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Biomedical subjects

Y Isaka

Publications and source records attributed to Y Isaka.

At least 73 records · Page 4Linked to original sources
PubMed1993

Cerebral blood flow in asymptomatic individuals--relationship with cerebrovascular risk factors and magnetic resonance imaging signal abnormalities.

We studied the relationship between cortical grey matter flow (CBF) and age, cerebrovascular risk factors and the severity of subcortical hypersignals (HS, hyperintensity score in MRI) in 47 asymptomatic subjects with cerebrovascular risk factors. Multiple regression analysis revealed that HS was most strongly related to CBF, and that hematocrit, age and evidence of ischemic change detected in the electrocardiogram also appeared to be independent determinants of CBF. Both the severity and location of hypersignals were correlated with CBF. The most significant negative correlation observed was that between CBF and HS in the basal ganglia-thalamic region, where the degree of signal abnormality was modest. Decreased CBF in asymptomatic subjects with cerebrovascular risk factors may be related to (1) microcirculatory disturbance associated with elevated hematocrit and an increase in the number of risk factors, and (2) functional suppression of cerebral cortex due to the neuronal disconnection associated with subcortical lesions. In addition, impaired cerebral circulation may be related to MRI signal abnormalities.

Adult↗
PubMed1993

Effect of chronic smoking on regional cerebral blood flow in asymptomatic individuals.

Correlations between cigarette smoking and cerebral blood flow (CBF) were determined. The purpose of the present study was to determine whether the level of cigarette use is a significant predictor of regional CBF (rCBF) when age, gender, mean arterial blood pressure, total cholesterol, fasting blood glucose, hematocrit, and presence of ST-T change and left ventricular hypertrophy on electrocardiogram (ECG) are controlled. We studied a continuous sample of 40 asymptomatic individuals including 20 smokers and 20 nonsmokers. Subjects (mean age 66.2 yr) had an average smoking index of 456 +/- 485.1 (mean +/- standard deviation) [(Number of cigarette/d) x (years of smoking history)]. Regional CBF was measured using the intravenous 133Xe injection method. Simple linear regression and multivariate regression analyses were performed, which modeled regional cerebral blood flow as a function of smoking index and other cerebrovascular disease risk factors. The male-to-female ratio was higher in the group of smokers (18/2) than in the group of nonsmokers (2/18) (P < 0.01). The mean hematocrit of smokers was significantly higher than that of nonsmokers (P < 0.01). There were no significant differences in other variables tested between the two groups. Simple linear regression analysis demonstrated a significant negative correlation of smoking index with CBF in whole brain (r = -0.33; P < 0.05), the right hemisphere (r = -0.34; P < 0.05), right parietal cortex (r = -0.36; P < 0.05), right occipital cortex (r = -0.34; P < 0.05) and left parietal cortex (r = -0.33; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1993

[The relationship of periventricular hyperintensity with cerebral blood flow and cerebrovascular reserve capacity in asymptomatic individuals].

Although periventricular hyperintensity (PVH) is frequently detected in elderly persons by magnetic resonance imaging (MRI), the relationship of such lesions with cerebral blood flow (CBF) and cerebrovascular reserve capacity has never been determined. We used acetazolamide-enhanced xenon-133 CBF and MRI to study 28 subjects with one or more cerebrovascular risk factors but with no neurological symptoms. According to MRI examinations on the transaxial slice of the body of the lateral ventricle, 10 subjects had no PVH (group O), 7 a partial PVH (group I), 6 a continuous PVH (group II), and 5 a confluent PVH which spreads over a wide area of the white matter (group III). There was no relationship between the severity of PVH and the resting cortical CBF (F = 2.7). However, the severity of PVH showed significant negative relationships with the acetazolamide-enhanced CBF (F = 9.5; p < 0.01), and the absolute increase of CBF from the resting state to the acetazolamide challenge (F = 5.1; p < 0.01). Our data suggest the importance of hemodynamic factors and the compensatory vasodilation in the pathogenesis of PVH in asymptomatic individuals.

Acetazolamide↗
PubMed1993

Cerebral blood flow and magnetic resonance imaging in locked-in syndrome.

The cerebral blood flow (CBF) of a patient suffering from locked-in syndrome (LiS) was examined before and after the onset using 99mTc-hexamethylpropyleneamine oxime single-photon emission computed tomography (SPECT) and the intravenous 133Xe injection method. The mean CBF during the locked-in state was 32.2 ml/100 g/min, a 42% reduction from the asymptomatic stage. SPECT showed profound reductions of perfusion in the bilateral cerebral cortices, subcortical regions and in the cerebellum, with a less marked reduction in the frontal cortices. On Day 49, the patient showed some minimal voluntary return with a moderate increase in mean CBF of 40.2 ml/100 g/min. The relative CBF values in the cerebral cortices and subcortical regions were restored, but the bilateral cerebellar hypoperfusion remained unchanged. SPECT and CBF are useful for a better characterization of the brain pathophysiology in LiS.

Aged↗
PubMed1992

Human sera from varicella-zoster virus (VZV) infections cross-react with human T cell leukaemia virus type 1 (HTLV-1): common epitopes in VZV gene 22 protein and HTLV-1 p19 gag protein.

Twenty-nine of 100 sera from patients recently infected with varicella-zoster virus (VZV) were found to cross-react with human T cell leukaemia virus type 1 (HTLV-1) antigen in the particle agglutination (PA) assay using HTLV-1 antigen-coated gelatin particles. Anti-VZV IgM antibodies were shown to be responsible for this cross-reactivity. Western blot analysis revealed that PA-positive anti-VZV sera reacted with the HTLV-1 gag p19 protein in HTLV-1-infected cells and recombinant p19 protein produced in Escherichia coli. By using a truncated p19, the cross-reactive region was located to the C-terminal 17 amino acids of p19. One oligopeptide derived from the C terminus, PQIPPPYVEPT (amino acids 115 to 125), was capable of inhibiting PA, suggesting that this peptide carries the cross-reactive epitope. A homologous sequence was found in the VZV gene 22 protein by database analysis, and the oligopeptide TNIPPPLALLR (amino acids 1330 to 1340) had the ability to inhibit PA. These findings suggest that some IgM antibodies against the VZV gene 22 protein produced in the early phase of VZV infection are cross-reactive with the HTLV-1 gag p19 protein because they recognize an antigenic determinant containing an IPPP tetrapeptide.

Agglutination Tests↗
PubMed1992

[A case of complete recanalization in the lower abdominal aorta by intraaortic infusion of a thrombolytic agent].

Intraarterial infusion of thrombolytic agent is useful in the treatment of obstructive arterial diseases in various vessels. However, few studies have shown that this treatment is useful for aortic occlusion. We report the case with complete recanalization in the lower abdominal aorta following intraaortic infusion of a thrombolytic agent. A 59-year-old man was admitted because of weakness and pain in the bilateral lower limbs at rest. Aortography showed complete occlusion of the abdominal aorta proximal to the inferior mesenteric artery. Both external arteries were supplied via rich collaterals. He was treated by intraaortic urokinase infusion of 2,100,000 units. Total recanalization in the abdominal aorta and both common iliac arteries was obtained. Intraaortic infusion of urokinase was shown to be effective treatment of occlusion in the abdominal aorta.

Aorta, Abdominal↗
PubMed1992

[Effect of chronic smoking on regional cerebral blood flow in asymptomatic individuals].

The chronic effects of cigarette smoking upon regional cerebral blood flow (rCBF) are unclear. The present study investigated the effects of smoking on rCBF assessed by intravenous 133Xe injection in 40 asymptomatic individuals. Analysis was performed using linear regression analysis and multiple regression analysis, creating a model of the rCBF as a function of cerebrovascular risk factor. The risk factors included smoking status, smoking index, age, gender, mean arterial blood pressure, total cholesterol, fasting blood glucose, hematocrit and STT change and left ventricular hypertrophy in electrocardiogram. The male-to-female ratio was higher in the smoking group (18/2) than that in the non-smoking group (2/18). Among the smokers, mean hematocrit was significantly higher than in the non-smokers (p < 0.01). There was no significant difference in rCBF and other variables between the two groups. Linear regression analysis revealed significantly negative correlations between smoking index and CBF in the whole brain (r = -0.33; p < 0.05), right hemisphere (r = -0.34; p < 0.05), right parietal cortex (r = -0.36; p < 0.05), right occipital cortex (r = -0.34; p < 0.05) and left parietal cortex (r = -0.33; p < 0.05). In other variables, age, male sex, hematocrit, left ventricular hypertrophy and STT change showed significantly negative correlations with rCBF. To reduce the effect of confounding variables in our assessment of the dose-related response, a multivariate regression analysis was carried out treating rCBF as a dependent variable and risk factors as independent variables. In the final model, age, hematocrit, male sex and presence of BCG changes remained as independent negative predictors for rCBF.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

[Cerebral blood flow distribution and reactivity during the symptom-free stages of transient ischemic attacks--a 99mTc-HMPAO SPECT study].

Even during the symptom-free stages, patients with transient ischemic attacks (TIA) often show cerebral blood flow (CBF) disturbances. For evaluating the factors which cause these abnormalities, we studied CBF and CBF reactivity to acetazolamide (Diamox) using a 99mTc-hexamethylpropyleneamine oxime (HMPAO) single photon emission computed tomography (SPECT). The results from CBF-SPECT were compared with X-ray computed tomography (CT), cerebral arteriogram, clinical characteristics of TIA and cerebrovascular risk factors. The overall sensitivity rates in detecting the lesion were 68% in CBF-SPECT and 9% in CT. The size of the hypoperfused area tended to be wide in patients who had intracranial, severe stenotic or multiple arterial lesions on the ipsilateral side. No such relations were found between CBF and other examinations. Brain hypoperfusion was located in the subcortical region in eight patients; two patients showed a small hypodense lesion on CT which corresponded to the hypoperfusion on SPECT, and three patients showed no arteriographic abnormality. Hypoperfusion in the cortex was seen in seven patients; all patients showed arteriographic abnormality, but no CT abnormality. The severity rating of the vascular stenosis and hypoperfusion, and the incidence of the intracranial lesions were higher in this group than the group with subcotical hypoperfusion. Seven patients showed fixed normoperfusion before and after diamox injection. Two patients with a subcortical small infarction showed fixed hypoperfusion even after diamox injection. Twelve patients showed focal hypoperfusion before diamox with a new filling-in after diamox. Only one patient showed resting hypoperfusion and decreased CBF reactivity to diamox.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetazolamide↗
PubMed1992

[Quantification of regional cerebral blood flow using 99mTc-HMPAO SPECT and intravenous 133Xe injection method].

We converted an absolute value of 133Xe-CBF (initial slope index, ISI) to the three dimensional CBF-SPECT using the intravenous 133Xe injection technique and 99mTc-HMPAO SPECT according to the microsphere model (method A), and the three compartment model described by Lassen et al. (method B): [formula: see text] [formula: see text] where f = flow in the region of interest (ROI), fr = flow in the reference region, C = count density of 99mTc-HMPAO SPECT in the ROI, Cr = count density of 99mTc-HMPAO SPECT in the reference region, and alpha = conversion to clearance ratio of HMPAO. We used alpha value of 1.5, and the whole cerebrum as a reference region. Four asymptomatic subjects and 15 patients with ischemic cerebrovascular disease were entered the study. In method A, excellent correlation was seen between ISI and SPECT-CBF in both of the cerebral hemisphere (r = 0.993; p < 0.001, n = 38) and the cerebellar hemisphere (r = 0.901; p < 0.001, n = 38). When back diffusion of HMPAO was corrected by method B, correlation coefficient of SPECT-CBF with ISI was equivalent to that in method A in the cerebrum (r = 0.978; p < 0.001, n = 38), while the correlation coefficient ih the cerebellum was lowered (r = 0.726; p < 0.001, n = 38) although high flow to low flow ratio was increased. Reproducibility of rCBF assessed 1 week apart from the first CBF-SPECT was highly reproducible in all of the brain regions; correlation coefficient ranged from 0.757 to 0.910 with a mean correlation coefficient of 0.834 (n = 11). The slope and intercept of the linear regression line between 2nd rCBF versus 1st CBF were 0.889 (range, 0.791-1.141) and 5.5 (range, -9.1-13.4), respectively. Regional CBF measured by method B was approximately 20% increase from that measured by method A. However, there was no significant difference in the reproducibility of rCBF between the two methods. Our results indicate that rCBF can be simply and noninvasively quantified using 99mTc-HMPAO SPECT and absolute unit of CBF measured by 133Xe injection technique. SPECT-CBF offers high resolution images and may be applicable for various cerebrovascular disorders in routine clinical use.

Adult↗
PubMed1992

[A new analytical method for simultaneous measurement of iothalamate and iohexol].

Glomerular filtration rate (GFR) is believed to be the overall index of renal function, and the renal clearance of inulin (Cin) obtained during constant intravenous infusion has long been accepted as the gold standard of GFR measurement. Because of a number of technical difficulties inherent in the assay of inulin concentration in urine and plasma, its utility in clinical practice is limited. Iothalamate, urographic contrast medium, which behaves and is excreted in a fashion similar to inulin, has been accepted as a good filtration marker. We examined whether GFR could be estimated by ionic contrast media, "iothalamate" and non-ionic contrast media, "iohexol", when the high-performance liquid chromatography (HPLC) system was used as the analytic method. In our HPLC system, iothalamate and iohexol could be simultaneously determined. The assay results gave linearity within the wide range of concentrations tested. In seventeen subjects, the renal clearances of creatinine, iothalamate, and iohexol (Ccr, Ciot, and Cioh) were compared with that of inulin. The slopes with zero intercept of Ccr vs Cin, Ciot vs Cin, and Cioh vs Cin were 1.24 +/- 0.02, 1.06 +/- 0.02, and 0.83 +/- 0.02, respectively. In conclusion, an excellent correlation of renal clearance of iothalamate with that of inulin was obtained in patients with a wide range of renal function and normal volunteers. This justifies the use of the single injection of iothalamate and HPLC system as the analytic method in the measurement of GFR.

Chromatography, High Pressure Liquid↗
PubMed1992

[Relationship between extent of brain hypoperfused area and functional outcome in patients with a small subcortical infarction: evaluation with X-ray CT, 123I-IMP cerebral perfusion SPECT and cerebral angiography].

We performed 123I-IMP single photon emission computed tomography (SPECT) in 43 patients who had a small infarction (less than 2 cm) in subcortical area and who were less than 1 month after onset of stroke. Hypoperfused area of brain was qualitatively assessed and was compared with functional outcome at 6-month after the stroke and the cerebral angiogram. Functional outcome was poorer in patients who had wider hypoperfused area in brain (chi 2 = 29.3; p less than 0.001). The extent of brain hypoperfused area showed a positive correlation with the degree of stenosis in the extracranial and/or intracranial arteries (r = 0.61; p less than 0.01). In patients who had no angiographic abnormality, the extent and the location of the hypoperfused area were equivalent to that of the low density area in CT. Thus 123I-IMP SPECT in patients with a small infarction may discriminate lacunar infarction from embolic or hemodynamic infarction, which was caused by vascular lesions of major cerebral arteries, in subcortical area. Our study suggests that functional outcome is better in lacunar infarction than embolic or hemodynamic infarction in subcortical area.

Aged↗
PubMed1992

[Platelet accumulation in abdominal aortic aneurysms and the effect of antiplatelet drugs: assessment by indium platelet scintigraphy].

A dual tracer technique using 111In labeled platelets and 99mTc labeled human serum albumin was applied to evaluate the in vivo thrombogenicity in 12 cases with abdominal aortic aneurysm (AAA) and the effect of antiplatelet drug on the thrombogenicity. The magnitude of platelet accumulation at AAA was expressed as the ratio of radioactivity of 111In platelets on the vascular wall to those in the blood pool (PAI; platelet accumulation index). Of the 12 patients with AAA, 11 had positive studies on baseline imaging and 1 had equivocally positive image. The PAI value (Mean +/- SD) over the AAA was 53.8 +/- 34.1% as compared to -8.6 +/- 4.4% in the control group (p less than 0.01). Seven patients with an AAA and positive baseline images were restudied during platelet active drug with 325 mg of aspirin. During treatment with aspirin, of 7 patients, 5 had positive images, of which 3 were decreased and others unchanged compared to baseline studies, 1 equivocally positive one and one negative one. The PAI value during treatment (21.9 +/- 18.6%) was significantly decreased compared to those in baseline study (52.1 +/- 23.9%). Our results suggest that the method used for platelet imaging in the present study may be useful for studying the in vivo thrombogenicity and the effect of platelet active drugs in AAA.

Aged↗
PubMed1992

Cerebral blood flow imaging with technetium-99m-HMPAO SPECT in a patient with chronic subdural hematoma: relationship with neuropsychological test.

We report the relationship between cerebral blood flow (CBF) and neuropsychologic tests in a patient with a chronic subdural hematoma suffering from severe dementia and left hemiparesis. Regional CBF was quantified using 99mTc-HMPAO SPECT and 133Xe-CBF. CBF-SPECT could detect the hematoma which was isodense by CT scan and the neuropsychological test improved remarkably with the increase in CBF after surgery. We conclude that if there is a strong clinical suspicion of subdural hematoma and CT scan is not diagnostic then CBF-SPECT may be valuable in localizing the hematoma and monitoring the effect of operation.

Aged↗
PubMed1991

Effect of TRK-100, a stable orally active prostacyclin analogue, on platelet function and plaque size in atherothrombotic strokes.

Patients with carotid atheromatous lesions were prospectively studied with indium-111 platelet imaging, platelet aggregability and B-mode real-time ultrasound tests to determine the short-term effects of orally active prostacyclin analogue TRK-100 (40 micrograms, three times daily for 4 weeks). To establish baseline values, all patients underwent indium-111 platelet imaging, platelet aggregation study and B-mode ultrasound. The results were positive for carotid plaque and platelet accumulation. Visual analysis showed repeated platelet scintigrams to be unchanged in five patients without antithrombotic therapy; repeated ultrasound studies showed no change in eight of ten plaques, while one showed progression and one regression of the plaque. In five TRK-100 treated patients, five of seven lesions with platelet accumulation at the baseline became negative, and two remained unchanged during the treatment; repeated B-mode ultrasound tests indicated eight of nine plaques remained unchanged, while one showed plaque size reduction. Quantitative analysis demonstrated that, TRK-100 significantly reduced the ADP aggregation (1 microM) from 55.2 +/- 21.3% to 24.0 +/- 14.7% (+/- SD; p less than 0.05) and the platelet accumulation index (25.7 +/- 17.2% vs 10.4 +/- 10.4%; p less than 0.05). However, there was no significant reduction in plaque scores during TRK-100 therapy compared with the baseline (2.70 +/- 2.75 mm vs 2.51 +/- 2.58 mm). The data obtained suggested that short-term TRK-100 therapy has an inhibitory effect on platelet accumulation in carotid atheroma but does not cause significant changes in plaque size.

Administration, Oral↗
PubMed1991

Functional alterations of human platelets following indium-111 labelling using different incubation media and labelling agents.

Human platelets were labelled in the absence or presence of plasma using indium-111 labelled oxine sulphate, tropolone or 2-mercaptopyridine-N-oxide (MPO). Under in vitro and in vivo conditions, platelet functions were evaluated by measuring their aggregability, survival, recovery and early distribution. High labelling efficiency was achieved in saline labelling, whereas with plasma labelling, it was necessary to concentrate the platelet-rich plasma to 4.8 x 10(6) platelets/microliters. The aggregation of platelets labelled in plasma or saline was compared with that of controls; platelets labelled in saline showed lower aggregability in 2 microM ADP but not in 5 microM ADP nor with collagen. No significant differences in platelet survival and recovery were noted between platelets labelled in plasma and those labelled in saline. Our results indicate that partial loss of ADP aggregability in vitro does not influence the in vivo viability of platelets labelled in saline. Scintigraphic studies showed that platelets labelled in a saline medium were temporarily sequestrated in the liver but not in the spleen or heart. Thus, platelet labelling in saline does not affect platelet function adversely, but platelets labelled in plasma are more desirable for assessing the early distribution of platelets in the reticuloendothelial system.

Adult↗