Search PubMed⌕ Search

Biomedical subjects

S Takagi

Publications and source records attributed to S Takagi.

At least 559 records · Page 31Linked to original sources
PubMed1984

Measurement of cerebral blood flow in the rat with intravenous injection of [11C]butanol by external coincidence counting: a repeatable and noninvasive method in the brain.

No method has been reported for measuring CBF, repeatedly and noninvasively, in the rat brain. A new method is described, which is noninvasive to the brain, skull, or cervical large vessels. Two pairs of coincidence detectors were positioned, one over the rat brain and the other at the loop of a catheter inserted into the femoral artery. The coincidence head curve and arterial curve were recorded after intravenous injection of 1-[11C]butanol in 15 rats. CBF was calculated by one-compartment curve fitting ( CBFo ) from 1-min data and with the recirculation corrected height/area method from 3-min data ( CBFh X 3 min) and 5-min data ( CBFh X 5 min). CBFo agreed well with CBFh X 5 min, although a slight overestimation was observed in CBFh X 3 min. The normal CBFo in the normocapnic group (n = 6, paCO2 36.7 +/- 2.3 mm Hg) was 1.76 +/- 0.49 ml/g min (mean +/- SD). A good correlation was observed between CBFo (y) and PaCO2 (x), and the regression line was y = 0. 0629x -0.715 (r = 0.88, p less than 0.0001). We concluded that this method gives the stable blood flow values noninvasively and with a minimum loss of blood (less than 0.28 ml per measurement). Applications of this method include activation studies, studies on the effect of drugs and treatments, and water and oxygen extraction fraction studies using different tracers in the same rat.

Animals↗
PubMed1984

A quantitative model for the measurement of cerebral vascular extraction fraction in vivo following intravenous injection: simulation studies.

A mathematical method has been developed by which the cerebral vascular extraction fraction of flow- and diffusion-limited tracers injected intravenously can be measured quantitatively. Successive injections of three tracers are required: a test tracer such as 15O-labeled water; a completely diffusible tracer as a reference tracer and also as a flow tracer; and a tracer for cerebral blood volume (CBV). The arterial tracer concentration curves and total integrated head counts of the test and reference tracers, as well as CBF and CBV values, are required to calculate the extraction fraction. No calibration is required between the head counts and arterial curves. No decay correction of the head and arterial activity is required, because isotopic decay is explicitly included in the equation. The effect of nonextracted test tracer can be corrected. Simulation studies have shown that the calculated extraction fraction values are not sensitive to measurement error in CBF, CBV, partition coefficient, change in measurement time, or time shift effect between the arterial and head data. If there is mixing of two different tissues in the brain, the calculated extraction fraction values are close to the weighted mean values of extraction fraction by relative weight of the tissues. It is concluded that it is possible to apply this method to human studies with a positron emission tomograph scanner and to animal studies with external coincidence detectors.

Antipyrine↗
PubMed1984

Environmental effects of natural radionuclides from coal-fired power plants.

The assessment of the environmental effects of natural radionuclides contained in fly ash released from a coal-fired power plant was carried out and the following results were obtained. Mean concentrations of U, Th and K in 28 kinds of domestic and foreign coals were 1.0 ppm, 3.3 ppm and 2300 ppm, respectively. A good correlation between U and Th concentrations appears evident. Natural radionuclide concentrations of bottom and fly ashes were approximately equal in both ashes, and the values were the same as those calculated by concentration in coal divided by ash content. Release rates of 40K and radionuclides of each decay chain of U or Th were evaluated in the range of 2 to 40,000 pCi/sec for model coal-fired power plants of 1000 MW and 250 MW. The natural radionuclide concentration in air in a plume at the maximum concentration point was 5 X 10(-9) to 5 X 10(-3) pCi/m3, and these values were below 1/200 of those of natural origin.

Air Pollutants↗
PubMed1984

Natural killer-interferon system in patients with preleukaemic states.

The natural killer (NK)-interferon (IFN) system was investigated in patients with preleukaemic states. Endogenous NK cell activity was markedly reduced in all 12 patients studied. No significant correlation was observed between the activity of NK cells and the percentage of blast cells in the peripheral blood or bone marrow. The frequency of large granular lymphocytes (LGL) in lymphocytes of the peripheral blood was not reduced in most patients. The percentage of target binding cells in patients was essentially the same as that in normal controls, and the activity of NK cells from normal donors was not affected by the coexistence of mononuclear cells obtained from the peripheral blood of patients. Furthermore, the alpha-IFN production in response to HeLa cells persistently infected with measles virus was reduced in all patients studied, except for one case with acquired idiopathic sideroblastic anaemia. The augmented activity of NK cells induced by alpha-IFN was variable, but remained at lower levels than the endogenous activity of NK cells in normal controls. These findings suggest that not only the intrinsic defect and reduced number of NK cells but also the dysfunction of the NK-IFN system may be responsible for the reduced activity of NK cells in patients with preleukaemic states.

Adult↗
PubMed1984

Study of oxytocin receptor: II. oxytocin and prostaglandin F2 alpha receptors in human myometria and amnion-decidua complex during pregnancy and labor.

Oxytocin receptors (OXT-R) and prostaglandin F2 alpha receptors (PGF2 alpha-R) in human myometrium, amnion and decidua during pregnancy and at parturition were examined in an effort to clarify their role in the initiation and maintenance of uterine contractions. The number of binding sites for OXT in myometria showed an increase as gestation advance (Ist trimester v.s. at term; 205 +/- 90 v.s. 671 +/- 98 fmol/mg protein, N = 5, p less than 0.01), and a rapid decrease following the onset of labor (254 +/- 60 fmol/mg protein, N = 5, p less than 0.02). On the other hand the number of PGF2 alpha-R, remained unchanged throughout pregnancy and in labor. This myometrial PGF2 alpha binding capacity was approximately 1/20 to 1/30 that of the OXT binding, while binding affinity was almost equal. The OXT-R both in amnion and decidua, which was 1/6 to 1/7 that in myometrium, showed no significant changes throughout pregnancy or after the onset of labor. Binding affinity for each tissue was almost the same and appeared to increase towards term but no statistical significance was detected. Present data confirmed the presence of OXT as well as PGF2 alpha receptors in the three functionally distinct entities of pregnant human uterus; myometrium, amnion, and decidua. Among the components, the OXT binding increased only in the myometrium during pregnancy, suggesting this tissue specifically responds to OXT. In contrast, there was a constant binding in myometria for PGF2 alpha.(ABSTRACT TRUNCATED AT 250 WORDS)

Amnion↗
PubMed1984

Choroid plexus cyst of the lateral ventricle in an elderly man. Case report.

The authors report a case of a symptomatic choroid plexus cyst located in the right lateral ventricle of a 64-year-old man who presented with focal epilepsy. The cyst was diagnosed by computerized tomography, and was proven pathologically at surgery. Total removal was accomplished, with subsequent disappearance of the seizures. A brief review of the literature is included.

Choroid Plexus↗
PubMed1984

[The interaction of oxytocin-prostaglandin receptors in human myometrium and amnio-decidua throughout pregnancy and in labor].

This study was designed to investigate the interaction of oxytocin and prostaglandin F2 alpha at the receptor level (OXT-R and PGF2 alpha-R) between the myometrium and amnio-decidua throughout pregnancy and at parturition in an effort to clarify which of the two is the first and/or triggering factor involved in the instigation of myometrial contractions. In rat myometria, it was recognized that PGF2 alpha-R increased from day 20 of pregnancy and preceded that of OXT-R from day 22 and thereafter both reached peak levels at delivery. In human myometria, on the other hand, OXT-R showed an increase as gestation advanced and when labor was initiated, a significant decrease was found regardless of the route of labor, while the PGF2 alpha-R the binding capacity of which was only 1/20-1/30 of OXT-R, did not change throughout pregnancy or in labor. The binding affinity of OXT-R in amnio-decidua increased as gestation advanced, while its binding capacity remained unchanged and after the onset of labor that of the amnion decreased significantly even though it was only 1/6-1/7 that of the myometrium. The binding affinity of myometrial OXT-R was elevated following the addition of PGF2 alpha before the onset of labor, but the converse could not be shown. These findings suggest that the instigation and maintenance of human labor may be firstly and/or initially dependent on the increase of the binding activity between OXT and OXT-R in the myometrium, and the PGF2 alpha may facilitate such activity by the allosteric effect on OXT-R directly or on the plasma membrane to increase its binding affinity.

Amnion↗