whether or not their origins had been covered by the stent. There was no statistically significant difference between the urea and electrolyte and renin levels of renal venous blood samples irrespective of whether or not the relevant kidney had a stent across its renal artery origin. Renal arterial blood samples showed no evidence of red blood cell fragmentation and histological examination of the kidneys showed no evidence of infarction or micro-emboli. Examination of the specimens by light and scanning electron microscopy demonstrated partial endothelialisation of the stents but the renal artery origins remained widely patent despite being crossed by at least one wire in all cases.Conclusions:It may be necessary to place stents across renal artery origins during endovascular repair of abdominal aortic aneurysms. It would appear that covering renal artery origins with a Wallstent has no effect on renal perfusion pressure or function in this short-term animal model

Nuclear spin polarization of solid deuterium-tritium

It appears that parallel alignment of deuteron and triton magnetic moments increases the cross section of the nuclear reaction T(d,n) He/sup 4/ by 50%, thereby promising a laser driver of perhaps half the original energy. Both ''brute-force'' and dynamic nuclear polarization are considered, and the many potential problems of the latter are considered. High nuclear polarization by the dynamic technique requires a small nucleus-to-unpaired electron ratio, a long longitudinal nuclear relaxation time and a short longitudinal electron relaxation time. Normal D-T is shown to be inadequate, and enriched and possibly very pure molecular DT will be required. The key variable is the nuclear relaxation time, which can either depend on the interaction with rotationally excited impurity molecules or on paramagnetic defects formed by the tritium radiation. Radiation-induced DT decomposition and rotational catalysis will combat one another to affect the DT purity. The expected atom density and fractionation effects are considered. There exists one frequency at which both D and T atoms can be pumped