Magnetoelectric Effect in Amorphous Ferromagnetic FeCoSiB/Langatate Monolithic Heterostructure for Magnetic Field Sensing.

This paper investigates the possibilities of creating magnetic field sensors using the direct magnetoelectric (ME) effect in a monolithic heterostructure of amorphous ferromagnetic material/langatate. Layers of 1.5 µm-thick FeCoSiB amorphous ferromagnetic material were deposited on the surface of the langatate single crystal using magnetron sputtering. At the resonance frequency of the structure, 107 kHz, the ME coefficient of linear conversion of 76.6 V/(Oe∙cm) was obtained. Furthermore, the nonlinear ME effect of voltage harmonic generation was observed with an increasing excitation magnetic field. The efficiency of generating the second and third harmonics was about 6.3 V/(Oe2∙cm) and 1.8 V/(Oe3∙cm), respectively. A hysteresis dependence of ME voltage on a permanent magnetic field was observed due to the presence of α-Fe iron crystalline phases in the magnetic layer. At the resonance frequency, the monolithic heterostructure had a sensitivity to the AC magnetic field of 4.6 V/Oe, a minimum detectable magnetic field of ~70 pT, and a low level of magnetic noise of 0.36 pT/Hz1/2, which allows it to be used in ME magnetic field sensors.

Converse Magnetoelectric Composite Resonator for Sensing Small Magnetic Fields.

Magnetoelectric (ME) thin film composites consisting of sputtered piezoelectric (PE) and magnetostrictive (MS) layers enable for measurements of magnetic fields passively, i.e. an AC magnetic field directly generates an ME voltage by mechanical coupling of the MS deformation to the PE phase. In order to achieve high field sensitivities a magnetic bias field is necessary to operate at the maximum piezomagnetic coefficient of the MS phase, harnessing mechanical resonances further enhances this direct ME effect size. Despite being able to detect very small AC field amplitudes, exploiting mechanical resonances directly, implies a limitation to available signal bandwidth along with the inherent inability to detect DC or very low frequency magnetic fields. The presented work demonstrates converse ME modulation of thin film Si cantilever composites of mesoscopic dimensions (25 mm × 2.45 mm × 0.35 mm), employing piezoelectric AlN and magnetostrictive FeCoSiB films of 2 µm thickness each. A high frequency mechanical resonance at about 515 kHz leads to strong induced voltages in a surrounding pickup coil with matched self-resonance, leading to field sensitivities up to 64 kV/T. A DC limit of detection of 210 pT/Hz1/2 as well as about 70 pT/Hz1/2 at 10 Hz, without the need for a magnetic bias field, pave the way towards biomagnetic applications.

[Influence of protamine on expression of tight junction proteins in Caco-2].

Action of polycation protein protamine on the expression of tight junction proteins (claudins-1, -2, -3 and occludin) which contribute to paracellular transport function was investigated on cellular models of tight (MDCK I cell line) and leaky (Caco-2 cell line) epithelium. The expression of claudins-1,-3 and occludin was observed in both cell lines by methods of immunocytochemistry. Influence of protamine (100 microg/ml; 30 min; apical) on fluorescence intensity of claudins-1, -3 was different in MDCK I and Caco-2 cells. Addition ofprotamine to the incubation medium of Caco-2 cells resulted in significant increase of claudin-3 expression by 45 % (p <0.01) in comparison with control, whereas claudin-1 and occludin expression did not alter. On the contrary, in MDCK I cells protamine induced the significant decrease ofclaudin-1 and -3 expression by 25 % (p <0.001) and 15 % (p < 0.01) respectively, whereas occludin expression did not alter. It was confirmed by the methods of confocal laser scanning microscopy that protamine alter the expression of claudins-1, -3 directly in the tight junctions. Our results suggest that charged chyme components may alter paracellular permeability of epithelium.

Endovascular occlusion of intracranial aneurysms of the posterior circulation: comparison of balloons, free coils and detachable coils in 38 patients.

We treated 38 patients with 39 aneurysms of the posterior circulation by an endovascular technique using balloons, free coils or Guglielmi detachable coils (GDC) from 1986 to May 1993. The patients ranged in age from 10 to 71 years. Subarachnoid haemorrhage was the most frequent presentation (29 patients), followed by mass effect (5 patients) and epilepsy (2 patients). Treatment consisted of embolisation of the aneurysm with preservation of the parent vessel (in 29) or occlusion of the parent vessel (in 5). Multiple procedures were performed in 12 patients (32%, maximum 3 embolisations, total 17 treatments), because of incomplete initial aneurysm occlusion (in 8 cases) or re-opening of the aneurysm (in 9). Treatment could not be achieved in 5 patients. Good to excellent aneurysm occlusion was obtained in 28 patients (72%). Little or no neurological impairment occurred in 31 patients (82%). Complications related to treatment (11 patients, 29%) included 4 cases of transient cerebral ischaemia, 7 of stroke resulting in minimal neurological impairment (in 5), severe impairment (in 1) and one death. There were 6 patients who died, of rebleeding from the same aneurysm (2), basilar stroke (1) and unrelated causes (3). Comparison of the different occlusion techniques showed that the best angiographic results were obtained with balloons (good to excellent aneurysm occlusion was obtained in 17 of 22 patients treated) and the GDC (12 of 13 patients), and that less good results were given by free coils (4 of 9 patients). Complications related to treatment were fewest in patients treated with GDC (1 of 16 treatments, including multiple procedures) or free coils (2 of 12 treatments) and were more frequent with balloons (6 of 27 treatments). All five treatment failures occurred with balloon embolisation, whereas treatment was possible in all cases treated with free coils or GDC.

[Endovascular treatment of intracranial aneurysms]. / Traitement endovasculaire des anévrismes intracrâniens.

Major improvements have been achieved in endovascular treatment of intracranial aneurysms during the last twenty years. Initial techniques of selective balloon occlusion were progressively replaced by the packing of the aneurysmal pouch with very small and soft metallic devices, named coils, with controlled detachment. In some rare cases, balloon occlusion is still used in order to occlude the parent vessel or to reverse the flow, especially in the vertebro-basilar system. Essential aims for the anaesthesiologist include: complete immobility of the patient throughout the endovascular procedure, systemic anticoagulation in order to avoid any thromboembolic complication during and after treatment, prevention and/or treatment of vasospasm, precise evaluation of fluid balance during the procedure. Our experience is based on 145 aneurysms in 135 patients, treated by endovascular route; 91 (63%) of them were revealed by a subarachnoid haemorrhage (SAH). Their main locations were: the carotid siphon (33.1%), the anterior communicating artery (19.3%), the basilar artery (17.2%) and the middle cerebral artery (17.2%). Thirty-seven of these aneurysms (25.5%) were very small in size with a diameter less than 4 mm. Total or sub-total (more than 90%) occlusion was achieved in 141 aneurysms (90.3%). Thromboembolic complications occurred in eight patients (5.9%), neurological sequelae in one. Other treatment-related complications included the migration of a coil outside the aneurysm in six cases (4.4%) without neurological deficit in one and five ruptures of the aneurysm (3.7%) during the procedure with one lethal issue due to the spontaneous bleeding of a controlateral arterio-venous malformation. Thirteen patients died (9.6%). The cause of the death was related on the initial SAH in 11 of them. The two others were both due to rupture: of a second untreated aneurysm in one case and of an associated arteriovenous malformation in the second one. At present the main indications of endovascular treatment are poor or non indications for neurosurgery. Due to the quality of results, endovascular therapy will be more and more used in case of ruptured or non ruptured aneurysms.

[Endovascular treatment of vasospasm]. / Traitement endovasculaire du vasospasme.

Various therapeutic strategies have been recently proposed to prevent the vasospasm after subarachnoid haemorrhage, and to avoid its clinical consequences. Despite these progresses, mortality and morbidity of delayed ischaemic consequences of vasospasm remain important. Two endovascular treatments have been proposed. The successful use of transluminal angioplasty for vasospasm was first reported by Zubkov in 1984. Transluminal angioplasty is very effective with clinical improvement when the treatment is undertaken without delay after the onset of symptoms. Limitations of this technique are the inaccessibility of distal arteries and the risks (vascular rupture or occlusion). More recently, to overcome these limitations, a selective intraarterial infusion of papaverine has been proposed. These infusions are less risky and can be employed in distal vasospasm. However, clinical results seem to be less favourable and often transient. These two techniques are still used with slightly different indications. According to our experience, it seems reasonable to reserve transluminal angioplasty for symptomatic vasospasm, associated with papaverine or not, and to use papaverine alone in all other cases.

Selective Intra-arterial Thrombolysis for Embolic Complications of Cerebral Endovascular Therapy.

SUMMARY: Cerebral thrombo-embolic complications seldom occur during intracranial endovascular therapeutic procedures. Yet, despite a systemic preventive regimen of pre-operative intravenous acetylsalicylic acid and effective systemic heparinisation, we encountered seven complications of this type over a period of five years, a 3.7 per thousand incidence (7/1858). Local intra-arterial thrombolysis performed immediately after the thrombo-embolic complication resulted in complete recanalization in five cases and partial recanalization in two. CT scans performed 24 hours after thrombolysis were normal in six of the seven patients. Only one female patient with partial recanalization showed a limited cortical infarct in the parietal distribution of the middle cerebral artery territory. In all seven cases recanalization of the occluded vessel resulted in a return to the baseline initial neurological status. This short series demonstrates the usefulness of emergent thrombolysis dealing with the thrombo-embolic complications of angiography or endovascular therapy. These results are in agreement with these experimental data showing that early recanalization can prevent macroscopically visible infarcts.

[Value of transcranial Doppler in the monitoring of aneurysmal subarachnoid hemorrhage treated with calcium inhibitors]. / Intérêt du Doppler transcrânien au cours de la surveillance des hémorragies méningées anévrismales traitées par inhibiteurs calciques.

Fifty four patients (33 male and 21 female, mean age 47) with spontaneous aneurysmal subarachnoid hemorrhages have been tested by repeated TCD: 25 of them were systematically administered intravenous Nimodipine when admitted at hospital, the 29 others constituted a reference group. There was no statistically significant difference between the two groups of patients for age, sex, initial clinical status, importance of bleeding at CT scan, localization of aneurysm or existence of an angiospasm, whether clinically symptomatic or not. In 72% of the cases, TCD allowed to prove the existence of an angiospasm when higher flow velocity was registered in cranial basal arteries. There was no significant difference between the two groups. The final clinical status of the patients seemed to be more favourable in the treated group. Yet it did not appear to be directly linked to the existence of a spasm or not. This argued in favour of a non-univocal mechanism of action of Nimodipine.

[Diluted albumin-dextran 40 combination in treating arteriopathy of the lower extremities by normovolemic hemodilution. The rheological effects]. / Association albumine diluée-Dextran 40 dans le traitement de l'artériopathie des membres inférieurs par hémodilution normovolémique. Incidences rhéologiques.

16 arteritic patients at stages II, III or IV according to Fontaine's ranking system were treated by normovolemic hemodilution (HDN). The procedure consisted of the daily withdrawal of 500 ml of blood, which was replaced by 250 ml of a 4% solution of human albumin and 250 ml of Dextran 40. The procedure was applied, on average, for three days in succession until the patient's hematocrit reached 0.30. The therapy was carried out over a total of 8 weeks in order to maintain hematocrit levels at between 0.30 and 0.35. Improvement was observed in clinical factors: a 100% increase in walking perimeter in stage II patients, disappearance of decubitus pain in stage III patients, wound healings in stage IV patients. The following rheological and platelet parameters were studied: plasma and blood viscosity with hematocrit level 0.40 and for seven speed of scissoring, red blood cell aggregation index, platelet aggregation, MDA platelet levels, plasma BTG. Clinical results revealed that by the 56th day of treatment, 8 patients had improved and 8 remained stationary (the condition of 3 of the "stationary" patients in fact worsened having evolved according to the normal development of arteritic disease). The improvements observed persist several months after normovolemic hemodilution has been discontinued, with the results for the longest studied patient going back as far as 15 months. With regard to the hemorheological parameters (which, on Day 0, are always disturbed), they tend to improve during the hospitalization period and stabilize at levels lying between the values measured on Day 0 and normal values.(ABSTRACT TRUNCATED AT 250 WORDS)

[Intentional normovolemic hemodilution in the medical treatment of lower limb arteritis]. / Hémodilution normovolémique intentionnelle dans le traitement médical de l'artérite des membres inférieurs.

Thirty patients suffering from arterial occlusive disease (stages II, III or IV of Fontaine's classification) were treated by isovolaemic haemodilution (IDH). Most of these patients received conventional medical treatment without success (negative selection). Angiography was performed on all patients prior to treatment. 500 ml of whole blood was withdrawn from each patient. 250 ml of dextran 40 mixed with 250 ml of 5% albumin solution was injected intravenously to avoid hypovolaemia. This procedure, carried out three or four times, was repeated until a haematocrit of 0.30 was reached. This haematocrit level of 0.30-0.35 was maintained for 60 days. The measurement of ankle systolic pressure, systolic index at rest, treadmill performance and lower limb thallium-201 muscular scintigraphy were used to assess laboratory efficiency. On the sixtieth day, 14 patients (46%) showed clinical improvement, nine were stable and arterial occlusive disease worsened in seven patients. Clinical improvement persisted for several months (15 months in one case). Clinically, it seemed that patients treated by IHD showed improvement of their arterial occlusive disease. However, the prediction of the chances of success of IHD, as well as the quantification of results by common laboratory examination, were difficult. Muscular scintigraphy with thallium-201 gave a good assessment as well as a quantifiable analysis of results.

[Effect of tritoqualine on the histamine levels of whole blood]. / Action de la tritoqualine sur le taux d'histamine du sang total.

For ten years now, tritoqualine, a histidine decarboxylase inhibitor, has been advocated in a prevention protocol for anaphylactoid reactions occurring during general anaesthesia. The present double-blind study aimed to quantify the effects of the drug on whole blood histamine levels. 44 patients were assigned at random to two different groups, one taking 300 mg t.i.d. tritoqualine for three days, and the other taking a placebo. The histamine levels were measured before the treatment and 12 h after the last dose of the drug after haemolysis of the sample, by the fluorometric technique preceded by column chromatography. In the group taking tritoqualine, the histamine level fell from a mean of 109 +/- 61 to 91 +/- 41 ng X ml-1, whereas it rose from a mean of 92 +/- 55 to 105 +/- 62 ng X ml-1 in the control group taking placebo. These variations were not statistically significant. In both groups were present four volunteers with a history of allergy; their histamine level fell from 107 +/- 35 to 71 +/- 36 ng X ml-1 after tritoqualine intake (p less than 0.05), whereas it rose from 76 +/- 19 to 162 +/- 36 ng X ml-1 after placebo (p less than 0.05). The small differences found in the whole blood histamine level 12 h after the last oral dose of the drug suggested that the present tritoqualine dose regimen was inadequate to achieve the aims of its prescription.