Ferromagnetic metal conversion directly from two-dimensional nickel hydroxide

We have demonstrated a direct metallic conversion from nickel hydroxide nanosheets to nickel metal nanostructures by thermal annealing in vacuum. The metal transition of the single-layer nanosheets deposited on a Si substrate was revealed by x-ray absorption near edge structure (XANES) measurements. The XANES signal significantly changed at annealing temperatures above 250 °C. The metal transition temperature coincides with the reported temperatures at which layered nickel hydroxide nanosheets are converted to nickel oxide nanosheets by calcination in air. Auger measurements confirmed that a dissociation of oxygen from the hydroxide nanosheet induces the metallic conversion. The converted nickel metallic structures exhibit ferromagnetic behavior revealed by x-ray magnetic circular dichroism (XMCD) measurement. Atomic force microscopy measurements indicate that diffusions of nickel atoms on the substrates leads to a structural change from a 2D-like structure to a particle-like structure.

A portable multi-channel recording system for analysis of acceleration and angular velocity in six dimension

A portable recording system was developed for analysis of more than three analog signals collected in field works. Stereo audio recorder, available as consumer products, was made use for a core cornponent of the system. For the two tracks of recording, a multiplexed analog signal is stored on one track, and reference code on the other track. The reference code indicates the start of one cycle for multiplexing and swiching point of each channel. Multiplexed signal is playbacked and decoded with a reference of the code to reconstruct original profiles of the signal. Since commercial stereo recorders have cut DC component off, a fixed reference voltage is inserted in the sequence of multiplexing. Change of voltage at switching from the reference to the data channel is measured from playbacked signal to get the original data with its DC component. Movement of vehicles and human head were analyzed by the system. It was verified to be capable to record and analyze multi-channel signal at a sampling rate more than 10Hz.

Comparison of dynamic and xenon computed tomography in the evaluation of cerebrovascular ischemia

Dynamic computed tomographic (DCT) scans with iodine contrast enhancement were compared with simultaneously obtained xenon CT studies of cerebral blood flow (CBF) in 15 patients with subacute or chronic cerebrovascular ischemic disease. Specifically, the width and corrected first moment (cMT1), as demonstrated by DCT, were compared with the regional CBF (rCBF) data and the rCBF map obtained with xenon CT. The DCT and rCBF images were well correlated in patients without, but poorly correlated in those with, leptomeningeal anastomotic collateral circulation. The correlation of rCBF and 1/width with 1/cMT1 was significant (r = 0.78, p less than 0.01) in the former, but not in the latter. These data were thought to reflect a difference in the tracer inflow pattern between the patients with and those without leptomeningeal anastomoses. Our series did not include patients with acute cerebral infarction or recanalization, which are thought to be associated with marked changes in cerebral blood volume in the affected region. However, the influence of cerebral blood volume should be studied in detail in our subacute or chronic series.

[Problems in the embolization therapy of spinal arteriovenous malformation]

Six cases with spinal arteriovenous malformation refractory to repetitive embolization therapy were reported. In these, de novo feeding arteries appeared after the emboli obliterated the proximal portion of the blood feeding system. Though the malformation disappeared after the embolization therapy in the angiograms of the original feeding arteries, the lesion was visualized in the follow-up angiogram from different segmental arteries via various collaterals. Through angiographic evaluation and magnetic resonance imaging were necessary to point out the "false angiographic disappearance" of the spinal arteriovenous malformation after the embolization therapy.

Two patients with meningioma visualized as high uptake by SPECT with N-isopropyl-p-iodo-amphetamine (I-123)

It has been reported that brain tumors show decreased IMP uptake, however, we encountered two cases of meningioma which had initially increased IMP uptake. SPECT was performed at 30 min, 2 hr and 6 hr after intravenous administration of IMP (3 mCi). The delayed images (2 and 6 h) showed decreased IMP uptake. These were convexity and parasagittal meningiomas which had tumor stains at angiography. Although the mechanism of IMP uptake in brain tumor is still unclear, this finding should be considered in the interpretation of IMP-SPECT.

[Cerebral blood flow in subarachnoid hemorrhage: analysis in patients with poor outcomes]

Cerebral blood flow (CBF) of 6 patients with poor outcome after subarachnoid hemorrhage is analyzed. Neurological grades of these patients were grade III in 2 and grade IV in 4 patients, and subarachnoid hemorrhage on CT was diffuse and thick in all patients. Cerebral blood flow was continuously measured for 7 to 19 days by the thermal diffusion flow probe with a peltier stack which was left on the cerebral cortex at the surgery for ruptured aneurysm. Moreover, CBF studies by cold xenon CT and 133Xe inhalation methods were also performed in discussing cases. At the same time intracranial pressure was monitored. Cerebral angiography was carried out in all except for 2 patients who died due to severe cerebral vasospasm. The initial CBF value of all patients was 20 to 40 ml/100 g/min (mean value: 27 ml/100 g/min), and these were significantly low compared to normal value (50 ml/100 g/min). Moreover, these CBF was substantially decreased several days after surgery in all patients, and it was marked in 3 patients who died. From these results it was clear that the degree of vasospasm is important to determine the prognosis. One of 3 patients who died had ruptured left posterior cerebral artery aneurysm with occlusion of bilateral internal carotid arteries. In this case further decrease of CBF due to vasospasm was observed in addition to low initial CBF resulting diffuse low flow in both hemispheres although extracranial to intracranial bypass was performed. On the other hand, it was also shown that the intracranial pressure was an important factor to influence the outcomes.(ABSTRACT TRUNCATED AT 250 WORDS)

[Regional cerebral blood flow images of single photon emission computed tomography by N-isopropyl-p-[I-123] iodoamphetamine in patients with brain tumor]

Regional cerebral blood flow (r-CBF) was studied by single photon emission computed tomography (SPECT) using N-isopropyl-p-[I-123] iodoamphetamine (IMP) in order to evaluate CBF in patients with brain tumor. Total 27 studies were carried out in 20 patient, including 8 patients with meningioma, 3 with glioblastoma multiforme, 2 with oligoastrocytoma, and 7 with other intracranial tumors. All CBF images by IMP-SPECT were obtained by using a rotating gamma camera with dual heads. In the serial scans, each scan was started at 20 minutes, 2 hours and 6 hours after intravenous injection of I-123 IMP (3 mCi). The all IMP-SPECT images were compared with cerebral angiogram, X-ray CT (plain and/or enhancement), and images of Kr-81 m SPECT and Tc-99 m SPECT. In 5 patients (4 patients with meningioma and 1 with glioblastoma multiforme) this comparative study was performed before and after surgery to evaluate the r-CBF changes surrounding tumor. The abnormal lesion on X-ray-CT was identified as hot area on CBF image by IMP-SPECT in two cases with meningioma, and in 14 cases the lesion showed cold area. Totally 80% of cases showed abnormal findings on CBF images by IMP-SPECT. The cases which showed no abnormal findings on IMP-SPECT images included 1 case with meningioma which located in frontal base, 2 with small intracranial brain tumor which was smaller than 2 cm in diameter, and 1 with pituitary adenoma. On the IMP-SPECT images scanned 2 hours after injection, hot area, which was identified in two cases with meningioma on the images 20 minutes after injection, was changed into cold area.(ABSTRACT TRUNCATED AT 250 WORDS)

[Intraoperative liquid embolization of an arteriovenous malformation in the basal ganglia and thalamic region]

Total three patients with arteriovenous malformation (AVM) in basal ganglia or thalamic region were treated by intraoperative liquid embolizations. These procedures were decided because of repeated hemorrhagic episodes. In the case with AVM in the head of the caudate nucleus which was fed by several anterior perforating arteries originated from anterior cerebral artery (A1 portion) and middle cerebral artery (M1 portion), frontotemporal craniotomy was performed. After the microsurgical dissection of these feeders, one of the feeders lenticulostriate artery, was cannulated with a small-caliber polyethylene catheter, 0.6 mm in outer diameter and 0.3 mm in inner diameter. A small amount of isobutyl 2-cyanoacrylate (IBCA) was injected through the catheter. Same procedure was carried out one month later. Postoperative angiograms revealed about 90% loss of AVM. In two cases with AVM which involved almost entire thalamus, subtemporal craniotomy was done. Feeding vessels which originated from posterior communicating artery and posterior cerebral artery (PCA) were carefully dissected under the operative microscope and one of them was prepared for cannulation with small catheter. When the small amount of IBCA was injected, proximal PCA and internal carotid artery were temporarily occluded. In both cases intraoperative embolization was carried out twice. Postoperative angiograms revealed that the size of AVM was decreased to 20% in one and 40% in the other. Although temporary postoperative deterioration of neurological deficits such as hemiparesis and visual disturbance was slightly noted in all cases, no hemorrhagic episode was experienced for 6 months, 1.5 and 2 years in each after embolization.

Cerebral hemodynamics in arteriovenous malformations: evaluation by single-photon emission CT

Cerebral hemodynamics in six patients with supratentorial arteriovenous malformations (AVMs) were studied by using single-photon emission CT with three types of radioactive isotopes: N-isopropyl-p-[123I] iodoamphetamine, 81mKr, and 99mTc-RBC in order to determine the local cerebral blood flow and blood volume associated with these malformations. The AVMs were shown to have high flow while other areas of the brain, including the contralateral hemisphere, had variable areas of diminished perfusion. There was increased blood volume in the regions of AVMs, and poor but evenly distributed blood volume in the other regions. CO2 reactivity during hypocapnia was preserved throughout the brain except for the region of the AVMs. In large AVMs, the ischemic state surrounding the nidus was considered to be caused mainly by the cerebral steal phenomenon.

[Digital subtraction angiography of the cerebral vessels by intraarterial injection]

Three hundred and fifty-seven digital subtraction angiography (DSA) were performed in 184 neurosurgical patients by intraarterial injection. Examinations consisted of 192 carotid angiography, 110 vertebral angiography, 23 aortography, 11 spinal angiography and 21 other angiography. In all examinations, visualization of the vessels was excellent and the complications were never experienced. High contrast sensitivity of DSA resulted in better visualization of tumor stains, phlebogram, and arteries in cerebral arteriovenous malformations with large shunt blood flow than conventional angiography. Selective catheterization into each cerebral arteries was not necessarily demanded for good opacification of the vessels because of high sensitivity. High contrast sensitivity also permitted low concentration of contrast material, small dose of contrast material, and slow injection rate. Low concentration of contrast material reduced pain and heat during injection especially in the external carotid and vertebral angiography. Using slow injection, recoiling of catheter into the aorta was reduced, so that injection from the innominate and subclavian arteries for visualization of origin of the cerebral arteries were always successful. Full study of cerebral arteries by Seldinger's method, if necessary, was easily achieved using DSA even in patient with high age or with severe atherosclerosis. Bolus injection of small dose of contrast material as well as serial imaging was helpful in evaluating hemodynamics in the lesion. Real time display of DSA reduced the time required for angiography and was very convenient for artificial embolization. Besides these advantages, DSA became comparable to conventional angiography in special resolution by use of intraarterial injection and could be a preoperative genuine examination as well as a screening method.

New small-caliber antithrombotic vascular prosthesis: experimental study

Vascular prostheses with the inner diameter smaller than 1 mm were implanted to the common carotid artery of rats, and their patency was examined. Four types of tubes were prepared for this purpose in Experiment 1: polyethylene (PE), poly-(acrylic acid)-grafted polyethylene (PE-AA), polyacrylamide-grafted polyethylene (PE-AAm), and poly(vinyl alcohol) (PVA) tubes. Comparative studies made using nonsuture anastomosis revealed that the PE-AAm and PVA tubes were antithrombotic, although disconnection was noted at the anastomotic sites within 1 week and 1 month, respectively. Thereafter in Experiment 2, the PVA tubes were implanted to the common carotid artery of 20 rats using conventional anastomosis. Neither anticoagulants nor fibrinolytic agents were used in both series of experiments. Patency of the PVA tubes was 80% after 1 week and 70% after 1 month. In patent cases after 1 month, the luminal surfaces of the prostheses and the host arteries were examined using scanning electron microscopy. The lumen of the arteries and anastomotic sites was covered with endothelial cells, while the lumen of the PVA tubes was free from thrombi and there was no neointima formation. So far, there has been reported no manmade material that has completely antithrombotic property in vivo. However, our studies disclosed that PVA is antithrombotic and one of the most promising materials for the inner surface of small vascular prostheses.

Experimental cerebral vasospasm. Part 2. Contractility of spastic arterial wall

We studied the mechanical properties of canine basilar arteries subjected to experimental subarachnoid hemorrhage (SAH). Smooth muscle contractility was determined from pressure-diameter curves obtained after subjecting the basilar arteries to three different conditions: Krebs-Ringer solution (KRS), Krebs-Ringer solution containing serotonin (5HT), and saline solution. Pressure-diameter curves obtained in KRS and 5HT are biphasic and have sharp flexions that yield flexion points. The pressure level at the flexion point increases as vasospasm increases. Strong constriction is retained up to that pressure above which the constriction is released abruptly. These data suggest that increasing the intraluminal pressure dilates the spastic artery nonlinearly and that induced hypertension could relieve the cerebral ischemia caused by vasospasm if blood pressure were maintained above the flexion point. The contractile response of spastic arterial wall to serotonin remains unchanged after SAH although the spastic constriction increases progressively and becomes maximal seven days after SAH. The lesser the arterial wall stiffness, the more efficiently it constricts. This means that the diminution of arterial stiffness observed after SAH might be one of the factors promoting the development of vasospasm.

Experimental cerebral vasospasm arterial wall mechanics and connective tissue composition

The elastic properties of the basilar artery were studied in control and treated dogs in which 3 ml of blood was injected intracisternally. Vascular specimens were resected transclivally as cylindrical segments and their external diameters were measured in vitro in the pressure range from 0 mm Hg to 250 mm Hg in the active condition of smooth muscle in Krebs-Ringer solution and in the passive condition in saline solution. The development of cerebral vasospasm was confirmed comparing the diameter difference between these two conditions. The experimental data indicated that vasospasm was most prominent on the 7th day after the treatment of blood injection. In the passive condition no significant dimensional change (i.e. radius and wall thickness) was observed between the control and the treated arteries at various pressure levels. These results imply that the luminal narrowing under vasospasm is not attributable to an irreversible organic change in the wall but to the constriction of vascular smooth muscle. The treated arteries are more distensible and have lower elastic moduli than the control arteries, possibly due to a change in the content of their connective tissues. These changes of the passive elastic properties of arterial walls after blood injection might be one of the factors affecting the development of cerebral vasospasm.

Biomechanical study on aging changes and vasospasm of human cerebral arteries

Mechanical properties of human intracranial arteries were studied with regard to their aging changes as well as cerebral vasospasm. There exists a considerable difference in the development of sclerosis between the intracranial and the extracranial arteries. Intracranial arteries are already stiff at birth and become stiffer with age. Their increase in stiffness is attributable to the marked thickening of their walls, which compensates for the decrease of their elastic modulus with age. The pressure-diameter curve of the intracranial vertebral arteries subjected to subarachnoid hemorrhage is biphasic and has a sharp flexion at the pressure of 180 mmHg when their smooth muscle is activated. Pressure elevation yields little change of diameter in the strongly constricted vessel up to the pressure level at the flexion point, above which the constriction is released abruptly. The existence of flexion point at a high pressure level is an important mechanical feature in considering the development of cerebral ischemia produced by the vasospasm.

[Clinical evaluation of artificial blood substitute (fluosol-DA 20%) in patients of cerebral ischemia]

The efficacy of perfluorochemicals (Fluosol-DA 20%) as an erythrocyte substitute and the changes of regional cerebral blood flow (r-CBF) following the administration of Fluosol-DA were studied. Seventy-three patients suffering from cerebral ischemic diseases were treated by 10 m/kg of Fluosol-DA. Intravenous infusions were performed 126 times. Clinical efficacy could be estimated by neurological signs, r-CBF and EEG findings in 53 patients who were in acute or subacute stage of diseases. These patients were classified into three groups; 1) Vasospasm group consists of 21 patients and 43 times of infusion, 2) Stenosis or occlusion group consists of 21 patients and 29 times of infusion, and 3) Others. Improvement occurred in 65.1% and 65.5% of vasospasm, and occlusion group, respectively. No aggravated case was noted. One out of 126 infusions showed an exanthema. Changes of r-CBF was measured in 20 cases on 32 hemispheres by either inhalation or intra-arterial infection of 133Xenon. r-CBF was increased 25.0% after the administration of Fluosol-DA when measured by intraarterial injection of 133Xenon. The increase of 16.9% in r-CBF was found in 11 cases by the inhalation method. These values were well correlated with that of animal study using monkeys measured by hydrogen clearance method. From the comparison of the effect of Fluosol-DA and Hespander on r-CBF, the mechanism of increased r-CBF by Fluosol-DA 20%, which contains 2.9% of hydroxyethyl-starch, was considered to be not solely due to the lowering of blood viscosities but also due to the dilating effect on cerebral vessels.

Efficacy of a blood substitute (Fluosol-DA, 20%) on cerebral ischemia

Fluosol-DA, 20%, was intravenously infused in 28 patients suffering from cerebrovascular disease, and was found to be effective in 60% of the cases with vasospasm and in 80% of the cases with stenosis and/or occlusion of the artery. Administration of the solution increases r-CBF by 10.1 to 37.9% when measured by either intra-arterial injection or inhalation of 133Xe. However, an increase of arterial oxygen tension appears to have little effect on r-CBF after administration of the solution. The increase of r-CBF caused by Fluosol-DA, 20%, may be due not only to the lowering viscosity of the mixed blood but also to its direct effect on dilating cerebral vessels.

Quantitative analysis of microstructural components of human cerebral arteries

Microstructural components were analyzed quantitatively by means of a microphotometric technique applied to three kinds of major cerebral arteries and two kinds of extracranial arteries of comparable size obtained from human autopsy subjects. No statistically significant difference was found in the fractions of three structural components, elastin (Fe), collagen (Fc), and smooth muscle (Fm), in the total of fractions of these three components and in the ratio between extracranial arteries. The Fe-values were significantly less in cerebral arteries than in extracranial arteries. The Fc/Fe ratios in cerebral arteries were about triple those in extracranial arteries. Although there was no statistically significant difference in the Fe- and the Fm-values between the two age groups, under 49 and over 50 years old, the Fc/Fe ratio were higher in the older age group. This change of microstructural composition with age was more prominent in cerebral arteries than in extracranial arteries.

Effects of a transfusion with a blood substitute (Fluosol-DA, 20%) on cerebral circulation in the monkey

Local cerebral blood flow (lCBF) and electroencephalogram were monitored in six monkeys after a transfusion using a perfluorochemical suspension (Fluosol-DA, 20%) that has been manufactured as a blood substitute and is known to be synthetic, biologically inert, and nontoxic and to have a high capacity for carrying oxygen. The animals were mechanically ventilated, and blood gases were maintained at physiological levels. Fluosol-DA, 20% was administered either by an exchange transfusion of 20 ml/kg or by an infusion of 8 ml/kg followed by an exchange transfusion of 12 ml/kg. lCBF was measured using the hydrogen clearance technique. An equation was proposed to estimate the tissue-blood partition coefficient of hydrogen; this coefficient is considered to be dependent upon the amount of perfluorochemicals in the blood and was used to calculate lCBF. Systemic blood pressure, pulse rate, central venous pressure, electroencephalogram, and gas analysis of the blood from the femoral artery, the femoral vein, and the superior sagittal sinus showed little change throughout the experiment. lCBF was increased by 12% (p less than 0.005) after the infusion of Fluosol-DA, 20% of 8 ml/kg and by 31% (p less than 0.02) after the exchange transfusion. Hyperventilation reduced lCBF significantly (p less than 0.005), which implies that the reactivity of the cerebral blood vessels to hypocarbia was not impaired by the administration of FLuosol-DA, 20%. Both the results of this study and the physical properties of Fluosol-DA, 20% suggest that this blood substitute can safely be used for normal human brains and that it might also be effective for ischemic brains.

Mechanical properties of human cerebral arteries: Part 2. Vasospasm

Mechanical properties of human intracranial vertebral arteries subjected to subarachnoid hemorrhage were studied. Their pressure-diameter curves are biphasic and have sharp flexion, called flexion points, at a pressure of 181.3 +/- 9.6 mm. Hg when their smooth muscle is activated by KCl 50 mM. The strong vasoconstriction, accompanied by little change in the vascular diameter, is retained up to the pressure level at the flexion point, above which the constriction is released abruptly. The existence of flexion points at a high pressure level is an important mechanical feature in considering the development and treatment of cerebral ischemia produced by vasospasm.

Mechanical properties of human cerebral arteries. Part 1: Effects of age and vascular smooth muscle activation

Mechanical properties of the smooth muscle component of human arteries were studied under passive and active conditions. There exists a considerable difference in the development of sclorosis in intracranial and extracranial arteries. Intracranial arteries were already stiff at birth and become stiffer with age. Their increase in stiffness is attributable to the marked thickening of their walls, which compensates for the decrease of their elasticity with age. Intracranial arteries constrict more than extracranial arteries, although the maximum active stress developed is essentially the same. This competency of intracranial arteries for vaso-constriction may be related to cerebral vasospasm.

Hypothalamo-pituitary-adrenal function in pituitary adenoma and craniopharyngioma. Part II: insulin test and clinical features

For the assessment of hypothalamic corticotropin releasing hormone (CRH) secretory function, insulin test, lysinevasopressin test, and rapid ACTH test were performed and plasma crotisol was assayed. Disturbances of CRH secretory activities were found not to be related with the degree of suprasellar extension of tumors, contents of tumors, the degree of visual disturbances, or the duration of symptoms, and it was supposed that more complex mechanisms were responsible for CRH secretory abnormalities.