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  • 1
    Electronic Resource
    Electronic Resource
    Establishment of the experimental conditions for inducing saccular cerebral aneurysms in primates with special reference to hypertension (1989)
    Springer
    Acta neurochirurgica 96 (1989), S. 132-136 
    Details
    ISSN: 0942-0940
    Keywords: Aneurysms in primates ; experimental conditions ; hypertension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To find out the optimum experimental conditions for the induction of saccular cerebral aneurysms in primates, various procedures for inducing renal hypertension were used in cynomolgous monkeys treated with ligation of unilateral carotid artery and betaamino-propionitrile feeding. Animals were divided into four groups. In the first group, both kidneys were simultaneously compressed with a figure-eight ligation. In the second group, the kidneys were ligated at an interval of one week. In the third and fourth groups, posterior branches of both renal arteries were ligated at the same time, or at an interval of one week, respectively. Hypertension about 200 mmHg was produced only in the last group and aneurysms were noted in more than half of these hypertensive animals. The best procedure for renal hypertension to induce cerebral aneurysms was proved to be ligation of the posterior branches of both renal arteries at an interval of one week. We can conclude that lasting severe hypertension is essential for inducing cerebral aneurysms in monkeys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01456172
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  • 2
    Electronic Resource
    Electronic Resource
    In vivo study of flow pattern at human carotid bifurcation with regard to aneurysm development (1992)
    Springer
    Acta neurochirurgica 115 (1992), S. 112-117 
    Details
    ISSN: 0942-0940
    Keywords: Flow pattern ; cerebral aneurysm ; endothelium ; shear stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to investigate the developmental mechanism of cerebral aneurysms, the in vivo flow pattern around human cervical carotid bifurcations was studied by flow visualization using digital subtraction angiography with an isotonic contrast medium. The blood stream containing the medium impinged on the apex, then proceeded along the walls of the branches. After opacification of the whole lumen around the apex, most of the medium was carried away, while some remained for a few seconds at the carotid sinus. In the internal carotid artery, the blood struck the wall at an oblique angle near the tops of the arterial curvatures. In cases with atheromatous plaque or kinking of the branch, the blood passed through the stenosed segment and moved upstream, indicating turbulence. The study suggests that haemodynamic forces around the apex consist mainly of impingement on the apex and shear stress to the wall at and around the apex. In branches, high shear stress seems to exist. It might be possible that high shear stress causes degenerative changes in the endothelial layer, initiating the formation of saccular and fusiform cerebral aneurysms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01406368
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Spontaneous saccular cerebral aneurysm in a rat (1991)
    Springer
    Acta neurochirurgica 109 (1991), S. 63-65 
    Details
    ISSN: 0942-0940
    Keywords: Spontaneous aneurysm in animal ; elastic lamina ; degenerative changes ; histopathology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A saccular cerebral aneurysm was incidentally found at the bifurcation of a fenestrated anterior cerebral artery of 35-week-old Sprague-Dawley rat. The animal had been fed a normal laboratory diet. The internal lamina extended for a short distance into the neck of the aneurysm and then suddenly disappeared. The medial layer ended abruptly at the neck of the aneurysm. The aneurysmal wall consisted mainly of connective tissue, and of some poorly stained fragments of elastic lamina. No evidence of polyarteritis nodosa or any other inflammatory reaction was obtained. These findings were the same as those observed in man. Therefore, this aneurysm proved to be of truly spontaneous origin. In contrast to experimental aneurysms in rats and in monkeys, in which aneurysms are observed very often, degenerative changes of the elastic lamina in spontaneous aneurysm in the rat were confined to the neck of the aneurysm. This fact may explain partly the difference in frequency between spontaneous and experimental aneurysms in animals. The present study indicates that degenerative changes of the elastic lamina play a very important role in the development of saccular cerebral aneurysms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01405700
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  • 4
    Electronic Resource
    Electronic Resource
    Degenerative changes in the internal elastic lamina relating to the development of saccular cerebral aneurysms in rats (1993)
    Springer
    Acta neurochirurgica 121 (1993), S. 76-81 
    Details
    ISSN: 0942-0940
    Keywords: Cerebral aneurysm ; internal elastic lamina ; degenerative changes ; catabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to investigate the developmental mechanism of saccular cerebral aneurysms, changes in the internal elastic lamina at the junction of the anterior cerebral artery and the olfactory artery were electronmicroscopically studied in 6 control and 6 experimental rats undergoing ligation of the left carotid artery and branches of both renal arteries. In the control group, spontaneous destructive changes occurred on the luminal side of the internal elastic lamina and progressed from the luminal towards the abluminal side as the elastic lamina advanced to the apex. Close to the apex, these changes invaded and disrupted the whole elastic lamina. The elastic lamina was replaced by sparsely lined up lumps of elastic tissue in the walls of early aneurysmal alterations, and was atrophied and disappeared totally in the walls of aneurysmal alterations that had reached an advanced stage. These spontaneous changes were in agreement with reports in the literature and our own previous investigations. From the findings in the experimental rats it becomes likely that the aneurysmal changes in the elastic lamina are exaggerated forms of the normal catabolic metabolism. Therefore its synthesis on the abluminal side no longer balances with the catabolism on the luminal side. It is strongly suggested that aneurysmal alterations progress from the luminal towards the abluminal side of arterial walls and that the lytic process of elastase might play a role in the degenerative changes in aneurysmal development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01405187
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  • 5
    Electronic Resource
    Electronic Resource
    Nonlinear anomalies of conducting media with conical microconstrictions (1999)
    Springer
    Technical physics letters 25 (1999), S. 142-144 
    Details
    ISSN: 1090-6533
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An investigation is made of the divergence of the higher moments of the field in conducting structures with conical singular regions. Calculations are made of the critical values of the parameters which determine the nonlinear anomalies of a medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1262380
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  • 6
    Electronic Resource
    Electronic Resource
    Lithium isotope separation on an ion exchange resin having azacrown ether as an anchor group (1997)
    Springer
    Journal of radioanalytical and nuclear chemistry 220 (1997), S. 229-231 
    Details
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A study on the separation of lithium isotopes was carried out with an ion exchange resin having 1,7,13-trioxa-4,10,16-triazacyclooctadecane (N3O3) as an anchor group. The lighter isotope,6Li concentrated in the resin phase, while the heavier isotope,7Li is enriched in the fluid phase. Upon column chromatography [0.6 cm (I. D.)×20 cm (height)] using 1.0M ammonium chloride solution as an eluent, single separation factor, α, 1.068 (6Li/7Li)resin/(6Li/7Li)solution was obtained by theGlueckauf method from the elution curve and isotope ratios.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02034861
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    Paper (German National Licenses)
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