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Biomedical subjects

N Mizukawa

Publications and source records attributed to N Mizukawa.

At least 19 recordsLinked to original sources
PubMed1992

Effect of hemodilution on cerebral hemodynamics and oxygen metabolism.

BACKGROUND AND PURPOSE: To evaluate the effects of hemodilution on cerebral hemodynamics and oxygen metabolism in the normal human brain, we measured regional cerebral blood flow, oxygen extraction fraction, oxygen metabolic rate, and regional cerebral blood volume in eight normal volunteers before and after hemodilution using positron emission tomography and oxygen-15-labeled gas inhalation technique. SUMMARY OF REPORT: Hemodilution was accomplished by phlebotomy of 400 ml and drip infusion of 500 ml low molecular weight dextran, which reduced hematocrit from 42.5% to 37.2% and arterial oxygen content from 19.1 to 16.9 ml/dl (both p less than 0.005). It also increased mean cerebral blood flow from 45.2 to 47.7 ml/100 ml/min (p less than 0.025), but decreased tissue oxygen delivery from 8.7 to 8.0 ml/100 ml/min (p less than 0.05) and cerebral blood volume from 4.9% to 4.6% (p less than 0.025) in the overall cortical gray matter. CONCLUSIONS: Our results indicate that hemodilution in the tested range does not improve oxygen transport or tissue oxygenation in the normal human brain, although it increases cerebral blood flow.

Adult↗
PubMed1992

Positron emission tomographic measurement of acute hemodynamic changes in primate middle cerebral artery occlusion.

Specific hemodynamic changes in acute ischemia were investigated using a middle cerebral artery occlusion primate model and positron emission tomography. The cerebral blood flow (CBF), cerebral blood volume, oxygen extraction fraction (OEF), and cerebral metabolic rate for oxygen were measured 1, 3, and 9 hours after occlusion. OEF showed an increase in ischemic areas, and especially where CBF was below 18 ml/100 gm/min 1 hour after occlusion the OEF increased significantly (0.69 +/- 0.20, p < 0.05). Nine hours after occlusion, the OEF values were lower compared to those 1 and 3 hours after occlusion. Areas where CBF ranged from 18 to 31 ml/100 gm/min showed an increase in OEF at all times (p < 0.05). Clearly, OEF changes remarkably in the acute stage.

Animals↗
PubMed1991

[An evaluation of cerebral blood flow and metabolism of reconstructive vascular surgery using positron emission tomography--a report of 4 cases].

Changes in cerebral hemodynamics due to reconstructive cerebral vascular surgery were evaluated using positron emission tomography (PET). Three minor stroke cases and 1 TIA case, brought on by main trunk stenosis, were included. STA-MCA anastomoses was performed in two of the cases and carotid endarterectomy was performed in the remaining two cases. CBF, CBV, OEF, CMRO2 and CBF/CBV were investigated using PET with the ROIs fixed in both normal and stenosis areas. On the two cases of STA - MCA anastomosis, clear hemodynamic improvement was not demonstrated. On the two carotid endarterectomy cases, the hemodynamic factors showed improvement.

Aged↗
PubMed1990

Impairment of CO2 reactivity in severe head injury patients: an investigation using thermal diffusion method.

For measurement of the cerebral blood flow (CBF) the thermal diffusion method is quite convenient and allows the chronological measurement of CBF and CO2 reactivity of cerebral vessels. We investigated the CO2 reactivity of fifteen head injury patients. The results showed that in head injury cases, the disturbance of the CO2 reactivity correlates well to poor outcome. Using thermal diffusion method, investigations of CO2 reactivity are useful for further understanding of the physiological state of head injury patients.

Adult↗
PubMed1990

Metabolic and hemodynamic aspects of peritumoral low-density areas in human brain tumor.

With the use of positron emission tomography, regional cerebral blood flow, oxygen utilization, and glucose utilization were measured in the peritumoral low-density areas on x-ray computed tomographic images in 23 patients with supratentorial brain tumors: 7 meningiomas, 11 malignant gliomas, and 5 metastatic brain tumors. Findings on positron emission tomography in these areas revealed characteristic patterns associated with the types of tumor and the degree of mass effect. It is likely that two different types of pathophysiological states exist in "peritumoral edema": 1) primary ischemia caused by mechanical compression by the tumor mass in meningiomas; and 2) primary metabolic suppression (mainly in oxygen metabolism) in malignant brain tumors.

Adult↗
PubMed1990

Positron emission tomographic studies on cerebral hemodynamics in patients with cerebral contusion.

Positron emission tomography is currently one of the most useful methods for measurements of cerebral hemodynamics and oxygen metabolism, because it facilitates accurate analysis of the local cerebral circulation in three-dimensional quantitative images. In this study, we performed positron emission tomography studies to measure cerebral circulation in a total of 11 patients who sustained head injuries with contusion. Several parameters were measured including regional cerebral blood flow, regional cerebral blood volume, permeability, and regional cerebral metabolic rate for oxygen. Data from brains both with and without contusion were analyzed for chronological changes, in the subacute stage from the 8th to 29th day and in the chronic stage until 360 days after the injury and compared with similar data in a group of normal subjects. It was concluded that in the subacute stage, regional cerebral blood flow decreased (26 +/- 7 and 39 +/- 10 ml/100 g/min) and regional cerebral blood volume increased (5.6 +/- 1.8 and 5.4 +/- 0.9 ml/100 g) both in areas of cerebral contusion and in areas remote from cerebral contusion and that permeability increased in areas of contusion but not in remote brain areas. In the chronic stage, these parameters showed a tendency for recovery.

Adolescent↗
PubMed1990

[Relationship between aging and renal function: a positron emission tomographic study].

Blood volume (V), blood flow (F) and glomerular filtration rate (GFR) per 100 g (100 ml) of kidney were calculated with C15O, H(2)15O and 68Ga-EDTA, to study age-related changes per unit tissue in 19 subjects using positron emission tomography. Age was negatively correlated with V, F and GFR. The aging-related decrease in V was less marked than those in F and GFR. Analysis by regression formula induced that F, GFR for subjects in their 70s are 76%, 46% and 55% for those in their 20s, respectively.

Adult↗
PubMed1990

[Evaluation of renal blood volume by PET--the aorta-kidney equilibrium monitored with C15O].

Twenty subjects inhaled C15O and its dynamics were monitored to determine when equilibrium between the aorta and kidney occurred. One minute after inhalation, the increase in radioactivity in the aorta paralleled that in the kidney, but thereafter, both declined slowly. The ratio of aorta/kidney radioactivity become constant 1 min after inhalation and remained unchanged for 4 min. Thus renal blood volume can be measured 1 min after inhalation of C15O its distribution in the aorta and kidney has attained equilibrium.

Administration, Inhalation↗
PubMed1989

Postoperative hemodynamic and metabolic changes in patients with subarachnoid hemorrhage.

Positron emission tomography was performed using an oxygen-15 gas inhalation technique to measure regional cerebral blood flow, metabolic rate for oxygen, oxygen extraction fraction, and cerebral blood volume in 13 patients with subarachnoid hemorrhage during the period of delayed vasospasm after surgery as well as in 10 volunteers as controls. Compared with the controls, the patients showed decreased hemoglobin concentration and decreased total arterial oxygen content due to postoperative hemodilution. Global reductions in the metabolic rate for oxygen and in the tissue oxygen supply were noted even in the apparently normal cortex of the patients in spite of adequate blood flow and adequate oxygen extraction fraction. In addition, regional reductions in blood flow and in perfusion reserve were seen in the cortical territory corresponding to cerebral vasospasm. Our results indicate that two processes are involved in the pathophysiology of cerebral vasospasm: 1) generalized impairment of oxygen metabolism with a reduced tissue oxygen supply, even in the apparently normal cortex, and 2) additional impairment of regional perfusion in the territory of vasospasm.

Adult↗
PubMed1989

[The Chronological changes in the cerebral blood flow and cerebral metabolic rate for glucose in the ischemic rabbit brain].

Chronological changes in regional cerebral blood flow (rCBF) and in the regional cerebral metabolic rate for glucose (rCMRGlu) were studied by a double tracer autoradiographic method in regions of local ischemia in rabbit brains. Local ischemia was produced by cautery of the bilateral vertebral artery, followed several days later by cautery of the left middle cerebral artery through a transorbital approach and ligation of the left common carotid artery. Autoradiography was performed, 2 hours, 6 hours, and 4 days after occlusion, by a double tracer method involving the use of 14C-iodo-antipyrine and 18F-fluoro-deoxyglucose. Absolute rCBF values were estimated by Sakurada's method and rCMRGlu values by Hutchins' formula. Histological examination was performed concurrently with the rCBF and rCMRGlu study. Mildly ischemic lesions (rCBF of 25 to 40 ml/100 g/min) were detected in the superior portion of the left frontal lobe, the left parietal lobe, and the left occipital lobe. Severely ischemic lesions (rCBF below 25 ml/100 g/min) were found in the lateral part of the left frontal lobe, the left temporal lobe, and the left caudate nucleus. In the mildly ischemic regions, rCMRGlu decreased in proportion to the decrease in rCBF. That is, matched low perfusion was observed, but there were no histological abnormalities. In severe ischemia the situation was quite different. Two hours after occlusion, most areas showed a decrease in rCMRGlu in proportion to the decrease in rCBF. However, 6 hours after occlusion, rCMRGlu decreased nonuniformly: in some places the decrease was dramatic and in others, rCMRGlu residue was found. Four days after occlusion, the reduction in rCMRGlu was again proportional to the rCBF decrease.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Renal blood volume vs. glomerular filtration rate: evaluation with C15O and 88Ga-ethylenediaminetetraacetic acid (EDTA) study.

68Ga-EDTA (ethylenediaminetetraacetic acid) is simply and economically obtained without a cyclotron. We used renal blood volume (RBV) values obtained by C15O studies for blood activity subtraction on renal time activity curves using a positron emission tomography for the determination of the glomerular filtration rate (GFR) by intravenous 68Ga-EDTA administration. Positive correlation was revealed between the GFR and RBV values, where the ratio of blood activity in whole renal activity increased relatively as GFR value decreased. The estimation using a correction equation derived from the correlation curve was possible without a C15O study.

Blood Volume↗
PubMed1989

[Positron emission tomographic evaluations on hemodynamics and glucose metabolism of brain tumors and perifocal edematous tissues].

Blood flow and glucose metabolism of the tumors and perifocal edematous tissues were evaluated using positron emission tomography (PET). Thirty-one brain tumor cases were investigated 12 non glial tumors (9 meningiomas and 3 metastatic tumors) and 19 gliomas (these were classified in 5 astrocytomas, 7 anaplastic astrocytomas and 7 glioblastomas, according to the malignancy). The diagnosis were confirmed pathologically in 30 cases. Cerebral blood flow (CBF), cerebral metabolic rate for oxygen (CMRO2), oxygen extraction fraction (OEF) and cerebral blood volume (CBV) were measured by O-15 labeled gases inhalation methods. Cerebral metabolic rate for glucose (CMFglu) were measured by F-18 Deoxyglucose intravenous injection method and calculated by Hutchins's formula. The rate constant (ks) and lumped constant (LC) used in this study were the same as those published by Phelps et al. in 1979. The blood flow and glucose metabolic rates of tumors were measured by the same methods. The results were as follows: 1) Meningiomas showed very high blood flow and blood volume with a wide range. The OEF and metabolic rate for glucose (MRglu) values were very low. 2) Metastatic tumors showed the low values of blood flow, metabolic rate for oxygen (MRO2) and OEF. 3) The blood flow and MRglu values on gliomas were varied with no significant differences between the three subgroups. On the other hands, as the malignancy of the glioma increased, a statistically significant increase in blood volume and a decrease in OEF were noted. 4) The OEF values from the various types of tumors studied were significantly lower than those obtained from the normal tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Dysautoregulation in patients with ruptured aneurysms: cerebral blood flow measurements obtained during surgery by a temperature-controlled thermoelectrical method.

We used a temperature-controlled thermoelectrical method, induced hypotension, and CO2 inhalation to obtain cerebral blood flow (CBF) measurements during surgery for investigation of the state of brain vasoreactivity in subarachnoid hemorrhage patients. The study included 11 patients who underwent 12 operations for ruptured intracranial aneurysms. The CBF data were analyzed to investigate the neurological state, presence or nonpresence of vasospasm, timing of the operation, and outcome of each patient. Autoregulation disturbance, in terms of reaction to hypotension, was consistently seen in patients in poor neurological states, and this disturbance was correlated with poor outcome. This simple monitoring system, used during emergency operations for ruptured aneurysm, was useful in predicting outcome.

Adult↗
PubMed1986

Lymphoid adenohypophysitis.

A rare case of lymphoid adenohypophysitis in a 28-year-old woman with temporal relation to pregnancy is described. A CT scan disclosed a round, contrast-enhancing sellar mass simulating pituitary adenoma, and endocrine evaluation showed mild hypopituitarism. Histological examination of the specimen obtained by transsphenoidal hypophysectomy after uneventful natural labour showed marked diffuse infiltration of mature lymphocytes with many germinal centers within lymphoid follicles. This finding was the same as previously reported. The present case makes a total of 15 cases reported in the world literature up to date. To our knowledge, no report has been documented in Japan.

Adenoma↗
PubMed1985

Spontaneous reduction in size of prolactin-producing adenoma after delivery. Case report.

The authors describe the case of a pregnant woman with a large prolactin-producing pituitary adenoma that regressed after delivery. The patient's neurological signs and symptoms spontaneously disappeared soon after delivery without treatment. Reduction in tumor size was confirmed on computerized tomography scans. It is hypothesized that the growth rate of a prolactinoma may be accelerated by estrogen.

Adenoma↗