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Biomedical subjects

I Nagata

Publications and source records attributed to I Nagata.

At least 307 records · Page 17Linked to original sources
PubMed1984

[Digital subtraction angiography of the cerebral vessels by intraarterial injection].

Three hundred and fifty-seven digital subtraction angiography (DSA) were performed in 184 neurosurgical patients by intraarterial injection. Examinations consisted of 192 carotid angiography, 110 vertebral angiography, 23 aortography, 11 spinal angiography and 21 other angiography. In all examinations, visualization of the vessels was excellent and the complications were never experienced. High contrast sensitivity of DSA resulted in better visualization of tumor stains, phlebogram, and arteries in cerebral arteriovenous malformations with large shunt blood flow than conventional angiography. Selective catheterization into each cerebral arteries was not necessarily demanded for good opacification of the vessels because of high sensitivity. High contrast sensitivity also permitted low concentration of contrast material, small dose of contrast material, and slow injection rate. Low concentration of contrast material reduced pain and heat during injection especially in the external carotid and vertebral angiography. Using slow injection, recoiling of catheter into the aorta was reduced, so that injection from the innominate and subclavian arteries for visualization of origin of the cerebral arteries were always successful. Full study of cerebral arteries by Seldinger's method, if necessary, was easily achieved using DSA even in patient with high age or with severe atherosclerosis. Bolus injection of small dose of contrast material as well as serial imaging was helpful in evaluating hemodynamics in the lesion. Real time display of DSA reduced the time required for angiography and was very convenient for artificial embolization. Besides these advantages, DSA became comparable to conventional angiography in special resolution by use of intraarterial injection and could be a preoperative genuine examination as well as a screening method.

Adolescent↗
PubMed1984

[Study on the vertebro-basilar system in "moyamoya" disease].

Posterior circulation in 82 children of "moyamoya" disease are studied. Two aspects of "moyamoya" disease, (ie; occlusive lesion of cerebral vessels and the development of abnormal vascular network as collateral channel,) are also detected in the vertebrobasilar system. Among 82 cases, 49 cases showed the occlusion of posterior cerebral artery at their quadrigeminal segment. Twenty-three showed the more proximal occlusive lesions. Vertebral artery occlusion were found in 3 cases. As the occlusive lesion progresses, abnormal vascular network at the posterior portion of skull base developed. This network consists mainly of thalamogeniculate artery, posterior choroidal artery, and also of other thalamoperforators. Visual field defect as an ischemic symptom of occipital lobe was detected in 9 cases (11%). Superficial temporal artery-middle cerebral artery anastomosis and encephalo-myo-synangiosis (temporal muscle graft), which were not considered to be so effective to the ischemia of the posterior circulation, were shown to exert indirect redistribution effect upon the vertebrobasilar system. However, this effect is such an indirect one that these surgical treatments cannot prevent the occurrence of ischemic stroke in the vertebrobasilar system. For this purpose, omentum transplantation to the occipital lobe may be needed as a method of direct revascularization.

Adolescent↗
PubMed1984

Effects of mazindol on lipid metabolism of human adipose tissue in vitro.

The interaction of mazindol with catecholamine in regulating peripheral lipid metabolism was studied in vitro. Noradrenaline-induced and adrenaline-induced glycerol release was augmented by addition of 50 ng mazindol. On the other hand, isoproterenol-induced glycerol release was suppressed by addition of 50 ng mazindol. Basal and dopamine-induced glycerol release was not altered by addition of 50 ng mazindol. These results suggest that mazindol may interact with alpha 2-adrenergic receptors in adipose tissue.

Adipose Tissue↗
PubMed1983

Comparison of plasma oxytocin levels during spontaneous labor and labor induced by amniotomy, prostaglandin F2 alpha, and prostaglandin E2.

Plasma concentrations of oxytocin in nine spontaneous labors (group 1), nine amniotomy-induced labors (group 2), six prostaglandin F2 alpha-induced labors (group 3), and five prostaglandin E2-induced labors (group 4) were determined at the stages of 1 to 7 days preceding the onset of labor, onset of labor, and established labor, by means of unextracted radioimmunoassay. The levels of oxytocin in the stage preceding the onset of labor in group 1 were not significantly different from the levels of oxytocin in the corresponding stages in groups 2, 3, and 4. However, the levels of oxytocin in the stages of onset of labor and established labor in group 1 were significantly higher than those in the corresponding stages in groups 2, 3, and 4. These results suggest that oxytocin plays a leading role in the onset and progress of spontaneous labor, whereas something other than oxytocin might be involved in the labor induced by amniotomy alone or by prostaglandins.

Adult↗
PubMed1983

Spinal cord arteriovenous malformations associated with spinal aneurysms.

Two patients with spinal cord arteriovenous malformations (AVMs) had coexisting spinal aneurysms on their main feeding arteries. The angiographic disappearance of these coexisting aneurysms after artificial embolization of the spinal cord AVMs suggests that hemodynamic stress is the important factor in the development of spinal aneurysms. The incidence of hemorrhage increases when spinal cord AVM is associated with spinal aneurysm.

Adolescent↗
PubMed1982

[Prostaglandin Production by the human placenta using a superfusion technique (author's transl)].

In order to clarify the onset mechanism of labor, we studied the prostaglandin production in human placenta tissues of different stage using a superfusion technique. 1) The placenta obtained at Cesarean section before the onset of labor (A): (1) In the control, the production of prostaglandins was not distinctly changed. (2) Administration of arachidonic acid increased gradually the production of PGs. PGs production showed the maximum values at 50-60 minutes fraction of the superfusion. Throughout the experiment, PG production became vigorously active. (3) Administration of oxytocin increased the production of PGs, too, in particular PGE2 and PGF2 alpha. 2) The placenta obtained at Cesarean section during delivery (B): (1) In the control, the production of PGs was not distinctly changed. (2) Administration of arachidonic acid increased the production of PGE2 and PGF2 alpha, but the production of PGs was lower as compared with (A). PGE1 did not change. (3) Oxytocin had no effect on the production of PGE1 and PGE2, but the production of PGF2 alpha showed the maximum values at 50-60 minutes fraction. 3) The delivered placenta (C): (1) In the control, the production of PGs was not distinctly changed. (2) Administration of arachidonic acid increased the production of PGs. (3) Oxytocin had no effect on the production of PGs. On the basis of these data, it may be appropriate to conclude as follows: The enzyme which has a high ability to produce PGs exists in the placenta before the onset of labor. But the enzyme keeps the resting condition by the some inhibiting factor of PG production. During delivery, the PG production by the placenta fell. This result means that the strong ability of the production of PGs by the placenta at this stage is not necessary. After the delivery, the production of PGs by the delivered placenta is unnecessary. It is substantiated Kato's theory which PGE is primarily involved in the onset of labor that the production ability of PGE was recognized only in the placenta of before the onset of labor. It is interesting that administration of oxytocin increased the production of PGF2 alpha and they are similar for the contraction-substance of uterus.

Alprostadil↗
PubMed1982

[Changes in the criteria for planned delivery in the National Defense Medical College Hospital with statistical analysis].

Planned deliveries have been attempted with the administration of prostaglandins E2 and F2 alpha since 1978. Eight hundred and eighteen prostaglandins-induced and 729 uninduced deliveries from January, 1978 to July, 1980 were statistically analyzed. The uninduced deliveries included 465 spontaneous and 264 stimulated labors. The cervical ripening was considered the basic requirement stimulated labors. The cervical ripening was considered the basic requirement for labor induction for the first year of study. However, spontaneous labor onset or the membranes rupture occurred before the induction in 52.4% of cases, where babies were large enough (3,052.6 +/- 33.4g, mean +/- SE, n = 154). Therefore, the cervical factor was excluded from the essential requirement for induction. Since the beginning of 1979, labor induction has been performed based on gestational age (38 weeks or more) and uterine fundal length (32cm or more). Laminaria tents were inserted into the unfavorable cervix the night before induction. Delivery time in the day, duration of labor, and birth weight of babies in the induced group were 2.04 +/- 0.18 p.m., 8.0 +/- 0.3 hours and 3,138.8 +/- 12.3g, respectively. Apgar scores and the amount of postpartum hemorrhage were not significantly different from those in the uninduced group. Similar results were obtained between the laminaria subgroup with unfavorable cervix and the non-laminaria subgroup with ripe cervix in the induced primigravidas.

Birth Weight↗
PubMed1981

Experimentally induced cerebral aneurysms in rats: VII. Scanning electron microscope study.

The luminal surfaces of experimentally induced cerebral aneurysms and the branching sites in the circle of Willis in rats were investigated by scanning electron microscopy. Gap formation at the junctions of the endothelial cells was one of the most obvious changes on the endothelial surface of the aneurysms. Many leukocytes were observed adhering to these gaps. Regressive changes of endothelial cells, such as balloonlike protrusions and craterlike depressions, were also found in the aneurysms. At the branching site, where cerebral aneurysms often develop, endothelial cells were disarranged, rounded, and varied in size. A deep groove was also found adjacent to the apex. The role of endothelial cells and leukocytes in the development of cerebral aneurysms is discussed.

Animals↗
PubMed1981

Experimental study on quantitative flow measurement by a Doppler flowmeter with a sound-spectrograph.

A bidirectional ultrasonic Doppler flowmeter equipped with a sound-spectrographic analyzer has enabled us to determine blood-flow direction and to obtain useful information from the flow pattern in assessing the cerebral blood flow transcutaneously or intraoperatively. Using a regulated flow system produced in a dog, we performed an experimental study in order to establish the optimal mode for its use and to study the reliability in the quantitative cerebral blood-flow measurements. Although we could not measure the absolute blood-flow volume directly with this apparatus, we were able to obtain useful, quantitative information on blood flow and flow pattern by placing the ultrasonic probe in an appropriate position with respect to a blood vessel.

Animals↗
PubMed1981

[Relationship between the onset of labor and prostaglandins in rabbit tissues before and after delivery (author's transl)].

1) The studies were performed to elucidate the mechanism of onset of labor. It was investigated in relation to the movement of prostaglandins in individual tissues of pregnant rabbits before and after labor with the onset of labor. 2) The rabbit uterus duplex used is convenient material to investigate the movement of PGs in the same rabbit at the different term. 3) The concentrations of PGs were measured by RIA. 4) The concentrations of PGs in blood and amniotic fluid were not essential to explain account for the mechanism of onset labor. 5) From the results of the PGs values before and after labor, we have been considered that the relative PGs at the onset of labor were PG E1 and PG E2 in the placenta. We infer that PG F2 alpha plays a leading role in uterine contraction, because the large amount of PG F2 alpha presented in decidual parietalis during delivery, and PG E1 and PG E2 play a role in uterine contraction, too.

Amniotic Fluid↗