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Biomedical subjects

A Tamura

Publications and source records attributed to A Tamura.

At least 487 records · Page 27Linked to original sources
PubMed1983

[Tomographic analysis of CBF in cerebral infarction].

Cerebral perfusion was examined in various types of occlusive disease by computed tomographic CBF method. The method utilized has several advantages over conventional studies using isotope, providing high resolution images in a direct relation to CT anatomy. Ten representative cases were presented from 25 consecutive cases of occlusive disease studied by this method. The method included inhalation of 40 to 60% xenon with serial CT scanning for 25 min. K (build-up rate), lambda (partition coefficient) and CBF values were calculated from HU for each pixel and Xe in expired air, based on Fick's principle, and displayed on CRT as K-, lambda- and CBF-map separately. CBF for gray matter of normal control was 82 +/- 11 ml/100 gm/min and that for white matter was 24 +/- 5 ml/100 gm/min. The ischemic threshold for gray matter appeared to be approximately 20 ml/100 gm/min, as blood flow in focus of complete infarction was below this level. Blood flow between 20-30 ml/100 gm/min caused some change on CT, such as localized atrophy, cortical thinning, loss of distinction between gray and white matter and decreased or increased density, which were considered to be compatible with pathological changes of laminar necrosis or gliosis with neuronal loss. In a case with occlusion of middle cerebral artery with subsequent recanalization, causing hemorrhagic infarct, hyperemia was observed in the infarcted cortex that was enhanced by iodine. Periventricular lucency observed in two cases, where blood flow was decreased below threshold, could be classified as "watershed infarction" mainly involving white matter. In moyamoya disease, blood flow in the anterior circulation was decreased near ischemic level, whereas that in basal ganglia and territory of posterior cerebral artery was fairly preserved, which was compatible with general angiographic finding of this disease.

Adult↗
PubMed1983

[Changes in CBF pattern after bypass surgery studied by CT with Xe enhancement].

UNLABELLED: Using a new method for rCBF measurement by serial CT scanning with non-radioactive xenon enhancement, CBF was measured before and/or after microsurgical anastomosis in five cases of focal cerebral ischemia. MATERIALS AND METHODS: Studies were carried out on 2 cases of MCA occlusion, 2 of IC occlusion, and 1 of "Moyamoya" disease. CBF was measured both before and after surgery in 4 cases, and the remaining case was measured after anastomosis. Pre-operative CBF was measured 1.4 +/- 0.5 months after the onset and post-operative CBF was 2 +/- 1 months after surgery. While 50 to 70% non-radioactive xenon was inhaled for 25 min and then discontinued, serial CT scanning was carried out every 3 min. K-map (clearance rate), lambda-map (partition coefficient), and CBF-map were displayed on CRT as images of each value. RESULTS: In all cases, initial pre-operative CBF decreased not only in the ipsilateral hemisphere, but also in the contralateral hemisphere. Especially in the major stroke cases, CBF reduction in the low density areas seen in CT was more than 75% of normal values. After microsurgical anastomosis, CBF increased in both hemispheres. In two cases of reversible ischemic attacks without any change in CT, the CBF markedly increased in central areas of ischemia and the CBF values became higher than normal value, that is hyperemia. On the contrary, in the central areas of the major stroke cases, that is, the low density areas in CT, CBF was still very low (under 25% of normal value) after anastomosis. However, in these cases, marked hyperemia was seen in the surrounding area of ischemic focus.

Adolescent↗
PubMed1983

Dynamic behaviour of amphiphilic lipids to penetrate into membrane of intact human erythrocytes and to induce change in the cell shape.

Shape change (crenation, echinocyte formation) of intact human erythrocytes induced by added phosphatidylcholine or lysophosphatidylcholine species with varying acyl chain lengths was dependent only on the amount of the lipid incorporated into the membrane (determined with 14C-labelled lipids), irrespective of the chain length. The chain length appears to determine the speed and the maximal extent of the lipid transfer from the outside medium into the membrane. The altered shape gradually reverted upon incubation at 37 degrees C, not at low temperature, until the cells reassumed their normal shape. Translocation of the incorporated lipid molecules from the outer to the inner leaflet of the membrane lipid bilayer occurred to a slight extent during the incubation.

Biological Transport↗
PubMed1982

Interaction of added amphiphilic lipids with the membrane of intact human erythrocytes to induce change in the cell shape.

Addition of an appropriate amount of amphiphilic lipid, such as fatty acid, lysophospholipid and medium-chain phospholipid, into a suspension of human erythrocytes (pH 7.4) at 37 degree C resulted in their incorporation into the membrane and induction of a cell shape change of crenation (echinocyte-spherocyte) type without causing hemolysis. The extent of the shape change was dependent on the amount of the lipid incorporated and the crenation disappeared on removing the incorporated molecules from the membrane. The crenation induced by acidic lipids was further altered drastically by resuspending the treated cells in media of pH 6, 7, and 8, whereas that induced by choline-phospholipid or -lysophospholipid was not so pH-dependent. Based on these results, the mechanism of this shape change is discussed.

Dose-Response Relationship, Drug↗
PubMed1982

Purification of Rickettsia tsutsugamushi by Percoll density gradient centrifugation.

Purification of Rickettsia tsutsugamushi has been achieved by Percoll density gradient centrifugation. The microorganisms purified showed good retention of infectivity and intracellular morphology. Budding rickettsiae in the egressing stage and intracellular rickettsiae in the multiplying process were harvested separately and purified by this technique. In electron microscopic observations, the intracellular rickettsiae obtained were surrounded with double membrane-layers of cell wall and cell membrane, and the budding rickettsiae were enveloped with an additional outermost membrane which may have originated from host cell membrane obtained in the budding process.

Animals↗
PubMed1982

Surface morphology of Rickettsia tsutsugamushi-infected mouse fibroblasts.

Sequential morphological changes of the L-cell surface after infection with Rickettsia tsutsugamushi (Gilliam strain) have been examined by scanning electron microscopy and ruthenium red staining technique. Adherence of inoculated rickettsiae to the host-cell surface and their engulfment by the cell were seen at 30 min and have still proceeded at 24 hr post infection (p.i.). Progeny rickettsiae which were lifting up the host cell membrane by budding were observed on the cell surface at 48 hr p.i. The budding of rickettsiae increased gradually in time and, at 96 hr after infection, covered almost the all host-cell surface except of the cell margin. Numerous microvilli observed on the surface of uninfected L-cells decreased gradually p.i.; they had almost disappeared when progeny rickettsiae occurred. Ruthenium red staining specimens clearly showed that the budding rickettsiae were surrounded with the host cell membrane. The following layers were distinguished from outside on: (1) ruthenium red positive fuzzy coat (25 nm thick); (2) a triple-layered cell membrane (5-6 nm); (3) outer and inner leaflets of the rickettsial cell-wall (7-8 nm and 2-2.5 nm, respectively); (4) periplasmic space (15-20 nm); (5) a triple-layered rickettsial cytoplasmic membrane (5-6 nm).

Animals↗
PubMed1982

[Computed tomographic measurement of regional cerebral blood flow by xenon enhancement (author's transl)].

The present study was conducted to overcome some of disadvantages of cerebral blood flow study by radionuclide, such as poor regionality of flow values and errors involved in pathological brains. Serial CT scanning was carried out during and after inhalation of 50 to 70% non-radioactive xenon in humans. Diffusible gas with high atomic number enhanced gray matter first 19 +/- 4 HU (mean +/- SD) on an average in Hounsfield unit (HU) and later white matter 24 +/- 4 HU. In seven normal subjects, blood flow in gray matter was 82 +/- 11 and that in white matter 24 +/- 5 ml/100 gm/min. Partition coefficient which is not readily obtainable by radionuclide study was 0.9 +/- 0.1 in normal gray matter and 1.4 +/- 0.2 in normal white matter. Two cases were presented to show k-map (clearance rate), lambda-map (partition coefficient) and CBF map, which displayed images of values calculated automatically, in black and white or color on CRT. The first case was a patient with metastatic brain tumor from lung in the left parietal region. The blood flow of the tumor was close to that of gray matter, whereas blood flow of edematous white matter surrounding the tumor was decreased to below 10 ml/100 g/min with partition coefficient ranged from 0 to 0.9. The second case was presented to demonstrate the resolution of the blood flow map obtained by this method. Multiple lacunar infarcts of the basal ganglia and white matter in the size of 1 to 3 mm, which were hardly identified on regular CT picture, were well visualized on CBF map. This method appeared to have several advantages over conventional isotope method and to provide useful clinical and research informations.

Aged↗
PubMed1981

Focal cerebral ischaemia in the rat: 1. Description of technique and early neuropathological consequences following middle cerebral artery occlusion.

A procedure for occluding the stem of the proximal middle cerebral artery of the rat is described. The operation is performed under anaesthesia through a small subtemporal craniectomy. After occlusion, 3 animals were perfused with carbon block and 8 with a FAM fixative (40% formaldehyde, glacial acetic acid, and methanol). The findings were compared with sham-operated animals. Carbon black studies demonstrated an area of impaired perfusion corresponding to the territory of the occluded artery in each animal. Neuropathological studies invariably showed that there was ischaemic brain damage in the cortex and basal ganglia. The frontal cortex was involved in every animal, as was the lateral part of the neostriatum; the sensorimotor and auditory cortex were involved in most animals, whereas the occipital cortex and medial striatum were involved only infrequently. The damage produced by ischaemia could be readily distinguished from the small local lesion seen at the surgical site in sham-operated animals. The ability to produce a consistent focal ischaemic lesion in the rodent brain provides a technical approach that is sufficiently reproducible to enable investigation of the pathophysiology of ischaemia using recently developed autoradiographic and neurochemical methods.

Animals↗
PubMed1981

Focal cerebral ischaemia in the rat: 2. Regional cerebral blood flow determined by [14C]iodoantipyrine autoradiography following middle cerebral artery occlusion.

Local cerebral blood flow has been measured by quantitative autoradiography, employing [14C]iodoantipyrine as tracer, in rats killed half an hour after occlusion of the middle cerebral artery. The results were compared with pattern of local cerebral blood flow (CBF) in sham-operated rats and with neuropathological findings. In every animal there was a profound reduction (to 13% of control levels)in blood flow in the neocortex previously by the occluded artery. The level of blood flow in the areas in which ischaemic brain damage occurred was 0.24 +/- 0.03 ml g-1 min-1 (mean +/- SEM). this level of CBF is considerably greater than that reported following a similar surgical procedure in cats and primates. Moderate reductions in blood flow were also seen outside the territory of the occluded artery and in parts of the opposite hemisphere. Absolute increases in blood flow (hyperaemia) were seen only in the substantia nigra and globus pallidus ipsilateral to the occlusion. It is of the middle cerebral artery are reflections of alterations in neuronal function and metabolic activity secondary to the ischaemic lesion.

Animals↗
PubMed1981

Roles of charged groups on the surface of membrane lipid bilayer of human erythrocytes in induction of shape change.

Shape changes of human erythrocytes were induced by partial hydrolysis of phospholipids in the membrane lipid bilayer outer leaflet as a result of the action of exogenous phospholipase A2 or D at pH 7.4 under non-hemolytic conditions. The extent of the shape change caused by phospholipase A2 or D altered drastically when the cells were put into a medium of more alkaline or acidic pH, whereas the shape of untreated cells and cells treated with phospholipase C showed only a mild dependence on pH. These pH-dependent shape changes of intact and phospholipase-treated cells were reversible. Removal of the majority of exposed sialic acid residues from the membrane outer surface by neuraminidase treatment had no influence on the cell shape, or on the pH-dependence of the shape change. These results suggest the importance of the electric charges of polar groups located directly on the surface of the membrane lipid bilayer in inducing cell shape changes.

Erythrocytes↗