Search PubMed⌕ Search

Biomedical subjects

H Naritomi

Publications and source records attributed to H Naritomi.

At least 55 records · Page 3Linked to original sources
PubMed1991

Sequential gadolinium-DTPA enhanced MRI studies in neuro-Behçet's disease.

Sequential gadolinium-DTPA (Gd-DTPA) enhanced MR images were obtained before and after steroid therapy in a case of neuro-Behçet's disease. Multiple scattered lesions, which could not be detected on pre- and post-contrast CT, were demonstrated mainly in the white matter of the pons and/or the cerebrum with both T1- and T2-weighted images. Some of these lesions, however, were not enhanced at all by infusion of Gd-DTPA. The Gd-DTPA infusion study demonstrated marked enhancement in the white matter of the pons and cerebrum. Some lesions not seen with T2-weighted images were also strongly enhanced by Gd-DTPA infusion at the acute stage. After steroid therapy, the symptoms and abnormal laboratory findings were resolved. The pontine and cerebral lesions on plain MR images remained unchanged even after resolution of the symptoms, suggesting that they were inactive old foci. On the other hand, the lesions detected in the enhancement study before steroid therapy disappeared with the repeat Gd-DTPA enhanced MR images hich were performed after resolution of the symptoms. Some active inflammatory lesions in neuro-Behçet's disease may be demonstrated only on Gd-DTPA enhanced MR images. Gd-DTPA enhanced MR imaging appears to be potentially useful for detecting active inflammatory lesions in neuro-Behçet's disease and for evaluating the efficacy of treatment.

Behcet Syndrome↗
PubMed1991

Experimental basis of multi-infarct dementia: memory impairments in rodent models of ischemia.

Memory is an intellectual function that is initially and consistently impaired in patients with vascular dementia. Experimental approaches to vascular dementia have so far been confined to investigations of memory impairments in rodent ischemic models. Unilateral middle cerebral artery (MCA) occlusion, multiple small embolization or transient four-vessel occlusion in rats produced acute single or multiple infarctions. In such rats, significant memory impairments occurred during the subacute or chronic phases, but were partially reversible. Permanent stenosis of both common carotid arteries in gerbils caused no ischemic changes at 1 day after stenosis but induced multiple infarctions after 1 week of stenosis, probably due either to chronic recurrent ischemia resulting from transient repetitive obstruction of the carotid arteries or to chronic low perfusion. The memory impairments in this model were persistent. Permanent bilateral common carotid artery occlusion in rats produced multiple infarctions plus white matter changes after 1 week of occlusion. Marked memory impairment was also observed in this model. The results of the above studies suggest that memory impairments due to ischemic causes may be partially reversible provided that the infarctions occur only once and are followed by flow recovery. Memory impairments, however, appear to persist if the brain is exposed to chronic recurrent ischemia or chronic moderately low perfusion. A repetitive or persistent low-flow state appears to be an important factor in determining the irreversibility of cognitive impairments.

Animals↗
PubMed1990

Subcortical auditory agnosia.

A case of generalized auditory agnosia without aphasia secondary to cardiogenic cerebral embolism is reported. The infarcts in this patient were localized within the bitemporal subcortices as confirmed by computerized axial tomography and magnetic resonance imaging. The findings suggested that interruption of both auditory radiations by bilateral subcortical lesions may play an important role in the occurrence of "cerebral auditory disorders."

Aged↗
PubMed1990

Non-invasive 31P NMR study on the development of brain membrane of gerbils and jimpy mice, a myelin-deficient mutant.

The broad background resonance observed in the in vivo 31P NMR spectra of adult murine heads was investigated in terms of phosphorus atoms in bone and membrane phospholipids. The broad background resonance was found to be weak in a juvenile and increase with advance of age. Fractionation of adult gerbil heads showed that the broad signal was derived from bone and membrane, of which myelin is the major component. The two origins of the broad background resonance exhibited considerably different line shapes in spectra, which enabled us to extract the membrane component from an intact murine head spectrum (sequential subtraction method). By the use of this method, the development of membrane in gerbil brain at various age grades could be estimated. The membrane component was shown to be suppressed in a mutant mouse, jimpy, which has a deficiency in myelin formation ability. Furthermore, the value of T1 of the membrane component was estimated to be 0.9 sec, which was in good agreement with previously reported values for excised brain.

Animals↗
PubMed1990

[Significance of periventricular hyperintensity on magnetic resonance images in stroke patients].

To clarify the significance of periventricular hyperintensity (PVH) on MRI-T2 images in stroke patients, clinical and experimental studies were performed. MRI (1.5 Tesla) was obtained in 153 patients with ischemic stroke. The PVH was observed in all the patients, although severe PVH was found only in 22% of the cases. Severe PVH was observed mainly in hypertensive elderly patients with multiple infarctions and impaired cognitive function. Regional cerebral blood flow was reduced in majority of these patients. The absence of aqueductal signal flow void, remarkable ventricular enlargement and abnormal RI cisternography+ were observed in 20% of the patients with severe PVH. In Wistar rats and gerbils, chronic low perfusion state was induced by occlusion or narrowing of both common carotid arteries, and histological studies were performed at 1 week, 1 month or 3 months after the surgery. Multiple infarctions, white matter changes and ventricular enlargement were observed in these animals. The results suggest that chronic low perfusion in the brain and/or abnormal cerebrospinal fluid circulation play a role in the development of PVH.

Adult↗
PubMed1990

Effect of bifemelane on the intracellular pH and energy state of the ischemic brain.

4-(o-Benzylphenoxy)-N-methylbutylamine hydrochloride (bifemelane, CAS 90293-01-9, Celeport) has been reported to exert a protective effect on the brain against ischemic insults. However, the underlying mechanism of this action has not yet been fully elucidated. The effects of bifemelane on the intracellular pH (pHi) and energy metabolism of the ischemic brain were examined in Mongolian gerbils using in vivo 31P nuclear magnetic resonance spectroscopy. Transient global ischemia was produced by clipping both common carotid arteries for 45 min, and the brain was reperfused by releasing the clips. Bifemelane (10 or 20 mg/kg) or normal saline was administered intraperitoneally 30 min prior to the ischemia. During the ischemia, adenosine triphosphate (ATP) and phosphocreatine (PCr) were markedly reduced in association with an increase in inorganic phosphate (Pi) and decrease in pHi in both the control and bifemelane groups. The extents of energy disturbance and intracellular acidosis in the three groups were identical. After reperfusion, ATP, PCr, Pi and pHi recovered towards the pre-ischemic levels in all the groups. In the bifemelane groups, the recovery of pHi was significantly faster than in the control group. Of the two bifemelane groups, the 20 mg/kg group showed more excellent pHi recovery as compared to the 10 mg/kg group. The energy recovery in the three groups were almost identical, although the 20 mg/kg group showed some tendency towards faster recovery as compared to the control group. The present results suggest that bifemelane may accelerate recovery of the pHi after cerebral ischemia. Such an action may contribute to the cerebral protective effects of this drug against ischemic insults.

Adenosine Triphosphate↗
PubMed1989

Estimation of vertebral arterial asymmetry by computed tomography.

In 80 patients with no stenotic lesions in the vertebrobasilar arterial system, a study was made of the relationship between the deviation of the basilar artery (BA) from the midline on computed tomography (CT) and the right-to-left vertebral arterial caliber difference on angiograms. In 66 patients (83%), the BA was visible on plain CT films, and 55 of them showed deviation of the BA to either side. In 44 of these patients (80%), the vertebral artery (VA) contralateral to the side of BA deviation had a larger caliber compared with the ipsilateral one on angiograms. In 6 patients whose unilateral VA terminated in the posterior inferior cerebellar artery (PICA) and showed an extremely small caliber compared to the contralateral one, the BA was always deviated to the side of the smaller VA. Our data suggest that the deviation of the BA on plain CT films may represent a good indicator for estimating the right-to-left VA caliber difference. At the time of vertebral angiography, injection of contrast medium should preferably be made from the larger VA in order to avoid laminar flow in the BA and to shorten the procedure. Prior estimation of the right-to-left VA caliber difference by CT may be of great benefit to the angiographic procedure.

Adult↗
PubMed1989

Effects of propentofylline on energy metabolism of the ischemic brain studied by in vivo 31P nuclear magnetic resonance spectroscopy.

The effects of 3-methyl-1-(5'-oxohexyl)-7-propylxanthine (propentofylline, HWA 285) on transient cerebral ischemia were studied in Mongolian gerbils by measuring the in vivo 31P nuclear magnetic resonance (NMR) spectra and cerebral water content. Transient ischemia was produced by bilateral common carotid artery occlusion for 30 min, which was followed by 60 min of reperfusion. Propentofylline (1, 2.5 or 30 mg/kg) or normal saline was administered intravenously at 2 min after the reperfusion. The 31P spectra during the occlusion showed a marked reduction in adenosine triphosphate (ATP) and phosphocreatine (PCr) with elevation of inorganic phosphate (Pi) in all groups. The intracellular pH (pHi) calculated from the chemical shift of Pi was markedly reduced in all groups. After the reperfusion, ATP, PCr, Pi and pHi gradually recovered towards the normal levels in the control group. In the 2.5 mg/kg propentofylline group, the energy recovery was significantly faster than in the controls. The cerebral water content measured at the end of reperfusion was significantly lower in the 2.5 mg/kg propentofylline group than in the controls. However, such cerebral protective effects were not observed in the 1 mg/kg and 30 mg/kg groups. The present results suggest that propentofylline may accelerate the energy recovery of the transiently ischemic brain and suppress the development of post-ischemic cerebral edema. The effects, however, were not dose-dependent in manner. The detailed mechanism of the effects requires further investigation.

Adenosine Triphosphate↗
PubMed1988

Flow thresholds for cerebral energy disturbance and Na+ pump failure as studied by in vivo 31P and 23Na nuclear magnetic resonance spectroscopy.

The relationships among CBF, cerebral energy metabolism, Na+ pump activity, and electrocorticograms (ECoG) following graded hypotension were studied in 48 gerbils. Energy metabolism and Na+ pump activity were estimated by in vivo 31P and 23Na nuclear magnetic resonance (NMR) spectroscopy, and CBF was determined by [14C]iodoantipyrine methods at the end of the experiments. The CBF measured in normotensive animals was 0.51 +/- 0.07 ml/g brain/min. Following graded hypotension, no 31P spectral change was observed until CBF fell to 0.21-0.27 ml/g brain/min, at which level the intracellular pH began to decrease in association with ECoG voltage reduction. At a CBF level of 0.18-0.23 ml/g brain/min, phosphocreatine (PCr) began to decrease in association with inorganic phosphate (Pi) elevation. At this level, ECoG became isoelectric, although no adenosine triphosphate (ATP) change yet resulted. At a flow level of 0.12-0.14 ml/g brain/min, ATP began to decrease gradually. At 0.04-0.05 ml/g brain/min, PCr and ATP virtually disappeared, and the 23Na signal intensity suddenly changed. The present study demonstrated flow thresholds for the development of tissue acidosis, PCr-Pi changes, and ATP reduction. It appears that functional suppression occurs prior to ATP changes, whereas Na+ pump failure results after ATP depletion.

Animals↗
PubMed1988

Identification of recent lacunar lesions in cases of multiple small infarctions by magnetic resonance imaging.

In nine patients with recent lacunar stroke who revealed multiple small lesions in x-ray computed tomography (CT) and magnetic resonance imaging (MRI), CT and MRI enhancement studies were performed on the same day employing iodinated contrast medium and gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA), respectively. In CT, the injection of contrast medium enhanced recent lesions in only four of the nine patients; furthermore, the effect was weak. In MRI, the injection of Gd-DTPA enhanced recent lesions in all patients except for one who was examined 4 weeks after ictus, and the effect was excellent. Recent infarcts could be identified only by Gd-DTPA-enhanced MRI in four of the nine patients. In patients with multiple small infarctions, identification of recent small infarcted lesions by CT or MRI is sometimes difficult; however, the use of Gd-DTPA in MRI makes it possible to distinguish recent infarcts from other lesions definitively.

Aged↗