Search PubMed⌕ Search

Biomedical subjects

Y Kuwabara

Publications and source records attributed to Y Kuwabara.

At least 145 records · Page 8Linked to original sources
PubMed1994

Prostaglandin biosynthesis in the umbilical artery and its relation to fetal growth.

Arachidonic acid metabolites were investigated in umbilical arteries of 16 normal pregnancies. Several prostaglandins (PGs) and hydroxyacids were synthesized by the umbilical artery. Prostaglandin I2, PGF2 alpha, PGE2 and PGD2 were found in the products, and PGI2 was the most abundant metabolite in the umbilical artery. The conversion rate of PGI2 from arachidonic acid is strongly correlated with the body weight of the baby (correlation coefficient: 0.621) and with the weight of the placenta (correlation coefficient: 0.668). PGI2 is known to be a strong vasodilator and anticoagulant, and is known to increase blood circulation. We therefore conclude that the PGI2-synthetic activity of the umbilical artery is strongly related to feto-placental blood flow and hence to fetal growth.

Adult↗
PubMed1994

Cerebral circulation and oxygen metabolism in childhood moyamoya disease: a perioperative positron emission tomography study.

Thirteen children with moyamoya disease who had no apparent cerebral infarction or hemorrhage were examined pre- and postoperatively by means of positron emission tomography (PET) to investigate the underlying cerebral circulation and metabolism and the effect of bypass surgery. The preoperative regional cerebral blood flow (rCBF) and mean transit time were significantly decreased and increased, respectively, in the cerebral cortex of these patients compared to control values. The regional cerebral blood volume (rCBV) and the regional oxygen extraction fraction (rOEF) had significantly increased to compensate for the reduced rCBF and perfusion pressure and also to maintain the regional cerebral metabolic rate of oxygen (rCMRO2). In the basal ganglia, rCBV elevation was more prominent than that in the cerebral cortex, although changes in rCBF, rOEF, and rCMRO2 were relatively minor. Postoperative improvements were observed predominantly near the cortex where bypass surgery had been performed and in the basal ganglia. Direct and combined indirect bypass procedures improved cerebral circulation more effectively than single indirect bypass surgery. Although the angiographic findings were not always compatible with the clinical results, the postoperative improvements on PET scans correlated with the disappearance of transient ischemic attacks. In addition to the clinical courses and angiographic findings, PET analysis was indispensable in evaluating the cerebral circulation and metabolism in childhood moyamoya disease.

Adolescent↗
PubMed1994

[A longitudinal study of CMRGlu in dementia of Alzheimer type].

We studied the serial changes of CMRGlu in 6 patients with dementia of Alzheimer type. All patients demonstrated moderately severe dementia at the initial PET scan. Serial PET scans were performed at an interval of 12 to 24 months. Five of the 6 patients showed a deterioration of clinical symptoms at the second scan. The global CMRGlu serially decreased in all patients. An asymmetry of CMRGlu in both the frontal and parietal regions was observed at the initial PET scan, while the direction of asymmetry was preserved at the second PET scan. The ratios (frontal/parietal and parietal/striatum) of CMRGlu showed no interval change. Therefore, CMRGlu was considered to decrease progressively throughout the entire brain in patients with moderately severe dementia of Alzheimer type.

Alzheimer Disease↗
PubMed1994

[The partial volume effect correction for pulmonary mass lesions using a 68Ga/68Ge transmission scan in PET study].

We tried to correct the partial volume effect for pulmonary mass lesions using a 68Ga/68Ge transmission scan. Initially, a fundamental study was done using spherical phantoms and good results were obtained. Next, a clinical evaluation was performed on 28 pulmonary mass lesions ranging in diameter from 0.8 cm to 8.0 cm. The tissue fractions of the mass lesions were obtained by a 68Ga/68Ge transmission scan, where the tissue fraction in the back muscles was assumed to have a value of 1. The tissue fraction of the surrounding lung field was subtracted from that of each mass lesions, and the net tissue fraction was thereby obtained. When no correction was required, the tumor/muscle count ratio (TMR) became higher in proportion with an increase in the mass size. After performing a correction, however, no correlation was observed between them. This method was both easy to perform and reliable, and it is thus considered to be useful for overcoming the partial volume effect in pulmonary mass lesions, although an underestimation may still occur in cases with mass lesions either near the great vessels or the chest wall.

Gallium Radioisotopes↗
PubMed1994

[A useful method to evaluate 11C-methionine uptake using positron emission tomography: determination of the optimal scanning time for evaluation and a comparison between the tumor-to-muscle ratio and the distribution absorption ratio].

We determined the optimal scanning time for evaluating 11C-methionine uptake and then compared the usefulness of the tumor-to-muscle ratio (TMR) with the distribution absorption ratio (DAR) using positron emission tomography. Forty-two PET studies were performed to examine 42 tumorous lesions, 25 normal lung tissues, 23 normal bone marrow and 39 blood pool. In the 42 lesions examined, the TMR at 5, 10-20, 20-32 and 32-40 minutes after 11C-methionine injection, compared with that at 45-60 minutes, was 96 +/- 23%, 91 +/- 8.6%, 94 +/- 6.9% and 96 +/- 6.9%, respectively. A correlation study between the TMR and the DAR demonstrated good results in both the normal tissue (r = 0.96) and the tumorous lesions (r = 0.93). In conclusion, the 11C-methionine uptake can be evaluated at any time from 10 minutes after the injection of 11C-methionine and both the TMR and the DAR are considered to be useful methods for evaluating 11C-methionine uptake using positron emission tomography.

Absorption↗
PubMed1994

[Pre and post operative evaluation of the perfusion reserve by acetazolamide 99mTc-HMPAO SPECT in patients with chronic occlusive cerebral arteries: a comparative study with PET].

We studied the pre and post-operative perfusion reserve using Diamox 99mTc-HMPAO SPECT in 7 patients with chronic occlusive cerebral arteries and then compared the results with PET. STA-MCA anastomosis was performed on 5 patients, while a carotid endarterectomy was done on 2 patients. The cerebral blood flow, the vascular response to CO2 or Diamox, the oxygen extraction fraction and transit time (CBV/CBF) were measured by PET. In the pre-operative state, the visual evaluations for hypoperfusion area at rest were agreed in 5 out of 7 patients in HMPAO SPECT and PET studies. In the remaining 2 patients, hypoperfusion areas were only detected in the PET study. The pre-operative evaluation of perfusion reserve was agreed in 2 patients. In the remaining 5 patients, 3 patients showed definite positive(++) in PET and positive(+) in HMPAO SPECT, and one patient showed positive (+) in PET and negative (-) in HMPAO SPECT. The post-operative change of hypoperfusion areas was well agreed in HMPAO SPECT and PET studies. However, the change of perfusion reserve was underestimated in HMPAO SPECT compared with PET. In the semiquantitative and quantitative analyses, the count rate ratios (affected/unaffected side) in HMPAO SPECT were apparently higher than those of CBF in PET. The postoperative change of the count rate ratios in HMPAO SPECT were smaller than those of CBF in PET. There was no significant correlation between the change in the ratio of the HMPAO SPECT after the administration of Diamox and the oxygen extraction fraction, and it was thus thought to be impossible to predict the areas with an increased oxygen extraction fraction. Thus, Diamox HMPAO SPECT may underestimate the areas of hypoperfusion or decrease in perfusion reserve when compared with PET. We should consider these limitations in the evaluation of pre and post operative cerebral hemodynamics.

Acetazolamide↗
PubMed1994

[Linealization correction for acetazolamide (Diamox) 99mTc-HMPAO SPECT image--a comparative study with PET].

We attempted to make a linearization correction for the acetazolamide 99mTc-HMPAO SPECT image. These results were compared to those by PET using the H2(15)O-bolus injection method. The subjects consisted of eleven patients with cerebrovascular diseases. The SPECT images were obtained by the double injection method in the resting state and after an administration of acetazolamide (1 g). Linearization correction was performed according to the Lassen's method. In this study, three different methods were compared, namely fixed Fr and alpha (70 ml/min/100 ml and 1.08), individual determination of Fr and alpha based on PET data, and finally the normalization of the two scan for administered dose, fixed Fr and alpha (50 ml/min/100 ml and 1.5). The corrected count rate ratios of the 99mTc-HMPAO SPECT images were correlated well with the values of regional cerebral blood flow measured by PET in all methods. Therefore, the first method was considered to be a simple and reliable one. In the last method, the relative change of cerebral blood flow after the administration of acetazolamide was calculated. The means of the percentage increase of cerebral blood flow were in good accord between 99mTc-HMPAO SPECT and PET. However, they showed much discrepancy when individually compared.

Acetazolamide↗
PubMed1993

Discordance between thallium-201 scintigraphy and coronary angiography in patients with Kawasaki disease: myocardial ischemia with normal coronary angiogram.

To assess the usefulness of radionuclide tests in detecting coronary occlusive lesions in children with Kawasaki disease, we compared the results of stress thallium-201 myocardial single photon emission computed tomography with dipyridamole infusion and coronary angiography in 34 patients (19 males and 15 females). Perfusion defects on the stress image only were categorized as transient and were attributed to coronary vascular disease in the presence of redistribution on the delayed image. Others were classified as persistent, due to myocardial damage. Five of the seven children (71%) with severe stenosis on coronary angiography showed persistent and/or transient perfusion defects. However, six of the 11 children (55%) with aneurysms but no obvious stenosis, and four of the 16 children (25%) with normal angiography, showed persistent and/or transient defects. After analyzing 20 individual segments of perfusion defects in the 15 children, six segments (30%) were attributed to the stenosis of supplying coronary arteries, six segments (30%) were related to the coronary aneurysms, and eight segments (40%) were unrelated to any abnormalities on angiography. Thus, significant discordance between the radionuclide and angiographic studies was demonstrated. These results suggest that coronary lesions, as conventionally defined by angiography and supplemented by echocardiography, may not completely identify all Kawasaki patients who may develop myocardial ischemia in the future or who had ischemia in the past.

Adolescent↗
PubMed1993

Esophageal schwannoma.

A 56-year-old woman was seen with an abnormal shadow on chest radiogram. Evaluation revealed an esophageal tumor, which was resected. The tumor was found in the muscular layers of the esophagus; esophageal schwannoma was diagnosed by light microscopic and immunohistochemical studies. There was no relationship between the tumor and vagus nerve. The tumor demonstrated partially invasive growth, and mitotic figures were occasionally observed.

Esophageal Neoplasms↗
PubMed1993

Cerebral glucose metabolism and striatal 18F-dopa uptake by PET in cases of chorea with or without dementia.

Cerebral glucose metabolism was studied by positron emission tomography with [18F]fluorodeoxyglucose in 12 patients with chorea due to different underlying diseases. The striatal 18F-dopa uptake was also studied with 6-L-[18F]fluorodopa in 6 of them. Five of them were diagnosed as Huntington's disease two were as 'sporadic progressive chorea and dementia' with characteristic symptoms and signs of Huntington's disease but no family histories, two were as choreoacanthocytosis, and two had hemichorea caused by suspected vascular lesions in the contralateral striatum revealed by MRI. Caudate and putaminal glucose metabolism decreased in chorea compared to the controls. Hemichorea showed decreased glucose metabolism only in the contralateral striatum. Moreover the glucose metabolism decreased in demented each 7 patients in the frontal, temporal and parietal cortices as well as in the striatum. The caudate and putaminal 18F-dopa uptake in patients with chorea showed no difference with that in the controls. The pathogenetic mechanism of chorea may involve decreased glucose metabolism and normal presynaptic dopaminergic activity in the striatum, and that of the demented state in chorea may also involve an additional decrease of the glucose metabolism in the frontal, temporal and parietal cortices.

Adult↗
PubMed1993

Evaluation of the ratio method compared with graphical analyses for estimating nigrostriatal function in human 18F-dopa PET studies with or without carbidopa.

The striatal to cerebellar (S/C) activity ratio for estimating nigrostriatal function was compared with the Patlak analyses in 18F-dopa (FD) positron emission tomography (PET) with pretreatment with 100 mg carbidopa (CD). Two different time-activity curves of plasma FD or cerebellar 18F were used for the Patlak analyses. The S/C ratio increased linearly with time for 120 min and the ratio at 120 min correlated closely with the uptake constants by the two Patlak analyses (r = 0.94, 0.96) in six normal volunteers and six parkinsonism patients. The S/C ratio and the uptake constant by the cerebellar Patlak analysis without CD also showed a fairly good correlation (n = 30, r = 0.85). Then, the S/C ratios with and without CD were compared. Since CD increased both the striatal and the cerebellar radioactivities proportionally within each subject, CD did not change the S/C ratios. The S/C ratios both with and without CD were simple and comparable to the uptake constants in the FD PET studies.

Adult↗
PubMed1993

Development of an artificial placenta: survival of isolated goat fetuses for three weeks with umbilical arteriovenous extracorporeal membrane oxygenation.

The purpose of our study was to examine the feasibility of long-term extrauterine incubation of an isolated premature fetus in artificial amniotic fluid with arteriovenous extracorporeal circulation. Two premature goat fetuses (age 120 and 128 days) were incubated in an isothermal artificial amniotic fluid incubator with arteriovenous extracorporeal membrane oxygenation via the umbilical vessels. We administered pancuronium bromide to suppress fetal movement and swallowing because movement and swallowing have been implicated in fetal deterioration during extrauterine fetal incubation. The fetuses maintained stable circulatory and respiratory parameters. The total incubation time was 494 and 543 h. The animals were then removed from the incubator and stimulated to initiate lung respiration. With ventilator support, both animals maintained stable blood-gas exchange and survived for more than 1 week. These results clearly indicate that umbilical arteriovenous extracorporeal membrane can effectively support extended extrauterine incubation of an isolated premature fetus.

Amniotic Fluid↗
PubMed1993

Intrauterine growth retardation and fetal losses are caused by epidermal growth factor deficiency in mice.

The plasma concentration of epidermal growth factor (EGF) in female mice increases during pregnancy. Sialoadenectomy (surgical removal of the submandibular glands) on day 13 of gestation attenuates the rise in plasma EGF and significantly reduces the percent of live pups on day 19 of pregnancy to 80% compared with 95% for the control animals. EGF replacement therapy given to the sialoadenectomized mice successfully prevented this reduction in the percent of live pups on day 19. The average weight of the live fetuses from sialoadenectomized mothers was significantly lower than those from the control mothers, i.e., 1.00 +/- 0.14 (SD) g vs. 1.13 +/- 0.07 g. The administration of anti-EGF antiserum to the sialoadenectomized mice further affected fetal viability; only 70% of the pups were alive on day 19, with a mean weight of 0.93 +/- 0.15 g. The mean weight of the fetal body and that of the liver caused by sialoadenectomy were similarly reduced, but the brain was not affected, which shows that the growth retardation was asymmetrical. These findings suggest that EGF plays a physiological role in fetal growth and that EGF deficiency may be a cause of asymmetrical intrauterine growth retardation, which might be due to uteroplacental dysfunction.

Animals↗
PubMed1993

[Stimulus time dependence of cerebral blood flow response to photic stimulation].

The time dependency of rCBF response to photic stimulation in the primary visual cortices was studied using H215O bolus-injection and PET. The subjects consisted of 5 normal volunteers aged from 25 to 40 years old. Their regional CBF was measured at 2 min and 7 min after the start of photic stimulation (frequency, 10 Hz). The percentage increases of rCBF were 19.6 +/- 7.9% (mean +/- SD, range: 8.9-27.6%) in the primary visual cortex on the left side and 23.2 +/- 13.6% (2.5-35.8%) on the right side at 2 min, respectively, while, in comparison, they were 25.3 +/- 20.0% (1.8-49.7%) on the left side and 25.3 +/- 16.4% (3.5-44.5%) on the right side at 7 min, respectively. No significant difference was found in the rCBF responses between at 2 min and 7 min. Therefore, the taming effect does not need to be considered when carrying out a photic stimulation study.

Adult↗
PubMed1993

[Difference in the distribution of 123I-IMP and 99mTc-HMPAO in the striatum--comparison with 15O-PET].

Brain perfusion SPECT studies of 123I-IMP and 99mTc-HMPAO were performed in 10 patients with various brain disorders and the difference in the distribution of 123I-IMP and 99mTc-HMPAO in the cortices and striatum was compared with the cerebral blood flow by 15O-PET method. The ratios of the radioactivity in 14 ROIs of the cortices, striatum and cerebellum to that of the reference region or the right frontal cortex were compared among the 3 studies. The coefficient variance between 123I-IMP and PET was 0.71 and that between 99mTc-HMPAO and PET was 0.74 in the regions excluding the striatum. The striatal activity ratio in 123I-IMP was slightly less than those in 99mTc-HMPAO and PET which were close to each other. The visual activity in the striatum in 123I-IMP was also slightly less than those in 99mTc-HMPAO and PET. All the striatal lesions of decreased perfusion diagnosed by PET were observed in 123I-IMP, however 2 lesions were missed in 99mTc-HMPAO. This seems to be relevant to the difference in the distribution of 123I-IMP and 99mTc-HMPAO.

Adolescent↗