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  • 1
    Electronic Resource
    Electronic Resource
    13C-selective two-stage IRMPD of mixtures of CHClF2 and HI (1990)
    Springer
    Applied physics 50 (1990), S. 385-392 
    Details
    ISSN: 1432-0649
    Keywords: 82.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The 13C-selective infrared multiple-photon decomposition (IRMPD) of mixtures of CHClF2 and HI was examined in collimated and focused beam geometries using a CO2TEA laser. The carbon-containing products were CH2F2 and CHF2I. The former product showed remarkably high 13C atom concentrations beyond 95% under selected experimental conditions, while the latter contained 25% or less. The observed results can be explained satisfactorily in terms of the consecutive two-stage IRMPD process occurring in a single irradiation procedure, where the first-stage IRMPD of natural CHClF2 produces 13C-enriched CHF2I via the insertion of the initial decomposition fragment CF2 into HI, and the second stage is the subsequent 13C-selective IRMPD of the CHF2I to form a CHF2 radical and an I atom. The CHF2 radical reacts with HI to form CH2F2. Decomposition probabilities of 12CHClF2 and 13CHClF2 were measured as a function of laser fluence to optimize enrichment conditions. Furthermore, partial decomposition probabilities or relative production yields were measured as functions of laser line, pressure of HI, and pressure of CHClF2. Both stages showed high 13C selectivities in the irradiation with the laser radiation around 1040 cm−1 and at fluences below 4 J cm−2. This mixture is one of the most promising chemical systems for the production of highly enriched 13C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00325091
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  • 2
    Electronic Resource
    Electronic Resource
    Endothelin causes contraction of canine and bovine arterial smooth muscle in vitro and in vivo (1990)
    Springer
    Acta neurochirurgica 104 (1990), S. 42-47 
    Details
    ISSN: 0942-0940
    Keywords: Endothelin ; neuropeptide Y ; angiotensin II ; cerebral arteries ; cerebral circulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have studied the effect of endothelin, an endothelium-derived peptide, on isolated canine and bovine cerebral arteries in vitro and on canine vertebral blood flow (VBF) in vivo. Endothelin produced a dose-dependent contraction of canine and bovine arterial smooth muscle with ED50 values ranging from 4 to 8 nM. The response to endothelin developed slowly and persisted as a sustained contraction. Maximal contraction by endothelin required the presence of extracellular calcium and was independent of the presence of endothelium. The maximal contraction produced by endothelin was approximately 2–3 times greater than that produced by neuropeptide Y or angiotensin II. The injection of endothelin into the vertebral artery decreased vertebral blood flow (VBF) dose-dependently without affecting systemic blood pressure or heart rate. The decrease in VBF produced by endothelin was long-lasting, like that produced by neuropeptide Y, but more potent. The present data, together with our previous study demonstrating that the intracisternal injection of endothelin induces an unusually long-lasting decrease in the basilar artery diameter angiographically, suggests that endothelin may act as a long-acting vasoconstrictor in cerebral vascular disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01842892
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  • 3
    Electronic Resource
    Electronic Resource
    Normovolaemic induced hypertension therapy for cerebral vasospasm after subarachnoid haemorrhage (1990)
    Springer
    Acta neurochirurgica 103 (1990), S. 18-26 
    Details
    ISSN: 0942-0940
    Keywords: Cerebral vasospasm ; haemorrhagic infarction ; intracranial aneurysm ; normovolaemic induced hypertension therapy ; subarachnoid haemorrhage ; Swan-Ganz catheter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We showed that normovolaemic induced hypertension therapy was effective in reducing ischaemic symptoms attributed to cerebral vasospasm in 41 patients after subarachnoid haemorrhage. By inducing hypertension to 25% to 50% above normal systolic arterial blood pressure, we observed that in 17 of 24 cases (71%) neurological deficits improved. In four cases of haemorrhagic infarction, the blood pressure rose to over 50% of systolic arterial pressure, and a low density area was confirmed on computerized tomography (CT) scan prior to vasospasm. Induced hypertension was therefore not considered when a low density area was revealed on CT scan. Restriction of fluid input is usually a factor in producing hypovolaemia after a neurosurgical operation. Intravascular volume expansion has been reported effective in reversing ischaemic deficits. However, according to Poiseuille's equation, increasing blood volume to a state of hypervolaemia can not enhance flow. The cerebral blood flow (CBF) was raised by increasing perfusion pressure, reducing viscosity, or increasing blood vessel diameter. Intravascular volume expansion elevates not only systemic arterial pressure, but also pulmonary artery wedge pressure over 18 mmHg and cardiac index over 2.2. Since pulmonary oedema and congestive heart failure may develop, one should monitor haemodynamic parameters with the Swan-Ganz catheter as a preventive measure. We emphasize that normovolaemic induced hypertension, maintaining haemodynamics subset 1 of the comparable haemodynamic subsets, is effective in raising perfusion pressure of CBF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01420187
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  • 4
    Electronic Resource
    Electronic Resource
    Dose escalation trial of a novel calcium antagonist, AT877, in patients with aneurysmal subarachnoid haemorrhage (1990)
    Springer
    Acta neurochirurgica 107 (1990), S. 11-15 
    Details
    ISSN: 0942-0940
    Keywords: Subarachnoid haemorrhage ; chronic cerebral vasospasm ; calcium antagonist ; AT877 ; HA 1077
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The initial dose-escalating clinical trial of a novel calcium antagonist, AT877, in patients with aneurysmal subarachnoid haemorrhage is reported. AT877 is characterized by its strong spasmolytic activity, its inhibition of intracellular calcium ion activity, and the inhibiton of several protein kinases. A total of 113 patients (Hunt and Hess grades I to IV) who had undergone surgery within 3 days of aneurysmal rupture entered the study. Patients were divided into 5 groups according to the total daily dose of AT877: I: 20 mg; II: 40 mg; III: 60 mg; IV: 90 mg; and V: 120–180 mg. AT877 was given by intravenous infusion over 30 min two or three times a day for 14 days after surgery. Although AT877 did not completely abolish angiographic vasospasm, severe vasospasm was seen less frequently in patients given higher doses. Vasospasm was the cause of a poor clinical outcome (Glasgow outcome scale rating 3 or greater) in 19%, 7%, 9%, 8%, and 6% of the patients in groups I to V, respectively. The results indicated a favourable clinical effect of AT877 at doses above 40 mg per day. Only mild hypotension was seen, even when 60 mg of AT877 was infused over 30 min. AT877 appears to be effective in patients with subarachnoid haemorrhage. Part of its effect may be attributable to protection of the brain from ischaemic insults due to chronic cerebral vasospasm. However, the drug still needs to be evaluated in a placebo-controlled double-blind trial (which is currently being carried out).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01402606
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of STA-MCA anastomosis for ischaemic oculopathy due to occlusion of the internal carotid artery (1990)
    Springer
    Acta neurochirurgica 103 (1990), S. 71-75 
    Details
    ISSN: 0942-0940
    Keywords: Ischaemic oculopathy ; venous stasis retinopathy ; neovascular glaucoma ; rubeosis iridis ; STA-MCA anastomosis ; EC-IC bypass surgery
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Effects of STA-MCA anastomosis on two patients with neovascular glaucoma due to occlusion of the internal carotid artery are presented. Both patients improved in visual acuity and central retinal artery pressure as well as in signs of transient ischaemic attack. Postoperative angiography showed a marked decrease in collateral flow through the ophthalmic artery, which is reversed from the normal direction, with the development of blood flow through the anastomosis. Discussion is offered indicating that the lack of collateral flow through both the anterior and posterior communicating arteries is important in addition to occlusion of the internal carotid artery in order to produce full-blown ischaemic oculopathy such as venous stasis retinopathy, neovascular glaucoma or rubeosis iridis. It is stressed that EC-IC bypass surgery should be performed soon after the appearance of ischaemia and before the development of neovascular glaucoma or rubeosis iridis in order to obtain normal vision. In ischaemic oculopathy the results of EC-IC bypass can be evaluated objectively and quantitatively by many noninvasive neuro-ophthalmological tests which are important in discussing the efficacy of the bypass surgery.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01420195
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  • 6
    Electronic Resource
    Electronic Resource
    Extracranial vertebral artery aneurysm with neurofibromatosis (1990)
    Springer
    Neuroradiology 31 (1990), S. 533-536 
    Details
    ISSN: 1432-1920
    Keywords: Extracranial vertebral artery aneurysm ; Neurofibromatosis ; Detachable balloon ; Endovascular occlusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary An extracranial vertebral artery aneurysm in a patient with neurofibromatosis is described. The aneurysm was treated by endovascular balloon occlusion of the proximal vetebral artery. The details of the therapeutic management are discussed, and the vascular manifestations of neurofibromatosis are reviewed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00340136
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