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Biomedical subjects

S Watanuki

Publications and source records attributed to S Watanuki.

At least 19 recordsLinked to original sources
PubMed1992

[Physiological evaluation of clothing made of new material for protection against the solar heat load].

The purpose of this study was to evaluate the effects of clothing made of a new material that is, the polyester staple containing the ceramics and to reflect the solar heat load on physiological responses during rest, exercise (50% VO2max) and recovery on a cycle ergometer. Six young female subjects exposed their back to an artificial solar heat load of an intensity of 680 kcal/m2/h with an air temperature of 30 degrees C. The data were compared to those obtained by wearing clothing made of cotton material. The results were as follows. The cardiac output and oxygen consumption obtained at the end of recovery were increased by solar heat load when the subjects wore cotton material. However, these values showed no significant increase when the subjects wore solar heat reflecting clothing. Furthermore, the cardiac output at the end of submaximal work and recovery were higher for the cotton material compared to the heat reflecting clothing in the solar heat load. The increase of cardiac output for the cotton material may show the increase of skin blood flow for the body heat dissipation. Those results suggest that the solar heat reflecting clothing may decrease the physiological strain like a blood redistribution for the body heat dissipation during exercise in summer sunlight.

Adult↗
PubMed1991

Absorbed dose estimates in positron emission tomography studies based on the administration of 18F-labeled radiopharmaceuticals.

Absorbed doses were estimated after intravenous administration of 18F-labeled radiopharmaceuticals in Positron Emission Tomography (PET) studies. These radiopharmaceuticals, [18F]-2-Fluoro-2-Deoxy-D-Glucose (FDG), 6-[18F]Fluoro-L-Dopa (FDOPA) and 18F-5-Fluorodeoxyuridine (FdUR), are used in clinical research at the Cyclotron and Radioisotope Center of Tohoku University. Radiopharmaceutical biokinetic values were measured in humans or extrapolated from animal experiments. Selective organ uptake and rapid clearance of activity from the blood were observed. High activity in the bladder contents of humans was found. Calculations were made by the MIRD method, modified to account for the differences in physique and organ mass between the Caucasian Reference Man and the Japanese one. The bladder wall receives the highest dose (more than 1.23 x 10(-1) mGy/MBq) when any of these compounds are administered. Other organs receiving high doses are the heart, brain and kidneys from FDG; the kidneys and pancreas from FDOPA, and the kidneys and small intestine from FdUR. These organs received absorbed doses of more than 2.7 x 10(-2) mGy/MBq. Effective dose equivalents of 2.4 x 10(-2), 2.6 x 10(-2) and 3.3 x 10(-2) mSv/MBq were estimated in the intravenous administration of 18F-FDG, 18F-FDOPA and 18F-FdUR, respectively.

Adult↗
PubMed1991

Measurement of D2 dopamine receptor-specific carbon-11-YM-09151-2 binding in the canine brain by PET: importance of partial volume correction.

Carbon-11-YM-09151-2 binds highly selectively to D2 dopamine receptors in the brain. Using this ligand, D2 dopamine receptor density (Bmax) and affinity (Kd) in canine striatum were measured. After administering various doses of the ligand in nine experiments, regional uptake was followed by repeated PET scanning for up to 80 min. D2 dopamine receptor specific binding at equilibrium was defined as striatal minus occipital activity after partial volume correction. Bmax and Kd were estimated by Scatchard analysis to be 40.3 pmole/ml of tissue and 22.9 nM, respectively. When a low mass dose of the ligand was administered, the bound-to-free ligand ratio in the striatum at equilibrium was consistent with the Bmax/Kd value obtained from the Scatchard analysis. The present study demonstrates the importance of partial volume correction and the Bmax/Kd measurement in a single PET study with carbon-11-YM-09151-2.

Animals↗
PubMed1991

Estimation of absorbed doses in humans due to intravenous administration of fluorine-18-fluorodeoxyglucose in PET studies.

Radiation absorbed doses due to intravenous administration of fluorine-18-fluorodeoxyglucose in positron emission tomography (PET) studies were estimated in normal volunteers. The time-activity curves were obtained for seven human organs (brain, heart, kidney, liver, lung, pancreas, and spleen) by using dynamic PET scans and for bladder content by using a single detector. These time-activity curves were used for the calculation of the cumulative activity in these organs. Absorbed doses were calculated by the MIRD method using the absorbed dose per unit of cumulated activity, "S" value, transformed for the Japanese physique and the organ masses of the Japanese reference man. The bladder wall and the heart were the organs receiving higher doses of 1.2 x 10(-1) and 4.5 x 10(-2) mGy/MBq, respectively. The brain received a dose of 2.9 x 10(-2) mGy/MBq, and other organs received doses between 1.0 x 10(-2) and 3.0 x 10(-2) mGy/MBq. The effective dose equivalent was estimated to be 2.4 x 10(-2) mSv/MBq. These results were comparable to values of absorbed doses reported by other authors on the radiation dosimetry of this radiopharmaceutical.

Adult↗
PubMed1990

Stability of cerebral blood flow and oxygen metabolism during normal aging.

Cerebral blood flow and oxygen metabolism in aged normal subjects were measured with positron emission tomography and their relationship with brain atrophy was evaluated. Brain atrophy progressed in a linear fashion during aging while cerebral blood flow and oxygen metabolism were well preserved. The finding suggests that brain atrophy is an aging process less dependent on cerebral blood flow and metabolism over the course of normal aging.

Aged↗
PubMed1989

Kinetic evaluation of 11C-1-aminocyclopentane carboxylic acid in rabbits bearing VX-2 tumors using positron emission tomography.

Tumor detection with 11C-1-aminocyclopentane carboxylic acid (11C-ACPC) showed that this amino acid has a high affinity for malignant tumors. We studied the kinetics of intravenously injected 11C-ACPC in the rabbit VX-2 tumor using positron emission tomography. Three female rabbits bearing VX-2 tumor in the thighs were used. High uptake of 11C-ACPC was seen in the tumor and liver. 11C-ACPC in plasma decreased rapidly after injection and its activity in the tumor increased with time. The kinetic evaluation of ACPC uptake into the tumor was performed using the unidirectional transport model. The average values of the transfer constant of 11C-ACPC for VX-2 tumor were 0.030 +/- 0.002 ml/min/g. This preliminary result may form the basis for a quantitative analysis of the in vivo distribution of 11C-labeled ACPC in tumors.

Amino Acids↗
PubMed1989

Effect of precooling on heat tolerance of resting men in a hot environment: comparison with seasonal effect on it.

Four healthy Japanese males volunteered as subjects. They were exposed to hot environment of 50 degrees C with 50% relative humidity for 61 minutes immediately after the precooling where they rested in a 10 degrees C for 30 minutes. Their physiological data were compared with that of a previous report (Iwanaga et al., 1983), in which we studied the physiological responses of the same subjects at rest in a 50 degrees C without precooling in summer and winter. After precooling (PC), all the four subjects completed heat exposure for 61 minutes. But without precooling in summer (NC), two of the subjects stopped heat exposure before 61 minutes because of hyperthermia. Rectal temperature (TR) was lower in PC than in NC before and during heat exposure. During heat exposure, TR in PC had risen at the 30th minute, but TR in NC at 20th minute. Whereas there was no difference in heart rate (HR) during heat exposure between summer and winter, in PC HR remained lower than in NC because rising time of HR was prolonged during heat exposure.

Acclimatization↗
PubMed1989

Quantitative evaluation of L-[methyl-C-11] methionine uptake in tumor using positron emission tomography.

Tumor uptake of L-[methyl-11C]methionine ([11C]Met) was assessed in six patients with brain tumors and three patients with lung cancer using positron emission tomography (PET). In arterial plasma samples taken at 5, 15, 30, and 60 min after injection, a fraction of [11C]Met was measured using high performance liquid chromatography in individual patients. Employing curve fitting, a history of [11C]Met activity was obtained as an input function. By means of sequential PET scannings and graphic analysis, uptake rate and distribution volume of [11C]Met in tumor tissue were calculated. In two studies irreversible uptake into the tumors was not seen when total plasma 11C activity was used as the input; however when [11C]Met plasma activity was used, definite irreversible uptake was seen, indicating tumor viability. In other studies, up to 24% underestimation of uptake rate was found. The present results demonstrated the importance of measuring [11C]Met in plasma for quantitative assessment of in vivo amino acid metabolism in tumors.

Adolescent↗
PubMed1988

Positron CT imaging of an impending stroke.

We present PET findings of a case of a transient ischemic attack which later progressed to cerebral infarction. Cerebral blood flow at the stroke focus in the right parietal cortex measured after a TIA attack and before stroke was as low as 24 ml/100 g/min with some increase in oxygen extraction fraction and blood volume. The condition was compatible with "misery perfusion". This case may be an example suggestive that the "misery perfusion sign" is a warning of impending stroke and its poor prognosis if left without appropriate treatments.

Aged↗
PubMed1988

Measurement of the ratio of cerebral oxygen consumption to glucose utilization by positron emission tomography: its consistency with the values determined by the Kety-Schmidt method in normal volunteers.

The regional interrelationship between cerebral oxygen consumption (CMRO2) and cerebral glucose utilization (CMRGlc) was studied in normal subjects using positron emission tomography (PET) and the 15O steady-state inhalation and the [18F]fluoro deoxyglucose method. The use of standard sets of rate constants and the model lumped constant of 0.52 as well as the regional blood-brain partition coefficient for water and the blood volume correction for oxygen extraction fraction provided a CMRO2/CMRGlc ratio of 4.89 in the cortical gray matter, 5.27 in the basal ganglia and 5.82 in the centrum semiovale (white matter). The values of CMRO2/CMRGlc for the basal ganglia and the white matter were consistent with those reported for the whole brain with the Kety-Schmidt method. There was no significant difference in the CMRO2/CMRGlc between the basal ganglia and the white matter indicating the similar nature of in vivo oxidative metabolism of glucose in neuron-rich region and glial cell-rich region.

Aged↗
PubMed1987

Myocardial imaging using 11C-CoQ10 with positron emission tomography.

The potential of 11C-labeled coenzyme Q10(CoQ10) as a myocardial imaging tracer was explored with positron emission tomography (PET). Serial myocardial imaging studies were performed using 11C-CoQ10, 45Ti-diethylenetriaminepentaacetic acid (45Ti-DTPA), and 2-deoxy-2-[18F]fluoro-D-mannose (18FDM) in the same dog. Cross sectional images of the heart with 11C-CoQ10 showed relatively high radioactivity in the blood pool, when compared with images taken with 18FDM. However, when the blood spillover of radioactivity is adequately corrected with 45Ti-DTPA data, it was found that 11C-CoQ10 accumulated in the myocardium with time.

Animals↗